Conditional Cancer Immunotherapy as a Safer Way to Step on the Gas.

In this issue, Kamata-Sakurai and colleagues describe an agonist antibody to CD137 (4-1BB) that takes on an active conformation in environments with high ATP concentrations, characteristic of tumors. This represents a novel advancement in developing immunotherapies that can be administered systemically, but act locally to induce antitumor immune responses without the usual attendant toxicities.See related article by Kamata-Sakurai et al., p. 158.