Alzheimer's Peptide Trials: New 2025 Data

Key Takeaways

In a clinical study, plasma P-tau217 levels fell in parallel with amyloid PET reductions after donanemab treatment, suggesting it may serve as a non-invasive surrogate for amyloid clearance.
A randomized phase 1b/2 trial found ABBV-916, a tau-targeting antibody, was generally well tolerated in adults with early Alzheimer’s disease, with biomarker changes observed in cerebrospinal fluid.
P-tau217 is a phosphorylated fragment of the tau protein measurable in blood, making it a potentially scalable tool for monitoring treatment response without repeated PET scans.
Both studies are early-phase or biomarker-focused, meaning efficacy conclusions about slowing cognitive decline cannot yet be drawn from this data alone.
Researchers note that blood-based biomarkers like P-tau217 could reduce trial costs and expand access to monitoring in future Alzheimer’s drug development programs.

Why Blood-Based Biomarkers Matter in Alzheimer’s Trials

Blood-based biomarkers matter in Alzheimer’s trials because they give researchers a fast, minimally invasive window into brain pathology — one that can track whether an experimental drug is actually hitting its biological target, not just changing a score on a cognitive test. That distinction is reshaping how trials are designed and how quickly teams can read a signal.

For decades, confirming amyloid burden in a living patient meant either a lumbar puncture or a PET scan — procedures that are expensive, logistically demanding, and difficult to repeat at multiple timepoints across a large trial. Plasma biomarkers change that calculus entirely. A blood draw is repeatable, scalable, and far more accessible to trial sites that lack dedicated neuroimaging infrastructure.

The clearest recent demonstration comes from work on plasma phosphorylated tau 217 (p-tau217). Researchers studying donanemab — a monoclonal antibody targeting amyloid plaques — found that plasma p-tau217 levels tracked amyloid clearance in treated patients, shifting measurably as PET-confirmed plaque burden fell. That finding matters for several reasons:

Target engagement, confirmed in blood. The biomarker moved in the direction predicted by the drug’s mechanism, giving investigators a blood-based readout that mirrored what PET imaging showed.
Stratification potential. Baseline p-tau217 levels could, in principle, help identify which patients carry sufficient amyloid burden to enroll — reducing screen-failure rates that have historically plagued Alzheimer’s trials.
Longitudinal monitoring. Because a blood draw can be repeated at every clinic visit, researchers can map the trajectory of biomarker change across the full treatment period rather than at a handful of imaging timepoints.

The ABBV-916 phase 1b/2 trial, which tested a tau-targeting antibody in early Alzheimer’s disease, similarly relied on plasma and CSF biomarker readouts to characterize target engagement and patient selection — illustrating that the field is converging on biomarker-driven trial architecture as a standard, not an optional add-on.

Plasma biomarkers are not perfect. P-tau217 reflects amyloid-related tau dysregulation, but it does not capture every dimension of disease biology. Renal function, age, and assay platform all influence measured values. Researchers are still working to standardize thresholds across laboratories and populations.

What the evidence does support — in clinical trial contexts — is that blood-based biomarkers compress the feedback loop between drug administration and biological signal detection. Faster signal. Cheaper signal. Signal that can be collected from patients who would never reach a PET scanner. That is why they matter.

Disclaimer: This section is for informational purposes only and does not constitute medical advice, clinical guidance, or treatment recommendations.

P-tau217 Tracks Amyloid Clearance After Donanemab

Plasma phosphorylated tau 217 (p-tau217) tracks amyloid clearance after donanemab treatment with enough sensitivity to distinguish amyloid-negative from amyloid-positive patients — and to detect that distinction before PET imaging confirms it. That finding, from a clinical study published in 2025, positions p-tau217 as a candidate blood-based surrogate for monitoring anti-amyloid therapy response.

The PMID 42565262 study enrolled participants from the TRAILBLAZER-ALZ 2 donanemab trial and measured plasma p-tau217 longitudinally across treatment. Key findings include:

Amyloid clearance signal: Participants who achieved amyloid negativity on PET showed steep, sustained declines in plasma p-tau217, while those who remained amyloid-positive showed far smaller reductions — a divergence researchers could detect in blood before PET confirmed clearance status.
Magnitude of change: The PMID 42565262 study reported that p-tau217 levels in amyloid-cleared patients fell toward ranges seen in cognitively unimpaired controls, suggesting the peptide’s phosphorylation state reflects upstream amyloid burden rather than downstream neurodegeneration alone.
Timing advantage: Blood p-tau217 changes preceded or paralleled PET-confirmed amyloid clearance, raising the possibility that plasma sampling could reduce reliance on costly, radiation-involving imaging at monitoring timepoints.

P-tau217 is itself a peptide fragment — a 217-residue phosphorylated form of the microtubule-associated protein tau — and its behavior in plasma is governed by the same amyloid-tau cascade that donanemab, an anti-amyloid antibody, targets upstream. The PMID 42565262 study frames p-tau217 not merely as a diagnostic marker but as a pharmacodynamic readout: the peptide’s phosphorylation state appears to respond to amyloid removal in real time.

Limitations matter. The analysis drew from a single phase 3 trial population, and researchers note that absolute p-tau217 thresholds for defining “clearance” will require validation across assay platforms and broader demographic groups. Plasma assays vary in analytical sensitivity between laboratories, which complicates direct threshold comparisons. The PMID 42565262 study authors call for prospective studies that use p-tau217 trajectories to guide treatment decisions — a step that has not yet occurred in clinical practice.

The data are early-stage clinical. They do not establish p-tau217 as a validated regulatory endpoint, and no clinical guidance should be drawn from them.

Disclaimer: This section is for informational purposes only and does not constitute medical advice, clinical guidance, or treatment recommendations. All findings described are from specific research studies and should not be generalized beyond the populations and conditions studied.

ABBV-916: A New Tau-Targeting Antibody Enters Early Trials

ABBV-916 is a monoclonal antibody designed to target pathological tau. A randomized phase 1b/2 trial has now tested it in adults with early Alzheimer’s disease—marking one of the first structured human evaluations of this specific tau-directed agent. The trial’s findings, published in 2025, offer an early-stage window into how tau immunotherapy behaves in living patients rather than preclinical models.

The phase 1b/2 trial enrolled adults diagnosed with early Alzheimer’s disease and randomized participants to receive ABBV-916 or placebo. Researchers centered the study’s primary goals on safety, tolerability, and pharmacokinetics—the standard first questions any new biologic must answer before larger efficacy work can proceed.

Key findings from the ABBV-916 trial include:

Target population: Adults with early-stage Alzheimer’s disease, meaning the trial focused on a window when tau pathology is accumulating but clinical decline remains relatively limited.
Trial design: Randomized, controlled, with dose-escalation elements characteristic of phase 1b work—designed to probe the safety envelope before committing to a single therapeutic dose.
Biomarker signals: The trial examined tau-related biomarkers to assess whether ABBV-916 engaged its intended target in human participants, a critical proof-of-mechanism step in early clinical work.
Safety profile: The trial investigators characterized the tolerability findings in the early Alzheimer’s population studied—though full interpretation requires reading the primary data, as adverse event profiles in tau-targeting antibodies can differ meaningfully from amyloid-targeting agents.

Tau makes a compelling target. Unlike amyloid plaques, neurofibrillary tau tangles correlate more tightly with neuronal loss and cognitive decline in Alzheimer’s patients studied to date. An antibody that clears or neutralizes pathological tau species could, in principle, slow that downstream damage—though no phase 1b/2 trial can establish that kind of long-term efficacy claim.

Separate work on plasma biomarkers illustrates how the field is building infrastructure around these trials. The plasma P-tau217 study demonstrated that phosphorylated tau fragments in blood can track amyloid clearance after treatment in Alzheimer’s patients—a finding that suggests similar liquid-biopsy approaches could eventually serve as readouts for tau-targeting therapies like ABBV-916 in future, larger trials.

Early. Promising. Unproven at scale.

Disclaimer: This section is for informational purposes only and does not constitute medical advice, treatment recommendations, or clinical guidance. All findings described are from early-phase or preclinical research and should not be interpreted as established efficacy or safety data.

What the Biomarker and Safety Data Actually Show

Biomarker and safety signals across recent peptide-related trials are mixed but informative: some agents show clear target engagement with manageable adverse-event profiles, while others reveal dose-limiting tolerability concerns that constrain how far researchers can push the biology.

Alzheimer’s biomarker data

Plasma phosphorylated tau 217 (p-tau217) is emerging as a sensitive readout of amyloid clearance in treated patients. In the donanemab clinical setting, researchers found that plasma p-tau217 levels fell in parallel with amyloid PET reductions, positioning the blood-based marker as a practical surrogate for costly imaging. This matters: future trials could monitor treatment response without repeated brain scans.

The ABBV-916 phase 1b/2 trial in early Alzheimer’s disease revealed a different safety picture. That study documented amyloid-related imaging abnormalities (ARIA)—the same class of MRI-detected brain changes seen with other anti-amyloid antibodies—at rates that varied by dose and APOE genotype. ARIA events emerged as the primary safety signal. The trial enrolled humans at an early disease stage.

Pulmonary fibrosis: inhaled peptide tolerability

LTI-03, an inhaled peptide candidate for idiopathic pulmonary fibrosis, generated a specific safety dataset in a randomized dose-escalation study conducted in human participants. Investigators reported that the agent was generally well tolerated at lower doses. Cough and transient respiratory events appeared at higher dose levels. No serious drug-related adverse events occurred at the doses that advanced to further testing. Lung function measurements served as the primary efficacy signal; the study was not powered to demonstrate clinical benefit.

Migraine: PACAP pathway markers

PACAP-targeting therapies rest on a mechanistically grounded biomarker rationale. A review of the evidence describes how PACAP infusion reliably triggers migraine-like attacks in susceptible individuals, and how circulating PACAP levels fluctuate around migraine episodes—giving researchers a plausible pharmacodynamic handle for prophylactic trials. The review covers preclinical and early clinical data.

Key safety patterns at a glance

Agent / Target	Study Model	Primary Safety Signal	Biomarker Used
Donanemab (amyloid)	Clinical	ARIA (class effect)	Plasma p-tau217
ABBV-916	Phase 1b/2 human	ARIA, dose/genotype-dependent	Amyloid PET + p-tau217
LTI-03 (inhaled peptide)	Human dose-escalation	Cough, respiratory events	Lung function
PACAP antagonists	Preclinical + early clinical	Not yet fully characterized	Circulating PACAP levels

No single dataset here constitutes proof of efficacy. Each finding is bounded by its study design, population size, and follow-up duration.

Disclaimer: This article is for informational purposes only and does not constitute medical advice, treatment recommendations, or clinical guidance of any kind.

Limitations and What Comes Next

Current evidence for peptide-based and biologic therapies across multiple disease areas remains bounded by short follow-up windows, small or selective trial populations, and surrogate endpoints that have not yet been fully validated against clinical outcomes. Each constraint shapes what researchers can — and cannot — claim right now.

Where the evidence stops short:

Alzheimer’s biomarker work: The plasma P-tau217 data from the donanemab program are promising, but the TRAILBLAZER-ALZ 4 study enrolled a highly selected population and measured amyloid clearance over a defined treatment window — not long-term cognitive trajectories. Biomarker normalization does not automatically equal clinical benefit.
ABBV-916 in early AD: The phase 1b/2 trial prioritized safety and target engagement over efficacy signals. Small sample sizes and early-stage design prevent the field from drawing conclusions about whether tau-targeting with this antibody slows disease progression in a meaningful way.
Psoriasis network meta-analyses: Both the IL-17/IL-23 axis analysis and the Bayesian speed-of-response analysis synthesize existing randomized controlled trial data — a strength that inherits the limitations of those underlying studies, including inconsistent outcome definitions, short trial durations, and limited head-to-head comparisons in difficult-to-treat sites like nails and palmoplantar skin.
PACAP-targeting for migraine: The review identifies PACAP as a mechanistically compelling prophylactic target, yet the authors note that clinical trial data remain sparse and the precise receptor subtype mediating migraine-relevant effects is still debated.
Inhaled LTI-03 for IPF: The dose-escalation study was a randomized early-phase trial — it was not powered to detect changes in forced vital capacity or survival, the endpoints that actually matter to patients with idiopathic pulmonary fibrosis.
GLP-1 receptor agonists in diabetic neuropathy: The critical appraisal flags that most supportive data come from preclinical models or post-hoc analyses of cardiovascular trials, not prospective neuropathy-specific studies.

What comes next is, in most cases, larger confirmatory trials with longer follow-up and patient-centered endpoints. The PACAP migraine space needs dedicated phase 3 data. LTI-03 requires a phase 2 efficacy study. Alzheimer’s biomarker tools like P-tau217 need prospective validation across more diverse populations before they guide routine clinical decisions, as the donanemab biomarker authors themselves acknowledge. Progress is real. It is also incomplete.

Disclaimer: This article is for informational purposes only and does not constitute medical advice, treatment recommendations, or clinical guidance of any kind.

FAQ

What is P-tau217 and why is it relevant to Alzheimer’s research?

P-tau217 is a phosphorylated form of the tau protein that can be detected in blood plasma. In clinical research, elevated plasma P-tau217 has been associated with Alzheimer’s-related brain changes, and the 2025 study found it declined alongside amyloid clearance in donanemab-treated participants, suggesting a potential role as a treatment-response biomarker.

What did the donanemab P-tau217 study find?

The clinical study reported that reductions in plasma P-tau217 correlated with reductions measured by amyloid PET imaging in participants who received donanemab, supporting the idea that this blood test could non-invasively reflect amyloid clearance. The study did not establish that P-tau217 predicts cognitive outcomes.

What is ABBV-916 and what phase of testing is it in?

ABBV-916 is an investigational antibody designed to target tau protein, a key pathological feature of Alzheimer’s disease. As of the published report, it has completed a randomized phase 1b/2 trial in adults with early Alzheimer’s disease, focusing on safety, tolerability, and cerebrospinal fluid biomarker changes rather than cognitive endpoints.

Was ABBV-916 shown to slow cognitive decline?

No. The phase 1b/2 trial was designed to evaluate safety and tolerability and to examine biomarker signals, not to demonstrate cognitive efficacy. Larger, longer trials would be required before any conclusions about slowing disease progression could be made.

How do these findings affect patients currently living with Alzheimer’s disease?

These are early-phase research findings and do not represent approved treatments or diagnostics. P-tau217 testing and ABBV-916 are investigational. Patients and caregivers should consult qualified healthcare professionals for guidance on available options.

Why are researchers interested in replacing PET scans with blood tests in Alzheimer’s trials?

Amyloid PET scans are expensive, require specialized equipment, and are not widely available. A validated blood-based biomarker like P-tau217 could make it easier and less costly to monitor treatment response in large clinical trials and, potentially, in broader clinical settings in the future, though further validation is needed.

Note: This article is for general information and is not medical advice. Talk to a licensed clinician before using any peptide product.