Non-viral Gene Therapy - Intracellular Delivery: Fundamentals and Applications - page 671

treatment in five HLA-B7-negative patients with stage IV melanoma. Three to
seven days post injection, pDNA could be detected by using PCR within biopsies
of treated tumor nodules, but was not found in the serum at any time. In addition,
recombinant HLA-B7 protein was measured in tumor biopsy tissue in all five
patients by immunochemistry, and immune responses to HLA-B7 and autologous
tumors could be detected as well. No antibodies to DNA could be detected in any
patient. One patient showed regression of injected nodules on two independent
treatments, which was accompanied by regression at distant sites. These studies
thus demonstrate the feasibility, safety, and therapeutic potential of local gene
therapy in humans using lipoplexes. Local delivery of lipoplexes containing HLA-
B7 in pulmonary artery of a patient with melanoma also demonstrated the well
tolerance of this formulation, and no adverse respiratory, cardiac immunologic or
other organ toxicities were detected (Nabel et al. 1994 ).
Lipid-based vectors have also been evaluated clinically in patients for the cor-
rection of cystic fibrosis (CF) defect. Lipoplexes of cystic fibrosis transmembrane
conductance regulator (CFTR) cDNA and lipid 67 were delivered in the nose and
the lung in CF patients in Great Britain (Alton et al. 1999 ). It was shown that no
mRNA for CFTR was detected in epithelial samples. Modest improvement in chlo-
ride transport was detected at both sites by transepithelial potential difference
measurements. However, significant inflammatory response was observed. In other
trials conducted in the USA, little or no chloride transport improvement has been
documented with lipoplexes based formulations, while significant inflammatory
responses were still observed in these trials (Noone et al. 2000 ; Ruiz et al. 2001 ).
The inflammatory toxicities have been considered to be related to the CpG of DNA.
Local gene transfer by lipoplexes for the therapy of alpha1-antitrypsin (AAT) defi-
ciency was reported by Brigham and colleagues (Brigham et al. 2000 ). It has been
demonstrated that the delivery of a normal AAT gene by CL to the respiratory epi-
thelium of deficient patients produces potentially therapeutic local AAT
concentrations.
Currently, however, only limited success has been reached in the case of lipo-
plexes-based gene therapy. In addition, local delivery is the most frequently
employed route in the performed clinical trials. Toxicity and efficiency are two
major issues found in these trials. Further development of safe and highly efficient
lipid-vectors is highly required for the successful gene therapy.

7.2 Polymer Vectors

In addition to lipoplexes, cationic polymers based polyplexes have also been used
for gene therapy in clinical trials. Ohana et al. performed the transfection study
using polyplexes based on a pDNA and jetPEI (22 kDa) in human patients with
bladder carcinoma (Ohana et al. 2004 ). The employed pDNA encoded for the
expression of diphtheria toxin A chain under the H19 promoter gene, an pater-
nally-imprinted, oncofetal gene commonly expressed in various tumor tissue.