Besides surgery, radiation therapy, endocrine therapy or chemotherapy, which were widely used in cancer patients for decades, the 21st century has seen the emergence of "targeted" therapy, resulting from the identification of molecular pathways in cells and their alterations in tumors. An increasing number of compounds targeting specific molecules or cancer cells have been developed and, for some of them, approved by the United States Food and Drug Administration (FDA) as well as other regulators in EU and Japan Additional new and more efficient types of compounds, are still in clinical trials, but are expected to gain future approval. More than eighty FDA-approved targeted therapies are described here, along with about eighty other promising compounds. These drugs are members of various therapy classes, including tyrosine kinase inhibitors; serine/threonine kinase inhibitors; dual specificity kinase inhibitors; lipid kinase inhibitors; poly ADP ribose polymerase inhibitors; monoclonal antibodies; microtubule targeting agents; histone deacetylase inhibitors; proteasome inhibitors; antimetabolites; immunomodulatory agents; DNA methyltransferase inhibitors; hedgehog pathway inhibitors; enzymes; protein translation inhibitors; vaccines, oncolytic viruses; chimeric antigen receptor T-cells (CAR-T); and so on. A series of "companion" diagnostics intended to be used as an indication for specific therapies, and approved to this aim are also mentioned. The book aims to present the broad landscape of compounds and companion diagnostics that are expected to pave the way towards a future of hope for cancer patients.