Amprion

Beyond Suspicion, Toward Precision

For a century, neurologists diagnosed Parkinson's disease the way their predecessors did - by watching a patient move. It is careful work, but by the standards of modern medicine it is a guess. Clinical diagnosis of parkinsonism is estimated to be wrong 33 to 44 percent of the time, and the proof of what was actually happening in the brain often arrived only at autopsy. Amprion, a diagnostics company headquartered in San Francisco with its clinical laboratory in San Diego, was built to close that gap.

The company's method is the Seed Amplification Assay, or SAA. Misfolded proteins such as alpha-synuclein behave in a prion-like way: a single deformed molecule can template others into the same broken shape. Amprion takes a small volume of a patient's cerebrospinal fluid and, in effect, coaxes any misfolded alpha-synuclein present to replicate itself until there is enough to detect. The result is a direct biological readout - evidence of the disease process itself, not an inference drawn from symptoms.

That capability is what earned the company an FDA Breakthrough Device Designation in 2019 and what put its assay at the center of one of the field's most important studies. Amprion's alpha-synuclein SAA was used in the Michael J. Fox Foundation's Parkinson's Progression Markers Initiative, and the resulting analysis of 1,123 participants - published in The Lancet Neurology in 2023 - not only separated Parkinson's patients from controls with high accuracy but revealed molecular subtypes that clinical observation had never seen.

From an autopsy to the living

The commercial expression of the science is a test now called SAAmplify-aSYN, launched in 2021 as the SYNTap Biomarker Test. It was the first commercially available validated alpha-synuclein SAA, and Amprion reports sensitivity around 96 percent and specificity around 92 percent, validated across more than 20,000 samples and 400-plus autopsy-confirmed cases. What once required a pathologist and a deceased patient can now be measured from a lumbar puncture while a person is alive and, potentially, still treatable.

Amprion has since extended the platform beyond a single protein. Next-generation SAAmplify panels, premiered at the Alzheimer's Association International Conference in 2024, read alpha-synuclein alongside total tau, pTau-181, amyloid-beta and NfL - an acknowledgment that real brains rarely carry one clean pathology. The tests support diagnosis across Parkinson's, dementia with Lewy bodies, Alzheimer's with Lewy body co-pathology, and multiple system atrophy.

Two customers, one molecule

Amprion sells into two worlds at once. On one side are neurologists and their patients, who order the physician-directed test that runs through the company's CAP-accredited, CLIA-certified laboratory. On the other are pharmaceutical developers, for whom Amprion provides biomarker services - the ability to enroll trial participants who genuinely have the pathology a drug is meant to treat, and to track that pathology over time. When Eli Lilly participated in the company's Series B, it was buying access to exactly that.

The market position is unusual. In the broader neurodegenerative biomarker field, larger names such as Roche, Fujirebio and Quanterix compete on amyloid-beta and tau immunoassays. Amprion's differentiation is the alpha-synuclein seed amplification assay, where its main alternatives have been academic RT-QuiC labs rather than commercial rivals. A 2025 distribution agreement with Mayo Clinic Laboratories - one of the most conservative names in diagnostics - extended the test's reach nationwide, and in 2026 the company added non-dilutive growth financing from Decathlon Capital Partners and a multimodal-assessment partnership with Modality.AI.

The guiding phrase on the company's wall is modest for a field chasing cures: "Improving the world, one molecule at a time." For Amprion, that is not a slogan so much as a description of the mechanism. A misfolded protein, amplified until it is impossible to miss, becomes a diagnosis - and a diagnosis, arriving early enough, becomes a chance to act.