Abeer H. A. Mohamed-Ahmed

Recent advances in development of amphotericin B formulations for the treatment of visceral leishmaniasis.

Purpose of review Amphotericin B (AmpB) is considered the first-line treatment for visceral leishmaniasis in areas in which resistance to antimony is prevalent. This review describes recent advances in clinically available and novel drug delivery systems of AmpB to treat visceral leishmaniasis. Recent findings Over the past two decades, lipid-based AmpB formulations developed to tackle the toxicity of AmpB have been used clinically for the treatment of visceral leishmaniasis. Liposomal AmpB (AmBisome) has been the most successful lipid formulation, and recent clinical studies on visceral leishmaniasis have shown the potential of single-dose AmBisome treatment as well as its use in short course combinations with other antileishmanial drugs. Current research is focussed on the development of more stable and affordable nonlipid formulations of AmpB. Although a diverse range of nonlipid-based AmpB formulations have been evaluated, none have yet reached the clinic. Summary Liposomal AmpB (AmBisome) has become a standard treatment, by intravenous infusion, for visceral leishmaniasis and the basis for new short course treatments. There have been extensive efforts to develop new AmpB formulations on the basis of polymers, lipids or physical aggregates of AmpB to replace the costly lipid-based formulations. However, no nonlipid-based AmpB delivery systems have yet reached the clinic.

Non-human tools for the evaluation of bitter taste in the design and development of medicines: a systematic review.

Taste evaluation is a crucial factor for determining acceptance of medicines by patients. The human taste panel test is the main method used to establish the overall palatability and acceptability of a drug product to a patient towards the end of development. Non-human in vitro and in vivo taste-evaluation tools are very useful for pre-formulation, quality control and screening of formulations. These non-human taste assessment tools can be used to evaluate all aspects of taste quality. The focus of this review is bitterness because it is a key aspect of taste in association with the development of medicines. In this review, recent in vitro (analytical) and in vivo (non-human) tools are described for the assessment of the bitter taste of medicines. Their correlations with human taste data are critically discussed. The potential for their use in early screening of the taste of active pharmaceutical ingredients (APIs) to expedite paediatric formulation development is also considered.

Noncovalent Complexation of Amphotericin-B with Poly(α-glutamic acid)

A noncovalent complex of amphotericin B (AmB) and poly(α-glutamic acid) (PGA) was prepared to develop a safe and stable formulation for the treatment of leishmaniasis. The loading of AmB in the complex was in the range of ∼20-50%. AmB was in a highly aggregated state with an aggregation ratio often above 2.0. This complex (AmB-PGA) was shown to be stable and to have reduced toxicity to human red blood cells and KB cells compared to the parent compound; cell viability was not affected at an AmB concentration as high as 50 and 200 μg/mL respectively. This AmB-PGA complex retained AmB activity against intracellular Leishmania major amastigotes in the differentiated THP-1 cells with an EC50 of 0.07 ± 0.03-0.08 ± 0.01 μg/mL, which is similar to Fungizone (EC50 of 0.06 ± 0.01 μg/mL). The in vitro antileishmanial activity of the complex against Leishmania donovani was retained after storage at 37 °C for 7 days in the form of a solution (EC50 of 0.27 ± 0.03 to 0.35 ± 0.04 μg/mL) and for 30 days as a solid (EC50 of 0.41 ± 0.07 to 0.63 ± 0.25 μg/mL). These encouraging results indicate that the AmB-PGA complex has the potential for further development.

Poly(methacrylic acid) complexation of amphotericin B to treat neglected diseases

Amphotericin B (AmB) is used to treat a neglected disease called visceral leishmaniasis (VL). We hypothesised that direct non-covalent association of AmB with poly(methacrylic acid) (PMAA) would replicate many of the properties of liposomal AmB (AmB-L), which is more efficacious than micellar AmB (AmB-D). Water-soluble AmB–PMAA complexes with AmB loadings ranging from ∼20 to 45% were reproducibly prepared. The AmB in the PMAA complex displayed similar aggregation properties to the AmB within AmB-L. The AmB–PMAA complex displayed low heamolytic properties while maintaining in vitro activity against Leishmania donovani amastigotes with no macrophage toxicity observed at an IC50 of 0.043 (±0.003) μM. AmB–PMAA complexes were well tolerated in vivo at a total dose of 6 mg kg−1 and both the complex (2.2 mg kg−1 AmB) and AmB-L (2.5 mg kg−1 AmB) achieved greater than 90% parasite inhibition in vivo after a single dose against L. donovani in HU3 infected BALB/c mice.

Preparation and characterisation of amphotericin B-copolymer complex for the treatment of leishmaniasis

A copolymer was used as a platform for solubilisation of an anti-leishmanial agent. A non-covalent complex of amphotericin B (AmB) and poly(vinylpyrrolidone-co-methacrylic acid) (PVM) sodium salt was prepared from a N-hydroxysuccinimide (NHS) active ester precursor polymer in an effort to improve the therapeutic index of AmB. Leishmaniasis is a neglected disease that can be effectively treated with AmB. Unfortunately AmB is poorly soluble and highly prone to aggregation and degradation. It is also toxic and the lipid formulations of AmB that can mediate this toxicity are too expensive and unstable to use in resource-limited regions of the world. We hypothesised that replacement of the lipids with an appropriate water-soluble polymer would be a viable strategy to address the issues of AmB solubility, toxicity and cost of the final medicine. Copolymer precursors of PVM were prepared using different ratios of the monomers, N-1-vinyl-2-pyrrolidone and N-methacryloxysuccinimide. Complexation of AmB was achieved by hydrolysis of the NHS moiety as a DMSO solution of the copolymer precursor and AmB was diluted with sodium hydroxide and water. The free AmB was removed from the AmB–PVM complex, and then freeze dried to give water-soluble (2 mg mL−1 AmB equivalents) complexes with AmB loadings ranging from 20 to 30 wt%. The AmB–PVM complex reduced the toxicity of AmB towards mammalian cells (THP-1 and KB cells) while retaining its activity against intracellular L. major amastigotes in macrophages derived from THP-1 cells. The EC50 of the complex ranged between 0.08 and 0.18 μg mL−1 which is quite similar to clinical AmB (Fungizone®) (0.06 ± 0.01 μg ml−1). Our results show that there is potential to develop safe and effective AmB–polymer complexes to treat leishmaniasis.

Antileishmanial Activity, Uptake, and Biodistribution of an Amphotericin B and Poly(α-Glutamic Acid) Complex

ABSTRACT A noncovalent, water-soluble complex of amphotericin B (AMB) and poly(α-glutamic acid) (PGA), with AMB loadings ranging from 25 to 55% (wt/wt) using PGA with a molecular weight range of 50,000 to 70,000, was prepared as a potential new treatment for visceral leishmaniasis (VL). The AMB-PGA complex was shown to be as active as Fungizone (AMB deoxycholate) against intracellular Leishmania donovani amastigotes in differentiated THP-1 cells. The in vitro uptake of the AMB-PGA complex by differentiated THP-1 cells was similar to that of Fungizone and higher than that of AmBisome (liposomal AMB). The AMB-PGA complex also displayed a dose-response profile similar to that of AmBisome in vivo in BALB/c mice against L. donovani, with 50% effective doses (ED50s) of 0.24 ± 0.03 mg/kg of body weight for the AMB-PGA complex and 0.24 ± 0.06 mg/kg for AmBisome. A biodistribution study with mice indicated that the AMB-PGA complex cleared more rapidly from plasma than AmBisome, with a comparable low level of distribution to the kidneys.

Comparative in vitro and in vivo taste assessment of liquid praziquantel formulations

The taste of pharmaceuticals strongly affects the compliance of patients. This study investigated the applicability of the electronic tongue and rodent brief-access taste aversion (BATA) model for the bitter compound praziquantel (PZQ) and taste masked liquid formulations for PZQ. In a comparative study maltodextrin (MD) Kleptose® linecaps 17 was selected as an alternative taste masking agent to two cyclodextrins; hydroxypropyl-beta-cyclodextrin (HP-β-CD) and sulfobutyl ether-beta-cyclodextrin (SBE-β-CD). A phase solubility study showed the highest affinity and solubilization capabilities for SBE-β-CD over HP-β-CD and MD, suggesting the highest taste masking ability for SBE-β-CD. No reliable results were achieved for PZQ with the Insent electronic tongue. Thus this system was not used for further evaluation of solutions with MD and CDs to confirm the results of the solubility study. In contrast the BATA model demonstrated conclusive responses for the aversiveness of PZQ. The concentration of PZQ inhibiting 50% of water lick numbers (called IC50 value) was 0.06mg/ml. In contrast to the phase solubility study, the MD enabled an equal taste masking effect in vivo in comparison to both CDs. Moreover HP-β-CD showed superior taste masking capabilities for PZQ compared to SBE-β-CD as the SBE-β-CD itself was less acceptable for the rodents than HP-β-CD. In conclusion, the BATA model was identified as a more efficient taste assessment tool for the pure PZQ and liquid formulations in contrast to the electronic tongue and the phase solubility study.

Quality and stability of extemporaneous pyridoxal phosphate preparations used in the treatment of paediatric epilepsy

To assess the pyridoxal 5′‐phosphate (PLP) content and stability of extemporaneous PLP liquids prepared from dietary supplements used for the treatment of vitamin B6‐dependent epilepsy.

An Ilomastat-CD Eye Drop Formulation to Treat Ocular Scarring

Purpose The purpose of this study was to develop a topical matrix metalloproteinase inhibitor preparation for antiscarring therapy. Methods The broad spectrum matrix metalloproteinase inhibitor ilomastat was formulated using 2-hydroxypropyl-β-cyclodextrin in aqueous solution. In vitro activity of ilomastat-cyclodextrin (ilomastat-CD) was examined using fibroblasts seeded in collagen. Permeation of ilomastat-CD eye drop through pig eye conjunctiva was confirmed using Franz diffusion cells. Ilomastat-CD eye drop was applied to rabbit eyes in vivo, and the distribution of ilomastat in ocular tissues and fluids was determined by liquid chromatography-mass spectroscopy. Results The aqueous solubility of ilomastat-CD was ∼1000 μg/mL in water and 1400 μg/mL in PBS (pH 7.4), which is greater than ilomastat alone (140 and 160 μg/mL in water and PBS, respectively). The in vitro activity of ilomastat-CD to inhibit collagen contraction in the presence of human Tenon fibroblast cells was unchanged compared to uncomplexed ilomastat. Topically administered ilomastat-CD in vivo to rabbit eyes resulted in a therapeutic concentration of ilomastat being present in the sclera and conjunctiva and within the aqueous humor. Conclusions Ilomastat-CD has the potential to be formulated as an eye drop for use as an antifibrotic, which may have implications for the prevention of scarring in many settings, for example glaucoma filtration surgery.

LC–MS analysis to determine the biodistribution of a polymer coated ilomastat ocular implant

ABSTRACT Ilomastat is a matrix metalloproteinase inhibitor (MMPi) that has shown the potential to inhibit scarring (fibrosis) by mediating healing after injury or surgery. A long lasting ocular implantable pharmaceutical formulation of ilomastat is being developed to mediate the healing process to prevent scarring after glaucoma filtration surgery. The ilomastat implant was coated with water permeable and biocompatible phosphoryl choline polymer (PC1059) displayed extended slow release of ilomastat in vitro and in vivo. The ocular distribution of ilomastat from the implant in rabbits at day 30 post surgery was determined by the extraction of ilomastat and its internal standard marimastat from the ocular tissues, plasma, aqueous humour and vitreous fluid followed by capillary‐flow liquid chromatography (cap‐LC), the column effluent was directed into a triple quadrupole mass spectrometer operating in product scan mode. The lower limits of quantification (LLOQs) were 0.3pg/&mgr;L for ocular fluids and plasma, and 3pg/mg for ocular tissues. The extraction recoveries were 90–95% for ilomastat and its internal standard from ocular tissues. Ilomastat was found in ocular fluids and tissues at day 30 after surgery. The level of ilomastat was 18 times higher in the aqueous humour than vitreous humour. The concentration ranking of ilomastat in the ocular tissues was sclera>bleb conjunctiva>conjunctiva (rest of the eye)>cornea. Mass spectrometry analysis to confirm the presence of ilomastat in the ocular tissues and fluids at day 30 post‐surgery establishes the extended release of ilomastat can be achieved in vivo, which is crucial information for optimisation of the ilomastat coated implant.