A Single Ascending Dose Study to Assess the Safety, Tolerability, Pharmacokinetics and Pharmacodynamics of CITY-FXI in Healthy Adults and Adults With FV Leiden or Prothrombin G20210A Mutation

February 18, 2026 updated by: City Therapeutics

A Phase 1, Randomised, Double-Blind, Placebo-Controlled Single Ascending Dose Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of CITY-FXI, a FXI Targeting siRNA, Administered Subcutaneously in Healthy Adults and Adults With Factor V Leiden or Prothrombin G20210A Mutation

This is a first-in-human (FIH), single-center, randomised, double-blind, placebo-controlled, single ascending dose (SAD) study evaluating the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of CITY-FXI in healthy adults and adults with Factor V Leiden (FVL) or prothrombin G20210A mutation.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

The study will be conducted in two parts:

  • Part A: Single Ascending Dose in Healthy Adults
  • Part B: Single Ascending Dose in Adults with Factor V Leiden (FVL) or Prothrombin G20210A Mutation

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
128

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 1

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Males and women of non-childbearing potential (WONCBP) aged 18 to 45 years (Part A only)
  • Male and female participants aged 18 to 60 (Part B only)
  • Body Mass Index (BMI) between 18 and 25 kg/m2 (inclusive) and a minimum weight of 50 kg
  • Ability and willingness to comply fully with all study procedures and lifestyle considerations
  • Confirmed diagnosis of FVL or prothrombin G20210A mutation via genetic testing (Part B only)
  • Women of childbearing potential (WOCBP) must agree to use acceptable highly effective contraceptive methods (Part B only)

Exclusion Criteria:

  • Any clinically significant systemic disease or disorder, including but not limited to cardiovascular, hepatic, or oncological conditions
  • History or evidence of any bleeding disorders
  • History of clinically significant spontaneous bleeding
  • Prior treatment with an investigational agent
  • Confirmed diagnosis of homozygous mutations, or combined thrombophilic defects of (Part B only)

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Sequential Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: CITY-FXI in Healthy Adults (Part A)
Drug: CITY-FXI
siRNA (subcutaneous injection)
Placebo Comparator: In Healthy Adults (Part A)
Drug: Placebo
Saline (subcutaneous injection)
Experimental: CITY-FXI in Adults with Factor V Leiden or Prothrombin G20210A Mutation (Part B)
Drug: CITY-FXI
siRNA (subcutaneous injection)
Placebo Comparator: In Adults with Factor V Leiden or Prothrombin G20210A Mutation (Part B)
Drug: Placebo
Saline (subcutaneous injection)

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Incidence, severity, and relationship of treatment-emergent adverse events (TEAEs)
Time Frame: Through study completion, up to Day 360
To evaluate the safety and tolerability of a single dose of CITY-FXI in healthy adults and adults with Factor V Leiden (FVL) or prothrombin G20210A mutation
Through study completion, up to Day 360

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Maximum plasma concentration (Cmax)
Time Frame: Day -1 to Day 3
To characterize the pharmacokinetics (PK) of a single dose of CITY-FXI in healthy adults and adults with FVL or prothrombin G20210A mutation
Day -1 to Day 3
Area under plasma concentration time curve (AUC) of CITY-FXI
Time Frame: Day -1 to Day 3
To characterize the pharmacokinetics (PK) of a single dose of CITY-FXI in healthy adults and adults with FVL or prothrombin G20210A mutation
Day -1 to Day 3
Amount excreted in urine (Ae) of CITY-FXI
Time Frame: Day -1 to Day 3
To characterize the pharmacokinetics (PK) of a single dose of CITY-FXI in healthy adults and adults with FVL or prothrombin G20210A mutation
Day -1 to Day 3
Change from baseline in levels of plasma Factor XI (FXI)
Time Frame: Up to Day 360
To characterize the pharmacodynamics (PD) of a single dose of CITY-FXI in healthy adults and adults with FVL or prothrombin G20210A mutation
Up to Day 360
Change from baseline of Factor XI (FXI) activity
Time Frame: Up to Day 360
To characterize the pharmacodynamics (PD) of a single dose of CITY-FXI in healthy adults and adults with FVL or prothrombin G20210A mutation
Up to Day 360
Change from baseline in activated partial thromboplastin time (aPTT)
Time Frame: Up to Day 360
To characterize the pharmacodynamics (PD) of a single dose of CITY-FXI in healthy adults and adults with FVL or prothrombin G20210A mutation
Up to Day 360

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
City Therapeutics

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
January 22, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
August 1, 2027

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
October 1, 2027

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
January 9, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
February 18, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
February 24, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
February 24, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
February 18, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
February 1, 2026

More Information

Terms related to this study

Keywords

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • FXI-1101
  • C24027 (Other Identifier: Richmond Pharmacology)

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

Clinical Trials on Prothrombin G20210A

Clinical Trials on CITY-FXI

Search Similar Trials

Sponsors and Collaborators

Medical Conditions

Drug Interventions

Conditions

Rare Diseases

Drug Interventions

Dietary Supplements

Sponsor/Collaborators

Locations

Cookie Settings

We use cookies to ensure that we give you the best experience on our website. For more details carefully read our Privacy and Cookies Policy. ...>>>You can change your preferences or withdraw your consent at any time by deleting the cookies from your website or computer as described in the policy. Please accept it and choose your preferences by ticking the corresponding boxes in the "Manage Settings" section below. Please carefully read our Terms of Service before you proceed with using any part of this website.
«Manage Settings