Bimatoprost sustained-release implants: Potential new pathway for glaucoma patients

Take-home: The bimatoprost sustained-release implant (bimatoprost SR, Allergan) improves compliance for patients with problematic compliance with topical IOP-lowering glaucoma drugs and controlled the IOP for 6 months after injection.

Reviewed by Thomas R. Walters, MD

Austin, TX-The bimatoprost sustained-release implant (bimatoprost SR, Allergan) offers a major advantage for patients, namely, improved compliance for those with problematic compliance with topical IOP-lowering glaucoma drugs. Almost three quarters of study patients experienced IOP control over the first six months of the phase 1/2 safety and efficacy trial.

The implant is a biodegradable device especially developed to make sure the drug gets to its target location in order to best control glaucoma. The implant, according to Thomas Walters, MD, is placed intracamerally in the eye using a prefilled, single-use applicator system that releases bimatoprost over an extended period.

Phase 1/2 trial

This is a prospective, 24-month, dose-ranging, controlled clinical trial in patients with open-angle glaucoma to evaluate the IOP-lowering effect and safety of bimatoprost sustained-release in patients with glaucoma. After a washout period, one eye (termed the study eye) of 75 patients was injected intracamerally with an implant containing one of four doses, i.e., 6, 10, 15, or 20 micrograms, of bimatoprost.

The fellow eye was treated with topical bimatoprost 0.03% once daily. Retreatment was permitted with the implant containing the three lower drug doses (6, 10, or 15 micrograms) beginning at 16 weeks after the start of the study until month 12. Topical IOP rescue drugs also could be administered to either eye of the patients. The primary outcome measures were the changes in the IOP compared with baseline and the development of any adverse events.

All study patients were older than 18 years and had open-angle glaucoma in the eye that received the implant. All had an IOP ranging from 22 to 36 mm Hg after the washout period.

Patients were excluded if they had a history of narrow-angle or closed-angle glaucoma or had undergone a surgery to removed cataract in which a posterior capsular tear occurred. In addition, they also were excluded if the central endothelial cell count was less than 2,000 cells/mm².

The mean patient age was 63.1 years, and the patients were evenly divided by gender. The mean baseline IOP in the study eye was 25.2 mm Hg and that in the fellow eye was 24.5 mm Hg.

“The IOP decreased significantly compared with baseline with all doses of the drug in the implant,” Dr. Walters reported.

Continued

Specifically, the mean overall IOP reductions from baseline through week 16 after the first implantation of the bimatoprost sustained-release device were 7.2, 7.4, 8.1, and 9.5 mm Hg with the 6-, 10-, 15-, and 20-microgram doses compared with an 8.4 mm Hg decrease in the pooled fellow eyes treated with topical bimatoprost. The IOP decreases in the study eyes reached significance (p ≤ .001).

The investigators commented that 92% and 72% of the study eyes did not need rescue or retreatment by week 16 and month 6, respectively. The most common adverse event was transient conjunctival hyperemia (median duration of 5 days), which developed within 2 days after the implant was injected.

In 24 eyes that did require another treatment to control IOP, the overall mean IOP reduction from the baseline IOP was 8.0 mm Hg through 16 weeks after the repeat bimatoprost sustained-release treatment. In those eyes, the IOP had to decrease by less than 20% compared with baseline after the first injection of the bimatoprost device at consecutive visits that were 1 or more weeks apart.

In addition, these eyes could not have received previous rescue therapy with a topical IOP-lowering medication and the safety level was adequate with the first implant, according to Dr. Walters.

The study investigators concluded based on their findings that the four doses of bimatoprost sustained-release were well tolerated and the decreases in IOP were comparable to those achieved with topical bimatoprost 0.03% in overall IOP reduction through week 16. In most patients, the implant successfully controlled the IOP for up to 6 months after implantation, and the second treatment in those patients who needed it showed similar efficacy. Most of the adverse effects were transient and associated with the actual injection process.

The investigators believe that the interim results of the phase 1/2 trial support further clinical development of the glaucoma implant.

Thomas R. Walters, MD

E: tom@nobhill.me

Dr. Walters is a consultant to Allergan. The phase 3 trial of the implant is currently under way. The bimatoprost sustained-release implant has not yet been approved by the FDA.