A summary of the experimental pig-to-human procedures featured in FRONTLINE's report and an overview of clinical trials in the U.S. and Europe

Diacrin's experimental treatment for stroke victims Maribeth Cook and Amanda Davis was an initial Phase 1 trial, in essence, a safety trial. There are two more phases to go.

Of the five patients involved in this Phase 1 trial, four appeared to have improved. One patient did not improve, and Amanda was one of two patients who had seizures.

Diacrin and the FDA called an immediate halt to the trial after Amanda's seizure. Further trials cannot proceed until the FDA finds out what caused the seizure and whether it had anything to do with the pig neural cell implants.

Jim Finn was part of Diacrin/Genzyme's Phase 1 safety trial. Twelve patients participated in this phase which was "open label," meaning everyone receives the treatment and the patients and doctors all know they got the treatment. The twelve were divided into two groups of six. One group was given cyclosporine to suppress their immune systems. In order to suppress their immune response, the other group was treated with a proprietory technology Diacrin has licensed from Massachusetts General. The technology coats the cells prior to transplantation with an antibody to protect against a molecule on the surface of the cell that tends to trigger the immune response. This Phase 1 trial showed indications of efficacy and no safety problems.

Eighteen patients with severe Parkinson's disease participated in Phase 2 clinical trials at three U.S. medical centers. Nine were injected with pig cells and nine were not. The FDA mandated the trial be "double-blinded" with surgical control so neither Diacrin nor the patients knew which ones were treated with the pig cells. The treated patients went into the operating room, a hole was drilled in their skulls and the cells were injected with a long needle that is targeted by using MRI and CT scans.

The nine patients in the control group, who didn't get the cells, went into the operating room for six hours under a general anesthesia, had the skin opened and had a divit put on the skull. The idea is when the patient woke up from anesthesia they would feel they had surgery and they could feel the dent in their head.

The only people that knew whether these patients got cells were the OR staff; the OR windows were covered. The patients were rated by a neurologist who had no idea who got the cells. The cells used were from a non-transgenic, but super-clean pigs.

Diacrin/Genzyme announced on March 16, 2001 that preliminary data indicates that 18 months after the procedure was done, both the treated and the control group seemed to improve, indicating a strong placebo effect.

Diacrin/Genzyme has postponed Phase 3 trials for Parkinson's patients until further studies are done on the Phase 2 data. The company hopes to report on this in July 2001.

If these proceed, they will be a "confirmatory trials." 32 new patients will be divided into two groups. One group will get the pig cell treatment and the other will receive more traditional medical care. All the patients will be monitored using the same measurement scales and the progress between those who get the cells and those who get the medical care will be compared. Patients and doctors will know who got the cells and who didn't.

Diacrin's treatment of epilepsy and Huntington's disease using pig cells are in Phase 1 trials using 6-12 patients with the disease, depending on the protocol.

In Phase 1 clinical trials during the late 1990s, approximately six patients facing acute liver failure were hooked up to a pig liver outside their body which filtered their blood while the patient waited for a human liver transplant. Robert Pennington was one of the people who had his life saved by this procedure. The pig liver used in his case came from a transgenic pig developed by Nextran.

Nextran has no plans to further develop this procedure. Essentially, the clinical trial was designed to see how the pig liver would perform pumping human blood through it, thus indicating how it would work if it were transplanted into a human.

Nextran says it is interested in filing for Phase 1 trials that would involve transplanting kidneys and hearts into humans. Kidney and hearts are less complicated than the liver in terms of the functions they have to perform.

Here's a summary of human clinical trials and studies on xenotransplantation done in both Europe and the U.S. , prepared by the Council of Europe. It includes statistics and a general summary on what has been shown in clinical trials done in the 1990s. A large majority of these trials involved pig neural cell transplants.