IL-4 "TUMOR VACCINE" GENE THERAPY TRIAL USING GTI VECTORS
IL-4 "TUMOR VACCINE" GENE THERAPY TRIAL USING GTI VECTORS was approved by NIH's Recombinant DNA Advisory Committee (RAC) at its Sept. 14-15 meeting. The protocol was proposed by Michael Lotze, MD, University of Pittsburgh, and employs vectors produced by Gaithersburg, Md.-based Genetic Therapy, Inc. The tumor vaccine will be composed of irradiated tumor cells from patients with metastatic melanoma, breast cancer, renal cell carcinoma or colon cancer "admixed with fibroblasts retrovirally transfected with the human IL-4 gene," Lotze's study summary states. The tumor vaccine trial was one of five gene transfer protocols calling for use of vectors manufactured by GTI to be approved at the RAC meeting. RAC approval is generally the first regulatory hurdle for gene therapy protocols. All five trials also await FDA approval. The four other protocols involving GTI vectors include: an NIH study of 12 HIV-infected adults with seronegative identical twins using gene marking to track CD4 and CD8 cell transplants; a non- small cell lung cancer gene therapy trial sponsored by Jack Roth, MD, University of Texas; and two gene marker trials that will evaluate the efficacy of bone marrow-purging procedures. One of the purging trials will evalutate the efficacy of an investigational device under development by Baxter. The NIH committee also approved three trials using vectors from Immunex spin-off Targeted Genetics to evaluate the efficacy of cytokine (GM-CSF and G-CSF) use in chemotherapy patients. All three trials are to be conducted by Friedrich Schuening, MD, Fred Hutchinson Cancer Research Center. RAC did not approve use of a commercial eukaryotic gene expression vector system derived from Semliki Forest Virus (SFV), and marketed by Gaithersburg, Md.-based Life Technologies, at Biosafety Level 2. Currently, SFV is classified by the Centers for Disease Control at Biosafety Level 3, which, among other requirements, necessitates negative air flow systems and double entryways. The committee's consensus was that the company had provided insufficient data on the frequency at which replication- competent virus emerges with use of the SFV system under typical conditions. Committee member Moselio Schaechter, PhD, Tufts University, noted in a Sept. 1 letter to Gary Temple, MD, Director of Research at Life Technologies, that SFV is known to have caused one death in an exposed laboratory worker. Additionally, the virus is also "thought to cause rather severe acute disease with a long convalescent period," Schaechter pointed out. RAC members discussed which assays should be required to demonstrate that the vectors used in trials are not replication competent, and cannot be used by different, otherwise incompetent, viruses to replicate. The consensus was that the issue should be addressed again at the upcoming December meeting. In the meantime, it was noted by several committee members that FDA will probably have published updated, more stringent standards in its "Points to Consider" document for gene transfer clinical trials.
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