A phase II trial of a reduced intensity conditioned (RIC) allogeneic hematopoietic cell transplant (HCT) with post-transplant cyclophosphamide (PTCy) for idiopathic severe aplastic anemia (SAA), paroxysmal nocturnal hemoglobinuria (PNH), acquired pure red cell aplasia (aPRCA), or acquired amegakaryocytic thrombocytopenia (aAT) utilizing population pharmacokinetic (popPK)-guided individual dosing of pre-transplant conditioning and differential dosing of low dose total body irradiation based on age, presence of myelodysplasia and/or clonal hematopoiesis.
Platelets <20,000/uL or transfusion dependent
Absolute neutrophil count <500/uL without hematopoietic growth factor support
Absolute reticulocyte count <60,000/uL AND bone marrow cellularity <50% (with < 30% residual hematopoietic cells)
Early myelodysplastic features (bone marrow (BM) blasts <5%), without history of MDS/AML pre-treatment.
Pregnant, breastfeeding or intending to become pregnant during the study. Persons of childbearing potential must have a negative pregnancy test (serum or urine) within 7 days of the start of treatment
Uncontrolled infection
Evidence of moderate or severe portal fibrosis or cirrhosis on biopsy
Known allergy to any of the study components
Parallel
Rituximab
DrugFor patients with EBV IgG seropositivity or EBV PCR positivity on pre-transplant evaluations, Rituximab 375 mg/m2 is given IV once on day -14 (+/-2 day) in the outpatient setting. Pre-medicate 30 minutes prior to rituximab with methylprednisolone (1 mg/kg) IV, acetaminophen 15 mg/kg (maximum 650mg) IV or PO and diphenhydramine 1 mg/kg (maximum 50mg) IV or PO.
Rabbit ATG
DrugRabbit ATG will be administered at doses and days indicated above, infused through a 0.22 micrometer filter over 4-6 hours. Pre-medicate 30 minutes prior to ATG infusion with methylprednisolone 1 mg/kg IV, (max dose = 125 mg), acetaminophen 15 mg/kg dose (max dose = 650 mg) enterally and diphenhydramine 1 mg/kg/dose (max dose = 50 mg) enterally or IV.
Cyclophosphamide
DrugCyclophosphamide 14.5 mg/kg is be given as a 2-hour infusion on day -6. If the patient is obese (actual body weight (ABW) \>/= 125% of the ideal body weight (IBW)), cyclophosphamide should be dosed using the adjusted body weight (AdjBW): 0.5(ABW-IBW) + IBW. Uroprotection with MESNA (14.5 mg/kg/day) in IV continuous infusion will be provided per institutional guidelines. Hyperhydration is not required for 14.5 mg/kg cyclophosphamide doses. Cyclophosphamide will be administered at 50 mg/kg using ABW over 2 hours on days +3 and +4. If the patient is obese (ABW \>/= 125% of the ideal body weight (IBW)), cyclophosphamide should be dosed using the adjusted body weight (AdjBW): 0.5(ABW-IBW) + IBW. Uroprotection with MESNA (50 mg/kg/day) in IV continuous infusion as well as hyperhydration will be provided per institutional guidelines.
Fludarabine
DrugFor all patients, fludarabine dosing will be model-based using Bayesian methodology IV every 24 hours on days -6 to -3 with a cumulative area under the curve (cAUC) of 20 mg\*hr/L.
Total Body Irradiation
RadiationFor patients age \>/= 25 years, with myelodysplasia, or clonal hematopoiesis, total body irradiation will be 4 Gy, provided in two fractions on day -1. For all other patients, total body irradiation will be 2 Gy provided in a single fraction on day -1. Each dose of 2 Gy will be given at a dose rate between 1 and 1.9 Gy/minute prescribed to the midplane of the patient at the level of the umbilicus.
Cell Infusion
Biological/VaccineOn day 0 the cells will be infused per cell source specific institutional guidelines.
Post-Transplant G-CSF
DrugBeginning on day +5, patients will receive G-CSF SQ or IV 5 micrograms/kg once daily until post-nadir ANC \> 1500/μL for 3 consecutive days or \>3000/μL for 1 day.
Tacrolimus
DrugTacrolimus will begin on day +5 at an initial dose of 0.03 mg/kg/day IV via continuous infusion. Goal trough levels will be 10-15 ug/mL until day +14 posttransplant, then decreased to a goal of 5-10 ng/mL thereafter. In the absence of GvHD, tacrolimus will discontinue at day +180 without a taper.
Mycophenolate Mofetil
DrugMycophenolate mofetil (MMF) therapy will begin on day +5. For pediatric service patients dosing of MMF will be 15 mg/kg/dose (max = 1000 mg) three times daily. For adult service patients dosing of MMF will be 15 mg/kg/dose (max = 1500 mg) twice daily. The same dosage is used orally or intravenously. Consider dose modification and/or pharmacokinetic measurements if renal and/or hepatic impairment (GFR\<25 mL/minute corrected). Stop MMF at Day +35 or 7 days after engraftment achieved (ANC\>500 x 106 neutrophils/L x 3 days) if later than day +35. If sufficient acute GvHD is observed to require systemic therapy, MMF should be continued for 7 days after initiation of systemic therapy. Afterward, use of MMF is at the discretion of the treating physician.
Incidence of grade 3-4 acute GvHD
Incidence of grade 3-4 acute graft-versus host disease (GvHD) at 1 year post HCT.
Incidence of chronic GvHD-free, failure-free survival (GFFS)
Incidence of chronic GvHD-free, failure-free survival (GFFS) 1 year post HCT
Incidence of chronic GvHD-free survival
Incidence of chronic GvHD-free survival at 1 year post HCT
Incidence of failure-free survival (GFFS)
Incidence of chronic GvHD-free, failure-free survival (GFFS) 2 years post HC
Incidence of neutrophil recovery
Incidence of neutrophil recovery at day 42 post HCT
Incidence of platelet recovery
Incidence of platelet recovery at 6 months post HCT
Incidence of grade 3-4 acute GvHD
Incidence of grade 3-4 acute GvHD at 100 days post HCT
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