Replimune Group Inc. (NASDAQ: REPL) presented final first-in-human data for its RP2 oncolytic immunotherapy at the American Society of Clinical Oncology annual meeting on May 31, 2026.

The Phase 1 trial enrolled 85 patients with advanced solid tumors who had received a median of 2 prior systemic therapies. The study evaluated RP2 both as a single treatment and in combination with nivolumab.

RP2 monotherapy achieved an objective response rate of 19.0% among 21 evaluable patients, with responses in uveal melanoma, esophagogastric adenocarcinoma, chordoma, and mucoepidermoid carcinoma. The combination with nivolumab showed a 19.1% response rate among 47 evaluable patients and a disease control rate of 48.9%.

In uveal melanoma patients specifically, the pooled response rate for both treatment approaches was 33.3%. Response duration was not reached in the monotherapy group, with responses ranging from 11.5 to 27.3+ months. The combination group showed a median response duration of 22.1 months.

The treatment demonstrated systemic activity, with tumor regression observed in both injected and non-injected lesions. All three monotherapy responders with non-injected lesions showed regression at distant sites.

The most common side effects were low-grade fever, chills, and fatigue. No Grade 4 or 5 treatment-related adverse events occurred, and the safety profile aligned with expected immune activation responses.

Based on these results, Replimune is conducting a randomized Phase 2/3 trial evaluating RP2 combined with nivolumab in patients with metastatic uveal melanoma.

RP2 is an engineered herpes simplex virus designed to kill tumor cells and activate immune responses against cancer.