17/11/2025
๐๐๐ ๐๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐
๐ผ ๐๐๐ง๐ช๐จ ๐๐๐๐ฉ ๐๐๐๐ก๐จ
The idea of using a virus, something that is known to cause disease, to fight cancer might sound counterintuitive. But in the past two decades, that idea has turned into one of the most intriguing frontiers in the field of oncology. This concept, known as oncolytic virotherapy, uses genetically engineered viruses to infect cancer cells and destroy them while sparing normal, healthy tissue.
The first clinical validation of oncolytic virotherapy came with ๐ง๐ฎ๐น๐ถ๐บ๐ผ๐ด๐ฒ๐ป๐ฒ ๐น๐ฎ๐ต๐ฒ๐ฟ๐ฝ๐ฎ๐ฟ๐ฒ๐ฝ๐๐ฒ๐ฐ (๐ง-๐ฉ๐๐), which was approved by the U.S. Food and Drug Administration (FDA) in 2015 for the treatment of advanced melanoma. T-VEC, made by modifying Herpes Simplex virus type 1 (HSV-1), marked the worldโs first oncolytic virus therapy to demonstrate safety and efficacy in humans. Its approval was hailed as a milestone; however, the treatmentโs success was largely limited to local or injectable lesions, and its benefit for patients with widespread or visceral melanoma leaves something to be desired.
This limitation pushed researchers to improve existing approaches or find an alternative oncolytic virotherapy, and so the stage was set for a new generation of oncolytic HSV-1 therapies: ๐ฅ๐ฃ๐ญ. RP1 is developed by Replimune and currently being studied and tested at Keck Medicine of USC. In a 2024 study published in Journal of Clinical Oncology, RP1, when used in combination with the checkpoint inhibitor nivolumab, produced notable tumor regression in patients with advanced melanomaโincluding those who were resistant to immunotherapy. The findings suggest that RP1 both boosts local tumor destruction and stimulate a broader, systemic immune response that is able to reach distant sites of the disease.
๐ผ ๐๐๐ฌ ๐๐๐ฃ๐ ๐ค๐ ๐๐ฃ๐๐๐๐ฉ๐๐ค๐ฃ
To understand what makes RP1 different, it helps to look at the mechanics of oncolytic therapy. When an oncolytic virus infects a tumor cell, it multiplies inside the cell until it bursts, releasing new viral particles and fragments of the tumor. Those fragments act like a flare for the immune system, drawing immune cells to the site and training them to recognize and attack similar cancer cells.
T-VEC, the first approved oncolytic HSV-1 therapy, achieves this using two key modifications. The virusโ natural virulence genes are removed so that it canโt damage healthy tissue, and a gene (GM-CSF) is added whose function is to help recruit immune cells to the tumor.
RP1 builds on the same backbone with a few several upgrades. It carries GALV-GP-R, a protein that causes infected tumor cells to fuse and die more aggressively, allowing the virus to spread more efficiently within the tumor. It is also designed in a way that would make it pair well with checkpoint inhibitors like nivolumab, which amplifies the immune activity the virus sets in motion. In other words, RP1 attempts to convert an immunologically โinvisibleโ tumor into a โvisibleโ one that immune cells can find and attack. This synergistic design may partly explain the encouraging early results seen in combination therapy. However, the data come from a small, open-label trial which means the sample size wasnโt large enough to draw firm conclusions. Whether RP1 can maintain its effectiveness outside of specialized cancer centersโand whether it can do so at a cost that health systems can manageโremains uncertain.
๐ผ ๐๐ฉ๐ง๐๐๐ฃ ๐ค๐ ๐๐ค๐จ๐จ๐๐๐๐ก๐๐ฉ๐ฎ
Worldwide, oncolytic virotherapy is steadily moving from an experimental idea to a treatment with real clinical application. Researchers are testing different viral genomes, such as DNX-2401 (adenovirus) for glioblastoma and pelareorep (reovirus) for breast tumors. However, HSV-1 remains the leading template because its genome can carry multiple therapeutic genes.
In the Philippines, oncolytic virus therapy is still more of a future goal rather than a current option. No local trials involving HSV-1 therapies or any oncolytic platform have been registered with the Philippine FDA or PHREB. Even access to existing treatments like T-VEC is limited to patients who can join international studies or travel to centers in Singapore or the U.S. The country also lacks capable facilities needed for producing clinical-grade viral therapies. Despite these constraints, tertiary centers such as UPโPGH Cancer Institute have already adopted checkpoint inhibitors and targeted therapiesโmaking them possible sites for future combination trials that pair immunotherapy with oncolytic viruses.
Ultimately, the promise of virotherapy will be judged not in laboratories but in the lives of patients waiting for better options. Whether the Philippines steps into this therapeutic innovation soon or much later, the momentum behind oncolytic viruses cannot be ignored. RP1 is part of a new generation of treatments that challenge old assumptions about what a virus can be. As global oncology moves forward, the real question is not whether these therapies will matter, but whether healthcare systems like ours can keep pace, because the future is arriving either way.
Article by VS Staffer
Pubmat by Chloe Reynaldo
