Abstract
OBJECTIVES: To evaluate the cost-effectiveness of donanemab, an anti-amyloid-β monoclonal antibody recently approved in Australia, for treating early-stage Alzheimer disease with confirmed amyloid-β pathology from healthcare system and societal perspectives. DESIGN: A Markov microsimulation model simulating long-term Alzheimer disease progression, treatment costs and health outcomes for donanemab compared with standard care. SETTING, PARTICIPANTS: Australian healthcare context, applying published clinical and economic inputs. A hypothetical cohort of people with early symptomatic Alzheimer disease, consistent with TRAILBLAZER-ALZ eligibility criteria: mean age 75 years, amyloid-β-positive, with mild cognitive impairment or mild dementia because of Alzheimer disease and excluding individuals with APOEE4 homozygotes, in line with the Australian labelling. Donanemab administered every 4 weeks with magnetic resonance imaging (MRI)-based amyloid-β-related imaging abnormalities monitoring and treatment suspension upon amyloid-β clearance or progression to severe Alzheimer disease, compared with standard care. MAIN OUTCOME MEASURES: Incremental costs, quality-adjusted life years (QALYs) and incremental cost-effectiveness ratios (ICERs). Secondary analyses included sensitivity and distributional equity analyses. RESULTS: Donanemab increased total healthcare costs ($300,689 vs. $178,121) and societal costs ($389,113 vs. $283,618) compared with standard care per capita, while improving health outcomes (4.38 vs. 4.01 QALYs) per capita. The ICER was $342,424 per QALY from the healthcare perspective and $294,701 per QALY from the societal perspective, exceeding frequently cited Australian willingness-to-pay thresholds. Sensitivity analyses identified drug cost and efficacy as key drivers of uncertainty. Distributional analysis suggested inequitable health gains by remoteness because of differences in diagnostic and treatment infrastructure. CONCLUSION: Donanemab provides clinical benefits but is unlikely to be cost-effective under current Australian thresholds. Policymakers should balance economic evidence with unmet need, equity considerations and healthcare sustainability when making reimbursement decisions. Further research using real-world evidence and disaggregated analyses by geography and socioeconomic status is warranted.