CHICAGO – Nivolumab, an investigational PD-1 inhibitor, shrank tumors by at least 30% in 33 of 107 pretreated patients with metastatic melanoma, based on results from an expanded phase I trial reported at the annual meeting of the American Society of Clinical Oncology.
An additional 11% of patients had prolonged stable disease or non-conventional, immune-related response profiles.
The findings build on favorable initial results reported at last year’s annual meeting for nivolumab in melanoma, renal cell carcinoma, and nonsmall cell lung cancer. The latest results in melanoma patients at follow-ups as long as 2 years indicate no new safety signals with nivolumab, which was associated with a 21% rate of grade 3-4 events. The rate of severe immune-related adverse events was 5%, and there were no cases of grade 3 or higher pneumonitis.
© ASCO/Scott Morgan
Dr. Mario Sznol
Median overall survival was nearly 17 months with nivolumab, with a 2-year survival rate of 43%. Median overall survival with vemurafenib (Zelboraf) is 16 months and with ipilimumab (Yervoy) is 10 months, with 2-year survival rates of 24% to 33% with ipilimumab, according to Dr. Mario Sznol, who presented the results from the phase I trial.
"We’re very excited that there is potential for even more activity [with nivolumab] in combination with other drugs," said Dr. Sznol, professor of medicine (medical oncology) at the Yale Cancer Center in New Haven, Conn.
Responses were seen at all five dose levels tested (0.1, 0.3, 1, 3, and 10 mg/kg), with a 41% objective response rate at the 3 mg/kg dose, which has been selected for evaluation in phase III studies.
Median overall survival across all doses of nivolumab was 16.8 months. It reached 20.3 months for the 3 mg/kg dose. The 1-year survival rate was 62% and the 2-year survival rate, 43%.
Patients in the nivolumab trial were representative of typical patients with advanced melanoma, Dr. Sznol said. All patients in the study had disease that worsened despite prior standard systemic therapies, 25% of them had three or more prior therapies and 63% had two or more prior therapies.
All had ECOG performance standards of 0 or 1. Patients received up to 12 cycles of treatment, with four doses of nivolumab per cycle, until discontinuation criteria were met.
Response has persisted after stopping treatment in 17 of 33 patients, with 12 of the 17 continuing to respond for at least 4 months, Dr. Sznol said.
The overall objective response rate included partial and complete responses. Dr. Sznol acknowledged that just one patient had a verified complete response to nivolumab and four others had near complete responses at 2 years. Historical response rates to immunotherapy drugs are 5%-10% in advanced melanoma, he noted, which is lower than the 30% response seen in these pretreated patients.
"I have seen a few relapses after 2 years of response, but some patients continue to do well at 4 years. One patient who has been off nivolumab for 2 years continues to do well at over 4 years," Dr. Sznol commented during a question and answer session.
To define the best candidates for nivolumab, molecular markers need to be identified to predict probable response, he added. As nivolumab is a PD-1 inhibitor, one potential marker is the protein PD-L1 on the surface of tumor cells, which is being studied in several other clinical trials.
The research was supported by Bristol-Myers Squibb. Dr. Sznol disclosed that he serves in a consultant or advisory role with Bristol-Myers Squibb.