A phase I dose escalation pharmacokinetic (PK) and pharmacodynamic (PD) study of weekly and twice weekly erlotinib in advanced stage solid malignancies

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3594 Background: Erlotinib is a potent oral TKI of the epidermal growth factor receptor (EGFR). At the current recommended daily dose of 150 mg/day there is activity in advanced stage NSCLC, but with frequent grade 1/2 rash and diarrhea. We performed a phase I dose escalation study of erlotinib with a once and twice weekly schedule to assess the PKs, PDs, and to determine if toxicities would be less on an intermittent but high dose schedule. Methods: A standard dose escalation schedule starting at 1,400 mg once/week and 600 mg twice/week with increments of 200 mg to 4 dose cohorts/schedule was utilized with three patients per cohort. A cycle consisted of 3 weeks of therapy. PKs were performed on cycle 1 and 2. PDs on normal skin punch biopsies were performed at baseline and after cycle 1. Tumour evaluation was done following every 2nd cycle. Subjects were treated until progression or unacceptable toxicity. Results: 32 patients were enrolled from Oct 2004-April 2006. Median age 58 years (28–74 years); median PS 1 (0–2); and median prior palliative systemic regimens 2 (0–6). In the once weekly schedule the maximum tolerated dose (MTD) was not reached with the top dose of 2,000 mg/week. A median of 2 cycles were delivered (1–14), with 3/13 patients achieving stable disease = 3 months. 4/13 patients had G1 rash and 6/13 patients G1 diarrhea during the first 2 cycles. In the twice weekly schedule the MTD was reached at 1,200 mg twice/week with 2/6 subjects experiencing G3 rash. The recommended dose level is 1,000 mg twice/week. A median of 4 cycles were delivered (1–28) with 2 partial responses, 1 minor response and 6 stable disease = 3 months out of 19 patients in total. G1/2 rash or diarrhea occurred in 13 and 9 patients respectively. No corneal toxicity was seen. The PK data demonstrated a variable but linear pattern. At 1,000 mg twice/week the median Cmax, Tmax and AUC0–24 hr was 6.28 μg/ml, 2 hours and 135 μg.h/ml respectively. PD analysis is ongoing. Conclusions: A once weekly and twice weekly high dose schedule of erlotinib is feasible, with MTD not reached in the once weekly schedule. A recommended dose of 1,000 mg twice/week has clinical activity, is generally well tolerated, and results in significantly higher systemic exposure than the 150 mg once daily dose. No significant financial relationships to disclose.