Phase I/II Study of Lapatinib in Combination With Paclitaxel as 1L Chemotherapy for ErbB2-positive MBC

This is an open-label, single-arm, Phase I/II study to evaluate the efficacy, safety and tolerability of weekly paclitaxel and lapatinib in subjects with ErbB2-overexpressing advanced or metastatic breast cancer who have not received prior therapy for metastatic disease. These subjects will receive weekly paclitaxel (80 mg/m2 IV for 3 weeks in a 4 week cycle) plus lapatinib (1500 mg once daily). Subjects will receive a daily dose of lapatinib until disease progression or withdrawal from study treatment due to unacceptable toxicity or withdrawal of consent. Subjects will be treated with paclitaxel for standard of 6 cycles, and may be continued at the discretion of investigators. If the subject experiences progression, an unacceptable toxicity related to paclitaxel, or termination of lapatinib therapy, paclitaxel therapy must be terminated any time of study period, even before 6 cycles of paclitaxel are given. This study consists of the Phase I and Phase II parts: Phase I part Tolerability and pharmacokinetics in 6 subjects will be evaluated in Phase I part of study and the tolerability criteria are set as follow: Tolerability criteria in first cycle; Concerning the safety tolerability of this trial, if 1 out of 6 first enrolled subjects meets the tolerability criteria, the study will proceed to phase II part and the regimen will judged as well tolerable. If 2 subjects meet the tolerability criteria, the sponsor will consult the safety review committee. GSK will finally judge based on the consultation regarding the tolerability and the medical significance. Grade 4 hematologic toxicities. Thrombocytopenia less than or equal to 25,000/mm3 Grade 3 or 4 and clinically significant non-haematologic toxicities. Inability to start cycle 2 within 2 weeks of scheduled dosing due to unresolved toxicity. For all 6 subjects enrolled, safety profiles occurred in cycle 1 are closely monitored individually. When considering the appropriateness of study continuation, not only the safety profiles noted in cycle 1 of this study, but also the safety profiles reported from pilot part of EGF104578 study and other relevant studies will be referred in order to make medical decisions. Phase II part After tolerability in 6 subjects enrolled in Phase I part is confirmed, further 6 subjects to be enrolled for Phase II part (i.e. total of 12 subjects). Subjects will receive a daily dose of lapatinib until disease progression or withdrawal from study treatment due to unacceptable toxicity or withdrawal of consent. All 12 subjects will be followed for survival.