The US Food and Drug Administration has rejected Pharmaxis’ cystic fibrosis drug Bronchitol because of inadequate trial data.

The Australian company received a complete response letter from the US regulators recommending that an additional clinical trial be conducted in order to obtain an approval for the drug.

Earlier in the year an FDA panel advised the regulator to not approve Bronchitol (mannitol dry power).

The response letter states: “The submitted data do not provide a favourable benefit-risk balance to support the use of inhaled mannitol in patients with cystic fibrosis six years of age and older. The determination of efficacy based on the two clinical trials are not adequate because of the treatment-related frequent early dropouts in trial 301 for which the primary statistical analyses did not account and the lack of statistical significance in trial 302 for the primary endpoint.”

The FDA was also concerned with the drug’s safety, particularly in paediatric patients with the occurrence of coughing up blood.

Pharmaxis chief executive Gary Phillips said the company was “disappointed” but it would follow up with the FDA to examine the parameters of an additional clinical trial. “The company remains committed to bringing Bronchitol to CF patients in the United States and the onus is now on Pharmaxis to work with the FDA to ensure Bronchitol is approved as soon as possible.”

The FDA has previously granted Bronchitol Orphan Drug designation for the treatment of patients with cystic Fibrosis. The drug is already approved in Australia for patients aged six and over and in the European Union those aged 18 years and over.  

Results from a Phase III bronchiectasis trial are expected in the next quarter, which, if positive, could see label extensions in Europe and Australia.