Roche has pulled out of a deal to develop a new antibiotic for treating superbug infections.

In 2013 the Swiss firm paid private partner Polyphor 500 million Swiss francs, with an additional  465 million francs earmarked for milestone payments, for the rights to the investigational drug RG7929/POL7080 for treating severe Pseudomonas aeruginosa infections. 

But in a statement the company said that it had come to the conclusion that “a streamlined development path as originally planned is no longer an option for Roche”

The rights to POL7080, which is currently in Phase II development, will now be fully returned to Polyphor.

Roche originally dropped out of the antibiotic field in the late 1990s, and its deal with Polyphor marked a rare case of a big pharma company investing in the low-margins area in recent years.

In its statement the company said that antimicrobial resistance poses a “major threat” to public health and that it would continue to focus on this disease area. In Janurary 2015 Roche it licensed an early-stage treatment for antibiotic resistance from Japan’s Meiji Seika Pharma and Fedora of Canada.

Earlier this month scientists warned that the world could be on the verge of a ‘post-antibiotic’ era after bacteria resistant to last-resort drugs were discovered in China.