PROBLEM TO BE SOLVED : To provide antibodies or antibody fragments and compositions that target a conformational epitope of a HER receptor. SOLUTION : An isolated antibody or antibody fragment binds to an inactive state of a HER receptor, blocks both ligand-dependent and ligand-independent signal transduction, and stabilizes the HER receptor in an inactive state, where the HER receptor is selected from the group consisting of HER1, HER2, HER3 and HER4. A pharmaceutical composition comprises the antibody or antibody fragment, and a pharmaceutical acceptable carrier. SELECTED DRAWING : None COPYRIGHT : (C)2019, JPO&INPIT