Shares in Swiss biopharmaceutical group Basilea took a hammering yesterday after US regulators stopped short of issuing a full green light for its antibiotic ceftobiprole, which is partnered with Johnson & Johnson.

The group’s share price plunged nearly 30% as investor confidence was rocked by the Food and Drug Administrations’ decision to issue an approvable letter for the drug, thereby delaying its entry onto the all-important US market.

The companies are seeking clearance to market the ceftobiprole - a first-in-class broad-spectrum cephalosporin - for the treatment of complicated skin and skin structure infections, including the notorious superbug MRSA. But while the FDA deemed the drug approvable, it has requested more information on its impact on diabetic foot infections, as well as more time to evaluate the clinical data in the file and inspect study sites before considering the all clear.

In a statement, Anthony Man, Basilea’s chief executive, said both companies are working together “to quickly address the questions from the FDA”, and according to media reports, although he was unable to provide a timeframe for completion of the additional requests, analysts are reportedly forecasting a setback of around nine-12 months for the drug.

Basilea and J&J unit Janssen-Cilag International submitted ceftobiprole for approval in Europe in June last year, and the drug is also awaiting clearance in Canada, Australia and other countries.