Formulation of stable isotonic lyophilized protein

Use of a lyophilized formulation comprising a monoclonal antibody and a lyoprotectant, wherein the molar proportion of lyoprotectant: antibody is 200-600 moles of lyoprotectant: 1 mole of antibody, wherein the ellloprotector is trehalose, and wherein the monoclonal antibody is an anti-HER2 antibody, in the preparation of a drug for the treatment of a cancer characterized by overexpression of the HER2 receptor.