Antitumor response was seen in five of eight patients treatedwith Genetic Therapy Inc.'s (GTI) gene therapy treatment forbrain tumors, the company announced on Wednesday. Three ofthe five patients "exhibited both decrease in tumor size andacute, treatment-induced changes in tumor consistency on MRIscans" while the other two patients showed acute changes intumor consistency, said GTI.

The preliminary results of the brain cancer trial werepresented at the 10th International Conference on Brain TumorResearch and Therapy in Stalheim, Norway. This is the firstbrain tumor gene therapy treatment to enter clinicals. Theprotocol was approved by both the Recombinant DNA AdvisoryCommittee (RAC) of the National Institutes of Health (NIH) andthe FDA.

The gene therapy consists of a cell that produces vectorparticles engineered to contain the gene for the enzymethymidine kinase (TK). The vector particles carry the TK geneinto dividing tumor cells and instruct the cells to produce TK,which is susceptible to the anti-viral drug ganciclovir. Patientsare then administered ganciclovir, which destroys tumor cellsthat have expressed the TK gene.

The company said the trial demonstrated "a correlationbetween dose of producer cells and degree of tumor response,"and that the treatment was well tolerated by all patients. Ofthe eight patients in the trial, two had metastatic brain tumors(renal cell carcinoma and melanoma) and six had glioblastomas.Two have died due to progression of the cancer.

The trial is being conducted in collaboration with NIH. Theprincipal investigator is Edward Oldfield, chief of the SurgicalNeurology Branch of the National Institute of NeurologicalDiseases and Stroke.

GTI (NASDAQ: GTII) also announced that it has developed animproved producer cell for use in gene therapy, which has"demonstrated increased potency in preclinical studies andconfers production advantages over GTI's earlier version of theproducer cell," the company stated. GTI will now use thisproducer cell in its brain tumor trials.

GTI, of Gaithersburg, Md., has also received RAC approval fortwo other brain tumor gene therapy protocols and is nowawaiting FDA approval. These trials differ from the current NIHtrial with regard to patient accrual. The NIH trial, which willeventually accrue a total of 20 patients, will include patientswith either primary brain tumors (originating in the brain) ormetastatic tumors (migrated to the brain) and tumors that areboth surgically and non-surgically accessible.

A pediatric brain tumor gene therapy protocol -- designed likethe NIH trial -- will be taken up at a RAC meeting this week.The RAC will also consider GTI's gene therapy protocol forbreast cancer. This therapy involves extracting bone marrowcells from breast cancer patients, inserting a multi-drugresistant (MDR) gene into the cells that makes them resistant tochemotherapy, and then returning the cells to the patient. Thetreatment would thus prevent chemotherapy from killing thegene-modified marrow.

GTI has over 15 gene therapy or gene transfer protocols inclinical trials. The company is now focusing on five diseaseareas: brain cancer, lung cancer, Gaucher's disease, cysticfibrosis and breast cancer. Gene therapy protocols for each ofthese diseases, except for breast cancer, have been approvedby RAC and are at various stages of FDA review -- except forthe already approved brain cancer protocol.0909GTI

-- Brenda Sandburg News Editor

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