Regeneron Pharmaceuticals Inc., maker of the macular degeneration therapy Eylea, fell the most in a year after another drug was shown to improve patients’ vision when used with Roche Holding AG’s Lucentis.

Regeneron declined 12 percent to $111.88 at 4 p.m. in New York, the biggest decline since April 2011. Princeton, New Jersey-based Ophthotech Corp. said in a statement Wednesday that its medicine Fovista taken with Lucentis helped vision in a 449-patient study more than the Roche drug by itself.

The therapies treat wet age-related macular degeneration, a leading cause of vision loss in the elderly. Eylea competes with Lucentis, which brought in 1.5 billion Swiss francs ($1.59 billion) in sales last year for Roche. Tarrytown, New York-based Regeneron, whose stock has more than doubled since Eylea was approved in November, expects its medicine to draw as much as $550 million in 2012 revenue.

“The data suggest that the treatment of wet AMD is likely to continue to evolve, and this is a negative for Regeneron as the company’s current valuation assumes consistently high sales of Eylea for a number of years,” Phil Nadeau, an analyst with Cowen & Co., wrote in a note Wednesday. “We are somewhat surprised by the magnitude of the weakness in Regeneron this morning, as Fovista itself is not yet a direct competitor to Eylea,” and could also be used with the Regeneron drug, he said.

Ophthotech is closely held.