Multiple sclerosis (MS) is a complex neurological disease that affects the central nervous system, leading to a wide range of symptoms and, over time, disability. One of the most important questions for people living with MS and their healthcare providers is whether medications can delay the progression of disability. The answer is nuanced, as it depends on the type of MS, the specific medication, and the stage of the disease.
MS medications, often called disease-modifying therapies (DMTs), primarily aim to reduce inflammation, prevent relapses, and limit new damage in the nervous system. In relapsing-remitting MS (RRMS), where patients experience flare-ups followed by periods of remission, many DMTs have been shown to reduce the frequency of relapses and new lesions visible on MRI scans. This reduction in inflammatory activity often correlates with a slower accumulation of disability, at least in the earlier stages of the disease.
However, disability progression in MS can occur in ways that are independent of relapses. This phenomenon is known as progression independent of relapse activity (PIRA). It means that even when relapses are controlled, some patients continue to experience worsening disability due to ongoing neurodegeneration and chronic inflammation. This is particularly relevant as RRMS transitions into secondary progressive MS (SPMS), a phase characterized by steady worsening of symptoms without clear relapses.
Recent research has shown that some newer medications can slow down this progression. For example, tolebrutinib, a Bruton’s tyrosine kinase (BTK) inhibitor, has demonstrated the ability to reduce disability progression by about 30% in people with non-relapsing SPMS. This drug works by targeting immune cells involved in both inflammation and the chronic damage that leads to disability worsening. Other therapies like ocrelizumab have shown benefits in reducing relapses in active SPMS and slowing progression in primary progressive MS (PPMS), though their effects on disability progression can vary depending on disease activity.
Interestingly, dosing schedules of some anti-CD20 therapies, such as rituximab and Kesimpta, have been studied to see if less frequent dosing affects outcomes. Findings suggest that extended-interval dosing does not increase relapse rates or disability progression, indicating that some patients might maintain disease control with lower or less frequent doses, though more research is needed to confirm these results.
Despite these advances, treating progressive forms of MS remains challenging. Many DMTs effective in RRMS do not have the same impact on disability progression in SPMS or PPMS, especially when the disease is inactive or non-relapsing. In these cases, symptom management and lifestyle interventions become crucial parts of care. Some medications approved for RRMS are used off-label in progressive MS, but their effectiveness varies.
In summary, MS medications can delay disability progression, particularly in relapsing forms of the disease by reducing inflammation and relapses. For progressive MS, newer therapies show promise in slowing disability worsening, but the effect is generally more modest and varies by individual. Ongoing research continues to explore better treatments that target the underlying mechanisms of progression beyond inflammation, aiming to improve long-term outcomes for all people with MS.
