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Fabry disease is an X-linked lysosomal storage disorder caused by loss of alpha-galactosidase A (α-Gal A) activity and is characterized by progressive accumulation of glycosphingolipids in multiple cells and tissues. FLT190, an investigational gene therapy, is currently being evaluated in a Phase 1/2 clinical trial in patients with Fabry disease (NCT04040049). FLT190 consists of a potent, synthetic capsid (AAVS3) containing an expression cassette with a codon-optimized human GLA cDNA under the control of a liver-specific promoter FRE1 (AAV2/S3-FRE1-GLAco). For mouse studies FLT190 genome was pseudotyped with AAV8 for efficient transduction. Preclinical studies in a murine model of Fabry disease (Gla-deficient mice), and non-human primates (NHPs) showed dose-dependent increases in plasma α-Gal A with steady-state observed 2 weeks following a single intravenous dose. In Fabry mice, AAV8-FLT190 treatment resulted in clearance of globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3) in plasma, urine, kidney, and heart; electron microscopy analyses confirmed reductions in storage inclusion bodies in kidney and heart. In NHPs, α-Gal A expression was consistent with the levels of hGLA mRNA in liver, and no FLT190-related toxicities or adverse events were observed. Taken together, these studies demonstrate preclinical proof-of-concept of liver-directed gene therapy with FLT190 for the treatment of Fabry disease.

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Mesenchymal stromal/stem cells (MSC) have been studied extensively for their potential use in the generation of connective tissues for both therapeutics and biomedical research. Here, using the NovoGen™bioprinting platform and osteogenic differentiation media discovered with the high throughput combinatorial platform CombiCult®, we report the rapid fabrication of, and efficient osteogenesis in, 3D, scaffold‐free, bioprinted tissue constructs containing adipose‐derived MSC (aMSC) or aMSC and endothelial cells (EC). Constructs were bioprinted in multi‐well tissue culture vessels enabling rapid generation of replicate tissues for interrogation with standard laboratory assays. Bioprinted constructs cultured in media used for aMSC propagation showed no signs of osteogenesis. Evaluation of bioprinted 3D tissue constructs maintained in CombiCult® (OsteoMax‐XF™, EMD Millipore) differentiation media revealed marked evidence of osteogenic differentiation. By 5d post‐printing, aMSC‐containing tissue constructs exposed to CombiCult® were found to contain osteopontin‐ and alkaline phosphatase‐positive cells and mineralization was confirmed by Alizarin Red S staining. Osteogenesis was associated with elevated levels of IL‐1α, IL‐6, IL‐8, CCL2 and CXCL1. Experiments were repeated with multiple lots of commercially‐sourced aMSC implicating utility of this model for a variety of MSC sources.

Introduction: Gaucher disease (GD), one of the most common lysosomal storage disorders, is an autosomal recessive condition resulting from mutations in the GBA gene that codes for the b-glucocerebrosidase (GCase) enzyme. Over 90% of patients have type 1 GD, which is characterised by lipid engorged macrophages (known as Gaucher cells) in multiple organs, including spleen, liver and bone marrow, with no overt involvement of the central nervous system (CNS). The current standard of care for type 1 GD patients includes enzyme replacement therapy (ERT), which provides good overall therapeutic benefit. However, ERT is administered intravenously every other week, resulting in a high cumulative cost and a significant treatment burden. Furthermore, disease manifestations, such as pulmonary and skeletal disease, remain unresolved with ERT. Gene therapy is emerging as a very promising avenue of treatment for various monogenic disorders and has the potential to provide sustained levels of GCase enzyme expression after a single treatment. Here we have evaluated liver-directed gene therapy in vitro and in vivo for the treatment of GD. Methods: Adeno-associated virus (AAV) constructs were optimised to express full-length wild-type GCase protein (GBA AAV) and packaged in AAV8 capsids for in vivo mouse studies, or our novel AAVS3 capsid for in vitro studies in a human cell line. GCase activity was determined fluorometrically with 4-Methylumbelliferyl-β-D-glucopyranoside and activity was based on a 4-methylumbelliferone standard curve. Levels of GCase in plasma, and uptake in GD target organs were compared between our GBA AAV optimized construct and ERT treatment with velaglucerase alfa (VPRIV®) in C57BL/6 wild type mice. Doses used ranged from 2x109 to 2x1012 vg/kg for GBA AAV constructs and 60 U/kg for ERT. Results: Our initial proof of concept studies for liver-directed AAV gene therapy of GD used an AAV construct encoding the native full-length human GBA cDNA (RC-04-01). After a single intravenous injection into mice, RC-04-01 led to a dose-dependent expression of GCase in liver and robust levels of enzymatically active GCase in plasma. Based on these preliminary data, 37 GBA AAV constructs with optimisations to the coding sequence and changes to the promoter, signal peptide, and polyA sequences were designed and evaluated in vitro for GCase production. Among them, 6 constructs outperformed RC-04-01 and were further tested in mice. Construct RC-04-26 showed the highest GCase activity levels both in vivo and in vitro. At a dose of 2x1012 vg/kg, RC-04-26 showed plasma active GCase levels up to 9.4-fold higher than RC-04-01. Upon GBA AAV infusion, plasma GCase levels were steady and sustained for the duration of the entire study period (9 months). In addition, RC-04-26 infusion into mice resulted in robust uptake of GCase by cells in spleen, bone marrow and lung, demonstrating that liver-produced GCase is taken up by macrophages present in the GD target organs. Lastly, GCase bioavailability was evaluated after a single administration of RC-04-26 or ERT. With velaglucerase alfa, GCase was rapidly cleared from the bloodstream and tissues. However, RC-04-26 resulted in sustained and steady levels of GCase, with an overall bioavailability of GCase uptake over 170-fold higher than with ERT. Conclusions: Our current data support the hypothesis that a single administration of an optimised liver directed GBA AAV vector results in sustained elevation of GCase in the bloodstream and higher level of GCase bioavailability for uptake into macrophages than velaglucerase alfa. This observation supports further development of AAV gene therapy for Gaucher disease with the potential for enhanced therapeutic benefit from a one-off administration. Disclosures Miranda: Freeline Therapeutics: Employment, Equity Ownership. Canavese:Freeline Therapeutics: Employment, Equity Ownership. Chisari:Freeline Therapeutics: Employment, Equity Ownership. Pandya:Freeline: Employment, Equity Ownership. Cocita:Freeline Therapeutics: Employment, Equity Ownership. Portillo:Freeline: Employment, Equity Ownership. McIntosh:Freeline Therapeutics: Consultancy, Equity Ownership. Kia:Freeline Therapeutics: Employment, Equity Ownership. Foley:Freeline: Employment, Equity Ownership. Dane:Freeline: Employment, Equity Ownership. Jeyakumar:Freeline Therapeutics: Employment, Equity Ownership. Sheridan:Freeline Therapeutics: Employment, Equity Ownership. Corbau:Freeline: Employment, Equity Ownership. Nathwani:Freeline: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties.