Summary
An international group of MS experts has proposed changing how MS is described. In a paper published in Nature Reviews Neurology, a workgroup convened by the International Advisory Committee on Clinical Trials in MS and co-led by the National Multiple Sclerosis Society (NMSS) and the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS) outlines a roadmap for moving toward new, biologically based disease descriptors.
The proposal reflects advances in our understanding of the biological processes involved in MS and recognizes that the current disease descriptors – relapsing-remitting MS (RRMS), secondary progressive MS (SPMS) and primary progressive MS (PPMS) – don’t fully capture the MS disease spectrum.
The experts recommend gradually moving toward disease descriptors that better reflect the biology of MS. During this transition, relapsing and progressive would continue to be used, while the current descriptors and terms like “active” and “non-active” would be phased out. Putting these new disease descriptors into practice will take time and ongoing collaboration among the research community, policymakers, clinicians, and people living with MS.
Background
Each person will experience MS differently. This includes how their disease progresses. Disability progression can result from relapses. Progression can also worsen gradually, even without relapses, because of ongoing inflammation and other changes in the brain and spinal cord (also called progression independent of relapse activity). Both play a role in disability progression over time, starting in the early stages of MS and continuing throughout the disease. The current disease descriptors don’t fully capture these processes.
Disease descriptors are used in MS research and clinical trials to study MS and develop new treatments, including disease modifying therapies (DMTs). In clinical care, they help healthcare professionals decide which DMT may be best for a person.
Disease descriptors are also used when treatments are approved by Health Canada and when provincial and territorial governments make decisions about which treatments will be covered. These decisions can affect whether a treatment is accessible to someone with MS.
Impact
This proposal does not immediately change how MS is diagnosed, described or treated. RRMS, SPMS and PPMS remain the disease descriptors commonly used in healthcare, research, and reimbursement practices.
The authors recommend introducing the new approach gradually. The roadmap starts with short-term work to put it into practice, followed by longer-term work to validate and refine the new ways of describing the disease.
Over time, a more biologically informed approach could help people with MS and their healthcare teams better understand what is happening in the disease and support more personalized treatment decisions leading to improved health outcomes.
Changes to how MS is described could also impact access to DMTs. In Canada, treatment coverage is often based on specific disease descriptions. If these descriptions change, drug plans will also need to change to reflect the new approach.
This is a global shift in how MS is described, and it will take time. Researchers, healthcare professionals, regulators, governments, and people living with MS will need to work together to support this change.
Reference
Thompson, A.J., Lublin, F.D., Rechtman, L. et al. Towards a biologically informed description of multiple sclerosis disease course — a roadmap for transition. Nat Rev Neurol (2026). https://doi.org/10.1038/s41582-026-01249-0