Post CAR Research Articles

T-Cell Telomere Length As a Biomarker to Predict Outcome in Patients Receiving CAR-T Immunotherapy

Introduction: CAR T-cells remain in a quiescent or dormant state when unstimulated, showing no proliferative activity. In contrast, upon specific antigen stimulation (i.e., CD19) CAR T-cells divide both in-vitro and in-vivo, initiate immune responses and can kill their target cells in the body. However, one of the major physiological immune changes with increased age is the progressive impairment of T-cell responses. This process termed immunosenescence (which may be similar T-cell exhaustion) is associated with the shortening of telomeres, specific DNA repeated sequences that protect the end of linear chromosomes from degradation and fusion with neighbor chromosomes. We aim to investigate change in T-cell telomere length with CAR-T cell therapy and its potential impact on outcome in patients receiving CART immunotherapy.Methods: We enrolled adult patients (age range: 30-80 years old) receiving CART immunotherapy for diffuse large B cell lymphoma (DLBCL), multiple myeloma (MM), mantle cell lymphoma (MCL), or follicular lymphoma (FL). We collected peripheral blood at two time points: i) pre-lymphodepletion therapy and ii) two weeks post CAR-T cell infusion. Peripheral blood mononuclear cells were isolated from blood via density gradient and T-cells isolated from PBMC with magnetic beads (negative selection). Telomere lengths are quantified from T-cells by using a highly sensitive technique called TeSLA (Telomere Shortest Length Assay) that allows absolute quantification of both the average telomere length and the lengths of critically short telomeres, which are believed to play a major role in promoting cell cycle arrest and T-cell exhaustion.Results: We identified 7 patients receiving CAR T cell therapy for hematological malignancies at University of Texas Southwestern Medical Center. The cohort included 7 patients, 2 patients with DLBCL and 1 patient with MCL receiving CD19 CAR-T Cell therapy and 4 patients with MM receiving BCMA CAR-T cell therapy. Median age of patient was 65 yrs. Median follow up was 273 days post CAR T-cell therapy with all patients being alive at last follow-up. Two patients experienced Grade I Cytokine release syndrome (CRS), two patients with Grade 2 CRS and one patient with Grade 2 ICANS. Our initial analysis shows that patients telomere lengths changes pre and post CAR T-cell infusion. Regarding change in critically short telomere (<1.6kb); 6 out of 7 patients had reduction the shorter telomere from BL to post CAR-T. We are currently evaluating the effect of change in telomere length on outcomes.Conclusions: CAR T-cell therapy is a game-changer for hematological malignancies; however, disease still relapse. Understanding the mechanics of poor response or relapse after CAR T-cell therapy is critical in advancing the field. Initial results suggest T-cell telomere length are significantly affected during CAR T-cell manufacturing process and post infusion. These results are potentially important as telomere length can be utilized as a biomarker to predict CAR T-cell therapy outcomes. [Display omitted] DisclosuresAnderson: Celgene, BMS, Janssen, GSK, Karyopharm, Oncopeptides, Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Awan: Verastem: Consultancy; Incyte: Consultancy; Cardinal Health: Consultancy; Dava Oncology: Consultancy; BMS: Consultancy; ADCT therapeutics: Consultancy; Beigene: Consultancy; Celgene: Consultancy; Karyopharm: Consultancy; Pharmacyclics: Consultancy; MEI Pharma: Consultancy; Merck: Consultancy; Kite pharma: Consultancy; Gilead sciences: Consultancy; Johnson and Johnson: Consultancy; Abbvie: Consultancy; Janssen: Consultancy; Astrazeneca: Consultancy; Genentech: Consultancy. Madanat: Onc Live: Honoraria; Blue Print Pharmaceutical: Honoraria; Geron Pharmaceutical: Consultancy; Stem line pharmaceutical: Honoraria. Patel: Celgene-BMS: Membership on an entity's Board of Directors or advisory committees; PVI: Honoraria; Agios: Membership on an entity's Board of Directors or advisory committees. Sweetenham: EMA Wellness: Membership on an entity's Board of Directors or advisory committees. Kansagra: Alynylam, Celgene/BMS, Cota Health, GSK, Janssen, Karyopharm, Oncopeptide, Pfizer, Takeda, Sanofi: Membership on an entity's Board of Directors or advisory committees.

Development of JCARH125: Optimization of a Fully Human Anti-Bcma CAR for Use in the Treatment of Multiple Myeloma

Development of JCARH125: Optimization of a Fully Human Anti-Bcma CAR for Use in the Treatment of Multiple Myeloma

Real-world evidence (RWE) study of CAR-T agents in leukemia and lymphoma patients.

e19573 Background: Chimeric antigen receptor T (CAR T) cell products are considered gene treatments, producing long term results, with just one infusion. Real world evidence on the two available CAR T cell products, tisagenlecleucel (T) and axicabtagene ciloleucel (AC) are limited in leukemia and lymphoma patients, specifically at the individual product level. This study presents treatment outcomes and resource utilization of these products from a payer perspective. Methods: Patients with evidence of CAR T administration per claims algorithm and from documentation from a prior authorization program from January 1, 2017 to May 30, 2020 were included; the CAR T administration was the index event. Baseline demographics and clinical characteristics, healthcare resource utilization (HCRU) for the CART T administration and pre and post CAR T administration for a fixed 6-month period, and previous treatments were captured and presented by product, using descriptive analytics. Results: The study population included 148 patients, mean age (SD): 57.4 (16.9), with 34% female, and 64% Commercial patients versus 36% Medicare patients, with a mean follow-up of 319 days (SD: 210). There were 15 leukemia patients, 119 lymphoma patients, and 14 patients with other indication in the study population; 71(48%) had evidence of being on a clinical trial during the study. The mean Charleson Comorbidity score at baseline was 3.9. Major comorbidities included anemia (71%), diseases of the heart (72%). 29(20%) patients were treated with T of which 24% were for leukemia and 76% for lymphoma and 67 (46%) were treated with AC of which 100% were for lymphoma, and 52 (35%) patients did not differentiate between products. Majority of the CAR T administration took place inpatient (84%). Baseline 6-month HCRU was 52% ER visits and 59% hospitalizations, compared to post 6-month utilization at 45% ER visits and 49% hospitalizations for the total population. 118 (80%) patients had evidence of prior treatment indicating that the CAR T was at least in the second line setting or higher. The most common priming chemotherapy was cyclophosphamide-fludarabine in 69 (47%) patients. Of the total population, 72% did not have any evidence of further treatment in the available follow-up time, specifically, 47% in the leukemia and 76% in the lymphoma populations, respectively. Conclusions: Majority of patients have evidence of prior treatments before the CAR T index date, indicating relapse. There is evidence of decrease in the HCRU subsequent to treatment, compared to pre period and 72% do not have subsequent treatment in the available follow-up time, indicating a high level of efficacy.

Association of PET/CT response assessment prior to CAR T-cell infusion with outcomes after CAR T-cell therapy in aggressive B-cell lymphomas.

e19568 Background: Anti-CD19 chimeric antigen receptor modified T-cell therapies (CAR-T) have expanded the treatment possibilities for many patients with relapsed/refractory (R/R) aggressive large B-cell lymphomas (B-NHL) but fails to achieve remissions in a considerable proportion of patients. In this study, we examined whether response to systemic therapy prior to CAR T-cell infusion is associated with outcome. Methods: We analyzed a retrospective dataset of R/R B-NHL patients (pts) treated with commercially available CAR-T at the University of Pennsylvania treated from April 2018 to August 2020. 18F-FDG PET/CT scans obtained directly prior to and after CAR-T therapy were re-evaluated for response by an independent radiologist using the Lugano 2014 criteria. Association between pre-therapy and post-therapy responses were examined using Fisher’s exact test. Results: 50 pts with aggressive R/R B-NHL were enrolled. 34 pts received tisagenlecleucel and 16 received axi-cel. Median age was 61 (range 29-82), and 27 pts (54%) were men. Most pts (n = 48, 96%) had ECOG performance status of 0-1, with a median number of 3 prior therapies (range 1-11). 14 (28%) of pts had LDH elevation at time of CAR T cell infusion. Median time from pre-therapy PET/CT to infusion was 47 days (range: 6-155). Median PFS was 3.4 months. Prior to CAR T cell infusion, responses were as follows: 12 complete response (CR), 9 partial response (PR), 8 stable disease (SD) and 21 progressive disease (PD). Post-therapy responses were: 20 CR, 5 PR, 2 SD, and 23 PD. 67% of pts with a CR pre-therapy had continued CR after CAR T-cell infusion, whereas 32% pf pts without a CR had a CR after infusion (p &lt; 0.05). There was a trend toward CR/PR immediately prior to CAR T cell infusion being significantly associated with CR after CAR-T. We found that high metabolic tumor volume ( &gt; 350cc vs ≤350cc) was associated with poorer PFS (log rank, p = 0.05). We did not find elevated LDH or use of bridging therapy to be associated with response to CAR-T. Conclusions: This is the largest report of lymphoma patients treated with CAR-T while in remission to date and suggests the importance of optimizing clinical response prior to CAR-T. Although patients in CR were excluded from the registrational trials, it is notable that patients in CR prior to CAR-T had a high rate of CR post CAR T cells despite the absence of active lymphoma on imaging. Longer follow-up is needed to confirm these early observations.

Immune imitation of tumor progression after anti-CD19 chimeric antigen receptor T cells treatment in aggressive B-cell lymphoma

We present three patients with aggressive non-Hodgkin’s B-cell lymphoma (NHL) who received anti-CD19 chimeric antigen receptor T (CAR T) cells therapy after failure of several lines of chemotherapy that developed pseudo-progression. One-week clinical and radiological findings were consistent with tumor progression. Positron emission tomography-computed tomography (PET-CT) at 1 month post CAR T cells administration was consistent with treatment response. The rapid tumor growth and subsequent resolution are suggestive of tumor pseudo-progression mediated secondary to infiltration and immune activation of CAR T cells. Overall, 56 adult patients with NHL were enrolled in a phase 1b/2 in house clinical study with CD19 CAR T cells. Out of them 22/56 patients progressed as per PET-CT the 1 month post CAR T cells. In 14 patients, signs of progression started 7–10 days after CAR T cells infusion. In 11/14 patients, it was true progression, while in 3 it was pseudo-progression. Additional studies are warranted to describe the extent of this phenomenon and evaluate correlation with the CAR T activity and long-term disease control.

Infectious Complications of BCMA-Targeted and CD19-Targeted Chimeric Antigen Receptor T-Cell Immunotherapy

Infectious Complications of BCMA-Targeted and CD19-Targeted Chimeric Antigen Receptor T-Cell Immunotherapy

Factors Predicting Long-Term Survival Following CD19 CAR T-Cell Therapy in Relapsed/Refractory B-Cell Acute Lymphoblastic Leukemia

Introduction Chimeric antigen receptor (CAR) T-cell therapy targeting CD19 has demonstrated promising efficacy in patients with relapsed and refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL). However, relapse after CART remains a major issue. Here, we analyzed the factors related to long-term efficacy, including overall survival (OS), leukemia-free survival (LFS) and cumulative relapse rate (CRR), following CAR-T therapy in 231 R/R B-ALL patients who achieved complete remission (CR) within one month after CAR T-cell therapy. Patients and Methods From April 2017 to March 2019, 254 patients with R/R B-ALL were enrolled onto one of five different clinical trials (NCT03173417; ChiCTR-ONC-17012829; NCT02546739; ChiCTR1800016541; and NCT03671460) at our center and received a second generation CD19+ CAR T-cell infusion. The median infused CAR T-cell dose was 3×105/kg (range: 0.2-10×105/kg). The CAR-T/T-cell ratio and the CD19+ B lymphocyte percentage in PBLC samples from 159 of the patients were analyzed using flow cytometry on day 0, 4, 7, 11, 14, 21, and 30 following CAR T-cell infusion. We performed single continuous variate factors analysis on the influence of the CAR-T/T-cell ratio and the percentage of CD19 + B-lymphocytes in day 30 post-infusion PBLC samples on the OS, LFS, and CRR. We also analyzed the impact of patient age, BM blast count, CAR-T-cell dose, and the interval time between CAR-T-cell therapy and consolidation allogeneic hematopoietic stem cell transplantation (allo-HSCT) on OS and LFS. Results Among 254 patients, 231 cases achieved CR within one month after CART therapy. A total of 211 CR patients had long-term follow-up of more than 30 days with a median follow-up of 12 months (1 to 29 months). On day 30 post CAR T-cell infusion, the median CAR-T/T-cell ratio in PBLC samples was 0.51% (range: 0%-44.8%), with 59 of 169 patients (34.9%) having a CAR-T/T-cell ratio of ≥1% and 85 of 169 patients (50.3%) with a CAR-T/T-cell ratio of ≥0.5%. The median percentage of CD19+ B lymphocytes in PBLC on day 30 was 0.0% (range: 0.0%-9.4%), of which 157 of 169 patients (92.9%) had &amp;lt;0.5% CD19+ B-cell lymphocytes, and 137 of 169 patients (81.1%) had &amp;lt;0.1% CD19+ B lymphocytes on day 30. Using a single continuous variate factors analysis, we found that increasing BM blasts and percentage of CD19+ B-lymphocytes in PBLC samples on day 30 correlated with a worse OS and LFS (Table 1). BM blasts of ≥70% were statistically significantly correlated with a worse OS and LFS when compared to BM blasts of &amp;lt;70% (2-year OS of 52.6% vs. 65.0%, p=0.041; 2-year LFS of 43.3% vs. 58.6%, p=0.023). Unlike the BM blast data, for the CD19+ B-lymphocytes percentage in PBLC samples on day 30, we not identify a cut-off threshold. The CAR-T/T-cell ratio in PBLC samples on day 30 had no influence on OS or LFS. Unfortunately, the CAR-T/T- cell ratio and CD19+ B-lymphocyte percentage data beyond day 30 following CAR T-cell therapy was lacking for most patients and further analysis could not be performed to understand the impact of these factors on long-term survival. In our analysis, CAR T-cell dose, the interval time between CAR T-cell infusion and allo-HSCT did not significantly correlate with OS, LFS, or relapse. The remaining 184 patients in CR received a consolidation allo-HSCT after a median interval time of 67 days post CAR T-cell therapy (range: 30-334 days). Thirty-two of these patients (17%) relapsed with a median time to relapse of 221 days (57-490 days). The remaining 27 patients received CAR T-cell therapy only and 11 (41%) relapsed with a median time to relapse of 100 days (53-398 days). None of the four factors above had an influence on the CRR in either the bridging into allo-HSCT group or the CAR-T only group (Table 2). Conclusions Using a single continuous variate factors analysis, we found that a high BM blast count and the percentage of CD19+ B-lymphocytes in PBLC samples from R/R ALL patients on day 30 predicted a worse OS and LFS while age, the CAR-T/T-cell ratio on day 30, CAR-T cell dose, and the interval time between CAR-T cell infusion and allo-HSCT had no clear impact on long-term outcomes. Disclosures No relevant conflicts of interest to declare.

Resource Utilization and Factors Prolonging Hospitalization for Patients with Relapsed and Refractory Large B-Cell Lymphoma Receiving Tisagenlecleucel Versus Axicabtagene Ciloleucel

Resource Utilization and Factors Prolonging Hospitalization for Patients with Relapsed and Refractory Large B-Cell Lymphoma Receiving Tisagenlecleucel Versus Axicabtagene Ciloleucel

MSKCC Early Experience Using Radiotherapy As a Bridging Strategy for Relapsed Diffuse Large B Cell Lymphoma before CD19 CAR T Therapy

MSKCC Early Experience Using Radiotherapy As a Bridging Strategy for Relapsed Diffuse Large B Cell Lymphoma before CD19 CAR T Therapy

Combination of NKTR-255, a Polymer Conjugated Human IL-15, with CD19 CAR T Cell Immunotherapy in a Preclinical Lymphoma Model

Background CD19 CAR T immunotherapy has been successful in achieving durable remissions in some patients with relapsed/refractory B cell lymphomas, but disease progression and loss of CAR T cell persistence remains problematic. Interleukin 15 (IL-15) is known to support T cell proliferation and survival, and therefore may enhance CAR T cell efficacy, however, utilizing native IL-15 is challenging due to its short half-life and poor tolerability in the clinical setting. NKTR-255 is a polymer-conjugated IL-15 that retains binding affinity to IL15Rα and exhibits reduced clearance, providing sustained pharmacodynamic responses. We investigated the effects of NKTR-255 on human CD19 CAR T cells both in vitro and in an in vivo xenogeneic B cell lymphoma model and found improved survival of lymphoma bearing mice receiving NKTR-255 and CAR T cells compared to CAR T cells alone. Here, we extend upon these findings to further characterize CAR T cells in vivo and examine potential mechanisms underlying improved anti-tumor efficacy. Methods CD19 CAR T cells incorporating 4-1BB co-stimulation were generated from CD8 and CD4 T cells isolated from healthy donors. For in vitro studies, CAR T cells were incubated with NKTR-255 or native IL-15 with and without CD19 antigen. STAT5 phosphorylation, CAR T cell phenotype and CFSE dilution were assessed by flow cytometry and cytokine production by Luminex. For in vivo studies, NSG mice received 5x105 Raji lymphoma cells IV on day (D)-7 and a subtherapeutic dose (0.8x106) of CAR T cells (1:1 CD4:CD8) on D0. To determine optimal start date of NKTR-255, mice were treated weekly starting on D-1, 7, or 14 post CAR T cell infusion. Tumors were assessed by bioluminescence imaging. Tumor-free mice were re-challenged with Raji cells. For necropsy studies mice received NKTR-255 every 7 days following CAR T cell infusion and were euthanized at various timepoints post CAR T cell infusion. Results Treatment of CD8 and CD4 CAR T cells in vitro with NKTR-255 resulted in dose dependent STAT5 phosphorylation and antigen independent proliferation. Co-culture of CD8 CAR T cells with CD19 positive targets and NKTR-255 led to enhanced proliferation, expansion and TNFα and IFNγ production, particularly at lower effector to target ratios. Further studies showed that treatment of CD8 CAR T cells with NKTR-255 led to decreased expression of activated caspase 3 and increased expression of bcl-2. In Raji lymphoma bearing NSG mice, administration of NKTR-255 in combination with CAR T cells increased peak CAR T cell numbers, Ki-67 expression and persistence in the bone marrow compared to mice receiving CAR T cells alone. There was a higher percentage of EMRA like (CD45RA+CCR7-) CD4 and CD8 CAR T cells in NKTR-255 treated mice compared to mice treated with CAR T cells alone and persistent CAR T cells in mice treated with NKTR-255 were able to reject re-challenge of Raji tumor cells. Additionally, starting NKTR-255 on D7 post T cell infusion resulted in superior tumor control and survival compared to starting NKTR-255 on D-1 or D14. Conclusion Administration of NKTR-255 in combination with CD19 CAR T cells leads to improved anti-tumor efficacy making NKTR-255 an attractive candidate for enhancing CAR T cell therapy in the clinic. Disclosures Chou: Nektar Therapeutics: Other: Travel grant. Fraessle:Technical University of Munich: Patents &amp; Royalties. Busch:Juno Therapeutics/Celgene: Consultancy, Equity Ownership, Research Funding; Kite Pharma: Equity Ownership; Technical University of Munich: Patents &amp; Royalties. Miyazaki:Nektar Therapeutics: Employment, Equity Ownership. Marcondes:Nektar Therapeutics: Employment, Equity Ownership. Riddell:Juno Therapeutics: Equity Ownership, Patents &amp; Royalties, Research Funding; Adaptive Biotechnologies: Consultancy; Lyell Immunopharma: Equity Ownership, Patents &amp; Royalties, Research Funding. Turtle:Allogene: Other: Ad hoc advisory board member; Novartis: Other: Ad hoc advisory board member; Humanigen: Other: Ad hoc advisory board member; Nektar Therapeutics: Other: Ad hoc advisory board member, Research Funding; Caribou Biosciences: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; T-CURX: Membership on an entity's Board of Directors or advisory committees; Juno Therapeutics: Patents &amp; Royalties: Co-inventor with staff from Juno Therapeutics; pending, Research Funding; Precision Biosciences: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Eureka Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Kite/Gilead: Other: Ad hoc advisory board member.

First-in-Human CD4 CAR Clinical Trial on Peripheral T-Cell Lymphoma

Background CD19 CAR T cell therapy has achieved success in treating acute lymphoblastic leukemia. However, the treatment for Sezary syndrome, an aggressive form of cutaneous peripheral T cell lymphoma (PTCL) has remained a challenge. Despite patients with Sezary syndrome typically receiving multiple treatments within their disease progression, the prognosis is poor with 5 year survival rate of only 24%. Therefore, it is crucial to establish a novel treatment for PTCLs. CD4 is uniformly expressed on most mature T cell lymphoma, which makes it a promising target for treating PTCLs. Here, we present the efficacy of CD4 CAR T cell in our preclinical study and the success in level 1 dose escalation clinical trial on patients with Sezary syndrome. Methods We engineered a CD4 CAR with scFv (single-chain variable fragment) with CD28 and 4-1BB co-activators fused to CD3zeta and a leader sequence of CD8. The efficacy of CD4 CAR was tested with CD4+ leukemic cell line, primary CD4+ PTCL patient samples and multiple mouse models. An alemtuzumab safety switch has also been established to ensure the elimination of CAR T cells following tumor eradication. Children and adults with PTCLs were enrolled in our phase 1 dose escalation trial to evaluate the safety and efficacy of CD4 CAR T cell antitumor activity. Results Coculture assays results showed that CD4 CAR T cells displayed profound tumor killing effects in leukemia cell lines, primary patient samples and multiple mouse model systems. Our preclinical findings suggest that CD4 CAR T cells is an effective approach in treating PTCLs. Patients enrolled in the phase 1 dose escalation trial have shown remarkable response to CD4 CAR T cells treatment. Noticeably, a 54-yr-old patient diagnosed with Sezary syndrome had achieved complete remission with CD4 CAR T cell therapy. Prior to admission, he had been having symptoms of erythroderma, pruritus and scaling of the skin for over 10 years and had been resistant to multiple lines of chemotherapy. Before the initiation of CAR therapy, patient's body skin has extensive leukemia infiltrate (Fig. 1A) confirmed with skin biopsy (Fig. 1B) with bone marrow and blood comprising 50% leukemic cells (Fig. 1C). Patient received a total dose of 3x10^6 /kg single dose CAR T cells, following which fluconazole and valacyclovir were administrated for infection prophylaxis. Since patient received CD4 CAR T cell infusion, the percentage of CAR T cells (Fig 1. D) in peripheral blood had continue to increase as well as NK cells. (Fig 1. E) On day 13, patient had achieved complete remission with the percentage of leukemia cells in blood decreased to zero (Fig. 1C). On day 28, the appearance of the skin had undergone drastic change from what was before the treatment. Noticeable skin regeneration on both legs of the patients was observed (Fig 1. F). Flow cytometry of bone marrow and peripheral blood confirmed the absence of tumor cells. In addition, Skin biopsy on multiple sites demonstrated absence of leukemia infiltrates post CAR treatment (Fig. 1G). Patient was subsequently discharged with no additional medication needed. Throughout the treatment, patient had developed no infections with Grade II CRS toxicity noted. No other toxicities were observed. Updated results on other patients enrolled in this clinical trial including adverse events will be presented. Conclusion Our first-in-human clinical trial demonstrates promising efficacy of CD4 CAR T cell therapy in treating patients with refractory Sezary syndrome. cCAR is able to eradicate leukemia blasts, exerting a profound tumor killing effect that is superior to traditional chemotherapies. Disclosures Pinz: iCell Gene Therapeutics LLC: Employment. Ma:iCAR Bio Therapeutics Ltd: Employment. Wada:iCell Gene Therapeutics LLC: Employment. Ma:iCell Gene Therapeutics LLC: Consultancy, Equity Ownership, Research Funding; iCAR Bio Therapeutics Ltd: Consultancy, Equity Ownership, Research Funding.

Early Experience Using Radiotherapy As a Salvage Treatment for Relapsed or Refractory Non-Hodgkin Lymphomas Following CD19 Chimeric Antigen Receptor Modified T-Cell Therapy

Anti-CD19 chimeric antigen receptor modified T-cells (CAR T) produce remarkable responses for relapsed/refractory diffuse large B-cell lymphoma but over half of patients will relapse. Disease progression post CAR T therapy remains challenging and without standard guidelines. Radiotherapy is potentially an important salvage approach, but limited data exists to guide optimal utilization. We reviewed the first 15 patients treated with salvage radiotherapy (SRT) following CAR T progression. All but two patients had DLBCL; one had blastoid variant mantle cell lymphoma and the other patient was best classified as a CD5+ high grade lymphoma not otherwise specified. Outcomes included post RT response, freedom from subsequent relapse (FFSR) and overall survival (OS). Patients were heterogeneous and heavily-treated with a median of 4 prior lines of pre-CAR T therapy (range 2-8). Median time to first post-CAR T relapse was 82 days and RT was part of the first salvage regimen for 73%. Most received SRT to a site that was previously avid pre-CAR T. Post SRT, there were 6 evaluable patients with limited stage relapse; objective response rate was 100% (n=3 CR and n=3 PR). For advanced-stage relapse, while many had in-field PR, nearly all had concomitant out-of-field progression. Median OS from first post-CAR T relapse was 11 months. Patients with localized vs. advanced stage relapse had significantly improved FFSR (hazard ratio, HR=0.11, p=0.009) and OS (HR 0.10, p=0.003). By second-line age-adjusted IPI (sAA-IPI), 40% were low or low-intermediate risk and lower sAA-IPI risk prognosticated improved OS post SRT (p=0.004). Four patients were bridged to allogeneic transplantation with SRT and at analysis, 3 were alive and NED with 4.9, 7.2 and 36.2 months of post-allogeneic transplant follow-up. The fourth patient was also NED but deceased from transplant-related complications. SRT following CAR T is feasible with powerful and diverse utility including local palliation for transplant-ineligible patients. For lower risk and localized relapses, SRT may be integrated with novel targeted agents, immunotherapies or transplantation to attempt durable remissions. Disclosures Palomba: Hemedicus: Other: Immediate Family Member, Speakers Bureau ; Merck &amp; Co Inc.: Other: Immediate Family Member, Consultancy (includes expert testimony); Seres Therapeutics: Other: Immediate Family Member, Equity Ownership and Membership on an entity's Board of Directors or advisory committees; STRAXIMM: Other: Immediate Family Member, Membership on an entity's Board of Directors or advisory committees; Kite Pharmaceuticals: Other: Immediate Family Member, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Noble Insights: Consultancy; Evelo: Other: Immediate family member, Equity Ownership; MSK (IP for Juno and Seres): Other: Immediate Family Member, Patents &amp; Royalties - describe: intellectual property rights . Sauter:Novartis: Consultancy; Sanofi-Genzyme: Consultancy, Research Funding; Juno Therapeutics: Consultancy, Research Funding; GSK: Consultancy; Spectrum Pharmaceuticals: Consultancy; Genmab: Consultancy; Precision Biosciences: Consultancy; Celgene: Consultancy; Kite/Gilead: Consultancy. Scordo:Angiocrine Bioscience, Inc.: Consultancy; McKinsey &amp; Company: Consultancy. Batlevi:Juno Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Park:Allogene: Consultancy; Amgen: Consultancy; AstraZeneca: Consultancy; Autolus: Consultancy; GSK: Consultancy; Incyte: Consultancy; Kite Pharma: Consultancy; Novartis: Consultancy; Takeda: Consultancy. Shah:Janssen: Research Funding; Amgen: Research Funding. Giralt:Celgene: Consultancy, Research Funding; Takeda: Consultancy; Sanofi: Consultancy, Research Funding; Amgen: Consultancy, Research Funding. Perales:NexImmune: Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; MolMed: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Omeros: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Consultancy, Honoraria; Medigene: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees; Kyte/Gilead: Research Funding; Miltenyi: Research Funding; Bellicum: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Meyers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Nektar Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees. Sadelain:Juno Therapeutics: Consultancy, Patents &amp; Royalties, Research Funding; Fate Therapeutics: Consultancy, Patents &amp; Royalties; Memorial Sloan Kettering Cancer Center: Employment.

Abstract LB-146: Phase I CD22 CAR T-cell trial updates

Abstract Introduction: Patients who relapse after or are resistant to CD19 targeting are in need of novel therapies. We previously reported on the initial experience with our highly-active, first-in-human, first-in-child, CD22 CAR trial in the first 21 subjects with ALL. We now report on the cumulative experience with 52 treated subjects. Methods: This phase I study of anti-CD22 CAR-T cells (Clinicaltrials.gov NCT02315612) enrolled subjects between the ages of 3-30 years with relapsed/refractory CD22+ disease. All subjects received fludarabine 25 mg/m2 x 3 days and cyclophosphamide 900 mg/m2 x 1 day for lymphodepletion. Disease assessments were performed prior to initiation of lymphodepletion and at day 28 (+/- 4 days) post CAR infusion. Three dose levels were explored; with an interim manufacturing modification incorporating CD4/CD8 bead T-cell selection (TCS); current dose is DL1-TCS. (Table 1) Results: The median age was 18.1 years (range, 4.4-30.6). 36 (69.2%) subjects had undergone HSCT; 30 (57.7%) had prior CD19 CAR; 22 (42.3%) had prior blinatumomab; 28 (53.8%) subjects had a CD19 negative population, including two who were inherently partial CD19 negative without prior targeted therapy. 46 (88.4%) experienced CRS, 5 (10.9%) had grade 3-4 CRS. Unique toxicities apparent with expanded experience included capillary leak syndrome (n=3), including one grade 5 event; atypical HUS (n=2), symptomatic coagulopathy (n=8) and HLH-like manifestations (n=18). The complete remission rate was 72.5% overall; 84% at the current dose level. This included complete remissions seen in subjects who were non-responders to CD19 CAR and/or blinatumomab. The longest remission is &amp;gt; 3 years (n=1) post-CAR. Relapse occurred at a median of 6 months post CAR in 23 (64%) subjects primarily due to CD22 modulation. 12 proceeded to HSCT following CD22 CAR. Conclusion: In the largest study of CD22 CAR T-cell therapy to date, this extended experience confirms the initial efficacy, while highlighting novel aspects of the toxicity profile that warrant special attention. Results from our study support further testing of this CD22 CAR in a phase 2 clinical trial. Treated SubjectsDL1 (3 x 10e5)DL2 (1 x 10e6)DL3 (3 x 10e6)DL2 TCS (1 x 10e6)DL1 TCS&amp;gt; (3 x 10e5)n5261827#19n, (% of all subjects)526 (11.5%)18 (34.6%)2 (3.8%)7 (13.4%)19 (36.5%)DemographicsMedian age, (range, years)18.1 (4.4-30.6)21.3 (7.3-22.7)16.7 (8.0-30.7)17.1 (7.9-26.4)12.8 (4.4-28.9)18.5 (4.9-30.4)Prior HSCT, n (%)36 (69.2%)6 (100%)13 (72.2%)2 (100%)6 (85.7%)9 (47.3%)Prior CD19 CAR, n (%)30 (57.7%)6 (100%)11 (61.1%)1 (50%)5 (71.4%)7 (36.8%)Prior Blinatumomab, n (%)22 (42.3%)1 (16.7%)4 (22.2%)2 (100%)2 (28.6%)13 (68.4%)Prior Inotuzumab, n (%)14 (26.9%)1 (16.7%)4 (22.2%)1 (50%)3 (42.9%)5 (26.3%)Prior CD22 CAR, n (%)3 (5.8%)0002 (28.6%)1 (5.3%)Any CD19 negative population (&amp;lt;90%+), n (%)28 (53.8%)4 (66.7%)9 (50%)05 (71.4%)10 (52.6%)&amp;gt;M2 marrow, n (%)38 (73.0%)4 (66.7%)11 (61.1%)2 (100%)6 (85.7%)15 (78.9%)Toxicity ProfileTotal with CRS, n (%)46 (88.4%)3 (50%)16 (88.9%)2 (100%)6 (85.7%)19 (100%)Amongst all CRSCRS Grades 1-2, n (% of all with CRS)41 (89.1%)3 (100%)15 (93.8%)2 (100%)6 (100%)15 (78.9%)CRS Grades &amp;gt; 3, n (% of all with CRS)5 (10.9%)01 (5.6%)004 (21.1%)Received Tocilizumab, n (%)19 (36.5%)03 (16.7%)04 (57.1%)12 (63.2%)Received Steroids, n (%)17 (32.7%)02 (11.1%)1 (50%)4 (57.1%)10 (52.6%)Developed symptomatic coagulopathy, n (%)8 (15.4%)03 (16.7%)04 (57.1%)1 (5.3%)Developed HLH, n (%)18 (34.6%)03 (16.7%)05 (71.4%)10 (52.6%)Developed CLS, n (%)3 (5.8%)01 (5.6%)^002Developed aHUS, n (%)2 (3.8%)0001 (14.2%)2Grade 5 events, n (%)2 (3.8%)02 (11.1%)000Response RateComplete Remissions, n (%)@37 (72.5%)*1 (16.7%)13 (76.5)**1 (50%)6 (85.7%)16 (84.2%)MRD negative CR, n(%)@32 (62.7)*1 (16.7%)10 (58.8%)**0 (0%)6 (85.7%)15 (78.9%)CRS: cytokine release syndrome, as graded per Lee et al. HLH: hemophagocytic lymphohistiocytosis, retrospectively identified and defined as present if the following criteria were met: peak ferritin &amp;gt;100,000 with at least one of the following criteria: a) liver function tests &amp;gt; grade 3, b) creatinine &amp;gt; grade 3, c) pulmonary edema &amp;gt;grade 3 or d) evidence of hemophagocytosis on the bone marrow. *51 subjects evaluable for response. One subject had a grade 5 toxicity prior to disease restaging; **17 subjects evaluable for response. One subject had a grade 5 toxicity prior to disease restaging; ^CLS developed into fatal adult respiratory distress syndrome; #Subject 27 had stable disease with the first infusion with grade 1 CRS not requiring steroids or tocilizumab and limited CAR expansion. Notably he had received a CD22 CAR construct at an outside hospital prior to treatment on this protocol. Data presented in this table reflect the response and toxicity profile following the second infusion as it informed the toxicity and response profile at this dose. @Reflects the best response at any time point without any interval therapy; &amp;gt;Implementation of pre-emptive tocilizumab dosing initiated in this cohort. Citation Format: Nirali N. Shah, Haneen Shalabi, Bonnie Yates, Constance Yuan, Haiying Qin, Amanda Ombrello, Hao-Wei Wang, Leah Hoffman, Minh Tran, Sandhya Panch, Maryalice Stetler-Stevenson, Jianjian Jin, Crystal Mackall, Steve Highfill, David Stroncek, Terry J. Fry. Phase I CD22 CAR T-cell trial updates [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-146.

S898 CD19+ RELAPSE POST CD19 CHIMERIC ANTIGEN RECEPTOR (CAR) T CELLS IN CHRONIC LYMPHOCYTIC LEUKEMIA (CLL) IS DETERMINED BY T CELL FITNESS

Background:Although exciting clinical data have been presented with the use of the two autologous CD19 CAR T cells approved for the treatment of ALL and refractory lymphomas, challenges remain and their use in CLL remains experimental. CD19 positive and negative relapses have been described for which different mechanisms of resistance have been proposed. CD19+ relapses could be related to the host immune microenvironment or due to inadequate T cell fitness due to exhaustion. Therefore, there is still a need for further pre‐clinical modelling using immunocompetent mice to explore CAR plus immunotherapy combinations to enhance efficacy. CLL is an ideal disease model to explore this as it is associated with a tumour supportive microenvironment and T cells exhibit multiple functional defects and features of exhaustion, features closely recapitulated in Em‐TCL1 (TCL1) mice, and induced in healthy mice by adoptive transfer (AT) of murine CLL splenocytes.Aims:To demonstrate the effect of CLL T cell dysfunction on CAR T cell efficacy and improve function using aPDL1 blocking antibodies.Methods:Immunocompetent C57BL/6 mice (WT) received AT of pooled 35 x106 syngeneic splenic TCL1 CLL cells. Syngeneic donor CAR T cells were generated from T cells from WT or WT mice given AT CLL with CLL load &gt;80% (AT CAR). CD3+ were magnetic bead enriched then activated with CD3/CD28 Dynabeads (Thermofisher) and r‐IL2 (Roche), transduced with retroviral supernatant from MSGV‐1D3–28Z‐1.3mut (CD19‐CD28) and cultured and expanded for 4 days before injection. Two groups received intraperitoneal (IP) aPDL1 10 mg/kg from D‐1 every 72 hours (with and without AT CAR T cells) and all groups (except aPDL1 alone) were given 100 mg/kg IP cyclophosphamide on D‐1. On D0 the CAR groups received 1.5–2x106 CAR T cells with aPDL1 continuing until W12. Mice were bled every two weeks starting D+7 from CAR T cells to assess CLL load, CAR/T cell subsets and groups were culled together when they got sick or peripheral blood (PB) CLL&gt;70%.Results:Compared to WT CAR T cells, AT CAR T cells proliferate less in culture, skew towards CD8 cells, exhibit significantly lower transduction efficiencies in CD8 cells and have higher expression of PD1+ in both CD4 and CD8 cells. All mice treated with CAR T cells cleared their CLL and normal B cells at D+7, and those mice treated with WT CAR T cells all remained in remission until W18, whereas 50–60% of mice treated with AT CAR T cells slowly relapsed from D+21. Spleen weights in WT CAR treated mice were equivalent to age matched controls whilst AT CAR treated mice had variable size by W18. The addition of aPDL1 to AT CAR T cells did not alter their performance from AT CAR T cells alone in any parameter examined. CAR T cell expansion in all groups was greatest at D+7 and the majority of CAR+ cells were CD8+ and PD1+. PD1+ expression was significantly higher in AT compared to WT CAR T cells at D+7.Summary/Conclusion:CD19+ relapse post CAR T cells is determined by T cell fitness as WT CAR T cells can prevent relapse and can normalise PD1+ expression and spleen size. CAR T cells derived from CLL T cells are less able to prevent CD19+ relapse and this is not improved using concurrent aPDL1, which also seems to have limited activity in treatment alone of AT TCL1 CLL. Ongoing studies using CAR plus immunotherapy and BTK inhibitor combinations are addressing which steps are necessary to optimize CAR T cell fitness.image

MDS AS A CAUSE FOR PROLONGED HEMATOLOGIC TOXICITY AFTER TREATMENT WITH CD19 TARGETED CAR‐T CELL THERAPY IN PATIENTS WITH RELAPSED REFRACTORY LYMPHOMA

Introduction: The advent of adoptive cellular therapy utilizing autologous T cells expressing chimeric antigen receptors (CAR-T) against CD19 has revolutionized relapsed and refractory B cell lymphoma treatment. CAR-T cell therapy, however, is not without toxicity. Other than cytokine release syndrome and neurotoxicity, hematologic toxicity occurs commonly as well. Grade 3 and above prolonged neutropenia and thrombocytopenia (longer than 4 weeks since T cell infusion) was seen in 15 to 40% and 18 to 40% of patients treated with CD19 CAR T cells in clinical trials respectively. The exact mechanism underlying the pathogenesis of prolonged hematologic toxicity in CAR-T cell therapy is not well understood. Interestingly, we identified four cases of prolonged cytopenias after CAR-T cell therapy due to the presence of myelodysplastic syndrome in patients receiving this treatment for relapsed refractory B cell lymphoma. Methods: We performed a retrospective review of four patients with relapsed refractory aggressive B cell lymphoma treated at our institution with CD19 directed autologous CAR-T cells. Results: Median age was 74 (range: 57-76). Two patients had GCB type, 2 had non-GCB type DLBCL. The median number of lines of therapy prior to CAR-T cell therapy was 5. All four patients had prior autologous stem cell transplantation. Median time to MDS diagnosis from CAR T infusion was 3 months (range: 2 to 3). One patient developed MDS after additional chemotherapy was given for relapsed disease. One patient had evidence of a dysplastic clone prior to CAR-T cell therapy. The remaining two patients did not have evidence of MDS until immediately after CAR-T cell therapy. Two patients developed severe CRS requiring tocilizumab and corticosteroids. One patient showed partial response to CAR-T cell therapy, while three others achieved CR, two of which have since relapsed. Discussion: We identified four patients with prolonged hematologic toxicity after CAR-T cell therapy due to MDS. These patients have multiple risk factors for the development of MDS including advanced age, and heavy pretreatment. In fact, one patient had evidence of MDS prior to CAR-T cell therapy, underscoring the potential benefit of providing CAR-T cell therapy earlier in the course of treatment. In addition, our findings suggest that a bone marrow study should be performed in patients with prolonged cytopenias post CAR T cell therapy. It is not clear if there is any direct contribution of CAR T cells and the resulting immune system disturbance to the development of MDS. Long term follow up of all patients receiving CAR T cell therapy is therefore crucial to assessment true incidence of MDS and establish association. Keywords: B-cell lymphoma; CD19. Disclosures: Herrera, A: Consultant Advisory Role: Gilead. Siddiqi, T: Consultant Advisory Role: Juno Therapeutics. Budde, E: Consultant Advisory Role: Gilead. 480 – WITHDRAWN

Safety and Feasibility of Chimeric Antigen Receptor T Cell Therapy after Allogeneic Stem Cell Therapy in Relapsed/ Refractory B Cell Lymphomas

Introduction Chimeric Antigen Receptor T (CAR T) cell therapy with axicabtagene ciloleucel and tisagenelecleucel has been approved by the United States FDA for treatment of relapsed/refractory large B cell lymphoma subtypes based on encouraging data from the ZUMA-1 and JULIET trials, respectively. However, neither of these trials included patients who had previously undergone allogeneic stem cell transplantation (alloHCT). Here, we report our experience of patients treated with CAR T cell therapy following a prior alloHCT for relapsed/ refractory B cell lymphomas. Methods/ Results Since the first FDA approval in October 2017, three patients underwent CAR T cell therapy after a prior alloHCT at our center. Details of patient, disease, alloHCT were obtained retrospectively from patient health records and are outlined in Figure 1 while details about CAR T therapy are elaborated in Figure 2. All three patients were treated for diffuse large B cell lymphoma and received axicabtagene ciloleucel at 269, 291 and 1914 days after alloHCT. T cell chimerism was 100% in one patient and 18% in another patient, while this information was not available for the third patient. At one-month post CAR T cell therapy, one patient had complete response, one had partial response, and one had progression of disease. Two patients without a complete response eventually died of progressive disease at 106 and 77 days post CAR T cell, respectively. One patient developed grade 2 cytokine release syndrome and grade 2 neurotoxicity; treated with tocilizumab and corticosteroids, respectively, with complete resolution of symptoms. This patient required intensive care unit admission for 5 days. The other 2 patients did not have any CAR T cell related adverse events. Two patients had a prior history of graft-versus-host disease (GVHD). One had prior moderate skin chronic GVHD and another had previous stage 2 gut GVHD along with possible liver GVHD (transaminitis only). GVHD had resolved at time of CAR T cell treatment, although one patient was still on immune suppression, which was discontinued prior to leukapheresis. Neither patient had worsening of GVHD symptoms or development of new symptoms related to acute or chronic GVHD following CAR T cell therapy. Conclusion Based on our series, it appears feasible to consider CAR T cell therapy treatment in patients with relapsed B cell lymphoma subtypes following an alloHCT, without concerns of worsening of GVHD. So far, there is one more report of 5 patients with DLBCL who received allogeneic gene modified T cells without worsening GVHD in these patients (Brudno et al JCO 2016). This needs to be further explored in a larger series of patients to confirm safety and efficacy of such utilization.

Conditioning Prior to CAR T Cells Predicts Response and Survival in Pediatric/Young Adult Relapse/Refractory (R/R) B-ALL

Introduction CD19-specific CAR T cells have clinical benefit in patients (pts) with R/R B-ALL. Several factors have been associated with response: conditioning chemotherapy, CD4/8 ratio, and post infusion CAR T cell expansion. Objective Determine feasibility of a multi-center CD19-specific CAR (19-28z) T cell product for R/R B-ALL, toxicity following infusion, and analysis of factors for optimal response. Methods Pediatric/young adults with R/R B-ALL were eligible for infusion. Patients received cyclophosphamide-based (Cy) conditioning of high dose (HD; 3g/m2) or low dose (LD; 1.5g/m2) chemotherapy. Outcomes of interest were complete response (CR) and overall survival (OS). Variables considered were conditioning regimen (HD vs LD), pre-treatment disease burden (MRD vs morphologic), complete remission (CR) status, absolute lymphocyte count (ALC) change, and in vivo CAR T cell expansion. Results 25 pts were included; 17 pts received HD-Cy and 8 pts received LD-Cy prior to CAR T cells. Among evaluable pts (n=24), CR/CRi was demonstrated in 94% and 38% for HD-Cy vs LD-Cy cohorts respectively (p=0a01). OS was superior in the HD-Cy cohort as compared to the LD-Cy cohort (median OS = not reached; NR) vs. 4a7 months (p=0a004; Figure 1). Lymphodepletion (Delta ALC: prior/following Cy) was higher in the HD-Cy cohort as compared to the LD-Cy cohort (p Findings In this preliminary analysis we demonstrate that dose intensity of conditioning chemotherapy positively correlated with CR and OS for pts treated with CAR T cells and confirms, to a lesser extent, pre-treatment disease burden impacts both CR and OS.

Thirty Day Resource Utilization after Chimeric Antigen Receptor (CAR) T Cell Infusion for Hematologic Malignancies

Background We aimed to characterize institutional resources utilized (other than T cell collection and CAR T cell manufacturing and infusion) peri-chimeric antigen receptor-modified (CAR) T cells administration. Methods Adult patients treated on selected investigator-initiated clinical trials of CAR T cell therapy at Memorial Sloan Kettering Cancer Center were identified from the institutional database. Utilization data was collected from the start of admission for CAR T cell infusion through the end of the initial admission for infusion or through 30 days following initial CAR T cell infusion, whichever was longer. Descriptive statistics were used to analyze the data. Results Between 6/2007 to 4/2018, 106 pts (56 pts (53%) B-cell acute lymphoblastic leukemia (ALL), 37 (35%) chronic lymphocytic leukemia (CLL), B-cell non-Hodgkin lymphoma (NHL), and 13 (12%) multiple myeloma (MM)) on 4 clinical trials receiving inpatient CAR T cell infusions. The median age was 53 yrs (range 22-77) with 65% male. The median length of stay for the admission during which CAR T cells was given was 23 days (range 4 -133), with ALL patients admitted longer (Figure 1). 43 (41%) spent at least one day in the intensive care unit (ICU), with a range of 0-43 days. Outpatient clinic visits through day 30 post CAR T cell infusion occurred in 57 (53%) patients. A total of 62,953 laboratory panels and 1,190 radiology studies done during the study time frame. Fourteen percent of the labs were complete blood counts, basic or comprehensive metabolic panels, or liver function tests. For the total population, ALL, CLL/NHL, MM, there were a median of 63.5 (range 13-368), 91.5 (21-368), 47 (13-167), and 51 (range 38-113) of these panels done per patient during the time frame, respectively. Among the radiology studies, 25% were CT scans, 10% MRIs, 7% PET scans, 5% ultrasounds, and 53% x-rays, with differences in patterns of use by disease type (Figure 2). Chemotherapy accounted for 328 units (0.8%) of the 41,331 units of medications given in this time frame. The median medication units per patient was 255 (range 35-2091), 423 (range 35-2091), 200 (range 41-1190), and 207 (range 90-666) for the total population, and the ALL, CLL/NHL, and MM pts, respectively. Thirty-two doses of tocilizumab were given to 25 patients (24%), with ALL pts receiving 23 of those doses (72%). Conclusion CAR T cell therapy utilizes many resources and can create challenges in institutional resource capacity. Identifying these resources will allow for better allocation and care delivery. Further refinement of CAR T cell products and improvements in CAR T cell-related toxicity management may permit safer delivery of this therapy and reduce costs per patient. Comparison with alternative therapies and analysis of resource utilization for the commercial CAR T cell products is warranted.

Exhausted CLL T Cells Mediated By PD1 Expression an Important Mechanism for CD19 CAR Efficacy in CLL in the Adoptive Transfer TCL1 Mouse Model

Exhausted CLL T Cells Mediated By PD1 Expression an Important Mechanism for CD19 CAR Efficacy in CLL in the Adoptive Transfer TCL1 Mouse Model

CAR22/19 Cocktail Therapy for Patients with Refractory/Relapsed B-Cell Malignancies

▪CD19 CAR T-cell (CAR-19) therapy have elicited great clinical responses in B-cell malignancies. However, CD19-negative relapse has emerged as a major challenge for the long-term disease control post CAR-19 therapy and conferred a dismal outcome to these pts. Recently, co-targeting of CD19/CD20, CD19/CD22 or CD19/CD123 has been proposed as a strategic approach to overcome antigen loss relapse after CAR-19 therapy. However, the infusion scheme has not yet been defined, the efficacy to avoid antigen escape has not been tested, and its toxicity remains to be assessed. Furthermore, the impact of genetic abnormalities on the outcome post CAR T-cell therapy has not been fully elucidated.We conducted an open-label, single-center and single-arm pilot study of sequential infusion of third generation CAR T-cell “cocktail” comprising both anti-CD22 and anti-CD19 CAR T-cells, which was registered with Chinese Clinical Trial Registry (ChiCTR, number ChiCTR-OPN-16008526).Between March 2016 and January 2018, a total of 89 eligibility pts completed CAR-22/19 “cocktail” infusion and were included for analysis. Of 89 pts (median age 36 years; range, 9-71), 51 had refractory/relapsed (R/R) B-cell acute lymphoblastic leukemia (B-ALL) and 38 had R/R B-cell non-Hodgkin lymphoma (B-NHL). The cutoff date for data collection was April 30, 2018, with a median follow-up of 7.6 months (mos) for B-ALL and 5.4 mos for B-NHL.CAR-22 and CAR-19 cells were given separately in 2 divided doses (range, 1 to 4 for CAR-22, and 1 to 5 for CAR-19) with a dose-escalation infusion. Eighty-one pts firstly received CAR-22 infusion, and then CAR-19 infusion, while 8 pts received CAR-19 first and CAR-22 later. B-ALL pts received 2.73±1.19×106/kg CAR-22 and 2.61±1.45×106/kg CAR-19; B-NHL pts received instead higher doses, i.e. 5.28±2.44 ×106/kg CAR-22 and 5.14±2.06 ×106/kg CAR-19.Of the 50 evaluable B-ALL pts, 48 (96.0%) achieved complete remission (CR)/or CR with incomplete count recovery (CRi) at the day 30 assessment. By sensitive multi-parameter flow cytometry (MFC) assay, 47 (94.0%) achieved MRD-negative CR/CRi. At a median follow-up of 7.6 mos (range, 1.3 to 22.2), the progression-free survival (PFS) of all B-ALL pts was 12.0 mos and the overall survival (OS) was not reached. Of the 13 pts with Ph+ B-ALL, 6 of whom had T315I mutation, 11 (84.6%) achieved MRD-negative CR/CRi. The PFS was 15.4 months, and the OS was not reached at a median follow-up of 13.5 months (range, 3 to 22.5). Of the 6 pts with MLL translocations (mainly MLL-AF6), 66.7% were progression-free and the median PFS was not reached. However, among pts with Ph-like ALL, the PFS was only 4.6 months. A total of 23 pts relapsed, however, antigen loss of CD19 and CD22 was not detected by MFC. Forty-Seven pts (92.2%) experienced cytokine release syndrome (CRS) and 11 (21.6%) had severe CRS (≥ grade 3). Except for 1 pt, all the severe cases were reversible. Seven pts (13.7%) developed neurotoxicity.At a minimum follow-up of 3 months, the overall response rate (ORR) and CR rate in 36 evaluable B-NHL pts was 72.2% and 50%, respectively. At the cutoff date for data collection, 50.5% of all pts remained progression-free. A total of 8 pts (26.7%) had relapsed with a median PFS of 2.6 months. Re-biopsy and immunophenotyping was performed in 3 relapsed pts and antigen loss of CD19 or CD22 was not detected. At a median follow-up of 5.4 months (range, 3.0 to 16.2), both PFS and OS of all pts were not reached. Of the 9 pts with MYC translocation, 8 had a response and 7 maintained their responses with a median follow-up of 10.1 months, including all the 4 pts with “double-hit” lymphoma (concurrently carrying MYC and BCL2 or BCL6 translocations). Of the 10 pts with del(17p) or TP53 mutation, 8 (80.0%) had a clinical response. With a median follow-up of 5.3 months, the PFS was 3.3 months, and 45.0% of these pts were progression-free. All the B-NHL pts experienced CRS, but only 21.1% had severe (grade 3 or 4), but reversible CRS and 13.2% developed reversible neurotoxicity.In summary, our results indicated that infusion of third generation CD22/19 CAR T-cell “cocktail” is feasible and safe for pts with B-cell malignancies. Co-targeting to CD19/CD22 is a promising approach for overcoming antigen escape relapse of CAR-19 therapy, but this remain to be fully tested. The treatment response predictive value of distinct genetic subtypes for CAR T-cell therapy should be considered for selection of pts for personalized immunotherapy. DisclosuresNo relevant conflicts of interest to declare.