Importance: High serum levels of interleukin 17F (IL-17F) at baseline have been associated with suboptimal response to interferon beta in patients with relapsing-remitting multiple sclerosis.
Objective: To further investigate the role of IL-17F in predicting treatment response to interferon beta-1b in patients with relapsing-remitting multiple sclerosis using the Singulex Erenna IL-17F immunoassay.
Design, setting, and patients: Serum samples were analyzed from 239 randomly selected patients treated with interferon beta-1b, 250 μg, for at least 2 years in the Betaferon Efficacy Yielding Outcomes of a New Dose Study.
Exposure: Treatment with interferon beta-1b, 250 μg, for at least 2 years.
Main outcome measures: Levels of IL-17F at baseline and month 6 as well as the difference between the IL-17F levels at month 6 and baseline were compared between the following: (1) patients with less disease activity vs more disease activity; (2) patients with no disease activity vs some disease activity; and (3) responders vs nonresponders.
Results: Levels of IL-17F measured at baseline and month 6 did not correlate with lack of response to treatment after 2 years using clinical and magnetic resonance imaging criteria. Relapses and new lesions on magnetic resonance imaging were not associated with pretreatment serum IL-17F levels. When patients with neutralizing antibodies were excluded, the results did not change. All patients with levels of IL-17F greater than 200 pg/mL were associated with poor response with some clinical or radiological activity.
Conclusions and relevance: An increase of IL-17F before and early after treatment with interferon beta-1b was not associated with poor response. These data do not support the value of IL-17F as a treatment response indicator for therapy of patients with multiple sclerosis with interferon beta, although high levels of IL-17F greater than 200 pg/mL may predict nonresponsiveness.