Treatment, risk factors, and outcome of adults with relapsed AML after reduced intensity conditioning for allogeneic stem cell transplantation

Immunological and Clinical Impact of Manipulated and Unmanipulated DLI after Allogeneic Stem Cell Transplantation of AML Patients

Allogeneic stem cell transplantation (allo-SCT) is the preferred curative treatment for several hematological malignancies. The efficacy of allo-SCT depends on the graft-versus-leukemia (GvL) effect. However, the prognosis of patients with relapsed acute myeloid leukemia (AML) following allo-SCT is poor. Donor lymphocyte infusion (DLI) is utilized after allo-SCT in this setting to prevent relapse, to prolong progression free survival, to establish full donor chimerism and to restore the GvL effect in patients with hematological malignancies. Thus, there are different options for the administration of DLI in AML patients. DLI is currently used prophylactically and in the setting of an overt relapse. In addition, in the minimal residual disease (MRD) setting, DLI may be a possibility to improve overall survival. However, DLI might increase the risk of severe life-threatening complications such as graft-versus-host disease (GvHD) as well as severe infections. The transfusion of lymphocytes has been tested not only for the treatment of hematological malignancies but also chronic infections. In this context, manipulated DLI in a prophylactic or therapeutic approach are an option, e.g., virus-specific DLI using different selection methods or antigen-specific DLI such as peptide-specific CD8+ cytotoxic T lymphocytes (CTLs). In addition, T cells are also genetically engineered, using both chimeric antigen receptor (CAR) genetically modified T cells and T cell receptor (TCR) genetically modified T cells. T cell therapies in general have the potential to enhance antitumor immunity, augment vaccine efficacy, and limit graft-versus-host disease after allo-SCT. The focus of this review is to discuss the different strategies to use donor lymphocytes after allo-SCT. Our objective is to give an insight into the functional effects of DLI on immunogenic antigen recognition for a better understanding of the mechanisms of DLI. To ultimately increase the GvL potency without raising the risk of GvHD at the same time.

The Graft-Versus-Leukemia Effect in AML

Allogeneic hematopoietic stem cell transplantation (allo-SCT) is the most established and commonly used cellular immunotherapy in cancer care. It is the most potent anti-leukemic therapy in patients with acute myeloid leukemia (AML) and is routinely used with curative intent in patients with intermediate and poor risk disease. Donor T cells, and possibly other immune cells, eliminate residual leukemia cells after prior (radio)chemotherapy. This immune-mediated response is known as graft-versus-leukemia (GvL). Donor alloimmune responses can also be directed against healthy tissues, which is known as graft-versus-host disease (GvHD). GvHD and GvL often co-occur and, therefore, a major barrier to exploiting the full immunotherapeutic benefit of donor immune cells against patient leukemia is the immunosuppression required to treat GvHD. However, curative responses to allo-SCT and GvHD do not always occur together, suggesting that these two immune responses could be de-coupled in some patients. To make further progress in successfully promoting GvL without GvHD, we must transform our limited understanding of the cellular and molecular basis of GvL and GvHD. Specifically, in most patients we do not understand the antigenic basis of immune responses in GvL and GvHD. Identification of antigens important for GvL but not GvHD, and vice versa, could impact on donor selection, allow us to track GvL immune responses and begin to specifically harness and strengthen anti-leukemic immune responses against patient AML cells, whilst minimizing the toxicity of GvHD.

Donor selection for a second allogeneic stem cell transplantation in AML patients relapsing after a first transplant: a study of the Acute Leukemia Working Party of EBMT

Second allogeneic stem-cell transplantation (SCT2) is a therapeutic option for patients with AML relapsing after a first transplant. Prior studies have shown similar results after SCT2 from the same or different donor; however, there are limited data on second non-T-depleted haplo-identical transplant in this setting. We retrospectively analyzed SCT2 outcomes in 556 patients, median age 46 years, relapsing after first transplant given in CR1. Patients were divided into three groups based on SCT2 donor (donor2): same donor (n = 163, sib/sib-112, UD/UD-51), different matched donor (n = 305, sib/different sib-44, sib/UD-93, UD/different UD-168), or haplo-donor (n = 88, sib/haplo-45, UD/haplo-43). Two-year leukemia-free survival (LFS) rate after SCT2 was 23.5%, 23.7%, and 21.8%, respectively (P = 0.30). Multivariate analysis showed no effect of donor2 type on relapse: hazard ratio (HR) 0.89 (P = 0.57) and 1.11 (P = 0.68) for different donor and haplo-donor compared to same donor, respectively. However, donor2 did predict for non-relapse mortality (NRM) after SCT2: HR 1.21 (P = 0.50) and 2.08 (P = 0.03), respectively, and for LFS: HR 1.00 (P = 0.97) and 1.43 (P = 0.07), respectively. In conclusion, SCT2 with the same or different matched donor is associated with similar outcomes in patients with relapsed AML. Non-T-depleted haplo-identical transplant may be associated with higher NRM, similar relapse rate and with no better results in this setting.

Survival of early posthematopoietic stem cell transplantation relapse of myeloid malignancies

Objective

Relapse of AML after allogeneic hematopoietic stem cell transplantation (HSCT) has a poor prognosis, and standard of care therapy is lacking. Early (<6 months) relapse is associated with dismal outcome, while the majority of relapses occur early after transplantation. A more precise indication which patients could benefit from reinduction therapy is warranted.

Methods

We retrospectively analyzed outcomes of 83 patients with postallogeneic HSCT relapse. Patients were divided based on intention to treat (curative vs supportive care).

Results

Of the 50 patients treated with curative intent, 44% reached complete remission (CR) upon reinduction chemotherapy, and of these patients, 50% survived. Two survivors reached CR after immunotherapy (donor lymphocyte infusion (DLI), without reinduction chemotherapy). Sixty‐nine percent of the survivors had received high‐intensity cytarabine treatment, followed by immunologic consolidation. Relapse <3 months after transplantation was predictive for adverse survival (P = .004), but relapse <6 months was not. In fact, >50% of the survivors had a relapse <6 months.

Conclusion

We confirmed the dismal prognosis of postallogeneic HSCT relapse. Importantly, our data demonstrate that patients fit enough to receive high‐dose chemotherapy, even when relapse occurred <6 months, had the best chance to obtain durable remissions, in particular when immunologic consolidation was performed after reaching CR.

What is the role of a second allogeneic hematopoietic cell transplant in relapsed acute myeloid leukemia?

Relapsed acute myeloid leukemia (AML) after an allogeneic hematopoietic cell transplant (allo-HCT) entails a poor prognosis. Treating these cases is challenging due to lack of effective therapies and, in some cases, poor performance status and/or presence of graft-versus-host disease (GVHD), among others. No randomized controlled trial (RCT) has ever been conducted comparing a second allo-HCT against other treatments. Existing data are mainly from observational studies or registries. Success of a second allo-HCT is dependent on appropriately selecting patients who might achieve best outcomes with reasonable non-relapse mortality (NRM) risk. Several factors are associated with worse outcomes, namely a shorter time from first allo-HCT to relapse or to the second allo-HCT, and AML not being in complete hematologic remission (CR). Patients relapsing earlier than 6 months or having active/persistent disease should be enrolled in clinical trials. Limitations of the published literature include retrospective small size studies, a heterogeneous population, and absence of information on somatic mutations, among others. Future studies assessing the role of a second allo-HCT should evaluate the impact of IDH1, IDH2, or others on outcomes; and the feasibility and efficacy of targeted therapies in the pre-, peri-, or post-second allo-HCT setting.

Salvage Therapy after Allogeneic Hematopoietic Cell Transplantation: Targeted and Low-Intensity Treatment Options in Myelodysplastic Syndrome and Acute Myeloid Leukemia

Patients with high-risk myeloid neoplasms, including myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), are offered allogeneic hematopoietic cell transplantation (alloHCT) to improve the likelihood of long-term disease control. More than 50% of patients with high-risk disease will relapse after HCT and face a poor prognosis with shortened survival. The recent development of targeted therapies and effective, low-intensity treatment strategies will likely improve the outcomes of these patients. In MDS, hypomethylating agents (HMAs) are the mainstay of salvage therapy but new treatments with APR-246 and luspatercept demonstrate excellent results in phase 1 and phase 3 clinical studies, respectively. In AML, new directed agents in the relapsed/refractory setting include gilteritinib (FLT3-ITD/-TKD), ivosidenib (IDH1), and enasidenib (IDH2). In patients without targetable mutations, HMAs may be used, and early data with venetoclax-based regimens are encouraging.

Natural Killer Immunotherapy for Minimal Residual Disease Eradication Following Allogeneic Hematopoietic Stem Cell Transplantation in Acute Myeloid Leukemia

The most common cause of death in patients with acute myeloid leukemia (AML) who receive allogeneic hematopoietic stem cell transplantation (allo-HSCT) is AML relapse. Therefore, additive therapies post allo-HSCT have significant potential to prevent relapse. Natural killer (NK)-cell-based immunotherapies can be incorporated into the therapeutic armamentarium for the eradication of AML cells post allo-HSCT. In recent studies, NK cell-based immunotherapies, the use of adoptive NK cells, NK cells in combination with cytokines, immune checkpoint inhibitors, bispecific and trispecific killer cell engagers, and chimeric antigen receptor-engineered NK cells have all shown antitumor activity in AML patients. In this review, we will discuss the current strategies with these NK cell-based immunotherapies as possible therapies to cure AML patients post allo-HSCT. Additionally, we will discuss various means of immune escape in order to further understand the mechanism of NK cell-based immunotherapies against AML.

Decitabine plus CLAG chemotherapy as a bridge to haploidentical transplantation in the setting of acute myeloid leukemia relapse after HLA-matched sibling transplantation: a case report

BACKGROUND

Patients with relapsed/refractory acute myeloid leukemia after hematopoietic stem cell transplantation (HSCT) have a poor prognosis, with a 2-year survival rate of 14%. The optimal treatment for these patients remains unclear. To treat these patients, we designed a new salvage regimen consisting of decitabine, cladribine, cytarabine, and granulocyte-stimulating factor (D-CLAG).

CASE PRESENTATION

Here, we describe a case of acute monocytic leukemia with a complex karyotype in a 38-year-old female patient who relapsed after her first HSCT, which was performed using a matched sibling donor. The patient did not respond to standard induction chemotherapy and subsequently achieved complete remission with the D-CLAG regimen. No severe hematological or extramedullary toxicity was observed. Subsequently, the patient received a second D-CLAG regimen as a bridge therapy and directly underwent haploidentical related HSCT. Following HSCT, the marrow showed complete hematologic and cytogenetic remission. Currently, 1 year after transplantation, the patient's general condition remains good.

CONCLUSIONS

This case suggests that the D-CLAG regimen can be an option for reinduction in relapsed refractory AML patients as a bridge to transplantation. Nevertheless, further research will be required in the future as this report describes only a single case.

[Diagnosis and treatment of acute myeloid leukemia : The updated 2018 Onkopedia Guideline]

In April 2018, an updated version of the previously published guidelines on acute myeloid leukemia (AML) from 2010 and 2017 was released. A revision was necessary because of two positive aspects: First, new data and insights on risk stratification and monitoring, and second, the clinical development and approval of new agents. The modified genetic risk classification allows a more precise distinction of different diagnostic groups and consequently a better matched post-remission treatment. The availability of new targeted drugs such as inhibitors turns genetic analyses from a mere prognostic tool into an instrument for treatment decisions. Several recently approved agents expand the treatment options for AML and raise hope for an improved prognosis and cure in the future.

Combination Lenalidomide and Azacitidine: A Novel Salvage Therapy in Patients Who Relapse After Allogeneic Stem-Cell Transplantation for Acute Myeloid Leukemia

PURPOSE

Salvage options for patients who relapse after allogeneic stem-cell transplantation (allo-SCT) for acute myeloid leukemia (AML) and myelodysplasia (MDS) remain limited, and novel treatment strategies are required. Both lenalidomide (LEN) and azacitidine (AZA) possess significant antitumor activity effect in AML. Administration of LEN post-transplantation is associated with excessive rates of graft-versus-host disease (GVHD), but AZA has been shown to ameliorate GVHD in murine transplantation models. We therefore examined the tolerability and activity of combined LEN/AZA administration in post-transplantation relapse.

PATIENTS AND METHODS

Twenty-nine patients who had relapsed after allo-SCT for AML (n = 24) or MDS (n = 5) were treated with sequential AZA (75 mg/m2 for 7 days) followed by escalating doses of LEN on days 10 to 30. Dose allocation and maximum tolerated dose (MTD) estimation were guided by a modified Bayesian continuous reassessment method (CRM).

RESULTS

Sequential AZA and LEN therapy was well tolerated. The MTD of post-transplantation LEN, in combination with AZA, was determined as 25 mg daily. Three patients developed grade 2 to 4 GVHD. There was no GVHD-related mortality. Seven of 15 (47%) patients achieved a major clinical response after LEN/AZA therapy. CD8+ T cells demonstrated impaired interferon-γ/tumor necrosis factor-α production at relapse, which was not reversed during LEN/AZA administration.

CONCLUSION

We conclude LEN can be administered safely post-allograft in conjunction with AZA, and this combination demonstrates clinical activity in relapsed AML/MDS without reversing biologic features of T-cell exhaustion. The use of a CRM model delivered improved efficiency in MTD assessment and provided additional flexibility. Combined LEN/AZA therapy represents a novel and active salvage therapy in patients who had relapsed post-allograft.

Infusion of donor-derived CD8+ memory T cells for relapse following allogeneic hematopoietic cell transplantation

Murine models showed that CD8⁺CD44^hi memory T (T_M) cells could eradicate malignant cells without inducing graft-versus-host disease (GVHD). We evaluated the feasibility and safety of infusing freshly isolated and purified donor-derived phenotypic CD8⁺ T_M cells into adults with disease relapse after allogeneic hematopoietic cell transplantation (HCT). Phenotypic CD8 T_M cells were isolated after unmobilized donor apheresis using a tandem immunomagnetic selection strategy of CD45RA depletion followed by CD8⁺ enrichment. Fifteen patients received CD8⁺ T_M cells at escalating doses (1 × 10⁶, 5 × 10⁶, or 10 × 10⁶ cells per kg). Thirteen received cytoreduction before CD8⁺ T_M cell infusion, and 9 had active disease at the time of infusion. Mean yield and purity of the CD8⁺ T_M infusion were 38.1% and 92.8%, respectively; >90% had CD8⁺ T effector memory phenotype, cytokine expression, and secretion profile. No adverse infusional events or dose-limiting toxicities occurred; GVHD developed in 1 patient (grade 2 liver). Ten patients (67%) maintained or achieved response (7 complete response, 1 partial response, 2 stable disease) for at least 3 months after infusion; 4 of the responders had active disease at the time of infusion. With a median follow-up from infusion of 328 days (range, 118-1328 days), median event-free survival and overall survival were 4.9 months (95% confidence interval [CI], 1-19.3 months) and 19.6 months (95% CI, 5.6 months to not reached), respectively. Collection and enrichment of phenotypic CD8⁺ T_M cells is feasible, well tolerated, and associated with a low incidence of GVHD when administered as a manipulated infusion of donor lymphocytes in patients who have relapsed after HCT. This trial was registered at www.clinicaltrials.gov as #NCT01523223.

Inhibition of Heme Oxygenase-1 Activity Enhances Wilms Tumor-1-Specific T-Cell Responses in Cancer Immunotherapy

Wilms tumor protein-1 (WT1) is an attractive target for adoptive T-cell therapy due to its expression in solid tumors and hematologic malignancies. However, T cells recognizing WT1 occur in low frequencies in the peripheral blood of healthy donors, limiting potential therapeutic possibilities. Tin mesoporphyrin (SnMP) is known to inhibit heme oxygenase-1 (HO-1), which has been shown to boost the activation and proliferation of human virus-specific T cells. We analyzed the influence of this effect on the generation of WT1-specific T cells and developed strategies for generating quantities of these cells from healthy donors, sufficient for adoptive T-cell therapies. HO-1 inhibition with SnMP increased WT1-specific T-cell frequencies in 13 (26%) of 50 healthy donors. To assess clinical applicability, we measured the enrichment efficiency of SnMP-treated WT1-specific T cells in response to a WT1-specific peptide pool and a HLA-A*02:01-restricted WT1 peptide by cytokine secretion assay. SnMP treatment resulted in a 28-fold higher enrichment efficacy with equal functionality. In conclusion, pharmacological inhibition of HO-1 activity with SnMP results in more efficient generation of functionally active WT1-specific T cells. This study demonstrates the therapeutic potentials of inhibiting HO-1 with SnMP to enhance antigen-specific T-cell responses in the treatment of cancer patients with WT1-positive disease.

Recipient ADAMTS13 Single-Nucleotide Polymorphism Predicts Relapse after Unrelated Bone Marrow Transplantation for Hematologic Malignancy

Relapse remains a major obstacle to the survival of patients with hematologic malignancies after allogeneic hematopoietic stem cell transplantation. A disintegrin-like and metalloprotease with a thrombospondin type 1 motif (ADMATS13), which cleaves von Willebrand factor multimers into less active fragments, is encoded by the ADAMTS13 gene and has a functional single-nucleotide polymorphism (SNP) rs2285489 (C > T). We retrospectively examined whether ADAMTS13 rs2285489 affected the transplant outcomes in a cohort of 281 patients who underwent unrelated human leukocyte antigen (HLA)-matched bone marrow transplantation for hematologic malignancies. The recipient ADAMTS13 C/C genotype, which putatively has low inducibility, was associated with an increased relapse rate (hazard ratio [HR], 3.12; 95% confidence interval [CI], 1.25–7.77; P = 0.015), resulting in a lower disease-free survival rate in the patients with a recipient C/C genotype (HR, 1.64; 95% CI, 1.01–2.67; P = 0.045). Therefore, ADAMTS13 rs2285489 genotyping in transplant recipients may be a useful tool for evaluating pretransplantation risks.

Relapse of Acute Myeloid Leukemia after Allogeneic Stem Cell Transplantation: Prevention, Detection, and Treatment

Acute myeloid leukemia (AML) is a phenotypically and prognostically heterogeneous hematopoietic stem cell disease that may be cured in eligible patients with intensive chemotherapy and/or allogeneic stem cell transplantation (allo-SCT). Tremendous advances in sequencing technologies have revealed a large amount of molecular information which has markedly improved our understanding of the underlying pathophysiology and enables a better classification and risk estimation. Furthermore, with the approval of the FMS-like tyrosine kinase 3 (FLT3) inhibitor Midostaurin a first targeted therapy has been introduced into the first-line therapy of younger patients with FLT3-mutated AML and several other small molecules targeting molecular alterations such as isocitrate dehydrogenase (IDH) mutations or the anti-apoptotic b-cell lymphoma 2 (BCL-2) protein are currently under investigation. Despite these advances, many patients will have to undergo allo-SCT during the course of disease and depending on disease and risk status up to half of them will finally relapse after transplant. Here we review the current knowledge about the molecular landscape of AML and how this can be employed to prevent, detect and treat relapse of AML after allo-SCT.

Outcomes following second allogeneic stem cell transplant for disease relapse after T cell depleted transplant correlate with remission status and remission duration after the first transplant

Background

Second allogeneic hematopoietic stem cell transplant (HCT) remains as an option for disease relapse after initial HCT.

Methods

We analyzed retrospectively the outcomes of 65 consecutive patients who underwent a second HCT for disease relapse at the University of Chicago. Univariate and multivariate analysis were conducted, and a scoring system was generated to select the patients who would benefit second HCT.

Results

All except four patients received T cell depleted (TCD) first HCT. The majority of patients had AML (n = 47) and high risk MDS (n = 5). The median age at second HCT was 45 years (11–73). 13 patients (20%) achieved CR before second HCT. 98% (n = 64) and 72% (n = 47) patients achieved neutrophil and platelet engraftment at a median interval of 10 and 18 days, respectively, following the second HCT. With a median follow up of 23 (5.5–140) months for survivors after second HCT, the estimated 2 years PFS was 17.5% and the 2 years OS was 22.6%. The day 100 cumulative incidence of non-relapse mortality rate was 23.6%, and the cumulative incidence of aGVHD and cGVHD were 16.9% and 7.7% respectively at 1 year after second HCT. In univariate analysis, patients with remission duration after first HCT of > 12 months and those in CR before second HCT had significantly better PFS and OS. A scoring system using disease status before second HCT (CR = 0 vs. non-CR = 1), and remission duration after first HCT (< 6 = 2, 6–12 = 1 and > 12 months = 0) was generated as an approach to classify patients into different risk categories in the purpose to provide guidance to the transplant physician to inform the outcomes to potential patients undergoing 2nd HCT. A score of < 2 (n = 26) identified a group with PFS and OS of 31.6% and 36.2% at 2 years after second HCT.

Conclusion

In conclusion, second HCT is a viable option for disease relapse after TCD HCT for patients entering second HCT in remission and/or remission duration > 12 months after first HCT with acceptable rates of GVHD and donor engraftment.

[Second allogeneic hematopoietic stem cell transplant: Guidelines from the francophone Society of bone marrow transplantation and cellular therapy (SFGM-TC)]

Disease recurrence and graft dysfunction after allogeneic hematopoietic stem cell transplantation (allo-HSCT) currently remain among the major causes of treatment failure in malignant and non-malignant hematological diseases. A second allo-HSCT is a valuable therapeutic option to salvage those situations. During the 8th annual harmonization workshops of the french Society of bone marrow transplantation and cellular therapy (SFGM-TC), a designated working group reviewed the literature in order to elaborate unified guidelines on feasibility, indications, donor choice and conditioning in the case of a second allo-HSCT. In case of relapse, a second allo-HSCT with reduced intensity or non-myeloablative conditioning is a reasonable option, particularly in patients with a good performance status (Karnofsky/Lansky>80%), low co-morbidity score (EBMT score≤3), a longer remission duration after the first allo-HSCT (>6 months), and who present low disease burden at the time of second allo-HSCT. Matched related donors tend to be associated with better outcomes. In the presence of graft dysfunction (primary and secondary graft rejection), an immunoablative conditioning regimen is recommended. A donor change remains a valid option, especially in the absence of graft-versus-host disease after the first allo-HSCT.

Measurable residual disease, conditioning regimen intensity, and age predict outcome of allogeneic hematopoietic cell transplantation for acute myeloid leukemia in first remission: A registry analysis of 2292 patients by the Acute Leukemia Working Party European Society of Blood and Marrow Transplantation

Patients with acute myeloid leukemia (AML) in morphological first complete remission (CR1) pre-allogeneic hematopoietic cell transplantation (HCT) may have measurable residual disease (MRD) by molecular and immunophenotyping criteria. We assessed interactions of MRD status with HCT conditioning regimen intensity in patients aged <50 years (y) or ≥50y. This was a retrospective study by the European Society for Blood and Marrow Transplantation registry. Patients were >18y with AML CR1 MRD NEG/POS and recipients of HCT in 2000-2015. Conditioning regimens were myeloablative (MAC), reduced intensity (RIC) or non-myeloablative (NMA). Outcomes included leukemia free survival (LFS), overall survival (OS), relapse incidence (RI), non-relapse mortality (NRM), chronic graft-vs-host (cGVHD), and GVHD-free and relapse-free survival (GRFS). The 2292 eligible patients were categorized into four paired groups: <50y MRD POS MAC (N = 240) vs RIC/NMA (N = 58); <50y MRD NEG MAC (N = 665) vs RIC/NMA (N = 195); ≥50y MRD POS MAC (N = 126) vs RIC/NMA (N = 230), and ≥50y MRD NEG MAC (N = 223) vs RIC/NMA (N = 555). In multivariate analysis RIC/NMA was only inferior to MAC for patients in the <50y MRD POS group, with worse RI (HR 1.71) and LFS (HR 1.554). Patients <50Y MRD NEG had less cGVHD after RIC/NMA HCT (HR 0.714). GRFS was not significantly affected by conditioning intensity in any group. Patients aged <50y with AML CR1 MRD POS status should preferentially be offered MAC allo-HCT. Prospective studies are needed to address whether patients with AML CR1 MRD NEG may be spared the toxicity of MAC regimens. New approaches are needed for ≥50y AML CR1 MRD POS.

Post-remission strategies for the prevention of relapse following allogeneic hematopoietic cell transplantation for high-risk acute myeloid leukemia: expert review from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Acute myeloid leukemia (AML) is an aggressive hematopoietic malignancy generally associated with poor prognosis. Allogeneic hematopoietic cell transplantation (alloHCT) continues to be the most potent anti-leukemia treatment for adult patients with intermediate and high-risk AML. However, disease relapse after alloHCT remains unacceptably high and is the primary cause of treatment failure and mortality following alloHCT. It is therefore that post-transplant early cellular or pharmacologic maintenance or preemptive strategies to enhance the graft-versus-leukemia effect or to eradicate persistent minimal residual disease have been of renewed interest, particularly with the availability of more sensitive technologies to measure residual AML. Although preliminary studies have demonstrated improved outcomes with the use of post-alloHCT remission therapies, prospective randomized trials are required to determine their clinical efficacy and role in the treatment of AML. On behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation, we summarize the available evidence on the use and efficacy of available pharmacologic post-remission therapies, including hypomethylating agents, deacetylase inhibitors, and tyrosine kinase inhibitors, as well as cellular therapies, including preemptive and prophylactic donor lymphocyte infusions for the prevention of relapse of AML.

Second allogeneic hematopoietic cell transplantation enables long-term disease-free survival in relapsed acute leukemia

Allogeneic hematopoietic cell transplantation (HCT) is the treatment of choice for high-risk myeloid and lymphoid leukemias. Relapse after allogeneic HCT is associated with a dismal prognosis and further therapeutic options are limited. One potential curative approach is a second allogeneic HCT. However, there is no consensus about optimal transplant modalities, suitable patients, and entities. We performed a retrospective analysis of our institutional database to evaluate risk factors that influence survival after a second allogeneic HCT for the treatment of relapsed acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). We identified 40 patients (AML, n = 29; ALL, n = 11) that received a second allogeneic HCT at our institution. At time of second HCT, 48% of patients were in complete remission (CR). Current overall survival (OS) was 14/40 patients with a median follow-up of 64 months (range 4-140) of patients alive resulting in a Kaplan-Meier estimated 2-year event-free survival (EFS) and OS of 32%, respectively. Cumulative incidence of non-relapse mortality (NRM) and relapse at 2 years was 31 and 37%, respectively. We identified several independent risk factors influencing OS: > 6 months from first to second transplant (p = 0.02), complete remission prior to transplant (p = 0.003), and the subsequent occurrence of chronic graft-versus-host disease (p = 0.003) were associated with a significantly improved OS. In conclusion, our data suggest that a second allogeneic HCT is a curative treatment option for relapsed acute leukemias in selected patients.

Strategies to enhance the graft versus tumour effect after allogeneic haematopoietic stem cell transplantation

Relapse of haematological malignancies after allogeneic haematopoietic stem cell transplant is a major cause of mortality. The immunological mechanisms that may lead to disease relapse may include immunological immaturity prior to reconstitution of the allogeneic immune system, tumour antigen downregulation or promotion of T-cell exhaustion by interactions with the tumour microenvironment. Current therapeutic strategies for post-transplant relapse are limited in their efficacy and alternative approaches are required. In this review, we discuss the mechanisms of T and NK-cell immune evasion that facilitate relapse of haematological malignancies after allogeneic stem cell transplantation, and explore emerging strategies to augment the allogeneic immune system in order to construct a more potent graft versus tumour response.

Donor lymphocyte infusion in myeloid disorders

A number of modalities including both pharmaceutical and cell-based treatments have long been tested and developed to prevent and treat relapses after allogeneic stem cell transplantation (allo-HSCT). The ability of donor T cells to recognize antigenic structures on leukemic cell surfaces and destroy them is a well-known fact. Based on this fact, the idea of using donor T cells to contribute to the development of adoptive immunotherapy has emerged. Donor lymphocytes are easy to obtain and donor lymphocyte infusions (DLI) have a simple rational while this treatment modality is an effective example of cellular therapy. The group of chronic myeloid leukemia patients who are more likely to benefit from DLI include: a) patients in the chronic phase of hematologic relapse and b) patients with molecular/cytogenetic relapse. DLI appear to be an appropriate treatment option to be used in combination with conventional chemotherapy or hypomethylating agents in the treatment of post-allo-HSCT relapse for acute myeloid leukemia and myelodysplastic syndrome, if:) the burden of tumor is low b) the relapse is at a molecular level rather than an overt hematologic relapse c) the patient has favorable cytogenetic characteristics d) time interval between transplantation and relapse is relatively longer (>5 months) e) response could be obtained after salvage therapies. In the event that minimal residual disease (MRD) or increasing mixed chimerism is detected, prompt administration of DLI for prophylactic purposes without waiting for a manifest relapse, was found to be effective in inducing a full donor chimerism and overcoming MRD and eventually preventing a manifest relapse.

Paramunity-inducing Factors (PINDs) in dendritic cell (DC) cultures lead to impaired antileukemic functionality of DC-stimulated T-cells

INTRODUCTION

Paramunity-inducing-Factors (PINDs) consist of attenuated/inactivated viruses of various poxvirus-genera, used in veterinary medicine as non-antigen-specific, non-immunising stimulators of the innate immune system against infectious and malignant diseases. Their danger-signaling-interactions were tested for their capacity to improve leukemic antigen-presentation on DC generated from AML-patients' blasts ('DC_leu') and DC-stimulation/activation of antileukemic T-cells.

METHODS

We analyzed, whether the addition of PINDs during DC cultures (15 healthy, 22 leukemic donors) and mixed lymphocyte culture (MLC, n = 15) with autologous (n = 6), allogeneic (n = 2) or T-cells after stem cell transplantation (SCT; n = 7) would alter the quality and quantity of DC, the composition of T-cell-subsets, and/or their antileukemic functionality (AF) as studied by FACS and functional Fluorolysis-cytotoxicity-assays.

RESULTS

Effects on 1. DC-cultures: PINDs in DC-cultures lead to increased proportions of mature DC and DC_leu, but reduced proportions of viable and overall, as well as TLR4- and TLR9-expressing DC. 2. MLC: PINDs increased early (CD8+) T-cell activation (CD69+), but reduced proportions of effector-T-cells after MLC 3. AF: Presence of PINDs in DC- and MLC-cultures reduced T-cells' as well as innate cells' antileukemic functionality. 4. Cytokine-release profile: Supernatants from PIND-treated DC- and MLC-cultures resembled an inhibitory microenvironment, correlating with impaired blast lysis.

CONCLUSIONS

Our data shows that addition of PINDs to DC-cultures and MLC result in a "blast-protective-capacity" leading to impaired AF, likely due to changes in the composition of T-/innate effector cells and the induction of an inhibitory microenvironment. PINDs might be promising in treating infectious diseases, but cannot be recommended for the treatment of AML-patients due to their inhibitory influence on antileukemic functionality.

Risk Factors Influencing Outcome of Acute Leukemia Patients Who Experience Relapse After Allogeneic Hematopoietic Stem-Cell Transplantation

BACKGROUND

Prognosis of acute leukemia patients who experience relapse after hematopoietic stem-cell transplantation (HSCT) remains poor. Identifying risk factors influencing outcome of these patients is essential.

PATIENTS AND METHODS

Follow-up of 234 acute leukemia patients who underwent allogeneic HSCT from matched related donor was performed for occurrence of posttransplantation relapse. Statuses of remission and survival were assessed at 6 months after treatment of relapse. Analysis of risk factors influencing postrelapse overall survival (prOS), complete remission (CR), and nonrelapse mortality (NRM) was carried out.

RESULTS

Posttransplantation relapse occurred in 43 patients (17.9%). After treatment, 11 patients (25.6%) experienced postrelapse remission, the prOS rate was 20.9% (9 patients), and the NRM rate was 25.6% (11 patients). Older age (P = .007) and failure to experience remission after relapse treatment (P = .027) were associated with lower prOS in multivariate analysis. Female sex (P = .027), posttransplantation extramedullary relapse (P = .001), and absence of postrelapse graft-versus-host disease P = .025) were associated with lower CR rate. Also, presence of extramedullary relapse (P = .011) was associated with lower risk of NRM whereas treatment of posttransplantation relapse with donor lymphocyte infusion with or without chemotherapy (P = .002) and occurrence of postrelapse graft-versus-host disease (P = .025) were associated with higher risk of NRM.

CONCLUSION

Survival of acute leukemia patients who experience relapse after allogeneic HSCT is poor, especially in elderly patients and those who do not experience remission after relapse treatment.

Higher Donor Apheresis Blood Volumes Are Associated with Reduced Relapse Risk and Improved Survival in Reduced-Intensity Allogeneic Transplantations with Unrelated Donors

Allogeneic hematopoietic stem cell transplantation (HSCT) with reduced-intensity conditioning (RIC) offers a curative option for patients with hematologic malignancies who are unable to undergo myeloablative conditioning, but its success is limited by high rates of relapse. Several studies have suggested a role for T cell doses in peripheral blood stem cell grafts in RIC HSCT. Because T cell dose is typically not known until after the collection, and apheresis blood volume is easily modifiable, we hypothesized that higher donor apheresis blood volumes would improve transplantation outcomes through an effect on graft composition. Thus, we analyzed the relationships between apheresis volume, graft composition, and transplantation outcomes in 142 consecutive patients undergoing unrelated donor allogeneic RIC HSCT. We found that apheresis volume ≥15 L was associated with a significantly decreased risk of relapse (adjusted hazard ratio [aHR], .48; 95% confidence interval [CI], .28 to .84]; P = .01) and improved relapse-free survival (aHR, .56; 95% CI, .35 to .89; P = .02) and overall survival (aHR, .55; 95% CI, .34 to .91; P = .02). A high apheresis volume was not associated with increased rates of acute or chronic graft-versus-host disease. These results demonstrate that an apheresis volume of at least 15 L is independently predictive of improved transplantation outcomes after RIC allogeneic HSCT.

Treatment of relapsed/refractory acute myeloid leukaemia in adults

The prognosis of relapsed acute myeloid leukaemia (AML) is poor and treatment is challenging. While the most potent treatment modality for patients who achieve a complete remission after relapse is still allogeneic haematopoietic cell transplantation (allo-HCT), both transplant-related mortality and relapse rates are high and many patients are not candidates for this approach. After a few decades of relative stasis in this field, a large number of novel approaches have become available to tackle this highly fatal disease. This is mostly due to our improved understanding of disease pathogenesis (including targetable mutations) and the anti-leukaemia potential of the immune system. Several small-molecule inhibitors and immunotherapeutic options are being explored in clinical trials and many more are in pre-clinical phase. Future studies will focus on novel and mechanistically driven combinations, sequential treatments, and low-toxicity maintenance strategies. While cure of relapsed/refractory AML without allo-HCT is currently unlikely, treatments are becoming less toxic and remissions are lasting longer.

Chimerism in Myeloid Malignancies following Stem Cell Transplantation Using FluBu4 with and without Busulfan Pharmacokinetics versus BuCy

In the era of precision medicine, the impact of personalized dosing of busulfan is not clear. We undertook a retrospective analysis of 78 patients with myeloid malignancies who received fludarabine and busulfan (FluBu4) with or without measuring Bu pharmacokinetics (Bu PK) and those who received busulfan with cyclophosphamide (BuCy). Fifty-five patients received FluBu4, of whom 21 had Bu PK measured, and 23 patients received BuCy. Total donor cell chimerism showed that the percentage of patients maintaining 100% donor chimerism on day 100 was 66.7%, 38.2%, and 73.9% in the FluBu4 with PK, FluBu4 with no PK, and BuCy, respectively (P = .001). Patients who had decreasing donor chimerism by day 100 were 23.8%, 52.9%, and 26.1% in the FluBu4 with PK, FluBu4 with no PK, and BuCy, respectively (P = .04). Bu PK group had fewer patients with less than 95% donor chimerism on day 30, which was not statistically significant, 5% (FluBu4 PK), 31% (FluBu4 with no PK), and 21% (BuCy) (P = .18). Survival distributions were not statistically significant (P = .11). Thus, personalized drug dosing can impact donor chimerism in myeloid malignancies. This will need to be examined in larger retrospective multicenter studies and prospective clinical trials.

Cells to prevent/treat relapse following allogeneic stem cell transplantation

Relapse of cancer remains one of the primary causes of treatment failure and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). A multitude of approaches have been used in the management of posttransplant relapse. This review focuses on recent data with cellular therapies designed to treat or prevent posttransplant relapse of hematologic malignancies, although many of these therapeutic approaches also have applications to solid tumors and in the nontransplant setting. Currently available cell therapies include second transplant, natural killer cells, monocyte-derived dendritic cell vaccines, and lymphocytes via donor lymphocyte infusion, antigen-primed cytotoxic T lymphocytes, cytokine-induced killer cells, marrow-infiltrating lymphocytes, and chimeric antigen receptor T cells. These treatment options offer the prospect for improved relapse-free survival after HSCT.

[Preventative and therapeutic relapse strategies after allogeneic hematopoietic stem cell transplantation: Guidelines from the Francophone society of bone marrow transplantation and cellular therapy (SFGM-TC)]

Disease relapse remains the first cause of mortality of hematological malignancies after allogeneic hematopoietic stem cell transplantation (allo-HCT). The risk of recurrence is elevated in patients with high-risk cytogenetic or molecular abnormalities, as well as when allo-HCT is performed in patients with refractory disease or with persistent molecular or radiological (PET-CT scan) residual disease. Within the frame of the 7th annual workshops of the francophone society for bone marrow transplantation and cellular therapy, the working group reviewed the literature in order to elaborate unified guidelines for the prevention and treatment of relapse after allo-HCT. For high risk AML and MDS, a post transplant maintenance strategy is possible, using hypomethylating agents or TKI anti-FLT3 when the target is present. For Philadelphia positive ALL, there was a consensus for the use of post-transplant TKI maintenance. For lymphomas, there are no strong data on the use of post-transplant maintenance, and hence a preemptive strategy is recommended based on modulation of immunosuppression, close follow-up of donor chimerism, and donor lymphocytes infusion. For multiple myeloma, even though the indication of allo-HCT is controversial, our recommendation is post transplant maintenance using bortezomib, due to its a good toxicity profile without increasing the risk of GVHD.

DNA-hypomethylating agents as epigenetic therapy before and after allogeneic hematopoietic stem cell transplantation in myelodysplastic syndromes and juvenile myelomonocytic leukemia

Myelodysplastic syndrome (MDS) is a clonal bone marrow disorder, typically of older adults, which is characterized by ineffective hematopoiesis, peripheral blood cytopenias and risk of progression to acute myeloid leukemia. Juvenile myelomonocytic leukemia (JMML) is an aggressive myeloproliferative neoplasm occurring in young children. The common denominator of these malignant myeloid disorders is the limited benefit of conventional chemotherapy and a particular responsiveness to epigenetic therapy with the DNA-hypomethylating agents 5-azacytidine (azacitidine) or decitabine. However, hypomethylating therapy does not eradicate the malignant clone in MDS or JMML and allogeneic hematopoietic stem cell transplantation (HSCT) remains the only curative treatment option. An emerging concept with intriguing potential is the combination of hypomethylating therapy and HSCT. Possible advantages include disease control with good tolerability during donor search and HSCT preparation, improved antitumoral alloimmunity, and reduced risk of relapse even with non-myeloablative regimens. Herein we review the current role of pre- and post-transplant therapy with hypomethylating agents in MDS and JMML.

Outcome after relapse of myelodysplastic syndrome and secondary acute myeloid leukemia following allogeneic stem cell transplantation: a retrospective registry analysis on 698 patients by the Chronic Malignancies Working Party of the European Society of Blood and Marrow Transplantation

No standard exists for the treatment of myelodysplastic syndrome relapsing after allogeneic stem cell transplantation. We performed a retrospective registry analysis of outcomes and risk factors in 698 patients, treated with different strategies. The median overall survival from relapse was 4.7 months (95% confidence interval: 4.1-5.3) and the 2-year survival rate was 17.7% (95% confidence interval: 14.8-21.2%). Shorter remission after transplantation (P<0.001), advanced disease (P=0.001), older age (P=0.007), unrelated donor (P=0.008) and acute graft-versus-host disease before relapse (P<0.001) adversely influenced survival. At 6 months from relapse, patients had received no cellular treatment, (i.e. palliative chemotherapy or best supportive care, n=375), donor lymphocyte infusion (n=213), or a second transplant (n=110). Treatment groups were analyzed separately because of imbalanced characteristics and difficulties in retrospectively evaluating the reason for individual treatments. Of the patients who did not receive any cellular therapy, 109 were alive at 6 months after relapse, achieving a median overall survival from this landmark of 8.9 months (95% confidence interval: 5.1-12.6). Their 2-year survival rate was 29.7%. Recipients of donor lymphocytes achieved a median survival from first infusion of 6.0 months (95% confidence interval: 3.7-8.3) with a 2-year survival rate of 27.6%. Longer remission after first transplantation (P<0.001) and younger age (P=0.009) predicted better outcome. Among recipients of a second transplant, the median survival from second transplantation was 4.2 months (95% confidence interval: 2.5-5.9), and their 2-year survival rate was 17.0%. Longer remission after first transplantation (P<0.001), complete remission at second transplant (P=0.008), no prior chronic graft-versus-host disease (P<0.001) and change to a new donor (P=0.04) predicted better outcome. The data enabled identification of patients benefiting from donor lymphocyte infusion and second transplantation, and may serve as a baseline for prospective trials.

Graft-versus-Leukemia Effect Following Hematopoietic Stem Cell Transplantation for Leukemia

The success of hematopoietic stem cell transplantation (HSCT) lies with the ability of the engrafting immune system to remove residual leukemia cells via a graft-versus-leukemia effect (GvL), caused either spontaneously post-HSCT or via donor lymphocyte infusion. GvL effects can also be initiated by allogenic mismatched natural killer cells, antigen-specific T cells, and activated dendritic cells of leukemic origin. The history and further application of this GvL effect and the main mechanisms will be discussed and reviewed in this chapter.

Ghrelin Protects the Thymic Epithelium From Conditioning-Regimen-Induced Damage and Promotes the Restoration of CD4+ T Cells in Mice After Bone Marrow Transplantation

BACKGROUND

The delay in immune reconstitution after hematopoietic stem cell transplantation (HSCT), especially a delay in central immune reconstitution, leads to opportunistic infections and disease relapse after transplantation and affects the long-term outcome of HSCT. This delay is mainly attributable to thymic damage after myeloablative chemotherapy and radiotherapy.

METHODS

We established a model of allogeneic bone marrow transplantation (BMT) in mice and administered ghrelin (GRL) 7 days before the conditioning regimen or the day after BMT to explore the effect of GRL on thymus.

RESULTS

All the GRL-treated mice, especially those administered GRL before the conditioning regimen, exhibited more intact thymic architecture and a more rapid restoration of CD4 T lymphocytes after BMT than those of the corresponding control mice. Moreover, the levels of T cell receptor excision circles were significantly higher in the mice treated with GRL before the conditioning regimen than in the control mice at 28 days after BMT.

CONCLUSIONS

Our findings suggest that GRL may be a novel potential therapeutic approach to protecting the thymic epithelium from conditioning regimen-induced damage and promoting rapid and durable thymic and peripheral CD4 T cell recovery after HSCT.

Comparison of Autologous and Unrelated Transplants for Cytogenetically Normal Acute Myelogenous Leukemia

Allogeneic stem cell transplantation (SCT) from an HLA-matched sibling donor (MSD) is a postremission treatment that offers a potential cure for adults with cytogenetically normal (CN) acute myelogenous leukemia (AML) in first complete remission (CR1). The best alternative in the absence of an MSD remains unclear, however. The aim of this study was to retrospectively compare the outcomes of autologous peripheral blood stem cell transplantation (auto-PBSCT; n = 177) and allogeneic bone marrow transplantation (BMT) from an HLA-matched unrelated donor (MUD; n = 173) in adult patients with CN-AML/CR1. Both the multivariate analysis (hazard ratio [HR], 1.18; 95% confidence interval [CI], 0.71 to 1.97; P = .53) and propensity score models (HR, 1.40; 95% CI, 0.80 to 2.43; P = .24) indicated that the leukemia-free survival (LFS) rate of auto-PBSCT was not significantly different from that of MUD-BMT. These results suggest that in the absence of an available MSD, auto-PBSCT remains a viable alternative as postremission therapy in patients with CN-AML/CR1.