The use of immune modulator therapeutics, a type of immunotherapy enhancing the body immune system response to cancer, was perceived as the beginning of a new era in cancer care. While still important and frequently used, some of these therapeutics produce uneven response rates, disease resistance, and serious side effects. The National Academies National Cancer Policy Forum, in collaboration with the Forum on Drug Discovery, Development, and Translation, hosted a public workshop to discuss challenges related to immunotherapy treatment resistance, as well as potential policy opportunities to improve the development of immunotherapies for cancer treatment.