Recombinant DNA Advisory Committee - 06/1-2/92 
Brenner stated that these approved protocols are designed to address the question of 
why patients relapse after autologous bone marrow transplantation for AML and 
neuroblastoma. Patients have been treated with a combination of transduced and 
untransduced autologous bone marrow cells. The transduced fraction represents 
approximately 30% of the patient's total number of bone marrow cells. Of the nine 
patients treated, four had neuroblastoma and five had AML. Eight of these patients 
have been evaluated, seven having engrafted spontaneously by day 35. Therefore, there 
is no indication that the transduction process affects bone marrow progenitor 
engraftment. One patient required granulocyte-macrophage colony stimulating factor 
(GM-CSF), but subsequently engrafted. 
Dr. Brenner noted that two deaths occurred on the protocol. The first patient died of 
progressive neuroblastoma and cardiomyopathy prior to engraftment. The second 
patient, with AML, died on day 14 from respiratory distress syndrome resulting from a 
gram-positive septicemia. 
Dr. Brenner presented data which showed that neomycin resistant colonies had been 
established from seven of the patients. These G418 resistant colonies represent both 
myeloid and erythroid lineages. No granulocyte/erythrocyte/megakaryocyte/monocyte 
(GEMM) or granulocyte/monocyte (GM) resistant colonies were observed. This result 
may be due to low transfection levels in these populations which are not detectable by 
this assay. He reported that polymerase chain reaction (PCR) positivity for the 
neomycin resistance gene was detected in day 35 autologous bone marrow mononuclear 
cells but not in peripheral blood mononuclear cells. 
Dr. Brenner addressed gene expression in these patients. He described two patients that 
have survived six months and who still exhibit G418 resistant colonies and PCR 
positivity. One of these patients was one who engrafted poorly at first and required GM- 
CSF. This patient exhibited G418 resistant T cell colonies throughout; however, 
hematopoietic colonies did not begin to appear until approximately three months. These 
results signify that long-term gene expression can be obtained after autologous bone 
marrow transplant and suggest possible progenitor and/or stem cell cycling. Since the 
efficiency of transduction is between 5% and 10%, these patients have less than 2% total 
G418 resistant cells. 
Dr. Brenner discussed the source of relapse. One of the nine patients with AML 
relapsed. Although the patient exhibited swift engraftment, peripheral blood blast cells 
were detected at day 65. This patient received a second allogeneic bone marrow 
transplant and has undetectable disease at day 130. He showed data that confirmed 
PCR positivity in the peripheral blood mononuclear fraction of cells, which corresponded 
to the increase in the blast cell count. 
Recombinant DNA Research, Volume 15 
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