Skin collection technique shown to be robust with an inter-operator Pearson’s correlation of >0.99

Castle Biosciences, Inc. (Nasdaq: CSTL), a company improving health through innovative tests that guide patient care, today announced a recent poster presentation highlighting data and concluding that its non-invasive skin scraping technique produces sufficient ribonucleic acid (RNA) to assess reproducible gene expression for its inflammatory skin disease pipeline test. The poster was presented at the 4^th Annual Revolutionizing Atopic Dermatitis (RAD) Conference, held in Baltimore and virtually, April 9-11, 2022.

Castle is developing a gene expression profile (GEP) test to predict response to systemic therapy in patients with moderate-to-severe psoriasis, atopic dermatitis (AD) and related inflammatory skin conditions. The poster, titled “Feasibility of a novel, non-invasive sample collection technique to develop a molecular test guiding therapeutic selection for patients with atopic dermatitis and psoriasis,” discusses the feasibility of its quick, non-invasive skin scraping technique to obtain RNA needed to assess the expression of molecular biomarkers in patients’ epidermis.

“Through this study, we were looking to find a sample collection method for Castle’s pipeline GEP test that would be simple for clinicians to use yet would provide enough RNA to adequately examine the expression of genes in a lab setting; and we believe we succeeded,” said Aaron S. Farberg, M.D., study author and dermatologist affiliated with Baylor Scott & White Health System and Derm Texas in Dallas. “The potential for this pipeline test to improve care for patients, by using their unique biology to guide selection of an effective medication for their disease, is notable, and I am excited by the possibility to better care for my patients, as I have seen how debilitating psoriasis and atopic dermatitis can be.”

The study used quantitative real-time polymerase chain reaction (RT-PCR) to evaluate the gene expression of a standard gene set of samples collected by gently scraping affected and non-affected skin from 20 patients with AD and 20 patients with psoriasis from two dermatology centers in the U.S. Overall, the study determined that the non-invasive skin scraping technique produced sufficient RNA to assess reproducible gene expression needed to develop a gene expression profile for Castle’s inflammatory skin disease pipeline test.

In 2021, Castle initiated a 4,800 patient, prospective, multi-center clinical study to develop and validate this pipeline test. The study currently has 52 committed sites and approximately 145 patients enrolled; initial validation and development data is expected in 2023. The Company expects to launch this pipeline test by the end of 2025.

About Psoriasis, Atopic Dermatitis and Related Conditions

Inflammatory skin disease accounts for a significant number of patient visits to both primary care and dermatology clinics across the U.S. every year. Psoriasis and atopic dermatitis are among the most common inflammatory skin conditions, and patient quality of life is severely impacted by these chronic diseases. Fortunately, systemic medications developed over the past 15 years have demonstrated a significant improvement in patients’ lives. In the U.S. alone, there are about 18 million patients diagnosed with psoriasis and atopic dermatitis, and approximately 450,000 patients annually are eligible for these systemic therapies. While there are now many effective treatments options available for those with moderate-to-severe disease, current clinical practice relies on a trial-and-error approach for therapy selection. To answer this unmet clinical need, Castle Biosciences is developing a gene expression profile test to predict response to systemic therapies for patients with moderate-to-severe psoriasis, atopic dermatitis and other related diseases. Personalized guidance for therapy selection and anticipated efficacy has the potential to improve patient health outcomes by enabling clinicians to select the best medication for their patients’ specific skin disease.

About Castle Biosciences

Castle Biosciences (Nasdaq: CSTL) is a leading diagnostics company improving health through innovative tests that guide patient care. The Company aims to transform disease management by keeping people first: patients, clinicians, employees and investors.

Castle’s current portfolio consists of tests for skin cancers, uveal melanoma and Barrett’s esophagus. Additionally, the Company has active research and development programs for tests in other diseases with high clinical need, including its test in development to predict systemic therapy response in patients with moderate-to-severe psoriasis, atopic dermatitis and related conditions. To learn more, please visit www.CastleBiosciences.com and connect with us on LinkedIn, Facebook, Twitter and Instagram.

DecisionDx-Melanoma, DecisionDx-CMSeq, DecisionDx-SCC, myPath Melanoma, DecisionDx DiffDx-Melanoma, DecisionDx-UM, DecisionDx-PRAME, DecisionDx-UMSeq and TissueCypher 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 potential of the skin scraping technique discussed in this press release to obtain sufficient RNA for use in our pipeline GEP test; the potential for our pipeline GEP test to improve care for patients by using their unique biology to guide selection of an effective medication for their disease; our expectation of receiving initial validation and development data for our pipeline GEP test in 2023 and launching our pipeline GEP test by the end of 2025; and the potential of personalized guidance for therapy selection and anticipated efficacy to improve patient health outcomes by assisting clinicians to select the best medication for their patients’ specific skin disease. The words “anticipates,” “believes,” “estimates,” “expects,” “intends,” “may,” “plans,” “projects,” “will,” “would” 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, the effects of the COVID-19 pandemic on our business and our efforts to address its impact on our business, subsequent study results and findings may contradict earlier study results and findings or may not support the results obtained in this study, including with respect to the discussion of our pipeline GEP test 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 fiscal year ended Dec. 31, 2021, 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.

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