FL401

FL401 is a next-generation antibody-cytokine fusion protein (immunocytokine) developed through a collaboration between Suzhou Forlong Biotechnology and Henlius. It consists of a monoclonal antibody targeting Programmed cell death 1 ligand 1 (PD-L1) fused to an Interleukin-15 (IL-15) superagonist. This dual-mechanism approach is designed to overcome immune suppression in the tumor microenvironment by simultaneously blocking the PD-1/PD-L1 checkpoint pathway and providing potent, localized stimulation of T cells and natural killer (NK) cells via the IL-15 receptor. By targeting PD-L1, FL401 aims to concentrate the IL-15 activity within the tumor, potentially enhancing efficacy while reducing systemic toxicity compared to non-targeted cytokine therapies. It is currently in early-stage development for the treatment of various solid tumors.