Repeated Administration of the Non-Viral Gene Transfer Agent pGM169/GL67A Does Not Induce Anti-CFTR or Anti-Plasmid Immunoresponses.

Griesenbach U, Alton EW, Armstrong DK, Boyd AC, Brand J, Calcedo R, Cheng S, Cunningham S, Davies JC, Dewar M, Doherty A, Elgmati HI, Gibson JSR, Gill DR, Higgins T, Hyde SC, Innes JA, Limberis MP, Manvell M, Meng C, Parra-Leiton J, Scheule RK, Soussi N, Soussi S, Wilson JM

Pediatric Pulmonology, Volume 50, Issue S41, Abstract 244

The North American Cystic Fibrosis Conference, Phoenix, 2015

Although most CF patients express CFTR protein (albeit mutant) and should therefore not recognise the wild-type CFTR protein as foreign, there is an inherent risk of activation of T cells against the recombinant wild-type protein after gene therapy. In addition, we have previously shown that approximately 10% of CF and non-CF subjects carry self-reactive CFTR-specific T cells (Calcedo et al, Hum Gene Ther Clin Dev 2013).

The reason for this is unknown and it is also unclear whether being positive for self-reactive T-cells affects disease severity or increases the risk of further T-cell activation after gene therapy. We have previously shown that a single dose of the non-viral formulation pGM169/GL67A does not induce immune-responses. The UKCFGTC has now completed a Phase 2b multi-dose gene therapy trial (ClinicalTrials.gov identification number - NCT01621867).

CF patients received 12 monthly doses of pGM169/GL67A or placebo by aerosol (116 completed 9 or more doses). Peripheral blood mononuclear cells (PBMC) were collected on two occasions prior to dose 1 to establish baseline levels for CFTR-specific T cells, approximately 4 weeks after Dose 4 or 5, and 2 to 4 weeks after Dose 12. A validated human IFN-γ ELISPOT assay to detect CFTR-specific T cells in PBMCs was performed. In addition we quantified anti-DNA antibodies (anti-nuclear and anti-cytoplasmic) in blood samples using a standard indirect fluorescence-based HEp-2 cell assay and anti-double-stranded DNA antibodies using a commercial ELiA dsDNA assay. Over 500 samples were analysed for each assay. Similar to our previous studies approximately 5% (active) to 10% (placebo) of patients carried self-reactive CFTR-specific T cells at baseline.

Encouragingly we did not observe any evidence for induction of immune responses to CFTR or the plasmid DNA in this Phase 2b trial. We will also discuss the success rates of PBMC extractions in the multi-centre trial, cell viability after prolonged storage and shipment from the UK to the US as well as assay failure rates.

Funded by the NIHR/EME Programme and the Cystic Fibrosis Trust