Human Gene Therapy Subcommittee - 11/21-22/91 
Dr. Cometta described the gene transfer portion of the protocol. Following bone 
marrow harvest, the majority of the patient's marrow will remain untreated. The first 3 
patients will have 10% of their marrow cells transduced with LNL6. The remaining 
patients will have 30% of their marrow transduced. There are no in vivo animal data 
indicating that these gene marking procedures will adversely affect the patient's ability to 
reconstitute. Bone marrow cells will be cryopreserved for 2 weeks to determine the 
efficiency of transduction and to perform safety testing. Finally, the marked cells will be 
transplanted into the patients. 
Dr. Cometta addressed the patient eligibility requirements. Patients will be in complete 
remission at the time of bone marrow harvest and will not have received cytotoxic drug 
therapy for a minimum of one month. Patients will exhibit no evidence of leukemia as 
verified by cytogenetic analysis. There is a minimum requirement of 2 x 10 8 nucleated 
cells/kilogram. This requirement is twice the number of cells normally required for 
bone marrow transplantation. Acquiring large numbers of cells will provide a backup 
supply for reinfusion in the event that there are safety concerns about the treated 
marrow or if the patient decides later not to participate in the gene marking. 
Regarding the differences between this protocol and Dr. Brenner's protocol, Dr. 
Cometta explained that ALL and AML adult patients are eligible for this protocol. Dr. 
Brenner's study involves only children with AML. The adult population proposed in this 
protocol has a much lower likelihood of survival. Since these patients are in second or 
later remission, they have a much higher proportion of leukemia cells than those eligible 
for Dr. Brenner's protocol. There is an option to treat a few patients who have 
refractory leukemia or are in early remission. However, these patients must have had 
marrow cells cryopreserved at the time they were in complete remission. 
Dr. Cometta explained that eligible patients must be between 18 and 65 years of age and 
must be able to provide informed consent. These patients must have a good 
performance status and have no detectable infection at the time of transplant. Also, 
patients must be human immunodeficiency vims (HIV) negative and have received a 
pretransplant, multi-organ assessment to ensure that they have adequate organ function 
to withstand the chemotherapy regimen. 
At the time of relapse, patients will be evaluated by PCR for the presence of the neo R 
marker gene. Dr. Cometta explained that leukemic blasts have been detectable by PCR 
analysis and that the sensitivity of this assay has been documented. Leukemic blast 
colonies have been grown in methylcellulose, and PCR demonstrates the presence of the 
marker gene in these colonies. NIH 3T3 amplification assays have been performed, and 
no replication-competent retrovirus has been detected. 
Dr. Cornetta addressed the issue of the effect of freezing on the transduction efficiency 
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