Traditional CAR-T cell therapies rely on the single chain variable fragment (scFv) or camelid nanobody as the antigen binding domain. However, the scFv requires a linker sequence for heavy-light chain pairing that increases the size of the antigen binding domain and risks anti-drug antibody (ADA) responses to the linker. Moreover, the camelid nanobody, although much smaller than the scFv and also bypasses the linker issue, still comes with challenges of a required complex humanization process with continued risk of ADA. Our proprietary HCAb Harbour Mice® successfully generate Fully Human Heavy-Chain Only Antibodies (HCAbs), thus overcoming challenges faced for scFvs and camelid nanobodies for CAR-T cell therapy.
To also greatly enhance the speed and precision to identify HCAb VHs most suitable for CAR-T cell therapy, we have established a rapid and direct CAR-based HCAb VH library screening platform. This platform involves multiple rounds of selective stimulation and cell sorting in combination with next-generation sequencing (NGS) analysis of recovered HCAb VHs. VHs are also cloned into an HCAb expression vector and screened for target-specific binding. Sequences of confirmed target-specific HCAb VH clones are then cross-referenced to the NGS datasets. This discovery platform is capable of rapidly identifying hundreds to thousands of HCAb VH clones with unrivaled sequence diversity and rigourous support for target specificity. Finally, we have confirmed that HCAb VH clones discovered by this platform provide superior CAR-T cell function compared to traditional scFvs and also have excellent binding specificity, stability and biophysical properties.
This groundbreaking fusion of our Fully Human HCAb technology with our robust and direct CAR-based HCAb library screening platform opens up unprecedented avenues for advancing CAR-T cell therapies.
