Trial of Dasatinib Plus Ixabepilone in 2nd or 3rd Line Metastatic Breast Cancer

In the Phase I portion of the study, patients will receive study treatment according to the assigned dose level. Ixabepilone will be administered over 1 hour on Days 1, 8, and 15 of a 28-day cycle. Dasatinib will be administered continuously starting on Day 1, Cycle 1 once daily (QD). Three patients will be enrolled at dose level 0 and observed for dose-limiting toxicity (DLT) for 1 course of treatment. Dose escalation or reduction will depend on the number of patients experiencing DLT as follows: * If 0 of 3 patients experiences a DLT, then 3 additional patients will be enrolled at the next higher dose level. * If 1 of 3 patients experiences a DLT, then 3 additional patients will be enrolled at that dose level. * If 2 of 3 or 3 of 3 patients experience a DLT, then 3 patients will be enrolled at the next lower dose unless 6 patients have already been treated at that dose. * If ≥2 of 6 patients experience a DLT at that dose level, then the MTD is considered to have been exceeded. At that point, 3 patients are treated at the next lower dose. * If no more than 1 of the 6 patients experiences a DLT, then the dose level will be escalated 1 level. Maximum-tolerated dose (MTD) is defined as the dose at which ≤1 of 6 patients experience DLT, and above which ≥2 of 6 patients experience DLT. In the Phase II portion of the study, dasatinib and ixabepilone will be administered at the MTD determined during Phase I. Dasatinib will be started on Day 1, Cycle 1 and will be administered continuously once daily. Ixabepilone will be administered over 1 hour on Days 1, 8, and 15 of a 28-day cycle. Patients will be treated with both agents for up to 8 cycles, after which stable or responding patients are eligible for monotherapy with dasatinib at the investigator's discretion in the absence of disease progression or unacceptable toxicity.