New Study Highlights Clinical Need for Molecular Guidance in Atopic Dermatitis Treatment Selection, Reinforcing the Value of AdvanceAD-Tx™

The 43-person assessment measured treatment experiences and testing interest, not AdvanceAD-Tx outcomes.

Rhea-AI Summary

Castle Biosciences (CSTL) highlighted a September 8 study of atopic dermatitis treatment experiences and interest in molecular testing.

In an assessment of 43 patients and caregivers, 55% of participants who had used targeted systemic therapies modified treatment due to lack of efficacy. Interest in molecular testing to guide treatment selection was 83% overall and 94% among respondents open to starting a new systemic therapy.

AdvanceAD-Tx is designed to guide systemic treatment for patients aged 12 or older with moderate-to-severe atopic dermatitis. An earlier prospective clinical validation study found that patients with a JAK Inhibitor Responder Profile given a JAK inhibitor were 5.5 times more likely to reach at least 90% improvement in the Eczema Area and Severity Index by three months, and achieved that response 3.8 times faster, than patients with the same profile given Th2-targeted therapy. Patients with a Th2 Molecular Profile had comparable outcomes with either therapy class.

Key Figures

Treatment modified for lack of efficacy: 55% Interest in molecular testing: 83% Interest in molecular testing: 94% +3 more

Treatment modified for lack of efficacy

55%

Participants who had used targeted systemic therapies

Interest in molecular testing

83%

All respondents

Interest in molecular testing

94%

Respondents open to initiating a new systemic therapy

Study participants

43 patients and caregivers

Patient experience and preferences study

EASI-90 response likelihood

5.5 times more likely

Earlier validation study; JAK Inhibitor Responder Profile treated with a JAK inhibitor versus Th2-targeted therapy

Time to EASI-90 response

3.8 times faster

Earlier validation study; JAK Inhibitor Responder Profile treated with a JAK inhibitor versus Th2-targeted therapy

Key Terms

gene expression profile (gep), rna expression, easi-90, janus kinase (jak) inhibitor

4 terms

gene expression profile (gep) technical

"a non-invasive gene expression profile (GEP) test designed to guide systemic treatment decisions"

A gene expression profile (GEP) is a snapshot of which genes in a cell or tissue are turned on and how strongly they are producing RNA, usually measured by lab tests that quantify many genes at once. For investors, GEPs matter because they serve as biological fingerprints used to classify diseases, predict how patients may respond to a therapy, and guide clinical trial design and diagnostic product development—similar to a city activity map that shows which neighborhoods are busy and which are quiet.

rna expression technical

"Using RNA expression data from lesional skin scraping samples"

RNA expression is the process and measurement of how much ribonucleic acid (RNA) a cell or tissue makes from a particular gene, reflecting which genes are active and to what extent. Investors care because changes in RNA expression can signal whether a drug, therapy, or disease is affecting target pathways—like reading a factory’s production logs to see which machines are running—which helps assess scientific progress and potential value of biotech developments.

easi-90 medical

"at least 90% improvement in Eczema Area and Severity Index (EASI-90) by three months"

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 (jak) inhibitor medical

"a Janus kinase (JAK) Inhibitor Responder Profile who were treated with a JAK inhibitor"

A janus kinase (JAK) inhibitor is a type of medicine that blocks a family of enzymes inside cells that act like message relays for the immune system and cell growth. By interrupting those internal “phone lines,” these drugs can reduce harmful inflammation or slow certain cancers; for investors, JAK inhibitors matter because clinical trial results, regulatory approvals, safety signals, and patent position directly affect market potential and company valuation.

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Study data showed more than half of patients who used targeted systemic therapies modified treatment due to lack of efficacy

Among patients surveyed in the study, 94% of those open to a new systemic therapy expressed interest in molecular testing to help identify a more effective treatment

FRIENDSWOOD, Texas, Sept. 24, 2026 /PRNewswire/ -- Castle Biosciences, Inc. (Nasdaq: CSTL), a company improving health through innovative tests that guide patient care, today announced the publication of a new study highlighting the challenges patients with atopic dermatitis (AD) experience in achieving their treatment goals and strong patient interest in molecular testing to help guide systemic therapy selection. The findings support the clinical need for molecular guidance in AD care. Castle's AdvanceAD-Tx test is designed to address this need by helping personalize systemic therapy decisions based on an individual patient's underlying disease biology.

"One thing came through clearly in this study: patients want better control of their disease and more information to help guide their treatment decisions," said study author Diego Ruiz Dasilva, M.D., board-certified dermatologist at Forefront Dermatology in Virginia Beach, Virginia. "AdvanceAD-Tx gives us an opportunity to bring objective molecular information into those conversations, helping personalize systemic treatment decisions and expedite the path to an effective therapy and symptom relief."

The study, published in Dermatology and Therapy, evaluated the treatment experiences, priorities and perspectives of patients with AD and their caregivers.¹ Key findings include:

• Among participants who had used targeted systemic therapies, 55% modified their treatment due to lack of efficacy.
• Overall, 83% of respondents expressed interest in molecular testing to guide treatment selection, increasing to 94% among those open to initiating a new systemic therapy.

The study included 43 patients and caregivers who participated in a 32-question assessment at the 2024 National Eczema Association Eczema Expo. Respondents identified itch control (70%), effective skin clearance (58%) and safety or absence of side effects (50%) as the most important factors when considering AD treatment. Among participants who had used systemic therapy, inadequate skin clearance and persistent itching were the most frequently reported reasons for switching systemic therapies or adding topical treatment.

This new paper complements an earlier prospective, multicenter clinical validation study in the Journal of the American Academy of Dermatology that demonstrated the ability of Castle's AdvanceAD-Tx test to identify differences in systemic therapy class response in patients with moderate-to-severe AD.² Patients identified by the test as having a Janus kinase (JAK) Inhibitor Responder Profile who were treated with a JAK inhibitor were 5.5 times more likely to achieve at least 90% improvement in Eczema Area and Severity Index (EASI-90) by three months and achieved that response 3.8 times faster than patients with the same molecular profile who were treated with a T helper type 2 (Th2)-targeted therapy. Patients identified by the test as having a Th2 Molecular Profile showed comparable clinical outcomes with either therapy class.

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. The test classifies patients into one of two molecular profiles: a Janus kinase (JAK) Inhibitor Responder Profile or a T helper type 2 (Th2) Molecular Profile.

The prospective clinical validation study showed that patients with a JAK Inhibitor Responder Profile given JAK inhibitor therapy experienced significantly greater clinical benefit — including improved and faster skin clearance (EASI-90), greater likelihood of achieving no itch and remaining flare-free, and better quality of life by three months — 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, Esopredict, 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 AdvanceAD-Tx's ability to (i) provide objective molecular information to help guide systemic therapy selection, (ii) help personalize treatment decisions based on an individual patient's underlying disease biology, (iii) help clinicians and patients make more informed treatment decisions, (iv) help patients get to an effective therapy and achieve relief from their symptoms sooner and (v) improve patient care and treatment outcomes. The words "believe," "can," "may," "designed," "goal" and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. We may not actually achieve the plans, 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 our 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 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, 2025, 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.

References:

1. Ruiz Dasilva D, Burshtein J, Weinberg J, et al. Patient experience and preferences for treatments in atopic dermatitis. Dermatol Ther (Heidelb). Published online September 8, 2026. doi:10.1007/s13555-026-01912-w
2. Silverberg JI, Eichenfield LF, Armstrong AW, et al. The 487-gene expression profile test guides systemic therapy selection to improve outcomes for patients with atopic dermatitis: results from a prospective trial. J Am Acad Dermatol. 2026. doi:10.1016/j.jaad.2026.02.034

Investor Contact:
Camilla Zuckero
czuckero@castlebiosciences.com

Media Contact:
Allison Marshall
amarshall@castlebiosciences.com

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SOURCE Castle Biosciences, Inc.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What did Castle Biosciences' atopic dermatitis study find about treatment changes and molecular testing?

Among participants who had used targeted systemic therapies, 55% modified treatment due to lack of efficacy. Overall, 83% of respondents expressed interest in molecular testing to guide treatment selection, rising to 94% among those open to starting a new systemic therapy.

How does Castle Biosciences' AdvanceAD-Tx test classify patients?

AdvanceAD-Tx uses RNA from a scraping of affected skin, without a biopsy, to evaluate 487 genes across 12 pathways. It classifies patients into a JAK Inhibitor Responder Profile or a Th2 Molecular Profile.

What treatment priorities did participants in Castle Biosciences' atopic dermatitis study report?

Respondents most often identified itch control (70%), effective skin clearance (58%), and safety or absence of side effects (50%) as important factors when considering treatment. The study used a 32-question assessment completed by 43 patients and caregivers at the 2024 National Eczema Association Eczema Expo.