According to the results of a Phase II clinical trial presented at a plenary session of the 2009 annual meeting of the American Society of Clinical Oncology (ASCO), treatment with chemotherapy plus the investigational drug BSI-201—a type of targeted therapy known as a PARP inhibitor—improved outcomes among women with triple-negative breast cancer.
Triple-negative breast cancer refers to breast cancer that is estrogen receptor-negative, progesterone receptor-negative, and HER2-negative. These cancers tend to be more aggressive than other types of breast cancer and do not respond to treatment with hormonal therapy or HER2-targeted therapy. Chemotherapy provides effective treatment for some women with triple-negative breast cancer, but more targeted and more effective treatments are clearly needed.
PARP stands for “poly (ADP-ribose) polymerase.” The PARP enzyme plays a role in DNA repair, including the repair of DNA damage from chemotherapy. Drugs that inhibit this enzyme may contribute to cancer cell death and increased sensitivity to chemotherapy.
The investigational PARP inhibitor BSI-201 was evaluated in a Phase II clinical trial among 116 women with metastatic, triple-negative breast cancer. Study participants were assigned to receive chemotherapy alone or chemotherapy plus BSI-201. Chemotherapy consisted of Gemzar® (gemcitabine) and Paraplatin® (carboplatin).
- 62% of women treated with chemotherapy plus BSI-201 experienced a clinical benefit compared with 21% of women treated with chemotherapy alone. Clinical benefit refers to either a reduction in detectable cancer or stable disease of at least six months.
- Median overall survival was 9.2 months among women treated with chemotherapy plus BSI-201 compared with 5.7 months among women treated with chemotherapy alone.
- Median survival without cancer progression was 6.9 months among women treated with chemotherapy plus BSI-201 compared with 3.3 months among women treated with chemotherapy alone.
- The occurrence of side effects was similar in the two groups.
The results of this study suggest that the addition of BSI-201 to chemotherapy improves outcomes among women with metastatic, triple-negative breast cancer.
In a separate Phase II clinical trial also presented at ASCO, the investigational PARP inhibitor olaparib was evaluated among 54 women with BRCA1 or BRCA2 mutations and previously treated, advanced breast cancer. All study participants were treated with olaparib alone, and more than one-third experienced tumor shrinkage.
 O’Shaughnessy J, Osborne C, Pippen J et al. Efficacy of BSI-201, a poly (ADP-ribose) polymerase-1 (PARP1) inhibitor, in combination with gemcitabine/carboplatin (G/C) in patients with metastatic triple negative breast cancer (TNBC): Results of a randomized phase II trial. Presented at the 2009 annual meeting of the American Society of Clinical Oncology, May 29-June 2, 2009, Orlando, FL. Abstract P3.
 Tutt A, Robson M, Garber JE et al. Phase II trial of the oral PARP inhibitor olaparib in BRCA-deficient advanced breast cancer. Presented at the 2009 annual meeting of the American Society of Clinical Oncology, May 29-June 2, 2009, Orlando, FL. Abstract CRA501.
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