NEW YORK (Reuters Health) - In a phase II study of women with metastatic triple-negative breast cancer (negative for estrogen receptor, progesterone receptor and HER-2), patients treated with the investigational poly ADP-ribose polymerase-1 (PARP-1) inhibitor BSI-201 in combination with standard gemcitabine and carboplatin chemotherapy had significantly better outcomes than women who received standard chemotherapy alone.

The results were announced Sunday during a plenary session at the American Society of Clinical Oncology's annual meeting in Orlando.

"The results of this study provide early evidence that BSI-201 is a promising treatment for women with triple-negative breast cancer, an aggressive form of the disease for which we need new, more effective therapies," Dr. Joyce O'Shaughnessy, co-director of the Breast Cancer Research Program at Baylor Charles A. Sammons Cancer Center in Dallas, said in a meeting statement.

PARP-1, a ubiquitous nuclear enzyme with roles in DNA base excision repair, is upregulated in the majority of triple-negative breast cancers. By inhibiting PARP-1, BSI-201 potentiates the effects of chemotherapy-induced DNA damage, Dr. O'Shaughnessy explained at an ASCO press briefing.

The clinical benefit rate in the study -- defined as complete and partial responses and stable disease of at least 6 months -- was 62% in the BSI-201 arm (57 women) versus 21% in the standard chemotherapy only arm (59 women), p = 0.0002.

Complete or partial response was observed in 48% of patients who received BSI-201 versus 16% who received standard chemotherapy only (p = 0.002).

Median progression-free survival was 6.9 months with BSI-201 versus 3.3 months without the investigational drug (p < 0.0001) and overall survival was 9.2 months vs 5.7 months, respectively, (p = 0.0005).

Adding BSI-201 to gemcitabine/carboplatin did not increase the frequency or severity of adverse events associated with gemcitabine/carboplatin chemotherapy, Dr. O'Shaughnessy reported.

BSI-201 is being developed by Sanofi-Aventis and its fully owned subsidiary, BiPar Sciences. A phase III trial with BSI-201 in metastatic triple-negative breast cancer is set to begin this summer.



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