* Biogen working on test for virus related to PML
* Says risk of PML less than originally believed
* Physicians expected to increase Tysabri use
By Toni Clarke
BOSTON, March 25 (Reuters) - Biogen Idec Inc (BIIB.O) said on Wednesday it is developing a test that can identify the presence of a virus that can cause a potentially deadly brain infection in certain patients taking its multiple sclerosis drug Tysabri, and hopes to have it available by year-end.
Cecil Pickett, Biogen’s head of research and development, said the company is working on an antibody-based test that can ascertain the presence in a patient’s blood of the JC virus, which can cause progressive multifocal leukoencephalopathy, or PML.
Tysabri, which Biogen co-markets with Ireland’s Elan CorpELN.I, is the biotech company’s most important product with 2008 sales of $813 million. But sales have been hurt by the drug’s association with PML.
It was withdrawn from the market in 2005 but reintroduced in July 2006 with stricter safety warnings as patients with the degenerative disease were willing to assume the risk given the drug’s clear benefits over other treatments.
Tysabri not only delays progression of MS but in some cases has shown improvement of disability.
Last month, Biogen scaled back growth projections for the drug, conceding it will not meet its previous forecast of 100,000 patients on Tysabri by the end of 2010.
But Dr. Al Sandrock, Biogen’s senior VP of neurology R&D, said the risk of developing PML appears to be less than originally believed.
Speaking at Biogen’s R&D Day for analysts and investors, Sandrock said since Tysabri’s reintroduction the PML rate is about 1 in 4,000 over 12 months of exposure. It was originally thought to be closer to 1 in 1,000.
Pickett said the company is placing a very high priority on developing the JC virus test, and hopes to have it available by the end of this year. But he said greater exposure to the virus does not necessarily predispose a patient to PML.
Other factors relating to a person’s immune system or mutations in the virus could also be involved, he said.
“It is a complicated research program and we need to sort these things out before we give guidance,” he said.
Five cases of PML have emerged in patients taking the drug since last July, and one has died.
Cambridge, Massachusetts-based Biogen emphasizes that patients who develop PML can now undergo a process called plasma exchange that removes Tysabri from their blood, meaning the disease is not necessarily fatal, which is helping give more confidence to physicians.
There have been suggestions that long-term Tysabri users stop taking the drug for a time — a so-called drug holiday — in order to reduce PML risk. Sandrock said Biogen is recommending against drug holidays as it likely decreases the drug’s benefit and may not improve safety.
“Within months you get a return of disease activity,” he said.
Roughly 60 percent of physicians believe Tysabri’s benefit outweigh its risk, Pickett said, down from 64 percent before the cases emerged in July. Still, data shows 74 percent of physicians expect to increase their use of the drug over the next six months.
Biogen’s shares closed up 67 cents, or 1.3 percent, at $51.52 on Nasdaq on Wednesday. (Additional reporting by Bill Berkrot in New York)
Reporting by Toni Clarke; Editing by Bernard Orr