A basis set of polyamine analogues was designed and synthesized. These compounds were used to initiate a systematic investigation of the role of chain length, terminal nitrogen alkyl group size, and symmetry of the methylene backbone in the antineoplastic properties of polyamine analogues. New synthetic methods predicated on our earlier polyamine fragment synthesis are described for accessing the tetraamines of interest. An unsymmetrically substituted diamine reagent, N-(tert-butoxycarbonyl)-N,N'-bis(mesitylenesulfonyl)-1,4-diaminobu tane, was developed for entry into unsymmetrical tetraamines. All of the tetraamines synthesized were first evaluated in a murine leukemia L1210 cell IC50 assay at 48 and 96 h. In an attempt to correlate this behavior with some aspect of polyamine metabolism, each compound was tested for its ability to compete with spermidine for the polyamine uptake apparatus, its impact on the polyamine biosynthetic enzymes ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC), and its effect on the polyamine-catabolizing enzyme spermidine/spermine N1-acetyltransferase (SSAT) and on polyamine pools. While there was no obvious correlation between the 48 and 96 h IC50's and the impact of the analogues on polyamine metabolism, there were other structure-activity relationships. Correlations were observed to exist between chain length and IC50's and between terminal alkyl substituents and impact on Ki, ODC, and AdoMetDC. Also, preliminary studies suggest a relationship may exist between the 48 and 96 h IC50 activities and the analogue's chronic toxicity in vivo. Finally, when the overall length of the polyamine backbone was held constant, the symmetry of the methylene chains of the polyamine fragments was shown to be unimportant to the compound's activity.

Additional structure-activity studies of desferrithiocin analogues are carried out. The effects of stereochemistry at C-4 on the ligands' iron clearing efficiency are reviewed and assessed using the enantiomers 4,5-dihydro-2-(2, 4-dihydroxyphenyl)thiazole-4(R)-carboxylic acid and 4,5-dihydro-2-(2, 4-dihydroxyphenyl)thiazole-4(S)-carboxylic acid. The utility of 4'-hydroxylation as a method of reducing the toxicity of desazadesferrithiocin analogues is also examined further with the synthesis and in vivo comparison of 4, 5-dihydro-2-(2-hydroxyphenyl)-4-methylthiazole-4(S)-carboxylic acid, which is the natural product 4-methylaeruginoic acid, and 4, 5-dihydro-2-(2,4-dihydroxyphenyl)-4-methylthiazole-4(S)-carboxylic acid. The stereochemistry at C-4 is shown to have a substantial effect on the iron clearing efficiency of desferrithiocin analogues, as does C-4'-hydroxylation on the toxicity profile. All of the compounds are evaluated in a bile-duct-cannulated rodent model to determine iron clearance efficiency and are carried forward to the iron-overloaded primate for iron clearing measurements. On the basis of the results of the present work, although 4,5-dihydro-2-(2, 4-dihydroxyphenyl)thiazole-4(S)-carboxylic acid is still the most promising candidate for clinical evaluation, 4,5-dihydro-2-(2, 4-dihydroxyphenyl)-4-methylthiazole-4(S)-carboxylic acid (4'-hydroxydesazadesferrithiocin) also merits further preclinical assessment.

A systematic investigation of the impact of spermidine analogues both in vitro and in vivo is described. The study characterizes the effects of these analogues on L1210 cell growth, polyamine pools, ornithine decarboxylase, S-adenosyl-L-methionine decarboxylase, spermidine/spermine N1-acetyltransferase, the maintenance of cellular charge, i.e., cationic equivalence associated with the polyamines and their analogues, and compares their ability to compete with spermidine for transport. The findings clearly demonstrate that the activity of the linear polyamine analogues is highly dependent on the length of the triamines and the size of the N(alpha),N(omega)-substituents. It appears that there is an optimum chain length for various activities and that the larger the N(alpha),N(omega)-alkyls, the less active the compound. Metabolic transformation including N-dealkylation of these compounds is also evaluated. While there is no monotonic relationship between chain length and the ability of the analogue to be metabolized, the dipropyl triamines are clearly more actively catabolized than the corresponding methyl and ethyl systems. A comparison of the triamines with the corresponding tetraamines is made throughout the text regarding both in vitro activity against L1210 cells and in vivo toxicity measurements, suggesting that several triamine analogues may offer therapeutic advantages over the corresponding tetraamines.