The purpose of this study is to determine the effectiveness of enzastaurin in the treatment of patients with metastatic breast cancer.

Inclusion Criteria:

• Clinical diagnosis of metastatic breast cancer or recurrent breast cancer where surgery can not be done for curative intent
• Have received prior therapy with an anthracycline (class of drugs) and a taxane (class of drugs).
• Tumors must not be positive for HER2, but if positive, the treatment plan should not include further treatment with the drug Herceptin.
• Disease that can be definitely measured on Cat Scans or other radiological tests.
• May have received high dose chemotherapy for autologous stem cell support greater than or equal to 6 months of starting this study.

Exclusion Criteria:

• More than 2 chemotherapy regimens for metastatic or locally recurrent disease.
• Have brain cancer from breast cancer
• Pregnant or breastfeeding
• Have an inability to swallow tablets
• Within 6 months have had a serious heart condition