Reviews/Anti Amyloid Antibodies/Low tau burden predicts better response
Selection · AMAB-SEL-02 · v2
Borderline: within 4 points of the Doubtful/Refuted boundary, so a re-grade could land either side.
The claim is that patients who start with less tau in the brain get more benefit from anti-amyloid treatment. To test that, you need a study comparing how much treatment helps people with low versus high starting tau. The one corpus paper that directly models treatment benefit against starting tau [20] found that donanemab slowed decline regardless of how much tau a patient started with. Several other papers [14][16][15][11][7] show that higher starting tau predicts faster cognitive decline, but that describes the natural course of the disease, not whether a drug works better in one group. The donanemab trials in this corpus [1][2] only enrolled patients in a middle tau range, so they cannot show how low-tau patients compare with high-tau patients on treatment. The panel concluded the corpus does not carry the claim and its single direct test runs against it.
No corpus paper demonstrates that lower baseline tau produces greater treatment benefit. The only paper directly modelling treatment benefit as a function of baseline tau, [20], reports that donanemab 'slowed disease progression irrespective of baseline tau positron emission tomography (PET) level within the evaluated population.' The prognostic papers establish that baseline tau predicts cognitive decline: [14] found tau PET outperformed MRI and amyloid PET at predicting MMSE change (R2 0.35 vs 0.24 vs 0.17 across all participants), and [16] found baseline tau-PET among the strongest independent predictors of decline. The donanemab RCT data [1][2] enrolled patients with 'intermediate tau levels,' reporting amyloid, tau and clinical associations but no low-versus-high baseline-tau benefit contrast. The contested point: The division is between prognosis and treatment-effect modification: the prognostic signal that baseline tau tracks decline [14][16] is real but does not speak to differential drug benefit. The one direct treatment-benefit test [20] contradicts the claim, yet it did so in a tau-restricted population, so the corpus can neither affirm nor firmly refute the high-versus-low-tau benefit contrast.
All 20 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.
The claim concerns treatment-effect modification (lower tau → greater benefit FROM therapy), but [14][16][15][11][7] measure baseline tau predicting cognitive DECLINE, largely in untreated/observational cohorts. That is prognosis, not treatment benefit; citing them in support is a category error.
The single paper that directly tests the claim [20] finds benefit irrespective of baseline tau — i.e. no treatment-effect modification — which contradicts rather than supports the claim.
Where it remains uncertain. The direct test [20] was conducted in a population enrolled at intermediate tau [1], so the restricted tau range limits power to detect any baseline-tau effect, and the corpus holds no primary subgroup result affirming the claim.
Aleatory
Even the trials present give variable signals; [2] reports most secondary outcomes 'showed no substantial difference,' so individual-level benefit varies independently of baseline tau.
Epistemic
The corpus contains no primary analysis comparing treatment benefit across low and high baseline tau strata; the landmark positive result is simply absent.
The load-bearing papers from a corpus of 20, each classified by what it does to the claim. Every DOI is taken from the corpus the claim was graded on.
Donanemab trial in an intermediate-tau population; reports treatment effects on tau but no lower-baseline-tau-greater-clinical-benefit result.
“The donanemab-induced slowing of tau was more pronounced in those with complete amyloid clearance and in brain regions identified later in the pathologic sequence.”
Panel auditInternal validity: medium · scope of inference: Early symptomatic AD with elevated amyloid and intermediate tau receiving donanemab; associations among amyloid, tau and clinical decline.Key limitations: post hoc analyses · intermediate-tau enrollment restricts baseline range · focus on amyloid not baseline tau
Confirms baseline tau predicts cognitive change (prognosis); indirect to the treatment-benefit claim.
“The findings of this prognostic study suggest that tau PET is a promising tool for predicting cognitive change that is superior to amyloid PET and MRI and may support the prognostic process in preclinical and prodromal stages of AD.”
Panel auditInternal validity: medium · scope of inference: CU, MCI and AD-dementia individuals; prognostic accuracy of baseline tau PET for cognitive decline.Key limitations: prognosis not treatment benefit · observational · short follow-up (~1.9 years)
Shows baseline tau is prognostic for decline — relevant context but does not establish differential treatment benefit.
“Baseline tau-PET and a composite baseline cognitive score were the strongest independent predictors of cognitive decline.”
Panel auditInternal validity: medium · scope of inference: Amnestic MCI and mild dementia; prediction of 2-year cognitive decline.Key limitations: prognosis not treatment benefit · sample size not reported · observational
Direct test of the claim; finds treatment benefit does NOT vary with baseline tau, contradicting the claim (in an intermediate-tau-restricted population).
“The disease-progression models show a clear treatment effect of donanemab on clinical efficacy regardless of baseline disease severity.”
Panel auditInternal validity: low · scope of inference: AD participants from phase 1 and TRAILBLAZER-ALZ; modeled donanemab effect across baseline tau PET.Key limitations: modeling/simulation not direct subgroup trial · within evaluated population only · no participant counts reported
4 of 20 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.
The corpus does not carry the treatment-benefit claim and its one direct test contradicts it, though in a tau-restricted population that limits firm refutation.
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.
Baseline-tau-stratified treatment benefit. The claim requires comparing treatment effect across low and high baseline tau, which no corpus paper provides; [20] tests benefit against tau but only within an intermediate-tau population. The panel rates this the highest-importance open gap for the claim, and names the study design that would close it: Prespecified subgroup or interaction analysis of an anti-amyloid RCT contrasting clinical benefit between low and high baseline tau-PET strata across the full tau range.
Open question: Does anti-amyloid treatment benefit differ between patients with low versus high baseline tau? Why it is still open: The only direct test [20] found benefit irrespective of baseline tau within an intermediate-tau population; no corpus paper compares low and high tau strata.
Priors is a sceptical first reader, not peer review, and not medical advice.
Release 2026-q4 · graded 21 Oct 2026 · protocol v0.19