A small study of melanoma patients is raising hopes that custom-made cancer vaccines may be more effective than current immune-based treatments. A recent paper in Nature reported all six patients had encouraging results.
The first cancer treatments used were drugs which interfere with molecules that block immune cells from attacking a tumor. If immune cells are not found, the treatment doesn’t do any good. This is a main reason immunotherapy drugs help only a small amount of cancers.
The second generation of cancer treatments are expected to be made of living cells called chimeric antigen receptor T cells (CAR-T). These are genetically engineered to help a molecule grab onto a matching molecule on a tumor cell and kill it. CAR-T cells can create an immune storm and have killed patients in clinical trials. Most CAR-T target only one molecule/antigen, so tumor cells without a match can escape the CAR-T cells.
In the new study, scientists studied neoantigen vaccines, created by sequencing the DNA of tumor cells. They look for mutations in the DNA and use algorithms to find which mutations make antigens that immune cells will grab. The vaccine is then loaded with antigen pieces called long peptides.
Patients received five shots the first month, then additional ones at 12 and 20 weeks. The strategy of selecting antigens worked; the T cells didn’t attack any healthy cells. After two years, four of the patients, who had melanoma spread to the lymph nodes, were cancer free. The other two patients, whose melanoma spread to the lungs, had tumors return, but after treatment with Keytruda, cancer became undetectable. All patients still carried anti-melanoma T cells in their blood, which proves the lasting effects of the vaccine.
Six patients is not enough to declare victory, but it is encouraging and justifies a larger clinical trial. Neon Therapeutics is already running a clinical trial of a neoantigen vaccine for bladder and lung cancer, as well as melanoma. Making an individualized neoantigen vaccine per patient would be expected to cost $60,000, leading to a market price tag of six figures.
Begley, Sharon. “Personalized cancer vaccines vanquish melanoma in small but encouraging study.” STAT News, 5 Jul 2017. Web. 6 Jul 2017.