RT-QuIC and PMCA: first synuclein amplification

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

Graham Fairfoul, Alison Green and colleagues (16 authors; National CJD Research and Surveillance Unit, Edinburgh, with Oxford Parkinson's researchers including Laura Parkkinen, Michele Hu and Richard Wade-Martins) for the RT-QuIC paper. It was funded by the Scottish Government's Chief Scientist Office and the Michael J. Fox Foundation. Mohammad Shahnawaz, Abhisek Mukherjee, Sandra Pritzkow and colleagues, senior author Claudio Soto (University of Texas Houston), for the PMCA papers; the 2020 paper was funded in part by the Michael J. Fox Foundation and US National Institutes of Health. Soto is a founder of Amprion Inc., which licensed the University of Texas patents on the method (declared in the 2020 paper).

What happened

Both methods work like a copy machine for misfolded protein: a trace of "seed" in a sample is mixed with normal alpha-synuclein, shaken or cycled so the seed converts more protein, and a dye reports the result.

In 2016, Fairfoul et al. (RT-QuIC, "real-time quaking-induced conversion") tested spinal fluid. Using 15 microlitres, sensitivity was 92% for dementia with Lewy bodies (pure cases; 65% in cases that also had Alzheimer pathology) and 95% for Parkinson's (19 of 20), with 100% specificity against controls and Alzheimer's. Tauopathies (PSP, CBD) were negative, and all 3 people with REM sleep behaviour disorder (a Lewy-body risk state) were positive.

In 2017, Shahnawaz et al. (JAMA Neurology) used a related method, protein misfolding cyclic amplification (PMCA), on spinal fluid from 76 Parkinson's patients and 97 controls: sensitivity 88.5%, specificity 96.9%.

In 2020, Shahnawaz et al. used PMCA on spinal fluid from 94 Parkinson's, 75 multiple system atrophy (MSA) and 56 control patients. It separated Parkinson's from MSA in 146 of 153 samples (95.4%), because the two diseases make different alpha-synuclein shapes ("strains"). This fits the patient-fibril shapes in landmark 27.

Why it moved us toward a cure

Slowing-the-disease drugs need to be tested in people who truly have the target. A test of the protein's own misfolding behaviour gave a direct readout of synuclein pathology in living patients. The approach was validated at scale in the PPMI cohort (landmark 24; landmark 9).

Outcome

Advanced. The principle became the 2023 assay and an FDA Letter of Support in 2024 (landmark 346). Limits remain: the tests show that pathology is present, not how fast it will progress, and the 2016 sample was small. No correction or retraction was found for the three papers; each drew only comment pieces (Europe PMC).

Sources

• Fairfoul et al., Ann Clin Transl Neurol 2016;3(10):812–818, DOI 10.1002/acn3.338, PMID 27752516 (abstract and full text via Europe PMC, PMC5048391; online 28 Aug 2016 per Alzforum record)
• Shahnawaz et al., JAMA Neurol 2017;74(2):163–172, DOI 10.1001/jamaneurol.2016.4547, PMID 27918765 (abstract via Europe PMC)
• Shahnawaz et al., Nature 2020;578:273–277, DOI 10.1038/s41586-020-1984-7, PMID 32025029 (full text PMC7066875)
• Siderowf et al., Lancet Neurol 2023, DOI 10.1016/S1474-4422(23)00109-6
• MJFF on the FDA Letter of Support, Sept 2024
• Correction: the Fairfoul paper is dated 2016 (some memory-based lists say 2017).
• Not yet verified: the origin of these methods in prion-disease testing; which laboratory method the 2023 study used beyond "previously described methods" in its abstract; the exact control group size breakdown for the 2017 paper (97 is the sum of 65 + 18 + 14 in the abstract).