The U.S. Food and Drug Administration (FDA) has approved Tauvid (flortaucipir F18) as an imaging radiotracer agent — a radioactive diagnostic tool — to efficiently detect clumps of tau protein in the brain, one of the hallmarks of Alzheimer’s disease.
“Alzheimer’s disease is a devastating condition that affects millions of Americans. This approval will provide health care professionals with a new type of brain scan to use in patients being evaluated for Alzheimer’s disease,” Charles Ganley, MD, director of the office of specialty medicine in the FDA’s Center for Drug Evaluation and Research, said in a press release.
Tauvid, which was approved under the FDA’s priority review designation, is the first imaging agent cleared for use in detecting tau-related damage. In patients with Alzheimer’s, tau proteins misfold in the brain, creating neurofibrillary tangles. This new agent will detect these tangles, and aid in the diagnosis of Alzheimer’s in adults with cognitive impairments.
Tracing agents had previously only been approved for the detection, after death, of amyloid-beta protein clumps, another hallmark of Alzheimer’s. The amyloid-beta clumps, or plaques, accumulate between nerve cells in the brain, disrupting their function. The use of the tracing agents post-mortem meant that a definite diagnosis of Alzheimer’s could only be obtained after the pathological evaluation of a patient’s brain after death.
“While there are FDA approved imaging drugs for amyloid pathology, this is the first drug approved for imaging tau pathology, one of the two neuropathological hallmarks of Alzheimer’s disease, and represents a major advance for patients with cognitive impairment being evaluated for the condition,” Ganley said.
The agent, delivered intravenously (into the vein), was designed to specifically detect abnormal tau protein aggregates, called tangles. It has shown a 25 times higher selectivity for tau over amyloid-beta clumps.
After injection, Tauvid binds to sites in the brain where abnormal tau protein accumulates, which will become visible during a PET scan imaging.
Tauvid’s efficacy as a radiotracer was tested in two clinical trials.
The open-label Phase 3 A16 study (NCT02516046) enrolled 156 patients with dementia, mild cognitive impairment, or normal cognition. All were terminally ill and consented to donate their brain for evaluation in an autopsy following their deaths.
The participants agreed to receive a single injection of the radiotracer and underwent PET imaging of their brains. Two independent groups of pathologists compared the analysis of the PET brain scans with Tauvid with that of traditional post-mortem brain analysis.
The analysis of 64 patients who died within nine months of the Tauvid brain scan showed that with Tauvid, pathologists were able to correctly detect tau-aggregates and exclude, with a high confidence, those without these changes.
The second Phase 3 study (NCT03901092) included the same group of patients with terminal illness who had participated in the previous trial, plus an additional 18 terminally ill patients and 159 individuals with cognitive impairment being evaluated for Alzheimer’s disease.
The study evaluated the degree of agreement between the five pathologists evaluating Tauvid brain scans, with scores ranging from zero to one. A score of zero meant no agreement and a score of one denoted complete agreement.
The analysis revealed an almost complete agreement between clinical assessments, with a score of 0.87 across all 241 patients. A separate subgroup analysis that included 82 terminally ill patients diagnosed after death and 159 patients with cognitive impairment revealed a score of 0.90 for those with cognitive impairment and 0.82 for the terminally ill.
The most common adverse reactions linked with Tauvid included headaches, injection site pain, and increased blood pressure.
Since Tauvid’s efficacy in detecting tau-aggregates was tested in patients with advanced disease, its efficacy may be lower in those at earlier stages, the FDA noted.
“The use of diagnostic imaging can help patients and their families plan for the future and make informed choices about their health and well-being, in addition to facilitating appropriate patient management for physicians,” said Reisa Sperling, MD, director of the Center for Alzheimer Research and Treatment at Brigham and Women’s Hospital and Massachusetts General Hospital, both in Boston, said in another press release.
“Determining the anatomic distribution and density of tau NFTs [neurofibrillary tangles] in the brain was previously possible only at autopsy,” Sperling said. “Now we have a way to obtain this important information in patients.”
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