Sec Form 3 Filing - Clarus Defined Exit I, L.P. @ Talaris Therapeutics, Inc. - 2021-05-06

FORM 3 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 Clarus Defined Exit I, L.P. 2. Issuer Name and Ticker or Trading Symbol Talaris Therapeutics, Inc. [ TALS] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O CLARUS VENTURES, LLC, 101 MAIN STREET, SUITE 1210 3. Date of Earliest Transaction (MM/DD/YY) 05/06/2021 (Street) CAMBRIDGE, MA02142 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ 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

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 Series A Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 4,859,812 I See Footnotes ( 2 ) ( 11 ) ( 12 ) ( 13 ) ( 14 ) Series A-1 Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 690,150 I See Footnotes ( 3 ) ( 9 ) ( 11 ) ( 12 ) ( 13 ) ( 14 ) Series A-1 Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 276,060 I See Footnotes ( 4 ) ( 9 ) ( 11 ) ( 12 ) ( 13 ) ( 14 ) Series A-1 Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 557,546 I See Footnotes ( 5 ) ( 10 ) ( 11 ) ( 12 ) ( 13 ) ( 14 ) Series A-1 Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 363,433 I See Footnotes ( 6 ) ( 10 ) ( 11 ) ( 12 ) ( 13 ) ( 14 ) Series A-1 Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 670,347 I See Footnotes ( 7 ) ( 10 ) ( 11 ) ( 12 ) ( 13 ) ( 14 ) Series A-1 Convertible Preferred Stock ( 2 ) ( 1 ) ( 1 ) Common Stock 134,047 I See Footnotes ( 8 ) ( 10 ) ( 11 ) ( 12 ) ( 13 ) ( 14 ) Series B Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 130,236 I See Footnotes ( 3 ) ( 9 ) ( 11 ) ( 12 ) ( 13 ) ( 14 ) Series B Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 52,094 I See Footnotes ( 4 ) ( 9 ) ( 11 ) ( 12 ) ( 13 ) ( 14 ) Series B Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 105,213 I See Footnotes ( 5 ) ( 10 ) ( 11 ) ( 12 ) ( 13 ) ( 14 ) Series B Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 68,582 I See Footnotes ( 6 ) ( 10 ) ( 11 ) ( 12 ) ( 13 ) ( 14 ) Series B Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 126,499 I See Footnotes ( 7 ) ( 10 ) ( 11 ) ( 12 ) ( 13 ) ( 14 ) Series B Convertible Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 25,296 I See Footnotes ( 8 ) ( 10 ) ( 11 ) ( 12 ) ( 13 ) ( 14 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Clarus Defined Exit I, L.P. C/O CLARUS VENTURES, LLC 101 MAIN STREET, SUITE 1210 CAMBRIDGE, MA02142 X Clarus DE II, L.P. C/O CLARUS VENTURES, LLC 101 MAIN STREET, SUITE 1210 CAMBRIDGE, MA02142 X Clarus IV-A, L.P. C/O CLARUS VENTURES, LLC 101 MAIN STREET, SUITE 1210 CAMBRIDGE, MA02142 X Clarus IV-B, L.P. C/O CLARUS VENTURES, LLC 101 MAIN STREET, SUITE 1210 CAMBRIDGE, MA02142 X Clarus IV-C, L.P. C/O CLARUS VENTURES, LLC 101 MAIN STREET, SUITE 1210 CAMBRIDGE, MA02142 X Clarus IV-D, L.P. C/O CLARUS VENTURES, LLC 101 MAIN STREET, SUITE 1210 CAMBRIDGE, MA02142 X Clarus Ventures DE GP, L.P. C/O CLARUS VENTURES, LLC 101 MAIN STREET, SUITE 1210 CAMBRIDGE, MA02142 X Clarus IV GP L.P. C/O CLARUS VENTURES, LLC 101 MAIN STREET, SUITE 1210 CAMBRIDGE, MA02142 X Blackstone Clarus DE L.L.C. C/O THE BLACKSTONE GROUP INC. 345 PARK AVENUE NEW YORK, NY10154 X Blackstone Clarus GP L.L.C. C/O THE BLACKSTONE GROUP INC. 345 PARK AVENUE NEW YORK, NY10154 X Signatures CLARUS DEFINED EXIT I, L.P., By: Clarus Ventures DE GP, L.P., its GP, By: Blackstone Clarus DE L.L.C., its GP, By: Blackstone Holdings II L.P., its sole member, By: Blackstone Holdings I/II GP L.L.C., its GP, By: /s/ Tabea Hsi, Senior Managing Director 05/06/2021 Signature of Reporting Person Date CLARUS DE II, L.P., By: Clarus Ventures DE GP, L.P., its GP, By: Blackstone Clarus DE L.L.C., its GP, By: Blackstone Holdings II L.P., its sole member, By: Blackstone Holdings I/II GP L.L.C., its GP, By: /s/ Tabea Hsi, Senior Managing Director 05/06/2021 Signature of Reporting Person Date CLARUS IV-A, L.P., By: Clarus IV GP, L.P., its GP, By: Blackstone Clarus GP L.P., its GP, By: Blackstone Clarus GP L.L.C., its GP, By: Blackstone Holdings I L.P., its sole member, By: Blackstone Holdings I/II GP L.L.C., its GP, By: /s/ Tabea Hsi, SMD 05/06/2021 Signature of Reporting Person Date CLARUS IV-B, L.P., By: Clarus IV GP, L.P., its GP, By: Blackstone Clarus GP L.P., its GP, By: Blackstone Clarus GP L.L.C., its GP, By: Blackstone Holdings I L.P., its sole member, By: Blackstone Holdings I/II GP L.L.C., its GP, By: /s/ Tabea Hsi, SMD 05/06/2021 Signature of Reporting Person Date CLARUS IV-C, L.P., By: Clarus IV GP, L.P., its GP, By: Blackstone Clarus GP L.P., its GP, By: Blackstone Clarus GP L.L.C., its GP, By: Blackstone Holdings I L.P., its sole member, By: Blackstone Holdings I/II GP L.L.C., its GP, By: /s/ Tabea Hsi, SMD 05/06/2021 Signature of Reporting Person Date CLARUS IV-D, L.P., By: Clarus IV GP, L.P., its GP, By: Blackstone Clarus GP L.P., its GP, By: Blackstone Clarus GP L.L.C., its GP, By: Blackstone Holdings I L.P., its sole member, By: Blackstone Holdings I/II GP L.L.C., its GP, By: /s/ Tabea Hsi, SMD 05/06/2021 Signature of Reporting Person Date CLARUS VENTURES DE GP, L.P., By: Blackstone Clarus DE L.L.C., its GP, By: Blackstone Holdings II L.P., its sole member, By: Blackstone Holdings I/II GP L.L.C., its GP, By: /s/ Tabea Hsi, Name: Tabea Hsi, Title: Senior Managing Director 05/06/2021 Signature of Reporting Person Date BLACKSTONE CLARUS DE L.L.C., By: Blackstone Holdings II L.P., its sole member, By: Blackstone Holdings I/II GP L.L.C., its general partner, By: /s/ Tabea Hsi, Name: Tabea Hsi, Title: Senior Managing Director 05/06/2021 Signature of Reporting Person Date CLARUS IV GP, L.P., By: Blackstone Clarus GP L.P., its GP, By: Blackstone Clarus GP L.L.C., its GP, By: Blackstone Holdings I L.P., its sole member, By: Blackstone Holdings I/II GP L.L.C., its GP, By: /s/ Tabea Hsi, SMD 05/06/2021 Signature of Reporting Person Date BLACKSTONE CLARUS GP L.L.C., By: Blackstone Holdings I L.P., its sole member, By: Blackstone Holdings I/II GP L.L.C., its GP, By: /s/ Tabea Hsi, Senior Managing Director 05/06/2021 Signature of Reporting Person Da te

Explanation of Responses:

( 1 )Each share of the Issuer's Series A Convertible Preferred Stock, Series A-1 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") is convertible at any time at the option of the holder and will automatically convert on a 1-for-5.35 basis into common stock of the Issuer upon the closing of the Issuer's initial public offering. The Preferred Stock has no expiration date. ( 2 )Reflects securities held directly by Clarus Lifesciences III, L.P. Clarus Ventures III GP, L.P. is the general partner of Clarus Lifesciences III, L.P. Blackstone Clarus III L.L.C. is the general partner of Clarus Ventures III GP, L.P. The sole member of Blackstone Clarus III L.L.C. is Blackstone Holdings II L.P. ( 3 )Reflects securities held directly by Clarus Defined Exit I, L.P. ( 4 )Reflects securities held directly by Clarus DE II, L.P. ( 5 )Reflects securities held directly by Clarus IV-A, L.P. ( 6 )Reflects securities held directly by Clarus IV-B, L.P. ( 7 )Reflects securities held directly by Clarus IV-C, L.P. ( 8 )Reflects securities held directly by Clarus IV-D, L.P. ( 9 )Clarus Ventures DE GP, L.P. is the general partner of each of Clarus Defined Exit I, L.P. and Clarus DE II, L.P. Blackstone Clarus DE L.L.C. is the general partner of Clarus Ventures DE GP, L.P. The sole member of Blackstone Clarus DE L.L.C. is Blackstone Holdings II L.P. ( 10 )Clarus IV GP, L.P. is the general partner of each of Clarus IV-A, L.P., Clarus IV-B, L.P., Clarus IV-C, L.P. and Clarus IV-D, L.P. Blackstone Clarus GP L.P. is the general partner of Clarus IV GP, L.P. Blackstone Clarus GP L.L.C. is the general partner of Blackstone Clarus GP L.P. The sole member of Blackstone Clarus GP L.L.C. is Blackstone Holdings I L.P. ( 11 )The general partner of each of Blackstone Holdings I L.P. and Blackstone Holdings II L.P. is Blackstone Holdings I/II GP L.L.C. The sole member of Blackstone Holdings I/II GP L.L.C. is The Blackstone Group Inc. The sole holder of the Series II preferred stock of The Blackstone Group Inc. is Blackstone Group Management L.L.C. Blackstone Group Management L.L.C. is wholly-owned by Blackstone's senior managing directors and controlled by its founder, Stephen A. Schwarzman. ( 12 )Due to the limitations of the electronic filing system certain Reporting Persons are filing a separate Form 3. ( 13 )Information with respect to each of the Reporting Persons is given solely by such Reporting Person, and no Reporting Person has responsibility for the accuracy or completeness of information supplied by another Reporting Person. ( 14 )Each of the Reporting Persons (other than to the extent it directly holds securities reported herein) disclaims beneficial ownership of the securities held by the other Reporting Persons, except to the extent of such Reporting Person's pecuniary interest therein, and, pursuant to Rule 16a-1(a)(4) under the Securities Exchange Act of 1934, each of the Reporting Persons (other than to the extent it directly holds securities reported herein) states that the inclusion of these securities in this report shall not be deemed an admission of beneficial ownership of all of the reported securities for purposes of Section 16 or for any other purpose.

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

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