Background

Pathogenic autoantibodies against aquaporin 4 (AQP4) in neuromyelitis optica spectrum disorder (NMOSD) cause central nervous system injury, with subsequent release of astroglial and neuronal proteins such as glial fibrillary acidic protein (GFAP), neurofilament light chain (NfL), ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) and Tau into the circulation. N-MOmentum is a randomized, placebo-controlled, double-masked trial of inebilizumab, a B-cell-depleting monoclonal antibody (NCT02200770).

Objectives

Investigate relationships of NfL, UCH-L1, Tau and serum (s)GFAP to disease activity and Expanded Disability Status Scale (EDSS) disability in N-MOmentum trial participants with either AQP4-immunoglobulin G (IgG) seropositive or seronegative NMOSD.

Methods

Serum biomarkers NfL, UCH-L1, Tau and sGFAP were measured using the single molecular array (SIMOA; Quanterix) in 1260 serial and attack-related samples from N-MOmentum participants (n=215) and healthy controls (HC; n=25).

Results

At baseline, biomarkers were elevated in subsets of patients with NMOSD (NfL, 16%; UCH-L1, 6%; Tau, 12%; sGFAP, 29%); NfL and UCH-L1 levels correlated with sGFAP (r=0.53 [p<0.001] and 0.18 [p=0.007]). Baseline elevations were significantly associated with increased attack risk (NfL, hazard ratio [HR] 2.5, p=0.01; UCH-L1, HR 2.8, p=0.039; Tau, HR 2.6, p=0.01; sGFAP, HR 3.03, p<0.001). After controlling for baseline sGFAP in Cox regressions, the other markers were not independently associated with attack risk (all HR <2; p>0.05). In the total cohort, a greater proportion of patients had an attack with placebo than inebilizumab (39% vs 12%). All biomarker levels increased after attacks and median-fold increases from baseline (95% confidence interval) trended higher with placebo than inebilizumab, reaching significance with sGFAP (NfL, 1.49 [0.93–3.37] vs 1.30 [0.84–2.14], p=0.4; UCH-L1, 6.70 [1.59–52.4] vs 1.85 [0.89–23], p=0.12; Tau, 2.19 [0.96–9.46] vs 1.09 [0.40–3.7], p=0.23; sGFAP, 20.2 [4.4–98] vs 1.11 [0.75–24.6], p=0.037). Following attacks, NfL correlated with EDSS score at attack assessments (R=0.55; p<0.001); other biomarkers did not correlate with EDSS score after controlling for NfL levels.

Conclusions

In NMOSD, serum NfL, UCH-L1 and Tau levels were higher than in HC; increased baseline sGFAP levels were associated with greater attack risk. Although sGFAP levels showed the greatest increase following attacks, NfL correlated with attack-related disability.

Background

The N-MOmentum trial of inebilizumab included patients with aquaporin 4-IgG seropositive (AQP4+) or seronegative (AQP4−) neuromyelitis optica spectrum disorder (NMOSD).

Objectives

To report AQP4− participant outcomes in N-MOmentum. .......................................................

Methods

Medical histories and screening data for AQP4− patients were assessed independently by 3 clinical experts before enrollment. Majority decision confirmed diagnoses using the 2006 criteria. Myelin oligodendrocyte glycoprotein-IgG (MOG) serology and annualized attack rates (AARs) were tested post hoc. These observations do not account for bias in estimates of effects on the AAR caused by regression to the mean, introduced by inclusion criteria requiring attacks during the 1 to 2 years before study entry.

Results

Only 18/50 AQP4− patients (36%) were eligible for randomization; 17 were randomized, 4 to placebo (1 MOG+) and 13 to inebilizumab (6 MOG+). Reasons for not enrolling prospective AQP4− NMOSD participants were mainly related to lack of fulfillment of MRI findings required by the 2006 criteria.

Owing to limited patient numbers, we compared the on-study to the pre-study AAR for treated participants to assess treatment effects.

For AQP4− participants (n=17), 40 attacks occurred in 23 patient-years of pre-study follow-up with mean AAR (95% confidence interval) of 1.72 (1.23–2.33). For MOG+ participants (n=7), 16 attacks occurred in 8.3 patient-years of pre-study follow-up with an AAR of 1.93 (1.11–3.14). For double-seronegative participants (n=10), 24 attacks occurred in 15 patient-years of pre-study follow-up with an AAR of 1.60 (1.02–2.38).

After receiving inebilizumab, AARs declined in all groups by the end of the randomized controlled period: AQP4− participants (n=13), 0.09 (0.02–0.26), or 3 attacks in 34.2 patient-years; MOG+ participants (n=6), 0.08 (0.002–0.464), or 1 attack in 12 patient-years; double-seronegative participants (n=7), 0.09 (0.011–0.326), or 2 attacks in 22 patient-years.

The benefit was sustained with longer-term inebilizumab exposure. At 120 days into the open-label period (OLP), during which all participants received inebilizumab, the AAR in AQP4− participants (n=17) remained low (0.069 [0.014–0.202]). No attacks were seen in any AQP4−, MOG+ or double seronegative patient during the OLP.

Conclusions

The N-MOmentum trial provides clinically important insight on the difficulty of correctly diagnosing AQP4− NMOSD and suggests that inebilizumab may have a benefit on AAR in these patients.