FDA Grants Breakthrough Device Designation to pTau 217 Blood Test for Alzheimer Disease Detection

The FDA granted a pTau 217 blood test (SpearBio), an assessment to detect Alzheimer disease in patients, a breakthrough device designation. According to experts, this designation recognizes the test’s potential to address a critical unmet need for the millions of US citizens who have been living with Alzheimer disease.¹

Image credit: SewcreamStudio | stock.adobe.com

Alzheimer disease is a life-altering, progressive condition that impacts both patients and their caregivers. It is essential to diagnose patients early in order to effectively improve outcomes and enable timely access to emerging treatment options. Currently, diagnostic methods such as PET scans and lumbar puncture cerebrospinal fluid analysis, can be invasive, costly, and logistically challenging. Additionally, measuring very low levels of pTau 217—a specific biomarker associated with neurodegenerative diseases, particularly Alzheimer disease—in plasma requires sensitivity and specificity beyond the reach of conventional immunoassay platforms.^1,2

Additionally, an important step preceding neurofibrillary tangles is hyperphosphorylation of tau and the development of paired helical filaments (PHF). Although experts note that PHFs are not neurotoxic on their own, with subsequent tau truncation, they can aggregate into neurodegenerative NFTs. Research into tau phosphorylation provides early insights into the emergence of tau pathology in Alzheimer disease.²

The pTau 217 assay uses successive proximity extension amplification reaction (SPEAR) technology which overcomes limitations of conventional proximity extension assays, dramatically reducing transient noise to achieve ultra-sensitive biomarker detection.² It enables more accurate differentiation of blood pTau217 from control and improve sample stratification.³

A recent poster discusses the use of ultrasensitive immunoassay platforms to reveal the clinical potential of blood-based protein biomarkers of Alzheimer disease, detecting them at low fg/mL levels for early prognosis, screening, and therapy monitoring. The conventional technologies face limited adoption because of specialized equipment needs, reagent immobilization, and high sample volume requirements.⁴

The study showcases the ability of SPEAR technology to detect and differentiate Neurofilament light, pTau 217, and pTau 231 at sub fg/mL levels from sub-microliter samples. These meet the demand for ultra-sensitive biomarker analysis with non-invasive, small-volume sample collection, as well as accessible platforms for frequent monitoring and high-throughput assay performance.⁴

Additionally, the study showed that SPEAR assay demonstrated strong limit of detection (LOD) and lower limit of quantification and 2 commercial readily available NFL antibody pairs. The LOD was measured at 51 and 90 fg/mL using 1 µL of 1:4 diluted plasma. Further, robust precision was indicated by low intraplate and lot-to-lot (6% and 7%, respectively).⁵

"Receiving FDA breakthrough device designation for our pTau 217 blood test marks an important milestone,” Feng Xuan, PhD, co-founder and CEO of SpearBio, said in a news release. "We are dedicated to providing [health care professionals] and patients with an affordable, accessible, and highly sensitive diagnostic solution that enables timely and accurate decision-making."¹

REFERENCES

1. Spear Bio Secures FDA Breakthrough Device Designation for its Novel pTau 217 Blood Test, Advancing Scalable Solutions for Early Alzheimer's Disease Diagnosis. PR Newswire. News release. January 13, 2025. Accessed January 13, 2025. https://www.prnewswire.com/news-releases/spear-bio-secures-fda-breakthrough-device-designation-for-its-novel-ptau-217-blood-test-advancing-scalable-solutions-for-early-alzheimers-disease-diagnosis-302348726.html

2. SpearBio. A novel approach to ultra-sensitive biomarker detection. Accessed January 13, 2025. https://spear.bio/spear-homogeneous-immunoassay-technology/

3. SpearBio. SPEAR immunoassays for neurology. Accessed January 13, 2025. https://spear.bio/biomarker-research-applications/immunoassays-neurology/

4. Wing Fan T, Kim WH, Thomas C, Jiang W, Tan J, Xuan F. Poster: Increased sensitivity and differentiation of pTau 217 and Neurofilament light using SPEAR technology. SpearBio. Accessed January 13, 2025. https://spear.bio/resource/a-scalable-solution-for-precisely-measuring-low-abundant-neurobiomarkers-from-micro-sampling/

5. Fan, TW. Wednesday-279 - A scalable solution for precisely measuring low abundant neurobiomarkers from micro-sampling. Presented at: Alzheimer’s Association International Conference (AAIC). Philadelphia, Pennsylvania. July 28-August 1, 2024.