Safety & expression of a single dose of lipid-mediated CFTR gene therapy to the upper & lower airways of patients with CF (2011)

Davies J C, Davies G, Gill D R, Hyde S C, Boyd A C, Innes A J, Porteous D J, Cheng S H, Scheule R K, Higgins T, Griesenbach U, Alton E W F W.

Pediatric Pulmonology, 46, Abstract 198

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In preparation for a multi-dose clinical trial (MDT) of CFTR gene therapy, we undertook a study to assess safety and dose-ranging with a single nebulised dose of pGM169/ GL67A [a CpG- free human CFTR plasmid with a CpG-free CMV enhancer and human elongation factor 1 alpha (hCEFI) promoter complexed with Genzyme Lipid 67A]. We also assessed transgene expression in the lung and upper airway with QRT-PCR on airway brushings and nasal and bronchial potential difference measurements.

Thirty-five adult patients with a baseline FEV1 of at least 60% predicted received a nebulised dose of 20 mL (n=17), 10 mL (n=10) or 5 mL (n=8). A short-lived, dose-related drop in FEV1 was observed over the next 6 hours (mean [SD]: 20 mL 25.7[10.2]%; 10 mL 17.7[9.9]%; 5 mL 13.0[4.4]%); this was well-tolerated, not accompanied by desaturation, showed a restrictive pattern and was unresponsive to bronchodilators.

Subjects also experienced a systemic inflammatory response, the symptoms of which responded well to anti-pyretics. This was similarly dose- related and limited, in general, to the first 24-48 hours post-dosing. A significant correlation between the magnitude of the FEV1 drop and the rise in white blood count, suggests that the former may be an inflammatory phenomenon. A cohort of 6 patients (4@10 mL; 2@5 mL) received 4 g paracetamol over an 18 hour period post-dosing; none of these patients developed a fever. Intriguingly, these subjects also appeared to have reduced systemic inflammatory responses. Ten patients underwent pre- and post-dosing bronchoscopies, the latter at either day 6 or day 14 post-dose. Molecular (mRNA) evidence of gene transfer was observed in some individuals. The majority of the patients' zero chloride isoproterenol responses increased towards non-CF values after gene therapy. Nineteen patients received a 2 mL nasal dose. Based on an a priori definition of a 'positive response' as a chloride secretory response outside the range of their personal pre-dose measurements, 11/19 patients responded.

The plasmid has been engineered to produce slow onset of transgene expression, but with extended duration. Interestingly, PD was notably more frequently positive when measured at later, rather than earlier time points. In the two most positive individuals, maximal zero chloride responses exceeded 10 mV (ie. in the normal non-CF range) and persisted to days 63 and 91 respectively. In conclusion, we consider the pulmonary and systemic side effects after 20 mL nebulised dose are excessive for repeated application. Those at 10 mL were more acceptable, whilst 5 mL produced only small changes. Symptoms are amenable to simple antipyretic treatment and the MDT will use either 5 or 10 mL. Gene expression was confirmed in both the lower and upper airways, and restoration of CFTR function in to the non-CF range has been observed out to 13 weeks following a single dose to the nose.

These data, together with our preclinical toxicity packages (see abstracts) support progression of this agent to the multi-dose clinical trial. Funded by the UK Cystic Fibrosis Trust.