Investigational Drug Information for Norketamine

What is the drug development status for Norketamine?

Norketamine is an investigational drug.

There have been 13 clinical trials for Norketamine. The most recent clinical trial was a Phase 1 trial, which was initiated on November 6^th 2024.

The most common disease conditions in clinical trials are Depressive Disorder, Major, Depressive Disorder, and Depression. The leading clinical trial sponsors are National Institute of Mental Health (NIMH), Lawson Health Research Institute, and Tampere University Hospital.

There are eighty-five US patents protecting this investigational drug and one hundred and thirty-one international patents.

Summary for Norketamine

US Patents	85
International Patents	131
US Patent Applications	254
WIPO Patent Applications	53
Japanese Patent Applications	18
Clinical Trial Progress	Phase 1 (2024-11-06)
Vendors	12

Recent Clinical Trials for Norketamine

Title	Sponsor	Phase
Pilot Study of RR-HNK in OCD	National Institutes of Health (NIH)	PHASE1
Pilot Study of RR-HNK in OCD	Carolyn Rodriguez	PHASE1
Investigation of the Antidepressant Effects of (2R,6R)-HNK, an Enhancer of Synaptic Glutamate Release, in Treatment-Resistant Depression	National Institute of Mental Health (NIMH)	PHASE2

See all Norketamine clinical trials

Clinical Trial Summary for Norketamine

Top disease conditions for Norketamine

Top clinical trial sponsors for Norketamine

See all Norketamine clinical trials

US Patents for Norketamine

Drugname	Patent Number	Patent Title	Patent Assignee	Estimated Expiration
Norketamine		Ketamine derivatives	Auckland Uniservices Limited (Auckland, NZ)
Norketamine		Neuro-attenuating ketamine and norketamine compounds, derivatives thereof, and methods	Amorsa Therapeutics, Inc. (Littleton, MA)
Norketamine		Assay for methoxetamine	Randox Laboratories Ltd. (GB)
Norketamine		Proline or proline derivatives for the treatment of dementia

International Patents for Norketamine

Drugname	Country	Document Number	Estimated Expiration	Related US Patent
Norketamine	Australia	AU2013328280	2032-10-08
Norketamine	Brazil	BR112015007647	2032-10-08
Norketamine	Canada	CA2922340	2032-10-08
Norketamine	China	CN104837810	2032-10-08

Norketamine Development Update, Patent Position, FDA Status, and Market Projection

Last updated: September 1, 2026

Norketamine is an active metabolite of ketamine, not an FDA-approved drug and not an established late-stage pharmaceutical program. Public development activity remains limited relative to ketamine and esketamine. The strongest commercial opportunity would require a sponsor to establish norketamine as a differentiated medicine with superior safety, durability, abuse liability, or administration characteristics. No approved norketamine product, Orange Book listing, FDA exclusivity period, or identifiable Phase 3 franchise currently supports a conventional market forecast.

What is norketamine and how does it differ from ketamine?

Norketamine is formed when ketamine is metabolized primarily through N-demethylation. It has pharmacologic activity at several targets, including the glutamatergic system, but its clinical profile differs from the parent drug.

Attribute	Norketamine	Ketamine	Esketamine
Chemical status	Active metabolite	Approved active drug	Enantiomer of ketamine
FDA approval	None	Yes, mainly anesthetic indications	Yes, Spravato
Approved psychiatric indication	None	None as a standalone antidepressant	Treatment-resistant depression and depressive symptoms with acute suicidal ideation under restricted use
Primary clinical role	Investigational or pharmacokinetic analyte	Anesthetic and off-label psychiatric treatment	Commercial psychiatric product
Delivery	No approved formulation	Injectable	Intranasal
Orange Book listing	None identified	Product-dependent	Spravato patents and exclusivities
Biosimilar relevance	None	None	None
Generic pathway	No approved reference product	Established for certain injectable products	Abbreviated new drug application challenges may depend on listed patents

Norketamine is often discussed alongside hydroxynorketamine, especially 2R,6R-hydroxynorketamine. These are different compounds. Hydroxynorketamine has attracted attention because preclinical studies suggested antidepressant activity without some of ketamine's dissociative effects, although translation to human efficacy remains unresolved.

The FDA label for KETALAR identifies norketamine as a metabolite of ketamine and describes lower potency relative to ketamine in certain pharmacologic contexts [1]. The SPRAVATO label also discusses ketamine metabolism and metabolite exposure, but does not establish norketamine as an approved active ingredient [2].

What is the current clinical development status of norketamine?

Norketamine has no publicly established registration program comparable to Spravato or an active ketamine-based Phase 3 program. Most published work falls into four categories:

1. Pharmacokinetic studies measuring norketamine after ketamine administration.
2. Biomarker research examining whether norketamine exposure correlates with antidepressant or analgesic response.
3. Preclinical studies of norketamine and hydroxynorketamine mechanisms.
4. Early medicinal chemistry and formulation work seeking compounds with ketamine-like efficacy and reduced dissociation.

The central development issue is that norketamine has mainly been evaluated as a metabolite of ketamine rather than as a standalone pharmaceutical product. That distinction creates a substantial regulatory burden. A sponsor would need to show that administered norketamine provides a clinically meaningful benefit that cannot be adequately attributed to ketamine or other metabolites.

Development milestones

Milestone	Current position
Discovery and pharmacology	Established in ketamine metabolism literature
Human exposure data	Available from ketamine studies
Standalone norketamine dosing program	No widely recognized late-stage program
Phase 2 efficacy package	No established public package supporting registration
Phase 3 program	None identified
FDA filing	None
FDA approval	None
Commercial product	None

ClinicalTrials.gov contains extensive ketamine and esketamine activity, but the existence of studies measuring norketamine does not establish norketamine as the investigational treatment. Trial records must be reviewed for the administered intervention, not simply for metabolite measurement [3].

What patents protect norketamine?

No clearly identifiable, commercially validated patent estate currently protects an approved norketamine product. Patent activity in this area is more likely to involve one of four categories:

• Norketamine or hydroxynorketamine compositions.
• Stereoisomerically enriched compounds.
• Pharmaceutical salts, prodrugs, or solid forms.
• Formulations and methods of treating depression, pain, or neurologic disorders.

The original ketamine molecule is old and has limited composition-of-matter exclusivity remaining. New protection would therefore depend on a genuinely novel norketamine form, a specific stereochemical composition, a prodrug, a formulation, or a method of use that satisfies patentability and written-description requirements.

How strong is the norketamine patent estate?

The apparent estate is weak as a commercial barrier because there is no established reference product and no recognized patent portfolio tied to a marketed norketamine medicine. A sponsor could obtain patents, but their value would depend on claim scope and clinical differentiation.

Patent category	Potential strength	Main vulnerability
Norketamine composition of matter	Low to moderate for new forms; weak for known compound	Prior-art and obviousness challenges
Enantiomer or stereochemical claims	Moderate if clinically differentiated	Prior art on ketamine stereoisomers and metabolites
Salt or solid-form claims	Moderate	Design-around and routine optimization arguments
Oral, injectable, or intranasal formulation	Moderate	Narrow claim scope and formulation obviousness
Method-of-use claims	Moderate	Requires credible clinical evidence and enforceability
Prodrug claims	Potentially strong	Must show unexpected pharmacokinetic or safety benefit
Manufacturing claims	Variable	Process alternatives may avoid infringement

A freedom-to-operate analysis would need to separate norketamine from esketamine, arketamine, hydroxynorketamine, and other ketamine analogues. Patent claims directed to ketamine metabolites may not cover every salt, stereoisomer, formulation, or route of administration.

What is the FDA regulatory status of norketamine?

Norketamine has no FDA approval, no FDA-approved label, and no Orange Book-listed product. It is not an approved active ingredient for depression, pain, anesthesia, or any other indication.

The likely regulatory path would be an Investigational New Drug application followed by Phase 1 safety and pharmacokinetic studies, even though human exposure has occurred after ketamine administration. Prior metabolite exposure would not eliminate the need to establish safety for intentional administration of norketamine as the active treatment.

A sponsor would likely need to characterize:

• Cardiovascular and central nervous system safety.
• Dissociation, sedation, and abuse liability.
• Repeated-dose toxicity.
• Reproductive and developmental toxicity where relevant.
• Pharmacokinetics across renal and hepatic impairment.
• Drug-drug interactions.
• Dose-response relationships.
• Comparative efficacy versus placebo and existing ketamine-based therapy.

For a psychiatric indication, the FDA would also scrutinize suicidality, dissociation, misuse, diversion, treatment durability, and treatment administration controls. A product administered in a clinic could face a REMS requirement if dissociation or abuse risk remains material.

When would norketamine lose exclusivity?

Norketamine has no current FDA exclusivity period to expire. Any future exclusivity would depend on the regulatory classification and the protection obtained.

Potential protection	Possible term or duration
New chemical entity exclusivity	Five years, if FDA classifies the approved product as an NCE
Orphan-drug exclusivity	Seven years, if an orphan indication is approved
New clinical investigation exclusivity	Three years for certain changes supported by new clinical studies
Pediatric exclusivity	Six additional months if statutory requirements are met
Composition or formulation patent	Generally 20 years from the effective nonprovisional filing date, subject to patent-term adjustment and extension
Patent-term extension	Potentially available for qualifying regulatory review, subject to statutory limits

The key issue is whether norketamine would qualify as a new chemical entity despite being a known ketamine metabolite. FDA classification is product-specific. A sponsor cannot assume that metabolite status guarantees or defeats NCE treatment.

What generic entry risks exist for norketamine?

There is currently no direct generic-entry risk because no norketamine reference product is approved. If a product is approved, generic risk would depend on the formulation and the scope of listed patents.

An injectable norketamine product could face earlier competition because injectable products often have simpler formulation requirements than controlled-release or intranasal products. An intranasal or extended-release product could obtain stronger formulation and device protection, but those claims would need to withstand obviousness and design-around challenges.

A generic competitor could target:

• The same active ingredient in a different salt.
• A different dosage form.
• A different device.
• A non-infringing method of use.
• An indication outside the scope of method patents.

Paragraph IV litigation would become relevant only after FDA approval and Orange Book listing. No current Paragraph IV dispute involving an approved norketamine product is established.

What patent litigation and licensing deals affect norketamine?

No major public patent litigation or settlement agreement involving an approved norketamine product has shaped the market. The commercial precedent comes from ketamine and esketamine.

Johnson & Johnson developed Spravato through Janssen and commercialized esketamine as a differentiated intranasal product rather than as norketamine. Spravato's commercial position is supported by regulatory approval, clinical data, manufacturing capability, distribution controls, and patent protection around the product and its use [2].

Norketamine has no comparable publicly established licensing transaction with a major pharmaceutical company. Any future licensing value would depend on proof of clinical differentiation, not on metabolite status alone.

How does norketamine compare with esketamine and arketamine?

Factor	Norketamine	Esketamine	Arketamine
Development maturity	Early or exploratory	Approved and commercial	Investigational
Human efficacy evidence	Limited as standalone therapy	Established through registrational trials	Developing
Dissociation risk	Unresolved	Clinically relevant	Intended to be lower, not established
Abuse liability	Unresolved	Managed through REMS and controlled administration	Unresolved
Commercial infrastructure	None	Established	None at scale
Patent value	Potentially new-product dependent	Existing marketed-product estate	Depends on new composition and use claims
Near-term revenue potential	Low	High relative to other ketamine derivatives	Low to moderate, development-dependent

The main commercial threat to norketamine would not necessarily be generic ketamine. It would be competing differentiated therapies, including esketamine, arketamine, psychedelic medicines, rapid-acting antidepressants, and conventional antidepressants with improved tolerability.

What is the market projection for norketamine?

A defensible base-case forecast assigns no near-term direct revenue to norketamine because there is no approved product, no identified Phase 3 program, and no established commercial sponsor.

Scenario-based outlook

Scenario	Development outcome	Commercial implication
Base case	Remains a metabolite and research tool	No standalone product revenue through the near term
Positive development case	Demonstrates antidepressant or analgesic benefit with lower dissociation or abuse liability	Potential specialty CNS product with premium pricing
Formulation-led case	A sponsor develops an extended-release, intranasal, or controlled-delivery product	Stronger differentiation and possible patent protection
Negative case	Efficacy does not separate from ketamine or safety remains problematic	Program abandonment or use limited to biomarker research

A positive product would likely target treatment-resistant depression, major depressive disorder, chronic pain, neuropathic pain, or an anesthesia-adjacent indication. Psychiatry offers higher pricing potential but also greater scrutiny over durability and abuse liability. Pain indications offer a larger patient pool but face intense generic competition and payer pressure.

The product's market ceiling would depend on four factors:

1. Demonstrated clinical benefit over esketamine or ketamine.
2. Lower dissociation and abuse liability.
3. Convenient administration outside specialized clinics.
4. Durable treatment effects with reduced dosing frequency.

Without those advantages, norketamine would likely compete as another ketamine-pathway therapy with limited pricing power. With a clear safety and convenience advantage, it could support a specialty CNS launch, but that outcome remains development-dependent rather than supported by current market evidence.

What is the competitive landscape for norketamine?

The relevant competitors include:

• Spravato, marketed by Johnson & Johnson.
• Generic racemic ketamine for approved anesthetic use and off-label psychiatric use.
• Arketamine programs.
• Hydroxynorketamine programs.
• Other rapid-acting antidepressants.
• Psychedelic-assisted therapies under development.
• Conventional antidepressants and augmentation products.

Spravato has the strongest commercial position because it has FDA approval, a defined treatment setting, clinical trial infrastructure, and payer familiarity. Norketamine would need to demonstrate more than mechanistic similarity to capture share from that franchise.

What are the key investment and licensing conclusions?

Norketamine is an early-stage scientific opportunity, not a current commercial asset. Its immediate value is concentrated in discovery, biomarker research, and possible lead optimization. The asset becomes commercially investable only after a sponsor demonstrates standalone clinical activity and a meaningful tolerability advantage.

Patent value is currently speculative. A stronger investment case would require a protected formulation, prodrug, stereochemical form, or method of use supported by human data. Manufacturing barriers are unlikely to be decisive for the parent metabolite, although specialized stereochemical control, impurity specifications, and controlled-delivery systems could create defensible know-how.

Key Takeaways

• Norketamine is an active ketamine metabolite, not an FDA-approved medicine.
• No established Phase 3 norketamine program, Orange Book listing, or FDA exclusivity period is publicly associated with the compound.
• Most human evidence concerns norketamine exposure after ketamine dosing, not standalone norketamine treatment.
• Hydroxynorketamine and arketamine are separate development assets and should not be treated as norketamine products.
• The patent position is potentially strongest for novel salts, formulations, prodrugs, stereochemical compositions, and clinically supported methods of use.
• Direct market revenue is unlikely in the near term under the base case.
• Commercial viability would require lower dissociation, lower abuse liability, greater durability, or a more convenient delivery system than ketamine and esketamine.

FAQs

Is norketamine the same drug as esketamine?

No. Esketamine is the S-enantiomer of ketamine. Norketamine is a demethylated metabolite produced after ketamine metabolism.

Can norketamine be prescribed for depression?

No. Norketamine has no FDA-approved depression indication and is not an approved prescription product.

Does norketamine have a unique mechanism of action?

Norketamine interacts with pharmacologic pathways affected by ketamine, but its full contribution to ketamine's clinical effects remains unresolved. Mechanistic activity alone has not established standalone therapeutic efficacy.

Could norketamine qualify for orphan-drug exclusivity?

Potentially, if a sponsor develops it for a qualifying rare disease and satisfies FDA orphan-drug requirements. No current orphan designation or orphan exclusivity for norketamine is established here.

Is norketamine likely to replace ketamine or Spravato?

Not on current evidence. Replacement would require clinical trials showing superior efficacy, safety, durability, convenience, or cost-effectiveness.

References

1. U.S. Food and Drug Administration. (2024). KETALAR (ketamine hydrochloride) injection prescribing information. https://www.accessdata.fda.gov/drugsatfda_docs/label/

2. U.S. Food and Drug Administration. (2024). SPRAVATO (esketamine hydrochloride) nasal spray prescribing information. https://www.accessdata.fda.gov/drugsatfda_docs/label/

3. National Library of Medicine. (2024). ClinicalTrials.gov search results for ketamine, norketamine, and hydroxynorketamine. https://clinicaltrials.gov/search

4. Zanos, P., Moaddel, R., Morris, P. J., et al. (2016). NMDAR inhibition-independent antidepressant actions of ketamine metabolites. Nature, 533(7604), 481-486. https://doi.org/10.1038/nature17998

5. Hashimoto, K. (2020). Molecular mechanisms of the rapid-acting and long-lasting antidepressant actions of (R)-ketamine. Biological Psychiatry, 87(2), 93-95. https://doi.org/10.1016/j.biopsych.2019.09.016