Quantitative Measures of Time to Loss of 15% Vital Capacity and Survival Extension in Slowly Progressive Amyotrophic Lateral Sclerosis (ALS) Patients Treated with the Immune Regulator NP001 Suggests an Immunopathogenic Subset of ALS

<b>Background/Objectives</b>: Overall survival in patients with amyotrophic lateral sclerosis (ALS) is linked to the rate of predicted respiratory vital capacity (PVC) loss. The objective of this study was to test whether changes in quantitative PVC measures over time linked to survival would define an immunopathogenic subset of ALS responsive to NP001, a regulator of innate immunity. <b>Methods</b>: In a retrospective study, data from intent-to-treat (ITT) population of two phase 2 trials of NP001 were evaluated for over time changes in PVC, time-to-event (TTE) loss of 15% PVC and PVC change from baseline, as linked to survival outcomes in patients treated with NP001 vs placebo. <b>Results</b>: Treatment with NP001 was associated with a significantly lower risk compared to placebo in the loss of 15% PVC over six months (<i>p</i> = 0.01; HR = 0.60, 95% CI: 0.39, 0.90). Data from the two trials were subsequently divided by a disease progression rate (DPR) value of 0.50 units of ALSFRS-R score lost per month for analysis of slow vs. rapid disease. In ALS patients with slowly progressive disease (DPR < 0.50), TTE PVC changes from baseline were slowed (<i>p</i> < 0.0005) and overall survival extended significantly (18.5 months) in NP001-treated vs. placebo groups. The rapidly progressive ALS patients (DPR ≥ 0.50) treated with NP001 showed no significant difference in PVC change or survival from the placebo group. <b>Conclusions</b>: These hypothesis-generating observations suggest that inflammation might play a significant role in the loss of respiratory function in a major subset of ALS patients.