targeted therapy
Meaning of targeted therapy: Treatment aimed at a single molecule a disease leans on, rather than at every fast-dividing cell in the body.
Definition of targeted therapy
Targeted therapy is treatment with a drug designed to act on one specific molecule that a disease depends on. In cancer that molecule is usually a protein driving cell growth, a receptor on the cell surface, or the product of a particular mutation. Because the drug is built around a defined target, a test is usually done first to confirm the target is actually present.
How does it differ from chemotherapy?
| Chemotherapy | Targeted therapy | |
|---|---|---|
| What it attacks | Any rapidly dividing cell | One named molecule |
| Test before treatment | Not usually required | Often required |
| Characteristic effects | Low blood counts, hair loss, nausea | Rash, diarrhea, blood pressure and liver changes |
| How it fails | Resistant cells survive | The target changes shape or a bypass route opens |
What kinds of target are there?
Signaling enzymes called kinases are the largest group; the small molecules that block them are swallowed as tablets and their names usually end in -ib. Surface proteins are addressed by antibodies given by infusion, with names ending in -mab. Other targets include hormone receptors, the enzymes a cell uses to repair broken DNA, and the signals a tumor sends to build itself a blood supply. Some targeted drugs are also used outside cancer, in rheumatoid arthritis, psoriasis and inflammatory bowel disease, where the target is an immune signal instead.
Does it cause fewer side effects?
It causes different ones, and not always fewer. The targeted molecule is rarely found only in the tumor, so blocking it affects healthy tissue that relies on the same pathway. Blocking the epidermal growth factor receptor produces an acne-like rash because skin needs that receptor. Blocking blood vessel growth raises blood pressure and slows wound healing. Some agents strain the liver or disturb heart rhythm. Compared with radiation therapy, which is confined to the area treated, these drugs travel everywhere the blood goes.
Why does it stop working?
Tumors adapt. A new mutation can reshape the target so the drug no longer fits, or the cell can switch to a parallel pathway that achieves the same growth signal by another route. This is why later-generation drugs are developed against known resistance mutations, and why the same target may be attacked from two directions at once.
Also known as
Used in a sentence
Molecular testing was requested to determine whether targeted therapy was an option.
Good to know
Side effects are different rather than automatically fewer, because the targeted molecule is usually present in healthy tissue as well as in the tumor.