Recombinant DNA Advisory Committee - 03/1-2/93 
Dr. Leventhal said that approval of this protocol should be deferred until the 
investigators submit data demonstrating the following: (1) regression of established 
tumor, (2) generation of CTL from human PBL from tumor-bearing patients in response 
to autologous tumor, (3) a quantitative correlation between Class II antigen expression 
and the amount of y-IFN, and (4) a quantitative correlation between the number of CTL 
generated per unit of y-IFN. 
Dr. Barber stated that it would not be appropriate to use the human vector in the animal 
model system because y-IFN is species-specific. Dr. Leventhal suggested that 
quantitative data should be submitted demonstrating the correlation between the 
generation of CTL from human PBL and the amount of human y-IFN produced. In 
addition, the investigators should identify a safe threshold of minimal expression. Dr. 
Leventhal said that this in vitro data would be acceptable in place of the in vivo data. 
Dr. Leventhal stated that she is not convinced that there is sufficient justification to 
conduct this protocol based on the data that was submitted. Dr. Parkman said that the 
important issue is whether the RAC should approve every protocol in which a cytokine 
gene is inserted into melanoma cells. There has to be evidence that the cytokine gene 
augments the immune response. 
Presentation-Dr. Darrow 
Dr. Darrow presented additional data to the RAC which was not included in the meeting 
materials. Blastogenesis data indicated a substantial increase in thymidine incorporation 
in response to y-IFN transduced tumor as compared to untransduced tumor. Dr. 
Parkman noted that the data was derived using established tumor cell lines. Dr. Darrow 
said that the cell line was derived from a melanoma patient, and that it had been 
cultured for a maximum of 5 weeks. Dr. Darrow presented a representative experiment 
with several different cell lines which demonstrated increased efficacy of CTL generation 
with y-IFN transduction. Dr. Darrow stated that these assays are performed after 4-5 
weeks in culture, because CTL activity peaks at this time and nonspecific killing is 
absent. This in vitro data substantiates the hypothesis that transduced cells induce a 
significant increase in the level of CTL activity; therefore, a similar response should be 
achieved in vivo. 
Discussion 
Dr. Leventhal said that the data is insufficient to satisfy her concerns. Data must be 
derived from multiple experiments and statistically analyzed. Dr. Miller said that he 
would recommend approval of the protocol contingent on the submission of additional 
data. Dr. Leventhal stated that contingent approval of this protocol would not be 
consistent with the standards that have been used for other investigators. 
Recombinant DNA Research, Volume 17 
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