Validation And Clinical Utility Of Elisa Methods For Quantification Of Amyloid-Beta Peptides In Cerebrospinal Fluid Specimens From Alzheimer'S Disease Studies

The aim of this study was to validate assays for measurement of amyloid-beta (A beta) peptides in cerebrospinal fluid (CSF) specimens according to regulatory guidance and demonstrate their utility with measurements in specimens from Alzheimer's disease (AD) studies. Methods based on INNOTEST (R) beta-AMYLOID((1-42)) and prototype INNOTEST (R) beta-AMYLOID((1-40)) ELISA kits were developed involving pre-analytical sample treatment with Tween-20 for reliable analyte recovery. Validation parameters were evaluated by repeated testing of CSF pools collected and stored in the same manner as clinical specimens. Intra- and inter-assay coefficients of variation were <= 11% and relative accuracy was within +/- 10% for both analytes. Dilutional linearity was demonstrated for both analytes from a spiked CSF pool, but not from a non-spiked native CSF pool. Recovery of standard A beta peptide spikes ranged from 77% to 93%. No interference was observed from the investigational drugs LY2811376, LY2886721, LY3002813, or semagacestat. A beta(1-40) and A beta(1-42) were stable in CSF for up to 8 hours at room temperature and during 5 freeze-thaw cycles from <= -20 degrees C and <= -70 degrees C. In frozen native CSF specimens, A beta(1-40) was mostly stable up to 3 years at <= 70 degrees C, whereas stability of A beta(1-42) was limited to 221 days. Dose-dependent changes in measured CSF A beta were observed in healthy volunteers up to 36 hours after treatment with the beta-site cleavage enzyme inhibitor LY2886721. In conclusion, rigorous validation tests have successfully demonstrated the strengths and operational limitations of these INNOTEST (R)-based assays. They have proved to be robust and reliable tools for pharmacodynamic evaluations of investigational AD therapeutics in clinical trials.