BACKGROUND Hemophilia B, an X-linked disorder, is ideally suited for gene therapy. We investigated the use of a new gene therapy in patients with the disorder. METHODS We infused a single dose of a serotype-8–pseudotyped, self-complementary adenovirus-associated virus (AAV) vector expressing a codon-optimized human factor IX (FIX) transgene (scAAV2/8-LP1-hFIXco) in a peripheral vein in six patients with severe hemophilia B (FIX activity, <1% of normal values). Study participants were enrolled sequentially in one of three cohorts (given a high, intermediate, or low dose of vector), with two participants in each group. Vector was administered without immunosuppressive therapy, and participants were followed for 6 to 16 months. RESULTS AAV-mediated expression of FIX at 2 to 11% of normal levels was observed in all participants. Four of the six discontinued FIX prophylaxis and remained free of spontaneous hemorrhage; in the other two, the interval between prophylactic injections was increased. Of the two participants who received the high dose of vector, one had a transient, asymptomatic elevation of serum aminotransferase levels, which was associated with the detection of AAV8-capsid–specific T cells in the peripheral blood; the other had a slight increase in liver-enzyme levels, the cause of which was less clear. Each of these two participants received a short course of glucocorticoid therapy, which rapidly normalized aminotransferase levels and maintained FIX levels in the range of 3 to 11% of normal values. CONCLUSIONS Peripheral-vein infusion of scAAV2/8-LP1-hFIXco resulted in FIX transgene expression at levels sufficient to improve the bleeding phenotype, with few side effects. Although immune-mediated clearance of AAV-transduced hepatocytes remains a concern, this process may be controlled with a short course of glucocorticoids without loss of transgene expression. (Funded by the Medical Research Council and others; ClinicalTrials.gov number, NCT00979238.)
Adeno-associated virus vectors (AAV) show promise for liver-targeted gene therapy. In this study, we examined the long-term consequences of a single intravenous administration of a self-complementary AAV vector (scAAV2/ 8-LP1-hFIXco) encoding a codon optimized human factor IX (hFIX) gene in 24 nonhuman primates (NHPs). A dose-response relationship between vector titer and transgene expression was observed. Peak hFIX expression following the highest dose of vector (2 × 10(12) pcr-vector genomes (vg)/kg) was 21 ± 3 µg/ml (~420% of normal). Fluorescent in-situ hybridization demonstrated scAAV provirus in almost 100% of hepatocytes at that dose. No perturbations of clinical or laboratory parameters were noted and vector genomes were cleared from bodily fluids by 10 days. Macaques transduced with 2 × 10(11) pcr-vg/kg were followed for the longest period (~5 years), during which time expression of hFIX remained >10% of normal level, despite a gradual decline in transgene copy number and the proportion of transduced hepatocytes. All macaques developed serotype-specific antibodies but no capsid-specific cytotoxic T lymphocytes were detected. The liver was preferentially transduced with 300-fold more proviral copies than extrahepatic tissues. Long-term biochemical, ultrasound imaging, and histologic follow-up of this large cohort of NHP revealed no toxicity. These data support further evaluation of this vector in hemophilia B patients.
To generate sufficient clinical-grade vector to support a phase I/II clinical trial of adeno-associated virus serotype 8 (AAV8)-mediated factor IX (FIX) gene transfer for hemophilia B, we have developed a large-scale, good manufacturing practice (GMP)-compatible method for vector production and purification. We used a 293T-based two-plasmid transient transfection system coupled with a three-column chromatography purification process to produce high-quality self-complementary AAV2/8 FIX clinical-grade vector. Two consecutive production campaigns using a total of 432 independent 10-stack culture chambers produced a total of *2Â10 15 vector genomes (VG) by dot-blot hybridization. Benzonase-treated microfluidized lysates generated from pellets of transfected cells were purified by group separation on Sepharose beads followed by anion-exchange chromatography. The virus-containing fractions were further processed by gel filtration and ultrafiltration, using a 100-kDa membrane. The vector was formulated in phosphate-buffered saline plus 0.25% human serum albumin. Spectrophotometric analysis suggested *20% full particles, with only low quantities of nonviral proteins were visible on silver-stained sodium dodecyl sulfate-polyacrylamide gels. A sensitive assay for the detection of replication-competent AAV was developed, which did reveal trace quantities of such contaminants in the final product. Additional studies have confirmed the long-term stability of the vector at À808C for at least 24 months and for at least 24 hr formulated in the clinical diluent and stored at room temperature within intravenous bags. This material has been approved for use in clinical trials in the United States and the United Kingdom.
, or 5 ؋ 10 7 50% egg infectious doses) was delivered by the intranasal route to each study participant. The vaccine was well tolerated by all the study participants. There was no sign of vaccine virus replication in the airway in any participant. Most children exhibited an increase in antibody binding and neutralizing responses toward hPIV-1 within 4 weeks from the time of vaccination. In several children, antibody responses remained above incoming levels for at least 6 months after vaccination. Data suggest that SeV may provide a benefit to 3-to 6-year-old children, even when vaccine recipients have preexisting cross-reactive antibodies due to previous exposures to hPIV-1. Results encourage the testing of SeV administration in young seronegative children to protect against the serious respiratory tract diseases caused by hPIV-1 infections. Human parainfluenza virus type 1 (hPIV-1) is a member of the Paramyxoviridae family. It is the major cause of laryngotracheobronchitis (croup) and can also mediate bronchiolitis and pneumonia, most commonly in children (1, 2). There have been previous attempts to develop a vaccine against hPIV-1, but no vaccine has yet been licensed (3,4). A study of a formalin-treated hPIV-1 vaccine in the 1960s demonstrated safety but not efficacy (5).We have pursued the development of a Jennerian (xenotropic) vaccine approach. Our previous studies showed that Sendai virus (SeV), a murine PIV, had both sequence and antigenic similarity with hPIV-1 (6-9). We found that hPIV-1 protected mice from SeV infections and that SeV safely protected nonhuman primates from hPIV-1 infections (10, 11). SeV has also proven successful as a recombinant vaccine for other paramyxovirus pathogens in animal models (12-18).Historically, SeV has never caused disease in humans. Upon the first discovery of the virus in 1952, there was some concern that SeV was an etiological agent for human respiratory infections, but it was later determined that SeV is a pathogen of mice, not of humans (2,19,20). Moreover, when we tested SeV in a dose escalation phase I clinical study in human adult volunteers, we found that it was well tolerated and enhanced hPIV-1-specific antibody responses in some individuals (21). As a follow-up to the adult study, we tested SeV in a dose escalation study in 3-to 6-year-old PIV-1-seropositive children, and we describe here the early safety, tolerability, and immunogenicity data in this age group. MATERIALS AND METHODS Participants.Ten healthy children between the ages of 3 and 6 years (six males, four females) were vaccinated in a phase I dose escalation study of the SeV vaccine. The protocol was reviewed and approved by the U.S.Food and Drug Administration (FDA) and the St. Jude Children's Research Hospital Institutional Review Board. The study was performed only after data from a phase I study with SeV in adults were reviewed and approved by a data safety monitoring board.Vaccine. The vaccine was an unmodified live SeV (Enders strain) propagated in chick egg (Spafas, Inc., Preston, CT) all...
5 Background: Hemophilia B (HB), an X-linked bleeding disorder, is ideally suited for gene therapy. We investigated a novel approach using peripheral vein infusion of a single dose of a serotype-8 pseudotyped self-complementary adeno-associated virus (AAV) vector expressing a codon-optimized coagulation factor IX (FIX) transgene (scAAV2/8-LP1-hFIXco). Methods: Six severe HB subjects (FIX ≤1%) were enrolled sequentially into one of three dose cohorts with two subjects in each group. Vector was administered without immunosuppression. The subjects were followed for 6–16 months post treatment. Results: AAV-mediated expression of FIX at 2–11% of normal was observed in all subjects. Four of the six have discontinued prophylaxis and remain free of spontaneous hemorrhage. The other two have increased the interval between FIX prophylaxes. A high-dose subject developed asymptomatic, transient elevation of serum transaminases associated with detection of AAV8 capsid specific T cells in peripheral blood. The second high-dose subject experienced a slight increase of liver enzymes, of less clear etiology. Treatment of each with a short course of steroids led to rapid normalization of the transaminases and maintenance of FIX levels in the 3–11% range. Conclusion: Peripheral vein administration of scAAV2/8-LP1-hFIXco was well tolerated and resulted in FIX transgene expression at levels sufficient to improve the bleeding phenotype. Immune-mediated clearance of AAV-transduced hepatocytes remains a concern but our data suggest that this process may be controlled with a short course of steroids without loss of transgene expression. Hence, our novel approach shows promise for gene therapy of HB and other protein deficiencies. (ClinicalTrials.gov number, NCT00979238) Disclosures: Nathwani: Amsterdam Molecular Therapeutics: Patents & Royalties. Gray:Amsterdam Molecular Therapeutics: Patents & Royalties. Davidoff:Amsterdam Molecular Therapeutics: Patents & Royalties.
Retroviral transduction of antifolate-resistant variants of human dihydrofolate reductase (hDHFR) into cells can increase their resistance to the cytotoxic effects of these drugs. We evaluated the ability of wild-type hDHFR and 20 mutant enzymes (13 with single-amino acid substitutions, 7 with two substitutions) to prevent growth inhibition in antifolate-treated CCRF-CEM cells. The wild-type enzyme and all of the variants significantly protected transduced cells from trimetrexate (TMTX)-induced growth inhibition. However, only half of the variants conferred more protection than does the wild-type enzyme. For the variants tested, the observed protective effect was higher for TMTX than for methotrexate (< or =7.5-fold increased resistance), piritrexim (< or =16-fold), and edatrexate (negligible). Transduction of the variants L22Y-F31S and L22Y-F31R led to the greatest protection against TMTX (approximately 200-fold). Protection from loss of cell viability was similar to protection from growth inhibition. The protection associated with a particular mutant hDHFR did not result from the level of expression: Efficient protection resulted from low affinity of the variant for antifolates, reasonable catalytic activity, and good thermal stability. Clones isolated from a polyclonal population of transduced cells varied by as much as 30-fold in their resistance to TMTX, the resistance differences depending on hDHFR expression levels.
248 We have developed a unique approach for the treatment of hemophilia B (HB) that is currently being tested in the clinic. This open-label Phase I/II clinical trial entails peripheral vein administration of a single dose of our novel self complementary AAV vector encoding a codon-optimised human FIX transgene (scAAV2/8-LP1-hFIXco) into adult subjects with severe HB. Our plan is to evaluate three dose levels, progressing to the intermediate and high doses only in the absence of toxicity in a minimum of two subjects each. Vector is being administered in the absence of immunosuppression. Thus far, two subjects have received peripheral vein infusion at the low dose, each without any side effects. Importantly, there were no adverse reactions during vector infusion and no subsequent evidence of hepatotoxicity. Overall, there were no significant changes in the complete blood count and serum chemistry panel. The longest follow-up is in the first subject, in whom plasma FIX levels increased from a baseline of <1% to between 1.5–2% of normal levels within 2 weeks. This level of transgene expression has been maintained for a period that extends beyond 5 months following vector infusion. Importantly, this subject has not required any treatment or prophylaxis with FIX concentrate over this period and remains free of spontaneous joint bleeds. A robust primary humoral response to AAV8 capsid protein was observed following vector infusion. Capsid-specific cytotoxic T cells were monitored by IFN-g ELISPOT and by staining for IFN-g, TNF-a, and CD107a followed by flow cytometry; this analysis showed no increase in AAV8 specific CD8+ T cells at any of the time points evaluated. Following vector administration there was transient, self-limited shedding of scAAV in some body fluids/excretions but vector was not detected in the semen. The same dose has recently been administered to a second patient without toxicity. The FIX level in this subject, who is on regular prophylaxis, is currently 2% of normal, 13 days after his last dose of prophylaxis which was given the same day as the vector and raised his level to 26%. His levels will be carefully monitored to more conclusively establish evidence of expression of transgenic FIX. A third patient is scheduled for treatment at the intermediate dose in the fall. These early data are highly encouraging and suggest that low doses of scAAV vector, when pseudotyped with serotype 8 capsid can mediate therapeutic levels of FIX for at least several months without provoking an immunological response of the type seen in the previous trial. Disclosures: High: Genzyme, Inc: Consultancy, Patents & Royalties; Third Rock Ventures: Consultancy; Novo-Nordisk: Consultancy; Shire, Inc.: Consultancy.
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