Abbisko Cayman Limited announced that its self-developed FGFR4 inhibitor, irpagratinib (ABSK011), a highly selective small molecule, has been granted Orphan Drug Designation ("ODD") by the U.S. Food and Drug Administration ("FDA") for the treatment of Hepatocellular Carcinoma ("HCC"). This is a voluntary announcement made by the Company. The Group cannot guarantee that irpagratinib ("ABSK011") will ultimately be successfully marketed.

Shareholders and potential investors of the Company are advised to exercise caution when dealing in the shares of the Company. By order of the Board. Abbisko Cayman Limited Dr. Xu Yao-Chang.

Chairman. Shanghai, April 25, 2024. As at the date of this announcement, the board of directors of the Company comprises Dr. Xu Yao-Chong, Dr. Yu Hongping and Dr. Chen Zhui as executive directors; Ms. Tang Yanmin as a non-executive director; and Dr. Sun Piaoyang, Mr. Sun Hongbin and Mr. Wang Lei as independent non-executive directors.

On April 25, 2024, Abbisko Therapeutics announced that its innovative FGFR4 inhibitor, ir pagratinib (AbsK011), has been granted ODD by FDA for the treatment of HCC. FDA grants ODD to investigational drugs and biologics that are intended for the treatment of rare diseases that affect fewer than 200,000 people in the U.S. Receiving ODD provides drug developers with various benefits designed to support the development of novel drugs and biologics, including marketing exclusivity for seven years upon FDA approval, tax credits for qualified clinical trial expenditures, and exemptions from FDA application and user fees. Irpagratinib is a highly selective FGFR4 small molecule inhibitor intended for the treatment of advanced solid tumors that present with abnormalities in the FGFR4 signaling pathway (e.g., ligand FGF19 amplification/overexpression, FGFR4 mutation/amplification/fusion), including advanced HCC, cholangiocarcinoma, breast cancer, among others.

The FGFR4 signaling pathway is a recognized and promising target for the treatment of HCC; Clinical data with irpagratinib have demonstrated improved potency and anti-tumor efficacy compared to competitors, among other favorable therapeutic properties. At the 2023 European Society of Medical Oncology (ESMO) conference, Abbisko Theraputics presented updated clinical data for irpagratinib demonstrating excellent preliminary efficacy and safety in patients with previously treated hepatocellular carcinoma with aberrant FGF19 expression, with an ORR of 40.7% in patients enrollment of BID cohort, significantly exceeding the previous FGFR4 inhibitors that have entered clinical trials globally. The company believe irpagratinib is potentially a novel and leading FGFR4 inhibitor for the treatment of HCC patients with hyper-activation of FGF19/FGFR4 pathway based on competitive landscape of FGFR4 inhibitors globally, according to Frost & Sullivan.

Based on epidemiological records from the International Agency for Research on Cancer (IARC), a specialized cancer agency of the World Health Organization (WHO), there were 42,284 new cases of primary liver and 31,078 attributable deaths in the United States in 2020, with rates highest among American Indian or Alaska Native individuals. HCC accounts for 85%-90% of primary liver cancers, with challenging treatment and poor prognosis. The ratio of incidence rate to fatality rate is high, which seriously threatens human life and health.