A Phase 2 Safety, Tolerability, PK, and Efficacy Study of CS-1103 Following Fentanyl Challenge With Naloxone Blockade
Fentanyl Overdose · Fentanyl Poisoning
What this study involves
The registry does not currently label this study as recruiting. Ask about its status before planning a screening visit.
- Study type
- Interventional
- Phase
- Phase 2
- Age range
- 18 years - 55 years
- Sex eligible
- All sexes
- Healthy volunteers
- Accepted
- Participants
- 16 Actual
These are starting points, not an eligibility decision. The research team must review the full requirements.
About the research
The purpose of the study is to evaluate the safety, tolerability, pharmacokinetics, and efficacy of CS-1103 (1,000 mg), given by intravenous (IV) infusion in healthy participants in the presence of a clinically relevant dose of fentanyl (200 μg, IV), with naloxone blockade (400 μg, IV).
Who may be able to participate?
The list below is the sponsor’s full registry wording. It can include conditions, prior treatment, test results and other requirements. A match in search does not mean you qualify.
Major Inclusion Criteria:
1. Healthy participants aged 18 to 55 years, inclusive;
2. Have prior experience with opioids, such as from a dental procedure, chronic pain management, or previous inpatient surgical procedure;
3. A body mass index between 18.0 to 30.0 kg/m2, inclusive, and a minimum body weight of 56 kg;
4. Females must not be lactating and must have a negative pregnancy test during screening and admission.
Major Exclusion Criteria:
1. Estimated glomerular filtration rate \<90 mL/min/1.73 m2;
2. History of cardiovascular disease;
3. History of any clinically important disease or disorder which, in the opinion of the Investigator, may interfere with safe study participation.
Treatment, groups and participation
The registry may describe treatments and study duration without a complete visit calendar. Ask the study team for the exact schedule, procedures, risks, costs and alternatives. Keep your usual care plan unless your treating clinician tells you otherwise.
- Assignment
- Random assignment
- Masking
- Quadruple masked
Placebo
Participants receive naloxone blockade (400 μg, IV), followed by fentanyl (200 μg, IV), followed by placebo (saline).
Drug: Naloxone Hydrochloride · Drug: Fentanyl · Drug: Sterile Saline
Active
Participants receive naloxone blockade (400 μg, IV), followed by fentanyl (200 μg, IV), followed by CS-1103 (1,000 mg, IV).
Drug: Naloxone Hydrochloride · Drug: Fentanyl · Drug: CS-1103
Naloxone Hydrochloride DRUG
Naloxone for intravenous administration
Fentanyl DRUG
Fentanyl for intravenous administration
Sterile Saline DRUG
Sterile Saline for intravenous administration
CS-1103 DRUG
CS-1103 for intravenous administration
What researchers are measuring
Outcome measures describe what is being studied. They are not proof that a treatment works.
Primary measures
Number of participants with CS-1103-related adverse events (AEs) assessed by physical examinations
Time frame: 3 days plus follow-up on Day 10
Physical examinations
Number of participants with CS-1103-related adverse events (AEs) assessed by electrocardiograms (ECGs)
Time frame: 3 days plus follow-up on Day 10
Digital 12-lead electrocardiograms (ECGs). Any correlation between CS-1103 plasma concentrations and changes in QT intervals will be noted
Number of participants with CS-1103-related adverse events (AEs) assessed by vital signs
Time frame: 3 days plus follow-up on Day 10
Blood pressure, pulse rate, respiratory rate, oxygen saturation, and body temperature
Number of participants with CS-1103-related adverse events (AEs) assessed by laboratory parameters
Time frame: 3 days plus follow-up on Day 10
Clinical chemistry, hematology, coagulation, and urinalysis
Time course of CS-1103 blood and urine concentrations
Time frame: 48 hours
Measurement of plasma and urine concentrations of CS-1103
Time course and magnitude of urine excretion of fentanyl
Time frame: 48 hours
Measurement of concentration of fentanyl in urine
Secondary measures
Effect of CS-1103 and fentanyl on QT interval
Time frame: 48 hours
Concentration-QT correlation performed on baseline-corrected QTcF time-matched with PK for fentanyl and CS-1103 in plasma
Effect of CS-1103 on the naloxone plasma and urine PK, if any
Time frame: 48 hours
Measurement of standard urine and plasma PK parameters between placebo and CS-1103 treated participants
Review the complete result tables and limitations in the official record.
Open official results ↗Research locations (1)
The overall study status and a local site’s status can differ. Confirm that location’s availability before traveling.
1 locations
California Clinical Trials Medical GroupGlendale, California, United StatesStatus unknown
Study team and timeline
- Lead sponsor
- Clear Scientific, Inc.
- Study start
- May 28, 2026 Actual
- Primary completion
- Jul 15, 2026 Actual
- Study completion
- Jul 22, 2026 Actual
- First posted
- Mar 9, 2026 Actual
- Last updated
- Nov 10, 2026 Actual
Official study contacts
No central contact is listed. Check the locations and the official record.
Official study title
A Phase 2 Randomized, Double-Blind, Placebo-Controlled Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Efficacy of a Single Dose of Intravenous CS 1103 Following a Single Intravenous Dose of Fentanyl in Healthy Subjects With Naloxone Blockade
Ask Wellness Clinical Research
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Source: ClinicalTrials.gov API v2. Information is submitted by sponsors and investigators. NLM does not approve the safety or science of all listed studies. Registry disclaimer.
Retrieved: Nov 12, 2026 · Last registry update: Nov 10, 2026