Dead bacteria take up the fight against cancer

Researchers at the Australian National University (ANU) have discovered that injecting dead bacteria into a solid tumour can trigger the immune system to attack the bacteria and, as a side effect, cause death of cancerous cells.

The novel cancer treatment is currently in Phase 1 clinical trial at Canberra Hospital. Results from the pre-clinical trial were published last September  in the British Medical Journal.

The lead researcher, Associate Professor Aude Fahrer, says the idea is so simple as to sound crazy.

The drug is an emulsion with the consistency of toothpaste, obtained by mixing an aqueous saline solution with an oil dissolving killed mycobacteria. The researchers injected the emulsion directly into the cancer of terminally ill patients, where the dead bacteria slowly released. 

Patients’ innate immune system recognised the bacteria as foreign and recruited killer T-cells to fight them. As a consequence, immune cells also recognised the cancer as an enemy to destroy.

Once the immune cells were activated, they multiplied and travelled around the body, killing cancer at the injection site and any metastases.

Fahrer says the treatment has several advantages on top of the encouraging preliminary results on safety and efficacy. 

It is simple to administer and only requires a few doses. Patients enrolled in the trial received two doses six weeks apart, while traditional chemotherapy and radiotherapy usually require repeated administration for extended periods. 

It has minimal side effects. Some patients reported a sting that lasted about half an hour after injection. Others had an overnight fever, a sign of the immune system kicking in.

“Compared to the side effects from chemotherapy, radiation therapy, and even some of the newer immunotherapies, these are trivial,” says Fahrer.

The treatment is also cheaper than other therapies. “We are looking at a drug that costs $5 to $20 a dose,” says Fahrer. In contrast, the cost of other immunotherapies can run to $40,000. The low cost would make the bacteria emulsion accessible for developing countries.

However, delivering the treatment directly into the cancer might limit its use in less accessible tumours and non-solid tumours such as blood cancers.

The idea of using killed bacteria to cure cancer isn’t new. In the 1890s, an American bone surgeon and cancer researcher Willian Coley, known as one of the fathers of cancer immunotherapy, injected dead bacteria into cancer patients. But the ANU team is the first to run a clinical trial, despite the lack of funding and support from pharma companies.

The team is now set to start the second phase of the clinical trial, when it plans to combine the bacteria emulsion with inhibitor drugs. 

“Inhibitor therapies release the brakes on the T-cells of the immune system,” says Fahrer. “So if this one stimulates the immune system and the other one releases the brakes on the immune system, we hope they might work synergistically.”