AstraZeneca has presented a mixed set of results from a late-stage trial of its investigational rheumatoid arthritis drug fostamatinib.

The Phase III study, called Oskira-1, had two primary endpoints. For the first, assessing the signs and symptoms of RA as measured by ACR20 response rates, fostamatinib achieved a statistically significant improvement in ACR20 response rate at 24 weeks compared to placebo.

However, fostamatinib, an oral spleen tyrosine kinase inhibitor, did not demonstrate a difference for an X-ray endpoint known as mTSS (modified Total Sharp Score) which tracks the progression of joint damage. AstraZeneca noted that the most commonly reported adverse events were typical of those seen in earlier studies, including hypertension, diarrhoea, nausea and headache.

Briggs Morrison, head of global medicines development at the Anglo-Swedish drugmaker, said the top-line results "provide important information on the efficacy and safety of fostamatinib and demonstrate that the compound has an effect on the signs and symptoms of RA". He added that the firm is awaiting the results of Oskira-2 and Oskira-3, expected later in the second quarter this year, "to further evaluate and characterise the profile" of the drug.

In December, fostamatinib failed to show a benefit versus AbbVie's blockbuster Humira (adalimumab) in a mid-stage trial and Panmure Gordon analyst Savvas Neophytou noted that the latest news on fostamatinib, which is licensed from Rigel Pharmaceuticals, "should provide investors with a reminder of the risks of drug development". He added that "we make no changes to forecasts because we do not have fostamatinib in our model".