Refractory Acute Myeloid Leukemia Research Articles

Impact of cladribine, cytarabine, and G-CSF (CLAG) as a bridging therapy prior to allogeneic hematopoietic stem cell transplantation in relapsed or refractory acute myeloid leukemia.

The combination of cladribine, cytarabine, and G-CSF (CLAG) has exhibited robust synergistic anti-leukemia activity as an induction therapy (IT) in acute myeloid leukemia (AML). However, the impact of CLAG as a bridging therapy (BT) administered between IT and allogeneic hematopoietic stem cell transplantation (allo-HSCT) for patients with relapsed or refractory (R/R) AML remains uncertain. In this retrospective study, we examined the efficacy of CLAG as a transitional strategy prior to allo-HSCT in R/R AML. We included 234 patients with R/R AML who received the modified busulfan plus cyclophosphamide conditioning regimen for allo-HSCT in our center during the past 6years, performed a propensity-score matching analysis, partitioned them into four distinct cohorts, and further integrated them into the CLAG group and non-CLAG group based on response to IT and utilization of CLAG. Our cohorts encompassed 12 patients in Cohort A (modified composite complete remission (mCRc) after IT, CLAG), 31 in Cohort B (mCRc after IT, non-CLAG), 35 in Cohort C (non-complete remission (non-CR) after IT, CLAG), and 80 in Cohort D (non-CR after IT, non-CLAG). Intriguingly, among patients with non-CR status, the administration of CLAG correlated with a notably statistically diminished risk of relapse and improved survival at 2-year follow-up (Cohort C vs. Cohort D). Employing CLAG as a BT prior to allo-HSCT demonstrates substantial effectiveness, a relative degree of safety, and manageable toxicity in selected R/R AML cases.

Effectiveness and safety of granulocyte colony-stimulating factor priming regimen for acute myeloid leukemia: A systematic review and meta-analysis of the Clinical Practice Guideline for the use of G-CSF 2022 from the Japan Society of Clinical Oncology.

The outcomes of relapsed or refractory acute myeloid leukemia (AML) remain poor. Although the concomitant use of granulocyte colony-stimulating factor (G-CSF) and anti-chemotherapeutic agents has been investigated to improve the antileukemic effect on AML, its usefulness remains controversial. This study aimed to investigate the effects of G-CSF priming as a remission induction therapy or salvage chemotherapy. We performed a thorough literature search for studies related to the priming effect of G-CSF using PubMed, Ichushi-Web, and the Cochrane Library. A qualitative analysis of the pooled data was performed, and risk ratios (RRs) with confidence intervals (CIs) were calculated and summarized. Two reviewers independently extracted and accessed the 278 records identified during the initial screening, and 62 full-text articles were assessed for eligibility in second screening. Eleven studies were included in the qualitative analysis and 10 in the meta-analysis. A systematic review revealed that priming with G-CSF did not correlate with an improvement in response rate and overall survival (OS). The result of the meta-analysis revealed the tendency for lower relapse rate in the G-CSF priming groups without inter-study heterogeneity [RR, 0.91 (95% CI 0.82-1.01), p=0.08; I2=4%, p=0.35]. In specific populations, including patients with intermediate cytogenetic risk and those receiving high-dose cytarabine, the G-CSF priming regimen prolonged OS. G-CSF priming in combination with intensive remission induction treatment is not universally effective in patients with AML. Further studies are required to identify the patient cohort for which G-CSF priming is recommended.

The efficacy of the combination of venetoclax and hypomethylating agents versus HAG agents in patients with acute myeloid leukemia: a retrospective study

ABSTRACT Objectives: The purpose of this study was to compare the effectiveness of the combination of venetoclax and hypomethylating agents with the HAG regimen. Methods: We studied 52 cases of newly diagnosed AML and 26 cases of relapsed refractory AML, (including AML patients with treatment-related and ELN-adverse risk disease (n = 50)). These patients were treated with venetoclax and hypomethylating agents and HAG regimens, respectively. Results: Twenty-nine patients newly diagnosed with acute myeloid leukemia were treated with VEN-HMA (venetoclax-hypomethylating agent), while 23 patients were treated with HAG. The median age of the VEN-HMA group was 70 years, while the HAG group had a median age of 69 years. The VEN-HMA group achieved a significantly higher rate of complete remission (82.7%) compared to the cohort treated with the HAG regimen (21.7%) (P < 0.001). At the same time, the VEN-HMA group exhibited a significant survival advantage compared to the HAG treatment group(HR = 0.328, 95%CI: 0.158-0.683, P = 0.003). In patients with relapsed and refractory acute myeloid leukaemia, 43.8% of patients in the VEN-HMA treatment group achieved complete remission, which was similar to the 50% in the HAG treatment group (P > 0.99). The median overall survival was similar between the VEN-HMA and HAG groups, with 4 and 3.67 months, respectively (P = 0.290). Conclusions: In conclusion, our analyses indicated that VEN-HMA resulted in better therapeutic outcomes compared to HAG for newly diagnosed AML patients, with higher rates of complete remission and overall survival. In relapsed/refractory AML patients, there was no significant difference in the efficacy of the two treatments and further studies with larger sample sizes are warranted.

Decitabine as epigenetic priming with CLAG induce improved outcome of relapsed or refractory acute myeloid leukemia in children

BackgroundDecitabine (DAC), a DNA methyltransferase inhibitor, has shown efficacy combined with chemotherapy for relapsed or refractory (R/R) acute myeloid leukemia (AML) in adults, but less is known about its efficacy in children. Accordingly, we conducted a study which involved a priming regimen consisting of DAC with cladribine, cytarabine, and granulocyte-stimulating factor (DAC-CLAG) and compared the efficacy and safety of this regimen with CLAG alone.MethodsA total of 39 R/R AML children who received the CLAG or DAC-CLAG regimen in Shanghai Children’s Hospital were retrospectively enrolled in this non-randomized study. These regimens were studied sequentially over time. Twenty-two patients received CLAG from 2015, while 17 patients were administered epigenetic priming with DAC before CLAG from 2020. Patients were subsequently bridged to stem cell transplantation (SCT) or consolidation chemotherapy. Complete remission (CR) and adverse effects were analyzed by Fisher’s exact test, and survival was analyzed by the Kaplan–Meier method.ResultsDAC-CLAG conferred a numerically higher CR compared to CLAG (70.59% vs 63.64%; P = 0.740). High CR rates occurred in patients with good cytogenetics (P = 0.029) and prior induction without cladribine (P = 0.099). The 1-year event-free survival (EFS) was 64.71% ± 11.59% and 63.31% ± 10.35% in the DAC-CLAG and CLAG group (P = 0.595), and 1-year overall survival (OS) was 81.45% ± 9.72% and 77.01% ± 9.04%, respectively (P = 0.265). The 1-year OS and EFS after SCT were higher in the DAC-CLAG than in the CLAG cohort (100% vs 92.31% ± 7.39%, P = 0.072; 92.31% ± 7.39% vs 85.71% ± 9.35%, P = 0.158). Univariate analysis revealed that a good prognosis included good cytogenetics (P = 0.002), non-complex karyotype (P = 0.056), CR on reinduction (P < 0.0001), and bridging to SCT (P = 0.0007). Use of a hypomethylating agent (P = 0.049) and bridging to SCT (P = 0.011) were independent prognostic factors. Grade 3/4 hematologic toxicity and infection were the main adverse events.ConclusionsDAC prior to the CLAG regimen improved remission in pediatric R/R AML, and was feasible and well tolerated. CLAG ± DAC as a salvage therapy prior to SCT induced improved survival.

The CD33xCD123xCD70 Multispecific CD3-Engaging DARPin MP0533 Induces Selective T Cell-Mediated Killing of AML Leukemic Stem Cells.

The prognosis of patients with acute myeloid leukemia (AML) is limited, especially for elderly or unfit patients not eligible for hematopoietic stem cell (HSC) transplantation. The disease is driven by leukemic stem cells (LSCs), which are characterized by clonal heterogeneity and resistance to conventional therapy. These cells are therefore believed to be a major cause of progression and relapse. We designed MP0533, a multispecific CD3-engaging DARPin (designed ankyrin repeat protein) that can simultaneously bind to three antigens on AML cells (CD33, CD123, and CD70), aiming to enable avidity-driven T cell-mediated killing of AML cells co-expressing at least two of the antigens. In vitro, MP0533 induced selective T cell-mediated killing of AML cell lines, as well as patient-derived AML blasts and LSCs, expressing two or more target antigens, while sparing healthy HSCs, blood, and endothelial cells. The higher selectivity also resulted in markedly lower levels of cytokine release in normal human blood compared to single antigen-targeting T-cell engagers. In xenograft AML mouse models, MP0533 induced tumor-localized T-cell activation and cytokine release, leading to complete eradication of the tumors while having no systemic adverse effects. These studies show that the multispecific-targeting strategy used with MP0533 holds promise for improved selectivity towards LSCs and efficacy against clonal heterogeneity, potentially bringing a new therapeutic option to this group of patients with high unmet need. MP0533 is currently being evaluated in a dose-escalation phase 1 study in patients with relapsed or refractory AML (NCT05673057).

Allogeneic Stem Cell Transplantation in Refractory Acute Myeloid Leukaemia.

Refractory acute myeloid leukaemia is very difficult to treat and represents an unmet clinical need. In recent years, new drugs and combinations of drugs have been tested in this category, with encouraging results. However, all treated patients relapsed and died from the disease. The only curative option is allogeneic transplantation through a graft from a healthy donor immune system. Using myeloablative conditioning regimens, the median overall survival regimens is 19%. Several so-called sequential induction chemotherapies followed by allogeneic transplantation conditioned by reduced intensity regimens have been developed, improving the overall survival to 25-57%. In the allogeneic transplantation field, continuous improvements in practices, particularly regarding graft versus host disease prevention, infection prevention, and treatment, have allowed us to observe improvements in survival rates. This is true mainly for patients in complete remission before transplantation and less so for refractory patients. However, full myeloablative regimens are toxic and carry a high risk of treatment-related mortality. In this review, we describe the results obtained with the different modalities used in more recent retrospective and prospective studies. Based on these findings, we speculate how allogeneic stem cell transplantation could be modified to maximise its therapeutic effect on refractory acute myeloid leukaemia.

Discovery of a Novel Orally Bioavailable FLT3-PROTAC Degrader for Efficient Treatment of Acute Myeloid Leukemia and Overcoming Resistance of FLT3 Inhibitors.

Fms-like tyrosine receptor kinase 3 (FLT3) proteolysis-targeting chimeras (PROTACs) represent a promising approach to eliminate the resistance of FLT3 inhibitors. However, due to the poor druggability of PROTACs, the development of orally bioavailable FLT3-PROTACs faces great challenges. Herein, a novel orally bioavailable FLT3-ITD degrader A20 with excellent pharmacokinetic properties was discovered through reasonable design. A20 selectively inhibited the proliferation of FLT3-ITD mutant acute myeloid leukemia (AML) cells and potently induced FLT3-ITD degradation through the ubiquitin-proteasome system. Notably, oral administration of A20 resulted in complete tumor regression on subcutaneous AML xenograft models. Furthermore, on systemic AML xenograft models, A20 could completely eliminate the CD45+CD33+ human leukemic cells in murine and significantly prolonged the survival time of mice. Most importantly, A20 exerted significantly improved antiproliferative activity against drug-resistant AML cells compared to existing FLT3 inhibitors. These findings suggested that A20 could serve as a promising drug candidate for relapsed or refractory AML.

Haploidentical transplantation in primary refractory/relapsed secondary vs de novo AML: from the ALWP/EBMT

AbstractWe compared the outcomes of haploidentical stem cell transplantation (haplo-HSCT) with posttransplant cyclophosphamide (PTCy) in 719 patients with primary refractory (PR) or first relapse (Rel) secondary acute myeloid leukemia (sAML; n = 129) vs those with de novo AML (n = 590), who received HSCT between 2010 and 2022. A higher percentage of patients with sAML vs de novo AML had PR disease (73.6% vs 58.6%; P = .002). In 81.4% of patients with sAML , the antecedent hematological disorder was myelodysplastic syndrome. Engraftment was 83.5% vs 88.4% in sAML and de novo AML, respectively (P = .13). In multivariate analysis, haplo-HSCT outcomes did not differ significantly between the groups: nonrelapse mortality hazard ratio (HR), 1.38 (95% confidence interval [CI], 0.96-1.98; P = .083), relapse incidence HR, 0.68 (95% CI, 0.4.7.-1.00; P = .051). The HRs for leukemia-free survival, overall survival, and graft-versus-host disease (GVHD)–free, and GVHD and relapse–free survival were 0.99 (95% CI, 0.76-1.28; P = .94), 0.99 (95% CI, 0.77-1.29; P = .97), and 0.99 (95% CI, 0.77-1.27; P = .94), respectively. We conclude that outcomes of haplo-HSCT with PTCy are not different for PR/Rel sAML in comparison with PR/Rel de novo AML, a finding of major clinical importance.

Abstract CT115: A first-in-human phase I study of CTX-712 in patients with advanced, relapsed or refractory malignant tumors (CTX-712-CL-01 study): Efficacy and safety in a hematologic malignancies cohort

Abstract Background: Mutations in genes encoding RNA splicing factors such as SF3B1, SRSF2, U2AF1, and ZRSR2, are common genetic aberrations in many forms of myeloid neoplasms. CTX-712 is a first-in-class, orally available, highly potent, and selective small molecule inhibitor of CDC2-like kinase (CLK), a key regulator of RNA splicing. Preclinical data show that CTX-712 demonstrated anti-proliferative activity in in-vitro and in-vivo models derived from hematologic malignancies. A phase I study of CTX-712 was conducted to evaluate the safety and the preliminary efficacy of CTX-712 in patients with relapsed or refractory acute myeloid leukemia (AML) and higher-risk myelodysplastic syndrome (MDS). Methods: The objectives of this cohort were to evaluate the dose-limiting toxicity (DLT), safety, pharmacokinetic (PK)/pharmacodynamic (PD) profiles, and preliminary efficacy of CTX-712 in patients with hematologic malignancies. A 3+3 design was used in two dose levels (70 mg and 105 mg twice a week (TW)) based on the safety data from the previous dose escalation cohort in patients with solid tumors. Results: As of data cutoff on November 20, 2023, a total of 14 patients (12 AML and 2 MDS) were enrolled in 70 mg TW (n=8) and 105 mg TW dose levels (n=6). DLT of Grade 4 pneumonia was observed in 1 of 3 DLT-evaluable patients in the 105 mg TW group. In the 70 mg TW group, no DLT was observed in 6 DLT-evaluable patients. Among the safety analysis population (n=14), median treatment duration was 76 days (Range 15-974 days). At data cutoff, treatment was ongoing in 1 patient and discontinued in 13 patients. The common any-grade adverse events (AEs) (≥30%) were diarrhea (57.1%) and nausea (42.9%). The most common Grade 3 or higher AE were white blood cell count decreased and tumor lysis syndrome (14.3%). In AML patients (n=12), complete remission (CR) was observed in 3 patients (25.0%), and CR with incomplete hematologic recovery (CRi) was observed in 1 patient (8.3%). The median time to remission was 67 days (Range 29-113 days), and the median duration of response was 281 days (Range 56-924 days). In MDS patients (n=2), CR was observed in 1 patient (50.0%). PK/PD profiles of the hematologic malignancies dose escalation cohort were comparable with those of the solid tumor cohort at the same dosage. Conclusions: CTX-712 demonstrated a manageable and tolerable safety profile and showed anti-tumor efficacy in patients with hematologic malignancies. Currently, a Phase I/II Study of CTX-712 in relapsed/refractory AML and higher risk MDS is ongoing using a new tablet formulation in the United States. Clinical trial information: jRCT2080224127 Citation Format: Hisayuki Yokoyama, Noriko Fukuhara, Koji Ando, Hiroatsu Iida, Takahiro Yamauchi, Suguru Fukuhara, Koji Izutsu, Yasushi Tanoue, Maki Yamamoto, Hirokazu Tozaki, Eiji Takahara, Shingo Shoji, Akio Mizutani, Daisuke Morishita, Robert W. Oda, Hiroshi Miyake, Noboru Yamamoto. A first-in-human phase I study of CTX-712 in patients with advanced, relapsed or refractory malignant tumors (CTX-712-CL-01 study): Efficacy and safety in a hematologic malignancies cohort [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT115.

Abstract CT142: Phase 1 study of BPI-23314, a novel BET inhibitor and degrader, in advanced myeloid leukemia (AML)

Abstract Background: The novel small-molecule inhibitor and degrader, BPI-23314, targeting of the bromodomain and extra-terminal domain (BET) family proteins, BPI-23314, has been showndemonstrated promising preclinical efficacy in hematologic malignancies. This Phase 1 study aims to evaluate the safety, pharmacokinetics, and preliminary efficacy of BPI-23314 monotherapy in patients with relapsed or refractory acute myeloid leukemia (R/R AML). Methods: This ongoing phase 1 study of BPI-23314 enrolled adult patients with R/R AML. Dose escalation was conducted using a standard 3+3 design, followed by additional expansion cohorts to further assess safety and preliminary efficacy. BPI-23314 tablets were administered orally once daily (QD) or twice daily (BID) in consecutive 21-day cycles. The key endpoints included determining the recommended Phase 2 dose (RP2D), safety, pharmacokinetics, and preliminary efficacy. Results: As of July 31, 2022, a total of 22 patients diagnosed with R/R AML were treated with BPI-23314 at seven different dose levels, ranging from 5 to 60 mg QD or 40 to 50 mg BID. The median age of the patients was 48 years (range: 19-68 years), and the median treatment duration was 6 weeks (range: 2-9 weeks). The median number of prior therapy lines was 3 (range: 1-4), with 15 (68.2%) being refractory to last line of therapy. Due to the high incidence of grade≥3 anemia, thrombocytopenia, and neutropenia among the patients at baseline, most treatment-emergent adverse events (TEAE) of hematologic toxicities were mainly correlated with disease progression. Only one patient experienced grade 3 treatment-related adverse events (TRAE) comprising anemia (4.5%) and neutropenia (4.5%). Non-hematologic TRAEs were predominantly of grade 1-2. The most common TRAEs (≥10%) were gastrointestinal reactions (10/22, 45.5%), hypertriglyceridemia (6/22, 27.3%), hyperbilirubinemia (4/22, 18.2%), elevated alanine aminotransferase levels (3/22, 13.6%), and increased gamma-glutamyl transferase levels (3/22, 13.6%). Gastrointestinal reactions characterized by nausea and/or diarrhea were the most commonly reported toxicities. The most common TEAEs associated with disease progression were infection and bleeding. No dose-limiting toxicity or treatment-related deaths were reported during the study period, and the maximum tolerated dose was not reached. Among the evaluable responses in all dose levels for R/R AML patients (n=21), one patient achieved complete response (CR) at a dosage of 40 mg BID while three patients maintained stable disease (SD) across various dosages, including QD at 60 mg and BID at both 40 mg and 50 mg. Furthermore, BPI-23314 demonstrated moderate elimination kinetics, with a plasma half-life ranging from 8.6 to 23.3 hours, while exhibiting dose-proportional exposure. Conclusion: BPI-23314 monotherapy exhibited preliminary clinical efficacy with manageable adverse events in patients with R/R AML. The study is ongoing. The satisfactory pharmacokinetic attribute and outstanding safety profile of BPI-23314 provide compelling rationales for further exploration of its therapeutic potential. Citation Format: Mingyuan Sun, Xiangyu Jin, Jing Guo, Xiaoyun Liu, Yan Xu, Hong Lan, Jiabing Wang, Jiangnan Zhen, Jing Yang, Lieming Ding, Junyuan Qi. Phase 1 study of BPI-23314, a novel BET inhibitor and degrader, in advanced myeloid leukemia (AML) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT142.

Abstract CT150: Trial in progress: A phase 1b single-arm, open-label, study of emavusertib (CA-4948) in combination with azacitidine and venetoclax in acute myeloid leukemia patients in complete response with measurable residual disease

Abstract Background: Emavusertib is a novel potent oral inhibitor of interleukin-1 receptor-associated kinase 4 (IRAK4) with additional inhibitory activity against FMS-like tyrosine kinase 3 (FLT3) and CDC-like kinases (CLK1/2/4). Inhibition of these onco-proteins may induce remission thereby addressing a critical unmet need for novel therapies in acute myeloid leukemia (AML). Clinical studies with emavusertib monotherapy have demonstrated a significant reduction in AML blasts with clinical and molecular responses, including patients with relapsed or refractory AML, previously treated with an HMA and/or FLT3 inhibitors (Metzeler 2022). Azacitidine + venetoclax (aza+ven) has been approved in newly diagnosed, unfit patients with AML. In the VIALE-A study, composite complete response (CRc) (CR, CRh, or CRi) in the absence of measurable residual disease (MRD) of &amp;lt;1 residual blast/1000 leukocytes (MRD negative [MRD−]) resulted in longer duration of response (DOR), event-free survival, and overall survival (OS), and better HSCT outcome compared with patients who achieved CRc but were MRD+ (Pratz, 2022). In pre-clinical studies, emavusertib in combination with aza+ven demonstrated synergistic antileukemic effects in AML cell lines, including azacitidine- or venetoclax-resistant cell lines. Adding emavusertib to aza+ven in MRD+ patients at the time of CR may convert MRD status without adding significant toxicity and confirm that emavusertib can be safely added to aza+ven as a potential new regimen in front-line therapy. Study Design: This is a single-arm, open-label Phase 1b trial evaluating safety and tolerability, PK, and conversion of MRD status with emavusertib as an add-on agent to aza+ven in AML patients who achieved CR or CRh with MRD+ based on local testing (EU CT Number 2023-505828-58-00). The primary objective of the study is to determine a safe and tolerable dosing schedule for the triple combination. Secondary objectives include MRD conversion rate, DOR, OS, and pharmacokinetics. The study will enroll approximately 24 patients at 5 to 10 sites globally. Patients will have received azacitidine and venetoclax as first line therapy and achieved CR or CRh after 1-6 cycles of aza/ven. If MRD status remains positive, emavusertib will be added to the existing well tolerated aza+ven regimen. The starting emavusertib dose is 200 mg BID for 7 days per cycle of 28 days. If well tolerated, duration of emavusertib treatment will be extended to 14 and 21, respectively; no intra-patient change of emavusertib dosing duration is planned. The patients will continue triple treatment (emavusertib+aza+ven) until consent withdrawal, disease progression, intolerable toxicity, or not achieving MRD- within 6 cycles of triple treatment. In this Phase 1b trial, MRD can be evaluated by local testing of bone marrow. Key exclusion criteria include residual toxicities and significant comorbidities. Citation Format: Reinhard von Roemeling, Adolfo De La Fuente, Claudio Cerchione, Sebastian Scholl, Jan Moritz Middeke, Gaurav S. Choudhary, Maria Lamar, Steven Angelides, Uwe Platzbecker. Trial in progress: A phase 1b single-arm, open-label, study of emavusertib (CA-4948) in combination with azacitidine and venetoclax in acute myeloid leukemia patients in complete response with measurable residual disease [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT150.

Assessment of CYP-Mediated Drug Interactions for Enasidenib Based on a Cocktail Study in Patients with Relapse or Refractory Acute Myeloid Leukemia or Myelodysplastic Syndrome.

As a selective and potent inhibitor targeting the isocitrate dehydrogenase-2 (IDH2) mutant protein, enasidenib obtained approval from the US Food and Drug Administration (FDA) in 2017 for adult patients with acute myeloid leukemia (AML) with an IDH2 mutation. In vitro investigations demonstrated that enasidenib affects various drug metabolic enzymes and transporters. This current investigation aimed to assess enasidenib on the pharmacokinetics (PKs) of CYP substrates, including dextromethorphan (CYP2D6 probe drug), flurbiprofen (CYP2C9 probe drug), midazolam (CYP3A4 probe drug), omeprazole (CYP2C19 probe drug), and pioglitazone (CYP2C8 probe drug), in patients with AML or myelodysplastic syndrome. Results showed that following the co-administration of enasidenib (100 mg, once daily) for 28 days, the PK parameters AUC(0-∞) and Cmax of dextromethorphan increased by 1.37 (90% confidence interval (CI): 0.96, 1.96) and 1.24 (90% CI: 0.94, 1.65)-fold, respectively, compared to dextromethorphan alone. For flurbiprofen, these parameters increased by 1.14 (90%CI: 1.01, 1.29) and 0.97 (90% CI 0.86, 1.08)-fold, respectively, when compared to flurbiprofen alone. Conversely, midazolam exhibited decreases to 0.57 (90% CI 0.34, 0.97) and 0.77 (90% CI 0.39, 1.53)-fold, respectively, in comparison to midazolam alone. The parameters for omeprazole increased by 1.86 (90% CI: 1.33, 2.60) and 1.47 (0.93, 2.31)-fold, respectively, compared to omeprazole alone, while those for pioglitazone decreased to 0.80 (90% CI: 0.62, 1.03) and 0.87 (90% CI: 0.65, 1.16)-fold, respectively, in comparison to pioglitazone alone. These findings provide valuable insights into dose recommendations concerning drugs acting as substrates of CYP2D6, CYP2C9, CYP3A4, CYP2C19, and CYP2C8 when administered concurrently with enasidenib.

Pursuing dynamics of minimal residual leukemic subclones in relapsed and refractory acute myeloid leukemia during conventional therapy.

Acute myeloid leukemia (AML) is characterized by clonal heterogeneity, leading to frequent relapses and drug resistance despite intensive clinical therapy. Although AML's clonal architecture has been addressed in many studies, practical monitoring of dynamic changes in those subclones during relapse and treatment is still understudied. Fifteen longitudinal bone marrow (BM) samples were collected from three relapsed and refractory (R/R) AML patients. Using droplet digital polymerase chain reaction (ddPCR), the frequencies of patient's leukemic variants were assessed in seven cell populations that were isolated from each BM sample based on cellular phenotypes. By quantifying mutant clones at the diagnosis, remission, and relapse stages, the distribution of AML subclones was sequentially monitored. Minimal residual (MR) leukemic subclones exhibit heterogeneous distribution among BM cell populations, including mature leukocyte populations. During AML progression, these subclones undergo active phenotypic transitions and repopulate into distinct cell population regardless of normal hematopoiesis hierarchic order. Of these, MR subclones in progenitor populations of patient BM predominantly carry MR leukemic properties, leading to more robust expansion and stubborn persistence than those in mature populations. Moreover, a minor subset of MR leukemic subclones could be sustained at an extremely low frequency without clonal expansion during relapse. In this study, we observed treatment persistent MR leukemic subclones and their phenotypic changes during the treatment process of R/R AML patients. This underscores the importance of preemptive inhibition of clonal promiscuity in R/R AML, proposing a practical method for monitoring AML MR subclones.

Prognostic Value of IGF2BP3 Gene Expression Levels in Patients with Acute Myeloid Leukemia

To investigate the relationship between IGF2BP3 gene expression and prognosis in patients with acute myeloid leukemia (AML). High throughput transcriptome sequencing was performed on bone marrow primary leukemia cells from 27 patients with AML in our center, the relationship between IGF2BP3 expression levels and clinical characteristics were analyzed and verify the samples from patients with newly treated AML and refractory AML. The expression level of IGF2BP3 gene were analyzed in 20 healthy subjects and 26 patients with AML. The expression of IGF2BP3 in two anthracycline-resistant cell lines (HL60/ADR, K562/ADR) was detected by RT-qPCR and Western blot, and the expression difference of IGF2BP3 was compared with that in sensitive cells (HL60, K562). The relationship between the expression level of IGF2BP3 in patients with AML and prognostic were analyzed through data analysis of 746 patients with AML, and the prognostic value of IGF2BP3 in AML was analyzed by multivariate Cox regression analysis. In the bone marrow primary leukemia cells of 27 AML patients in our center, the expression level of IGF2BP3 in patients with refractory AML was significantly higher than that in chemotherapy sensitive patients (P =0.0343). The expression of IGF2BP3 in leukemia patients with extramedullary infiltration (EMI) was significantly higher than that in AML patients without extramedullary infiltration (P =0.0049). Compared with healthy subjects (n=20), IGF2BP3 expression in AML patients (n=26) was higher (P =0.0009). The expression of IGF2BP3 mRNA in the anthracycline resistant cell lines (HL60/ADR, K562/ADR) was significantly higher than that in the sensitive cell lines (K562/ADR vs K562,P =0.0430; HL60/ADR vs HL60, P =0.7369). Western blot results showed that the expression of IGF2BP3 protein in mycin resistant cells was significantly higher than that in sensitive cells (P < 0.001). qPCR results showed that the expression level of IGF2BP3 mRNA in refractory AML patients was significantly higher than that in patients with chemotherapy sensitive (P =0.002). High expression of IGF2BP3 was associated with poor prognosis in AML (P < 0.05) in 3 large sample cohorts of AML patients. Univariate and multivariate prognostic analyses demonstrated that high expression of IGF2BP3 was significantly associated with shorter event-free survival (EFS, HR=1.887, P =0.024) and overall survival (OS, HR=1.619, P =0.016). The high expression of IGF2BP3 gene may be an important factor in the poor prognosis of AML, suggesting that IGF2BP3 gene may be a new molecular marker for the clinical prognosis evaluation and treatment strategy of AML.

Pharmacological p38 MAPK inhibitor SB203580 enhances AML stem cell line KG1a chemosensitivity to daunorubicin by promoting late apoptosis, cell growth arrest in S-phase, and miR-328-3p upregulation

Acute myeloid leukaemia (AML) is characterized by uncontrolled proliferation of myeloid progenitor cells and impaired maturation, leading to immature cell accumulation in the bone marrow and bloodstream, resulting in hematopoietic dysfunction. Chemoresistance, hyperactivity of survival pathways, and miRNA alteration are major factors contributing to treatment failure and poor outcomes in AML patients. This study aimed to investigate the impact of the pharmacological p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 on the chemoresistance potential of AML stem cell line KG1a to the therapeutic drug daunorubicin (DNR). KG1a and chemosensitive leukemic HL60 cells were treated with increasing concentrations of DNR. Cell Titer-Glo®, flow cytometry, phosphokinase and protein arrays, Western blot technology, and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) were employed for assessment of cell viability, half-maximal inhibitory concentration (IC50) determination, apoptotic status detection, cell cycle analysis, apoptosis-related protein and gene expression monitoring. Confocal microscopy was used to visualize caspase and mitochondrial permeability transition pore (mPTP) activities. Exposed at various incubation times, higher DNR IC50 values were determined for KG1a cells than for HL60 cells, confirming KG1a cell chemoresistance potential. Exposed to DNR, late apoptosis induction in KG1a cells was enhanced after SB203580 pretreatment, defined as the combination treatment. This enhancement was confirmed by increased cleavage of poly(ADP-ribose) polymerase, caspase-9, caspase-3, and augmented caspase-3/-7 and mPTP activities in KG1a cells upon combination treatment, compared to DNR. Using phosphokinase and apoptosis protein arrays, the combination treatment decreased survival Akt phosphorylation and anti-apoptotic Bcl-2 expression levels in KG1a cells while increasing the expression levels of the tumor suppressor p53 and cyclin-dependent kinase inhibitor p21, compared to DNR. Cell cycle analysis revealed KG1a cell growth arrest in G2/M-phase caused by DNR, while combined treatment led to cell growth arrest in S-phase, mainly associated with cyclin B1 expression levels. Remarkably, the enhanced KG1a cell sensitivity to DNR after SB203580 pretreatment was associated with an increased upregulation of miR-328-3p and slight downregulation of miR-26b-5p, compared to DNR effect. Altogether, these findings could contribute to the development of a new therapeutic strategy by targeting the p38 MAPK pathway to improve treatment outcomes in patients with refractory or relapsed AML.

Devimistat plus chemotherapy vs chemotherapy alone for older relapsed or refractory patients with AML: results of the ARMADA trial

AbstractAcute myeloid leukemia (AML) is an aggressive cancer of the myeloid lineage. Outcomes in older patients are poor, with high rates of resistant and relapsed disease. Devimistat is a lipoic acid analog that inhibits mitochondrial metabolism. Devimistat combined with high-dose cytarabine and mitoxantrone resulted in promising phase 1 and 2 response rates especially in older patients. Therefore, the phase 3 ARMADA 2000 trial was conducted in patients aged ≥50 years with relapsed or refractory AML. The study randomized patients between devimistat combined with high-dose cytarabine and mitoxantrone (CHAM) or 1 of 3 control treatment regimens without devimistat: high-dose cytarabine and mitoxantrone; mitoxantrone, etoposide, and cytarabine; or fludarabine, cytarabine, and filgrastim. Overall, 265 patients consented to participate from 56 sites across 11 countries, and 200 patients were randomized, 98 patients to the devimistat arm and 102 patients to the control arm. The safety profile was consistent with high-dose cytarabine–based salvage regimens. There were 18 (9%) deaths on study (11 on CHAM and 7 on control). The study failed to meet its primary end point, with a complete remission (CR) rate of 20.4% in the devimistat arm compared with 21.6% in the control arm (P = .57). Overall survival was not statistically significantly different between the study arms, with a median of 8.9 months in the CHAM arm compared with 6.2 months in the control arm (P = .62). In conclusion, devimistat added to chemotherapy did not improve the CR rate or survival in patients aged ≥50 years with relapsed or refractory AML. This trial was registered at www.ClinicalTrials.gov as #NCT03504410.

Abstract 5592: HMGA1 modulates chromatin state and transcriptional networks involved in plasticity in refractory myeloid leukemia

Abstract Although High Mobility Group A1 (HMGA1) chromatin regulators are overexpressed in refractory acute myeloid leukemia (AML) and diverse solid tumors, targetable mechanisms underlying HMGA1 remain elusive. HMGA1 is highly expressed in stem cells and poorly differentiated cancers where it modulates chromatin structure to activate developmental gene networks. In AML arising from JAK2V617F myeloproliferative neoplasms (MPN), HMGA1 is required for leukemogenesis by inducing transcriptional networks that drive aberrant proliferation and cell fate. Like MPN AML, KMT2A-rearranged (KMT2A-r) AML is refractory to therapy and highly lethal. KMT2A-r AML is caused by rearrangements of the KMT2A gene, which encode abnormal fusion proteins that induce pro-leukemogenic genes, including HOX genes. While prior work identified KMT2A fusion partners and protein complexes, this has not led to better therapies for most patients. We therefore sought to examine HMGA1 function in KMT2A-r AML. We hypothesized that: 1) HMGA1 drives plasticity in KMT2A-r AML by altering chromatin state and transcriptional networks, and, 2) Targeting HMGA1 will enhance sensitivity to therapy. In two KMT2A-r AML patient cohorts, HMGA1 is highly overexpressed compared to CD34+ stem and progenitors from healthy controls, suggesting it drives leukemogenesis. To define HMGA1 function, we silenced HMGA1 using CRISPR or short hairpin RNA in KMT2A-r cell lines (MOLM-14, THP-1, MV4-11). Strikingly, silencing HMGA1 disrupts proliferation and clonogenicity in vitro, while prolonging survival in immunosuppressed mice transplanted with KMT2A-r AML cells. Intriguingly, leukemic cells that engraft in the bone marrow from the pool of cells with HMGA1 silencing express higher levels of HMGA1, suggesting that escape from gene silencing and a specific level of HMGA1 is required for leukemic engraftment and expansion. HMGA1 also increases in KMT2A-r AML cells that become resistant to cytarabine (AraC), suggesting that HMGA1 endows AML cells with the capacity to survive and expand after AraC. Because repression of tumor suppressors was recently defined as a mechanism of therapy resistance in AML, we also examined tumor suppressor pathways in both JAK2V617F and KMT2A-r AML. Intriguingly, HMGA1 occupies the promoter region of the CDKN1A locus by chromatin immunoprecipitation and represses its expression in KMT2A-r and JAK2V617F AML cells. To define additional mechanisms underlying HMGA1 in KMT2A-r AML, multi-omics studies are underway. In preliminary work thus far, we also found that HMGA1 induces HOX genes. Together, these findings implicate HMGA1 as a promising therapeutic target and novel epigenetic regulator in KMT2A-r AML by altering chromatin state and downstream gene expression. Citation Format: Bailey E. West, Jung-Hyun Kim, Audrey-Ann Supreme, Iliana Herrera, Zanshé Thompson, Li Z. Luo, Faiza Shaik, Joseph Kim, Hyunsung Woo, Soheil Meshinchi, Rhonda E. Ries, Linda M. Resar. HMGA1 modulates chromatin state and transcriptional networks involved in plasticity in refractory myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5592.

Abstract 6323: Preclinical evaluation of CB-012, an allogeneic anti-CLL-1 CAR-T cell therapy, that exhibits specific and potent toxicity in acute myeloid leukemia (AML) xenograft models

Abstract Background: CLL-1 is a compelling therapeutic target for AML as it is highly expressed on AML tumor cells and leukemic stem cells but is not expressed on hematopoietic stem cells. CB-012 was engineered with a next-generation Cas12a CRISPR hybrid RNA-DNA (chRDNA) genome-editing technology and leverages both checkpoint disruption and immune cloaking armoring strategies to potentially improve antitumor activity. The CB-012 anti-CLL-1 CAR was developed with a fully human scFv and the CD28 costimulatory domain and is currently in development for the treatment of relapsed or refractory AML (r/r AML). Here we describe preclinical studies that supported the CB-012 IND clearance by the FDA in October 2023. Methods: Cas12a chRDNA guides were implemented to generate five genome edits in the manufacture of CB-012. A multiplex genome-editing strategy was designed to enhance the antitumor activity of CB-012 through prevention of GvHD, PD-1 checkpoint disruption, and suppression of allograft rejection. In vitro and in vivo studies evaluated the specificity of antigen binding, antigen-dependent activity, and toxicologic potential. Results: CB-012 demonstrated potent antigen-dependent expansion and cytotoxic activity against CLL-1+ human AML cell lines and patient-derived cells in co-cultures. In AML xenograft models, a single dose of CB-012 CAR-T cells resulted in robust tumor control, leading to significant prolongation of survival. CB-012 co-culture with multiple CLL-1-negative cell types representing vital tissues demonstrated that the anti-CLL-1 scFv does not exhibit tissue cross-reactivity. In an unbiased cell surface protein microarray, the anti-CLL-1 scFv demonstrated highly specific interaction with human CLL-1, with no detectable non-specific interactions. CB-012 CAR-T cells exhibited limited tissue infiltration and expansion in treatment naïve, immunocompromised murine models. Conclusion: CB-012, the first allogeneic anti-CLL-1 CAR-T cell therapy using both checkpoint disruption and immune cloaking armoring, demonstrated specific and potent CLL-1-targeted cytolytic activity in vitro and in vivo. Specificity of the anti-CLL-1 scFv was demonstrated in an unbiased protein-binding study and no adverse safety signals were observed from CB-012 in murine toxicology models. These preclinical studies supported the IND clearance of CB-012, which is being evaluated in the AMpLify trial, a Phase 1, first-in-human clinical trial for patients with r/r AML (NCT06128044). Citation Format: Brian Francica, Elizabeth Garner, Sai Namburi, Cian Colgan, Tristan Fowler, Devin Mutha, Art Aviles, Morena Stanaway, Raymond Guo, Zili An, Erin Kelly, Emilie Degagne, George Kwong, Leslie Edwards, Emma Jakes, McKay Shaw, Benjamin Schilling, Jeremy Huynh, Ricky Luu, Max Sidorov, Rhonda Mousali, Mikk Otsmaa, Peter Lauer, Justin Skoble, Steven Kanner. Preclinical evaluation of CB-012, an allogeneic anti-CLL-1 CAR-T cell therapy, that exhibits specific and potent toxicity in acute myeloid leukemia (AML) xenograft models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6323.

Abstract 6728: Preclinical development of QL325, a novel T cell engager targeting CLEC12A-positive AML

Abstract Despite advancement in targeted therapies, treatment options for patients with acute myeloid leukemia (AML) that provide a tolerable and durable response remain elusive. We have developed a CD3 bispecific antibody, QL325, targeting CLEC12A, a c-type lectin protein that is highly expressed on AML blasts. Normally, CLEC12A expression is mostly confined to the CD34+CD38- progenitor population and largely absent on normal and regenerating bone marrow stem cells. Our bispecific antibody is configured in a 2 + 1 format, with bivalent avidity binding to CLEC12A, monovalent low affinity binding to CD3, and an effector-null Fc for extending half-life. In our preclinical studies, QL325 induced CLEC12A -dependent activation and proliferation of T cells. Redirected T cell-dependent cytotoxicity mediated by QL325 was restricted to AML cancer cells expressing CLEC12A. QL325 demonstrated dose dependent suppression of tumor growth in xenograft models of AML, significantly more potent than a clinical benchmark antibody. In non-human primates, QL325 was tolerated up to 0.03 mg/kg for IV dosing and under 0.1 mg/kg for SC dosing, well above the predicted effective therapeutic dose. A phase 1 clinical trial is currently ongoing to determine the safety and early efficacy in patients with refractory or relapsed AML. Citation Format: Shenda Gu, Hieu V. Tran, Shihao Chen, Ke Liu, Xin Zhang, Linchao Jia, Ruixue Ma, Jiayu Fu. Preclinical development of QL325, a novel T cell engager targeting CLEC12A-positive AML [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6728.

Abstract 7123: Biomarker-targeted alkylator and DNA damage repair inhibitor combination for refractory and relapsed acute myeloid leukemia (AML)

Abstract Isocitrate dehydrogenase 1 and 2 (IDH1/2) convert isocitrate to α-ketoglutarate in the tricarboxylic acid (TCA) cycle. A missense mutation in IDH1/2 leads to accelerated conversion of α-ketoglutarate into 2-hydroxyglutarate (2-HG), an oncometabolite that competitively inhibits α-ketoglutarate-dependent dioxygenases including Ten-Eleven Translocation (TET) enzymes. TET enzymes are DNA demethylases that convert 5-methylcytosine to 5-carboxycytosine and regulate CpG island promoter methylation signatures. In IDH1/2 mutant glioma, inhibition of TET2 enzyme by 2-HG can lead to promoter hypermethylation of O6-methylguanine methyltransferase (MGMT) and reduce its expression. Approximately 10-15% of de novo or treatment-related AML harbor mutually exclusive mutations in IDH1/2 or TET2, and emerging resistance towards clinical IDH1/2 inhibitors, therefore warrants novel therapeutic options. We performed a pan-cancer TCGA analysis and observed MGMT promoter hypermethylation and reduced expression in IDH1/2 AML. Our independent study on 10 AML patients (5 IDH1/2 and 5 TET2 mutant) corroborated the TCGA data and showed a significantly reduced expression of MGMT in comparison to 7 wild-type AML samples. As MGMT resolves O6-alkylguanine lesions during DNA damage, we performed an exhaustive alkylator screen, where temozolomide (TMZ) and our novel compound KL-50 emerged as the top hits that imparted a maximum therapeutic index in multiple MGMT (MGMT+/–) isogenic AML cell line models. Both TMZ and KL-50 induced MGMT-dependent DNA strand breaks and replication stress and activated ATM and ATR DNA damage response pathways in a time-dependent manner. Inhibition of ATR activation with Ceralasertib, an ATR inhibitor (ATRi) currently in clinical trials for chronic myelomonocytic leukemia and myelodysplastic syndromes, imparted a profound MGMT-dependent synergy with TMZ and KL-50. Researchers have established in glioma that mismatch repair (MMR) loss confers resistance to TMZ, and reported studies also show evidence of MMR loss in refractory or relapsed AML patients. Thus, we developed numerous MMR-deficient isogenic AML cell lines in an MGMT+/– background and observed MMR loss-mediated resistance to TMZ and abrogation of its synergy with ATRi. Unlike TMZ, KL-50 retained a profound synergy with ATRi in an MGMT-dependent manner irrespective of MMR status. We are currently investigating our novel KL-50 and ATRi combination in MGMT/MMR isogenic cell line-based in vivo AML models and in AML patient-derived xenografts to establish it as a promising novel biomarker-targeted therapy for AML patients. Citation Format: Prateek Bhardwaj, Ranjini Sundaram, Amro Baassiri, Martin Matthews, Jennifer VanOudenhove, Susan Gueble, Stephanie Halene, Ranjit Bindra. Biomarker-targeted alkylator and DNA damage repair inhibitor combination for refractory and relapsed acute myeloid leukemia (AML) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7123.