An enrichment strategy for clinical trials in SPMS

Abstract

Background: We recently compared clinical outcomes in secondary progressive MS (SPMS) clinical trials and found an association of timed 25 foot walk (T25FW) worsening events and baseline disability scores. It is unclear whether disability worsening in clinical trials is comparable to that seen in clinical practice. Objective: The objective of this study is to compare disability worsening between the IMPACT and ASCEND data sets and data from the Calgary MS clinic and to characterize the association of baseline T25FW and expanded disability status scale (EDSS) scores with disability worsening. Methods: We combined the three data sets and investigated the impact of baseline characteristics on disability worsening with a logistic regression model. We calculated T25FW, EDSS, and ‘EDSS or T25FW’ worsening events as a function of ascending cut-off baseline disability scores. Results: Data source was not associated with T25FW worsening at 12 months. There was a strong association of baseline T25FW and EDSS cut-off scores with T25FW worsening. No such association was present for the EDSS and ‘EDSS or T25FW’. Conclusion: Our results suggest that it is possible to ‘enrich’ a trial cohort for expected T25FW worsening events using specific baseline T25FW and EDSS cut-off scores. These analyses inform the selection of inclusion criteria for clinical trials in SPMS.