Refractory Acute Lymphoblastic Leukemia Research Articles

Abstract 7259: Effectiveness and comparison of CAR-T cell therapies for synovial sarcoma; HER2-targeted CAR-T and NKG2D-based CAR-T

Abstract Introduction: In Japan since 2019, CAR-T cell therapy has been used to treat patients with relapsed or refractory B-cell acute lymphoblastic leukemia and diffuse large B-cell lymphoma and has shown excellent clinical results. Clinical studies of CAR-T cell therapies targeting various antigens, such as HER2, have been conducted, but the therapeutic outcome in sarcoma is still limited. We have previously reported that HER2-targeted CAR-T cells show antitumor effects for synovial sarcoma in vitro. The purpose of this study is to compare HER2-targeted CAR-T cells and NKG2D-based CAR-T cells in antitumor effect and specific responses for synovial sarcoma in vitro. Materials and Methods: Surface expressions of HER2 and NKG2D ligands on three synovial sarcoma cell lines were detected by using recombinant human HER2 Fc chimeric protein and that of NKG2D, followed by staining with PE-conjugated anti-human IgG secondary antibody. We generated 4-1BB-type second generation CAR-T cells targeting NKG2D ligands and examined their antitumor effects and specific responses against synovial sarcoma cells. In addition, we compared the differences between HER2-targeted CAR-T cells and NKG2D-based CAR-T cells by co-culturing with synovial sarcoma cells using short-term assay (WST-8 assay), long-term assay (Real-time Cell Analysis) and CD107a assay. Results: HER2 and NKG2D ligands were found to be expressed by flow cytometry in three synovial sarcoma cell lines. In vitro, NKG2D-based CAR-T cells showed antitumor effects against synovial sarcoma cells, including degranulation and cytokine production. Furthermore, NKG2D-based CAR-T cells showed stronger antitumor effects than HER2-targeted CAR-T cells in both short- and long-term assays and expressed higher levels of CD107a. Conclusions: In this study, NKG2D-based CAR-T cells showed more antitumor effects than HER2-targeted CAR-T cells in vitro. Although the reason for this is not clear, we hypothesize that NKG2D ligands may be induced in synovial sarcoma cells by co-culture with CAR-T cells because HER2 is a cancer-specific antigen, whereas NKG2D ligands are ligands for activating receptors of natural killer cells. Further studies, including in vivo studies, will be conducted to verify the difference in anti-tumor effects between these CAR-T cells. Citation Format: Tomohiro Miyazaki, Chihaya Imai, Naoki Oike, Yudai Murayama, Takashi Ariizumi, Minori Baba, Yasushi Kasahara, Hiroyuki Kawashima. Effectiveness and comparison of CAR-T cell therapies for synovial sarcoma; HER2-targeted CAR-T and NKG2D-based CAR-T [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7259.

ADCT-602, a Novel PBD Dimer-containing Antibody-Drug Conjugate for Treating CD22-positive Hematologic Malignancies.

Relapsed or refractory B-cell acute lymphoblastic leukemia (R/R B-ALL) and lymphomas have poor patient outcomes; novel therapies are needed. CD22 is an attractive target for antibody-drug conjugates (ADCs), being highly expressed in R/R B-ALL with rapid internalization kinetics. ADCT-602 is a novel CD22-targeting ADC, consisting of humanized mAb hLL2-C220, site specifically conjugated to the pyrrolobenzodiazepine dimer-based payload tesirine. In preclinical studies, ADCT-602 demonstrated potent, specific cytotoxicity in CD22-positive lymphomas and leukemias. ADCT-602 was specifically bound, internalized, and trafficked to lysosomes in CD22-positive tumor cells; after cytotoxin release, DNA interstrand crosslink formation persisted for 48 hours. In the presence of CD22-positive tumor cells, ADCT-602 caused bystander killing of CD22-negative tumor cells. A single ADCT-602 dose led to potent, dose-dependent, in vivo antitumor activity in subcutaneous and disseminated human lymphoma/leukemia models. Pharmacokinetic analyses (rat and cynomolgus monkey) showed excellent stability and tolerability of ADCT-602. Cynomolgus monkey B cells were efficiently depleted from circulation after one dose. Gene signature association analysis revealed IRAK1 as a potential marker for ADCT-602 resistance. Combining ADCT-602 + pacritinib was beneficial in ADCT-602-resistant cells. Chidamide increased CD22 expression on B-cell tumor surfaces, increasing ADCT-602 activity. These data support clinical testing of ADCT-602 in R/R B-ALL (NCT03698552) and CD22-positive hematologic cancers.

Nelarabine-containing salvage therapy and conditioning regimen in transplants for pediatric T-cell acute lymphoblastic leukemia and lymphoma.

Therapy for relapsed or refractory (r/r) T-cell acute lymphoblastic leukemia (T-ALL) and T-cell lymphoblastic lymphoma (T-LBL) in children is challenging, and new treatment methods are needed. We retrospectively analyzed eight patients with r/r T-ALL (five patients) and T-LBL (three patients) who were treated with nelarabine (NEL) plus etoposide, cyclophosphamide, and intrathecal therapy, administered 3days apart. Five patients achieved a complete response, and the other three achieved a partial response (PR). All patients underwent hematopoietic stem cell transplantation (HSCT) after two cycles of treatment, except for one patient who received one cycle. Three patients who had previously received HSCT were treated with reduced-intensity conditioning regimens, including fludarabine, melphalan, and NEL; one survived for over 5years after the second HSCT. Grade 2 neuropathy occurred in one patient, but other severe toxicities commonly associated with NEL were not observed during NEL administration in combination with chemotherapy. The 2-year overall survival and event-free survival rates were 60.0% and 36.5%, respectively. The addition of NEL to reinduction chemotherapy was useful in achieving remission and did not lead to excessive toxicity. In addition, a conditioning regimen, including NEL, appeared to be effective in patients who had previously undergone HSCT.

A phase 1/2 study of mini-hyper-CVD plus venetoclax in patients with relapsed/refractory acute lymphoblastic leukemia

AbstractPreclinical studies suggest that Bcl-2 inhibition with venetoclax has antileukemic activity in acute lymphoblastic leukemia (ALL) and may synergize with conventional chemotherapy. We designed a phase 1/2 clinical trial to evaluate the safety and efficacy of low-intensity chemotherapy in combination with venetoclax in adults with relapsed or refractory ALL. Patients received the mini-hyper-CVD regimen (dose-attenuated hyperfractionated cyclophosphamide, vincristine, and dexamethasone alternating with methotrexate and cytarabine) in combination with venetoclax (200 mg or 400 mg daily) on days 1 to 14 in cycle 1 and on days 1 to 7 in consolidation cycles. Twenty-two patients were treated. The median number of prior therapies was 2 (range, 1-6). Thirteen patients (59%) had undergone prior allogeneic stem cell transplant (allo-SCT), and 7 of 18 patients (39%) with B-cell ALL had previously received both inotuzumab ozogamicin and blinatumomab. The recommended phase 2 dose of venetoclax in the combination regimen was 400 mg daily. The composite complete remission (CR) and CR with incomplete hematologic recovery (CRi) rate was 57% (CR, 43%; CRi, 14%), and 45% of responders achieved measurable residual disease negativity by multiparameter flow cytometry. Four patients proceeded to allo-SCT. The median duration of response was 6.3 months. The median overall survival was 7.1 months, and the 1-year overall survival rate was 29%. The most common grade ≥3 nonhematologic adverse events were infection in 17 patients (77%) and febrile neutropenia in 4 patients (18%). Overall, the combination of mini-hyper-CVD plus venetoclax was active in heavily pretreated relapsed/refractory ALL. Further development of venetoclax-based combinations in ALL is warranted. This trial is registered at www.clinicaltrials.gov as #NCT03808610.

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.

Dose-Dense Mini-Hyper-CVD, Inotuzumab Ozogamicin and Blinatumomab Achieves Rapid MRD-Negativity in Philadelphia Chromosome-Negative B-cell Acute Lymphoblastic Leukemia

BackgroundThe combination of low-intensity chemotherapy and inotuzumab ozogamicin (INO), with sequential blinatumomab, is highly effective in older adults with newly diagnosed B-cell acute lymphoblastic leukemia (ALL) and in relapsed or refractory B-cell ALL. Earlier, “dose-dense” administration of blinatumomab could lead to earlier and deeper measurable residual disease (MRD) responses and better outcomes. Patients and MethodsWe performed a retrospective analysis of the safety and efficacy of a dose-dense regimen of mini-hyper-CVD (mini-hyperfractionated cyclophosphamide, vincristine, and dexamethasone alternating with mini-methotrexate and cytarabine), INO, and blinatumomab in patients with B-cell ALL. ResultsTwenty-one patients were treated (frontline, n = 9; MRD consolidation, n = 4; relapsed/refractory, n = 8). In the frontline cohort, all patients achieved CR/CRi and MRD negativity by flow cytometry at the end of cycle 1. Across the frontline and MRD consolidation cohorts, 10/11 patients (91%) achieved next-generation sequencing MRD negativity at a sensitivity of 10−6, including 6/10 evaluable patients (60%) who achieved next-generation sequencing MRD negativity after cycle 1. The CR/CRi rate in the relapsed/refractory cohort was 63%, and all responders achieved MRD negativity by flow cytometry at the end of cycle 1. The 1-year overall survival rate for the combined cohort of the frontline and MRD-positive patients was 83%. No new safety signals were observed with the dose-dense mini-hyper-CVD, INO, and blinatumomab regimen. ConclusionDose-dense delivery of mini-hyper-CVD, INO, and blinatumomab was safe and resulted in rapid and deep MRD negativity in patients with B-cell ALL. This regimen is now being prospectively evaluated in both the frontline and relapsed/refractory settings.

Determinants of outcomes and advances in CD19-directed chimeric antigen receptor therapy for B-cell acute lymphoblastic leukemia.

Relapsed and refractory B-cell acute lymphoblastic leukemia (B-ALL) is an aggressive B-cell neoplasm associated with poor outcomes. Conventional multiagent chemotherapy and bispecific antibody therapy may induce remission; however, relapse rates remain high and overall survival is poor. Chimeric antigen receptor T-cell (CAR-T) therapy provides durable, deep complete remission, and long-term cures in relapsed and refractory B-ALL. However, with this new treatment modality, 10%-30% of patients do not achieve remission, and over 50% experience relapse after therapy. Currently, there are two approved CD19-specific CAR-T cell constructs in B-ALL, Tisagenlecleucel and Brexucabtagene Autoleucel by the United States Food and Drug Administration, and the European Medicines Agency (EMA). In this review, we discuss patients, disease, and CAR-T predictors of outcomes in B-ALL. We describe the two approved CD19-directed CAR-T cell products, review the current literature, and discuss factors associated with high risks of therapy failure and future direction in CAR-T cell therapy for B-ALL.

Impact of inotuzumab ozogamicin on outcome in relapsed or refractory acute B-cell lymphoblastic leukemia patients prior to allogeneic hematopoietic stem cell transplantation and risk of sinusoidal obstruction syndrome/venous occlusive disease.

We evaluated 58 patients with relapsed or refractory (r/r) acute B-lymphoblastic leukemia (B-ALL; median age 42.5 years; range, 16-69 years), treated with inotuzumab ozogamicin (INO) between 2016-2022 and who received an allogeneic hematopoietic stem cell transplantation (allo-HCT) consecutively. Forty-seven (81%) of the 58 patients were heavily pretreated receiving intensive chemotherapy +/- tyrosine kinase inhibitor, blinatumomab in 24 (41%) and allo-HCT at first-line in 11 (19%) patients. Complete remission rate prior to allo-HCT was 84%. Median follow-up was 30.5 months and median overall survival (OS) measured from start of INO was 11.2 months. One- and 2-year OS rates were 50% (95% confidence interval [CI]: 38.4-56.1) and 36.7% (95% CI: 25.5-52.9), respectively. Sinusoidal obstruction syndrome/venous occlusive disease (SOS/ VOD) after allo-HCT occurred in 17 (29%) patients. Of those, nine (53%) patients died due to SOS/VOD and multi-organ failure. Two had received >2 INO cycles (3 cycles, 5 cycles, N=1, each), all others ≤2 INO cycles prior to allo-HCT. Logistic regression analysis revealed conditioning with double alkylators (P=0.038) and allo-HCT during first-line therapy (P=0.050) as significant risk factors for SOS/VOD and in trend allo-HCT ≤60 days from last INO application (P=0.07), whereas number of INO cycles before allo-HCT and time between last INO application and allo-HCT were not significant. Relapse/progressive disease occurred in 20 (34%) patients. Of those, five (25%) patients are still alive, whereas 15 succumbed of their disease. Treatment with INO seems to be an effective approach with successful bridge-to-transplant. However, risk of SOS/VOD is high, necessitating continuous monitoring and recognition of SOS/VOD risk factors.

Infections in children following chimeric antigen receptor T-cell therapy for B-cell acute lymphoblastic leukemia.

CD19-directed chimeric antigen receptor T-cell (CAR-T) therapy is transforming care for pediatric patients with relapsed or refractory B-cell acute lymphoblastic leukemia (B-ALL). There are limited pediatric-specific data concerning the infection risks associated with CD19 CAR-T therapy and the adequacy of current antimicrobial prophylaxis guidelines for these patients. We describe the antimicrobial prophylaxis used and the types of infectious occurring in the first 100 days following CAR-T therapy for relapsed or refractory B-cell ALL in children and adolescents (≤18 years) at our centre. Twenty-seven patients received their first CAR-T infusion (CTI) during the study period. Almost all patients (96%) had a comprehensive Infectious Diseases review prior to CTI, which informed a personalised prophylaxis or fever/sepsis plan in six (22%). Overall, six (22%) patients had one or more infections during the study period including five (19%, 0.9 per 100 days-at-risk) from days 0-30 and three (n = 20, 15%, 0.6 per 100 days-at-risk) from days 31-100. Bacterial blood stream infections were the most common type of infection encountered during both time periods, and one patient had probable pulmonary aspergillosis. There were no infection-related deaths. Our study contributes important information on the spectrum of infections encountered in pediatric patients with B-ALL post CAR-T therapy. Overall, the burden of infectious complications post CAR-T therapy in our cohort is lower than previously reported in the literature. Results suggest that our prophylaxis recommendations are effective in this population.

Novel chimeric antigen receptor targets and constructs for acute lymphoblastic leukemia: Moving beyond CD19.

Acute lymphoblastic leukemia (ALL) is the second most common acute leukemia in adults with a poor prognosis with relapsed or refractory (R/R) B-cell lineage ALL (B-ALL). Anti-CD19 chimeric antigen receptor (CAR) T-cell therapy has shown excellent response rates in RR B-ALL, but most patients relapse due to poor persistence of CAR T-cell therapy or other tumor-associated escape mechanisms. In addition, anti-CD19 CAR T-cell therapy causes several serious side effects such as cytokine release syndrome and neurotoxicity. In this review, we will discuss novel CAR targets, CAR constructs, and various strategies to boost CARs for the treatment of RR B-ALL. In addition, we discuss a few novel strategies developed to reduce the side effects of CAR.

Interleukin-8 Rs4073 Genotypes as Prognostic Predictors for Childhood Acute Lymphocytic Leukemia.

Interleukin 8 (IL-8) is highly expressed in refractory acute lymphocytic leukemia (ALL) cells. This study aimed to investigate the contribution of IL-8 polymorphisms to the risk of childhood ALL. The genotypes of IL-8 rs4073, rs2227306, rs2227543, and rs1126647 were determined in 266 childhood ALL cases and 266 controls using the PCR-RFLP method. Additionally, we assessed whether the interactions of these genotypes with age and sex contributed to childhood ALL risk. The distributions of genotypic and allelic frequencies of IL-8 rs4073, rs2227306, rs2227543, and rs1126647 were not significantly different between childhood ALL cases and controls (all p>0.05). However, carriers of the variant AA genotype at IL-8 rs4073 had a significantly higher risk of childhood ALL among those aged ≤3.5 years and among girls (OR=2.39 and 3.32, 95%CI=1.21-4.73 and 1.51-7.30, p=0.0182 and 0.0042, respectively). In the stratification analysis, IL-8 rs4073 AT and AA genotypes were associated with higher childhood ALL risk classification and shorter survival time (OR=2.21 and 4.13, 95%CI=1.29-3.78 and 1.87-9.10, p=0.0054 and 0.0002, respectively). There was no positive association for rs2227306, rs2227543, or rs1126647 (all p>0.05). The A allele of IL-8 rs4073 can serve as a diagnostic predictor for childhood ALL, but only in girls and patients younger than or equal to 3.5 years old. More importantly, it can serve as a prognostic marker for high-risk classification and shorter survival time. Further validation studies can help extend the use of this prognostic predictor in clinical practice.

One-Stop No-Edited Allogenic CAR-T Therapy Bridging HSCT to Treat Children with Relapse and Refractory Acute Lymphoblastic Leukemia: A Prospective Clinical Study from a Single Center

Object: Chimeric Antigen Receptor T-Cell (CAR-T) therapy has been developed to be the most effective treatment for relapse and refractory(R/R) B-cell acute lymphoblastic leukemia(B-ALL). However, in some patients prolonged chemotherapy and previous autologous-CAR-T(auto-CAR-T) therapy severely impaired lymphocyte function leading to inability in vitro expansion for effective CAR-T therapy. To address this challenge, we designed this clinical trail to use one-stop no-edited allogenic CAR-T（allo-CART）bridging to same donor conditioning free HSCT to treat children with R/R B-ALL. Methods: Myeloablative conditioning was given to reducing the leukemia burden and clearing lymphatic function for these active ALL. After that allo-CART was used to regain the immune killing effect and clear leukemia cells. Same donor seamless conditioning free HSCT were performed to rapid reconstruction of hematopoietic cells to overcome Immune effector cell associated hematologic toxicity post CAR-T therapy. Ex vivo TCRαβ+ T-cell depleted hematopoietic stem cell were transplanted for haplo-identical donor (HID) to minimize allogeneic reactivation and only macophenolate mofetil (MMF) were given for GHVD prophylaxis and to avoid more immunosuppressive to injury CART effect. Results: From October 2020 to April 2023, 16 extremely R/R B-ALL children with the median age of 10y (1.5-17) were recruited in this study, all patients relapsed 2-5 times and failure of 1-3 times auto-CART therapy with mean blast 70.6%±28.8%. Myeloablative conditioning with total body irradiation (12GY，-7d to -5d),Flu (160mg/m2, -5 to -2d) and CTX (120mg/kg，-4d to -3d) were given. After conditioning all patients received no-edited family donor allo-CAR-T therapy with the average cart (5.29±2.92)×10 6/kg, 3 from matched sibling donor (MSD) and 13 from haplo identical donor(HID). 6 patients received CD22-targeted CAR-T therapy due to loss of CD19 after previous auto-CART and another 10 received bispecific CD19/CD22-targeted CAR-T therapy. Immediately after the peak of cytokine release syndrome (CRS), median 11 days (range: 8-34 days), same allo-CART donor hematopoietic stem cell were transplanted with the median CD34+cells(6.88±2.77)×10 6 /kg and TCRαβ+T cells(18.65±16.10)×10 4 /kg for TCRαβ+depleted HSCT. After median follow-up of 8 (range 3 to 34) months for the surviving patients. Out of the 16 patients, 6 (37.5%) achieved CR after conditioning, 13 (81.3%) achieved CR after CAR-T therapy and 15 (93.8%) got CR at one month post HSCT. Among the 16 patients, 15 experienced CRS (above grade 1) and one accompanied by immune effector cell-associated neurotoxicity syndrome (ICANS), but no one died of CRS. 13(81.2%) patients developed acute graft-versus-host disease (aGvHD) before transplant mainly presented with skin GVHD except 3(18.9%) had a grade III GVHD which easily be resolved. Before HSCT, all patients achieved complete chimerism with donor T-cells. Almost every one experienced several episode infection during these therapy. Until the last follow-up, 2 cases relapsed and 5 died (2 died of infections, 1 died of relapse and 2 died of GvHD combined thrombotic microangiopathy and infection). Despite being a cohort of R/R patients with non-CR, the estimated overall survival (OS) at 1 year was 58.7%±16.0%, event-free survival (EFS) was 44.4%±14.2%. Conclusion: For children with repeated relapsed B-ALL failure of previous auto-CART, Allo-CART treat can be considered as long as CART targets still presented. One-stop no-edited same donor allo-CART bridging to conditioning free HSCT provides a chance of survival for these extremely refractory/relapsed B-ALL with manageable CRS and GVHD, but more serious infection.

Impact of Prior Response to Blinatumomab on Outcomes of Brexucabtagene Autoleucel (Brexu-cel) in Adult Patients with Relapsed or Refractory (r/r) B-Cell Acute Lymphoblastic Leukemia (B-ALL): Results from the Real-World Outcomes Collaborative of CAR-T in Adult ALL (ROCCA)

Introduction: Brexucabtagene autoleucel (brexu-cel) is an autologous anti-CD19 chimeric antigen receptor (CAR) T-cell therapy approved for adults with relapsed or refractory (r/r) B-cell acute lymphoblastic leukemia (B-ALL). Blinatumomab is a CD19-directed bispecific T-cell engager that is also approved for r/r B-ALL, and often used as early salvage therapy. Data in the pediatric/AYA population suggest that patients who did not respond to blinatumomab may have inferior outcomes to CD19-directed CAR-T products compared to those who have achieved a response to blinatumomab or were blinatumomab-naïve (Myers et al. J Clin Oncol 2022). In this study, we evaluate the response to blinatumomab and subsequent response to brexu-cel in adults with r/r B-ALL. Methods: Retrospective data were collected from 25 centers across the U.S. as part of the real-world outcomes collaborative study of CAR-T in B-ALL (ROCCA). Consecutive patients treated with brexu-cel from 2021 to 2023 were categorized by blinatumomab exposure status. Those exposed were separated into “blinatumomab responders” (B-R), defined as patients achieving a CR/CRi in response to any number of cycles of blinatumomab, and “non-responders” (B-NR). Each cohort was compared for outcomes of interest. The primary outcome was CR/CRi rate at day 28 following brexu-cel administration. Secondary outcomes were duration of response (DOR), progression-free survival (PFS), and overall survival (OS). Survival outcomes were calculated from day of brexu-cel infusion and were not censored for allogeneic hematopoietic cell transplantation or maintenance therapy. All living patients were censored at data cutoff on June 30, 2023. Survival comparisons were made by log rank test. Results: Among 152 patients who received brexu-cel, the median follow-up time was 8.4 months. Eighty-eight (57%) of 152 r/r B-ALL brexu-cel recipients had received blinatumomab prior to apheresis. The median number of pre-apheresis blinatumomab cycles was 2 (range 1-12). The baseline characteristics of B-R, B-NR, and blinatumomab-naïve (B-NV) patients were similar, including pre-apheresis disease burden and receipt of maintenance therapy following brexu-cel infusion (Table 1). Seventy percent (N= 62) of the blinatumomab-exposed patients were B-R, while 30% (N=26) were B-NR. Rates of CR/CRi at day 28 following brexu-cel infusion were similar between B-R, B-NR, and B-NV patients (79% vs 84% vs 78%, respectively). Most of these remissions were negative for measurable residual disease (MRD), with similar MRD negativity rates in the three groups (table 2). 1-year DOR and PFS were significantly higher in the B-NV group compared to B-R or B-NR (77% vs 49% vs 50%, p<.0001; 60% vs 37% vs 30%, p<.0001). B-NV and B-R had better 1-year survival compared to B-NR (71% vs 65% vs 32%, p<.0001). There were more CD19-negative relapses following brexu-cel in B-NR (29%) and B-R (18%) compared to B-NV patients (8%), although this was not statistically significant. Conclusions: Brexu-cel induced deep responses in a majority of adults with r/r B-ALL, irrespective of prior exposure or response to blinatumomab. Similar to data published by the pediatric CAR-T cell groups, our data draw speculation that adult patients who did not respond to blinatumomab experience shorter overall survival following brexu-cel compared to those who responded to or did not receive blinatumomab. This should be confirmed in a larger, prospective clinical trial. Because this analysis could not account for patients who achieved durable remission after blinatumomab, these differences may not reflect superiority of sequencing brexu-cel before blinatumomab. The higher number of CD19-negative relapses in the blinatumomab-exposed cohort add to the interest in pursuing strategies to address antigen escape following CAR-T cell therapy directed against a previously targeted antigen.

Mini-Hyper-CVD Plus Venetoclax for Treatment of Older Adults with Newly Diagnosed Ph-Negative B-ALL or T-ALL

Introduction Treatment of Philadelphia chromosome (Ph)-negative acute lymphoblastic leukemia (ALL) in older patients (pts) is challenging due to poor tolerance of conventional chemotherapy and chemo-resistant disease. Pre-clinical work demonstrates that lymphoblasts are BCL2-dependent and sensitive to the BCL2 inhibitor venetoclax (VEN). We hypothesized that VEN plus dose-reduced hyper-CVD (cyclophosphamide, vincristine, dexamethasone) chemotherapy would be well tolerated and effective in older pts. We previously reported the safety and tolerability of VEN plus hyper-CVD in newly diagnosed and relapsed/refractory (R/R) pts (Jain ASH 2019), with a maximum tolerated dose of VEN 600 mg daily on days 1-21 per 28-day cycle. Preliminarily efficacy was promising in newly diagnosed pts, which prompted study extension to phase (P) 2, enrolling newly diagnosed older pts with Ph-negative (neg) B-ALL and T-ALL. Methods Pts with Ph-neg B-ALL or T-ALL were enrolled in a multi-center Phase Ib/II study (NCT03319901). In P1, both R/R pts and newly diagnosed pts ≥ 60 years (yrs) were enrolled. In P2, only newly diagnosed pts ≥ 55 yrs old or ≥ 50 yrs old with BMI ≥ 35 kg/m2 were enrolled. Pts began with VEN ramp-up (P1 over 7d; P2 over 3d) to target dose (P1: dose level [DL]1 400 mg/d; DL2 600 mg/d; P2 400 mg/d), Figure 1. Hyper-CVD, including central nervous system (CNS) prophylaxis with intrathecal chemotherapy, was then given with VEN per DL for 21/28 days per cycle, for up to 8 cycles. Following completion of hyper-CVD courses, pts received VEN plus POMP maintenance for up to 2 yrs. Pts were recommended to receive fewer than 8 cycles of hyper-CVD in the setting of toxicity or to proceed to allogeneic hematopoietic stem cell transplant (HSCT) per physician discretion. This report updates follow-up of the newly diagnosed pts enrolled in P1 and the P2 cohort. Complete remission (CR) was defined as <5% marrow blasts, no evidence of extramedullary or CNS leukemia, ANC >1.0 K/uL and platelets >100 K/uL. Measurable residual disease (MRD) was evaluated by multicolor flow cytometry (MFC) and negative defined as <0.01%. Survival outcomes are presented via Kaplan Meier. Results In total, 30 newly diagnosed pts [P1 11 (DL1=3; DL2=8); P2 18] were treated with a median age of 68 yrs (range, 57-81 yrs, n=12 [40%] ≥70 yrs); n=15 (50%) women, n=4 (13%) Hispanic, and n=1 (3%) Black. Twenty-three (77%) pts had B-ALL and 7 (23%) pts had T-ALL (6/7 early T-cell precursor). Two (6%) pts had central nervous system (CNS) involvement at diagnosis (1-CNS3, 1-CNS2). High risk genetics were present in 56% (13/23) of B-ALL pts: TP53 (n=9 associated with complex [n=3] or hypodiploid [n=5] karyotype), KMT2A (n=1), IKZF1 abnormality (n=2), and Ph-like (n=1). Eight B-ALL pts had received prior chemotherapy for multiple myeloma (n=6; n=4 auto HSCT, n=5 lenalidomide), diffuse large B-cell lymphoma (n=1, RCHOP), and breast cancer (n=1, docetaxel, carboplatin, trastuzumab). The median number of hyper-CVD cycles received was 4 (range 1-8) among the 27 pts who have completed the hyper-CVD phase of treatment (3 pts are currently receiving consolidation). Mortality within 30 days was 3% (n=1). One patient died in CR due to sepsis during cycle 4. Venetoclax did not impair count recovery: median time from C1 to C2 was 34 days (range 27-47). Dose adjustments of VEN occurred in 4 pts (15%). An MRD-neg CR was achieved in 25/30 (83%) pts. The median cycles to achieve both CR and MRD negativity by MFC was one (range: CR 1-2 cycles; MRD negativity 1-4 cycles). Remaining pts had refractory disease (n=4, 13%), or were not assessed (n=1, 3%) due to early death. Of the 25 pts who achieved CR, 11/25 (44%) received allogeneic HSCT in CR1 after a median of 200 days (range 138 to 347). With a median follow-up of 16.4 months, the estimated 12- and 24-month OS are 82.1% (95% CI 66, 98) and 74.6% (95% CI 54, 95), Figure 2; and RFS are 82.9% (95% CI 65, 100.0) and 67.8% (95% CI 44, 92), respectively. At data cut-off, 22 pts (73%) are alive. Death events (n=8, 27%) were due to early mortality (n=1, related to both ALL and infection), post HSCT complications (n=3), refractory ALL (n=1), relapsed ALL (n=1), sepsis in CR (n=1), and complications of cardiac surgery in CR (n=1). Conclusion In this ongoing study, the addition of VEN to hyper-CVD in newly diagnosed ALL was well tolerated with encouraging responses. A future amendment will incorporate blinatumomab consolidation for pts with B-ALL.

A Phase I Study of Venetoclax in Combination with Inotuzumab Ozogamicin for Relapsed or Refractory ALL in Adults

Introduction Adults with acute lymphoblastic leukemia (ALL), especially those who are older and/or have unfavorable disease biology frequently relapse. Inotuzumab ozogamicin (INO), an anti-CD22 monoclonal antibody covalently linked to calicheamicin, is approved for treatment of relapsed or refractory (R/R) CD22+ ALL. Although INO induces measurable residual disease negative (MRD-neg) complete remission (CR) in >75% of patients (pts), the duration of response (DOR) is limited (<6 months). Pre-clinical work demonstrates that malignant lymphoblasts are BCL2-dependent (Del Gaizo Moore Blood 2008). Initial results of the BCL2 inhibitor venetoclax (VEN) combination therapies for ALL are promising (Jain ASH 2019, Pullarkat Cancer Discov 2021). Due to distinct mechanisms of activity, non-overlapping toxicity, and possible synergy (Kirchhoff Blood 2021), we hypothesized that INO and VEN can be safely and effectively combined. Study Design and Eligibility This is an investigator-sponsored phase I study (NCT05016947) with a 3+3 dose escalation design. The primary objective is to determine the maximum tolerated dose (MTD) of VEN plus INO at the FDA-approved doses in adults with R/R CD22+ ALL. Secondary objectives assess efficacy (hematologic response, MRD by multi-parametric flow cytometry [MFC] threshold <0.01%, and DOR). A 14 pt expansion cohort is planned. Dose-limiting toxicity (DLT) is defined as treatment-related CTCAE v5 non-heme toxicity grade 3+, sinusoidal obstructive syndrome (SOS) any grade, or liver toxicity during Induction (Ind) Cycle (C) 1 and/or failure of hematologic recovery (ANC ≥500, Plts ≥25 K/mL) by day 42 of Ind C1 in responding pts. Eligibility: ≥18 years (yrs); ALL (≥5% blasts) or LBL (marrow involvement not required); CD22 expression on ≥20% of blasts; R/R to one or more cycles of CC or in the case of Philadelphia-chromosome (Ph)-positive ALL, failed by two or more TKIs, or refractory to/ineligible for ponatinib; ≥60 days from bone marrow transplant (BMT), and off immune suppression ≥2 weeks; adequate liver and kidney function; no history of liver disease including SOS; blast count ≤25 K/mL prior to treatment; no symptomatic central nervous system (CNS) disease. Pts with prior INO or VEN treatment for R/R ALL are excluded. Regimen Pts are treated with a VEN Ramp-Up over 3 days (DL1: 100/200/200; DL2: 100/200/400) followed by Induction C1: IV INO days 1, 8, 15 (0.8/0.5/0.5 mg/m2) and VEN daily per DL days 1-21. DEX 10 mg/m2 IV/PO is administered during Ramp-Up and Ind C1 days 1-4 (7 days total). Pts with >5% blasts after C1 receive Ind C2 without DEX. Pts with <5% blasts after Ind (1 or 2 cycles) continue with up to four 28-day consolidation cycles (INO 0.5 mg/m2 days 1, 8, 15 plus VEN per DL days 1-21). Pts receive CNS prophylaxis with intrathecal chemotherapy. Results The 2-level dose-escalation phase has been completed; we enrolled 9 pts (5 female/4 male) with Ph-negative (n=7) or Ph-positive (n=2) ALL. The median age was 45 yrs (range 25 -74). Pts had received 1 (n=5) or 2 (n=4) prior lines of therapy. DL1 enrolled 3 pts without DLT. All DL1 pts achieved an MRD-neg CR and bridged to consolidation: 1 pt XRT to involved disease site (ankle) after 3 cycles and 2 pts to BMT after 2 cycles (Table). Three pts enrolled at DL2; no DLTs were observed. All achieved an MRD-neg CR. Two pts bridged to consolidation (donor lymphocyte infusion after 3 cycles, blinatumomab after 5 cycles) while 1 pt with KMT2A-r ALL experienced early relapse with lineage switch during second cycle. A confirmatory cohort of 3 pts enrolled at DL2 without DLT. All achieved a CR (n=2, MRD-neg; n=1, MRD-pos). The pt with MRD-pos CR as best response proceeded to blinatumomab as bridge to BMT after 2 cycles with 2 pts continuing treatment (currently cycle 2). Overall, CR was achieved in 100% (9/9) of pts with 7/8 (87%) achieving MRD-negativity. With median follow-up of 195 days (95% CI 80 - NR), 2 pts have relapsed 48 (on treatment) and 177 (after BMT) days from registration while other pts remain alive in CR. Non-heme grade 3-4 AEs include febrile neutropenia (2), DIC (1), tumor lysis syndrome (1), anxiety (1), hypertension (1), and hypotension (1). There have been no SOS. There were no delays in count recovery during C1, with median time from C1 to C2 being 30 days (range 27-42). Conclusion VEN 400mg x 21 days in combination with INO at standard doses was well tolerated and declared the recommended phase 2 dose (RP2D) with a CR rate of 100%.

Results from the Phase 1 Portion of a Trial of Oral Ixazomib Combined with Chemotherapy in Relapsed/Refractory Acute Lymphoblastic Leukemia or Lymphoma in Children, Adolescents and Young Adults: A Report from the Therapeutic Advances in Childhood Leukemia and Lymphoma (TACL) Consortium

ACKNOWLEDGEMENT Proteasome inhibitors potentiate anti-tumor effects of standard cytotoxic chemotherapy in childhood leukemia. Ixazomib is an oral proteasome inhibitor that has a shorter proteasome dissociation half-life than bortezomib, which leads to a higher tumor-to-blood ratio inhibition. We performed a phase 1 trial to determine the dose limiting toxicities (DLT), Recommended Phase 2 Dose (RP2D) of ixazomib in pediatric patients with relapsed/refractory acute lymphoblastic leukemia (ALL) or lymphoma (LL). Patients ≤ 21 years of age with relapsed or refractory ALL (with ≥ 5% detectable disease in the marrow) or LL were eligible. Ixazomib was combined with 28-day blocks of well-established, relapsed ALL backbone chemotherapy. Block 1 contained vincristine (1.5 mg/m 2/dose IV Days 1, 8, 15, 22), dexamethasone (5 mg/m 2/dose IV or oral twice daily Days 1-14), PEG-asparaginase (2500 IU/m 2/dose IV Days 2, 15) and daunorubicin (60 mg/m 2/dose IV Day 1) (VXLD). An optional Block 2 contained vincristine (1.5 mg/m 2/dose IV Day 1), dexamethasone (3 mg/m 2/dose oral twice daily Days 1-5), methotrexate (1000 mg/m 2/dose IV over 36 hours Day 8), PEG-asparaginase (2500 IU/m 2/dose IV Day 9), cyclophosphamide (440 mg/m 2/dose IV Days 15-19) and etoposide (100 mg/m 2/dose IV Days 15-19). An additional optional Maintenance Block contained vincristine (1.5 mg/m 2/dose IV Day 1), prednisone (20 mg/m 2/dose oral twice daily Days 1-5), mercaptopurine (75 mg/m 2/dose oral daily) and methotrexate (20 mg/m 2/dose oral weekly). Intrathecal therapy was given throughout with agents and dosing based on the patient's CNS disease status upon study entry. Ixazomib was given orally and tested at two dose levels (DL) (DL1: 1.6 mg/m 2/dose; DL2: 2 mg/m 2/dose) using a 3+3 design and was given during Block 1 on Days 1, 4, 8 and 11; during Block 2 on Days 1, 4, 8, 15 and 18 and during Maintenance on Days 1, 8 and 15. DLTs during Block 1 only were utilized to make DL escalation decisions and determine the RP2D. Patients without Down Syndrome (DS) entered Cohort A, used to determine the P2RD. Patients with DS were eligible for a 1 DL lagging descriptive-only Cohort B. Ten patients were treated; nine in Cohort A (n = 3 at DL1 and n = 6 at DL2) and one in Cohort B (DL1). Median age (range) at study entry was 10.5 years (5 - 20 years). Nine patients had B-ALL and one had T-ALL. Most were heavily pretreated with a median (range) of 3.4 (1 - 7) previous remission attempts with six having had prior immunotherapy and three patients having had at least one prior hematopoietic stem cell transplant. After Block 1, two patients received Block 2 and one received Maintenance. In Block 1 of Cohort A, non-hematological Grade 3/4 adverse events (AE) possibly, probably or definitely related to ixazomib or the backbone chemotherapy were limited and included neutropenic fever (n = 7), increased AST (n = 3), increased ALT (n = 2) and hypokalemia (n = 2). Two septic events occurred (n = 1 in Cohort A (Grade 3) and n = 1 in Cohort B (Grade 4)). Block 2 and Maintenance AEs were not significantly different than those seen in Block 1. No deaths or DLTs occurred. Response assessment showed that at DL1 two of three patients had a Complete Remission (CR) both of whom were Minimal Residual Disease (MRD) negative (-) and at DL2 three of six patients had a CR, two of whom were MRD- and two patients had a CR with incomplete count recovery (CRi). The overall response rate (CR + CRi) was 78% (7 of 9 patients). With a minimum of 20 months of follow-up six of nine patients in Cohort A and the single patient in Cohort B are still alive. All three deceased patients died of disease progression. Ixazomib can be combined with standard chemotherapy with an acceptable safety profile and an encouraging early efficacy signal in pediatric relapsed ALL including those with DS. The RP2D of Ixazomib combined with chemotherapy is 2 mg/m 2/dose, which is being used in the ongoing phase 2/expansion cohort of the study. We acknowledge the TACL Consortium's scientific contribution to and participation in this study, including participating member institutions, investigators, research teams, and the TACL Operations Center. Takeda Pharmaceuticals Company provided the investigative drug and funding in support of this trial.

Multinational Retrospective Analysis of Bridging Therapy Prior to Chimeric Antigen Receptor T Cells for Relapsed/Refractory Acute Lymphoblastic Leukemia in Children and Young Adults

Background: Chimeric antigen receptor (CAR) T cells targeting CD19 are a well-established treatment option for children and young adults suffering from relapsed and/or refractory B-lineage acute lymphoblastic leukemia. Nonetheless, there is still insufficient data about the proper management of bridging therapy between eligibility for therapy and administration of CAR T cells taking into consideration that most of the patients are heavily pretreated. Bridging therapy has been designed to achieve a low leukemia burden prior to CAR T cell infusion. However, systematic data of bridging therapy are still limited and the effect of bridging therapy on outcome, side effects and response to CAR T cell therapy is still poorly understood. With this retrospective, multinational, large-scale study, we strive to understand the impact of low- and high-intensity bridging regimens on a variety of outcome parameters in order to improve the basis for clinical decision making in bridging therapy prior to CAR T cell administration. Methods: Real-world data were collected from 83 patients receiving 88 CAR T cell therapies from twelve different sites in Germany, Austria and Switzerland. Data were collected anonymously via paper case report forms and subsequently analyzed. Performed treatments were classified into the categories 1) no systemic therapy, 2) low-intensity therapy and 3) high-intensity therapy. Bridging therapies were defined as high-intensity if at least one chemotherapeutic agent of the following was given: cyclophosphamide/ifosfamide, etoposide, anthracyclines or other agents with high toxicity potential (intravenous methotrexate, platinum-based antineoplastic drugs, thiotepa, high-dose cytarabine, fludarabine). Low-intensity bridging therapies comprised the administration of steroids, vincristine, low-dose cytarabine, PEG-asparaginase/Erwinia asparaginase and oral maintenance therapy (mercaptopurine, thioguanine, oral methotrexate, hydroxyurea). The administration of specific chemotherapeutic agents as well as immunotherapies and targeted therapies was assessed. CAR therapies comprised CD19 2 nd generation CAR T cell products from commercial and academic providers. We then analyzed the impact of different bridging regimens on several outcome parameters such as overall and disease-free survival, adverse events, tumor burden and performance status at defined time points (eligibility, leukapheresis if performed, lymphodepletion/CAR T cell infusion). Results: 33 of 88 treatments were classified as high-intensity and 34 as low-intensity bridging regimens. Prior to 13 CAR T cell administrations no systemic bridging therapy was given, 8 of 88 bridging regimens could not be stratified due to incomplete data (Figure 1). Between eligibility and apheresis, mostly low-intensity therapy or no systemic therapy was given. Within the period between apheresis and CAR T cell infusion, treatment diversified due to the heterogeneity of the cohort. Patient characteristics are listed in Table 1. Patients receiving a high-intensity bridging therapy had a significantly higher tumor burden at time point of eligibility defined by blasts in bone marrow and by measurement of minimal residual disease (MRD) compared to patients treated with a low-intensity or no systemic bridging therapy. Tumor burden within the two groups converged over the time of bridging therapy. However, at time of lymphodepletion, patients in the high-intensity group showed a significantly lower performance status indicated by Karnofsky/Lansky score than patients in the low-intensity/no systemic therapy group, reflecting the higher toxicity potential. Furthermore, these patients suffered significantly more often from bacterial adverse events and mucositis. Neither overall nor disease-free survival differed significantly between the two bridging regimen groups. Conclusion: In this retrospective cohort data, a high-intensity bridging therapy has not improved the outcome of CAR T cell therapy in terms of overall and disease-free survival. Yet high-intensity bridging therapy has caused more mucositis, bacterial adverse events and worsened the performance status. Our study suggests that a low-intensity bridging regimen may be preferred whenever tumor burden and disease kinetics allow this treatment strategy.

Impact of Salvage and Bridging Therapy in Adult Patients with Refractory B-Cell Acute Lymphoblastic Leukemia (B-ALL) Referred for Anti-CD19 CAR T-Cell Therapy: An Intention to Treat Analysis

Background: Prognosis of relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia (ALL) is poor, particularly after allogeneic hematopoietic cell transplantation (alloHCT). In this setting, several CAR T-cell products targeting CD19 (CART19) have been able to achieve complete response (CR) rates of 70 to 90%. However, a significant proportion of these patients still relapse. Several studies focus on the effect of the CART19 product on efficacy, however, information on how salvage therapy (ST) and bridging therapy (BT) can modulate the outcomes of CART19 therapy is scarce. Methods: We report the outcomes of all adult patients with R/R B-ALL intended for treatment (aphaeresis performed) with available CART19 products in a single institution from Jul 2017 to Jul 2023. This includes patients intended to receive the academic varnimcabtagene autoleucel (var-cel) in the CART19-BE-01 trial and the consecutive compassionate use and hospital exemption programs, as well as with commercially available tisagenleuceucel (tisa-cel). Lymphodepletion was performed with fludarabine (90 or 120 mg/m 2) and cyclophosphamide (900 or 1000 mg/m 2), followed by the infusion var-cel or tisa-cel, respectively. We analyzed all ST (treatment administered after last relapse before CART19-apheresis) and BT (treatment administered after apheresis and before CART19 infusion) performed, and analyzed the impact of BT on PFS and OS after apheresis. Results: A total of 74 adult B-ALL patients underwent leukapheresis and CART19 (var-cel/tisa-cel) production. At screening patients had a median age of 34 years (19-78), 45% were females, with a median of 3 prior lines of therapy (2-7) including inotuzumab (69%), blinatumomab (27%) and allo-HCT (84%). After last relapse, 92% of patients received ST with a median of 1 (0-3) treatment line, including inotuzumab (48%), high-dose chemotherapy (28%), low-dose chemotherapy (21%), TKIs (12%), blinatumomab (9%), radiotherapy (7%) and DLIs (4%). The overall response to ST prior apheresis was MRD-negative CR (28%), MRD-positive CR (22%), partial response (4%) and progressive disease (PD) in 46%. After apheresis was secured, BT was performed in 76% of patients with a median of 1 (0-2) bridging line, including low-dose chemotherapy (44%), intrathecal therapy (23%), high-dose chemotherapy (15%), TKIs (15%), inotuzumab (14%), radiotherapy (3.5%), blinatumomab (1.8%) and DLIs (1.8%). BT was not administered in 24% (8/74) of patients mainly due to morphological remission at screening (83%) and frailty (11%). The overall response to BT prior CART19 infusion was MRD-negative CR (31%), MRD-positive CR (12%), partial response (7%) and progressive disease (47%), with a 3% treatment related mortality (TRM) events attributed to BT. Inotuzumab administration occurred either as ST or BT to CART19 in 86% of patients (the remaining 14% was previouly given as bridge to allo-HCT), and was able to achieve MRD-negative CR in 42% of patients. The overall control of the disease after BT either worsened (51%), remained similar (14%), or improved (35%). After this, 12% (n=9) of CART19 treatments were not performed due to progressive disease (33%), TRM (22%), therapeutic alternative (22%), and production failure (11%). Infused patients achieved an MRD-negative CRR of 90% with a median PFS of 11,2 months. There were no differences in OS between patients with ≥5% or <5% bone marrow (BM) blast counts either before apheresis (ITT, figure 1) or after BT prior to CART19 infusion. However, despite the lack of apparent impact of this disease burden categorization on the OS at both timepoints, a statistically significant difference was observed after categorizing patients regarding the response to BT (figure 2), with a median PFS of 6.6 vs 18.6 months if the overall disease status of the patients either worsened or remained stable/improved after BT (p=0.0002). Conclusions: To the best of our knowledge this could be one of the first studies focusing on the impact of ST and BT in adult patients with R/R B-ALL referred for CART19 therapy. These results suggest that the potentially synergistic impact of bridging therapy may be mediated more by the modulation exerted by BT on the proliferative kinetics of the disease rather than on the absolute tumour burden of the patient. More detailed results on the independent impact of each type of BT will be provided in the final presentation.

CD22 CAR T Cell-Related IEC-HS Is Associated with an IFN-γ Cytokine Signature

Introduction Chimeric antigen receptor T-cell therapy targeting CD22 (CAR22) shows promise for patients with relapsed / refractory B-cell acute lymphoblastic leukemia (ALL) and large B cell lymphoma (LBCL) (Fry et al. Nat Med 2018; Baird et al. Blood 2020). The overall response rate for CAR22 in adults who received prior CD19 CAR therapy is 100% and 68% in ALL and LBCL respectively (Tandem 2023) (NCT04088890). However, 33% of pediatric ALL patients who received CAR22 developed immune effector cell-associated hemophagocytic lymphohistiocytosis-like syndrome (IEC-HS) (Shah et al. JCO 2020). IEC-HS is characterized by hyperferritinemia, cytopenias, coagulopathy and end organ damage. Pediatric ALL data suggest many cytokines including IFN-γ, IL-1β, IL-18 and TNF-α are upregulated in IEC-HS (Ishii et al. JCI 2020, Lichtenstein et al. Blood 2021). Here, we report the clinical features and cytokines associated with IEC-HS after CAR22 infusion in predominantly adult subjects with ALL and LBCL. Methods Plasma was collected weekly from Day 0 to 28 for 54 patients (ALL: n = 16, LBCL: n = 38; adult: n = 51, pediatrics: n = 3) who were treated with CAR22 manufactured using an automated, closed-system Miltenyi CliniMACS Prodigy device. Three dose levels were tested (ALL: 3 x 10 5 cells/kg, LBCL dose level 1 (DL1): 1 x 10 6 cells/kg, LBCL dose level 2 (DL2): 3 x 10 6 cells/kg). Clinical characteristics associated with IEC-HS were retrospectively collected and graded according to consensus criteria (Hines et al. TCT 2023). Eighty cytokines were quantified in batch via multiplexed fluorescence immunoassay (Luminex) to generate mean fluorescent indices (MFIs). Unsupervised hierarchical clustering using Euclidean distance and ward.D2 linkage were employed to analyze cytokine dynamics. Statistical analyses were performed using R (v 4.2.2). Results 8 of 54 (15%) patients developed IEC-HS, all were ≥18 years old. 5 patients had LBCL, 3 had ALL. 5 cases were grade 2, 3 were grade 4. Median onset was D+12 (range 8 - 21). All patients had prior CRS with median onset at D+1 (range 0 - 9). The 3 ALL patients had ongoing CRS and spectral overlap with IEC-HS at time of diagnosis whereas LBCL patients' CRS resolved prior to IEC-HS onset. IEC-HS patients had significant increases in inflammatory markers (ferritin, CRP, LDH, triglycerides), coagulation markers (INR, PTT), cytopenias (hemoglobin, platelets) and transaminases (Table 1). Patients most commonly received high-dose glucocorticoids, tocilizumab and anakinra. Additional agents for grade 4 IEC-HS included anti-thymoglobulin, dasatanib and emapalumab. 5 of 8 patients developed serious infections requiring IV antimicrobials including bacteremia, invasive fungal infections and viral reactivation. 5 patients with IEC-HS died after achieving complete response: 3 due to IEC-HS and concomitant infection, 1 from t-AML and 1 lost to follow up. IEC-HS occurred more frequently at higher doses in LBCL where multiple doses were tested (DL2: 33% vs DL1: 7%, p = 0.08). Peak serum CAR22 concentration was markedly elevated in patients who developed IEC-HS compared to those who did not (median 648 vs 42 cells/µL, p<0.001). Unsupervised hierarchical clustering performed on serial cytokine measurements identified a signature of IFN-γ-related cytokines including CXCL9, CXCL10, TNFα, FasL, IL6 and IL18 as being closely related in IEC-HS (Figure 1). Most cytokines in the signature peaked at D+14, consistent with onset of clinical IEC-HS. Peak levels of nearly all cytokines in the interferon-γ cluster were significantly elevated in IEC-HS patients compared to patients who did not develop IEC-HS, and this cluster contained most cytokines with significant increases in peak levels (Figure 1). Conclusions IEC-HS is a potentially life-threatening toxicity associated with CAR22 across age and underlying malignancy. The high rates of non-relapse mortality and severe infections in this study highlight the importance of understanding the immune dysregulation underlying IEC-HS. Higher CAR22 dose and expansion were associated with IEC-HS, indicating optimal dosing as a potential preventive strategy. The observed IFN-γ cytokine signature is consistent with myeloid cell activation and Th1 T-cell skewing that likely contributes to IEC-HS pathogenesis. These cytokines may be amenable to therapeutic intervention and further study of approaches targeting JAK/STAT and IFN-γ are warranted.

Venous Thromboembolism (VTE) in Post-CAR-T Patients - a Meta-Analysis of Phase 2 & 3 Clinical Trials

Introduction: Chimeric Antigen Receptor T- cells (CAR-T) therapy is genetically engineered T cells that provide durable responses for patients with certain hematological malignancies. CAR-T therapy continues to expand as a treatment option for various malignant conditions. ICANS and CRS, a clinical syndrome of neurological symptoms, fever, hypotension, and hypoxia, are potentially serious complications of post-CAR-T. Both of these complications can, in turn, increase the risk of VTE. Only a few case reports and retrospective analyses have described the risk of VTE. The primary objective of this systematic review and meta-analysis is to review the data from phase 2 and 3 clinical trials to determine the incidence and risk of VTE post-CAR-T treatment. Material and methods: The National Institute of Health (NIH) library, Cochrane Library, and ClinicalTrials.gov database were scoured for all phase 2 and phase 3 clinical trials, completed by March 7, 2023, on CAR-T cell therapy. Two reviewers independently verified the results. Several data points were extracted. A biostatistician conducted the meta-analysis using the Meta package in the R version 4.1.2 (Balduzzi, Rücker, & Schwarzer, 2019; R Core Team, 2021). The endpoints of interest were the odds ratio and relative risk of developing VTE while in CRS using the Mantel-Haenszel method. Result: Nine phase 2 & 3 trials (Seven phase 2 and two phase 3 trials) were identified and were included in our study. The incidence of CRS, ICANS, and VTE was obtained from the toxicity list and supplemental data for analysis. Only KTE-X19 studying Brexucabtagene (Tecartus) for relapsed or refractory adult B-cell acute lymphoblastic leukemia and Relapsed or refractory Mantle-Cell Lymphoma mentioned the incidence of one and three cases of VTE, respectively, in patients getting CAR-T cell therapy. The total number of patients reviewed from these studies was 1784, of which 1017 received CAR-T cell therapy. The odds of VTE were 99.9995% lower than CRS, OR = 0.0005, 95% CI [0.0001, 0.0017] in patients receiving a CAR-T infusion, p < .0001. The Relative risk of VTE was 0.0050, 95% CI [0.0019, 0.0132]. The test of heterogeneity (p = .0430) suggests the presence of heterogeneous results. The heterogeneity statistic I2 is 49.86%, indicating moderate heterogeneity (percentage of variation across studies due to heterogeneity rather than chance). The odds of VTE were 99.9999% lower than no VTE, OR = 0.0001, 95% CI [0.0001, 0.0004], p <.0001 with a Relative risk of 0.0039, 95% CI [0.0015, 0.0105]. Discussion: CRS is a known risk factor for VTE. In patients with underlying malignancy undergoing CAR-T therapy, the risk can be much higher than those without malignancy who develop CRS for other reasons. In a retrospective single-center observational study, Hashmi et al. reported an 11% incidence of VTE in lymphoma patients treated with CAR-T directed against the CD-19 receptor. Our systematic review and metanalysis didn't find a statistically increased risk of VTE in the patients getting CAR-T cell therapy despite the risk of CRS/ ICANS and underlying malignancy. The findings suggest that the thrombotic risks are either low or were not reported in the interval specified in the studies. The need for thromboprophylaxis must be made on a case-by-case basis, factoring in other risk factors such as underlying disease, cytopenia, and other medical comorbidities. Conclusion: The Incidence of VTE is low following CAR-T therapy despite the risks, and the need for thromboprophylaxis should be based on individual patient characteristics. Patient selection, exclusion criteria, and short follow-up periods following phase 2 trials might impact our study results. In a long-term phase 3 trial, collecting data for VTE may be needed to appropriately stratify patients for their VTE risk so that an appropriate thromboprophylaxis can be recommended to prevent an additional serious complication post-CAR-T.