Xilio Therapeutics, Inc. is a clinical-stage biotechnology company. The Company is engaged in discovering and developing masked immuno-oncology, or I-O, therapies with the goal of significantly improving outcomes for people living with cancer without the systemic side effects of current I-O treatments. Its pipeline products include Vilastobart, Efarindodekin alfa, XTX501, and masked T cell engagers. Vilastobart is an investigational masked, Fc-enhanced anti-CTLA-4 designed to block CTLA-4 and deplete regulatory T cells when activated (unmasked) in the tumor microenvironment (TME). XTX501 is a novel bispecific PD-1 / masked IL-2 designed to selectively stimulate PD-1 positive, antigen-experienced T cells and enhance their function. Its masked T cell engager programs consist of PSMA and STEAP1 with co-stimulation and CLDN18.2. The masked T cell engagers include molecules with one or more tumor-associated antigen (TAA) binding domains and a CD3 targeting domain.