Alpha/Beta TCD HCT in Patients With Inherited BMF Disorders

300 cGy with thymic shielding on day -6

10 mg/kg IV daily on days -5, -4, -3, and -2

35 mg/m2 IV daily on days -5, -4, -3, and -2

1 mg/kg IV q12h on days -5, -4, -3, -2, and -1

T cell receptor alpha/beta depletion (α/β TCD) peripheral blood stem cell (PBSC) transplantation on day 0

Initiate G-CSF 5mcg/kg per day IV on day +1 (continue until ANC \>2.5 x 10\^9/L for 3 consecutive days or single day ANC \>3000 Arm 1 and Arm 3)

5 mg/kg IV daily on days -5, -4, -3, and -2

200 mg/m2 IV once on day -1

Busulfan 0.6 mg/kg if \> 4 years old and/or \>12 kg (0.8 mg/kg IV if ≤ 4 years old and/or ≤ 12 kg) is given IV over 2 hours every 12 hours for 2 days.

Alemtuzumab 0.2 mg/kg is given IV over 2 hours daily for 5 days (total dose 1 mg/kg)

If available, MEL dosing will be model-based using Bayesian methodology. If Bayesian methodology is unavailable, MEL dosing will be weight-based: MEL 70 mg/m2 for patients ≥10 kg (2.35 mg/kg for patients \<10 kg\^) IV for one dose over 30 minutes.

Rituximab will be given once on treatment plans 1-3 on day -1.