A scanning electron microscopy image of the wall of a hollow fiber along with liver cells. Credit: Vital Therapies

People waiting for liver transplants may soon have a new option. Vital Therapies, a medical device company based in San Diego, CA, is testing a system made up of human liver cells that mimics the function of the organ, giving time for an ailing liver to regenerate or for a donor liver to become available. About 2500 people in the U.S. die every year waiting for a donor liver.

While the overall approach is similar to kidney dialysis, mimicking liver function is far more complicated. In addition to filtering blood, the liver makes thousands of proteins and other molecules. At the heart of the device, called an Extracorporeal Liver Assist Device (ELAD), are human cells derived from a liver tumor--unlike typical liver cells, these so-called immortalized cells can be grown successfully outside the body. The cells are grown around a series of hollow fibers, through which the patients' plasma flows. Toxins in the plasma flow through the fiber membrane, where they are metabolized by the liver cells. The cells also synthesize essential proteins, such as blood-clotting factors, which diffuse back into the plasma. The filtered plasma is then recombined with the cellular components of blood and returned to the patient.

A clinical trial in China found that patients treated with the ELAD fared significantly better than those who did not get the treatment. Another study began in the United States in October.

However, while early tests have been promising, the field is littered with failures. According to an article from the Associated Press:

Previous attempts have seemed promising, too, only to fizzle later. A Mayo Clinic review last year found half a dozen different methods under development but none yet proven to reduce death. In fact, the maker of an earlier version of the ELAD went bankrupt in the midst of a 2002 study that gave some hints the device might help at least sometimes.

...The FDA is asking if three to 10 days of ELAD liver support improves 30-day survival over the similarly ill who get today's standard supportive care. Among the safety issues to get close scrutiny: The device's cells initially were derived from a liver tumor and are encased to ensure none of those cells enter a patient's body. Doctors also will ask if any benefit is big enough to cover what could be a $30,000 price tag.