A Gene Expression-based Blood Diagnostic for Symptomatic Transthyretin Amyloidosis Revealing Male and Female-specific Signatures

Early diagnosis of transthyretin (TTR) amyloid diseases remains challenging because of variable disease penetrance. Currently, patients must have an amyloid positive tissue biopsy to be eligible for disease modifying therapies. Early diagnosis is often difficult because the patient exhibits apparent symptoms of polyneuropathy or cardiomyopathy, but has a negative amyloid biopsy. Thus, there is a pressing need for more objective, quantitative diagnostics and biomarkers of TTR-aggregation-associated polyneuropathy and cardiomyopathy. This is especially true in the context of clinical trials demonstrating significant disease modifying effects, e.g. when the TTR tetramer stabilizer tafamidis was administered to familial amyloid polyneuropathy (FAP) patients early in the disease course. When asked if the findings of the tafamidis registration trial were sufficiently robust to provide substantial evidence of efficacy for a surrogate endpoint that is reasonably likely to predict a clinical benefit the advisory committee said yes, but the FDA rejected the tetramer stabilization surrogate biomarker required for orphan tafamidis approvalhence, acceptable biomarkers are badly needed. Herein, we explored whether peripheral blood cell mRNA expression profiles could differentiate symptomatic from asymptomatic V30M FAP patients, and if such a profile would normalize upon tafamidis treatment. We demonstrate that blood cell gene expression patterns reveal sex-independent as well as male and female specific inflammatory signatures in symptomatic FAP patients, but not in asymptomatic carriers, that normalize in FAP patients 6 months after tafamidis treatment. Thus these signatures have potential both as an early diagnostic and as a surrogate biomarker for measuring response to treatment in FAP patients.

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Kurian SM, Novais M, Whisenant T, Gelbart T, Buxbaum JN, Kelly JW, Coelho T, Salomon DR