The Food and Drug Administration says that a woman passed away due to a brain infection with Rituxan about 18 months after being administered the last dose of the drug.

Rituxan is a first-of-its-kind treatment for rheumatoid arthritis and is marketed in by Genentech and Biogen Idec, two leading U.S. biotechnology companies. Moreover, it is used to treat non-Hodgkin’s lymphomas.

The patient who died was diagnosed more than one year and a half after not taking the drug anymore as part of an enduring safety clinical extension study, according to a warning issued by MedWatch, the Food and Drug Administration’s reporting system for adverse events. The person had also received chemotherapy agents and radiation treatment for cancer about nine months prior to the development of the infection.

Cases of progressive multifocal leukoencephalitis, the viral infection that led to the patient’s death, have been reported in the past in other people taking the drug for unapproved uses, lupus counting among these. But what the agency wanted to highlight is that the most recent case is the first one reported in a patient taking Rituxan for rheumatoid arthritis.

Tara Cooper, a spokeswoman for Genentech Inc., drew attention to the fact that on the medicine’s label the risks of the rare viral disease were already mentioned, The Associated Press reported. "The patient had a number of confounding factors that make it difficult to assess the potential role, if any, that Rituxan exposure may have played," Cooper stated.