Small Molecule Inhibition of PDE6D-RAS Interaction Suppresses the Growth of Acute Lymphoblastic Leukemia Cell Lines

Abstract The activation of RAS signaling has been shown to act as the driver of both de novo and relapsed, chemotherapy resistant acute lymphoblastic leukemia (ALL). Full RAS transformation requires the activity of the small RAS-related C3 botulinum toxin substrate (RAC) protein family, including the hematopoietic-specific RAC2 GTPase and we have previously demonstrated the role of RAC in specific leukemia types. Even though relapsed ALL patients have a 34% overall prevalence of RAS-activating mutations, KRASG12C mutations were not present, suggesting that the only RAS inhibitor currently available (G12C-specific) would not be effective in treating these patients. Phosphodiester 6 subunit delta (PDE6D), initially identified as a subunit of rod-specific photoreceptor phosphodiesterase, is now also known as a transporter of prenylated cargo. In fact, PDE6D has been shown to modulate the activity of RAS family proteins by regulating their subcellular location. When active, RAS proteins migrate to the cell membrane where they interact with a number of effectors triggering pro-survival downstream pathways including the mitogen-activated protein kinase / extracellular signaling-regulated kinase (MAPK/ERK) and the phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT). MAPK/ERK and PI3K/AKT pathways in particular are believed to synergize to induce survival and cellular transformation. We carried out a biological screen of small molecular compounds that assessed the inhibition of RAS-mutated ALL cell lines' proliferation through MTT assays, inhibition of RAC activation and the absence of inhibition of normal hematopoietic progenitor growth in colony forming unit (CFU) assays. Lead compounds were further evaluated for their lipophilicity, solubility and potency of biological activity. Here we report the identification of DW0254 which demonstrates arrest of proliferation and induction of apoptosis in RAS-mutant human B- and T-ALL cell lines. We have identified PDE6D as the putative target of this compound through photoaffinity labeling mass spectroscopy (PAL-MS). The cocrystal structure of DW0254 with recombinant PDE6D demonstrated that this small molecule fits inside the hydrophobic pocket and forms hydrogen bond interactions with residues Q88, Y149 and R61. From a molecular perspective, the occupation of the pocket by DW0254 leads to decreased interaction between PDE6D and farnesylated RAS. This impairment of PDE6D's ability to transport RAS leads to the delocalization of both mutant-NRAS and -KRAS4B proteins from the cell membrane to the cytosol, confirmed by real-time fluorescent imaging of recombinant GFP-RAS proteins. Ultimately, RAS delocalization upon DW0254 binding to PDE6D leads to decreased activation of both MAPK/ERK and PI3K/AKT pathways, and potent inhibition of RAC GTPases. CRISPR Cas9 saturating mutagenesis experiments confirmed that mutations in the farnesyl binding pocket leads to compound resistance, giving direct evidence that leukemia growth arrest is caused by molecule binding to PDE6D. Cells that showed increased IC 50 to DW0254 after mutagenesis did not exhibit resistance to Deltarasin, a previously described PDE6D inhibitor. DW0254 anti-leukemic activity was confirmed in an ex vivo murine xenograft model using short-term treated human NRAS-mutated ALL cell line P12-ICHIKAWA. After transplant, DW0254 treated cells showed impaired tumorigenic and engraftment potential when compared to vehicle controls. In conclusion, we have identified DW0254, a PDE6D inhibitor that has anti-leukemic activity in RAS-mutated ALL cell lines. We have successfully co-crystalized this compound with PDE6D showing binding to its farnesyl binding pocket and confirmed that the mechanisms of action of this inhibitor involve the loss of membrane localization of RAS and consequent inhibition of signaling to its downstream effectors. Pocket mutations validate the hypothesis that the effects observed derive from the binding of DW0254 to PDE6D and not from off-target effects. Ex vivo experiments show promising anti-leukemic effects and set the basis for future compound optimization. Disclosures De Vita: Novartis: Current Employment. Anighoro: Relation Therapeutics: Current Employment; Evotec SAS: Ended employment in the past 24 months. Autelitano: Evotec SAS: Current Employment. Beaumont: Evotec SAS: Current Employment. Klingbeil: Evotec SAS: Current Employment. Ermann: Evotec SAS: Ended employment in the past 24 months. Williams: BioMarin: Membership on an entity's Board of Directors or advisory committees, Other: Insertion Site Advisory Board; Geneception: Membership on an entity's Board of Directors or advisory committees, Other: Scientific Advisory Board; Emerging Therapy Solutions: Membership on an entity's Board of Directors or advisory committees, Other: Chief Scientific Chair; Beam Therapeutics: Membership on an entity's Board of Directors or advisory committees, Other: Scientific Advisory Board; Alerion Biosciences: Other: Co-founder (now licensed to Avro Bio, potential for future milestones/royalties); Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Steering Committee, Novartis ETB115E2201 (eltrombopag in aplastic anemia). Advisory fees donated to NAPAAC.; Orchard Therapeutics: Membership on an entity's Board of Directors or advisory committees, Other: Membership on a safety advisory board (SAB): SAB position ended 05/20/2021. Co-founder , Patents & Royalties: Potential for future royalty/milestone income, X-SCID. Provided GMP vector for clinical trial, Research Funding; bluebird bio: Membership on an entity's Board of Directors or advisory committees, Other: Insertion Site Analysis Advisory Board, Patents & Royalties: BCH licensed certain IP relevant to hemoglobinopathies to bluebird bio. The current license includes the potential for future royalty/milestone income. Bluebird has indicated they will not pursue this as a clinical program and BCH is negotiating return of, Research Funding.

Download Full-text

Simultaneous Kinase Inhibition with Ibrutinib and BCL2 Inhibition with Venetoclax As a Therapeutic Strategy for Acute Lymphoblastic Leukemia

Blood ◽

10.1182/blood-2019-131288 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 3950-3950

Author(s):

Christopher A. Eide ◽

Stephen E Kurtz ◽

Andy Kaempf ◽

Nicola Long ◽

Jessica Leonard ◽

...

Keyword(s):

Clinical Trial ◽

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Mononuclear Cells ◽

Ex Vivo ◽

Lymphoblastic Leukemia ◽

Single Agent ◽

Advisory Committees ◽

Equity Ownership

Background: In patients with acute lymphoblastic leukemia (ALL), patient outcomes vary considerably by patient age group, specific genetic subtypes, and treatment regimen. Large-scale sequencing efforts have uncovered a spectrum of mutations and gene fusions in ALL, suggesting that combinations of agents will be required to treat these diseases effectively. Previous preclinical studies have shown efficacy of the BCL2 inhibitor venetoclax alone or in combination in ALL cells (Chonghaile et al., Can Disc 2014; Leonard et al, STM 2018), and the multi-kinase inhibitor ibrutinib (approved for patients with chonic lymphoblastic leukemia (CLL)) has also shown potent activity in subsets of ALL (Kim et al., Blood 2017). However, the combination of ibrutinib and venetoclax has not been evaluated to date in patients with ALL. Methods: We used a functional ex vivo screening assay to evaluate the potential efficacy of the combination of ibrutinib and venetoclax (IBR+VEN) across a large cohort (n=808) of patient specimens representing a broad range of hematologic malignancies. Primary mononuclear cells isolated from leukemia patients were plated in the presence of graded concentrations of venetoclax, ibrutinib, or the combination of both FDA-approved drugs. IC50 and AUC values were derived from probit-based regression for each response curve. A panel of clinical labs, treatment information, and genetic features for tested ALL patient specimens was collated from chart review. Single and combination drug treatment sensitivity were compared within groups by Friedman test, across groups by Mann-Whitney test, and with continuous variables by Spearman rank correlation. Results: Consistent with clinical data and previous literature, IBR+VEN was highly effective in CLL specimens ex vivo (median IC50=0.015 µM). Intriguingly, among specimens from 100 unique ALL patients, we also observed that IBR+VEN demonstrated significantly enhanced efficacy by AUC and IC50 compared to either single agent (p<0.001; median IC50=0.018 µM). In contrast, evaluation of this combination on primary mononuclear cells from two healthy donors showed little to no sensitivity. Breakdown of combination sensitivity (as measured by AUC) by a variety of clinical and genetic features revealed no associations with gender or specimen type. Among continuous variables tested, age was modestly correlated with combination AUC (Spearman r = 0.26) and increased blasts in the bone marrow were associated with increased sensitivity to the combination (Spearman r = -0.41; p = 0.0068). More broadly, specimens from patients with B-cell precursor disease (B-ALL) were more sensitive to IBR+VEN than those with T-cell precursor leukemia (T-ALL) (p = 0.0063). Within the B-ALL patient samples, those harboring the BCR-ABL1 fusion were significantly less sensitive to IBR+VEN than other subtypes of B-ALL (p = 0.0031). Within the T-ALL subset, there was a trend toward reduced sensitivity in patients with evidence of mutations in NOTCH1, though statistical significance was not reached. Evaluation of the combination using an expanded 7x7 concentration matrix in human ALL cell lines revealed varying degrees of sensitivity. For example, IBR+VEN showed enhanced efficacy in RCH-ACV B-ALL cells and showed synergy for the majority of drug-pair concentrations by the highest single agent (HSA) method (ibrutinib, venetoclax, and combination IC50: 0.60, 3.4, and 0.28 uM, respectively). Conclusion: Our findings suggest that the IBR+VEN combination, currently approved for patients with CLL, also demonstrates impressive efficacy against primary leukemia cells from ALL patients, warranting further investigation as a treatment strategy in the clinic to continue to improve outcomes for patients. Disclosures Leonard: Amgen: Research Funding. Druker:Cepheid: Consultancy, Honoraria; Pfizer: Other: PI or co-investigator on clinical trial(s) funded via contract with OHSU., Research Funding; Merck & Co: Patents & Royalties: Dana-Farber Cancer Institute license #2063, Monoclonal antiphosphotyrosine antibody 4G10, exclusive commercial license to Merck & Co; Dana-Farber Cancer Institute (antibody royalty): Patents & Royalties: #2524, antibody royalty; OHSU (licensing fees): Patents & Royalties: #2573, Constructs and cell lines harboring various mutations in TNK2 and PTPN11, licensing fees ; Gilead Sciences: Other: former member of Scientific Advisory Board; Beta Cat: Membership on an entity's Board of Directors or advisory committees, Other: Stock options; Aptose Biosciences: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Amgen: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; ALLCRON: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Patents & Royalties, Research Funding; Pfizer: Research Funding; Aileron Therapeutics: #2573, Constructs and cell lines harboring various mutations in TNK2 and PTPN11, licensing fees , Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Other: PI or co-investigator on clinical trial(s) funded via contract with OHSU., Research Funding; Novartis: Other: PI or co-investigator on clinical trial(s) funded via contract with OHSU., Patents & Royalties: Patent 6958335, Treatment of Gastrointestinal Stromal Tumors, exclusively licensed to Novartis, Research Funding; GRAIL: Equity Ownership, Other: former member of Scientific Advisory Board; Patient True Talk: Consultancy; The RUNX1 Research Program: Membership on an entity's Board of Directors or advisory committees; Vivid Biosciences: Membership on an entity's Board of Directors or advisory committees, Other: Stock options; Beat AML LLC: Other: Service on joint steering committee; CureOne: Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy; ICON: Other: Scientific Founder of Molecular MD, which was acquired by ICON in Feb. 2019; Monojul: Other: former consultant; Blueprint Medicines: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Burroughs Wellcome Fund: Membership on an entity's Board of Directors or advisory committees. Tyner:Petra: Research Funding; Agios: Research Funding; Array: Research Funding; Gilead: Research Funding; Genentech: Research Funding; Janssen: Research Funding; Syros: Research Funding; Takeda: Research Funding; Seattle Genetics: Research Funding; AstraZeneca: Research Funding; Seattle Genetics: Research Funding; Array: Research Funding; Aptose: Research Funding; Incyte: Research Funding; Syros: Research Funding; Takeda: Research Funding; Petra: Research Funding; Agios: Research Funding; Constellation: Research Funding; Aptose: Research Funding; Gilead: Research Funding; Incyte: Research Funding; AstraZeneca: Research Funding; Constellation: Research Funding; Janssen: Research Funding; Genentech: Research Funding.

Download Full-text

Mapping the Glucocorticoid Gene Regulatory Network and Alterations That Contribute to Steroid Resistance in Childhood Acute Lymphoblastic Leukemia

Blood ◽

10.1182/blood-2021-153002 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 674-674

Author(s):

Brennan P. Bergeron ◽

Jonathan Diedrich ◽

Yang Zhang ◽

Qian Dong ◽

Daniel Ferguson ◽

...

Keyword(s):

Board Of Directors ◽

Cell Lines ◽

Regulatory Network ◽

Ex Vivo ◽

Lymphoblastic Leukemia ◽

Regulatory Elements ◽

Steroid Resistance ◽

Advisory Committees ◽

Gene Regulatory ◽

Accessible Chromatin

Abstract Acute lymphoblastic leukemia (ALL) is the most prevalent childhood cancer and despite improved survival rates, relapsed ALL is still among the most common causes of cancer death in children. Although changes in the expression of specific genes have been linked to chemotherapeutic resistance, relatively little is understood of the pharmacogenomic impact of the noncoding, cis-regulatory landscape governing gene regulation. Glucocorticoids (GCs; i.e. steroids) are a mainstay of contemporary, multi-drug chemotherapy in ALL, and GC resistance is predictive of both relapse and poor clinical outcome in ALL. Because GCs function through activation of glucocorticoid receptor (GR), a nuclear receptor transcription factor that interacts directly with cis-regulatory elements, unveiling the glucocorticoid gene regulatory network (GC-GRN) in leukemia cells is crucial to understanding not only the biological mechanism of apoptosis, but also illuminating gene regulatory mechanisms contributing to GC resistance. To test the hypothesis that alterations to the GC-GRN are important contributors to steroid resistance in ALL, we comprehensively mapped cellular responses to GCs in human ALL cell lines using >100 independent functional genomic datasets. This comprehensive approach uncovered thousands of genes and cis-regulatory elements that were responsive to GCs, and further identified >38,000 high-confidence glucocorticoid response elements (GREs) in the ALL genome. A closer examination of these data revealed GR binding profiles that were consistent with the long-range flexible billboard model of gene regulation. By further integrating our results with genetic and epigenetic data in primary ALL cells from patients enrolled on St. Jude clinical trials, we identified 45 DNA sequence variants associated with ex vivo GC resistance that map to GREs and functionally validated an associated variant within the TLE1 gene locus. We also uncovered 1929 accessible chromatin sites (FDR<0.1) in primary ALL cells that were associated with ex vivo GC resistance, and these GC-resistance accessible chromatin sites were highly enriched at GREs determined from ALL cell lines (p<2.2x10 -16). High-throughput pharmacogenomic CRISPRi screening in human ALL cell lines with a library of >10,000 sgRNAs targeting >1000 GR binding events at putative GC-resistance accessible chromatin sites identified a subset of GR binding sites implicated in GC resistance. Overall, these data indicate that GCs initiate pervasive, genome-wide effects on the leukemia epigenome and transcriptome, and that genetic and epigenetic alterations to GREs are mechanisms contributing to GC resistance in childhood ALL. Disclosures Pui: Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Novartis: Other: Data Monitoring Committee. Evans: Princess Máxima Center for Pediatric Oncology, Scientific Advisory Board, Chair: Membership on an entity's Board of Directors or advisory committees; BioSkryb, Inc.: Membership on an entity's Board of Directors or advisory committees; St. Jude Children's Research Hospital, Emeritus Member (began Jan 2021): Ended employment in the past 24 months.

Download Full-text

Clonal Tracking By Whole Genome Sequencing Permits Comprehensive Mapping of the Genomic Landscape in Pre- and Post-Gene Therapy Sickle Cell Patients

Blood ◽

10.1182/blood-2021-152262 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 559-559

Author(s):

Alyssa H. Cull ◽

Michael Spencer Chapman ◽

Marioara Ciuculescu ◽

Emily Mitchell ◽

Myriam Armant ◽

...

Keyword(s):

Gene Therapy ◽

Stem Cell ◽

Board Of Directors ◽

Sickle Cell ◽

Research Funding ◽

Phylogenetic Trees ◽

Insertion Site ◽

Advisory Board ◽

Advisory Committees ◽

Genomic Landscape

Abstract Recent advances in clonal stem cell tracking strategies have enabled interrogation of unperturbed human hematopoiesis. Whole genome sequencing (WGS) can be used to map the clonal dynamics of hematopoietic stem and progenitor cells (HSPCs) by employing spontaneous somatic mutations as unique clonal tags (Lee-Six et al., Nature, 2018). These tags allow for retrospective analysis of individual stem cell clones and the construction of phylogenetic trees mapping out stem cell relatedness, with mutations being acquired in a near-linear fashion over the course of an individual's life. The unprecedented level of information obtained in these studies is particularly well-suited to understanding genomic changes in gene therapy trials aimed at curing diseases such as sickle cell disease (SCD). In addition to mapping relatedness between stem cells, sequencing data can be used to better define mutational signatures for HSPC clones that have been successfully gene-modified as well as those that lack an integrated copy of the therapeutic vector. Given this method's ability to identify low frequency mutations in individual HSPC clones, mutations with extremely low variant allele frequencies can be detected much more readily than through traditional bulk sequencing approaches, something that is particularly relevant given recent safety concerns in some SCD gene therapy trials. In this study, we have mapped the clonal dynamics of HSPCs obtained from pre- and post-gene therapy samples from 4 SCD patients who have undergone autologous gene therapy performed using a BCL11A shmiR lentivirus vector (NCT 03282656, 12-36 months follow-up). HSPCs from mobilized peripheral blood (pre-gene therapy), bone marrow aspirates (both pre- and post-gene therapy) or unmobilized peripheral blood (post-gene therapy) were expanded as single clones and 1508 individual colonies were then sequenced using WGS to an average sequencing depth of 12.3x. Initial results indicate that the mean mutation burden per cell in a pre-gene therapy sample is elevated for some patients compared to what would be expected based on patient age in similar studies. In pre-gene therapy samples, the structure of the phylogenetic trees appeared to be highly polyclonal, indicating that there were no significant clonal expansion events prior to gene therapy. In one patient where we undertook extensive profiling, approximately 15-20 excess mutations per HSPC were observed across the entire genome 24 months after transplantation, presumably acquired as a consequence of gene therapy and/or reconstitution post-transplantation, which is equivalent to approximately one year of normal ageing without a transplantation intervention. However, no clonal expansions or driver mutations were identified at this 24 month follow-up timepoint, suggesting that no strong selective advantage or pre-leukemic events were present prior to or following the gene therapy protocol. Extending this approach to a wider range and larger number of patients will allow for comprehensive mapping of the genomic landscape and clonal evolution of stem cells in sickle cell patients and will also set the stage for improved assessment of safety and potential leukemia-initiating events in the context of gene therapy. Disclosures Esrick: bluebird bio: Consultancy. Williams: bluebird bio: Membership on an entity's Board of Directors or advisory committees, Other: Insertion Site Analysis Advisory Board, Patents & Royalties: BCH licensed certain IP relevant to hemoglobinopathies to bluebird bio. The current license includes the potential for future royalty/milestone income. Bluebird has indicated they will not pursue this as a clinical program and BCH is negotiating return of, Research Funding; BioMarin: Membership on an entity's Board of Directors or advisory committees, Other: Insertion Site Advisory Board; Beam Therapeutics: Membership on an entity's Board of Directors or advisory committees, Other: Scientific Advisory Board; Emerging Therapy Solutions: Membership on an entity's Board of Directors or advisory committees, Other: Chief Scientific Chair; Geneception: Membership on an entity's Board of Directors or advisory committees, Other: Scientific Advisory Board; Alerion Biosciences: Other: Co-founder (now licensed to Avro Bio, potential for future milestones/royalties); Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Steering Committee, Novartis ETB115E2201 (eltrombopag in aplastic anemia). Advisory fees donated to NAPAAC.; Orchard Therapeutics: Membership on an entity's Board of Directors or advisory committees, Other: Membership on a safety advisory board (SAB): SAB position ended 05/20/2021. Co-founder , Patents & Royalties: Potential for future royalty/milestone income, X-SCID. Provided GMP vector for clinical trial, Research Funding. Campbell: Mu Genomics: Current holder of individual stocks in a privately-held company, Membership on an entity's Board of Directors or advisory committees. Kent: STRM.bio: Research Funding.

Download Full-text

A Novel Small Molecule Inhibitor Of Deubiquitylating Enzyme USP14 and UCHL5 Induces Apoptosis In Myeloma Cells and Overcomes Bortezomib Resistance

Blood ◽

10.1182/blood.v122.21.1923.1923 ◽

2013 ◽

Vol 122 (21) ◽

pp. 1923-1923 ◽

Cited By ~ 1

Author(s):

Ze Tian ◽

Padraig D'Arcy ◽

Xin Wang ◽

Arghya Ray ◽

Yu-Tzu Tai ◽

...

Keyword(s):

Cell Viability ◽

Er Stress ◽

Board Of Directors ◽

Cell Lines ◽

Mammalian Cells ◽

Ubiquitin Ligases ◽

Advisory Board ◽

In Vivo Studies ◽

Advisory Committees ◽

Inhibition Of Proliferation

Abstract Introduction Proteasome inhibitors have demonstrated that targeting ubiquitin proteasome pathway (UPS) is an effective therapy in multiple myeloma (MM). More recent studies have focused on targeting enzymes modulating protein ubiquitin conjugation/deconjugation upstream of the proteasome rather than the proteasome itself, with the goal of producing more specific, potent, and less toxic therapies targeting UPS. Ubiquitylation is a dynamic reversible process coordinated by many enzymes: ubiquitin ligases attach ubiquitin to proteins allowing for their degradation, whereas deubiquitylating enzymes (DUBs) deconjugate ubiquitin from target proteins, thereby preventing their proteasome-mediated degradation. Importantly, many human diseases are linked to dysfunction of ubiquitin ligases and/or DUBs, suggesting that inhibitors of ubiquitylating or DUBs represent a potential therapeutic strategy.In mammalian cells, three DUBs are associated with the proteasome: USP14, UCHL5/Uch37, and Rpn11. In the present study, we examined the expression of USP14 and UCHL5 in MM by western blot and Immunohistochemistry (IHC). Results Our results show that DUBs USP14 and UCHL5 are more highly expressed in primary MM patient tumor cells and MM cell lines than in normal plasma cells and peripheral blood mononuclear cells (PBMCs). Additionally, USP14 and UCHL5 siRNA knockdown significantly decrease MM cell viability (p < 0.001) in a CellTiter Glo assay. A novel 19S regulatory particle inhibitor b-AP15 selectively blocks deubiquitylating activity of USP14 and UCHL5 without inhibiting activity of other DUBs, proteases and proteasome; Importantly, b-AP15 decreases cell viability in MM cell lines as well as patient MM cells, without markedly affecting PBMCs from normal healthy donors. Moreover, b-AP15 inhibits proliferation of MM cells even in the presence of bone marrow stroma cells and overcomes bortezomib-resistance. Mechanistic studies show that b-AP15 triggers MM cell arrest via downregulation of CDC25C, CDC2 and cyclinB1, followed by caspase-dependent apoptosis through activation of intrinsic and extrinsic apoptotic pathways. b-AP15, like bortezomib, induces ER stress evidenced by the upregulation of ER stress-related proteins p-IRE-alpha, and p-eIF2. In vivo studies using subcutaneous and disseminated human MM xenograft models show that b-AP15 is well tolerated, inhibits tumor growth, and prolongs survival (p < 0.001). In concert with our in vitro study, IHC analysis of tumor tissues showed inhibition of proliferation, induction of apoptosis, and accumulation of ubiquitinated proteins, assessed by staining with ki67, caspase-3, and UB-k48 antibodies, respectively. Finally, combining b-AP15 with SAHA, lenalidomide, or dexamethasone induces synergistic anti-MM activity. Conclusion Our preclinical data showing efficacy of b-AP15 in MM disease models validates targeting DUBs upstream of the proteasome in the ubiquitin proteasomal cascade to overcome proteasome inhibitor resistance, and provides the framework for clinical evaluation of USP14/UCHL5 inhibitors to improve patient outcome in MM. Disclosures: Tai: Onyx: Consultancy. Richardson:Celgen, Inc., Millenium: Membership on an entity’s Board of Directors or advisory committees. Chauhan:Vivolux: Consultancy. Anderson:Oncoprep: Scientific founder:, Scientific founder: Other; Acetylon: Scientific founder, Scientific founder Other; Sonofi Aventis: Advisory board, Advisory board Other; Gilead: Advisory board, Advisory board Other; Onyx: Advisory board, Advisory board Other; Celgene : Membership on an entity’s Board of Directors or advisory committees.

Download Full-text

Lin28B/Let-7 Axis Regulates Multiple Myeloma Proliferation By Enhancing c-Myc and Ras Survival Pathways

Blood ◽

10.1182/blood.v122.21.273.273 ◽

2013 ◽

Vol 122 (21) ◽

pp. 273-273

Author(s):

Salomon Manier ◽

John T Powers ◽

Antonio Sacco ◽

Michaela R Reagan ◽

Michele Moschetta ◽

...

Keyword(s):

Multiple Myeloma ◽

Cell Proliferation ◽

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Advisory Board ◽

Loss Of Function ◽

Advisory Committees ◽

Expression Levels ◽

Gain And Loss

Abstract Background MicroRNAs (miRNAs) play a pivotal role in tumorigenesis, due to their ability to target mRNAs involved in the regulation of cell proliferation, survival and differentiation. Lin28B is an RNA binding protein that regulates Let-7 miRNA maturation. Lin28B and Let-7 have been described to act as oncogenes or tumor suppressor genes, respectively, as demonstrated both in solid cancer and hematologic malignancies. However, the role of the Lin28B/Let-7 axis in Multiple Myeloma (MM) has not been studied. Method Lin28B level expression in MM patients was studied using previously published gene expression profiling (GEP) datasets. Let-7 expression levels were assessed in CD138+ primary MM cells and bone marrow stromal cells (BMSCs) by using PCR, as well as in circulating exosomes using miRNA array (Nanostring® Technology). Exosomes were collected from both normal and MM peripheral blood, using ultracentrifugation; and further studied by using electron microscopy and immunogold labeling for the detection of CD63 and CD81. The knockdown of Lin28B was performed on MM cell lines (U266, MM.1S, MOLP-8) by using a lentiviral Lin28B shRNA. Gain- and loss-of function studies for Let-7 were performed using Let-7 mimic and anti-Let-7 transfection in MM cell lines (MM1S, U266) and primary BMSCs. Cell proliferation has been evaluated by using thymidine assays. Effects of Let-7 and Lin28B on signaling cascades have been evaluated by western blot. Results Two independent GEP datasets (GSE16558; GSE2658) were analyzed for Lin28B expression, showing a significantly higher level in MM patients compared to healthy controls. In addition, high Lin28B levels correlated with a shorter overall survival (p = 0.0226). We next found that the Let-7 family members are significantly down-regulated in MM primary cells, particularly Let-7a and b (5 fold change, p < 0.05), as demonstrated by using qRT-PCR. Similarly, miRNA arrays showed a lower expression of Let-7-related miRNAs in circulating exosomes obtained from MM patients compared to healthy individuals. We further dissected the functional relevance of Lin28B in MM cells, by performing Lin28 knockdown (KD) in MM cell lines (U266, MOLP-8). This led to a significant decrease in MM cell proliferation associated with G1 phase cell cycle arrest. This was supported by up-regulation of Let-7 and down-regulation of c-Myc, Ras and Cyclin D1 in Lin28 KD MM cells. To further prove that Lin28B-dependent effects on MM cells are mediated by Let7, we next showed that let-7 gain- and loss-of-function studies regulate MM cell proliferation and Myc expression. Lin28B regulation in MM cells is dependent on Let-7, as demonstrated by an increase of both cell proliferation and c-Myc expression after anti-Let-7 transfection in the Lin28B KD cells. We therefore studied the regulation of Let-7 in MM cells through the interaction with BMSCs. Let-7 expression levels were significantly lower in BMSCs obtained from MM patients compared to healthy donors. Interestingly, the Let-7 expression level in MM cells was increased after co-culture with Let-7 over-expressing BMSCs, associated with a decrease of both cell proliferation and c-Myc expression. This suggests a potential transfer of Let-7 from BMSCs to MM cells. Conclusion This work describes a new signaling pathway involving Lin28B, Let-7, Myc and Ras in MM. Let-7 expression in MM cells is also regulated through the interaction of MM cells with BMSCs, leading to cell proliferation and Myc regulation in MM. Interference with this pathway might offer therapeutic perspectives. Disclosures: Leleu: CELGENE: Honoraria; JANSSEN: Honoraria. Daley:Johnson and Johnson: Consultancy, Membership on an entity’s Board of Directors or advisory committees; MPM Capital: Consultancy, Membership on an entity’s Board of Directors or advisory committees; Verastem: Consultancy, Membership on an entity’s Board of Directors or advisory committees; Epizyme: Consultancy, Membership on an entity’s Board of Directors or advisory committees; iPierian: Consultancy, Membership on an entity’s Board of Directors or advisory committees; Solasia, KK: Consultancy, Membership on an entity’s Board of Directors or advisory committees. Ghobrial:Onyx: Advisoryboard Other; BMS: Advisory board, Advisory board Other, Research Funding; Noxxon: Research Funding; Sanofi: Research Funding.

Download Full-text

Identification of Target Pathways Induced By the Multiple Myeloma Tumor Microenvironment Using Activity-Based Protein Profiling and Ex Vivo Protein Kinase Inhibitor Screening

Blood ◽

10.1182/blood.v128.22.3288.3288 ◽

2016 ◽

Vol 128 (22) ◽

pp. 3288-3288

Author(s):

Mark B Meads ◽

Paula Oliveira ◽

Allison Distler ◽

Maria Silva ◽

Karen Burger ◽

...

Keyword(s):

Bone Marrow ◽

Protein Kinase ◽

Board Of Directors ◽

Cell Lines ◽

High Throughput ◽

Ex Vivo ◽

Bone Marrow Stroma ◽

Advisory Committees ◽

Viability Assay ◽

Marrow Stroma

Abstract Multiple myeloma (MM) is a heterogeneous plasma cell neoplasm that remains all but incurable despite recent advances in treatment. Indeed, nearly all patients eventually experience disease progression or relapse due to a reservoir of residual myeloma cells that appear to persist through pro-survival signaling from interactions with the tumor microenvironment (TME), leading to eventual clonal expansion. Thus, identifying targets that are induced in MM by the TME may reveal new and important targets amenable to therapeutic intervention. To develop a non-biased method to screen bone marrow specimens from myeloma patients for activated targets throughout the course of disease, we used a combination of activity-based protein profiling (ABPP) and a high-throughput protein kinase inhibitor (PKI) screen using a platform that recapitulates the TME. Target validation was then performed using ex vivo functional screens of pathways using MM patient specimens. The MM cell lines MM1.S, H929, and OPM2 were grown in mono-culture or co-culture with HS5 bone marrow stroma cells for 24h and lysates were enriched for ATP binding proteins by affinity purification versus a chemical probe (ActivX, Thermo). Tryptic peptides were measured using discovery proteomics (nano-UPLC and QExactive Plus mass spectrometer). Using this method, 176, 136, and 85 kinases out of a total of 1511, 1409, and 1281 proteins were preferentially enriched by 2-fold change from MM1.S, H929, and OPM2 myeloma cells grown in co-culture conditions with HS5 bone marrow stroma, respectively. Of these, 42 kinases were common to all three and 87 were common to two of three MM cell lines. Kinases were chosen for target validation after pathway analysis using the Kyoto Encyclopedia of Genes and Genomes database to identify signaling networks. To identify functionally relevant signaling networks identified via ABPP experiments, the same MM cell lines were simultaneously screened with 30 protein kinase inhibitors (PKIs) in a novel high throughput viability assay. This label-free method measures the viability of MM cells grown in a collagen matrix with bone marrow stroma cells in 384-well plates to simulate the TME by capturing brightfield images every 30 minutes for 96h using a motorized microscope equipped with an incubation chamber. Digital image analysis software measures live cell numbers by detecting membrane motion and generates viability curves as a function of drug concentration and exposure time (Khin et al. Cancer Research 2014). This functional screen confirming known MM survival networks, validated 12 kinases/PKIs in the context of the TME and highlighted novel targetable pathways. To provide an additional level of screening, the same PKIs were tested in CD138-MACS-selected cells from 15 MM patient specimens in a high-throughput viability assay. Eight PKIs targeting IGFR, PLK1, Abl, mTOR, FAK/Pyk2, ALK, Akt, and Casein Kinase-1δ (CK1δ)/CK1ε also showed significant activity in the 15 primary MM specimens. Our three-tiered pharmaco-proteomic screen identified eight kinases critical to MM survival in the context of the TME. Notably, a highly specific in-house inhibitor of Casein Kinase 1δ/CK1ε, SR-3029, which targets the Wnt/β-catnenin pathway, was identified as the most effective compound assessed as a single agent in our ex vivo viability assay in all patients with an average 36h LD50 of 290nM. This compound is under further investigation in MM (Submitted Abstract: Burger, et al, ASH 2016). Additional studies are underway to functionally interrogate the pathways identified in this screen, including ErbB1/EGFR, EphA1 and AMPK. Future work will optimize this method for evaluation of primary bone marrow specimens with ABPP followed by functional validation to better predict potential clinical response at different disease stages. We anticipate that this iterative "at the moment of care" approach is critical because drug resistant tumor phenotypes fluctuate with therapy, and this strategy can track and define clinically relevant changes in tumor cells in situ after the selection pressures applied by exposure to therapy. Disclosures Shain: Novartis: Speakers Bureau; Amgen/Onyx: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda/Millennium: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Signal Genetics: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.

Download Full-text

Pediatric-Inspired Chemotherapy Incorporating Pegaspargase Is Safe and Results in High Rates of MRD Negativity in Adults Ages 18-60 with Philadelphia Chromosome-Negative Acute Lymphoblastic Leukemia and Lymphoblastic Lymphoma

Blood ◽

10.1182/blood-2018-99-115486 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 4013-4013 ◽

Cited By ~ 2

Author(s):

Mark Blaine Geyer ◽

Ellen K. Ritchie ◽

Arati V. Rao ◽

M. Isabella Cazacu ◽

Shreya Vemuri ◽

...

Keyword(s):

Acute Lymphoblastic Leukemia ◽

Board Of Directors ◽

Research Funding ◽

Lymphoblastic Leukemia ◽

Philadelphia Chromosome ◽

Advisory Board ◽

Lymphoblastic Lymphoma ◽

Advisory Committees ◽

Grade 3

Abstract Introduction: Among adolescents and young adults with (w/) acute lymphoblastic leukemia (ALL) or lymphoblastic lymphoma (LBL), treatment using a pediatric (vs. adult) regimen appears to achieve superior event-free (EFS) and overall survival (OS); this observation has driven increased interest in adapting pediatric regimens for middle-aged adults w/ ALL/LBL. However, greater risk of toxicities associated w/ asparaginase complicates administration of pediatric-inspired regimens in adults. We therefore designed a pediatric-inspired chemotherapy regimen w/ doses of pegaspargase (PEG) rationally synchronized to limit overlapping toxicities w/ other chemotherapeutic agents. Methods: We conducted a phase II multi-center trial in adults ages 18-60 w/ newly-diagnosed Philadelphia chromosome-negative (Ph-) ALL/LBL (NCT01920737). Pts w/ Ph+ ALL or Burkitt-type ALL were ineligible. The treatment regimen consisted of 2-phase induction (I-1, I-2), followed by consolidation w/ 2 courses of alternating high-dose methotrexate-based intensification and reinduction, followed by 3 years of maintenance (Figure 1). PEG 2000 IU/m2 was administered in each of the 6 intensive courses of induction/consolidation at intervals of ≥4 weeks. Minimal residual disease (MRD) was assessed in bone marrow (BM) by multiparameter flow cytometry (FACS) on day (d) 15 of I1 and following I-1 and I-2. Any detectable MRD (even <0.01% of BM WBCs) was considered positive. Toxicities were assessed by CTCAE v4.0. Results: 39 pts were enrolled (30M, 9F), w/ B-ALL (n=28), T-ALL (n=7), B-LBL (n=3), and T-LBL (n=5). Median age at start of treatment was 38.3 years (range 20.2-60.4), w/ 18 pts age 40-60. Grade 3-4 toxicities associated w/ PEG are summarized in Table 1. Grade 3-4 hyperbilirubinemia was observed post-PEG in I-1 in 9 pts, but only recurred thereafter in 1/8 pts resuming PEG. Pts completing consolidation on protocol (n=16) received median of 6 doses of PEG (range, 2-6). Four pts developed hypersensitivity to PEG and subsequently received Erwinia asparaginase. PEG was discontinued in 4 additional pts due to hepatotoxicity (n=2), pancreatitis (n=1), and physician preference (n=1). Of pts w/ available response assessments, 35/36 (97%) achieved morphologic complete response (CR) or CR w/ incomplete hematologic recovery (CRi) following I-1 (n=34) or I-2 (n=1). Both pts not achieving CR/CRi after I-I had early T-precursor ALL; one of these pts was withdrawn from study, and the other (w/ M2 marrow after I-1) achieved CR after I-2. Of the pts w/ ALL (excluding LBL) w/ available BM MRD assessments, 11/28 (39%) achieved undetectable MRD by FACS following I-1; 18/22 (82%) achieved undetectable MRD by FACS following I-2. Of the pts w/ LBL w/ available BM MRD assessments, 7/7 (100%) achieved or maintained undetectable MRD by FACS following I-1 and I-2. Ten pts underwent allogeneic hematopoietic cell transplantation (alloHCT) in CR1. Seven pts experienced relapse at median 15.2 months from start of treatment (range, 5.4-30.4), of whom 6 subsequently underwent 1st (n=5) or 2nd (n=1) alloHCT. Of the 11 pts w/ ALL w/ undetectable MRD following I-1, only one has relapsed. Five patients have died, including 2 pts in CR1 (from sepsis and multi-organ system failure), and 3 pts in relapse. At median follow-up of 22.3 months among surviving pts (range, 1.0-48.1), median EFS and OS (Figure 2A&B) have not been reached (EFS not censored at alloHCT). 3-year EFS was 62.1% (95% CI: 38.4-78.9%) and 3-year OS was 80.0% (95% CI: 57.5-91.4%). Conclusions: PEG can be incorporated into pediatric-inspired chemotherapy regimens w/ manageable toxicity for appropriately selected adults up to age 60 w/ Ph- ALL/LBL. While PEG-related AEs are common, few pts require permanent discontinuation of asparaginase. Grade 3-4 hyperbilirubinemia was common, particularly post-I-1, but recurred infrequently when PEG was continued. Two induction courses resulted in a high rate of MRD negativity post-I-2 and translated to a low rate of relapse. Though further follow-up is required, 3-year EFS is encouraging. Data regarding asparaginase enzyme activity and silent inactivation w/ neutralizing anti-PEG antibody will be presented. Ongoing and future studies will additionally investigate whether incorporating novel therapies (e.g. blinatumomab, nelarabine) into frontline consolidation therapy may reduce risk of relapse among adults receiving PEG-containing regimens. Disclosures Geyer: Dava Oncology: Honoraria. Ritchie:Celgene: Consultancy, Other: Travel, Accommodations, Expenses, Speakers Bureau; NS Pharma: Research Funding; Incyte: Consultancy, Speakers Bureau; ARIAD Pharmaceuticals: Speakers Bureau; Astellas Pharma: Research Funding; Bristol-Myers Squibb: Research Funding; Novartis: Consultancy, Other: Travel, Accommodations, Expenses, Research Funding, Speakers Bureau; Pfizer: Consultancy, Research Funding. Rao:Kite, a Gilead Company: Employment. Tallman:Daiichi-Sankyo: Other: Advisory board; AROG: Research Funding; Cellerant: Research Funding; AbbVie: Research Funding; BioSight: Other: Advisory board; Orsenix: Other: Advisory board; ADC Therapeutics: Research Funding. Douer:Shire: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead Sciences: Consultancy; Amgen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz Pharmaceuticals: Consultancy; Pfizer: Honoraria; Spectrum: Consultancy. Park:Kite Pharma: Consultancy; Juno Therapeutics: Consultancy, Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy; Novartis: Consultancy; Shire: Consultancy; Pfizer: Consultancy; Adaptive Biotechnologies: Consultancy.

Download Full-text

CD38low Natural Killer Cells Transiently Expressing CD16F158V m-RNA Potentiates the Therapeutic Activity of Daratumumab Against Multiple Myeloma with Minimal Effector NK Cell Fratricide

Blood ◽

10.1182/blood-2018-99-118926 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 3199-3199 ◽

Cited By ~ 2

Author(s):

Subhashis Sarkar ◽

Sachin Chauhan ◽

Arwen Stikvoort ◽

Alessandro Natoni ◽

John Daly ◽

...

Keyword(s):

Nk Cells ◽

Cell Line ◽

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Nk Cell ◽

Ex Vivo ◽

Advisory Committees ◽

Cd38 Expression ◽

Rpmi 8226

Abstract Introduction: Multiple Myeloma (MM) is a clonal plasma cell malignancy typically associated with the high and uniform expression of CD38 transmembrane glycoprotein. Daratumumab is a humanized IgG1κ CD38 monoclonal antibody (moAb) which has demonstrated impressive single agent activity even in relapsed refractory MM patients as well as strong synergy with other anti-MM drugs. Natural Killer (NK) cells are cytotoxic immune effector cells mediating tumour immunosurveillance in vivo. NK cells also play an important role during moAb therapy by inducing antibody dependent cellular cytotoxicity (ADCC) via their Fcγ RIII (CD16) receptor. Furthermore, 15% of the population express a naturally occurring high affinity variant of CD16 harbouring a single point polymorphism (F158V), and this variant has been linked to improved ADCC. However, the contribution of NK cells to the efficacy of Daratumumab remains debatable as clinical data clearly indicate rapid depletion of CD38high peripheral blood NK cells in patients upon Daratumumab administration. Therefore, we hypothesize that transiently expressing the CD16F158V receptor using a "safe" mRNA electroporation-based approach, on CD38low NK cells could significantly enhance therapeutic efficacy of Daratumumab in MM patients. In the present study, we investigate the optimal NK cell platform for generating CD38low CD16F158V NK cells which can be administered as an "off-the-shelf"cell therapy product to target both CD38high and CD38low expressing MM patients in combination with Daratumumab. Methods: MM cell lines (n=5) (MM.1S, RPMI-8226, JJN3, H929, and U266) and NK cells (n=3) (primary expanded, NK-92, and KHYG1) were immunophenotyped for CD38 expression. CD16F158V coding m-RNA transcripts were synthesized using in-vitro transcription (IVT). CD16F158V expression was determined by flow cytometry over a period of 120 hours (n=5). 24-hours post electroporation, CD16F158V expressing KHYG1 cells were co-cultured with MM cell lines (n=4; RPMI-8226, JJN3, H929, and U266) either alone or in combination with Daratumumab in a 14-hour assay. Daratumumab induced NK cell fratricide and cytokine production (IFN-γ and TNF-α) were investigated at an E:T ratio of 1:1 in a 14-hour assay (n=3). CD38+CD138+ primary MM cells from newly diagnosed or relapsed-refractory MM patients were isolated by positive selection (n=5), and co-cultured with mock electroporated or CD16F158V m-RNA electroporated KHYG1 cells. CD16F158V KHYG1 were also co-cultured with primary MM cells from Daratumumab relapsed-refractory (RR) patients. Results: MM cell lines were classified as CD38hi (RPMI-8226, H929), and CD38lo (JJN3, U266) based on immunophenotyping (n=4). KHYG1 NK cell line had significantly lower CD38 expression as compared to primary expanded NK cells and NK-92 cell line (Figure 1a). KHYG1 electroporated with CD16F158V m-RNA expressed CD16 over a period of 120-hours post-transfection (n=5) (Figure 1b). CD16F158V KHYG1 in-combination with Daratumumab were significantly more cytotoxic towards both CD38hi and CD38lo MM cell lines as compared to CD16F158V KHYG1 alone at multiple E:T ratios (n=4) (Figure 1c, 1d). More importantly, Daratumumab had no significant effect on the viability of CD38low CD16F158V KHYG1. Moreover, CD16F158V KHYG1 in combination with Daratumumab produced significantly higher levels of IFN-γ (p=0.01) upon co-culture with CD38hi H929 cell line as compared to co-culture with mock KHYG1 and Daratumumab. The combination of CD16F158V KHYG1 with Daratumumab was also significantly more cytotoxic to primary MM cell ex vivo as compared to mock KHYG1 with Daratumumab at E:T ratio of 0.5:1 (p=0.01), 1:1 (p=0.005), 2.5:1 (p=0.003) and 5:1 (p=0.004) (Figure 1e). Preliminary data (n=2) also suggests that CD16F158V expressing KHYG1 can eliminate 15-17% of primary MM cells from Daratumumab RR patients ex vivo. Analysis of more Daratumumab RR samples are currently ongoing. Conclusions: Our study provides the proof-of-concept for combination therapy of Daratumumab with "off-the-shelf" CD38low NK cells transiently expressing CD16F158V for treatment of MM. Notably, this approach was effective against MM cell lines even with low CD38 expression (JJN3) and primary MM cells cultured ex vivo. Moreover, the enhanced cytokine production by CD16F158V KHYG1 cells has the potential to improve immunosurveillance and stimulate adaptive immune responses in vivo. Disclosures Sarkar: Onkimmune: Research Funding. Chauhan:Onkimmune: Research Funding. Stikvoort:Onkimmune: Research Funding. Mutis:Genmab: Research Funding; OnkImmune: Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Research Funding; Celgene: Research Funding; Novartis: Research Funding. O'Dwyer:Abbvie: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; BMS: Research Funding; Glycomimetics: Research Funding; Onkimmune: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Download Full-text

Effects of BCL11A Shmir-Induced Post-Transcriptional Silencing on Distributions of HbF in Single-RBCs and Reticulocytes

Blood ◽

10.1182/blood-2021-150186 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 967-967

Author(s):

Nicolas Hebert ◽

Erica B. Esrick ◽

Myriam Armant ◽

Christian Brendel ◽

Marioara Felicia Ciuculescu ◽

...

Keyword(s):

Sickle Cell Disease ◽

Board Of Directors ◽

Sickle Cell ◽

Research Funding ◽

Insertion Site ◽

Fetal Hemoglobin ◽

Fold Increase ◽

Advisory Board ◽

Cell Disease ◽

Advisory Committees

Abstract NH and EE equally contributed. ADW and PB co-signed. The expression of fetal hemoglobin (HbF) is one of the main targets of sickle cell disease treatment, as it inhibits the polymerization of hemoglobin S. The hypothesis of an inhibitory threshold of HbF per red blood cell (RBC) has been suggested, 1 although not well defined, as the overall percentage of HbF does not reflect the heterogeneous distribution of HbF per cell. Likewise, the qualitative analysis of RBCs containing HbF, called F cells, is neither reproducible nor clinically interpretable, due to low expression. 2 We have developed a technique for measuring the amount of HbF per cell, to determine thresholds of HbF expression per RBC correlated with clinical and biological effects. 2 Among genes controlling its expression, BCL11A has a major repressive effect on the expression of gamma globin/HbF during the fetal to adult hemoglobin switch. Post-transcriptional silencing of BCL11A, using lentivirus expression of a shRNA embedded in a microRNA architecture (shmiR) to re-activate γ-globin expression, is safe and demonstrates high levels of %HbF in a pilot clinical study (NCT 03282656). 3 Here, we show the quantitative measurement of HbF per RBC and reticulocyte. Methods: During patient follow-up, HbF quantification per single cell RBC was performed using a fluorescent HbF antibody. 2 Addition of an anti-CD71 fluorescent antibody allowed selection of reticulocyte sub-populations for determining their HbF content. Fold-increase in percentage of RBC versus percentage of reticulocyte were calculated. Kinetics of HbF/RBC and HbF/Reticulocyte were modeled using mixed effects polynomial linear regression to account for the correlation between repeated data over time. Results: With a median follow-up of 15 months [12-20] after gene transfer, figure 1 shows the mathematical modeling of single-RBC HbF measurement representing RBC percentage containing at least 2, 4, 6, 8 and 10 pg of HbF. Percentage of RBC above each threshold was higher compared to 14 hydroxyurea treated patients for 6 months. Figure 2 shows fold increase between reticulocytes and RBCs with same thresholds of HbF/cell. For low thresholds, RBCs were found in same percentage as reticulocytes whereas RBCs containing increasing levels of HbF were found in higher percentage than reticulocytes, until 6pg/cell showing a clear selective advantage for red cells with a threshold ≥ 6pg/cell of HbF. Figure 3 shows different kinetics of HbF increase according to two different transduction strategies with 2 enhancers in patients 2-4 compared to one enhancer in patients 6-8. Conclusion: BCL11A down-regulation in six clinical trial subjects was associated with an in vivo selection process RBCs with ≥ 6pg HbF per cell attained with different engraftment kinetics, depending on transduction processes, and ultimately stable high level and broadly distributed HbF. 1 Steinberg MH, Chui DH, Dover GJ, Sebastiani P, Alsultan A. Fetal hemoglobin in sickle cell anemia: a glass half full? Blood. 2014 Jan 23;123(4):481-5. 2 Hebert N, Rakotoson MG, Bodivit G, et al. Individual red blood cell fetal hemoglobin quantification allows to determine protective thresholds in sickle cell disease. Am. J. Hematol. 3 Esrick EB, Lehmann LE, Biffi A, et al. Post-Transcriptional Genetic Silencing of BCL11A to Treat Sickle Cell Disease. N. Engl. J. Med. 2021;384(3):205-215. Figure 1 Figure 1. Disclosures Esrick: bluebird bio: Consultancy. Audureau: GBT: Honoraria. Higgins: Sebia, Inc.: Honoraria; Danaher Diagnostics: Consultancy. Williams: BioMarin: Membership on an entity's Board of Directors or advisory committees, Other: Insertion Site Advisory Board; Geneception: Membership on an entity's Board of Directors or advisory committees, Other: Scientific Advisory Board; Emerging Therapy Solutions: Membership on an entity's Board of Directors or advisory committees, Other: Chief Scientific Chair; Beam Therapeutics: Membership on an entity's Board of Directors or advisory committees, Other: Scientific Advisory Board; Alerion Biosciences: Other: Co-founder (now licensed to Avro Bio, potential for future milestones/royalties); Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Steering Committee, Novartis ETB115E2201 (eltrombopag in aplastic anemia). Advisory fees donated to NAPAAC.; Orchard Therapeutics: Membership on an entity's Board of Directors or advisory committees, Other: Membership on a safety advisory board (SAB): SAB position ended 05/20/2021. Co-founder , Patents & Royalties: Potential for future royalty/milestone income, X-SCID. Provided GMP vector for clinical trial, Research Funding; bluebird bio: Membership on an entity's Board of Directors or advisory committees, Other: Insertion Site Analysis Advisory Board, Patents & Royalties: BCH licensed certain IP relevant to hemoglobinopathies to bluebird bio. The current license includes the potential for future royalty/milestone income. Bluebird has indicated they will not pursue this as a clinical program and BCH is negotiating return of, Research Funding. Bartolucci: AGIOS: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Lecture fees, Steering committee, Research Funding; Jazz Pharma: Other: Lecture fees; Emmaus: Consultancy; Addmedica: Consultancy, Other: Lecture fees, Research Funding; INNOVHEM: Other: Co-founder; Hemanext: Consultancy; GBT: Consultancy; Bluebird: Consultancy, Research Funding; F. Hoffmann-La Roche Ltd: Consultancy; Fabre Foundation: Research Funding.

Download Full-text

Amino Acid Stress Response Genes Promote L-Asparaginase Resistance in Pediatric Acute Lymphoblastic Leukemia

Blood ◽

10.1182/blood-2021-152940 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 3304-3304

Author(s):

Daniel Ferguson ◽

J. Robert McCorkle ◽

Qian Dong ◽

Erik Bonten ◽

Wenjian Yang ◽

...

Keyword(s):

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Lymphoblastic Leukemia ◽

Acid Stress ◽

Leukemia Cells ◽

P Value ◽

Newly Diagnosed ◽

Advisory Committees ◽

Primary Leukemia

Abstract Understanding the genomic and epigenetic mechanisms of drug resistance in pediatric acute lymphoblastic leukemia (ALL) is critical for further improvements in treatment outcome. The role of transcriptomic response in conferring resistance to l-asparaginase (LASP) is poorly understood, beyond asparagine synthetase (ASNS). We defined reproducible LASP response genes in LASP resistant and sensitive ALL cell lines (n = 7) as well as primary leukemia samples from newly diagnosed patients. We identified 2219 response genes (absolute log 2FC > 1.5, FDR p-value <0.05) with ~16.5% being reproduced in more than one cell line. Defining target genes of the amino acid stress response related transcription factor ATF4 in ALL cell lines using ChIP-seq revealed 25% of genes that changed expression after LASP treatment were direct targets of the ATF4 transcription factor. A total of 17,117 significantly differentially bound ATF4 sites were identified (FDR p-value <0.01) and 97.8% of these sites displayed an increase in ATF4 binding following LASP treatment. SLC7A11 was found to be a response gene in cell lines and patient samples as well as a direct target of ATF4. SLC7A11 was also one of only 2.4% of response genes with basal level gene expression that also correlated with LASP ex vivo resistance in primary leukemia cells from 212 newly diagnosed children enrolled on St. Jude Total Therapy 16. Experiments using chemical inhibition of SLC7A11 with sulfasalazine, gene overexpression, and partial gene knockout recapitulated LASP resistance or sensitivity in ALL cell lines. These findings show the importance of assessing changes in gene expression following treatment with an antileukemic agent for its association with drug resistance and highlights that many response genes may not differ in their basal expression in drug resistant leukemia cells. Disclosures Stock: Pfizer: Consultancy, Honoraria, Research Funding; amgen: Honoraria; agios: Honoraria; jazz: Honoraria; kura: Honoraria; kite: Honoraria; morphosys: Honoraria; servier: Honoraria; syndax: Consultancy, Honoraria; Pluristeem: Consultancy, Honoraria. Mullighan: Amgen: Current equity holder in publicly-traded company; Illumina: Membership on an entity's Board of Directors or advisory committees; AbbVie: Research Funding; Pfizer: Research Funding. Pui: Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Novartis: Other: Data Monitoring Committee. Evans: Princess Máxima Center for Pediatric Oncology, Scientific Advisory Board, Chair: Membership on an entity's Board of Directors or advisory committees; BioSkryb, Inc.: Membership on an entity's Board of Directors or advisory committees; St. Jude Children's Research Hospital, Emeritus Member (began Jan 2021): Ended employment in the past 24 months.

Download Full-text