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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.

Acetaminophen (APAP) is one of the most commonly used drugs worldwide, and APAP-induced liver injury is the most frequent cause of acute liver failure in developed countries. However, the mechanisms of APAP-induced hepatotoxicity are not well understood, and treatment options for the disorder are very limited. Here, we show that TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) is a major mediator of APAP-induced liver injury in mice, and its blockade markedly ameliorates the liver failure. In APAP-treated mice, TRAIL was expressed in the liver, spleen, and peripheral blood primarily by CD11b+Gr1+ neutrophils. The concentration of soluble TRAIL in the blood, and the frequencies of TRAIL+ leukocytes in the spleen and liver positively correlated with the severity of liver injury. APAP sensitized hepatocytes to TRAIL-induced apoptosis by upregulating the expression of the TRAIL receptor DR5 (death receptor 5), presumably through its transcription factor CHOP (C/EBP homologous protein). Importantly, blocking TRAIL with a soluble DR5-Fc fusion protein (sDR5-Fc) significantly attenuated APAP-induced liver injury, the hepatic infiltration of leukocytes, the levels of inflammatory cytokines, and the mortality of mice. When administered alongside N-acetylcysteine, sDR5-Fc further protected against APAP-induced acute liver injury. Thus, the TRAIL-DR5 signaling pathway plays a key role in APAP-induced liver inflammation and failure, and its blockade represents an effective new strategy to treat the liver disease.