Compass Therapeutics, Inc. (CMPX) received an amended Schedule 13G from a group of Blackstone-related entities reporting a reduced ownership position. As of December 31, 2025, the reporting group beneficially owned an aggregate 6,126,182 shares of common stock, representing 3.4% of the class, based on 177,572,498 shares outstanding as of September 30, 2025. Blackstone Annex Master Fund L.P. directly holds 2,447,820 shares, and Spruce Street Aggregator L.P. directly holds 3,678,362 shares. The filing states that, as of that date, the reporting persons no longer beneficially own more than five percent of Compass Therapeutics’ common stock and describes this as an exit filing. The group also certifies that the securities were not acquired to change or influence control of the company and includes standard disclaimers that certain parties may be deemed beneficial owners only through their control of the direct holders.
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Insights
Blackstone-linked holders report CMPX stake reduced to 3.4%, triggering an exit 13G filing.
Several entities affiliated with Blackstone report aggregate beneficial ownership of 6,126,182 shares of Compass Therapeutics common stock, or 3.4% of shares outstanding as of September 30, 2025. Direct holdings sit in Blackstone Annex Master Fund L.P. and Spruce Street Aggregator L.P.
The group discloses that, as of December 31, 2025, it no longer beneficially owns more than 5% of the company, making this an exit filing under Schedule 13G rules. The entities include standard language disclaiming beneficial ownership except to the extent they directly hold securities.
The certification states the position is not held for the purpose of changing or influencing control. Actual portfolio impact depends on how these ownership changes compare with prior positions, which is not detailed in this excerpt, so the information mainly updates public float and large-holder visibility.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
(Amendment No. 1)
Compass Therapeutics, Inc.
(Name of Issuer)
Common Stock, $0.0001 par value per share
(Title of Class of Securities)
20454B104
(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.
20454B104
1
Names of Reporting Persons
Blackstone Annex Master Fund 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
2,447,820.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
2,447,820.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
2,447,820.00
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)
1.4 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP No.
20454B104
1
Names of Reporting Persons
Spruce Street Aggregator 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
3,678,362.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
3,678,362.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
3,678,362.00
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)
2.1 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP No.
20454B104
1
Names of Reporting Persons
Blackstone Alternative Asset Management Associates 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
6,126,182.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
6,126,182.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
6,126,182.00
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)
3.4 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP No.
20454B104
1
Names of Reporting Persons
Blackstone Holdings 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
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
6,126,182.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
6,126,182.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
6,126,182.00
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)
3.4 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP No.
20454B104
1
Names of Reporting Persons
Blackstone Holdings I/II GP L.L.C.
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
6,126,182.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
6,126,182.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
6,126,182.00
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)
3.4 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP No.
20454B104
1
Names of Reporting Persons
Blackstone Inc.
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
6,126,182.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
6,126,182.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
6,126,182.00
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)
3.4 %
12
Type of Reporting Person (See Instructions)
CO
SCHEDULE 13G
CUSIP No.
20454B104
1
Names of Reporting Persons
Blackstone Group Management L.L.C.
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
6,126,182.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
6,126,182.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
6,126,182.00
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)
3.4 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP No.
20454B104
1
Names of Reporting Persons
Stephen A. Schwarzman
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
UNITED STATES
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
6,126,182.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
6,126,182.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
6,126,182.00
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)
3.4 %
12
Type of Reporting Person (See Instructions)
IN
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
Compass Therapeutics, Inc.
(b)
Address of issuer's principal executive offices:
80 Guest Street, Suite 601, Boston, MA 02135
Item 2.
(a)
Name of person filing:
This Schedule 13G is being filed by Blackstone Annex Master Fund L.P. ("Annex Fund"), Spruce Street Aggregator L.P. ("Spruce"), Blackstone Alternative Asset Management Associates LLC ("BAAMA"), Blackstone Holdings II L.P. ("Holdings II"), Blackstone Holdings I/II GP L.L.C. ("Holdings GP"), Blackstone Inc. ("Blackstone"), Blackstone Group Management L.L.C. ("Blackstone Management"), and Stephen A. Schwarzman (together with Annex Fund, Spruce, BAAMA, Holdings II, Holdings GP, Blackstone and Blackstone Management, the "Reporting Persons").
(b)
Address or principal business office or, if none, residence:
The principal business address of each of the Reporting Persons is:
345 Park Avenue
New York, NY 10154
(c)
Citizenship:
Annex Fund is a Cayman Islands limited partnership. Spruce is a Cayman Islands exempted limited partnership. BAAMA is a limited liability company organized under the laws of the State of Delaware. Holdings II is a limited partnership organized under the laws of the State of Delaware. Holdings GP is a limited liability company organized under the laws of the State of Delaware. Blackstone is a corporation organized under the laws of the State of Delaware. Blackstone Management is a limited liability company organized under the laws of the State of Delaware. Mr. Schwarzman is a citizen of the United States of America.
(d)
Title of class of securities:
Common Stock, $0.0001 par value per share
(e)
CUSIP No.:
20454B104
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:
Items 5 through 9 and 11 of each of the cover pages to this Schedule 13G are incorporated herein by reference.
As of December 31, 2025, Annex Fund directly holds 2,447,820 shares of Common Stock, $0.0001 par value per share per share ("Common Stock") of Compass Therapeutics, Inc. (the "Issuer") and Spruce directly holds 3,678,362 shares of Common Stock.
BAAMA is the general partner of the Annex Fund and Spruce. Holdings II is the sole member of BAAMA. Holdings GP is the general partner of Holdings II. Blackstone is the sole member of Holdings GP. Blackstone Management is the sole holder of the Series II preferred stock of Blackstone. Blackstone Management is wholly owned by its senior managing directors and controlled by its founder, Stephen A. Schwarzman.
Each Reporting Person may be deemed to beneficially own the Common Stock of the Issuer directly or indirectly controlled by it or him, but neither the filing of this Schedule 13G nor any of its contents shall be deemed to constitute an admission that any such Reporting Person (other than any Reporting Person to the extent they directly hold Issuer securities) is the beneficial owner of Common Stock of the Issuer referred to herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended (the "Act"), or for any other purpose and each of the Reporting Persons expressly disclaims beneficial ownership of such shares of Common Stock. The filing of this statement should not be construed to be an admission that any member of the Reporting Persons are members of a "group" for the purposes of Section 13(d) and 13(g) of the Act.
(b)
Percent of class:
Each of the Reporting Persons may be deemed to be the beneficial owner of the percentage of shares of Common Stock listed on such Reporting Person's cover page. Calculations are based on 177,572,498 shares of Common Stock of the Issuer outstanding as of September 30, 2025, as disclosed in the Issuer's Registration Statement on Form S-3 filed with the Securities and Exchange Commission on December 30, 2025. As of December 31, 2025, Reporting Persons no longer beneficially own more than five percent of the Common Stock. This filing represents an exit filing for the Reporting Persons.
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
See each cover page hereof.
(ii) Shared power to vote or to direct the vote:
See each cover page hereof.
(iii) Sole power to dispose or to direct the disposition of:
See each cover page hereof.
(iv) Shared power to dispose or to direct the disposition of:
See each cover page hereof.
Item 5.
Ownership of 5 Percent or Less of a Class.
Ownership of 5 percent or less of a class
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.
Blackstone Annex Master Fund L.P.
Signature:
/s/ Stephen O'Connor
Name/Title:
By: Blackstone Alternative Asset Management Associates LLC, its general partner, By: Stephen O'Connor, Authorized Person
Date:
02/13/2026
Spruce Street Aggregator L.P.
Signature:
/s/ Stephen O'Connor
Name/Title:
By: Blackstone Alternative Asset Management Associates LLC, its general partner, By: Stephen O'Connor, Authorized Person
Date:
02/13/2026
Blackstone Alternative Asset Management Associates LLC
Signature:
/s/ Stephen O'Connor
Name/Title:
Stephen O'Connor, Authorized Person
Date:
02/13/2026
Blackstone Holdings II L.P.
Signature:
/s/ Victoria Portnoy
Name/Title:
Victoria Portnoy Managing Director - Assistant Secretary
Date:
02/13/2026
Blackstone Holdings I/II GP L.L.C.
Signature:
/s/ Victoria Portnoy
Name/Title:
Victoria Portnoy Managing Director - Assistant Secretary
Date:
02/13/2026
Blackstone Inc.
Signature:
/s/ Victoria Portnoy
Name/Title:
Victoria Portnoy Managing Director - Assistant Secretary
Date:
02/13/2026
Blackstone Group Management L.L.C.
Signature:
/s/ Victoria Portnoy
Name/Title:
Victoria Portnoy Managing Director - Assistant Secretary
What stake in Compass Therapeutics (CMPX) do the Blackstone-related funds report?
The Blackstone-related reporting group discloses beneficial ownership of 6,126,182 shares of Compass Therapeutics common stock, representing 3.4% of the outstanding shares. This percentage is calculated using 177,572,498 shares outstanding as of September 30, 2025.
Which Blackstone entities directly hold Compass Therapeutics (CMPX) shares?
Blackstone Annex Master Fund L.P. directly holds 2,447,820 CMPX shares, and Spruce Street Aggregator L.P. directly holds 3,678,362 CMPX shares. Other Blackstone-affiliated entities are reported as indirect beneficial owners through their control relationships with these funds.
Why is this Schedule 13G/A for Compass Therapeutics (CMPX) described as an exit filing?
The filing states that as of December 31, 2025 the reporting persons no longer beneficially own more than five percent of CMPX common stock. Because they dropped below the 5% threshold, this amended Schedule 13G is characterized as an exit filing.
How was the ownership percentage in Compass Therapeutics (CMPX) calculated in this 13G/A?
The reported 3.4% beneficial ownership is based on 177,572,498 shares of CMPX common stock outstanding as of September 30, 2025, as disclosed in the company’s Form S-3. The reporting group’s 6,126,182 shares are measured against that share count.
Do the Blackstone reporting persons seek to influence control of Compass Therapeutics (CMPX)?
The certification states the securities were not acquired and are not held for the purpose of changing or influencing control of Compass Therapeutics. It also notes they are not held in connection with any transaction having that purpose, other than activities tied to a specific nomination rule.
Who signed the Compass Therapeutics (CMPX) Schedule 13G/A on behalf of the Blackstone entities?
The filing is signed by Stephen O’Connor, acting as an authorized person for certain Blackstone entities, and by Victoria Portnoy, Managing Director and Assistant Secretary, as well as by Stephen A. Schwarzman himself, each on February 13, 2026.
