Aclaris Therapeutics Completes Enrollment in Phase 2 Trial of Bosakitug (ATI-045) in Atopic Dermatitis

Rhea-AI Summary

Aclaris Therapeutics (NASDAQ: ACRS) completed enrollment in a randomized, double-blind, placebo-controlled Phase 2 trial of bosakitug (ATI-045) for moderate-to-severe atopic dermatitis, enrolling 109 patients. Top-line results are expected in the fourth quarter of 2026.

The trial's primary endpoint is percent change from baseline in EASI at week 24; secondary endpoints include EASI-50/75/90, IGA, BSA, and PP-NRS. Safety, PD biomarkers, and PK will be assessed. The company cites a 23-day natural half-life and potential dosing convenience as product attributes.

Positive

• Enrollment complete for Phase 2 with 109 patients
• Top-line results expected in Q4 2026
• Compound reported 23-day natural half-life (potential dosing advantage)

Negative

• Phase 2 results pending; efficacy unproven until Q4 2026
• Primary endpoint measured at 24 weeks, extending time to definitive readout

News Market Reaction – ACRS

-5.67%

2 alerts

-5.67% News Effect

+8.3% Peak Tracked

-$27M Valuation Impact

$441M Market Cap

0.3x Rel. Volume

On the day this news was published, ACRS declined 5.67%, reflecting a notable negative market reaction. Argus tracked a peak move of +8.3% during that session. Our momentum scanner triggered 2 alerts that day, indicating moderate trading interest and price volatility. This price movement removed approximately $27M from the company's valuation, bringing the market cap to $441M at that time.

Data tracked by StockTitan Argus on the day of publication.

Key Figures

Sample size: 109 patients Half-life: 23 days Primary endpoint timepoint: Week 24

3 metrics

Sample size 109 patients Phase 2 bosakitug trial in moderate-to-severe atopic dermatitis

Half-life 23 days Bosakitug natural half-life cited as supporting convenient dosing

Primary endpoint timepoint Week 24 Percent change from baseline in EASI at week 24

Market Reality Check

Price: $3.69 Vol: Volume 1,431,295 is at 0....

low vol

$3.69 Last Close

Volume Volume 1,431,295 is at 0.55x the 20-day average, indicating subdued trading activity ahead of the trial update. low

Technical Shares at $3.88 are trading above the $2.37 200-day MA and about 20.65% below the 52-week high of $4.89.

Peers on Argus

Pre‑news, ACRS was up 3.74% while key biotech peers showed mixed to negative mov...

Pre‑news, ACRS was up 3.74% while key biotech peers showed mixed to negative moves (e.g., SLN down 10.26%, IPHA down 3.6%, TLSA down 2.99%, IMMP down 3.57%, PRQR up 1.14%), suggesting stock‑specific drivers rather than a sector rotation.

Previous Clinical trial Reports

5 past events · Latest: Jan 06 (Positive)

Same Type Pattern 5 events

Date	Event	Sentiment	Move	Catalyst
Jan 06	Phase 1a interim data	Positive	+0.0%	Positive interim Phase 1a ATI‑052 safety and PK/PD data in healthy adults.
Jul 29	Phase 2a top-line data	Positive	-1.3%	Phase 2a ATI‑2138 AD trial met primary endpoint with strong EASI improvement.
Jun 23	Phase 1a/1b start	Positive	-4.1%	Initiation of ATI‑052 Phase 1a/1b program targeting TSLP and IL‑4R.
Jun 02	Bosakitug Phase 2 start	Positive	-1.4%	Start of bosakitug Phase 2 AD trial following strong Phase 2a efficacy signals.
Sep 17	Phase 2a first dosing	Positive	-1.7%	First patient dosed in Phase 2a ATI‑2138 trial for moderate‑to‑severe AD.

Pattern Detected

Clinical trial updates have generally been positive in content but followed by flat to negative one‑day moves, with an average move of -1.7% across recent clinical trial headlines.

Recent Company History

Over the past 18 months, Aclaris has repeatedly advanced its immuno‑inflammatory pipeline through clinical milestones. Prior clinical trial updates for bosakitug, ATI‑052, and ATI‑2138 highlighted strong efficacy, safety, and pharmacodynamic signals, yet near‑term price reactions often hovered around 0% or modestly negative. The current announcement that bosakitug’s Phase 2 trial in atopic dermatitis has fully enrolled builds directly on the June 2025 Phase 2 initiation and earlier Phase 2a efficacy data, reinforcing a steady progression toward a pivotal readout expected in late 2026.

Historical Comparison

-1.7% avg move · Past clinical trial headlines for ACRS averaged a -1.7% one‑day move, so a pre‑news gain of 3.74% ah...

clinical trial

-1.7%

Average Historical Move clinical trial

Past clinical trial headlines for ACRS averaged a -1.7% one‑day move, so a pre‑news gain of 3.74% ahead of this enrollment milestone looks relatively stronger than usual.

Clinical news shows stepwise advancement: ATI‑052 from Phase 1a start to positive interim data and on to Phase 1b, ATI‑2138 from first dosing in Phase 2a to positive top‑line results, and bosakitug from Phase 2 initiation in atopic dermatitis to full Phase 2 enrollment with a defined late‑2026 readout timeline.

Market Pulse Summary

The stock moved -5.7% in the session following this news. A negative reaction despite a clinical mil...

Analysis

The stock moved -5.7% in the session following this news. A negative reaction despite a clinical milestone would fit a pattern where Aclaris’ generally positive trial updates previously coincided with average one‑day moves of -1.7%. Completion of enrollment fixes the path to a late‑2026 readout but does not change the inherent trial risk or the company’s loss‑making profile. Weakness could also reflect concerns about future capital needs and typical biotech event‑risk repricing ahead of data.

Key Terms

tslp, eczema area and severity index (easi), validated investigator global assessment (iga), body surface area (bsa), +4 more

8 terms

tslp medical

"the potential role of TSLP as a therapeutic target in this setting"

TSLP (thymic stromal lymphopoietin) is an immune-system signaling protein that acts like an alarm, triggering inflammation in conditions such as asthma and allergic disease. Investors watch TSLP because drugs that block its action can reduce symptoms and prevent flares; successful clinical trials or approvals for TSLP-targeting therapies can materially change a biotech company's prospects, market value, and potential market size for respiratory and allergic treatments.

eczema area and severity index (easi) medical

"The primary efficacy endpoint is percent change from baseline in Eczema Area and Severity Index (EASI)"

A standardized clinical score that combines how much skin is affected and how severe the symptoms are to produce a single number measuring eczema severity — like a single thermometer reading that sums up a patient's condition. Investors watch EASI because it is often used as a key trial result showing whether a treatment works; larger, consistent improvements can drive regulatory approval, prescribing uptake and a drug’s commercial value.

validated investigator global assessment (iga) medical

"Secondary endpoints at week 24 include EASI response ... validated Investigator Global Assessment (IGA) response"

A validated Investigator Global Assessment (IGA) is a standardized, clinician-rated scale used in medical trials to judge the overall severity or improvement of a skin condition at a glance. It matters to investors because it acts like a consistent movie-rating system for patient outcomes: a clear, comparable measure that regulators and payers use to judge whether a treatment works, influencing trial success, approval odds, and commercial value.

body surface area (bsa) medical

"Secondary endpoints at week 24 include ... body surface area (BSA) response"

Body surface area (BSA) is a calculated estimate of the total external surface of a person’s body, typically expressed in square meters and derived from height and weight. It matters to investors because clinicians use BSA to determine drug doses, medical device sizes and who qualifies for clinical trials—like a tailor’s measurements ensuring a proper fit—which can influence safety, trial outcomes, regulatory approval and the commercial market for therapies and devices.

peak pruritus numerical rating scale (pp-nrs) medical

"and Peak Pruritus Numerical Rating Scale (PP-NRS) score, relative to baseline"

A patient-reported scale that asks people to rate the worst level of itching they experienced over a set period, usually on a 0–10 scale where higher numbers mean more severe itch. Like a thermometer for itch, it gives a simple, comparable number researchers and regulators use to judge whether a treatment actually reduces symptoms; investors watch changes in this score because it can determine trial success, labeling claims and commercial appeal.

pharmacodynamic (pd) biomarkers medical

"Safety, tolerability, pharmacodynamic (PD) biomarkers, and pharmacokinetic profile (PK)"

Pharmacodynamic (PD) biomarkers are measurable signs in the body that show whether a drug is interacting with its intended target or producing the expected biological effect. They matter to investors because they provide early, objective evidence a therapy is working or engaging its mechanism—like a dashboard light showing a car’s engine response—which can reduce development risk, guide go/no‑go decisions, and affect the likelihood and timing of value inflection points.

pharmacokinetic profile (pk) medical

"pharmacodynamic (PD) biomarkers, and pharmacokinetic profile (PK) will also be assessed"

Pharmacokinetic profile (PK) describes how a drug moves through the body over time — how quickly it is absorbed, how it spreads to tissues, how the body breaks it down, and how it is cleared. Investors care because PK shapes dosing rules, safety, drug interactions and real-world effectiveness; like knowing how long a cup of coffee keeps you alert, PK predicts how a medicine performs for patients and how viable it is as a product.

placebo-controlled medical

"completed patient enrollment in its randomized, double-blind, placebo-controlled Phase 2 trial"

"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.

AI-generated analysis. Not financial advice.

- Top Line Results Expected in the Fourth Quarter of 2026 -

WAYNE, Pa., March 18, 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 completed patient enrollment in its randomized, double-blind, placebo-controlled Phase 2 trial of bosakitug (ATI-045) in patients with moderate-to-severe atopic dermatitis (AD). Top line results are expected in the fourth quarter of 2026.

“The strong interest in participating in this Phase 2 trial reflects the urgent need for innovative solutions in atopic dermatitis and the excitement surrounding bosakitug and the potential role of TSLP as a therapeutic target in this setting,” said Dr. Jesse Hall, Chief Medical Officer of Aclaris. “Given the compound’s potential best-in-class potency and long natural half-life of 23 days, bosakitug has the potential to maximize TSLP inhibition in the skin while providing convenient dosing. We are proud to achieve this important milestone, and grateful to the participating physicians and patients for choosing to join our trial.”

This randomized, double-blind, placebo-controlled Phase 2 trial will evaluate the efficacy and safety of bosakitug in 109 patients with moderate-to-severe atopic dermatitis. The primary efficacy endpoint is percent change from baseline in Eczema Area and Severity Index (EASI) at week 24. Secondary endpoints at week 24 include EASI response (EASI-50, EASI-75, EASI-90), validated Investigator Global Assessment (IGA) response, body surface area (BSA) response, and Peak Pruritus Numerical Rating Scale (PP-NRS) score, relative to baseline. Safety, tolerability, pharmacodynamic (PD) biomarkers, and pharmacokinetic profile (PK) will also be assessed.

About Bosakitug (ATI-045)

Bosakitug is an investigational humanized anti-thymic stromal lymphopoietin (TSLP) monoclonal antibody that specifically binds to human TSLP, blocking its interaction with the receptor complex and disrupting signal transduction. This mechanism prevents immune cells targeted by TSLP from releasing proinflammatory cytokines. Bosakitug has potential best-in-class properties, including a very high affinity to TSLP, very high potency, an extremely low dissociation rate from TSLP leading to long residence time and enhanced neutralization activity, and a half-life that can potentially support an extended dosing interval. In a single arm Phase 2a trial in patients with moderate-to-severe AD, bosakitug demonstrated a strong safety profile and improvements in efficacy measures at week 26 (end of study) including EASI-75 scores in 94% of participants that were sustained beyond the last dose and clear or nearly clear skin in 88% of participants as measured by IGA scores of 0/1. Bosakitug has the potential to treat a variety of atopic, immunologic, and respiratory diseases. Aclaris has the exclusive worldwide rights to bosakitug, excluding Greater China.

About Thymic Stromal Lymphopoietin (TSLP)

TSLP is an alarmin - a cytokine that is a master regulator of Type 2 (Th2) immune response at the barrier surfaces of skin and the respiratory/gastrointestinal tract in major allergic and inflammatory diseases - that has been validated as a relevant therapeutic target. TSLP drives eosinophilic and neutrophilic inflammation and acts on a wide variety of adaptive, innate, and structural cells, and is involved in induction phase and effector phase as well as non-Th2 processes. Since TSLP sits at the top of the inflammatory cascade, it activates downstream targets such as IL-4, IL-5, IL-13, IL-17, and other molecules elaborated from T cells like CCL17. The expression of TSLP is elevated in individuals with respiratory and skin diseases.

About Atopic Dermatitis

Atopic dermatitis (AD) is the most common type of eczema, affecting approximately 10 million children and 17 million adults in the United States. Worldwide prevalence estimates that AD affects over 200 million people worldwide. It is estimated that 1 in 10 individuals will develop eczema during their lifetime. Common symptoms include dry, cracked, itchy patches of skin or small raised bumps, that can occur anywhere on the body. The affected skin can become inflamed, warm, thickened, and damaged with prolonged scratching. A study by Asthma and Allergy Foundation of America noted that about 40% of those affected with the disease have moderate or severe symptoms. AD can significantly affect a patient’s quality of life, with patients with moderate-to-severe AD having a higher prevalence of social dysfunction and sleep impairment.

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 bosakitug (ATI-045), including the timing to report results from its Phase 2 trial of bosakitug in atopic dermatitis, the potential for bosakitug to optimize TSLP inhibition in the skin at low therapeutic doses while providing convenient dosing, the potential for bosakitug to be a best-in-class anti-TSLP monoclonal antibody, and the therapeutic potential for bosakitug including in a variety of 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, 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, 2025, 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 did ACRS announce about bosakitug (ATI-045) enrollment on March 18, 2026?

Aclaris announced completion of enrollment in the Phase 2 bosakitug trial, with 109 patients enrolled. According to the company, the study is randomized, double-blind, placebo-controlled and will assess efficacy and safety through week 24.

When will ACRS report top-line results for the bosakitug Phase 2 trial?

Top-line results are expected in the fourth quarter of 2026. According to the company, the readout will cover primary and secondary endpoints at week 24, plus safety, PD biomarkers, and PK data.

What is the primary endpoint of ACRS's bosakitug (ATI-045) Phase 2 study?

The primary endpoint is percent change from baseline in EASI at week 24. According to the company, secondary measures include EASI-50/75/90, IGA response, BSA response, and PP-NRS score at week 24.

How many patients are enrolled in ACRS's bosakitug Phase 2 atopic dermatitis trial?

The trial enrolled 109 patients with moderate-to-severe atopic dermatitis. According to the company, the randomized, double-blind design will compare bosakitug versus placebo over a 24-week efficacy period.

What dosing or pharmacokinetic feature did ACRS highlight for bosakitug (ATI-045)?

Aclaris highlighted a reported 23-day natural half-life for bosakitug, suggesting dosing convenience. According to the company, this half-life could support sustained TSLP inhibition in the skin if clinical efficacy is confirmed.