CStone Wins Hong Kong Approval for Gastrointestinal Tumor Drug

CStone Pharmaceuticals, a Suzhou, China-based immuno-oncology company, has won approval in Hong Kong for Ayvakit (avapritinib) to treat patients with gastrointestinal stromal tumors (GIST) harboring a PDGFRA D842V mutation. The nod to Ayvakit marks the first time a precision therapy has been approved in Hong Kong for this specific disease setting. 

GIST is a rare cancer of the connective tissue of the gut. It arises from cells in the walls of the GI tract, such as in the stomach or small intestine. 5-6% of GIST cases are caused by a PDGFRA (platelet-derived growth factor receptor A) D842V mutation, the most common PDGFRA exon 18 mutation. 

CStone CEO Frank Jiang noted that Ayvakit’s approval in Hong Kong is the company’s first in the region. 

“Earlier this year, Ayvakit was also approved in Mainland China and Taiwan. We are very glad to provide this innovative treatment to more GIST patients whose tumors harbor the PDGFRA D842V mutation,” said Jiang.

Inhibitor of PDGFRA Mutant Kinases 

Ayvakit is a selective and orally available inhibitor of KIT and PDGFRA mutant kinases. It is discovered by Massachusetts, US-based Blueprint Medicines. Blueprint licensed the drug, along with two other clinical candidates, to CStone in 2018 for development and marketing in Mainland China, Hong Kong, Macau, and Taiwan. 

The Hong Kong Department of Health (DOH) approved Ayvakit based on results of the Navigator study, a Phase 1 trial evaluating the safety and efficacy of the drug in patients with unresectable (inoperable) and metastatic GIST. 

Given in 300 mg or 400 mg daily doses, Ayvakit displayed overall response rates of 95% in 38 patients with GIST with PDGFRA D842V mutation. The duration of response for all dosing groups lasted a median of 27.6 months. 

Common side effects observed in the study were anemia, increased blood bilirubin, decreased white blood cell count, and swelling among others.  

Approvals of Ayvakit in Other Countries

The NMPA approval of Ayvakit for GIST with PDGFRA exon 18 mutation came earlier this March. The drug has also been for the same disease settings in Taiwan, the EU and the US. 

The US FDA has additionally approved Ayvakit to treat adults with advanced systemic mastocytosis, a progressive disorder where mast cells grow out of control.

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Joy Lin

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