The anti–PD-1 agent nivolumab may have some utility as monotherapy in the treatment of naive advanced clear cell renal cell carcinoma (ccRCC), according results from a new phase 2 clinical trial (HCRN GU16-260).
Patients received nivolumab (Opdivo, Bristol-Myers Squibb) monotherapy in the first phase of the study, with qualifying patients moving on to dual therapy with nivolumab and the anti–CTLA-4 agent ipilimumab (Yervoy, Bristol-Myers Squibb).
“At the moment, monotherapy with anti–PD-1 is not FDA approved in patients with treatment-naive ccRCC. Based on the results of this study, it might be applicable in patients with favorable risk disease where only tyrosine kinase inhibitors or TKI-containing combinations are approved,” lead investigator Michael Atkins, MD, said in an interview. The study was published online in the Journal of Clinical Oncology.
“It shows the contribution of [nivolumab] to the combination in treatment-naive patients. This data was not previously available as nivolumab monotherapy had only been formally tested in patients with prior history of TKI therapy. It also gives valuable information on the role of PD-L1 as a biomarker in response and landmark progression-free survival in patients treated with anti–PD-1 monotherapy,” said Dr. Atkins, who serves as deputy director of the Georgetown Lombardi Comprehensive Cancer Center in Washington, D.C.
Patients with higher expression rates of PD-L1 had a higher overall response rate and higher probability of progression-free survival at 1 year.
“ but there is concern about risk of toxicity if ipilimumab is added. These might include elderly patients and those with a history or autoimmune conditions,” Dr. Atkins said.
Next on the agenda for the researchers are more extensive biomarker studies of the tissues obtained in the phase 2 study. They hope to identify factors that predict response and resistance in the absence of confounders like combination therapy, primary versus metastatic tumors, and use of nonimmunotherapy endpoints. They will also track treatment-free survival following cessation of therapy at 2 years.
The study “provides much needed first-line data for check point inhibitor monotherapy in an era that is heavily invested in combination strategies,” Martin Voss, MD, wrote in an accompanying editorial. Further studies currently in progress should shed even more light on monotherapy in this patient population. These include the phase 3 CheckMate 8Y8 trial comparing nivolumab with ipilimumab/nivolumab in untreated patients, and the phase 3 PDIGREE23 trial, which is comparing upfront, response-adaptive ipilimumab/nivolumab with escalation through addition of TKIs in patients with progressive disease and de-escalation to nivolumab monotherapy in patients who achieve a complete response, and randomization between the two strategies for nonprogressive disease and non–complete response patients.
However, these phase 3 studies are limited to intermediate- to poor-risk patients. For favorable-risk patients, small cohort studies like HCRN GU16-260 represent the best currently available guide to treatment, Dr. Voss wrote.
In part A of the study, 123 patients received nivolumab for 96 weeks. 35 patients who experienced progressive disease or had a best response of stable disease at 48 weeks became eligible for part B, in which they received the combination of nivolumab and ipilimumab for 12 weeks, and then nivolumab monotherapy for 48 weeks. All patients underwent PD-L1 testing, and tumors were categorized by percentage of tumor cells expressing PD-L1 as 0%, 1%-5%, greater than 5%-20%, and greater than 20%.
The overall objective response rate was 34.1%. 6.5% had a complete response. Patients categorized by International Metastatic RCC Database Consortium category as intermediate or poor risk had an ORR of 25.0%. Those categorized as favorable risk had an ORR of 57.1%, with a complete response rate of 11.4%. Just one patient with favorable risk had progressive disease at their 12-week CT scan. The ORR was higher with increasing percentages of PD-L1 expression, from 26.9% in PD-L1 0 to 50% in PD-L1 1-20 and 75.0% in PD-L1 greater than 20% (P = .002). Five of 7 (71.4%) patients with PD-L1 values of 1 or more had a tumor response to nivolumab monotherapy, but 14 of 23 (60.9%) of those with favorable risk disease and PD-L1 of zero also responded.
The median duration of response was 27.6 months, and progression-free survival was 34.6% at 1 year in the PD-L1 0 and 75.0% in the PD-L1 greater than 20 categories (P = .050). Among patients eligible for part B, the ORR was 11.4%.
Dr. Atkins has consulted or been on the advisory board for Bristol-Myers Squibb.