Glaucoma Eye Drops Being Evaluated for Retinal Diseases
UF-021 (Unoprostone isopropyl) is a drug administered topically in eye drops, which has been approved for the treatment of glaucoma in the United States under the trade name Rescula. This drug is now being tested as a potential treatment for both retinitis pigmentosa (RP) and dry age-related macular degeneration (AMD). For these uses, the drug will be marketed as Ocuseva.
The company developing this drug in North America, Sucampo Pharmaceuticals, has announced that it hopes to launch a dry AMD trial in 2011, and an early-stage trial of unoprostone isopropyl for RP has already been completed in Japan. Results of this retinitis pigmentosa trial were reported at the recent 2011 meeting of the Association for Research in Vision and Ophthalmology in Florida.
Retinitis pigmentosa trial
The trial involved 112 patients with mid- to late-stage retinitis pigmentosa, who were being treated at six Japanese centres. All were between ages 20 and 65 years of age. This was a phase II trial, the stage of testing in which the efficacy and safety of different doses of a drug are usually compared. In this case, UF-021 was used in a 0.15% ophthalmic solution, and two different dose levels were tested of either one drop each time, or two. Some patients received a placebo instead, with no active drug, as controls. Participant gave themselves the eye drops, twice daily for 24 weeks.
The investigators used a machine called a microperimeter 1 (MP-1) to evaluate the participants’ vision in the very centre of the retina. The change in the retina’s sensitivity to light, between the beginning and the end of the treatment period, was measured in decibels; the higher the number of decibels, the more the sensitivity of the retina had improved. Thus a person whose sensitivity increased by a higher number of decibels would be able to see in dimmer light, indicating that the function of cells in the centre of the retina had been improved by the treatment.
The findings of this Japanese study were very encouraging. The central visual sensitivity of RP patients who received the highest dose of UF-021 was significantly improved, as early as four weeks after the start of treatment, and it continued to improve thereafter. The highest dose of UF-021 was more likely than the placebo to produce at least a 3 decibel improvement in light sensitivity. People receiving the highest dose were also more likely to report improvements in “social life functions due to vision”, and less likely to lose vision. The treatment also helped protect vision. Over the six months of the study, 21.2 per cent of people receiving the placebo lost some visual sensitivity, whereas only 2.6 per cent of people receiving the highest dose of drug lost any sensitivity.
Some people did experience eye irritation when using the UF-021 eye drops, and one person stopped participating in the study because of this irritation. However, no serious adverse events were reported in people using the drug-containing drops.
The lower dose of the drug did not produce any statistically significant improvement in vision, although there was a trend towards improvement. Further studies of the drug will likely focus on the higher dose.
Treatments such as this, which are already approved to treat another condition, can move much more quickly though clinical trials, because many of the safety issues have already been addressed. Sucampo Pharmaceuticals has received an orphan drug designation in the United States to help the company develop this drug further as a treatment for retinitis pigmentosa.
“This is just one of many new treatments that are being tested for RP and AMD, says Dr. Bill Stell, Director of Research Programs, FFB. "Proposed treatments range from systemically or topically administered drugs, to intraocular injections of drugs or agents of gene therapy, to implantation of cells or electronic devices. While we encourage all of these developments, systemic or topical drugs are especially exciting as candidates for treating retinal degenerations because they are relatively easy to take, innocuous, and inexpensive. While we still have a long way to go, I am really optimistic about the future of treatments such as this.”