An appropriate assessment strategy with validated anti-drug antibody (ADA) assays is critical for comparative evaluation of immunogenicity between a proposed biosimilar and its reference product. The strategy should aim to identify potential differences in immune responses between these products. While an ADA assay employing the proposed biosimilar product as the detecting reagent has been generally recommended for such evaluation, a product-specific assay using the product of interest may be of use as it offers a capability of detecting antibodies against specific epitopes from the respective product. Regardless of assay strategy, the performance of the assay must be fully assessed and method needs to be validated to meet the comparative purpose of immunogenicity assessment.