Primary Leukemia Research Articles

Clinical Characteristics and Prognosis of Primary Plasma Cell Leukemia and Newly Diagnosed Multiple Myeloma Under the New IMWG Definition Criteria

Background: Recently, the International Myeloma Working Group (IMWG) has recommended new primary plasma cell leukemia (pPCL) definition criteria, which require the presence of ≥ 5% circulating plasma cells in peripheral blood smears. The objective of this study was to investigate the clinical characteristics and prognosis of new-defined pPCL and newly diagnosed multiple myeloma (NDMM). Methods: This was a single-center, retrospective study including patients diagnosed with new-defined pPCL or NDMM at Zhongda Hospital, China, between January 2010 and December 2022. Results: There were 23 pPCL patients and 264 NDMM patients in our cohort. Generally, pPCL patients were younger than NDMM patients (median diagnostic age: 63 vs. 67 years old, p=0.018). The 1q21+ aberration was predominantly found in NDMM (p= 0.038) whereas t(11;14) dominated in pPCL (p= 0.017). Notably, pPCL exhibited a lower platelet level (p< 0.001) and a higher frequency of non-hyperdiploid karyotypes (p= 0.03) in contrast to NDMM. The median overall survival (OS) and progression-free survival (PFS) in NDMM were notably superior to those observed in pPCL (HR: 0.41, p= 0.001, HR: 0.38, p< 0.001, respectively). Interestingly, the OS in NDMM was 3 times longer than that in pPCL in females (p< 0.01) while no difference was found between NDMM and pPCL in males (p= 0.078). Moreover, NDMM patients treated with proteasome inhibitor (PI)-based treatment showed a significantly better prognosis than pPCL patients receiving the same treatment (OS: p< 0.01, PFS: p< 0.01, respectively). Similar findings were observed for patients undergoing either autologous stem cell transplantation (ASCT) or CD38 antibody treatment, both presenting a favorable prognosis in NDMM. However, no significant difference emerged between the two groups in terms of immunomodulatory drugs (IMiDs)-based or PI+IMiDs-based regimens. Multivariate analysis indicated elevated lactate dehydrogenase (LDH) was an independent predictor of adverse prognosis in NDMM (HR: 3.12, p<0.01). Conclusion: Our study revealed the clinical features and prognosis of pPCL and NDMM patients according to the new diagnostic criteria. The findings highlighted a generally improved prognosis in NDMM compared to pPCL, especially among female patients or those treated with PI-based regimens. It is important to note that our study had a limited sample size, potentially introducing some bias. We hope well-designed and long-term follow-up studies can be conducted to provide more reliable results.

Cebpβ/IL1/TNFα Positive Feedback Loop Drives Drug Resistance of BCL2 and MDM2 Inhibitors in Monocytic Leukemia Cells

Introduction:Ventoclax-based combinations have emerged as a new standard of care for patients with acute myeloid leukemia (AML) who are not suitable for intense chemotherapy. Not all patients respond to these treatments, and those who do may relapse. MDM2 inhibitors are promising therapeutics for treating TP53 wild-type tumors, including most de novo AML cases, with numerous compounds currently in pre-clinical and clinical evaluation. However, clinical trials of MDM2 inhibitors have shown modest and variable clinical activity. Functional genomic data showed that monocytic leukemia (FAB M4/M5) is resistant to venetoclax-based therapies and MDM2 inhibitors. Notably, venetoclax and an MDM2 inhibitor, idasanutlin, demonstrated a strong positive correlation in the Beat AML cohort. We hypothesize that upregulation of certain myeloid transcription factors in monocytic leukemia may confer intrinsic resistance to BCL2 and MDM2 inhibitors, while certain environmental cues upregulated in these cells may confer extrinsic drug resistance. Additionally, there may be crosstalk between these intrinsic and extrinsic mechanisms. Methods: We performed differential expression gene (DEG) analysis of transcription factors (TFs) between M4/M5 and M0/M1 samples in the Beat AML and TCGA AML cohort. We overexpressed seven myeloid TFs (SPI1, CEBPB, CEBPD, JUNB, IRF8, KLF4, and MAFB) that are upregulated in M4/M5 and performed competitive drug assays. We treated M4/M5 and M0/M1 samples with venetoclax and idasanutlin, in the presence of a panel of myeloid cytokines and measured cell viabilities. A Luminex assay on monocyte supernatants from M4/M5 and M0/M1 AML samples were conducted to identify dysregulated cytokines. Furthermore, RNAseq DEG and immunoblot analysis were performed on CEBPB-overexpressing cell lines and IL-1-treated AML samples to elucidate the underlying mechanisms. Results: CEBPB overexpression conferred drug resistance to a broad range of BH3 mimetics, venetoclax combinations, and MDM2 inhibitors. RNA-seq and immunoblot analyses demonstrated that CEBPB overexpression downregulated CASP3, CASP6, BCL2, and TP53 pathway targets (CDKN1A, PMAIP1, BBC3, BMF, TP53), while upregulated MCL1, BCL2A1, and the NF-κB/IL-1/TNF pathway at transcription and/or translation levels. Phenotyping analysis showed that CEBPB overexpression drives myelo/monocytic differentiation. In accordance, CEBPB expression in primary AML correlates with drug responses of idasanutlin, venetoclax, and many venetoclax combinations. Additionally, primary monocytic leukemia expresses significantly higher levels of IL-1/TNF family genes, BCL2A1, and reduced CASP3, CASP6, and BCL2. Abnormal monocytes, but not granulocytes, T cells, or blasts from M4/M5 leukemia, extrinsically protect leukemia blasts from venetoclax and MDM2 inhibition by secreting elevated IL-1 and TNFα. IL-1β/TNFα treatment drove myelo/monocytic differentiation and up-regulated inflammatory cytokines, including an autoregulatory loop, as well as a number of cytokine receptors, such as IL1R1, TNFRSF1R, TNFRSF2R, and CSF2RB. Remarkably, IL-1α/IL-1β and TNFα uniquely upregulated CEBPB expression in M4/M5 cells and protected them from apoptosis induced by venetoclax and MDM2 inhibitors. Conversely, TNFα treatment induced augmented extrinsic apoptosis in M0/M1 leukemia cells. Interestingly, treatment with venetoclax and idasanutlin led to a feedback upregulation of CEBPB, IL-1β, and/or TNFα, along with their respective receptors, and promoted myelomonocytic differentiation. IL-1/TNFα antagonists or an IRAK inhibitor alone did not kill leukemia cells, but they showed synergistic cytotoxicity when combined with venetoclax and idasanutlin. Conclusions: In summary, we have described a positive feedback loop between CEBPB, IL-1/TNFα, and monocytic differentiation in monocytic leukemia that contributes to intrinsic and extrinsic drug resistance against BCL2 and MDM2 inhibitors. This crosstalk and the consequent drug resistance are further reinforced by venetoclax/MDM2 inhibition treatment. Combining venetoclax or idasanutlin with IL-1/TNFα antagonists or an IRAK inhibitor can abrogate the feedback loop and induce synergistic cytotoxic effects, offering promising therapeutic strategies to enhance the treatment efficacy of venetoclax and MDM2 inhibitors for monocytic leukemia.

A Phase II Study of Flumatinib with Chemotherapy for Newly Diagnosed BCR::ABL1-Positive Acute Lymphoblastic Leukemia in Adults: Updated Results from RJ-ALL2020.2A Trial

Background The introduction of the second-generation TKIs further improved outcomes in BCR::ABL1-positive acute lymphoblastic leukemia (BCR::ABL1+ ALL). Flumatinib is a novel second-generation TKI approved in China in 2019. It has shown better efficacy compared to imatinib in clinical trials of CML, but few reports are available in ALL. Herein, we report the updated results of the RJ-ALL2020.2A trial, which is the first reported registered clinical trial of flumatinib in adult BCR::ABL1+ ALL last year. The enrollment will be completed at the end of Aug. 2023. Methods In this prospective phase II study, patient (pt) eligibility mainly includes: 18≤age＜65 years; newly diagnosed BCR::ABL+ ALL; with adequate organ function. Once the diagnosis is confirmed, the combination of flumatinib (600mg/day) and VIP-based chemotherapy regimen (Vincristine/Idarubicin/Prednisone) is given promptly. Allo-HSCT is recommended for all eligible pts. Blinatumomab is allowed to administer for MRD clearance before allo-HSCT. All pts receive central nervous system (CNS) prophylaxis once achieving remission. The choice of subsequent salvage treatments is based on the discretion of physicians. Multiparameter flow cytometry (minimal residual disease[MRD]<10 -4) and RT-qPCR (BCR-ABL1 transcript<10 -5) are used to monitor MRD. The primary endpoints are MRD clearance, PFS, and OS. (Clinical Trial Registration Number: ChiCTR2100042248) Results From Dec. 2020 to Jun. 2023, 81 adult pts with de novo BCR::ABL1+ ALL were enrolled. Seventy-eight pts were included in the efficacy and safety assessment (3 were excluded due to the short duration of treatment), and 76 were available for survival analysis (2 withdrew). Median age was 42 years (range, 18-63). Median WBC count at diagnosis was 38.7×10 9/L (0.6-675.3). Four pts had primary CNS leukemia (Table 1). Among 78 pts, 75 (96.2%) achieved CR/CRi at the end of induction, and 78 (100%) achieved CR/CRi at any time. No early death occurred during the induction course. MRD flow negative rates were 67.1% (51/76) and 79.7% (55/69), while the CMR rates were 31.1% (23/74) and 52.2% (36/69) at the end of induction and 3 months, respectively. With a median follow-up time of 16.2 months (range, 1.8-29.2), the estimated 2-year PFS and OS rates were 64.8% and 81.3% (Figure 1). Among the 69 survived pts, 61 were in continuous remission, and 8 were relapsed (4 had CNS involvement). Among 7 deaths, 6 died of disease progression (4 had CNS involvement), and 1 of pulmonary infection post-HSCT. There was a survival superiority in pts who achieved MRD flow negativity (PFS: p=0.091, OS: p=0.005) or CMR (PFS: p=0.055; OS: p=0.033) at 3 months. With a median time of 6.4 months (range, 1.6-10.3) from diagnosis, 46 pts (median age of 39 years [range, 20-60]) received allo-HSCT with 45 pts in CR1. The MRD flow negativity and CMR rates were 82.2% (37/45) and 70.5% (31/44) before HSCT, respectively. PFS and OS significantly improved in patients who underwent HSCT (PFS: p<0.001, OS: p=0.012). In multivariate analysis for PFS and OS, MRD flow negativity at 3 months (PFS: HR: 0.129, p=0.016; OS: HR: 0.151, p=0.029) and allo-HSCT (PFS: HR: 0.247, p=0.036; OS: HR: 0.176, p=0.042) still had a significant effect on PFS and OS as protective factors. When including CMR as a variable, CMR at 3 months (PFS: HR: 0.221, p=0.02; OS: HR: 0.115, p=0.054) and allo-HSCT (PFS: HR: 0.169, p=0.01; OS: HR: 0.139, p=0.021) had the similar impact on survival. Among 75 pts evaluable for ABL1 mutations, 24 (32%) pts were mutated, and T315I was the most frequently identified (75%). Pts with T315I mutation showed a poorer outcome than non-T315I mutation (PFS: p<0.001, OS: p=0.01). Meanwhile, the safety profiles of the flumatinib-based therapy were acceptable. Non-hematological AEs were mostly G1-2, which were reversible rapidly after symptomatic management. Most of the G3-4 AEs were hematological, possibly related to chemotherapy. No permanent discontinuation or death related to flumatinib was observed. Conclusion This prospective study further confirmed the efficacy and safety of the promising second-generation TKI flumatinib combined with chemotherapy in newly-diagnosed Chinese adult pts with BCR::ABL1+ ALL. Achieving MRD flow negativity or CMR at 3 months and bridging allo-HSCT could further improve survival. The long-term follow-up data will be disclosed soon.

Compared to Venetoclax Plus Hypomethylating Agents, High Dose Cytarabine Based Intensive Chemotherapy Induction for Newly Diagnosed Acute Myeloid Leukemia (AML) Leads to a Faster Remission Resulting in Better Survival

Hypomethylating agents plus venetoclax is a commonly used induction regimen for newly diagnosed AML patients who are not eligible for standard intensive chemotherapy (IC). Due to the high remission rates and the easier administration of Venetoclax plus hypomethylating agents in the outpatient settings and community practices, some patients receive such induction even if IC eligible. We retrospectively analyzed 206 newly diagnosed AML patients, age 56-80 years who received either Venetoclax plus hypomethylating agents (n=65) or high dose cytarabine based IC ( n=141) to assess the difference in remission rates, time to achieve remission and the impact of time to achieving remission on survival endpoints. Patients who received IC ( FLAG or CLAG +/- Idarubicin) were younger ( median age 66 (56,79) vs 73(56,79) years, p<0.001) but had similar race distribution, NCCN cytogenetics risk and distribution of primary versus secondary leukemia compared to patients with hypomethylating agents plus venetoclax. Patients who received IC has similar chance of achieving CR (89% vs 71%, p=0.89) and transplant rate compared to venetoclax/hypomethylating agents. Patients who received IC had better DFS (p=0.026), a trend towards better OS (p=0.06) and similar relapse risk (p=0.69) compared to venetoclax/hypomethylating agents (figure 1). In a logistic regression analysis, patients who received IC and patients with favorable/intermediate risk AML had higher likelihood of achieving CR in the first 60 days post induction ( HR 2.34, 95% CI 1.19-4.61; P=0.01 for IC versus Venetoclax/hypometh; and HR 0.24 , 95% CI 0.12-0.49, P<0.001 for NCCN adverse versus favorable/intermediate risk AML). A cox model for survival endpoints where age was factored into three equal size groups (56-63, 64-70 and 71-79) and NCCN risk fitted as strata, was performed on survival endpoints. Achieving CR1 within 60 days of induction treatment had significant impact on overall survival (HR 0.24, 95% CI 0.13-0.46, p<0.001). Our data shows that among patients aged 55-80 years with newly diagnosed AML, receiving high dose cytarabine based IC have similar rates but more likely to achieve CR within 60 days than venetoclax plus hypomethylating agents. Achieving CR within 60 days of induction is a predictor of better overall survival. Based on our analysis, high dose cytarabine based IC should remain the preferred choice for patients eligible for such treatment.

Distinct Genetic Features in Peripheral Blood Represent the Characteristics of Circulating Plasma Cells in Primary Plasma Cell Leukemia

Clonal plasma cells in peripheral blood (PB) are crucial for diagnosing plasma cell neoplasm. The diagnostic criteria for plasma cell leukemia (PCL) have recently been revised to 5% or more circulating plasma cells (CPCs) in PB. Considering that CPCs are an independent worse prognostic factor in multiple myeloma (MM), elucidating how many CPCs are sufficient for distinguishing patients between PCL and other plasma cell neoplasm is important yet uncertain. These CPCs have been recently discussed in MM, characterized by more immature phenotype, clonogenic potential, and high expression of cancer stem cell (CTC) markers. Though the exact mechanism of peripheral circulation still needs further studies, MM CTCs are considered subclones of bone marrow (BM) plasma cells. On the other hand, previous studies regarding PB plasma cells in primary PCL (pPCL) have been mainly focused on similar characteristics to BM plasma cells. Considering significant prognostic differences based on CPCs, PB from PCL patients should have distinct features. Previous studies on PCL revealed that high genetic heterogeneity and accumulation of diverse high-risk genetic abnormalities eventually led to the disease. Therefore, we aimed to investigate the genetic profile of CPCs in PCL to exhibit proper evidence for diagnostic criteria and improve the current practices. We retrospectively identified patients diagnosed with PCL from 2015 to 2017 at Seoul National University Hospital. Our study population included 4 pPCL and 2 secondary PCL (sPCL) patients. We retrospectively collected patients' clinical information and laboratory test results and performed targeted sequencing using the NGS panel of 647 genes related to hematologic malignancies. In all analyzed samples, 51 in PB and 40 variants in BM were detected in pPCL. The median number of variants in pPCL patients was 11 per patient (range 5-25) in PB and 10 per patient (range 3-17) in BM. When comparing variant allele frequency (VAF) between the paired samples, there was a moderate correlation (R=0.44, P<0.05). Similarly, a moderate correlation was observed in both pPCL (R=0.41, P<0.05) and sPCL (R=0.47, P<0.05) groups. When comparing paired variants between PB and BM, 38 were commonly detected in both samples in pPCL patients. Fifteen variants were identified in only one of the two samples, 12 in PB and 3 in BM. Most variants showed a heterogeneous distribution of genes. We checked the paired samples using an Integrative genomics viewer. As a result, twelve pPCL and thirteen sPCL variants were identified in the paired samples. These variants were initially excluded in the filtering process because of low VAF. Consequently, three unique variants were identified in each pPCL and sPCL group, which were considered truly unique. In pPCL patients, MED12, VPS13B variant from PB, and ZMYM3 variant from BM were identified in one of the paired samples. In sPCL patients, unique variants were identified in ARID1A, FANCE, and TP53. In addition, we determined that PB VAF is higher than BM VAF in shared variants of pPCL patients. Conversely, BM VAF tended to be higher than PB VAF in sPCL. However, plasma cell% was generally higher in BM than PB, regardless of pPCL or sPCL. Therefore, the differences in the percentage of plasma cells between PB and BM samples cannot explain the unique variants detected in only one of the paired samples. pPCL is an aggressive disease characterized by a markedly high diversity of heterogeneous mutation distribution and high mutational burden. The clinical outcomes of pPCL are still poor in the novel agent era. There is an urgent need to improve the current diagnosis and treatment strategy. As shown in this study, CPCs in pPCL are not simply part of the malignant plasma cells shed from the BM but have characteristics distinct from them. In this study, we exhibited that PB variants had higher VAF than BM variants, and some unique variants were identified only in the PB samples. Conversely, in sPCL, more diverse variants were detected mainly in BM samples, and VAF was also higher in BM than PB. Considering unique variants detected in PB and the high genetic heterogeneity of the disease, PB should be included in the diagnosis of PCL to determine the exact genetic profile.

Development of Next Generation Antibody-Polymer-Drug Conjugates for Treatment of Multiple Myeloma

Background: Antibody-drug conjugates (ADCs) are an effective class of cancer therapeutics, but current ADCs face stability challenges, resulting in premature payload release and off-target toxicity. To overcome this, we developed a novel strategy using antibody-polymer-based drug conjugates (pADCs). Our pADCs have a number of advantages compared to currently FDA approved ADCs, including: 1) Increased drug payload without altering binding site numbers, ensuring maximum drug loading without affecting antigen and Fc binding; 2) Potential for synergistic immunotherapy and chemotherapy; 3) Improved pharmacokinetics and reduced immunogenicity with modification using water-soluble N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer, providing significant stealth effect; and 4) Enhanced stability under physiological conditions, reducing premature payload release and off-target toxicity. Panobinostat, a pan-HDAC (histone deacetylase) inhibitor, enhances CD38 expression and improves pADC efficiency against MM cells. Our hypothesis is that our pADC system induces strong cytotoxicity, further enhanced by panobinostat-induced CD38 upregulation, leading to more efficient treatment outcomes. Methods:mAbs decorated with cyclooctyne (DBCO) moieties in the hinge region were prepared in two steps: mAbs were reduced with tris(2-carboxyethyl)phosphine (TCEP), then thiol groups were capped with DBCO-PEG4-Mal. Azide-functionalized semitelechelic (ST) polymer-drug conjugates (ST-P-drug-N3) were synthesized via RAFT polymerization. Antibody-polymer-drug conjugates were prepared by CLICK chemistry. MM.1S and RPMI 8226 cell lines (ATCC) were used as the MM cell model. The cell internalization was revealed by confocal imaging. Primary MM cells were collected from the aspirate of eight patients with primary plasma cell leukemia and isolated via Ficoll centrifugation. CD38 upregulation was done by incubating with 10 or 25 nM panobinostat for 24 h and the apoptosis detection employed Annexin V and Propidium Iodide staining followed by flow cytometry analysis. Results: A series of CLICK-able mAbs and semitelechelic polymer-drug conjugates were synthesized. Among them, we firstly prepared Epirubicin (EPI)-based pADCs, such as DARA-P-EPI, ISA-P-EPI and DRO-P-EPI (Fig.1A). Unlike naked mAbs, pADCs can induce EPI concentration-dependent cytotoxicity. Surface calreticulin (CRT) was assessed and demonstrated the induction of EPI-dependent immunogenic cell death on MM.1S cells (Fig.1B). The pADC mechanism of action involves binding to cell surface antigens, internalization via endosomes, and subsequent cleavage of drugs at lysosomes by cathepsin B. This minimizes premature drug release and reduces off-target toxicity (Fig.1C). Ex vivo studies on patient MM cells revealed that pADCs induced significantly higher apoptosis compared to naked mAbs and free EPI, highlighting their efficacy (Fig.1D). CD38-based pADC's efficacy was enhanced by pretreatment with panobinostat (Fig.1F), which increased CD38 expression (Fig.1E). When incubating with NK cells and pADC, the number of target cells decreased significantly indicating the pADC preserve the original mAb ADCC functionality. Notably, co-treatment of RPMI8226 cells with anti-CD38 and GDC0980, a PI3k/mTOR inhibitor, significantly improved cytotoxicity, suggesting DARA's potential for chemo sensitization (Fig.1G). Conclusion: pADC's innovative design offers a high likelihood of successful clinical development and holds significant promise for MM therapy. Moreover, the unique mechanism provides potential to effectively overcome mAb and multiple drug resistance. Its facile nature allows for easy incorporation of multiple types of payloads into the ADC, making its synthesis highly scalable .

A Prognostic Model Integrating Circulating Clonal Plasma Cells into R-ISS and PET-CT Based Tumor Burden in Transplant-Ineligible Multiple Myeloma

Introduction: Circulating clonal plasma cell (cCPC) is an easily obtained and non-invasive biomarker in multiple myeloma (MM), providing distinct prognostic information from the revised-international staging system (R-ISS). However, its prognostic relevance has been investigated primarily in transplant-eligible and clinical trial settings. Consequently, there is limited data on the impact of cCPC on outcomes and optimal cut-off values in transplant-ineligible (TIE) MM patients. Moreover, appropriate combinations to refine risk stratification, such as tumor burden measured by positron emission tomography-computed tomography (PET-CT), have yet to be fully explored. Methods: We performed a retrospective analysis on newly diagnosed TIE-MM patients with available peripheral blood (PB) flow cytometry (FCM) and PET-CT data from 2011 to 2021. Patients with primary plasma cell leukemia (n=8), defined as >5% monoclonal plasma cells in PB, were excluded from the study. Quantification of cCPC was performed using 6-color (2011-2016) or 8-color (2017-2021) FCM staining for CD19, CD56, CD38, CD138, cytoplasmic κ, and cytoplasmic λ to confirm monoclonality (Beckman Coulter, USA), which required at least 150000 mononuclear cell counts with the detectable limit at 0.01% (10 -4) based on previous reports (Gonsalves et al). Tumor burden was assessed by calculating total lesion glycolysis (TLG) using the following formula: the mean standardized uptake value (SUV) multiplied by the total tumor volume with an absolute SUV >2.5, using Metavol Software (Hokkaido University, Japan). Receiver operating curve analysis with the Youden index was employed to determine the optimal cutoff for predicting 2-year progression-free survival (PFS) and 5-year overall survival (OS). The predictive performance of R-ISS, cCPC, and TLG alone, along with their combinations, was compared using Harrell's concordance index (c-index). Results: 114 patients with TIE-MM were analyzed. The median age was 78 years (interquartile range [IQR] 73-83). The number of patients classified as R-ISS Ⅰ, Ⅱ, and Ⅲ was 12 (10.5%), 82 (71.9%), and 20 (17.5%), respectively. Most patients (85.1%) received proteasome inhibitor-based induction remission therapy. cCPCs were detectable in 90 patients (80.7%), with a median level of 6 ×10 -4 (IQR 1-22). Regarding tumor burden, 73 patients (64%) had at least one fluorodeoxyglucose avid lesion with a median TLG of 34.7 (IQR 0-268). cCPC levels were significantly correlated with CPC in bone marrow (R =0.24, P =0.01) but not with TLG (R =-0.01, P =0.88) and involved free light chain levels (R =0.07, P =0.41). The optimal cut-off values in predicting 2-year PFS and 5-year OS were 9 and 10 ×10 -4 for cCPC, and 325 and 343 for TLG, respectively. For simplicity, we classified >10 ×10 -4 for cCPC and >300 for TLG as high-risks. Notably, approximately two-thirds of the patients (62.3%) had at least one high-risk feature (Figure 1). Both high cCPC and TLG showed significant associations with worse OS and PFS (5-year OS rate: cCPC high vs. low, 40.2% vs. 69.3%; TLG high vs. low, 38% vs. 64.5%; 2-year PFS rate: cCPC high vs. low, 45.7% vs. 69.1%; TLG high vs. low, 46.4% vs. 64% all P < 0.05). These factors retained prognostic significance after adjustment for R-ISS on multivariate analysis. Finally, we constructed a novel predictive model integrating RISS, cCPC, and TLG. This model discriminated OS among patients with 0 (5-year OS rate, 80% [95% confidence interval 68.4%-93.6%]), 1 (50.5% [37.7%-67.7%]), and ≧2 factors (29% [13.3%-63.5%], P <0.001, Figure 2). The c-index was the highest (0.651) in this combined model compared to the single use of these risk factors (0.585, 0.594, and 0.569). Conclusions: We demonstrated the prognostic impact of cCPC, which is independently associated with R-ISS and TLG, on real-world TIE-MM patients. The new prediction model, integrated with these different clinical and biological features, may provide robust outcome discrimination.

Low-Dose IA with Venetoclax Regimen As Induction Therapy for Newly Diagnosed Acute Myeloid Leukemia

Abstract Background: The IA regimen (combination of idarubicin and cytarabine) is used as the most common induction of remission therapy for acute myeloid leukemia, with the complete response (CR) rates of up to 70%. Addition of the BCL-2 inhibitor venetoclax(Ven) to chemotherapy can increase apoptosis priming. In order to further improve the remission rate and prolong survival, our center uses a low-dose IA regimen combined with Venetoclax to treat newly diagnosed primary acute myeloid leukemia under 60 years old. Methods: We retrospectively analyzed 15 patients with newly diagnosed AML, who was under 60 years old. Patients received idarubicin (6mg/m2 IV for 3-days) and cytarabine (60mg/m2 IV for 5-days) with oral venetoclax (400mg daily for 2 weeks) for induction, followed by the same chemo-free regimen for consolidation if patients responded to induction therapy. And then analyze the effects of this regimen on complete remission (CR) rate, minimal residual disease (MRD) negative CR rate, relapse-free survival (RFS), overall survival (OS), and adverse events. Findings: Between January, 2021 and June, 2023, 15 patients were treated with this regimen. The median age was 43 years (IQR, 36-43) and the median follow-up was 4.25 (IQR, 2.73-15.6) months. Among all patients, the ORR was 86.7% (95% CI 62, 96), the CR rate was 80.0% (95% CI 55, 93), and the MRD negative rate was 66.7% (95% CI 42, 85). According to 2022 ELN risk classification by genetics, the ORR in favorable risk patients were 50.0% (1/2), intermediate risk patients were 100% (7/7), adverse risk patients were 83.3%(5/6). Those who had epigenetic modification mutations (NPM1, FLT3-ITD, CEBPA) were more likely to benefit from this regimen. The most common grade 3 and 4 adverse reactions were neutropenia, thrombocytopenia, and anemia. Conclusion: As induction and consolidation therapy whose adverse reactions were tolerable, the low-dose IA with Venetoclax regimen produces deep remission for the patients with newly diagnosed primary AML.

The Clinical Menin Inhibitor Ziftomenib and the Nuclear Export Inhibitor Selinexor Synergistically Inhibit the Growth of MLL-r AML

CONCLUSION Menin is a scaffold protein that interacts with oncogenic histone-lysine-N-methyltransferase MLL1 (KMT2A)-fusion protein (FP) complex in MLL-rearranged ( MLL-r) AML. Menin inhibitors that evict menin from this interaction have been shown to be active against MLL-r and NPM1MT leukemia by modulating the expression of the leukemogenic homeobox A9 ( HOXA9) gene and its co-factor, MEIS1. Recent evidence showed that menin inhibitors can activate a tumor-suppressive network via a non-canonical transcriptional program through UTX. On the other hand, selective inhibitor of nuclear export (SINE) against XPO1/CRM1 has been shown to have robust anti-leukemia activity via enrichment of tumor suppressor proteins in the nucleus. In the present study, we hypothesized that menin and nuclear export inhibition would synergistically suppress AML cell proliferation and possibly sensitize menin inhibitor-resistant cells. We have used the clinical-stage menin inhibitor ziftomenib and SINE compound selinexor to simultaneously target menin-KMT2A protein-protein interactions and nuclear export. To assess growth inhibition, an ATP-based cell proliferation assay was used. Combination synergy was determined using CalcuSyn Version 2.0 synergy software. Stem-like progenitor cells were isolated using the StemSpan CD34+ expansion kit (StemCell Tech). Colony formation efficiency was determined using a Methocult assay (StemCell Tech). Gene and protein expression was detected using quantitative real-time PCR and western blotting. Flow cytometric analysis was performed to detect cell death and cell cycle status. We have performed the whole transcriptomic analysis via the RNA sequencing approach. The clinical candidate drug ziftomenib, in combination with selinexor, synergistically inhibited the growth of MLL-r AML cell lines (MV4;11 and MOLM13) (CI<1) [Fig.1A]. The combination of menin and XPO1 inhibitors significantly suppressed colony formation of CD34+ MLL-r progenitor stem cells derived from primary patient samples but was not toxic to normal CD34+ human hematopoietic progenitor stem cells (HPSCs). Menin inhibitor treatment caused the downregulation of menin protein along with its downstream targets HOXA9, MEIS1, and FLT3 in western blot analysis. Interestingly, selinexor also reduced menin, HOXA9, and MEIS1 protein levels. The combination enhanced menin down-expression, suggesting a molecular basis for the synergy between the two compounds. Ziftomenib suppressed the expression of menin in a time-dependent manner, which is evident as early as six hours of treatment. The combination showed increased CD11b, a marker of monocytic differentiation in MV4-11 treated cells. The combination also significantly enhanced both early and late apoptotic cell death in MLL-rearranged AML cells compared to either compound alone. Compared to controls, ziftomenib and selinexor-treated samples individually showed increased apoptotic and decreased G2/M populations, significantly enhanced in the combination. We observed differential expression of certain mRNAs and micro RNAs (miRs) in MV4-11 treated cells. The TMEM191B, SH3TC1, and SULT1C2 mRNAs were upregulated by ziftomenib and selinexor, which are enhanced further in the combination group. On the contrary, CENPK, CKS2, KIF18A, and H2BC4 mRNAs were downregulated by a single agent or combination. Among miRs, hsa-miR-34a-5p, hsa-miR-142-3p, hsa-miR-26b-5p were upregulated, and hsa-miR-33b-3p, hsa-miR-4454, hsa-miR-210-3p and hsa-miR-130b-3p [reported to be an essential lineage-specific codriver of MLL-AF4 leukemia] were downregulated by single agent or combination. Such mRNAs and miRs panels could serve as biomarkers for treatment response. MV4-11 cell line-derived xenografts in NSG mice showed a significant difference in survival in the combination arm compared to any single agent. Metronomic dosing also showed robust improvement in survival in the combination arm. Patient-derived xenografted NSG mice model using human primary MLLr re-transplantable leukemia cells showed improved survival in the combination arm [Fig. 1B]. These preclinical findings demonstrate that simultaneous inhibition of the menin-KMT2A interaction and nuclear export is a viable strategy for the treatment of MLL-r AML. Ongoing experiments with functional proteomic analysis will be presented at the ASH meeting.

Primary Acute Myeloid Leukemia Cells Trigger Distinct Activation Patterns in Expanded NK Cells

Increasing efforts are devoted to implement immunotherapies for the treatment of acute myeloid leukemia (AML). Recently, natural killer (NK) cell-based immunotherapy has shown initial encouraging results. However, which patients are most likely to benefit from NK cell-based treatments remains poorly understood. Here, we investigate the responses of NK cells to ex vivo co-cultures with 55 primary AML samples using single-cell transcriptomics. We identify a subgroup of AML patients eliciting strong responses in NK cells and define the molecular programs in NK cells and other microenvironmental cell types triggered by diverse AML cells. We performed functional single-cell immune profiling on co-cultures of primary expanded NK cells and 55 bone marrow (BM) samples from AML patients at diagnosis. We used NK cells expanded using irradiated K562-41BB-L-mbIL-21 feeder cells, resulting in a product commonly used in clinical trials. All expanded NK cells were from one single healthy donor displaying an HLA-C1C2 allotype.We investigated NK cell-treated and untreated cultures through multiplexed single-cell RNA sequencing (scRNA-seq) to dissect adaptive changes in both NK and AML BM cells upon their interaction. In total, we investigated 121 samples through scRNA-seq: 11 monocultures of expanded NK cells, 55 AML BM cells and 55 co-cultures of AML BM cells and expanded NK cells. scRNA-seq yielded 95,715 high quality cells (791 cells per sample on average), including 31,882 NK cells (483 cells per sample on average) and 63,833 AML BM cells (580 cells per sample on average). Unsupervised clustering of the cells revealed distinct clusters separating expanded NK cells from AML cells (Fig. 1a). We studied the sensitivity of leukemic cells to NK cytotoxicity using high-throughput flow cytometry. We further integrated the results with genetic and clinical data of the AML patients to characterize the mechanisms of action driving the transcriptomic responses and leukemic cell susceptibility to NK cell killing. After 24 h co-culture, scRNA-seq revealed that AML BM cells induced distinct gene expression states in the NK cells. The observed tumor-induced NK states were predominantly enriched in co-cultured samples and not found in NK cell monocultures which mostly consisted of resting-state NK cells. Across the co-cultures, half of the AML samples triggered at least 30% of NK cells to change from resting to tumor-induced states (Fig. 1b). Out of the 28 AML samples causing the strongest NK cell induction, 54% primarily triggered a type I interferon (IFN) signature, characterised by expression of genes encoding MX1, OAS1, and IRF7. In contrast, the other 46% mainly induced an activated phenotype, including expression of TNFRSF18 ( GITR), TNFRSF9 ( 4-1BB), TIGIT and HAVCR2 ( TIM-3). Killer cell immunoglobulin-like receptors-HLA ligand mismatchesare well known causes of NK alloreactivity. Thus, we explored whether HLA-C matched (C1C2, n=24) and mismatched (C1C1 or C2C2, n=28) AML samples influenced NK cell responses. Interestingly, no significant difference in the NK cell induction states was observed between matched and mismatched samples (Mann-Whitney p = 0.57). NK cell treatment also induced responses in the patients' own T cells. Both CD4+ and CD8+ T cells upregulated IFN-ɣ and type I IFN genes upon co-culture. The type I IFN signature in CD8+ T cells was mainly found in AML samples triggering strong NK cell induction. CD8+ T cells also upregulated cytotoxicity genes including FASLG and TNFSF10 (TRAIL), along with inhibitory molecules such as LAG3, suggesting that NK cells can promote effector functions of T cells. Our results suggest that AML BM cells from different patients trigger a heterogeneous response in expanded NK cells. Only in half of the cases, the leukemic BM cells induced substantial activation of NK cells. The observed variation in NK states was not determined by HLA-C allotypes, suggesting that other tumor cell features are responsible for the responses. This underscores the importance of understanding the molecular drivers of tumor and NK cell interaction. Our data additionally show that NK cell-based immunotherapy may be able to promote the functionality of the patient's own T cells, demonstrating how our ex vivo modeling approach can help to refine the mechanism of action of immunotherapies. Our work paves the way for identifying subgroups of AML patients responding to NK cell-based immunotherapies.

Ex Vivo Drug Sensitivity Evaluation of a ZMYM2::FGFR1 Fusion-Positive 8p11 Myeloproliferative Syndrome (EMS) Leukemia

Introduction : Fibroblast growth factor receptors (FGFRs) are conserved single transmembrane receptor tyrosine kinases (RTKs) with an extracellular ligand-binding domain and a cytoplasmic tyrosine kinase domain. They play vital roles in cellular proliferation, survival, development, fetal organogenesis, metabolism, and tissue repair. 8p11 myeloproliferative syndrome (EMS) is a hematologic malignancy caused by a translocation of the fibroblast growth factor receptor 1 (FGFR1) gene on chromosome 8p11-12. The most common fusion partner of FGFR1 is the zinc-finger domain ZNF198 (also known as ZMYM2) on chromosome 13q12. Pemigatinib is approved for FGFR fusion positive myeloid/lymphoid neoplasms (MLNs), and other FGFR inhibitors are being tested in clinical trials. However, EMS patients still face a poor prognosis and drug resistance, necessitating further research to overcome these challenges. This study evaluated ex vivo drug screening assay data generated from ZMYM2::FGFR1 positive primary leukemia samples throughout the course of an EMS patient's clinical response and validated these findings on a ZMYM2::FGFR1 positive cell line. Methods : Ex vivo and drug screening experiments were performed on freshly isolated primary patient samples and a ZMYM2::FGFR1-expressing cell line. The fusion was confirmed using FISH, and additional clinical specimens were collected with informed patient consent. Ex vivo drug sensitivity assays were conducted on patient mononuclear cells isolated from blood and bone marrow. IL-3 dependent BaF3 cells were infected with retrovirus containing a ZMYM2::FGFR1-V5 construct. ZMYM2::FGFR1 transformed BaF3 cells were evaluated with single agent and drug combination panels. Sanger sequencing of the FGFR portion of the fusion was performed on patient samples to confirm the breakpoint and identify potential mutations affecting sensitivity to Ponatinib throughout the course of treatment. Results : Sample were obtained with informed consent from a 36-year-old man diagnosed with 8p11 myeloproliferative syndrome and a ZMYM2::FGFR1 fusion along with a RUNX1 R201Q mutation. Ex vivo drug screens performed on isolated mononuclear cells demonstrated sensitivity to Ponatinib and Pemigatinib. He underwent treatment with HyperCVAD plus Ponatinib and subsequently HyperCVAD with Ponatinib and Velcade (Bortezomib) to CR1, FISH for FGFR1 rearrangement was undetected. He was scheduled to proceed with hematopoietic stem cell transplant (HSCT), however his pre-transplant bone marrow biopsy showed return of his FGFR1 translocation by FISH. Ex vivo drug screening assays confirmed resistance to Ponatinib, but continued sensitivity to Pemigatinib. He was transitioned to treatment with single agent Pemigatinib and was able to re-clear his FGFR1 fusion by FISH, and has since undergone hematopoietic stem cell transplantation. He remains in remission on post-transplant Pemigatinib maintenance therapy. Sanger sequencing performed at the time of progression on Ponatinib identified a nucleotide alteration resulting in an amino acid substitution (FGFR1 F686L; ZMYM2::FGFR1 F1171L) within the kinase domain that could contribute to decreased Ponatinib sensitivity. Bortezomib and Axitinib exhibited high efficacy on the patient's sample. Ex vivo drug assays performed on ZMYM2::FGFR1 transformed BaF3 cells confirmed the efficacy of Pemigatinib and Ponatinib. Other FGFR inhibitors, including Olverematinib, AZD4547, Axitinib, Cediranib, Dovitinib, and Lenvatinib, also demonstrated exquisite sensitivity. Despite extensive screening, no other single agents or drug combinations exhibited increased effectiveness in the ZMYM2::FGFR1 transformed BaF3 cells except for Trametinib, a MEK inhibitor, and the combination of Belvarafenib (RAF inhibitor) and Gilteritinib (FLT3 inhibitor). Conclusions : Ex vivo drug sensitivity assays demonstrated the highly selective efficacy of FGFR inhibitors in ZMYM2::FGFR1 fusion-positive leukemia cells and a fusion-expressing BaF3 cell line. Mutations in the FGFR1 kinase domain (ZMYM2::FGFR1 F1171L) could contribute to Ponatinib insensitivity. These ex vivo drug screening results provide further support for ongoing clinical trials which are investigating the use of single agent Pemigatinib and other FGFR1 inhibitors for the treatment of patients with FGFR1-fusion positive leukemias.

Synergistic Growth Inhibition of NPM1 Mutant AML PDX By Combined Therapy with BCL-2 Inhibitor Venetoclax (ABT-199) and Menin Inhibitor DS-1594b In Vivo

Introduction: Mixed-lineage-leukemia (MLL) translocations are prevalent in hematologic malignancies, resulting in aggressive leukemias resistant to standard therapies and low 5-year survival rates. These translocations lead to the production of MLL fusion proteins that promote leukemia development by enhancing proliferation, inhibiting hematopoietic differentiation, and driving leukemogenesis. Acute myeloid leukemia (AML), an aggressive blood cancer with a grim prognosis, particularly in elderly patients, frequently involves mutations in the nucleophosmin (NPM1) gene. Importantly, the interaction between Menin, MLL, and MLL fusion proteins play a crucial role in the pathogenesis of AML, both with MLL rearrangements (MLLr) and in leukemias carrying NPM1 mutations. Inhibition of the Menin-MLL interaction using novel Menin inhibitors has demonstrated efficacy in pre-clinical and clinical studies for both AML subsets. In this study, we investigate the effectiveness of the novel Menin-MLL inhibitor DS-1594b, developed by Daiichi Sankyo Co. Ltd., in combination with the BCL-2 antagonist venetoclax (ABT-199), in a patient-derived xenograft (PDX) model of NPM1-mutated acute leukemia. We have previously reported synergistic lethality and differentiation-inducing effects of this drug combination in both AML cell lines and primary leukemia samples in vitro (Ciaurro et al., Blood 2022). Our findings shed light on the potential of this therapeutic combination for the targeted treatment of AML with NPM1 mutations. Methods: NSG mice (female, 8-10 weeks old) were purchased from Jackson Laboratory. Mice were inoculated via the tail vein with NPM1m PDX/luc/GFP (3×10 6 cells). Once leukemia engraftment was confirmed by bioluminescent imaging mice were randomized in 4 groups: vehicle, ABT199, DS-1594b alone, and combination. After 12 days drugs were administered as follows: DS1594b at a dosage of 50 mg/kg by oral gavage for 4 weeks; ABT-199 at a dosage of 50 mg/kg by oral gavage for 2 weeks and 100mg/kg for the other 2 weeks. NSG mice were euthanized by CO 2 inhalation at the endpoint of the study in accordance with IACUC protocols. BM and spleens were harvested in a sterile environment and flushed in HBSS with 1% FBS. For CyTOF data spleen cells were initially barcoded and stained with metal-conjugated antibodies according to Fluidigm's protocols and samples were analyzed by CyTOF (Helios) Mass Cytometer. Results: New in vitro data confirmed synergistic lethality on additional AML cell lines and demonstrated upregulation of PARP-C and Caspase3-C apoptosis pathways using western blot analysis. Further, additional 3 primary AML patient samples showed additive or synergistic growth inhibition when treated with combination of drugs. In the in vivo experiment with NPM1m PDX/luc/GFP AML PDX model, we found that co-treatment with DS-1594b and venetoclax for four weeks resulted in a greater reduction in AML burden compared to treatment with either agent alone or a vehicle control as shown by Bioluminescence imaging. Moreover, weight of mice in the combo group was not significantly affected, while mice lost weight in vehicle and in single agent cohort due to rapid disease progression. The survival curve clearly demonstrated the benefits of the combination treatment, with the DS-1594b group having modest anti-tumor efficacy, and the combination group showing the greatest efficacy (Fig. 1A). To study the effects on cell differentiation, we used CyTOF technique, which allowed us to analyze a complete panel of 30 markers. We found two populations of cells, which we named populations (pop) 3 and pop 4, that were enriched in the group treated with the combination of drugs compared to the control group (Fig 1B). These populations of cells had higher levels of expression of CD33 and CD38, which are well-known markers of cellular differentiation. Conclusions: In this study, we present the in vivo effectiveness of DS-1594b in combination with venetoclax in a PDX model of NPM1-mutated AML. Moreover, the combination treatment exhibits differentiation-inducing effects, which contribute to its therapeutic effectiveness, and was safe. Overall, our findings strongly indicate that the combination of DS-1594b and venetoclax exhibits promising anti-leukemic activity in vivo and holds potential as a therapeutic strategy for AML patients with mtNPM1 mutations.

KDM6A Modulates Anti-Tumor Immune Response By Integrating Immunogenic Cell Death in Human Acute Myeloid Leukemia

Identifying tumor cell-epigenetic regulation of immune activation in acute myeloid leukemia (AML) would be instrumental in developing next-generation of targeted therapy. AML cells have low mutational burden; inefficient ‘cross-presentation’ through conventional dendritic cells (DC) and immune activation are the major challenges for AML immunomodulation. ‘Immunogenic cell death’ (ICD) represents changes in the composition of the tumor cell surface as well as the release of ‘damage associated molecular patterns’ (DAMPs) in the tumor microenvironment that stimulates the dysfunctional immune system. DAMPs in turn operate on a series of receptors expressed by DCs and natural killer (NK) cells and contribute to long-lasting, protective anti-tumor immunity. For example, plasma membrane exposure of endoplasmic-reticulum (ER)-translocated calreticulin (ecto-CRT), which functions as an ‘eat me’ signal, is an important hallmark of ICD. Previous study suggested that calreticulin (CALR) promotes immunity and type I interferon-dependent survival in mice with AML (Fucikova, Blood 2016; Chen, Oncoimmunology 2017). In addition, ecto-CRT on malignant blasts correlated with improved NK cell-mediated cytotoxicity in AML patients with superior overall survival (Truxova, Haematologica 2020). Ecto-CRT has also been identified as an endogenous sterile ligand for NK cells (Sen Santara, Nature 2023). Nevertheless, molecular regulation of ICD in the context of epigenetic derangements and inflammation and its implication in AML immunotherapeutic modulation is poorly understood. KDM6A is a histone 3 lysine 27 demethylase that plays tumor suppressor function in AML (Gozdecka, Nat Genet 2018; Sera, Blood 2021). KDM6A escapes X-chromosome inactivation, and loss-of-function deletion or point mutations associate with resistance to ‘3+7‘ chemotherapy (Stief, Leukemia 2020). We have identified that in comparison to control AML cells, deficiency of KDM6A ( KDM6A-kd) associated with daunorubicin/etoposide-induced ICD, which was manifested by significant increase (2-3 fold , P<0.05) in ecto-CRT, plasma membrane exposure of pE1F2α, HSP70 and HSP90 with extracellular release of HMGB1 and ATP. Similarly, pharmacological inhibition of JmjC catalytic function using GSK-J4 sensitized human AML lines as well as primary AML patient bone marrow-derived CD34 + hematopoietic stem/progenitor cells to ICD. Induction in ICD was accompanied by an elevated type I interferon production that was functionally active in promoting interferon regulated gene expression. Interestingly, treatment with acute recombinant IFN-β caused an increase in activated STAT1 and inflammatory gene expression in KDM6A-kd AML cells compared to control AML. Corroborating these results, gene set enrichment analysis revealed a significant enrichment (NES=1.708, P=0.007) of upregulated type I interferon signatures (n=40) in Kdm6a -/- primary leukemia cells. Re-analysis of ChIP-seq results indicated 1647 Kdm6a occupied genes, which were upregulated upon Kdm6a loss. Gene ontology (GO) analysis of the 1647 genes further suggested an enrichment ( P<0.001) of type I interferon-responsive GO terms, indicating Kdm6a role in interferon signaling. Ecto-CRT level relies on premortem ER stress. In OHSU AML, KDM6A expression correlates with ER stress/unfolded protein response. Mechanistically, quantitative-ChIP and promoter-reporter assays indicated that KDM6A-kd de-repressed ICD induced expression of ATF4 and HSPA5 through chromatin and transcriptional remodeling. In agreement with these findings, AML blasts-healthy immune cells ex vivo co-culture experiments revealed that increase in ICD in KDM6A-kd AML was associated with activation (~2-foldincrease inCD80 +CD86 +, P<0.05) and phagocytic function of DCs. Loss of KDM6A was shown to bestow ‘BRCAness’ (Boila, Leukemia 2023), and PARP inhibition itself can cause ICD and augment tumor immunity. We observed that there was a significant induction in ICD and expression of NKG2D ligands ULBP1, ULBP5 in KDM6A-kd AML cells treated with olaparib. In addition, olaparib and GSK-J4 treatment showed additive effects in ICD and immune activation using primary AML CD34 + cells. Together, we illustrate that KDM6A regulates ICD through epigenetic mechanisms, while KDM6A deficient AML subtypes could be sensitized with immunomodulatory targeted therapy.

Recent Updates in Venetoclax Combination Therapies in Pediatric Hematological Malignancies

Venetoclax is a strongly effective B-cell lymphoma-2 inhibitor (BCL-2) with an ability to selectively restore the apoptotic potential of cancerous cells. It has been proven that in combination with immunotherapy, targeted therapies, and lower-intensity therapies such as hypomethylating agents (HMAs) or low-dose cytarabine (LDAC), the drug can improve overall outcomes for adult patients with acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), and multiple myeloma (MM), amongst other hematological malignancies, but its benefit in pediatric hematology remains unclear. With a number of preclinical and clinical trials emerging, the newest findings suggest that in many cases of younger patients, venetoclax combination treatment can be well-tolerated, with a safety profile similar to that in adults, despite often leading to severe infections. Studies aim to determine the activity of BCL-2 inhibitor in the treatment of both primary and refractory acute leukemias in combination with standard and high-dose chemotherapy. Although more research is required to identify the optimal venetoclax-based regimen for the pediatric population and its long-term effects on patients’ outcomes, it can become a potential therapeutic agent for pediatric oncology.

Preclinical evidence for the effective use of TL-895, a highly selective and potent second-generation BTK inhibitor, for the treatment of B-cell malignancies

TL-895 (formerly known as M7583) is a potent, highly selective, adenosine triphosphate (ATP)-competitive, second-generation, irreversible inhibitor of Bruton’s tyrosine kinase (BTK). We characterized its biochemical and cellular effects in in vitro and in vivo models. TL-895 was evaluated preclinically for potency against BTK using IC50 concentration–response curves; selectivity using a 270-kinase panel; BTK phosphorylation in Ramos Burkitt’s lymphoma cells by ProteinSimple Wes analysis of one study; anti-proliferative effects in primary chronic lymphocytic leukemia (CLL) blasts; cell viability effects in diffuse large B-cell lymphoma (DLBCL) and mantle-cell lymphoma (MCL) cell lines; effects on antibody-dependent cell-mediated cytotoxicity (ADCC) from Daudi cells and chromium-51 release from human tumor cell lines; and efficacy in vivo using four MCL xenograft model and 21 DLBCL patient-derived xenograft (PDX) models (subtypes: 9 ABC, 11 GCB, 1 Unclassified). TL-895 was active against recombinant BTK (average IC50 1.5 nM) and inhibited only three additional kinases with IC50 within tenfold of BTK activity. TL-895 inhibited BTK auto-phosphorylation at the Y223 phosphorylation site (IC50 1–10 nM). TL-895 inhibited the proliferation of primary CLL blasts in vitro and inhibited growth in a subset of activated DLBCL and MCL cell lines. TL-895 inhibited the ADCC mechanism of therapeutic antibodies only at supra-clinical exposure levels. TL-895 significantly inhibited tumor growth in the Mino MCL xenograft model and in 5/21 DLBCL PDX models relative to vehicle controls. These findings demonstrate the potency of TL-895 for BTK and its efficacy in models of B-cell lymphoma despite its refined selectivity.

GDF11/SMAD Regulated Splicing of GATA1 Is Associated with Response to Luspatercept in Lower-Risk Myelodysplastic Syndromes (LR-MDS)

Introduction: Luspatercept is an erythroid maturation agent that promotes late-stage erythropoiesis in patients with LR-MDS. While it is known that luspatercept, a modified activin receptor ligand trap, binds to GDF11 and Activin B, the mechanism by which these ligands trigger a decrease in red blood cell (RBC) formation is unknown. Luspatercept was approved by the FDA following the phase 3 MEDALIST study, but biomarkers of response are currently unknown. Results:In a large cohort of primary MDS CD34+ samples, GDF11 expression was significantly higher in MDS samples than in age-matched healthy controls (183 MDS samples vs 17 controls, P < 0.05). GDF11 was detected in primary MDS sera and was substantially elevated in the refractory anemia (RA) and RA with ring sideroblasts (RARS) MDS subgroups. Activin receptor 2B (ACVR2B), the receptor of GDF11, was also overexpressed in MDS samples, and its expression was confirmed by immunohistochemistry (IHC) in the bone marrows of primary MDS patients. GDF11/ACVR2B activates SMAD2, and we found that the overexpression of SMAD2 in CD34+ cells was associated with more severe anemia in MDS patients. RNA-seq and SMAD2 ChIP-seq analyses were then performed to determine the downstream effects of GDF11 in erythroid progenitors. Human CD34+ primary cells were utilized to generate BFU-E stage erythroid progenitors. We discovered that GDF11 promotes an abnormal erythroid gene expression program characterized by increased expression of pro-apoptotic and early erythroid differentiation-related genes. SMAD2 binding was detected in regulatory regions of early erythroid (including GATA1), proinflammatory, and apoptotic transcripts using ChIP-seq analysis with p-SMAD2. In a zebrafish model, administration of GDF11 caused a decrease in erythroid cells, which was rescued by treatment with luspatercept (Wobus et al. Leukemia 2021 35(10):2936-47). Luspatercept inhibited the phosphorylation and activation of SMAD2 in response to GDF11 stimulation in primary hematopoietic cells and leukemia cell lines. Importantly, luspatercept could reverse the growth-inhibiting effects of MDS-derived sera on primary hematopoietic progenitors. Finally, to identify biomarkers associated with clinical responses, we analyzed phase 3 MEDALIST study samples collected before and after treatment with lupatercept. RNA-seq analysis was performed on bone marrow samples from responders (R; n = 14) and non-responders (NR; n = 9) (Figure). Analysis of pre-treatment/screening bone marrow transcriptomes revealed no significant differences between R and NR in global gene expression. Analysis of splice isoforms between the two cohorts revealed strikingly greater differences. Most differential splicing events were observed in NR (702 in R vs 5232 in NR). The most prevalent splicing modifications were exon skipping events, and most functional pathways affected by differential exon usage were RNA splicing related. GATA1, the master erythroid transcription factor, was spliced differently in R at baseline, which was an intriguing observation. Response to luspatercept was found to be associated with exon 2 skipping, resulting in a shortened isoform of GATA1. R had a greater proportion of the short GATA1 isoform than NR (12% in R versus 6% in NR; P = 0.04). We analyzed ChIP-seq data from primary erythroid cells to determine the effect of GDF11/SMAD2 activation on GATA1 splicing. GDF11 stimulation resulted in SMAD2 binding to the second intron of GATA1. CRISPR-mediated deletion of the SMAD2 binding region in primary erythroid progenitors increased expression of the GATA1 long isoform. Next, we performed a CRISPR-mediated deletion of exon 2 of GATA1, resulting in a predominance of GATA1 short isoform expression and a decrease in erythroid output. In CRISPR-modified primary erythroid cells with a predominant short GATA1 isoform (exon 2-deleted cells), luspatercept was able to reverse the inhibition induced by GDF11. Conclusions: These results demonstrate that MDS cases that respond to luspatercept are associated with a relatively high level of expression of functionally deficient GATA1 short isoform. We further demonstrate that GDF11 stimulates the production of the GATA1 short isoform via SMAD2 binding to intron 2 of the GATA1 gene. The regulation of a GATA1 splicing isoform by GDF11/SMAD2 is associated with clinical responses to luspatercept, according to these novel findings.

Developing “Off-the-Shelf” CLL1 CAR-DNT Therapeutics for the R/R Acute Myeloid Leukemia

Background: Acute myeloid leukemia (AML) is one of the most common and highly heterogeneous hematological malignancy. The prognosis is poor especially for the elderly patients. For Relapsed/Refractory(R/R) AML patients, the one-year overall survival rate is merely 20%. CAR-T cells have shown tremendous therapeutic benefits for ALL, DLBCL and MM. One of the limitations of current CAR-T therapies is the use of autologous T cells. This can be limiting due to the cost, complicated manufacturing process, rapid disease progression, and manufacturing failures etc. Therefore, there is a need to develop the ready-to-use allogeneic cell product. Double negative T (DNT) cells are the ideal candidate for AML cell therapy as they naturally kill AML cells, and have been successfully administered to AML patients with therapeutic benefit without causing GvHD. Relying on their own natural immune activated receptors, DNT cells could lyse a wide range of tumors independent of TAA expression, which have more advantages compared to the conventional CAR-T cells. In our study, we developed the allogeneic product of CAR-DNT cells targeting C-type lectin-like molecule-1 (CLL1), which is a promising target due to its over-expression in primary AML cells and leukemia stem cells, while absence on hematopoietic stem/progenitor cells. Methods: We developed a humanized single chain variable fragment (scFv) with specific recognition of human CLL1 antigen by screening from 62 murine-derived CLL1 antibodies. Then, we designed a second-generation CLL1 CAR structure containing 4-1BB-CD3ζ and transduced it into the DNT cells by lentivirus. To clarify the GvH and HvG reactions of DNT cells, we performed the mixed lymphocyte reaction experiments in vitro and compared DNT cells with TCR and B2M double knockout T(DKO) cells and TCR knockout T(TKO) cells. We evaluated the anti-tumor function of CLL1 CAR-DNT cells through killing experiments by different effector-to-target ratios and multiple stimulations with AML cell lines (THP1 and HL60). Furthermore, we speculated that the CAR structure plays a critical role in both tumoricidal function and persistence of CAR-DNT cells. We designed nearly 20 enhanced CAR structures based on the signaling pathway of DNT cells. These newly designed structures have been tested in vitro and will be confirmed in vivo. Results: The humanized anti-CLL1 scFv candidate H1-3Q2 demonstrated high specificity toward human CLL1 antigen at the Membrane Protein Array. H1-3Q2 based CAR-T cells showed good tumor suppression in vivo. However, due to the heterogenous expression of CLL1 in AML, CLL1 CAR-T cells may not be able to eliminate AML cancer cells completely. While DNT cells could naturally lyse tumor cells through the receptors like NKG2D and DNAM-1, providing them with lots of advantages. Moreover, DNT cells have the potential to be used as allogenic cell therapy product. Co-culturing allogenic PBMCs or umbilical cord blood with DNT cells for up to 72 hours resulted in little or no killing reaction, indicated a low risk of GvHD. Conversely, the PBMCs from three different donors were used to attack allogenic DNT cells or DKO/TKO T cells in vitro. The killing effect on DKO/TKO T cells gradually increased over time, while no effect on DNT cells was observed even after 192 hours. This suggested that DNT cells are not easily cleared by host immune cells. DNT cells could efficiently lyse various hematological and solid tumor cell lines, particularly showing high sensitivity towards AML cells. The introduction of the CAR moiety further enhanced the specificity of DNT cells. The in vitro killing results demonstrated that CLL1 CAR-DNT cells exhibited stronger and faster AML resistance compared with CAR-T cells, and even eliminated tumor cells that have lost TAA. However, CLL1 CAR-DNT cells showed limited proliferation in the multiple-stimulation assays. To address this, we designed enhanced CAR structures. Screening by multiple-challenge assays, the fifth-generation CAR exhibited outstanding proliferation and superior tumor lysis ability in vitro. Conclusions: Our findings demonstrate that CAR-DNT product is an ideal candidate for allogeneic adoptive immunotherapy and exhibits superior tumoricidal function. This study underscores the potential of the “off-the-shelf” CLL1 CAR-DNT cell product for treating R/R AML.

Ultra High-Risk Multiple Myeloma Patients with Multi-Hit Tumours and SKY92 High Risk Signature Are at Increased Risk of Early Relapse Even When Treated with Extended Intensified Induction and Consolidation - Results from the Optimum/Muknine Trial

Background: We recently reported improved outcomes for patients with ultra-high risk (UHiR) newly diagnosed multiple myeloma (NDMM) by double hit/≥2 high-risk cytogenetic abnormalities (HRCA) and/or SKY92 risk signature or primary plasma cell leukemia (pPCL) in the OPTIMUM/MUKnine (NCT03188172; Kaiser et al, JCO 2023) trial. However, some participants still relapsed within the first 18 months of treatment despite stratified intensive therapy with Dara-CVRd, V-ASCT and extended Dara-VR(d) consolidation. In this analysis we characterise factors associated with early progression. Methods: In OPTIMUM, patients with UHiR NDMM (≥2 HRCA: t(4;14), t(14;16), t(14;20), gain(1q), del(1p), del(17p) or SKY92 high risk signature) or with pPCL received up to 6 cycles of Dara-CVRd induction, V-ASCT, 6 cycles Dara-VRd (Cons1) and 12 cycles Dara-VR (Cons2), before moving to monthly Dara-R maintenance until progression. OPTIMUM recruited 107 UHiR patients, including 9 pPCL. In this exploratory analysis, baseline clinical, laboratory and tumour molecular characteristics were compared between patients who experienced an Early Relapse, defined by MM relapse or MM-related death within 18 months from registration and those who did not, using descriptive statistics and hypothesis testing using two-sample t-tests or chi squared tests. Baseline characteristics were also compared by minimal residual disease (MRD; 10 -5 sensitivity by flow cytometry) status at the end of induction to elucidate whether baseline factors associated with early MRD negativity were overlapping with those associated with Early Relapse. Median follow-up was 51.5 months, and all patients had been on study for over 44 months. Results: Twenty-three (21%) of 107 UHiR patients experienced Early Relapse, versus 84 (79%) who did not. Patient age and gender were not different between groups. Platelet levels as a continuous variable were lower in the Early Relapse group vs those without (mean 179/nL, standard deviation (SD) 92/nL vs. mean 223/nL, SD 77/nL; P=0.0247), whereas haemoglobin, serum creatinine, calcium, presence of soft tissue plasmacytomas (PCM), bone lytic lesions or plasma cell bone marrow infiltration on diagnostic trephine were similar. ISS stage distribution differed between groups (P=0.0203): most Early Relapse participants were ISS stage 2 (13/23 (56.5%) vs 30/84 (35.7%) without Early Relapse), whereas ISS stage 3 was nominally similar (34.8% vs 31.0%). Most notably, only one of the 29 ISS stage 1 patients in OPTIMUM experienced Early Relapse. 57 of 107 (53.3%) patients entered OPTIMUM with ≥2 HRCA at diagnosis, and, of these, seven carried 3 HRCA. Five of seven participants (71.4%) with 3 HRCA experienced Early Relapse, opposed to only seven out of 50 (14%) with only 2 HRCA. 82 of 107 (76.6%) were SKY92 high risk at baseline. Only two of the 24 participants (8.3%) with SKY92 standard risk experienced Early Relapse, as opposed to 20 out of 82 (24.4%) with SKY92 high risk. Of individual HRCAs, only presence of del(17p) was associated with early relapse (P=0.002): 8 of 16 (50%) participants with del(17p) tumours experienced Early Relapse. However, seven of these 8 Early Relapse del(17p) tumours (88%) were also positive for SKY92 high risk signature. In contrast, the majority (62%) of del(17p) that did not relapse early were SKY92 standard risk. Of the 107 UHiR patients, 6 did not reach end of induction and 14 had no MRD result. Of 87 participants with interpretable MRD result at end of induction (EOI), 51% tested MRD-negative (44/87). Of clinical factors, only presence of PCM was associated with insufficient response (P=0.017, 5/5 MRD-positive), whereas ISS stage was not associated with MRD at EOI. Only one of four participants (25%) with 3 HRCA had MRD-negative status at EOI vs 66% of those with 2 HRCA. Also, the majority of patients (62%) identified by SKY92 high risk only were still MRD-positive. Conclusions: Our results suggest that presence of 3 or more HRCA, SKY92 high risk signature or del(17p) combined with SKY92 high risk are all associated with increased risk of Early Relapse despite intensified OPTIMUM treatment, and could help identify patients early who are candidates for novel, innovative first-line therapeutic approaches. Results also suggest utility of integrated molecular diagnostics, including gene expression risk profiling, to support clinical decision making in the era of advanced front-line combination therapies.

Primary and Secondary Plasma Cell Leukemia Risk Stratification By Circulating Plasma Cells

Plasma cell leukemia (PCL) is a rare plasma cell dyscrasia associated with poor outcomes. PCL can present de novo as primary PCL (pPCL) or from preceding multiple myeloma as secondary PCL (sPCL). The International Myeloma Working Group (IMWG) in 2021 updated the diagnostic criteria for pPCL using circulating plasma cells (CPC) to ≥5% instead of ≥20% as both carry similar survival. In this single center retrospective analysis, we compared clinical features and overall survival (OS) for 104 patients: with pPCL ≥5% CPC ( N = 35), sPCL 5-19% CPC (sPCL-A) ( N = 11), sPCL ≥20% CPC (sPCL-B) ( N = 38), and spillover group 1-4% CPC regardless of newly diagnosed or secondary status ( N = 20). Mean ages were 57 - 59 years old for all groups (range: 25 - 84) with no difference in age between groups ( p = 0.90). There was a slight predominance of females (54.8%) over males and blacks (53.9%) over non-blacks. More patients with pPCL were black (65.7%) compared to sPCL and spillover groups, although this difference was not statistically significant ( p = 0.35). pPCL patients presented with the highest mean WBC at diagnosis (23.4 x10 9/L) compared to sPCL-A (5.5 x10 9/L), sPCL-B (12.2 x10 9/L), and spillover (7.2 x10 9/L) groups ( p <0.001). Patients in all groups were anemic (hemoglobin 7.8 - 9.3 g/dL), thrombocytopenic (platelets 60.2 - 101.2 x 10 9/L), and had abnormal renal function (creatinine 1.4 - 2.7 mg/dL), elevated LDH (918.7 - 1515.5 units/L, highest in sPCL-A), and elevated uric acid levels (5.9 - 8.2 mg/dL). sPCL patients and spillover group had more lytic lesions on skeletal survey ( p = 0.009) and positron emission tomography (PET) ( p = 0.02) compared to patients with pPCL. sPCL-A patients had higher incidences of lymphadenopathy ( N = 5/11, 62.5%, p = 0.02) and central nervous system invasion ( N = 4/11, 36.4%, p = 0.02) compared to other groups. There was no difference in incidence of extramedullary disease ( p = 0.29) between groups. Over 90% of patients with PCL had high-risk cytogenetics with 63% carrying a complex karyotype. Hypodiploidy was seen more often in patients with pPCL and sPCL-B compared to sPCL-A and spillover ( p = 0.005). There was no difference between groups in incidence of deletion 17p ( p = 0.53). All patients benefited in terms of OS from daratumumab (HR 0.44, 95% CI 0.25 - 0.76; p = 0.004), IMiDs (HR 0.13, 95% CI 0.08 - 0.23; p <0.001), PIs (HR 0.43, 95% CI 0.25 - 0.75; p = 0.003), chemotherapy (HR 0.56, 95% CI 0.32 - 0.98; p = 0.04), and autologous hematopoietic stem cell transplantation (HR 0.33, 95% CI 0.16 - 0.71; p = 0.004). DVT-PACE type regimens (dexamethasone-bortezomib-thalidomide-cisplatin-doxorubicin-cyclophosphamide-etoposide) are used for pPCL and may be less effective in sPCL and spillover patients who have been heavily pretreated. We noted no benefit in OS for all patients including pPCL, sPCL-A, sPCL-B, and spillover groups who received DVT-PACE (HR 0.97, 95% CI 0.62 - 1.50, p = 0.88). The lack of OS benefit in pPCL patients receiving DVT-PACE persisted on multivariate analysis when adjusting for PCL group alone (HR 0.79, 95% CI 0.50 -1.26; p = 0.33) and PCL group, age, platelet count, and presence of high-risk cytogenetics (HR 1.11, 95% CI 0.63 - 1.94; p = 0.72). After median follow-up of 6.70 months, median OS was 7.14 months for the entire cohort with 92.3% ( N = 96) deceased. On univariate analysis, male sex, age >58 years old, high-risk cytogenetics, LDH >604 units/L, creatinine >1.40 mg/dL, hemoglobin <8.3 g/dL, platelets <53.5 x10 9/L, lytic lesions on skeletal survey and on PET, extramedullary disease on PET, and plasmacytoma were associated with inferior median OS (Table 1). pPCL had higher median OS (13.1 months) compared to sPCL-A (3.1 months, p = 0.03) and sPCL-B (3.5 months, p = 0.003) (Figure 1). There was no statistically significant difference in median OS between pPCL (13.1 months) and spillover patients (10 months) ( p = 0.48) as well as sPCL-A (3.1 months) and sPCL-B (3.5 months) ( p = 0.80). Although the spillover group was associated with a trend towards better OS compared to sPCL-A and sPCL-B groups, this was not statistically significant, which may be due to low N which is a limitation of the study. Further research is required to better understand the clinical features, treatment responses, and outcomes of pPCL, sPCL, and spillover group (1-4% CPC).

Carfilzomib in Combination with Dexamethasone, Cyclophosphamide, Etoposide, and Cisplatin (KDCEP) for the Treatment of Relapsed/Refractory Aggressive Plasma Cell Dyscrasias

Background: Dexamethasone with Cyclophosphamide, Etoposide and Cisplatin (DCEP) is an effective regimen in aggressive relapsed/refractory MM (RRMM) with overall response rates (ORR) as high as 58% [Dadacaridou, M. et al JBUON 2007]. ORR is lower (35 - 45%) in patients (pts) exposed to novel therapeutics such as immunomodulatory agents (IMiD), proteasome inhibitors (PI), and anti-CD38 antibodies (mAb) [Park, Silvia et al Ann. Hematol 2014; Goldsmith, Scott et al. Blood2021]. The addition of bortezomib (V) to DCEP demonstrated ORR of 47% [Valla, Kelly et al. Blood 2014]. Due to common use of V front-line, most pts are V exposed by the time treatment for relapse is indicated; therefore, we began using carfilzomib (K) with DCEP. K has been utilized with DPACE with ORR of 77% [Alsouqi, A. et al. Clin Lymphoma Myeloma Leuk 2021], however an anthracycline may not be feasible in heavily pretreated pts. We present the first reported outcomes of RRMM pts treated with KDCEP. Methods:This is a case series from the University of Utah Huntsman Cancer Institute of all consecutive pts treated with KDCEP from 2017-2022, conducted under IRB approval. Demographic, disease, treatment, and response data were retrospectively collected. Responses were assessed by IMWG criteria, and adverse events were graded by CTCAE v.5. Descriptive statistics were utilized; a Kaplan-Meier estimate was used for the time to event analysis. Results:Six pts received KDCEP (Table 1). The median age was 63.5 years (range 47 - 73). All pts had ECOG performance status of 1-2, and 67% were male. Median prior treatment lines were 2.5 (range 2 - 7) with 33% undergoing prior autologous stem cell transplant (autoHCT). All pts were exposed to V with 67% refractory. Thirty-three percent had prior K exposure, however none were considered refractory to K, and 67% were refractory to a PI, IMiD and mAb. Two pts received KDCEP as chemo-mobilization prior to autoHCT. All pts had IgG or IgA disease with 67% having high risk cytogenetics (33% 17p del, 50% gain 1q21) and 1 pt had primary plasma cell leukemia. R-ISS stage at diagnosis was: stage 3 (n=2), stage 2 (n=1) unknown (n=3). All pts had baseline echocardiograms with ejection fractions prior to treatment ranging from 57 - 78%. Pts received K on Days 1 and 8 of each 28-day cycle, prophylactic growth factor, and standard antimicrobial prophylaxis. Two pts received 2 cycles, all others received 1. The overall response rate was 100% and included the following best responses: PR (n = 4), VGPR (n = 1), CR (n = 1). One patient that initially achieved a PR relapsed within 60 days and died awaiting enrollment on a clinical trial, however all other pts were successfully bridged to their next line of therapy. Five pts had MRD data available after treatment, each demonstrating detectable MRD. Median progression free survival was 6.7 months. Median time to ANC nadir was 11 days (range 9-14) and to ANC recovery, defined as ANC > 1000/uL, was 18 days (range 14 - 23). Median time to platelet nadir was 12.5 days (range 9-23) and to platelet recovery, defined as platelets > 100 k/uL, was 25 days (range 20 - NR). Median time to next cycle or treatment was 43 days (range 31-54). Sixty-seven percent of pts had a grade ≥ 3 toxicity including neutropenic fever (n=2), sepsis due to pseudomonas bacteremia (n=1), and septic thrombophlebitis (n=1). No cardiac toxicities or treatment related deaths were observed. Discussion:In this cohort of heavily pre-treated pts who received KDCEP, ORR was high indicating the regimen is active in this population. KDCEP may be a viable option for RRMM pts, particularly in those who are triple class refractory or with high risk cytogenetic abnormalities. Our data suggests that KDCEP may be an effective regimen to bridge patients to the next line of therapy; however all patients should be monitored closely for infection.