The FDA has granted a priority review designation to pexidartinib (Daiichi Sankyo Company, Limited) for the treatment of adults with symptomatic tenosynovial giant cell tumor (TGCT).
The disease is associated with severe morbidity or functional limitations, and for some patients, surgery is not feasible. TGCT is a non-malignant tumor of the joint or tendon sheath and currently, there are no approved systemic therapies. Patients are usually diagnosed in their 20s to 50s, and women can be twice as likely to develop a tumor as men.
In January 2019, the American Society of Clinical Oncology (ASCO) selected pexidartinib as one of five significant advancements in the treatment of rare diseases, calling it the first promising investigational therapy for TGCT.
FDA approval was based on results from the phase 3 ENLIVEN study of pexidartinib, an investigational, novel, oral small molecule that inhibits colony stimulating factor-1 receptor (CSF1R), a primary growth driver of abnormal cells in the synovium that cause TGCT.
ENLIVEN, a pivotal, double-blind, randomized, global, multicenter phase 3 study, evaluated pexidartinib in patients with symptomatic advanced TGCT for whom surgical removal of the tumor would be associated with possible worsening functional limitation or severe morbidity. One hundred and twenty patients were randomized to receive either pexidartinib or placebo at 1,000 mg/day for two weeks followed by 800 mg/day for 22 weeks. The study’s primary endpoint was the percentage of patients who achieved a complete or partial response after 24 weeks of treatment.
In addition to priority review designation, pexidartinib was granted breakthrough therapy and orphan drug designations.
Source: Seeking Alpha, February 5, 2019