Miracle Poison Holds Gateway To Novel Therapeutics

Botulinum toxin, a buzzword in the world of cosmetics is best known to people as a tool that makes the frown lines disappear. On the other side it is also a deadly poison, also known as "miracle poison," approved by the F.D.A. to treat a suite of maladies like chronic migraines, uncontrolled blinking, and certain muscle spasms. Botulinum toxin proteins can be engineered to find new yet different protein targets with high selectivity, a critical advance towards potential new treatments for everything from neuroregeneration to cytokine storm, as per a study at Harvard University and the Broad Institute.

The team successfully first reprogrammed proteases (enzymes that cut proteins to either activate or deactivate them) to cut entirely new protein targets, even some with little or no similarity to the native targets of the starting proteases, and to simultaneously avoid engaging their original targets. This led to the evolution of custom proteases with tailor-made instructions for which protein to cut.

The "classical challenge in biology" is designing treatments that can cross into a cell. The botulinum toxin proteases can enter neurons in large numbers, giving them a wider reach that makes them all the more appealing as potential therapeutics.

Proteases – The Novel Therapeutics

Unlike gene-editing technologies that tend to correct only genetic errors of the disease, protease-based therapies help address certain acute illnesses, like neurological damage following a stroke (not caused by a genetic error). The body's ability to heal something like nerve damage through a temporary or even one-time treatment can be boosted by the proteins.

The long-awaited therapy that utilizes proteases to treat diseases surpasses even the antibodies treatment, which can only attack specific alien substances in the body. Proteases can do more than just destroy their target. They could, for example, also reactivate dormant proteins. Lack of proper technology that would generate proteases to cleave protein targets remained a primary reason for not being widely adopted as human therapeutics.

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A technological advancement developed by the study team called PACE (phage-assisted continuous evolution) is capable of evolving dozens of generations of proteins a day with minimal human intervention. The proteases were designed to stop cutting certain targets and become far more selective by recognizing an entirely new target, one outside its natural wheelhouse.

"At the outset, we didn't know if it was even feasible to take this unique class of proteases and evolve them or teach them to cleave something new because that had never been done before. You end up with a powerful tool to do intracellular therapy in theory ", says, Blum.

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The New Era of Disease Treatment

The "moonshot" was outperformed by the proteases as they evolved four proteases from three families of botulinum toxin using PACE technology.

It was found that all four proteases retained their valuable ability to enter cells. They had no detected activity on their original targets and cut their new targets with a high level of specificity (ranging from 218- to more than 11,000,000-fold).

Although theoretically, this work provides a strong foundation for the rapid generation of many new proteases with new capabilities, further studies are required to assess the long-term performance of proteases in treating humans.

The limitation of the study lies in the fact that proteins may not serve as ideal treatment targets in chronic diseases because, over time, the body's immune system will recognize them as alien substances and attack and defuse them.

While botulinum toxin lasts longer than most proteins in cells, the team's evolved proteins might end up with shorter lifetimes, which could diminish their effectiveness. The proteases could however be effective for temporary treatments since the body’s immune system takes time to identify foreign substances.

"We're still trying to understand the system's limitations, but in an ideal world we can think about using these toxins to theoretically cleave any protein of interest", says, Blum. They just have to choose which proteins to go after next. The study thereby provides critical perspective on the potential medical applications and targets for the proteases.

Source-Medindia