Annexon, Inc. ownership disclosure: Reporting Persons led by Biotechnology Value Fund entities report beneficial ownership positions in Annexon common stock as of the close of business on March 31, 2026. The filing lists individual holdings including 4,644,823 shares for BVF, 3,399,850 shares for BVF2 and 522,906 shares for Trading Fund OS.
The filing states an aggregate holding of 8,698,173 shares attributable through related entities and managed accounts, representing approximately 5.4% for certain reporting persons based on 160,474,333 shares outstanding plus 2,027,384 shares issued on March 27, 2026 upon exercise of pre-funded warrants.
Positive
None.
Negative
None.
Insights
Schedule 13G/A discloses passive group ownership totaling 8,698,173 shares.
The statement itemizes beneficial ownership by related entities: BVF (4,644,823 shares), BVF2 (3,399,850 shares) and Trading Fund OS (522,906 shares). Percentages are calculated using 160,474,333 shares outstanding plus 2,027,384 shares issued on March 27, 2026.
Ownership is presented with customary disclaimers and attribution among general partners, managers and related entities; voting/dispositive powers are shown as shared where applicable. Future filings will show any material changes in holdings.
Group structure central to attribution and voting/dispositive clarity.
The disclosure explains how GP and manager relationships (BVF GP, BVF GPH, Partners, BVF Inc., and Mr. Lampert) may be deemed to beneficially own aggregated positions while many entities disclaim direct beneficial ownership. The filing flags a Partners Managed Account holding of 130,594 shares.
Investors should note the shared voting/dispositive power figures reported on the cover page and the explicit disclaimers; these affect who is treated as beneficial owner for Section 13 reporting.
Key Figures
BVF beneficial ownership:4,644,823 sharesBVF2 beneficial ownership:3,399,850 sharesTrading Fund OS beneficial ownership:522,906 shares+4 more
7 metrics
BVF beneficial ownership4,644,823 sharesAs of March 31, 2026
BVF2 beneficial ownership3,399,850 sharesAs of March 31, 2026
Trading Fund OS beneficial ownership522,906 sharesAs of March 31, 2026
Aggregate shares attributable8,698,173 sharesAggregate across related Reporting Persons as of March 31, 2026
Shares outstanding used160,474,333 sharesOutstanding as of March 25, 2026 per Form 10-K
Shares issued on exercise2,027,384 sharesIssued on March 27, 2026 upon exercise of pre-funded warrants
Reported ownership percentage (certain persons)5.4%Percent of class for Partners, BVF Inc. and Mr. Lampert
"As of the close of business on March 31, 2026, (i) BVF beneficially owned 4,644,823 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.
Partners Managed Accountfinancial
"held in a certain Partners managed account (the "Partners Managed Account"), including 130,594 Shares"
Pre-Funded Warrantsfinancial
"issued to the Reporting Persons and the Partners Managed Account on March 27, 2026, upon the exercise of certain Pre-Funded Warrants"
Pre-funded warrants are financial instruments that give investors the right to purchase a company's stock at a set price, but with most or all of the purchase price paid upfront. They function like a coupon or gift card for stock, allowing investors to buy shares later at a fixed price, which can be beneficial if they want to avoid future price increases. This makes them important for investors seeking flexibility and certainty in their investment plans.
Schedule 13G/Aregulatory
"Annexon, Inc. SCHEDULE 13G/A (Amendment No. 4) signed May 15, 2026"
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.
See more from StockTitan in Google Search and AI answers.Adds StockTitan as a preferred source · opens Google
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
(Amendment No. 4)
Annexon, Inc.
(Name of Issuer)
Common Stock, par value $0.001 per share
(Title of Class of Securities)
03589W102
(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):
03589W102
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
4,644,823.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
4,644,823.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
4,644,823.00
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)
2.9 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP Number(s):
03589W102
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
4,644,823.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
4,644,823.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
4,644,823.00
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)
2.9 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP Number(s):
03589W102
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
3,399,850.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
3,399,850.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
3,399,850.00
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 Number(s):
03589W102
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
3,399,850.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
3,399,850.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
3,399,850.00
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)
OO
SCHEDULE 13G
CUSIP Number(s):
03589W102
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
522,906.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
522,906.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
522,906.00
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):
03589W102
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
522,906.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
522,906.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
522,906.00
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):
03589W102
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
8,044,673.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
8,044,673.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
8,044,673.00
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)
5.0 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP Number(s):
03589W102
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
8,698,173.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
8,698,173.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
8,698,173.00
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)
5.4 %
12
Type of Reporting Person (See Instructions)
IA, PN
SCHEDULE 13G
CUSIP Number(s):
03589W102
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
8,698,173.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
8,698,173.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
8,698,173.00
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)
5.4 %
12
Type of Reporting Person (See Instructions)
CO
SCHEDULE 13G
CUSIP Number(s):
03589W102
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
8,698,173.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
8,698,173.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
8,698,173.00
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)
5.4 %
12
Type of Reporting Person (See Instructions)
IN
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
Annexon, Inc.
(b)
Address of issuer's principal executive offices:
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, par value $0.001 per share
(e)
CUSIP No.:
03589W102
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 4,644,823 Shares, (ii) BVF2 beneficially owned 3,399,850 Shares, and (iii) Trading Fund OS beneficially owned 522,906 Shares.
BVF GP, as the general partner of BVF, may be deemed to beneficially own the 4,644,823 Shares beneficially owned by BVF.
BVF2 GP, as the general partner of BVF2, may be deemed to beneficially own the 3,399,850 Shares beneficially owned by BVF2.
Partners OS, as the general partner of Trading Fund OS, may be deemed to beneficially own the 522,906 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 8,044,673 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 8,698,173 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 130,594 Shares held in the Partners Managed Account.
BVF Inc., as the general partner of Partners, may be deemed to beneficially own the 8,698,173 Shares beneficially owned by Partners.
Mr. Lampert, as a director and officer of BVF Inc., may be deemed to beneficially own the 8,698,173 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 upon a denominator that is the sum of (i) 160,474,333 Shares outstanding as of March 25, 2026, as disclosed in the Issuer's Annual Report on Form 10-K filed with the Securities and Exchange Commission on March 30, 2026, and (ii) 2,027,384 Shares issued to the Reporting Persons and the Partners Managed Account on March 27, 2026, upon the exercise of certain Pre-Funded Warrants previously held by them.
As of the close of business on March 31, 2026, (i) BVF beneficially owned approximately 2.9% of the outstanding Shares, (ii) BVF2 beneficially owned approximately 2.1% 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 2.9% of the outstanding Shares, (v) BVF2 GP may be deemed to beneficially own approximately 2.1% 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 5.0% of the outstanding Shares, and (viii) each of Partners, BVF Inc. and Mr. Lampert may be deemed to beneficially own approximately 5.4% 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.
Not Applicable
Item 6.
Ownership of more than 5 Percent on Behalf of Another Person.
If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required.
Partners, BVF Inc. and Mr. Lampert share voting and dispositive power over the Shares beneficially owned by BVF, BVF2 and Trading Fund OS and held in the Partners Managed Account.
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 with the Securities and Exchange Commission on May 26, 2022.
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.
What stake does Biotechnology Value Fund (BVF) report in ANNX?
BVF reports beneficial ownership of 4,644,823 shares as of March 31, 2026. That amount is reported as approximately 2.9% of the class under the filing's denominator calculation.
How much does BVF II (BVF2) own in Annexon (ANNX)?
BVF2 reports beneficial ownership of 3,399,850 shares as of March 31, 2026. The filing states this represents approximately 2.1% of the outstanding shares using the disclosed denominator.
What is the aggregate position reported by the group in ANNX?
Related reporting persons disclose an aggregate of 8,698,173 shares held through affiliated entities and a managed account as of March 31, 2026. Certain reporting persons are attributed with approximately 5.4% on that basis.
What outstanding share figures does the filing use to calculate percentages?
Percentages are calculated using 160,474,333 shares outstanding as of March 25, 2026 plus 2,027,384 shares issued on March 27, 2026 upon exercise of pre-funded warrants, per the filing.
Does the filing show who holds voting or dispositive power over these shares?
Cover-page items report shared voting and dispositive power for the listed entities (for example, shared power of 8,044,673 for BVF GPH). The filing ties vote/disposition figures to the cover-page items rather than restating them in Item 4.
