Basic ScienceEarly Phase 1dOccLSNCT05953038
LSD Occupancy of the Serotonin 2A Receptor in the Human Brain
A Early Phase 1 study testing Lysergic Acid Diethylamide Tartrate in people with Basic Science, run by Copenhagen University Hospital, Rigshospitalet at 1 site in Denmark.
Trial summary
The investigators wish to quantify the relation between administered dose of lysergic acid diethylamide (LSD), plasma LSD levels, and occupancy at the serotonin 2A receptor (5-HT2AR) using [11C]CIMBI-36 positron emission tomography. Read more about this study
- Who is it for?
- Ages 18 to 75 yearsHealthy volunteers can take part
- Conditions the study is for
- Basic Science
- What is being tested?
- Lysergic Acid Diethylamide Tartrate
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 40 participants
- Where
- 1 siteDenmark
- Study dates
- 8 Nov 2023to 31 Dec 2027
- Phase
- Early Phase 1
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 75 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Healthy individual between 18-75 years old
Who cannot join
- Current or past history of primary psychiatric illness (The Diagnostic and Statistical Manual of Mental Disorders IV axis-I or World Health Organisation International Classification of Diseases-10 diagnostic classification)
- Current or past history of primary psychiatric illness (The Diagnostic and Statistical Manual of Mental Disorders IV axis-I or World Health Organisation International Classification of Diseases-10 diagnostic classification) in a first degree relative (i.e., parents, siblings)
- Current or past history of neurological disease, significant somatic condition/disease
- Use of medication that could potentially influence results (e.g.., drugs that act on relevant components of the serotonin system or may interfere with metabolism of study drug)
- Non-fluent Danish language skills
- Profound visual or auditory impairments
Show all 23Show fewer
- Severe learning disability
- Pregnancy on the scan date, verified by a pregnancy test (test omitted if confirmed that individual is post-menopausal)
- Lactation (females)
- Contraindications for magnetic resonance imaging (e.g., pacemaker, claustrophobia, etc.)
- Contraindications for positron emission tomography
- Alcohol or drug abuse
- Allergy to administered compounds
- Participant in research study with >10 millisievert exposure within the past year or significant occupational exposure to radioactive substances
- Abnormal ECG (ECG indicating current or previous heart disease or predisposition to heart disease, e.g., QT prolongation) or use of QT prolonging medication
- Use of psychedelic substance within the preceding six months
- Blood donation up to three months before the study (i.e., more than 500ml of blood)
- Head injury or concussion resulting in loss of consciousness for more than 2 min
- Haemoglobin levels < 7.8 mmol/l for women and 8.4 mmol/l for men
- Ferritin levels outside normal range (12-300 µg/L)
- Body-weight < 50 kg or > 110kg
- body-mass index > 35
- Individual assessment by research staff deeming drug administration unsafe due to ethical or psychological circumstance of the participant
Trial locations and contacts
1 site in 1 country.
About this study
Official title: Lysergic Acid Diethylamide Occupancy of the Serotonin 2A Receptor in the Human Brain
The investigators wish to quantify the relation between administered dose of lysergic acid diethylamide (LSD), plasma LSD levels, and occupancy at the serotonin 2A receptor (5-HT2AR) using [11C]CIMBI-36 positron emission tomography.
Read the detailed description
Healthy participants will be administered one of a single dose of lysergic acid diethylamide (LSD) between 25 and 200 micrograms equivalent freebase. They will receive [11C]CIMBI-36 positron emission tomography (PET) scans at baseline and twice following LSD administration during peak and declining drug effects. PET scans will be acquired in a simultaneous PET/Magnetic Resonance Imaging (MRI) scanner which will also collect functional brain imaging data. Venous blood samples will be repeatedly drawn during acute drug effects for quantification of plasma LSD levels. Participants will also repeatedly rate their subjective drug intensity on a scale from 0 to 10 during acute drug effects. Together these data will inform the dose-binding relation of LSD at the serotonin (5-HT) 2A receptor, the primary site of action. This data will also inform the relation between 5-HT2A receptor binding by LSD and the induced subjective effects, as well as the effects on functional brain activity as measured with functional MRI.
- Conditions
- Basic Science
- Being tested
- Lysergic Acid Diethylamide Tartrate
- Keywords
- Lysergic acid diethylamide, PET, Psychedelic, Hallucinogen, Physiological Effects of Drugs, Psychotropic Drugs, Ergolines, Serotonin, Serotonin Agents, Neurotransmitter Agents, Molecular Mechanisms of Pharmacological Action
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Lysergic Acid Diethylamide TartrateDrug
Also called LSD, d-LSD, LSD-25
D-Lysergic Acid Diethylamide (LSD) D-tartrate as oral drinking solution (water / ethanol 20% m/m)
| Study group | Role | What they receive |
|---|---|---|
| LSD dose-ranging group | Experimental | All participants will receive between 25 and 200 micrograms of lysergic acid diethylamide equivalent as freebase, single blinded with respect to dose. Simultaneous PET/MR imaging will be performed during acute drug effects. Receives: Drug: Lysergic Acid Diethylamide Tartrate |
What is being measured
The primary outcome is the main question the study is designed to answer.
Plasma LSD - serotonin 2A receptor (5-HT2AR) occupancy relation
Occupancy will be estimated by comparing non-displaceable binding potential (BPND) values using baseline and intervention rescans as calculated using a simplified reference tissue model (SRTM). Occupancy values will be compared to plasma lysergic acid diethylamide (LSD) levels.
Measured: Within 24 hours following drug administration
Secondary outcomes (5)
Subjective drug intensity - 5-HT2AR occupancy relation
Occupancy will be calculated as described above. Subjective drug intensity is collected during positron emission tomography (PET) scans by asking participants.
Measured: Within 24 hours following drug administration
fMRI network disintegration - 5-HT2AR occupancy relation
functional magnetic resonance imaging (fMRI) data will be used to estimate functional-network connectivity using a standard functional brain atlas. Then the relation between decreases in functional network connectivity and 5-HT2AR occupancy will be estimated.
Measured: Within 24 hours following drug administration
fMRI brain entropy - 5-HT2AR occupancy relation
fMRI brain entropy will be estimated by the shannon entropy of dynamic conditional correlation of within and between network connectivity as well as the lempel-ziv complexity of concatenated binarised blood-oxygen level dependent (BOLD) signals across regions. The relation between each of these measures with 5-HT2AR occupancy will be estimated.
Measured: Within 24 hours following drug administration
Cerebral perfusion - 5-HT2AR occupancy relation
Cerebral perfusion will be estimated using arterial spin labelling. The relation between this measure and 5-HT2AR occupancy will be estimated.
Measured: Within 24 hours following drug administration
Administered LSD dose - 5-HT2AR occupancy relation
Administered dose (25 to 200 mcg) will be compared with peak LSD occupancy to determine what doses produce maximal occupancy at the 5-HT2AR.
Measured: Within 24 hours following drug administration
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted19 Jul 2023
- Study start8 Nov 2023
- Primary completionDec 2027 (estimated)
- Study completion31 Dec 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Basic ScienceStudies of the same condition, open and under way.
- More trials run by Copenhagen University Hospital, RigshospitaletThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Early Phase 1
- Primary purpose
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Model description
- Each participant will be given one of 25, 50, 75, 100, 125, 150, 175 or 200 micrograms of lysergic acid diethylamide (LSD) equivalent as freebase.
- Masking
- None (open label)
- Enrolment
- 40 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Copenhagen University Hospital, Rigshospitalet
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Gitte Moos Knudsen, Copenhagen University Hospital, Rigshospitalet
- Investigators
- Gitte M Knudsen, DMsc, MD, Principal investigator, Copenhagen University Hospital, Rigshospitalet
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05953038
- Sponsor's protocol ID
- H-21060056
- Other IDs
- 2021-002633-42
- Acronym
- dOccLS
- Status last verified
- Jul 2026
- First submitted
- 14 Feb 2023
- Last updated
- 2 Jul 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 2 Jul 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Lysergic Acid Diethylamide Occupancy of the Serotonin 2A Receptor in the Human Brain
- ClinicalTrials.gov ID
- NCT05953038
- Acronym / sponsor ID
- dOccLS / H-21060056
- Conditions
- Basic Science
- Keywords
- Lysergic acid diethylamide, PET, Psychedelic, Hallucinogen, Physiological Effects of Drugs, Psychotropic Drugs, Ergolines, Serotonin
- Phase
- Early Phase 1
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 40 participants (estimated)
- Lead sponsor
- Copenhagen University Hospital, RigshospitaletUniversity, hospital or other
- Study start
- 8 Nov 2023 (actual)
- Primary completion
- Dec 2027 (estimated)
- Study completion
- 31 Dec 2027 (estimated)
- First posted
- 19 Jul 2023 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The investigators wish to quantify the relation between administered dose of lysergic acid diethylamide (LSD), plasma LSD levels, and occupancy at the serotonin 2A receptor (5-HT2AR) using [11C]CIMBI-36 positron emission tomography.
Detailed description
Healthy participants will be administered one of a single dose of lysergic acid diethylamide (LSD) between 25 and 200 micrograms equivalent freebase. They will receive [11C]CIMBI-36 positron emission tomography (PET) scans at baseline and twice following LSD administration during peak and declining drug effects. PET scans will be acquired in a simultaneous PET/Magnetic Resonance Imaging (MRI) scanner which will also collect functional brain imaging data. Venous blood samples will be repeatedly drawn during acute drug effects for quantification of plasma LSD levels. Participants will also repeatedly rate their subjective drug intensity on a scale from 0 to 10 during acute drug effects. Together these data will inform the dose-binding relation of LSD at the serotonin (5-HT) 2A receptor, the primary site of action. This data will also inform the relation between 5-HT2A receptor binding by LSD and the induced subjective effects, as well as the effects on functional brain activity as measured with functional MRI.
Study design
- Primary purpose
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
- Model description
- Each participant will be given one of 25, 50, 75, 100, 125, 150, 175 or 200 micrograms of lysergic acid diethylamide (LSD) equivalent as freebase.
| Arm | Type | Receives |
|---|---|---|
| LSD dose-ranging group | Experimental | Drug: Lysergic Acid Diethylamide TartrateAll participants will receive between 25 and 200 micrograms of lysergic acid diethylamide equivalent as freebase, single blinded with respect to dose. Simultaneous PET/MR imaging will be performed during acute drug effects. |
Who may qualify
- Ages
- 18 to 75 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (1 listed)
- Healthy individual between 18-75 years old
Key exclusion criteria (23 listed)
- Current or past history of primary psychiatric illness (The Diagnostic and Statistical Manual of Mental Disorders IV axis-I or World Health Organisation International Classification of Diseases-10 diagnostic classification)
- Current or past history of primary psychiatric illness (The Diagnostic and Statistical Manual of Mental Disorders IV axis-I or World Health Organisation International Classification of Diseases-10 diagnostic classification) in a first degree relative (i.e., parents, siblings)
- Current or past history of neurological disease, significant somatic condition/disease
- Use of medication that could potentially influence results (e.g.., drugs that act on relevant components of the serotonin system or may interfere with metabolism of study drug)
- Non-fluent Danish language skills
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Lysergic Acid Diethylamide TartrateAlso: LSD, d-LSD, LSD-25D-Lysergic Acid Diethylamide (LSD) D-tartrate as oral drinking solution (water / ethanol 20% m/m) | Drug | LSD dose-ranging group |
Primary outcome
Plasma LSD - serotonin 2A receptor (5-HT2AR) occupancy relation
Time frame: Within 24 hours following drug administration
Occupancy will be estimated by comparing non-displaceable binding potential (BPND) values using baseline and intervention rescans as calculated using a simplified reference tissue model (SRTM). Occupancy values will be compared to plasma lysergic acid diethylamide (LSD) levels.
5 secondary outcomes
Subjective drug intensity - 5-HT2AR occupancy relation
Time frame: Within 24 hours following drug administration
fMRI network disintegration - 5-HT2AR occupancy relation
Time frame: Within 24 hours following drug administration
fMRI brain entropy - 5-HT2AR occupancy relation
Time frame: Within 24 hours following drug administration
Cerebral perfusion - 5-HT2AR occupancy relation
Time frame: Within 24 hours following drug administration
Administered LSD dose - 5-HT2AR occupancy relation
Time frame: Within 24 hours following drug administration
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 2 Jul 2026.
- Lab study homepageLink provided by the sponsor.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Gitte M Knudsen, DMsc, MD principal investigator
Copenhagen University Hospital, Rigshospitalet
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Early Phase 1 study testing Lysergic Acid Diethylamide Tartrate in people with Basic Science, run by Copenhagen University Hospital, Rigshospitalet at 1 site in Denmark.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 1 inclusion and 23 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 2 Jul 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Denmark. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Early Phase 1 (sometimes called Phase 0) studies give a very small amount of a treatment to a few people, mainly to see how the body handles it.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Plasma LSD - serotonin 2A receptor (5-HT2AR) occupancy relation (time frame: Within 24 hours following drug administration). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 2 Jul 2026.