Aclaris Therapeutics Announces Top-line Results from 12-Week Phase 2b Trial of Oral Zunsemetinib (ATI-450) for Moderate to Severe Rheumatoid Arthritis and Provides Corporate Update

— Study Did Not Meet Primary or Secondary Efficacy Endpoints in Rheumatoid Arthritis —

— Efficacy Results Do Not Support Further Development of Zunsemetinib —

— Company to Host Conference Call and Webcast Today at 8:00 AM ET —

WAYNE, Pa., Nov. 13, 2023 (GLOBE NEWSWIRE) -- Aclaris Therapeutics, Inc. (NASDAQ: ACRS), a clinical-stage biopharmaceutical company focused on developing novel drugs for immuno-inflammatory diseases, today announced top-line results from a Phase 2b study of zunsemetinib (ATI-450), an investigational oral MK2 inhibitor, in subjects with moderate to severe rheumatoid arthritis (RA; ATI-450-RA-202).

ATI-450-RA-202 is a Phase 2b, randomized, multicenter, double-blind, placebo-controlled, dose-ranging study to investigate the efficacy, safety, tolerability, pharmacokinetics and pharmacodynamics of two doses of zunsemetinib plus methotrexate (MTX) versus placebo plus MTX in patients with moderate to severe RA who have had an inadequate response to MTX alone. The study enrolled 251 patients across three treatment arms (ATI-450 20mg BID, ATI-450 50mg BID, Placebo BID) at approximately 40 trial sites in the United States, Poland, Bulgaria and Czech Republic. The primary efficacy endpoint is the proportion of patients achieving an ACR20 response following 12 weeks of treatment. Secondary efficacy endpoints included ACR50 response, ACR70 response, DAS28-CRP and other pertinent RA measures.

Results
In the trial, patients administered either the 20mg or 50mg dose did not meet the primary endpoint of ACR20 response or any of the secondary efficacy endpoints at 12 weeks, including ACR50 response, ACR70 response, and DAS28-CRP. There was no notable differentiation between zunsemetinib and placebo across any measures of efficacy at week 12.   No meaningful safety findings were observed.  

Based on the overall program results, Aclaris will discontinue further development of the ATI-450 program, including halting enrollment of Aclaris’ ongoing Phase 2a trial of zunsemetinib in psoriatic arthritis.

“We are deeply disappointed with the results of this trial and for patients suffering from rheumatoid arthritis. We would like to thank the patients and investigators for their participation in the trial, and I am proud of our team for their commitment to its execution,” stated Doug Manion, M.D., Aclaris’ Chief Executive Officer. “Despite this setback, we continue to look forward to the upcoming results of our Phase 2b trial of ATI-1777 in atopic dermatitis and initiating our Phase 2 clinical development program for ATI-2138.”