Human Gene Therapy Subcommittee - 11/21-22/91 
(3) proportionality experiments demonstrating the limits of ability to quantitate 
differences in the ratio of LNL6 and GINa will be performed and a stopping rule 
will be inserted that will terminate the experiment if the data are uninterpretable; 
(4) the language of the informed consent document should be simplified, and the 
section describing extra biopsy procedures should be moved from the 
biomodulator section to the viral marking section. 
Dr. Economou asked if the HGTS wanted him to perform a "spiking" experiment. He 
said that a marked TIL could be added to melanoma cell lines and PCR could be 
performed to determine the level of detection. Dr. Epstein said that the investigators 
already have a good sense as to the number of marked lymphocytes detectable per gram 
of tissue. 
Dr. Miller asked if PBL grown in IL-2 produced the same response as TIL. Dr. 
Economou said that PBL were not expanded for the same length of time as TIL; 
however, the same response has been observed with LAK cells. LAK cells are the result 
of short-term culture of PBL in high doses of IL-2, not long-term as this protocol 
proposes. Dr. Miller said that the real question is whether or not these are TIL or long- 
term cultured PBL. 
Dr. Miller addressed the issue that in the current protocol (without the gene marking) 
patients have received cell populations that express a variety of phenotypes which have 
resulted in tumor regression for some patients. Dr. Miller asked Dr. Economou to 
explain the rationale for using a CD8( + ) purified population of cells. Dr. Economou 
responded that there are a number of variables that need to be addressed: (1) the dose 
of the biological response modifier necessary to obtain maximum cytotoxicity, (2) the 
differences in individual tumors that allow them to be recognized by different 
immunological molecules, and (3) the phenotype of the cell population that is 
administered. Dr. Economou said that the use of CD4( + ) versus CD8( + ) is the next 
logical issue that needs to be addressed. 
Dr. Miller said that there is the safety issue concerning the patient. There is no 
rationale for choosing a purified cell population from TIL if the response is unknown. 
Dr. Economou said that animal experiments demonstrate that adoptive immunotherapy 
of CD8( + ) cells elicits a tumor-specific response. 
Dr. Parkman said that this is the best protocol that the HGTS has reviewed. This 
protocol has an internal control designed to look at T cells from the peripheral blood 
expanded in ID2 compared to TIL that are expanded from the tumor; a definitive result 
should be obtained concerning the therapeutic benefits of TIL versus PBL. 
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