tm267838-1_sctot_DIV_04-exhibita1b - none

Exhibit (a)(1)(B)

LETTER OF TRANSMITTAL

To Tender Shares of Common Stock
of

ARCELLX, INC.

a Delaware corporation

$115.00 net per share in cash
plus one (1) contractual contingent value right (“CVR”) per share, which represents the right to receive one contingent cash payment of $5.00 per CVR, payable on March 31, 2030, if a specified milestone is achieved on
or prior to December 31, 2029

Pursuant to the Offer to Purchase
Dated March 6, 2026

RAVENS SUB, INC.

a wholly owned subsidiary of

GILEAD SCIENCES, INC.

THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT ONE MINUTE
AFTER 11:59 P.M., EASTERN TIME, ON APRIL 2, 2026,
UNLESS THE OFFER IS EXTENDED OR EARLIER TERMINATED.

The Depositary for the Offer is:

	By Mail:			By express mail, courier, or other expedited service:
	Computershare Trust Company, N.A. Attn: Voluntary Corporate Actions P.O. Box 43011 Providence, Rhode Island 02940-3011			Computershare Trust Company, N.A. Attn: Voluntary Corporate Actions 150 Royall Street, Suite V Canton, Massachusetts 02021

Delivery of this Letter of Transmittal to an address other than as set forth above will not constitute a valid delivery to the Depositary (as defined below). You must sign this Letter of Transmittal in the appropriate space provided therefor below, with signature guaranteed, if required, and complete the Internal Revenue Service (the “IRS”) Form W-9 included in this Letter of Transmittal, if required. Stockholders who are not United States persons (within the meaning of Section 7701(a)(30) of the Internal Revenue Code of 1986, as amended) should submit a properly completed and signed IRS Form W-8BEN or IRS Form W-8BEN-E, as applicable, or other appropriate IRS Form W-8. Failure to provide the information on IRS Form W-9 or an appropriate IRS Form W-8, as applicable, may subject you to United States federal income tax backup withholding on any payments made to you pursuant to the Offer (as defined below). The instructions set forth in this Letter of Transmittal should be read carefully before you tender any of your Shares (as defined below) into the Offer (as defined below).

		DESCRIPTION OF SHARES TENDERED
		Name(s) and Address(es) of Registered Holder(s) (Please fill in, if blank, exactly as name(s) appear(s) in book-entry form. If there is any error in the name or address shown below, please make the necessary corrections) (Attach additional signed list if necessary)				Total Number of Shares Tendered*
		Total Shares



		* Unless otherwise indicated, it will be assumed that all Shares described in the chart above are being tendered.

The Offer is being made to all holders of the shares of common stock, par value $0.001 per share (“Shares”), of Arcellx, Inc., a Delaware corporation (the “Company”). Ravens Sub, Inc., a Delaware corporation (“Purchaser”), is not aware of any jurisdiction in which the making of the Offer or the acceptance thereof would be prohibited by securities, “blue sky” or other valid laws of such jurisdiction. If Purchaser becomes aware of any U.S. state in which the making of the Offer or the acceptance of Shares pursuant thereto would not be in compliance with an administrative or judicial action taken pursuant to a U.S. state statute, Purchaser will make a good faith effort to comply with any such law. If, after such good faith effort, Purchaser cannot comply with any such law, the Offer will not be made to the holders of Shares in such state. In any jurisdictions where applicable laws require the Offer to be made by a licensed broker or dealer, the Offer shall be deemed to be made on behalf of Purchaser by one or more registered brokers or dealers licensed under the laws of such jurisdiction to be designated by Purchaser.

Unless an Agent’s Message (as defined in Section 3 of the Offer to Purchase, dated as of March 6, 2026 (together with any amendments or supplements thereto, the “Offer to Purchase”)) is utilized, this Letter of Transmittal is to be used by stockholders of the Company, for delivery of Shares to an account maintained by Computershare Trust Company, N.A., the depositary and paying agent for the Offer (the “Depositary”), at the Depositary Trust Company (“DTC”) (as described in Section 2 of the Offer to Purchase and pursuant to the procedures set forth in Section 3 thereof).

Additional Information if Shares are Being Delivered by Book-Entry Transfer

☐

CHECK HERE IF TENDERED SHARES ARE BEING DELIVERED BY BOOK-ENTRY TRANSFER MADE TO AN ACCOUNT MAINTAINED BY THE DEPOSITARY WITH DTC AND COMPLETE THE FOLLOWING (NOTE THAT ONLY FINANCIAL INSTITUTIONS THAT ARE PARTICIPANTS IN THE SYSTEM OF DTC MAY DELIVER SHARES BY BOOK-ENTRY TRANSFER):

	Name of Tendering Institution:
	DTC Account Number						Transaction Code Number

NOTE: SIGNATURES MUST BE PROVIDED BELOW.
PLEASE READ ACCOMPANYING INSTRUCTIONS CAREFULLY

Ladies and Gentlemen:

The undersigned hereby tenders to Ravens Sub, Inc., a Delaware corporation (“Purchaser”) and wholly owned subsidiary of Gilead Sciences, Inc., a Delaware corporation (“Parent”), the above described shares of common stock, par value $0.001 per share (“Shares”), of Arcellx, Inc., a Delaware corporation (the “Company”), pursuant to Purchaser’s offer to purchase each outstanding Share that is validly tendered and not validly withdrawn, at a price per Share of (i) $115.00 per Share (the “Closing Amount”), net to the seller in cash, without interest, subject to any withholding tax, plus (ii) one CVR, which represents the right to receive one contingent payment of $5.00 per CVR in cash, without interest, and subject to any withholding tax, payable on March 31, 2030, subject to cumulative worldwide Sales (as defined in the CVR Agreement (as defined below)) of the Company’s anitocabtagene autoleucel (anito-cel) product exceeding $6.0 billion on or prior to December 31, 2029 and the other terms and conditions set forth in a contingent value rights agreement (the “CVR Agreement”) to be entered into by and among Parent, Computershare, Inc., a Delaware corporation (“Computershare”), and its affiliate, Computershare Trust Company, N.A., a federally chartered trust company, upon the terms and subject to the conditions (including the Minimum Tender Condition (as defined in the Offer to Purchase)) described in the Offer to Purchase, dated as of March 6, 2026 (the “Offer to Purchase”), and in this Letter of Transmittal (this “Letter of Transmittal” which, together with the Offer to Purchase, as each may be amended and supplemented from time to time, collectively constitute the “Offer”), receipt of which is hereby acknowledged. The undersigned understands that Parent reserves the right to designate another wholly owned direct or indirect Delaware corporate subsidiary to act as Purchaser, in which event all references to Purchaser shall be deemed references to such other subsidiary.

Upon the terms and subject to the conditions of the Offer (and if the Offer is extended or amended, the terms of any such extension or amendment), and effective upon acceptance for payment of Shares tendered herewith and not validly withdrawn on or prior to the Expiration Date (as defined in Section 1 of the Offer to Purchase) in accordance with the terms of the Offer, the undersigned hereby sells, assigns and transfers to or upon the order of Purchaser all right, title and interest in and to all Shares that are being tendered hereby (and any and all dividends, distributions, rights, other Shares or other securities issued or issuable in respect thereof on or after the date hereof (collectively, “Distributions”)) and irrevocably constitutes and appoints each of the designees of Purchaser as the true and lawful agents and attorneys-in-fact of the undersigned with respect to such Shares (and any and all Distributions), with full power of substitution (such power of attorney being deemed to be an irrevocable power coupled with an interest in Shares tendered by this Letter of Transmittal), to (i) transfer ownership of such Shares (and any and all Distributions) on the account books maintained by DTC or otherwise held in book-entry form (including Shares held in book-entry form on the books of the Company or Computershare Trust Company, N.A., the Company’s transfer agent), together, in any such case, with all accompanying evidences of transfer and authenticity, to or upon the order of Purchaser, (ii) present such Shares (and any and all Distributions) for transfer on the books of the Company and (iii) receive all benefits and otherwise exercise all rights of beneficial ownership of such Shares (and any and all Distributions), all in accordance with the terms and subject to the conditions of the Offer.

By executing this Letter of Transmittal (or taking action resulting in the delivery of an Agent’s Message, as defined in Section 3 of the Offer to Purchase), the undersigned hereby irrevocably appoints each of the designees of Purchaser the attorneys-in-fact and proxies of the undersigned, each with full power of substitution, to (i) vote at any annual or special meeting of the Company stockholders or any adjournment or postponement thereof or otherwise in such manner as each such attorney-in-fact and proxy or its, his or her substitute shall in its, his or her sole discretion deem proper with respect to, (ii) execute any written consent concerning any matter as each such attorney-in-fact and proxy or its, his or her substitute shall in its, his or her sole discretion deem proper with respect to and (iii) otherwise act as each such attorney-in-fact and proxy or its, his or her substitute shall in its, his or her sole discretion deem proper with respect to, all Shares (and any and all Distributions) tendered hereby and accepted for payment by Purchaser. This appointment will be effective if and when, and only to the extent that, Purchaser accepts such Shares for payment pursuant to the Offer. This power of attorney and proxy are irrevocable and are granted in

consideration of the acceptance for payment of such Shares in accordance with the terms of the Offer. Such acceptance for payment shall, without further action, revoke any prior powers of attorney and proxies granted by the undersigned at any time with respect to such Shares (and any and all Distributions), and no subsequent powers of attorney, proxies, consents or revocations may be given by the undersigned with respect thereto (and, if given, will not be deemed effective). Purchaser reserves the right to require that, in order for Shares to be deemed validly tendered, immediately upon Purchaser’s acceptance for payment of such Shares, Purchaser or its designees must be able to exercise full voting, consent and other rights with respect to such Shares (and any and all Distributions), including voting at any meeting of the Company’s stockholders.

The undersigned hereby represents and warrants that the undersigned has full power and authority to tender, sell, assign and transfer any and all Shares tendered hereby (and any and all Distributions) and that, when the same are accepted for payment by Purchaser, Purchaser will acquire good and unencumbered title to such Shares (and such Distributions), free and clear of all liens, restrictions, charges and encumbrances and the same will not be subject to any adverse claims. The undersigned hereby represents and warrants that the undersigned is the registered owner of Shares, or the undersigned is a participant in DTC whose name appears on a security position listing as the owner of Shares. The undersigned will, upon request, promptly execute and deliver any additional documents and instruments deemed by the Depositary or Purchaser to be necessary or desirable to complete the sale, assignment and transfer of Shares tendered hereby (and any and all Distributions). In addition, the undersigned shall remit and transfer promptly to the Depositary for the account of Purchaser all Distributions in respect of any and all of Shares tendered hereby, accompanied by appropriate documentation of transfer, and, pending such remittance and transfer or appropriate assurance thereof, Purchaser shall be entitled to all rights and privileges as owner of each such Distribution and may withhold the entire purchase price of Shares tendered hereby or deduct from such purchase price the amount or value of such Distribution as determined by Purchaser in its sole discretion.

It is understood that the undersigned will not receive payment for Shares unless and until Shares are accepted for payment, together with such additional documents and instruments as the Depositary may require, and, in the case of a book-entry transfer, ownership of Shares is validly transferred on the account books maintained by DTC, and until the same are processed for payment by the Depositary.

IT IS UNDERSTOOD THAT THE METHOD OF DELIVERY OF SHARES AND ALL REQUIRED DOCUMENTS (INCLUDING DELIVERY THROUGH DTC) IS AT THE OPTION AND RISK OF THE UNDERSIGNED AND THAT THE RISK OF LOSS OF SUCH SHARES AND DOCUMENTS SHALL PASS ONLY AFTER THE DEPOSITARY HAS ACTUALLY RECEIVED SHARES BY BOOK-ENTRY CONFIRMATION (AS DEFINED BELOW) OR A LETTER OF TRANSMITTAL (AS APPLICABLE). IF DELIVERY IS BY MAIL, IT IS RECOMMENDED THAT ALL SUCH DOCUMENTS BE SENT BY PROPERLY INSURED REGISTERED MAIL WITH RETURN RECEIPT REQUESTED. DELIVERY WILL BE DEEMED EFFECTIVE AND RISK OF LOSS AND TITLE WILL PASS FROM THE OWNER ONLY WHEN RECEIVED BY THE DEPOSITARY. IN ALL CASES, SUFFICIENT TIME SHOULD BE ALLOWED TO ENSURE TIMELY DELIVERY.

All authority herein conferred or agreed to be conferred shall not be affected by, and shall survive the death or incapacity of the undersigned, and any obligation of the undersigned hereunder shall be binding upon the heirs, executors, administrators, personal representatives, trustees in bankruptcy, successors and assigns of the undersigned. Except as stated in the Offer to Purchase, this tender is irrevocable.

The undersigned understands that the valid tender of Shares pursuant to any of the procedures described in the Offer to Purchase and in the instructions hereto will constitute the undersigned’s acceptance of the terms and conditions of the Offer. Purchaser’s acceptance of such Shares for payment will constitute a binding agreement between the undersigned and Purchaser upon the terms and subject to the conditions of the Offer (and if the Offer is extended or amended, the terms and conditions of such extension or amendment). The undersigned recognizes that under certain circumstances set forth in the Offer, Purchaser may not be required to accept for payment any Shares tendered hereby.

Unless otherwise indicated under “Special Payment Instructions,” a check will be issued for the purchase price of all Shares purchased in the name(s) of the registered holder(s) appearing above under “Description of Shares Tendered.” Similarly, unless otherwise indicated under “Special Delivery Instructions,” the check for the purchase price of all Shares purchased will be mailed to the address(es) of the registered

holder(s) appearing above under “Description of Shares Tendered.” In the event that the boxes entitled “Special Payment Instructions” and “Special Delivery Instructions” are both completed, the check for the purchase price of all Shares purchased will be issued in the name(s) of the person(s) so indicated. Unless otherwise indicated herein in the box entitled “Special Payment Instructions,” any Shares tendered herewith by book-entry transfer that are not accepted for payment will be credited by book-entry transfer by crediting the account at DTC designated above. The undersigned recognizes that Purchaser has no obligation, pursuant to the “Special Payment Instructions,” to transfer any Shares from the name of the registered holder thereof if Purchaser does not accept for payment any Shares so tendered.

		SPECIAL PAYMENT INSTRUCTIONS (See Instructions 1, 4, 5 and 6):
		To be completed ONLY if the check for the purchase price of Shares accepted for payment is to be issued in the name of someone other than the undersigned. Issue check to:
		Name: (Please Print)
		Address: (Include Zip Code)
		(Taxpayer Identification No. (e.g., Social Security No.)) (Also complete, as appropriate, IRS Form W-9 included below)

		SPECIAL DELIVERY INSTRUCTIONS (See Instructions 1, 4, 5 and 6)
		To be completed ONLY if the check for the purchase price of Shares accepted for payment is to be mailed to someone other than the undersigned or to the undersigned at an address other than that shown above. Mail check to:
		Name: (Please Print)
		Address:
		(Include Zip Code)

IMPORTANT
STOCKHOLDER: YOU MUST SIGN BELOW
(U.S. Holders: Please complete and return the IRS Form W-9 included below)
(Non-U.S. Holders: Please obtain, complete and return appropriate IRS Form W-8)

(Signature(s) of Holder(s) of Shares)

Dated:

Name(s):

(Please Print)

Capacity (full title) (See Instruction 4):

Address:

(Include Zip Code)

Area Code and Telephone No.:

Tax Identification No. (e.g., Social Security No.) (See IRS Form W-9 included below):

(Must be signed by registered holder(s) exactly as name(s) appear(s) on a security position listing or by person(s) authorized to become registered holder(s) by documents transmitted herewith. If signature is by a trustee, executor, administrator, guardian, attorney-in-fact, agent, officer of a corporation or other person acting in a fiduciary or representative capacity, please set forth full title and see Instruction 4.)

INSTRUCTIONS
FORMING PART OF THE TERMS AND CONDITIONS OF THE OFFER

1. Guarantee of Signatures. No signature guarantee is required on this Letter of Transmittal (a) if this Letter of Transmittal is signed by the registered holder(s) (which term, for purposes of this Instruction, includes any participant in DTC’s systems whose name appears on a security position listing as the owner of Shares) of Shares tendered herewith, unless such registered holder has completed either the box entitled “Special Payment Instructions” or the box entitled “Special Delivery Instructions” on this Letter of Transmittal or (b) if such Shares are tendered for the account of a financial institution ( including most commercial banks, savings and loan associations and brokerage houses) that is a member in good standing of the Securities Transfer Agents Medallion Program or any other “eligible guarantor institution,” as such term is defined in Rule 17Ad-15 under the Securities Exchange Act of 1934, as amended (each, an “Eligible Institution”). In all other cases, including those referred to above, all signatures on this Letter of Transmittal must be guaranteed by an Eligible Institution. See Instruction 4.

2. Requirements of Tender. No alternative, conditional or contingent tenders will be accepted. In order for Shares to be validly tendered pursuant to the Offer, one of the following procedures must be followed:

Either a properly completed and duly executed Letter of Transmittal, together with any required signature guarantees (in respect of Shares tendered by any means other than book-entry transfer through DTC) or, in the case of a book-entry transfer through DTC, an Agent’s Message in lieu of this Letter of Transmittal, and any other required documents, must be received by the Depositary at the appropriate address set forth on the front page of this Letter of Transmittal, and such Shares must be delivered according to the procedures set forth in Section 3 of the Offer to Purchase or a timely confirmation of a book-entry transfer of Shares into the Depositary’s account at DTC (a “Book-Entry Confirmation”) must be received by the Depositary, in each case before the Expiration Date.

The method of delivery of Shares, this Letter of Transmittal and all other required documents, including delivery through DTC, is at the election and risk of the tendering stockholder. Shares will be deemed delivered only when actually received by the Depositary (including, in the case of a book-entry transfer, by Book-Entry Confirmation). If delivery is by mail, then registered mail with return receipt requested, properly insured, is recommended. In all cases, sufficient time should be allowed to ensure timely delivery.

No fractional Shares will be purchased. By executing this Letter of Transmittal, the tendering stockholder waives any right to receive any notice of the acceptance for payment of Shares.

3. Inadequate Space. If the space provided herein is inadequate, the number of Shares tendered should be listed on a separate signed schedule attached hereto.

4. Signatures on Letter of Transmittal; Stock Powers and Endorsements.

(a) Joint Holders. If any of Shares tendered hereby are held of record by two or more persons, all such persons must sign this Letter of Transmittal.

(b) Evidence of Fiduciary or Representative Capacity. If this Letter of Transmittal is signed by a trustee, executor, administrator, guardian, attorney-in-fact, officer of a corporation or other legal entity or other person acting in a fiduciary or representative capacity, such person should so indicate when signing, and proper evidence satisfactory to the Depositary of the authority of such person so to act must be submitted. Proper evidence of authority includes a power of attorney, a letter of testamentary or a letter of appointment.

5. Stock Transfer Taxes. Except as otherwise provided in this Instruction 5, Purchaser or any successor entity thereto will pay all stock transfer taxes with respect to the transfer and sale of any Shares to it pursuant to the Offer (for the avoidance of doubt, transfer taxes do not include U.S. federal income taxes or withholding taxes). If, however, consideration is to be paid to any person(s) other than the registered holder(s), or if Share(s) are registered in the name of any person(s) other than the person(s) signing this Letter of Transmittal, Purchaser will not be responsible for any stock transfer or similar taxes (whether imposed on the registered holder(s) or such other person(s) or otherwise) payable on account of the transfer,

and such taxes will be the responsibility of the registered owner, and no consideration shall be paid in respect of such Share(s) unless evidence satisfactory to Purchaser of the payment of such taxes, or exemption therefrom, is submitted.

6. Special Payment and Delivery Instructions. If a check is to be issued for the purchase price of any Shares tendered by this Letter of Transmittal in the name of any person(s) other than the signer of this Letter of Transmittal or if a check is to be returned to any person(s) other than the person(s) signing this Letter of Transmittal or to an address other than that shown in this Letter of Transmittal, the appropriate boxes on this Letter of Transmittal must be completed.

7. Tax Withholding. Under U.S. federal income tax laws, the Depositary may be required to withhold a portion of any payments made to certain stockholders pursuant to the Offer. To avoid such backup withholding, a tendering stockholder that is a United States person (within the meaning of Section 7701(a)(30) of the Internal Revenue Code of 1986, as amended), and, if applicable, each other U.S. payee, is required to (a) provide the Depositary with a correct Taxpayer Identification Number (“TIN”) on IRS Form W-9, which is included herein, and to certify, under penalty of perjury, that such number is correct and that such stockholder or payee is not subject to backup withholding of federal income tax or (b) otherwise establish a basis for exemption from backup withholding. Failure to provide the information on the IRS Form W-9 may subject the tendering stockholder or payee to backup withholding at the applicable rate (currently 24%), and such stockholder or payee may be subject to a penalty imposed by the IRS. See the enclosed IRS Form W-9 and the instructions thereto for additional information.

Certain stockholders or payees (including, among others, corporations) may not be subject to backup withholding. Exempt stockholders or payees that are United States persons should furnish their TIN, check the appropriate box on the IRS Form W-9 and sign, date and return the IRS Form W-9 to the Depositary in order to avoid backup withholding. A stockholder or other payee that is not a United States person may qualify as an exempt recipient by providing the Depositary with a properly completed IRS Form W-8BEN or IRS Form W-8BEN-E, as applicable, or other appropriate IRS Form W-8, signed under penalties of perjury, attesting to such stockholder or payee’s foreign status or by otherwise establishing an exemption. An appropriate IRS Form W-8 may be obtained from the Depositary or the IRS website (www.irs.gov).

Backup withholding is not an additional tax. Rather, the federal income tax liability of persons subject to backup withholding will be reduced by the amount of tax withheld. If backup withholding results in an overpayment of taxes, a refund or credit may be obtained from the IRS if eligibility is established and appropriate procedure is followed.

Information reporting to the IRS may also apply to the receipt of cash pursuant to the Offer.

If you are awaiting a TIN, please complete the “Certificate of Taxpayer Awaiting Identification Number” box below and complete the IRS Form W-9 included in this Letter of Transmittal.

8. Irregularities. All questions as to the validity, form, eligibility (including time of receipt) and acceptance for payment of any tender of Shares will be determined by Purchaser, in its sole discretion, which determination shall be final and binding on all parties. However, stockholders may challenge Purchaser’s determinations in a court of competent jurisdiction. Purchaser reserves the absolute right to reject any and all tenders determined by it not to be in proper form or the acceptance for payment of which may, in the opinion of its counsel, be unlawful. Purchaser also reserves the absolute right to waive any defect or irregularity in the tender of any Shares of any particular stockholder, whether or not similar defects or irregularities are waived in the case of other stockholders. No tender of Shares will be deemed to have been validly made until all defects and irregularities have been waived or cured within such time as Purchaser shall determine. None of Parent, Purchaser, the Depositary, Innisfree M&A Incorporated (the “Information Agent”) or any other person will be under any duty to give notice of any defects or irregularities in tenders or incur any liability for failure to give any such notice. Purchaser’s interpretation of the terms and conditions of the Offer (including the Letter of Transmittal and the instructions thereto) will be final and binding.

9. Questions and Requests for Additional Copies. The Information Agent may be contacted at the address and telephone number set forth on the last page of this Letter of Transmittal for questions and/or requests for additional copies of the Offer to Purchase, this Letter of Transmittal and other tender offer

materials. You may also contact your broker, dealer, commercial bank, trust company or other nominee for assistance. Such copies will be furnished promptly at Purchaser’s expense.

This Letter of Transmittal, properly completed and duly executed, together with any required signature guarantees (in respect of Shares tendered by any means other than book-entry transfer through DTC) or, in respect of Shares tendered by book-entry transfer through DTC, an Agent’s Message (in lieu of this Letter of Transmittal) and a Book-Entry Confirmation into the Depositary’s account at DTC, together with any other documents required by this Letter of Transmittal or the Depositary, must be received before the Expiration Date.

		CERTIFICATE OF TAXPAYER AWAITING IDENTIFICATION NUMBER
		I certify under the penalties of perjury that a taxpayer identification number has not been issued to me, and either (a) I have mailed or delivered an application to receive a taxpayer identification number to the appropriate Internal Revenue Service Center or Social Security Administration Office, or (b) I intend to mail or deliver an application in the near future. I understand that if I do not provide a taxpayer identification number to the Depositary or otherwise establish an exemption from backup withholding, 24% of all reportable payments made to me will be withheld, but will be refunded to me if I provide a certified taxpayer identification number within 60 days.
		Signature:			Date: