Strategies for modifying drug residence time and ocular bioavailability to decrease treatment frequency for back of the eye diseases

A review on revolutionizing ophthalmic therapy: Unveiling the potential of chitosan, hyaluronic acid, cellulose, cyclodextrin, and poloxamer in eye disease treatments

Ocular disorders, encompassing both common ailments like dry eye syndrome and more severe situations for instance age-related macular degeneration, present significant challenges to effective treatment due to the intricate architecture and physiological barriers of the eye. Polysaccharides are emerging as potential solutions for drug delivery to the eyes due to their compatibility with living organisms, natural biodegradability, and adhesive properties. In this review, we explore not only the recent advancements in polysaccharide-based technologies and their transformative potential in treating ocular illnesses, offering renewed optimism for both patients and professionals but also anatomy of the eye and the significant obstacles hindering drug transportation, followed by an investigation into various drug administration methods and their ability to overcome ocular-specific challenges. Our focus lies on biological adhesive polymers, including chitosan, hyaluronic acid, cellulose, cyclodextrin, and poloxamer, known for their adhesive characteristics enhancing drug retention on ocular surfaces and increasing bioavailability. A detailed analysis of material designs used in ophthalmic formulations, such as gels, lenses, eye drops, nanofibers, microneedles, microspheres, and nanoparticles, their advantages and limitations, the potential of formulations in improving therapeutic outcomes for various eye conditions. Moreover, we underscore the discovery of novel polysaccharides and their potential uses in ocular drug delivery.

Polymeric microneedles for the eye: An overview of advances and ocular applications for minimally invasive drug delivery

Ocular drug delivery is challenging due to the presence of tissue barriers and clearance mechanisms. Most widely used topical formulations need frequent application because of poor permeability, short retention, and low bioavailability. Invasive intraocular injections and implants that deliver drugs at the target site are associated with infections, inflammation, and even vision loss post-use. These gaps can be addressed by a delivery platform that can efficiently deliver drug with minimal tissue damage. Microneedles were introduced as a delivery platform for overcoming dermal barriers with minimal tissue damage. After the successful clinical transition of microneedles in the transdermal drug delivery, they are now being extensively studied for ocular applications. The attributes of minimally invasive application and the capability to deliver a wide range of therapeutics make microneedles an attractive candidate for ocular drug delivery. The current manuscript provides a detailed overview of the recent advancements in the field of microneedles for ocular use. This paper reviews research focusing on polymeric microneedles and their pharmaceutical and biopharmaceutical properties. A brief discussion about their clinical translation and regulatory concerns is also covered. The multitude of research articles supports the fact that microneedles are a potential, minimally invasive drug delivery platform for ophthalmic use.

Recent advances in the treatment and delivery system of diabetic retinopathy

Diabetic retinopathy (DR) is a highly tissue-specific neurovascular complication of type 1 and type 2 diabetes mellitus and is among the leading causes of blindness worldwide. Pathophysiological changes in DR encompass neurodegeneration, inflammation, and oxidative stress. Current treatments for DR, including anti-vascular endothelial growth factor, steroids, laser photocoagulation, and vitrectomy have limitations and adverse reactions, necessitating the exploration of novel treatment strategies. This review aims to summarize the current pathophysiology, therapeutic approaches, and available drug-delivery methods for treating DR, and discuss their respective development potentials. Recent research indicates the efficacy of novel receptor inhibitors and agonists, such as aldose reductase inhibitors, angiotensin-converting enzyme inhibitors, peroxisome proliferator-activated receptor alpha agonists, and novel drugs in delaying DR. Furthermore, with continuous advancements in nanotechnology, a new form of drug delivery has been developed that can address certain limitations of clinical drug therapy, such as low solubility and poor penetration. This review serves as a theoretical foundation for future research on DR treatment. While highlighting promising therapeutic targets, it underscores the need for continuous exploration to enhance our understanding of DR pathogenesis. The limitations of current treatments and the potential for future advancements emphasize the importance of ongoing research in this field.

Smart design of patient centric long-acting products: from preclinical to marketed pipeline trends and opportunities

INTRODUCTION

We see a development in the field of long-acting products to serve patients with chronic diseases by providing benefits in adherence, efficacy and safety of the treatment. This review investigates features of long-acting products on the market/pipeline to understand which drug substance (DS) and drug product (DP) characteristics likely enable a successful patient-centric, low-dosing frequency product.

AREAS COVERED

This review evaluates marketed/pipeline long-acting products with greater than one week release of small molecules and peptides by oral and injectable route of administration (RoA), with particular focus on patient centricity, adherence impact, health outcomes, market trends, and the match of DS/DP technologies which lead to market success.

EXPERT OPINION

Emerging trends are expected to change the field of long-acting products in the upcoming years by increasing capability in engineered molecules (low solubility, long half-life, high potency, etc.), directly developing DP as long-acting oral/injectable, increasing the proportion of products for local drug delivery, and a direction towards more subcutaneous, self-administered products. Among long-acting injectable products, nanosuspensions show a superiority in dose per administration and dosing interval, overwhelming the field of infectious diseases with the recently marketed products.

Penetrating-peptide-mediated non-invasive Axitinib delivery for anti-neovascularisation

The unique physiological makeup of the eye limits the use of small-molecule drugs for treating the posterior segment of the eye. Nevertheless, transmembrane-peptide-mediated non-invasive drug delivery can serve as an ideal treatment strategy, as it is capable of delivering small-molecule drugs across the membrane in the form of eye drops, thereby achieving the effective treatment of neovascularisation in the posterior cavity. In this study, we screened and compared the posterior segment distribution of two poly(ethylene glycol)-distearoylphosphatidylethanolamine carriers modified using targeting-peptides. Thereafter, a transmembrane peptide (i.e., PENE) with a greater ability of transmembrane delivery was selected for delivering the anti-vascular drug (i.e., Axitinib) to the posterior segment of the eye. Using two different mouse models with fundus neovascular diseases, the complete non-invasive delivery of Axitinib to the posterior segment of the eye was confirmed using the targeted system; the designed eye drops (i.e., PENE-nanoparticles) could achieve drug distribution to the retina and veins of the eye as well as good drug permeability for renewal. Moreover, using the eye-drop treatment, neovascularisation was substantially reduced, demonstrating the high efficacy of this drug delivery system. This study, which combines nanodrug-loading technology and the transmembrane delivery of penetrating-peptides to achieve the goal of the non-invasive delivery of small-molecule drugs through the dense blood vessels of the sclera, shows wide applicability and considerably expands the use of ocular drugs. Thus, this study is expected to help develop a more acceptable drug administration strategy for the drug treatment of the posterior segment of the eye.

Modifiable Determinants of Satisfaction with Intravitreal Treatment in Patients with Neovascular Age-Related Macular Degeneration

BACKGROUND

The success of intravitreal treatment for neovascular age-related macular degeneration (nAMD) depends on maximal adherence to treatment, which in turn requires patient satisfaction.

OBJECTIVE

The aim of this study was to assess the factors associated with nAMD patient satisfaction to implement actions to improve treatment experiences and increase adherence.

DESIGN

This was a prospective, observational, analytical, cross-sectional study.

SUBJECTS

Our study included 100 consecutive nAMD patients under intravitreal treatment for at least 1 year.

METHODS

Patients completed the Macular Disease Treatment Satisfaction Questionnaire (MacTSQ) and the EuroQol Visual Analog Scale (EQ VAS). A logistic regression was estimated to model the low values of the satisfaction score (MacTSQ < 50).

RESULTS

The mean age of patients was 82.1 ± 7.8 years and 62% were female. Males (p = 0.002) and patients who improved their visual acuity (p = 0.004) were more satisfied, while patients who received a higher number of injections (p = 0.036) and treatment in both eyes (p = 0.001) were less satisfied. Higher health-related quality of life was related to higher satisfaction. The sensitivity and specificity of the predictive model were 75.8% and 76.1%, respectively. Factors independently associated with low satisfaction were female sex (odds ratio [OR] 6.84), going to the clinic alone (OR 8.51), longer duration of treatment (OR 0.62), receiving treatment in both eyes (OR 3.54), and suffering a decline in visual acuity (OR 3.30). The questionnaire revealed patients' needs for more information and injection points closer to their homes.

CONCLUSIONS

Well-defined areas for improvement were identified, i.e. to improve the information offered to each patient, to incorporate new long-acting drugs, and to establish locations for injection services in peripheral areas.

Recent advances in ophthalmic preparations: Ocular barriers, dosage forms and routes of administration

The human eye is a complex organ with unique anatomy and physiology that restricts the delivery of drugs to target ocular tissues/sites. Recent advances in the field of pharmacy, biotechnology and material science have led to development of novel ophthalmic dosage forms which can provide sustained drug delivery, reduce dosing frequency and improve the ocular bioavailability of drugs. This review highlights the different anatomical and physiological factors which affect ocular bioavailability of drugs and explores advancements from 2016 to 2020 in various ophthalmic preparations. Different routes of drug administration such as topical, intravitreal, intraocular, juxtascleral, subconjunctival, intracameral and retrobulbar are discussed with their advances and limitations.

Synthesis and Characterization of Novel Succinyl Chitosan-Dexamethasone Conjugates for Potential Intravitreal Dexamethasone Delivery

The development of intravitreal glucocorticoid delivery systems is a current global challenge for the treatment of inflammatory diseases of the posterior segment of the eye. The main advantages of these systems are that they can overcome anatomical and physiological ophthalmic barriers and increase local bioavailability while prolonging and controlling drug release over several months to improve the safety and effectiveness of glucocorticoid therapy. One approach to the development of optimal delivery systems for intravitreal injections is the conjugation of low-molecular-weight drugs with natural polymers to prevent their rapid elimination and provide targeted and controlled release. This study focuses on the development of a procedure for a two-step synthesis of dexamethasone (DEX) conjugates based on the natural polysaccharide chitosan (CS). We first used carbodiimide chemistry to conjugate DEX to CS via a succinyl linker, and we then modified the obtained systems with succinic anhydride to impart a negative ζ-potential to the polymer particle surface. The resulting polysaccharide carriers had a degree of substitution with DEX moieties of 2–4%, a DEX content of 50–85 μg/mg, and a degree of succinylation of 64–68%. The size of the obtained particles was 400–1100 nm, and the ζ-potential was −30 to −33 mV. In vitro release studies at pH 7.4 showed slow hydrolysis of the amide and ester bonds in the synthesized systems, with a total release of 8–10% for both DEX and succinyl dexamethasone (SucDEX) after 1 month. The developed conjugates showed a significant anti-inflammatory effect in TNFα-induced and LPS-induced inflammation models, suppressing CD54 expression in THP-1 cells by 2- and 4-fold, respectively. Thus, these novel succinyl chitosan-dexamethasone (SucCS-DEX) conjugates are promising ophthalmic carriers for intravitreal delivery.

Ocular and systemic pharmacokinetics of BI-X, a nanobody targeting VEGF and Ang-2, after intravitreal dosing in cynomolgus monkeys - Evidence for half-life extension by albumin

Half-life extension strategies to reduce the intravitreal dosing frequency of biomolecules for the treatment of retinal neovascular diseases are attracting increasing interest. This study investigated ocular and systemic pharmacokinetics of the trivalent nanobody BI-X (with affinity to VEGF, Ang-2 and human albumin) in cynomolgus monkeys after intravitreal injection. BI-X concentrations were measured in serial samples of plasma, vitreous humor, aqueous humor and retina. Ocular pharmacokinetics of BI-X exhibited two phases. Initially up to 2-4 weeks after dosing, BI-X concentrations in vitreal, aqueous humor and retina declined with half-lives of around 3 days, which is comparable to macromolecules with a similar molecular weight. Thereafter, only vitreal concentrations were measurable, with a terminal half-life of 13.2 days, which is considerably longer than expected based on the BI-X molecular weight or hydrodynamic radius. It is hypothesized that binding of BI-X to low levels of intraocular albumin resulted in this half-life extension. BI-X was detectable in plasma up to 10 weeks post-dosing. Plasma pharmacokinetics of BI-X exhibited a similar biphasic disposition profile to the vitreous body, with a terminal half-life of 11.8 days, thus reflecting input kinetics from the eye. In conclusion, an important half-life extension principle based on vitreal albumin binding could be confirmed in a primate model, and the data obtained can potentially be translated to humans taking into account the differing vitreal albumin concentrations.

Ophthalmic Magnetic Resonance Imaging: Where Are We (Heading To)?

Magnetic resonance imaging of the eye and orbit (MReye) is a cross-domain research field, combining (bio)physics, (bio)engineering, physiology, data sciences and ophthalmology. A growing number of reports document technical innovations of MReye and promote their application in preclinical research and clinical science. Realizing the progress and promises, this review outlines current trends in MReye. Examples of MReye strategies and their clinical relevance are demonstrated. Frontier applications in ocular oncology, refractive surgery, ocular muscle disorders and orbital inflammation are presented and their implications for explorations into ophthalmic diseases are provided. Substantial progress in anatomically detailed, high-spatial resolution MReye of the eye, orbit and optic nerve is demonstrated. Recent developments in MReye of ocular tumors are explored, and its value for personalized eye models derived from machine learning in the treatment planning of uveal melanoma and evaluation of retinoblastoma is highlighted. The potential of MReye for monitoring drug distribution and for improving treatment management and the assessment of individual responses is discussed. To open a window into the eye and into (patho)physiological processes that in the past have been largely inaccessible, advances in MReye at ultrahigh magnetic field strengths are discussed. A concluding section ventures a glance beyond the horizon and explores future directions of MReye across multiple scales, including in vivo electrolyte mapping of sodium and other nuclei. This review underscores the need for the (bio)medical imaging and ophthalmic communities to expand efforts to find solutions to the remaining unsolved problems and technical obstacles of MReye, with the objective to transfer methodological advancements driven by MR physics into genuine clinical value.

Therapeutic Ophthalmic Lenses: A Review

An increasing incidence of eye diseases has been registered in the last decades in developed countries due to the ageing of population, changes in lifestyle, environmental factors, and the presence of concomitant medical conditions. The increase of public awareness on ocular conditions leads to an early diagnosis and treatment, as well as an increased demand for more effective and minimally invasive solutions for the treatment of both the anterior and posterior segments of the eye. Despite being the most common route of ophthalmic drug administration, eye drops are associated with compliance issues, drug wastage by lacrimation, and low bioavailability due to the ocular barriers. In order to overcome these problems, the design of drug-eluting ophthalmic lenses constitutes a non-invasive and patient-friendly approach for the sustained drug delivery to the eye. Several examples of therapeutic contact lenses and intraocular lenses have been developed, by means of different strategies of drug loading, leading to promising results. This review aims to report the recent advances in the development of therapeutic ophthalmic lenses for the treatment and/or prophylaxis of eye pathologies (i.e., glaucoma, cataract, corneal diseases, or posterior segment diseases) and it gives an overview of the future perspectives and challenges in the field.

Fab-Nanolipoprotein Conjugate Causes Vitreous Opacity and Cataracts Following a Single Intravitreal Administration in New Zealand White Rabbits

One strategy employed to prolong the ocular half-life of large molecule therapeutics is via covalent attachment to a carrier, resulting in an increase in size thereby slowing their clearance from the eye. Rabbit antigen-binding fragment conjugated to nanolipoprotein (RabFab-NLP) is a novel conjugate intended to prolong ocular half-life through an increase in hydrodynamic radius compared to Fab alone (∼12 vs ∼3 nm). Nanolipoproteins are mimetics of endogenous high-density lipoproteins and consist of lipids and apolipoproteins (ApoE422k), both biologically derived materials. The objective of this study was to evaluate the ocular toxicity and toxicokinetics of RabFab-NLP after a single intravitreal administration in New Zealand White rabbits. Serum toxicokinetic data suggested a significant increase in ocular residence time of RabFab-NLP compared to RabFab alone. Ophthalmic examinations showed that RabFab-NLP caused vitreous and lens opacities as early as day 3 and day 8 postdose, respectively, which persisted for the entire study duration to day 30. The RabFab-NLP-related microscopic findings were present in the lens, vitreous cavity, and/or optic nerve head. Based on the observed ocular toxicity, a single intravitreal dose of 1.3 mg/eye RabFab-NLP was not tolerated and caused vitreous opacity and cataracts in rabbit eyes.

Dual-acting therapeutic proteins for intraocular use

Intravitreally injected antibody-based medicines have revolutionised the treatment of retinal disease. Bispecific and dual-functional antibodies and therapeutic proteins have the potential to further increase the efficacy of intraocular medicines.

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.

Chitosan and its Derivatives for Ocular Delivery Formulations: Recent Advances and Developments

Chitosan (CS) is a hemi-synthetic cationic linear polysaccharide produced by the deacetylation of chitin. CS is non-toxic, highly biocompatible, and biodegradable, and it has a low immunogenicity. Additionally, CS has inherent antibacterial properties and a mucoadhesive character and can disrupt epithelial tight junctions, thus acting as a permeability enhancer. As such, CS and its derivatives are well-suited for the challenging field of ocular drug delivery. In the present review article, we will discuss the properties of CS that contribute to its successful application in ocular delivery before reviewing the latest advances in the use of CS for the development of novel ophthalmic delivery systems. Colloidal nanocarriers (nanoparticles, micelles, liposomes) will be presented, followed by CS gels and lenses and ocular inserts. Finally, instances of CS coatings, aiming at conferring mucoadhesiveness to other matrixes, will be presented.

Efficacy and safety of Suprachoroidal Triamcinolone Acetonide in cases of resistant diabetic Macular Edema

Objective

To evaluate the safety and efficacy of Suprachoroidal Triamcinolone Acetonide (SCTA) injection in patients with treatment resistant Diabetic Macular Edema (DME).

Methods

This was a prospective non randomized interventional study conducted in the vitreoretinal department of Al Ehsan Welfare Eye Hospital, Lahore, Pakistan from March 2018 to September 2018. A total of 24 eyes of 24 patients were included. Baseline Best Corrected Visual Acuity (BCVA), Intra Ocular Pressure (IOP) and Central Subfield Thickness (CST) was recorded. After SCTA, patient was followed up at one and three months and same clinical parameters were recorded again and results analyzed.

Results

Out of 24 patients, 11(45.83%) were males and 13(54.16%) were females. Mean pre injection CST was 636.5 ± 200.11 um. Mean pre injection BCVA was 0.8 ± 0.24 on ETDRS chart. Mean post injection CST at one and three months was 304.54 ± 67.43 and 302.66 ± 66.93 um. Mean post injection BCVA at one and three months was 0.47 ± 0.3 and 0.45 ± 0.27 on ETDRS chart. The results were statistically significant for pre and post injection CST at both one and three months (p-value < 0.00001). Pre and post injection BCVA was also statistically significant (p-value < 0.05).

Conclusion

Preliminary evidence suggests that SCTA is well tolerated and may help in improving functional and structural outcomes of treatment resistant DME.

Polysaccharides in Ocular Drug Delivery

Polysaccharides, such as cellulose, hyaluronic acid, alginic acid, and chitosan, as well as polysaccharide derivatives, have been successfully used to augment drug delivery in the treatment of ocular pathologies. The properties of polysaccharides can be extensively modified to optimize ocular drug formulations and to obtain biocompatible and biodegradable drugs with improved bioavailability and tailored pharmacological effects. This review discusses the available polysaccharide choices for overcoming the difficulties associated with ocular drug delivery, and it explores the reasons for the dependence between the physicochemical properties of polysaccharide-based drug carriers and their efficiency in different formulations and applications. Polysaccharides will continue to be of great interest to researchers endeavoring to develop ophthalmic drugs with improved effectiveness and safety.

Identification and characterization of an octameric PEG-protein conjugate system for intravitreal long-acting delivery to the back of the eye

Innovative protein engineering and chemical conjugation technologies have yielded an impressive number of drug candidates in clinical development including >80 antibody drug conjugates, >60 bispecific antibodies, >35 Fc-fusion proteins and >10 immuno-cytokines. Despite these innovations, technological advances are needed to address unmet medical needs with new pharmacological mechanisms. Age-related eye diseases are among the most common causes of blindness and poor vision in the world. Many such diseases affect the back of the eye, where the inaccessibility of the site of action necessitates therapeutic delivery via intravitreal (IVT) injection. Treatments administered via this route typically have vitreal half-lives <10 days in humans, requiring frequent administration. Since IVT injection is burdensome to patients, there exists a strong need to develop therapeutics with prolonged residence time in the eye. We report here a strategy to increase retention of a therapeutic fragment antibody (Fab) in the eye, using an anti-complement factor D Fab previously optimized for ocular delivery. Polyethylene glycol structures, varying in length, geometry and degree of branching, were coupled to the Fab via maleimide-activated termini. A screening strategy was developed to allow for key determinants of ocular half-life to be measured in vitro. After compound selection, a scalable process was established to enable tolerability and pharmacokinetic studies in cynomolgus monkeys, demonstrating an increase in vitreal half-life with no associated adverse events. Further, we show that the technique for compound selection, analytical characterization, and scalable production is general for a range of antibody fragments. The application of the technology has broad impact in across many therapeutic areas with the first major advancement in the treatment of an important ocular disease.