SUZHOU, BEIJING, September 25, 2020—CStone Pharmaceuticals (“CStone”, HKEX: 2616) and its strategic partner Genetron Holdings Limited (“Genetron Health”, Nasdaq: GTH) today announced the successful launch of a multi-center clinical trial in China for the joint development of a companion diagnostic (CDx) test for avapritinib. This represents a key milestone in the companies’ collaboration. Avapritinib is a kinase inhibitor discovered by CStone’s partner Blueprint Medicines.

CStone and Genetron Health are jointly developing a CDx kit to detect the D842V mutation in the human platelet-derived growth factor receptor alpha (PDGFRA) gene using a polymerase chain reaction (PCR)-based method. The CDx test kit utilizes a real-time PCR fluorescent probe, combined with specific primers, Taqman probes, and highly specific Taq enzymes, to detect the mutation with high specificity and sensitivity in DNA samples. The test has been validated by the testing center of the National Medical Products Administration (NMPA).

CStone submitted New Drug Applications for avapritinib in PDGFRA exon 18 mutant gastrointestinal stromal tumors (GIST) to regulatory agencies in Taiwan and the Chinese Mainland in March and April 2020, respectively. The Chinese regulatory application has been accepted by the Center for Drug Evaluation (CDE) of the NMPA for priority review. Data from the Phase I/II bridging study of avapritinib presented at the China Society of Clinical Oncology annual meeting in 2020 showed that avapritinib was generally well tolerated in Chinese patients, with a safety profile that is consistent with previously published results in global studies. Preliminary results demonstrated the robust clinical activity of avapritinib in Chinese patients with GIST harboring the PDGFRA D842V mutation. Among 8 evaluable patients with PDGFRA D842V mutant GIST who received 300 mg QD doses of avapritinib, all of the patients had evidence of tumor regression in target lesions, and 5 patients achieved a partial response. The overall response rate (ORR) was 62.5% . The other 3 patients had stable disease.

With the rapid development of targeted therapy, immunotherapy, and other innovative anti-cancer drugs, companion diagnostics have become an integral part of precision therapy in oncology. The collaboration between Genetron Health and CStone is designed to enhance the commercial potential of avapritinib in China pending regulatory approval, maximize benefits to patients, and promote the development of precision medicine for GIST.

About Avapritinib

Avapritinib is a kinase inhibitor approved by the U.S. Food and Drug Administration (FDA) under the brand name AYVAKIT™ for the treatment of adults with unresectable or metastatic GIST harboring a PDGFRA exon 18 mutation, including PDGFRA D842V mutations. Previously, the U.S. FDA granted Breakthrough Therapy Designation to avapritinib for the treatment of adult patients with unresectable or metastatic GIST harboring the PDGFRA D842V mutation.

Avapritinib is not approved for the treatment of any other indication in the U.S. by the FDA or for any indication in any other jurisdiction by any other health authority.

Blueprint Medicines is developing avapritinib globally for patients with advanced and indolent systemic mastocytosis (SM). The FDA granted breakthrough therapy designation to avapritinib for the treatment of advanced SM, including the subtypes of aggressive SM, SM with an associated hematologic neoplasm and mast cell leukemia.

CStone and Blueprint Medicines have an exclusive collaboration and license agreement for the development and commercialization of avapritinib and certain other drug candidates in Mainland China, Hong Kong, Macau, and Taiwan. Blueprint Medicines retains development and commercial rights for avapritinib in the rest of the world.

CStone submitted an NDA for avapritinib to the TFDA and the China NMPA in March and April 2020, respectively, for the treatment of adult patients with unresectable or metastatic GIST harboring a PDGFRA exon 18 mutation. In July 2020, avapritinib received priority review designation from the China NMPA.

About CStone Pharmaceuticals

CStone Pharmaceuticals (HKEX: 2616) is a biopharmaceutical company focused on developing and commercializing innovative immuno-oncology and precision medicines to address the unmet medical needs of cancer patients in China and worldwide. Established in 2015, CStone has assembled a world-class management team with extensive experience in innovative drug development, clinical research, and commercialization. The company has built an oncology-focused pipeline of 15 drug candidates with a strategic emphasis on immuno-oncology combination therapies. Currently, 5 late-stage candidates are at pivotal trials. With an experienced team, a rich pipeline, a robust clinical development-driven business model and substantial funding, CStone's vision is to become globally recognized as a leading Chinese biopharmaceutical company by bringing innovative oncology therapies to cancer patients worldwide.

About Genetron Holdings Limited

Genetron Holdings Limited (“Genetron Health” or the “Company”) is a leading precision oncology platform company in China that specializes in cancer molecular profiling and harnesses advanced technologies in molecular biology and data science to transform cancer treatment. The Company has developed a comprehensive oncology portfolio that covers the entire spectrum of cancer management, addressing needs and challenges from early screening, diagnosis and treatment recommendations, as well as continuous disease monitoring and care. Genetron also partners with global biopharmaceutical companies and offers customized services and products. For more information, please visit ir.genetronhealth.com.

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