(Adds secondary endpoint, analyst comment)
Jan 8 (Reuters) - An experimental drug from Biogen Idec Inc showed evidence of biological repair of the optic nerve in a mid-stage study in patients with acute optic neuritis, an inflammation of the optic nerve that can lead to vision loss.
The drug is also being tested in patients with multiple sclerosis, an inflammatory disease that attacks the protective covers of nerve cells. Current treatments focus on decreasing inflammation rather than regenerating cells. That study's results are due in 2016, the company said.
Biogen shares were up 2 percent at $361 in premarket trading, after rising as much as 6 percent.
"This is the first clinical trial to provide evidence of biological repair in the central nervous system by facilitating remyelination following an acute inflammatory injury," Alfred Sandrock, Biogen chief medical officer said in a statement.
Remyelination is the regeneration of the insulating myelin sheath of a nerve.
The drug failed to meet the trial's secondary endpoint, including change in thickness of the retinal layers and visual function, Biogen said.
The most common cause of acute optic neuritis is multiple sclerosis, an area where Biogen has produced the leading drugs Tecfidera and Tysabri.
"If successful, this could be a transformative therapeutic approach," Evercore ISI analyst Mark Schoenebaum said in a research note. "The data are encouraging, but certainly not definitive."
The trial on the drug, called Anti-LINGO-1, demonstrated an improvement in recovery of optic nerve latency, or the time it takes for a signal to travel from the retina to the visual cortex. The company said it showed a 34 percent improvement versus a placebo treatment.
The company said that in the intent-to-treat population, which includes patients who did not complete the study, there was a positive trend but results did not reach statistical significance.
Biogen said there were 82 patients in the trial, that the drug was generally well tolerated and that three people experienced severe adverse effects.
A Biogen spokeswoman described the number of people who did not finish the study as being low, but didn't provide a figure.
(Reporting by Caroline Humer; Editing by Bernadette Baum)