Design, synthesis and biological evaluation of pleiotropic prodrugs activated by cholinesterases and releasing a 5-HT4R agonist, with in vivo antiamnesic activity

Acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) are hydrolases that specialize in the cleavage of esters such as acetylcholine. However, they can also cleave the carbamate group of certain drugs, such as rivastigmine. This leads to inhibition of these ChEs and preservation of acetylcholine (ACh), their physiological substrate, providing symptomatic benefits in Alzheimer's disease (AD). The present work aims to exploit ChE's capacity to cleave synthetic carbamates, not only to inhibit these enzymes but also to release a potent 5-HT 4 receptor partial agonist upon interaction, thereby exerting an additional disease-modifying effect in AD. Such carbamates would behave as pleiotropic prodrugs. This work relates to the synthesis of the latter compounds and the kinetic study of their enzymatic inhibition to select one of the best candidates from the synthesized compounds for a preliminary in vivo study in an AD model. The latter has been achieved by administering the drug intranasally to bypass the blood-brain barrier (BBB) and avoid peripheral side effects. This has required a special formulation, which was created using liposomes embedded in a thermosensitive mucoadhesive gel. When administered intranasally, the pleiotropic prodrug demonstrated a clear antiamnesic effect in vivo in mice, providing proof of concept for further investigations.