From 'Targeted Therapy' to Targeted Therapy

In early 2000, the term 'targeted therapy' became popular and was used to indicate all types of tyrosine kinase inhibitors (TKI). However, the term targeted therapy had been used much earlier. Targeting tumor metabolism was already considered as targeted therapy, with methotrexate and 5-fluorouracil as the most successful examples. Hormone therapy is another successful type of targeted therapy. Imatinib was the first TKI for the fusion protein BCR-ABL and represented a breakthrough in the treatment of chronic myeloid leukemia. Many other TKIs have been introduced into the clinic, but most were less specific and had multiple targets, and therefore, by definition, not targeted. However, with the introduction of TKIs developed specifically against mutations in the active site of a TK, more truly targeted TKI have been approved, such as new anaplastic lymphoma kinase echinoderm microtubule-associated protein-like 4 (ALK-EML4) inhibitors and the epidermal growth factor-T790M-targeted osimertinib. This article summarizes the content of the Burger-Kelland award lecture given by the Author in February 2019 during the 40th EORTC-PAMM Group meeting in Verona, Italy and reviews the development of various targeted agents.