ALX-0681 neutralizes VWF activity as shown by suppression of RICO. RICO activity was measured in plasma of the control (●; n = 4), preventive (□; n = 4), and therapeutic (; n = 4) animals as a function of time (days). The lower limit of quantification (LLOQ) and upper limit of quantification (ULOQ) of the RICO assay were 10% and 145%, respectively, and are indicated by a dashed line. The pharmacologic threshold is established at 20% activity and is indicated by a dotted line. Results were analyzed with a χ² test. Data are represented as means ± SD. “a” indicates a significant difference between control and preventive animals (P < .01); “b,” a significant difference between control and therapeutic animals (P < .01).