London - Could simply swallowing a pill containing probiotic bacteria help destroy lethal cancers? That’s the hope of a new clinical trial being run by a British bioscience company at a leading London university.
Probiotic yoghurts, which promise to promote healthy gut bacteria, have been in shops since the nineties, but scientists are divided about whether commercially sold probiotics can deliver real benefits.
However, emerging scientific knowledge shows that having a diverse array of microbes in our gut, sourced from food, encourages the immune system to operate more effectively.
It is on this theory - that microbes can be harnessed to improve cancer care - that the new British trial is based.
Scientists at 4D Pharma Plc and oncologists at University College London are testing a probiotic strain of bacteria, Enterococcus gallinarum, in 120 patients with conditions such as breast, prostate, bladder, lung and kidney cancer.
The bacterium is found in the bowel and in foods such as cheese and olives. The drug version, called MRx0518, was made from samples taken from healthy guts.
Researchers say that it seems E. gallinarum can stimulate the body to secrete specialist immune cells that can attack tumours.
This is crucial, as MRx0518 is designed to be used with a cancer treatment called immunotherapy, which helps patients’ own immune systems identify cancer cells and destroy them. This approach has taken decades to refine, as learning how to manipulate the immune system without harming patients has proved a challenge.
Immunotherapy drugs such as pembrolizumab (Keytruda) have scored some notable successes against melanoma, non small-cell lung cancer, kidney cancer, bladder cancer, head and neck cancers and Hodgkin lymphoma.
Recent figures show that nearly 25 percent of patients who received pembrolizumab as an initial treatment for advanced non small-cell lung cancer were still alive after five years - a huge gain over the historical five-year survival rate of only five percent.
However, despite such success, many patients’ immune systems do not respond effectively to the therapy or are stimulated for only a limited time before the benefit fades and the cancer returns.
It is hoped a targeted probiotic could improve these outcomes. Patients will be given the probiotic in the month or so between them being diagnosed with cancer and undergoing surgery to remove the tumour. Biopsies at these points will be compared to see how much the tumour has or hasn’t shrunk.
The trial will also see if MRx0518 can reactivate pembrolizumab’s effects in cancer patients who initially showed a benefit, but then stopped responding to the drug.
Already, trials have flagged the potential benefit of healthy gut bacteria in defeating cancers. In 2017, the journal Science reported patients with melanoma who had more diverse beneficial bacteria in their guts had better success with their cancer treatment.