GlaxoSmithKline has increased its shareholding in US partner Theravance, relecting its high hopes for the asthma/chronic obstructive pulmonary disease experimental drug Relovair.

The companies have entered into an agreement which will see GSK purchase almost 5.8 million shares of Theravance common stock at a price of $22.50 per share, or around $129.4 million. This will take the UK drug major's stake to approximately 19% from 12%.

Moncef Slaoui, GSK's R&D chief, said “we were keen to take advantage of this opportunity to increase our shareholding in Theravance". He added that "this reflects the confidence we have in the Relovair programme and the wider late stage respiratory pipeline that we have built up through the collaboration".

Relovair is a combination of the inhaled corticosteroid fluticasone furoate and the long-acting beta agonist vilanterol trifenatate. It is in Phase III trials in patients with COPD and asthma and is widely seen as a replacement for GSK's biggest earner Advair/Seretide (salmeterol and fluticasone).

Third-quarter sales of the latter asthma/COPD combo were up 5% at £1.24 billion and although Advair goes off-patent next year, GSK has previously stated it does not expect generic competiton any time soon, due to the technical difficulties linked to making inhaled drugs.