CADTH’s findings remained aligned with the sponsor’s: the addition of eculizumab to standard of care (SOC) is not a cost-effective option at a willingness-to-pay (WTP) threshold of $50,000 per quality-adjusted life-year (QALY). CADTH accounted for some limitations, including changing the model’s relapse definition, selecting an alternate parametric distribution for time to first relapse, assuming lifelong treatment, capturing costs associated with administration and vaccination, and assuming eculizumab would be administered in outpatient clinics. In CADTH’s base case, eculizumab plus SOC was associated with an incremental cost-effectiveness ratio (ICER) of $1,508,152 per QALY gained compared with SOC alone in neuromyelitis optica spectrum disorder (NMOSD) patients who are anti-aquaporin-4 (AQP4) antibody positive. A price reduction of 96% would be required for eculizumab plus SOC to achieve an ICER below a WTP threshold of $50,000 per QALY. The results of CADTH’s reanalysis are highly dependent on the treatment effects of eculizumab plus SOC compared to SOC alone. Several limitations were associated with the PREVENT trial (e.g., the absence of relevant outcomes related to subsequent relapses after the first relapse; high rates of major protocol deviation) that could not be addressed by CADTH. In the submitted model, the majority of the incremental clinical benefits were found to occur beyond the trial observed period; there is high uncertainty associated with this extrapolation. The cost-effectiveness of eculizumab compared to rituximab, mitoxantrone, or intravenous immunoglobulin (IVIG) is unknown in the absence of both direct and indirect treatment comparisons. Interpretation of the economic results therefore warrants careful consideration.