A Double-Blind, Placebo-Controlled, Dose-Escalation Phase 1 Study to Assess the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Single and Multiple Doses of ION-957943 (IONIS FXI-LRX, a GalNAc Conjugated 2'-MOE Chimeric Antisense Oligonucleotide Inhibitor of Factor XI) Administered Subcutaneously to Healthy Volunteers

This will be a Phase 1, double-blind, randomized, placebo-controlled, dose-escalation study conducted at a single center. The study consists of 4 escalating single-dose cohorts (n = 8 per cohort, randomized 3 IONIS FXI-LRx active:1 placebo), 3 escalating multiple-dose cohorts with weekly Study Drug (IONIS FXI-LRx or placebo) administration for 8 healthy volunteers per cohort, randomized 3 active:1 placebo, and 1 multiple-dose cohort of 10 healthy volunteers randomized 3 active:2 placebo with Study Drug administration every 4 weeks.

Approximately 66 healthy volunteers are planned to be enrolled in this study. Additional healthy volunteers may be added to better assess the safety, tolerability or pharmacokinetic profile of IONIS FXI-LRx to meet study objectives.