Comparison of RT-qPCR With Branched DNA to Quantify a Lipid Nanoparticle-Encapsulated mRNA Therapeutic in Serum and Liver Tissue Samples From Nonclinical PK Studies.

Abstract

While the branched DNA (bDNA) assay is an established bioanalytical method for measurement of lipid nanoparticle (LNP)-encapsulated messenger RNA (mRNA) pharmacokinetic parameters, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) has been considered as an alternative platform. RT-qPCR and bDNA platforms were compared for sensitivity, specificity, correlation, and overall assay performance using serum and tissue samples from 2 nonclinical mouse studies of a therapeutic mRNA candidate, LNP-PAH-mRNA, which encodes for human phenylalanine hydroxylase enzyme. Pharmacokinetic parameter noncompartmental analysis was completed using Phoenix WinNonlin. The assays were compared using simple linear regression and Bland-Altman analyses. Sensitivity ranged from 0.05 to 6.40 ng/mL for the bDNA assays, from 0.00000761 to 7.61 ng/mL in serum, and from 0.000179 to 179 ng/g in tissue for the RT-qPCR assay. Inter-assay accuracy was within ± 10%, inter-assay precision was ≤ 10%, and the total error for both assays was ≤ 20%. RT-qPCR serum mRNA concentrations were 2- to fourfold lower compared with the bDNA assay, whereas tissue samples were comparable between assays. A linear relationship with - 0.37 to - 0.02 systematic bias demonstrated acceptable concordance. Bland-Altman plots demonstrated close equivalence, with a negative bias of < 0.5, and ≥ 95% of the data points were within the 95% limits of agreement. The comparison of the RT-qPCR with bDNA assay platforms for quantification of pharmacokinetic properties of an mRNA-LNP therapeutic has demonstrated acceptable concordance. This comparison reinforces the use of the RT-qPCR, a widely accessible strategy, as an alternative platform for the quantification of subsequent mRNA-LNP therapeutics.