Table 5.
| Analytic and in vitro studies | These evaluations involve extensive in vitro characterization and comparison of the biosimilar and its reference product concerning their physicochemical and biological properties, such as amino acid sequencing and folding, the proportion of glycan and non-glycan components in their structure, stability profile, cellular mechanisms of action, cell receptor interactions, and product- and process-related impurities. Analytical evaluation reveals variations in the functional and structural properties. Analytic evaluation for insulin includes protein content, amino acid sequence, secondary structure, higher order structure, functional activity (receptor binding, dissociation, and downstream biochemical cellular action), size variants (aggregates), and conjugate variants. For metabolic endpoints, various functional assays are available including assays measuring glycogen formation, lipogenesis, inhibition of stimulated lipolysis, as well as glucose transport, which can be studied in a variety of cells. |
| Preclinical in vivo studies | Animal studies are carried out if the scientific question cannot be answered in vitro. The information obtained is used in determining the appropriateness of proceeding to human clinical trials. Limited immunogenicity testing is possible for insulin. Toxicity studies are limited by hypoglycemia if higher dose levels are used. Potency studies have high variability. |
| Clinical PD/PK studies | Comparative human PK and PD studies provide different types of information. PK studies measure how the body handles insulin, while PD studies measure how the hormone acts on the body. The objective is to evaluate the bioequivalence of PK and PD characteristics of the biosimilar to its reference product. The studies support a demonstration of biosimilarity with the assumption that similar exposure (and PD response) provides similar efficacy and safety. In the absence of specific acceptance limits for biological medicinal products in general and for insulin specifically, the conventional acceptance range for bioequivalence (80%-125% [90% CI for PK and PD]) is recommended. 16 Evaluation of clinically relevant measures of insulin action is assessed by euglycemic clamp studies. In these clamp experiments, insulin has to be administered by subcutaneous injection of insulin and the blood glucose levels are maintained (“clamped”) at a predefined level utilizing a variable glucose infusion. |
| Clinical safety studies | When necessary, safety studies should be performed with a specific focus on immunogenicity. People with T1D are the preferred population. |
Abbreviations: CI, confidence interval; PD, pharmacodynamic; PK, pharmacokinetic; T1D, type 1 diabetes.