MK-3475 and other cancer immunotherapies could offer an alternative to the targeted therapy approach of the past decade, in which drugs act on genetic mutations that drive tumor growth. Targeted therapies are an alternative to chemotherapy, which kills all fast-growing cells—both cancerous and healthy ones, causing severe nausea and other debilitating side effects. Despite some successes with targeted therapy, cancer cells still tend to become resistant to such drugs. Plus, designing cancer drugs for each cancer-causing mutation is hugely challenging.
In a way, cancer immunotherapy marks a return to a less targeted strategy—which brings up a tantalizing possibility: since these drugs don’t target tumor cells with specific mutations, they may be able to treat any type of cancer. And unlike a single drug, the immune system can adapt, making it hard for tumors to develop resistance to it. “We’ve just scratched the surface about the particular tumors that can use [immunotherapy agents],” said Johns Hopkins University oncologist Julie Brahmer. “It’s an exciting time.”