ALD-52

ALD-52 (1-acetyl-LSD) is the 1-acetyl derivative of LSD, historically associated with the "Orange Sunshine" acid of the 1960s and one of the earliest known N-acylated lysergamides. Although 1-acyl substitution reduces affinity and efficacy at the 5-HT2A receptor by one to two orders of magnitude relative to LSD, pharmacological studies show that ALD-52 is rapidly and efficiently deacetylated in vivo to yield high plasma concentrations of LSD, supporting its classification as a prodrug. Consistent with this, it induces the 5-HT2A-mediated head-twitch response in mice with relatively high potency and produces a classic serotonergic psychedelic experience in humans of roughly LSD-like strength. It has re-emerged as a research chemical alongside related acyl derivatives such as 1P-LSD and 1cP-LSD, and in silico toxicology work has begun to profile its potential genotoxic and cardiopulmonary liabilities.