11:50am Wednesday 29 January 2020

NIH ends Transcranial Doppler (TCD) with Transfusions Changing to Hydroxyurea (TWiTCH) clinical trial due to early results

The DSMB is an independent group of experts that regularly reviews accumulating data from ongoing clinical trials and advises the sponsor and the study investigators on the safety of research participants and those yet to be recruited into a trial. 

The DSMB’s planned first interim analysis of the TWiTCH study data indicated that the study had reached its primary and most important endpoint. As such, they recommended that the study end due to early results, particularly given that the strength of the statistical finding was unlikely to change with the collection of additional data. After reviewing the DSMB recommendation, the NHLBI decided to end the study early due to attainment of the primary endpoint.

The TWiTCH study sought to determine whether giving daily doses of hydroxyurea (currently the only FDA-approved drug for sickle cell disease) lowers the TCD blood velocity in children with sickle cell disease (SCD) to a similar degree as blood transfusions. Children with sickle cell disease who are at a higher risk for stroke are identified by measuring the velocity of blood flow to the brain by TCD ultrasound studies. Children with the highest TCD velocities have a greater risk of strokes. The early review showed that hydroxyurea reduces TCD blood velocities to a similar degree as blood transfusions.

The results of this study show that hydroxyurea is not inferior to (that is, no worse than) regular blood transfusions in lowering TCD velocities in children with sickle cell disease who are at high risk for stroke.

Study participants have been notified about the trial’s early ending. Guided by the advice of their physicians, study participants will have the opportunity to receive the care they feel is best suited for them.


  • W. Keith Hoots, MD, Director, Division of Blood Diseases and Resources at the NHLBI
  • Russell Ware, MD, PhD, Principal Investigator, Cincinnati Children’s Hospital
  • Barry Davis, MD, PhD, Principal Investigator, UT Houston School of Public Health


For more information or to schedule an interview with Dr. Keith Hoots, please contact the NHLBI Communications Office at 301-496-4236 or nhlbi_news@nhlbi.nih.gov.

The National Heart, Lung, and Blood Institute (NHLBI) is a component of the National Institutes of Health. NHLBI plans, conducts, and supports research related to the causes, prevention, diagnosis, and treatment of heart, blood vessel, lung, and blood diseases and sleep disorders. The Institute also administers national health education campaigns on women and heart disease, healthy weight for children, and other topics. NHLBI press releases and other materials are available online at http://www.nhlbi.nih.gov.

About the National Institutes of Health (NIH): NIH, the nation’s medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.

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