Recombinant DNA Advisory Committee - 12/3-4/92 
Presentation-Dr. McDonagh 
Dr. McDonagh explained that only 5 animals have been studied using a head-to-head 
comparison of the Harvey-based and Moloney-based vectors. Dr. D. Miller asked about 
the specific Moloney-based vector used for the in vivo experiments. Dr. McDonagh 
explained that the original vector containing the splice donor and acceptor sites and the 
codon 185 C-terminus mutation was used for the animal experiments. Two of the 5 
animals demonstrated a 3 to 4-fold increase in copy number with the Moloney-based 
vector, whereas 3 of six animals showed an increase in copy number using the Harvey- 
based vector. These experiments have been performed using only fibroblast cell lines, 
not primary hematopoietic cells. Dr. D. Miller asked whether all of the Moloney 
constructs contain human cDNA. Dr. McDonagh said that all of the Moloney constructs 
contain human cDNA as well as the Harvey constructs. 
Dr. Murray asked if human bone marrow cells have been transduced and selected with 
chemotherapeutic agents to demonstrate gene expression. Dr. McDonagh said that these 
human experiments have not been performed; however, gene expression has been 
demonstrated in rhesus cells. Rhesus and human cells probably function in a 
comparable manner. 
Dr. Nienhuis said that the preliminary data is adequate to support the protocol. Murine 
data demonstrates that the MDR gene can be expressed in murine stem cells and that 
protective immunity can be conferred. In the in vitro primate system, MDR-1 
transduction and expression have been demonstrated. Long-term reconstitution (up to 
seven months) with gene modified cells has also been demonstrated. At this point in 
time, it is appropriate to proceed with the human study. 
Committee Motion 
A motion was made by Dr. Leventhal and seconded by Dr. Zallen to defer approval of 
the protocol. Approval is deferred until the investigators return to the RAC with the 
following: (1) data demonstrating that human cDNA CD34( + ) cells can be transduced 
in vitro with the actual vector that will be used for the human clinical protocol, (2) a 
description of the assays that will be performed to monitor gene expression, (3) the 
methods by which gene expression will be compared in tumor and ABM cells, and (4) 
data demonstrating the clinical endpoint for bone marrow recovery, i.e., what is the 
period of time required for the detection of polymorphonuclear leukocytes? What is the 
standard error for this recovery period? 
Dr. Post asked the investigators how long it will take them to prepare for human clinical 
trials. Dr. Nienhuis responded that 6 to 8 weeks would be required to complete the 
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Recombinant DNA Research, Volume 16 
