Strategies for UF/DF-Based Impurity Removal in the Post-conjugation Purification of Antibody-Drug Conjugates

Antibody-drug conjugates (ADCs) are increasinglyprevalentas investigational and marketed treatments for a variety of cancersand other diseases. The structures of most ADCs comprise a small-moleculecomponent (the drug-linker) chemically conjugated to a monoclonalantibody, and this hybrid construct presents a number of challengesfor Chemistry, Manufacturing, and Controls (CMC) development. A SmallMolecule Considerations for ADC Development Working Group (WG) hasbeen established within the IQ Consortium to serve as a forum forbiopharmaceutical industry companies to discuss development strategiesfor ADCs, with a focus on the drug-linker portion. The preceding paperfrom the WG presented results from a benchmarking survey of IQ membercompanies on a number of topics relating to drug-linker development.One of the key findings was that ultrafiltration/diafiltration (UF/DF)is used by all responding companies for purification of the ADC followingthe conjugation step and is a critical operation for control of small-moleculeimpurities in the ADC drug substance. UF/DF is well established inmonoclonal antibody processing, but to date, there are relativelyfew literature reports detailing its application to ADCs. To helpaddress this gap, this manuscript presents results and analysis froma more focused survey of IQ member companies on the application ofUF/DF for post-conjugation purification of ADCs. Insight is providedinto practical considerations such as common operating parameters,relative efficiency of removal of different types of impurities, technicalchallenges, and application of emerging technologies. In addition,recommendations are offered on where to start when developing a UF/DFprocess for a new ADC. The overall goals are to provide an overviewof current industry practices for UF/DF purification of ADCs and tospur further communication and innovation in this area.