Liver-specific inactivation of Cideb improves metabolic profiles and ameliorates steatohepatitis and fibrosis in animal models for MASH

Background and Aims: Germline mutations in CIDEB, a lipid droplet (LD)-associated protein, confer protection against various liver diseases in humans. Whether liver-specific inhibition of CIDEB will bring clinical benefits remains to be determined. We aim to establish preclinical proof of concept by testing GalNac-conjugated Cideb siRNAs in animal models for obesity and MASH and to develop siRNA drug candidates for clinical investigations. Method: Surrogate siRNAs targeting mouse Cideb were designed and evaluated via a panel of assays. In vivo administration of the surrogate siRNAs was conducted in diet-induced obesity model and CDAA-HFD model for MASH. Plasma and liver lipid levels were measured, and liver histopathological features were analyzed. RNA-Seq analysis of liver tissues was performed to gain a comprehensive mechanistic understanding of Cideb target biology. Concurrently, humanized CIDEB knock-in mice were generated as a research tool to aid human therapeutic siRNAs discovery and development. Results: Single administration of a potent surrogate siRNA resulted in more than 80% target knockdown up to two weeks. In the DIO model, Cideb knockdown led to significant reductions of plasma total cholesterol (TC) and triglyceride (TG) levels, a significant decrease in hepatic macro-steatosis and notable body weight loss. In the CDAA-HFD model, Cideb siRNA treatment significantly reduced liver weight as well as liver TC and TG levels. Furthermore, remarkable reductions of hepatic steatosis and total NAS score were observed with a concomitant amelioration of liver fibrosis. Transcriptome analyses revealed key mechanisms upon Cideb inactivation beyond lipid metabolism. Conclusion: CIDEB exhibits significant potential as a therapeutic target for the treatment of MASH. Liver-targeting siRNA candidates are being developed to test the therapeutic hypothesis in humans. Overall design: To study the mechanism of action of the Cideb knockdown in MASH, the CDAA-HFD mouse model was utilized. The model was treated with the saline as vehicle, GFT505 as a positive control, a siRNA with scramble sequence as a negative control, and the surrogate siRNA targeting mouse Cideb. Gene expression profiling was conducted using RNA-seq on liver samples from the various groups.