Organization and Description of the Business	3 Months Ended
Mar. 31, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of the Business	1. ORGANIZATION AND DESCRIPTION OF THE BUSINESS Description of Business Tempest Therapeutics is a clinical-stage biotechnology company developing a pipeline of advanced CAR-T cell therapy product candidates to treat cancer. Tempest is headquartered in Brisbane, California. Reverse Stock Split On December 3, 2024, the Company’s stockholders approved a proposal to effect an amendment to the Company’s Restated Certificate of Incorporation to implement a reverse stock split. On April 4, 2025, the Company filed a certificate of amendment to the Company’s Restated Certificate of Incorporation with the Secretary of State of the State of Delaware to effect the one-for-thirteen (1:13) reverse stock split of its outstanding common stock (the “Reverse Stock Split”). On April 8, 2025, the Company effected the Reverse Stock Split. Pursuant to their terms, a proportionate adjustment was made to the per share exercise price and number of shares issuable under all of the Company’s outstanding options and warrants, and the number of shares authorized for issuance pursuant to the Company’s equity incentive plans have been reduced proportionately. The Reverse Stock Split did not reduce the number of authorized shares of common stock and did not alter the par value. No fractional shares were issued as a result of the Reverse Stock Split. Stockholders of record who would have otherwise been entitled to receive a fractional share received a cash payment in lieu thereof. The Reverse Stock Split affected all stockholders proportionately and did not affect any stockholder’s percentage ownership of the Company’s common stock (except to the extent that the Reverse Stock Split resulted in any stockholder owning only a fractional share). Liquidity and Going Concern The Company has incurred operating losses since inception. As of March 31, 2026, the Company had $1.8 million of cash and cash equivalents. While the Company implemented cost reductions in 2025, the Company has finite cash resources available to fund its operations. In April 2025, the Company announced plans to explore a full range of strategic alternatives to advance its promising clinical stage programs and maximize stockholder value. The Company retained MTS Health Partners, L.P., an internationally recognized financial advisor with substantial experience in the biotechnology industry, to support it with the strategic evaluation process. Further to such evaluations, as part of the cost reductions, the Company reduced its workforce by 21 of 26 full-time employees, which became effective April 30, 2025. Further, in support of such efforts, on June 5, 2025, each of Stephen Brady, the Company’s Chief Executive Officer and President, Samuel Whiting, the Company’s Executive Vice President and Chief Medical Officer, and Nicholas Maestas, the Company’s Chief Financial Officer and Head of Corporate Strategy, transitioned to consulting arrangements with the Company, pursuant to which they continued to serve the Company in their respective executive roles. The Company incurred $3.2 million of one-time cash severance payments, benefits and other related costs (excluding non-cash charges associated with stock-based compensation), with the majority of such costs incurred in the second quarter of 2025. On February 3, 2026, the Company closed the Asset Acquisition (as defined below). Pursuant to the Asset Purchase Agreement (as defined below), Factor (as defined below) has made the Funding Commitment (as defined below) to provide the Company with financial support for at least 18 months following the closing of the Asset Acquisition, up to a maximum amount of $20.0 million that is inclusive of any amounts raised and received by the Company after the date of the Asset Purchase Agreement, on the terms and subject to the conditions and other provisions of a funding commitment letter contemplated by and entered into concurrently with the Asset Purchase Agreement. However, there is significant uncertainty as to whether we will be able to satisfy the terms and conditions and other provisions set forth in the funding commitment letter, and, if we are unable to do so, we may be limited in the amount of funding that we are able to access under the Funding Commitment or we may not be able to access any funds under the Funding Commitment. The timing of any additional funding from Factor is uncertain. As of March 31, 2026, $13.8 million of availability remained under the Funding Commitment. Further, as detailed below under “—Private Placement,” the Company has undertaken other steps to increase its cash and cash equivalents. On March 20, 2026, the Company entered into a securities purchase agreement for the sale of securities for approximately $2.0 million in gross proceeds (excluding up to approximately $4.0 million of aggregate gross proceeds that may be received in the future upon the cash exercise of the Common Warrants), before deducting placement agent fees and other offering expenses payable by the Company. The Company expects that its existing cash and cash equivalents will fund the Company’s projected operating expense requirements through less than 12 months from the date our consolidated financial statements were available to be issued. Accordingly, there is substantial doubt about the Company’s ability to continue to operate as a going concern for a period of 12 months from the date of issuance of these consolidated financial statements. The accompanying financial statements were prepared on a going concern basis, which contemplates the realization of assets and the satisfaction of liabilities in the normal course of business. These financial statements do not include any separate adjustments relating to the recovery of recorded assets or the classification of liabilities; however, such adjustments may be necessary in the future when the Company is unable to continue as a going concern. The Company is actively exploring a range of options to raise additional funds. Acquisition of Erigen Assets On November 19, 2025, the Company executed an Asset Purchase Agreement (the “Asset Purchase Agreement”) with Erigen LLC, a Delaware limited liability company (“Erigen”), and Factor Bioscience Inc., a Delaware corporation (“Factor,” and together with Erigen, “Sellers”), pursuant to which Sellers agreed to sell and transfer to the Company all right, title and interest of Sellers in and to all of the assets primarily related to (a) the autologous BCMA/CD19 dual-targeting CAR T-cell therapy known as TPST-2003, (b) the autologous CD70/CD70 dual-targeting CAR T-cell therapy known as TPST-2206, (c) the allogeneic BCMA/CD19 dual-targeting CAR T-cell therapy with a gene edit in the TRAC locus that inactivates the T cell receptor known as TPST-3003, and (d) the allogeneic CD70/CD70 dual-targeting CAR T-cell therapy with a gene edit in the TRAC locus that inactivates the T cell receptor known as TPST-3206 (collectively referred to herein as the “Erigen Assets”), in exchange for an aggregate purchase price of 8,268,495 shares of the Company’s common stock to be issued to Erigen on behalf of both Sellers. On February 3, 2026, the Company completed the acquisition of the Erigen Assets (the “Erigen Closing”) under the Asset Purchase Agreement (the “Asset Acquisition”) and issued to Erigen 8,268,495 shares of the Company’s common stock. Based on the closing price of the Company’s common stock price of $2.41 per share on February 3, 2026, the aggregate fair value of equity issued in the Asset Acquisition was approximately $19.9 million. The Company accounted for the Asset Acquisition as an asset acquisition. In addition to the $19.9 million in aggregate fair value of equity issued, approximately $2.2 million in transaction costs were capitalized as part of the total cost of the Asset Acquisition, totaling $22.1 million expensed as acquired in-process research and development during the three months ended March 31, 2026. During the year ended December 31, 2025, approximately $2.2 million of transaction costs were incurred and expensed as General and administrative expense prior to the closing of the Asset Acquisition. The fair value of the shares issued was recorded as an increase to common stock (at par) and additional paid-in capital on the date of the Erigen Closing. Pursuant to the Asset Purchase Agreement, Factor has made a funding commitment (the “Funding Commitment”) to provide the Company with financial support for at least 18 months following the Erigen Closing, up to a maximum amount of $20.0 million that is inclusive of any amounts raised and received by us after the date of the Asset Purchase Agreement, on the terms and subject to the conditions and other provisions of a funding commitment letter contemplated by and entered into concurrently with the Asset Purchase Agreement. In November 2025, Erigen entered into an Amended and Restated Master Services Agreement with Factor (the “Factor MSA”), which was assigned to the Company in connection with the Erigen Closing pursuant to the Asset Purchase Agreement. Under the Factor MSA, the Company is obligated to pay Factor a service fee and all non-cancellable obligations in the amount specified in each work order associated with the agreement for the provision of services. The term of each work order terminates upon completion of the services under such work order, unless terminated earlier. The Company can terminate the Factor MSA or any work order at any time upon 30 days’ prior written notice and immediately upon written notice if Factor breaches the Factor MSA or any work order, as the case may be, and does not fully cure the breach to the Company's satisfaction within 30 days. Upon termination any work order, unless the applicable work order expressly provides otherwise, the Company will pay Factor fees for all services performed and reimburse Factor for all authorized, non-cancellable expenses reasonably incurred in connection with such services prior to termination. In March 2026 the Board of the Company approved and authorized the execution of Work Order No. 1 under the Factor MSA for R&D services beginning April 2026. Under this agreement, the Company is committed to pay Factor for services through March 31, 2027. As of March 31, 2026, no amounts were incurred or payable under this arrangement. In April 2026, the Company paid Factor a deposit of $0.4 million under Work Order No. 1 of the Factor MSA related to the clinical advancement of TPST-2003. On May 11, 2026, the Company entered into a letter agreement (the “Letter Agreement”) with Factor relating to certain payment obligations of the Company under the Factor MSA and Work Order No. 1 (the “Work Order”). Pursuant to the Letter Agreement, Factor agreed to permanently waive its right to receive the first $2.1 million payable by the Company to Factor under the Factor MSA and the Work Order. In addition, Factor agreed to return to the Company a deposit of $0.2 million previously made by the Company under the Work Order, for an interim period subject to certain conditions. Warrant Dividend On January 20, 2026, the Company’s Board of Directors declared a record date of January 30, 2026 (the “Record Date”), for the distribution of a dividend (the “Warrant Dividend”) in the form of a warrant to purchase a share of the Company’s common stock (collectively, the “Warrants”) for each share of common stock outstanding on the Record Date at an exercise price of $18.48 per share. The Warrants were issued on the terms and conditions described in the Warrant Agreement, dated February 3, 2026, between the Company, Computershare Inc., and its affiliate, Computershare Trust Company, N.A., as Warrant Agent, on February 3, 2026. In addition, on February 3, 2026, certain warrants that were outstanding on the Record Date also received Warrants on a one-for-one basis, pursuant to the terms of such warrants (together with the Warrant Dividend, the “Warrant Distribution”). In the aggregate, 6,784,989 Warrants were issued pursuant to the Warrant Distribution. Private Placement On March 20, 2026, the Company entered into a securities purchase agreement (the “Purchase Agreement”) with (a) two institutional investors (the “Institutional Investors”) and (b) Factor (together with the Institutional Investors, each, an “Investor” and, together, the “Investors”), pursuant to which the Company agreed to issue and sell in a private placement (the “Private Placement”) an aggregate of 462,964 shares (the “Shares”) of the Company’s common stock, and, in lieu of common stock, pre-funded warrants to purchase up to 462,963 shares of common stock (the “2026 Pre-Funded Warrants”), in each case accompanied by (i) Series A warrants to purchase up to 925,927 shares of common stock (the “Series A Warrants”) and (ii) Series B warrants to purchase up to 925,927 shares of common stock (the “Series B Warrants” and, together with the Series A Warrants, the “Common Warrants”). The Shares and the Pre-Funded and Common Warrants are immediately separable and were issued separately. The combined purchase price per Share and accompanying Common Warrants was $2.16 and the combined purchase price per Pre-Funded Warrant and accompanying Common Warrants was $2.159. The gross proceeds to us from the Private Placement were approximately $2.0 million (excluding up to approximately $4.0 million of aggregate gross proceeds that may be received in the future upon the cash exercise of the Common Warrants), before deducting placement agent fees and other offering expenses payable by the Company. All 2026 Pre-Funded Warrants were subsequently exercised in April 2026. Pursuant to the Purchase Agreement, the Company agreed to seek approval from our stockholders for the issuance of the shares issuable upon exercise of the Common Warrants within 90 days following the date of the Purchase Agreement (the “Stockholder Approval”). The Series A Warrants will become exercisable on the effective date of the Stockholder Approval (the “Stockholder Approval Date”) and have a term of five years from the later of the Stockholder Approval Date and the Effectiveness Date (as defined below). The Series B Warrants will become exercisable on the Stockholder Approval Date and have a term of twenty-four months from the later of the Stockholder Approval Date and the Effectiveness Date. The Common Warrants have an exercise price of $2.16 per share. The Pre-Funded Warrants are exercisable immediately following the closing date of the Private Placement have an exercise price of $0.001 per share and may be exercised at any time until exercised in full. In addition, pursuant to the Purchase Agreement, the Company agreed not to sell any shares of the Company’s common stock or any securities convertible into or exercisable or exchangeable into shares of common stock, subject to certain customary exceptions, for a period of thirty (30) days after the Effectiveness Date. In connection with the Private Placement, the Company entered into a registration rights agreement with the Investors (the “Registration Rights Agreement”), pursuant to which the Company agreed to file registration statements under the Securities Act with the SEC covering the resale of the Shares to be issued in the Private Placement and the shares of the Company’s common stock underlying the Common Warrants and Pre-Funded Warrants no later than 15 calendar days following the date of the Purchase Agreement, and to use reasonable best efforts to have the registration statement declared effective by 45 calendar days following the date of the Purchase Agreement, and in any event no later than 75 calendar days following the date of the Purchase Agreement in the event of a “full review” by the SEC (the “Effectiveness Date”). The registration statement was filed on April 2, 2026 and declared effective on April 9, 2026. ATM Program On July 23, 2021, the Company entered into a sales agreement with Jefferies LLC (“Jefferies”), pursuant to which the Company may sell, from time to time at its sole discretion through Jefferies, as its sales agent, shares of its common stock having, up to an aggregate sales price of $100.0 million of its common stock through Jefferies (the “Prior ATM Program”). As of June 20, 2024, the Company had sold an aggregate 9,017,110 shares of its common stock for gross proceeds of $42.7 million ($41.5 million net of commissions and estimated expenses) under the Prior ATM Program. On June 20, 2024, the Company and Jefferies terminated the Prior ATM Program and entered a new Open Market Sale Agreement (the “Sales Agreement”) to sell shares of common stock from time to time through Jefferies acting as sales agent (the “ATM Program”). The Company will pay Jefferies a commission up to 3.0% of the gross sales proceeds of any shares of its common stock sold through Jefferies under the ATM Program and also has provided Jefferies with indemnification and contribution rights. Pursuant to the prospectus supplement dated June 20, 2024 filed by the Company with the U.S. Securities and Exchange Commission (“SEC”), the Company was able to offer and sell up to $205.0 million of its shares of common stock pursuant to the Sales Agreement. On February 6, 2025, the Company filed a prospectus supplement with the SEC limiting the availability under the ATM Program to $14.5 million. On June 11, 2025, in connection with the RDO (as defined below), the Company delivered written notice to Jefferies that it was suspending and terminating the prospectus supplement, dated February 6, 2025, related to the ATM Program (the “ATM Prospectus”). The Company will not make any sales of its securities pursuant to the Sales Agreement, unless and until a new prospectus, prospectus supplement or a new registration statement is filed. Other than the termination of the ATM Prospectus, the Sales Agreement remains in full force and effect. Under current SEC regulations, if at any time the Company's public float is less than $75.0 million, and for so long as the Company’s public float remains less than $75.0 million, the amount the Company can raise through primary public offerings of securities in any 12-month period using shelf registration statements is limited to an aggregate of one-third of the Company's public float, which is referred to as the baby shelf rules. As of the three months ended March 31, 2026, the Company has not sold any shares, pursuant to the ATM Program. Registered Direct Offerings On June 11, 2025, the Company sold an aggregate of 405,000 shares of the Company’s common stock and pre-funded warrants to purchase 334,000 shares of its common stock (the “June 2025 Pre-Funded Warrants”) in a registered direct offering (“June RDO”). The offering price was $6.25 per share of common stock and $6.249 per June 2025 Pre-Funded Warrant, which is the price of each share of common stock sold in the RDO, minus the $0.001 exercise price per June 2025 Pre-Funded Warrant. The net proceeds from the RDO were approximately $4.1 million, after deducting placement agent fees and offering expenses payable by the Company. As of March 31, 2026, all June 2025 Pre-Funded Warrants were exercised. On November 24, 2025, the Company sold an aggregate of 487,000 shares of the Company's common stock, pre-funded warrants to purchase 685,414 shares of its common stock (the “November 2025 Pre-Funded Warrants”) and warrants to purchase an aggregate of 1,172,414 shares of common stock (the “Common Warrants”) in a registered direct offering (the “November RDO”). The combined purchase price of each share of common stock and accompanying Common Warrant was $3.625. The combined purchase price of each November 2025 Pre-Funded Warrants and accompanying Common Warrant was $3.624 (equal to the combined purchase price per share of common stock and accompanying Common Warrant, minus $0.001) The exercise price of the Common Warrants is $3.50 per share. The net proceeds from the RDO were approximately $3.8 million, after deducting placement agent fees and estimated offering expenses payable by the Company. As of March 31, 2026, all November 2025 Common Warrants remained outstanding. As of March 31, 2026, all November 2025 Pre-Funded Warrants had been exercised.

Organization and Description of the Business

3 Months Ended

Mar. 31, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Organization and Description of the Business

1. ORGANIZATION AND DESCRIPTION OF THE BUSINESS

Description of Business

Tempest Therapeutics is a clinical-stage biotechnology company developing a pipeline of advanced CAR-T cell therapy product candidates to treat cancer. Tempest is headquartered in Brisbane, California.

Reverse Stock Split

On December 3, 2024, the Company’s stockholders approved a proposal to effect an amendment to the Company’s Restated Certificate of Incorporation to implement a reverse stock split. On April 4, 2025, the Company filed a certificate of amendment to the Company’s Restated Certificate of Incorporation with the Secretary of State of the State of Delaware to effect the one-for-thirteen (1:13) reverse stock split of its outstanding common stock (the “Reverse Stock Split”).

On April 8, 2025, the Company effected the Reverse Stock Split. Pursuant to their terms, a proportionate adjustment was made to the per share exercise price and number of shares issuable under all of the Company’s outstanding options and warrants, and the number of shares authorized for issuance pursuant to the Company’s equity incentive plans have been reduced proportionately. The Reverse Stock Split did not reduce the number of authorized shares of common stock and did not alter the par value.

No fractional shares were issued as a result of the Reverse Stock Split. Stockholders of record who would have otherwise been entitled to receive a fractional share received a cash payment in lieu thereof. The Reverse Stock Split affected all stockholders proportionately and did not affect any stockholder’s percentage ownership of the Company’s common stock (except to the extent that the Reverse Stock Split resulted in any stockholder owning only a fractional share).

Liquidity and Going Concern

The Company has incurred operating losses since inception. As of March 31, 2026, the Company had $1.8 million of cash and cash equivalents. While the Company implemented cost reductions in 2025, the Company has finite cash resources available to fund its operations. In April 2025, the Company announced plans to explore a full range of strategic alternatives to advance its promising clinical stage programs and maximize stockholder value. The Company retained MTS Health Partners, L.P., an internationally recognized financial advisor with substantial experience in the biotechnology industry, to support it with the strategic evaluation process. Further to such evaluations, as part of the cost reductions, the Company reduced its workforce by 21 of 26 full-time employees, which became effective April 30, 2025. Further, in support of such efforts, on June 5, 2025, each of Stephen Brady, the Company’s Chief Executive Officer and President, Samuel Whiting, the Company’s Executive Vice President and Chief Medical Officer, and Nicholas Maestas, the Company’s Chief Financial Officer and Head of Corporate Strategy, transitioned to consulting arrangements with the Company, pursuant to which they continued to serve the Company in their respective executive roles. The Company incurred $3.2 million of one-time cash severance payments, benefits and other related costs (excluding non-cash charges associated with stock-based compensation), with the majority of such costs incurred in the second quarter of 2025.

On February 3, 2026, the Company closed the Asset Acquisition (as defined below). Pursuant to the Asset Purchase Agreement (as defined below), Factor (as defined below) has made the Funding Commitment (as defined below) to provide the Company with financial support for at least 18 months following the closing of the Asset Acquisition, up to a maximum amount of $20.0 million that is inclusive of any amounts raised and received by the Company after the date of the Asset Purchase Agreement, on the terms and subject to the conditions and other provisions of a funding commitment letter contemplated by and entered into concurrently with the Asset Purchase Agreement. However, there is significant uncertainty as to whether we will be able to satisfy the terms and conditions and other provisions set forth in the funding commitment letter, and, if we are unable to do so, we may be limited in the amount of funding that we are able to access under the Funding Commitment or we

may not be able to access any funds under the Funding Commitment. The timing of any additional funding from Factor is uncertain. As of March 31, 2026, $13.8 million of availability remained under the Funding Commitment.

Further, as detailed below under “—Private Placement,” the Company has undertaken other steps to increase its cash and cash equivalents. On March 20, 2026, the Company entered into a securities purchase agreement for the sale of securities for approximately $2.0 million in gross proceeds (excluding up to approximately $4.0 million of aggregate gross proceeds that may be received in the future upon the cash exercise of the Common Warrants), before deducting placement agent fees and other offering expenses payable by the Company.

The Company expects that its existing cash and cash equivalents will fund the Company’s projected operating expense requirements through less than 12 months from the date our consolidated financial statements were available to be issued. Accordingly, there is substantial doubt about the Company’s ability to continue to operate as a going concern for a period of 12 months from the date of issuance of these consolidated financial statements. The accompanying financial statements were prepared on a going concern basis, which contemplates the realization of assets and the satisfaction of liabilities in the normal course of business. These financial statements do not include any separate adjustments relating to the recovery of recorded assets or the classification of liabilities; however, such adjustments may be necessary in the future when the Company is unable to continue as a going concern.

The Company is actively exploring a range of options to raise additional funds.

Acquisition of Erigen Assets

On November 19, 2025, the Company executed an Asset Purchase Agreement (the “Asset Purchase Agreement”) with Erigen LLC, a Delaware limited liability company (“Erigen”), and Factor Bioscience Inc., a Delaware corporation (“Factor,” and together with Erigen, “Sellers”), pursuant to which Sellers agreed to sell and transfer to the Company all right, title and interest of Sellers in and to all of the assets primarily related to (a) the autologous BCMA/CD19 dual-targeting CAR T-cell therapy known as TPST-2003, (b) the autologous CD70/CD70 dual-targeting CAR T-cell therapy known as TPST-2206, (c) the allogeneic BCMA/CD19 dual-targeting CAR T-cell therapy with a gene edit in the TRAC locus that inactivates the T cell receptor known as TPST-3003, and (d) the allogeneic CD70/CD70 dual-targeting CAR T-cell therapy with a gene edit in the TRAC locus that inactivates the T cell receptor known as TPST-3206 (collectively referred to herein as the “Erigen Assets”), in exchange for an aggregate purchase price of 8,268,495 shares of the Company’s common stock to be issued to Erigen on behalf of both Sellers.

On February 3, 2026, the Company completed the acquisition of the Erigen Assets (the “Erigen Closing”) under the Asset Purchase Agreement (the “Asset Acquisition”) and issued to Erigen 8,268,495 shares of the Company’s common stock. Based on the closing price of the Company’s common stock price of $2.41 per share on February 3, 2026, the aggregate fair value of equity issued in the Asset Acquisition was approximately $19.9 million.

The Company accounted for the Asset Acquisition as an asset acquisition. In addition to the $19.9 million in aggregate fair value of equity issued, approximately $2.2 million in transaction costs were capitalized as part of the total cost of the Asset Acquisition, totaling $22.1 million expensed as acquired in-process research and development during the three months ended March 31, 2026. During the year ended December 31, 2025, approximately $2.2 million of transaction costs were incurred and expensed as General and administrative expense prior to the closing of the Asset Acquisition. The fair value of the shares issued was recorded as an increase to common stock (at par) and additional paid-in capital on the date of the Erigen Closing.

Pursuant to the Asset Purchase Agreement, Factor has made a funding commitment (the “Funding Commitment”) to provide the Company with financial support for at least 18 months following the Erigen Closing, up to a maximum amount of $20.0 million that is inclusive of any amounts raised and received by us after the date of the Asset Purchase Agreement, on the terms and subject to the conditions and other provisions of a funding commitment letter contemplated by and entered into concurrently with the Asset Purchase Agreement.

In November 2025, Erigen entered into an Amended and Restated Master Services Agreement with Factor (the “Factor MSA”), which was assigned to the Company in connection with the Erigen Closing pursuant to the Asset Purchase Agreement. Under the Factor MSA, the Company is obligated to pay Factor a service fee and all non-cancellable obligations in the amount specified in each work order associated with the agreement for the provision of services. The term of each work order terminates upon completion of the services under such work order, unless terminated earlier. The Company can terminate the Factor MSA or any work order at any time upon 30 days’ prior written notice and immediately upon written notice if Factor breaches the Factor MSA or any work order, as the case may be, and does not fully cure the breach to the Company's satisfaction within 30 days. Upon termination any work order, unless the applicable work order expressly provides otherwise, the Company will pay Factor fees for all services performed and reimburse Factor for all authorized, non-cancellable expenses reasonably incurred in connection with such services prior to termination.

In March 2026 the Board of the Company approved and authorized the execution of Work Order No. 1 under the Factor MSA for R&D services beginning April 2026. Under this agreement, the Company is committed to pay Factor for services through March 31, 2027. As of March 31, 2026, no amounts were incurred or payable under this arrangement. In April 2026, the Company paid Factor a deposit of $0.4 million under Work Order No. 1 of the Factor MSA related to the clinical advancement of TPST-2003.

On May 11, 2026, the Company entered into a letter agreement (the “Letter Agreement”) with Factor relating to certain payment obligations of the Company under the Factor MSA and Work Order No. 1 (the “Work Order”). Pursuant to the Letter Agreement, Factor agreed to permanently waive its right to receive the first $2.1 million payable by the Company to Factor under the Factor MSA and the Work Order. In addition, Factor agreed to return to the Company a deposit of $0.2 million previously made by the Company under the Work Order, for an interim period subject to certain conditions.

Warrant Dividend

On January 20, 2026, the Company’s Board of Directors declared a record date of January 30, 2026 (the “Record Date”), for the distribution of a dividend (the “Warrant Dividend”) in the form of a warrant to purchase a share of the Company’s common stock (collectively, the “Warrants”) for each share of common stock outstanding on the Record Date at an exercise price of $18.48 per share. The Warrants were issued on the terms and conditions described in the Warrant Agreement, dated February 3, 2026, between the Company, Computershare Inc., and its affiliate, Computershare Trust Company, N.A., as Warrant Agent, on February 3, 2026. In addition, on February 3, 2026, certain warrants that were outstanding on the Record Date also received Warrants on a one-for-one basis, pursuant to the terms of such warrants (together with the Warrant Dividend, the “Warrant Distribution”). In the aggregate, 6,784,989 Warrants were issued pursuant to the Warrant Distribution.

Private Placement

On March 20, 2026, the Company entered into a securities purchase agreement (the “Purchase Agreement”) with (a) two institutional investors (the “Institutional Investors”) and (b) Factor (together with the Institutional Investors, each, an “Investor” and, together, the “Investors”), pursuant to which the Company agreed to issue and sell in a private placement (the “Private Placement”) an aggregate of 462,964 shares (the “Shares”) of the Company’s common stock, and, in lieu of common stock, pre-funded warrants to purchase up to 462,963 shares of common stock (the “2026 Pre-Funded Warrants”), in each case accompanied by (i) Series A warrants to purchase up to 925,927 shares of common stock (the “Series A Warrants”) and (ii) Series B warrants to purchase up to 925,927 shares of common stock (the “Series B Warrants” and, together with the Series A Warrants, the “Common Warrants”). The Shares and the Pre-Funded and Common Warrants are immediately separable and were issued separately. The combined purchase price per Share and accompanying Common Warrants was $2.16 and the combined purchase price per Pre-Funded Warrant and accompanying Common Warrants was $2.159. The gross proceeds to us from the Private Placement were approximately $2.0 million (excluding up to approximately $4.0 million of aggregate gross proceeds that may be received in the future upon the cash exercise of the Common Warrants), before deducting placement agent fees and other offering expenses payable by the Company. All 2026 Pre-Funded Warrants were subsequently exercised in April 2026.

Pursuant to the Purchase Agreement, the Company agreed to seek approval from our stockholders for the issuance of the shares issuable upon exercise of the Common Warrants within 90 days following the date of the Purchase Agreement (the “Stockholder Approval”). The Series A Warrants will become exercisable on the effective date of the Stockholder Approval (the “Stockholder Approval Date”) and have a term of five years from the later of the Stockholder Approval Date and the Effectiveness Date (as defined below). The Series B Warrants will become exercisable on the Stockholder Approval Date and have a term of twenty-four months from the later of the Stockholder Approval Date and the Effectiveness Date. The Common Warrants have an exercise price of $2.16 per share. The Pre-Funded Warrants are exercisable immediately following the closing date of the Private Placement have an exercise price of $0.001 per share and may be exercised at any time until exercised in full. In addition, pursuant to the Purchase Agreement, the Company agreed not to sell any shares of the Company’s common stock or any securities convertible into or exercisable or exchangeable into shares of common stock, subject to certain customary exceptions, for a period of thirty (30) days after the Effectiveness Date.

In connection with the Private Placement, the Company entered into a registration rights agreement with the Investors (the “Registration Rights Agreement”), pursuant to which the Company agreed to file registration statements under the Securities Act with the SEC covering the resale of the Shares to be issued in the Private Placement and the shares of the Company’s common stock underlying the Common Warrants and Pre-Funded Warrants no later than 15 calendar days following the date of the Purchase Agreement, and to use reasonable best efforts to have the registration statement declared effective by 45 calendar days following the date of the Purchase Agreement, and in any event no later than 75 calendar days following the date of the Purchase Agreement in the event of a “full review” by the SEC (the “Effectiveness Date”). The registration statement was filed on April 2, 2026 and declared effective on April 9, 2026.

ATM Program

On July 23, 2021, the Company entered into a sales agreement with Jefferies LLC (“Jefferies”), pursuant to which the Company may sell, from time to time at its sole discretion through Jefferies, as its sales agent, shares of its common stock having, up to an aggregate sales price of $100.0 million of its common stock through Jefferies (the “Prior ATM Program”). As of June 20, 2024, the Company had sold an aggregate 9,017,110 shares of its common stock for gross proceeds of $42.7 million ($41.5 million net of commissions and estimated expenses) under the Prior ATM Program. On June 20, 2024, the Company and Jefferies terminated the Prior ATM Program and entered a new Open Market Sale Agreement (the “Sales Agreement”) to sell shares of common stock from time to time through Jefferies acting as sales agent (the “ATM Program”). The Company will pay Jefferies a commission up to 3.0% of the gross sales proceeds of any shares of its common stock sold through Jefferies under the ATM Program and also has provided Jefferies with indemnification and contribution rights. Pursuant to the prospectus supplement dated June 20, 2024 filed by the Company with the U.S. Securities and Exchange Commission (“SEC”), the Company was able to offer and sell up to $205.0 million of its shares of common stock pursuant to the Sales Agreement. On February 6, 2025, the Company filed a prospectus supplement with the SEC limiting the availability under the ATM Program to $14.5 million. On June 11, 2025, in connection with the RDO (as defined below), the Company delivered written notice to Jefferies that it was suspending and terminating the prospectus supplement, dated February 6, 2025, related to the ATM Program (the “ATM Prospectus”). The Company will not make any sales of its securities pursuant to the Sales Agreement, unless and until a new prospectus, prospectus supplement or a new registration statement is filed. Other than the termination of the ATM Prospectus, the Sales Agreement remains in full force and effect.

Under current SEC regulations, if at any time the Company's public float is less than $75.0 million, and for so long as the Company’s public float remains less than $75.0 million, the amount the Company can raise through primary public offerings of securities in any 12-month period using shelf registration statements is limited to an aggregate of one-third of the Company's public float, which is referred to as the baby shelf rules. As of the three months ended March 31, 2026, the Company has not sold any shares, pursuant to the ATM Program.

Registered Direct Offerings

On June 11, 2025, the Company sold an aggregate of 405,000 shares of the Company’s common stock and pre-funded warrants to purchase 334,000 shares of its common stock (the “June 2025 Pre-Funded Warrants”) in a registered direct offering (“June RDO”). The offering price was $6.25 per share of common stock and $6.249 per June 2025 Pre-Funded Warrant, which is the

price of each share of common stock sold in the RDO, minus the $0.001 exercise price per June 2025 Pre-Funded Warrant. The net proceeds from the RDO were approximately $4.1 million, after deducting placement agent fees and offering expenses payable by the Company. As of March 31, 2026, all June 2025 Pre-Funded Warrants were exercised.

On November 24, 2025, the Company sold an aggregate of 487,000 shares of the Company's common stock, pre-funded warrants to purchase 685,414 shares of its common stock (the “November 2025 Pre-Funded Warrants”) and warrants to purchase an aggregate of 1,172,414 shares of common stock (the “Common Warrants”) in a registered direct offering (the “November RDO”). The combined purchase price of each share of common stock and accompanying Common Warrant was $3.625. The combined purchase price of each November 2025 Pre-Funded Warrants and accompanying Common Warrant was $3.624 (equal to the combined purchase price per share of common stock and accompanying Common Warrant, minus $0.001) The exercise price of the Common Warrants is $3.50 per share. The net proceeds from the RDO were approximately $3.8 million, after deducting placement agent fees and estimated offering expenses payable by the Company. As of March 31, 2026, all November 2025 Common Warrants remained outstanding. As of March 31, 2026, all November 2025 Pre-Funded Warrants had been exercised.