New research shows a one-two hit from an experimental vaccine combo is significantly more effective at fighting off treatment-resistant cancers in animal models than either approach by itself—and the Department of Defense is throwing down money to move the science into the clinic.
Researchers at Thomas Jefferson University in Philadelphia tested a combination platform consisting of viral and bacterial vaccine approaches in animals with recurrent colorectal cancer that had spread beyond the colon, and found the duo approach decreased metastases and increased survival, according to new findings published June 23 in npj Vaccines.
The Philadelphia team had previously developed a vaccine treatment based around adenovirus, a common virus that can train the immune system to stop cancer from coming back. While the viral approach can promote a highly effective immune response, the effect usually does not last long.
Because of this, boosters are often required to create the best immune response, a practice most people are now all too familiar with after the COVID-19 pandemic. However, adenovirus boosters aren’t particularly effective; to keep the primed immune system fighting back against recurring cancer, a different type of booster is needed.
The researchers turned to a bacteria-based vaccine approach, using a modified form of Listeria monocytogenes, part of the bacteria species typically found in contaminated food that can cause the infection listeriosis, that doesn’t make mice or people sick. Unlike the adenovirus approach, the listeria vaccine doesn’t create a strong immune response, but instead boosts the already existing response.
When the scientists used the adenovirus-based vaccine to prime the immune system in mice, and later provided the Listeria-based booster, immune cells that attack cancer multiplied 15-fold.
"The vaccine platforms are not unique," said Jefferson team lead Adam Snook, Ph.D., associate professor of pharmacology and experimental therapeutics. "But nobody's put them together into a combination vaccine, yet that's when we saw the immune response really take off."
The findings pave the way for new methods for preventing recurring cancers in humans—a potential the Department of Defense is very interested in, according to a June 23 release. Recently, the agency granted Snook and colleague Babar Bashir, M.D., assistant professor of medical oncology, an undisclosed amount to carry the combo into a phase 1 clinical trial. The researchers are currently manufacturing the vaccine and intend to begin patient enrollment next year.
So, the old adage holds true: two really is better than one. The researchers hope others take note, saying the dual approach holds promise for other cancers and even diseases such as HIV and malaria, which currently lack effective vaccine strategies.