Drug manufacturer Novartis has reported that two people with MS taking the oral drug fingolimod (FTY720) in clinical trials experienced problems with infections, leading to a fatality in one case. The firm said the role of the medicine in the cases was unclear and that the trial will continue.
Independent experts recommended that clinical trials with the drug should continue as planned.
Novartis said it was in talks with health authorities and experts to try and improve awareness of the risks of infections and how these may be reduced.
"Both cases involved confounding factors, including the use of very high doses of steroids in the first patient and the delayed use of antiviral therapy in the second patient," it said.
The company said FTY720's role in the cases was unclear but could not be excluded, since its mechanism of action leads to suppression of the immune system, which can increase the risk of infection.
Novartis has previously stated that it expects to submit the once-daily therapy for approval before the end of 2009 with a view to launching the drug in 2010.