Background

In clinical trials, the probability of confirmed disability worsening (CDW) is significantly lower with intramuscular (IM) interferon beta-1a (IFNβ1a) and peginterferon beta-1a (PEG) treatment than with placebo in patients with relapsing forms of multiple sclerosis (RMS). Registry data provides information on disability outcomes with long-term treatment.

Objectives

To examine the long-term effects of IM IFNβ1a and PEG on real-world effectiveness in participants with RMS from the North American Research Committee on Multiple Sclerosis (NARCOMS) registry.

Methods

This analysis included NARCOMS participants diagnosed with RMS who initiated IM IFNβ1a treatment between April 2004 and October 2019 (N=760) or PEG between October 2014 and October 2019 (N=116). Patient-reported outcomes were collected every 6 months. The primary endpoint was 6-month CDW, defined as a ≥1-point increase in Patient Determined Disease Steps (PDDS) score sustained for ≥6 months. Separate analyses were conducted in the IM IFNβ1a and PEG cohorts. A Kaplan-Meier analysis assessed the cumulative probability of CDW; participants were censored if they discontinued treatment or had no additional follow-up. Only participants who completed ≥2 surveys with treatment history and ≥3 surveys with PDDS history were included in the CDW analysis (IM IFNβ1a: N=760; PEG: n=81). Progression to secondary progressive multiple sclerosis (SPMS) was analysed in IM IFNβ1a participants who completed ≥50% of their surveys (n=630) and in PEG participants (n=102).

Results

At the first survey on treatment in IM IFNβ1a and PEG participants, the mean age was 49.7 and 53.0 years, respectively, the mean (standard deviation [SD]) disease duration was 11.1 (8.6) and 15.8 (7.9) years, respectively, and 8.4% and 91.2% had prior disease modifying therapy (DMT) use, respectively. The median PDDS score at the first survey was 2.0 for both populations, indicating moderate disability. The cumulative probability of remaining free of CDW was 77.6% and 43.6% at 2 and 11 years of IM IFNβ1a treatment, respectively, and 84.4% at 2 years of PEG treatment. The cumulative probability of participant-reported progression to SPMS was 1.2% and 12.0% at 2.5 and 11 years in IM IFNβ1a participants, respectively, and 3.3% at 2.5 years in PEG participants.

Conclusions

These results support clinical trial data showing the effectiveness of IM IFNβ1a and PEG in preventing CDW and demonstrate their long-term effectiveness in RMS patients.

This study is funded by Biogen. Biogen funded the analyses and writing support for this abstract. Writing support was provided by Ashfield Healthcare Communications (Middletown, CT, USA).