A digital enzyme-linked immunosorbent assay for ultrasensitive measurement of amyloid-β 1–42 peptide in human plasma with utility for studies of Alzheimer’s disease therapeutics

Table 10 Comparison of prototype digital enzyme-linked immunosorbent assay (Simoa) amyloid-β 1–42 peptide assay with the Quanterix commercial Simoa assay in the context of use as a pharmacodynamic marker in β-site amyloid precursor protein cleaving enzyme 1 inhibitor clinical trials

ELISA	LLOQ (pg/ml; ±20%)	Mean baseline (pg/ml) (SD)	Maximum percentage reduction (SD)	Maximum quantifiable percentage reduction (±20%)
Quanterix commercial Aβ_1–42 assay performance
Aβ_1–42 peptide calibrator
Quanterix	0.274 (0.220–0.329)^a	17.1 (2.16)^b	64 (5)^c	98 (96.5–98.7)
Fujirebio	0.824 (0.659–0.989)^a	39.6 (4.93)^b	64 (5)^c	98 (95.4–98.3)
Prototype Simoa Aβ_1–42 assay performance
Aβ_1–42 peptide calibrator
Quanterix	1.2 (0.96–1.44)	18.7 (2.04)^d	75 (3)^e	94 (92.3–94.9)
Fujirebio	2.8 (2.24–3.36)	44.35 (4.99)^d	79 (3)^e	94 (92.4–94.9)

Aβ amyloid-β, ELISA Enzyme-linked immunosorbent assay, LLOQ Lower limit of quantification
Note: Quanterix assay data show the maximum reduction of signal observed in I4O-MC-BACA and the assay’s maximum quantifiable percentage reduction limit for the Quanterix commercial assay. Prototype Simoa assay data show results for the same parameters when using the newly developed Simoa assay
^aLLOQ based on lowest standard with replicate performance <20% coefficient of variation
^bBaseline values are calculated from study I4O-MC-BACA (not shown)
^cMaximum percentage reduction calculated from 35-mg dose group of study I4O-MC-BACA (not shown)
^dMean baseline values are calculated from study I4O-MC-BACA (Table 3)
^eMaximum percentage reduction calculated from 35-mg dose group of study I4O-MC-BACA (Table 5)

ISSN: 1758-9193