Two more cases of a rare brain infection have emerged in users of the multiple-sclerosis drug Tysabri, sold by Biogen Idec Inc. and Elan PLC, the first such incidences since Biogen stopped updating investors of the situation in July.
At that time, Biogen had confirmed 11 cases of progressive multifocal leukoencephalopathy, or PML, since the drug's relaunch in July 2006; Tysabri was pulled from the U.S. market in 2005 because of PML concerns.
A Biogen spokeswoman said the Cambridge, Mass., biotech company is neither commenting on nor confirming the existence of additional cases as long as the PML rate is consistent with the rate of one-in-1,000 patients implied by the label. The new cases appear to be in line with the label's rate.
An editorial published in the New England Journal of Medicine last week revealed a new case that occurred in Europe.
The latest case, also in Europe, was confirmed by Ralf Gold of the Ruhr University Bochum in Germany, who presented the case at the European Committee for Treatment and Research in Multiple Sclerosis that ended Saturday.
Like any public company, Biogen is required to disclose developments deemed material to its business, but the biotech company has said Tysabri's risk profile is accurately detailed in its label after providing weekly updates on new PML cases through July 24, the third anniversary of Tysabri`s relaunch.
Duration of therapy is believed to play a role in Tysabri's PML risk as most cases occurred after patients took the drug for more than a year. Biogen has opposed patients taking treatment breaks--referred to as "drug holidays"--because it can cause MS symptoms to return.
As of June 30, about 43,300 patients were taking Tysabri, with more than 30,000 on it for more than a year, and about 10,000 on it for more than two years.
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.
Wall Street has closely watched the number of cases in gauging Tysabri's sales trajectory because it is the key growth driver for both companies.
Sanford Bernstein analyst Geoffrey Porges said the two new cases "[add] to the dissatisfaction about the company's decision to suspend regular disclosure of the rate of cases, particularly as a large bolus of patients are now reaching what appears to be a point of increased event risk."
Mr. Porges said the new cases were "not necessarily alarming" because the ratio remains below the label-implied rate, but he stressed that there seems to be a connection to PML risk and duration of therapy.
PML re-emerged in Tysabri patients in July 2008, two years after the relaunch, and 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.