Safety and Biocompatibility of Aflibercept-Loaded Microsphere Thermo-Responsive Hydrogel Drug Delivery System in a Nonhuman Primate Model

Hydrogels in Ophthalmology: Novel Strategies for Overcoming Therapeutic Challenges

The human eye's intricate anatomical and physiological design necessitates tailored approaches for managing ocular diseases. Recent advancements in ophthalmology underscore the potential of hydrogels as a versatile therapeutic tool, owing to their biocompatibility, adaptability, and customizability. This review offers an exploration of hydrogel applications in ophthalmology over the past five years. Emphasis is placed on their role in optimized drug delivery for the posterior segment and advancements in intraocular lens technology. Hydrogels demonstrate the capacity for targeted, controlled, and sustained drug release in the posterior segment of the eye, potentially minimizing invasive interventions and enhancing patient outcomes. Furthermore, in intraocular lens domains, hydrogels showcase potential in post-operative drug delivery, disease sensing, and improved biocompatibility. However, while their promise is immense, most hydrogel-based studies remain preclinical, necessitating rigorous clinical evaluations. Patient-specific factors, potential complications, and the current nascent stage of research should inform their clinical application. In essence, the incorporation of hydrogels into ocular therapeutics represents a seminal convergence of material science and medicine, heralding advancements in patient-centric care within ophthalmology.

Evaluating the Efficacy of a Thermoresponsive Hydrogel for Delivering Anti-Collagen Antibodies to Reduce Posttraumatic Scarring in Orthopedic Tissues

Excessive posttraumatic scarring in orthopedic tissues, such as joint capsules, ligaments, tendons, muscles, and peripheral nerves, presents a significant medical problem, resulting in pain, restricted joint mobility, and impaired musculoskeletal function. Current treatments for excessive scarring are often ineffective and require the surgical removal of fibrotic tissue, which can aggravate the problem. The primary component of orthopedic scars is collagen I-rich fibrils. Our research team has developed a monoclonal anti-collagen antibody (ACA) that alleviates posttraumatic scarring by inhibiting collagen fibril formation. We previously established the safety and efficacy of ACA in a rabbit-based arthrofibrosis model. In this study, we evaluate the utility of a well-characterized thermoresponsive hydrogel (THG) as a delivery vehicle for ACA to injury sites. Crucial components of the hydrogel included N-isopropylacrylamide, poly(ethylene glycol) diacrylate, and hyaluronic acid. Our investigation focused on in vitro ACA release kinetics, stability, and activity. Additionally, we examined the antigen-binding characteristics of ACA post-release from the THG in an in vivo context. Our preliminary findings suggest that the THG construct exhibits promise as a delivery platform for antibody-based therapeutics to reduce excessive scarring in orthopedic tissues.

An Update on Strategies to Deliver Protein and Peptide Drugs to the Eye

In the past few decades, advancements in protein engineering, biotechnology, and structural biochemistry have resulted in the discovery of various techniques that enhanced the production yield of proteins, targetability, circulating half-life, product purity, and functionality of proteins and peptides. As a result, the utilization of proteins and peptides has increased in the treatment of many conditions, including ocular diseases. Ocular delivery of large molecules poses several challenges due to their high molecular weight, hydrophilicity, unstable nature, and poor permeation through cellular and enzymatic barriers. The use of novel strategies for delivering protein and peptides such as glycoengineering, PEGylation, Fc-fusion, chitosan nanoparticles, and liposomes have improved the efficacy, safety, and stability, which consequently expanded the therapeutic potential of proteins. This review article highlights various proteins and peptides that are useful in ocular disorders, challenges in their delivery to the eye, and strategies to enhance ocular bioavailability using novel delivery approaches. In addition, a few futuristic approaches that will assist in the ocular delivery of proteins and peptides were also discussed.

Intravitreal Anti-Vascular Endothelial Growth Factor Therapies for Retinal Disorders

Vascular endothelial growth factors (VEGFs) are key mediator of retinal and choroidal neovascularization as well as retinal vascular leakage leading to macular edema. As such, VEGF plays an important role in mediating visually significant complications associated with common retinal disorders such as diabetic retinopathy, retinal vein occlusion, and age-related macular degeneration. Various drugs that inhibit vascular endothelial growth factors (anti-VEGF therapies) have been developed to minimize vision loss associated with these disorders. These drugs are injected into the vitreous cavity in a clinic setting at regular intervals. This article provides an overview of the various anti-VEGF drugs used in ophthalmology and the common retinal conditions that benefit from this therapy.

Novel Drug Delivery Methods and Approaches for the Treatment of Retinal Diseases

This review discusses emerging approaches to ocular drug delivery for retinal diseases. Intravitreal injections have proven to be an effective, safe, and commonly used drug delivery method. However, the optimal management of chronic retinal diseases requires frequent intravitreal injections over extended periods of time. Although this can be achieved in a clinical trial environment, it is difficult to replicate in routine clinical practice. In addition, frequent treatment increases the risk of complications, incurs more costs, and increases the treatment burden for patients and caregivers. Given the aging global population and diabetes pandemic, there is an urgent need for drug delivery methods that support more durable retinal therapy while maintaining the efficacy and safety of currently available intravitreal therapies. Several innovative drug delivery methods are currently being investigated. These include sustained-release implants and depots using prodrugs, microparticles, and hydrogels, surgically implanted reservoirs, gene therapy via submacular injections or suprachoroidal injections, as well as topical and systemic therapies.

Innovative Strategies for Drug Delivery to the Ocular Posterior Segment

Innovative and new drug delivery systems (DDSs) have recently been developed to vehicle treatments and drugs to the ocular posterior segment and the retina. New formulations and technological developments, such as nanotechnology, novel matrices, and non-traditional treatment strategies, open new perspectives in this field. The aim of this mini-review is to highlight promising strategies reported in the current literature based on innovative routes to overcome the anatomical and physiological barriers of the vitreoretinal structures. The paper also describes the challenges in finding appropriate and pertinent treatments that provide safety and efficacy and the problems related to patient compliance, acceptability, effectiveness, and sustained drug delivery. The clinical application of these experimental approaches can help pave the way for standardizing the use of DDSs in developing enhanced treatment strategies and personalized therapeutic options for ocular pathologies.

Novel Approaches in the Drug Development and Delivery Systems for Age-Related Macular Degeneration

The number of patients with ocular disorders has increased due to contributing factors such as aging populations, environmental changes, smoking, genetic abnormalities, etc. Age-related macular degeneration (AMD) is one of the common ocular disorders which may advance to loss of vision in severe cases. The advanced form of AMD is classified into two types, dry (non-exudative) and wet (exudative) AMD. Although several therapeutic approaches are explored for the management of AMD, no approved therapy can substantially slow down the progression of dry AMD into the later stages. The focus of researchers in recent times has been engaged in developing targeted therapeutic products to halt the progression and maintain or improve vision in individuals diagnosed with AMD. The delivery of anti-VEGF agents using intravitreal therapy has found some success in managing AMD, and novel formulation approaches have been introduced in various studies to potentiate the efficacy. Some of the novel approaches, such as hydrogel, microspheres, polymeric nanoparticles, liposomes, implants, etc. have been discussed. Apart from this, subretinal, suprachoroidal, and port delivery systems have also been investigated for biologics and gene therapies. The unmet potential of approved therapeutic products has contributed to several patent applications in recent years. This review outlines the current treatment options, outcomes of recent research studies, and patent details around the novel drug delivery approach for the treatment of AMD.

Simultaneous Release of Aflibercept and Dexamethasone from an Ocular Drug Delivery System

PURPOSE

Intravitreal injections of anti-vascular endothelial growth factors (anti-VEGF) are the current standard of care for patients with choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD). There is a growing subset of patients that does not respond to anti-VEGF monotherapy treatment. Some patients, however, do respond to combination therapy of corticosteroids and anti-VEGF. This treatment requires monthly/bimonthly injections of anti-VEGF and semi-annual injections of corticosteroid. A drug delivery system (DDS) that simultaneously releases multiple drugs could benefit these patients by reducing the number of injections. The purpose of this study was to characterize the simultaneous release of aflibercept and dexamethasone from a biodegradable microparticle- and nanoparticle-hydrogel DDS.

METHODS

Dexamethasone-loaded nanoparticles and aflibercept-loaded microparticles were created using modified single- and double-emulsion techniques, respectively. Then, microparticles and nanoparticles were embedded into a thermoresponsive, biodegradable poly(ethylene glycol)-co-(L-lactic acid) diacrylate (PEG-PLLA-DA)-N-isopropylacrylamide (NIPAAm) hydrogel DDS. Drug release studies and characterization of DDS were conducted with varying doses of microparticles and nanoparticles.

RESULTS

The combination aflibercept-loaded microparticle- and dexamethasone-loaded nanoparticle- hydrogel (Combo-DDS) achieved a total release time of 224 days. Small decreases were seen in swelling ratio and equilibrium water content for Combo-DDS compared to monotherapy aflibercept-loaded microparticle-hydrogel DDS (AFL-DDS) and monotherapy dexamethasone-loaded nanoparticle-hydrogel DDS (DEX-DDS). Bioactivity of aflibercept was maintained in Combo-DDS compared to AFL-DDS.

CONCLUSIONS

The Combo-DDS was able to extend and control the release of both aflibercept and dexamethasone simultaneously from a single DDS. This may eliminate the need for separate dosing regiments of anti-VEGF and corticosteroids for wet AMD patients.

Polymer based sustained drug delivery to the ocular posterior segment: barriers and future opportunities for the treatment of neovascular pathologies

There is an increasing momentum in research and pharmaceutical industry communities to design sustained, non-invasive delivery systems to treat chronic neovascular ocular diseases that affect the posterior segment of the eye including age-related macular degeneration and diabetic retinopathy. Current treatments include VEGF blockers, which have revolutionized the standard of care for patients, but their maximum therapeutic benefit is hampered by the need for recurrent and invasive administration procedures. Currently approved delivery systems intended to address these limitations exploit polymer technology to regulate drug release in a sustained manner. Here, we critically review sustained drug delivery approaches for the treatment of chronic neovascular diseases affecting the ocular posterior segment, with a special emphasis on novel and polymeric technologies spanning the spectrum of preclinical and clinical investigation, and those approved for treatment. The mechanism by which each formulation imparts sustained release, the impact of formulation characteristics on release and foreign body reaction, and special considerations related to the translation of these systems are discussed.

Retinal Diseases: The Next Frontier in Pharmacodelivery

The future continuous growth of the global older population augments the burden of retinal diseases worldwide. Retinal characteristics isolating and protecting the sensitive neuro-retina from the rest of the ocular tissues challenge drug delivery and promote research and development toward new horizons. In this review, we wish to describe the unmet medical needs, discuss the novel modes of delivery, and disclose to the reader a spectrum of older-to-novel drug delivery technologies, innovations, and the frontier of pharmacodelivery to the retina. Treating the main retinal diseases in the everlasting war against blindness and its associated morbidity has been growing steadily over the last two decades. Implants, new angiogenesis inhibitor agents, micro- and nano-carriers, and the anchored port delivery system are becoming new tools in this war. The revolution and evolution of new delivery methods might be just a few steps ahead, yet its assimilation in our daily clinical work may take time, due to medical, economical, and regulatory elements that need to be met in order to allow successful development and market utilization of new technologies. Therefore, further work is warranted, as detailed in this Pharmaceutics Special Issue.

Novel and investigational therapies for wet and dry age-related macular degeneration

Age-related macular degeneration (AMD) is a macular degenerative eye disease, the major cause of irreversible loss of central vision. In this review, we highlight current progress and future perspectives of novel and investigational therapeutic strategies in the drug pipeline, including anti-vascular endothelial growth factor (VEGF) agents, bispecific antibodies, biosimilars, small molecules, gene therapy, and long-acting drug delivery strategies for both dry and wet AMD. We anticipate that biologics with dual functionalities and combined therapies with long-acting capabilities will lead the wet AMD pipeline. Sustained-release platforms also show potential. However, significant breakthroughs are yet to be made for dry AMD. The personalized approach might be well suited in the scenario of diverse genetic variations in both conditions. Teaser: AMD is the leading cause of global blindness in the developed world. This article highlights investigational therapeutics, such as antibodies, Bi-specifics, small molecules, biosimilars, gene therapy and long-acting strategies (Port Delivery System), for this condition.

Uncovering of intraspecies macular heterogeneity in cynomolgus monkeys using hybrid machine learning optical coherence tomography image segmentation

The fovea is a depression in the center of the macula and is the site of the highest visual acuity. Optical coherence tomography (OCT) has contributed considerably in elucidating the pathologic changes in the fovea and is now being considered as an accompanying imaging method in drug development, such as antivascular endothelial growth factor and its safety profiling. Because animal numbers are limited in preclinical studies and automatized image evaluation tools have not yet been routinely employed, essential reference data describing the morphologic variations in macular thickness in laboratory cynomolgus monkeys are sparse to nonexistent. A hybrid machine learning algorithm was applied for automated OCT image processing and measurements of central retina thickness and surface area values. Morphological variations and the effects of sex and geographical origin were determined. Based on our findings, the fovea parameters are specific to the geographic origin. Despite morphological similarities among cynomolgus monkeys, considerable variations in the foveolar contour, even within the same species but from different geographic origins, were found. The results of the reference database show that not only the entire retinal thickness, but also the macular subfields, should be considered when designing preclinical studies and in the interpretation of foveal data.

Targeting vascular endothelial growth factor using retinal gene therapy

Pharmacotherapies targeting vascular endothelial growth factor (VEGF) have revolutionized the management for neovascular retinal disorders including diabetic retinopathy and neovascular age-related macular degeneration. However, the burden of frequent injections, high cost, and treatment resistance in some patients remain unresolved. To overcome these challenges, newer generations of anti-angiogenic biological therapies, engineered proteins, implantable delivery systems, and biopolymers are currently being developed to enable more sustained, longer-lasting treatments. The use of gene therapies for pathologic angiogenesis has garnered renewed interests since the first FDA-approval of a gene therapy to treat inherited retinal diseases associated with biallelic RPE65 mutations. Newer generations of viral vectors and novel methods of intraocular injections helped overcome ocular barriers, improving the efficiency of transduction as well as safety profile. In addition, unlike current anti-VEGF gene therapy strategies which employ a biofactory approach to mimic existing pharmacotherapies, novel genome editing strategies that target pro-angiogenic factors at the DNA level offer a unique and distinct mechanistic approach that can potentially be more precise and lead to a permanent cure. Here, we review current anti-VEGF therapies and newer pharmacologic agents under development, examine technologies and progress in adapting anti-VEGF gene therapies, and explore the future application of CRISPR-Cas9 technology to suppress ocular angiogenesis.

Recent trends in drug-delivery systems for the treatment of diabetic retinopathy and associated fibrosis

Diabetic retinopathy is a frequent microvascular complication of diabetes and a major cause of visual impairment. In advanced stages, the abnormal neovascularization can lead to fibrosis and subsequent tractional retinal detachment and blindness. The low bioavailability of the drugs at the target site imposed by the anatomic and physiologic barriers within the eye, requires long term treatments with frequent injections that often compromise patient's compliance and increase the risk of developing more complications. In recent years, much effort has been put towards the development of new drug delivery platforms aiming to enhance their permeation, to prolong their retention time at the target site and to provide a sustained release with reduced toxicity and improved efficacy. This review provides an overview of the etiology and pathophysiology of diabetic retinopathy and current treatments. It addresses the specific challenges associated to the different ocular delivery routes and provides a critical review of the most recent developments made in the drug delivery field.

Ocular Drug Delivery to the Retina: Current Innovations and Future Perspectives

Treatment options for retinal diseases, such as neovascular age-related macular degeneration, diabetic retinopathy, and retinal vascular disorders, have markedly expanded following the development of anti-vascular endothelial growth factor intravitreal injection methods. However, because intravitreal treatment requires monthly or bimonthly repeat injections to achieve optimal efficacy, recent investigations have focused on extended drug delivery systems to lengthen the treatment intervals in the long term. Dose escalation and increasing molecular weight of drugs, intravitreal implants and nanoparticles, hydrogels, combined systems, and port delivery systems are presently under preclinical and clinical investigations. In addition, less invasive techniques rather than intravitreal administration routes, such as topical, subconjunctival, suprachoroidal, subretinal, and trans-scleral, have been evaluated to reduce the treatment burden. Despite the latest advancements in the field of ophthalmic pharmacology, enhancing drug efficacy with high ocular bioavailability while avoiding systemic and local adverse effects is quite challenging. Consequently, despite the performance of numerous in vitro studies, only a few techniques have translated to clinical trials. This review discusses the recent developments in ocular drug delivery to the retina, the pharmacokinetics of intravitreal drugs, efforts to extend drug efficacy in the intraocular space, minimally invasive techniques for drug delivery to the retina, and future perspectives in this field.

Treatment Efficacy and Biocompatibility of a Biodegradable Aflibercept-Loaded Microsphere-Hydrogel Drug Delivery System

Purpose

To evaluate the in vivo treatment efficacy and biocompatibility of a biodegradable aflibercept-loaded microsphere-hydrogel drug delivery system (DDS) in a laser-induced choroidal neovascularization (CNV) rat model.

Methods

Two weeks after CNV induction, animals were randomly assigned into four experimental groups: (1) no treatment, (2) single intravitreal (IVT) injection of blank DDS, (3) bimonthly bolus IVT aflibercept injections, and (4) single IVT injection of aflibercept-DDS. CNV lesion sizes were monitored longitudinally using fluorescence angiography and multi-Otsu thresholding for 6 months. For safety and biocompatibility assessment, an additional three non-CNV animals received a blank DDS injection. Electroretinogram, intraocular pressure, and clinical ophthalmoscopic examinations were performed.

Results

The average lesion areas at week 0 (treatment intervention) were (1) 8693 ± 628 µm² for no treatment, (2) 8261 ± 709 µm² for blank DDS, (3) 10,368 ± 885 µm² for bolus, and (4) 10,306 ± 1212 µm² for aflibercept-DDS. For the nontreated groups, CNV lesion size increased by week 2 and remained increased throughout the study. The treated groups exhibited CNV size reduction after week 2 and remained for 6 months. At week 22, the average percent changes in CNV lesion area were +38.87% ± 7.08%, +34.19% ± 9.93%, -25.95% ± 3.51%, and -32.69% ± 5.40% for the above corresponding groups. No signs of chronic inflammation and other ocular abnormalities were found.

Conclusions

The aflibercept-DDS was effective in treating CNV lesions for 6 months and is safe, well tolerated, and biocompatible.

Translational Relevance

The proposed DDS is a promising system to reduce IVT injection frequency for anti-vascular endothelial growth factor treatment.

Williams G, Brocchini S, Awwad S. Injectables and Depots to Prolong Drug Action of Proteins and Peptides

Proteins and peptides have emerged in recent years to treat a wide range of multifaceted diseases such as cancer, diabetes and inflammation. The emergence of polypeptides has yielded advancements in the fields of biopharmaceutical production and formulation. Polypeptides often display poor pharmacokinetics, limited permeability across biological barriers, suboptimal biodistribution, and some proclivity for immunogenicity. Frequent administration of polypeptides is generally required to maintain adequate therapeutic levels, which can limit efficacy and compliance while increasing adverse reactions. Many strategies to increase the duration of action of therapeutic polypeptides have been described with many clinical products having been developed. This review describes approaches to optimise polypeptide delivery organised by the commonly used routes of administration. Future innovations in formulation may hold the key to the continued successful development of proteins and peptides with optimal clinical properties.