with evidence of any replication competent virus will not be utilized. The 
3T3 amplification and S+L- assays are thought to be capable of detecting a 
single replication competent viral particle per ml (41). 
Prior safety studies have shown that exposure of primates to large 
infusions of infectious murine amphotrophic virus produce no acute pathologic 
effects (44). In a study of 21 primates receiving retroviral mediated gene- 
modified autologous bone marrow cells no animal showed evidence of toxicity 
related to the gene transfer as long as 5 years after infusion (45), 
unpublished data) . 
It should be emphasized, however, that tumor will be transduced with the 
retroviral vector supernatant and then the tumor will be washed extensively 
and then grown for several weeks in the absence of supernatant. The tumor 
will then be washed extensively again prior to injection into the patient and 
patients will thus not be exposed directly to the retroviral vector. 
VII . Statistical Considerations. 
Up to 14 patients with each type of cancer will be treated. If no 
responses are seen in these first 14 patients no further patients with that 
histologic type of cancer will be admitted to the protocol. 
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