PARP inhibitors are a promising, novel class of anticancer agents. Iniparib (BSI-201) is an intravenously administered PARP1 inhibitor under development by BiPar Sciences Inc, a subsidiary of sanofi-aventis, under license from Octamer Inc, for the potential treatment of cancer. Iniparib, either alone or in combination with chemotherapy, had significant antitumor activity in preclinical studies in vitro and in vivo. Phase I clinical trials in patients with solid tumors demonstrated that treatment with iniparib was associated with minimal toxicity. Encouraging results were observed in a randomized phase II clinical trial, which demonstrated that the addition of iniparib to gemcitabine and carboplatin led to an improvement in clinical benefit rate, progression-free survival and overall survival in patients with metastatic triple-negative breast cancer (TNBC) compared with gemcitabine and carboplatin alone. A phase III clinical trial to test the survival benefit of iniparib in combination with gemcitabine and carboplatin in metastatic TNBC has completed accrual. Another phase III clinical trial will evaluate the overall survival of patients with newly diagnosed stage IV squamous NSCLC treated with gemcitabine and carboplatin with or without iniparib. Several phase II clinical trials of iniparib as a single agent or in combination with chemotherapy are ongoing in other tumor types, such as ovarian and uterine cancer, NSCLC and glioblastoma. These trials will clarify the role of iniparib in the treatment of cancer, including TNBC.