An investigational new PARP inhibitor, BMN 673, is showing early responses in patients with heavily pretreated, advanced, BRCA-related cancers of the breast and ovary, according to phase I clinical trial results presented here at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics, held Oct. 19-23.
When there is damage to DNA in human cells, two proteins, PARP 1 and 2, recruit proteins that can repair the damage associated with loss of BRCA proteins. Mutations in BRCA genes often result in inefficient repair of damaged DNA, which increases the risk for developing certain cancers, including cancers of the breast and ovary. Inhibiting PARP, therefore, prevents the repair of damaged DNA, leading to cell death. While some PARP inhibitors have been tested in various settings, none are approved to date.
"BMN 673 is the most potent PARP inhibitor in clinical development and has optimized pharmaceutical properties: it is well absorbed orally, has substantial single-agent antitumor activity, and has a long half-life allowing once-daily dosing," said Zev A. Wainberg, M.D., assistant professor of medicine at the Jonsson Comprehensive Cancer Center of the University of California Los Angeles School of Medicine. "The clinical data to date are promising and compare favorably with results from clinical trials with other PARP inhibitors. We observed high objective and clinical benefit response rates in BRCA-related breast and ovarian cancers at low, oral, once-daily doses.
"Based on this phase I study, we feel there's a good chance that patients with BRCA-related cancers who meet the study eligibility criteria will have disease control for a meaningful period of time with relatively few side effects. However, randomized trials are necessary to demonstrate whether this will translate into improvements in progression-free and overall survival relative to currently available therapies," said Wainberg.
He and colleagues conducted a phase I trial to evaluate the safety and efficacy of BMN 673 in a two-stage dose escalation/expansion study. So far, they have recruited 39 and 41 patients to the escalation phase and expansion phase, respectively. Patients were 18-82 years old, and they had undergone one to 13 prior therapies.