Figure 1.

Schematic representation of tumour endoprotease-activated prodrugs (TAPs). The prodrug is composed of three domains: a potent therapeutic agent (effector), an endoprotease-cleavable peptide sequence (trigger) and a linker to join the trigger to the effector. This TAP remains inactive until activation of the trigger. The presence of the endoprotease in the tumour but not in the ‘normal' tissues results in activation of the TAP trigger selectively in the tumour, causing the release of the potent effector and a subsequent therapeutic effect.