Avoiding the needlePosted: Thursday 17 January 2019 at 11:30
We have previously looked at the potential of eye drops to replace injections as a treatment for age-related macular degeneration (AMD) – but that’s far from the only approach being tested.
Regular anti-VEGF injections are a lifeline for many people with wet AMD and other macular diseases. But they can also be uncomfortable, inconvenient and, if you need one every four to eight weeks, a real pain to schedule your life around. So teams of researchers across the world are investigating different ways to keep sight just as stable with fewer injections.
Earlier this year, two trials reported that people being treated with an anti-VEGF drug called abicipar every eight or even 12 weeks were just as likely to have stable vision as those having ranibizumab (Lucentis®) injections every four. The research isn’t over yet as researchers are keen to understand the longer-term effects, especially as people being treated with abicipar were more likely to have the side effect of inflammation in their eye. If abicipar is eventually approved, it could mean that someone with wet AMD needs only six or eight injections a year, rather than up to 13.
After each injection, the amount of anti-VEGF drug in the eye gradually falls until there’s not enough left to have an effect on the retina. Instead of “topping up” the levels with frequent injections, people on the LADDER trial had a refillable implant inserted into their eye that gradually released ranibizumab at one of three doses.
Of the people getting the highest dose, around 80 percent were able to wait at least six months before their implant – which is slightly longer than a grain of rice – needed refilling, and their vision was preserved in a similar way to someone having monthly injections. Phase 3 trials, with more people, are planned to start before the end of 2018.
The drug company that produces Eylea® (aflibercept) has also investigated whether it would work in a refillable port. Steroid implants are already used to treat other eye conditions, although these dissolve inside the eye rather than being refilled.
As a cancer treatment, stereotactic radiotherapy (SRT) uses precisely targeted radiation to attack tumours inside the body. Several beams of radiation are angled from different directions - each one is relatively weak and undamaging, but where they overlap, the effect of the radiation is stronger.
A couple of studies are investigating whether using a small dose of radiation (around the same amount you’d be exposed to during a dental x-ray) at the same time as the first injection of ranibizumab could be more effective than the injection on its own. Three beams of radiation are angled so they target the new, leaky blood vessels in the retina.
One study has found that although the effects of SRT are not immediate, people who had x-ray treatment as well as injections had better visual acuity after three to four months. People in both groups had the standard three “loading doses”, but a year later, the SRT therapy group had needed 1.45 further injections to keep their vision stable, compared with 2.64 for the group who had injections only.
Another option might involve implanting a tiny pump into the eye that’s loaded with several doses of an anti-VEGF drug. These can then be triggered as needed using a remote control. A trial of 11 people with diabetic macular oedema found that pumps containing up to eight years’ dose of ranibizumab could be safely implanted, triggered at will and removed after 90 days. There’s still some work to do on getting the dosing right, as only seven of them received enough of the drug through the pump to treat their eye condition.
More recently a Korean team has suggested using a similar micropump to treat AMD and other eye conditions, this time triggered by a magnetic field.