The proposed study will be a prospective, open-label, single-center, safety and feasibility phase 1 trial of allogeneic bone marrow-derived mesenchymal stromal cell (BM-MSC) delivery though cardiopulmonary bypass (CPB) using a homogeneous population of infants with congenital heart disease (CHD) who will be undergoing a two-ventricle repair within the first six months of life

This study is a prospective, open-label, single-center, safety and feasibility phase 1 trial of allogeneic bone marrow-derived mesenchymal stromal cell (BM-MSC) delivery though cardiopulmonary bypass (CPB) using a homogeneous population of infants with congenital heart disease (CHD) who will be undergoing a two-ventricle repair within the first six months of life. The dose-escalation methods with a modified continual reassessment at the five dose levels (1x10^6, 10x10^6, 20x10^6, 40x10^6, 80x10^6, cells/kg) will be performed to determine safety and feasibility of allogeneic BM-MSC infusion during pediatric cardiac surgery and the maximum tolerated dose in infants with CHD. In addition to the primary objective of assessing the safety and feasibility of BM-MSC delivery through CPB, our secondary objectives are designed to develop biological signature measures and clinical outcome measures feasible for use in larger efficacy and effectiveness trials with a particular focus on neurodevelopmental outcome and early postoperative course after BM-MSC treatment. We will determine actual magnitude of differences in neuroimaging and neurodevelopmental variables and postoperative inflammatory and pathophysiological variables after BM-MSC delivery in infants with CHD. Enrollment, follow-up, and analysis are planned to occur over 36 months for the treatment and initial follow-up portions of the study. Long-term follow-up until 18 months of age will be subsequently reported.

Inclusion Criteria:

• Neonatal and young infantile patients who are ≤ 6 months of age

• Scheduled to undergo reparative two-ventricle repair for congenital heart defects without aortic arch reconstruction, including the following:

  a. D-Transposition of the Great Arteries (d-TGA) Group: i. d-TGA with intact ventricular septum (d-TGA, IVS) ii. d-TGA with ventricular septal defect (d-TGA, VSD) b. Ventricular Septal Defect (VSD) Group: i. VSD without aortic arch obstruction (AAO) ii. Complete common atrioventricular canal defect (CAVC) c. Tetralogy of Fallot (TOF) Group: i. Tetralogy of Fallot (TOF) ii. Tetralogy of Fallot with Pulmonary Atresia (TOF,PA) iii. Truncus arteriosus (TA) iv. Double outlet right ventricle (DORV)

• Scheduled surgery at or before three months of age.

• Parent/guardian capable of providing informed consent.

Exclusion Criteria:

• Birth weight less than 2.0 kg
• Recognizable phenotypic syndrome
• Associated extracardiac anomalies of greater than minor severity
• Previous cardiac surgery
• Associated cardiovascular anomalies requiring aortic arch reconstruction and/or additional open cardiac surgical procedures in infancy
• Prior severe hypoxic event
• Significant screening test values that place subjects at increased risk of complications from participation in the study