intravitreal tumor necrosis factor inhibitors in the treatment of refractory diabetic macular edema: a pilot study from the Pan-American Collaborative Retina Study Group. Retina. 2011;31:298-303. [PMID: 21099452 DOI: 10.1097/iae.0b013e3181eac7a6]

Diabetic retinopathy: current concepts and emerging therapy

More Americans become blind each year from microvascular complications of diabetes than from any other cause. Several studies have indicated that tight glucose control and lifestyle modification can dramatically reduce the incidence and prevalence of diabetic retinopathy. Research over the past several years has yielded a tremendous increase in our knowledge of the pathogenesis of the damage to the retina that occurs in diabetes and has facilitated our ability to intervene and control the damage. New intravitreal medical therapies supported by government- and industry-supported research are gradually replacing standard laser photocoagulation for the treatment of all forms of retinopathy.

Biomarkers in diabetic retinopathy and the therapeutic implications

The main problem both in type 1 (T1DM) and type 2 (T2DM) diabetes is the development of chronic vascular complications encompassing micro- as well as macrocirculation. Chronic complications lower the quality of life, lead to disability, and are the cause of premature death in DM patients. One of the chronic vascular complications is a diabetic retinopathy (DR) which leads to a complete loss of sight in DM patients. Recent trials show that the primary cause of diabetic retinopathy is retinal neovascularization caused by disequilibrium between pro- and antiangiogenic factors. Gaining knowledge of the mechanisms of action of factors influencing retinal neovascularization as well as the search for new, effective treatment methods, especially in advanced stages of DR, puts special importance on research concentrating on the implementation of biological drugs in DR therapy. At present, it is antivascular endothelial growth factor and antitumor necrosis factor that gain particular significance.

Neuropeptides and diabetic retinopathy

Diabetic retinopathy, a common complication of diabetes, develops in 75% of patients with type 1 and 50% of patients with type 2 diabetes, progressing to legal blindness in about 5%. In the recent years, considerable efforts have been put into finding treatments for this condition. It has been discovered that peptidergic mechanisms (neuropeptides and their analogues, activating a diverse array of signal transduction pathways through their multiple receptors) are potentially important for consideration in drug development strategies. A considerable amount of knowledge has been accumulated over the last three decades on human retinal neuropeptides and those elements in the pathomechanisms of diabetic retinopathy which might be related to peptidergic signal transduction. Here, human retinal neuropeptides and their receptors are reviewed, along with the theories relevant to the pathogenesis of diabetic retinopathy both in humans and in experimental models. By collating this information, the curative potential of certain neupeptides and their analogues/antagonists can also be discussed, along with the existing clinical treatments of diabetic retinopathy. The most promising peptidergic pathways for which treatment strategies may be developed at present are stimulation of the somatostatin-related pathway and the pituitary adenylyl cyclase-activating polypeptide-related pathway or inhibition of angiotensinergic mechanisms. These approaches may result in the inhibition of vascular endothelial growth factor production and neuronal apoptosis; therefore, both the optical quality of the image and the processing capability of the neural circuit in the retina may be saved.

Local therapies for inflammatory eye disease in translation: past, present and future

Despite their side-effects and the advent of systemic immunosuppressives and biologics, the use of corticosteroids remains in the management of patients with uveitis, particularly when inflammation is associated with systemic disease or when bilateral ocular disease is present. The use of topical corticosteroids as local therapy for anterior uveitis is well-established, but periocular injections of corticosteroid can also be used to control mild or moderate intraocular inflammation. More recently, intraocular corticosteroids such as triamcinolone and steroid-loaded vitreal inserts and implants have been found to be effective, including in refractory cases. Additional benefits are noted when ocular inflammation is unilateral or asymmetric, when local therapy may preclude the need to increase the systemic medication.

Implants in particular have gained prominence with evidence of efficacy including both dexamethasone and fluocinolone loaded devices. However, an appealing avenue of research lies in the development of non-corticosteroid drugs in order to avoid the side-effects that limit the appeal of injected corticosteroids. Several existing drugs are being assessed, including anti-VEGF compounds such as ranibizumab and bevacizumab, anti-tumour necrosis factor alpha antibodies such as infliximab, as well as older cytotoxic medications such as methotrexate and cyclosporine, with varying degrees of success. Intravitreal sirolimus is currently undergoing phase 3 trials in uveitis and other inflammatory pathways have also been proposed as suitable therapeutic targets. Furthermore, the advent of biotechnology is seeing advances in generation of new therapeutic molecules such as high affinity binding peptides or modified high affinity or bivalent single chain Fab fragments, offering higher specificity and possibility of topical delivery.

Molecular basis of the inner blood-retinal barrier and its breakdown in diabetic macular edema and other pathological conditions

Breakdown of the inner endothelial blood-retinal barrier (BRB), as occurs in diabetic retinopathy, age-related macular degeneration, retinal vein occlusions, uveitis and other chronic retinal diseases, results in vasogenic edema and neural tissue damage, causing loss of vision. The central mechanism of altered BRB function is a change in the permeability characteristics of retinal endothelial cells caused by elevated levels of growth factors, cytokines, advanced glycation end products, inflammation, hyperglycemia and loss of pericytes. Subsequently, paracellular but also transcellular transport across the retinal vascular wall increases via opening of endothelial intercellular junctions and qualitative and quantitative changes in endothelial caveolar transcellular transport, respectively. Functional changes in pericytes and astrocytes, as well as structural changes in the composition of the endothelial glycocalyx and the basal lamina around BRB endothelium further facilitate BRB leakage. As Starling's rules apply, active transcellular transport of plasma proteins by the BRB endothelial cells causing increased interstitial osmotic pressure is probably the main factor in the formation of macular edema. The understanding of the complex cellular and molecular processes involved in BRB leakage has grown rapidly in recent years. Although appropriate animal models for human conditions like diabetic macular edema are lacking, these insights have provided tools for rational design of drugs aimed at restoring the BRB as well as for design of effective transport of drugs across the BRB, to treat the chronic retinal diseases such as diabetic macular edema that affect the quality-of-life of millions of patients.

Gene therapy for noninfectious uveitis

Noninfectious intraocular inflammatory disease remains a significant cause of visual loss, even with current systemic immunosuppression. Alternative novel treatments are thus required, particularly for severe forms of posterior uveitis. Encouraging results from several phase I/II clinical trials of gene therapy for monogenic retinal disorders have paved the way for the development of this approach for other ocular conditions. Gene therapy for uveitis offers the possibility of potent, self-regulating, long-term disease control following a single treatment and without systemic side effects. To date, gene therapy approaches using interleukin-10, interleukin-1 receptor antagonist, interferon-alpha, soluble TNF-alpha receptors, and alpha-MSH gene transfer have been used successfully to attenuate experimental animal models of uveitis. This review evaluates these preclinical studies, considers the route to clinical application, and explores future targets and approaches.

Long-term effects of intravitreal infliximab for treatment of sight-threatening chronic noninfectious uveitis

PURPOSE

This study aimed to evaluate the safety and long-term effects of infliximab on chronic noninfectious uveitis with measuring best corrected visual acuity (BCVA) and central macular thickness (CMT).

METHOD

Ten eyes of 7 patients were included in this prospective case series. All the patients had noninfectious anterior and posterior uveitis that was unresponsive to conventional treatments for 3 months. About 1.5 mg of infliximab in 0.15 cc was injected intravitreally and the patients were followed for 6 months. BCVA was measured by Snellen chart and grading of vitritis was measured according to binocular indirect ophthalmoscope score before injection, 4 weeks, 3 months, and 6 months after the injection. CMT was measured 1 day before injection and compared with the same factors 4 weeks and 6 months after the injection.

RESULTS

Mean of LogMAR before injection was 1.37±0.43 that changed to 0.67±0.55 and 1.38±0.36 one month and 6 months after the injection, respectively. Mean CMT before injection was 673.2±338.39 that changed to 456.4±317.46 and 659.3±342.48, 4 weeks and 6 months after the injection, respectively. Mean vitreous haziness grade before injection, 4 weeks, 3 months, and 6 months after the injection was 2.7, 0.95, 2.3, and 2.6, respectively.

CONCLUSIONS

Intravitreal Infliximab may be used in treatment of noninfectious uveitis. It probably improves the vision and decreases the macular edema but its effect is temporary and repeated injections may be needed to achieve the best therapeutic goal.

Diabetic macular edema: new trends in management

The treatment of diabetic macular edema may be evolving from a laser ablative approach into a pharmacotherapeutic approach. The exponential growth that has occurred over the past decade in the retinal pharmacotherapy field has led to the development of several pharmacotherapies for retinal vascular diseases such as diabetic macular edema. Many of these agents, in the form of intravitreal injections or sustained delivery devices, have already undergone clinical trial testing for safety and efficacy and many others are currently being similarly evaluated. Some of these agents have proven to be more efficacious than traditional laser therapy, and it is possible that traditional laser therapy for diabetic macular edema may be abandoned altogether in the near future, especially with the introduction of the micropulse laser. However, more research and experience is still needed in order to determine the best treatment agent or combination of therapeutic modalities, as well as the best treatment regimen for a given patient. In this article, we briefly review the major new developments in the field of diabetic macular edema treatment. In addition, we touch on some of the promising forthcoming therapies.

Intravitreal infliximab for sight-threatening relapsing uveitis in Behçet disease: a pilot study in 15 patients

PURPOSE

To assess the safety and to conduct a preliminary assessment of efficacy of intravitreal infliximab, an anti-tumor necrosis factor antibody, for sight-threatening relapsing uveitis in Behçet disease.

DESIGN

Prospective, noncomparative, interventional pilot study.

METHODS

A single intravitreal injection of infliximab (1 mg/0.05 mL) was given to 15 patients with relapsing posterior uveitis at the onset of a unilateral attack. Best-corrected visual acuity, anterior chamber cells, vitreous haze, and posterior eye segment inflammation were assessed at baseline and at 1, 7, 14, and 30 days after treatment.

RESULTS

Ocular or extra-ocular side effects were not observed. Baseline best-corrected visual acuity (mean logarithm of minimal angle of resolution, 0.74; range, 0.15 to 1.7) improved significantly by day 7 and continued to improve through day 30 after infliximab (mean, 0.30; P < .0001). Profound decreases in anterior chamber cells and vitreous haze (both P < .0001), as well as beneficial effects in retinal vasculitis (P = .0001) and retinitis (P = .001) were evident through day 30. Cystoid macular edema persisted in 9 of 11 eyes affected, but central macular thickness decreased from a baseline mean of 434 to 309 mm at the end of follow-up (P < .0001). Lack of systemic treatment at baseline in 4 patients or background immunosuppressive medications, which remained unchanged during follow-up, did not influence significantly these responses; additional treatment was not required.

CONCLUSIONS

These findings suggest that intraocularly produced or acting tumor necrosis factor, or both, is crucial in Behçet disease-associated relapsing uveitis and that intravitreal infliximab should be considered when systemic administration is not feasible or contraindicated. Further studies may identify patients for whom intravitreal infliximab is preferable to systemic treatment.

Uveitis, the Comparison of Age-Related Macular Degeneration Treatments Trials (CATT), and intravitreal biologics for ocular inflammation

PURPOSE

To provide perspective on the implications of the Comparison of Age-Related Macular Degeneration Treatments Trials (CATT) on intravitreal biologic agents in uveitis and retinal diseases in which ocular inflammatory pathways are central to their pathogenesis.

DESIGN

Interpretative essay.

METHODS

Literature review and interpretation.

RESULTS

Besides the clear importance of CATT from a patient treatment perspective in age-related macular degeneration (AMD), these data highlight the critical relevance of highly specific protein immunotherapies offered with biologic agents. The CATT trial also provides a reminder regarding the importance of rigorous efficacy and safety monitoring required when administering intravitreal biologic therapy. Within the field of uveitis, systemic and local biologics have been used to effectively treat uveitis, targeting pathways implicated in both angiogenesis and inflammation (eg, tumor necrosis factor-α [TNF-α] and interleukin-2 pathways), and research on intravitreal biologic therapy for uveitis and AMD will continue to expand. With over 25 ongoing clinical trials on intravitreal biologic therapy for AMD, enthusiasm for vanguard biologic therapies should be tempered by judicious monitoring for adverse events.

CONCLUSION

The importance of the CATT trial encompasses day-to-day treatment decisions for AMD, as well as lessons on how biologics for ocular disease should be implemented into clinical practice. Specifically, the introduction of intravitreal biologic therapies into clinical practice for uveitis, AMD, and other ocular diseases in which inflammation is involved should be guided by a clear understanding of the immunotherapeutic agent and its molecular target and with rigorous monitoring for both patient benefit and patient safety.

Review and update of intraocular therapy in noninfectious uveitis

PURPOSE OF REVIEW

To review new clinically relevant data regarding the intraocular treatment of noninfectious uveitis.

RECENT FINDINGS

Triamcinolone acetonide, the most commonly used intravitreal corticosteroid for treatment of uveitis and uveitic macular oedema has a limited duration of action and is associated with a high risk of corticosteroid-induced intraocular pressure (IOP) rise and cataract. Recent advances have led to the development of sustained-release corticosteroid devices using different corticosteroids such as dexamethasone and fluocinolone acetonide. Treatment options for patients who have previously exhibited corticosteroid hypertensive response have also expanded through the use of new noncorticosteroid intravitreal therapeutics such as methotrexate and antivascular endothelial growth factor (anti-VEGF) agents.

SUMMARY

Ozurdex dexamethasone implant appears to have a better safety profile, and a slightly long-lasting effect than triamcinolone acetonide. The Retisert implant allows the release of corticosteroids at a constant rate for 2.5 years, but it requires surgical placement and its use is associated with a very high risk of cataract and requirement for IOP-lowering surgery. For patients who are steroid responders, methotrexate may offer a better alternative to corticosteroid treatment than anti-VEGF agents, but controlled trials are required to confirm this.