The prescribing label for Biogen Inc's big-selling oral multiple sclerosis drug Tecfidera has been updated to include a warning of potential liver injury that could require hospitalization, the company said on Wednesday.
However, the updated label says signs of liver injury resolved when those patients stopped taking the medicine.
Tecfidera, the world's top-selling oral MS treatment, accounts for about a third of Biogen revenue. It had sales of $1.03 billion in the third quarter.
The new liver injury information can be found in a warning section under prescribing information on the drug's website tecfidera.com. Biogen said the label changes were finalized with the U.S. Food and Drug Administration on Jan. 19.
"Clinically significant cases of liver injury have been reported in patients treated with Tecfidera in the postmarketing setting. The onset has ranged from a few days to several months after initiation of treatment with Tecfidera," the warning reads.
A Biogen spokeswoman said there have been 14 cases of liver injury reported out of some 230,000 patients treated with Tecfidera.
Symptoms of liver injury include significant elevations above normal of serum aminotransferases and bilirubin, the warning says.
While the abnormalities resolved when patients stopped taking the medicine, some cases required hospitalization. None of the reported cases resulted in liver failure, liver transplant, or death, the warning says.
Liver enzyme monitoring is standard practice for many multiple sclerosis drugs, so the warning does not represent an added burden for prescribing physicians. It remains to be seen if this tempers enthusiasm for the widely-used medicine or if it will hurt sales.
"While this is something to be highlighted to physicians, in my opinion this is not going to materially change market share or future (sales) projections," said RBC Capital Markets analyst Michael Yee, who forecast 2017 Tecfidera sales exceeding $4 billion.
"There was already mention of some rare cases of elevated liver enzymes in the initial label," Yee noted.
Biogen is scheduled to report fourth-quarter results on Thursday and likely will be asked to discuss the implications of the updated Tecfidera warning.
Biogen shares were up 9 cents at $273.91.
(Reporting by Bill Berkrot; Editing by Alan Crosby)