Progression Independent of Relapse Activity in Multiple Sclerosis Subtypes

Disability accumulation can occur with relapse associated worsening (RAW) and with progression independent of relapse activity (PIRA). Prior studies have demonstrated that PIRA is common, occurs frequently in early multiple sclerosis (MS), and happens even with highly effective MS therapies. (NEJM JW Neurol Jan 2021 and JAMA Neurol 2020; 77:1132). To further examine the relative contributions of RAW and PIRA to disability progression, investigators evaluated more than 27,000 patients with up to 15 years' MS duration.

In relapsing-remitting (RR) MS, PIRA led to sustained disability more often than RAW did in real-world datasets (47.3% vs. 26.9%) and in phase 3 trials (34.5% vs. 32.7%). PIRA led to sustained disability in 76.7% to 77.7% in sec…