Abstract
PurposeTo compare the safety and efficacy of fixed-dose tafluprost/timolol combination (Taf/T-FDC) with those of fixed-dose latanoprost/timolol combination (Lat/T-FDC) by measuring the intraocular pressure (IOP)-lowering effect, ocular pharmacokinetics, and ocular surface toxicity.MethodsThe IOP-lowering effect of Taf/T-FDC and Lat/T-FDC in ocular normotensive monkeys was evaluated at 4 and 8 h after instillation in study A, at 12, 14, 16, and 18 h after instillation in study B, and at 24, 26, 28, and 30 h after instillation in study C. Drug penetration into the eye was evaluated by measuring the concentrations of timolol, tafluprost acid (active metabolic form of tafluprost), and latanoprost acid (active metabolic form of latanoprost) using liquid chromatography coupled with tandem mass spectrometry after single instillation of Taf/T-FDC or Lat/T-FDC to Sprague Dawley rats. Cytotoxicity following 1–30 min exposure of SV40-transformed human corneal epithelial cells to Taf/T-FDC or Lat/T-FDC was analyzed using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assays. Undiluted and 10-fold diluted solutions of each FDC were evaluated.ResultsThe IOP-lowering effect of Taf/T-FDC was almost equivalent to that of Lat/T-FDC at 4–8 h after instillation. The peak IOP reduction of Taf/T-FDC and Lat/T-FDC was observed at 8 h after instillation, and there is no difference between the two. The difference between them was observed at 24–30 h after instillation, and Taf/T-FDC demonstrated a significantly greater IOP-lowering effect than Lat/T-FDC at 24–30 h after instillation. The IOP-lowering effect of Taf/T-FDC was sustained up to 30 h after instillation, while that of Lat/T-FDC had almost disappeared at 28 h after instillation. Timolol concentrations in aqueous humor after Taf/T-FDC instillation were higher than those after Lat/T-FDC instillation (Cmax, 3870 ng/mL vs 1330 ng/mL; AUCinf, 3970 ng·h/mL vs 1250 ng·h/mL). The concentrations of tafluprost acid and latanoprost acid in aqueous humor after instillation of Taf/T-FDC and Lat/T-FDC, respectively, were similar to those after instillation of mono-preparations of tafluprost and latanoprost, respectively. The cytotoxic effect of Taf/T-FDC to the human corneal epithelial cells was significantly lower than that of Lat/T-FDC at all evaluated time points in both undiluted and 10-fold diluted FDCs.ConclusionTaf/T-FDC provides increased IOP-lowering effect duration and lower potential ocular surface toxicity than Lat/T-FDC.
Highlights
Glaucoma, a neurodegenerative ocular disease characterized by selective loss of retinal ganglion cells (RGCs) and resultant visual field defects, is the second leading cause of blindness worldwide
The peak intraocular pressure (IOP) reduction of Taf/T-Fixed-dose combination (FDC) and Lat/T-FDC was observed at 8 h after instillation, and there is no difference between the two
The difference between them was observed at 24–30 h after instillation, and Taf/T-FDC demonstrated a significantly greater IOP-lowering effect than Lat/T-FDC at 24–30 h after instillation
Summary
A neurodegenerative ocular disease characterized by selective loss of retinal ganglion cells (RGCs) and resultant visual field defects, is the second leading cause of blindness worldwide. Glaucoma patients are initially treated with pharmacological monotherapy, such as prostaglandin analogue (PGA) or beta-adrenergic antagonist; in more than 40% patients, additional IOP-lowering drugs are required to control their IOP; two or more drugs are used in the treatment [4,5,6]. The addition of a second drug increases the complexity of treatment regimens and incidence of dosing errors [7, 8]. Separate instillation times (by at least 5–10 min) are recommended to avoid diluting and/or washing of either drug from cul-de-sac [9]; this approach is very inconvenient for patients. There is a significant clinical concern regarding reduction in the pharmacological effects of instilled drugs in patients who do not follow these recommendations. Francis et al indicated that FDC therapies provide better IOP control than unfixed combinations therapies in real-life settings [11]
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