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Abstract Introduction Intravenous vitamin C was administered following hematopoietic stem cell transplant to mitigate nonrelapse mortality (NRM) in a Phase II clinical trial. Methods Patients with advanced hematologic malignancies received IV vitamin C, 50 mg/kg/day, in three divided doses on days 1–14 after HSCT, followed by 500 mg bid oral until 6 months. Results All patients enrolled (55) were deficient in vitamin C at day 0 and had restoration to normal levels. Vitamin C recipients had a trend for lower nonrelapse mortality (NRM, 11% vs. 25%, p‐value = 0.07) compared with propensity score‐matched historical controls. A similar trend toward improved survival was observed (82% vs. 62% p = 0.06), with no attributable grade 3 and 4 toxicities to vitamin C. Conclusion In patients undergoing allogeneic HSCT, repletion of vitamin C is feasible and may reduce NRM and improve overall survival. Randomized trials in large uniform cohorts of patients are needed to confirm the utility of this easily available and inexpensive therapy.

Abstract Objectives Immune recovery following haematopoietic cell transplantation (HCT) functions as a dynamical system. Reducing the duration of intense immune suppression and augmenting antigen presentation has the potential to optimise T‐cell reconstitution, potentially influencing long‐term outcomes. Methods Based on donor‐derived T‐cell recovery, 26 patients were adaptively randomised between mycophenolate mofetil (MMF) administered for 30‐day post‐transplant with filgrastim for cytokine support (MMF30 arm, N = 11), or MMF given for 15 days with sargramostim (MMF15 arm, N = 15). All patients underwent in vivo T‐cell depletion with 5.1 mg kg−1 antithymocyte globulin (administered over 3 days, Day −9 through to Day −7) and received reduced intensity 450 cGy total body irradiation (3 fractions on Day −1 and Day 0). Patients underwent HLA‐matched related and unrelated donor haematopoietic cell transplantation (HCT). Results Clinical outcomes were equivalent between the two groups. The MMF15 arm demonstrated superior T‐cell, as well as T‐cell subset recovery and a trend towards superior T‐cell receptor (TCR) diversity in the first month with this difference persisting through the first year. T‐cell repertoire recovery was more rapid and sustained, as well as more diverse in the MMF15 arm. Conclusion The long‐term superior immune recovery in the MMF15 arm, administered GMCSF, is consistent with a disproportionate impact of early interventions in HCT. Modifying the ‘immune‐milieu’ following allogeneic HCT is feasible and may influence long‐term T‐cell recovery.