ASLAN Pharmaceuticals (ASLN) 6-KAmendment No. 2 to the Open Market Sale Agreementsm

Exhibit 99.1

AMENDMENT NO. 2 TO THE OPEN MARKET SALE AGREEMENTSM

April 12, 2024

JEFFERIES LLC

520 Madison Avenue

New York, New York 10022

Ladies and Gentlemen:

This Amendment No. 2 to the Open Market Sale AgreementSM (this “Amendment No. 2”) is entered into as of the date first written above by ASLAN Pharmaceuticals Limited, an exempted company incorporated with limited liability in the Cayman Islands (the “Company”), and Jefferies LLC (“Agent”), which are parties to that certain Open Market Sale AgreementSM, dated October 9, 2020 (the “Original Agreement”), as amended on September 13, 2022 (the “Amendment No. 1” and collectively with the Original Agreement, the “Sale Agreement”). All capitalized terms not defined herein shall have the meanings ascribed to them in the Sale Agreement. The parties, intending to be legally bound, hereby amend the Sale Agreement as follows:

1. The term “Settlement Date” as defined in Section 1 to the Sale Agreement is hereby deleted in its entirety and replaced with the following:

“Settlement Date” means the second business day following each Trading Day (or such earlier day as is industry practice for regular-way trading) during the period set forth in the Issuance Notice on which Shares are sold pursuant to this Agreement, when the Company shall deliver to the Agent the amount of Shares sold on such Trading Day and the Agent shall deliver to the Company the Issuance Price received on such sales.”

2. The first sentence of Section 2(a) to the Sale Agreement is hereby deleted in its entirety and replaced with the following:

“(a) Registration Statement. The Company has prepared and filed with the Commission a shelf registration statement on Form F-3 (File No. 333-270835) that contains a base prospectus (the “Base Prospectus”).”

3. The Company hereby represents and warrants that the representations and warranties of the Company as set forth in Section 2 of the Sale Agreement (except as modified herein) are true and correct as of the date of this Amendment No. 2, save with respect to Section 2(f) to the Sale Agreement, the Company ceased to be an “emerging growth company” as of January 1, 2024.

4. The Sale Agreement, as amended by this Amendment No. 2, represents the entire agreement between the Company, on the one hand, and the Agent, on the other hand, with respect to the subject matter thereof and hereof and supersede all prior and contemporaneous agreements, understandings, inducements and conditions, express or implied, oral or written, of any nature whatsoever with respect to the subject matter hereof. Except as specifically amended hereby in this Amendment No. 2, all of the terms of the Sale Agreement shall remain in full force and effect and are hereby ratified and confirmed in all respects. Neither this Amendment No. 2 nor any term hereof may be amended except pursuant to a written instrument executed by the Company and the Agent. In the event that any one or more of the provisions contained herein, or the application thereof in any circumstance, is held invalid, illegal or unenforceable as written by a court of competent jurisdiction, then such provision shall be given full force and effect to the fullest possible extent that it is valid, legal and enforceable, and the remainder of the terms and provisions herein shall be construed as if such invalid, illegal or unenforceable term or provision was not contained herein, but only to the extent that giving effect to such provision and the remainder of the terms and provisions hereof shall be in accordance with the intent of the parties as reflected in this Amendment No. 2. All references in the Sale Agreement to the “Agreement” shall mean the Original Agreement as amended by the Amendment No. 1 and this Amendment No. 2; provided, however, that all references to the “date of this Agreement” in the Original Agreement shall continue to refer to the date of the Original Agreement.

5. This Amendment No. 2 shall be governed by and construed in accordance with the internal laws of the State of New York applicable to agreements made and to be performed in such state. Any legal suit, action or proceeding arising out of or based upon this Amendment No. 2 or the transactions contemplated hereby may be instituted in the federal courts of the United States of America located in the Borough of Manhattan in the City of New York or the courts of the State of New York in each case located in the Borough of Manhattan in the City of New York (collectively, the “Specified Courts”), and each party irrevocably submits to the exclusive jurisdiction (except for proceedings instituted in regard to the enforcement of a judgment of any such court, as to which such jurisdiction is non-exclusive) of such courts in any such suit, action or proceeding. Service of any process, summons, notice or document by mail to such party’s address set forth in the Sale Agreement shall be effective service of process for any suit, action or other proceeding brought in any such court. The parties irrevocably and unconditionally waive any objection to the laying of venue of any suit, action or other proceeding in the Specified Courts and irrevocably and unconditionally waive and agree not to plead or claim in any such court that any such suit, action or other proceeding brought in any such court has been brought in an inconvenient forum.

6. This Amendment No. 2 may be executed in two or more counterparts, each one of which shall be an original, with the same effect as if the signatures thereto and hereto were upon the same instrument. Any signature to this Amendment No. 2 may be delivered by facsimile transmission, electronic mail delivery (including portable document format (PDF) file) or any electronic signature complying with the U.S. federal ESIGN Act of 2000 or the New York Electronic Signature and Records Act or other transmission method and any counterpart so delivered shall be deemed to have been duly and validly delivered and be valid and effective for all purposes to the fullest extent permitted by applicable law.

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If the foregoing correctly sets forth the understanding between the Company and the Agent, please so indicate in the space provided below for that purpose, whereupon this letter shall constitute a binding amendment to the Sale Agreement between the Company and the Agent.