Neutralizing antibodies to 500 μg interferon beta-1b: 28-month results of the IDEAS extension trial

The Interferon Dose Escalation Assessment of Safety extension trial monitored neutralizing antibodies to interferon beta-1b in patients who currently or had previously received the double dose ( 500 mu g) for up to 28 months. Fifteen patients entered the extension trial; five patients were neutralizing antibody-positive at the start of the trial. The present study demonstrates that when neutralizing antibodies develop in patients receiving higher doses of interferon beta-1b they tend to persist for a prolonged period, although neutralizing antibody titers tend to decrease over time and some patients may revert to neutralizing antibody-negative status.