By latching onto bacteria and detonating at just the right moment, a new drug could help take out the leading cause of bacterial infections in humans worldwide.

The drug, a deadly combo of an antibody glued to an antibiotic, specifically seeks and destroys Staphylococcus aureus—even the difficult-to-kill, drug-resistant variety, methicillin-resistant staph (MRSA). In mice infected with MRSA, the dynamic duo fought off the infection better than the standard antibiotic treatment of vancomycin, researchers report in Nature. If the findings hold true in humans, the new superdrug could vastly improve the success rates of MRSA infection treatments, some of which can fail up to 50 percent of the time.

That fail rate is likely linked to staph’s stealthy infection strategy, the authors note. Inside a victim, the bacteria battle immune cells that try to gobble them up. Once sucked into the cells, the bacteria normally get digested into un-infectious bits. But some of the bacteria can dodge death and hide out. Instead of a death chamber, the cells become bacterial getaway cars, leaving killer antibiotics in the dust and giving the germs a ride around the circulatory system to uninfected organs and tissues.

Standard antibiotic treatments can fight off staph at infection sites. But those cellular stowaways are left unscathed, leaving patients with lingering or recurring infections.

The new superdrug, on the other hand, specifically targets those stowaways. The antibody part of the drug tightly binds to acids on staph’s surface. When the bacteria get sucked into an immune cell, the antibody-antibiotic combo drug sticks with it. Once inside, cellular enzymes blast the drug apart, freeing and activating the antibiotic. In this case, the researchers found that a derivative of the common antibiotic rifampicin, called rifalogue, worked best. Bacteria that survive the cells’ digestion attempt ultimately succumb to the newly free rifalogue.

In lab tests, more than ten thousand copies of the superdrug could clamp onto a bacterium, towing more than enough rifalogue to deliver a deadly dose inside the cell. In mice, the superdrug was orders of magnitude more powerful at wiping out MRSA than vancomycin or antibody treatments alone.

But, for now, there are no guarantees that the superdrug will be that effective in human patients. Researchers point out that the human immune system may produce competing antibodies that bind to staph, possibly elbowing out the superdrug.

Still, whether this particular antibody-antibiotic pair is successful in humans may not matter in the long run. Researchers can continue to try new combinations, even reviving antibiotics that failed to make it through the development pipeline. Antibiotics that may be toxic or bad at circulating through the human body on their own could be highly effective when glued to a bacteria-targeting partner. And researchers could make pairings with antibodies that target other infectious microbes, creating a host of other potential new therapies.

Nature, 2015. DOI:10.1038/nature16057 (About DOIs).

correction: the original version of this piece suggested MRSA treatments fail about half the time. The correct figure is that some treatments can fail up to half the time.