The field of glaucoma just hit a major milestone: In March, the Food and Drug Administration approved the first sustained-release, intraocular pressure (IOP)-lowering implant (bimatoprost SR; Durysta).
The implant will hopefully be available for use in June. Here is the skinny on this implant.
Why is sustained release medication so exciting, particularly for glaucoma patients?
Studies have shown that 30% to 80% of glaucoma patients are non-adherent to medications. Barriers to adherence are multifold and include forgetfulness, difficulty with drop instillation, need for frequent administration, poor understanding of the disease, medication cost and medication side effects. As an implant, bimatoprost SR has the potential to decrease patient treatment burden.
What is bimatoprost SR and how does it work?
Bimatoprost SR is a rod-shaped biodegradable intracameral implant containing 10 micrograms of bimatoprost. Since the medication is placed intracamerally, the total dose of bimatoprost contained in the 10-mcg implant is similar to the amount of bimatoprost in a single drop of the ophthalmic bimatoprost 0.03% solution.
Bimatoprost is a prostaglandin analogue that decreases IOP by increasing uveoscleral outflow. The implant can be injected into the anterior chamber at the slit lamp or in a minor procedure room. The phase 3 results so far suggest that the implant can result in IOP reduction close to 30% at the 12-week time point and is not inferior to topical timolol.
Is it safe?
Based on the phase 1 and 2 study, there were no reported cases of endophthalmitis, cystoid macular edema, eyelash growth, iris hyperpigmentation or eyelid retraction. Conjunctival hyperemia was reported in 35% of patients who received the implant, compared with 29% of patients who received topical bimatoprost.
However, conjunctival hyperemia was greater in the first two days after implantation; beyond the first two days, the implant group had less rates of hyperemia compared to the topical bimatoprost group. As one would expect, periorbital adverse effects were less common in the bimatoprost SR group compared to the topical bimatoprost group.
The bimatoprost SR group did have slightly higher rates of nonspecific adverse events such as eye pain, eye irritation, lacrimation and conjunctival hemorrhage. The reduction in endothelial cell density at two years was slightly greater in the implant group compared to the topical bimatoprost group. The phase 3 results will shed more light on safety as they enrolled significantly more patients.
How long does the medication last?
The implant was designed to last four to six months. However, the effects are lasting longer than expected. In the phase 1 and 2 study, 40% of patients did not require additional IOP lowering treatment for at least one year after a single implant; there was an 80% probability that patients did not require additional treatment for at least one additional year after three consecutive implants (every four months) in the phase 3 studies.
So, what’s the catch?
At this time, the FDA has only approved bimatoprost SR for single use per eye. Allergan is working to collect additional data through the ongoing phase 3 studies to support FDA label enhancements, including multiple administrations.
Who is the ideal candidate?
The FDA has approved bimatoprost SR use in open angle glaucoma and ocular hypertension. Personally, I plan to offer it to patients who have: 1) a history of good response to topical bimatoprost, 2) an open angle and 3) no underlying corneal endothelial issues.
What does the future hold?
Sustained-release medication is a burgeoning field, and I am optimistic it will transform our treatment paradigm for glaucoma and reduce the burden on our patients.
Our future is bright with experimental sustained-release options that range from external rings, punctal plugs, gel-forming drops, subconjunctival and intrascleral implants, injectable agents and intracameral implants. Platforms that can incorporate multiple medications and have a favorable safety profile will be the most likely to truly transform this field.
||About the author: Natasha Nayak Kolomeyer, MD, is a glaucoma specialist at Wills Eye Hospital in Philadelphia, Pa. She joined the YO Info Editorial Board in 2019.