Monoclonal antibodies directed against aggregated forms of beta amyloid, including LEQEMBI, can cause amyloid related imaging abnormalities (ARIA), characterized as ARIA with edema (ARIA-E), which can be observed on MRI as brain edema or sulcal effusions, and ARIA with hemosiderin deposition (ARIA-H), which includes microhemorrhage and superficial siderosis. ARIA-H can occur spontaneously in patients with Alzheimer’s disease. ARIA-H associated with monoclonal antibodies directed against aggregated forms of beta amyloid generally occurs in association with an occurrence of ARIA-E. ARIA-H of any cause and ARIA-E can occur together. ARIA is usually asymptomatic, although serious and life-threatening events, including seizure and status epilepticus, rarely can occur. When present, reported symptoms associated with ARIA may include headache, confusion, visual changes, dizziness, nausea, and gait difficulty. Focal neurologic deficits may also occur. Symptoms associated with ARIA usually resolve over time.
Incidence of ARIA
Symptomatic ARIA occurred in 3% (5/161) of patients treated with LEQEMBI in Study 1 [see Clinical Studies (14)]. Clinical symptoms associated with ARIA resolved in 80% of patients during the period of observation.
Including asymptomatic radiographic events, ARIA was observed in 12% (20/161) of patients treated with LEQEMBI, compared to 5% (13/245) of patients on placebo in Study 1. ARIA-E was observed in 10% (16/161) of patients treated with LEQEMBI compared with 1% (2/245) of patients on placebo. ARIA-H was observed in 6% (10/161) of patients treated with LEQEMBI compared with 5% (12/245) of patients on placebo. There was no increase in isolated ARIA-H (i.e., ARIA-H in patients who did not also experience ARIA-E) for LEQEMBI compared to placebo.
Intracerebral hemorrhage greater than 1 cm in diameter was reported in one patient in Study 1 after treatment with LEQEMBI compared to none on placebo. Events of intracerebral hemorrhage, including fatal events, in patients taking LEQEMBI have also been reported in other studies.
ApoE ε4 Carrier Status and Risk of ARIA
In Study 1, 6% (10/161) of patients in the LEQEMBI group were apolipoprotein E ε4 (ApoE ε4) homozygotes, 24% (39/161) were heterozygotes, and 70% (112/161) were noncarriers. The incidence of ARIA was higher in ApoE ε4 homozygotes than in heterozygotes and noncarriers among patients treated with LEQEMBI. Of the 5 patients treated with LEQEMBI who had symptomatic ARIA (see Incidence of ARIA), 4 were ApoE ε4 homozygotes, 2 of whom experienced severe symptoms. In addition, an increased incidence of symptomatic and overall ARIA in ApoE ε4 homozygotes compared to heterozygotes and noncarriers in patients taking LEQEMBI has been reported in other studies. The recommendations on management of ARIA do not differ between ApoE ε4 carriers and noncarriers [see Dosage and Administration (2.3)]. Consider testing for ApoE ε4 status to inform the risk of developing ARIA when deciding to initiate treatment with LEQEMBI.
Radiographic Findings
The radiographic severity of ARIA associated with LEQEMBI was classified by the criteria shown in Table 3.
Table 3: ARIA MRI Classification Criteria| ARIA Type | Radiographic Severity |
| Mild | Moderate | Severe |
| ARIA-E | FLAIR hyperintensity confined to sulcus and/or cortex/subcortex white matter in one location <5 cm | FLAIR hyperintensity 5 to 10 cm in single greatest dimension, or more than 1 site of involvement, each measuring <10 cm | FLAIR hyperintensity >10 cm with associated gyral swelling and sulcal effacement. One or more separate/ independent sites of involvement may be noted. |
| ARIA-H microhemorrhage
| ≤ 4 new incident microhemorrhages | 5 to 9 new incident microhemorrhages | 10 or more new incident microhemorrhages |
ARIA-H superficial siderosis | 1 focal area of superficial siderosis | 2 focal areas of superficial siderosis | > 2 areas of superficial siderosis |
The majority of ARIA-E radiographic events occurred early in treatment (within the first 7 doses), although ARIA can occur at any time and patients can have more than 1 episode. The maximum radiographic severity of ARIA-E in patients treated with LEQEMBI was mild in 4% (7/161) of patients, moderate in 4% (7/161) of patients, and severe in 1% (2/161) of patients. Resolution on MRI occurred in 62% of ARIA-E patients by 12 weeks, 81% by 21 weeks, and 94% overall after detection. The maximum radiographic severity of ARIA-H microhemorrhage in patients treated with LEQEMBI was mild in 4% (7/161) of patients and severe in 1% (2/161) of patients; 1 of the 10 patients with ARIA-H had mild superficial siderosis.
Concomitant Antithrombotic Medication and Other Risk Factors for Intracerebral Hemorrhage
Patients were excluded from enrollment in Study 1 for baseline use of anticoagulant medications. Antiplatelet medications such as aspirin and clopidogrel were allowed. During the study, if anticoagulant medication was used because of intercurrent medical events that required treatment for 4 weeks or less, treatment with LEQEMBI was to be temporarily suspended. Patients who received LEQEMBI and an antithrombotic medication (aspirin, other antiplatelets, or anticoagulants) did not have an increased risk of ARIA-H compared to patients who received placebo and an antithrombotic medication. The majority of exposures to antithrombotic medications were to aspirin; few patients were exposed to other antiplatelet drugs or anticoagulants, limiting any meaningful conclusions about the risk of ARIA or intracerebral hemorrhage in patients taking other antiplatelet drugs or anticoagulants. Because intracerebral hemorrhages greater than 1 cm in diameter have been observed in patients taking LEQEMBI, additional caution should be exercised when considering the administration of antithrombotics or a thrombolytic agent (e.g., tissue plasminogen activator) to a patient already being treated with LEQEMBI.
Additionally, patients were excluded from enrollment in Study 1 for the following risk factors for intracerebral hemorrhage: prior cerebral hemorrhage greater than 1 cm in greatest diameter, more than 4 microhemorrhages, superficial siderosis, evidence of vasogenic edema, evidence of cerebral contusion, aneurysm, vascular malformation, infective lesions, multiple lacunar infarcts or stroke involving a major vascular territory, and severe small vessel or white matter disease. Caution should be exercised when considering the use of LEQEMBI in patients with these risk factors.
Monitoring and Dose Management Guidelines
Recommendations for dosing in patients with ARIA-E depend on clinical symptoms and radiographic severity [see Dosage and Administration (2.3)]. Recommendations for dosing in patients with ARIA-H depend on the type of ARIA-H and radiographic severity [see Dosage and Administration (2.3)]. Use clinical judgment in considering whether to continue dosing in patients with recurrent ARIA-E.
Baseline brain MRI and periodic monitoring with MRI are recommended [see Dosage and Administration (2.3)]. Enhanced clinical vigilance for ARIA is recommended during the first 14 weeks of treatment with LEQEMBI. If a patient experiences symptoms suggestive of ARIA, clinical evaluation should be performed, including MRI if indicated. If ARIA is observed on MRI, careful clinical evaluation should be performed prior to continuing treatment.
There is no experience in patients who continued dosing through symptomatic ARIA-E or through asymptomatic, but radiographically severe, ARIA-E. There is limited experience in patients who continued dosing through asymptomatic but radiographically mild to moderate ARIA-E. There are limited data in dosing patients who experienced recurrent ARIA-E.
The Alzheimer’s Network for Treatment and Diagnostics (ALZ-NET) is a voluntary provider-enrolled patient registry that collects information on treatments for Alzheimer’s disease, including LEQEMBI. Providers may obtain information about the registry at www.alz-net.org or contact [email protected].