RP1 Immunotherapy in Solid Organ Transplant Recipients With Skin Cancer

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A novel oncolytic immunotherapy may show antitumor activity in solid organ transplant recipients with skin cancer, according to new findings presented by Migden et al at the American Association for Cancer Research (AACR) Annual Meeting 2024 (Abstract CT003).


"Organ transplant recipients face an increased risk of nonmelanoma skin cancers, and the standard treatment includes immune checkpoint inhibitors. Unfortunately, these therapies can cause rejection of the transplanted organ,” explained lead study author Michael Migden, MD, Professor of Dermatology at The University of Texas MD Anderson Cancer Center.

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. The new oncolytic immunotherapy RP1 is a modified herpes simplex virus (HSV-1).

Study Methods and Results

In the new 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 the RP1 therapy. They then collected tumor biopsies for biomarker analyses and monitored the patients’ HSV-1 immune status.

The researchers found that the patients who received the RP1 therapy 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 in the production of the immune checkpoint protein PD-L1 within the tumor cells—suggesting increased antitumor immune activation.

The researchers reported that RP1 monotherapy was well tolerated. There was no evidence of transplant rejection; and adverse effects, including fatigue, chills, and fever, were minimal.


“Data from this study suggest RP1 monotherapy offers a promising possible alternative for this vulnerable patient population,” Dr. Migden concluded.

Disclosure: The research in this study was sponsored by Replimune. For full disclosures of the study authors, visit

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