Injecting tumours with gangrene-causing bacteria could help fight late-stage cancers, study reveals

Study in patients without other options identified safe dose which would shrink tumours without causing sepsis or 'gas gangrene'

The bacterium Clostridium novyi-NT exploits the inherent differences between healthy and cancerous tissue, which helps make it a very precise anticancer agent (Getty)

A gangrene-causing bacteria which can be harmful at high doses may help treat late stage cancer patients where other options have failed, medical trials have shown.

Safety tests on a new type of “bacterial therapy” found that tumours which have become resistant to other treatments became necrotic and shrank when injected with bacterial spores.

University of Texas doctors used a strain of bacteria related to the lethal hospital superbug clostridium difficile, which has been modified to make it less harmful to humans.

Clostridium novyi-NT needs a very low oxygen environment to survive; this means it won’t develop in healthy tissue with a good blood supply, but dense, rapidly growing tumours are a perfect host.

“By exploiting the inherent differences between healthy and cancerous tissue, Clostridium novyi-NT represents a very precise anti-cancer therapeutic that can specifically attack a patient’s cancer,” said Dr Filip Janku, of the university’s Anderson Cancer Center.

The bacteria could be particularly powerful in tandem with a new generation of cancer treatments known as immunotherapies, which stimulate the immune system to identify and attack tumours, he added.

The findings are being presented on Sunday at the International Cancer Immunotherapy Conference in New York and, while they have not yet been published in a scientific journal, they have already sparked further trials.

Potential new medical treatments require multiple rounds of human testing, first to check their safety and then to prove they consistently improve survival across large populations of patients.

In the trials, Dr Janku and his colleagues were chiefly concerned with finding what doses could be safely used.

They enrolled 24 patients with solid tumours that had become resistant to conventional chemotherapy and other treatments, and injected them with between 10,000 and three million bacterial spores.

The authors report that the two patients given the largest dose developed severe sepsis and “gas gangrene”. As a result the team identified a safe dose of one million spores where side effects were “manageable”.

In the remaining 22 patients the early results showed the treatment stopped their tumours growing, and in 23 per cent of cases the tumours shrank in size by more than 10 per cent.

However, the final tumour reduction might be even greater, Dr Janku said, because the treatment initially causes inflammation and makes the tumour swell up with immune cells attacking it.

This treatment method has two strengths: in 46 per cent of cases the bacterial spores germinated and started multiplying, rapidly causing necrosis and cell death in the tumour; however even when the spores did not develop, because oxygen levels or other conditions weren’t right, the presence of these bacterial spores helped trigger immune system cells to wake up and begin attacking the tumour.

“From these preliminary results, it appears that Clostridium novyi-NT is able to activate the immune response besides causing tumour destruction,” Dr Janku added.

“We were extremely encouraged by the results of this trial, especially in patients with advanced sarcomas, where immunotherapy hasn’t proven very efficacious.

“This bacteriolytic strategy has the potential to be clinically meaningful, especially in combination with checkpoint inhibitors, for patients with advanced solid tumours.”