ATHN Transcends:
Hemophilia Natural History Arm

The Hemophilia Natural History Arm is part of the Hemophilia cohort under ATHN Transcends. The study arm was formerly known as ATHN 7: A Natural History Cohort Study of the Safety, Effectiveness, and Practice of Treatment for People with Hemophilia. It is a longitudinal, observational cohort study arm that aims to determine the safety of therapy when used for participants with hemophilia with or without inhibitors. Safety is measured according to medical events in the European Haemophilia Safety Surveillance (EUHASS) protocol 2018, which includes:

  • Allergic or other acute events
  • Treatment-emergent side effects of therapy
  • Transfusion transmitted infections
  • Inhibitor development
  • Thrombosis
  • Cardiovascular events
  • Malignancies
  • Neurological events
  • Death

In addition to the modified EUHASS endpoints, the following events will be collected as adverse events of special interest (AESI):

  • The occurrence of thrombotic microangiopathies, injection site reactions and cases of potential drug-induced liver injury
  • The development of anti-drug antibodies, to be measured and confirmed, if feasible
  • Severe, unanticipated bleeding
  • Hospitalizations

This study arm will also evaluate the effectiveness and practice of non-factor products, bypassing agents, or coagulation factor replacement products in patients with hemophilia. Eligible participants must have congenital hemophilia A or B of any severity with or without inhibitors receiving a current therapy, a non-factor product, or for whom use of a non-factor product is a possibility.

Enrolling Fall 2020 in the Hemophilia Natural History Arm
ATHN Transcends is being implemented at HTCs in phases. The Hemophilia Natural History Arm is the first study arm to open. Participants who were previously enrolled in ATHN 7: Hemophilia Natural History Study will be asked if they want to transition into the Hemophilia Natural History Arm. HTCs will keep ATHN 7: Hemophilia Natural History Study open until all participants have been transitioned into ATHN Transcends. At that time, ATHN 7 will be closed. ATHN will provide supplemental materials to help guide HTCs through the process of opening enrollment for ATHN Transcends study arms, closing the original study protocols (i.e., ATHN 7: Hemophilia Natural History Study), and more.

To learn more about ATHN Transcends and the Hemophilia Natural History Arm, email

To learn more about ATHN 7: Hemophilia Natural History Study, visit