Targeted therapy is a form of cancer treatment that interferes with specific molecules cancer cells rely on to grow, divide, and survive. Unlike traditional chemotherapy, which damages rapidly dividing cells broadly, targeted drugs home in on defined molecular abnormalities, often leading to more precise effects and different side effect profiles.

Many targeted therapies focus on proteins encoded by mutated or overactive genes. Examples include drugs that block overexpressed receptors on the cell surface, such as HER2 in certain breast cancers, or inhibit abnormal signaling proteins inside the cell, such as BCR ABL in chronic myeloid leukemia. Others target enzymes like tyrosine kinases that transmit growth signals, or proteins that cancer cells use to repair DNA damage.

Some therapies work by depriving tumors of the blood supply they need to grow, inhibiting molecules involved in angiogenesis like VEGF. Others harness the immune system indirectly, for example by targeting proteins that influence how immune cells recognize cancer, although these are often classified as immunotherapies.

Research has revealed that tumors are genetically diverse and can evolve resistance. Cancer cells may activate alternative signaling pathways, acquire new mutations, or amplify drug targets. This has driven development of next generation inhibitors, combination therapies, and treatment strategies guided by molecular diagnostics that match drugs to the specific alterations in a person’s tumor.

Overall, targeted therapy has transformed treatment for several cancers, leading to longer survival and improved quality of life for many patients, while ongoing research aims to extend these benefits and overcome resistance.