Bifunctional LYTAC Mediates Hepatocytes-Hepatic Stellate Cells Crosstalk by Regulating 5-HT2A Receptor Degradation and Antagonism to Synergistically Ameliorate Hepatic Fibrosis.

Hepatic fibrosis is characterized by persistent hepatocyte injury and activation of hepatic stellate cells (HSCs), leading to excessive extracellular matrix deposition and impaired liver function. 5-hydroxytryptamine (5-HT) promotes HSCs activation and fibrogenesis via the 5-HT2A receptor (5-HT2AR, a GPCR). Herein, we developed novel bifunctional lysosome-targeting chimeras (LYTACs) by conjugating a potent 5-HT2AR antagonist to a triantennary N-acetylgalactosamine (tri-GalNAc) ligand by using precisely optimized linkers. LY-res-3 induced potent, rapid, and selective degradation of endogenous 5-HT2AR in asialoglycoprotein receptor (ASGPR)-positive hepatocytes. Mechanistic studies confirmed that LY-res-3 mediates inhibition of TGF-β release in hepatocytes, with this activity strictly dependent on ASGPR-mediated 5-HT2AR endocytosis, followed by lysosomal degradation. Crucially, the bifunctional molecule concurrently maintained significant antagonism against 5-HT2AR in activated HSCs, effectively blocking TGF-β downstream signaling. By combining targeted degradation with receptor antagonism, this strategy establishes a novel therapeutic modality targeting hepatocyte-HSCs crosstalk in liver fibrosis. Furthermore, it provides a powerful and generalizable method for developing hepatic-selective degraders against other challenging GPCRs implicated in liver fibrosis.