Results from a phase 2 study are suggesting that the poly ADP-ribose polymerase (PARP) inhibitor veliparib may be active and tolerated in women with persistent or recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer who carry a germline BRCA1 or BRCA2 mutation.1 Activity of veliparib in this phase 2 study met the minimal efficacy benchmark to be considered of clinical interest and demonstrated response in both platinum-sensitive and platinum-resistant patients. In addition, secondary endpoint assessments (progression-free survival [PFS] and overall survival [OS]) were found to be favorable.
“This is pretty impressive in this patient population. The longest follow-up we have is well over 2 years. It has been about 3 years since we started the trial,” said lead study author Robert Coleman, MD, professor and vice chair of clinical research at the University of Texas MD Anderson Cancer Center in Houston.
Dr. Coleman, who recently presented the study findings at the Society of Gynecologic Oncology Annual Meeting on Women’s Cancer in Tampa, FL, said PARP inhibitors prevent cancer cells from repairing themselves after experiencing DNA damage. He said previous studies have shown that veliparib is effective in combination with chemotherapy, but this study showed that it may be effective as a single agent.
The trial included 50 women who had recurrent or persistent epithelial ovarian, peritoneal, or fallopian tube cancer that carried a germline BRCA1 or BRCA2 mutation. The mean age of the patients was 57 years (range, 37 to 94 years) and 30 of the 50 patients were platinum-resistant. Veliparib was administered at 400 mg twice a day with up to two dose reductions for toxicity. One cycle was 28 days and the median number of cycles administered in the study was 5.5 (range, 1 to 16 cycles). In this study, 46 patients (92%) had prior radiation and 47 patients (94%) had prior immunotherapy.1
The researchers found that 13 patients (26%) responded positively to the therapy, including 2 patients in whom the tumors disappeared completely. In addition, disease was stabilized for more than 4 months in nearly half of the women (n=24). Median PFS was 8.11 months and 44% of the patients were event-free at 6-month follow-up. Dr. Coleman said 20% of the platinum-resistant patients and 35% of platinum-sensitive patients demonstrated favorable tumor response.1
“Given the type of patient on the trial, we were pleased…the response rates are good,” said Dr. Coleman in an interview with ChemotherapyAdvisor.com. “In platinum-resistant patients, there has been the feeling that PARP inhibitors don’t work, but we showed that is not the case.”
Dr. Coleman noted that the agent was well tolerated and the most common adverse events were fatigue, nausea, vomiting, and anemia. However, one grade 4 adverse event (thrombocytopenia) occurred. A total of 24 patients (48%) underwent dose reductions during the study.
Don Dizon, MD, director of the Oncology Sexual Health Clinic at Massachusetts General Hospital, Boston, MA, said administering this agent to women with ovarian cancer who harbor a BRCA1 or BRCA2 mutation continues to be of significant interest. “There are multiple PARP inhibitors undergoing clinical testing, with one (olaparib) now in phase 3 trials as part of primary treatment and a separate one for patients experiencing a platinum-sensitive relapse, which is defined as a recurrence greater than 6 months from end of prior treatment,” Dr. Dizon told ChemotherapyAdvisor.com. “This study shows yet again that PARP inhibitors as a class have activity in BRCA–mutation-associated ovarian cancers. Whether one is better than the other will require further study, but this trial reaffirms the clinical value of these agents in ovarian cancer.”
- Coleman RL, Sill M, Aghajanian C, et al. A phase II evaluation of the potent, highly selective PARP inhibitor veliparib in the treatment of persistent or recurrent epithelial ovarian, fallopian tube, or primary peritoneal cancer in patients who carry a germline BRCA1 or BRCA2 mutation—a Gynecologic Oncology Group study (Abstract 136). Presented at the Society of Gynecologic Oncology Annual Meeting, March 22-25, Tampa, FL.