While ABCB1 (P-glycoprotein 1) upregulation after paclitaxel administration is well known, there is currently no clinically available method for preventing or overcoming it. To develop a therapy able to prevent ABCB1 upregulation and paclitaxel resistance, several ABCB1 inhibitors have been evaluated in combination with paclitaxel in preclinical model systems. Pulsed-dose lapatinib and paclitaxel are synergistic and inhibition of ABCB1 by lapatinib increases sensitivity to paclitaxel. Lapatinib is FDA approved, orally available, and previously studied in combination with weekly paclitaxel for breast cancer at doses of 1000mg to 1250mg daily (7000-8250mg per week). This trial will use twice-daily dosing of lapatinib at a starting dose of 750 mg for 2 days (1500mg a day and 3000mg weekly dose), which is less than half of the continuous dose and has been shown to achieve plasma concentrations at 48 hours that are associated with synergy. Therefore, these findings can be translated into a novel, well-tolerated, and convenient combination regimen with significant potential for clinical activity. This trial will be a phase I dose-escalation study of lapatinib and paclitaxel for platinum-resistant ovarian cancer, which will establish the phase II dose for subsequent efficacy trials.
