Positive allosteric modulator of the GABA-A receptor counteracts hepatic fibrosis with profound anti-obesity action

Background: Obesity-associated MASLD and its progression towards MASH-related advanced fibrosis is a growing global health concern. Targeting γ-aminobutyric acid type A (GABA) signaling has shown promise in mitigating liver injury. In this study we investigated the novel compound HK3, a positive allosteric modulator of the GABA-A receptor, for treating MASH with a particular focus on obesity and liver fibrosis. Experimental Approach: Human-derived 3D MASH spheroids and human hepatic stellate cells (LX2) were treated with increasing concentrations of HK3 or its derivative HK1 to assess their anti-steatotic, anti-inflammatory and anti-fibrotic efficacy. Molecular and transcriptional responses were assessed by immunoblotting, ELISA, RT-PCR and RNA sequencing. The in vivo effects of HK3 were evaluated in a CCl4-induced fibrosis or a diet-induced obesity (DIO) mouse model. Adipocytes (3T3-L1) and visceral adipose tissue (VAT) from C57BL/6 mice were treated with HK3 or HK1 to determine their impact on mitochondrial respiratory function by extracellular flux analysis or high-resolution respirometry.Results: HK3 reduced intracellular lipid content, interleukin secretion, and pro-collagen 1αI level in the organotypic 3D human MASH model. In hepatic stellate cells, HK3 and HK1 dose dependently attenuated TGF-β1-induced fibrotic, and inflammatory biomarker expression and diminished cell migration. In vivo, HK3 prevented fibrosis progression in a CCl4 mouse model and reduced body fat mass and cholesterol load in a DIO mouse model. In line, HK3 increased proton leakage and mitochondrial uncoupling efficiency in adipocytes and VAT. Conclusion: Our novel thioacrylamide GABA-A receptor modulator HK3 simultaneously targets hepatic steatosis, inflammation and specifically fibrosis in several preclinical MASH models, while reducing body fat mass through mitochondrial uncoupling of adipocytes. Thus, HK3 offers a promising multi-targeted first-in-class pharmacological approach for obesity-associated MASLD.