A Randomized, Multicenter, Phase III Trial of Tacrolimus/Methotrexate Versus Post-Transplant Cyclophosphamide/Tacrolimus/Mycophenolate Mofetil in Non-Myeloablative/Reduced Intensity Conditioning Allogeneic Peripheral Blood Stem Cell Transplantation (BMT CTN 1703; Progress III); Companion Study: Microbiome and Immune Reconstitution in Cellular Therapies and Hematopoietic Stem Cell Transplantation (BMT CTN 1801; Mi-Immune)

Mobilized PBSC grafts will be administered on Day 0 to all patients according to individual institutional guidelines after appropriate processing and quantification has been performed by the local laboratory. Stem cells are administered through an indwelling central venous catheter. If infusion occurs over two days, Day 0 is the first day the infusion is initiated.

Tacrolimus will be given per institutional practices, orally at a dose of 0.05-0.06 mg/kg/day or intravenously at a dose of 0.02-0.03 mg/kg/day starting on Day -3. The dose of tacrolimus may be rounded to the nearest 0.5 mg for oral formulations. Subsequent dosing will be based on blood levels per institutional guidelines with a suggested range of 5-15. If patients are on medications which alter the metabolism of tacrolimus (e.g.concurrent CYP3A4 inhibitors), the initial starting dose and subsequent doses should be altered as per institutional practices. Tacrolimus taper can be initiated at a minimum of 90 days post HCT if there is no evidence of active GVHD. The rate of tapering will be done according institutional practices and patients should be off tacrolimus by Day 180 post HCT if there is no evidence of active GVHD.

Methotrexate will be administered at the doses of 15 mg/m2 IV bolus on Day +1, and 10 mg/m2 IV bolus on Days +3, +6 and +11 after hematopoietic stem cell infusion. Methotrexate should be dose reduced, given with leucovorin rescue, or held for complications such as severe mucositis per institutional guidelines.

Mobilized PBSC grafts will be administered on Day 0 to all patients according to individual institutional guidelines after appropriate processing and quantification has been performed by the local laboratory. Stem cells are administered through an indwelling central venous catheter. If infusion occurs over two days, Day 0 is the first day the infusion is initiated.

Tacrolimus will be given per institutional practices, orally at a dose of 0.05-0.06 mg/kg/day or intravenously at a dose of 0.02-0.03 mg/kg/day starting Day +5. Starting tacrolimus dose can be modified to account for possible drug interactions (e.g. concurrent CYP3A4 inhibitor use) according to institutional guides. Serum levels of tacrolimus will be measured at Day +7 and then should be checked weekly thereafter, and the dose adjusted accordingly to maintain a suggested level of 5-15 ng/mL. Tacrolimus taper can be initiated at a minimum of 90 days post HCT if there is no evidence of active GVHD. The rate of tapering will be done according to institutional practices but patients should be off tacrolimus by Day 180 post HCT if there is no evidence of active GVHD

MMF will be given at a dose of 15 mg/kg/dose ter in die (TID) (based upon actual body weight) with the maximum total daily dose not to exceed 3 grams (1g TID, IV or PO). MMF prophylaxis will start Day +5 and discontinue after the last dose on Day +35, or may be continued if active GVHD is present.

Cyclophosphamide \[50 mg/kg ideal body weight (IBW); if actual body weight (ABW) \< IBW, use ABW\] will be given on Day +3 (between 60 and 72 hours after the start of the PBSC infusion) and on Day +4 post-transplant (approximately 24 hours after Day +3 cyclophosphamide). Cyclophosphamide will be given as an IV infusion over 1-2 hours (depending on volume).