SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person* Bain Capital Life Sciences Investors, LLC (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 05/25/2023	3. Issuer Name and Ticker or Trading Symbol Annexon, Inc. [ ANNX ]
		4. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)	5. If Amendment, Date of Original Filed (Month/Day/Year)
			6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock	5,401,926	I	See footnote(1)(6)(7)(8)(9)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Warrant (right to buy)	07/11/2022	06/30/2025	Common Stock	774,943(4)	5.8069	I	See footnote(2)(6)(7)(8)(9)
Pre-Funded Warrant (right to buy)	07/11/2022	(5)	Common Stock	2,739,475(4)	0.001	I	See footnote(3)(6)(7)(8)(9)

1. Name and Address of Reporting Person* Bain Capital Life Sciences Investors, LLC (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip)

1. Name and Address of Reporting Person* Bain Capital Life Sciences Fund, L.P. (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip)

1. Name and Address of Reporting Person* Bain Capital Life Sciences Partners, LP (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip)

1. Name and Address of Reporting Person* BCIP Life Sciences Associates, LP (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip)

Explanation of Responses:

1. Represents 2,940,627 shares of Common Stock held by Bain Capital Life Sciences Fund, L.P. ("BCLS Fund I"), 2,160,298 shares of Common Stock held by BCLS I Investco, LP ("BCLS I Investco") and 301,001 shares of Common Stock held by BCIP Life Sciences Associates, LP ("BCIPLS" and, together with BCLS Fund I and BCLS I Investco, the "Bain Capital Life Sciences Entities").

2. Represents a warrant to purchase 774,943 shares of Common Stock held by BCLS I Investco.

3. Represents a pre-funded warrant to purchase 2,739,475 shares of Common Stock held by BCLS I Investco.

4. BCLS I Investco is prohibited from exercising the warrant to purchase Common Stock referred to in footnote (2) above or the pre-funded warrant to purchase Common Stock referred to in footnote (3) above if the Bain Capital Life Sciences Entities would, in the aggregate, beneficially own more than 9.99% of the total number of shares of Common Stock then issued and outstanding immediately after giving effect to such exercise.

5. The pre-funded warrant does not expire.

6. Bain Capital Life Sciences Partners, LP ("BCLSP") is the general partner of BCLS Fund I. As a result, BCLSP may be deemed to share voting and dispositive power with respect to the securities held by BCLS Fund I. BCLSP disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.

7. BCLS I Investco GP, LLC ("BCLS I Investco GP"), whose manager is BCLS Fund I, is the general partner of BCLS I Investco. As a result, each of BCLSP, BCLS Fund I and BCLS I Investco GP may be deemed to share voting and dispositive power with respect to the securities held by BCLS I Investco. Each of BCLSP, BCLS Fund I and BCLS I Investco GP disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.

8. Boylston Coinvestors, LLC is the general partner of BCIPLS.

9. Bain Capital Life Sciences Investors, LLC ("BCLSI") is the general partner of BCLSP and governs the investment strategy and decision making process with respect to investments held by BCIPLS. As a result, BCLSI may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. BCLSI disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.

Remarks:

	Bain Capital Life Sciences Investors, LLC, By: /s/ Ricky Sun, Title: Partner	05/30/2023
	Bain Capital Life Sciences Fund, L.P., By: Bain Capital Life Sciences Partners, LP, its general partner, By: Bain Capital Life Sciences Investors, LLC, its general partner, By: /s/ Ricky Sun, Title: Partner	05/30/2023
	Bain Capital Life Sciences Partners, LP, By: Bain Capital Life Sciences Investors, LLC, its general partner, By: /s/ Ricky Sun, Title: Partner	05/30/2023
	BCIP Life Sciences Associates, LP, By: Boylston Coinvestors, LLC, its general partner, By: /s/ Ricky Sun, Title: Authorized Signatory	05/30/2023
	** Signature of Reporting Person	Date
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