Implants designed to release glaucoma drugs over several months are most helpful for patients who are particularly challenged by administering eyedrops, researchers say.
The US Food and Drug Administration approved Allergan's bimatoprost implant (Durysta) in March 2020, and it became available June 23, said E. Randy Craven, MD, from Johns Hopkins University, Baltimore, Maryland. At least five other extended-release products for lowering intraocular pressure (IOP) are in the pipeline.
Who Needs an Implant?
Craven, who helped develop the bimatoprost implant, gave an overview of the drugs at the American Academy of Ophthalmology (AAO) 2020 Annual Meeting.
While he would like to prescribe the implant to most of his patients, insurers have been unwilling to pay for it, he told Medscape Medical News. "Personally, for me, I've been using it more as a special circumstances case for right now."
The bimatoprost implant, which holds the drug in a solid polymer matrix, biodegrades over time. In clinical trials, it maintained IOP as consistently as timolol maleate drops administered regularly for at least 6 months. For most patients, that benefit continued for a year. And IOP stayed in the safe range for a quarter of patients for as long as 2 years, Craven said.
"Potentially, there's some extracellular matrix remodeling going on in the tubercular outflow system and maybe the uveal tissue that's allowing the actual matrix itself of the outflow system to be more permeable," he said.
The procedure for the bimatoprost implant is not difficult. "Basically, it's a few-minutes' procedure that could be done anywhere from a slit lamp to a procedure room in the office, or in a surgery center or hospital," Craven said. "It just depends on the doctor's comfort and the insurance and regulations."
The biggest hurdle to using the implant has been approval from patients' insurance companies, Craven said. At $1000, the implant is much more expensive than eyedrops.
"I've been using it for patients who really need something like this," he said, "someone who has early dementia or who lives alone and can't get drops in, someone who has surface tolerability issues with topical drops or who is bothered by the appearance of the eye."
Lack of insurance coverage has also proved a stumbling block for Natasha Kolomeyer, MD, from Wills Eye Hospital, Philadelphia, Pennsylvania. She recently had to forgo placing the device in some patients who might have benefited, including one with schizophrenia and another with posttraumatic stress disorder, conditions that kept them from using eyedrops.
The bimatoprost implant comes with other limitations, she noted. Under its current label, it can only be used once, and it can cause a decrease in corneal endothelial cell density.
Several competing treatments are moving through the pipeline:
Allergan has completed phase 2 trials of a ring-shaped device that is inserted into the conjunctival cul-de-sac and that also elutes bimatoprost. "Some people can't tolerate it, but if you're having side effects, you can take it out easily," said Kolomeyer.
Envisia has completed phase 2 trials of a biodegradable travoprost implant. "They found that the results were encouraging," Craven said.
Glaukos's iDose, a titanium implant that elutes travoprost, has also completed phase 2. "They found that it seemed to give pretty good pressure control," said Craven. This device has the advantage that it might be reusable, but on the other hand, the procedure for implanting it is more difficult than with the bimatoprost implant.
PolyActiva is in phase 2 with a biodegradable implant that elutes latanoprost free acid. "A free acid seems to have a higher binding affinity inside of the eye," said Craven.
Ocular Therapeutix has completed phase 1 with OTX-TIC, a bioresorbable intracameral implant for delivering travoprost. Its OTX-TP, an intracanalicular insert that also delivered travoprost, fell short of its primary phase 3 endpoints.
Eventually these devices are likely to help not only those patients who can't put in eyedrops but also those who simply don't want to think about doing that, said Kolomeyer. As well, delivering medication closer to its anatomic target on a regular schedule may result in better control of the disease, Craven pointed out.
Craven and Kolomeyer agreed that the new delivery systems will work best if they can be paired with home tonometry so that patients don't have to visit their ophthalmologists frequently to make sure the devices working. One such device for this purpose, the iCare Home Tonometer, is already available, but it is too expensive for many patients, Kolomeyer said.
These barriers seem sure to become lower as more research is conducted and more devices are approved, she concluded. "We're going to know a lot more about it in the upcoming 2 years and look forward to having more options."
Craven is a consultant to Allergan. Kolomeyer has disclosed no relevant financial relationships.
American Academy of Ophthalmology (AAO) 2020 Annual Meeting: Session SYM19V. Presented November 15, 2020
Laird Harrison writes about science, health and culture. His work has appeared in magazines, newspapers , and online publications. He is at work on a novel about alternate realities in physics. Harrison has taught writing at San Francisco State University, UC Berkeley Extension and the Writers Grotto. Visit him at lairdharrison.com or follow him on Twitter: @LairdH .
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Cite this: Extended-Release Glaucoma Drugs Eagerly Anticipated - Medscape - Nov 19, 2020.