FDA Approves Lantheus’s Tauklarify, a Brain-Scan Agent That Maps Alzheimer’s Tau Tangles

The FDA has approved Tauklarify, a radioactive imaging agent from Lantheus Holdings that lets doctors see one of Alzheimer’s defining features on a brain scan: clumps of tau protein.

Cleared August 17, 2026, it is used with positron emission tomography to image the brains of adults with cognitive impairment being evaluated for Alzheimer’s, helping identify tau neurofibrillary tangle pathology. Patients receive an intravenous dose of about 185 MBq (5 mCi) before scanning.

Two proteins, two different stories

Alzheimer’s is marked by two hallmark proteins: amyloid-beta plaques outside cells and tau tangles inside them. Amyloid PET imaging is already established, and tau imaging adds a complementary view.

The complementarity is more meaningful than it sounds, because the two proteins behave quite differently.

Amyloid accumulates early, plateaus, and correlates poorly with symptoms — many cognitively normal older adults have substantial amyloid, and the amount present tells you little about how impaired someone is. It is close to a binary indicator: the pathology is present or it is not.

Tau behaves differently. It appears later, spreads through the brain in a characteristic sequence, and correlates far more closely with cognitive symptoms and their severity. Where tau has reached predicts what a person is struggling with.

Why that makes tau imaging a staging tool

The practical distinction is that amyloid imaging answers whether and tau imaging answers how far.

An amyloid scan establishes that Alzheimer’s pathology is present, which is what current amyloid-targeting therapies require before treatment. A tau scan describes the extent and distribution of the process that actually tracks with decline — information relevant to prognosis, to explaining a patient’s specific pattern of symptoms, and potentially to selecting treatment.

The evidence

Approval was supported by two blinded-read studies analysing images from more than 500 subjects, spanning people with mild cognitive impairment, mild Alzheimer’s dementia, and cognitively unimpaired individuals.

Independent readers, blinded to clinical information and to amyloid-beta PET results, classified scans as positive or negative for tau pathology, with high accuracy and strong agreement between readers.

The blinding to amyloid results is the methodologically important detail. Amyloid and tau status correlate, so a reader who knew a patient was amyloid-positive would be primed to call the tau scan positive. Removing that information tests whether the tau image carries independent information.

Inter-reader agreement is the other figure that matters, and it is frequently the weak point of imaging agents. A scan producing different answers depending on who reads it is not a diagnostic test.

Why the timing matters

“Tau PET imaging provides information that complements amyloid PET and other diagnostic tools,” said Lantheus CEO Mary Anne Heino.

As amyloid-targeting therapies reach patients, tools characterising the underlying disease more precisely become more important. Those drugs are expensive, require infusion, and carry real risks including brain swelling and bleeding — so identifying who is likely to benefit matters more than it did when nothing could be done.

There is emerging evidence that tau burden influences response to anti-amyloid treatment, with patients at earlier tau stages appearing to benefit more. If that holds, tau imaging becomes a treatment-selection tool rather than only a descriptive one.

The tension with blood tests

Worth noting the countervailing trend. Blood-based Alzheimer’s tests measuring phosphorylated tau have reached clearance and are far cheaper and more accessible than PET.

Blood markers indicate whether tau pathology is present. They cannot show where it is, and spatial distribution is precisely what determines symptoms and stage. The two are likely to divide the work — blood tests identifying who has the pathology, imaging characterising those who need staging or are being considered for treatment.

Why tau spreads in a predictable pattern

The staging value of tau imaging rests on a feature of the pathology that amyloid does not share, and it is worth explaining.

Tau tangles appear first in a small brainstem region and in structures around the medial temporal lobe, then progress to adjacent limbic areas, and finally to the wider cortex. That sequence is consistent enough across patients that pathologists have used it for decades to stage the disease in post-mortem tissue.

The consistency suggests tau spreads between connected neurons rather than appearing independently throughout the brain — propagating along anatomical circuits in a manner sometimes compared to prion behaviour, though the analogy is contested.

What that means practically is that a tau scan can be read as a position along a known trajectory rather than merely a quantity. Knowing tau has reached limbic regions but not the wider cortex places a patient at a specific stage with implications for what comes next — information a measure of total burden, or a blood test reporting presence, cannot provide.

PET remains expensive and infrastructure-dependent, which will limit tau imaging to specialist centres regardless of its clinical value. Regulatory news, not medical advice.