Long-term follow-up for multiple sclerosis patients initially treated with interferon-beta and glatiramer acetate

Objective: Our goal was to compare subjects treated with glatiramer acetate (GA) and interferon-beta (IFN-13) in terms of long-term clinical outcomes. Methods: Subjects enrolled in the CLIMB who initiated either GA or IFN-13 within five years of disease onset and prior to 2008 were identified (n = 150 for GA and n = 144 for IFN-13). The two treatment groups were compared in terms of long-term clinical outcomes: time to EDSS 4, time to EDSS 6 and EDSS score seven years after treatment initiation. Baseline confounders included in our analysis were age, gender, disease duration, attacks in the previous year, EDSS prior to treatment initiation, and year of treatment initiation. The groups were compared using three approaches to handle confounders: multiple regression adjusting for confounders, adjustment for the propensity score, and inverse probability of treatment weighting. In addition, we assessed potential predictors of differential treatment response using multiple regression models including appropriate interaction terms. Results: Subjects initially treated with GA had a slightly higher hazard of reaching EDSS 4 and EDSS 6, but the difference between the groups was not statistically significant (adjusted HR for EDSS 4 = 1.48; 95% CI: 0.77,2.84; p =.24; adjusted HR for EDSS 6 = 1.46; 95% CI: 0.70,3.05; p =.316). For the EDSS score at year 7, there was also only a small difference between the groups. Subjects treated with GA had a longer time until treatment cessation (adjusted HR = 0.70; 95% CI: 0.53,0.93; p =.012). The interaction models did not show strong evidence for the baseline predictors being associated with treatment response. Conclusions: Subjects treated with glatiramer acetate and interferon-beta had similar long-term clinical course.