ARTICLE ABSTRACTThis study was designed to evaluate the safety, pharmacokinetics, and clinical activity of pazopanib combined with paclitaxel to determine the recommended phase II dose in the first-line setting in patients with advanced solid tumors. Patients were enrolled in a 3+3 dose-escalation design to determine the maximum tolerated regimen (MTR) of once daily pazopanib plus paclitaxel administered every 3 weeks at four dose levels (DL1-4). Safety, pharmacokinetics, pharmacogenetics, and disease assessments were performed. Twenty-eight patients received treatment. One patient at DL1 had dose-limiting toxicity (DLT) of elevated hepatic enzymes. After pazopanib discontinuation, liver enzyme concentrations remained high until a concurrent medication, simvastatin, was discontinued. This patient had the defective CYP2C8*3*3 genotype. At DL2, 1 patient had DLT of elevated hepatic enzymes with rash and 1 patient had DLT of rash. The MTR was paclitaxel 150 mg/m2 plus pazopanib 800 mg. The most common toxicities were alopecia, fatigue, hypertension, nausea, diarrhea, dysgeusia, neutropenia, myalgia, hair color changes, and peripheral neuropathy. Coadministration of pazopanib and paclitaxel resulted in a 38% increase in systemic exposure to paclitaxel, relative to administration of paclitaxel alone, at the MTR. Of the 28 patients treated with the combination, 10 achieved a partial response and 10 achieved stable disease of ≥12 weeks. Pazopanib 800 mg daily plus paclitaxel 150 mg/m2 every 3 weeks was the recommended phase II dose, with a manageable safety profile, and with clinical activity in both melanoma and non–small cell lung cancer that suggest further evaluation of this combination is warranted. Mol Cancer Ther; 14(2); 461–9. ©2014 AACR.