Recombinant adeno-associated viral vectors (rAAV) currently constitute a real therapeutic strategy for the sustained correction of diverse genetic conditions. Though a wealth of preclinical and clinical studies have been conducted with rAAV, the oncogenic potential of these vectors is still controversial, particularly when considering liver-directed gene therapy. Few preclinical studies and the recent discovery of incomplete wild-type AAV2 genomes integrated in human hepatocellular carcinoma biopsies have raised concerns on rAAV safety. In the present study, we have characterized the integration of both complete and partial rAAV2/5 genomes in nonhuman primate tissues and clinical liver biopsies from a trial aimed to treat acute intermittent porphyria. We applied a new multiplex linear amplification-mediated polymerase chain reaction (PCR) assay capable of detecting integration events that are originated throughout the rAAV genome. The integration rate was low both in nonhuman primates and patient's samples. Importantly, no integration clusters or events were found in genes previously reported to link rAAV integration with hepatocellular carcinoma development, thus showing the absence of genotoxicity of a systemically administered rAAV2/5 in a large animal model and in the clinical context.

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.

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 viruses (AAVs) have become highly promising tools for research and clinical applications in the central nervous system (CNS). However, specific delivery of genes to the cell type of interest is essential for the success of gene therapy and therefore a correct selection of the promoter plays a very important role. Here, AAV8 vectors carrying enhanced green fluorescent protein (eGFP) as reporter gene under the transcriptional control of different CNS-specific promoters were used and compared with a strong ubiquitous promoter. Since one of the main limitations of AAV-mediated gene delivery lies in its restricted cloning capacity, we focused our work on small-sized promoters. We tested the transduction efficacy and specificity of each vector after stereotactic injection into the mouse striatum. Three glia-specific AAV vectors were generated using two truncated forms of the human promoter for glial fibrillar acidic protein (GFAP) as well as a truncated form of the murine GFAP promoter. All three vectors resulted in predominantly glial expression; however we also observed eGFP expression in other cell-types such as oligodendrocytes, but never in neurons. In addition, robust and neuron-specific eGFP expression was observed using the minimal promoters for the neural protein BM88 and the neuronal nicotinic receptor β2 (CHRNB2). In summary, we developed a set of AAV vectors designed for specific expression in cells of the CNS using minimal promoters to drive gene expression when the size of the therapeutic gene matters.

Background The efficacy and safety of high vs. medium doses of glucocorticoids for the treatment of COVID‐19 patients has shown mixed outcomes in controlled trials and observational studies. We aimed to evaluate the effectiveness of methylprednisolone 250 mg bolus vs. dexamethasone 6 mg in patients with severe COVID‐19. Methods A randomized, open‐label, controlled trial was conducted between February and August 2021 at four hospitals in Spain. The trial was suspended after the first interim analysis since the investigators considered that continuing the trial would be futile. Patients were randomly assigned in a 1:1 ratio to receive dexamethasone 6 mg once daily for up to 10 days or methylprednisolone 250 mg once daily for 3 days. Results Of the 128 randomized patients, 125 were analysed (mean age 60 ± 17 years, 82 males [66%]). Mortality at 28 days was 4.8% in the 250 mg methylprednisolone group vs. 4.8 % in the 6 mg dexamethasone group (absolute risk difference, 0.1% [95% CI, ‐8.8 to 9.1%], P =0.98). None of the secondary outcomes (admission to the intensive care unit, non‐invasive respiratory or high‐flow oxygen support, additional immunosuppressive drugs, or length of stay) or prespecified sensitivity analyses were statistically significant. Hyperglycaemia was more frequent in the methylprednisolone group at 27.0 vs. 8.1 % (absolute risk difference, ‐18.9% [95% CI, ‐31.8 to ‐ 5.6%], P =0.007). Conclusions Among severe but not critical patients with COVID‐19, 250 mg/d for 3 days of methylprednisolone compared with 6 mg/d for 10 days of dexamethasone did not result in a decrease in mortality or intubation.