Geron Corp. the developer of biopharmaceuticals for cancer and chronic degenerative diseases treatments said U.S. regulators put a clinical hold to its investigational cell therapy for spinal cord injury.

By putting the GRNOPC1 on hold the Food and Drug Administration suspended development of the drug . The group expressed its disappointment since the submission has been in development for four years and has been based on discussions with regulators.

We have not yet received a letter from the FDA explaining the decision to place the submission on hold, so we are unable to comment specifically, said Thomas Okarma, Executive Officer in a statement.

Geron shares fell as much as 19.39 percent to $3.95 on Nasdaq closing trading on Wednesday.