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.
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.
Cabaletta Bio’s DSG3-CAART cross-reactivity screening against the MPA and follow-up studies demonstrated a lack of off-target interactions, and supported further development efforts to bring this novel approach to patients with unmet need. MPA data satisfied the FDA request for CAAR specificity screening on a broad array, without the requirement for additional tissue cross-reactivity studies.
“These preclinical studies supported an investigational new drug application enabling an open-label, phase I trial to evaluate the safety and preliminary efficacy of DSG3-CAART in patients with active anti-DSG3 mucosal PV inadequately managed by standard-care therapy.”
Cabaletta Bio’s DSG3-CAART therapy is being evaluated in a Phase 1 open-label study to determine the maximum tolerated dose in mucosal-dominant PV patients (mPV) NCT04422912.
Towards IND: Specificity Profiling of Antibody Therapies Using the Membrane Proteome Array
- Re-examine the long-held assumption that antibodies are exquisitely specific
- Learn what to do next if your molecule shows detectable off-target binding
- Discover how Membrane Proteome Array specificity data is used to satisfy regulatory requirements