Randomized, masked trial finds IOP-lowering benefit from within-class, monotherapy switch

Key Points

Jeffrey A. Kammer, MD, assistant professor of ophthalmology, Vanderbilt University, The Vanderbilt Eye Institute, Nashville, TN, was the principal investigator in this phase IV multicenter study titled the Bimatoprost Data Evaluation (BDE).

"For patients whose IOP is not adequately controlled by initial monotherapy with latanoprost, there have historically been two options as it relates to pharmacotherapy," Dr. Kammer said. "The first option includes continuing monotherapy using a medication from another pharmacologic class, but that can involve increased dosing frequency. Alternatively, a second medication can be added, but that introduces cost as well as compliance issues.

The BDE study enrolled 266 patients at 17 sites across the United States. To be eligible for inclusion, patients were required to have an IOP that did not reach an investigator-determined target IOP after a >30 day trial of latanoprost monotherapy.

The latanoprost-treated patients were randomly assigned 1:1 to be switched to bimatoprost or travoprost. IOP measurements were obtained at screening, baseline, and after 1 and 3 months of therapy in the morning (8 to 10 a.m.) and in the afternoon (3 to 5 p.m.). A diurnal IOP value was calculated from those data.

Baseline mean IOP was about 19 mm Hg and similar in the bimatoprost and travoprost groups. After 1 month, both medications were effective in lowering mean IOP. However, mean IOP was significantly lower in the bimatoprost group compared with the patients treated with travoprost (17.1 versus 17.7 mm Hg; p = 0.009).

Further IOP lowering was achieved in both groups at 3 months, but again the mean IOP was significantly lower among patients treated with bimatoprost compared with travoprost (17 versus 17.5 mm Hg; p = 0.024), Dr. Kammer reported.

Subgroup analysis

A subgroup analysis was also performed including patients whose baseline diurnal IOP was between 16 and 20 mm Hg. There were equal numbers of patients in the two treatment groups included, and there was no significant difference in their mean baseline IOP. Outcomes of the switch in this subgroup were similar to those seen in the overall study population-both medications demonstrated efficacy in further lowering IOP, and again, bimatoprost was significantly more effective than travoprost at 1 and 3 months based on comparisons of mean diurnal IOP. However, among these patients with relatively low baseline IOPs, the difference in IOP-lowering effect favoring bimatoprost was even more profound.

Patients treated with bimatoprost achieved a mean 1.6-mm Hg reduction from baseline IOP at 1 month and a further benefit at 3 months. In the travoprost group, the mean IOP reduction at 1 month was only 0.6 mm Hg, and there was a modest loss of effect at 3 months.

"These outcomes suggest that when seeking to lower IOP further in patients with glaucoma whose IOP is already within the statistically normal range, bimatoprost might be a better option," Dr. Kammer said.

When considering the overall population and the subgroup with low baseline IOPs, the results from this study demonstrated a median IOP drop of 2 mm Hg in both bimatoprost subgroups and ranged from 0.5 to 1 mm Hg in the two travoprost subgroups.