Filgrastim support in allogeneic HSCT for myeloid malignancies: a review of the role of G-CSF and the implications for current practice

State of the CAR-T: Risk of Infections with Chimeric Antigen Receptor T-Cell Therapy and Determinants of SARS-CoV-2 Vaccine Responses

Chimeric antigen receptor T cell (CAR-T) therapy has shown unprecedented response rates in patients with relapsed/refractory (R/R) hematologic malignancies. Although CAR-T therapy gives hope to heavily pretreated patients, the rapid commercialization and cumulative immunosuppression of this therapy predispose patients to infections for a prolonged period. CAR-T therapy poses distinctive short- and long-term toxicities and infection risks among patients who receive CAR T-cells after multiple prior treatments, often including hematopoietic cell transplantation. The acute toxicities include cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome. The long-term B cell depletion, hypogammaglobulinemia, and cytopenia further predispose patients to severe infections and abrogate the remission success achieved by the living drug. These on-target-off-tumor toxicities deplete B-cells across the entire lineage and further diminish immune responses to vaccines. Early observational data suggest that patients with hematologic malignancies may not mount adequate humoral and cellular responses to SARS-CoV-2 vaccines. In this review, we summarize the immune compromising factors indigenous to CAR-T recipients. We discuss the immunogenic potential of different SARS-CoV-2 vaccines for CAR-T recipients based on the differences in vaccine manufacturing platforms. Given the lack of data related to the safety and efficacy of SARS-CoV-2 vaccines in this distinctively immunosuppressed cohort, we summarize the infection risks associated with Food and Drug Administration-approved CAR-T constructs and the potential determinants of vaccine responses. The review further highlights the potential need for booster vaccine dosing and the promise for heterologous prime-boosting and other novel vaccine strategies in CAR-T recipients. © 2021 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.

Planned Granulocyte Colony-Stimulating Factor Adversely Impacts Survival after Allogeneic Hematopoietic Cell Transplantation Performed with Thymoglobulin for Myeloid Malignancy

The in vivo depletion of recipient and donor T lymphocytes using antithymocyte globulin (ATG; Thymoglobulin) is widely adopted in allogeneic hematopoietic stem cell transplantation (HCT) to reduce the incidence of both graft failure and graft-versus-host disease (GVHD). However, excess toxicity to donor lymphocytes may hamper immune reconstitution, compromising antitumor effects and increasing infection. Granulocyte-colony stimulating factor (G-CSF) administered early after HCT may increase ATG-mediated lymphotoxicity. This study aimed to investigate the effect of an interaction between ATG and post-transplantation granulocyte colony-stimulating factor (G-CSF) on allogeneic HCT outcomes, using the Center for International Blood and Marrow Transplant Research (CIBMTR) registry. We studied patients age ≥18 years with acute myelogenous leukemia (AML) and myelodysplastic syndrome (MDS) who received Thymoglobulin-containing preparative regimens for HLA-matched sibling/unrelated or mismatched unrelated donor HCT between 2010 and 2018. The effect of planned G-CSF that was started between pretransplantation day 3 and post-transplantation day 12 was studied in comparison with transplantations that did not include G-CSF. Cox regression models were built to identify risk factors associated with outcomes at 1 year after transplantation. A total of 874 patients met the study eligibility criteria, of whom 459 (53%) received planned G-CSF. HCT with planned G-CSF was associated with a significantly increased risk for nonrelapse mortality (NRM) (hazard ratio [HR] 2.03; P <.0001; 21% versus 12%) compared to HCT without G-CSF. The 6-month incidence of viral infection was higher with G-CSF (56% versus 47%; P = .007), with a particular increase in Epstein-Barr virus infections (19% versus 11%; P = .002). The observed higher NRM with planned G-CSF led to lower overall survival (HR, 1.52; P = .0005; 61% versus 72%). There was no difference in GVHD risk between the treatment groups. We performed 2 subgroup analyses showing that our findings held true in patients age ≥50 years and in centers where G-CSF was used in some, but not all, patients. In allogeneic peripheral blood HCT performed with Thymoglobulin for AML and MDS, G-CSF administered early post-transplantation resulted in a 2-fold increase in NRM and a 10% absolute decrement in survival. The use of planned G-CSF in the early post-transplantation period should be carefully considered on an individual patient basis, weighing any perceived benefits against these risks.

Absence of damaging effects of stem cell donation in unrelated donors assessed by FISH and gene variance screening

ASTRACT

Granulocyte-Colony-Stimulating factor (G-CSF) is currently the standard mobilising agent for peripheral blood stem cell (PBSC) donation. Concerns that it may trigger chromosome aberrations similar to those observed in leukaemia patients were refuted but long-term effects of G-CSF mobilisation on genome integrity remains unclear. In the setting of a multi-centre clinical trial we screened blood samples from 50 PBSC donors at cellular and gene level for aberrations common in haematological malignancies using fluorescence in situ hybridisation (FISH) and next generation sequencing (NGS) assays. Analysis of samples collected before, on the day of donation, 90 and 180 days after G-CSF admission confirmed the absence of short-term effects in PBSC donors on both quiescent and dividing cells. This data did not differ from the results of 50 individuals tested 3-5 years after bone marrow donation and 50 healthy persons. NGS using a panel targeting 54 genes recurrently affected in myeloid disorders (TruSight Myeloid panel, Illumina) showed that the gene profiles of samples from 48 PBSC donors remained stable throughout the study period. These data strongly indicate absence of detrimental effects on the genome integrity caused by PBSC donation.

The granulopoietic cytokine granulocyte colony-stimulating factor (G-CSF) induces pain: analgesia by rutin

Rutin is a glycone form of the flavonol quercetin and it reduces inflammatory pain in animal models. Therapy with granulocyte colony-stimulating factor (G-CSF) is known by the pain caused as its main side effect. The effect of rutin and its mechanisms of action were evaluated in a model of hyperalgesia induced by G-CSF in mice. The mechanical hyperalgesia induced by G-CSF was reduced by treatment with rutin in a dose-dependent manner. Treatment with both rutin + morphine or rutin + indomethacin, at doses that are ineffectual per se, significantly reduced the pain caused by G-CSF. The nitric oxide (NO)-cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG)-ATP-sensitive potassium channel (K_ATP) signaling pathway activation is one of the analgesic mechanisms of rutin. Rutin also reduced the pro-hyperalgesic and increased anti-hyperalgesic cytokine production induced by G-CSF. Furthermore, rutin inhibited the activation of the nuclear factor kappa-light-chain enhancer of activated B cells (NFκB), which might explain the inhibition of the cytokine production. Treatment with rutin upregulated the decreased mRNA expression of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) combined with enhancement of the mRNA expression of the Nrf2 downstream target heme oxygenase (HO-1). Intraperitoneal (i.p.) treatment with rutin did not alter the mobilization of neutrophils induced by G-CSF. The analgesia by rutin can be explained by: NO-cGMP-PKG-K_ATP channel signaling activation, inhibition of NFκB and triggering the Nrf2/HO-1 pathway. The present study demonstrates rutin as a promising pharmacological approach to treat the pain induced by G-CSF without impairing its primary therapeutic benefit of mobilizing hematopoietic progenitor cells into the blood.

[Comparative study on the efficacy and safety between pegfilgrastim (PEG-rhG-CSF) and recombinant human granulocyte colony-stimulating factor in promoting hematopoietic recovery after allogeneic hematopoietic stem cell transplantation after hematological malignancy]

Objective: To observe the efficacy and safety between Pegfilgrastim (PEG-rhG-CSF) and Recombinant human granulocyte colony stimulating factor (rhG-CSF) in hematological malignancy after allogeneic hematopoietic stem cell transplantation (allo-HSCT) . Methods: 157 patients after allo-HSCT were enrolled in this study from June 2015 to November 2016. Two agents of G-CSF were used to stimulate hematopoietic recovery after transplantation. There were 65 cases in PEG-rhG-CSF and 92 cases in rhG-CSF groups. Patients in PEG-rhG-CSF group were given a single subcutaneous dose of 6 mg on the first day and +8 d, while cases in rhG-CSF group were given in dose of 5 μg·kg(-1)·d(-1) by subcutaneous injection from +1 d continuing to neutrophils more than 1.5×10(9)/L, and then the indicators and survival rates in two groups after transplantation were compared. Results: ①There were no significant differences of the neutrophil implantation time[13.5 (8-12) d vs 13 (9-24) d, P=0.393] and platelet implantation time [14 (9-160) d vs 14 (9-92) d, P=0.094] between PEG-rhG-CSF and rhG-CSF groups respectively. There were no significant differences in terms of neutropenia period (P=0.435) , number of cases who got fever during neutropenia (P=0.622) , and the median time of fever in neutropenia period (P=0.460) , respectively between the two groups. There were no significant differences of erythrocyte and platelet transfusions (P=0.074, P=0.059) within 1 month after transplantation. ②There were no significant differences with regard to the incidences of acute GVHD[23.1% (15/65) vs 34.8% (32/92) , P=0.115], chronic GVHD[20.0% (13/65) vs 32.6% (32/92) , P=0.081], Ⅱ-Ⅳdegree of acute GVHD[30.0% (13/65) vs 30.4% (30/92) , P=0.287] and extensive chronic GVHD[9.2% (6/65) vs 20.7% (19/92) , P=0.135] between PEG-rhG-CSF and rhG-CSF groups. ③There were no significant differences in terms of disease free survival (DFS) (62.5% vs 61.4%, P=0.478) and overall survival (OS) (67.4% vs 67.3%, P=0.718) between PEG-rhG-CSF and rhG-CSF groups. ④There was no significant difference of the non-relapse mortality (NRM) between PEG-rhG-CSF and rhG-CSF groups[20.5% (95%CI 11.4%-37.0%) vs 32.6% (95%CI 22.2%-47.9%) , P=0.141]. The relapse rate was not statistically significant[14.9% (95%CI 7.4%-29.8%) vs 10.0% (95%CI 5.0%-20.0%) , P=0.299]. Conclusion: Compared with rhG-CSF, PEG-rhG-CSF could reduce the times of injection. There were no differences in terms of hematopoietic recovery, the incidence of GVHD, relapse rate, DFS and OS rates after allo-HSCT between two groups.

Bendamustine with Total Body Irradiation Limits Murine Graft-versus-Host Disease in Part Through Effects on Myeloid-Derived Suppressor Cells

Graft-versus-host disease (GVHD) remains a significant challenge in allogeneic hematopoietic cell transplantation (HCT). An underinvestigated strategy to reduce GVHD is the modification of the preparative conditioning regimen. In the present study, we aimed to evaluate GVHD associated with bendamustine (BEN) conditioning in conjunction with total body irradiation (TBI) as an alternative to the standard myeloablative regimen of cyclophosphamide (CY) and TBI. We demonstrate that BEN-TBI conditioning, although facilitating complete donor chimerism, results in significantly less GVHD compared with CY-TBI. In BEN-TBI-conditioned mice, suppressive CD11b⁺Gr-1^high myeloid cells are increased in the blood, bone marrow, spleen, and intestines. When Gr-1^high cells are depleted before transplantation, the beneficial effects of BEN-TBI are partially lost. Alternatively, administration of granulocyte colony-stimulating factor, which promotes CD11b⁺Gr-1⁺ myeloid cell expansion, is associated with a trend toward increased survival in BEN-TBI-conditioned mice. These findings indicate a potential role of myeloid-derived suppressor cells in the mechanism by which BEN allows engraftment with reduced GVHD. BEN-TBI conditioning may present a safer alternative to CY-TBI conditioning for allogeneic HCT.

European experience and risk factor analysis of donor cell-derived leukaemias/MDS following haematopoietic cell transplantation

Donor cell leukaemia (DCL) is a rare complication of allogeneic haematopoietic cell transplantation (HCT). We have investigated the prevalence and outcome of donor cell haematology malignancies within centres registered with the European Society of Blood and Marrow transplantation (EBMT). We have sought to identify risk factors to shed light on the pathogenesis of DCL as a model for leukaemogenesis. DCL cases were identified by questionnaire and a follow-up questionnaire requested detailed data. Control subjects from the EBMT registry who had not developed DCL were used for a matched pair analysis to identify risk factors. We identified 38 patients with DCL; the estimated prevalence was 80.5/100,000 transplants. Patients were predominantly treated for haematological malignancy. A clone was retrospectively identified in 7/25 (28%) donors for whom data was available. Overall survival was poor with 29/38 patients dead a median of 11 (range 0-91) months after DCL diagnosis. Matched case-pair analysis identified three factors on multivariate analysis as significantly associated with an increased risk for DCL: use of growth factors within the first 100 days after transplantation, in vivo T-cell depletion and multiple allografts. The risk factors identified, support reduced immune surveillance and replicative stress as pathogenic in the development of DCL.

Involvement of urokinase receptor in the cross-talk between human hematopoietic stem cells and bone marrow microenvironment

Hematopoietic stem cells (HSCs) reside in bone marrow (BM) and can be induced to mobilize into the circulation for transplantation. Homing and lodgement into BM of transplanted HSCs are the first critical steps in their engraftment and involve multiple interactions between HSCs and the BM microenvironment.uPAR is a three domain receptor (DIDIIDIII) which binds urokinase, vitronectin, integrins. uPAR can be cleaved and shed from the cell surface generating full-length and cleaved soluble forms (suPAR and DIIDIII-suPAR). DIIDIII-suPAR can bind fMLF receptors through the SRSRY sequence (residues 88-92).We previously reported the involvement of soluble uPAR in HSC mobilization. We now investigate its possible role in HSC homing and engraftment.We show similar levels of circulating full-length suPAR in healthy donors and in acute myeloid leukemia (AML) patients before and after the pre-transplant conditioning regimen. By contrast, levels of circulating DIIDIII-suPAR in AML patients are higher as compared to controls and significantly decrease after the conditioning.We found that suPAR and uPAR84-95, a uPAR-derived peptide which mimics active DIIDIII-suPAR, induce a significant increase in Long Term Culture (LTC)-Initiating Cells (ICs) and in the release of clonogenic progenitors from LTCs of CD34+ HSCs. Further, suPAR increases adhesion and survival of CD34+ KG1 AML cells, whereas uPAR84-95 increases their proliferation.Thus, circulating DIIDIII-suPAR, strongly increased in HSC mobilization, is indeed down-regulated by pre-transplant conditioning, probably to favour HSC homing. BM full-length suPAR and DIIDIII-suPAR may be involved in HSC lodgement within the BM by contributing to a suitable microenvironment.

Granulocyte-colony stimulating factor (G-CSF)-induced mechanical hyperalgesia in mice: Role for peripheral TNFα, IL-1β and IL-10

Granulocyte-colony stimulating factor (G-CSF) is a therapeutic approach to increase peripheral neutrophil counts after anti-tumor therapies. Pain is the major side effect of G-CSF. Intraplantar administration of G-CSF in mice induces mechanical hyperalgesia. However, the peripheral mechanisms involved in this effect were not elucidated. Therefore, the participation of pronociceptive cytokines tumor necrosis factor (TNF) alpha (TNFα), interleukin (IL)-1 beta (IL-1β) and antinociceptive cytokine IL-10 in G-CSF-induced mechanical hyperalgesia in mice was investigated. G-CSF-induced mechanical hyperalgesia was inhibited by systemic and local treatment with etanercept and IL-1 receptor antagonist (IL-1ra) or TNF receptor 1 (TNFR1) deficiency and increased in IL-10 deficient mice. In agreement, G-CSF injection induced significant TNFα, IL-1β and IL-10 production in paw tissue. G-CSF-induced hyperalgesia was dose-dependently inhibited by thalidomide (5-45mg/kg) and pentoxifylline (0.5-13.5mg/kg), and treatment with these drugs inhibited G-CSF-induced TNFα, IL-1β and IL-10 production. The combined treatment with pentoxifylline or thalidomide with morphine, at doses that are ineffective as single treatment, diminished G-CSF-induced hyperalgesia through inhibiting cytokine production. Indomethacin also reduces G-CSF hyperalgesia alone or combined with pentoxifylline or thalidomide. Thus, G-CSF-induced hyperalgesia might be mediate by peripheral production of pronociceptive cytokines TNFα and IL-1β and down-regulated by IL-10. Systemic IL-1ra reduced G-CSF-induced increase of peripheral neutrophil counts. However, local treatment with morphine, IL-1ra or etanercept, and systemic treatment with indomethacin, etanercept, thalidomide and pentoxifylline did not alter G-CSF-induced mobilization of neutrophils. Therefore, this study advances in the understanding of G-CSF-induced hyperalgesia and suggests therapeutic approaches for its control.

Infectious complications of stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) is an accepted treatment for a variety of hematologic malignancies. The profound immunosuppression these patients experience adversely affects their risk of infection. This risk is much higher than in the general population and requires aggressive diagnostic and therapeutic interventions. The chapter will outline the major infections after HSCT.

Acute GVHD prophylaxis with standard-dose, micro-dose or no MTX after fludarabine/melphalan conditioning

MTX is a standard component of acute GVHD prophylaxis. However, its use can be limited by toxicity. On the basis of disease risk, we prospectively assigned 132 consecutive patients from January 2005 to February 2011 undergoing first allogeneic hematopoietic cell transplant after conditioning with fludarabine and melphalan to acute GVHD prophylaxis with tacrolimus/MTX (TAC/MTX, N=22), TAC/micro-dose MTX/mycophenolate mofetil (TAC/μMTX/MMF, N=78) or TAC/MMF (TAC/MMF, N=32), to optimize acute GVHD prevention and decrease mortality. The median (range) follow-up was 24 (0.8-60) months. The median patient ages (range) were 37 (23-63), 56 (20-68) and 54 (22-68) years (P<0.0001) for TAC/MTX, TAC/μMTX/MMF and TAC/MMF, respectively. The 100-day cumulative incidences of grade III-IV acute GVHD were 19, 23 and 49% (P=0.015), respectively. The cumulative incidences of severe chronic GVHD at 1 year were 38, 29 and 79% (P<0.001), respectively. Regimen-related toxicities were not significantly different among the three prophylaxis regimens. PFS and OS were equivalent between the TAC/MTX and TAC/μMTX/MMF arms despite significantly older patients in the latter arm, and both had superior PFS and OS than the TAC/MMF arm. Acute GVHD prophylaxis with TAC/μMTX/MMF is as effective as TAC/MTX and superior to TAC/MMF.

Proteomic analysis of murine bone marrow niche microenvironment identifies thioredoxin as a novel agent for radioprotection and for enhancing donor cell reconstitution

Hematopoiesis is regulated by the bone marrow (BM) niche microenvironment. We recently found that posttransplant administration of AMD3100 (a specific and reversible CXCR4 antagonist) enhanced donor cell engraftment and promoted recovery of all donor cell lineages in a congeneic mouse transplant model. We hypothesized that AMD3100 enhances donor cell reconstitution in part by modulating the levels and constitution of soluble factors in the niche microenvironment. In the current study, the effects of the BM extracellular fluid (supernatant) from AMD3100-treated transplant recipient mice on colony-forming units (CFUs) were examined. A semiquantitative, mass spectrometry-based proteomics approach was used to screen for differentially expressed proteins between the BM supernatants of PBS-treated transplant mice and AMD3100-treated transplant mice. A total of 178 proteins were identified in the BM supernatants. Thioredoxin was among the 32 proteins that displayed greater than a twofold increase in spectral counts in the BM supernatant of AMD3100-treated transplant mice. We found that thioredoxin increased CFUs in a dose-dependent manner. Thioredoxin improved hematopoiesis in irradiated mice and protected mice from radiation-related death. Furthermore, ex vivo exposure to thioredoxin for 24 hours enhanced the long-term repopulation of hematopoietic stem cells. Additionally, combined posttransplant administration of thioredoxin and AMD3100 improved hematologic recovery in primary and secondary transplant recipient mice. Our studies demonstrated that factors in the BM niche microenvironment play a critical role in hematopoiesis. Identifying these factors provides clues on potential novel targets that can be used to enhance hematologic recovery in hematopoietic stem cell transplan`tation.

Effects of spleen status on early outcomes after hematopoietic cell transplantation

To assess the impact of spleen status on engraftment, and early morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT), we analyzed 9,683 myeloablative allograft recipients from 1990 to 2006; 472 had prior splenectomy (SP), 300 splenic irradiation (SI), 1,471 with splenomegaly (SM), and 7,440 with normal spleen (NS). Median times to neutrophil engraftment (NE) and platelet engraftment (PE) were 15 vs 18 days and 22 vs 24 days for the SP and NS groups, respectively (P<0.001). Hematopoietic recovery at day +100 was not different across all groups, however the odds ratio of days +14 and +21 NE and day +28 PE were 3.26, 2.25 and 1.28 for SP, and 0.56, 0.55, and 0.82 for SM groups compared to NS (P<0.001), respectively. Among patients with SM, use of peripheral blood grafts improved NE at day +21, and CD34+ cell dose >5.7 × 10(6)/kg improved PE at day+28. After adjusting variables by Cox regression, the incidence of GVHD and OS were not different among groups. SM is associated with delayed engraftment, whereas SP prior to HCT facilitates early engraftment without having an impact on survival.

Spontaneous subcapsular splenic hematoma associated with filgrastim in a patient undergoing allogeneic hematopoietic stem cell transplantation

OBJECTIVE

To report the development of a spontaneous subcapsular splenic hematoma following filgrastim administration in a patient undergoing an allogeneic hematopoietic stem cell transplant.

CASE SUMMARY

A 60-year-old female with myelodysplastic syndrome was admitted for a reduced-intensity allogeneic hematopoietic stem cell transplant from an unrelated donor. She received filgrastim 5 μg/kg starting on day 1 to accelerate neutrophil recovery. On day 5, she began reporting severe left chest-wall pain. Contrast-enhanced computed tomography of the abdomen/pelvis revealed a spontaneous subcapsular splenic hematoma. Upon discontinuation of filgrastim, the pain fully resolved. The patient was subsequently rechallenged with filgrastim, which led to recurrence of the left-sided chest-wall pain. Filgrastim was discontinued and the patient reported resolution of the pain.

DISCUSSION

Filgrastim has been associated with splenic hematoma and splenic rupture, predominantly in healthy donors undergoing mobilization of peripheral blood stem cells. Although splenic rupture attributed to filgrastim in a patient undergoing allogeneic hematopoietic stem cell transplantation has been reported, to our knowledge, this is the first case report to establish causality. Using the Naranjo probability scale, an objective causality assessment revealed that the adverse drug event was highly probable.

CONCLUSIONS

Although filgrastim-induced splenomegaly, splenic hematomas, and splenic rupture are rare, clinicians working in the bone marrow transplant setting should be cognizant of the potential of growth factors to cause these adverse events.

Granulocyte-colony stimulating factor (G-CSF) induces mechanical hyperalgesia via spinal activation of MAP kinases and PI3K in mice

Granulocyte-colony stimulating factor (G-CSF) is a current pharmacological approach to increase peripheral neutrophil counts after anti-tumor therapies. Pain is most relevant side effect of G-CSF in healthy volunteers and cancer patients. Therefore, the mechanisms of G-CSF-induced hyperalgesia were investigated focusing on the role of spinal mitogen-activated protein (MAP) kinases ERK (extracellular signal-regulated kinase), JNK (Jun N-terminal Kinase) and p38, and PI(3)K (phosphatidylinositol 3-kinase). G-CSF induced dose (30-300 ng/paw)-dependent mechanical hyperalgesia, which was inhibited by local post-treatment with morphine. This effect of morphine was reversed by naloxone (opioid receptor antagonist). Furthermore, G-CSF-induced hyperalgesia was inhibited in a dose-dependent manner by intrathecal pre-treatment with ERK (PD98059), JNK (SB600125), p38 (SB202190) or PI(3)K (wortmanin) inhibitors. The co-treatment with MAP kinase and PI(3)K inhibitors, at doses that were ineffective as single treatment, significantly inhibited G-CSF-induced hyperalgesia. Concluding, in addition to systemic opioids, peripheral opioids as well as spinal treatment with MAP kinases and PI(3)K inhibitors also reduce G-CSF-induced pain.

Selective enhancement of donor hematopoietic cell engraftment by the CXCR4 antagonist AMD3100 in a mouse transplantation model

The interaction between stromal cell-derived factor-1 (SDF-1) with CXCR4 chemokine receptors plays an important role in hematopoiesis following hematopoietic stem cell transplantation. We examined the efficacy of post transplant administration of a specific CXCR4 antagonist (AMD3100) in improving animal survival and in enhancing donor hematopoietic cell engraftment using a congeneic mouse transplantation model. AMD3100 was administered subcutaneously at 5 mg/kg body weight 3 times a week beginning at day +2 post-transplant. Post-transplant administration of AMD3100 significantly improves animal survival. AMD3100 reduces pro-inflammatory cytokine/chemokine production. Furthermore, post transplant administration of AMD3100 selectively enhances donor cell engraftment and promotes recovery of all donor cell lineages (myeloid cells, T and B lymphocytes, erythrocytes and platelets). This enhancement results from a combined effect of increased marrow niche availability and greater cell division induced by AMD3100. Our studies shed new lights into the biological roles of SDF-1/CXCR4 interaction in hematopoietic stem cell engraftment following transplantation and in transplant-related mortality. Our results indicate that AMD3100 provides a novel approach for enhancing hematological recovery following transplantation, and will likely benefit patients undergoing transplantation.