Castle Biosciences is a molecular diagnostics company that develops and commercializes proprietary tests designed to provide personalized, clinically actionable information to improve treatment decisions and patient outcomes, with a primary focus on skin cancers, uveal melanoma, and gastroenterological diseases. Pulse 2.0 interviewed Castle Biosciences founder, CEO, and President Derek Maetzold to learn more.
Derek Maetzold’s Background
Could you tell me more about your background? Maetzold said:
“Before I started Castle Biosciences, I spent 24 years in pharmaceutical development and commercialization, focused primarily on new product development through business licensing and commercial oversight of pre-approved therapies. Immediately prior to starting Castle, I moved to Houston to prepare a public biotechnology company for the launch of their first commercial product. After that company was sold, I started thinking that it may be time to try something on my own. Biotech in general was a space where I was comfortable, so naturally, I started thinking of opportunities that could leverage my experience and knowledge of the industry and areas where I knew gaps existed.”
Formation Of The Company
How did the idea for the company come together? Maetzold shared:
“I started Castle after realizing there was a big gap in how cancer patients were being treated. Clinicians were relying mainly on traditional staging, looking at tumor size, thickness or how far it had spread. While helpful, relying on that information alone to develop an individual patient’s treatment plan is limiting.”
“Two former colleagues, Toby Juvenal (now our Chief Commercial Officer) and Kristen Oelschlager (now our Chief Operating Officer), joined me when we started Castle. Together, we saw an opportunity to serve patients with rare cancers, those often overlooked because most companies were focused on larger-market cancers like breast, lung, or prostate. We asked ourselves: why shouldn’t patients with less common cancers have access to the same genomic insights guiding care in the bigger cancer types?”
“By analyzing the activity of specific genes in a tumor, we can see how aggressive it might be, or whether tissue is malignant or benign. We wanted to bring that level of precision to cancers where options were limited, giving doctors more than just pathology to make decisions.”
“Our goal from the beginning was simple: use tumor biology to give patients and clinicians better tools to make better treatment decisions. And that goal has grown into our vision and mission today: to transform disease management by putting people first and improve health through innovative tests that guide patient care.”
“In addition, to provide the best return to our shareholders, we decided to only focus on tests that required a proprietary algorithm – we now call that AI of course – such that our tests would be clinically unique versus generic.”
Core Products
What are the company’s core products and features? Maetzold explained:
“Castle’s innovative portfolio of commercial and pipeline tests targets unmet clinical need along the patient care continuum.“
“We currently market five proprietary tests designed to answer clinical questions and address treatment plan challenges primarily facing dermatologists and gastroenterologists. Our test for invasive cutaneous melanoma, DecisionDx-Melanoma, is a proprietary gene expression profile (GEP) test that uses an individual patient’s tumor biology to predict the likelihood of sentinel lymph node positivity and, separately, the risk of subsequent metastasis. Dermatologists use our results to guide both the decision to consider avoiding a sentinel lymph node biopsy surgical procedure as well as to recommend surveillance imaging follow-up by an oncologist. DecisionDx-SCC is our GEP test that predicts likelihood of response to adjuvant radiation therapy as well as risk of metastasis in patients with cutaneous squamous cell carcinoma who have one or more risk factors. Clinicians use our results to guide both the decision to initiate adjuvant radiation therapy as well as surveillance imaging and referrals to oncologists. Our TissueCypher test for use in Barrett’s esophagus disease identifies patients who are at risk of developing high grade dysplasia or esophageal adenocarcinoma. The test helps doctors determine if their patient should be referred for consideration of esophageal eradication therapy which has been shown to halt progression to esophageal adenocarcinoma. TissueCypher is the world’s first precision medicine test designed to predict future development of esophageal cancer in patients with Barrett’s esophagus. We also have two other proprietary tests. One, DecisionDx-UM, is the standard of care in uveal melanoma staging. The other is MyPath Melanoma, which provides pathologists and dermatologists with a highly accurate, objective result to aid in the diagnosis of suspicious pigmented lesions.”
Challenges Faced
Have you faced any challenges in your sector of work recently? Maetzold acknowledged:
“One of the biggest challenges we’ve faced is the complexity of the reimbursement landscape, both Medicare and commercial. Consistent reimbursement is critical to ensuring patients have access to molecular diagnostic tests, but shifting evidence goals and payment rates can create real uncertainty.”
“Rather than letting that slow us down, we took a proactive approach. We diversified our portfolio by developing and acquiring tests that not only address areas of high unmet clinical need but also have clear reimbursement pathways or already have some reimbursement in hand. That strategy has allowed us to apply our commercial model more broadly, accelerate adoption and deliver more predictable revenue, all while reaching more patients.”
“For example, after the success of DecisionDx-Melanoma, which has now been ordered more than 200,000 times by over 15,500 clinicians, we expanded our portfolio with tests like MyPath Melanoma and TissueCypher. These additions helped strengthen our resilience to reimbursement headwinds while extending our mission to improve care for more patients. In fact, in 2024 we delivered more than 96,000 test reports, a 36% increase over 2023, demonstrating steady growth despite external pressures.”
“We’ve also leaned into advocacy. Castle has been active in championing biomarker reform laws in Texas and at the national level to expand insurance coverage of comprehensive biomarker testing. As a board member of the Coalition for 21st Century Medicine, I’ve worked alongside other leaders in diagnostics, research and patient advocacy to advance the belief that advanced diagnostics are central to the future of quality, affordable healthcare.”
“In short, by staying ahead of reimbursement challenges, diversifying our portfolio and advocating for systemic reform, we’ve not only navigated headwinds but continued to grow and expand our impact for patients.”
Evolution Of The Company’s Technology
How has the company’s technology evolved since launching? Maetzold noted:
“When we started, most of the molecular diagnostics field was focused on common cancers like breast or lung. We saw an opportunity to do the opposite by serving smaller, often overlooked patient populations, thus our early work centered on rare cancers.”
“At first, we partnered with academic groups to bring promising tests to market. Our goal was to in-license, clinically validate and commercialize those tests, then deliver them to the physicians and patients who needed them. We made some great choices – and, admittedly, a few that didn’t have the clinical impact we had hoped and highlighted a reality of oncology: even if a test is accurate, it only matters if it can meaningfully change patient care. That became a guiding principle for us: does this test actually help doctors and patients make better decisions and, subsequently, change their outcomes?”
“Over time, we built our own research programs. One of our first successes was DecisionDx-Melanoma, which has been shown to reduce unnecessary sentinel lymph node biopsy surgeries (commonly used to see if a patient’s melanoma has spread) and has also been associated with measurable impact on survival. Continued evidence backing our DecisionDx-Melanoma test has shown that precision medicine can improve patient outcomes, which is a fantastic outcome for patients and clinicians.”
“We’ve also stayed open to innovation from outside Castle that aligns with our mission. A great example is our acquisition of a small company that developed a spatialomics platform called TissueCypher. The test quantifies protein expression in specific areas of biopsy tissue as well as morphological changes from patients with Barrett’s esophagus, the only known precursor to esophageal adenocarcinoma. The TissueCypher test is designed to identify those patients with Barrett’s esophagus who are at risk of progression to esophageal adenocarcinoma and could benefit from earlier intervention.”
“We’ve also worked hard to develop an R&D engine within Castle that stays focused on real-world questions we can solve, while staying humble enough to recognize we can’t solve them all alone.”
Significant Milestones
What have been some of the company’s most significant milestones? Maetzold cited:
“Castle has come a long way since we began in 2008. Our very first test, DecisionDx-UM, launched in 2009, and it’s now the standard of care for uveal melanoma (UM). Today, about 80% of newly diagnosed UM patients receive that test, which is something we’re really proud of.”
“Another big milestone came in 2019, when we went public on the Nasdaq under the ticker CSTL. That was an important step in financing the expanded access to our tests.”
“In late 2024, we reached an important milestone with TissueCypher, our test for patients with Barrett’s esophagus, surpassing 25,000 reports delivered. TissueCypher is the first spatialomics test designed to predict which patients with Barrett’s esophagus are at risk of progressing to esophageal cancer. By distinguishing between low- and high-risk patients, TissueCypher helps clinicians make more personalized management decisions, whether that means reducing unnecessary procedures for some patients or intervening earlier for others.”
“Our flagship test, DecisionDx-Melanoma, has also been a game-changer for patients with melanoma. It provides personalized insights into how a patient’s melanoma might progress, helping doctors tailor treatment plans. This year, the test surpassed 200,000 orders, a milestone that represents 200,000 opportunities to deliver hope and clarity to patients and clinicians. It also earned Breakthrough Device designation from the FDA, further underscoring its potential to improve melanoma outcomes.”
“Each of these milestones reflects our commitment to advancing precision diagnostics and making a real difference in patient care.”
“And shortly, we are on track to release a non-cancer test, one that we expect will assist dermatologists in selecting which systemic therapy to start on their patients who are diagnosed with moderate-to-severe atopic dermatitis, a disease that affects approximately 24 million U.S. patients.”
Customer Success Stories
Can you share any specific customer success stories? Maetzold highlighted:
“Our customers are essentially the clinicians who order our tests to help guide the care of their patients and the patients themselves. I encourage you to watch a few of our patient stories to learn more about the significant impact that our tests can have on a patient’s care journey and their life.”
Funding/Revenue
Are you able to discuss funding and/or revenue metrics? Maetzold revealed:
“2024 was a strong year for us. We reported revenue of $332 million, which was up 51% from the prior year and ahead of our guidance. We also strengthened our balance sheet, ending the year with $293 million in cash and investments, about $50 million more than in 2023. Operationally, we generated $64.9 million in cash, compared to using cash in the prior year, and we moved from a net loss of $57.5 million in 2023 to a net income of $18.2 million in 2024. On an adjusted EBITDA basis, we delivered $75 million versus a loss in the previous year.”
“This financial performance reflects the strong growth we’re seeing in test adoption. In 2024, we delivered more than 96,000 test reports, a 36% increase from 2023. Our dermatologic tests, including DecisionDx-Melanoma and DecisionDx-SCC, grew 17% year-over-year, and TissueCypher, our test for Barrett’s esophagus, saw 130% growth, compared to 2023.”
“Overall, these results underscore both the demand for our tests and our ability to scale while maintaining strong financial performance.”
Favorite Memory
What has been your favorite memory working for the company so far? Maetzold reflected:
“One of my favorite memories was ringing the bell at Nasdaq when Castle went public. In that moment, I thought back to our early days, when the idea of becoming a public company felt like a distant dream. Standing there with my colleagues, I felt an overwhelming sense of humility and gratitude as that achievement was a direct correlation of the team that we have built at Castle and the impact we were having on patient care. In other words, it wasn’t just about reaching a milestone; it was a celebration of the years of hard work, sacrifice and teamwork that brought us there and set Castle on the path we’re on today.”
Differentiation From The Competition
What differentiates the company from its competition? Maetzold affirmed:
“What sets Castle apart from the competition is our unwavering people-first mindset and strong culture. Over the past 18 years, we’ve grown from just three employees to nearly 800 across Texas, Arizona, Pennsylvania and beyond. That growth has been fueled by a culture that attracts and empowers people who are deeply committed to patient care and driven by innovation.”
“That culture isn’t just something we talk about: it’s been consistently recognized. For the past four years, Castle has been named a Top Workplace USA, an honor based entirely on anonymous employee feedback gathered through our annual employee survey. In our most recent survey in June 2025, 94% of our employees participated, and we scored above industry benchmarks in workplace experience. Regionally, we’ve also earned Top Workplace awards in Arizona and Houston, as well as national recognition for culture excellence in areas like innovation, leadership, purpose and values, compensation and benefits, and work-life flexibility.”
“At the end of the day, our culture is what differentiates us. It’s what allows us to attract and retain incredible people who are passionate about advancing patient care, and that’s the foundation for everything we do as a company.”
Future Company Goals
What are some of the company’s future goals? Maetzold emphasized:
“Looking ahead, our focus is on strong execution and smart capital allocation to ensure we’re set up for success in 2025 and beyond. That includes continuing to evolve our commercial team, advancing focused R&D efforts and pursuing strategic opportunities that complement our current portfolio.”
“On the M&A side, our strategy is about building long-term value. For example, we’ve been expanding our GI franchise, starting with the acquisition of Cernostics in 2021 and most recently with Previse in 2025. Previse brings a strong technology pipeline, including opportunities to apply multiomics to Barrett’s esophagus testing and to develop a non-endoscopic sample collection device that could expand GI screening and diagnostics.”
“We’re also excited about our collaboration with SciBase, which we announced in June 2025. This collaboration centers on using Electrical Impedance Spectroscopy (EIS) to develop a test that can predict flares in patients with atopic dermatitis, a disease that affects approximately 24 million people in the U.S. If successful, this could be a valuable tool for clinicians already using our skin cancer tests.”
“Additionally, as I mentioned earlier, we’re advancing our own pipeline in atopic dermatitis. We’re developing a molecular test to predict treatment response for patients with moderate-to-severe atopic dermatitis who are candidates for systemic therapy, be it an injectable biologic or an oral therapy. Based upon our analysis to date, we believe that our development program has been successful. Specifically, we have identified a genomic signature which has been validated in an independent patient cohort that identifies patients who are likely to have strong relief from their atopic dermatitis symptoms; specifically in their response as measured by three core indexes: first is an improvement in their Eczema Area and Severity Index, or EASI, score, second is improvement in itch symptoms, and third is a reduction in flares. Assuming continued success with our validation assessments, we expect to launch this pipeline test by the end of 2025.”
“Overall, our goal is to keep building a pipeline that addresses real unmet needs while staying true to our mission of improving health through innovative tests that guide patient care.”
