RESEARCH MONOGRAPH · KDC-MN-332

Cutamesine (SA-4503)

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

Our opinion on this compound

65/100

Underrated sigma-1 selective agonist with a real but small post-stroke clinical signal

Cutamesine is one of the more genuinely interesting sigma-1 selective tools and we think it's been undersold relative to its evidence base. Originally developed by M's Science in Japan as SA-4503, the receptor selectivity is high (200-fold over sigma-2 and clean across the usual off-targets), and the in vivo pharmacology has been replicated in multiple labs.

The clinical story is small but real. Urfer and colleagues ran a phase 2 in stroke patients (the AWARE trial, 2014, J Stroke), and showed an interesting if not statistically dominant signal on functional recovery over 28 days post-stroke. The mechanism story is plausible: sigma-1 sits at the ER-mitochondrial interface, stabilizes IP3R-mediated calcium transfer, and chronic agonism appears to be neuroprotective in ischemic and neurodegenerative models. Hayashi and Su's foundational sigma-1 receptor biology work is the right context.

Mechanism: high-affinity sigma-1 agonist, oral bioavailability is good, half-life supports daily dosing, brain penetration is solid. The downstream signaling involves chaperone function at ER membranes, IP3R modulation, and indirect effects on multiple receptor systems (NMDA, dopaminergic, monoaminergic) via sigma-1's role as a 'pluripotent modulator.' Maurice and colleagues have most of the better reviews.

What people miss: the sigma-1 receptor mechanism is genuinely weird and interesting. It's not a classical GPCR, doesn't directly signal in the standard sense, instead acts as a calcium-sensitive chaperone protein that modulates downstream pathways by stabilizing other receptors and channels. Cutamesine is one of the cleaner pharmacological tools for probing that biology in vivo without the SSRI-confound that plagues fluvoxamine (the most common 'sigma-1 agonist' in clinical literature is actually an SSRI with sigma-1 activity, which makes interpretation messy).

For research it's a useful selective sigma-1 agonist when you want to avoid the off-target serotonergic effects of fluvoxamine, the muscarinic effects of Anavex 2-73, or the polypharmacology of pridopidine. Clean pharmacological probe.

Sourcing: research-grade cutamesine is available but harder to find than the more mainstream sigma-1 tools, HPLC verification is necessary, lot-to-lot variability can be an issue with smaller-scale suppliers.

What we like: clean selectivity, real clinical data, foundational sigma-1 pharmacology tool, slept-on by the broader research community.

What we dont like: limited availability, no further clinical development happening, sigma-1 biology itself is still partly mysterious which limits interpretation.

Worth knowing for sigma-1 work. Properly underrated.

Evidence: 55
Mechanism: 70
Reliability: 65
Safety: 80
Sourcing: 60
Value: 60
Signal: 65
Staying power: 65

Plain-language summary Intrigue 58 / 100

Cutamesine (SA-4503) is a selective sigma-1 receptor agonist developed at Santen Pharmaceutical in Japan. The sigma-1 receptor is a chaperone protein at the contact zones between mitochondria and endoplasmic reticulum, regions where cells coordinate calcium handling and stress responses, making it an unusual drug target. The compound has been investigated for ischemic stroke recovery and major depression in small clinical trials with mixed results. The sigma-1 mechanism is genuinely novel and underexplored, but development has stalled and the compound has not advanced beyond early-phase work. 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.

Selective sigma-1 receptor agonist

A selective sigma-1 receptor agonist developed for ischemic stroke recovery and major depressive disorder.

Abstract

Cutamesine (SA-4503; CAS 165377-44-6; molecular formula C19H30N2O2; molecular weight 318.45) is a selective sigma-1 receptor agonist developed at Santen Pharmaceutical and licensed to M's Science. The compound has high sigma-1 affinity (Ki approximately 17 nM) with greater than 100-fold selectivity over sigma-2 and minimal off-target binding. Sigma-1 is a chaperone protein at the mitochondria-associated ER membrane that modulates ion channels, calcium signaling, and stress response. Phase 2 trials in ischemic stroke recovery (60 mg, 28 days starting within 72 hours of stroke) showed modest improvement; phase 2 in MDD showed mixed efficacy. Plasma half-life is approximately 5 hours. The compound is the cleanest available research probe for sigma-1 pharmacology. Used as the canonical selective sigma-1 agonist in academic research.

Mechanism of action

Selective sigma-1 receptor agonist (greater than 100-fold over sigma-2); chaperone protein modulator at mitochondria-associated ER membrane.

Reported research dose ranges

Trial doses 1 to 60 mg in the published literature.

References

Hayashi T, Su TP. Sigma-1 receptor chaperones at the ER-mitochondrion interface regulate Ca(2+) signaling and cell survival. Cell 2007.
Urfer R, et al. Phase II trial of the sigma-1 receptor agonist cutamesine (SA4503) for recovery enhancement after acute ischemic stroke. Stroke 2014.
Ishikawa M, et al. The sigma-1 receptor agonist SA4503 in major depressive disorder. J Clin Psychopharmacol 2007.

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KDC-MN-332

The full reference document is provided strictly for research use only. It reports research dose ranges from the published literature, not instructions for use in humans or animals.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

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Cutamesine (SA-4503)

Abstract

Mechanism of action

Reported research dose ranges

References

Read the full monograph

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Abstract

Mechanism of action

Reported research dose ranges

References

Read the full monograph

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