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Systemic AMD treatment shows promise, must be studied prospectively
CHICAGO — A systemic treatment for neovascular age-related macular degeneration is showing promising results, said Philip J. Rosenfeld, MD, PhD. He presented a summary of recent findings with the VEGF-blocking agent bevacizumab here during Retina Subspecialty Day at the American Academy of Ophthalmology meeting.
The drug, which is approved for use in colorectal cancer, is attractively priced for this off-label ophthalmic application, but its safety profile in the eye is unknown, Dr. Rosenfeld said.
“Avastin (bevacizumab, Genentech) isn’t going to go away. The retrospective results are too promising and the pricing is too attractive,” Dr. Rosenfeld said. “It needs to be studied prospectively, and it needs to be compared to Lucentis.”
Lucentis (ranibizumab) is being studied in clinical trials by Genentech for the treatment of wet AMD.
The cost of Avastin is particularly enticing, Dr. Rosenfeld said. For instance, he said, the cost of a single dose of Macugen (pegaptanib, Pfizer/Eyetech) costs between $1,000 and $3,300, whereas a single dose of Avastin is about $5.50 per eye.
Avastin is a full-length humanized monoclonal antibody directed at VEGF. It was the first anti-VEGF agent approved for the treatment of metastatic colorectal cancer in the United States.
Use of Avastin for AMD is off-label, Dr. Rosenfeld stressed. In cancer patients, Avastin with chemotherapy has also been shown to prolong survival, he said.
“I’m sure that Avastin penetrates the human retina better than the monkey retina, but it probably does not penetrate as well as Lucentis,” he said. “What we need to find out is how much is enough. Avastin probably has twice the half life in the vitreous cavity than Lucentis.”
Patients at the Bascom Palmer Eye Institute in Miami have been offered Avastin as a salvage treatment if their condition has continued to decline despite being treated with other therapies, Dr. Rosenfeld said. Initial results show that a 1 mg dose of Avastin yields a “dramatic response” within 1 week, stabilizing the patient’s condition through 5 months of follow-up, he said.
The first 40 patients treated with the Avastin salvage therapy received an average of 1.8 injections over 3 months, Dr. Rosenfeld said. After 3 months, the patients had a slight improvement in visual acuity and an average decrease of retinal thickness on optical coherence tomography of more than 100 µm, he said.
The safety of systemic Avastin as it relates to the eye is unknown, Dr. Rosenfeld said.
“We feel confident that even after a high dosage, there are no bad effects, but we need to study systemic patients,” he said. “We know that Avastin was injected into a monkey eye in the 1990s without any serious problems.”
To minimize the risk of endophthalmitis, Dr. Rosenfeld said it is necessary to have a sterile solution of Avastin prepared by a credentialed pharmacy using sterile techniques.
“Systemic Avastin does have potential for an increase in hypertension and a doubling of thromboembolic events,” he said. “There have been no other adverse events of a high-dose systemic therapy.”