Biotherapeutics have been on the center stage in the pharmaceutical industry portfolios and accounted for almost one-half of recent new drug approvals. The majority of these products are monoclonal antibodies (mAbs), recombinant proteins, hormones, cytokines, growth factors, gene therapy products and gene-silencing/editing therapies. The potential immunogenicity of biological products results in the elicitation of anti-drug antibodies (ADA). This undesired immune response is an important safety concern for biopharmaceutical industry and regulatory authorities.
The immunogenicity of a biotherapeutic is dependent on several factors such as protein aggregation, post translational modifications, protein folding, impurities in the formulation, route of administration, mode of action, patient population, treatment regimen and several other factors. The ADA response can potentially lead to allergic reactions and/or reduce or neutralize drug activity affecting drug exposure and thereby altering PK/PD profile. In some instances, this response may also result in hazardous cross-reactivity with endogenous proteins.
In view of these anticipated adversary effects of biotherapeutics, global regulatory authorities recommend that ADA responses be measured and evaluated from a safety perspective. The recommendation is a multi-tiered ADA testing paradigm which includes developing specific binding assays to detect all antibodies to the biotherapeutic drug. This approach involves a three-step process; 1) initial rapid and sensitive screening assay to measure low and high affinity ADA, 2) a confirmatory assay to establish that the detected ADA is specific to the biotherapeutic, 3) characterizing the ADA response by titration and neutralization assays.
One of the most critical reagents for developing these immunogenicity assays is the ADA positive control (PC). The PC contains a purified preparation of antibodies specific to the biotherapeutic drug. In majority of cases, this ADA positive control is generated by immunizing animals in the presence or absence adjuvants and affinity purifying biotherapeutic specific polyclonal antibodies. The fact that the assays are as good as the reagents used to develop them is particularly true in the case of immunogenicity assays. The FDA requires that screening and confirmatory assays achieve a sensitivity of at least 100 ng/mL of ADA in a given matrix. In addition, the ADA positive control is used to determine the assay cut point, drug tolerance, specificity & selectivity, matrix interference, minimum required dilution, precision, reproducibility, robustness and sample stability.
In generating a suitable ADA positive control, several options such as host species to raise antibodies, immunization methodology, antibody screening strategy and antibody purification procedure need to be carefully considered. The selection of a particular method used is dependent primarily on the nature of the drug molecule to which the antibodies need to be generated and the specific demands of the drug development program.
Leveraging our experience in handling a broad range of antigen types, optimized immunization schedules & procedures, and the integration of various strategies, we are able to generate quality antibody reagents with much higher success rates, increased sensitivity and higher yields even against poor antigens such as oligonucleotide therapeutics.