Practical method for preparing nanosuspension formulations for toxicology studies in the discovery stage: formulation optimization and in vitro/in vivo evaluation of nanosized poorly water-soluble compounds

An ADAM10 Exosite Inhibitor Is Efficacious in an In Vivo Collagen-Induced Arthritis Model

Rheumatoid arthritis is a systemic autoimmune inflammatory disease that affects millions of people worldwide. There are multiple disease-modifying anti-rheumatic drugs available; however, many patients do not respond to any treatment. A disintegrin and metalloproteinase 10 has been suggested as a potential new target for RA due to its role in the release of multiple pro- and anti-inflammatory factors from cell surfaces. In the present study, we determined the pharmacokinetic parameters and in vivo efficacy of a compound CID3117694 from a novel class of non-zinc-binding inhibitors. Oral bioavailability was demonstrated in the blood and synovial fluid after a 10 mg/kg dose. To test efficacy, we established the collagen-induced arthritis model in mice. CID3117694 was administered orally at 10, 30, and 50 mg/kg/day for 28 days. CID3117694 was able to dose-dependently improve the disease score, decrease RA markers in the blood, and decrease signs of inflammation, hyperplasia, pannus formation, and cartilage erosion in the affected joints compared to the untreated control. Additionally, mice treated with CID 3117694 did not exhibit any clinical signs of distress, suggesting low toxicity. The results of this study suggest that the inhibition of ADAM10 exosite can be a viable therapeutic approach to RA.

Nanocrystal Preparation of Poorly Water-Soluble Drugs with Low Metal Contamination Using Optimized Bead-Milling Technology

Nanocrystal preparation using bead milling is an important technology to enhance the solubility of poorly water-soluble drugs. However, there are safety concerns regarding the metal contaminants generated during bead milling. We have previously reported optimized bead-milling parameters that could minimize metal contamination and demonstrated comparable performance to NanoCrystal^®, a world-leading contamination-free technology. This study aimed to investigate the applicability of optimized milling parameters for preparing nanocrystals of several poorly water-soluble drugs exhibiting various physicochemical properties. Using our optimized bead-milling parameters, we found that all the tested drugs could be ground into nanosized particles within 360 min. Notably, fenofibrate, which has a low melting point, could be ground into nanosized particles owing to the low level of heat generated during bead milling. Additionally, the concentration of metal contaminants in all the drugs prepared using the optimized milling parameters were approximately ten to twentyfold lower than those prepared without the optimized parameters and were comparable to those prepared using polycarbonate beads, known to minimize metal contamination during bead milling. Our results provide insights into the development of drug nanocrystals with low metal contamination using bead milling.

Preparation of PLGA Nanoparticles by Milling Spongelike PLGA Microspheres

Currently, emulsification-templated nanoencapsulation techniques (e.g., nanoprecipitation) have been most frequently used to prepare poly-d,l-lactide-co-glycolide (PLGA) nanoparticles. This study aimed to explore a new top-down process to produce PLGA nanoparticles. The fundamental strategy was to prepare spongelike PLGA microspheres with a highly porous texture and then crush them into submicron-sized particles via wet milling. Therefore, an ethyl formate-based ammonolysis method was developed to encapsulate progesterone into porous PLGA microspheres. Compared to a conventional solvent evaporation process, the ammonolysis technique helped reduce the tendency of drug crystallization and improved drug encapsulation efficiency accordingly (solvent evaporation, 27.6 ± 4.6%; ammonolysis, 65.1 ± 1.7%). Wet milling was performed on the highly porous microspheres with a D₅₀ of 64.8 μm under various milling conditions. The size of the grinding medium was the most crucial factor for our wet milling. Milling using smaller zirconium oxide beads (0.3~1 mm) was simply ineffective. However, when larger beads with diameters of 3 and 5 mm were used, our porous microspheres were ground into submicron-sized particles. The quality of the resultant PLGA nanoparticles was demonstrated by size distribution measurement and field emission scanning electron microscopy. The present top-down process that contrasts with conventional bottom-up approaches might find application in manufacturing drug-loaded PLGA nanoparticles.

A Systematic Approach to the Development of Cilostazol Nanosuspension by Liquid Antisolvent Precipitation (LASP) and Its Combination with Ultrasound

Nanosizing is an approach to improve the dissolution rate of poorly soluble drugs. The first aim of this work was to develop nanosuspension of cilostazol with liquid antisolvent precipitation (LASP) and its combination with ultrasound. Second, to systematically study the effect of bottom-up processing factors on precipitated particles’ size and identify the optimal settings for the best reduction. After solvent and stabilizer screening, in-depth process characterization and optimization was performed using Design of Experiments. The work discusses the influence of critical factors found with statistical analysis: feed concentration, stabilizer amount, stirring speed and ultrasound energy governed by time and amplitude. LASP alone only generated particle size of a few microns, but combination with ultrasound was successful in nanosizing (d10 = 0.06, d50 = 0.33, d90 = 1.45 µm). Micro- and nanosuspension’s stability, particle morphology and solid state were studied. Nanosuspension displayed higher apparent solubility than equilibrium and superior dissolution rate over coarse cilostazol and microsuspension. A bottom-up method of precipitation-sonication was demonstrated to be a successful approach to improve the dissolution characteristics of poorly soluble, BCS class II drug cilostazol by reducing its particle size below micron scale, while retaining nanosuspension stability and unchanged crystalline form.

Development of Novel Bead Milling Technology with Less Metal Contamination by pH Optimization of the Suspension Medium

To develop novel contamination-less bead milling technology without impairing grinding efficiency, we investigated the effect of the formulation properties on the grinding efficiency and the metal contamination generated during the grinding process. Among the various formulations tested, the combination of polyvinylpyrrolidone and sodium dodecyl sulfate was found to be suitable for efficiently pulverizing phenytoin. However, this stabilization system included a relatively strong acid, which raised the concern of possible corrosion of the zirconia beads. An evaluation of the process clearly demonstrated that acidic pH promoted bead dissolution, suggesting that this could be suppressed by controlling the pH of the suspension. Among the various pH values tested, the metal contamination generated during the grinding process could be significantly reduced in the optimized pH range without significant differences in the particle size of the phenytoin suspension after pulverization. In addition, the contamination reduction by pH optimization in the presence of physical contact among the beads was approximately 10-times larger than that without bead contact, suggesting that pH optimization could suppress not only bead dissolution but also the wear caused by bead collisions during the grinding process. These findings show that pH optimization is a simple but effective approach to reducing metal contamination during the grinding process.

Three-dimensional aspects of formulation excipients in drug discovery: a critical assessment on orphan excipients, matrix effects and drug interactions

Formulation/pharmaceutical excipients play a major role in formulating drug candidates, with the objectives of ease of administration, targeted delivery and complete availability. Many excipients used in pharmaceutical formulations are orphanized in preclinical drug discovery. These orphan excipients could enhance formulatability of highly lipophilic compounds. Additionally, they are safe in preclinical species when used below the LD50 values. However, when the excipients are used in formulating compounds with diverse physico-chemical properties, they pose challenges by modulating study results through their bioanalytical matrix effects. Excipients invariably present in study samples and not in the calibration curve standards cause over-/under- estimation of exposures. Thus, the mechanism by which excipients cause matrix effects and strategies to nullify these effects needs to be revisited. Furthermore, formulation excipients cause drug interactions by moderating the pathways of drug metabolizing enzymes and drug transport proteins. Although it is not possible to get rid of excipient driven interactions, it is always advised to be aware of these interactions and apply the knowledge to draw meaningful conclusions from study results. In this review, we will comprehensively discuss a) orphan excipients that have wider applications in preclinical formulations, b) bioanalytical matrix effects and possible approaches to mitigating these effects, and c) excipient driven drug interactions and strategies to alleviate the impacts of drug interactions.

Optimizing Oral Bioavailability in Drug Discovery: An Overview of Design and Testing Strategies and Formulation Options

For discovery teams working toward new, orally administered therapeutic agents, one requirement is to attain adequate systemic exposure after oral dosing, which is best accomplished when oral bioavailability is optimized. This report summarizes the bioavailability challenges currently faced in drug discovery, and the design and testing methods and strategies currently utilized to address the challenges. Profiling of discovery compounds usually includes separate assessments of solubility, permeability, and susceptibility to first-pass metabolism, which are the 3 most likely contributors to incomplete oral bioavailability. An initial assessment of absorption potential may be made computationally, and high throughput in vitro assays are typically performed to prioritize compounds for in vivo studies. The initial pharmacokinetic study is a critical decision point in compound evaluation, and the importance of the effect the dosing vehicle or formulation can have on oral bioavailability, especially for poorly water soluble compounds, is emphasized. Dosing vehicles and bioavailability-enabling formulations that can be used for discovery and preclinical studies are described. Optimizing oral bioavailability within a chemical series or for a lead compound requires identification of the barrier limiting bioavailability, and methods used for this purpose are outlined. Finally, a few key guidelines are offered for consideration when facing the challenges of optimizing oral bioavailability in drug discovery.

Nanomilling of Drugs for Bioavailability Enhancement: A Holistic Formulation-Process Perspective

Preparation of drug nanoparticles via wet media milling (nanomilling) is a very versatile drug delivery platform and is suitable for oral, injectable, inhalable, and buccal applications. Wet media milling followed by various drying processes has become a well-established and proven formulation approach especially for bioavailability enhancement of poorly water-soluble drugs. It has several advantages such as organic solvent-free processing, tunable and relatively high drug loading, and applicability to a multitude of poorly water-soluble drugs. Although the physical stability of the wet-milled suspensions (nanosuspensions) has attracted a lot of attention, fundamental understanding of the process has been lacking until recently. The objective of this review paper is to present fundamental insights from available published literature while summarizing the recent advances and highlighting the gap areas that have not received adequate attention. First, stabilization by conventionally used polymers/surfactants and novel stabilizers is reviewed. Then, a fundamental understanding of the process parameters, with a focus on wet stirred media milling, is revealed based on microhydrodynamic models. This review is expected to bring a holistic formulation-process perspective to the nanomilling process and pave the way for robust process development scale-up. Finally, challenges are indicated with a view to shedding light on future opportunities.

Nanosuspension formulations of poorly water-soluble compounds for intravenous administration in exploratory toxicity studies: in vitro and in vivo evaluation

This study was conducted to investigate the use of a nanosuspension for intravenous injection into dogs to increase exposure without toxic additives for preclinical studies in the discovery stage. Nanosuspensions were prepared with a mixer mill and zirconia beads with a vehicle of 2% (w/v) poloxamer 338, which was confirmed to lead to no histamine release in dogs. Sterilized nanosuspensions of poorly water-soluble compounds, cilostazol (Cil), spironolactone (Spi) and probucol (Pro), at 10 mg ml(-1) were obtained by milling for 30 min, followed by autoclaving for 20 min at 121 °C and milling for 30 min (mill-autoclave-mill method). The particle sizes (d50) of Cil, Spi and Pro were 0.554, 0.484 and 0.377 µm, respectively, and the percentages of the nominal concentration were 79.1%, 99.6% and 75.4%, respectively. In chromatographic data, no extra peaks were observed. The particle size of Cil was 0.564 µm after storage for 16 days at 2-8 °C. Cil in nanosuspension, but not in microsuspension, rapidly dissolved in dog plasma. Cil nanosuspension at 0.4 mg kg(-1) and Cil saline solution at 0.03 mg kg(-1) , around the saturation solubility, were intravenously administered to dogs. Nanosuspension increased exposure. The versatility of the mill-autoclave-mill method was checked for 15 compounds, and the particle size of 12 compounds was in the nano range. The nanosuspension optimized in this study may be useful for intravenous toxicological and pharmacological studies in the early stage of drug development. Copyright © 2016 John Wiley & Sons, Ltd.

Improved oral absorption of cilostazol via sulfonate salt formation with mesylate and besylate

Objective

Cilostazol is a Biopharmaceutical Classification System class II drug with low solubility and high permeability, so its oral absorption is variable and incomplete. The aim of this study was to prepare two sulfonate salts of cilostazol to increase the dissolution and hence the oral bioavailability of cilostazol.

Methods

Cilostazol mesylate and cilostazol besylate were synthesized from cilostazol by acid addition reaction with methane sulfonic acid and benzene sulfonic acid, respectively. The salt preparations were characterized by nuclear magnetic resonance spectroscopy. The water contents, hygroscopicity, stress stability, and photostability of the two cilostazol salts were also determined. The dissolution profiles in various pH conditions and pharmacokinetic studies in rats were compared with those of cilostazol-free base.

Results

The two cilostazol salts exhibited good physicochemical properties, such as nonhygroscopicity, stress stability, and photostability, which make it suitable for the preparation of pharmaceutical formulations. Both cilostazol mesylate and cilostazol besylate showed significantly improved dissolution rate and extent of drug release in the pH range 1.2–6.8 compared to the cilostazol-free base. In addition, after oral administration to rats, cilostazol mesylate and cilostazol besylate showed increases in C_max and AUC_t of approximately 3.65- and 2.87-fold and 3.88- and 2.94-fold, respectively, compared to cilostazol-free base.

Conclusion

This study showed that two novel salts of cilostazol, such as cilostazol mesylate and cilostazol besylate, could be used to enhance its oral absorption. The findings warrant further preclinical and clinical studies on cilostazol mesylate and cilostazol besylate at doses lower than the usually recommended dosage, so that it can be established as an alternative to the marketed cilostazol tablet.