Genentech, Inc. confirmed on October 11th that it is taking steps to prevent its biologic cancer drug Avastin from being used instead of its chemically similar biologic Lucentis to treat wet macular degeneration, a leading cause of blindness.

In a letter sent to 1,500 retina specialists, Genentech said its wholesalers as of Nov. 30th would no longer provide Avastin to compounding pharmacies, which divide a dose of Avastin suitable for cancer patients into tiny doses for use in the eye.

Genentech said hospital pharmacies would still be able to purchase Avastin, so retina specialists in hospitals that do their own compounding would still have access to the drug.

While biologic Avastin has never been approved for treatment of eye disease, it's mechanism of action is similar to Lucentis and many eye doctors -- who began using it before Lucentis was approved in June 2006 -- have continued using it because it is so much less expensive.

A once-monthly dose of Lucentis --- which is injected directly into the eye -- costs about $2,000. A syringe containing the dose of Avastin used to treat patients with wet macular degeneration costs $40 to $50.

In the letter explaining its decision, Genentech noted that Lucentis was approved specifically for use in the eyes, and said the FDA has expressed concern that third-party splitting of Avastin into doses for the eye carried risk of contamination and serious eye infection.

Dr. Philip Rosenfeld, a University of Miami ophthalmologist who was one of the first doctors to use Avastin in the eye, suggested Genentech's real concern was that use of Avastin was cutting into sales of Lucentis.

"The retinal community is deeply saddened by the decision Genentech has made to restrict the availability of Avastin in the United States," Rosenfeld said.

While Genentech said it never intended for Avastin to be used in the eye, the National Eye Institute is now sponsoring a trial that will directly compare Avastin and Lucentis as a treatment for macular degeneration. Genentech has refused to support the comparative study.