Deciphera Pharmaceuticals, Inc. announced updated results from the ongoing Phase 1/2 study of vimseltinib, an orally administered, potent, and highly selective switch-control kinase inhibitor of CSF1R, for the treatment of patients with tenosynovial giant cell tumor (TGCT) not amenable to surgery. Results from the Phase 1 and Phase 2 portions of the study are being presented as separate posters, titled “Efficacy and safety of vimseltinib in tenosynovial giant cell tumour (TGCT): Phase 2 expansion” and “Safety and efficacy of vimseltinib in tenosynovial giant cell tumour (TGCT): Long-term phase 1 update” at the ESMO Congress 2022 on September 11 and September 12, respectively. Results from the Phase 2 portion of the study are being presented on September 11, 2022 in a poster presentation, summarized below.

Updated results from the Phase 1 study are being presented in a poster presentation on September 12. The Phase 1 data summarized below are based on the previously released abstract with a data cutoff date of February 18, 2022. The Phase 1 poster presentation remains under embargo until September 12, 2022 and will include updated data based on a May 6, 2022 data cutoff date.

Safety and Efficacy of Vimseltinib in Tenosynovial Giant Cell Tumour (TGCT): Long-term Phase 1 Update: The Phase 1/2 study of vimseltinib is an open-label, multicenter study evaluating the safety, efficacy, pharmacokinetics, and pharmacodynamics of vimseltinib in patients with solid tumors and TGCT. The data presented from the Phase 1 update include long-term safety and efficacy for patients with TGCT from the dose escalation portion of the study. Dose Cohorts and Demographics: As of the February 18, 2022 cutoff date, 32 patients were enrolled in three dose cohorts: Phase 1 Cohort 5 (n=8): 30 mg loading dose daily for five days followed by a maintenance dose of 30 mg twice a week.

Phase 1 Cohort 8 (n=12): 30 mg loading dose daily for three days followed by a maintenance dose of 10 mg daily. Phase 1 Cohort 9 (n=12): 20 mg loading dose daily for three days followed by a maintenance dose of 6 mg daily. 32 patients were evaluable for efficacy by Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 at the data cutoff; response data is based on independent radiological review (IRR) except for one patient that did not have an IRR.

Antitumor Activity and Treatment Duration: Clinical Benefit Rate: 100% of patients demonstrated clinical benefit, defined as patients with complete response, partial response, or stable disease, without disease progression. Objective Response Rate: 69% ORR (CR=1, PR=21). Most responses were achieved within six months.

Treatment Duration: The median duration of treatment was 16.4 months with 59% of patients remaining on treatment as of the data cutoff date in February 2022. The data presented from the Phase 2 expansion portion of the ongoing Phase 1/2 study includes safety, efficacy, and preliminary patient-reported outcome data in patients with TGCT treated with vimseltinib at the recommended Phase 2 dose (RP2D; 30 mg twice weekly) enrolled in two cohorts. Cohort A includes TGCT patients with no prior anti-CSF1/CSF1R (previous therapy with imatinib or nilotinib is allowed) and Cohort B includes patients with prior anti-CSF1/CSF1R (previous therapy with only imatinib or nilotinib are not eligible).