Design, Synthesis, and Evaluation of Novel Pyruvate DehydrogenaseKinase Inhibitors

Aims: The present work describes the synthesis and the biological evaluation of novel compounds acting as pyruvate dehydrogenase kinase (PDK) inhibitors. These drugs should become a new therapeutic approach for the treatment of pathologies improved by the control of the blood lactate level. Methods: Four series of compounds belonging to N-(4-(N-alkyl/aralkylsulfamoyl)phenyl)-2- methylpropanamides and 1,2,4-benzothiadiazine 1,1-dioxides were prepared and evaluated as PDK inhibitors. Results: The newly synthesized N-(4-(N-alkyl/aralkylsulfamoyl)phenyl)-2-methylpropanamides structurally related to previously reported reference compounds 4 and 5 were found to be potent PDK inhibitors (i.e. 10d: IC50 = 41 nM). 1,2,4-Benzothiadiazine 1,1-dioxides carrying a (methyl/ trifluoromethyl)-propanamide moiety at the 6-position were also designed as conformationally restricted ring-closed analogues of N-(4-(N-alkyl/aralkylsulfamoyl)phenyl)-2-hydroxy-2-methylpropanamides. Most of them were found to be less potent than their ring-opened analogues. Interestingly, the best choice of hydrocarbon side chain at the 4-position was the benzyl chain, providing 11c (IC50 = 3.6 μM) belonging to “unsaturated” 1,2,4-benzothiadiazine 1,1-dioxides, and 12c (IC50 = 0.5 μM) belonging to “saturated’ 1,2,4-benzothiadiazine 1,1-dioxides. Conclusion: This work showed that ring-closed analogues of N-(4-(N-alkyl/aralkylsulfamoyl) phenyl)- 2-hydroxy-2-methylpropanamides were less active as PDK inhibitors than their corresponding ring-opened analogues. However, the introduction of a bulkier substituent at the 4-position of the 1,2,4-benzothiadiazine 1,1-dioxide core structure, such as a benzyl or a phenethyl side chain, was allowed, opening the way to the design of new inhibitors with improved PDK inhibitory activity.