AstraZeneca is asking US regulators to give the go-ahead to market its combination respiratory drug Symbicort for young asthmatics.

The Anglo-Swedish firm has submitted a supplemental New Drug Application to the US Food and Drug Administration for Symbicort (budesonide/formoterol) for the long-term maintenance treatment of asthma in paediatric patients aged 6 to 11. The inhaled drug is currently approved for patients 12 and older.

The firm’s submission package is based on “a robust clinical development programme” consisting of five Phase III trials which demonstrated that Symbicort 80/9 mcg twice daily had a similar safety profile to budesonide or formoterol on their own. Lead investigator Jeffrey Leflein, from Allergy & Immunology Associates of Ann Arbor, Michigan, said the data shows that the treatment could benefit child patients whose asthma is not significantly controlled by conventional corticosteroids.

The filing is part of AstraZeneca’s strategy of widening the use of Symbicort in the USA which was launched there in June 2007. Last month it also put in an application to the FDA to market the combination therapy for chronic obstructive pulmonary disease.

Furthermore it forms part of the firm’s bid to compete with GlaxoSmithKline’s GlaxoSmithKline’s combination drug Advair/Seretide (salmeterol and fluticasone), though the latter is well-established across the Atlantic for both asthma and COPD and sales this year should top £4 billion. Symbicort sales last year were in the region of $1.6 billion.

Expanding the drug in the USA is important for AstraZeneca seeing as the European Patent Office revoked the firm’s patent for the use of Symbicort as a treatment for asthma in October. Last month it lost another European patent covering the drug's use for COPD.