Ocular Implants for Drug Delivery: Improving Patient Outcomes

Did you know that there are already 11 ocular implants on the market and over 30 in development? (See Table 1 and Figure 2). Every year, more and more people live with eye disease or vision impairment of some kind, requiring treatment to avoid additional vision loss or blindness.

In 2010, approximately 4 million people had some kind of vision impairment, a number expected to climb to roughly 7 million by 2030 and more than 12 million by 2050. Cases of macular degeneration alone — which grew 18% from 2000 to 2010 — are expected to more than double by 2050.¹

That growth, spurred in part by an aging population, creates new demand and opportunities in the ocular pharmaceutical space.

Ocular implants — small devices designed to be inserted into the eye and deliver a drug locally over an extended period — are rapidly gaining ground as a treatment option. As patients continue to seek out convenient, less invasive treatments, the demand for these implants will continue to increase.

Figure-1-Vision-Impairment, Lubrizol CDMO Division — Figure 1: Incidence of vision impairment.

The Current State of Ophthalmic Drug Delivery

Generally, ocular drug delivery falls into one of two categories: anterior and posterior.

Anterior drug delivery methods are most often topical and include dosage forms such as eye drops and ointments. These medications are applied to the front portion of the eye.

Thanks in large part to their ease of use, anterior delivery treatments make up the majority of widely available ophthalmic treatments. In 2020, more than 62% of revenue from ophthalmic drugs came from topical treatments.² However, they come with significant drawbacks in treating some eye conditions, particularly those that affect the posterior (back) portion of the eye as topicals cannot reach this area.

However, they come with significant drawbacks in treating some eye conditions, particularly those that affect the posterior (back) portion of the eye as topicals cannot reach this area.

Posterior drug delivery methods are less common than their anterior counterparts, partly because reaching the back portion of the eye, mainly the retina, can be challenging. Posterior treatment methods include injections or implants into the vitreous or other surrounding tissue toward the back of the eye.

Posterior treatments can be challenging for both drug developers and patients, however. For example, maintaining the appropriate concentration of a drug in the vitreous — the fluid that fills the eye and keeps the retina in place — can be difficult with injections. Additionally, the molecular weight of a drug can influence how it is eliminated by the patient’s system, making formulation design difficult. Furthermore, for patients, the process of receiving injections in the eye can be unpleasant, and the frequency of treatments inconvenient.

All of this makes ocular implants a particularly attractive treatment option for patients, as they offer well-controlled dosing over a longer period of time than injections and can treat retinal disorders.

Types of Ocular Implants

Ocular implants present a unique solution to the challenges of treating posterior eye disorders, and many are already commercially available, including Allergan’s Ozurdex^® dexamethasone intravitreal implant and Allergan’s Durysta™ bimatoprost implant, prescribed for a range of posterior eye conditions.

Broadly, ocular implants come in both biodegradable (bioresorbable) and non-biodegradable (biodurable) forms.

Bioresorbable implants are inserted into the patient’s eye and safely absorbed by the body over time. These implants combine a drug with a polymer — often polylactic-co-glycolic acid (PLGA) — which degrades over time, releasing a drug.
Biodurable implants do not break down over time and may be removed or refilled once the treatment is complete. These implants often encapsulate a pharmaceutical inside a polymer — such as Lubrizol’s Pathway™ thermoplastic polyurethane (TPU), ethylene vinyl acetate (EVA), or silicone.

Each type of implant has advantages and disadvantages. Bioresorbable implants eliminate the need for patients to undergo a follow-up procedure, but they may not be suitable for use with all drugs. Biodurable implants can offer longer, more controlled drug release, but they may require patients to undergo a second procedure to remove them.

Overall, however, implants present a significant improvement for patients and require less frequent administration than ocular injections. When treated with an implant, patients who had previously relied on traditional injections could extend their time between treatments by weeks or even months.

Read the full article from the Lubrizol CDMO Division blog here