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Substrate-derived biomarkers are necessary in slowly progressing monogenetic diseases caused by single-enzyme deficiencies to identify affected patients and serve as surrogate markers for therapy response. N-glycanase 1 (NGLY1) deficiency is an ultra-rare autosomal recessive disorder characterized by developmental delay, peripheral neuropathy, elevated liver transaminases, hyperkinetic movement disorder and (hypo)-alacrima. We demonstrate that N-acetylglucosamine-asparagine (GlcNAc-Asn; GNA), is the analyte most closely associated with NGLY1 deficiency, showing consistent separation in levels between patients and controls. GNA accumulation is directly linked to the absence of functional NGLY1, presenting strong potential for its use as a biomarker. In agreement, a quantitative liquid chromatography with tandem mass spectrometry assay, developed to assess GNA from 3 to 3000 ng/ml, showed that it is conserved as a marker for loss of NGLY1 function in NGLY1-deficient cell lines, rodents (urine, cerebrospinal fluid, plasma and tissues) and patients (plasma and urine). Elevated GNA levels differentiate patients from controls, are stable over time and correlate with changes in NGLY1 activity. GNA as a biomarker has the potential to identify and validate patients with NGLY1 deficiency, act as a direct pharmacodynamic marker and serve as a potential surrogate endpoint in clinical trials.

Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the alpha-galactosidase A (GLA) gene, which encodes the exogalactosyl hydrolase, alpha-galactosidase A (α-Gal A). Deficient α-Gal A activity results in the progressive, systemic accumulation of its substrates, globotriaosylceramide (Gb3) and globotriaosylsphingosine (Lyso-Gb3), leading to renal, cardiac, and/or cerebrovascular disease and early demise. The current standard treatment for Fabry disease is enzyme replacement therapy, which necessitates lifelong biweekly infusions of recombinant enzyme. A more long-lasting treatment would benefit Fabry patients. Here, a gene therapy approach using an episomal adeno-associated viral 2/6 (AAV2/6) vector that encodes the human GLA cDNA driven by a liver-specific expression cassette was evaluated in a Fabry mouse model that lacks α-Gal A activity and progressively accumulates Gb3 and Lyso-Gb3 in plasma and tissues. A detailed 3-month pharmacology and toxicology study showed that administration of a clinical-scale-manufactured AAV2/6 vector resulted in markedly increased plasma and tissue α-Gal A activities, and essentially normalized Gb3 and Lyso-Gb3 at key sites of pathology. Further optimization of vector design identified the clinical lead vector, ST-920, which produced several-fold higher plasma and tissue α-Gal A activity levels with a good safety profile. Together, these studies provide the basis for the clinical development of ST-920., Graphical Abstract

Fabry disease, a lysosomal storage disorder resulting from the deficient activity of α-galactosidase A (α-Gal A), is characterized by cardiac, renal, and/or cerebrovascular disease due to progressive accumulation of the enzyme's substrates, globotriaosylceramide (Gb3) and globotriaosylsphingosine (Lyso-Gb3). We report here the preclinical evaluation of liver-targeted in vivo genome editing using zinc-finger nuclease (ZFN) technology to insert the human α-galactosidase A (hGLA) cDNA into the albumin "safe harbor" locus of Fabry mice, thereby generating an albumin-α-Gal A fusion protein. The mature α-Gal A protein is secreted into the circulation for subsequent mannose-6-phosphate receptor-mediated tissue uptake. Donor vector optimization studies showed that replacing the hGLA cDNA signal peptide sequence with that of human iduronate 2-sulfatase (IDS) achieved higher transgene expression. Intravenous adeno-associated virus (AAV) 2/8-mediated co-delivery of the IDS-hGLA donor and ZFNs targeting the albumin locus resulted in continuous, supraphysiological plasma and tissue α-Gal A activities, which essentially normalized Gb3 and Lyso-Gb3 levels in key tissues of pathology. Notably, this was achieved with10% of hepatocytes being edited to express hGLA, occurring mostly via non-homologous end joining (NHEJ) rather than homology-directed repair (HDR). These studies indicate that ZFN-mediated in vivo genome editing has the potential to be an effective one-time therapy for Fabry disease.

Mucopolysaccharidosis type I (MPS I) is a severe disease due to deficiency of the lysosomal hydrolase α-L-iduronidase (IDUA) and the subsequent accumulation of the glycosaminoglycans (GAG), leading to progressive, systemic disease and a shortened lifespan. Current treatment options consist of hematopoietic stem cell transplantation, which carries significant mortality and morbidity risk, and enzyme replacement therapy, which requires lifelong infusions of replacement enzyme; neither provides adequate therapy, even in combination. A novel in vivo genome-editing approach is described in the murine model of Hurler syndrome. A corrective copy of the IDUA gene is inserted at the albumin locus in hepatocytes, leading to sustained enzyme expression, secretion from the liver into circulation, and subsequent uptake systemically at levels sufficient for correction of metabolic disease (GAG substrate accumulation) and prevention of neurobehavioral deficits in MPS I mice. This study serves as a proof-of-concept for this platform-based approach that should be broadly applicable to the treatment of a wide array of monogenic diseases., In vivo genome editing following a single injection of ZFN and IDUA donor encoding AAV8 resulted in metabolic correction and neurological benefit in a murine model of MPS I. These results enable a currently open clinical trial to evaluate targeted genome engineering for MPS I in humans.

Mucopolysaccharidosis type II (MPS II) is an X-linked recessive lysosomal disorder caused by deficiency of iduronate 2-sulfatase (IDS), leading to accumulation of glycosaminoglycans (GAGs) in tissues of affected individuals, progressive disease, and shortened lifespan. Currently available enzyme replacement therapy (ERT) requires lifelong infusions and does not provide neurologic benefit. We utilized a zinc finger nuclease (ZFN)-targeting system to mediate genome editing for insertion of the human IDS (hIDS) coding sequence into a “safe harbor” site, intron 1 of the albumin locus in hepatocytes of an MPS II mouse model. Three dose levels of recombinant AAV2/8 vectors encoding a pair of ZFNs and a hIDS cDNA donor were administered systemically in MPS II mice. Supraphysiological, vector dose-dependent levels of IDS enzyme were observed in the circulation and peripheral organs of ZFN+donor-treated mice. GAG contents were markedly reduced in tissues from all ZFN+donor-treated groups. Surprisingly, we also demonstrate that ZFN-mediated genome editing prevented the development of neurocognitive deficit in young MPS II mice (6–9 weeks old) treated at high vector dose levels. We conclude that this ZFN-based platform for expression of therapeutic proteins from the albumin locus is a promising approach for treatment of MPS II and other lysosomal diseases., AAV-mediated in vivo delivery of ZFN and IDS donor resulted in site-specific gene insertion and dose-dependent IDS expression in a mouse model of MPS II. These results support a currently open clinical trial, the first ever in vivo human genome editing study to be conducted.

Site-specific genome editing provides a promising approach for achieving long-term, stable therapeutic gene expression. Genome editing has been successfully applied in a variety of preclinical models, generally focused on targeting the diseased locus itself; however, limited targeting efficiency or insufficient expression from the endogenous promoter may impede the translation of these approaches, particularly if the desired editing event does not confer a selective growth advantage. Here we report a general strategy for liver-directed protein replacement therapies that addresses these issues: zinc finger nuclease (ZFN) -mediated site-specific integration of therapeutic transgenes within the albumin gene. By using adeno-associated viral (AAV) vector delivery in vivo, we achieved long-term expression of human factors VIII and IX (hFVIII and hFIX) in mouse models of hemophilia A and B at therapeutic levels. By using the same targeting reagents in wild-type mice, lysosomal enzymes were expressed that are deficient in Fabry and Gaucher diseases and in Hurler and Hunter syndromes. The establishment of a universal nuclease-based platform for secreted protein production would represent a critical advance in the development of safe, permanent, and functional cures for diverse genetic and nongenetic diseases.

Fabry disease (FD), an X-linked lysosomal storage disease, is caused by mutations in the GLA gene encoding α-galactosidase A (α-GalA). FD is characterized by progressive systemic accumulation of the enzyme’s substrates, globotriaosylceramide (Gb3) and lyso-Gb3, leading to renal, cardiac and/or cerebrovascular disease and culminating in premature demise. FD is treated by enzyme replacement therapy (ERT), however the short enzyme half-life necessitates life-long biweekly infusions. A more effective and long-lasting treatment would benefit FD patients. An AAV-mediated liver-targeted gene therapy was evaluated in a mouse model (GLAKO) that lacks α-GalA activity and accumulates high levels of Gb3/lyso-Gb3 in plasma and tissues. This strategy employs an episomal AAV (serotype 2/6) vector encoding human GLA cDNA (hGLA) driven by a liver-specific promoter. One-time administration of increasing amounts of AAV-hGLA cDNA generated using a clinical scale manufacturing process resulted in supraphysiological expression of plasma α-GalA (over 300-fold of WT) by study day 15, was well tolerated, and was stable for 3 months post-injection. Dose-dependent increases in α-GalA activities were achieved in liver, heart and kidney with a corresponding reduction of Gb3/lyso-Gb3. This initial vector was compared to an improved cDNA vector in a 1-month study using two different AAV doses in wild type C57BL/6 mice. The improved cDNA vector produced on average 7-fold higher levels of plasma α-GalA activity at study day 28 than mice administered the same dose of the initial cDNA. The high levels of α-GalA activity seen in these studies, along with the concomitant marked reduction in the accumulated Gb3/lyso-Gb3 in key tissues of the GLAKO mouse model, provide “proof-of-concept” for AAV-mediated targeting of hepatocytes to express therapeutic levels of human α-GalA. The clinical scale manufacturing process developed for these studies will enable rapid development and production in 2019 of clinical-grade material featuring the improved cDNA construct.

Cellular DNA double-strand break-repair pathways have evolved to protect the integrity of the genome from a continual barrage of potentially detrimental insults. Inherited mutations in genes that control this process result in an inability to properly repair DNA damage, ultimately leading to developmental defects and also cancer predisposition. Here, we describe a patient with a previously undescribed syndrome, which we have termed RIDDLE syndrome (radiosensitivity, immunodeficiency, dysmorphic features and learning difficulties), whose cells lack an ability to recruit 53BP1 to sites of DNA double-strand breaks. As a consequence, cells derived from this patient exhibit a hypersensitivity to ionizing radiation, cell cycle checkpoint abnormalities, and impaired end-joining in the recombined switch regions. Sequencing of TP53BP1 and other genes known to regulate ionizing radiation-induced 53BP1 foci formation in this patient failed to detect any mutations. Therefore, these data indicate the existence of a DNA double-strand break-repair protein that functions upstream of 53BP1 and contributes to the normal development of the human immune system.

Unrepaired DNA double-strand breaks can lead to apoptosis or tumorigenesis. In mammals double-strand breaks are repaired mainly by nonhomologous end-joining mediated by the DNA–PK complex. The core protein of this complex, DNA–PKcs, is a DNA-dependent serine/threonine kinase that phosphorylates protein targets as well as itself. Although the (auto)phosphorylation activity has been shown to be essential for repair of both random double-strand breaks and induced breaks at the immunoglobulin locus, the corresponding phosphatase has been elusive. In fact, to date, none of the putative phosphatases in DNA double-strand break repair has been identified. Here we show that protein phosphatase 5 interacts with DNA–PKcs and dephosphorylates with surprising specificity at least two functional sites. Cells with either hypo- or hyperphosphorylation of DNA–PKcs at these sites show increased radiation sensitivity.

Mucopolysaccharidosis type I (MPS I) is characterized by progressive neurodegeneration, and premature death (

Hunter syndrome (Mucopolysaccharidosis Type II, MPS II) is a rare X-linked lysosomal disorder caused by lack of functional iduronate-2 sulfatase (IDS) enzyme and subsequent accumulation of glycosaminoglycans (GAG) in affected individuals. Manifestations include skeleton dysplasia, splenohepatomegaly, cardiopulmonary obstruction, and shortened life expectancy. In severe cases there is also neurologic impairment. Enzyme replacement therapy (ERT) is currently the only FDA-approved treatment to manage disease progression; however, ERT does not affect neurological aspects of the disease and requires that patients receive long and costly infusions of replacement factor on a frequent basis. We have developed a zinc-finger nuclease (ZFN) approach to insert the human IDS (hIDS) coding sequence into the albumin locus using AAV2/8 vectors. In this study IDS-deficient MPS II mice (n= 8-13 per group, age 7-8 weeks) were treated by intravenous infusion of a mixture of ZFN-encoding AAV vectors along with an AAV vector encoding the hIDS partial cDNA flanked by albumin sequence homology arms at three different vector doses. Wild-type littermates, untreated MPS II mice, and MPS II animals infused only with the hIDS donor vector (without ZFN-encoding vectors) were included as controls. Successful insertion of the hIDS coding sequence will result in hIDS expression regulated by the endogenous albumin promoter. Plasma and tissue IDS activities as well as urine and tissue GAG contents were monitored throughout the study to evaluate the effectiveness of the treatment. Sufficient animals were maintained for neurobehavioral testing at four-months post-injection to determine whether the treatment is neurologically beneficial. We found that IDS activities in the plasma of the treated groups were 10- to 100-fold higher than wild-type and stably expressed through the entire study duration in a dose-dependent fashion, while only very low levels of IDS activity were found in the animals infused with hIDS donor vector alone. At 4 weeks post-treatment IDS activities in peripheral tissues ranged from 1% to 200% wild-type in a dose-dependent fashion, while in the hIDS donor-only group enzyme activity was not detected in any tissue except liver (10% that of wild-type). We observed up to 2% of the wild-type IDS activity in the brains of animals administered the complete set of AAV vectors, while no IDS activity was observed in the brains of animals infused with the IDS donor vector alone. Urine GAGs were reduced in all of the ZFN + Donor treatment groups regardless of the vector dose. Tissue GAGs in the treatment groups were also decreased, but GAG content in the brain was not different from untreated MPS II litter mates at the initial analysis conducted four weeks post-treatment. No tissue GAG reduction was observed in animals infused with hIDS donor vector alone. Before conclusion of this study, animals from all six groups will be tested in the Barnes Maze as neurobehavioral assessment to determine the neurological effect of targeted hIDS expression in the liver. These results together with hIDS expression and GAG level data from final necropsy tissues will be presented. These results demonstrate that ZFN can be effectively used to mediate in vivo insertion of the hIDS coding sequence into the albumin locus with resultant stable and high-level hIDS enzyme expression and metabolic correction in MPS II.

In somatic cells, Holliday junctions can be formed between sister chromatids during the recombinational repair of DNA breaks or after replication fork demise. A variety of processes act upon Holliday junctions to remove them from DNA, in events that are critical for proper chromosome segregation. In human cells, the BLM protein, inactivated in individuals with Bloom’s syndrome, acts in combination with topoisomerase IIIα, RMI1 and RMI2 (BTR complex) to promote the dissolution of double Holliday junctions1,2. Cells defective for BLM exhibit elevated levels of sister chromatid exchanges (SCEs) and patients with Bloom’s syndrome develop a broad spectrum of early-onset cancers caused by chromosome instability3. MUS81–EME1 (refs 4-7), SLX1–SLX4 (refs 8-11) and GEN1 (refs 12, 13) also process Holliday junctions but, in contrast to the BTR complex, do so by endonucleolytic cleavage. Here we deplete these nucleases from Bloom’s syndrome cells to analyse human cells compromised for the known Holliday junction dissolution/resolution pathways. We show that depletion of MUS81 and GEN1, or SLX4 and GEN1, from Bloom’s syndrome cells results in severe chromosome abnormalities, such that sister chromatids remain interlinked in a side-by-side arrangement and the chromosomes are elongated and segmented. Our results indicate that normally replicating human cells require Holliday junction processing activities to prevent sister chromatid entanglements and thereby ensure accurate chromosome condensation. This phenotype was not apparent when both MUS81 and SLX4 were depleted from Bloom’s syndrome cells, suggesting that GEN1 can compensate for their absence. Additionally, we show that depletion of MUS81 or SLX4 reduces the high frequency of SCEs in Bloom’s syndrome cells, indicating that MUS81 and SLX4 promote SCE formation, in events that may ultimately drive the chromosome instabilities that underpin early-onset cancers associated with Bloom’s syndrome.

Genome editing has the potential to provide long-term therapeutic gene expression in vivo. We have previously demonstrated efficient editing in a mouse model of hemophilia B through liver-directed adeno-associated viral vector (AAV) delivery of a zinc finger nuclease (ZFN) pair and a corrective donor. We determined that homology is not necessary to achieve efficient levels of genome editing in adult mice, consistent with the fact that quiescent cells, including adult hepatocytes, are not thought to be amenable to homology directed repair (HDR). As a consequence of the donor containing a splice acceptor, both HDR and homology independent vector integration are capable of driving human factor 9 (hF.IX) expression. In this study we sought to determine whether hF.IX expression in mice treated as neonates, undergoing substantial hepatocyte proliferation, is predominantly the result of HDR or homology independent genome editing. Provided the efficacy is not substantially reduced, an HDR dependent approach would impose additional constraints on targeting. Treatment of neonatal hF9mut mice (harboring the ZFN target site) with 1x1011 vg AAV8-ZFN and 5x1011 vg AAV8-Donor via retro-orbital injection resulted in a drastic difference in hF.IX expression between donors with and without homology 10 weeks post injection (Homology: 1531 ± 174.5 ng/mL vs. No-homology: 146.1 ± 5.8 ng/mL; n=12 and 7, respectively). We next asked whether HDR could be stimulated even more specifically through the induction of DNA single strand breaks at the target site. We treated neonatal mice with homologous or non-homologous donors, as well as ZFNs or ZFNickases (in which one FokI nuclease domain was inactivated with the D450A mutation). ZFNickases were indeed active, resulting in ~250 ng/mL hF.IX 4 weeks post injection (Figure 1). Interestingly, we could not detect hF.IX in mice treated with ZFNickase and no-homology donor (LOD: 15ng/mL). To rule out the possibility that this was simply due to the lower efficacy of ZFNickases compared to ZFNs, we increased the ZFNickase dose 4 fold. Four weeks post treatment, we observed substantial levels of hF.IX in mice treated with homologous donor (2041 ± 269 ng/mL) and were again unable to detect hF.IX in mice treated with the non-homologous donor (n=10 and 7, respectively). These data point to homology directed repair as the primary mechanism of protein production for genome editing in neonatal mouse liver, and suggest improvements in both efficacy and specificity can be made through deeper understanding of the molecular requirements of this approach. Figure 1. Figure 1. Disclosures Anguela: Spark Therapeutics, Inc.: Employment, Equity Ownership, Patents & Royalties. Doyon:Sangamo BioSciences: Employment. Wechsler:Sangamo BioSciences: Employment. Paschon:Sangamo BioSciences: Employment. Davidson:Spark Therapeutics: Consultancy. Gregory:Sangamo BioSciences: Employment. Holmes:Sangamo BioSciences: Employment. High:Spark Therapeutics: Employment, Equity Ownership, Patents & Royalties.

Hemophilia is an attractive target for gene therapy, since activity levels as low as 1% to 2% of normal are beneficial and levels of ~5% prevent spontaneous bleeding. Our goal was to provide a single treatment that permanently enables hepatic production of therapeutic levels of hFIX activity to decrease or potentially eliminate the need for prophylactic treatment in hemophilia B patients. We performed targeted in vivo genome editing using 1) two zinc finger nucleases (ZFNs) targeting intron 1 of the albumin locus, and 2) a human F9 donor template construct. The ZFNs and donor template are encoded on separate hepatotropic adeno-associated virus serotype 2/6 (AAV2/6) vectors injected intravenously, resulting in targeted insertion of a corrected copy of the hF9 gene into the albumin locus in a proportion of liver hepatocytes. The albumin locus was selected as a "safe harbor" as production of this most abundant plasma protein exceeds 10 g/day, and moderate reductions in those levels are well-tolerated. These genome edited hepatocytes produce normal hFIX in therapeutic quantities, rather than albumin, driven by the highly active albumin enhancer/promoter, to treat hemophilia B; the genetic modification is expected to be sustained even in the face of hepatocyte turnover, making this approach attractive for treating young children with hemophilia before the appearance of significant organ damage. Transformed and primary human hepatocytes transduced in vitro with AAV2/6 encoding human albumin ZFNs and a promoterless hF9 transgene were shown to secrete hFIX. Extensive molecular analyses demonstrated that this was due to targeted integration of the hF9 transgene at the albumin locus and splicing of this gene into the albumin transcript. By employing AAV2/6 delivery of murine-specific ZFNs in vivo, stable levels of hFIX were observed in blood of mice injected with the albumin ZFNs and hF9 transgene donor. C57BL/6 mice were administered vehicle (n=20) or AAV2/6 vectors (n=25) encoding mouse surrogate reagents at 1.0 x1013 vector genome (vg)/kg via tail vein injection. ELISA analysis of plasma hFIX in the treated mice showed peak levels of 50-1053 ng/mL that were sustained for the duration of the 6-month study. Analysis of FIX activity from mouse plasma confirmed bioactivity commensurate with expression levels. Next, we report the feasibility of this approach in non-human primates (NHPs), showing that a single intravenous co-infusion of AAV2/6 vectors encoding the NHP targeted albumin-specific ZFNs and a human F9 donor at 1.2x1013 vg/kg (n=5/group) resulted in >50 ng/mL (>1% of normal) in this large animal model. The use of higher AAV2/6 doses (up to 1.5x1014 vg/kg) yielded plasma hFIX levels up to 1000 ng/ml (or 20% of normal) in several animals and up to 2000 ng/ml (or 50% of normal) in a single animal, for the duration of the study (3 months). The treatment was well tolerated in mice and NHPs, with no significant toxicological findings related to AAV2/6 ZFN + donor treatment in either species at therapeutic doses. Together, these data support a clinical trial to determine if a single co-administration of ZFN and donor AAV vectors is sufficient to enable therapeutic and potentially lifelong production of the clotting factor for the treatment of Hemophilia B. Disclosures Wechsler: Sangamo BioSciences: Employment. Meyer:Sangamo Biosciences Inc: Employment. Spratt:Sangamo Biosciences Inc: Employment. Greengard:Sangamo Biosciences Inc: Employment. Santiago:Sangamo Biosciences Inc: Employment. Sproul:Sangamo Biosciences Inc: Employment. Surosky:Sangamo Biosciences Inc: Employment. Paschon:Sangamo Biosciences Inc: Employment. Dubois-Stringfellow:Sangamo Biosciences Inc: Employment. Ando:Sangamo Biosciences Inc: Employment. Nichol:Sangamo Biosciences Inc: Employment. Rebar:Sangamo BioSciences: Employment. Holmes:Sangamo BioSciences: Employment.

Lysosomal storage diseases (LSDs) represent a group of inherited metabolic disorders associated with mutations in genes encoding lysosomal enzymes leading to systemic accumulation of toxic storage materials. Manifestations include organomegaly, skeletal dysplasias, cardiopulmonary obstruction, and severe neurologic impairment, often leading to death by age 10. Current LSD therapies include enzyme replacement therapy, substrate reduction therapy and hematopoietic stem cell transplant (HSCT). However, all of these therapies are expensive, incompletely effective, and HSCT is associated with significant risk of morbidity and mortality. Due to the unmet need genome editing strategies are proposed to permanently modify patient cells by genetically complementing the LSD defect. This is achieved by utilizing engineered zinc finger nucleases (ZFNs) to introduce a DNA cut at the target locus, mediating integration of a therapeutic LSD donor cDNA. To ensure long-term expression of the transgenes in vivo we target the albumin locus as a “safe harbor” in hepatocytes via co-delivery of the albumin ZFNs and LSD donors by adeno-associated virus (AAV). This system exploits the high transcriptional activity of the native albumin enhancer/promoter; uses stably modified hepatocytes to potentially allow long-term expression of the inserted transgene; and utilizes an endogenous promoter obviating this requirement in the AAV payload. We have previously exploited AAV-mediated in vivo targeting of the murine albumin “safe harbor” locus for the synthesis of therapeutic levels of FVIII and FIX to overcome the clotting defect in hemophilic mice. Using the same approach, we co-delivered mouse albumin ZFNs with donor constructs encoding either human iduronate-2-sulfatase (IDS) deficient in Hunter syndrome, α-L-iduronidase (IDUA) for Hurler syndrome, or Glucocerebrosidase (GBA) for Gaucher disease via AAV in WT mice. We show stable integration of the LSD donors at the albumin locus, resulting in liver-specific expression and secretion of these proteins into plasma. This led to a 4-fold (GBA), 10-fold (IDUA) or 100-fold (IDS) increase in enzymatic activity in the plasma, demonstrating that the secreted proteins are functional. Importantly, increased activity was also detected in secondary tissues (spleen) showing efficient uptake and activity in distal tissues. Moreover, preliminary data in MPSI and MPSII mice suggests these levels of IDS and IDUA expression may lead to correction of the enzyme deficiency. IDS, IDUA and GBA expression remained stable throughout the study (up to 2 months), while expression of FIX has been stable for >1 yr suggesting this process results in long-term protein expression. In summary, our data provide proof of concept for ZFN-mediated targeting of the albumin locus in hepatocytes as an in vivo protein replacement platform to express different proteins associated with lysosomal storage diseases.

Skeletal complications, particularly fracture, can be one of the most debilitating consequences of Gaucher disease (GD). Understanding the risk factors for fracture and the relationship to timing of initiation of treatment is important for successful evaluation and management of patients. The International Collaborative Gaucher Group (ICGG) Gaucher Registry is a multinational, observational study (sponsored by Genzyme, a Sanofi company, Cambridge, MA) that captures clinical outcomes in both treated and untreated GD patients. Descriptive statistics and an adjusted logistic regression model were used to evaluate demographics and risk factors in patients enrolled in the ICGG Registry with GD type 1who had experienced a fracture. A total of 4047 patients with GD type 1 in the ICGG Registry who had received imiglucerase had sufficient bone and splenectomy data for analyses. Of these, 46% were male, the median age of diagnosis was 15 years of age, and 336 patients (8%) had experienced a fracture during treatment. Splenectomized patients were nearly twice as likely to have a fracture compared to those who were not (OR 1.930; p = b0.0001). The presence of bone pain or bone crisis (acute pain requiring immobilization, narcotics, and accompanied by periosteal elevation, elevated WBC count, fever and/or debilitation of N3 days) was a predictor of fracture, even if reported considerably prior to the fracture itself. Patients with bone pain were 2.5 times more likely to have a fracture (OR 2.683; p = b0.0001); those with bone crises were nearly twice as likely (OR 1.739; p = b0.0004). Additionally, early treatment decreased fracture risk. Patients who did not begin treatment until after the age of 25 were 30% (OR 1.373; p = 0.0132) more likely to have a fracture. The 3711 patients who did not have a fracture were diagnosed (median age: 14 years) and treated (median age: 27 years) younger than the 336 with a fracture who were diagnosed (median age: 17.5 years) and treated (median age: 37 years) later. Understanding risk factors, symptoms, and treatment patterns is important to avoid potential fractures. Splenectomy, bone pain, and bone crisis substantially elevate risk of fractures in patients on therapy, and should be considered early warning signs. Younger age at treatment initiation lowers the risk of fracture, suggesting that developing bone pathologymay be interrupted when early treatment is provided.

Genome editing utilizing engineered zinc finger nucleases (ZFNs) is a promising approach to achieve long-term expression of therapeutic genes in vivo. We have previously demonstrated in vivotargeting of the endogenous murine albumin locus as a “safe harbor” for high levels of protein production, resulting in sufficient Factor IX to correct the disease phenotype in hemophilia B mice. Targeted insertion of the donor sequence into the genome offers multiple advantages. First, we are able to exploit the high transcriptional activity of the native albumin enhancer/promoter. Second, by obviating the need for these regulatory elements within the donor, we expand the effective carrying capacity of adeno-associated viral (AAV) vectors to enable delivery of larger transgenes that may not package efficiently, such as coagulation factor 8. B-Domain Deleted Factor VIII (BDD-F8) cDNA is approximately 4.4kb. Inclusion of required enhancer/promoter elements results in a construct that exceeds the ideal packaging limitations of rAAV vectors. However, since these regions are not required for our gene editing approach the promoterless hBDD-F8 donor remained below the AAV packaging capacity. Importantly, intravenous delivery of 5e11 vg of AAV8-mAlb-ZFN and 5e11 vg of AAV8-BDD-F8-Donor to hemophilia A mice resulted in 54.6% (±4.1%) FVIII activity in the blood 2 weeks following administration - confirming the potential of the albumin locus to express high levels of the targeted transgene. To further optimize in vivo ZFN-based genome editing with a view toward the ultimate clinical use of this technology, we sought methods to further increase ZFN potency (and thus limit the dose of AAV necessary for function). Of several strategies pursued (e.g. codon optimization and inclusion of a intron in the expression cassette) the most successful was to deploy separate vectors expressing each individual ZFN rather than a single vector encoding a dual expression cassette carrying both ZFNs separated by a 2A fusion peptide. Using next generation sequencing (Illumina’s MiSeq) technology to quantify insertions and deletions indicative of DNA cleavage and repair, we observed a >3-fold increase in ZFN potency in vivo by transitioning from the dual expression vector to two individual ZFN vectors at equivalent total vector doses. Given the encouraging results obtained in mice, we next sought to examine the effectiveness of targeting the albumin locus in non-human primates (NHPs). Importantly, a single intravenous co-injection of two individual AAV vectors encoding each of the NHP targeted albumin-specific ZFNs resulted in persistent levels of gene modification in liver biopsies from treated Rhesus macaques - demonstrating successful in vivocleavage in a large animal model. These data support the use of ZFN technology in the targeting of endogenous loci with large therapeutic transgenes that are not ideally suited for episomal AAV based expression (such as F.VIII). Together our results support the further investigation of genome editing at the albumin locus as a novel method for in vivo protein replacement. Disclosures: Doyon: Sangamo BioSciences, Inc.: Employment. Wechsler:Sangamo BioSciences, Inc.: Employment. Paschon:Sangamo BioSciences: Employment. Gregory:Sangamo BioSciences: Employment. Holmes:Sangamo BioSciences: Employment. Rebar:Sangamo BioSciences: Employment. High:Novo Nordisk: Consultancy, Member of a grant review committee, Member of a grant review committee Other; Intrexon: Consultancy; Genzyme, Inc.: Membership on an entity’s Board of Directors or advisory committees; Elsevier, Inc.: royalties from textbook, royalties from textbook Patents & Royalties; BristolMyersSquibb: Consultancy, membership on a Data Safety and Monitoring Board, membership on a Data Safety and Monitoring Board Other; bluebirdbio, Inc.: Consultancy, Equity Ownership, Membership on an entity’s Board of Directors or advisory committees; BioMarin: Consultancy; Alnylam Pharmaceuticals: Consultancy, Membership on an entity’s Board of Directors or advisory committees; Shire : Consultancy; Benitec: Consultancy.

The B806-866 antenna complex was isolated from cytoplasmic membranes of the green thermophilic bacterium Chloroflexus aurantiacus. The membranes were treated with 7 M urea at 50 degrees C, the B806-866 antenna complex was solubilized with a mixture of Noni-fjdet P-40 (octylphenoxypolyethoxyethanol (Sigma)) and sodium dodecylsulphate (2:1) and isolated by sucrose density gradient centrifugation. This antenna complex was characterized by reversed-phase chromatography (fast polypeptide and polynucleotide liquid chromatography), amino acid and sequence analyses. The B806-866 antenna of Chloroflexus aurantiacus consists of two polypeptides: the B806-866-alpha and B806-866-beta polypeptides in an apparent stoichiometric ratio of 1:1, which may be equivalent to the structural elementary unit found in the antenna systems of many species of Rhodospirillaceae.

A polypeptide soluble in organic solvents was isolated from whole membrane fractions of the green thermophilic bacterium Chloroflexus aurantiacus by chromatography on Sephadex LH-60, Whatman DE-32 and Bio Gel P-10. The complete amino acid sequence of this 4.9 kDa polypeptide (44 amino acid residues) was determined. The polypeptide shows a 3-domain structure, similar to the domain structure of the antenna BChI polypeptides of purple photosynthetic bacteria, and sequence homologies (27–39%) to the light-harvesting α-polypeptides of the B870 (890) antenna complexes from purple bacteria. Therefore, the 4.9 kDa polypeptide is designated B(808-866)-α. The typical His residue (conserved His residue identified in all antenna polypeptides of purple bacteria as possible BChI binding site) is found within the hydrophobic domain, which extends from Asn 10 to Leu 30.

The BChlc polypeptide was isolated from chlorosomes of the green bacterium Chloroflexus aurantiacus on Sephadex LH-60. The complete amino acid sequence of this 5.6 kDa polypeptide (51 amino acid residues) was determined. Most probably the 5.6 kDa polypeptide forms an α-helix between Trp 5 and Ile 42 with an asymmetrical (bipolar) distribution of polar amino acid residues along the helix axis: (i) At one side of the α-helix 5 Gln and 2 Asn residues are the possible binding sites for 7 BChlc molecules, (ii) On the other side Ser, Thr, His residues seem to be polypeptide-polypeptide interaction sites within the BChlc-protein complexes. It appears that the BChl-protein complex (chlorosome subunit, 5.2 × 6 nm) composed of 12 5.6 kDa polypeptides corresponds to the 'globular units' found by electron microscopy within the chlorosomes.

The bacteriochlorophyll a-binding polypeptide B806–866-β was extracted from membranes of the green thermophilic bacterium Chloroflexus aurantiacus with chloroform/methanol/ammonium acetate. Purification of the antenna polypeptide (6.3 kDa) was achieved by chromatography on Sephadex LH-60, Whatman DE-32 and by FPLC. The complete amino acid sequence (53 amino acid residues) was determined. The B806–866-β polypeptide is sequence homologous to the antenna β-polypeptides of purple bacteria (27–40%) and exhibits the characteristic three domain structure of the B870, B800–850 and B800–820 antenna complexes. The two typical His residues, conserved in all antenna β-polypeptides of purple bacteria, were found: His-24 lies within the N-terminal hydrophilic domain and His-42 within the central hydrophobic domain. This polypeptide together with the previously described α-polypeptide form the basic structural unit of the B806–866 antenna complex from C. aurantiacus.