Again and again one has to learn the lesson that animal models don’t always predict the outcome in humans. Thalidomide was safe in animals but in humans caused frightful birth defects. Fialuridine was a promising antiviral designed to counter hepatitis B. It was tested in mice, rats, dogs, monkeys, and woodchucks, at doses hundreds of times higher than would ever be tested on humans. Not a single animal showed a toxic reaction. But even minimal amounts of the drug were fatal to human volunteers, killing five of them; two others survived only after having liver transplants. Nothing in Henry’s
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