EXPERIMENTS aimed at curing brain damage in stroke patients by injecting them with fetal brain cells from pigs have been suspended after reports of worrying side effects. Diacrin, the company based in Charlestown, Massachusetts, which developed the treatment, halted recruitment of volunteers for the trial last week.
“One patient developed seizures a week after transplant,” says Thomas Fraser, the president of Diacrin. “Another had minor brain swelling and muscular fatigue,” he says. “They were the fourth and fifth patients, and three had been treated previously without any adverse events,” he adds.
The company is trying to find out if the equipment or the injected cells were to blame. Fraser says that cells were injected with a tube—or catheter—that was quite large and this could have triggered problems. Also, one of the patients was diabetic, and the seizure may have been due to fluctuating sugar levels. “We’re being very cautious,” he says.
Advertisement
The programme, at the Beth Israel Deaconess Medical Center in Boston, began last September and is the first to use pig cells for treating stroke damage. In pre-clinical trials on rats with strokes, the pig cells helped the rodents to recover mobility. “In the rats, you could see neurons growing and hooking up in the stroke damage site, actually filling the hole,” says Fraser.
The cells are taken from pig fetuses and coated with fragments of mouse antibodies prior to treatment. They mask molecules called MHC-1 that live on the surface of the pig cells. These molecules would otherwise identify the pig cells as foreign in the people who have the transplants. Because the antibody fragments hide MHC-1 and the pig cells that carry it, the recipient’s immune system won’t reject the transplant.
Tens of patients with Parkinson’s and Huntington’s diseases have already been treated with brain injections of the cells without any adverse effects. And so far there has been no sign of porcine endogenous retroviruses spreading to human cells, a major worry in the field of xenotransplantation.
Despite the setback last week, Diacrin hopes to restart the stroke trial. “We’re working with the FDA and would not restart without their say so,” says Fraser. He is also hopeful that the FDA will soon give Diacrin the go-ahead for the world’s first attempt to treat spinal injuries with cells taken from the spinal cords of pig fetuses. “They’d be injected into the spinal cord on both sides of the site of injury to form a partial splice,” says Fraser.
The company hopes to start trials of this treatment this spring on six patients at the Albany Medical Center in Albany, New York, and at Washington University Medical Center in St Louis. Diacrin has also recently applied for a patent (www.derwent.com/resource/interest.html) covering use of the fetal pig spinal cells for treating spine injuries and other neurodegenerative diseases such as multiple sclerosis and amyotrophic lateral sclerosis or Lou Gehrig’s disease.
