Identification of New Antileishmanial Leads from Hits Obtained by High-Throughput Screening

Abstract

A previous screen of ϳ200,000 compounds from the PubChem database identified 70 compounds possessing 50% effective concentrations (EC 50 s) below 1 M against Leishmania major promastigotes that were not toxic to mammalian epithelial cancer cells at this concentration (E. Combinations of existing antileishmanial drugs have also been studied. Different combinations of treatment with single-dose liposomal amphotericin B followed by short courses of miltefosine were extremely effective, with a single dose of liposomal amphotericin B at 5 mg/kg of body weight followed by a 10-day course of miltefosine resulting in a cure rate of 98% (32). This combination was evaluated together with other combinations consisting of (i) a single dose of 5 mg/kg liposomal amphotericin with a 10-day course of paromomycin and (ii) a 10-day course of both paromomycin and miltefosine, with all of these combinations providing a cure rate of 97% or greater (33). When given in a single 10 mg/kg dose, liposomal amphotericin B was shown to be highly effective against VL, producing a cure rate of 95.7% (30). Single-dose liposomal amphotericin B is proposed to play a central role in a VL elimination program in India, Nepal, and Bangladesh (12).SharlowDespite these improvements in VL treatment on the Indian subcontinent, unmet needs in leishmaniasis chemotherapy still exist. In Africa, only the antimonial drug sodium stibogluconate and liposomal amphotericin B are registered for treating VL. Antimonial compounds, which have been replaced by the drugs listed above for treating VL on the Indian subcontinent due to widespread antimonial resistance (31), have been used for many years against leishmaniasis, and their use is plagued by the long duration of therapy and by the associated side effects (15,18,23,31). Liposomal amphotericin B appears to be less effective against VL in Brazil (1) and in Africa (1, 14, 26) compared to India, and the expense of liposomal amphotericin B also limits its widespread use (9). Paromomycin is inexpensive and is thus a good candidate for VL treatment in African countries, but a 15 mg/kg/day regimen of paramomycin for 21 days was inferior to standard treatment with sodium stibogluconate (20 mg/kg

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

“…FICs were used for constructing the isobolograms, with the sum of the FICs (⌺FICs) being equal to the FIC of DB766 plus the FIC of posaconazole, thus allowing the determination of the nature of the DB766-posaconazole interaction. The susceptibility of intracellular ␤-lactamase-expressing L. donovani to DB766, posaconazole, and fixed-ratio combinations of these two compounds was determined as outlined previously (13). FIC, ⌺FIC, and mean ⌺FIC values were calculated as described above for L. donovani axenic amastigotes.…”

“…Leishmania donovani MHOM/SD/62/ 1S-CL2 D promastigotes were adapted to axenic amastigote forms by culturing the former at 37°C in a humidified 5% CO 2 atmosphere in axenic amastigote medium as described previously (12). For intracellular assays, ␤-lactamase-expressing L. donovani promastigotes (provided by Frederick Buckner, University of Washington) were maintained as outlined earlier (13). Wild-type and CYP5122A1 half-knockout (HKO) promastigotes of L. donovani MHOM/IN/80/DD8 (14) were used in DB766 and ketoconazole susceptibility assays.…”

Evaluation of Arylimidamides DB1955 and DB1960 as Candidates against Visceral Leishmaniasis and Chagas' Disease: In Vivo Efficacy, Acute Toxicity, Pharmacokinetics, and Toxicology Studies

“…The potency of AIAs and control compounds for VL (amphotericin B) and for CD (Bz) against intracellular L. amazonensis and L. donovani and bloodstream trypomastigotes and amastigotes of T. cruzi strain Y was determined as follows. Intracellular Leishmania assays were conducted as described previously for L. donovani (29) and L. amazonensis (13). For the analysis of the effects of the compounds upon bloodstream trypomastigote forms, 5 ϫ 10 6 /ml parasites were incubated for 24 h at 37°C in RPMI 1640 medium supplemented with 10% fetal calf serum in the presence or absence of serial dilutions of each compound.…”

Drug Discovery Algorithm for Cutaneous Leishmaniasis

“…In this regard, we note that de Muylder and others have recently compared the frequency of in vitro hits by using promastigotes, axenic amastigotes, and within-macrophage amastigotes for 909 compounds, 8 and a publication by Zhu and others is also now available. 9 The in vitro experience of de Muylder and others suggested that screening against the promastigote stage of L. donovani, although more suitable for automation, fails to identify all active compounds and leads to numerous false-positive hits. 8 In vivo evaluation of potential oral agents for CL agents.…”