Proceedings from the National Cancer Institute's Second International Workshop on the Biology, Prevention, and Treatment of Relapse After Hematopoietic Stem Cell Transplantation: part III. Prevention and treatment of relapse after allogeneic transplantation

Applications of 18F-Fluorodesoxyglucose PET Imaging in Leukemia

The main finding that 18F-FDG PET imaging can reveal in patients with leukemias is the presence of bone marrow (BM) infiltration in both acute or chronic forms. This ability can influence and guide the use of BM biopsy but also assess to therapy response. Additionally 18F-FDG PET imaging has been reported as particularly useful for the diagnosis of leukemias in patients with non specific symptoms. In the case of acute leukemias it revealed also a role for the evaluation of extramedullary forms while in the case of chronic forms a role for the assessment of Richter transformation has been reported.

Cell-Based Treatment in Acute Myeloid Leukemia Relapsed after Allogeneic Stem Cell Transplantation

Allogeneic stem cell transplant (ASCT) remains the only treatment option for patients with high-risk acute myeloid leukemia (AML). Recurrence of leukemic cells after ASCT represents a dramatic event associated with a dismal outcome, with a 2-year survival rate of around 20%. Adoptive cell therapy (ACT) is a form of cell-based strategy that has emerged as an effective therapy to treat and prevent post-ASCT recurrence. Lymphocytes are the principal cells used in this therapy and can be derived from a hematopoietic stem cell donor, the patient themselves, or healthy donors, after being engineered to express the chimeric antigen receptor (CAR-T and UniCAR-T). In this review, we discuss recent advances in the established strategy of donor lymphocyte infusion (DLI) and the progress and challenges of CAR-T cells.

CD34 Chimerism Directed Donor Lymphocyte Infusion With or Without Azacitidine Results in Reduced Relapse and Superior Overall Survival When Full Donor Chimerism is Achieved in Allogeneic Stem Cell Transplant Recipients With Acute Myeloid Leukaemia/Myelodysplastic Syndrome

BACKGROUND

Regular monitoring of CD34 donor chimerism (DC) is a highly sensitive method of predicting relapse in allogeneic stem cell transplant (alloHSCT) recipients with AML/MDS. A fall of CD34 DC below 80% is an indicator of ensuing relapse. There are limited studies assessing the efficacy of donor lymphocyte infusion (DLI) triggered by mixed CD34 DC (MDC), in addressing falling chimerism.

PATIENTS AND METHODS

We performed a retrospective analysis of consecutive alloHSCT patients between 2012 to 2023 who received DLI (with or without azacitidine) for CD34 MDC without morphologic relapse at the time of infusion.

RESULTS

Of the 21 patients with follow up CD34 DC available, 14 (66.7%) achieved CD34 full donor chimerism (FDC) following DLI with or without azacitidine (dli-FDC), while 7 (33.3%) did not (dli-MDC). The 2-year cumulative incidence of relapse (CIR) was significantly lower in dli-FDC compared to dli-MDC (21.4% vs. 85.7%, P < 0.001), correlating with superior overall survival (OS; median years not reached vs. 0.67 years [95% CI, 0.58-ND], P < .001). Rates of grade II-IV acute GVHD post-DLI were 14.9%, and moderate-severe cGVHD was 42.8% in the dli-FDC group. The 5-year nonrelapse mortality (NRM) of the dli-FDC group was 7.1% following DLI.

CONCLUSION

Our study shows the restoration of CD34 FDC post-DLI is associated with reduced relapse and improved overall survival, with low NRM.

[Preventive and therapeutic strategies for relapse after hematopoietic stem cell transplant for pediatric AML (SFGM-TC)]

Treatment of pediatric high-risk acute myeloid leukemia (AML), defined either on molecular or cytogenetic features, relies on bone marrow transplant after cytologic remission. However, relapse remains the first post-transplant cause of mortality. In this 13th session of practice harmonization of the francophone society of bone marrow transplantation and cellular therapy (SFGM-TC), our group worked on recommendations regarding the management of post-transplant relapse in AML pediatric patients based on international literature, national survey and expert opinion. Overall, immunomodulation strategy relying on both measurable residual disease (MRD) and chimerism evaluation should be used for high-risk AML. In very high-risk (VHR) AML with a 5-year overall survival ≤30 %, a post-transplant maintenance should be proposed using either hypomethylating agents, combined with DLI whenever possible, or FLT3 tyrosine kinase inhibitors if this target is present on leukemia cells. In the pre-emptive or early relapse settings (< 6 months post-transplant), treatments combining DLI, Azacytidine and Venetoclax should be considered. Access to phase I/II trails for targeted therapies (menin, IDH or JAK inhibitors) should be discussed in each patient according to the underlying molecular abnormalities of the disease.

Continuously improving outcome over time after second allogeneic stem cell transplantation in relapsed acute myeloid leukemia: an EBMT registry analysis of 1540 patients

Second allogeneic stem cell transplantation (alloSCT2) is among the most effective treatments for acute myeloid leukemia (AML) relapse after first alloSCT (alloSCT1). Long-term EBMT registry data were used to provide large scale, up-to-date outcome results and to identify factors for improved outcome. Among 1540 recipients of alloSCT2, increasing age, better disease control and performance status before alloSCT2, more use of alternative donors and higher conditioning intensity represented important trends over time. Between the first (2000-2004) and last (2015-2019) period, two-year overall and leukemia-free survival (OS/LFS) increased considerably (OS: 22.5-35%, LFS: 14.5-24.5%). Cumulative relapse incidence (RI) decreased from 64% to 50.7%, whereas graft-versus-host disease and non-relapse mortality (NRM) remained unchanged. In multivariable analysis, later period of alloSCT2 was associated with improved OS/LFS (HR = 0.47/0.53) and reduced RI (HR = 0.44). Beyond, remission duration, disease stage and patient performance score were factors for OS, LFS, RI, and NRM. Myeloablative conditioning for alloSCT2 decreased RI without increasing NRM, leading to improved OS/LFS. Haploidentical or unrelated donors and older age were associated with higher NRM and inferior OS. In summary, outcome after alloSCT2 has continuously improved over the last two decades despite increasing patient age. The identified factors provide clues for the optimized implementation of alloSCT2.

Transplant Eligible and Ineligible Elderly Patients with AML-A Genomic Approach and Next Generation Questions

The management of elderly patients diagnosed with acute myelogenous leukemia (AML) is complicated by high relapse risk and comorbidities that often preclude access to allogeneic hematopoietic cellular transplantation (allo-HCT). In recent years, fast-paced FDA drug approval has reshaped the therapeutic landscape, with modest, albeit promising improvement in survival. Still, AML outcomes in elderly patients remain unacceptably unfavorable highlighting the need for better understanding of disease biology and tailored strategies. In this review, we discuss recent modifications suggested by European Leukemia Network 2022 (ELN-2022) risk stratification and review recent aging cell biology advances with the discussion of four AML cases. While an older age, >60 years, does not constitute an absolute contraindication for allo-HCT, the careful patient selection based on a detailed and multidisciplinary risk stratification cannot be overemphasized.

A phase 1 trial of 8-chloro-adenosine in relapsed/refractory acute myeloid leukemia: An evaluation of safety and pharmacokinetics

BACKGROUND

This study evaluated the safety, pharmacokinetics (PK), and pharmacodynamics (PD) of 8-chloro-adenosine (8-Cl-Ado) in patients with relapsed/refractory acute myeloid leukemia (AML).

METHODS

8-Cl-Ado was administered daily for 5 days; the starting dose was 100 mg/m2 , the highest dose tested was 800 mg/m2 . The end points were toxicity, disease response, and PK/PD measurements.

RESULTS

The predominant nonhematologic toxicity was cardiac with grade ≥3 toxicity. Plasma PK in all patients suggested heterogeneity among patients, yet, some dose-dependency for the accumulation of 8-Cl-Ado. Two 8-Cl-Ado metabolites accumulated at similar levels to 8-Cl-Ado. Cellular PK in eight patients indicated accumulation of 8-Cl-ATP, which was associated with AML blast cytoreduction in peripheral blood. The authors determined the RP2D of 8-Cl-Ado to be 400 mg/m2 .

CONCLUSIONS

Given the cardiac adverse events observed, patients require monitoring for arrhythmias and QT interval during infusion. Although peripheral blood cytoreduction was observed, responses were transient, suggesting combination strategies will be required.

A genome-wide association study on hematopoietic stem cell transplantation reveals novel genomic loci associated with transplant outcomes

Introduction

Data on genomic susceptibility for adverse outcomes after hematopoietic stem cell transplantation (HSCT) for recipients are scarce.

Methods

We performed a genome wide association study (GWAS) to identify genes associated with survival/mortality, relapse, and severe graft-versus-host disease (sGvHD), fitting proportional hazard and subdistributional models to data of n=1,392 recipients of European ancestry from three centres.

Results

The single nucleotide polymorphism (SNP) rs17154454, intronic to the neuronal growth guidant semaphorin 3C gene (SEMA3C), was genome-wide significantly associated with event-free survival (p=7.0x10-8) and sGvHD (p=7.5x10-8). Further associations were detected for SNPs in the Paxillin gene (PXN) with death without prior relapse or sGvHD, as well as for SNPs of the Plasmacytoma Variant Translocation 1 gene (PVT1, a long non-coding RNA gene), the Melanocortin 5 Receptor (MC5R) gene and the WW Domain Containing Oxidoreductase gene (WWOX), all associated with the occurrence of sGvHD. Functional considerations support the observed associations.

Discussion

Thus, new genes were identified, potentially influencing the outcome of HSCT.

Hematopoietic cell transplantation (HCT) in MDS patients of older age

Hematopoietic cell transplantation (HCT) has evolved to an essential treatment in younger and more recently in elderly patients with myelodysplastic syndrome (MDS), the age group with the highest incidence. Less intense conditioning regimens and improvements in supportive therapy have reduced considerably transplant related mortality and in the same time increased the access to this curative treatment. Timing of HCT in the course of the disease assumes a crucial role. Detection of disease progression, geriatric assessment, comorbidity evaluation, and identification of transplant-specific risks are becoming increasingly important in this context. Novel statistical methods, molecular biomarkers, and quantification of tumor burden pre- and post-HCT will play an essential role in years to come. More effective and less toxic treatments to reduce the tumor burden before and/or after HCT are expected to improve the outcome. In this review article we discuss the current views and what we can expect.

Relapse of acute myeloid leukemia after allogeneic stem cell transplantation: immune escape mechanisms and current implications for therapy

Acute myeloid leukemia (AML) is a heterogeneous disease characterized by the expansion of immature myeloid cells in the bone marrow (BM) and peripheral blood (PB) resulting in failure of normal hematopoiesis and life-threating cytopenia. Allogeneic hematopoietic stem cell transplantation (allo-HCT) is an established therapy with curative potential. Nevertheless, post-transplant relapse is common and associated with poor prognosis, representing the major cause of death after allo-HCT. The occurrence of relapse after initially successful allo-HCT indicates that the donor immune system is first able to control the leukemia, which at a later stage develops evasion strategies to escape from immune surveillance. In this review we first provide a comprehensive overview of current knowledge regarding immune escape in AML after allo-HCT, including dysregulated HLA, alterations in immune checkpoints and changes leading to an immunosuppressive tumor microenvironment. In the second part, we draw the line from bench to bedside and elucidate to what extend immune escape mechanisms of relapsed AML are yet exploited in treatment strategies. Finally, we give an outlook how new emerging technologies could help to improve the therapy for these patients, and elucidate potential new treatment options.

Human CD34+-derived complete plasmacytoid and conventional dendritic cell vaccine effectively induces antigen-specific CD8+ T cell and NK cell responses in vitro and in vivo

Allogeneic stem cell transplantation (alloSCT) can be curative for hemato-oncology patients due to effective graft-versus-tumor immunity. However, relapse remains the major cause of treatment failure, emphasizing the need for adjuvant immunotherapies. In this regard, post-transplantation dendritic cell (DC) vaccination is a highly interesting strategy to boost graft-versus-tumor responses. Previously, we developed a clinically applicable protocol for simultaneous large-scale generation of end-stage blood DC subsets from donor-derived CD34+ stem cells, including conventional type 1 and 2 DCs (cDC1s and cDC2s), and plasmacytoid DCs (pDCs). In addition, the total cultured end-product (DC-complete vaccine), also contains non-end-stage-DCs (i.e. non-DCs). In this study, we aimed to dissect the phenotypic identity of these non-DCs and their potential immune modulatory functions on the potency of cDCs and pDCs in stimulating tumor-reactive CD8+ T and NK cell responses, in order to obtain rationale for clinical translation of our DC-complete vaccine. The non-DC compartment was heterogeneous and comprised of myeloid progenitors and (immature) granulocyte- and monocyte-like cells. Importantly, non-DCs potentiated toll-like receptor-induced DC maturation, as reflected by increased expression of co-stimulatory molecules and enhanced cDC-derived IL-12 and pDC-derived IFN-α production. Additionally, antigen-specific CD8+ T cells effectively expanded upon DC-complete vaccination in vitro and in vivo. This effect was strongly augmented by non-DCs in an antigen-independent manner. Moreover, non-DCs did not impair in vitro DC-mediated NK cell activation, degranulation nor cytotoxicity. Notably, in vivo i.p. DC-complete vaccination activated i.v. injected NK cells. Together, these data demonstrate that the non-DC compartment potentiates DC-mediated activation and expansion of antigen-specific CD8+ T cells and do not impair NK cell responses in vitro and in vivo. This underscores the rationale for further clinical translation of our CD34+-derived DC-complete vaccine in hemato-oncology patients post alloSCT.

Development of a novel pyroptosis-related LncRNA signature with multiple significance in acute myeloid leukemia

Background: Pyroptosis, a programmed cell death (PCD) with highly inflammatory form, has been recently found to be associated with the origin of hematopoietic malignancies. Long noncoding RNA (lncRNA) had emerged as an essential mediator to regulate gene expression and been involved in oncogenesis. However, the roles of pyroptosis-related lncRNA (PRlncRNA) in acute myeloid leukemia (AML) have not yet been completely clarified. Methods: We collected AML datasets from public databases to obtain PRlncRNA associated with survival and constructed a PRlncRNA signature using Lasso-Cox regression analysis. Subsequently, we employed RT-PCR to confirm its expression difference and internal training to further verify its reliability. Next, AML patients were classified into two subgroups by the median risk score. Finally, the differences between two groups in immune infiltration, enrichment analysis and drug sensitivity were further explored. Results: A PRlncRNA signature and an effective nomogram combined with clinicopathological variables to predict the prognosis of AML were constructed. The internal validations showed that the PRlncRNA risk score model was an accurate and productive indicator to predict the outcome of AML. Furthermore, this study indicated that higher inflammatory cell and immunosuppressive cells, and less sensitive to conventional chemotherapy drugs were highlighted in the high-risk group. Conclusion: Through comprehensive analysis of PRlncRNA model, our study may offer a valuable basis for future researches in targeting pyroptosis and tumor microenvironment (TME) and provide new measures for prevention and treatment in AML.

Prognostic factors of second hematopoietic allogeneic stem cell transplantation among hematological malignancy patients relapsed after first hematopoietic stem cell transplantation: A single center study

Introduction

We aimed to evaluate prognostic factors of a second allogeneic stem cell transplantation (allo-HSCT2) among hematological malignancy patients who have relapsed after the first allo-HSCT(allo-HSCT1).

Methods

We retrospectively analyzed 199 hematological malignancy patients who received allo-HSCT2 as a salvage treatment post allo-HSCT1 relapse between November 2012 and October 2021.

Results

The median age at allo-HSCT2 was 23 (range: 3-60) years. The median time to relapse after HSCT1 was 9 (range: 1-72) months. Prior to allo-HSCT2, patients had the following hematopoietic cell transplantation-comorbidity indexes (HCT-CI): 127 with a score of 0, 52 with a score of 1, and 20 with a score of 2 or greater. Fifty percent of patients received chimeric antigen receptor (CAR) T-cell therapy following HSCT1 relapse. Disease status was minimal residual disease (MRD)-negative complete remission (CR) among 119 patients, MRD-positive CR among 37 patients and non-remission (NR) for 43 patients prior to allo-HSCT2. Allo-HSCT2 was performed from a new donor in 194 patients (97.4%) and 134 patients (67.3%) received a graft with a new mismatched haplotype. The median follow-up time was 24 months (range: 6-98 months), and the 2-year OS and LFS were 43.8% ± 4.0% and 42.1% ± 4.1%, respectively. The 2-year cumulative incidence of relapse (CIR) and non-relapse mortality (NRM) was 30.0%±4.8% and 38.5%±3.8%, respectively. Cox regression multivariate analysis showed that disease statusof MRD-negative CR, HCT-CI score of 0 prior to allo-HSCT2, and new mismatched haplotype donor were predictive factors of improved OS and LFS compared to patients without these characteristics. Based on these three favorable factors, we developed a predictive scoring system for patients who received allo-HSCT2. Patients with a prognostic score of 3 who had the three factors showed a superior 2-year OS of 63.3% ± 6.7% and LFS of 63.3% ± 6.7% and a lower CIR of 5.5% ± 3.1% than patients with a prognostic score of 0. Allo-HSCT2 is feasible and patients with good prognostic features prior to allo-HSCT2 -disease status of CR/MRD- and HCT-CI score of 0 as well as a second donor with a new mismatched haplotype could have the maximal benefit from the second allo-HSCT.

Conclusions

Allo-HSCT2 is feasible and patients with good prognostic features prior to allo-HSCT2 -disease status of CR/MRD- and HCT-CI score of 0 as well as a second donor with a new mismatched haplotype could have the maximal benefit from the second allo-HSCT.

The mythological chimera and new era of relapse prediction post-transplant

Allogeneic hemopoietic stem cell transplantation is the treatment of choice for high-risk or relapsed acute leukemia. However, unfortunately, relapse post-transplant continues to be the most common cause of treatment failure with 20-80% of patients relapsing based on disease risk and status at transplant. Advances in molecular profiling of different hematological malignancies have enabled us to monitor low level disease before and after transplant and develop a more personalized approach to the management of these disease including early detection post-transplant. While, in general, detectable disease by morphology remains the gold standard to diagnosing relapse, multiple approaches have allowed detection of cancer cells earlier, using peripheral blood-based methods with sensitivities as high as 1:10⁶, together called minimal/measurable residual disease (MRD) detection. However, a in significant number of patients with acute leukemia where no such molecular markers exist it remains challenging to detect early relapse. In such patients who receive transplantation, chimerism monitoring remains the only option. An increase in mixed chimerism in post allogeneic HCT patients has been correlated with relapse in multiple studies. However, chimerism monitoring, while commonly accepted as a tool for assessing engraftment, has not been routinely used for relapse detection, at least in part because of the lack of standardized, high sensitivity, reliable methods for chimerism detection. In this paper, we review the various methods employed for MRD and chimerism detection post-transplant and discuss future trends in MRD and chimerism monitoring from the viewpoint of the practicing transplant physician.

Clinical and Cytogenetic Characterization of Early and Late Relapses in Patients Allografted for Myeloid Neoplasms with a Myelodysplastic Component

An improved understanding of relapse kinetics is required to optimize detection and treatment strategies for the post-transplant relapse of myeloid neoplasms. Therefore, we retrospectively analyzed data from 91 patients allografted for MDS (n = 54), AML-MRC (n = 29) and chronic myelomonocytic leukemia (CMML, n = 8), who relapsed after transplant. Patients with early (<12 months, n = 56) and late relapse (>12 months, n = 35) were compared regarding patient-, disease- and transplant-related factors, including karyotype analyses at diagnosis and relapse. After a median follow-up of 17.4 months after relapse, late relapses showed improved outcomes compared with early relapses (2-yr OS 67% vs. 32%, p = 0.0048). Comparing frequency of distinct patient-, disease- and transplant-related factors among early and late relapses, complex karyotype (p = 0.0004) and unfavorable disease risk at diagnosis (p = 0.0008) as well as clonal evolution at relapse (p = 0.03) were more common in early than in late relapses. Furthermore, patients receiving transplant without prior cytoreduction or in complete remission were more frequently present in the group of late relapses. These data suggest that cytogenetics rather than disease burden at diagnosis and transplant-related factors determine the timepoint of post-transplant relapse and that upfront transplantation may be favored in order to delay relapse.

Can GCSF-stimulated donor lymphocyte infusions improve outcomes for relapsed disease following allogeneic hematopoietic cell transplantation? A systematic review and meta-analysis

Donor lymphocyte infusions (DLI) can produce graft-versus tumor effects to treat relapse after allogeneic hematopoietic cell transplantation, however, durable responses remain uncommon. A systematic review and meta-analysis are needed to clarify whether DLI collected after stimulation with granulocyte colony-stimulating factor (GCSF; G-DLI) can improve clinical outcomes. Sixteen studies (4 controlled) involving 585 patients were identified in a systematic search up to 17 September 2020. A meta-analysis demonstrated no significant difference in the risk of all-cause mortality (RR: 0.94, 95% CI 0.52-1.68, p = 0.82; n = 3 studies) or relapse-related mortality (RR: 0.72, 0.44-1.18, p = 0.19; n = 3 studies) between G-DLI and conventional DLI (C-DLI) groups. G-DLI products had similar mean CD3+ cells compared to C-DLI products, but median CD34+ cells/kg were increased. No improvement in disease progression, complete response rates, or risk of developing GVHD was observed with G-DLI, however, greater non-relapse mortality was observed compared to C-DLI. Alternative approaches to enhancing graft-versus-tumor effects are needed.

Role of NK cells in cord blood transplantation and their enhancement by the missing ligand effect of the killer-immunoglobulin like receptor

Natural killer (NK) cells are the first lymphocytes reconstituted after allogenic hematopoietic stem cell transplantation (HSCT). Especially, in cord blood transplantation (CBT), the increase in the number of NK cells is sustained for a long period. Although there are conflicting results, many studies show that early reconstitution of NK cells is associated with favorable CBT outcomes, suggesting that maximizing NK cell functions could improve the CBT outcome. Killer immunoglobulin-like receptors (KIRs) include inhibitory and stimulatory receptors, which can regulate NK-cell activity. Because some of the KIRs have HLA class I as their ligand, the KIR—ligand interaction on NK cells can be lost in some cases of CBT, which results in the activation of NK cells and alters HSCT outcome. Thus, effects of KIR–ligand mismatch under various conditions have been widely examined; however, the results have been controversial. Among such studies, those using the largest number of CBTs showed that HLA—C2 (KIR2DL1—ligand) mismatches have a favorable effect on the relapse rate and overall survival only when the CBT used methotrexate for graft-versus-host disease prophylaxis. Another study suggested that KIR—ligand mismatch is involved in reducing the relapse of acute myeloid leukemia, mediated by reactivation of cytomegalovirus. These results indicate that activation of NK cells by KIR—ligand mismatch may have favorable effects on CBT outcomes and could help enhance the NK-cell function.

Day +60 WT1 assessment on CD34 selected bone marrow better predicts relapse and mortality after allogeneic stem cell transplantation in acute myeloid leukemia patients

The aim of this study was to evaluate the role of WT1 expression after allogeneic stem cell transplantation (alloHSCT) in patients with acute myeloid leukemia (AML). We studied WT1 expression in bone marrow cells from 50 patients in complete remission on day +60 after transplant. WT1 was assessed on unfractionated bone marrow mononuclear cells (MNC) and on CD34+ selected cells (CD34+). A ROC curve analysis identified 800 WT1 copies on CD34+ selected cells, as the best cut-off predicting relapse (AUC 0.842, p=0.0006, 85.7% sensitivity and 81.6% specificity) and 100 copies in MNC (AUC 0.819, p=0.007, 83.3% sensitivity and 88.2% specificity). Using the 800 WT1 copy cut off in CD34+ cells, the 2 year cumulative incidence of relapse was 12% vs 38% (p=0.005), and 2 year survival 88% vs 55% (p=0.02). Using the 100 WT1 copy cut off in unfractionated MNC, the 2 year cumulative incidence of relapse 13% vs 44% (p=0.01) and the 2 year survival 88% vs 55% (p=0.08). In a multivariate Cox analysis WT1 expression in CD34 cells proved to highly predictive of relapse (p=0.004); also WT1 expression on unfractionated cells predicted relapse (p=0.03). In conclusion, day-60 WT1 expression after allogeneic HSCT is a significant predictor of relapse, particularly when tested on CD34+ selected bone marrow cells.

Relapse after allogeneic hematopoietic stem cell transplantation in acute myeloid leukemia: an overview of prevention and treatment

Despite therapeutic progress in acute myeloid leukemia (AML), relapse post-allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains a major challenge. Here, we aim to provide an overview of prevention and treatment of relapse in this population, including cell-based and pharmacologic options. Post-transplant maintenance therapy is used in patients who have undetectable measurable residual disease (MRD), while pre-emptive treatment is administered upon detection of MRD. Prompt transfusion of prophylactic donor lymphocyte infusion (DLI) was found to be effective in preventing relapse and overcoming the negative impact of detectable MRD. In addition, patients with persistent targetable mutations can benefit from targeted post-transplant pharmacological interventions. IDH inhibitors have shown promising results in relapsed/refractory AML. Hypomethylating agents, such as decitabine and azacitidine, have been studied in the post-allo-HSCT setting, both as pre-emptive and prophylactic. Venetoclax has been shown effective in combination with hypomethylating agents or low-dose cytarabine in patients with newly diagnosed AML, especially those unfit for intensive chemotherapy. FLT3 inhibitors, the topic of another section in this review series, have significantly improved survival in FLT-3-ITD mutant AML. The role of other cell-based therapies, including CAR-T cells, in AML is currently being investigated.

mRNA-based therapeutics: powerful and versatile tools to combat diseases

The therapeutic use of messenger RNA (mRNA) has fueled great hope to combat a wide range of incurable diseases. Recent rapid advances in biotechnology and molecular medicine have enabled the production of almost any functional protein/peptide in the human body by introducing mRNA as a vaccine or therapeutic agent. This represents a rising precision medicine field with great promise for preventing and treating many intractable or genetic diseases. In addition, in vitro transcribed mRNA has achieved programmed production, which is more effective, faster in design and production, as well as more flexible and cost-effective than conventional approaches that may offer. Based on these extraordinary advantages, mRNA vaccines have the characteristics of the swiftest response to large-scale outbreaks of infectious diseases, such as the currently devastating pandemic COVID-19. It has always been the scientists’ desire to improve the stability, immunogenicity, translation efficiency, and delivery system to achieve efficient and safe delivery of mRNA. Excitingly, these scientific dreams have gradually been realized with the rapid, amazing achievements of molecular biology, RNA technology, vaccinology, and nanotechnology. In this review, we comprehensively describe mRNA-based therapeutics, including their principles, manufacture, application, effects, and shortcomings. We also highlight the importance of mRNA optimization and delivery systems in successful mRNA therapeutics and discuss the key challenges and opportunities in developing these tools into powerful and versatile tools to combat many genetic, infectious, cancer, and other refractory diseases.

Comparison of Outcomes After Second Allogeneic Hematopoietic Cell Transplantation Versus Donor Lymphocyte Infusion in Allogeneic Hematopoietic Cell Transplant Patients

BACKGROUND

Allogeneic hematopoietic cell transplantation (HCT) is potentially curative for hematological disease however can be complicated by relapse or graft failure (GF), for which second-HCT and donor lymphocyte infusions (DLI) are performed. This study aimed to compare outcomes following the two interventions.

METHODS

We retrospectively investigated 89 patients with relapse or GF after first-HCT, 50 (56%) underwent second HCT and 39 (44%) received (DLI), from June 2011 to September 2020.

RESULTS

Median age at intervention was 55 years (19-72). Second-HCT was performed for relapse in 19 patients and for GF in 31 patients (primary GF in 11 and secondary in 20 patients), same donor was used in 25 (50%) patients. DLI was performed for relapse in 20 and for secondary GF in 19 patients. Median number of DLI administered was 2 (range 1-11). Univariate analysis demonstrated 2 year overall survival (OS) for second-HCT was superior when performed for relapse (65%) compared to GF (44%) (P = .03). For DLI patients, 2 year OS was 49% for GF and 45% for relapse patients (P = .49). For relapse as an indication, second-HCT demonstrated borderline superiority compared to DLI (P = .07). Multivariable analysis demonstrated for OS for the entire cohort demonstrated donor mismatch (HR 0.50, 95% CI 0.26%-0.94%, P = .03), KPS at time of intervention (HR 2.10, 95% CI 1.14%-3.85%, P = .02) and time from first-HCT to intervention (HR 0.51, 95% CI 0.28%-0.93%, P = .03) as significant variables.

CONCLUSION

Second-HCT may improve outcomes when performed for relapse post-transplant if patients achieve remission again, while DLI may be reserved for patients with active disease.

CombiFlow: combinatorial AML-specific plasma membrane expression profiles allow longitudinal tracking of clones

Acute myeloid leukemia (AML) often presents as an oligoclonal disease whereby multiple genetically distinct subclones can coexist within patients. Differences in signaling and drug sensitivity of such subclones complicate treatment and warrant tools to identify them and track disease progression. We previously identified >50 AML-specific plasma membrane (PM) proteins, and 7 of these (CD82, CD97, FLT3, IL1RAP, TIM3, CD25, and CD123) were implemented in routine diagnostics in patients with AML (n = 256) and myelodysplastic syndrome (n = 33). We developed a pipeline termed CombiFlow in which expression data of multiple PM markers is merged, allowing a principal component-based analysis to identify distinctive marker expression profiles and to generate single-cell t-distributed stochastic neighbor embedding landscapes to longitudinally track clonal evolution. Positivity for one or more of the markers after 2 courses of intensive chemotherapy predicted a shorter relapse-free survival, supporting a role for these markers in measurable residual disease (MRD) detection. CombiFlow also allowed the tracking of clonal evolution in paired diagnosis and relapse samples. Extending the panel to 36 AML-specific markers further refined the CombiFlow pipeline. In conclusion, CombiFlow provides a valuable tool in the diagnosis, MRD detection, clonal tracking, and understanding of clonal heterogeneity in AML.

Case Report: Preemptive Treatment With Low-Dose PD-1 Blockade and Azacitidine for Molecular Relapsed Acute Myeloid Leukemia With RUNX1-RUNX1T1 After Allogeneic Hematopoietic Stem Cell Transplantation

Acute myeloid leukemia (AML) patients who develop hematological relapse (HR) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) generally have dismal clinical outcomes. Measurable residual disease (MRD)-directed preemptive interventions are effective approaches to prevent disease progression and improve prognosis for molecular relapsed patients with warning signs of impending HR. In this situation, boosting the graft-vs-leukemia (GVL) effect with immune checkpoint inhibitors (ICIs) might be a promising prevention strategy, despite the potential for causing severe graft-vs-host disease (GVHD). In the present study, we reported for the first time an AML patient with RUNX1-RUNX1T1 who underwent preemptive treatment with the combined application of tislelizumab (an anti-PD-1 antibody) and azacitidine to avoid HR following allo-HSCT. On day +81, molecular relapse with MRD depicted by RUNX1-RUN1T1-positivity as well as mixed donor chimerism occurred in the patient. On day +95, with no signs of GVHD and an excellent eastern cooperative oncology group performance status (ECOG PS), the patient thus was administered with 100 mg of tislelizumab on day 1 and 100 mg of azacitidine on days 1-7. After the combination therapy, complete remission was successfully achieved with significant improvement in hematologic response, and the MRD marker RUNX1-RUNX1T1 turned negative, along with a complete donor chimerism in bone marrow. Meanwhile, the patient experienced moderate GVHD and immune-related adverse events (irAEs), successively involving the lung, liver, lower digestive tract and urinary system, which were well controlled by immunosuppressive therapies. As far as we know, this case is the first one to report the use of tislelizumab in combination with azacitidine to prevent post-transplant relapse in AML. In summary, the application of ICIs in MRD positive patients might be an attractive strategy for immune modulation in the future to reduce the incidence of HR in the post-transplant setting, but safer clinical application schedules need to be explored.

Prognostic impact of chromosomal changes at relapse after allogeneic hematopoietic cell transplantation for acute myeloid leukemia or myelodysplastic syndrome

Chromosome analysis is a powerful prognostic tool in myeloid malignancies. Recipients who experience relapse after allogeneic hematopoietic cell transplantation (allo-HCT) often show chromosomal changes between diagnosis and relapse. However, the clinical impact of chromosomal changes and the efficacy of post-relapse treatment according to chromosomal changes have not been fully investigated. We retrospectively analyzed 72 recipients who had experienced relapse after allo-HCT for acute myeloid leukemia or myelodysplastic syndrome. We categorized them into two groups: with or without clonal chromosomal changes at relapse after allo-HCT. Post-relapse survival was shorter in the clonal chromosomal change group (median 117 days vs 275 days, P = 0.019). Moreover, acquisition of chromosome 7 abnormality or complex changes tended to be associated with inferior survival in a univariate analysis (median 92 days vs median 173 days, P = 0.043), and this adverse impact was confirmed in a multivariate analysis (hazard ratio 2.07, P = 0.024). The patterns of chromosomal changes from diagnosis to relapse after allo-HCT were heterogenous, and further investigations are required to clarify the effect of individual chromosomal changes.

Acute myeloid leukemia relapse after allogeneic hematopoietic stem cell transplantation: a retrospective study from a single institution

Objective

The outcomes of patients with acute myeloid leukemia (AML) who relapse after allogeneic hematopoietic stem cell transplantation (allo-HSCT) are poor. However, the risk factors for relapse in this context remain unclear.

Methods

We retrospectively assessed 84 consecutive adult AML patients who underwent allo-HSCT and achieved complete remission (CR). These patients were dichotomized into non-relapse (n = 58) and relapse (n = 26) groups, and the cumulative relapse rates and associated risk factors were examined. We also examined the treatments for and outcomes of patients with AML relapse after allo-HSCT.

Results

Non-CR status before allo-HSCT and high-risk cytogenetics were significant risk factors for AML relapse in univariate analysis, and non-CR status was also identified as a risk factor in multivariate analysis. The cumulative AML relapse rates after allo-HSCT were significantly higher in patients with non-CR (70.0%) compared with patients with CR (25.6%). Only 2 of the 26 relapsed patients remained alive on the study-censored day.

Conclusions

Non-CR status before allo-HSCT was a significant risk factor for AML relapse after allo-HSCT. Patients with AML relapse after allo-HSCT had poor outcomes due to a lack of response to salvage remission-induction chemotherapy or treatment-related adverse events.

Effective Immunosurveillance After Allogeneic Hematopoietic Stem Cell Transplantation in Acute Myeloid Leukemia

The number of patients receiving allogeneic hematopoietic stem cell transplantation (alloHCT) has increased constantly over the last years due to advances in transplant technology development, supportive care, transplant safety, and donor availability. Currently, acute myeloid leukemia (AML) is the most frequent indication for alloHCT. However, disease relapse remains the main cause of therapy failure. Therefore, concepts of maintaining and, if necessary, reinforcing a strong graft-versus-leukemia (GvL) effect is crucial for the prognosis and long-term survival of the patients. Over the last decades, it has become evident that effective immunosurveillance after alloHCT is an entangled complex of donor-specific characteristics, leukemia-associated geno- and phenotypes, and acquired resistance mechanisms. Furthermore, adoption of effector cells such as natural killer (NK) cells, alloreactive and regulatory T-cells with their accompanying receptor repertoire, and cell–cell interactions driven by messenger molecules within the stem cell and the bone marrow niche have important impact. In this review of pre- and posttransplant elements and mechanisms of immunosurveillance, we highlight the most important mechanisms after alloHCT.

Differential effects of donor lymphocyte infusion upon treatment response and GVHD according to relapse level and donor sources in patients with myelodysplastic syndrome

INTRODUCTION

Donor lymphocyte infusion (DLI) is one of the effective options for post-transplant disease control of myelodysplastic syndrome (MDS). Its success or failure depends on the induction of antitumor immune reactions, durability of clinical responses, and severity of unwanted toxicities mainly from graft-versus-host disease (GVHD).

METHODS

By analyzing 61 patients receiving DLI for post-transplant MDS relapse, we assessed treatment outcomes and affecting factors, especially focusing on the level of relapse (hematological, molecular, and imminent relapse).

RESULTS

The response rate (42.1%, 36.4%, 72.7%), and overall survival (OS) at 2 years (27.8%, 45.5%, 70.1%) were different for each relapse level with imminent relapse group showing the most promising results. For OS, response to DLI or pre-DLI chemotherapy, and time to relapse were independent prognostic factors. Meanwhile, post-DLI GVHD and time to relapse were independently predictive for DLI response; post-DLI GVHD was predictive for DLI response, but not for OS, suggesting a potential detrimental impact of GVHD on survival. The incidence of GVHD and GVHD-related deaths were 37.7% and 10.0%, respectively, and CD3+ cell doses triggering GVHD tended to be lower in cases with haploidentical donor or imminent relapse.

CONCLUSION

Despite being limited by small number of cases and its retrospective nature, this study again demonstrated the therapeutic effects of DLI in relapsed MDS, and that earlier detection and intervention at lower level relapse might possibly be associated with better results. Furthermore, we propose that tailored cell dosing schedule based on relapse level and donor source may be helpful in minimizing fatal GVHD.

Bile acids regulate intestinal antigen presentation and reduce graft-versus-host disease without impairing the graft-versus-leukemia effect

Acute graft-versus-host disease (GvHD) causes significant mortality in patients undergoing allogeneic hematopoietic cell transplantation. Immunosuppressive treatment for GvHD can impair the beneficial graft-versus-leukemia effect and facilitate malignancy relapse. Therefore, novel approaches that protect and regenerate injured tissues without impeding the donor immune system are needed. Bile acids regulate multiple cellular processes and are in close contact with the intestinal epithelium, a major target of acute GvHD. Here, we found that the bile acid pool is reduced following GvHD induction in a preclinical model. We evaluated the efficacy of bile acids to protect the intestinal epithelium without reducing anti-tumor immunity. We observed that application of bile acids decreased cytokine-induced cell death in intestinal organoids and cell lines. Systemic prophylactic administration of tauroursodeoxycholic acid (TUDCA), the most potent compound in our in vitro studies, reduced GvHD severity in three different murine transplantation models. This effect was mediated by decreased activity of the antigen presentation machinery and subsequent prevention of apoptosis of the intestinal epithelium. Moreover, bile acid administration did not alter the bacterial composition in the intestine suggesting that its effects are cell-specific and independent of the microbiome. Treatment of human and murine leukemic cell lines with TUDCA did not interfere with the expression of antigen presentation-related molecules. Systemic T-cell expansion and especially their cytotoxic capacity against leukemic cells remained intact. This study establishes a role for bile acids in the prevention of acute GvHD without impairing the graft-versus-leukemia effect. In particular, we provide a scientific rationale for the systematic use of TUDCA in patients undergoing allogeneic hematopoietic cell transplantation.

Relapse after Allogeneic Stem Cell Transplantation of Acute Myelogenous Leukemia and Myelodysplastic Syndrome and the Importance of Second Cellular Therapy

Patients with acute myelogenous leukemia (AML) or myelodysplastic syndrome (MDS) who relapse after allogeneic hematopoietic cell transplantation (allo-HCT) generally have poor overall survival (OS). Interventions that result in improved OS after relapse are not well established. The efficacy of second cellular therapy and specific indications are matters of debate. This study was conducted to evaluate factors associated with postrelapse survival and the efficacy of a second course of cellular therapy. We retrospectively analyzed consecutive patients with AML and MDS who underwent a first allo-HCT between 2010 and 2017 at our center but subsequently relapsed. One hundred and four patients with AML and 44 patients with MDS were included (total n = 148). Bone marrow (BM) and peripheral blood stem cell grafts were either unmodified or T cell-depleted (TCD) by CD34⁺ selection ex vivo. Forty-five patients (30.4%) received a second cellular therapy after relapse, either a second allo-HCT (n = 28; 18.9%) or donor leukocyte infusion (DLI) (n = 17; 11.5%). The median age at transplantation was 60 years (range, 24 to 78 years). The median time to relapse (TTR) after transplantation was 6.5 months (range, 1 to 60.9 months), and the ensuing median OS was 6 months (95% confidence interval [CI], 4.8 to 8.9 months). In univariable analysis, longer TTR, relapse type (measurable residual disease versus morphologic), relapse occurring in the most recent years, and receipt of cellular therapy after relapse were associated with better outcomes, whereas adverse cytogenetics and/or abnormality of TP53, as well as NPM1 mutation in patients with AML, were associated with adverse outcomes. Relapse type, year of relapse, and a variable resulting from the combination of TTR and receipt of second cellular therapy remained significantly associated with postrelapse survival in multivariable analysis. In a separate multivariable model, adjusted only for TTR, relapse type, and receipt of second cellular therapy, an adverse effect of NPM1 mutation on survival was confirmed. We could not show an effect of post-transplantation maintenance on survival after relapse. In both univariable and multivariable analysis, we found a positive association for second cellular therapy with survival after relapse in patients who relapsed early (<6 months) after allo-HCT and a similar trend in patients who relapsed late (>12 months) after transplantation. Two-year OS after a second cellular therapy was 44.9% (95% CI, 28.5% to 61.4%), and it was significantly better in patients with <5% BM blasts before cell infusion. We could not show different effects on survival after second cellular therapy for DLI versus second allo-HCT in univariable analysis. Survival after relapse is improving over time, but this remains a challenging event, especially for patients who relapse early after transplantation. We found that a second cellular therapy could offer a benefit even in these cases. Nonetheless, more research is needed to clarify the most appropriate treatment choices after relapse. These are probably driven by underlying genetic and immunologic conditions, which should be the focus of future studies.

Outcomes of pediatric patients who relapse after first HCT for acute leukemia or MDS

Disease relapse remains a major cause of treatment failure in patients receiving allogeneic hematopoietic cell transplantation (alloHCT) for high-risk acute leukemias or myelodysplastic syndromes (MDS). Comprehensive data on outcomes after post-transplant relapse are lacking, especially in pediatric patients. Our objective was to assess the impact of various transplant-, patient-, and disease-related variables on survival and outcomes in patients who relapse after alloHCT. We describe our institutional experience with 221 pediatric patients who experienced disease relapse after their first alloHCT for acute leukemias or MDS between 1990 and 2018. In a multivariable model, being in first complete remission at first alloHCT, longer duration of remission after alloHCT, experiencing GVHD and receiving a transplant in a more recent time period were significantly associated with a higher likelihood of receiving a second alloHCT after post-transplant relapse. Of these variables, only longer interval from alloHCT to relapse, receiving a second alloHCT or DLI, and receiving a transplant in a more recent time period were associated with improved overall survival. Our data support pursuing second alloHCT for patients who have experienced relapse after their first transplant, as that remains the only salvage modality with a reasonable chance of inducing long-term remission.

Azacitidine and prophylactic donor lymphocyte infusions after hematopoietic stem cell transplantation for pediatric high-risk acute myeloid leukemia

Post-hematopoietic stem cell transplantation (HSCT) maintenance therapy using azacitidine and prophylactic donor lymphocyte infusions (DLI) was implemented for high-risk acute myeloid leukemia. Azacitidine was started on day +60 as a 5 day course every 28 days for 6 cycles. DLI was given every 6 weeks for 3 doses starting after day +120. Ten patients were treated on this protocol. With a 90% one-year disease free survival, we report this post-HSCT maintenance therapy is feasible, safe, and well tolerated.

Post-transplantation cyclophosphamide reduces the incidence of acute graft-versus-host disease in patients with acute myeloid leukemia/myelodysplastic syndromes who receive immune checkpoint inhibitors after allogeneic hematopoietic stem cell transplantation

Background

Immune checkpoint inhibitors (ICIs) are being used after allogeneic hematopoietic stem cell transplantation (alloHCT) to reverse immune dysfunction. However, a major concern for the use of ICIs after alloHCT is the increased risk of graft-versus-host disease (GVHD). We analyzed the association between GVHD prophylaxis and frequency of GVHD in patients who had received ICI therapy after alloHCT.

Methods

A retrospective study was performed in 21 patients with acute myeloid leukemia (n=16) or myelodysplastic syndromes (n=5) who were treated with antiprogrammed cell death protein 1 (16 patients) or anticytotoxic T lymphocyte-associated antigen 4 (5 patients) therapy for disease relapse after alloHCT. Associations between the type of GVHD prophylaxis and incidence of GVHD were analyzed.

Results

Four patients (19%) developed acute GVHD. The incidence of acute GVHD was associated only with the type of post-transplantation GVHD prophylaxis; none of the other variables included (stem cell source, donor type, age at alloHCT, conditioning regimen and prior history of GVHD) were associated with the frequency of acute GVHD. Twelve patients received post-transplantation cyclophosphamide (PTCy) for GVHD prophylaxis. Patients who received PTCy had a significantly shorter median time to initiation of ICI therapy after alloHCT compared with patients who did not receive PTCy (median 5.1 months compared with 26.6 months). Despite early ICI therapy initiation, patients who received PTCy had a lower observed cumulative incidence of grades 2–4 acute GVHD compared with patients who did not receive PTCy (16% compared with 22%; p=0.7). After controlling for comorbidities and time from alloHCT to ICI therapy initiation, the analysis showed that PTCy was associated with a 90% reduced risk of acute GVHD (HR 0.1, 95% CI 0.02 to 0.6, p=0.01).

Conclusions

ICI therapy for relapsed acute myeloid leukemia/myelodysplastic syndromes after alloHCT may be a safe and feasible option. PTCy appears to decrease the incidence of acute GVHD in this cohort of patients.

Feasibility and Outcomes of a Third Allogeneic Hematopoietic Stem Cell Transplantation: A Retrospective Analysis from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Few therapeutic options are available for patients with acute myeloid or lymphoblastic leukemia (AML/ALL) relapsing after a second allogeneic stem cell transplantation (alloSCT2). In selected patients a third allogeneic stem cell transplantation (alloSCT3) has been used, but no detailed analysis is available so far. The European Society for Blood and Marrow Transplantation (EBMT) registry was screened for patients with acute leukemia (AL) receiving alloSCT3 from an identical or alternative donor to treat AL in either haematological relapse or disease persistence after alloSCT2 between 2001 and 2018. Feasibility, efficacy, outcome, and risk factors of this approach were analyzed retrospectively. Forty-five patients (median age, 37 years, range 12-71) with AML (n=34) or ALL (n=11) were identified. Eleven patients received alloSCT3 in complete remission (CR), 34 had active disease. Fifteen patients were transplanted from the same donor at all three transplants, 30 patients had at least 2 different donors. Between alloSCT2 and alloSCT3, the donor was changed in 25 patients. After alloSCT3, 38 patients engrafted, and 26 achieved CR or CR with incomplete hematological reconstitution (CRi). Acute graft-versus-host disease (GvHD) grade II-IV was observed in 19%, chronic GvHD occurred in 13%. After 1-year, cumulative incidences of leukemia relapse and non-relapse mortality were 47% and 42%, respectively. Median progression free and overall survival (PFS/OS) from alloSCT3 were 2.5 and 4 months, respectively, 1-year PFS and OS were 11% and 20%,. Outcome was improved in patients with at least one donor change (1-year PFS/OS: 17%/30%), further factors for better outcome included an unrelated donor for alloSCT3, Karnofsky performance score >80, and more recent year of alloSCT3. Only patients with AML achieved >1 year OS. In conclusion, results after a third alloSCT are poor, limiting this procedure to few, highly selected patients. Recurrent relapses of acute leukemia after alloSCT remain an unmet therapeutic need.

Make Your Cake and Eat It: Refueling of Immune Fitness in AML Post Allo-HCT Using Baking Soda

Although there has been a recent renaissance in the availability of new therapeutic options for patients with acute myeloid leukemia (AML), survival rates remain low coupled with a high incidence of relapse. Enhancing T cell and immune function has become an effective therapeutic approach in hematological malignancies. However, AML cells can modulate the bone marrow microenvironment by changing extracellular nutrient and biochemical availability which can metabolically regulate immune function. Here we review the findings by Uhl et al. showing that T cell metabolism and function can be boosted by treatment with sodium bicarbonate to counteract the metabolic changes induced by lactic acid produced by leukemia cells.

Survival following relapse after allogeneic hematopoietic cell transplantation for acute leukemia and myelodysplastic syndromes in the contemporary era

OBJECTIVE/BACKGROUND

Relapse is the most common cause of treatment failure after allogeneic hematopoietic cell transplantation (alloHCT). No standard of care exists, and a wide range of treatments are used for post-alloHCT relapse. In the recent era, several novel therapies including targeted agents are available for acute lymphocytic leukemia (ALL), acute myeloid leukemia (AML), and myelodysplastic syndrome (MDS).

METHODS

We reviewed outcomes after alloHCT relapse, with or without use of these newer agents for ALL, AML, and MDS. In total, 115 adults with relapsed or refractory ALL (n = 17), AML (n = 67), and MDS (n = 31) at median 5 (range, 1-64) months after their first alloHCT in 2010-2018 were included.

RESULTS

Median follow-up was 19 (range, 6-80) months after relapse from alloHCT. Targeted agents were given to 29 (25%) patients. In multivariable analysis, use of targeted agent at any time point after relapse was not associated with survival. Matched unrelated (vs. matched sibling; hazard ratio [HR] 1.70; p = .027) or haploidentical donor grafts (vs. matched sibling; HR 2.69; p = .003), presence of grade II-IV acute graft-versus-host disease before relapse (HR 2.46; p < .001), and less than 12 months from HCT to relapse (<6 vs. > 12 months; HR 6.34; p < .001; 6-12 vs. > 12 months; HR 3.16; p = .005) were adverse prognostic factors for post-relapse survival.

CONCLUSION

Outcomes after alloHCT relapse remain poor regardless of the novel agent use. Innovative treatment strategies are needed to improve outcomes after relapse post-alloHCT.

Treatment of myeloid malignancies relapsing after allogeneic hematopoietic stem cell transplantation with venetoclax and hypomethylating agents-a retrospective multicenter analysis on behalf of the German Cooperative Transplant Study Group

Treatment of relapse after allogeneic hematopoietic stem cell transplantation (alloHSCT) remains a great challenge. Aiming to evaluate the combination of venetoclax and hypomethylating agents (HMAClax) for the treatment of relapse of myeloid malignancies after alloHSCT, we retrospectively collected data from 32 patients treated at 11 German centers. Venetoclax was applied with azacitidine (n = 13) or decitabine (n = 19); 11 patients received DLI in addition. HMAClax was the first salvage therapy in 8 patients. The median number of cycles per patient was 2 (1–19). All but 1 patient had grade 3/4 neutropenia. Hospital admission for grade 3/4 infections was necessary in 23 patients (72%); 5 of these were fatal. In 30 evaluable patients, overall response rate (ORR) was 47% (14/30, 3 CR MRD^neg, 5 CR, 2 CRi, 1 MLFS, 3 PR). ORR was 86% in first salvage patients versus 35% in later salvage patients (p = 0.03). In 6 patients with molecular relapse (MR), ORR was 67% versus 42% in patients with hematological relapse (HR) (n = 24, p = n.s.). After a median follow-up of 8.4 months, 25 patients (78%) had died and 7 were alive. Estimated median overall survival was 3.7 months. Median survival of patients with HMAClax for first versus later salvage therapy was 5.7 and 3.4 months (p = n.s.) and for patients with MR (not reached) compared to HR (3.4 months, p = 0.024). This retrospective case series shows that venetoclax is utilized in various different combinations, schedules, and doses. Toxicity is substantial and patients who receive venetoclax/HMA combinations for MR or as first salvage therapy derive the greatest benefit.

Low Level Donor Chimerism of CD19 CAR-T Cells Returned to Complete Donor Chimerism in Patients with Relapse After Allo-Hematopoietic Stem Cell Transplant

Purpose

To investigate the donor chimerism changes and curative effects associated with the use of autologous anti-CD19 chimeric antigen receptor (CAR) T cells with B-cell acute lymphoblastic leukemia (B-ALL) presenting with a low donor chimerism level and relapse after allogeneic hematopoietic stem cell transplant (allo-HSCT).

Methods

Nine patients with B-ALL showing low donor chimerism level and relapse after allo-HSCT were enrolled. Patients 1–3 received CD19 CAR-T cell therapy using cells derived from autologous peripheral blood mononuclear cells (PBMCs) (comprising a mixture of patient and original donor cells) as their donors could not provide PBMCs. Samples from the other six patients (Patients A–F) were investigated only in vitro. The changes in the degree of donor chimerism, function of the CD19 CAR-T cells and T cells in all nine patients were analyzed in vitro. The therapeutic effects and adverse events (AEs) were also evaluated in Patients 1–3.

Results

The CAR-T cells and T cells in all nine patients showed complete donor chimerism restoration following a 12-day culture period in vitro. These CD19 CAR-T cells demonstrated strong cytotoxicity towards Nalm 6 cells in vitro except in patients 3 and D. In the latter patients, the absolute numbers of all subsets, especially the CD8 + T-cell absolute numbers in peripheral blood were very low. Patients 3 and D showed relatively short durations from transplant to recurrence and received chemotherapy after relapse. In the patients receiving CD19 CAR-T cell therapy, the most commonly observed AE was grade 1 to 2 cytokine release syndrome. None of the cases showed acute graft-versus-host disease during treatment. Patients 1 and 2 achieved complete response with complete restoration of donor chimerism. Patient 3, who received the same CD19 CAR-T cell therapy, did not respond to this therapy.

Conclusion

CD19 CAR-T cells derived from patients relapsed after allo-HSCT with a low level of donor chimerism were effective for salvage therapy and could restore to complete donor chimerism after 12 days’ culture in vitro.

Trial Registration

Humanized CD19 CAR-T cell therapy for relapse or refractory B-cell lymphoma or acute B lymphocytic leukemia, ChiCTR1800019622, Registered 24 November 2018, http://www.chictr.org.cn/index.aspx.

Haploidentical transplants for patients with relapse after the first allograft

Relapse after allogeneic hematopoietic stem-cell transplantation (AHSCT) is associated with very poor outcomes. A second transplant offers the possibility of long-term disease control. We analyzed outcomes with haploidentical donors for second allograft at our institution. All consecutive patients with hematological malignancies (N = 29) who relapsed after AHSCT and underwent a haploidentical transplant (haploSCT) as second transplant between February 2009 and October 2018 were included. Median age was 36 years (interquartile range (IQR) 24-60); 83% of patients had high/very high disease risk index; 61% of AML/MDS patients had high-risk cytogenetics; and only 24% were in complete remission at transplant. With a median follow-up of 46.9 months, the 3-year relapse, non-relapse mortality (NRM), progression-free survival (PFS) and overall survival (OS) were 30%, 39%, 31% and 40%, respectively. In multivariable analysis (MVA), comorbidity index (HCT-CI) and detectable donor-specific anti-HLA antibodies (DSA) prior to second transplant were significantly associated with worse outcomes. Patients with HCT-CI <3 and without DSA had 3-year PFS and OS of 53% and 60.3%, respectively. Our findings suggest that haploSCT as second AHSCT is feasible and potentially curative. Lower HCT-CI and no DSA were associated with lower NRM and improved survival. Haploidentical grafts might be a preferred donor source for second AHSCT as these are high-risk patients who frequently need to proceed urgently to transplant.

Applications of PET in Diagnosis and Prognosis of Leukemia

As a malignant hematopoietic stem cell disease, leukemia remains life-threatening due to its increasing incidence rate and mortality rate. Therefore, its early diagnosis and treatment play a very important role. In the present work, we systematically reviewed the current applications and future directions of positron emission tomography (PET) in patients with leukemia, especially ¹⁸F-FDG PET/CT. As a useful imaging approach, PET significantly contributes to the diagnosis and treatment of different types of leukemia, especially in the evaluation of extramedullary infiltration, monitoring of leukemia relapse, detection of Richter’s transformation (RT), and assessment of the inflammatory activity associated with acute graft versus host disease. Future investigations should be focused on the potential of PET/CT in the prediction of clinical outcomes in patients with leukemia and the utility of novel radiotracers.

Hypomethylating agent-based post-transplant strategies to maximize the outcome of high-risk acute myeloid leukemia after allogeneic stem cell transplantation

INTRODUCTION

Clinical outcomes of patients diagnosed with high-risk acute myeloid leukemia (AML) are poor, and relapse or refractoriness is main cause of treatment failure, even in those who underwent standard allogeneic stem cell transplantation (allo-SCT). Therefore, innovative or additional approaches are necessary to overcome refractoriness to the graft-versus-leukemia (GVL) effect immediately after allo-SCT.

AREAS COVERED

Hypomethylating agents (HMA) present a feasible option that can be adopted during the post-transplant phase. Moreover, combination strategies based on HMA may induce a synergistic effect by promoting anti-leukemic effects that overcome residual leukemic burden, and it is a well-tolerated therapeutic option for high-risk disease. Relevant literatures published in the last 30 years were searched from PubMed to review the topic of AML, allo-SCT, and HMAs.

EXPERT OPINION

Post-transplant therapy is strongly needed to improve the outcomes of allogeneic transplantation for certain AML patients classified with high-risk disease. In that sense, prophylactic and preemptive HMAs are a promising additive therapy for allogeneic recipients.

PD-L1 siRNA-mediated silencing in acute myeloid leukemia enhances anti-leukemic T cell reactivity

Acute myeloid leukemia (AML) is an immune-susceptible malignancy, as demonstrated by its responsiveness to allogeneic stem cell transplantation (alloSCT). However, by employing inhibitory signaling pathways, including PD-1/PD-L1, leukemia cells suppress T cell-mediated immune attack. Notably, impressive clinical efficacy has been obtained with PD-1/PD-L1 blocking antibodies in cancer patients. Yet, these systemic treatments are often accompanied by severe toxicity, especially after alloSCT. Here, we investigated RNA interference technology as an alternative strategy to locally interfere with PD-1/PD-L1 signaling in AML. We demonstrated efficient siRNA-mediated PD-L1 silencing in HL-60 and patients' AML cells. Importantly, WT1-antigen T cell receptor⁺ PD-1⁺ 2D3 cells showed increased activation toward PD-L1 silenced WT1⁺ AML. Moreover, PD-L1 silenced AML cells significantly enhanced the activation, degranulation, and IFN-γ production of minor histocompatibility antigen-specific CD8⁺ T cells. Notably, PD-L1 silencing was equally effective as PD-1 antibody blockade. Together, our study demonstrates that PD-L1 silencing may be an effective strategy to augment AML immune-susceptibility. This provides rationale for further development of targeted approaches to locally interfere with immune escape mechanisms in AML, thereby minimizing severe toxicity. In combination with alloSCT and/or adoptive T cell transfer, this strategy could be very appealing to boost graft-versus-leukemia immunity and improve outcome in AML patients.