Early treatment responses to peginterferon beta-1a are associated with longer-term clinical outcomes in patients with relapsing-remitting multiple sclerosis: Subgroup analyses of ADVANCE and ATTAIN

•Early peginterferon beta-1a initiation was associated with better 2-year outcomes.•Early treatment reduced black hole conversion from new/enlarging T2 or Gd+ lesions.•Peginterferon beta-1a Q2W increased rates of no evidence of disease activity (NEDA).•MRI activity and NEDA status at 2 years predicted clinical outcomes at 3–4 years.•Improved disease control was seen in newly and non–newly diagnosed patients.