Elan Corp and Biogen Idec have started enrolling for a major head-to-head trial comparing the firm’s Tysabri with two other multiple sclerosis blockbusters, Teva Pharmaceutical Industries’ Copaxone and Merck KGaA’s Rebif.

The 1,800-patient, 27-country Phase IIIb study, called SURPASS, is designed to evaluate switching to Tysabri (natalizumab) from Copaxone (glatiramer acetate) or Rebif (interferon beta-1a) in patients with relapsing remitting MS. It will provide direct comparative data of different treatment options for patients who experience breakthrough disease activity, Elan and Biogen added.

SURPASS will also look to determine whether early use of Tysabri leads to better outcomes for MS patients. Carlos Paya, president at Elan, said that “despite significant advances in treatment, the unmet medical need for many MS patients remains great and this study supports our commitment to continuing to advance the standard of care”.

Currently the primary completion date for the trial is December 2012, and the study completion date is May 2013.