Interferons were introduced for multiple sclerosis in the early 1990s, after US-Canadian trials showed effects on clinical relapse rate and magnetic resonance imaging (MRI) spots, which were taken as surrogate outcomes for disability.1 The drug companies who marketed the interferons, and later glatiramer acetate, were given extended patent protection under the Orphan Drug Act. Under the terms of this act surrogate markers of response to treatment can be relied on if experts certify their validity. The lack of data on hard outcomes of disability, such as the need to use a stick or wheelchair, was accepted because multiple sclerosis is a 30-40 year disease, with only half of those affected becoming moderately disabled in a decade, and keeping trials intact beyond a few years proved difficult.

Many specialists thought the visually obvious spots on MRI “were the disease.” As a result MRI scanning soon became indispensable for multiple sclerosis trials and individual high profile MRI centres capitalised on lucrative contracts with industry. Over the next two decades, little effort was made to validate the suppression of MRI spots against hard disease outcomes. Amid the enthusiasm for short term MRI monitoring of the impact of interferons, their lack of impact on long term disability (despite …