Recent innovations with drugs in clinical trials for neurotrophic keratitis and refractory corneal ulcers

The role of topical insulin in ocular surface restoration: A review

Corneal epithelial defects are one of the most common ocular disorders. Restoring corneal integrity is crucial to reduce pain and regain function, but in cases of neurotrophic or desensitized corneas, healing can be significantly delayed. Treating neurotrophic corneas is challenging for ophthalmologists, and surgical intervention is often indicated to manage refractory cases that are unresponsive to medical therapy. Over the last decade, as more expensive therapeutics reach the market, topical insulin has returned to the forefront as an affordable option to improve corneal wound healing. There is still a paucity of data on the use and the efficacy of topical insulin, with no consensus regarding its indications, preparation, or posology. Here we review the literature on topical insulin for corneal and ocular surface pathologies, with a focus on the current evidence, its mechanisms of action, and its safety profile. Additionally, we share our experience in the field and provide a potential framework for future research.

Neurotrophic keratopathy: General features and new therapies

Neurotrophic keratopathy is an uncommon degenerative corneal disorder characterized by compromised corneal sensory innervation resulting in the formation of epithelial defects and nonhealing corneal ulcers. Various treatment modalities are available to stabilize disease progression, improve patient well-being, and prevent vision loss. For eligible patients, medical and surgical reinnervation have emerged as pioneering therapies, holding promise for better management. We present a comprehensive review of the disorder, providing an update relevant to ophthalmologists on pathogenesis, diagnosis, treatment options, and novel therapies targeting pathophysiological pathways.

Comprehensive dry eye therapy: overcoming ocular surface barrier and combating inflammation, oxidation, and mitochondrial damage

BACKGROUND

Dry Eye Disease (DED) is a prevalent multifactorial ocular disease characterized by a vicious cycle of inflammation, oxidative stress, and mitochondrial dysfunction on the ocular surface, all of which lead to DED deterioration and impair the patients' quality of life and social functioning. Currently, anti-inflammatory drugs have shown promising efficacy in treating DED; however, such drugs are associated with side effects. The bioavailability of ocular drugs is less than 5% owing to factors such as rapid tear turnover and the presence of the corneal barrier. This calls for investigations to overcome these challenges associated with ocular drug administration.

RESULTS

A novel hierarchical action liposome nanosystem (PHP-DPS@INS) was developed in this study. In terms of delivery, PHP-DPS@INS nanoparticles (NPs) overcame the ocular surface transport barrier by adopting the strategy of "ocular surface electrostatic adhesion-lysosomal site-directed escape". In terms of therapy, PHP-DPS@INS achieved mitochondrial targeting and antioxidant effects through SS-31 peptide, and exerted an anti-inflammatory effect by loading insulin to reduce mitochondrial inflammatory metabolites. Ultimately, the synergistic action of "anti-inflammation-antioxidation-mitochondrial function restoration" breaks the vicious cycle associated with DED. The PHP-DPS@INS demonstrated remarkable cellular uptake, lysosomal escape, and mitochondrial targeting in vitro. Targeted metabolomics analysis revealed that PHP-DPS@INS effectively normalized the elevated level of mitochondrial proinflammatory metabolite fumarate in an in vitro hypertonic model of DED, thereby reducing the levels of key inflammatory factors (IL-1β, IL-6, and TNF-α). Additionally, PHP-DPS@INS strongly inhibited reactive oxygen species (ROS) production and facilitated mitochondrial structural repair. In vivo, the PHP-DPS@INS treatment significantly enhanced the adhesion duration and corneal permeability of the ocular surface in DED mice, thereby improving insulin bioavailability. It also restored tear secretion, suppressed ocular surface damage, and reduced inflammation in DED mice. Moreover, it demonstrated favorable safety profiles both in vitro and in vivo.

CONCLUSION

In summary, this study successfully developed a comprehensive DED management nanosystem that overcame the ocular surface transmission barrier and disrupted the vicious cycle that lead to dry eye pathogenesis. Additionally, it pioneered the regulation of mitochondrial metabolites as an anti-inflammatory treatment for ocular conditions, presenting a safe, efficient, and innovative therapeutic strategy for DED and other inflammatory diseases.

Efficacy of Plasma Rich in Growth Factors (PRGF) in Stage 1 Neurotrophic Keratitis

Background/Aims

Neurotrophic keratitis (NK) is a neurodegenerative disease that can lead to corneal hypoesthesia, decreased tear production, and epitheliopathy. Based on the severity of ocular surface damage, NK is classified into 3 stages. Stage 1 NK is characterized by superficial punctate keratopathy, tear film instability, and reduced corneal sensation. The therapeutic efficacy of PRGF eye drops for NK stages 2 and 3 has been previously reported. In this study, we evaluated the efficacy and safety of autologous PRGF eye drops in improving corneal sensitivity and other ocular surface clinical signs in patients with stage 1 NK.

Methods

Retrospective chart review.

Results

26 eyes of 15 stage 1 NK patients (seven males, eight females), aged 76.3 ± 12.1 years, were included in the study. The mean treatment duration was 2 ± 1.8 months. With PRGF treatment, corneal sensitivity increased from 2.8 to 4.5 cm in 53.8% (14/26) (p < 0.01), TBUT increased from 3.6 to 5.0 s in 69.2% (18/26) (p < 0.01), and Schirmer score increased from 13.7 to 16.8 mm in 80.7% (21/26) of treated eyes (p < 0.01). Similarly, an improvement in corneal staining (punctate epithelial erosions) and MMP-9 levels was seen in 80.7% (n = 21) and 65.4% (n = 17) of treated eyes, respectively. BCVA improvement was seen in 26.9% of treated eyes (n = 7).

Conclusions

This study demonstrates the effective role of PRGF therapy in recovering corneal sensation and tear film function and in the healing of corneal erosions in stage 1 NK patients.

Prevalence and clinical characteristics of neurotrophic keratopathy in hispanic population in northeastern Mexico

PURPOSE

To evaluate the prevalence and clinical characteristics of neurotrophic keratopathy (NK) in northeastern Mexico.

METHODS

Retrospective cross-sectional study in which NK patients admitted to our ophthalmology clinic between 2015 and 2021 were consecutively enrolled. Data regarding demographics, clinical characteristics, and comorbidities were collected at the time diagnosis of NK was made.

RESULTS

In the period from 2015 to 2021, a total of 74,056 patients were treated and of these 42 had a diagnosis of neurotrophic keratitis. The prevalence found was 5.67 [CI95 3.95-7.38] in 10,000 cases. The mean age observed was 59 ± 17.21 years occurring more frequently in males in 59% and with corneal epithelial defects in 66.7%. The most frequent antecedents were the use of topical medications in 90%, the presence of diabetes mellitus 2 in 40.5% and systemic arterial hypertension in 26.2%. A higher proportion of male patients with corneal alterations and a higher proportion of female patients with corneal ulcerations and/or perforation were observed.

CONCLUSION

Neurotrophic keratitis is an underdiagnosed disease with a broad clinical spectrum. The antecedents that were contracted corroborate what was reported in the literature as risk factors. The prevalence of the disease in this geographical area was not reported, so it is expected to increase over time when searching for it intentionally.

Effectiveness of topical insulin for the treatment of surface corneal pathologies

The Purpose is to identify, through a systematic literature review, the current evidence regarding the effectiveness of topical insulin treatment in ocular surface pathologies. A literature search was implemented in Medline (Pubmed), Embase and Web Of Science medical indexing databases by using keywords such as "insulin" AND "cornea" OR "corneal" OR "dry eye" in published papers in English or Spanish within the last eleven years (2011-2022). Nine papers were identified with 180 participants from the United States, Spain, Ireland, Canada, Portugal and Malaysia, with persistent refractory epithelial defects and secondary to vitrectomy, whose extension of the lesion was from 3,75mm² to 65.47mm². The preparation was dissolved with artificial tears and the insulin concentration ranged from 1 IU/ml to 100 IU/ml. In all cases, the resolution of the clinical picture was complete with a healing time from 2.5 days to 60.9 days, the latter being a secondary case to a difficult-to-control caustic burn. Topical insulin has been effective for the treatment of persistent epithelial defects. The intermediate action and low concentrations showed a shorter resolution time in neurotrophic ulcers and induced during vitreoretinal surgery.

Neurotization of the human cornea - A comprehensive review and an interim report

We present a comprehensive review of existing literature on surgical corneal neurotization (SCN) as a treatment modality for neurotrophic keratopathy (NK) with an interim report of seven cases where SCN was performed using the indirect approach and followed up till 18 months postoperatively to look for improvement in ocular surface, corneal sensations, and nerve regeneration by using in vivo confocal microscopy (IVCM). A literature search was performed for publications with keywords “corneal nerves,” “neurotization,” “esthesiometry,” “corneal anesthesia,” and “neurotrophic keratopathy.” All literature available till December 31, 2020 was reviewed and included to describe NK and its management options, particularly SCN. NK is associated with absent or reduced corneal sensations and is managed using a step-ladder algorithm ranging from medical management for symptomatic relief to surgical corneal neurotization. Both direct and indirect approaches of SCN have a favorable outcome with reduced surgical morbidity in the indirect approach using sural nerve graft. Post neurotization, corneal sensation recovery may take up to 3–6 months, while nerve regeneration on confocal microscopy can take as long as 6 months–1 year.

Cutting Edge: Topical Recombinant Nerve Growth Factor for the Treatment of Neurotrophic Keratopathy-Biologicals as a Novel Therapy for Neurotrophic Keratopathy

ABSTRACT

Ophthalmologists find management of neurotrophic keratopathy (NK) challenging because conventional therapy lacks efficacy and may result in permanent loss of vision. Recombinant nerve growth factor (cenegermin) targets the underlying pathogenesis of NK by regenerating corneal nerves and healing the corneal epithelium through promotion of proliferation, maturing corneal epithelial cells. It has been approved as Food Drug Association-approved treatment of NK. In this article, the background, clinical trials, and impact of recombinant nerve growth factor as the first neurotrophic factor for the restoration of corneal integrity, homeostasis, and corneal nerve regeneration are discussed.

Use of Plasma Rich in Growth Factors and ReGeneraTing Agent Matrix for the Treatment of Corneal Diseases

This study aimed to investigate the use of Plasma Rich in Growth Factors (PRGF) associated with tissue ReGeneraTing Agent (RGTA) drops for the treatment of noninfectious corneal ulcers. RGTA treatment was applied (one drop every two days); however, if ulcer closure was not achieved, PRGF eye drops treatment was added (four times/day). The time taken to reach the ulcer closure, the Best Corrected Visual Acuity (BCVA), intraocular pressure (IOP), Visual Analog Scale (VAS, in terms of frequency and severity of symptoms), and Ocular Surface Disease Index (OSDI) were evaluated. Seventy-four patients (79 eyes) were included, and the mean age was 56.8 ± 17.3 years. The neurotrophic corneal ulcer was the most frequent disorder (n = 27, 34.2%), mainly for herpes virus (n = 15, 19.0%). The time of PRGF eye drops treatment associated with the RGTA matrix was 4.2 ± 2.2 (1.5–9.0) months, and the follow-up period was 44.9 ± 31.5 months. The ulcer closure was achieved in 76 eyes (96.2%). BCVA, VAS and OSDI improved from the baseline (p < 0.001), and IOP remained unchanged (p = 0.665). RGTA and PRGF in noninfectious ulcers were effective and could be a therapeutic alternative for this type of corneal disease.

Solid Platelet‑rich Plasma Combined with Silicone-hydrogel Soft Contact Lens for Non-healing Corneal Ulcers: A Case Series

Purpose: To present a case series of non-healing corneal ulcers treated by solid activated platelet-rich plasma (PRP) combined with silicone-hydrogel soft contact lens.Methods: Three eyes from three patients with unresponsive corneal ulcers were included. A clot of PRP was applied directly onto the corneal ulcer and covered with a soft contact lens. The primary outcome was corneal healing. Changes in corneal ulcer area were measured by analyzing slit-lamp photographs taken using ImageJ software.Results: Successful corneal healing was achieved in all patients within two weeks, with no recurrences or signs of infection through the last follow-up. In two of the three cases, treatment was applied twice.Conclusions: This novel procedure was easy to perform, economically advantageous, and a possible alternative to surgical approaches for enhancing epithelial wound healing in patients with non-healing corneal ulcers. Further prospective and comparative studies are needed to assess the efficacy of this treatment.

Neurotrophic keratitis after penetrating keratoplasty for lattice dystrophy

Purpose

To report clinical outcomes of a patient with unilateral neurotrophic keratitis following penetrating keratoplasty for lattice dystrophy treated with topical recombinant human nerve growth factor.

Observations

A 75-year-old male with lattice dystrophy and history of herpes simplex keratitis, presented with recurrent neurotrophic ulceration in the right eye two years following penetrating keratoplasty. The patient was successfully treated with topical recombinant human nerve growth factor.

Conclusion

Neurotrophic keratitis is a rare chronic disorder that affects quality of life due to the risk of vision loss. Topical recombinant human nerve growth factor is a novel and effective treatment option that may help improve optical quality and patient's satisfaction as shown in this case of recurrent neurotrophic keratitis.

Pigment Epithelium-Derived Factor Peptide Promotes Corneal Nerve Regeneration: An In Vivo and In Vitro Study

Purpose

To investigate the potential of a pigment epithelium-derived factor (PEDF) peptide 44-mer to promote nerve regeneration in a rabbit corneal nerve injury model to demonstrate its neurotrophic ability in cultivated mouse trigeminal neuron cells.

Methods

Subconjunctival or intrastromal injection of 44-mer on the cornea was performed in a rabbit model of corneal nerve injury created by corneal epithelial debridement. Immunocytochemical analysis (44-mer, anti-tubulin III, SMI312, CD11b, and α-SMA) and in vivo confocal microscopy were performed. Corneal sensation was estimated using a Cochet-Bonnet corneal esthesiometer. Primary cultivated mouse trigeminal neurons were used to examine the in vitro neurotrophic ability of 44-mer. The cellular morphology and the immunocytochemical staining with anti-tubulin III and SMI312 in different concentrations of 44-mer were compared, and a quantitative assessment of neurite outgrowth was performed.

Results

Immunohistochemical staining showed the retention of 44-mer in the corneal stroma for at least 7 days after a single dose of corneal intrastromal injection and promoted corneal nerve regeneration revealed by in vivo confocal microscopy. Corneal esthesiometer demonstrated gradual recovery of the corneal sensation in 44-mer-treated eyes with a lower corneal touch threshold than wounded vehicles and closer to baseline at 3 weeks after corneal injury (P < 0.001). In vitro studies showed a dose-dependent neurotrophic effect of 44-mer in cultivated trigeminal neuron cells.

Conclusions

The 44-mer showed in vivo and in vitro corneal neurotrophic abilities. Our results suggest that intrastromal injection of 44-mer into the corneal stroma may have a potential role in treating diseases related to corneal nerve damage.

Role of the Neurokinin-1 Receptor in the Promotion of Corneal Epithelial Wound Healing by the Peptides FGLM-NH2 and SSSR in Neurotrophic Keratopathy

Purpose

Neurotrophic keratopathy is a corneal epitheliopathy induced by trigeminal denervation that can be treated with eyedrops containing the neuropeptide substance P (or the peptide FGLM-NH₂ derived therefrom) and insulin-like growth factor 1 (or the peptide SSSR derived therefrom). Here, we examine the mechanism by which substance P (or FGLM-NH₂) promotes corneal epithelial wound healing in a mouse model of neurotrophic keratopathy.

Methods

The left eye of mice subjected to trigeminal nerve axotomy in the right eye served as a model of neurotrophic keratopathy. Corneal epithelial wound healing was monitored by fluorescein staining and slit-lamp examination. The distribution of substance P, neurokinin-1 receptor (NK-1R), and phosphorylated Akt was examined by immunohistofluorescence analysis. Cytokine and chemokine concentrations in intraocular fluid were measured with a multiplex assay.

Results

Topical administration of FGLM-NH₂ and SSSR promoted corneal epithelial wound healing in the neurotrophic keratopathy model in a manner sensitive to the NK-1R antagonist L-733,060. Expression of substance P and NK-1R in the superficial layer of the corneal epithelium decreased and increased, respectively, in model mice compared with healthy mice. FGLM-NH₂ and SSSR treatment suppressed the production of interleukin-1α, macrophage inflammatory protein 1α (MIP-1α) and MIP-1β induced by corneal epithelial injury in the model mice. It also increased the amount of phosphorylated Akt in the corneal epithelium during wound healing in a manner sensitive to prior L-733,060 administration.

Conclusions

The substance P–NK-1R axis promotes corneal epithelial wound healing in a neurotrophic keratopathy model in association with upregulation of Akt signaling and attenuation of changes in the cytokine-chemokine network.

Real Life Data on Efficacy and Safety of Topical NGF Eye Drops (Cenegermin)

Background Topical NGF eye drops (Cenegermin) were approved in 2015 as an orphan drug for the treatment of neurotrophic keratopathy (NK). The active substance Cenegermin is a recombinant form of human NGF (nerve growth factor).

Objectives Presentation of efficacy and safety of Cenegermin for use in patients in an university real-life setting.

Material and Methods Retrospective study at the Köln University Eye Hospital from 2017 to 2019 with n = 11 eyes. Average follow-up was 13.5 ± 7.1 months. Reasons for treatment were neurotrophic keratopathy stage II and III, clinically mostly in combination with corneal neovascularization.

Results Seven eyes with a NK II and 4 eyes with a NK III with a median observation period of 13.6 months (range 1.2 – 20.3 months) from a total of 11 patients were included. The median patient age was 42.8 ± 23.6 years (range 18 – 75 years). Before the start of therapy, the median erosion area measured 3.1 ± 1.4 × 1.9 ± 1.1 mm and the median ulcer area had a size of 2.3 ± 1.1 × 2.1 ± 0.8 mm. After the start of therapy with Cenegermin (application 6×/day), the epithelial defect closed in all 11 study eyes (100%) within 4 – 12 weeks (mean: 49 d ± 9 d). In 9 out of 10 patients (90%) pre-existing corneal neovascularization regressed significantly (p < 0.001). Before the start of therapy, a value in the Luneau test of 2.9 ± 1.9 (minimum 1/6, maximum 4/6) was found and rose to a median value of 4.2 ± 1.7 (minimum 2/6, maximum 6/6) after 18 months (p = 0.015). Therapy with Cenegermin had no long-term effect on intraocular pressure: the pressure ranged between 13.2 ± 4.1 mmHg (minimum 8 mmHg, maximum 21 mmHg). Under therapy with NGF eye drops, 67% of the patients, after an initial decrease, showed a long-term improvement in visual acuity (BSCVA) from 0.72 ± 0.31 to 0.46 ± 0.29 logMAR after 18 months (p = 0.005). Relapses in form of a corneal erosion in the long-term follow-up were observed in only one eye. One patient had to stop therapy because of local pain, no other local and systemic side effects were observed.

Conclusion This real-life series on the use of Cenegermin in a university context shows a good effectiveness of the substance for epithelial closure in various underlying diseases (100% within 12 weeks). There is a long-term improvement in vision and corneal sensitivity. Larger real-life cohorts with various underlying diseases should follow.

Corneal Neurotization and Novel Medical Therapies for Neurotrophic Keratopathy

Purpose of Review

Neurotrophic keratopathy (NK) is a degenerative corneal disease characterized by decreased corneal sensibility and impaired corneal healing. In this article, we review surgical techniques for corneal neurotization (CN) and novel medical therapies for the treatment of NK.

Recent Findings

In recent decades, there has been a paradigm shift in the treatment strategies for NK. New minimally invasive direct and indirect CN approaches have demonstrated efficacy at improving best-corrected visual acuity and central corneal sensation while decreasing surgical morbidity. In addition, several targeted medical therapies, such as recombinant human nerve growth factor (rhNGF), regenerating agents (RGTA), and nicergoline, have shown promise in improving corneal epithelial healing. Of these options, cenegermin (Oxervate®, Dompé), a topical biologic medication, has emerged as an approved medical treatment for moderate to severe NK.

Summary

NK is a challenging condition caused by alterations in corneal nerves, leading to impairment in sensory and trophic function with subsequent breakdown of the cornea. Conventional therapy for NK depends on the severity of disease and focuses primarily on protecting the ocular surface. In recent years, numerous CN techniques and novel medical treatments have been developed that aim to restore proper corneal innervation and promote ocular surface healing. Further studies are needed to better understand the long-term efficacy of these treatment options, their target populations, and the potential synergistic efficacy of combined medical and surgical treatments.