Aclaris Therapeutics, Inc. 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. Additional Pipeline Updates: ATI-1777 (Topical ?Soft?

JAK1/3 Inhibitor): In June 2021, Aclaris announced positive results from its Phase 2a trial in patients with moderate to severe atopic dermatitis. ATI-1777 was designed to provide maximal activity against skin lesions whilst minimizing potential toxicities related to systemic exposure. Around the end of the year, Aclaris expects to provide the results of its 250 patient, 6-arm, Phase 2b study in patients with mild, moderate or severe atopic dermatitis, including adults and children as young as 12 years old, across approximately 30 clinical trial sites in the United States.

ATI-2138 (Oral Covalent ITK/JAK3 Inhibitor): Aclaris recently reported results of a multiple ascending dose study of ATI-2138 in healthy volunteers showing promising pharmacokinetic and pharmacodynamic properties that could positively impact T cell-mediated diseases. Aclaris anticipates beginning the Phase 2 program in early 2024 with ulcerative colitis as the initial indication, with other indications under consideration. ATI-2231 (Oral MK2 Inhibitor): ATI-2231 is a potential treatment for pancreatic cancer and metastatic breast cancer as well as in preventing bone loss in patients with metastatic breast cancer.

Aclaris is supporting Washington University in a first-in-human investigator-initiated Phase 1a trial of ATI-2231 in patients with advanced solid tumor malignancies. Aclaris is discontinuing its current efforts on ATI-2231 as a potential treatment for immuno-inflammatory diseases. Confluence Discovery Technologies and KINect® Platform: Aclaris?

world class discovery team continues to innovate by targeting the human kinome to address areas of high unmet medical need. Cash Position: As of September 30, 2023, Aclaris had aggregate cash, cash equivalents and marketable securities of $187.0 million.