Sorafenib Therapy Is Associated with Improved Outcomes for FMS-like Tyrosine Kinase 3 Internal Tandem Duplication Acute Myeloid Leukemia Relapsing after Allogeneic Hematopoietic Stem Cell Transplantation

Consensus on the monitoring, treatment, and prevention of leukaemia relapse after allogeneic haematopoietic stem cell transplantation in China: 2024 update

The consensus in 2018 from The Chinese Society of Haematology (CSH) on the monitoring, treatment, and prevention of leukaemia relapse after allogeneic haematopoietic stem cell transplantation (HSCT) facilitated the standardization of clinical practices in China and progressive integration with the world. To integrate recent developments and further improve the consensus, a panel of experts from the CSH recently updated the following consensus: (1) integrate risk-adapted, measurable residual disease (MRD)-guided strategy on modified donor lymphocyte infusion (DLI) and interferon-α into total therapy, which was pioneered and refined by Chinese researchers; (2) provide additional evidence of the superiority of haploidentical HSCT (the dominant donor source in China) to matched HSCT for high-risk populations, especially for pre-HSCT MRD-positive patients; (3) support the rapid progress of techniques for MRD detection, such as next-generation sequencing (NGS) and leukaemia stem cell-based MRD detection; and (4) address the role of new targeted options in transplant settings. In conclusion, the establishment of a "total therapy" strategy represents a great step forward. We hope that the consensus updated by Chinese scholars will include the latest cutting-edge developments and inspire progress in post-HSCT relapse management.

[Preventing relapse of acute leukemias and myelodysplastic syndromes in post-allograft transplantation: Prophylactic and preemptive strategies (SFGM-TC)]

Disease relapse remains the first cause of mortality of hematological malignancies after allogeneic hematopoietic stem cell transplantation (allo-HCT) for acute myeloid and lymphoid leukemia (AML and ALL) and for myelodysplastic syndroms (MDS). More and more patients are eligible for allo-HCT over the years and for many of them, only reduced intensity conditioning is possible, which is associated with a higher risk of relapse. Knowledge and biotechnology allow us to better identify diseases at very high risk of relapse and to measure residual disease before allo-HCT. Planning post-transplant maintenance treatment as part of a prophylaxis strategy is now feasible. Monitoring biomarkers of residual disease and post-transplant chimerism after allo-HCT allows a preemptive strategy. Within the frame of the 14th annual workshops of the Francophone Society for Bone Marrow Transplantation and Cell Therapy, the working group reviewed the literature and discussed novel strategies and therapies used to prevent relapse post-allo-HCT. Innovative drugs have been developed recently. Their toxicity profile allows their use post-allo-HCT, albeit with precaution. We reviewed the use of FLT3 inhibitors for AML, BCR::ABL inhibitors for Philadelphia chromosome for ALL, hypomethylating agents and Bcl-2 inhibitors for AML and MDS. The indications of immunomodulation and infusion of donor lymphocytes have been reviewed. Finally, we outlined methods of follow-up and support for patients receiving these prophylactic treatments.

[Second allogeneic (update). Guidelines from the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC)]

Relapse after allogeneic hematopoietic cell transplantation (allo-HCT) remains a major concern because it is associated with poor survival. A second allo-HCT is a valid option in this situation. During the 13th annual harmonization workshops of the francophone Society of bone marrow transplantation and cellular therapy (SFGM-TC), a designated working group reviewed the literature in order to update the second allo-HCT recommendations elaborated during the previous workshop (2016). The main indication for a second allo-HCT remains relapse of initial hematologic malignancy. Disease status; complete remission (CR), and relapse time after the first allo-HCT>6 months impact positively the overall survival of patients after the second allo-HCT. Donor change is a valid option, particularly if there is HLA loss on leukemic cells after a first haploidentical or following a mismatched allo-HCT is documented. Reduced intensity conditioning is recommended, while a sequential protocol is a reasonable option in patients with proliferative disease. A post-transplant maintenance strategy after hematological recovery is recommended as soon as day 60, even if the immunosuppressive treatment has not yet been stopped. Hypomethylating agents, and targeted therapies such as anti FLT3, anti BCL2, anti-IDH1/2, TKI, anti-TP53, anti-CD33, anti-CD19, anti-CD22, anti-CD30, check point inhibitors, and CAR-T cells can be used as a bridge to transplant or as an alternative treatment to the second allo-HCT.

Sorafenib plus triplet therapy with venetoclax, azacitidine and homoharringtonine for refractory/relapsed acute myeloid leukemia with FLT3-ITD: A multicenter phase 2 study

BACKGROUND

Patients with relapsed or refractory acute myeloid leukemia (R/R AML) and FLT3-internal tandem duplication (FLT3-ITD) respond infrequently to salvage chemotherapy.

OBJECTIVE

To investigate the efficacy of sorafenib plus triplet therapy with venetoclax, azacitidine, and homoharringtonine (VAH) as a salvage therapy in this population.

METHODS

This multicenter, single-arm, phase 2 study was conducted at 12 hospitals across China. Eligible patients had R/R AML with FLT3-ITD (aged 18-65 years) who were treated with VAH. The primary endpoint was composite complete remission (CRc) after two cycles. Secondary outcomes included the overall response rate (ORR), safety, and survival.

RESULTS

Between July 9, 2020, and March 19, 2022, 58 patients were assessed for eligibility, 51 of whom were enrolled. The median patient age was 47 years (interquartile range [IQR] 31-57). CRc was 76.5% with ORR of 82.4%. At a median follow-up of 17.7 months (IQR, 8.7-24.7), the median duration of CRc was not reached (NR), overall survival was 18.1 months (95% confidence interval [CI], 11.8-NR) and event-free survival was 11.4 months (95% CI, 5.6-NR). Grade 3 or 4 adverse events occurring in ≥10% of patients included neutropenia in 47 (92.2%), thrombocytopenia in 41 (80.4%), anemia in 35 (68.6%), febrile neutropenia in 29 (56.9%), pneumonia in 13 (25.5%), and sepsis in 6 (11.8%) patients. Treatment-related death occurred in two (3.9%) patients.

CONCLUSIONS

The sorafenib plus VAH regimen was well tolerated and highly active against R/R AML with FLT3-ITD. This regimen may be a suitable therapeutic option for this population, but larger population trials are needed to be explored.

TRIAL REGISTRATION

Clinical Trials Registry: NCT04424147.

Novel Approaches to Treatment of Acute Myeloid Leukemia Relapse Post Allogeneic Stem Cell Transplantation

The management of patients with acute myeloid leukemia (AML) relapsed post allogeneic hematopoietic stem cell transplantation (HSCT) remains a clinical challenge. Intensive treatment approaches are limited by severe toxicities in the early post-transplantation period. Therefore, hypomethylating agents (HMAs) have become the standard therapeutic approach due to favorable tolerability. Moreover, HMAs serve as a backbone for additional anti-leukemic agents. Despite discordant results, the addition of donor lymphocytes infusions (DLI) generally granted improved outcomes with manageable GvHD incidence. The recent introduction of novel targeted drugs in AML gives the opportunity to add a third element to salvage regimens. Those patients harboring targetable mutations might benefit from IDH1/2 inhibitors Ivosidenib and Enasidenib as well as FLT3 inhibitors Sorafenib and Gilteritinib in combination with HMA and DLI. Conversely, patients lacking targetable mutations actually benefit from the addition of Venetoclax. A second HSCT remains a valid option, especially for fit patients and for those who achieve a complete disease response with salvage regimens. Overall, across studies, higher response rates and longer survival were observed in cases of pre-emptive intervention for molecular relapse. Future perspectives currently rely on the development of adoptive immunotherapeutic strategies mainly represented by CAR-T cells.

Impact of genetic patterns on sorafenib efficacy in patients with FLT3-ITD acute myeloid leukemia undergoing allogeneic hematopoietic stem cell transplantation: a multi-center, cohort study

Sorafenib therapy improves overall survival (OS) in patients with FLT3 internal tandem duplication (ITD) acute myeloid leukemia (AML) undergoing allogeneic hematopoietic stem cell transplantation. We explored the efficacy of sorafenib therapy in this population with different concomitant genetic patterns. In this multi-center, cohort study, we enrolled patients with FLT3-ITD AML undergoing allogenic hematopoietic cell transplantation. Patients with sorafenib maintenance post-transplantation for at least four weeks were allocated to the sorafenib group, and otherwise to the control group. Endpoints were OS, disease-free survival, and relapse for the whole cohort and OS for genetic pattern subgroups. Among 613 patients enrolled, 275 were in the sorafenib and 338 the control group. Median follow-up was 36.5 (interquartile range (IQR), 25.2-44.7) months post-transplantation. The 3-year OS post-transplantation was 79.6% (95% confidential interval (CI) 74.8%-84.6%) and 65.2% (95% CI 60.3%-70.6%) (Hazard ratio (HR) 0.50, 95% CI 0.37-0.69; P < 0.0001) in both groups. Sorafenib maintenance post-transplantation improved OS in the favorable (HR 0.33, 95% CI 0.14-0.77; P = 0.011) and adverse (HR 0.56, 95% CI 0.33-0.93; P = 0.026) ELN 2017 risk subgroups. Patients with mutated NPM1, DNMT3A, co-occurring NPM1/DNMT3A, "activated signaling" and "DNA methylation" genes benefited in OS from sorafenib maintenance, while those carrying CEBPA, "tumor suppressors" and "myeloid transcription factors" genes did not. Patients with FLT3-ITDhigh and FLT3-ITDlow AML both benefited in OS from sorafenib maintenance. Our results identify the response of genetic patterns to sorafenib maintenance, providing new viewpoints for the optimal use of sorafenib in FLT3-ITD AML in the transplantation setting.

Donor lymphocyte infusion in Acute Myeloid Leukemia

Donor lymphocyte infusion (DLI) is an important treatment modality in the management of relapsed hematological malignancies after allogeneic hematopoietic cell transplantation (allo-HCT). Donor T lymphocytes can be used in a therapeutic, pre-emptive or prophylactic manner in an attempt to stimulate a graft versus leukemia (GVL) effect and eradicate residual disease or even prevent relapse in a high-risk setting. DLIs are not without complications, however, graft versus host disease (GVHD) in particular. Data to date is limited to retrospective and small prospective studies. This review summarizes the available literature on approaches to managing relapse, dosing and timing of DLI, complications and potential future therapies.

Sorafenib maintenance after allogeneic haemopoietic stem-cell transplantation in patients with FLT3-ITD acute myeloid leukaemia: long-term follow-up of an open-label, multicentre, randomised, phase 3 trial

BACKGROUND

Our open-label, multicentre, randomised, phase 3 trial showed that sorafenib maintenance after haematopoietic stem-cell transplantation (HSCT) improved overall survival and reduced relapse for patients with FLT3 internal tandem duplication (FLT3-ITD) acute myeloid leukaemia undergoing allogeneic HSCT. Here, we present a post-hoc analysis on the 5-year follow-up data of this trial.

METHODS

This phase 3 trial, done in seven hospitals in China, included patients with FLT3-ITD acute myeloid leukaemia undergoing allogeneic HSCT, who were aged 18-60 years, had an Eastern Cooperative Oncology Group performance status of 0-2, had composite complete remission before and after transplantation, and had haematopoietic recovery within 60 days after transplantation. Patients were randomly assigned (1:1) to receive sorafenib maintenance (400 mg orally twice daily) or non-maintenance (control) at 30-60 days after transplantation. Randomisation was done with permuted blocks (block size four) via an interactive web-based system. Investigators and participants were not masked to group assignment. The primary endpoint was the 1-year cumulative incidence of relapse, which was reported previously. For this updated analysis, the 5-year endpoints were overall survival; cumulative incidence of relapse; non-relapse mortality; leukaemia-free survival; graft-versus-host disease (GVHD)-free, relapse-free survival (GRFS); cumulative incidence of chronic GVHD; and late effects in the intention-to-treat population. The trial is registered with ClinicalTrials.gov, NCT02474290, and is complete.

FINDINGS

Between June 20, 2015, and July 21, 2018, 202 patients were randomly assigned to sorafenib maintenance (n=100) or non-maintenance (n=102). Median follow-up was 60·4 months (IQR 16·7-73·3). Extended follow-up showed improved overall survival (72·0% [95% CI 62·1-79·7] vs 55·9% [45·7-64·9]; hazard ratio [HR] 0·55, 95% CI 0·34-0·88; p=0·011), leukaemia-free survival (70·0% [60·0-78·0] vs 49·0% [39·0-58·3]; 0·47, 0·30-0·73; p=0·0007), and GRFS (58·0% [47·7-67·0] vs 39·2% [29·8-48·5]; 0·56, 0·38-0·83; p=0·0030), lower cumulative incidence of relapse (15·0% [8·8-22·7] vs 36·3% [27·0-45·6]; 0·33, 0·18-0·60; p=0·0003), and no increase in non-relapse mortality (15·0% [8·8-22·7] vs 14·7% [8·6-22·3]; 0·79, 0·39-1·62; p=0·98) for patients in the sorafenib group compared with those in the control group. The 5-year cumulative incidence of chronic GVHD (54·0% [43·7-63·2] vs 51·0% [40·8-60·3]; 0·82, 0·56-1·19; p=0·73) did not differ significantly between the two groups and we did not find substantial differences in late effects between the two groups. There were no treatment-related deaths.

INTERPRETATION

With extended follow-up, sorafenib maintenance after transplantation is associated with improved long-term survival and reduced relapse rates compared with non-maintenance, further supporting this strategy as a standard of care for patients with FLT3-ITD acute myeloid leukaemia undergoing allogeneic HSCT.

FUNDING

None.

TRANSLATION

For the Chinese translation of the abstract see Supplementary Materials section.

Post-transplant maintenance therapy in acute myeloid leukemia after allogeneic hematopoietic stem cell transplantation harmonizing multiple therapeutic modalities including targeted therapy, immunotherapy and cellular therapy

Allogeneic hematopoietic stem cell transplant (HCT) has improved survival for patients with acute myeloid leukemia (AML), especially for those at high risk of relapse. However, relapse remains the leading cause of treatment failure post-HCT, occurring in around 35-45% of patients, and leading to dismal outcomes. Strategies to reduce relapse risk are urgently needed, especially in the early post-transplant period before activation of the graft-versus-leukemia (GVL) effect. Maintenance therapy is a course of treatment given post-HCT with the expectation of reducing relapse risk. While there are currently no therapies approved for maintenance therapy for AML after HCT, there are a number of studies and ongoing investigations examining the role of maintenance therapies that include targeted agents against FLT3-ITD, BCL2, or IDH mutations, hypomethylating agents, immunomodulatory therapies and cellular therapies. In this review, we discuss the mechanistic and clinical data for post-transplant maintenance therapies in AML and strategies for maintenance therapy for AML after HCT.

FLT3-inhibitor therapy for prevention and treatment of relapse after allogeneic hematopoietic cell transplantation

The curative potential of allogeneic hematopoietic cell transplantation (allo-HCT) for acute myeloid leukemia (AML) relies on the graft-versus-leukemia (GVL)-effect. Relapse after allo-HCT occurs in a considerable proportion of patients, and has a dismal prognosis with very limited curative potential, especially for patients with FLT-ITD-mutated AML. Since the first description of sorafenib for treatment of FLT3-ITD-mutated AML, several clinical trials have tried to determine the efficacy of FLT3 inhibitors for preventing and treating AML relapse after allo-HSCT, but many questions regarding differences among compounds and mechanisms of action remain unanswered. This review provides an overview on the established and evolving use of FLT3 inhibitors to prevent or treat relapse of AML in the context of allo-HCT, focusing on the recently discovered immunogenic potential of some FLT3 inhibitors and addressing the possible mechanisms of leukemia drug-escape.

A phase 2 study of sorafenib combined with conventional therapies in refractory central nervous system leukemia

BACKGROUND

Patients with refractory central nervous system leukemia (CNSL) have a dismal prognosis and lack effective therapy. Case reports have shown that sorafenib is effective against brain metastases, including leukemia.

METHODS

To explore the efficacy of sorafenib combined with conventional therapies for refractory CNSL, a phase 2 study was conducted. The primary end point was the complete remission rate (CRR) within 8 weeks of treatment. Secondary end points included the overall response rate (ORR), event-free survival (EFS), overall survival (OS), and adverse events (AEs).

RESULTS

Twenty-six patients with refractory CNSL were enrolled; they included 17 with isolated CNSL, 7 with hematological relapse, and 2 with another extramedullary relapse. After 8 weeks of treatment, 21 patients achieved complete remission, 2 achieved partial remission, and 3 achieved no remission for a CRR of 80.8% (95% CI, 62.1%-91.5%) and an ORR of 88.5% (95% CI, 71.0%-96.0%). Twenty patients survived, and 6 died. The 2-year EFS and OS rates were 75.0% (95% CI, 54.5%-88.3%) and 76.9% (95% CI, 54.2%-90.4%), respectively. Six patients experienced grade 3 or 4 treatment-related AEs, including moderate chronic graft-vs-host disease (n = 3), grade 3 or 4 acute graft-vs-host disease (n = 2), and grade 3 skin rash (n = 1). No treatment-related deaths occurred during the therapy of refractory CNSL.

CONCLUSIONS

Sorafenib combined with conventional therapies is effective and safe for refractory CNSL.

LAY SUMMARY

Sorafenib combined with conventional therapies is effective and safe for refractory central nervous system leukemia.

Optimization of Donor Lymphocyte Infusion for AML Relapse After Allo-HCT in the Era of New Drugs and Cell Engineering

Donor lymphocyte infusion (DLI) is a key strategy for the treatment of AML relapse after allogeneic hematopoietic cell transplantation (allo-HCT) and has been used for either prophylactic, pre-emptive, or therapeutic purposes. However, the prognosis of these patients remains dismal even after DLI infusion (2-year overall survival, ~25%), and the efficacy is achieved at the cost of toxicities such as graft-versus-host (GVH) disease. Attempts to optimize DLI efficacy and safety, such as dose/timing modification and the use of cytoreduction, before DLI have been performed previously. Recently, a great number of novel targeted and immunomodulatory agents have emerged. Some of them, such as hypomethylating agents, FLT3 and Bcl-2 inhibitors, have been used in combination with DLI, aiming to enhance the graft-versus-leukemia effect. Moreover, manipulation of the DLI graft through cell selection (e.g., donor NK cells) or cell engineering (donor CAR-T cells) has shown potentially superior anti-tumor effects but less GVH effect than conventional DLI in clinical trials. This review summarizes the recent advances on the use of DLI for the prophylaxis/treatment of AML relapse and discusses future strategies which may further improve the treatment efficacy.

Recent advances of targeted therapy in relapsed/refractory acute myeloid leukemia

Despite advances in the understanding of disease pathobiology, treatment for relapsed or refractory acute myeloid leukemia (R/R AML) remains challenging. The prognosis of R/R AML remains extremely poor despite chemotherapy and bone marrow transplants. Discoveries on recurrent and novel genetic mutations, such as FLT3-ITD and IDH1/IDH2, critical signaling pathways, and unique molecular markers expressed on the surface of leukemic cells have been under investigation for the management of R/R AML. Other than monoclonal antibodies, diabodies, and triabodies are new targeted therapies developed in recent years and will be the new direction of immunotherapy. Targeted agents combined intensive regimens can be viable options for salvage therapy and as bridges to allogeneic transplant. Future directions will focus on novel, efficient and targeted combinations, low-toxicity maintenance, and individualized precision strategies. Here, we review the major recent advances of targeted therapies in the treatment of R/R AML.

Clinical Benefits and Safety of FMS-Like Tyrosine Kinase 3 Inhibitors in Various Treatment Stages of Acute Myeloid Leukemia: A Systematic Review, Meta-Analysis, and Network Meta-Analysis

BACKGROUND

Given the controversial roles of FMS-like tyrosine kinase 3 inhibitors (FLT3i) in various treatment stages of acute myeloid leukemia (AML), this study was designed to assess this problem and further explored which FLT3i worked more effectively.

METHODS

A systematic review, meta-analysis and network meta-analysis (NMA) were conducted by filtering PubMed, Embase, Cochrane library, and Chinese databases. We included studies comparing therapeutic effects between FLT3i and non-FLT3i group in AML, particularly FLT3(+) patients, or demonstrating the efficiency of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in FLT3(+) AML. Relative risk (RR) with 95% confidence intervals (CI) was used for estimating complete remission (CR), early death and toxicity. Hazard ratio (HR) was used to assess overall survival (OS), event-free survival (EFS), relapse-free survival (RFS) and cumulative incidence of relapse (CIR).

RESULTS

After addressing all criteria, 39 studies were eventually analyzed. Better CR was accomplished by FLT3i in untreated AML (RR 0.88, p = 0.04) and refractory and relapsed FLT3(+) AML (rrAML) (RR 0.61, p < 0.01) compared to non-FLT3i arm, followed by improved survival (untreated AML: OS, HR 0.76; EFS, HR 0.67; RFS, HR 0.72; all p < 0.01; FLT3(+) rrAML: OS, HR 0.60, p < 0.01; RFS, HR 0.40, p = 0.01). In addition, allo-HSCT improved survival in FLT3(+) AML (OS, HR 0.53; EFS, HR 0.50; RFS, HR 0.57; CIR, HR 0.26; all p < 0.01), which was further prolonged by FLT3i administrated after allo-HSCT (OS, HR 0.45; RFS, HR 0.34; CIR, HR 0.32; all p < 0.01). Additionally, FLT3i consistently improved OS (p < 0.05) regardless of FLT3-ITD ratio, when compared to non-FLT3i group. Besides, FLT3i showed significantly increased risk of thrombocytopenia, neutropenia, anemia, skin- and cardiac-related adverse effects, increased alanine aminotransferase, and increased risk of cough and dyspnea (p < 0.05). In NMA, gilteritinib showed the highest probability for improved prognosis.

CONCLUSIONS

FLT3i safely improved prognosis in induction/reinduction stage of FLT3(+) AML and further boosted survival benefits from allo-HSCT as maintenance therapy, suggesting better prognosis if FLT3i is combined before and after allo-HSCT. In NMA, gilteritinib potentially achieved the best prognosis, which should be identified in direct trials.

Maintenance therapy in acute myeloid leukemia after allogeneic hematopoietic stem cell transplantation

Relapse remains the main cause of treatment failure in acute myeloid leukemia (AML) undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). Emerging evidence has demonstrated that AML patients might benefit from maintenance therapy post-transplantation, especially for high-risk AML patients. In this mini-review, we will summarize targeted drugs, such as hypomethylating agents, FLT3 inhibitors and isocitrate dehydrogenase inhibitors, as maintenance therapy post-transplantation in AML patients undergoing allo-HSCT.

Relapse of acute myeloid leukemia after allogeneic hematopoietic cell transplantation: clinical features and outcomes

Posttransplant relapse represents the greatest obstacle to the success of allogeneic hematopoietic cell transplantation (HCT) for patients with acute myeloid leukemia (AML). This study investigated clinical features and outcomes of posttransplant relapse of AML based on data for 1265 patients with AML suffering relapse after allogeneic HCT conducted during complete remission (CR). Relapse occurred at a median of 6.1 months. The incidence rate of relapse peaked at 29.0 per 100 patient-years during the first 3-6 months period post transplant, after which the rate declined over time, and after 3 years remained consistently at less than 1 per 100 patient-years. The probability of overall survival (OS) after posttransplant relapse was 19% at 2 years, with 68% of deaths being attributed to leukemia. The interval from transplantation to relapse was identified as the strongest indicator for OS. Donor lymphocyte infusion (DLI) and second allogeneic HCT (HCT2) were administered to 152 (12%) and 481 (38%) patients, respectively. Landmark analyses showed some signs of survival benefit when these procedures were performed during CR, but no benefit was gained when performed during non-CR. Our findings clarify clinical features of posttransplant relapse of AML, and indicate the urgent need for developing effective bridging to cellular therapies.

Novel agents targeting leukemia cells and immune microenvironment for prevention and treatment of relapse of acute myeloid leukemia after allogeneic hematopoietic stem cell transplantation

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.

Clinical Outcomes in Patients with FLT3-ITD-Mutated Relapsed/Refractory Acute Myelogenous Leukemia Undergoing Hematopoietic Stem Cell Transplantation after Quizartinib or Salvage Chemotherapy in the QuANTUM-R Trial

Despite the substantial clinical activity of fms-related tyrosine kinase 3 (FLT3) inhibitors in relapsed or refractory (R/R) FLT3-ITD‒positive acute myelogenous leukemia (AML), durable remissions and prolonged survival in this population require allogeneic hematopoietic stem cell transplantation (allo-HSCT). Quizartinib, a once-daily oral, highly potent, and selective FLT3 inhibitor, significantly prolonged overall survival (OS) and improved clinical benefit compared with salvage chemotherapy (median OS, 6.2 months versus 4.7 months; hazard ratio [HR], .76; 95% confidence interval [CI], .58 to .98; P = .018; composite complete remission [CRc] rate, 48% versus 27%; median duration of CRc, 2.8 months versus 1.2 months; mortality rate, .8% versus 14% by day 30, 7% versus 24% by day 60) in patients with R/R FLT3-ITD AML in the phase 3 QuANTUM-R trial. In this post hoc analysis, we described the characteristics of and clinical outcomes in patients who underwent on-study HSCT in QuANTUM-R at the investigator's discretion and institutional practices. Of 367 randomized patients, 78 (32%) in the quizartinib arm and 14 (11%) in the salvage chemotherapy arm underwent on-study allo-HSCT without any intervening therapy for AML after quizartinib or study-specified salvage chemotherapy. Pooled data of patients from both treatment arms showed a longer median overall survival (OS) in transplant recipients versus those treated without allo-HSCT (12.2 months versus 4.4 months; HR, .315; 95% CI, .233 to .427). Pooled data also showed a longer median OS in patients with a last recorded response of CRc before allo-HSCT versus patients without a CRc (20.1 months versus 8.8 months; HR, .506; 95% CI, .296 to .864). By treatment arm, the median OS was 25.1 months with quizartinib and 20.1 months with salvage chemotherapy in patients with a last recorded response of CRc before allo-HSCT. Forty-eight patients in the quizartinib arm continued quizartinib treatment after allo-HSCT. In the 31 patients with a last recorded response of CRc before allo-HSCT who continued quizartinib after allo-HSCT, the median OS was 27.1 months. Continuation of quizartinib after allo-HSCT was tolerable, and no new safety signals were identified. These results suggest that post-transplantation survival following salvage chemotherapy and quizartinib treatment are similar. However, quizartinib response occurs more frequently than with salvage chemotherapy, potentially allowing more patients to undergo transplantation and achieve durable clinical benefit. In addition, post-transplant quizartinib was found to be tolerable and may be associated with prolonged survival in some patients, highlighting its potential value in the management of patients with FLT3-ITD R/R AML.

Sorafenib maintenance in patients with FLT3-ITD acute myeloid leukaemia undergoing allogeneic haematopoietic stem-cell transplantation: an open-label, multicentre, randomised phase 3 trial

BACKGROUND

Findings of retrospective studies suggest that sorafenib maintenance post-transplantation might reduce relapse in patients with FLT3 internal tandem duplication (FLT3-ITD) acute myeloid leukaemia undergoing allogeneic haematopoietic stem-cell transplantation. We investigated the efficacy and tolerability of sorafenib maintenance post-transplantation in this population.

METHODS

We did an open-label, randomised phase 3 trial at seven hospitals in China. Eligible patients (aged 18-60 years) had FLT3-ITD acute myeloid leukaemia, were undergoing allogeneic haematopoietic stem-cell transplantation, had an Eastern Cooperative Oncology Group performance status of 0-2, had composite complete remission before and after transplantation, and had haematopoietic recovery within 60 days post-transplantation. Patients were randomly assigned (1:1) to sorafenib maintenance (400 mg orally twice daily) or non-maintenance (control) at 30-60 days post-transplantation. Randomisation was done with permuted blocks (block size four) and implemented through an interactive web-based randomisation system. The primary endpoint was the 1-year cumulative incidence of relapse in the intention-to-treat population. This trial is registered with ClinicalTrials.gov, NCT02474290; the trial is complete.

FINDINGS

Between June 20, 2015, and July 21, 2018, 202 patients were enrolled and randomly assigned to sorafenib maintenance (n=100) or control (n=102). Median follow-up post-transplantation was 21·3 months (IQR 15·0-37·0). The 1-year cumulative incidence of relapse was 7·0% (95% CI 3·1-13·1) in the sorafenib group and 24·5% (16·6-33·2) in the control group (hazard ratio 0·25, 95% CI 0·11-0·57; p=0·0010). Within 210 days post-transplantation, the most common grade 3 and 4 adverse events were infections (25 [25%] of 100 patients in the sorafenib group vs 24 [24%] of 102 in the control group), acute graft-versus-host-disease (GVHD; 23 [23%] of 100 vs 21 [21%] of 102), chronic GVHD (18 [18%] of 99 vs 17 [17%] of 99), and haematological toxicity (15 [15%] of 100 vs seven [7%] of 102). There were no treatment-related deaths.

INTERPRETATION

Sorafenib maintenance post-transplantation can reduce relapse and is well tolerated in patients with FLT3-ITD acute myeloid leukaemia undergoing allogeneic haematopoietic stem-cell transplantation. This strategy could be a suitable therapeutic option for patients with FLT3-ITD acute myeloid leukaemia.

FUNDING

None.

Advances in targeted therapy for acute myeloid leukemia

Acute myeloid leukemia (AML) is a clonal malignancy characterized by genetic heterogeneity due to recurrent gene mutations. Treatment with cytotoxic chemotherapy has been the standard of care for more than half of a century. Although much progress has been made toward improving treatment related mortality rate in the past few decades, long term overall survival has stagnated. Exciting developments of gene mutation-targeted therapeutic agents are now changing the landscape in AML treatment. New agents offer more clinical options for patients and also confer a more promising outcome. Since Midostaurin, a FLT3 inhibitor, was first approved by US FDA in 2017 as the first gene mutation-targeted therapeutic agent, an array of new gene mutation-targeted agents are now available for AML treatment. In this review, we will summarize the recent advances in gene mutation-targeted therapies for patients with AML.

Clinical implications of recurrent gene mutations in acute myeloid leukemia

Acute myeloid leukemia (AML) is a genetically heterogeneous clonal malignancy characterized by recurrent gene mutations. Genomic heterogeneity, patients’ individual variability, and recurrent gene mutations are the major obstacles among many factors that impact treatment efficacy of the AML patients. With the application of cost- and time-effective next-generation sequencing (NGS) technologies, an enormous diversity of genetic mutations has been identified. The recurrent gene mutations and their important roles in acute myeloid leukemia (AML) pathogenesis have been studied extensively. In this review, we summarize the recent development on the gene mutation in patients with AML.

Durable remission of post-transplant relapsed FLT3-ITD AML in response to gilteritinib administration after a second transplant from the same donor

Patients with FMS-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) acute myeloid leukemia (AML) respond to conventional induction chemotherapy, with remission rates similar to those seen in other subtypes; however, they are much more likely to relapse and relapse is rapid. For this reason, eligible patients receive consolidation therapy with early allogenic transplantation, but the recurrence rate remains high, even after transplantation. Moreover, the optimal therapy for patients with FLT3-ITD AML who relapse after allogeneic hematopoietic stem cell transplantation remains unclear. Here, we report a case in which graft-versus-leukemia (GVL) effects were induced by gilteritinib administration after a second transplant from the same donor, resulting in sustained remission of early FLT3-ITD AML relapse after allogeneic transplantation. Several studies suggest that the benefits of FLT3 tyrosine kinase inhibitors (FLT3-TKI) after allogeneic transplantation are attributable to GVL induction, as well as direct effects on FLT3 mutation-positive leukemia cells. With this in mind, we induced lymphodepletion using L-PAM to further enhance GVL induction by donor lymphocytes and FLT3-TKI. We believe that enhancement of GVL induction by lymphodepletion should be considered before FLT3-TKI use, if the prognosis is very poor, such as in patients with recurrence following allogeneic transplantation.