Interferon beta is the first-line treatment for relapsing-remitting multiple sclerosis, but the drug can induce neutralising antibodies against itself, which might reduce its effectiveness. Per Soelberg Sorensen from Copenhagen University Hospital, Denmark, and colleagues measured neutralising antibodies every year for up to five years among 541 patients with multiple sclerosis, randomly selected from all patients who started treatment with interferon beta in Denmark between 1996 and 1999.
The time to first relapse was substantially longer (by 244 days) for patients who were antibody-negative after one year of interferon-beta treatment compared with patients who were antibody-positive. The yearly relapse rate was increased more than 50% in patients who developed antibodies compared with those who did not.
Patients developed neutralising antibodies independent of age, sex, disease duration, and prognosis at the start of treatment. The presence of antibodies did not affect overall disease outcome.
Per Soelberg Sorensen comments: "Our findings suggest that the presence of neutralising antibodies against interferon beta reduces the clinical effect of the drug. In patients who are not doing well on interferon beta, the presence of such antibodies should prompt consideration about a change of treatment to other drug therapies such as glatiramer acetate or mitoxantrone."