Identification of Phenylpyrazolone Dimers as a New Class of Anti‐Trypanosoma cruzi Agents

Abstract

Chagas disease is becoming a worldwide problem; it is currently estimated that over six million people are infected. The two drugs in current use, benznidazole and nifurtimox, require long treatment regimens, show limited efficacy in the chronic phase of infection, and are known to cause adverse effects. Phenotypic screening of an in‐house library led to the identification of 2,2′‐methylenebis(5‐(4‐bromophenyl)‐4,4‐dimethyl‐2,4‐dihydro‐3H‐pyrazol‐3‐one), a phenyldihydropyrazolone dimer, which shows an in vitro pIC50 value of 5.4 against Trypanosoma cruzi. Initial optimization was done by varying substituents of the phenyl ring, after which attempts were made to replace the phenyl ring. Finally, the linker between the dimer units was varied, ultimately leading to 2,2′‐methylenebis(5‐(3‐bromo‐4‐methoxyphenyl)‐4,4‐dimethyl‐2,4‐dihydro‐3H‐pyrazol‐3‐one (NPD‐0228) as the most potent analogue. NPD‐0228 has an in vitro pIC50 value of 6.4 against intracellular amastigotes of T. cruzi and no apparent toxicity against the human MRC‐5 cell line and murine cardiac cells.

Efficacy of Novel Pyrazolone Phosphodiesterase Inhibitors in Experimental Mouse Models of Trypanosoma cruzi

“…To answer that, some of the most active compounds on amastigotes were evaluated on the Y strain, whereby no significant variation was noted, hence arguing against variability in drug susceptibility according to parasite strain. The present findings corroborate previous studies (20) showing that the pyrazolone NPD-227 has quite similar potency upon intracellular amastigotes regardless of the studied strain (Y and Colombiana, with EC 50 values of 0.1 and 0.5 M, respectively). Prior exposure of mammalian cells to NPD-227 before infection by T. cruzi did not impact clearance or reduction of parasite intracellular load, while pretreatment using the aromatic diamidine DB569 induced a 85% reduction of parasite burdens.…”

“…Twenty millimolar stock solutions (in 100% dimethyl sulfoxide [DMSO], maximum final concentration of 1% in assays) were prepared using the set of 17 pyrazolone test compounds (Fig. 1) synthetized as reported (20), except NPD-977, NPD-126, and NPD-134, which were prepared by analogous methods and their chemical characterization is given in Table 1. As a reference drug, benznidazole (N-benzyl-2-[2-nitroimidazol-1-yl]acetamide2-nitroimidazole) (Laboratório Farmacêutico do Estado de Pernambuco, Brazil) was used in parallel (25).…”

“…Among them, derivatives containing the pyrazolone nucleus were shown to be active on bacteria and fungi (16), on the nervous system (17,18), and as anticancer agents (19). The pyrazolone NPD-227 is a potent in vitro anti-T. cruzi agent with 50% effective concentration (EC 50 ) values ranging between 0.1 and 0.5 M against intracellular forms belonging to different discrete typing units (DTU-II for the Y strain and DTU-I for the Colombiana strain) (20).…”

Exploring the Antiplasmodial 2‐Aminopyridines as Potential Antitrypanosomal Agents

“…brucei growth at an IC 50 of 3.2 μM. However, values in this range are typical of antitrypanosomal compounds in early development …”