Phase I/II study of sorafenib and temsirolimus for patients with recurrent glioblastoma (GBM) (NABTC 05–02)

Abstract

2006 Background: The activity of targeted molecular therapy with single agents has been disappointing in GBM. Combination therapy simultaneously targeting both the PI3k/Akt/mTOR and the MAP kinase pathway may be more effective. Methods: The North American Brain Tumor Consortium conducted a phase I/II study of sorafenib (VEGFR/PDGFR/Raf inhibitor) in combination with temsirolimus (mTOR inhibitor) in recurrent GBM. Eligibility criteria included histologically proven GBM, radiologic progression, > 18 years old, KPS > 60, adequate bone marrow reserve, and organ function. There was no limit on the number of prior relapses for phase I and no more than two prior relapses for phase II. No enzyme-inducing antiepileptic drugs were allowed. Dose-finding used a standard 3 + 3 design with the MTD defined as the dose with DLTs in 1/6 or fewer patients. The primary endpoint for the phase II component was PFS6 (p0 = 15%; p1 = 35%). A 2-stage design was used. If > 4 of the initial 19 patients achieved PFS6, an additional 14 patients would be accrued for a total of 33 patients. Results: In phase I, 13 patients were enrolled. Median age was 50 years (32–59); median prior chemotherapy 1 (1–3). The initial doses were sorafenib 200 mg bid and temsirolimus 25 mg intravenously once weekly. The MTD was 400 mg bid of sorafenib daily combined with 25 mg of temsirolimus weekly. At this dose 1/6 patients had a DLT (grade 3 thrombocytopenia). Other grade 3 or 4 toxicities included transaminitis, hypophosphatemia, fatigue, diarrhea, and hyperlipidemia. Pharmacokinetic data were similar to that for single agent sorafenib and temsirolimus suggesting that there were no significant interaction between the two drugs. In phase II, 19 patients were accrued to stage I. Median age 50 years (24–64); median prior relapses 1 (range 1–2). One patient was found not to have GBM on central review. No patient remained progression free at 6 months, although two patients stopped treatment prior to 26 weeks for other than progression (alternative therapy, cerebral ischemia). As result, the study was terminated and did not proceed to the second stage. Conclusions: The combination of sorafenib and temsirolimus was moderately well-tolerated but did not demonstrate sufficient efficacy in recurrent GBM to warrant further investigation. No significant financial relationships to disclose.