['Adaptive seamless designs (ASDs) have been proposed to test multiple candidate compounds using an interim decision point which allows potentially effective therapies to be taken into the next design stage and to be assessed using a phase III outcome.', 'To determine whether ASDs are feasible in secondary progressive multiple sclerosis (SPMS) and to compare them with conventional trial designs.', 'We develop an innovative adaptive trial design for SPMS, which builds on recent developments in statistical methodology. A literature search and individual clinical datasets were used to inform a framework to run simulations to evaluate the proposed design.', 'ASDs are feasible in SPMS with MRI informing an interim decision point and Expanded Disability Status Scale (EDSS) as the final disability endpoint. Furthermore ASDs are more efficient than conventional designs with sample size savings of up to 40%. Sample sizes of 1000-1250 patients are sufficient to test up to four experimental treatments. Controlled recruitment is important to realize the full benefits of ASDs.'] Does a novel adaptive design strategy increase the efficiency of clinical trials in secondary progressive multiple sclerosis?