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Abstract Background: Parenteral DNA methyltransferase inhibitors (DNMTi) such as azacitidine and decitabine (DEC), including an attenuated 3-day regimen, are recommended in the NCCN Guidelines for patients (pts) with lower-risk myelodysplastic syndromes (LR-MDS) with clinically significant cytopenias. However, parenteral administration requires frequent clinic visits, which imposes a substantial burden on pts, particularly those requiring long-term therapy. Oral DMTIs offer more flexible dosing and maintenance of pts' autonomy. Oral DEC-cedazuridine (DEC-C) is a fixed-dose combination tablet containing DEC (35 mg) and cedazuridine (100 mg). ASTX727-03 (NCT03502668) is a randomized, open-label, multicenter, phase 1/2 clinical trial evaluating safety, efficacy, and pharmacokinetics (PK) of various DEC-C doses and regimens in pts with LR-MDS. Phase 1 identified a 5-day regimen of DEC 10 mg/cedazuridine 100 mg as the optimized low-dose (LD) regimen. Phase 2 compares this LD regimen with the attenuated standard-dose (SD) regimen. Here, we report phase 2 results on efficacy, safety, PK, and pharmacodynamic (PD) data. Methods: Adults (aged ≥18 years) with International Prognostic Scoring System (IPSS) low-risk or Intermediate-1 MDS, ECOG PS 0−2, and ≥1 cytopenia or red blood cell (RBC) transfusion dependence were randomized 1:1 to receive oral DEC-C LD (10 mg x 5 days) or SD (35 mg x 3 days). The primary endpoint was hematologic response. Secondary endpoints included PK, PD (by LINE-1 demethylation), time to bone marrow blasts >5%, leukemia-free survival (LFS), overall survival (OS), and safety. Results: As of October 31, 2024, 81 pts were treated (LD arm: n=40; SD arm: n=41) and completed a median of 8.8 months on treatment. At cutoff, 17 (42.5%) and 12 (28.6%) LD and SD pts, respectively, were still continuing the study; 9 (22.5%) and 6 (14.6%) pts respectively, had discontinued treatment due to hematopoietic stem cell transplant. Median age was 70 (LD) and 75 (SD) years; 75.0% (LD) and 68.3% (SD) had IPSS Int-1 risk MDS and 60.0% vs 41.5% had IPSS-Molecular Lower-Risk MDS (very low, low, or moderate-low). Low-risk prognostic scoring system risk distribution was similar: Category 1 (2.5% vs 4.9%), Category 2 (47.5% vs 46.3%), and Category 3 (50.0% vs 48.8%). After a median follow-up of 29.3 months, median OS was 23.9 months (95% confidence interval [CI]: 13.0, not estimable [NE]) in the LD arm vs 26.0 months (95% CI: 19.4, 28.5) in the SD arm. Median LFS was 23.8 months (95% CI: 13.0, NE) and 25.7 months (95% CI: 17.8, 26.5), respectively. Hematologic improvement per International Working Group 2006 criteria was achieved in 27.5% (LD) and 26.8% (SD) of pts. Among RBC transfusion–dependent pts, 52.4% (LD) and 37.5% (SD) achieved ≥56-day independence and 47.6% (LD) and 20.8% (SD) achieved ≥112-day independence. Pts received a median of 10 (LD) and 9 (SD) cycles. Delayed cycles occurred in 72.5% (LD) vs 82.9% (SD) of pts; dose reductions occurred in 40.0% (LD) and 46.3% (SD) of pts. Both treatment regimens caused a decrease in blood counts, reaching a nadir before recovering in each cycle. Neutropenia was more pronounced during early cycles and was more severe in the SD arm. Blood counts across all lineages remained stable or improved through ≥12 cycles with the LD arm, suggesting a more favorable safety and tolerability profile. Grade ≥3 adverse events (AEs) occurred in 85.0% and 90.2% of pts in the LD and SD arms, respectively; treatment discontinuation due to AEs occurred in 2.5% and 17.1% of pts, respectively. Most commonly reported treatment-emergent AEs were anemia (42.5% LD, 39.0% SD), fatigue (32.5% LD, 43.9% SD), and thrombocytopenia (37.5% LD, 39.0% SD). Three deaths occurred in the trial: 2 in the LD arm, which were both unrelated to study treatment, and 1 in the SD arm (Pseudomonal bacteremia in Cycle 1), which was treatment related. Total AUC0–24 was 199 ng*h/mL in the LD arm and 465 ng*h/mL in the SD arm; AUC for all cycles of the LD arm was approximately half of the SD arm. Maximal % LINE-1 demethylation rate was lower with LD than SD, but narrowed by Cycle 3. Conclusion: LD oral DEC-C demonstrated comparable clinical benefit to SD oral DEC-C, with improved safety and tolerability, including fewer dose modifications and less severe myelosuppression. These findings support LD DEC-C as a potential optimal regimen for pts with LR-MDS. Clinical trial registration: NCT03502668

Abstract Introduction: The first-generation BCL2 inhibitor,venetoclax, is an effective treatment for CLL/SLL, but its usage may be limited by toxicity. Sonrotoclax, a next-generation BCL2 inhibitor, is a more selective and pharmacologically potent inhibitor of BCL2 than venetoclax, with a shorter half-life and no drug accumulation. BGB-11417-101 (NCT04277637) is an ongoing, phase 1/1b, dose-escalation/expansion study in patients with B-cell malignancies. Presented here are preliminary data for sonrotoclax + obinutuzumab in patients with treatment-naive (TN) CLL/SLL in BGB-11417-101. Methods: Obinutuzumab is administered intravenously at 100 mg on day (D) 1, 900 mg on D2, 1,000 mg on D8 and D15 of cycle (C) 1, and then 1,000 mg on D1 of C2-6 of each 28-day cycle. Beginning on C2D1, sonrotoclax is administered orally once daily with ramp-up to the target doses, 160 or 320 mg. Patients can continue treatment until progressive disease (PD), unacceptable toxicity, or undetectable minimal residual disease (uMRD4; <1 CLL cell per 10,000 leukocytes [<0.01%]) in peripheral blood (PB) by next-generation sequencing (NGS; ClonoSEQ) after 15 treatment cycles. Study endpoints include safety per NCI-CTCAE v5.0, overall response rate (ORR) per iwCLL guidelines, and MRD status in PB per modified ERIC flow cytometry (FC) assay or NGS, depending on the timepoint. Tumor lysis syndrome (TLS) is assessed per Howard (2011) criteria. Results: As of May 16, 2025, 55 patients with TN CLL/SLL were enrolled (160 mg, n=20; 320 mg, n=35), and 21 patients (all 320 mg) have discontinued sonrotoclax + obinutuzumab (due to uMRD4 per NGS as protocol-mandated [n=17], PI decision uMRD4 per FC [n=2], and PD [n=2]). Four patients discontinued obinutuzumab only per PI decision (160 mg, n=1), thrombocytopenia (320 mg, n=2), and prostate cancer prior to starting sonrotoclax (160 mg, n=1). For all patients, the median age was 62 y, 65% were male, and 89% were White. At baseline, 14% of patients (8/55) had high tumor burden and 58% (31/53) had unmutated IGHV. Median study follow-up was 8.9 months (range, 0.4-25.4 months) for all patients; 6.4 months (range, 0.4-9.0 months) for 160 mg; and 16.0 months (range, 2.9-25.4 months) for 320 mg. Maximum tolerated dose was not reached. The most common any-grade treatment-emergent AEs (TEAEs) were thrombocytopenia (56%), infusion-related reaction (56%), and neutropenia (49%). Neutropenia was the most common grade ≥3 TEAE (38%). No deaths due to TEAEs occurred, and no TEAEs led to sonrotoclax discontinuation. Two cases of laboratory TLS occurred after C1D1 of obinutuzumab prior to starting sonrotoclax; no clinical or laboratory TLS occurred during sonrotoclax ramp up. No meaningful safety differences were observed among sonrotoclax dose cohorts. In 37 efficacy-evaluable patients (160 mg, n=7; 320 mg, n=30), the ORR was 89%; for the 320-mg cohort, ORR was 93% (28/30). Complete response (CR) rates (CR + CR with incomplete marrow recovery [CRi]) were 46% (all patients) and 43% (320 mg). For 23 patients in the 320 mg cohort who reached the C15 MRD assessment, the best C15 uMRD4 rate per FC was 87% (20/23; 2 not evaluable; 1 missing); per NGS, the uMRD4 rate at C15 was 78% (18/23; 5 missing). All patients with an available C15 MRD assessment achieved uMRD4 and remain in remission as of the data cutoff date. The median time from reaching sonrotoclax target dose to uMRD4 was 2.3 months (range, 1.4-5.6 months) in the 320-mg cohort. Three patients experienced PFS events: 1 died from an indeterminate cause (160 mg, discontinued treatment after C1D9 of obinutuzumab) and 2 had PD (320 mg; both Richter's transformation at C6 and C2). Conclusions: Sonrotoclax + obinutuzumab was generally well tolerated in patients with TN CLL/SLL, with no sonrotoclax discontinuations or deaths due to TEAEs. No laboratory or clinical TLS events occurred during sonrotoclax ramp-up. Encouraging antitumor activity was observed with sonrotoclax 320 mg. High rates of blood uMRD4 occurred early and deepened over time. All patients with an available C15 MRD assessment by NGS or FC achieved uMRD4 and remain in remission. A registrational phase 3 study (CELESTIAL-RRCLL, BGB-11417-303) assessing this combination with sonrotoclax 320 mg is currently recruiting.

Abstract Background: Multiple myeloma (MM) is always preceded by monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM). While these precursor conditions are asymptomatic, they are not entirely benign and carry a lifelong risk of progression to MM. Unlike other cancers defined by pathology, malignant transformation from MGUS or SMM to MM has so far relied on demonstration of clinical end-organ damage or high tumor cell burden (i.e. SLiM criteria, SV Rajkumar Lancet Onc 2014), as morphology and cytogenetics cannot reliably distinguish them. Methods: To identify genomic features underlying clinical behavior in MGUS and SMM, a total of 374 patients with SMM (n= 290) or MGUS (n=84) with available whole exome (whole exome sequencing, WES, n=190) or whole genome sequencing (whole genome sequencing WGS, n=184) were included in the study. Overall, none of the patients had evidence of SLiM or CRAB criteria at the time of the biopsy. Based on the center of origin and availability of WES and WGS, 227 and 97 patients were used to form our study training and validation set. The study was designed in two parts: 1) defining a new classification for MM precursor conditions; 2) integrating genomics to existing prognostic score to improve accuracy in identifying patients at imminent risk of progression. Overall, 68 patients in the training set were either lost to follow-up or enrolled in a clinical trial and they were only included in the classification part of the study. Results: By leveraging the distribution of established MM-defining genomic events (Maura et al. JCO 2024) in the training set, we developed a workflow that differentiates MGUS and SMM into two genomically distinct entities: one with evidence of neoplastic transformation (i.e., genomic MM) and one without (i.e., genomic MGUS). Overall, 39% of MGUS and 91% of SMM cases had genomic evidence of neoplastic transformation in the training set (i.e., genomic MM). When we applied the same workflow and classification to the validation set, 46% and 83% of MGUS and SMM had evidence of neoplastic transformation, respectively. Importantly, none of the patients classified as genomic-MGUS progressed to MM in either the training or validation cohorts, with a median follow-up of 40 and 61 months, respectively. Moreover, all patients with IMWG 2/20/20 high risk SMM were classified as genomic MM in both the training and validation set. Interestingly, 5 out of 62 (8%) patients enrolled in early intervention trials for high risk SMM were genomically classified as genomic-MGUS. Overall, these data demonstrated that the MM genomic background and neoplastic transformation can be acquired very early in time, even before the SMM phase, in line with what observed in solid tumors. To avoid overestimating the prognostic impact of myeloma-defining genomic events—which are, by definition, enriched in the genomic-MM group compared to genomic-MGUS—we restricted our prognostic analysis to patients in whom transformation has already occurred (genomic-MM). In fact, distinct genomic drivers may predict malignant transformation but not necessarily the risk of imminent progression to MM once transformation has occurred. After running 5-fold cross validations corrected for IMWG 2/20/20, only presence of RAS mutations, genomic events involving MYC, presence of neoplastic copy number variant (CNV) signatures and APOBEC mutagenesis were predictive of early progression in the training set. Adding the presence of high-risk myeloma-defining genomic events to the IMWG 2/20/20 model (i.e., genomic-IMWG) significantly improves the accuracy of predicting MM progression in both the training (c-index 0.69 vs. 0.74) and validation sets (c-index 0.74 vs. 0.79), compared to the IMWG 2/20/20 alone. Conclusion: By leveraging comprehensive genomic profiling integrated with the clinical IMWG 2/20/20 risk score, we propose a novel classification and prognostication system for MM precursor conditions, which will better define patients who may benefit from early therapeutic intervention versus watch-and-wait monitoring.

Abstract Introduction AL amyloidosis is a rare disorder caused by amyloid fibrils produced by clonal plasma cells, leading to serious organ dysfunction. Cardiac involvement is a major risk factor for poor survival. CD38-binding Daratumumab (D) targets plasma cells and, with bortezomib, cyclophosphamide and dexamethasone (VCd) is the only approved regimen for newly diagnosed AL amyloidosis. The ANDROMEDA phase 3 study showed significant improvements in hematologic responses, major organ deterioration progression free survival and overall survival, compared with VCd alone. The AQUARIUS study (NCT05250973) evaluated cardiac safety of different D-VCd schedules and potential cardiac toxicity mitigation strategies. Methods This multicenter, open-label, phase 2 study enrolled 151 newly diagnosed AL amyloidosis patients at 37 sites in 10 countries. Patients enrolled in either Cohort 1 (n=120, cardiac involvement [Mayo 2004 stage II/IIIA], randomized 2:1 to receive D + immediate VCd or D + deferred VCd) or Cohort 2 (n=31, racial or ethnic minorities with ≥1 any organ involvement, treated with D + immediate VCd). Immediate VCd began on Cycle 1, deferred VCd on Cycle 4. The primary safety endpoint was the incidence of cardiac treatment emergent adverse events (TEAEs). Cardiac assessments included HS TroponinT, NT-proBNP, echocardiogram (ECHO), ECG, NYHA, and the 6-minute walk test (6MWT). Clinical cardiac signs and symptoms (S&S) were assessed at baseline and monthly. Selected, clinically relevant grade ≥3 and/or serious cardiac TEAEs were defined as Major Cardiac TEAE and were assessed by an independent adjudication committee for causality. Patients were followed for 12 treatment cycles or 12 months from first dose (if treatment discontinued prior to 12 cycles). Results 142 patients from both cohorts had cardiac involvement and received at least one dose of D + immediate VCd (n=103) or D + deferred VCd (n=39). Baseline characteristics were balanced between the two groups, including Mayo 2004 stage (IIIa: immediate VCd, 35.0%; deferred VCd, 35.9%; II: immediate VCd, 62.1%; deferred VCd, 53.8%). Treatment duration (median: 10.4 months) and proportion completing ≥10 cycles (79% vs 85%) were similar. Serious cardiac TEAEs occurred at similar rates across groups (immediate VCd, 7.8%; deferred VCd, 7.7%). The most common serious cardiac TEAE (MedDRA term) was cardiac failure (immediate VCd, 5.8%; deferred VCd, 2.6%). Two deaths occurred within 60 days of first study treatment, both were in the immediate VCd group, cardiac-related and unrelated to treatment. The immediate VCd group had fewer cardiac TEAEs overall (48.5% vs 61.5%) but experienced them more frequently during Cycles 1-3 than deferred VCd (35.9% vs 28.2%). This trend reversed for Cycles 4-6 (immediate VCd, 17.7%; deferred VCd, 28.9%). Cardiac TEAEs were low for both groups for Cycles 7-9 (immediate VCd, 9.3%; deferred VCd, 12.1%) and Cycles 10-12 (immediate VCd, 7.4%; deferred VCd, 12.1%). Levels of NT-proBNP, HS troponin T, the 6MWT, and overall cardiac S&S improved similarly for both treatment groups. Rate of cardiac TEAEs of any grade was similar for Mayo stage III patients in the two groups (immediate VCd, 73.0%; deferred VCd, 68.8%) whereas for Mayo stage II patients the incidence was higher in the deferred group (35.9% vs 57.1%). Twenty patients (Immediate VCd, 13; deferred VCd, 7) experienced 30 Major Cardiac TEAEs (selected grade ≥3 and/or serious). Adjudicators attributed 28 events primarily to amyloid cardiomyopathy and 2 events primarily to treatment. These 20 patients had higher baseline Mayo stage (IIIa: 70% vs 29.5%) than the remaining patients (n=122), higher baseline median NT-proBNP (4862 ng/L vs 1723 ng/L) and overall S&S score (7.5 vs 4.0). Several ECHO measures were worse at baseline in these 20 patients (notably, median GLS: -8.8% vs -13.7% and E prime lateral: 4.4 cm/s vs 6.1 cm/s) as was 6MWT (median distance: 319 m vs 363 m). Complete Response (CR) rates were similar in both groups: immediate VCd, 62.1%; deferred VCd, 59.0%. Median time to CR was 64 days for the immediate VCd group and 113 days for the deferred VCd group. Conclusion The D-VCd regimen (immediate or deferred) had a manageable safety profile consistent with previous studies. Cardiac TEAEs were similar between regimens, and their emergence correlated with the start of VCd. Major cardiac events were associated with underlying disease and baseline risk factors that are quantifiable and monitorable.

Abstract Background: B-cell maturation antigen (BCMA)-targeted T cell engagers (TCEs) have emerged as a highly potent immunotherapy for relapsed/refractory multiple myeloma (MM). However, both primary and acquired resistance significantly limit the durability of responses. Antigen escape and development of dysfunctional T cell responses are a significant driver of relapse post-therapy. Here, we preclinically interrogate if continual versus intermittent/response-adapted dosing differently affects development of resistance, the translatability to clinical resistance mechanisms, and how tumor-intrinsic or microenvironmental factors shape the development of resistance to BCMA-TCEs. Methods: We utilized a syngeneic transplantable Vk*MYC MM model which permits clonal tracking through unique immunoglobulin rearrangements. Two cohorts of tumor-bearing mice were treated with a murine surrogate BCMA-TCE using distinct strategies: (1) continuous weekly dosing until disease progression, and (2) an “ intermittent/response-adapted” strategy, where treatment was paused after initial response and resumed upon detection of M-spike. At time of relapse on therapy, RNA-seq was performed on isolated tumor cells to investigate mutations in- or loss of Tnfrsf17/BCMA. Single-cell RNA sequencing (scRNA-seq) was also performed on 189,025 cells isolated from bone marrow and extramedullary sites. Results: Both continuous and intermittent treatment regimens resulted in similar overall survival. BCMA-TCE treatment induced a distinctive pattern of disease progression, with para- and extra-medullary dissemination observed in 31% (17/54) of treated mice—regardless of treatment schedule. Given this treatment-induced dissemination hasn't been historically observed in our model, we further profiled BCMA expression and infiltrating immune cells to understand relapse mechanisms at these sites. Furthermore, we noted lower BCMA expression in tumors from continuously treated mice compared to untreated or stop-and-go cohorts. Importantly, reduced BCMA expression occurred without loss of plasma cell identity indicating that lineage switching may not be occurring as observed in other hematological malignancies treated similarly (Ruella, 2023, Nat Rev Drug Discov); malignant cells retained high expression of canonical plasma cell markers Irf4, Prdm1, Xbp1, Sdc1. We identified three mechanisms of acquired resistance:Genomic BCMA loss: Complete and irreversible loss of BCMA due to retrotransposition of IAP particles into the first intron of Tnfrsf17, disrupting transcription of downstream exons. This represented a genomic mechanism of antigen escape occurring with continual and prolonged TCE dosing, disrupting transcription and eliminating surface BCMA.Transient BCMA downregulation: Transient downregulation of BCMA expression associated with rapid disease relapse under continuous treatment. Tumors exhibited low BCMA levels and widespread dissemination in paramedullary sites. However, re-transplantation into naïve hosts led to restoration of BCMA expression and re-sensitization to TCE, indicating antigen loss was not permanent.Resistance without antigen loss: In the intermittent dosing regimen, several cases achieved complete remission after two doses, relapsed after treatment pause, and were not controlled after subsequent retreatment. Despite preserved BCMA expression and absence of BCMA mutations or deletions, tumors were refractory to retreatment, suggesting a tumor extrinsic mechanism of resistance. scRNA-seq analysis of the tumor microenvironment is ongoing and the role of uniquely identified immune infiltrates, like NK-like lymphocytes and distinct macrophages, in shaping the cell responses is under consideration. Conclusion: Resistance to BCMA-TCE therapy in the Vk*MYC model of MM arises through multiple mechanisms including genomic antigen loss and transient antigen downregulation. Continuous therapy drives selective pressure leading to target loss via genomic or epigenetic routes, while intermittent dosing preserves antigen but permits resistance to TCE, potentially through immune escape mediated by microenvironmental changes. These insights underscore the translatability of the Vk*MYC model for evaluating rational combination therapies to mitigate these resistance mechanisms. All procedures performed on animals were in accordance with regulations and established guidelines and were reviewed and approved by an IACUC or through an ethical review process.

Abstract Background: For patients with B-cell acute lymphoblastic leukemia (B-ALL), extramedullary relapse after allogeneic hematopoietic stem cell transplantation (allo-HSCT) carries an extremely unfavorable prognosis. As a new immunotherapy, chimeric antigen receptor T (CAR-T) cell therapy has shown remarkable effects in refractory or relapsed B-ALL (r/r B-ALL). However, there is still a lack of evidence for its efficacy and safety in patients with extramedullary relapse after allo-HSCT. The aim of this study was to evaluate the safety and efficacy of allogeneic CAR-T in such high-risk populations. Method: We conducted a prospective clinical study, during which 7 patients with B-ALL who experienced extramedullary relapse after allo-HSCT were enrolled between October 2019 and January 2025. These patients all received allogeneic CD19 CAR-T cell therapy. We prospectively evaluated the safety, efficacy, and survival outcomes following CAR-T treatment. This study was registered at www.chictr.org.cn (No. ChiCTR2000036350). Results: This study included 7 patients with extramedullary relapse after allo-HSCT. Median age was 21 years (range: 15 - 46 years), and the median follow-up time was 415 days (range: 130 - 1320 days). The last follow-up was conducted until July 5, 2025. All the patients were classified as high-risk patients before transplantation. Four of them were Philadelphia chromosome/BCR-ABL positive (Ph+). The sites of extramedullary relapse included: 5 cases of central nervous system (among which 2 cases were accompanied by BCR-ABL molecular relapse in the bone marrow), 1 case of testicular relapse, and 1 case of extensive extramedullary relapse. The median interval from transplantation to extramedullary relapse was 628 days (44 - 1225 days). All patients received chemotherapy, radiotherapy or targeted therapy to reduce tumor burden before infusion. The infusion dose of CAR-T cells was 4 - 10 × 10⁶/kg. After infusion, one patient developed grade 3 cytokine release syndrome (CRS) and grade 4 immune effector cell-related neurotoxicity syndrome (ICANS), while the remaining patients did not experience grade 2 or higher CRS or ICANS. No patients developed graft-versus-host disease (GVHD), and all adverse events were resolved. In terms of therapeutic efficacy, one patient was considered unresponsive at the first assessment after infusion (54 days after infusion). The remaining 6 patients all achieved complete remission (CR) efficacy. The median duration of CR was 275 days (range: 120 - 1305 days). During the follow-up period, one patient suffered from central nervous system relapse again at 275 days post-infusion, while the other 5 maintained a continuous CR. The expansion of CAR-T cells in peripheral blood peaked between days 8 to 15 post-infusion, with a median peak of 1.90E+05 copies/μg DNA (range: 1.78E+04 – 3.18E+05 copies/μg DNA), and the longest duration of detectable expansion was 1320 days. Furthermore, CAR-T cells were detected in the cerebrospinal fluid of three patients, indicating their capability for targeted migration and central nervous system infiltration. Conclusion: Overall, allogeneic CAR-T therapy has demonstrated excellent safety and durable anti-leukemia effects in high-risk ALL patients with extramedullary relapse after transplantation.

Abstract Background: The addition of the CD19/CD3 bispecific T-cell engager, blinatumomab, to standard consolidation chemotherapy in adults with ALL who achieved a measurable residual disease negative (MRDneg) remission (CR), demonstrated an improvement in 3-year overall survival (OS, 85% vs 68%, HR 0.41, P=0.002) and 3-year relapse-free survival (RFS, 80% vs 64%, HR 0.53) compared to conventional chemotherapy in the ECOG-ACRIN E1910 study (Litzow et al, NEJM 2024). Given the complex therapy in this study, treatment delays and modifications are expected. We herein explored the impact of such delays on patient outcomes. Methods: In the phase 3 ECOG-ACRIN E1910 trial (NCT02003222), adults aged 30-70 years with newly diagnosedALL who had achieved MRDneg CR following induction and intensification were randomized to consolidation chemotherapy with blinatumomab (blina arm) or chemotherapy alone (chemo arm). We examined the association between the timing of the initiation of maintenance therapy and OS and RFS. The expected duration of consolidation was 252 days vs 126 days for patients on the blina and chemo arms, respectively. For this analysis, participants were classified into two groups (no/short delay or long delay) depending on whether they started on time/before or after the median time between the beginning of consolidation and start of maintenance therapy for their treatment group (medians: 335 days, range, 181-457 days vs 176 days, range, 139-265 days for blina and chemo arms, respectively). Multivariate analyses of OS and RFS were performed to examine the effect of no/short delay vs. long delay in starting maintenance. Patients were stratified according to their assigned consolidation treatment arm, and the models were further adjusted for age, sex, white blood cell count, platelets, hemoglobin, peripheral blood blasts, bone marrow blasts, performance status and genetic-genomic risk at diagnosis. Results: Of the 488 patients enrolled, 224 MRDneg patients were randomized to consolidation chemotherapy with or without blinatumomab and 135 of the 224 went on to maintenance therapy on study (N= 66 on blina arm and 69 on chemo arm, respectively). The median follow-up from the time of maintenance registration was 43.4 months. There were no significant differences in baseline characteristics between patients in either arm who experienced no/short delay or long delay. In the blina group, 60 of 66 patients (90.9%) received all 8 cycles of consolidation therapy of which 31 (45.6%) had long delays. Sixty-eight of 69 patients on the chemo arm (98.5%) received all cycles of consolidation therapy, of which 34 (50%) had a long delay. Strikingly, patients who had a long delay before initiation of maintenance had a significant improvement in OS in multivariate analysis compared to patients who had no/short delay (HR 0.31, 95% CI: 0.11-0.91; P =0.03). However, within each treatment group, OS benefit did not reach statistical significance (blina arm: HR 0.04, 95% CI: 0.001-1.64; P =0.09; chemo arm: HR 0.32, 95% CI: 0.08-1.38; P =0.13). Similar results were observed for RFS in multivariate analysis (HR 0.40, 95% CI: 0.16-1.01; P =0.05), though this impact on improved RFS was noted in the chemo arm but not in blinatumomab treated patients (blina arm: HR 0.56, 95% CI: 0.10-3.24; P =0.52; chemo arm: HR 0.19, 95% CI: 0.04-0.83; P=0.03). Additionally, patients who had no/short delay before starting maintenance experienced a longer median duration of maintenance treatment (blina arm, 548 days; chemo arm, 708 days) compared to patients who had a long delay (blina arm 488 days; chemo arm 598 days) before initiation of maintenance (P=0.0008). Conclusion: In the phase 3 randomized ECOG-ACRIN E1910 clinical trial, long delays between initiation of consolidation therapy and start of maintenance therapy were associated with improved OS compared to no/short delays. However, within each treatment group (blina or chemo), no significant difference of OS was observed. We postulate that these longer delays allowed more patients to receive all of the recommended protocol-assigned therapy thereby resulting in improved survival. Furthermore, patients who had no/short delays had a significantly longer duration of maintenance therapy. These data indicate that treatment delays during consolidation do not worsen survival. Further studies are being done to better understand why patients with long delays had better overall survival.

Abstract Background: Relapsed or refractory (R/R) acute lymphoblastic leukemia (ALL) and lymphoblastic lymphoma (LL) remain challenging to treat, particularly in older patients and those with a T-cell phenotype. Venetoclax (VEN), a selective BCL-2 inhibitor, has shown preclinical synergy with vincristine (VCR) in multiple preclinical ALL models. Following the previously reported establishment of the recommended Phase II dose (RP2D), we now report the results of the Phase II (Ph2) portion of EA9152 (VEN 600 mg daily with weekly L-VCR 2.25 mg/m² IV or VCR 1.5 mg/m2 IV capped at 2 mg), evaluating efficacy and safety in this high-risk population. Methods: This open-label, multicenter Phase II study enrolled adults (≥18 years) with R/R B- or T-cell ALL or LL. The phase II portion of this trial was a single-arm, open-label study evaluating the combination of VEN (600 mg po D1–28) with either L-VCR (2.25 mg/m² IV weekly x4) or vincristine sulfate (VCR) (1.4 mg/m² IV weekly x4). Following the market withdrawal of L-VCR in the United States in April 2022, no new patients were initiated on this formulation and patients already receiving L-VCR were transitioned to VCR at the start of their next treatment cycle or sooner if necessitated by drug availability. Prior VCR but not VEN exposure was permitted in Ph2. The primary endpoint was achievement of a complete response or complete response with incomplete count recovery CR + CRi rate by end of cycle 3. Secondary endpoints included measurable residual disease (MRD) response, progression free survival (PFS), overall survival (OS), and safety. The association of phenotype with response and time-to-event were evaluated using Fisher's exact test and the Cox proportional hazards model, respectively. Results: Twenty-one eligible patients were treated (B-cell ALL/LL: n=12; T-cell ALL/LL: n=9). The trial was terminated early after 22/56 patients were accrued on account of withdrawal of sponsor support. Median age was 50 years and 76.2% were male. Performance status was 0–1 in 85.7%. All patients had received prior chemotherapy; 47.6% had undergone prior transplant. Median number of treatment cycles was 1 (2 for B-cell, 1 for T-cell). By end of cycle 3, no patients in the B-cell cohort (0/12; 90% CI, 0.00–0.22) achieved CR or CRi, 8 had stable disease (SD). In the T-cell cohort, 1 of 9 patients (11.1%; 90% CI, 0.01–0.43) achieved CR, 1 achieved PR and 1 had SD. There was no statistically significant difference in CR + CRi rate between phenotypes (p=0.43). None of the patients achieved an MRD-negative CR/CRi by flow cytometry or molecular methods. At the time of this analysis, 16 of 21 patients had died. Median overall survival (OS) was 4.3 months (95% CI, 1.5–22.0) for B-cell and 10.2 months (95% CI, 2.0–16.4) for T-cell patients (HR 1.32, p=0.60). Median PFS was 2.9 months (95% CI, 1.7–3.7) for B-cell and 1.2 months (95% CI, 0.7–4.6) for T-cell cohorts (HR 2.18, p=0.18). Grade 3–5 treatment-related adverse events occurred in most patients. One T-cell patient experienced grade 5 respiratory failure. Among 16 patients enrolled under the revised protocol using VCR, only 1 experienced grade 3 peripheral motor neuropathy, and no peripheral sensory neuropathy was reported (combined AE rate 0.06; 90% CI, 0.00–0.26). Tumor lysis syndrome was not observed in this cohort. Conclusions: The combination of VEN at the established RP2D and L-VCR/VCR was feasible and had an acceptable safety profile in heavily pretreated patients with R/R ALL/LL. However, response rates, including CR/CRi and MRD negativity, were limited, particularly in the B-cell cohort. Median OS and PFS remain poor in both subtypes, highlighting the need for improved strategies in this high-risk population. Venetoclax, in combination with other chemotherapy regimens, has shown encouraging response rates warranting continued exploration of its benefit in ALL.

Abstract In this study, we investigated tumor intrinsic mechanisms of resistance to cevostamab, a bispecific T-cell engager targeting Fc receptor-like protein 5 (FCRL5) and CD3 that has shown promising clinical activity and durable responses in advanced MM. Longitudinal bone marrow aspirates from nine MM patients treated with cevostamab were analyzed. All patients had previously been treated with both immunomodulatory drugs (IMiDs) and proteasome inhibitors (PI) and eight patients had received daratumumab prior to cevostamab, which was, on average, the 6th line of treatment (mean treatment duration 220±273 days). Five of nine patients responded with ≥PR. Whole genome and transcriptome sequencing was performed on sorted CD138+ MM cells at baseline, and whole exome and transcriptome sequencing was performed on five and three samples, respectively, following cevostamab discontinuation. Baseline FCRL5 expression levels did not correlate with clinical response. However, in one non-responder patient, FCRL5 expression increased four-fold after 28 days of treatment. Given the location of the FCRL5 gene on chromosome 1q—commonly amplified in advanced MM—we evaluated the presence of Gain(1q) in our study cohort. All patients whose best response was ≤PR (n=6) harbored a Gain(1q), whereas it was absent in those who achieved VGPR and sCR (n=3). Crucially, one of the patients that achieved sCR was initially treated with 60 mg of cevostamab for one year and then escalated to a higher dose cohort (90 mg) in the second year. At progression, a clonal FCRL5E115A missense mutation (allelic frequency = 56%) and a subclonal FCRL5G455Efs*19(allelic frequency = 5%) frameshift deletion mutation were detected, both absent at baseline. The missense mutation was located on the extracellular domain of FCRL5 targeted by cevostamab. To validate the functional impact of FCRL5E115Aand FCRL5G455Efs*19 on the sensitivity to cevostamab in vitro, we generated a FCRL5 knockout (KO) model utilizing CRISPR-Cas9 technology in OPM2 MM cells. In vitro cevostamab cytotoxicity assay with PBMCs and pan T cells from healthy donors at various effector to target (E:T) ratios confirmed a complete loss of cevostamab sensitivity in our FCRL5KO models. cDNA encoding patient-derived FCRL5 alterations (FCRL5E115Aand FCRL5G455Efs*19) as well as FCRL5wtwere cloned into mammalian expression vector and reintroduced into FCRL5KO cells. Cevostamab sensitivity was reinstated by FCRL5wt expression in KO cells. In contrast, FCRL5E115A conferred complete resistance to cevostamab (p<0,001) and FCRL5G455Efs*19 depicted a significant decline in cevostamab sensitivity relative to FCRL5wt expressing models. Additional experiment utilizing direct stochastic optical reconstruction microscopy (dSTORM) are ongoing to monitor the membrane localization of FCRL5 mutants. By integrating genomic, transcriptomic and functional data with clinical outcomes, this work is the first to report on acquired FCRL5 mutations causing resistance to cevostamab. We hypothesize that the prolonged treatment duration may have contributed to the acquisition of the target mutations and note a subsequent durable sCR response to BCMA-targeted immunotherapy in the same patient, suggesting immune-related factors such as T cell exhaustion, were not drivers of cevostamab resistance. Due to the limited sample size, these findings require validation in larger cohorts. Nonetheless, our findings begin to elucidate tumor intrinsic mechanisms associated with cevostamab resistance.

Abstract Introduction: Multiple Myeloma (MM) is a complex hematologic malignancy, where patients often display one or more potentially high risk cytogenetic alterations associated with poor outcomes. Traditional high risk cytogenetics events in myeloma, such as NSD2 t(4;14) translocations, gain of 1q21, or deletion of 17p13, have often been studied in isolation, but emerging evidence suggests the combination of these high risk alterations has a greater negative prognostic impact than any on their own. This has been recently reflected in risk stratification guidelines from IMS and IMWG, which consider certain events, such as t(4;14), as high risk only in combination with gain of 1q21 or deletion of 1p32. Still, the mechanisms through which multi-hit high risk events disrupt the microenvironment and promote poor outcomes remains unclear. We hypothesize that myelomas with multiple high risk alterations remodel the immune environment to promote tumor progression and immune escape. Methods: To study the role of multi-hit high risk cytogenetics on the immune microenvironment, we analyzed CD138-bone marrow aspirate single-cell RNA sequencing (scRNAseq) data from 337 newly diagnosed MM patients from the MMRF CoMMpass study, generated as part of the Immune Atlas initiative. Cytogenetic alterations for these patients were derived from whole-genome and whole-exome sequencing of CD138+ bone marrow aspirates from the MMRF CoMMpass cohort. Patients were classified as multi-hit high-risk MM if they exhibited either (i) two high-risk cytogenetic events, including NSD2 t(4;14), MAF t(14;16), del(17p13), or (ii) one high-risk event with gain of 1q21. Results: Based on cytogenetic information, 33 patients in the Immune Atlas cohort were classified as 'multi-hit’ high-risk, while 34 patients had only a single high-risk alteration. These multi-hit high risk patents displayed significantly worse progression free survival compared to standard risk patients, adjusting for age, therapy, and ASCT (HR=2.34, p<7.2e-5), while single-hit patients showed a non-significant trend towards worse outcomes (HR=1.51, p=0.071). The most frequent multi-hit risk event in the cohort was NSD2 t(4;14) in combination with 1q21, observed in 23 patients. Compositional analysis of the immune populations in the scRNAseq data revealed that relative to both standard and single-hit high risk patients, multi-hit high risk patients displayed significant reductions in IFN-I stimulated CD4+ and CD8+ T cell populations, marked by decreased expression for antiviral response markers such as ISG15, XAF1, and IFI44L. Enrichment of inflammatory CD16+ non-classical monocytes was also observed. Further analysis of the most frequent multi-hit risk event, NSD2 with 1q21, revealed distinct enrichment of late-activated cytotoxic HLA+ CD8+T cells and cytotoxic CD4+.T cells. Neither alteration was observed in patients with single-hit NSD2 or 1q21. Further analysis on the interactions between high risk events revealed distinct transcriptomic profiles dependent on the high risk events involved, particularly in multi-hit events involving mutations or deletions of TP53 or gain of 1q21. Reduction in IFN-I signaling across various immune populations was primarily restricted to multi-hit risk events involving gain of 1q21. Conversely, patients with biallelic loss of TP53 displayed significant enrichment of these same IFN-I populations. Given this contrast in IFN-I signaling spanning multiple immune subtypes, we hypothesized that the malignant myeloma cells might similarly display altered IFN-I activity. Utilizing CD138+ myeloma bulk RNA sequencing data from CoMMpass, we found that IFN-I response scores strongly correlated between paired scRNA immune and bulk RNAseq tumor datasets (R2: 0.75, p=1.63e-32). Across 660 patients with bulk RNAseq and cytogenetic data, we confirmed significant reductions in IFN-I response scores in tumor cells in multi-hit high risk involving 1q21, and significant enrichment in those with complete loss of TP53 relative to standard-risk MM. Conclusions: Overall, we do observe that MM patients with multiple high risk cytogenetic alterations display distinct immunologic traits relative to standard risk or single-hit high risk patients in addition to significantly worse outcomes. Furthermore, we find variability in the immune alterations observed based on the cytogenetic events involved, further illustrating the heterogeneity in how MM shapes the immune microenvironment.