WASHINGTON -- Flortaucipir F18 (Tauvid), a radioactive PET tracer, became the first drug approved by the FDA to in people being evaluated for Alzheimer's disease late Thursday.
PET imaging with flortaucipir F18 can help estimate the density and distribution of aggregated tau neurofibrillary tangles, a primary marker of Alzheimer's disease.
"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," said Charles Ganley, MD, director of Office of Specialty Medicine in the FDA's Center for Drug Evaluation and Research.
The tracer is administered intravenously and binds to sites in the brain associated with tau protein misfolding.
"Determining the anatomic distribution and density of tau neurofibrillary tangles in the brain was previously possible only at autopsy," Reisa Sperling, MD, director of the Center for Alzheimer Research and Treatment at Brigham and Women's Hospital and Massachusetts General Hospital, said in a . "Now we have a way to obtain this important information in patients."
Two clinical studies involving terminally ill older adults assessed flortaucipir's ability to predict Alzheimer's pathology. In a subset of patients, researchers compared imaging data to autopsy findings. Flortaucipir F18 PET predicted B3 level of tau pathology (Braak stage V or VI, indicating tau deposition in wide areas of the neocortex) with sensitivity ranging from 92.3% to 100.0% and specificity ranging from 52.0% to 92.0%.
The most common adverse reactions reported in clinical trials were headache (1.4%), injection site pain (1.2%), and increased blood pressure (0.8%).
The tracer's ability to detect tau pathology was assessed in people with generally severe stages of dementia and may be lower among those in earlier stages of cognitive decline.
Flortaucipir F18 is not indicated for evaluating patients for chronic traumatic encephalopathy (CTE), the FDA stated. The tracer recently showed only a modest correlation between imaging findings and post-mortem CTE pathology in a former National Football League player.
The agency granted approval to Avid Radiopharmaceuticals, a subsidiary of Eli Lilly. Flortaucipir F18 will have at first, which will expand in response to commercial demand and payor reimbursement, the company said.
Medicare coverage will be particularly important, given the demographics associated with Alzheimer's disease and dementia; it has been a significant issue for uptake of PET tracers for beta amyloid plaques such Avid's florbetapir (AmyVid). The Centers for Medicare and Medicaid Services has insisted on seeing evidence of clinical benefit before agreeing to full coverage. Despite studies pointing in that direction, the agency has on amyloid tracers.