The present invention relates to pharmaceutical compositions containing a combination of a first antigen-binding molecule and a second antigen-binding molecule, wherein the first antigen-binding molecule and the second antigen-binding molecule are not linked by a covalent bond, and they are more likely to form a heterodimer than homodimers when mixed in solution. Furthermore, the present invention relates to antigen-binding molecules, therapeutic methods, and screening methods that are associated with the combination.