The Role of CAR T-Cell Therapy in Relapsed/Refractory Adult B-ALL.

CAR T-cell therapy is a recent therapeutic advancement that has transformed the management of relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL). To date, there are 2 FDA-approved CAR-T products for R/R B-ALL: tisagenlecleucel in patients aged <26 years and brexucabtagene autoleucel in those aged ≥18 years. This review summarizes the pivotal clinical trials that led to FDA approval of these 2 products and highlight emerging data addressing key questions pertinent to CAR-T utilization in the rapidly evolving landscape of R/R ALL management. These include optimal sequencing of CAR-T among other novel immunotherapeutic agents, the role of consolidation and maintenance following CAR-T, novel CAR-T constructs currently under clinical development, and strategies to optimize use of commercially available CAR-T products to improve patient outcomes.

KTE-X19 anti-CD19 CAR T-cell therapy in adult relapsed/refractory acute lymphoblastic leukemia: ZUMA-3 phase 1 results.

ZUMA-3 is a phase 1/2 study evaluating KTE-X19, an autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy, in adult relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL). We report the phase 1 results. After fludarabine-cyclophosphamide lymphodepletion, patients received a single infusion of KTE-X19 at 2 × 106, 1 × 106, or 0.5 × 106 cells per kg. The rate of dose-limiting toxicities (DLTs) within 28 days after KTE-X19 infusion was the primary end point. KTE-X19 was manufactured for 54 enrolled patients and administered to 45 (median age, 46 years; range, 18-77 years). No DLTs occurred in the DLT-evaluable cohort. Grade ≥3 cytokine release syndrome (CRS) and neurologic events (NEs) occurred in 31% and 38% of patients, respectively. To optimize the risk-benefit ratio, revised adverse event (AE) management for CRS and NEs (earlier steroid use for NEs and tocilizumab only for CRS) was evaluated at 1 × 106 cells per kg KTE-X19. In the 9 patients treated under revised AE management, 33% had grade 3 CRS and 11% had grade 3 NEs, with no grade 4 or 5 NEs. The overall complete remission rate correlated with CAR T-cell expansion and was 83% in patients treated with 1 × 106 cells per kg and 69% in all patients. Minimal residual disease was undetectable in all responding patients. At a median follow-up of 22.1 months (range, 7.1-36.1 months), the median duration of remission was 17.6 months (95% confidence interval [CI], 5.8-17.6 months) in patients treated with 1 × 106 cells per kg and 14.5 months (95% CI, 5.8-18.1 months) in all patients. KTE-X19 treatment provided a high response rate and tolerable safety in adults with R/R B-ALL. Phase 2 is ongoing at 1 × 106 cells per kg with revised AE management. This trial is registered at www.clinicaltrials.gov as #NCT02614066.

Sequencing antigen-targeting antibodies and cellular therapies in adults with relapsed/refractory B-cell acute lymphoblastic leukemia.

The recent approvals of four CD19-or CD22-targeted therapies for B-cell acute lymphoblastic leukemia (B-ALL) have transformed the treatment of relapsed/refractory (r/r) disease. Adults with r/r B-ALL are usually eligible for all options, but there are no studies directly comparing these agents, and the treating physician must decide which to select. Each therapy has notable activity as a single agent but has limitations in particular settings, and the optimal choice varies. These therapies can be complementary and used either sequentially or concomitantly. Here, we review the current landscape of antigen-targeted therapies for r/r B-ALL and discuss considerations for their use.

Characterisation of infections in patients with acute myeloid leukaemia receiving venetoclax and a hypomethylating agent.

We investigated the incidence of invasive fungal infections (IFIs) and other infectious complications in patients receiving venetoclax and hypomethylating agent therapy for acute myeloid leukaemia (AML). This retrospective, multicentre cohort study included adult patients with AML who received at least one cycle of venetoclax and either azacitidine or decitabine between January 2016 and August 2020. The primary outcome was the incidence of probable or confirmed IFI. Secondary outcomes included antifungal prophylaxis prescribing patterns, incidence of bacterial infections, and incidence of neutropenic fever hospital admissions. Among 235 patients, the incidence of probable or confirmed IFI was 5.1%. IFI incidence did not differ significantly according to age, antifungal prophylaxis use, or disease status. In the subgroup of patients with probable or confirmed IFIs, six (50%) were receiving antifungal prophylaxis at the time of infection. The overall incidence of developing at least one bacterial infection was 33.6% and 127 (54%) patients had at least one hospital admission for febrile neutropenia. This study demonstrated an overall low risk of developing probable or confirmed IFI as well as a notable percentage of documented bacterial infections and hospital admissions due to neutropenic fever.

KTE-X19 for relapsed or refractory adult B-cell acute lymphoblastic leukaemia: phase 2 results of the single-arm, open-label, multicentre ZUMA-3 study.

BACKGROUND: Despite treatment with novel therapies and allogeneic stem-cell transplant (allo-SCT) consolidation, outcomes in adult patients with relapsed or refractory B-precursor acute lymphoblastic leukaemia remain poor, underlining the need for more effective therapies. METHODS: We report the pivotal phase 2 results of ZUMA-3, an international, multicentre, single-arm, open-label study evaluating the efficacy and safety of the autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy KTE-X19 in adult patients with relapsed or refractory B-precursor acute lymphoblastic leukaemia. Patients were enrolled at 25 sites in the USA, Canada, and Europe. Eligible patients were aged 18 years or older, with Eastern Cooperative Oncology Group performance status of 0-1, and morphological disease in the bone marrow (>5% blasts). After leukapheresis and conditioning chemotherapy, patients received a single KTE-X19 infusion (1 × 106 CAR T cells per kg bodyweight). The primary endpoint was the rate of overall complete remission or complete remission with incomplete haematological recovery by central assessment. Duration of remission and relapse-free survival, overall survival, minimal residual disease (MRD) negativity rate, and allo-SCT rate were assessed as secondary endpoints. Efficacy and safety analyses were done in the treated population (all patients who received a dose of KTE-X19). This study is registered with ClinicalTrials.gov, NCT02614066. FINDINGS: Between Oct 1, 2018, and Oct 9, 2019, 71 patients were enrolled and underwent leukapheresis. KTE-X19 was successfully manufactured for 65 (92%) patients and administered to 55 (77%). The median age of treated patients was 40 years (IQR 28-52). At the median follow-up of 16·4 months (13·8-19·6), 39 patients (71%; 95% CI 57-82, p<0·0001) had complete remission or complete remission with incomplete haematological recovery, with 31 (56%) patients reaching complete remission. Median duration of remission was 12·8 months (95% CI 8·7-not estimable), median relapse-free survival was 11·6 months (2·7-15·5), and median overall survival was 18·2 months (15·9-not estimable). Among responders, the median overall survival was not reached, and 38 (97%) patients had MRD negativity. Ten (18%) patients received allo-SCT consolidation after KTE-X19 infusion. The most common adverse events of grade 3 or higher were anaemia (27 [49%] patients) and pyrexia (20 [36%] patients). 14 (25%) patients had infections of grade 3 or higher. Two grade 5 KTE-X19-related events occurred (brain herniation and septic shock). Cytokine release syndrome of grade 3 or higher occurred in 13 (24%) patients and neurological events of grade 3 or higher occurred in 14 (25%) patients. INTERPRETATION: KTE-X19 showed a high rate of complete remission or complete remission with incomplete haematological recovery in adult patients with relapsed or refractory B-precursor acute lymphoblastic leukaemia, with the median overall survival not reached in responding patients, and a manageable safety profile. These findings indicate that KTE-X19 has the potential to confer long-term clinical benefit to these patients. FUNDING: Kite, a Gilead Company.

Anthracyclines in a patient with acute leukemia and severe cardiomyopathy requiring mechanical support: A case report.

INTRODUCTION: For young adult patients with acute leukemia, both the efficacy and cardiotoxicity of anthracycline-based regimens have been documented. We report the case of a patient with severe cardiomyopathy, mechanically supported by a left ventricular assist device (LVAD), who subsequently developed Philadelphia-chromosome positive acute lymphoblastic leukemia (Ph + ALL). To our knowledge, this is the first report of anthracycline administration in a patient with heart failure requiring mechanical support. CASE REPORT: Our 27-year-old female patient was diagnosed with Ph + B-ALL as part of workup for leukocytosis. Past medical history included non-ischemic cardiomyopathy with a left ventricular ejection fraction of 30-35% and moderate-severe right ventricular dysfunction, for which LVAD had been placed 4 years previously. MANAGEMENT & OUTCOME: After shared decision-making and multidisciplinary discussions, we felt that hyperfractionated cyclophosphamide, doxorubicin, vincristine, and dexamethasone alternating with cytarabine and high-dose methotrexate in addition to ponatinib (HyperCVAD-ponatinib) best balanced the patient's goals for aggressive treatment with the potential for rapid and durable remissions. The patient received a single reduced dose of doxorubicin alongside dexrazoxane with her first cycle of HyperCVAD-ponatinib. She attained a complete molecular response 22 days later and remains in remission (with stable cardiac function) 30 months later on maintenance therapy. DISCUSSION: In conclusion, LVAD placement is not an absolute contra-indication to anthracyclines if such therapies offer the best opportunity for a durable response.

Anti-CD117 antibody depletes normal and myelodysplastic syndrome human hematopoietic stem cells in xenografted mice.

The myelodysplastic syndromes (MDS) represent a group of clonal disorders that result in ineffective hematopoiesis and are associated with an increased risk of transformation into acute leukemia. MDS arises from hematopoietic stem cells (HSCs); therefore, successful elimination of MDS HSCs is an important part of any curative therapy. However, current treatment options, including allogeneic hematopoietic cell transplantation (HCT), often fail to ablate disease-initiating MDS HSCs, and thus have low curative potential and high relapse rates. Here, we demonstrate that human HSCs can be targeted and eliminated by monoclonal antibodies (mAbs) that bind cell-surface CD117 (c-Kit). We show that an anti-human CD117 mAb, SR-1, inhibits normal cord blood and bone marrow HSCs in vitro. Furthermore, SR-1 and clinical-grade humanized anti-human CD117 mAb, AMG 191, deplete normal and MDS HSCs in vivo in xenograft mouse models. Anti-CD117 mAbs also facilitate the engraftment of normal donor human HSCs in MDS xenograft mouse models, restoring normal human hematopoiesis and eradicating aggressive pathologic MDS cells. This study is the first to demonstrate that anti-human CD117 mAbs have potential as novel therapeutics to eradicate MDS HSCs and augment the curative effect of allogeneic HCT for this disease. Moreover, we establish the foundation for use of these antibody agents not only in the treatment of MDS but also for the multitude of other HSC-driven blood and immune disorders for which transplant can be disease-altering.

Bimodal expression of potential drug target CLL-1 (CLEC12A) on CD34+ blasts of AML patients.

OBJECTIVES: This study aims to retrospectively assess C-lectin-like molecule 1 (CLL-1) bimodal expression on CD34+ blasts in acute myeloid leukemia (AML) patients (total N = 306) and explore potential CLL-1 bimodal associations with leukemia and patient-specific characteristics. METHODS: Flow cytometry assays were performed to assess the deeper immunophenotyping of CLL-1 bimodality. Cytogenetic analysis was performed to characterize the gene mutation on CLL-1-negative subpopulation of CLL-1 bimodal AML samples. RESULTS: The frequency of a bimodal pattern of CLL-1 expression of CD34+ blasts ranged from 8% to 65% in the different cohorts. Bimodal CLL-1 expression was most prevalent in patients with MDS-related AML (P = .011), ELN adverse risk (P = .002), NPM1 wild type (WT, P = .049), FLT3 WT (P = .035), and relatively low percentages of leukemia-associated immunophenotypes (P = .006). Additional immunophenotyping analysis revealed the CLL-1- subpopulation may consist of pre-B cells, immature myeloblasts, and hematopoietic stem cells. Furthermore, (pre)-leukemic mutations were detected in both CLL-1+ and CLL-1- subfractions of bimodal samples (N = 3). CONCLUSIONS: C-lectin-like molecule 1 bimodality occurs in about 25% of AML patients and the CLL-1- cell population still contains malignant cells, hence it may potentially limit the effectiveness of CLL-1-targeted therapies and warrant further investigation.

Functional Status as Measured by Geriatric Assessment Predicts Inferior Survival in Older Allogeneic Hematopoietic Cell Transplantation Recipients.

Allogeneic hematopoietic cell transplantation (alloHCT) has been increasingly offered to older adults with hematologic malignancies. However, optimal methods to determine fitness for alloHCT have yet to be defined. We evaluated the ability of a comprehensive geriatric assessment (CGA) to predict post-alloHCT outcomes in a single-center prospective cohort study of patients age 50 years and older. Outcomes included overall survival (OS), progression-free survival (PFS), and nonrelapse mortality (NRM). A total of 148 patients were included, with a median age of 62 years (range, 50 to 76 years). In multivariate regression analysis, several CGA measures of functional status were predictive of post-alloHCT outcomes, after adjusting for traditional prognostic factors. Any deficit in instrumental activities of daily living (IADL) was associated with inferior OS (hazard ratio [HR], 1.81, 95% confidence interval [CI], 1.07 to 3.08; P = .03) and PFS (HR, 1.85; 95% CI, 1.15 to 2.99; P = .01). A Medical Outcomes Study Physical Health scale (MOS-PH) score <85 was associated with inferior OS (HR, 1.96; 95% CI, 1.13 to 3.40; P = .02), PFS (HR, 1.75; 95% CI, 1.07 to 2.88; P = .03), and increased NRM (subdistribution HR, 2.57; 95% CI, 1.12 to 5.92; P = .03). MOS-PH score was also associated with the number of non-hematologic grade ≥3 adverse events within the first 100 days after alloHCT (rate ratio, 1.61; 95% CI, 1.04 to 2.49; P = .03). These findings support previous work suggesting that IADL is an important prognostic tool prior to alloHCT. MOS-PH is newly identified as an additional metric to identify older patients at higher risk of poor post-alloHCT outcomes, including toxicity and NRM.

Phase 2 Study of Anti-Human Cytomegalovirus Monoclonal Antibodies for Prophylaxis in Hematopoietic Cell Transplantation.

Human cytomegalovirus (HCMV) can cause significant disease in immunocompromised patients, and treatment options are limited by toxicities. CSJ148 is a combination of two anti-HCMV human monoclonal antibodies (LJP538 and LJP539) that bind to and inhibit the functions of viral HCMV glycoprotein B (gB) and the pentameric complex, consisting of glycoproteins gH, gL, UL128, UL130, and UL131. In this phase 2, randomized, placebo-controlled trial, we evaluated the safety and efficacy of CSJ148 for prophylaxis of HCMV in patients undergoing allogeneic hematopoietic stem cell transplantation. As would be expected in the study population, all the patients (100%) reported at least one treatment-emergent adverse event. There were 22 deaths during this study, and over 80% of the patients receiving placebo or CSJ148 developed at least one adverse event of grade 3 or higher severity. No subject who received antibody developed a hypersensitivity- or infusion-related reaction. CSJ148-treated patients showed trends toward decreased viral load, shorter median duration of preemptive therapy, and fewer courses of preemptive therapy. However, the estimated probability that CSJ148 decreases the need for preemptive therapy compared to placebo was 69%, with a risk ratio of 0.89 and a 90% credible interval of 0.61 to 1.31. The primary efficacy endpoint was therefore not met, indicating that CSJ148 did not prevent clinically significant HCMV reactivation in recipients of allogeneic hematopoietic cell transplants. (This study has been registered at ClinicalTrials.gov under identifier NCT02268526 and at EudraCT under number 2017-002047-15.).

Limitation in Patient-Reported Function Is Associated with Inferior Survival in Older Adults Undergoing Autologous Hematopoietic Cell Transplantation.

Although the use of geriatric assessment (GA) in the allogeneic hematopoietic cell transplantation (HCT) setting has been reported, few studies have evaluated the impact of patient-reported function on autologous HCT (autoHCT) outcomes. In this study, GA, including the administration of Functional Assessment of Cancer Therapy-Bone Marrow Transplant (FACT-BMT) quality of life tool, was performed in 184 patients age ≥50 years (median age, 61 years; range, 50 to 75 years) before autoHCT. Associations among GA findings, quality of life metrics, and post-transplantation outcomes were evaluated using Cox regression. Indications for autoHCT included multiple myeloma (73%), non-Hodgkin lymphoma (20%), and other disorders (7%). The median progression-free survival (PFS) was 28 months, whereas the median overall survival (OS) was not reached. In unadjusted analysis, both PFS and OS were significantly associated with 5 GA components: limitation in instrumental activities of daily living, patient-reported Karnofsky Performance Status (KPS), and the Physical, Functional, and BMT subscale scores of the FACT-BMT. In multivariate analysis, 3 components-limitation in instrumental activities of daily living, patient-reported KPS, and FACT-BMT Physical subscale-remained predictive of both PFS and OS when adjusted for age, provider-reported KPS, disease status, and HCT comorbidity index. In older adults undergoing autoHCT, limitation in any 1 of 3 patient-reported measures of functional status was independently associated with inferior PFS and OS, even after adjusting for known prognostic factors.

Ibrutinib for Chronic Graft-versus-Host Disease After Failure of Prior Therapy: 1-Year Update of a Phase 1b/2 Study.

Chronic graft-versus-host disease (cGVHD) is a life-threatening complication of allogeneic stem cell transplantation. In a Phase 1b/2, open-label study (PCYC-1129; ClinicalTrials.gov identifier NCT02195869) involving 42 patients with active cGVHD who were steroid-dependent or -refractory, the activity and safety of ibrutinib, a once-daily inhibitor of Bruton's tyrosine kinase, was demonstrated. Here we report extended follow-up for patients in this study. After a median follow-up of 26 months (range, .53 to 36.7 months), best overall response rate in the all treated population was 69% (29 of 42), with 13 patients (31%) achieving a complete response and 16 patients (38%) achieving a partial response. Sustained responses of ≥20, ≥32, and ≥44 weeks were seen in 20 (69%), 18 (62%), and 16 (55%) of the 29 responders, respectively. Of 26 patients with ≥2 involved organs, 19 (73%) showed responses in ≥2 organs. Six of 10 patients (60%) with ≥3 involved organs showed responses in ≥3 organs. Eleven of 18 patients (61%) who had sclerosis at baseline showed a sclerotic response (39% with complete response, 22% with partial response). Twenty-seven of 42 patients (64%) reached a corticosteroid dose of <.15 mg/kg/day during the study; 8 discontinued corticosteroid treatment and remained off corticosteroid at study closure. Safety findings for this updated analysis were consistent with the safety profile seen at the time of the original analysis. Common grade ≥3 adverse events (AEs) were pneumonia (n = 6), fatigue (n = 5), and diarrhea (n = 4). The onset of new grade ≥3 AEs decreased from 71% in the first year of treatment to 25% in the second year (n = 12). AEs leading to discontinuation occurred in 18 patients (43%). At a median follow-up of >2 years, ibrutinib continued to produce durable responses in patients with cGVHD who had failed previous systemic therapy. In this pretreated, high-risk population, clinically meaningful benefit and an acceptable safety profile were observed with additional follow-up for ibrutinib. These results demonstrate a substantial advance in the therapeutic management of patients with cGVHD.

Ibrutinib for chronic graft-versus-host disease after failure of prior therapy.

Chronic graft-versus-host disease (cGVHD) is a serious complication of allogeneic stem cell transplantation with few effective options available after failure of corticosteroids. B and T cells play a role in the pathophysiology of cGVHD. Ibrutinib inhibits Bruton tyrosine kinase in B cells and interleukin-2-inducible T-cell kinase in T cells. In preclinical models, ibrutinib reduced severity of cGVHD. This multicenter, open-label study evaluated the safety and efficacy of ibrutinib in patients with active cGVHD with inadequate response to corticosteroid-containing therapies. Forty-two patients who had failed 1 to 3 prior treatments received ibrutinib (420 mg) daily until cGVHD progression. The primary efficacy end point was cGVHD response based on 2005 National Institutes of Health criteria. At a median follow-up of 13.9 months, best overall response was 67%; 71% of responders showed a sustained response for ≥20 weeks. Responses were observed across involved organs evaluated. Most patients with multiple cGVHD organ involvement had a multiorgan response. Median corticosteroid dose in responders decreased from 0.29 mg/kg per day at baseline to 0.12 mg/kg per day at week 49; 5 responders discontinued corticosteroids. The most common adverse events were fatigue, diarrhea, muscle spasms, nausea, and bruising. Plasma levels of soluble factors associated with inflammation, fibrosis, and cGVHD significantly decreased over time with ibrutinib. Ibrutinib resulted in clinically meaningful responses with acceptable safety in patients with ≥1 prior treatments for cGVHD. Based on these results, ibrutinib was approved in the United States for treatment of adult patients with cGVHD after failure of 1 or more lines of systemic therapy. This trial was registered at www.clinicaltrials.gov as #NCT02195869.

Recommendations for the assessment and management of measurable residual disease in adults with acute lymphoblastic leukemia: A consensus of North American experts.

Measurable residual disease (MRD) that persists after initial therapy is a powerful predictor of relapse and survival in acute lymphoblastic leukemia (ALL). However, the optimal use of this information to influence therapeutic decisions is controversial. Herein, we comprehensively review the role of MRD assessment in adults with ALL, including methods to quantify residual leukemia cells during remission, prognostic impact of MRD across ALL subtypes, and available therapeutic approaches to eradicate MRD. This review presents consensus statements and provides an evidence-based framework for practicing hematologists and oncologists to use MRD information to make rational treatment decisions in adult patients with ALL.

Ibrutinib efficacy and tolerability in patients with relapsed chronic lymphocytic leukemia following allogeneic HCT.

Ibrutinib, a potent and irreversible small-molecule inhibitor of both Bruton's tyrosine kinase and interleukin-2 inducible kinase (ITK), has been used to treat relapsed/refractory chronic lymphocytic leukemia (CLL) with prolongation of progression-free and overall survival. Here, we present 27 patients with relapsed CLL following allogeneic hematopoietic cell transplant (HCT) who subsequently received ibrutinib salvage therapy. Sixteen of these patients were part of multi-institutional clinical trials and achieved an overall response rate of 87.5%. An additional 11 patients were treated at Stanford University following US Food and Drug Administration approval of ibrutinib; 7 (64%) achieved a complete response, and 3 (27%) achieved a partial response. Of the 9 patients treated at Stanford who had mixed chimerism-associated CLL relapse, 4 (44%) converted to full donor chimerism following ibrutinib initiation, in association with disease response. Four of 11 (36%) patients evaluated by ClonoSeq achieved minimal residual disease negativity with CLL <1/10 000 white blood cells, which persisted even after ibrutinib was discontinued, in 1 case even after 26 months. None of the 27 patients developed graft-versus-host-disease (GVHD) following ibrutinib initiation. We postulate that ibrutinib augments the graft-versus-leukemia (GVL) benefit through a T-cell-mediated effect, most likely due to ITK inhibition. To investigate the immune modulatory effects of ibrutinib, we completed comprehensive immune phenotype characterization of peripheral B and T cells from treated patients. Our results show that ibrutinib selectively targets pre-germinal B cells and depletes Th2 helper cells. Furthermore, these effects persisted after drug discontinuation. In total, our results provide evidence that ibrutinib effectively augments GVL without causing GVHD.

Mechanistic rationale for targeting the unfolded protein response in pre-B acute lymphoblastic leukemia.

The unfolded protein response (UPR) pathway, a stress-induced signaling cascade emanating from the endoplasmic reticulum (ER), regulates the expression and activity of molecules including BiP (HSPA5), IRE1 (ERN1), Blimp-1 (PRDM1), and X-box binding protein 1 (XBP1). These molecules are required for terminal differentiation of B cells into plasma cells and expressed at high levels in plasma cell-derived multiple myeloma. Although these molecules have no known role at early stages of B-cell development, here we show that their expression transiently peaks at the pre-B-cell receptor checkpoint. Inducible, Cre-mediated deletion of Hspa5, Prdm1, and Xbp1 consistently induces cellular stress and cell death in normal pre-B cells and in pre-B-cell acute lymphoblastic leukemia (ALL) driven by BCR-ABL1- and NRAS(G12D) oncogenes. Mechanistically, expression and activity of the UPR downstream effector XBP1 is regulated positively by STAT5 and negatively by the B-cell-specific transcriptional repressors BACH2 and BCL6. In two clinical trials for children and adults with ALL, high XBP1 mRNA levels at the time of diagnosis predicted poor outcome. A small molecule inhibitor of ERN1-mediated XBP1 activation induced selective cell death of patient-derived pre-B ALL cells in vitro and significantly prolonged survival of transplant recipient mice in vivo. Collectively, these studies reveal that pre-B ALL cells are uniquely vulnerable to ER stress and identify the UPR pathway and its downstream effector XBP1 as novel therapeutic targets to overcome drug resistance in pre-B ALL.

Multigene Measurable Residual Disease Assessment Improves Acute Myeloid Leukemia Relapse Risk Stratification in Autologous Hematopoietic Cell Transplantation.

We report here the largest study to date of adult patients with acute myeloid leukemia (AML) tested for measurable residual disease (MRD) at the time of autologous hematopoietic cell transplantation (auto-HCT). Seventy-two adult patients who underwent transplantation between 2004 and 2013 at a single academic medical center (University of California San Francisco) were eligible for this retrospective study based on availability of cryopreserved granulocyte colony-stimulating factor (GCSF)-mobilized autologous peripheral blood progenitor cell (PBPC) leukapheresis specimens ("autografts"). Autograft MRD was assessed by molecular methods (real-time quantitative PCR [RQ-PCR] for Wilms tumor 1 (WT1) alone or a multigene panel) and by multiparameter flow cytometry (MPFC). WT1 RQ-PCR testing of the autograft had low sensitivity for relapse prediction (14%) and a negative predictive value of 51%. MPFC failed to identify MRD in any of 34 autografts tested. Combinations of molecular MRD assays, however, improved prediction of post-auto-HCT relapse. In multivariate analysis of clinical variables, including age, gender, race, cytogenetic risk category, and CD34+ cell dose, only autograft multigene MRD as assessed by RQ-PCR was statistically significantly associated with relapse. One year after transplantation, only 28% patients with detectable autograft MRD were relapse free, compared with 67% in the MRD-negative cohort. Multigene MRD, while an improvement on other methods tested, was however suboptimal for relapse prediction in unselected patients, with specificity of 83% and sensitivity of 46%. In patients with known chromosomal abnormalities or mutations, however, better predictive value was observed with no relapses observed in MRD-negative patients in the first year after auto-HCT compared with 83% incidence of relapse in the MRD-positive patients (hazard ratio, 12.45; P = .0016). In summary, increased personalization of MRD monitoring by use of a multigene panel improved the ability to risk stratify patients for post-auto-HCT relapse. WT1 RQ-PCR and flow cytometric assessment for AML MRD in autograft samples had limited value for predicting relapse after auto-HCT. We demonstrate that cryopreserved autograft material presents unique challenges for AML MRD testing because of the masking effects of previous GCSF exposure on gene expression and flow cytometry signatures. In the absence of information regarding diagnostic characteristics, sources other than GCSF-stimulated PBSC leukapheresis specimens should be considered as alternatives for MRD testing in AML patients undergoing auto-HCT.

Quantification of Acute Lymphoblastic Leukemia Clonotypes in Leukapheresed Peripheral Blood Progenitor Cells Predicts Relapse Risk after Autologous Hematopoietic Stem Cell Transplantation.

Since the incorporation of tyrosine kinase inhibitors into the treatment of Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL), the notion that all patients with "high-risk" ALL uniformly require allogeneic (allo) hematopoietic cell transplantation (HCT) has received increasing scrutiny. Although multiple studies have shown superiority of alloHCT over autologous (auto) hematopoietic cell transplantation for high-risk patients, these findings may be explained, in part, by contamination of the peripheral blood progenitor cell (PBPC) leukapheresis product by residual leukemic cells in patients undergoing autoHCT. We retrospectively evaluated minimal residual disease (MRD) using next-generation sequencing (NGS) in the PBPC leukapheresis product of 32 ALL patients who underwent autoHCT. Twenty-eight patients (88%) had diagnostic samples with quantifiable immunoreceptor rearrangements to follow for MRD. Twelve (38%) patients had Ph+ B-ALL, 12 (38%) had Philadelphia chromosome-negative (Ph-) B-ALL, and 4 (14%) had T cell ALL. With a median follow-up of 41 months (range, 3 to 217), median relapse-free survival (RFS) and overall survival for the entire cohort were 3.2 and 4.2 years, respectively; at 5 years after transplantation, 42% of patients remain alive and relapse free. Using MRD detection at a threshold of ≥ 1 × 10(-6), median RFS for patients with detectable MRD was 6.5 months and was not reached for patients without detectable disease (P = .0005). In multivariate analysis, the only factor significantly associated with relapse was the presence of MRD ≥1 × 10(-6) (odds ratio, 23.8; confidence interval, 1.8 to 312.9; P = .0158). Our findings suggest that NGS for MRD detection can predict long-term RFS in patients undergoing autoHCT for high-risk ALL.