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lovo-cel (bb1111; LentiGlobin for sickle cell disease [SCD]) gene therapy (GT) comprises autologous transplantation of hematopoietic stem and progenitor cells transduced with the BB305 lentiviral vector encoding a modified β-globin gene (β

Sickle cell disease is characterized by the painful recurrence of vaso-occlusive events. Gene therapy with the use of LentiGlobin for sickle cell disease (bb1111; lovotibeglogene autotemcel) consists of autologous transplantation of hematopoietic stem and progenitor cells transduced with the BB305 lentiviral vector encoding a modified β-globin gene, which produces an antisickling hemoglobin, HbAIn this ongoing phase 1-2 study, we optimized the treatment process in the initial 7 patients in Group A and 2 patients in Group B with sickle cell disease. Group C was established for the pivotal evaluation of LentiGlobin for sickle cell disease, and we adopted a more stringent inclusion criterion that required a minimum of four severe vaso-occlusive events in the 24 months before enrollment. In this unprespecified interim analysis, we evaluated the safety and efficacy of LentiGlobin in 35 patients enrolled in Group C. Included in this analysis was the number of severe vaso-occlusive events after LentiGlobin infusion among patients with at least four vaso-occlusive events in the 24 months before enrollment and with at least 6 months of follow-up.As of February 2021, cell collection had been initiated in 43 patients in Group C; 35 received a LentiGlobin infusion, with a median follow-up of 17.3 months (range, 3.7 to 37.6). Engraftment occurred in all 35 patients. The median total hemoglobin level increased from 8.5 g per deciliter at baseline to 11 g or more per deciliter from 6 months through 36 months after infusion. HbAOne-time treatment with LentiGlobin resulted in sustained production of HbA

Correlation between the levels of CD133 (PROM1) mRNA with that of ALDH1A3 mRNA in lung adenocarcinoma tissues from TCGA portal

Loss of monoubiquitination of histone H2B (H2Bub1) was found to be associated with poor-differentiation and enhanced malignancy of lung adenocarcinoma. This study investigated the association and impact of the ubiquitin-specific peptidase 22 (USP22), an H2Bub1 deubiquitinase, on stem cell-like characteristics and cisplatin resistance in cancer-initiating cells (CIC) from primary lung adenocarcinoma. CICs were isolated, enriched, and characterized from patient-derived cancer tissues using both in vitro tumorsphere formation and in vivo xenograft assays. USP22 was determined to be predominantly expressed in CICs, a subpopulation of cells with high expression of the stem cell biomarkers, CD133 and CD44. The expression of USP22 in CICs is markedly reduced upon FBS/retinoic acid-induced differentiation. Moreover, knockdown of USP22 significantly suppressed tumorsphere formation and xenograft growth in NOD-SCID gamma (NSG) mice. Notably, USP22 and aldehyde dehydrogenase (ALDH) activity were elevated in tumorsphere cells that survived cisplatin treatment, whereas knockdown of USP22 significantly sensitizes tumorsphere cells to cisplatin. Interestingly, ALDH1A3, a predominant ALDH isozyme implicated in enhancing cisplatin resistance in lung adenocarcinoma, is significantly downregulated upon knockdown of USP22 in tumorsphere cells. Furthermore, knockdown of ALDH1A3 significantly sensitizes tumorsphere cells to cisplatin. Combined, these data demonstrate that USP22, predominantly expressed in CD133+ CICs, plays a critical role in tumorigenicity and cisplatin resistance in lung adenocarcinoma.Implications: Targeting USP22 represents a potential therapeutic approach to suppress CICs in lung adenocarcinoma partially through downregulation of ALDH1A3 expression. Mol Cancer Res; 16(7); 1161–71. ©2018 AACR.

Osteosarcoma (OS) is an aggressive malignant bone cancer, with refractory and metastatic disease remaining a significant challenge. Transforming growth factor-β1 (TGF-β) is a potent immune suppressive cytokine in OS and the TGF-β is increased in the sera of OS patients and this increase is associated with high-grade OS and lung metastases. Therefore, blocking TGF-β1 signaling may be a novel therapy for OS treatment. Here we show that blocking TGF-β1 signaling using TGF-βR1 inhibitor, Vactosertib, significantly inhibited OS proliferation in vitro and in vivo. Notably, Vactosertib inhibits c-Myc expression in the OS cells. Vactosertib increased immune effectors (IFNγ+CD8+ cells and NK cells) and inhibited immune suppressors (M2-like TAM, MDSC) in the OS tumor microenvironment. Our results suggest that inhibition of TGF-β1 signaling is an effective therapeutic strategy against OS through a multi-pronged approach that targets tumor intrinsic and extrinsic factors to achieve optimal immune-effector functions and maximal clinical response.

Gene therapy with LentiGlobin for sickle cell disease (bb1111, lovotibeglogene autotemcel) consists of autologous transplantation of a patient's hematopoietic stem cells transduced with the BB305 lentiviral vector that encodes the β

Betibeglogene autotemcel (beti-cel) gene therapy (GT) for patients with transfusion-dependent β-thalassemia uses autologous CD34+ cells transduced with BB305 lentiviral vector (LVV), which encodes a modified β-globin gene. BB305 LVV also contains select HIV sequences for viral packaging, reverse transcription, and integration. This case report describes a patient successfully treated with beti-cel in a phase 1/2 study (HGB-204; #NCT01745120) and subsequently diagnosed with wild-type (WT) HIV infection. From 3.5 to 21 months postinfusion, the patient stopped chronic red blood cell transfusions; total hemoglobin (Hb) and GT-derived HbAT87Q levels were 6.6 to 9.5 and 2.8 to 3.8 g/dL, respectively. At 21 months postinfusion, the patient resumed transfusions for anemia that coincided with an HIV-1 infection diagnosis. Quantitative polymerase chain reaction assays detected no replication-competent lentivirus. Next-generation sequencing confirmed WT HIV sequences. Six months after starting antiretroviral therapy, total Hb and HbAT87Q levels recovered to 8.6 and 3.6 g/dL, respectively, and 3.5 years postinfusion, 13.4 months had elapsed since the patient’s last transfusion. To our knowledge, this is the first report of WT HIV infection in an LVV-based GT recipient and demonstrates persistent long-term hematopoiesis after treatment with beti-cel and the ability to differentiate between WT HIV and BB305-derived sequences.

Vector-mediated mutagenesis remains a major safety concern for many gene therapy clinical protocols. Indeed, lentiviral-based gene therapy treatments of hematologic disease can result in oligoclonal blood reconstitution in the transduced cell graft. Specifically, clonal expansion of hematopoietic stem cells (HSCs) highly expressing HMGA2, a chromatin architectural factor found in many human cancers, is reported in patients undergoing gene therapy for hematologic diseases, raising concerns about the safety of these integrations. Here, we show for the first time in vivo multilineage and multiclonal expansion of non-human primate HSCs expressing a 3' UTR-truncated version of HMGA2 without evidence of any hematologic malignancy >7 years post-transplantation, which is significantly longer than most non-human gene therapy pre-clinical studies. This expansion is accompanied by an increase in HSC survival, cell cycle activation of downstream progenitors, and changes in gene expression led by the upregulation of IGF2BP2, a mRNA binding regulator of survival and proliferation. Thus, we conclude that prolonged ectopic expression of HMGA2 in hematopoietic progenitors is not sufficient to drive hematologic malignancy and is not an acute safety concern in lentiviral-based gene therapy clinical protocols.

In this work we provide preclinical data to support initiation of a first-in-human trial for sickle cell disease (SCD) using an approach that relies on reversal of the developmental fetal-to-adult hemoglobin switch. Erythroid-specific knockdown of BCL11A via a lentiviral-encoded microRNA-adapted short hairpin RNA (shRNAmiR) leads to reactivation of the gamma-globin gene while simultaneously reducing expression of the pathogenic adult sickle β-globin. We generated a refined lentiviral vector (LVV) BCH-BB694 that was developed to overcome poor vector titers observed in the manufacturing scale-up of the original research-grade LVV. Healthy or sickle cell donor CD34+ cells transduced with Good Manufacturing Practices (GMP)-grade BCH-BB694 LVV achieved high vector copy numbers (VCNs) >5 and gene marking of >80%, resulting in a 3- to 5-fold induction of fetal hemoglobin (HbF) compared with mock-transduced cells without affecting growth, differentiation, and engraftment of gene-modified cells in vitro or in vivo. In vitro immortalization assays, which are designed to measure vector-mediated genotoxicity, showed no increased immortalization compared with mock-transduced cells. Together these data demonstrate that BCH-BB694 LVV is non-toxic and efficacious in preclinical studies, and can be generated at a clinically relevant scale in a GMP setting at high titer to support clinical testing for the treatment of SCD.

Key Points Ability to accurately attribute adverse events post–gene therapy is required to describe the benefit-risk of these novel treatments. A SCD patient developed myelodysplastic syndrome post-LentiGlobin treatment; we show how insertional oncogenesis was excluded as the cause.

International audience; Hematopoietic stem cell transplantation (HSCT) is a therapy used for multiple malignant and nonmalignant diseases, with chemotherapy used for pretransplantation myeloablation. The post-HSCT brain contains peripheral engrafted parenchymal macrophages, despite their absence in the normal brain, with the engraftment mechanism still undefined. Here we show that HSCT chemotherapy broadly disrupts mouse brain regenerative populations, including a permanent loss of adult neurogenesis. Microglial density was halved, causing microglial process expansion, coinciding with indicators of broad senescence. Although microglia expressed cell proliferation markers, they underwent cell cycle arrest in S phase with a majority expressing the senescence and antiapoptotic marker p21. In vivo single-cell tracking of microglia after recovery from chemical depletion showed loss of their regenerative capacity, subsequently replaced with donor macrophages. We propose that HSCT chemotherapy causes microglial senescence with a gradual decrease to a critical microglial density, providing a permissive niche for peripheral macrophage engraftment of the brain.

Loss of monoubiquitination of histone H2B (H2Bub1) was found to be associated with poor-differentiation and enhanced malignancy of lung adenocarcinoma. This study investigated the association and impact of the ubiquitin-specific peptidase 22 (USP22), an H2Bub1 deubiquitinase, on stem cell-like characteristics and cisplatin resistance in cancer-initiating cells (CIC) from primary lung adenocarcinoma. CICs were isolated, enriched, and characterized from patient-derived cancer tissues using both in vitro tumorsphere formation and in vivo xenograft assays. USP22 was determined to be predominantly expressed in CICs, a subpopulation of cells with high expression of the stem cell biomarkers, CD133 and CD44. The expression of USP22 in CICs is markedly reduced upon FBS/retinoic acid-induced differentiation. Moreover, knockdown of USP22 significantly suppressed tumorsphere formation and xenograft growth in NOD-SCID gamma (NSG) mice. Notably, USP22 and aldehyde dehydrogenase (ALDH) activity were elevated in tumorsphere cells that survived cisplatin treatment, whereas knockdown of USP22 significantly sensitizes tumorsphere cells to cisplatin. Interestingly, ALDH1A3, a predominant ALDH isozyme implicated in enhancing cisplatin resistance in lung adenocarcinoma, is significantly downregulated upon knockdown of USP22 in tumorsphere cells. Furthermore, knockdown of ALDH1A3 significantly sensitizes tumorsphere cells to cisplatin. Combined, these data demonstrate that USP22, predominantly expressed in CD133+ CICs, plays a critical role in tumorigenicity and cisplatin resistance in lung adenocarcinoma. Implications: Targeting USP22 represents a potential therapeutic approach to suppress CICs in lung adenocarcinoma partially through downregulation of ALDH1A3 expression. Mol Cancer Res; 16(7); 1161–71. ©2018 AACR.

Lentiviral vector (LVV)-mediated transduction of human CD34+ hematopoietic stem and progenitor cells (HSPCs) holds tremendous promise for the treatment of monogenic hematological diseases. This approach requires the generation of a sufficient proportion of gene-modified cells. We identified staurosporine, a serine/threonine kinase inhibitor, as a small molecule that could be added to the transduction process to increase the proportion of genetically modified HSPCs by overcoming a LVV entry barrier. Staurosporine increased vector copy number (VCN) approximately 2-fold when added to mobilized peripheral blood (mPB) CD34+ cells prior to transduction. Limited staurosporine treatment did not affect viability of cells post-transduction, and there was no difference in in vitro colony formation compared to vehicle-treated cells. Xenotransplantation studies identified a statistically significant increase in VCN in engrafted human cells in mouse bone marrow at 4 months post-transplantation compared to vehicle-treated cells. Prostaglandin E2 (PGE2) is known to increase transduction efficiency of HSPCs through a different mechanism. Combining staurosporine and PGE2 resulted in further enhancement of transduction efficiency, particularly in short-term HSPCs. The combinatorial use of small molecules, such as staurosporine and PGE2, to enhance LVV transduction of human CD34+ cells is a promising method to improve transduction efficiency and subsequent potential therapeutic benefit of gene therapy drug products. Keywords: lentiviral, HSPC, transduction

Background: The ongoing Phase 1/2 HGB-206 study (NCT02140554) of LentiGlobin for SCD (bb1111) GT uses a modified human β-globin gene that expresses an anti-sickling hemoglobin (HbA T87Q). The relationships between biological outcomes, clinical outcomes, and clonality in the initial cohort (Group A) and the cohort treated after substantial changes were made to the study protocol and manufacturing process to improve clinical benefit (Group C) are presented here. Methods: Patients (pts; ≥18 in Group A and ≥12-≤50 yrs in Group C) with SCD and recurrent severe vaso-occlusive events (VOEs), overt stroke, or tricuspid regurgitant jet velocity of >2.5 m/s, were enrolled. The initial protocol (cell collection and target busulfan dose) and manufacturing process in Group A was modified to improve cell dose, transduction efficiency, HbA T87Q expression, and clinical benefit. CD34+ cells (collected by bone marrow [BM] harvesting in Group A and plerixafor mobilization/apheresis in Group C) were transduced with BB305 lentiviral vector (LVV). LentiGlobin was infused after myeloablative busulfan conditioning. Transduction, SCD-related outcomes, clonality, and safety were assessed; data are median (min-max) unless otherwise stated. Results: As of 17 February 2021, there were 61.5 (55.5-66.1) months of follow-up post-LentiGlobin infusion in Group A (n=7) and 17.3 (3.7-37.6) months in Group C (n=35). After protocol and manufacturing modifications, median drug product vector copy number (DP VCN) and transduction efficiency were increased in Group C (3.7 c/dg with 80.3% transduced cells) compared with Group A (0.6 c/dg with 27.7% transduced cells). Peripheral blood (PB) VCN stabilized by Month 6 post-infusion and was sustained throughout follow up in both groups; however, the median PB VCN was correspondingly higher in Group C than in Group A (1.45 c/dg vs 0.09 c/dg). A higher DP VCN, %LVV+, and PB VCN in Group C generated increased HbA T87Q of 5.2 (2.6-8.8) g/dL (n=30) compared with HbA T87Q of 0.5 (0.1-1.8) g/dL (n=7) in Group A at Month 6. This was associated with near pancellular expression of HbA T87Q at ≥6 months post-infusion in Group C with a mean of 87% of red blood cells containing β A-T87Q by 18 months (n=14). Group C featured significantly higher median unique insertion sites (UIS) than Group A (p = 1.43 x 10 -12;Fig 1), consistent with increased polyclonality. Critically, median UIS also correlated strongly with PB VCN (Spearman rho = 0.97; Fig 1) and HbA T87Q at Month 6 post-infusion and was associated with improved clinical efficacy in Group C, with complete resolution of severe VOEs and near normal levels of key hemolysis markers. In Group C, the only treatment (tx) emergent serious adverse events (TESAEs) reported in >1 pt were abdominal pain, nausea, opioid withdrawal syndrome, and vomiting (n=2, 5.7% each). No events of malignancy were reported in Group C. One event of sudden death, considered unlikely related to LentiGlobin, occurred >18 months post-tx in a patient with significant baseline SCD-related cardiopulmonary disease. In Group A, the most common TESAE was sickle cell anemia with crisis (n=4, 57%). Two events of acute myeloid leukemia (AML) were reported in Group A pts at 3 and 5 years post-tx, both of which were considered unlikely related to the LVV. Both pts had classic AML driver mutations identified post-diagnosis. One pt died of AML and the second pt is receiving therapy for AML. The modifications made in Group C are anticipated to reduce risk of AML. To monitor safety, BM and PB will be screened for the presence of AML driver mutations prior to treatment, and patients already treated will have regular cytogenetic screening in addition to BB305 LVV integration site analysis. Summary: Alterations to the protocol and manufacturing process in HGB-206 resulted in improved cell dose, transduction efficiency, HbA T87Q expression, and clinical outcomes in Group C compared with Group A. Polyclonality was strongly correlated to PB VCN and HbA T87Q production, indicating that superior engraftment of LVV-transduced cells leads to favorable clinical outcomes. The safety profile post-LentiGlobin for all treated patients with SCD remains generally consistent with the risks of autologous stem cell transplant, myeloablative busulfan conditioning, and underlying SCD. Figure 1 Figure 1. Disclosures Thompson: Baxalta: Research Funding; Biomarin: Research Funding; bluebird bio, Inc.: Consultancy, Research Funding; Celgene/BMS: Consultancy, Research Funding; CRISPR Therapeutics: Research Funding; Vertex: Research Funding; Editas: Research Funding; Graphite Bio: Research Funding; Novartis: Research Funding; Agios: Consultancy; Beam: Consultancy; Global Blood Therapeutics: Current equity holder in publicly-traded company. Kwiatkowski: Bluebird Bio: Other: Consultancy Fees; Imara: Other: Consultancy Fees; Celgene: Honoraria; Silence Therapeutics: Honoraria; Agios: Honoraria; ApoPharma: Research Funding; Novartis: Research Funding; Bluebird Bio: Research Funding; Sangamo: Research Funding; Terumo BCT: Research Funding. Aygun: National Heart, Lung, Blood Institute: Research Funding; Global Blood Therapeutics: Consultancy; National Institute of Nursing Research: Research Funding; Patient Centered Outcomes Research Institute: Research Funding; bluebird bio, Inc.: Membership on an entity's Board of Directors or advisory committees, Research Funding. Schmidt: GeneWerk GmbH, Heidelberg, Germany: Current equity holder in publicly-traded company; German Cancer Research Center, Heidelberg, Germany: Current Employment. Pierciey: bluebird bio, Inc.: Current Employment, Current equity holder in publicly-traded company. Whitney: bluebird bio, Inc.: Current Employment, Current equity holder in publicly-traded company. Rogers: bluebird bio, Inc.: Current Employment, Current equity holder in publicly-traded company. Nnamani: bluebird bio, Inc.: Current Employment, Current equity holder in publicly-traded company. Foos: bluebird bio, Inc.: Current Employment, Current equity holder in publicly-traded company. Miller: bluebird bio, Inc.: Current Employment, Current equity holder in publicly-traded company. Zhang: bluebird bio, Inc.: Current Employment, Current equity holder in publicly-traded company. Lynch: bluebird bio, Inc.: Current Employment, Current equity holder in publicly-traded company. Walters: Vertex pharmaceuticals: Consultancy; Ensoma, Inc.: Consultancy; BioLabs, Inc: Consultancy; AllCells, Inc: Consultancy. Kanter: Fulcrum Therapeutics, Inc.: Consultancy; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Forma: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Agios: Honoraria, Membership on an entity's Board of Directors or advisory committees; Beam: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; Graphite Bio: Consultancy; GuidePoint Global: Honoraria; Fulcrum Tx: Consultancy. Bonner: bluebird bio, Inc.: Current Employment, Current equity holder in publicly-traded company.

Gene therapy currently in development for hemoglobinopathies utilizes ex vivo lentiviral transduction of CD34+ hematopoietic stem and progenitor cells (HSPCs). A small-molecule screen identified prostaglandin E2 (PGE2) as a positive mediator of lentiviral transduction of CD34+ cells. Supplementation with PGE2 increased lentiviral vector (LVV) transduction of CD34+ cells approximately 2-fold compared to control transduction methods with no effect on cell viability. Transduction efficiency was consistently increased in primary CD34+ cells from multiple normal human donors and from patients with β-thalassemia or sickle cell disease. Notably, PGE2 increased transduction of repopulating human HSPCs in an immune-deficient (nonobese diabetic/severe combined immunodeficiency/interleukin-2 gamma receptor null [NSG]) xenotransplantation mouse model without evidence of in vivo toxicity, lineage bias, or a de novo bias of lentiviral integration sites. These data suggest that PGE2 improves lentiviral transduction and increases vector copy number, therefore resulting in increased transgene expression. As a result, PGE2 may be useful in clinical gene therapy applications using lentivirally modified HSPCs., Heffner et al. performed a small-molecule screen and identified prostaglandin E2 (PGE2) as a positive mediator of lentiviral transduction of CD34+ cells. Their data suggest that PGE2-mediated improvements in transduction efficiency may aid in clinical gene therapy applications using lentivirally modified HSPCs.

Introduction LentiGlobin for SCD GT contains autologous CD34+ hematopoietic stems cells (HSCs) encoding β-globin with the anti-sickling T87Q mutation (βA-T87Q) and is being evaluated in the ongoing Phase 1/2 HGB-206 Study (NCT02140554) in patients with SCD. Levels of GT-derived hemoglobin (HbAT87Q) in 7 initial patients (Group A) were suboptimal but were maintained for ≥ 30 months of follow-up post-treatment, suggesting durable transgene expression. To increase HbAT87Q production, protocol and manufacturing changes were made (Group B; N=2). In addition, HSC collection by plerixafor mobilization and apheresis was instituted in Group C. Objective Provide an update on safety and efficacy of LentiGlobin for SCD in HGB-206 Group C. Methods Adults with severe SCD (including recurrent vaso-occlusive crisis [VOC] and acute chest syndrome [ACS]) were enrolled. CD34+ HSCs were harvested by apheresis following plerixafor mobilization and transduced with BB305 lentiviral vector (LVV). Patients received myeloablative busulfan conditioning, were infused with LentiGlobin drug product (DP) and monitored for adverse events (AEs), Hb fractions, and other parameters. LVV presence in transduced cells (%LVV+) was measured by qPCR of individual colonies from colony-forming unit assays from pre-infusion DP) and post-infusion from CD34+ bone marrow (BM) HSCs and peripheral blood mononuclear cells (PBMCs). Data are shown as median (min-max). Results As of 7 March 2019, 13 Group C patients received DP, with follow-up of 9.0 (1.0-15.2) months. All but 1 patient had neutrophil and platelet engraftment as of the data cut date. Median HbS was ≤50% of total Hb in those with ≥6 months follow-up (n=8; Figure 1). Total unsupported Hb at last visit in patients with ≥6 months of follow-up was 11.5 (10.2-15.0) g/dL, with HbAT87Q levels of 5.3 (4.5-8.8) g/dL. Six of these 8 patients had a history of VOCs or ACS; the annualized VOC+ACS rate decreased from 5.3 (3-14) pre-treatment to 0 (0-2) post-treatment (Figure 2). A decrease in hemolysis markers was also seen post-DP. Most common non-hematologic Grade ≥ 3 AEs were febrile neutropenia (n=10) and stomatitis (n=7). Serious AEs occurred in 6 patients; the most frequent were nausea and vomiting. To date, there have been no cases of DP-related AEs, graft failure, vector-mediated replication competent lentivirus, or clonal dominance. The %LVV+ colonies from PBMCs at 9 months and BM at 12 months post-DP infusion (n=5) were 79.2 (67.0-88.4) % and 81.5 (60.6-88.1) %, respectively, indicating stable engraftment of transduced cells from DP (%LVV+ was 80 [71-88] %). Conclusions Patients in HGB-206 Group C show stable LentiGlobin engraftment, with median total Hb >10 g/dL and median HbS ≤50% of total Hb in those with ≥6 months follow-up. The decrease in SCD-related complications and hemolysis in this cohort demonstrate a strong therapeutic benefit of LentiGlobin in patients with SCD.

Background Dysregulated histone methyltransferase G9a may represent a potential cancer therapeutic target. The roles of G9a in tumorigenesis and therapeutics are not well understood in non-small cell lung cancer (NSCLC). Here we investigated the impact of G9a on tumor growth and signaling pathways in NSCLC. Methods Immunohistochemistry analyzed G9a expression in NSCLC tissues. Both siRNA and selective inhibitor were used to target G9a. The impact of targeting G9a on key genes, signaling pathways and growth were investigated in NSCLC cells by RNA sequencing analysis, rescue experiments, and xenograft models. Results Overexpression of G9a (≥ 5% of cancer cells showing positive staining) was found in 43.2% of 213 NSCLC tissues. Multiple tumor-associated genes including HP1α, APC2 are differentially expressed; and signaling pathways involved in cellular growth, adhesion, angiogenesis, hypoxia, apoptosis, and canonical Wnt signaling pathways are significantly altered in A549, H1299, and H1975 cells upon G9a knockdown. Additionally, targeting G9a by siRNA-mediated knockdown or by a selective G9a inhibitor UNC0638 significantly inhibited tumor growth, and dramatically suppressed Wnt signaling pathway in vitro and in vivo. Furthermore, we showed that treatment with UNC0638 restores the expression of APC2 expression in these cells through promoter demethylation. Restoring HP1α and silencing APC2 respectively attenuated the inhibitory effects on cell proliferation and Wnt signaling pathway in cancer cells in which G9a was silenced or suppressed. Conclusions These findings demonstrate that overexpressed G9a represents a promising therapeutic target, and targeting G9a potentially suppresses growth and Wnt signaling pathway partially through down-regulating HP1α and epigenetically restoring these tumor suppressors such as APC2 that are silenced in NSCLC. Electronic supplementary material The online version of this article (10.1186/s12943-018-0896-8) contains supplementary material, which is available to authorized users.

Background LentiGlobin for Sickle Cell Disease (SCD) gene therapy contains ex-vivo lentiviral vector (LVV)-mediated addition of a modified β-globin gene (βA-T87Q) into autologous CD34+ hematopoietic stem cells (HSCs). The safety and efficacy of LentiGlobin for SCD is being evaluated in the ongoing Phase 1/2 HGB-206 study (NCT02140554). Early data suggest that highly efficient HSC transduction and engraftment of long-term repopulating HSCs are needed to prevent sickle-related complications. Implementation of a refined manufacturing process resulted in a median vector copy number (VCN) of 3.8 (2.8-5.6) vector copies/diploid genome and median % transduced cells (% LVV+) of 80 (71-88) % in the drug product (DP). These DP improvements correlated with robust HbAT87Q production and better clinical outcomes in the recently treated cohort. Here we describe results of exploratory assays performed in this subset of patients to evaluate how DP characteristics impact SCD RBC physiology by assessing: 1) engraftment and persistence of LVV transduced cells in the bone marrow (BM) and peripheral blood (PB), 2) effect of VCN on βA-T87Q and βS levels in PBMC-derived erythroid colonies, 3) proportion of RBCs expressing βA-T87Q, and 4) impact of intracellular βA-T87Q and βS levels on RBC sickling. These assays are also underway in earlier study patients and will be presented. Methods Individual colonies were isolated from colony-forming unit (CFU) assays performed on DP (prior to infusion), CD34+ HSCs from BM aspirates post-DP infusion, and on PBMCs post-DP infusion. To evaluate engraftment of transduced cells, presence of LVV was determined by qPCR of individual colonies. βS expression in individual colonies was assessed by ultra-performance liquid chromatography. βA-T87Q expression in RBCs was assessed by a single cell western blot (scWB) assay, using concurrent staining with two antibodies, a novel antibody specific for βS and the other recognizing both βA and βA-T87Q. Percentage of sickled RBCs was quantified by imaging flow cytometry performed on RBCs exposed to 2% O2. Data are presented as median (min-max). Results The percentages of LVV+ colonies from PBMCs at 9 months and BM at 12 months post-infusion in 5 patients were 79.2 (67.0-88.4) % and 81.5 (60.6-88.1) %, respectively, consistent with stable engraftment of transduced cells. The proportion of erythroid and myeloid colonies from DP, BM and PBMCs with a given VCN was determined to assess the impact of VCN on engraftment of transduced cells. We observed a reduction in high-VCN progenitors obtained from PBMCs and BM post-infusion vs DP. PBMCs from one patient were used to generate erythroid colonies for VCN and HbS expression assessments: colonies with VCN = 1 had 62 (33-87) % contribution of βS and colonies with VCN ≥ 3 had 23 (0-55) % βS, suggesting a negative relationship between VCN and % βS expression. To investigate how the 80% LVV transduction efficiency in the DP relates to βA-T87Q expression in RBCs, we evaluated βS and βA-T87Q expression in individual RBCs by scWB assay at various time points after DP infusion (Fig 1). The proportion of RBCs positive for βA-T87Q at last study visit in 8 patients with ≥ 9 months of follow-up was 83.0 (65.5-95.8) %; with > 90% of RBCs positive for βA-T87Q in 4 patients. The proportion of sickled RBCs was assessed from untreated patients with SCD, individuals with sickle cell trait and patients with ≥ 6 months of follow-up post-LentiGlobin treatment (n=7). The % sickled RBCs from LentiGlobin treated patients, while similar to that from trait individuals, was significantly lower compared to that in untreated patients with SCD. Summary These data demonstrate consistent engraftment and persistence of LVV-transduced cells following LentiGlobin gene therapy. The decrease in frequency of high-VCN progenitors from post-treatment PB or BM compared to DP suggests that these high-VCN progenitors may not contribute to gene-modified cell population in the long term. Further, these early data suggest that LentiGlobin gene therapy results in nearly pancellular βA-T87Q expression and reduction in βS expression,which impacts the pathophysiology of SCD as demonstrated by a reduction in RBC sickling. Together, these results begin to describe the complex relationship between characteristics of VCN and transduction efficiency in the HSCs in the DP, and the cellular physiology of erythroid lineage descendants after LentiGlobin gene therapy. Disclosures Bonner: bluebird bio, Inc.: Employment, Equity Ownership. Kanter:Novartis: Consultancy, Honoraria; Imara: Consultancy; Sangamo: Consultancy, Honoraria; Modus: Consultancy, Honoraria; Guidepoint Global: Consultancy; GLG: Consultancy; Cowen: Consultancy; Jeffries: Consultancy; Medscape: Honoraria; Rockpointe: Honoraria; Peerview: Honoraria; SCDAA: Membership on an entity's Board of Directors or advisory committees; NHLBI: Membership on an entity's Board of Directors or advisory committees; bluebird bio, Inc.: Consultancy. Macari:bluebird bio, Inc.: Employment, Equity Ownership. Lane:bluebird bio, Inc.: Employment, Equity Ownership. Lewis:bluebird bio, Inc.: Employment, Equity Ownership. Coles:bluebird bio, Inc.: Employment, Equity Ownership. Kassenaar:bluebird bio, Inc.: Employment, Equity Ownership. Mynampati:bluebird bio, Inc.: Employment, Equity Ownership. Schulze:bluebird bio, Inc.: Employment, Equity Ownership. Hebert:bluebird bio, Inc.: Employment, Equity Ownership. Walters:Editas Medicine: Consultancy; TruCode: Consultancy; AllCells, Inc: Consultancy. Thompson:Baxalta: Research Funding; Novartis: Consultancy, Research Funding; bluebird bio, Inc.: Consultancy, Research Funding; Celgene: Consultancy, Research Funding. Asmal:bluebird bio, Inc: Employment, Equity Ownership. Pierciey:bluebird bio, Inc.: Employment, Equity Ownership.

An important goal in gene therapy and stem cell transplant is to expand hematopoietic stem cells (HSCs) without causing hematopoietic abnormalities. This is particularly challenging in humans and other primates, where expansion protocols that work in mouse models are often less effective in primate HSCs. One approach is to test genes that have led to clonal expansions by vector insertion site effects in human gene therapy trials. In this study, we recreated a mutant HMGA2 cDNA that was associated with a benign clonal expansion in a patient treated on a β-thalassemia gene therapy trial. A lentiviral vector was generated that expressed a cDNA for human HMGA2 with a 3’ UTR deletion that eliminates all seven let-7 microRNA binding sites and thereby avoids the known repressive effects of let-7 miRNAs on HMGA2 expression. A gamma-retroviral MSCV promoter was used to express this mutant HMGA2 cDNA along with an Ires-GFP cassette. Bone marrow CD34+ cells were collected for Nemestrina Macaques and half the cells were transduced with the lentiviral vector containing the HMGA2-GFP construct while the other half was transduced with a mCherry control vector. The transduction efficiencies were approximately the same prior to transplant. At three months post transplantation, the marking in the peripheral blood mononuclear cells was 2.9% GFP+ and 1.1% mCherry+ for animal #16, and was 2.7% GFP+ and 3.2% mCherry+ for animal #27, suggesting relatively equivalent and low levels of transduction of repopulating cells. The HMGA2-GFP marking progressively increased over 21 and 26 months in the peripheral blood leukocytes to 39% for #16 and 41% for #27 while the mCherry marked cells have decreased (Fig 1AFig 1A). Equivalent levels of marking were seen in various mature peripheral blood lineages, including circulating erythyrocytes, suggesting that expansion had occurred in pluripotent HSCs. This HSC expansion was further demonstrated by a marking analysis in bone marrow cells that showed 44.6% and 75.2% GFP marking in the CD34+CD45RA- HSC compartment for animal #16 and #27 respectively, at the latest time point. Clonality analyses using vector integration sites (VIS) showed overall oligoclonal marking in both the GFP+ and mCherry+ cells in both animals (Fig 1BFig 1B). The top most frequent VISs were present in all PB lineages indicating that expansion had occurred in multiple HSC clones. The WBC counts, lineage distribution in the peripheral blood, the percentage of CD34+ cells in the bone marrow and all the mature lineages in the peripheral blood are all within the normal range, demonstrating lack of any detectable hematopoietic abnormality. Gene expression microarray analysis of RNA from sorted BM CD34+GFP+ and CD34+mCherry+ cells showed sharp upregulation of several genes in the HMGA2-expressing cells, particularly the IGF2BP gene, a known downstream target of HMGA2. In summary, our data show that long-term HSCs from non-human primates can be progressively expanded in vivo over several years by overexpressing HMGA2. This could be useful for gene therapy, particularly for expanding and obtaining high numbers of transduced erythrocytes and granulocytes for diseases in which a naturally occurring selection advantage is not present.View Large Image | Download PowerPoint Slide

Gene therapy for congenital hematopoietic disorders frequently relies on ex vivo lentiviral transduction of isolated CD34+ hematopoietic progenitor cells. Through a high-throughput small molecule screen, we identified PGE2 as a positive mediator of lentiviral transduction of hematopoietic stem and progenitor cells enriched from mobilized peripheral blood (PB CD34+ cells). CD34+ cells transduced with a VSVG-pseudotyped lentiviral vector in the presence of cytokines and 10 uM PGE2 yielded a vector copy number per cell (VCN) approximately 2-fold higher than CD34+ cells transduced in the absence of PGE2. This effect was seen consistently in 16 of 16 tested normal human donors in vitro, as well as primary CD34+ cells from both thalassemia and sickle cell disease patients. Importantly, PGE2 was observed to improve transduction of prospectively-isolated CD34+CD38- hematopoietic stem cells - a sub-population thought to be enriched for the long term repopulating stem cell. Transduction improvements were not associated with increased viral entry, but were associated with elevated expression of cAMP genes, supporting a post-entry mechanism of action that involves cAMP signaling downstream of prostaglandin receptors. Lastly, in a mouse xenotransplantation model of hematopoietic stem cell transplant, transduction of PB CD34+ cells in the presence of PGE2 improved VCN levels in engrafted human CD45+ cells 4-5 months post-transplant by ~2-fold without adversely affecting overall human cell engraftment. These data suggest that PGE2-mediated improvements in lentiviral transduction of human CD34+ cells could result in higher transduction efficiency and provide potential benefit in clinical gene therapy applications.

Lentiviral vector (LVV) mediated transduction of CD34+ hematopoietic stem and progenitor cells holds tremendous promise for the treatment of monogenic diseases of the blood. Critical to the success of this ex vivo gene therapy approach is the generation of a sufficient proportion of gene-modified cells. Here we investigated the potential of staurosporine, a protein kinase inhibitor, to enhance the transduction of LVVs in mobilized peripheral blood CD34+ cells both in vitro and in vivo. Staurosporine treatment has been previously demonstrated to increase HIV-1 integration in metaphase-arrested cells and shown to cause chromatin relaxation in metaphase cells (Manioui et al., Virology 2004). Additionally, in a separate study staurosporine treatment led to a 150% increase in transduction of CAp24+ CD4+ T cells (Permanyer et al., PLoS One 2013). Staurosporine increases vector copy number (VCN) approximately 2-fold when added to human mobilized peripheral blood (mPB) CD34+ enriched cells prior to transduction. The mechanism of this VCN improvement was investigated using the BLAM assay and a 1.5-fold improvement in viral entry was demonstrated. This effect was observed in at least six different mPB CD34+ cell lots that had various levels of transducibility. Interestingly, the effect of increased LVV transduction was most striking with low transducing cell lots and the effect diminished in higher transducing cell lots. Staurosporine treatment did not affect viability of cells post-transduction and there was no difference in in vitro colony formation in staurosporine-treated cells compared to vehicle-treated cells. NSG mice transplanted with cells transduced in the presence of 400 nM or 800 nM staurosporine demonstrated a statistically significant 3-fold and 4-fold increase in VCN in human CD45+ cells in bone marrow at 4 months post-transplantation compared to vehicle-treated cells. Importantly, there was no significant difference in engraftment nor any observed lineage-bias between groups. Based on these observations, the use of staurosporine to enhance LVV transduction of human CD34+ cells is a promising method to improve the potential therapeutic benefit of gene therapy drug products.

Background Patients with severe sickle cell disease (SCD) may benefit from β-globin gene transfer into autologous hematopoietic stem cells (HSC). Successful HBB gene transfer requires vector-mediated transduction of primitive HSCs. Steady-state bone marrow (BM) is the default HSC source in patients with SCD. Normal human BM contains up to 30% CD34+CD19+ pro-B cells and other lineage-committed cell types (CD34dim) that will not contribute to improved long-term erythropoiesis via gene therapy; these cells mobilize at low rates. CD34+ cell yields from BM harvest (BMH) are typically lower than those after mobilization and peripheral blood (PB) apheresis; multiple rounds of BMH may be required to obtain adequate cell doses for autologous gene therapy (GT) protocols. As G-CSF can cause life-threatening SCD complications and is contraindicated, plerixafor, a CXCR4 receptor antagonist, may accomplish HSC mobilization without the neutrophil or endothelial activation that elicit vaso-occlusion. We modified the protocol for the HGB-206 phase 1 study of LentiGlobin GT in severe SCD (NCT02140554) to assess HSC mobilization with plerixafor alone, followed by apheresis and transduction of mobilized cells. We also characterized BM-derived and plerixafor-mobilized HSC populations from patients with SCD. Methods HGB-206 is a phase 1 study of LentiGlobin Drug Product (DP), which contains autologous HSCs transduced ex vivo with the betibeglogene darolentivec (BB305) lentiviral vector, in patients with severe SCD (defined as a history of recurrent vaso-occlusive crisis [VOC], acute chest syndrome, stroke, or tricuspid regurgitant jet velocity of >2.5 m/s). Patients in group B receive 240 µg/kg plerixafor followed 4-6 hours later by apheresis, processing ~3 total blood volumes to collect backup HSCs. If < 1.5 x 106 CD34+ cells are collected, patients undergo a second day of apheresis. Cells collected in excess of those required for backup in case of graft failure are transduced with BB305 lentiviral vector for exploratory analyses. Group B patients then proceed to BMH to obtain cells for clinical DP manufacture. Group C will receive DP manufactured from mobilized PB. Mass cytometry (CyTOF) was used to analyze ex vivo cultured CD34+ cells with over 35 cell surface markers. Results To date, 3 patients have undergone plerixafor mobilization. Patients had a transient 1.5- to 3-fold increase in peak white blood cell and absolute neutrophil levels after plerixafor. Peak absolute CD34+ cell counts in PB were 170, 58, and 160 x 106 CD34+ cells/liter. A total of 15.3, 5.6, and 9.0 x 106 CD34+ cells/kg were collected in a single day of apheresis, and no subsequent apheresis or mobilization was required. In the same study, a mean of 5.0 (range 0.3-10.8) x 106 CD34+ cells/kg were collected per BMH (N=21). The mobilization and apheresis procedures had an acceptable toxicity profile. No dose-limiting toxicities were observed after plerixafor dosing. One patient had a single VOC approximately 48 hours after receiving plerixafor; this patient also experienced VOCs of similar severity after BMH. In contrast, after 21 BMHs in 9 patients, 18 ≥ grade 3 AEs were reported in 6 patients, primarily pain. Ex vivo cultured CD34+ cells isolated from BMH consisted of an average of 41.0% (17.3%-50.7%) CD34dim cells, with 16%-50% of the CD34dim cells expressing lymphoid markers. In contrast, ex vivo cultured CD34+ cells isolated from plerixafor mobilized PB contained an average of 8.2% (1.5-19.5%) CD34dim cells. Similar drug product vector copy numbers were obtained after research-scale transduction of CD34+ cells from marrow and PB from the same patient. Conclusion Initial results suggest that obtaining adequate doses of CD34+ cells from plerixafor-mobilized PB of patients with SCD may be safe and feasible, without the life-threatening complications associated with G-CSF, and with fewer, less invasive procedures compared with BMH. PB-derived CD34+ cells may contain lower proportions of lineage-committed CD34+ cells than BM-derived cells from patients with SCD. Cells collected by BMH and PB mobilization/apheresis appear to have an equivalent transduction efficiency. Together these results indicate that it may be possible to use plerixafor-only mobilization in clinical studies of autologous HSC GT in SCD. Results of mobilization, apheresis, and DP manufacturing at clinical scale for additional patients will be available for presentation. Disclosures Pierciey: bluebird bio: Employment. Kanter: American Society of Hematology (Sickle Cell Disease Guideline Panel): Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; MUSC: Other: The site PI for sponsored research conducted at MUSC who receives funds from: Novartis, bluebird bio, GBT, Sancillo, Apopharma, Pfizer; NHLBI (sickle cell disease research advisory committee): Membership on an entity's Board of Directors or advisory committees, Research Funding; Sancillo: Research Funding; Apopharma: Research Funding; Pfizer: Research Funding; GBT: Research Funding; Bluebird Bio: Membership on an entity's Board of Directors or advisory committees, Research Funding. Kwiatkowski: Novartis: Research Funding; Bluebird Bio: Research Funding; Apopharma: Research Funding; Agios: Consultancy, Honoraria; Ionis: Consultancy, Honoraria. Thompson: Novartis: Consultancy, Research Funding; bluebird bio: Consultancy, Research Funding; Baxalta: Research Funding; Celgene: Consultancy, Research Funding. Shestopalov: bluebird bio: Employment, Equity Ownership. Bonner: bluebird bio: Employment, Equity Ownership. Joseney-Antoine: bluebird bio: Employment, Equity Ownership. Asmal: bluebird bio: Employment, Equity Ownership. Walters: bluebird bio: Research Funding; ViaCord Processing Lab: Other: Medical Director; Sangamo Therapeutics: Consultancy; AllCells, Inc: Other: Medical Director.

Current manufacturing of clinical grade lentiviral vectors (LVVs) for gene therapy applications commonly relies on transient transfection of adherent 293T cells. Improvements in production efficiency and scalability would provide value in meeting the needs for increased amounts of vector required for clinical development. An inducible producer cell line grown in suspension culture represents a potentially more scalable manufacturing process for LVV production which eliminates the need for costly plasmid and transfection reagents. We have engineered a packaging cell line by introducing doxycycline-inducible Gag-Pol, Rev, and VSVG envelope genes into a suspension cell line. Packaging cell clones were isolated by single cell sorting and screened by qPCR for the presence of the delivered genes. Virus production was assessed by transient transfection of a lentiviral vector and doxycycline treatment. A titer of up to 5.0E6 transduction units per milliliter (TU/mL) was observed with packaging cell line stability demonstrated after greater than four months of continuous passage. Next, a self-inactivating lentiviral vector was excised from its plasmid backbone and ligated in vitro to a linear neomycin resistance cassette and used to transfect the lentiviral packaging cell line to generate a panel of producers. Following two weeks of G418 drug selection, adherent colonies were plucked and screened for viral production followed by single cell sorting to isolate individual producer clones. From five different plucked colonies with titers greater than 3.0E6 TU/mL, more than 100 clones were screened and 7 were identified that produced a harvest titer greater than 1.0E7 TU/mL. Four of these clones were successfully re-adapted to suspension and scaled up to 3L culture. LVV generated from individual producer clones was compared for the ability to transduce adult mobilized CD34+ hematopoietic stem cells (HSCs). Interestingly, the vector copy number (VCN) in CD34+ HSCs for the LVV derived from the producer cells varied between clones. Clones that produced the highest VCN have been chosen for further characterization in order to better understand the differences in HSC transduction. These lentiviral producer cell lines represent an important first step toward the creation of a manufacturing process that can better support clinical and commercial development of HSC lentiviral gene therapy.

Single-stranded DNA oligonucleotides (ODNs) can be used to direct the exchange of nucleotides in the genome of mammalian cells in a process known as gene editing. Once refined, gene editing should become a viable option for gene therapy and molecular medicine. Gene editing is regulated by a number of DNA recombination and repair pathways whose natural activities often lead to single- and double-stranded DNA breaks. It has been previously shown that introduction of a phosphorotioated ODN, designed to direct a gene-editing event, into cells results in the activation of γH2AX, a well-recognized protein biomarker for double-stranded DNA breakage. Using a single copy, integrated mutant enhanced green fluorescent protein (eGFP) gene as our target, we now demonstrate that several types of ODNs, capable of directing gene editing, also activate the DNA damage response and the post-translational modification of proliferating cell nuclear antigen (PCNA), a signature modification of replication stress. We find that the gene editing reaction itself leads to transient DNA breakage, perhaps through replication fork collapse. Unmodified specific ODNs elicit a lesser degree of replication stress than their chemically modified counterparts, but are also less active in gene editing. Modified phosphothioate oligonucleotides (PTOs) are detrimental irrespective of the DNA sequence. Such collateral damage may prove problematic for proliferation of human cells genetically modified by gene editing.

Production of lentiviral vectors for clinical gene transfer trials is challenging due to the cost of acquiring GMP-grade plasmids and the labor intensive nature of making vectors via transient transfection. To facilitate clinical grade lentiviral vector production, we developed a packaging cell line, GPRG, which was used to make a fully stable producer, GPRG-EF1α-hgcOPT. This stable producer is presently supporting two clinical trials for the treatment of X-SCID. While initial results in one of these trials have been positive, the output and potency of this line mandates repeated production runs to supply enough vector for larger subjects, producing only enough for 2-3 cases per 6 day run. A second generation packaging cell line, GPRTG, has been developed and tested as a future platform for lentiviral gene transfer trials. This new cell line expresses codon-optimized HIV-1 gagpol, rev and tat. Expression of Rev, Tat and Vesicular Stomatitis Virus G proteins (VSV-G) are regulated by a Tet-Off/On system. We have improved the performance of the GPRTG cell line relative to GPRG by including the expression of HIV-1 Tat while decreasing the expression of Rev and by the independent re-insertion of the Rev, Tat and VSV-G packaging components. We generated a second fully stable producer, GPRTG-EF1α-hgcOPT, expressing the identical insulated SIN vector as in the first generation line. Both cell lines produce high titer vector preparations (>107 tu/ml) and are stable for at least 3 months of continuous passage. Although the vector titers are similar, GPRTG-EF1α-hgcOPT generated vector shows increased transduction efficiency of hCD34+ cells. PCR analysis of bulk CFU-GMs indicates a 2-fold increase in vector positive colonies and 3-5 fold increase in vector copy number with vector from GPRTG-EF1α-hgcOPT as compared to vector generated from GPRG-EF1α-hgcOPT when used at similar MOIs. We hypothesize that the basis for enhanced transduction efficiency of GPRTG derived vector is due to the expression of Tat and reduced expression of Rev each of which may affect vector transduction potency. In support of this hypothesis, our data show that transiently prepared vectors made with Rev only or in the presence of highly abundant Rev transduce hCD34+ cells less efficiently. We are currently employing the second generation cell line, GPRTG, to support future and on-going clinical protocols to treat other rare hematologic disorders including Wiskott-Aldrich Syndrome and Chronic Granulomatous Disease.