Differential pharmacology and clinical utility of preservative-free tafluprost in the treatment of ocular hypertension and glaucoma

A triple crosslinked micelle-hydrogel lacrimal implant for localized and prolonged therapy of glaucoma

Glaucoma is a chronic disease that requires lifelong treatment, whereas, discomfort caused by frequent medication may affect the quality of life. Moreover, the therapeutic efficacy of traditional local administration was unsatisfactory due to the rapid ocular clearance mechanism and the ocular barrier. Herein, a triple crosslinked micelle-hydrogel lacrimal implant with low polymer content was fabricated for localized and prolonged therapy of glaucoma. Latanoprost and timolol were simultaneously entrapped in the PEG-PLA micelles with high encapsulation efficiency and further loaded into the triple crosslinked hydrogel, facilitating a double sustained release of drugs. Subsequently, the implant was constructed by a unique molecular orientation fixation technology, which enables the implant to be fixed in the lacrimal duct. The triple crosslinked micelle-hydrogel lacrimal implant manifested a distinguished physicochemical characterization to sustain the release of latanoprost and timolol. In vitro release experiment demonstrated the duration of two drugs was extended for up to 28 days. The in vivo test of elevated intraocular pressure (IOP) in a rabbit model revealed that the IOP-lowering effects were sustained longer than 28 days as expected. The relative pharmacological availability (PA) of lacrimal implants was 5.7 times greater than that of the eye drops. The results of the studies on ocular irritation and histological examination demonstrated the good safety of the lacrimal implant. In conclusion, the triple crosslinked micelle-hydrogel lacrimal implant could effectively lower the IOP with splendid compatibility, demonstrating the promising prospect in the long-term noninvasive treatment of glaucoma.

Tafluprost Ophthalmic Solution 0.0015 %: A Review in Glaucoma and Ocular Hypertension

Tafluprost ophthalmic solution 0.0015 % preserved with benzalkonium chloride (BAK) 0.001 % is available in several Asian countries, including Japan. In pivotal trials, BAK-preserved tafluprost ophthalmic solution 0.0015 % lowered intraocular pressure (IOP) more effectively than placebo in Asian patients with normal-tension glaucoma and was at least as effective as latanoprost ophthalmic solution 0.005 % in Asian patients with primary open-angle glaucoma or ocular hypertension. In other prospective studies in Asian patients with glaucoma or ocular hypertension, tafluprost ophthalmic solution 0.0015 % was at least as effective as latanoprost ophthalmic solution 0.005 % or travoprost ophthalmic solution 0.004 % in terms of IOP lowering, and was considered easier to use and/or store. The efficacy of tafluprost ophthalmic solution 0.0015 % was maintained in the longer term. Tafluprost ophthalmic solution 0.0015 % was generally well tolerated. In conclusion, BAK-preserved tafluprost ophthalmic solution 0.0015 % remains a useful option for the treatment of Asian patients with glaucoma and ocular hypertension.

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.