Xilio Therapeutics, Inc. ownership disclosure: a group of Bain Capital Life Sciences entities filed Amendment No. 4 to a Schedule 13G/A reporting beneficial ownership of 9.99% of Common Stock, equal to 664,021 shares as of March 31, 2026.
The filing states that BCLS II Equity holds a pre-funded warrant to purchase up to 1,116,245 shares but is contractually blocked from exercising if it would cause the Reporting Persons to exceed the 9.99% Beneficial Ownership Blocker. The ownership calculation uses 5,982,839 shares outstanding as reported in the Issuer's Definitive Proxy Statement dated April 28, 2026.
Positive
None.
Negative
None.
Insights
Bain Capital entities report a 9.99% passive stake limited by a blocker tied to a pre-funded warrant.
The filing shows BCLS II Equity holds a pre-funded warrant for 1,116,245 shares but is restricted by a contractual Beneficial Ownership Blocker that caps collective beneficial ownership at 9.99%. The beneficial ownership figure of 664,021 shares is calculated using the issuer's reported 5,982,839 shares outstanding.
Governance implications depend on whether the position is passive under Rule 13d-1; the filing uses Rule 13d-1(k)(1) joint reporting. Subsequent filings would show any conversion/exercise or changes in the blocker status.
Key Figures
Beneficial ownership:664,021 sharesPre-funded warrant:1,116,245 sharesShares outstanding used:5,982,839 shares+1 more
4 metrics
Beneficial ownership664,021 sharesAs of March 31, 2026
Pre-funded warrant1,116,245 sharesWarrant held by BCLS II Equity
Shares outstanding used5,982,839 sharesAs reported in Definitive Proxy Statement dated April 28, 2026
"BCLS II Equity held a pre-funded warrant to purchase up to 1,116,245 shares"
A pre-funded warrant is a financial instrument that gives the holder the right to buy shares of a company's stock at a set price, with most of the purchase cost already paid upfront. It functions like a nearly fully paid option, allowing investors to secure shares quickly while minimizing the amount of additional money they need to invest later. This helps investors gain ownership rights efficiently, often used to avoid certain regulatory restrictions or to prepare for future stock purchases.
Beneficial Ownership Blockerregulatory
"BCLS II Equity is prohibited from exercising its pre-funded warrant if... would collectively beneficially own more than 9.99%"
A beneficial ownership blocker is a legal or structural device that prevents a shareholder from being treated as the ultimate owner of enough shares to trigger control, reporting, or voting thresholds. Think of it like a speed bump that stops an investor from reaching a stake size that would force corporate disclosure or change control rights. Investors care because it affects who controls the company, how shares vote, regulatory filings, takeover risk and therefore potential value or liquidity of their holdings.
Rule 13d-1(k)(1)regulatory
"file this jointly in accordance with the provisions of Rule 13d-1(k)(1)"
The filing reports a collective beneficial ownership of 664,021 shares, equal to 9.99% of Common Stock as of March 31, 2026. This percentage is calculated using 5,982,839 shares outstanding cited from a April 28, 2026 proxy statement.
What is the pre-funded warrant mentioned in the XLO filing?
The filing discloses that BCLS II Equity holds a pre-funded warrant to purchase up to 1,116,245 shares. Exercise is subject to a contractual Beneficial Ownership Blocker preventing collective ownership above 9.99%.
Does the filing say Bain Capital will exercise the warrant?
The filing does not state an intent to exercise; it only describes the pre-funded warrant and the contractual Beneficial Ownership Blocker that would prevent exercise if ownership would exceed 9.99%. No exercise direction is provided in this excerpt.
Which entities jointly filed the Schedule 13G/A for XLO?
The Schedule 13G/A is filed jointly by Bain Capital Life Sciences Fund II, L.P., BCIP Life Sciences Associates, LP, and BCLS II Equity Opportunities, LP, with related Bain Capital entities named as managers and general partners.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
(Amendment No. 4)
Xilio Therapeutics, Inc.
(Name of Issuer)
Common Stock, par value $0.0001 per share
(Title of Class of Securities)
98422T209
(CUSIP Number)
03/31/2026
(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)
schemaVersion:
SCHEDULE 13G
CUSIP Number(s):
98422T209
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
664,021.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
664,021.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
664,021.00
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)
9.99 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP Number(s):
98422T209
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
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
CUSIP Number(s):
98422T209
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
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"), and BCLS II Equity Opportunities, LP, a Delaware limited partnership ("BCLS II Equity" and, together with BCLS Fund II and BCIPLS, 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.
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 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 May 15, 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.:
98422T209
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 March 31, 2026, (i) BCLS II Equity held a pre-funded warrant to purchase up to 1,116,245 shares of Common Stock, (ii) BCLS Fund II held no shares of Common Stock and (iii) BCIPLS 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 II Equity may be deemed to beneficially own 9.99% of the outstanding shares of Common Stock, representing 664,021 shares of Common Stock as of March 31, 2026.
The calculation of beneficial ownership is based on (i) 5,982,839 shares of Common Stock outstanding, as reported by the Issuer in its Definitive Proxy Statement filed with the Securities and Exchange Commission on April 28, 2026, and (ii) 664,021 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.
BCLS II Equity Opportunities, LP
Signature:
/s/ Andrew Hack
Name/Title:
Andrew Hack, Partner of Bain Capital Life Sciences Investors, LLC
Date:
05/15/2026
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:
05/15/2026
BCIP Life Sciences Associates, LP
Signature:
/s/ Andrew Hack
Name/Title:
Andrew Hack, Authorized Signatory of Boylston Coinvestors, LLC
