after enrollment you will attend a baseline visit where a physical exam, vital‑sign check, and blood sample are taken to record your initial health status.

you will begin taking apixaban orally at a dose of 10 mg once each day.

you will also receive the first subcutaneous injection of vortosiran (or matching placebo) as directed by the study staff.

each day you will swallow one tablet of apixaban (10 mg).

the tablet should be taken at the same time each day, with or without food, and you should not miss any doses.

you will receive additional subcutaneous injections of vortosiran (or placebo) according to the study schedule, typically every few weeks.

the injection is given under the skin by a trained professional; the exact dose is defined by the protocol and will not be changed by you.

you will return to the clinic for visits at weeks 4, 8, 12, and 16.

at each visit blood will be drawn to measure factor xi activity, a‑ptt, pt/inr, and to check for any antibodies against the study drug.

vital signs and any side effects, including bleeding, will be recorded.

throughout the 16‑week treatment period you should watch for signs of bleeding, such as unusual bruising, nosebleeds, or blood in urine or stool, and report them to the study team promptly.

any other symptoms or changes in health are also recorded as adverse events.

at the week‑16 visit a comprehensive assessment is performed, including the primary measurement of the percent change in factor xi activity from baseline.

the study medication is discontinued after this final evaluation unless the protocol specifies a longer follow‑up.