Phase I Safety, Pharmacokinetic, and Pharmacodynamic Study of SAR245408 (XL147), an Oral Pan-Class I PI3K Inhibitor, in Patients with Advanced Solid Tumors

PURPOSE: SAR245408 is a pan-class I phosphoinositide 3-kinase (PI3K) inhibitor. This phase I study determined the maximum tolerated dose (MTD) of two dosing schedules first 21 days of a 28-day period (21/7) and continuous once-daily dosing (CDD), pharmacokinetic and pharmacodynamic profiles, and preliminary efficacy. EXPERIMENTAL DESIGN: Patients with refractory advanced solid malignancies were treated with SAR245408 using a 3 + 3 design. Pharmacokinetic parameters were determined after single and repeated doses. Pharmacodynamic effects were evaluated in plasma, hair sheath cells, and skin and tumor biopsies. RESULTS: Sixty-nine patients were enrolled. The MTD of both schedules was 600 mg; dose-limiting toxicities were maculopapular rash and hypersensitivity reaction. The most frequent drug-related adverse events included dermatologic toxicities, diarrhea, nausea, and decreased appetite. Plasma pharmacokinetics showed a median time to maximum concentration of 8 to 22 hours, mean terminal elimination half-life of 70 to 88 hours, and 5- to 13-fold accumulation after daily dosing (first cycle). Steady-state concentration was reached between days 15 and 21, and exposure was dose-proportional with doses up to 400 mg. SAR245408 inhibited the PI3K pathway (∼40%-80% reduction in phosphorylation of AKT, PRAS40, 4EBP1, and S6 in tumor and surrogate tissues) and, unexpectedly, also inhibited the MEK/ERK pathway. A partial response was seen in one patient with advanced non-small cell lung cancer. Eight patients were progression-free at 6 months. Pharmacodynamic and clinical activity were observed irrespective of tumor PI3K pathway molecular alterations. CONCLUSIONS: SAR245408 was tolerable at doses associated with PI3K pathway inhibition. The recommended phase II dose of the capsule formulation is 600 mg administered orally with CDD.