BAX 335 hemophilia B gene therapy clinical trial results: potential impact of CpG sequences on gene expression.

Gene therapy has the potential to maintain therapeutic blood clotting factor IX (FIX) levels in patients with hemophilia B by delivering a functional human F9 gene into liver cells. This phase 1/2, open-label dose-escalation study investigated BAX 335 (AskBio009, AAV8.sc-TTR-FIXR338Lopt), an adeno-associated virus serotype 8 (AAV8)-based FIX Padua gene therapy, in patients with hemophilia B. This report focuses on 12-month interim analyses of safety, pharmacokinetic variables, effects on FIX activity, and immune responses for dosed participants. Eight adult male participants (aged 20-69 years; range FIX activity, 0.5% to 2.0%) received 1 of 3 BAX 335 IV doses: 2.0 × 1011; 1.0 × 1012; or 3.0 × 1012 vector genomes/kg. Three (37.5%) participants had 4 serious adverse events, all considered unrelated to BAX 335. No serious adverse event led to death. No clinical thrombosis, inhibitors, or other FIX Padua-directed immunity was reported. FIX expression was measurable in 7 of 8 participants; peak FIX activity displayed dose dependence (32.0% to 58.5% in cohort 3). One participant achieved sustained therapeutic FIX activity of ∼20%, without bleeding or replacement therapy, for 4 years; in others, FIX activity was not sustained beyond 5 to 11 weeks. In contrast to some previous studies, corticosteroid treatment did not stabilize FIX activity loss. We hypothesize that the loss of transgene expression could have been caused by stimulation of innate immune responses, including CpG oligodeoxynucleotides introduced into the BAX 335 coding sequence by codon optimization. This trial was registered at www.clinicaltrials.gov as #NCT01687608.

A systematic review of adeno-associated virus gene therapy clinical trials for HIV - A potential solution for patients with haemophilia and HIV?

INTRODUCTION: In the past HIV infection was a common complication of haemophilia therapy. Gene therapy trials in Haemophilia patients using rAAV have shown promising results; Unfortunately, the majority of gene therapy trials studies have excluded HIV positive patients. We decided to systematically review the published clinical trials using rAAV for HIV prevention. METHODS: A comprehensive literature search was performed to identify studies evaluating clinical trials using rAAV for HIV. The search was conducted using the MEDLINE/PubMed databases. Search keywords included 'gene therapy', 'adeno-associated virus', 'HIV' and 'clinical trial'. RESULTS: Three studies met our inclusion criteria. Two were phase 1 studies and one was a phase 2 study. One study examined an AAV coding for human monoclonal IgG1 antibody whereas the other two studies delivered a vector coding for viral protease and part of reverse transcriptase. All studies administered the vaccine intramuscularly and showed a response as well a good safety profile. DISCUSSION: The concept of using a viral vector to prevent a viral infection is revolutionary. Due to the paucity of information regarding application of any gene therapy in HIV patients and the potential use of gene therapy in haemophilia patients with HIV in the future warrants attention.

Recombinant long-acting glycoPEGylated factor IX in hemophilia B: a multinational randomized phase 3 trial.

This multinational, randomized, single-blind trial investigated the safety and efficacy of nonacog beta pegol, a recombinant glycoPEGylated factor IX (FIX) with extended half-life, in 74 previously treated patients with hemophilia B (FIX activity ≤2 IU/dL). Patients received prophylaxis for 52 weeks, randomized to either 10 IU/kg or 40 IU/kg once weekly or to on-demand treatment of 28 weeks. No patients developed inhibitors, and no safety concerns were identified. Three hundred forty-five bleeding episodes were treated, with an estimated success rate of 92.2%. The median annualized bleeding rates (ABRs) were 1.04 in the 40 IU/kg prophylaxis group, 2.93 in the 10 IU/kg prophylaxis group, and 15.58 in the on-demand treatment group. In the 40 IU/kg group, 10 (66.7%) of 15 patients experienced no bleeding episodes into target joints compared with 1 (7.7%) of 13 patients in the 10 IU/kg group. Health-related quality of life (HR-QoL) assessed with the EuroQoL-5 Dimensions visual analog scale score improved from a median of 75 to 90 in the 40 IU/kg prophylaxis group. Nonacog beta pegol was well tolerated and efficacious for the treatment of bleeding episodes and was associated with low ABRs in patients receiving prophylaxis. Once-weekly prophylaxis with 40 IU/kg resolved target joint bleeds in 66.7% of the affected patients and improved HR-QoL. This trial was registered at www.clinicaltrials.gov as #NCT01333111.

Impact of inhibitors on hemophilia A mortality in the United States.

The previously published mortality studies are limited in hemophilia populations but suggest that there is no increased risk of mortality in factor VIII inhibitor patients. This retrospective study analyzed surveillance data collected on 7,386 males with severe hemophilia A over a 13-year period to assess the association between a current inhibitor and death. During the study period, 432 participants died, among whom 48 were patients with an inhibitor. Clinical characteristics most strongly associated with death were increased number of reported bleeds, signs of liver disease, infection with either HIV or HCV, and the presence of inhibitor. Patients who underwent successful tolerization were not considered inhibitor patients in our analysis. In a multivariable analysis, the odds of death were 70% higher among patients with a current inhibitor compared to those without an inhibitor (P < 0.01). Deaths among patients with inhibitors were much more likely to be attributed to bleeding complications than those among patients without an inhibitor (42 vs. 12%, P < 0.0001). We conclude that males with severe hemophilia A and a current inhibitor are at increased risk of death.

Optimizing Liver Health Before and After Gene Therapy for Hemophilia A.

Gene therapy for severe hemophilia A employs an adeno-associated virus (AAV) vector and liver-specific promoters that depend on healthy hepatocyte function to achieve safe and long-lasting increases in FVIII activity. Thus, hepatocyte health is an essential aspect of safe and successful gene therapy. Many people living with hemophilia A have current or past chronic hepatitis C virus infection, metabolic dysfunction-associated steatosis or steatohepatitis, or other conditions that may compromise the efficacy and safety of AAV-mediated gene therapy. In addition, gene therapy may induce an immune response to transduced hepatocytes, leading to liver inflammation and reduced FVIII activity. The immune response can be treated with immunosuppression, but close monitoring of liver function tests and factor levels is necessary. The long-term risk of hepatocellular carcinoma associated with gene therapy is unknown. Routine screening by imaging for hepatocellular carcinoma, preferable every 6 months, is essential in patients at high risk and recommended in all recipients of hemophilia A gene therapy. This paper describes our current understanding of the biologic underpinnings of how liver health affects hemophilia A gene therapy, and provides practical clinical guidance for assessing, monitoring, and managing liver health both before and after gene therapy.

Factor IX ectopically expressed in platelets can be stored in alpha-granules and corrects the phenotype of hemophilia B mice.

We developed 2bF9 transgenic mice in a hemophilia B mouse model with the expression of human factor IX (FIX) under control of the platelet-specific integrin alphaIIb promoter, to determine whether ectopically expressing FIX in megakaryocytes can enable the storage of FIX in platelet alpha-granules and corrects the murine hemophilia B phenotype. FIX was detected in the platelets and plasma of 2bF9 transgenic mice by both antigen and activity assays. Approximately 90% of total FIX in blood was stored in platelets, most of which is releasable on activation of platelets. Immunostaining demonstrated that FIX was expressed in platelets and megakaryocytes and stored in alpha-granules. All 2bF9 transgenic mice survived tail clipping, suggesting that platelet-derived FIX normalizes hemostasis in the hemophilia B mouse model. This protection can be transferred by bone marrow transplantation or platelet transfusion. However, unlike our experience with platelet FVIII, the efficacy of platelet-derived FIX was limited in the presence of anti-FIX inhibitory antibodies. These results demonstrate that releasable FIX can be expressed and stored in platelet alpha-granules and that platelet-derived FIX can correct the bleeding phenotype in hemophilia B mice. Our studies suggest that targeting FIX expression to platelets could be a new gene therapy strategy for hemophilia B.

Adeno-associated virus serotype 8 ApoA-I gene transfer reduces progression of atherosclerosis in ApoE-KO mice: comparison of intramuscular and intravenous administration.

Apolipoprotein A-I (ApoA-I)/high-density lipoprotein (HDL)-raising treatments are effective antiatherosclerotic strategies. We have compared the antiatherogenic effects of human ApoA-I (hApoA-I) overexpression by intraportal and intramuscular gene transfer in atherosclerotic ApoE-knockout mice. Atherosclerotic lesions were induced by atherogenic diet. After atherosclerosis induction, a group of animals was killed and served as atherosclerosis baseline-control group. The remaining animals were randomized into the following groups: (1) atherosclerosis-progression-control, (2) intraportal/vector administration, and (3) intramuscular/vector administration. Aortas and hearts were processed for atherosclerotic quantification by en face Sudan IV and Oil Red-O, respectively. Liver and muscle specimens were processed for protein/gene expression analysis. A sustained increase in hApoA-I/HDL plasma levels was observed in both transduced groups. hApoA-I overexpression abolished plaque progression versus progression-control group. hApoA-I overexpression significantly reduced lesion macrophage, feature indicative of plaque stabilization. Scavenger receptor class-B type I (SR-BI), but not ATP-binding cassette, sub-family A (ABCA), member 1 (ABCA-1), was significantly upregulated in treated groups versus progression-controls. The results of this study show a similar effect of hApoA-I/HDL overexpression on plaque progression/stabilization by 2 different routes of administration. Our results showing similar effects using either intramuscular administration and intraportal route of administration may have significant clinical implications, given the reduced medical risk to patient and cost of intramuscular injections.

Phenotype correction of hemophilia A mice by spliceosome-mediated RNA trans-splicing.

Conventional gene therapy of hemophilia A relies on the transfer of factor VIII (FVIII; encoded by the F8 gene) cDNA. We carried out spliceosome-mediated RNA trans-splicing (SMaRT) to repair mutant FVIII mRNA. A pre-trans-splicing molecule (PTM) corrected endogenous FVIII mRNA in F8 knockout mice with the hemophilia A phenotype, producing sufficient functional FVIII to correct the hemophilia A phenotype. This is the first description of phenotypic correction of a genetic defect by RNA repair in a knockout animal model. Our results indicate the feasibility of using SMaRT to repair RNA for the treatment of genetic diseases.

Safe and sustained overexpression of functional apolipoprotein A-I/high-density lipoprotein in apolipoprotein A-I-null mice by muscular adeno-associated viral serotype 8 vector gene transfer.

High levels of high-density lipoprotein (HDL) have protective effects against atherosclerosis and cardiovascular diseases. The postulated mechanism of action for these benefits is an enhanced reverse cholesterol transport. Apolipoprotein A-I (ApoA-I) is the major protein of HDL. The clinical benefits of raising ApoA-I/HDL have been clearly established by clinical and epidemiological studies. Despite these observations, there are not very effective pharmacological means for raising HDL. ApoA-I gene delivery by viral vectors seems a promising strategy to raise ApoA-I/HDL levels. Sustained gene expression in animals and humans has been attained using adeno-associated viral (AAV) vectors. The aim of the present study was to determine the efficiency, safety, and biological activity of human ApoA-I intramuscularly delivered using an AAV vector in mice. AAV serotype 8 vectors encoding for human ApoA-I transgene were administered intraportally and intramuscularly in ApoA-I- deficient animals. ApoA-I levels were measured every 2 weeks post administration. The effectiveness of the generated HDL was tested in vitro in cholesterol-loaded macrophages. The administration of the vectors resulted in a significant and sustained increase in ApoA-I and HDL plasma levels for up to 16 weeks at similar extent by both routes of administration. Activity of the generated HDL in removal of cholesterol from cholesterol-loaded macrophages was similar in both groups. Our data suggest that intramuscular AAV8-mediated gene transfer of human ApoA-I results in a significant and maintained increase in ApoA-I and functional HDL.

Intrathecal long-term gene expression by self-complementary adeno-associated virus type 1 suitable for chronic pain studies in rats.

BACKGROUND: Intrathecal (IT) gene transfer is an attractive approach for targeting spinal mechanisms of nociception but the duration of gene expression achieved by reported methods is short (up to two weeks) impairing their utility in the chronic pain setting. The overall goal of this study was to develop IT gene transfer yielding true long-term transgene expression defined as > or = 3 mo following a single vector administration. We defined "IT" administration as atraumatic injection into the lumbar cerebrospinal fluid (CSF) modeling a lumbar puncture. Our studies focused on recombinant adeno-associated virus (rAAV), one of the most promising vector types for clinical use. RESULTS: Conventional single stranded rAAV2 vectors performed poorly after IT delivery in rats. Pseudotyping of rAAV with capsids of serotypes 1, 3, and 5 was tested alone or in combination with a modification of the inverted terminal repeat. The former alters vector tropism and the latter allows packaging of self-complementary rAAV (sc-rAAV) vectors. Combining both types of modification led to the identification of sc-rAAV2/l as a vector that performed superiorly in the IT space. IT delivery of 3 x 10e9 sc-rAAV2/l particles per animal led to stable expression of enhanced green fluorescent protein (EGFP) for > or = 3 mo detectable by Western blotting, quantitative PCR, and in a blinded study by confocal microscopy. Expression was strongest in the cauda equina and the lower sections of the spinal cord and only minimal in the forebrain. Microscopic examination of the SC fixed in situ with intact nerve roots and meninges revealed strong EGFP fluorescence in the nerve roots. CONCLUSION: sc-rAAVl mediates stable IT transgene expression for > or = 3 mo. Our findings support the underlying hypothesis that IT target cells for gene transfer lack the machinery for efficient conversion of the single-stranded rAAV genome into double-stranded DNA and favor uptake of serotype 1 vectors over 2. Experiments presented here will provide a rational basis for utilizing IT rAAV gene transfer in basic and translational studies on chronic pain.

RNA repair for haemophilia A.

The mainstay of gene transfer studies is the use of wild-type cDNAs to effect phenotypic correction of diseases. However, this strategy is not feasible for genetic diseases caused either by mutations of large genes or by dominant-negative mutations, or where the regulation of the gene is critical. In this review, we will discuss a novel RNA reprogramming strategy - spliceosome-mediated RNA trans-splicing - where the pre-messenger RNA is modified by the splicing of two independent RNA species. The use of trans-splicing to effect phenotypic change in the hereditary bleeding disorder haemophilia A will be discussed.

Current and future prospects for hemophilia gene therapy.

Here we review the recent literature on Hemophilia gene transfer/therapy. Gene therapy is one of several new technologies being developed as a treatment for bleeding disorders. We will discuss current and pending clinical efforts and attempt to relate how the field is trending. In doing so, we will focus on the use of recombinant Adeno-associated viral (rAAV) vector-mediated gene transfer since all currently active trials are using this vector. Recent exciting results embody nearly 20 years of preclinical and translational research. After several early clinical attempts, therapeutic factor levels that can now be achieved reflect several modifications of the original vectors. Patterns of results are slowly starting to emerge as different AAV vectors are being tested. As with any new technology, there are drawbacks, and the potential for immune/inflammatory and oncogenic risks have emerged and will be discussed.

The burden of inhibitors in haemophilia patients.

The burden of disease in haemophilia patients has wide ranging implications for the family and to society. There is evidence that having a current inhibitor increases the risk of morbidity and mortality. Morbidity is increased by the inability to treat adequately and its consequent disabilities, which then equates to a poor quality of life compared with non-inhibitor patients. The societal cost of care, or `burden of inhibitors', increases with the ongoing presence of an inhibitor. Therefore, it is clear that successful eradication of inhibitors by immune tolerance induction (ITI) is the single most important milestone one can achieve in an inhibitor patient. The type of factor VIII (FVIII) product used in ITI regimens varies worldwide. Despite ongoing debate, there is in vitro and retrospective clinical evidence to support the use of plasma-derived VWF-containing FVIII concentrates in ITI regimens in order to achieve early and high inhibitor eradication success rates.

Intrathecal gene transfer by adeno-associated virus for pain.

Chronic pain is among the most prevalent medical problems, affecting more than half of patients with advanced cancer and many with other common diseases. Current analgesics often fail to provide satisfactory symptom relief and frequently cause severe side effects. Intrathecal (IT) gene transfer is an attractive method for pain research in rodent models, because it allows targeting of a wide variety of secretable peptides and proteins to the spinal cord, an important neural center for the processing of nociceptive signals. The potential of IT gene transfer for improving opioid therapy and for validating new analgesic targets, such as cytokines involved in spinal glial activation, is discussed. The IT space has been notoriously resistant to efficient gene transfer, limiting therapeutic gene expression to less than 2 weeks with most vector systems. Recent progress with adeno-associated virus (AAV) technology allowed efficient long-term gene expression, facilitating studies reflective of the chronic nature of many pain states. AAV is one of the most advanced gene therapy vectors currently undergoing clinical trials for a variety of disorders. In patients, AAV vectors could be administered intrathecally by a lumbar puncture, a safe procedure routinely performed at the bedside. AAV vectors may therefore become an important tool for translational studies to validate newly identified therapeutic targets in clinical pain states.

New paradigms for gene transfer: RNA trans-splicing and small interfering RNA as therapeutic strategies.

If successful, the sustained and regulated expression of therapeutic proteins secreted from a variety of tissues would revolutionize the medical treatment of hematologic diseases. The current paradigm that has dominated the gene therapy field since its inception has been the transfer of complementary DNAs (cDNAs) that encode for therapeutic proteins. The transfer of cDNAs can only correct autosomal recessive and sex-linked disorders. In most cases, cDNAs are constructed that lack their endogenous regulatory elements and therefore lose their intrinsic regulation of gene expression. In this article we will describe the use of RNA species to either suppress unwanted gene activity or to repair defective genes. Examples of RNA inhibition and repair will be discussed.

Lentivirus vector purification using anion exchange HPLC leads to improved gene transfer.

Recombinant lentiviral vectors stably transduce both dividing and nondividing cells. Virus pseudotyping with vesicular stomatitis virus envelope G (VSV-G) protein broadens the host range of lentiviral vector and enables vector concentration by ultra-centrifugation. However, as a result of virus vector concentration, contaminating protein debris derived from vector-producing cell culture media is toxic to target cells and reduces the transduction efficiency. Here we report a new and rapid technique for purifying lentivirus vector using the strong anion exchange column that significantly improves gene transfer rates. We purified VSV-G pseudotyped self-inactivating lentivirus vector and obtained two protein elution peaks (Peak 1 and Peak 2) corresponding to transducing activity. Peak 1 viral particles were 4-8 times more effective in transducing target cells than Peak 2 or non-purified (pre-HPLC) viral particles. We used purified lentivirus vector expressing the human Fanconi anemia group A (FANCA) gene to transduce murine hematopoietic stem/progenitor cells. We observed a consistent 2- to 3-fold increase in gene transfer rates using Peak 1 purified virus compared with non-purified virus. We conclude that the purification method using the HPLC system provides the highly purified virus vector that reduces cell toxicity and significantly improves gene transfer in primary cells.

Hemophilia gene therapy: novel rAAV vectors and RNA repair strategy.

Hemophilia results from a deficiency of coagulation Factor VIII or IX and manifests clinically as spontaneous bleeding into the large joints and soft tissue. Current treatment relies on the intravenous infusion of recombinant or purified Factor proteins. Factor infusion is effective, but transient due to the short half-life of Factor proteins. Recent developments in gene transfer technology have led to new strategies using molecular therapeutics as permanent treatment for bleeding disorders. This review describes recent novel molecular strategies for the treatment of the hemophilias.

AAV vectors for hemophilia B gene therapy.

Adeno-associated viral (AAV) vector is attracting significant interest for use in gene therapy for genetic diseases, because of its unique and advantageous characteristics, compared to other currently available viral vectors. Eight natural serotypes of AAV have been identified, of which AAV serotype 2 is the one best characterized and most widely used in current gene delivery studies. The application of AAV serotype 2 in hemophilia B gene therapy is a promising development in gene therapy for genetic diseases such as hemophilia. Preliminary studies have demonstrated relation and distinction of host, genome sequences, replication, tropism, packaging of recombinant virions and cross-reactivity of neutralizing antibodies among different serotypes of AAV. This review summarizes the progress of studies in AAV serotypes and pertinent applications in hemophilia B gene therapy. The latest progress in gene delivery of coagulant factor IX (for hemophilia B) using AAV serotype vectors is described in detail.

Hemophilia clinical gene therapy: brief review.

Genetic correction of hemophilia A and B was long considered amenable to the available gene transfer technologies. This assumption has come to fruition with the recent results of a phase I/II trial for hemophilia B. Here we review the clinical application of gene therapy for the hemophilia's as a paradigm of the evolution of gene transfer science and technology. This review is not intended as comprehensive but rather to highlight current clinical developments of gene therapy for the hemophilias.