-- Data show 81 percent overall survival rate at 24 months --

SUZHOU, China, 6th July, 2020 -- The partner of CStone Pharmaceuticals (“CStone”, HKEX: 2616), Blueprint Medicines, announced on June 29 that The Lancet Oncology published data from the NAVIGATOR clinical trial showing an 81 percent overall survival (OS) rate at 24 months and a well-tolerated safety profile for avapritinib in patients with advanced PDGFRA D842V mutant gastrointestinal stromal tumor (GIST). The paper, titled “Avapritinib in advanced PDGFRA D842V-mutant gastrointestinal stromal tumour (NAVIGATOR): a multicentre, open-label, phase 1 trial,” was published online in The Lancet Oncology on 29, 2020.

Blueprint Medicines has an exclusive collaboration and license agreement with CStone Pharmaceuticals for the development and commercialization of avapritinib, fisogatinib and pralsetinib in Mainland China, Hong Kong, Macau and Taiwan. Blueprint Medicines retains development and commercial rights for all three licensed products in the rest of the world.

Highlights from The Lancet Oncology Publication Data

The Lancet Oncology paper reported efficacy and safety results from the NAVIGATOR trial, including all patients enrolled in the dose escalation part of the trial and the subset of patients with PDGFRA D842V mutant GIST enrolled in the expansion part of the trial. The efficacy population comprised 56 patients with PDGFRA D842V mutant GIST. The safety population comprised 82 patients, including 26 patients with non-PDGFRA D842V mutant GIST enrolled in the dose escalation part of the trial. All results were as of a data cutoff date of November 16, 2018.

In patients with PDGFRA D842V mutant GIST, the overall response rate (ORR) was 88 percent (95% CI: 76-95%) with 9 percent of patients achieving a complete response. Avapritinib demonstrated durable clinical benefit in this patient population with a 12-month duration of response rate of 70 percent (95% CI: 54-87%), a 12-month progression-free survival (PFS) rate of 81 percent (95% CI: 69-93%) and a 24-month OS rate of 81 percent (95% CI: 67-94%).

Avapritinib was generally well-tolerated with most treatment-related adverse events (AEs) reported as Grade 1 or 2. The most common treatment-related AEs were nausea, fatigue, diarrhea, periorbital edema, anemia, decreased appetite, vomiting and memory impairment. Cognitive effects occurred in 40 percent of patients, with the majority of events reported as Grade 1.

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. Avapritinib is the first precision therapy approved in the U.S. to treat a genomically defined population of patients with GIST and the only highly active treatment for PDGFRA exon 18 mutant GIST. The U.S. FDA granted Breakthrough Therapy Designation to avapritinib for the treatment of 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 the treatment of advanced, smoldering and indolent systemic mastocytosis (SM). The U.S. 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.

About GIST

GIST is a sarcoma, or tumor of bone or connective tissue, of the GI tract. Tumors arise from cells in the wall of the GI tract and occur most often in the stomach or small intestine. Most patients are diagnosed between the ages of 50 to 80, and diagnosis is typically triggered by GI bleeding, incidental findings during surgery or imaging and, in rare cases, tumor rupture or GI obstruction.

About 5 to 6 percent of primary GIST cases are caused by a PDGFRA D842V mutation, the most common PDGFRA exon 18 mutation. Prior to the U.S. FDA approval of avapritinib, there were no highly effective treatments for PDGFRA D842V mutant GIST. Published data have shown poor outcomes in patients with PDGFRA D842V mutant GIST treated with imatinib and other approved therapies, including a median OS of 15 months, a median PFS of 3 months and an ORR of 0 percent.1

Reference

1 Cassier PA, Fumagalli E, Rutkowski P., et al. Outcome of patients with platelet-derived growth factor receptor alpha-mutated gastrointestinal stromal tumors in the tyrosine kinase inhibitor era. Clin Cancer Res. 2012;18(16):4458-4464.

About CStone

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, five late-stage candidates are at or near 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.

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