The world's most dangerous poison can be of great benefit as a drug

Pål Stenmark sees botulinum toxin – the world's most dangerous poison – as a lego building kit he can change so that it gets new features. One goal is to develop new and more effective drugs, including for pain. Through molecular genealogy, he has also found a new family of botulinum toxins, where a variant can fight malaria mosquitoes.

The nerve agent botulinum toxin, or botox as it is commonly called, is best known for having a beneficial effect on wrinkles. The poison paralyzes the skin's muscles so that they relax. But Botox is also used in healthcare for a variety of problems, such as chronic migraines, severe sweating and cramping muscles.
"I was once at Astrid Lindgren Hospital to see how it is used. They treated a girl with a CP injury. She had cramps in her calf that forced her to walk on her toes. But when you injected some botox into the muscles, they relaxed and then she could walk almost normally," says Pål Stenmark, professor of biochemistry at Stockholm University.

For over ten years he has studied various botulinum toxins and he knows the toxic protein into the smallest atomic detail. He sees it as a lego building kit that he can change to give it new features and become even more useful.


Has made one of the world's most dangerous poisons even more toxic

Pål Stenmark sees botulinum toxins as Lego building kits that can change to give them new features and become even more useful. Photo: Rickard Kihlström

In one project, Pål Stenmark has, among other things, made sure that what is already one of the world's most dangerous poisons has become even more toxic.
"Because botulinum toxins are proteins that you inject into your body, it can work just like a vaccine. The immune system can learn to recognize it. If you need large doses and repeated treatments, there is a risk that you will get an immune response that inactivates the drug," says Pål Stenmark.

If the immune system begins to recognize botulinum toxins, it simply becomes immune to the treatment and it loses its effect. To get around this problem, Pål Stenmark's research group has optimized a botulinum toxin, so that the poison connects to the nerve cells more efficiently. This can reduce the amounts injected into the body, which in turn reduces the risk of the immune cells detecting the protein.
"We have shown that the new toxin works better in test tube and animal experiments. Now we hope that it will soon be tested in clinical studies in humans," says Pål Stenmark.


Working on converting the poison into several drugs

His research group is also redesigning various botulinum toxins to work better as medicines for migraines, sweating and various forms of cramping muscles, for example. In addition, they try to produce toxins that connect to nerves that convey pain, known as sensory nerves. If the toxin can paralyze sensory nerves, it will act as a pain medicine.
"We think it's fun to rebuild these toxins, so that they affect nerve cells in many different new ways," says Pål Stenmark.

In his work, he uses so-called X-ray crystallography and cryoelectron microscopy. These are methods that make it possible to obtain three-dimensional images of what proteins look like. Thanks to these images, it is possible to map how botulinum toxins connect to different nerve cells, and understand how they need to be rebuilt to have new effects in the body.



Molecular genealogy unexpectedly gave a bite in Japan

By looking for molecular relatives of botulinum toxins in a giant gene database, Pål Stenmark has also found a completely new variant of the poison. From the database he obtained a genetic family tree with all known botulinum toxins. But there was also a strange branch in the family tree that stood out.
At first I thought something had gone wrong. But it was a bacterium that had been found in Japan," says Pål Stenmark.

The bacterium came from a child who had contracted botulism, a disease in which you become paralyzed by botulinum toxins. It turned out that the bacterium contained a completely new variant of botulinum toxin, the first found in 50 years.


Botulinum toxin from mangrove swamps can fight malaria

Since then, the new family of botulinum toxins has been expanded with two more members. A relatively harmless variant found Pål Stenmark in bacteria from cow poop; A more interesting variant he found through a collaboration with American researchers, who had isolated a different bacterium from mangrove swamps in Malaysia.
"That toxin was found to kill malaria mosquitoes, but not other mosquitoes, which is very special. For example, it does not kill our Swedish mosquitoes," says Pål Stenmark.

"Now the researchers are trying to understand how the poison can be so selective. The hope is that it will lead to a new pesticide against malaria mosquitoes.
How can you research a deadly toxin?
But how can you really research something as deadly as botulinum toxins?
The toxin consists of three parts. We work with some at a time and then it is harmless", says Pål Stenmark.

This – that it is the most dangerous poison in the world – fascinates him:
"The Russian nerve agents are nothing against this. It is the most potent poison there is. This also makes it as useful as a drug."

Text: Ann Fernholm

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