Rapid plaque clearance with anti-amyloid therapy for Alzheimer's disease: in consideration of donanemab treatment duration from real-world cases

To assess the possibility that individualized duration of donanemab treatment might enable early pausing of therapy, and to explore the possible utility of plasma P-tau²¹⁷ as a biomarker for treatment response monitoring in real-time, two unrelated patients with early-stage Alzheimer's disease were treated with donanemab at the Icahn School of Medicine at Mount Sinai. Clinical progress was monitored via medical chart review, including serial brain MRI, amyloid PET scans, and blood-based biomarker assays (Quanterix Simoa® and Fujirebio Lumipulse®). Both patients achieved complete amyloid clearance as judged by amyloid PET prior to their 6th and 9th infusions, which were significantly earlier than the 12-month mark typically recommended for follow-up amyloid assessment. In agreement with the amyloid PET, concurrently measured plasma P-tau²¹⁷ levels fell within a low range. Treatment was discontinued for both patients. These patients highlight the possibility of individualized treatment durations for anti-amyloid therapy with donanemab, guided by biomarker response. Early cessation following rapid plaque clearance could reduce healthcare costs and minimize exposure to the risk of amyloid-related imaging abnormalities and the generation of neutralizing antibodies. Plasma P-tau²¹⁷ warrants further investigation as a reliable, cost-effective surrogate for PET scans to monitor real-time treatment response and guide the timing of discontinuation.