Olutasidenib in recurrent/relapsed locally advanced or metastatic IDH1-mutated chondrosarcoma: phase 1b/2 trial

Chondrosarcomas are rare cartilaginous neoplasms with limited treatment options. Isocitrate dehydrogenase 1/2 (mIDH1/2) mutations occur in 65% of chondrosarcomas. Here we report safety and efficacy of olutasidenib, an mIDH1 inhibitor, evaluated in patients with locally advanced or metastatic mIDH1 chondrosarcoma (Clinicaltrials.gov identifier: NCT03684811). The primary endpoint was objective response rate by tumor evaluation; secondary endpoints included adverse events, progression-free and overall survival. Patients received olutasidenib 150 mg twice daily. Twenty-three patients were enrolled; 16 were diagnosed with conventional chondrosarcoma (cCS). Median age was 57 (range, 30-71) years. In 21 response-evaluable patients, 11 (52%) had stable disease, 8 (38%) had progressive disease, and 2 (10%) were not evaluable. Median progression-free survival (mPFS) was 2.0 months (95% confidence interval [95%CI]: 1.7, 4.7); median overall survival was 16.0 months (95%CI: 7.7, not reached). Among patients with cCS, 10 (63%) had stable disease; 6 (38%) had progressive disease; mPFS was 3.5 months (95%CI: 1.7, 5.1). Median overall survival in cCS patients was 19.0 months (95% CI: 7.7, not reached). No dose-limiting toxicities were reported during the study. Olutasidenib was well tolerated and conferred disease control in cCS. Study limitations include open-label design and low patient sample due to rarity of cCS.