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

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.

[Efficacy and safety of Venetoclax in the treatment of 25 patients with recurrent hematologic malignancies after an allogeneic hematopoietic stem cell transplantation]

Objegtive: To investigate the efficacy and safety of preemptive/salvage therapy with venetoclax (VEN) in patients with recurrence after allogeneic hematopoietic stem cell transplantation (allo-HSCT) . Methods: Retrospective analysis the clinical data of 25 patients with minimal residual disease (MRD) positive or morphological recurrence after allo-HSCT treated with VEN in the hematological Hospital of Chinese Academy of Medical Sciences from 2021.2 to 2021.11, there were 15 MRD positive patients (preemptive treatment group) and 10 morphological recurrence patients (salvage treatment group) . The dose of VEN in both groups was 400 mg/d, which was reduced to 100 mg/d when combined with azole antifungal drugs. Results: ①In the preemptive group, there were 7 males and 8 females, with a median age of 32 (18-52) years; There were 13 cases of acute myeloid leukemia (AML) , 1 case of acute lymphoblastic leukemia (ALL) and 1 case of primary myelofibrosis (PMF) ; the median time from MRD positive to the application of VEN was 2.5 (0-12.5) months. The median course of treatment was 2 (1-4) . On the 7th day of the first course of treatment, the median concentration of VEN was 1945 (688-5383) μg/L. After one course of VEN treatment, MRD in 8 patients turned negative (major responses) , MRD in 4 patients decreased by 50% compared with that before treatment, 3 cases were ineffective, and the overall response rate (ORR) was 80% (12/15) . On the 7th day of treatment, 3 of the 9 patients with VEN blood concentration <1 000 μg/L or >3 000 μg/L turned negative for MRD (33.3%) , and 5 of the 6 patients with VEN blood concentration between 1000 and 3000 μg/L turned negative for MRD (83.3%) . Grade 3/4 neutropenia occurred in 5 patients (33%) and grade 3/4 thrombocytopenia occurred in 5 patients (33%) , there were no new cases of severe infection and death. ②In the salvage group, there were 7 males and 3 females, with a median age of 44 (28-59) years; there were 6 cases of AML, 2 cases of ALL, 1 case of atypical chronic myeloid leukemia (aCML) , 1 case of refractory hemopenia with multiline dysplasia (MDS-RCMD) ; the median time from relapse to application of VEN was 0 (0-1) months. The median treatment was 1 (1-2) course. The median concentration of VEN on the 7th day of the first course of treatment was 2 419 (1 200-6 155) μg/L. After one course of VEN treatment, 3 cases achieved complete remission (CR) (major responses) and 3 cases achieved partial remission (PR) , 4 cases were ineffective and the ORR was 60% (6/10) . On the 7th day of treatment, 1 of the 4 patients with VEN blood concentration >3 000 μg/L achieved CR (25%) , and 2 of the 6 patients with VEN blood concentration between 1 000 and 3 000 μg/L achieved CR (33.3%) . Grade 3/4 neutropenia and grade 3/4 thrombocytopenia occurred in 10 patients (100%) . One patient died of severe pulmonary infection. ③The median follow-up was 4.5 (1-8.5) months. The overall survival rate (OS) of the preemptive group and the salvage group were (70.2±12.7) % and (50.0± 15.8) %, respectively (χ(2)=1.873, P=0.171) . The OS of patients with and without primary response to one course of VEN were (90.9±8.7) % and (36.2±14.7) % respectively (χ(2)=6.843, P=0.009) . Three patients with TP53 mutation achieved the major responses after VEN treatment. Conclusion: Preemptive/salvage therapy with VEN after allo-HSCT in patients with hematological malignancies is effective and well tolerated, monitoring the concentration of VEN is expected to improve the curative effect. The prognosis of patients who fail to reach the major responses after one course of preemptive/salvage treatment with VEN is poor, so they need to switch to other treatment schemes as soon as possible.

Venetoclax and donor lymphocyte infusion for early relapsed acute myeloid leukemia after allogeneic hematopoietic cell transplantation. A retrospective multicenter trial

Prognosis in patients with post allogeneic HCT-early relapse of acute myeloid leukemia (<6 months post HCT) is dismal and response to salvage treatment is < 20%. In addition, majority of patients at this early point are unable to withstand intensive salvage chemotherapy. We hypothesized that the combination of donor lymphocyte infusion (DLI) and venetoclax may result in increased response in this difficult to treat patient group. We retrospectively analyzed 22 patients from February 2017-December 2019, who were given the Venetoclax/DLI combination. Median age was 65 (43-75) years. There were no cases of tumor lysis syndrome. Microbiology documented infections occurred in 8 patients (36%). Majority were able to tolerate the protocol without admissions. Acute GVHD was observed in 4 (18%) patients and cGVHD was observed in 6 (27%) patients. Overall response was observed in 11 (50%) patients (CR, n = 4; CRi, n = 1; CRp, n = 4; MLFS n = 2). Median time to response was 28 (18-67) days and median cycles of venetoclax 2 [1-8] and duration of response were 135 (31-564) days. Median survival was 6.1 months (95% CI .73-11.4). Cox regression model for survival showed decreased WBC at relapse, GVHD and better performance status were associated with better survival. These results may endorse the hypothesis that enhancing alloreactivity combined with venetoclax is safe and efficacious and should be further investigated in prospective trials.

Measurable residual disease (MRD) testing for acute leukemia in EBMT transplant centers: a survey on behalf of the ALWP of the EBMT

Detectable measurable residual disease (MRD) is a key prognostic factor in both acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) patients. Thus, we conducted a survey in EBMT transplant centers focusing on pre- and post-allo-HCT MRD. One hundred and six centers from 29 countries responded. One hundred had a formal strategy for routine MRD assessment, 91 for both ALL and AML. For ALL (n = 95), assessing MRD has been routine practice starting from 2010 (range, 1990-2019). Techniques used for MRD assessment consisted of PCR techniques alone (n = 27), multiparameter flow cytometry (MFC, n = 16), both techniques (n = 43), next-generation sequencing (NGS) + PCR (n = 2), or PCR + MFC + NGS (n = 7). The majority of centers assessed MRD every 2-3 months for 2 (range, 1-until relapse) years. For AML, assessing MRD was routine in 92 centers starting in 2010 (range 1990-2019). Assessment of MRD was by PCR (n = 23), MFC (n = 13), both PCR and MFC (n = 39), both PCR and NGS (n = 3), and by all three techniques (n = 14). The majority assesses MRD for AML every 2-3 months for 2 (range, 1-until relapse) years. This survey is the first step in the aim to include MRD status as a routine registry capture parameter in acute leukemia.