MK-8690

MK-8690 (formerly known as PRA-052) is an investigational, fully human monoclonal antibody that targets and blocks the CD30 ligand (CD30L, also known as CD153 or TNFSF8). By inhibiting the CD30/CD30L signaling pathway, MK-8690 exerts pleiotropic anti-inflammatory effects on both innate and adaptive immune responses, offering a therapeutic mechanism distinct from tumor necrosis factor (TNF) antagonists. Originally co-developed by Prometheus Biosciences and Dr. Falk Pharma, the asset was acquired by Merck through its acquisition of Prometheus in 2023. In late 2025, Merck terminated the co-development agreement with Dr. Falk Pharma to assume full global rights and sole responsibility for the program. MK-8690 is currently in Phase 2 clinical development for the treatment of moderately to severely active ulcerative colitis.