Patients were evaluated, on average, every 4 months. At each visit an interval history of any relapse, Incapacity Status Scale, Functional Systems Scale, Expanded Disability Status Scale (EDSS), and a proprietary graded neurologic examinations were obtained.
Annual MRI of the brain using a contrast-enhanced MS protocol was also obtained for most patients.
Breakthrough disease was defined as continued clinical relapses, new T2 or enhanced lesions on MRI, or worsening of EDSS or neurologic examination.
Five patients did not tolerate the increase in frequency of administration. IFNβ neutralizing antibody testing was performed on 25 patients while on twice-weekly dosing, and one patient who failed twice-weekly IFNβ had consistently elevated titers on two determinations (4%).
African-American patients, patients with a higher EDSS score when switching, and patients with a longer duration of stability on once-weekly treatment were less likely to respond.