Results from two mid-stage clinical trials that added nesvacumab to Eylea "did not provide sufficient differentiation to warrant Phase 3 development", Regeneron said on Monday.

"We knew from the start that it would be difficult to improve on the already high bar set by Eylea," said president and chief scientific officer, George Yancopoulos.

Eylea, on which Regeneron has partnered with Bayer, generates annual sales of $5 billion (£3.74 billion) but faces looming competition from an experimental Novartis drug known as RTH258, which has shown advantages over Eylea in clinical trials run by the Swiss group.

Both drugs are designed primarily to treat wet, age-related macular degeneration, where abnormal, leaky blood vessels can cause blindness. The condition affects 20-25 million people worldwide.

(Reporting by Ben Hirschler; Editing by David Goodman)

Stocks treated in this article : Regeneron Pharmaceuticals, Bayer, Novartis