A new class of antibiotics created by clever chemistry

As concerns about bacterial resistance to antibiotics grow, researchers are racing to find new kinds of drugs to replace ones that are no longer effective. One promising new class of molecules called acyldepsipeptides - ADEPs - kills bacteria in a way that no marketed antibacterial drug does - by altering the pathway through which cells rid themselves of harmful proteins.

Now, researchers from Brown University and the Massachusetts Institute of Technology have shown that giving the ADEPs more backbone can dramatically increase their biological potency. By modifying the structure of the ADEPs in ways that make them more rigid, the team prepared new ADEP analogs that are up to 1,200 times more potent than the naturally occurring molecule.

A paper describing the research was released on-line by the Journal of the American Chemical Society.

"The work is significant because we have outlined and validated a strategy for the enhancing the potency of this promising class of antibacterial drug leads," said Jason Sello, professor of chemistry at Brown and the paper's senior author. "The molecules that we have synthesized are among the most potent antibacterial agents ever reported in the literature."

ADEPs kill bacteria by a mechanism by that is distinct from all clinically available anti-bacterial drugs. They work by binding to a protein in bacterial cells that acts as a "cellular garbage disposal," as Sello describes it. This barrel-shaped protein, called ClpP, breaks down proteins that are misfolded or damaged and could be harmful to the cell. However, when ClpP is bound by an ADEP, it's no longer so selective about the proteins it degrades In essence, the binding by ADEP causes the garbage disposal to run amok and devour healthy proteins throughout the cell. For bacteria, a runaway ClpP is deadly.

ADEPs have been shown to kill bacteria that cause staph infections, some kinds of pneumonia, tuberculosis, and other types of infection in the lab. The molecules have also been reported to cure bacterial infections in mice and rats.

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