CD22 CAR T cells demonstrate high response rates and safety in pediatric and adult B-ALL: Phase 1b results

Chimeric antigen receptor (CAR) T cells targeting CD22 (CD22-CAR) provide a therapeutic option for patients with CD22+ malignancies with progression after CD19-directed therapies. Using on-site, automated, closed-loop manufacturing, we conducted parallel Phase 1b clinical trials investigating a humanized CD22-CAR with 41BB costimulatory domain in children and adults with heavily treated, relapsed/refractory (r/r) B-ALL. Of 19 patients enrolled, 18 had successful CD22-CAR manufacturing, and 16 patients were infused. High grade (3-4) cytokine release syndrome (CRS) and immune effector-cell-associated neurotoxicity syndrome (ICANS) each occurred in only one patient; however, three patients experienced immune-effector-cell-associated hemophagocytic lymphohistiocytosis-like syndrome (IEC-HS). Twelve of 16 patients (75%) achieved CR with an overall 56% MRD-negative CR rate. Duration of response was overall limited (median 77 days), and CD22 expression was downregulated in 4/12 (33%) available samples at relapse. In summary, we demonstrate that closed-loop manufacturing of CD22-CAR T cells is feasible and is associated with a favorable safety profile and high CR rates in pediatric and adult r/r B-ALL, a cohort with limited CD22-CAR reporting.

Management of post-autologous transplant relapse in patients with T-cell lymphomas

Autologous hematopoietic cell transplantation (AHCT) is often used as a consolidation for patients with peripheral T-cell lymphomas (PTCLs) due to the poor prognosis associated with this heterogenous group of disorders. However, a significant number of patients will experience post-AHCT disease relapse. Here, we report a retrospective study of consecutive 124 patients with PTCLs who underwent AHCT from 2008 to 2020. With a median follow-up of 6.01 years following AHCT, 49 patients (40%) experienced disease relapse. As expected, more patients who were not in first complete remission experienced post-AHCT relapse. Following relapse, majority of the patients (70%) receiving systemic therapies intended as bridging to curative allogeneic HCT. However, only 18 (53%) patients eventually underwent allogeneic HCT. The estimated 3-year OS among patients proceeding to allogeneic HCT was 72% (95% CI 46%-87%). Our report details the pattern of post-AHCT relapse and the management of relapsed disease using different therapeutic modalities.

Utilization of Autologous Hematopoietic Cell Transplantation Over Time in Multiple Myeloma: A Population-Based Study

PURPOSE

Autologous hematopoietic cell transplantation (autoHCT) is associated with survival benefits in multiple myeloma (MM), but utilization remains low and differs by sociodemographic factors. Prior population-based studies have not fully captured autoHCT utilization or examined relationships between sociodemographic factors and autoHCT trends over time.

PATIENTS AND METHODS

We used a novel data linkage between the California Cancer Registry, Center for International Blood and Marrow Transplant Research, and hospitalizations to capture autoHCT in a population-based MM cohort (n = 29, 109; 1991-2016). Due to interactions by treatment era, stratified multivariable Cox proportional hazards regression models determined factors associated with autoHCT.

RESULTS

The frequency of MM patients who received autoHCT increased from 5.7% (1991-1995) to 27.4% (2011-2016). In models by treatment era, patients with public/no (vs. private) health insurance were less likely to receive autoHCT (2011-2016 Medicare hazard ratio (HR) 0.70, 95% confidence interval (CI): 0.63-0.78; Medicaid HR 0.81, CI: 0.72-0.91; no insurance HR 0.56, CI: 0.32-0.99). In each treatment era, Black/African American (vs. non-Hispanic White) patients were less likely to receive autoHCT (2011-2016 HR 0.83, CI: 0.72-0.95). Hispanic patients were less likely to undergo autoHCT, most prominently in the earliest treatment era (1991-1995 HR 0.58, 95% CI: 0.37-0.90; 2011-2016 HR 1.07, CI: 0.96-1.19). Patients in lower socioeconomic status neighborhoods were less likely to utilize autoHCT, but differences decreased over time.

CONCLUSIONS

Despite increases in autoHCT utilization, sociodemographic disparities remain. Identifying and mitigating barriers to autoHCT is essential to ensuring more equitable access to this highly effective therapy.

CAR19 monitoring by peripheral blood immunophenotyping reveals histology-specific expansion and toxicity

Chimeric antigen receptor (CAR) T cells directed against CD19 (CAR19) are a revolutionary treatment for B-cell lymphomas. CAR19 cell expansion is necessary for CAR19 function but is also associated with toxicity. To define the impact of CAR19 expansion on patient outcomes, we prospectively followed a cohort of 236 patients treated with CAR19 (brexucabtagene autoleucel or axicabtagene ciloleucel) for mantle cell (MCL), follicular (FL), and large B-cell lymphoma (LBCL) over the course of five years and obtained CAR19 expansion data using peripheral blood immunophenotyping for 188 of these patients. CAR19 expansion was higher in patients with MCL compared to other lymphoma histologic subtypes. Notably, patients with MCL had increased toxicity and required four-fold higher cumulative steroid doses than patients with LBCL. CAR19 expansion was associated with the development of cytokine release syndrome (CRS), immune effector cell associated neurotoxicity syndrome (ICANS), and the requirement for granulocyte colony stimulating factor (GCSF) after day 14 post-infusion. Younger patients and those with elevated lactate dehydrogenase (LDH) had significantly higher CAR19 expansion. In general, no association between CAR19 expansion and LBCL treatment response was observed. However, when controlling for tumor burden, we found that lower CAR19 expansion in conjunction with low LDH was associated with improved outcomes in LBCL. In sum, this study finds CAR19 expansion principally associates with CAR-related toxicity. Additionally, CAR19 expansion as measured by peripheral blood immunophenotyping may be dispensable to favorable outcomes in LBCL.

Gilteritinib as Post-Transplant Maintenance for Acute Myeloid Leukemia With Internal Tandem Duplication Mutation of FLT3

PURPOSE

Allogeneic hematopoietic cell transplantation (HCT) improves outcomes for patients with acute myeloid leukemia (AML) harboring an internal tandem duplication mutation of FLT3 (FLT3-ITD) AML. These patients are routinely treated with a FLT3 inhibitor after HCT, but there is limited evidence to support this. Accordingly, we conducted a randomized trial of post-HCT maintenance with the FLT3 inhibitor gilteritinib (ClinicalTrials.gov identifier: NCT02997202) to determine if all such patients benefit or if detection of measurable residual disease (MRD) could identify those who might benefit.

METHODS

Adults with FLT3-ITD AML in first remission underwent HCT and were randomly assigned to placebo or 120 mg once daily gilteritinib for 24 months after HCT. The primary end point was relapse-free survival (RFS). Secondary end points included overall survival (OS) and the effect of MRD pre- and post-HCT on RFS and OS.

RESULTS

Three hundred fifty-six participants were randomly assigned post-HCT to receive gilteritinib or placebo. Although RFS was higher in the gilteritinib arm, the difference was not statistically significant (hazard ratio [HR], 0.679 [95% CI, 0.459 to 1.005]; two-sided P = .0518). However, 50.5% of participants had MRD detectable pre- or post-HCT, and, in a prespecified subgroup analysis, gilteritinib was beneficial in this population (HR, 0.515 [95% CI, 0.316 to 0.838]; P = .0065). Those without detectable MRD showed no benefit (HR, 1.213 [95% CI, 0.616 to 2.387]; P = .575).

CONCLUSION

Although the overall improvement in RFS was not statistically significant, RFS was higher for participants with detectable FLT3-ITD MRD pre- or post-HCT who received gilteritinib treatment. To our knowledge, these data are among the first to support the effectiveness of MRD-based post-HCT therapy.

Comparison of Vital Status, Cause of Death, and Follow-Up after Hematopoietic Cell Transplantation in Linked Center for International Blood and Marrow Transplant Research and California Cancer Registry Data, 1991 to 2018

Assessing outcomes following hematopoietic cell transplantation (HCT) poses challenges due to the necessity for systematic and often prolonged patient follow-up. Linking the HCT database of the Center for International Blood and Marrow Transplant Research (CIBMTR) with cancer registry data may improve long-term outcome ascertainment, but the reliability of mortality data in death certificates from cancer registries among HCT recipients remains unknown. We compared the classification of vital status and primary cause of death (COD), as well as the length of follow-up between the CIBMTR and California Cancer Registry (CCR) to assess the possibility of supplementing the CIBMTR with cancer registry data. This retrospective study leveraged a linked CIBMTR-CCR dataset. We included patients who were California residents at the time of HCT and received a first allogeneic (allo) or autologous (auto) HCT for a hematologic malignancy diagnosed during 1991-2016. Follow-up was through 2018. We analyzed 18,450 patients (alloHCT, n = 8232; autoHCT, n = 10,218). The Vital status agreement was 97.7% for alloHCT and 97.2% for autoHCT. Unknown COD was higher in CIBMTR (12.9%) than in CCR (1.6%). After excluding patients with unknown COD information, the overall agreement of primary COD (cancer versus noncancer) was 53.7% for alloHCT and 83.2% for autoHCT. This agreement was lower within the first 100 days post-HCT (alloHCT, 31.0%; autoHCT, 54.6%). Compared with CIBMTR, deaths due to cancer were higher in CCR (alloHCT, 90.0%; autoHCT, 90.1% versus alloHCT, 47.3%; autoHCT, 82.5% in CIBMTR). CIBMTR reports more frequently noncancer-related deaths, including graft-versus-host disease and infections. The cumulative incidence of cancer-specific mortality at 20 years differed, particularly for alloHCT (CCR, 53.7%; CIBMTR, 27.6%). The median follow-up among alive patients was longer in CCR (alloHCT, 6.0 years; autoHCT, 4.7 years) than in CIBMTR (alloHCT, 5.0 years; autoHCT, 3.8 years). Our findings highlight the completeness of vital status data in CIBMTR but reveal substantial disagreement in primary COD. Consequently, caution is required when interpreting HCT studies that use only death certificates to estimate cause-specific mortality outcomes. Improving the accuracy of COD registration and follow-up completeness by developing communication pathways between cancer registries and hospital-based cohorts may enhance our understanding of late effects and long-term outcomes among HCT survivors.

INSPIRED Symposium Part 4A: Access to CAR T Cell Therapy in Unique Populations with B Cell Acute Lymphoblastic Leukemia

The approval of tisagenlecleucel (tisa-cel) for use in children with B cell acute lymphoblastic leukemia (B-ALL) was based on the phase 2 ELIANA trial, a global registration study. However, the ELIANA trial excluded specific subsets of patients facing unique challenges and did not include a sufficient number of patients to adequately evaluate outcomes in rare subpopulations. Since the commercialization of tisa-cel, data have become available that support therapeutic indications beyond the specific cohorts previously eligible for chimeric antigen receptor (CAR) T cells targeted to CD19 (CD19 CAR-T) therapy on the registration clinical trial. Substantial real-world data and aggregate clinical trial data have addressed gaps in our understanding of response rates, longer-term efficacy, and toxicities associated with CD19 CAR-T in special populations and rare clinical scenarios. These include patients with central nervous system relapsed disease, who were excluded from ELIANA and other early CAR-T trials owing to concerns about risk of neurotoxicity that have not been born out. There is also interest in the use of CD19 CAR-T for very-high-risk patients earlier in the course of therapy, such as patients with persistent minimal residual disease after 2 cycles of upfront chemotherapy and patients with first relapse of B-ALL. However, these indications are not specified on the label for tisa-cel and historically were not included in eligibility criteria for most clinical trials; data addressing these populations are needed. Populations at high risk of relapse, including patients with high-risk cytogenetic lesions, infants with B-ALL, patients with trisomy 21, and young adults with B-ALL, also may benefit from earlier treatment with CD19 CAR-T. It is important to prospectively study patient-reported outcomes given the differential toxicity expected between CD19 CAR-T and the historic standard of care, hematopoietic cell transplantation. Now that CD19 CAR-T therapy is commercially available, studies evaluating potential access disparities created by this very expensive novel therapy are increasingly pressing.

Implementation of a Pilot Clinic for Pediatric to Adult Cancer Survivorship Transitions

Childhood cancer survivors are recommended to have lifelong survivorship care, yet many become disengaged during pediatric to adult care transitions. We implemented a pilot clinic for adult survivors of pediatric or adolescent and young adult (AYA) leukemia transitioning to adult-focused survivorship care. The clinic featured AYA-specific care, bidirectional communication with primary care, and a quality improvement (QI) cycle. During the 1-year QI period, 27 patients were seen and 21 completed postvisit interviews. The clinic was positively received by patients and primary care providers, showed promise for improving self-management and care coordination, and highlighted the need for novel approaches to connect survivors with primary care.

Healthcare resource utilization and costs during first salvage therapy for relapsed or refractory acute myeloid leukemia in the United States

Real-world US healthcare resource utilization (HRU) and costs during first salvage therapy for relapsed/refractory (R/R) acute myeloid leukemia (AML) are described using IBM MarketScan® data (1/1/2007-6/30/2020). Treatments included high- (HIC) and low-intensity chemotherapy (LIC) alone, and gilteritinib, other FLT3 tyrosine kinase inhibitors (TKIs), and venetoclax with or without chemotherapy. Patients were diagnosed with R/R AML at ≥18 years of age between 1/1/2017-12/31/2019. Patient monthly all-cause HRU and costs were analyzed using a fixed-effects model. Data from 399 patients were analyzed (HIC, n = 104; LIC, n = 133; gilteritinib, n = 14; other FLT3 TKIs, n = 68; venetoclax, n = 80). Inpatient HRU was generally highest with HIC, whereas outpatient HRU was generally highest with LIC and venetoclax. Total all-cause incremental monthly costs appeared to be highest with HIC ($171,982) and similar for LIC ($60,512), gilteritinib ($47,218), other FLT3 TKIs ($43,218), and venetoclax ($77,566). Results highlight HRU and cost differences for R/R AML during first salvage therapy.

Next-Generation Sequencing-Based MRD in Adults with ALL Undergoing Hematopoietic Cell Transplantation

Measurable residual disease (MRD) is an adverse prognostic factor in adult acute lymphoblastic leukemia (ALL) patients undergoing hematopoietic cell transplantation (HCT). Next-generation sequencing (NGS) can detect MRD with a sensitivity of 10-6, but the prognostic value of NGS-based MRD in adult ALL patients undergoing HCT remains minimally studied. To evaluate the prognostic value of NGS-based MRD in adult ALL patients undergoing HCT. Patients with ALL aged ≥18 years old who underwent allogeneic HCT at Stanford University or Oregon Health & Science University between January 2014-April 2021 and who were evaluated for MRD using the NGS-based clonoSEQ assay were included in this study. MRD was assessed pre-HCT (MRDpre) and for up to 1 year post-HCT (MRDpost). Patients were followed for leukemia relapse and survival for up to 2 years post-HCT. 158 patients had a trackable clonotype for MRD monitoring. The cumulative incidence of relapse was increased at all levels of MRDpre, including in patients who had low MRDpre of <10-4 (HR 3.56, 95% CI, 1.39-9.15). In multivariable analysis, MRDpre level remained significantly prognostic; however, detectable MRDpost was the strongest predictor of relapse (HR 4.60, 95% CI, 3.01-7.02). In exploratory analyses limited to B-cell ALL patients, detection of post-HCT IgH MRD clonotypes, rather than non-IgH MRD clonotypes, were associated with relapse. In this analysis across two large transplant centers, we found that detection of MRD by NGS at a level of 10-6 offers significant prognostic value in adults with ALL undergoing HCT.

Abstract 1128: Lineage tracing of CAR T cells in patients with B cell malignancies

Autologous T cells genetically engineered to express a chimeric antigen receptor (CAR) targeting CD19 and/or CD22 have achieved high complete response rates in patients with hematologic malignancies, but &gt;50% of patients progress following therapy. Here, we sought to understand key T cell intrinsic factors impacting efficacy: CAR T cell expansion, persistence, and homing to the tumor. Using an endogenous T cell receptor (TCR) sequence as a ‘barcode’, we followed individual T cell clonotypes at the single-cell level from pre-manufacture apheresis and infusion products to tumor-involved lymph node and blood at peak and late expansion in 22 adult patients with relapsed or refractory large B cell lymphoma (LBCL) or acute lymphoblastic leukemia (ALL) treated with axicabtagene ciloleucel, an FDA-approved CD19-CAR T cell immunotherapy, or bispecific CD19/CD22 CAR T cells on an investigator-initiated trial (NCT03233854). The resulting CAR T cell atlas comprises matched transcriptome (scRNA-seq) and surface protein expression (CITE-seq) for 846,344 cells from 97 samples, with 215,045 unique TCR clonotypes identified, including 8,747 clonotypes that could be traced across 2+ timepoints in CAR mRNA+ cells. This atlas enabled us to ask: “What were the phenotypes of ‘successful’ CAR T cell clonotypes with optimal homing, expansion, and persistence properties at the time of infusion or pre-manufacture apheresis?” We found that successful T cell clonotypes at apheresis had juvenile features, including IL7R expression. Conversely, successful clonotypes in the infusion product had elevated interferon pathway activity and effector signatures, including GZMB expression. Further, we built a cell-cell interactome using all live cells from on-treatment biopsies and identified a set of 149 specific ligand-receptor pairs significantly enriched in patients who progressed. Finally, we defined dynamics of TCR clonotypes with predicted specificities for viral and self-antigens. These analyses pinpoint the identities of source T cells and infusion CAR T cells with properties impacting efficacy, and also identify ligand-receptor pairs that could be modulated to enhance CAR T cell response in the tumor at the genetic or pharmacological level. This work was supported in part by the Parker Institute for Cancer Immunotherapy, California Institute for Regenerative Medicine, Kite Pharma, and Stanford Cancer Institute.

Citation Format: Zinaida Good, Mark P. Hamilton, Jay Y. Spiegel, Sreevidya Kurra, Moksha H. Desai, Snehit Prabhu, Shin-Heng Chiou, Christine Y. Yeh, Yiyun Chen, Eric Yang, Michael G. Ozawa, Fang Wu, Matthew J. Frank, Lori Muffly, Gursharan K. Claire, Juliana Craig, Maria I. Iglesias, Sushma Bharadwaj, Katherine A. Kong, Dhananjay Wagh, John Coller, Mark M. Davis, Sylvia K. Plevritis, Bita Sahaf, David B. Miklos, Crystal L. Mackall. Lineage tracing of CAR T cells in patients with B cell malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1128.

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.

Continuous EEG monitoring detects nonconvulsive seizure and Ictal-Interictal Continuum abnormalities in moderate to severe ICANS following systemic CAR-T therapy

Background and Purpose

Immune Cell Effector Associated Neurotoxicity Syndrome (ICANS) is common amongst patients receiving CD19 targeted Chimeric Antigen Receptor T-cell (CAR-T) therapy. The purpose of this study is to characterize the incidence of seizures and ictal-interictal continuum (IIC) abnormalities in patients with ICANS.

Methods

Retrospective review of consecutive patients treated with axicabtagene ciloleucel (axi-cel) for recurrent high-grade systemic lymphoma at Stanford Medical Center between 2/2016-6/2019. Electronic medical records (EMR) were reviewed for clinical features, treatment information, EEG data, CRS (cytokine release syndrome)/ICANS severity, and clinical outcomes.

Results

Fifty-six patients met inclusion criteria. 85.7% of patients developed CRS, and 58.9% developed ICANS. Twenty-eight patients had EEG monitoring, of whom 26 had ICANS. Median duration of EEG monitoring was 30 hours (range .5-126 hours). Four patients (7.1%) had seizures (1 patient had a clinical generalized seizure, 2 patients had clinical and nonconvulsive seizures, and 1 patient had an isolated non-convulsive seizure). Ictal-interictal continuum abnormalities were common, of which generalized periodic discharges (GPDs) with triphasic morphology and GPDs with epileptiform morphology were most frequently seen. Generalized periodic discharges with triphasic wave morphology were found across Grade 2-3 peak ICANS severity, however the majority (86%) of patients with epileptiform GPDs had Grade 3 peak ICANS severity.

Conclusions

Among patients receiving axi-cel, seizure occurred in 7.1% of the total cohort, representing 12% of patients with ICANS. Ictal-interictal continuum abnormalities are also seen in patients with ICANS, most commonly GPDs. 75% of patients with seizures had nonconvulsive seizures supporting the use of continuous video EEG monitoring in this population.

SOHO State of the Art Updates and Next Questions: Measurable Residual Disease in Acute Lymphoblastic Leukemia - Optimization and Innovation in 2022 and Beyond

Measurable residual disease (MRD) is an established component of acute lymphoblastic leukemia (ALL) management in both children and adults. Society guidelines and expert consensus documents include assessment of MRD as the standard of care following induction therapy, consolidation therapy, and at additional time points, depending on the treatment regimen administered. Further, the approval of blinatumomab for MRD+ B-ALL has advanced the concept of MRD response as a clinical endpoint in ALL. Although the utility of MRD in ALL has been well defined over the last decades, several questions remain. In this review we focus on areas of ongoing controversy and exploration in ALL MRD, including the following: (1) Does increasing the depth of MRD assessment add prognostic value? (2) Is there a role for ongoing MRD monitoring once patients achieve MRD response? (3) Can MRD assessment of the peripheral blood be substituted for bone marrow? (4) Should MRD assays be applied to the analysis of the central nervous system (CNS)? Ongoing studies should answer the majority of these questions in the coming years.

Treatment-related toxicities associated with hospitalization in children, adolescents, and young adults with acute lymphoblastic leukemia: population level analysis

Treatment-related toxicities (TRTs) are a potential cause of survival disparities in patients with acute lymphoblastic leukemia (ALL). We aimed to identify the most frequent TRTs associated with hospitalizations at a population level in children, adolescents and young adults (AYAs). We used the California Cancer Registry linked to a statewide hospital discharge database to identify children and AYAs with TRTs within 3 years of diagnosis. We assessed the frequency of TRTs, length of stay (LOS), admission rates associated with TRTs and TRTs impact on survival. Febrile neutropenia, hypertension, and thrombocytopenia were the most common TRTs for both children and AYAs. AYAs had longer median LOS compared to children for most toxicities. AYAs at non-specialized cancer centers (SCCs) had higher frequency of admissions associated with TRTs compared to non-SCC. Cardiovascular, respiratory, gastrointestinal, renal, and infectious TRTs were associated with worse survival. This study demonstrates the burden of TRTs in patients with ALL.

Measurable residual disease in acute lymphoblastic leukemia: methods and clinical context in adult patients

Measurable residual disease (MRD) is the most powerful independent predictor of risk of relapse and long-term survival in adults and children with acute lymphoblastic leukemia (ALL). For almost all patients with ALL there is a reliable method to evaluate MRD, which can be done using multi-color flow cytometry, quantitative polymerase chain reaction to detect specific fusion transcripts or immunoglobulin/T-cell receptor gene rearrangements, and high-throughput next-generation sequencing. While next-generation sequencing-based MRD detection has been increasingly utilized in clinical practice due to its high sensitivity, the clinical significance of very low MRD levels (<10-4) is not fully characterized. Several new immunotherapy approaches including blinatumomab, inotuzumab ozogamicin, and chimeric antigen receptor T-cell therapies have demonstrated efficacy in eradicating MRD in patients with B-ALL. However, new approaches to target MRD in patients with T-ALL remain an unmet need. As our MRD detection assays become more sensitive and expanding novel therapeutics enter clinical development, the future of ALL therapy will increasingly utilize MRD as a criterion to either intensify or modify therapy to prevent relapse or de-escalate therapy to reduce treatment-related morbidity and mortality.

Post-infusion CAR TReg cells identify patients resistant to CD19-CAR therapy

Approximately 60% of patients with large B cell lymphoma treated with chimeric antigen receptor (CAR) T cell therapies targeting CD19 experience disease progression, and neurotoxicity remains a challenge. Biomarkers associated with resistance and toxicity are limited. In this study, single-cell proteomic profiling of circulating CAR T cells in 32 patients treated with CD19-CAR identified that CD4+Helios+ CAR T cells on day 7 after infusion are associated with progressive disease and less severe neurotoxicity. Deep profiling demonstrated that this population is non-clonal and manifests hallmark features of T regulatory (TReg) cells. Validation cohort analysis upheld the link between higher CAR TReg cells with clinical progression and less severe neurotoxicity. A model combining expansion of this subset with lactate dehydrogenase levels, as a surrogate for tumor burden, was superior for predicting durable clinical response compared to models relying on each feature alone. These data credential CAR TReg cell expansion as a novel biomarker of response and toxicity after CAR T cell therapy and raise the prospect that this subset may regulate CAR T cell responses in humans.

Abstract 3603: Reverse fate mapping of CD19-targeted CAR T cells in patients with large B-cell lymphoma

Autologous T cells genetically engineered to express a chimeric antigen receptor targeting CD19 (CD19-CAR) have achieved high complete response rates in patients with hematologic malignancies, but &gt;50% of patients progress following therapy. Here, we sought to understand key T-cell intrinsic factors impacting efficacy, namely CAR T-cell expansion, persistence, and homing to the tumor. Using an approach called reverse fate mapping, we followed individual T-cell clones at the single-cell level from pre-manufacture apheresis to the infusion product, tumor-involved lymph node, and blood at peak and late expansion in 12 adult patients with relapsed or refractory large B-cell lymphoma treated with axicabtagene ciloleucel, an FDA-approved CD19-CAR T-cell immunotherapy. The resulting CAR T-cell atlas comprises matched transcriptome (scRNA-seq) and surface protein expression (CITE-seq) for 322,028 cells from 44 samples, with 119,397 unique T-cell receptor (TCR) clonotypes identified. This atlas enabled us to ask questions like: “What were the phenotypes of the most successful CAR T-cell clones at the time of infusion or pre-manufacture apheresis?” We found that T-cell clonotypes with juvenile features at apheresis, including IL7R expression, were the most successful at expansion to higher frequencies in the infusion product, while clones with effector gene expression programs, such as those encoding perforin and granzymes, contracted between apheresis and product. Conversely, it was GZMK-expressing T cells in pre-manufacture apheresis that were dominant in the tumor early following CAR T-cell infusion. Further, T-cell clonotypes with active effector programs at infusion dominated at peak expansion. Finally, we defined active expression modules and pathways in the infusion product for CAR T-cell clones that homed to the tumor or became dominant at late expansion. These analyses pinpoint the molecular mechanisms that could be modulated to rationally steer CAR T-cell differentiation trajectories at the genetic or pharmacological level. This work was supported in part by the Parker Institute for Cancer Immunotherapy, California Institute for Regenerative Medicine, Kite Pharma, and Stanford Cancer Institute.

Citation Format: Zinaida Good, Mark P. Hamilton, Jay Y. Spiegel, Sreevidya Kurra, Moksha Desai, Snehit Prabhu, Eric Yang, Michael G. Ozawa, Paul J. Hanson, Fang Wu, Matthew J. Frank, John H. Baird, Lori Muffly, Gursharan K. Claire, Juliana Craig, Katherine A. Kong, Dhananjay Wagh, John Coller, Sylvia K. Plevritis, Bita Sahaf, David B. Miklos, Crystal L. Mackall. Reverse fate mapping of CD19-targeted CAR T cells in patients with large B-cell lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3603.

Allogeneic Hematopoietic Cell Transplantation for Adult Acute Lymphoblastic Leukemia in the Modern Era

Allogeneic hematopoietic cell transplantation (HCT) remains an important treatment for adults with acute lymphoblastic leukemia (ALL). We hypothesized that advances in ALL and transplantation have resulted in improved HCT outcomes in recent years. In this study, we evaluated the characteristics and outcomes of adult ALL patients undergoing allogeneic HCT over the last decade. Patients with ALL aged 18 years and older who underwent allogeneic HCT at Stanford University between 2008 and 2019 were included in this study. Patients were divided into 2 eras based on year of HCT: 2008 to 2013 (earlier era) and 2014 to 2019 (later era). A total of 285 patients were included: 119 patients underwent HCT in the earlier era and 166 in the later era. Patients who underwent transplantation in the later era were more likely to be Hispanic (38% versus 21%) and to have an HCT-comorbidity index ≥3 (31% versus 18%). Donor source for HCT also differed with an increase in the use of HLA-mismatched donor sources (38% versus 24%), notably umbilical cord blood in the later era (16% versus 0%). Patients in the later era were less likely to undergo transplantation with active disease (4% versus 16%); pre-HCT rates of measurable residual disease were similar across the eras (38% versus 40%). In unadjusted analyses, overall survival (OS) improved across eras, with 2-year estimates for the later and earlier eras of 73% (95% confidence interval [CI], 66%-80%) versus 55% (95% CI, 46%-64%), respectively. Multivariable analysis confirmed the association between later era and OS (hazard ratio = 0.52, 95% CI, 0.34-0.78). Finally, among patients relapsing after HCT (25% in later era and 33% in earlier era), the use of novel immunotherapies increased in the later era (44% versus 3%), as did the median OS after post-HCT relapse (16 months versus 8 months, P< .001). OS after HCT for adult ALL has improved in recent years. This is due, in part, to a significant improvement in the ability to effectively salvage adults with ALL relapsing after HCT.

Innovative Approaches to the Management of Acute Lymphoblastic Leukemia Across the Age Spectrum

Adults compose nearly half of all patients diagnosed with acute lymphoblastic leukemia (ALL) and historically have had poor survival compared with pediatric patients. Recently approved therapies, such as monoclonal antibodies, CAR T-cell constructs, and next-generation tyrosine kinase inhibitors, have improved survival in relapsed and refractory ALL, and studies are now examining incorporating these treatments and others into the upfront setting. In adolescent and young adult patients, use of pediatric-based regimens has already improved survival compared with historical controls, and the addition of monoclonal antibodies, such as inotuzumab ozogamicin and blinatumomab, may further enhance this survival benefit. In older adults, approaches have centered on minimizing conventional chemotherapy to decrease toxicity by incorporating monoclonal antibodies and other novel therapies to increase efficacy. With the addition of tyrosine kinase inhibitors to chemotherapy for patients with Philadelphia chromosome-positive ALL, survival of this once poor-prognosis ALL subtype now approaches or exceeds outcomes of other subtypes of adult ALL. Further refinements in the backbone treatment regimen and optimal consolidation approaches will likely improve survival further. Although allogeneic hematopoietic stem cell transplant was previously routinely used as consolidation for adults with ALL, incorporation of measurable residual disease and other risk stratification strategies has enabled better identification of patients who will benefit from allogeneic hematopoietic stem cell transplant. Ongoing clinical trials investigating these approaches will continue the evolution of treatment approaches for adults with ALL, with further improvement in outcomes anticipated.

Controversies in the Treatment of Adolescents and Young Adults with Philadelphia Chromosome-Negative B-Cell Acute Lymphoblastic Leukemia

PURPOSE OF THE REVIEW

The incidence of acute lymphoblastic leukemia (ALL) has been increasing steadily in the adolescent and young adult (AYA) population. In this review article focused on the management of AYAs with Philadelphia chromosome-negative (Ph-) B-ALL, we examine topics of clinical interest and identify areas of controversy in need of further investigation.

RECENT FINDINGS

We explore four areas of active investigation: pediatric-inspired front-line treatment regimens, the optimal time of measurable residual disease (MRD) assessment, the role of hematopoietic stem cell transplant and the optimal salvage therapy for relapsed/refractory B-ALL in AYAs. There has been rapid advancement in the management of ALL in the AYA patient population, which has resulted in improved outcomes. We must build on the successes by continuing to promote multi-center innovative clinical research with clinical trial populations reflecting the AYA ALL patient spectrum. The incorporation of novel targeted immunotherapy into front-line treatment will be transformative and redefine treatment paradigms in the coming years.

Adding Centralized Electronic Patient-Reported Outcome Data Collection to an Established International Clinical Outcomes Registry

The importance of patient-reported outcomes (PROs) in cellular therapies, including hematopoietic cell transplantation (HCT) is highlighted in this study. Longitudinal collection of PROs in a registry is recommended for several reasons, yet to date, PROs are not routinely collected from HCT patients to augment clinical registry data. The aim of this study was to determine the feasibility of electronic PRO data collection by a national clinical outcomes registry, by assessing differences between who does and does not report PROs. We conducted a cross-sectional pilot collection of PROs from HCT recipients after treatment using computer-adapted tests from the Patient-Reported Outcome Measurement Information System (PROMIS). We implemented centralized data collection through the Center for International Blood and Marrow Transplant Research (CIBMTR) among patients who underwent HCT for myelodysplastic syndromes (MDS), were at least 6 months post-HCT, and spoke English or Spanish. The main objective was identifying patient, disease, and transplant-related differences associated with completion of electronic PROs. Patients were excluded from analysis if they were determined to be ineligible (deceased, did not speak English or Spanish, refused to be contacted by the CIBMTR). A total of 163 patients were contacted and potentially eligible to participate; of these, 92 (56%) enrolled and 89 (55%) completed the PRO assessment. The most frequent reason for incomplete surveys was inability to contact patients (n = 88), followed by declining to participate in the study (n = 37). There were no sociodemographic or age differences between those who completed the PRO survey (n = 89) and eligible nonresponders (n = 155). Patient scores were within 3 points of the US average of 50 for all symptoms and functioning except physical functioning. Responders and nonresponders did not exhibit meaningfully different sociodemographic characteristics. Difficulty contacting patients posed the greatest barrier and also provided the greatest opportunity for improvement. Once enrolled, survey completion was high. These results support standardizing centralized PRO data collection through the CIBMTR registry.

Randomized Phase III BMT CTN Trial of Calcineurin Inhibitor-Free Chronic Graft-Versus-Host Disease Interventions in Myeloablative Hematopoietic Cell Transplantation for Hematologic Malignancies

PURPOSE

Calcineurin inhibitors (CNI) are standard components of graft-versus-host disease (GVHD) prophylaxis after hematopoietic cell transplantation (HCT). Prior data suggested that CNI-free approaches using donor T-cell depletion, either by ex vivo CD34 selection or in vivo post-transplant cyclophosphamide (PTCy) as a single agent, are associated with lower rates of chronic GVHD (cGVHD).

METHODS

This multicenter phase III trial randomly assigned patients with acute leukemia or myelodysplasia and an HLA-matched donor to receive CD34-selected peripheral blood stem cell, PTCy after a bone marrow (BM) graft, or tacrolimus and methotrexate after BM graft (control). The primary end point was cGVHD (moderate or severe) or relapse-free survival (CRFS).

RESULTS

Among 346 patients enrolled, 327 received HCT, 300 per protocol. Intent-to-treat rates of 2-year CRFS were 50.6% for CD34 selection (hazard ratio [HR] compared with control, 0.80; 95% CI, 0.56 to 1.15; P = .24), 48.1% for PTCy (HR, 0.86; 0.61 to 1.23; P = .41), and 41.0% for control. Corresponding rates of overall survival were 60.1% (HR, 1.74; 1.09 to 2.80; P = .02), 76.2% (HR, 1.02; 0.60 to 1.72; P = .95), and 76.1%. CD34 selection was associated with lower moderate to severe cGVHD (HR, 0.25; 0.12 to 0.52; P = .02) but higher transplant-related mortality (HR, 2.76; 1.26 to 6.06; P = .01). PTCy was associated with comparable cGVHD and survival outcomes to control, and a trend toward lower disease relapse (HR, 0.52; 0.28 to 0.96; P = .037).

CONCLUSION

CNI-free interventions as performed herein did not result in superior CRFS compared with tacrolimus and methotrexate with BM. Lower rates of moderate and severe cGVHD did not translate into improved survival.

Measurable residual disease status and FLT3 inhibitor therapy in patients with FLT3-ITD mutated AML following allogeneic hematopoietic cell transplantation

Measurable residual disease (MRD) is associated with poor prognosis in acute myeloid leukemia (AML), even after allogeneic hematopoietic cell transplantation (HCT). New next-generation sequencing (NGS) methods have emerged as a highly sensitive and specific method to detect MRD. In addition to defining the role of post-HCT MRD monitoring in FLT3-ITD mutated AML, there is great interest in the optimal use of oral FLT3 tyrosine kinase inhibitors (FLT3 inhibitors) to maintain remission following HCT. In this study, we evaluated the clinical impact of sensitive FLT3 MRD testing early after HCT and maintenance FLT3 inhibitor use at our transplant center. We found that there was a trend towards inferior progression-free survival (PFS) for patients with early post-HCT MRD, but that overall survival (OS) was not significantly impacted by MRD. The use of maintenance FLT3 inhibitors led to a significantly superior PFS and OS in our cohort, and improved PFS and OS in both MRD-negative and MRD-positive patients. Altogether, our results demonstrate the prognostic significance of NGS-based MRD monitoring for FLT3-ITD and the ability of post-HCT maintenance therapy to prevent relapse and death in FLT3-ITD mutated AML.

Historical perspective and a glance into the antibody-based conditioning regimens: A new era in the horizon?

The hematopoietic cell transplantation practice has changed significantly over the years. More than 1500 centers around the globe are offering transplant for different types of diseases. This growth was driven by improving the efficacy and the safety of the procedure and the ability to use alternate donors. These improvements made the procedure feasible in virtually all patients in need for it. With the availability of novel therapies and targeted agents, we may be witnessing a new transplant-era. These agents may help to circumvent some of the remaining limitations of the procedure and open the doors for new indications. Herein, we review historical transplant milestones, the accomplishments that led to the modern transplant practice and we discuss the idea of minimal-intensity conditioning and the possibility to adopt chemotherapy and radiation-free preparative regimens in the near future.

Chronic medical conditions and late effects after acute myeloid leukaemia in adolescents and young adults: a population-based study

BACKGROUND

Curative-intent treatment of acute myeloid leukaemia (AML) can lead to multiple chronic medical conditions ('late effects'). Little is known about the burden of late effects in adolescent and young adult (AYA, 15-39 years) survivors of AML. We aimed to estimate the cumulative incidence and investigate the main predictors of late effects among these patients.

METHODS

During 1996-2012, 1168 eligible AYAs with AML who survived ≥2 years after diagnosis were identified in the California Cancer Registry. Late effects were reported from State hospital discharge data, and patients were followed through 2014. Hazard ratios and 95% confidence intervals of late effects occurrence were estimated using Cox proportional hazard models, adjusted for sociodemographic and clinical factors.

RESULTS

The most common late effects at 10 years after diagnosis were: endocrine (26.1%), cardiovascular (18.6%) and respiratory (6.6%), followed by neurologic (4.9%), liver/pancreatic (4.3%), renal (3.1%), avascular necrosis (2.7%) and second primary malignancies (2.4%). Of 1168 survivors, 547 (46.8%) received a haematopoietic stem cell transplant (HSCT). After multivariable adjustments, AYAs who underwent HSCT or had a non-favourable risk AML experienced ∼2-fold or higher increased likelihood of all late effects. Additionally, AYAs of Hispanic, Black or Asian/Pacific Islander (vs non-Hispanic White) race/ethnicity and those who resided in lower socio-economic neighbourhoods were at higher risk of numerous late effects.

CONCLUSIONS

Our findings underscore the need for long-term surveillance for the prevention, early detection and treatment of late effects, and can inform the development of AYA-focused consensus-based guidelines that will ultimately improve the quality of life and survival of these young vulnerable patients.

CD22-directed CAR T-cell therapy induces complete remissions in CD19-directed CAR-refractory large B-cell lymphoma

The prognosis of patients with large B-cell lymphoma (LBCL) that progresses after treatment with chimeric antigen receptor (CAR) T-cell therapy targeting CD19 (CAR19) is poor. We report on the first 3 consecutive patients with autologous CAR19-refractory LBCL who were treated with a single infusion of autologous 1 × 106 CAR+ T cells per kilogram targeting CD22 (CAR22) as part of a phase 1 dose-escalation study. CAR22 therapy was relatively well tolerated, without any observed nonhematologic adverse events higher than grade 2. After infusion, all 3 patients achieved complete remission, with all responses continuing at the time of last follow-up (mean, 7.8 months; range, 6-9.3). Circulating CAR22 cells demonstrated robust expansion (peak range, 85.4-350 cells per microliter), and persisted beyond 3 months in all patients with continued radiographic responses and corresponding decreases in circulating tumor DNA beyond 6 months after infusion. Further accrual at a higher dose level in this phase 1 dose-escalation study is ongoing and will explore the role of this therapy in patients in whom prior CAR T-cell therapies have failed. This trial is registered on clinicaltrials.gov as #NCT04088890.

Stem Cell Mobilization in Multiple Myeloma: Comparing Safety and Efficacy of Cyclophosphamide +/- Plerixafor versus Granulocyte Colony-Stimulating Factor +/- Plerixafor in the Lenalidomide Era

Growth factor and chemotherapy-based stem cell mobilization strategies are commonly used to treat patients with multiple myeloma. We retrospectively compared 398 patients mobilized between 2017 and 2020 using either cyclophosphamide (4 g/m²) plus granulocyte colony-stimulating factor (G-CSF) or G-CSF alone, with on demand plerixafor (PXF) in both groups. Although total CD34⁺ yield was higher after chemomobilization compared with G-CSF +/- PXF (median, 13.6 × 10⁶/kg versus 4.4 × 10⁶/kg; P < .01), achievement of ≥2 × 10⁶ CD34⁺ cells (95% versus 93.7%; P = .61) and rates of mobilization failure (5% versus 6.3%; P = .61) were similar. Fewer patients required PXF with chemomobilization (12.3% versus 49.5%; P < .01), and apheresis sessions were fewer (median, 1 [range, 1 to 4] versus 2 [range, 1 to 5]). The rate of complications, including neutropenic fever, emergency department visits, and hospitalizations, was higher after chemomobilization (30% versus 7.4%; P < .01). Previous use of ≤6 cycles of lenalidomide did not impair cell yield in either group. The median cost of mobilization was 17.4% lower in the G-CSF +/- PXF group (P = .01). Between group differences in time to engraftment were not clinically significant. Given similar rates of successful mobilization, similar engraftment time, and less toxicity and lower costs compared with chemomobilization, G-CSF with on-demand PXF may be preferable in myeloma patients with adequate disease control and limited lenalidomide exposure.

Hepatic veno-occlusive disease in allogeneic stem cell transplant recipients with prior exposure to gemtuzumab ozogamicin or inotuzumab ozogamicin

Hepatic veno-occlusive disease (VOD/sinusoidal obstructive syndrome) represents a constellation of clinical findings including right upper quadrant pain, jaundice, hepatomegaly, and ascites. In the post-hematopoietic stem cell transplant (SCT) setting, the reported incidence has been 10-15%, with severe VOD historically resulting in high mortality rates. Novel agents including calicheamicin conjugated with CD33 (gemtuzumab ozogamicin; GO) and CD22 (inotuzumab ozogamicin; InO) are increasingly used for the treatment of acute myeloid leukemia and acute lymphoblastic leukemia, respectively. Both GO and InO are highly active, but also have unique hepatotoxicity profiles, including a higher risk of VOD in recipients of SCT. Introduction of GO and InO into pre-SCT leukemia management adds additional complexity to SCT patient selection and toxicity monitoring. In this article, we describe and review the risks and management associated with VOD in SCT recipients exposed to GO and InO.

Late Effects in Survivors of Adolescent and Young Adult Acute Lymphoblastic Leukemia

Background

Knowledge regarding late effects (medical conditions and subsequent neoplasms) in survivors of adolescent and young adult (AYA) acute lymphoblastic leukemia (ALL) is lacking.

Methods

Using the population-based California Cancer Registry linked with California hospitalization data, we evaluated late effects in 1069 AYAs (aged 15-39 years) diagnosed with ALL in California between 1995 and 2012 and surviving a minimum of 3 years from diagnosis.

Results

The estimated 10-year cumulative incidence of subsequent endocrine disease (28.7%, 95% confidence interval [CI] = 25.8% to 31.6%) and cardiac disease (17.0%, 95% CI = 14.6% to 19.5%) were strikingly high; avascular necrosis (9.6%, 95% CI = 7.8% to 11.6%), liver disease (6.5%, 95% CI = 5.0% to 8.3%), respiratory disease (6.2%, 95% CI = 4.8% to 8.0%), seizure and/or stroke (4.3%, 95% CI = 3.1% to 5.8%), renal disease (3.1%, 95% CI = 2.1% to 4.4%), and second neoplasms (1.4%, 95% CI = 0.7% to 2.4%) were estimated to occur at 10 years with the reported frequencies. Multivariable analyses including the entire patient cohort demonstrated that public or no insurance (vs private and/or military insurance) and receipt of hematopoietic cell transplantation were independently associated with the occurrence of all late effects considered. In multivariable analyses limited to the 766 AYAs who were not transplanted, we continued to find a statistically significant association between public and no insurance and the occurrence of all late effects. Frontline regimen type (pediatric vs adult) was not statistically significantly associated with any of the late effect categories.

Conclusions

This large population-based analysis is among the first to describe late effects in survivors of AYA ALL. The strong association between insurance type and late effects suggests that AYAs with public or no insurance may have reduced access to survivorship care following completion of ALL therapy.

Treatment Complications and Survival Among Children and Young Adults With Acute Lymphoblastic Leukemia

PURPOSE

We previously demonstrated lower early mortality for young adults (YAs) with acute lymphoblastic leukemia (ALL) who received induction treatment at specialized cancer centers (SCCs) versus community hospitals. The aim of this study is to determine the impact of inpatient location of treatment throughout therapy on long-term survival, complications, and cost-associations that have not yet been evaluated at the population level.

METHODS

Using the California Cancer Registry linked to a hospitalization database, we identified patients, 0-39 years of age, diagnosed with first primary ALL who received inpatient treatment between 1991 and 2014. Patients were classified as receiving all or part or none of their inpatient treatment at an SCC within 3 years of diagnosis. Inverse probability-weighted, multivariable Cox regression models estimated the associations between location of treatment and sociodemographic and clinical factors with survival. We compared 3-year inpatient costs overall and per day by age group and location of care.

RESULTS

Eighty-four percent (0-18 years; n = 4,549) of children and 36% of YAs (19-39 years; n = 683) received all treatment at SCCs. Receiving all treatment at an SCC was associated with superior leukemia-specific (hazard ratio [HR], 0.76; 95% CI, 0.67 to 0.88) and overall survival (HR, 0.87; 95% CI, 0.77 to 0.97) in children and in YAs (HR, 0.71; 95% CI, 0.61 to 0.83; HR, 0.70; 95% CI, 0.62 to 0.80) even after controlling for complications. The cost of inpatient care during the full course of therapy was higher in patients receiving all of their care at SCCs.

CONCLUSION

Our results demonstrate that inpatient treatment at an SCC throughout therapy is associated with superior survival; therefore, strong consideration should be given to referring these patients to SCCs.