Some of the most common cancers in the United States could soon be treated using a common virus, a groundbreaking new study suggests.
Chinese scientists have developed a modified virus found in birds that causes cancer cells to produce sugars that the immune system can easily recognize and attack.
The experimental therapy was tested on 23 patients suffering from eight different cancers – including breast, lung and skin – whose disease had not responded to standard treatments.
All but one patient saw their tumors shrink or stop growing after receiving infusions once a week for eight to 12 weeks.
The scientists also tested the therapy on five monkeys with liver cancer and found that all lived longer than those given a placebo.
Experts not involved in the research said it was promising, especially since the therapy was used to target such a wide range of cancers.
But they added that rigorous trials would still be needed before the treatment could be proven safe and made available to Americans — a process that would take years.
The treatment, called NDV-GT, works by prompting the body to mount an immune response similar to what it would produce during organ transplant rejection.
Liver cancer presented before treatment (left) and a month and a half after the patient received the experimental treatment using a virus
Immunologist and surgeon Yongxiang Zhao of Guangxi Medical University in Nanning came up with the idea while studying patients who received pig organ transplants, which is an emerging and experimental field of medicine.
Human antibodies immediately attach to the sugars that coat the surface of pig cells, leading to immense and rapid rejection of the transplanted tissue.
Dr. Zhao wondered if this process could be harnessed and used to treat cancer.
Its experimental therapy uses a genetically engineered Newcastle disease virus, which can be fatal to birds but causes only mild, if any, illness in humans. It differs from the virus that causes avian flu.
The virus is not strong enough to provoke a strong enough immune response, so the team engineered it to carry the genetic instructions for an enzyme called α 1,3-galactotransferase.
This enzyme coats cancer cells with a sugar found in pig organ tissue.
Antibodies in the immune system bind to this sugar, prompting white blood cells to attack and destroy cancer cells, leaving healthy cells intact.
The treatment was first tested on ten monkeys suffering from liver cancer.
The five monkeys given a placebo died within four months. Those who received the therapy survived more than six months.
In the human trial, scientists recruited patients with eight types of cancer:liver, esophagus, rectum, ovaries, lungs, breast, skin and cervix.
The results were positive.
After two years, two patients saw their tumors shrink, but they had not completely disappeared. Tumor growth stopped in five participants.
For others, tumor growth initially stopped but then resumed. Only two participants experienced no positive effects from the treatment, while two others withdrew from the trial before the end of the first year.
Scan of an ovarian cancer patient before treatment (left) and three months after treatment with the investigational therapy
The patients all suffered from stage four or advanced stage three cancer, with which patients often only survive a few months.
Dr. Brian Lichty, an immuno-oncologist at McMaster University in Canada, told Nature that the treatment was still in the “early days” but that early results were good.
He also said it was “a little unusual” that the treatment showed promise in such a wide range of cancers.
“I hope it will hold up to further clinical testing,” he added.
Researchers said the treatment will now enter phases two and three of clinical trials. The treatment was revealed in the journal Cell.
About 2 million Americans are diagnosed with cancer each year and 608,000 die from it.
Among the most common are breast cancer, lung cancer and melanoma, which together account for around 608,000 cases per year, or just over 25% of cases.
The new therapy is known as oncolytic viral therapy, which uses a virus to destroy cancer cells without affecting healthy cells.
The FDA has approved one such therapy so far, called T-VEC, which uses a modified herpes virus to treat melanoma.
It was approved in 2015, but only for advanced melanoma that cannot be removed surgically and does not tend to be more effective than other treatments.
Late last year, a scientist revealed that she had also reversed her stage three breast cancer using the same method: by combining a measles virus and a flu-like pathogen and modifying them to attack tumors.
