Novel Arylimidamides for Treatment of Visceral Leishmaniasis

Abstract

Arylimidamides (AIAs) represent a new class of molecules that exhibit potent antileishmanial activity (50% inhibitory concentration [IC 50 ], <1 M) against both Leishmania donovani axenic amastigotes and intracellular Leishmania, the causative agent for human visceral leishmaniasis (VL). A systematic lead discovery program was employed to characterize in vitro and in vivo antileishmanial activities, pharmacokinetics, mutagenicities, and toxicities of two novel AIAs, DB745 and DB766. They were exceptionally active (IC 50 < 0.12 M) against intracellular L. donovani, Leishmania amazonensis, and Leishmania major and did not exhibit mutagenicity in an Ames screen. DB745 and DB766, given orally, produced a dose-dependent inhibition of liver parasitemia in two efficacy models, L. donovani-infected mice and hamsters. Most notably, DB766 (100 mg/kg of body weight/day for 5 days) reduced liver parasitemia in mice and hamsters by 71% and 89%, respectively. Marked reduction of parasitemia in the spleen (79%) and bone marrow (92%) of hamsters was also observed. Furthermore, these compounds distributed to target tissues (liver and spleen) and had a moderate oral bioavailability (up to 25%), a large volume of distribution, and an elimination half-life ranging from 1 to 2 days in mice. In a repeat-dose toxicity study of mice, there was no indication of liver or kidney toxicity for DB766 from serum chemistries, although mild hepatic cell eosinophilia, hypertrophy, and fatty changes were noted. These results demonstrated that arylimidamides are a promising class of molecules that possess good antileishmanial activity and desirable pharmacokinetics and should be considered for further preclinical development as an oral treatment for VL.Leishmaniasis, a neglected tropical disease, is caused by parasitic protozoa of the genus Leishmania, including 20 species that are pathogenic for humans (21). Clinical manifestations of leishmaniasis mainly consist of cutaneous, mucocutaneous, visceral, and post-kala-azar dermal leishmaniasis, with symptoms ranging from skin and mucosal ulceration to systemic infection that is fatal if left untreated (6). An estimated 12 million people are currently infected with Leishmania, and up to 350 million people in 88 countries are at risk of infection (35). Approximately 2 million new cases of leishmaniasis are believed to occur annually, with 1.5 million for cutaneous leishmaniasis and 0.5 million for visceral leishmaniasis (VL). In macrophages, Leishmania amastigotes adapt to thrive in an acidic subcellular compartment, the parasitophorous vacuole (PV; pH ϳ5) (2), where they maintain a neutral intracellular pH within the parasite by an energy-dependent process (9). Multiple layers of membrane barriers (i.e., host macrophage plasma membrane, phagolysosomal membrane, and Leishmania amastigote plasma membrane) presumably present a formidable challenge for chemotherapeutic agents to target Leishmania parasites in mammalian hosts.Current chemotherapies for leishmaniasis have many limitations, including resis...

Studies on the Antileishmanial Mechanism of Action of the Arylimidamide DB766: Azole Interactions and Role of CYP5122A1

“…Drugs and reagents. The CellTiter reagent was obtained from Promega (Madison, WI), miltefosine was purchased from Cayman Chemical Company (Ann Arbor, MI), and DB1111, DB766, DB745, and DB1852 were synthesized according to known methods (5,8,16). All other reagents were purchased from Sigma-Aldrich (St. Louis, MO), unless otherwise indicated.…”

“…Although the design of AIAs was inspired by diamidine antimicrobials such as pentamidine, AIAs possess physicochemical properties that are distinct from those of diamidines (5). These differences are believed to translate into improved activity against intracellular pathogens, such as Mycobacterium tuberculosis (6), Trypanosoma cruzi (7), and Leishmania (8).…”

Unveiling the effects of berenil, a DNA-binding drug, on Trypanosoma cruzi: implications for kDNA ultrastructure and replication

“…These compounds have been tested successfully against T. cruzi bloodstream trypomastigotes (de ) and against L. donovani (Wang et al 2010), thus representing alternative drugs for trypanosomiasis treatments. Diamidines promote ultrastructural modifications in T. cruzi amastigotes that are similar to those described in this work, especially mitochondrial swelling and kDNA disorganization (Silva et al 2007).…”

The adaptive potential of a survival artist: characterization of thein vitrointeractions ofToxoplasma gondiitachyzoites with di-cationic compounds in human fibroblast cell cultures

“…Since its discovery, pentamidine has been successfully applied to treat African trypanosomiasis, leishmaniasis, and malaria in humans, and the pentamidinederivative diminazene aceturate is commonly used for trypanosome chemotherapy in livestock (Werbovetz, 2006). More recently, novel analogues, known as arylimidamides, with a more favourable pharmacokinetic profile, improved bioavailability and lower host toxicity were shown to be effective against Leishmania donovani and Trypanosoma cruzi in vitro and in vivo (Wang et al 2010;Batista et al 2010a).…”