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. Author manuscript; available in PMC: 2022 Apr 23.
Published in final edited form as: Methods Enzymol. 2021 Dec 23;664:199–220. doi: 10.1016/bs.mie.2021.11.008

Figure 1.

Figure 1.

The ester prodrug concept. Carboxylate-containing drugs are poorly permeable due to Coulombic repulsion. Masking the negative charge makes the drug more readily permeable in a nonspecific fashion. The active drug is revealed only in cells that contain an enzyme capable of hydrolyzing the ester bond to reveal the active moiety. In a targeted prodrug strategy, only cells that contain such an esterase would incur the effects of the drug.