Metabolism of 1-0-[1'-14C]octadecyl-sn-glycerol in Leishmania donovani promastigotes. Ether lipid synthesis and degradation of the ether bond

Tolerability and Safety of Miltefosine for the Treatment of Cutaneous Leishmaniasis

Miltefosine, an orally administered drug, is an important component of the therapeutic arsenal against visceral and mucosal forms of leishmaniasis. However, data regarding the safety and tolerability of miltefosine treatment for cutaneous leishmaniasis (CL) are relatively limited. The aim of this study was to evaluate the tolerability, safety, and adverse events (AEs) of miltefosine treatment in patients with CL. In this cohort study, we reviewed the medical records of all miltefosine-treated patients between 1 January 2016 and 31 December 2022, at Israel Defense Forces military dermatology clinics and the dermatology and Tropical Medicine Clinics at Chaim Sheba Medical Center, Ramat-Gan, Israel. A total of 68 patients (54 males, 79%) with a median age of 30.3 ± 15.6 years (range: 18-88) were included in this study. Leishmania species were identified as L. major (n = 37, 54.4%), L. tropica (n = 12, 17.6%), L. braziliensis (n = 18, 26.5%), and L. infantum (n = 1, 1.5%) using polymerase chain reaction (PCR). Miltefosine tablets were administered orally at a dose of 50 mg, three times daily, for 28 days. Overall, 44 patients (65%) completed the 28-day treatment, and the remaining patients required dose reduction or early discontinuation of treatment. AEs (of any degree) were common, reported in 91% of patients. Both previously reported and previously unreported AEs were documented. Gastrointestinal symptoms (66.1%) and malaise (23.5%) typically occurred during the first two weeks of treatment and tended to subside. Other AEs, including acute renal failure (20.6%), sudden and severe pleuritic chest pain (7.6%), acne exacerbation (11.8%), suppuration of CL lesions (17.8%), and AEs related to the male genitourinary system (39.6% of males), typically occurred towards the end of treatment. The latter included testicular pain, epididymitis, diminution or complete absence of ejaculate, inability to orgasm, and impotence. Severe AEs necessitated treatment discontinuation (29.4%) or hospitalization (10.3%). URTI-like symptoms, arthritis, cutaneous eruption, pruritus, and laboratory abnormalities were also observed. Overall, the cure rate (for all patients combined) evaluated 3 months after the completion of treatment was 60%. The tolerability of miltefosine treatment for CL is low. Close clinical and laboratory monitoring is required during treatment, as severe AEs are not uncommon. As new insights regarding its toxicities emerge, further studies are required to define the role of miltefosine in the treatment of CL.

The preclinical discovery and development of oral miltefosine for the treatment of visceral leishmaniasis: a case history

INTRODUCTION

Visceral leishmaniasis (VL) is a vector-borne disease caused by Leishmania donovani or Leishmania infantum. Closely related to poverty, VL is fatal and represents one of the main burdens on public health in developing countries. Treatment of VL relies exclusively on chemotherapy, a strategy still experiencing numerous limitations. Miltefosine (MF) has been used in the chemotherapy of VL in some endemic areas, and has been expanded to other regions, being considered crucial in eradication programs.

AREAS COVERED

This article reviews the most relevant preclinical and clinical aspects of MF, its mechanism of action and resistance to Leishmania parasites, as well as its limitations. The authors also give their perspectives on the treatment of VL.

EXPERT OPINION

The discovery of MF represented an enormous advance in the chemotherapy of VL, since it was the first oral drug for this neglected disease. Beyond selection of resistant parasites due to drug pressure, several other factors can lead to treatment failure such as, for example, factors intrinsic to the host, parasite and the drug itself. Although its efficacy as a monotherapy has reduced over recent years, MF is still an important alternative in VL chemotherapy, especially when used in combination with other drugs.

Miltefosine for visceral and cutaneous leishmaniasis: drug characteristics and evidence-based treatment recommendations

Miltefosine is the only recognized oral agent with potential to treat leishmaniasis. Miltefosine had demonstrated very good cure rates for visceral leishmaniasis (VL) in India, Nepal, and Bangladesh, but high rates of clinical failures have been recently reported. Moderate efficacy has been observed for VL in East Africa, whereas data from Mediterranean countries and Latin America are scarce. Results have not been very promising for patients coinfected with VL and human immunodeficiency virus. However, miltefosine's long half-life and its oral administration could make it a good option for maintenance prophylaxis. Good evidence of efficacy has been documented in Old World cutaneous leishmaniasis (CL), and different cure rates among New World CL have been obtained depending on the geographical areas and species involved. Appropriate regimens for New World mucocutaneous leishmaniasis need to be established, although longer treatment duration seems to confer better results. Strategies to prevent the development and spread of miltefosine resistance are urgently needed.

Anthelmintic effects of alkylated diamines and amino alcohols against Schistosoma mansoni

Polyamines are substances involved in many aspects of cell growth, division, and differentiation. Because of the metabolic differences between host cells and parasite cells, polyamine metabolism has been considered as a potential target for the chemotherapy of parasitic diseases. The aim of this work was to evaluate the schistosomicidal activity of different N-alkylated diamines (3a-3h), amino alcohols (4a-4d), and glycosylated amino alcohols (10a-10d). Compounds were prepared by synthetic methods and submitted to in vitro evaluation against adult worms of Schistosoma mansoni. At 100 μM, 3b, 3e, and 3h as well as 4a, 4b, 4d, 10a, 10b, and 10d resulted in 100% mortality of adult schistosomes. Compound 3d (12.5 to 100 μM) caused the death of 100% of both male and female adult schistosomes, while 3f (12.5 to 100 μM) resulted in 100% mortality of only male adult worms, whereas no mortality in female worms was observed. Compounds 3d and 3f were also able to reduce viability and decrease production of developed eggs in comparison with the negative control group. Diamines 3d and 3f may represent useful lead compounds for further optimization in order to develop new schistosomicidal agents.

In vitro leishmanicidal activity of N-dodecyl-1,2-ethanediamine

Polyamine biosynthesis and inhibition in parasites have been an attractive chemotherapeutic approach in the design of novel antiparasitic drugs. We study in this work the effect of N-dodecyl-1,2-ethylenediamine (NDDE) on the morphology and replication of Leishmania using macrophages cultured from the peritoneal exudate of mice infected in vitro with three species of Leishmania: Leishmania (Leishmania) amazonensis, Leishmania (Viannia) brasiliensis and Leishmania (Leishmania) chagasi. The results showed that NDDE inhibited Leishmania amastigotes multiplication into inflammatory peritoneal cells in concentrations which were not toxic to mammalian cells (0.5-1μg/mL). An intracellular disorganization of the promastigote forms was observed by transmission electron microscopy after 3 to 24h of treatment with 1μg/mL NDDE, suggesting that this compound affects the viability of the parasite by an autophagy pathway.

Therapeutic switching in leishmania chemotherapy: a distinct approach towards unsatisfied treatment needs

Current drugs for the treatment of visceral leishmaniasis are inadequate. No novel compound is in the pipeline. Since economic returns on developing a new drug for neglected disease, leishmaniasis is so low that therapeutic switching represents the only realistic strategy. It refers to "alternative drug use" discoveries which differ from the original intent of the drug. Amphotericin B, paromomycin, miltefosine and many other drugs are very successful examples of "new drugs from old". This article reviews the discovery, growth and current status of these drugs and concluded that the potential of this approach (therapeutic switching) may use in the development of new antileishmanials in future also.

Cell biology of host-parasite membrane interactions in leishmaniasis

Molecular interactions at the host-parasite interface are crucial for the outcome of microbial infection, particularly in infection by intracellular parasites, such as Leishmania donovani and Leishmania mexicana, whose natural transmission begins with the delivery of the promastigote stage by the sandfly vector into the susceptible host. The ensuing event is intracellular parasitism of macrophages in the host by the amastigote stage. The establishment of this event in leishmaniasis must follow the sequence: (1) Leishmania-macrophage attachment; (2) entry of Leishmania species into macrophages; (3) intra-macrophage survival and differentiation of Leishmania species; and (4) intracellular multiplication of Leishmania species. This sequence precedes all clinical symptoms and pathological consequences in different forms of the disease. Study of these cellular events in Leishmania-macrophage systems in vitro indicates that host-parasite membrane interactions dictate many of the cellular events. Some morphological and functional changes of macrophages in response to leishmanial infection are related to their membrane activities, i.e. endocytosis and exocytosis. Leishmania parasites undergo profound plasma membrane-related changes, on entry into macrophages, at the morphological, antigenic and molecular levels. Most of these changes probably reflect necessary steps for the transition of Leishmania species from an extracellular to an intracellular life. The remarkable ability of Leishmania species subsequently to live in the secondary lysosome of the macrophage may also be due to certain intrinsic structures and dynamic properties of the parasite plasma membrane. Further analysis of leishmanial surface molecules and their interactions with macrophages is essential in any attempt to understand the pathogenic mechanism in leishmaniasis.

Miltefosine – discovery of the antileishmanial activity of phospholipid derivatives

Miltefosine (hexadecylphosphocholine, Impavidotrade mark), a novel antiprotozoal drug used for the treatment of visceral and cutaneous leishmaniasis, was identified and evaluated independently in the early 1980s as a potential anticancer drug in Germany and as an antileishmanial drug in the UK. Although miltefosine is not the most active compound of its class against Leishmania parasites in vitro, the early demonstration of activity after oral administration in experimental models of visceral leishmaniasis helped to bring this compound to the attention of WHO TDR for further development in a unique collaboration model with the pharmaceutical industry (Zentaris GmbH). Miltefosine is active against most Leishmania species, including those that cause cutaneous disease.

Miltefosine: oral treatment of leishmaniasis

The well-known problems of classic treatment of the leishmaniases with pentavalent antimony (reduced efficacy), difficulties of administration and increasing frequency and severity of adverse events have stimulated the search for new drugs to treat these diseases. Other injectable, oral and topical drugs have not been consistently effective, especially in the modern World. Beginning in 1998, Indian researchers conducted several trials with hexadecylphosphocholine (miltefosine) in patients with visceral leishmaniasis, and in 1999, clinical studies were initiated in Colombia for cutaneous disease. More than 2500 patients have been treated, including patients with diffuse cutaneous leishmaniasis, mucosal disease and patients coinfected with HIV. Cure rates between 91 and 100% were reached with a dose of 2.5 mg/kg/day for 28 days, with no difference between treatment-naive and relapsing patients. Mild gastrointestinal events were present in 35-60% of patients and 10-20% had mild transaminase and creatinine elevations. Miltefosine has potent leishmanicidal activity as a consequence of its interference in parasite metabolic pathways and the induction of apoptosis. Miltefosine is the first effective and safe oral agent with the potential to treat all major clinical presentations of leishmaniasis.

Antiprotozoal activities of phospholipid analogues

The antiprotozoal activity of phospholipid analogues, originally developed as anti-cancer drugs, has been determined in the past decade. The most susceptible parasites are Leishmania spp. and Trypanosoma cruzi with activity also shown against Trypanosoma brucei spp., Entamoeba histolytica and Acanthamoeba spp. Miltefosine, an alkylphosphocholine, was registered for the oral treatment of visceral leishmaniasis (VL) in India in March 2002. This review will focus on the biological activities of phospholipid analogues. Biochemical and molecular targets and mechanism(s) of action have been studied extensively in tumor cells but have not been determined in protozoa.

Leishmanicidal activity of some aliphatic diamines and amino-alcohols

A number of aliphatic diamines and amino-alcohols and several of their alkyl, acyl and carbamoyl derivatives, have been synthesised and evaluated in vitro on cultures of Leishmania spp. In general, diamine derivatives resulted to be more potent than their amino-alcohol or amino-ether analogues. Two diamine derivatives (8b and 9d) and one amino-alcohol (6a) showed a fair inhibition of parasite growth, at concentrations below 10 microg/mL, with potencies close to that of the reference drug, amphotericin B. Some SAR considerations have been deduced.

Ether--lipid (alkyl-phospholipid) metabolism and the mechanism of action of ether--lipid analogues in Leishmania

Ether-lipid (alkyl-phospholipid) analogues such as Miltefosine possess potent in vitro and in vivo anti-leishmanial activity and these compounds are currently undergoing clinical trials in humans. These analogues are also effective against Trypanosoma cruzi and Trypanosoma brucei subspecies but their mode of action is not known. Leishmania have high levels of ether-lipids and these are mainly found in the glycosylphosphatidylinositol-anchored glycolipids and glycoproteins present on the surface of the parasites. In Leishmania mexicana promastigotes we have studied both the initiating steps for the biosynthesis of ether-lipids, and key remodelling steps. The effect of Miltefosine and Edelfosine, on key enzymes involved in the metabolism of ether-lipids has been studied. The enzymes include dihydroxyacetonephosphate acyltransferase, sn-l-acyl-2-lyso-glycero-3-phosphocholine and sn-l-alkyl-2-lyso-glycero-3-phosphocholine acyltransferases. We confirm that the initiating steps in ether-lipid metabolism in Leishmania are present in glycosomes, and that Miltefosine or Edelfosine did not perturb these enzymes. The metabolism of the latter phosphatidylcholine base intermediates, which may be involved in the remodelling of acyl- and alkyl-glycerophospholipids, was also seemingly associated with glycosomes. Both Miltefosine and Edelfosine inhibited this microbody (glycosomal) located alkyl-specific-acyl-CoA acyltransferase in a dose-dependent manner with an inhibitory concentration of 50 microM. It is suggested therefore that a perturbation of ether-lipid remodelling could be responsible for the anti-leishmanial action of these drugs.

The dihydroxyacetonephosphate pathway for biosynthesis of ether lipids in Leishmania mexicana promastigotes

Biosynthetic studies using both [14C]- and [32P]-labelled substrates and a cell-free system to synthesise 1-O-alkyl moieties in glycerolipids, have shown that the three initial steps in ether-lipid biosynthesis in Leishmania mexicana promastigotes resemble those described for mammals and are associated with glycosomes. Purified glycosomes were able to sequentially synthesise the first intermediates of the ether-lipid biosynthetic pathway [acyl-dihydroxyacetonephosphate (DHAP), alkyl-DHAP and acyl/alkyl-glycerol-3-phosphate (G3P)] when incubated in the presence of radiolabelled DHAP, palmitoyl-CoA, hexadecanol and NADPH. However, when glycosomes were incubated under the same conditions in the presence of radiolabelled G3P, a rapid synthesis of acyl-G3P and phosphatidic acid was observed without any formation of alkyl-G3P, suggesting that the enzyme alkyl-synthase recognises only acyl-DHAP as substrate. Both the DHAP acyltransferase (DHAP-AT) and alkyl-DHAP synthase activities were located inside glycosomes whereas the alkyl/acyl-DHAP oxidoreductase activity was associated with the cytoplasmic face of the glycosomal membrane. The G3P acyltransferase (G3P-AT) and lyso-phosphatidic acid acyltransferase activities were not found inside glycosomes. The results suggest that the DHAP-AT and G3P-AT activities are catalysed by two distinct enzymes associated with different sub-cellular compartments.

Plasticity in chromosome number and testing of essential genes in Leishmania by targeting

We attempted to generate homozygous dhfr-ts (dihydrofolate reductase-thymidylate synthase) knockouts in virulent Leishmania major, an asexual diploid protozoan parasite. Transfection of a neo (neomycin phosphotransferase) targeting fragment yielded heterozygous replacement lines with high efficiency. However, second transfections with a hyg (hygromycin B phosphotransferase) targeting fragment in the presence of metabolites shown to rescue homozygous knockouts in attenuated Leishmania did not yield the expected dhfr-ts- thymidine auxotrophs obtained previously with attenuated lines. Molecular karyotype, Southern blot, and flow cytometric DNA content analysis of clonal transfectants revealed three classes: (i) genomic tetraploids, containing two wild-type dhfr-ts chromosomes and one neo and one hyg replacement chromosome; (ii) aneuploid trisomic lines with one wild-type dhfr-ts and one neo and one hyg replacement chromosome; (iii) diploids bearing homologous integration of the targeting fragment without replacement. Aneuploid and tetraploid lines predominated. This confirms the common impression that natural populations of Leishmania are often aneuploid. The remarkable ability of these parasites to undergo and tolerate changes in chromosome number suggests a general method for testing whether genes are essential for growth in vitro, as the ability of Leishmania to simultaneously undergo homologous gene replacement while retaining wild-type genes by increasing chromosome number provides a diagnostic and positive experimental result. Our results show that virulent Leishmania require at least one copy of dhfr-ts and argue that DHFR-TS plays an unanticipated role in addition to its role in the de novo synthesis of thymidine. These results also have implications for genetic tests of the organization of Leishmania populations.

Lipid analyses of isolated surface membranes of Leishmania donovani promastigotes

Constituent lipids of surface membranes (SM) isolated from Leishmania donovani promastigotes were analyzed and compared with those obtained from whole cells and an isolated kinetoplast-mitochondrion fraction (KM). On a dry weight basis, the total extractable lipids constituted approximately 47%, 12% and 24% of the SM, cells and KM, respectively. The total lipids of SM, cells and KM all were composed of approximately 70% phospholipids (PL), 20-25% neutral lipids and 5-10% glycolipids. Sterols and diglycerides composed 60% and 30%, respectively, of the various neutral lipid fractions. Several mannose- and galactose-containing glycolipids were fractionated but not identified. The glycolipid fractions from cells and SM had demonstrable antigenic activities with rabbit anti-SM sera. Striking quantitative differences were apparent between the PL profiles of the 3 cellular components examined. The PL of SM, whole cells and KM, respectively, were composed of: 15%, 51% and 24% phosphatidylcholine; 37%, 13% and 11% phosphatidylethanolamine (PE); 18%, 10% and 14% phosphatidylinositol; 10%, 1% and 4% phosphatidylserine and traces of cardiolipin, phosphatidylglycerol and phosphatidic acid. An unknown PL containing sphingosine, choline and vicinal hydroxyl groups but no free amino moieties made up approximately 19% of the PL of SM and whole cells, but it constituted approximately 27% of the PL of KM. The PL side chain constituents of whole cells and SM were composed mainly of longchain fatty acids (C18-20). Further, over 50% of the PE of SM was in the alkyl and alK-1-enyl ether forms. These SM properties might contribute to the organism's resistance to digestion in the hydrolytic environs of both its insect vector and mammalian hosts.