For patients paralyzed by spinal cord injuries, Geron Corp.'s stem cell research was the shining hope. The biotech firm showered scientists with millions of dollars to develop a treatment to reverse spinal damage. The therapy was the first treatment derived from embryonic stem cells to be cleared by the Food and Drug Administration for testing in humans.

But last week, Geron abruptly pulled the plug on its pioneering trial and the rest of its stem cell business, including early work on treatments for heart ailments, diabetes and other diseases. Pursuing futuristic cures through regenerative medicine was financially riskier than focusing on the company's two cancer drugs, which were further along in development, company executives said. People who had pinned their hopes on stem cells reacted with dismay.

"It was like someone ripped my heart out," said Sabrina Cohen, who was paralyzed in a car accident in 1992 and runs a research foundation in Miami. At first blush, Geron's decision called into question the plausibility of curing diseases with embryonic stem cells. They have the ability to grow into any kind of cell in the body, and laboratories around the world have spent hundreds of millions of dollars trying to turn them into replacement parts such as insulin-secreting islet cells for people with diabetes.