T. J. Atchison wheels up a ramp outside his home in Chatom, Ala., April 12, 2011. Atchison, 21, who was paralyzed in a car crash in 2010, has identified himself as the volunteer who was treated by researchers with human embryonic stem cells. (David Bundy)

Geron Corp. of Menlo Park, Calif., said the move was the result of a business decision to focus on developing cancer therapies exclusively.

“In the current environment of capital scarcity and uncertain economic conditions, we intend to focus our resources on advancing our ... two novel and promising oncology drug candidates,” said John A. Scarlett, Geron’s chief executive officer, in a statement. “By narrowing our focus to the oncology therapeutic area, we anticipate having sufficient financial resources to reach these important near-term value inflection points for shareholders without the necessity of raising additional capital. This would not be possible if we continue to fund the stem cell programs at the current levels.”

The company is “seeking partners with the technical and financial resources to enable further development” of its stem cell therapy, the company said.

“Our employees, collaborators and shareholders can be proud of the pioneering role they have played to advance our stem cell technology into the clinic,” Scarlett said. “Stem cells continue to hold great medical promise. We believe that our leadership role in the field and the quality of our stem cell assets — which are widely recognized as being among the most innovative, comprehensive and advanced cell therapy programs in the world — will be an important point of differentiation in our discussions to partner these assets.”

Although the company will not treat any additional patients, researchers will continue to follow the four patients treated so far, “accruing data and updating FDA and the medical community on their progress,” the company said.

Many scientists think embryonic stem cells could represent one of the most important advances in medicine. Because the cells can morph into virtually any cell or tissue, researchers hope they will eventually produce cures for a host of ailments, including heart disease, cancer, Alzheimer’s and paralysis.

But the field is fraught with political, moral and ethical controversies. Days-old embryos have been destroyed to obtain the cells, which critics consider immoral. After many delays, the Food and Drug Administration last year finally approved two experiments testing therapies created from embryonic stem cells in humans, including a study testing Geron’s experiment treatment on 10 patients partially paralyzed by spinal cord injuries. Both studies were designed primarily to determine whether the approach is safe.

The studies have been seen by supporters and opponents of embryonic stem cell research as potentially pivotal to the future of the research. Some worried that not enough basic studies and tests had been done in animals before injecting cells into recently paralyzed patients. Others wondered whether patients who are struggling to come to terms with a devastating injury can make that kind of risky decision just two weeks after such a trauma.

Many proponents feared that if something goes wrong — or even if the cells fail to show any sign of helping patients — it could be a major blow for the field at a time when federal funding for the research is under attack in courts and Congress.

In October 2010, doctors in Atlanta injected millions of cells made from embryonic stem cells into the spine of a 21-year-old Alabama nursing student who had been partially paralyzed in a car accident less than two weeks earlier. Subsequently, three other similar patients have been treated. The only results Geron has released so far indicate that none of them has suffered any significant adverse effects.

In July, a team at the UCLA Jules Stein Eye Institute in Los Angeles that performed two delicate 30-minute procedures in which they carefully infused 50,000 retinal pigmented epithelial cells made from embryonic stem cells into one eye of two patients in the hopes cells would replace those ravaged by two incurable eye ailments. The only results from that trial released so far indicate that no safety problems have arisen.

Supporters of the research said they were disappointed.

“This trial was a difficult but important one and will help future cell transplantation clinical trials move forward in important ways,” said Keith Tansey of the Shepherd Center in Atlanta, where two of the patients were treated.