Rationale and design of the prospective and retrospective observational study of Avonex and Rebif (PROOF) for the treatment of relapsing-remitting multiple sclerosis

Previous studies comparing the two available interferon beta (IFNbeta)-1a products, Avonex and Rebif, for the treatment of relapsing-remitting multiple sclerosis (RRMS) have been limited and of short duration. Therefore, the Prospective and Retrospective Observational Study of Avonex and Rebif (PROOF) was designed to provide long-term (up to 5 years) comparative data on the efficacy, safety, and tolerability of these two agents. Patients with RRMS receiving treatment with either Avonex * 30 mug intramuscularly once weekly or Rebifdagger 44 mug subcutaneously three times weekly from 12 to 24 months are being enrolled and will continue their respective treatments for the 36-month duration of the study. The primary efficacy endpoint will be change in brain parenchymal fraction, which will be evaluated through magnetic resonance imaging scans by blinded radiologists. Secondary endpoints will include the following: relapse rates; intravenous steroid use; the proportion of patients with an increase of greater than or equal to1 point on the Expanded Disability Status Scale (EDSS) and with an increase in EDSS score sustained for 6 months; mean change in EDSS score; cumulative number of new or enlarging T2 lesions; T2 and T1 lesion volumes; gadolinium-enhanced lesion number and volume; and safety and tolerability. The study design of PROOF will permit more meaningful conclusions regarding the optimal IFNbeta-1a product for the long-term treatment of patients with multiple sclerosis.