Glatiramer acetate versus interferon beta-1a for subcutaneous administration: comparison of outcomes among multiple sclerosis patients.

ABSTRACT

INTRODUCTION: We compared the outcomes of multiple sclerosis (MS) patients treated with either glatiramer acetate (GA) (Copaxone, Teva Pharmaceutical Industries, Israel) or interferon beta-1a for subcutaneous administration (IFN beta-1a-SC) (Rebif, Merck Serono, Switzerland). METHODS: Data were obtained from i3's Lab Rx Database from July 2001 to June 2006. We established an 'intent-to-treat' (ITT) cohort (n=845) of patients diagnosed with MS who began therapy on either GA (n=542) or IFN beta-1a-SC (n=303) and had continuous insurance coverage from 6 months before to 24 months after the date they began taking the medication. We also created a 'continuous use' (CU) cohort (n=410) of individuals who, in addition to the criteria listed above, used either GA or IFN beta-1a-SC within 28 days of the end of the 2-year-post period. Using multivariate regressions, we examined both the 2-year total direct medical costs and the likelihood of relapse associated with the use of these two MS medications. We defined relapse as either being hospitalised with a diagnosis of MS, or being diagnosed with MS during an outpatient visit and then prescribed steroids within a 7-day period. All regressions controlled a wide range of factors that have potentially affected outcomes. RESULTS: In the ITT cohort, patients who started therapy on GA had a significantly lower 2-year risk of relapse (5.92% versus 10.89%; P=0.0305), as well as significantly lower 2-year total medical costs (US$41,786 versus US$49,030; P=0.0002). In the CU cohort, patients who used GA also had a significantly lower 2-year risk of relapse (1.94% versus 9.09%; P=0.0049) and significantly lower total medical costs (US$45,213 versus US$57,311; P<0.0001). CONCLUSIONS: Results indicate that, compared with the use of IFN beta-1a-SC, use of GA is associated with significantly lower probability of relapse as well as significantly lower 2-year total direct medical costs. In addition, these results are more pronounced among patients defined as continuous users.