Our primary focus at Castle Biosciences is on developing and offering biomarker based cancer diagnostic assays that support the physician in making better treatment decisions for their patients with orphan cancers.

We are pursuing this mission by focusing on proprietary molecular diagnostic assays (or tests) that assist oncologists in individual risk-stratification. We have branded our tests as 'DecisionDx-...' because we believe that the results, as part a comprehensive baseline evaluation, will enable more personalized treatment plan decisions to be made by physicians. Our aim is to bring the promise of personalized medicine to those individuals afflicted with orphan cancers.

Two laboratory elements are important to the comprehensive baseline evaluation of an individual:

• Accurate diagnosis, and
• Risk stratification

While risk stratification tools have been / are being developed for common cancers, a gap exists in the orphan cancer area. By working with leading academic institutions, we hope to identify, develop, and offer laboratory tests to oncologists that will effectively close that gap.

We achieve our mission through both in-licensing appropriate assays as well as supporting the development of our current assays such that they better meet the needs of patients and their physicians.

The following template when evaluating license opportunities:

Biomarker based molecular diagnostic assays that...
Impact comprehensive baseline evaluation	Meet orphan cancer benefits	We can conduct
-  Change or impact treatment planning decisions,     may include changes in surveillance frequency as     well as treatment decisions;  -  Multiple treatment options available now, or shortly  -  Good 2nd line treatments, but with risk/benefit     concerns  -  Aggressive cancers	-  Benefit <40,000 patients per year  -  Concentrated physician base     (= 50% of patients treated directly or     influenced by top 125 cancer centers)  -  1st to market opportunity  -  Clear intellectual property	-  Transferable and performable with     limited capital equipment investment

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Development efforts for DecisionDx-GBM

The DecisionDx-GBM assay was discovered at The University of Texas M. D. Anderson Cancer Center for risk stratification of glioblastoma multiforme (also known as grade 4 anaplastic astrocytoma).

The assay has been fully validated.

The RTOG-0825 study is a two-arm, multi-center cooperative group study evaluating the first line use of bevacizumab (Avastin®, Genentech / Roche) with radiation plus temozolomide compared to radiation plus temozolomide. The DecisionDx-GBM molecular signature is one of two stratification factors used in this study. The study was initiated in April, 2009.

The RTOG-0525 study is a two-arm, multi-center cooperative group study evaluating two different dosing regimens of first line temozolomide. The DecisionDx-GBM molecular signature is being analyzed.

The DecisionDx-GBM assay is also being incorporated into a number of other prospective studies.

Development efforts for DecisionDx-UM

The DecisionDx-UM was discovered at Washington University in St Louis in the laboratory of Dr. J. William Harbour.

The assay has been fully validated in uveal melanoma. The DecisionDx-UM is also the subject of an ongoing, NEI sponsored study.

Preliminary data suggests that this assay may have application in other melanoma cancers.

Development efforts for DecisionDx-LEA

The DecisionDx-LEA assay was discovered at The University of Texas M. D. Anderson Cancer Center for risk stratification of localized esophageal adenocarcinoma. This multi-protein expression assay is being developed to predict responsiveness to first line, pre-surgical radiation with adjunctive chemotherapy treatment.

The aim of this assay is to prospectively stratify patients into one of three groups:
- Patients whose tumor may exhibit a complete pathologic response to neoadjuvant radiation and chemotherapy (approximately 25% of patients tested), thereby impacting the decision to proceed to surgery;
- Patients whose tumor may exhibit non-responsiveness or refractoriness to neoadjuvant radiation and chemotherapy (approximately 25% of patients tested), thereby impacting the decision to order neoadjuvant treatment prior to surgical resection; and
- Patients who cannot be stratified into one of the two above groups in which case proceeding with the standard of care neoadjuvant therapy and surgical resection.

The initial validation study demonstrated high sensitivity and specificity for detection of both the complete pathologic response group and the non-responsive group.

The final validation study (n>200) is the focus of an ongoing NIH-sponsored study with data analysis complete during 1H2010.

Preliminary data suggests that this assay may have application in other non-esophageal adenocarcinomas.

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