AstraZeneca plc (NYSE:AZN) (LON:AZN)’s drug fostamatinib apparently did poorly in a late-stage study of its effectiveness. The rheumatoid arthritis pill would have provided an alternate form of treatment for the painful autoimmune disease. Most current treatments for RA include Humira, an inject-able drug made by a competitor. The failure of fostamatinib puts AstraZeneca plc (NYSE:AZN) (LON:AZN) behind its competitor Pfizer Inc. (NYSE:PFE), which has also developed a pill to treat rheumatoid arthritis.

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Reuters reports that this latest trial of fostamatinib set two goals for the drug, and it only met one of them. The drug reportedly showed a significant improvement in participants’ ACR20 response rate, which is a test used to assess RA. However, it failed to show improvements in the progression of the disease as shown through joint damage on X-rays.

In addition, patients who took the drug reported diarrhea and higher blood pressure. Those same side effects were noted in previous trials of the drug. In addition, studies comparing fostamatinib to Humira in RA patients found that Humira worked better. High blood pressure is an especially big concern for AstraZeneca plc (NYSE:AZN) (LON:AZN) because it could keep the drug from even being approved by the Food and Drug Administration.

This latest study casts a lot of doubt on the future of the drug. Data from Thomson Reuters indicates very low sales forecasts for the drug. However, Humira has sold over $9 billion all over the world.

Also investors are growing concerned about the low number of new products AstraZeneca plc (NYSE:AZN) (LON:AZN) has in the pipeline in comparison to the large number of patent expirations it has over the next three years.