Shares in Anglo-Swedish drugmaker AstraZeneca were in the ascendancy this morning after it revealed that its combination drug for asthma, Symbicort, had been approved in the USA.

Symbicort (formoterol and budesonide) will tap into a market currently dominated by GlaxoSmithKline’s own two-in-one asthma drug Advair (salmeterol and fluticasone), which had total sales of £3 billion ($5.6bn) last year, £1.7 billion of which came from the US market alone. Symbicort is already sold in Europe and various other parts of the world.

That potential market makes Symbicort’s US launch one of the key pipeline events for AstraZeneca in 2006, and its shares were up nearly 3.5% in mid-morning trading as investors reacted favourably to the news, even though the company has indicated it does not intend to start selling Symbicort in the USA until the middle of 2007.

The US market for asthma drugs was worth more than $10 billion last year, and the fastest-growing segment of this market has been fixed-dose combination treatments which combine a bronchodilator to tackle symptoms with an inhaled steroid to target the underlying inflammation of the lungs in asthma. Their growth reflects that fact that, in many patients, asthma remains poorly controlled, with admissions to hospital staying at a steady rate despite the ready availability of treatment.

Advair currently has the combination market to itself in the USA, but Symbicort is expected to mount a strong challenge, particularly if its labelling can be quickly extended to include flexible dosing data that will allow patients to increase the dose if their symptoms are bad. This data could be filed in the autumn, according to analysts at Datamonitor.

But Symbicort’s approved labelling – for the control of asthma in patients aged 12 and over – is not as broad as that for Advair, which can be used in children as young as four and also has an approved indication in chronic obstructive pulmonary disease.

In addition to Advair and Symbicort, another near-term entrant could be SkyePharma’s Flutiform (formoterol and fluticasone), which is in Phase III testing and could reach the market in 2009. SkyePharma recently signed a US licensing deal with Kos Pharmaceuticals for this product.

AstraZeneca said Symbicort will be made available in a pressurised metered dose inhaler (pMDI) in the USA, as this is the most commonly used and prescribed delivery device in the US market. The USA will be the first country where Symbicort will be available in this type of device.