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FT819 is a first-of-kind, allogeneic, off-the-shelf CAR T-cell therapy derived from a clonal master induced pluripotent stem cell (iPSC) line precisely engineered to insert a novel 1XX anti-CD19 chimeric antigen receptor (CAR) under the regulation of the T-cell receptor alpha constant (TRAC) locus for optimized control of anti-tumor activity and to completely delete T-cell receptor (TCR) expression to eliminate the potential of graft-versus-host disease (GvHD). Unlike conventional allogeneic CAR T-cell therapies which require repeatedly sourcing of T cells from various donors as the starting material, the use of a clonal master engineered iPSC line serves as a renewable starting cell source and ensures routine mass production of a uniformly engineered, homogenous CAR T-cell product for broad patient access. T cell-derived iPSCs were generated using a proprietary non-integrating cellular reprogramming system and genetically modified to integrate a novel anti-CD19 1XX CAR into both alleles of the TRAC gene. After single cell subcloning, each engineered iPSC clone was screened for multiple critical quality attributes including pluripotency, identity, genomic stability, cassette integration, on/off-target integration, T-cell differentiation propensity, and CAR T-cell function. Accordingly, the ideal single cell-derived engineered iPSC clone was selected as the clonal master iPSC line for FT819 and was converted into a master cell bank (MCB). The iPSC MCB serves as a renewable source for the routine GMP manufacture of FT819 drug product. The FT819 production process consists of three stages: 1) generation of CD34-expressing hematopoietic progenitor cells from iPSCs (>90% CD34+ cells post enrichment); 2) lineage-specification to T cells followed by T-cell expansion (>5e5 fold expansion); and 3) fill/finish and cryopreservation of the drug product. As an example, in an initial small-scale manufacturing campaign, a total of 2.5 × 10 10 FT819 CAR T-cells were generated and filled and finished starting from one vial of the MCB. The FT819 drug product was tested on safety, identity, purity, and potency. The final product was comprised of CD45+CD7+ lymphocytes (>99%), with homogeneous CAR expression (>99% CAR+) and lacking expression of TCRαβ (not detected) on the cell surface. Importantly, there were no residual iPSCs detected in the FT819 drug product. The FT819 drug product exhibited potent and consistent effector function against NALM6 leukemia cells. The FT819 drug product is currently being used in a landmark Phase I study (NCT04629729), the first-ever iPSC-derived T-cell therapy to undergo clinical investigation, for the treatment of patients with relapsed/refractory B-cell lymphoma, chronic lymphocytic leukemia and precursor B-cell acute lymphoblastic leukemia. In summary, FT819 is a first-of-kind, off-the-shelf, CAR T-cell therapy uniquely derived from a clonal multiplexed-engineered master iPSC line. The novel manufacturing paradigm enables mass production of a uniformly engineered, homogenous cell therapy product that is available on-demand for broad patient access. A multi-center Phase 1 study of FT819 is currently ongoing for the treatment of B-cell malignancies. Key Words: cancer immunotherapy, cell therapy, CAR-T, CD19, allogeneic, induced pluripotent stem cell, iPSC, clonal master iPSC line, engineered, off-the-shelf, cGMP, production, manufacturing, FT819 Disclosures Yuan: Fate Therapeutics, Inc.: Current Employment. Clarke: Fate Therapeutics, Inc.: Current Employment. Lai: Fate Therapeutics, Inc.: Current Employment. Chang: Fate Therapeutics, Inc.: Current Employment. Yang: Fate Therapeutics, Inc.: Current Employment. Hsia: Fate Therapeutics, Inc.: Current Employment. Abujarour: Fate Therapeutics, Inc.: Current Employment. Lee: Fate Therapeutics, Inc.: Current Employment. van der Stegen: Fate Therapeutics, Inc.: Current Employment. Shaked: Fate Therapeutics, Inc.: Current Employment. Jalloh: Fate Therapeutics, Inc.: Current Employment. Moreno: Fate Therapeutics, Inc.: Current Employment. ORourke: Fate Therapeutics, Inc.: Current Employment. Sung: Fate Therapeutics, Inc.: Current Employment. Gutierrez: Fate Therapeutics, Inc.: Current Employment. Rezner: Fate Therapeutics, Inc.: Current Employment. Eberhart: Fate Therapeutics, Inc.: Current Employment. Magdaleno: Fate Therapeutics, Inc.: Current Employment. Farnan: Fate Therapeutics, Inc.: Current Employment. Plavsic: Fate Therapeutics, Inc.: Current Employment. Bressi: Fate Therapeutics, Inc.: Current Employment. Rivière: Centre for Commercialization of Cancer Immunotherapy: Other: Provision of Services; Fate Therapeutics: Other: Provision of Services, Patents & Royalties; The Georgia Tech Research Corporation (GTRC): Other: Provision of Services (uncompensated); FloDesign Sonics: Other: Provision of Services; Juno Therapeutics: Patents & Royalties. Valamehr: Fate Therapeutics, Inc.: Current Employment.

The development of chimeric antigen receptor (CAR) T cell therapeutics is widely recognized as a significant advancement for the treatment of cancer. However, several obstacles currently impede the broad use of CAR T cells, including the inherent process variability, cost of manufacturing, the absolute requirement for precise and uniform genetic editing in the allogeneic setting, and the challenge to keep pace with clonal heterogeneity and tumor growth. Utilizing our previously described induced pluripotent stem cell (iPSC)-derived T (iT) cell platform, we illustrate here the unique ability to address these challenges by creating a consistent CAR iT cell product that can be repeatedly manufactured in large quantities from a renewable iPSC master cell bank that has been engineered to mitigate the occurrence of graft versus host disease (GvHD), antigen escape and tumor relapse. Utilizing our proprietary cellular reprogramming and engineering platform and stage-specific T cell differentiation protocol, we demonstrate that iPSC can be engineered at the single cell level to generate a fully characterized clonal iPSC line, which can then be accessed routinely to yield CAR iT cells in a highly scalable manufacturing process (>100,000 fold expansion). Through bi-allelic targeting of a CAR into the T cell receptor alpha constant (TRAC) region, we generated CAR iT cells with uniform CAR expression (99.0 ± 0.5% CAR+) and complete elimination of T cell receptor (TCR) expression to avoid GvHD in the allogeneic setting. We elected to utilize the 1XX-CAR configuration, which has demonstrated superior anti-tumor performance relative to other CAR designs and when introduced into iT cells displayed enhanced antigen specificity (% specific cytotoxicity at E:T=10:1, antigen positive group: 86.4 ± 7.8; antigen null group: 8.9 ± 3.5). To enhance persistence without reliance on exogenous cytokine support, we engineered signaling-fusion complexes, including IL-7 receptor fusion (RF), into iPSC and studied its impact on iT phenotype, persistence, and efficacy. In vitro, IL-7RF clones demonstrated improved anti-tumor activity in a serial antigen dependent tumor challenge assay (Day 10, relative tumor counts, IL-7RF group: 1.95 ± 0.01; control group: 57.56 ± 4.55, P Collectively, the described studies demonstrate that iPSCs are an ideal cellular source to generate large-quantities of uniformly multi-edited off-the-shelf CAR T cell products that include a best-in-class CAR design, enhanced product modalities, and complete elimination of TCR expression to avoid the potential of GvHD while maintaining high anti-tumor efficacy in allogeneic setting. Disclosures Hsia: Fate Therapeutics Inc.: Current Employment. Clarke:Fate Therapeutics Inc.: Current Employment, Current equity holder in publicly-traded company. Lee:Fate Therapeutics, Inc.: Current Employment. Robbins:Fate Therapeutics, Inc.: Current Employment. Denholtz:Fate Therapeutics, Inc: Current Employment. Hanok:Fate Therapeutics, Inc.: Current Employment. Carron:Fate Therapeutics, Inc.: Current Employment. Navarrete:Fate Therapeutics, Inc.: Current Employment. ORourke:Fate Therapeutics, Inc.: Current Employment. Sung:Fate Therapeutics, Inc.: Current Employment. Gentile:Fate Therapeutics, Inc.: Current Employment. Nguyen:Fate Therapeutics, Inc.: Current Employment. Valamehr:Fate Therapeutics, Inc: Current Employment, Current equity holder in publicly-traded company.

Genetic engineering of T cells using a chimeric antigen receptor targeting CD19 antigen (CAR19) is now a well-established treatment of B cell malignancies. While cellular immunotherapies are entering front line treatment, substantial limitations currently hamper the broad application of adoptive T cell therapies in diverse patient population including dysfunctional starting material, lack of product consistency and purity post genetic engineering and inefficient quantity produced for true on-demand availability. FT819 is a first-of-kind off-the-shelf CAR19-T cell product generated from a renewable pluripotent stem cells for large-scale clinical manufacturing. We previously reported the engineering and characterization of the FT819 clonal master cell bank (MCB) derived from a single cell comprising targeted integration of a novel CD19 1XX CAR into the T-cell receptor (TCR) α constant locus to provide optimally regulated CAR expression and elimination of graft versus host (GvH) response. Here we preview the nonclinical study for the original investigational new drug application of FT819. Derived in a manufacturing process analogous to pharmaceutical drug product development, pilot runs from the MCB demonstrated FT819 can be consistently and uniformly manufactured in cGMP compliance, cryopreserved at clinical scale to support off-the-shelf clinical application with greater than 1e5 fold increase in cellular yield from the starting MCB and can be thawed and directly used for facilitated treatment. Repeatedly, FT819 displayed a uniform product profile of ≥95% CAR+, TCR-, CD45+, CD7+ and CD3+ [intracellular] with majority of CD8 T cells expressing CD8β. FT819 global gene expression profile displayed high similarity to primary CAR19-T cells confirming its identity as a T lymphocyte. Functional assessment demonstrated that FT819 possesses potent antigen specific cytolytic activity against leukemia and lymphoma cell lines (p=0.0004). Additional specificity studies demonstrated on-target, off-tumor cytolysis of CD19+ B cells in mixed lymphocyte reaction assay (85% lysis of CD19+ B cells versus < 2% lysis of T cells). Inability of FT819 to produce a GvH response was confirmed in a co-culture assay with anti-TCR crosslinking antibodies. Disseminated leukemia xenograft mouse studies demonstrated the ability of directly thawed and infused FT819 to control tumor growth (p=0.0003 at day 21). In a systemic administered leukemia model FT819 also showed sustained localization in the bone marrow up to 45 days post injection. Ongoing in vivo studies will assess long-term survival and avoidance of GvH disease. Collectively, these studies demonstrate that FT819 is a potent, consistent and uniform CAR19 T cell product and can be effectively and safely used off-the-shelf in the treatment of B cell malignancies with an original Phase 1 clinical trial planned in 2020. Citation Format: Mili Mandal, Raedun Clarke, Sjoukje van der Stegen, Chia-Wei Chang, Yi-Shin Lai, Alec Witty, Mushtaq Husain, Cheng-Jang Wu, Bi-Huei Yang, Chad Dufaud, Gloria Hsia, Helena Shaked, Laurel Stokely, Helen Chu, Mochtar Pribadi, Gilberto Hernandez, Jason ORourke, Alma Gutierrez, Ramzey Abujarour, Tom Lee, Jolanta Stefanski, Juan Zhen, Meilan Wu, Isabelle Riviere, Michel Sadelain, Bahram Valamehr. FT819 path to IND: First-of-kind off-the-shelf CAR19 T-cell for B cell malignancies [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3245.

Long-term follow-up of adoptive transfer of autologous T cells expressing a chimeric antigen receptor (CAR) directed to CD19 antigen has demonstrated encouraging, durable clinical outcome in various B cell malignancies. However, to make such CAR-T cells available to a broader base and to reach a more diverse patient population, challenges associated with product consistency, cost of manufacture, precision genetic engineering and on-demand availability still need to be addressed. FT819 is a first-of-kind off-the-shelf CAR-T cell product candidate derived from a renewable master pluripotent cell line. FT819 comprises precise genetic engineering of multiple targeting events at the single cell level and is produced using a clonally-derived master cell bank (MCB) that serves as the starting material to support consistent and reproducible clinical manufacturing. The engineered features of FT819 include the targeted integration of a novel CD19 1XX-CAR into the T-cell receptor α constant (TRAC) locus to provide antigen specificity, enhanced efficacy and temporally-regulated CAR expression driven by an endogenous (TCR) promoter. Such features are designed to also eliminate the possibility of graft versus host disease (GvHD) by nullifying the TCR. To develop the MCB for FT819, αβ T cells were reprogrammed into induced pluripotent stem cells (iPSCs) and subsequently engineered to direct CD19 1XX-CAR into the TRAC locus with knockout of the TCR. To generate clonal lines, engineered iPSCs were sorted by flow cytometry for various markers and single cells were seeded into individual wells of feeder-free 96-well plates. Engineered iPSC clones were screened for integration of CAR into the TRAC locus by amplifying the genomic DNA flanking the homologous recombination site and confirmed by a SNP phasing assay. Clones were further screened for random integration of donor template by quantitative PCR and the CAR copy number was confirmed by droplet digital PCR. Genome stability of each clone was also confirmed by karyotype analysis. Overall, the described screening initiative surveyed 774 clones to select the ideal MCB for FT819. Utilizing our stage-specific T cell differentiation and expansion protocol, we demonstrated that T cells derived from the FT819 (FT819-iTs) expanded greater than 100,000-fold during the clinical manufacturing process and the cells expressed greater than 95% T lymphocyte markers such as CD45, CD7, intracellular CD3, and TRAC-regulated CAR. Further modifications to the T cell differentiation protocol resulted in enhanced expression of CD8 αβ from less than 25% to greater than 70% of the total population. In addition, expression of CD2, CD5, and CD27 was increased by approximately 5- to 20-fold. In vitro functional studies showed that FT819-iTs possess antigen specificity as confirmed by cytokine release and cytotoxic T lymphocytes (CTL) assays. Upon stimulation with a wild type acute lymphoblastic leukemia line, Nalm-6, FT819-iTs expressed 30% CD107a/b compared to 2% when stimulated by Nalm-6 CD19KO. In an in vitro CTL assay, greater than 80% of Nalm-6 WT cells were lysed with effector to target (E:T) ratio at 10:1 as compared to Nalm-6-CD19KO, which showed less than 10% lysis at the same E:T ratio. Finally, in an in vivo tumor model, FT819-iTs generated from our original and modified T cell differentiation protocols showed similar tumor burden control and prolonged survival rate when compared to primary CAR-T cells (days of survival >80days, p>0.1). In a more stringent in vivo model, FT819-iTs generated from the modified differentiation protocol demonstrated higher anti-tumor response and better animal survival rate compared to iTs from the original T cell differentiation protocol (Day 30 p Disclosures Chang: Fate Therapeutics: Employment. Van Der Stegen:Memorial Sloan Kettering Cancer Center: Employment. Mili:Fate Therapeutics: Employment. Clarke:Fate Therapeutics: Employment. Lai:Fate Therapeutics: Employment. Witty:Fate Therapeutics: Employment. Lindenbergh:Memorial Sloan Kettering Cancer Center: Employment. Yang:Fate Therapeutics: Employment. Husain:Fate Therapeutics: Employment. Shaked:Fate Therapeutics: Employment. Groff:FATE THERAPEUTICS: Employment. Stokely:Fate Therapeutics: Employment. Abujarour:Fate Therapeutics, Inc.: Employment. Lee:Fate Therapeutics, Inc.: Employment. Chu:Fate Therapeutics: Employment. Pribadi:Fate Therapeutics, Inc.: Employment. ORourke:Fate Therapeutics: Employment. Gutierrez:Fate Therapeutics: Employment. Riviere:Juno Therapeutics: Consultancy, Equity Ownership, Research Funding; Fate Therapeutics: Consultancy; Memorial Sloan Kettering Cancer Center: Employment. Sadelain:Memorial Sloan Kettering Cancer Center: Employment; Fate Therapeutics: Consultancy, Patents & Royalties; Juno Therapeutics: Consultancy, Patents & Royalties, Research Funding. Valamehr:Fate Therapeutics, Inc: Employment.

Human pluripotent stem cells (PSCs) provide a promising resource to produce immune cells for adoptive cellular immunotherapy to better treat and potentially cure otherwise lethal cancers. Cytotoxic T cells and natural killer (NK) cells can now be routinely produced from human PSCs. These PSC-derived lymphocytes have phenotype and function similar to primary lymphocytes isolated from peripheral blood. PSC-derived T and NK cells have advantages compared with primary immune cells, as they can be precisely engineered to introduce improved anti-tumor activity and produced in essentially unlimited numbers.

Adoptive transfer of autologous T cells expressing chimeric antigen receptor (CAR) has shown great promise in the treatment of blood malignancies. Challenges for the application of current CAR T cell therapies to broader and more diverse patient populations include inherent variability, cost of manufacture, and the requirement for precise genetic engineering to generate a highly homogenous and consistent CAR T cell product. We have previously reported pre-clinical data supporting the development of FT819, a first-of-kind off-the-shelf CAR T cell product candidate. FT819 is generated from a renewable clonal master human induced pluripotent stem cell (hiPSC) line derived from a single cell engineered to contain bi-allelic disruption of the T cell receptor (TCR) and a novel CD19 CAR targeted into the T cell receptor α constant (TRAC) locus to provide antigen specificity and enhanced efficacy while eliminating the possibility of graft versus host disease. For the manufacture of a clinical-grade FT819 clonal master hiPSC line, we sourced peripheral blood mononuclear cells from a fully consented and eligible donor with protocol overseen by an independent Institutional Review Board. Sourced T cells were enriched (>98%) through positive selection for TCRαβ, and cryopreserved cells were confirmed to have stable genome by karyotyping. Using our proprietary non-integrating cellular reprogramming platform, αβ T cells were reprogrammed into hiPSCs. Concurrently with the reprogramming process, reprogrammed cells received nuclease and donor template to mediate targeting of CD19 CAR into the TRAC locus with bi-allelic knockout of the TCR. To generate clonal lines, engineered cells were sorted by flow cytometry for various markers and single cells were seeded into individual wells of feeder-free 96-well plates. hiPSC clones were screened for bi-allelic integration of CAR into the TRAC locus by amplifying the genomic DNA flanking the homologous recombination site and confirmed by a SNP phasing assay. Clones were further screened for random integration of donor template by quantitative PCR (qPCR), and the CAR copy number was confirmed by droplet digital PCR. Out of 545 hiPSC clones screened, 27 clones (5%) had bi-allelic TRAC targeting with no detectable random integration. Maintenance of pluripotency was confirmed in 19 out of the 27 engineered hiPSC clones (70%). Seventeen clones were further tested and were confirmed to be footprint-free of transgenic reprogramming factors. Of the 18 clones tested for genomic stability, 12 clones had normal karyotypes (67%). Validated, TRAC-targeted hiPSC clones were cryopreserved (~150 vials per clone) and are currently being assessed for off-target editing, differentiation propensity into highly-functional T cells, genomic stability, clone identity, sterility and lack of mycoplasma detection. In summary, using our novel iPSC technology platform for reprogramming, single cell engineering and multiplex high-throughput screening of hiPSCs, we have generated clinical-grade clonal master hiPSC lines in support of our first-of-kind clinical trials evaluating FT819 allogenic off-the-shelf hiPSC-derived TCR-less TRAC-CAR19 T cells for the treatment of blood malignancies. Citation Format: Ramzey Abujarour, Yi-Shin Lai, Mochtar Pribadi, Tom Lee, Megan Robinson, Chelsea Ruller, Sjoukje Van der Stegen, Xiuyan Wang, Jolanta Stefanski, Juan Zhen, Jason Dinella, Greg Bonello, Janel Huffman, Helen Chu, Raedun Clarke, Alec Witty, Amanda Medcalf, Jaeger Davis, Stacey Moreno, Pieter Lindenbergh, Isabelle Riviere, Michel Sadelain, Bahram Valamehr. Generation of novel single cell-derived engineered master pluripotent cell line as a renewable source for off-the-shelf TCR-less CAR T cells in support of first-of-kind clinical trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-073.

The advent of off-the-shelf chimeric antigen receptor (CAR) T cell therapeutics is widely recognized to be a major potential advancement for the treatment of cancer. Several obstacles currently hamper the broad use of CAR T cells, including the inherent variability and cost of manufacturing of autologous cellular populations, the absolute requirement for precise genetic editing in the allogeneic setting, and the challenge to keep pace with clonal heterogeneity. Here we present pre-clinical data for FT819, a first-of-kind off-the-shelf human induced pluripotent stem cell (hiPSC)-derived CAR T cell product. FT819 is defined by the precise genetic engineering of multiple targeting events at the single cell level to create a clonal master iPSC line. The engineered features include the targeted integration of a novel, modified CD19 CAR into the T cell receptor α (TRAC) locus to provide antigen specificity and enhanced efficacy while eliminating the possibility of graft versus host disease (GvHD), and the expression of a high-affinity, non-cleavable form of CD16 (hnCD16) to deliver an adjustable system to address tumor antigen escape. Through a proprietary cellular reprogramming platform, peripheral blood derived T cells are converted to hiPSCs, engineered to contain the modified CD19 CAR targeted into the TRAC locus and hnCD16, and clonally selected to create a master hiPSC line (TRAC-TiPSC, FT819). Molecular characterization of the TRAC-TiPSC master cell line by 5' junction, 3' junction and internal sequence PCR confirmed homology directed repair and bi-allelic targeting of the CD19 CAR into the TRAC locus. The origin of the clonal master cell bank was confirmed to be a TCRαβ T cell by PCR-mediated detection of TCRδ locus deletion and methyl-seq analysis of the TCRα locus. Flow cytometric analysis demonstrated the maintenance of a uniform population of hiPSCs (>95% SSEA4/TRA-1-81/OCT4/NANOG) and expression of hnCD16 transgene (>95% CD16). Utilizing our stage-specific T cell differentiation protocol, we demonstrate that the TRAC-TiPSCs yield TRAC-iT cells with uniform expression of the CAR (>95%), complete elimination of TCR surface expression and clinically enabling expansion through the manufacturing process (>50,000 fold). To confirm the lack of alloreactivity conferred by the deletion of endogenous TCR expression, mixed lymphocyte reactions were performed using TRAC-iT, primary TCR+ T cells and primary TCR+CAR+ T cells as responders and HLA-mismatched peripheral blood mononuclear cells (PBMCs) as targets. In comparison to primary T cells and primary CAR-T cells, TRAC-iT did not respond and proliferate in response to TCR stimulation or HLA-mismatched PBMCs indicating that the risk of GvHD was alleviated. In vitro functional studies established that TRAC-iT possess a potent cytotoxic T lymphocyte response to CD19 antigen challenge in a similar manner to peripheral blood CAR T cells as demonstrated by expression of markers indicative of degranulation (CD107a/b, Granzyme B), T cell activation (CD69, CD25), and production of INFγ, TNFα and IL2. Importantly, TRAC-iT targeted tumor in an antigen specific manner as verified by lysis of CD19+, but not CD19-, tumor cell lines as seen by in vitro cytolytic assays (50% killing E:T; TRAC-iT = 1:8, primary CAR-T = 1:4). In vivo studies demonstrated that TRAC-iT cells effectively control tumor progression in a mouse model of acute lymphoblastic leukemia Nalm6 (TRAC-iT versus no treatment, p Disclosures Clarke: Fate Therapeutics Inc.: Employment. Chang:Fate Therapeutics Inc.: Employment. Husain:Fate Therapeutics Inc.: Employment. Lai:Fate Therapeutics Inc.: Employment. Peralta:Fate Therapeutics Inc.: Employment. Stokely:Fate Therapeutics Inc.: Employment. Abujarour:Fate Therapeutics Inc.: Employment. Dinella:Fate Therapeutics Inc.: Employment. Lee:Fate Therapeutics Inc.: Employment. Pribadi:Fate Therapeutics Inc.: Employment. Chu:Fate Therapeutics Inc.: Employment. Truong:Fate Therapeutics Inc.: Employment. Sabouri-Ghomi:Fate Therapeutics Inc.: Employment. Meza:Fate Therapeutics Inc.: Employment. Riviere:Juno Therapeutics, a Celgene Company: Membership on an entity's Board of Directors or advisory committees, Research Funding; Fate Therapeutics Inc.: Research Funding. Sadelain:Juno Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Fate Therapeutics Inc.: Research Funding. Valamehr:Fate Therapeutics Inc.: Employment.

To gain insight into mechanisms controlling SRY (sex determining region Y)-box 2 (Sox2) protein activity in mouse embryonic stem cells (ESCs), the endogenous Sox2 gene was tagged with FLAG/Hemagglutinin (HA) sequences by homologous recombination. Sox2 protein complexes were purified from Sox2/FLAG/HA knockin ESCs, and interacting proteins were defined by mass spectrometry. One protein in the complex was poly ADP-ribose polymerase I (Parp1). The results presented below demonstrate that Parp1 regulates Sox2 protein activity. In response to fibroblast growth factor (FGF)/extracellular signal-regulated kinase (ERK) signaling, Parp1 auto-poly ADP-ribosylation enhances Sox2-Parp1 interactions, and this complex inhibits Sox2 binding to octamer-binding transcription factor 4 (Oct4)/Sox2 enhancers. Based on these results, we propose a unique mechanism in which FGF signaling fine-tunes Sox2 activity through posttranslational modification of a critical interacting protein, Parp1, and balances the maintenance of ESC pluripotency and differentiation. In addition, we demonstrate that regulation of Sox2 activity by Parp1 is critical for efficient generation of induced pluripotent stem cells.

Background Volume overload is frequently encountered and is associated with cardiovascular risk factors in patients with chronic kidney disease ( CKD) . However, the relationship between volume overload and adverse outcomes in CKD is not fully understood. Methods and Results A prospective cohort of 338 patients with stage 3 to 5 CKD was followed for a median of 2.1 years. The study participants were stratified by the presence or absence of volume overload, defined as an overhydration index assessed by bioimpedance spectroscopy exceeding 7%, the 90th percentile for the healthy population. The primary outcome was the composite of estimated glomerular filtration rate decline ≥50% or end‐stage renal disease. The secondary outcome included a composite of morbidity and mortality from cardiovascular causes. Animal models were used to simulate fluid retention observed in human CKD . We found that patients with volume overload were at a higher risk of the primary and secondary end points in the adjusted Cox models. Furthermore, overhydration appears to be more important than hypertension in predicting an elevated risk. In rats subjected to unilateral nephrectomy and a high‐salt diet, the extracellular water significantly increased. This fluid retention was associated with an increase in blood pressure, proteinuria, renal inflammation with macrophage infiltration and tumor necrosis factor‐α overexpression, glomerular sclerosis, and cardiac fibrosis. Diuretic treatment with indapamide attenuated these changes, suggesting that fluid retention might play a role in the development of adverse outcomes. Conclusions Volume overload contributes to CKD progression and cardiovascular diseases. Further research is warranted to clarify whether the correction of volume overload would improve outcomes for CKD patients.

We have recently used CRISPR-Cas to correct the HBB gene in induced Pluripotent Stem Cells (iPSC) derived from patients with Sickle Cell Disease (SCD) and to correct the JAK3 gene in iPSC derived from patients with Severe Combine Immune Deficiency (SCID). Off-target mutations were minimized, if not eliminated, by use of paired guide RNAs and the Cas9 nickase. When erythroid progenitors (EP) produced from corrected SCD iPSC are transplanted into NSG mice, a complete switch from gamma- to beta-globin gene expression occurs within 24 hours and high levels of beta mRNA are synthesized; the betaA:betaS ratio is 60:40. Hematopoietic progenitors produced from corrected SCID iPSC can be differentiated into T cell populations that express a full repertoire of T Cell Receptors (TCRs). These results suggest that CRISPR-Cas enhanced gene replacement may provide safe and effective therapies for many erythroid and lymphoid disorders. In an alternative approach, we electroporated a preformed, biochemical complex composed of a guide RNA (gRNA), a modified recombinant Cas9 (mrCas9) and a single stranded oligodeoxnucleotide (ssODN) into sickle iPSC or primary sickle CD34+ hematopoietic progenitors. Sixty-five percent of sickle iPSC colonies contained at least one corrected allele. When homozygous corrected colonies were differentiated into erythroid progenitors and transplanted into NSG mice, human erythroid cells expressed 100% HbA. When primary sickle CD34+ hematopoietic progenitors were electroporated with the gRNA/mrCas9/ssODN complex and differentiated into erythroid cells in vitro, HbA was expressed at 30-40%. These results suggest that primary bone marrow CD34+ cells that are isolated from patients with sickle cell disease, beta-thalassemia, SCID, DBA and other hematopoietic disorders may be electroporated with specific gRNA/mrCas9/ssODN complexes and transplanted into patients to rapidly, safely and effectively treat these debilitating disorders. Disclosures No relevant conflicts of interest to declare.

We report the derivation of induced pluripotent stem (iPS) cells from adult skin fibroblasts using a single, polycistronic lentiviral vector encoding the reprogramming factors Oct4, Sox2, and Klf4. Porcine teschovirus-1 2A sequences that trigger ribosome skipping were inserted between human cDNAs for these factors, and the polycistron was subcloned downstream of the elongation factor 1 alpha promoter in a self-inactivating (SIN) lentiviral vector containing a loxP site in the truncated 3′ long terminal repeat (LTR). Adult skin fibroblasts from a humanized mouse model of sickle cell disease were transduced with this single lentiviral vector, and iPS cell colonies were picked within 30 days. These cells expressed endogenous Oct4, Sox2, Nanog, alkaline phosphatase, stage-specific embryonic antigen-1, and other markers of pluripotency. The iPS cells produced teratomas containing tissue derived from all three germ layers after injection into immunocompromised mice and formed high-level chimeras after injection into murine blastocysts. iPS cell lines with as few as three lentiviral insertions were obtained. Expression of Cre recombinase in these iPS cells resulted in deletion of the lentiviral vector, and sequencing of insertion sites demonstrated that remnant 291-bp SIN LTRs containing a single loxP site did not interrupt coding sequences, promoters, or known regulatory elements. These results suggest that a single, polycistronic “hit and run” vector can safely and effectively reprogram adult dermal fibroblasts into iPS cells. Disclosure of potential conflicts of interest is found at the end of this article.

SummaryMutations of the Janus family kinase JAK3 gene cause severe combined immunodeficiency (SCID). JAK3 deficiency in humans is characterized by the absence of circulating T cells and natural killer (NK) cells with normal numbers of poorly functioning B cells (T–B+NK–). Using SCID patient-specific induced pluripotent stem cells (iPSCs) and a T cell in vitro differentiation system, we demonstrate a complete block in early T cell development of JAK3-deficient cells. Correction of the JAK3 mutation by CRISPR/Cas9-enhanced gene targeting restores normal T cell development, including the production of mature T cell populations with a broad T cell receptor (TCR) repertoire. Whole-genome sequencing of corrected cells demonstrates no CRISPR/Cas9 off-target modifications. These studies describe an approach for the study of human lymphopoiesis and provide a foundation for gene correction therapy in humans with immunodeficiencies.