Perspectives About Self-Immolative Drug Delivery Systems.

Self-immolative drug delivery system is one of the delivery systems, which have drawn attention, in recent research, highlighting the improvement they generate in drug selectivity and efficacy. Self-immolative linkers, or spacers, are covalent groups, which have the role of cleavaging two bonds between a protector group and a drug, in the case of drug delivery systems, after a stimuli.The cascade of reactions allows to control the release of the drug. The choice of the adequate self-immolative linker is essential and depend on many variables and goals as well. Many approaches can be explored when designing a system adequate for achieving these goals, especially prodrugs. Some of the most used stimuli-responses for self-immolative drugs - enzyme triggers, chemical triggers, as pH, redox system, 1,4-, 1,6-, 1,8-eliminations, photodegradable triggers, multiple triggers, among others - are described in this ten-year review, along with their application as theranostic agents. We intend that the examples presented in this review inspire researchers working on drug delivery systems to further explore their application.