VWF and von Willebrand disease (hereditary or acquired): VWF inhibitors are generally rare, with rates as low as 0.4% across all VWD types observed in a retrospective analysis of 1,650 VWD patients.17Inhibitors are more common in type 3 VWD,11with prevalences ranging from 6.2 to 19.2% in different cohort studies.6, 12, 17None of the 33 patients in the WIL-31 study developedde novoVWF inhibitors while on wilate prophylaxis, consistent with previous data from clinical studies with wilate.