Semicarbazone--a versatile therapeutic pharmacophore for fragment based anticonvulsant drug design

During the last fifteen years, semicarbazones have been extensively investigated for their anticonvulsant properties. 4-(4-Flurophenoxy) benzaldehyde semicarbazone (C0102862, V102862) was discovered as a lead molecule and is being developed as a potent antiepileptic drug, with maximal electroshock (MES) ED₅₀ of i.p. 12.9 mg kg⁻¹. In MES (oral screen), this compound has a protective index (PI = TD₅₀/ED₅₀ > 315) higher than carbamazepine (PI 101), phenytoin (PI > 21.6) and valproate (PI 2.17). The compound is a potent sodium channel blocker. Other semicarbazones have demonstrated activity in various chemoshock screens, like subcutaneous pentylenetetrazole, subcutaneous strychnine, subcutaneous picrotoxin and subcutaneous bicculine. Semicarbazones are also GABA-transaminase inhibitors. Extensive structure- -activity relationship has demonstrated that F, Cl, Br and NO₂ substituents in the arylhydrophobic pocket and a hydrogen bonding domain (HBD) are generally found in active anticonvulsant agents.