Abstract: Patients with relapsed or refractory acute lymphoblastic leukemia (ALL) have a dismal prognosis. CD19 is homogenously expressed in B-precursor ALL and can be targeted by the investigational bispecific T cell–engager antibody blinatumomab. A phase II trial was performed to determine clinical activity in this patient cohort. Patients and Methods Thirty-six patients with relapsed or refractory B-precursor ALL were treated with blinatumomab in cycles of 4-week continuous infusion followed by a 2-week treatment-free interval in a single-arm study with a dose-finding stage and an extension stage. The primary end point was complete remission (CR) or CR with partial hematologic recovery (CRh). Major secondary end points included minimal residual disease (MRD) response, rate of allogeneic hematopoietic stem-cell transplantation (HSCT) realization, relapse-free survival (RFS), overall survival (OS), and incidence of adverse events (AEs). Results Median age was 32 years (range, 18 to 77 years). Twenty-five patients (69%) achieved a CR or CRh, with 88% of the responders achieving an MRD response. Median OS was 9.8 months (95% CI, 8.5 to 14.9), and median RFS was 7.6 months (95% CI, 4.5 to 9.5). Thirteen responders (52%) underwent HSCT after achieving a CR or CRh. The most frequent AE during treatment was pyrexia (grade 1 or 2, 75%; grade 3, 6%). In six patients with nervous system or psychiatric disorder AEs and in two patients with cytokine release syndrome, treatment had to be interrupted or discontinued. These medical events were resolved clinically. Conclusion The data support further investigation of blinatumomab for the treatment of adult patients with relapsed or refractory ALL in a larger confirmatory study.

Abstract: Introduction Although the labeled CD19 targeting CAR-T cell constructs axi-cel and tisa-cel are generally associated with an acceptable safety profile, non-relapse deaths can occur. Little is known about timing, causes and predictors of NRM following SOC CAR-T cell therapy for LBCL. Here, we analyzed frequency, causes, and risk factors of non-relapse deaths with focus on late NRM (beyond 4 weeks after dosing) using registry data provided by the DRST, the national partner of the EBMT. Methods Patients were selected from 356 consecutive patients who received SOC CAR-T treatment of LBCL between November 2018 and April 2021 at 21 German centers and were registered with the DRST/EBMT. Baseline patient, disease, and transplant data were collected from MED-A cellular therapy forms. Centers were contacted to provide additional treatment and follow-up information. Patients with late NRM (defined as NRM occurring beyond 4 weeks after dosing without prior LBCL relapse or progression) were compared with all patients surviving progression-free the 4-week landmark after dosing without subsequent NRM. Cumulative incidences of NRM were calculated considering relapse/progression as competing event. Results The analysis set consisted of 312 patients surviving progression-free at least 28 days after CAR-T treatment and remained alive until the end of follow-up or had a documented cause of death. Median age was 61 years (19-83), 66% were male, 52% had an IPI ≥3, 13 had an ECOG score & gt;1, 70% had received ≥3 treatment lines, 33% had failed a prior HCT, and 78% were refractory at lymphodepletion. 50% had been treated at a center contributing ≥20 cases with axi-cel (52%) or tisa-cel (48%). Grade ≥3 CRS and grade ≥3 neurotoxicity (NT) had occurred in 11% each, and 7% had no neutrophil recovery at day 100 post dosing or at last follow-up, whatever was earlier. With a median follow-up of 11.2 months, 124 patients (40%) had died, 109 (35%) LBCL-related, and 15 (5%) because of NRM. The cumulative incidence of late NRM at 12 months post dosing was 4.3% (95%CI 2.0-6.6). Causes of NRM were infections in 10 patients (bacterial or fungal sepsis/pneumonia 6; viral/atypical pneumonia/encephalitis 4); late NT 2; hyperinflammatory syndrome 1; 2 nd malignancy 1; unknown 1). Of note, 5 of the 6 lethal fungal/bacterial infections occurred subsequent to high grade NT. There was no significant difference between patients experiencing and not experiencing NRM in terms of age, gender, IPI, ECOG, pretreatment lines, prior HCT, disease status at lymphodepletion, and grade ≥3 CRS frequency. However, a significantly larger proportion of patients with late NRM had failed neutrophil recovery (27% vs 5%, p 0.011), had experienced grade ≥3 NT (40% vs 10%, p 0.0031), and/or had received axi-cel (93% vs 51%, p 0.001). Patients having neutrophil non-recovery and/or grade ≥3 NT had a 12-month NRM incidence of 16% (95%CI 5.1-26.9) vs 2.5% (95%CI 0.3-4.7) in patients with none of these 2 factors. Conclusions Late NRM in patients receiving SOC CAR-T treatment for LBCL is largely driven by infections. Risk factors for late NRM appear to be protracted neutropenia and higher grade NT, suggesting that intensified anti-bacterial/anti-fungal prophylaxis may be considered in patients with persisting critical neutropenia or exposed to high-dose steroids for NT treatment. Figure 1 Figure 1. Disclosures Dreger: BMS: Consultancy; AstraZeneca: Consultancy, Speakers Bureau; Bluebird Bio: Consultancy; AbbVie: Consultancy, Speakers Bureau; Gilead Sciences: Consultancy, Speakers Bureau; Janssen: Consultancy; Novartis: Consultancy, Speakers Bureau; Riemser: Consultancy, Research Funding, Speakers Bureau; Roche: Consultancy, Speakers Bureau. Schubert: Gilead: Consultancy. Holtick: Sanofi: Honoraria; Celgene: Honoraria. Subklewe: Miltenyi: Research Funding; Takeda: Speakers Bureau; Gilead: Consultancy, Research Funding, Speakers Bureau; Klinikum der Universität München: Current Employment; MorphoSys: Research Funding; Novartis: Consultancy, Research Funding, Speakers Bureau; Roche: Research Funding; Seattle Genetics: Consultancy, Research Funding; Pfizer: Consultancy, Speakers Bureau; Janssen: Consultancy; BMS/Celgene: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy, Research Funding, Speakers Bureau. Bastian: Abbvie: Other; Amgen: Consultancy, Honoraria; Astra Zeneca: Honoraria, Other; BMS and Celgene: Consultancy, Honoraria, Other; Kite-Gilead: Consultancy, Honoraria; MSD: Consultancy, Honoraria, Other, Research Funding; Novartis: Consultancy, Honoraria, Other, Research Funding; Pentixafarm: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Roche: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Other, Research Funding. Ayuk: Gilead: Honoraria; Celgene/BMS: Honoraria; Janssen: Honoraria; Takeda: Honoraria; Miltenyi Biomedicine: Honoraria; Mallinckrodt/Therakos: Honoraria, Research Funding; Novartis: Honoraria. Marks: Kite/Gilead: Membership on an entity's Board of Directors or advisory committees; Kite/Gilead: Honoraria; Merck: Consultancy; AbbVie: Other: Meeting attendance. Penack: Priothera: Consultancy; Takeda: Research Funding; Incyte: Research Funding; Neovii: Honoraria; Pfizer: Honoraria; Therakos: Honoraria; Novartis: Honoraria; MSD: Honoraria; Jazz: Honoraria; Gilead: Honoraria; Astellas: Honoraria; Shionogi: Consultancy; Omeros: Consultancy. Koenecke: EUSA Pharm: Consultancy; Kite/Gilead: Consultancy; BMS/Celgene: Consultancy; Janssen: Consultancy; Novartis: Consultancy. Von Bonin: Daiichi Sankyo: Other: traveling support and advisory fees; Novartis: Other: traveling support and advisory fees; Kite/Gilead: Other: traveling support and advisory fees. Stelljes: Novartis: Consultancy, Speakers Bureau; MSD: Consultancy, Speakers Bureau; Pfizer: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Medac: Speakers Bureau; Celgene/BMS: Consultancy, Speakers Bureau; Kite/Gilead: Consultancy, Speakers Bureau. Glass: BMS: Consultancy; Helios Klinik Berlin-Buch: Current Employment; Kite: Consultancy; Novartis: Consultancy; Riemser: Research Funding; Roche: Consultancy, Research Funding, Speakers Bureau. Baldus: Novartis: Honoraria; Amgen: Honoraria; Celgene/BMS: Honoraria; Jazz: Honoraria. Vucinic: MSD: Honoraria; Novartis: Honoraria; Gilead: Honoraria, Other: Travel Sponsoring; Janssen: Honoraria, Other: Travel Sponsoring; Abbvie: Honoraria, Other: Travel Sponsoring. Topp: Universitatklinikum Wurzburg: Current Employment; Celgene: Consultancy, Research Funding; Janssen: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding; Novartis: Consultancy; Roche: Consultancy, Research Funding; Gilead: Research Funding; Regeneron: Consultancy, Research Funding; Macrogeniecs: Research Funding; Amgen: Consultancy, Research Funding. Schroers: BMS/Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; GSK: Consultancy, Honoraria; Takeda: Honoraria. Hanoun: AstraZeneca: Honoraria; Abbvie: Other: travel expenses; Novartis: Research Funding. Thomas: AbbVie: Honoraria, Speakers Bureau; Art tempi: Honoraria, Speakers Bureau; BMS/Celgene: Consultancy, Honoraria, Other, Research Funding, Speakers Bureau; EUSA Pharma: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Other; Kite/Gilead: Honoraria, Other, Research Funding, Speakers Bureau; Medigene: Consultancy, Honoraria, Other; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other; Pfizer: Consultancy, Honoraria, Other, Speakers Bureau. Kröger: Novartis: Research Funding; Riemser: Honoraria, Research Funding; Sanofi: Honoraria; Neovii: Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Gilead/Kite: Honoraria; Celgene: Honoraria, Research Funding; AOP Pharma: Honoraria. Bethge: Novartis: Consultancy, Honoraria, Speakers Bureau; Miltenyi Biotec: Consultancy, Honoraria, Research Funding, Speakers Bureau; Kite-Gilead: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Celgene: Consultancy, Honoraria, Speakers Bureau.

Abstract: Abstract 670 Introduction: Relapsed/refractory B-precursor ALL in adults has a dismal prognosis with only 35–40% of patients reaching a hematological complete remission (CR) with a median overall survival of 4–6 months. An exploratory phase II trial was conducted in this patient population with blinatumomab, a bispecific T-cell engaging (BiTE®) antibody that directs cytotoxic T-cells to CD19 expressing target cells. Methods: The primary endpoint was hematological CR or CR with partial hematological recovery (CRh*) within 2 cycles of blinatumomab. Secondary endpoints included overall survival (OS) and safety. Blinatumomab was administered by continuous intravenous infusion for 28 days followed by a 14-day treatment-free interval. Responding patients had the option to receive 3 additional cycles of treatment or to proceed to allogeneic hematopoietic stem cell transplantation (HSCT). Three dosing regimens were explored (Table 1) to identify the optimal regimen with respect to efficacy and toxicity. Results: 36 patients were treated; 26 out of the 36 treated patients (72%) achieved a hematological CR/CRh*. Ten out of 26 (38%) responders had a CRh*. 24 out 26 (92%) responders achieved also a molecular response (minimal residual disease level below 10−4 as measured by PCR) within the first 2 cycles. Twenty out of 21 (95%) patients in first relapse responded whereas only 6 out of 15 (40%) of the remaining patients achieved a hematological CR/CRh*. Thirteen patients proceeded to allogeneic HSCT in CR/CRh* after blinatumomab treatment, and one of them developed a medullary CD19− relapse after allogeneic HSCT. The other 13 responders did not receive allogeneic HSCT. Eight of these 13 patients relapsed: 2 relapses were CD19− (1 medullary and 1 extramedullary); 3 were CD19+ (1 medullary and 2 extramedullary), and 3 were with pending CD19 status (all 3 medullary). The median survival for all 36 treated patients is 9.0 months with a median follow-up time for OS of 10.7 months. For patients who achieved a CR/CRh*, the median survival is 14.1 months whereas for patients who failed blinatumomab therapy the median survival is 6.6 months. Cytokine release syndrome (CRS) and CNS events were reported as medically important events. Two patients with high tumor burden and no cytoreductive prephase required treatment interruption or discontinuation. CRS syndrome could be either prevented or treated by adapting a dexamethasone regimen for patients resulting in no further treatment interruption due to CRS. Fully reversible adverse drug events of the CNS leading to treatment interruption were observed in 6 patients: 3 patients with seizures and 3 patients with encephalopathy. CNS symptoms fully resolved, and all 6 patients were able to resume treatment at a lower dose; however, 2 out of these 6 patients had a recurrent event and permanently discontinued. One patient stopped treatment due to fungal infection leading to death. As final dose and schedule, 5 μg/m2/day in week 1 and 15 μg/m2/day for the remaining treatment (as in cohorts 2a and 3) was selected for further investi-gation based on safety and efficacy considerations. In the extension cohort, cohort 3 (n=18), the most common treatment emergent adverse events (TEAE) were pyrexia (70%), headache (39%), tremor (30%) and fatigue (30%). Summary: The final dosing regimen of blinatumomab produced exceptionally high complete hematological and molecular remission rates and was well-tolerated. Updated follow-up information regarding duration of response and survival will be presented. A global phase II study to confirm these data is being conducted. Disclosures: Topp: Amgen: Consultancy; Affimed: Consultancy. Goekbuget:AMGEN: Consultancy, Honoraria, Research Funding. Zugmaier:Amgen: Employment. Mergen:Amgen Research Munich GmbH: Employment. Bargou:Amgen: Consultancy, Honoraria.

Abstract: Abstract 252 Adult patients with relapsed/refractory B-precursor acute lymphoblastic leukemia (ALL) have a dismal prognosis with low complete remission (CR) rates with intensive salvage chemotherapy which are not durable. Blinatumomab is a bispecific T-cell engaging (BiTE®) antibody construct that directs cytotoxic T-cells to CD19 expressing B-cells. In collaboration with the German Multicenter Study Group for Adult Lymphoblastic Leukemia (GMALL), an open-label, multicenter, single-arm, exploratory phase II trial is being conducted to evaluate efficacy and safety of blinatumomab in adult patients with relapsed/refractory B-precursor ALL. The primary endpoint for this trial is the rate of patients who reach CR or CR with partial hematological recovery (CRh*) within 2 cycles of blinatumomab treatment. Secondary endpoints are the rate of minimal residual disease (MRD) response (defined by an MRD level below the quantitative detection limit of 10−4), time to hematological relapse and overall survival. Blinatumomab is administered by continuous intravenous infusion for 28-days followed by a 14-day treatment-free interval. Responding patients could proceed to allogeneic hematopoietic stem cell transplantation (HSCT) or receive a total of up to 5 cycles of blinatumomab treatment. Three dose levels have been explored as shown in Table 1.Table 1.Summary of Dose Cohorts and OutcomesCohortPatients TreatedInitial Dose Week 1, Cycle 1 μg/m2/dayDose Week 2, Cycle 1 μg/m2/dayDose Weeks 3–4, Cycle 1 μg/m2/dayMaintenance Dose, Subsequent Cycles μg/m2/dayCR or CRh*Serious Adverse EventsnPts171515151551562a551515154222b65153030354310 planned5151515n.a.n.a.n.a. As of June 30, 2011, 43 cycles have been administered to a total of 18 patients (range 1–5; median 2). Twelve out of 18 patients have reached a complete remission within the first 2 cycles of single agent blinatumomab corresponding to a response rate of 67%. Of these 12 responding patients, 75% had complete hematologic recovery of peripheral blood counts. All 12 responders reached MRD negativity within the first 2 cycles and included 3 patients with t(4;11) and 1 patient with Ph-positive B-precursor ALL. Four responders proceeded to allogeneic HSCT; one experienced a CD19-negative hematological relapse after HSCT. Two responders relapsed during treatment; one had a CD19-positive extramedullary, and one a CD19-negative bone marrow relapse. The remaining 6 non-transplanted responders are still in hematological complete remission. The most common adverse events were pyrexia and chills. In cohort 1, one patient with a high tumor burden developed disseminated intravascular coagulation (DIC)/cytokine release syndrome (CRS) leading to treatment discontinuation. The implementation of a cytoreductive pre-phase and a lower initial dosing at 5μg/m2/day during the first week prevented further treatment discontinuations in such patients. Four patients had fully reversible CNS serious adverse events that led in 1 patient to discontinuation of treatment, and in 3 patients to temporary interruption of treatment. These 3 patients resumed treatment at a lower dose without further interruptions during the following cycles. There were no deaths related to blinatumomab. Blinatumomab as single agent induced an unprecedented high rate of complete hematological and MRD responses in adult patients with relapsed/refractory B-precursor ALL. A lower dose of 5μg/m2/day for the initial week of treatment, as tested in cohort 2a, demonstrated a favorable safety profile while maintaining efficacy. A maintenance dose of 30μg/m2/day, as tested in cohort 2b, did not further improve the already high efficacy but increased the number of adverse events. Therefore, the dosing of cohort 2a was selected as the basis for cohort 3 and will be applied to further clinical development in this patient population. Updated results of the study will be presented. Disclosures: Topp: Micromet: Consultancy, Honoraria. Goekbuget:Micromet: Consultancy. Zugmaier:Micromet: Employment. Klappers:Micromet AG: Employment. Mergen:Micromet Inc: Employment. Bargou:Micromet: Consultancy, Honoraria.

Abstract: Ten of 36 patients (28%) achieved an OS ≥30 months in a blinatumomab study in relapsed/refractory acute lymphoblastic leukemia. Long-term survival may be associated with T-cell expansion, B-cell depletion, and a minimal residual disease response.

Abstract: CD19-directed chimeric antigen receptor (CAR) T cells have evolved as new standard-of-care (SOC) treatment in patients with relapsed/refractory large B-cell lymphoma (LBCL). Here, we report the first German real-world data on SOC CAR-T cell therapies with the aim to explore risk factors associated with outcome. Patients who received SOC axicabtagene ciloleucel (axi-cel) or tisagenlecleucel (tisa-cel) for LBCL and were registered with the German Registry for Stem Cell Transplantation (DRST) were eligible. Main outcomes analyzed were toxicities, response, overall survival (OS), and progression-free survival (PFS). We report 356 patients who received axi-cel (n=173) or tisa-cel (n=183) between November 2018 and April 2021 at 21 German centers. Whereas the axi-cel and tisa-cel cohorts were comparable for age, sex, LDH, IPI, and pretreatment, the tisa-cel group comprised significantly more patients with poor performance status, ineligibility for ZUMA-1, and need for bridging, respectively. With a median follow-up alive of 11 months, Kaplan-Meier estimates of OS, PFS, and non-relapse mortality (NRM) 12 months after dosing were 52%, 30%, and 6%, respectively. While NRM was largely driven by infections subsequent to prolonged neutropenia and/or severe neurotoxicity and significantly higher with axi-cel, significant risk factors for PFS on multivariate analysis included bridging failure, elevated LDH, age, and tisa-cel use. In conclusion, this study suggests that important outcome determinants of CD19-directed CAR-T cell treatment of LBCL in the real-world setting are bridging success, CAR-T product selection, LDH, and the absence of prolonged neutropenia and/or severe neurotoxicity. These findings may have implications for designing risk-adapted CAR-T cell therapy strategies.

Abstract: Introduction: Relapsed/refractory (r/r) B-precursor ALL in adults has an unfavorable prognosis with a median overall survival of 4–8 months and a 5-year survival of 〈 10%. Long-term follow-up data are presented from an exploratory phase 2 study with blinatumomab, an investigational bispecific T-cell engager (BiTE®) antibody construct that directs cytotoxic T-cells to CD19-expressing target cells (Topp MS et al. Blood 2012;120(21):670). Methods: The primary endpoint was hematologic complete remission (CR) or CR with partial hematologic recovery (CRh*) within 2 cycles of blinatumomab. Secondary endpoints included rate of minimal residual disease (MRD) response (defined as 〈 10-4), overall survival (OS), and relapse-free survival (RFS). Blinatumomab was administered by continuous intravenous infusion for 28 days followed by a 14-day treatment-free interval. Responding patients had the option to receive 3 additional cycles of treatment or to proceed to allogeneic hematopoietic stem cell transplantation (aHSCT). Results: 36 patients were treated; 25 (69%) responded, with 15 (42%) achieving CR and 10 (28%) CRh*. MRD response was achieved in 22 (88%) of these 25 patients with CR or CRh*. Thirteen patients with CR or CRh* proceeded to aHSCT after blinatumomab treatment. In addition, one patient with hypocellular bone marrow and MRD response after the first cycle underwent aHSCT. Follow-up for RFS is 22.4 months; median RFS is 8.8 months. Median follow-up for OS is 30.2 months; median OS is 12.9 months. Ten patients (28%) are alive at 29.7 months (Figure). We analyzed the characteristics of the 10 living long-term survivors, defined as OS of 2 years or longer, seven of whom were relapse-free. The age of these 10 patients at the time of first infusion ranged from 21 to 72 years; the blast count at screening ranged from 8% to 97% (median, 56%). Four of the 10 patients alive had received aHSCT prior to blinatumomab treatment. Of the six patients without a prior aHSCT, two were primary refractory; two had the first relapse within 12 months and two after 12 months post first diagnosis. In the 10 surviving patients blinatumomab treatment induced CR in seven patients, CRh* in two patients, and blast-free hypo-cellular bone marrow in one patient. All 10 surviving patients had an MRD response following blinatumomab treatment. The patient with hypocellular bone marrow received a transplant after the first cycle before potential recovery of blood counts qualifying for CR/CRh* could occur. Seven of the surviving patients underwent aHSCT after blinatumomab, including four patients who received a second aHSCT after they had already received an aHSCT prior to blinatumomab. One of the three patients who did not undergo aHSCT after CRh* had grade 4 cytokine release syndrome requiring resuscitation after 1 day of blinatumomab treatment and has remained in ongoing remission for 22 months without any further treatment aside from 5 cycles of blinatumomab. Another one of these three patients, who had a grade 3 neurologic event on day 2 of cycle 2, has remained in ongoing remission for 34 months without any further treatment aside from 5 cycles of blinatumomab. The third of these three patients had two CD19-positive relapses after CR following blinatumomab treatment. The patient was retreated with 3 cycles of blinatumomab, resulting twice in CR and MRD response. Two of the 10 surviving patients relapsed after blinatumomab and aHSCT; one patient with a CD 19-negative relapse achieved another hematologic remission by chemotherapy. Summary: These data show that patients with r/r ALL, who achieved MRD response and received subsequent aHSCT following blinatumomab immunotherapy may achieve long-term survival longer than 2 years. Studies with a larger sample size are warranted to confirm these data. Two patients with grade 3 or 4 toxicities showed long-term survival without aHSCT after blinatumomab. Figure Figure. Disclosures Zugmaier: Amgen Inc.: Equity Ownership; Amgen Research (Munich) GmbH: Employment. Off Label Use: This presentation will discuss the off-label use of blinatumomab, as this agent is not approved for use by the FDA, EMA or any other regulatory authorities.. Goekbuget:Amgen Inc.: Consultancy, Honoraria, Research Funding. Viardot:Amgen Inc.: Membership on an entity's Board of Directors or advisory committees, Travel support Other; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Travel support, Travel support Other; Janssen: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Travel support Other. Horst:Amgen Inc.: Honoraria, Research Funding. Brueggemann:Amgen Inc.: Consultancy, Research Funding. Holland:Amgen Inc.: Employment, Equity Ownership. Schmidt:Amgen Inc.: Equity Ownership; Amgen Research (Munich) GmbH: Employment. Mergen:Amgen Inc.: Equity Ownership; Amgen Research (Munich) GmbH: Employment. Bargou:Amgen Inc.: Consultancy, Honoraria. Topp:Amgen Inc.: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Abstract: Introduction The CD19 targeting CAR-T cell constructs axicabtagene ciloleucel (axi-cel) and tisagenlecleucel (tisa-cel) have become an accepted standard salvage treatment of LBCL beyond the second line. Patients scheduled for approved CAR-T cell therapies usually have 4-8 weeks wait time for CAR-T cell infusion, thus often requiring bridging strategies in rapidly progressing patients to achieve disease control until start of lymphodepletion. It is still unclear, however, if the adverse impact of active progressive lymphoma can be overcome by successful bridging. We have addressed this question using registry data provided by the German Registry for Stem Cell Transplantation (DRST), the national partner of the EBMT. Methods We analyzed 356 consecutive patients who received standard of care axi-cel (n=173) or tisa-cel (n=183) treatment of LBCL between November 2018 and April 2021 at 21 German centers and were registered with the DRST/EBMT. Baseline patient, disease, and transplant data were collected from MED-A cellular therapy forms. Centers were contacted to provide additional treatment and follow-up information. Predictors of progression-free survival (PFS) were analyzed by uni- and multivariate comparisons. Results Compared to the approval trials, patients were of poor risk with 58% presenting with elevated LDH at lymphodepletion and 71% having received ≥3 pretreatment lines, resulting in ineligibility for the ZUMA-1 study in 87% of cases. Kaplan-Maier estimates of overall survival, PFS and non-relapse mortality (NRM) 12 months after dosing were 52%, 30% and 7%, respectively. Information on bridging was available for 355 patients (99%). Of these, 279 patients (78%) underwent at least one line of bridging attempt, whereas bridging was deemed unnecessary in 76 patients (22%). A wide variety of modalities were employed for bridging, with the most frequent being chemoimmunotherapy (n=188), chemotherapy (n=41), radiation (n=30), immunotherapy (n=12) and steroids (n=6). Bridging resulted in disease control (CR/PR) in 58 of 270 patients evaluable for response (21%). With a median follow-up of 11 months, 12-month PFS rates for patients without bridging, successful bridging, and bridging failure were 41%, 52%, and 20%, respectively, p= & lt;0.001 (Figure). Of note, an increased LDH at lymphodepletion did not impair PFS within the bridging responders, but affected the outcome of those patients who did not respond or not undergo bridging (p & lt;0.0001). The adverse impact of bridging failure on PFS was confirmed after multivariable adjustment for confounders (p=0.001, HR 2.083; 95% CI 1.358-3.195). Other significant risk factors for PFS on multivariate analysis were elevated LDH (p=0.012, HR 1.46; 95% CI 1.08-1.96), tisa-cel (p=0.0109, HR 1.41; 95% CI 1.06-1.88) and ECOG (p=0.021, HR 1.22; 95% CI 1.03-1.45). Conclusion The results of this large German GLA/DRST analysis suggest that effective bridging can overcome the adverse impact of active disease on the outcome of standard-of-case CD19 CAR-T therapy. With current treatment strategies, however, bridging is often unsuccessful, highlighting the need for exploring innovative tools for inducing temporary LBCL control for CAR-T therapy preparation. Figure 1 Figure 1. Disclosures Bethge: Novartis: Consultancy, Honoraria, Speakers Bureau; Kite-Gilead: Consultancy, Honoraria, Speakers Bureau; Miltenyi Biotec: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Celgene: Consultancy, Honoraria, Speakers Bureau. Schmitt: TolerogenixX: Current holder of individual stocks in a privately-held company; Novartis: Other: Travel grants, Research Funding; Kite Gilead: Other: Travel grants; Apogenix: Research Funding; MSD: Membership on an entity's Board of Directors or advisory committees; Bluebird Bio: Other: Travel grants; Hexal: Other: Travel grants, Research Funding. Holtick: Celgene: Honoraria; Sanofi: Honoraria. Borchmann: Gilead Sciences: Honoraria; BMS/Celgene: Honoraria; Janssen: Honoraria; Miltenyi Biotech: Honoraria; Novartis: Honoraria. Subklewe: Klinikum der Universität München: Current Employment; Pfizer: Consultancy, Speakers Bureau; Roche: Research Funding; Novartis: Consultancy, Research Funding, Speakers Bureau; MorphoSys: Research Funding; Janssen: Consultancy; Seattle Genetics: Consultancy, Research Funding; Takeda: Speakers Bureau; Miltenyi: Research Funding; Gilead: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy, Research Funding, Speakers Bureau; BMS/Celgene: Consultancy, Research Funding, Speakers Bureau. von Tresckow: Roche: Consultancy, Honoraria; Kite-Gilead: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Pentixafarm: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Other: congress and travel support, Research Funding; MSD: Consultancy, Honoraria, Other: congress and travel support, Research Funding; BMS-Celgene: Consultancy, Honoraria, Other: congress and travel support; AstraZeneca: Honoraria, Other: congress and travel support; Amgen: Consultancy, Honoraria; AbbVie: Other: congress and travel support; Takeda: Consultancy, Honoraria, Other, Research Funding. Ayuk: Gilead: Honoraria; Mallinckrodt/Therakos: Honoraria, Research Funding; Janssen: Honoraria; Takeda: Honoraria; Miltenyi Biomedicine: Honoraria; Celgene/BMS: Honoraria; Novartis: Honoraria. Kroeger: Novartis: Honoraria; AOP Pharma: Honoraria; Gilead/Kite: Honoraria; Riemser: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Sanofi: Honoraria; Neovii: Honoraria, Research Funding. Wulf: Takeda: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Clinigen: Consultancy, Honoraria. Marks: Merck: Consultancy; Kite/Gilead: Honoraria; AbbVie: Other: Meeting attendance; Kite/Gilead: Membership on an entity's Board of Directors or advisory committees. Penack: Astellas: Honoraria; Gilead: Honoraria; Jazz: Honoraria; Omeros: Consultancy; Shionogi: Consultancy; Priothera: Consultancy; Incyte: Research Funding; Takeda: Research Funding; Therakos: Honoraria; Pfizer: Honoraria; Neovii: Honoraria; Novartis: Honoraria; MSD: Honoraria. Koenecke: Kite/Gilead: Consultancy; BMS/Celgene: Consultancy; Janssen: Consultancy; Novartis: Consultancy; EUSA Pharm: Consultancy. Von Bonin: Kite/Gilead: Other: traveling support and advisory fees; Novartis: Other: traveling support and advisory fees; Daiichi Sankyo: Other: traveling support and advisory fees. Stelljes: Amgen: Consultancy, Speakers Bureau; Celgene/BMS: Consultancy, Speakers Bureau; Medac: Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Pfizer: Consultancy, Research Funding, Speakers Bureau; MSD: Consultancy, Speakers Bureau; Kite/Gilead: Consultancy, Speakers Bureau. Glass: BMS: Consultancy; Helios Klinik Berlin-Buch: Current Employment; Kite: Consultancy; Novartis: Consultancy; Riemser: Research Funding; Roche: Consultancy, Research Funding, Speakers Bureau. Baldus: Novartis: Honoraria; Amgen: Honoraria; Celgene/BMS: Honoraria; Jazz: Honoraria. Vucinic: Janssen: Honoraria, Other: Travel Sponsoring; Novartis: Honoraria; Abbvie: Honoraria, Other: Travel Sponsoring; Gilead: Honoraria, Other: Travel Sponsoring; MSD: Honoraria. Topp: Celgene: Consultancy, Research Funding; Kite, a Gilead Company: Consultancy, Research Funding; Roche: Consultancy, Research Funding; Novartis: Consultancy; Janssen: Consultancy; Amgen: Consultancy, Research Funding; Gilead: Research Funding; Regeneron: Consultancy, Research Funding; Macrogeniecs: Research Funding; Universitatklinikum Wurzburg: Current Employment. Schroers: BMS/Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; GSK: Consultancy, Honoraria; Takeda: Honoraria. Thomas: Abbvie: Honoraria, Speakers Bureau; Art tempi: Honoraria, Speakers Bureau; BMS-Celgene: Consultancy, Honoraria, Other: travel support, Research Funding, Speakers Bureau; EUSA Pharma: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Other: travel support; Kite-Gilead: Honoraria, Other: travel support, Research Funding, Speakers Bureau; Medigene: Consultancy, Honoraria, Other: Travel support; Novartis: Consultancy, Honoraria, Other: travel support, Speakers Bureau; Pfizer: Consultancy, Honoraria, Other: Travel support, Speakers Bureau. Dreger: Bluebird Bio: Consultancy; BMS: Consultancy; AbbVie: Consultancy, Speakers Bureau; Riemser: Consultancy, Research Funding, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Roche: Consultancy, Speakers Bureau; Gilead Sciences: Consultancy, Speakers Bureau; Janssen: Consultancy; AstraZeneca: Consultancy, Speakers Bureau.

Abstract: 6500^ Background: Blinatumomab is a bispecific T-cell engaging (BiTE) antibody that directs cytotoxic T-cells to CD19 expressing target cells. Methods: In adult patients with relapsed/refractory B-precursor ALL, a phase II dose ranging trial is being conducted to evaluate efficacy and safety of blinatumomab. The primary endpoint is the rate of hematological complete remission (CR) or CR with partial hematological recovery (CRh*) within 2 cycles of blinatumomab treatment. Blinatumomab is administered by continuous intravenous infusion for 28-days followed by a 14-day treatment-free interval. Responding patients can receive 3 additional cycles of treatment or proceed to bone marrow transplantation. Three dose levels were explored as shown in the table. Results: In total 36 patients have been enrolled, 25 are currently evaluable. Seventeen out of 25 treated patients (68%) reached a hematological CR/CRh* and a minimal residual disease (MRD) response (MRD level 〈 10 -4 ) within the first 2 cycles. Five out of 17 responders (29%) showed a CRh* due to partial recovery of platelets. For the first 18 patients, response duration is 7.1 months and the median follow-up time for overall survival (OS) is 9.7 months (median not reached). Six cases of relapses have been recorded of which 3 were CD19 + , and 3 CD19 - . As final dose 5 µg/m²/day in week 1 and 15 µg/m²/day for the remaining treatment (cohort 2a and 3) was selected. In these cohorts (n=12), the most common treatment emergent adverse events (TEAEs, all grade 1-2) were pyrexia (67%), headache (33%) and tremor (33%). TEAEs of grade ≥3 (7 in 5 patients, no grade 4), irrespective of relationship, were infections, confusion, epilepsy, hypertension and thrombocytopenia. Conclusions: The final dose was well-tolerated and produced an exceptionally high complete remission rate. A global phase 2 study to confirm these data is underway. [Table: see text]