Scientists from Swiss pharmaceutical company Roche recently developed a combination of antibodies and antibiotics for a drug therapy that could fight against Methicillin-resistant Staphylococcus aureus (MRSA) infections.
The new drug therapy would arm an antibody with antibiotic to penetrate and kill microbes hidden inside cells.
"Most conventional antibiotics are fantastic at killing Staph outside cells, but poor at killing it inside the cell," said immunologist Sanjeev Mariathasan, a researcher at Genentech, the company's biotech unit. "So the question was how do you kill the bacteria when it gets inside the cell?"
Researchers said that to test their drug therapy, they infected mice with MRSA, and treated them with either vancomycin or the experimental combination drug, the antibody-antibiotic conjugate (AAC).
The team reported the AAC was a thousand times more effective in destroying MRSA found in mouse cells, which standard antibiotics were unable to kill.
Mariathasan compared the treatment to a stealth bomb. The AAC is first inactive until it invades a cell. Enzyme activity inside the cell breaks the bond between the antibiotic and the antibody. The antibiotic is then activated unto the targeted bacteria.
At Genentech, a similar technique is used for a chemotherapy drug, which led to the creation of Kadcyla, a breast cancer drug. The technique raises hopes for treating chronic infections that can occur after heart surgery and relapses in tuberculosis patients.
Meanwhile, microbiologist Wolf-Dietrich Hardt, who provided commentary for the study, said the technique could reduce antibiotic resistance because only the targeted bacteria are exposed to the therapy. The technique could also diminish the harmful effects of antibiotics on healthy microorganisms which live in the gut.
Most experimental treatments are not successful because they are toxic at the required doses needed for a therapeutic effect, researchers say. Other antibiotics also do not work when they are used through pills, injections or intravenous lines in which they fail to deliver the drug directly into the targeted cell.
"To me the most exciting perspective is the ability to tap this large resource of antimicrobial drugs that have not survived the pipeline," said Hardt. He added that AACs could help scientists revisit drugs and fill the empty pipeline.
The team's findings are published in the journal Nature.
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