Nivolumab and ipilimumab
Dr. McGregor is leading a phase II trial (NCT03333616) testing a combination of nivolumab and ipilimumab in patients with a variety of advanced rare GU malignancies, including bladder and upper tract carcinoma of variant histology (BUTCVH), adrenal tumors, CRGCT, PSCC, and prostate cancer of variant histology (PCVH).
“When trials are designed, these patients are often forgotten,” Dr. McGregor noted. “We said, let’s do a trial for all rare GU tumors and just sort of assess and look for a signal, and, hopefully, find a signal that we can then take to the next level.”
Along with appropriate disease phenotype, trial eligibility depended upon an ECOG performance status of 0-2 and no prior exposure to checkpoint inhibitors. Treatment-naive patients were allowed. All participants received nivolumab 3 mg/kg and ipilimumab 1 mg/kg IV every 3 weeks for four doses, followed by maintenance nivolumab at a dose of 480 mg every 4 weeks.
Most recent results, published in Cancer, included data from 55 patients, including 19 with BUTCVH, 18 with adrenal tumors, and 18 with other tumors.3 After a median follow-up of 9.9 months, 28 patients (51%) received all four doses of the regimen, 25 of whom received maintenance therapy with a median of four cycles.
Overall, nine patients (16%) responded to therapy, six of whom (67%) maintained their response for at least 9 months. Two responses were complete, and seven were partial. Median progression-free survival was 2.8 months.
Twenty-two patients (39%) had grade 3 or higher treatment-related adverse events, approximately one-quarter (23%) needed high-dose steroids, and a slightly greater proportion (27%) discontinued the regimen because of adverse events. Three patients exhibited grade 5 toxicity, and one patient death was treatment related. A closer look at the efficacy data suggested that one disease subgroup benefited much more than the others. The overall response rate among 19 patients with BUTCVH was 37%, compared with 6% in the other two cohorts.
“A response rate of 37% compares quite favorably to anything we’ve seen to date,” Dr. McGregor said. “It’s remarkable that [this response] was seen across histologies – we saw this in urachal, we saw this in adenocarcinoma – we really saw this across the board. This is very, very, very intriguing data.”
The phase II trial is ongoing at multiple centers across the country, including the Dana-Farber/Harvard Cancer Center, Boston, the University of Texas MD Anderson Cancer Center, Houston, the Moores Cancer Center at University of California Health, San Diego, the Ohio State University Comprehensive Cancer Center, Columbus, and the Winship Cancer Institute of Emory University, Atlanta.
“We accrued this trial in just under 18 months,” Dr. McGregor said. “I think this shows that with a well-designed trial, we can actually study these diseases and improve outcomes in these patients.” According to Dr. McGregor, the current findings deserve further investigation, potentially including expansion of the BUTCVH cohort. Recruitment is ongoing for a fourth cohort involving patients with tumors that exhibit neuroendocrine differentiation.