Target-Directed Development of a Proposed Biosimilar Rituximab (GP2013): Comparability of Antibody-Dependent Cellular Cytotoxicity Activity and Pre-Clinical Pharmacokinetics and Pharmacodynamics with Originator Rituximab

Biosimilars are biologics approved by highly-regulated markets to be similar to existing agents that aim to offer more affordable treatment, thereby increasing patient access. Development of a biosimilar involves extensive characterization of the originator product over several years and a target-directed iterative development process to ensure a product that is highly comparable to the originator with similar clinical efficacy, safety and quality. Using antibody-dependent cellular cytotoxicity (ADCC), a main mode of action of rituximab, we illustrate how functional/structural relationship can be engineered into a biosimilar to ensure comparability at the in vitro level. Here we also present pre-clinical data confirming in vivo comparability for the proposed biosimilar rituximab GP2013, in terms of pharmacokinetics (PK), pharmacodynamics (PD) and efficacy.

By employing a highly sensitive glycan quantitation method, relevant post-translational glycosylation patterns were assessed for their impact on in vitro ADCC relative potency data using the Raji and NK3.3 cell lines as target- and effector cells, respectively. Subsequently, bioactivity of GP2013 and originator rituximab were evaluated in a dose-response manner across a wide concentration range against SU-DHL-4 (diffuse large B-cell lymphoma) and Daudi (Burkitt's lymphoma) cell lines using freshly purified human NK cells. In vivo anti-tumor activity was assessed in two xenograft SCID mouse models of non-Hodgkin's lymphoma (SU-DHL-4 and Jeko-1 cell lines). Comparative PK and PD were assessed in single (5 mg/kg, n=14) and multiple (20 or 100 mg/kg, n=8) dose studies in cynomolgus monkeys, the pharmacologically most relevant species.

GP2013 and originator rituximab showed similar ADCC potency against both SU-DHL-4 and Daudi cells, with ADCC being reflective of engineered glycosylation patterns and structure-function relationships. In both xenograft mouse models, GP2013 and originator rituximab inhibited tumor growth to a similar extent, including at the more sensitive sub-optimal dose levels that are most likely to identify any potential differences. In primates, PK analysis confirmed bioequivalence between GP2013 and originator rituximab with nearly identical AUC values and 90% CIs entirely within the standard acceptance range of 0.8–1.25. Bioequivalence of PD response (B-cell depletion) was also shown, with 95% CIs of areas under the effect-time curves (AUEC) ratios for relative change from baseline in B-cell populations within the 0.8–1.25 acceptance range. The use of different doses indicated that comparable exposure and PD response can be expected for GP2013 and originator rituximab using indication-specific dosing regimens.

This pre-clinical comparability exercise confirms that GP2013 and originator rituximab are pharmacologically similar with regard to ADCC potency, anti-tumor activity, PK exposure (AUC) and B-cell depletion. As such, it is hypothesized that GP2013 will show similar efficacy and safety as the originator product in ongoing clinical trials across different clinical indications.

da Silva:Sandoz Biopharmaceuticals/HEXAL AG: Employment. Kronthaler:Sandoz Biopharmaceuticals/HEXAL AG: Employment. Meyer:Sandoz Biopharmaceuticals/HEXAL AG: Employment. Papandrikopoulou:Sandoz Biopharmaceuticals/HEXAL AG: Employment. Stangler:Sandoz Biopharmaceuticals/HEXAL AG: Employment. Visser:Sandoz Biopharmaceuticals/HEXAL AG: Employment.