Maze Therapeutics, Inc. received an updated Schedule 13G/A from several affiliated Third Rock Ventures funds reporting their ownership of the company’s common stock. Third Rock Ventures IV, L.P. directly holds 4,473,958 shares of common stock, which represents approximately 9.3% of Maze’s outstanding shares based on 48,119,440 shares outstanding as of November 3, 2025. Third Rock Ventures V, L.P. directly holds 950,800 shares, representing about 2.0% of the outstanding stock on the same basis.
Related general partner entities (Third Rock Ventures GP IV, L.P., TRV GP IV, LLC, Third Rock Ventures GP V, L.P., and TRV GP V, LLC) may be deemed to share voting and dispositive power over these shares, but they report no sole voting or dispositive power. The reporting persons expressly disclaim the existence of a “group” for regulatory purposes.
Positive
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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
(Amendment No. 1)
Maze Therapeutics, Inc.
(Name of Issuer)
Common Stock, $0.001 par value per share
(Title of Class of Securities)
578784100
(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.
578784100
1
Names of Reporting Persons
Third Rock Ventures IV, 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
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
4,473,958.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
4,473,958.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
4,473,958.00
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)
9.3 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP No.
578784100
1
Names of Reporting Persons
Third Rock Ventures GP IV, 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
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
4,473,958.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
4,473,958.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
4,473,958.00
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)
9.3 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP No.
578784100
1
Names of Reporting Persons
TRV GP IV, LLC
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
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
4,473,958.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
4,473,958.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
4,473,958.00
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)
9.3 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP No.
578784100
1
Names of Reporting Persons
Third Rock Ventures V, 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
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
950,800.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
950,800.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
950,800.00
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)
2.0 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP No.
578784100
1
Names of Reporting Persons
Third Rock Ventures GP V, 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
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
950,800.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
950,800.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
950,800.00
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)
2.0 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP No.
578784100
1
Names of Reporting Persons
TRV GP V, LLC
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
950,800.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
950,800.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
950,800.00
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)
2.0 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
Maze Therapeutics, Inc.
(b)
Address of issuer's principal executive offices:
171 Oyster Point Boulevard, Suite 300, San Francisco, CA 94939
Item 2.
(a)
Name of person filing:
(i) Third Rock Ventures IV, L.P. ("TRV IV");
(ii) Third Rock Ventures GP IV, L.P. ("TRV GP IV"), which is the sole general partner of TRV IV;
(iii) TRV GP IV, LLC ("TRV GP IV LLC"), which is the sole general partner of TRV GP IV;
(iv) Third Rock Ventures V, L.P. ("TRV V");
(v) Third Rock Ventures GP V, L.P. ("TRV GP V"), which is the sole general partner of TRV V; and
(vi) TRV GP V, LLC ("TRV GP V LLC"), which is the sole general partner of TRV GP V.
(b)
Address or principal business office or, if none, residence:
The address of the principal business office of each of the Reporting Persons is Third Rock Ventures, LLC, 201 Brookline Ave, Suite 1401, Boston, MA 02215.
(c)
Citizenship:
Each of TRV IV, TRV GP IV, TRV V and TRV GP V is a Delaware limited partnership. Each of TRV GP IV LLC and TRV GP V LLC is a Delaware limited liability company.
(d)
Title of class of securities:
Common Stock, $0.001 par value per share
(e)
CUSIP No.:
578784100
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:
(i) TRV IV directly owns 4,473,958 shares of Common Stock (the "IV Shares")
(ii) TRV GP IV is the general partner of TRV IV and may be deemed to beneficially own the IV Shares.
(iii) TRV GP IV LLC is the general partner of TRV GP IV and may be deemed to beneficially own the IV Shares.
(iv) TRV V directly owns 950,800 shares of Common Stock (the "V Shares").
(v) TRV GP V is the general partner of TRV V and may be deemed to beneficially own the V Shares.
(vi) TRV GP V LLC is the general partner of TRV GP V and may be deemed to beneficially own the V Shares.
Each of TRV IV, TRV GP IV, and TRV GP IV LLC, on the one hand, and TRV V, TRV GP V and TRV GP V LLC, on the other hand, disclaim the existence of a "group" for purposes of Rule 13d-5 of the Securities Exchange Act of 1934, as amended, and nothing contained in this report shall be deemed an admission that any such group exists or may exist.
(b)
Percent of class:
The IV shares represent approximately 9.3% of the outstanding shares of Common Stock.
The V shares represent approximately 2.0% of the outstanding shares of Common Stock.
The percent of class was calculated based on 48,119,440 shares of common stock issued and outstanding as of November 3, 2025, as disclosed in the Issuer's 10-Q filed with the Securities and Exchange Commission on November 6, 2025.
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
TRV IV - 0
TRV GP IV - 0
TRV GP IV LLC - 0
TRV V - 0
TRV GP V - 0
TRV GP V LLC - 0
(ii) Shared power to vote or to direct the vote:
TRV IV - 4,473,958 shares
TRV GP IV - 4,473,958 shares
TRV GP IV LLC - 4,473,958 shares
TRV V - 950,800 shares
TRV GP V - 950,800 shares
TRV GP V LLC - 950,800 shares
(iii) Sole power to dispose or to direct the disposition of:
TRV IV - 0
TRV GP IV - 0
TRV GP IV LLC - 0
TRV V - 0
TRV GP V - 0
TRV GP V LLC - 0
(iv) Shared power to dispose or to direct the disposition of:
TRV IV - 4,473,958 shares
TRV GP IV - 4,473,958 shares
TRV GP IV LLC - 4,473,958 shares
TRV V - 950,800 shares
TRV GP V - 950,800 shares
TRV GP V LLC - 950,800 shares
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:
Not Applicable
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.
Third Rock Ventures IV, L.P.
Signature:
/s/ Kevin Gillis
Name/Title:
Kevin Gillis, COO of TRV GP IV, LLC, general partner of Third Rock Ventures GP IV, L.P., general partner of Third Rock Ventures IV, L.P.
Date:
02/13/2026
Third Rock Ventures GP IV, L.P.
Signature:
/s/ Kevin Gillis
Name/Title:
Kevin Gillis, Chief Operating Officer of TRV GP IV, LLC, general partner of Third Rock Ventures GP IV, L.P
Date:
02/13/2026
TRV GP IV, LLC
Signature:
/s/ Kevin Gillis
Name/Title:
Kevin Gillis, Chief Operating Officer of TRV GP IV, LLC
Date:
02/13/2026
Third Rock Ventures V, L.P.
Signature:
/s/ Kevin Gillis
Name/Title:
Kevin Gillis, COO of TRV GP V, LLC, general partner of Third Rock Ventures GP V, L.P., general partner of Third Rock Ventures V, L.P.
Date:
02/13/2026
Third Rock Ventures GP V, L.P.
Signature:
/s/ Kevin Gillis
Name/Title:
Kevin Gillis, Chief Operating Officer of TRV GP V, LLC, general partner of Third Rock Ventures GP V, L.P.
Date:
02/13/2026
TRV GP V, LLC
Signature:
/s/ Kevin Gillis
Name/Title:
Kevin Gillis, Chief Operating Officer of TRV GP V, LLC
What does Third Rock Ventures report owning in Maze Therapeutics (MAZE)?
Third Rock Ventures IV, L.P. reports owning 4,473,958 shares of Maze Therapeutics common stock and Third Rock Ventures V, L.P. reports 950,800 shares. Together, these stakes reflect significant institutional interest across multiple affiliated investment vehicles.
What percentage of Maze Therapeutics’ stock is held by Third Rock funds?
Third Rock Ventures IV, L.P. reports holding about 9.3% of Maze Therapeutics’ common stock, while Third Rock Ventures V, L.P. reports about 2.0%. These percentages are calculated from 48,119,440 shares outstanding as of November 3, 2025.
Do the Third Rock entities have sole or shared voting power over MAZE shares?
The filing states the Third Rock entities have zero sole voting or dispositive power. Instead, they report shared voting and shared dispositive power over the 4,473,958 shares held by TRV IV and the 950,800 shares held by TRV V through their general partner structures.
Which Third Rock entities are included in this Maze Therapeutics Schedule 13G/A?
The filing covers Third Rock Ventures IV, L.P., Third Rock Ventures GP IV, L.P., TRV GP IV, LLC, Third Rock Ventures V, L.P., Third Rock Ventures GP V, L.P., and TRV GP V, LLC. Each entity’s role is tied to direct ownership or general partner control over the reported shares.
How was the ownership percentage in Maze Therapeutics (MAZE) calculated?
The Schedule 13G/A explains that percentages were computed using 48,119,440 Maze Therapeutics common shares outstanding as of November 3, 2025. This share count comes from Maze’s Form 10-Q filed on November 6, 2025, and provides the denominator for the 9.3% and 2.0% stakes.
Do the Third Rock entities acknowledge forming a group in this MAZE ownership filing?
The reporting entities state that each of TRV IV, TRV GP IV, TRV GP IV LLC, TRV V, TRV GP V, and TRV GP V LLC disclaims the existence of a “group” under Rule 13d-5. They also say nothing in the report should be viewed as an admission that such a group exists.
