Disappointments for Sanofi's iniparib in Ph III breast cancer study and Ipsen's Irosustat

French drug major Sanofi (Euronext: SAN) announced negative results from a new Phase III study of iniparib (BSI-201) in metastatic triple-negative breast cancer (mTNBC). The drug has previously been seen by analysts as having a blockbuster potential, with peak sales exceeding $1 billion a year.

The study did not reach statistical significance for the co-primary endpoints of overall survival (HR=0.88, 95% CI: 0.69, 1.12; p=0.28 versus pre-specified at 0.04) or PFS (HR=0.79, 95% CI: 0.65, 0.98; p=0.027 versus pre-specified at 0.01). The most common adverse events (Grade 3/4, >5%) were neutropenia, thrombocytopenia, anemia, fatigue, increase in alanine aminotransferase and dyspnea.

The results, which were presented at the annual meeting of the American Society of Clinical Oncology (ASCO) in Chicago, are the second recent disappointment with iniparib. Earlier this year, Sanofi and its subsidiary, BiPar Sciences (acquired in 2009), announced that a randomized Phase III trial evaluating: iniparib in patients with metastatic triple-negative breast cancer (mTNBC) did not meet the pre-specified criteria for significance for co-primary endpoints of overall survival and progression-free survival (The Pharma Letter January 21).