Ocular Drug Distribution and Safety of a Noninvasive Ocular Drug Delivery System of Dexamethasone Sodium Phosphate in Rabbit

In Vitro/Ex Vivo Release Study of a Ground Umbilical Cord Matrix Loaded with Dexamethasone

Eye drops containing steroids and antibiotics are widely used to treat a large range of ocular diseases of the ocular surface. They require frequent instillation or a high dosage, which can affect quality of life. We developed a biomaterial from human umbilical cord that can be loaded with drugs before being placed in the inferior conjunctival fornix. In the present work, this viro-inactivated, freeze-dried, and sterile foam was loaded with dexamethasone phosphate. We studied the release kinetic of 100 mg of biomaterial loaded with 100 µg of dexamethasone phosphate. Assays have shown that the product can be loaded with 100 µg of dexamethasone and allows a progressive release over time for at least 48 h. In addition, when compared with the instillation of the same dexamethasone quantity (100 µg), instilled regularly via eye-drop solution at 0.79 mg/mL, the drug penetration through corneal tissues was better with the dexamethasone-loaded biomaterial.

Non-aqueous formulations in topical ocular drug delivery - a paradigm shift?

Topical eyedrop application is the preferred route for drug delivery to anterior segment tissues; however, the challenge of overcoming the eye's anatomical and physiological barriers while minimising tissue toxicity has restricted developments in this field. Aqueous vehicles have traditionally been used, which typically require several additives and preservatives to achieve physiologically compatible and sterile eyedrops, elevating their toxicity potential. Non-aqueous vehicles have been suggested as efficient alternatives for topical drug delivery as they can address many of the limitations associated with conventional aqueous eyedrops. However, despite their obvious advantages, non-aqueous eyedrops remain poorly researched and few non-aqueous formulations are currently available in the market. This review challenges the conventional hypothesis that aqueous solubility is a prerequisite to ocular drug absorption and establishes a rationale for using non-aqueous vehicles for ocular drug delivery. Recent advances in the field have been detailed and future research prospects have been explored, pointing towards a paradigm shift in eyedrop formulation in the near future.

A review of the clinical applications of drug delivery systems for the treatment of ocular anterior segment inflammation

Ocular anterior segment inflammation is a medical problem that is seen in cases of cataract surgery and non-infectious anterior uveitis. Inadequately treated anterior segment inflammation can lead to sight-threatening conditions such as corneal oedema, glaucoma and cystoid macular oedema. The mainstay of treatment for anterior segment inflammation is topical steroid eye-drops. However, several drawbacks limit the critical value of this treatment, including low bioavailability, poor patient compliance, relatively difficult administration manner and risk of blurring of vision and ocular irritation. A drug delivery system (DDS) that can provide increased bioavailability and sustained delivery while being specifically targeted towards inflamed ocular tissue can potentially replace daily eye-drops as the gold standard for management of anterior segment inflammation. The various DDS for anti-inflammatory drugs for the treatment of anterior segment inflammation are listed and summarised in this review, with a focus on commercially available products and those in clinical trials. Dextenza, INVELTYS, Dexycu and Bromsite are examples of DDS that have enjoyed success in clinical trials leading to FDA approval. Nanoparticles and ocular iontophoresis form the next wave of DDS that have the potential to replace topical steroids eye-drops as the treatment of choice for anterior segment inflammation. With the current relentless pace of ophthalmic drug delivery research, the pursuit of a new standard of treatment that eliminates the problems of low bioavailability and patient compliance may soon be realised.

Transscleral Iontophoresis for Noninvasive Ocular Drug Delivery of Macromolecules

Purpose: The objectives were to investigate the effect of transscleral iontophoresis of macromolecules in vitro and in vivo, to study the importance of electroosmosis on macromolecules of low charge to mass ratio, and to evaluate transscleral iontophoresis efficacy in a choroidal neovascularization (CNV) animal model. Methods: Through in vitro transport experiments, the permeability coefficients of macromolecules [eg, immunoglobulin G (IgG), dextran 70 kDa] were determined under different conditions. The effect of ionic strength formulations and iontophoretic conditions was studied on the distribution of IgG and bevacizumab into the eye in vivo. Magnetic resonance imaging (MRI) was utilized to evaluate in vivo real time distribution of gadolinium-labeled albumin (Galbumin) following iontophoresis. The efficacy between no treatment, intravitreal injection (IVT), and iontophoresis of bevacizumab on a CNV model of subretinal injection of adeno-associated virus encoding human VEGF-165 was investigated. Results: The permeability data suggested a significant effect of ionic strength on the iontophoretic transport of macromolecules. Transscleral iontophoresis of IgG at 4 mA with a low ionic strength formulation was about 600 times greater than passive diffusion and 14-fold over a conventional formulation in vitro. Approximately 0.6 mg of bevacizumab can be delivered into the rabbit eye in vivo with a 20-min treatment of iontophoresis. MRI showed that Galbumin was in the posterior tissues after iontophoresis. In the CNV model, the iontophoresis and IVT methods of bevacizumab delayed retinal neovascularization by 4 and 8 weeks, respectively. Conclusions: Transscleral iontophoresis is capable of delivering macromolecule drugs through the conjunctiva and sclera, eventually exposing the retina/choroid to the drugs.

Novel ophthalmic formulation of myriocin: implications in retinitis pigmentosa

Myriocin is an antibiotic derived from Mycelia sterilia, and is a potent inhibitor of serine palmitoyltransferase, the enzyme involved in the first step of sphingosine synthesis. Myriocin, inhibiting ceramide synthesis, has a great potential for treatment of diseases characterized by high ceramide levels in affected tissues, such as retinitis pigmentosa (RP). Drug delivery to the retina is a challenging task, which is generally by-passed through intravitreal injection, that represents a risky invasive procedure. We, therefore, developed and characterized an ophthalmic topical nanotechnological formulation based on a nanostructured lipid carrier (NLC) and containing myriocin. The ocular distribution of myriocin in the back of the eye was assessed both in rabbits and mice using LC-MS/MS. Moreover, rabbit retinal sphingolipid and ceramides levels, after myriocin-NLC (Myr-NLC) eye drops treatment, were assessed. The results demonstrated that Myr-NLC formulation is well tolerated and provided effective levels of myriocin in the back of the eye both in rabbits and mice. We found that Myr-NLC eye drops treatment was able to significantly decrease retinal sphingolipid levels. In conclusion, these data suggest that the Myr-NLC ophthalmic formulation is suitable for pharmaceutical development and warrants further clinical evaluation of this eye drops for the treatment of RP.

Novel Dexamethasone Sodium Phosphate Treatment (DSP-Visulex) for Noninfectious Anterior Uveitis: A Randomized Phase I/II Clinical Trial

PURPOSE

Frequent steroid drops represent a challenge in patient compliance. This study evaluated the safety and efficacy of 5 minute topical dexamethasone sodium phosphate-Visulex (DSP-Visulex) treatment regimen (two applications on the first week then weekly after) compared to daily prednisolone acetate 1% (PA) for noninfectious anterior uveitis.

MATERIALS AND METHODS

Forty-four patients were randomized to 8% DSP-Visulex with placebo eye drops (8% group, n = 14), 15% DSP-Visulex with placebo eye drops (15% group, n = 15), or Vehicle-Visulex with PA eye drops (PA group, n = 15). Patients received daily eye drops and Visulex treatments on days 1, 3, 8, and 15 with an optional treatment on day 22. Efficacy measures were change in anterior chamber cell (ACC) count from baseline and proportion of patients with zero ACC count at days 8, 15, and 29. Safety measures were adverse events (AEs), visual acuity, ocular symptoms, and intraocular pressure (IOP).

RESULTS

ACC resolution over time was similar among the three groups. The percentage of patients with clear ACC was 18%, 22%, and 15% on day 8; 27%, 56%, and 54% on day 15; and 90%, 88%, and 77% on day 29 for the 8%, 15%, and PA groups, respectively. The numbers of reported AEs were 10, 36, and 12 for the 8%, 15%, and PA groups, respectively. Ten patients among all groups experienced treatment-related AEs, which included headache, eye pain, corneal abrasion, conjunctival/corneal staining, conjunctivitis, visual acuity reduction, and keratitis all of which were resolved during the timeframe of patients' participation in the study. IOP elevation was noted in the PA group throughout the study, whereas IOP elevation in the DSP-Visulex groups was observed at day 3 but not thereafter.

CONCLUSIONS

The efficacy of the DSP-Visulex applications was comparable to the daily PA drops in the treatment of noninfectious anterior uveitis. Both 8% and 15% DSP-Visulex treatments were safe and well tolerated.