AstraZeneca’s bid to get its new infant lung drug motavizumab onto the market has suffered a setback with the news that regulators in the USA are not satisfied with the Biologics License Application submitted for the monoclonal antibody.

The Anglo-Swedish drugmaker has received a complete response letter from the US Food and Drug Administration asking for additional information on motavizumab, which has been developed for the prevention of serious respiratory syncytial virus (RSV) disease. AstraZeneca got the rights to motavizumab through its $15.6 billion acquisition of MedImmune and the monoclonal antibody is the follow-up to Synagis (palivizumab), which had third-quarter sales of $124 million.

AstraZeneca did not seem too downbeat about the FDA letter, though it did not reveal the specific nature of the agency’s concerns. It said that “MedImmune is confident that it can respond to the outstanding questions and, based on the company’s current understanding, does not foresee a need to conduct further trials”.

The unit will continue discussions with the FDA reviewers and, “subject to this dialogue, currently expects to resubmit in the first half of 2009”, AstraZeneca stated. Motavizumab was filed in January this year so the FDA’s move means that any launch is facing a considerable delay.

When the BLA was originally filed, MedImmune said it planned to market the drug through its own sales force in the USA and through a partnership with Abbott Laboratories elsewhere. Each year, up to an estimated 125,000 infants in the USA are hospitalised with severe RSV infections.