Recombinant DNA Advisory Committee - 5/30-31/91 
said he also would like to know what level of totipotency the investigators were capable of 
determining in the colonies. 
Dr. Mclvor suggested that Dr. Deisseroth provide a flow chart of exactly what is going to be 
done as there are many steps involved in this protocol. And finally, he asked if the colonies 
could be analyzed microscopically as far as their varying morphology to determine whether 
they are leukemic or normal in an attempt to provide support for the BCR-ABL PCR data. 
He said that he felt there was a significant possibility that even though there are leukemic 
cells in the marrow they will not come up tagged in the relapse material, and thus there is a 
good chance that the results of the protocol may be uninformative. He said one way of 
dealing with this would be to keep trying to increase the transduction frequency or attempt 
to label all of the marrow cells. He said he felt it was important that both the investigators, 
as well as the patients, be aware of this possibility that no information at all will be gained 
from this gene tagging. 
Dr. Post said he felt that it was evident from the protocol that there was no doubt that 
leukemic cells are being given back to the patient in the autologous marrow and that this 
experiment is only an attempt to figure out which set of leukemic cells is responsible for the 
relapse. He asked Dr. Deisseroth to comment on this and correct him if this was not the case. 
In response to Dr. Leventhal's questions, Dr. Deisseroth said that the critical time for 
interpreting the experiment and the therapeutic outcome is at the time of relapse. However, 
on an experimental level this may not clarify the question, but he said they would also be 
analyzing marked marrow samples taken from patients incidental to their regularly scheduled 
clinically-driven evaluations of the marrow to look at the level of leukemic cells as well as any 
information that can be gathered on the level of the virally marked blasts. He said that at the 
present time the only technique for doing this is the molecular assay which he had presented. 
However, he noted they were involved in developing another method to analyze the presence 
of these retroviral sequences using saturated DNA proves for the neo sequences which will 
be used to stain a cell so that they can discriminate between normal and leukemic cells on a 
cell-by-cell basis under the microscope. He said this technique had not been perfected but 
they will continue to work on it. 
As far as the early stopping rules. Dr. Deisseroth said they had not been included in the 
protocol at this point, but he assured Dr. Leventhal that they would be inserted into the 
protocol. 
In response to Dr. R. Murray's concerns. Dr. Deisseroth said that he agreed that the issues 
of therapy should be separated from the marking, and what they have done is split away all 
therapy from the marking protocol and they now have a separate protocol for the therapy 
which patients will read over and be able to sign an informed consent document on prior to 
being approached about the marking protocol. He said he purposely left some information 
about the therapy in the marking protocol because he felt it was important to provide 
information to the patient on the marking protocol in the context of the therapeutic setting. 
Recombinant DNA Research, Volume 14 
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