Roche team develops armed antibody in antibiotic fight

Researchers at Roche have developed a new weapon to fight hard-to-treat bacteria by arming an antibody with an antibiotic to reach and kill bugs hidden inside cells.

The approach is similar to an existing technique used by scientists at the Swiss group's biotech unit Genentech, which arms antibodies with a chemotherapy drug to tackle cancer. That system led to the development of the breast cancer drug Kadcyla.

In a paper in the journal Nature, the Genentech team reported their new antibody-antibiotic conjugate (AAC) killed Staphylococcus aureus in mice that standard potent antibiotics failed to destroy.

Drug-resistant strains of S. aureus, or MRSA, are an increasing concern in hospitals, where they can be deadly to vulnerable patients.

The new AAC is designed to be inactive until it enters a cell, when enzyme activity releases the antibiotic.

In an accompanying Nature commentary, Wolf-Dietrich Hardt at Zurich's Institute of Microbiology said it remains to be seen whether the AACs would be as good at treating bacterial infections in humans as in mice.

But the approach is seen as promising, since it should cut the emergence of antibiotic resistance by reducing exposure of other bacteria to active drug, while also limiting damage to the body's beneficial microbes.

In addition, it may allow scientists to look again at past antibiotic drug candidates that were deemed too toxic to use but which might be tolerated if loaded onto a highly targeted antibody "missile".

Swiss drugmaker Roche, which last launched an antibiotic in 1982, has recently stepped up investment in the field, amid growing public concern about the emergence of drug-resistant superbugs.

(Reporting by Ben Hirschler; editing by Adrian Croft)