Prospective Validation Study in JAAD Demonstrates Castle Biosciences’ AdvanceAD-Tx™ Test Identifies Patients More Likely to Achieve Faster and Deeper Responses with JAK Inhibitor Therapy in Moderate-to-Severe Atopic Dermatitis

Rhea-AI Summary

Castle Biosciences (Nasdaq: CSTL) reported a prospective multicenter validation in JAAD showing its AdvanceAD-Tx test stratifies moderate-to-severe atopic dermatitis patients by molecular profile to predict response to JAK inhibitor therapy.

About 30% of patients were classified as a JAK Inhibitor Responder Profile; those treated with a JAKi were 5.5x more likely to reach EASI-90 by three months (45.5% vs 8.3%, p=0.021) and achieved responses nearly four times faster (p=0.049). Results also showed higher vIGA-AD clear rates, itch resolution, flare-free status, and DLQI 0 in the JAK responder subgroup.

Positive

• 30% of patients identified with a JAK Inhibitor Responder Profile
• Patients with JAK profile had 5.5x likelihood of EASI-90 by three months
• 45.5% EASI-90 rate on JAKi vs 8.3% on Th2 therapy (p=0.021)
• 36.4% vIGA-AD clear (0) rate on JAKi vs 0% on Th2 therapy (p=0.006)

Negative

• AdvanceAD-Tx classified only about 30% as JAK responders, limiting immediate applicability
• Castle reports a limited access commercial launch in late 2025, which may slow broad adoption

Key Figures

Genes evaluated: 487 genes Biology pathways: 12 pathways Responder profile share: 30% of patients +5 more

8 metrics

Genes evaluated 487 genes AdvanceAD-Tx gene expression profile panel

Biology pathways 12 pathways Inflammatory and cutaneous biology pathways analyzed

Responder profile share 30% of patients Identified as JAK Inhibitor Responder Profile in validation cohort

EASI-90 response 45.5% vs. 8.3% (p=0.021) JAKi vs. Th2 therapy in JAK Inhibitor Responder Profile patients by 3 months

Time to response 5.5x more likely; ~4x faster (p=0.049) JAKi vs. Th2 in JAK Inhibitor Responder Profile for EASI-90

Skin clearance 36.4% vs. 0% (p=0.006) vIGA-AD 0 (clear) with JAKi vs. Th2 in responder profile

No itch rate 45.5% vs. 8.3% (p=0.021) Patient-reported “no itch” with JAKi vs. Th2 in responder profile

Flare-free patients 54.5% vs. 16.7% (p=0.041) Flare-free at 3 months with JAKi vs. Th2 in responder profile

Market Reality Check

Price: $31.34 Vol: Volume 621,762 is 1.48x t...

normal vol

$31.34 Last Close

Volume Volume 621,762 is 1.48x the 20-day average of 420,382, indicating elevated trading interest ahead of/around this data publication. normal

Technical Shares at $31.34 are trading above the 200-day MA of $26.48, but sit 29.22% below the 52-week high and 114.8% above the 52-week low.

Peers on Argus

CSTL fell 6.92% while sector momentum flags mixed pressure: GRAL down 46.28%, TW...

1 Up 2 Down

CSTL fell 6.92% while sector momentum flags mixed pressure: GRAL down 46.28%, TWST down 2.84%, and PSNL up 2.69%. Broader diagnostics/clinical tools names show cross-currents, suggesting part of the move may reflect sector dynamics rather than this trial result alone.

Common Catalyst Peers like MYGN also reported clinical/analytical study data with modest negative price reaction, pointing to a research-data news cycle rather than a single-company event.

Historical Context

5 past events · Latest: Feb 05 (Neutral)

Pattern 5 events

Date	Event	Sentiment	Move	Catalyst
Feb 05	Earnings call scheduling	Neutral	-7.3%	Set date and time for Q4 and full-year 2025 results call.
Jan 11	Prelim 2025 results	Positive	+0.8%	Preliminary 2025 revenue above guidance and strong core test growth.
Dec 19	Inducement equity grants	Neutral	-0.4%	RSU inducement grants to new employees under 2022 Inducement Plan.
Dec 17	Uveal melanoma study	Positive	+1.6%	DecisionDx-UM + PRAME outperformed mutation analysis for survival prediction.
Dec 12	TissueCypher meta-analysis	Positive	+1.7%	Meta-analysis confirmed TissueCypher better identifies high-risk BE patients.

Pattern Detected

Recent history shows generally constructive reactions to positive clinical and preliminary financial updates, while scheduling-related or routine items have sometimes coincided with drawdowns.

Recent Company History

Over the past few months, Castle Biosciences has highlighted multiple data and corporate milestones. In Dec 2025, positive clinical evidence for DecisionDx-UM and TissueCypher correlated with modest gains of 1.56% and 1.74%. Preliminary 2025 results on Jan 11, 2026 showing revenue above guidance saw a small 0.81% rise. By contrast, a neutral earnings date announcement on Feb 5, 2026 coincided with a 7.32% decline. Today’s AdvanceAD-Tx validation fits the pattern of data-driven news building out the test portfolio.

Market Pulse Summary

This announcement adds clinically validated support for AdvanceAD-Tx, showing JAK inhibitor–treated ...

Analysis

This announcement adds clinically validated support for AdvanceAD-Tx, showing JAK inhibitor–treated responder-profile patients achieved EASI-90 in 45.5% vs 8.3% on Th2 therapy, with multiple outcomes reaching significant p-values. It follows prior positive studies for DecisionDx-UM and TissueCypher in late 2025. Investors may watch future financial updates, adoption trends after the late 2025 limited launch, and additional peer-reviewed data as key markers of test traction.

Key Terms

easi-90, janus kinase inhibitor, t helper type 2 (th2), dermatology life quality index, +1 more

5 terms

easi-90 medical

"more likely to achieve near-clear skin (EASI-90), faster time to response"

A clinical-trial endpoint that measures a 90% improvement in a patient’s eczema signs and affected skin area compared with their baseline score. It’s a high bar for treatment effectiveness—like cutting nine out of ten problem spots—and matters to investors because achieving EASI-90 can signal a therapy is substantially better than existing options, boosting chances of regulatory approval, market adoption, and commercial value.

janus kinase inhibitor medical

"responses when treated with a Janus kinase inhibitor (JAKi) compared to"

A janus kinase inhibitor is a type of medicine that blocks enzymes called Janus kinases, which help cells send signals that drive inflammation, immune reactions, and some blood cell growth. Think of it as turning down a dimmer switch on overactive immune signals to reduce disease activity. Investors track these drugs because regulatory approvals, trial results, safety concerns, and patent protection directly affect potential sales and company valuation.

t helper type 2 (th2) medical

"compared to T helper type 2 (Th2)-targeted therapies."

T helper type 2 (Th2) are a subgroup of white blood cells that direct parts of the immune system by signaling other cells to make certain antibodies and drive allergy-related inflammation. They matter to investors because drugs, vaccines, or diagnostics that raise or lower Th2 activity can change treatment outcomes for allergies, asthma and related conditions, so clinical or regulatory news tied to Th2 biology can materially affect companies working in immunology — think of Th2 as a thermostat that controls one immune circuit.

dermatology life quality index medical

"achievement of a Dermatology Life Quality Index (DLQI) score of 0, indicating no impact"

A Dermatology Life Quality Index (DLQI) is a short, patient-completed questionnaire that measures how much a skin condition affects a person’s daily life, similar to a customer satisfaction score for health. Investors watch DLQI results because they show whether a treatment meaningfully improves patients’ day-to-day well-being, which can influence regulatory decisions, market demand, pricing, and insurance coverage — all drivers of a therapy’s commercial value.

dlqi medical

"Life Quality Index (DLQI) score of 0, indicating no impact of disease"

The Dermatology Life Quality Index (DLQI) is a brief, patient-completed questionnaire that measures how much a skin condition affects everyday activities, emotions, work and social life. As a widely used patient-reported outcome in clinical studies and regulatory reviews, DLQI scores act like a customer satisfaction rating for treatments — they help show whether a therapy meaningfully improves patients’ lives, which can influence regulatory decisions, adoption and commercial value.

AI-generated analysis. Not financial advice.

Study data show that AdvanceAD-Tx can stratify patients by molecular profile identifying those more likely to achieve near-clear skin (EASI-90), faster time to response and meaningful patient-reported benefits when treated with JAK inhibitor therapy compared to a Th2-targeted therapy

FRIENDSWOOD, Texas, Feb. 19, 2026 (GLOBE NEWSWIRE) -- Castle Biosciences, Inc. (Nasdaq: CSTL), a company improving health through innovative tests that guide patient care, today announced the publication of a prospective, multicenter clinical validation study in the Journal of the American Academy of Dermatology (JAAD) demonstrating that its AdvanceAD-Tx test can identify patients with moderate-to-severe atopic dermatitis (AD) who are significantly more likely to achieve greater and faster clinical responses when treated with a Janus kinase inhibitor (JAKi) compared to T helper type 2 (Th2)-targeted therapies.¹

“Atopic dermatitis can look similar on the surface, but the biology driving the disease can differ meaningfully from patient to patient,” said Mark G. Lebwohl, M.D., senior study author, dean for clinical therapeutics and professor and chairman emeritus of the Kimberly and Eric J. Waldman Department of Dermatology at the Icahn School of Medicine at Mount Sinai in New York. “This study shows that AdvanceAD-Tx can provide objective molecular insight to help clinicians better align systemic therapy choices with an individual patient’s disease biology earlier in the treatment journey and improve outcomes that matter to patients.”

AdvanceAD-Tx is a non-invasive gene expression profile test designed to provide objective molecular insight to help guide systemic treatment decision making for patients 12 years of age and older with moderate-to-severe AD who are considering systemic therapy. Using simple lesional skin scrapings, no biopsy required, the test evaluates the expression of 487 genes across 12 inflammatory and cutaneous biology pathways and reports one of two actionable molecular profiles — a JAK Inhibitor Responder Profile or a Th2 Molecular Profile — to help clinicians better understand the underlying immune biology of an individual patient’s disease.

Results from the independent validation cohort demonstrated that approximately 30 percent of patients studied were identified by the AdvanceAD-Tx test as having a JAK Inhibitor Responder Profile. Among these patients, those treated with a JAKi were 5.5 times more likely to achieve at least 90 percent improvement in Eczema Area and Severity Index (EASI-90) by three months compared to those treated with Th2–targeted therapies (45.5% vs. 8.3%, p=0.021), and they achieved a response nearly four times faster (p=0.049). Patients with a JAK Inhibitor Responder Profile who were treated with a JAKi were also significantly more likely to:

• Achieve near-complete or complete skin clearance, as reflected by a Validated Investigator Global Assessment score of clear (vIGA-AD 0, 36.4% vs 0%, p=0.006)
• Report higher rates of “no itch” (45.5% vs. 8.3%, p=0.021)
• Remain flare-free by three months (54.5% vs. 16.7%, p=0.041)
• Report improved quality of life, including achievement of a Dermatology Life Quality Index (DLQI) score of 0, indicating no impact of disease on quality of life (45.5% vs. 8.3%, p=0.021)

In contrast, patients identified with a Th2 Molecular Profile showed no statistically significant differences in clinical or patient-reported outcomes when taking a JAKi or Th2-targeted therapy, supporting shared decision making between clinicians and patients regarding treatment selection based on patient preference, clinician experience and other clinical considerations.

“Together, these results highlight how aligning systemic therapy selection with an individual patient’s molecular profile may help streamline care by reducing unnecessary treatment changes and accelerating meaningful clinical improvement,” said Rebecca Critchley-Thorne, Ph.D., vice president, research and development, at Castle Biosciences. “By better understanding the biology driving each patient’s disease, AdvancedAD-Tx can help clinicians move beyond non–molecularly guided prescribing and enable more confident, evidence-based decisions earlier in the treatment journey.”

The new publication follows Castle’s recent limited access commercial launch of AdvanceAD-Tx in late 2025. The full paper is available online.

About AdvanceAD-Tx
AdvanceAD-Tx is a non-invasive gene expression profile (GEP) test designed to guide systemic treatment decisions for patients aged 12 years and older with moderate-to-severe atopic dermatitis (AD). Using RNA expression data from lesional skin scraping samples—no biopsy required—the test evaluates 487 genes across 12 inflammatory and cutaneous biology pathways to reveal the underlying immune biology driving an individual patient’s disease. Results classify patients into one of two molecular profiles: Janus Kinase (JAK) Inhibitor Responder Profile or T helper 2 (Th2) Molecular Profile.

The prospective, clinical validation study showed that the test identifies a subset of patients with a JAK Inhibitor Responder Profile who experience significantly greater clinical benefit—including improved and faster skin clearance (EASI-90), reduced itch, fewer flares and better quality of life by three months—when treated with a JAK inhibitor therapy compared to those treated with a Th2-targeted therapy. AdvanceAD-Tx provides clinicians with objective, molecular-based insights to help personalize systemic treatment decisions and improve care for patients. Learn more at https://castlebiosciences.com/tests/therapy-guidance/advancead-tx/overview. 

About Castle Biosciences 
Castle Biosciences (Nasdaq: CSTL) is a leading diagnostics company improving health through innovative tests that guide patient care. With a primary focus in dermatologic and gastroenterological disease, we develop personalized, clinically actionable solutions that help improve disease management and patient outcomes.

We put people first—empowering patients and clinicians and informing care decisions through rigorous science and advanced molecular tests that support more confident treatment planning. To learn more, visit www.CastleBiosciences.com and connect with us on LinkedIn, Instagram, Facebook and X. 

DecisionDx-Melanoma, DecisionDx-CMSeq, i31-SLNB, i31-ROR, DecisionDx-SCC, MyPath Melanoma, AdvanceAD-Tx, TissueCypher, DecisionDx-UM, DecisionDx-PRAME and DecisionDx-UMSeq are trademarks of Castle Biosciences, Inc.

Forward-Looking Statements
This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended, which are subject to the “safe harbor” created by those sections. These forward-looking statements include, but are not limited to, statements concerning: the ability of AdvanceAD-Tx to (i) provide objective molecular insight, (ii) help clinicians better align systemic therapy choices with an individual patient’s disease biology earlier in the treatment journey, (iii) improve outcomes that matter to patients, and (iv) help streamline care by reducing unnecessary treatment changes and accelerating meaningful clinical improvement; and the accuracy of the 487-GEP tests. The words “designed,” “may”, “can”, and similar expressions are intended to identify forward intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements that we make. These forward looking statements involve risks and uncertainties that could cause actual results to differ materially from those in the forward-looking statements, including, without limitation: subsequent study or trial results and findings may contradict earlier study or trial results and findings or may not support the results obtained in these studies, including with respect to the discussion of our tests in this press release; actual application of our tests may not provide the aforementioned benefits to certain patients; and the risks set forth under the heading “Risk Factors” in our Annual Report on Form 10-K for the year ended December 31, 2024, and our subsequent Quarterly Reports on Form 10-Q, each as filed or to be filed with the SEC, and in our other filings with the SEC. The forward-looking statements are applicable only as of the date on which they are made, and we do not assume any obligation to update any forward-looking statements, except as may be required by law.

1. Silverberg JI, Eichenfield LF, Armstrong AW, Bagel J, Lockshin B, Boh E, Koo J, Farberg AS, Goldberg MS, Quick AP, Lebwohl MG, The 487-gene expression profile test guides systemic therapy selection to improve outcomes for patients with atopic dermatitis: Results from a prospective trial, Journal of the American Academy of Dermatology (2026), doi: https://doi.org/10.1016/ j.jaad.2026.02.034.

Investor Contact:
Camilla Zuckero
czuckero@castlebiosciences.com

Media Contact:
Allison Marshall
amarshall@castlebiosciences.com

Source: Castle Biosciences, Inc.

FAQ

What does the JAAD study say about Castle Biosciences' AdvanceAD-Tx and JAK inhibitor response (CSTL)?

AdvanceAD-Tx identified patients more likely to respond faster and deeper to JAK inhibitors. According to the company, about 30% were JAK responder profile and had higher EASI-90 and vIGA-AD clear rates on JAKi versus Th2 therapy.

How much more likely were AdvanceAD-Tx JAK responders (CSTL) to reach EASI-90 by three months?

JAK responder patients were 5.5 times more likely to reach EASI-90 by three months. According to the company, rates were 45.5% with JAKi versus 8.3% with Th2-targeted therapy (p=0.021).

Does AdvanceAD-Tx predict faster time to response on JAK inhibitors for CSTL patients?

Yes. JAK responder patients achieved responses nearly four times faster compared with Th2 therapy. According to the company, the time-to-response difference reached statistical significance (p=0.049) in the validation cohort.

What patient-reported benefits did AdvanceAD-Tx JAK responders (CSTL) experience?

JAK responder patients reported higher rates of itch resolution, flare-free status and DLQI 0. According to the company, examples include 45.5% no itch and 45.5% DLQI 0 versus 8.3% on Th2 therapy (p=0.021).

How widely applicable is AdvanceAD-Tx based on the JAAD validation for CSTL investors?

The test classified roughly 30% of study patients as JAK responders, indicating limited immediate reach. According to the company, the majority of patients had other profiles, underscoring targeted rather than universal applicability.