Boserolimab (also known as MK-5890) is a humanized monoclonal antibody designed to act as an agonistic immune modulator. Its primary function is to specifically target and bind to the CD27 receptor. By engaging CD27, Boserolimab provides a co-stimulatory signal to T cells, mimicking the effect of the natural ligand, CD70. This co-stimulation is intended to enhance T cell mediated immune responses, promoting the proliferation and activation of cytotoxic T lymphocytes (CTLs). This mechanism makes it a candidate for cancer immunotherapy, where the goal is to boost the body's immune attack against malignant cells.