As antibody drug conjugates continue to evolve, so too must analytical approaches for characterization. Here’s a snapshot of just some of the interesting research taking place.
Antibody drug conjugates are a rapidly growing therapeutic pipeline, with a 16 percent growth seen within the past year alone. Often referred to as “biological missiles”, ADCs are the primary weapon of choice to deliver chemotherapy drugs to targeted cancerous cells without damaging nearby cells. Now, drug developers are on a mission to expand the target ranges of this continuously evolving therapeutic modality to include immuno, dermatological, gastrointestinal, and musculoskeletal diseases.The construct of an ADC hasn’t changed since 2000. Consisting of a linker, payload, and monoclonal antibody, ADCs have high specific targeting abilities and strong killing effects to accurately and efficiently destroy cancer cells. The specificity and cytotoxicity of next-generation ADCs is getting better but there is still room for improvement. Some developmental trends for next generation ADC drugs include:using ADCs to target mutant proteinsimproving antibody internalization and increasing tumor specificity with ADCs formulated with bispecific antibodiesusing two different payload combinations to reduce drug resistanceimproving penetration efficiency and delivery of payload by abandoning the traditional structure of mAbs and choosing to couple the payload to a polypeptide fragment with a smaller molecular weight.2 And this is just a snapshot of what’s going on. I haven’t even touched on the many opportunities to innovate the payload selection!Despite my simplified initial description of ADCs, these modalities are complex in structure and function – and the complexity will only increase one generation after the next. Thus, an area I am passionate about is analysis. One of the critical quality attributes of an ADC is determining and monitoring drug-to-antibody Ratio (DAR) during development and production. Used as a parameter for potency and efficacy, DAR measurement has always been via hydrophobic interaction chromatography (HIC). Despite being considered the gold standard, executing HIC methodologies are labor-intensive and time-consuming. True DAR distributions are often not accurately determined because of the presence of overlapping or poorly resolved peaks with HIC methods. Over the years, orthogonal methods have been adopted in the hope of addressing the challenges of DAR characterization via HIC, such as capillary electrophoresis, capillary isoelectric focusing, ion exchange chromatography, reversed-phase liquid chromatography, and size exclusion chromatography, but none have been able to meet the separation and or non-denaturing condition demands, independent of a detector such as UV or MS. To address these challenges, I was inspired by a recent publication from Ma et al describing a native reversed-phase (nRP) LC-MS method approach that uses novel, hydrophobic surface LC column chemistries. This nRPLC-MS approach enables the nondenatured separation and simultaneous characterization of different DAR species and its related isomers, allowing characterization of DAR species without fractionation and buffer exchanges. The elution profile of the DAR species, including DAR0, prove to be a MS-compatible alternative to HIC. I believe this method can be readily applied for high-throughput screening and characterization of ADCs across different conjugation methods and payload classes.Innovative alternative strategies enabled by new LC column chemistries such as nRPLC-MS mentioned in Ma et are part of the evolution of chromatographic column chemistries to watch for the future. The demand for increased method development efficiencies without compromising data quality will only increase over time. Time-to-market drug timelines are of the essence for drug developers, and nobody has time to deal with methods that compromise the data required to make critical drug decisions.
