Combining GlaxoSmithKline's respiratory drug Advair with Pfizer and Boehringer Ingelheim's Spiriva does not significantly reduce exacerbations in patients with chronic obstructive pulmonary disease, a new study claims.

In the trial carried out by Canadian researchers, the results of which have been published in the Annals of Internal Medicine, 449 patients with moderate to severe COPD were tested to see which of three inhaler regimens best prevented exacerbations.

Exacerbations occurred in 63% of patients treated with Spiriva (tiotropium) and in 65% given Spiriva and GSK’s Serovent (salmeterol), while only 60% of those given tiotropium plus Advair (fluticasone and salmeterol experienced exacerbations, but this was not statistically significant. However, the researchers did find that the latter group had significantly improved lung function, quality of life, and hospitalisation.

GSK responded by saying that the study was underpowered and that statistical significance for the comparison between treatment groups for the primary endpoint was probably not achieved due to low patient numbers, and the company insisted that clear trends have emerged regarding the effectiveness of the Advair/Spiriva combination.

Nevertheless, the study does GSK no favours, coming as it does just a month after data from the major 6,100-patient COPD clinical trial (TORCH) showed that Advair fell short of statistically showing that it decreases the mortality rate. The firm has asked regulators to add the TORCH data to the drug’s label to help its sales force promote Advair, which had sales of £862 million in the fourth quarter of 2006.