Abbisko Therapeutics Obtained Approval from U.S. FDA for Pivotal Global Multi-center Phase III Clinical Trial of CSF-1R Inhibitor Pimicotinib (ABSK021)

16 March 2023, Shanghai – Abbisko Therapeutics Co., Ltd. (HKEX Stock Code: 2256. HK, referred to as “Abbisko Therapeutics” hereafter) announced that the U.S. FDA had approved its CSF-1R inhibitor pimicotinib（ABSK021）for a randomized, double-blind, placebo-controlled, multicenter Phase III clinical study in patients with giant cell tumor of the tendon sheath. This is another important milestone after pimicotinib was approved for breakthrough therapy designation in China and the U.S.. Pimicotinib is the first small-molecule inhibitor in Abbisko’s pipeline that has been approved for Phase III clinical trial in both China and the U.S., and the first CSF-1R inhibitor developed in China entering global Phase III clinical trial. Pimicotinib showed significant anti-tumor efficacy with a preliminary ORR of 68% in the clinical Phase Ib trial for the treatment of advanced tenosynovial giant cell tumor（“TGCT”）and has good safety and PK/PD characteristics.

PHASE III ABSK021-301 STUDY

The Phase III ABSK021-301 study is a randomized, double-blind, placebo-controlled, multi-centered clinical trial designed to evaluate the safety and efficacy of ABSK021 in patients with TGCT. This study consists of two parts. Part 1 is a double-blind phase, eligible patients will be randomized to ABSK021 treatment group or matching placebo group and will receive 50mg QD of ABSK021 or matching placebo (28 days/cycle) until completion of Part 1. Patients who complete Part 1 will be eligible to continue in Part 2 of the study. Part 2 is an open-label treatment phase, and all patients entering this phase will receive 50mg QD of open-label ABSK021 until 24 weeks of dosing or withdrawal from the study. Approximately 100 patients are planned to be enrolled, and the primary endpoint is 25-Week ORR by Blinded Independent Review Committee. The global multicenter Phase III study will be conducted simultaneously in the U.S. and China.

Pimicotinib is a novel, orally available, highly selective and potent small molecule CSF-1R inhibitor, independently developed by Abbisko Therapeutics. It has been granted the breakthrough therapy designation by both China NMPA and the U.S. FDAfor the treatment of TGCT that is not amenable to surgery. TGCT is a locally aggressive neoplasm with an annual incidence rate of 43 per million person-years worldwide. It mainly results in swelling, pain, stiffness, and decreased activity of the affected joints which seriously affect the patient’s quality of life. There is currently no approved drug available in China, and only one systemic therapy agent has been approved in the U.S.. However, it is only available through the Risk Evaluation and Mitigation Strategy (REMS) Program due to potential liver injuries it may cause. There are unmet medical needs of TGCT patients in both China and the U.S..

Abbisko has completed a Phase Ia dose escalation study for pimicotinibin the U.S., with Phase Ib expansion ongoing in both the U.S. and China. In addition to TGCT, Abbisko is actively exploring the potential of pimicotinib in treating other indications including many types of solid tumors in clinic, and has obtained approval from NMPA to conduct a Phase II clinical study in chronic graft-versus-host disease. Abbisko has collaborated with Sperogenix in exploring its potential for treating ALS and other CNS diseases. As of the date of this press release, no highly selective CSF-1R inhibitor has been approved in China.