Preclinical studies evaluating the effect of semifluorinated alkanes on ocular surface and tear fluid dynamics

Long-Term Safety and Efficacy of Perfluorohexyloctane Ophthalmic Solution for the Treatment of Patients With Dry Eye Disease: The KALAHARI Study

PURPOSE

The aim of this study was to assess the long-term safety and efficacy of perfluorohexyloctane (PFHO) ophthalmic drop (formerly NOV03) for treatment of dry eye disease (DED).

METHODS

KALAHARI was a phase 3, multicenter, single-arm, open-label extension study in patients aged 18 years or older with DED associated with Meibomian gland dysfunction who completed the randomized, double-masked, hypotonic saline-controlled GOBI study. Patients instilled 1 drop of PFHO (MIEBO, Bausch + Lomb) 4 times daily in both eyes for 52 weeks. Safety assessments included adverse events, best-corrected visual acuity, slit-lamp biomicroscopy, intraocular pressure, and dilated fundoscopy. Efficacy end points included change from GOBI study baseline in total corneal fluorescein staining and eye dryness score (0-100 visual analog scale).

RESULTS

Overall, 208 patients from GOBI (PFHO [n = 97]; saline [n = 111]) were rolled over into KALAHARI. Twenty-nine patients (13.9%) had ≥1 ocular adverse event, with most being mild or moderate in severity; the most common ocular adverse events were vitreous detachment (1.9%), allergic conjunctivitis (1.4%), blurred vision (1.4%), and increased lacrimation (1.4%). Other safety end points were unremarkable. For patients continuing PFHO from GOBI, improvements in total corneal fluorescein staining and visual analog scale dryness scores observed in GOBI were maintained throughout KALAHARI. Patients treated with saline in GOBI and switched to PFHO in KALAHARI showed improvements in total corneal fluorescein staining and visual analog scale scores by week 4 that were maintained for the rest of the study.

CONCLUSIONS

PFHO was safe and well tolerated and maintained efficacy for improving signs and symptoms of DED in this year-long study of patients with DED associated with Meibomian gland dysfunction.

Polystyrene Sulfonate Resin as an Ophthalmic Carrier for Enhanced Bioavailability of Ligustrazine Phosphate Controlled Release System

Topical ocular sustained-release drug delivery systems represent an effective strategy for the treatment of ocular diseases, for which a suitable carrier has yet to be sufficiently developed. Herein, an eye-compatible sodium polystyrene sulfonate resin (SPSR) was synthesized with a uniform particle size of about 3 μm. Ligustrazine phosphate (LP) was adsorbed to SPSR by cation exchange to form LP@SPSR. LP@SPSR suspension eye drops were further developed using the combination of Carbopol 934P and xanthan gum as suspending agents. The LP@SPSR suspension showed a sustained release in vitro, which was consistent with the observed porcine corneal penetration ex vivo. Pharmacokinetics in tear fluid of rabits indicated that LP@SPSR suspension led to prolonged ocular retention of LP and a 2-fold improved the area under the drug concentration-time curve (AUC0-t). Pharmacokinetics in the aqueous humor of rabbits showed 2.8-fold enhancement in the AUC0-t compared to LP solution. The LP@SPSR suspension exhibited no cytotoxicity to human corneal epithelial cells, nor irritation was observed in rabbit eyes. Thus, the LP@SPSR suspension has been validated as a safe and sustained release system leading to enhanced ophthalmic bioavailability for treating ocular diseases.

Efficacy of a new water-free topical cyclosporine 0.1% solution for optimizing the ocular surface in patients with dry eye and cataract

This is a pooled analysis from 2 phase III clinical trials investigating a water-free topical cyclosporine 0.1% for the treatment of moderate to severe dry eye. The analyses included 1162 patients: 35% with cataract, 20% with pseudophakia, and 45% without cataract. Demographics or baseline characteristics were comparable across groups except for age and vision. The cyclosporine-treated patients achieved large mean improvements from baseline by day 15: -3.7 in patients without cataract, -3.2 in patients with cataract, and -3.1 in pseudophakic patients. These improvements were statistically significantly higher compared with the respective vehicle groups. In the cataract subgroup, 59% of patients treated with cyclosporine achieved ≥3 grade improvements in corneal staining score, as early as day 15. The magnitude of the effect and early onset of action make this new cyclosporine solution a promising candidate for preoperative management of ocular surface in patients undergoing cataract surgery.

Long-Term Safety and Efficacy of a Water-Free Cyclosporine 0.1% Ophthalmic Solution for Treatment of Dry Eye Disease: ESSENCE-2 OLE

PURPOSE

The ESSENCE-2 Open-Label Extension study aimed to demonstrate long-term safety, tolerability, and efficacy of a novel water-free, nonpreserved topical cyclosporine 0.1% ophthalmic solution (US brand name VEVYE) for patients with dry eye disease (DED).

METHODS

This was a Phase 3, prospective, multicenter, open-label, clinical study. All patients received cyclosporine 0.1% ophthalmic solution and dosed each eye twice a day for 52 weeks. Primary safety end points were ocular and nonocular adverse events (AEs). Secondary safety end points included visual acuity, biomicroscopy, intraocular pressure, and dilated fundoscopy. Efficacy end points, such as total corneal fluorescein staining (tCFS) score (National Eye Institute [NEI] Scale), ocular symptoms (visual analog scale [VAS]), and Schirmer tear test, were also assessed.

RESULTS

A total of 202 patients were enrolled from the ESSENCE-2 study. At week 52, 175 patients (86.6%) completed ESSENCE-2 open-label extension. A total of 55 patients (27.5%) reported 74 ocular treatment-emergent adverse events (TEAEs). The most common ocular AE was instillation site pain (6.5%), which was of mild intensity in all cases. Patients showed statistically significant improvements in all prespecified efficacy end points compared with baseline at each visit. Corneal staining improvements were early and stabilized over time while tear production improved continuously. Symptomatology improvement followed these effects with scores reaching a minimum after 1 year of treatment.

CONCLUSIONS

The water-free cyclosporine 0.1% ophthalmic solution was safe and well tolerated during long-term use. The results demonstrated sustained 1-year efficacy, in both signs and symptoms of DED, and may help understand short and long-term healing dynamics in a predominant inflammatory DED population.

Recent United States Developments in the Pharmacological Treatment of Dry Eye Disease

Dry eye disease (DED) can arise from a variety of factors, including inflammation, meibomian gland dysfunction (MGD), and neurosensory abnormalities. Individuals with DED may exhibit a range of clinical signs, including tear instability, reduced tear production, and epithelial disruption, that are driven by different pathophysiological contributors. Those affected often report a spectrum of pain and visual symptoms that can impact physical and mental aspects of health, placing an overall burden on an individual's well-being. This cumulative impact of DED on an individual's activities and on society underscores the importance of finding diverse and effective management strategies. Such management strategies necessitate an understanding of the underlying pathophysiological mechanisms that contribute to DED in the individual patient. Presently, the majority of approved therapies for DED address T cell-mediated inflammation, with their tolerability and effectiveness varying across different studies. However, there is an emergence of treatments that target additional aspects of the disease, including novel inflammatory pathways, abnormalities of the eyelid margin, and neuronal function. These developments may allow for a more nuanced and precise management strategy for DED. This review highlights the recent pharmacological advancements in DED therapy in the United States. It discusses the mechanisms of action of these new treatments, presents key findings from clinical trials, discusses their current stage of development, and explores their potential applicability to different sub-types of DED. By providing a comprehensive overview of products in development, this review aims to contribute valuable insights to the ongoing efforts in enhancing the therapeutic options available to individuals suffering from DED.

Perfluorohexyloctane Ophthalmic Solution: A Review in Dry Eye Disease

Perfluorohexyloctane ophthalmic solution (Miebo®) is a single-entity, water-, steroid- and preservative-free, first-in-class semifluorinated alkane that is approved in the USA for the treatment of the signs and symptoms of dry eye disease (DED). DED is often linked with meibomian gland dysfunction (MGD), which causes an excessive evaporation of tears. Perfluorohexyloctane ophthalmic solution stabilizes the lipid layer of the tear film and inhibits tear evaporation by forming a monolayer at the air-liquid interface. In the phase III GOBI and MOJAVE trials in adults with DED associated with MGD, one drop of perfluorohexyloctane ophthalmic solution instilled in each eye four times daily over 8 weeks resulted in statistically significant and clinically meaningful improvements in the signs and symptoms of DED compared with hypotonic saline (0.6%). The agent was generally well tolerated, with most ocular adverse events being mild or moderate in severity. The efficacy and tolerability of perfluorohexyloctane ophthalmic solution was sustained for up to 52 weeks in an extension study (KALAHARI). As the first and currently the only prescription treatment approved in the USA directly addressing the pathophysiology of excessive tear evaporation, perfluorohexyloctane ophthalmic solution is a valuable emerging option for the management of DED.

Progress in Ocular Drug Delivery: Challenges and Constraints

The eye has several dynamic and static barriers in place to limit the entry of foreign substances including therapeutics. As such, efficient drug delivery, especially to posterior segment tissues, has been challenging. This chapter describes the anatomical and physiological challenges associated with ocular drug delivery before discussing constraints with regard to formulation parameters. Finally, it gives an overview of advanced drug delivery technologies with a specific focus on recently marketed and late-stage clinical trial products.

Influence of perfluorohexyloctane (Evotears®) on higher order aberrations

PURPOSE

To prospectively assess the effect of regular application of perfluorohexyloctane (F6H8; Evotears®) on the tear film lipid layer, higher order aberrations (HOA) and the repeatability of measurements in healthy eyes.

METHODS

This prospective clinical study included 104 eyes treated with F6H8 four times daily for four weeks (group A) and 101 eyes that served as controls (group B). Measurements were performed with the WASCA aberrometer (Carl Zeiss Meditec GmbH, Jena, Germany). Main outcome measurement in addition to subjective refraction were the root mean square values of HOA measured before and after the intervention.

RESULTS

Regular use of F6H8 over a period of four weeks significantly increases HOA in healthy eyes (p < 0.05). In addition, the repeatability of measurement increases after the application of F6H8.

CONCLUSION

F6H8 may be a suitable treatment option to improve the accuracy of refractive assessment, although it increases HOA. Further studies are needed to confirm the effect on HOA and the repeatability of measurement.

Perfluorohexyloctane in dry eye disease: A systematic review of its efficacy and safety as a novel therapeutic agent

Perfluorohexyloctane (F6H8), a physically and chemically inert synthetic compound, has recently emerged as a promising candidate for the treatment of DED due to its unique properties. A systematic review that only include full-length randomized controlled studies (RCTs), reporting the effects of F6H8 in three databases, PubMed, Scopus and Web of Science, was performed according to the PRISMA statement. The search period was performed between June 1, 2023, and June 21, 2023. The Cochrane risk of bias tool was used to analyze the quality of the studies selected. A total of six RCTs were included in this systematic review. F6H8 tear substitutes treatment achieved a higher improvement than control group interventions in most of the reported variables. The mean differences between both groups were in favor of F6H8 and were as follow: eye dryness score (EDS) base on a visual analogue scale (VAS) of -6.12 ± 4.3 points, ocular surface disease index (OSDI) questionnaire score of -2.8 ± 2.3 points, lipid layer thickness (LLT) of 11.4 ± 10.4 μm, total corneal fluorescein staining (tCFS) of -0.8 ± 0.3 points and ocular treatment-emergent adverse events (TEAEs) of -0.66 ± 1.7. Tear film break-up time (TBUT) was the only variable in favor of control group with a mean of -0.5 ± 0.4 s. Patient satisfaction after F6H8 tear substitutes treatment was high. Therefore, F6H8 tear substitutes improve dry eye symptoms and signs with a satisfactory tolerability and could be recommended in patients with DED.

NOV03 for Signs and Symptoms of Dry Eye Disease Associated With Meibomian Gland Dysfunction: The Randomized Phase 3 MOJAVE Study

PURPOSE

To evaluate the efficacy and safety of NOV03 (perfluorohexyloctane) ophthalmic drop for the treatment of signs and symptoms of dry eye disease (DED) associated with meibomian gland dysfunction (MGD).

DESIGN

Randomized, double-masked, controlled trial.

METHODS

Patients ≥18 years of age with a history of DED and signs of MGD were randomly assigned 1:1 to treatment with NOV03 or hypotonic saline (0.6%) 4 times daily for 8 weeks. The primary sign and symptom endpoints were change from baseline to week 8 in total corneal fluorescein staining (tCFS; National Eye Institute scale) and eye dryness score (0-100 visual analog scale), respectively.

RESULTS

A total of 620 patients (NOV03, n = 311; saline, n = 309) were randomized and treated. Least-squares (LS) mean change from baseline to week 8 was statistically significantly greater for NOV03 compared with saline for both tCFS (-2.3 vs -1.1; LS mean treatment difference, -1.2 [95% confidence interval -1.7 to -0.8]; P < .001) and visual analog scale dryness score (-29.4 vs -19.2; LS mean treatment difference, -10.2 [95% CI -14.4 to -6.1]; P < .001), with statistically significant between-group differences observed as early as week 2. The incidence of ocular adverse events was similar for NOV03 (12.9%) and saline (12.3%). There were no serious adverse events and no adverse events leading to treatment discontinuation.

CONCLUSIONS

In this randomized controlled trial of patients with DED associated with MGD, NOV03 significantly reduced both signs and symptoms of DED compared with hypotonic saline control. NOV03 was well tolerated, with an adverse event profile similar to that of saline.

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.

Preclinical characterization of water-free cyclosporine eye drops - factors impacting ocular penetration ex vivo and in vivo

Although the efficacy of Cyclosporine A (CsA) in the management of ocular inflammation is well-demonstrated, ocular delivery remains challenging due to its hydrophobic nature. The semifluorinated alkane, perfluorobutylpentane (F4H5) has previously been suggested as an efficient vehicle for preparation of CsA eyedrops. Here we evaluated the influence of drop volume and the formulation aid, ethanol (EtOH), on ocular penetration of CsA and compared it to that of the commercial eyedrop, Ikervis, ex vivo and in vivo. Moreover, conjunctival and corneal tolerability after EtOH addition were evaluated ex vivo. The F4H5/EtOH vehicle was well tolerated and resulted in better corneal CsA penetration (AUC_{(0 - 4h)}: 63,008 ± 3,946 ng.h.g^-1) than Ikervis (AUC_{(0 - 4h)}: 10,328 ± 1,462 ng.h.g^-1) or F4H5 alone (AUC_{(0 - 4h)}: 50,734 ± 3,472 ng.h.g^-1) ex vivo. Interestingly, in vivo the CsA concentration in cornea, conjunctiva and lacrimal glands observed after administration of the F4H5 formulation (AUC_{(0.133-24 h)}: 7,741 ± 1,334 ng.h.g^-1, 1,313 ± 291 ng.h.g^-1, 48.2 ± 26.3 ng.h.g^-1) and F4H5/EtOH both at a reduced dose of 11 µl (AUC_{(0.133-24 h)}: 9,552 ± 1,738 ng.h.g^-1, 1,679 ± 285 ng.h.g^-1, 50.3 ± 21.1 ng.h.g^-1) was similar or even greater than what was observed on administration of 50 µl Ikervis (AUC_{(0.133-24 h)}: 9,943 ± 1,413 ng.h.g^-1, 2,069 ± 263 ng.h.g^-1, 30.6 ± 18.4 ng.h.g^-1). Thus, F4H5-based eyedrops were shown to deliver CsA more efficiently to anterior ocular tissues at a reduced dose in comparison to Ikervis, reducing dose wastage and minimizing any potential systemic side effects.

Perfluorohexyloctane Eye Drops for Dry Eye Disease Associated With Meibomian Gland Dysfunction in Chinese Patients: A Randomized Clinical Trial

Importance

Meibomian gland dysfunction (MGD) is a leading cause of evaporative dry eye disease (DED). Medical and surgical management for DED is limited; therefore, new treatment options are sought.

Objective

To evaluate the efficacy and safety of SHR8058 (perfluorohexyloctane) eye drops in Chinese patients with DED associated with MGD through 57 days.

Design, Setting, and Participants

This was a randomized, multicenter, double-masked, saline-controlled, phase 3 clinical trial conducted from February 4, 2021, to September 7, 2022. Patients were recruited from the departments of ophthalmology in 15 hospitals in China. Patients with DED associated with MGD were enrolled between February 4 and July 1, 2021. The diagnosis was based on patient complaint of DED symptoms, an ocular surface disease index of 25 or higher, tear film break-up time of 5 seconds or less, Schirmer I test without anesthesia results of 5 mm or more at 5 minutes, total corneal fluorescein staining (tCFS) score of 4 to 11, and an MGD score of 3 or higher.

Interventions

Eligible participants were randomly assigned 1:1 to receive perfluorohexyloctane eye drops or 0.6% sodium chloride [NaCl]) 4 times per day.

Main Outcomes and Measures

The primary end points were the changes from baseline in tCFS and eye dryness scores at day 57.

Results

A total of 312 participants were included in the analysis: 156 (mean [SD] age, 45.4 [15.2] years; 118 female [75.6%]) in the perfluorohexyloctane group and 156 (mean [SD] age, 43.7 [15.1] years; 127 female [81.4%]) in the NaCl group. Both primary end points were achieved, ie, changes from baseline at day 57 of tCFS score (mean [SD], -3.8 [2.7] vs -2.7 [2.8]) and eye dryness score (mean [SD], -38.6 [21.9] vs -28.3 [20.8]) in the perfluorohexyloctane group were superior to the control group, with estimated mean differences of -1.14 (95% CI, -1.70 to -0.57; P < .001) and -12.74 (95% CI, -17.20 to -8.28, P < .001), respectively. Improvements on both end points appeared to be noted on day 29 and day 15, respectively, and maintained through day 57. Compared with the control, perfluorohexyloctane eye drops also alleviated symptoms including pain (mean [SD] tCFS score, 26.7 [23.7] vs -18.7 [22.5]; P = .003), awareness of DED symptoms (mean [SD] tCFS score, -38.1 [25.1] vs -23.7 [27.6]; P < .001), and frequency of dryness (mean [SD] tCFS score, -43.3 [23.8] vs -29.1 [24.8]; P < .001). Treatment-emergent adverse events occurred in 34 participants (21.8%) and 40 participants (25.6%) in the perfluorohexyloctane and control groups, respectively.

Conclusions and Relevance

Results of this randomized clinical trial demonstrate that perfluorohexyloctane eye drops significantly ameliorated the signs and symptoms of DED associated with MGD with a rapid efficacy as well as satisfactory tolerability and safety through 57 days. Findings support the use of these eye drops if results can be confirmed independently and over longer time periods.

Trial Registration

ClinicalTrials.gov Identifier: NCT05515471.

Dry Eye Disease Associated with Meibomian Gland Dysfunction: Focus on Tear Film Characteristics and the Therapeutic Landscape

Meibomian gland dysfunction (MGD) is highly prevalent and is the leading cause of evaporative dry eye disease (DED). MGD is characterized by a reduction in meibum secretion and/or a change in meibum composition that results in the disruption of the tear film lipid layer and an increase in the tear film evaporation rate. Excessive evaporation causes tear film instability, desiccation, tear hyperosmolarity, inflammation, and apoptosis of ocular surface cells, resulting in a continuous cycle of DED. The primary treatment goal for DED associated with MGD is to restore the tear film lipid layer and decrease evaporation, thereby reducing ocular signs and symptoms. The management of MGD includes home care options (eyelid hygiene, warming eye masks, ocular lubricants) and office-based treatments (manual expression, microblepharoexfoliation, thermal pulsation, intense pulsed light, intraductal probing). Topical ophthalmic prescription medications attempt to alter various factors that may contribute to DED (e.g., inflammation, bacterial growth, inadequate tear production). In this review, clinical evidence regarding available treatments and emerging therapies from randomized studies in patients with DED associated with MGD is summarized. Although some treatment modalities have been evaluated specifically for DED patients with MGD, large-scale randomized controlled trials are needed to confirm efficacy and safety in this patient population. Currently, there are no approved prescription pharmacologic treatments specifically indicated for DED associated with MGD, and those medications approved for the treatment of DED do not target the key driver of the disease (i.e., excessive evaporation). NOV03 (perfluorohexyloctane; under review with the US Food and Drug Administration) is the most advanced emerging therapy for DED associated with MGD and has demonstrated statistically significant improvements in both signs and symptoms in randomized controlled trials. Development of novel pharmacotherapies will improve therapeutic options and allow for a more individualized approach for patients with DED associated with MGD.

Artificial Tears: A Systematic Review

Artificial tears are the mainstay of dry eye disease management, but also have a role in corneal abrasion and wound healing, pain and inflammation management, conjunctivitis, keratitis, contact lens rewetting and removal, and foreign body removal. A systematic review of randomized controlled trials (PROSPERO registration CRD42022369619) comparing the efficacy of artificial tears in patients with dry eye to inform prescribing choices using Web of Science, PubMed and Medline databases identified 64 relevant articles. There is good evidence that artificial tears improve symptoms of dry eye disease within a month of regular use, applied about four times a day, but signs generally take several months to improve. Not all patients with dry eye disease benefit from artificial tears, so if there is no benefit over a month, alternative management should be considered. Combination formulations are more effective than single active ingredient artificial tears. Artificial tears containing polyethylene glycol are more effective than those containing carboxymethylcellulose/carmellose sodium and hydroxypropyl methylcellulose. Those classified as having evaporative dry eye disease, benefit from artificial tears with liposomes, especially of higher concentration. The data available is limited by the definition of dry eye disease applied in published studies being variable, as well as the disease severity examined and compliance with artificial tears being rarely quantified.

NOV03 for Dry Eye Disease Associated with Meibomian Gland Dysfunction: Results of the Randomized Phase 3 GOBI Study

PURPOSE

To evaluate the efficacy and safety of NOV03 (perfluorohexyloctane) ophthalmic drop in patients with dry eye disease (DED) associated with meibomian gland dysfunction (MGD).

DESIGN

Eight-week, phase 3, multicenter, randomized, double-masked, saline-controlled study.

PARTICIPANTS

Adults ≥ 18 years with a history of DED for ≥ 6 months, tear film breakup time of ≤ 5 seconds, Schirmer I test (without anesthesia) score ≥ 5 mm, MGD score ≥ 3 (0-15 scale), and total corneal fluorescein staining (tCFS) score ≥ 4 and ≤ 11 (0-15 National Eye Institute [NEI] scale).

METHODS

Patients were randomized 1:1 to NOV03 or hypotonic (0.6%) saline 4 times daily.

MAIN OUTCOME MEASURES

The primary sign and symptom end points were change from baseline in tCFS and eye dryness score (0-100 visual analog scale [VAS]) at week 8. Key secondary end points were change from baseline in eye dryness score at week 2, tCFS at week 2, eye burning or stinging score (0-100 VAS) at week 8, and central corneal fluorescein staining (cCFS; 0-3 NEI scale) at week 8.

RESULTS

Of the 599 patients randomized, 597 were treated (NOV03, n = 303; saline, n = 294). At week 8, improvement from baseline was significantly greater (P < 0.001) with NOV03 versus saline for tCFS (least square [LS] mean treatment difference, -0.97; 95% confidence interval [CI]: -1.40, -0.55) and VAS dryness score (-7.6; 95% CI: -11.8, -3.4). Improvement from baseline also significantly (P < 0.01) favored NOV03 on all key secondary end points: LS mean treatment difference (95% CI) was -4.7 (-8.2, -1.2) for VAS dryness score at week 2, -0.6 (-0.9, -0.2) for tCFS at week 2, -5.5 (-9.5, -1.6) for VAS burning or stinging score at week 8, and -0.2 (-0.4, -0.1) for cCFS at week 8. Most ocular adverse events (AEs) were mild in severity; no serious ocular AEs occurred. One patient discontinued NOV03 because of an AE (eye irritation).

CONCLUSIONS

In patients with DED associated with MGD, NOV03 demonstrated statistically significant and clinically meaningful improvements versus hypotonic saline in signs and symptoms of DED and was well tolerated.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Deciphering the Action of Perfluorohexyloctane Eye Drops to Reduce Ocular Discomfort and Pain

Perfluorohexyloctane (F6H8) eyedrops have been recently introduced in Europe as a product to treat dry eye disease, based on its ability to reduce tear film instability in Meibomian gland dysfunction and evaporative dry eye disease, although its mechanism of action is still unknown. In the present pilot study, we evaluated the effects of the ocular instillation of a single drop of commercial F6H8 eyedrops in 20 healthy humans (9 women/11 men), measuring: (a) Corneal surface temperature (CST) from infrared video images; (b) tear volume using phenol red threads; (c) blinking frequency; and (d) ocular surface sensations (cold, dryness, pricking, foreign body, burning, itching, gritty, eye fatigue, watering eyes, and light-evoked discomfort sensations; scored using 10 cm Visual Analog Scales), before and 5–60 min after F6H8 or saline treatment. CST decreased and tearing and blinking frequency increased significantly after F6H8 but not after saline solution. When applied unilaterally, CST decreased only in the F6H8-treated eye. No sensations were evoked after F6H8 or saline. The corneal surface temperature reduction produced by topical F6H8 does not evoke conscious ocular sensations but is sufficient to increase the activity of corneal cold thermoreceptors, leading to an increased reflex lacrimation and blinking that may relieve dry eye condition thus reducing ocular discomfort and pain.

Ocular Distribution of Papaverine Using Non-aqueous Vehicles

Papaverine, a poorly soluble opium alkaloid, has recently been shown to reduce retinal inflammation due to which it may have therapeutic application in the management of Leber's hereditary optic neuropathy. In this study, papaverine eyedrops based on medium chain triglycerides were prepared and the effect of diethyl glycol monoethyl ether (DGME) on their ocular distribution was evaluated using an ex vivo porcine eye model. The route of drug penetration was also studied by orienting the eye to expose either only the cornea or the sclera to the formulation. Furthermore, in vivo studies were performed to confirm ocular tolerability and evaluate ocular drug distribution. Our results showed increased papaverine concentrations in the cornea and sclera in the presence of DGME but with a slight reduction in the retina-choroid (RC) drug concentration when administered via the corneal route, suggesting that DGME enhances drug accumulation in the anterior ocular tissues but with little effect on posterior drug delivery. In vivo, the papaverine eyedrop with DGME showed good ocular tolerability with the highest drug concentration being observed in the cornea (1.53 ± 0.28 μg/g of tissue), followed by the conjunctiva (0.74 ± 0.18 μg/g) and sclera (0.25 ± 0.06 μg/g), respectively. However, no drug was detected in the RC, vitreous humor or plasma. Overall, this study highlighted that DGME influences ocular distribution and accumulation of papaverine. Moreover, results suggest that for hydrophobic drugs dissolved in hydrophobic non-aqueous vehicles, transcorneal penetration via the transuveal pathway may be the predominant route for drug penetration to posterior ocular tissues. Graphical abstract.

Formulation Considerations for the Management of Dry Eye Disease

Dry eye disease (DED) is one of the most common ocular surface disorders characterised by a deficiency in quality and/or quantity of the tear fluid. Due to its multifactorial nature involving several inter-related underlying pathologies, it can rapidly accelerate to become a chronic refractory condition. Therefore, several therapeutic interventions are often simultaneously recommended to manage DED efficiently. Typically, artificial tear supplements are the first line of treatment, followed by topical application of medicated eyedrops. However, the bioavailability of topical eyedrops is generally low as the well-developed protective mechanisms of the eye ensure their rapid clearance from the precorneal space, thus limiting ocular penetration of the incorporated drug. Moreover, excipients commonly used in eyedrops can potentially exhibit ocular toxicity and further exacerbate the signs and symptoms of DED. Therefore, formulation development of topical eyedrops is rather challenging. This review highlights the challenges typically faced in eyedrop development, in particular, those intended for the management of DED. Firstly, various artificial tear supplements currently on the market, their mechanisms of action, as well as their application, are discussed. Furthermore, formulation strategies generally used to enhance ocular drug delivery, their advantages and limitations, as well as their application in commercially available DED eyedrops are described.