NEFL and myeloid sarcoma: The search for treatments to prevent disability progression in MS remains a major unmet need.31 So far, only a few trials in progressive MS have included neurofilaments as markers of disease worsening and treatment response, and all these studies have focused on NfL.6,12,27,32 For example, the SPRINT-MS study,32 which demonstrated that ibudilast could reduce brain atrophy in progressive MS, found no difference in either serum or CSF NfL between treatment arms, possibly due to the limited anti-inflammatory effects of ibudilast.