In these systems, the role of the linker is essential because if properly conceived, it can induce a spatiotemporal release of the drug, which is of paramount importance to minimize offtarget toxicity and achieve optimized therapeutic effect. In this context, drug linkers are usually designed to be sensitive to endogenous stimuli (e.g., pH, enzyme concentration, reducing environment) or, to a lesser extent, to exogenous stimuli (e.g., light, magnetic field).