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Embryonic Stem Cells' Safety Weighed by FDA Advisers (Update2)  (2008-04-10)
  by Elizabeth Lopatto, Bloomberg

Embryonic stem cells that may cure diseases also carry new risks, from the danger improper cells will be implanted to the prospect they may travel to the wrong parts of the body, companies told U.S. advisers today.

Geron Corp., Novocell Inc. and Advanced Cell Technology Inc. appeared before a Food and Drug Administration advisory panel weighing how to ensure safety in human tests of the decade-old cell technology. The companies plan to test treatments in people as soon as this year.

Stem cells are attractive for treatment because they can grow and change into other cell forms. That can also bring unintended consequences, including creation of tumors. Because stem cells can last a lifetime, the FDA is asking the companies and scientists how long patients should be followed and how best to monitor them during studies.

``We've talked about how long we need to monitor people for, and the answer is forever,' said panel member Gordon Weir, a professor of medicine at Harvard Medical School in Boston, during the meeting. ``We're putting in these cells, and we don't know what they're going to cause in terms of trouble.'

The FDA may require ``particularly strong' evidence early in studies that stem-cell treatments are effective, said Steven Bauer, chief of the FDA's Cell and Tissue Therapy branch, during the daylong hearing in Gaithersburg, Maryland. The agency also may require longer trials of stem-cell therapies than it does for conventional drugs, said Mercedes Serabian, a supervisory toxicologist for the FDA, after the meeting.

Mouse Embryos

Scientists discovered ways to get stem cells from mouse embryos about 20 years ago, and in 1998 determined how to obtain them from human embryos and cultivate them, according to the National Institutes of Health. Since then, scientists have manipulated embryonic stem cells in the lab to create different types of tissue cells to treat disease.

Researchers need to confirm the type of cell they are working with at every stage of development, said Melissa Carpenter, the vice president of research and development at Novocell.

``You need to make sure, especially if you're handling multiple cell products, that the cell product you're delivering is the one you think you're delivering,' Carpenter said at the meeting. Labs must identify abnormalities in cell cultures before they go into people and make sure the cells stay where they're implanted, she said.

Producing Insulin

Novocell, based in San Diego, is using stem cells to create insulin-producing cells for diabetics.

Scientists even face challenges in creating a placebo to mimic the cloudy solutions that typically contain stem cells, said Jonathan Dinsmore, general manager and senior vice president of Advanced Cell.

``It's important to use control cells and blind your experimental team, which is difficult with cell therapy,' Dinsmore said. Double-blind studies, in which the researchers and patients don't know who gets the actual treatment, are considered the gold standard for drug trials.

Advanced Cell of Alameda, California, is using embryonic cells for an experimental treatment of eye diseases, including macular degeneration, a market the company estimates at $28 billion. Macular degeneration weakens the part of the eye responsible for sharp vision and affects about 15 percent of people over the age of 75, according to the National Institutes of Health.

`Tricky to Maintain'

Researchers must carefully store the fragile cells, Jane Lebkowski, the senior vice president of regenerative medicine at Geron, told the panel.

``Anyone who has used embryonic stem cells knows that these cells can be tricky to maintain,' Lebkowski said.

Geron, of Menlo Park, California, is attempting to treat spinal cord injuries by turning stem cells into a type of nerve cell that insulates the spinal cord.

Geron rose 61 cents, or 13 percent, to $5.40 at 4:30 p.m. in Nasdaq Stock Market composite trading. Advanced Cell Technology was unchanged at 12 cents in over-the-counter trading. Novocell is closely held.

There are two types of stem cells. Embryonic cells, created shortly after conception, can become any other cell type in the body. Their use is controversial because harvesting them destroys the embryo. Use of so-called adult stem cells, which exist in tiny numbers within grown organs, are more limited and able to morph only into certain types of cells.

Having considered embryonic cells today, the advisers will hold a hearing tomorrow on use of adult cells. The panel will also discuss possible rule changes for designing studies of other biotechnology products, including gene therapy.

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