It is estimated that about 40 percent of patients with advanced melanoma, the deadliest form of skin cancer, will initially respond to an immunotherapy, but about a quarter of those 40 percent will relapse within three years of treatment. In order to identify the mechanisms by which resistance to PD-1 inhibition is mediated, UCLA researchers studied biopsies of melanoma tumors taken before and after treatment with Keytruda (pembrolizumab) in patients whose cancer had returned. Continue reading →