(1S)-Calcitriol (1α,25-Dihydroxy-3-epi-vitamin-D3) is a natural metabolite of 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3). (1S)-Calcitriol exhibits potent vitamin D receptor (VDR)-mediated actions such as inhibition of keratinocyte growth or suppression of parathyroid hormone secretion.In Vitro: 3‐epi‐Calcitroic acid is an end product of (1S)-Calcitriol (1α,25-Dihydroxy-3-epi-vitamin-D3; 3‐epi‐1a,25(OH)2D3) metabolism by rat CYP24A1.