Bain Capital Life Sciences–affiliated funds report a significant but capped stake in Xilio Therapeutics, Inc. As of the close of business on December 31, 2025, they collectively beneficially owned 7,372,686 shares of Xilio common stock, equal to 9.99% of the outstanding shares.
The holdings include 992,111 shares held by Bain Capital Life Sciences Fund II, L.P. and 120,833 shares held by BCIP Life Sciences Associates, LP, plus a pre-funded warrant held by BCLS II Equity Opportunities, LP to purchase 15,627,441 shares. Because of a 9.99% “Beneficial Ownership Blocker,” only 6,259,742 warrant shares are counted in current beneficial ownership.
This percentage is calculated using 67,540,930 Xilio shares outstanding, as reported in a Form 8-K, together with the warrant shares counted under the blocker. The group certifies that the securities are not held with the purpose or effect of changing or influencing control of Xilio.
Positive
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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
(Amendment No. 3)
Xilio Therapeutics, Inc.
(Name of Issuer)
Common Stock, par value $0.0001 per share
(Title of Class of Securities)
98422T100
(CUSIP Number)
12/31/2025
(Date of Event Which Requires Filing of this Statement)
Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
Rule 13d-1(b)
Rule 13d-1(c)
Rule 13d-1(d)
SCHEDULE 13G
CUSIP No.
98422T100
1
Names of Reporting Persons
Bain Capital Life Sciences Fund II, L.P.
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
CAYMAN ISLANDS
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
992,111.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
992,111.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
992,111.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
1.3 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP No.
98422T100
1
Names of Reporting Persons
BCIP Life Sciences Associates, LP
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
120,833.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
120,833.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
120,833.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
0.2 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP No.
98422T100
1
Names of Reporting Persons
BCLS II Equity Opportunities, LP
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
6,259,742.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
6,259,742.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
6,259,742.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
8.5 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP No.
98422T100
1
Names of Reporting Persons
BCLS II Investco, LP
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
0.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
0.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
0.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
0 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
Xilio Therapeutics, Inc.
(b)
Address of issuer's principal executive offices:
828 Winter Street, Suite 300, Waltham, Massachusetts 02451
Item 2.
(a)
Name of person filing:
This Schedule 13G is being filed jointly by Bain Capital Life Sciences Fund II, L.P., a Cayman Islands exempted limited partnership ("BCLS Fund II"), BCIP Life Sciences Associates, LP, a Delaware limited partnership ("BCIPLS"), BCLS II Equity Opportunities, LP, a Delaware limited partnership ("BCLS II Equity"), and BCLS II Investco, LP, a Delaware limited partnership ("BCLS II Investco" and, together with BCLS Fund II, BCIPLS and BCLS II Equity, the "Reporting Persons").
Bain Capital Life Sciences Investors, LLC, a Delaware limited liability company ("BCLSI"), is the manager of Bain Capital Life Sciences Investors II, LLC, a Cayman Islands limited liability company ("BCLSI II"), which is the general partner of BCLS Fund II.
BCLS II Investco (GP), LLC, a Delaware limited liability company ("BCLS II Investco GP"), whose manager is BCLS Fund II, is the general partner of BCLS II Investco.
Boylston Coinvestors, LLC, a Delaware limited liability company ("Boylston"), is the general partner of BCIPLS. BCLSI governs the investment strategy and decision-making process with respect to investments held by BCIPLS.
BCLS Fund II is the manager of BCLS II Equity Opportunities GP, LLC, a Delaware limited liability company ("BCLS II Equity GP" and, together with the Reporting Persons, BCLSI, BCLSI II, BCLS II Investco GP and Boylston, the "Bain Capital Life Sciences Entities"), which is the general partner of BCLS II Equity.
As a result, BCLSI may be deemed to share voting and dispositive power with respect to the securities held by the Reporting Persons.
The Reporting Persons have entered into a Joint Filing Agreement, dated February 17, 2026, pursuant to which the Reporting Persons have agreed to file this Schedule 13G jointly in accordance with the provisions of Rule 13d-1(k)(1) promulgated under the Act.
(b)
Address or principal business office or, if none, residence:
The principal business address for each of the Bain Capital Life Sciences Entities is 200 Clarendon Street, Boston, Massachusetts 02116.
(c)
Citizenship:
See Item 2(a) hereof.
(d)
Title of class of securities:
Common Stock, par value $0.0001 per share
(e)
CUSIP No.:
98422T100
Item 3.
If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)
Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)
Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)
Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)
Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)
An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)
An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)
A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)
A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)
A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)
A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:
(k)
Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.
Ownership
(a)
Amount beneficially owned:
As of the close of business on December 31, 2025, (i) BCLS Fund II held 992,111 shares of Common Stock, (ii) BCIPLS held 120,833 shares of Common Stock, (iii) BCLS II Equity held a pre-funded warrant to purchase 15,627,441 shares of Common Stock, and (iv) BCLS II Investco held no shares of Common Stock.
BCLS II Equity is prohibited from exercising its pre-funded warrant if, as a result of such exercise, the Reporting Persons would collectively beneficially own more than 9.99% of the total number of shares of Common Stock then issued and outstanding immediately after giving effect to the exercise (the "Beneficial Ownership Blocker"). Accordingly, pursuant to Rule 13d-3 of the Act and the relationships described herein, BCLS Fund II, BCIPLS and BCLS II Equity may be deemed to collectively beneficially own 9.99% of the outstanding shares of Common Stock, representing 7,372,686 shares of Common Stock as of December 31, 2025.
The calculation of beneficial ownership of the Reporting Persons is based on (i) 67,540,930 shares of Common Stock outstanding, as reported by the Issuer in its Form 8-K filed with the Securities and Exchange Commission on January 5, 2026, and (ii) 6,259,742 shares of Common Stock issuable upon the exercise of the pre-funded warrant held by BCLS II Equity, which reflects the Beneficial Ownership Blocker.
(b)
Percent of class:
See Item 4(a) hereof.
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
0
(ii) Shared power to vote or to direct the vote:
See Item 4(a) hereof.
(iii) Sole power to dispose or to direct the disposition of:
0
(iv) Shared power to dispose or to direct the disposition of:
See Item 4(a) hereof.
Item 5.
Ownership of 5 Percent or Less of a Class.
Not Applicable
Item 6.
Ownership of more than 5 Percent on Behalf of Another Person.
Not Applicable
Item 7.
Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
Not Applicable
Item 8.
Identification and Classification of Members of the Group.
Not Applicable
Item 9.
Notice of Dissolution of Group.
Not Applicable
Item 10.
Certifications:
By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.
SIGNATURE
After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.
Bain Capital Life Sciences Fund II, L.P.
Signature:
/s/ Andrew Hack
Name/Title:
Andrew Hack, Partner of Bain Capital Life Sciences Investors, LLC
Date:
02/17/2026
BCIP Life Sciences Associates, LP
Signature:
/s/ Andrew Hack
Name/Title:
Andrew Hack, Authorized Signatory of Boylston Coinvestors, LLC
Date:
02/17/2026
BCLS II Equity Opportunities, LP
Signature:
/s/ Andrew Hack
Name/Title:
Andrew Hack, Partner of Bain Capital Life Sciences Investors, LLC
Date:
02/17/2026
BCLS II Investco, LP
Signature:
/s/ Andrew Hack
Name/Title:
Andrew Hack, Partner of Bain Capital Life Sciences Investors, LLC
What ownership stake in Xilio Therapeutics (XLO) do the Bain Capital Life Sciences entities report?
The Bain Capital Life Sciences entities report beneficial ownership of 7,372,686 shares of Xilio common stock, equal to 9.99% of the company’s outstanding shares as of December 31, 2025, based on the issuer’s disclosed share count and warrant mechanics.
Which Bain Capital Life Sciences funds hold Xilio Therapeutics (XLO) shares and warrants?
The filing lists Bain Capital Life Sciences Fund II, L.P., BCIP Life Sciences Associates, LP, BCLS II Equity Opportunities, LP, and BCLS II Investco, LP. The first two hold common shares, while BCLS II Equity holds a large pre-funded warrant position.
How many Xilio Therapeutics (XLO) shares does each reporting Bain Capital entity beneficially own?
As of December 31, 2025, BCLS Fund II held 992,111 Xilio shares and BCIPLS held 120,833 shares. BCLS II Equity held a pre-funded warrant to purchase 15,627,441 shares, of which 6,259,742 are counted toward beneficial ownership due to a blocker.
What is the 9.99% Beneficial Ownership Blocker mentioned for Xilio Therapeutics (XLO)?
The pre-funded warrant held by BCLS II Equity includes a 9.99% Beneficial Ownership Blocker, preventing exercise if it would cause the reporting group to beneficially own more than 9.99% of Xilio’s outstanding common stock immediately after the exercise.
What Xilio Therapeutics (XLO) share count is used to calculate Bain Capital’s ownership percentage?
The reported 9.99% ownership is based on 67,540,930 Xilio common shares outstanding, as disclosed in a Form 8-K, plus 6,259,742 shares issuable under the pre-funded warrant that are included within the 9.99% ownership cap.
Are the Bain Capital Life Sciences entities seeking control of Xilio Therapeutics (XLO)?
The reporting holders certify that their Xilio securities were not acquired and are not held for the purpose or with the effect of changing or influencing control of the issuer, and not in connection with any transaction having that control-related purpose.
