Inhibitors of ergoesterol

Diverse azolic products have been used with success in human and veterinary medicine. These drugs interface in sterol synthesis, and together with other heterocyclic nitrogenated compounds belong to the group of drugs that inhibit ergosterol synthesis. T. cruzi has ergosterol; the antimycotic prevents its synthesis without affecting the human host, who has cholesterol. Cholesterol differs from

ergosterol by the presence of a 24-methyl group and double bonds in 7A and 22A. The three enzymes that produce the methylation and the double bonds of ergosterol do not have counterparts in mammalian cholesterol synthesis. Several of these azolic products have been studied for Chagas disease treatment: miconazole, econa- zole, ketoconazole, itraconazole, fluconazole, ravuconazole, and posaconazole (Fig. 31.2). With these drugs a parasitological cure has been obtained in mice with acute and chronic Chagas disease.¹⁶

Ketoconazole, itraconazole, and DO 870 inhibit cytochrome P450-dependent lenosterol C14 demethylase, thus reducing ergoesterol synthesis. Although mammals have this enzyme; it is much less sensitive to the drugs than those of fungi or of T. cruzi. Itraconazole has been applied in the treatment of chronic indeterminate Chagas disease and CCC. The drug prevents cardiopathy, compared to controls without therapy, and improves 50% of the electrocardiographic alterations of patients with CCC. Twenty percent of these cases are “cured” of parasites, determined by xenodiagnosis, PCR in blood, hybridization probes in blood, PCR in dejections, and hybridization probes in dejections of triatomines

Figure 31.2 Chemical structure of triazole derivatives, inhibitors of Trypanosoma cruzi sterol C14a sterol demethylase.

applied to these patients. However, none of the “cured” cases presented a negative conventional serology (indirect hemagglutination [HAI], indirect IF, or ELISA) for T. cruzi.^10,17,18 When the drug DO 870 was administered to mice with acute infection (10⁵ T. cruzi Y strain), the treated animals lived longer than the controls without treatment or treated with NF or ketoconazole, 105 days survival versus 21. A 60% cure was obtained by control of parasitemia, hemocultures, and PCR. When this therapy was applied to mice with chronic infection (10⁴ T. cruzi Bertoldo strain), after 40—50 days 50% of the controls survived and 30% of these had negative PCR, while the parasitological cure was 80—90% in the treated group.¹⁶ Today DO 870 has been discontinued, but posaconazole (SCH 56592), MS-207, 147 (Ravuconazole), VR-9825, and TAK-187 have demonstrated activity against T. cruzi in vitro and in vivo. Of these compounds, posaconazole has proved to be efficient, and have very good tolerance in studies performed in patients with oropharyngeal candidiasis.¹⁹ It has been observed that the majority of these compounds (Posaconazole, Ravuconazole, VR-9825, and TAK-187) have activity against T. cruzi strains partially resistant to NF, benznidazole (BNZ), and in which ketaconazole does not function.²⁰ Posaconazole with amiodarona, an antiarrhythmic drug, has a synergistic activity against T. cruzi in vitro and in vivo.²¹

A multinational study started in 2011 with 145 chronic chagasic patients with an indeterminate period treated with posaconazole (POS) for 60 days. The patients were divided into four groups: (1) Received POS 400 mg twice a day; (2) Received POS 400 mg twice a day plus 200 mg BNZ twice a day; (3) Received placebo 400 mg twice a day; and (4) Received BNZ 200 mg twice a day plus placebo 400 mg twice a day. The results of the efficiency of the drugs will be ready in 2016 (Stop Chagas Phase II2011).^22,23

In 2011 a study in Spain started with 79 patients with chronic indeterminate Chagas disease treated with BNZ or POS for 60 days (Chagasazol). The patients were divided into three groups: (1) received BNZ 150 mg twice a day; (2) received POS 400 mg twice a days (high dose); and (3) POS 100 mg twice day (low dose). The treatment failure at 12 months of follow up was 38.4% for BNZ, 80.7% and 92.3% for POS high and low dose, respectively.

In 2011 in Cochabamba and Tarija, Bolivia, a survey was performed with ravuconazole (RAV, compound E1224) phase II for 60 days in chronic chagasic patients with an indeterminate period. 230 patients were divided into five groups of 46 patients each. Group I, II, and III received RAV in high, middle, and low doses, respectively. The group IV received placebo and the group V received BNZ. The adherence of the drug was good, the secondary effects were scarce, but the compliance of the drug (RAV) in acute cases was 30% lower than the 70—75% obtained with NF and BNZ, respectively²⁴ (Table 31.2).

Ofloxacine

Ofloxacine is an inhibitor of topoisomerase II, an essential enzyme for bacteria. This drug blocks the differentiation of amastigotes in tissue cultures.

Table 31.2 Comparative efficacy of posaconazole, ravuconazole, and benznidazole for the treatment of chronic indeterminate Chagas disease

* Positive T. cruzi PCR. ^(a) Estimated; ^(b) Twice daily; ^(c) Amount not specified; ^(d) Study ongoing.

Source: Modified from Keenan M, Chaplin J. A new era for Chagas disease drug discovery? In: Lawton G, Witty D, editors. Progress in medicinal chemistry, vol. 54; 2015. p. 185—230.

Ultramicroscopy shows morphological alterations of the kinetoplast of T. cruzi, suggesting that ofloxacine destroys the parasites. In vivo experiments did not confirm the utility of this enzymatic inhibitor.