Iniparib Disappoints in Breast Cancer, But Study Results Hint at Second-Line Therapy Benefit

Latest study results on PARP inhibitor iniparib disappointing, but may be helpful in second-line therapy.

The much anticipated data from the iniparib study in metastatic triple negative breast cancer produced a few more answers to whether the drug works, but they weren’t the answers many were hoping for. With interest high in PARP inhibitors (a relatively new class of targeted agents) after a promising phase 2 study, the phase 3 trial quickly met accrual as patients’ and doctors’ expectations for similar results grew.

When the announcement came earlier this year that the study had not reached its goal of overall survival and progression-free survival, questions arose as to how the phase 3 data could be so different from the overwhelming positive results of the phase 2 trial. Lead investigator Joyce O’Shaughnessy, MD, of Texas Oncology in Dallas, shared that the addition of iniparib to gemcitabine and carboplatin only gained one month in median progression-free survival, and overall survival only improved from 11.1 to 11.8 months.

However, this may not be the end of the line for iniparib. When responses from newly diagnosed women were separated out from those of previously treated women, the numbers suggested another story. For reasons yet unknown, women with one to two prior treatments for advanced breast cancer seemed to improve on the drug when looking at both progression-free survival (4.2 months versus 2.9 months) and overall survival (10.8 months versus 8.1 months). Another trial will be needed to confirm these suggested findings. And with confirmation that the drug’s maker, Sanofi-Aventis, will continue testing the drug in breast cancer, another trial may not be too far off.