Novel analogs of valproic acid and methods of medical treatment using the same

A compound of formula I or a pharmaceutically acceptable salt thereof: wherein R1 is deuterium or hydrogen. The deuterated valproic acid compound of formula I is selected from 2-[(2,2,3,3-D4)propyl](4,4,5,5-D4)pentanoic acid and 2-[(2,2,3,3-D4)propyl](2,4,4,5,5-D5)pentanoic acid and salts thereof, preferably sodium salts. Also disclosed is a pharmaceutical composition comprising the deuterated valproic acid compound of formula I and a pharmaceutical vehicle. The deuterated valproic acid compounds of formula I are for use in the treatment of conditions associated with excess fibrin, thrombus formation, fibrosis, bipolar disorders, migraine headaches, epilepsy or conditions wherein inhibition of histone deacetylase (HDAC) is beneficial. A method of treating an abnormal condition associated with excess fibrin, thrombus formation and/or fibrosis comprising administering a therapeutically effective amount of the deuterated valproic acid compound of formula I is also disclosed. Methods of treating bipolar disorder, migraine headaches or epilepsy are also disclosed. The compounds of the invention exhibit reduced formation of the toxic 4-ene metabolite and therefore have reduced hepatotoxicity.