v3.26.1
Summary of Significant Accounting Policies
6 Months Ended
Jun. 30, 2026
Accounting Policies [Abstract]  
Summary of Significant Accounting Policies Summary of Significant Accounting Policies
Basis of Presentation
Our unaudited condensed consolidated financial statements include the accounts of Castle Biosciences, Inc. and our wholly owned subsidiaries and have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”). All intercompany accounts and transactions have been eliminated in consolidation.
We have a history of recurring net losses and negative cash flows and as of June 30, 2026, we had an accumulated deficit of $240.9 million. We believe our $62.1 million of cash and cash equivalents and $204.7 million of marketable investment securities as of June 30, 2026, and anticipated revenue from our test reports, will be sufficient to meet our cash requirements through at least the 12-month period following the date that these unaudited condensed consolidated financial statements were issued.
Unaudited Interim Financial Information
The accompanying condensed consolidated balance sheet as of June 30, 2026; the condensed consolidated statements of operations, the condensed consolidated statements of comprehensive (loss) income and the condensed consolidated statements of stockholders’ equity, each for the three and six months ended June 30, 2026 and 2025; and the condensed consolidated statements of cash flows for the six months ended June 30, 2026 and 2025 are unaudited. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of our consolidated financial position as of June 30, 2026, the results of our consolidated operations for the three and six months ended June 30, 2026 and 2025 and our consolidated cash flows for the six months ended June 30, 2026 and 2025. The financial data and other information disclosed in these notes related to the three and six months ended June 30, 2026 and 2025 are also unaudited. The results for the three and six months ended June 30, 2026 are not necessarily indicative of results to be expected for the year ending December 31, 2026, any other interim periods, or any future year or period. The balance sheet as of December 31, 2025 included herein was derived from the audited financial statements as of that date. Certain disclosures have been condensed or omitted from the unaudited condensed consolidated financial statements. These unaudited condensed consolidated financial statements should be read in conjunction with our audited consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2025 filed with the Securities and Exchange Commission on February 26, 2026.
Use of Estimates
The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Significant items subject to such estimates include revenue recognition, the valuation of stock-based compensation, assessing future tax exposure and the realizability of deferred tax assets, the useful lives and recoverability of long-lived assets, the goodwill impairment test, the valuation of acquired intangible assets, the valuation of contingent consideration, and other contingent liabilities. We base these estimates on historical and anticipated results, trends, and various other assumptions that we believe are reasonable under the circumstances, including assumptions as to future events. These estimates form the basis for making judgments about the carrying values of assets and liabilities and recorded revenues and expenses that are not readily apparent from other sources. Actual results could differ from those estimates and assumptions.
Cash and Cash Equivalents including Concentrations of Credit Risk
Cash equivalents consist of short-term, highly liquid investments with original maturities of three months or less. Our cash equivalents consist of money market funds, which are not insured by the Federal Deposit Insurance Corporation (“FDIC”), that are primarily invested in short-term United States (“U.S.”) government obligations. Cash deposits at financial institutions may exceed the amount of insurance provided by the FDIC. Management believes that we are not exposed to significant credit risk on our cash deposits due to the financial position of the financial institutions in which deposits are held.
Marketable Investment Securities
Our marketable investment securities are comprised of debt and equity securities. All debt securities are recognized in accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 320, Investments-Debt Securities (“ASC 320”). Management determines the appropriate classification of debt securities at the time of purchase and re-evaluates such determination at each balance sheet date. Debt securities that are classified as available-for-sale (“AFS”) are recorded at fair value in accordance with ASC 320. We recognize the unrealized gains and losses related to changes in fair value as a separate component of accumulated other comprehensive income within total stockholders’ equity, net of any related deferred income tax effects, on the condensed consolidated balance sheets. Debt securities that are classified as held-to-maturity (“HTM”) are reported at amortized cost in accordance with ASC 320. Premiums or discounts from par value are amortized to interest income over the life of the underlying investment and are included in interest income in the condensed consolidated statements of operations. Realized gains and losses on AFS and HTM debt securities, if any, are calculated at the individual security level and included in interest income in the condensed consolidated statements of operations. Impairments of AFS or HTM debt securities, if any, are recorded in the condensed consolidated statements of operations. See Notes 5 and 11 for further details.
Our equity securities consist of investments in shares of common stock which are listed and traded on the Nasdaq Global Market and certain foreign exchanges. All equity securities are recognized in accordance with ASC Topic 321, Investments-Equity Securities (“ASC 321”) and reported at their readily determinable fair values based on quoted market prices where changes in fair value are included in net gains (losses) on equity securities in the condensed consolidated statements of operations. For investments denominated in a foreign currency, the fair value is remeasured into U.S. dollars using exchange rates in effect at each balance sheet date in accordance with ASC Topic 830, Foreign Currency Matters (“ASC 830”). As a result, changes in fair value include the effects of both market price movements and foreign currency exchange rate fluctuations. All changes in a marketable security’s fair value are reported in earnings as they occur, and the sale of our equity securities does not necessarily give rise to a significant gain or loss. Investments in equity securities are classified as either current or long-term depending upon management’s intentions. We updated our terminology to refer to these investments as equity securities rather than trading securities to align with the terminology in ASC 321. See Notes 5 and 11 for further details.
Contingent Consideration
Under the terms of business combinations or asset acquisitions, we may be required to pay additional consideration if specified future events occur or certain conditions are met. In May 2025, we acquired Capsulomics, Inc., d/b/a Previse (“Previse”), which was recorded as an asset acquisition, and agreed to pay additional consideration of up to $2.5 million in cash based on the achievement of certain commercial milestones (the “Earnout Payments”). We account for the contingent consideration as a liability in accordance with ASC 450-20, Loss Contingencies (“ASC 450-20”) when it is both probable and reasonably estimable. In accordance with ASC 450-20, we recorded the contingent consideration at the amount required to settle the respective obligation, and subsequent changes are recognized as adjustments to the cost basis of the acquired assets. These changes are allocated to the acquired assets based on their relative fair values as of the date of acquisition. During the six months ended June 30, 2026, we made aggregate Earnout Payments of $1.0 million upon the achievement of certain commercial milestones.
Contingent consideration is classified as current in the condensed consolidated balance sheets based on the contractual timing of future settlement.
Revenue Recognition
In accordance with ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”), we follow a five-step process to recognize revenues: (1) identify the contract with the customer, (2) identify the performance obligations, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations and (5) recognize revenues when the performance obligations are satisfied. We have determined that we have a contract with the patient when the treating clinician orders the test. Our contracts generally contain a single performance obligation, which is the delivery of the test report, and we satisfy our performance obligation at a point in time upon the delivery of the test report to the treating clinician, at which point we can bill for the report. The amount of revenue recognized reflects the amount of consideration to which we expect to be entitled, or the transaction price, and considers the effects of variable consideration. See Note 3 for further details.
Collaborative Arrangements
We assess whether our licensing and other agreements are collaborative arrangements based on whether they involve joint operating activities and whether both parties have active participation in the arrangement and are exposed to significant risks and rewards. For arrangements that we determine are collaborations, we identify each unit of account and then determine whether a customer relationship exists for that unit of account. If we determine that a performance obligation within the collaborative arrangement is with a customer, we apply ASC 606.
If a portion of a distinct bundle of goods or services within the collaborative arrangement is not with a customer, we apply recognition and measurement based on an analogy to authoritative accounting literature or, if there is no appropriate analogy, a reasonable, rational, and consistently applied accounting policy election. To the extent the arrangement is within the scope of ASC Topic 808, Collaborative Arrangements (“ASC 808”), we assess whether aspects of the arrangement are within the scope of other accounting literature.
In June 2025, we entered into a Collaboration and License Agreement with SciBase Holding AB (“SciBase”). Following approval under the Swedish Screening of Foreign Direct Investments Act in the third quarter of 2025, we completed our investment in SciBase. The agreement aims to jointly develop products for dermatologic diseases, initially focused on atopic dermatitis, by combining SciBase’s Electrical Impedance Spectroscopy technology with our diagnostic and development expertise. Under the arrangement, we hold development and commercialization rights in North America, while SciBase retains rights in certain other territories. SciBase is entitled to royalties on our product sales, a mark-up on product sales to us, and a milestone payment upon achieving specified sales thresholds. Development costs are shared; however, SciBase deferred its initial clinical development costs for the initial indication and we will recover those costs through future royalty payments reductions.
We determined the agreement is a collaborative arrangement under ASC 808. Certain elements of the arrangement, including license rights and sales-based royalty provisions, represent transactions with a customer and are therefore accounted for under ASC 606. Other elements, such as shared development activities and cost reimbursements, are accounted for in accordance with ASC 808 and presented as reductions to research and development (“R&D”) expenses.
Accounts Receivable and Allowance for Credit Losses
We classify accounts receivable balances that are expected to be paid more than one year from the condensed consolidated balance sheet date as noncurrent assets. The estimated timing of payment utilized as a basis for classification as noncurrent is determined by analyses of historical payor-specific payment experience, adjusted for known factors that are expected to change the timing of future payments.
We accrue an allowance for credit losses against our accounts receivable based on management’s current estimate of amounts that will not be collected. We have elected the practical expedient under ASC Topic 326, Financial Instruments - Credit Losses (“ASC 326”) to assume that current conditions as of the balance sheet date do not change for the remaining life of our accounts receivable. Accordingly, management’s estimates are based on historical loss information adjusted for current conditions. We generally do not perform evaluations of customers’ financial condition and generally do not require collateral. Historically, our credit losses have not been significant. The allowance for credit losses was zero as of June 30, 2026 and December 31, 2025. Adjustments for implicit price concessions attributable to variable consideration, as discussed below, are incorporated into the measurement of the accounts receivable balances and are not part of the allowance for credit losses.
Convertible Loan Receivable
On November 7, 2025, we entered into a Convertible Loan Agreement with SciBase (the “Convertible Loan Receivable”), pursuant to which we loaned SEK 20.0 million, approximately $2.1 million based on the exchange rate in effect on November 7, 2025. The Convertible Loan Receivable bears interest at a rate of 2.00% plus the three-month Stockholm Interbank Offered Rate (“STIBOR”), payable quarterly. SciBase may prepay all or a portion of the Convertible Loan Receivable at any time. The Convertible Loan Receivable matures on November 7, 2030, at which time we have the option, at our sole discretion, to convert the outstanding principal plus accrued interest into shares of SciBase that are listed on the Nasdaq First North Growth Market in Sweden, receive full repayment in cash, or receive a combination of cash and shares.
We accounted for the convertible loan as a receivable within the scope of ASC Topic 310, Receivables. The carrying amount of the convertible loan is presented at amortized cost, within other assets - long-term in the condensed consolidated balance sheets. The Convertible Loan Agreement is remeasured into U.S. dollars using exchange rates in effect at each balance sheet date in accordance with ASC 830 with changes in exchange rates recognized in earnings. In addition, the embedded conversion feature to shares of SciBase did not meet the definition of a derivative and was not bifurcated from the host contract under ASC Topic 815, Derivatives and Hedging. We have determined that expected credit losses associated with the loan are insignificant and, accordingly, have not recorded a credit loss allowance under ASC Topic 326-20, Financial Instruments - Credit Losses.
Interest income on the Convertible Loan Receivable is recognized quarterly and included in interest income in the condensed consolidated statements of operations. Accrued interest receivable is recorded within prepaid expenses and other current assets in the condensed consolidated balance sheets.
Property and Equipment
Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the related assets, generally ranging from 5 to 39 years. Leasehold improvements are amortized on a straight-line basis over the shorter of the estimated useful life of the asset or the term of the lease. Leasehold improvements primarily relate to office and laboratory facilities in Phoenix, Arizona and Pittsburgh, Pennsylvania, and are generally depreciated over the remaining lease terms, which expire in 2034 and 2033, respectively.
Maintenance and repairs are expensed as incurred, and material improvements are capitalized. Interest costs incurred during the construction of major capital projects are capitalized until the underlying asset is ready for its intended use, at which point the capitalized interest costs are amortized using the straight-line method over the estimated useful life of the underlying asset. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the condensed consolidated balance sheets and any resulting gain or loss is reflected in the condensed consolidated statements of operations in the period realized.
Goodwill
Goodwill represents the excess of the purchase price over the fair value of the net tangible and intangible assets acquired in a business combination. Goodwill is not amortized, but is tested for impairment. We test goodwill for impairment in the fourth quarter of each fiscal year and when events, or changes in circumstances, indicate that it may be impaired. Events and changes in circumstances indicating that goodwill may be impaired include sustained declines in the price of our common stock, increased competition, changes in macroeconomic developments, unfavorable government or regulatory developments and changes in coverage or reimbursement conditions.
Goodwill is tested for impairment at the reporting unit level where goodwill is held. Testing begins with completion of an optional qualitative assessment. If the qualitative assessment suggests that impairment is more likely than not, quantitative testing is conducted. If the qualitative assessment is bypassed, we proceed directly to quantitative testing. Quantitative testing consists of comparing the carrying value of goodwill to its estimated fair value. Impairment of goodwill is the condition that exists when the carrying value exceeds its fair value. Amounts by which carrying value exceed fair value, up to the total amount of goodwill allocated to the reporting unit, are recognized as an impairment loss in the condensed consolidated statements of operations.
Accrued Compensation
We accrue for liabilities under discretionary employee and executive bonus plans. Our estimated compensation liabilities are based on progress against corporate objectives approved by our board of directors, compensation levels of eligible individuals and target bonus percentage levels. Our board of directors reviews and evaluates the performance against these objectives and ultimately determines the actual achievement levels attained. We also accrue for liabilities under employee sales incentive bonus plans with accruals based on performance achieved to date compared to established targets. As of June 30, 2026 and December 31, 2025, we accrued approximately $17.4 million and $28.1 million, respectively, for liabilities associated with these bonus plans. These amounts are classified as current accrued liabilities in the condensed consolidated balance sheets based on the expected timing of payment.
Stock-Based Compensation
Stock-based compensation expense for equity instruments is measured based on the grant-date fair value of the awards. For stock option awards, and purchase rights made under the 2019 Employee Stock Purchase Plan (the “ESPP”), the fair value is estimated on the date of grant using the Black-Scholes option-pricing valuation model. For restricted stock units (“RSUs”) and performance-based restricted stock units (“PSUs”), the fair value is equal to the closing price of our common stock on the date of grant. For awards with graded vesting and only service conditions, we recognize compensation costs on a straight-line basis over the requisite service period of the awards. For stock options and RSUs, the requisite service period is generally the award’s vesting period (typically four years). PSUs vest upon the achievement of certain performance conditions and the provision of service with us through a specified period. Accruals of compensation cost for PSUs are based on the probable outcome of the performance conditions and are reassessed each reporting period. We recognize compensation cost for PSUs separately for each vesting tranche on a ratable basis over the requisite service period. The requisite service period for PSUs is based on an analysis of vesting requirements and performance conditions for the particular award. Certain employees are entitled to acceleration of vesting of a portion of their awards upon retirement, subject to age, service and notice requirements (“Retirement Policy”). Stock-based awards falling into the scope of the Retirement Policy are accounted for as a modification of existing awards under ASC Topic 718, Compensation – Stock Compensation. The modifications do not result in the recognition of incremental compensation cost; however, they do result in a new estimate of the requisite service period, which we reassess at each balance sheet date. For the ESPP, the requisite service period is generally the period of time from the offering date to the purchase date. Forfeitures are accounted for as they occur.
Comprehensive (Loss) Income
Comprehensive (loss) income is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources. Comprehensive (loss) income is made up of net (loss) income plus net unrealized (loss) on marketable investment securities, which is our only other item of other comprehensive (loss) income.
Recently Adopted Accounting Pronouncements
In July 2025, the FASB issued ASU No. 2025-05, Financial Instruments—Credit Losses (Topic 326): Practical Expedient for Certain Current Receivables (“ASU 2025-05”), which provides a practical expedient for estimating expected credit losses on current accounts receivable and contract assets arising from transactions under ASC 606. The practical expedient allows entities to assume that current conditions remain unchanged over the remaining life of the receivables. ASU 2025-05 is effective for annual periods beginning after December 15, 2025, including interim periods within those annual periods. We adopted the standard effective January 1, 2026, with no impact on our consolidated financial statements.
Accounting Pronouncements Yet to be Adopted
In November 2024, the FASB issued ASU No. 2024-03, Income Statement—Reporting Comprehensive Income (Subtopic 220-40)—Expense Disaggregation Disclosures: Disaggregation of Income Statement Expenses (“ASU 2024-03”), which specifies additional disclosure requirements. The amendments in ASU 2024-03 require disclosure about the composition of certain income expense line items, such as purchases of inventory, employee compensation, and other expenses, as well as disclosure about selling expenses. The ASU is effective for fiscal years beginning after December 15, 2026, and interim periods beginning after December 15, 2027. Early adoption is permitted. We are currently evaluating the impact this update will have on the consolidated financial statements and disclosures.
In September 2025, the FASB issued ASU No. 2025-06, Intangibles—Goodwill and Other-Internal-Use Software (Subtopic 350-40): Targeted Improvements to the Accounting for Internal-Use Software (“ASU 2025-06”), which modernizes the accounting for internal-use software costs. The amendments in ASU 2025-06 remove all references to prescriptive and sequential software development stages throughout ASC 350-40. The ASU is effective for annual periods beginning after December 15, 2027, including interim periods within those annual periods. Early adoption is permitted. We are currently evaluating the impact this update will have on the consolidated financial statements and disclosures.
We have evaluated all other recently issued, but not yet effective, accounting pronouncements and do not believe that these accounting pronouncements will have any material impact on the consolidated financial statements or disclosures upon adoption.