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

Inclusion Criteria:

* 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)

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 (e.g., FVL with prothrombin G20210A mutation) (Parts B and C only)