Background::
The treatment of major depressive disorder (MDD) with available antidepressant drugs is characterized by considerable ineffectiveness. Classical psychedelics such as psilocybin and N,N-dimethyltryptamine (DMT), which act primarily as 5-hydroxytryptamine 2A (5-HT
2A
) receptor agonists, have shown preliminary efficacy for inducing long-term remission in MDD after one or two doses. GM-2505 is a novel, 5-HT
2A
receptor agonist, developed for treating MDD.
Methods::In this single-ascending dose, randomized, placebo-controlled, double-blind study, we characterized GM-2505’s safety, tolerability, pharmacokinetics (PK), and pharmacodynamic (PD) profile in 48 healthy participants.
Results::
Single intravenous (IV) doses up to 20 mg demonstrated an acceptable safety profile of mild transient adverse events, short-term, non-clinically significant increases in blood pressure and pulse, and no significant changes in electrocardiographs, consistent with other 5-HT
2A
receptor agonists. In general, GM-2505
Cmax
and AUC
last
increased dose proportionally, with
t1/2
of 40–50 minutes. Generally, dose-dependent effects were observed for neuroendocrine hormones, several neuropsychological and neurophysiological measures, and subjective drug effects. Dose-related effects were also observed in resting-state electroencephalography (rsEEG), with decreased power in the low frequency rsEEG bands (theta and alpha), and increased in the high frequency bands (slow and fast gamma).
Conclusions::
These PD findings were similar in nature and magnitude to other 5-HT
2A
receptor agonists that have been studied clinically. In line with the GM-2505 PK profile, the duration of cardiovascular and subjective effects was shorter than psilocybin but longer than DMT, demonstrating a potentially more practical temporal profile for use in a supervised clinical setting compared to longer-acting 5-HT
2A
receptor agonists, with an optimal dose range of 10–15 mg IV. Clinical trial (ISRCTN64428072) registration: https://www.isrctn.com/ISRCTN64428072.