Biodegradable derivatives of tranexamic acid as transdermal permeation enhancers

The purpose of this work was to develop a novel approach to transdermal permeation enhancer design, based on utilizing some favorable properties of their metabolites. As an example of this concept, a series of carbamic acid salts of tranexamic acid (TXA) esters was synthesized, because TXA was previously shown to improve skin barrier homeostasis. Enhancement activities of 1% TXA derivatives dispersed in both hydrophilic and lipophilic vehicles were evaluated in vitro using human skin and theophylline as a model drug. Dispersed in an aqueous donor vehicle, the dodecyl ester showed the enhancement ratio (ER) of 4.3+/-0.9, which is almost 2 times higher than that of 1-dodecylazepan-2-one (Azone; 2.2+/-0.7). From an isopropyl-myristate suspension, the decyl ester was the most effective enhancer (4.9+/-1.4), while Azone was inactive. Decomposition of the carbamate in a slightly acidic environment was shown by FTIR; hydrolysis of the pertinent ester by porcine esterase was monitored by TLC and HPLC. Biodegradable enhancers of this type could mediate easier and faster recovery of the skin barrier after transdermal delivery through the action of the released TXA.

Design of plasma kallikrein inhibitors: functional and structural requirements of plasma kallikrein inhibitors

The synthetic plasma kallikrein (PK) inhibitor trans-4-aminomethylcyclohexanecarbonylphenylalanine-4-carboxyme thylanilide (PKSI-527) consists of three parts. Each part was replaced by analogues in an attempt to improve the potency and the selectivity of PKSI-527. Among the peptides examined, trans-4-aminomethylcyclohexanecarbonylphenylalanine-4-carboxyan ilide (peptide 16) inhibited PK with a high selectivity and an IC50 value of 2.7 microM, being as potent as PKSI-527.

Development of active center-directed plasmin and plasma kallikrein inhibitors and studies on the structure-inhibitory activity relationship

The molecule of trans-4-aminomethylcyclohexanecarbonylphenylalanine 4-carboxymethylanilide (8), which is a potent and selective inhibitor of plasma kallikrein, can be divided into three parts (P1, P1' and P2'), each of which contains one of the rings. In order to study the role of each part in the manifestation of potent and selective inhibitory activity and the relationship between the structure and inhibitory activities toward plasmin, plasma kallikrein, urokinase and thrombin, each part was substituted with various other moieties to give many kinds of analogs and their inhibitory activities against the above enzymes were examined. Among them, trans-4-aminomethylcyclohexanecarbonyl-O-2-bromobenzyloxycarbon yltyrosine 4-acetylanilide (12) inhibited plasmin and plasma kallikrein with IC50 values of 2.3 x 10(-7) M and 3.7 x 10(-7) M, and K(i) values of 1.2 x 10(-7) M and 1.3 x 10(-7) M, respectively.

Synthesis of trans-4-aminomethylcyclohexanecarbonyl-L- and -D-phenylalanine-4-carboxymethylanilide and examination of their inhibitory activity against plasma kallikrein

Based on studies of structure-activity relationship, trans-4-aminomethylcyclohexanecarbonyl-L-phenylalanine-4-carbox ymethylanilide (Tra-Phe-APAA) was designed as a selective plasma kallikrein inhibitor and synthesized. Tra-Phe-APAA inhibited plasma kallikrein with a Ki value of 0.81 microM, while it inhibited glandular kallikrein, plasmin, urokinase, factor Xa and thrombin with Ki values of greater than 500, 390, 200, greater than 500, and greater than 500 microM, respectively. However, its stereoisomer, Tra-D-Phe-APPA did not exhibit any detectable inhibitory activity against the above enzymes.

[The synthesis of 4'-(2-carboxyethyl)phenyl trans-4-aminomethyl cyclohexane carboxylate hydrochloride (cetraxate hydrochloride) by means of enzymatic debenzylation]

Cetraxate hydrochloride (1) (antiulcer agent) has been industrially produced by the chemical protective method of p-hydroxy propionic acid derivatives. Screening of enzymes which quantitatively hydrolyzed cetraxate benzyl ester hydrochloride (2) into 1 was undertaken to establish a novel enzymatic method of production of 1. It was found that the enzyme activity for debenzylation of 2 is contained in cellulase enzymes originated from Aspergillus sp. Lower alkyl groups or phenyl groups of p-hydroxy propionic acid derivatives are likewise selectively hydrolyzed by the cellulase enzyme. This enzymatic synthetic method is very useful for the industrial preparation of 1.

Tranexamic acid derivatives with enhanced absorption

Derivatives of the antifibrinolytic drug tranexamic acid [trans-4-(aminomethyl)cyclohexanecarboxylic acid] containing one or two tranexamic acid moieties were synthesized. Most of the derivatives have good stability in acidic and neutral solutions but are easily hydrolyzed in plasma. By measuring the amount of tranexamic acid excreted in the urine after an oral dose, relative absorptions of a number of derivatives in the rat were estimated. Most of the derivatives showed greater absorption than tranexamic acid itself. 1-[(Ethoxycarbonyl)oxy]ethyl trans-4-(amino-methyl)cyclohexanecarboxylate hydrochloride was chosen for studies in man.