There is also historical
precedent for the concept, dating back to the 1800s when researchers observed tumor regression in patients infected with certain bacteria. Since the 1970s, a weakened bacterial strain called
Bacillus Calmette-Guérin has been effectively used to treat bladder cancer.
Now, researchers are exploring new approaches: engineering bacteria to stimulate antitumor immunity or to deliver cancer-killing drugs. The results, so far, have been promising.
At this year’s
AACR Annual Meeting, researchers
reported that patients treated with a modified form of
Salmonella survived nearly twice as long as patients who received standard therapy.
In the phase II clinical trial, presented by
Daniel Saltzman, MD, PhD, a professor and oncologist at the University of Minnesota Medical School, 28 patients with metastatic pancreatic cancer received an oral dose of modified
Salmonella in combination with a standard chemotherapy regimen.
Salmonella cultured on an agar plate. Getty Images.
The
Salmonella used in the trial were engineered to express the immune-stimulating protein IL-2. When ingested by the patient, the modified bacteria are thought to colonize primary and metastatic tumors and express IL-2, which in turn, recruits cancer-killing immune cells to the tumor sites.
“This bypasses the need to systemically administer IL-2 as well as the challenges of delivering the drug itself into solid tumors,” Saltzman explained.
Patients treated with the
Salmonellaregimen had a median overall survival of 24 months, compared with 13 months for patients treated with chemotherapy alone in prior clinical trials. None of the serious adverse events reported in the study were found to be caused by the
Salmonella treatment.
Looking forward, the researchers plan to evaluate the therapy in a randomized phase III clinical trial and are also investigating the potential of this approach to treat other solid tumors.