Dr Najjar on Data for the Oncolytic Virus VET3-TGI in Advanced Solid Tumors

When we looked specifically at where those responses were occurring, they were occurring in patients with cutaneous malignancies, which is why we went on to really enrich and focus on that population.”

Yana Najjar, MD, an associate professor of medicine and director of the Clinical and Translational Research Center at University of Pittsburgh Medical Center Hillman Cancer Center, discussed efficacy data from the phase 1/1b STEALTH-001 trial (NCT06444815) evaluating intratumoral VET3-TGI, an oncolytic vaccinia virus encoding a TGF-β inhibitor and interleukin-12 (IL-12), alone or with atezolizumab (Tecentriq), in patients with advanced solid tumors, and explained why the program is now focused on cutaneous malignancies.

Data presented at the 2026 SITC Annual Meeting showed that as of the September 2026 data cutoff, 20 patients had received intratumoral VET3-TGI as either monotherapy (n = 16) or in combination with atezolizumab (n = 4). Najjar’s presentation focused on 12 patients with sufficient follow-up to assess efficacy, comprising patients with cutaneous malignancies (n = 7) such as Merkel cell carcinoma (MCC) n = 3), melanoma (n = 3), and cutaneous squamous cell carcinoma (n = 1), plus patients with other non-cutaneous solid tumors (n = 5).

In the overall evaluable cohort (n = 12), the objective response rate (ORR) by blinded independent central review was 42%, and the disease control rate was 75%. However, responses were concentrated in patients with cutaneous disease, Najjar explained. In this subgroup, the ORR was 71%, comprising 1 complete response (CR) and 4 partial responses (PRs). All 3 patients with MCC responded (1 CR, 2 PRs), as did 2 of 3 patients with melanoma. Responses were also observed in non-injected lesions, and all responders remained on study treatment at data cutoff, with treatment durations ranging from 10 to 19 months; the median duration of response was not reached.

According to Najjar, the cutaneous cohort was heavily pretreated, with a median of 3 prior lines of therapy (range, 1-9). All patients in this group had progressed on prior anti–PD-1/PD-L1 therapy, and more than 40% had progressed on dual checkpoint blockade with a CTLA-4 inhibitor plus an anti–PD-(L)1 agent.

No dose-limiting toxicities were reported through the maximum feasible dose, and treatment-related adverse effects were mostly grade 1 or 2. Monotherapy and combination expansion cohorts focused on cutaneous malignancies are ongoing, with additional studies planned to confirm clinical activity in this population.