"These results validate that ATI-052 is a highly potent and well tolerated bispecific antibody that has the potential to be highly effective in a variety of inflammatory and immunological disorders," said Dr. Neal Walker, Chief Executive Officer of Aclaris. "Based on the strong safety and tolerability profile and dose proportional pharmacokinetic and pharmacodynamic profiles that support the potential for an extended dosing schedule of up to every three months and the potential for synergistic efficacy resulting from its dual inhibition of TSLP and IL-4Rα, we are rapidly progressing this molecule through two proof-of-concept studies and plan to initiate a Phase 2b program in the fourth quarter of 2026."

Continued Dr. Walker, "We also intend to initiate a phased multi-part Phase 2b basket study in lichen planus with ATI-2138 later this year. ATI-2138 is the only known drug that hits pathogenic T cells, the key drivers of interface dermatitis disorders like LP, by inhibiting both TCR and effector cytokine mediated activation - and as such we believe it is an ideal mechanistic fit for this indication. LP causes debilitating symptoms and significant impacts to quality of life across the spectrum of subtypes; there are no therapeutic options approved for use in this disease. We expect our Phase 2b program to initially focus on erosive mucosal and cutaneous LP, starting in the second half of this year, and move into lichen planopilaris shortly thereafter."

ATI-052: Anti-TSLP/IL-4Rα Bispecific Antibody

Full Top Line Phase 1a SAD/MAD Results

ATI-052 is an investigational anti-TSLP and anti-IL-4Rα bispecific antibody that exhibits high binding affinity to, and dual blockade of, both the TSLP receptor signal transduction and downstream IL-4Rα activation thereby inhibiting this central proinflammatory pathway. By addressing the shared receptor IL-4Rα, ATI-052 blocks IL-4 and IL-13 biological activity, key cytokines driving Th2 inflammation. The Company provided interim results in January 2026 (press release here). Today's update provides full top line results including:

  • ATI-052 exhibited a potential best-in-class pharmacokinetic (PK) profile, including an estimated half-life of approximately 45 days1. Dose proportional PK was observed across the pharmacologic dose range, including dose proportional increases in Cmax (maximum peak concentration) and AUC (area under the curve; a measure representing total systemic exposure).
  • Pharmacodynamic (PD) results validate the potency of ATI-052, including robust target engagement and near complete target occupancy. ATI-052 demonstrated complete and sustained inhibition through at least week 20 (four months post last dose) of ex vivo TSLP stimulated CCL17/TARC and at least week 12 (two months post last dose) of ex vivo IL-4 stimulated CCL17/TARC in the 480 mg MAD cohort.
  • The combination of the strong and sustained PK duration and PD effect supports the potential for up to every three-month dosing.
  • No impact of anti-drug antibodies (ADA) on PK or PD has been observed in this trial.
  • ATI-052 was well tolerated and demonstrated a favorable safety profile across all SAD and MAD cohorts, consistent with the interim results; no safety signals including conjunctivitis were observed.

Phase 1a SAD/MAD Trial Design

The randomized, blinded, placebo-controlled Phase 1a portion of the first-in-human study was designed to evaluate the safety, tolerability, PK, and PD of subcutaneously administered ATI-052 in healthy adults receiving SAD and MAD doses. In the SAD portion, four cohorts of 8 healthy volunteers each were randomized 3:1 to receive a single dose of ATI-052 (30, 120, 360, or 720 mg) or placebo. In the MAD portion, two cohorts of 8 healthy volunteers each were randomized 3:1 to receive five doses of two dose levels of ATI-052 (240 or 480 mg) or placebo administered every 7 days. Participants were followed for safety for approximately 16 weeks for the SAD cohorts and 20 weeks for the MAD cohorts.

Ongoing and Future Clinical Trials

In January 2026, Aclaris announced the initiation of a Phase 1b proof-of-concept (POC) trial in patients with atopic dermatitis (EASI >21). In February 2026, the Company initiated a Phase 1b POC trial in patients with asthma on GINA (Global Initiative for Asthma) steps 2-4 treatment prior to screening. Enrollment is ongoing in both trials, and top line results from both are expected in the second half of 2026.

Given the results observed to date and its mechanism of action targeting TSLP as well as effects of IL-4 and IL-13 through blockade of the shared receptor IL-4Rα, the Company announced its intent to initiate a Phase 2b program with ATI-052, initially targeting asthma, in the fourth quarter of 2026.

ATI-2138: Selective ITK/JAK3 Inhibitor

ATI-2138 is a highly potent and selective novel investigational pharmacologic agent that acts as a dual inhibitor of interleukin-2-inducible T cell kinase (ITK) and Janus kinase 3 (JAK3); the dual mechanism enables deep suppression of pathogenic T-cells via inhibition of TCR signaling and effector cytokine activation.

Aclaris intends to initiate a phased multi-part Phase 2b basket study of ATI-2138 in lichen planus (LP), an unaddressed chronic, inflammatory, CD8+/Th1-driven interface dermatitis impacting approximately 0.1% to 1.0% of the population. The trial is expected to comprise the three most common LP subtypes: erosive mucosal, cutaneous, and lichen planopilaris (LPP), a rare form of LP that causes permanent hair loss. The most common symptoms of LP include sores, pain, difficulty eating, severe itch, scales/plaques, hair loss, and fatigue; quality of life is also affected in most patients, including due to anxiety and depression. There is also the potential for malignancy in certain subtypes. Disease management has focused on immunosuppression and symptom control; there are currently no FDA-approved therapies. Despite the lack of therapeutic options, approximately 40% of patients seek treatment. An oral agent like ATI-2138 has the potential to provide rapid symptom and itch relief and address multi-site (cutaneous, oral, and scalp) disease involvement. The Company estimates that the potential market opportunity in the U.S. for an oral therapeutic for LP exceeds $1.0 billion with opportunity up to $4.0 billion. Aclaris expects to initiate Part A (erosive mucosal; cutaneous) of this trial in the second half of 2026 and intends to move into Part B (LPP) soon thereafter.

"Lichen planus remains a challenging, immune-mediated disease with significant patient burden, and there is a clear need for additional therapies that can more effectively address both its symptoms and underlying pathology," said Dr. Johann Gudjonsson, MD, PhD, Arthur C. Curtis Professor of Skin Molecular Immunology, University of Michigan Skin Research Center.