Background:
* Post-transplantation cyclophosphamide (PTCy) reduces rates of severe acute and chronic graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation (HCT) and safely facilitates human leukocyte antigen (HLA)-haploidentical HCT
* When clinically translated, the dose (50 mg/kg) and timing (days +3 and +4) of PTCy used were partly extrapolated from murine major histocompatibility complex (MHC)-matched skin allografting models and were partly empirical
* In both MHC-haploidentical and MHC-disparate murine HCT models, a dose of 25 mg/kg/day was superior to 50 mg/kg/day on days +3 and +4 in terms of protection against GVHD severity and mortality. Lower dosing of PTCy also was associated with less broad reduction of T-cell numbers after PTCy and lower toxicity than higher dosing.
* In patients on an NIH study using myeloablative conditioning and bone marrow as the graft source, a dose of 25 mg/kg/day on days +3/+4 has been associated with more rapid engraftment, less toxicity, and potentially better immune function without an increase in acute GVHD.
* The optimal dosing of PTCy potentially may differ depending on the graft source (bone marrow versus peripheral blood stem cells) and HLA disparity (HLA-matched vs. HLA-partially mismatched).
Objective:
* Phase I: Determine the lowest effective dose of post-transplantation cyclophosphamide (PTCy) in combination with sirolimus and mycophenolate mofetil (MMF) as graft-versus-host disease (GVHD) prophylaxis after reduced intensity conditioning and peripheral blood stem cell transplantation (PBSCT), as assessed by primary graft failure AND Grade III-IV acute GVHD as the dose limiting toxicities (DLTs). This lowest effective dose will be evaluated in parallel for HLA-matched and HLA-haploidentical HCT in different arms of the study.
* Phase II: Evaluate the efficacy of PTCy, at the lowest dose determined for each HLA-matching arm from phase I, as assessed by 1-year GVHD-free relapse-free survival (GRFS) rate.
Eligibility:
-Recipient Participant:
* Histologically or cytologically confirmed hematologic malignancy with standard indication for allogeneic hematopoietic cell transplantation
* Age \>= 50 years or 18-49 years but considered ineligible for myeloablative conditioning.
* At least one potentially suitable HLA-haploidentical or 10/10 (HLA-A, B, C, DR, DQ) related or unrelated donor.
* Karnofsky performance score \>= 70
* Adequate organ function
Design:
* Open-label, multi-center, non-randomized, phase I/II study.
* All recipient participants will receive reduced intensity conditioning, peripheral blood stem cell (PBSC) HCT, and GVHD prophylaxis with PTCy, MMF, and sirolimus.
* There will be two parallel arms: one using HLA-haploidentical donors and one using HLA-matched related or unrelated donors.
* A small pilot of 10 evaluable participants per arm will receive the standard PTCy 50 mg/kg/day on days +3/+4 to obtain a limited amount of comparative clinical, pharmacokinetic, and T-cell immunophenotyping data.
* The study will proceed to a novel phase I time-to-event Bayesian optimal interval (TITE-BOIN) trial design to find the lowest acceptable dose of PTCy for each arm. Primary graft failure and grade III-IV aGVHD at day +100 post-transplant are defined PTCy dose-limiting toxicities.
* Three dose levels of PTCy: 35, 25, and 15 mg/kg/day on days +3 and +4 are planned in each arm of phase I.
* Recipient participants will be evaluated for development of grade III-IV acute GVHD (aGVHD) and primary graft failure at day +100 as the dose-limiting toxicities. Once the optimal PTCy dose for PBSC transplantation is determined for each arm, we will conduct a phase II expansion for each arm to estimate the efficacy of PTCy in combination with sirolimus and mycophenolate mofetil as GVHD prophylaxis. 1-year GRFS rate will be the primary endpoint during the phase II part.
