CB-2679d-GT

CB-2679d-GT is an investigational adeno-associated virus (AAV)-based gene therapy for hemophilia B developed by Catalyst Biosciences. It encodes a novel high-potency Factor IX variant containing three amino acid substitutions (R318Y/R338E/T343R) that enhance three key functional attributes: increased catalytic activity, higher affinity for activated Factor VIII, and resistance to antithrombin inhibition. In preclinical studies, CB-2679d-GT demonstrated superior hemostatic efficacy compared to the current standard Padua variant (R338L), showing approximately 3-fold improvement in clotting activity, 4-8 fold reduction in bleeding time, and 4-fold reduction in blood loss volume. The therapy aims to provide sustained Factor IX expression while potentially allowing for lower and safer vector doses compared to existing gene therapies.