Alzheimer's Therapy Targeting Amyloid Plaques: The Case for Amyloid Diagnosis

GE Healthcare

The United States Food and Drug Administration (FDA) has approved a medication called Aduhelm (aducanumab), a therapy that is intended for patients with Alzheimer’s disease. It is a landmark moment: the drug, which targets and reduces the build-ups of amyloid-beta plaque in the brain, is the first commercially available treatment directed at this defining pathology of Alzheimer’s disease, rather than just easing its symptoms. It has been evaluated in clinical trials in patients who had a positive amyloid PET scan and mild cognitive impairment or mild dementia caused by Alzheimer’s disease. 
 
But appropriate patient access to this therapy remains a challenge. That’s because the main federal programs designed to help cover healthcare costs for U.S. citizens currently exclude a procedure crucial to aiding accurate diagnosis of Alzheimer’s disease. This is the amyloid positron emission tomography (PET) scan. After administration of a radiopharmaceutical, the images from an amyloid PET scan are evaluated to identify whether amyloid plaques, one of the hallmark pathologies of this neurodegenerative disease, are present or not. 
 
“PET scans are currently the gold standard in terms of amyloid biomarkers in Alzheimer's disease,” explains Anja Mett, a global product leader in neurology for GE Healthcare. “Accurate diagnosis of Alzheimer’s disease is critical, but it’s not always easy to diagnose patients based on clinical signs and symptoms alone,” says Mett. “These amyloid imaging agents actually enable detection of the plaques that the newly approved therapy is targeting.” 
 
Patient groups will welcome the green light from the FDA for aducanumab, which is manufactured by Massachusetts-based Biogen. Previously there were no treatments available to alter the progressive path of Alzheimer’s. Aducanumab is the first medication that has been shown to reduce amyloid-beta plaques, which the FDA considers “reasonably likely to result in clinical benefit.” Around 6.2 million Americans have Alzheimer’s, and that number is expected to more than double by 2050.[1] Many of those patients suffer from mild cognitive impairment or mild dementia, and could now be eligible to receive the drug. 
 
The cost for this new therapy is expected to be $56,000 per patient per year, on average [2]. The U.S. federal and state authorities will need, therefore, to consider how to manage the benefits and the cost effectiveness of this new therapy. The likely best way of achieving this is by improving patient access to amyloid PET scans, the diagnostic technique that was used in Biogen’s clinical trials to identify patients for treatment with aducanumab. 
 
Research shows that, in the brains of Alzheimer’s patients, abnormal levels of amyloid-beta clump together, while another protein, ‘tau’, forms tangles. Together, the clumps and tangles disrupt the function of neurons, although scientists are still working to understand the exact mechanism by which they damage the brain. 
 
The diagnostic procedure involves the administration of an amyloid imaging agent which can then show up the tell-tale amyloid-beta build-ups during brain scans. VizamylTM[5] is GE Healthcare’s amyloid imaging agent. Mett explains that PET imaging agent compounds, which contain a radioactive isotope, bind to the amyloid protein. The PET camera detects the radiation emitted by the isotope, yielding an image of the extent and location of the amyloid plaques in the brain. 
 
The FDA approved PET amyloid imaging agents in 2012 and 2014, but Medicaid and Medicare, the government-sponsored programs aimed at covering healthcare costs for U.S. citizens, currently exclude the related PET amyloid scans from their coverage. This severely limits access to a test and so limits the ability to receive a more accurate diagnosis throughout the U.S. In fact, coverage for PET amyloid scans is only available via Coverage with Evidence Development protocols, which involves extensive data gathering through clinical trials.
 
“It is essential that access to a more accurate diagnosis is easy and universal for all patients, especially when considering that, in general, lower-income groups are disproportionately affected by cognitive impairment,” says Mett. “It’s also important to note that the diagnostic procedure for Alzheimer’s is a small percentage of the overall economic impact of the disease.”
 
Mett points out that Medicare already covers the PET tracers that are routinely being used in the diagnostic work-up for oncology patients. “Patients suffering from cognitive impairment or Alzheimer's disease deserve the same access to a more accurate diagnosis.”
 
Providing coverage for the imaging procedure and agents would not only help more appropriate patient selection for the therapy, it may also help to enhance the clinical confidence and accuracy of Alzheimer’s diagnosis. When used as an adjunct to clinical workup, PET amyloid imaging can assist in ruling out the disease, as well as supporting its diagnosis. The Imaging Dementia — Evidence for Amyloid Scanning (IDEAS) study, which involved a subset of more than 11,000 patients across the U.S. with mild cognitive impairment or dementia, reported that over 60% of the patients received a change in management and over one-third received a change in diagnosis following a PET amyloid scan.[3] Another recent paper published in the Journal of Alzheimer’s Disease showed that when clinicians diagnosed the disease as an underlying symptom without a PET scan, up to one third of patients were later shown not to have any amyloid-beta plaques, and for the vast majority their diagnoses were revised.[4]
 
Says Mett: “Now that the first FDA-approved therapy targeting amyloid beta is available, the potential for patients and caregivers seeking a timely, accurate diagnosis as well as access to new treatment options has never been greater.”
 

[1] Alzheimer’s Association. 2021 Alzheimer’s Disease Facts and Figures
[2] Biogen and Eisai launch multiple initiatives to help patients with Alzheimer’s disease
access ADUHELM™
[3] Rabinovici, GD et al, JAMA 2019; 321:1286-
[4] Enrico R. Fantoni, Anastasia Chalkidou, John T. O’ Brien, Gill Farrar and Alexander
Hammers, 2018, Journal of Alzheimer’s Disease 63 (2018) 783–796
 

Product Indications and Important Safety Information – Vizamyl

PRODUCT INDICATIONS AND USE
VIZAMYL™ (Flutemetamol F 18 Injection) is indicated for positron-emission tomography (PET)
imaging of the brain to estimate β-amyloid neuritic plaque density in adult patients with cognitive
impairment who are being evaluated for Alzheimer’s disease (AD) or other causes of cognitive
decline. A negative scan indicates sparse to no neuritic plaques, inconsistent with a diagnosis of
AD at the time of image acquisition. A negative scan result reduces the likelihood that a patient’s
cognitive impairment is due to AD. A positive scan indicates moderate to frequent amyloid neuritic
plaques. This amount of amyloid neuritic plaque has been shown to be present in patients with AD
but may also be present in patients with other neurologic conditions as well as in older people
with normal cognition. Vizamyl is an adjunct to other diagnostic evaluations.
Limitations: A positive scan does not establish a diagnosis of AD or other cognitive disorder. The
safety and effectiveness of Vizamyl have not been established for predicting the development of
dementia or other neurologic conditions or for monitoring responses to therapies.
Important Safety Information About VIZAMYL™ (Flutemetamol F 18 Injection)
CONTRAINDICATIONS
• Known hypersensitivity to Vizamyl or any excipient, including polysorbate 80
WARNINGS AND PRECAUTIONS
• Hypersensitivity Reactions: Reactions such as flushing and dyspnea have been observed
within minutes following administration and may occur in patients with no history of
exposure to Vizamyl. Before administering Vizamyl, ask patients about prior reactions to
drugs, especially those containing polysorbate 80. Have resuscitation equipment and
trained personnel available
• Risk for Image Misinterpretation and Other Errors: Errors may occur while interpreting
Vizamyl positron-emission tomography (PET) images. Image interpretation is
performed independently of the patient’s clinical information. The use of clinical
information in the interpretation of Vizamyl images has not been evaluated and may
lead to errors. Extensive brain atrophy may limit the ability to distinguish grey and
white matter on a Vizamyl scan. Motion artifacts may distort the image. Images should
be interpreted only by readers who have completed a reader training program
available from GE Healthcare
• Radiation Risk: Like all radiopharmaceuticals, Vizamyl contributes to a patient’s longterm,
cumulative radiation exposure and cancer risk. Ensure safe handling to protect
patients and healthcare workers from unintentional radiation exposure
ADVERSE REACTIONS
• The most commonly reported adverse reactions in clinical trials were flushing (2%),
increased blood pressure (2%), headache (1%), nausea and dizziness (1%)
DRUG INTERACTIONS
• Drug-drug interaction studies have not been performed in patients to establish the extent,
if any, to which concomitant medications may alter Vizamyl image results
USE IN SPECIFIC POPULATIONS
• Pregnancy: All radiopharmaceuticals, including Vizamyl, have potential to cause fetal
harm. There are no available data on Vizamyl in pregnant woman to evaluate drug
associated risk of major birth defects, miscarriage or adverse maternal or fetal outcome
Advise women about the potential for adverse pregnancy outcomes based on the
radiation dose and gestational timing of exposure
• Lactation: There are no data on presence of flutemetamol or its metabolites in human
milk. The benefits of breastfeeding should be considered along with the mother’s clinical
need for Vizamyl and any potential adverse effects on the breastfed child. Because many
drugs are excreted in human milk and there is a potential for radiation exposure to
nursing infants, advise a lactating woman to interrupt breastfeeding and pump and
discard breast milk for 24 hours after administration to minimize radiation exposure to a
breastfeeding infant
• Pediatric Use: Vizamyl is not indicated for use in pediatric patients
• Geriatric Use: No overall differences in safety were observed between older and
younger subjects
OVERDOSAGE
• The clinical consequence of overdosing with Vizamyl has not been reported. It is
unknown whether or not flutemetamol is dialyzable. The major risks of overdosage
relate to increased radiation exposure and long-term risk for neoplasia. In case of
overdose of radioactivity, hydration and frequent urination should be encouraged
Prior to Vizamyl administration, please read the full Prescribing Information for additional
Important Safety Information.
To report SUSPECTED ADVERSE REACTIONS, contact GE Healthcare at 800 654 0118 (option 2, then
option 1) or the FDA at 800 FDA 1088 or www.fda.gov/medwatch.