[Lani]

Not sure I understand your question

Do you mean are there 3 targeted drugs for bc or do you mean are there any her3 targetted drugs?

Approved targeted drugs against bc are tamoxifen, AIs both targeted vs ER, herceptin vs her2, avastin vs VEGFR...there are also EGFR targeted monoclonal antibody drugs but they are approved for head and neck cancer.

Then there are the tyrosine kinase inhibitors which are more promiscous (yes, that is the word they use) as most target more than one receptor eg lapatinib targets egfr and her2

There is a monoclonal antibody not yet approved that prevents her2 and her3 from dimerizing It is called pertuzumab and Genentech has it in trials.

Hope this answered your question