For one year, nine healthy volunteers took a cocktail of three common drugs — growth hormone and two diabetes medications — and on average shed 2.5 years of their biological ages, measured by analysing marks on a person’s genomes. The participants’ immune systems also showed signs of rejuvenation.
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Checking the effect of the drugs on the participants’ epigenetic clocks was an afterthought.
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Horvath used four different epigenetic clocks to assess each patient’s biological age, and he found significant reversal for each trial participant in all of the tests. “This told me that the biological effect of the treatment was robust,” he says. What’s more, the effect persisted in the six participants who provided a final blood sample six months after stopping the trial, he says.