To give us an author’s perspective, Jihua Chen of Regeneron Pharmaceuticals (NY, USA) answers some of our questions probing his latest research publication and his current research focus. Jihua discusses the impact of the paper published in Bioanalysis and also outlines some of the major challenges faced by scientists hoping to develop reliable and robust bridging anti-drug antibody (ADA) assays.
Dr Jihua Chen is a Senior Staff Scientist in the Assay Development Group at Regeneron Pharmaceuticals Inc. He supervises scientists in the development and validation of immunoassays (PK, ADA, neutralizing antibody (NAb) and biomarker) used in bioanalyses for both nonclinical and clinical studies in a regulated GLP environment. He obtained his PhD degree from Albert Einstein College of Medicine (NY, USA) and did his postdoc training at Dana Farber Cancer Institute (MA, USA) before joining Regeneron.
QWhat inspired you to work in this field of bioanalysis?
Right after my postdoc, I wanted to work on something that could directly benefit patients. I was interested in how antibody drugs perform and immunogenicity associated with their administration. I was also interested in the relationship between drug efficacy and changes in other proteins related to the mechanism of action of the drug (biomarkers). I joined Regeneron because it was focused on science and helping patients. In my role in the Assay Development Group I develop and validate PK, biomarker, ADA and NAb assays to support the entire Regeneron pipeline, under a regulated environment.
Q What impact would you like to see/expect to see as a result of your publication?
Immunogenicity assessment is really critical during the drug development program. However, we often face difficulties in dealing with soluble targets and their interference in the assays. The common approach to overcome target interference in ligand binding assays is the use of target-specific antibodies to block the interfering signal after acid dissociation. This is usually performed under neutral assay pH. However, standard anti-target antibodies may not be effective in some cases. Therefore, other strategies such as the use of target binding proteins and soluble target receptors can be used. Our paper demonstrates that a better understanding of the interactions between the drug and its target (e.g. pH effect), in addition to the use of different anti-target blocking reagents, can result in a successful target interference mitigation strategy. Furthermore, testing of clinical or nonclinical study samples with high levels of the endogenous target protein can be a critical tool to determine the effectiveness of the target interference mitigation strategy employed. These are some of the key messages of the paper, which we think will be useful to other groups.
Q What are the next steps for your research and this field of bioanalysis?
We are currently working on another manuscript about mitigating multimeric target interference in a bridging ADA assay. Since in this particular case the anti-target antibodies were ineffective at reducing target interference, two different approaches were used: 1) competition for target binding by a soluble target receptor and an accessory protein and 2) target immunodepletion. Interestingly, for both strategies, assay pH conditions also needed to be optimized. Our data has shown that modifying assay pH can certainly play an important role in eliminating target interference. Different pH conditions can be used in bridging ADA assays to either disrupt or enhance various interactions between drug, ADA, drug target, and labeled drug molecules. However, the specific pH conditions for each individual ADA assay need to be carefully evaluated because changes in pH may also have unintended consequences. Recently, a white paper has also been published describing a number of strategies to mitigate drug target interference in ADA and NAb assays.
Q Are there any particular challenges in this area of bioanalysis that you are watching at the moment, and any you think we should be keeping an eye on?
Besides target interference, drug tolerance is another challenge in bridging ADA assays. Several companies have been asked by the regulatory agencies to re-develop their ADA and/or NAb assays to improve their drug tolerance, so the presence of an immune response can be evaluated in presence of drug. I think some of the regulatory agencies have concerns over whether negative ADA results with study samples really reflect the absence of an immune response or are the result of the poor drug tolerance of some of these assays. Therefore, the development of highly drug tolerant ADA and NAb assays becomes critical. Several highly drug tolerant ADA assay formats have recently been published and are very promising. However, although an increase in positive ADA and NAb results have been generated with these methods, these additional signals are all low titer responses and their clinical relevance is a point of discussion. We are very interested to know how these methods and these data will be used to really evaluate the immunogenicity incidence of different biotherapeutics.
Q Do you have any advice for anyone who may be interested in working in this field?
In order to develop ligand binding assays that generate reliable and relevant data, any bioanalytical scientist needs to really understand the target biology for each drug program. This will enable them to better design assays accordingly. In addition, whenever new approaches or strategies are used, one needs to carefully weigh the benefit of each strategy against the risk of introducing any potential artifacts to the assay.
The opinions expressed in this interview are those of the interviewee and do not necessarily reflect the views of Bioanalysis Zone or Future Science Group.