Aclaris Therapeutics has announced topline results from its Phase IIb trial in zunsemetinib. Image credit: Pavel Kapysh / Aclaris.

Aclaris Therapeutics’s stocks have plummeted after the company announced it will discontinue the development of zunsemetinib after a Phase IIb trial in rheumatoid arthritis (RA) failed to meet its primary and secondary endpoints.

The clinical-stage biopharmaceutical company announced topline results of its Phase IIb study (NCT05279417) of zunsemetinib (ATI-450), an investigational oral MK2 inhibitor, in patients with moderate to severe RA on 13 November.

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The candidate failed to show any notable efficacy difference compared to placebo at week 12, leading Aclaris to discontinue the development of the candidate. This includes discontinuing enrolment of Aclaris’ ongoing Phase IIa trial investigating zunsemetinib in psoriatic arthritis.

The company’s stock price dropped from Friday’s closing price of $4.75 to $0.69 following the announcement.

CEO Dr Doug Manion said: “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.”

Phase IIb study

The randomised, double-blind, placebo-controlled study was investigating the drug’s efficacy, safety, tolerability, pharmacokinetics and pharmacodynamics. The study enrolled 251 patients across three treatment arms of 20mg and 50mg doses of zunsemetinib or placebo. The trial opened approximately 40 sites in the US, Poland, Bulgaria and the Czech Republic.

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The primary efficacy endpoint was the American College of Rheumatology (ACR) 20 response after 12 weeks of treatment. Secondary efficacy endpoints included the ACR50 and ACR70 responses, as well as Disease Activity Score-28 for Rheumatoid Arthritis with CRP (DAS28-CRP) and other RA measures.

Investigators reported that there was no notable differentiation between zunsemetinib and placebo across any measures of efficacy at week 12. No meaningful safety findings were observed.   

Other pipeline candidates

According to GlobalData’s Pharmaceutical Intelligence Centre, Aclaris has registered 44 clinical trials, comprising 33 completed, three ongoing, three withdrawn, three terminated and two planned trials. GlobalData is the parent company of Clinical Trials Arena.

In June 2021, Aclaris announced positive results from its Phase IIa trial of ATI-1777 in patients with moderate to severe atopic dermatitis.

Despite the setback, the company is continuing the development of two candidates, ATI-2138 in patients with T cell-mediated diseases and ATI-2231 as a potential treatment for pancreatic cancer and metastatic breast cancer, as well as in preventing bone loss in patients with metastatic breast cancer. However, ATI-2231 is being discontinued as a potential treatment for immuno-inflammatory diseases.