Reviews/Anti Amyloid Antibodies/Amyloid clearance and clinical outcomes
Amyloid · AMAB-AMY-02 · v2
Several independent trials show that when an anti-amyloid antibody removes amyloid from the brain, patients also tend to decline more slowly: lecanemab did both in its main trial [4] and over longer follow-up [2], [6], and a within-trial analysis of donanemab linked amyloid reduction to clinical measures [1]. A pooled model treated amyloid reduction as a stand-in for clinical efficacy [14]. But the picture is not clean: gantenerumab removed a large amount of amyloid yet did not slow decline [5]. The strongest supportive model used one drug's data to predict that same drug's effect, and the donanemab link held only in one genetic subgroup. The panel judged the group-level relationship real in direction but inconsistent, because the corpus contains a clear case of clearance without benefit and no direct cross-trial test.
Positive anti-amyloid trials from different sponsors show amyloid clearance and slower decline occurring together: lecanemab reduced amyloid by -59.1 centiloids and slowed CDR-SB decline (difference -0.45) in Clarity AD [4], with benefit maintained to 36 months in the open-label extension [2] and reproduced in the Asian subgroup [6]. A post hoc donanemab analysis tied percentage amyloid reduction to clinical change [1], and a semi-mechanistic pooled model framed amyloid change as a surrogate of efficacy [14]. Against this, gantenerumab lowered amyloid by -66.44 and -56.46 centiloids and reached amyloid-negative status in 28.0% and 26.8% of patients yet produced no significant clinical benefit (differences -0.31, P=0.10; -0.19, P=0.30) [5]. The corpus therefore demonstrates co-occurrence in some programmes and an outright dissociation in another. The contested point: The evidence divides on whether the association is a reliable group-level correlation or merely a tendency that holds for some drugs and not others. Gantenerumab [5] is an in-corpus case of substantial clearance without clinical benefit, and the most explicit surrogacy support [14] is a single-sponsor lecanemab-only model, while the donanemab link [1] reached significance only in APOE e4 carriers.
All 19 papers behind this claim with their DOIs and what each does to it, the panel’s arbitration, the evidence gap map and the open research questions. Free, and sent to your inbox.
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One reviewer's only job is to attack the finding. The challenges below were weighed before the grade was set.
Gantenerumab [5] is an in-corpus group-level dissociation: amyloid-negative status in ~28% with -66.44/-56.46 CL reductions, yet CDR-SB differences were non-significant (-0.31, P=0.10; -0.19, P=0.30). Clearance without benefit directly contradicts a clean correlation.
The strongest surrogacy evidence [14] is an Eisai-sponsored, lecanemab-only pooled model (1 citation) that uses lecanemab's data to predict lecanemab's effect — circular, not an independent cross-drug group-level correlation.
Where it remains uncertain. Gantenerumab lowered amyloid by -66.44 and -56.46 centiloids with no significant clinical benefit (-0.31, P=0.10; -0.19, P=0.30) [5], breaking a clean correlation.
Aleatory
Gantenerumab clinical differences were small with wide confidence intervals spanning no effect (-0.66 to 0.05; -0.55 to 0.17) [5], leaving sampling variability as part of why benefit was not detected.
Epistemic
Gantenerumab removed large amounts of amyloid yet showed no significant clinical benefit [5], so the direction of the group-level relationship is not established across drugs.
Inferential
The surrogacy model is lecanemab-only, pooling Study 201 and Clarity AD and using lecanemab data to predict lecanemab's effect [14], so it cannot establish a cross-drug group-level correlation.
The load-bearing papers from a corpus of 19, each classified by what it does to the claim. Every DOI is taken from the corpus the claim was graded on.
Dose/clearance-response linking amyloid reduction to clinical change, but restricted to APOE e4 carriers.
“A disease-progression model found a significant association between percentage amyloid reduction and change on the integrated Alzheimer Disease Rating Scale only in apolipoprotein E (APOE) ε4 carriers (95% CI, 24%-59%; P < .001).”
Panel auditInternal validity: medium · scope of inference: Early symptomatic Alzheimer disease, elevated amyloid and intermediate tau, treated with donanemab; association strongest in APOE ε4 carriers.Key limitations: post hoc analysis · association significant only in APOE ε4 subgroup · single antibody and trial
Sustained amyloid suppression accompanied by sustained clinical benefit over time.
“Across clinical and HRQoL endpoints, lecanemab-treated participants continued to benefit through 36 months.”
Panel auditInternal validity: low · scope of inference: Early Alzheimer's disease participants continuing open-label lecanemab out to 36 months.Key limitations: open-label, no concurrent placebo · co-occurrence not a correlation analysis · OLE sample size not stated
A single drug producing both large amyloid reduction and clinical benefit (CDR-SB difference -0.45) — a positive group-level data point.
“there were greater reductions in brain amyloid burden with lecanemab than with placebo (difference, -59.1 centiloids; 95% CI, -62.6 to -55.6)”
Panel auditInternal validity: high · scope of inference: Early Alzheimer's disease (MCI or mild dementia) with confirmed amyloid, over 18 months.Key limitations: co-occurrence across arms, not a within-trial correlation statistic · single antibody · 18-month horizon
Counter-evidence: substantial amyloid clearance without clinical benefit, breaking a clean group-level correlation.
“the use of gantenerumab led to a lower amyloid plaque burden than placebo at 116 weeks but was not associated with slower clinical decline”
Panel auditInternal validity: high · scope of inference: Early Alzheimer's disease with confirmed amyloid, treated with gantenerumab over 116 weeks.Key limitations: amyloid-negative status reached in only ~27-28% · smaller amyloid reduction than other antibodies · single antibody
4 of 19 papers shown. The full review lists all of them, with the panel’s arbitration →
Claims are graded at each quarterly release, and re-graded between releases only when a pivotal trial lands. Every change is a new version of the claim.
A real but imperfect group-level association, undermined by an in-corpus clearance-without-benefit counter-example and circular/subgroup-limited supportive evidence.
Release 2026-q4 re-graded every claim from its corpus under protocol v0.19. An earlier release's grade is shown for the record; it came from an earlier protocol and is not a movement.
Assumptions that carry weight but are not themselves established.
The panel records the gap that would most move the claim, and the study that would close it.
Cross-trial meta-regression across antibodies. The claim is about a group-level relationship, but the corpus only has within-drug trials and one single-drug model, so the across-class correlation is inferred rather than measured. The panel rates this the highest-importance open gap for the claim, and names the study design that would close it: A meta-regression pooling arm-level amyloid change and clinical change across lecanemab [4], donanemab [1] and gantenerumab [5] and other agents to estimate the slope and its consistency.
Open question: Across independent anti-amyloid agents, does arm-level amyloid clearance predict arm-level clinical benefit? Why it is still open: The corpus has within-drug co-occurrence [4], [2], [6], [1] and a counter-example [5] but no cross-trial meta-regression testing the group-level slope.
Priors is a sceptical first reader, not peer review, and not medical advice.
Release 2026-q4 · graded 21 Oct 2026 · protocol v0.19