Chemical Insights into Topical Agents in Intraocular Pressure Management: From Glaucoma Etiopathology to Therapeutic Approaches

Glaucoma encompasses a group of optic neuropathies characterized by complex and often elusive etiopathology, involvihttng neurodegeneration of the optic nerve in conjunction with abnormal intraocular pressure (IOP). Currently, there is no cure for glaucoma, and treatment strategies primarily aim to halt disease progression by managing IOP. This review delves into the etiopathology, diagnostic methods, and treatment approaches for glaucoma, with a special focus on IOP management. We discuss a range of active pharmaceutical ingredients used in glaucoma therapy, emphasizing their chemical structure, pharmacological action, therapeutic effectiveness, and safety/tolerability profiles. Notably, most of these therapeutic agents are administered as topical formulations, a critical aspect considering patient compliance and drug delivery efficiency. The classes of glaucoma therapeutics covered in this review include prostaglandin analogs, beta blockers, alpha agonists, carbonic anhydrase inhibitors, Rho kinase inhibitors, and miotic (cholinergic) agents. This comprehensive overview highlights the importance of topical administration in glaucoma treatment, offering insights into the current state and future directions of pharmacological management in glaucoma.

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.

A 6-month study comparing efficacy, safety, and tolerability of the preservative-free fixed combination of tafluprost 0.0015% and timolol 0.5% versus each of its individual preservative-free components

Introduction

The efficacy, safety and tolerability of the preservative-free (PF) fixed combination (FC) of tafluprost 0.0015% and timolol 0.5% (once daily) were compared to those of the individual components (PF tafluprost 0.0015% once daily and PF timolol 0.5% twice daily) in patients with open-angle glaucoma or ocular hypertension inadequately controlled on prior timolol or prostaglandin monotherapy for 6 months.

Methods

A stratified, double-masked, randomized, multicenter phase III study was conducted. A total of 189 prior timolol users were randomized within the timolol stratum (TS) to receive either FC (n = 95) or timolol 0.5% (TIM; n = 94). Furthermore, a total of 375 prior prostaglandin analog (PGA) users were randomized within the prostaglandin stratum (PS) to receive either FC (n = 188) or tafluprost 0.0015% (TAF; n = 187). To be eligible for participation in the study, the patients were required to have an intraocular pressure (IOP) of ≥22 mmHg when on timolol (TIM) or of ≥20 mmHg when on PGA in either treated eye at the screening and end-of-run-in visits. In addition to these, the study included visits at baseline, 2 and 6 weeks, 3 and 6 months and at a post-study visit. IOP was measured at 8 a.m., 10 a.m., 4 p.m., and 8 p.m.

Results

In the TS, a significant reduction from baseline IOP was seen with FC and TIM throughout the study. Average diurnal IOP change from baseline at month 3 was −8.55 mmHg (32%) for FC and −7.35 mmHg (28%) for TIM. The model-based treatment difference (FC–TIM) was −0.885 mmHg [95% confidence interval (CI) −1.745 to −0.024; p = 0.044] demonstrating the superiority of FC over TIM. In the PS, a significant reduction in IOP was seen with both FC and TAF throughout the study. The average diurnal IOP change from baseline at month 3 was −8.61 mmHg (33%) for FC and −7.23 mmHg (28%) for TAF. The model-based treatment difference (FC–TAF) was −1.516 mmHg (95% CI −2.044 to −0.988; p < 0.001) demonstrating the superiority of FC over TAF. In the TS, related ocular adverse events (AEs) were more frequent for patients treated with FC compared to TIM (16.8% versus 6.4%), whereas related non-ocular AEs were more frequent with TIM compared to FC (2.1% versus 0.0%). In the PS, AEs were similarly distributed between FC and TAF. The frequency of conjunctival hyperemia of FC was low (6.4%).

Conclusion

The preservative-free fixed combination of tafluprost and timolol provided a substantial and significant IOP reduction in both strata. The IOP reduction was superior to both tafluprost 0.0015% and timolol 0.5% when given as monotherapies. Overall, the study treatments were safe and well tolerated.

Funding

Santen Oy, Tampere, Finland.

Electronic supplementary material

The online version of this article (doi:10.1007/s12325-014-0163-3) contains supplementary material, which is available to authorized users.

Intraocular pressure-lowering combination therapies with prostaglandin analogues

Intraocular pressure (IOP) reduction is currently the only therapeutic approach demonstrated to preserve visual function in patients with glaucoma. The first line of glaucoma treatment consists of topical IOP-lowering medications, usually initiated as monotherapy. A significant proportion of patients require more than one medication to reach a target IOP at which optic nerve damage will not progress. As prostaglandin analogues (PGAs) are the most effective class for reducing IOP, one of the other commonly used classes (β-adrenoceptor antagonist [β-blocker], carbonic anhydrase inhibitor or α(2)-adrenoceptor agonist) is frequently combined with a PGA. In the last decade, the use of fixed combinations containing two medications in a single bottle has steadily increased. Fixed combinations have the potential to simplify the dosing regimen, increase patient adherence, avoid the washout effect of the second drop on the first medication instilled, decrease exposure to preservatives and, sometimes, reduce the cost of treatment. Clinical trials have evaluated PGA-based fixed combinations versus unfixed combinations (individual components administered concomitantly) or versus individual monotherapies; however, any advantage that the fixed combinations may have in terms of IOP-lowering efficacy is still debated. For these reasons, the PGA-based fixed combinations are not approved by regulatory authorities in some countries, such as the US. We review the published studies evaluating the efficacy and tolerability of the IOP-lowering unfixed and fixed combination therapies with PGAs. Regarding unfixed combinations, the review shows that α(2)-adrenergic agonists-PGA and carbonic anhydrase inhibitor-PGA combinations seem to be at least as effective at reducing IOP as the β-blocker-PGA combinations. As for the fixed combinations, the review shows that the three PGA-timolol fixed combinations are more effective than their component medications used separately as monotherapy and are better tolerated than the three respective prostaglandins. The three PGA-timolol fixed combinations are less effective at reducing IOP than the unfixed combinations but are better tolerated. The advantage of the fixed combinations in terms of patient adherence and persistence is supported by a very small number of studies and remains to be more accurately determined. Most studies, but not all, seem to show that PGA-timolol fixed combinations are more effective than other available β-blocker fixed combinations (dorzolamide-timolol fixed combinations) at reducing IOP and are similarly tolerated.

Randomized clinical trial of the efficacy and safety of preservative-free tafluprost and timolol in patients with open-angle glaucoma or ocular hypertension

PURPOSE

To compare the efficacy and safety of tafluprost, a preservative-free (PF) prostaglandin analogue, with PF timolol in patients with open-angle glaucoma or ocular hypertension.

DESIGN

Randomized, double-masked, multicenter clinical trial.

METHODS

After discontinuation and washout of existing ocular hypotensive treatment, patients who had intraocular pressure (IOP) ≥23 and ≤36 mm Hg in at least 1 eye at the 08:00 hour time point were randomized 1:1 to 12 weeks of treatment with either PF tafluprost 0.0015% or PF timolol 0.5%. IOP was measured 3 times during the day (08:00, 10:00, 16:00 hours) at baseline and at weeks 2, 6, and 12. It was hypothesized that PF tafluprost would be noninferior to PF timolol over 12 weeks with regard to change from baseline IOP. The trial was powered for a noninferiority margin of 1.5 mm Hg at each of the 9 time points assessed.

RESULTS

A total of 643 patients were randomized and 618 completed (PF tafluprost = 306, PF timolol = 312). IOPs at the 3 time points assessed during the baseline visit ranged from 23.8 to 26.1 mm Hg in the PF tafluprost group and 23.5 to 26.0 mm Hg in the PF timolol group. IOPs at the 3 time points assessed during the 12-week visit ranged from 17.4 to 18.6 mm Hg for PF tafluprost and 17.9 to 18.5 mm Hg for PF timolol. At all 9 time points, the upper limits of the 2-sided 95% confidence intervals for the difference between treatments in IOP lowering were less than the prespecified noninferiority margin. Similar percentages of PF tafluprost and PF timolol patients reported ocular pain/stinging/irritation (4.4% vs 4.6%) and pruritus (2.5% vs 1.5%). The percentages of PF tafluprost and PF timolol patients reporting conjunctival hyperemia were 4.4% vs 1.2% (nominal P = .016).

CONCLUSIONS

The IOP-lowering effect of PF tafluprost was noninferior to that of PF timolol. PF tafluprost is an efficacious and generally well-tolerated ocular hypotensive agent.

Efficacy and safety of tafluprost 0.0015% versus latanoprost 0.005% eye drops in open-angle glaucoma and ocular hypertension: 24-month results of a randomized, double-masked phase III study

PURPOSE

The objective of the study was to compare the long-term efficacy and safety of tafluprost 0.0015% with latanoprost 0.005% eye drops in patients with open-angle glaucoma or ocular hypertension.

METHODS

This double-masked, active-controlled, parallel-group, multinational, multicentre, phase III study was conducted at 49 centres in 8 countries. Eligible patients were assigned to treatment administered once daily at 20:00 hrs for up to 24 months. Change from baseline intraocular pressure (IOP) was the primary efficacy variable. Adverse events were recorded and ocular safety was evaluated. Both tafluprost and latanoprost were preserved with benzalkonium chloride.

RESULTS

From 533 patients randomized, 402 patients completed 24 months of therapy. Both treatments had a substantial IOP-lowering effect which persisted throughout the study (-7.1 mmHg for tafluprost and -7.7 mmHg for latanoprost at 24 months). Although the IOP-lowering effect during the study was slightly larger with latanoprost, this difference was clinically small and the noninferiority of tafluprost to latanoprost over all diurnal IOP measurements was shown with anova and almost reached with ancova (upper limits of the 95% confidence intervals 1.38 and 1.52 for the overall period, respectively). The noninferiority limit was 1.5 mmHg.

CONCLUSIONS

Tafluprost is a new effective and well-tolerated treatment for glaucoma and ocular hypertension.