WASHINGTON – according to findings from the ongoing phase 1b NT-001study of patients with metastatic melanoma, smoking-associated non–small cell lung cancer (NSCLC), and bladder cancer.
Dr. Siwen Hu-Lieskovan
No vaccine-related serious adverse events occurred in 34 patients in a per-protocol set who were treated with the regimen, Siwen Hu-Lieskovan, MD, PhD, reported at the annual meeting of the Society for Immunotherapy of Cancer.
“We found that NEO-PV-01 in combination with nivolumab was very safe; we did not see any grade 3 to grade 4 toxicity associated with the combination,” said Dr. Hu-Lieskovan, a medical oncologist at the University of California, Los Angeles.
Most adverse events that occurred were mild and related to the local injection, she noted.
Although safety was the primary endpoint of the study, Dr. Hu-Lieskovan and her colleagues also looked at immune responses and treatment efficacy, however, with respect to translational data her presentation addressed only the findings in the melanoma and lung cancer patients.
All patients exhibited an immune response to the vaccine, with 56% of the epitopes generating CD4- and/or CD8-positive T cell responses.
“These immune responses were very durable and still could be detected 52 weeks into the treatment,” she said. Additionally, epitope spreading – increased immune response targeting nonvaccine epitopes (which is indirect evidence of vaccine-induced tumor toxicity) – was observed in 8 of 10 patients tested.
The study subjects, including 16 adults with melanoma, 11 with NSCLC, and 7 with bladder cancer, were treated with nivolumab every 2 weeks for 12 weeks prior to vaccination (while their personalized vaccine was being developed). NEO-PV-01 – which included up to 20 unique peptides plus the immunostimulant poly-ICLC – was then administered subcutaneously in five priming doses followed by two booster doses over the next 12 weeks. Of note, very few patients had programmed cell death protein 1 expression of 50% or greater, including only 13.3%, 28.6%, and 0% of the melanoma, NSCLC, and bladder cancer patients, respectively, and tumor mutation burden was consistent with published reports, she said.
As for efficacy, 11 of 16 melanoma patients (68.6%) had either a partial response (8 pre vaccination and an additional 3 post vaccination) or stable disease. One (6.3%) had a postvaccination complete response, Dr. Hu-Lieskovan said.
“[This is] much better than the historical data,” she noted, adding that 12 patients (75%) are still on the study and continuing treatment with response duration of at least 39.7 weeks.
Of the 11 NSCLC patients, 5 (45.5%) had a partial response (3 pre vaccination and 2 post vaccination), and none had a complete response. Seven (63.6%) remained on the study and were continuing treatment, and response duration was at least 30.6 weeks.
An exploratory analysis of tumor responses after vaccination showed that the majority of melanoma patients and half of the lung cancer patients had further tumor shrinkage after vaccination, and some patients were converted to responders. Most – including some with stable or progressive disease – stayed on treatment, she said.
The findings demonstrate that NEO-PV-01 is very well tolerated and associated with post vaccine responses observed after week 24.
“We saw evidence of vaccination-induced immune response specific to the injected vaccine, as well as epitope spreading, and the T cells induced by these neoantigens can traffic into the tumor and they seem to be functional,” she concluded.
Dr. Hu-Lieskovan reported receiving consulting fees and/or research support from Amgen, BMS, Genmab, Merck, and Vaccinex. She is the UCLA site principal investigator for the NT-001 study and has conducted contracted research for Astellas, F Star, Genentech, Nektar Therapeutics, Neon Therapeutics, Pfizer, Plexxikon, and Xencor.
SOURCE: Hu-Lieskovan S et al. SITC 2018, Abstract 07.