Interferon alpha-2a treatment of relapsing-remitting multiple sclerosis: disease activity resumes after stopping treatment.

We evaluated the long-lasting effects of systemic high-dose recombinant interferon alpha-2a (rIFNA) in relapsing-remitting (RR) MS after discontinuing treatment in a single-blind randomized placebo-controlled trial with 20 RR clinically definite MS patients using either nine million IU intramuscular rIFNA (n = 12) or placebo (n = 8) every other day for 6 months. Follow-up continued for a further 6 months without IFN treatment. In rIFNA-treated patients, main outcome measures, significantly different from placebo during treatment, returned, after discontinuing treatment, to values similar to placebo or baseline. Active MRI lesions per patient increased from 0.08 +/- 0.08 to 1.2 +/- 0.4 (p < 0.02), number of patients with clinical MRI signs of disease activity from 2 of 12 to 8 to 12 (P < 0.04), lymphocyte IFN gamma production from 3.0 +/- 0.7 to 12.4 +/- 2.2 IU/mL (p < 0.01), lymphocyte tumor necrosis factor alpha production from 5.8 +/- 0.9 to 18.9 +/- 6.3 pg/mL (p < 0.05). All side effects of rIFNA treatment disappeared after discontinuing the drug. The reduction of clinical MRI signs of disease activity and the immunologic effects were temporary and restricted to the period of rIFNA administration. The depression of many immunologic and clinical MRI responses during drug administration and their simultaneous return to baseline after discontinuing the drug strongly argue all observed changes were related to drug administration.