Erbb-2 and erbb-3 binding bispecific antibodies for use in the treatment of cells that have an nrg1 fusion gene

A method of treating non-small cell lung cancer or pancreatic cancer in a subject, wherein the method comprises administering to the subject a bispecific antibody that comprises a first antigen-binding site that can bind an extracellular part of ErbB-2, and a second antigen-binding site that can bind an extracellular part of ErbB-3, wherein cells of said cancer comprise an NRG1 fusion gene comprising at least a portion of the NRG1-gene fused to a sequence from a different chromosomal location;

• the first antigen-binding site comprising a heavy chain CDR1 comprising the amino acid sequence of SEQ ID NO:40, a heavy chain CDR2 comprising the amino acid sequence of SEQ ID NO:41, and a heavy chain CDR3 comprising the amino acid sequence SEQ ID NO:42;
• and
• the second antigen-binding site comprising a heavy chain CDR1 comprising the amino acid sequence of SEQ ID NO:54, a heavy chain CDR2 comprising the amino acid sequence of SEQ ID NO:55, and a heavy chain CDR3 comprising the amino acid sequence SEQ ID NO:56;
• and
• wherein the first antigen binding site and the second antigen binding site comprise a light chain CDR1 comprising the amino acid sequence of SEQ ID NO:75, a light chain CDR2 comprising the amino acid sequence of SEQ ID NO:76, and a light chain CDR3 comprising the amino acid sequence SEQ ID NO:77.