Shares in GlaxoSmithKline have taken a battering after the UK drugs major said it will push ahead with filings this year for its new chronic obstructive pulmonary disease and asthma drug Relovair on the back of what some observers believe is unimpressive data.

GSK and partner Theravance announced the completion of the Phase III registration programme for Relovair (fluticasone/vilanterol) in patients with COPD and of all but one of the pivotal asthma studies. For COPD, GSK intends to submit regulatory applications in the USA and Europe in mid-2012 and an asthma submission will be made at the same time in the latter; talks are ongoing with the Food and Drug Administration about the regulatory requirements for a US asthma indication.

GSK respiratory chief Darrell Baker said the firm sees Relovair as one of its most important assets. He added that "having undertaken an initial assessment of these data we believe they support our plan to seek global approvals".

However the pile of data GSK and Theravance presented on the drug, which has been dubbed 'Super Advair' as it is the follow-up product to its biggest-selling drug Advair (salmeterol/fluticasone), left analysts underwhelmed.

The COPD programme includes two studies that each enrolled 1,620 patients with chronic obstructive pulmonary disease (COPD) and investigated three doses (200/25mcg, 100/25mcg and 50/25mcg) of Relovair compared to vilanterol alone. In the first trial, showed that all doses of the new combo led to significant reductions in the annual rate of moderate to severe exacerbations compared to vilanterol alone, but in the second study, the reductions were not significant at the highest dose (200/25mcg). In both trials, GSK that all doses of Relovair demonstrated numerical increases in lung function compared with vilanterol, "but not all increases were significant".

Not superior to Advair

Full results from the studies will be presented at future scientific meetings but observers have picked up on two trials that compared Relovair to Advair and failed to meet "the predefined threshold for superiority on 0-24 hour weighted mean FEV1". Deutsche Bank analyst Mark Clark described the data as poor and the failure to beat Advair would reduce Relovair's potential. "This means any advantage is limited to its once- versus twice-daily format," he added.

Luisa Hector at Credit Suisse issued a research note saying that Relovair was expected to be a “significant driver” of growth at GSK, making the results a disappointment. Investors were certainly concerned and GSK's stock fell over 4% to just under £14.37, while Theravance shares crashed 19% to $16.39.