Structure-activity relationship of new growth inhibitors of Trypanosoma cruzi.

Several drugs bearing the 4-phenoxyphenoxy skeleton and other closely related structures were designed, synthesized, and evaluated as antiproliferative agents against Trypanosoma cruzi, the etiologic agent of Chagas' disease. The new class of drugs was envisioned by modifying the nonpolar 4-phenoxyphenoxy moiety replacing selected aromatic protons by different groups via electrophilic aromatic substitution reactions as well as introducing a sulfur atom at the polar extreme. Of the designed compounds, sulfur-containing derivatives were shown to be potent antireplicative agents against T. cruzi. Among these drugs, 4-phenoxyphenoxyethyl thiocyanate (compound 56) proved to be an extremely active growth inhibitor of the epimastigote forms of T. cruzi and displayed an IC50 of 2.2 microM. Under the same assay conditions, this drug was much more active than Nifurtimox, one of the drugs currently in clinical use to control this disease. This thiocyanate derivative was also a very active inhibitor against the intracellular form of the parasite at the nanomolar level. Other sulfur derivatives prepared also exhibited very potent antiproliferative action against T. cruzi. The presence of a sulfur atom at the polar extreme for this family of compounds seems to be very important for biological action because this atom was always associated with high inhibition values. 4-Phenoxyphenoxyethyl thiocyanate presents very good prospective not only as a lead drug but also as a potential chemotherapeutic agent.

Design, synthesis, and biological evaluation of new growth inhibitors of Trypanosoma cruzi (epimastigotes).

As a continuation of our project aimed at the search for new chemotherapeutic agents against Chagas' disease, several drugs structurally related to the insect growth regulator Fenoxycarb and the naturally occurring juvenile hormone of insects were designed, synthesized, and evaluated as antiproliferative agents against the parasite responsible of this disease. Isoprenoid derivatives (compounds 33, 34, 36, and 37) were potent growth inhibitors of Trypanosoma cruzi epimastigotes. In addition, taking into account the high activity observed for compound 30 and the inhibitory action of related compounds, the allyl ether moiety bonded at the polar extreme of these inhibitors proved to be a promising group for the design of new drugs.