Measurable Residual Disease Levels Research Articles

How I treat newly diagnosed acute lymphoblastic leukemia.

Treatment algorithms differ for adult patients with Philadelphia-negative (Ph-) and Philadelphia-positive (Ph+) acute lymphoblastic leukemia (ALL). For Ph- ALL intensive induction-consolidation chemotherapy using "pediatric-inspired" protocols is a standard of care. Allogeneic hematopoietic cell transplantation (allo-HCT) from either an HLA-matched sibling, unrelated or haploidentical donor should be considered for patients with high estimated risk of relapse. Inadequate response at the level of measurable residual disease (MRD) is the strongest adverse prognostic factor. Patients with B-ALL and detectable MRD should be treated with blinatumomab. In the future, the use of blinatumomab and/or inotuzumab ozogamycin in addition to first-line chemotherapy may become a new standard of care reducing the role of allo-HCT. For patients with Ph+ ALL, tyrosine kinase inhibitors (TKI) are the most important components of treatment protocols, while the intensity of chemotherapy may be reduced. Allo-HCT is recommended for all patients treated with imatinib along with low-intensity chemotherapy. Results of phase-II studies using front-line dasatinib or ponatinib in sequence or in combination with blinatumomab are very promising. Such a strategy may allow the avoidance of systemic chemotherapy. The future role of allo-HCT in this context appears uncertain.

Performance of a novel eight-color flow cytometry panel for measurable residual disease assessment of chronic lymphocytic leukemia.

Measurable residual disease (MRD) is an important prognostic indicator of chronic lymphocytic leukemia (CLL). Different flow cytometric panels have been developed for the MRD assessment of CLL in Western countries; however, the application of these panels in China remains largely unexplored. Owing to the requirements for high accuracy, reproducibility, and comparability of MRD assessment in China, we investigated the performance of a flow cytometric approach (CD45-ROR1 panel) to assess MRD in patients with CLL. The European Research Initiative on CLL (ERIC) eight-color panel was used as the "gold standard." The sensitivity, specificity, and concordance rate of the CD45-ROR1 panel in the MRD assessment of CLL were 100% (87/87), 88.5% (23/26), and 97.3% (110/113), respectively. Two of the three inconsistent samples were further verified using next-generation sequencing. In addition, the MRD results obtained from the CD45-ROR1 panel were positively associated with the ERIC eight-color panel results for MRD assessment (R = 0.98, p < 0.0001). MRD detection at low levels (≤1.0%) demonstrated a smaller difference between the two methods (bias, -0.11; 95% CI, -0.90 to 0.68) than that at high levels (>1%). In the reproducibility assessment, the bias was smaller at three data points (within 24, 48, and 72 h) in the CD45-ROR1 panel than in the ERIC eight-color panel. Moreover, MRD levels detected using the CD45-ROR1 panel for the same samples from different laboratories showed a strong statistical correlation (R = 0.99, p < 0.0001) with trivial interlaboratory variation (bias, 0.135; 95% CI, -0.439 to 0.709). In addition, the positivity rate of MRD in the bone marrow samples was higher than that in the peripheral blood samples. Collectively, this study demonstrated that the CD45-ROR1 panel is a reliable method for MRD assessment of CLL with high sensitivity, reproducibility, and reliability.

Analytical Performance Evaluation of a Digital Real-Time PCR for Quantifying Major BCR::ABL1 Transcripts.

Accurate quantification of the BCR::ABL1 transcripts is essential for measurable residual disease (MRD) monitoring in chronic myeloid leukemia (CML) after tyrosine kinase inhibitor (TKI) treatment. This study evaluated the newly developed digital real-time PCR method, Dr. PCR, as an alternative reverse transcription-PCR (qRT-PCR) for MRD detection. The performance of Dr. PCR was assessed using reference and clinical materials. Precision, linearity, and correlation with qRT-PCR were evaluated. MRD levels detected by Dr. PCR were compared with qRT-PCR, and practical advantages were investigated. Dr. PCR detected MRD up to 0.0032%IS (MR4.5) with excellent precision and linearity and showed a strong correlation with qRT-PCR results. Notably, Dr. PCR identified higher levels of MRD in 12.7% (29/229) of patients than qRT-PCR, including six cases of MR4, which is a critical level for TKI discontinuation. Dr. PCR also allowed for sufficient ABL1 copies in all cases, while qRT-PCR necessitated multiple repeat tests in 3.5% (8/229) of cases. Our study provides a body of evidence supporting the clinical application of Dr. PCR as a rapid and efficient method for assessing MRD in patients with CML under the current treatment regimen.

Impact of measurable residual disease in combination with CD19 on postremission therapy choices for adult t(8;21) acute myeloid leukemia in first complete remission.

The post-remission therapy (PRT) choices for adult t(8;21) acute myeloid leukemia (AML) in first complete remission (CR1) need to be further explored. We aimed to investigate the impact of measurable residual disease (MRD) combined with CD19 on PRT choices for adult t(8;21) AML in CR1. A total of 150 t(8;21) AML patients were enrolled, including 67 underwent chemotherapy (CMT) and 83 allogeneic hematopoietic stem cell transplantation (allo-SCT) as PRT in CR1. Subgroup analyses were performed according to MRD level after three cycles of chemotherapy combined with CD19 expression. Multivariate analysis indicated MRDhigh after three courses of treatment (HR, 0.14 [95% CI, 0.03-0.66]; p = 0.013) and CD19 negativity (HR, 0.14 [95% CI, 0.02-0.96]; p = 0.045) were risk factors for relapse, while allo-SCT was protective factor for relapse (HR, 0.34 [95% CI, 0.15-0.75]; p = 0.008). Grouped by MRD after three courses of chemotherapy, allo-SCT had lower CIR (p < 0.001) and better OS (p = 0.003) than CMT for MRDhigh patients, CMT showed a higher CIR (35.99% vs. 15.34%, p = 0.100) but comparable OS (p = 0.588) than allo-SCT for MRDlow patients. Grouped by CD19 expression, allo-SCT demonstrated lower CIR (p < 0.001) and better OS (p = 0.002) than CMT for CD19- patients. CMT had a higher CIR (41.37% vs. 10.48%, p = 0.007) but comparable OS (p = 0.147) than allo-SCT for CD19+ patients. Grouped by MRD combined with CD19, MRDhigh /CD19+ subsets were identified out of CD19+ patients benefiting from allo-SCT with lower CIR (p = 0.002) and superior OS (p = 0.020) than CMT. CMT preserved comparable CIR (p = 0.939) and OS (p = 0.658) with allo-SCT for MRDlow /CD19+ patients. MRDlow /CD19- subsets were also identified from MRDlow patients requiring allo-SCT with lower CIR (p < 0.001) and superior OS (p = 0.008) than CMT. Allo-SCT maintained lower CIR (p < 0.001) and superior OS (p = 0.008) than CMT for MRDhigh /CD19- patients. MRD combined with CD19 might optimize PRT choices for adult t(8;21) AML patients in CR1.

Impact of hemodilution on flow cytometry based measurable residual disease assessment in acute myeloid leukemia

Measurable residual disease (MRD) measured in the bone marrow (BM) of acute myeloid leukemia (AML) patients after induction chemotherapy is an established prognostic factor. Hemodilution, stemming from peripheral blood (PB) mixing within BM during aspiration, can yield false-negative MRD results. We prospectively examined hemodilution by measuring MRD in BM aspirates obtained from three consecutive 2 mL pulls, along with PB samples. Our results demonstrated a significant decrease in MRD percentages between the first and second pulls (P = 0.025) and between the second and third pulls (P = 0.025), highlighting the impact of hemodilution. Initially, 39% of MRD levels (18/46 leukemia-associated immunophenotypes) exceeded the 0.1% cut-off, decreasing to 30% (14/46) in the third pull. Additionally, we assessed the performance of six published methods and parameters for distinguishing BM from PB samples, addressing or compensating for hemodilution. The most promising results relied on the percentages of CD16dim granulocytic population (scarce in BM) and CD117high mast cells (exclusive to BM). Our findings highlight the importance of estimating hemodilution in MRD assessment to qualify MRD results, particularly near the common 0.1% cut-off. To avoid false-negative results by hemodilution, it is essential to collect high-quality BM aspirations and preferably utilizing the initial pull for MRD testing.

The effectiveness of blinatumomab in clearing measurable residual disease in pediatric B-cell acute lymphoblastic leukemia patients detected by next-generation sequencing.

Blinatumomab improved survival outcomes in B-cell acute lymphoblastic leukemia (B-ALL) patients with measurable residual disease (MRD) <10-4 . However, data on blinatumomab clearing MRD with high sensitivity of 10-6 remain scarce. This study evaluates the effectiveness of blinatumomab in eradicating extremely low level (up to <10-6 ) of MRD, as detected by next-generation sequencing (NGS), in children with B-ALL. Patients (n = 19) whose MRD was undetectable by multiparameter flow cytometry (MFC) (sensitivity of 10-4 ) but detectable by NGS after chemotherapy and followed by blinatumomab consolidation were included retrospectively. After one course of blinatumomab, 13/19 patients (68%) successfully achieved NGS-MRD clearance (undetectable). With a median follow-up of 13.3 months, three of patients who were NGS-MRD positive relapsed within 1.8 months, while another three remained complete remission. Our study was the first to demonstrate that blinatumomab could further eradicate MRD after patients achieve MFC-MRD undetectable in B-ALL patients.

Using Peripheral Blood (PB) Measurable Residual Disease (MRD) Levels to Predict &amp;lt;0.01% Bone Marrow Disease (BM uMRD4): Identification of Effective PB Targets for CLL Treatment Cessation in the Ibrutinib+Venetoclax Arm of the FLAIR Trial

CONCLUSIONS Time-limited treatments for CLL are under investigation but the optimal target for treatment cessation is not fully clear. Bone marrow (BM) measurable residual disease (MRD) is usually the most sensitive measure but would be too invasive to guide treatment in a routine setting. The iwCLL threshold of BM uMRD4 (&amp;lt;0.01%) has been demonstrated to be a powerful indicator of improved outcomes across multiple different trials and the aim of this analysis is to determine the feasibility of using PB MRD analysis to identify patients who have attained BM uMRD4. FLAIR (ISRCTN01844152) is an open-label, randomised, controlled, phase 3 trial comparing ibrutinib plus rituximab (IR) with fludarabine, cyclophosphamide and rituximab (FCR), subsequently amended to compare ibrutinib plus venetoclax (I+V) and ibrutinib alone (I) with FCR. Paired PB &amp; BM samples were scheduled at: (1) response assessment 9 months after randomization in all arms (n=1086); (2) end of treatment after 72 months in the ibrutinib-containing arms (n=137, most I/I+V participants have not reached this timepoint yet); and (3) confirmation of BM uMRD4 for initiation of planned stopping rules in participants with sustained PB uMRD4 defined as &amp;lt;0.01% PB MRD at 3 timepoints over 6 months (n=188 in the I+V arm). MRD analysis was performed using an ERIC-compliant 8-colour flow cytometry assay targeting acquisition of 2.2 million events (detection limit MRD5/0.001%). As the target could not always be met due to sample/laboratory limitations, stringent uMRD4 assessing 500 thousand leucocytes (detection limit 0.005%) was also evaluated. Table 1 shows the BM vs. PB MRD levels for different treatment arms and timepoints. The greatest discrepancy was observed in participants receiving FCR with a median 0.8log higher disease in the BM vs. PB. Participants receiving ibrutinib monotherapy had similar PB and BM MRD levels while the addition of either rituximab or venetoclax was associated with slightly higher (median &amp;lt;0.1 log) BM vs. PB MRD levels for both IR and I+V arms. The difference did not persist in the IR arm but remained during I+V treatment in some cases, with median &amp;gt;0.59 log higher BM vs. PB MRD levels in 29/182 participants achieving PB uMRD4 but with detectable BM MRD. Table 1 also shows the proportion of cases that attain BM uMRD4 according to different PB MRD thresholds. For participants with rituximab exposure in the past 3 months, BM uMRD4 was attained in 75-88% of participants with PB uMRD5, and only 43-76% of participants with stringent uMRD4. For participants with PB dMRD5 (0.001-0.01% MRD), only 14-52% achieved BM uMRD4. However, participants on I+V with either PB uMRD5 or stringent uMRD4 attained BM uMRD4 in 94-96% of cases. Planned cessation of treatment in the FLAIR trial was guided by sustained PB uMRD4, defined as 3 successive results with &amp;lt;0.01% PB disease over six months with confirmation of BM uMRD4 at the final time point. This strategy in the I+V arm is highly effective in achieving improved progression-free and overall survival compared to FCR [see related abstract]. Sustained PB uMRD4 led to BM assessments in 188 participants of which 173/188 (92%) attained BM uMRD4. High sensitivity PB MRD gave concordant results to BM MRD4 analysis in 91% of participants (172/188), while 9/188 (5%) had PB dMRD5 / BM uMRD4 (7/9 had detectable BM MRD in the range 0.002-0.007% and 2/9 had BM uMRD5/&amp;lt;0.001%) and 7/188 (4%) had PB uMRD5/stringent uMRD4 but with persistent BM dMRD4 (median 0.02% BM MRD, range 0.01-0.055%). PB MRD level correlates closely with BM MRD level but there is lower concordance at the 0.01%/MRD4 threshold after recent cessation of therapeutic antibody. PB uMRD4 is not a suitable target for treatment cessation as the majority of patients with 0.001%-0.01% PB MRD have &amp;gt;0.01% BM disease. For the identification of people attaining BM uMRD4 (&amp;lt;0.01%) on I+V treatment, sustained PB uMRD4 was &amp;gt;90% effective. For translation into MRD-guided treatment in future routine clinical practice, BM assessment may be replaced with PB MRD monitoring if the 0.001%/MRD5 threshold is applied.

The Effectiveness of Blinatumomab in Clearing Next-Generation Sequencing Measurable Residual Disease in Pediatric Patients with B-Cell Acute Lymphoblastic Leukemia

Introduction Blinatumomab is a bispecific T-cell engager antibody designed to redirect CD3+ T cells to bind to CD19+ target cells in relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL). Measurable residual disease (MRD) is a significant prognostic factor for relapse and overall survival in B-ALL. Blinatumomab consolidation therapy has been shown to improve MRD remission (&amp;lt;10 -4), as detected by multiparameter flow cytometry (MFC) or reverse transcriptase-polymerase chain reaction (PCR), and survival outcomes in children with high-risk first relapsed B-ALL. The next-generation sequencing (NGS)-MRD is a highly sensitive technique that can detect very low levels of MRD (&amp;lt;10 -6) in patients who were considered “MRD negative” by less sensitive MFC or PCR technologies. Early achievement of NGS-MRD negativity (&amp;lt;10 -6) can help in identifying patients who have a very low risk of relapse. It has been suggested that blinatumomab treatment could help to attain deeper responses than that measured with a MRD sensitivity level of 10 -4. However, data on blinatumomab clearing MRD with high sensitivity of 10 -6 remain scarce. Hence, we evaluated the effectiveness of blinatumomab in eradicating extremely low level of MRD (&amp;lt;10 -6), as detected by NGS, in children with B-ALL. Methods Pediatric B-ALL patients who were MFC-MRD negative (&amp;lt;10 -4) but NGS-MRD positive (sensitivity of 10 -6) after chemotherapy followed by blinatumomab consolidation therapy between October 2021 and February 2023, were studied retrospectively. At diagnosis, NGS analysis was performed by high-throughput deep level sequencing using the Seq-MRD ® (ImmuQuad Biotech, Hangzhou, China) to detect clonal rearrangements. Genomic DNA was extracted from bone marrow samples using QIAamp DNA Mini kit (Qiagen, Hilden, Germany), amplified by quantitative PCR and sequenced using the Illumina® Novaseq PE150 (Illumina ® Novaseq, San Diego, USA) platform. The sequences of immunoglobulin heavy chain (IGH) variable (V), diversity (D), and joining (J) (IGH -VDJ), IGH-DJ, immunoglobulin kappa light chain (IGK), immunoglobulin kappa deleting element (IGKDE) and immunoglobulin light chain (IGL) were assessed for clonality with dominant index sequence(s). Results Overall, 19 patients were enrolled. The baseline patient characteristics are shown in Table 1. Median age at diagnosis was 4.4 years (range 0.3-10.6), with males accounting for 84% of patients. Eight patients (42%) had at least 1 unfavorable genetic abnormality (i.e., KMT2A rearrangement, E2A-PBX1). Seventeen (89%) patients had ≥2 Ig clonal rearrangement at diagnosis. In total, NGS detected 71 clonal rearrangements, including 27 IGH clonal rearrangements in 15 (79%) patients, 9 IGH-DJ in 6 (32%), 14 IGK in 8 (42%), 6 IGKDE in 9 (32%), and 12 IGL in 8 (42%) patients. All patients achieved hematological complete response (CR) with MFC-MRD &amp;lt;10 -4 after the induction or consolidation chemotherapy. However, all these patients were identified to be MRD positive by NGS, including NGS-MRD &amp;gt;10 -6 and positive but not quantifiable (NGS-MRD &amp;lt;10 -6). Though the patients were MFC-MRD negative, 19 IGH clones, 4 IGH-DJ clones, 8 IGK clones, 7 IGKDE clones and 3 IGL clones were still persisted. After blinatumomab, MRD negativity rate by MFC was 95% (18/19) and the NGS-MRD negativity rate was 68% at 10 -6 (13/19). The rate of MRD clearance after blinatumomab per NGS was 69% and 67% in CR1 and CR2 patients, respectively. The clearance rates of IGH, IGK, IGL, IGH-DJ, and IGKDE were 75%, 67%, 33%, 100%, and 83%, respectively (Table 2). Three NGS-MRD negative patients with available NGS-MRD at pre-, mid-, and post-treatment achieved MRD clearance rapidly after blinatumomab treatment that was maintained durably through day 28. Three of 6 NGS-MRD positive patients relapsed after blinatumomab with 3 being IGH positive and 2 being IGL positive. Conclusion To the best of our knowledge, for the first time it has been demonstrated that blinatumomab could further eradicate MRD in patients achieving MFC-MRD &amp;lt;10 -4. Advanced MRD detection using NGS and blinatumomab made deeper molecular remission in B-ALL patients achievable. Further large-scale studies are warranted to verify the prognostic value of NGS in detecting lower levels of MRD in ALL patients treated in the current immunotherapy era.

Kinetics and Biology of Circulating Tumor Cells (CTCs) and Measurable Residual Disease (MRD): Two Dynamic High-Risk Clones in Multiple Myeloma (MM)

BACKGROUND CTCs and MRD are two small clones associated with a high risk of progression in smoldering MM (SMM) and post treatment relapse in active MM. Despite growing knowledge about their clinical significance and biological features, these questions remain unanswered: 1) What is the prognostic value of CTC and MRD kinetics? 2) Is MM dissemination and on-treatment resistance driven by specific genomic alterations? 3) Are CTCs and MRD genetically related? AIM Analyze the kinetics and molecular features of CTCs and MRD in SMM and MM patients. METHODS CTC kinetics were investigated using NGF in 164 SMM patients with ≥3 assessments collected every 6 months in the iMMunocell study. MRD kinetics were investigated using NGF in 277 MM patients with ≥4 assessments in BM aspirates after induction, transplant, consolidation, and yearly during maintenance (GEM2012MENOS65-GEM2014MAIN trials). Unsupervised clustering based on CTC and MRD kinetics was performed using CONNECTOR. Molecular features of BM tumor cells at diagnosis were compared to paired CTCs in 94 SMM and MM patients and to paired MRD in 96 MM patients. In 10 cases, genomic data from tripartite BM tumor cells, CTCs, and MRD was available. Tumor samples were isolated based on patient-specific aberrant phenotypes using FACS. Whole exome and RNA-seq were performed in 343 and 217 samples, respectively. RESULTS Based on the assessment of CTCs in 754 PB samples, SMM patients clustered into 3 groups: sustained undetectable (n = 20), stable (n = 71) and evolving (n = 73) CTC levels. With a median follow-up of 2 years, the respective 2y progression-free rates were 100%, 94% and 81% ( P =.003). Risk stratification based on CTC kinetics (C-index 0.68) outperformed a single baseline assessment (C-index 0.61) and, along with the IMWG 20/2/20 model, had independent prognostic value (HR 3.4; P = .01). Patients with high risk cytogenetics showed more frequently evolving CTC levels. Studying genetic drivers of tumor egress, we found CTCs to closely resemble BM tumor cells (88% concordance at copy number [CNA] and somatic mutational [SNV] level). No recurrent cell-specific SNV or CNA was identified. CTC's transcriptional profile revealed 268 DEGs enriched in interferon alpha, gamma response and cell-adhesion pathways. Next, the prognostic value of MRD dynamics was analyzed according to 1,759 assessments, identifying 3 patient clusters: sustained undetectable (n = 100), stable (n = 104), and evolving (n = 73) MRD levels. Respective 6-year rates of PFS after consolidation were 90%, 75% and 5% ( P &amp;lt;.001), and of OS were 94%, 95% and 66% ( P&amp;lt;.001). Risk stratification based on MRD kinetics (C-index 0.82) outperformed a single MRD assessment before maintenance (C-index 0.62), the R-ISS (C-index 0.57) and R2-ISS (C-index 0.61) at diagnosis. MRD cells showed heterogeneous genomic evolution (60% median concordance) diverging from BM tumor cells at diagnosis due to de novo CNA and SNV that emerged at a subclonal level, particularly after transplant. After induction, MM driver mutations were detected or remained clonal in 13/19 (68%) MRD, whereas after transplant, this was true for only 5/13 (38%) MRD. No recurrent cell-specific SNV or CNA was identified. The transcriptional signature of MRD was treatment dependent, with common molecular features of on-treatment resistance found in all 96 patient-paired samples analyzed after various treatment stages. The 334 DEGs were commonly enriched in KRAS signaling hallmarks. Genomic profiles of tripartite BM tumor cells, CTCs and MRD from 10 MM patients confirmed a patient-specific mutational landscape with genomic heterogeneity in MRD. For instance, one patient exhibited BRAF &amp; DIS3 mutations and del(13q) detected at baseline in BM tumor cells and CTCs, which persisted in MRD. After induction, de novo clonal SNVs, including a NEK11 mutation, emerged, followed by the appearance of 3 subclonal CNA after transplant, possibly contributing to resistance. CONCLUSIONS This is the largest dataset analyzing the kinetics and molecular features of CTCs and MRD in SMM and active MM. We showed superior prognostic value of CTC and MRD kinetics over single assessments. Tumor dissemination seems to be driven by transcriptional priming rather than acquired secondary genetic events, while on-treatment resistance is linked to genomic and transcriptional evolution, without recurrent genetic alterations and with common molecular signatures of resistance.

Reshaping MRD Detection Strategies: Next-Generation Sequencing and High DNA Input Identify Previously Missed Measurable Residual Disease in Peripheral Blood of B-Cell Precursor Acute Lmyphoblastic Leukemia

Background: In acute lymphoblastic leukemia (ALL), measurable residual disease (MRD) is the most important prognostic factor. MRD is traditionally quantified in bone marrow aspirates (BM) using real-time quantitative polymerase chain reaction (RQ-PCR) according to EuroMRD standards. Since the emergence of modern molecular methods, it has been a continuous effort to enable MRD assessment from peripheral blood (PB). The less invasive material collection would allow closer MRD monitoring and solve technical challenges of BM aspiration, such as skewed or non-representative MRD values due to hemodilution and unequal distribution of leukemic cells. While several studies demonstrated comparable MRD values of BM and PB in T-ALL, in B-cell precursor ALL (BCP-ALL) MRD determination from PB is still a challenge. Mean MRD levels in PB are considerably lower than in BM and frequently escape detection. Additionally, paired samples show a highly variable MRD level ratio in both pediatric and adult cases (Kotrova et al, Leukemia 2020). Objective: BCP-ALL cases with known MRD positivity in the BM likely also harbor MRD positive cells in the PB, even when missed by traditional methods. With more sensitive assays, either by increased DNA input or by application of amplicon-based next generation sequencing (NGS), MRD detection from PB may improve in these cases. Methods: We retrospectively selected PB - BM sample pairs of 74 BCP-ALL patients with BM MRD positivity (43 with quantifiable MRD positivity and 31 with positivity below quantitative range) and sufficient leftover DNA from a cohort of patients treated according to GMALL protocols, where conventional RQ-PCR of clonal immunoglobuline heavy chain (IGH) VJ/DJ gene rearrangements failed to detect PB MRD. MRD had been determined by standard RQ-PCR with 1.5 µg DNA in BM and PB, respectively, according to the EuroMRD guidelines (van der Velden et al, Leukemia 2007). PB samples were re-tested for MRD with high DNA input RQ-PCR using 6.6 µg DNA and amplicon-based NGS, each using 6.6 µg DNA, as well as standard input NGS. NGS analyses of corresponding PB and BM samples were performed with the EuroClonality amplicon-based NGS assay (Brüggemann et al, Leukemia 2019). Identification and quantification of leukemia-derived clonotypes was done using ARResT/Interrogate. Results: In total, 74 BCP-ALL patients with pre/c-B-ALL (n=60) and pro-B-ALL (n=14) were included. Patient age ranged from 19 - 71 years with a median of 44.5. In all included samples (56 in first-line therapy and 18 salvage treatment), BM was MRD positive and PB was MRD negative in standard RQ-PCR at a sensitivity of at least 10 -4. To assess the effect of high DNA input alone, RQ-PCR was repeated in PB with high DNA input for 59 patients and 63 IGH VJ/DJ markers. At least one positive signal was detected in 19/59 patients (32%) and 20/63 markers (32%) (FIGURE 1A). NGS was performed for 73 PB samples and 84 markers using standard and high DNA input. With standard DNA input, MRD could be detected for 19/73 patients (26%) and 21/84 markers (25%) (FIGURE 1A). In the high input approach, MRD was detected in 36/73 patients (49%) and 40/84 markers (48%) (FIGURE 1A). A quantifiable MRD value was identified in 17 patients and 19 markers. All markers with quantifiable NGS MRD positivity in PB showed higher MRD values in the corresponding BM sample and MRD values below 10 -4 (FIGURE 1B). No correlation of MRD in paired samples could be demonstrated (Pearson correlation coefficient: 0.09) (FIGURE 1B). Conclusion: In BCP-ALL, MRD detection from PB is challenging with conventional methods. Increased DNA input and amplicon-based NGS allowed detection of MRD in a subset of PB samples that were negative in standard RQ-PCR. With identical DNA input, NGS showed a higher sensitivity than RQ-PCR and best results were achieved when high DNA input and NGS were combined, identifying MRD in nearly half of the PB samples. These results demonstrate that PB can be a valuable tool for early MRD detection in BCP-ALL when adjusting traditional MRD assessment strategies. However, in half of the samples, MRD was still missed by high input NGS. Even with assays improved for sensitivity, PB therefore cannot fully replace BM for MRD assessment in BCP-ALL yet and should rather be considered to complement BM analyses or in cases where BM is not accessible.

Role of Allogeneic Stem Cell Transplantation in Preventing Relapse in Adult BCR::ABL1-like Acute Lymphoblastic Leukemia

Background Philadelphia-like acute lymphoblastic leukemia (Ph-like ALL) is characterized by the activation of several kinase pathways that promote treatment resistance leading to poor survival of patients at all ages. Despite the use of tyrosine kinase inhibitors in the Ph-like ABL-class subtype (15% Ph-like ALL), there is not a consensus approach for treatment of most patients (JAK-class especially), and the role of allogeneic stem cell transplantation (alloSCT) has scarcely been explored so far (i.e., mandatory vs. MRD-oriented). Objective To assess the outcome of Ph-like patients enrolled in the ongoing ALL19 trial from the Programa Español de Tratamientos en Hematología (PETHEMA) for adults (18-60y) with Ph-negative ALL, and to evaluate the effectiveness of alloSCT in first complete remission (CR). Methods In the ALL19 trial, patients are allocated to alloSCT according both to the end of induction (EOI) measurable residual disease (MRD) level and to high-risk genetic markers such as low-hypodiploidy, KMT2A rearrangement, TP53 biallelic alteration and concomitant deletion of IKZF1 and CDKN2A/B. Therefore, BCR::ABL1-like subtype was not a criteria for early transplantation unless meeting either poor MRD clearance at EOI or concomitant deletion of IKZF1+CDKN2A/B. Patients with MRD≥0.01% on day+35 (EOI) and/or high-risk genetics were assigned to early alloSCT (preceded by 1 cycle of consolidation chemotherapy) while those with good MRD clearance and standard risk genetics received early and delayed consolidation (3 cycles each) and maintenance therapy. Bone marrow or peripheral blood samples were analyzed by G-banding+FISH, SNP array (750K Affymetrix, Thermo Fisher) and next generation sequencing (NGS, with a custom DNA gene panel, Illumina) at diagnosis in 4 reference laboratories. MRD was centrally assessed by next generation flow cytometry with a sensitivity up to 2x10 -6. Results Twenty-four Ph-like out of 248 adult BCP ALL (10%) were detected. Baseline characteristics were similar between Ph-like and the remaining BCP-ALL. Most Ph-like ALL patients showed the JAK-class profile (20/24 [83%]: 17/24 CRLF2 rearrangement[r], 1/24 JAK2r, 1 BLNK::DNTT and 1 JAK2 R683 mutation), 3/24 belonged to the ABL-class subtype (2 ABL2r, 1 NUP214::ABL1) and 1 patient was identified by RNAseq (gene expression profiling similar to BCR::ABL1 ALL) without identifying any rearrangement. Regarding secondary genetic alterations, 17/24 (71%) patients showed the IKZF1 plus profile, 10/23 (43%) harbored JAK2 R683 mutation, 4/23 N/KRAS mutations, 2/23 CRLF2 mutation and 1/23 showed mutations in several genes such as IKZF1, NR3C1 or FLT3, among others. There were no significant differences in the probability of achieving CR between Ph-like and the remaining BCP ALL (15/20 [75%] vs. 137/162 [85%], p=0.334). However, EOI MRD level of Ph-like individuals was significantly poorer (MRD&amp;lt;0.01% Ph-like 4/15 [27%] vs. other BCP-ALL 85/136 [63%], p=0.007). By intention to treat, most Ph-like patients (17/19, 89%) were allocated to alloSCT (vs. 91/153 [59%] in the other BCP-ALL, p=0.011) due to either EOI MRD≥0.01% (9/18), IKZF1+CDKN2A/B concomitant deletions (3/18) or both (6/18). The 2-y overall survival (OS) in both groups was not significantly different (57% [95% CI, 27%-78%] vs. 67% [55%-77%, p=0.304]) (Figure 1). Interestingly, most Ph-like patients died due to treatment-related toxicity (2 transplant-related mortality, 1 CART-related, 1 during induction, 1 in CR and 1 by COVID-19 infection). The 2-y cumulative incidence of relapse (CIR) was also similar (Ph-like 27% [8%-50%] vs. other BCP-ALL 35% [25%-45%], p=0.946) (Figure 1). Conclusions Despite the short follow up of this series, our results show that Ph-like ALL patients have poorer EOI MRD clearance and higher rate of alloSCT realization than the remaining BCP ALL patients, without significant differences in outcome. This suggests that early alloSCT in first CR might overcome the poor prognosis of Ph-like ALL patients. Funding Funded in part by: PI10/01417 y FIS PI19/01183 Ministerio de Salud Carlos III, JCyL_SA118P20, FMM21/002_AP176752021, “La Caixa” Foundation, Pfizer Spain, Fundación PETHEMA. This project has received funding from the Innovative Medicines Initiative 2 Joint Undertaking (JU) under grant agreement No IMI001-07. The JU receives support from the European Union's Horizon 2020 research and innovation programme and EFPIA.

Venetoclax and Azacitidine for Molecular Relapse during First Line Intensive Chemotherapy in Patients with NPM1 Mutated or Core Binding Factor (CBF) AML. a Study from the Dataml Registry

Introduction: Molecular follow-up (FU) for AML patients (pts) with NPM1 mutation, RUNX1::RUNX1T1 or CBFB::MYH11 fusion transcripts has been established over the last ten years. Real-time quantitative PCR (qPCR) is the gold standard for the evaluation of measurable residual disease (MRD) in pts undergoing intensive chemotherapy (IC). Failure to achieve a deep molecular response is a strong predictive factor of relapse and survival and may guide post remission therapy (Ivey A, NEJM 2016). Moreover, the ELN MRD working party recommended a schedule for molecular FU and recently established a definition of molecular relapse (Heuser M, Blood 2021). However, there is no therapeutic consensus for pts with molecular relapse before overt clinical relapse. Frontline allogeneic hematopoietic cell transplantation (alloHCT), salvage IC or even waiting for morphological relapse in order to screen molecular characteristics of the relapsing disease or propose a clinical trial, may be discussed with pts. Venetoclax with azacitidine (VEN/AZA) was recently approved in unfit AML pts and demonstrated a particular efficacy in NPM1-mutated AML. In this study, we thought to describe the safety and efficacy of VEN/AZA in pts with NPM1 mutated or CBF AML in molecular relapse after first line IC. Methods: Pts of the DATAML registry with the following criteria were included in this study : AML with NPM1 mutation, RUNX1::RUNX1T1 or CBFB::MYH11 transcripts, first line IC, morphological complete remission (CR), no alloHCT in first line, regular monitoring of MRD by qPCR in bone marrow (BM) and/or blood, molecular relapse defined according to ELN2021 guidelines on two successive samples, at least one cycle of VEN/AZA. Pts with molecular relapse followed by morphological relapse before VEN/AZA or those who relapsed after alloHCT were not included. Treatment: First line IC was cytarabine 200 mg/m² d1-7 with idarubicin 9mg/m²/d1-5 or daunorubicin 90mg/m²/d1-3 in pts 18-60y or cytarabine 100 mg/m² d1-7 with idarubicin 8mg/m²/d1-5 and lomustine 200 mg/m²/d1 in pts &amp;gt; 60y. Post remission therapy was intermediate or high dose cytarabine or mini-consolidations according to age and performance status. Midostaurin was added in FLT3-mutated pts. At time of molecular relapse, pts received off label venetoclax 400 mg/d (d1-14, d1-21 or d1-28 according to centers) with no ramp-up and azacitidine 75 mg/m²/d subcutaneously (d1-5, d8-9). Antifungal/antibiotic prophylaxis and G-CSF use were not systematically recommended. Results: Twenty-two pts treated with VEN/AZAfrom 21/09/2020 to30/03/2023 were included. Their characteristics at diagnosis were: female (n= 14), median age 55y (range 27-71), de novo AML (n=21), median WBC (68 giga/L, range 2.32-339.7), NPM1 mutation (n=20), CBFB::MYH11 (n=2), FLT3 mutation (n=13). All pts achieved first CR after one cycle of induction chemotherapy. Pts received a median of three consolidation cycles. All but three pts had negative MRD or low level MRD (LL-MRD) in blood and/or BM at the end of consolidation. The median time between CR1 and molecular relapse was 9.5 months (range, 1-50). The median time between molecular relapse and first VEN/AZA cycle was 51 days. During first cycle of VEN/AZA, 12, 5 and 5 pts received 14, 21 or 28 days venetoclax, respectively; 19 were treated as out-pts, 4 received posaconazole and GCSF was used in 11 pts. 12 and 3 pts had grade 3-4 neutropenia or febrile neutropenia (FN), respectively. Only 3 pts (14%) were hospitalized for FN. The median number of VEN/AZA cycles was 2 (range 1-12). After C1+/-C2, 10 (45%) and 11 pts (55%) had undetectable or LL MRD in blood, respectively (Fig1). 20 pts were bridged to alloHCT in morphological CR after a median of 2 cycles (range, 1-4). Only one pt had a molecular progression before transplantation after 2 cycles. Two pts died, one had a molecular relapse after 7 cycles and progress rapidly to frank relapse, the other one died of post-transplant complication while in CR with undetectable MRD. All other pts remained in CR at date of last news. With a median FU from D1C1 of 13.5 months, median OS wat not reached and 1y-OS was 86% (Fig2). Conclusion: In the setting of molecular relapse, VEN/AZA is safe, prevent overt relapse, and induce a high rate of molecular response before alloHCT. Molecular relapse becomes a major therapeutic challenge. Clinical trial endpoints should include the treatment of molecular relapse as an event for RFS and EFS estimation.

Minimal Residual Disease Detection By Single Cell DNA Sequencing Technology: A Feasible Approach for Clinical Application and Identification of the Landscape of MRD Clones

Introduction:Despite recent advances in AML treatment, patients continue to relapse and become chemotherapy resistant, leading to poor long-term overall survival. The identification of this measurable residual disease (MRD), defined as the post-therapy presence of leukemic cells, currently stands as one of the most well-established risk factors. The abnormal phenotypic and molecular characteristics of AML cells offer an opportunity for disease monitoring using techniques like multiparameter flow cytometry (MFC) and qPCR, which are currently considered the gold standard for MRD detection. However, these techniques have limitations. The aim of this study was to validate a different approach using single-cell DNA sequencing (scDNAseq) technology to detect MRD in patients achieving complete response (CR) and to characterize the genomic landscape of MRD clones and the potential identification of clonal evolution. Methods:We selected 24 cryopreserved bone marrow samples from 15 AML patients who participated in the QUIWI-PETHEMA clinical trial (NCT04107727) and achieved CR after induction and consolidation (n=20). 4 diagnosis samples were analyzed to determine genomic differences between the MRD clone and the initial leukemic population. All patients had bulk targeted NGS data available at diagnosis. Selection of CD34+ and/or CD117+ cells was performed using magnetic beads for enrichment of blasts and Mission Bio multiome single cell DNA+protein was performed using an AML-related 469 amplicon panel and 19 surface antibody mix. Multiplex of 3 independent samples was performed in each library preparation. Analysis was done according to manufacturer's instructions. MRD was also analyzed using MFC (n=14) EuroFlow panel with a limit of detection of 0.1% aberrant cells. RNA qRT-PCR was used in cases with NPM1 mutations (n=6). Quantification of MRD by scDNAseq was calculated according to the enrichment performance obtained from the manufacturer and the percentage of mutant cells. Results: The concordance between gold standard techniques for MRD and scDNAseq was 75% (15/20) (Table 1). Concordance between MFC and scDNAseq was 78% (11/14). The 3 discordant cases, positives by scDNAseq, MRD levels ranged between 0.04-0.09%, below the consensus cutoff of 0.1% to define MRD+. These results suggest that scDNAseq may complement MFC in the detection of very low levels of MRD. Concordance with qRT-PCR was 66% (4/6), but we only detected one patient with a persistent NPM1 clone. Taking advantage of the single cell approach, we were able to assess the genomic landscape of MRD clones and the clonal evolution in sequential samples. The number of clones/subclones and the number of variants per clone varied between patients with positive MRD as shown in Table 1. Interestingly, we analyzed 4 samples at diagnosis by scDNAseq and observed 2 cases in which MRD mutation was already present at diagnosis but was not informed as VAF was &amp;lt; 1%. In 4 patients, we detected small clones (around 1%) that remained unchanged in size despite treatment, suggesting that they likely represent clonal hematopoiesis. In 6 cases, consecutive samples were obtained showing clearance of some clones with other ones remaining stable (UPN2), progressive clearance of clones (UPN3, UPN4), acquisition of new clones (UPN9) and clearance of some clones and acquisition of new ones (UPN15) (Figure 1). Integration of scDNA and cell surface protein expression in the same cell allowed us to perform mutation-clone specific immunophenotypic analysis. Some cases showed a clear pattern in which one of the mutant clones had a significantly higher expression of some markers that was correlated with previous flow cytometry data (e.g. UPN1). Conclusions: Our study suggests that the use of scDNA technology is a feasible approach for detection of MRD in AML patients. Moreover, the use of this approach in sequential samples may allow deciphering clonal evolution, the co-occurrence of different mutations including potential clonal hematopoiesis mutations and identifying winner clones potentially responsible for disease persistence and relapse. Finally, the integration of mutations and surface antibody markers in the same cell provides a means for identifying the presence of mutations in different cell populations. Validation of these results in larger series of patients and correlation with clinical outcome are the next steps for validation of this technology.

Pivekimab Sunirine (PVEK, IMGN632), a CD123-Targeting Antibody-Drug Conjugate, in Combination with Azacitidine and Venetoclax in Patients with Newly Diagnosed Acute Myeloid Leukemia

Background In unfit patients (pts) with newly diagnosed (ND) AML, long-term survival remains short (mOS 14.7 months) despite improved responses (CR 37% and CR/CRi 66%) with azacitidine (AZA) and venetoclax (VEN) (VIALE-A, DiNardo NEJM 2020). In a pooled analysis of AZA-VEN in ND AML pts with poor risk cytogenetics the response rates were higher in TP53wt pts (CR/CRi 70%) compared with TP53mut pts (CR/CRi 41%) (Pollyea Clin Cancer Res 2022). The measurable residual disease (MRD)-negative rate was 41% in AZA-VEN treated pts in VIALE-A which was associated with improved survival (Pratz JCO 2022). Pivekimab sunirine (PVEK, IMGN632) is a first-in-class antibody-drug conjugate (ADC) comprising a high-affinity CD123 antibody, cleavable linker, and an indolinobenzodiazepine pseudodimer (IGN) payload. The novel IGN payload alkylates DNA and causes single strand breaks without crosslinking (Kovtun Blood Adv 2018). Methods This is an ongoing, open-label, multicenter, Phase 1b/2 study of PVEK in combination with AZA +VEN in adults with ND CD123-positive AML (any CD123+ expression by local flow cytometry or IHC). Pts received the recommended phase 2 dose of PVEK 0.045 mg/kg IV on D7 + AZA 75 mg/m 2 SC or IV daily on D1-7 + VEN up to 400 mg PO daily for 14 to 28 days (based on cohort assignment) in a 28-day cycle. Bone marrow assessment was performed at D14 (cohort 1) or D21 (cohort 2) of cycle 1 to determine VEN duration. The primary endpoints are composite CR rate (CCR [CR+CRh+CRp+CRi]), MRD rate (assessed centrally [Hematologics, Inc.] by flow cytometry; &amp;lt;0.1% defined as negative) and duration of remission. Key secondary endpoints are safety, pharmacokinetics and immunogenicity. Responses were determined using ELN 2017 criteria (with the addition of CRh) and a 14-day post-marrow count recovery window. Results As of July 17, 2023, data is available for 50 ND pts (n=25 per cohort) treated with PVEK+AZA+VEN and are aggregately reported here. The median age was 74 years (range, 46-83), 42% were ≥ 75 years old, 26% had secondary AML, 64% were ELN 2017 adverse risk, and 38% had a TP53mut. The most common non-hematologic treatment-emergent adverse events (TEAE) (all grades [grade 3+]) seen in &amp;gt; 20% of all pts were febrile neutropenia (44% [38%]), constipation (42% [2%]), peripheral edema (36% [4%]), diarrhea (36% [2%]), hypophosphatemia (32% [0%], nausea (28% [4%]), and hypokalemia (24% [2%]). No veno-occlusive disease (VOD) events were reported. In responders, the median time to achieve absolute neutrophil count ≥500/µL and platelet count ≥50,000/µL was 35.5 days (range, 20-55) and 22 days (range, 20-55), respectively. The median post-remission cycle delay (beyond cycle day 28) was 14 days. Two pts discontinued PVEK due to a TEAE (edema; marrow aplasia). The 60-day mortality was 4%. In the ITT population (N=50) the CR rate was 52% (26/50), and the CCR rate was 66% (33/50). In pts ≥ 75 years old, the CCR rate was 76% (16/21). In pts known to be TP53wt, both the CR and CCR rate was 88% (22/25). Additional response subsets in Table 1. Twenty-one pts received 9-14 days of VEN, 9 pts received 15-21 days of VEN and 20 pts received ≥ 22 days of VEN in cycle 1; of those who received ≤ 14 days of VEN the CR rate was 71% (15/21) and the CCR rate was 76% (16/21). Of the 26 pts who achieved CCR and had an MRD-evaluable sample, 73% (19/26) achieved MRD negativity (CCR MRD-, &amp;lt;0.1% residual blasts); notably all had undetectable MRD levels (lower level of detection is 0.02%). MRD-negativity was achieved rapidly with a median of 1.7 months (range, 0.8-4.5). CCR MRD- rates were high across major molecular subsets, including FLT3 (ITD/TKD) at 100% (7/7), IDH1/2 at 89% (8/9), and NPM1 at 89% (8/9), as well as ELN risk groups (intermediate 80% [8/10]; adverse 64% [9/14]). Conclusion With a manageable safety profile in pts with ND AML, the PVEK+AZA+VEN triplet demonstrated anti-leukemia activity with robust CR rates and early MRD negative responses in a cohort enriched for adverse disease characteristics (64% ELN adverse risk; 38% TP53mut). Encouraging CCR MRD- rates were observed across cytogenetic/molecular subsets, and the majority of responding pts achieved early and deep remissions, which may translate to improved clinical outcomes. The regimen was well tolerated with no new safety signals, and the addition of PVEK to the AZA-VEN backbone did not appear to meaningfully prolong count recovery.

Post-Hoc Analysis of Measurable Residual Disease from BMT-CTN 1506/Morpho: FLT3-ITD Variant Allele Frequency and Survival Are Highly Correlated

Background: BMT CTN 1506/MORPHO was a randomized study of the FLT3 inhibitor gilteritinib versus placebo as post-transplant (HCT) maintenance therapy for patients (pts) with FLT3-ITD acute myeloid leukemia (AML). Patients with FLT3-ITD AML in first remission underwent HCT and then were randomized, in double-blind fashion, to either gilteritinib or placebo for 24 months. The primary endpoint was relapse-free survival (RFS), and a pre-specified secondary endpoint was the effect of measurable residual disease (MRD) on survival as detected by a highly sensitive assay for FLT3-ITD mutations. In the primary analysis, while RFS was higher for pts randomized to gilteritinib, the difference did not reach the pre-determined threshold for significance (HR: 0.679; 95% CI: 0.459, 1.005; 2-sided p-value: 0.0518). However, in the secondary analysis, the 50.6% of pts who had MRD detectable pre- or post-HCT had significantly higher RFS with gilteritinib (HR of relapse or death=0.515, 95% CI: 0.316, 0.838, p = 0.0065). In this post-hoc analysis, we examined 1) the impact on RFS of different levels of FLT3-ITD variant allele frequency (VAF) pre-randomization (immediately before or after HCT but prior to randomization to gilteritinib or placebo); 2) the impact of the presence of multiple mutations detected as MRD pre-HCT; and 3) the eradication of FLT3-ITD clones detected post-HCT during follow up on gilteritinib or placebo. Methods: First-pull marrow aspirates were collected from pts at two time points pre-randomization (pre-HCT and between 30-90 days post-HCT), as well as at 3, 6, 12, 18, and 24 months post-randomization. For MRD detection (performed at Invivoscribe; San Diego, CA), 700 ng input DNA was amplified by polymerase chain-reaction (PCR) using 25 cycles and primers flanking exons 14 and 15 of FLT3, followed by next-generation sequencing (NGS) analysis of the amplicons. Variant allele frequency (VAF) was calculated as FLT3 mutant reads/total FLT3 reads. For pts with multiple FLT3-ITD mutations, the VAF used in analysis was the sum of the VAFs for each FLT3-ITD variant. The lower limit of blank (LOB) of the assay is estimated to be 1 x 10 -6 VAF. For terminology, VAF &amp;gt; 1 x 10 -6 and &amp;lt; 1 x 10 -5 is referred to as MRD6, VAF &amp;gt; 1 x 10 -5 and &amp;lt; 1 x 10 -4 is MRD5, VAF &amp;gt; 1 x 10 -4 or greater is MRD4, and MRD0 equals no detectable MRD. Results: MRD was evaluated in 350/356 (98.3%) pts pre-HCT and 347/356 (97.5%) pts post-HCT. MRD was detected in 46% of pts pre-HCT and 19.9% prior to randomization, including 4.5% who did not have detectable MRD pre-HCT. The variant allele frequency (VAF) of detectable MRD ranged from a low of 1.09 x 10 -6 to a high of 3.0 x 10 -1. More than a single mutation was detected in 51 pts pre-HCT. Most of these 51 pts had 2 clones, but the total ranged from 2-9. The presence of more than one mutation detected as MRD immediately pre-HCT was associated with worse RFS compared with all other pts (MRD-positive with only one clone and MRD-negative), irrespective of treatment arm (Figure 1A; HR=2.428, 95% CI: 1.555, 3.792, P &amp;lt; 0.001). There was no significant difference in age, mutation length, VAF, or karyotype between pts with more than one mutation and those with single mutations. However, if the VAFs of pts with multiple FLT3-ITD mutations were summed and treated as a single value, then the median VAF for pts with multiple mutations was higher than for those with single mutations (2.14 x 10 -4 vs. 3.12 x 10 -5). The VAF (including the summed VAFs of pts with multiple mutations) at multiple levels correlated very closely with RFS after HCT. To illustrate this quantitative effect of peri-HCT FLT3-ITD VAF on RFS, Kaplan-Meier analysis of pts on the placebo arm grouped by MRD level is displayed in Figure 1B. In the 71 pts with MRD detectable post-HCT, the MRD was eradicated in 69% of pts on gilteritinib versus 44% of pts on placebo. Conclusions Pts with multiple FLT3-ITD mutations have a worse prognosis, which may simply be a reflection of increased disease burden (VAF). The quantity of FLT3-ITD MRD appears to highly correlate with outcome. Gilteritinib appears to augment the effect of HCT, as evidenced by increased eradication of MRD post-HCT. These data illustrate the potential utility of the PCR-NGS FLT3-ITD MRD assay in the management of pts with FLT3-ITD AML.

Chemotherapy-Sparing Induction Followed By Consolidation and Maintenance with Blinatumomab and Concurrent Oral Tyrosine Kinase Inhibitor Therapy for Newly-Diagnosed Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia: Primary Endpoint Results from the Blissphall Study

Background: Oral ABL-targeted kinase inhibitors (TKIs) have transformed treatment of BCR::ABL+ (Philadelphia chromosome-positive, Ph+) acute lymphoblastic leukemia (ALL). Induction (IND) w/ corticosteroids (CS) and dasatinib (DAS) alone results in morphologic complete response (mCR) rates approaching 100% but low rates of measurable residual disease (MRD) negativity; addition of intensive chemotherapy to TKIs adds risks of myelosuppression. DAS + the CD3/CD19 bispecific T-cell engager blinatumomab (BLIN) is effective consolidation (CONSOL) for Ph+ ALL, though ABL kinase mutations conferring resistance can arise early in therapy (Foà, NEJM, 2020). We designed a phase II study of BLIN as part of a chemotherapy sparing strategy in pts w/ Ph+ ALL (BLISSPHALL), introducing BLIN as early as 6 weeks into treatment for pts in mCR, w/ aim of expediting MRD clearance and suppressing resistant clones early in disease course, and including a maintenance (MAINT) phase of BLIN + TKI for pts in molecular response. Methods: We conducted a multicenter trial of TKI + CS IND and TKI + BLIN CONSOL + MAINT in adults (≥18 yrs) w/ newly-diagnosed (ND) Ph+ ALL (NCT04329325). Study schema is depicted in Figure 1. Pts received CS pre-phase w/ prednisone (PRED) or dexamethasone (DEX) followed by modified GIMEMA LAL1205 IND (DEX + DAS 140 mg/d w/ DAS dose adjustments or TKI change per protocol) w/ intrathecal methotrexate (IT MTX) d22, 43 and bone marrow (BM) MRD assessments including FACS and BCR::ABL1 PCR. Pts in mCR on d43 could proceed to CONSOL w/ 3 cycles (C) of TKI + BLIN 28 mcg/d IVCI, d1-28, w/ 14d off BLIN between cycles and BM MRD assessment/IT MTX after each cycle. TKI was given continuously including between BLIN cycles. Pts in protocol-defined complete molecular response (CMR; MRD negative by FACS and no detectable BCR::ABL1 transcripts) after CONSOL could proceed to MAINT (C4-7 BLIN + TKI, 28d off between cycles). The primary objective is to determine the proportion of evaluable pts achieving CMR by the end of CONSOL (≤ 3C BLIN + TKI). Secondary objectives include safety/toxicity of BLIN + DAS, duration of CMR, incidence of relapse, event-free/overall survival. Toxicities were defined by CTCAE v5.0. Results: 17 pts enrolled (12 women, 5 men) w/ median age 50 yrs (range 22-87); BCR::ABL1 transcript type p190 (n=15) or p210 (n=2). Median follow-up 11.7 months (range 3-24). All began DAS 140 mg/d as initial TKI; 4 changed TKI for DAS intolerance per protocol (bosutinib, n=2; ponatinib [PON], n=2) and remained on study; TKI was changed to PON in 1 other pt to optimize BCR::ABL1 transcript suppression pre-allogeneic transplant (alloHCT) and that pt was withdrawn from study. Two had interruption or delay of BLIN due to toxicity (grade [G] 3 transaminase elevation, n=1; G2 cytokine release syndrome, n=1); BLIN was resumed in both. Figure 2 lists nonhematologic adverse effects (AEs) seen in ≥2 pts at least possibly related to TKI or BLIN while on study. One pt developed G3 pancreatitis after DAS was changed to PON; TKI was changed back to DAS. There were no G4-5 AEs. All pts (100%) achieved mCR during IND (median d22). Ten achieved CMR to date (5 during IND, 5 during CONSOL) and 6 did not achieve CMR; determination pending in 1 pt. By FACS, 16/17 achieved BM MRD negativity; 13/14 evaluable pts had no evidence of malignant clonal IgH rearrangement (IgHR) by next generation sequencing (NGS). Notably, 3 pts w/ persistent low-level BCR::ABL1 transcripts had no evidence of malignant clonal IgHR by NGS but were withdrawn post-CONSOL as protocol required BCR::ABL1 PCR negativity to proceed to MAINT. Two pts relapsed, both after achieving CMR (one declined CONSOL and self-discontinued TKI; one had extramedullary (EM) relapse w/ ABL T315I mutation). Four pts underwent alloHCT in CR1 (rising MRD levels on study leading to change in therapy, n=1; persistent BCR::ABL1 PCR positivity, n=2; IKZF1 plus phenotype, n=1); one underwent alloHCT in CR2 following EM relapse. Conclusions: DAS + CS IND w/ addition of BLIN to TKI in mCR leads to high rates of deep molecular response w/ low risk of early relapse and low rates of severe regimen-related toxicity in pts w/ ND Ph+ ALL. Use of PON (vs DAS) as initial TKI w/ BLIN may further suppress resistant clones. Further f/u is needed to confirm durability of CMR w/ BLIN + TKI CONSOL ± MAINT in absence of alloHCT and whether pts w/ persistent BCR::ABL1 PCR positivity and no malignant clonal IgHR by NGS exhibit similar outcomes to those in CMR.

Genomic breakpoint-specific monitoring of measurable residual disease in pediatric non-standard-risk acute myeloid leukemia.

Pediatric acute myeloid leukemia (AML) is a highly heterogeneous disease making standardized measurable residual disease (MRD) assessment challenging. Currently, patient-specific DNA-based assays are only rarely applied for MRD assessment in pediatric AML. We tested whether quantification of genomic breakpoint-specific sequences via quantitative polymerase chain reaction (gDNA-PCR) provides a reliable means of MRD quantification in children with non-standardrisk AML and compared its results to those obtained with state-of-the-art ten-color flow cytometry (FCM). Breakpointspecific gDNA-PCR assays were established according to Euro-MRD consortium guidelines. FCM-MRD assessment was performed according to the European Leukemia Network guidelines with adaptations for pediatric AML. Of 77 consecutively recruited non-standard-risk pediatric AML cases, 49 (64%) carried a chromosomal translocation potentially suitable for MRD quantification. Genomic breakpoint analysis returned a specific DNA sequence in 100% (41/41) of the cases submitted for investigation. MRD levels were evaluated using gDNA-PCR in 243 follow-up samples from 36 patients, achieving a quantitative range of at least 10-4 in 231/243 (95%) of samples. Comparing gDNA-PCR with FCM-MRD data for 183 bone marrow follow-up samples at various therapy timepoints showed a high concordance of 90.2%, considering a cut-off of ≥0.1%. Both methodologies outperformed morphological assessment. We conclude that MRD monitoring by gDNA-PCR is feasible in pediatric AML with traceable genetic rearrangements and correlates well with FCM-MRD in the currently applied clinically relevant range, while being more sensitive below that. The methodology should be evaluated in larger cohorts to pave the way for clinical application.

Clinical and prognostic profile of SRSF2 and related spliceosome mutations in patients with acute myeloid leukemia.

Mutations in splicing factor (SF) genes are frequently detected in myelodysplastic syndrome, but their clinical and prognostic relevance in acute myeloid leukemia (AML) have rarely been reported. A total of 368 newly diagnosed non-M3 AML patients were included in this study. Next generation sequencing including four SF genes was performed on the genomicDNA. The clinical features and survival were analyzed using statistical analysis. We found that 64 of 368 patients harbored SF mutations. The SF mutations were much more frequently found in older or male patients. SRSF2 mutations were shown obviously co-existed with IDH2 mutation. The level of measurable residual disease after first chemotherapy was higher in SF-mutated patients compared to that in SF-wild patients, while the complete remission rate was significantly decreased. And the overall survival of SF-mutated patients was shorter than that of SF-wild patients. Moreover, our multivariable analysis suggests that the index of male, Kit mutation or ZRSR2 mutation was the independent risk factor for overall survival. SRSF2mut was associated with older age, higher proportion of peripheral blasts or abnormal cell proportion by flow cytometry. SF mutation is a distinct subgroup of AML frequently associated with clinic-biological features and poor outcome. SRSF2mut could be potential targets for novel treatment in AML.

Role of measurable residual disease quantified by 4 to 6 color flow cytometry before allogeneic hematopoietic stem cell transplantation for high-risk Philadelphia-negative acute lymphoblastic leukemia

Background: Measurable residual disease (MRD) status before allogeneic hematopoietic stem cell transplantation (AHSCT) is commonly associated with a high risk of relapse. It is still uncertain whether AHSCT could overcome the negative impact of MRD positivity (MRD+), especially in patients with high-risk Philadelphia negative acute lymphoblastic leukemia (Ph-negative ALL). Materials and methods: An observational retrospective study was conducted on patients with high-risk Ph-negative ALL who underwent AHSCT between January 2005 and June 2022. The patients selected were in complete remission (CR): with 80% in CR1 (n = 69) and 20% in CR2 (n = 17). Graft sources were bone marrow (BM) in 71% of patients and peripheral blood stem cells in 29% of patients. The conditioning regimen was TBI or chemotherapy-based (CT). Bone marrow MRD level was quantified using 4-6 color multiparametric flow cytometry (MFC). The threshold for MRD positivity was ≥ 0.1%. Results: The study included 86 patients (45 B-ALL and 41 T-ALL) with a median age of 18 years (range, 4–55 years). The median level of MRD pre-AHSCT (pre-MRD) was 0.4×10-3 (range, 0.01-75.6×10-3). After a median follow-up of 25 months (range 1-205 months), the cumulative incidence of relapse (CIR) was significantly higher in the MRD+ group (39% vs. 20%, p = 0.04). The median time of relapse post-AHSCT was 14 months (range, 1-203 months) in the MRD+ group and 32 months (range, 4-209 months) in the MRD- group (p = 0.28). Non-relapse mortality (NRM) was 15% in both groups (p = 0.97). The 2-year estimated overall survival (OS) and event-free survival (EFS) were 61% vs. 74% (p = 0.07) and 58% vs. 70% (p = 0.10) in the MRD+ and MRD- groups, respectively. A subgroup analysis in MRD+ patients showed that a TBI-based conditioning regimen was distinctly associated with lower CIR (22% vs. 60% respectively, p = 0.04), improved OS (82% vs. 36% respectively, p = 0.007) and better EFS (73% vs. 38%, p = 0.04) compared to CT-based. In a multivariate analysis, pre-AHSCT MRD+ status and non-TBI-based conditioning were significantly associated with inferior OS (OR, 2.30; 95% CI, [1.027-5.168], p = 0.04 and OR, 3.91; 95% CI, [1.624-9.418], p = 0.002, respectively). The only predicting factor of lower EFS was the non-TBI-based regimen (OR, 2.82; 95% CI, [1.308-6.097], p = 0.008). Non-TBI-based and CR2 were significantly associated with higher CIR (OR, 6.25; 95% CI, [1.947-20.055], p = 0.002 and OR, 4.74; 95% CI, [1.197-18.791], p = 0.03, respectively). Peripheral stem cell source was significantly associated with higher NRM (OR, 6.55; 95% CI, [1.488-28.820], p = 0.01). Conclusion: High-risk Ph-negative ALL patients with MRD ≥ 10-3 prior AHSCT had lower OS compared to MRD- patients and may benefit from TBI as a conditioning regimen before AHSCT.

Prognostic Value of Measurable Residual Disease in Patients with AML Undergoing HSCT: A Multicenter Study

Allogeneic hematopoietic stem cell transplantation (HSCT) represents the best therapeutic option for many patients with acute myeloid leukemia (AML). However, relapse remains the main cause of mortality after transplantation. The detection of measurable residual disease (MRD) by multiparameter flow cytometry (MFC) in AML, before and after HSCT, has been described as a powerful predictor of outcome. Nevertheless, multicenter and standardized studies are lacking. A retrospective analysis was performed, including 295 AML patients undergoing HSCT in 4 centers that worked according to recommendations from the Euroflow consortium. Among patients in complete remission (CR), MRD levels prior to transplantation significantly influenced outcomes, with overall (OS) and leukemia free survival (LFS) at 2 years of 76.7% and 67.6% for MRD-negative patients, 68.5% and 49.7% for MRD-low patients (MRD < 0.1), and 50.5% and 36.6% for MRD-high patients (MRD ≥ 0.1) (p < 0.001), respectively. MRD level did influence the outcome, irrespective of the conditioning regimen. In our patient cohort, positive MRD on day +100 after transplantation was associated with an extremely poor prognosis, with a cumulative incidence of relapse of 93.3%. In conclusion, our multicenter study confirms the prognostic value of MRD performed in accordance with standardized recommendations.