Days Of Fludarabine Research Articles

CD27-Armored BCMA-CAR T Cell (CBG-002) Therapy for Relapsed and Refractory Multiple Myeloma: A Phase I Clinical Trial

Introduction: Several BCMA CAR T-cell products have been approved for relapsed or refractory multiple myeloma (RRMM), but long-term response has not been established. There is growing interest in the use of next-generation CAR T-cell therapy in RRMM. CBG002 is an armored BCMA CAR T-cell product engineered to constitutively express CD27, which binds CD70 to promote T-cell proliferation and differentiation. In vitro, CBG-002 cells exhibited enhanced proliferation, greater cytotoxicity and a higher proportion of memory T cells compared to control BCMA-CAR T cells; in animal models, CBG-002 infusion also resulted in improved tumor control and prolonged survival in MM xenograft mice. Based on the preclinical data, we conducted a phase I clinical trial to evaluate its safety and efficacy in patients with RRMM. Methods: This is a single-arm, open-label, phase I study (NCT04706936). Key eligibility criteria were RRMM patients who had received at least 3 prior regimens, including a proteasome inhibitor and an immunomodulatory drug; the percentage of BCMA expression ≥50% on myeloma cells, detected by either flow cytometry and immunohistochemistry. Patients received 3 days of fludarabine (30 mg/m 2) and cyclophosphamide (300 mg/m 2) followed by a single dose of CBG-002 infusion. The dose-escalation study follows a “3+3” design with 1×10 6/kg, 2×10 6/kg and 3×10 6/kg CAR-T cell cohorts. The primary endpoint was safety, including grade 3 or 4 treatment-emergent adverse events (TEAEs) and dose-limiting toxicities (DLTs); The secondary endpoints were overall response rate (ORR), duration of response (DOR), progression-free survival (PFS) and overall survival (OS). Results: As of June 25, 2023, 12 patients were enrolled and 1 patient was later excluded due to <50% BCMA expression. Among the evaluable 11 patients, there were 9 males and 2 females; median age was 52 years (range 36-66), 5/11 (45.5%) patients had high-risk cytogenetics including complex karyotype, t(4;14),1q21 amplification and del(17p), 4 (36.4%) had extramedullary disease (EMD). The median number of prior treatments was 5 (range 3-7); 7/11 pts were triple-agent exposed and refractory; 5/11 underwent ASCT. The most common TEAEs were neutropenia (G3/4 63.6%), thrombocytopenia (G3/4 36.4%) and anemia (G3/4 45.5%). Nine patients developed G1/2 CRS, which resolved spontaneously except for 2 patients who required steroids and tocilizumab, and no patients developed G3/4 CRS or ICANS. The median time to onset of CRS was 7 days (range 5-21) and the median duration was 6 days (range 5-8). At a median follow-up of 9 months, the ORR was 81.8%, including sCR/CR of 63.6%, VGPR 9.1% and PR 9.1%. After infusion, 8 pts were MRD negative in bone marrow by flow cytometry at day 28, 5 pts continued at month 3. The median OS was 14 months and the OS rate was 100%. The median PFS was 9 months and the PFS rate was 60%. The CBG-002 kinetics paralleled peripheral blood sCD27 levels with a median time to peak of 15 days (range 7-14). The fold increase in sCD27 levels was significantly higher in responders (12.1, range 1.2-83.8) than in non-responders (1.68, range 0.81-9.45). Conclusions: In this phase I study, CBG-002, a CD27-armored BCMA-CAR T therapy has demonstrated remarkable safety and clinical activity in RRMM patients.

A Phase 1 Dose Escalation Trial of Third-Generation CD19-Directed CAR T-Cells Incorporating CD28 and Toll-like Receptor 2 (TLR2) Intracellular Domains for Relapsed or Refractory B-Cell Non-Hodgkin Lymphomas (ENABLE)

Introduction: Chimeric antigen receptor (CAR) T cell therapies directed against CD19 and incorporating either CD28 or 4-1BB intracellular co-stimulatory domains are a standard of care for relapsed or refractory (r/r) B-cell lymphomas. CD19-directed CAR T-cell products employing CD28 co-stimulation yield high response rates, but have been associated with higher rates of immune effector cell-associated neurotoxicity syndrome (ICANS) and severe cytokine release syndrome (CRS) than 4-1BB co-stimulated products. There is a need for CAR T-cell products that combine high efficacy with low toxicity. Toll-like receptor 2 (TLR2) is expressed by T-cells, and its engagement enhances T-cell expansion, modulates cytokine production, and promotes long-lived T-cell memory. In preclinical studies, interposition of an intracellular domain from TLR2 between CD28 and CD3ζ resulted in reduced CAR T-cell production of ICANS-associated cytokines GM-CSF and IFN-γ, while maintaining production of the homeostatic cytokine IL-7. We investigated the safety and efficacy of a novel third generation CD19-directed CAR T-cell product, which combines CD28 and TLR2 co-stimulatory domains ( Figure). Methods: We completed a first-in-human phase 1 dose escalation trial of WZTL-002, comprising autologous 1928T2z CAR T-cells (‘ENABLE’, NCT04049513) for patients with r/r B-cell non-Hodgkin lymphomas (B-NHL). A 3+3 dose escalation design was used, with doses from 5 × 10 4 to 1 × 10 6 viable CAR T-cells/kg body weight. Eligible participants had radiologically assessable disease, satisfactory organ function and no central nervous system (CNS) involvement by lymphoma. Bridging therapy was permitted after leukapheresis and pending CAR T-cell manufacture and release. WZTL-002 CAR T-cells were administered intravenously after 3 days of fludarabine (30mg/m 2/day) and cyclophosphamide (500mg/m 2/day) lymphodepletion. Adverse events (AEs) were graded by CTCAE 5.0 except CRS and ICANS (graded by American Society for Transplantation and Cellular Therapy criteria). Response assessment was by PET/CT at month 3, per Lugano 2014 criteria. Pharmacokinetic analyses were by droplet digital PCR for CAR transgenes in blood mononuclear cells. Results: Of 21 patients treated within the dose escalation trial, median age was 57 years (range 23 - 70); 10 (48%) were female; 4 (19%) Māori. Lymphomas were of large cell histology in 17 (81%, Table). Participants had received a median of 4 prior lines of therapy, including autograft in 11 (52%) and allograft in 1. Product phenotyping showed WZTL-002 CAR T-cells were median 49% CD4 +, 41% CD8 + and 34% CD62L +. As of June 14 2023, all patients had reached the primary follow-up timepoint (3 months after WZTL-002 administration). Grade ≥ 3 AEs occurring in ≥ 10% of recipients were: neutropenia (95%), lymphopenia (57%), hypogammaglobulinemia (57%), anaemia (43%), febrile neutropenia (43%), thrombocytopenia (24%) and tumor pain (19%). Grade 1 - 2 CRS occurred in 13 patients (62%); 6 received tocilizumab and 3 dexamethasone. No CRS of grade ≥ 3, and no ICANS of any grade, occurred. Two grade 4 cytopenia dose limiting toxicities occurred at day 21 (one each at 5 × 10 5 and 1 × 10 6 cells/kg), both resolved to grade 2 by day 90. Maximum tolerated dose was not reached. Responses were seen at all dose levels with complete metabolic response in 11 (52%) at month 3. WZTL-002 CAR T-cells expanded at all dose levels. Among recipients of 0.5 - 1.0 × 10 6 CAR T-cells/kg (n = 12), median peak CAR T-cell level (C max) was 93,950 transgene copies/μg genomic DNA (reached at median day 10) and CAR T-cells persisted in 9 of 11 assessed (82%) at day 90. A recommended phase 2 dose (RP2D) range of 0.5 - 1 × 10 6/kg was selected. Conclusions: In this dose escalation trial of a novel third-generation CD19-directed CAR T-cell product that combines CD28 and TLR2 co-stimulatory domains for r/r B-NHL, we observed no severe CRS, no ICANS of any grade and complete responses at all dose levels. At RP2D, in vivo CAR T-cell expansion was similar to or greater than other CD19-directed products. In conjunction with preclinical findings, this study suggests interposition of a TLR2 domain between CD28 and CD3ζ domains may reduce CAR T-cell-related ICANS risk while retaining efficacy. Enrolment to a dose expansion cohort has commenced and will assess outpatient management and the safety and efficacy of WZTL-002 CAR T-cells manufactured using a closed automated process.

Interim Phase I Clinical Data of FT576 As Monotherapy and in Combination with Daratumumab in Subjects with Relapsed/Refractory Multiple Myeloma

Introduction: Despite the recent FDA approval of autologous chimeric antigen receptor (CAR) T-cell therapies targeting B-cell maturation antigen (BCMA), multiple myeloma (MM) remains incurable and relapsed/refractory (R/R) disease remains an area of high unmet medical need. Additionally, patient access to autologous CAR T-cell therapies is currently limited due to manufacturing constraints, the need for bridging therapy, and potentially life-threatening toxicities including cytokine release syndrome and neurologic toxicities (Munshi et al. 2021). Off-the-shelf natural killer (NK) cell therapies may offer an improved therapeutic profile and broader patient access than autologous CAR T-cell therapies. FT576 is a first-of-kind, multiplexed-engineered BCMA CAR NK cell therapy generated from a clonal master engineered induced pluripotent stem cell line, which can be used as a renewable source for the mass production of off-the-shelf NK cells of uniform composition. FT576 is engineered with 4 modalities to combine multifaceted innate immunity with multi-antigen-targeting capability: (1) high-affinity 158V, non-cleavable CD16 (hnCD16) Fc receptor for augmented antibody-dependent cellular cytotoxicity; (2) IL-15/IL-15 receptor fusion that promotes NK cell persistence; (3) CD38 knockout to mitigate NK cell fratricide by CD38-directed monoclonal antibodies (mAbs) and that provides improved metabolic fitness and resistance to oxidative stress within the tumor microenvironment; and (4) a BCMA-directed CAR to target plasma cells. These modalities are designed to enhance the potency and persistence of FT576 and to enable multi-antigen targeting when combined with tumor-targeting mAbs. In preclinical studies, FT576 combined with the anti-CD38 mAb daratumumab demonstrated highly effective tumor control compared to either treatment alone or to primary CAR T cells in a disseminated MM xenograft model (Goodridge et al. 2021), suggestive that limitations in MM treatment confounded by clonal heterogeneity and antigen loss can be overcome with a dual antigen-targeting approach. Methods: This is a Phase I trial of FT576 in patients with R/R MM. The primary objectives are to assess safety and tolerability and to determine the recommended Phase II dose of FT576, given as single or multiple doses, as monotherapy and in combination with daratumumab in R/R MM. Key secondary objectives include anti-tumor activity and pharmacokinetics. The dose-escalation stage of the trial has the following 4 arms: single-dose FT576 monotherapy on Day 1 (Regimen A); multi-dose FT576 monotherapy on Days 1 and 15 (Regimen A1); single-dose FT576 + daratumumab on Day 1 (Regimen B); and multi-dose FT576 + daratumumab on Days 1 and 15 (Regimen B1). Dose levels of FT576 starting from 100 million cells/dose are being evaluated using a modified toxicity probability interval dose-escalation design. Daratumumab is administered per approved dose and schedule. Outpatient conditioning chemotherapy consists of 3 consecutive days of fludarabine and cyclophosphamide administered prior to the first dose of FT576. Results: As of a data cutoff date of 18 Jul 2022, 9 patients with R/R MM were treated and evaluable for safety and efficacy, in the first 2 dose levels of Regimen A (n = 6) and in the first dose level of Regimen B (n = 3). No dose-limiting toxicities, and no events of any grade of cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome, or graft-versus-host disease (GvHD), were observed. Conclusions: Administration of a single dose of FT576 at 100 or 300 million cells/dose alone or in combination with daratumumab is safe and well tolerated thus far without CRS, neurotoxicity, or GvHD. Interim clinical data, including safety and tolerability and initial anti-tumor activity, from the ongoing Phase I dose-escalation study of FT576 will be presented at the conference.

A high hematopoietic cell transplantation comorbidity Index (HCT-CI) does not impair outcomes after non-myeloablative allogeneic stem cell transplantation in acute myeloid leukemia patients 60 years or older

For most acute myeloid leukemia (AML) patients an allogeneic hematopoietic stem cell transplantation (HSCT) offers the highest chance of cure. The introduction of less toxic non-myeloablative conditioning (NMA) regimes enabled older and/or comorbid patients to be consolidated with an allogeneic HSCT. While the hematopoietic cell transplantation comorbidity index (HCT-CI) predicted outcomes in many younger patient cohorts its impact in older AML patients receiving NMA-HSCT remains unknown. Here we analyzed 289 AML patients 60 years or older (median age 66, range 60-77 years) undergoing NMA-HSCT (2 or 3 Gray total body irradiation and 3 days of fludarabine 30 mg/m2). HCT-CI risk was low, intermediate, or high in 36%, 31%, and 33% of patients, respectively. Non-relapse mortality (NRM), cumulative incidence of relapse (CIR), and overall survival (OS) did not differ between HCT-CI groups. The HCT-CI also did not impact outcomes when considering the European LeukemiaNet 2017 risk at diagnosis or the measurable residual disease (MRD) status at HSCT. Notably, MRD-negative older NMA-transplanted AML patients had a beneficial OS of 49% after 5 years. Since a higher HCT-CI did not impair outcomes, age or comorbidities per se should not impede NMA-HSCT, presenting a feasible consolidation option for this group of AML patients.

Allogeneic Hematopoietic Stem-Cell Transplantation for GATA2 Deficiency Using a Busulfan-Based Regimen

Background: GATA2 deficiency is an increasingly recognized bone marrow failure syndrome responsible for: MonoMAC, monocytopenia with atypical mycobacterial infection (MAC); DCML, dendritic cell, monocyte and lymphoid cell deficiency; Emberger syndrome with lymphedema and monosomy 7; and familial myelodysplastic syndrome (MDS)/acute myelogenous leukemia (AML). GATA2 deficiency can be reversed by hematopoietic stem cell transplantation (HSCT). However, the intensity of conditioning required to ensure engraftment and reverse the myelodysplastic syndrome (MDS) characteristic of the disease remains controversial.Methods: We carried out a prospective study of allogeneic HSCT in 22 patients (mean age 26 years; range 17 to 45 years) with GATA2 deficiency, or the MonoMac syndrome, using a myeloablative, busulfan-based conditioning regimen. All 22 patients had MDS and two had AML. Eleven patients had clonal cytogenetic changes in the bone marrow. There were two matched related donor (MRD) recipients, 13 matched unrelated donor (URD) recipients, and 7 haploidentical related donor recipients. MRD and URD recipients received conditioning with 4 days of busulfan (days -6 to -3) to target an AUC between 3600 and 4800 min*microm/L and 4 days of fludarabine 40 mg/m2/day (days -6 to -3). Haploidentical related donor recipients received low-dose cyclophosphamide for two days (days -6 and -5), fludarabine 30 mg/m2/day for 5 days (days -6 to -2), 2-3 days of busulfan depending upon cytogenetics, along with 200 cGY total body irradiation (TBI) on day -1. MRD and URD recipients received tacrolimus and short course methotrexate for post-transplant graft-versus-host disease (GVHD) prophylaxis, whereas haploidentical recipients received high-dose post-transplant cyclophosphamide (PT/CY) followed by tacrolimus and mycophenolate mofetil for GVHD prophylaxis.Results: Nineteen of the 22 patients are alive with resolution of the clinical phenotype and correction of the bone marrow MDS with eradication of the cytogenetic changes at a median follow-up of 23 months (range, 6 to 48 months) giving an overall disease-free survival of 86 percent. The three deaths all occurred in the URD group. Of the three deaths, one resulted from refractory acute myelogenous leukemia (AML), and two from complications related to treatment for GVHD. There was a 26 percent incidence of grade III-IV acute GVHD (aGVHD) in the MRD and URD groups, and no grade III-IV aGVHD in the haploidentical related donor cohort. Similarly, there was a 46 percent incidence of chronic GVHD (cGVHD) in the MRD and URD cohort, whereas two of the 7 (28 percent) of the haploidentical related donor recipients had cGVHD.Conclusions: Despite overall disease-free survival of 86 percent with eradication of the clonal cytogenetic abnormalities in the bone marrow, GVHD remains a limitation in the MRD and URD cohorts treated with standard post-transplant tacrolimus/methotrexate prophylaxis for GVHD. We are currently de-escalating the busulfan dosing based on the AUC in all cohorts and incorporating PT/CY in the MRD and URD cohorts to decrease toxicity and reduce the incidence of aGVHD and cGVHD. Together with our previous studies using a nonmyeloablative regimen, it appears that when GATA2 deficiency patients are transplanted when they have a hypocellular bone marrow with MDS and without cytogenetic changes, a nonmyeloablative regimen results in reliable engraftment in GATA2 deficiency since the GATA2 deficient marrow has a proliferative disadvantage. However, with clonal progression and unfavorable cytogenetic changes and/or a hypercellular marrow, where the malignant clone has a proliferative advantage, a higher dose regimen results in more reliable engraftment and eradication of the clone. Studies to identify the precise level of conditioning for the stages of the disease are ongoing. DisclosuresNo relevant conflicts of interest to declare.

KarMMa-4: Idecabtagene vicleucel (ide-cel, bb2121), a BCMA-directed CAR T-cell therapy in high-risk newly diagnosed multiple myeloma.

TPS8053 Background: High-risk (R-ISS stage III) newly diagnosed multiple myeloma (NDMM) has a poor prognosis (median PFS, 29 mo), highlighting the need for novel disease-targeting approaches (Palumbo A, et al. J Clin Oncol 2015;33:2863-2869). Ide-cel, a BCMA-directed CAR T cell therapy, demonstrated deep, durable responses in heavily pretreated patients (pts) with relapsed and refractory MM (RRMM; Raje N, et al. N Engl J Med 2019;380:1726-1737; Munshi NC, et al. J Clin Oncol 2020;38[suppl 15]. Abstract 8503), including those with high-risk (R-ISS stage III) RRMM. In this population, earlier use of ide cel—when there may be more bone marrow reserve, more healthy peripheral blood mononuclear cells, a less compromised immune status, and less extensive disease to debulk before cell therapy—may result in improved outcomes vs standard therapies and offer an opportunity to replace transplant with CAR T cell therapy. Methods: KarMMa-4 (NCT04196491), a multicenter, open-label, phase 1, single-arm study, is currently evaluating ide-cel in pts with high-risk NDMM, defined as R-ISS stage III (ISS stage III [serum ß2 microglobulin ≥ 5.5 mg/L] and cytogenetic abnormalities t(4;14), del(17p), and/or t(14;16) by interphase FISH; or ISS stage III and serum LDH > ULN). Pts must have received ≤ 3 cycles of the induction regimens listed below, be aged ≥ 18 years, and have ECOG PS 0-1. Nonsecretory MM and CNS involvement are exclusion criteria. Pts can enroll between induction cycles 1 and 3. Permitted cycle 1 regimens are carfilzomib + lenalidomide (LEN) + dexamethasone (DEX) ± daratumumab (DARA; KRd ± DARA), LEN + bortezomib (BOR) + DEX ± DARA (RVd ± DARA), or cyclophosphamide + BOR + DEX (CyBorD). Induction cycles 2-4 are limited to KRd or RVd, with DEX omitted during cycle 3. Pts will undergo T cell collection via leukapheresis after cycle 3, and ide-cel will be manufactured during cycle 4. Stem cell collection for future use may be conducted after cycle 3 (following leukapheresis) or 4 (before lymphodepletion). Ide-cel is infused after 2 days of rest following lymphodepletion with 3 days of fludarabine 30 mg/m2 + cyclophosphamide 300 mg/m2. LEN-based maintenance may be provided upon bone marrow recovery or 90 days after ide-cel infusion, whichever is later. Dose-limiting toxicity and safety are the primary endpoints. Secondary endpoints include complete response (CR) rate and overall response rate, duration of response, time to CR, time to start of maintenance, feasibility of initiating maintenance, PFS, overall survival, and pharmacokinetics. Exploratory endpoints include LEN maintenance safety, minimal residual disease, immunogenicity and biomarkers. The starting ide-cel target dose is 450 × 106 CAR+ T cells, with dose escalation/de-escalation (150, 300, and 800 × 106 CAR+ T cells). Upon determination of optimal target dose, 12 pts will be enrolled in the dose-expansion phase. Clinical trial information: NCT04196491.

Lifileucel (LN-144), a cryopreserved autologous tumor infiltrating lymphocyte (TIL) therapy in patients with advanced melanoma: Evaluation of impact of prior anti-PD-1 therapy.

9505 Background: Immune checkpoint inhibitors (ICI) have become standard of care for treatment of metastatic melanoma. Most patients with advanced melanoma progress on ICI and treatment options are limited for these patients. Progression may be through primary resistance (lack of response) or secondary resistance (initial response then progression). Lifileucel is an adoptive cell therapy using TIL, that has shown efficacy in patients with advanced melanoma who progress on/after an anti-PD-1 (Sarnaik, 2020). We present the 28-month (mos) follow-up data and highlight the impact of prior anti-PD-1 response and duration of exposure on outcome with lifileucel. Methods: C-144-01 is a Phase 2, open-label, multicenter study of efficacy and safety of lifileucel in patients with advanced melanoma who have progressed on anti-PD-1 therapy and BRAFi ± MEKi, if BRAF V600+. We report long-term follow up on Cohort 2 (N = 66). Tumors were resected at local sites, processed in central GMP facilities for TIL production in a 22-day manufacturing process. Therapy consisted of nonmyeloablative lymphodepletion using 2 days of cyclophosphamide and 5 days of fludarabine, a single infusion of lifileucel, and up to six doses of IL-2. Objective response rate (ORR) was assessed by RECIST 1.1. Data cutoff was Dec. 14, 2020. Results: Baseline characteristics: 3.3 mean prior therapies (100% anti-PD-1; 80% anti-CTLA-4; 23% BRAFi/MEKi), high baseline tumor burden (106 mm mean target lesion SOD), 42% liver/brain lesions, 40.9% LDH > ULN. ORR by investigator was 36.4% (3 CR, one new CR developed at 24 mos; 21 PR). Median duration of response (mDOR) was not reached at median follow-up of 28 mos (DOR range: 2.2- 35.2 mos). In responders, the median cumulative duration and median prior lines of anti-PD-1 therapy was 4.4 mos (range: 1.4-22.5 mos), and 1.5 (range: 1-4). Data in Table demonstrates a meaningful increase in DOR to TIL with primary anti-PD-1 resistance and lower duration of time on prior anti-PD-1 therapy. No new safety risks have been identified for lifileucel during long-term follow-up. Conclusions: One-time lifileucel treatment results in a 36.4% ORR, and mDOR was not reached at 28 mos of median study follow up. One PR converted to a new CR at 24 months as responses continue to deepen. DOR is positively associated with primary resistance to prior anti-PD-1 therapy and with shorter cumulative prior duration of anti-PD-1 therapy. Lifileucel may offer a better clinical outcome when used earlier upon detection of progression on prior anti-PD-1 rather than retreatment with anti-PD-1 based regimens. Clinical trial information: NCT02360579. [Table: see text]

A Phase I Study of FT819, a First-of-Kind, Off-the-Shelf, iPSC-Derived TCR-Less CD19 CAR T Cell Therapy for the Treatment of Relapsed/Refractory B-Cell Malignancies

A Phase I Study of FT819, a First-of-Kind, Off-the-Shelf, iPSC-Derived TCR-Less CD19 CAR T Cell Therapy for the Treatment of Relapsed/Refractory B-Cell Malignancies

A Phase I Study of CD19-Targeted 19(T2)28z1xx CAR T Cells in Adult Patients with Relapsed or Refractory B-Cell Malignancies

Background: Autologous CAR T cell therapy targeting the B-cell specific surface antigen CD19 has demonstrated favorable clinical responses in relapsed or refractory (R/B) B-cell lymphomas (BCL). However, despite 40-60% initial complete response (CR) rates, only a subset of patients experience durable remissions, and there is a need to further improve the efficacy of CAR therapies by preventing relapse and attaining a deeper CR. We hypothesized that the redundancy of CD28 and CD3V signaling in a CAR design incorporating all 3 CD3Vimmunoreceptor tyrosine-based activation motifs (ITAMs) might foster counterproductive T cell differentiation and exhaustion, and therefore created a new CD19 CAR construct with calibrated CAR activation potential by mutating 2 of the 3 ITAMs, termed 1XX. In systemic ALL mouse models, 19-28z1XX CAR induced effective tumor eradication at low CAR T cell doses with improved survival compared to conventional 19-28z CAR. Further preclinical studies demonstrated that the enhanced therapeutic benefit resulted from the reduced strength of activation mediated by the 19-28z1XX CAR, achieving a favorable balance of effector and memory functions, thereby enhancing persistence of functional CAR T cells and promoting effective elimination of CD19+ leukemia at lower T cell doses than needed with 19-28z CAR T cells (Feucht J et al. Nat Med 2019). To further improve the persistence of functional CAR T cells, we screened different humanized CD19-directed scFv in the context of a 19-28z1XX CAR design and proved high specificity and functionality of 19-28z1XX CARs containing a novel humanized scFv T2 - termed 19(T2)28z1XX. Study Design and Methods: This study is a single center Phase I clinical trial of 19(T2)28z1XX in patients with R/R B-cell malignancies at Memorial Sloan Kettering Cancer Center (NCT04464200). Key disease eligibility criteria include R/R diffuse large B cell lymphoma (DLBCL), high grade BCL, primary mediastinal BCL, indolent BCL and chronic lymphocytic leukemia (CLL). Patients with prior CD19 CAR therapies are eligible as long as expression of CD19 is confirmed. Key exclusion criteria include ongoing immunosuppression such as systemic GvHD therapy and active CNS disease. The study uses a 3+3 dose-escalation design to identify the maximum tolerated dose for BCL. There are 5 planned flat-dose levels. Patients will receive conditioning chemotherapy consisting of 3 days of fludarabine and cyclophosphamide followed by a single infusion of 19(T2)28z1XX CAR T cells. In the dose-escalation phase, patients with DLBCL, high grade BCL, and primary mediastinal BCL are eligible to participate. Once the recommended phase 2 dose (RP2D) is determined, the study will open to dose expansion phase with two cohorts. Cohort 1 includes DLBCL, high grade BCL and primary mediastinal BCL (i.e. same eligibility criteria as the dose-escalation phase). Cohort 2 will include patients with indolent BCL, CLL, and Richter's transformation. The dose-expansion part of the trial is designed to further characterize the safety, efficacy, and pharmacokinetics of 19(T2)28z1XX CAR in multiple indications. The primary objective of the trial is to evaluate safety and tolerability and determine the recommended Phase 2 dose of 19(T2)28z1XX. Key secondary objectives include evaluation of 19(T2)28z1XX's efficacy and cellular kinetics. Exploratory objectives include assessment of B cell aplasia, and analysis of serum cytokines. The trial has begun enrollment in August 2020. The investigators are hopeful this study will lead to development of improved CD19 CAR T cell therapy with enhanced efficacy and favorable toxicity profiles with lower infused T cell dose. Disclosures Park: AstraZeneca: Consultancy; Servier: Consultancy, Research Funding; Autolus: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Novartis: Consultancy; Minverva: Consultancy; Artiva: Membership on an entity's Board of Directors or advisory committees; Fate Therapeutics: Research Funding; Kite: Consultancy, Research Funding; Incyte: Consultancy, Research Funding; Genentech/Roche: Research Funding; Juno Therapeutics: Research Funding; GSK: Consultancy; Intellia: Consultancy; Allogene: Consultancy. Riviere:Fate Therapeutics Inc.: Consultancy, Other: Ownership interest , Research Funding; FloDesign Sonics: Consultancy, Other: Ownership interest; Juno Therapeutics: Other: Ownership interest, Research Funding; Takeda: Research Funding; Atara: Research Funding. Palomba:Genentech: Research Funding; Juno Therapeutics, a Bristol-Meyers Squibb Company: Honoraria, Research Funding; Regeneron: Research Funding; Novartis: Honoraria; Merck: Honoraria; Celgene: Honoraria; Pharmacyclics: Honoraria. Brentjens:BMS: Research Funding; Gracell Therapeutics: Consultancy; Juno Therapeutics (a Bristol Myers Squibb company): Patents & Royalties. Sadelain:Atara: Patents & Royalties, Research Funding; Fate Therapeutics: Patents & Royalties, Research Funding; Minerva: Other: Biotechnologies , Patents & Royalties; Mnemo: Patents & Royalties; Takeda: Patents & Royalties, Research Funding. OffLabel Disclosure: Cyclophosphamide and fludarabine will be used as conditioning therapy prior to 19(T2)28z1XX CAR T cell administration.

KarMMa-4: Idecabtagene Vicleucel (ide-cel, bb2121), a BCMA-Directed CAR T-Cell Therapy, in High-Risk Newly Diagnosed Multiple Myeloma

BACKGROUND: Despite the introduction of novel agents, patients with high-risk (Revised International Staging System [R-ISS] stage III) newly diagnosed multiple myeloma (NDMM) have a poor prognosis (median progression-free survival [PFS], 29 months), highlighting the need for novel disease-targeting approaches (Palumbo A, et al. J Clin Oncol. 2015;33:2863-2869). The BCMA-directed CAR T cell therapy ide-cel demonstrated deep, durable responses in heavily pretreated patients with relapsed and refractory MM (RRMM; Raje N, et al. N Engl J Med. 2019;380:1726-1737; Munshi NC, et al. J Clin Oncol. 2020;38[suppl] [abstract 8503]), including those with high-risk (R-ISS stage III) RRMM. Earlier use in this population-where there is potentially more bone marrow reserve, more healthy peripheral blood mononuclear cells, a less compromised immune status, and less extensive disease to debulk before cell therapy-may result in improved outcomes and offer an opportunity to replace transplant with CAR T cell therapy. KarMMa-4 is a multicenter, open-label, phase 1, single-arm study of ide-cel in patients with high-risk NDMM (R-ISS stage III disease per International Myeloma Working Group criteria). STUDY DESIGN: KarMMa-4 is enrolling patients with NDMM who have high-risk disease, defined as R-ISS stage III (ISS stage III [serum b2 microglobulin ≥ 5.5 mg/L] and cytogenetic abnormalities t(4;14), del(17p), and/or t(14;16) by interphase fluorescence in situ hybridization; or ISS stage III and serum lactate dehydrogenase > upper limit of normal). Patients must have received ≤ 3 cycles of the induction regimens listed below, be aged ≥ 18 years, and have Eastern Cooperative Oncology Group performance status 0-1. Patients with nonsecretory myeloma or central nervous system involvement are excluded. Patients can enroll between cycle 1 and cycle 3 of induction. Permitted induction regimens for cycle 1 are carfilzomib + lenalidomide + dexamethasone ± daratumumab (KRd ± DARA), lenalidomide + bortezomib + dexamethasone ± daratumumab (RVd ± DARA), or cyclophosphamide + bortezomib + dexamethasone (CyBorD). Induction regimens for cycles 2-4 are limited to KRd or RVd, with dexamethasone omitted during cycle 3. All patients will undergo leukapheresis for T cell collection after cycle 3, and ide-cel will be manufactured during cycle 4 of induction. Stem cell collection for future use may be conducted after cycle 3 (following leukapheresis) or cycle 4 (before lymphodepletion). Ide-cel is infused after 2 days of rest following lymphodepletion with 3 days of fludarabine 30 mg/m2 + cyclophosphamide 300 mg/m2. Lenalidomide-based maintenance may be provided upon bone marrow recovery or 90 days after ide-cel infusion, whichever is later. The primary endpoints are dose-limiting toxicity and safety. Secondary endpoints include complete response rate and overall response rate, duration of response, time to complete response, time to start of maintenance, feasibility of initiating maintenance, PFS, overall survival, and pharmacokinetics. Exploratory endpoints include safety of lenalidomide maintenance therapy, minimal residual disease, immunogenicity and biomarkers. The starting ide-cel target dose is 450 × 106 CAR+ T cells, with dose escalation/de-escalation (150, 300, and 800 × 106 CAR+ T cells). After identification of the optimal target dose, 12 patients will be enrolled in the dose-expansion phase. KarMMa-4 is registered at ClinicalTrials.gov: NCT04196491. Disclosures Usmani: Celgene: Other; Abbvie: Consultancy; Sanofi: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Other: Speaking Fees, Research Funding; Janssen: Consultancy, Honoraria, Other: Speaking Fees, Research Funding; SkylineDX: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding; Merck: Consultancy, Research Funding; Incyte: Research Funding; Pharmacyclics: Research Funding; Array Biopharma: Research Funding; GSK: Consultancy, Research Funding; BMS, Celgene: Consultancy, Honoraria, Other: Speaking Fees, Research Funding; Amgen: Consultancy, Honoraria, Other: Speaking Fees, Research Funding. Berdeja:Servier: Consultancy; Poseida: Research Funding; Lilly: Research Funding; Legend: Consultancy; Kite Pharma: Consultancy; Kesios: Research Funding; Karyopharm: Consultancy; Prothena: Consultancy; Acetylon: Research Funding; Amgen: Consultancy, Research Funding; Abbvie: Research Funding; Vivolux: Research Funding; Novartis: Research Funding; Bluebird: Research Funding; Bioclinica: Consultancy; BMS: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Cellularity: Research Funding; Constellation: Research Funding; CRISPR Therapeutics: Consultancy, Research Funding; CURIS: Research Funding; EMD Sorono: Research Funding; Genentech, Inc.: Research Funding; Janssen: Consultancy, Research Funding; Glenmark: Research Funding; Teva: Research Funding; Takeda: Consultancy, Research Funding. Truppel-Hartmann:bluebird bio, Inc: Current Employment, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); F. Hoffmann La Roche: Current equity holder in publicly-traded company, Ended employment in the past 24 months. Casadebaig:Bristol-Myers Squibb Company: Current Employment. Wortman-Vayn:Bristol-Myers Squibb Company: Current Employment. Shelat:Bristol-Myers Squibb Company: Current Employment. Novick:Bristol-Myers Squibb Company: Current Employment. Shah:GSK, Amgen, Indapta Therapeutics, Sanofi, BMS, CareDx, Kite, Karyopharm: Consultancy; BMS, Janssen, Bluebird Bio, Sutro Biopharma, Teneobio, Poseida, Nektar: Research Funding.

A Phase I Study of FT538, a First-of-Kind, Off-the-Shelf, Multiplexed Engineered, iPSC-Derived NK Cell Therapy As Monotherapy in Relapsed/Refractory Acute Myelogenous Leukemia and in Combination with Daratumumab or Elotuzumab in Relapsed/Refractory Multiple Myeloma

Background: Allogeneic natural killer (NK) cell therapies have been well-tolerated with documented anti-tumor activity in patients with relapsed/refractory (r/r) hematologic malignancies including acute myelogenous leukemia (AML) and multiple myeloma (MM) (Lupo et al. 2019). Allogeneic NK cell therapies may offer an improved safety profile characterized by the absence of cytokine release syndrome and neurologic toxicity compared with T-cell therapies (Liu et al. 2020). However, in comparison to T cells, NK cells have limited in vivo expansion and a short half-life, and the potential to generate deeper and more durable anti-tumor responses through multi-dose administration is limited by the inability to consistently manufacture and administer more than one dose of allogeneic NK cells. The monoclonal antibodies (mAbs) daratumumab and elotuzumab have demonstrated clinical benefit and are approved for the treatment of MM (Darzalex® USPI, Empliciti® USPI). However, durable responses and disease-free survival remain limited. Engagement of the Fc portion of the mAb with CD16 on NK cells, which promotes antibody-dependent cellular cytotoxicity (ADCC), is a major contributor to the efficacy of daratumumab and elotuzumab. It is hypothesized that more clinically meaningful outcomes may be achieved by combining therapeutic mAbs with allogeneic NK cells engineered to enhance ADCC. FT538 is an investigational, first-of-kind, multiplexed engineered NK cell therapy generated from a clonal master engineered induced pluripotent stem cell (iPSC) line, which can be used as a renewable source for the mass production of off-the-shelf NK cells for broad patient access. FT538 is engineered with three modalities for enhanced innate immunity: (1) high-affinity 158V, non-cleavable CD16 Fc receptor for augmented ADCC; (2) interleukin (IL)-15/IL-15 receptor fusion that promotes cytokine-autonomous persistence; and (3) CD38 knockout to mitigate NK cell fratricide by CD38-directed mAbs. In preclinical studies, FT538 combined with daratumumab against MM targets demonstrated avoidance of daratumumab-mediated fratricide and significantly enhanced ADCC in vitro in a serial stimulation cytotoxicity assay compared with peripheral blood NK cells, and the combination of FT538 with daratumumab led to highly effective tumor control compared with daratumumab alone in an in vivo MM xenograft model (Bjordahl et al. 2019). Study Design and Methods: This study is a multicenter, multi-dose, Phase I clinical trial of FT538 in patients with r/r AML or r/r MM. The primary objectives are to determine the recommended Phase II dose of FT538 as monotherapy in r/r AML and in combination with daratumumab or elotuzumab in r/r MM. Key secondary objectives include evaluation of FT538 safety and tolerability, anti-tumor activity, and pharmacokinetics (PK) as monotherapy in r/r AML and combined with mAbs in r/r MM. Exploratory objectives include characterization of FT538 pharmacodynamics as assessed by peripheral blood biomarkers, assessment of minimal residual disease, and characterization of the tumor microenvironment in pre- and post-treatment tumor biopsies. The dose-escalation part of the trial utilizes a 3+3 design to identify the maximum tolerated dose of up to three doses of FT538 on Days 1, 8, and 15 as a monotherapy in r/r AML (Regimen A) and in combination with daratumumab (Regimen B) or elotuzumab (Regimen C) in r/r MM. The dose-expansion part of the trial will further characterize the safety, efficacy, and PK of FT538 in all regimens. The trial will test up to five FT538 dose levels ranging from 50 million to 1.5 billion cells. Up to 105 patients will be enrolled. The mAbs in Regimens B and C will be administered based on dosing schedules per their respective prescribing information. Lympho-conditioning consisting of three consecutive days of fludarabine and cyclophosphamide will be administered prior to the first dose of FT538. Key inclusion criteria include r/r disease after standard approved therapies for r/r AML or r/r MM, as applicable, measurable disease for r/r MM, and adequate organ function. Key exclusion criteria include active central nervous system disease, need for systemic immunosuppressive therapy, and prior allograft organ transplant. This trial is expected to begin patient enrollment in 2020. Disclosures Janakiram: Takeda, Fate, Nektar: Research Funding. Siegel:Karyopharma: Consultancy, Honoraria; Takeda: Consultancy, Honoraria, Speakers Bureau; Merck: Consultancy, Honoraria, Speakers Bureau; Celulatiry: Consultancy; BMS: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Amgen: Consultancy, Honoraria, Speakers Bureau. Shih:Fate Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company. Weymer:Fate Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company. Valamehr:Fate Therapeutics, Inc: Current Employment, Current equity holder in publicly-traded company. Chu:Roche Holding AG: Current equity holder in publicly-traded company; Fate Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company. Miller:Fate Therapeutics, Inc: Consultancy, Patents & Royalties, Research Funding; GT Biopharma: Consultancy, Patents & Royalties, Research Funding; Vycellix: Consultancy; Onkimmune: Honoraria, Membership on an entity's Board of Directors or advisory committees; Nektar: Honoraria, Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure: Cyclophosphamide and fludarabine will be used as lympho-conditioning therapy prior to FT538 administration.

KarMMa-3: A Phase 3 Study of Idecabtagene Vicleucel (ide-cel, bb2121), a BCMA-Directed CAR T Cell Therapy Vs Standard Regimens in Relapsed and Refractory Multiple Myeloma

KarMMa-3: A Phase 3 Study of Idecabtagene Vicleucel (ide-cel, bb2121), a BCMA-Directed CAR T Cell Therapy Vs Standard Regimens in Relapsed and Refractory Multiple Myeloma

Successful Treatment of Refractory Acute Lymphoblastic Leukemia with Tisagenlecleucel in the Setting of Life-Threatening Infection

Tisagenlecleucel is a CD19 directed immunotherapy approved for the treatment of young patients with relapsed or refractory precursor B-cell acute lymphoblastic leukemia (ALL). The most important toxicity related to tisagenlecleucel therapy is cytokine release syndrome (CRS). CRS is an exaggerated systemic inflammatory response that occurs frequently along with T-cell expansion following the administration of tisagenlecleucel. Tisagenlecleucel guidelines recommend delaying treatment when an active infection is present due to the concern that the pre-existing inflammatory response associated with infection may predispose patients to severe CRS. We describe two cases where tisagenlecleucel was successfully administered to patients in the setting of life-threatening infection. Patient 1 is a 23-year-old Caucasian male with refractory Philadelphia chromosome negative B-cell ALL who had received prior treatment with chemotherapy, blinatumomab, inotuzumab ozogamicin and a haploidentical stem cell transplant (SCT) followed by multiple Zalmoxis infusions. Five months following SCT he relapsed. At relapse, he underwent leukapheresis followed by bridging chemotherapy with ifosfamide and etoposide. He developed severe neutropenia and respiratory failure associated with a right lower lung consolidation. A biopsy demonstrated a mucormycosis infection and he required surgical debridement including resection of portions of the lung, diaphragm and liver. At this time, he had 92% blasts in the bone marrow. Eleven days after his surgery he received tisagenlecleucel despite being persistently febrile. Prior to the infusion, he received a modified lymphodepleting chemotherapy regimen including two days of fludarabine and cytarabine. Due to severe neutropenia, he was receiving granulocyte transfusions. These were discontinued prior to the infusion and resumed after 12 days. CRP and ferritin the day prior to infusion were 26.2 mg/dL and 18,419 ng/mL. He remained persistently febrile for 13 days post-infusion. He received a single dose of tociluzimab 7 days following his infusion due to high fevers. He did not require any treatment with corticosteroids for CRS. The absolute neutrophil count recovered to >500x103/µL at 31 days post infusion. A bone marrow aspirate done 26 days post-infusion did not show any evidence of leukemia by multicolor flow cytometry (MFC). He remains alive without evidence of disease 11 months after treatment with tisagenlecleucel. Patient 2 is a 4-year-old Hispanic female with refractory B-cell ALL found to have a TP53 deletion and t(1;19). She had received prior treatment with chemotherapy, blinatumomab and local radiation therapy to the site of extramedullary disease found in the left maxillary sinus at relapse. She underwent leukapheresis and received bridging chemotherapy with mercaptopurine and methotrexate. After 3 days of lymphodepleting chemotherapy she developed septic shock and E. Coli bacteremia. She became severely ill requiring continuous renal replacement therapy for 5 days and extracorporeal membrane oxygenation (ECMO) for 6 days. Shortly after ECMO decannulation she developed fever and was found to have multiple pulmonary opacities concerning for fungal infection. Blasts were noted in the peripheral blood. Sixteen days after presenting with septic shock and 11 days from ECMO she received tisagenlecleucel. CRP at the time of infusion was 22.9 mg/dL. She developed persistent fevers post-infusion for 17 days. She received two doses of tociluzimab 20- and 21-days post-infusion due to recurrence of high fever and reactive lymphadenopathy with third spacing and concern for renovascular compromise. She did not require any treatment with corticosteroids for CRS. Bone marrow aspirate done 32 days post-infusion did not show any evidence of leukemia by MFC. The absolute neutrophil count recovered to >500x103/µL at 59 days post infusion. The patient remained without evidence of disease for 7 months following treatment but died due to infectious complications with persistent pancytopenia. Tisagenlecleucel is a potentially life-saving treatment for relapsed and refractory B-cell acute lymphoblastic leukemia in children and young adults 24 years of age or younger. Tisagenlecleucel is an option for the treatment of patients with active infection and/or inflammation with progressive leukemia when no other therapeutic alternative exists. Disclosures August: Novartis Pharmaceuticals: Speakers Bureau. Myers:Novartis Pharmaceuticals: Consultancy, Speakers Bureau.

JCARH125, Anti-BCMA CAR T-cell Therapy for Relapsed/Refractory Multiple Myeloma: Initial Proof of Concept Results from a Phase 1/2 Multicenter Study (EVOLVE)

JCARH125, Anti-BCMA CAR T-cell Therapy for Relapsed/Refractory Multiple Myeloma: Initial Proof of Concept Results from a Phase 1/2 Multicenter Study (EVOLVE)

Allogeneic Hematopoietic Stem Cell Transplantation for GATA2 Deficiency Using a Busulfan-Based Regimen

Allogeneic hematopoietic stem cell transplantation (HSCT) reverses the bone marrow failure syndrome due to GATA2 deficiency. The intensity of conditioning required to achieve reliable engraftment and prevent relapse remains unclear. Here, we describe the results of a prospective study of HSCT in 22 patients with GATA2 deficiency using a busulfan-based conditioning regimen. The study included 2 matched related donor (MRD) recipients, 13 matched unrelated donor (URD) recipients, and 7 haploidentical related donor (HRD) recipients. MRD and URD recipients received 4 days of busulfan and 4 days of fludarabine. HRD recipients received low-dose cyclophosphamide for 2 days, fludarabine for 5 days, 2 to 3 days of busulfan depending on cytogenetics, and 200 cGy total body irradiation. MRD and URD recipients received tacrolimus and short-course methotrexate for graft-versus-host disease (GVHD) prophylaxis. HRD recipients received high-dose post-transplant cyclophosphamide (PTCy) followed by tacrolimus and mycophenolate mofetil. At a median follow-up of 24 months (range, 9 to 50), 19 of 22 patients were alive with reversal of the disease phenotype and correction of the myelodysplastic syndrome, including eradication of cytogenetic abnormalities. Three patients died: 1 from refractory acute myelogenous leukemia, 1 from GVHD, and 1 from sepsis. There was a 26% incidence of grades III to IV acute GVHD in the MRD and URD groups and no grades III to IV acute GVHD in the HRD cohort. Similarly, there was a 46% incidence of chronic GVHD in the MRD and URD cohorts, whereas only 28% of HRD recipients developed chronic GVHD. Despite excellent overall disease-free survival (86%), GVHD remains a limitation using standard prophylaxis for GVHD. We are currently extending the use of PTCy to the MRD and URD cohorts to reduce GVHD.

Haploidentical Related Donor Hematopoietic Stem Cell Transplantation for Dedicator-of-Cytokinesis 8 Deficiency Using Post-Transplantation Cyclophosphamide

Dedicator-of-cytokinesis 8 (DOCK8) deficiency, a primary immunodeficiency disease, can be reversed by allogeneic hematopoietic stem cell transplantation (HSCT); however, there are few reports describing the use of alternative donor sources for HSCT in DOCK8 deficiency. We describe HSCT for patients with DOCK8 deficiency who lack a matched related or unrelated donor using bone marrow from haploidentical related donors and post-transplantation cyclophosphamide (PT/Cy) for graft-versus-host disease (GVHD) prophylaxis. Seven patients with DOCK8 deficiency (median age, 20 years; range, 7 to 25 years) received a haploidentical related donor HSCT. The conditioning regimen included 2 days of low-dose cyclophosphamide, 5 days of fludarabine, 3 days of busulfan, and 200 cGy total body irradiation. GVHD prophylaxis consisted of PT/Cy 50 mg/kg/day on days +3 and +4 and tacrolimus and mycophenolate mofetil starting at day +5. The median times to neutrophil and platelet engraftment were 15 and 19 days, respectively. All patients attained >90% donor engraftment by day +30. Four subjects developed acute GVHD (1 with maximum grade 3). No patient developed chronic GVHD. With a median follow-up time of 20.6 months (range, 9.5 to 31.7 months), 6 of 7 patients are alive and disease free. Haploidentical related donor HSCT with PT/Cy represents an effective therapeutic approach for patients with DOCK8 deficiency who lack a matched related or unrelated donor.

Tandem Autologous Followed By Nonmyeloablative Allogeneic Transplantation in Relapsed High Risk Follicular Lymphoma Leads to Excellent Long Term Progression-Free Survival after 8 Years of Follow-up

Many new therapeutic agents have been approved for follicular lymphoma (FL) but none appear to be curative. Despite novel agents, some patients (pts) experience early relapse, become chemorefractory or suffer transformation into more aggressive lymphomas. Options for these pts are limited. High dose chemotherapy with autologous stem transplant (ASCT) prolongs progression free survival (PFS) and overall survival (OS) in FL pts in first relapse and registry data shows favorable outcome with ASCT in cases of histologic transformation. However, ASCT is usually not curative. Myeloablative allogeneic transplant (MT) has produced long term PFS but is hampered by significant non relapse mortality (NRM) while nonmyeloablative transplant (NMT) has a higher relapse rate compared to MT especially in high risk pts. Finally, many transplant studies have excluded these high risk pts such as those with chemorefractory or transformed disease.We hypothesized that a tandem transplant consisting of an ASCT followed by a NMT would confer the same benefit as a MT without the associated high NRM by separating the high dose chemotherapy from graft versus host disease (GVHD) while preserving the graft versus lymphoma effect. The goal of our study was to improve long term PFS in high risk FL pts.We therefore initiated a prospective protocol in April 2003, for pts with high risk relapsed FL as defined by chemorefractory disease, early 1st relapse, >1st relapse or transformation into aggressive histology. At least one therapy was attempted to document chemosensitivity prior to ASCT. However, regardless of disease status prior to transplant, pts underwent ASCT followed 3 months later by an outpatient NMT from an HLA-identical sibling. NMT comprised 5 days of fludarabine 30 mg/m2/day and cyclophosphamide 300mg/m2/day followed by an infusion of >2x106CD34+ cells/kg. GVHD prophylaxis, chosen to take advantage of the low incidence of acute (a) GVHD and the putative protective effect of chronic (c) GVHD, consisted of tacrolimus starting on day (D) - 8 to achieve levels of 8-12 nmol/L then tapered off by D+100 or D+180 depending on disease risk and of mycophenolate mofetil 1g bid from D+2 to D+50. We previously reported on 27 pts with a follow-up (f/u) of 3 years (yrs). We now report a larger cohort of 40 pts with a median f/u of 8 yrs.Up until July 2015, 40 pts were enrolled with a median age of 50 yrs (34-65). Pts had previously been treated with a median of 3 lines of therapy (2-6). Median time from diagnosis to ASCT was 33 months. Disease status at ASCT was: 14 CR, 16 PR and 10 refractory. Conditioning for ASCT included BEAM/BEAC (n=39), and Cy-TBI (n=1). In addition, 4 pts received radiotherapy after ASCT to sites of previously bulky disease. Median time between ASCT and NMT was 138 days (75-238). Pre NMT disease status was: 25 CR, 12 PR and 3 refractory.Engraftment was prompt in all pts after ASCT and median neutrophil and platelet recovery were respectively 13 days (0-19) and 0 day (0-18) post NMT. Seven pts (18%) developed aGVHD: 2 grade II and 5 grade III. Overall, 29 pts (73%) developed cGVHD: 1 mild, 13 moderate and 15 severe according to NIH revised criteria. Median time to discontinuation of immunosuppression was 22 months. To date, 2 pts have progressed at 11 and 59 months post NMT (one died from relapse and one is now in CR after chemotherapy and DLI) and 5 pts died from either GVHD related complications (n=4) or unknown cause (n=1). All pts alive at last f/u were in CR. With a median f/u of 8 yrs in surviving pts (1-12), OS is 95% at 3 and 5 yrs and 82% at 8 yrs. PFS is 92% at 3yrs, 89% at 5 yrs and 80% at 8 yrs. NRM and relapse rate at 8 yrs are 18% and 6% respectively.Based on our current results in 40 pts, we conclude that ASCT followed by sibling NMT for high risk relapsed FL is associated with excellent disease response and PFS. Furthermore, this tandem strategy appears to be safe and well tolerated. The incidence of cGVHD remains high but could in part explain the impressive PFS in this high risk cohort. This approach should now be further explored in a multi institution setting, include matched unrelated donors and consider the addition of rituximab post-transplant to reduce the incidence and severity of cGVHD with the hope that relapse will not be increased. [Display omitted] DisclosuresBusque:Pfizer: Honoraria, Speakers Bureau; BMS: Honoraria, Speakers Bureau; Novartis: Honoraria, Research Funding, Speakers Bureau.

Complete Remissions of Adult T-cell Leukemia with Anti-CD25 Recombinant Immunotoxin LMB-2 and Chemotherapy to Block Immunogenicity

Adult T-cell leukemia (ATL) is usually CD25(+) and rapidly fatal. Anti-CD25 recombinant immunotoxin LMB-2 had phase I activity limited by immunogenicity and rapid growth. To prevent antidrug antibodies and leukemic progression between cycles, a phase II trial was performed with LMB-2 after cyclophosphamide and fludarabine. ATL patients received cyclophosphamide and fludarabine days 1 to 3 and 2 weeks later began up to 6 cycles at 3-week intervals of cyclophosphamide and fludarabine days 1 to 3 followed by LMB-2 30-40 μg/kg i.v. days 3, 5, and 7. Three different dose levels of cyclophosphamide and fludarabine were used, 20+200 (n = 3), 25+250 (n = 12), and 30+300 mg/m(2) (n = 2). Of 17 patients enrolled and treated with fludarabine and cyclophosphamide for cycle-1, 15 received subsequent cycle(s) containing LMB-2 and were therefore evaluable for response. Lack of antibody formation permitted retreatment in most patients. Of 10 evaluable leukemic patients receiving 25+250 or 30+300 mg/m(2) of fludarabine and cyclophosphamide, 6 (60%) achieved complete remission (CR) and 2 (20%) partial remission (PR), and all 5 with >25% leukemic cells achieved CR. No responses were achieved in 5 with lymphomatous ATL or lower fludarabine and cyclophosphamide doses. Median CR duration for the 6 CRs was 40 weeks. One is without detectable ATL at 47 months. Toxicity was mostly attributable to fludarabine and cyclophosphamide. Capillary leak from LMB-2 was non-dose limiting. One patient in CR died of a preexisting infection. LMB-2, administered with fludarabine and cyclophosphamide to prevent antidrug antibodies and rapid intercycle progression, is highly effective in achieving CR in leukemia ATL. Fludarabine and cyclophosphamide dose/schedule is important for safety and efficacy in this high-risk population.

Cytomegalovirus and Effect on Early Chimerism in Patients with Myeloid Disorders Undergoing Stem Cell Transplantation Using Reduced Toxicity Ablative Conditioning Regimen

Cytomegalovirus (CMV) remains a significant cause of morbidity after allogeneic hematopoietic stem cell transplantation (SCT). The influence of CMV on the chimerism in reduced toxicity ablative conditioning SCT in myeloid disorders is ill defined. A recent report published in Blood by Sellar et al showed that in patients who received alemtuzumab-based regimen, the group of patients who were recipient positive (R+)/ Donor negative (D-) had CMV-specific T cells that are exclusively of recipient origin and significantly influenced the chimerism status toward recipients. To explore the impact of seropositivity and seronegativity of CMV in recipients and donors on early chimerism, we undertook a retrospective analysis of patients with myeloid disorders who received four days of fludarabine and busulfan with or without anti-thymocyte globulin (ATG) at our center in the last 10 years.Methods: Chimerism assay was performed using a quantitative fluorescence-based short tandem repeat-polymerase chain reaction (STR-PCR) with capillary electrophoresis for PCR product resolution.Results: 42 patients were identified and included in the study. All patients received fludarabine (40 mg/m2/day x 4 doses), busulfan (3.2mg/kg/dose IV x 4 doses). Of these 42 patients, 25 had anti-thymocyte globulin. There were 28 male and 14 female patients with a median age of 62 years (range 48-74yrs). Median time to follow up was 8 months (0.8-54 months). Disease risk was considered advanced in 21 patients, intermediate in 4 and early in 17. Median blast number at time of SCT was 5%. Stem cell source included peripheral blood in all patients. There were no primary graft failures. Total recipient cell chimerism showed increase or persistence of recipient chimerism in 5/11 (45%) of R+D- vs 2/6 (33.3%) of R-D- in the group of patients who received ATG, p=1.0, with a mean of recipient chimerism at day 100 of 20.4% in the R+D- group compared to a mean of 17% in the R-D- group. In the group who did not get ATG, recipient chimerism persistence or increase was not that different between the R+D- patients 3/4 (75%) compared to 4/4 (100%) in patients who were seronegative for CMV (R-), p=1.0. The mean of recipient chimerism at day 100 in the R+D- no ATG group was 23.25% with a median of 12% while the mean and median at day 100 in the R- no ATG group were 35.25% and 19.5% respectively (p=0.573).When looking at the persistence or increase in recipient chimerism in the group of patients who were R+D-, in those who got ATG it was 45% increase vs 75% increase in those who did not get ATG (p=0.569) with a median of 12% vs 0% respectively (p=0.49). Also increase or persistence of recipient chimerism was 33.3 % in patients who were R- and got ATG vs 100% in R- no ATG patients (p=0.076)with median at day 100 of 0 vs 19.5% (p=0.098).Conclusion: In this small cohort from a single center, we found that in patients with myeloid disorders who received reduced toxicity ablative conditioning regimen, the group of patients who received ATG, there was no statistically significant increase in recipient chimersim in the R+D- group compared to R-D- group. This is different from what Sellar et al found in a small group of patients who received alemtuzumab. These results may indicate a difference between ATG and alemtuzumab in the effect of CMV seropositivity and negativity on the recipient chimerism, which need to be studied further in a larger retrospective or prospective study. This is especially important in myeloid disorders since persistent or increase in recipient chimerism may identify high-risk patient cohorts who may benefit from additional therapeutic interventions. DisclosuresNo relevant conflicts of interest to declare.

High Rates of Early Donor Chimerism in Intermediate and Poor Risk Patients Undergoing Stem Cell Transplantation Using Reduced Toxicity Ablative Conditioning Regimen Incorporating Busulfan Pharmacokinetics

Abstract Reduced toxicity ablative conditioning regimens are increasingly used for allogeneic stem cell transplantation (allo-SCT). The impact of early donor cell chimerism on outcomes of T cell–replete reduced-intensity conditioning SCT in myeloid disorders is ill defined. To explore the impact of measuring busulfan pharmacokinetics in conditioning regimens on early donor chimerism, we undertook a retrospective analysis of patients with myeloid disorders who received four days of fludarabine and busulfan with or without measuring busulfan pharmacokinetics at our center in the last 10 years. Methods: Chimerism assay was performed using a quantitative fluorescence-based short tandem repeat– polymerase chain reaction (STR-PCR) with capillary electrophoresis for PCR product resolution. Results: Thirty patients were identified and included in the analysis. All patients were conditioned with fludarabine (40 mg/m2/day x 4 doses), busulfan (3.2mg/kg/dose IV x 4 doses). Of these thirty patients, 7 had busulfan pharmacokinetics measured. There were 21 male and 9 female patients with a median age of 62 years (range 48–72yrs). Median time to follow up was 13.3 months. Diagnoses included AML (N=17), MDS (N=10), MPN (N=1), CMML (N=2). Disease risk was considered advanced in 17 patients, intermediate in 3 and early in 10. All patients in the busulfan pharmacokinetic group had advanced disease except one had early disease. Regarding cytogenetics, all patients in the busulfan pharmacokinetics group had high or intermediate risk cytogenetics. Median blast number at time of SCT was 5%. Stem cell source included peripheral blood in all patients. Eleven patients received matched related donor (MRD) SCT, 15 had matched unrelated donor (MUD) SCT and 4 had mismatched unrelated donor (MMUD) SCT. Prophylaxis of GVHD consisted of tacrolimus and methotrexate in MRD, and tacrolimus, methotrexate and anti-thymocyte globulin in MUD and MMUD. All patients engrafted neutrophils and platelets promptly (median 13 and 14 days, respectively). There were no primary graft failures. Total Donor cell Chimerism analysis in the Busulfan pharmacokinetics group showed 100% donor at both time points (days 30, 100) in all patients except in one who relapsed at day 30 (85.7%). While in the non-pharmacokinetics group only 7 out of 23 (30%) patients had complete chimerism at day 30 and day 100. Complete donor chimerism at day 100 in the non-pharmacokinetics group was 47.8% compared to 85.7% in the pharmacokinetic group (p=0.18). Ten out of 23 patients (43.5%) in the non-pharmacokinetics group had decreasing donor chimerism by day 100, while in the pharmacokinetic group only one patient (14%) who relapsed had decreasing donor chimerism by day 100 with an odds ratio of 0.241 (95% Confidence Interval =0.025-2.357; p-value=0.22). None developed sinusoidal obstructive syndrome. Conclusion: In this small cohort of consecutive patients from a single center, we found that patients with myeloid disorders who received fludarabine busulfan for 4 days incorporating busulfan pharmacokinetics had a trend for higher rates of early complete donor chimerism and less decreasing donor chimerism by day100, although not statistically significant, despite having intermediate or high risk disease at time of SCT. Longer follow up is needed for our patients to see if there is effect on relapse or survival but previous studies have showed that low or decreasing donor chimerism early after SCT is an independent risk factor for relapse and impaired survival. This is especially important in myeloid disorders. Busulfan pharmacokinetics may help target better level for inducing early total donor chimerism and donor chimerism may identify high-risk patient cohorts who may benefit from additional therapeutic interventions. These results should be interpreted with caution given the retrospective design of the study and the small number of patients. Disclosures No relevant conflicts of interest to declare.