Anti-TREM2 Antibody AL002 Fails Completed Phase 2 Trial, Extension Study Halted

A 381-person Phase 2 trial of AL002, an antibody designed to activate the microglial receptor TREM2, ran its full course and did not slow decline in early Alzheimer's disease, according to a peer-reviewed report and the trial's public registration; developer Alector and partner AbbVie have since discontinued the study's long-term extension.

AL002, a TREM2-targeting antibody developed by Alector with AbbVie, did not slow cognitive or functional decline in a completed, randomized, placebo-controlled Phase 2 trial of 381 people with early Alzheimer's disease, according to peer-reviewed results published in Nature Medicine and the trial's public registration on ClinicalTrials.gov. The 96-week study, called INVOKE-2 (NCT04592874), ran its full planned course rather than being stopped early on an interim look; Alector first disclosed the negative topline result in November 2024 and has since discontinued a long-term extension study that had enrolled nearly all eligible participants.

TREM2 is a receptor on microglia, the brain's resident immune cells, and AL002 was designed to activate it directly, testing whether boosting innate immune signaling could slow Alzheimer's independent of removing amyloid plaques. Participants were randomized to one of three AL002 doses or placebo, given as monthly infusions, at sites in 11 countries. The trial did not meet its primary endpoint, change on the Clinical Dementia Rating Sum of Boxes scale, and researchers reported no favorable effect on secondary clinical or functional measures, no significant change on Alzheimer's fluid biomarkers, and no reduction of brain amyloid on PET imaging.

The published paper reports the antibody did engage its target biologically, lowering soluble TREM2 and raising osteopontin in cerebrospinal fluid, even though this activity did not translate into a clinical benefit. Safety monitoring found brain swelling or microhemorrhages known as ARIA in a substantial share of AL002 treated participants, reported at a scientific conference as 29 percent with ARIA-E and 27 percent with ARIA-H, more frequent and more severe in carriers of the APOE4 gene variant. After the November 2024 readout, Alector cut about 17 percent of its workforce, 41 of 238 employees, and said it would review the trial data before deciding on the future of its TREM2 research; AbbVie had paid Alector 205 million dollars upfront in 2017 to co-develop the antibody.

The result does not settle whether TREM2 itself is a workable Alzheimer's target: other TREM2-directed antibodies and small molecules from different developers remain in earlier stages of testing, and researchers who reviewed INVOKE-2 have said the field is still working out dosing and patient selection for this receptor. For now, INVOKE-2 stands as the most advanced completed test of a TREM2 agonist in Alzheimer's disease, and it did not show a clinical benefit.