Top-line results from Enanta Pharmaceuticals Inc.'s Argon-1 phase IIa study of EDP-305 for the treatment of nonalcoholic steatohepatitis (NASH) found one of the two doses of the drug tested met the study's primary endpoint, alanine aminotransferase (ALT) reduction at week 12, contributing further evidence for the drug's mechanism of action, farnesoid X receptor (FXR) agonism. But the non-biopsy study appears to have left investors without proof for something more even more valuable: a clear case for differentiation vs. FXR first-mover Ocaliva (obeticholic acid, Intercept Pharmaceuticals Inc.). Appearing to reflect the sentiment, Enanta's shares (NASDAQ:ENTA) fell 15.1% to $60.51 on Thursday.