New Japanese Trial for Retinitis Pigmentosa Drug

February 12, 2013 - The Japan Science and Technology Agency (JST) has committed funds to a human trial of unoprostone isopropyl. This drug, applied topically (in eye drops), was first developed in Japan to treat glaucoma. However, in early human studies it has also shown promise for the treatment of retinitis pigmentosa (RP) as well as age-related macular degeneration (AMD).

The new phase 3 trial will likely take place in several Japanese centres, beginning in 2013, thanks to this major investment from the Japanese government. Phase 3 trials specifically test the therapeutic efficacy a drug, providing the information needed for it to be approved for clinical use.

Previous Trials 

Early stages of human testing, already completed in Japan, tested the drug’s safety and determined its most appropriate dose. These early trials, called phase 1/2 trials, involved 112 patients with mid- to late-stage retinitis pigmentosa at six Japanese centres. All were between 20 and 65 years old.

The trials showed that the topical drug was safe in these RP patients. The most common side-effect was irritation and burning in the eyes when the drops were administered. 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 studies also showed that the highest dose tested was the most effective (two drops of a 0.15% ophthalmic solution, twice a day). People who received the highest dose of drug in these early trials were more likely than people who received a fake drug (placebo), to have significant improvement in their night-time and dim-light vision. They were also more likely to report improvements in their “social life functions due to vision.”

Perhaps most exciting, the trial clearly showed that the treatment could help to protect vision from further deterioration. Over the six months of the study, 21.2% of people receiving the placebo lost some visual sensitivity, whereas only 2.6% of those receiving the highest dose of drug lost any sensitivity. 

Unoprostone has several unique effects in the eye. Apparently its major therapeutic effect in retinal degeneration is to stop the process of cell death, called apoptosis. Learn more about neuroprotective therapies like unoprostone.

Unoprostone may also improve blood flow to the retina. This action may be helpful in RP, and may be even more relevant to the treatment of AMD. It is suggested (but still not proven) that this effect might reduce the likelihood that a person with dry AMD would develop wet AMD. An early phase 2 trial testing unoprostone in people with dry AMD is now underway in Europe.

Availability in North America

Unoprostone isopropyl is already approved as a treatment for glaucoma in many countries. It is sold under the trade name Rescula and marketed by the pharmaceutical company, Sucampo.

It was first approved in the United States, in 2000, for limited use as a back-up drug for glaucoma. However the conditions of its approval limited it marketing and it was never sold.

Recently, Sucampo made a new application to the Food and Drug Administration in the United States to expand the drug’s use for glaucoma. This was approved in Dec 2012, and the company plans to begin selling Rescula in the United States in mid-February. Currently there are no plans to market this drug in Canada.

Visit the Sucampo web site for details about this drug and the side effects seen when used to treat people with glaucoma.

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