The US Just Greenlit High-Tech Alternatives to Animal Testing

Animal testing has long been necessary for a drug to gain approval by the US Food and Drug Administration—but it may be on its way out. A new law seeks to replace some lab animal use with high-tech alternatives.

The FDA Modernization Act 2.0, signed by President Biden at the end of December with widespread bipartisan support, ends a 1938 federal mandate that experimental drugs must be tested on animals before they are used in human clinical trials. While the law doesn’t ban animal testing, it allows drugmakers to use other methods, such as microfluidic chips and miniature tissue models, which use human cells to mimic certain organ functions and structures.

“We have many important drugs that have been developed using animal tests. But as we get into some of these more difficult diseases, especially neurological diseases, the animal models just aren't serving us as well,” says Paul Locke, a scientist and lawyer at Johns Hopkins University who studies alternatives to animal testing. “We need new ways to really unlock the molecular mechanisms that are causing these diseases, and the alternatives I think hold great promise.”

Locke and other advocates point to studies that have shown animal testing to be an unreliable predictor of toxicity in humans. And plenty of drugs work in mice but aren’t effective in people. An estimated 90 percent of drug candidates in clinical trials never reach the market, and drugs that target the brain typically have an even higher failure rate. These inconsistencies, combined with the time, expense, and ethical issues associated with using animals, have led scientists to develop alternative testing methods that aim to better recapitulate human physiology.

These include microfluidic organs-on-chips—clear, flexible polymer gadgets about the size of a computer memory stick that contain different kinds of human cells and push fluid through tiny channels to mimic blood flow. The first successful chip containing living human cells, a lung model, was described in 2010 by Donald Ingber and his team at Harvard University’s Wyss Institute. The miniaturized device was able to carry out basic functions of the lung, including exchanging oxygen and carbon dioxide. Researchers at the Wyss Institute and elsewhere have gone on to create chips that simulate the liver, stomach and intestine, brain, skin, and more, using them to test the effects of drugs and environmental toxins.

Then there are organoids—tiny, three-dimensional blobs of tissue grown in the lab. In 2008, Japanese biologist Yoshiki Sasai showed that, under the right conditions, it is possible to transform stem cells into neural tissue in a dish. By feeding cells certain nutrients and genetic instructions, scientists can coax them to self-organize into structures that resemble miniature organs and contain several cell types. Though no bigger than a pea, these models have some of the characteristics of full-size hearts and brains, and because they’re grown in a lab dish, they provide scientists with a detailed window into how organs form and develop. They’ve also been shown to predict patient responses to certain drugs, including cystic fibrosis medications and chemotherapy.