CellPro Inc. announced Tuesday that the National Institutes ofHealth (NIH) will conduct two new human gene therapy trials-- one in patients with metastatic breast cancer and the otherin patients suffering from multiple myeloma -- utilizing itsstem cell concentration technology.

Joyce O'Shaughnessy of the National Cancer Institute will headthe breast cancer trial and Cynthia M. Dunbar of the nationalHeart, Lung and Blood Institute will conduct the myelomastudy. The two trials will study bone marrow engraftment inpatients after marrow-killing, high-dose chemotherapy and/orradiation by inserting a marker gene into purified stem cells.

Bone marrow transplantation is one of the key therapiesemployed in battling cancer and hinges on a relatively simpleconcept. Cancer patients have malignant cells in their blood andbone marrow (the body's factory for blood cells). Doctorsattempt to kill, or purge, as many cancerous blood cells aspossible through chemotherapy and radiation to prepare thepatient to receive new bone marrow. That marrow can comeeither from the patient (an autologous transplant) or from agenetically matched donor (an allogeneic transplant). In theU.S. today, about 50 percent of transplants performed areautologous and 50 percent are allogeneic.

In an autologous transplant, a patient's bone marrow, whichconsists of stem cells and progenitor cells, is extracted andfrozen. After the blood is purged of cancerous cells, the marrowis reinjected to repopulate the body with (theoretically)healthy cancer-free blood cells. The hitch is that it doesn'talways work.

According to Lee Parker, CellPro's director of investor relations,the two new trials could provide an answer to one of the mosthaunting questions of autologous bone marrow transplants:When a patient suffers a relapse after receiving a bone marrowtransplant, is it because chemotherapy failed to kill all of thecancerous cells or because cancerous cells remained in thepatient's own stem cells and were reintroduced during thetransplant?

"The idea is to genetically mark all of the stem cells before youtransplant them into the patient," said Parker. "Then, when thepatient relapses, you study the cancerous cells. If any of themhave the gene marker on them, you know that the stem cellscarried the cancer."

CellPro's technology will enable the NIH to use highly purifiedstem cells for the transplants in the two new trials. The normalbone marrow aspirate used in transplants is a fractionatedlayer of white blood cells and stem cells from a centrifuge,which amounts to 200 to 300cc of liquid. Using CellPro'stechnology, a mixture of approximately 4.5cc of material that is90 percent T cells and only 10 percent white blood cells can beused in a transplant. Getting rid of the extraneous white bloodcells and other blood elements is important because it isbelieved that they could be cancer carriers. According toParker, most researchers believe that the stem cells do notcarry cancer, but no one is sure.

Paul Martin, a bone marrow specialist at the Fred HutchinsonCancer Research Center in Seattle, said he is skeptical that thenew trials or CellPro's system would dramatically changetransplant technology. Since 1969, physicians at FredHutchinson have performed more than 5,000 bone marrowtransplants, more than any other transplant center in the U.S.

"One of the questions still out there is whether or not purifiedstem cells all by themselves can give rise to durabletransplants in human beings," Martin said. "And anotherquestion that arises is how do you separate marked malignantcells from marked normal cells? I think this kind of work couldyield a small piece of the solution, but that could be a long wayinto the future."

Stock in the Bothell, Wash., company (NASDAQ:CPRO) was up 63cents a share on Tuesday to $20.75.

-- Lisa Piercey Business Editor

(c) 1997 American Health Consultants. All rights reserved.

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