Donanemab Treatment for Alzheimer's Disease Linked to Significant ARIA Risk, Analysis Reveals
Key Insights
Secondary analysis of TRAILBLAZER trials shows donanemab significantly increases risk of amyloid-related imaging abnormalities (search) (ARIA (search)) in early Alzheimer's disease (search) patients, with 37% of treated participants experiencing ARIA versus 14.2% in placebo groups.
Most ARIA (search) events occurred early in treatment, with 58.3% of ARIA-E (search) cases appearing by the third infusion, and risk factors included APOE4 (search) status, baseline imaging findings, and elevated mean arterial pressure.
While most ARIA (search) events were mild to moderate and asymptomatic, some led to severe complications including death, underscoring the need for careful patient selection and regular monitoring during treatment.
A secondary analysis of clinical trial data from the TRAILBLAZER development program has revealed that treatment with donanemab (Kisunla; Eli Lilly) significantly increases the risk of amyloid-related imaging abnormalities (search) (ARIA (search)) in patients with early symptomatic Alzheimer's disease (search). The findings, published on March 10 in JAMA Neurology, highlight important safety considerations for this recently FDA-approved amyloid (search)-directed antibody.
The analysis, led by Dr. John Sims of Eli Lilly and Company, examined data from nearly 2,000 participants across phase 2 and 3 trials. Results showed that ARIA (search) occurred in 37.0% of patients receiving donanemab compared to just 14.2% in the placebo group. An additional open-label extension involving approximately 1,000 participants receiving donanemab reported an ARIA frequency of 32%.
Types and Frequency of ARIA Events
The researchers identified two primary types of ARIA (search) events. ARIA with edema or effusions (ARIA-E (search)) occurred in 24.4% of donanemab recipients in the placebo-controlled trials and 19.8% in the open-label extension. ARIA with microhemorrhages or hemosiderin deposits (ARIA-H (search)) was observed in 31.3% and 27.2% of participants, respectively. The frequency of isolated ARIA-H (11.7%-12.5%) and macrohemorrhage (0.2%-0.4%) remained similar across all study groups.
Timing and Risk Factors
Most ARIA (search) events presented early in the treatment course, with 58.3% of ARIA-E (search) cases appearing by the third infusion. Confusion and headache were the symptoms most frequently associated with these events.
The analysis identified several risk factors that correlated with increased ARIA (search) occurrence:
- Higher number of APOE4 alleles
- Presence of microhemorrhages at baseline
- Cortical superficial siderosis
- Greater amyloid plaque burden
- Elevated mean arterial pressure
Interestingly, the use of antihypertensive medications appeared to reduce the risk of ARIA (search) events.
Serious Adverse Events and Fatalities
While most ARIA (search) events were mild to moderate and asymptomatic, some led to severe complications and death. In the placebo-controlled trials, 17 deaths occurred in the donanemab groups compared to 12 in the placebo groups. Three deaths in the phase 3 trial were directly linked to serious ARIA.
In the long-term extension of the phase 3 trial, a participant heterozygous for APOE4 (search) died from ARIA-E (search) after the fifth donanemab dose. Another patient suffered a fatal intracranial hemorrhage following thrombolytic therapy for suspected stroke-like symptoms, with subsequent MRI revealing severe ARIA-E.
Study Population and Protocol
The trials included participants with a mean age of 73.7 years, with approximately 55.6% being women. All had early symptomatic Alzheimer's disease (search) with elevated amyloid (search) levels at baseline. Treatment consisted of donanemab or placebo administered intravenously every 4 weeks for up to 72 weeks, with outcomes assessed at 76 weeks.
The secondary analysis incorporated data from the phase 2 TRAILBLAZER-ALZ and phase 3 TRAILBLAZER-ALZ 2 trials, conducted from 2017 to 2023, as well as an open-label addendum. The pooled analysis included 257 participants from TRAILBLAZER-ALZ, 1,736 from TRAILBLAZER-ALZ 2, and 1,053 from the addendum.
Regulatory Context and Risk Mitigation
Donanemab, which received FDA approval in 2024 as the first amyloid (search)-directed antibody for Alzheimer's treatment, carries a boxed warning for ARIA-E (search) and ARIA-H (search). The label notes that while ARIA (search) is often asymptomatic, it can mimic ischemic stroke and lead to serious intracerebral hemorrhages. It also specifically warns that APOE4 (search) homozygotes face an increased risk of ARIA with amyloid-targeting therapies.
The researchers acknowledged the limited long-term data on patients who experienced ARIA (search) and emphasized the need to build this knowledge base. They suggested potential risk mitigation strategies, including:
- Modified dose titration strategy, which showed promise in TRAILBLAZER-ALZ 2 following protocol amendments and in preliminary results from the phase 3b TRAILBLAZER-6 study
- Implementation of 4-week MRI evaluations, which reduced the risk of symptomatic ARIA-E by approximately 36% and serious ARIA by a statistically nonsignificant 23.9%
These findings underscore the importance of careful patient selection and regular monitoring during donanemab treatment for Alzheimer's disease (search), particularly during the early infusions when ARIA (search) risk appears highest.