Sec Form 4 Filing - Castelein Caley @ Tourmaline Bio, Inc. - 2023-10-19

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Castelein Caley 2. Issuer Name and Ticker or Trading Symbol Tourmaline Bio, Inc. [ TRML] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O TOURMALINE BIO, INC., 27 WEST 24TH STREET, SUITE 702 3. Date of Earliest Transaction (MM/DD/YY) 10/19/2023 (Street) NEW YORK, NY10010 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 10/19/2023 A 496,519 ( 1 ) A 496,519 D Common Stock 10/19/2023 A 458,039 A 458,039 I By KVP Capital, LP ( 4 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Stock Option (Right to Buy) $ 9. 46 10/23/2023 A 10,000 ( 5 ) 10/22/2033 Common Stock 10,000 $ 0 10,000 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Castelein Caley C/O TOURMALINE BIO, INC. 27 WEST 24TH STREET, SUITE 702 NEW YORK, NY10010 X Signatures /s/ Brad Middlekauff, Attorney-in-Fact 10/23/2023 Signature of Reporting Person Date

Explanation of Responses:

( 1 )39,996 of these shares are subject to a repurchase option in favor of the Issuer in the event that the Reporting Person's continuous service is terminated. Such repurchase option shall lapse in equal monthly installments until such shares are fully vested on June 1, 2026. ( 2 )Received in exchange for 6,224,374 shares of common stock of Tourmaline Bio, Inc. ("Tourmaline") pursuant to an Agreement and Plan of Merger dated as of June 22, 2023 (the "Merger Agreement") by and among Tourmaline, the Issuer and Terrain Merger Sub, Inc., a wholly owned subsidiary of the Issuer ("Merger Sub"). Under the terms of the Merger Agreement, on October 19, 2023, Merger Sub merged with and into Tourmaline (the "Merger"), with Tourmaline surviving the Merger as a wholly owned subsidiary of the Issuer. Upon the closing of the Merger, each share of Tourmaline common stock was converted into the right to receive 0.07977 of a share of the Issuer's common stock, after giving effect to a reverse stock split of the Issuer's common stock of 10-for-1. Subsequent to the Merger, the name of the Issuer was changed from Talaris Therapeutics, Inc. to Tourmaline Bio, Inc. ( 3 )Received in exchange for 5,741,986 shares of Tourmaline common stock pursuant to the Merger Agreement. ( 4 )These shares are held by KVP Capital, LP ("KVP"). The Reporting Person is the Managing Member of KVP Capital GP, LLC, the General Partner of KVP and, as such, has sole voting and investment power with respect to the shares held by KVP. The Reporting Person disclaims beneficial ownership of the shares held by KVP except to the extent of his pecuniary interest therein and this report is not an admission that the Reporting Person is the beneficial owner of these securities for purposes of Section 16 or for any other purpose. ( 5 )100% of the shares subject to the option vest on the earlier of October 23, 2024 or the date of the Issuer's 2024 Annual Meeting of Stockholders, subject to the Reporting Person's continued service on such vesting date.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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