Amendment: SEC Form SCHEDULE 13D/A filed by Compass Therapeutics Inc.

601 Lexington Avenue, 54th Floor, New York, New York 10022.

OrbiMed Advisors is a limited liability company organized under the laws of Delaware and a registered investment adviser under the Investment Advisers Act of 1940, as amended. OrbiMed GP is a limited liability company organized under the laws of Delaware. Carl L. Gordon is a member of OrbiMed Advisors. Sven H. Borho is a member of OrbiMed Advisors. W. Carter Neild is a member of OrbiMed Advisors. Geoffrey C. Hsu is a member of OrbiMed Advisors. C. Scotland Stevens is a member of OrbiMed Advisors. David P. Bonita is a member of OrbiMed Advisors. Peter A. Thompson is a member of OrbiMed Advisors. Matthew S. Rizzo is a member of OrbiMed Advisors. Mona Ashiya is a member of OrbiMed Advisors. Trey Block is the Chief Financial Officer of OrbiMed Advisors.

Not applicable.

Not applicable.

Item 2(a) is incorporated herein by reference.

Not applicable.

The Reporting Persons from time to time intend to review their investment in the Issuer on the basis of various factors, including the Issuer's business, financial condition, results of operations and prospects, general economic and industry conditions, the securities markets in general and those for the Issuer's Shares in particular, as well as other developments and other investment opportunities. Based upon such review, the Reporting Persons will take such actions in the future as the Reporting Persons may deem appropriate in light of the circumstances existing from time to time. If the Reporting Persons believe that further investment in the Issuer is attractive, whether because of the market price of Shares or otherwise, they may acquire Shares or other securities of the Issuer either in the open market or in privately negotiated transactions. Similarly, depending on market and other factors, the Reporting Persons may determine to dispose of some or all of the Shares currently owned by the Reporting Persons or otherwise acquired by the Reporting Persons either in the open market or in privately negotiated transactions. Except as set forth in this Schedule 13D, the Reporting Persons have not formulated any plans or proposals which relate to or would result in: (a) the acquisition by any person of additional securities of the Issuer or the disposition of securities of the Issuer, (b) an extraordinary corporate transaction, such as a merger, reorganization or liquidation, involving the Issuer or any of its subsidiaries, (c) a sale or transfer of a material amount of the assets of the Issuer or any of its subsidiaries, (d) any change in the present Board of Directors or management of the Issuer, including any plans or proposals to change the number or term of directors or to fill any existing vacancies on the board, (e) any material change in the Issuer's capitalization or dividend policy of the Issuer, (f) any other material change in the Issuer's business or corporate structure, (g) any change in the Issuer's charter or bylaws or other instrument corresponding thereto or other action which may impede the acquisition of control of the Issuer by any person, (h) causing a class of the Issuer's securities to be deregistered or delisted from a national securities exchange or to cease to be authorized to be quoted in an inter-dealer quotation system of a registered national securities association, (i) a class of equity securities of the Issuer becoming eligible for termination of registration pursuant to Section 12(g)(4) of the Act or (j) any action similar to any of those enumerated above.

The following disclosure is based upon 171,572,498 outstanding Shares, as set forth in the Issuer's Rule 424(b)(5) Prospectus filed with the SEC on August 13, 2025. As of the date of this filing, OrbiMed Private Investments V - KA, LP ("OPI V-KA"), a limited partnership organized under the laws of Delaware, holds 15,219,994 Shares constituting approximately 8.9% of the issued and outstanding Shares. OrbiMed GP is the general partner of OPI V-KA, pursuant to the terms of the limited partnership agreement of OPI V-KA, and OrbiMed Advisors is the managing member of OrbiMed GP, pursuant to the terms of the limited liability company agreement of OrbiMed GP. As a result, OrbiMed Advisors and OrbiMed GP share power to direct the vote and disposition of the Shares held by OPI V-KA and may be deemed directly or indirectly, including by reason of their mutual affiliation, to be the beneficial owners of the Shares held by OPI V KA. OrbiMed Advisors exercises this investment and voting power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and W. Carter Neild, each of whom disclaims beneficial ownership of the Shares held by OPI V-KA. In addition, OrbiMed Advisors and OrbiMed GP, pursuant to their authority under the limited partnership agreements of OPI V-KA, caused OPI V-KA to enter into the agreements referred to in Item 6 below.

Item 5(a) is incorporated by reference herein.

Not applicable.

Not applicable.

Not applicable.

In addition to the relationships between the Reporting Persons described in Items 2 and 5 above, OrbiMed GP is the general partner of OPI V-KA, pursuant to the terms of the limited partnership agreement of OPI V KA. Pursuant to this agreement and relationship, OrbiMed GP has discretionary investment management authority with respect to the assets of OPI V-KA. Such authority includes the power to vote and otherwise dispose of securities held by OPI V-KA. The number of outstanding Shares of the Issuer attributable to OPI V-KA is 15,219,994. OrbiMed GP, pursuant to its authority under the limited partnership agreement of OPI V-KA, may be considered to hold indirectly 15,219,994 Shares. OrbiMed Advisors is the managing member of OrbiMed GP, pursuant to the terms of the limited liability company agreement of OrbiMed GP. Pursuant to these agreements and relationships, OrbiMed Advisors and OrbiMed GP have discretionary investment management authority with respect to the assets of OPI V-KA. Such authority includes the power of OrbiMed GP to vote and otherwise dispose of securities held by OPI V-KA. The number of outstanding Shares attributable to OPI V-KA is 15,219,994 Shares. OrbiMed Advisors, pursuant to its authority under the terms of the limited liability company agreement of OrbiMed GP, may also be considered to hold indirectly 15,219,994 Shares. Carl L. Gordon ("Gordon"), a member of OrbiMed Advisors, is a member of the Board of Directors of the Issuer and, accordingly, OrbiMed Advisors and OrbiMed GP may have the ability to affect and influence control of the Issuer. From time to time, Gordon may receive stock options or other awards of equity-based compensation pursuant to the Issuer's compensation arrangements for non-employee directors. Pursuant to an agreement with OrbiMed Advisors and OrbiMed GP, Gordon is obligated to transfer any securities issued under any such stock options or other awards, or the economic benefit thereof, to OrbiMed Advisors and OrbiMed GP, which will in turn ensure that such securities or economic benefits are provided to OPI V-KA. Additionally, OPI V-KA and certain other stockholders of the Issuer are party to registration rights agreements with the Issuer, summaries of which are set forth in Amendment No. 3.

------------------------------------------------------------------------------------------------------------------------------------- Exhibit Description ------------------------------------------------------------------------------------------------------------------------------------- 1. Joint Filing Agreement among OrbiMed Advisors LLC and OrbiMed Capital GP V LLC. ------------------------------------------------------------------------------------------------------------------------------------- 2. Registration Rights Agreement by and among the Issuer and the investors signatory thereto dated June 19, 2020 (incorporated by reference to Exhibit 10.7 to the Issuer's From 8-K filed with the SEC on June 23, 2020 (File No. 000-55939)). ------------------------------------------------------------------------------------------------------------------------------------- 3. Registration Rights Agreement by and among the Issuer and the investors signatory thereto, dated November 2, 2022 (incorporated by reference to Exhibit 10.1 to the Issuer's Form 10-Q filed with the SEC on November 9, 2022 (File No. 001-39696)). -------------------------------------------------------------------------------------------------------------------------------------