RESEARCH MONOGRAPH · KDC-MN-172

Arketamine

May 9, 2026 Kodiac biolabs Research Revised May 30, 2026 2 min read

Our opinion on this compound

65/100

The R-enantiomer that might be the more interesting half of the ketamine story

Arketamine is (R)-ketamine, the other enantiomer in the racemic mixture. For decades it was treated as the less-active half because S-ketamine has higher NMDA affinity at the channel-blocking site, but Hashimoto's group in Japan and several other labs have been publishing preclinical and early clinical work suggesting arketamine produces antidepressant effects comparable to or better than esketamine, with markedly less dissociation and less psychotomimetic burden.

If that holds up, it's a big deal. The whole problem with ketamine-class antidepressants is balancing efficacy with the dissociative experience, the abuse potential, and the receptor desensitization profile. An enantiomer that delivers the antidepressant cascade without the dissociation would be a real advance, and arketamine is the leading candidate for that.

Mechanistically the story is that arketamine has lower direct NMDA channel-blocking potency than S, but produces equal or greater downstream BDNF, synaptic, and behavioral effects in rodent models. The proposed explanation involves the hydroxynorketamine metabolites (particularly (2R,6R)-HNK, an arketamine metabolite that may have antidepressant activity without NMDA blockade) and possibly different effects on AMPA trafficking. Honestly the mechanistic picture is still being worked out.

Clinical data is early but interesting. Perception Neuroscience (Atai-affiliated) ran a phase 2 in treatment-resistant depression with arketamine and reported positive signal. Other groups have done open-label and small controlled work showing antidepressant response without the dissociation that characterizes S-ketamine. None of this is settled, the trials are small, and replication at scale is what matters.

Sourcing: single-isomer R-ketamine is available from research suppliers, more expensive than racemic, requires chiral HPLC for purity verification, and is similarly controlled depending on jurisdiction.

Safety profile is presumably similar to other ketamine enantiomers but with the open question about whether the lower dissociative burden translates to lower abuse liability and lower urinary toxicity at chronic exposures. We dont have the long-term human data to answer that yet.

What we like: this is genuinely one of the more interesting questions in modern antidepressant pharmacology, and arketamine has a real shot at being the better-tolerated half of a class that's reshaping psychiatry. What we dont like: the trials are still small and Perception's program is the only late-stage shot at the moment.

Worth watching closely.

Evidence: 50
Mechanism: 70
Reliability: 60
Safety: 75
Sourcing: 60
Value: 45
Signal: 78
Staying power: 80

Plain-language summary Intrigue 78 / 100

Arketamine is the R-enantiomer of ketamine (the other half of the racemate). Animal studies suggest the antidepressant effects may be longer-lasting than esketamine with fewer dissociative side effects. Investigated as an alternative depression treatment. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

R-enantiomer NMDA antagonist

The (R)-enantiomer of ketamine, currently in clinical development for depression with reportedly more sustained antidepressant action and fewer dissociative effects.

Abstract

Arketamine (R-ketamine; CAS 33643-47-9) is the (R)-enantiomer of ketamine, currently in clinical development by Perception Neuroscience and others. The (R)-enantiomer has lower NMDA receptor affinity than the (S)-enantiomer (esketamine), but rodent data suggest more sustained antidepressant effects with reduced dissociative side effects. Phase 2 trials are ongoing. Mechanism includes NMDA modulation but with secondary mechanisms (BDNF/TrkB pathway, mGluR effects) that may underlie the differential clinical profile. Not currently FDA approved.

Mechanism of action

R-enantiomer; lower NMDA affinity than (S)-enantiomer but rodent data suggest more sustained antidepressant action.

Reported research dose ranges

Phase 2 trials ongoing; clinical doses not established.

References

Hashimoto K. Rapid-acting antidepressant ketamine, its metabolites and other candidates. Pharmacol Ther 2019.

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KDC-MN-172

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Arketamine

Abstract

Mechanism of action

Reported research dose ranges

References

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Abstract

Mechanism of action

Reported research dose ranges

References

Read the full monograph

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