Fitusiran improves hemostasis in FX deficiency. (A) f10^low mice received 2 doses of fitusiran at a 1-week interval. Seven days after the last dose, plasma was analyzed for antithrombin activity in nontreated (red symbols) and fitusiran-treated f10^low mice (blue). Each symbol represents an individual mouse, and horizontal bars represent mean values. Statistical analysis was performed using an unpaired Student t test. (B-C) TF-induced thrombin generation in nontreated (red curves) and fitusiran-treated (green curves) f10^low mice. Plasma levels of FX were <1% (B) or plasmas were spiked with FX (2% of normal plasma) before measuring thrombin generation. Solid lines represent median values, and colored areas represent interquartile range. Detailed values of thrombin generation parameters (lag time, ETP, thrombin peak, and time to peak) are summarized in Table 2. (D-E) The number of clots over a 30-minute period observed in f10^low mice (red) and fitusiran-treated f10^low mice (blue) that did (E) or did not (D) receive low-dose FX (1 U/kg) 5 minutes before injury. Each symbol represents an individual mouse. Horizontal bars represent median values. Statistical analysis was performed using an unpaired Student t test.