Sec Form 3 Filing - BAY CITY CAPITAL LLC @ Xilio Therapeutics, Inc. - 2021-10-21

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 BAY CITY CAPITAL LLC 2. Issuer Name and Ticker or Trading Symbol Xilio Therapeutics, Inc. [ XLO] 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) 1000 4TH STREET, SUITE 500 3. Date of Earliest Transaction (MM/DD/YY) 10/21/2021 (Street) SAN RAFAEL, CA94901 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

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 B Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 665,696 I See footnotes ( 3 ) ( 4 ) Series C Preferred Stock ( 2 ) ( 2 ) ( 2 ) Common Stock 151,294 I See footnotes ( 3 ) ( 4 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other BAY CITY CAPITAL LLC 1000 4TH STREET, SUITE 500 SAN RAFAEL, CA94901 X Signatures /s/ Bay City Capital GF Xinde International Life Sciences USD Fund, L.P., a Cayman Islands exempt limited partnership, By: Bay City Capital GF XINDE Investment Management Co., a Cayman Islands company, its General Partner, By: Fred Craves, Director 10/21/2021 Signature of Reporting Person Date /s/ Bay City Capital LLC, a Delaware limited liability company, By: Fred Craves, Managing Director 10/21/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The Series B Preferred Stock automatically converts into the number of shares of Common Stock as shown in Column 3 without payment of further consideration at the holder's election or upon closing of the initial public offering of the Issuer's common stock. The shares have no expiration date. ( 2 )The Series C Preferred Stock automatically converts into the number of shares of Common Stock as shown in Column 3 without payment of further consideration at the holder's election or upon closing of the initial public offering of the Issuer's common stock. The shares have no expiration date. ( 3 )Bay City Capital LLC, a Delaware limited liability company (BCC), Bay City Capital JV Management I LLC, a Delaware limited liability company (Management I), Bay City Capital GF XINDE Investment Management Co., a Cayman Islands company (Management Co.), and Bay City Capital GF Xinde International Life Sciences USD Fund, L.P., a Cayman Islands exempt limited partnership (USD Fund) are deemed to be a group for the purposes of Section 13(d) under the Securities Exchange Act of 1934. Management Co. is the general partner of USD Fund and has voting and dispositive power with respect to the securities held by USD Fund. BCC is the manager of, and an advisor to, Management I, and Management I holds an equity interest in Management Co. ( 4 )Represent securities held by USD Fund, including indirect interests of BCC, Management I, and Management Co. BCC, Management I and Management Co. each disclaims beneficial ownership with respect to these securities, except to the extent of their pecuniary interest therein.

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).

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