Aclaris Therapeutics Initiates Phase 1b Proof-of-Concept Trial in Patients with Asthma with its Novel Bispecific Anti-TSLP/IL-4Rα Antibody ATI-052

Rhea-AI Summary

Aclaris Therapeutics (NASDAQ: ACRS) has initiated a randomized, double-blind, placebo-controlled Phase 1b proof-of-concept trial of its bispecific anti-TSLP/IL-4Rα antibody ATI-052 in asthma, following a Phase 1b start in atopic dermatitis.

The ~16-patient study (3:1 randomization) will assess safety, tolerability, PK, PD biomarkers including FeNO and blood eosinophils, and FEV1. Top-line results for both POC trials are expected in the second half of 2026, with a Phase 2b program planned for H2 2026.

Positive

• Positive Phase 1a interim safety and tolerability results
• Concentration-dependent pharmacodynamics observed at lowest dose
• Top-line results from both POC trials expected in H2 2026

Negative

• Phase 1b asthma trial is small (~16 patients), limiting statistical power
• Phase 2b program is planned but not yet initiated (timing H2 2026)

Key Figures

Phase: Phase 1b Randomization ratio: 3:1 Planned enrollment: 16 patients +2 more

5 metrics

Phase Phase 1b Proof-of-concept trial of ATI-052 in asthma

Randomization ratio 3:1 ATI-052 vs placebo in Phase 1b asthma trial

Planned enrollment 16 patients Asthma Phase 1b POC trial sample size

GINA treatment steps Steps 2–4 Baseline asthma therapy level before screening

Program timing Second half of 2026 Expected topline POC results and Phase 2b start

Market Reality Check

Price: $3.25 Vol: Volume 1,702,066 is 1.45x...

normal vol

$3.25 Last Close

Volume Volume 1,702,066 is 1.45x the 20-day average of 1,174,655, indicating elevated interest ahead of ATI-052 asthma data. normal

Technical Shares at $3.25 are trading above the 200-day MA of $2.21, and about one-third below the $4.89 52-week high.

Peers on Argus

ACRS gained 0.31% with mixed peer moves: IPHA +2.47%, IMMP +3.23%, SLN +0.60%, w...

ACRS gained 0.31% with mixed peer moves: IPHA +2.47%, IMMP +3.23%, SLN +0.60%, while TLSA fell 2.34% and PRQR was flat. This pattern points to stock-specific interest around ATI-052 rather than a broad biotech rotation.

Historical Context

5 past events · Latest: Feb 04 (Neutral)

Pattern 5 events

Date	Event	Sentiment	Move	Catalyst
Feb 04	Conference participation	Neutral	+2.0%	Announcement of senior management presentations at two February 2026 healthcare conferences.
Jan 27	Preclinical data	Positive	+1.3%	ATI-2138 showed rapid, near-complete hair regrowth versus control and ritlecitinib in murine model.
Jan 12	Trial initiation	Positive	+0.8%	Initiation of Phase 1b POC trial of ATI-052 in atopic dermatitis with supportive Phase 1a safety data.
Jan 06	Interim trial results	Positive	+0.0%	Positive Phase 1a ATI-052 data showing favorable safety, ≥26-day half-life, and robust pathway inhibition.
Dec 19	Index inclusion	Positive	-2.2%	Addition to the Nasdaq Biotechnology Index effective Dec 19, 2025 under index eligibility criteria.

Pattern Detected

Recent clinically focused announcements have generally led to modest positive moves, though major index inclusion and some positive trial readouts have seen flat or negative reactions.

Recent Company History

Over the past few months, Aclaris has steadily advanced its pipeline and visibility. Positive interim Phase 1a data for ATI-052 on Jan 6, 2026 and subsequent initiation of Phase 1b POC in atopic dermatitis on Jan 12, 2026 set up today’s asthma POC start as the next logical step. Additional catalysts included ATI-2138 preclinical alopecia data on Jan 27, 2026, conference participation news on Feb 4, 2026, and addition to the Nasdaq Biotechnology Index in Dec 2025.

Market Pulse Summary

This announcement advances ATI-052, a bispecific anti-TSLP/IL-4Rα antibody, into a Phase 1b proof-of...

Analysis

This announcement advances ATI-052, a bispecific anti-TSLP/IL-4Rα antibody, into a Phase 1b proof-of-concept asthma trial with about 16 patients, complementing an ongoing atopic dermatitis study. It builds directly on previously reported positive Phase 1a safety and pharmacodynamic data. Investors may track upcoming topline results, planned Phase 2b programs in the second half of 2026, and how these milestones fit alongside other pipeline assets like ATI-2138.

Key Terms

bispecific, placebo-controlled, double-blind, pharmacokinetics, +3 more

7 terms

bispecific medical

"potential best-in-class investigational bispecific anti-TSLP/IL-4Rα antibody"

A bispecific molecule is a therapeutic designed to bind two different biological targets at once — imagine a two-headed key that fits two locks simultaneously. For investors, bispecific therapies matter because that dual-action can make a treatment more effective or selective, potentially improving clinical results, altering safety profiles, and creating a stronger commercial edge; those factors directly affect development risk, regulatory chances, and future revenue prospects.

placebo-controlled medical

"initiated a placebo-controlled Phase 1b proof-of-concept (POC) trial of ATI-052"

"Placebo-controlled" describes a testing method where one group receives the actual treatment or intervention, while another group receives a harmless, inactive version called a placebo. This approach helps determine whether the real treatment has genuine effects beyond psychological expectations. For investors, understanding this ensures confidence that reported benefits are real and not influenced by bias or false perceptions.

double-blind medical

"The randomized (3:1), double-blind, placebo-controlled Phase 1b POC trial"

A double-blind process means that neither the people conducting an activity nor the people involved know certain key details, such as who is receiving a treatment or a placebo. This approach helps prevent bias from influencing the results, making the outcome more trustworthy. For investors, it ensures that decisions or judgments are based on unbiased information rather than preconceived opinions or expectations.

pharmacokinetics medical

"demonstrated a strong safety and tolerability profile, extended pharmacokinetics"

Pharmacokinetics is the study of how a substance, such as a drug or chemical, moves through and is processed by the body over time. It tracks how it is absorbed, distributed, broken down, and eventually eliminated. For investors, understanding pharmacokinetics helps gauge the effectiveness, safety, and potential risks of new medications or treatments, which can influence a company’s success and valuation in the healthcare industry.

pharmacodynamics medical

"concentration-dependent pharmacodynamics even at the lowest dose"

Pharmacodynamics is how a drug actually affects the body — the strength, type and duration of its effects and the relationship between dose and response. Think of it like how turning a thermostat changes room temperature: it shows what the drug does and how much is needed to get the desired effect. Investors care because these properties drive clinical success, dosing convenience, safety profile and competitive advantage, all of which influence commercial potential and regulatory approval.

feno medical

"PD biomarker assessments including FeNO (fractional exhaled nitric oxide)"

FeNO (fractional exhaled nitric oxide) is a breath test that measures the level of nitric oxide gas produced in the lungs, used as a sign of airway inflammation often linked to asthma. It matters to investors because FeNO levels are used in clinical decisions, regulatory studies and to gauge the effectiveness of respiratory drugs and diagnostic devices, so changes in FeNO-related data or approvals can affect sales, trial outcomes and market value—like a fever reading for lung inflammation.

fev1 medical

"and efficacy measures including FEV1"

FEV1 stands for forced expiratory volume in one second, a medical measurement of how much air a person can forcibly exhale in one second during a breathing test. Think of it like timing how quickly someone can blow out a candle — it gives a clear snapshot of lung strength and airflow. Investors watch FEV1 because changes in this measure are used to judge whether respiratory drugs or devices work, which affects regulatory approval, market potential, and sales forecasts.

AI-generated analysis. Not financial advice.

WAYNE, Pa., Feb. 24, 2026 (GLOBE NEWSWIRE) -- Aclaris Therapeutics, Inc. (NASDAQ: ACRS), a clinical-stage biopharmaceutical company focused on developing novel product candidates for immuno-inflammatory diseases, today announced that it has initiated a placebo-controlled Phase 1b proof-of-concept (POC) trial of ATI-052, the Company’s potential best-in-class investigational bispecific anti-TSLP/IL-4Rα antibody, in asthma. This announcement follows the recent initiation of the Company’s Phase 1b POC trial of ATI-052 in atopic dermatitis (AD). Planning is ongoing for a Phase 2b program encompassing asthma and atopic dermatitis as potential first indications. The Company expects to initiate this program in the second half of 2026.

“The start of 2026 has been a period of strong execution and momentum across our clinical programs, broadly, and with ATI-052 specifically,” said Dr. Jesse Hall, Chief Medical Officer of Aclaris. “The positive Phase 1a interim results for ATI-052 exceeded our expectations and demonstrated a strong safety and tolerability profile, extended pharmacokinetics, and concentration-dependent pharmacodynamics even at the lowest dose. Following the January announcement that we had initiated our POC trial in atopic dermatitis, we have now initiated our POC trial in asthma. We expect to provide top line results from both trials in the second half of 2026 and start the Phase 2b program shortly thereafter.”

The randomized (3:1), double-blind, placebo-controlled Phase 1b POC trial will evaluate the safety, tolerability, and efficacy of ATI-052 compared to placebo in approximately 16 patients with asthma on GINA (Global Initiative for Asthma) steps 2-4 treatment prior to screening. Endpoints that will be assessed include safety and tolerability parameters; pharmacokinetic parameters; respiratory pharmacodynamic (PD) biomarker assessments including FeNO (fractional exhaled nitric oxide); blood PD biomarker assessments including blood eosinophil count and endogenous cytokines/chemokines and inflammation markers in plasma/serum; and efficacy measures including FEV1.

Top line results from this trial and the ongoing Phase 1b POC trial in AD are expected in the second half of 2026.

About ATI-052

ATI-052 is an investigational humanized anti-TSLP and anti-IL-4Rα bispecific antibody that simultaneously inhibits thymic stromal lymphopoietin (TSLP) and interleukin-4 receptor (IL-4Rα) with high affinity and potency. By targeting TSLP, which sits at the top of the inflammatory cascade, it inhibits a broad range of inflammation; by targeting IL-4Rα, it blocks downstream signaling of both IL-4 and IL-13, which are key cytokines involved in Th2-mediated inflammation and allergic diseases. ATI-052 exhibits potential best-in-class potency and utilizes the same TSLP antigen-binding fragment (Fab) region as the Company’s monoclonal antibody bosakitug (ATI-045), retaining the dissociation kinetics, long residence time, and high potency advantages over comparator antibodies, but is engineered to bind more tightly to the neonatal Fc receptor (FcRn) to extend its half-life. ATI-052 has the potential to treat a variety of atopic, immunologic and respiratory diseases. Aclaris has the exclusive worldwide rights to ATI-052, excluding Greater China.

About Aclaris Therapeutics, Inc.

Aclaris Therapeutics, Inc. is a clinical-stage biopharmaceutical company developing a pipeline of novel product candidates to address the needs of patients with immuno-inflammatory diseases who lack satisfactory treatment options. The company has a multi-stage portfolio of product candidates powered by a robust R&D engine. For additional information, please visit www.aclaristx.com and follow Aclaris on LinkedIn.
        
Cautionary Note Regarding Forward-Looking Statements

Any statements contained in this press release that do not describe historical facts may constitute forward-looking statements as that term is defined in the Private Securities Litigation Reform Act of 1995. These statements may be identified by words such as “anticipate,” “believe,” “expect,” “intend,” “may,” “plan,” “potential,” “will,” and similar expressions, and are based on Aclaris’ current beliefs and expectations. These forward-looking statements include expectations regarding its development plans for ATI-052, including the timing to report results from its Phase 1b trials of ATI-052 in AD and asthma, the timing to initiate a Phase 2b program including asthma and AD, the potential for ATI-052 to be a best-in-class anti-TSLP/IL-4Rα bispecific monoclonal antibody, and the therapeutic potential for ATI-052 including in other atopic, immunologic and respiratory diseases. These statements involve risks and uncertainties that could cause actual results to differ materially from those reflected in such statements. Risks and uncertainties that may cause actual results to differ materially include uncertainties inherent in the conduct of clinical trials, potential changes to interim, topline and preliminary data as more subject data become available, Aclaris’ reliance on third parties over which it may not always have full control, Aclaris’ ability to enter into strategic partnerships on commercially reasonable terms, the uncertainty regarding the macroeconomic environment and other risks and uncertainties that are described in the Risk Factors section of Aclaris’ Annual Report on Form 10-K for the year ended December 31, 2024, and other filings Aclaris makes with the U.S. Securities and Exchange Commission from time to time. These documents are available under the “SEC Filings” page of the “Investors” section of Aclaris’ website at www.aclaristx.com. Any forward-looking statements speak only as of the date of this press release and are based on information available to Aclaris as of the date of this release, and Aclaris assumes no obligation to, and does not intend to, update any forward-looking statements, whether as a result of new information, future events or otherwise.

Aclaris Therapeutics Contact:

Will Roberts
Senior Vice President
Corporate Communications and Investor Relations
(484) 329-2125
wroberts@aclaristx.com

FAQ

What is Aclaris (ACRS) announcing about ATI-052 in asthma on February 24, 2026?

Aclaris has initiated a randomized, double-blind Phase 1b POC trial of ATI-052 in asthma. According to the company, the trial will enroll about 16 patients (3:1 randomization) and assess safety, PK, PD biomarkers and FEV1, with top-line results due in H2 2026.

What endpoints will the ACRS Phase 1b ATI-052 asthma trial measure?

The trial will measure safety, tolerability, pharmacokinetics, PD biomarkers, and efficacy endpoints like FEV1. According to the company, PD assessments include FeNO, blood eosinophil count, endogenous cytokines/chemokines, and inflammation markers in plasma/serum.

When does Aclaris expect results and next steps for ATI-052 (ACRS)?

Aclaris expects top-line results from the ATI-052 POC trials in the second half of 2026. According to the company, a Phase 2b program covering asthma and atopic dermatitis is planned to start in the second half of 2026 shortly after top-line readouts.

What did Aclaris report about ATI-052 Phase 1a interim data for investors?

The company reported that Phase 1a interim results showed strong safety, tolerability, extended PK, and dose-dependent PD signals. According to the company, those findings exceeded expectations and supported advancing ATI-052 into Phase 1b POC trials in asthma and atopic dermatitis.

How large is the ACRS Phase 1b asthma study and which patients qualify?

The Phase 1b POC trial will include approximately 16 patients randomized 3:1 to ATI-052 or placebo. According to the company, eligible participants are asthma patients treated at GINA steps 2-4 prior to screening.