3-[(4-Fluorophenyl)sulfonyl]-2-hydroxy-2-methylpropanoic Acid-d4 is the isotope labelled analog of 3-[(4-Fluorophenyl)sulfonyl]-2-hydroxy-2-methylpropanoic Acid (F595620); an impurity of Bicalutamide (B382000) which is a non-steroidal peripherally active antiandrogen. Also used as an antineoplastic (hormonal).