Development of Blood-based Circular RNA Biomarkers for Alzheimer's Disease

PROJECT SUMMARY—This Phase I application targets PAS-19-316 to address the priorities for a) new, cost- effective, minimally-invasive biomarkers that could be used for screening and b) research that would identify new biomarkers that could serve as surrogate measures for disease progression in Alzheimer’s Disease and Related Dementias (AD/ADRD). Specifically, Vivid Genomics is exploring the use of circular RNAs (circRNAs) in blood as a biomarker of AD and AD progression, including the possible identification of presymptomatic AD. The enormous public health challenge of AD is complicated by the lack of accessible, non-invasive tools for definitively diagnosing the disease prior to death. Although imaging and AD biomarkers in cerebrospinal fluid (CSF) can provide insight into disease status, they are not ideal for routine screening. Recently reported blood- based screens for amyloid b and phosphorylated tau (p-tau) represent a significant advance, but they require methods that are not easily scalable or may not have adequate sensitivity in early disease. In addition, they assess the presence of amyloid b and p-tau at a particular point in time and cannot currently be used to indicate the rate of disease progression or future likelihood of decline. Thus, developing new scalable, cost-effective, minimally-invasive blood-based biomarkers could provide a much-needed tool for routine screening in high-risk individuals, routine follow-up to track AD progression, or ongoing monitoring to assess treatment efficacy. Recent findings indicate several circRNAs differentially expressed in the brains of patients with and without AD are significantly associated with AD diagnosis, clinical severity, and neuropathological severity. In addition, changes in circRNA expression can be detected even in presymptomatic patients. Preliminary studies indicate these markers are also differentially expressed in blood, providing a basis for exploring blood-based circRNAs as biomarkers of AD and/or AD progression. In this proof-of-concept Phase I SBIR, Vivid proposes to identify multiple circRNAs whose expression in blood is associated with AD diagnosis, clinical severity, and/or neuro- pathological severity. Aim. Identify blood-based circRNAs that are associated with AD status and AD- biomarker positivity. RNA-seq will be used to analyze circRNAs in blood from 300 patients in the Knight Alzheimer's Disease Research Center cohort. A rank-ordered list of circRNAs of interest will be developed based on the strength of their association with AD traits adjusted for median transcript integrity score, age of onset, batch, sex, and genetic ancestry. Associations and rank order will then be validated in blood from 300 patients in the AD Neuroimaging Initiative (ADNI) cohort. Go/No-Go Criterion: Identify ≥ 2 blood-based circRNAs correlated with one or more AD traits (FDR lt 0.05). Impact—Proof-of-concept would provide a foundation for development of blood-based circRNAs as biomarkers of AD and/or AD progression. Validation and regulatory clearance would provide a scalable, cost-effective, minimally-invasive alternative to current biomarkers, which could support routine screening of high-risk individuals and inform treatment decisions and clinical trial designs.