Optimization and Characterization of Novel ALCAM-Targeting Antibody Fragments for Transepithelial Delivery

Activated leukocyte cell adhesion molecule (ALCAM) is a that supports T activation, migration, and (lymph)angiogenesis has been shown to contribute the pathology of various immune-mediated disorders, including asthma corneal graft rejection. In contrast monoclonal antibodies (mAbs) targeting ALCAM’s expressed binding partner CD6, no ALCAM-targeting mAbs have thus far entered clinical development. This likely linked with broad expression ALCAM on many different types, which increases risk eliciting unwanted treatment-induced side effects upon systemic mAb application. Targeting in surface-exposed tissues, such as lungs or cornea, by topical application could circumvent this issue. Here, we report development stability- affinity-improved anti-ALCAM fragments cross-species reactivity towards mouse, rat, monkey, human ALCAM. Fragments generated either mono- bivalent formats potently blocked ALCAM–CD6 interactions competition ELISA, but only efficiently inhibited ALCAM–ALCAM transmigration assay. The displayed clear size-dependence their ability penetrate epithelium. Furthermore, intranasal delivery reduced infiltration mouse model asthma, confirming target for lungs.