Phase 1 dose escalation trial of vv-DD-hIL-2-RG-1 (vaccinia virus double deleted) administration by intratumoral injection for metastatic gastrointestinal tumors: The regional immuno-oncology trial - 3 (RIOT-3) protocol

<h2>Abstract</h2> Current treatments for metastatic gastrointestinal malignancies have poor outcomes, necessitating a novel approach to treatment. Oncolytic therapy with vaccinia viruses has previously shown promising results in terms of safety and anti-tumor efficacy. In addition to direct viral cytotoxic effects, oncolytic therapy has the potential to stimulate adaptive immunity against infected tumor cells by altering the tumor microenvironment. The immunostimulatory effects of oncolytic vaccinia vectors have been maximized through the use of recombinant vectors encoding interleukin-2 (IL-2), a potent cytokine that signals T cell activity and proliferation. This report details the use of a novel oncolytic vaccinia vector-- vvDD-hIL-2-RG-1—which encodes a rigid peptide-linked, membrane-bound form of IL-2, designed to maximize the local immunomodulatory activity following intra-tumoral injection. RIOT-3 is a phase 1, open-label, single-dose, dose-escalation trial investigating intratumoral injection of vvDD-hIL-2-RG-1. Up to 18 participants with metastatic gastrointestinal cancer who have failed systemic chemotherapy or immunotherapy will be enrolled. The primary study objective is to determine the safety and maximal tolerated and feasible doses for intratumoral injection via a 3+3 dose escalation design. Secondary objectives include quantifying viral replication, pharmacokinetics, and immune response to vvDD-hIL-2-RG-1 intratumoral injection, as well as efficacy assessment by RECIST criteria. Previous preclinical data in a murine model have demonstrated that IL-2-bound vaccinia oncolytic virus is safe and exerts dose-dependent anti-tumor activity. RIOT-3 will explore the application of this novel oncolytic viral approach in patients with advanced gastrointestinal malignancies who have failed conventional therapies. The trial is registered at ClinicalTrials.gov; NCT07001592 (registered May 6th, 2025).