Clinical trials involving embryonic stem cells to treat spinal-cord injury have been approved by the US Food and Drug Administration (FDA).
This is the first time embryonic stem cells will be tested on humans.
Geron Corporation, which developed the treatment, said the FDA had removed a clinical hold on its GRNOPC1 therapy.
It hopes to start testing GRNOPC1 on humans by the end of this year, enrolling eight to 10 patients across the US.
The trial will last about two years, with each patient being studied for one year.
The FDA accepted Geron's January 2009 study application, but then placed any potential study on hold last August because some mice treated with GRNOPC1 developed spinal cysts, reports The Sydney Morning Herald.
However, Geron claims to have found a new way to test GRNOPC1 and said it did not see any cysts in a separate animal study.
A successful test would lead to larger and longer studies that would focus on the effectiveness of GRNOPC1.
The company says it will monitor patients for 15 years for safety.