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Why must steroid drugs be able to cross a cell membrane?

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Gleevec; imatinib — drug Docking of the anticancer drug Gleevec (imatinib) in the abl domain of the bcr-abl tyrosine kinase. Abnormalities in bcr-abl stimulate the continuous proliferation of bone marrow stem cells, causing an increase in myelogenous cells (granulocytes and macrophages) in the body and leading to chronic myelogenous leukemia (CML).

Steroid drugs must be able to cross the cell membrane because their specific receptors are located within the cell, specifically in the cytoplasm or the nucleus.12

Unlike many other drugs that bind to receptors located on the exterior surface of the cell membrane, the interaction between a steroid and its receptor occurs internally. Once the steroid crosses the membrane and binds to its receptor, the resulting drug-receptor complex interacts directly with DNA to activate or repress gene transcription. This process regulates the synthesis of specific proteins, which is the fundamental mechanism by which these agents exert their physiological effects. Because this critical binding event takes place inside the cell, the ability to permeate the cell membrane is an essential requirement for the drug's activity.13