While existing immunotherapies have changed cancer care, there are several types of cancer where they have limited or no efficacy. Pheast Therapeutics is addressing that by looking to macrophages, part of the innate immune system. These white blood cells gobble up pathogens, cancer cells, and other foreign substances. Certain tumors, though, can evade their attack by expressing checkpoints that serve as “don’t eat me” signals. Pheast is developing macrophage checkpoint inhibitors to block these signals and enlist macrophages in the fight against cancers. We spoke to Roy Maute, cofounder and CEO of Pheast Therapeutics, about how tumors evade the innate immune system, the company’s experimental macrophage checkpoint inhibitor, and its initial focus on ovarian and triple negative breast cancer.