Examining the correlations between GSK-3 inhibitory properties and anti-convulsant efficacy of valproate and valproate-related compounds Geoff H. Werstuck, a, * Anna J. Kim, a Timothy Brenstrum, b Stephan A. Ohnmacht, b Ella Panna b and Alfredo Capretta b, * a Department of Biochemistry and Biomedical Sciences, Henderson Research Centre, 711 Concession Street, Hamilton Ontario, Canada L8V 1C3 b Department of Chemistry, McMaster University, Hamilton, Ontario, Canada L8S 4M1 Received 18 August 2004; revised 6 September 2004; accepted 7 September 2004 Available online 1 October 2004 Abstract—A family of compounds based upon the chemical structure of valproate were synthesized and assayed for their a inhibit glycogen synthase kinase (GSK)-3 a and b activity in vitro. This data is correlated to the known anti-convulsant prop these compounds in order to determine the potentialrole of GSK-3 inhibition in the therapeutic efficacy of these drugs. 2004 Elsevier Ltd. All rights reserved. Valproic acid (VPA, 2-propylpentanoic acid) is a potent and widely prescribed drug that acts both as an anti- convulsant in the treatment of epilepsy and as a mood stabilizer to control bipolar disorder. 1,2 The anti-convul- sant effects of valproate occur at plasma concentrations over 0.35 mM and toxicity is observed at concentrations over 1.4 mM. 1,3 Exposureto valproateis known to induce a variety of cellular responses, however the mech- anism(s) by which valproate alleviates convulsions and modifies behavior is still unclear. 4–6 One potential, phy- siologically relevant targetof valproate is the enzyme glycogen synthase kinase (GSK)-3. The two isoforms, GSK-3 a and b, were initially identified as homologous kinases that phosphorylate the rate-limiting enzyme in glycogen synthesis. 7 Over the last20 years the list of GSK-3 substrateshasgrown to encompassa broad array of proteins that are involved in several important regulatory and developmental pathways including translation initiation factor eIF2be, transcription factors CREB, c-Jun, c-Myc, c-Myb, HSF-1, ATP-citrate lysase and tau. 8 As a result,a great deal of interest has been focused upon GSK-3 as a potentialtherapeutic target in the treatment of cancer, diabetes, and neurodegener- ative diseases. The ability of valproateto inhibit GSK-3 activity remains controversial. 5,9 A number of compounds that are chemically related to valproate have been shown to exhibit similar anti-convulsant propertiesin animal models.Very little is known,however,regarding the effects of these compounds on potential cellular targets. The presentreportprovidesinsightinto the effectof VPA on GSK-3 activity in an attempt to determine the relationship between GSK-3 inhibition and the thera- peutic efficacy of VPA as an anti-convulsant. We have prepared a small library of compounds including some withpreviouslydeterminedanti-convulsantactivity and tested for their ability to inhibit GSK-3 a and b. As shown in Scheme 1, commercially available valproic acid (1) was converted to its corresponding acid chloride and then treated with either methanolic ammonia to give valpromide (2) or hydroxylamine to give the val- propylhydroxamic acid (3). Esterification of1 under Fischer conditions allowed for the preparation of methyl valproate (4) which could, in turn, be treated with LDA at 78 C to give the enolate and converted to either the a-iodo (5) or the a-methyl(6) systems shown. Exposure of 5 to DBU allowed for elimination to the a,b-unsatu- rated ester (7), which could be readily hydrolyzed to its 0960-894X/$ - see front matter 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.bmcl.2004.09.013 Keywords: GSK-3; Valproate. * Correspondingauthors. Tel.: +1 9055259140x27318; fax: +1 9055222509 (G.H.W.); e-mailaddresses: gwerstuck@thrombosis. hhscr.org; capretta@mcmaster.ca Bioorganic & MedicinalChemistry Letters 14 (2004) 5465–5467