During a pilot clinical study, Emory University researchers implanted retinal pigment epithelial (RPE) cells attached to microcarriers (Spheramine") into the brains of six patients with advanced PD. The microcarriers are necessary for the cells to survive after implantation, and form the basis for this novel therapy. RPE cells, normally found in the back of the eye, are cultured under standardized conditions to produce cells for this treatment. These cells provide a source of increased dopamine production. Dopamine is a neurotransmitter in the brain that is found in steadily decreasing amounts as PD progresses. The implanted cells serve as a new potential source of dopamine production in these patients.
Parkinson's disease is a progressive neurological disorder that affects a person's ability to move, causing tremor, slowness and stiffness of muscles. Because of the malfunctioning and loss of cells in the brain that make dopamine, most PD treatments are aimed at restoring dopamine deficiency. The longer a patient has the disease, the greater the loss of dopamine-producing cells, requiring an increase in medications, which often leads to side effects. Therefore, new ways to restore dopamine are needed.
"In most cases, Parkinson's patients respond well to medications," says Dr. Watts. "But for those who have been on medications for an extended period of time – say 10 to15 years – their response to medications tends to fluctuate throughout the day. This novel technique can potentially give patients something beyond what we can do with current medications alone."
In this new cell therapy, hundreds of millions of cells are grown in cell culture, and are attached to microscopic gelatin beads (or microcarriers) to create the novel cellular product Spheramine, under development by Titan Pharmaceuticals, Inc. In this pilot study, neurosurgeons implanted approximately 325,000 cells through a needle in five different areas of the striatum, the part of the brain that controls movement, during MRI-guided stereotaxic surgery. The cells can then survive on the microcarriers in the striatum and continually provide a source of increased dopamine production.
Participants showed improvement in their tremor, stiffness, slow movement and balance, the most common motor functions affected by Parkinson's disease, throughout the two-year follow-up period. They also continued improvement in measures of quality of life and activities of daily living.
"The six participants in this pilot study are two years post-treatment," Dr. Watts explains. "The improvements that we saw six to 12 months after implantation, which were promising, have been maintained up to 24 months now, which continues to be encouraging. These data now lead us to move to the next step, a multi-center, controlled, double-blind trial."
In this recently begun phase IIb research study, half of participants will receive Spheramine implanted on each side of the brain and half will receive a "placebo," in which participants will undergo an imitation surgery and will not have any brain surgery or cells implanted. Neither patients nor doctors will know who received the treatment. Only the neurosurgeon will know who received Spheramine. Participants will be followed closely and examined for final results at 12 months. Researchers are looking for efficacy as well as safety measures in this study. Researchers plan to enroll 68 participants in the multi-center study. Emory will serve as one of the neurological and neurosurgical centers.
"In the pilot study, the first human intracerebral retinal cell implantation study, we only implanted one side of the brain for safety reasons and to lessen the potential for complications," says Dr. Watts. "But since Parkinson's disease is a disorder that affects both sides of the brain, the phase IIb study will evaluate bilateral implantation – that is injections of Spheramine into both sides of the brain. Participants will receive a total of 650,000 RPE cells, with 325,000 implanted on each side. So we'll scale up the dose, but not by increasing the amount put into each striatum."
Dr. Watts says this new cell therapy is an important step, but it needs to be evaluated in a further rigorous manner during a controlled, double-blind study, which is now underway. "We're pleased that the improvement has continued out to two years of follow-up, and we hope this new study will also demonstrate significant benefits to PD patients."
Media Contacts: Janet Christenbury, 404/727-8599, jmchris@emory.edu
Kathi O. Baker, 404/727-9371, kobaker@emory.edu