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