Competition in the eye drug market is heating up, with an experimental drug from private U.S. biotech Ophthotech showing impressive results when added to Roche's Lucentis in a large mid-stage clinical trial.

That could be bad news in the longer term for Regeneron Pharmaceuticals, whose recently launched Eylea has been making rapid inroads in the U.S. by winning business from Roche.

Ophthotech's Fovista works in a different way to Lucentis and Eylea, making it a potentially valuable add-on therapy that could set a new standard for treatment.

If the drug can duplicate those results in final-stage trials, Ophthotech could be a natural takeover target for Roche as it seeks to shore up its position in the multibillion-dollar-a-year age-related macular degeneration (AMD) market, some investors believe.

AMD is the leading cause of blindness among the elderly.

An eventual sale of the company would realise gains for Ophthotech's venture capital backers including SV Life Sciences Advisers, Novo Ventures, HBM Partners and Clarus Ventures.

In the Phase IIb clinical trial involving 449 patients with wet AMD, those receiving Fovista and Lucentis gained a mean of 10.6 letters of vision on a standard reading chart at 24 weeks, against 6.5 letters for patients on Lucentis alone, Ophthotech said on Wednesday.

Geoff Meacham, an analyst at JP Morgan, said the 62% increase in visual outcome relative to Lucentis alone raised the bar in treating wet AMD - which is more severe than dry AMD - and suggested a new competitive threat for Eylea.

While Lucentis and Eylea work by blocking a protein called VEGF, Fovista is an anti-PDGF treatment, making it a complementary therapy in fighting AMD.

Fovista has been tested in Phase I and II studies with Lucentis as the Roche drug was the lone approved drug for the eye condition in its class at the time the trials were planned and conducted. But it could be combined with other treatments.

"We are confident it can be paired with any of the VEGFs out there in fixed combination or co-formulation," Ophthotech's Chief Executive and co-founder Samir Patel said in a telephone interview.

He said the company was working to design its phase III strategy for Fovista, but declined to divulge any details. Ophthotech is based in Princeton, N.J.

Regeneron's Eylea has been selling well since it was approved in the U.S. last November, reflecting the fact that annual treatment costs are about 45% lower and patients need roughly only half as many injections in the eye as with Lucentis.

As a result, Regeneron in April nearly doubled its 2012 sales forecast for Eylea for a second time, to $500-$550 million.

Regeneron has full marketing rights to Eylea in the U.S. and will share overseas profits equally with Bayer if it wins regulatory approval in other countries.

Novartis sells Lucentis outside the United States.