A novel oncolytic immunotherapy showed antitumor activity in solid organ transplant recipients with skin cancer, according to findings presented by Migden et al at the American Association for Cancer Research (AACR) Annual Meeting 2024. Oncolytic immunotherapy uses viruses to target and destroy cancer cells while also stimulating the body’s immune response against the tumors. The viruses are modified to selectively infect and replicate within cancer cells, leading to their destruction. RP1 is a modified herpes simplex virus (HSV-1).

In the phase Ib/II ARTACUS study, researchers assigned 27 solid organ transplant recipients with cutaneous squamous cell carcinoma or Merkel cell carcinoma and a median age of 68 years to receive RP1. They then collected tumor biopsies for biomarker analyses and monitored the patients’ HSV-1 immune status. Patients who received RP1 achieved an objective response rate of 34.8% and a complete response rate of 21.7%.

Following treatment, the patients’ tumor samples showed an increase in CD8-positive T cells entering the tumor as well as an increase in the production of PD-L1 within the tumor cells—suggesting increased antitumor immune activation. “Data from this study suggest RP1 monotherapy offers a promising possible alternative for this vulnerable patient population,” concluded lead study author Michael Migden, MD, Professor of Dermatology at The University of Texas MD Anderson Cancer Center.