SCHEDULE 13G/A 0001484870 XXXXXXXX LIVE 1 Common Stock, $0.0001 par value per share 12/31/2025 0001738021 Compass Therapeutics, Inc. 20454B104 80 Guest Street Suite 601 Boston MA 02135 Rule 13d-1(c) Blackstone Annex Master Fund L.P. b E9 0 2447820 0 2447820 2447820 N 1.4 PN Spruce Street Aggregator L.P. b E9 0 3678362 0 3678362 3678362 N 2.1 PN Blackstone Alternative Asset Management Associates LLC b DE 0 6126182 0 6126182 6126182 N 3.4 OO Blackstone Holdings II L.P. b DE 0 6126182 0 6126182 6126182 N 3.4 PN Blackstone Holdings I/II GP L.L.C. b DE 0 6126182 0 6126182 6126182 N 3.4 OO Blackstone Inc. b DE 0 6126182 0 6126182 6126182 N 3.4 CO Blackstone Group Management L.L.C. b DE 0 6126182 0 6126182 6126182 N 3.4 OO Stephen A. Schwarzman b X1 0 6126182 0 6126182 6126182 N 3.4 IN Compass Therapeutics, Inc. 80 Guest Street, Suite 601, Boston, MA 02135 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"). The principal business address of each of the Reporting Persons is: 345 Park Avenue New York, NY 10154 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. Y 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. 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. See each cover page hereof. See each cover page hereof. See each cover page hereof. See each cover page hereof. N Y Y Y Y Y N 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. Blackstone Annex Master Fund L.P. /s/ Stephen O'Connor 02/13/2026 Spruce Street Aggregator L.P. /s/ Stephen O'Connor 02/13/2026 Blackstone Alternative Asset Management Associates LLC /s/ Stephen O'Connor 02/13/2026 Blackstone Holdings II L.P. /s/ Victoria Portnoy 02/13/2026 Blackstone Holdings I/II GP L.L.C. /s/ Victoria Portnoy 02/13/2026 Blackstone Inc. /s/ Victoria Portnoy 02/13/2026 Blackstone Group Management L.L.C. /s/ Victoria Portnoy 02/13/2026 Stephen A. Schwarzman /s/ Stephen A. Schwarzman 02/13/2026