Clarity AD (lecanemab phase 3 trial imaging)

Clarity AD is the phase 3 trial of lecanemab, an anti-amyloid antibody, in early Alzheimer disease. Eisai sponsored it with funding from Biogen. An 18-month double-blind core phase compared lecanemab 10 mg/kg every two weeks with placebo and was followed by an open-label extension. The trial MRI tracks amyloid-related imaging abnormalities (ARIA) under treatment. This entry records what the publications say about that imaging; the images are not available outside the sponsor.

Composition

The core phase included 1795 people, 897 on placebo and 898 on lecanemab; 938 were women. 1107 had mild cognitive impairment due to Alzheimer disease and the rest mild Alzheimer dementia. In the open-label extension, 1612 people received at least one dose of lecanemab.

Acquisition

Non-contrast brain MRI was acquired on 1.5 T or 3 T scanners at screening and at weeks 9, 13, 27, 53 and 79 of the core phase. The standard protocol had a sagittal 3D T1-weighted scan (GE IR-prep fast SPGR, Philips 3D TFE or Siemens MPRAGE) at about 1.25 x 1.25 x 1.2 mm, plus 2D axial FLAIR, T2* gradient echo, T2 turbo spin echo and diffusion scans with 5 mm slices. Clario qualified the scanners and ran ongoing quality control. FLAIR was used for ARIA-E, T2* for ARIA-H and the 3D T1 mainly for brain volume.

Annotations

Scans were read both locally and centrally for ARIA. In the core phase ARIA-E occurred in 113 of 898 lecanemab participants (12.6%) and 15 of 897 on placebo (1.7%); ARIA-H in 152 (16.9%) and 80 (8.9%), with microhemorrhages in 126 and 68 and superficial siderosis in 50 and 21. No image-level labels are published.

Known limitations

• The safety paper states its data are not available, and Eisai's data sharing listing names tabular data and documents, not images.
• People with more than four microhemorrhages or extensive white matter pathology on screening MRI were excluded.
• PET substudies, sites per country and the reader protocol are not described in the sources used here.