Recombinant DMA Advisory Committee - 09/14-15/92 
gene marked marrow cells and have recovered from hematopoietic reconstitution with 
CD34( + ) cells. Gene marking data is currently being collected. Dr. Haselkom asked if 
any of the other investigators with approved gene marking protocols have observed 
patient relapse. Dr. Deisseroth said that other investigators have reported relapse. Dr. 
Haselkom asked if purging is introduced as a part of the CLL protocol, there must be a 
sense that relapse is due to the transducing cells. Dr. Deisseroth stated that data 
obtained from Dr. Brenner's protocols for AML indicate that at the time of relapse, 
patients exhibited gene marked leukemic cells suggesting that cells present in the marrow 
contribute to the evolution of relapse in AML. Dr. Deisseroth asked Dr. Brenner to 
confirm these results. 
Dr. Brenner said that a total of 13 patients have entered the gene marking protocols at 
St. Jude Children's Hospital in Memphis, Tennessee, seven with neuroblastoma and six 
with AML. Two AML patients and no neuroblastoma patients have relapsed. One 
relapsed AML patient had no distinctive leukemic markers, but there were large 
numbers of blasts which produced malignant appearing colonies that were marked with 
the neo R gene. The second relapsed patient had two distinctively leukemic clone 
markers CD56 and CD34, and a distinctive translocation. The translocation produces a 
unique leukemic transcript. This cell population was purified on its phenotypic basis, 
cultured, and colonies selected. The resulting colonies contained both the leukemic 
transcript and the neo R gene. Therefore, for the first AML patients remission has 
demonstrated that the reinfused marrow contributes to relapse. The effect of purging 
and frequency are still unknown at this time. 
Dr. Leventhal asked for clarification regarding the first relapsed AML patient. Dr. 
Brenner explained that the first patient had CD34( + ) blasts in their circulation at the 
time of relapse that were separated by FACS and grown up to colonies. Two percent of 
the blast colonies expressed the neo R gene. It is unlikely that these are normal 
progenitor cells contaminating the population. Dr. Deisseroth noted that Dr. Brenner's 
results were obtained without any additional fractionation procedures. The CLL 
protocol includes two steps to remove the abnormal leukemic cells. 
Dr. Parkman said that the title of the protocol indicates that peripheral blood cells will 
be transduced and administered to the patient; however, it is not discussed in the 
protocol. Dr. Deisseroth concurred that peripheral blood would not be included in this 
protocol. Dr. Deisseroth clarified the fractionation and labelling procedure as requested 
by Dr. Parkman. Ninety percent of the ABM cells will be fractionated over the CD34 
column. This CD34 enriched population of cells will then undergo CD 19 negative 
selection. This double fractionated population of cells will be transduced with GINa. 
The remaining 10% of unfractionated cells will undergo CD19(-) selection only prior to 
transduction with LNL6. If lymphoid cells contain both markers at the time of relapse, 
then CD34( + ) fractionation is of no benefit in the selection process. 
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Recombinant DNA Research, Volume 16 
