Explained: The First Human Trial Of Virus That Can Kill Cancer

The first clinical trials of a modified pox virus that's aimed at killing cancerous cells and stimulating the immune system to respond to cancer better have started in 10 sites in Australia and the United States. 

The modified virus called 'Vaxinia', developed by the US-based City of Hope Comprehensive Cancer Center, is an 'oncolytic virus', which has been genetically modified to selectively infect and kill cancer cells, spare healthy cells, and further trigger the immune system against cancerous cells.

Animal studies have so far been promising, according to City of Hope. It said, "The City of Hope-developed oncolytic virus has been shown to shrink colon, lung, breast, ovarian and pancreatic cancer tumors in preclinical laboratory and animal models."

The first trial subject has been injected with the virus. It will have a total of 100 subjects.

Here we explain how this treatment works, how the trial will proceed, and what hopes this new treatment method brings for people suffering from cancer.

How does Vaxinia work?

The modified pox virus Vaxinia, whose technical name is CF33-hNIS, not just kills cancerous cells but also trains the immune system against them — like a vaccine does.

Vaxinia works by entering cells, duplicating itself, and causing the infected cell to burst, releasing thousands of new Vaxinia particles that act as antigens and stimulate the immune system to attack nearby cancer cells, explains Science Direct. This aspect makes Vaxinia more promising. 

"Our previous research demonstrated that oncolytic viruses can stimulate the immune system to respond to and kill cancer, as well as stimulate the immune system to be more responsive to other immunotherapies, including checkpoint inhibitors," said said Dr Daneng Li of City of Hope.

However, nothing is known about how Vaxinia would do in humans, as human trial results are not always in line with animal studies that precede human trials.

"Results seen in animals do not always directly translate to human patients. There are a lot of reasons for this, obviously, but the researchers are hopeful this virus could improve patients’ chance to fight back against cancer," notes the science and tech site BGR.

How will Vaxinia trial proceed?

The first priority is to test the safety of Vaxinia. Once safety is demonstrated, the trial would move onward to assess efficacy.

The trial will start by delivering a low dose of Vaxinia to cancer patients with metastatic or advanced solid tumors who have had at least two prior lines of standard of care treatment either as an injection directly into tumors or intravenously, said City of Hope in a statement.

It added, "Once patients in the single therapy group have been treated with the lowest doses of CF33-hNIS [Vaxinia] and acceptable safety has been demonstrated, certain new study participants will receive the experimental oncolytic virus in combination with the immunotherapy pembrolizumab, an engineered antibody that improves the immune system’s ability to fight cancer-causing cells."

The trials will run for 24 months. The City of Hope has entered into a partnership with the Australian biotech company Imugene for the trial and production of Vaxinia. 

How is Vaxinia promising?

Vaxinia is promising as this is not just expected to kill cancerous cells but is also expected to train the immune system to kill cancerous cells. It's like a crossover between a drug and a vaccine. 

Moreover, when administered with other therapies, Vaxinia is expected to increase their effectiveness. 

"Early research shows oncolytic viruses can prime a person’s immune system and increase the level of PD-L1 in tumors, making immunotherapy more effective against cancer," said City of Hope in a statement. 

If successful, Vaxinia would be the second virus-based cancer treatment in the United States. In 2015, the US Food and Drug Administration approved a treatment based on herpes virus that demostrated successfully treated melanoma, the deadliest skin cancer. 

Lately, the "vaccine approach" — which Vaxinia partly works on — has been tested too. In 2021, phase 3 trials of a personalised cancer vaccine, AV-GBM-1, was shown to improve outcomes for patients with glioblastoma, a type of brain cancer, compared to standard of care, according to cancer-focussed Cure magazine.