Genetically Modified Herpesvirus Shows Promise in Treating Advanced Melanoma
A novel approach to cancer treatment—utilizing a modified herpesvirus—is demonstrating significant potential in combating late-stage melanoma, offering hope to patients with limited options. Early clinical trials reveal that the therapy, combined with immunotherapy, has led to tumor reduction in a substantial portion of individuals whose cancer had become resistant to conventional medications.
The Challenge of Advanced Melanoma
Melanoma, the most dangerous form of skin cancer, accounts for a disproportionate number of skin cancer deaths despite being less common than other types. While advancements in immunotherapy over the past decade have improved outcomes for many, roughly half of those with advanced disease eventually exhaust all viable treatment avenues. This underscores the urgent need for innovative therapies.
Harnessing a Virus to Fight Cancer
Researchers are now exploring the potential of a genetically engineered herpes simplex virus type 1 (HSV-1), commonly known as the virus responsible for cold sores, to selectively target and destroy cancer cells. This modified virus, designated RP1, has been meticulously engineered to remove its ability to cause illness while simultaneously enhancing its anti-cancer properties.
“The concept of just a few injections into the patients’ tumors leading to long-lasting control of their cancer throughout the body is a powerful testimony to the power of our immune system in eradicating cancer cells, with minimal side effects,” stated a leading oncologist not involved in the trial.
How RP1 Works
The team behind RP1 strategically deleted genes within HSV-1 that allow it to infect normal, healthy cells. Simultaneously, they bolstered genes that promote cancer cell death and stimulate the body’s immune response. This dual approach ensures that the virus preferentially attacks cancer cells, leaving healthy tissue largely unharmed.
According to one of the study’s co-authors, “Normal healthy cells also have the ability to fight off viruses through the immune system, whereas cancer cells are not as adept at avoiding virus infection this way.” This difference in cellular response is key to RP1’s targeted efficacy.
Clinical Trial Results: Significant Tumor Reduction
In a recent trial involving 140 patients with advanced melanoma that had progressed despite standard immunotherapy, RP1, administered via direct injection into tumors every two weeks for up to eight doses, combined with the immunotherapy drug nivolumab, yielded promising results. Investigators observed tumor shrinkage of at least 30% in approximately one-third of participants.
Remarkably, the benefits extended beyond the injected tumors. Additional tumors, even those not directly treated with RP1, also shrank or disappeared at a comparable rate. This suggests that RP1 triggers a systemic anti-cancer response, effectively targeting cancer cells throughout the body.
“That expands the potential effectiveness of the drug because some tumors may be more difficult or impossible to reach,” explained a researcher involved in the study.
Promising Comparisons to Existing Therapies
The observed response rate of one-third is considered favorable when compared to other available treatments. TIL therapy, another advanced treatment option, achieves similar response rates but is associated with more significant side effects and requires hospitalization for close monitoring. A combination of nivolumab with relatlimab offers a safer profile but demonstrates a lower response rate of around 1 in 6.
“Considering the low side effect profile and lack of much better options, one-third for RP1 is viewed as being quite favorable,” noted a senior oncologist. Furthermore, RP1 distinguishes itself with a minimal risk of serious systemic side effects.
Looking Ahead: FDA Review and Phase 3 Trials
RP1, in combination with nivolumab, is currently under priority review by the U.S. Food and Drug Administration, with a potential decision on accelerated approval anticipated as early as July 2025.
To further validate these findings, researchers have initiated a phase 3 trial, IGNYTE-3, encompassing 41 sites and a larger patient cohort. Patients living with advanced melanoma may be eligible to participate in this trial; individuals interested should consult with their physician or visit the trial’s page on ClinicalTrials.gov.
“I would stay tuned to see what happens with this,” one expert commented. “With so few other drugs being used in melanoma, this new approval could change how we treat this cancer quite dramatically.”
