Efficacy of immune suppression tapering in treating relapse after reduced intensity allogeneic stem cell transplantation

Acute Myeloid Leukemia: 2025 Update on Diagnosis, Risk-Stratification, and Management

DISEASE OVERVIEW

Acute myeloid leukemia (AML) is a bone marrow stem cell cancer that is often fatal despite available treatments. Diagnosis, risk assessment, monitoring, and therapeutic management of AML have changed dramatically in the last decade due to increased pathophysiologic understanding, improved assessment technology, and the addition of at least 12 approved therapies.

DIAGNOSIS

The diagnosis is based on the presence of immature leukemia cells in the blood, and/or bone marrow or less often in extra-medullary tissues. New biological insights have been integrated into recent classification systems.

RISK ASSESSMENT

The European Leukemia Network has published risk classification algorithms for both intensively and non-intensively treated patients based on cytogenetic and on molecular findings. Prognostic factors may differ based on the therapeutic approach.

MONITORING

Our increasing ability to quantify lower levels of measurable residual disease (MRD) potentially allows better response assessment, as well as dynamic monitoring of disease status. The incorporation of MRD findings into therapeutic decision-making is rapidly evolving.

RISK ADAPTED THERAPY

The availability of 12 newly approved agents has been welcomed; however, optimal strategies incorporating newer agents into therapeutic algorithms are debated. The overarching approach integrates patient and caregiver goals of care, comorbidities, and disease characteristics.

Ibrutinib for therapy of steroid-refractory chronic graft-versus-host disease: a multicenter real-world analysis

ABSTRACT

To examine the activity of ibrutinib in steroid-refractory chronic graft-versus-host disease (SR-cGVHD) after the US Food and Drug Administration approval, we conducted a multicenter retrospective study. Data were standardly collected (N = 270 from 19 centers). Involved organs included skin (75%), eye (61%), mouth (54%), joint/fascia (47%), gastrointestinal (GI) (26%), lung (27%), liver (19%), genital (7%), and others (4.4%). The National Institutes of Health (NIH) severity was mild in 5.7%, moderate 42%, and severe 53%. Thirty-nine percent had overlap subtype. Karnofsky performance status (KPS) was ≥80% in 72%. The median prednisone was 0.21 mg/kg (0-2.27). Ibrutinib was started at a median of 18.2 months after cGVHD onset and in earlier lines of therapy (second line, 26%; third, 30%; fourth, 21%; fifth, 9.6%; sixth, 10%; seventh or higher, 1.2%). Among evaluable patients, the 6-month NIH overall response rate (ORR; complete response [CR]/partial response [PR]) was 45% (PR 42%; CR 3%). The median duration of response was 15 months (range, 1-46). Liver involvement had association with 6-month ORR (multivariate [MVA] odds ratio, 5.49; 95% confidence interval [CI], 2.3-14.2; P < .001). The best overall response was 56%, with most (86%) achieving by 1 to 3 months. With a median follow-up for survivors of 30.5 months, failure-free survival (FFS) was 59% (53%-65%) at 6 months and 41% (36%-48%) at 12 months. On MVA, increased age (hazard ratio [HR], 1.01; 95% CI, 1.0-1.02; P = .033), higher baseline prednisone (HR, 1.92; 95% CI, 1.09-3.38; P = .032), and lung involvement (HR, 1.58; 95% CI, 1.1-2.28; P = .016) had worse FFS. Ibrutinib discontinuation was most commonly due to progressive cGVHD (44%) or toxicity (42%). These data support that ibrutinib has activity in SR-cGVHD, provide new insight into factors associated with response and FFS, and demonstrate the toxicity profile associated with discontinuation.

Evaluating the cost, cost-effectiveness and survival of an eHealth-facilitated integrated care model for allogeneic stem cell transplantation: Results of the German SMILe randomized, controlled implementation science trial

PURPOSE

eHealth-facilitated integrated care models (eICMs) have proved effective in improving outcomes for chronically ill patients. However, evidence on cost-effectiveness of eICMs is scarce so far. Allogeneic stem cell transplantation (alloSCT) recipients' post-discharge treatment costs and mortality are greatly influenced by complications. Within the international, multicentric SMILe implementation science project, the eHealth-facilitated SMILe integrated care model (SMILe-ICM) was developed to support patients minimize complications' effects within the first year post-alloSCT. Using initial effectiveness findings from the first center that implemented the SMILe-ICM, this study provides a cost and cost-effectiveness evaluation considering one-year and long-term survival effects, post-discharge costs, and patient-related factors.

METHODS

A single-center hybrid effectiveness implementation randomized controlled trial was conducted at a German university hospital from 2/2020 to 8/2022. Eligible alloSCT patients were randomized to the SMILe-ICM or usual care, i.e., one pre-transplant educational nursing visit followed by a physician-led follow-up. The intervention group received usual care plus the SMILe-ICM's four intervention modules (i.e., monitoring of medical/symptom-related parameters, medication adherence, infection prevention, physical activity). All modules were delivered by Advanced Practice Nurses (APNs) in face-to-face visits, combined with continuous online support. Daily, patients entered seventeen medical and symptom-related parameters to the SMILe App, so that APNs could monitor for and investigate possible pre-complication signs. Healthcare utilization costs were assessed at eight time-points (d+30 post-alloSCT-d365) on fourteen self-reported cost indicators and validated against health records. To calculate costs, we applied German standardized unit costs. Cost- and cost-effectiveness were analyzed in five steps: 1.) Calculate total costs, including for the alloSCT inpatient stay and post-discharge follow-up. 2.) Determine life-years gained (survival) as a health benefit unit. 3.) Calculate overall and rehospitalization-free survival estimates. 4.) Calculate the intervention's long-term cost-effectiveness, including extended follow-up, rate of survival until day 1000, and restricted mean survival time. 5.) Contrast these long-term estimates to current post-discharge costs with comparable patient-related factors (age ≥ or < 65, living alone, gender).

RESULTS

Seventy-two patients participated (n = 36/group). Total intergroup healthcare utilization and post-discharge costs differed, but non-significantly. Survival rates improved with the SMILe-ICM (88% vs. 80%) at least until day +1000. Rehospitalization-free survival showed improvement (38% vs. 30%); however, considering this sample size, both findings were nonsignificant. Cost-effectiveness analysis showed an overall post-discharge cost-effectiveness of 35,364.01€/patient and 6,742€/life year gained - a mean of 79.21 additional days of life for an intervention investment of 1.464€/patient in the first year post-alloSCT. One-year cost-effectiveness was highest for patients living alone. Younger age correlated with longer survival but higher costs.

CONCLUSION

The SMILe-ICM appears to offer survival and rehospitalization benefits, particularly for vulnerable groups, e.g., patients living alone. Larger, adequately powered studies are needed to validate these findings.

Graft-Versus-Host Disease Mouse Models: A Clinical-Translational Perspective

A variety of graft-versus-host disease (GVHD) models have been developed in mice for the purpose of allowing laboratory investigation of the pathobiology, prevention, and treatment of GVHD in humans. While such models are crucial in advancing our knowledge in this field, there are some key limitations that need to be considered when translating laboratory discoveries into the clinical context. This chapter will discuss current clinical practices in transplantation and GVHD and the relative strengths and weaknesses of mouse models that attempt to replicate these states.

Tracking Rare Single Donor and Recipient Immune and Leukemia Cells after Allogeneic Hematopoietic Cell Transplantation Using Mitochondrial DNA Mutations

Combined tracking of clonal evolution and chimeric cell phenotypes could enable detection of the key cellular populations associated with response following therapy, including after allogeneic hematopoietic stem cell transplantation (HSCT). We demonstrate that mitochondrial DNA (mtDNA) mutations coevolve with somatic nuclear DNA mutations at relapse post-HSCT and provide a sensitive means to monitor these cellular populations. Furthermore, detection of mtDNA mutations via single-cell assay for transposase-accessible chromatin with select antigen profiling by sequencing (ASAP-seq) simultaneously determines not only donor and recipient cells but also their phenotype at frequencies of 0.1% to 1%. Finally, integration of mtDNA mutations, surface markers, and chromatin accessibility profiles enables the phenotypic resolution of leukemic populations from normal immune cells, thereby providing fresh insights into residual donor-derived engraftment and short-term clonal evolution following therapy for post-transplant leukemia relapse. As throughput evolves, we envision future development of single-cell sequencing-based post-transplant monitoring as a powerful approach for guiding clinical decision-making. Significance: mtDNA mutations enable single-cell tracking of leukemic clonal evolution and donor-recipient origin following allogeneic HSCT. This provides unprecedented insight into chimeric cellular phenotypes of early immune reconstitution, incipient relapse, and quality of donor engraftment with immediate translational potential for future clinical post-transplant monitoring and decision-making.

Outcomes of patients undergoing third hematopoietic cell transplantation for hematologic malignancies

With advancements in novel therapeutics, it is unclear whether third hematopoietic cell transplantation (HCT3) has a place in the treatment of recurrent hematopoietic malignancies. We evaluated patients with hematologic malignancies who underwent HCT3 between 2000-2020. Nine patients, with a median age of 18 (9-68) years at HCT3 with acute myelogenous leukemia (n = 5), acute lymphoblastic leukemia (n = 2), myelodysplastic syndrome (n = 1), or undifferentiated acute leukemia (n = 1), were identified. The median time between first HCT and HCT3 was 3.9 (0.7-13.6) years. Indication for HCT3 was relapse (n = 8) or graft failure (n = 1) after second HCT. At HCT3, seven of nine patients were in complete remission by flow cytometry. All experienced robust donor engraftment by one month after HCT3 (≥ 90% CD3) while one died at day + 24 of multi-organ failure and was not evaluable for chimerism. In total, eight patients died from relapse (n = 4), non-relapse, (n = 3) or unknown (n = 1) causes at a median of 0.6 (range, 0.1 - 9.9) years after HCT3. After HCT3, estimated overall survival at 6 months, 1 year, and 5 years was 88%, 63%, and 22%, respectively. In this highly selected group, HCT3 provided a treatment option although long-term survival was still dismal.

Feasibility and safety of the discontinuation of systemic immunosuppressive treatment after single-unit cord blood transplantation in adults

We retrospectively evaluated the incidence, factors, and clinical outcomes of the discontinuation of immunosuppressive treatment (IST) after single-unit unrelated cord blood transplantation (CBT) in adults receiving cyclosporine-based graft-versus-host disease (GVHD) prophylaxis at our institute. Among the 309 patients who achieved engraftment, 247 were able to discontinue IST with a median follow-up of 121 months for survivors. The cumulative incidence of the discontinuation of IST was 46.2% at 180 days, 72.8% at 2 years, and 79.3% at 5 years post-CBT. In the multivariate analysis, discontinuation of IST after CBT was significantly associated with the requirement for steroid therapy (hazard ratio [HR]: 0.46; P < 0.001) and the recent calendar year of CBT (HR: 1.79; P < 0.001). In the conditional landmark analysis at 180 days, discontinuation of IST was not associated with the development of extensive chronic GVHD (HR: 1.00; P = 0.989), non-relapse mortality (HR: 0.49; P = 0.122), relapse (HR: 1.46; P = 0.388), or overall survival (HR: 1.91; P = 0.065). Our data showed that successful discontinuation of IST is common after single-unit CBT in adults. Discontinuation of IST did not affect subsequent outcomes, suggesting that discontinuation of IST is both feasible and safe in adults undergoing single-unit CBT.

The role and novel use of natural killer cells in graft-versus-leukemia reactions after allogeneic transplantation

Allogeneic hematopoietic cell transplantation (HCT) has transformed over the past several decades through enhanced supportive care, reduced intensity conditioning (RIC), improved human leukocyte antigen (HLA) typing, and novel graft-versus-host disease (GVHD)-prevention and treatment strategies. Most notably, the implementation of post-transplantation cyclophosphamide (PTCy) has dramatically increased the safety and availability of this life-saving therapy. Given reductions in nonrelapse mortality (NRM) with these advances, the HCT community has placed even greater emphasis on developing ways to reduce relapse - the leading cause of death after HCT. When using RIC HCT, protection from relapse relies predominantly on graft-versus-leukemia (GVL) reactions. Donor lymphocyte infusion (DLI), adoptive cellular therapy, checkpoint inhibition, and post-HCT maintenance strategies represent approaches under study that aim to augment or synergize with the GVL effects of HCT. Optimizing donor selection algorithms to leverage GVL represents another active area of research. Many of these strategies seek to harness the effects of T cells, which for decades were felt to be the primary mediators of GVL and the focus of investigation in relapse reduction. However, there is growing interest in capitalizing on the ability of natural killer (NK) cells to yield potent anti-tumor effects. A potential advantage of NK cell-based approaches over T cell-mediated is the potential to reduce NRM in addition to relapse. By decreasing infection, without increasing the risk of GVHD, NK cells may mitigate NRM, while still yielding relapse reduction through identification and clearance of cancer cells. Most T cell-focused relapse-prevention strategies must weigh the benefits of relapse reduction against the increased risk of NRM from GVHD. In contrast, NK cells have the potential to reduce both, potentially tipping the scales significantly in favor of survival. Here, we will review the role of NK cells in GVL, optimization of NK cell match or mismatch, and burgeoning areas of research in NK cell therapy such as adoptive transfer and chimeric antigen receptor (CAR) NK cells.

Patient-Specific Measurable Residual Disease Markers Predict Outcome in Patients With Myelodysplastic Syndrome and Related Diseases After Hematopoietic Stem-Cell Transplantation

PURPOSE

Clinical relapse is the major threat for patients with myelodysplastic syndrome (MDS) undergoing hematopoietic stem-cell transplantation (HSCT). Early detection of measurable residual disease (MRD) would enable preemptive treatment and potentially reduced relapse risk.

METHODS

Patients with MDS planned for HSCT were enrolled in a prospective, observational study evaluating the association between MRD and clinical outcome. We collected bone marrow (BM) and peripheral blood samples until relapse, death, or end of study 24 months after HSCT. Patient-specific mutations were identified with targeted next-generation sequencing (NGS) panel and traced using droplet digital polymerase chain reaction (ddPCR).

RESULTS

Of 266 included patients, estimated relapse-free survival (RFS) and overall survival (OS) rates 3 years after HSCT were 59% and 64%, respectively. MRD results were available for 221 patients. Relapse was preceded by positive BM MRD in 42/44 relapses with complete MRD data, by a median of 71 (23-283) days. Of 137 patients in continuous complete remission, 93 were consistently MRD-negative, 39 reverted from MRD+ to MRD-, and five were MRD+ at last sampling. Estimated 1 year-RFS after first positive MRD was 49%, 39%, and 30%, using cutoff levels of 0.1%, 0.3%, and 0.5%, respectively. In a multivariate Cox model, MRD (hazard ratio [HR], 7.99), WHO subgroup AML (HR, 4.87), TP53 multi-hit (HR, 2.38), NRAS (HR, 3.55), and acute GVHD grade III-IV (HR, 4.13) were associated with shorter RFS. MRD+ was also independently associated with shorter OS (HR, 2.65). In a subgroup analysis of 100 MRD+ patients, presence of chronic GVHD was associated with longer RFS (HR, 0.32).

CONCLUSION

Assessment of individualized MRD using NGS + ddPCR is feasible and can be used for early detection of relapse. Positive MRD is associated with shorter RFS and OS (ClinicalTrials.gov identifier: NCT02872662).

How I reduce and treat posttransplant relapse of MDS

ABSTRACT

Allogeneic hematopoietic stem cell transplantation (HSCT) is the only potentially curative option for patients with high-risk myelodysplastic syndromes (MDS). Advances in conditioning regimens and supportive measures have reduced treatment-related mortality and increased the role of transplantation, leading to more patients undergoing HSCT. However, posttransplant relapse of MDS remains a leading cause of morbidity and mortality for this procedure, necessitating expert management and ongoing results analysis. In this article, we review treatment options and our institutional approaches to managing MDS relapse after HSCT, using illustrative clinical cases that exemplify different clinical manifestations and management of relapse. We address areas of controversy relating to conditioning regimen intensity, chemotherapeutic bridging, and donor selection. In addition, we discuss future directions for advancing the field, including (1) the need for prospective clinical trials separating MDS from acute myeloid leukemia and focusing on posttransplant relapse, as well as (2) the validation of measurable residual disease methodologies to guide timely interventions.

Innovations in conditioning and post-transplant maintenance in AML: genomically informed revelations on the graft-versus-leukemia effect

Acute Myeloid Leukemia (AML) is the prototype of cancer genomics as it was the first published cancer genome. Large-scale next generation/massively parallel sequencing efforts have identified recurrent alterations that inform prognosis and have guided the development of targeted therapies. Despite changes in the frontline and relapsed standard of care stemming from the success of small molecules targeting FLT3, IDH1/2, and apoptotic pathways, allogeneic stem cell transplantation (alloHSCT) and the resulting graft-versus-leukemia (GVL) effect remains the only curative path for most patients. Advances in conditioning regimens, graft-vs-host disease prophylaxis, anti-infective agents, and supportive care have made this modality feasible, reducing transplant related mortality even among patients with advanced age or medical comorbidities. As such, relapse has emerged now as the most common cause of transplant failure. Relapse may occur after alloHSCT because residual disease clones persist after transplant, and develop immune escape from GVL, or such clones may proliferate rapidly early after alloHSCT, and outpace donor immune reconstitution, leading to relapse before any GVL effect could set in. To address this issue, genomically informed therapies are increasingly being incorporated into pre-transplant conditioning, or as post-transplant maintenance or pre-emptive therapy in the setting of mixed/falling donor chimerism or persistent detectable measurable residual disease (MRD). There is an urgent need to better understand how these emerging therapies modulate the two sides of the GVHD vs. GVL coin: 1) how molecularly or immunologically targeted therapies affect engraftment, GVHD potential, and function of the donor graft and 2) how these therapies affect the immunogenicity and sensitivity of leukemic clones to the GVL effect. By maximizing the synergistic action of molecularly targeted agents, immunomodulating agents, conventional chemotherapy, and the GVL effect, there is hope for improving outcomes for patients with this often-devastating disease.

The graft versus leukemia effect: donor lymphocyte infusions and cellular therapy

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative therapy for many hematologic malignancies as well as non-malignant conditions. Part of the curative basis underlying HSCT for hematologic malignancies relies upon induction of the graft versus leukemia (GVL) effect in which donor immune cells recognize and eliminate residual malignant cells within the recipient, thereby maintaining remission. GVL is a clinically evident phenomenon; however, specific cell types responsible for inducing this effect and molecular mechanisms involved remain largely undefined. One of the best examples of GVL is observed after donor lymphocyte infusions (DLI), an established therapy for relapsed disease or incipient/anticipated relapse. DLI involves infusion of peripheral blood lymphocytes from the original HSCT donor into the recipient. Sustained remission can be observed in 20-80% of patients treated with DLI depending upon the underlying disease and the intrinsic burden of targeted cells. In this review, we will discuss current knowledge about mechanisms of GVL after DLI, experimental strategies for augmenting GVL by manipulation of DLI (e.g. neoantigen vaccination, specific cell type selection/depletion) and research outlook for improving DLI and cellular immunotherapies for hematologic malignancies through better molecular definition of the GVL effect.

Immunology of cord blood T-cells favors augmented disease response during clinical pediatric stem cell transplantation for acute leukemia

Allogeneic hematopoietic stem cell transplantation (HSCT) has been an important and efficacious treatment for acute leukemia in children for over 60 years. It works primarily through the graft-vs.-leukemia (GVL) effect, in which donor T-cells and other immune cells act to eliminate residual leukemia. Cord blood is an alternative source of stem cells for transplantation, with distinct biological and immunological characteristics. Retrospective clinical studies report superior relapse rates with cord blood transplantation (CBT), when compared to other stem cell sources, particularly for patients with high-risk leukemia. Xenograft models also support the superiority of cord blood T-cells in eradicating malignancy, when compared to those derived from peripheral blood. Conversely, CBT has historically been associated with an increased risk of transplant-related mortality (TRM) and morbidity, particularly from infection. Here we discuss clinical aspects of CBT, the unique immunology of cord blood T-cells, their role in the GVL effect and future methods to maximize their utility in cellular therapies for leukemia, honing and harnessing their antitumor properties whilst managing the risks of TRM.

The delicate balance of graft versus leukemia and graft versus host disease after allogeneic hematopoietic stem cell transplantation

INTRODUCTION

The curative basis of allogeneic hematopoietic stem cell transplantation (HSCT) relies in part upon the graft versus leukemia (GvL) effect, whereby donor immune cells recognize and eliminate recipient malignant cells. However, alloreactivity of donor cells against recipient tissues may also be deleterious. Chronic graft versus host disease (cGvHD) is an immunologic phenomenon wherein alloreactive donor T cells aberrantly react against host tissues, leading to damaging inflammatory symptoms.

AREAS COVERED

Here, we discuss biological insights into GvL and cGvHD and strategies to balance the prevention of GvHD with maintenance of GvL in modern HSCT.

EXPERT OPINION/COMMENTARY

Relapse remains the leading cause of mortality after HSCT with rates as high as 40% for some diseases. GvHD is a major cause of morbidity after HSCT, occurring in up to half of patients and responsible for 15-20% of deaths after HSCT. Intriguingly, the development of chronic GvHD may be linked to lower relapse rates after HSCT, suggesting that GvL and GvHD may be complementary sides of the immunologic foundation of HSCT. The ability to fine tune the balance of GvL and GvHD will lead to improvements in survival, relapse rates, and quality of life for patients undergoing HSCT.

Dermatologic complications in transplantation and cellular therapy for acute leukemia

Adoptive cellular immunotherapy, mainly hematopoietic stem cell transplant and CAR-T cell therapy have revolutionized treatment of patients with acute leukemia. Indications and inclusion criteria for these treatments have expanded in recent years. While these therapies are associated with significant improvements in disease response and overall survival, patients may experience adverse events from associated chemotherapy conditioning, engraftment, cytokine storm, supportive medications, and post-transplant maintenance targeted therapies. Supportive oncodermatology is a growing specialty to manage cutaneous toxicities resulting from the anti-cancer therapies. In this review, we summarize diagnosis and management of the common cutaneous adverse events including drug eruptions, graft-versus-host disease, neoplastic and paraneoplastic complications in patients undergoing cellular therapies.

Acute myeloid leukemia: 2023 update on diagnosis, risk-stratification, and management

DISEASE OVERVIEW

Acute myeloid leukemia (AML) is a frequently fatal bone marrow stem cell cancer characterized by unbridled proliferation of malignant marrow stem cells with associated infection, anemia, and bleeding. An improved understanding of pathophysiology, improvements in measurement technology and at least 10 recently approved therapies have led to revamping the diagnostic, prognostic, and therapeutic landscape of AML.

DIAGNOSIS

One updated and one new classification system were published in 2022, both emphasizing the integration of molecular analysis into daily practice. Differences between the International Consensus Classification and major revisions from the previous 2016 WHO system provide both challenges and opportunities for care and clinical research.

RISK ASSESSMENT AND MONITORING

The European Leukemia Net 2022 risk classification integrates knowledge from novel molecular findings and recent trial results, as well as emphasizing dynamic risk based on serial measurable residual disease assessment. However, how to leverage our burgeoning ability to measure a small number of potentially malignant myeloid cells into therapeutic decision making is controversial.

RISK ADAPTED THERAPY

The diagnostic and therapeutic complexity plus the availability of newly approved agents requires a nuanced therapeutic algorithm which should integrate patient goals of care, comorbidities, and disease characteristics including the specific mutational profile of the patient's AML. The framework we suggest only represents the beginning of the discussion.

Diagnosis and management of AML in adults: 2022 recommendations from an international expert panel on behalf of the ELN

The 2010 and 2017 editions of the European LeukemiaNet (ELN) recommendations for diagnosis and management of acute myeloid leukemia (AML) in adults are widely recognized among physicians and investigators. There have been major advances in our understanding of AML, including new knowledge about the molecular pathogenesis of AML, leading to an update of the disease classification, technological progress in genomic diagnostics and assessment of measurable residual disease, and the successful development of new therapeutic agents, such as FLT3, IDH1, IDH2, and BCL2 inhibitors. These advances have prompted this update that includes a revised ELN genetic risk classification, revised response criteria, and treatment recommendations.

Azacitidine and donor lymphocyte infusion for patients with relapsed acute myeloid leukemia and myelodysplastic syndromes after allogeneic hematopoietic stem cell transplantation: A meta-analysis

Background

For patients with relapsed acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) after allogeneic hematopoietic stem cell transplantation (allo-HSCT), azacitidine with donor lymphocyte infusion (DLI) is a feasible option to perform a preemptive or salvage treatment. However, its efficacy lacked comprehensive analysis, and this study aimed to fill this gap.

Methods

We searched potential studies in PUBMED, EMBASE, and the Cochrane Central Register of Controlled Trials. Thirteen studies involving 811 patients were analyzed. The inverse variance method was used to calculate the pooled proportion and 95% confidence interval (CI). Subgroup analysis was performed to explore the source of heterogeneity.

Results

The rate of pooled complete remission + partial remission (CR + PR), CR, and 2-year overall survival (OS) were 30% (95% CI: 22%-39%), 21% (95% CI: 16%-28%), and 31% (95% CI: 27%-35%), respectively. The pooled acute graft-versus-host disease (GvHD) and chronic GvHD rates were 15% (95% CI: 9%-23%) and 14% (95% CI: 8%-23%), respectively. Adverse cytogenetics and a higher percentage of bone marrow (BM) blasts at relapse were correlated with worse CR + PR and CR (interaction p < 0.05). Higher 2-year OS was found in patients with lower BM blasts at relapse or a longer time from allo-HSCT to relapse (interaction p < 0.05). Furthermore, the preemptive treatment for molecular relapse/minimal residual disease positivity resulted in much better outcomes than that for hematological relapse, both in terms of CR and 2-year OS (interaction p < 0.001).

Conclusion

The regimen of azacitidine and DLI could safely improve the outcomes of relapsed AML/MDS after allo-HSCT, especially in those with signs of early relapse. The administration of targeted medicines in azacitidine-based therapies may further improve the outcomes of relapsed AML/MDS.

Adding venetoclax to fludarabine/busulfan RIC transplant for high-risk MDS and AML is feasible, safe, and active

Adding the selective BCL-2 inhibitor venetoclax to reduced-intensity conditioning chemotherapy (fludarabine and busulfan [FluBu2]) may enhance antileukemic cytotoxicity and thereby reduce the risk of posttransplant relapse. This phase 1 study investigated the recommended phase 2 dose (RP2D) of venetoclax, a BCL-2 selective inhibitor, when added to FluBu2 in adult patients with high-risk acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), and MDS/myeloproliferative neoplasms (MPN) undergoing transplant. Patients received dose-escalated venetoclax (200-400 mg daily starting day -8 for 6-7 doses) in combination with fludarabine 30 mg/m2 per day for 4 doses and busulfan 0.8 mg/kg twice daily for 8 doses on day -5 to day -2 (FluBu2). Transplant related-toxicity was evaluated from the first venetoclax dose on day -8 to day 28. Twenty-two patients were treated. At study entry, 5 patients with MDS and MDS/MPN had 5% to 10% marrow blasts, and 18 (82%) of 22 had a persistent detectable mutation. Grade 3 adverse events included mucositis, diarrhea, and liver transaminitis (n = 3 each). Neutrophil/platelet recovery and acute/chronic graft-versus-host-disease rates were similar to those of standard FluBu2. No dose-limiting toxicities were observed. The RP2D of venetoclax was 400 mg daily for 7 doses. With a median follow-up of 14.7 months (range, 8.6-24.8 months), median overall survival was not reached, and progression-free survival was 12.2 months (95% confidence interval, 6.0-not estimable). In patients with high-risk AML, MDS, and MDS/MPN, adding venetoclax to FluBu2 was feasible and safe. To further address relapse risk, assessment of maintenance therapy after venetoclax plus FluBu2 transplant is ongoing. This study was registered at clinicaltrials.gov as #NCT03613532.

Clinical Utility of the Detection of the Loss of the Mismatched HLA in Relapsed Hematological Patients After Haploidentical Stem Cell Transplantation With High-Dose Cyclophosphamide

Haploidentical hematopoietic stem cell transplantation (Haplo-HSCT) with high-dose cyclophosphamide (PTCy) has resulted in a low incidence of graft-vs.-host disease (GVHD), graft failure, and non-relapse mortality. However, post-transplantation relapse remains a common cause of treatment failure in high-risk patients. Unraveling the mechanisms of relapse is therefore crucial for designing effective relapse treatment strategies. One of these mechanisms is the loss of the mismatched HLA on the recipient's leukemic cells. To study the incidence and clinical relevance of this phenomenon, we analyzed 181 patients treated with Haplo-HSCT with PTCy (2007–2019), of which 37 relapsed patients after transplantation. According to the kit employed for HLA-loss analysis, among 22 relapsed patients, we identified HLA loss at relapse in 6 of the 22 patients (27%) studied. Based on the results obtained, the genomic loss of HLA was more common in females than males (66 vs. 33%) and HLA-loss relapses occurred later than classical relapses (345 vs. 166 days). Moreover, the patients with HLA-loss had a greater presence of active disease at the time of transplantation and had undergone a larger number of treatment lines than the group with classical relapses (66 vs. 43% and 66 vs. 18%, respectively). Four of these relapses were studied retrospectively, while two were studied prospectively, the results of which could be considered for patient management. Additionally, two relapsed patients analyzed retrospectively had myeloid neoplasms. One patient had not undergone any treatment, and three had undergone donor lymphocyte infusions (DLIs) and chemotherapy. All presented severe GVHD and disease progression. In contrast, the two patients studied prospectively had a lymphoid neoplasm and were not treated with DLIs. One of them was treated with chemotherapy but died from disease progression, and the other patient underwent a second Haplo-HSCT from a different donor and is still alive. We can conclude that the detection of HLA-loss at the onset of relapse after Haplo-HSCT with PTCy could help in clinical practice to select appropriate rescue treatment, thereby avoiding the use of DLIs or a second transplantation from the same donor.

Checkpoint inhibition to prevent or treat relapse in allogeneic hematopoietic cell transplantation

In the past decades, survival has improved after allogeneic hematopoietic cell transplantation (allo-HCT) due largely to advances in the prevention of graft-vs.-host disease (GVHD) and opportunistic infection. However, few inroads have been made into the problem of leukemia relapse which is the primary reason for failure of allo-HCT. The graft-vs.-leukemia (GVL) response, in which engrafted immunocompetent donor immune cells can eliminate leukemia cells, is acknowledged as the foundation upon which the curative potential of allo-HCT is based. Despite our strongly held faith in its existence, we remain unable to define GVL on a mechanistic level. T cells, in part, mediate GVL though the roles of specific T cell subsets, NK cells, B cells, macrophages remain elusive. A higher frequency of marrow-infiltrating T cells expressing PD-1, CTLA-4, and TIM-3 and other immune checkpoints have been observed in relapsed patients compared to those in remission. Studies have described the association of T cells expressing an exhausted phenotype with response to immune manipulation post-HCT. In light of these observations and the well documented activity of immune checkpoint blockade (CPB) in transplant naïve patients with hematologic malignancies, considerable interest has developed in evaluating strategies incorporating CPB to address relapse post-HCT. While checkpoint inhibitors may be provocative agents to test, they also raise concern for potential induction of GVHD and uncontrollable immune breakthrough events. This review will lay the framework upon which CPB is being utilized post-HCT, describe early clinical results, and lay out future directions.

Immunophenotyping of the PD-L1-positive cells in angioimmunoblastic T cell lymphoma and Hodgkin disease

Objective

Programmed death-1 (PD-1) and its ligand PD-L1 are now used as predictive biomarkers to guide clinical decisions. Precise characterization of PD-L1-positive cells may contribute to our knowledge of which patients derive benefit from the PD-L1 blockade therapy.

Results

To address this issue, we performed immunophenotyping of PD-L1-positive cells in Hodgkin lymphoma and in angioimmunoblastic T cell lymphoma (AITL) employing multiple immunofluorescent immunolabeling. We found that PD-L1-positive cells and PD-1-positive cells both in Hodgkin lymphoma and in AITL belong to two completely different cell lineages. In both lymphomas, PD-1 was found exclusively in T-lymphocytes, whereas PD-L1 was revealed in the tumor microenvironment cells including macrophages. PD-L1 was also detected in CD30-positive cells in Hodgkin lymphoma but not in AITL. The marker of B-cell lineage, CD20, was not detectable in PD-L1-positive cells both in AITL and in Hodgkin. Our study highlights the importance of comprehensive assessment of PD-1/PD-L1 regulatory pathways for employing PD-L1 as a predictive biomarker in clinical practice. PD-L1-antibody therapy is proven in Hodgkin lymphoma. Comparative immunophenotyping of the PD-1/PD-L1 axis provides a support for attempts to prove this principle also for AITL.

Disease risk and GVHD biomarkers can stratify patients for risk of relapse and nonrelapse mortality post hematopoietic cell transplant

The graft-versus-leukemia (GVL) effect after allogeneic hematopoietic cell transplant (HCT) can prevent relapse but the risk of severe graft-vs-host disease (GVHD) leads to prolonged intensive immunosuppression and possible blunting of the GVL effect. Strategies to reduce immunosuppression in order to prevent relapse have been offset by increases in severe GVHD and non-relapse mortality (NRM). We recently validated the MAGIC algorithm probability (MAP) that predicts the risk for severe GVHD and NRM in asymptomatic patients using serum biomarkers. In this study we tested whether the MAP could identify patients whose risk for relapse is higher than their risk for severe GVHD and NRM. The multicenter study population (n=1604) was divided into two cohorts: historical (2006–2015, n=702) and current (2015–2017, n=902) with similar non-relapse mortality, relapse, and survival. On day 28 post-HCT, patients who had not developed GVHD (75% of the population) and who possessed a low MAP were at much higher risk for relapse (24%) than severe GVHD and NRM (16% and 9%); this difference was even more pronounced in patients with a high disease risk index (relapse 33%, NRM 9%). Such patients are good candidates to test relapse prevention strategies that might enhance GVL.

Molecular remission using low-dose immunotherapy for relapsed refractory Philadelphia chromosome-positive precursor B-cell acute lymphoblastic leukemia post-allogeneic stem cell transplant

Adults with relapsed/refractory acute lymphoblastic leukemia have a poor prognosis. While current immunotherapies are promising, they are toxic, with graft-versus-host disease a major complication of allogeneic therapy. Here, we report a patient with high-risk relapsed/refractory Philadelphia chromosome-positive B-cell acute lymphoblastic leukemia (ALL) following chemotherapy induction, matched related donor allogeneic hematopoietic stem cell transplantation (allo-HCT), donor lymphocyte infusion and two tyrosine kinase inhibitors. The patient achieved a complete molecular and cytogenetic remission with minimal adverse events or evidence of GVHD following recombinant human IL-2 (rIL-2), in combination with a tyrosine kinase inhibitor (TKI). There was a ninefold increase in natural killer (NK) cell activity and natural killer T cells (NKT) cells (CD2⁺CD26⁺). Personalized low dose recombinant human IL-2-mediated NK cell stimulation represents an effective, nontoxic immunotherapy administered in the outpatient setting for relapsed acute lymphoblastic leukemia and warrants further investigation.

The role of FLT3 inhibitors as maintenance therapy following hematopoietic stem cell transplant

Activating mutations in FLT3 in acute myeloid leukemia (AML) portend a poor prognosis, and targeting FLT3 with a tyrosine kinase inhibitor has been an area of intense research recently. Most FLT3 mutated AML patients undergo hematopoietic stem cell transplantation (HSCT) as standard of care but a significant proportion of patients relapse. Although the use of FLT3 inhibitors in the pre-HSCT perspective is more clearly defined, its use in the post-HSCT scenario, when most relapses occur, remains unclear. In this review, we comprehensively present the data on the recent and ongoing studies evaluating the role of various FLT3 inhibitors in AML with a particular focus in the post-HSCT setting.

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.

Allogeneic Hematopoietic Cell Transplantation for Older Adults with Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a disease that affects adults aged 65 years and above, and survival in this population is poor. Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative therapy for these patients but is underutilized due to frequent comorbidities and perceived higher risk of treatment-related mortality and non-relapse mortality. Increasing data supports the utility of allo-HCT in fit older patients after intensive chemotherapy resulting in improvement of outcomes. With the development of reduced intensity and non-myeloablative conditioning regimens that are associated with lower rates of treatment-related toxicity and mortality, this has allowed more older patients with AML to receive allo-HCT. In this review, we provide some guidance on appropriate selection of older patients as transplant candidates, benefits and risks associated with allo-HCT, conditioning regimen choice, and stem cell transplant sources as they relate to the conduct of stem cell transplantation in older patients.

Tyrosine kinase inhibitors and immune checkpoint blockade in allogeneic hematopoietic cell transplantation

Advances in the prevention of graft-versus-host disease (GVHD) and opportunistic infection have improved survival after allogeneic hematopoietic cell transplantation (allo-HCT) in the past decade. However, few inroads have been made into the treatment or prevention of relapse of the underlying malignancy for which allo-HCT is being performed. The introduction of US Food and Drug Administration-approved agents with significant activity in a variety of hematologic malignancies provides an opportunity to evaluate these interventions in the allo-HCT setting. Some of the most promising new agents include tyrosine kinase inhibitors (TKIs) directed at bcr-abl, kinase inhibitors targeting fms-like tyrosine kinase 3, and immune checkpoint inhibitors blocking both CTLA4 and PD-1. Data have emerged indicating potential efficacy of these agents in preventing or treating relapse, though definitive evidence remains elusive. However, potential toxicity can be considerable, highlighting the need for further clinical trials to define the therapeutic window. This review explores the immunologic and clinical consequence of treatment with both TKIs and checkpoint inhibitors in the peri- and post-allo-HCT setting.

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.