AstraZeneca Rheumatoid Arthritis Drug Fails to Meet Both Primary Endpoints

Andrew Klips  |

AstraZeneca PLC (AZN) said on Friday that top-line results from its OSKIRA-1 Phase III testing fostamitinib for rheumatoid arthritis (RA) hit one endpoint, but failed to show a necessary improvement in modified Total Sharp Score (mTSS).

The study evaluated 923 patients who had demonstrated a poor response previously to methotrexate over six months.

The London-based drug maker had two primary endpoints in the trial of fostamatinib, the first oral spleen tyrosine kinase inhibitor targeting RA. The first was met as the new drug candidate achieved a statistical improvement in ACR20 response rates assessing the signs and symptoms of RA (tenderness and swelling in the joints) in both study arms that received 100 mg twice daily or escalated doses compared to the placebo group.

However, the drug failed to deliver a statistically significant outcome when it came to X-ray outputs, called mTSS, versus the placebo group at 24 weeks in either dosing group.

Hypertension, diarrhea, nausea, headache and a common cold were side effects, as with previous trials, but safety and tolerability were again within parameters.

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“These 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 rheumatoid arthritis,” Briggs W. Morrison, MD, Executive Vice President of Global Medicines Development and Chief Medical Officer.

AstraZeneca, the second biggest drug maker in the U.K., has two other Phase III clinical trials ongoing that are assessing the safety and efficacy of fosamitinib for RA, OSKIRA -2 and OSKIRA-3. OSKIRA-2 also is testing the drug in patients that have been treated with methotrexate. OSKIRA-3 is testing fosamitinib in patients with with inadequate response to TNF-α antagonists. While the data from OSKIRA-1 was not perfect, the company intends to evaluate all of the data cumulatively to characterize the profile of the drug as a new RA therapy.

Results from the other two trials are due later this quarter.

Fosamitinib is trying to make it to market to compete with Abbvie’s (ABBV) Humira and Pfizer’s (PFE) Zejianz. In December, AstraZeneca disclosed that fosamitinib was outperformed by Humira in a Phase IIb trial. Fosamitinib is given in pill form as opposed to the injectable Humira.

Investors are taking the news in stride on Friday with shares of AZN trading ahead by 19 cents at $50.32. Shares have advanced about 25 percent in the past 52 weeks, including a spike of more than 13 percent in the past month.

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