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

NCT07430397 | Recruiting Phase 1

• 2 other identifiers: FXI-1101C24027
• Study Type: interventional
• Target: 128
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Factor V Leiden; Prothrombin G20210A

Keywords

Factor XI; siRNA

Outcome Measures

Primary Outcomes (1)

• Incidence, severity, and relationship of treatment-emergent adverse events (TEAEs)

  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 Outcomes (6)

• Maximum plasma concentration (Cmax)

  Day -1 to Day 3

• Area under plasma concentration time curve (AUC) of CITY-FXI

  Day -1 to Day 3

• Amount excreted in urine (Ae) of CITY-FXI

  Day -1 to Day 3

• Change from baseline in levels of plasma Factor XI (FXI)

  Up to Day 360

• Change from baseline of Factor XI (FXI) activity

  Up to Day 360

Study Arms (4)

CITY-FXI in Healthy Adults (Part A)

EXPERIMENTAL

Drug: CITY-FXI

In Healthy Adults (Part A)

PLACEBO COMPARATOR

Drug: Placebo

CITY-FXI in Adults with Factor V Leiden or Prothrombin G20210A Mutation (Part B)

EXPERIMENTAL

Drug: CITY-FXI

In Adults with Factor V Leiden or Prothrombin G20210A Mutation (Part B)

PLACEBO COMPARATOR

Drug: Placebo

Interventions

CITY-FXI DRUG

siRNA (subcutaneous injection)

CITY-FXI in Adults with Factor V Leiden or Prothrombin G20210A Mutation (Part B); CITY-FXI in Healthy Adults (Part A)

Placebo DRUG

Saline (subcutaneous injection)

In Adults with Factor V Leiden or Prothrombin G20210A Mutation (Part B); In Healthy Adults (Part A)

Eligibility Criteria

• Age: 18 Years - 60 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• 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)

You may not qualify if:

• 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)

Sponsors & Collaborators

• City Therapeutics: lead

Study Sites (1)

Richmond Pharmacology

London, SE1 1YR, United Kingdom

RECRUITING

Central Study Contacts

City Therapeutics

CONTACT

857-219-5440; clinicaltrials@citytx.com

Study Design

• Study Type: interventional
• Phase: phase 1
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, INVESTIGATOR
• Purpose: TREATMENT
• Intervention Model: SEQUENTIAL
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: January 9, 2026
• First Posted: February 24, 2026
• Study Start: January 22, 2026
• Primary Completion (Estimated): August 1, 2027
• Study Completion (Estimated): October 1, 2027
• Last Updated: February 24, 2026

Record last verified: 2026-02

Locations

GB (1)