As a form of molecular personalized medicine,targeted therapy blocks the growth of cancer cells by interfering with specific targeted molecules needed for Carcinogenesis and tumor growth, rather than by simply interfering/ destroying all rapidly dividing cells (e.g. with traditional chemotherapy). Because most agents for targeted therapy are biopharmaceuticals, the term biologic therapy is sometimes synonymous with targeted therapy when used in the context of cancer therapy. Targeted cancer therapies block specific proteins or genes that help cancers grow and spread. Targeted therapies are approved for many types of cancer, including those of the breast, prostate, colon, and lung. But they only work if the tumor has the right target. And targeted therapies can often stop working if the target changes or your cancer finds a way around the treatment. There are two main types of targeted therapies: small molecule medicines and monoclonal antibodies.

Small molecule medicines are small enough to slip inside cancer cells and destroy them. Eg Imatinib, Sunitinib, Sorafenib, Geftinib, Erlotinib, Crizotinib etc

Monoclonal antibodies are too big to get into cells. Instead, they attack targets on the outside of cells or right around them. Eg Rituximab, Trastuzumab, Alemtuzumab.