A small molecule iodobenzamide with potential cytotoxic and antineoplastic activities. Although the mechanism of action is unknown, iniparib appears to be cytotoxic in cells with DNA alterations or DNA damage, like that found in tumor cells with mutations in the ataxia telangiectasia mutated (ATM) gene. ATM encodes a serine/threonine protein kinase and mutations of the gene are associated with ataxia telangiectasia and contribute to certain cancers such as T-cell acute lymphoblastic leukemia, B-cell chronic lymphocytic leukemia and B-cell non-Hodgkin lymphomas.

A substance being studied in the treatment of breast cancers caused by mutations (changes) in the BRCA1 and BRCA2 genes. It is also being studied in the treatment of other types of cancer. It blocks an enzyme involved in many functions of the cell, including the repair of DNA damage. DNA damage may be caused by normal cell actions, UV light, some anticancer drugs, and radiation used to treat cancer. BSI-201 may cause cancer cells to die. It is a type of poly(ADP-ribose) polymerase inhibitor.