SCHEDULE 13D/A 0001214659-25-003193 0001232621 XXXXXXXX LIVE 2 Common Stock, par value $0.00001 per share 03/10/2025 false 0001962918 00445A100 Acelyrin, Inc.

4149 LIBERTY CANYON RD. AGOURA HILLS CA 91301

Kevin Tang 858-200-3830 4747 Executive Drive Suite 210 San Diego CA 92121 0001232621 N TANG CAPITAL MANAGEMENT, LLC WC N DE 0.00 8824693.00 0.00 8824693.00 8824693.00 N 8.8 OO Tang Capital Management, LLC ("TCM") shares voting and dispositive power over such shares with Tang Capital Partners, LP ("TCP"), Tang Capital Partners International, LP ("TCPI") and Kevin Tang. The percentages used herein are based on 100,325,569 shares of Common Stock outstanding as of November 8, 2024, as set forth in the Issuer's Quarterly Report filed on Form 10-Q that was filed with the Securities and Exchange Commission on November 13, 2024. 0001178579 N KEVIN TANG WC N X1 0.00 8824693.00 0.00 8824693.00 8824693.00 N 8.8 IN Kevin Tang shares voting and dispositive power over such shares with TCP, TCPI and TCM. 0001191935 N TANG CAPITAL PARTNERS, LP WC N DE 0.00 4963009.00 0.00 4963009.00 4963009.00 N 5.0 PN TCP shares voting and dispositive power over such shares with TCM and Kevin Tang. Y TANG CAPITAL PARTNERS INTERNATIONAL, LP WC N DE 0.00 3861684.00 0.00 3861684.00 3861684.00 N 3.8 PN TCPI shares voting and dispositive power over such shares with TCM and Kevin Tang. 0002036763 N TANG CAPITAL PARTNERS III, INC WC N NV 0.00 0.00 0.00 0.00 0.00 N 0 CO 0002036770 N TANG CAPITAL PARTNERS IV, INC WC N NV 0.00 0.00 0.00 0.00 0.00 N 0 CO 0001970065 N CONCENTRA BIOSCIENCES, LLC WC N DE 0.00 0.00 0.00 0.00 0.00 N 0 OO Common Stock, par value $0.00001 per share Acelyrin, Inc. 4149 LIBERTY CANYON RD. AGOURA HILLS CA 91301 This Schedule 13D/A (this "Statement") amends the Schedule 13D (the "Original Schedule 13D") filed on February 20, 2025, as amended on February 27, 2025. Items 3, 5 and 7 of the Statement are hereby amended and supplemented to the extent hereinafter expressly set forth. Except as amended hereby, the original disclosure set forth in the Statement shall remain unchanged. All capitalized terms used and not expressly defined herein have the respective meanings ascribed to such terms in the Original Schedule 13D. Item 3 of the Original Schedule 13D is hereby amended to add the following: Since February 27, 2025 the Reporting persons have expended an aggregate of approximately $4.1 million to purchase 1,526,365 shares of the Issuer's Common Stock through the open market. The Common Stock was acquired in the ordinary course of business. The information previously provided in response to Item 5 is hereby amended and restated by replacing the text thereof in its entirety with the following: The information set forth in the cover pages of this Schedule 13D is hereby incorporated by reference into this Item 5. As of the date hereof the Reporting Persons beneficially own an aggregate of 8,824,693 shares of the Issuer's Common Stock, representing 8.8% of the outstanding shares. See item 5(a) above. Schedule A attached hereto as Exhibit 3 describes all transactions in the Issuer's Common Stock that were effected during the past 60 days by the Reporting Persons. No person other than a Reporting Person has the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, Common Stock beneficially owned by the Reporting Persons. Not applicable Exhibit 1: Joint Filing Agreement by and among the Reporting Persons (filed as Exhibit 1 of the 13D filed on February 20, 2025 by the Reporting Persons with respect to the Common Stock of the Issuer). Exhibit 2: Acquisition Proposal, dated February 20, 2025, sent from Concentra to the Issuer (filed as Exhibit 2 of the 13D filed on February 20, 2025 by the Reporting Persons with respect to the Common Stock of the Issuer). Exhibit 3: Schedule A: Transactions during the past 60 days (as amended). TANG CAPITAL MANAGEMENT, LLC /s/ Kevin Tang 03/12/2025 KEVIN TANG /s/ Kevin Tang 03/12/2025 TANG CAPITAL PARTNERS, LP /s/ Kevin Tang 03/12/2025 TANG CAPITAL PARTNERS INTERNATIONAL, LP /s/ Kevin Tang 03/12/2025 TANG CAPITAL PARTNERS III, INC /s/ Kevin Tang 03/12/2025 TANG CAPITAL PARTNERS IV, INC /s/ Kevin Tang 03/12/2025 CONCENTRA BIOSCIENCES, LLC /s/ Kevin Tang 03/12/2025