Vimseltinib for patients with tenosynovial giant cell tumor: A multicenter, open-label, phase 2 trial.

Tenosynovial giant cell tumor (TGCT) is a locally aggressive neoplasm caused by dysregulation of the colony-stimulating factor 1 (CSF1) gene. Patients report substantial pain, stiffness, and declining physical function; those whose disease is not amenable to surgery require systemic therapy. Vimseltinib is an oral, switch-control kinase inhibitor of the CSF1 receptor (CSF1R). Here, the authors report safety and efficacy of vimseltinib in patients with TGCT based on prior treatment. Cohort A included patients who did not receive prior specific anti-CSF1/CSF1R agents (n = 46; prior imatinib/nilotinib allowed), and cohort B included patients who received prior specific agents (n = 20). The phase 2 (expansion) portion of this ongoing, multicenter, open-label, phase 1/2 study (NCT03069469) enrolled adults (≥18 years) with histologically-confirmed TGCT not amenable to surgery. Patients received vimseltinib 30 mg twice weekly (recommended phase 2 dose). The primary objectives were to assess safety and antitumor activity; secondary objectives included assessment of active range of motion (ROM) and patient-reported outcomes. Most treatment-emergent adverse events were grade 1/2, and there was no evidence of cholestatic hepatotoxicity or drug-induced liver injury. Best overall response rates were 64% (29 of 45) and 37% (7 of 19) for cohorts A and B after mean follow-up of 23 and 19 months, respectively. Most patients experienced meaningful improvements in active ROM and patient-reported physical function, stiffness, health status, and pain. Vimseltinib had a manageable safety profile, demonstrated durable antitumor activity, and provided functional and symptomatic improvements in patients with TGCT, offering an effective treatment option regardless of previous treatment with anti-CSF1/CSF1R agents.