Neurofilament light chain (NfL) is a biomarker of neuroaxonal injury in multiple sclerosis (MS). Thalamic atrophy occurs early and may be a sensitive marker of overall brain damage. Ocrelizumab (OCR) reduced brain atrophy and NfL in patients with relapsing MS (RMS) and those with primary progressive MS (PPMS).
To examine the independent impact of OCR and baseline (BL) NfL on thalamic volume (TV) and clinical progression in patients with PPMS and RMS, including those with RMS without acute BL activity (i.e. no gadolinium–enhancing [Gd+] lesions or relapse in the last 3 months).
Patients were from OPERA I/II (RMS, n=1,421) and ORATORIO (PPMS, n=596). Thalamic atrophy was calculated as annualized percentage TV change (PTVC) from Wk 24 to the end of controlled treatment (ORATORIO, Wk 120; OPERA I/II, Wk 96). OCR treatment (vs IFNβ-1a [RMS] or placebo [PPMS]) and log-transformed BL NfL were examined for associations with PTVC (linear regression) and 24-week confirmed disability progression (Cox regression) adjusting for BL demographic and disease characteristics.
In patients with PPMS and RMS, OCR treatment (PTVC: +0.47% and +0.33%, respectively) and lower BL NfL (+0.20% and +0.33% per 2-fold lower NfL) independently associated with a smaller TV reduction (all p<0.005). Adjusting for BL NfL level, Gd+ lesion count, T2 lesion volume and BL disability, OCR still reduced disability progression on Expanded Disability Status Scale (EDSS) (PPMS, hazard ratio [HR]=0.73; RMS, HR=0.65; both p<0.05]), 9-Hole Peg Test (9HPT) (PPMS, HR=0.53, p=0.002; RMS, HR=0.52, p=0.059), Timed 25-Foot Walk (T25FW) (PPMS, HR=0.79, p=0.063), Symbol Digit Modalities Test (RMS, HR=0.54, p=0.002) and time to EDSS 6 (RMS, HR=0.42, p=0.009). In patients with PPMS, higher BL NfL was associated with worsening on 9HPT (HR=1.34 per 2-fold higher NfL), T25FW (HR=1.19) and time to EDSS 7 (HR=1.78) (all p<0.05). In patients with RMS without acute BL activity, higher BL NfL was associated with EDSS worsening (HR=1.49), progression independent of relapse activity (PIRA) (HR=1.61), 9HPT (HR=2.1) and time to EDSS 6 (HR=2.24) (all p<0.05).
Ocrelizumab treatment remained associated with reduced thalamic atrophy and clinical progression after adjusting for baseline NfL and other factors. Higher BL NfL was associated with increased rates of thalamic atrophy and clinical progression in patients with PPMS and those with RMS without acute disease activity.