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

Abstract

2005 Background: Single agent targeted therapy has been disappointing in GBM. Combination therapy simultaneously targeting both EGFR and the MAP kinase pathway may be more effective. Methods: The NABTC conducted a phase I/II study of sorafenib (VEGFR/PDGFR/Raf inhibitor) in combination with erlotinib (EGFR inhibitor) in recurrent GBM. Eligibility criteria included histologically proven GBM, radiologic progression, > 18 yrs old, KPS > 60, adequate bone marrow reserve, and organ function. There was no limit on the number of prior therapies 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 and the MTD was 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, 17 patients were enrolled. Median age 50 years (35–69); median prior chemotherapy 1 (1–3). The initial doses were sorafenib 200 mg bid and erlotinib 100mg qd. MTD was 400 mg bid of sorafenib daily combined with 100 mg of erlotinib daily. At this dose 1/6 evaluable patients had a DLT (grade 4 lipase). Other grade 3 or 4 toxicities included transaminitis, hypertension, hypophosphatemia, and increased lipase. Pharmacokinetic studies showed no alterations in sorafenib PK, but no accumulation of erlotinib, suggesting a drug-drug interaction with sorafenib altering erlotinib metabolism or clearance. In phase II, 19 patients were accrued to stage I. Median age 51 years (30–75); median prior chemotherapy 2 (range 1–3). Phase II toxicity and outcome data are not yet mature but will be available at the time of presentation. Conclusions: This combination was moderately well-tolerated. MTD was below other combination phase I studies. Sorafenib affected the PK of erlotinib preventing drug accumulation. Phase II toxicity and outcome data will be reported. [Table: see text]