On May 31, 2026 Replimune Group, Inc. (NASDAQ: REPL), a clinical-stage biotechnology company pioneering the development of novel oncolytic immunotherapies, reported final first-in-human data for RP2 alone and in combination with nivolumab in patients with advanced solid tumors during an oral session at the 2026 American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) annual meeting.
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Key findings are detailed below.
Oral Presentation: RP2 oncolytic immunotherapy alone and in combination with nivolumab (nivo) in patients with advanced solid tumors: Final safety, efficacy, and biomarker results from the phase 1 first-in-human (FIH) study; Date/Time: May 31, 2026, 9:12 AM CDT; Location: Arie Crown Theater; Abstract: 2504; Presenter: Joseph Sacco, PhD, MBChB
The Phase 1 first-in-human trial enrolled 85 heavily pretreated patients with advanced solid tumors, including uveal melanoma, colorectal cancer, head and neck cancers, pancreatic cancer, cutaneous melanoma, and sarcoma.
Patients had received a median of 2 prior lines of systemic therapy; 42% had received prior immune checkpoint inhibitor (ICI) therapy
RP2 monotherapy achieved an objective response rate (ORR) of 19.0% (4/21 evaluable patients), with responses observed in uveal melanoma, esophagogastric adenocarcinoma, chordoma, and mucoepidermoid carcinoma
RP2 in combination with nivolumab achieved an ORR of 19.1% (9/47 evaluable patients), with a disease control rate of 48.9%
In uveal melanoma, where a randomized Phase 2/3 trial is enrolling, the pooled ORR (RP2 in combination with nivolumab and RP2 monotherapy) was 33.3%
Responses were durable: median duration of response was not reached in the monotherapy group (range: 11.5–27.3+ months) and was 22.1 months in the combination group (range: 2.8–35.2+ months)
Tumor regression was observed in both injected and non-injected lesions, including in all 3 monotherapy responders who had non-injected lesions, demonstrating a systemic immune response beyond the site of injection
Translational analyses demonstrated that RP2 reprogrammed tumors from immunologically "cold" to immune-inflamed, upregulated T-cell cytotoxicity and antigen presentation pathways, and significantly expanded HSV-1-specific and tumor-associated (MAGE) TCR clones, confirming the intended mechanism of action and systemic immune engagement.
RP2 monotherapy and RP2 in combination with nivolumab were well tolerated with no unexpected toxicities, no Grade 4 or 5 treatment-related adverse events, and no increase in immune-related adverse events beyond the expected profile of nivolumab alone; the most common events were low-grade pyrexia, chills, and fatigue, consistent with systemic immune activation
Based on these results, RP2 is being evaluated in combination with nivolumab in patients with metastatic uveal melanoma in a randomized Phase 2/3 trial (NCT06581406)
About RP2
RP2 is based on a proprietary strain of herpes simplex virus engineered and genetically armed with a fusogenic protein (GALV-GP R-) and GM-CSF intended to maximize tumor killing potency, the immunogenicity of tumor cell death and the activation of a systemic anti-tumor immune response. RP2 additionally expresses an anti-CTLA-4 antibody-like molecule, as well as GALV-GP R- and GM-CSF. RP2 is intended to provide targeted and potent delivery of these proteins to the sites of immune response initiation in the tumor and draining lymph nodes, with the goal of focusing systemic-immune-based efficacy on tumors and limiting off-target toxicity.
(Press release, Replimune, MAY 31, 2026, View Source [SID1234666251])