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LSD Occupancy of the Serotonin 2A Receptor in the... — Clinical Trial Details | Blossom

Clinical TrialHealthy VolunteersLSDActive not recruiting

LSD Occupancy of the Serotonin 2A Receptor in the Human Brain (dOccLS)

Early‑Phase interventional dose-ranging study (n=40) assessing LSD single doses (25–200 µg) to quantify 5‑HT2A receptor occupancy in healthy participants using [11C]CIMBI‑36 PET/MR.

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Target Enrollment

40 participants

Study Type

Phase I interventional

Design

Non-randomized

Registry

CTG / NCT05953038

Detailed Description

Healthy participants (18–75 years) receive a single oral dose of LSD (one of 25–200 µg) in a single‑blinded, dose‑ranging design to characterise dose–plasma–receptor occupancy relationships.

Participants undergo baseline and two post‑dose [11C]CIMBI‑36 PET scans in a simultaneous PET/MR scanner at peak and declining effects; repeated venous sampling quantifies plasma LSD and repeated subjective intensity ratings (0–10) capture acute effects.

Study Protocol

Preparation

sessions

Dosing

1 sessions

Locations

Neurobiology Research Unit, Rigshospitalet — Copenhagen, Denmark

Related Publications

Open AccessindividualPrimary

Molecular, haemodynamic, and functional effects of LSD in the human brain

Using simultaneous PET–MRI in healthy volunteers, this first integrated molecular and functional neuroimaging study quantifies LSD occupancy at cerebral serotonin 2A receptors and establishes a dose–occupancy relationship while revealing an anticlockwise hysteresis between plasma levels and subjective effects. LSD produced distinct haemodynamic and functional changes — increasing global cerebral and internal carotid artery flow without altering artery diameter and reducing global connectivity (GCOR), with GCOR changes negatively correlated with CBF and differing from effects of psilocybin — findings relevant to clinical development.

Published: June 18, 2025
Journal: MedRvix
Authors: McCulloch, D. E-W., Larsen, K., Johansen, A., Johansen, S. S., Jensen, P. S., Reveles Jensen, K. H., Holze, F., Falck, N., Neufeld, V., Steenstrup, E., Andersen, T. L., Skov-Andersen, P., Spanggård, A., Geisler, M., Randrup, P. P., Shulganov, V., Nielsen, M. K. K., Svarer, C., Fisher, P. M., Knudsen, G. M., Nykjær, C. H., Stenbæk, D. S.

Integration

sessions

Study Arms & Interventions

LSD dose-ranging

experimental

Single-blind dose-ranging group; each participant receives one single oral dose (25–200 µg) with simultaneous PET/MR during acute effects.

Interventions

LSD25 - 200 µg
via Oral• single dose• 1 doses total
Oral D‑tartrate drinking solution (water/ethanol 20% m/m); participants single-blinded to dose (one of 25,50,75,100,125,150,175,200 µg).

Participants

Ages

18 – 75

Sexes

Male & Female

BMI

0 - 35

Psychosis History

Excluded

Inclusion Criteria

Healthy individual between 18-75 years old

Exclusion Criteria

Current or past history of primary psychiatric illness (DSM‑IV axis‑I or ICD‑10); current or past primary psychiatric illness in a first degree relative (parents, siblings); current or past history of neurological disease or significant somatic condition; use of medication that could influence results (e.g., drugs acting on the serotonin system or interfering with metabolism of study drug); non-fluent Danish language skills; profound visual or auditory impairments; severe learning disability; pregnancy on scan date (verified by pregnancy test; omitted if post‑menopausal); lactation (females); contraindications for MRI (e.g., pacemaker, claustrophobia); contraindications for PET; alcohol or drug abuse; allergy to administered compounds; participation in research with >10 millisievert exposure within past year or significant occupational exposure to radioactive substances; abnormal ECG or use of QT‑prolonging medication; use of psychedelic substance within preceding six months; blood donation up to three months before study (>500 ml); head injury/concussion with loss of consciousness >2 min; haemoglobin <7.8 mmol/l (women) or <8.4 mmol/l (men); ferritin outside normal range (12-300 µg/L); body-weight <50 kg or >110 kg; body-mass index >35; individual assessment deeming drug administration unsafe due to ethical or psychological circumstances

Study Details

Status
Active not recruiting
Phase
Phase I
Type
interventional
Design
Non-randomized
Target Enrollment40 participants
Timeline
Start: 2023-11-08
End: 2024-12-31
Compound
LSD
Topic
Healthy Volunteers

Study Team

Sponsors & Collaborators

Rigshospitalet, Denmark
Primary Sponsor