Tafluprost: The First Preservative-Free Prostaglandin to Treat Open-Angle Glaucoma and Ocular Hypertension

How latanoprost changed glaucoma management

Glaucoma is currently considered one of the leading causes of severe visual impairment and blindness worldwide. Topical medical therapy represents the treatment of choice for many glaucoma patients. Introduction of latanoprost, 25 years ago, with an entirely new mechanism of action from that of the antiglaucoma drugs used up to that time was a very important milestone. Since then, due mainly to their efficacy, limited systemic side effects and once daily dosing, prostaglandin analogues (PGAs) have become as the first-choice treatment for primary open-angle glaucoma. PGAs are in general terms well tolerated, although they are associated with several mild to moderate ocular and periocular adverse events. Among them, conjunctival hyperemia, eyelash changes, eyelid pigmentation, iris pigmentation and hypertrichosis around the eyes are the most prevalent. The objective of this paper is to review the role of PGAs in the treatment of glaucoma over the 25 years since the launch of Latanoprost and their impact on clinical practice outcomes.

Prodrugs as empowering tools in drug discovery and development: recent strategic applications of drug delivery solutions to mitigate challenges associated with lead compounds and drug candidates

The delivery of a drug to a specific organ or tissue at an efficacious concentration is the pharmacokinetic (PK) hallmark of promoting effective pharmacological action at a target site with an acceptable safety profile. Sub-optimal pharmaceutical or ADME profiles of drug candidates, which can often be a function of inherently poor physicochemical properties, pose significant challenges to drug discovery and development teams and may contribute to high compound attrition rates. Medicinal chemists have exploited prodrugs as an informed strategy to productively enhance the profiles of new chemical entities by optimizing the physicochemical, biopharmaceutical, and pharmacokinetic properties as well as selectively delivering a molecule to the site of action as a means of addressing a range of limitations. While discovery scientists have traditionally employed prodrugs to improve solubility and membrane permeability, the growing sophistication of prodrug technologies has enabled a significant expansion of their scope and applications as an empowering tool to mitigate a broad range of drug delivery challenges. Prodrugs have emerged as successful solutions to resolve non-linear exposure, inadequate exposure to support toxicological studies, pH-dependent absorption, high pill burden, formulation challenges, lack of feasibility of developing solid and liquid dosage forms, first-pass metabolism, high dosing frequency translating to reduced patient compliance and poor site-specific drug delivery. During the period 2012-2022, the US Food and Drug Administration (FDA) approved 50 prodrugs, which amounts to 13% of approved small molecule drugs, reflecting both the importance and success of implementing prodrug approaches in the pursuit of developing safe and effective drugs to address unmet medical needs.

Ligand-induced activation and G protein coupling of prostaglandin F2α receptor

Prostaglandin F_2α (PGF_2α), an endogenous arachidonic acid metabolite, regulates diverse physiological functions in many tissues and cell types through binding and activation of a G-protein-coupled receptor (GPCR), the PGF_2α receptor (FP), which also is the primary therapeutic target for glaucoma and several other diseases. Here, we report cryo-electron microscopy (cryo-EM) structures of the human FP bound to endogenous ligand PGF_2α and anti-glaucoma drugs LTPA and TFPA at global resolutions of 2.67 Å, 2.78 Å, and 3.14 Å. These structures reveal distinct features of FP within the lipid receptor family in terms of ligand binding selectivity, its receptor activation, and G protein coupling mechanisms, including activation in the absence of canonical PIF and ERY motifs and G_q coupling through direct interactions with receptor transmembrane helix 1 and intracellular loop 1. Together with mutagenesis and functional studies, our structures reveal mechanisms of ligand recognition, receptor activation, and G protein coupling by FP, which could facilitate rational design of FP-targeting drugs.

Trends in development and quality assessment of pharmaceutical formulations - F2α analogues in the glaucoma treatment

The ocular delivery route presents a number of challenges in terms of drug administration and bioavailability. The low bioavailability following topical ophthalmic administration shows that there is a clear need for in-depth research aimed at finding both more efficacious molecules and formulations precisely targeted at the site of action. Continuous technological development will eventually result in improved bioavailability, lower dosages, reduced toxicity, fewer adverse effects, and thus better patient compliance and treatment efficacy. Technological development, as well as increasingly stringent quality requirements, help stimulate analytical progress. This is also clearly evident in the case of medicinal products used in the treatment of glaucoma, which are the subject of this review. Impurity profiling of PGF2α analogues, either in the pure substance or in the finished formulation, is a crucial step in assessing their quality. The development of specific, accurate and precise stability-indicating analytical methods for determining the content and related substances seems to be an important issue in relation to this tasks. A total of 27 official and in-house analytical methods are presented that are used for the analysis of latanoprost, travoprost and bimatoprost. The conditions for chromatographic separation with UV or MS/MS detection and the available results obtained during method validation are described. In addition, several aspects are discussed, with particular emphasis on the instability of the analogues in aqueous solution and the phenomenon of isomerism, which affects a potentially large number of degradation products.

Aqueous Prostaglandin Eye Drop Formulations

Glaucoma is one of the leading causes of irreversible blindness worldwide. It is characterized by progressive optic neuropathy in association with damage to the optic nerve head and, subsequently, visual loss if it is left untreated. Among the drug classes used for the long-term treatment of open-angle glaucoma, prostaglandin analogues (PGAs) are the first-line treatment and are available as marketed eye drop formulations for intraocular pressure (IOP) reduction by increasing the trabecular and uveoscleral outflow. PGAs have low aqueous solubility and are very unstable (i.e., hydrolysis) in aqueous solutions, which may hamper their ocular bioavailability and decrease their chemical stability. Additionally, treatment with PGA in conventional eye drops is associated with adverse effects, such as conjunctival hyperemia and trichiasis. It has been a very challenging for formulation scientists to develop stable aqueous eye drop formulations that increase the PGAs' solubility and enhance their therapeutic efficacy while simultaneously lowering their ocular side effects. Here the physiochemical properties and chemical stabilities of the commercially available PGAs are reviewed, and the compositions of their eye drop formulations are discussed. Furthermore, the novel PGA formulations for glaucoma treatment are reviewed.

A Pooled Assessment of Ocular Surface Disease After Switching from Preserved Prostaglandins to Tafluprost Across Six Countries in Asia

Background

Preserved prostaglandin analogs (PGAs) have been linked to ocular surface disease (OSD). While the benefits of preservative-low (PL) or -free (PF) Tafluprost (Santen Inc., Japan) were reported in real-world studies in Western countries, this is the first study in Asia to assess the effectiveness and safety of switching from preserved PGA to PL or PF-Tafluprost.

Methods

We conducted a meta-analysis on studies that included adults (>18 years of age) with a Corneal Fluorescein Staining Score (CFS) >1. These individuals had switched to PL or PF-tafluprost after using a preserved PGA therapy for at least 3 months for glaucoma and were identified from Santen’s tafluprost study database. A total of six studies from South Korea, Philippines, Malaysia, Singapore, Thailand, Taiwan were pooled for analysis.

Results

An intraocular pressure (IOP) reduction of 5.9% (0.91 mmHg) was seen in 265 patients. However, this result was not statistically significant (95% CI: −3.64, 1.81; Figure 1). Among 132 patients, a 47.9% reduction in the CFS (95% CI: −3.65, −1.91) was seen. Tear film break-up (n=183) significantly increased by 1.06 seconds (95% CI: 0.65, 1.47). In 88 patients, the bulbar conjunctiva score decreased by −0.46 (95% CI: −0.81, −0.10) and palpebral conjunctiva score decreased by −0.42 (95% CI: −0.67–0.17). One or more new adverse reactions were reported in 3% of the individuals after switching.

Conclusion

Tafluprost IOP reduction is comparable to other PGAs, with significant improvements in the ocular surface and minimal adverse reactions which were already previously reported.

The treatment of glaucoma using topical preservative-free agents: an evaluation of safety and tolerability

Introduction: Preservative-free (PF) medications represent a valuable treatment strategy in the lifelong management of glaucoma. By removing preservative toxicity, PF formulations provide tangible clinical benefits to glaucoma patients worldwide. They improve tolerability and adherence, leading to a positive impact in long-term intraocular pressure (IOP) control.Areas covered: A critical review of the subject is provided, including selected evidence on the safety and tolerability of currently available topical PF formulations. Cumulative evidence confirms that topical PF medications are at least equally efficacious to their preserved equivalents. There is convincing short-term evidence for superior tolerability and safety of PF formulations compared to preserved medications. The long-term benefits and success of PF therapy requires further elucidation.Expert opinion: Successful stepwise administration of medical therapy for glaucoma remains elusive. There is a greater risk for ocular toxicity and therapy failure with preserved topical glaucoma therapy. Currently available and emerging PF therapy options potentially optimize lifelong stepwise glaucoma therapy and may enhance outcome. To avert complications from preservatives leading to poor adherence, ideally, future antiglaucoma therapy should become 100% PF. There are still key aspects of PF therapy that warrant further investigation.

Preservative-Free Prostaglandin Analogs and Prostaglandin/Timolol Fixed Combinations in the Treatment of Glaucoma: Efficacy, Safety and Potential Advantages

Glaucoma therapy-related ocular surface disease (OSD) is a serious pathology with a broad spectrum of insidious clinical presentations and complex pathogenesis that undermines long-term glaucoma care. Preservatives, especially benzalkonium chloride (BAK), contained in topical intraocular pressure-lowering medications frequently cause or aggravate OSD in glaucoma. Management of these patients is challenging, and to date often empirical due to the scarcity of controlled long-term clinical trials. Most of the available data are extracted from case series and retrospective analysis. Preservative-free prostaglandins and prostaglandin/timolol fixed combinations are novel options developed to remove the harmful impact of preservatives, especially BAK, upon ocular tissues. Based on what is currently known on the value of preservative-free antiglaucoma therapies it is tempting to speculate how these new therapies may affect the future medical management of all glaucoma patients. This article provides a comprehensive and critical review of the current literature on preservative-free prostaglandins and preservative-free prostaglandin/timolol fixed combinations.

Effects of sustained daily latanoprost application on anterior chamber anatomy and physiology in mice

Latanoprost is a common glaucoma medication. Here, we study longitudinal effects of sustained latanoprost treatment on intraocular pressure (IOP) in C57BL/6J mice, as well as two potential side-effects, changes in iris pigmentation and central corneal thickness (CCT). Male C57BL/6J mice were treated daily for 16 weeks with latanoprost. Control mice were treated on the same schedule with the preservative used with latanoprost, benzalkonium chloride (BAK), or handled, without ocular treatments. IOP and CCT were studied at pre-treatment, 2 "early" time points, and 2 "late" time points; slit-lamp analysis performed at a late time point; and expression of corneal and iridial candidate genes analyzed at the end of the experiment. Latanoprost lowered IOP short, but not long-term. Sustained application of BAK consistently resulted in significant corneal thinning, whereas sustained treatment with latanoprost resulted in smaller and less consistent changes. Neither treatment affected iris pigmentation, corneal matrix metalloprotease expression or iridial pigment-related genes expression. In summary, latanoprost initially lowered IOP in C57BL/6J mice, but became less effective with sustained treatment, likely due to physiological adaptation. These results identify a new resource for studying changes in responsiveness associated with long-term treatment with latanoprost and highlight detrimental effects of commonly used preservative BAK.

A Novel Convergent Synthesis of the Potent Antiglaucoma Agent Tafluprost

Tafluprost (AFP-168, 5) is a unique 15-deoxy-15,15-difluoro-16-phenoxy prostaglandin F₂α (PGF_2α) analog used as an efficacious ocular hypotensive agent in the treatment of glaucoma and ocular hypertension, as monotherapy, or as adjunctive therapy to β-blockers. A novel convergent synthesis of 5 was developed employing Julia–Lythgoe olefination of the structurally advanced prostaglandin phenylsulfone 16, also successfully applied for manufacturing of pharmaceutical grade latanoprost (2), travoprost (3) and bimatoprost (4), with an aldehyde ω-chain synthon 17. The use of the same prostaglandin phenylsulfone 16, as a starting material in parallel syntheses of all commercially available antiglaucoma PGF_2α analogs 2–5, significantly reduces manufacturing costs resulting from its synthesis on an industrial scale and development of technological documentation. Another key aspect of the route developed is deoxydifluorination of a trans-13,14-en-15-one 30 with Deoxo-Fluor. Subsequent hydrolysis of protecting groups and final esterification of acid 6 yielded tafluprost (5). The main advantages are the preparation of high purity tafluprost (5) and the application of comparatively cheap reagents. The preparation and identification of two other tafluprost acid derivatives, tafluprost methyl ester (32) and tafluprost ethyl amide (33), are also described.

Preservative-free tafluprost in the treatment of open-angle glaucoma or ocular hypertension in India: a phase III clinical trial

AIM

The aim of this study was to evaluate the efficacy and safety of preservative-free (PF) tafluprost compared with PF timolol in Indian subjects with open-angle glaucoma (OAG) or ocular hypertension.

METHODS

This was a randomised, multicentre, double-masked, phase III trial. Subjects aged 18-80 years, following washout of current medication, with intraocular pressure (IOP) ≥ 24 and ≤ 36 mmHg in at least one eye were randomised in a 1:1 ratio to 0.0015% PF tafluprost or 0.5% PF timolol for 4 weeks. IOP was measured at 08:00, 10:00 and 16:00 hours at baseline and at weeks 2 and 4. The primary efficacy end-point was the mean diurnal IOP change from baseline at week 4, and PF tafluprost was considered non-inferior to PF timolol if the upper bound of the 95% confidence interval (CI) for between-treatment differences was ≤ 1.5 mmHg. The secondary end-point was the proportion of subjects with ≥ 25% reduction in IOP from baseline at week 4.

RESULTS

In total, 190 subjects were randomised, 95 each, to PF tafluprost and PF timolol treatment. PF tafluprost was non-inferior to PF timolol with respect to diurnal IOP changes from baseline over 4 weeks. The mean PF tafluprost-PF timolol difference in the diurnal IOP change was -1.7 (95% CI -2.6 to -0.7), suggestive of superiority for PF tafluprost. The secondary end-point was achieved in a higher proportion of PF tafluprost group subjects. Both PF tafluprost and PF timolol were well-tolerated with similar incidences of adverse events.

CONCLUSIONS

PF tafluprost was safe and efficacious in reducing IOP in Indian subjects.

Mechanisms of benzalkonium chloride toxicity in a human trabecular meshwork cell line and the protective role of preservative-free tafluprost

BACKGROUND

Benzalkonium chloride (BAK) is a controversial ophthalmic preservative because of its prominent side-effect profile. In this study, we examined the mechanism of BAK toxicity in human trabecular meshwork cells (HTMC) and compared the effects of BAK with tafluprost free acid, which is an active form of tafluprost commercially available in a preservative-free formulation.

METHODS

Primary HTMC were treated with different BAK concentrations over various exposure times. Cell viability was quantified using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenol tetrazolium bromide assay, and apoptosis was measured by enzyme-linked immunosorbent assay. The cell viability of primary HTMC exposed to various concentrations and times of tafluprost free acid was also determined. Cells were treated with BAK and tafluprost free acid for 30 min at 37°C, and cell viability was again assessed. The effect of BAK on the gap junction protein Connexin-43 (Cx43) expression was subsequently examined.

RESULTS

BAK treatment resulted in a dose- and time-dependent decline in cell viability. Apoptosis increased following BAK treatment. Tafluprost-free acid treatment did not significantly affect cell viability. Tafluprost co-treatment with BAK resulted in an increase in cell viability as compared with BAK treatment alone. BAK treatment upregulated Cx43 expression in HTMC.

CONCLUSIONS

These results demonstrate that BAK is harmful to the health of cultured HTMC. Tafluprost is both safe and cytoprotective against BAK for these HTMC. The effect of tafluprost on the gap junctions of the HTM should be further investigated.

Effects of prostaglandin analogues on aqueous humor outflow pathways

Elevated intraocular pressure (IOP) is the most prevalent risk factor for glaucoma. All treatments, whether surgical or pharmaceutical, are aimed at lowering IOP. Prostaglandin analogues are a first line therapy for glaucoma due to their ability to reduce IOP, once-daily dosing, efficacy, and minimal side-effect profile. Whereas prostaglandin analogues have been known to alter aqueous humor outflow through the unconventional (uveoscleral) pathway, more recent evidence suggests their action also occurs through the conventional (trabecular) pathway. Understanding how prostaglandin analogues successfully lower IOP is important, as this information may lead to the discovery of new molecular targets for future therapeutic intervention. This review explores the current understanding of prostaglandin analogue biology as it pertains to IOP reduction and improved aqueous humor outflow facility.

Effects of several anti-glaucoma medications on the circadian intraocular pressure fluctuations in patients with primary open-angle glaucoma

PURPOSE

The purpose of the present study was to elucidate the effects of several anti-glaucoma medications on the circadian intraocular pressure (IOP) fluctuations in patients with primary open-angle glaucoma (POAG).

PATIENTS AND METHODS

POAG patients (n=61; 61 eyes) with or without glaucoma medications were included. IOP measurement at 14 time points (12, 15, 18, 21, 0, 6, 9, 12, 15, 18, 21, 0, 6, and 9 o'clock) was performed over a period of 48 h. IOP changes occurring in the first 24 h and the subsequent 24 h were evaluated by several therapeutic factors.

RESULTS

A nocturnal acrophase pattern was observed in all the eyes with POAG. The shape of the first 24 h IOP curve was similar to that of the following 24 h IOP curves. However, there were fewer overall IOP levels in the second 24 h time period. Circadian IOP fluctuation patterns exhibited in each eye on the 1st and 2nd days were single acrophase patterns: diurnal acrophase (1st day, 54.0%; 2nd day, 60.7%) and nocturnal acrophase (1st day, 36.1%; 2nd day, 31.1%), and no single acrophase patterns: flat (1st day, 6.6%; 2nd day, 4.9%) and double acrophase (1st day, 3.3%; 2nd day, 3.3%). Among the different medication groups, a nocturnal acrophase circadian pattern was observed in the patient groups being treated by combinations of prostaglandin analog (PG) and β blocker or PG, β blocker and carbonic anhydrase inhibitor (CAI). However, this was not apparent in patient groups with or without single anti-glaucoma medications or a combination of PG and CAI.

CONCLUSIONS

The present study of IOP monitoring patients with POAG over a period of 48 h indicated that their changes in circadian patterns of IOP were affected by types of anti-glaucoma medications.

How ocular surface disease impacts the glaucoma treatment outcome

The treatment goals for glaucoma are lowering the intraocular pressure and preservation of vision. Topical hypotensive drops are the standard form of therapy which is often associated with some symptoms of toxicity, ocular inflammation, allergy, or ocular surface disease (OSD). OSD is a common comorbidity in glaucoma patients, and its prevalence with glaucoma increases with age. Use of topical treatment could additionally increase symptoms of OSD mostly due to preservatives added to multidose medication bottles used to reduce the risk of microbial contamination. This toxicity has been particularly associated with BAK, the most commonly used preservative which damages conjunctival and corneal epithelial cells and significantly aggravates OSD symptoms. OSD adversely affects patients' quality of life causing discomfort and problems with vision which in turn may result in noncompliance, lack of adherence, and eventually visual impairment. In the management of glaucoma patients OSD symptoms should not be overlooked. If they are present, topical glaucoma treatment should be adapted by decreasing the amount of drops instilled daily, using BAK-free or preservative-free medication and lubricants if necessary. Awareness of the presence and importance of OSD will in turn improve patients' adherence and compliance and thus ultimately the preservation of long-term vision.

Eyelash growth induced by topical prostaglandin analogues, bimatoprost, tafluprost, travoprost, and latanoprost in rabbits

PURPOSE

Prostaglandin analogues (PGA) are ocular hypotensive agents used for the treatment of glaucoma. Hypertrichosis of the eyelashes has been reported in humans as a side effect. Eyelash growth was investigated with clinical trials in people using bimatoprost. Scattered reports of eyelash growth during the treatment of glaucoma with other PGA are also found in the literature. We investigated the effect of 4 different topical PGA on eyelash length.

METHODS

Forty New Zealand white rabbits were divided into 4 groups and received daily topical application of bimatoprost, tafluprost, travoprost, and latanoprost in the left eye for 4 weeks. The right eye received no treatment. Eyelash length was measured in both eyes before and after treatment using a stainless steel digital caliper.

RESULTS

Bimatoprost and tafluprost groups had significant increases in eyelash length. We did not observe significant eyelash growth in rabbits receiving travoprost and latanoprost after 1 month of treatment.

CONCLUSIONS

Today, only bimatoprost is approved for growing eyelashes, and our research shows that tafluprost could be further explored by the cosmetic and pharmaceutical industry. Additional research using travoprost and latanoprost as agents for eyelash growth should be performed in the future using prolonged treatment periods to determine whether or not these PGA induce eyelash growth, and investigate other possible side effects.