AstraZeneca’s experimental rheumatoid arthritis pill fostamatinib met only one of two goals in a late-stage clinical trial, leaving the future of one of the group’s few advanced pipeline products uncertain.

Fostamatinib is a potential competitor to injectable drugs like AbbVie’s Humira and Pfizer’s recently launched Xeljanz pill in a $20 billion-plus market. Disappointing results from earlier tests, however, mean investor hopes for the medicine are low.

AstraZeneca said on Friday that two doses of the drug achieved a statistically significant improvement at 24 weeks in a test assessing signs and symptoms of the disease - the so-called ACR20 response rate.

But it failed to show an improvement as measured by X-ray using the modified Total Sharp Score, according to results from the OSKIRA-1 Phase III study.

Side effects seen among patients taking the drug were similar to those experienced in earlier studies, including hypertension, diarrhoea, nausea, headache and common cold.

Analysts are particularly concerned about the hypertension effect, since raised blood pressure could be a serious obstacle to approval.

AstraZeneca licensed fostamatinib in 2010 from Rigel Pharmaceuticals and the U.S. biotech company’s fortunes are closely tied to the medicine.

Briggs Morrison, head of global medicines development at Britain’s second-biggest drugmaker, said the latest study findings showed the new pill had an effect on the signs and symptoms of rheumatoid arthritis.

“We will await the results of the remaining Phase III studies, OSKIRA-2 and OSKIRA-3, to further evaluate and characterize the profile of fostamatinib as a potential treatment for rheumatoid arthritis,” he added.

The OSKIRA-2 and OSKIRA-3 results are expected later in the second quarter of 2013.

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Reuters