(11β,17α)-17-[(Ethoxycarbonyl)oxy]-11-hydroxy-3-oxo-androsta-1,4-diene-17-carboxylic acid-d5 is labelled (11β,17α)-17-[(Ethoxycarbonyl)oxy]-11-hydroxy-3-oxo-androsta-1,4-diene-17-carboxylic acid (E890570) which is a derivative of Loteprednol Etabonate (L471400) which is an ophthalmic corticosteroid.