The first drug that regrows teeth is about to enter clinical trials  

After reporting successful animal trials, a team of researchers from Japan is now set to start human trials for a drug that can regrow teeth. If successful, the drug could open up new ways of treating a lack of teeth, particularly in people suffering from genetic disorders.

Animals such as sharks and alligators can continuously regrow teeth. But humans can't. We have two rows of teeth and that's pretty much it. But there is evidence that we also have the "buds" for a third set. Katsu Takahashi, lead researcher and head of the dentistry and oral surgery department at the Medical Research Institute Kitano Hospital in the city of Osaka says we can get humans to grow this third-generation dentition.

"The idea of growing new teeth is every dentist's dream. I've been working on this since I was a graduate student. I was confident I'd be able to make it happen," the researcher says.

The work starts with gene studies on mice. Several researchers around the world showed that when some genes are deleted from mice, this causes them to grow fewer teeth. This got other researchers thinking: what if the opposite were also true? What if you could genetically alter mice to get them to grow more teeth?

As it turns out, Takahashi found that mice lacking a specific gene indeed had an increased number of teeth. The researcher and his colleagues zoomed in on a protein called USAG-1 that seems to stop more teeth from growing. Consequently, blocking that protein enables more teeth to grow.

A new tooth is seen growing in a mouse treated with tooth regrowth medicine. Image credits: Katsu Takahashi, head of the dentistry and oral surgery department at the Medical Research Institute Kitano Hospital.

It's pretty stunning that a single gene has so much impact on dentition. But it gets even crazier. When Takahashi and his research team developed neutralizing antibody medicine that blocked USAG-1, they managed to get mice born without some teeth to regrow the said teeth. In other words, they developed the first tooth-regrowing treatment in the world.

Around 1 in 100 people has an incomplete set of teeth, a condition called anodontia. Genetic factors are thought to be one of the driving factors in this, particularly in people lacking 6 or more teeth. As you can imagine, this lack of teeth can cause substantial discomfort for chewing and speaking, and as this condition is present from birth, its effects propagate for people's entire lives.

Of course, just because the drug works on mice doesn't necessarily mean it will work on humans. But Takahashi is optimistic. "We hope to pave the way for the medicine's clinical use," the researcher says.

Initially, the drug will be targeted at people suffering from anodontia, but if it's successful, the drug can be used in all sorts of dental treatments. Are cavities damaging a tooth beyond repair? Let's just grow a new one. Lost a tooth or several in an accident? Get third-gen teeth to grow. There's no shortage of applications for such a drug.

Before clinical trials can start, however, the team has to show that the drug is safe in humans and can be tested without any negative side effects. If this turns out to be the case, the team will also deploy human trials, which could end up benefiting millions of patients.

Takahashi and his team have developed a prospective schedule where they expect safety studies to be concluded by 2025 and efficacy and optimal dose studies to be concluded by 2028. Then, if everything goes according to plan, by 2029, the team could have larger clinical trials. Hopefully, by the end of this decade, the first dental regrowth medicine could be on its way.

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