Biopharmaceutical company CStone Pharmaceuticals (HKEX:2616) reported on Monday the start of treatment of the first patient in China under the Phase I registrational study of BLU-667 in collaboration with its partner Blueprint Medicines.

This clinical trial of of BLU-667 is a part of the partnership's ongoing, global Phase I ARROW trial that is designed to evaluate its overall response rate (ORR), duration of response, pharmacokinetics, pharmacodynamics and safety in patients with RET-altered non-small cell lung cancer (NSCLC), medullary thyroid cancer (MTC) and other advanced solid tumors.

NSCLC reportedly accounts for 80-85% of all lung cancers and RET fusions occur in approximately 1-2% of all NSCLC cases. Thyroid cancer is the most common type of endocrine cancer and has shown rising incidence rates in recent years.

According to the company, BLU-667 is an investigational, once-daily oral precision therapy specifically designed for highly potent and selective targeting of oncogenic RET alterations.

In conjunction, the updated results from the company's ARROW clinical trial of BLU-667 showed durable anti-tumor activity regardless of RET-altered tumor type and was well-tolerated. These patients with RET-fusion NSCLC and RET-mutant MTC received a starting dose of 400mg once daily, which is the recommended Phase 2 dose.

Across all patients, BLU-667 was well-tolerated and most adverse events reported by investigators were Grade 1 or 2, concluded the company.