Preclinical studies of a death receptor 5 fusion protein that ameliorates acute liver failure

Acute liver failure (ALF) is a life-threatening disease with a high mortality rate. There is an urgent need to develop new drugs with high efficacy and low toxicity. In this study, we produced a pharmaceutical-grade soluble death receptor 5 (sDR5)-Fc fusion protein for treating ALF and evaluated the pharmacology, safety, pharmacokinetics, efficacy, and mechanisms of sDR5-Fc in mice, rats, and cynomolgus monkeys. sDR5-Fc bound with high affinity to both human and monkey tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) effectively blocked TRAIL-induced apoptosis in vitro and significantly ameliorated ALF induced by concanavalin A (Con A) in mice. Mechanistically, sDR5-Fc inhibited hepatocyte death and reduced inflammation in vivo. Furthermore, sDR5-Fc attenuated the production of inflammatory cytokines by splenocytes activated with Con A or an anti-CD3 antibody in vitro. Consistent with these results, splenocytes from TRAIL^-/- mice produced much lower levels of inflammatory cytokines than those from TRAIL^+/+ mice. In cynomolgus monkeys, sDR5-Fc was safe and well tolerated when intravenously administered as a single dose of up to 1200 mg/kg or multiple doses of 100 mg/kg. After treatment with a single dose, linear pharmacokinetics with a mean half-life of > 1.9 days were observed. After 12 weekly doses, sDR5-Fc exposure increased in an approximately dose-proportional manner, and the mean accumulation ratio ranged from 1.82- to 2.11-fold. These results support further clinical development of our sDR5-Fc protein as the first TRAIL-targeting drug for ALF treatment. KEY MESSAGES: sDR5-Fc binds with high affinity to TRAIL to effectively block TRAIL-induced apoptosis. sDR5-Fc ameliorates Con A-induced acute liver failure in mice by inhibiting hepatocyte death and inflammation. sDR5-Fc or TRAIL knockout attenuates the production of inflammatory cytokines by activated splenocytes in vitro. sDR5-Fc is safe and well tolerated in acute or long-term toxicity study.