​
Exhibit (a)(1)(C)​
Offer to Purchase
All Outstanding Shares of Common Stock
of
Tourmaline Bio, Inc.
at
$48.00 per share in cash
Pursuant to the Offer to Purchase dated September 29, 2025
by
Torino Merger Sub Inc.
an indirect wholly owned subsidiary of
Novartis AG

​ | ​ | THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT ONE MINUTE FOLLOWING 11:59 P.M., EASTERN TIME, ON OCTOBER 27, 2025, UNLESS THE OFFER IS EXTENDED OR EARLIER TERMINATED. | ​ | ​

September 29, 2025​
To Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees:
We have been engaged by Torino Merger Sub Inc., a Delaware corporation (“Purchaser”) and an indirect wholly owned subsidiary of Novartis AG, a company limited by shares (Aktiengesellschaft) incorporated under the laws of Switzerland (“Parent”), to act as information agent (the “Information Agent”) in connection with Purchaser’s offer to purchase all of the outstanding shares of common stock, par value $0.0001 per share (the “Shares”), of Tourmaline Bio, Inc., a Delaware corporation (“Tourmaline”), at a price of $48.00 per Share, in cash, without interest and subject to any withholding of taxes required by applicable legal requirements. Such offer is being made upon the terms and subject to the conditions set forth in the Offer to Purchase (as it may be amended, supplemented or otherwise modified from time to time, the “Offer to Purchase”) and in the related Letter of Transmittal (as it may be amended, supplemented or otherwise modified from time to time, the “Letter of Transmittal”) which, together with the Offer to Purchase, collectively constitute the “Offer.” Please furnish copies of the enclosed materials to those of your clients for whom you hold Shares registered in your name or in the name of your nominee.
The conditions to the Offer are described in Section 15 of the Offer to Purchase.
For your information and for forwarding to your clients for whom you hold Shares registered in your name or in the name of your nominee, we are enclosing the following documents:
1.
The Offer to Purchase;
​
2.
The Letter of Transmittal (including Guidelines for Certification of Taxpayer Identification Number on IRS Form W-9) for your use in accepting the Offer and tendering Shares and for the information of your clients;
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3.
A form of letter which may be sent to your clients for whose accounts you hold Shares registered in your name or in the name of your nominee, with space provided for obtaining such clients’ instructions with regard to the Offer;
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4.
Tourmaline’s Solicitation/Recommendation Statement on Schedule 14D-9; and
​
5.
A return envelope addressed to Computershare Trust Company, N.A. (the “Depositary”) for your use only.
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We urge you to contact your clients as promptly as possible. Please note that the Offer and withdrawal rights will expire at one minute following 11:59 P.M., Eastern Time, on October 27, 2025, unless the Offer is otherwise extended or earlier terminated.

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The Offer is being made pursuant to an Agreement and Plan of Merger, dated as of September 8, 2025 (as it may be amended, supplemented or otherwise modified from time to time, the “Merger Agreement”), by and among Tourmaline, Parent and Purchaser, pursuant to which, after consummation of the Offer and the satisfaction or waiver of certain conditions, Purchaser will merge with and into Tourmaline in accordance with Section 251(h) of the General Corporation Law of the State of Delaware (the “DGCL”), upon the terms and subject to the conditions set forth in the Merger Agreement, with Tourmaline continuing as the surviving corporation and becoming an indirect wholly owned subsidiary of Parent (the “Merger,” and together with the Offer and the other transactions contemplated by the Merger Agreement, the “Transactions”).
Tourmaline’s board of directors has unanimously (i) determined that the Merger Agreement and the consummation of the Transactions are advisable, fair to and in the best interests of, Tourmaline and its stockholders, (ii) determined that the Merger shall be governed and effected in accordance with Section 251(h) of the DGCL, (iii) authorized and approved the execution, delivery and performance by Tourmaline of the Merger Agreement and the consummation of the Transactions, and (iv) resolved to recommend that the holders of Shares accept the Offer and tender their Shares to Purchaser pursuant to the Offer.
For Shares to be validly tendered to Purchaser pursuant to the Offer, the share certificates or confirmation of receipt of such Shares under the procedure for book-entry transfer, together with a properly completed and duly executed Letter of Transmittal, including any required signature guarantees, or an “Agent’s Message” ​(as defined in the Offer to Purchase) in the case of book-entry transfer, and any other documents required in the Letter of Transmittal, must be timely received by the Depositary.
Purchaser will not pay any fees or commissions to any broker or dealer or to any other person (other than to the Depositary and the Information Agent as described in the Offer to Purchase) in connection with the solicitation of tenders of Shares pursuant to the Offer. Purchaser will, however, upon request, reimburse brokers, dealers, commercial banks and trust companies for reasonable and necessary costs and expenses incurred by them in forwarding materials to their customers. Except as set forth in Instruction 6 of the Letter of Transmittal, Purchaser will pay all stock transfer taxes applicable to its purchase of Shares pursuant to the Offer.
Any inquiries you may have with respect to the Offer should be addressed to, and additional copies of the enclosed materials may be obtained from, the Information Agent at the addresses and telephone numbers set forth on the back cover of the Offer to Purchase.
Very truly yours,
Innisfree M&A
Incorporated
Nothing contained herein or in the enclosed documents shall render you, the agent of Purchaser, the Information Agent or the Depositary or any affiliate of any of them or authorize you or any other person to use any document or make any statement on behalf of any of them in connection with the Offer other than the enclosed documents and the statements contained therein.
The Information Agent for the Offer is:
Innisfree M&A Incorporated
501 Madison Avenue, 20th floor
New York, New York 10022
Stockholders may call: (877) 800-5186 (toll-free from the United States or Canada) or
+1 (412) 232-3651 (from outside of the United States or Canada)
Banks and Brokers may call collect: (212) 750-5833
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