The Need
Autoantibodies against desmoglein 3 (DSG3) cause painful mucosal blisters in mucosal pemphigus vulgaris (mPV). Cabaletta Bio developed DSG3-CAART (Chimeric AutoAntibody Receptor T cell) therapy to eliminate these autoantibodies by targeting the corresponding pool of antigen-specific B cells. To progress the clinical development of their novel DSG3-CAART precision cellular immunotherapy, Cabaletta Bio needed to demonstrate the specificity of DSG3-CAART and document the lack of off-target interactions for their IND applications.
The Solution
Membrane Proteome Array Specificity Testing
The Membrane Proteome Array (MPA) was used as an unbiased, high-throughput approach to assess the specificity of DSG3-CAART and identify potential off-target binding interactions. The soluble extracellular region of the DSG3-CAART was Fc-tagged and screened on the MPA. This array consists of over 5,300 unique, unfixed, native conformation membrane proteins and represents 94% of the human membrane proteome.
Cabaletta Bio’s molecule was successfully screened on the MPA and showed strong binding with Px44 (an anti-DSG3 positive control) as well as binding to an internal control FCGR1A. A marginal level of above background binding to CLEC4M was observed, however further studies showed that expression of this target did not trigger DSG3-CAART activity.
