ALBERT

Beschreibung: Key Points Daratumumab is effective against T-ALL in human xenograft models. CD38 is a novel target with broad potential in the treatment of T-ALL.

Beschreibung: Introduction: Primitive extranodal lymphomas are a heterogeneous group of malignant lymphoid hematological developed from the mucosa-associated lymphoid tissue (MATL) or sites that have acquired MALT after repeated stimulation. The particularity of this type of affection reside: the access to diagnosis which is difficult and therapeutic approach which respond to the ATB, antiviral, surgery and RT. They represent 24-48% of lymph node lymphomas and they are increasing. The incidence of lymphoma is growing in the world, it is approximately 16.8 / 105inhabitants. In Algeria in 2012, the incidence of lymph node lymphomas in adults was 2.24 / 100,000. Lymphomas Diffuse large B-cell phenotype (DLBCL) represent 50-60% of lymphomas, it is the most common histological type. Goals of the study: 1-analyze the epidemiological characteristics (gender, age, geographical distribution, annual incidence). 2- Identify anatomical sites. 3- Specify the clinical and prognostic features Patients and methods: It's is a multicenter, retrospective study over a period between 2010-2014. The study population included all pts over 15 years and having an extranodal DLBCL at 18 hematology centers and 4 cancer centers. Data were collected on data sheets distributed to the various services involved in the study. The diagnosis is made on the histological examination of a biopsy of the affected organ. The clinical, biological and imaging results allowed us to classify and identify prognostic factors for pts. Results: Among 1057 sheets of extranodal lymphomas, the type DLBCL is specified in 562 (53%) cases, distributed in 325 men and 237 women (sex ratio M/F: 1.36). The average age at diagnosis is 51 years (16-88) with a peak in the age group 50-60 years. The overall annual incidence of 0.31/105 inhabitants/year and the specific incidence for patients over 15 years is 0.42 / 105inhabitants/year. PS 0-1: 323 / 543pts (60%). Number of pts (pts) by place of care: Annaba 65, Sétif: 60, CAC Constantine: 53, Tizi Ouzou: 49, Blida Cac: 41, CMPC-hematology: 40, Tlemcen: 30, Beni- Méssous- hematology: 29, CAC CPMC: 24, EHUOran: 23, hematology CAC Batna: 22, CHU Oran: 19, HMRUO: 17, Blida-hematology: 16, HCA:16, SBA: 15, CAC Béni-Messous: 14, EPH Mascara: 10, HMRU Oran: 9, Bejaia: 7, hematology CHU Batna: 2, hematology Cne:1. Number of cases according to anatomical localisation: Stomach: 180, Intestine: 31, Colon 12, Tonsils: 70, Cavum: 31, nasal cavities: 11, Bones: 43, mediastinum: 41, SNC: 29, Skin: 25, Rate / MO :15, Thyroid: 12, soft Parties: 10, Breast: 6, lung / pleural: 5, Liver: 5, Others: 36. The clinical symptomatology is very heterogeneous, specifically of the affected organ. Clinical stage is specified in 549 cases, according to Ann Arbor: SCIE: 272 (49%), SCIIE: 149 (27%), SCIIIE: 31 (6%), SCIV: 97 (18%). The International Prognostic Index adjusted for age (IPIaa) include: for pts less than 60 years: Low (F): 70 (23%), lower intermediate (IF): 130 (43%), intermediate high (IE) : 69 (23%), high (H): 32 (11%); for over 60 years Topics: F: 33 (23%), MI: 53 (37%) IE: 41 (28%), E: 17 (12%). Comments: As with other types of lymphoma, there is a male predominance and a peak incidence in the age group 50-60 years. The higher number of pts in the center and east of the country is probably related to a denser population in these regions. The histological type DLBCL at 53% is in agreement whith what it is conventionally reported. The incidence of 0.31/105inhabitants/year extranodal DLBCL is lower than the overall nodal DLBCL, however, the incidence of extranodal NHL is rarely determined. The number of cases of extranodal lymphomas described in this study is certainly below the actual number because this group of disorders is supported by various specialties related to the location of lymphoma. Extranodal lymphomas has a clinical polymorphism, but it is recognized that gastric and tonsillar locations are the most common, the other despite their rarity, require attention from management. This type of lymphoma is characterized by a preponderance of localized stages unlike ganglion lymphomas where the extended stages predominate. Likewise distribution by IPIaa not exceeding one pejorative factor is more common. Conclusion: Extranodal DLBCL are rare, they are characterized by a diversity clinicopathological that challenges us to homogenization of their treatment in multidisciplinary level. Disclosures No relevant conflicts of interest to declare.

Beschreibung: The authors report the interaction between Down syndrome, a major genetic leukemia predisposition condition, and inherited genetic alleles associated with increased susceptibility to childhood acute lymphoblastic leukemia.

Beschreibung: Key Points Ph-like ALL is characterized by a diverse array of genetic alterations activating cytokine receptor and tyrosine kinase signaling. Pediatric patients with Ph-like ALL can be identified in real time for effective treatment stratification.

Beschreibung: Introduction. Prior studies have described a subset of B-progenitor ALL cases with a distinct gene expression profile and/or deletions involving ERG (encoding the ETS family member v-ets avian erythroblastosis virus E26 oncogene), however the relationship of these alterations and their role in leukemogenesis are poorly understood. We performed integrated genomic and epigenetic analyses, biochemical studies and leukemogenesis assays to define the genetic basis of this form of ALL. Methods. We studied 1674 childhood, adolescent and young adult B-progenitor ALL cases with microarray gene expression profiling and/or RNA-sequencing data to enable the identification of ERG ALL by unsupervised clustering and predictive analysis of microarrays. Detailed genomic analysis was performed for 144 ERG ALL cases, including whole genome (N=38), exome (n=46) and/or RNA-sequencing (n=57) cases, and single nucleotide polymorphism array analysis. Epigenetic profiling, including whole genome bisulfite sequencing, chromatin immunoprecipitation and sequencing for ERG and histone modifications and ATAC-sequencing were performed for a subset of 8 xenografted ERG tumors and reference cell lines. ERG transcript expression was measured by analysis of RNA-seq analysis and quantitative RT-PCR assays, and by interrogation of TCGA and PCGP RNA-seq data. The function of ERG isoforms was evaluated by EMSA and transcriptional reporter assays, immunofluoresence, colony forming assays and retroviral bone marrow transplant assays. Results. One hundred and forty four cases (8.6%) of B-ALL cases exhibited a distinct gene expression profile and lacked known chromosomal rearrangements (ERG ALL). Such cases had favorable outcome. Eighty cases (55.6%) had focal deletions of ERG with no evidence of oncogenic or chimeric ERG fusions. The deletions were most commonly heterozygous and involving exons 3-7 (n=27) or 3-9 (n=22) of 10 coding exons, and less commonly involving exon 1, or a larger region of the gene. No ERG deletions were identified in non-ERG ALL. Two cases harbored missense mutations in the ETS domain. Analysis of whole genome and exome sequencing data of 71 cases identified a high frequency of alterations of lymphoid transcription factors (46.5%; IKZF1 36.7%, PAX5 11.3%); mutation of transcription factors otherwise uncommon in ALL (21%; MYC, MYCBP2, MGA, ZEB2, GATA3); activation of signaling pathways, most commonly NRAS or KRAS (35.2%); cell cycle regulation (22.5%); and epigenetic modifiers (56.3%), most commonly KMT2D, SETD2, ARID2 and NCOR1. Notably, the five year event-free survival of ERG ALL cases with IKZF1 alterations exceeded 85% in both St Jude and Children's Oncology Group cohorts. We observed striking transcriptional deregulation at the ERG locus. Most (51/56) ERG- deleted cases expressed an ERG isoform encoded by a novel exon in intron 6 that splices in frame to distal exons, resulting in expression of a truncated C-terminal ERG protein that lacks the pointed and central regulatory domains, but retains the ETS and transactivation domain (ERGalt). ERGalt was also present in most (36/44) cases lacking an ERG deletion, and was strongly associated with presence of ERGalt protein in leukemic cells. We also identified expression of an Antisense Long non-coding RNA associated with the ERG locus (ALE) in ERG ALL. ERGalt and ALE were absent, or uncommonly expressed at very low levels in non-ERG ALL. ERGalt was absent, and ALE rarely expressed in non-ALL PCGP and TCGA samples. ERGalt and point mutant ERG were retained in the nucleus, bound DNA targets and acted as competitive inhibitors of wild type (WT) ERG in transcriptional reporter assays. Lineage-negative Arf -null bone marrow cells transduced with ERG WT induced an aggressive erythro-megakaryoblastic leukemia; in contrast ERGalt induced an immature lymphoid progenitor leukemia. Conclusions. Genomic alterations drive aberrant transcription of ERG, resulting on expression of a truncated, C-terminal oncogenic ERG protein. This represents a novel mechanism of transcription factor deregulation in leukemia. As a subset of ERG ALL cases lack ERG deletion, and as IKZF1 alterations are not associated with inferior outcome in this form of ALL, diagnostic approaches must incorporate gene expression profiling in addition to identification of ERG and IKZF1 alterations to accurately identify this form of leukemia. Disclosures Evans: Prometheus Labs: Patents & Royalties: Royalties from licensing TPMT genotyping. Stock:Gilead: Membership on an entity's Board of Directors or advisory committees. Voorhees:Oncopeptides: Consultancy; Onyx Pharmaceuticals: Research Funding; GSK: Consultancy; Oncopeptides: Research Funding; Janssen: Research Funding; A Takeda Oncology Company: Consultancy, Research Funding; Celgene: Consultancy; Millennium Pharmaceuticals: Consultancy, Research Funding; Acetylon Pharmaceuticals, Inc.: Research Funding; Novartis: Consultancy; Array BioPharma: Consultancy; GSK: Research Funding; Celgene: Research Funding. Hunger:Spectrum Pharmaceuticals: Consultancy; Jazz Pharmaceuticals: Consultancy; Sigma Tau: Consultancy; Merck: Equity Ownership. Mullighan:Incyte: Consultancy; Amgen: Honoraria.

Beschreibung: Introduction: Although recent studies have refined the classification of B-progenitor and T-lineage acute lymphoblastic leukemia into gene-expression based subgroups, a comprehensive integration of significantly mutated genes and pathways for each subgroup is needed to understand disease etiology. Methods: We studied 2789 children, adolescents and young adults (AYA) with newly diagnosed B-ALL (n=2,322 cases) or T-ALL (n=467) treated on Children's Oncology Group (n=1,872) and St. Jude Children's Research Hospital trials (n=917). The cohort comprised childhood NCI standard-risk (41.8%; age range 1-9.99 yrs, WBC ≤ 50,000/ml), childhood NCI high-risk (44.5%; age range ≥10 to 15.99 yrs) and AYA (9.9%; age range 16-30.7 yrs). Genomic analysis was performed on tumor and matched-remission samples using whole transcriptome sequencing (RNA-seq; tumor only; n=1,922), whole exome sequencing (n=1,659), whole genome sequencing (n=757), and single nucleotide polymorphism array (n=1,909). Results: For B-ALL, 2104 cases (90.6%) were classified into 26 subgroups based on RNA-seq gene expression data and aneuploidy or other gross chromosomal abnormalities (iAMP21, Down syndrome, dicentric), deregulation of known transcription factors by rearrangement or mutation (PAX5 P80R, IKZF1 N159Y), or activation of kinase alterations (Ph+, Ph-like). For T-ALL, cases were classified into 9 previously described subtypes based on dysregulation of transcription factor genes and gene expression. In 1,659 cases subject to exome sequencing (1259 B-ALL, 405 T-ALL) we identified 18,954 nonsynonymous single nucleotide variants (SNV) and 2,329 insertion-deletion mutations (indels) in 8,985 genes. Overall, 161 potential driver genes were identified by the mutation-significance detection tool MutSigCV or by presence of pathogenic variants in known cancer genes. Integration of sequence mutations and DNA copy number alteration data in B-ALL identified 7 recurrently mutated pathways: transcriptional regulation (40.6%), cell cycle and tumor suppression (38.0%), B-cell development (34.5%), epigenetic regulation (24.7%), Ras signaling (33.0%), JAK-STAT signaling (12.0%) and protein modification (ubiquitination or SUMOylation, 5.0%). The top 10 genes altered by deletion or mutation in B-ALL were CDKN2A/B (30.1%), ETV6 (27.0%), PAX5 (24.6%), CDKN1B (20.3%), IKZF1 (17.6%), KRAS (16.5%), NRAS (14.6%), BTG1 (7.5%) histone genes on chromosome 6 (6.9%) and FLT3 (6.1%), and for T-ALL, CDKN2A/B (74.7%), NOTCH1 (68.2%), FBXW7 (21.3%), PTEN (20.5%) and PHF6 (18.2%) (Figure 1A). We identified 17 putative novel driver genes involved in ubiquitination (UBE2D3, UBE2A, UHRF1, and USP1), SUMOylation (SAE1, UBE2I), transcriptional regulation (ZMYM2, HMGB1), immune function (B2M), migration (CXCR4), epigenetic regulation (DOT1L) and mitochondrial function (LETM1). We also observed variation in the frequency of genes and pathways altered across B-ALL subtypes (Figure 1B). Interestingly, alteration of SAE1 and UBA2, novel genes that form a heterodimeric complex important for SUMOylation, and UHRF1 were enriched in ETV6-RUNX1 cases. Deletions of LETM1, ZMYM2 and CHD4 were associated with near haploid and low hypodiploid cases. Deletion of histone genes on chromosome 6 and alterations of HDAC7 were enriched in Ph+ and Ph-like ALL. Mutations in the RNA-binding protein ZFP36L2 were observed in PAX5alt, DUX4 and MEF2D subgroups. Genomic subtypes were prognostic. ETV6-RUNX1, hyperdiploid, DUX4 and ZNF384 ALL were associated with good outcome (5-yr EFS 91.1%, 87.2%, 91.9% and 85.7%, respectively), ETV6-RUNX1-like, iAMP21, low hyperdiploid, PAX5 P80R and PAX5alt were associated with intermediate outcome (5-yr EFS 68.6%, 72.2%, 70.8%, 77.0% and 70.9%, respectively), whilst KMT2A, MEF2D, Ph-like CRLF2 and Ph-like other conferred a poor prognosis (55.5%, 67.1%, 51.5% and 62.1%, respectively). TCF3-HLF and near haploid had the worst outcome with 5-yr EFS rates of 27.3% and 47.2%, respectively. Conclusions: These findings provide a comprehensive landscape of genomic alterations in childhood ALL. The associations of mutations with ALL subtypes highlights the need for specific patterns of cooperating mutations in the development of leukemia, which may help identify vulnerabilities for therapy intervention. Disclosures Gastier-Foster: Bristol Myers Squibb (BMS): Other: Commercial Research; Incyte Corporation: Other: Commercial Research. Willman:to come: Patents & Royalties; to come: Membership on an entity's Board of Directors or advisory committees; to come: Research Funding. Raetz:Pfizer: Research Funding. Borowitz:Beckman Coulter: Honoraria. Zweidler-McKay:ImmunoGen: Employment. Angiolillo:Servier Pharmaceuticals: Consultancy. Relling:Servier Pharmaceuticals: Research Funding. Hunger:Jazz: Honoraria; Amgen: Consultancy, Equity Ownership; Bristol Myers Squibb: Consultancy; Novartis: Consultancy. Loh:Medisix Therapeutics, Inc.: Membership on an entity's Board of Directors or advisory committees. Mullighan:Amgen: Honoraria, Other: speaker, sponsored travel; Loxo Oncology: Research Funding; AbbVie: Research Funding; Pfizer: Honoraria, Other: speaker, sponsored travel, Research Funding; Illumina: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: sponsored travel.

Beschreibung: Key Points In a multicenter, randomized phase 3 trial, MPR-R was not superior over MPT-T with respect to response rate, PFS, and OS. Grade 3/4 hematologic toxicity requiring growth factor support occurred with MPR-R vs clinically significant neuropathy with MPT-T.

Beschreibung: Introduction Bone Marrow Transplant (BMT) is a potentially curative treatment for malignant and non-malignant blood disorders and has demonstrated impressive outcomes in autoimmune diseases. Prior to BMT, patients are prepared with high-dose chemotherapy alone or with total body irradiation, and both are associated with early and late morbidities, such as infertility, secondary malignancies and organ toxicity; and substantial risk of mortality. This greatly limits the use of BMT in malignant and non-malignant conditions. To address these issues, we are developing antibody drug conjugates (ADCs) targeting hematopoietic stem cells (HSCs) and immune cells to more safely condition patients for BMT. Results To enable simultaneous HSC and immune cell depletion for BMT we investigated targeting human CD45, a protein expressed exclusively on nearly all blood cells including HSCs. Antibody discovery campaigns identified several antibodies with sub-nanomolar affinities for human and non-human primate (NHP) CD45. We then created anti-CD45 ADCs with drug payloads including DNA-damaging, tubulin-targeting and RNA polymerase-inhibiting molecules. An ADC developed with alpha-amanitin (an RNA polymerase II inhibitor) enabled potent in vitro killing of primary human CD34+ HSCs and immune cells (40-120 picomolar IC50s). With this anti-CD45 amanitin ADC (CD45-AM), we explored depletion of HSCs and immune cells in vivo using humanized NSG mice. A single dose of 1 or 3 mg/kg CD45-AM enabled 〉95% depletion of human CD34+ cells in the bone marrow as assessed 7 or 14 days post-administration (Figure, n = 3/group, p values 〈 0.05); 〉95% depletion of human B-, T- and myeloid cells was observed in the periphery and bone marrow (Figure, p values 〈 0.05). Control non-targeting isotype matched-ADCs and anti-CD45 antibody not bearing a toxin had minimal effect on either HSC or immune cells. In hematopoietic malignancies, an anti-CD45 ADC would ideally reduce disease burden and enable BMT. In a model of acute lymphoblastic leukemia (REH cell line, n = 10 mice/group), and 3 patient-derived models of FLT3+NPM1+ acute myeloid leukemia (n = 4-5 mice/group per model), a single dose of 1 mg/kg CD45-AM more than doubled the median survival and several mice survived disease-free (p values 〈 0.001). Anti-CD45 antibodies have been investigated for BMT conditioning in patients as naked antibodies that rely on Fc-effector function to deplete lymphocytes (Biol Blood Marrow Transplant. 2003 9(4): 273-81); or as radioimmunotherapy (Blood. 2006 107(5): 2184-2191). These agents demonstrated infusion-related toxicities likely due to effector function elicited by the wild-type IgG backbone. To address this issue, we created anti-CD45 antibodies with reduced Fc-gamma receptor binding that prevented cytokine release in vitro and in humanized mice. As BMT will likely require fast clearing ADCs to avoid depleting the incoming graft, we also created fast-half-life CD45-AM variants with a t½ of 8-15 hours in mice. To determine the safety and pharmacokinetic properties of regular and fast half-life Fc-silent variants in an immune-competent large animal we tested these in cynomolgus monkeys. Single doses (3 mg/kg, iv, n = 3/group) of fast and regular half-life Fc-silent unconjugated anti-CD45 antibodies were both well tolerated in cynomolgus monkeys and displayed pharmacokinetic properties suitable for BMT. Conclusion These results demonstrate that targeting CD45 with an amanitin ADC results in potent in vitro and in vivo human HSC and immune cell depletion. This new CD45-AM ADC also significantly reduced disease burden in multiple leukemia models. Our results indicate Fc-silencing may avoid infusion-related toxicities observed with previous CD45 mAbs. An alpha-amanitin ADC targeted to CD45 may be appropriate for preparing patients for BMT since we hypothesize it may i) be non-genotoxic; ii) effectively deplete both HSC and immune cells; iii) avoid bystander toxicity, due to amanitin's poor cell permeability as a free toxin; and iv) kill cycling and non-cycling cells, the latter being necessary for effective HSC depletion. As our anti-CD45 ADCs are cross-reactive, we are currently investigating their HSC and immune cell depletion activity in vivo in NHPs to enable further preclinical development of these transplant conditioning agents. Disclosures Palchaudhuri: Magenta Therapeutics: Employment, Equity Ownership, Patents & Royalties; Harvard University: Patents & Royalties. Pearse:Magenta Therapeutics: Employment, Equity Ownership, Patents & Royalties. Proctor:Magenta Therapeutics: Employment, Equity Ownership. Hyzy:Magenta Therapeutics: Employment, Equity Ownership. Aslanian:Magenta Therapeutics: Employment, Equity Ownership. McDonough:Magenta Therapeutics: Employment, Equity Ownership. Sarma:Magenta Therapeutics: Employment, Equity Ownership. Brooks:Magenta Therapeutics: Employment, Equity Ownership. Bhat:Magenta Therapeutics: Employment. Ladwig:Magenta Therapeutics: Employment, Equity Ownership. McShea:Magenta Therapeutics: Employment, Equity Ownership. Kallen:Magenta Therapeutics: Employment, Equity Ownership. Li:Magenta Therapeutics: Employment, Equity Ownership. Panwar:Magenta Therapeutics: Employment, Equity Ownership, Patents & Royalties. Dushime:Magenta Therapeutics: Employment, Equity Ownership. Sawant:Magenta Therapeutics: Employment, Equity Ownership. Adams:Magenta Therapeutics: Employment, Equity Ownership. Falahee:Magenta Therapeutics: Employment, Equity Ownership, Patents & Royalties. Lamothe:Magenta Therapeutics: Employment, Equity Ownership. Gabros:Magenta Therapeutics: Employment, Equity Ownership. Kien:Magenta Therapeutics: Employment, Equity Ownership. Gillard:Magenta Therapeutics: Employment, Equity Ownership. McDonagh:Magenta Therapeutics: Employment, Equity Ownership, Patents & Royalties. Boitano:Magenta Therapeutics: Employment, Equity Ownership, Patents & Royalties. Cooke:Magenta Therapeutics: Employment, Equity Ownership, Patents & Royalties.

Beschreibung: Introduction Targeted antibody drug conjugates (ADCs) to mouse CD45 or mouse CD117 have recently been shown to effectively prepare immunocompetent mice for whole bone marrow transplants (Palchaudhuri et al. Nature Biotech 2016 34:738-745; and Czechowicz et al. Blood 2016 128:493). This new targeted approach to conditioning using ADCs has the potential to expand the utility of transplantation if it can be successfully translated to humans. The anti-CD45 or anti-CD117 antibodies used previously were coupled to saporin (SAP), a ribosome-inhibiting protein, which once internalized elicits cytotoxicity in a cell cycle-independent manner. Both anti-CD45-saporin (CD45-SAP) and anti-CD117-saporin (CD117-SAP) ADCs have been shown to effectively deplete bone marrow hematopoietic stem cells (HSCs) as single dosed agents, creating vacancies that enable efficient autologous HSC engraftment (〉95% long-term donor chimerism). Results To further investigate and develop the utility of these tool ADCs in murine transplant models, we explored CD45-SAP (1.9 mg/kg, iv) and CD117-SAP (1 mg/kg, iv) in an allogeneic minor mismatch transplant model (Balb/c donor into DBA/2 recipients). The ADCs were used alone or in combination with an additional immune depleting agent, clone 30F11 (25 mg/kg, IP), a naked anti-CD45 antibody that mimics ATG by relying on effector function to enable potent peripheral B- and T -cell depletion. In addition to the lymphodepleting antibody, we included post-transplant Cytoxan (200 mg/kg, IP) to prevent GvHD. To compare the CD45-SAP and CD117-SAP to conventional conditioning methods, we investigated sub-lethal total body irradiation (TBI, 2Gy) or pre-transplant Cytoxan (200 mg/kg, IP) in combination with the immunosuppressants. Conditioned mice were transplanted with 2x107 whole bone marrow cells, and chimerism assessed over 12 weeks. CD45-SAP or CD117-SAP in combination with immunosuppressants (30F11 and post-transplant Cytoxan) enabled 〉85% peripheral donor chimerism at 12 weeks post-transplantation. Multilineage reconstitution was observed in the T-, B- and myeloid cell compartments with 〉80%, 〉90% and 〉90% donor chimerism respectively in both CD45-SAP and CD117-SAP groups. In contrast, 2Gy TBI in combination with immunosuppressants (30F11 and post-transplant Cytoxan) resulted in only 5% donor engraftment. Multi-dosing with 30F11 (QDx3) plus 2Gy TBI and post-transplant Cytoxan increased the peripheral donor chimerism to 40%. Pre-transplant Cytoxan plus 30F11 (QDx3) and post-transplant Cytoxan yielded 20% donor chimerism. For all groups, stem cell chimerism in the bone marrow matched the peripheral chimerism. Conclusion These results indicate anti-CD45 or anti-CD117 ADCs may be used in combination with immunosuppression to enable highly efficient allogeneic transplants in a minor mismatch model (〉85% donor chimerism). CD45-SAP and CD117-SAP were more effective at conditioning versus 2Gy TBI or pre-transplant Cytoxan. Future experiments will investigate anti-CD45 and anti-CD117 ADCs in additional allogeneic models. Disclosures Palchaudhuri: Magenta Therapeutics: Employment, Equity Ownership, Patents & Royalties; Harvard University: Patents & Royalties. Hyzy:Magenta Therapeutics: Employment, Equity Ownership. Proctor:Magenta Therapeutics: Employment, Equity Ownership. Adams:Magenta Therapeutics: Employment, Equity Ownership. Pearse:Magenta Therapeutics: Employment, Equity Ownership, Patents & Royalties. Sarma:Magenta Therapeutics: Employment, Equity Ownership. Aslanian:Magenta Therapeutics: Employment, Equity Ownership. Gillard:Magenta Therapeutics: Employment, Equity Ownership. Lamothe:Magenta Therapeutics: Employment, Equity Ownership. Burenkova:Magenta Therapeutics: Employment, Equity Ownership. Brooks:Magenta Therapeutics: Employment, Equity Ownership. Gabros:Magenta Therapeutics: Employment, Equity Ownership. McDonagh:Magenta Therapeutics: Employment, Equity Ownership, Patents & Royalties. Boitano:Magenta Therapeutics: Employment, Equity Ownership, Patents & Royalties. Cooke:Magenta Therapeutics: Employment, Equity Ownership, Patents & Royalties.

Beschreibung: CD19-specific chimeric antigen receptor (CAR) T cell therapies have been highly effective against B cell malignancies. We previously demonstrated that differential responses to anti-CD19 CAR T cell therapy in chronic lymphocytic leukemia (CLL) are associated with early memory T cell signature in apheresed, pre-manufacturing T-cells (CAR T-cell precursors). We tested the hypothesis that the composition of CAR-T precursor cells determines clinical efficacy in adult and pediatric Acute Lymphoblastic Leukemia (ALL), Non-Hodgkin's Lymphoma (NHL), Multiple Myeloma (MM), and CLL. Apheresed T cells were engineered to express 4-1BB plus CD3-zeta-signaling CARs targeting CD19, or B cell maturation antigen (BCMA). The same 9-day manufacturing process was used for all trials. CAR T cell kinetics were monitored using a CAR gene-specific quantitative PCR assay and standard clinical response assessments were performed. Apheresed T cells from 36 CLL, 30 adult ALL, 58 pediatric ALL, 33 NHL, and 25 MM patients were immunophenotyped by flow cytometry. The CLL cohort was used to discover phenotypically distinct subpopulations associated with the two main response groups; these associations were validated in the remaining patient cohorts. Eight CD8+ T cell populations or clusters were identified using the shared-nearest-neighbor clustering method (PMID: 31178118) in the CLL cohort. T cell subsets exhibiting naive (cluster 6) or early memory (cluster 4) features were significantly enriched in responding patients, whereas an effector memory CD8 subpopulation (cluster 2) marked the non-responding patients. Mapping these clusters onto apheresed CD8+ T cells from the other four diseases showed that cluster 4 predicted response to CAR T cell therapy in NHL and myeloma but not in adult and pediatric ALL. We also examined the expression of activation-regulated molecules including HLA-DR, Ki67, and exhaustion-related molecules PD1, CTLA4, TIM3, and LAG3. A CD27+ CD8+ population expressing low level CTLA4 but none of the activation or negative regulatory molecules was significantly enriched in responding CLL patients; this cluster validated in NHL and myeloma. A similar analysis on apheresed CD4+ T cells identified an early memory population (cluster 6) enriched in CLL responders, which expresses CCR7 and CD27 but not CD45RO, CD127, CD28, or other late memory/effector molecules. However, this population did not validate in any of the other diseases. Though not statistically significant, the CD4+ clusters with the largest effect size for enrichment in responders from NHL and myeloma trials exhibited early memory T cell features and lack of HLA-DR expression, suggesting that quiescent early memory state in CD4 may also be associated with clinical responses. A separate analysis of checkpoint inhibitory receptors and activation markers in memory CD4 T cell subsets confirmed the early memory, non-activated state of this population in CLL and was validated in myeloma but none of the other diseases. In vivo activation was a shared theme in CD4+ T cells for non-responding patients as well, though these CLL-defined CD4+ apheresed T cells clusters did not significantly validate in other diseases. In summary, our data confirm and extend our predictive biomarker profile in CLL to mature B cell and plasma cell malignancies by showing that a non-cycling, non-activated early memory CD8+ T cell population in pre-manufacturing cells was validated as a biomarker in myeloma, and NHL. We also showed that responder-associated apheresed CD4+ T cells with early memory features identified in CLL after CD19 CAR T infusions are validated in myeloma after BCMA CAR T. Thus, differentiation state and in vivo activation, and potentially exhaustion, separate response groups. Our findings inform next-generation CAR T-cell manufacturing using the populations identified herein as a starting population. Disclosures Pruteanu: Novartis: Employment. Cohen:Poseida Therapeutics, Inc.: Research Funding. Garfall:Surface Oncology: Consultancy; Novartis: Research Funding; Janssen: Research Funding; Amgen: Research Funding; Tmunity: Research Funding. Milone:Novartis: Patents & Royalties: patents related to tisagenlecleucel (CTL019) and CART-BCMA; Novartis: Research Funding. Gill:Novartis: Research Funding; Tmunity: Research Funding; Carisma: Equity Ownership, Research Funding; Sensei: Consultancy; Aro: Consultancy; Fate: Consultancy. Frey:Novartis: Research Funding. Ruella:Nanostring: Consultancy, Speakers Bureau; Novartis: Patents & Royalties: CART for cancer; AbClon: Membership on an entity's Board of Directors or advisory committees. Lacey:Novartis: Patents & Royalties: Patents related to CAR T cell biomarkers; Tmunity: Research Funding; Novartis: Research Funding. Svoboda:Merck: Research Funding; BMS: Consultancy, Research Funding; Incyte: Research Funding; Pharmacyclics: Consultancy, Research Funding; Celgene: Research Funding; Kite: Consultancy; Seattle Genetics: Consultancy, Research Funding; Kyowa: Consultancy; AstraZeneca: Consultancy. Chong:Tessa: Consultancy; Novartis: Consultancy; Merck: Research Funding. Fraietta:LEK Consulting: Consultancy; Cabaletta: Research Funding; Tmunity: Research Funding. Davis:Cabaletta: Research Funding; Tmunity: Research Funding. Nasta:Rafael: Research Funding; Aileron: Research Funding; Takeda/Millennium: Research Funding; Incyte: Research Funding; Roche/Genentech: Research Funding; Merck: Consultancy; Atara: Research Funding; Debiopharm: Research Funding. Levine:CRC Oncology: Consultancy; Vycellix: Membership on an entity's Board of Directors or advisory committees; Tmunity Therapeutics: Equity Ownership; Novartis: Consultancy, Patents & Royalties, Research Funding; Cure Genetics: Consultancy; Avectas: Membership on an entity's Board of Directors or advisory committees; Brammer Bio: Membership on an entity's Board of Directors or advisory committees; Incysus: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy. Maude:Kite: Consultancy; Novartis: Consultancy. Schuster:Nordic Nanovector: Honoraria; Pfizer: Honoraria; AstraZeneca: Honoraria; Pharmacyclics: Honoraria, Research Funding; Genentech: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Loxo Oncology: Honoraria; Merck: Honoraria, Research Funding; Acerta: Honoraria, Research Funding; Novartis: Honoraria, Patents & Royalties: Combination Therapies of CAR and PD-1 Inhibitors with royalties paid to Novartis, Research Funding; AbbVie: Honoraria, Research Funding; Gilead: Honoraria, Research Funding. Stadtmauer:Celgene: Consultancy; Tmunity: Research Funding; Novartis: Consultancy, Research Funding; Takeda: Consultancy; Janssen: Consultancy; Amgen: Consultancy; Abbvie: Research Funding. Grupp:Novartis: Consultancy, Research Funding; Roche: Consultancy; GSK: Consultancy; Cure Genetics: Consultancy; Humanigen: Consultancy; CBMG: Consultancy; Novartis: Research Funding; Kite: Research Funding; Servier: Research Funding; Jazz: Other: study steering committees or scientific advisory boards; Adaptimmune: Other: study steering committees or scientific advisory boards. Porter:Incyte: Membership on an entity's Board of Directors or advisory committees; American Board of Internal Medicine: Membership on an entity's Board of Directors or advisory committees; Kite: Membership on an entity's Board of Directors or advisory committees; Glenmark Pharm: Membership on an entity's Board of Directors or advisory committees; Immunovative: Membership on an entity's Board of Directors or advisory committees; Genentech: Employment; Wiley and Sons: Honoraria; Novartis: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding. June:Novartis: Research Funding; Tmunity: Other: scientific founder, for which he has founders stock but no income, Patents & Royalties. Melenhorst:Novartis: Research Funding, Speakers Bureau; Parker Institute for Cancer Immunotherapy: Research Funding; Stand Up to Cancer: Research Funding; Incyte: Research Funding; IASO Biotherapeutics, Co: Consultancy; Simcere of America, Inc: Consultancy; Shanghai Unicar Therapy, Co: Consultancy; Colorado Clinical and Translational Sciences Institute: Membership on an entity's Board of Directors or advisory committees; Genentech: Speakers Bureau; National Institutes of Health: Research Funding.