A Study to Determine the Antitumor Activity and Evaluate the Safety of MKC-1

Inclusion Criteria: * Histologically or cytologically confirmed advanced or metastatic adenocarcinoma of the breast * 18 years or older * Karnofsky performance status greater than or equal to 70% * Radiographic or physical examination evidence of at least one site of unidimensionally-measurable disease, using the Response Evaluation Criteria in Solid Tumors (RECIST) criteria * Must have failed both a taxane and an anthracycline, given sequentially or in combination, either in an adjuvant or metastatic setting * All acute toxicity of any prior chemotherapy, surgery or radiotherapy must have resolved to National Cancer Institute Common Toxicity Criteria (NCI CTC) Grade less than or equal to 1 * Lab results, within 10 days of MKC-1 administration: * Hemoglobin less than or equal to 9 g/dL * Absolute neutrophil count greater than or equal to 1.5 x 10\^9/L * Platelet count greater than or equal to 75 x 10\^9/L * Serum creatinine less than or equal to 1.5 x ULN (upper limit of normal) * AST less than or equal to 2.5 x ULN * Serum albumin greater than or equal to LLN (lower limit of normal) * Total bilirubin less than or equal to ULN * Alkaline phosphatase less than or equal to 2.5 x ULN * Signed informed consent Exclusion Criteria: * Pre-existing hepatomegaly with disease measures greater than or equal to 2 cm below the costal margin, secondary to malignancy * Administration of cancer specific therapy within the following periods prior to study drug initiation: * chemotherapy less than 3 weeks prior * hormonal therapy less than one week prior * radiation therapy less than 2 weeks prior * Be pregnant or lactating; not employing effective birth control * Known central nervous system (CNS) metastases unless treated, clinically stable and not requiring steroids * Clinical evidence of bowel obstruction, active uncontrolled malabsorption syndromes or a history of total gastrectomy * Administration of any investigational agent (therapeutic or diagnostic) within 4 weeks prior to receipt of study medication * Uncontrolled hypercalcemia (serum calcium-corrected greater than 12 mg/dL) * Serious cardiac condition * Any medical conditions that, in the investigator's opinion would impose excessive risk to the patient * Patients with previous malignancies unless free of recurrence for at least 5 years except basal cell carcinoma of the skin or carcinoma-in-situ of the uterine cervix * Treatment with antiretroviral therapy metabolized through CYP3A4