An investigational study to determine the safety/tolerability, and efficacy of a notch signaling pathway inhibitor in patients with metastatic or locally advanced breast cancer and other advanced solid tumors.

Inclusion Criteria:

• Women or men greater than or equal to 18 years of age
• ECOG status less than or equal to 2 (a measurement to determine your ability to perform daily activities)
• In Parts I, III, and IV, patient must have a histologically confirmed, metastatic or locally advanced solid tumor that has failed to respond to standard therapy, progressed despite standard therapy, or for which standard therapy does not exist. There is no limit on the number of prior treatment regimens
• In Part II, only breast cancer patients are eligible
• In Part V, only patients with Numb negative breast cancer (i.e., tumor shows Numb immunoreactivity in less than 10% of the neoplastic cells assessed) are eligible
• Patient has recovered from and is at least 2 weeks from previous antineoplastic therapy, including chemotherapy, biological therapy (including Herceptin), hormonal therapy, radiotherapy, or surgery

Exclusion Criteria:

• Patient has had an investigational treatment in the preceding 21 days
• Uncontrolled congestive heart failure or myocardial infarction (heart attack) within 3 months of study start
• History of hepatitis B or C or HIV
• Patient has the presence of clinically apparent central nervous system metastases or carcinomatous meningitis. Patients with CNS metastases who have completed a course of radiotherapy and are clinically stable in the judgment of the investigator are eligible
• Patients with "currently active" second malignancy, other than non-melanoma skin cancer, should not be enrolled. Patients are not considered to have a "currently active" malignancy if they have completed therapy for prior malignancy and are considered by their physician to be at <30% risk of relapse