A novel high mobility group box 1 neutralizing chimeric antibody attenuates drug‐induced liver injury and postinjury inflammation in mice

Abstract

Acetaminophen (APAP) overdoses are of major clinical concern. Growing evidence underlines a pathogenic contribution of sterile postinjury inflammation in APAP‐induced acute liver injury (APAP‐ALI) and justifies development of anti‐inflammatory therapies with therapeutic efficacy beyond the therapeutic window of the only current treatment option, N‐acetylcysteine (NAC). The inflammatory mediator, high mobility group box 1 (HMGB1), is a key regulator of a range of liver injury conditions and is elevated in clinical and preclinical APAP‐ALI. The anti‐HMGB1 antibody (m2G7) is therapeutically beneficial in multiple inflammatory conditions, and anti‐HMGB1 polyclonal antibody treatment improves survival in a model of APAP‐ALI. Herein, we developed and investigated the therapeutic efficacy of a partly humanized anti‐HMGB1 monoclonal antibody (mAb; h2G7) and identified its mechanism of action in preclinical APAP‐ALI. The mouse anti‐HMGB1 mAb (m2G7) was partly humanized (h2G7) by merging variable domains of m2G7 with human antibody‐Fc backbones. Effector function‐deficient variants of h2G7 were assessed in comparison with h2G7 in vitro and in preclinical APAP‐ALI. h2G7 retained identical antigen specificity and comparable affinity as m2G7. 2G7 treatments significantly attenuated APAP‐induced serum elevations of alanine aminotransferase and microRNA‐122 and completely abrogated markers of APAP‐induced inflammation (tumor necrosis factor, monocyte chemoattractant protein 1, and chemokine [C‐X‐C motif] ligand 1) with prolonged therapeutic efficacy as compared to NAC. Removal of complement and/or Fc receptor binding did not affect h2G7 efficacy. Conclusion: This is the first report describing the generation of a partly humanized HMGB1‐neutralizing antibody with validated therapeutic efficacy and with a prolonged therapeutic window, as compared to NAC, in APAP‐ALI. The therapeutic effect was mediated by HMGB1 neutralization and attenuation of postinjury inflammation. These results represent important progress toward clinical implementation of HMGB1‐specific therapy as a means to treat APAP‐ALI and other inflammatory conditions. (Hepatology 2016;64:1699‐1710).

Key Events Participating in the Pathogenesis of Alcoholic Liver Disease

“…HMGB1 was discovered over 30 years ago, as an endogenous inflammatory mediator and now serves as a prototype for the class of inflammatory activators tagged as “alarmins” [99]. HMGB1 is a key mediator of inflammation, macrophage proliferation, TNFα production and collagen-I deposition.…”

“…HMGB1 can be released either passively by dying cells or actively during an inflammatory response [99] and from LPS-activated macrophages during sepsis [106]. It is normally found in the nucleus but can undergo post-translational modifications and, as a result, it translocates to the cytosol and is ultimately secreted.…”

“…Looking at both human samples and mouse models, the Nieto Lab found that HMGB1 was increased in disease progression and ablation of Hmgb1 in hepatocytes protected from ALD in mice [107], suggesting that HMGB1 could be a pivotal regulator and perhaps a biomarker of liver injury. Likewise, a novel HMGB1 neutralizing chimeric antibody has been shown to attenuate acetaminophen-induced liver injury and post-injury inflammation in mice [99], demonstrating that HMGB1-specific therapy reduces toxicity and inflammation in acute liver injury and in chronic liver diseases.…”

Utilizing Mechanistic Biomarkers in Treating Paracetamol Hepatotoxicity

“…Accordingly, blocking leukocyte DAMP receptors such as toll‐like receptor 9 has shown promise in preclinical models of PCM toxicity . The merits of neutralizing HMGB1 directly have also been demonstrated in animal studies . Expanding the therapeutic repertoire for PCM overdose beyond NAC therefore seems an attainable objective for future research.…”

Novel circulating- and imaging-based biomarkers to enhance the mechanistic understanding of human drug-induced liver injury

“…Pre-clinically, hepatocyte specific HMGB1 ablation has been shown to result in 100 % survival following an APAP dose that is usually lethal in mice [47]. Furthermore, studies have shown that anti-HMGB1 antibodies and knocking out Hmgb1 in the liver reduces hepatic inflammation and liver injury in mouse models of APAP poisoning [43,45,49]. Anti-HMGB1 antibodies are in development for the treatment of human disease [28].…”