IO Biotech is a clinical-stage biopharmaceutical company developing therapeutic cancer vaccines. Its lead product, Cylembio (IO102-IO103), is designed to activate a patient's T cells to attack two immunosuppressive proteins — IDO and PD-L1 — that are overexpressed in cancer cells and the tumor microenvironment. Unlike checkpoint inhibitors, which block PD-1/PD-L1 signaling, Cylembio directly kills PD-L1- and IDO-expressing cells and converts the tumor microenvironment into a more pro-inflammatory state. Cylembio is intended to be used in combination with approved checkpoint inhibitors like pembrolizumab (Keytruda) or nivolumab (Opdivo), not as a standalone therapy. Cylembio's most advanced indication is first-line advanced melanoma, where a 407-patient Phase 3 trial comparing Cylembio plus pembrolizumab to pembrolizumab alone is underway, with a PFS readout expected in Q3 2025. The FDA granted Cylembio Breakthrough Therapy Designation in advanced melanoma in 2020. Beyond melanoma, IO Biotech is running Phase 2 trials in NSCLC and head and neck cancer. The company's broader T-win platform is designed to generate a family of vaccines targeting different immunosuppressive proteins, with two earlier-stage candidates — IO112 (Arginase 1) and IO170 (TGFβ1) — in preclinical development. IO Biotech has no approved products or revenue, funds operations through equity and debt, and outsources all manufacturing to CDMOs.