Causal relationship between liver fat reduction and clinical outcomes in human genetic studies and randomized clinical trials of metabolic-dysfunction associated steatohepatitis

Reliance on invasive liver biopsy endpoints is a major limiting factor in new therapeutic development for metabolic dysfunction-associated steatohepatitis (MASH). While liver fat accumulation is considered a driver of early disease, liver fat reduction is not recognized as a surrogate endpoint by health authorities. Here, we conducted the largest-to-date genome-wide association study (GWAS) of liver fat in 79,642 people with magnetic resonance imaging and developed a polygenic score with liver fat-lowering alleles across 55 genomic loci. In a separate set of 714,886 individuals, a 30% relative liver fat reduction due to the polygenic score was associated with 39% lower odds of liver cirrhosis and 41% lower odds of hepatocellular carcinoma, consistent with a strong causal relationship between lifelong liver fat differences and advanced liver clinical outcomes. A systematic review and meta-analysis of 20 randomized controlled trials including a total of 3,502 MASH patients showed that treatment-induced liver fat reductions were associated with MASH resolution (meta-regression slope in % units of the outcome for each 1% relative reduction in liver fat from baseline, β = -0.70%, p<0.001) and fibrosis improvement (β = -0.24%, p<0.001). These findings demonstrate the profound etiologic impact of liver fat in MASH and provide compelling evidence for liver fat reductions as a reasonably likely surrogate endpoint for future clinical development.