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NCT Number: NCT07430397

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

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.

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Key information

Conditions

Factor V Leiden Prothrombin G20210A

Age range

18 year–60 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 1

Primary location

About this study

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

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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)

Treatment and study plan

CITY-FXI

Drug

siRNA (subcutaneous injection)

Placebo

Drug

Saline (subcutaneous injection)

Primary outcomes

  1. 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

Secondary outcomes

  1. 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

  2. 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

  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

  4. 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

  5. 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

  6. 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

Study contacts

Contact information is provided by the study sponsor or research team.

City Therapeutics

CONTACT

[email protected]

857-219-5440

Sponsors and collaborators

Lead sponsor

City Therapeutics

Industry

Registry information

Official study title

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

Important dates

Study start
2026
Primary completion
2027
Study completion
2027
First posted
Feb 24, 2026
Registry last updated
Feb 24, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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