Some thoughts on the QR method for analytical similarity evaluation.

As indicated in a recent published draft guidance on comparative analytical assessment, the United States (US) Food and Drug Administration (FDA) seems to suggest the use of quality range (QR) method for analytical similarity evaluation. It is a concern that the use of QR method for analytical similarity evaluation could potentially approve biological products which are not deemed biosimilar to the reference biological products. In this article, the limitations and potential risk for the use of the QR method for analytical similarity evaluation are discussed. Alternatively, two modified versions of the QR method, which are referred to as effect size (ES) mQR and plausibility interval (PI) mQR methods are suggested. The performance and statistical properties of the mQR methods are evaluated via extensive clinical trial simulation under various scenarios. The results indicate that the modified versions of the QR method not only overcome the limitations of the QR method for analytical similarity evaluation, but also can potentially help in detecting reference product changes during manufacturing process.