Plasma neurofilament light (pNfL) was associated with characteristics indicative of future clinical and radiologic disability progression in MS, according to findings published in Neurology. Jens Kuhle, MD, PhD, and colleagues examined the potential role of pNfL as a biomarker of disease progression and response to treatment in 4,185 samples from 1,452 patients with secondary progressive MS (SPMS) and 1,172 samples from 378 patients with primary progressive MS (PPMS). Baseline pNfL levels were higher in SPMS than in PPMS (P<0.0001), and higher baseline pNfL levels were associated with older age, higher Expanded Disability Status Scale score, more gadoliniumenhancing lesions, and higher T2 lesion load (all P<0.05). Regardless of treatment, high compared with low baseline pNfL levels were associated with significantly higher risks of confirmed 3- and 6-month disability progression, earlier wheelchair dependence, cognitive decline, and higher rates of brain atrophy. Baseline pNfL levels were associated with eventual disability progression and the extent of brain atrophy irrespective of presence or absence of acute disease activity. Levels of pNfL were lower in treated patients and higher in those who experienced disability progression.