Isolation of a new human scFv antibody recognizing a cell surface binding site to CEACAM1. Large yield production, purification and characterization in E. coli expression system

• Optimal purification strategy for a high yield production of scFv anti-CEACAM1.
• scFv shows a high binding reactivity in ELISA, IF an flow cytometry studies.
• scFv is a naturally occurring mixture of monomer and dimer fully characterized.
• scFv at 37 °C shows the dimer behaves as a reservoir converting slowly into monomer.
• scFv at 37 °C has a t½ for binding CEACAM1 of 12 h as demonstrated by ELISA.

The CEACAM1 cell adhesion molecule has recently received considerable interest as a tumour target antigen since its re-expression often occurs in the advanced stages of multiple malignancies including malignant melanoma, non-small cell lung cancer and other types of solid tumors. In this study, we describe the expression-purification and characterization of the new single chain variable fragment (scFv) antibody named DIATHIS1, that recognizes the N-terminal IgV-like domain present in CEACAM1. Three validation batches show that the production process is robust and reproducible. The scFv DIATHIS1 is formulated as a naturally occurring mixture of monomer and dimer. The antibody is biophysically stable at low temperature (−80 °C), different concentrations and remains biologically active for at least 24 months. The thermal stability of scFv DIATHIS1 at 37 °C shows important features for its activity in vivo. The dimer behaves as a reservoir converting slowly into monomer. The monomer and dimer forms of scFv DIATHIS1 were isolated and characterized, showing high reactivity for CEACAM1. This new composition of antibody could have advantageous pharmacokinetics parameters over conventional scFv for in vivo applications.