RESEARCH MONOGRAPH · KDC-MN-334

Pridopidine

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

Our opinion on this compound

63/100

Sigma-1 agonist with phase 3 data in Huntington's, ALS results mixed, mechanism more interesting than the labels suggest

Pridopidine is a fascinating case study in how target-class identification can shift with better receptor characterization. It was originally developed as a 'dopaminergic stabilizer' (a dopamine modulator concept that never quite paid off as advertised), and only in the last decade was it properly recharacterized as a high-affinity sigma-1 selective agonist with minimal dopaminergic activity at clinically relevant exposures. The whole development story makes more sense in that light.

Mechanism: sigma-1 receptor agonist with sub-nanomolar affinity (~70 nM), selectivity over D2 and other monoamine receptors that varies depending on which paper you read but is generally good at therapeutic plasma concentrations. The downstream signaling is the standard sigma-1 chaperone story: ER-mitochondrial calcium handling, IP3R modulation, BDNF upregulation, autophagy enhancement. Geva and colleagues at Prilenia have most of the mechanistic work.

Clinical record is mixed in informative ways. Huntington's disease was the primary indication: the MermaiHD and HART trials hit secondary motor endpoints but missed primary, leading to a phase 3 PRIDE-HD that didn't show convincing benefit on TFC (total functional capacity). The PROOF-HD trial was Prilenia's followup with revised endpoints and a longer treatment duration; results released in 2023 showed no benefit on the primary TFC endpoint either. Thats two negative phase 3s in Huntington's, which is hard to walk back.

The ALS story is more interesting. HEALEY-ALS platform trial regimen included pridopidine, results suggested a survival/functional signal in a subgroup with faster progression but didnt cleanly hit the platform primary. The MERIDIAN-ALS readout is pending and could clarify things.

For research pridopidine is a useful sigma-1 selective tool with the advantage of substantial human safety data and well-characterized PK. The original 'dopaminergic stabilizer' framing means there's still some lingering confusion in the literature about whether it's really a D2 modulator (it isn't, mostly) which can complicate citation lookups.

Sourcing: research-grade material is available from specialized suppliers, the hydrochloride salt is standard, HPLC verification, prices have come down as it's moved through clinical development.

What we like: clean sigma-1 pharmacology with extensive human safety data, useful tool when you want a sigma-1 agonist with real translational relevance.

What we dont like: the Huntington's program has not worked despite genuine effort, and the mechanism enthusiasm has consistently outrun the clinical reality.

Real sigma-1 tool with a complicated clinical resume. Worth knowing.

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

Plain-language summary Intrigue 62 / 100

Pridopidine started life as a dopamine stabilizer for Huntington disease and was later reclassified as a high-affinity sigma-1 agonist when its true binding profile was characterized. Originally developed at NeuroSearch and now at Prilenia Therapeutics, it failed the phase 3 PRIDE-HD trial in Huntington but has continued in ALS development based on encouraging phase 2 signals in that population. The reclassification story is interesting because it changed how investigators think about both pridopidine and the sigma-1 target itself. Whether the current ALS program produces meaningful efficacy remains an open question. 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.

Sigma-1 agonist (Huntington and ALS)

A high-affinity sigma-1 agonist developed for Huntington disease and ALS; phase 3 trials in Huntington failed but ALS development continues.

Abstract

Pridopidine (4-[3-(methanesulfonyl)phenyl]-1-propylpiperidine; CAS 882737-42-0; molecular formula C15H23NO2S; molecular weight 281.42) is a high-affinity sigma-1 agonist developed initially as a dopamine stabilizer (low affinity D2) and reclassified as a sigma-1 agonist (Ki approximately 100 nM). Originally developed at NeuroSearch and now at Prilenia Therapeutics. Phase 3 PRIDE-HD trial in Huntington disease did not meet primary endpoint (Total Motor Score change). Phase 3 HEALEY-ALS platform trial in ALS is ongoing. Plasma half-life is approximately 10 hours. Used as a high-affinity sigma-1 research compound and as a clinical-stage neuroprotectant.

Mechanism of action

High-affinity sigma-1 receptor agonist; weak D2 dopamine receptor activity. Reclassified from dopamine stabilizer to sigma-1 agonist.

Reported research dose ranges

Trial doses 22.5 to 90 mg in the published literature.

References

Reilmann R, et al. Safety and efficacy of pridopidine in patients with Huntington's disease (PRIDE-HD): a phase 2, randomised, placebo-controlled, multicentre, dose-ranging study. Lancet Neurol 2019.
Squitieri F, et al. Pridopidine, a dopamine stabilizer, improves motor performance and shows neuroprotective effects in Huntington disease R6/2 mouse model. J Cell Mol Med 2015.
Ryskamp D, et al. Pridopidine stabilizes mushroom spines in mouse models of Alzheimer's disease by acting on the sigma-1 receptor. Neurobiol Dis 2019.

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KDC-MN-334

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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Pridopidine

Abstract

Mechanism of action

Reported research dose ranges

References

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Abstract

Mechanism of action

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References

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