Obeticholic acid as an index farnesoid X receptor scaffold in metabolic dysfunction-associated steatohepatitis: a testable model for efficacy-liability separation and biomarker interpretation.

Obeticholic acid (OCA) is not approved for metabolic dysfunction-associated steatohepatitis (MASH), and the United States development pathway for its use in precirrhotic NASH ended after regulatory non-approval. The compound is still useful scientifically, because no other farnesoid X receptor (FXR) agonist has produced a comparable human dataset in steatohepatitis. A frequent interpretive problem is that histological benefit, low-density lipoprotein cholesterol (LDL-C) elevation, pruritus and possible liver-intrinsic injury are compressed into one FXR activation continuum. This hypothesis-driven narrative article argues for a narrower reading. OCA is treated here as an index scaffold that separates clinical response, systemic lipid risk, tolerability and candidate liver-intrinsic sterol-stress biology into distinct evidence layers. We first place OCA in the current MASLD/MASH therapeutic setting, then outline hepatic and intestinal FXR pharmacology relevant to the model. Human OCA data, cross-scaffold observations from non-bile acid FXR agonists, and mechanistic work on FATP5/SLC27A5, cholesterol stress and ACOX1 are then reassessed. Within the proposed model, FATP5 is a putative OCA-linked substrate-entry node supported mainly by preclinical and humanized-transporter work. Cholesterol retention, free-cholesterol burden, cholesterol crystals, macrophage crown-like structures, IL-1beta signaling and hepatic stellate-cell activation are better handled as a candidate sterol-stress liability branch. ACOX1 is interpreted as a context-dependent modifier, not as a validated therapeutic target. The model is not a class-wide claim for all FXR agonists. It should be tested, and if necessary rejected, using matched FXR target engagement, paired human tissue and human multicellular systems.