Anti-VEGF drug targets diabetic macular edema

Las Vegas-The 1-year results of a study that evaluated the effects of pegaptanib sodium (Macugen, Eyetech Pharmaceuticals) on diabetic macular edema indicates that the drug might provide some patients with improved visual acuity and reduced central retinal thickness compared with no treatment with short follow-up (36 weeks).

In addition, patients may be less likely to need additional focal photocoagulation, reported Neil M. Bressler, MD, at the American Academy of Ophthalmology annual meeting.

"The 36-week evaluation of pegaptanib that studied the feasibility of pursuing the use of the anti-vascular endothelial growth factor (VEGF) for diabetic macular edema was published in Ophthalmology (2005; 112:1747-1757). In that study, the subjects were randomly assigned to one of three doses [0.3 mg, 1 mg, or 3 mg] of pegaptanib given at baseline-at week 0-or sham treatment. This treatment was repeated at weeks 6 and 12. At the discretion of the investigators, additional injections of pegaptanib or the sham treatment were given at weeks 18, 24, and 30," Dr. Bressler explained. He is the James P. Gills Professor of Ophthalmology, The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore.

A total of 172 subjects with diabetic macular edema were enrolled at 39 centers worldwide. At baseline the mean visual acuity (approximate Snellen equivalent) was 20/80 and the central macular thickness on OCT among treatment groups varied from 425 to 450 µm.

"The mean visual acuity change was somewhat better in the pegaptanib group. By week 36, in the 0.3-mg pegaptanib group there was a mean positive change of five letters, suggesting that there might be a beneficial effect on the visual acuity," Dr. Bressler reported.

"After the last injection at week 30 and out to week 52 and week 82, although the subjects could still receive focal laser photocoagulation, no additional pegaptanib was administered and there were fewer letters of visual acuity lost in the 0.3-mg pegaptanib group compared with the sham group," he said. Dr. Bressler cautioned that it is unknown how these cases would have done if pegaptanib treatment were compared with focal photocoagulation at the initial visit, or would have compared with a combination of pegaptanib with focal photocoagulation at the initial visit.

Visual acuity gains

When the investigators evaluated the subjects who gained 10 or 15 or more letters of visual acuity, somewhat more patients in the pegaptanib groups did so compared with the sham-treated patients at week 36; at week 52 the visual gain of 10 or more letters remained somewhat better in the pegaptanib groups. At week 82, there were still a few more subjects in the pegaptanib group that gained visual acuity compared with the sham-treated patients.

However, the number of cases with these outcomes at weeks 52 and 82 was too small to be able to determine confidently if there was a true difference in favor of pegaptanib with respect to these outcomes. Again, it also is unknown if focal photocoagulation were applied at the initial visit, if laser treatment would have been better than pegaptanib alone, or if outcomes might have been improved if both pegaptanib and focal photocoagulation were applied at the initial visit.

There also were anatomic changes that were evaluated. After the last injection at week 30, there was very little change in the sham-treated patients in the central macular thickness as witnessed at week 36. However, in the pegaptanib-treated patients, there was a mean change of 50 to 75 µm in decreased macular thickness.