Background/Purpose: Biosimilars are biologics approved by highly-regulated markets as similar to existing agents, with the aim of offering more affordable treatment and 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 present pre-clinical data confirming in vivocomparability for the proposed biosimilar rituximab GP2013, in terms of pharmacokinetics (PK), pharmacodynamics (PD) and efficacy.

Methods: 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.

Results: 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.

Conclusion: 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, GP2013 is anticipated to show similar efficacy and safety as the originator product in ongoing clinical trials across different clinical indications.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/target-directed-development-of-a-proposed-biosimilar-rituximab-gp2013-comparability-of-antibody-dependent-cellular-cytotoxicity-activity-and-pre-clinical-pharmacokinetics-and-pharmacodynamics-with/