Positive early results from the first phase of human testing for a unique colorectal cancer vaccine are proving promising. A newly published study outlining the Phase I trial results suggests the vaccine is safe, and stimulates immune activation, paving the way for larger human trials.

Colorectal cancer is the second biggest cancer killer globally. It is not only tricky to diagnose early, but many current treatments are only marginally effective. Almost half of patients receiving surgical resections still don't survive due to the cancer's propensity for recurrence.

The new vaccine treatment is designed to stimulate a patient's immune system to attack and destroy the cancer. Immunotherapy treatments traditionally work by training the immune system to recognize a foreign agent so it is primed to identify and kill those substances when they naturally appear in the body. Tumor cells are notoriously tricky to target in this regard as they often closely resemble normal healthy cells.

The big breakthrough that inspired this specific vaccine was the discovery that almost all colorectal cancers seem to express a molecule called GUCY2C. This particular molecule is also found naturally in intestinal epithelial cells, however, its compartmentalized presence in those cells means any vaccine that targets it should only direct immune cells to tumors and not healthy intestinal tissue.

This first human trial of the vaccine was primarily designed to establish a safety profile for the treatment. Ten patients, with either stage I or II colon cancer, were administered a single shot of the vaccine and followed up for six months. The results were positive, with no serious adverse effects reported. Extensive blood sampling also revealed the vaccine did successfully promote increased activity of specific anti-tumor immune cells, suggesting the treatment does trigger the desired immune response.

"This pivotal study provides some of the first evidence that it may be possible to safely direct a patient's own immune system to seek and destroy this cancer type," says Karen Knudsen, from the Sidney Kimmel Cancer Center. "This is a true milestone – made possible through the scientists and clinicians in our colorectal cancer team working in synchrony."

The next step for the research is to move into larger Phase II trials involving more patients with endpoints to clearly evaluate the efficacy of the vaccine. From the data generated by the Phase I trial the researchers have already modified the vaccine to hopefully be more effective in stimulating the desired immune response. It is also hoped that the vaccine will be effective for more than just colorectal cancer. Recent research has suggested the GUCY2C molecule is also expressed by gastric, esophageal and pancreatic cancers, meaning this prospective vaccine could be useful in targeting a large number of common cancers.

"The goal of the study to begin this fall is to show that version 2.0 of the vaccine is even better and that it may benefit a much bigger group of the overall cancer patient population," says Adam Snook, first author on the new study.

The new research was published in the Journal for Immunotherapy of Cancer.