A novel pharmacological inhibitor of MAP4K4 activity attenuates metabolic dysfunction-associated steatohepatitis

BACKGROUND AND AIMS: Metabolic dysfunction-associated steatotic liver disease (MASLD) is a progressive condition and a leading driver of global liver-related morbidity. Its advanced form, metabolic dysfunction-associated steatohepatitis (MASH), is characterized by hepatic steatosis, inflammation, hepatocellular ballooning, and fibrosis. This study aimed to define the significance of MAP4K4 (mitogen-activated protein kinase kinase kinase kinase 4) as a therapeutic target and to evaluate a novel small-molecule inhibitor, glucosyl pyrrolo-pyrimidinone (GPPD), for the mitigation of MASH. METHODS: MAP4K4 expression was immunohistochemically quantified in liver biopsies from healthy individuals (n=5) and MASLD patients (n=20). The in vitro efficacy of GPPD and genetic MAP4K4-silencing (siRNA) was assessed in human primary hepatocytes, mouse hepatic organoids, HepG2, and AML12 cells challenged with oleic acid. For in vivo validation, mice were fed a high-fat/high-fructose/high-cholesterol diet and treated with GPPD for 30-weeks (n=8/group). Livers were analyzed using single-nuclei RNA sequencing to identify the molecular mechanisms of GPPD-mediated hepatoprotection. Data was analyzed using ANOVA models and expressed as mean ± standard deviation (SD) with differences considered significant at p < 0.05. RESULTS: Hepatic MAP4K4 expression was significantly elevated in MASLD patients compared to healthy controls, correlating with disease severity. In multiple in vitro models, both genetic silencing and GPPD treatment significantly attenuated steatosis. In vivo, prophylactic GPPD administration reduced body mass gain and adiposity while protecting against hepatic steatosis, inflammation, injury, and fibrosis. Mechanistically, while GPPD directly inhibited MAP4K4 activity, its hepatoprotective effects were associated with suppression of CaMK2 (calcium/calmodulin-dependent protein kinase II). CONCLUSIONS: Our results demonstrate that glucosyl pyrrolo-pyrimidinone treatment mitigates steatohepatitis with fibrosis by regulating MAP4K4-CaMK2 axis. Further investigation of GPPD will advance its development as an effective future therapeutic strategy against MASH. IMPACT AND IMPLICATIONS: This study identifies the MAP4K4-CaMK2 signaling axis as a critical pathway in the pathogenesis of MASH. By demonstrating that GPPD-mediated inhibition of this pathway attenuates key hallmarks of MASH - including steatosis, inflammation, and fibrosis - our findings provide a mechanistic framework for future therapeutic intervention. Moreover, targeting MAP4K4 may address significant unmet needs of patients who are ineligible for currently approved treatments. Collectively, this research establishes a translational foundation for the development of next-generation small molecules designed at restoring metabolic homeostasis across the disease continuum.