This phase 1b study assessed the maximum tolerated dose (MTD), safety, and pharmacokinetics of motesanib (a small-molecule antagonist of VEGF receptors 1, 2, and 3; platelet-derived growth factor receptor; and Kit) administered once daily (QD) or twice daily (BID) in combination with erlotinib and gemcitabine in patients with solid tumors.Patients received weekly intravenous gemcitabine (1000 mg/m2) and erlotinib (100 mg QD) alone (control cohort) or in combination with motesanib (50 mg QD, 75 mg BID, 125 mg QD, or 100 mg QD; cohorts 1-4); or erlotinib (150 mg QD) in combination with motesanib (100 or 125 mg QD; cohorts 5 and 6).Fifty-six patients were enrolled and received protocol-specified treatment. Dose-limiting toxicities occurred in 11 patients in cohorts 1 (n = 2), 2 (n = 4), 3 (n = 3), and 6 (n = 2). The MTD of motesanib in combination with gemcitabine and erlotinib was 100 mg QD. Motesanib 125 mg QD was tolerable only in combination with erlotinib alone. Frequently occurring motesanib-related adverse events included diarrhea (n = 19), nausea (n = 18), vomiting (n = 13), and fatigue (n = 12), which were mostly of worst grade < 3. The pharmacokinetics of motesanib was not markedly affected by coadministration of gemcitabine and erlotinib, or erlotinib alone. Erlotinib exposure, however, appeared lower after coadministration with gemcitabine and/or motesanib. Of 49 evaluable patients, 1 had a confirmed partial response and 26 had stable disease.Treatment with motesanib 100 mg QD plus erlotinib and gemcitabine was tolerable. Motesanib 125 mg QD was tolerable only in combination with erlotinib alone.ClinicalTrials.gov NCT01235416.