Safety and tolerability of the protein C activator AB002 in end-stage renal disease patients on hemodialysis: a randomized phase 2 trial

The protein C system regulates blood coagulation, inflammation, and vascular integrity. AB002 is an injectable protein C activating enzyme under investigation to safely prevent and treat thrombosis. In preclinical models, AB002 is antithrombotic, cytoprotective, and anti-inflammatory. Since prophylactic use of heparin is contraindicated during hemodialysis in some end-stage renal disease (ESRD) patients, we propose using AB002 as a short-acting alternative to safely limit blood loss due to clotting in the dialysis circuit. This phase 2, randomized, double-blind, placebo-controlled, single-dose study evaluates the safety and tolerability of AB002 administered into the hemodialysis line of ESRD patients during hemodialysis at one study center in the United States (ClinicalTrials.gov: NCT03963895). In this study, 36 patients were sequentially enrolled into two cohorts and randomized to AB002 or placebo in a 2:1 ratio. In cohort 1, patients received 1.5 µg/kg AB002 (n = 12) or placebo (n = 6); in cohort 2, patients received 3 µg/kg AB002 (n = 12) or placebo (n = 6). Patients underwent five heparin-free hemodialysis sessions over 10 days and were dosed with AB002 or placebo during session four. Here we show that AB002 is safe and well-tolerated in ESRD patients, with no treatment-related adverse events. Clinically relevant bleeding did not occur in any patient, and the time to hemostasis at the vascular access sites is not affected by AB002. As far as we are aware, this proof-of-concept study is the first clinical trial assessing the therapeutic potential of protein C activation. The results herein support additional investigation of AB002 to safely prevent and treat thrombosis in at-risk populations. Some people with kidney disease require hemodialysis, a process in which a machine filters the blood to remove waste products. The process of hemodialysis can trigger blood clotting in the hemodialysis circuit. Therefore, the blood-thinner heparin is commonly used to prevent blood from clotting. However, some patients cannot tolerate heparin. Here we describe a clinical trial in which we tested whether a drug called AB002 is safe and can reduce hemodialysis circuit clotting in people with permanent kidney disease (end-stage renal disease) undergoing hemodialysis. AB002 appears to be safe and well-tolerated, and we observed reduced clotting without any signs of increased bleeding. Further studies are required in more patients to determine whether AB002 can be used routinely during hemodialysis to safely prevent or treat blood clots. Verbout et al. report findings from a phase 2 proof-of-concept study of the protein C activator AB002 in patients with end stage renal disease undergoing heparin-free hemodialysis. AB002 appears safe and well-tolerated, while demonstrating reduced dialyzer clot severity and no increased bleeding at the vascular access site compared to placebo.