Landmark 346 · Research infrastructure
FDA letter of support for the seed assay
In short
On 19 August 2024 the FDA told the Critical Path for Parkinson's consortium it supports using the spinal-fluid alpha-synuclein seed amplification assay (SAA) to select participants for trials, the second such letter in Parkinson's (the first, in March 2015, was for DaTscan).
- What it is
- Research infrastructure
- Outcome
- Confirmed and built on
- When
- 2024
- Research lane
- Biomarkers
- Last checked
- 20 Oct 2026
The research record
This is the project's file for this landmark, as written and checked. Sources are listed at the end; anything not yet confirmed is marked "Not yet verified".
Who
The FDA's Office of Drug Evaluation Sciences (signed by Jeffrey Siegel and Emily Freilich) wrote to Diane Stephenson of the Critical Path for Parkinson's consortium (landmark 226). The letter names the Michael J. Fox Foundation's PPMI cohort as the key supporting evidence and says an MJFF-led initiative has supported validation of the assay. The Foundation announced the letter on 9 September 2024.
What happened
Letter DDT-BMQ-000157 "encourages the further study and use" of the SAA in human cerebrospinal fluid (CSF) to make trials of early intervention more efficient. Its recommended context of use is a susceptibility/risk biomarker for enrichment: pick participants who test positive for pathological synuclein. It covers Parkinson's, dementia with Lewy bodies and related syndromes, including REM sleep behaviour disorder. It cites the biological staging system NSD-ISS (landmark 28), and its supporting document covers results in several independent observational cohorts and in two recent randomised trials of synuclein-targeted drugs (not named in the letter).
The letter is not a formal qualification. It asks for patient-level data sharing, and says more experience is needed to show the assay's value as a selection tool. It supports a binary (positive/negative) result only.
Why it moved us toward a cure
The assay itself (landmark 9) shows who has the target biology. The letter signals regulators will accept trials that enrol by this test, including prevention trials in people with no symptoms. It follows the 2015 DaTscan letter (landmark 79).
Outcome
Advanced. It covers CSF only, and the test shows pathology is present, not how fast it will progress. No formal qualification submission, letter of intent or qualification plan was found on 20 Oct 2026.
Sources
- FDA Letter of Support DDT-BMQ-000157, 19 Aug 2024
- MJFF news, 9 Sep 2024
- Letter text read in full from the FDA PDF on 20 Oct 2026.
- Not yet verified: the contents of the supporting data document; which trials have used the letter.
How it connects
Built on
- builds on DAT scans qualified for trials · 2015
- uses Critical Path for Parkinson's · 2015
- builds on Seed amplification assay · 2023
- uses NSD-ISS and SynNeurGe definitions · 2024
Led to
None recorded.