Novel multispecific antibody platform, multispecific antibodies and a method to make the antibodies is disclosed here. The CH3 domain harboring polypeptide chains of the Fc-regions are modified by increasing the positive charge of one chain and negative charge of another chain. Heterodimer formation in cotransfection with the modified chains is comparable to formation of wild type antibodies when same cell line is transfected with wild type polypeptides. Moreover, the modification provides a simple one step purification of the heterodimers.