"Intravitreal Pegaptanib Shows Promise As Diabetic Retinopathy Treatment: Presented at ASRS/EVRS"
By Jill Stein
CANNES, FRANCE -- September 18, 2006 -- Blockade of selective vascular endothelial growth factor (VEGF) with pegaptanib sodium injection (Macugen(R)) postpones disease progression in patients with diabetic retinopathy and significant diabetic macular edema (DME).
These results, from a phase 2 study, were presented here at the jointly held 24[th Annual American Society of Retinal Specialists (ASRS) and 5th Annual European VitreoRetinal Society (EVRS) meeting.
"The findings are important because there are currently no treatments which do not involve destruction of tissue," pointed out Victor H. Gonzalez, MD, director, Valley Retina Institute, McAllen, Texas. "Diabetic retinopathy is the number 1 cause of blindness in American adults, and a treatment which controls retinopathy without sacrificing tissue provides hope for these individuals."
Current treatments involve the off-label use of other agents, such as triamcinolone acetonide, however, these treatments are associated with secondary complications such as the formation of cataracts and important pressure elevations, he added. Laser therapy is the only treatment that has been proven to be effective but is associated with loss of visual function because of the tissue that is sacrificed at the periphery to help preserve central vision.
Any treatment that can complement or reduce the use of laser therapy needs serious consideration, he said.
Dr. Gonzalez noted that 10 patients in the study with active neovascularization receiving 0.3 mg pegaptanib showed significant regression of neovascularization at week 3, regardless of lesion size or location.
"There are very few wows, and this is definitely a wow," Dr. Gonzalez said. "Once we brought the VEGF levels down the DME improved, the neovascularization improved, and visual acuity either stabilized or improved in all of the patients," he noted.
In a presentation on September 12th, Dr. Gonzalez presented findings obtained in 172 patients with clinically significant DME who had been randomized to treatment with intravitreal injections of pegaptanib (0.3 mg, 1 mg, or 3 mg) or sham injections at enrollment, at week 6, and week 12. Additional injections and/or laser photocoagulation were given for an additional 18 weeks, as needed.
All treatment groups were similar with respect to baseline demographic and clinical characteristics.
Study outcomes included visual acuity, retinal thickness, and need for additional photocoagulation therapy. The effects of active treatment on retinal neovascularization and severity of retinopathy were also assessed.
Results showed that pegaptanib-treated patients had better outcomes than did the sham group on all measures.
Visual acuity with the 0.3 mg dose improved by 4.7 letters versus a decrease of 0.4 letters with sham (P =.04). Significantly more pegaptanib-treated patients maintained or gained from 5 to 10 letters than did sham patients.
The 0.3 mg pegaptanib dose nearly halved the need for laser treatment. "Thus, 25% of pegaptanib needed laser treatment versus 50% of the sham group," Dr. Gonzalez said. "This is particularly noteworthy because, although laser therapy has been demonstrated to work, anywhere we apply laser we cause a local area of scarring which is cumulative over time. Anytime we can delay or avoid having to laser a patient and are improving the severity of the retinopathy, our patients win."
Sixteen patients in the series had retinal neovascularization in the study eye. Eight of the 13 patients who were treated with the new selective anti-VEGF agent had regression of neovascularization versus none of the three sham-treated patients. None of the 4 fellow eyes of patients in the pegaptanib group with active neovascularization demonstrated regression.
Regression in the 0.3 mg pegaptanib patients was seen at week 36.
Overall, 28% of the pegaptanib group and 13% of the sham cohort had an improvement in their Early Treatment of Diabetic Retinopathy Study (ETDRS) severity of at least 1 step.
Pegaptanib 0.3 mg was associated with a 58 mm3 decrease in macular volume while sham treatment was associated with a 12 mm3 increase.
There were no systemic or ocular adverse effects seen with pegaptanib treatment. To date, there have been no significant systemic adverse effects in any trials with pegaptanib.
While the results are promising, Dr. Gonzalez said, the findings require corroboration in a phase 3 trial. If the results hold up, it is possible that this agent can help decrease the severe vision loss associated with advanced diabetic retinopathy, he added.
Pegaptanib, which is indicated for the treatment of neovascular (wet) age-related macular degeneration, is also being investigated for use in infants with retinopathy of prematurity.
The study was sponsored by (OSI) Eyetech, and Pfizer Inc.
[Presentation title: Pegaptanib Sodium in Diabetic Retinopathy: Improvements in Diabetic Macular Edema, Retinal Neovascularization, and Severity of Diabetic Retinopathy.]
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