NEW YORK (Dow Jones)--Biogen Idec Inc. (BIIB) reported another case of a rare brain infection in users of the multiple sclerosis drug Tysabri in the company's final weekly update Friday.
The latest patient represents the 11th case of progressive multifocal leukoencephalopathy, or PML, since the drug's relaunch in July 2006 and the fourth announced over the past seven updates. Tysabri - sold with Ireland's Elan Corp. (ELN) - was pulled from the U.S. market in 2005 because of PML concerns.
The total amount of cases remains below the risk rate on Tysabri's label, Biogen has said. However, the recent increase raises questions as to whether now is the time to stop the updates and adds to concerns that patients may stop taking Tysabri for a time to avoid developing the infection.
Duration of therapy is believed to play a role in Tysabri's PML risk, but such breaks - referred to as "drug holidays" - are opposed by Biogen and could hurt sales of a key growth driver for the company.
In the latest confirmed case, the patient took Tysabri for 29 doses, continuing a trend as those in the last six reported cases have each had therapy for two years or longer.
The latest patient was located in the U.S. This is notable because it's only the third such U.S. patient. Eight of the previous 10 cases have occurred overseas, and it's unknown why that has been the case.
The PML incidence remains below the long-projected risk of one in 1,000 patients developing the infection. After the previous case, a Jefferies & Co. research note last month put the revised PML incidence at one in 2,490 after 12-month Tysabri therapy; one in 1,400 after 18-month therapy; and one in 680 after 24-month therapy.
Tysabri receives strong support from patients and doctors because of the drug's perceived effectiveness. That support has remained steady because patients are well-aware of the PML risk before they start taking Tysabri for the otherwise debilitating disease of MS.
Nonetheless, the number of PML cases has frustrated Biogen's aim of making Tysabri into a blockbuster drug. The company has invested in treatments for PML and ways to mitigate the infection - once thought to be almost always fatal - and in persuading doctors that PML's risk in Tysabri patients is less severe and less likely. Of the 11 confirmed cases since the relaunch, one has died.
Biogen began issuing weekly updates in January after receiving criticism for its previous policy of disclosing new cases through 8-K filings with the Securities and Exchange Commission. From the start, Biogen had determined July 24 would be the final date because it was around the third anniversary of Tysabri's relaunch, by which time the company expected the risk/benefit profile to be clearer.
Tysabri was pulled from the U.S. market in 2005 after three initial cases, including two deaths.
The Food and Drug Administration allowed Tysabri to be reintroduced in 2006 because of the drug's effectiveness in fighting the degenerative disease, and under monitoring rules and a prohibition on using it in combination with other MS drugs. The system was aimed at reducing PML incidence.
Wall Street Journal