Exhibit (a)(1)(D)

Offer to Purchase

All Outstanding Shares of Common Stock

of

DYNAVAX TECHNOLOGIES CORPORATION

at

$15.50 PER SHARE, NET IN CASH

Pursuant to the Offer to Purchase dated January 12, 2026

by

SAMBA MERGER SUB, INC.

an indirect wholly owned subsidiary

of SANOFI

 

January 12, 2026

To Our Clients:

Enclosed for your consideration are the Offer to Purchase, dated January 12, 2026 (the “Offer to Purchase”), and the related letter of transmittal (the “Letter of Transmittal”), in connection with the offer by Samba Merger Sub, Inc., a Delaware corporation (“Purchaser”) and an indirect wholly owned subsidiary of Sanofi, a French société anonyme (“Parent”), to purchase all of the outstanding shares of common stock par value $0.001 per share (each, a “Share” and, collectively, the “Shares”) of Dynavax Technologies Corporation, a Delaware corporation (the “Company”), for $15.50 per Share, in cash (such amount or any higher amount per share paid pursuant to the Offer, being the “Offer Price”), without interest, subject to any applicable withholding taxes, upon the terms and subject to the conditions set forth in the Offer to Purchase and in the related Letter of Transmittal (which, together with the Offer to Purchase, as they may be amended or supplemented from time to time, collectively constitute the “Offer”).

Also enclosed is the Company’s Solicitation/Recommendation Statement on Schedule 14D-9.

THE BOARD OF DIRECTORS OF DYNAVAX TECHNOLOGIES CORPORATION UNANIMOUSLY RECOMMENDS THAT STOCKHOLDERS TENDER ALL OF THEIR SHARES TO PURCHASER PURSUANT TO THE OFFER.

We or our nominees are the holder of record of Shares held for your account. A tender of such Shares can be made only by us as the holder of record and pursuant to your instructions. The Letter of Transmittal is furnished to you for your information only and cannot be used by you to tender Shares held by us for your account.

We request instructions as to whether you wish us to tender any or all of the Shares held by us for your account, upon the terms and subject to the conditions set forth in the enclosed Offer to Purchase and the Letter of Transmittal.

Please note carefully the following:

1. The offer price for the Offer is $15.50 per Share in cash, without interest, subject to any applicable withholding taxes.

2. The Offer is being made for all outstanding Shares.

3. The Offer is being made pursuant to an Agreement and Plan of Merger, dated as of December 23, 2025 (as it may be amended, supplemented or otherwise modified from time to time, the “Merger Agreement”), by and among the Company, Parent and Purchaser. The Merger Agreement provides, among other things, that, as soon as practicable following the consummation of the Offer and subject to the satisfaction or waiver of certain conditions, Purchaser will merge with and into the Company pursuant to Section 251(h) of the General Corporation Law of the State of Delaware, as amended (the “DGCL”), with the Company continuing as the surviving corporation and an indirect wholly owned subsidiary of Parent upon the terms and subject to the conditions set forth in the Merger Agreement, (the “Merger,” and together with the Offer and the other transactions contemplated by the Merger Agreement, the “Transactions”). The Merger will be effected without a vote of the Company’s stockholders in accordance with Section 251(h) of the DGCL.

4. The Board of Directors of the Company has unanimously: (a) determined that entry into the Merger Agreement and the Transactions are advisable and fair to, and in the best interests of, the Company and its stockholders; (b) determined that the Merger shall be governed and effected in accordance with Section 251(h) of the DGCL; (c) authorized and approved the execution, delivery and performance by the Company of the Merger Agreement and the consummation of the Transactions, including the Offer and the Merger; and (d) resolved to recommend that the holders of Shares accept the Offer and tender their Shares to Purchaser pursuant to the Offer.

5. The Offer will expire at one minute following 11:59 P.M., Eastern Time, on February 9, 2026, unless the Offer is extended by the Purchaser or earlier terminated. Previously tendered Shares may be withdrawn at any time until the Offer has expired, and if not previously accepted for payment at any time, after March 13, 2026, pursuant to SEC (as defined in the Offer to Purchase) regulations or earlier terminated in accordance with its terms or the terms of the Merger Agreement.

6. The Offer is not subject to a financing condition. The obligation of Purchaser to accept for payment and pay for Shares validly tendered (and not validly withdrawn) pursuant to the Offer is subject to the conditions set forth in Section 15 of the Offer to Purchase (collectively, the “Offer Conditions”). Among the Offer Conditions are: (a) the Minimum Condition (as defined below); (b) the Regulatory Condition (as defined below); (c) the accuracy of the Company’s representations and warranties set forth in the Merger Agreement as of specified times, and the performance of the Company’s covenants set forth in the Merger Agreement, in each case, to specified standards of materiality; and (d) since the date of the Merger Agreement, there not having occurred a Material Adverse Effect (as defined in the Offer to Purchase) that is continuing. The “Minimum Condition” means that there shall have been validly tendered in the Offer and “received” by the “depositary” (as such terms are used in Section 251(h) of the DGCL), and not validly withdrawn, prior to the Expiration Date, that number of Shares that, together with the number of Shares, if any, then owned beneficially by Parent and Purchaser (together with their wholly owned subsidiaries), represents at least a majority of the Shares outstanding as of the consummation of the Offer; and the “Regulatory Condition,” requires (i) that any applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, shall have expired or been terminated and (ii) the satisfaction of certain additional antitrust and foreign investment (FDI) filings and the absence of certain orders or laws prohibiting the Offer or the Merger.

If you wish to have us tender any or all of your Shares, then please so instruct us by completing, executing, detaching and returning to us the Instruction Form on the detachable part hereof. An envelope to return your instructions to us is enclosed. If you authorize tender of your Shares, all such Shares will be tendered unless otherwise specified on the Instruction Form.

Your prompt action is requested. Your Instruction Form should be forwarded to us in ample time to permit us to submit the tender on your behalf before the expiration of the Offer.

The Offer is being made to all holders of Shares. 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

 

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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 (nor will tenders be accepted from or on behalf of) 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.

 

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INSTRUCTION FORM

With Respect to the Offer to Purchase

All Outstanding Shares of Common Stock

of

DYNAVAX TECHNOLOGIES CORPORATION

at

$15.50 PER SHARE, NET IN CASH

Pursuant to the Offer to Purchase dated January 12, 2026

by

SAMBA MERGER SUB, INC.

an indirect wholly owned subsidiary

of

SANOFI

The undersigned acknowledge(s) receipt of your letter and the enclosed Offer to Purchase, dated January 12, 2026 (the “Offer to Purchase”), and the related letter of transmittal (the “Letter of Transmittal”) in connection with the offer by Samba Merger Sub, Inc., a Delaware corporation (“Purchaser”) and an indirect wholly owned subsidiary of Sanofi, a French société anonyme (“Parent”), to purchase all of the outstanding shares of common stock, par value $0.001 per share (the “Shares”), of Dynavax Technologies Corporation, a Delaware corporation (the “Company”), for $15.50 per Share, in cash (the “Offer Price”), without interest, subject to any applicable withholding taxes, upon the terms and subject to the conditions set forth in the Offer to Purchase and in the related Letter of Transmittal (which, together with the Offer to Purchase, as they may be amended or supplemented from time to time, collectively constitute the “Offer”).

The undersigned hereby instruct(s) you to tender to Purchaser the number of Shares indicated below (or, if no number is indicated, all Shares) which are held by you for the account of the undersigned, upon the terms and subject to the conditions set forth in the Offer.

The method of delivery of this document is at the election and risk of the tendering stockholder. If delivery is by mail, then using registered mail with return receipt requested, properly insured, is recommended. In all cases, sufficient time should be allowed to ensure delivery by the expiration of the Offer.

 

Number of Shares to be Tendered:		SIGN HERE
Shares*		Signature(s)
Account No.                Dated    , 20   Area Code and Phone Number
Tax Identification Number or Social Security Number		Please Print name(s) and address(es) here

 

*	Unless otherwise indicated, it will be assumed that all Shares held by us for your account are to be tendered.

 

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