The makers of Botox have been celebrating — and no, it's not because they found a better way to smooth wrinkles.
The company, Allergan Inc. of Irvine, announced in June that the Food and Drug Administration approved its new method to test Botox's potency. Instead of having to test every batch on live animals, it can now run a test on cells in a lab dish.
It took 10 years for Allergan scientists to perfect the new test. If it's approved in all the countries where Botox is sold, Allergan expects to eliminate the need for at least 95% of its animal testing within three years.
"Our hat is off to the company," says Martin Stephens, vice president for animal research issues at the Humane Society of the United States in Washington, D.C.
The government says that every new compound people might be exposed to — whether it's the latest wonder drug, lipstick shade, pesticide or food dye — must be tested to make sure it isn't toxic. Usually, this requires animals. Allergan's new test is one of several under development, or already in use, that could change that.
U.S. agencies have already approved alternative tests to replace many experiments on animals' eyes and skin. Scientists are now developing tests for toxins that cause organ damage, birth defects, and other problems. These new tests could make animal toxicity experiments obsolete in the next 10 to 20 years, says David Jacobson-Kram, associate director for pharmacology and toxicology at the FDA's Center for Drug Evaluation and Research in Silver Spring, Md.
In addition to being more humane, these experiments often promise better results more quickly and cheaply than the classic tests with mice or rabbits.
"Both the science and animal welfare can benefit," Stephens says.
Even scientists who work with animals would prefer not to. According to a 2006 survey by the journal Nature, 78% of biologists would like to eliminate animal experiments (although only 80% of those thought it would be possible).
"None of us take any pleasure in using animals in research," Jacobson-Kram says.
Labs in the United States use nearly 1 million mammals per year, according to 2009 statistics from the U.S. Department of Agriculture. However, that number excludes mice and rats — the most popular laboratory workhorses — because the U.S. Animal Welfare Act does not cover them. In a 2008 article in the journal Alternatives to Laboratory Animals, a group of animal activists estimated that the total number of research animals used in the U.S. is closer to 17 million, including rodents, birds, reptiles, amphibians and fish.
Toxicity testing uses some 10% of these animals, estimates Thomas Hartung, director of the Johns Hopkins Center for Alternatives to Animal Testing in Baltimore. Another 15% go toward vaccine testing, he says, and a small number are used in education. The rest are in biomedical research labs.
Animal toxicity tests are classic experiments but don't necessarily yield the best possible results. One downside is that the results of animal tests often fail to predict what will happen in people. Just consider: Chocolate is bad for dogs but OK for people.
According to a classic 2000 study in the journal Regulatory Toxicology and Pharmacology, rodent experiments predict toxicity to humans just 43% of the time. "We are not 70-kilogram rats," Hartung says.
These tests haven't kept pace with scientific progress. When researchers first developed toxicity tests decades ago, animals were "convenient black boxes," Stephens says. Scientists didn't understand how a chemical could sicken an animal, but they could see whether the creature lived or died.
That's the principle behind the "Lethal Dose, 50%" test, invented in 1927. It asks how much of a given toxin will kill half of the animals exposed to it. Until June, this was the test Allergan had to use.
Now, scientists have a much better understanding of the inner workings of animals and people. For example, concerns about botulism as a bioterrorism agent have prompted copious research on how botulinum toxin, the active ingredient in Botox, causes paralysis.
Once inside a nerve cell, the toxin cuts a crucial protein in half. Without that protein, the cell can no longer release neurotransmitters, bringing nerve activity to a standstill. This is how Botox not only wipes away frown lines but also treats 21 other conditions, including muscle spasms and migraines.
For their new test, Allergan scientists grow nerve cells in a dish. Then they squirt in different doses from their latest batch of Botox and check the neurotransmitter-pumping protein after a few days to see how much of it is cut versus whole. The entire test takes about a week.
The new approach allows the scientists to test many more doses of the drug and obtain precise results, says Tim Terrell, Allergan's senior vice president for drug safety evaluation. (The company still has to use animals in other tests, such as those to determine the toxicity of standard compounds they compare to Botox.)
Also this year, the U.S. Interagency Coordinating Committee on the Validation of Alternative Methods — an umbrella organization that represents the FDA, the National Institutes of Health, the Consumer Product Safety Commission and other federal agencies — accepted a new test for eye irritants.
The old method, developed by FDA scientists in 1944, was to dribble the chemical in rabbits' eyes and observe what happened. The new test uses a device called a cytosensor microphysiometer. It relies on the fact that healthy, functioning cells release acid into their surroundings, while sick or dying cells produce less acid. Thus, by adding a potential toxin to the device and measuring the acidity of the liquid surrounding the cells, researchers can determine whether the chemical damaged them.
Several more alternatives are in the works. At Drexel University in Philadelphia, for example, scientists are taking on one of the greatest challenges in drug development, liver damage. Liver toxicity is a common reason that new medicines don't make it to market, says molecular biologist Michael Bouchard.
Bouchard and his colleagues start with human liver cells and grow them in tiny tunnels that are similar to the organ's natural channels. The scientists can flow any chemical through the tubes and watch for signs of sickness. The researchers are still optimizing the system, but they have already used it to study infections in liver cells.
And in Madison, Wis., Stemina Biomarker Discovery Inc. is using embryonic stem cells to address another great challenge in toxicity studies: whether a chemical will cause birth defects. Animal tests for this correctly predict human results a little more than 50% of the time, according to a 2005 review in the journal Biogenic Amines. Toxicologists might as well flip a coin.
Stemina researchers have examined the kinds of molecules stem cells make when exposed to different toxins, and they've identified a couple dozen that they think are key indicators of birth defects. If the cells produce those molecules in response to a potential new toxin, chances are it would cause birth defects too.
The test is accurate 87% of the time, says Elizabeth Donley, the company's chief executive. It's also faster and cheaper, she adds.
Rodger Curren, president of the Institute for In Vitro Sciences in Gaithersburg, Md., says tests like these can persuade researchers to abandon compounds if they are toxic to cells in a dish. But if a compound is safe for cells, scientists usually have to confirm its safety in animals.
At least, Curren says, the new tests can save animals from exposure to the nastiest of chemicals.