While antibody therapeutics have proven to be successful in recent years, they are not without drawbacks. The large size of antibodies can prevent their effective use against certain cancers, as well as prevent them from crossing the blood-brain barrier. Additionally, many antibodies require post-translational modifications and must be produced in eukaryotic cells, decreasing their yield and increasing costs of production.

To overcome the existing drawbacks of current antibody and non-antibody synthetic protein approaches, the inventors have generated a novel, small recombinant antigen-binding protein platform produced in e. coli. 

S22Fc antibody-like protein is a representative example of this platform that has been engineered to bind HER2, HER3, EGFR and interact with the Fc receptor on immune effector cells to enhance the activity of the immune system. S22Fc is effective at treating anti-EGFR and anti-HER2 antibody resistant tumors with demonstrated in vivo POC.