C1K (Charis Biosciences)

C1K (also known as Charis 1000) is a long-acting recombinant human interleukin-2 (IL-2) analog developed by Charis Bioscience, a biotechnology company spun off from Seoul National University Hospital. The drug is designed to overcome the limitations of native IL-2 therapy, such as its short half-life and severe systemic toxicities (e.g., vascular leak syndrome), by utilizing a long-acting formulation that allows for subcutaneous administration. C1K acts as an agonist of the interleukin-2 receptor, stimulating the expansion and activation of effector T cells and natural killer (NK) cells, which are critical for an effective anti-tumor immune response. It is currently being evaluated in Phase 1 clinical trials for the treatment of advanced solid tumors, including triple-negative breast cancer (TNBC), both as a monotherapy and potentially in combination with other immunotherapies.