FDA Approves Tau PET Tracer MK-6240 for Alzheimer Diagnostic Workup

The FDA has approved Tauklarify (florquinitau F 18 injection, previously known as MK-6240), a tau-targeted PET imaging agent for adults with cognitive impairment who are being evaluated for Alzheimer disease (AD). The scan identifies patients with tau neurofibrillary tangle (NFT) pathology, helping clinicians better characterize where a patient stands in the disease process.¹

The approval was announced by Enigma Biomedical USA (EB USA), which developed the agent through its former subsidiary Cerveau Technologies before selling that subsidiary to Lantheus in 2023 to complete development and commercialization; the 2 companies have continued to collaborate on the product since. Tauklarify previously received FDA Fast Track designation. Of note, the approval carries a limitation of use: safety and effectiveness have not been established for evaluating non-AD tauopathies.¹

"Tauklarify imaging will enable improved understanding of the status of Alzheimer's disease patients across the spectrum of cognitive impairment, including those in the early stages of the disease," Samantha Budd Haeberlein, PhD, chief medical officer of EB USA, said in a statement.¹ “Two large, independent clinical studies demonstrated the efficacy and safety of Tauklarify in assessing the status of NFTs in patients being evaluated for Alzheimer's disease. As Alzheimer research moves towards an increased focus on early disease detection and treatment, Tauklarify is uniquely suited to address those emerging needs.”

How we got here

The FDA accepted the new drug application (NDA) for MK-6240 in October 2025, setting a Prescription Drug User Fee Act (PDUFA) target action date of August 13, 2026.² At the time of NDA acceptance, MK-6240 was already in use across nearly 100 active clinical trials. The tracer was first characterized preclinically in 2016, when in vitro and monkey PET studies showed high-affinity, selective binding to neurofibrillary tangle-rich cortical regions with rapid, uniform brain distribution.³

Rick Hiatt, president and CEO of EB USA, added that the approval “demonstrates its ongoing commitment to be the premier developer of imaging biomarkers for neurological pathologies to accelerate the development, approval, and adoption of effective therapies to treat neurodegenerative diseases.”¹

Studies supporting approval

Tauklarify's approval was based on 2 clinical studies in which 5 independent blinded readers per study classified scans as positive or negative for tau NFT pathology, compared against a pre-established reference standard based on cognitive status and amyloid beta PET pathology. Together, the studies included scans from 617 subjects: 152 with mild AD dementia, 157 with mild cognitive impairment, and 308 cognitively unimpaired individuals.¹

Both studies met their pre-specified success criteria. Study 1 (n = 279) showed reader positive percent agreement (PPA) ranging from 80% (95% CI, 72%-86%) to 88% (95% CI, 82%-93%), with negative percent agreement (NPA) from 98% (95% CI, 94%-99%) to 99% (95% CI, 95%-100%). Study 2 (n = 338) showed PPA ranging from 68% (95% CI, 61%-75%) to 82% (95% CI, 76%-87%), with NPA from 93% (95% CI, 89%-96%) to 99% (95% CI, 96%-100%).

Inter-reader agreement was high in both studies, with a generalized Fleiss' kappa of 0.92 in Study 1 and 0.86 in Study 2. Safety was evaluated in 1,734 subjects; the most commonly reported adverse reactions were headache (0.7%), nausea (0.2%), injection site reactions (0.1%), dizziness (0.1%), and abdominal discomfort (0.1%).

Sterling Johnson, PhD, Jean R. Finley Professor of Geriatrics and Dementia and associate director of the Wisconsin Alzheimer's Disease Research Center, who was not involved in the approval submission, called it “an important and critical step forward," noting his center has used MK-6240 as its tau imaging agent of choice in academic research “based on several clinically important features, particularly its high dynamic range.”

Complementary head-to-head data

Separate from the studies supporting approval, additional evidence has compared Tauklarify against Tauvid (flortaucipir), the only other FDA-approved F-18 tau-targeted PET imaging agent. The HEAD study, published in The Lancet in May 2026, offered the most direct such comparison to date: a prospective, multicenter, within-participant study across 8 North American sites that enrolled 775 individuals, 682 of whom completed tau PET with both agents within a 45-day window, alongside amyloid PET and detailed cognitive assessment.⁴

MK-6240 showed greater discriminative accuracy than flortaucipir for AD-related cognitive impairment, one of the study's 2 coprimary outcomes (area under the curve, 0.93 [95% CI, 0.89-0.95] vs 0.86 [95% CI, 0.75-0.91]; P < .0001). On the second coprimary outcome, frequency of tau positivity, MK-6240 detected neocortical tau pathology more than twice as often as flortaucipir among cognitively unimpaired participants, and more frequently among cognitively impaired participants (28% vs 16%).⁴ An earlier, smaller comparison of the 2 tracers, published in 2022, similarly found that MK-6240 showed a greater dynamic range in standardized uptake value ratio estimates than flortaucipir.⁵

About TAUKLARIFY

Lantheus has framed Tauklarify as one of several tools, alongside amyloid PET and blood-based biomarkers, intended to guide diagnosis and treatment selection as more than 100 disease-modifying AD therapies, including roughly 30 targeting tau, remain in development.⁶ In February 2024, the company also announced a collaboration with the National Institute on Aging to supply MK-6240 for CLARiTI, a 5-year, NIH-funded, multisite study spanning all 37 Alzheimer's Disease Research Centers in the US, designed to generate etiologic profiles for mixed dementia using imaging and blood-based biomarkers.⁷

Following approval, Lantheus said it intends to continue supporting AD therapeutic programs through its Pharma Solutions business while it assesses the path toward broader commercial availability of Tauklarify, noting its approach will stay aligned with partner needs and developments across the AD treatment landscape; the company has not specified a commercial launch timeline.⁶

Important Safety Information

Warnings and Precautions

Risk of misdiagnosis: Tauklarify's performance for identifying tau NFT pathology was assessed in subjects expected to have predominantly no NFT pathology (cognitively unimpaired and amyloid beta PET-negative) or predominantly clinically significant NFT pathology associated with AD (cognitively impaired and amyloid beta PET-positive); performance may be lower in patients at earlier stages of the pathological spectrum. A negative scan does not necessarily exclude tau NFT pathology, and a positive scan does not necessarily indicate histopathologically confirmed pathology; additional evaluation should be considered when clinical uncertainty remains.

Radiation risk: Tauklarify contributes to a patient's overall long-term cumulative radiation exposure, which is associated with increased cancer risk; safe drug handling practices should be followed, and patients should be advised to hydrate before and after administration and void frequently afterward.

Adverse Reactions

The most commonly reported adverse reactions (incidence ≥0.1%) were headache, discomfort, nausea, injection site reactions, and dizziness.

Drug Interactions

CYP1A2 inducers, including tobacco smoking, should be avoided for at least 7 days before Tauklarify administration.

Use in Specific Populations

Lactation: Breastfeeding should be temporarily discontinued; lactating women should pump and discard breast milk for a minimum of 4 hours after administration.

REFERENCES
1. Enigma Biomedical USA Announces FDA Approval of TAUKLARIFY™ (florquinitau F 18 injection) for Use in Patients Being Evaluated for Alzheimer's Disease. News release. Enigma Biomedical USA. August 14, 2026. Accessed August 14, 2026. https://www.businesswire.com/news/home/20260814732640/en/Enigma-Biomedical-USA-Announces-FDA-Approval-of-TAUKLARIFY-florquinitau-F-18-injection-for-Use-in-Patients-Being-Evaluated-for-Alzheimers-Disease
2. Lantheus Announces FDA Acceptance of New Drug Application for MK-6240, a PET Imaging Agent Targeting Tau in Alzheimer's Disease. News release. Lantheus. October 28, 2025. Accessed August 14, 2026. https://www.globenewswire.com/news-release/2025/10/28/3175415/0/en/Lantheus-Announces-FDA-Acceptance-of-New-Drug-Application-for-MK-6240-a-PET-Imaging-Agent-Targeting-Tau-in-Alzheimer-s-Disease.html
3. Hostetler ED, Walji AM, Zeng Z, et al. Preclinical Characterization of 18F-MK-6240, a Promising PET Tracer for In Vivo Quantification of Human Neurofibrillary Tangles. J Nucl Med. 2016;57(10):1599-1606. doi:10.2967/jnumed.115.171678
4. Povala G, Bellaver B, Lussier FZ, et al. Comparison of [18F]flortaucipir and [18F]MK6240 for the detection of tau pathology in Alzheimer's disease (HEAD): a multicentre, prospective, cross-sectional, within-participant study. Lancet. 2026;407(10544):2217-2226. doi:10.1016/S0140-6736(26)00417-4
5. Gogola A, Minhas DS, Villemagne VL, et al. Direct Comparison of the Tau PET Tracers [18F]Flortaucipir and [18F]MK-6240 in Human Subjects. J Nucl Med. 2022;63(1):108-116. doi:10.2967/jnumed.120.254961
6. Lantheus Announces FDA Approval of TAUKLARIFY™ (Florquinitau F 18 Injection), an F18-Labeled Tau PET Imaging Agent for Alzheimer's Disease. News release. Lantheus Holdings, Inc. August 14, 2026. Accessed August 14, 2026. https://www.globenewswire.com/news-release/2026/08/14/3341697/0/en/Lantheus-Announces-FDA-Approval-of-TAUKLARIFY-Florquinitau-F-18-Injection-an-F18-Labeled-Tau-PET-Imaging-Agent-for-Alzheimer-s-Disease.html
7. Lantheus Announces Collaboration to Provide Novel Tau Imaging Agent for Large Consortium Clinical Trial Sponsored by the National Institute on Aging. News release. Lantheus. February 13, 2024. Accessed August 14, 2026. https://finance.yahoo.com/news/lantheus-announces-collaboration-novel-tau-133000553.html