WASHINGTON (Reuters) – U.S. drug reviewers on Tuesday said Roche Holding AG’s eye drug Lucentis appeared to help diabetic patients with a vision-robbing eye condition, but questioned whether two different doses of the drug were equally safe and effective.

Staff from the U.S. Food and Drug Administration reviewed Lucentis ahead of an advisory panel of outside experts, which meets on Thursday to vote on whether to recommend approval of an expanded use of the drug, which is administered monthly by injection.

Lucentis is already approved for two other eye conditions. Roche is hoping to widen its use to people with diabetic macular edema (DME), the most common cause of moderate vision loss in patients with diabetes. There are currently no FDA-approved drugs for DME, a leading cause of vision loss among people of working age.

DME is currently treated by laser, which stops blood vessel leakage and can slow vision loss but rarely leads to vision improvement.

In clinical trials Lucentis, made by Roche unit Genentech, helped patients see at least 15 extra letters on an eye chart, the primary goal of the study, FDA reviewers said.

People were also generally able to sustain the improvement in vision for at least 24 months — although those who took the 0.5 mg dose lost a bit of vision after the 18th month.

Both doses were generally safe, although there were slightly more deaths at the higher dose — 11 people who received the 0.5 mg dose died during the clinical trials, compared to seven taking the 0.3 mg dose and three receiving a placebo, or sham injection. Each group contained 250 patients.

The FDA will ask advisers to recommend whether both doses of the drug should be approved for use against DME.

DME is a swelling of the retina that occurs in diabetics who suffer from retinopathy — the most common diabetic eye disease that involves damaged blood vessels leaking fluid into the retina. It causes blurred vision and severe vision loss.

About 75,000 new cases of DME are estimated to develop among Americans each year — and Genentech said about 560,000 Americans in total are affected by the disease.

If approved for DME Lucentis will likely compete with a highly promising drug being tested by Regeneron Pharmaceuticals Inc and Roche’s own cancer drug Avastin, which works in a similar manner as Lucentis.

Roche shares were slightly down at 167.5 Swiss francs, while shares of Regeneron were up 1.3 percent at $124.07 in morning trading on Nasdaq.

Avastin, which is not approved for eye disease, costs a fraction of the Lucentis price when cut into the small doses needed for eye injection. It has been used extensively off label in place of Lucentis, hurting sales of the eye drug.

A U.S. government study last year found the two drugs to be similarly effective for macular degeneration treatment.

Genentech has said Avastin increased the risk of stroke and heart attack in cancer trials and noted that diabetics are already at much higher risk for serious heart problems.

Lucentis is already approved to treat wet age-related macular degeneration — the leading cause of blindness among the elderly. It is also approved for macular edema following retinal vein occlusion (RVO), a swelling or thickening of the part of the retina responsible for central vision.

(Reporting by Anna Yukhananov; Editing by Gerald E. McCormick, John Wallace and Sofina Mirza-Reid)