A phase Ib/II study of imatinab and everolimus in patients with PDGFRA+ synovial sarcoma.

Abstract

10558 Background: Our group previously reported that PDGFRA is the most highly overexpressed kinase gene in synovial sarcoma. Our preclinical studies also demonstrated synergistic anti-tumor activity by inhibiting both PDGFRA and mTOR signaling with imatinib and rapamycin respectively in PDGFRA + synovial sarcoma cell lines. Based on these data, a phase Ib/II study to evaluate the toxicity and efficacy of imatinib and everolimus was undertaken. Methods: The primary endpoint of the phase 1b portion of the study was to determine the maximum tolerated dose (MTD) of everolimus administered with imatinib. Starting dose of everolimus and imatinib was 5 mg/day and 400 mg/day respectively. Response rate (RR) by RECIST was the primary end-point of the Phase II study. The phase II study used a Simon two stage design. 9 patients (pts) were to be accrued initially. If there were no responses, further accrual would be stopped and treatment declared ineffective. If there was at least 1 response, an additional 15 pts would be accrued for a total of 24. Key eligibility: metastatic disease, any number of priors. Pre and post treatment tumor biopsies were mandated. Results: 12 pts were treated.5 M and 7 F, median age 44 (range: 22-71), median priors 4 (range: 0 - 6). Two DLTs were observed at dose level 2 (10 mg everolimus /400 mg imatinib) with grade 3 transaminases and hypophosphatemia. Everolimus 5 mg/ imatinib 400 mg was the MTD in the phase II study. 10 pts evaluable for response, included 4 pts treated at the MTD in the Phase 1b study. There were no RECIST responses. Stable disease was observed in 3 pts (7, 7, 19 mos.). Western blot and IHC analysis of matched pair tumor biopsies indicate inhibition of p-AKT, p-S6 and decreases in Ki 67. Conclusions: Imatinib and everolimus failed to achieve its primary response endpoint. However, prolonged stable disease in 3 pts in association with inhibition of PDGFRA and mTOR suggest clinical benefit and biological effect for this drug combination. Clinical trial information: CTEP 8603.