The FDA approved a second tau PET imaging agent in 2026, giving doctors a new option for scanning brain tau tangles during Alzheimer's workups. For people with mild cognitive impairment (MCI), that means more accurate staging and prognosis tools are becoming available, though rollout and routine use remain limited for now. Tau PET uses a radioactive tracer and a PET scanner to visualize tau neurofibrillary tangles, one of the two hallmark proteins (alongside amyloid) that build up in Alzheimer's disease. On August 14, 2026, the FDA approved Tauklarify (florquinitau F 18, formerly known as MK-6240), made by Lantheus, for adults with cognitive impairment who are being evaluated for Alzheimer's disease, according to SNMMI's announcement.
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.
Table of Contents
- What Tauklarify Is and Why It's a Second Option
- How Accurate Is the New Tracer Compared to the Older One?
- When Is Tau PET Actually Appropriate for MCI?
- What Tau PET Can and Can't Tell You About Treatment
- Will Patients Actually Be Able to Get the New Scan?
- Frequently Asked Questions
What Tauklarify Is and Why It's a Second Option
Tauklarify is only the second tau PET tracer ever approved by the FDA. The first, flortaucipir F-18 (brand name Tauvid, made by Eli Lilly), has been available since 2020, as reported by NeurologyLive. Having a second approved agent gives clinicians and imaging centers a choice rather than a single pathway.
Lantheus's FDA labeling is specific about scope: Tauklarify's safety and effectiveness have not been established for evaluating tauopathies outside of Alzheimer's disease, according to the Lantheus release reported by Barchart. That means a positive scan should be interpreted only in the context of suspected Alzheimer's-type tau pathology, not other conditions that also involve abnormal tau buildup, such as some frontotemporal dementias. For a reader with MCI, the practical takeaway is narrow but important: this tracer is built and labeled specifically for the Alzheimer's workup pathway, not as a general-purpose tau test for any memory concern.
How Accurate Is the New Tracer Compared to the Older One?
A multicenter trial called the HEAD study scanned 682 people with both tracers within 45 days of each other and compared their performance directly. Florquinitau (Tauklarify's active ingredient) showed higher accuracy than flortaucipir in distinguishing Alzheimer's disease from other causes of cognitive impairment, with an area-under-the-curve (a standard accuracy measure) of 0.93 versus 0.86, according to The Lancet. The newer tracer also flagged neocortical tau positivity — meaning tau spread into the outer regions of the brain, which signals more advanced disease — in 28% of scans, compared with 16% for the older tracer.
That gap suggests florquinitau may be more sensitive to picking up tau spread at earlier or more subtle stages, which is particularly relevant for someone with MCI whose disease trajectory is still uncertain. Neither of these numbers means the older tracer is obsolete. Tauvid remains FDA-approved and has years of established clinical use behind it, which matters for availability in the near term, covered in Section 4.
When Is Tau PET Actually Appropriate for MCI?
Having an imaging option does not mean it belongs in every workup. The Society of Nuclear Medicine and Molecular Imaging (SNMMI) and the Alzheimer's Association jointly updated their Appropriate Use Criteria, the first revision since 2013, rating tau PET as appropriate in 5 of 17 real-world clinical scenarios, uncertain in 6, and rarely appropriate in 6, according to SNMMI. Evaluating and predicting prognosis specifically in people with MCI is among the strongest-evidence uses listed.
The same criteria caution against overuse. Ordering amyloid and tau PET together is generally not recommended as routine practice, and both scans are rarely appropriate for people without cognitive symptoms — even those who carry the APOE4 gene variant linked to higher Alzheimer's risk — or for legal, insurance, or employment purposes, according to the Alzheimer's Association's visual guide. In March 2026, EANM and SNMMI jointly published a consensus statement giving nuclear medicine practitioners detailed guidance on when to order tau PET, how to perform the scan, and how to interpret results in patients with suspected Alzheimer's, covering both flortaucipir and newer tracers like florquinitau, according to the guideline published by SNMMI and EANM. For someone with MCI, this means a tau scan is most likely to be ordered when prognosis and disease-staging information would actually change clinical decisions, not as a routine add-on to every memory evaluation.
- Tau PET is well-supported for staging and predicting outcomes in MCI.
- It is not recommended for people without symptoms, regardless of genetic risk.
- Pairing amyloid and tau PET as a routine combination is discouraged.
- It should not be used for non-medical purposes like legal or insurance determinations.
What Tau PET Can and Can't Tell You About Treatment
Amyloid PET and tau PET serve different roles in an Alzheimer's workup. Amyloid PET is used to determine whether someone qualifies for anti-amyloid drugs and to monitor how they respond to treatment.
Tau PET, by contrast, may help predict whether a person will benefit from treatment and can help stage how advanced the disease is in someone with MCI, according to SNMMI's appropriate use criteria announcement. One gap remains unresolved: using tau PET to track treatment response over time — that is, repeating the scan months or years later to see whether tau burden has changed — is still rated uncertain in the appropriate use criteria. That means a clinician may order a baseline tau scan to help with staging and prognosis, but shouldn't yet expect a follow-up tau scan to serve as a routine way to measure whether a drug is working.
Will Patients Actually Be Able to Get the New Scan?
Approval does not mean immediate access. As of its August 2026 approval, Lantheus had not yet detailed Tauklarify's commercial availability or rollout timeline, so patients referred for tau PET may still default to the longer-established Tauvid scan at many imaging centers in the near term, according to NeurologyLive. Corporate changes could also shape how quickly Tauklarify reaches clinics.
On August 3, 2026, Curium agreed to acquire Lantheus for up to $8 billion — $102.50 per share in cash plus up to $12 per share in milestone-based payments through 2030 — in a deal expected to close in the first half of 2027, according to Fierce Pharma. An acquisition of this size, closing while the new tracer is still rolling out, could affect production capacity and distribution timing as more imaging centers try to add Tauklarify to their offerings. For a person with MCI asking their neurologist about tau PET today, the realistic near-term answer is that the established Tauvid scan is more likely to be available immediately, while Tauklarify becomes accessible on a center-by-center basis as Lantheus — and eventually Curium — build out supply.
Frequently Asked Questions
Is Tauklarify available everywhere now that it's FDA-approved?
Not yet uniformly. Lantheus had not detailed commercial rollout timing as of the August 2026 approval, so many centers still rely on the older Tauvid tracer while Tauklarify becomes available site by site.
Does a tau PET scan replace an amyloid PET scan?
No. Amyloid PET determines eligibility for and monitors anti-amyloid drug treatment, while tau PET helps predict treatment benefit and stage disease severity — they answer different clinical questions.
Can tau PET be used just because someone carries the APOE4 gene?
No. The updated appropriate use criteria rate tau PET as rarely appropriate for people without cognitive symptoms, even those with APOE4, regardless of genetic risk.
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