Treatment of visceral leishmaniasis with sterically stabilized liposomes containing camptothecin

Nanomaterials for detection of biomolecules and delivering therapeutic agents in theragnosis: A review

Nanomaterials are emerging facts used to deliver therapeutic agents in living systems. Nanotechnology is used as a compliment by implementing different kinds of nanotechnological applications such as nano-porous structures, functionalized nanomaterials, quantum dots, carbon nanomaterials, and polymeric nanostructures. The applications are in the initial stage, which led to achieving several diagnoses and therapy in clinical practice. This review conveys the importance of nanomaterials in post-genomic employment, which includes the design of immunosensors, immune assays, and drug delivery. In this view, genomics is a molecular tool containing large databases that are useful in choosing an apt molecular inhibitor such as drug, ligand and antibody target in the drug delivery process. This study identifies the expression of genes and proteins in analysis and classification of diseases. Experimentally, the study analyses the design of a disease model. In particular, drug delivery is a boon area to treat cancer. The identified drugs enter different phase trails (Trails I, II, and III). The genomic information conveys more essential entities to the phase I trials and helps to move further for other trails such as trails-II and III. In such cases, the biomarkers play a crucial role by monitoring the unique pathological process. Genetic engineering with recombinant DNA techniques can be employed to develop genetically engineered disease models. Delivering drugs in a specific area is one of the challenging issues achieved using nanoparticles. Therefore, genomics is considered as a vast molecular tool to identify drugs in personalized medicine for cancer therapy.

The Natural Alkaloid Tryptanthrin Induces Apoptosis-like Death in Leishmania spp

Leishmaniasis is a vector-borne disease against which there are no approved vaccines, and the treatment is based on highly toxic drugs. The alkaloids consist of a chemical class of natural nitrogen-containing substances with a long history of antileishmanial activity. The present study aimed at determining the antileishmanial activity and in silico pharmacokinetic and toxicological potentials of tryptanthrin alkaloid. The anti-Leishmania amazonensis and anti-L. infantum assays were performed against both promastigotes and intracellular amastigotes. Cellular viability was determined by parasites’ ability to grow (promastigotes) or differentiate (amastigotes) after incubation with tryptanthrin. The mechanisms of action were explored by mitochondrion dysfunction and apoptosis-like death evaluation. For the computational pharmacokinetics and toxicological analysis (ADMET), tryptanthrin was submitted to the PreADMET webserver. The alkaloid displayed anti-promastigote activity against L. amazonensis and L. infantum (IC₅₀ = 11 and 8.0 μM, respectively). Tryptanthrin was active against intracellular amastigotes with IC₅₀ values of 75 and 115 μM, respectively. Mitochondrial membrane depolarization was observed in tryptanthrin-treated promastigotes. In addition, parasites undergoing apoptosis-like death were detected after 18 h of exposure. In silico ADMET predictions revealed that tryptanthrin has pharmacokinetic and toxicological properties similar to miltefosine. The results presented herein demonstrate that tryptanthrin is an interesting drug candidate against leishmaniasis.

Nanostructured delivery systems with improved leishmanicidal activity: a critical review

Leishmaniasis is a vector-borne zoonotic disease caused by protozoan parasites of the genus Leishmania, which are responsible for numerous clinical manifestations, such as cutaneous, visceral, and mucocutaneous leishmaniasis, depending on the site of infection for particular species. These complexities threaten 350 million people in 98 countries worldwide. Amastigotes living within macrophage phagolysosomes are the principal target of antileishmanial treatment, but these are not an easy target as drugs must overcome major structural barriers. Furthermore, limitations on current therapy are related to efficacy, toxicity, and cost, as well as the length of treatment, which can increase parasitic resistance. Nanotechnology has emerged as an attractive alternative as conventional drugs delivered by nanosized carriers have improved bioavailability and reduced toxicity, together with other characteristics that help to relieve the burden of this disease. The significance of using colloidal carriers loaded with active agents derives from the physiological uptake route of intravenous administered nanosystems (the phagocyte system). Nanosystems are thus able to promote a high drug concentration in intracellular mononuclear phagocyte system (MPS)-infected cells. Moreover, the versatility of nanometric drug delivery systems for the deliberate transport of a range of molecules plays a pivotal role in the design of therapeutic strategies against leishmaniasis. This review discusses studies on nanocarriers that have greatly contributed to improving the efficacy of antileishmaniasis drugs, presenting a critical review and some suggestions for improving drug delivery.

Perspectives on biologically active camptothecin derivatives

Camptothecins (CPTs) are cytotoxic natural alkaloids that specifically target DNA topoisomerase I. Research on CPTs has undergone a significant evolution from the initial discovery of CPT in the late 1960s through the study of synthetic small-molecule derivatives to investigation of macromolecular constructs and formulations. Over the past years, intensive medicinal chemistry efforts have generated numerous CPT derivatives. Three derivatives, topotecan, irinotecan, and belotecan, are currently prescribed as anticancer drugs, and several related compounds are now in clinical trials. Interest in other biological effects, besides anticancer activity, of CPTs is also growing exponentially, as indicated by the large number of publications on the subject during the last decades. Therefore, the main focus of the present review is to provide an ample but condensed overview on various biological activities of CPT derivatives, in addition to continued up-to-date coverage of anticancer effects.

Trypanosomatids topoisomerase re-visited. New structural findings and role in drug discovery

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There is an urgent need of new treatments against trypanosomatids-borne diseases.

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DNA topoisomerases are pointed as potential drug targets against unicellular parasites.

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Trypanosomatids have a full set of DNA topoisomerases in both nucleus and kinetoplast.

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TopII and TopIII are located in the kinetoplast and fully involved in kDNA replication.

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Tritryps TopIB differ in structure from mammalian’s pointing to an attractive target.

The Trypanosomatidae family, composed of unicellular parasites, causes severe vector-borne diseases that afflict human populations worldwide. Chagas disease, sleeping sickness, as well as different sorts of leishmaniases are amongst the most important infectious diseases produced by Trypanosoma cruzi, Trypanosoma brucei and Leishmania spp., respectively. All these infections are closely related to weak health care services in low-income populations of less developed and least economically developed countries. Search for new therapeutic targets in order to hit these pathogens is of paramount priority, as no effective vaccine is currently in use against any of these parasites. Furthermore, present-day chemotherapy comprises old-fashioned drugs full of important side effects. Besides, they are prone to produce tolerance and resistance as a consequence of their continuous use for decades. DNA topoisomerases (Top) are ubiquitous enzymes responsible for solving the torsional tensions caused during replication and transcription processes, as well as in maintaining genomic stability during DNA recombination. As the inhibition of these enzymes produces cell arrest and triggers cell death, Top inhibitors are among the most effective and most widely used drugs in both cancer and antibacterial therapies. Top relaxation and decatenation activities, which are based on a common nicking–closing cycle involving one or both DNA strands, have been pointed as a promising drug target. Specific inhibitors that bind to the interface of DNA-Top complexes can stabilize Top-mediated transient DNA breaks. In addition, important structural differences have been found between Tops from the Trypanosomatidae family members and Tops from the host. Such dissimilarities make these proteins very interesting for drug design and molecular intervention. The present review is a critical update of the last findings regarding trypanosomatid’s Tops, their new structural features, their involvement both in the physiology and virulence of these parasites, as well as their use as promising targets for drug discovery.

Nanotechnology in therapeutics: a focus on nanoparticles as a drug delivery system

Continuing improvement in the pharmacological and therapeutic properties of drugs is driving the revolution in novel drug delivery systems. In fact, a wide spectrum of therapeutic nanocarriers has been extensively investigated to address this emerging need. Accordingly, this article will review recent developments in the use of nanoparticles as drug delivery systems to treat a wide variety of diseases. Finally, we will introduce challenges and future nanotechnology strategies to overcome limitations in this field.

Indotecan (LMP400) and AM13-55: two novel indenoisoquinolines show potential for treating visceral leishmaniasis

Visceral leishmaniasis is an emerging neglected tropical disease (NTD) caused by the protozoan Leishmania infantum in the countries bordering the Mediterranean Basin. Currently there is no effective vaccine against this disease, and the therapeutic approach is based on toxic derivatives of Sb(V). Therefore, the discovery of new therapeutic targets and the development of drugs designed to inhibit them comprise an extremely important approach to fighting this disease. DNA topoisomerases (Top) have been identified as promising targets for therapy against leishmaniasis. These enzymes are involved in solving topological problems generated during replication, transcription, and recombination of DNA. Being unlike that of the mammalian host, type IB DNA topoisomerase (TopIB) from Leishmania spp. is a unique bisubunit protein, which makes it very interesting as a selective drug target. In the present investigation, we studied the effect of two TopIB poisons with indenoisoquinoline structure, indotecan and AM13-55, on a murine BALB/c model of infected splenocytes with L. infantum, comparing their effectiveness with that of the clinically tested leishmanicidal drug paromomycin. Both compounds have high selectivity indexes compared with uninfected splenocytes. SDS-KCl-precipitable DNA-protein complexes in Leishmania promastigotes and in vitro cleaving assays confirmed that these drugs are Top poisons. The inhibitory potency of both indenoisoquinolines on L. infantum recombinant TopIB was assessed in vitro, with results showing that indotecan was the most active compound, preventing the relaxation of supercoiled DNA. Experimental infections in susceptible BALB/c mice treated with 2.5 mg/kg body weight/day once every other day for a total of 15 days showed that indotecan cleared more than 80% of the parasite burden of the spleen and liver, indicating promising activity against visceral leishmaniasis.

Current developments in the therapy of protozoan infections

Protozoan parasites cause serious human and zoonotic infections, including life-threatening diseases such as malaria, African and American trypanosomiasis, and leishmaniasis. These diseases are no more common in the developed world, but together they still threaten about 40% of the world population (WHO estimates). Mortality and morbidity are high in developing countries, and the lack of vaccines makes chemotherapy the only suitable option. However, available antiparasitic drugs are hampered by more or less marked toxic side effects and by the emergence of drug resistance. As the main prevalence of parasitic diseases occurs in the poorest areas of the world, the interest of the pharmaceutical companies in the development of new drugs has been traditionally scarce. The establishment of public-private partnerships focused on tropical diseases is changing this situation, allowing the exploitation of the technological advances that took place during the past decade related to genomics, proteomics, and in silico drug discovery approaches. These techniques allowed the identification of new molecular targets that in some cases are shared by different parasites. In this review we outline the recent developments in the fields of protease and topoisomerase inhibitors, antimicrobial and cell-penetrating peptides, and RNA interference. We also report on the rapidly developing field of new vectors (micro and nano particles, mesoporous materials) that in some cases can cross host or parasite natural barriers and, by selectively delivering new or already in use drugs to the target site, minimize dosage and side effects.

Drug delivery strategies for therapy of visceral leishmaniasis

IMPORTANCE OF THE FIELD

Visceral leishmaniasis (VL) is the most overwhelming type of leishmaniasis associated with the poverty of developing countries and usually mortal if untreated. Most of the conventionally used dosage forms offer us the shortcomings of toxic side effects and emergence of drug resistance. Several efforts have been made to overcome the barriers involved in the treatment of VL. Colloidal carriers extensively represent the drug delivery systems (DDSs) for intracellular localization of antileishmanial compounds in macrophage-rich organs such as liver, spleen and bone marrow. These DDSs offer superior therapeutic efficacy over the conventional treatment in terms of site-specific drug delivery with reduced side effects. However, after 35 years of research in the field, AmBisome (Amphotericin B liposome for injection, Astellas Pharma US, Inc.) is the only DDS used against the VL.

AREAS COVERED IN THIS REVIEW

A literature search was performed (for drugs and DDSs against VL) on PubMed and through Google.

WHAT THE READER WILL GAIN

This review aims to describe the pathophysiology of VL and its current conventional treatment with special reference to DDSs designed against VL.

TAKE HOME MESSAGE

On reviewing the conventional drugs and DDSs developed against VL, it is concluded that advances in the field of targeted drug delivery can result in more efficient strategies for the therapy of VL.

Deletion study of DNA topoisomerase IB from Leishmania donovani: searching for a minimal functional heterodimer

The substantial differences between trypanosomal and leishmanial DNA topoisomerase IB concerning to their homologues in mammals have provided a new lead in the study of the structural determinants that can be effectively targeted. Leishmania donovani, the causative agent of visceral leishmaniasis, contains an unusual heterodimeric DNA topoisomerase IB. The catalytically active enzyme consists of a large subunit (LdTopIL), which contains the non-conserved N-terminal end and the phylogenetically conserved “core” domain, and of a small subunit (LdTopIS) which harbors the C-terminal region with the characteristic tyrosine residue in the active site. Heterologous co-expression of LdTopIL and LdTopIS genes in a topoisomerase I deficient yeast strain, reconstitutes a fully functional enzyme LdTopIL/S which can be used for structural studies. An approach by combinatorial cloning of deleted genes encoding for truncated versions of both subunits was used in order to find out structural insights involved in enzyme activity or protein-protein interaction. The role played by the non-conserved N-terminal extension of LdTopIL in both relaxation activity and CPT sensitivity has been examined co-expressing the full-length LdTopIS and a fully active LdTopIΔS deletion with several deletions of LdTopIL lacking growing sequences of the N-terminal end. The sequential deletion study shows that the first 26 amino acids placed at the N-terminal end and a variable region comprised between Ala548 to end of the C-terminal extension of LdTopIL were enzymatically dispensable. Altogether this combinatorial approach provides important structural insights of the regions involved in relaxation activity and for understanding the atypical structure of this heterodimeric enzyme.

Targeting atypical trypanosomatid DNA topoisomerase I

Tropical diseases produced by kinetoplastid protozoa are among humanity's costliest banes, owing to high mortality and the economic burden resulting from morbidity. Drug resistant strains of parasites, together with insecticide-resistant vectors, are contributing to their increased prevalence in the developing world. Their extension now threatens industrialized countries because of opportunistic infections in immuno-compromised individuals. Current chemotherapy is expensive, has undesirable side effects and, in many patients, is only marginally effective. Based on the clinical success of camptothecin derivatives as anticancer agents, DNA topoisomerases have been identified as targets for drug development. The substantial differences in homology between trypanosome and leishmania DNA topoisomerase IB compared with the human form provides a new lead in the study of the structural determinants that can be targeted.

DNA topoisomerase I from parasitic protozoa: A potential target for chemotherapy

The growing occurrence of drug resistant strains of unicellular prokaryotic parasites, along with insecticide-resistant vectors, are the factors contributing to the increased prevalence of tropical diseases in underdeveloped and developing countries, where they are endemic. Malaria, cryptosporidiosis, African and American trypanosomiasis and leishmaniasis threaten human beings, both for the high mortality rates involved and the economic loss resulting from morbidity. Due to the fact that effective immunoprophylaxis is not available at present; preventive sanitary measures and pharmacological approaches are the only sources to control the undesirable effects of such diseases. Current anti-parasitic chemotherapy is expensive, has undesirable side effects or, in many patients, is only marginally effective. Under this point of view molecular biology techniques and drug discovery must walk together in order to find new targets for chemotherapy intervention. The identification of DNA topoisomerases as a promising drug target is based on the clinical success of camptothecin derivatives as anticancer agents. The recent detection of substantial differences between trypanosome and leishmania DNA topoisomerase IB with respect to their homologues in mammals has provided a new lead in the study of the structural determinants that can be effectively targeted. The present report is an up to date review of the new findings on type IB DNA topoisomerase in unicellular parasites and the role of these enzymes as targets for therapeutic agents.

Role of nanotechnology in targeted drug delivery and imaging: a concise review

The use of nanotechnology in drug delivery and imaging in vivo is a rapidly expanding field. The emphases of this review are on biophysical attributes of the drug delivery and imaging platforms as well as the biological aspects that enable targeting of these platforms to injured and diseased tissues and cells. The principles of passive and active targeting of nanosized carriers to inflamed and cancerous tissues with increased vascular leakiness, overexpression of specific epitopes, and cellular uptake of these nanoscale systems are discussed. Preparation methods-properties of nanoscale systems including liposomes, micelles, emulsions, nanoparticulates, and dendrimer nanocomposites, and clinical indications are outlined separately for drug delivery and imaging in vivo. Taken together, these relatively new and exciting data indicate that the future of nanomedicine is very promising, and that additional preclinical and clinical studies in relevant animal models and disease states, as well as long-term toxicity studies, should be conducted beyond the "proof-of-concept" stage. Large-scale manufacturing and costs of nanomedicines are also important issues to be addressed during development for clinical indications.

Alternative administration of camptothecin analogues

In order to improve the therapeutic index of camptothecin (CPT) analogues, alternative administration of CPT analogues is being evaluated. Topotecan, irinotecan, rubitecan, lurtotecan and 9-aminocamptothecin have been administered orally with response rates equivalent to that seen after intravenous administration, where applicable. Oral availability and administration of some of the newer CPT analogues, including diflomotecan (BN80915) and grimatecan (ST1481), have also shown promising results. Aerosolisation of liposomal 9-nitrocamptothecin has been studied in patients with advanced malignancies involving the lung, demonstrating systemic antitumour activity. Intrathecal administration of topotecan has been studied in children with refractory neoplastic meningitis. It is well tolerated and associated with some antitumour activity. Intraperitoneal administration of topotecan as consolidation therapy in patients with ovarian cancer has shown promising results. Transdermal administration of rubitecan has been studied in mice. So far, no CPT has been approved for an alternative route of administration.

Topoisomerase I amino acid substitutions, Gly185Arg and Asp325Glu, confer camptothecin resistance in Leishmania donovani

The antitumor compound camptothecin (CPT) is also recognized for its specific activity against Leishmania donovani topoisomerase I (Topo-I). In consequence, defining CPT resistance mechanisms represents an important strategic tool in the acquisition of a better understanding of its mode of action. In the present study, we selected a single highly resistant L. donovani strain termed LdRCPT.160 by stepwise exposure to CPT. Gene sequencing revealed two single nucleotide mutations in the LdRCPT.160 LdTOP1A gene, resulting in two amino acid substitutions (Gly185Arg and Asp325Glu) in the protein. Moreover, these two substitutions observed in the LdTOP1A protein were correlated with a decreased Topo-I DNA relaxation activity in these resistant parasites. Nevertheless, there was no change in the LdTOP1A gene expression level. Interestingly, transfection studies of the LdRCPT.160 LdTOP1A gene in its wild-type counterpart showed that it induced CPT resistance. Site-directed mutagenesis studies demonstrated that, despite a substantial level of resistance conferred by the Gly185Arg and Asp325Glu substitutions separately, both were essential to reach a high-resistance phenotype. Of interest, the amino acid substitutions observed in LdRCPT.160 LdTOP1A protein occurred near the amino acids previously predicted to interact with CPT, providing new insight into the mechanism of CPT molecular action.

Novel camptothecin analogue (gimatecan)-containing liposomes prepared by the ethanol injection method

Small-sized liposomes have several advantages as drug delivery systems, and the ethanol injection method is a suitable technique to obtain the spontaneous formation of liposomes having a small average radius. In this paper, we show that liposomal drug formulations can be prepared in situ, by simply injecting a drug-containing lipid(s) organic solution into an aqueous solution. Several parameters should be optimized in order to obtain a final suitable formulation, and this paper is devoted to such an investigation. Firstly, we study the liposome size distributions determined by dynamic light scattering (DLS), as function of the lipid concentration and composition, as well as the organic and aqueous phases content. This was carried out, firstly, by focusing on POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) then on the novel L-carnitine derivative PUCE (palmitoyl-(R)-carnitine undecyl ester chloride), showing that it is possible to obtain monomodal size distributions of rather small vesicles. In particular, depending on the conditions, it was possible to achieve a population of liposomes with a mean size of 100 nm, when a 50 mM POPC ethanol solution was injected in pure water; in the case of 50 mM PUCE the mean size was around 30 nm, when injected in saline (0.9% NaCl). The novel anticancer drug Gimatecan, a camptothecin derivative, was used as an example of lipophilic drug loading by the injection method. Conditions could be found, under which the resultant liposome size distributions were not affected by the presence of Gimatecan, in the case of POPC as well as in the case of PUCE. To increase the overall camptothecin concentration in the final liposomal dispersion, the novel technique of "multiple injection method" was used, and up to a final 5 times larger amount of liposomal drug could be reached by maintaining approximately the same size distribution. Once prepared, the physical and chemical stability of the liposome formulations was satisfactory within 24, as judged by DLS analysis and HPLC quantitation of lipids and drug. The Gimatecan-containing liposomes formulations were also tested for in vitro and in vivo activity, against the human nonsmall cell lung carcinoma NCI-H460 and a murine Lewis lung carcinoma 3 LL cell lines. In the in vitro tests, we did not observe any improvement or reduction of the Gimatecan pharmacological effect by the liposomal delivery system. More interestingly, in the in vivo Lewis lung carcinoma model, the intravenously administration of liposomal Gimatecan formulation showed a mild but significant increase of Tumor Volume Inhibition with respect to the oral no-liposomal formulation (92% vs. 86 %, respectively; p < 0.05). Finally, our study showed that the liposomal formulation was able to realize a delivery system of a water-insoluble drug, providing a Gimatecan formulation for intravenous administration with a preserved antitumoral activity.

Formulation and biopharmaceutical issues in the development of drug delivery systems for antiparasitic drugs

The development of really new antiparasitic drugs to market level is a very rare event. A large number of lead structures have already been screened and discarded, the market is large but poor, and the administrative barriers are increasingly high and costly. Novel antiparasitics must not only be better, they must also be substantially safer than the existing repertoire. There are two major aspects to drug development. One is the strategy of pathogen-specific biochemical intervention, the other the strategy of optimal formulation and application. This review focuses on the latter. In finding and adapting innovative and "intelligent", i.e. parasite- and disease-specific formulations and delivery systems, established but deficient drugs might be optimised, enhancing their efficiency and reducing negative side effects at relatively low cost. Further, many promising new ideas are severely hampered by the low water solubility of the antiparasitic drug. Here as well, some of the innovative drug formulation and delivery systems discussed below might offer highly efficient, while technologically simple, solutions.

Camptothecin delivery methods

Camptothecin has shown significant antitumor activity to lung, ovarian, breast, pancreas, and stomach cancers. Camptothecin, however, like a number of other potent anticancer agents such as paclitaxel, is extremely water insoluble. Furthermore, pharmacology studies have determined that prolonged schedules of administration given continuously are required. Thus, this insolubility has restricted its clinical application. For these reasons, a number of water-soluble analogs have been synthesized and a number of different formulation approaches have been investigated. In this review, we examine each of these approaches and discuss their advantages and limitations.

Long-circulating sterically stabilized liposomes as carriers of agents for treatment of infection or for imaging infectious foci

Liposomes are considered as potential carriers for biologically active compounds. One evident drawback of 'classical' liposomes is their fast elimination by cells of the mononuclear phagocyte system (MPS), primarily by liver and spleen. An important breakthrough in this respect is the development of long-circulating liposomes among which liposomes coated with polyethyleneglycol (PEG), the so-called 'sterically stabilized' liposomes (SSL). An important characteristic of SSL is that their prolonged blood residence time and infectious target localization is relatively independent of the lipid dose, particle size or lipid composition of the bilayer. SSL are applied as carriers of antimicrobial agents to achieve infectious target localization, to reduce side effects, or to serve as a micro-reservoir in the circulation. In addition, radiolabelled SSL are used to image infectious and inflammatory foci.