Cyanoguanidine prodrugs

#The present invention relates to novel pyridyl cyanoguanidine prodrugs and their inclusion in pharmaceutical compositions, as well as their use in the manufacture of medicaments.

#Pyridyl cyanoguanidines such as pinacidil (N-1,2,2-trimethylpropyl-N′-cyano-N″-(4-pyridyl)guanidine) were originally discovered to be potassium channel openers and were consequently developed as antihypertensive agents. Replacement of the side chain of pinacidil by longer aryl-containing side chains caused a loss of the antihypertensive activity, but such compounds were, on the other hand, found to show antitumour activity on oral administration in a rat model carrying Yoshida ascites tumours.

#Different classes of pyridyl cyanoguanidines with antiproliferative activity are disclosed in, for instance, EP 660 823, WO 98/54141, WO 98/54143, WO 98/54144, WO 98/54145, WO 00/61559 and WO 00/61561. The structure-activity relationships (SAR) of such compounds are discussed in C. Schou et al., Bioorganic and Medicinal Chemistry Letters 7(24), 1997, pp. 3095–3100, in which the antiproliferative effect of a number of pyridyl cyanoguanidines was tested in vitro on different human lung and breast cancer cell lines as well as on normal human fibroblasts. The compounds were also tested in vivo in nude mice carrying a human lung cancer tumour xenograft. Based on the SAR analysis, a specific compound (N-(6-(4-chlorophenoxy)hexyl)-N′-cyano-N″-(4-pyridyl)guanidine) was selected for its high antiproliferative activity in vitro and potent antitumour activity in the nude mouse model.

#Definitions

#In the present context, the term “prodrug” is intended to indicate a derivative of an active compound which does not, or does not necessarily, exhibit the physiological activity of the active compound, but which may be subjected to enzymatic cleavage such as hydrolysis in vivo so as to release the active compound on administration of the prodrug. In this particular instance, the prodrug comprises the active compound which in itself is highly lipophilic provided with a side chain with predominantly hydrophilic properties imparting improved solubility characteristics to the prodrug, thereby making it more suitable for parenteral administration in the form of a solution or for oral administration to obtain an improved bioavailability. More specifically, the hydrophilic side chain selected for the compounds of the present invention comprises an ester or carbonate group of formula R6—X3—(Y3)n—C(O)O—CHR1— (wherein R6, R1, X3, Y3 and n are as indicated above).

#The term “alkyl” is intended to indicate a univalent radical derived from straight, branched or cyclic alkane by removing a hydrogen atom from any carbon atom, preferably comprising from 1–8 carbon atoms. The term includes the subclasses primary, secondary and tertiary alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec.-butyl, isobutyl, tert.-butyl, isopentyl, isohexyl, cyclohexyl, cyclopentyl and cyclopropyl.