The Japanese scientist Tasuku Honjo made a revolutionary discovery in 1992: a human protein that acts as a brake on the body's defenses, called PD-1. By removing this obstacle, with a drug called nivolumab, the immune system is able to attack cancer cells with greater ferocity. Honjo himself, winner of the Nobel Prize in Medicine five years ago, calculates that the medication has probably saved the life of hundreds of thousands of people since its approval in 2014. Nivolumab—already authorized for many types of cancer: skin, lung, kidney, bladder, liver—is not, however, a panacea. More than half of melanoma cases with metastases are resistant to the drug. A scientific team, headed by the Spanish doctor Antoni Ribas (Barcelona, 57 years old), suggests this Thursday a new strategy to counterattack cancer.