On behalf of the Board of Directors of Penumbra, Inc., which we refer to as “Penumbra,” we are pleased to enclose the accompanying proxy statement/prospectus relating to the proposed transaction between Penumbra and Boston Scientific Corporation, which we refer to as “Boston Scientific.” We are requesting that you take certain actions as a holder, which we refer to as a “Penumbra Stockholder,” of common stock, par value $0.001 per share, of Penumbra, which we refer to as “Penumbra Shares.”

The Board of Directors of Penumbra and Boston Scientific have each unanimously approved an agreement that provides for the acquisition by Boston Scientific of Penumbra in a cash and stock transaction. Pursuant to the Agreement and Plan of Merger, dated as of January 14, 2026, among Boston Scientific, Pinehurst Merger Sub, Inc., a wholly owned subsidiary of Boston Scientific, which we refer to as “Merger Sub,” and Penumbra, which (as the same may be amended from time to time) we refer to as the “Merger Agreement,” Merger Sub will merge with and into Penumbra, which we refer to as the “Merger,” with Penumbra surviving as a wholly owned subsidiary of Boston Scientific.

Boston Scientific and Penumbra have a shared commitment to innovation and clinical excellence to help advance patient care. The proposed Merger is an exciting opportunity that we believe will enable us to accelerate access to our innovations and help more patients, physicians and hospitals globally. By combining Penumbra’s advanced technology and dedicated employees with Boston Scientific’s global reach, our goal is to expand access to our products all over the world.

In the Merger, at the effective time of the Merger, which we refer to as the “Effective Time”, each issued and outstanding Penumbra Share (but excluding (i) shares held by Penumbra in treasury or owned by any direct or indirect wholly owned Penumbra Subsidiary and each share owned by Merger Sub, Boston Scientific or any direct or indirect wholly owned subsidiary of Boston Scientific immediately prior to the Effective Time, which we refer to as “Cancelled Shares”, and (ii) shares outstanding immediately prior to the Effective Time and held by a holder or beneficial holder that or who is entitled to demand and has properly demanded appraisal for such shares in accordance with, and who complies in all respects with, Section 262 of the General Corporation Law of the State of Delaware, which we refer to as the “DGCL”, and such shares as “Dissenting Shares”), will, subject to the proration provisions of the Merger Agreement, be cancelled and will be converted automatically into the right to receive, at the election of the holder thereof in accordance with, and subject to the terms, conditions and procedures set forth in the Merger Agreement, the following consideration (collectively with, if applicable, cash in lieu of any fractional Boston Scientific Shares and any dividends or other distributions payable pursuant to the Merger Agreement, the “Merger Consideration”), in each case, without interest:

The election right for Penumbra Stockholders will be subject to proration in accordance with the terms of the Merger Agreement and as more fully described in the accompanying proxy statement/prospectus, which is

applicable in the event the Cash Consideration is undersubscribed or oversubscribed. The Merger Agreement provides that the total number of Penumbra Shares that will be entitled to receive the Cash Consideration pursuant to the preceding paragraph will be equal to 73.26% of the aggregate number of Penumbra Shares issued and outstanding immediately prior to the Effective Time (other than Cancelled Shares and Dissenting Shares), and the total number of Penumbra Shares that will be entitled to receive the Stock Consideration pursuant to the preceding paragraph will be equal to 26.74% of the aggregate number of Penumbra Shares issued and outstanding immediately prior to the Effective Time (other than Cancelled Shares and Dissenting Shares), in each case, rounded to the nearest whole number. In the event of proration, Penumbra Stockholders might receive a portion of their Merger Consideration in a form they did not elect. No fractional Boston Scientific Shares will be issued in the Merger, and Penumbra Stockholders will receive cash in lieu of any fractional Boston Scientific Shares to which they otherwise would have been entitled, in accordance with the terms and conditions of the Merger Agreement.

At the announcement of the transactions contemplated by the Merger Agreement, which we refer to as the “Transactions,” the parties valued the Merger Consideration at $374.00 per Penumbra Share based on the ability of a Penumbra Stockholder to elect either $374.00 in cash per Penumbra Share or 3.8721 Boston Scientific Shares per Penumbra Share (valued at $374.00 per Penumbra Share based on the volume weighted average price of $96.59 per Boston Scientific Share over the last 10 trading days ending on and including January 13, 2026, two trading days before the public announcement of the Transactions), subject to proration. Although the Cash Consideration is fixed at $374.00 in cash per Penumbra Share, the value of the Stock Consideration will fluctuate with the market price of Boston Scientific Shares, and the values of the Cash Consideration and the Stock Consideration at the completion of the Merger may not be the same. Accordingly, the value of the Stock Consideration at the time of completion of the Merger could be greater than, less than or the same as the value of the Cash Consideration. On March 27, 2026, the latest practicable date prior to the date of this proxy statement/prospectus, the value of the Stock Consideration was $267.83 per Penumbra Share, based on the closing trading price of Boston Scientific Shares on such date as reported on the New York Stock Exchange. We urge you to obtain current market quotations of Boston Scientific Shares (trading symbol “BSX”) prior to making your Cash Election or Stock Election.

Based on the number of Penumbra Shares outstanding as of March 27, 2026, the last practicable trading day before the date of the accompanying proxy statement/prospectus, Boston Scientific is expected to issue approximately 43,866,267 Boston Scientific Shares in the aggregate in the Merger, with former Penumbra Stockholders owning, in the aggregate, approximately 2.87% of the Boston Scientific Shares immediately following the Merger (without giving effect to any Boston Scientific Shares held by Penumbra Stockholders prior to the Merger).

The special meeting of Penumbra Stockholders, which we refer to as the “Special Meeting”, will be held on May 6, 2026, at 10:00 a.m. Pacific Time in building 1310 on Penumbra’s campus at One Penumbra Place, Alameda, CA 94502. At the Special Meeting, we will ask the Penumbra Stockholders to approve the Merger and other related business. Information about the Special Meeting and the Merger is contained in the accompanying proxy statement/prospectus. In particular, see “Risk Factors” beginning on page 34. We urge you to read the accompanying proxy statement/prospectus carefully and in its entirety.

The Special Meeting will be held solely in person and there will not be a live webcast. If you plan to attend the Special Meeting, please note that attendance will be limited to Penumbra Stockholders as of the record date for the Special Meeting, which we refer to as the “Record Date.” Each Penumbra Stockholder may be asked to present valid photo identification, such as a driver’s license or passport. Penumbra Stockholders holding stock in brokerage accounts or by a bank or other nominee may be required to show a brokerage statement or account statement reflecting stock ownership as of the Record Date. Cameras, recording devices, and other electronic devices will not be permitted at the Special Meeting. You may contact Penumbra Investor Relations at investors@penumbrainc.com to obtain directions to the Special Meeting.

Whether or not you plan to attend the Special Meeting, please vote as soon as possible to make sure that your shares are represented at the meeting. If you do not vote, it will have the same effect as voting “AGAINST” the Merger.

Our Board of Directors unanimously recommends that Penumbra Stockholders vote “FOR” each of the proposals to be considered at the Special Meeting.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the Merger, the adoption of the Merger Agreement or any other transaction described in the accompanying proxy statement/prospectus, or passed upon the adequacy or accuracy of the disclosure in the accompanying proxy statement/prospectus. Any representation to the contrary is a criminal offense.

The accompanying proxy statement/prospectus is dated April 1, 2026 and is first being mailed on or about April 1, 2026.

On January 14, 2026, Penumbra, Inc., which we refer to as “Penumbra,” Boston Scientific Corporation, which we refer to as “Boston Scientific,” and Pinehurst Merger Sub, Inc., which we refer to as “Merger Sub,” entered into an Agreement and Plan of Merger, which (as the same may be amended from time to time) we refer to as the “Merger Agreement,” a copy of which is attached as Annex A to the accompanying proxy statement/prospectus.

NOTICE IS HEREBY GIVEN that a special meeting, which we refer to as the “Special Meeting,” of holders of common stock, par value $0.001 per share, of Penumbra, which we refer to as “Penumbra Shares,” will be held will be held on May 6, 2026, at 10:00 a.m. Pacific Time in building 1310 on Penumbra’s campus at One Penumbra Place, Alameda, CA 94502. We are pleased to notify you of and invite you to attend the Special Meeting.

At the Special Meeting, you will be asked to consider and vote on the following matters:

The board of directors of Penumbra has fixed the close of business on March 26, 2026 as the record date for the Special Meeting, which we refer to as the “Record Date.” Only holders of record of Penumbra Shares as of the close of business on the Record Date are entitled to notice of, to attend and to vote at, the Special Meeting or any adjournment or postponement thereof.

The Special Meeting will be held solely in person and there will not be a live webcast. If you plan to attend the Special Meeting, please note that attendance will be limited to Penumbra Stockholders as of the Record Date. Each Penumbra Stockholder may be asked to present valid photo identification, such as a driver’s license or passport. Penumbra Stockholders holding stock in brokerage accounts or by a bank or other nominee may be required to show a brokerage statement or account statement reflecting stock ownership as of the Record Date. Cameras, recording devices, and other electronic devices will not be permitted at the Special Meeting. You may contact Penumbra Investor Relations at investors@penumbrainc.com to obtain directions to the Special Meeting.

The board of directors of Penumbra unanimously recommends that Penumbra Stockholders vote “FOR” the Merger Proposal, “FOR” the Advisory Compensation Proposal and “FOR” the Adjournment Proposal.

Under Delaware law, Penumbra Stockholders who do not vote in favor of the Merger Proposal will have the right to seek appraisal and obtain payment in cash for the fair value of their Penumbra Shares, as determined by the Court of Chancery of the State of Delaware, if the Merger is completed, but only if they strictly comply with the procedures prescribed by Delaware law. These procedures are summarized in “Appraisal Rights” beginning on page 123 of the accompanying proxy statement/prospectus. In addition, the text of the applicable provisions of Delaware law is attached as Annex C to the accompanying proxy statement/prospectus.

Your vote is important. We cannot complete the transactions contemplated by the Merger Agreement unless Penumbra Stockholders approve the Merger Proposal. The affirmative vote of the holders of a majority of the issued and outstanding Penumbra Shares entitled to vote on the Merger Agreement is required to approve the Merger Proposal.

Each copy of the proxy statement/prospectus mailed to Penumbra Stockholders is accompanied by a form of proxy card with instructions for voting.

Whether or not you plan to attend the Special Meeting, we urge you to please promptly complete, sign, date and return the accompanying proxy card in the enclosed postage-paid envelope or authorize the individuals named on the accompanying proxy card to vote your shares by calling the toll-free telephone number or by using the internet as described in the instructions included with the accompanying proxy card. If your shares are held in the name of a bank, broker, trustee or other nominee, please follow the instructions on the voting instruction card furnished by such bank, broker, trustee or other nominee. Even if you have voted by proxy, you may still vote in person if you attend the Special Meeting. Please note, however, that if your shares are held in the name of a bank, broker, trustee or other nominee and you wish to vote at the Special Meeting, you must obtain a proxy issued in your name from that record holder in order to be entitled to vote in person at the Special Meeting.

If you have any questions regarding the accompanying proxy statement/prospectus, you may contact Innisfree, Penumbra’s proxy solicitor, at:

This proxy statement/prospectus incorporates important business and financial information about Boston Scientific Corporation and Penumbra, Inc. from other documents that Boston Scientific and Penumbra have filed with the U.S. Securities and Exchange Commission and that are contained in or incorporated by reference into this proxy statement/prospectus. For a listing of documents incorporated by reference into this proxy statement/prospectus, please see “Where You Can Find More Information” beginning on page 207 of this proxy statement/prospectus. This information is available for you to review, without charge, through the SEC’s website at www.sec.gov.

You may request copies of this proxy statement/prospectus and any of the documents incorporated by reference into this proxy statement/prospectus or other information concerning Penumbra, Inc., without charge, by telephone or written request directed to:

You may also request a copy of this proxy statement/prospectus and any of the documents incorporated by reference into this proxy statement/prospectus or other information concerning Boston Scientific Corporation, without charge, by telephone or written request directed to:

In order for you to receive timely delivery of the documents in advance of the special meeting of Penumbra, Inc. stockholders to be held on May 6, 2026, your request for such information must be received no later than five business days prior to the date of the special meeting, by April 29, 2026.

The proxy statement/prospectus is also available in the Investor Relations section of Penumbra, Inc.’s website at https://www.penumbrainc.com/investors/sec-filings/. The information on Penumbra, Inc.’s website is not part of this proxy statement/prospectus. References to Penumbra, Inc.’s website in this proxy statement/prospectus are intended to serve as textual references only.

This document, which forms part of a registration statement on Form S-4 filed with the SEC by Boston Scientific (File No. 333-293872), constitutes a prospectus of Boston Scientific under Section 5 of the Securities Act, with respect to the Boston Scientific Shares to be issued to Penumbra Stockholders pursuant to the Merger Agreement. This document also constitutes a proxy statement of Penumbra under Section 14(a) of the Exchange Act. It also constitutes a notice of meeting with respect to the Special Meeting at which Penumbra Stockholders will be asked to consider and vote upon a proposal to adopt the Merger Agreement.

Boston Scientific has supplied all information contained or incorporated by reference into this proxy statement/prospectus relating to Boston Scientific, and Penumbra has supplied all information contained or incorporated by reference into this proxy statement/prospectus relating to Penumbra.

Boston Scientific and Penumbra have not authorized anyone to provide you with information that is different from or in addition to that contained in or incorporated by reference into this proxy statement/ prospectus. Boston Scientific and Penumbra do not take any responsibility for, or provide any assurance as to the reliability of, any other information others may give you. This proxy statement/prospectus is dated April 1, 2026, and you should not assume that the information contained in this proxy statement/prospectus is accurate as of any date other than such date. Further, you should not assume that the information incorporated by reference into this proxy statement/prospectus is accurate as of any date other than the date of the incorporated document. Neither the mailing of this proxy statement/prospectus to Penumbra Stockholders nor the issuance by Boston Scientific of Boston Scientific Shares pursuant to the Merger Agreement will create any implication to the contrary.

All currency amounts referenced in this proxy statement/prospectus are in U.S. dollars, unless otherwise indicated. Additionally, unless otherwise indicated or as the context otherwise requires:

The following questions and answers are intended to briefly address some commonly asked questions regarding the Merger, the Merger Agreement and the Special Meeting. We urge you to read carefully the remainder of this proxy statement/prospectus because the information in this section may not provide all the information that might be important to you in determining how to vote. Additional important information is also contained in the annexes to, and the documents incorporated by reference in, this proxy statement/prospectus. See “Where You Can Find More Information” beginning on page 207 of this proxy statement/prospectus.

Boston Scientific Shares are listed for trading on the NYSE under the symbol “BSX” and Penumbra Shares are listed for trading on the NYSE under the symbol “PEN.” The following table presents the closing trading prices of Boston Scientific Shares and Penumbra Shares, as reported on the NYSE on: January 14, 2026, the last full trading day prior to the public announcement of the Merger Agreement; and March 27, 2026, the latest practicable date prior to the date of this proxy statement/prospectus:

The table also presents the equivalent value of the Stock Consideration per Penumbra Share on those dates:

The above table shows only historical comparisons. These comparisons may not provide meaningful information to Penumbra Stockholders in determining whether to approve the Merger Agreement because the value of the Merger Consideration will fluctuate based on the market price of Boston Scientific Shares. As a result, Penumbra Stockholders are urged to obtain current market quotations for Boston Scientific Shares and Penumbra Shares and to review carefully the other information contained in (or incorporated by reference into) this proxy statement/prospectus in considering whether to approve the Merger Proposal. The market prices of Boston Scientific Shares and Penumbra Shares will fluctuate between the date of this proxy statement/prospectus and the date of completion of the Merger. No assurance can be given concerning the market prices of Boston Scientific Shares or Penumbra Shares before or after the Effective Time.

This proxy statement/prospectus and the documents that are incorporated into this proxy statement/ prospectus by reference contain forward-looking statements within the meaning of Section 27A of the Securities Act and Section 21E of the Exchange Act. Forward-looking statements may be identified by words like “anticipate,” “expect,” “project,” “believe,” “plan,” “estimate,” “intend” and similar words. These forward-looking statements are based on the beliefs, assumptions and estimates of Boston Scientific and Penumbra using information available to them at the time and are not intended to be guarantees of future events or performance. These forward-looking statements include, among other things, statements regarding the financial and business impact of the Transactions and anticipated benefits of the Transactions, the closing of the Transactions and the timing thereof, the ability to obtain required regulatory and stockholder approvals, the possibility that competing offers will be made, potential litigation relating to the Transactions, business plans and strategy, product launches and product performance and impact, clinical programs, and expected financial results. If Boston Scientific’s and Penumbra’s underlying assumptions turn out to be incorrect, or if certain risks or uncertainties materialize, actual results could vary materially from the expectations and projections expressed or implied by their forward-looking statements. These factors, in some cases, have affected and in the future (together with other factors) could affect the ability of Boston Scientific and Penumbra to implement its respective business strategies and may cause actual results to differ materially from those contemplated by the statements expressed in this proxy statement/prospectus and the documents that are incorporated into this proxy statement/prospectus by reference. As a result, readers are cautioned not to place undue reliance on any of Boston Scientific’s and Penumbra’s forward-looking statements.

In addition to the risk factors described under “Risk Factors” beginning on page 34, factors that may cause such differences include, among other things:

All of these factors are difficult or impossible to predict accurately and many of them are beyond the control of Boston Scientific and Penumbra. For a further list and description of these and other important risks and uncertainties that may affect each of Boston Scientific’s and Penumbra’s businesses and future operations, see Part I, Item 1A — Risk Factors in Boston Scientific’s and Penumbra’s respective most recent Annual Report on Form 10-K filed with the SEC, which are incorporated by reference in this proxy statement/ prospectus and may be updated in Part II, Item 1A — Risk Factors in Quarterly Reports on Form 10-Q each company has filed or will file hereafter. See “Where You Can Find More Information” on page 207. Boston Scientific and Penumbra each disclaim any intention or obligation to publicly update or revise any forward-looking statements to reflect any change in our expectations or in events, conditions or circumstances on which those expectations may be based, or that may affect the likelihood that actual results will differ from those contained in the forward-looking statements, except as required by securities and other applicable laws. This cautionary statement is applicable to all forward-looking statements contained in this proxy statement/ prospectus and the documents that are incorporated into this proxy statement/prospectus by reference.

In addition to the other information included in, incorporated by reference in, or found in the annexes attached to, this proxy statement/prospectus, including the matters addressed in “Cautionary Statement Regarding Forward-Looking Statements” beginning on page 32, you should carefully consider the following risk factors in deciding how to vote for the proposals to be considered at the Special Meeting. See “Where You Can Find More Information”beginning on page 207 for more information about the documents incorporated by reference in this proxy statement/prospectus. Additional risks and uncertainties not presently known to Boston Scientific or Penumbra or that are not currently believed to be important also may adversely affect the Transactions and Boston Scientific following the Transactions.

Upon the Effective Time, each Stock Election Share will, subject to the proration provisions of the Merger Agreement, be cancelled and will be converted automatically into the right to receive 3.8721 validly issued, fully paid and non-assessable Boston Scientific Shares. The market price of Boston Scientific Shares at the Effective Time may vary significantly from the market price of Boston Scientific Shares on the date of the Merger Agreement, the date of this proxy statement/prospectus and the date of the Special Meeting. Because the Stock Consideration is based on a fixed exchange ratio, the value of the Stock Consideration that Penumbra Stockholders who elect to receive the Stock Consideration will receive upon completion of the Merger may be higher or lower than the value of the Stock Consideration on such earlier dates. Accordingly, Penumbra Stockholders who elect to receive the Stock Consideration will not know or be able to calculate at the time of the Special Meeting the market value of the Stock Consideration they will receive upon completion of the Merger. If the market value of Boston Scientific Shares falls between the date of this proxy statement/prospectus and the time the Stock Consideration is actually received, the value of the Stock Consideration received may be less than the value of the Stock Consideration such Penumbra Stockholder may anticipate receiving.

Stock price changes may result from a variety of factors, including, among others, general market and economic conditions, changes in Boston Scientific’s and Penumbra’s respective businesses, operations and prospects, market assessments of the likelihood that the Merger will be completed, the timing of the Merger, regulatory considerations and other risk factors set forth or incorporated by reference in this proxy statement/ prospectus. Many of these factors are beyond Boston Scientific’s and Penumbra’s control.

You are urged to obtain current market quotations for Boston Scientific Shares and for Penumbra Shares.

The election right for Penumbra Stockholders will be subject to proration in accordance with the terms of the Merger Agreement, which is applicable in the event the Cash Consideration is undersubscribed or oversubscribed. The Merger Agreement provides that the total number of Penumbra Shares that will be entitled to receive the Cash Consideration will be equal to 73.26% of the aggregate number of Penumbra Shares issued and outstanding immediately prior to the Effective Time (other than Excluded Shares), and the total number of Penumbra Shares that will be entitled to receive the Stock Consideration will be equal to 26.74% of the aggregate number of Penumbra Shares issued and outstanding immediately prior to the Effective Time (other than Excluded Shares), in each case, rounded to the nearest whole number.

As a result, if the Cash Consideration is undersubscribed or oversubscribed, then adjustments will be made to the Merger Consideration to be paid to Penumbra Stockholders to proportionately reduce the Cash Consideration or the Stock Consideration, as applicable, received by such Penumbra Stockholders in the manner described in “The Merger Agreement — Merger Consideration — Proration and Allocation of the Merger Consideration” beginning on page 80 of this proxy statement/prospectus.

Thus, Penumbra Stockholders might receive a portion of their Merger Consideration in a form they did not elect. In addition, if the aggregate Merger Consideration to be paid to any Penumbra Stockholder would result in such Penumbra Stockholder receiving a fractional Boston Scientific Share, cash will be paid in lieu of such fractional Boston Scientific Share.

The obligations of Boston Scientific and Penumbra to complete the Merger are subject to the satisfaction or waiver of a number of conditions, including, among others, the adoption of the Merger Agreement by Penumbra Stockholders by the affirmative vote of at least a majority of the issued and outstanding Penumbra Shares, the expiration or termination of the waiting period under the HSR Act, and the receipt of clearances or approvals under (or the expiration or termination of applicable waiting periods under) the antitrust, competition or foreign investment laws of certain non-U.S. jurisdictions. For a more complete summary of the required regulatory approvals and other conditions to the completion of the Merger, see the section titled “The Merger — Regulatory Approvals Required for the Merger” beginning on page 76 of this proxy statement/ prospectus and the section titled “The Merger Agreement — Conditions to the Closing of the Merger” beginning on page 101 of this proxy statement/prospectus.

Although Boston Scientific and Penumbra have agreed in the Merger Agreement to use their reasonable best efforts to complete the Merger as promptly as practicable (including, in the case of Boston Scientific, agreeing to (i) litigate in the event the Merger is challenged and (ii) if necessary, divest assets and/or accept certain non-divestiture remedies with respect to businesses, properties or assets that generated up to $300 million in revenue for the year ending December 31, 2025, as further described in the section of this proxy statement/prospectus captioned “The Merger Agreement — Regulatory Filings”), many of the closing conditions are not within Boston Scientific’s or Penumbra’s control, and neither company can predict when or if these conditions will be satisfied. If any of these conditions are not satisfied or waived prior to January 14, 2027, which deadline may be extended to January 14, 2028 under certain circumstances, it is possible that the Merger Agreement will be terminated. The failure to satisfy all of the required conditions could delay the completion of the Merger for a significant period of time or prevent it from occurring. There can be no assurance that the closing conditions will be satisfied or waived or that the Merger will be completed. For a more detailed description, see the Risk Factor titled — “Failure to complete the Merger could negatively affect the stock price and the future business and financial results of Penumbra” beginning on page 37 of this proxy statement/prospectus.

In addition, any waiver of the closing conditions may not require resolicitation of Penumbra Stockholders, in which case the parties will have the discretion to complete the Merger and the Transactions without seeking further approval of Penumbra Stockholders.

Before the Merger may be completed, any applicable waiting period (and any extension thereof) under the HSR Act relating to the Merger must have expired or been terminated. The obligations of Boston Scientific and Penumbra to complete the Merger are also subject to the receipt of clearances or approvals under (or the expiration or termination of applicable waiting periods under) the antitrust, competition or foreign investment laws of certain non-U.S. jurisdictions. Under the Merger Agreement, Boston Scientific and Penumbra have agreed to use their reasonable best efforts to obtain regulatory approvals, consents and clearances (including, in the case of Boston Scientific, agreeing to (i) litigate in the event the Merger is challenged and (ii) if necessary, divest assets and/or accept certain non-divestiture remedies with respect to businesses, properties or assets that generated up to $300 million in revenue for the year ending December 31, 2025, as further described in the section of this proxy statement/prospectus captioned “The Merger Agreement — Regulatory Filings”), and therefore may be required to comply with conditions, terms, obligations or restrictions imposed by governmental authorities. There can be no assurance that such conditions, terms, obligations or restrictions will not have the effect of delaying completion of the Merger or imposing additional material costs on or materially limiting the revenues of Boston Scientific following the completion of the Merger. In addition, neither Boston Scientific nor Penumbra can provide assurance that any such conditions, terms, obligations or restrictions will not result in the delay or abandonment of the Merger.

When considering the recommendation of the Penumbra Board that Penumbra Stockholders approve the Merger Proposal and the Advisory Compensation Proposal, Penumbra Stockholders should be aware that directors and executive officers of Penumbra have certain interests in the Merger that may be different from, or in addition to, the interests of Penumbra Stockholders more generally. These interests include, among others, the treatment of

outstanding equity awards pursuant to the Merger Agreement, and continued indemnification and directors’ and officers’ liability insurance. In addition, as of the date of this proxy statement/prospectus, it is anticipated that Adam Elsesser will join the Boston Scientific Board upon Closing. Prior to and following the Closing, certain of Penumbra’s other executive officers may have discussions with and may enter into agreements with Boston Scientific or the Surviving Corporation, their subsidiaries or their respective affiliates regarding service with, or the right to purchase or participate in the equity of, Boston Scientific, the Surviving Corporation or one or more of its affiliates. See the section titled “The Merger — Interests of Penumbra’s Directors and Executive Officers in the Merger” beginning on page 72 of this proxy statement/prospectus for a more detailed description of these interests. The Penumbra Board was aware of these interests and considered them, among other matters, in evaluating and negotiating the Merger Agreement, in reaching its decision to approve the Merger Agreement and the consummation of the Merger, and in recommending that Penumbra Stockholders vote in favor of the Merger Agreement proposal.

For more information, see “The Merger — Interests of Penumbra’s Directors and Executive Officers in the Merger” beginning on page 72 of this proxy statement/prospectus.

The Merger Agreement contains provisions that make it more difficult for Penumbra to sell its business to a party other than Boston Scientific. These provisions include a general prohibition on Penumbra soliciting any company takeover proposal or offer for a competing transaction. In addition, upon termination of the Merger Agreement, Penumbra is required to pay Boston Scientific a termination fee of $525 million if the Merger Agreement is terminated in certain circumstances including Penumbra entering into a definitive agreement with respect to a superior proposal or an adverse recommendation change.

The opinion delivered by PWP, Penumbra’s financial advisor, addresses the fairness of the aggregate Merger Consideration to be received by Penumbra Stockholders, from a financial point of view, to such holders only as of the date that the Merger Agreement was executed. The Penumbra board has not obtained an updated fairness opinion as of the date of this proxy statement/prospectus and Penumbra does not anticipate asking its financial advisor to update its opinion prior to the Closing. Changes in the operations and prospects of Boston Scientific or Penumbra, general market and economic conditions and other factors that may be beyond their control, and on which the fairness opinion was based, may alter the value of Boston Scientific or Penumbra or the prices of Boston Scientific Shares or Penumbra Shares by the time the Merger is completed.

The opinion delivered by PWP is included as Annex B to this proxy statement/prospectus. For a description of the opinion and a summary of the material financial analysis performed in connection with rendering such opinion, please refer to “The Merger — Opinion of Penumbra’s Financial Advisor — Perella Weinberg Partners LP” beginning on page 64 of this proxy statement/prospectus.

Uncertainty about the effect of the Merger Agreement and the Merger on Penumbra’s customers, employees, suppliers, vendors, and business partners may have an adverse effect on Penumbra’s business and operations that may be material to Penumbra. For example, Penumbra’s employees may experience uncertainty about their roles following the Merger. There can be no assurance Penumbra will be able to attract and retain key talent, including senior leaders, engineers, salespeople, and others to the same extent that Penumbra has previously been able to attract and retain employees. Any loss or distraction of such employees could have a material adverse effect on Penumbra’s business and operations. In addition, Penumbra has diverted, and will continue to divert, significant management attention and resources towards the completion of the Merger, which could materially adversely affect Penumbra’s business and results of operations.

Moreover, Penumbra’s customers may experience uncertainty associated with the Merger, including with respect to possible changes to our products, technology or policies. Similarly, Penumbra’s suppliers, vendors, business partners and distribution channels may experience uncertainty associated with the Merger, including with respect to current or future business relationships with Penumbra. Uncertainty may cause customers to refrain from

purchasing Penumbra’s products and to instead purchase our competitors’ products, and suppliers, vendors and business partners may seek to change existing business relationships, which could result in an adverse effect on Penumbra’s business, results of operations and financial condition in a way that may be material to Penumbra.

Pursuant to the terms of the Merger Agreement, until the Merger becomes effective or the Merger Agreement is terminated, Penumbra is subject to certain restrictions on the conduct of its business, including in certain cases restrictions on Penumbra’s ability to enter into certain material contracts, acquire or dispose of assets outside of the ordinary course of business, incur indebtedness or make unbudgeted capital expenditures. These restrictions may prevent Penumbra from taking actions with respect to its business that Penumbra may consider advantageous, and result in Penumbra’s inability to respond effectively to competitive pressures and industry developments and may otherwise harm its business and results of operations.

If the Merger is not completed for any reason, including as a result of Penumbra Stockholders failing to approve the Merger Agreement proposal, the ongoing business of Penumbra may be adversely affected and, without realizing any of the benefits of having completed the Merger, Penumbra could be subject to a number of negative consequences, including the following:

In addition, upon termination of the Merger Agreement, under certain circumstances, Penumbra is required to pay Boston Scientific a termination fee of $525 million, including in the event of Penumbra entering into an Acquisition Agreement with respect to a superior proposal or an adverse recommendation change. Finally, Penumbra could be subject to litigation related to any failure to complete the Merger or related to any proceeding commenced against Penumbra to perform its obligations under the Merger Agreement. If the Merger is not completed, any of these risks may materialize and may adversely affect Penumbra’s businesses, financial condition, financial results and stock price.

Boston Scientific’s obligation to complete the Merger is not conditioned upon its obtaining financing for the Merger. Boston Scientific anticipates that approximately $11 billion will be required to pay the aggregate Cash Consideration payable in connection with the Merger and to pay fees and expenses relating to the Merger and the other Transactions.

Boston Scientific intends to fund the aggregate Cash Consideration payable in connection with the Merger with a combination of (i) existing cash resources; (ii) third party debt financing, which may include issuances under Boston Scientific’s commercial paper program; and (iii) proceeds from the issuance of one or more senior unsecured debt securities. In connection with the Merger, on February 26, 2026, Boston Scientific entered into the following

agreements with Wells Fargo Bank, National Association and the other lenders party thereto: (1) a 364-day revolving credit facility, in an aggregate principal amount of up to $2.0 billion; (2) a 364-day delayed draw term loan facility in an aggregate principal amount of up to $1.0 billion, which may be drawn to fund the Merger at Closing; (3) a 364-day delayed draw term loan facility in an aggregate principal amount of up to $5.0 billion, which may be drawn to fund the Merger at Closing and, if so drawn, shall be repaid or refinanced with the proceeds of any issuance of senior unsecured debt securities referenced above; and (4) the refinancing of Boston Scientific’s Existing Revolving Credit Agreement, pursuant to which the Existing Revolving Credit Agreement was refinanced to, among other things, increase the aggregate revolving credit commitments from $2.75 billion to $3.0 billion and extend the maturity to February 26, 2031. Each of the Existing Revolving Credit Agreement and the 364-day revolving credit facility provide backing for Boston Scientific’s commercial paper program, and outstanding commercial paper backed by either facility will directly reduce borrowing capacity under such facility.

The funding of these facilities are subject to customary terms and conditions precedent for such borrowing as set forth in the debt commitment letter, including, among others, (i) that the Merger shall have been consummated substantially concurrently with the funding under such facilities substantially in accordance with the terms of the Merger Agreement, (ii) the absence of a material adverse effect of Boston Scientific and its subsidiaries since December 31, 2024 and (iii) the absence of certain events of default. There is a risk that these conditions will not be satisfied and the financing may not be available when required. In the event that the financing contemplated by the debt commitment letter and the other debt facilities described above are not available, there is a risk that alternative financing may not be available on acceptable terms, in a timely manner or at all. See “The Merger — Financing of the Merger” beginning on page 75 of this proxy statement/prospectus for more information.

The completion of the Transactions may trigger change in control provisions in certain agreements to which Penumbra is a party. If Penumbra and Boston Scientific are unable to negotiate waivers of those provisions, the counterparties may exercise their rights and remedies under the agreements, potentially terminating the agreements or seeking monetary damages. Even if Penumbra and Boston Scientific are able to negotiate waivers, the counterparties may require a fee for such waivers or seek to renegotiate the agreements on terms less favorable to Penumbra or Boston Scientific.

Securities class action lawsuits and derivative lawsuits are often brought against public companies that have entered into acquisition, merger or other business combination agreements like the Merger Agreement. Even if such a lawsuit is without merit, defending against these claims can result in substantial costs and divert management time and resources. An adverse judgment could result in monetary damages, which could have a negative impact on Boston Scientific’s and Penumbra’s respective liquidity and financial condition.

Further, one of the conditions to the completion of the Transactions is that no injunction or law by any governmental entity of competent jurisdiction will be in effect that has the effect of restraining, enjoining or otherwise prohibiting the consummation of the Transactions. As such, if an injunction prohibiting the consummation of the Transactions is obtained, that injunction may prevent the Transactions from becoming effective or from becoming effective within the expected timeframe.

If you are a Penumbra Stockholder and want to make a valid Cash Election or Stock Election, you will be required to deliver your Certificates (unless your shares are Book-Entry Shares, in which case you should follow the instructions set forth in the Election Form), and a properly completed and signed Election Form, accompanied by duly executed transmittal materials included in the Election Form, to the Exchange Agent. Because the actual election deadline is not currently known, Penumbra and Boston Scientific will issue a press release announcing the date of the election deadline at least five business days, but no more than twenty business days, before that deadline. For further details on the determination of the election deadline, see “The Merger Agreement — Merger

Consideration — Election Procedures” beginning on page 82 of this proxy statement/prospectus. The election deadline will be on or before 5:00 p.m., New York City time, on the date that is five business days prior to Boston Scientific’s good faith estimate of the Closing Date (or such other time and date as Boston Scientific and Penumbra will agree). You will not be able to sell any Penumbra Shares that you have delivered as part of your election unless you revoke your election before the deadline by providing written notice to the Exchange Agent. If you do not revoke your election, you will not be able to liquidate your investment in Penumbra Shares for any reason until you receive cash and/or Boston Scientific Shares in the Merger. In the time between the election deadline and the Closing, the trading price of Boston Scientific Shares or Penumbra Shares may decrease, and you might otherwise want to sell your Penumbra Shares to gain access to cash, make other investments, or reduce the potential for a decrease in the value of your investment. The date that you will receive your Merger Consideration will depend on the Closing Date, which is uncertain. The Closing Date might be later than expected due to unforeseen events.

Under the terms of the Merger Agreement, Penumbra is subject to certain restrictions on the conduct of its business prior to completing the Merger which may adversely affect its ability to execute certain of its business strategies, including the ability in certain cases to enter into or amend contracts, acquire or dispose of assets, incur indebtedness or incur capital expenditures. Such limitations could adversely affect Penumbra’s business and operations prior to the completion of the Merger.

Boston Scientific is subject to a more limited set of restrictions on the conduct of its business prior to completing the Merger which may adversely affect its ability to execute certain of its business strategies, including the ability in certain cases to amend its organizational documents, pay dividends or distributions (subject to certain exceptions, including for regular quarterly cash dividends in the ordinary course consistent with past practice), or split, combine, or reclassify Boston Scientific Shares. Such limitations could adversely affect Boston Scientific’s business and operations prior to the completion of the Merger.

Each of the risks described above may be exacerbated by delays or other adverse developments with respect to the completion of the Merger.

In addition, subject to certain exceptions, Penumbra has agreed to use reasonable best efforts to carry on its business in the ordinary course and, to the extent consistent therewith, to use reasonable best efforts to preserve substantially intact Penumbra’s current business organizations, to keep available the services of Penumbra’s current officers and employees and to preserve Penumbra’s relationships with significant customers, suppliers, licensors, licensees, distributors, lessors and others having significant business dealings with Penumbra, in each case, during the period between the date of the Merger Agreement and the Closing Date.

For further discussion, see “The Merger Agreement — Conduct of Business Pending the Merger” beginning on page 89 of this proxy statement/prospectus.

Based on the number of Penumbra Shares as of March 27, 2026, and the number of Boston Scientific Shares as of March 27, 2026, it is expected that, immediately after completion of the Transactions, former Penumbra Stockholders will own approximately 2.87% of the outstanding Boston Scientific Shares. Consequently, former Penumbra Stockholders will have less influence over the management and policies of Boston Scientific than they currently have over the management and policies of Penumbra.

If the Merger is completed, Penumbra Stockholders will cease to have any equity interest in Penumbra and will not participate in its earnings or any future growth, except indirectly through ownership of the Boston Scientific Shares received as part of the Merger Consideration.

Boston Scientific believes that there are significant benefits and synergies that may be realized through leveraging the products, scale and combined businesses of Boston Scientific and Penumbra. However, the efforts to realize these benefits and synergies will be a complex process and may disrupt both companies’ existing operations if not implemented in a timely and efficient manner. The anticipated benefits of the Merger will depend, in part, on Boston Scientific and Penumbra’s ability to integrate the operations and business of Penumbra into Boston Scientific’s existing business in an efficient and timely manner, to combine systems and management controls and to integrate relationships with industry contacts and business partners. The full benefits of the Merger, including the anticipated sales or growth opportunities, may not be realized as expected or may not be achieved within the anticipated time frame, or at all. Failure to achieve the anticipated benefits of the Merger could adversely affect Boston Scientific’s results of operations or cash flows, cause dilution to the earnings per share of Boston Scientific, decrease or delay any accretive effect of the Merger and negatively impact the price of Boston Scientific Shares.

In addition, Boston Scientific will be required to devote significant attention and resources prior to the Closing to prepare for the post-Closing integration and operation of the Surviving Corporation and, following the Closing, to successfully align the business practices and operations of Boston Scientific and Penumbra. This process may disrupt the businesses and, if ineffective, would limit the anticipated benefits of the Merger.

Boston Scientific will incur substantial expenses in connection with and as a result of completing the Merger, and, following the completion of the Merger, Boston Scientific expects to incur additional expenses in connection with combining the businesses and operations of Boston Scientific and Penumbra. Factors beyond Boston Scientific’s control could affect the total amount or timing of these expenses, many of which, by their nature, are difficult to estimate accurately. Moreover, diversion of management focus and resources from the day-to-day operation of the business to matters relating to the Transactions could adversely affect Boston Scientific’s business, regardless of whether the Merger is completed.

Boston Scientific and Penumbra are dependent on the experience and knowledge of their officers and other key employees to execute their business plans. Each company’s success until the Merger and the Surviving Corporation’s success after completion of the Merger will depend in part upon the ability of Boston Scientific and Penumbra to retain key management personnel and other key employees. Current and prospective employees of Boston Scientific and Penumbra may experience uncertainty about their roles within the combined company following the Merger, which may have an adverse effect on the ability of each of Boston Scientific and Penumbra to attract or retain key management and other key personnel. Accordingly, no assurance can be given that the combined company will be able to attract or retain key management personnel and other key employees of Boston Scientific and Penumbra to the same extent that Boston Scientific and Penumbra have previously been able to attract or retain their own employees.

As a result of the Transactions, Penumbra Stockholders will no longer be Penumbra Stockholders. Former Penumbra Stockholders who receive stock consideration will become Boston Scientific Stockholders, and their rights as stockholders will be governed by the terms of Boston Scientific’s governing corporate documents. See the section titled “Comparison of Stockholders Rights” for a discussion of the different rights associated with Boston Scientific Common Stock.

Upon completion of the Transactions, Penumbra Stockholders who receive the Stock Consideration will become Boston Scientific Stockholders. Boston Scientific’s business differs in important respects from that of

Penumbra, and accordingly, the market price of Boston Scientific Shares after the completion of the Transactions may be affected by factors different from those currently affecting the market prices of Boston Scientific Shares and Penumbra Shares, respectively. As a result, the market price of Boston Scientific Shares may fluctuate significantly following completion of the Transactions and Penumbra Stockholders could lose the value of their investment in Boston Scientific Shares. For a discussion of the businesses of Boston Scientific and Penumbra and of some important factors to consider in connection with those businesses, see the documents incorporated by reference into this proxy statement/prospectus and referred to under “Where You Can Find More Information.”

In addition, if former Penumbra Stockholders or any other holders of Boston Scientific Shares sell substantial amounts of Boston Scientific Shares in the public market following consummation of the transactions, this could depress the market price of Boston Scientific Shares.

In connection with the completion of the Merger, based on the number of Penumbra Shares as of March 27, 2026, and the number of outstanding Penumbra equity awards currently estimated to be payable in Boston Scientific Shares at the Closing, Boston Scientific will issue approximately 43,866,267 Boston Scientific Shares. The issuance of these new Boston Scientific Shares will cause dilution to current Boston Scientific Stockholders and could have the effect of depressing the market price of Boston Scientific Shares.

Boston Scientific has not historically paid cash dividends on Boston Scientific Shares and currently does not intend to pay cash dividends on Boston Scientific Shares. As a result, you may only receive a return on your investment in Boston Scientific Shares if the trading price of your Boston Scientific Shares increases.

Provisions of Delaware law and of the Boston Scientific Charter and the Boston Scientific By-Laws could make it more difficult for a third party to acquire control of Boston Scientific or have the effect of discouraging a third party from attempting to acquire control of Boston Scientific. For example, Boston Scientific is subject to Section 203 of the DGCL, which would make it more difficult for another party to acquire Boston Scientific without the approval of the Boston Scientific Board. For additional information concerning these provisions, see “Description of Boston Scientific’s Capital Stock.”

In addition to the risks described above, Boston Scientific and Penumbra are, and will continue to be, subject to the risks described in Boston Scientific’s Annual Report on Form 10-K for the fiscal year ended December 31, 2025 and Penumbra’s Annual Report on Form 10-K for the fiscal year ended December 31, 2025, as may be updated by subsequent Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, all of which are filed with the SEC and incorporated by reference into this proxy statement/prospectus. See the section titled “Where You Can Find More Information” for the location of information incorporated by reference into this proxy statement/prospectus.

This section contains information for Penumbra Stockholders about the Special Meeting that Penumbra has called for Penumbra Stockholders to consider and vote on the Merger Proposal and other related matters. This proxy statement/prospectus is accompanied by a notice of the Special Meeting, and a form of proxy card that the Penumbra Board is soliciting for use by Penumbra Stockholders at the Special Meeting and at any adjournments or postponements of the Special Meeting.

The Special Meeting will be held on May 6, 2026, at 10:00 a.m. Pacific Time in building 1310 on Penumbra’s campus at One Penumbra Place, Alameda, CA 94502. You may contact Penumbra Investor Relations at investors@penumbrainc.com to obtain directions to the Special Meeting. The Special Meeting will be held solely in person and there will not be a live webcast.

Each Penumbra Stockholder who attends the Special Meeting may be asked to present valid photo identification, such as a driver’s license or passport. Penumbra Stockholders holding stock in brokerage accounts or by a bank or other nominee may be required to show a brokerage statement or account statement reflecting stock ownership as of the Record Date. Cameras, recording devices, and other electronic devices will not be permitted at the Special Meeting.

Only Penumbra Stockholders of record as of the close of business on the Record Date are entitled to receive notice of, to attend and to vote at, the Special Meeting or any adjournment or postponement thereof. Please note, however, that if your Penumbra Shares are held in the name of a bank, broker, trustee or other nominee and you wish to vote at the Special Meeting, you must obtain a proxy issued in your name from the Penumbra Stockholder of record in order to be entitled to vote in person at the Special Meeting.

At the Special Meeting, Penumbra Stockholders will be asked to consider and vote on the following proposals:

The Penumbra Board recommends that you vote “FOR” the Merger Proposal and “FOR” the Advisory Compensation Proposal and “FOR”the Adjournment Proposal. See “The Merger Agreement — The Penumbra Board’s Recommendation; Penumbra Adverse Recommendation Change” beginning on page 95 for a more detailed discussion of the Penumbra Board’s recommendation.

The Penumbra Board has fixed the close of business on March 26, 2026 as the Record Date for determination of Penumbra Stockholders entitled to notice of and to vote at the Special Meeting. As of the Record Date, there were 39,324,084 Penumbra Shares outstanding.

Holders of a majority of the total number of issued Penumbra Shares as of the Record Date and entitled to vote at the Special Meeting must be present or represented by proxy at the Special Meeting to constitute a quorum for the transaction of business at the Special Meeting. If you fail to submit a proxy or to vote at the Special Meeting, or fail to instruct your bank, broker, trustee or other nominee how to vote, your Penumbra Shares will not be counted towards a quorum. Marks to “ABSTAIN” on any proposal are considered present for purposes of establishing a quorum.

In the event that a quorum is not present at the Special Meeting, it is expected that the Special Meeting will be adjourned or postponed. If the Special Meeting is postponed or adjourned, it will not affect the ability of holders of record of Penumbra Shares as of the Record Date to exercise their voting rights or to revoke any previously granted proxy using the methods described below; however, if a new Record Date is set for an adjourned meeting, a new quorum will be required to be established.

At the Special Meeting, each Penumbra Share is entitled to one vote on all matters properly submitted to Penumbra Stockholders.

As of the Record Date, Penumbra’s directors and executive officers and their affiliates owned and were entitled to vote approximately 1,139,118 Penumbra Shares, representing approximately 2.9% of the outstanding Penumbra Shares. We currently expect that Penumbra’s directors and executive officers will vote their shares in favor of the Merger Proposal and the other proposals to be considered at the Special Meeting, although none of them has entered into any agreements obligating them to do so.

A broker non-vote occurs when a bank, broker, trustee or other nominee is not permitted to vote on a “non-routine” matter without instructions from the beneficial owner of the shares and the beneficial owner fails to provide the bank, broker, trustee or other nominee with such instructions. Broker non-votes only count toward a quorum if at least one proposal is presented with respect to which the bank, broker, trustee or other nominee has discretionary authority. All proposals to be voted on at the Special Meeting will be “non- routine” matters, and, as such, broker non-votes, if any, will not be counted as present and entitled to vote for purposes of determining a quorum at the Special Meeting. If your bank, broker, trustee or other nominee holds your Penumbra Shares in “street name,” such entity will vote your Penumbra Shares only if you provide instructions on how to vote by complying with the voter instruction form sent to you by your bank, broker, trustee or other nominee with this proxy statement/prospectus.

The Special Meeting will be held on May 6, 2026, at 10:00 a.m. Pacific Time in building 1310 on Penumbra’s campus at One Penumbra Place, Alameda, CA 94502, where Penumbra Stockholders will be able to attend the Special Meeting, submit questions and vote in person. The Special Meeting will be held solely in person and there will not be a live webcast. You may contact Penumbra Investor Relations at investors@penumbrainc.com to obtain directions to the Special Meeting.

You are entitled to attend the Special Meeting only if you were a Penumbra Stockholder of record as of the close of business on the Record Date, or you held your Penumbra Shares beneficially in the name of a bank, broker, trustee or other nominee as of the Record Date, or you hold a valid proxy for the Special Meeting. Each Penumbra Stockholder may be asked to present valid photo identification, such as a driver’s license or passport. Penumbra Stockholders holding stock in brokerage accounts or by a bank or other nominee may be required to show a brokerage statement or account statement reflecting stock ownership as of the Record Date. Cameras, recording devices, and other electronic devices will not be permitted at the Special Meeting.

You may ask questions during the Special Meeting if you attend in person. To ensure the Special Meeting is conducted in a manner that is fair to all Penumbra Stockholders, Penumbra may exercise discretion in determining the order in which questions are answered and the amount of time devoted to any one question. Penumbra reserves the right to edit or reject questions it deems inappropriate or not relevant to the Special Meeting’s limited purpose. Pursuant to the Penumbra Bylaws, the chairperson of the Penumbra Board will have the right and authority to prescribe such rules and regulations for the conduct of the Special Meeting.

A Penumbra Stockholder may vote by proxy or at the Special Meeting in person. If you hold your Penumbra Shares in your name as a holder of record, to submit a proxy, you, as a Penumbra Stockholder, may use one of the following methods:

If you intend to submit your proxy by telephone or via the internet, you must do so by 11:59 p.m. Eastern Time on the day before the Special Meeting. If you intend to submit your proxy by mail, your completed proxy card must be received prior to the Special Meeting.

Penumbra requests that Penumbra Stockholders vote by telephone, over the internet or by completing and signing the accompanying proxy card and returning it to Penumbra as soon as possible in the enclosed postage-paid envelope. When the accompanying proxy card is returned properly executed, the Penumbra Shares represented by it will be voted at the Special Meeting in accordance with the instructions contained on the proxy card. If you make no specification on your proxy card as to how you want your shares voted before signing and returning it, your proxy will be voted “FOR” the Merger Proposal, “FOR” the Advisory Compensation Proposal and “FOR” the Adjournment Proposal.

If a holder’s Penumbra Shares are held in “street name” by a bank, broker, trustee or other nominee, the holder should check the voting form used by that firm to determine whether the holder may vote by telephone or the internet.

If your Penumbra Shares are held in “street name” through a bank, broker, trustee or other nominee, you must instruct the bank, broker, trustee or other nominee on how to vote your Penumbra Shares. Your bank, broker, trustee or other nominee will vote your Penumbra Shares only if you provide specific instructions on how to vote by following the instructions provided to you by your bank, broker, trustee or other nominee. To vote in person at the Special Meeting, you must obtain a valid proxy from your bank, broker, trustee or other nominee.

You may not vote Penumbra Shares held in a brokerage or other account in “street name” by returning a proxy card directly to Penumbra.

Further, banks, brokers, trustees or other nominees who hold Penumbra Shares on behalf of their customers may not give a proxy to Penumbra to vote those Penumbra Shares with respect to any non- routine matters without specific instructions from you, as banks, brokers, trustees and other nominees do not have discretionary voting power on any non-routine matters that will be voted upon at the Special Meeting, including the Merger Proposal, the Advisory Compensation Proposal and the Adjournment Proposal.

If you are a holder of record of Penumbra Shares, you may revoke your proxy at any time before it is voted by:

If you hold your Penumbra Shares through a bank, broker, trustee or other nominee, you may change your vote by:

A revocation or later-dated proxy received by Penumbra after the vote will not affect the vote. If the Special Meeting is postponed or adjourned, it will not affect the ability of Penumbra Stockholders of record as of the Record Date to exercise their voting rights or to revoke any previously granted proxy using the methods described above; however, if a new Record Date is set for an adjourned meeting, a new quorum will be required to be established.

As permitted by applicable law, only one copy of this proxy statement/prospectus is being delivered to Penumbra Stockholders residing at the same address, unless such Penumbra Stockholders have notified Penumbra of their desire to receive multiple copies of the proxy statement/prospectus.

Penumbra will promptly deliver, upon oral or written request, a separate copy of the proxy statement/ prospectus to any Penumbra Stockholder residing at an address to which only one copy of such document was mailed. Requests for additional copies should be directed to Penumbra’s Investor Relations at (925) 826-7933 or Innisfree, Penumbra’s proxy solicitor, at:

To assist in the solicitation of proxies, Penumbra has retained Innisfree M&A Incorporated, for a fee of $50,000 plus a success fee of $25,000 upon approval of the Merger Proposal and reimbursement of out-of-pocket expenses for its services. Penumbra may also request banks, brokers, trustees and other intermediaries holding Penumbra Shares beneficially owned by others to send this proxy statement/ prospectus to, and obtain proxies from, the beneficial owners and may reimburse such record holders for their reasonable out-of-pocket expenses in so doing. Solicitation of proxies by mail may be supplemented by telephone and other electronic means, advertisements and personal solicitation by the directors, officers or employees of Penumbra. No additional compensation will be paid to Penumbra’s directors, officers or employees for solicitation.

If you need assistance in completing your proxy card, have questions regarding the Special Meeting or would like additional copies of this proxy statement/prospectus, please contact Penumbra’s Investor Relations at (925) 826-7933 or Innisfree, Penumbra’s proxy solicitor, at:

Penumbra is asking Penumbra Stockholders to approve and adopt the Merger Agreement and the Transactions, including the Merger. Penumbra Stockholders should read this proxy statement/prospectus carefully and in its entirety, including the annexes, for more detailed information concerning the Merger Agreement and the Merger. A copy of the Merger Agreement is attached to this proxy statement/prospectus as Annex A.

After careful consideration, the Penumbra Board unanimously determined that the Merger and the other Transactions to be consummated by Penumbra are advisable to, fair to, and in the best interests of, Penumbra and the Penumbra Stockholders, unanimously approved the Merger Agreement and resolved that the adoption of the Merger Agreement be recommended to the stockholders of Penumbra. See “The Merger Agreement — The Penumbra Board’s Recommendation; Penumbra Adverse Recommendation Change” beginning on page 95 of this proxy statement/prospectus for a more detailed discussion of the Penumbra Board’s recommendation.

Penumbra is providing Penumbra Stockholders with the opportunity to cast a vote, on an advisory (non-binding) basis, to approve the compensation payments that may be paid or become payable by Penumbra to its named executive officers, as determined in accordance with Item 402(t) of Regulation S-K, in connection with the merger as disclosed in the section titled “The Merger — Interests of Penumbra’s Directors and Executive Officers in the Merger — Quantification of Potential Payments and Benefits to Penumbra’s Named Executive,” including the table titled “Golden Parachute Compensation” and the accompanying footnotes, and the related narrative disclosure (referred to as the “golden parachute” compensation), as required by Section 14A of the Exchange Act.

Through this proposal, Penumbra is asking Penumbra Stockholders to indicate their approval, on an advisory (non-binding) basis, of the compensation that Penumbra’s named executive officers will or may be eligible to receive in connection with the merger as described in the sections of this proxy statement/ prospectus referred to above.

You should carefully review the golden parachute compensation information disclosed in the sections of this proxy statement/prospectus referred to above. The Penumbra Board unanimously recommends that Penumbra Stockholders approve the following resolution:

“RESOLVED, that the stockholders of Penumbra approve, solely on an advisory, non-binding basis, the golden parachute compensation that will or may be paid or become payable to Penumbra’s named executive officers in connection with the merger, as disclosed pursuant to Item 402(t) of Regulation S-K in the section titled “The Merger — Interests of Penumbra’s Directors and Executive Officers in the Merger — Quantification of Potential Payments and Benefits to Penumbra’s Named Executive Officers,” including the table titled “Golden Parachute Compensation” and the accompanying footnotes, and the related narrative disclosure.”

The vote on the Advisory Compensation Proposal is a vote separate and apart from the vote on the Merger Proposal and the Adjournment Proposal. Accordingly, you may vote to approve the Merger Proposal and/or the Adjournment Proposal and vote not to approve the Advisory Compensation Proposal, and vice versa. The approval of the Advisory Compensation Proposal by Penumbra Stockholders is not a condition to the completion of the Merger. Because the vote on the Advisory Compensation Proposal is advisory only, it will not be binding on either Penumbra or Boston Scientific. Accordingly, if the Merger Proposal is approved and the Merger is completed, the merger-related compensation may be paid to Penumbra’s named executive officers to the extent payable in accordance with the terms of the applicable employment agreements and other compensation agreements and arrangements even if Penumbra Stockholders fail to approve the advisory vote regarding the Advisory Compensation Proposal.

The Advisory Compensation Proposal requires the affirmative vote of the holders of a majority of the votes cast by the Penumbra Stockholders present or represented by proxy and entitled to vote at the Special Meeting. Failures to vote, broker non-votes and abstentions will have no effect on the vote for this proposal (assuming a quorum is present).

The Special Meeting may be adjourned or postponed to another time or place, if necessary or appropriate, to solicit additional proxies if there are insufficient votes at the time of the Special Meeting to approve the Merger Proposal or to ensure that any supplement or amendment to this proxy statement/ prospectus is timely provided to Penumbra Stockholders.

If, at the Special Meeting, the number of Penumbra Shares present or represented and voting in favor of the Merger Proposal is insufficient to approve the Merger Proposal, Penumbra intends to move to adjourn or postpone the Special Meeting in order to enable the Penumbra Board to solicit additional proxies for approval of the Merger Proposal. In that event, Penumbra will ask Penumbra Stockholders to vote on the Adjournment Proposal, but not the Merger Proposal or the Advisory Compensation Proposal.

In this proposal, Penumbra is asking Penumbra Stockholders to authorize the holder of any proxy solicited by the Penumbra Board on a discretionary basis to vote in favor of adjourning the Special Meeting to another time and place for the purpose of soliciting additional proxies, including the solicitation of proxies from Penumbra Stockholders who have previously voted. Pursuant to the DGCL, the Special Meeting may be adjourned without new notice being given, so long as the new date, time and place of the reconvened Special Meeting are announced at the Special Meeting at which the adjournment is taken, and any business may be transacted at the reconvened Special Meeting that might have been transacted on the original date of the Special Meeting. Pursuant to the DGCL, if, however, the adjournment is for more than thirty days, or if after the adjournment a new record date is fixed for the adjourned meeting, a notice of the adjourned meeting must be given to each stockholder of record entitled to vote at the meeting. The approval of the adjournment proposal by Penumbra Stockholders is not a condition to completion of the Merger; however, pursuant to the Merger Agreement, Penumbra may not adjourn the Special Meeting without the prior written consent of Boston Scientific and the Special Meeting may not be adjourned to a date later than the fifth business say preceding the Outside Date or for more than twenty business days in the aggregate from the originally scheduled date of the Special Meeting.

Penumbra, Inc. is a Delaware corporation headquartered in Alameda, California. Penumbra, the world’s leading thrombectomy company, is focused on developing the most innovative technologies for challenging medical conditions such as ischemic stroke, venous thromboembolism such as pulmonary embolism, and acute limb ischemia. Its broad portfolio, which includes computer assisted vacuum thrombectomy (CAVT), centers on removing blood clots from head to toe with speed, safety and simplicity. By pioneering these innovations, it supports healthcare providers, hospitals and clinics in more than 100 countries, working to improve patient outcomes and quality of life. As of December 31, 2025, Penumbra had, on a consolidated basis, approximately $1.827 billion in total assets, total stockholders’ equity of approximately $1.428 billion and 39,229,670 issued and outstanding Penumbra Shares.

Penumbra’s principal executive offices are located at One Penumbra Place, Alameda, California 94502, and its telephone number at that address is (510) 748-3200. Penumbra’s website is www.penumbrainc.com. Information contained on Penumbra’s website or that can be accessed through its website is not incorporated into and does not constitute a part of this proxy statement/prospectus. Penumbra has included its website address only as an inactive textual reference and does not intend it to be an active link to its website.

Penumbra Shares are listed on the NYSE under the symbol “PEN.”

Boston Scientific Corporation is a Delaware corporation headquartered in Marlborough, Massachusetts. Boston Scientific transforms lives through innovative medical technologies that improve the health of patients around the world. As a global medical technology leader for more than 45 years, it advances science for life by providing a broad range of high-performance solutions that address unmet patient needs and reduce the cost of healthcare. Its portfolio of devices and therapies helps physicians diagnose and treat complex cardiovascular, respiratory, digestive, oncological, neurological and urological diseases and conditions.

Boston Scientific’s principal executive offices are located at 300 Boston Scientific Way, Marlborough, Massachusetts 01752-1234, and its telephone number at that address is (508) 683-4000. Boston Scientific’s website is www.bostonscientific.com. Information contained on Boston Scientific’s website or that can be accessed through its website is not incorporated into and does not constitute a part of this proxy statement/ prospectus. Boston Scientific has included its website address only as an inactive textual reference and does not intend it to be an active link to its website.

Boston Scientific Shares are listed on the NYSE under the symbol “BSX.”

Pinehurst Merger Sub, Inc., a wholly owned subsidiary of Boston Scientific, is a Delaware corporation incorporated on January 13, 2026, for the purpose of effecting the Merger. Merger Sub has not conducted any activities other than those incidental to its formation and the matters contemplated by the Merger Agreement. Merger Sub’s principal executive offices are located at 300 Boston Scientific Way, Marlborough, Massachusetts 01752-1234, and its telephone number at that address is (508) 683-4000.

Upon the terms and subject to the conditions of the Merger Agreement, Merger Sub will merge with and into Penumbra, with the separate corporate existence of Merger Sub thereupon ceasing and Penumbra continuing as the Surviving Corporation and a wholly owned subsidiary of Boston Scientific. As a result of the Merger, Penumbra Shares will no longer be publicly traded, and will be delisted from the NYSE. In addition, the Penumbra Shares will be deregistered under the Exchange Act, and Penumbra will no longer file periodic reports under the Exchange Act with the SEC. If the Merger is completed, you will not own any shares of the capital stock of the Surviving Corporation.

The Effective Time will occur upon the filing of a certificate of merger with the Secretary of State of the State of Delaware (or at such other date and time agreed upon by Penumbra and Boston Scientific and specified in the certificate of merger).

At the Effective Time, each Penumbra Share issued and outstanding immediately prior to the Effective Time (other than Excluded Shares) will, subject to the proration provisions of the Merger Agreement, be cancelled and will be converted automatically into the right to receive, at the election of the holder thereof in accordance with, and subject to the terms, conditions and procedures set forth in the Merger Agreement, the following consideration (collectively with, if applicable, cash in lieu of any fractional Boston Scientific Shares and any dividends or other distributions payable pursuant to the Merger Agreement), in each case, without interest:

The election right for Penumbra Stockholders will be subject to proration in accordance with the terms of the Merger Agreement and as more fully described in the section of this proxy statement/prospectus captioned “The Merger Agreement — Merger Consideration — Proration and Allocation of the Merger Consideration,” which is applicable in the event the Cash Consideration is undersubscribed or oversubscribed. The Merger Agreement provides that the total number of Penumbra Shares that will be entitled to receive the Cash Consideration pursuant to the preceding paragraph will be equal to 73.26% of the aggregate number of Penumbra Shares issued and outstanding immediately prior to the Effective Time (other than Excluded Shares), and the total number of Penumbra Shares that will be entitled to receive the Stock Consideration pursuant to the preceding paragraph will be equal to 26.74% of the aggregate number of Penumbra Shares issued and outstanding immediately prior to the Effective Time (other than Excluded Shares), in each case, rounded to the nearest whole number. In the event of proration, Penumbra Stockholders might receive a portion of their Merger Consideration in a form they did not elect. No fractional Boston Scientific Shares will be issued in the Merger, and Penumbra Stockholders will receive cash in lieu of any fractional Boston Scientific Shares to which they otherwise would have been entitled, in accordance with the terms and conditions of the Merger Agreement.

You may elect a different form of Merger Consideration for each Penumbra Share you own. You may elect to receive (i) solely the Cash Consideration for each Penumbra Share you own, (ii) solely the Stock Consideration for each Penumbra Share you own or (iii) if you own more than one Penumbra Share, a combination of the Cash Consideration for a selected number of Penumbra Shares you own and the Stock Consideration for the remaining number of Penumbra Shares you own. Whether you receive your elected form of Merger Consideration for each Penumbra Share you own will depend on the election(s) of other Penumbra Stockholders and the proration mechanism referenced in the immediately preceding paragraph. For example, if you elect to receive solely the Cash Consideration for each Penumbra Share you own or solely the Stock Consideration for each Penumbra Share you own, and all other Penumbra Stockholders make the same election, the Merger Consideration you receive will vary to the maximum extent possible compared to your original election. In such instance, you would receive the Cash Consideration for 73.26% of your Penumbra Shares and the Stock Consideration for 26.74% of your Penumbra Shares, in each case, rounding Penumbra Shares to the nearest whole number. The following examples illustrate the proration mechanism in the case of an oversubscription or an undersubscription of the Cash Consideration (both if you elect solely the oversubscribed form of Merger Consideration for each Penumbra Share you own and if you elect a combination of the Cash Consideration and the Stock Consideration for your Penumbra Shares). Note that for illustrative purposes, the following examples (i) assume a total of 39,229,670 Penumbra Shares issued and outstanding as of January 12, 2026, and (ii) do not round Penumbra Shares to the nearest whole number.

At the announcement of the Transactions, the parties valued the Merger Consideration at $374.00 per Penumbra Share based on the ability of a Penumbra Stockholder to elect either $374.00 in cash per Penumbra Share or 3.8721 Boston Scientific Shares per Penumbra Share (valued at $374.00 per Penumbra Share based on the volume weighted average price of $96.59 per Boston Scientific Share over the last 10 trading days ending on and including January 13, 2026, two trading days before the public announcement of the Transactions), subject to proration. Although the Cash Consideration is fixed at $374.00 in cash per Penumbra Share, the value of the Stock Consideration will fluctuate with the market price of Boston Scientific Shares, and the values of the Cash Consideration and the Stock Consideration at the completion of the Merger may not be the same. Accordingly, the value of the Stock Consideration at the time of completion of the Merger could be greater than, less than or the same as the value of the Cash Consideration. On March 27, 2026, the latest practicable date prior to the date of this proxy statement/prospectus, the value of the Stock Consideration was $267.83 per Penumbra Share, based on the closing trading price of Boston Scientific Shares on such date as reported on the NYSE. We urge you to obtain current market quotations of Boston Scientific Shares (trading symbol “BSX”) prior to making your Cash Election or Stock Election.

Based on the number of Penumbra Shares outstanding as of March 27, 2026, the last practicable trading day before the date of this proxy statement/prospectus, Boston Scientific is expected to issue approximately 43,866,267

Boston Scientific Shares in the aggregate in the Merger, with former Penumbra Stockholders owning, in the aggregate, approximately 2.87% of the Boston Scientific Shares immediately following the Merger (without giving effect to any Boston Scientific Shares held by Penumbra Stockholders prior to the Merger).

For more information, please see the section of this proxy statement/prospectus captioned “The Merger Agreement — Merger Consideration.”

Penumbra Stockholders may elect to receive (i) solely the Cash Consideration, (ii) solely the Stock Consideration or (iii) if the Penumbra Stockholder owns more than one share, a combination of the Cash Consideration for a selected number of shares and the Stock Consideration for the remaining number of shares. The election will be subject to the election of other Penumbra Stockholders and the proration mechanism described in the section titled “The Merger Agreement — Merger Consideration — Proration and Allocation of the Merger Consideration.”

An Election Form, including a letter of transmittal and related instructions, will initially be mailed not less than twenty business days prior to the anticipated Election Deadline (or on such other date as Boston Scientific and Penumbra shall mutually agree) to each Penumbra Stockholder as of the close of business on the Election Form Record Date. The Election Form will allow Penumbra Stockholders to specify: (i) the number of such Penumbra Stockholder’s Penumbra Shares with respect to which to make a Cash Election; and (ii) the number of such Penumbra Stockholder’s Penumbra Shares with respect to which to make a Stock Election. Any Penumbra Shares (other than Excluded Shares) with respect to which the Exchange Agent has not received an effective, properly completed Election Form on or before the Election Deadline will be deemed to be Non-Election Shares. Penumbra and Boston Scientific will issue a press release announcing the date of the Election Deadline at least five business days prior to the Election Deadline. If the Closing Date is delayed to a subsequent date, the Election Deadline will be similarly delayed to a subsequent date, and Penumbra and Boston Scientific will promptly announce any such delay and, when determined, the rescheduled Election Deadline.

Penumbra Stockholders wishing to make an election must properly complete and deliver to the Exchange Agent an Election Form by the Election Deadline, accompanied by duly executed transmittal materials included in the Election Form, along with, if their Penumbra Shares are not Book-Entry Shares, any Certificates. The Election Form will also include delivery instructions with respect to Book-Entry Shares. The Election Form will be provided to Penumbra Stockholders in a separate mailing and is not being provided with this proxy statement/prospectus.

Further, any election shall have been effective only if the Exchange Agent shall have actually received a properly completed Election Form (including any required letter of transmittal, any Certificates and any other documents required by the Election Form), by the Election Deadline. If any election is not properly made with respect to any Penumbra Shares, such election shall be deemed to be not in effect, and the Penumbra Shares covered by such election will be deemed to be Non-Election Shares, unless a proper election is thereafter timely made.

Penumbra Stockholders who do not make an election will be treated as having elected to receive Cash Consideration or Stock Consideration in accordance with the proration methodology in the Merger Agreement, which is described in the section titled “The Merger Agreement — Merger Consideration — Proration and Allocation of the Merger Consideration.”

The Merger Agreement provides that, at the Effective Time, subject to all applicable federal, state and local tax withholding requirements:

Subject to the consummation of the Merger, the Penumbra ESPP will terminate effective immediately prior to the Effective Time. The Penumbra ESPP will be frozen and suspended at the end of the “offering period” in progress as of January 15, 2026, and following January 15, 2026, until the Effective Time, no new offering periods will be commenced under the Penumbra ESPP, no new participants will be permitted to commence participation in the Penumbra ESPP, and no current participants will be permitted to effectuate changes to their elections or contributions to the Penumbra ESPP.

See “The Merger Agreement” beginning on page 79 of this proxy statement/prospectus for additional and more detailed information regarding the legal documents that govern the Merger, including the conditions to completion of the Merger and the provisions for terminating or amending the Merger Agreement.

The following is a summary of events, meetings and discussions that are relevant to the decision of the Penumbra Board to approve the Merger Agreement and recommend that the Penumbra Stockholders adopt the Merger Agreement.

From time to time, Penumbra’s executives speak with executives of other medical technology companies regarding their respective businesses and industry developments. For example, Adam Elsesser, Penumbra’s Chairman and Chief Executive Officer, and Michael F. Mahoney, Boston Scientific’s Chairman and Chief Executive Officer, attended a dinner along with other industry leaders on January 14, 2025, in connection with the J.P. Morgan Healthcare Conference, during which they discussed industry dynamics and their respective backgrounds and businesses. At such time, there was no discussion of any potential transaction between Boston Scientific and Penumbra. On January 14, 2025, Penumbra’s stock closed at $252.89 per Penumbra Share.

In late October 2025, Penumbra presented landmark STORM-PE trial data at the Transcatheter Cardiovascular Therapeutics Conference. On October 28, 2025, while attending the conference, Mr. Elsesser and Dr. Arani Bose, Penumbra’s co-founder and a member of the Penumbra Board, had an informal, unscheduled discussion with Joseph M. Fitzgerald, Boston Scientific’s Executive Vice President and Group President, Cardiovascular. During such conversation, they discussed the trajectory of both respective businesses, and Mr. Fitzgerald expressed his opinion that Penumbra could be an ideal strategic fit for Boston Scientific, but at such time, there was no discussion of any potential transaction between Boston Scientific and Penumbra. On October 28, 2025, Penumbra’s stock closed at $235.50 per Penumbra Share.

In addition, in late October 2025, a fellow industry executive made a personal introductory connection between Mr. Elsesser and the Chief Executive Officer of Company A, a large publicly-traded healthcare company in the medical technology industry. This introduction led to a call between Mr. Elsesser and Company A’s CEO, on

November 11, 2025. During the call, they discussed their respective backgrounds, as well as dynamics and recent activity in their respective businesses and across the broader industry, and Company A’s CEO also shared the general business priorities of Company A. Company A’s CEO did not make a proposal during the call nor did he suggest that Company A would be making a proposal to Penumbra with respect to any transaction in the future, and Mr. Elsesser interpreted this discussion to mean Company A was not interested in pursuing an acquisition of Penumbra in the near-term. Since this call, neither the Chief Executive Officer nor any other representative of Company A has contacted Mr. Elsesser to request a follow-up discussion, nor has Company A made a proposal to Penumbra with respect to any transaction.

On December 8, 2025, a senior business development executive of Boston Scientific had a phone conversation with a representative of PWP, whom Boston Scientific was aware had a historical relationship with Penumbra senior management, about the industry landscape and Penumbra’s business momentum, including the recent release of STORM-PE data, and the late October discussion between Mr. Fitzgerald and Mr. Elsesser. During such conversation, the representative of PWP and the executive of Boston Scientific discussed the possibility of arranging a conversation between Messrs. Mahoney and Elsesser as a follow up to the conversation between Messrs. Elsesser and Fitzgerald.

On December 10, 2025, Messrs. Mahoney and Elsesser scheduled a dinner meeting in Boston, Massachusetts for December 15, 2025.

On December 15, 2025, Messrs. Mahoney and Elsesser met for their scheduled dinner in Boston, where Mr. Elsesser discussed Penumbra’s history, including the evolution of Penumbra’s vascular business and potential new opportunities in its neuro business. Mr. Mahoney discussed the evolution of Boston Scientific’s business over the course of his thirteen years as its CEO, and expressed an interest in Boston Scientific exploring a potential acquisition of Penumbra, noting that Boston Scientific would need to better understand Penumbra’s product portfolio and financial outlook before proceeding with any such transaction. Mr. Elsesser expressed that the Penumbra Board could potentially be open to a strategic transaction with Boston Scientific, but that in considering such a strategic transaction, he would expect the Penumbra Board to prioritize value, transaction certainty and the preservation of Penumbra’s culture of innovation. Mr. Mahoney indicated that any transaction would likely involve a mix of cash consideration and stock consideration in order to drive alignment and shared long-term value creation. Messrs. Mahoney and Elsesser then agreed that, subject to the parties first entering into a mutually acceptable mutual nondisclosure agreement and, in the case of Mr. Elsesser, discussions with the Penumbra Board, executives of Boston Scientific would meet with executives of Penumbra to discuss Penumbra’s business and financial results so that Boston Scientific could consider whether to submit a preliminary non-binding proposal to acquire Penumbra on a more-informed basis for consideration by the Penumbra Board.

On December 16, 2025, Messrs. Mahoney and Elsesser, as a follow up to the matters discussed at their dinner the previous evening, discussed next steps, including the need to negotiate and execute a mutual nondisclosure agreement and arrange for the time of and likely participants in a Penumbra management presentation on December 22, 2025.

From December 17, 2025 to December 19, 2025, Penumbra and Boston Scientific negotiated the terms of a mutual nondisclosure agreement, and on December 19, 2025, the parties entered into a mutual nondisclosure agreement, which included a customary, mutual standstill provision, which standstill would not prevent Boston Scientific from making a private proposal to the Penumbra Board and would terminate upon Penumbra’s entry into a definitive acquisition agreement for an alternative transaction and the occurrence of certain other customary events. Thereafter, until the execution of the Merger Agreement the parties engaged in due diligence with respect to both Penumbra and Boston Scientific.

On December 19, 2025, at a meeting of the Penumbra Board, Mr. Elsesser provided the Penumbra Board with a summary of his and Penumbra’s recent communications with Boston Scientific, noting that, if the Penumbra Board was in favor of exploring the potential transaction, Penumbra executives would provide Boston Scientific with a management presentation on December 22, 2025. Mr. Elsesser provided the Penumbra Board with a high-level overview of potential considerations for a possible transaction that he had discussed with Mr. Mahoney at their dinner meeting, and the Penumbra Board discussed with Mr. Elsesser potential benefits to Penumbra and the Penumbra Stockholders of a strategic transaction with Boston Scientific. The Penumbra Board then authorized Penumbra’s management to continue discussions with Boston Scientific relating to a potential transaction.

Later on December 19, 2025, Mr. Elsesser confirmed with a senior business development executive of Boston Scientific the agenda for the management presentation scheduled for December 22, 2025.

On December 22, 2025, Mr. Elsesser provided a management presentation by videoconference to Mr. Mahoney, Mr. Fitzgerald, and certain other executives of Boston Scientific, including a description of Penumbra’s product portfolio, business dynamics, and medium-term financial outlook for the business through fiscal year 2028 (the “Medium-Term Outlook”). Johanna Roberts, Penumbra’s Executive Vice President and General Counsel, and a representative of PWP were also present.

The next day, at the request of Boston Scientific, a follow-up management session on certain key topics requested by Boston Scientific was held by videoconference between Mr. Elsesser and executives of Boston Scientific, with a representative of PWP also present.

On December 24, 2025, Mr. Mahoney communicated with Mr. Elsesser that he expected to provide feedback to Penumbra early the following week.

On December 29, 2025, at the request of Mr. Mahoney, Messrs. Mahoney and Elsesser met via conference call, at which time Mr. Mahoney stated to Mr. Elsesser that Boston Scientific intended to submit a written preliminary non-binding proposal to Penumbra, and summarized the terms that would be included in the proposal. Mr. Mahoney further noted key areas of further diligence, including a review of potential synergies, and Messrs. Mahoney and Elsesser discussed potential timing for a potential transaction.

Later on December 29, 2025, Boston Scientific delivered a written preliminary non-binding proposal for an acquisition of Penumbra at a value of $365 per Penumbra Share, comprised of $274 per Penumbra Share in cash consideration and a fixed number of Boston Scientific Shares having a value at the time of signing of a definitive agreement equal to $91, based on a fixed exchange ratio over a specified measurement period. The letter also stated that Boston Scientific’s proposal would not be subject to approval of Boston Scientific Stockholders or any financing contingency, and that Boston Scientific was prepared to (i) pay a reverse termination fee equal to 5% of the aggregate equity value payable in the transaction in the event the parties are unable to obtain regulatory clearances for the proposed transaction on or prior to the date that is twenty-four months following execution of a definitive transaction agreement, (ii) commit to litigate in the event the transaction is challenged by regulatory authorities and (iii) if necessary, divest assets that generated revenue of up to $250 million in fiscal year 2025. On December 29, 2025, Penumbra’s stock closed at $314.89 per Penumbra Share.

On December 30, 2025, the Penumbra Board held a meeting, with members of Penumbra’s senior management and, at the invitation of the Penumbra Board, representatives of PWP and Davis Polk & Wardwell LLP (“Davis Polk”), Penumbra’s outside counsel, in attendance. Mr. Elsesser reviewed with the Penumbra Board the recent discussions with representatives of Boston Scientific, and discussed with the Penumbra Board the terms of the written preliminary non-binding proposal submitted by Boston Scientific on December 29, 2025. Representatives of Davis Polk reviewed with the Penumbra Board its fiduciary duties in considering a strategic business combination transaction, as well as other legal considerations in considering a strategic transaction, including the regulatory process that would be required before a business combination could be completed. At the request of the Penumbra Board, representatives of PWP provided a preliminary illustrative financial analysis of an acquisition transaction involving Penumbra. The Penumbra Board then discussed, together with its advisors, the likelihood of either a financial sponsor or another strategic buyer being able and willing to make a proposal that would be competitive with that submitted by Boston Scientific. Following discussion, it was the Penumbra Board’s judgment that the terms of Boston Scientific’s proposal were not sufficiently attractive for the Penumbra Board to transact, and that Boston Scientific would need to improve its purchase price per Penumbra Share and the contractual commitments it would be willing to make to obtain the regulatory clearances that would be required to complete the transaction. The Penumbra Board also determined that because Boston Scientific Shares were an attractive form of consideration, Penumbra should request that the price be paid half in cash and half in Boston Scientific Shares. The Penumbra Board then authorized Penumbra’s management and PWP to continue discussions with Boston Scientific with a view towards improving Boston Scientific’s proposal while the Penumbra Board continued to evaluate its strategic alternatives, including the alternative of remaining an independent company. The Penumbra Board also concluded that, at least for the time being, the risks of soliciting additional bids, including the risk of further management distraction and of leaks in a sector with a history of leaks, outweighed the reasonable potential benefits.

On December 30, 2025, Mr. Elsesser contacted Mr. Mahoney and conveyed to Mr. Mahoney the Penumbra Board’s feedback on Boston Scientific’s written preliminary non-binding proposal. Mr. Mahoney indicated to Mr. Elsesser that he and his team would consider Penumbra’s feedback.

On December 31, 2025, at Mr. Mahoney’s request, Messrs. Mahoney and Elsesser met via conference call, at which meeting Mr. Mahoney indicated to Mr. Elsesser that Boston Scientific would be submitting a revised, written preliminary non-binding proposal for an acquisition of Penumbra, and summarized the terms that would be included in the revised proposal. Messrs. Mahoney and Elsesser also discussed timing considerations and the mutual due diligence reviews that would need to be completed before any definitive transaction agreement could be signed.

Later on December 31, 2025, Boston Scientific delivered a revised, written preliminary non-binding proposal proposing an acquisition of Penumbra at a value of $370 per Penumbra Share, comprised of $270 per Penumbra Share in cash consideration and a fixed number of Boston Scientific Shares having a value at the time of signing of a definitive agreement equal to $100, based on a fixed exchange ratio over a specified measurement period. The letter also stated that Boston Scientific was prepared to (i) pay a reverse termination fee equal to $885 million (approximately 6% of the aggregate estimated equity value payable in the transaction) in the event the parties are unable to obtain regulatory clearances for the proposed transaction on or prior to the date that is twenty-four months following execution of a definitive transaction agreement, (ii) commit to litigate in the event the transaction is challenged by regulatory authorities and (iii) if necessary, divest assets that generated revenue of up to $300 million based on fiscal year 2025 numbers. The letter also revised Boston Scientific’s proposal to require a 21-day period whereby Penumbra would negotiate a strategic transaction exclusively with Boston Scientific, and to require that Penumbra would agree to pay Boston Scientific a termination fee equal to $553 million (approximately 3.75% of the aggregate estimated equity value payable in the transaction) if, following entry into a definitive transaction agreement, the Penumbra Board changes its recommendation in favor of the transaction or terminates the definitive transaction agreement with Boston Scientific to enter into an agreement with a third party in respect of a competing superior transaction. On December 31, 2025, Penumbra’s stock closed at $310.91 per Penumbra Share.

On January 2, 2026, the Penumbra Board held a meeting, with members of Penumbra’s senior management and, at the invitation of the Penumbra Board, representatives of PWP and Davis Polk also in attendance. Mr. Elsesser reviewed with the Penumbra Board management’s discussions with representatives of Boston Scientific, and discussed with the Penumbra Board the terms of the revised, written non-binding proposal submitted by Boston Scientific on December 31, 2025. At the request of the Penumbra Board, representatives of PWP provided a preliminary illustrative financial analysis of Boston Scientific’s revised $370 per Penumbra Share proposal, based on a preliminary version of Penumbra’s long-range plan. The Penumbra Board discussed, together with its advisors, the potential likelihood of a strategic transaction with an alternative counterparty and potentially seeking alternative proposals, including whether financial sponsors and/or other strategic buyers would be likely to make a superior proposal relative to Boston Scientific’s revised, written non-binding proposal at this time, as well as the increased likelihood of a potential leak that would result from contacting other potential parties, and the potential adverse impact on Boston Scientific’s proposal should a leak occur. Penumbra’s management then reviewed with the Penumbra Board a preliminary version of Penumbra’s long-range financial plan, noting that Penumbra’s management was continuing to verify certain expense assumptions. A representative of Davis Polk reviewed with the Penumbra Board its fiduciary duties in considering a strategic business combination transaction. Following discussion, the Penumbra Board authorized Penumbra’s management and PWP to continue discussions with Boston Scientific while the Penumbra Board continued to evaluate Penumbra’s strategic alternatives, with a view towards continuing to improve the terms of Boston Scientific’s proposal, including seeking to increase the price per Penumbra Share payable by Boston Scientific, reducing the termination fee that would be payable by Penumbra in certain circumstances and avoiding any requirement to exclusively negotiate with Boston Scientific to maintain flexibility if a competing proposal emerged. The Board also concluded that, in light of the attractiveness and strategic benefits of Boston Scientific’s revised proposal, the Penumbra Board’s assessment that it would be unlikely that any other acquirer would make an offer superior to Boston Scientific’s revised proposal at this time, and the heightened chance of a leak in the event other potential acquisition bids were solicited and the risks to Boston Scientific’s proposal if such a leak were to occur, it was in the best interests of Penumbra and its stockholders to not solicit other potential offers at this time.

Later on January 2, 2026, Messrs. Mahoney and Elsesser met via conference call, and Mr. Elsesser conveyed to Mr. Mahoney the Penumbra Board’s feedback on Boston Scientific’s revised proposal. Messrs. Mahoney and Elsesser also discussed the approach to their mutual due diligence reviews, including in respect of Penumbra’s employees, if the process were to continue. On January 2, 2026, Penumbra’s stock closed at $309.42.

On January 3, 2026, at Mr. Mahoney’s request, Messrs. Mahoney and Elsesser met again via conference call, at which point Mr. Mahoney indicated again, on a preliminary and non-binding basis, that Boston Scientific would be willing to revise its proposal to increase its purchase price to $374 per Penumbra Share, reduce the termination fee payable by Penumbra to approximately 3.5% of the aggregate purchase price payable in the transaction and remove its requirement for exclusivity, but that he would recommend to the Boston Scientific Board that this be Boston Scientific’s “best and final” proposal. Because the Penumbra Board viewed Boston Scientific Shares as an attractive form of consideration for Penumbra Stockholders, Messrs. Mahoney and Elsesser also discussed potentially allowing Penumbra Stockholders to elect the form of consideration to be received for their Penumbra Shares, subject to proration as the number of Boston Scientific Shares available as part of the aggregate consideration would be capped. In addition, Messrs. Mahoney and Elsesser also discussed that, if the Merger Agreement permitted Penumbra Stockholders to elect the form of their consideration in the Merger, Mr. Elsesser consider electing to receive the Merger Consideration with respect to his Penumbra Shares entirely in the form of Boston Scientific Shares, subject to proration, and Boston Scientific’s desire to disclose Mr. Elsesser’s intended election in the press release announcing the parties’ entry into the Merger Agreement, in order to highlight Mr. Elsesser’s commitment to and confidence in the merits of the proposed transaction. Mr. Mahoney also noted that Boston Scientific might propose that Mr. Elsesser join the Boston Scientific Board if the proposed transaction were to be completed.

On January 5, 2026, the Penumbra Board held a meeting, with members of Penumbra’s senior management and, at the invitation of the Penumbra Board, representatives of PWP and Davis Polk, in attendance. Mr. Elsesser provided the Penumbra Board with a summary of the status of negotiations between Penumbra and Boston Scientific, including the terms of the revised proposal conveyed to him orally by Mr. Mahoney on January 3, 2026. Following discussion, the Penumbra Board determined, in light of the attractiveness of the proposal, it was in the best interests of Penumbra Stockholders to seek expeditiously to sign definitive documentation for the proposed transaction. Mr. Elsesser also noted that he and Mr. Mahoney had discussed potentially allowing Penumbra Stockholders to elect the form of consideration to be received for their Penumbra Shares, subject to proration, and that, to evidence his commitment to and confidence in the merits of the proposed transaction if one were approved, that he elect to receive Boston Scientific Shares for all his Penumbra Shares, subject to proration. The Penumbra Board was supportive of both these proposals. Mr. Elsesser further noted that Mr. Mahoney had mentioned the possibility of Mr. Elsesser joining the Boston Scientific Board if the proposed transaction were completed, and expressed to the Penumbra Board his willingness to do so, should the Penumbra Board believe it was in the best interests of Penumbra and the Penumbra Stockholders. A representative of Davis Polk then reviewed with the Penumbra Board its fiduciary duties in considering the proposed transaction with Boston Scientific. As part of such discussion, Surbhi Sarna, a member of the Penumbra Board, noted for the other Penumbra Board members in connection with the Penumbra Board’s review and discussion of the proposed transaction certain prior employment and ongoing business relationships she had with Boston Scientific. Following discussion, including input from representatives of Davis Polk, the Penumbra Board determined that such relationships would not disqualify Ms. Sarna from participating in discussions regarding the proposed transaction. Penumbra management then discussed Penumbra’s long-range financial plan, noting that management was in the process of finalizing its projections and would submit the final projections through fiscal year 2035 to the Penumbra Board for approval to provide to PWP for use in its financial analysis of Penumbra and the proposed transaction with Boston Scientific. Following discussion, the Penumbra Board authorized management to continue to pursue the proposed transaction on the terms Mr. Elsesser discussed with Mr. Mahoney and that were presented at the meeting, and to provide Boston Scientific with access to due diligence information in furtherance of such a transaction. Also at this meeting, the Penumbra Board formally approved engaging PWP as Penumbra’s financial advisor and Davis Polk as Penumbra’s outside counsel with respect to a potential change in control transaction, as well as the terms of their respective engagements. The Penumbra Board selected PWP and Davis Polk due to their respective reputations and experience in the medical technology sector, their respective expertise and qualifications in transactions of this nature, and their respective deep familiarity with Penumbra and the industry in which it operates.

Later on January 5, 2026, Mr. Mahoney communicated to Mr. Elsesser that the Boston Scientific Board was supportive of the proposal Mr. Mahoney had discussed with Mr. Elsesser on January 3, 2026, and subsequently, Boston Scientific delivered a revised, written preliminary non-binding proposal that contained terms consistent with

the revised proposal orally conveyed by Mr. Mahoney to Mr. Elsesser on January 3, 2026, and discussed with the Penumbra Board, proposing an acquisition of Penumbra at a value of $374 per Penumbra Share, comprised of $274 per Penumbra Share in cash consideration and a fixed number of Boston Scientific Shares having a value at the time of signing of a definitive agreement equal to $100, based on a fixed exchange ratio over a specified measurement period. The proposal also reflected the inclusion of the previously discussed cash/stock election mechanisms. The letter also increased the absolute value Boston Scientific was prepared to pay as a reverse termination fee to $900 million (approximately 6% of the aggregate estimated equity value payable in the transaction) in the event the parties are unable to obtain regulatory clearances for the proposed transaction on or prior to the date that is twenty-four months following execution of a definitive transaction agreement, and reduced the termination fee that would be payable by Penumbra to $525 million (or approximately 3.5% of the total estimated equity value in the transaction) if the definitive transaction agreement were terminated by Boston Scientific following a change by the Penumbra Board of its recommendation in favor of the transaction with Boston Scientific or Penumbra were to terminate the definitive transaction agreement with Boston Scientific to enter into an agreement with a third party in respect of a competing superior transaction. Further, the revised proposal removed the requirement for exclusive negotiations that had been included in Boston Scientific’s December 31^st proposal.

Also on January 5, 2026, PWP sent to Boston Scientific a proposed “clean team” confidentiality agreement drafted by Davis Polk to govern the treatment of competitively sensitive due diligence information. The parties negotiated the terms of this agreement and executed it on January 6, 2026.

Also on January 5, 2026, Penumbra provided access to Boston Scientific and its advisors to an electronic data room containing Penumbra due diligence information. From January 7, 2026 through January 14, 2026, each of Boston Scientific and Penumbra and their respective advisors engaged in a series of due diligence and “reverse” due diligence discussions regarding aspects of each other’s businesses.

On January 7, 2026, representatives of Allen Overy Shearman Sterling US LLP (“A&O Shearman”), Boston Scientific’s outside counsel, delivered an initial draft of the Merger Agreement to Davis Polk. Thereafter, the parties negotiated the terms of the Merger Agreement and related documents.

On January 8, 2026, Penumbra’s management made immaterial updates to the forecasted results for 2026 included in the Medium-Term Outlook (the “2026 Forecast Updates”) that reflected further visibility into Penumbra’s results for the fourth quarter of 2025, but which were otherwise materially consistent with (and were made available to Boston Scientific as an update to) the Medium-Term Outlook that had previously been provided to Boston Scientific.

On January 9, 2026, representatives of Davis Polk and A&O Shearman met by conference call to discuss Penumbra’s preliminary feedback to Boston Scientific’s January 7, 2026 draft of the Merger Agreement.

Also on January 9, 2026, executives of Boston Scientific held a meeting via conference call with Mr. Elsesser to discuss employee matters relevant to the potential transaction. No discussions or commitments for post-closing employment or compensation with respect to members of Penumbra’s management were held or made by Boston Scientific at such time, and no Penumbra executive was presented with proposed terms regarding their post-closing employment with Boston Scientific or Penumbra, other than Boston Scientific’s expressed desire that Mr. Elsesser become a member of the Boston Scientific Board if the proposed transaction were to be completed.

On January 11, 2026, the Penumbra Board held a meeting, with members of Penumbra’s senior management and, at the invitation of the Penumbra Board, representatives of PWP and Davis Polk in attendance. Members of Penumbra management reviewed with the Penumbra Board management’s long- range financial plan through fiscal year 2035, which was materially consistent with the preliminary version discussed with the Penumbra Board in its January 2^nd and January 5^th meetings and reflected the 2026 Forecast Updates. Following discussion, the Penumbra Board approved management’s long-range financial plan, which was materially consistent with the Medium-Term Outlook that had been provided to Boston Scientific, for use in the strategic process and by PWP for purposes of its financial analysis of Penumbra and the proposed transaction with Boston Scientific, as more fully described in the section entitled “— Certain Financial Projections.” A representative of Davis Polk reviewed the Penumbra Board’s fiduciary duties in the context of considering a potential strategic acquisition transaction with Boston Scientific. The Penumbra Board then reviewed with Penumbra management and representatives of PWP the status of discussions with Boston Scientific and the extensive due diligence completed by Boston Scientific and “reverse” due diligence completed by Penumbra. Mr. Elsesser reiterated to the Penumbra Board that Boston Scientific had expressed a desire for him to join the Boston Scientific Board following the closing of the proposed transaction. Mr. Elsesser

reiterated to the Penumbra Board his willingness to do so, should the Penumbra Board believe it was in the best interests of Penumbra and the Penumbra Stockholders. Mr. Elsesser also reminded the Penumbra Board that Boston Scientific had requested that he consider electing to receive the Merger Consideration with respect to his Penumbra Shares entirely in the form of Boston Scientific Shares, subject to proration, which he said he would be willing to do if the Penumbra Board believed that was desirable. Following discussion, the Penumbra Board concluded that it would be in the best interests of Penumbra and the Penumbra Stockholders for Mr. Elsesser to join the Boston Scientific Board and to elect to receive the Merger Consideration with respect to his Penumbra Shares entirely in the form of Boston Scientific Shares, subject to proration. A representative of PWP then presented to the Penumbra Board a preliminary illustrative financial analysis of Boston Scientific’s revised $374 per Penumbra Share proposal, which utilized Penumbra’s long-range financial plan approved by the Penumbra Board earlier in the meeting. Penumbra Board then discussed, together with management and its advisors, Penumbra’s strategic alternatives, including other potential counterparties, and the alternative of remaining a stand-alone company and pursuing Penumbra’s long-range financial plan, including reasons why a strategic transaction with an alternative counterparty, including a financial sponsor and the most likely strategic buyers, was unlikely to be feasible, and the risks of leaks that would potentially result from outreach to such parties and likely damage to Boston Scientific’s current proposal should a leak occur. Representatives of Davis Polk then provided the members of the Penumbra Board with an update on the status and proposed terms and conditions of the Merger Agreement, including the proposed cash/stock election mechanisms and the provisions relating to regulatory undertakings, transaction protection and Boston Scientific’s proposal for the treatment of Penumbra’s equity incentive awards in the proposed transaction, all of which were still under negotiation between the parties and their advisors.

Following discussion, the Penumbra Board determined that Boston Scientific was not likely to further increase its $374 per Penumbra Share proposal and that a termination fee equal to 3.50% of Penumbra’s fully diluted equity value as of the time of the execution of the Merger Agreement would not be preclusive of receiving a topping bid following announcement of a transaction and determined to accept such amounts in order to focus the negotiations on the open points in the Merger Agreement, including those relating to Boston Scientific’s regulatory undertakings.

On January 13, 2026, an attorney at A&O Shearman not involved in the potential transaction was contacted by a member of a media outlet soliciting information or comment on a rumored transaction between Boston Scientific and Penumbra. Subsequent to this, representatives of Boston Scientific discussed these rumors with a representative of PWP and reiterated Boston Scientific’s continued commitment to the transaction. On January 13, 2026, Penumbra’s stock closed at $300.97 per Penumbra Share.

On January 14, 2026, representatives of PWP, on behalf of Penumbra, and Boston Scientific discussed and agreed upon the measurement period over which the stock portion of the Merger Consideration would be calculated, such that Penumbra Stockholders would have the right to elect to receive $374.00 in cash or 3.8721 Boston Scientific Shares (valued at $374.00 based on the volume weighted average price of Boston Scientific Common Stock over the last 10 trading days ending January 13, 2026), subject to proration, so that the total transaction consideration would be paid approximately 73% in cash and approximately 27% in Boston Scientific Common Shares.

Later on January 14, 2026, Davis Polk and A&O Shearman negotiated the remaining unresolved points in the draft Merger Agreement and finalized the Merger Agreement and disclosure letter delivered by each of Penumbra and Boston Scientific.

Still later on January 14, 2026, the Penumbra Board met, with members of Penumbra’s senior management present, and, at the invitation of the Penumbra Board, representatives of PWP and Davis Polk. A representative of Davis Polk reviewed the Penumbra Board’s fiduciary duties in the context of considering the proposed transaction between Boston Scientific and Penumbra. Penumbra management updated the members of the Penumbra Board on the status of the proposed transaction with Boston Scientific and noted that rumors had been circulating in the public markets about Penumbra potentially entering into a strategic transaction with Boston Scientific. Penumbra management further updated the Penumbra Board that the due diligence and reverse due diligence reviews regarding the proposed transaction with Boston Scientific were complete, and that Penumbra and Boston Scientific had negotiated and finalized the proposed Merger Agreement with respect to the proposed Merger. It was the Penumbra Board’s judgment that the rumors circulating in the public markets about Penumbra potentially entering into a strategic transaction provided further reason for the Penumbra Board to move quickly towards execution of a definitive transaction agreement with Boston Scientific. A representative of PWP then referred the Penumbra Board to PWP’s relationship disclosure letter, dated January 5, 2026, which was shared with the Penumbra Board prior to the meeting regarding its relationships with Penumbra and Boston Scientific, noting that, except in connection with

PWP’s engagement as financial advisor to Penumbra in connection with the proposed transaction with Boston Scientific and in connection with PWP’s engagement as an advisor to Penumbra in connection with a share repurchase program in 2024, no material relationship existed between PWP or its affiliates, on the one hand, and Boston Scientific or Penumbra, on the other hand, pursuant to which PWP or its affiliates had in the past two years received or anticipated receiving compensation. A representative of PWP informed the Penumbra Board that Penumbra had not received any inbound indications of interest from other companies, including Company A, relating to any strategic transactions, and the Penumbra Board again discussed, together with the representatives of PWP, the likelihood of either a financial sponsor or another strategic buyer being able and willing to make a competitive proposal, concluding that an alternative proposal from another counterparty (whether a financial sponsor or strategic buyer) that would be competitive with the proposed transaction with Boston Scientific continued to be unlikely. Following discussion, the Penumbra Board concluded that, given the attractiveness of Boston Scientific’s proposal, the risks of soliciting additional bids, including the risk of further management distraction and the risk presented by rumors of takeover speculation of Penumbra, outweighed the reasonable potential benefits. At the request of the Penumbra Board, representatives of PWP reviewed with the Penumbra Board PWP’s financial analysis of the transaction, and rendered to the Penumbra Board its oral opinion, subsequently confirmed by delivery of a written opinion dated January 14, 2026, that, as of the date of such opinion, and based upon and subject to, among other things, the various assumptions and limitations discussed with the Penumbra Board, as of January 14, 2026, the right to receive at the election of the holders of shares of Penumbra Common Stock (other than Excluded Shares) and subject to certain limitations and proration procedures set forth in the Merger Agreement (as to which PWP expressed no opinion) the Merger Consideration pursuant to the Merger Agreement was fair, from a financial point of view, to such holders, as more fully described in the section entitled “— Opinion of Penumbra’s Financial Advisor — Perella Weinberg Partners LP.” The written opinion delivered by PWP to the Penumbra Board is attached to this proxy statement/prospectus as Annex B. Representatives of Davis Polk then reviewed with the Penumbra Board the terms of the Merger Agreement, the final execution version of which had been previously distributed to the members of the Penumbra Board, along with the certificate of incorporation for the surviving company in the Merger and a substantially final version of the disclosure letter to be delivered by Penumbra.

Following additional discussion and consideration of the Merger Agreement and the Merger and the other Transactions, the Penumbra Board unanimously (i) determined that the Merger Agreement, the Merger and the other Transactions to be consummated by Penumbra pursuant to the Merger Agreement are advisable and fair to, and in the best interests of, Penumbra and the Penumbra Stockholders, (ii) duly authorized and approved the execution, delivery and performance by Penumbra of the Merger Agreement and the consummation by Penumbra of the Transactions to be consummated by Penumbra pursuant to the Merger Agreement, including the Merger, (iii) resolved, subject to certain circumstances set forth in the Merger Agreement, to recommend adoption of the Merger Agreement by the Penumbra Stockholders and (iv) directed that the adoption of the Meger Agreement be submitted to a vote of the Penumbra Stockholders.

Later on January 14, 2026, Penumbra and Boston Scientific executed the Merger Agreement.

On January 15, 2026, prior to the opening of the financial markets, Penumbra and Boston Scientific issued a joint press release announcing the execution of the Merger Agreement.

In evaluating the Merger Agreement and the Transactions, including the Merger, the Penumbra Board consulted with Penumbra’s senior management, representatives of Davis Polk, its outside legal counsel, and PWP, its financial advisor. In reaching its decision to approve the Merger Agreement, and in recommending that Penumbra Stockholders vote in favor of the adoption of the Merger Agreement, the Penumbra Board considered numerous positive factors relating to the Merger Agreement, the Merger and the other Transactions, including the following material factors (which factors are not necessarily presented in order of relative importance):

The Penumbra Board also considered potential risks related to the Merger but concluded that the anticipated benefits of the Merger were likely to substantially outweigh these risks. These potential risks include the following:

The foregoing discussion of the information and factors considered by the Penumbra Board is not intended to be exhaustive, but includes the material factors considered by the Penumbra Board. In reaching its decision to approve the Merger Agreement, the Merger, and the other Transactions, the Penumbra Board did not quantify or assign any relative weights to the factors considered, and individual directors may have given different weights to different factors. The Penumbra Board considered all these factors as a whole, including through its discussions with Penumbra’s management and financial and legal advisors, in evaluating the Merger Agreement, the Merger, and the other Transactions.

For the reasons set forth above, the Penumbra Board unanimously (i) determined that the Merger Agreement, the Merger and the other Transactions to be consummated by Penumbra pursuant to the Merger Agreement are advisable and fair to, and in the best interests of, Penumbra and the Penumbra Stockholders, (ii) duly authorized and approved the execution, delivery and performance by Penumbra of the Merger Agreement and the consummation by Penumbra of the Transactions to be consummated by Penumbra pursuant to the Merger Agreement, including the Merger, (iii) resolved, subject to certain circumstances set forth in the Merger Agreement, to recommend adoption of the Merger Agreement by the Penumbra Stockholders and (iv) directed that the adoption of the Meger Agreement be submitted to a vote of the Penumbra Stockholders.

In considering the recommendation of the Penumbra Board, you should be aware that certain directors and executive officers of Penumbra may have interests in the Merger that are different from, or in addition to, interests of Penumbra Stockholders generally and may create potential conflicts of interest. The Penumbra Board was aware of these interests and considered them when evaluating and negotiating the Merger Agreement, the Merger and the other Transactions, and in recommending to Penumbra Stockholders that they vote in favor of the Merger Proposal, the Compensation Proposal and the Adjournment Proposal. See “The Merger — Interests of Penumbra’s Directors and Executive Officers in the Merger” beginning on page 72 of this proxy statement/prospectus.

It should be noted that this explanation of the reasoning of the Penumbra Board and all other information presented in this section is forward-looking in nature and, therefore, should be read in light of the factors discussed in “Cautionary Statement Regarding Forward-Looking Statements” on page 32 of this proxy statement/prospectus.

For the reasons set forth above, the Penumbra Board recommends that Penumbra Stockholders vote “FOR” the Merger Proposal and “FOR” the other proposals to be considered at the Special Meeting.

Penumbra retained PWP to act as its financial advisor in connection with the Merger. The Penumbra Board selected PWP due to its reputation and experience in the medical technology sector and its expertise and qualifications in transactions of this nature. PWP, as part of its investment banking business, is continually engaged in performing financial analyses with respect to businesses and their securities in connection with mergers and acquisitions and other transactions as well as for corporate and other purposes.

On January 14, 2026, at the request of the Penumbra Board, PWP rendered its oral opinion, subsequently confirmed in writing, to the Penumbra Board, that, as of the date of such opinion, and based upon and subject to, among other things, the various assumptions and limitations set forth therein, the right to receive at the election of the holders of shares of Penumbra Common Stock (other than Excluded Shares) and subject to certain limitations and proration procedures set forth in the Merger Agreement (as to which PWP expressed no opinion) the Merger Consideration in the Merger pursuant to the Merger Agreement was fair, from a financial point of view, to such holders.

The full text of PWP’s written opinion, dated January 14, 2026, which sets forth, among other things, the assumptions made, procedures followed, matters considered, and limitations described in the opinion, is attached hereto as Annex B and is incorporated by reference herein.

For purposes of rendering its opinion, PWP, among other things:

For purposes of its opinion, PWP assumed and relied upon, without assuming any responsibility for independent verification, the accuracy and completeness of all of the financial, accounting, legal, tax, regulatory and other information provided to, discussed with or reviewed by it (including information that was available from public sources) and further relied upon the assurances of management of Penumbra that they are not aware of any facts or circumstances that would make such information inaccurate or misleading in any material respect. With respect to the Penumbra Forecasts, PWP was advised by management of Penumbra and assumed, with the Penumbra Board’s consent, that the Penumbra Forecasts had been reasonably prepared on bases reflecting the best currently available estimates and good faith judgments of management of Penumbra as to the future financial performance of Penumbra and the other matters covered thereby, and PWP expressed no view as to the reasonableness of the Penumbra Forecasts or the assumptions on which they were based. PWP was not provided with, and did not have access to, financial forecasts relating to Boston Scientific prepared by management of Boston Scientific. In arriving at its opinion, PWP did not make nor was provided with any independent valuation or appraisal of the assets or liabilities (including any contingent, derivative or off-balance-sheet assets or liabilities) of Penumbra, Boston Scientific or any of their respective subsidiaries. PWP did not assume any obligation to conduct, nor did it conduct, any physical inspection of the properties or facilities of Penumbra, Boston Scientific or any other party. PWP did not evaluate the solvency of any party to the Merger Agreement, or the impact of the Merger thereon, including under any applicable laws relating to bankruptcy, insolvency or similar matters. See the section entitled “— Certain Financial Projections” for a description of the Penumbra Forecasts.

PWP assumed that the final Merger Agreement would not differ from the draft of the Merger Agreement that it reviewed in any respect material to its analysis or opinion. PWP also assumed that (i) the representations and warranties of all parties to the Merger Agreement and all other related documents and instruments that are referred to therein are true and correct in all respects material to its analysis and its opinion, (ii) each party to the Merger Agreement and such other related documents and instruments will fully and timely perform all of the covenants and agreements required to be performed by such party in all respects material to its analysis and its opinion, and (iii) the Merger would be consummated in a timely manner in accordance with the terms set forth in the Merger Agreement,

without any modification, amendment, waiver or delay that would be material to its analysis or its opinion. In addition, PWP assumed that in connection with the receipt of all approvals and consents required in connection with the proposed Merger, no delays, limitations, conditions or restrictions would be imposed that would be material to its analysis.

PWP’s opinion addressed only the fairness from a financial point of view, as of the date thereof, to the holders of shares of Penumbra Common Stock (other than holders of Excluded Shares) of the Merger Consideration to be received by such holders in the proposed Merger pursuant to the Merger Agreement. PWP was not asked to, and it did not, offer any opinion as to any other term of the Merger Agreement or any other document contemplated by or entered into in connection with the Merger Agreement, the form or structure of the Merger or the likely timeframe in which the Merger would be consummated. PWP did not express any opinion with respect to the allocation of the Merger Consideration among the holders of shares of Penumbra Common Stock. In addition, PWP expressed no opinion as to the fairness of the amount or nature of any compensation to be received by any officers, directors or employees of any party to the Merger Agreement, or any class of such persons, whether relative to the Merger Consideration or otherwise. PWP did not express any opinion as to the fairness of the Merger to, or any consideration received in connection with the Merger by, the holders of any other class of securities, creditors or other constituencies of Penumbra. Nor did PWP express any opinion as to any tax or other consequences that may result from the transactions contemplated by the Merger Agreement or any other related document. PWP’s opinion did not address any legal, tax, regulatory or accounting matters, as to which PWP understood Penumbra had received such advice as it deemed necessary from qualified professionals.

PWP’s opinion was for the information and assistance of the Penumbra Board in connection with, and for the purpose of its evaluation of, the Merger. PWP’s opinion is not intended to be and does not constitute a recommendation to any holder of shares of Penumbra Common Stock as to how such holder should vote or otherwise act with respect to the proposed Merger or any other matter. PWP expressed no opinion as to what the value of the Boston Scientific Common Stock actually will be when issued or the prices at which Penumbra Common Stock or Boston Scientific Common Stock will trade at any time, including following announcement or completion of the Merger. PWP’s opinion was necessarily based on financial, economic, market, monetary and other conditions as in effect on, and the information made available to it as of, the date of its opinion. Subsequent developments may affect PWP’s opinion and the assumptions used in preparing it, and PWP does not have any obligation to update, revise, or reaffirm its opinion.

The following is a summary of the material financial analyses performed by PWP and reviewed with the Penumbra Board in connection with PWP’s opinion and does not purport to be a complete description of the financial analyses performed by PWP. The order of analyses described below does not represent the relative importance or weight given to those analyses by PWP. Some of the summaries of the financial analyses include information presented in tabular format. In order to fully understand PWP’s financial analyses, the tables must be read together with the text of each summary. The tables alone do not constitute a complete description of the financial analyses. Considering the data below without considering the full narrative description of the financial analyses, including the methodologies and assumptions underlying the analyses, could create a misleading or incomplete view of PWP’s financial analyses.

PWP reviewed and compared certain financial information for Penumbra with corresponding financial information, ratios and public market multiples for seven publicly traded companies in the medical device industry with a market capitalization between $2.8 billion and $27.6 billion (the “Selected Publicly Traded Companies”). Although none of the Selected Publicly Traded Companies is identical to Penumbra, PWP selected these companies because they had publicly traded equity securities and were deemed to be similar to Penumbra in one or more respects, including operating in the medical device industry. PWP selected the companies used in the analysis on the basis of its experience and knowledge of companies in the industry and its professional judgement.

The seven publicly traded companies selected by PWP were:

For Penumbra and each of the Selected Publicly Traded Companies, PWP calculated and compared financial information and various financial market multiples and ratios based on company filings for historical information as of January 13, 2026, the Penumbra Forecasts and Wall Street consensus third party research estimates from Capital IQ, FactSet and Wall Street analysts published prior to January 13, 2026.

Based on the multiples of enterprise value (“EV”) to calendar year 2026 estimated (“2026E”) revenue and 2027 estimated (“2027E”) revenue and EV to 2026E EBITDA, in each case, described above, PWP’s analysis of the various Selected Publicly Traded Companies and on professional judgments made by PWP, PWP (i) applied a range of multiples of 5.0x-7.0x to EV/2026E Revenue of Penumbra of $1,577 million based on Wall Street consensus third party research estimates to derive a range of implied values from $211 per share to $291 per share, compared to the implied value of the Merger Consideration of $374.00 per share to be received by the holders of shares of Penumbra Common Stock (other than holders of Excluded Shares) in the Merger pursuant to the Merger Agreement, (ii) applied a range of multiples of 4.0x-6.0x to EV/2027E Revenue of Penumbra of $1,792 million based on Wall Street consensus third party research estimates to derive a range of implied values from $193 per share to $284 per share, compared to the implied value of the Merger Consideration of $374.00 per share to be received by the holders of shares of Penumbra Common Stock (other than holders of Excluded Shares) in the Merger pursuant to the Merger Agreement, and (iii) applied a range of multiples of 20.0x-40.0x to EV/2026E EBITDA of Penumbra of $277 million based on Wall Street consensus third party research estimates to derive a range of implied values from $153 per share to $292 per share, compared to the implied value of the Merger Consideration of $374.00 per share to be received by the holders of shares of Penumbra Common Stock (other than holders of Excluded Shares) in the Merger pursuant to the Merger Agreement.

Although the Selected Publicly Traded Companies were used for comparison purposes, no business of any Selected Publicly Traded Company was either identical or directly comparable to Penumbra’s business. Accordingly, PWP’s comparison of the Selected Publicly Traded Companies and its analysis of the results of such comparisons was not purely mathematical, but instead necessarily involved complex considerations and judgments concerning differences in financial and operating characteristics and other factors that could affect the relative values of the Selected Publicly Traded Companies.

Using publicly available information as of January 13, 2026, PWP reviewed the financial terms of selected precedent transactions (the “Selected Transactions”) involving companies that operated in, or were exposed to, the medical device industry. PWP selected these transactions in the exercise of its professional judgment and experience because PWP deemed them to be most similar in size, scope and impact on the industry to Penumbra or otherwise relevant to the Merger.

For each of the Selected Transactions, PWP calculated and compared the resulting EV in the transaction as a multiple of last twelve months (“LTM”) revenue at the announcement of the transaction, the next twelve months (“NTM”) revenues based on Wall Street consensus third party research estimates, and the NTM EBITDA based on Wall Street consensus third party research estimates. The following table lists the Selected Transactions:

PWP observed that the median LTM EV/Revenue multiple (based on the deal values set forth above for the Selected Transactions was 8.5x, that the median NTM EV/Revenue multiple for the Selected Transactions was 7.2x, and that the median NTM EV/EBITDA multiple for the Selected Transactions was 28.7x.

Based on the multiples of LTM EV/Revenue, NTM EV/Revenue, and NTM EV/EBITDA described above, PWP’s analyses of the various Selected Transactions and on professional judgments made by PWP, PWP (i) applied a range of multiples of 7.0x to 10.0x to Penumbra’s 2025 LTM EV/Revenue of $1,404 million based on publicly filed financial statements and information provided by Penumbra management to derive a range of implied values of approximately $260 to $366 per share of Penumbra Common Stock, (ii) applied a range of multiples of 6.0x to 8.5x to Penumbra’s 2026E NTM EV/Revenue of $1,577 million based on Wall Street consensus third party research estimates to derive a range of implied values of approximately $251 to $350 per share of Penumbra Common Stock, and (iii) applied a range of multiples of 20.0x to 50.0x to Penumbra’s 2026E NTM EV/EBITDA of $277 million based on Wall Street consensus third party research estimates to derive a range of implied values of approximately $153 to $362 per share of Penumbra Common Stock. PWP compared these ranges to the implied value of the Merger Consideration of $374.00 per share to be received by the holders of shares of Penumbra Common Stock (other than holders of Excluded Shares) in the Merger pursuant to the Merger Agreement.

Although the Selected Transactions were used for comparison purposes, none of the Selected Transactions nor the companies involved in them was either identical or directly comparable to the Merger or Penumbra. Accordingly, PWP’s comparison of the Selected Transactions and its analysis of the results of such comparisons was not purely mathematical, but instead necessarily involved complex considerations and judgments.

PWP conducted an illustrative discounted cash flow analysis for Penumbra based on the Penumbra Forecasts to derive a range of implied enterprise values for Penumbra by:

PWP estimated the range of perpetuity growth rates utilizing its professional judgment and experience, taking into account market expectations regarding long-term real growth of gross domestic product and inflation.

PWP used discount rates ranging from 9.0% to 11.0%, which were derived from Penumbra’s weighted average cost of capital determined by the application of the capital asset pricing model based on PWP’s experience and

professional judgment, and which took into account certain company-specific metrics, including Penumbra’s target capital structure, the cost of long-term debt, forecasted tax rate and predicted Barra beta, as well as certain financial metrics for the United States financial markets generally.

From the range of implied enterprise values, PWP derived a range of implied equity values for Penumbra. To calculate the implied equity value from the implied enterprise value, PWP added cash and cash equivalents and subtracted financing leases, in each case as provided by Penumbra management. PWP calculated implied values per share by dividing the implied equity values by the applicable diluted shares (based upon the number of issued and outstanding shares and other equity interests), based on information provided by Penumbra management, and using the treasury stock method for calculation of option dilution.

This analysis resulted in an implied per share equity value reference range for the Penumbra Common Stock of $255 to $420 per share. PWP compared this range to the implied value of the Merger Consideration of $374.00 per share to be received by the holders of shares of Penumbra Common Stock (other than holders of Excluded Shares) in the Merger pursuant to the Merger Agreement.

PWP observed the following additional information that was not considered part of PWP’s financial analysis with respect to its opinion, but which were noted as reference data for the Penumbra Board:

PWP reviewed the closing prices of the Penumbra Common Stock on the NYSE for the 52 weeks ended on January 13, 2026. PWP observed that during such period, the intraday trading price of the Penumbra Common Stock ranged from $221 to $325 per share. PWP compared this range to the implied value of the Merger Consideration of $374.00 per share to be received by the holders of shares of Penumbra Common Stock (other than holders of Excluded Shares) in the Merger pursuant to the Merger Agreement.

PWP also reviewed analyst price targets per share of Penumbra Common Stock prepared and published by 18 equity research analysts prior to January 13, 2026. The range of such price targets was $266 to $388 per share. PWP compared this range to the implied value of the Merger Consideration of $374.00 per share to be received by the holders of shares of Penumbra Common Stock (other than holders of Excluded Shares) in the Merger pursuant to the Merger Agreement. The price targets published by equity research analysts do not necessarily reflect current market trading prices for shares of Penumbra Common Stock and these estimates are subject to uncertainties, including the future financial performance of Penumbra and future financial market conditions.

The preparation of a fairness opinion is a complex process and is not necessarily susceptible to partial analysis or summary description. Selecting portions of the analyses or of the summary set forth herein, without considering the analyses or the summary as a whole, could create an incomplete view of the processes underlying PWP’s opinion. In arriving at its fairness determination, PWP considered the results of all of its analyses and did not attribute any particular weight to any factor or analysis considered. Rather, PWP made its determination as to fairness on the basis of its experience and professional judgment after considering the results of all of its analyses. No company or transaction used in the analyses described herein as a comparison is directly comparable to Penumbra or the Merger.

PWP prepared the analyses described herein for purposes of providing its opinion to the Penumbra Board as to the fairness, from a financial point of view, as of the date of such opinion, of the Merger Consideration to be received by the holders of shares of Penumbra Common Stock (other than holders of Excluded Shares) in the Merger pursuant to the Merger Agreement. These analyses do not purport to be appraisals or necessarily reflect the prices at which businesses or securities actually may be sold. PWP’s analyses were based in part upon the Penumbra Forecasts and other third-party research analyst estimates, which are not necessarily indicative of actual future results, which may be significantly more or less favorable than suggested by PWP’s analyses. Because these analyses are inherently subject to uncertainty, being based upon numerous factors or events beyond the control of the parties to the Merger Agreement or their respective advisors, none of Penumbra, PWP or any other person assumes responsibility if future results are materially different from those forecasted by Penumbra management or third parties.

PWP has acted as financial advisor to Penumbra with respect to the Merger. Pursuant to the terms of the engagement letter between PWP and Penumbra, dated January 5, 2026, Penumbra agreed to pay PWP $5.0 million in cash, upon delivery by PWP of its opinion or the determination by PWP that it would not be able to deliver an opinion containing the conclusion sought by Penumbra in the context of the Merger. Penumbra also has agreed to pay PWP an additional fee, which is contingent upon consummation of the Merger, of approximately $109.6 million (following reduction by the opinion fee previously paid to PWP by Penumbra). PWP will also be entitled to receive a termination fee equal to a portion of any compensation that Penumbra may receive as a result of the termination of the Merger Agreement. In addition to the fees for professional services of PWP, Penumbra agreed to reimburse PWP for reasonable, documented, out-of-pocket expenses incurred in connection with the undertakings described in the engagement letter that may arise, and to indemnify PWP for certain liabilities and other items that may arise, out of its engagement by Penumbra.

PWP and its affiliates, as part of their investment banking business, are regularly engaged in performing financial analyses with respect to businesses and their securities in connection with mergers and acquisitions, negotiated underwritings, competitive biddings, secondary distributions of listed and unlisted securities, private placements and other transactions as well as for estate, corporate and other purposes.

Except in connection with PWP’s engagement as financial advisor to Penumbra in connection with the Merger and in connection with PWP’s engagement as an advisor to Penumbra in connection with a share repurchase program in 2024, during the two-year period prior to the date of PWP’s opinion, no material relationship existed between PWP or its affiliates, on the one hand, and Boston Scientific or Penumbra, on the other hand, pursuant to which PWP or its affiliates received or anticipated receiving compensation.

PWP and its affiliates in the future may provide investment banking and other financial services to Boston Scientific or its affiliates or equity holders and/or Penumbra and in the future may receive compensation for the rendering of these services. In the ordinary course of its business activities, PWP and its affiliates may at any time hold long or short positions, and may trade or otherwise effect transactions, for its own account or the accounts of customers or clients, in (i) debt, equity or other securities (or related derivative securities) or financial instruments (including bank loans or other obligations) of Penumbra, Boston Scientific or any of their respective affiliates and (ii) any currency or commodity that may be material to the parties or otherwise involved in the Merger. The issuance of PWP’s opinion was approved by a fairness opinion committee of PWP.

Penumbra does not as a matter of course publicly disclose long term projections as to future performance, revenues, operating income, or other financial results. However, Penumbra management prepared the Penumbra Forecasts at the request of the Penumbra Board in the ordinary course of business, which were provided to and reviewed by the Penumbra Board and subsequently used in connection with the Penumbra Board’s analysis of the Transactions. The Penumbra Forecasts are included in this proxy statement/prospectus solely because (1) the Penumbra Forecasts were made available to PWP for use in its financial analyses in connection with rendering its opinion to the Penumbra Board as described in the section entitled “The Merger Agreement — Opinion of Penumbra’s Financial Advisor — Perella Weinberg Partners LP” and (2) the Penumbra Forecasts were made available to the Penumbra Board, including in connection with its consideration of the Transactions, and approved by the Penumbra Board for use by PWP in its financial analyses in connection with rendering its opinion to the Penumbra Board. Only the Penumbra Forecasts through 2028 (excluding Unlevered Free Cash Flow) were made available to Boston Scientific in connection with its consideration of the Transactions. The Penumbra Forecasts are not included in this proxy statement/prospectus to influence any stockholder to make any investment decision with respect to the Merger, including whether or not to seek appraisal rights with respect to Penumbra Shares.

The Penumbra Forecasts were not prepared with a view toward public disclosure or with a view toward complying with the guidelines established by the American Institute of Certified Public Accountants for preparation and presentation of prospective financial data, published guidelines of the SEC regarding forward-looking statements or GAAP.

The Penumbra Forecasts are forward-looking statements. Important factors that may affect actual results and cause the Penumbra Forecasts not to be achieved include, but are not limited to, the risks and uncertainties described below and those described in the section entitled “Cautionary Statement Regarding Forward-Looking Statements.” Although the Penumbra Forecasts are presented with numerical specificity, they reflect numerous estimates and assumptions made by Penumbra with respect to industry performance, general business, economic, regulatory,

market and financial conditions and other future events, as well as matters specific to Penumbra’s business, all of which are difficult or impossible to predict accurately and many of which are beyond Penumbra’s control. The Penumbra Forecasts reflect assumptions as to certain potential business decisions that are subject to change. Without limiting the generality of the foregoing, the Penumbra Forecasts include assumptions relating to revenue growth, expenses and certain cash flow and tax items. The Penumbra Forecasts cover several years and such information by its nature becomes less reliable with each successive year. The Penumbra Forecasts were prepared on a standalone basis without giving effect to the Merger. Furthermore, the Penumbra Forecasts do not take into account the effect of any failure of the Merger to be completed and should not be viewed as accurate or continuing in that context.

The inclusion of the Penumbra Forecasts should not be regarded as an indication that Penumbra, Boston Scientific, PWP, any of their respective affiliates, officers, directors, advisors or other representatives or anyone who received this information then considered, or now considers, them a reliable prediction of future events, and this information should not be relied upon as such. The inclusion of the Penumbra Forecasts herein should not be deemed an admission or representation by Penumbra or Boston Scientific that it views such Penumbra Forecasts as material information. The inclusion of the Penumbra Forecasts in this proxy statement/prospectus should not be regarded as an indication that the Penumbra Forecasts will necessarily be predictive of actual future events given the inherent risks and uncertainties associated with such long- range forecasts. No representation is made by Penumbra or any other person regarding the Penumbra Forecasts or Penumbra’s ultimate performance compared to such information. The Penumbra Forecasts should be evaluated, if at all, in conjunction with the historical financial statements and other information about Penumbra contained in its public filings with the SEC. For additional information, see the section entitled “Where You Can Find More Information.” In light of the foregoing factors, and the uncertainties inherent in the Penumbra Forecasts, stockholders are cautioned not to place undue reliance on the Penumbra Forecasts.

The Penumbra Forecasts included in this document have been prepared by, and are solely the responsibility of, Penumbra’s management. Neither PricewaterhouseCoopers LLP, nor any other independent accountant, has audited, reviewed, examined, compiled or applied agreed-upon procedures with respect to the Penumbra Forecasts and, accordingly, PricewaterhouseCoopers LLP does not express an opinion or any other form of assurance with respect thereto. The PricewaterhouseCoopers LLP report incorporated by reference in this document relates to Penumbra’s previously issued financial statements. It does not extend to the Penumbra Forecasts and should not be read to do so.

Some of the Penumbra Forecasts are “non-GAAP financial measures,” which are financial performance measures that are not calculated in accordance with the published guidelines of the SEC regarding projections or GAAP. The non-GAAP financial measures used in the Penumbra Forecasts were used by the Penumbra Board in connection with its evaluation of the Transactions and, at the direction of the Penumbra Board, by PWP for purposes of its financial analyses and opinion delivered to the Penumbra Board. These non- GAAP financial measures should not be viewed as a substitute for GAAP financial measures, and may be different from non-GAAP financial measures used by other companies. Furthermore, there are limitations inherent in non-GAAP financial measures, because they exclude charges and credits that are required to be included in a GAAP presentation. Accordingly, these non-GAAP financial measures should be considered together with, and not as an alternative to, financial measures prepared in accordance with GAAP.

The following table presents the Penumbra Forecasts:

The Penumbra Forecasts set forth above have not been updated or revised to reflect information or results after the date they were prepared or as of the date of this proxy statement/prospectus.

PENUMBRA DOES NOT INTEND TO UPDATE OR OTHERWISE REVISE THE PENUMBRA FORECASTS TO REFLECT CIRCUMSTANCES EXISTING AFTER THE DATE WHEN MADE OR TO REFLECT THE OCCURRENCE OF FUTURE EVENTS, EVEN IN THE EVENT THAT ANY OR ALL OF THE ASSUMPTIONS UNDERLYING THE PENUMBRA FORECASTS ARE NO LONGER APPROPRIATE.

In considering the recommendation of the Penumbra board that Penumbra Stockholders vote “FOR” the Merger Proposal and the Advisory Compensation Proposal, Penumbra Stockholders should be aware that the directors and executive officers of Penumbra may have interests in the Merger that are different from, or in addition to, those of Penumbra Stockholders generally.

These interests are described below. The Penumbra Board was aware of and considered these interests, among other matters, in evaluating and negotiating the Merger Agreement and the Merger, in approving the Merger Agreement, and in recommending the approval of the Merger Proposal and Advisory Compensation Proposal. The Merger will be a “change of control” for purposes of the Penumbra executive compensation plans and agreements described below.

For purposes of this disclosure, the named executive officers of Penumbra are Adam Elsesser, Chairman and Chief Executive Officer, Maggie Yuen, Chief Financial Officer, Johanna Roberts, Executive Vice President, General Counsel and Secretary, Shruthi Narayan, President, and Lambert Shiu, Chief Accounting Officer.

For purposes of this disclosure, Penumbra’s non-employee directors are: Arani Bose, M.D., Bridget O’Rourke, Harpreet Grewal, Janet Leeds, Surbhi Sarna and Thomas C. Wilder.

Except as otherwise specifically noted, for purposes of quantifying the potential payments and benefits described in this section, the following assumptions were used:

The amounts indicated below are estimates based on multiple assumptions (including the assumptions described above) that may or may not actually occur or be accurate on the relevant date, and do not reflect certain compensation actions that may occur before completion of the Transactions. Accordingly, the actual amounts received may differ materially from the estimates set forth below.

All unvested Penumbra RSUs held by Penumbra’s executive officers and non-employee directors will vest immediately upon the Effective Time, subject to the award recipient’s continued service through the Effective Time. For further details regarding treatment of any Penumbra Equity Awards granted to Penumbra’s executive officers and non-employee directors following the date hereof, please see “— Treatment of Penumbra Options and Penumbra RSUs” beginning on page 52.

For an estimate of the amounts that would be payable to each of Penumbra’s named executive officers at the Effective Time, see the section entitled “— Quantification of Potential Payments and Benefits to Penumbra’s Named Executive Officers” beginning on page 73.

Subject to the consummation of the Merger, the Penumbra ESPP will terminate effective immediately prior to the Effective Time. The Penumbra ESPP will be frozen and suspended at the end of the “offering period” in progress as of January 15, 2026, and following January 15, 2026, until the Effective Time, no new offering periods will be commenced under the Penumbra ESPP, no new participants will be permitted to commence participation in the Penumbra ESPP, and no current participants will be permitted to effectuate changes to their elections or contributions to the Penumbra ESPP. Maggie Yuen, Chief Financial Officer, and Lambert Shiu, Chief Accounting Officer, are participants in the Penumbra ESPP.

Prior to the closing of the Merger, Penumbra, in consultation with Boston Scientific, may implement measures intended to mitigate potential tax liabilities under Sections 280G and 4999 of the Code. No specific actions have been taken to date to mitigate the potential impact of Sections 280G and 4999 of the Code.

Pursuant to the terms of the Merger Agreement, the non-employee directors and executive officers will be entitled to certain ongoing indemnification and insurance coverage for a period of six years following the consummation of the Merger under the director’s and officer’s liability insurance policies of Penumbra. For additional information with respect to the indemnification and insurance coverage, see the section of this proxy statement/prospectus entitled “— The Merger Agreement — Indemnification and Insurance.”

As of the date of this proxy statement/prospectus, it is anticipated that Adam Elsesser will join the Boston Scientific Board upon Closing. Other than the foregoing, as of the date of this proxy statement/ prospectus, none of Penumbra’s executive officers has entered into any agreement with Boston Scientific or any of its affiliates regarding service with, or the right to purchase or participate in the equity of, the Surviving Corporation or one or more of its affiliates. Prior to and following the Closing, however, certain of Penumbra’s executive officers may have discussions with and may enter into agreements with Boston Scientific or the Surviving Corporation, their subsidiaries or their respective affiliates regarding service with, or the right to purchase or participate in the equity of, Boston Scientific, the Surviving Corporation or one or more of its affiliates.

The information set forth below is required by Item 402(t) of Regulation S-K regarding compensation that is based on or otherwise relates to the Merger that the Penumbra named executive officers could receive in connection with the Merger. Except as otherwise specifically noted, the disclosure below uses the relevant assumptions described above under “— Certain Assumptions.”

The amounts indicated below are estimates based on multiple assumptions (including the assumptions described above) that may or may not actually occur or be accurate on the relevant date, and do not reflect certain compensation actions that may occur before completion of the Merger. Accordingly, the actual amounts received by our named executive officers may differ materially from the estimates set forth below.

For 12 months following the Effective Time (or, if shorter, an employee’s remaining period of employment), Boston Scientific will provide (or cause to provide) each employee of Penumbra and of each of the Penumbra Subsidiaries as of the Effective Time (each, a “Continuing Employee”): (i) a base salary or wage rate that is no less favorable than the base salary or wage rate provided by Penumbra or its subsidiaries to such Continuing Employee as of immediately prior to the Effective Time, (ii) incentive opportunities no less favorable in the aggregate than the incentive opportunities provided by Boston Scientific or its subsidiaries to similarly situated employees of Boston Scientific or its subsidiaries and (iii) employee benefits (including severance but excluding any employee share purchase plan) that are substantially comparable in the aggregate to the employee benefits provided either (A) by Penumbra or its subsidiaries to such Continuing Employees immediately prior to the Effective Time or (B) by Boston Scientific or its subsidiaries to similarly situated employees of Boston Scientific or its subsidiaries.

Under the Merger Agreement, certain indemnification and insurance rights exist in favor of Penumbra’s current and former directors and officers. See “The Merger Agreement — Indemnification and Insurance” beginning on page 96 for information about these rights.

Under the DGCL, if the Merger is completed, record Penumbra Stockholders who do not vote in favor of the Merger Proposal and who otherwise properly exercise and perfect their appraisal rights will be entitled to seek appraisal for, and obtain payment in cash for the judicially determined fair value of, their Penumbra Shares, in lieu of receiving the Merger Consideration. The “fair value” could be higher or lower than, or the same as, the Merger Consideration. The relevant provisions of the DGCL are included as Annex C to this proxy statement/prospectus. Penumbra Stockholders are encouraged to read these provisions carefully and in their entirety. Moreover, due to the complexity of the procedures for exercising and perfecting the right to seek appraisal, Penumbra Stockholders who are considering exercising and perfecting that right are encouraged to seek the advice of legal counsel. Failure to comply strictly with these provisions may result in loss of the right of appraisal. Boston Scientific Stockholders are not entitled to appraisal of their Boston Scientific Shares or dissenters’ rights with respect to the Merger in connection with the Merger under Delaware law. For a more complete description of Penumbra Stockholders’ appraisal rights, see “Appraisal Rights” beginning on page 123 of this proxy statement/prospectus.

Boston Scientific prepares its financial statements in accordance with GAAP. The Merger will be accounted for as a business combination using the acquisition method of accounting in accordance with Accounting Standards Codification Topic 805, Business Combinations. Boston Scientific will be treated as the acquirer for accounting

purposes and will record the identifiable assets acquired and liabilities assumed from Penumbra at their respective fair values as of the closing date of the Merger. The excess of the purchase price over the fair value of the identifiable net assets acquired will be recorded as goodwill.

The exchange of Penumbra Shares by a Penumbra Stockholder for cash and Boston Scientific Shares in the Merger will be a taxable transaction for U.S. federal income tax purposes. Accordingly, any Penumbra Stockholder that is a U.S. Holder generally will recognize gain or loss for U.S. federal income tax purposes in an amount equal to the difference, if any, between (i) the sum of the amount of cash (including any cash received in lieu of any fractional Boston Scientific Shares) and the fair market value as of the Effective Time of the Merger of the Boston Scientific Shares received in the Merger and (ii) the U.S. Holder’s adjusted tax basis in the Penumbra Shares exchanged in the Merger.

Any such gain or loss generally will be capital gain or loss and generally will be long-term capital gain or loss if the U.S. Holder’s holding period in the Penumbra Common Stock immediately prior to the Merger is more than one year. For U.S. Holders that are individuals, estates or trusts, long-term capital gain generally is taxed at preferential rates. The deductibility of capital losses is subject to limitations.

A U.S. Holder will have a tax basis in the Boston Scientific Shares received in the Merger equal to the fair market value of such shares as of the Effective Time of the Merger. A U.S. Holder’s holding period for Boston Scientific Shares received in exchange for Penumbra Shares in the Merger will begin on the date immediately following the Closing Date.

A Non-U.S. Holder generally will not be subject to U.S. federal income tax with respect to the exchange of Penumbra Shares for cash and Boston Scientific Shares in the Merger unless such Non-U.S. Holder has certain connections to the U.S. as described in “Material U.S. Federal Income Tax Consequences of the Merger — Non-U.S. Holders.” A Non-U.S. Holder may be subject to backup withholding with respect to payments made pursuant to the Merger unless such Non-U.S. Holder certifies that it is not a U.S. person or otherwise establishes an exemption.

Each Penumbra Stockholder should consult its own tax advisor to determine the particular tax consequences of the Merger to such stockholder in light of such Penumbra Stockholder’s particular circumstances.

For a more detailed description of the U.S. federal income tax consequences of the Merger, please see “Material U.S. Federal Income Tax Consequence of the Merger” beginning on page 107 of this proxy statement/prospectus.

Boston Scientific’s obligation to complete the Merger is not conditioned upon its obtaining financing for the Merger. Boston Scientific anticipates that approximately $11 billion will be required to pay the aggregate Cash Consideration payable in connection with the Merger and to pay fees and expenses relating to the Merger and the other Transactions.

Boston Scientific intends to fund the aggregate Cash Consideration payable in connection with the Merger with a combination of: (i) existing cash resources; (ii) third party debt financing, which may include issuances under Boston Scientific’s commercial paper program; and (iii) proceeds from the issuance of one or more senior unsecured debt securities. In connection with the Merger, on February 26, 2026, Boston Scientific entered into the following agreements with Wells Fargo Bank, National Association and the other lenders party thereto: (1) a 364-day revolving credit facility, in an aggregate principal amount of up to $2.0 billion; (2) a 364-day delayed draw term loan facility in an aggregate principal amount of up to $1.0 billion, which may be drawn to fund the Merger at Closing; (3) a 364-day delayed draw term loan facility in an aggregate principal amount of up to $5.0 billion, which may be drawn to fund the Merger at Closing and, if so drawn, shall be repaid or refinanced with the proceeds of any issuance of senior unsecured debt securities referenced above; and (4) the refinancing of Boston Scientific’s Existing Revolving Credit Agreement, pursuant to which the Existing Revolving Credit Agreement was refinanced to, among other things, increase the aggregate revolving credit commitments from $2.75 billion to $3.0 billion and extend the maturity to February 26, 2031. Each of the Existing Revolving Credit Agreement and the 364-day revolving credit facility provide backing for Boston Scientific’s commercial paper program, and outstanding commercial paper backed by either facility will directly reduce borrowing capacity under such facility.

Prior to the completion of the Merger, Boston Scientific has agreed to use its reasonable best efforts to cause the Boston Scientific Shares to be issued in connection with the Transaction to be approved for listing on the NYSE. The listing of the Boston Scientific Shares on the NYSE, subject to official notice of issuance, is also a condition to completion of the Transaction. For more detailed information, see “Description of Boston Scientific’s Capital Stock” beginning on page 111 of this proxy statement/prospectus.

If the Transaction is completed, Penumbra Shares will be delisted from the NYSE and deregistered under the Exchange Act, and Penumbra will no longer be required to file periodic reports with the SEC with respect to the Penumbra Shares.

For more detailed information, see “Description of Boston Scientific Capital Stock” beginning on page 111 of this proxy statement/prospectus.

The rights of Penumbra Stockholders are governed by Penumbra Charter, the Penumbra Bylaws and the DGCL. To the extent you receive any stock consideration in the Merger, your rights as a stockholder of Boston Scientific Shares will be governed by the Boston Scientific Charter, the Boston Scientific By-Laws and the DGCL. Your rights under the Penumbra Charter and Penumbra Bylaws will differ in some respects from your rights under the Boston Scientific Charter and Boston Scientific By-Laws. For more detailed information regarding a comparison of your rights as a Penumbra Stockholder and as a Boston Scientific Stockholder, see “Comparison of Stockholder Rights” beginning on page 115 of this proxy statement/ prospectus.

The Transactions are currently expected to be completed in 2026. Neither Penumbra nor Boston Scientific can predict, however, the actual date on which the Transactions will be completed, or if the Merger will be completed at all, because completion of the Merger is subject to conditions beyond each company’s control, including obtaining the necessary regulatory approvals.

See “The Merger Agreement — Conditions to the Closing of the Merger” beginning on page 101 of this proxy statement/prospectus.

The Merger is subject to the provisions of the HSR Act and cannot be completed until Penumbra and Boston Scientific each files a notification and report form under the HSR Act with the DOJ and the FTC, and the waiting period (and any extension thereof) applicable to the consummation of the Merger under the HSR Act or any agreement with the DOJ or the FTC not to complete the Merger has expired or been terminated. Penumbra, Boston Scientific and Merger Sub have agreed in the Merger Agreement to make an appropriate filing of all notification and report forms as required by the HSR Act within twenty business days after the date of the Merger Agreement (unless a different date is agreed to by the parties). The waiting period under the HSR Act applicable to the Merger is 30 calendar days following the parties’ filings of their respective HSR Act notification and report forms, unless the waiting period is terminated earlier or extended. If the DOJ or FTC issues a request for additional information and documentary materials (a “Second Request”), prior to the expiration of the initial waiting period, the parties must observe an additional waiting period, which would begin to run only after both parties have substantially complied with such Second Request, unless the waiting period is terminated earlier.

Penumbra and Boston Scientific each filed a notification and report form under the HSR Act with the DOJ and the FTC on February 13, 2026. On March 16, 2026, Penumbra and Boston Scientific each received a Second Request from the FTC in connection with the FTC’s review of the Merger. The issuance of the Second Request extends the waiting period under the HSR Act until 30 days after both Penumbra and Boston Scientific have substantially complied with the Second Request, unless the waiting period is extended voluntarily by the parties or terminated earlier by the FTC. Penumbra and Boston Scientific expect to promptly respond to the Second Request and to continue to work cooperatively with the FTC in its review of the Merger.

Subject to a pending referral at the parties’ request, the Merger is expected to be subject to clearance or approval under the competition laws of the European Union. In addition, the Merger is subject to clearance or approval under the competition laws and the foreign investment laws of certain other non-U.S. jurisdictions. The Merger cannot be completed until Penumbra and Boston Scientific obtain clearance or approval to consummate the Merger, or applicable waiting periods have expired or been terminated, in each such non-U.S. jurisdiction. Penumbra and Boston Scientific have agreed in the Merger Agreement to initiate the appropriate steps towards filing of all notification filings, forms or submissions as required by the antitrust, competition or foreign investment laws of each such non-U.S. jurisdiction no later than 50 calendar days (except as otherwise agreed between Penumbra and Boston Scientific) following the date of the Merger Agreement (and in any event prior to the expiration of any applicable legal deadline).

Boston Scientific, Merger Sub and Penumbra have agreed to use their reasonable best efforts to take all actions that are necessary, appropriate or desirable to obtain all regulatory approvals required to complete the Transactions, subject to certain limitations as set forth in the Merger Agreement. Under and subject to the terms and conditions of the Merger Agreement, Boston Scientific has agreed to (i) pay Penumbra a termination fee in an amount equal to $900 million in the event the Merger Agreement is terminated prior to the consummation of the Merger in certain circumstances relating to the failure to obtain required antitrust approvals or clearances, (ii) litigate in the event the Merger is challenged and (iii) if necessary, divest assets and/or accept certain non-divestiture remedies with respect to businesses, properties or assets that generated up to $300 million in revenue for the year ending December 31, 2025, as further described in the section of this proxy statement/prospectus captioned “The Merger Agreement — Regulatory Filings.”

Although Boston Scientific and Penumbra expect that all required regulatory clearances and approvals will be obtained, neither Boston Scientific nor Penumbra can assure you that these regulatory clearances and approvals will be timely obtained, obtained at all or that the granting of these regulatory clearances and approvals will not involve the imposition of additional conditions, restrictions, qualifications, requirements or limitations on the completion of the Merger, including the requirement to divest assets, license or hold separate assets or terminate existing relationships and contractual rights, or agree to other remedies, or require changes to the terms of the Merger Agreement, or that a challenge to the Merger on antitrust grounds or other regulatory grounds will not be made, or if such challenge is made, what the result will be. These conditions or changes could result in the conditions to the Merger not being satisfied. There is currently no way to predict how long it will take to obtain all of the required regulatory approvals or whether such approvals will ultimately be obtained and there may be a substantial period of time between the approval of the Merger Proposal by Penumbra Stockholders and the completion of the Merger.

At any time before or after the Effective Time, notwithstanding the expiration or termination of any waiting period, the DOJ, FTC or any state or foreign government or regulatory authority could take action under applicable antitrust, competition or foreign investment laws as it deems necessary or desirable in the public interest, including seeking to enjoin the consummation of the Merger, seeking divestiture of substantial assets of one or both of the parties, requiring the parties to license or hold separate assets or terminate existing relationships and contractual rights, or requiring the parties to agree to other remedies. In addition, private parties may seek to take legal action under applicable antitrust or competition laws under certain circumstances, including by seeking to intervene in the regulatory process or litigate to enjoin or overturn regulatory approvals. Any of these potential actions could significantly impede, delay or even preclude the consummation of the Merger. Neither Boston Scientific nor Penumbra can be certain that a challenge to the Merger will not be made or that, if a challenge is made, Boston Scientific or Penumbra, as applicable, will prevail.

In connection with the Merger Proposal, Boston Scientific has filed a Registration Statement on Form S-4, of which this proxy statement/prospectus forms a part, that must be declared effective by the SEC and pursuant to which the issuance of Boston Scientific Shares to be issued as the Stock Consideration in the Merger will be registered with the SEC.

Boston Scientific Shares are listed for trading on the NYSE under the symbol “BSX.” Penumbra Shares are listed on the NYSE under the symbol “PEN.”

Under the terms of the Merger Agreement, it is a condition to the consummation of the Merger that the Boston Scientific Shares to be issued as the Stock Consideration in the Merger be approved for listing on the NYSE, subject to official notice of issuance. Neither Boston Scientific nor Penumbra will be required to complete the Merger if such shares are not authorized for listing on the NYSE, subject to official notice of issuance.

Following the Effective Time, the Penumbra Shares currently listed on the NYSE will be delisted from such exchange and deregistered under the Exchange Act.

To the knowledge of the Penumbra management team, there are not any lawsuits or other legal proceedings currently pending or contemplated against Penumbra relating to the Merger. As of March 30, 2026, Penumbra and Boston Scientific have received three Demand Letters, which generally allege that the proxy statement/prospectus that forms a part of the Registration Statement on Form S-4 filed with the SEC by Boston Scientific on February 27, 2026 contains disclosure deficiencies in violation of U.S. federal securities laws. The Demand Letters seek corrective disclosures in the proxy statement/prospectus in advance of the Special Meeting.

Penumbra and Boston Scientific believe that the disclosures in this proxy statement/prospectus comply fully with applicable law. It is possible that additional or similar demand letters may be received by Penumbra, the Penumbra Board, Boston Scientific and/or the Boston Scientific Board, and/or that complaints may be filed alleging similar or additional deficiencies between the date of this proxy statement/prospectus and consummation of the Merger. If any such additional demand letters are received or any complaints are filed, absent new or different allegations that are material, Penumbra and/or Boston Scientific will not necessarily disclose such demand letters or complaints.

Boston Scientific did not pay cash dividends on Boston Scientific Shares in 2025, 2024 or 2023, and currently does not intend to pay cash dividends on Boston Scientific Shares. The declaration of any future dividends will be at the discretion of the Boston Scientific Board and will be determined after consideration of various factors, including earnings, cash requirements, the financial condition of Boston Scientific and other factors deemed relevant by the Boston Scientific Board.

The following summary describes the material provisions of the Merger Agreement. The descriptions of the Merger Agreement in this summary and elsewhere in this proxy statement/prospectus are not complete and are qualified in their entirety by reference to the full text of the Merger Agreement, a copy of which is attached to this proxy statement/prospectus as Annex A and incorporated into this proxy statement/prospectus by reference. You should carefully read and consider the entire Merger Agreement, which is the legal document that governs the Merger, because this summary may not contain all the information about the Merger Agreement that is important to you. The rights and obligations of the parties are governed by the express terms of the Merger Agreement and not by this summary or any other information contained in this proxy statement/prospectus.

The representations, warranties, covenants and agreements described below and included in the Merger Agreement (i) were made only for purposes of the Merger Agreement and as of specific dates; (ii) were made solely for the benefit of the parties to the Merger Agreement; and (iii) may be subject to important qualifications, limitations and supplemental information agreed to by Penumbra, Boston Scientific and Merger Sub in connection with negotiating the terms of the Merger Agreement and contained in the confidential disclosure schedules to the Merger Agreement. In addition, the representations and warranties have been included in the Merger Agreement for the purpose of allocating contractual risk among Penumbra, Boston Scientific and Merger Sub rather than to establish matters as facts, and may be subject to standards of materiality applicable to such parties that differ from those applicable to investors. Except in the limited circumstances set forth in the Merger Agreement, stockholders are not third-party beneficiaries under the Merger Agreement and should not rely on the representations, warranties, covenants and agreements or any descriptions thereof as characterizations of the actual state of facts or condition of Penumbra, Boston Scientific or Merger Sub or any of their respective affiliates or businesses. Moreover, information concerning the subject matter of the representations and warranties may change after the date of the Merger Agreement. In addition, you should not rely on the covenants in the Merger Agreement as actual limitations on the respective businesses of Penumbra, Boston Scientific and Merger Sub, because the parties may take certain actions that are either expressly permitted in the confidential disclosure schedules to the Merger Agreement or as otherwise consented to by the appropriate party, which consent may be given without prior notice to the public. The Merger Agreement is described below, and included as Annex A, only to provide you with information regarding its terms and conditions, and not to provide any other factual information regarding Penumbra, Boston Scientific, Merger Sub or their respective businesses. Accordingly, the representations, warranties, covenants and other agreements in the Merger Agreement should not be read alone, and you should read the information provided elsewhere in this proxy statement/prospectus and in Penumbra’s and Boston Scientific’s filings with the SEC regarding Penumbra, Boston Scientific, and their respective businesses.

The Merger Agreement provides that, upon the terms and subject to the conditions of the Merger Agreement and in accordance with the DGCL, at the Effective Time, Merger Sub will be merged with and into Penumbra. As a result of the Merger, (a) the separate corporate existence of Merger Sub will cease, and Penumbra will continue as the Surviving Corporation of the Merger and a wholly owned subsidiary of Boston Scientific and (b) the Merger will have the effects set forth in the Merger Agreement, the Certificate of Merger and in the applicable provisions of the DGCL. At the Effective Time, all of the property, rights, privileges and powers of Penumbra and Merger Sub will vest in the Surviving Corporation, and all of the debts, liabilities and duties of Penumbra and Merger Sub will become the debts, liabilities and duties of the Surviving Corporation. If the Merger is consummated, Penumbra securities will be delisted from the NYSE and deregistered under the Exchange Act, as promptly as practicable after the Effective Time.

At the Effective Time, the Penumbra Charter as in effect as of the Effective Time will be amended and restated in its entirety to read as set forth in Exhibit A to the Merger Agreement, as the second amended and restated certificate of incorporation of Penumbra, until thereafter amended as provided therein or by applicable law. Boston Scientific and Penumbra will take such actions reasonably necessary to cause the Penumbra Bylaws as in effect as of the Effective Time to be amended in their entirety pursuant to the Merger to conform to the bylaws of Merger Sub as in effect immediately prior to the Effective Time (except that the name of the Surviving Corporation will be “Penumbra, Inc.”), and such bylaws as so amended and restated will be the bylaws of the Surviving Corporation until thereafter amended as provided therein or by applicable law.

Unless otherwise designated by Boston Scientific, the directors of Merger Sub immediately prior to the Effective Time will be the initial directors of the Surviving Corporation and the officers of Merger Sub immediately

prior to the Effective Time or such other individuals designated by Boston Scientific as of the Effective Time will be the initial officers of the Surviving Corporation, in each case until their respective successors are duly elected or appointed and qualified or until the earlier of their death, resignation or removal in accordance with the certificate of incorporation and bylaws of the Surviving Corporation.

Unless the Merger Agreement has been terminated in accordance with its terms, the Closing will take place by electronic exchange of the required Closing deliverables at 8:00 a.m. Eastern Time on the fifth business day after the satisfaction or written waiver (where permissible under applicable law) of all of the conditions to Closing set forth in the Merger Agreement (other than those conditions that by their terms are to be satisfied at the Closing (subject to their satisfaction or written waiver (where permissible))), unless another time, date or place is agreed to in writing by Boston Scientific and Penumbra. The date on which the Closing occurs is referred to in the Merger Agreement as the Closing Date. On the Closing Date, or on such other date as Boston Scientific and Penumbra may agree to in writing, Boston Scientific, Merger Sub and Penumbra will cause the Certificate of Merger to be executed and filed with the Secretary of State of the State of Delaware in such form as required by and in accordance with Section 251 of the DGCL. The Merger will become effective at the Effective Time.

At the Effective Time, by virtue of the Merger and without any action on the part of Boston Scientific, Merger Sub, Penumbra or the holders of Penumbra Shares, each Penumbra Share issued and outstanding immediately prior to the Effective Time (other than Excluded Shares) will, subject to the proration provisions of the Merger Agreement, be cancelled and will be converted automatically into the right to receive, at the election of the holder thereof in accordance with, and subject to the terms, conditions and procedures set forth in the Merger Agreement, the following consideration (collectively with, if applicable, cash in lieu of any fractional Boston Scientific Shares and any dividends or other distributions payable pursuant to the Merger Agreement), in each case, without interest:

Each Penumbra Share to be converted into the right to receive the Merger Consideration as provided in this section of this proxy statement/prospectus captioned “The Merger Agreement — Merger Consideration” will, at the Effective Time, no longer be outstanding and will be automatically cancelled and will cease to exist, and the holders of Certificates or Book-Entry Shares, which immediately prior to the Effective Time represented such Penumbra Shares, will, from and after the Effective Time, cease to have any rights with respect to such Penumbra Shares other than the right to receive, upon surrender or transfer of such Certificates or Book-Entry Shares in accordance with the terms of the section of this proxy statement/prospectus captioned “The Merger Agreement — Exchange and Payment Procedures,” the Merger Consideration.

The Merger Agreement provides that, notwithstanding anything in the Merger Agreement to the contrary, the total number of Penumbra Shares that shall be entitled to receive the Cash Consideration pursuant to the preceding section of this proxy statement/prospectus captioned “The Merger Agreement — Merger Consideration — Penumbra Common Stock” will be equal to 73.26% of the aggregate number of Penumbra Shares issued and outstanding immediately prior to the Effective Time (other than Excluded Shares) (the “Maximum Cash Share Number”), and the total number of Penumbra Shares that shall be entitled to receive the Stock Consideration pursuant to the preceding section of this proxy statement/ prospectus captioned “The Merger Agreement — Merger Consideration — Penumbra Common Stock” will be equal to 26.74% of the aggregate number of Penumbra Shares issued and outstanding immediately prior to the Effective Time (other than any Excluded Shares), in each case, rounded to the nearest whole number.

Promptly after (and in any event no later than five business days after) the Effective Time, Boston Scientific will cause the Exchange Agent to effect the allocation among Penumbra Stockholders of rights to receive the Cash Consideration and the Stock Consideration as follows:

Cash will be paid in lieu of fractional Boston Scientific Shares as described in the next sentence. Each Penumbra Stockholder or a holder of Penumbra Equity Awards who would otherwise have been entitled to receive a fraction of a Boston Scientific Share or Boston Scientific Shares shall receive in lieu of cash (rounded to the nearest cent) (x) equal to the product obtained by multiplying (i) the fractional share to which such person (after taking into account (A) all Certificates surrendered by such holder and all Book-Entry Shares or (B) in the case of holders of Penumbra Equity Awards, all Penumbra Shares that were subject to Penumbra Equity Awards that were formerly

held by such holder and were converted into the right to receive the Stock Consideration) would otherwise be entitled, by (ii) the average of the volume weighted averages of the trading prices of Boston Scientific Common Stock on the NYSE (as reported by Bloomberg L.P. or, if not reported therein, in another authoritative source mutually selected by parties in good faith) on each of the ten consecutive trading days ending on the trading day that is two trading days prior to the Closing Date or (y) pursuant to other to customary procedures and methodologies used by the Exchange Agent.

An Election Form, including a letter of transmittal and related instructions, will initially be mailed not less than twenty business days prior to the anticipated Election Deadline (or on such other date as Boston Scientific and Penumbra shall mutually agree) to each Penumbra Stockholder as of the close of business on the Election Form Record Date. The Election Form will allow Penumbra Stockholders to specify: (i) the number of such Penumbra Stockholder’s Penumbra Shares with respect to which to make a Cash Election; and (ii) the number of such Penumbra Stockholder’s Penumbra Shares with respect to which to make a Stock Election. Any Penumbra Shares (other than Excluded Shares) with respect to which the Exchange Agent has not received an effective, properly completed Election Form on or before the Election Deadline will be deemed to be Non-Election Shares.

Penumbra Stockholders wishing to make an election must properly complete and deliver to the Exchange Agent an Election Form by the Election Deadline, accompanied by duly executed transmittal materials included in the Election Form, along with, if their Penumbra Shares are not Book-Entry Shares, any Certificates. The Election Form will also include delivery instructions with respect to Book-Entry Shares. The Election Form will be provided to Penumbra Stockholders in a separate mailing and is not being provided with this proxy statement/prospectus. Penumbra and Boston Scientific will issue a press release announcing the date of the Election Deadline at least five business days prior to the Election Deadline. If the Closing Date is delayed to a subsequent date, the Election Deadline will be similarly delayed to a subsequent date, and Penumbra and Boston Scientific will promptly announce any such delay and, when determined, the rescheduled Election Deadline.

Neither Boston Scientific nor Penumbra is making any recommendation as to the Merger Consideration. Each Penumbra Stockholder must make his or her own decision with respect to such election.

Any Election Form may be revoked or changed by the authorized person properly submitting such Election Form, by written notice received by the Exchange Agent prior to the Election Deadline. In the event an Election Form is revoked prior to the Election Deadline, the Penumbra Shares represented by such Election Form shall become Non-Election Shares, except to the extent a subsequent election is properly made with respect to any or all of such Penumbra Shares prior to the Election Deadline. All elections shall be automatically deemed revoked upon receipt by the Exchange Agent of written notification from the parties that the Merger Agreement has been terminated in accordance with the terms hereof. If an election is revoked, any Certificates and other documents received by the Exchange Agent shall be promptly returned to the stockholder submitting the same to the Exchange Agent.

Subject to applicable law, there will be paid to the holder of the Boston Scientific Shares issued in exchange for Certificates or Book-Entry Shares, without interest, (i) at the time of delivery of such Boston Scientific Shares by the Exchange Agent, the amount of dividends or other distributions, if any, with a record date after the Effective Time before the time such Boston Scientific Shares were paid, and (ii) at the appropriate payment date, the amount of dividends or other distributions, if any, with a record date after the Effective Time but prior to such delivery of such Boston Scientific Shares by the Exchange Agent, and a payment date subsequent to such delivery of such Boston Scientific Shares by the Exchange Agent, payable with respect to such Boston Scientific Shares.