Geron Corporation has announced data from its GRNOPC1 phase I study. In this study, four different patients who had experienced spinal cord injury were treated with injections of the embryonic stem cell-derived cell line GRNOPC1. This cell line is a stable, oligodendrocyte progenitor cell (OPC) line. Oligodendrocytes surround the axons for many central nervous system neurons. This insulation allows the nerve impulses that travel through these axons to travel much faster than they normally would. This insulation is essential for proper physiological function. However during spinal cord injury, oligodendrocytes are destroyed and the insulation attenuates, thus leading to the continuing decrease in neurological function after spinal cord injury. Implantation OPCs have been shown in mice to increase neurological function after a spinal cord. Therefore, the implantation of OPCs in humans who have suffered from spinal cord might improve their neurological function.
Geron introduced OPCs from the embryonic stem cell-derived cell line GRNOPC1 into the spinal cords of four human patients who had suffered from a recent spinal cord injury. These patients were all classified as American Spinal Injury Association (ASIA) Impairment Scale grade A thoracic spinal cord injuries. ASIA grade A is the worse category and indicates a complete spinal cord injury where no motor or sensory function has been preserved in the sacral segments S4-S5. These patients all received a dose of two million GRNOPC1 cells. These cells were injected into the lesion site, and the injection utilized a syringe positioning device that Geron actually designed. The OPC cells were administered between 7 and 14 days after injury, and a drug that suppresses the immune system called tacrolimus was given for to temporarily suppress the immune response from the time of injection until 46 days after the injection. After this the tacrolimus dose tapered and withdrawn completely by 60 days after the stem cell injection.
The patients were evaluated by determining the sensory and motor ability of the patient’s legs. There were also MRI scans of the spinal cord, but patients are at different stages in the evaluation period. One patient has experienced the 365-day follow-up whereas another patient has just had the 30-day follow up. The patients will be examined for five years after the procedure and after that, they will be interviewed by telephone until nine years after the procedure.
To date, the examinations have shown no surgical complications during or after the procedures, no adverse events related to the injection procedures or to GRNOPC1, a few mild adverse events related to tacrolimus, n evidence of cavitation in the spinal cord at the injury sites on MRI, no unexpected neurological changes, no evidence of immune responses to GRNOPC1.
There is no evidence to date of immune rejection of GRNOPC1, an allogeneic cell therapy, including after withdrawal of the immunosuppressive drug.