G. Insertional Mutagenesis. Retroviral vector DNA is inserted randomly into the genome of 
proliferating cells. The random nature of this integration has the potential of an untoward 
insertional event. If the insertion disrupts a gene essential for maintaining cell function, that 
particular cell will die. Since the gene transfer will occur most predominantly in tumor 
cells, the vector insertion site will result in the death of a few tumor cells without GCV, 
which should not pose a problem. The risk of oncogenic transformation with these 
replication-incompetent retroviral vectors cannot be accurately estimated since that has never 
been a documented occurrence in animals or man. While this is a real risk, this risk must be 
very low, especially in this protocol, where all vector containing cells will be killed by GCV 
within 2-3 weeks of injection of the producer cells. Based upon available data, the risk of 
death secondary to their tumor far exceeds any risk of insertional mutagenesis. 
H. Ganciclovir sodium (GCV; Cytovene®). The GCV used in this trial will be obtained from 
Syntex corporation (Palo Alto, CA). GCV is an approved drug for cytomegalovirus (CMV) 
retinitis therapy in immunocompromised individuals. The drug is given by IV infusion over 
1 hour (dose of 5 mg/kg) twice daily for 14-21 days. FDA approved guidelines (where 
applicable), administration procedures, drug interactions, and patient monitoring will be 
followed. A copy of the Cytovene® product monograph has been provided to the 
Recombinant DNA Activities office. There is minimal information regarding the use of 
GCV for the treatment of humans as a method to destroy HS-tk gene transduced human 
cells. Further information about toxicity is being generated in the initial NIH trial. To date, 
no toxicities have been noted in the first patient. GCV has been noted to cross the blood- 
brain barrier. The cerebral spinal fluid (CSF)/plasma ratio has been estimated in 3 patients at 
various time intervals with ratios ranging from 0.24 to 0.7 (0.31-0.68 ^g/mL in the CSF 
and 0.44-2.20 ^ig/mL in the plasma). Peak plasma levels have been documented to reach 
9/ig/mL. These CSF and plasma levels are expected to be within the range of GCV levels 
needed to kill the HS-tk transduced cells based on in vitro studies (0.5/zg/mL will prevent 
growth of HS-tk-transduced tumor cells). If the patient has evidence of renal impairment, 
the dose will be adjusted as suggested in the GCV monograph. 
Granulocytopenia (absolute neutrophil count (ANC) of < 1000 cells/mm 3 ) in 40% of patients 
and thrombocytopenia (<_ 50,000 platelets/mm 3 ) in 20% are the most frequent side effects. 
This data was collected in CMV infected AIDS patients, who may have been more 
susceptible to marrow suppression, due to other opportunistic infections or drug therapy. 
The actual risk to our patients is unknown. Each patient will be closely monitored for the 
development of granulocytopenia and thrombocytopenia. The development of an ANC of 
<500 cells/mm 3 or a platelet count of <25,000 platelets/mm 3 will require a dose 
interruption or decrease until the ANC is >750 cells/mm 3 platelet count is >40,000 
platelets/mm 3 . Other side effects occurring in approximately 2% of patients include anemia, 
fever, rash and abnormal liver function. Fever and chills will be treated with acetominophen 
(650 mg every 4 hours) and rash with diphenhydramine (50mg every 6 hours). See the 
mongraph for complete toxicity criteria. Our treatment protocol will use the known tolerated 
dose (lOmg/kg/day) in non-infected patients for only 14 days. 
Recombinant DNA Research, Volume 17 
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