Targeting Breast Cancer: The Familiar, the Emerging, and the Uncharted Territories.

Breast cancer became the most diagnosed cancer in the world in 2020. Chemotherapy is still the leading clinical strategy in breast cancer treatment, followed by hormone therapy (mostly used in hormone receptor-positive types). However, with our ever-expanding knowledge of signaling pathways in cancer biology, new molecular targets are identified for potential novel molecularly targeted drugs in breast cancer treatment. While this has resulted in the approval of a few molecularly targeted drugs by the FDA (including drugs targeting immune checkpoints), a wide array of signaling pathways seem to be still underexplored. Also, while combinatorial treatments have become common practice in clinics, the majority of these approaches seem to combine molecularly targeted drugs with chemotherapeutic agents. In this manuscript, we start by analyzing the list of FDA-approved molecularly targeted drugs for breast cancer to evaluate where molecular targeting stands in breast cancer treatment today. We will then provide an overview of other options currently under clinical trial or being investigated in pre-clinical studies.