Drug-delivery micropump for chronic retina disorders

By Michelle Dalton, ELS; Reviewed by Mark S. Humayun, MD, PhD, and Julia A. Haller, MD

Los Angeles-The “first-in-man” implant of a novel ophthalmic drug delivery system (Posterior MicroPump, Replenish Inc.) in patients with diabetic macular edema (DME) demonstrates that use of the device “is feasible and warrants further development,” according to Mark S. Humayun, MD, PhD.

The small, refillable ocular drug pump-implanted through minimally invasive surgery-delivers the “appropriate amount of drug needed at determined intervals,” said Dr. Humayun, professor of ophthalmology, USC Eye Institute, Keck School of Medicine, Los Angeles.

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Localizing drug delivery has the advantage of avoiding systemic side effects, which has been a potential concern with current retinal disease treatments. Both suprachoroidal and intravitreal delivery may eliminate this issue altogether.

The pump provides the capabilities for delivering a programmable microdose direct to the eye. The cannula, inserted through the pars plana, is programmed wirelessly.

The device was initially designed to solve adherence issues for patients with glaucoma, said Dr. Humayun, adding that noncompliance issues result in almost $300 billion of direct and indirect medical costs yearly in the United States. This version of the device is smaller than the one designed for glaucoma, but it has a larger reservoir volume.

As a result, the pump is refilled via a 31-gauge needle. The device also has a separate console unit that is used to fill and refill the implant.

“The pump has been shown to be capable of use for more than 7 years and further longevity tests are ongoing to determine how much longer it can work,” Dr. Humayun said.

The reservoir can be replenished within 2 minutes in the clinic, he added, thus alleviating some of the pressure of increased patient loads.

“This marks a new direction in ocular bioelectronics devices, and our second-generation [micropump] can hold up to 100 microliters,” he said. “This device has a lot of potential, with multiple chambers for different drug delivery.”

As with most novel devices, Dr. Humayun said, “additional clinical studies are required to further validate our findings, but controlled drug delivery via this pump for chronic diseases of the retina is feasible.”

First look at research

Eleven subjects with DME and visual acuity of logMAR 0.30 or worse were included in the initial study for the pump. The device, filled with ranibizumab, was implanted using similar techniques used for implanting a glaucoma drainage device.

After implantation, the device was wirelessly controlled to deliver a preprogrammed dosage of ranibizumab.

Comprehensive ophthalmic examinations and optical coherence tomography were performed biweekly for 90 days. At day 90, the device was explanted and the subjects thereafter received standard of care.

No serious adverse events were reported after 90 days. All subjects exhibited a normal course of healing. One patient had a small vitreous hemorrhage from the sclerotomy site at week 1, which did not cause a decrease in visual acuity and was resorbed at postoperative week 4.

“There were no reported instances of foreign body sensation,” Dr. Humayun added. “Transient diplopia only elicited in extreme gaze positions was minimal and resolved completely within 6 weeks postoperatively.”

Out of the 11 subjects, the micropump device delivered the preprogrammed dosage within 20% of target in seven subjects. For the successful seven subjects, there was an improvement in visual acuity and retinal thickness at day 28 compared with baseline.

In four subjects, the device had a slower rate of delivery than desirable clinically, and the team decided to complete the dosing regiment using intravitreal injection.

Of the four unsuccessful attempts, the pump itself was damaged during implantation in one case, and in the other three cases, the pump was unable to deliver the dose within the allotted time, Dr. Humayun said. Improvements are being made for the next study.

No subject had loss of visual acuity during the study.

The device is for investigational use only and not yet approved for commercial distribution. 

Mark S. Humayun, MD, PhD

P: 323/442-6523  

E: humayun@hsc.usc.edu

This article was adapted from Dr. Humayun’s presentation at the 2014 meeting of the American Society of Retina Specialists. Dr. Humayun is inventor of the technology and co-founder of Replenish Inc.