Yi, Cecilia Arana

Abstract Clonal cytopenia of undetermined significance (CCUS) represents a distinct disease entity characterized by myeloid-related somatic mutations with a variant allele fraction of ≥2% in individuals with unexplained cytopenia(s) but without a myeloid neoplasm (MN). Notably, CCUS carries a risk of progressing to MN, particularly in cases featuring high-risk mutations. Understanding CCUS requires dedicated studies to elucidate its risk factors and natural history. Our analysis of 357 patients with CCUS investigated the interplay between clonality, cytopenia, and prognosis. Multivariate analysis identified 3 key adverse prognostic factors: the presence of splicing mutation(s) (score = 2 points), platelet count of <100 × 109/L (score = 2.5), and ≥2 mutations (score = 3). Variable scores were based on the coefficients from the Cox proportional hazards model. This led to the development of the clonal cytopenia risk score (CCRS), which stratified patients into low- (score of <2.5 points), intermediate- (score of 2.5 to <5), and high-risk (score of ≥5) groups. The CCRS effectively predicted 2-year cumulative incidence of MN for low- (6.4%), intermediate- (14.1%), and high-risk (37.2%) groups, respectively, by the Gray test (P < .0001). We further validated the CCRS by applying it to an independent CCUS cohort of 104 patients, demonstrating a c-index of 0.64 (P = .005) in stratifying the cumulative incidence of MN. Our study underscores the importance of integrating clinical and molecular data to assess the risk of CCUS progression, making the CCRS a valuable tool that is practical and easily calculable. These findings are clinically relevant, shaping the management strategies for CCUS and informing future clinical trial designs.

Abstract Clonal cytopenia of undetermined significance (CCUS) is defined by a myeloid driver mutation in the context of otherwise unexplained cytopenia. CCUS has an inherent risk of progressing to myeloid neoplasm. However, it is unknown how exposure to previous cytotoxic therapy may impact the risk of progression and survival. We stratified patients with CCUS by prior exposure to DNA-damaging therapy. Of 151 patients, 46 (30%) had received cytotoxic therapy and were classified as therapy-related CCUS (t-CCUS), whereas 105 (70%) had de novo CCUS. A lower proportion of t-CCUS had hypercellular marrows (17.8% vs 44.8%, P = .002) but had higher median bone marrow blast percentages. After a median follow-up of 2.2 years, t-CCUS had significantly shorter progression-free survival (PFS, 1.8 vs 6.3 years; hazard ratio [HR], 2.1; P = .007) and median overall survival (OS; 3.6 years vs not reached; HR, 2.3; P = .007) compared with CCUS. Univariable and multivariable time-to-event analyses showed that exposure to cytotoxic therapy independently accounted for inferior PFS and OS. Despite the similarities in clinical presentation between CCUS and t-CCUS, we show that exposure to prior cytotoxic therapies was an independent risk factor for inferior outcomes. This suggests that t-CCUS represents a unique clinical entity that needs more stringent monitoring or earlier intervention strategies.

Abstract Venetoclax + hypomethylating agent (Ven‐HMA) is currently the standard frontline therapy for older/unfit patients with newly diagnosed acute myeloid leukemia (ND‐AML). Our objective in the current retrospective study of 301 adult patients (median age 73 years; 62% de novo) with ND‐AML was to identify molecular predictors of treatment response to Ven‐HMA and survival; European LeukemiaNet (ELN) genetic risk assignment was favorable 15%, intermediate 16%, and adverse 69%. Complete remission, with (CR) or without (CRi), count recovery, was documented in 182 (60%) patients. In multivariable analysis, inclusive of mutations only, “favorable” predictors of CR/CRi were NPM1 (86% vs. 56%), IDH2 (80% vs. 58%), and DDX41 (100% vs. 58%) and “unfavorable” TP53 (40% vs. 67%), FLT3‐ ITD (36% vs. 63%), and RUNX1 (44% vs. 64%) mutations; significance was sustained for each mutation after adjustment for age, karyotype, and therapy‐related qualification. CR/CRi rates ranged from 36%, in the presence of unfavorable and absence of favorable mutation, to 91%, in the presence of favorable and absence of unfavorable mutation. At median follow‐up of 8.5 months, 174 deaths and 41 allogeneic stem cell transplants (ASCT) were recorded. In multivariable analysis, risk factors for inferior survival included failure to achieve CR/CRi (HR 3.4, 95% CI 2.5–4.8), adverse karyotype (1.6, 1.1–2.6), TP53 mutation (1.6, 1.0–2.4), and absence of IDH2 mutation (2.2, 1.0–4.7); these risk factors were subsequently applied to construct an HR‐weighted risk model that performed better than the ELN genetic risk model (AIC 1661 vs. 1750): low ( n = 130; median survival 28.9 months), intermediate ( n = 105; median 9.6 months), and high ( n = 66; median 3.1 months; p < .001); survival in each risk category was significantly upgraded by ASCT. The current study identifies genotype signatures for predicting response and proposes a 3‐tiered, CR/CRi‐based, and genetics‐enhanced survival model for AML patients receiving upfront therapy with Ven‐HMA.

Background Venetoclax (Ven) in combination with hypomethylating agent (HMA) is the standard treatment for newly diagnosed elderly/unfit patients with acute myeloid leukemia (AML). Treatment options for patients with relapsed/refractory (RR) disease following Ven-HMA are limited in the absence of targetable mutations. In a recent phase 2 study, the addition of Ven to cladribine (CDA) plus low-dose cytarabine (LDAC), in newly-diagnosed elderly/unfit AML, resulted in complete remission with (CR) or without (CRi) count recovery rate of 93% ( J Clin Oncol 20;40(33)). In the current study, we share our experience with this regimen in patients relapsed or refractory to Ven-HMA, treated outside of clinical trials. Methods Under an institutional review board approved minimum risk protocol, the Mayo Clinic (MN, AZ, FL) database was searched to identify patients with AML who failed treatment with Ven-HMA and subsequently received at least one cycle of salvage therapy with Ven-CDA-LDAC: Ven 100-400 mg, dose adjusted, d1-21, CDA 5 mg/m 2 d1-5, LDAC 20 mg twice daily d1-10, outside of clinical trials. Cytogenetic and molecular studies were performed at the time of Ven-CDA-LDAC initiation in most cases, by conventional karyotype and next-generation sequencing, respectively. The 2022 European LeukemiaNet (ELN) criteria were applied to define risk and response. Survival was calculated from the time of Ven-CDA-LDAC treatment start to last follow-up or death. Results Patient characteristics A total of 39 RR AML patients (median age 65 years, 67% male, 64% de novo), with prior exposure to Ven-HMA, received Ven-CDA-LDAC (median 1 cycle; range 1-5). Study patients had received one ( n=16), two ( n=14), three ( n=5), four ( n=2), five ( n=1) or nine ( n=1) prior therapies, including Ven-HMA. Nine (23%) patients had relapsed following allogeneic hematopoietic stem cell transplant (AHSCT). ELN cytogenetic risk included intermediate (46%, n=18), and adverse (54%, n=21). Mutations involved TP53 in 9 patients (23%), K/ NRAS in 8 (21%), RUNX1 in 7 (18%), TET2 in 6 (15%), ASXL1 in 5 (13%), and STAG2 in 5 (13%). Response and toxicity Eleven (28%) patients achieved CR ( n=2; 5%) or CRi ( n=9; 23%); median time to response was 1 month and median response duration 3.4 months. In addition, 2 (5%) patients each experienced partial remission (PR) and bone marrow aplasia without fulfilling criteria for morphologic leukemia free state. Measurable residual disease (MRD) was negative by multiparametric flow cytometry in 2 of 7 (29%) informative CR/CRi cases. CR/CRi rates were higher in females (54% vs 15%; p=0.01), de novo vssecondary AML (40% vs 7%; p=0.02), and absence of adverse karyotype (50% vs 9%; p&lt;0.01), K/NRAS (35% vs 0%, p=0.01), ASXL1 (32% vs 0%, p=0.05), or STAG2 mutations (32% vs 0%, p=0.05) (Table 1). Multivariable analysis confirmed superior response in de novo AML (p&lt;0.01), absence of adverse karyotype, (p&lt;0.01), and absence of K/NRAS mutations (p=0.02). CR/CRi rates were not significantly affected by relapsed vs refractory setting ( p=0.95), number of prior therapies ( p=0.51), prior AHSCT ( p=0.64), or TP53 mutations ( p=0.64) (Table 1). Treatment-emergent toxicities included infections (49%, n=19), comprising bacteremia ( n=11), pneumonia ( n=10), peri-rectal abscess ( n=6), and laboratory evidence of tumor lysis syndrome (3%, n=1). Survival At a median follow-up of 3.9 months, from initiation of Ven-CDA-LDAC, 31 deaths (79%), 6 relapses (15%), and 7 AHSCT (18%; including 5 in CR/CRi, 1 in aplasia) were documented. Median survival following Ven-CDA-LDAC was 4.6 months, and superior in the presence vs absence of CR/CRi (8.1 vs 2.9 months; p=0.01), and in patients receiving AHSCT (10.5 vs 3.4 months; p=0.02). Absence of adverse karyotype was also associated with superior survival (6 vs 3.4 months; p=0.05). Multivariable analysis confirmed the favorable survival impact of CR/CRi ( p=0.03) and AHSCT ( p=0.05); survival impact was not apparent for secondary AML ( p=0.29) or K/NRAS ( p=0.70) or TP53 ( p=0.10) mutations. Conclusions The current study suggests transplant bridging value for Ven-CDA-LDAC in AML patients relapsed or refractory to Ven-HMA, especially in the absence of adverse karyotype or K/NRAS mutation. AHSCT and achievement of CR/CRi appear to be indispensable for favorable post-Ven-CDA-LDAC survival.

BACKGROUND: Recent World Health Organization (WHO) classifications (5 th edition), International Consensus Classification (ICC) recognized TP53-mutated ( TP53mut) myeloid neoplasms (MNs) as a distinct subcategory, acknowledging their uniformly poor outcomes. However, there are critical differences between the two guidelines in how TP53 allelic status is assigned. Both WHO-5 and ICC acknowledged the poor outcome of multi-hit TP53mut but excluded single-hit TP53mut. These changes are driven by a pivotal study demonstrating favourable outcome of single-hit TP53mut, however this study predominantly included de novo myelodysplastic syndromes (MDS) cases (Bernard et al. Nat Med 2020). In contrast, we previously reported poor outcome of TP53mut therapy-related myeloid neoplasm (t-MN) irrespective of the allelic status of TP53 (Hiwase et al Blood 2022andShah et al BCJ 2023). Finally, the ICC removed the subcategory of “therapy-related,” substituting it with diagnostic qualifiers instead. The WHO has grouped t-MN with secondary MN and renamed it as “myeloid neoplasm post cytotoxic therapy,” with the assertion that only multi-hit T P53mut MDS occurring post-cytotoxic therapy have poor outcome compared with single-hit. METHODS: We analyzed one of the largest international cohorts of TP53mut MN (n=544) with full characterization of TP53mut allele status utilizing uniform ICC criteria and similar large numbers of de novo and t-MN cases managed at Mayo Clinic Enterprise (USA) and South Australian MDS Registry, Adelaide (Australia) with clinical, integrated genomic profiling, and long-term follow-up. RESULTS: In our cohort of TP53mut MN (n=544), 475 (87.3%) MN had TP53mut variant allele frequency (VAF) of ≥10% and thus satisfied ICC criteria for TP53mut MN. Majority of TP53mut t-MN presented with MDS (bone marrow (BM) blasts 0-9%) compared de novo MN (62% vs. 48%; P=0.0012). While acute myeloid leukemia (AML) (BM blasts ≥20%) were more prevalent in TP53mutde novo MN compared to t-MN (38% vs. 24%; P= 0.001) and there was no difference in frequency of MDS/AML (BM blasts 10-19%) between the two cohorts (14% vs. 14%; P=0.8) ( Figure 1A). Majority of TP53mut were observed in the DNA-binding domain in t-MN and de novo MN (95% vs. 96.2%; P=0.48). However, mutations in Tetramer Domain were more frequent in t-MN (4.3% vs. 0.3%; P=0.002), whereas those in the TAD2 domain were more frequent in de novo TP53mut MN (2.4 vs. 0%; P =0.006). Integrating the mutation, conventional G-banding cytogenetic, copy number variation (CNV), FISH, and SNP array analysis, TP53mut MDS (BM blast 0-9%; n=260) were classified as multi-hit (n=179, 68.9%) or multi-equivalent (n=35, 13.5%) and single-hit (n=46, 17.7%) (Arber et al. Blood 2022). Striking enrichment of multi-hit/multi-hit equivalent was observed in TP53mut t-MDS compared to de novo MDS (91% vs. 72%; P&lt;0.0001). While single-hit TP53mut were prevalent in de novo MDS compared to t-MDS (28% vs. 9%; P&lt;0.0001). Importantly, median overall survival (OS) of single-hit was significantly longer than multi-hit de novo MDS (25.4 vs. 7.2 months; P=0.0002). In contrast to this we did not observe OS difference between single-hit and multi-hit TP53mut t-MDS (11.6 vs. 10.9 months; P =0.73) ( Figure 1B). CONCLUSION: Our study based on a large international cohort of T53mut MN provides compelling evidence that in contrast to de novo MDS, single hit TP53mut t-MDS is associated with poor outcome. Our data supports the consideration of single hit t-MDS as a multi-hit equivalent.

Background and Significance Dysregulation of alternative splicing, caused by abnormal expression or mutation of splicing factors, has been identified as an important contributor to the genesis and progression of cancer, and suggested as a novel target for anticancer treatment. CDC2-like kinases (CLK) represent a family of dual-specificity tyrosine and serine-threonine kinases that are involved in the regulation of splicing by phosphorylation of serine/arginine-rich splicing factors (SRSFs) which play a central role in exon recognition. CTX-712 is an orally available, potent, selective, and a first-in-class pan-CLK inhibitor (CLK 1-4), that inhibits phosphorylation of SRSFs resulting in significant antitumor activity in vitro and multiple xenograft models in vivo. CTX-712 formulated in capsules is currently being evaluated in an ongoing first-in-man study in Japan, evaluating tolerability and early efficacy in patients with solid tumors or hematologic malignancies (JapicCTI-184188). Preliminary data from the Japanese study were presented during ASCO 2022 and ASH 2022, and showed an acceptable safety profile (doses up to 175 mg (MTD 140 mg) twice a week in 28-day cycles, observed DLTs included dehydration, decreased platelets, hypokalemia, and pneumonia) with early signs of clinical antitumor activity (2 partial responses / 26 treated solid tumor patients, 5 complete remissions and complete remission with incomplete hematologic recovery/ 8 treated patients with AML or MDS), warranting further clinical investigations.. (J Clin Oncol (2022) 40(16_suppl):3080. Blood (2022) 140(Supplement 1):6211-2.). This abstract details a second study with CTX-712 that has just been initiated. Study Design and Methods A new film-coated tablet formulation will be evaluated in this phase 1/2 multicenter, open-label study of CTX-712 in patients with (mutated or wild type spliceosomes genes) relapsed/refractory AML, higher risk MDS (IPSS-R intermediate, high, or very high), or high marrow blast (≥5 %) MDS/MPN (including CMML). The phase 1 part of the study will be conducted at 4 US sites, and all sites are currently open for enrolment. The study allows patients with performance status 0, 1, or 2, adequate organ function, and up to four prior lines of therapy. Due to potential risk of interactions (in vitro studies suggest CYP3A4 as main metabolic pathway for CTX-712), concomitant use of strong CYP3A4 inhibitors is prohibited. Use of azole antifungals that are not strong CYP3A4 inhibitors (e.g., isavuconazole) is permitted. The phase 1 part of the study consists of dose-escalation (sequential standard 3 + 3 design), where cohorts of 3 (or 6) patients will receive ascending doses of CTX-712 once weekly in a 28-day cycle with continuous monitoring of emerging clinical PK, PD, safety, and efficacy data, to determine the recommended phase 2 dose (RP2D) based on the suggestion by the Safety Review Committee (SRC). The protocol defines five different dose levels (20-140 mg, once weekly) but also authorizes the SRC to suggest up to two interim dose levels or alternate schedules (e.g., dosing two times a week) if supported by emerging data. The suggested RP2D will be used in a confirmatory phase 1 expansion cohort where an additional 10 patients (total n = 16; 8 patients with AML and 8 patients with MDS) will be treated to gain further confidence in the selected dose level. The phase 2 part of the study will commence after the RP2D has been identified and confirmed and aims at evaluating therapeutic activity in R/R AML (Cohort 2a) or R/R HR-MDS (Cohort 2b), in addition to confirmation of the safety profile. Clinical trial registry number: NCT05732103

Background: Outcomes of adults with relapsed/refractory T-cell acute lymphoblastic leukemia (T-ALL) has remained poor. CD38 is a transmembrane glycoprotein that is highly expressed in T-ALL and is potentially targetable with CD38 blocking agents [Naik J et al. Haematologica 2019, Bride KL et al. Blood 2018, Tembhare et al. J Immunother Cancer 2020]. XmAb18968 is a novel CD38-CD3 bi-specific T-cell engager with Fc domain modified to minimize Fcγ receptor binding and non-selective T-cell activation resulting in reduced cytokine release without compromising target cell killing. We designed a phase I clinical trial to assess the safety and tolerability of XmAb18968 in patients with T-ALL. Methods: We conducted a multicenter, open label, phase I dose escalation study of XmAb18968 (NCT05038644). Patients aged ≥18 years with relapsed/refractory T-ALL or T-lymphoblastic lymphoma (T-LBL), ECOG PS 0-2 and adequate organ function were eligible. Major exclusion criteria are hematopoietic cell transplantation within 6 months of enrollment, prior therapy with daratumumab in the last 6 months and active acute graft-versus-host disease. Dose escalation was conducted using 3+3 design, and 4 separate dose levels were studied [0.8mg, 1mg, 1.3mg, 1.5mg]. XmAb18968 was administered intravenously on days 1, 8, 15, 22 on a 28-day cycle. During cycle 1 alone, day 1 dose was fractionated and administered over 2 days to minimize the risk of significant cytokine release syndrome (CRS). Treatment was continued until progression or unacceptable toxicity. The primary objective was to determine the safety and dose limiting toxicity (DLT) and secondary objective was to determine the preliminary efficacy. Correlative studies included pharmacokinetics, characterizing changes in serum cytokines and phenotypic expression of activated T-cells and leukemic cells, correlation of the phenotypic expression with changes in transcriptome at the single-cell level, proteomics evaluation of cytokine secretion at the single-cell level and correlation of response with N-glycan profiling, quantitative site-occupancy, and direct glycopeptide analysis. Results: Four patients with relapsed/refractory T-ALL have been enrolled so far at dose level 1 (0.8mg) with 3 of them being evaluable for response (one patient came off study before DLT period). Median age was 62 years (34-74), all response evaluable patients had early T-precursor ALL (ETP-ALL), and one patient (25%) was previously treated with allogeneic HCT, CD7 CAR-T therapy and daratumumab. Grade 3 or higher adverse events are summarized in Table 1. CRS grades 1 was noted in 25% of patients, no grade ≥3 CRS or neurotoxicity (any grade) was seen. Of the 3 evaluable total patients, 2 patients had achieved complete response (CR) after 1 cycle of therapy (one patient had prior allogeneic HCT, CD7 CAR-T therapy and daratumumab) (Table 2). The two responders remain on treatment. Conclusions: XmAb18968, a novel CD-38 bispecific antibody appears safe and is showing response at the starting dose level in T-ALL. The study is currently enrolling additional patients with T-ALL. Updated analysis with additional patients and details on correlative studies examining mechanisms of therapeutic efficacy will be reported at the main meeting.

Background and Rationale: Systemic mastocytosis (SM) is a clonal hematologic neoplasm characterized by abnormal accumulation of mast cells which can lead to symptoms related to mast cell degranulation and/or, in the case of advanced systemic mastocytosis (AdvSM), organ dysfunction due to mast cell infiltration. AdvSM is a category of SM comprised of aggressive systemic mastocytosis (ASM), mast cell leukemia (MCL), and SM with an associated hematologic neoplasm (SM-AHN). Among these, SM-AHN is the most common subtype, accounting for approximately 70% of AdvSM. A KIT D816V mutation found in up to 95% of SM cases is the primary oncogenic driver, making it a key therapeutic target. Avapritinib, a highly potent and selective inhibitor of D816V mutant KIT, has demonstrated high rates of rapid, deep, and durable responses in all AdvSM subtypes, including SM-AHN. However, a recent analysis of the EXPLORER study showed that avapritinib-treated patients were still at risk for progression of the AHN component, despite continued control of mast cell disease burden, indicating that combination therapy is likely to be required for optimal control of SM-AHN due to its inherent molecular complexity. Hypomethylating agents (HMA) form the backbone of therapy for advanced myelodysplastic syndrome (MDS) and myelodysplastic/myeloproliferative neoplasm (MDS/MPN), hematologic neoplasms most likely to co-occur with SM in patients (pts) with SM-AHN. To date, the combination of HMA and KIT inhibitors has not been clinically evaluated. In this study, we aim to assess the safety and tolerability of the combination of avapritinib and decitabine in patients with SM-AHN. Study design: The primary objective of the study is to establish the recommended dose (RP2D) of avapritinib in combination with decitabine based on dose-limiting toxicity, overall safety, and clinical activity data. A dose evaluation steering committee (DESC) comprised of participating investigators will review the totality of safety and efficacy data to determine RP2D. Secondary endpoints include SM overall response rate by the end of 6 cycles by the m-IWG consensus criteria and proposed ECNM-AIM criteria ( Gotlib et al., J Allergy Clin Immunol Pract, 2022), as well as incidence and frequency of adverse events. Exploratory endpoints will consist of patient reported outcomes, progression free survival, overall survival, and correlative biomarkers linked to mast cell disease or AHN. Adult pts with a diagnosis of SM-AHN by the WHO 2022 classification criteria will be eligible for inclusion. Eligible pts must have any of the following myeloid AHN per WHO 2022 criteria: MDS, chronic myelomonocytic leukemia, MDS/MPN with neutrophilia, MDS/MPN with SF3B1 mutation and thrombocytosis, or MDS/MPN- not otherwise specified. Patients with MDS must have intermediate, high- or very-high risk by IPSS-R. Patients with very-low or low-risk MDS by IPSS-R must be intolerant/refractory to ESA or have serum EPO &gt; 200 U/L. A baseline platelet count of ≥ 75 x 10 9/L and ≥ 25 x 10 9/L will be required for inclusion in the dose-finding and the dose-expansion phases, respectively (Figure). Key exclusion criteria include a diagnosis of acute myeloid leukemia, history of intracranial hemorrhage or risk of major hemorrhage, prior treatment with avapritinib or decitabine with documented progression in SM or AHN component, respectively, or history of treatment with alternative KIT inhibitor or azacitidine within 4 weeks of study treatment initiation. In the dose finding part of the study, a Bayesian adaptive design will be employed to assess different doses of avapritinib (50 to 200 mg PO daily) in combination with fixed doses of decitabine (oral decitabine/cedazuridine: 35/100 mg/day or intravenous decitabine: 20 mg/m 2/day on days 1-5) in a 28-day treatment cycle. Close attention will be paid to treatment-emergent thrombocytopenia with protocol-driven treatment holds and dose modification strategies employed when platelet count drops below 50 x 10 9/L. After RP2D is determined, an additional 10 patients will be enrolled in the dose expansion phase. Patients with platelet count ≥ 25 x 10 9/L and &lt; 75 x 10 9/L, will receive lead-in dosing with decitabine or decitabine/cedazuridine with the ability to add avapritinib if sufficient platelet thresholds are achieved. This study will open at 7 sites in the United States and is anticipated to open in January 2024.