The study was designed by the principal investigators and by clinical experts in pediatric trial design, hematology, and neurology in collaboration with the sponsor, Berlin Heart, and the Food and Drug Administration. Data were gathered by study coordinators at each site and were analyzed by the sponsor and independent academic statisticians in collaboration with the study investigators. The investigators had full access to the data. Data monitoring was performed by a contract research organization (Alquest). Data confidentiality was required by contractual agreement between each study site and the sponsor. The decision to submit the manuscript for publication was made by members of the publication committee (see the Supplementary Appendix) and the sponsor. All authors participated in writing, revising, and reviewing the manuscript. The academic authors and the authors who are employees of the sponsor vouch for the accuracy and completeness of the data and analysis and the fidelity of the study to the trial protocol. The study protocol (available at NEJM.org) was approved by the institutional review board at each participating center, and written informed consent was provided by a parent or legal guardian for all study participants.