Phase I open label liver-directed gene therapy clinical trial for acute intermittent porphyria.

BACKGROUND & AIMS: Acute intermittent porphyria (AIP) results from porphobilinogen deaminase (PBGD) haploinsufficiency, which leads to hepatic over-production of the neurotoxic heme precursors porphobilinogen (PBG) and delta-aminolevulinic acid (ALA) and the occurrence of neurovisceral attacks. Severe AIP is a devastating disease that can only be corrected by liver transplantation. Gene therapy represents a promising curative option. The objective of this study was to investigate the safety of a recombinant adeno-associated vector expressing PBGD (rAAV2/5-PBGD) administered for the first time in humans for the treatment of AIP. METHODS: In this phase I, open label, dose-escalation, multicenter clinical trial, four cohorts of 2 patients each received a single intravenous injection of the vector ranging from 5×10(11) to 1.8×10(13) genome copies/kg. Adverse events and changes in urinary PBG and ALA and in the clinical course of the disease were periodically evaluated prior and after treatment. Viral shedding, immune response against the vector and vector persistence in the liver were investigated. RESULTS: Treatment was safe in all cases. All patients developed anti-AAV5 neutralizing antibodies but no cellular responses against AAV5 or PBGD were observed. There was a trend towards a reduction of hospitalizations and heme treatments, although ALA and PBG levels remained unchanged. Vector genomes and transgene expression could be detected in the liver one year after therapy. CONCLUSIONS: rAAV2/5-PBGD administration is safe but AIP metabolic correction was not achieved at the doses tested in this trial. Notwithstanding, the treatment had a positive impact in clinical outcomes in most patients. LAY SUMMARY: Studies in an acute intermittent porphyria (AIP) animal model have shown that gene delivery of PBGD to hepatocytes using an adeno-associated virus vector (rAAV2/5-PBG) prevent mice from suffering porphyria acute attacks. In this phase I, open label, dose-escalation, multicenter clinical trial we show that the administration of rAAV2/5-PBGD to patients with severe AIP is safe but metabolic correction was not achieved at the doses tested; the treatment, however, had a positive but heterogeneous impact on clinical outcomes among treated patients and 2 out of 8 patients have stopped hematin treatment. CLINICAL TRIAL NUMBER: The observational phase was registered at Clinicaltrial.gov as NCT 02076763. The interventional phase study was registered at EudraCT as n° 2011-005590-23 and at Clinicaltrial.gov as NCT02082860.

Safety and liver transduction efficacy of rAAV5-cohPBGD in nonhuman primates: a potential therapy for acute intermittent porphyria.

Acute intermittent porphyria (AIP) results from haplo-insufficient activity of porphobilinogen deaminase (PBGD) and is characterized clinically by life-threatening, acute neurovisceral attacks. To date, liver transplantation is the only curative option for AIP. The aim of the present preclinical nonhuman primate study was to determine the safety and transduction efficacy of an adeno-associated viral vector encoding PBGD (recombinant AAV serotype 5-codon-optimized human porphobilinogen deaminase, rAAV5-cohPBGD) administered intravenously as part of a safety program to start a clinical study in patients with AIP. Macaques injected with either 1 × 10(13) or 5 × 10(13) vector genomes/kg of clinical-grade rAAV5-cohPBGD were monitored by standardized clinical parameters, and vector shedding was analyzed. Liver transduction efficacy, biodistribution, vector integration, and histopathology at day 30 postvector administration were determined. There was no evidence of acute toxicity, and no adverse effects were observed. The vector achieved efficient and homogenous hepatocellular transduction, reaching transgenic PBGD expression levels equivalent to 50% of the naturally expressed PBGD mRNA. No cellular immune response was detected against the human PBGD or AAV capsid proteins. Integration site analysis in transduced liver cells revealed an almost random integration pattern supporting the good safety profile of rAAV5-cohPBGD. Together, data obtained in nonhuman primates indicate that rAAV5-cohPBGD represents a safe therapy to correct the metabolic defect present in AIP patients.

Adeno-associated viral vector serotype 5 poorly transduces liver in rat models.

Preclinical studies in mice and non-human primates showed that AAV serotype 5 provides efficient liver transduction and as such seems a promising vector for liver directed gene therapy. An advantage of AAV5 compared to serotype 8 already shown to provide efficient correction in a phase 1 trial in patients suffering from hemophilia B, is its lower seroprevalence in the general population. Our goal is liver directed gene therapy for Crigler-Najjar syndrome type I, inherited severe unconjugated hyperbilirubinemia caused by UGT1A1 deficiency. In a relevant animal model, the Gunn rat, we compared the efficacy of AAV 5 and 8 to that of AAV1 previously shown to be effective. Ferrying a construct driving hepatocyte specific expression of UGT1A1, both AAV8 and AAV1 provided an efficient correction of hyperbilirubinemia. In contrast to these two and to other animal models AAV5 failed to provide any correction. To clarify whether this unexpected finding was due to the rat model used or due to a problem with AAV5, the efficacy of this serotype was compared in a mouse and two additional rat strains. Administration of an AAV5 vector expressing luciferase under the control of a liver specific promoter confirmed that this serotype poorly performed in rat liver, rendering it not suitable for proof of concept studies in this species.

Development of a liver-specific Tet-on inducible system for AAV vectors and its application in the treatment of liver cancer.

Recombinant adeno-associated virus (rAAV) are effective gene delivery vehicles that can mediate long-lasting transgene expression. However, tight regulation and tissue-specific transgene expression is required for certain therapeutic applications. For regulatable expression from the liver we designed a hepatospecific bidirectional and autoregulatory tetracycline (Tet)-On system (Tet(bidir)Alb) flanked by AAV inverted terminal repeats (ITRs). We characterized the inducible hepatospecific system in comparison with an inducible ubiquitous expression system (Tet(bidir)CMV) using luciferase (luc). Although the ubiquitous system led to luc expression throughout the mouse, luc expression derived from the hepatospecific system was restricted to the liver. Interestingly, the induction rate of the Tet(bidir)Alb was significantly higher than that of Tet(bidir)CMV, whereas leakage of Tet(bidir)Alb was significantly lower. To evaluate the therapeutic potential of this vector, an AAV-Tet(bidir)-Alb-expressing interleukin-12 (IL-12) was tested in a murine model for hepatic colorectal metastasis. The vector induced dose-dependent levels of IL-12 and interferon-γ (IFN-γ), showing no significant toxicity. AAV-Tet(bidir)-Alb-IL-12 was highly efficient in preventing establishment of metastasis in the liver and induced an efficient T-cell memory response to tumor cells. Thus, we have demonstrated persistent, and inducible in vivo expression of a gene from a liver-specific Tet-On inducible construct delivered via an AAV vector and proved to be an efficient tool for treating liver cancer.

Molecular therapy for obesity and diabetes based on a long-term increase in hepatic fatty-acid oxidation.

UNLABELLED: Obesity-induced insulin resistance is associated with both ectopic lipid deposition and chronic, low-grade adipose tissue inflammation. Despite their excess fat, obese individuals show lower fatty-acid oxidation (FAO) rates. This has raised the question of whether burning off the excess fat could improve the obese metabolic phenotype. Here we used human-safe nonimmunoreactive adeno-associated viruses (AAV) to mediate long-term hepatic gene transfer of carnitine palmitoyltransferase 1A (CPT1A), the key enzyme in fatty-acid ß-oxidation, or its permanently active mutant form CPT1AM, to high-fat diet-treated and genetically obese mice. High-fat diet CPT1A- and, to a greater extent, CPT1AM-expressing mice showed an enhanced hepatic FAO which resulted in increased production of CO(2) , adenosine triphosphate, and ketone bodies. Notably, the increase in hepatic FAO not only reduced liver triacylglyceride content, inflammation, and reactive oxygen species levels but also systemically affected a decrease in epididymal adipose tissue weight and inflammation and improved insulin signaling in liver, adipose tissue, and muscle. Obesity-induced weight gain, increase in fasting blood glucose and insulin levels, and augmented expression of gluconeogenic genes were restored to normal only 3 months after AAV treatment. Thus, CPT1A- and, to a greater extent, CPT1AM-expressing mice were protected against obesity-induced weight gain, hepatic steatosis, diabetes, and obesity-induced insulin resistance. In addition, genetically obese db/db mice that expressed CPT1AM showed reduced glucose and insulin levels and liver steatosis. CONCLUSION: A chronic increase in liver FAO improves the obese metabolic phenotype, which indicates that AAV-mediated CPT1A expression could be a potential molecular therapy for obesity and diabetes.

Adeno-associated virus liver transduction efficiency measured by in vivo [18F]FHBG positron emission tomography imaging in rodents and nonhuman primates.

Recombinant adeno-associated virus 5 (rAAV5) represents a candidate vector with unique advantages for the treatment of hepatic disorders because of its narrow hepatic tropism. Noninvasive in vivo imaging of transgene expression provides an important tool with which to quantify the transduction efficiency, and duration and location, of transgene expression. In this study, we used positron emission tomography (PET) and positron emission tomography-computed tomography (PET-CT) imaging to monitor liver transduction efficacy in rodents and nonhuman primates that received rAAV5 vector encoding herpes simplex virus thymidine kinase (HSV-TK). HSV-TK expression in liver was also measured by immunohistochemistry. Notable differences in liver transduction efficiency were found, dependent on the animal species and sex. Male rodents were better transduced than females, as previously described. Moreover, male nonhuman primates also displayed increased hepatic expression of the rAAV5-delivered transgene, indicating that differences in rAAV-mediated liver transduction can be anticipated in humans. Our results demonstrate the high sensitivity and reproducibility of PET, using HSV-TK and [(18)F]FHBG, to detect gene expression after rAAV vector administration into living animals, confirming the utility of this technology in the quantification of transgene expression, even at low expression levels. However, we also describe how an immune response against HSV-TK hampered analysis of long-term expression in nonhuman primates.

Insulin-like growth factor I gene transfer to cirrhotic liver induces fibrolysis and reduces fibrogenesis leading to cirrhosis reversion in rats.

UNLABELLED: We investigated whether gene transfer of insulin-like growth factor I (IGF-I) to the hepatic tissue was able to improve liver histology and function in established liver cirrhosis. Rats with liver cirrhosis induced by carbon tetrachloride (CCl(4)) given orally for 8 weeks were injected through the hepatic artery with saline or with Simian virus 40 vectors encoding IGF-I (SVIGF-I), or luciferase (SVLuc). Animals were sacrificed 8 weeks after vector injection. In cirrhotic rats we observed that, whereas IGF-I was synthesized by hepatocytes, IGF-I receptor was predominantly expressed by nonparenchymal cells, mainly in fibrous septa surrounding hepatic nodules. Rats treated with SVIGF-I showed increased hepatic levels of IGF-I, improved liver function tests, and reduced fibrosis in association with diminished alpha-smooth muscle actin expression, up-regulation of matrix metalloproteases (MMPs) and decreased expression of the tissue inhibitors of MMPs TIM-1 and TIM-2. SVIGF-I therapy induced down-regulation of the profibrogenic molecules transforming growth factor beta (TGFbeta), amphiregulin, platelet-derived growth factor (PDGF), connective tissue growth factor (CTGF), and vascular endothelium growth factor (VEGF) and induction of the antifibrogenic and cytoprotective hepatocyte growth factor (HGF). Furthermore, SVIGF-I-treated animals showed decreased expression of Wilms tumor-1 (WT-1; a nuclear factor involved in hepatocyte dedifferentiation) and up-regulation of hepatocyte nuclear factor 4 alpha (HNF4alpha) (which stimulates hepatocellular differentiation). The therapeutic potential of SVIGF-I was also tested in rats with thioacetamide-induced liver cirrhosis. Also in this model, SVIGF-I improved liver function and reduced liver fibrosis in association with up-regulation of HGF and MMPs and down-regulation of tissue inhibitor of metalloproteinase 1 (TIMP-1). CONCLUSION: IGF-I gene transfer to cirrhotic livers induces MMPs and hepatoprotective factors leading to reversion of fibrosis and improvement of liver function. IGF-I gene therapy may be a useful alternative therapy for patients with advanced cirrhosis without timely access to liver transplantation.

Effect of adeno-associated virus serotype and genomic structure on liver transduction and biodistribution in mice of both genders.

Recombinant adeno-associated viral (AAV) vectors have unique properties, which make them suitable vectors for gene transfer. Here we assess the liver transduction efficiency and biodistribution of AAV-pseudotyped capsids (serotypes) 1, 5, 6, and 8, combined with single-stranded and double-stranded genomic AAV2 structures carrying the luciferase reporter gene after systemic administration. The analysis was performed in vivo and ex vivo, in male and female mice. Gender-related differences in AAV-mediated transduction and biodistribution were shown for the four serotypes. Our data confirm the superiority of AAV8 over the rest of the serotypes, as well as a significant advantage of double-stranded genomes in terms of liver transduction efficiency, particularly in females. Regarding biodistribution, AAV5 displayed a narrower tropism than the other serotypes tested, transducing, almost exclusively, the liver. Interestingly, AAV1 and AAV8, in particular those having single-stranded genomes, showed high transduction efficiency of female gonads. However, no inadvertent germ line transmission of AAV genomes was observed after breeding single-stranded AAV8-injected female mice with untreated males. In conclusion, double-stranded AAV8 vectors led to the highest levels of liver transduction in mice, as demonstrated by luciferase expression. Nevertheless, the transduction of other organs with AAV8 vectors could favor the use of less efficient serotypes, such as AAV5, which display a narrow tropism.

Treatment of chronic viral hepatitis in woodchucks by prolonged intrahepatic expression of interleukin-12.

Chronic hepatitis B is a major cause of liver-related death worldwide. Interleukin-12 (IL-12) induction accompanies viral clearance in chronic hepatitis B virus infection. Here, we tested the therapeutic potential of IL-12 gene therapy in woodchucks chronically infected with woodchuck hepatitis virus (WHV), an infection that closely resembles chronic hepatitis B. The woodchucks were treated by intrahepatic injection of a helper-dependent adenoviral vector encoding IL-12 under the control of a liver-specific RU486-responsive promoter. All woodchucks with viral loads below 10(10) viral genomes (vg)/ml showed a marked and sustained reduction of viremia that was accompanied by a reduction in hepatic WHV DNA, a loss of e antigen and surface antigen, and improved liver histology. In contrast, none of the woodchucks with higher viremia levels responded to therapy. The antiviral effect was associated with the induction of T-cell immunity against viral antigens and a reduction of hepatic expression of Foxp3 in the responsive animals. Studies were performed in vitro to elucidate the resistance to therapy in highly viremic woodchucks. These studies showed that lymphocytes from healthy woodchucks or from animals with low viremia levels produced gamma interferon (IFN-gamma) upon IL-12 stimulation, while lymphocytes from woodchucks with high viremia failed to upregulate IFN-gamma in response to IL-12. In conclusion, IL-12-based gene therapy is an efficient approach to treat chronic hepadnavirus infection in woodchucks with viral loads below 10(10) vg/ml. Interestingly, this therapy is able to break immunological tolerance to viral antigens in chronic WHV carriers.

Intrahepatic injection of recombinant adeno-associated virus serotype 2 overcomes gender-related differences in liver transduction.

The liver is an attractive organ for gene therapy because of its important role in many inherited and acquired diseases. Recombinant adeno-associated viruses (rAAVs) have been shown to be good candidates for liver gene delivery, leading to long-term gene expression. We evaluated the influence of the route of administration on rAAV-mediated liver transduction by comparing levels of luciferase expression in the livers of male and female mice after injection of rAAV serotype 2, using three different routes of administration: intravenous (IV), intraportal (IP), or direct intrahepatic (IH) injection. To determine transgene expression we used a noninvasive optical bioluminescence imaging system that allowed long-term in vivo analysis. After IV injection dramatic differences in liver transgene expression were observed, depending on gender. When IP injection was used the differences were reduced although they were still significant. Interestingly, direct intrahepatic injection of rAAV vectors was associated with the fastest and strongest onset of luciferase expression. Moreover, no gender differences in liver transduction were observed and luciferase expression was confined to the site of injection. Thus, direct intrahepatic injection of rAAV offers specific advantages, which support the potential of this route of administration for future clinical applications.