Experimental therapy fights untreatable brain cancer with genetically modified HERPES virus

The virus that causes cold sores and genital herpes could be used to fight one of the deadliest forms of brain cancer.

Researchers from Brigham and Women’s Hospital in Boston, Massachusetts found the herpes simplex virus can trigger a response in the body that would provoke a person’s immune system to attack brain cancer cells.

The treatment, called CAN-3110, is modified to ensure healthy cells are not also killed.

Ennio Chiocca, chair of the department of neurosurgery at Brigham and Women’s hospital, told Gizmodo: ‘Unlike other therapies so far, we have been able to show that one single timepoint administration of CAN-3110 is sufficient to activate the patient’s own immune cells to traffic and fight off the cancer and we show that this links to survival responses.’

The researchers found that even in patients with existing antibodies to herpes, the treatment boosted the immune system’s response to the brain cancer

Brain cancers are very difficult to treat, with more than 84,000 people diagnosed with a primary brain tumor per year. The most diagnosed form, a glioblastoma (GBM) is one of the deadliest types of cancer, and the form that killed John McCain and President Joe Biden’s son Beau Biden.

Traditional cancer treatments like chemotherapy and radiation often cannot rid the body of all of the cancer and GBM is considered incurable, with an average length of survival around eight months.

Dr Chiocca explained GBM is able to escape the body’s own immune cells, which try to fight off the tumor.

In the lab, his team engineered a tumor selective biologic agent based on the cold sore virus.

The idea was this could be injected into GBM patients to ‘reshape’ the GBM to make it less able to override the patient’s immune cells.

The treatment contains a gene, named ICP34.5, which helps the herpes virus cause disease in humans through cold sores or genital herpes.

The researchers think this gene is key to triggering a strong enough immune response to brain cancer cells.

In a Phase I study published in Nature, the team gave 41 patients with recurrent GBM a single dose of CAN-3110.

The main aim of Phase I trials is to confirm the drug is safe and well-tolerated. However, two patients did experience a seizure, which could possibly be linked to the medication.

Among the participants, roughly two-thirds already had antibodies to the herpes virus from previous infections. 

The researchers found, however, that even in patients with existing antibodies, the CAN-3110 treatment boosted the immune system’s response to the cancer. 

The team measured the enhanced immune response by measuring the level of T cells, a type of immune cell, which had increased.

The median survival rate for the group with antibodies was roughly 14 months, while those without previous exposure to herpes had a survival rate of eight months — the average survival rate for GBM.

More studies are needed to determine if CAN-3110 could be an effective treatment for brain cancer, especially in people without existing herpes antibodies and the team is now working on a study to give patients multiple doses of the treatment over four months.