Tauklarify is a new tau PET imaging agent, approved by the FDA on August 14, 2026 for adults with cognitive impairment being evaluated for Alzheimer's disease, while amyloid PET remains a separate, older test that measures a different protein (Lantheus investor release). For someone with mild cognitive impairment (MCI), the two scans are not interchangeable: amyloid PET is generally the more sensitive early-detection tool, while tau PET tracks how far disease has spread and correlates more closely with symptom stage (Alzheimer's Association AUC summary). Tauklarify is the brand name for florquinitau F 18 injection, previously known in research as MK-6240, sponsored by Lantheus and Enigma Biomedical. It binds to tau neurofibrillary tangles, a hallmark protein buildup inside neurons that spreads as Alzheimer's progresses, and makes that buildup visible on a PET scan (Healio).
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Official resources:
- Read the official guidance from Lantheus — Use this primary source to verify the official guidance.
- Read the official guidance from Healio — Use this primary source to verify the official guidance.
Table of Contents
- What the FDA approval actually covers
- How tau PET and amyloid PET differ in what they measure
- Who qualifies for a tau PET scan under the appropriate use criteria
- Safety profile and what to expect from the scan itself
- What remains unestablished, including for mild cognitive impairment specifically
- Frequently Asked Questions
What the FDA approval actually covers
The approval authorizes Tauklarify for brain PET imaging in adults with cognitive impairment who are being evaluated for Alzheimer's disease, specifically to identify whether tau neurofibrillary tangle pathology is present. The label does not establish the tracer's use for non-Alzheimer's tauopathies, such as progressive supranuclear palsy or other tau-related conditions, so a Tauklarify scan is not validated to diagnose those disorders (Healio). The approval rested on two blinded reader studies that compared scan readings against a reference pathology standard.
Positive percent agreement ranged from 68% to 88%, and negative percent agreement ranged from 93% to 99%, across participants who had MCI, mild Alzheimer's dementia, or no cognitive impairment (NeurologyLive). Those numbers mean the scan is better at correctly ruling out tau pathology than at catching every case where it's present — a meaningful gap for anyone relying on a single scan to settle the question. The FDA label itself carries a caution worth repeating in plain terms: a negative Tauklarify scan does not necessarily rule out tau pathology, and a positive scan does not necessarily confirm it at the tissue level. Results require correlation with other clinical findings rather than being read as a stand-alone verdict (Practical Neurology).
How tau PET and amyloid PET differ in what they measure
Amyloid PET and tau PET image two different proteins that build up in Alzheimer's disease, and they answer different clinical questions. Amyloid PET detects amyloid-beta plaques, which tend to appear earlier in the disease process, making it the more sensitive tool for flagging early Alzheimer's pathology. Tau PET detects neurofibrillary tangles, which spread in a pattern that tracks more closely with a person's actual stage of cognitive decline (Alzheimer's Association AUC summary). The 2025 Appropriate Use Criteria from the Alzheimer's Association and the Society of Nuclear Medicine and Molecular Imaging treat the two scans as having distinct, non-interchangeable roles rather than recommending them as a routine combined test.
A clinician choosing between them, or deciding to order both, is weighing different information each one provides, not picking a "better" version of the same test. That distinction shows up directly in how often each scan is rated appropriate for MCI or dementia patients. Across 17 modeled clinical scenarios, amyloid PET was rated appropriate in 7 of them, while tau PET was rated appropriate in 5 (Alzheimer's Association/SNMMI AUC). Neither test is endorsed for broad screening; both are reserved for cases where Alzheimer's is suspected but remains uncertain after a specialist evaluation, and only when the result would actually change how the patient is managed.
Who qualifies for a tau PET scan under the appropriate use criteria
The 2025 criteria set a specific bar before either scan is considered appropriate: a specialist must have already evaluated the patient and Alzheimer's disease must remain diagnostically uncertain, and the result must be expected to change clinical management (Alzheimer's Association/SNMMI AUC). A scan ordered simply because a patient or family wants more information, without that uncertainty and without a plan for how the result changes care, falls outside the criteria.
For people specifically with mild cognitive impairment, this matters because MCI is itself a diagnosis of uncertainty — not everyone with MCI has underlying Alzheimer's pathology, and not everyone who has it will progress to dementia. Both amyloid and tau PET are tools for narrowing that uncertainty in appropriate candidates, not routine tests for everyone carrying an MCI diagnosis.
- A tau PET scan under these criteria generally requires: a documented specialist cognitive evaluation, persistent diagnostic uncertainty about Alzheimer's as the cause, and a clear reason the result would change the treatment or monitoring plan.
- A scan ordered outside those conditions sits outside the criteria the field currently uses to judge appropriateness.
Safety profile and what to expect from the scan itself
Tauklarify's safety was assessed in 1,734 subjects. The most common adverse reactions were headache, occurring in 0.7% of subjects, nausea in 0.2%, and injection-site reactions in 0.1%.
No serious safety signal was identified in the reported data (Psychiatric Times). For most patients, that places the physical burden of the scan itself well below the cognitive and emotional weight of the diagnostic process it's part of.
What remains unestablished, including for mild cognitive impairment specifically
Published coverage of the Tauklarify label documents no claim that the scan predicts future cognitive decline or can be used to monitor disease progression or treatment response over time. Those uses fall outside the approved indication, which is limited to identifying tau pathology at a single point in time to support an Alzheimer's evaluation (Lantheus investor release). There's also a known class-wide limitation worth factoring in at the MCI stage specifically.
For flortaucipir (marketed as Tauvid), a longer-marketed tau tracer, the Journal of Nuclear Medicine reports that its ability to distinguish Alzheimer's from other neurodegenerative diseases drops substantially in patients with MCI compared to those with more advanced dementia (AuntMinnie). Tauklarify is a different tracer with its own approval data, but this pattern illustrates a limitation that clinicians weigh across the tau PET class when interpreting results in patients whose cognitive symptoms are still mild. A reader with MCI considering a tau PET scan should expect that the test is one piece of evidence a specialist combines with clinical history and other findings, not a single number that settles the diagnosis on its own.
Frequently Asked Questions
Can Tauklarify replace an amyloid PET scan?
No. The two scans measure different proteins and the Appropriate Use Criteria treat them as serving distinct roles rather than one substituting for the other (Alzheimer's Association AUC summary).
Does a positive Tauklarify scan confirm Alzheimer's disease?
Not on its own. The FDA label states a positive scan does not necessarily indicate histopathologically confirmed tau pathology, so results need correlation with other clinical findings (Practical Neurology).
Can Tauklarify be used to track whether a treatment is working?
That use is not part of the approved indication; published label coverage documents no claim for monitoring progression or treatment response (Lantheus investor release).
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