July 11, 2025, 12:49 pm | Read time: 5 minutes
Modified Herpes Virus as a Weapon Against Skin Cancer? A new study suggests it might work—even for metastases deep within the body that have been difficult to target. This combination therapy could offer new hope, especially for patients with advanced melanoma where conventional immunotherapies have failed.
In Germany alone, the number of annual new cases of skin cancer rose from about 144,000 to approximately 224,000 between 2007 and 2015. Especially with malignant melanoma, the most aggressive form of skin cancer, therapeutic options are often severely limited in advanced stages.1 Particularly with malignant melanoma–the most aggressive form–current treatments often reach their limits in the late stages of the disease. New approaches, such as virus-based immunotherapies, are therefore increasingly becoming the focus of research. One of these experimental therapies has now been examined in an international study–with surprisingly positive results.2
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Overview
In Search of New Therapies
The focus of the study is a combination therapy for patients with advanced malignant melanoma, where previous treatments such as anti-PD1 or anti-CTLA-4 have shown no effect. The therapy consisted of a genetically modified herpes simplex virus type 1 (RP1) and the immune checkpoint inhibitor nivolumab. RP1 is designed to destroy cancer cells and simultaneously trigger an immune response against the cancer throughout the body.
The multicenter Phase 1/2 IGNYTE study investigated whether this combination is also effective against untreated metastases located deep within the body–such as in the liver or lungs. Additionally, researchers analyzed the tolerability and potential differences between superficial and visceral injections.
Study Design and Implementation
The IGNYTE study is an open-label, multicenter Phase 1/2 study. In the part of the study presented at the ASCO Congress 2025, 140 patients with advanced melanoma were included, whose disease had progressed under previous immunotherapy.
The treatment involved an initial low dose of injections, followed by higher doses every two weeks for up to eight cycles. Starting with the second RP1 injection, patients also received nivolumab (240 milligrams every two weeks), later in maintenance therapy every two to four weeks–over a period of up to two years.
The injections were administered either superficially (skin, subcutaneous) or deep/visceral under imaging guidance. The evaluation of tumor development was standardized according to RECIST 1.1 by a central, independent committee.
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Herpes Virus Caused Tumor Shrinkage
The new combination therapy showed surprisingly good results in many patients: Tumors shrank significantly in about one-third of participants. On average, this effect lasted for almost three years.
A total of 197 tumors were examined. Of these, 78 were directly treated with the herpes virus RP1, while the remaining 119 tumors were not. Notably, both treated and untreated tumors shrank.
Particularly striking:
- Almost 99 percent of the directly treated tumors became smaller.
- But around 97 percent of the untreated tumors also shrank.
A noticeable reduction of more than 30 percent occurred in
- about 94 percent of the treated tumors and
- approximately 79 percent of the untreated tumors.
Even in hard-to-reach tumors in internal organs, many tumors shrank, even if they were not directly injected.
Additionally, it was observed that patients who received the virus deep into the body (such as in organ metastases) responded more frequently than patients who were only treated superficially.
How Safe Was the Therapy?
The new treatment was generally well tolerated. Only a few patients developed more severe side effects–and among those treated deep in the body, they occurred even less frequently.
Specifically:
- About 14 out of 100 patients treated superficially (e.g., on the skin, subcutaneously) experienced more severe side effects.
- For patients with injections into deeper organs like the liver or lungs, it was only about eight out of 100.
In very few cases, a so-called pneumothorax occurred–where air enters the space between the lung and chest wall, which can cause breathing difficulties. This happened in three out of 52 lung injections, or just under six percent. Notably, there were no severe complications, such as internal bleeding or liver function problems, in cases where the virus was injected into the liver.
What Do These Results Mean?
The researchers demonstrated that the therapy is effective even outside the directly treated tumor sites. Other cancerous lesions in the body–even in deep organs–also responded, indicating that the virus activates the immune system throughout the body to fight the cancer.
Especially in advanced skin cancer, where many patients no longer respond to standard medications, this method could offer new hope. Previously, such deep-seated tumors were difficult to reach and treat. The fact that the virus is effective even there is therefore a significant advancement.3
What Points Should Be Considered?
It is important to evaluate these results with caution. The results presented at the congress are from phases one and two of the clinical study, which examined the safety, side effects, dosage, and efficacy of RP1 in combination with nivolumab in a limited patient population. There was no comparison group with patients who only received the standard treatment. In phase three, the scientists aim to confirm their results in a global population of over 400 participants.
Another point to consider is that the study was funded by the company Replimune, which developed the virus. Some of the participating doctors also work in an advisory capacity for the company–including Dr. Gino In, who co-led the study. In drug development, researchers often have such connections and are required to disclose them.3
On the positive side, the study was conducted at multiple recognized cancer centers worldwide–including in Germany, France, Spain, the United Kingdom, and the United States. This speaks to the quality of the data.
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Conclusion
The new combination therapy for patients with advanced malignant melanoma has shown promising results. Even untreated tumors deep within the body responded significantly and shrank visibly, as observed by the researchers.
If the data from the phase-3 clinical trial also proves convincing, the new therapy could offer a real treatment option for many patients–especially those with hard-to-reach, poorly treatable tumors.