Monovalent antibodies fragments useful as therapeutic agents

An antibody fragment comprising a single arm antigen binding and Fc region queaumenta stability of said antibody fragment compared to a Fab molecule that comprendedicho arm antigen binding, wherein the Fc region comprises a complex of first and segundopolipeptidos Fc, wherein one but not both of the Fc polypeptides is an N delextremo truncated heavy chain, and wherein said antibody fragment specifically binds to c-met.