Recombinant DMA Advisory Committee - 6/9-10/94 
explained that at peak levels, GCV ranges between 4.5 and 10 //g per ml and that 12.5 
/ig per ml causes bone marrow toxicity. Dr. Evans commented that GCV use is not 
needed for the present short term experiment of 1 week. 
Dr. Evans justified the use of IRAP based on its safety profile in human trials. There 
has been no toxicity or immunosuppression associated with the use of IRAP. Murine 
studies were conducted involving MFG-IRAP transduced hematopoietic stem cells that 
were transferred to syngeneic irradiated host animals. No toxicity was observed in 
animals that expressed between 2 and 300 ng per ml of human IRAP for life. Upon 
subsequent challenge with human IL-1, a blocking response was observed. IRAP works 
well in vivo with rabbits and in vitro with mouse cells. Dr. Straus asked whether IRAP 
expression was sustained in the murine experiment. Is there a diminished response to 
pathogen challenge? Dr. Evans responded that these experiments have not been 
performed. 
Responding to Dr. Miller's question about the MFG vector, Dr. Robbins said the 
proposed vector includes a frameshift mutation that blocks viral gag protein expression. 
The vector has previously been referred to as MFG-C, but is indicated as MFG in the 
present protocol. 
Responding to Dr. Parkman's question regarding protection of the joint from tissue 
destruction. Dr. Evans explained that GAG release into the synovial fluid has been used 
to measure joint cartilage destruction. In the rabbit experiments, IRAP gene 
transduction blocked GAG release. Dr. Parkman agreed that these biochemical data 
reflect acute phase joint destruction, but a more relevant model is the effect of IRAP on 
the chronic phase of the disease. Dr. Evans said that the proposed 7-day study is not for 
the purpose of achieving clinical improvement, but to answer the question of whether the 
transduced IRAP gene is biologically active in an arthritic joint. Therefore, a more 
sensitive biochemical response has been chosen for this study. Dr. Evans said that most 
clinical studies on IRAP have been conducted by Synergen (Boulder, Colorado), and 
most of these data has not been published. The present study is independent of 
Synergen. Dr. Evans emphasized that the primary purpose of the study is to use the 
IRAP gene to develop a gene delivery system for treating joint diseases. If positive 
results are obtained, the same system can be adopted for future efficacy trials. 
Committee Motion 
Dr. Parkman made a motion to approve the protocol using the vector that does not 
contain the HSV-TK gene and submission of additional experiments on transduction 
efficiency. Dr. Evans concurred. Dr. Miller made a friendly amendment that safety data 
should be provided demonstrating no adverse effects of transduced cells outside the joint 
tissues. Dr. Parkman accepted the amendment. 
The RAC approved a motion made by Dr. Parkman and seconded by Dr. Zallen to 
accept the protocol submitted by Drs. C. H. Evans and Paul Robbins of the University of 
Pittsburgh, Pittsburgh, Pennsylvania, by a vote of 13 in favor, 0 opposed, and 1 
Recombinant DNA Research, Volume 19 
[327] 
