PARP inhibitor Iniparib decreases tumors, increases survival time

The PARP inhibitor iniparib (BSI-201) boosted overall survival by nearly five months when used with chemotherapy for metastatic triple-negative breast cancer compared with chemotherapy alone, according to results from a phase II trial of 123 patients published online in the New England Journal of Medicine. The median overall survival was 12.3 months for those on the PARP inhibitor-plus-chemo regimen and 7.7 for chemo alone. The drug combination shrank tumors and increased the time they took to progress.

Below is a news release from Sanofi-Aventis, maker of iniparib:

BRIDGEWATER, N.J., Jan. 5, 2011 /PRNewswire/ -- Sanofi-aventis (EURONEXT: SAN and NYSE: SNY) and its wholly-owned subsidiary, BiPar Sciences, today announced that The New England Journal of Medicine (NEJM) published the final phase II data for the investigational drug iniparib* (BSI-201) demonstrating significant clinical benefit in women with metastatic triple negative breast cancer (mTNBC) when iniparib was administered in combination with chemotherapy agents gemcitabine/carboplatin. Although not a pre-specified endpoint, overall survival also was significantly increased in women who received iniparib. The study, "Iniparib plus Chemotherapy in Metastatic Triple-Negative Breast Cancer," was published in the January 5, 2011, online version of the NEJM and will be published in the January 20, 2011, print edition. These findings were presented at the 35th European Society for Medical Oncology (ESMO) Congress in Milan, Italy.

"These published data show that the addition of iniparib to gemcitabine and carboplatin provided a significant improvement in clinical benefit in women with metastatic triple negative breast cancer, an aggressive form of breast cancer with no approved standard treatments that target this particular tumor subtype," said Joyce O'Shaughnessy, M.D., lead investigator of the study and co-chair of the Breast Cancer Research Program, Baylor-Charles A. Sammons Cancer Center, Texas Oncology, US Oncology in Dallas.

According to the study results, 56 percent of patients in the iniparib (BSI-201) group showed a clinical benefit – defined as a complete or partial response or stable disease of at least six months – compared with 34 percent (P=0.01) of patients in the chemotherapy group alone. Median progression-free survival in the iniparib (BSI-201) group was 5.9 months compared with 3.6 months in the chemotherapy group (95% CI (0.39-0.90) HR=0.59, P=0.01). The overall response rate was 52 percent in the iniparib (BSI-201) group versus 32 percent (P=0.02) in the chemotherapy group alone. Although it was not a pre-specified endpoint of the trial, median overall survival among women who received iniparib (BSI-201) was 12.3 months, compared with 7.7 months among women who received chemotherapy alone – translating to a 43 percent reduction in the risk of death (95% CI, (0.36-0.90) HR=0.57, P=0.01).

In the phase II iniparib (BSI-201) study, the most common any grade adverse events in the iniparib (BSI-201) arm were neutropenia, anemia, thrombocytopenia, fatigue/asthenia, nausea and constipation. The most common grade 3/4 adverse events in the iniparib treatment arm were neutropenia, anemia, thrombocytopenia, leukopenia and fatigue/asthenia. There were two fatal adverse events (3.4%) in the chemotherapy-alone group and three (5.3%) in the iniparib (BSI-201) group, all attributed to disease progression within 30 days of receiving study treatment. A large phase III study is ongoing and results are expected in 2011.

"The positive iniparib phase II data in this difficult to treat form of breast cancer is encouraging and underscores the innovative science and approach we have taken as we continue to investigate iniparib's potential to address this unmet medical need," said Atul Dhir M.D., CEO, BiPar Sciences, a wholly- owned subsidiary of sanofi-aventis.

About the Phase II Iniparib Study

This multicenter, open-label, randomized study included 123 women with mTNBC. The primary endpoints were safety and tolerability and clinical benefit rate of iniparib (BSI-201) defined as a complete or partial response or stable disease of at least six months. Secondary endpoints included overall response rate and progression-free survival. Overall survival also was assessed, although it was not a pre-specified endpoint of the trial. Patients received gemcitabine/carboplatin alone (chemotherapy group) or in combination with iniparib (BSI-201) until disease progression or unacceptable toxicity. Patients in the chemotherapy group whose disease progressed were allowed to cross over to the iniparib (BSI-201) plus chemotherapy group. Efficacy analyses were conducted on the intent-to-treat (ITT) population.

About Iniparib

Iniparib (BSI-201) is a novel investigational anti-tumor agent with poly (ADP-ribose) polymerase (PARP) inhibitory activity in preclinical models. Iniparib (BSI-201) is in phase III trials for patients with mTNBC and squamous non-small cell lung cancer, as well as in phase II trials for patients with ovarian, uterine and brain cancers.

The U.S. Food and Drug Administration (FDA) granted Fast Track designation to iniparib (BSI-201) for mTNBC. The regulatory submissions are planned for Q1 2011 in the United States and Q2 2011 in the European Union.

About Triple-Negative Breast Cancer (TNBC)

When patients are diagnosed with breast cancer, their tumors are routinely tested for the presence of estrogen and progesterone receptors and for the over-expression of HER2. However, 15 to 20 percent of all breast cancers lack over-expression of all three proteins – giving rise to the term "triple negative breast cancer" or TNBC. Research has shown TNBC can be difficult to treat, leading the disease to be associated with poorer outcomes than other types of breast cancer. Women with TNBC are not candidates for hormonal therapy such as tamoxifen or the targeted therapy Herceptin, leaving chemotherapy as the standard treatment.

About sanofi-aventis Oncology

Sanofi-aventis Oncology is targeting cancer on many fronts in an effort to address unmet medical needs for a broad range of patients. Starting with a deep understanding of the mechanisms by which cancer develops, grows and spreads, as well as identifying the right science early in the discovery process, the company employs innovative approaches to bring the right medicines to the right patients. There are currently more than 10 investigational compounds in development across a broad scientific platform, including cytotoxic, antimitotic, anti-angiogenic agents, antivascular agents as well as supportive care therapies. Three of these compounds are now being investigated in phase III clinical studies aimed at multiple solid and hematologic tumors.

About sanofi-aventis

Sanofi-aventis U.S. is an affiliate of sanofi-aventis, a leading global pharmaceutical company that discovers, develops and distributes therapeutic solutions to help improve the lives of patients. Sanofi-aventis is listed in Paris (EURONEXT: SAN) and in New York (NYSE: SNY).

For more information, www.sanofi-aventis.us or www.sanofi-aventis.com.

About BiPar Sciences

BiPar Sciences is a biopharmaceutical organization dedicated to pioneering novel tumor-selective therapies designed to address urgent unmet needs of cancer patients. Located in South San Francisco, California, BiPar is a wholly-owned subsidiary of sanofi-aventis. For more information, please visit www.biparsciences.com.

Medpage Today has an article on the findings, as does Internal Medicine News, and Medscape Today.