Development of a sensitive trial-ready poly(GP) CSF biomarker assay forC9orf72-associated frontotemporal dementia and amyotrophic lateral sclerosis

Abstract

ObjectiveA GGGGCC repeat expansion in the C9orf72 gene is the most common cause of genetic frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). As potential therapies targeting the repeat expansion are now entering clinical trials, sensitive biomarker assays of target engagement are urgently required. Our objective was to develop such an assay.MethodsWe used the single molecule array (Simoa) platform to develop an immunoassay for measuring poly(GP) dipeptide repeat proteins (DPRs) generated by the C9orf72 repeat expansion in cerebrospinal fluid (CSF) of people with C9orf72-associated FTD/ALS.Results and conclusionsWe show the assay to be highly sensitive and robust, passing extensive qualification criteria including low intraplate and interplate variability, a high precision and accuracy in measuring both calibrators and samples, dilutional parallelism, tolerance to sample and standard freeze–thaw and no haemoglobin interference. We used this assay to measure poly(GP) in CSF samples collected through the Genetic FTD Initiative (N=40 C9orf72 and 15 controls). We found it had 100% specificity and 100% sensitivity and a large window for detecting target engagement, as the C9orf72 CSF sample with the lowest poly(GP) signal had eightfold higher signal than controls and on average values from C9orf72 samples were 38-fold higher than controls, which all fell below the lower limit of quantification of the assay. These data indicate that a Simoa-based poly(GP) DPR assay is suitable for use in clinical trials to determine target engagement of therapeutics aimed at reducing C9orf72 repeat-containing transcripts.

Blood biomarkers in ALS : challenges, applications and novel frontiers

“…Plasma and CSF levels of both NfL and pNfH have been included as secondary outcome measures (see Table 2). 111 The ASO therapeutic approach has also been extended to the treatment of ALS induced by the C9orf72 gene mutation (BIIB078), 112 with a novel immunoassay to test CSF levels of GP dipeptide repeat used as a disease biomarker 113 . It was recently announced, however, that this trial is being stopped due to a lack of efficacy 114…”

“…111 The ASO therapeutic approach has also been extended to the treatment of ALS induced by the C9orf72 gene mutation (BIIB078), 112 with a novel immunoassay to test CSF levels of GP dipeptide repeat used as a disease biomarker. 113 It was recently announced, however, that this trial is being stopped due to a lack of efficacy. 114 The administration of sodium phenylbutyrate-taurursodiol (AMX0035), a drug thought to reduce endoplasmic reticulum stress and restore mitochondrial energy deficits, has given promising results.…”

microRNA-based predictor for diagnosis of frontotemporal dementia

“…Brain imaging and several biofluid proteins have been proposed as biomarkers for both ALS and FTD (Al Shweiki et al , 2019; Ashton et al , 2021; Bellini et al , 2022; Benussi et al , 2019; Bian et al , 2008; Borroni et al , 2015; Bourbouli et al , 2017; Bright et al , 2019; Chouliaras et al , 2022; Das et al , 2022; Delaby et al , 2020; Eratne et al , 2022; Feneberg et al , 2018; Forgrave et al , 2019; Goncalves et al , 2017; Gonzalez-Garza et al , 2018; Hansson et al , 2019; Hu et al , 2013; Jiskoot et al , 2019; Katisko et al , 2021; Katisko et al , 2020; Krishnan et al , 2022; McCarthy et al , 2018; Meeter et al , 2017; Meeter et al , 2018; Niikado et al , 2019; Oeckl et al , 2022; Prado et al , 2018; Rossi et al , 2018; Sheikh-Bahaei et al , 2017; Silva-Spinola et al , 2022; Teunissen et al , 2016; Thijssen et al , 2022; Turner et al , 2009; van der Ende et al , 2020; Verde et al , 2021; Wilson et al , 2022; Xu et al , 2016). Among the proteins, noticeable are neurofilament light chain (NfL), TDP-43 and, phospho-tau, amyloid beta and glial fibrillary acidic protein (GFAP).…”

Biomarkers for amyotrophic lateral sclerosis

“…Current efforts aim to develop sensitive and robust assays fulfilling the analytical requirements for clinical trials. Wilson et al [25] recently described a trial-ready assay to measure poly(GP) in CSF with extensive validation, including intra-assay and interassay variation, parallelism, freeze-thaw stability, and robustness against blood contamination. They confirmed increased poly(GP) levels in C9orf72 mutation carriers with 100% specificity and sensitivity against controls and a large window to detect target engagement.…”