SEC Form 4

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* SEIDENBERG BETH C (Last) (First) (Middle) C/O ACELYRIN, INC. 4149 LIBERTY CANYON RD. (Street) AGOURA HILLS CA 91301 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol ACELYRIN, Inc. [ SLRN ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X Director X 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 05/09/2023
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) X Form filed by One Reporting Person Form filed by More than One Reporting Person
	Rule 10b5-1(c) Transaction Indication Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	05/09/2023		C(1)		8,540,729	A	(1)	8,540,729	I	See footnote(2)
Common Stock	05/09/2023		P(3)		1,250,000	A	$18	9,790,729	I	See footnote(2)
Common Stock	05/09/2023		P(4)		60,000	A	$18	60,000	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Series A Redeemable Convertible Preferred Stock	(5)	05/09/2023		C			4,056,795	(5)	(5)	Common Stock(6)	4,056,795	(5)	0	I	See footnote(2)
Series B Redeemable Convertible Preferred Stock	(5)	05/09/2023		C			2,445,786	(5)	(5)	Common Stock(6)	2,445,786	(5)	0	I	See footnote(2)
Series C Redeemable Convertible Preferred Stock	(5)	05/09/2023		C			2,038,148	(5)	(5)	Common Stock(6)	2,038,148	(5)	0	I	See footnote(2)
Director Stock Option (right to buy)	$18	05/09/2023		J(6)			23,243	(7)	05/03/2033	Class A Common Stock(6)	23,243	$0.00	0	D
Director Stock Option (right to buy)	$18	05/09/2023		J(6)		23,243		(7)	05/03/2033	Common Stock(6)	23,243	$0.00	23,243	D

Explanation of Responses:

1. Represents shares of Common Stock received upon conversion of shares of the reported series of preferred stock on a one-for-one basis without payment of further consideration.

2. Shares held directly by Westlake BioPartners Fund II, L.P., or Westlake Fund II. Westlake BioPartners GP II, LLC, or Westlake GP II, is the general partner of Westlake Fund II. Westlake GP II may be deemed to have sole voting and dispositive power with regard to the shares held directly by Westlake Fund II. The Reporting Person and Sean E. Harper are the Managing Directors of Westlake GP II and share voting and dispositive power over the shares held by Westlake Fund II, each of whom disclaims beneficial ownership of the shares held by Westlake Fund II except to the extent of such person's pecuniary interest therein, if any.

3. Represents shares of Common Stock purchased in the Issuer's initial public offering of Common Stock (the "IPO").

4. Represents shares of Common Stock purchased through a directed share program in the IPO.

5. Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

6. Each share of Class A Common Stock was reclassified into one share of Common Stock immediately prior to the completion of the IPO.

7. 1/36 of the shares subject to the option vest on June 4, 2023, and 1/36 of the shares subject to the option vest in equal monthly installments thereafter, subject to the Reporting Person's continued service.

Remarks:

	/s/ Mina Kim, Attorney-in-fact	05/11/2023
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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