Aclaris Therapeutics’ Novel ITK/JAK3 Inhibitor ATI-2138 Demonstrates Rapid and Sustained Hair Regrowth in Validated Murine Model of Alopecia Areata (AA)

Rhea-AI Summary

Aclaris Therapeutics (NASDAQ: ACRS) reported preclinical results showing its oral ITK/JAK3 inhibitor ATI-2138 produced rapid, near-complete, and sustained hair regrowth in a validated murine reversal model of alopecia universalis versus control and ritlecitinib.

At 300 ppm in chow, mean hair regrowth was 37% at week 2, 87% at week 4, and 93% at week 6 for ATI-2138 versus 25%, 48%, and 78% respectively for ritlecitinib. ATI-2138 is highly selective for ITK and JAK3 (>1,000-fold versus other JAKs). Aclaris expects to initiate a Phase 2b trial in H1 2026.

Positive

• Mean hair regrowth 37% at week 2 (ATI-2138, 300 ppm)
• Mean hair regrowth 87% at week 4 (ATI-2138, 300 ppm)
• Mean hair regrowth 93% at week 6 (ATI-2138, 300 ppm)
• Outperformed ritlecitinib at matched 300 ppm doses through week 6
• Selectivity >1,000-fold against other JAK isoforms
• Phase 2b trial expected to start in H1 2026

Negative

• Findings are preclinical in a murine model and not clinical proof
• Efficacy measured with drug delivered in chow may not mirror human dosing
• Comparator data limited to ritlecitinib at a single tested dose (300 ppm)

News Market Reaction

+1.31%

20 alerts

+1.31% News Effect

-14.0% Trough in 32 hr 57 min

+$5M Valuation Impact

$419M Market Cap

0.5x Rel. Volume

On the day this news was published, ACRS gained 1.31%, reflecting a mild positive market reaction. Argus tracked a trough of -14.0% from its starting point during tracking. Our momentum scanner triggered 20 alerts that day, indicating elevated trading interest and price volatility. This price movement added approximately $5M to the company's valuation, bringing the market cap to $419M at that time.

Data tracked by StockTitan Argus on the day of publication.

Key Figures

Hair regrowth week 2 ATI-2138: 37% Hair regrowth week 2 ritlecitinib: 25% Hair regrowth week 4 ATI-2138: 87% +5 more

8 metrics

Hair regrowth week 2 ATI-2138 37% Murine alopecia universalis model, 300 ppm ATI-2138

Hair regrowth week 2 ritlecitinib 25% Murine alopecia universalis model, 300 ppm ritlecitinib

Hair regrowth week 4 ATI-2138 87% Murine alopecia universalis model, 300 ppm ATI-2138

Hair regrowth week 4 ritlecitinib 48% Murine alopecia universalis model, 300 ppm ritlecitinib

Hair regrowth week 6 ATI-2138 93% Murine alopecia universalis model, 300 ppm ATI-2138

Hair regrowth week 6 ritlecitinib 78% Murine alopecia universalis model, 300 ppm ritlecitinib

ATI-2138 dose levels 100 ppm and 300 ppm Formulated in chow in murine model

Ritlecitinib dose level 300 ppm Formulated in chow in murine model

Market Reality Check

Price: $3.58 Vol: Volume 2377150 is at 0.78...

normal vol

$3.58 Last Close

Volume Volume 2377150 is at 0.78x the 20-day average of 3040849, indicating no outsized trading spike ahead of this news. normal

Technical Shares at $3.82 were trading above the 200-day MA of $2.00, yet sat 21.88% below the 52-week high and above the 52-week low of $1.05 before this update.

Peers on Argus

ACRS fell 15.11% while several biotech peers also traded lower: IPHA -0.56, IMMP...

ACRS fell 15.11% while several biotech peers also traded lower: IPHA -0.56, IMMP -1.24, PRQR -3.98, SLN -10.98, with TLSA flat. The downside in ACRS exceeded typical peer moves but occurred alongside broader weakness in related biotech names.

Historical Context

5 past events · Latest: Jan 12 (Positive)

Pattern 5 events

Date	Event	Sentiment	Move	Catalyst
Jan 12	Clinical trial start	Positive	+0.8%	Initiation of Phase 1b proof-of-concept trial in atopic dermatitis for ATI-052.
Jan 06	Clinical data update	Positive	+0.0%	Positive interim Phase 1a results for bispecific antibody ATI-052 in healthy adults.
Dec 19	Index inclusion	Positive	-2.2%	Addition of Aclaris Therapeutics to the Nasdaq Biotechnology Index (NBI).
Nov 25	Conference participation	Neutral	-0.7%	Announcement of participation in the Piper Sandler 37th Annual Healthcare Conference.
Nov 06	Earnings and pipeline	Neutral	+0.4%	Q3 2025 financial results with ATI-2138 Phase 2a data and cash of $167.2M.

Pattern Detected

Recent news has generally been positive or neutral, with share price reactions modest and sometimes diverging from upbeat clinical and index-related updates.

Recent Company History

Over the last few months, Aclaris has highlighted clinical and corporate milestones, including positive Phase 2a ATI-2138 data and Q3 2025 results, with cash of $167.2M and a net loss of $14.6M. The company advanced ATI-052 into a Phase 1b proof-of-concept trial for atopic dermatitis and reported favorable Phase 1a safety and pharmacodynamic data. Aclaris was also added to the Nasdaq Biotechnology Index. These updates showed pipeline and balance sheet development, while share reactions were generally modest, making today’s sharp decline on positive preclinical ATI-2138 data stand out.

Market Pulse Summary

This announcement highlights robust preclinical efficacy for ATI-2138, with hair regrowth reaching 8...

Analysis

This announcement highlights robust preclinical efficacy for ATI-2138, with hair regrowth reaching 87% at week 4 and 93% at week 6 in a validated murine alopecia universalis model, outperforming ritlecitinib. It extends earlier ATI-2138 clinical progress cited in prior updates and underscores Aclaris’s focus on immuno-inflammatory diseases. Investors may track the planned Phase 2b trial timing in 1H 2026 and subsequent human data to see how these findings translate clinically.

Key Terms

jak3, th1, th2, th17, +3 more

7 terms

jak3 medical

"ATI-2138 is a potent and selective inhibitor of ITK and JAK3 with dual pharmacology"

JAK3 is an enzyme inside immune cells that helps relay signals from molecules on the cell surface to the cell’s control center, guiding how immune cells grow and respond. Investors care because drugs that block or alter JAK3 can change immune activity and form the basis of therapies for autoimmune diseases, transplant rejection and some cancers; successful JAK3-targeting drugs can create major revenue streams but also carry safety and regulatory risk.

th1 medical

"downregulate Th1, Th2, Th17, TCR (ITK) and fibrosis pathway markers"

Th1 (T helper 1) cells are a type of immune cell that help coordinate the body’s defense against infections by activating other immune cells and promoting inflammation when needed. Think of them as frontline coordinators that tell the immune system to attack certain threats; their activity matters to investors because drugs, vaccines or diagnostics that boost, suppress, or measure Th1 responses can affect clinical outcomes, regulatory approval, market demand and safety profiles.

th2 medical

"downregulate Th1, Th2, Th17, TCR (ITK) and fibrosis pathway markers"

Th2 (T-helper type 2) cells are a subset of immune white blood cells that coordinate antibody-driven responses by releasing chemical signals that tell other immune cells and antibody-producing cells how to react, especially in allergies and certain infections. Investors watch Th2 pathways because many drugs aim to dial these signals up or down to treat asthma, eczema and allergic diseases — think of them as a thermostat companies target to reduce harmful immune overreactions.

th17 medical

"downregulate Th1, Th2, Th17, TCR (ITK) and fibrosis pathway markers"

Th17 are a subtype of white blood cells that help direct the body’s immune response, especially by promoting inflammation to fight infections. For investors, Th17 matters because excessive or misdirected Th17 activity is implicated in autoimmune and inflammatory diseases, making it a common target for drugs, diagnostics and biomarkers; think of them as a faucet that can either help put out a fire or, if stuck open, flood a room and cause damage.

tcr medical

"ATI-2138 is an investigational oral compound that interrupts T cell receptor (TCR) signaling"

TCR stands for T‑cell receptor, a protein on the surface of certain immune cells that recognizes pieces of disease or abnormal cells like a lock recognizing a specific key. Investors see it as a target for therapies that reprogram a patient’s immune cells to hunt cancer or infected cells, so advances or setbacks in TCR-based treatments can strongly affect clinical prospects, regulatory risk and company valuation.

alopecia universalis medical

"assessed using a reversal model of murine alopecia universalis, the most severe AA phenotype"

Alopecia universalis is an autoimmune condition that causes complete loss of hair on the scalp and body because the immune system mistakenly attacks hair follicles. Investors track it because successful treatments, clinical trial progress, or regulatory approvals can create or change market opportunities for drugmakers and medical device companies, similar to how a breakthrough product can open a new customer base and revenue stream in other industries.

cytokines medical

"inhibiting ITK and JAK3 signaling of IL-2 receptor common gamma chain (IL-2Rγc) cytokines"

Small proteins produced by immune and other cells that act as on/off signals or “text messages,” telling cells to ramp up, calm down, grow, or move during infection, injury, or disease. Investors watch cytokines because they are common drug targets and biomarkers—changes in cytokine activity can make a therapy work, cause serious side effects, or determine clinical trial and regulatory outcomes, all of which affect a company’s value.

AI-generated analysis. Not financial advice.

- ATI-2138 Outperforms Ritlecitinib in Reversal Model of Alopecia Universalis, the Most Severe AA Phenotype -

WAYNE, Pa., Jan. 27, 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 recent positive preclinical results from its potent and selective ITK/JAK3 inhibitor ATI-2138 in a murine model of severe alopecia areata (AA). In this model of hair loss, conducted by Dr. Angela Christiano at Columbia University, ATI-2138 demonstrated rapid, near complete, and sustained hair regrowth compared to control and ritlecitinib.

“ATI-2138 is a potent and selective inhibitor of ITK and JAK3 with dual pharmacology that has been demonstrated to downregulate Th1, Th2, Th17, TCR (ITK) and fibrosis pathway markers, and reduce itch; this makes it an excellent mechanistic fit in a variety of I&I diseases, including across the spectrum of inflammatory alopecias​,” said Dr. Roland Kolbeck, Chief Scientific Officer of Aclaris. “The mice used in this model of severe alopecia areata were significantly older and more difficult to treat than those typically studied; despite that, ATI-2138 induced an accelerated response and near complete regrowth after only four weeks that was sustained through the end of study, and outperformed ritlecitinib.”

Continued Dr. Kolbeck, “The murine model of alopecia areata has been well-validated and is highly predictive of clinical responses in human trials of JAK inhibitors, including ritlecitinib. The rapid onset of hair regrowth in mice treated with ATI-2138 is compelling, since this drug is differentiated from other JAK inhibitors due to its dual targeting of ITK as well as JAK3.”

ATI-2138 is an investigational oral compound that interrupts T cell receptor (TCR) signaling by inhibiting ITK and JAK3 signaling of IL-2 receptor common gamma chain (IL-2Rγ_c) cytokines in lymphocytes (including IL-2, IL-4, and IL-15), thus regulating T cell expansion, differentiation and activation upstream (ITK) and downstream (JAK3). It is highly potent for both ITK and JAK3, and more than 1,000-fold selective against other JAK isoforms. This unique pharmacology may provide a highly potent and complete anti-inflammatory response. ATI-2138 has the potential to treat a variety of inflammatory, atopic, and autoimmune diseases, including alopecias (hair loss).

ATI-2138 and ritlecitinib were assessed using a reversal model of murine alopecia universalis, the most severe AA phenotype. Mice were randomized to control or drug formulated in chow (100 or 300 ppm ATI-2138; 300 ppm ritlecitinib) after hair loss was established. Hair regrowth was assessed at baseline and weeks 2, 4, and 6.

• Rapid onset of hair regrowth was observed at week 2 in mice receiving 300 ppm ATI-2138 (mean percent hair regrowth of 37%) and reached near peak effect at week 4 (mean percent hair regrowth of 87%) compared to 300 ppm ritlecitinib (25% and 48%, respectively). Mice receiving control chow showed no improvement in hair regrowth.
• At week 6, the mean percent hair regrowth was 93% for ATI-2138 (300 ppm) compared to 78% for ritlecitinib (300 ppm). Mice receiving control chow showed no improvement in hair regrowth.

Given the uniquely potent and selective mechanism of ATI-2138, Aclaris is assessing additional indications for ATI-2138, including alopecias, and expects to initiate a Phase 2b trial in the first half of 2026.

About ATI-2138

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). ITK regulates T cell receptor signal transduction and inhibition of this kinase can affect T cell differentiation and activation. JAK3 is a key signal transduction kinase that forms a heterodimer with JAK1, modulates JAK1 phosphorylation of signal transducer and activator of transcription 5 (STAT5), and regulates cytokines that signal through the IL-2Rγ_c to affect lymphocyte proliferation and activation. The efficacy results exhibited in preclinical animal models of inflammation and autoimmune diseases, coupled with the favorable safety, pharmacokinetics, and pharmacodynamics profile in healthy human SAD and MAD studies and a Phase 2a trial in atopic dermatitis, support the potential for ATI-2138 to affect several human inflammatory diseases and further investigation of this molecule in patients with atopic and autoimmune diseases that are dependent on T cell function and/or IL-2Rγ_c signaling.

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-2138, including the timing of initiating a Phase 2b trial and the potential indication for such trial, and the therapeutic potential for ATI-2138, including in inflammatory, atopic, and autoimmune diseases including alopecias. 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, 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

A graphic accompanying this announcement is available at https://www.globenewswire.com/NewsRoom/AttachmentNg/84a52e9f-e571-47d3-ada2-8c947c90a3b7 

FAQ

What were the ATI-2138 hair regrowth results in the ACRS murine study?

At 300 ppm, ATI-2138 produced mean hair regrowth of 37% at week 2, 87% at week 4, and 93% at week 6.

How did ATI-2138 (ACRS) compare to ritlecitinib in the alopecia universalis model?

ATI-2138 outperformed ritlecitinib at 300 ppm: 87% vs 48% mean regrowth at week 4 and 93% vs 78% at week 6.

What is ATI-2138's mechanism and selectivity described by ACRS?

ATI-2138 inhibits ITK and JAK3, interrupting TCR and common gamma chain cytokine signaling, with >1,000-fold selectivity versus other JAK isoforms.

When does Aclaris (ACRS) expect to begin clinical testing of ATI-2138?

Aclaris expects to initiate a Phase 2b trial of ATI-2138 in the first half of 2026.

Are the ACRS ATI-2138 results proof of efficacy in humans?

No; the results are preclinical in mice and do not by themselves confirm human clinical efficacy.