ViroMissile's IDOV-Safe Shows 30-46% Response Rate in Treatment-Resistant Colorectal Cancer
Key Insights
ViroMissile (search)'s IDOV-Safe oncolytic virus achieved a 30% objective response rate in heavily pretreated patients with pMMR/MSS metastatic colorectal cancer (search), a population historically resistant to checkpoint inhibitors.
Patients without liver metastases demonstrated particularly strong responses with a 46.2% objective response rate and median progression-free survival of 10.8 months.
The Phase I study of 55 patients showed manageable safety with only one Grade 4 treatment-related adverse event and no treatment-related deaths.
ViroMissile (search)'s investigational oncolytic virus IDOV-Safe has demonstrated promising anti-tumor activity in patients with proficient mismatch repair/microsatellite stable (pMMR/MSS) metastatic colorectal cancer (search), achieving response rates of 30-46% in a patient population historically resistant to immunotherapy. The Phase I data will be presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting.
The investigator-initiated study, led by Lin Shen, MD, at Peking University Cancer Hospital & Institute (search) in Beijing, evaluated IDOV-Safe in combination with fruquintinib (a VEGF (search) inhibitor) and toripalimab (a PD-1 (search) inhibitor) in 55 patients with pMMR/MSS metastatic colorectal cancer (search) (mCRC). This patient population has limited treatment options and poor response to checkpoint inhibitor-based immunotherapy.
Efficacy Results Show Promise in Difficult-to-Treat Population
In the key expansion cohort of 20 patients receiving the sequential combination strategy, IDOV-Safe demonstrated an objective response rate (ORR) of 30.0% and a disease control rate (DCR) of 70.0%, with a median progression-free survival (PFS) of 8.7 months. Notably, patients without liver metastases showed even more encouraging results, with an ORR of 46.2%, DCR of 84.7%, and median PFS of 10.8 months, compared to a median PFS of 3.7 months in patients with liver metastases.
"Achieving a 30-46% response rate in pMMR/MSS metastatic colorectal cancer (search), a setting where checkpoint inhibitors have largely fallen short, represents an encouraging signal that warrants further investigation," said Nanhai George Chen, PhD, Founder and Chief Executive Officer of ViroMissile (search).
Safety Profile Supports Continued Development
The study demonstrated a manageable safety profile across all dose levels. While 62% of patients experienced Grade 3 or higher treatment-related adverse events (TRAEs), only one Grade 4 TRAE was reported as a dose-limiting toxicity (DLT). The most common TRAEs were transient fever, thrombocytopenia, and neutropenia. Importantly, no treatment-related deaths were observed throughout the study.
Study Design and Platform Validation
The Phase I trial employed a triplet 3+3 dose-escalation design to assess dose-limiting toxicities and determine the maximum tolerated dose and recommended expansion dose. Expansion cohorts evaluated IDOV-Safe in combination with fruquintinib with or without toripalimab across three combination strategies: sequential, early, and IO-free. Primary and secondary endpoints included safety, objective response rate, disease control rate, and progression-free survival.
Chen emphasized that the findings validate a core hypothesis underlying ViroMissile (search)'s IDOV platform: "that systemic delivery of an oncolytic virus can prime immune responses even in tumors historically considered immune-cold." The company plans to advance this approach into a contemplated registrational Phase 2 study.
The poster presentation, titled "Intravenous oncolytic virus IDOV-Safe in pMMR/MSS metastatic colorectal cancer (search)" (Abstract #3536), will be presented by Tong Xie, MD, of Peking University Cancer Hospital & Institute (search) on Saturday, May 30th, at Poster Board 290 during the ASCO Annual Meeting in Chicago.