Patricia Escobar

Sensitivities of Leishmania species to hexadecylphosphocholine (miltefosine), ET-18-OCH3 (edelfosine) and amphotericin B

The sensitivities of both promastigote and amastigote stages of six species of Leishmania, L. donovani, L. major, L. tropica, L. aethiopica, L. mexicana and L. panamensis, were determined in vitro to the phospholipid drugs hexadecylphosphocholine (HPC, miltefosine) and ET-18-OCH(3) (edelfosine). In all assays L. donovani was the most sensitive species, with ED(50) values in the range of 0.12-1.32 microM against promastigotes and 1.2-4.6 microM against amastigotes. L. major was the least sensitive species in the majority of assays with ED(50) values for HPC in the range of 4.8-13.1 microM against promastigotes and for HPC and ET-18-OCH(3) in the range of 7.5-37.1 microM against amastigotes. Amphotericin B deoxycholate was used as the standard drug and gave submicromolar ED(50) values in all assays; L. mexicana was the least sensitive species to this drug.

Activities of Hexadecylphosphocholine (Miltefosine), AmBisome, and Sodium Stibogluconate (Pentostam) against Leishmania donovani in Immunodeficient scid Mice

ABSTRACT In both scid and BALB/c mouse-Leishmania donovani models, hexadecyphosphocholine (miltefosine) and AmBisome had similar levels of activity. In contrast, sodium stibogluconate (Pentostam) was significantly less active againstL. donovani in scid mice than in BALB/c mice. The in vitro anti-leishmanial activity of miltefosine was similar in peritoneal macrophages derived from both scid and BALB/c mice, whereas Pentostam and AmBisome were significantly more active in the latter.

In vitro activity of anti-leishmanial drugs against Leishmania donovani is host cell dependent.

OBJECTIVESnTo evaluate the in vitro activity of anti-leishmanial drugs against intracellular Leishmania donovani amastigotes in different types of macrophages.nnnMETHODSnMouse peritoneal macrophages (PEMs), mouse bone marrow-derived macrophages (BMMPhi), human peripheral blood monocyte-derived macrophages (PBM Phi) and differentiated THP-1 cells were infected with L. donovani. Cultures were incubated with sodium stibogluconate, amphotericin B deoxycholate (Fungizone), miltefosine or paromomycin sulphate over six concentrations in 3-fold serial dilutions for 5 days. Analysis was based on percentage inhibition of infected macrophages and EC(50)/EC(90) values estimated using sigmoidal curve-fitting.nnnRESULTSnThe rank order of drug activity was the same in the different macrophage populations: amphotericin B > miltefosine > sodium stibogluconate > paromomycin. However, significant (P < 0.05) differences were observed between populations. Amphotericin B was more active in PEMs and BMM Phi (EC(50) 0.02-0.06 microM) compared with PBM Phi and differentiated THP-1 cells (EC(50) 0.08-0.40 microM) and miltefosine was more active in PBM Phi (EC(50) 0.16-0.74 microM) compared with PEMs and BMM Phi (EC(50) 2.60-7.67 microM). Sodium stibogluconate displayed highest activity in PBM Phi (EC(50) 1.38-1.89 microg Sb(v)/mL), followed by PEMs (EC(50) 21.75-27.79 microg Sb(v)/mL) and BMM Phi and differentiated THP-1 cells (EC(50) 28.96-112.77 microg Sb(v)/mL). Paromomycin showed highest activity in PBM Phi (EC(50) 80.03-104.38 microM) and PEMs (EC(50) 75.42-201.63 microM).nnnCONCLUSIONSnIn vitro activity of anti-leishmanial drugs is host cell dependent. This has implications for: (i) the evaluation of in vitro drug activity; (ii) the evaluation of drug susceptibility of clinical isolates; and (iii) the standardization of anti-leishmanial drug assays.

Development of bis-thiazoles as inhibitors of triosephosphate isomerase from Trypanosoma cruzi. Identification of new non-mutagenic agents that are active in vivo.

The neglected disease American trypanosomiasis is one of the major health problems in Latin America. Triosephosphate isomerase from Trypanosoma cruzi (TcTIM), the etiologic agent of this disease, has been proposed as a druggable target. Some bis-benzothiazoles have been described as irreversible inhibitors of this enzyme. On the other hand, new bioactive furane-containing thiazoles have been described as excellent in vivo anti-T. cruzi agents. This encouraged us to design and develop new bis-thiazoles with potential use as drugs for American trypanosomiasis. The bis-thiazol 5, 3,3-allyl-2,2-bis[3-(2-furyl)-2-propenylidenehydrazono]-2,2,3,3-tetrahydro-4,4-bisthiazole, showed the best in vitro anti-T. cruzi profile with a higher selectivity index than the reference drugs Nifurtimox and Benznidazole against amastigote form of the parasite. This derivative displayed marginal activity against TcTIM however the bis-thiazol 14, 3-allyl-2-[3-(2-furyl)-2-propenylidenehydrazono]-3-phenyl-2-(3-phenyl-2-propenylidenehydrazono]-2,2,3,3-tetrahydro-4,4-bisthiazole, was an excellent inhibitor of the enzyme of the parasite. The absence of both in vitro mutagenic and in vivo toxicity effects, together with the activity of bis-thiazol 5in vivo, suggests that this compound is a promising anti-T. cruzi agent surpassing the hit-to-lead stage in the drug development process.

Antiprotozoal activity of essential oils derived from Piper spp. grown in Colombia

Plant species of the genus Piper are widely distributed throughout the Colombian territory. Eleven Piper spp. essential oils (EO1–EO11) were chemically characterized and tested against Trypanosoma cruzi, Leishmania (Leishmania) infantum and mammalian cells using standard in vitro assays. The selectivity index (SI) was calculated by the ratio of CC50 host cells to IC50 parasites. The EO from Piper var. brachypodom, obtained from two different locations (EO10 and EO11) in Chocó (Colombia), was active on the T. cruzi. It inhibited growth of epimastigotes (EO10: IC50 0.34u2009μg/mL; SI: 89.82) and amastigotes (EO11: IC50 22.72u2009μg/mL; SI: 2.31). EO11 was active against Leishmania (L.) infantum promastigotes (IC50 23.68u2009μg/mL; SI: 2.65), and less active on amastigotes (IC50 62.82u2009μg/mL). The EO10’s major component was trans-β-caryophyllene, which inhibited the T. cruzi (IC50 24.54u2009μg/mL) and L. the infantum (IC50 53.39u2009μg/mL), intracellular forms with some toxicity on Vero (CC50 12.93u2009μg/mL) and THP-1 (CC50 143.85u2009μg/mL). α-Pinene, the main constituent of Piper bredermeyeri, was active against the T. cruzi epimastigotes (IC50 2.74u2009μg/mL; SI: 4.22) and amastigotes (IC50 1.92u2009μg/mL; SI: 6.02). Linalool, limonene, 1,8-cineole and safrole were not active on intracellular parasites. The low SI obtained with both Piper brachypodon and trans-β-caryophyllene indicates a narrow window in their parasite-specific activity. Novel formulations contained active EOs or components could be designed in order to avoid toxicities and improve the cell internalization.

Identification of a New Amide-Containing Thiazole as a Drug Candidate for Treatment of Chagas' Disease

ABSTRACT Although the parasitic infection Chagas disease was described over 100 years ago, even now there are not suitable drugs. The available drugs nifurtimox and benznidazole have limited efficacies and tolerances, with proven mutagenic effects. Attempting to find appropriate drugs to deal with this problem, here we report on the development and pharmacological characterization of new amide-containing thiazoles. In the present study, we evaluated the in vitro and in vivo effects of new candidates against Trypanosoma cruzi, the etiological agent of Chagas disease. The lead amide-containing thiazole derivative had potent in vitro activity, an absence of both in vitro mutagenic and in vivo clastogenic effects, and excellent in vitro selectivity and in vivo tolerance. The compound suppressed parasitemia in mice, modifying the anti-T. cruzi antibodies like the reference drug, benznidazole, and displayed the lowest mortality among the tested drugs. The present evidence suggests that this compound is a promising anti-T. cruzi agent surpassing the lead optimization stage in drug development and leading to a candidate for preclinical study.