Current Report by Foreign Issuer (Form 6-K)

INCORPORATION BY REFERENCE

The information included in this Report on Form 6-K is hereby incorporated by reference into the Company's Registration Statements on Form F-3 (File No. 333-283998 and No. 333-281621) (including any prospectuses forming a part of such registration statement) and is to be a part thereof from the date on which this Report on Form 6-K is filed, to the extent not superseded by documents or reports subsequently filed or furnished.

CASI Pharmaceuticals Announces Sale of Equity Interests in Alesta

CASI Pharmaceuticals, Inc. (OTCQB: CASIF, the "Company"), a clinical-stage biopharmaceutical company developing CID-103, an anti-CD38 monoclonal antibody, for patients with organ transplant rejection and autoimmune diseases, today reported that the Company sold its equity interests in Alesta Therapeutics B.V. ("Alesta") to BioMarin Pharmaceutical Inc. ("BioMarin") in connection with BioMarin's acquisition of Alesta pursuant to a Share Purchase Agreement. The transaction closed on August 31, 2026.

Under the terms of the transaction agreement, the Company received approximately US$5.9 million in net cash proceeds at closing, and may be entitled to receive its allocable portion of additional contingent payments upon the achievement of specified development and regulatory milestones. Any such future payments are subject to the terms and conditions of the transaction agreement and are not assured. The Company will make further announcements accordingly when and if such payments are received.

BioMarin's acquisition of Alesta was structured to retain ALE1 within Alesta. Prior to the closing, Alesta completed the spin-out of all non-ALE1 assets to a new entity. The Company's existing licensed rights to CID-103 remain unchanged as a result of the transaction.

Forward-Looking Statements

This announcement contains forward-looking statements. These statements are made under the "safe harbor" provisions of the U.S. Private Securities Litigation Reform Act of 1995. These forward-looking statements can be identified by terminology such as "will," "expects," "anticipates," "future," "intends," "plans," "believes," "estimates," "confident" and similar statements. Among other things, the business outlook and quotations from management in this announcement, as well as the Company's strategic and operational plans, contain forward-looking statements. The Company may also make written or oral forward-looking statements in its periodic reports to the U.S. Securities and Exchange Commission (the "SEC"), in its annual report to shareholders, in press releases and other written materials and in oral statements made by its officers, directors or employees to third parties. Statements that are not historical facts, including statements about the Company's beliefs and expectations, are forward-looking statements. Forward-looking statements involve inherent risks and uncertainties. A number of factors could cause actual results to differ materially from those contained in any forward-looking statement. Further information regarding these and other risks is included in the Company's filings with the SEC. All information provided herein is as of the date of this announcement, and the Company undertakes no obligation to update any forward-looking statement, except as required under applicable law. We caution readers not to place undue reliance on any forward-looking statements contained herein.