If there is such a thing as a holy grail in cancer research, a secret spell or golden ring that can ward off any and all forms of the disease, it probably lives somewhere in the realm of immunotherapy. A new category of immunotherapy drugs, called checkpoint inhibitors, take the brakes off the immune system and let the T cells do their job: attack cancer. They've been approved for more than 25 different types of cancer.  However, the average response rate for checkpoint inhibitors is 20 to 30%, which means that it's not working for 70% of the people who take it. So that's the project now: to extend the benefits of immunotherapy to all cancer patients, instead of to just a few. And the best way to do that, it seems, is by doubling down, by pairing immunotherapy with other therapies so patients can benefit from both. Sound logical? Sure. Sound easy? Not on your life. It's called combination immunotherapy, and it's what this episode of Unraveled is about.