Association of ranibizumab (Lucentis®) or bevacizumab (Avastin®) with dexamethasone and triamcinolone acetonide: An in vitro stability assessment

Preparation, physicochemical, and retinal anti-angiogenic evaluation of poloxamer hydrogel containing dexamethasone/avastin-loaded chitosan-N-acetyl-L-cysteine nanoparticles

This study was meant to describe a Poloxamer hydrogel combining Chitosan-N-acetyl-L-cysteine (CNAC) nanoparticles to increase loading and sustained intravitreal administration of Avastin macromolecule. To increase the drug's efficacy and reduce the interfacial fluid pressure in a formulation, dexamethasone was used. To do so, CNAC was synthesized. Then, Avastin- loaded CNAC nanoparticles were prepared and optimized. The resulting hydrogel's sol-gel transition time and viscosity were determined using poloxamer and hydroxypropylmethylcellulose (HPMC). In vitro and in vivo investigations of Avastin-loaded CNAC nanoparticles and hydrogel comprising dexamethasone/Avastin-loaded CNAC nanoparticles were determined. In vitro, the drug release profile of optimized hydrogel containing Avastin-loaded CNAC nanoparticles was sustained and controlled over 256 h. The obtained results point to poloxamer/HPMC (18 %/0.5 %) as the best formulations for this hydrogel to develop a sol-gel transition. About 97 % of dexamethasone was released from the hydrogel within 18 h. In vivo results indicated that the optimized formulation compared with free Avastin could improve Diabetic retinopathy (DR). Consequently, we infer that this new drug delivery method may enhance Avastin intravitreal administration, lowering the frequency, danger, and expense of heavy intravitreal injections and resulting in improved treatment of posterior eye segment neovascularization and concomitant vitreoretinal disorders.

Photonic Crystal-Embedded Molecularly Imprinted Contact Lenses for Controlled Drug Release

As a noninvasive eye disease detection and drug delivery device, contact lenses can improve eye bioavailability and enable continuous drug delivery. In order to monitor the release of drugs in real time, molecularly imprinted contact lenses (MICLs) based on photonic crystals (PCs) were prepared for the treatment of diabetes-related diseases. The specific adsorption of molecularly imprinted polymers on dexamethasone sodium phosphate (DSP) increased the drug loading and optimized the drug release behavior. At the same time, the drug release ensures the rapid color report during the loading and releasing of drugs due to the volume and refractive index change of the hydrogel matrix. The continuous and slow release of DSP by MICLs in artificial tears was successfully monitored through structural color changes, and the cytotoxicity test results showed that the MICL had good biocompatibility. Therefore, MICLs with a PC structure color have great biomedical potentiality in the future.

Heat-stability study of various insulin types in tropical temperature conditions: New insights towards improving diabetes care

Strict storage recommendations for insulin are difficult to follow in hot tropical regions and even more challenging in conflict and humanitarian emergency settings, adding an extra burden to the management of people with diabetes. According to pharmacopeia unopened insulin vials must be stored in a refrigerator (2-8°C), while storage at ambient temperature (25-30°C) is usually permitted for the 4-week usage period during treatment. In the present work we address a critical question towards improving diabetes care in resource poor settings, namely whether insulin is stable and retains biological activity in tropical temperatures during a 4-week treatment period. To answer this question, temperature fluctuations were measured in Dagahaley refugee camp (Northern Kenya) using log tag recorders. Oscillating temperatures between 25 and 37°C were observed. Insulin heat stability was assessed under these specific temperatures which were precisely reproduced in the laboratory. Different commercialized formulations of insulin were quantified weekly by high performance liquid chromatography and the results showed perfect conformity to pharmacopeia guidelines, thus confirming stability over the assessment period (four weeks). Monitoring the 3D-structure of the tested insulin by circular dichroism confirmed that insulin monomer conformation did not undergo significant modifications. The measure of insulin efficiency on insulin receptor (IR) and Akt phosphorylation in hepatic cells indicated that insulin bioactivity of the samples stored at oscillating temperature during the usage period is identical to that of the samples maintained at 2-8°C. Taken together, these results indicate that insulin can be stored at such oscillating ambient temperatures for the usual four-week period of use. This enables the barrier of cold storage during use to be removed, thereby opening up the perspective for easier management of diabetes in humanitarian contexts and resource poor settings.

Simultaneous dexamethasone intravitreal implant and anti-VEGF therapy for neovascular age-related macular degeneration resistant to anti-VEGF monotherapy

PURPOSE

To evaluate the efficacy of a dexamethasone intravitreal implant in combination with intravitreal anti-VEGF agents for treatment resistant neovascular age-related macular degeneration (nvAMD).

METHODS

This study was designed as a single-center, retrospective interventional case series. Consecutive patients with treatment-resistant nvAMD underwent simultaneous combined injection of anti-VEGF agent and dexamethasone intravitreal implant. Eighteen patients with mean age of 81.5 years were included. Patients received average of 26.3 anti-VEGF injections before dual therapy, with mean follow up of 8.2 months after dual therapy.

RESULTS

Dual therapy produced a significant mean decrease in CFT (126.3 μm), compared to a mean increase of 29.9 μm when treated with anti-VEGF monotherapy (p=0.0017). Patients also had mean decrease in MCV of -0.85 mm³ with dual therapy compared with anti-VEGF monotherapy (p=0.0014). There was a moderate correlation between the number of prior anti-VEGF injections and the magnitude of anatomic response, suggesting that shorter disease duration may positively influence response to combined treatment. Although there was a slight trend towards improved mean visual acuity after dual therapy, these differences did not reach statistical significance. Nevertheless, with combination treatment, 33% of patients gained one or more lines of vision. Dual therapy resulted in a significantly lower number of required anti-VEGF injections (4.25 vs 5.33) and an increase of the anti-VEGF injection-free interval to 1.41 months from 1.12 months during the 6 months following dual therapy compared to the same interval before dual therapy. Dual therapy was well tolerated; two eyes developed mild IOP elevation effectively managed with topical therapy and one patient developed worsening cataract.

CONCLUSIONS

Combined treatment of anti-VEGF with the dexamethasone intravitreal implant is a viable alternative for treatment-resistant nvAMD, and may reduce treatment burden. Earlier treatment with dual therapy may be beneficial to maximize anatomic and visual outcomes in these patients.

Rational design of therapeutic mAbs against aggregation through protein engineering and incorporation of glycosylation motifs applied to bevacizumab

The aggregation of biotherapeutics is a major hindrance to the development of successful drug candidates; however, the propensity to aggregate is often identified too late in the development phase to permit modification to the protein's sequence. Incorporating rational design for the stability of proteins in early discovery has numerous benefits. We engineered out aggregation-prone regions on the Fab domain of a therapeutic monoclonal antibody, bevacizumab, to rationally design a biobetter drug candidate. With the purpose of stabilizing bevacizumab with respect to aggregation, 2 strategies were undertaken: single point mutations of aggregation-prone residues and engineering a glycosylation site near aggregation-prone residues to mask these residues with a carbohydrate moiety. Both of these approaches lead to comparable decreases in aggregation, with an up to 4-fold reduction in monomer loss. These single mutations and the new glycosylation pattern of the Fab domain do not modify binding to the target. Biobetters with increased stability against aggregation can therefore be generated in a rational manner, by either removing or masking the aggregation-prone region or crowding out protein-protein interactions.

Intravitreal combination of dexamethasone sodium phosphate and bevacizumab in the treatment of exudative AMD

The purpose of this study is to investigate the efficacy and safety of intravitreal dexamethasone sodium phosphate (DSP) combined with bevacizumab for the treatment of neovascular age-related macular degeneration (AMD). In this non comparative case study, 30 eyes of 27 patients with CNV due to AMD received intravitreal DSP (0.2 mg) and bevacizumab (1.25 mg) during a 6-month PRN (pro re nata) dosing regimen. Visual acuity, macular thickness and intraocular pressure (IOP) were monitored and recorded. After 6 months, mean retinal thickness decreased from 423.5 ± 75.3 to 228.2 ± 34.5 and mean visual acuity improved from 0.9 ± 0.39 logMAR to 0.53 ± 0.34 (p = 0.001) logMAR. During the trial period, 81 intravitreal injections were performed in 30 eyes, thus the mean number of injections per eye was 2.7 ± 1.1. 86.7% of the eyes required 3 or less injections while only 13.3% needed 4 or more injections. None of the patients, phakic or pseudophakic, manifested an elevation of IOP during the treatment, ranging between 12 and 22 mmHg. Combined DSP and bevacizumab offers encouraging results in the challenge of AMD treatment, providing immediate response of macular edema, reduced number of intravitreal injections and stabilization or improvement of visual acuity.

Implantable MicroPump for Drug Delivery in Patients with Diabetic Macular Edema

PURPOSE

To demonstrate the safety and surgical feasibility of the first-in-man ocular implant of a novel Posterior MicroPump Drug Delivery System (PMP) in patients with diabetic macular edema (DME) and to report on the device capabilities for delivering a programmable microdose.

METHODS

This was a single center, single arm, open-label, prospective study. Eleven patients with DME and visual acuity equal to or worse than 20/40 were included. The PMP prefilled with ranibizumab was implanted into the subconjunctival space. After implantation, the PMP was wirelessly controlled to deliver a programmed microdose. Comprehensive ophthalmic exams and optical coherence tomography were performed biweekly for 90 days. At the end of the study, the PMP was explanted and the subjects thereafter received standard of care for DME (i.e., laser or intravitreal injections).

RESULTS

All 11 surgical implantations were without complications and within the skill sets of a retinal surgeon. No serious adverse events occurred during the follow-up period. At no point were visual acuity and central foveal thickness worse than baseline in the implanted eye. The PMP delivered the programmed ranibizumab dosage in seven subjects. The remaining four patients received a lower than target dose, and the treatment was complemented with standard intravitreal injection.

CONCLUSIONS

This study demonstrates the first-in-man safety of the Replenish MicroPump implant for a period of 90 days and its capability to deliver a microdose into the vitreous cavity. Further studies to enable longer-term safety and to demonstrate the feasibility of multiple programmable drug delivery are necessary.

Asymmetric flow field-flow fractionation in the field of nanomedicine

Asymmetric flow field-flow fractionation (AF4) is a widely used and versatile technique in the family of field-flow fractionations, indicated by a rapidly increasing number of publications. It represents a gentle separation and characterization method, where nonspecific interactions are reduced to a minimum, allows a broad separation range from several nano- up to micrometers and enables a superior characterization of homo- and heterogenic systems. In particular, coupling to multiangle light scattering provides detailed access to sample properties. Information about molar mass, polydispersity, size, shape/conformation, or density can be obtained nearly independent of the used material. In this Perspective, the application and progress of AF4 for (bio)macromolecules and colloids, relevant for "nano" medical and pharmaceutical issues, will be presented. The characterization of different nanosized drug or gene delivery systems, e.g., polymers, nanoparticles, micelles, dendrimers, liposomes, polyplexes, and virus-like-particles (VLP), as well as therapeutic relevant proteins, antibodies, and nanoparticles for diagnostic usage will be discussed. Thereby, the variety of obtained information, the advantages and pitfalls of this emerging technique will be highlighted. Additionally, the influence of different fractionation parameters in the separation process is discussed in detail. Moreover, a comprehensive overview is given, concerning the investigated samples, fractionation parameters as membrane types and buffers used as well as the chosen detectors and the corresponding references. The perspective ends up with an outlook to the future.

The effect of subconjunctival ranibizumab on corneal and anterior segment neovascularization: study on an animal model

PURPOSE

To evaluate the effect of subconjunctival anti-vascular endothelial growth factor (VEGF) ranibizumab on corneal and anterior segment neovascularization.

METHODS

In this experimental study and laboratory investigation, chemical cauterization was utilized to induce corneal neovascularization in 16 rabbits randomly divided in 2 equal groups. Cauterized eyes were either treated with 0.1 mL (1 mg) of subconjunctival ranibizumab or administered a sham injection. A third group of 4 rabbits served as control for side effects after ranibizumab administration. All animals were monitored daily for 14 days and the extent of corneal scarring and neovascularization was measured on days 1, 7, and 14. After enucleation, ocular tissues were separated under a surgical microscope and VEGF levels were measured with ELISA. Statistical analysis was performed to compare the extent of corneal neovascularization and VEGF levels between treated and untreated eyes.

RESULTS

Subconjunctival ranibizumab inhibited corneal neovascularization significantly both in the first and the second week compared to untreated controls (p = 0.006 and p = 0.001, respectively). The VEGF levels were significantly lower in all anterior segment tissues like the cornea, iris, aqueous humor, and conjunctiva of the treated eyes (p<0.01). The reduction of VEGF levels ranged from 19% to 73% in different ocular tissues. Corneal scarring was not significantly affected by anti-VEGF treatment (p = 0.7). No side effects were noticed.

CONCLUSIONS

Early subconjunctival administration of ranibizumab may successfully inhibit alkali-induced corneal neovascularization in an animal model. Subconjunctival ranibizumab reduces VEGF levels significantly not only in the cornea and the bulbar conjunctiva but also in the aqueous humor and the iris.

Identification of aggregation breakers for bevacizumab (Avastin®) self-association through similarity searching and interaction studies

Aggregation is a common challenge in the optimization of therapeutic antibody formulations. Since initial self-association of two monomers is typically a reversible process, the aim of this study is to identify different excipients that are able to shift this equilibrium to the monomeric state. The hypothesis is that a specific interaction between excipient and antibody may hinder two monomers from approaching each other, based on previous work in which dexamethasone phosphate showed the ability to partially reverse formed aggregates of the monoclonal IgG1 antibody bevacizumab back into monomers. The current study focuses on the selection of therapeutically inactive compounds with similar properties. Adenosine monophosphate, adenosine triphosphate, sucrose-6-phosphate and guanosine monophosphate were selected in silico through similarity searching and docking. All four compounds were predicted to bind to a protein-protein interaction hotspot on the Fc region of bevacizumab and thereby breaking dimer formation. The predictions were supported in vitro: An interaction between AMP and bevacizumab with a dissociation constant of 9.59±0.15 mM was observed by microscale thermophoresis. The stability of the antibody at elevated temperature (40 °C) in a 51 mM phosphate buffer pH 7 was investigated in presence and absence of the excipients. Quantification of the different aggregation species by asymmetrical flow field-flow fractionation and size exclusion chromatography demonstrates that all four excipients are able to partially overcome the initial self-association of bevacizumab monomers.

Acute glaucoma in a patient with an Artisan® due to trabecular blockage after combined intravitreal treatment for macular oedema

CASE REPORT

We present a 71-year-old patient with an Artisan(®) implant and macular oedema associated with unsatisfactory response to repeated intravitreal corticosteroids. An intravitreal Trigon(®) and Avastin(®) combined injection was given, and acute glaucoma developed. Anterior chamber washout was performed to resolve the rise in intraocular pressure. In spite of an excellent macular response, this was only temporary, and the corneal endothelium, which had remained competent so far, suffered irreversible damage.

DISCUSSION

The combination of both treatments, along with the particular anatomic features in these patients, may have been precipitating factors in this unfortunate outcome.