British scientists presenting a paper at the recent European Society for Medical Oncology 2022 (ESMO) say their findings suggest that a genetically modified herpes virus may offer hope to cancer patients who have exhausted all other treatments: a trial involving 39 patients showed significant efficacy.
The researchers note that the virus, called RP2, is a genetically modified herpes simplex virus that tackles late-stage cancers by “striking in quick succession”: first by destroying their cells and then by letting the immune system do its work. Specifically, when RP2 is injected directly into a tumor, it multiplies inside the cancer cells and then ruptures them from the inside; it also blocks a protein called CTLA-4, which acts as a “brake” on the immune system; and the modified RP2 produces a special molecule that stimulates the immune system. The researchers explained that they were injected with CTLA-4, which acts as a “brake” on the immune system.
The researchers explained that they biopsied the patients before and after the RP2 injections and found positive changes in the tumor’s “immune microenvironment” – the area around the tumor. . The injections resulted in more immune cells in the area, including CD8+ T cells, and “turned on” genes associated with the immune response against cancer.
The patients in the trial had a variety of cancers: skin, esophageal and head and neck cancers. No other treatment was available, and even modern immune checkpoint inhibitors did not help. Of the 39 people enrolled in the trial, 9 were treated with RP2 only and the other 30 were treated with RP2 in combination with nivolumab.
The results showed that the three patients treated with RP2 only had shrinking tumors, including the patient with salivary gland cancer whose tumor completely disappeared and whose cancer had not recurred after 15 months. Two other patients with esophageal cancer and uveal melanoma had shrunken cancers. And of the seven beneficiaries who received the combination therapy, six had cancer that had not worsened in 14 months. In addition most of the side effects reported by the patients were fever, chills and fatigue, which required no medical intervention.
The study leader, Kevin Harrington, said, “Our preliminary trial results suggest that this transgenic herpesvirus may be a new treatment option for some patients with advanced cancer – including those who do not respond to other forms of immunotherapy.”
Next, the researchers hope to continue exploring the therapeutic potential of RP2 in more cancer patients.
