Biotechnology Value Fund and related entities reported beneficial ownership of Compass Therapeutics common stock. As of the close of business on March 31, 2026, the filing shows BVF beneficially owned 4,142,020 shares and BVF2 beneficially owned 3,028,951 shares. The statement uses the issuer's disclosed shares outstanding of 180,087,915 shares as of February 27, 2026 to calculate percentages. The filing lists shared voting and dispositive power figures across affiliated entities and includes customary disclaimers of beneficial ownership among group members.
Positive
None.
Negative
None.
Insights
Large institutional stakes reported across affiliated BVF entities; holdings are disclosed as shared control.
The filing details that BVF holds 4,142,020 shares and BVF2 holds 3,028,951 shares as of March 31, 2026. Percentages are computed against 180,087,915 shares outstanding as of February 27, 2026, producing approximately 2.3% and 1.7% stakes respectively.
Ownership is presented through a nested group structure with shared voting and dispositive power. Subsequent filings or amendments could change group allocations; any material change in holdings would appear in later reports.
Filing follows Schedule 13G/A conventions with explicit disclaimers and group attribution language.
The statement enumerates affiliated entities (GPs, Partners, holding companies) and includes disclaimers where entities "disclaim beneficial ownership." It also ties percentage calculations to an issuer 10-K disclosure of shares outstanding.
For precision, note that shared voting/dispositive power lines are highlighted on the cover pages; the filing preserves standard Group attribution and non-admission language used in passive investor schedules.
Key Figures
BVF holdings:4,142,020 sharesBVF2 holdings:3,028,951 sharesShares outstanding:180,087,915 shares+2 more
5 metrics
BVF holdings4,142,020 sharesBeneficial ownership as of March 31, 2026
BVF2 holdings3,028,951 sharesBeneficial ownership as of March 31, 2026
Shares outstanding180,087,915 sharesIssuer disclosure as of February 27, 2026 (Form 10-K)
Trading Fund OS holdings476,311 sharesBeneficial ownership as of March 31, 2026
Aggregate Partners-affiliated holdings7,764,842 sharesAggregate beneficial ownership reported for Partners and affiliates
"As of the close of business on March 31, 2026, BVF beneficially owned 4,142,020 shares"
Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.
shared dispositive powerregulatory
"Shared Dispositive Power 4,142,020.00"
Schedule 13G/Aregulatory
"Signed: Schedule 13G/A amendment filing and group identification"
A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.
What stake does Biotechnology Value Fund (BVF) report in Compass Therapeutics (CMPX)?
BVF reports beneficial ownership of 4,142,020 shares as of March 31, 2026. This represents approximately 2.3% of the 180,087,915 shares outstanding disclosed in the issuer's Form 10-K as of February 27, 2026.
How many shares does BVF II (BVF2) report owning in CMPX?
BVF2 reports beneficial ownership of 3,028,951 shares as of March 31, 2026. That stake is approximately 1.7% of the issuer's 180,087,915 shares outstanding referenced in the filing.
What aggregate holdings do the BVF-related entities report and how is percentage calculated?
Affiliated entities are reported in aggregate positions such as 7,764,842 shares for Partners-affiliated holdings. Percentages use the issuer's disclosed 180,087,915 shares outstanding as of February 27, 2026 from the Form 10-K.
Does the filing indicate who has voting or dispositive power over these CMPX shares?
The filing shows shared voting and shared dispositive power figures for the affiliated entities (for example, 4,142,020 shared power for BVF). Specific sole/shared breakdowns are provided on the cover-page items referenced in the statement.
Are there disclaimers about beneficial ownership among the Reporting Persons?
Yes. Several affiliated entities expressly disclaim beneficial ownership of shares held by other Reporting Persons, and the filing states it should not be construed as an admission of beneficial ownership by any Reporting Person.
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)
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):
20454B104
1
Names of Reporting Persons
BIOTECHNOLOGY VALUE 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
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
4,142,020.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
4,142,020.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
4,142,020.00
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)
2.3 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP Number(s):
20454B104
1
Names of Reporting Persons
BVF I GP 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
4,142,020.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
4,142,020.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
4,142,020.00
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)
2.3 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP Number(s):
20454B104
1
Names of Reporting Persons
BIOTECHNOLOGY VALUE FUND II 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
3,028,951.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
3,028,951.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
3,028,951.00
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)
1.7 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP Number(s):
20454B104
1
Names of Reporting Persons
BVF II GP 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
3,028,951.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
3,028,951.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
3,028,951.00
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)
1.7 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP Number(s):
20454B104
1
Names of Reporting Persons
Biotechnology Value Trading Fund OS 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
CAYMAN ISLANDS
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
476,311.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
476,311.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
476,311.00
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)
0.3 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP Number(s):
20454B104
1
Names of Reporting Persons
BVF Partners OS Ltd.
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
476,311.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
476,311.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
476,311.00
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)
0.3 %
12
Type of Reporting Person (See Instructions)
CO
SCHEDULE 13G
CUSIP Number(s):
20454B104
1
Names of Reporting Persons
BVF GP HOLDINGS 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
7,170,971.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
7,170,971.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
7,170,971.00
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)
4.0 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP Number(s):
20454B104
1
Names of Reporting Persons
BVF PARTNERS L P/IL
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
7,764,842.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
7,764,842.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
7,764,842.00
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)
4.3 %
12
Type of Reporting Person (See Instructions)
IA, PN
SCHEDULE 13G
CUSIP Number(s):
20454B104
1
Names of Reporting Persons
BVF INC/IL
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
7,764,842.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
7,764,842.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
7,764,842.00
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)
4.3 %
12
Type of Reporting Person (See Instructions)
CO
SCHEDULE 13G
CUSIP Number(s):
20454B104
1
Names of Reporting Persons
LAMPERT MARK N
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
7,764,842.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
7,764,842.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
7,764,842.00
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)
4.3 %
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, BOSTON, MA, 02135
Item 2.
(a)
Name of person filing:
Biotechnology Value Fund, L.P. ("BVF")
BVF I GP LLC ("BVF GP")
Biotechnology Value Fund II, L.P. ("BVF2")
BVF II GP LLC ("BVF2 GP")
Biotechnology Value Trading Fund OS LP ("Trading Fund OS")
BVF Partners OS Ltd. ("Partners OS")
BVF GP Holdings LLC ("BVF GPH")
BVF Partners L.P. ("Partners")
BVF Inc.
Mark N. Lampert ("Mr. Lampert")
Each of the foregoing is referred to as a "Reporting Person" and collectively as the "Reporting Persons."
(b)
Address or principal business office or, if none, residence:
Biotechnology Value Fund, L.P.
44 Montgomery St., 40th Floor
San Francisco, California 94104
BVF I GP LLC
44 Montgomery St., 40th Floor
San Francisco, California 94104
Biotechnology Value Fund II, L.P.
44 Montgomery St., 40th Floor
San Francisco, California 94104
BVF II GP LLC
44 Montgomery St., 40th Floor
San Francisco, California 94104
Biotechnology Value Trading Fund OS LP
PO Box 309 Ugland House
Grand Cayman, KY1-1104
Cayman Islands
BVF Partners OS Ltd.
PO Box 309 Ugland House
Grand Cayman, KY1-1104
Cayman Islands
BVF GP Holdings LLC
44 Montgomery St., 40th Floor
San Francisco, California 94104
BVF Partners L.P.
44 Montgomery St., 40th Floor
San Francisco, California 94104
BVF Inc.
44 Montgomery St., 40th Floor
San Francisco, California 94104
Mark N. Lampert
44 Montgomery St., 40th Floor
San Francisco, California 94104
(c)
Citizenship:
Biotechnology Value Fund, L.P.
Delaware
BVF I GP LLC
Delaware
Biotechnology Value Fund II, L.P.
Delaware
BVF II GP LLC
Delaware
Biotechnology Value Trading Fund OS LP
Cayman Islands
BVF Partners OS Ltd.
Cayman Islands
BVF GP Holdings LLC
Delaware
BVF Partners L.P.
Delaware
BVF Inc.
Delaware
Mark N. Lampert
United States
(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:
As of the close of business on March 31, 2026, (i) BVF beneficially owned 4,142,020 shares of the Issuer's Common Stock, $0.0001 par value per share (the "Shares"), (ii) BVF2 beneficially owned 3,028,951 Shares and (iii) Trading Fund OS beneficially owned 476,311 Shares.
BVF GP, as the general partner of BVF, may be deemed to beneficially own the 4,142,020 Shares beneficially owned by BVF.
BVF2 GP, as the general partner of BVF2, may be deemed to beneficially own the 3,028,951 Shares beneficially owned by BVF2.
Partners OS, as the general partner of Trading Fund OS, may be deemed to beneficially own the 476,311 Shares beneficially owned by Trading Fund OS.
BVF GPH, as the sole member of each of BVF GP and BVF2 GP, may be deemed to beneficially own the 7,170,971 Shares beneficially owned in the aggregate by BVF and BVF2.
Partners, as the investment manager of BVF, BVF2 and Trading Fund OS, and the sole member of Partners OS, may be deemed to beneficially own the 7,764,842 Shares beneficially owned in the aggregate by BVF, BVF2 and Trading Fund OS and held in a certain Partners managed account (the "Partners Managed Account"), including 117,560 Shares held in the Partners Managed Account.
BVF Inc., as the general partner of Partners, may be deemed to beneficially own the 7,764,842 Shares beneficially owned by Partners.
Mr. Lampert, as a director and officer of BVF Inc., may be deemed to beneficially own the 7,764,842 Shares beneficially owned by BVF Inc.
The foregoing should not be construed in and of itself as an admission by any Reporting Person as to beneficial ownership of any Shares owned by another Reporting Person. BVF GP disclaims beneficial ownership of the Shares beneficially owned by BVF. BVF2 GP disclaims beneficial ownership of the Shares beneficially owned by BVF2. Partners OS disclaims beneficial ownership of the Shares beneficially owned by Trading Fund OS. BVF GPH disclaims beneficial ownership of the Shares beneficially owned by BVF and BVF2. Each of Partners, BVF Inc. and Mr. Lampert disclaims beneficial ownership of the Shares beneficially owned by BVF, BVF2 and Trading Fund OS and held in the Partners Managed Account, and the filing of this statement shall not be construed as an admission that any such person or entity is the beneficial owner of any such securities.
(b)
Percent of class:
The following percentages are based on 180,087,915 Shares outstanding as of February 27, 2026, which is the total number of Shares outstanding as disclosed in the Issuer's Annual Report on Form 10-K filed with the Securities and Exchange Commission on March 5, 2026.
As of the close of business on March 31, 2026, (i) BVF beneficially owned approximately 2.3% of the outstanding Shares, (ii) BVF2 beneficially owned approximately 1.7% of the outstanding Shares, (iii) Trading Fund OS beneficially owned less than 1% of the outstanding Shares, (iv) BVF GP may be deemed to beneficially own approximately 2.3% of the outstanding Shares, (v) BVF2 GP may be deemed to beneficially own approximately 1.7% of the outstanding Shares, (vi) Partners OS may be deemed to beneficially own less than 1% of the outstanding Shares, (vii) BVF GPH may be deemed to beneficially own approximately 4.0% of the outstanding Shares, and (viii) each of Partners, BVF Inc. and Mr. Lampert may be deemed to beneficially own approximately 4.3% of the outstanding Shares (less than 1% of the outstanding Shares are held in the Partners Managed Account).
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
See Cover Pages Items 5-9.
(ii) Shared power to vote or to direct the vote:
See Cover Pages Items 5-9.
(iii) Sole power to dispose or to direct the disposition of:
See Cover Pages Items 5-9.
(iv) Shared power to dispose or to direct the disposition of:
See Cover Pages Items 5-9.
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.
If a group has filed this schedule pursuant to §240.13d-1(b)(1)(ii)(J), so indicate under Item 3(j) and attach an exhibit stating the identity and Item 3 classification of each member of the group. If a group has filed this schedule pursuant to §240.13d-1(c) or §240.13d-1(d), attach an exhibit stating the identity of each member of the group.
See Exhibit 99.1 to the Schedule 13G filed by the Reporting Persons with the Securities and Exchange Commission on October 29, 2025.
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.
