SL-279137 is a best-in-class bi-functional fusion protein that targets PD-L1 on malignant cells and 41BB on immune cells (lymphocytes, antigen presenting cells, and NK cells). The ARC consists of PD-1 linked to 41BBL, providing checkpoint blockade (PD1 axis) and potent costimulation (41BB axis). PD-L1 is often over expressed in malignancies to help evade a cytotoxic T cell response. Therefore, the ARC will preferentially coat tumor cells and prevent PD-1 from becoming activated on T cells. By linking to tumor cells, the 41BBL side of the ARC can bind to 41BB on the surface of activated T cells in the tumor microenvironment (among other immune cells) and elicit enhanced T cells proliferation, cytokine secretion, cytolytic activity, and survival.