Pittsburgh - An experimental artificial liver system that uses human cells to filter blood plasma is undergoing trials in the hope that it will serve as a successful bridge for patients awaiting a transplant following sudden acute liver failure.
The extracorporeal liver assist device (ELAD) is being studied to evaluate its safety and effigacy at a dozen medical institutions across America, including the University of Pittsburgh medical centre (UPMC).
At any given time, approximately five percent of the 17 000 people needing liver transplants in the United States have acute liver failure and are not expected to live more than a week without a transplant, according to a representative at the medical centre.
By using a line of human liver cells cultivated from a hepatoblastoma, a type of liver tumour, the ELAD appears to be able to perform some of the liver functions that have been lost, including the manufacture of certain proteins and the filtering of some toxins in the blood, said Dr Peter Linden, a principal investigator for the study at UPMC.
"Even given the best standard of care, there is no answer for a liver that is dying and can't repair itself," he said.
The ELAD, which was developed by VitaGen of California, and has not yet received approval from the United States Food and Drug Administration, is one of a handful of devices researchers hope can either be used to give patients' livers time to heal themselves or keep people alive until a transplant can be performed.
One such device, developed by Excorp Medical of Minnesota, and also tested in Pittsburgh, uses pig liver cells to perform a similar service, although Excorp president and CEO Dan Miller says the intention of that system is to give patients' own livers time to heal.
"It's definitely an exciting area. It's early in the game. Until recently, there haven't been very many promising technologies," Miller said.
Eventually, VitaGen wants to enrol 30 patients in its Phase II study, which could lead to more widespread testing, depending on the results.
Since early last year, two UPMC patients suffering acute liver failure were placed on the machine and received successful transplants. In one case, the patient suffered an unusual blood-clotting problem and required a five-organ transplant, including the liver, small bowel, stomach, pancreas and duodenum.
One of the patients was on the machine for a day and a half; the other about 48 hours.
Even though patients in these sorts of sudden liver failures are typically placed on a list for a liver transplant, that doesn't always mean an organ is available. The ELAD may be able to help bridge the gap, Linden said.
About the size of a washing machine, the ELAD works in a manner similar to kidney dialysis, in which waste products are removed from the blood. In this case, a pump pushes the patient's blood through a catheter into a large filter in the machine, which separates blood cells from plasma.
Then the plasma is pushed through cartridges containing the human liver cells for cleaning. Unlike some other machines - such as one developed by HemoCleanse of Indiana, that uses charcoal and other materials to clean the blood - the ELAD may also be able to create certain proteins, as a real liver does. The blood is recombined and pumped back into the patient.
Among the 12 medical centres involved in the ELAD study are those at the Universities of Miami, Chicago, Massachusetts and Columbia.
Linden said that when a patient is randomly selected to go on the ELAD, the cartridges are ordered from southern California, where the cells are kept in an incubator. Once they arrive - typically within a day - the patient is placed on the machine while he or she waits for a transplant. In some cases, it is hoped that the patient's own liver will regenerate itself.
They undergo standard therapy - which may include mechanical ventilation, dialysis and blood medications - in addition to using the ELAD. Some patients do not go on the ELAD, serving as a control group for the study.
HemoCleanse's president, Robert Truitt, said the cell-based liver assist systems tend to be very expensive but that the research is exciting since it may provide the best alternative when end-stage liver failure is imminent.
Linden said the biggest downside may be that the ELAD requires almost constant monitoring to make sure it is operating properly.
"Development of an artificial liver is a daunting challenge because of the many complex functions that the liver performs," said Dr George Mazariegos, assistant professor of surgery at the University of Pittsburgh's transplantation institute. "But the need is urgent, as more than two thousand patients needing liver transplants die on the national waiting list each year."
- Sapa-AP