Background: Pazopanib (pazo) is an oral tyrosine kinase inhibitor of VEGFR, PDGFR and c-Kit. It is a weak inhibitor of CYP3A4 and CYP2C8 and may decrease paclitaxel (P) clearance. Daily pazo with P and carboplatin (C) every 21 days was not feasible on a previous study. We hypothesized that pazo dosed intermittently and on a different day from P and C may be tolerable. We sought to determine the maximum tolerated dose (MTD), dose-limiting toxicity (DLT), and pharmacokinetics (PK) of pazo with weekly P and C. Methods: Using a 3+3 standard design, a schedule of P 60-80 mg/m² and C AUC2 on days 1, 8, and 15 with pazo 400-800 mg on days 2-5, 9-12, and 16-26 on a 28-day cycle was evaluated. Pazo alone could be continued if P and C were omitted due to maximal benefit or toxicity. PK was collected during cycles 1 and 2. Results: 34 patients (pts) were treated over 6 dose levels (Table). Mean age 57 (37-79). Tumor types: breast (22), lung (3) and other (9); 27 had prior platinum. Delay in starting cycle 2 due to grade 3 neutropenia was a DLT at dose level 2 and 5. Pts on 5A missed dosing during C1 and C2 due to neutropenia and required subsequent growth factor, and this was deemed unlikely to be sustainable long-term. All grade toxicities included anemia (62%), neutropenia (59%), and thrombocytopenia (56%). Protocol-defined MTD was not determined. PK analysis showed a dose proportional increase in pazo concentration, consistent with previous reports. Pazo did not alter the PK of C. C_max of P was higher C2D1 vs C1D1; mean C_max ratio between C2D1:C1D1 was 1.63 (95% CI:1.29-1.96). There were 11 objective responses (3 CRs, 8 PRs). Five breast pts were on pazo alone for a median of 9 cycles (2-52) with CR (2), PR (2) and SD (1); a squamous cell of unknown primary in CR received 22 cycles. Clinical trial information: NCT01407562Conclusions: PK confirm that pazo is a weak inhibitor of CYP3A4 and CYP2C8. Myelosuppression was a major adverse event at all dose levels. MTD was not determined. Antitumor activity was achieved with this alternate combination schedule and sustained responses from sequential pazo monotherapy was observed.