Antiparasitic efficacies

Webster, L. T., Jr, Tracy, J. W., Blumer, J. L., Catto, B. A. and Sissors, D. L. (1984) Relationships of niridazole metabolism to antiparasitic efficacy and host toxicity. In Proceedings oflUPHAR Ninth International Congress of Pharmacology. Macmillan, London, pp. 363-367. 

Enyzme catalysis is thus essential for all life. Hence the selective inhibition of critical enzymes of infectious organisms (e.g., viruses, bacteria, and multicellular parasites) is an attractive means of chemotherapeutic intervention for infectious diseases. This strategy is well represented in modem medicine, with a significant portion of antiviral, antibiotic, and antiparasitic drugs in clinical use today deriving their therapeutic efficacy through selective enzyme inhibition (see Table 1.1 for some examples). 

The naturally occuring avermectins are a family of eight, pentacyclic structures containing a sixteen-membered macrolide ring which are produced by Streptomyces avermitilis (Fig. 6) [60]. These eight compounds differ in structure due to the variability of PKS starter unit at C-25, the 0-methylation pattern at C-5, and the hydration-dehydration pattern at C-22/C-23. Other closely related natural products include the milbemycins and the nemadectins. The avermectins exhibit potent broad spectrum antiparasitic activity, and the semi-synthetic Ivermectin 29 (hydrogenated avermectin Bl) displays even greater efficacy [60,61]. 

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