Safer Human Testing Of Drugs With New Cutting-Edge Cell Research
In 1993, five out of 15 liver patients who participated in a medical trial following the American Federal Drug Administration's (FDA's) instructions died. The patients had been treated with the substance fialuridin that should treat them for the disease hepatitis B. The substance was tested in the laboratory and on animals and had been evaluated as safe for human testing.
Surprisingly it turned out that the substance was acutely lethal to humans and led to extensive liver failure. Five patients died and two others only survived because they received a liver transplant.
When researchers develop new medicines, there are not just billions of dollars and years of research on the line. Patient safety is also at stake.
Now, new research from the University of Southern Denmark shows that the safety for people participating in medical experiments can be improved.
"With our new technique the pharmaceutical industry can better avoid harmful or even fatal effects on medical test subjects," says cell researcher Stephen Fey from the University of Southern Denmark.
When a new drug is developed, its individual active substances are first tested for adverse effects. All substances in the world are potentially deadly if the dose is high enough - this was first stated by the German-Swiss scientist Paracelsus (1493 - 1541) in the Renaissance. The challenge is to find substances that have a positive, healing effect and not a toxic or deadly one.
The substances are often tested on human liver cells in the laboratory. If liver cells do not respond negatively to the substance, scientists move to testing animals and finally humans. But despite all this work, only 10 per cent of the substances being tested on humans actually work as intended. 90 per cent do not. At worst, they are toxic, and in extreme cases, test subjects die.
"The success rate can be better than the 10 per cent", explains Stephen Fey, associate professor in the Department of Biochemistry and Molecular Biology at the University of Southern Denmark.
Together with his colleague Krzysztof Wrzesinski, postdoc at the same place, he is the leading scientist behind the groundbreaking discovery. The researchers' work is published in two articles in the journal Toxicology Research, issues 2 and 3, 2013.
"The breakthrough is that now we can test drugs on human liver cells that are more natural than the cell lines used by the pharmaceutical industry. Laboratory cells today do not have much in common with the natural cells that live in the human body, "says Stephen Fey.
In a human body, cells are able to communicate with each other and exchange valuable information. If cells that think they are alone they behave differently than they do when other cells are around. The isolated cells spend all their energy on multiplying and therefore can no longer perform their advanced functions.
The reason that laboratories work with cells that poorly communicate with each other, is not laziness, nor ignorance. In order to keep the cells alive, you have to expose them to a rather rough treatment that removes their ability to communicate. If you leave the cell line inside a container and feed them, they multiply and become overcrowded - the problem is that they will pile up on top of each other. This will prevent the bottom cells from getting oxygen and nutrients and this will eventually kill them.
In order to prevent the cells from dying, an enzyme called trypsin can be added to detach the cells from each other so that the cells can be dispersed into less crowded conditions. Trypsinisation will thus 'keep the laboratory cells alive' - but it kills their ability to communicate.
"Cells grown in normal laboratory conditions do not react like natural cells in the human body, and therefore they all-too-often give erroneous messages about how a drug works in the human organism. When you are testing the toxicity of a substance - which you always do because of the possible dangers - there is a risk that the trypsin-treated cells report back that they can tolerate the substance, but when one tests the substance on a real person, the effect can actually be fatal, "explains Stephen Fey.
In extreme cases, studies show that both laboratory grown cells and animals tolerate a drug, but human test subjects don't - as seen in as in the U.S. fialuridin-tragedy (and several other studies since).
"With our 3D culture method, cells mimic cells in the human body better and thus we get more appropriate results," says Stephen Fey.
"By avoiding trypsinizing cells, they keep their ability to communicate. To avoid using trypsin, cells are grown in small round 3D structures, called spheroids, in a solution, which is constantly being turned. This tricks them into thinking that they are in a tissue surrounded by blood in a natural human body, "explains Stephen Fey.
He refers to cells grown in this way as 3D cell cultures because they live in a three dimensional space as opposed to the traditional methods (which use trypsin) and grow cells on a two-dimensional surface, the bottom of a container.
The researchers from SDU have managed to grow human liver cells, which have a lot more similarities with liver cells in the human body and thus are a lot more valuable than the trypsinized cells, normally used by the pharmaceutical industry.
"Our research shows that we can now predict the dose at which a substance becomes toxic for humans more accurately than before and thus reduce the risk of poisoning test persons" explains Stephen Fey.
Original work is published in Toxicology Research: After trypsinisation, 3D spheroids of C3A hepatocytes need 18 days to re-establish similar levels of key Physiological functions to those seen in the liver, Toxicol. Res., 2013, vol 2
HepG2/C3A 3D spheroids exhibit stable physiological functionality for at least 24 days after recovering from trypsinisation, Toxicol. Res., 2013, vol 3.
University of Southern Denmark
Source: EurekAlert!, the online, global news service operated by AAAS, the science society
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