The present invention relates to antibody-drug conjugate compounds of Formula I : €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ Ab-(L-D) p €ƒ€ƒ€ƒ€ƒ€ƒ I where one or more maytansinoid drug moieties (D) are covalently linked by L to an antibody (Ab) which binds to an ErbB receptor, or which binds to one or more tumor-associated antigens or cell-surface receptors. These compounds may be used in methods of diagnosis or treatment of cancer, and other diseases and disorders.
