Recombinant DNA Advisory Committee- 9/12-13/94 
as an inclusion criterion. According to a literature report, people who are seropositive 
have less adverse effects from live adenovirus infection of the respiratory tract. He did 
not know whether it was critical. 
In terms of adenovirus versus AAV, Dr. Crystal pointed out that adenovirus has no 
potential for malignancy and has been widely used as a vaccine. AAV does, at least in a 
limited way, integrate into the host cell chromosomes and has potential for insertional 
mutagenesis and potential for malignancy. Adenovirus vectors are veiy effective for 
transducing genes into target cells. Another advantage is that adenovirus vectors only 
cause transient expression, but treatment would have to be repeated for long-term effects. 
Regarding the patient number in Part A of the study, 7 dosage escalations with 2 in each 
group will be carried out. It is necessary to have some consistency before moving to the 
next higher dosage level or to Part C of repeat dosage study. 12 patients will be needed 
in Part B of the study with 4 patients in 3 groups. The study will start with 1 patient, and 
then a second at the same dose. If no efficacy is seen, it will move to the next higher 
level using a half log dose increase. There will be a 3 week interval between each cohort. 
For repeat administration, there will be a 2 week interval. 
Responding to the question of increased adverse reactions in repeat vector administration, 
Dr. Crystal said that there are two parallel animal studies, both for a duration of 6 
months. There is no increased inflammation with multiple doses at 6 months. 
Regarding the question of comparative animal and human dosage, Dr. Crystal stated that 
lung surface is proportional to the height of the individual. Yet it is difficult to compare 
directly to animals. In animal studies, a small volume of vector is either dripped directly 
into the trachea or expelled under light pressure. It is different from administration to 
humans. The surface tension of the lung is such that the applied liquid will soon spread 
out, so there is no accumulation of the volume over a small area. Dr. Crystal contended 
that it was not likely to have a few cells getting an extremely high multiplicity of infection. 
The dosage chosen for the present study is based on the original RAC approved protocol 
and subsequent discussion with FDA officials. 
Dr. D. Ginsburg asked how widely the liquid applied through a bronchoscope will spread. 
Dr. Crystal said when 100 /il of methylene blue dye marker is applied to the lung, it 
spreads to a cylinder area of 2 inch in diameter and 4 cm in length. From this data, the 
MOI is estimated to be 250. 
* 
Responding to the question of vector replication at high multiplicity of infection. Dr. 
Crystal said the literature report described infection of transformed cells such as HeLa 
cells. For normal airway epithelial cells or cells from CF patients, no replication was 
detected with the present vector, up to a MOI of 1,000. It is true in his study in cotton rat 
airways. 
As to the expression level with the new vector using a CMV promoter, Dr. Crystal said 
that there is 10-fold difference in expression of the CFTR gene as compared with the old 
Recombinant DNA Research, Volume 20 
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