Alnylam completes enrollment of phase 2 mivelsiran trial in cerebral amyloid angiopathy; starts Down syndrome study

Alnylam Pharmaceuticals/Mivelsiran (ALN-APP)

At AAIC 2026, Alnylam said the cAPPricorn-1 phase 2 of mivelsiran in cerebral amyloid angiopathy is fully enrolled, with the rate of new brain microbleeds on MRI as the primary endpoint and first results expected in 2028. It also started APPlauDS in people with Down syndrome, who carry an extra APP gene copy and develop Alzheimer's early. Phase 1 data showed deep, durable cuts in amyloid markers without brain swelling.

• Top dose: mean maximum CSF reductions of 89.9% (sAPPβ) and 70.2% (Aβ42).
• Exposure up to 30 months; no increase in ARIA risk versus placebo.
• APPlauDS runs at about 30 sites worldwide.