ABSTRACT
The ancestral origins of the lytic cell death mode, necroptosis, lie in host defense. However, the dysregulation of necroptosis in inflammatory diseases has led to widespread interest in targeting the pathway therapeutically. This mode of cell death is executed by the terminal effector, the MLKL pseudokinase, which is licensed to kill following phosphorylation by its upstream regulator, RIPK3 kinase. The precise molecular details underlying MLKL activation are still emerging and, intriguingly, appear to mechanistically-diverge between species. Here, we report the structure of the human RIPK3 kinase domain alone and in complex with the MLKL pseudokinase. These structures reveal how human RIPK3 structurally differs from its mouse counterpart, and how human RIPK3 maintains MLKL in an inactive conformation prior to induction of necroptosis. Residues within the RIPK3:MLKL C-lobe interface are crucial to complex assembly and necroptotic signaling in human cells, thereby rationalizing the strict species specificity governing RIPK3 activation of MLKL.
Subject(s)
Cell Death/physiology , Necroptosis/physiology , Protein Kinases/chemistry , Protein Kinases/metabolism , Receptor-Interacting Protein Serine-Threonine Kinases/chemistry , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Animals , Cell Death/genetics , HT29 Cells , Humans , Mice , Necroptosis/genetics , Phosphorylation , Protein Conformation , Protein Interaction Domains and Motifs , Protein Kinases/genetics , Receptor-Interacting Protein Serine-Threonine Kinases/genetics , Recombinant Proteins , Signal TransductionABSTRACT
Necroptosis is an inflammatory form of programmed cell death that has been implicated in various human diseases. Compound 2 is a more potent analogue of the published compound 1 and inhibits necroptosis in human and murine cells at nanomolar concentrations. Several target engagement strategies were employed, including cellular thermal shift assays (CETSA) and diazirine-mediated photoaffinity labeling via a bifunctional photoaffinity probe derived from compound 2. These target engagement studies demonstrate that compound 2 binds to all three necroptotic effector proteins (mixed lineage kinase domain-like protein (MLKL), receptor-interacting serine/threonine protein kinase 1 (RIPK1) and receptor-interacting serine/threonine protein kinase 3 (RIPK3)) at different levels in vitro and in cells. Compound 2 also shows efficacy in vivo in a murine model of systemic inflammatory response syndrome (SIRS).
Subject(s)
Necroptosis/drug effects , Phenylurea Compounds/therapeutic use , Protein Kinase Inhibitors/therapeutic use , Signal Transduction/drug effects , Sulfonamides/therapeutic use , Animals , Cell Line, Tumor , Female , Humans , Mice, Inbred C57BL , Phenylurea Compounds/metabolism , Phenylurea Compounds/pharmacokinetics , Protein Binding , Protein Kinase Inhibitors/metabolism , Protein Kinase Inhibitors/pharmacokinetics , Protein Kinases/metabolism , Receptor-Interacting Protein Serine-Threonine Kinases/antagonists & inhibitors , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Sulfonamides/metabolism , Sulfonamides/pharmacokinetics , Systemic Inflammatory Response Syndrome/drug therapyABSTRACT
Genetic alterations in the fibroblast growth factor receptors (FGFRs) have been described in multiple solid tumours including bladder cancer, head and neck and lung squamous cell carcinoma (SqCC). However, recent clinical trials showed limited efficacy of FGFR-targeted therapy in lung SqCC, suggesting combination therapy may be necessary to improve patient outcomes. Here we demonstrate that FGFR therapy primes SqCC for cell death by increasing the expression of the pro-apoptotic protein BIM. We therefore hypothesised that combining BH3-mimetics, potent inhibitors of pro-survival proteins, with FGFR-targeted therapy may enhance the killing of SqCC cells. Using patient-derived xenografts and specific inhibitors of BCL-2, BCL-XL, and MCL-1, we identified a greater reliance of lung SqCC cells on BCL-XL and MCL-1 compared to BCL-2 for survival. However, neither BCL-XL nor MCL-1 inhibitors alone provided a survival benefit in combination FGFR therapy in vivo. Only triple BCL-XL, MCL-1, and FGFR inhibition resulted in tumour volume regression and prolonged survival in vivo, demonstrating the ability of BCL-XL and MCL-1 proteins to compensate for each other in lung SqCC. Our work therefore provides a rationale for the inhibition of MCL-1, BCL-XL, and FGFR1 to maximize therapeutic response in FGFR1-expressing lung SqCC.
Subject(s)
Antineoplastic Agents/pharmacology , Carcinoma, Squamous Cell/drug therapy , Lung Neoplasms/drug therapy , Myeloid Cell Leukemia Sequence 1 Protein/antagonists & inhibitors , Receptors, Fibroblast Growth Factor/antagonists & inhibitors , bcl-X Protein/antagonists & inhibitors , Animals , Apoptosis/drug effects , Apoptosis Regulatory Proteins/metabolism , Bcl-2-Like Protein 11/metabolism , Carcinoma, Squamous Cell/metabolism , Cell Line, Tumor , Drug Therapy, Combination/methods , Humans , Lung Neoplasms/metabolism , Mice , Mice, Inbred NOD , Mice, SCID , Xenograft Model Antitumor Assays/methodsABSTRACT
A number of diazepines are known to inhibit bromo- and extra-terminal domain (BET) proteins. Their BET inhibitory activity derives from the fusion of an acetyl-lysine mimetic heterocycle onto the diazepine framework. Herein we describe a straightforward, modular synthesis of novel 1,2,3-triazolobenzodiazepines and show that the 1,2,3-triazole acts as an effective acetyl-lysine mimetic heterocycle. Structure-based optimization of this series of compounds led to the development of potent BET bromodomain inhibitors with excellent activity against leukemic cells, concomitant with a reduction in c-MYC expression. These novel benzodiazepines therefore represent a promising class of therapeutic BET inhibitors.
ABSTRACT
Anaemia is a major global health problem arising from diverse causes and for which improved therapeutic strategies are needed. Erythroid cells can undergo apoptotic cell death and loss of pro-survival BCL-XL is known to trigger apoptosis during late-stage erythroid development. However, the mechanism by which loss or pharmacological blockade of BCL-XL leads to erythroid cell apoptosis remains unclear. Here we sought to identify the precise stage of erythropoiesis that depends on BCL-XL. We also tested whether deficiency of BIM or PUMA, the two main pro-apoptotic antagonists of BCL-XL, could prevent reticulocyte death and anaemia caused by BCL-XL loss. Using an in vivo mouse model of tamoxifen-inducible Bclx gene deletion and in vitro assays with a BCL-XL-selective inhibitor, we interrogated each stage of erythrocyte differentiation for BCL-XL dependency. This revealed that reticulocytes, but not orthochromatic erythroblasts, require BCL-XL for their survival. Surprisingly, concurrent loss of BIM or PUMA had no significant impact on the development of anemia following acute BCL-XL deletion in vivo. However, analysis of mixed bone marrow chimaeric mice revealed that loss of PUMA, but not loss of BIM, partially alleviated impaired erythropoiesis caused by BCL-XL deficiency. Insight into how the network of pro-survival and pro-apoptotic proteins works will assist the development of strategies to mitigate the effects of abnormal cell death during erythropoiesis and prevent anaemia in patients treated with BCL-XL-specific BH3-mimetic drugs.
Subject(s)
Anemia/genetics , Apoptosis Regulatory Proteins/genetics , Apoptosis/genetics , Bcl-2-Like Protein 11/genetics , Gene Expression Regulation , Tumor Suppressor Proteins/genetics , bcl-X Protein/genetics , Anemia/metabolism , Anemia/pathology , Animals , Apoptosis Regulatory Proteins/deficiency , Bcl-2-Like Protein 11/deficiency , Benzothiazoles/pharmacology , Cell Survival , Disease Models, Animal , Erythroblasts/metabolism , Erythroblasts/pathology , Erythropoiesis/genetics , Gene Deletion , Humans , Isoquinolines/pharmacology , Mice , Mice, Knockout , Organ Specificity , Protein Domains , Reticulocytes/metabolism , Reticulocytes/pathology , Signal Transduction , Tamoxifen/pharmacology , Tumor Suppressor Proteins/deficiency , bcl-X Protein/antagonists & inhibitors , bcl-X Protein/deficiencyABSTRACT
Lung squamous cell carcinoma (SqCC) is a molecularly complex and genomically unstable disease. No targeted therapy is currently approved for lung SqCC, although potential oncogenic drivers of SqCC have been identified, including amplification of the fibroblast growth factor receptor 1 (FGFR1). Reports from a recently completed clinical trial indicate low response rates in patients treated with FGFR tyrosine kinase inhibitors, suggesting inadequacy of FGFR1 amplification as a biomarker of response, or the need for combination treatment. We aimed to develop accurate models of lung SqCC and determine improved targeted therapies for these tumors. We show that detection of FGFR1 mRNA by RNA in situ hybridization is a better predictor of response to FGFR inhibition than FGFR1 gene amplification using clinically relevant patient-derived xenograft (PDX) models of lung SqCC. FGFR1-overexpressing tumors were observed in all histologic subtypes of non-small cell lung cancers (NSCLC) as assessed on a tissue microarray, indicating a broader range of tumors that may respond to FGFR inhibitors. In FGFR1-overexpressing PDX tumors, we observed increased differentiation and reduced proliferation following FGFR inhibition. Combination therapy with cisplatin was able to increase tumor cell death, and dramatically prolonged animal survival compared to single-agent treatment. Our data suggest that FGFR tyrosine kinase inhibitors can benefit NSCLC patients with FGFR1-overexpressing tumors and provides a rationale for clinical trials combining cisplatin with FGFR inhibitors. Mol Cancer Ther; 16(8); 1610-22. ©2017 AACR.
Subject(s)
Carcinoma, Squamous Cell/drug therapy , Cisplatin/therapeutic use , Lung Neoplasms/drug therapy , Receptor, Fibroblast Growth Factor, Type 1/antagonists & inhibitors , Xenograft Model Antitumor Assays , Animals , Carcinoma, Squamous Cell/genetics , Cell Differentiation/drug effects , Cell Line, Tumor , Cell Proliferation/drug effects , Cisplatin/pharmacology , Genotype , Humans , Lung Neoplasms/genetics , Mice, Inbred NOD , Phosphatidylinositol 3-Kinases/metabolism , Phosphoinositide-3 Kinase Inhibitors , RNA, Messenger/genetics , RNA, Messenger/metabolism , Receptor, Fibroblast Growth Factor, Type 1/genetics , Receptor, Fibroblast Growth Factor, Type 1/metabolism , Survival AnalysisABSTRACT
Many cancers overexpress one or more of the six human pro-survival BCL2 family proteins to evade apoptosis. To determine which BCL2 protein or proteins block apoptosis in different cancers, we computationally designed three-helix bundle protein inhibitors specific for each BCL2 pro-survival protein. Following in vitro optimization, each inhibitor binds its target with high picomolar to low nanomolar affinity and at least 300-fold specificity. Expression of the designed inhibitors in human cancer cell lines revealed unique dependencies on BCL2 proteins for survival which could not be inferred from other BCL2 profiling methods. Our results show that designed inhibitors can be generated for each member of a closely-knit protein family to probe the importance of specific protein-protein interactions in complex biological processes.
Subject(s)
Gene Expression Regulation, Neoplastic/genetics , Neoplasms/genetics , Proto-Oncogene Proteins c-bcl-2/genetics , Apoptosis/genetics , Computational Biology , Humans , Neoplasms/pathology , Protein Structure, Secondary , Proto-Oncogene Proteins c-bcl-2/chemistryABSTRACT
New therapeutic targets are needed to address the poor prognosis of patients with high-risk multiple myeloma. Myeloma cells usually express a range of the prosurvival BCL2 proteins. To define the hierarchy of their relative importance for maintaining the survival of myeloma cells, we targeted each of them in a large panel of cell lines, using pharmacological inhibitors or gene editing or by peptide-based approaches, alone or in combination. The majority of well-established immortalized cell lines (17/25) or low-passage myeloma cell lines (5/7) are readily killed when MCL1 is targeted, even including those cell lines sensitive to BCL2 inhibition. Targeting MCL1 also constrained the growth of myeloma in vivo. We also identified a previously unrecognized subset of myeloma that is highly BCLXL-dependent, and has the potential for cotargeting MCL1 and BCLXL. As MCL1 is pivotal for maintaining survival of most myelomas, it should be prioritized for targeting in the clinic once high-quality, validated inhibitors become available.
Subject(s)
Molecular Targeted Therapy , Multiple Myeloma/drug therapy , Multiple Myeloma/pathology , Myeloid Cell Leukemia Sequence 1 Protein/metabolism , Proto-Oncogene Proteins c-bcl-2/metabolism , Antineoplastic Agents/pharmacology , Apoptosis/drug effects , CRISPR-Cas Systems/genetics , Cell Line, Tumor , Cell Survival/drug effects , Gene Editing , Humans , Ligands , Peptides/pharmacology , Small Molecule Libraries/pharmacologyABSTRACT
Inhibition of prosurvival BCL2 family members can induce autophagy, but the mechanism is controversial. We have provided genetic evidence that BCL2 family members block autophagy by inhibiting BAX and BAK1, but others have proposed they instead inhibit BECN1. Here we confirm that small molecule BH3 mimetics can induce BAX- and BAK1-independent MAP1LC3B/LC3B lipidation, but this only occurred at concentrations far greater than required to induce apoptosis and dissociate canonical BH3 domain-containing proteins that bind more tightly than BECN1. Because high concentrations of a less-active enantiomer of ABT-263 also induced BAX- and BAK1-independent LC3B lipidation, induction of this marker of autophagy appears to be an off-target effect. Indeed, robust autophagic flux was not induced by BH3 mimetic compounds in the absence of BAX and BAK1. Therefore at concentrations that are on target and achievable in vivo, BH3 mimetics only induce autophagy in a BAX- and BAK1-dependent manner.
Subject(s)
Autophagy , Microtubule-Associated Proteins/metabolism , Aniline Compounds/pharmacology , Animals , Apoptosis/drug effects , Autophagy/drug effects , Biphenyl Compounds/pharmacology , Bridged Bicyclo Compounds, Heterocyclic/pharmacology , Cells, Cultured , Mice , Nitrophenols/pharmacology , Piperazines/pharmacology , Proto-Oncogene Proteins c-bcl-2/metabolism , Sulfonamides/pharmacology , bcl-2 Homologous Antagonist-Killer Protein/drug effects , bcl-2 Homologous Antagonist-Killer Protein/metabolism , bcl-2-Associated X Protein/drug effects , bcl-2-Associated X Protein/metabolismABSTRACT
Necroptosis is considered to be complementary to the classical caspase-dependent programmed cell death pathway, apoptosis. The pseudokinase Mixed Lineage Kinase Domain-Like (MLKL) is an essential effector protein in the necroptotic cell death pathway downstream of the protein kinase Receptor Interacting Protein Kinase-3 (RIPK3). How MLKL causes cell death is unclear, however RIPK3-mediated phosphorylation of the activation loop in MLKL trips a molecular switch to induce necroptotic cell death. Here, we show that the MLKL pseudokinase domain acts as a latch to restrain the N-terminal four-helix bundle (4HB) domain and that unleashing this domain results in formation of a high-molecular-weight, membrane-localized complex and cell death. Using alanine-scanning mutagenesis, we identified two clusters of residues on opposing faces of the 4HB domain that were required for the 4HB domain to kill cells. The integrity of one cluster was essential for membrane localization, whereas MLKL mutations in the other cluster did not prevent membrane translocation but prevented killing; this demonstrates that membrane localization is necessary, but insufficient, to induce cell death. Finally, we identified a small molecule that binds the nucleotide binding site within the MLKL pseudokinase domain and retards MLKL translocation to membranes, thereby preventing necroptosis. This inhibitor provides a novel tool to investigate necroptosis and demonstrates the feasibility of using small molecules to target the nucleotide binding site of pseudokinases to modulate signal transduction.
Subject(s)
Apoptosis , Necrosis , Protein Kinases/metabolism , Adenosine Triphosphate/metabolism , Amino Acid Motifs , Amino Acid Sequence , Animals , Binding Sites , Cell Membrane/metabolism , Enzyme Activation , Inhibitory Concentration 50 , Mice , Mice, Transgenic , Molecular Sequence Data , Mutation , Phosphorylation , Protein Structure, Secondary , Protein Structure, Tertiary , Protein Transport , Receptor-Interacting Protein Serine-Threonine Kinases/metabolism , Recombinant Proteins/metabolism , Sequence Homology, Amino AcidABSTRACT
INTRODUCTION: The bromodomain (BRD) and extra-C terminal domain (BET) protein family consists of four members (BRD2, BRD3, BRD4 and BRDT). These "epigenetic readers" bind to acetyllysine (KAc) residues on the tails of histones H3 and H4, and regulate chromatin structure and gene expression. There is increasing evidence of their role in human disease, and recently a number of small-molecule inhibitors have been reported. There is increasing interest in the inhibition of BET proteins for a variety of therapeutic applications that have resulted in considerable patent activity from academia and biotechnology and pharmaceutical companies. AREAS COVERED: Data supporting the use of BET inhibitors in treating disease are outlined, and the current patent literature is discussed. The survey is focused on patents claiming compounds as BET inhibitors and additional patents covering compounds now reported as BET inhibitors have been included. EXPERT OPINION: There is now compelling preclinical data demonstrating BET inhibition as a strategy to target processes known to be involved in disease development and progression with clinical trials of two bona fide BET inhibitors now underway. Patent activity in this area is increasing with initial activity focused on variations to reported BET inhibitors and more recent patents disclosing novel chemotypes as BET inhibitors.
Subject(s)
Nuclear Proteins/antagonists & inhibitors , Animals , Drug Design , Drug and Narcotic Control , Epigenesis, Genetic/drug effects , Gene Expression Regulation/drug effects , Humans , Molecular Structure , Nuclear Proteins/chemistry , Nuclear Proteins/metabolism , Patents as Topic , Protein Structure, Tertiary , RNA-Binding Proteins/antagonists & inhibitors , RNA-Binding Proteins/chemistry , RNA-Binding Proteins/metabolism , Structure-Activity Relationship , Transcription Factors/antagonists & inhibitors , Transcription Factors/chemistry , Transcription Factors/metabolismABSTRACT
Kinetic experiments were performed on the catalytic cycle of a trifunctional organocatalyst-promoted counterion catalysis of asymmetric aza-Morita-Baylis-Hillman reactions. The catalysis was found to be first order in the trifunctional catalyst with the Michael addition as the rate-limiting step. Temperature variation changed the rate of catalysis but not the enantioselectivity of the reaction.
Subject(s)
Aldehydes/chemistry , Imines/chemistry , Alcohols/chemical synthesis , Alcohols/chemistry , Aldehydes/chemical synthesis , Amines/chemical synthesis , Amines/chemistry , Catalysis , Imines/chemical synthesis , Kinetics , Stereoisomerism , TemperatureABSTRACT
Tropheryma whipplei, which causes Whipple disease, is found in human feces and may cause gastroenteritis. To show that T. whipplei causes gastroenteritis, PCRs for T. whipplei were conducted with feces from children 2-4 years of age. Western blotting was performed for samples from children with diarrhea who had positive or negative results for T. whipplei. T. whipplei was found in samples from 36 (15%) of 241 children with gastroenteritis and associated with other diarrheal pathogens in 13 (33%) of 36. No positive specimen was detected for controls of the same age (0/47; p = 0.008). Bacterial loads in case-patients were as high as those in patients with Whipple disease and significantly higher than those in adult asymptomatic carriers (p = 0.002). High incidence in patients and evidence of clonal circulation suggests that some cases of gastroenteritis are caused or exacerbated by T. whipplei, which may be co-transmitted with other intestinal pathogens.
Subject(s)
Actinomycetales Infections/microbiology , Gastroenteritis/microbiology , Tropheryma/isolation & purification , Actinomycetales Infections/epidemiology , Actinomycetales Infections/physiopathology , Blotting, Western , Child, Preschool , DNA, Bacterial/genetics , DNA, Bacterial/isolation & purification , Diarrhea/microbiology , Feces/microbiology , Female , France/epidemiology , Gastroenteritis/epidemiology , Gastroenteritis/physiopathology , Humans , Incidence , Male , Phylogeny , Polymerase Chain Reaction , Prospective Studies , Tropheryma/geneticsABSTRACT
Fast and enantioselective aza-Morita-Baylis-Hillman reactions between electron-deficient or electron-rich aromatic N-tosyl imines and methyl vinyl ketone were achieved at ambient temperature using asymmetric counterion-directed catalysis promoted by trifunctional organocatalysts with a Brønsted base as the activity switch after protonation with benzoic acid.
Subject(s)
Aza Compounds/chemical synthesis , Phenols/chemistry , Phosphines/chemistry , Temperature , Aza Compounds/chemistry , Benzoic Acid/chemistry , Catalysis , Imines/chemistry , Ketones/chemistry , Molecular Structure , Protons , StereoisomerismABSTRACT
This report describes the case of a 10-year-old boy with cutaneous leishmaniasis presumed to be caused by Leishmania major and successfully treated with oral azithromycin. Clinical studies using azithromycin for the treatment of cutaneous leishmaniasis are reviewed.
Subject(s)
Azithromycin/therapeutic use , Leishmaniasis, Cutaneous/drug therapy , Child , Humans , MaleSubject(s)
Hydrocephalus/virology , Lymphocytic Choriomeningitis/diagnosis , Lymphocytic choriomeningitis virus/isolation & purification , Acyclovir/therapeutic use , Anti-Bacterial Agents/therapeutic use , Antiviral Agents/therapeutic use , Brain/pathology , Cefotaxime/therapeutic use , Child, Preschool , Humans , Hydrocephalus/surgery , Lymphocytic Choriomeningitis/drug therapy , Lymphocytic choriomeningitis virus/genetics , Magnetic Resonance Imaging , Male , RNA, Viral/cerebrospinal fluid , RNA, Viral/isolation & purification , Tomography, X-Ray Computed , Vancomycin/therapeutic use , Ventriculoperitoneal Shunt , VentriculostomyABSTRACT
Vaccines are essential to prevent, control (as for poliomyelitis) or eradicate (as for smallpox) infectious diseases. In some cases, when a curative treatment is not available or efficient, they are the only way to fight the spread of the disease, by prevention. The national recommended childhood immunization schedule may vary each year and in each country (changes in infections characters, outbreaks, new vaccines availability...). In this review, new patterns in childhood vaccination in France are discussed.
Subject(s)
Immunization Programs/statistics & numerical data , Immunization Schedule , Adolescent , Child , Child Welfare , Child, Preschool , Communicable Diseases/immunology , Disease Outbreaks , France , Humans , Infant , Public PolicyABSTRACT
BACKGROUND: France is the European country with the highest number of imported malaria cases (7,500 in 2000). The aim of this prospective study was to evaluate the nature and efficacy of prophylactic measures in children under 15 years of age referred for malaria. METHODS: Post travel questionnaires were given to the parents of malarial children in the emergency room. The study took place in two university hospitals in Marseilles, southern France, from August to October 2001. RESULTS: Eighty-eight children under 15 years of age were included in this 3-month period. Most of them had been infected in Comoro archipelago. Almost two-thirds used bed nets, but only 47% did so every night. Sprayed bed nets were used by 23%. Average compliances with cutaneous repellents, bedroom repellents and long-sleeved clothing were 32%, 24% and 26%, respectively. Air conditioners were uncommon. Only 22% of the children used chemoprophylaxis correctly, according to French recommendations. Five percent did not use any chemoprophylaxis, and 61% reported non recommended drug use. Although all the children traveled to chloroquine-resistant areas, chemoprophylaxis with mefloquine was less common than that with chloroquine + proguanil. No child fully complied with French recommendations concerning both anti mosquito measures and chemoprophylaxis. CONCLUSIONS: Insufficient use of antimalaria precautions by traveling families is associated with the high incidence of pediatric imported malaria in southern France. Travelers' education should be increased to allow the optimization of malaria prophylaxis.
Subject(s)
Antimalarials/therapeutic use , Culicidae , Insect Bites and Stings/prevention & control , Malaria/drug therapy , Malaria/prevention & control , Adolescent , Animals , Bedding and Linens/statistics & numerical data , Child , Child, Preschool , Chloroquine/therapeutic use , Clothing/statistics & numerical data , Emergency Service, Hospital , Female , France , Health Care Surveys , Humans , Infant , Insect Repellents/therapeutic use , Malaria/microbiology , Male , Mefloquine/therapeutic use , Patient Compliance/statistics & numerical data , Plasmodium/isolation & purification , Proguanil/therapeutic use , Prospective Studies , Travel/statistics & numerical dataABSTRACT
The leishmaniases are protozoan diseases caused by Leishmania parasites. The first-line treatment of its visceral forms is pentavalent antimony (meglumine antimoniate or sodium stibogluconate), but toxicity is frequent with this drug. Moreover antimony unresponsiveness is increasing in Leishmania infantum and L. donovani foci, both in immunocompetent and in immunosuppressed patients. Amphotericin B is a polyene macrolide antibiotic that binds to sterols in cell membranes. It is the most active antileishmanial agent in use. Its infusion-related and renal toxicity may be reduced by lipid-based delivery. Liposomal amphotericin B (AmBisome); Gilead Science, Paris, France) seems to be less toxic than other amphotericin B lipid formulations (Amphocil); Liposome Technology Inc., Menlo Park, CA, USA, Amphotec); Ben Venue Laboratories Inc., Bedford, OH, USA). Optimal drug regimens of AmBisome) vary from one geographical area to another. In the Mediterranean Basin, a total dose of 18 mg/kg (3 mg/kg on days 1-5 and 3 mg/kg on day 10) could be used as first-line treatment of visceral leishmaniasis in immunocompetent patients. In immunocompromised patients, especially those co-infected with HIV, relapses are frequent with AmBisome), as with other drugs.