Importance of single or blended polymer types for controlled in vitro release and plasma levels of a somatostatin analogue entrapped in PLA/PLGA microspheres

Patient-Centric Long-Acting Injectable and Implantable Platforms─An Industrial Perspective

The increasing focus on patient centricity in the pharmaceutical industry over the past decade and the changing healthcare landscape, driven by factors such as increased access to information, social media, and evolving patient demands, has necessitated a shift toward greater connectivity and understanding of patients' unique treatment needs. One pharmaceutical technology that has supported these efforts is long acting injectables (LAIs), which lower the administration frequency for the patient's provided convenience, better compliance, and hence better therapeutical treatment for the patients. Furthermore, patients with conditions like the human immunodeficiency virus and schizophrenia have positively expressed the desire for less frequent dosing, such as that obtained through LAI formulations. In this work, a comprehensive analysis of marketed LAIs across therapeutic classes and technologies is conducted. The analysis demonstrated an increasing number of new LAIs being brought to the market, recently most as aqueous suspensions and one as a solution, but many other technology platforms were applied as well, in particular, polymeric microspheres and in situ forming gels. The analysis across the technologies provided an insight into to the physicochemical properties the compounds had per technology class as well as knowledge of the excipients typically used within the individual formulation technology. The principle behind the formulation technologies was discussed with respect to the release mechanism, manufacturing approaches, and the possibility of defining predictive in vitro release methods to obtain in vitro in vivo correlations with an industrial angle. The gaps in the field are still numerous, including better systematic formulation and manufacturing investigations to get a better understanding of potential innovations, but also development of new polymers could facilitate the development of additional compounds. The biggest and most important gaps, however, seem to be the development of predictive in vitro dissolution methods utilizing pharmacopoeia described equipment to enable their use for product development and later in the product cycle for quality-based purposes.

Injectable controlled-release systems for the prevention and treatment of infectious diseases

Pharmaceutical drugs, including vaccines, pre- and post-exposure prophylactics, and chronic drug therapies, are crucial tools in the prevention and treatment of infectious diseases. These drugs have the ability to increase survival and improve patient quality of life; however, infectious diseases still accounted for more than 10.2 million deaths in 2019 before the COVID-19 pandemic. High mortality can be, in part, attributed to challenges in the availability of adequate drugs and vaccines, limited accessibility, poor drug bioavailability, the high cost of some treatments, and low patient adherence. A majority of these factors are logistical rather than technical challenges, providing an opportunity for existing drugs and vaccines to be improved through formulation. Injectable controlled-release drug delivery systems are one class of formulations that have the potential to overcome many of these limitations by releasing their contents in a sustained manner to reduce the need for frequent re-administration and improve clinical outcomes. This review provides an overview of injectable controlled drug delivery platforms, including microparticles, nanoparticles, and injectable gels, detailing recent developments using these systems for single-injection vaccination, long-acting prophylaxis, and sustained-release treatments for infectious disease.

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.

3D printing of polylactic acid: recent advances and opportunities

Bio-based polymers are a class of polymers made by living organisms, a few of them known and commercialized yet. Due to poor mechanical strength and economic constraints, they have not yet seen the extensive application. Instead, they have been an appropriate candidate for biological applications. Growing consumer knowledge of the environmental effect of polymers generated from petrochemical sources and a worldwide transition away from plastics with a lifespan of hundreds of years has resulted in greater interest in such hitherto unattainable sectors. Bio-based polymers come in various forms, including direct or "drop-in" replacements for their petrochemical counterparts with nearly identical properties or completely novel polymers that were previously unavailable, such as polylactide. Few of these bio-based polymers offer significantly improved technical specifications than their alternatives. Polylactic acid (PLA) has been well known in the last decade as a biodegradable thermoplastic source for use in 3DP by the "fused deposition modeling" method. The PLA market is anticipated to accomplish 5.2 billion US dollars in 2020 for its industrial usage. Conversely, 3DP is one of the emerging technologies with immense economic potential in numerous sectors where PLA is one of the critical options as the polymer source due to its environmentally friendly nature, glossiness, multicolor appearance, and ease of printing. The chemical structure, manufacturing techniques, standard features, and current market situation of PLA were examined in this study. This review looks at the process of 3DP that uses PLA filaments in extrusion-based 3DP technologies in particular. Several recent articles describing 3D-printed PLA items have been highlighted.

Research progress of bone-targeted drug delivery system on metastatic bone tumors

Bone metastases are common in malignant tumors and the effect of conventional treatment is limited. How to effectively inhibit tumor bone metastasis and deliver the drug to the bone has become an urgent issue to be solved. While bone targeting drug delivery systems have obvious advantages in the treatment of bone tumors. The research on bone-targeted anti-tumor therapy has made significant progress in recent years. We introduced the related tumor pathways of bone metastases. The tumor microenvironment plays an important role in metastatic bone tumors. We introduce a drug-loading systems based on different environment-responsive nanocomposites for anti-tumor and anti-metastatic research. According to the process of bone metastases and the structure of bone tissue, we summarized the information on bone-targeting molecules. Bisphosphate has become the first choice of bone-targeted drug delivery carrier because of its affinity with hydroxyapatite in bone. Therefore, we sought to summarize the bone-targeting molecule of bisphosphate to identify the modification effect on bone-targeting. And this paper discusses the relationship between bisphosphate bone targeting molecular structure and drug delivery carriers, to provide some new ideas for the research and development of bone-targeting drug delivery carriers. Targeted therapy will make a more outstanding contribution to the treatment of tumors.

The industrial design, translation, and development strategies for long-acting peptide delivery

INTRODUCTION

Peptides are widely recognized as therapeutic agents in the treatment of a wide range of diseases, such as cancer, diabetes etc. However, their use has been limited by their short half-life, due to significant metabolism by exo- and endo-peptidases as well as their inherent poor physical and chemical stability. Research with the aim of improving their half-life in the body, and thus improving patient compliance (by decreasing the frequency of injections) has gained significant attention.

AREAS COVERED

This review outlines the current landscape and industrial approaches to achieve extended peptide exposure and reduce dosing frequency. Emphasis is placed on identifying challenges in drug product manufacturing and desirable critical quality attributes that are essential for activity and safety, providing insights into chemistry and design aspects impacting peptide release, and summarizing important considerations for CMC developability assessments of sustained release peptide drugs.

EXPERT OPINION

Bring the patient and disease perspective early into development. Substantial advances have been made in the field of sustained delivery of peptides despite their complexity. The article will also highlight considerations for early-stage product design and development, providing an industrial perspective on risk mitigation in developing sustained release peptide drug products.

Initial Formation of the Skin Layer of PLGA Microparticles

Poly(lactide-co-glycolide) (PLGA) has been extensively used in making long-acting injectable formulations. The critical factors affecting the PLGA formulation properties have been adjusted to control the drug release kinetics and obtain desirable properties of PLGA-based drug delivery systems. The PLGA microparticle formation begins as soon as the drug/PLGA-dissolved in the organic solvent phase (oil phase) is exposed to the water phase. The initial skin (or shell) formation on the oil droplets occurs very quickly, sometimes in the matter of milliseconds, and studying the process has been difficult. The skin formation on the PLGA emulsion droplet surface that can affect the subsequent hardening steps is examined. PLGA droplets with different compositions are prepared. Using collimated light and a high-speed camera made it possible to detect the diffusion of acetonitrile from the oil phase into the water phase during the oil droplet formation. Although the skin formation is not visible on the surface of the oil phase droplet with the current setup, the droplet shapes, solid strand formation, and the difference in the spreading time suggest that the initial contact time between the oil and water phases in the range of a few seconds is critical to the properties of the skin.

Drug release from in situ forming implants and advances in release testing

In situ forming implants, defined as liquid formulations that generate solid or semisolid depots following administration, have shown a range of advantages in drug delivery. This drug delivery strategy allows localized delivery, sustained drug release over periods of days to months, and is a less invasive option compared to traditional solid implants which typically require surgical implantation. Unfortunately, there are a number of quality control challenges in terms of drug release testing of these delivery systems which is likely to have contributed to the relatively few commercially available in situ forming implant products. This article reviews current marketed in situ forming implant products, FDA guidance on in vitro release testing, and formulation and environmental parameters influencing drug release from in situ forming implants. Formulation considerations for development of biological agents loaded in situ forming implants are also discussed. The advantages and limitations of typically used in vitro release testing methods are summarized. Difficulties in the development of in vitro-in vivo correlations (IVIVCs) for in situ forming implant are discussed. The knowledge presented will be helpful for the development of in situ forming implants, as well as for the development of appropriate in vitro testing methods and IVIVCs.

Preparation and in vivo/in vitro characterization of Ticagrelor PLGA sustained-release microspheres for injection

The objective of this paper was to develop a PLGA carrier Ticagrelor sustained-release microspheres preparation, which was expected to continue to release Ticagrelor for 14 days with a high encapsulation rate. Ticagrelor microspheres were prepared successfully with average diameter of 7.31 µm, drug loading of 12.49 ± 0.32% and EE up to 79.09 ± 1.69%. In the release medium of PH7.4 PBS, the microspheres showed good drug release behavior in vitro. In vivo release results also showed that the sustained-release microspheres could effectively control drug release in vivo and maintain a relatively stable blood drug concentration for about 2 weeks. The results indicate that Ticagrelor sustained-release microspheres can be used for long-term treatment of acute coronary syndrome.

A sensitive in vitro performance assay reveals the in vivo drug release mechanisms of long-acting medroxyprogesterone acetate microparticles

Today, a growing number of subcutaneously administered depot formulations enable continuous delivery of poorly soluble compounds over a longer time period. The modified liberation is considered to be a rate-limiting step in drug absorption and thus impacts therapeutic efficacy and product safety. In the present approach, a mechanism-based pharmacokinetic model of the commercial microparticle formulation depo-subQ provera 104™ (Sauter mean diameter of 5.08 ± 1.63 µm) was established. The model was verified using human pharmacokinetic data from three different clinical trials. Further, the effects of drug release, injection site and patient population on the pharmacokinetic profile were investigated. For this purpose, the drug release was assessed using the novel dispersion releaser technology, whereby a biorelevant medium reflecting major characteristics of the subcutaneous tissue (including ion background, buffer capacity and protein concentration) was used. The established model provided an effective prediction of the key pharmacokinetic parameters, including C_max, T_max and AUC_all. Only in presence of 55% of fetal bovine serum (using a novel simulated subcutaneous interstitial fluid), the release assay was capable to discriminate between microparticles before and after storage.

In vitro-in vivo correlation of parenteral PLGA microspheres: Effect of variable burst release

Development of IVIVCs is a very complicated process, especially for complex drug products such as parenteral PLGA microspheres with multiphasic drug release characteristics. Specifically, microspheres that exhibit an initial burst release phase are even more challenging since the in vitro and in vivo burst release phases may not be comparable if drug absorption is rate-limiting at this stage. Therefore, the objectives of the present work were: 1) to investigate the predictability of developed IVIVCs for the in vivo burst release phase based on the in vitro burst release phase of the formulations; and 2) to evaluate the impact of variable burst release on the predictability of the developed IVIVCs for two different types of microsphere-based drug products. Accordingly, Risperdal Consta® (Risperidone) and Lupron Depot® (Leuprolide acetate, LA) were selected as model products. Compositionally equivalent risperidone and LA formulations with variable burst release phases were prepared with manufacturing process changes (such as solvent systems and mixing methods). The prepared microspheres exhibited differences in critical physicochemical properties (such as particle size, porosity, average pore diameter, and drug distribution) and hence differences in their in vitro release characteristics (such as variable burst release and release rate). The in vitro and in vivo (rabbit model (intramuscular injection) burst release were similar for the risperidone microspheres but were significantly different for the LA microspheres. This had an impact on the complexity of the developed IVIVC models. Level A IVIVCs with the ability to predict various types of burst release were developed using time scaling and shifting factors. Moreover, it was observed that IVIVCs developed using formulations with less variation in burst release had better predictability and vice-versa. Thus, the present research has provided a comprehensive understanding of the impact of the burst release phase on the development, complexity, and predictability of IVIVCs for complex parenteral microspheres containing a variety of therapeutic molecules.

Novel Dissolution Approach for Tacrolimus-Loaded Microspheres Using a Dialysis Membrane for in Vitro-in Vivo Correlation

The aim of this study was to establish a novel approach to in vitro dissolution evaluation using a combination of the paddle method and a dialysis membrane, both to predict the overall in vivo performance of tacrolimus microspheres and also to identify a suitable dissolution test method to describe the in vivo initial burst phenomenon. This new dissolution method for evaluating the release of tacrolimus from microspheres consisted of rotating a customized paddle inside a dialysis membrane using a conventional paddle apparatus. Findings were compared with a method in which the paddle was rotated outside the dialysis membrane, the conventional paddle method, and the flow-through cell method. We concluded that the paddle method with a dialysis membrane and internal agitation, which was designed to mimic in vivo conditions, predicted the overall pharmacokinetic (PK) profile of tacrolimus microspheres whereas the conventional paddle method described the initial burst. These findings suggest that it may not be possible to predict both the PK profile and initial burst using a single analysis method. We therefore recommend that evaluation of the initial burst be performed separately. In conclusion, we propose that combination of the paddle method with a dialysis membrane and internal agitation to evaluate the overall PK profile, together with the paddle method to describe the in vivo initial burst, represents a novel approach to in vitro dissolution evaluation for microsphere formulations.

In Vitro and In Vivo Correlation of Bone Morphogenetic Protein-2 Release Profiles from Complex Delivery Vehicles

Local sustained delivery of bioactive molecules from biomaterials is a promising strategy to enhance bone regeneration. To optimize delivery vehicles for bone formation, the design characteristics are tailored with consequential effect on bone morphogenetic protein-2 (BMP-2) release and bone regeneration. Complying with the 3R principles (Replacement, Reduction, and Refinement), the growth factor release is often investigated in vitro using several buffers to mimic the in vivo physiological environment. However, this remains an unmet need. Therefore, this study investigates the in vitro-in vivo correlation (IVIVC) of BMP-2 release from complex delivery vehicles in several commonly used in vitro buffers: cell culture model, phosphate buffered saline, and a strong desorption buffer. The results from this study showed that the release environment affected the BMP-2 release profiles, creating distinct relationships between release versus time and differences in extent of release. According to the guidance set by the U.S. Food and Drug Administration (FDA), IVIVC resulted in level A internal predictability for individual composites. Since the IVIVC was influenced by the BMP-2 loading method and composite surface chemistry, the external predictive value of the IVIVCs was limited. These results show that the IVIVCs can be used for predicting the release of an individual composite. However, the models cannot be used for predicting in vivo release for different composite formulations since they lack external predictability. Potential confounding effects of drug type, delivery vehicle formulations, and application site should be added to the equation to develop one single IVIVC applicable for complex delivery vehicles. Altogether, these results imply that more sophisticated in vitro systems should be used in bone regeneration to accurately discriminate and predict in vivo BMP-2 release from different complex delivery vehicles.

Multifunctional targeting vinorelbine plus tetrandrine liposomes for treating brain glioma along with eliminating glioma stem cells

Malignant brain glioma is the most lethal and aggressive type of cancer. Surgery and radiotherapy cannot eliminate all glioma stem cells (GSCs) and blood–brain barrier (BBB) restricts the movement of antitumor drugs from blood to brain, thus leading to the poor prognosis with high recurrence rate. In the present study, the targeting conjugates of cholesterol polyethylene glycol polyethylenimine (CHOL-PEG₂₀₀₀-PEI) and D-a-tocopheryl polyethylene glycol 1000 succinate vapreotide (TPGS₁₀₀₀-VAP) were newly synthesized for transporting drugs across the BBB and targeting glioma cells and GSCs. The multifunctional targeting vinorelbine plus tetrandrine liposomes were constructed by modifying the targeting conjugates. The studies were undertaken on BBB model, glioma cells, GSCs, and glioma-bearing mice. In vitro results showed that multifunctional targeting drugs-loaded liposomes with suitable physicochemical property could enhance the transport drugs across the BBB, increase the intracellular uptake, inhibit glioma cells and GSCs, penetrate and destruct the GSCs spheroids, and induce apoptosis via activating related apoptotic proteins. In vivo results demonstrated that multifunctional targeting drugs-loaded liposomes could significantly accumulate into brain tumor location, show the specificity to tumor sites, and result in a robust overall antitumor efficacy in glioma-bearing mice. These data suggested that the multifunctional targeting vinorelbine plus tetrandrine liposomes could offer a promising strategy for treating brain glioma.

Recent advances in testing of microsphere drug delivery systems

INTRODUCTION

This review discusses advances in the field of microsphere testing.

AREAS COVERED

In vitro release-testing methods such as sample and separate, dialysis membrane sacs and USP apparatus IV have been used for microspheres. Based on comparisons of these methods, USP apparatus IV is currently the method of choice. Accelerated in vitro release tests have been developed to shorten the testing time for quality control purposes. In vitro-in vivo correlations using real-time and accelerated release data have been developed, to minimize the need to conduct in vivo performance evaluation. Storage stability studies have been conducted to investigate the influence of various environmental factors on microsphere quality throughout the product shelf life. New tests such as the floating test and the in vitro wash-off test have been developed along with advancement in characterization techniques for other physico-chemical parameters such as particle size, drug content, and thermal properties.

EXPERT OPINION

Although significant developments have been made in microsphere release testing, there is still a lack of guidance in this area. Microsphere storage stability studies should be extended to include microspheres containing large molecules. An agreement needs to be reached on the use of particle sizing techniques to avoid inconsistent data. An approach needs to be developed to determine total moisture content of microspheres.

Preparation and in vivo evaluation of insulin-loaded biodegradable nanoparticles prepared from diblock copolymers of PLGA and PEG

The aim of this study was to design a controlled release vehicle for insulin to preserve its stability and biological activity during fabrication and release. A modified, double emulsion, solvent evaporation, technique using homogenisation force optimised entrapment efficiency of insulin into biodegradable nanoparticles (NP) prepared from poly (DL-lactic-co-glycolic acid) (PLGA) and its PEGylated diblock copolymers. Formulation parameters (type of polymer and its concentration, stabiliser concentration and volume of internal aqueous phase) and physicochemical characteristics (size, zeta potential, encapsulation efficiency, in vitro release profiles and in vitro stability) were investigated. In vivo insulin sensitivity was tested by diet-induced type II diabetic mice. Bioactivity of insulin was studied using Swiss TO mice with streptozotocin-induced type I diabetic profile. Insulin-loaded NP were spherical and negatively charged with an average diameter of 200-400 nm. Insulin encapsulation efficiency increased significantly with increasing ratio of co-polymeric PEG. The internal aqueous phase volume had a significant impact on encapsulation efficiency, initial burst release and NP size. Optimised insulin NP formulated from 10% PEG-PLGA retained insulin integrity in vitro, insulin sensitivity in vivo and induced a sustained hypoglycaemic effect from 3h to 6 days in type I diabetic mice.

In vitro-in vivo correlation for complex non-oral drug products: Where do we stand?

In vitro–in vivo correlation (IVIVC) is a predictive mathematical model describing the relationship between an in vitro property and a relevant in vivo response of drug products. Since the U.S. Food and Drug Administration (FDA) published a regulatory guidance on the development, evaluation, and applications of IVIVC for extended release (ER) oral dosage forms in 1997, IVIVC has been one of the most important issues in the field of pharmaceutics. However, even with the aid of the FDA IVIVC Guidance, only very limited Abbreviated New Drug Application (ANDA) submission for ER oral drug products included adequate IVIVC data to enable the completion of bioequivalence (BE) review within first review cycle. Establishing an IVIVC for non-oral dosage forms has remained extremely challenging due to their complex nature and the lack of in vitro release methods that are capable of mimicking in vivo drug release conditions. This review presents a general overview of recent advances in the development of IVIVC for complex non-oral dosage forms (such as parenteral polymeric microspheres/implants, and transdermal formulations), and briefly summarizes the knowledge gained over the past two decades. Lastly this review discusses possible directions for future development of IVIVC for complex non-oral dosage forms.

In vitro-in vivo correlation of parenteral risperidone polymeric microspheres

The objective of the present study was to determine whether an in vitro-in vivo correlation (IVIVC) can be established for polymeric microspheres that are equivalent in formulation composition but prepared with different manufacturing processes. Risperidone was chosen as a model therapeutic and poly(lactic-co-glycolic acid) (PLGA) with similar molecular weight as that used in the commercial product Risperdal® Consta® was used to prepare risperidone microspheres. Various manufacturing processes were investigated to produce the risperidone microspheres with similar drug loading (approx. 37%) but distinctly different physicochemical properties (e.g. porosity, particle size and particle size distribution). In vitro release of the risperidone microspheres was investigated using different release testing methods (such as sample-and-separate and USP apparatus 4). In vivo pharmacokinetic profiles of the risperidone microsphere formulations following intramuscular administration were determined using a rabbit model. Furthermore, the obtained pharmacokinetic profiles were deconvoluted using the Loo-Riegelman method and the calculated in vivo release was compared with the in vitro release of these microspheres. Level A IVIVCs were established and validated for the compositionally equivalent risperidone microspheres based on the in vitro release data obtained using USP apparatus 4. The developed IVIVCs demonstrated good predictability and were robust. These results showed that the developed USP apparatus 4 method was capable of discriminating PLGA microspheres that are equivalent in formulation composition but with manufacturing differences and predicting their in vivo performance in the investigated animal model.

Polymeric nanoparticles and microparticles for the delivery of peptides, biologics, and soluble therapeutics

Biologically derived therapeutics, or biologics, are the most rapidly growing segment of the pharmaceutical marketplace. However, there are still unmet needs in improving the delivery of biologics. Injectable polymeric nanoparticles and microparticles capable of releasing proteins and peptides over time periods as long as weeks or months have been a major focus in the effort to decrease the frequency of administration. These particle systems fit broadly into two categories: those composed of hydrophilic and those composed of hydrophobic polymeric scaffolds. Here we review the factors that contribute to the slow and controlled release from each class of particle, as well as the effects of synthesis parameters and product design on the loading, encapsulation efficiency, biologic integrity, and release profile. Generally, hydrophilic scaffolds are ideal for large proteins while hydrophobic scaffolds are more appropriate for smaller biologics without secondary structure. Here we also introduce a Flash NanoPrecipitation method that has been adopted for encapsulating biologics in nanoparticles (40-200nm) at high loadings (50-75wt.%) and high encapsulation efficiencies. The hydrophilic gel interior and hydrophobic shell provide an opportunity to combine the best of both classes of injectable polymeric depots.

On-demand one-step synthesis of monodisperse functional polymeric microspheres with droplet microfluidics

A simple and robust method for one-step synthesis of monodisperse functional polymeric microspheres was established by generation of reversed microemulsion droplets in aqueous phase inside microfluidic chips and controlled evaporation of the organic solvent. Using this method, water-soluble nanomaterials can be easily encapsulated into biodegradable Poly(D,L-lactic-co-glycolic acid) (PLGA) to form functional microspheres. By controlling the flow rate of microemulsion phase, PLGA polymeric microspheres with narrow size distribution and diameters in the range of ∼50-100 μm were obtained. As a demonstration of the versatility of the approach, high-quality fluorescent CdTe:Zn(2+) quantum dots (QDs) of various emission spectra, superparamagnetic Fe3O4 nanoparticles, and water-soluble carbon nanotubes (CNTs) were used to synthesize fluorescent PLGA@QDs, magnetic PLGA@Fe3O4, and PLGA@CNTs polymeric microspheres, respectively. In order to show specific applications, the PLGA@Fe3O4 were modified with polydopamine (PDA), and then the silver nanoparticles grew on the surfaces of the PLGA@Fe3O4@PDA polymeric microspheres by reducting the Ag(+) to Ag(0). The as-prepared PLGA@Fe3O4@PDA-Ag microspheres showed a highly efficient catalytic reduction of the 4-nitrophenol, a highly toxic substance. The monodisperse uniform functional PLGA polymeric microspheres can potentially be critically important for multiple biomedical applications.

In vitro-in vivo correlation from lactide-co-glycolide polymeric dosage forms

The objective of this study was to compare the in vitro behavior of four long-acting subcutaneous risperidone formulations with in vivo performance, with the intent of establishing an IVIVC. Two copolymers of PLGA (50:50 and 75:25) were used to prepare four microsphere formulations of risperidone, an atypical antipsychotic. In vitro behavior was assessed at the physiological temperature (37 °C) using the ‘modified dialysis’ technique. The in vitro release profile demonstrated rank order behavior with Formulations A and B, prepared using the 50:50 copolymer, exhibiting rapid drug release, while Formulations C and D, prepared using 75:25 PLGA, released drug in a slower manner. In vivo profiles were obtained by two approaches, i.e., deconvolution using the Nelson–Wagner equation (the FDA recommended approach) and using fractional AUC. With both in vivo approaches, the 50:50 PLGA preparations released drug faster than the 75:25 PLGA microspheres, exhibiting the same rank order observed in vitro. Additionally, profiles for the four formulations obtained using the deconvolution approach were nearly superimposable with fractional AUC, implying that the latter procedure could be used as a substitute for the Nelson–Wagner method. A comparison of drug release profiles for the four formulations revealed that in three of the four formulations, in vivo release was slightly faster than that in vitro, but the results were not statistically significant (P > 0.0001). An excellent linear correlation (R² values between 0.97 and 0.99) was obtained when % in vitro release for each formulation was compared with its corresponding in vivo release profile, obtained by using fraction absorbed (Nelson–Wagner method) or fractional AUC. In summary, using the four formulations that exhibited different release rates, a Level A IVIVC was established using the FDA-recommended deconvolution method and fractional AUC approach. The excellent relationship between in vitro drug release and the amount of drug absorbed in vivo in this study was corroborated by the nearly 1:1 correlation (R² greater than 0.97) between in vitro release and in vivo performance. Thus, the results of the current study suggest that proper selection of an in vitro method to assess drug release from long-acting injectables will aid in obtaining a Level A IVIVC.

Long-term delivery of protein therapeutics

INTRODUCTION

Proteins are effective biotherapeutics with applications in diverse ailments. Despite being specific and potent, their full clinical potential has not yet been realized. This can be attributed to short half-lives, complex structures, poor in vivo stability, low permeability, frequent parenteral administrations and poor adherence to treatment in chronic diseases. A sustained release system, providing controlled release of proteins, may overcome many of these limitations.

AREAS COVERED

This review focuses on recent development in approaches, especially polymer-based formulations, which can provide therapeutic levels of proteins over extended periods. Advances in particulate, gel-based formulations and novel approaches for extended protein delivery are discussed. Emphasis is placed on dosage form, method of preparation, mechanism of release and stability of biotherapeutics.

EXPERT OPINION

Substantial advancements have been made in the field of extended protein delivery via various polymer-based formulations over last decade despite the unique delivery-related challenges posed by protein biologics. A number of injectable sustained-release formulations have reached market. However, therapeutic application of proteins is still hampered by delivery-related issues. A large number of protein molecules are under clinical trials, and hence, there is an urgent need to develop new methods to deliver these highly potent biologics.

IVIVC from Long Acting Olanzapine Microspheres

In this study, four PLGA microsphere formulations of Olanzapine were characterized on the basis of their in vitro behavior at 37°C, using a dialysis based method, with the goal of obtaining an IVIVC. In vivo profiles were determined by deconvolution (Nelson-Wagner method) and using fractional AUC. The in vitro and in vivo release profiles exhibited the same rank order of drug release. Further, in vivo profiles obtained with both approaches were nearly superimposable, suggesting that fractional AUC could be used as an alternative to the Nelson-Wagner method. A comparison of drug release profiles for the four formulations revealed that the in vitro profile lagged slightly behind in vivo release, but the results were not statistically significant (P < 0.0001). Using the four formulations that exhibited different release rates, a Level A IVIVC was established using the deconvolution and fractional AUC approaches. A nearly 1 : 1 correlation (R² > 0.96) between in vitro release and in vivo measurements confirmed the excellent relationship between in vitro drug release and the amount of drug absorbed in vivo. The results of this study suggest that proper selection of an in vitro method will greatly aid in establishing a Level A IVIVC for long acting injectables.

Preparation of bioactive interferon alpha-loaded polysaccharide nanoparticles using a new approach of temperature-induced water phase/water-phase emulsion

The aim of this study was to develop a temperature-induced polyethylene glycol (PEG) water phase/polysaccharide water-phase emulsion approach for preparing interferon alpha-2b (IFNα-2b)-loaded polysaccharide nanoparticles. IFNα-2b was first added to a mixture of an aqueous solution of PEG and polysaccharide. The mixture solution was stirred in a magnetic stirrer at a rate of 2000 rpm for 45 seconds at 0°C ± 0.5°C. The solution was then prefrozen at different temperatures. The polysaccharide and IFNα-2b partitioned in the polysaccharide phase were preferentially separated out as the dispersed phase from the mixture solution during the prefreezing process. Then the prefrozen sample was freeze-dried to powder form. In order to remove the PEG, the powder was washed with dichloromethane. Once IFNα-2b was loaded into the polysaccharide nanoparticles, these nanoparticles could gain resistance to vapor–water and water–oil interfaces to protect IFNα-2b. The antiviral activity of the polysaccharide nanoparticles in vitro was highly preserved (above 97%), while the antiviral activity of IFNα-2b–loaded polysaccharide nanoparticles using the control water-in-oil-in-water method was only 71%. The antiviral activity of the IFNα-2b from blood samples was also determined on the basis of the activity to inhibit the cytopathic effects of the Sindbis virus on Follicular Lymphoma cells (FL). The antiviral activity in vivo was also highly preserved (above 97%). These polysaccharide nanoparticles could be processed to different formulations according to clinical requirements.

The effect of poly(d,l-lactide-co-glycolide)-alendronate conjugate nanoparticles on human osteoclast precursors

Nanoparticles (NPs) formed from polymers conjugated with bisphosphonates (BPs) allow the bone targeting of loaded drugs, such as doxorubicin, for the treatment of skeletal tumours. The additional antiosteoclastic effect of the conjugated BP could contribute to the inhibition of tumour-associated bone degradation. With this aim, we have produced NPs made of poly(d,l-lactide-co-glycolide) (PLGA) conjugated with alendronate (ALE). To show if ALE retained the antiosteoclastic properties after the conjugation with PLGA and the production of NPs, we treated human osteoclasts, derived from circulating precursors, with PLGA-ALE NPs and compared the effects on actin ring generation, apoptosis and type-I collagen degradation with those of free ALE and with NPs made of pure PLGA. PLGA-ALE NPs disrupted actin ring, induced apoptosis and inhibited collagen degradation. Unexpectedly, also NPs made of pure PLGA showed similar effects. Therefore, we cannot exclude that in addition to the observed antiosteoclastic activity dependent on ALE in PLGA-ALE NPs, there was also an effect due to pure PLGA. Still, as PLGA-ALE NPs are intended for the loading with drugs for the treatment of osteolytic bone metastases, the additional antiosteoclastic effect of PLGA-ALE NPs, and even of PLGA, may contribute to the inhibition of the disease-associated bone degradation.

Effect of the Lactide/Glycolide Ratio and Molecular Weight of PLGA on the Bovine BMPs Microspheres Systems

The present investigation was aimed at optimization of BMPs loaded PLGA microspheres formulations resulting in improved encapsulation efficiency and sustained release of BMPs by varying the molecular weight and copolymer composition of PLGA. Double-emulsion solvent evaporation method was used to prepare the microspheres. The effect of polymer molecular weight and copolymer composition on particle properties and release behavior in vitro was reported. The particle size and encapsulation efficiency increased with increase in molecular weight and lactide content of PLGA. While BMPs release in vitro decreased with increase in molecular weight and lactide content of PLGA. SEM pictures revealed that almost all microspheres were spherical but internal morphology was different. The morphology of PLGA microspheres with exorbitant molecular weight(100kD) was anomalistic whereas the morphology of PLGA microspheres with higher glycolide content(50) have porous structures.

Formulation of sustained-release microspheres of granulocyte macrophage colony stimulating factor by freezing-induced phase separation with dextran and encapsulation with blended polymers

This study aimed to assess the potential merits of formulating sustained-release microspheres of recombinant human granulocyte macrophage colony stimulating factor (rhGM-CSF) via freezing-induced phase separation (FIPS) of the protein with dextran followed by encapsulation with binary mixture of poly(lactic-co-glycolic acid) (PLGA) 2A (MW∼12K) and 3A (MW∼47K) or of PLGA2A and polylactic acid (PLA; MW∼83K). The formulated dextran particles and microspheres were characterized in vitro for loading, aggregation, bioactivity and release behavior of the protein where appropriate. rhGM-CSF retained about 60% of bioactivity with no significant aggregation after each formulation step. Encapsulation of protein-loaded dextran particles attained only 80% with the PLGA2A and PLGA3A blend, but 100% with the PLGA2A and PLA mixture. The former formulation exhibited a triphasic in-vitro release profile typical of PLGA microspheres while the latter revealed a much lower initial burst followed by a steady and complete release of rhGM-CSF with preserved bioactivity over a 15-day period.

Development of interferon alpha-2b microspheres with constant release

Interferon alpha-2b (IFNα-2b) is an important immune regulator used widely in clinic. However, frequent subcutaneous injection and substantial toxicity decrease patients' compliance. So, drug delivery with more precisely controlled drug release is urgent for IFNα-2b. Microsphere is a promising sustained drug delivery system, which has been studied widely for delivery of proteins. However, it was found difficult to keep proteins' activity and guarantee complete release. In this study, we solidified IFNα-2b as microparticles firstly by co-lyophilizing it with gelatin and ZnSO(4). Microspheres were then prepared. The preparing procedure and formulation were optimized with encapsulation efficiency and in vitro release as main parameters. Finally, the microspheres were prepared by S/O/W method with microparticle size about 5 μm and PEGT/PBT-PLGA (9:1, w/w) as matrix material. The diameter of microspheres was 28.94 μm, the encapsulation efficiency was 86.01%, the burst release was 16.69%, the cumulative release was 83.06% at 23th day, and IFNα-2b was released from microspheres with a zero-order profile. These microspheres also demonstrated sustained and steady release for about 13 days in rats. In conclusion, the procedure and formulation used in this study were supposed to be successful to keep IFNα-2b active and released constantly and completely.

Preparation of ONO-1301-loaded poly(lactide-co-glycolide) microspheres and their effect on nerve conduction velocity

Objectives

The aim of this study was to prepare poly(lactide-co-glycolide) (PLGA) microspheres containing ONO-1301, a novel long-acting prostacyclin agonist with thromboxane synthase inhibitory activity, with 10% of drug released in the initial burst and a sustained-release period of about 3 weeks after administration. The effect of PLGA type (molecular weight and the lactide/glycolide (L/G) ratio in PLGA), the preparative conditions and the particle size on the in-vitro release profile were examined. The effect of optimized ONO-1301-loaded PLGA microspheres on delayed nerve condition velocity (NCV) was investigated in streptozotocin (STZ) induced diabetic rats.

Methods

ONO-1301 PLGA microspheres were produced by the oil-in-water emulsion/solvent evaporation method. Drug release from the prepared microspheres was monitored in phosphate buffer solution at 37°C for 4 weeks by high-performance liquid chromatography. The in-vivo study was performed in STZ-induced diabetic rats treated with optimized ONO-1301 PLGA microspheres (10 mg/kg by intramuscular or subcutaneous injection every 3 weeks). NCV was measured in the thigh 4, 8 and 12 weeks after induction.

Key findings

The molecular weights of PLGA, the L/G ratio in PLGA and the particle diameter all affected the length of the sustained release period. Drug release from microspheres containing PLGA 5050 (MW 50 000, L/G 50/50), with an average diameter of about 30 µm, could be sustained for 3 weeks in vitro. In the in-vivo study, delayed NCV was significantly increased by treatment with these ONO-1301 PLGA microspheres once every 3 weeks, in comparison with vehicle only.

Conclusion

Local intramuscular injection of sustained-release ONO-1301 PLGA microspheres improved delayed NCV in STZ-induced diabetic rats.

Albumin-based nanoparticles as magnetic resonance contrast agents: I. Concept, first syntheses and characterisation

To develop a platform for molecular magnetic resonance imaging, we prepared gadolinium-bearing albumin-polylactic acid nanoparticles in the size range 20-40 nm diameter. Iterative cycles of design and testing upscaled the synthesis procedures to gram amounts for physicochemical characterisation and for pharmacokinetic testing. Morphological analyses showed that the nanoparticles were spheroidal with rough surfaces. Particle sizes were measured by direct transmission electron microscopical measurements from negatively contrasted preparations, and by use of photon correlation spectroscopy; the two methods each documented nanoparticle sizes less than 100 nm and generally 10-40 nm diameter, though with significant intrabatch and interbatch variability. The particles' charge sufficed to hold them in suspension. HSA retained its tertiary structure in the particles. The nanoparticles were stable against turbulent flow conditions and against heat, though not against detergents. MRI imaging of liquid columns was possible at nanoparticle concentrations below 10 mg/ml. The particles were non-cytotoxic, non-thrombogenic and non-immunogenic in a range of assay systems developed for toxicity testing of nanoparticles. They were micellar prior to lyophilisation, but loosely structured aggregated masses after lyophilisation and subsequent resuspension. These nanoparticles provide a platform for further development, based on non-toxic materials of low immunogenicity already in clinical use, not expensive, and synthesized using methods which can be upscaled for industrial production.

Nanoscalar structures of spray-dried zein microcapsules and in vitro release kinetics of the encapsulated lysozyme as affected by formulations

Sustained release of antimicrobials may be a viable solution to enhance the bioavailability during the shelf life of food products. In this work, spray-drying was used to encapsulate a model antimicrobial of lysozyme in corn zein. The effects of zein/lysozyme (20:1 to 4:1) and zein/thymol (1:0 to 4:1) ratios on the microstructures of microcapsules and in vitro release profiles of the encapsulated lysozyme were investigated. In all cases, less lysozyme was released at higher pH, resulting from stronger molecular attraction between zein and lysozyme. Nanoscalar matrix structures of microcapsules were correlated with release characteristics of the encapsulated lysozyme. At intermediate zein/lysozyme (10:1) and zein/thymol (50:1) ratios, microcapsules had a continuous matrix structure and showed sustained release (11.1-65.3%) of lysozyme at pH 6 over 49 days. This work may be developed into practical food grade delivery systems of antimicrobials.

A novel biomaterial for osteotropic drug nanocarriers: synthesis and biocompatibility evaluation of a PLGA–ALE conjugate

Background & aims: Osteotropic drug-delivery systems have been proposed as a means to provide drugs with affinity to bone tissues. Drugs or proteins have been linked chemically to bone-seeking agents, such as bisphosphonates (BPs); alternatively, drug-loaded nanoparticles have been used to target specific tissues, such as tumor areas. In our current research, these approaches were merged by synthesizing a novel bone-seeking polymer conjugate, from which targetable nanoparticles can be produced. Materials & methods: An amino-BP, alendronate (ALE) was bound covalently to a biodegradable polymer, poly(lactic-co-glycolide) (PLGA), containing a free end carboxylic group. Blood compatibility and cytotoxicity were assessed in vitro. Results & discussion: By a classical solvent-evaporation method, nanoparticles with a mean size of 200–300 nm were prepared from the conjugate; sterilization was achieved by γ-irradiation, confirming their potential as injectable drug nanocarriers. Owing to the presence of the BP residue, PLGA–ALE nanoparticles were adsorbed onto hydroxyapatite to a higher extent than pure PLGA nanoparticles. The PLGA–ALE conjugate did not induce either hemolysis or alterations of the plasmatic phase of coagulation, or cytotoxic effects on endothelial cells and trabecular osteoblasts. Conclusion: The prepared conjugate represents a novel biomaterial that is able to provide nanoparticles, which can be further loaded with drugs, such as anticancer agents, and addressed to osteolytic or other bone diseases.