The next consideration relates to the probability that the Ad.CB-CFTR virus can replicate, 
spread and be transmitted. We believe that this will be unlikely based on our xenograft 
experiments which failed to recover any recombinant virus from the lumen within 7-10 days 
after exposure to titers of virus which will exceed that administered to the patients by 100 to 
1000-fold. In order to assure that this does not occur we will keep the patients in isolation for 
a period of 10 days following the treatment. The patient's nasal swabs and sputum will be 
evaluated for Ad.CB-CFTR sequences before discharge. If there is evidence of ongoing spread the 
patient will be asked to stay in the hospital for additional days. We think this will be extremely 
unlikely. The other possible situation that could lead to spread is if the patient becomes 
superinfected with a homologous wild type virus which mobilizes the recombinant genome. It is 
impossible for this to occur through the generation of a replication competent virus containing 
the minigene due to size limitaions of packaging. The spread of the genome would have to occur 
by adenoviral functions provided in trans. We think this is highly unlikely and should not 
prevent the study. In order to address this potential concern we will work with the referring 
physician to be particulary cognizant of signs ans symptoms characteristic of adenoviral 
infections and will continue to survey nasal swabs for Ad.CB-CFTR sequences using the PCR 
assay. 
VC Potential Benefits. 
This is a phase I study so there will be no actual benefits to the patients involved in the 
experimental protocol. This study could have enormous benefit to the larger community of CF 
patients for a variety of reasons. Despite tremendous investment of resources by the 
pharmaceutical industry, management of the pulmonary complications of CF is inadequate; 
patients eventually succumb to these complications by the age of thirty. The information gained 
in this study will provide information that is critical to the eventual development of effective 
treatments of the lung disease of CF by gene therapy. We hope to evaluate the overall safety of 
this approach as well as to assess the feasibility of obtaining genetic reconstitution that is 
therapeutic and stable. We do not believe that this trial will actually be therapeutic to the 
patient because the therapy will be administered to such as small surface area of the airway. 
For this very reason, it is felt that the procedure will not compromise pulmonary function if 
deleterious to the segment. 
We consider this an extremely important study with respect to evaluating the potential use of 
recombinant adenoviruses in the treatment of cystic fibrosis. We would consider this a 
successful experiment if we can answer the critical questions addressing the safety and efficacy 
of this approach to gene therapy in cystic fibrosis. However, based on our extensive work in 
animal models were believe there is a reasonable chance that the study will show recombinant 
adenoviruses are capable of safely transferring recombinant CFTR genes to the cystic fibrosis 
airway and that the genes function for a prolonged period of time. 
An important barrier to gene transfer into the surface epithelium of the airway is that the cells 
are relatively quiescent with approximately 0.1% of the cells going through the cell cycle at 
any one time. For this reason, approaches to gene therapy which depend on integration of the 
transgene into the recipient cell's chromosome, such as recombinant retroviruses, will not be 
effective. Recombinant adenoviruses have the capability of transducing genes into nondividing 
cells and maintaining the transgene as an extrachromosomal element. We have used the human 
xenograft system to evaluate the stability of adenoviral mediated recombinant gene expression. 
We have found that recombinant adenoviruses are capable of efficiently transferring genes into 
nondividing fully differentiated cells of the surface epithelium and that the recombinant gene 
expression is stable for the longevity of the grafts which is approximately 4 weeks. 
Furthermore this occurs in the absence of viral protein expression or detectable viral 
replication. Presuming the viral genome is stable in the cell, the persistence of recombinant 
gene expression becomes dependent on the lifespan of the cell. As described above the cells of the 
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