ATHN 8: U.S. Cohort Study of Previously Untreated Patients (PUPs) with Congenital Hemophilia

ATHN 8: PUPs Matter Study is the first national cohort study focused on previously untreated patients (PUPs) that will provide a platform for ongoing clinical research studies to improve the outcomes of this vulnerable population. In-depth clinical and laboratory data will be collected, especially during high-risk periods for antibody development.

ATHN 8: PUPs Matter Study is a longitudinal, observational study aimed at determining the percentage of PUPs with confirmed inhibitors within the first 50 exposure days. In addition, the study seeks to determine:

  • Risk factors associated with inhibitor development in the previously untreated population
  • Percentage of eligible patients enrolled at each treatment site
  • Mean age at diagnosis and first exposure to factor replacement treatment
  • Number of exposure days prior to inhibitor development and the number of transient inhibitors.

With a key focus on data quality, ATHN 8: PUPs Matter Study data collected will include demographics, medical and hemophilia history, birth and family history, bleeding events, clotting factor replacement and non-factor replacement products used for treatment, inhibitor testing results, and HTC or hospital visits during study participation.

To learn more about ATHN 8: PUPs Matter Study, email ATHN at

ATHN 8: PUPs Matter Study is funded by CSL Behring and Blood Center of Wisconsin through a grant from Shire. The study is being conducted in collaboration with the Blood Center of Wisconsin.