Immunogenicity assay supporting clinical development of RGB-19, a proposed biosimilar to RoActemra®

The aim of the work was to develop and validate an anti-drug antibody (ADA) assay for RGB-19, a proposed biosimilar to tocilizumab, capable of detecting anti-tocilizumab antibodies in the presence of high concentrations of soluble IL-6 receptor (sIL-6R), the drug's pharmacological target.

A bridging electrochemiluminescent immunoassay was applied. To mitigate target interference, sarilumab - a high-affinity anti-sIL-6R antibody - was incorporated into the sample preparation. The assay was validated per EMA and FDA guidelines.

The assay demonstrated high sensitivity, robust precision, and selectivity across normal and diseased matrices. Drug tolerance exceeded 280 µg/mL at regulatory sensitivity thresholds, and target tolerance was confirmed up to 1000 ng/mL sIL-6R. Performance monitoring during Phase I and III clinical sample analysis confirmed stability and acceptable false-positive rates.

The validated ADA assay effectively neutralized sIL-6R interference and provided reliable immunogenicity assessment for RGB-19 clinical trials. Its robustness supports biosimilarity evaluation and ensures compliance with regulatory standards. Validation of this ADA assay is essential for regulatory compliance and patient safety. By ensuring accurate ADA detection under clinically relevant conditions, it supports biosimilarity demonstration and streamlines regulatory review, ultimately facilitating timely access to cost-effective biologic therapies.

https://jrct.mhlw.go.jp.Identifiers are: jRCT2031230029 and jRCT2031220512.