Factor V LeidenPhase 1NCT07430397
A Single Ascending Dose Study to Assess the Safety, Tolerability, Pharmacokinetics and Pharmacodynamics of CITY-FXI in Healthy Adults, Adults With FV Leiden or Prothrombin G20210A Mutation, and Adults With a History of Provoked Venous Thromboembolism
A Phase 1 study testing CITY-FXI in people with Factor V Leiden and Prothrombin G20210A, run by City Therapeutics at 1 site in United Kingdom.
Trial summary
This is a first-in-human (FIH), single-center, randomized, double-blind, placebo-controlled, single ascending and multiple dose study evaluating the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of CITY-FXI in healthy adults, adults with Factor V Leiden (FVL) or prothrombin G20210A mutation… Read more about this study
- Who is it for?
- Ages 18 to 65 yearsHealthy volunteers can take part
- Conditions the study is for
- Factor V Leiden, Prothrombin G20210A, Venous Thromboembolism (VTE)
- What is being tested?
- CITY-FXI
- Type of treatment
- Injection or infusion
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 182 participants
- Where
- 1 siteUnited Kingdom
- Study dates
- 22 Jan 2026to Apr 2028
- Phase
- Phase 1
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 65 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Males and women of non-childbearing potential (WONCBP) aged 18 to 45 years (inclusive, for Part A only)
- Male and female participants aged 18 to 60 (inclusive, for Part B only), and aged 18 to 65 years (inclusive, for Part C only)
- Body Mass Index (BMI) between 18 and 25 kg/m2 (inclusive, for Part B only) and 18 and 35 kg/m2 (inclusive, for Part C only) and a minimum weight of 50 kg (Parts A, B, and C)
- 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 (Parts B and C only)
- History of provoked venous thromboembolism (VTE) within the last 10 years and/or confirmed diagnosis of heterozygosity for FVL and prothrombin G20210A mutation via genetic testing (Part C only)
Who cannot join
- 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 (e.g., FVL with prothrombin G20210A mutation) (Parts B and C only)
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United Kingdom1 site, 1 recruiting
- Recruiting
Richmond Pharmacology
London, SE1 1YR
Dr. Ulrike Lorch, +44 0207 042 5800, volunteer@richmondpharmacology.com
About this study
Official 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, Adults With Factor V Leiden or Prothrombin G20210A Mutation, and Adults With a History of Provoked Venous Thromboembolism
This is a first-in-human (FIH), single-center, randomized, double-blind, placebo-controlled, single ascending and multiple dose study evaluating the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of CITY-FXI in healthy adults, adults with Factor V Leiden (FVL) or prothrombin G20210A mutation, and adults with a history of provoked venous thromboembolism (VTE).
Read the detailed description
The study will be conducted in three 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
- Part C: Multiple Doses in Adults with FVL or Prothrombin G20210A Mutation and/or a History of Provoked Venous Thromboembolism (VTE)
- Being tested
- CITY-FXI, Placebo
- Keywords
- Factor XI, siRNA
- Medical subject headings
- Venous Thromboembolism
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
CITY-FXIDrug
siRNA (subcutaneous injection)
PlaceboDrug
Saline (subcutaneous injection)
| Study group | Role | What they receive |
|---|---|---|
| CITY-FXI in Healthy Adults (Part A) | Experimental | Not described Receives: Drug: CITY-FXI |
| In Healthy Adults (Part A) | Placebo comparator | Not described Receives: Drug: Placebo |
| CITY-FXI in Adults with Factor V Leiden or Prothrombin G20210A Mutation (Part B) | Experimental | Not described Receives: Drug: CITY-FXI |
| In Adults with Factor V Leiden or Prothrombin G20210A Mutation (Part B) | Placebo comparator | Not described Receives: Drug: Placebo |
| CITY-FXI in Adults with FVL, Prothrombin G20210A Mutation, and/or a History of Provoked VTE (Part C) | Experimental | Not described Receives: Drug: CITY-FXI |
| In Adults with FVL, Prothrombin G20210A Mutation, and/or a History of Provoked VTE (Part C) | Placebo comparator | Not described Receives: Drug: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
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, and of a multiple dose regimen of CITY-FXI in adults with FVL or prothrombin G20210A mutation and/or a history of provoked VTE
Measured: Through study completion, up to Day 360
Secondary outcomes (6)
Maximum plasma concentration (Cmax)
To characterize the pharmacokinetics (PK) of a single dose of CITY-FXI in healthy adults and adults with FVL or prothrombin G20210A mutation, and of a multiple dose regimen of CITY-FXI in adults with FVL or prothrombin G20210A mutation and/or a history of provoked VTE
Measured: Day 1 to Day 3 (Parts A and B); Days 1, 2, 91, 92 (Part C)
Area under plasma concentration time curve (AUC) of CITY-FXI
To characterize the pharmacokinetics (PK) of a single dose of CITY-FXI in healthy adults and adults with FVL or prothrombin G20210A mutation, and of a multiple dose regimen of CITY-FXI in adults with FVL or prothrombin G20210A mutation and/or a history of provoked VTE
Measured: Day 1 to Day 3 (Parts A and B); Days 1, 2, 91, 92 (Part C)
Amount excreted in urine (Ae) of CITY-FXI
To characterize the pharmacokinetics (PK) of a single dose of CITY-FXI in healthy adults and adults with FVL or prothrombin G20210A mutation
Measured: Day 1 to Day 3 (Parts A and B)
Change from baseline in levels of plasma Factor XI (FXI)
To characterize the pharmacodynamics (PD) of a single dose of CITY-FXI in healthy adults and adults with FVL or prothrombin G20210A mutation, and of a multiple dose regimen of CITY-FXI in adults with FVL or prothrombin G20210A mutation and/or a history of provoked VTE
Measured: Up to Day 360
Change from baseline of Factor XI (FXI) activity
To characterize the pharmacodynamics (PD) of a single dose of CITY-FXI in healthy adults and adults with FVL or prothrombin G20210A mutation, and of a multiple dose regimen of CITY-FXI in adults with FVL or prothrombin G20210A mutation and/or a history of provoked VTE
Measured: Up to Day 360
Change from baseline in activated partial thromboplastin time (aPTT)
To characterize the pharmacodynamics (PD) of a single dose of CITY-FXI in healthy adults and adults with FVL or prothrombin G20210A mutation, and of a multiple dose regimen of CITY-FXI in adults with FVL or prothrombin G20210A mutation and/or a history of provoked VTE
Measured: Up to Day 360
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted24 Feb 2026
- Study start22 Jan 2026
- Primary completionMar 2028 (estimated)
- Study completionApr 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Factor V LeidenStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 1
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Sequential
- Masking
- Double blind
- Who is masked
- Participant, Investigator
- Enrolment
- 182 participants (estimated)
Sponsor and investigators
- Lead sponsor
- City Therapeutics
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Medical Director, Study director, City Therapeutics
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07430397
- Sponsor's protocol ID
- FXI-1101
- Other IDs
- C24027
- Status last verified
- Sep 2026
- First submitted
- 9 Jan 2026
- Last updated
- 25 Sep 2026
- Results posted
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
Study at a glance
From the registry record, last updated by the sponsor on 25 Sep 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official 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, Adults With Factor V Leiden or Prothrombin G20210A Mutation, and Adults With a History of Provoked Venous Thromboembolism
- ClinicalTrials.gov ID
- NCT07430397
- Acronym / sponsor ID
- FXI-1101
- Keywords
- Factor XI, siRNA
- Phase
- Phase 1
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 182 participants (estimated)
- Lead sponsor
- City TherapeuticsIndustry (pharma, biotech, devices)
- Study start
- 22 Jan 2026 (actual)
- Primary completion
- Mar 2028 (estimated)
- Study completion
- Apr 2028 (estimated)
- First posted
- 24 Feb 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This is a first-in-human (FIH), single-center, randomized, double-blind, placebo-controlled, single ascending and multiple dose study evaluating the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of CITY-FXI in healthy adults, adults with Factor V Leiden (FVL) or prothrombin G20210A mutation, and adults with a history of provoked venous thromboembolism (VTE).
Detailed description
The study will be conducted in three 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
- Part C: Multiple Doses in Adults with FVL or Prothrombin G20210A Mutation and/or a History of Provoked Venous Thromboembolism (VTE)
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Sequential
- Masking
- Double blind (participant, investigator)
- Number of arms
- 6
| Arm | Type | Receives |
|---|---|---|
| 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 |
| CITY-FXI in Adults with FVL, Prothrombin G20210A Mutation, and/or a History of Provoked VTE (Part C) | Experimental | Drug: CITY-FXI |
| In Adults with FVL, Prothrombin G20210A Mutation, and/or a History of Provoked VTE (Part C) | Placebo comparator | Drug: Placebo |
Who may qualify
- Ages
- 18 to 65 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (7 listed)
- Males and women of non-childbearing potential (WONCBP) aged 18 to 45 years (inclusive, for Part A only)
- Male and female participants aged 18 to 60 (inclusive, for Part B only), and aged 18 to 65 years (inclusive, for Part C only)
- Body Mass Index (BMI) between 18 and 25 kg/m2 (inclusive, for Part B only) and 18 and 35 kg/m2 (inclusive, for Part C only) and a minimum weight of 50 kg (Parts A, B, and C)
- 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)
Key exclusion criteria (5 listed)
- 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 (e.g., FVL with prothrombin G20210A mutation) (Parts B and C only)
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| CITY-FXIsiRNA (subcutaneous injection) | Drug | CITY-FXI in Adults with FVL, Prothrombin G20210A Mutation, and/or a History of Provoked VTE (Part C), CITY-FXI in Adults with Factor V Leiden or Prothrombin G20210A Mutation (Part B), CITY-FXI in Healthy Adults (Part A) |
| PlaceboSaline (subcutaneous injection) | Drug | In Adults with FVL, Prothrombin G20210A Mutation, and/or a History of Provoked VTE (Part C), In Adults with Factor V Leiden or Prothrombin G20210A Mutation (Part B), In Healthy Adults (Part A) |
Primary outcome
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, and of a multiple dose regimen of CITY-FXI in adults with FVL or prothrombin G20210A mutation and/or a history of provoked VTE
6 secondary outcomes
Maximum plasma concentration (Cmax)
Time frame: Day 1 to Day 3 (Parts A and B); Days 1, 2, 91, 92 (Part C)
Area under plasma concentration time curve (AUC) of CITY-FXI
Time frame: Day 1 to Day 3 (Parts A and B); Days 1, 2, 91, 92 (Part C)
Amount excreted in urine (Ae) of CITY-FXI
Time frame: Day 1 to Day 3 (Parts A and B)
Change from baseline in levels of plasma Factor XI (FXI)
Time frame: Up to Day 360
Change from baseline of Factor XI (FXI) activity
Time frame: Up to Day 360
Change from baseline in activated partial thromboplastin time (aPTT)
Time frame: Up to Day 360
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 25 Sep 2026.
Related trials for Factor V Leiden
RecruitingObservational study
Engagement Study for Participants With Factor V Leiden and Prothrombin G20210A Mutations
Factor V Leiden, Prothrombin G20210A
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Medical Director study director
City Therapeutics
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1 study testing CITY-FXI in people with Factor V Leiden and Prothrombin G20210A, run by City Therapeutics at 1 site in United Kingdom.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 7 inclusion and 5 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 25 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United Kingdom. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact City Therapeutics (857-219-5440, clinicaltrials@citytx.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Incidence, severity, and relationship of treatment-emergent adverse events (TEAEs) (time frame: Through study completion, up to Day 360). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 25 Sep 2026.