Sec Form 4 Filing - Lin Shao-Lee @ ACELYRIN, Inc. - 2023-05-09

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

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, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Lin Shao-Lee 2. Issuer Name and Ticker or Trading Symbol ACELYRIN, Inc. [ SLRN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Chief Executive Officer (Last) (First) (Middle) C/O ACELYRIN, INC., 4149 LIBERTY CANYON RD. 3. Date of Earliest Transaction (MM/DD/YY) 05/09/2023 (Street) AGOURA HILLS, CA91301 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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 ) 1,161,747 A 1,161,747 I See footnote ( 2 ) Class A Common Stock 05/09/2023 J( 3 ) 1,107,213 ( 4 ) D $ 0 0 D Common Stock 05/09/2023 J( 3 ) 1,107,213 ( 4 ) A $ 0 1,107,213 D Common Stock 05/09/2023 F 337,179 ( 5 ) D $ 24.69 770,034 ( 6 ) D Class A Common Stock 05/09/2023 J( 3 ) 677,813 D $ 0 0 I See footnote ( 7 ) Common Stock 05/09/2023 J( 3 ) 677,813 A $ 0 677,813 I See footnote ( 7 ) Class A Common Stock 05/09/2023 J( 3 ) 354,969 D $ 0 0 I See footnote ( 8 ) Common Stock 05/09/2023 J( 3 ) 354,969 A $ 0 354,969 I See footnote ( 8 ) Class A Common Stock 05/09/2023 J( 3 ) 354,969 D $ 0 0 I See footnote ( 9 ) Common Stock 05/09/2023 J( 3 ) 354,969 A $ 0 354,969 I See footnote ( 9 ) Class A Common Stock 05/09/2023 J( 3 ) 349,898 D $ 0 0 I See footnote ( 10 ) Common Stock 05/09/2023 J( 3 ) 349,898 A $ 0 349,898 I See footnote ( 10 ) Class A Common Stock 05/09/2023 J( 3 ) 5,070 D $ 0 0 I See footnote ( 11 ) Common Stock 05/09/2023 J( 3 ) 5,070 A $ 0 5,070 I See footnote ( 11 )

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 7. Title and Amount of Underlying Securities (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 of Derivative Security: 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 B Redeemable Convertible Preferred Stock ( 1 ) 05/09/2023 C 978,314 ( 1 ) ( 1 ) Common Stock ( 3 ) 978,314 ( 1 ) 0 I See footnote ( 2 ) Series C Redeemable Convertible Preferred Stock ( 1 ) 05/09/2023 C 183,433 ( 1 ) ( 1 ) Common Stock ( 3 ) 183,433 ( 1 ) 0 I See footnote ( 2 ) Employee Stock Option (right to buy) $ 18 05/09/2023 J( 3 ) 774,788 ( 12 ) 05/03/2033 Class A Common Stock ( 3 ) 774,788 $ 0 0 D Employee Stock Option (right to buy) $ 18 05/09/2023 J( 3 ) 774,788 ( 12 ) 05/03/2033 Common Stock ( 3 ) 774,788 $ 0 774,788 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Lin Shao-Lee C/O ACELYRIN, INC. 4149 LIBERTY CANYON RD. AGOURA HILLS, CA91301 X Chief Executive Officer Signatures /s/ Mina Kim, Attorney-in-fact 05/11/2023 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion ofthe Issuer's initial public offering of Common Stock (the "IPO"), all shares of preferred stock automatically converted into shares of CommonStock. ( 2 )Shares held directly by Woodland Hills Partners LLC, for which the Reporting Person serves as a managing member. ( 3 )Each share of Class A Common Stock was reclassified into one share of Common Stock immediately prior to the completion of the IPO. ( 4 )Represents Restricted Stock Units ("RSUs"). Each RSU represents a contingent right to receive one share of the Issuer's Common Stock upon settlement. ( 5 )Represents shares that have been withheld by the Issuer to satisfy the income tax withholding obligations in connection with the net settlement of RSUs, and not a discretionary sale by the Reporting Person. The Common Stock settled and RSUs held by the Reporting Person remain subject to the terms of a lock-up agreement by and between the Reporting Person and certain underwriters of the IPO. ( 6 )Represents 303,237 shares of Common Stock and 466,797 RSUs after the net settlement of vested RSUs into shares of Common Stock upon the completion of the IPO. The remaining RSUs will continue to settle into shares of Common Stock as they vest thereafter, subject to the Reporting Person's continued service. ( 7 )Shares held directly by Shao-Lee Lin, Trustee of the Shao-Lee Lin Trust u/a/d September 23, 2005, for which the Reporting Person serves as trustee. ( 8 )Shares held directly by Shao-Lee Lin 2020 Gift Trust Dtd 7/16/20, for which the Reporting Person's spouse serves as trustee. ( 9 )Shares held directly by Lin Family 2020 Gift Trust Dtd 7/16/20, for which the Reporting Person's spouse shares voting and investment power. ( 10 )Shares held directly by Susie Jun 2020 Gift Trust dtd 7/16/20, for which the Reporting Person serves as trustee. ( 11 )Shares held directly by Susie Jun, Trustee of the Susie Jun Trust U/A/D September 23, 2005, for which the Reporting Person's spouse serves as trustee. ( 12 )1/4 of the shares subject to the option vest on May 4, 2024, and 1/48 of the shares subject to the option vest in equal monthly installments thereafter, subject to the Reporting Person's continued service.

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