ALBERT

Description: Monoclonal antibody (mAb) treatment is an effective therapeutic strategy for many cancer types, though there remains meaningful opportunity to improve mAb efficacy by optimizing the interaction with natural killer (NK) cells to enhance antibody-dependent cellular cytotoxicity (ADCC). NK cells are an ideal effector cell for combined use with tumor-targeting mAbs, as NK cells effect both innate tumoricidal capacity and ADCC. CD38-targeting mAbs, such as daratumumab, are effective in treating multiple myeloma (MM) and achieve their efficacy through multiple mechanisms, including ADCC. However, because activated NK cells express high levels of CD38, daratumumab induces NK cell depletion through fratricide, potentially reducing treatment effectiveness. Adoptive NK cell immunotherapy therefore has the potential to augment daratumumab's ADCC activity if fratricide can be reduced or prevented. FT538 is an off-the-shelf adoptive NK cell immunotherapy product candidate designed for enhanced cellular persistence and ADCC while avoiding anti-CD38 mAb induced fratricide. It is derived from induced pluripotent stem cells (iPSC) engineered to lack CD38 expression, which we have previously shown to eliminate daratumumab-induced fratricide among iPSC-derived NK cells, resulting in enhanced long-term daratumumab-mediated ADCC. FT538 is engineered to express an IL-15 receptor alpha fusion protein (IL-15RF; IL-15 tethered to IL-15 receptor α) to enhance persistence and a high-affinity non-cleavable CD16 (hnCD16, FcRγIII) to increase ADCC. To support the clinical translation of FT538, and to enable the repeatable and scalable cell production to support off-the-shelf availability of a uniform NK cell product, a clinical-grade master pluripotent stem cell line was developed. The FT538 master pluripotent stem cell line was created by reprogramming donor fibroblasts into iPSCs using our non-integrating cellular reprogramming platform, and cells were further genetically edited by targeting IL-15RF and hnCD16 to the CD38 locus. Clonal iPSC lines were generated and screened for precise knock-in and knock-out edits at the CD38 locus and a lack of off-target genome integration (15% total success rate for CD38-/-IL-15RF+CD16+). Selected engineered iPSC clones were confirmed to be free of reprogramming transgenes and to maintain genomic stability. Engineered iPSC clones were additionally tested for their NK cell differentiation potential and function, and a single clone was selected to serve as the renewable starting material for cGMP manufacturing and clinical development. Upon differentiation and expansion FT538 demonstrated a mature NK cell phenotype with expression of NK cell receptors including NKp30, NKp46, NKG2D, KIR, NKG2A, and DNAM-1. The functional impact of CD38 knockout on FT538 NK cells was confirmed in an in vitro fratricide assay, where peripheral blood (PB)-NK cells exhibited fratricide at a frequency of 33% after 3 hr culture with increasing daratumumab concentrations. In contrast, FT538 cells were entirely resistant (

Description: As the field of human induced pluripotent stem cell (hiPSC) research continues to advance, and as the clinical investigation of genetically-engineered hiPSC-derived cellular therapeutics begins to emerge, safety concerns relating to the administration of genetically-altered cells must be addressed and mitigated. A number of strategies including recombinant peptides, monoclonal antibodies, small molecule-modulated enzyme activity and gene-specific modifications have been explored to facilitate the selective elimination of aberrant cells. Of these, the application of genetically-encoded inducible "suicide" systems that can be rapidly activated by a specific non-toxic chemical inducer represents a very attractive, targeted approach for eliminating administered cells without damaging surrounding cells and tissues. Most previous studies have employed viral vectors and short promoters to stably introduce suicide-genes, including herpes complex virus thymidine kinase or inducible caspase-9 (iCasp9), into human cells. The use of viral vectors can lead to random integration events which can disrupt or activate disease-related genes, potentially causing deleterious effects. In addition, many artificial promoters and genome regions are prone to epigenetic silencing in both pluripotent and differentiated states, resulting in cells becoming unresponsive to suicide gene induction. Thus, it is of great importance to identify optimal integration sites and promoters in order to maintain functional suicide gene responses and facilitate the development of genetically-engineered cellular therapeutics. To effectively select and test suicide systems under the control of various promoters in combination with different safe harbor loci integration strategies, we took advantage of our proprietary hiPSC platform, which enables single cell passaging and high-throughput, 96-well plate-based flow cytometry sorting. In a single hiPSC per well manner, we utilized both nuclease-independent and nuclease-dependent strategies to efficiently and precisely integrate various suicide gene expression cassettes in AAVS1 or ROSA26 safe harbor loci. Several integration vectors, each containing a suicide gene expression cassette downstream of various exogenous and endogenous promoters, including endogenous AAVS1 or ROSA26, cytomegalovirus, elongation factor 1α, phosphoglycerate kinase, hybrid CMV enhancer/chicken β-actin and ubiquitin C promoters, were tested to systematically analyze and compare the activity of different suicide systems in both hiPSCs and hiPSC-derived differentiated cells. To conduct high-throughput analyses of these integration and expression strategies, we selected an iCasp9 suicide gene platform where rapid caspase-9 mediated cell death can be induced by small molecule chemical inducers of dimerization such as AP1903. Several endogenous promoters were found to drive persistent expression of iCasp9 during clonal expansion of hiPSCs, but the expression level was determined to be too low to effectively respond to AP1903 treatment. Expression of iCasp9 under the control of various exogenous promoters was lost during prolonged clonal expansion of hiPSCs, and failed to drive AP1903-induced cell death. However, one promoter maintained high levels of iCasp9 expression during the long-term clonal expansion of hiPSCs. Furthermore, these iCasp9-integrated clonal lines underwent rapid cell death in the presence of AP1903, and no residual cell survival was observed when cultures were allowed to recover in the absence of the dimerizing molecule. To test whether epigenetic landscape alterations would abrogate suicide gene-mediated response, hiPSC clones were differentiated into three somatic lineages in vitro and were found to be completely subject to AP1903-induced cell death. Clones were also specifically differentiated towards hematopoietic cells to demonstrate complete induction of cell death by AP1903 treatment. When injected into NSG mice to form teratomas, similar cell death-mediated response was observed in vivo. Notably, one hiPSC clone contained certain rare cells and did escape induced cell death, and this clone and these rare cells were characterized to assess the molecular mechanisms of escape. Our study describes novel findings toward designing optimal safety systems for integration into hiPSC-derived cellular therapies. Disclosures Huang: Fate Therapeutics Inc: Employment. Lan:Fate Therapeutics Inc: Employment. Parone:Fate Therapeutics Inc: Employment. Clarke:Fate Therapeutics Inc: Employment. Abujarour:Fate Therapeutics Inc: Employment. Robinson:Fate Therapeutics Inc: Employment. Meza:Fate Therapeutics Inc: Employment. Lee:Fate Therapeutics Inc: Employment. Shoemaker:Fate Therapeutics Inc: Employment. Valamehr:Fate Therapeutics Inc: Employment.

Description: Cellular immunotherapies are poised to transform the treatment of cancer and immunological disorders. In the most promising setting to date, genetic modification to the T lymphocytes in the form of chimeric antigen receptors (CAR) has dramatically increased therapeutic efficacy with reported initial complete remission rates in acute lymphoblastic leukemia ranging between 80-100%. However, pressing challenges remain to be solved to ensure that engineered T-cell immunotherapies can be cost-effectively and consistently manufactured, and safely and reliably delivered at the scale necessary to support wide patient base commercialization. Human induced pluripotent stem cell (hiPSC) derived T lymphocytes represent a unique, renewable source of genetically engineered T cells for "off-the-shelf" immunotherapy. Through the precise genetic engineering at the hiPSC stage, clonal and uniform populations of modified cell lines can be banked and reliably tapped into on demand to generate highly efficacious T cells for therapeutic applications. Although great progress has been made, several challenges need to be addressed including the ability to enhance effector function through genome-engineering of persistence, targeting, histocompatibility and controlled safety mechanisms at the hiPSC juncture while retaining the capacity to efficiently and reproducibly generate the intricate stages of lymphocyte development in an accurate and scalable process. We have previously demonstrated that our proprietary reprogramming platform supports efficient and rapid derivation of clonal hiPSC lines with properties indicative of the naïve state of pluripotency. In addition to maintaining a homogeneous population of hiPSCs, our platform enables efficient multi-gene and multi-loci targeted engineering at a single cell level resulting in clonal population of pluripotent cell lines with desired genetic attributes. Here we will provide an update on our "off-the-shelf" T-cell immunotherapy preclinical program where engineered hiPSC lines are uniquely used as the renewable starting material. We will also highlight our novel differentiation platform to derive definitive hematopoietic progenitor cells termed hemogenic endothelium (HE); a well-defined, small molecule-driven, staged process that is currently being translated into cGMP (current good manufacturing practice) settings. The highly efficient differentiation system (on average 〉65% hiPSC to CD34 conversion) delivers approximately 100 CD34+ HE cells per each input hiPSC, representing a highly scalable process that is further expanded during lymphocyte differentiation and maturation. To validate that the iCD34+ HE is definitive in nature we demonstrate that during further hematopoietic differentiation the emerging CD43+ hematopoietic cells exhibit Notch dependency and high expression of key genes such as MYB and the HOXA cluster, found only in definitive hematopoietic progenitors. The hiPSC-derived HE exhibits multi-lineage potential and can be successfully cryopreserved and banked, serving as a highly-stable cell bank for subsequent therapeutic use. Through genetic modifications at the single cell hiPSC stage, we confer antigen-specificity via the expression of temporally inducible CARs as premature expression of CAR proteins during in vitro differentiation has been found to skew development towards innate-lymphoid like lineages. Utilizing our stage-specific hematopoietic differentiation platform we have identified the optimal developmental window to induce the expression of CAR proteins to maintain optimal differentiation towards functional effector lymphocytes. The hiPSC-derived engineered T lymphocytes are currently under preclinical investigation for in vitro and in vivo effector function including thymic rejuvenation, T cell repertoire repopulation, target specific recognition and enhanced killing potential. Preliminary data suggests that hiPSC-derived lymphocytes are functional and can home to their respective niche to support initial repopulation in vivo. Our study continues to support that naïve hiPSCs are an ideal renewal source for "off-the-shelf" hematopoietic cell-based immunotherapies and represent a potentially exponential advancement in adoptive T cell therapy. Disclosures Clarke: Fate Therapeutics: Employment. Groff:Fate Therapeutics: Employment. Sasaki:Fate Therapeutics: Employment. Bauer:Fate Therapeutics: Employment. Lee:Fate Therapeutics: Employment. Lan:Fate Therapeutics: Employment. Burrascano:Fate Therapeutics: Employment. Abujarour:Fate Therapeutics: Employment. Bonello:Fate Therapeutics: Employment. Robinson:Fate Therapeutics: Employment. Foster:Fate Therapeutics: Employment, Equity Ownership. Robbins:Fate Therapeutics: Employment, Equity Ownership. Wolchko:Fate Therapeutics: Employment. Shoemaker:Fate Therapeutics: Employment, Equity Ownership. Abbot:Fate Therapeutics: Employment. Valamehr:Fate Therapeutics, Inc: Employment.

Description: Induced pluripotent stem cell (iPSC)-derived effector cells offer distinct advantages for immune therapy over existing patient- or donor- derived platforms, both in terms of scalable manufacturing from a renewable starting cellular material and precision genetic engineering that is performed at the single-cell level. iPSC derived natural killer (iNK) cells offer the further advantage of innate reactivity to stress ligands and MHC downregulation and the potential to recruit downstream adaptive responses. These unique features form the basis of our multi-antigen targeted chimeric antigen receptor (CAR) CAR-iNK cell product candidate, termed FT596, which is further combined with additional functionality to enhance effector function. FT596 is consistently manufactured from a master iPSC line engineered to uniformly express an NK cell-calibrated CD19-targeting CAR (CD19-CAR), an enhanced functioning high-affinity, non-cleavable CD16 (hnCD16) and a recombinant fusion of IL-15 and IL-15 receptor alpha (IL-15RF) for cytokine-autonomous persistence. The design of the CD19-CAR involved exploiting the intrinsic polyfunctionality of NK cells, which function by engaging multiple signaling pathways activated through combinations of distinct germline encoded receptors. Using this approach, the transmembrane region of activating receptor NKG2D, combined with the intracellular signaling domains of SLAM co-receptor 2B4 and CD3ζ, proved the most effective in triggering antigen specific functional responses in NK cells. Chimerization of an anti-CD19 scFv onto this NKG2D-2B4-CD3ζ signaling platform produced specific in vitro recognition of CD19+ B cell lymphoma cells in short-term and long-term NK cytotoxicity assays (〉80% and

Description: Encouraging clinical outcomes in autologous cellular immunotherapy have garnered hope and excitement. However, considerable challenges and limitations of patient-derived cancer immunotherapies remain and need to be addressed in order to consistently deliver reliable and efficacious therapies with broadened applicability. Human induced pluripotent stem cells (hiPSCs) are a unique, renewable source for the continuous generation of cellular therapeutics for the treatment of hematological and non-hematological malignancies, and represent a highly promising approach for overcoming many of the limitations of autologous therapy. To advance the promise of hiPSC technology as an "off-the-shelf" source of cellular therapeutics, several considerations need to be addressed. Enabling cell transfer across histocompatibility barriers to permit persistence and therapeutic efficacy in an allogeneic setting is a key requirement. In addition to improving persistence, the ability to overcome histocompatibility barriers may facilitate multi-dosing regimens which may be a requirement in more advanced and complicated disease settings. Genetic incompatibilities between donor and recipient among the classical human leukocyte antigen (HLA) molecules is the leading cause of alloresponse by the host immune system and is currently mitigated by immunosuppressive strategies. Unfortunately, this treatment strategy is not only a stressful event for the patient but also damages the endogenous immune system, compromising the patient's ability to continue to fight the disease and opportunistic infections. Genetic editing of the HLA genes to generate histocompatible universal cell products is a viable opportunity that is currently being investigated. In addition to selective editing of unique genes to avoid a T cell mediated alloresponse, additional considerations such as natural killer (NK) cell-mediated rejection will need to be addressed. We have previously demonstrated that our proprietary reprogramming platform supports efficient and rapid derivation of clonal hiPSC lines with properties indicative of the naïve state of pluripotency. In addition to maintaining a homogeneous renewable population of hiPSCs, our platform is amenable to precise multi-gene and multi-loci targeted engineering at the single cell level, in both nuclease -dependent and -independent strategies. Furthermore, we have shown through small molecule-guided differentiation protocols, these highly-stable pluripotent cell lines can be banked and repeatedly tapped to consistently produce homogenous populations of immune cells with enhanced effector properties. Here we demonstrate a multi-faceted and comprehensive approach for the generation of immune tolerant hiPSCs and hiPSC-derived immune effector cells. We successfully combined deletion of classical HLA molecules with enforced expression of robust immunosuppressive proteins, including non-classical HLA molecules, to generate clonal hiPSC lines with the ability to escape immune rejection for "off-the-shelf" (OTS-hiPSCs) cellular immunotherapy. Utilizing in vitro real-time quantitative live cell analysis we determined that OTS-hiPSCs elicit a significantly decreased cytotoxic response from both activated peripheral blood (PB)-NK cells and primed PB-T cells compared to wildtype controls. Furthermore we demonstrate that OTS-hiPSCs exhibit improved persistence in xenograft studies in vivo. Bilateral teratomas were formed in a non-conditioned, fully immune-competent recipient mice using luciferized wildtype and OTS-hiPSCs. Daily bioluminescence imaging over a period of 7 days revealed a significant increase (〉50 fold difference) in persistence of OTS-hiPSCs compared to wildtype hiPSCs during the 60-144 hour post injection window. Lastly we demonstrate that OTS-hiPSCs can successfully differentiate into functional effector lymphocytes using our potent chemically-defined monolayer hematopoietic differentiation platform. Our current studies focus on the functional characterization of OTS-hiPSC-derived effector lymphocytes in humanized mouse models and generating increased potency of OTS-hiPSC-derived effector lymphocytes through precise genetic engineering of antigen targeting and costimulatory proteins to create and optimized source of "off-the-shelf" cell-based immunotherapies. Disclosures Bauer: Fate Therapeutics: Employment. Clarke:Fate Therapeutics: Employment. Sasaki:Fate Therapeutics: Employment. Groff:Fate Therapeutics: Employment. Lee:Fate Therapeutics: Employment. Lan:Fate Therapeutics: Employment. Abujarour:Fate Therapeutics: Employment. Bonello:Fate Therapeutics: Employment. Burrascano:Fate Therapeutics: Employment. Robinson:Fate Therapeutics: Employment. Bjordahl:Fate Therapeutics, Inc: Employment. Gaidarova:Fate Therapeutics: Employment. Abbot:Fate Therapeutics: Employment. Wolchko:Fate Therapeutics: Employment. Shoemaker:Fate Therapeutics: Employment, Equity Ownership. Valamehr:Fate Therapeutics, Inc: Employment.

Description: Human induced pluripotent stem cells (hiPSCs) are a unique population of cells that can serve as an unlimited source for "off-the-shelf" cellular immunotherapeutics. Similar to master cell lines used in the manufacture of monoclonal antibodies, engineered hiPSC lines have the potential to serve as a renewable cell source for the consistent manufacture of homogeneous populations of effector cells for the treatment of thousands of patients. However, the creation of an effective master line is largely dependent on the ability to genetically edit hiPSCs in a precise, efficient and clonal manner. Furthermore, the genetically edited hiPSCs must maintain their inherent ability to continuously self-renew while retaining ability to express engineered modalities upon directed differentiation to the cell type of choice. We have previously reported the use of stage-specific media compositions to enable the footprint-free generation and long-term maintenance of single cell naïve hiPSCs with enhanced clonogenicity, an attribute critical for the derivation of engineered single cell-derived lines. Here we demonstrate the use of our naïve hiPSC platform to precisely introduce, in a site-specific manner, multiple genes into multiple safe harbor loci. By combining our single-cell naïve hiPSC platform with different nuclease-independent and -dependent strategies, we are able to generate large numbers of precisely engineered iPSC clones. The single cell-derived hiPSC clones were subsequently screened in a multiplexed fashion for successful multi-parameter engineering, maintained pluripotency and propensity for differentiation with lack of undesired phenotypes and genomic alterations. Using this approach, we derived individual clones containing a uniform population (〉99%) of multi-engineered modalities consisting of tumor targeting, a controllable safety switch and a tracking marker. Moreover, we show that engineered modalities are expressed in undifferentiated and differentiated hiPSCs, including being expressed in 〉95% of both CD34 positive hematopoietic progenitor cells and CD56 positive natural killer cells. Furthermore, we have generated hiPSC clones with dual suicide genes (inducible Caspase 9 (iCasp9) and Herpes simplex virus thymidine kinase (HSV-TK)) targeted into two independent safe harbor loci, in both mono- and bi-allelic manner. The dual-targeted hiPSC clones were confirmed to have specific insertions into the predicted sites and were screened to exclude random insertions. Concurrent activation of both suicide genes led to complete elimination of engineered hiPSCs and no treatment-refractory cells were observed unlike the case when only one suicide gene was activated. In addition to robust targeted insertions, we were able to generate small insertions and deletions in up to 70% of naïve hiPSCs without selection and homozygous knockout of gene of interest in 100% of cells after selection. Finally, we will discuss efforts to temporally synchronize ectopic gene expression through endogenously regulated promoters by simultaneous endogenous gene disruption and transgene insertion. Overall, we show our naïve hiPSC platform is an ideal renewable source to efficiently generate, genetically engineer, isolate and bank clonally-derived homogenous population of pluripotent cells. These highly-stable pluripotent clonal banks can be repeatedly tapped to facilitate the consistent production of homogenous populations of potent, persistent, scalable and safer off-the-shelf cellular immunotherapeutics. Disclosures Abujarour: Fate Therapeutics: Employment. Lan:Fate Therapeutics: Employment. Lee:Fate Therapeutics: Employment. Bonello:Fate Therapeutics: Employment. Meza:Fate Therapeutics: Employment, Equity Ownership. Robinson:Fate Therapeutics: Employment. Clarke:Fate Therapeutics: Employment. Truong:Fate Therapeutics: Employment, Equity Ownership. Robbins:Fate Therapeutics: Employment, Equity Ownership. Rezner:Fate Therapeutics, Inc: Employment, Equity Ownership. Abbot:Fate Therapeutics: Employment. Shoemaker:Fate Therapeutics: Employment, Equity Ownership. Valamehr:Fate Therapeutics, Inc: Employment.

Description: Natural Killer (NK) cells play a crucial role in immunosurveillance and form a first line of defense against cancer. In comparison to other lymphocytes, NK cells are unique in their capability to elicit tumoricidal responses without the need for antigen presentation or prior sensitization. Clinical data from bone marrow transplant and allogeneic NK immunotherapy suggest that MHC mismatch is advantageous in promoting graft-versus-leukemia without eliciting graft-versus-host, providing evidence that NK cells hold promisa as an allogeneic, universal immunotherapeutic. Further, the anti-tumor effect of many monoclonal antibodies is mediated through binding of the low-affinity Fc receptor CD16 on NK cells, which induces tumor cell killing through antibody-dependent cellular cytotoxicity (ADCC). Thus, NK cells represent a unique source of effector cells that can be combined with monoclonal antibodies, bispecific engagers or chimeric antigen receptors to direct tumor specificity and enhance cytotoxicity. Despite the significant potential of NK cell therapy, current clinical practices are limited by the need for large numbers of healthy NK cells, lack of in vivo persistence, and a burdensome manufacturing strategy that requires donor cell extraction, modulation, expansion and re-introduction per each patient. The ability to generate universally histocompatible and genetically-enhanced NK cells from continuously renewable human induced pluripotent stem cell (hiPSC) lines offers the potential to develop a true "off-the-shelf" cellular immunotherapy. While NK differentiation from hiPSC has been demonstrated, the clonal derivation of engineered hiPSCs to improve effector function has been challenging and the scalability and robustness of the differentiation method has been limited by skewed development towards primitive hematopoiesis and the cumbersome use of embryoid bodies. Here we highlight our "off-the-shelf" NK cell therapy preclinical program by demonstrating robust and highly scalable generation of functionally mature, genetically targeted and universally histocompatible NK cells. This program utilizes our previously described naïve hiPSC platform where we uniquely create clonal lines of precisely engineered, renewable hiPSCs and drive definitive hematopoiesis in a highly scalable manner. Because hiPSC differentiation is lineage directed, minimal cellular contamination is seen, including the lack of T and B cells, in the final product. Through precise genetic engineering of naïve hiPSC lines, we have engineered HLA-class I deficient NK cells uniformly expressing a high affinity, non-cleavable version of the Fc receptor CD16 (NcHaCD16-NK). The hiPSC-derived NcHaCD16-NKs display markers of maturity, including CD16, KIR, NCRs, and CD94. When compared to conventional cord blood and peripheral blood sourced NK cells, NcHaCD16-NKs exhibit superior cytotoxicity and production of effector cytokines in response to both solid and liquid tumor cell challenge in vitro. NcHaCD16-NKs exhibit augmented cytokine response following Fc-mediated stimulation, demonstrating function competence of the engineered CD16 construct. Because surface expression of CD16 is resistant to activation-induced shedding, NcHaCD16-NKs continuously maintain enhanced ADCC while retaining the capacity for general cytotoxicity. Importantly, the hiPSC-derived hematopoietic cells can be successfully cryopreserved and banked, serving as a highly-stable cell bank for subsequent therapeutic use. Preliminary data also shows NcHaCD16-NKs elicit preferred specificity for cancer stem cells as defined by expression of ALDH1 and surface markers such as CD24. In conclusion, the outlined preclinical data demonstrate the potential therapeutic utility of NK cells developed via precision genetic engineering of a renewable, scalable hiPSC platform, and highlights the therapeutic value of NcHaCD16-NKs as an ideal ADCC-mediated "off-the-shelf" NK cell-based immunotherapeutic product with augmented persistence, anti-tumor capacity and preclinical efficacy. Disclosures Bjordahl: Fate Therapeutics, Inc: Employment. Clarke:Fate Therapeutics: Employment. Gaidarova:Fate Therapeutics: Employment. Groff:Fate Therapeutics: Employment. Rogers:Fate Therapeutics, Inc: Employment. Moreno:Fate Therapeutics, Inc.: Employment, Equity Ownership. Abujarour:Fate Therapeutics, Inc.: Employment. Bonello:Fate Therapeutics, Inc.: Employment. Lee:Fate Therapeutics: Employment. Lan:Fate Therapeutics: Employment. Burrascano:Fate Therapeutics: Employment. Bauer:Fate Therapeutics: Employment. Robinson:Fate Therapeutics: Employment. Sasaki:Fate Therapeutics, Inc.: Employment. Kim:Fate Therapeutics, Inc.: Employment. Robbins:Fate Therapeutics: Employment, Equity Ownership. Rezner:Fate Therapeutics, Inc: Employment, Equity Ownership. Abbot:Fate Therapeutics: Employment. Wolchko:Fate Therapeutics: Employment. Shoemaker:Fate Therapeutics: Employment, Equity Ownership. Valamehr:Fate Therapeutics, Inc: Employment.

Description: 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

Description: T lymphocytes that express an anti-CD19 chimeric antigen receptor (CAR) to redirect target specificity exhibit remarkable remissions in B cell malignancies. However, these cells are typically produced in a patient-specific manner that is relatively inefficient and expensive. Additionally, CAR-T cell treatment can lead to severe adverse events (SAEs) such as cytokine release syndrome (CRS) and neurotoxicity, as well as graft versus host disease (GvHD) when given in allogeneic setting. To circumvent these safety issues while maintaining multi-faceted anti-tumor activity, we developed an off-the-shelf natural killer (NK) cell consisting of a novel CAR combined with other effector mechanisms to enhance targeted cytotoxicity. NK cells are potent anti-tumor effector cells that play an important role in innate and adaptive immunity. Multiple clinical studies have demonstrated that adoptive transfer of allogeneic NK cells can induce durable remissions in patients with cancers that have relapsed or are refractory to standard therapies without detection of SAEs such as CRS. However, NK cells are challenging to genetically engineer, and are dependent on cytokine support for persistence and exhibit donor-to-donor variability factors that make it difficult to create a consistent clinical product from NK cells. Here we report the use of human induced pluripotent stem cells (iPSCs) to produce a renewable source of precisely engineered NK cells. This iPSC platform was utilized to evaluate a combination of CARs comprised of distinct NK-cell specific signaling and transmembrane domains with an autonomous protein to create a persistent and targeted NK cell immunotherapy. The selected NK cell optimized CAR (NK-CAR) backbone contains an NKG2D transmembrane domain, a 2B4 co-stimulatory domain, and a CD3ζ signaling domain to mediate a potent NK cell activating signal. To provide directed anti-tumor activity, anti-CD19 scFv was added to the NK-CAR backbone, engineered at the iPSC stage and subsequently differentiated on-demand to produce a uniform population of CAR-expressing NK cells. In addition, an IL-15RF fusion transgene was introduced to provide self-stimulating signals to support NK cell function and persistence. The IL-15RF construct was created by fusing IL-15Rα to IL-15 at the C-terminus through a flexible linker. As a third modality, a metalloprotease ADAM17-resistant version of the high-affinity CD16a (hnCD16) 158V variant was introduced at the iPSC stage to augment antibody-dependent cellular-cytotoxicity (ADCC) when used in combination with monoclonal antibodies. The selected iPSC clone exhibits stable expression of all three modalities and represents a renewable source of starting material for the reproducible generation of NK cells consisting of NK-CAR, IL-15RF and hnCD16 with product purity that is greater than 95% CD45+CD56+ with a product expansion greater than one million-fold over the course of the manufacturing process. In preclinical studies, these multi-functional engineered NK cells demonstrated enhanced directed cytotoxicity against CD19+ tumor targets when compared to non-engineered NK cells or iPSC-derived NK cells engineered with other CAR constructs. Additionally, the multi-functional engineered iPSC-CAR-NK cells significantly reduced tumor burden in a xenograft model of B acute lymphoblastic leukemia (p

Description: 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