Ph-like Acute Lymphoblastic Leukemia Research Articles

Comprehensive detection of CRLF2 alterations in acute lymphoblastic leukemia: a rapid and accurate novel approach.

Introduction: Acute lymphoblastic leukemia (ALL) is a prevalent childhood cancer with high cure rate, but poses a significant medical challenge in adults and relapsed patients. Philadelphia-like acute lymphoblastic leukemia (Ph-like ALL) is a high-risk subtype, with approximately half of cases characterized by CRLF2 overexpression and frequent concomitant IKZF1 deletions. Methods: To address the need for efficient, rapid, and cost-effective detection of CRLF2 alterations, we developed a novel RT-qPCR technique combining SYBR Green and highresolution melting analysis on a single plate. Results: The method successfully identified CRLF2 expression, P2RY8::CRLF2 fusions, and CRLF2 and JAK2 variants, achieving a 100% sensitivity and specificity. Application of this method across 61 samples revealed that 24.59% exhibited CRLF2 overexpression, predominantly driven by IGH::CRLF2 (73.33%). High Resolution Melting analysis unveiled concurrent CRLF2 or JAK2 variants in 8.19% of samples, as well as a dynamic nature of CRLF2 alterations during disease progression. Discussion: Overall, this approach provides an accurate identification of CRLF2 alterations, enabling improved diagnostic and facilitating therapeutic decision-making.

Efficacy and safety of chimeric antigen receptor T-cell therapy followed by allogeneic hematopoietic stem cell transplantation in 21 patients with Ph-like acute lymphoblastic leukemia

Objective: To evaluate the efficacy and safety of chimeric antigen receptor T-cell (CAR-T) therapy followed by allogeneic hematopoietic stem cell transplantation (allo-HSCT) in patients with Ph-like acute lymphoblastic leukemia (Ph-ALL) . Methods: Patients with Ph-ALL who underwent CAR-T therapy followed by allo-HSCT from March 2018 to August 2023 at the First Affiliated Hospital of Soochow University were included, and their clinical data were retrospectively analyzed. Results: Of the 21 patients, 14 were male and 7 were female. The median age at the time of CAR-T therapy was 22 (6-50) years. Seven patients had ABL1-like rearrangements, and 14 had JAK-STAT rearrangements. Prior to CAR-T therapy, 12 patients experienced hematologic relapse; 7 were multiparameter flow cytometry minimal residual disease (MFC-MRD) -positive and 2 were MFC-MRD-negative. CAR-T cells were derived from patients' autologous lymphocytes. Nine patients were treated with CD19 CAR-T cells, and 12 were treated with CD19/CD22 CAR-T cells. After assessment on day 28 after CAR-T therapy, 95.2% of the patients achieved complete remission, with an MRD-negative remission rate of 75%. Nineteen patients developed grade 0-2 cytokine release syndrome (CRS) and 2 patients suffered grade 3 CRS, all cases of which resolved after treatment. All patients underwent allo-HSCT after CAR-T therapy. The median time from CAR-T therapy to allo-HSCT was 63 (38-114) days. Five patients experienced relapse after CAR-T therapy, including four with hematologic relapse and one with molecular relapse. The 3-year overall survival (OS) rates in the ABL1 and JAK-STAT groups were (83.3±15.2) % and (66.6±17.2) %, respectively (P=0.68) . The 3-year relapse-free survival (RFS) rates were (50.0±20.4) % and (55.6±15.4) % in the ABL1 and JAK-STAT groups, respectively. There was no significant difference in 3-year OS or RFS between the two groups. Conclusions: CAR-T therapy followed by allo-HSCT leads to rapid remission in most patients with Ph-ALL and prolongs leukemia-free survival.

Diagnostic and therapeutic advances in adults with acute lymphoblastic leukemia in the era of gene analysis and targeted immunotherapy.

Acute lymphoblastic leukemia (ALL) is one of the most rapidly changing hematological malignancies with advanced understanding of the genetic landscape, detection methods of minimal residual disease (MRD), and the development of immunotherapeutic agents with good clinical outcomes. The annual incidence of adult ALL in Korea is 300-350 patients per year. The WHO classification of ALL was revised in 2022 to reflect the molecular cytogenetic features and suggest new adverse- risk subgroups, such as Ph-like ALL and ETP-ALL. We continue to use traditional adverse-risk features and cytogenetics, with MRD-directed post-remission therapy including allogeneic hematopoietic cell transplantation. However, with the introduction of novel agents, such as ponatinib, blinatumomab, and inotuzumab ozogamicin incorporated into frontline therapy, good MRD responses have been achieved, and overall survival outcomes are improving. Accordingly, some clinical trials have suggested a possible era of chemotherapy-free or transplantation-free approaches in the near future. Nevertheless, relapse of refractory ALL still occurs, and some poor ALL subtypes, such as Ph-like ALL and ETP-ALL, are unsolved problems for which novel agents and treatment strategies are needed. In this review, we summarize the currently applied diagnostic and therapeutic practices in the era of advanced genetic analysis and targeted immunotherapies in United States and Europe and introduce real-world Korean data.

Promoter swapping of truncated PDGFRB drives Ph-like acute lymphoblastic leukemia

Philadelphia chromosome (Ph)-like acute lymphoblastic leukemia (ALL) is a subset of ALL that demonstrated a high treatment failure rate. One of the hallmarks of Ph-like ALL is PDGFRB gene fusion, with fusion partner proteins often harboring dimerization domains and enhancing the kinase activity of PDGFRB. We determined a novel oncogenic PDGFRB fusion gene, NRIP1::PDGFRB, from a pediatric patient with ALL, encoding a protein with the carboxy-terminal kinase domain of PDGFRB, without the partner peptide. We confirmed the oncogenic potential of NRIP1::PDGFRB in vitro and the efficacy of all ABL1-specific inhibitor generations, including imatinib, dasatinib, nilotinib, and ponatinib, in suppressing this potential. PDGFRB activation mechanism may include juxtamembrane domain truncation in the predicted peptide. In conclusion, we determined a novel fusion gene pattern in Ph-like ALL.

A Multicenter Analysis of Allogeneic Transplant Outcomes in Patients with Philadelphia-like (Ph-like) Acute Lymphoblastic Leukemia (ALL)

Background: Ph-like ALL is a high-risk subset of B-lineage ALL that responds poorly to standard chemotherapy regimens. While allogeneic hematopoietic cell transplantation (HCT) is routinely recommended for patients with Ph-like ALL, large multicenter data addressing its role is limited. Here, we conducted a multicenter study to evaluate the role of HCT in adolescent and young adult (AYA) and adult patients (pts) with Ph-like ALL and compare their outcomes to pts with Ph-pos and Ph-neg (non-Ph-like) ALL. Methods: The study included pts (age ≥18) with B-lineage ALL who received HCT in first complete remission (CR1) at 3 academic centers (MD Anderson Cancer Center, City of Hope and Mayo Clinic) between 2006 and 2021. Pts were divided into 3 main subgroups: Ph-like, Ph-pos and Ph-neg ALL. Ph-like ALL cases were identified using cumulative data obtained by targeted RNA sequencing, conventional cytogenetics, FISH studies, whole genome chromosomal microarray and flow cytometry. Measurable residual disease (MRD) prior to HCT was measured using flow cytometry with a sensitivity of 0.01% for Ph-neg and Ph-like ALL, and with a PCR assay for BCR::ABL1 for Ph-pos ALL. MRD-negativity was defined as <0.01%. Predictors of relapse were evaluated in univariate and multivariate analysis using Fine-Gray sub-distribution hazard models considering non-relapse mortality (NRM) as a competing risk. Results: 673 patients were identified, 83 (12.3%) had Ph-like ALL, of which 73% had CRLF2-alterations. The remaining patients were classified either as Ph-pos (N=271, 40.3%) or Ph-neg ALL (N=319, 47.4%). Patients with Ph-like ALL were younger (median age 40 years vs 48 and 46 years for Ph-pos and Ph-neg ALL, respectively, p=0.01), more likely to be of Hispanic ethnicity (69% vs 32% and 48% for Ph-pos and Ph-neg ALL respectively, p<0.001). Patients with Ph-like ALL were also more likely to have induction failure (24% vs 2% and 11% for Ph-pos and Ph-neg ALL, respectively, p=0.001). A summary of pts characteristics for each subgroup can be found in Table 1. The median follow-up was 30, 52 and 48 months for patients with Ph-like, Ph-pos and Ph-neg ALL, respectively. In univariate analysis, 3-yr OS and PFS did not differ significantly (66% and 59% vs 59% and 54%, p=0.1) between patients with Ph-like and Ph-neg ALL, respectively. Similarly, the cumulative incidence of relapse was comparable between patients with Ph-like and Ph-neg ALL (22% vs 20%, respectively, p=0.7). In contrast, the 3-yr OS (75%, p<0.001) and PFS (70%, p=0.001) were significantly higher and relapse rate significantly lower (12%, p=0.003) in pts with Ph-pos ALL compared with Ph-like or Ph-neg ALL (Figure 1). The inferior survival in patients with Ph-like and Ph-neg ALL was likely attributable to higher relapse rates (22% and 20% vs 12%, respectively, p=0.003) compared to Ph-pos ALL. Finally, the 3-yr NRM rate in patients with Ph-like ALL was comparable (20% vs 18% and 23%, respectively, p>0.1) to Ph-pos and Ph-neg ALL. We confirmed that the relapse rate in patients with Ph-like ALL was comparable to the rate in pts with Ph-neg ALL (HR=1.02, 95% CI 0.6-1.8, p=0.9) on multivariate analysis (MVA). Ph-pos ALL was associated with a significantly lower relapse rate compared with Ph-neg ALL (HR=0.4, 95% CI 0.3-0.7, p<0.001). MRD positivity prior to allo-HCT was the only additional significant predictor for relapse on MVA (HR=2.9, 95% CI 1.8-4.7, p<0.001). Conclusions: HCT appears to overcome the poor prognosis of patients with Ph-like ALL. Despite higher induction failure rates, patients with Ph-like ALL undergoing HCT in CR1 had similar outcomes to other Ph-neg ALL subsets. The impact of effective salvage therapy leading to MRD-negativity in CR1 in this group is under investigation and will be reported. Further studies are needed to assess the impact of different Ph-like alterations on HCT outcomes. Outcomes for patients with Ph-pos ALL are significantly better than other groups, likely due to the use of TKIs pre- and post-HCT.

Frontline Combination of 3 rd Generation TKI Olverembatinib and Blinatumomab for Ph+/Ph-like ALL Patients

Background The combination of dasatinib and blinatumomab represented a chemotherapy-free treatment approach, which had been employed in the management of newly diagnosed Philadelphia chromosome-positive acute lymphoblastic leukemia (ALL). A recent study demonstrated that combination therapy of ponatinib with blinatumomab may achieve better efficacy, with a complete molecular response (CMR) rate of 87%. However, some patients required dose reduction or even discontinuation of ponatinib for the occurrence of cardiovascular adverse events. Olverembatinib, a potent third-generation tyrosine kinase inhibitor (TKI), showed both favorable tolerability and significant efficacy in patients with TKI-resistant chronic myeloid leukemia. But its effectiveness in ALL remained unaddressed. Our recent study, a frontline combination of Olverembatinib and PDT-ALL-2016 regime in Ph+ALL, had shown a promising outcome, achieving a complete molecular response (CMR) rate of 84.6% at day 90. Herein, we explored the clinical efficacy of the frontline combination of Olverembatinib and blinatumomab for the treatment of Ph+ and ABL-class Ph-like ALL. Methods From April 2022 to May 2023, 13 patients with Ph+/Ph-like ALL treated with olverembatinib (40mg once every other day) and blinatumomab (administered for a total of 2 weeks followed by 2 weeks of break) were enrolled (Figure 1a). Two patients (15.4%, 2/13) were in Ph-like ALL group with TEL-ABL and EBF1-PDGFRB fusion gene. Five patients (38.5%, 5/13), with a median age of 58 years old, were received ≥2 cycles and eight patients (61.5%, 8/13), with a median age of 34.5 years old, were treated with 1 cycle before HSCT. Result With a median follow-up of 7 months, all patients (100%, 13/13) achieved complete remission (CR) after one cycle of treatment. Among them, nine patients (72.7%, 9/13) achieved complete molecular remission (CMR) after one cycle, and ten patients (90.1%, 10/13) after two cycles. Notably, all patients (100%, 13/13) achieved CMR within three months of olverembatinib and blinatumomab treatment (Figure 1b). The 6-month overall survival (OS) rate was 100% and the 6-month event-free survival (EFS) rate was 87.5% (Figure 1 c and d). One patient with ABL mutation EE255V died due to relapse after HSCT. The regimen was overall well tolerated. For hematologic toxicity, one patient (7.7%, 1/13) experienced grade 1 neutrophil decrease. Regarding non-hematologic toxicity, five patients (38.4%, 5/13) developed infections during treatment, including COVID-19 and herpes zoster. Five patients (38.4%, 5/13) experienced decreased levels of immunoglobulins. Ten patients (76.9%, 10/13) experienced grade 1 cytokine release syndrome (CRS). Importantly, there were no interruptions in dosing of olverembatinib during treatment while no cardiovascular adverse events were observed. Conclusion This is the first report on the combination of olverembatinib with blinatumomab for the treatment of Ph+/Ph-like ALL. Among the 13 patients enrolled, a notable rate of CR and CMR was observed, which holds promise for improved long-term survival. Additionally, the combination of olverembatinib and blinatumomab exhibited minimal adverse events, both in terms of hematologic and non-hematologic toxicities. Notably, fewer cardiovascular adverse events that required discontinuation of treatment compared to ponatinib were observed. Altogether, these findings strongly indicated that combination therapy of olverembatinib with blinatumomab has the potential to become a new standard of care in the frontline treatment of Ph+/Ph-like ALL. However, further clinical trials are needed to definitively establish the efficacy of this treatment approach and validate the potential benefits. This research was supported by the National Natural Science Foundation of China(NFSC82170163, 81970147), Clinical Study of Nanfang Hospital(LC2016ZD009/2019CR012).

Philadelphia-like B-Cell Acute Lymphoblastic Leukemia in a Largely Hispanic Population: Disease Features and Outcomes in the Era of Immunotherapy a Single Institutional Study

Introduction: Philadelphia (Ph)-like B-cell acute lymphoblastic leukemia (ALL) is a high-risk subgroup of B- cell ALL with distinct genotypes, unified by a gene expression profile similar to Ph-positive ALL but lacking the BCR: ABL1 fusion. Previous studies have noted the increased prevalence of Ph-like B-cell ALL in Hispanic patients. Our study evaluates Ph-like B- cell ALL clinical/genomic features and outcomes in a predominantly Hispanic population. Methods: This is a retrospective chart review of ALL patients that underwent treatment for B-cell ALL at Norris Comprehensive Cancer Center (NCCC) between 2011 and 2023. Identification of fusions associated with Ph-like B-cell ALL was performed using cumulative results from RNA-seq, conventional cytogenetics, and fluorescence in situ hybridization (FISH) with reflex gene fusion transcript analysis. Additionally, we used the Anchored Multiplex PCR™-based multi-gene NGS assay designed to detect known and novel fusions and elevated gene expression levels using a proprietary algorithm in ALL. Cumulative incidence of relapse (CIR) was evaluated using competing risk regression (Fine-Gray method), with death as a competing outcome. Overall survival (OS) and event-free survival (EFS) were analyzed using Cox proportional hazards model. Events of interest for EFS were relapse, treatment failure, and death. Ph-negative B-cell ALL patients were set as the reference for survival analysis. Results: 253 patients were included with a median age at diagnosis of 42 years (range: 18-80). ALL subtypes included 64(25.3%) Ph-like, 77(30.4%) Ph-positive, and 112(44.3%) Ph-negative. Most were Hispanic (N = 186, 73.5%), and the median follow-up time was 27 months. The 3-year OS, EFS, and CIR were 81.3% (95% CI 75.7-87.4%), 49.1% (95% CI 42.7-56.5%), and 39.9% (95% CI 33.0-46.7%). CRLF2 related mutations constituted 44(68.8%) of Ph-like patients, with 9(14.0%) CRLF2-P2RY8, 24(37.5%) CRLF2-IGH, and 11(17.2%) CRLF2-other gene rearrangements. 19 Ph-like patients had non-CRLF2 mutations consisting of 13(20.3%) IGH, 3(4.7%) ABL1/2, 3(4.7%) JAK2, and 1(1.6%) EPOR rearrangements. Compared to Ph-negative, Ph-like patients were more likely to have a refractory disease (20.6% vs. 6.2% P=0.006) and require Blinatumomab (67.2% vs. 39.3% P<0.001), with a non-significant trend towards lower rates of CR (84.1% vs 90.9% P=0.21). Ph-like patients had significantly worse EFS (HR = 1.63; 95% CI 1.09-2.45; P=0.018), but similar OS (HR = 0.88; 95% CI 0.39-1.99; P=0.75) and CIR (HR = 1.06; 95% CI 0.65-1.70; P = 0.83). Ph-positive patients displayed improved EFS relative to Ph-negative (HR = 0.56; 95% CI 0.35-0.91; P = 0.018), similar OS (HR = 0.73; 95% CI 0.35-1.50; P = 0.39), and a trend towards improved CIR (HR = 0.67; 95% CI 0.40-1.10; P=0.11). When controlling for age, sex, and treatment type, EFS was worse in Ph-like (HR = 1.57; 95% CI 1.03-2.41; P = 0.037) and improved in Ph-positive (HR = 0.56; 95% CI 0.33-0.93; P = 0.026). Our incidences of CRLF2 mutations in Ph-like patients aged>40 compared to age ≤40 was (73.3% vs 64.7%, P=0.591). On subgroup analysis of Ph-like patients, univariate regression revealed CRLF2-related Ph-like patients had a worse CIR (HR = 5.68; 95% CI 1.91-16.9; P = 0.002) but similar OS(P=0.99) and EFS(P=0.18). PAX5 expression was also a predictor of poor OS (HR = 8.89; 95% CI 1.06-74.7; P = 0.044) and EFS (HR = 2.51; 95% CI 1.09-5.77; P = 0.031), with a trend towards increased CIR (HR = 2.30; 95% CI 0.92 -5.78; P = 0.075). Compared to non-CRLF2 mutations, CRLF2-Ph-like had worse CIR (HR = 5.68; 95% CI 1.91 -16.9; P = 0.002). Relative to Ph-like patients who achieved MRD negativity during induction, patients who remained MRD positive had worse CIR(HR = 2.92; 95% CI 1.23 -6.94; P = 0.015) and EFS (HR = 4.32; 95% CI 1.890-9.84; P < 0.001). However, after controlling for Blinatumomab administration, the effect diminished (CIR: P=0.73, EFS P=0.28). There were no differences in EFS(P=0.34), CIR(P=0.69), and OS(P=0.36) between Ph-like patients who were transplanted vs not. Conclusions: Ph-like B- Cell ALL represents a high-risk disease subtype of adult B-ALL, with poor EFS and frequent treatment failure. CRLF2 translocation confers worse CIR and EFS within Ph-like patients and requires novel treatment approaches.

Long-Term Follow up for SWOG 1318: Combination of Dasatinib, Prednisone, and Blinatumomab for Older Patients with Philadelphia-Chromosome (Ph) Positive Acute Lymphoblastic Leukemia (ALL)

Tyrosine kinase inhibitors (TKIs) have improved the outcomes of patients with Philadelphia chromosome positive (Ph+) acute lymphoblastic leukemia (ALL). Many older patients (pts) are not good candidates for intensive chemotherapy and are treated with TKIs plus corticosteroids or low-intensity chemotherapy. Although the remission rates with this approach have been high, the median disease-free survival (DFS) has been short. Therefore, novel treatment strategies are needed. This trial evaluated the feasibility of combining the TKI dasatinib with prednisone and blinatumomab in older pts with Ph+ ALL. Here we present updated results (median follow-up, 4.3 years). Methods: This trial was activated through the NCTN in January 2015 and closed to accrual in April 2021. Pt eligibility included: age ≥ 65 years; Ph+ or Ph-like ALL (with dasatinib-sensitive fusions or mutations); newly diagnosed or relapsed/ refractory; no evidence of central nervous system (CNS) disease; and adequate organ function. Treatment: For induction, pts received dasatinib 140 mg/d orally (PO) Days 1-56 along with prednisone 60 mg/m 2/d PO Days 1-24. Pts achieving complete remission (CR) or CR with incomplete count recovery (CRi) (Day 28 or Day 56) continued dasatinib until Day 84, followed by 3 cycles of post-remission therapy (PRT) with blinatumomab/ dasatinib. Pts not achieving CR or CRi by Day 56 received re-induction with blinatumomab. The response rate was assessed on Day 35 of blinatumomab. Pts not achieving CR/ CRi could receive a second cycle of blinatumomab. This was followed by 3 cycles of PRT with blinatumomab/ dasatinib. Maintenance therapy consisted of prednisone 60 mg/m 2/d x 5 days every 28 days for a total of 18 cycles, along with dasatinib 140 mg po qd indefinitely. CNS prophylaxis included intrathecal (IT) methotrexate every 4-6 weeks x 8 doses. IT methotrexate was given at least 2 days apart from blinatumomab. Response was assessed at Days 28, 56, and 84, and additional time points were dependent on response. Minimal residual disease (MRD) was assessed centrally by multi-color flow cytometry on Day 28. Statistics: A total of 24 eligible patients were accrued. The primary objective was the feasibility of the combination therapy. The combination was to be deemed feasible if the dose-limiting toxicity (DLT) was < 33%. DLT included: > Grade 3 non-hematologic toxicities (excluding nausea, vomiting, diarrhea) and Grade 4 neutropenia lasting > 42 days. The primary results were reported in 2022 with a median of 2.7 years of follow-up. Herein, we report long-term outcomes for these patients. Results: The median age was 73 years (range 65-87). All pts had newly diagnosed Ph+ ALL; 79% of Ph+ pts had additional cytogenetic abnormalities. During induction, 2 pts experienced treatment-related non-hematologic Grade 4 toxicities. No Grade 4 or higher treatment-related non-hematologic toxicities occurred during post-remission therapy or maintenance. The toxicity of the combination was deemed acceptable. Twenty-two of 24 pts (92%) achieved a CR during dasatinib and prednisone induction therapy. Four did not receive PRT (2 due to adverse events, 1 to receive a transplant, and 1 because of insurance issues). Sixteen pts who achieved CR had MRD data. Six of 16 pts (38%) were MRD undetectable by multi-color flow cytometry on Day 28. Most sites also monitored patients' blood or bone marrow with real-time quantitative PCR to quantify the BCR-ABL1 transcript for molecular response. Of 19 patients analyzed, 17 (89%) were in a major or complete molecular remission at some time point after treatment, with at least 12 of these patients achieving complete molecular remission. Four patients remain on maintenance. The median follow- up for pts who are alive is 4.3 years (range 2.6-6.5 years). The median overall survival (OS) is 6.5 years (95% CI 3-NA) and the median DFS has not been reached as of June 29, 2023. Kaplan-Meier 3-year estimates of OS and DFS are 75% (95% CI 52%-88%) and 72% (95% CI 49%-87%), respectively (Figure). Of the 8 relapses, 4 patients were CD19+ and 3 had T315I mutations. Conclusions: Median DFS and OS with dasatinib and blinatumomab in this older group of Ph+ ALL patients remain excellent despite only 1 patient proceeding to an allogeneic transplant. Further correlative studies (single cell transcriptomics and DNA methylation sequencing) are being planned to evaluate predictors of relapse and will be presented at the meeting.

A Single Center, 10-Year Experience of CALGB-10403 Regimen in AYA Population with Philadelphia-Chromosome Negative Acute Lymphoblastic Leukemia

INTRODUCTION: The use of pediatric-inspired regimens for the treatment of acute lymphoblastic leukemia (ALL) has now become the standard of care in adolescents and adults (AYA). One such regimen, CALGB 10403, had higher rates of event free survival (EFS) and overall survival (OS) compared with historical controls using adult ALL regimens. It was shown to be feasible and efficacious in fit patients up to the age of 40 (Wendy Stock et al., Blood 2019). In 2012, based on emerging data on the improved efficacy of pediatric-inspired regimens in AYA patients, CALGB 10403 was adopted as the standard-of-care regimen in this population at Karmanos Cancer Institute (KCI), an adult cancer treatment center. Here we report our single center, real world experience of using this regimen in a Philadelphia chromosome negative (Ph-) AYA population, approximately 10 years after its adoption. METHODS: We conducted a retrospective chart review of consecutive AYA (ages 18-39) patients with Ph- ALL treated with CALGB 10403 regimen between January 2012 and June 2023 at KCI. Patients who received alternative regimens due to distance from KCI were excluded. Baseline demographic, clinical and molecular characteristics were noted. High-risk cytogenetics were defined as KMT2A rearrangements, hypodiploidy with a chromosome number ≤43, and complex karyotype. Testing for Ph-like ALL was not available in most patients. Beginning in 2019, clonoSEQ assay was used to test for minimal residual disease (MRD), with MRD negativity defined at a threshold of less than 10 -4. Incidence of adverse effects and treatment related mortality were reported to describe safety. Complete response (CR) rate, OS and PFS were used as efficacy outcomes. Kaplan-Meier curves were used to estimate OS and PFS. RESULTS: A total of 17 Ph- AYA patients were treated at KCI with a median age at diagnosis of 25 years (range 18-34). Males and females had a near equal representation (47% and 53%). The patients were predominantly White (64%). The majority of patients had a good ECOG performance status of 0 or 1 (88%). The diagnosis was B-ALL in 9 (53%) and T-ALL in 8 (47%) patients. High risk cytogenetics were present in 3 (80%) of the evaluable patients. None of the patients had CNS involvement at diagnosis. Baseline laboratory parameters expressed as medians were bone marrow blast percentage 80%, WBC count 9.2 x1000/mm 3, hemoglobin 8.4 g/dL, platelets 109 x1000/mm 3, and LDH 480. The median duration of follow-up was 54 months. 15 (88%) patients had CR with induction, and MRD was negative in 4 (57%) of the 7 evaluable patients. 2 (12%) patients had primary refractory disease. One of the patients with refractory disease underwent further therapy with blinatumomab, inotuzumab, CAR-T and allogeneic stem cell transplantation and is alive at 16 months from diagnosis. Another underwent salvage with hyper-CVAD and allogeneic stem cell transplant, and is currently alive at 88 months from diagnosis. Two additional patients were MRD positive after induction (course I) but subsequently attained MRD negativity. One of these eventually relapsed 7.5 months from diagnosis with a mixed phenotypic (T/myeloid) leukemia and died at 10 months, while the other is currently under treatment. An additional patient with CR1 and unknown MRD status had CNS relapse at 35 months, underwent successful hyper-CVAD, reintroduction of intrathecal chemotherapy and allo-HSCT salvage and is alive at 122 months. The 5-year PFS and OS were 74.5% and 94% respectively and the medians were not reached for both. Noteworthy adverse effects include neutropenic fever (65%), liver function tests (LFT) abnormalities (70%), and neuropathy from vincristine (70%). Peg-asparaginase administration was associated with pancreatitis in 12%, thromboembolism in 30% and hypersensitivity reactions in 24% requiring switching to alternative forms of asparaginase products (erwinia and Rylaze). These toxicities were manageable and there were no treatment-related deaths in our cohort. CONCLUSIONS: The pediatric-inspired regimen CALGB 10403 was safe and efficacious in our AYA Ph- ALL population with no deaths due to treatment and a 5-year overall survival of 94%. Toxicities, especially from peg-asparaginase, should be closely monitored. While most patients will attain durable remission/cure, the minority with refractory or relapsed disease can still be successfully salvaged to achieve long term survival.

Genomic determinants of outcome in acute lymphoblastic leukemia: A Children’s Oncology Group study.

10015 Background: While cure rates for childhood acute lymphoblastic leukemia (ALL) exceed 90%, half of relapses arise in those originally classified with standard risk (SR) disease. Methods: We performed genome/transcriptome sequencing of diagnostic and germline samples of children with SR (n=1381) B-ALL or high-risk (HR) B-ALL with favorable cytogenetics ( ETV6: RUNX1 or double trisomy (DT) of chromosomes (chr) 4+10; n=115) to identify predictors of relapse. We used a case-control study to analyze 439 patients who relapsed and 1057 who remained in complete remission for > 5 years. Results: Genomic subtype was associated with relapse. Unbalanced ETV6:RUNX1 translocations were more common than balanced in relapse patients (OR=2.01, CI=1.25-3.20, P=0.002). Conversely, balanced TCF3:PBX1 translocations were more often associated with relapse than unbalanced in TCF3:PBX1 ALL (OR=0.11, CI=0.01-0.50, P=0.003). A striking finding was the high relapse rate in PAX5 altered ALL (57 of 116 cases (49%); OR=3.29, CI=2.16-5.01, P=3.49x10-8). The nature of the heterogeneous PAX5 driver alterations of this subtype influenced relapse risk, with internal PAX5 amplifications and biallelic PAX5 alterations associated with the highest risk. Specific chr gains influenced outcome in hyperdiploid ALL, with gain of chr 10 and disomy of chr 7 associated with favorable outcome (OR=0.27, CI=0.17-0.42, P=8.02x10-10, St Jude Children’s Research Hospital (SJCRH) validation cohort: OR=0.22, CI=0.05-0.80, P=0.009), while disomy of chr 10 and 17 and gain of chr 6 were enriched in patients that relapsed (OR=7.16, CI=2.63-21.51, P=2.19x10-5; SJCRH cohort: OR=21.32, CI=3.62-119.30, P=0.0004). Genomic alterations were also associated with relapse in a subtype-dependent manner, including alterations of INO80 in ETV6:RUNX1, IKZF1 and CREBBP in hyperdiploid, and FHIT in Ph-like ALL. Conclusions: Genetic subtype, aneuploidy patterns, and secondary genomic alterations influence risk of relapse in children otherwise classified with SR ALL, or HR ALL with favorable genetics. Comprehensive genomic analysis is required for optimal risk stratification and treatment allocation, and particularly to study reduction of therapy in the lowest risk patients. [Table: see text]

Clinical features and prognosis of pediatric acute lymphocytic leukemia with JAK-STAT pathway genetic abnormalities: a case series.

The objective of this study is to explore the clinical features and outcomes of pediatric patients with acute lymphoblastic leukemia (ALL) harboring JAK-STAT signaling pathway genetic abnormalities. This retrospective case series examined the clinical data of pediatric patients diagnosed with ALL harboring JAK-STAT pathway genetic abnormality at the Children's Hospital of the Capital Institute of Pediatrics between January 2016 and January 2022. Bone marrow next-generation sequencing was used to reveal the JAK pathway abnormalities. Descriptive statistics were used. From 432 children with ALL during the study period, eight had JAK-STAT pathway genetic abnormalities. Regarding immunotyping, there were four patients with common-B cell types and one with pre-B cell type. The three patients with T-ALL had early T-cell precursor(ETP) type, pre-T cell type, and T cell type. Gene mutations were more common than fusion genes. There was no central nervous system involvement in eight patients. All patients were considered at least at intermediate risk before treatments. Four patients underwent hematopoietic stem cell transplantation (HSCT). One child had a comprehensive relapse and died. The child had a severe infection and could not tolerate high-intensity chemotherapy. Another child relapsed 2years after HSCT and died. Disease-free survival was achieved in six children. JAK-STAT pathway genetic abnormalities in pediatric Ph-like ALL are rare. Special attention should be paid to treatment-related complications, such as infection and combination therapy (chemotherapy, small molecule targeted drugs, immunotherapy, etc.) to reduce treatment-related death and improve long-term quality of life.

Neurofibromatosis Symptom-Lacking B-Cell Lineage Acute Lymphoblastic Leukemia with Only an NF1 Gene Pathogenic Variant

Next-generation sequencing technology has improved molecular genetic analysis, and many molecular genetic studies have been utilized for diagnostic classification, risk stratification, and prognosis prediction of acute lymphoblastic leukemia (ALL). Inactivation of neurofibromin or Nf1, a protein derived from the NF1 gene, causes Ras pathway regulation failure, which is related to leukemogenesis. Pathogenic variants of the NF1 gene in B-cell lineage ALL are uncommon, and in this study, we reported a pathogenic variant that is not registered in any public database. The patient diagnosed with B-cell lineage ALL had no clinical symptoms of neurofibromatosis. Studies on the biology, diagnosis, and treatment of this uncommon disease, as well as other related hematologic neoplasms, such as acute myeloid leukemia and juvenile myelomonocytic leukemia, were reviewed. Biological studies included epidemiological differences among age intervals and pathways for leukemia, such as the Ras pathway. Diagnostic studies included cytogenetic, FISH, and molecular tests for leukemia-related genes and ALL classification, such as Ph-like ALL or BCR-ABL1-like ALL. Treatment studies included pathway inhibitors and chimeric antigen cell receptor T-cells. Resistance mechanisms related to leukemia drugs were also investigated. We believe that these literature reviews will enhance medical care for the uncommon diagnosis of B-cell lineage ALL.

Role of Cytogenetics and FISH in Laboratory Workup of B Cell Precursor Acute Lymphoblastic Leukemia

AbstractModern therapeutic protocols in acute leukemias risk stratify disease based on genetic characterization of the neoplastic cells and their response to treatment. Genetic characterization is routinely performed by cytogenetic testing of leukemic cells and is a standard component of modern risk-adapted therapy in acute lymphoblastic leukemia (ALL). High-throughput technologies like RNA sequencing have identified multiple novel subtypes in recent years. The cytogenetic strategy using GTG and fluorescent in-situ hybridization (FISH) has to be adapted to identify not only the primary principal chromosomal abnormalities but also the novel subtypes. In the review, we describe a systematic comprehensive cytogenetic strategy that integrates information from immunophenotyping, flow-based DNA ploidy, and karyotyping complemented by targeted FISH studies to identify more than 70% of genetic abnormalities described in B cell precursor ALL. The simplified strategy includes a four-probe FISH and flow ploidy strategy, ± karyotyping that identifies high risk (KMT2A, BCR::ABL1, hypodiploidy, iAMP21) and standard risk (ETV6::RUNX1 and high hyperdiploid) cytogenetic groups. The extended FISH panel includes probes targeting MEF2D, ZNF384, and CRLF2 rearrangements that are used intuitively on integrating the immunophenotyping features that characterize these entities. The strategy also includes a systematic approach to identify masked hypodiploidy integrating targeted FISH analysis directed toward identifying monosomies of chromosomes 7, 15, and 17 and flow cytometry-based DNA ploidy analysis. The recently described PH-like ALL is characterized by ABL class fusions and rearrangements of CRLF2 and JAK2 genes. FISH analysis using break-apart probes can be used to identify these aberrations. The cytogenetic approach also includes FISH analysis to identify intragenic and whole gene deletions of the IKZF1 genes that identify a subset of patients associated with high risk of treatment failure.

Dasatinib/prednisone induction followed by blinatumomab/dasatinib in Ph+ acute lymphoblastic leukemia.

Novel treatment strategies are needed for the treatment of Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) in older patients. This trial evaluated the feasibility and outcomes with the anti-CD19 bispecific T-cell-engaging antibody, blinatumomab, in combination with dasatinib and steroids. Patients 65 years of age or older with Ph+ or Ph-like ALL (with dasatinib-sensitive fusions/mutations) were eligible and could be newly diagnosed or relapsed/refractory. Induction therapy consisted of dasatinib/prednisone. Patients not achieving response by day 56 proceeded to blinatumomab reinduction therapy. Patients achieving response with induction or reinduction therapy proceeded to blinatumomab/dasatinib postremission therapy for 3 cycles followed by dasatinib/prednisone maintenance. All patients received central nervous system prophylaxis with intrathecal methotrexate for a total of 8 doses. Response was assessed at days 28, 56, and 84 and at additional time points based on response parameters. Measurable residual disease was assessed centrally by 8-color flow cytometry at day 28. A total of 24 eligible patients with newly diagnosed Ph+ ALL were enrolled with a median age of 73 years (range, 65-87 years). This combination was safe and feasible. With a median of 2.7 years of follow-up, 3-year overall survival and disease-free survival were 87% (95% confidence interval [CI], 64-96) and 77% (95% CI, 54-90), respectively. Although longer follow-up is needed, these results are encouraging, and future trials are building on this backbone regimen. This trial was registered at www.clinicaltrials.gov as #NCT02143414.

High response rates and transition to transplant after novel targeted and cellular therapies in adults with relapsed/refractory acute lymphoblastic leukemia with Philadelphia-like fusions.

Philadelphia (Ph)-like acute lymphoblastic leukemia (ALL) is associated with a poor response to standard chemotherapy. However, outcomes with novel antibody and cellular therapies in relapsed/refractory (r/r) Ph-like ALL are largely unknown. We conducted a single-center retrospective analysis of adult patients (n= 96) with r/r B-ALL and fusions associated with Ph-like who received novel salvage therapies. Patients were treated with 149 individual novel regimens (blinatumomab=83, inotuzumab ozogamicin [InO]=36, and CD19CAR T cells=30). The median age at first novel salvage therapy was 36 years (range; 18-71). Ph-like fusions were IGH::CRLF2 (n= 48), P2RY8::CRLF2 (n= 26), JAK2 (n= 9), ABL-class (n= 8), EPOR::IGH (n= 4) and ETV6::NTRK2 (n= 1). CD19CAR T cells were administered later in the course of therapy compared to blinatumomab and InO (p< .001) and more frequently in recipients who relapsed after allogeneic hematopoietic cell transplantation (alloHCT) (p= .002). Blinatumomab was administered at an older age compared to InO and CAR T-cells (p= .004). The complete remission (CR)/CR with incomplete hematologic recovery (CRi) rates were 63%, 72%, and 90% following blinatumomab, InO and CD19CAR, respectively, among which 50%, 50%, and 44% of responders underwent consolidation with alloHCT, respectively. In multivariable analysis, the type of novel therapy (p= .044) and pretreatment marrow blasts (p= .006) predicted the CR/CRi rate, while the Ph-like fusion subtype (p= .016), pretreatment marrow blasts (p= .022) and post-response consolidation with alloHCT (p< .001) influenced event-free survival. In conclusion, novel therapies are effective in inducing high remission rates in patients with r/r Ph-like ALL and successfully transitioning the responders to alloHCT.

Genomic and proteomic characterization of Philadelphia-like B-lineage acute lymphoblastic leukemia: A report of Indian patients.

The gold standard for the identification of Philadelphia (Ph)-like acute lymphoblastic leukemia (ALL) patients is gene expression profiling. Because of its diverse nature, its identification is extremely difficult and expensive. On the genomic and proteomic landscape of Ph-like ALL patients, there is a paucity of published literature from developing countries. The authors used digital barcoded nCounter NanoString gene expression profiling for its detection, followed by molecular and proteomic characterization using fluorescence in situ hybridization and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The authors found 32.05% Ph-like ALL patients and their median age at presentation was considerably higher than Ph-negative ALL cases (p=.0306). Furthermore, we identified 20% CRLF2 overexpressed cases having 8.33% CRLF2-IGH translocation with concomitant R683S mutation and 8.33% CRLF2-P2RY8 translocation. In 80% of CRLF2 downregulated cases, we identified 10% as having JAK2 rearrangement. Minimal residual disease-positivity was more common in Ph-like ALL cases (55.55% vs. 25% in Ph-negative ALL cases). Immunoglobulin J chain (Jchain), small nuclear ribonucleoprotein SmD1 (SNRPD1), immunoglobulin κ constant (IGKC), NADH dehydrogenase (ubiquinone) 1 α subcomplex subunit 2 (NDUFA2), histone H2AX (H2AFX), charged multivesicular body protein 4b (CHMP4B), and carbonyl reductase (NADPH) (CBR1) proteins were identified to be substantially expressed in Ph-like ALL patients, using LC-MS/MS. Gene enrichment analysis indicated that involvement of spliceosomal mediated messenger RNA splicing pathway and four microRNAs was statistically significant in Ph-like ALL patients. For the first time, we have described incidence, molecular, and proteomic characterization of Ph-like ALL, in developing nations. In developing countries, detecting Philadelphia (Ph)-like B-lineage acute lymphoblastic leukemia is complicated and challenging due to its diverse genetic landscape. There is no well-defined and cost-effective methodology for its detection. The incidence of this high-risk subtype is very high in adult cases, and there is an urgent need for its accurate detection. We have developed an online PHi-RACE classifier for its rapid detection, followed by delineating the genomic and proteomic landscape of Ph-like acute lymphoblastic leukemias for the first time in Indian patients.

Fish-ing for PH-like acute lymphoblastic leukemia

Fish-ing for PH-like acute lymphoblastic leukemia

Novel Salvage Therapies Are Highly Effective in Adults with Relapsed/Refractory Acute Lymphoblastic Leukemia (ALL) with Philadelphia (Ph)-like Fusions

Philadelphia (Ph)-like ALL is associated with poor response to standard chemotherapy and frequently necessitates novel salvage therapies to attain remission. However, outcomes of novel therapies in relapsed/refractory (r/r) Ph-like ALL remains largely unknown, except for a few reported small case series. Here, we retrospectively studied outcomes of adult patients (pts) with r/r B-cell ALL who completed at least one cycle of a novel salvage therapy [blinatumomab (blina), inotuzumab (INO), or CD19CAR T cells (CAR)] at City of Hope from 2012 to 2022 and had post treatment disease assessment. We only included pts with documented fusions associated with Ph-like ALL, identified by accumulative results of RNAseq, conventional cytogenetics, FISH, and whole genome SNP array analysis. Complete remission (CR)/CR with incomplete hematologic recovery (CRi) rate was the primary endpoint and leukemia-free survival (LFS) and overall survival (OS) were secondary endpoints. LFS was defined as the period from the date of response to individual therapy to the date of relapse or death, whichever came first; LFS was censored among responders. at the last follow-up if pts were alive and relapse-free. We identified 96 pts with r/r B-cell ALL with Ph-like fusions who received 149 individual novel therapies; 83 (86%) pts were treated with blina, 36 (38%) with INO, and 30 (31%) with CAR [commercial; n=10; investigational: n=20]. Median age at the time of first novel salvage therapy was 36 years (range; 18-71), 69% of pts were males and 89% were Hispanic. Ph-like fusions including IGH-CRLF2, P2RY8-CRLF2, ABL1/2,JAK2-, EPOR- and ETV6-NTRK2-fusion were seen in 50%, 27%, 8%, 9%, 4% and 1% of the cohort, respectively. Pts with CAR therapy had more prior lines of therapy compared to blina and INO (3 vs 1 vs 2; p<0.001), more frequently underwent prior allogeneic transplant (57% vs 12% vs 22%; p=0.002), and had a trend toward more extramedullary disease at the time of initiating therapy (27% vs 0 vs 6%; p= 0.065). Blina was administered at older median age compared to INO and CAR (36 vs 33 vs 29; p=0.004). Pts treated with INO had a trend toward higher marrow blasts% at the time of starting therapy (80 vs 60 vs 50; p= 0.065) compared to CAR and blina, respectively. Prior novel therapies were given for relapse to 7% (n=6), 75% (n=27), and 70% (n= 21) before blina, INO and CAR, respectively. The CR/CRi rates were 63%, 72%, and 90% after blina, INO and CAR, with corresponding negative minimal residual disease (MRD-) rate among evaluable responders (defined as <0.01% leukemic cells in the bone marrow by multicolor flow cytometry) of 86%, 73%, and 96%, respectively. Among responders, 50%, 50%, and 44% of pts receiving blina, INO or CAR, respectively; underwent consolidation with allogeneic transplant. CR/CRi rates for pts treated with INO with/without prior lines of novel therapy were 74% and 67%, respectively. CR/CRi were 90% and 89% for CAR pts treated with/without prior novel therapies. The median follow up since the first salvage novel therapy was 13.1 months (range; 0.6-109.5), and the median OS was 21.6 months (range; 15.1-27.8). In multivariable analysis, type of novel therapy (p= 0.044) and marrow blasts [per 5% increase] (p=0.006) independently predicted CR/CRi rate, while the Ph-like fusion subgroup was associated with LFS (p= 0.013), with 6-months LFS of 45%, 67%, and 90% for pts carrying IGH-CRLF2, P2RY8-CRLF2 and other fusions, respectively. Yet, LFS was not different among pts receiving individual novel salvage therapies (p=0.30), and the 6-month LFS for blina, INO and CAR were 60%, 55% and 66%, respectively. To our knowledge, our study is the largest experience evaluating outcomes of novel salvage therapies for Ph-like ALL. Our results show that novel therapies are highly effective in r/r ALL with Ph-like fusions, leading to high remission rate, MRD- response and transition to transplant consolidation at remission. Prior novel therapies did not adversely impact response to subsequent novel therapies. Therefore, the early introduction of novel therapies in pts with Ph-like ALL is of great interest and could potentially lead to improvement in frontline therapy outcomes in this high-risk entity. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Multicenter Phase I Study of Post-Transplant Low-Dose Inotuzumab Ozogamicin to Prevent Relapse of Acute Lymphoblastic Leukemia

Background: The curative potential of allogeneic transplant (alloHCT) in patients with acute lymphoblastic leukemia (ALL) is hampered by relapse, the major cause of treatment failure. Risk factors for relapse include measurable residual disease (MRD) before or after alloHCT, transplantation in second complete remission (CR) or beyond, and reduced intensity conditioning (RIC) regimens. In ALL patients, relapse rates range from 30% to 50%, with most relapses occurring within the first year after alloHCT. After relapse, options for disease control are limited, and consequently overall survival (OS) is poor. Post-alloHCT maintenance may reduce MRD, provide time for a graft-versus-leukemia effect to develop, and ultimately decrease relapse rates and prolong progression-free-survival (PFS) and overall survival (OS). Inotuzumab ozogamicin (INO) is an anti-CD22 monoclonal antibody bound to calicheamicin and approved to treat relapsed ALL. With the hypothesis that low-dose INO would be safe and reduce relapse rates, we conducted a phase I study to define INO dose in this setting. Herein we present the results of this multicenter study. Methods: Eligibility included patients aged 16-75 who underwent alloHCT for CD22+ALL and were in CR after transplant, had a high risk for relapse after alloHCT (MRD before or after alloHCT, transplantation,in second CR or beyond, RIC regimen, lymphoid blast crisis of chronic myeloid leukemia, or Ph-like ALL), had adequate graft and organ function after transplant (platelets > 50 ANC > 1000), did not have active grade III/IV aGVHD or any active liver GVHD, and had no history of hepatic VOD. Patients were consented after transplant. The primary objective was to define a post-alloHCT maximum tolerated dose (MTD) of INO. Secondary objectives included describing the safety profile of INO, determining the rate of hepatic veno-occlusive disease (VOD) in this setting, evaluating non-relapse mortality (NRM), PFS and OS at 1-year post-alloHCT, and determining if INO at these doses is effective at eradicating MRD. Pre-treatment tests included a bone marrow biopsy and aspirate to assess disease state and MRD. The trial design was a 3+3 model. The study treatment consisted of 28-day cycles (initially planned for 4 cycles, increased up to 12 cycles) of INO starting at dose level 0 (0.3mg/m2; n= 4), then 0.4 mg/m2 (n= 3), 0.5 mg/m2 (n= 6) and 0.6 mg/m2 (n= 5) given on cycle day 1. The first cycle was initiated between day 40 and 100 post-alloHCT. Pre-defined dose limiting toxicities (DLT) included VOD, prolonged cytopenia (more than 28 days), severe toxicities ascribed to INO, and death. If there were no DLTs experienced in first two cycles of a cohort, subsequent patients were enrolled in the next highest dose level. Results: We have enrolled 19 patients (18 treated, Table 1) with a median follow up of 18.1 months and a median number of 3 doses (range, 1-9). Only treated patients are included in analyses. The median time to first INO dose was 84 days (range, 47-100) after alloHCT. There was one DLT (prolonged thrombocytopenia) and the study reached the final pre-defined dose of 0.6mg/m2. No VOD was observed. The most common toxicity was thrombocytopenia (42.1% of patients; 31.6% experienced grade 3 or 4 thrombocytopenia), neutropenia (31.6% of patients, 15.8% experienced grade 3 or 4 neutropenia), and nausea/vomiting (42% of patients, all grade 1 or 2). 68% of patients received reduced intensity or non-myeloablative conditioning. OS at 1-year post-alloHCT was 94.4% and PFS was 88.9%. One-year NRM was 5.5%. One patient died of aGVHD on 0.6mg/m2 and one patient relapsed on 0.5mg/m2 at 7 months post-alloHCT. Another patient relapsed from Ph-like ALL 23 months post-alloHCT. Seven of the patients enrolled either had MRD before (n = 4) or after alloHCT (n = 3) as measured by flow cytometry, PCR, or NGS. For patients with MRD before or after alloHCT, 1-year OS and PFS are 100% (Figure 1). The 1-year PFS and OS of recipients of RIC transplants was 83.3% and 91.7%. Conclusions: We have determined that INO at doses of 0.3, 0.4, 0.5 and 0.6mg/m2 was well tolerated and that 0.6 mg/m2 is the MTD. Thrombocytopenia may be the DLT. The low observed relapse rate and favorable safety profile justify investigating low-dose INO as maintenance therapy after alloHCT in a phase II trial. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Pediatric Preclinical Testing Consortium Evaluation of the MCL1 Inhibitor, AMG 176, Against Xenograft Models of Acute Lymphoblastic Leukemia

Introduction: Children diagnosed with acute lymphoblastic leukemia (ALL) experience close to a 90% likelihood of cure, however the outcome for high-risk subtypes remains poor. Evasion of apoptosis is a hallmark of cancer, with dysregulation of the BCL-2 family of proteins often reported (Delbridge et al, Nat Rev Cancer 16:99-109, 2016). The BCL-2 family consists of the anti-apoptotic MCL1, BCL-2 and BCLXL as well as pro-apoptotic proteins. AMG 176, a first-in-class MCL1 inhibitor, previously demonstrated potent apoptosis-inducing activity in the nanomolar range against cell lines and patient explants of human hematological malignancies (Caenepeel et al, Cancer Discov 8:1582-97, 2018). Furthermore, discontinuous oral administration of AMG 176 inhibited the growth of human acute myeloid leukemia and multiple myeloma tumor xenografts in vivo at well-tolerated doses. AMG 176 has entered clinical evaluation for patients with hematological malignancies. Therefore, it was of interest for the Pediatric Preclinical Testing Consortium (PPTC) to evaluate the in vivo efficacy of AMG 176 against its patient-derived xenograft (PDX) models of pediatric ALL. Methods:MCL1, BCL-2 and BCLXL mRNA expression was quantified by RNA-seq (http://pedcbioportal.kidsfirstdrc.org). For in vitro cytotoxicity assays, cells were treated with AMG 176 (10 μM - 1 pM) or DMSO control for 24 h and cell viability was determined by AlamarBlue assay and expressed as IC50values. AMG 176 was evaluated in vivo against a panel of 38 ALL PDXs in a single mouse trial format. Each PDX was inoculated via tail vein injection into one NSG mouse (1-5 x 106 cells per mouse). Engraftment and drug responses were determined by enumerating the proportion of human versus mouse CD45+ (%huCD45+) cells in the peripheral blood (PB) at weekly intervals. Treatment with AMG 176 (provided by Amgen, Inc.) began once the %huCD45+ was ≥1% in each mouse and consisted of 60 mg/kg via oral gavage 2 days on, 5 days off for 2 weeks. The experimental endpoint was pre-defined as the %huCD45+ reaching 25% in the PB. Drug efficacy was assessed by event-free survival (EFS) and stringent objective response measures (Houghton et al, Pediatr Blood Cancer 49:928-40, 2007). For the pharmacokinetic (PK) study naïve NSG mice were treated with either vehicle or AMG 176 (60 mg/kg) and groups of 3 mice harvested up to 24 h post-treatment. Plasma samples were collected for analysis of AMG 176 using acetonitrile protein precipitation and LC-MS/MS with gradient elution on a Phenomenex Kinetex XB-C18 (3.0 x 50 mm, 2.6 µm) analytical column. Results:MCL1 mRNA expression ranged from 21-282 FPKM across a panel of 90 ALL PDXs representing 6 broad ALL subtypes (B-cell precursor, BCP-ALL; Ph+-ALL; Ph-like ALL; mixed-lineage leukemia-rearranged, MLLr-ALL; T-cell ALL, T-ALL; and early T-cell precursor ALL, ETP-ALL). Thirty eight of the 90 ALL PDXs were selected for in vivo evaluation of AMG 176 activity based on their profiles of MCL1, BCL-2 and BCLXL mRNA expression. AMG 176 was well tolerated in the efficacy study, with only 3 mice experiencing >10% weight loss. Mouse EFS values ranged from 3.5 to 47.8 days from treatment initiation, however no PDX achieved an objective response (remission) with all but one PDX exhibiting progressive disease. The Ph-like ALL PDX, ALL-102 (MCL1 expression 71.8 FPKM) scored a stable disease and had the highest EFS value (47.8 days). In an effort to explain the poor in vivo activity of AMG 176 several follow-up studies were performed. First, the in vitro IC50 values elicited by the AMG-176 stock against 5 leukemia cell lines (MOLM-13, 1.6 µM; NB-4, 2.0 µM; Kasumi-1, 1.6 µM; THP-1, 1.2 µM; and U-937,1.3 µM) were comparable to published data. Second, C18 LC-MS analysis revealed major and minor peaks consistent with theoretical peaks with negligible degradation. Third, PK study results demonstrated that the AMG 176 plasma concentration peaked at 8.5 µM, one hour after administration, with an AUC of 87.7 µM*hr and t1/2 of 4.1 h. This AUC was markedly lower than that in athymic nude mice treated at the same dose (1,120 µM*hr). Conclusions: AMG 176 exhibited modest in vivo activity against a large range of pediatric ALL PDXs, with the best response defined as stable disease in a single PDX. PK data suggest that AMG 176 systemic exposures in NSG mice may not be sufficient to elicit meaningful and prolonged regressions in pediatric ALL PDXs. (Supported by NCI Grants CA199000 and CA199222)