(M1330-10-66) Case Study: Assessing Innovator vs. Biosimilar mAb Stability to Minimize Immunogenic Risk

Purpose: There is increasing evidence that sub-micron aggregates (100-1000 nm) in biotherapeutic formulations are associated with an increased immunogenic risk. A patient’s immune system could recognize the protein aggregate as an infectious particle, such as a virus, and produce an unwanted immune response. This response can range from general inflammation to the development of anti-bodies to the biotherapeutic. The FDA recently issued a guideline to address this concern, outlining what is currently expected and what will eventually be required in the future from biotherapeutic developers to avoid this risk¹. Aggregation can occur at any point within the delivery chain, e.g. during/after cold storage, buffer change and/or pH, shear-stress, or shaking. Currently, there is no universal recipe for an ideal, stability-enhancing formulation composition. Considering the cost to produce biotherapeutics is estimated to be $2.6 billion USD over a 10 year period, there has already been a growing effort by biotherapeutic developers to develop screening assays that can be used to create stability profiles in the early development phase of the biotherapeutic pipeline.

Methods: First, stability predictors that use dynamic light scattering (DLS), static light scattering (SLS), electrophoretic light scattering (SLS), and differential scanning calorimetry (DSC), producing parameters such as the Stokes radius (R_S), interaction parameter (k_D), aggregation onset temperature (T_Agg), 2^nd virial coefficient (B₂₂), effective charge (Z_Eff), and melting point temperature (T_M), all of which are predictive of aggregation propensity. Second, stability descriptors, to confirm the size & count of sub-micron (SmP) & sub-visible (SVP) particles using technologies like nanoparticle tracking analysis (NTA) & analytical imaging (AI), and to assess the developability using techniques like micro-capillary viscometry to measure the viscosity (η).

Results: In this case study, we compared the stability predictors and descriptors between two mAb products, the Innovator product (mAb A) and the biosimiliar product (mAb B). Interestingly, all of the stability predictors in Table 1 suggest that the mAb B biosimilar formulation composition will exhibit greater stability than the mAb A innovator formulation composition. Furthermore, the predictions are in strong agreement with stability descriptors. These combined assays suggest that the biosimiliar product is more stable than the innovator product, and as a result likely presents a lower immunogenic risk.

Conclusion: Stability predictors (R_S, k_D, T_Agg, B₂₂, Z_Eff, T_M) predict that the biosimiliar product (mAb B) is more stable than the innovator product (mAB A). Stability descriptors (C_total, SmP count, η‎_Rel ) agree with the stability predictors. Biosimiliar product likely has lower immunogenic risk than innovator product.

References: Guidance for Industry, Immunogenicity Assessment for Therapeutic Protein Products, Food and Drug Administration, August 2014.

Table 1: Stability profiles for mAb A innovator and mAb B biosimilar samples.

Figure 1: DLS (left) and SLS (right) Debye plots for the innovator mAb A and biosimilar mAb B formulations, with only the biosimilar mAb B exhibiting a positive DLS interaction value.

Figure 2: Differential scanning calorimetry profiles for the mAb A innovator (US source & EU source) and the mAb B biosimilar products.