Relapse remains the worst life-threatening complications after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in patients with acute myeloid leukemia (AML), whose prognosis has been historically dismal. Given the rapid development of genomics and immunotherapies, the interference strategies for AML recurrence have been changing these years. More and more novel targeting agents that have received the U.S. Food and Drug Administration (FDA) approval for de novo AML treatment have been administrated in the salvage or maintenance therapy of post-HSCT relapse. Targeted strategies that regulate the immune microenvironment of and optimize the graft versus leukemia (GVL) effect of immune cells are gradually improved. Such agents not only have been proven to achieve clinical benefits from a single drug, but if combined with classic therapies, can significantly improve the poor prognosis of AML patients who relapse after allo-HSCT. This review will focus on currently available and promising upcoming agents and also discuss the challenges and limitations of targeted therapies in the allogeneic hematopoietic stem cell transplantation community.

Acute myeloid leukemia (AML) with KMT2A rearrangement (KMT2A-r) is associated with poor prognosis, but the benefit of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for KMT2A-r AML is unclear. We reviewed adult AML patients treated within the TROPHY group and identified 292 cases of KMT2A-r AML, 254 (87.0%) of whom achieved first complete remission (CR1) and 192 (75.6%) of CR1 patients underwent allo-HSCT. We show that allo-HSCT is an independent favorable prognostic factor in CR1 patients for both overall survival (OS) (hazard ratio [HR] = 0.56, 95% confidence interval [CI]: 0.45–0.69, P < 0.001) and cumulative incidence of relapse (CIR) (HR = 0.01, 95% CI: 0.005–0.04, P < 0.001). Among allo-HSCT recipients, survival outcomes were comparable between patients with KMT2A::MLLT3 and those with other 11q23/KMT2A rearrangements (3-year OS: 74.3% vs. 77.5%, P = 0.97; 3-year event-free survival [EFS]: 55.2% vs. 62.2%, P = 0.34; 3-year CIR: 24.4% vs. 20.8%, P = 0.32). Both multiparameter flow cytometry-based measurable residual disease (MFC-MRD) and KMT2A-r MRD determined by quantitative PCR prior to allo-HSCT were associated with worse transplant outcomes. Multivariable analysis identified detectable KMT2A-r MRD at allo-HSCT as a significant risk factor for reduced EFS (HR = 2.46, 95% CI: 1.32–4.60, P = 0.005). These findings confirm the survival benefit of allo-HSCT in adult patients with KMT2A-r AML and underscore the prognostic value of KMT2A-r MRD prior to transplantation.

Background: Primary bone B-cell lymphoma (PB-DLBCL) is a rare entity for which existing data is limited. Whether radiotherapy (RT) should be omitted in the modern treatment of PB-DLBCL is still under debate. We used the SEER database to compare the outcomes among adult patients treated with and without RT in rituximab era. Methods: We included adult patients with PB-DLBCL diagnosed from 2002 to 2016 from SEER 18. The effect of RT on overall survival (OS) using univariate (UVA) and multivariate (MVA) Cox proportional regression and propensity score matching (PSM) was assessed for the entire cohort and subgroups by stages. We calculated the standardized incidence ratio to estimate the short- and long-term risk for second primary malignancies (SPM) from 2002 to 2016 in SEER 18 and 1983–2016 in SEER 9. Results: A total of 1,320 patients were identified, including 856 with early-stage (ES) and 464 with advanced-stage (AS). A decreasing trend was observed in the ES cohort after 2002, while the rate of RT utilization remained stable in the AS cohort over the past three decades. Most patients in ES (63.9%) underwent RT, whereas only 42.2% of AS patients received it. RT significantly improved survival both in UVA and MVA (P < 0.001, P = 0.010, respectively). PSM analysis further validated the survival advantage of RT (P = 0.018). Moreover, a novel web-based prediction model was established to individualize the potential benefit from RT. In subgroup analyses, OS was improved with RT in those who had ES disease (p < 0.001) but not in those who had AS disease (P = 0.776). With short-term follow up in SEER 18, none of the subgroups showed a significantly elevated risk of developing SPMs. However, RT significantly elevated the late toxicities of second malignancies in ES patients diagnosed at the age of 18–39 or those with appendicular sites of bone involvement. Conclusion: This population-based analysis is the largest PB-DLBCL dataset to date and demonstrates a significant survival benefit associated with RT in early stages rather than advanced stages. In the absence of randomized controlled trials, RT should be considered in ES disease with cautions of second cancers in specific subsets of patients.

Currently, the graft-versus-host disease (GVHD) prophylaxis consists of an immunosuppressive therapy mainly based on antithymocyte globulin (ATG) or post-transplant cyclophosphamide (PTCy). GVHD remains a major complication and limitation to successful allogeneic haploidentical hematopoietic stem cell transplantation (haplo‐HSCT). We modified the ATG-based GVHD prophylaxis with the addition of basiliximab in the setting of haplo-HSCT and attempted to explore the appropriate dosages. We conducted a retrospective analysis of 239 patients with intermediate- or high-risk hematologic malignancies who received haplo-HSCT with unmanipulated peripheral blood stem cells combined or not with bone marrow. All patients received the same GVHD prophylaxis consisting of the combination of methotrexate, cyclosporine or tacrolimus, mycofenolate-mofetil, and basiliximab with different doses of ATG (5-9mg/kg). With a median time of 11 days (range, 7-40 days), the rate of neutrophil engraftment was 96.65%. The 100-day cumulative incidences (CIs) of grade II–IV and III–IV aGVHD were 15.8 ± 2.5% and 5.0 ± 1.5%, while the 2-year CIs of total cGVHD and extensive cGVHD were 9.8 ± 2.2% and 4.1 ± 1.5%, respectively. The 3-year CIs of treatment-related mortality (TRM), relapse, overall survival (OS), and disease-free survival (DFS) were 14.6 ± 2.6%, 28.1 ± 3.4%, 60.9 ± 3.4%, 57.3 ± 3.4%, respectively. Furthermore, the impact of the reduction of the ATG dose to 6 mg/kg or less in combination with basiliximab on GVHD prevention and transplant outcomes among patients was analyzed. Compared to higher dose of ATG(>6mg/kg), lower dose of ATG (≤6mg/kg) was associated with a significant reduced risk of CMV viremia (52.38% vs 79.35%, P<0.001), while the incidences of aGVHD and cGVHD were similar between the two dose levels. No significant effect was found with regard to the risk of relapse, TRM, and OS. ATG combined with basiliximab could prevent GVHD efficiently and safely. The optimal scheme of using this combined regimen of ATG and basiliximab is that administration of lower dose ATG (≤6mg/kg), which seems to be more appropriate for balancing infection control and GVHD prophylaxis.

Metabolic reprogramming is a key focus of targeted therapies in acute myeloid leukemia (AML). The mitochondrial sirtuin SIRT5 removes succinyl groups from specific lysines and impacts cell metabolism, but its role in AML tumorigenesis has not been extensively explored. A recent study highlighted that SIRT5 regulates AML cell activity by modulating glutamine metabolism, but its molecular targets in AML remain unclear. This study aims to identify the substrates of SIRT5 in AML. It was found that a total of 83 proteins with 121 lysine (K) residues showed increased succinylation after SIRT5 knockdown, as determined by succinylome analysis of MOLM-13 cells. SIRT5 was validated to interact with HADHA, a key molecule in the fatty acid oxidation pathway. Knockdown of SIRT5 resulted in hypersuccinylation and reduced enzymatic activity of HADHA. Mimetic mutations of lysine indicated that SIRT5 desuccinylates HADHA at K644. Inhibiting SIRT5 or HADHA increased sensitivity to venetoclax (VEN) in both VEN-sensitive and VEN-resistant cell lines. SIRT5 knockdown enhanced VEN-mediated suppression of mitochondrial metabolism and improved the survival of AML-transplanted NSG mice when combined with VEN. This study reveals the role of SIRT5 in AML metabolic regulation and provides valuable insights for developing SIRT5-targeted drugs and combination therapies with metabolic inhibitors.

Background: Metabolic reprogramming is the core characteristic of tumors during the development of tumors, and cancer cells can rely on metabolic changes to support their rapid growth. Nevertheless, an overall analysis of metabolic markers in acute myeloid leukemia (AML) is absent and urgently needed. Methods: Within this work, genetic expression, mutation data and clinical data of AML were queried from Genotype-Tissue Expression (GTEx) database, The Cancer Genome Atlas (TCGA) database and Gene Expression Omnibus (GEO) database. The tumor samples of TCGA were randomly divided into a training group (64 samples) and an internal validation group (64 samples) at one time, and the tumor samples of GEO served as two external validation groups (99 samples, 374 samples). According to the expression levels of survival-associated metabolic genes, we divided all TCGA tumor samples into high, medium and low metabolism groups, and evaluated the immune cell activity in the tumor microenvironment of the three metabolism groups by single-sample gene set enrichment analysis (ssGSEA) algorithm. Finally, we examined the mutations and prognostic effects of each model gene. Results: Four metabolism-related genes were screened and applied to construct a prognostic model for AML, giving excellent results. As for the area under the curve (AUC) value of receiver operating characteristic (ROC) curve, the training group was up to 0.902 (1-year), 0.81 (3-year), and 0.877 (5-year); and the internal and external validation groups also met the expected standards, showing high potency in predicting patient outcome. Univariate and multivariate prognostic analyses indicated that the riskScore obtained from our prognostic model was an independent prognostic factor. ssGSEA analysis revealed the high metabolism group had higher immune activity. Single and multiple gene survival analysis validated that each model gene had significant effects on the overall survival of AML patients. Conclusions: In our study, a high-efficiency prognostic prediction model was built and validated for AML patients. The results showed that metabolism-related genes could become potential prognostic biomarkers for AML.