Castle Biosciences announced that a prospective, multicenter validation study published in the Journal of the American Academy of Dermatology on February 19, 2026 confirms the clinical utility of its AdvanceAD‑Tx gene‑expression profile test for moderate‑to‑severe atopic dermatitis (AD). The study enrolled patients across multiple centers and identified 30 % of participants as having a JAK inhibitor responder profile. Those patients treated with a JAK inhibitor were 5.5 times more likely to achieve at least 90 % improvement in the Eczema Area and Severity Index (EASI‑90) by three months compared with patients treated with T‑helper‑2 targeted therapies (45.5 % vs. 8.3 %, p = 0.021).
The validation also showed that JAK inhibitor responders achieved a response nearly four times faster (p = 0.049) and experienced greater reductions in itch, fewer flares, and improved quality of life at three months. Patients with a T‑helper‑2 molecular profile did not show a statistically significant difference in outcomes between JAK inhibitor and T‑helper‑2 therapies, underscoring the value of molecular stratification for personalized treatment selection. The study’s findings support Castle’s strategy of expanding its precision‑diagnostics portfolio beyond dermatology into systemic therapy guidance for chronic inflammatory diseases.
Castle’s AdvanceAD‑Tx was launched in late 2025 under a limited‑access commercial model. In the third quarter of 2025, Castle reported revenue of $83.0 million, down from $85.8 million in the same period a year earlier, and a gross margin of 75 %, compared with 79 % in Q3 2024. Core test volumes for DecisionDx‑Melanoma and TissueCypher grew 37 % year‑over‑year, providing a strong revenue base that underpins the company’s ability to invest in new tests such as AdvanceAD‑Tx.
"We are extremely pleased with our excellent fourth quarter and full year preliminary results, which reflect both the strength of our innovative test portfolio and the dedication of the entire Castle team. We exited 2025 exhibiting strong execution and leadership across our dermatologic and gastrointestinal franchises and a strong balance sheet, positioning us well, we believe, to capitalize on our growth opportunities in 2026 and beyond. This includes the November 2025, limited access launch of AdvanceAD‑Tx™, our new test designed to help guide systemic treatment decisions for patients with moderate‑to‑severe atopic dermatitis, which materially expands our total addressable market," said CEO Derek Maetzold. Senior study author Dr. Mark G. Lebwohl added, "Atopic dermatitis can look similar on the surface, but the biology driving the disease can differ meaningfully from patient to patient. 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."
Analysts responded positively to the study and Castle’s recent financial performance. KeyBanc raised its price target to $50 from $36 and maintained an Overweight rating, citing the company’s strong test volume growth and the strategic significance of the new atopic dermatitis platform in a $33 billion market. The validation study, combined with Castle’s robust core test performance, positions the company to accelerate adoption of AdvanceAD‑Tx and secure payer coverage for its precision‑diagnostics solutions.
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