5-Chloro-αET (code name PAL-526), or 5-chloro-AET, also known as 5-chloro-α-ethyltryptamine, is a serotonergic agent of the tryptamine and α-alkyltryptamine families.^[1] It is the derivative of α-ethyltryptamine (αET or AET) with a 5-chloro substitution.^[1] Analogues of 5-chloro-αET include 5-fluoro-αET, 5-chloro-αMT, and 5-fluoro-αMT.^[1]

The drug is known to act as a potent serotonin releasing agent (SRA) and relatively weak serotonin 5-HT_2A receptor near-full agonist.^[1] It shows negligible induction of norepinephrine and dopamine release but does act as a very weak dopamine reuptake inhibitor (DRI).^[1] 5-Chloro-αET's EC₅₀Tooltip half-maximal effective concentration and IC₅₀Tooltip half-maximal inhibitory concentration values are 33.2 nM for serotonin release, 249 nM (E_maxTooltip maximal efficacy = 87%) for serotonin 5-HT_2A receptor agonism (7.5-fold lower than for serotonin release), 1,838 nM for dopamine reuptake inhibition (55-fold lower than for serotonin release), and >10,000 nM for norepinephrine release.^[1] The monoamine release assays were performed in rat brain synaptosomes.^[1]

Several close analogues of 5-chloro-αET, including 5-chloro-αMT and 5-fluoro-αMT, are known to be potent monoamine oxidase inhibitors (MAOIs), specifically of monoamine oxidase A (MAO-A).^[2]