Coarse-Grained Molecular Dynamics Simulations of Paclitaxel-Loaded Polymeric Micelles.

A continuous manufacturing technology based on coaxial turbulent jet in coflow was previously developed to produce paclitaxel-loaded polymeric micelles. Herein, coarse-grained molecular dynamics (CG-MD) simulations were implemented to better understand the effect of the material attributes (i.e., the drug-polymer ratio and the ethanol concentration) and process parameters (i.e., temperature) on the self-assembly process of polymeric micelles as well as to provide molecular details on micelle instability. An all-atom (AA) poly (ethylene glycol)-poly (lactic acid) (PEG-PLA) polymer model was developed as the reference for parameterizing a coarse-grained (CG) model, and the AA polymer model was further validated with experimental glass transition temperature (Tg). The model transferability was verified by comparing structural properties between the AA and CG models. The CG model was further validated with experimental data, including micelle particle size measurements and drug encapsulation efficiency. Furthermore, the encapsulation of paclitaxel into the polymeric micelles was included in the simulations, taking into consideration the interactions between the paclitaxel and the polymers. The results from various points of view demonstrated a strong dependence of the shape of the micelles on the drug encapsulation, with micelles transitioning from spherical to ellipsoidal structures with an increasing paclitaxel amount. Simulation data were also used to identify the critical aggregation number (i.e., the number of polymer and drug molecules required for transition from one shape to another). Improved micellar structural stability was found with a larger micellar size and less solvent accessibility. Lastly, an evaluation was performed on the micellar dissociation free energy using a steered molecular dynamics simulation over a range of temperatures and ethanol concentrations. These simulations revealed that at higher ethanol and temperature conditions, micelles become destabilized, resulting in greater paclitaxel release. The increased drug release was determined to originate from the solvation of the hydrophobic core, which promoted micellar swelling and an associated reduction in hydrophobic interactions, leading to a loosely packed micellar structure.

Factors Influencing the Immunogenicity and Immunotoxicity of Cyclic RGD Peptide-Modified Nanodrug Delivery Systems.

c(RGDyK)-modified liposomes have been shown to be immunogenic and potentially trigger acute systemic anaphylaxis upon repeated intravenous injection in both BALB/c nude mice and ICR mice. However, questions concerning the potential influence of mouse strains, immunization routes, drug carrier properties, and changes in c(RGDyK) itself on the immunogenicity and resultant immunotoxicity (anaphylaxis) of cyclic RGD peptide-modified nanodrug delivery systems remain unanswered. Here, these potential impact factors were investigated, aiming to better understand the immunological properties of cyclic RGD peptide-based nanodrug delivery systems and seek for solutions for this immunogenicity-associated issue. It was revealed that anaphylaxis caused by intravenous c(RGDyK)-modified drug delivery systems might be avoided by altering the preimmunization route (i.e., subcutaneous injection), introducing positively charged lipids into the liposomes and by using micelles or red blood cell membrane (RBC)-based drug delivery systems as the carrier. Different murine models showed different incidences of anaphylaxis following intravenous c(RGDyK)-liposome stimulation: anaphylaxis was not observed in both SD rats and BALB/c mice and was less frequent in C57BL/6 mice than that in ICR mice. In addition, enlarging the peptide ring of c(RGDyK) by introducing amino sequence serine-glycine-serine reduced the incidence of anaphylaxis post the repeated intravenous c(RGDyKSGS)-liposome stimulation. However, immunogenicity of cyclic RGD-modified drug carriers could not be reversed, although some reduction in IgG antibody production was observed when ICR mice were intravenously stimulated with c(RGDyK)-modified micelles, RBC membrane-based drug delivery systems and c(RGDyKSGS)-liposomes instead of c(RGDyK)-liposomes. This study provides a valuable reference for future application of cyclic RGD peptide-modified drug delivery systems.

Formulation and evaluation of itraconazole liposomes for Hedgehog pathway inhibition.

Itraconazole (ITZ) is an FDA-approved antifungal agent that has recently been explored for novel biological properties. In particular, ITZ was identified as a potent inhibitor of the hedgehog (Hh) pathway, a cell signalling pathway that has been linked to a variety of cancers and accounts for ∼25% of paediatric medulloblastoma (MB) cases. To date, there is not a targeted therapeutic option for paediatric MB, resulting in long-term side effects such as hormone deficiency, organ damage and secondary cancers. A primary obstacle for developing targeted therapy for brain ailments is the presence of the blood-brain barrier (BBB), which protects the brain from potentially harmful substances. Due to its size and hydrophobicity, ITZ does not penetrate the BBB. Alternatively, liposomes are being increasingly used within the clinic to increase drug bioavailability, target specificity and BBB permeability. With this in mind, we have successfully developed ITZ-containing liposomes with an optimal size for BBB penetration (<100 nm) and encapsulation efficiency (∼95%) by utilizing a continuous manufacturing approach-turbulent coaxial jet in co-flow. Our preliminary in vitro data demonstrate that these liposomes inhibit the Hh pathway, albeit at a reduced level in comparison to free ITZ. (196/250 words).

Liposome Formation Using a Coaxial Turbulent Jet in Co-Flow.

PURPOSE: Liposomes are robust drug delivery systems that have been developed into FDA-approved drug products for several pharmaceutical indications. Direct control in producing liposomes of a particular particle size and particle size distribution is extremely important since liposome size may impact cellular uptake and biodistribution. METHODS: A device consisting of an injection-port was fabricated to form a coaxial turbulent jet in co-flow that produces liposomes via the ethanol injection method. By altering the injection-port dimensions and flow rates, a fluid flow profile (i.e., flow velocity ratio vs. Reynolds number) was plotted and associated with the polydispersity index of liposomes. RESULTS: Certain flow conditions produced unilamellar, monodispersed liposomes and the mean particle size was controllable from 25 up to >465 nm. The mean liposome size is highly dependent on the Reynolds number of the mixed ethanol/aqueous phase and independent of the flow velocity ratio. CONCLUSIONS: The significance of this work is that the Reynolds number is predictive of the liposome particle size, independent of the injection-port dimensions. In addition, a new model describing liposome formation is outlined. The significance of the model is that it relates fluid dynamic properties and lipid-molecule physical properties to the final liposome size.

Drug Distribution in Microspheres Enhances Their Anti-Inflammatory Properties in the Gottingen Minipig.

The foreign body reaction (FBR), one of the body's defense mechanisms against foreign materials, results in loss of implant biocompatibility. A popular strategy to prevent FBR is the constant release of dexamethasone in the tissue surrounding the implant. However, FBR prevention has not been sufficiently studied in large animal models, which offer a better representation of the human subcutaneous tissue physiology. Accordingly, a long-term strategy to prevent FBR to subcutaneous implants in a large animal model is necessary to translate the existing research for clinical applications. Here, a poly(lactic-co-glycolic) (PLGA) microsphere/poly(vinyl alcohol) (PVA) hydrogel composite coating for one-month prevention of FBR in Gottingen minipigs was developed. A modified PLGA microsphere formulation process is presented, that utilizes coprecipitation of dexamethasone and PLGA. Traditional methods result in heterogeneous distribution of large drug crystals in the microsphere matrix, which in turn results in low drug loading since the drug crystal size is close to that of the microspheres. The modified microsphere preparation method showed homogeneous distribution of dexamethasone, which in turn gave rise to increased drug loading, low burst release, and minimal lag phase. Elimination of the lag phase was dictated from previous work that compared FBR between rats and minipigs. The ability of the coatings to improve implant biocompatibility was successfully tested in vivo via histological examination of explanted tissue from the area surrounding the implants. The biocompatible coatings presented here are suitable for miniaturized implantable devices, such as biosensors, that require constant communication with the local microenvironment.

Microspheres prepared with PLGA blends for delivery of dexamethasone for implantable medical devices.

PURPOSE: To develop and characterize microspheres using poly (lactic-co-glycolic acid) (PLGA) blends (PLGA5050 (25 KD) and PLGA6535 (70 KD)) for dexamethasone delivery to prevent foreign body response to implantable biosensors. METHODS: A single emulsion based oil/water solvent evaporation/extraction method was used to prepare microspheres. RESULTS: All the microspheres prepared exhibited the typical triphasic release profile, but with different initial burst release, lag phase and zero order release rates. The burst release was reduced when the two PLGA were mixed at a molecular level, whereas increase in burst release was observed when phase separation occurred. Microspheres prepared using PLGA blends had significantly shorter lag phase. The activation energy (Ea) of dexamethasone release from microspheres was similar to the Ea value of PLGA degradation. The release kinetics were significantly enhanced under accelerated conditions (45 and 53°C) without altering the release mechanism of the post-burst phase. A rank order correlation between accelerated and "real-time" release kinetics was observed. CONCLUSIONS: Polymer blends of PLGA can produce microspheres with reduced lag time. The accelerated release testing conditions investigated can discriminate the formulations and predict "real-time" release. Such accelerated release testing can be used as a rapid screening method to facilitate formulation development.

Freeze-anneal-thaw cycling of unilamellar liposomes: effect on encapsulation efficiency.

PURPOSE: Freeze-thaw cycling is an important processing step in the preparation of liposomes that leads to the encapsulation of drug molecules. There is considerable variability in the number of freeze-thaw cycles reported in the literature. This work is designed to aid in liposomal formulation design by gaining an insight into the drug encapsulation process and an understanding of liposome stabilization during various thawing conditions. METHODS: The effects of different thawing temperatures, as well as "annealing" at subzero temperatures on a liposome formulation, are reported here. RESULTS: Two freeze-anneal-thaw (FANNT) cycles (freezing to -196°C, annealing at -1.4°C for ~30 min, thawing at 65°C) resulted in the maximum predicted encapsulation efficiency without causing any significant change in particle size or zeta potential. Annealing at -22°C was shown to be destabilizing due to limited hydration of the liposomes in the frozen state. CONCLUSIONS: It was shown that two important processes are occurring during the FANNT cycling that affect liposome encapsulation efficiency. The first is drug diffusion in the frozen state and the second is fusion/destabilization of the liposomes. This is the first report on the annealing of liposomes and understanding the mechanism of drug encapsulation using the freeze-thaw cycling method.

Impact of manufacturing variables on product performance of contraceptive levonorgestrel intrauterine systems.

The development of Levonorgestrel Intrauterine Systems (LNG-IUSs) stands as a formidable challenge due to their intricate design and reliance on specialized manufacturing methods. Pharmaceutical manufacturers face a labyrinth of process variables that demand precise identification and comprehension to establish a robust product design to ensure consistent performance. The current manuscript navigates through this complexity, describing a small-scale processing method for LNG-IUSs via addition and condensation curing processes, as well as investigating the influence of key manufacturing variables on LNG-IUS product performance. Different mixing speeds and time exhibited distinct impact on drug content uniformity within the IUS drug-polymer reservoirs. Surprisingly, no variation in drug release rates were observed. Curing temperature and time were the critical processing parameters of IUSs which were dependent on the polymer type (polydimethylsiloxane, PDMS) and drug loading. At lower curing temperatures, crosslinking in PDMS remained relatively unaffected, irrespective of drug loading. By contrast, elevating curing temperatures resulted in a drastic reduction in PDMS crosslinking densities at higher drug loading. This was attributed to increased drug volume fraction within the matrix, impeding optimal prepolymer chain mobility and rearrangement which is crucial for complete crosslinking. Interestingly, rapid curing led to increased PDMS crystallinity, thereby retarding drug release rates while concurrently compromising mechanical properties. PDMS curing chemistry, such as condensation cure (no filler) and addition cure (cured at room temperature), did not affect drug release rates of the LNG-IUSs. In the condensation cure-based LNG-IUS, the formulations prepared without filler had higher drug release rates than those containing silica or diatomaceous earth fillers. Overall, the present study unravels the intricate interplay between PDMS characteristics, processing variables, and product performance, offering fundamental insights into product design and manufacturing of brand and generic LNG-IUS products.

Tailoring drug release from long-acting contraceptive levonorgestrel intrauterine systems.

The wide array of polydimethylsiloxane (PDMS) variants available on the market, coupled with the intricate combination of additives in silicone polymers, and the incomplete understanding of drug release behavior make formulation development of levonorgestrel intrauterine systems (LNG-IUSs) formidable. Accordingly, the objectives of this work were to investigate the impact of excipients on formulation attributes and in vitro performance of LNG-IUSs, elucidate drug release mechanisms, and thereby improve product understanding. LNG-IUSs with a wide range of additives and fillers were prepared, and in vitro drug release testing was conducted for up to 12 months. Incorporating various additives and/or fillers (silica, silicone resins, silicone oil, PEG, etc.) altered the crystallization kinetics of the crosslinked polymer, the viscosity, and the microstructure. In addition, drug-excipient interactions can occur. Interestingly, additives which increased matrix hydrophobicity and hindered PDMS crystallization facilitated dissolution and permeation of the lipophilic LNG. The influence of additives and lubricants on the mechanical properties of LNG-IUSs were also evaluated. PDMS chemical substitution and molecular weight were deemed to be most critical polymer attributes to the in vitro performance of LNG-IUSs. Drugs with varying physicochemical characteristics were used to prepare IUSs, modeling of the release kinetics was performed, and correlations between release properties and the various physicochemical attributes of the model drugs were established. Strong correlations between first order release rate constants and both drug solubility and Log P underpin the partition and diffusion-based release mechanisms in LNG-IUSs. This is the first comprehensive report to provide a mechanistic understanding of material-property-performance relationships for IUSs. This work offers an evidence-based approach to rational excipient selection and tailoring of drug release to achieve target daily release rates in vivo. The novel insights gained through this research could be helpful for supporting development of brand and generic IUS products as well as their regulatory assessment.

Manufacturing process of liposomal Formation: A coarse-grained molecular dynamics simulation.

A method of producing liposomes has been previously developed using a continuous manufacturing technology that involves a co-axial turbulent jet in co-flow. In this study, coarse-grained molecular dynamics (CG-MD) simulations were used to gain a deeper understanding of how the self-assembly process of liposomes is affected by the material attributes (such as the concentration of ethanol) and the process parameters (such as temperature), while also providing detailed information on a nano-scale molecular level. Specifically, the CG-MD simulations yield a comprehensive internal view of the structure and formation mechanisms of liposomes containing DPPC, DPPG, and cholesterol molecules. The importance of this work is that structural details on the molecular level are proposed, and such detail is not possible to obtain through experimental studies alone. The assessment of structural properties, including the area per lipid, diffusion coefficient, and order parameters, indicated that a thicker bilayer was observed at higher ethanol concentrations, while a thinner bilayer was present at higher temperatures. These conditions led to more water penetrating the interior of the bilayer and an unstable structure, as indicated by a larger contact area between lipids and water, and a higher coefficient of lipid lateral diffusion. However, stable liposomes were found through these evaluations at lower ethanol concentrations and/or lower process temperatures. Furthermore, the CG-MD model was further compared and validated with experimental and computational data including liposomal bilayer thickness and area per lipid measurements.

Parenteral iron nutrition: Iron dextran-poloxamer thermosensitive hydrogel for prolonged intramuscular iron supplementation.

The objective of this study was to evaluate the potential of novel poloxamer thermosensitive hydrogels (PTHs) formulations for prolonged release of iron dextran particles (IDP) for intramuscular (IM) injection. The thermosensitive behaviour helps to avoid hepcidin overexpression and toxicity by releasing IDPs without iron accumulation in injection or deposit sites. We hypothesized that novel PTH formulation would prolong iron liberation compared to the commercial iron dextran formulation (FEDEX). PTHs loaded with IDPs were developed with increasing iron content (0.1, 0.2 and 0.4 g of iron/g of poloxamer) and characterized as a prolonged release IM iron supplement. The PTHs had a biocompatible pH for IM injection (6.4) and thermosensitive viscosity, increasing from ∼50 (4 °C) to ∼3000 mPa.s (37 °C). PTHs were successfully injected in the sol state (at 4 °C) into pork meat at 37 °C, transitioning to the gel state in situ (in ∼60-190 s). Structural characterization indicated that there were no PTH-IDP chemical interactions, suggesting that IDP entrapment in PTHs was physical upon gelation. In vitro release studies revealed that iron release from PTH (0.4 g of iron/g of poloxamer) reached 100 % by day 10, whereas 100 % release from FEDEX was complete in 4 h. This novel iron PTH formulation achieved a 60 times long iron release compared to the commercial product. In conclusion, the reported strategy shows adequate IDP entrapment/release properties for prolonged iron release following ex vivo IM injection using biocompatible materials. These results provide a strong basis for future preclinical evaluation to elucidate aspects such as drug release, local irritation, biocompatibility, and efficacy.

Physicochemical characterization of anionic lipid-based ternary siRNA complexes.

Physicochemical characterization is a useful tool in understanding lipoplex assemblies and their correlation to biological activity. Anionic lipid-based ternary siRNA complexes composed of anionic liposomes (DOPG/DOPE), calcium ions and siRNA, have recently been shown to be safe and efficient in a breast cancer cell culture model. In the present work, the effects of various formulation parameters such as liposome composition (DOPG/DOPE ratio) and anionic lipid/Ca2+/siRNA molar charge ratio, on the physicochemical attributes (particle size, surface charge, siRNA loading efficiency and serum stability) of these ternary anionic lipoplexes were evaluated. Particle size, siRNA loading efficiency and serum stability correlated with the in vitro silencing efficiency of these lipoplexes. For example, large lipoplex particles (5/2.5/1 anionic lipid/Ca2+/siRNA molar charge ratio) showed less efficient silencing while absolute serum stability and high siRNA loading (1.3/2.5/1 anionic lipid/Ca2+/siRNA molar charge ratio), exhibited maximum silencing in breast cancer cells. The physicochemical properties also indicated that the siRNA exists in the complexed and/or encapsulated form within the lipoplexes, depending on the anionic lipid/siRNA charge ratio. Based on these studies a model representing lipid-siRNA association within the anionic lipoplexes prepared under various formulation conditions is proposed. Physicochemical attributes can be utilized to estimate in vitro activity of lipid-siRNA complexes and understand their morphology.

A miniaturized transcutaneous system for continuous glucose monitoring.

Implantable sensors for continuous glucose monitoring hold great potential for optimal diabetes management. This is often undermined by a variety of issues associated with: (1) negative tissue response; (2) poor sensor performance; and (3) lack of device miniaturization needed to reduce implantation trauma. Herein, we report our initial results towards constructing an implantable device that simultaneously address all three aforementioned issues. In terms of device miniaturization, a highly miniaturized CMOS (complementary metal-oxide-semiconductor) potentiostat and signal processing unit was employed (with a combined area of 0.665 mm(2)). The signal processing unit converts the current generated by a transcutaneous, Clark-type amperometric sensor to output frequency in a linear fashion. The Clark-type amperometric sensor employs stratification of five functional layers to attain a well-balanced mass transfer which in turn yields a linear sensor response from 0 to 25 mM of glucose concentration, well beyond the physiologically observed (2 to 22 mM) range. In addition, it is coated with a thick polyvinyl alcohol (PVA) hydrogel with embedded poly(lactic-co-glycolic acid) (PLGA) microspheres intended to provide continuous, localized delivery of dexamethasone to suppress inflammation and fibrosis. In vivo evaluation in rat model has shown that the transcutaneous sensor system reproducibly tracks repeated glycemic events. Clarke's error grid analysis on the as-obtained glycemic data has indicated that all of the measured glucose readings fell in the desired Zones A & B and none fell in the erroneous Zones C, D and E. Such reproducible operation of the transcutaneous sensor system, together with low power (140 µW) consumption and capability for current-to-frequency conversion renders this a versatile platform for continuous glucose monitoring and other biomedical sensing devices.

Long-acting PLGA microspheres: Advances in excipient and product analysis toward improved product understanding.

Poly(lactic-co-glycolic acid) (PLGA) microspheres are a sustained-release drug delivery system with several successful commercial products used for the treatment of a variety of diseases. By utilizing PLGA polymers with different compositions, therapeutic agents can be released over durations varying from several weeks to several months. However, precise quality control of PLGA polymers and a fundamental understanding of all the factors associated with the performance of PLGA microsphere formulations remains challenging. This knowledge gap can hinder product development of both innovator and generic products. In this review, variability of the key release controlling excipient (PLGA), as well as advanced physicochemical characterization techniques for the PLGA polymer and PLGA microspheres are discussed. The relative merits and challenges of different in vitro release testing methods, in vivo pharmacokinetic studies, and in vitro-in vivo correlation development are also summarized. This review is intended to provide an in-depth understanding of long-acting microsphere products and consequently facilitate the development of these complex products.

Mucoadhesive drug delivery systems: a promising non-invasive approach to bioavailability enhancement. Part I: biophysical considerations.

INTRODUCTION: Mucoadhesive drug delivery systems (MDDS) are specifically designed to interact and bind to the mucosal layer for localized, prolonged, and/or targeted drug delivery. Over the past 4 decades, different sites have been explored for mucoadhesion including the nasal, oral, and vaginal cavities, the gastrointestinal tract and ocular tissues. AREAS COVERED: The present review aims to provide a comprehensive understanding of different aspects of MDDS development. Part I focuses on the anatomical and biological aspects of mucoadhesion, which include a detailed elucidation of the structure and anatomy of the mucosa, the properties of mucin, the different theories of mucoadhesion and evaluation techniques. EXPERT OPINION: The mucosal layer presents a unique opportunity for effective localization as well as systemic drug delivery via MDDS. Formulation of MDDS requires a thorough understanding of the anatomy of mucus tissue, the rate of mucus secretion and turnover, and the physicochemical properties of mucus. Further, the moisture content and the hydration of polymers are crucial for interaction with mucus. A confluence of different theories used to explain the mechanism of mucoadhesion is useful for understanding the mucoadhesion of different MDDS and their evaluation is subject to factors, such as the site of administration, type of dosage form, and duration of action. [Figure: see text].

Reverse engineering of Perseris and development of compositionally equivalent formulations.

Six injectable, long-acting in situ forming implant drug products based on poly(lactide-co-glycolide) (PLGA) and N-Methyl-2-Pyrrolidone (NMP) are available on the market. However, generic products, which would likely be more affordable for patients, are not yet available. This is partially due to the unique complexity of these formulations as well as the inherent heterogeneity of PLGA and the challenges in the manufacture and characterization of this polymer. This article focuses on a comprehensive characterization of Perseris (risperidone) in situ forming implant drug product, and the development of compositionally equivalent formulations. The molecular weight (MW), lactide/glycolide (L/G) ratio, end group, blockiness and glass transition temperature (Tg) of PLGA, as well as the crystal form and particle size of risperidone powder used in Perseris were identified through reverse engineering. The dissolved/suspended drug ratio in the final implant suspension for administration, as well as the real-time drug solid state in the solidified Perseris drug depot were investigated. Two compositionally equivalent formulations prepared using customized PLGA polymers with similar properties to the Perseris PLGA showed similar in vitro release and swelling behavior to Perseris as demonstrated using a novel adapter-based dissolution method. The novelty of this dissolution method lies in its ability to control implant shape, generate reproducible data, distinguish different release phases, as well as identify formulation changes. The knowledge gained in this work and the methodology established for characterization of the implant formulations are important for implant formulation development.

In situ forming risperidone implants: Effect of PLGA attributes on product performance.

Despite the unique advantages of injectable, long-acting in situ forming implant formulations based on poly(lactide-co-glycolide) (PLGA) and N-Methyl-2-Pyrrolidone (NMP), only six products are commercially available. A better understanding of PLGA will aid in the development of more in situ forming implant innovator and generic products. This article investigates the impact of slight changes in PLGA attributes, i.e., molecular weight (MW), lactide:glycolide (L/G) ratio, blockiness, and end group, on the in vitro and in vivo performance of PLGA-based in situ forming implant formulations. Perseris (risperidone) for extended-release injectable suspension was selected as the reference listed drug (RLD). A previously developed adapter-based USP 2 method was used for the in vitro release testing of various risperidone implant formulations. A rabbit model was used to determine the in vivo pharmacokinetic profiles of the formulations (subcutaneous administration) and deconvolution (Loo-Riegelman method) was conducted to obtain the in vivo release profiles. The results showed that a 5 KDa difference in the MW (19.2, 24.2, 29.2 KDa), a 5% variation in the L/G ratio (85/15, 80/20, 75/25) and the end-cap (acid vs ester) all significantly impacted the formulation behavior both in vitro and in vivo. Higher MW, higher L/G ratio and ester end-cap PLGA all resulted in longer release durations. The formulations prepared with polymers with different blockiness values (within the blockiness range tested) did not show differences in in vitro and in vivo release. An in vitro-in vivo correlation (IVIVC) was not developed due to the different in vitro and in vivo phase separation rates, swelling tendencies and consequent significantly different release profiles. This is the first report evaluating the impact of PLGA property variation (over a narrow range) on the performance of in situ forming implants. The knowledge gained will provide a better understanding of the mechanisms underlying risperidone in situ forming implant performance and will aid the development of future products.

In vivo characterization of Perseris and compositionally equivalent formulations.

Perseris is asubcutaneous extended-release risperidone in situ forming implant (suspension) indicated for the treatment of adult schizophrenia. Owing to the release rate controlling polymer poly(lactide-co-glycolide) (PLGA), one injection of Perseris can deliver risperidone for one month, which significantly reduces the administration frequency and improves patient compliance. The PLGA and drug used in Perseris was previously identified through reverse engineering and two compositionally equivalent formulations (F-1 and F-2) showing similar in vitro drug release were developed. The current work focuses on in vivo exploration of Perseris and the developed compositionally equivalent formulations using a rabbit model and further evaluate the sameness of the developed formulations compared to Perseris. The in vivo pharmacokinetic (PK) profiles, drug absorption rate, phase separation rate, macro appearance, weight loss as well as the water uptake of the solidified drug depots at different time points were investigated and compared with the in vitro release data as well as with dog and human in vivo data available in literature. Results show that the rabbit PK profile of Perseris was relevant with those obtained from both the dog model and the clinical data, indicating that the rabbit model is appropriate for investigation of the in vivo performance of risperidone implants. Consistent with their similar in vitro drug release, the two compositionally equivalent formulations demonstrated similar PK profiles, drug absorption rates, weight loss and swelling in vivo compared to Perseris. Although the erosion mechanism appeared to be similar between in vitro and in vivo, there were in vitro-in vivo differences concerning the drug release kinetics, phase separation rates and swelling behavior. This work provides a comprehensive in vitro/in vivo understanding of Perseris and the developed compositionally equivalent formulations, which will be beneficial for future development of generic as well as novel PLGA in situ forming implant products.

Investigating structural attributes of drug encapsulated microspheres with quantitative X-ray imaging.

The intra-sphere and inter-sphere structural attributes of controlled release microsphere drug products can greatly impact their release profile and clinical performance. In developing a robust and efficient method to characterize the structure of microsphere drug products, this paper proposes X-ray microscopy (XRM) combined with artificial intelligence (AI)-based image analytics. Eight minocycline loaded poly(lactic-co-glycolic acid) (PLGA) microsphere batches were produced with controlled variations in manufacturing parameters, leading to differences in their underlying microstructures and their final release performances. A representative number of microspheres samples from each batch were imaged using high resolution, non-invasive XRM. Reconstructed images and AI-assisted segmentation were used to determine the size distribution, XRM signal intensity, and intensity variation of thousands of microspheres per sample. The signal intensity within the eight batches was nearly constant over the range of microsphere diameters, indicating high structural similarity of spheres within the same batch. Observed differences in the variation of signal intensity between different batches suggests inter-batch non-uniformity arising from differences in the underlying microstructures associated with different manufacturing parameters. These intensity variations were correlated with the structures observed from higher resolution focused ion beam scanning electron microscopy (FIB-SEM) and the in vitro release performance for the batches. The potential for this method for rapid at-line and offline product quality assessment, quality control, and quality assurance is discussed.

Protein encapsulation in unilamellar liposomes: high encapsulation efficiency and a novel technique to assess lipid-protein interaction.

PURPOSE: To encapsulate a large amount of protein (superoxide dismutase, SOD) into unilamellar liposomes using a simple process and to investigate the lipid-protein interaction. METHOD: To achieve protein encapsulation, preformed unilamellar empty liposomes were mixed with SOD and subjected to freeze-thaw cycling. To investigate the lipid-protein interaction, a novel light scattering technique was used. RESULTS: Up to 50% protein encapsulation was achieved at ∼150 nm. There was no significant change in particle size following the freeze-thaw cycling. SOD had a strong interaction with DPPC liposomes containing high concentration of cholesterol. Light scattering data revealed that in some cases the SOD molecules were present inside the lipid bilayer. CONCLUSIONS: The method reported here allows great flexibility in the manufacturing process as the liposome preparation and protein-loading operations can be separated. Accordingly, empty liposomes can be prepared without concern about protein stability, making the manufacturing process more flexible and easy to control and ultimately leading to improved product quality. To explain the SOD-lipid interaction, a "pocket-embedding" theory was proposed. The encapsulation method reported here can be applied to hydrophilic small molecules as well as most hydrophilic proteins to achieve high encapsulation efficiency.