1. N-(benzyloxycarbonyl)glycine esters and amides as new anticonvulsants
M Geurts, J H Poupaert, G K Scriba, D M Lambert J Med Chem. 1998 Jan 1;41(1):24-30. doi: 10.1021/jm970086f.
Glycine is a small neutral amino acid exhibiting weak anticonvulsant activities in vivo. Recently, studies have demonstrated that N-(benzyloxycarbonyl)glycine (1) antagonized seizures superior to glycine in addition to activity in the maximal electroshock (MES) test, a convulsive model where glycine is inactive. In the present study a series of ester and amide derivatives of 1 as well as esters of N-(3-phenylpropanoyl)glycine (5) have been prepared. The compounds were evaluated in the MES test as well as in several chemically induced seizure models. Among the derivatives investigated, N-(benzyloxycarbonyl)glycine benzylamide (16) was the most potent compound exhibiting an anticonvulsant activity in the MES test comparable to the drug phenytoin. Median effective doses (ED50) of 4.8 and 11.6 mg/kg were determined at 30 min and 3 h after i.p. administration, respectively. Compound 16 also effectively suppressed tonic seizures in different chemically induced models such as the strychnine, 3-mercaptopropionic acid, and pentylenetetrazole tests. Moreover, the compound studied here did not show acute neurotoxicity in the rotorod test up to a dose of 150 mg/kg. It is concluded that N-(benzyloxycarbonyl)glycine amides, especially 16, are potent anticonvulsant agents.
2. 3-Hydroxymethylphenytoin valproic acid ester, a new prodrug combining two anticonvulsant drugs
G K Scriba Arch Pharm (Weinheim). 1996 Dec;329(12):554-5. doi: 10.1002/ardp.19963291208.
3-Hydroxymethylphenytoin valproic acid ester (VAL-PHT) was designed as a new prodrug combining valproic acid and phenytoin, two anticonvulsant drugs with different pharmacological profiles. The compound was hydrolyzed by rat plasma esterases in vitro but exhibited only activity in the maximal electroshock seizure test (MES test) after intraperitoneal administration to mice. The compound did not protect against pentylenetetrazole-induced seizures. It is concluded that VAL-PHT acts as a prodrug displaying the anticonvulsant profile of phenytoin.
3. Anticonvulsant activity of phenytoin-lipid conjugates, a new class of phenytoin prodrugs
G K Scriba, D M Lambert, J H Poupaert J Pharm Pharmacol. 1995 Mar;47(3):197-203. doi: 10.1111/j.2042-7158.1995.tb05778.x.
The anticonvulsant activity of phenytoin-lipid conjugates obtained by covalent binding of 3-hydroxy-methylphenytoin to dimyristoylglycerides via a succinidyl linkage, to 2-(1,3-dimyristoylglyceryl)butyric acid and to 3-myristoyl-2-myristoylmethylpropionic acid was evaluated in the maximal electroshock (MES) test and the seizure threshold test with subcutaneous pentetrazol. The phenytoin-lipid conjugates were less active than the parent drug in the MES test after intraperitoneal administration as suspensions, but exhibited comparable activity when injected as a solution in dimethylsulphoxide. They also protected mice from MES-induced seizures following oral administration of aqueous suspensions of the compounds or when incorporated into emulsions. The anticonvulsant activity could be correlated to in-vitro pancreatic lipase-mediated hydrolysis. The bis-deacyl derivatives were at least as active but in some cases also more toxic than phenytoin. Oral administration of two of the lipid conjugates resulted in a faster onset of the anticonvulsant activity compared with the administration of an equimolar dose of phenytoin itself. All compounds were inactive in the subcutaneous pentetrazol test. It is concluded that the lipids act as prodrugs of phenytoin, which is generated by lipolysis upon oral administration.
