In Tamoxifen’s case, a drug first developed as a potential contraceptive languished for many years before its present application was found. Furthermore, its propensity to cause liver tumours in rats, a toxicity problem that thankfully does not carry over into humans, was not detected until after the drug had been on the market for many years. If it had been found in preclinical testing, the drug would almost certainly have been withdrawn from the pipeline.
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Even when drugs with evidence of anticancer activity in preclinical in vivo models are given at their maximum tolerated doses, they frequently fail to produce useful activity in humans.
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It’s been well known for maybe two decades that many of these preclinical human cancer models have very little predictive power in terms of how actual human beings – actual human tumours inside patients – will respond…Preclinical models of human cancer, in large part, stink…Hundreds of millions of dollars are being wasted every year by drug companies using these [animal] models…
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