Secondary analysis results
The new analysis comprised 2,066 patients who had the opportunity to complete the full 18-month trials by March 20, 2019. The full intent-to-treat population of the trials comprised 3,285 patients with mild cognitive impairment caused by Alzheimer’s disease or mild Alzheimer’s disease dementia.
In the secondary analysis of EMERGE’s intent-to-treat population, patients who took the highest dose of aducanumab (10 mg/kg every month) showed 23% lower functional and cognitive decline on the trial’s primary endpoint of Clinical Dementia Rating–Sum of Boxes (CDR-SB) at 18 months when compared with placebo. The rate of decline was slowed by a nonsignificant 14% among users of the lower dose (6 mg/kg monthly).Secondary endpoints for the high-dose group in EMERGE showed 27% slower cognitive decline on the 13-item cognitive subscale of the AD Assessment Scale (ADAS-Cog13) and 40% lower decline in function among patients with mild cognitive impairment based on the MCI version of the AD Cooperative Study–Activities of Daily Living Inventory (ADCS-ADL-MCI).
However, data from the ENGAGE trial, which had the same primary endpoint, were not positive. CDR-SB scores worsened 2% more among high-dose aducanumab users but low-dose users slowed decline by a nonsignificant 12% when compared with placebo.“Exposure to high-dose aducanumab was important for efficacy,” the company noted in a slide set presented at an Oct. 22 investors webcast. “Differences in exposure to high-dose aducanumab largely explain the different results between the futility analysis and the new analysis of this larger dataset, as well as the different results between the two studies.”
In EMERGE, changes in secondary endpoints among patients who had the opportunity to complete the full 18-month trials included:
- Mini Mental State Exam (MMSE): Significant 23% decrease in rate of decline in the high-dose group and nonsignificant 3% increase in decline in the low-dose group.
- ADAS-Cog13: Significant 25% decrease for high-dose users and nonsignificant 10% decrease for low dose.
- ADCS-ADL-MCI: Significant decreases of 46% for high-dose and 20% for low-dose users.
The ENGAGE secondary endpoints of high- vs. low-dose patients who completed the full trials were:
- MMSE: Significant 13% increase, nonsignificant 3% decrease.
- ADAS-Cog13: Nonsignificant 2% decrease, nonsignificant 1% decrease.
- ADCS-ADL-MCI: Significant 12% declines in both dosage groups.
All of the positive cognitive and functional results tracked along with results of amyloid PET imaging and CSF biomarkers. In EMERGE, amyloid plaque binding declined about 27% in the high-dose group and about 16% in the low-dose group, reflecting plaque clearance. Phosphorylated tau in CSF decreased by about 17 pg/mL and 10 pg/mL, respectively, and total tau decreased by 160 pg/mL and 120 pg/mL. Tau decreases indicate a slowing of neuronal damage.
In ENGAGE, amyloid plaque binding decreased by about 24% in the high-dose group and by about 16% in the low-dose group. Phosphorylated tau dropped by about 10 pg/mL and 11 pg/mL, respectively. But total tau dropped more in the low-dose group than in the high-dose group (about –100 pg/mL vs. –20 pg/mL).
Biogen said the amyloid PET imaging biomarker results and CDR-SB scores in both studies were consistent with each other in a subset of patients with “sufficient exposure to 10 mg/kg,” which was defined as “10 or more uninterrupted 10-mg/kg dosing intervals at steady-state.”
The most common adverse events were amyloid related imaging abnormalities–edema (ARIA-E), which occurred in 35%, and headache in 20%. The majority of patients who experienced ARIA-E (74%) were asymptomatic; episodes generally resolved within 4-16 weeks, typically without long-term sequelae.
Dr. Aisen is a consultant for Biogen and on the aducanumab steering committee. None of the other sources in this article have any financial relationship with Biogen or Eisai.
This article was updated 10/23/19.