In pursuit of a gene transfer agent with efficient pulmonary transduction, the UK Respiratory Gene Therapy Consortium has developed a lentiviral vector pseudotyped with the envelope proteins, F and HN from Sendai virus (rSIV.F/HN). In contrast to other viral vectors, pulmonary rSIV.F/HN delivery achieves sustained gene expression ( ~ 2 years in mice) in the lungs and systemic circulation following a single dose. Here, we investigate the application of the rSIV.F/HN vector-platform for wider indications, including systemic disorders that require serum expression of therapeutic proteins. To assess the potential for rSIV.F/HN to produce systemic proteins, intravenous vector delivery was characterised and compared against intrapulmonary administration, achieved via 'nasal sniffing'. Both delivery routes achieved sustained (at least 1 year) systemic expression of the secreted reporter protein Gaussia luciferase. Systemic rSIV.F/HN delivery resulted in widespread protein expression across multiple organs, accompanied by the generation of significant anti-vector neutralising antibodies limiting vector readministration. Conversely, localised airway transduction was observed following pulmonary administration, which we have previously shown is not an impediment to efficient vector readministration. These data support intrapulmonary rSIV.F/HN delivery for systemic protein production, with sustained high-level transgene expression and feasible readministration.

Targeting of the nasal epithelium for sustained therapeutic protein secretion represents a potential non-invasive lentiviral vector application strategy. Using reporter imaging, molecular, and radiopharmaceutical tracing methods in mice, we have developed an intranasal (nose-only) dosing strategy with a Sendai virus envelope glycoprotein pseudotyped lentiviral vector (rSIV.F/HN). Using multiple (up to 10) small-volume (5 μL) intranasal bolus applications, a technetium radiotracer showed >90% liquid retention in the murine head and <1% in the lung. Following vector administration, transgene expression was dose-related in the nose, with minimal lung expression. No acute nasal toxicity was associated with nose-only delivery. Next, we compared levels of a secreted protein, Gaussia luciferase (Gluc), in the airways and serum after nose-only and intravenous administration of rSIV.F/HN-Gluc (2e8 TU/mouse). Gluc expression in the nose and lungs was higher following nose-only versus intravenous administration. Serum levels were similar after either route of administration. Finally, nose-only delivery of rSIV.F/HN encoding granulocyte-macrophage colony-stimulating factor (GM-CSF) led to sufficient lung levels of this therapeutic protein to correct disease biomarkers in a mouse model of pulmonary alveolar proteinosis. We conclude that non-invasive administration of a lentiviral vector to the nasal epithelium provides a safe and convenient route for secreted protein production and is readily translatable into humans.

The rapid spread of infectious diseases presents a significant global threat, with seasonal influenza viruses, leading to 290,000-650,000 deaths annually. Emerging high pathogenic influenza strains from animals such as H5N1 and H7N9 further exacerbates pandemic risks. While developing effective vaccines and therapeutics is critical, the evaluation of these interventions is constrained by the requirement for high biosafety containment facilities. To circumvent these challenges, we developed S-Lux, a replication-deficient, single-cycle recombinant influenza virus expressing firefly luciferase (Flux) as a reporter protein. S-Lux can be pseudotyped with haemagglutinin from avian influenza, H5 and H7, enabling real-time monitoring of viral infection in vivo, and facilitate therapeutic antibody evaluation in low-containment facilities. In mice, S-Lux infection resulted in dose-dependent bioluminescent expression in the mouse airways and allowed evaluation of neutralising monoclonal antibodies and clearance of infected cells in mice. To extend this system, we generated ES-Lux by pseudotyping with the Ebola Glycoprotein (GP) and demonstrated that ES-Lux can be used to evaluate the efficacy of Ebola GP-targeting antibodies in vivo. Together, S-Lux and ES-Lux enable robust, simple and time-efficient assessment of antiviral therapy targeting influenza and Ebola virus in vivo, overcoming biosafety constraints that limit traditional efficacy studies.

Rationale and objective Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. CFTR modulators offer significant improvements, but similar to 10% of patients remain nonresponsive or are intolerant. This study provides an analysis of rSIV.F/HN, a lentiviral vector optimised for lung delivery, including CFTR protein expression, functional correction of CFTR defects and genomic integration site analysis in preparation for a first-in-human clinical trial. Methods Air-liquid interface cultures of primary human bronchial epithelial cells (HBECs) from CF patients (F508del/F508del), as well as a CFTR-deficient immortalised human lung epithelial cell line mimicking class I (CFTR-null) homozygous mutations, were used to assess transduction efficiency. Quantification methods included a novel proximity ligation assay for CFTR protein expression. For assessment of CFTR channel activity, Ussing chamber studies were conducted. The safety profile was assessed using integration site analysis and in vitro insertional mutagenesis studies. Results rSIV.F/HN expressed CFTR and restored CFTR-mediated chloride currents to physiological levels in primary F508del/F508del HBECs as well as in a class I cells. In contrast, the latter could not be achieved by small-molecule CFTR modulators, underscoring the potential of gene therapy for this mutation class. Combination of rSIV.F/HN-CFTR with the potentiator ivacaftor showed a greater than additive effect. The genomic integration pattern showed no site predominance (frequency of occurrence <= 10%), and a low risk of insertional mutagenesis was observed in an in vitro immortalisation assay. Conclusions The results underscore rSIV.F/HN as a promising gene therapy vector for CF, providing a mutation-agnostic treatment option.

We have developed a third-generation lentiviral vector pseudotyped with Sendai virus F and HN envelope proteins (rSIV.F/HN) expressing functional cystic fibrosis transmembrane conductance regulator (CFTR) as a gene therapy for cystic fibrosis (BI 3720931). Here, we assessed transduction efficiency and acute toxicology of the rSIV.F/HN vector expressing an enhanced green fluorescent protein (EGFP) reporter gene in non-human primates (NHPs). Intubated male cynomolgus monkeys received one aerosolized dose of vector (n = 3) or placebo (n = 3). Toxicology was assessed by histopathology, clinical pathology, cytokine levels, and changes in body and organ weight. Transduction efficiency was quantified by EGFP immunohistochemistry in airway epithelial cells and vector-specific mRNA and DNA in the lung 7 days post-dosing. There were no vector-related clinical observations, mortalities, or changes in body or organ weight. Clinical pathology and cytokine analyses were unremarkable. Minimal mixed-cell centriacinar inflammation was observed in 1/3 vector-treated animals. Airway epithelial cell transduction efficiency was 9%-12%. Genomic DNA vector integration was detected in 6.7% of lung epithelial cells. Vector-specific mRNA levels were ∼45× endogenous CFTR mRNA levels in lung epithelium and ∼16× in bronchial brushings. This study extends earlier findings of rSIV.F/HN-based in vivo gene transfer in mice to NHPs, demonstrating transduction efficiency without relevant toxicity.

Cystic fibrosis (CF) is a genetic disease caused by mutations in the CFTR (cystic fibrosis transmembrane conductance regulator) gene. Although CF is a multiorgan disease, the leading causes of morbidity and mortality are related to progressive lung disease. Current understanding of the effects of the broad spectrum of CFTR mutations on CFTR function has allowed for the development of CFTR modulator therapies. Despite the remarkable impact that these therapies have had, there remains a significant proportion of people with CF (estimated at 10-15% of the global CF population) who are genetically ineligible for, or intolerant of, current CFTR-targeting therapies and whose therapeutic needs remain unmet. Inhaled genetic therapies offer the prospect of addressing the unmet pulmonary treatment need in people with CF, with several approaches, including gene addition therapy (the focus of this review), RNA-based therapies, antisense oligonucleotides, and gene editing, being explored. Various nonviral and viral vectors have been investigated for CF gene addition therapy for mutation-agnostic restoration of CFTR function in the lungs. Lentiviral vectors offer the prospect of highly efficient and long-lasting gene expression, and the potential to be safely and, in contrast to other commonly used viral vectors, effectively redosed. A third-generation lentiviral vector pseudotyped with Sendai virus F and HN envelope proteins (rSIV.F/HN) has been developed for the treatment of CF. Promising preclinical results support the progression of this vector carrying a full-length CFTR transgene (BI 3720931) into a first-in-human clinical trial expected to begin in 2024.