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NCI Dictionary of Cancer Terms


small-molecule drug  listen  (… MAH-leh-kyool ...)

  A substance that is able to enter cells easily because it has a low molecular weight. Once inside the cells, it can affect other molecules, such as proteins, and may cause cancer cells to die. This is different from drugs that have a large molecular weight, such as monoclonal antibodies, which are not able to get inside cells very easily. Many targeted therapies are small-molecule drugs or small molecule inhibitors.