ERBB2 and cancer: Indeed, our BsAb and a mouse specific BsAb, BsPDL1 × rErbB2, which targets PDL1 and HER2 [54], showed enhanced antitumor activities relative to that of monotherapies with mAbs at equal molar doses in vivo, although the latter is a monovalent BsAb that did not inhibit tumor cell growth in vitro, suggesting that combining HER2 and PD1/PDL1 blockades might improve the treatment of HER2-overexpressing cancers.