Castle Biosciences Presents Data from Suite of Dermatologic Cancer Genomic Tests at Fall Clinical Dermatology Conference 2021

The Company also highlights the study design for its pipeline program to predict response to systemic therapeutics in patients diagnosed with moderate to severe inflammatory dermatologic conditions

Castle Biosciences, Inc. (Nasdaq: CSTL), applying innovative diagnostics to transform disease management and improve patient outcomes, today announced recent poster presentations on the Company’s suite of dermatologic cancer gene expression profile (GEP) tests, as well as a poster describing the study design for its inflammatory skin disease pipeline initiative at the 2021 Fall Clinical Dermatology Conference, held Oct. 21-24.

DecisionDx®-Melanoma:

DecisionDx-Melanoma is Castle’s prognostic gene expression profile test for cutaneous melanoma. The Company utilizes two proprietary algorithms, i31-ROR and i31-SLNB, to produce an integrated test result designed to provide a precise, personalized prediction of risk of recurrence and likelihood of sentinel lymph node (SLN) positivity, respectively, by integrating DecisionDx-Melanoma with traditional assessment of the clinicopathologic features of a patient’s tumor.

The company presented new data on the capabilities of these independently validated algorithms through a poster titled, “Integrating the 31-gene expression profile and clinicopathologic data to determine the risk of sentinel lymph node positivity and recurrence-free survival in cutaneous melanoma.” The poster can be found here.

“The risks associated with a melanoma diagnosis can lead to several different clinical procedures, including sentinel lymph node biopsy (SLNB), and many patients experience regional recurrence, distant metastasis or even death,” said Bob Cook, Ph.D., senior vice president of research and development of Castle Biosciences. “The study results demonstrated that integrating the DecisionDx-Melanoma result with assessment of clinical and pathologic features improved individualized risk prediction for SLNB positivity, regional recurrence and distant metastasis, which could help clinicians make more informed and personalized risk-stratification decisions.”

Study methods and findings:

• The purpose of the study was to demonstrate the combined ability of two independently validated algorithms that incorporate the DecisionDx-Melanoma result with clinicopathologic features to predict individual SLNB positivity risk and recurrence-free survival (RFS).
• Using artificial intelligence techniques, two algorithms were developed:
  • The i31-GEP-SLNB (i31-SLNB) algorithm, developed from 1398 cases and validated in an independent cohort of 1674 cases, was developed to determine the individual likelihood of SLN positivity.
  • The i31-GEP-outcomes (i31-ROR) algorithm, developed from 1581 cases and validated in an independent cohort of 523 cases, was developed to provide personalized survival predictions for recurrence-free survival (RFS), distant metastasis-free survival (DMFS) and melanoma-specific survival (MSS).
• The i31-SLNB algorithm identified 31.2% (135/433) of patients with a <5% likelihood of SLN positivity who could potentially forego the SLNB surgical procedure. These patients all received a low-risk i31-ROR result and had high survival rates (>98% RFS, DMFS and MSS), reinforcing the i31-ROR algorithm’s risk prediction precision.
• In the SLN negative population, 20% of patients were identified as high risk by the i31-ROR algorithm and had five-year RFS rates that were like those for patients with a positive SLNB (e.g., Stage III disease) (47.7% vs. 48.7%, respectively).
• Overall, using National Comprehensive Cancer Network (NCCN) treatment guidelines, the test identified 44.8% (194/433) of patients who may have been able to avoid SLNB or were re-stratified as low or high risk compared to SLN status alone.
• The i31-ROR algorithm was able to stratify patients with Stage IIB-IIC melanoma according to risk of recurrence with an absolute recurrence difference of 20% at 12 months. This is of particular interest given the recent announcement of the absolute treatment effect of Pembrolizumab in patients with Stage IIB-IIC melanoma of 5.7% at 12 months.
• The study data demonstrated that DecisionDx-Melanoma’s integrated test result, using both i31-ROR and i31-SLNB algorithms, identified patients who may potentially forego SLNB and provide a more precise prediction of high and low risk of recurrence for more personalized patient care decisions.

Comprehensive Diagnostic Offering:

Castle’s Comprehensive Diagnostic Offering (CDO) leverages the strengths of both myPath® Melanoma and DecisionDx® DiffDx™-Melanoma, two GEP tests designed to provide a highly accurate, objective result to aid dermatopathologists and dermatologists in characterizing difficult-to-diagnose melanocytic lesions.

Castle presented data validating the company’s implementation of its CDO via a poster presentation entitled “A comprehensive diagnostic offering workflow increases the rate of actionable results of the 23- and 35-gene expression profile tests for use as ancillary diagnostic tools for difficult-to-diagnose melanocytic lesions.” The poster can be viewed here.

“Since Castle’s acquisition of the myPath laboratory earlier this year, we have looked forward to demonstrating the value that these two diagnostic GEP tests can offer together,” said Matthew S. Goldberg, M.D., first study author and medical director at Castle Biosciences. “We are pleased to have evidence that demonstrated the complementary power of these tests, which could enable physicians to make more confident diagnoses for patients with difficult-to-diagnose melanocytic lesions and to create individualized care plans by interpreting the patient’s gene expression profile in the context of the clinical, laboratory and histopathologic information.”

Study methods and findings:

• This study highlighted the results of all CDO clinical cases submitted to Castle Biosciences between June 30-Aug. 31, 2021. Using the Company’s CDO workflow, all adult cases not receiving an actionable result of benign or malignant from myPath Melanoma had the opportunity to be run using DecisionDx DiffDx-Melanoma.
• myPath Melanoma returned nonactionable classifications 22.3% of the time (nonactionable classifications are comprised of the combined total of intermediate risk results [12.9%] and technical failures [9.4%]).
• The nonactionable cases underwent additional testing using DecisionDx DiffDx-Melanoma, at which point an additional 20.9% of originally submitted cases received an actionable result. Only 1.1% of cases received an intermediate result from both tests; the technical failure rate of both tests combined was 0.2%.
• Leveraging both tests as a comprehensive diagnostic workflow substantially improved the reporting of clinically actionable results from a historic rate of 77.8% for myPath Melanoma alone to 98.7% when used in conjunction with DecisionDx DiffDx-Melanoma.

Psoriasis, Atopic Dermatitis and Related Conditions:

Inflammatory skin diseases, like psoriasis and atopic dermatitis, severely impact a patient’s quality of life. While there are many effective treatment options available for those with moderate-to-severe disease, current clinical practice relies on a costly and time-consuming trial-and-error approach to determine an individual patient’s response to systemic therapies. To answer this unmet clinical need, Castle Biosciences is developing a GEP test designed 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.

Castle initiated an IRB-approved clinical study to develop and validate one or more gene expression signatures to guide treatment selection in patients with psoriasis, atopic dermatitis and related conditions. The study’s design was presented via a poster titled “A study to help guide management decisions in patients with psoriasis and atopic dermatitis.” The poster can be viewed here.

“Patients with psoriasis and atopic dermatitis could benefit immensely from a more straightforward path to finding an effective therapeutic treatment option for their inflammatory skin disease,” said Aaron S. Farberg, M.D., the study’s first author and dermatologist at Baylor University Medical Center in Dallas. “Based on a history of success, Castle Biosciences is well positioned to potentially identify a molecular signature that could aid in finding the appropriate drug selection for a patient, based on their unique disease biology, saving patient time, money and contributing to a more effective use of healthcare resources.”

Study design:

• Up to 4,850 patients between two and 85 years of age diagnosed with psoriasis, atopic dermatitis or a related disorder will be prospectively enrolled in the study.
• At enrollment, disease severity will be documented. Superficial layers of diseased and healthy skin will be collected from participants. Clinical data including systemic treatment type, dose, response and side effects will be logged at subsequent visits.
• RNA from samples will be isolated, and an unbiased assessment of RNA expression levels using microarray will be performed.

Through this study protocol, Castle is aiming to develop a GEP test that may help guide therapeutic choice for patients with moderate-to-severe psoriasis and atopic dermatitis for whom clinical diagnosis or drug selection may be challenging, thereby potentially decreasing the amount of time and money spent on finding a successful treatment option for each patient.

DecisionDx®-SCC:

DecisionDx-SCC is Castle’s prognostic 40-GEP test designed to use a patient’s tumor biology to predict individual risk of metastasis for patients diagnosed with high-risk cutaneous squamous cell carcinoma (SCC) having one or more risk factors.

Castle presented data on DecisionDx-SCC through a poster entitled “Real-world clinical usage data demonstrates appropriate utilization of the prognostic 40-gene expression profile test for cutaneous squamous cell carcinoma with one or more risk factors.”

Study methods and findings:

• The objective of the study was to demonstrate independent prognostic value of DecisionDx-SCC via analyses with existing risk assessment methods and report on the early clinical usage of DecisionDx-SCC.
• Summary metrics were generated on the first 1000 samples received for DecisionDx-SCC testing that met clinical testing criteria. Metrics on early clinical usage include:
  • Technical reliability of DecisionDx-SCC was 96.3%.
  • 69.0% of samples received DecisionDx-SCC Class 1 results, 26.0% received DecisionDx-SCC Class 2A results and 1.3% received DecisionDx-SCC Class 2B results.
  • 52% of tested patients had three or more risk factors.
• This study demonstrated that the intended use population (high-risk SCC patients with one or more risk factors) aligned with the cases that were submitted for clinical testing.
• The study also found that DecisionDx-SCC results can be applied as an adjunct to enhance SCC risk stratification and contribute to risk-appropriate surveillance and treatment decisions.

About DecisionDx-Melanoma

DecisionDx®-Melanoma is a gene expression profile test that uses an individual patient’s tumor biology to predict individual risk of cutaneous melanoma metastasis or recurrence, as well as sentinel lymph node positivity, independent of traditional staging factors, and has been studied in more than 5,700 patient samples. Using tissue from the primary melanoma, the test measures the expression of 31 genes. The test has been validated in four archival risk of recurrence studies of 901 patients and six prospective risk of recurrence studies including more than 1,600 patients. Impact on patient management plans for one of every two patients tested has been demonstrated in four multicenter and single-center studies including more than 560 patients. The consistent performance and accuracy demonstrated in these studies provides confidence in disease management plans that incorporate DecisionDx-Melanoma test results.

In addition to reporting Class results, the Company also reports results that predict risk of recurrence and likelihood of sentinel lymph node positivity. Castle utilizes its proprietary algorithms, i31-ROR and i31-SLNB, to produce an integrated DecisionDx-Melanoma test result.

Through June 30, 2021, DecisionDx-Melanoma has been ordered 78,277 times for use in patients with cutaneous melanoma. More information about the test and disease can be found at www.CastleTestInfo.com.

About Castle Biosciences’ Comprehensive Diagnostic Offering for Difficult-to-Diagnose Melanocytic Lesions

Castle Biosciences’ comprehensive diagnostic offering leverages the strengths of myPath® Melanoma and DecisionDx® DiffDx™-Melanoma. These gene expression profile tests are designed to provide a highly accurate, objective result to aid dermatopathologists and dermatologists in characterizing difficult-to-diagnose melanocytic lesions. Of the approximately 2 million suspicious pigmented lesions biopsied annually in the U.S., Castle estimates that approximately 300,000 of those cannot be confidently classified as either benign or malignant through traditional histopathology methods. For these cases, the treatment plan can also be uncertain. Obtaining highly accurate, objective ancillary testing can mean the difference between a path of overtreatment or the risk of undertreatment. Interpreted in the context of other clinical, laboratory and histopathologic information, myPath Melanoma and DecisionDx DiffDx-Melanoma are designed to reduce uncertainty and provide confidence for dermatopathologists and help dermatologists deliver more informed patient management plans.

More information about the test and disease can be found at www.CastleTestInfo.com.

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 designed 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 DecisionDx-SCC

DecisionDx-SCC is a 40-gene expression profile test that uses an individual patient’s tumor biology to predict individual risk of cutaneous squamous cell carcinoma metastasis for patients with one or more risk factors. The test result, in which patients are stratified into a Class 1 (low), 2A (moderate) or 2B (high) risk category, predicts individual metastatic risk to inform risk-appropriate management.

Peer-reviewed publications have demonstrated that DecisionDx-SCC is an independent predictor of metastatic risk and that integrating DecisionDx-SCC with current prognostic methods can add positive predictive value to clinician decisions regarding staging and management.

More information about the test and disease can be found at www.CastleTestInfo.com.

About Castle Biosciences

Castle Biosciences (Nasdaq: CSTL) is a commercial-stage dermatologic diagnostics company focused on providing physicians and their patients with personalized, clinically actionable genomic information to make more accurate treatment decisions. The Company currently offers tests for patients with cutaneous melanoma (DecisionDx®-Melanoma, DecisionDx® -CMSeq), cutaneous squamous cell carcinoma (DecisionDx®-SCC), suspicious pigmented lesions (myPath® Melanoma, DecisionDx® DiffDx™-Melanoma,) and uveal melanoma (DecisionDx®-UM, DecisionDx®-PRAME and DecisionDx®-UMSeq). For more information about Castle’s gene expression profile tests, visit www.CastleTestInfo.com.

Castle also has active research and development programs for tests in other dermatologic 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. Castle Biosciences is based in Friendswood, Texas (Houston), and has laboratory operations in Phoenix.

For more information, visit www.CastleBiosciences.com.

DecisionDx-Melanoma, DecisionDx-CMSeq, DecisionDx-SCC, myPath Melanoma, DecisionDx DiffDx-Melanoma, DecisionDx-UM, DecisionDx-PRAME and DecisionDx-UMSeq are trademarks of Castle Biosciences, Inc.

Forward-Looking Statements

The information in this press release contains forward-looking statements and information 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 DecisionDx-Melanoma’s ability to provide a precise, personalized prediction of risk of recurrence and likelihood of sentinel lymph node positivity, improve individualized risk prediction for SLNB positivity, regional recurrence and distant metastasis, and help clinicians make more informed decisions about the personalized care that each patient requires to ensure the best possible outcome for their disease, Castle’s Comprehensive Diagnostic Offering ability to provide a highly accurate, objective result to aid dermatopathologists and dermatologists in characterizing difficult-to-diagnose melanocytic lesions and the complementary power of the tests that make up such offering, inclusive of the ability to enable physicians to make more confident diagnoses for patients with difficult-to-diagnose melanocytic lesions and create individualized care plans based on the patient’s gene expression profile, Castle’s development of a gene expression profile test to predict response to systemic therapies for patients with moderate to severe psoriasis, atopic dermatitis and other related diseases, improve patient health outcomes ,enable clinicians to select the best medication for their patients’ specific skin disease, and save patient’s time and money as well as Castle’s ability to develop such a test, and DecisionDx-SCC’s ability to predict individual risk of cutaneous squamous cell carcinoma metastasis for patients with one or more risk factors and enhance SCC risk stratification and contribute to risk-appropriate surveillance and treatment decisions. 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 that contradict earlier study results and findings, DecisionDx-Melanoma’s, Castle’s Comprehensive Diagnostic Offering, DecisionDx-SCC’s and Castle’s gene expression profile test to predict response to systemic therapies for patients with moderate to severe psoriasis, atopic dermatitis and other related diseases, ability to provide the aforementioned benefits to patients, Castle’s ability to develop a gene expression profile test to predict response to systemic therapies for patients with moderate to severe psoriasis, atopic dermatitis and other related diseases and the risks set forth in our Quarterly Report on Form 10-Q for the quarter ended June 30, 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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