FDA-Approved Tau PET Scan Could Help Clarify Complex Alzheimer’s Cases
A new imaging test may improve Alzheimer’s diagnosis by measuring tau tangles in the brain.
When doctors are trying to figure out whether Alzheimer’s is the right diagnosis for an individual with cognitive impairment, they turn to biomarker testing to detect the disease’s hallmark proteins in the blood, cerebrospinal fluid, and brain.
While these tests provide a good proxy measurement of beta-amyloid plaques in the brain, they aren’t as attuned to the other key hallmark, tau tangles.
The Food and Drug Administration (FDA) last month approved a new radiotracer developed by Lantheus, Tauklarify — previously known as MK-6240 — that binds to tangles and allows for visualization on a PET imaging scan.
A head-to-head comparison against another FDA-approved tau tracer, Tauvid, showed that this one may be more sensitive to the disease, clarify the diagnosis in a complex case, and help identify the individuals who might benefit most from anti-amyloid medications.
“As the field continues to advance, clinicians are seeking a more complete understanding of this disease, with tau PET imaging providing information that complements amyloid PET and other diagnostic tools,” Mary Anne Heino, executive chairperson and CEO of Lantheus, said in a press release.
What is Tauklarify and how accurate is it?
Radiotracers are molecules that are attached to a radioactive isotope that emits a safe level of radioactivity that is detectable on a PET scan. Tauklarify binds to tau tangles in the brain, and when it’s imaged, the radioactive portion lights up, providing a measure of the distribution and amount of tau in the brain.
Tauklarify’s approval is supported by two studies of over 500 participants. Independent experts looked at Tauklarify scans to determine an Alzheimer’s diagnosis and compared their answers to a diagnosis based on an amyloid PET scan and cognitive evaluation.
The first study found 80 to 88 percent agreement on positive scans and 98 to 99 percent agreement on negative scans. In the second study, the agreement on positive scans ranged from 68 to 82 percent, while it remained 93 to 99 percent on the negative scans.
Across over 1,700 individuals, the radiotracer was safe with few side effects. The most common were headache and nausea, which both occurred in less than 1 percent of the individuals who received the radiotracer.
“I don’t think every patient being considered for an anti-amyloid treatment will automatically need a tau PET scan,” Davide Cappon, director of neuropsychology at Tufts Medical Center, told Being Patient. “Initially, I think it will be particularly helpful in more complex or atypical cases, or when we want a better sense of how advanced the disease is.”
Sometimes, someone who may be positive for beta-amyloid might not have any tau, meaning that another condition might cause their symptoms, explained Dr. Tharick A. Pascoal, a neurologist and associate professor at the University of Pittsburgh, who conducted a head-to-head study comparing tau radiotracers..
The new test could “inform decisions about anti-amyloid therapy, which appears to provide the greatest benefit in patients with limited tau pathology,” he added.
FAQs
Both Tauklarify and Tauvid are FDA-approved radiotracers that detect tau tangles. A head-to-head study suggests that Tauklarify may be more sensitive at detecting tangles early.
Less than one percent of individuals who received Tauklarify experienced side effects. The most common ones were headache and nausea.
Brian health specialists may order this PET scan during their assessment of an individual who they suspect has cognitive impairment or memory problems due to Alzheimer’s. If the case is complex or other biomarkers don’t provide a clear answer, Tauklarify may be used.
