Cell‐penetrable nanobodies (transbodies) that inhibit the tyrosine kinase activity of EGFR leading to the impediment of human lung adenocarcinoma cell motility and survival

Most patients suffering from non–small cell lung cancer (NSCLC) have epidermal growth factor receptor (EGFR) overexpression. Currently, EGFR tyrosine kinase inhibitors (TKIs) that act as the ATP‐analogs and monoclonal antibodies (MAbs) to EGFR‐ectodomain that block intracellular signaling are used for the treatment of advanced NSCLC. Unfortunately, adverse effects due to the TKI off‐target and drug resistance occur in a significant number of the treated patients while some NSCLC genotypes do not respond to the therapeutic MAbs. Thus, a more effective remedy for the treatment of EGFR‐overexpressed cancers is deemed necessary. In this study, VH/V_HH displayed‐phage clones that are bound to recombinant EGFR‐TK were fished‐out from a humanized‐camel VH/V_HH phage display library. VH/V_HH of three phage‐infected Escherichia coli clones (VH18, V_HH35, and VH36) were linked molecularly to nonaarginine (R9) for making them cell penetrable. R9‐VH18, R9‐V_HH35, and R9‐VH36 were cytotoxic to human adenocarcinomic alveolar basal epithelial cells (A549) at the fifty percent inhibitory concentration (IC₅₀) 0.181 ± 0.132, 0.00961 ± 0.00516, and 0.00996 ± 0.00752 μM, respectively, which were approximately 1000‐fold more effective than small molecular TKIs. R9‐VH18 and R9‐VH36 also delayed cancer cell migration in a scratch‐wound assay. Computerized homology modeling and intermolecular docking revealed that VH18 and V_HH35 used CDR3 to interact with EGFR‐TK residues close to the catalytic site, which might sterically hinder the ATP‐binding of the TK; VH36 used CDR2 to bind at the asymmetric dimerization surface, which might disrupt EGFR dimerization leading to inhibition of intracellular signaling. The humanized‐cell penetrable nanobodies have a high potential for developing further towards a clinical application.