Summary of Significant Accounting Policies | 2. Basis of Presentation The accompanying consolidated financial statements for the years ended December 31, 2020 and 2019, have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) and Generally Accepted Accounting Principles in the United States (“U.S. GAAP”) for financial information, which prescribes elimination of all significant intercompany accounts and transactions in the accounts of the Company and its wholly owned subsidiary, Cue Biopharma Securities Corporation, Inc., which was incorporated in the Commonwealth of Massachusetts in December 2018. Public Offerings In June 2019, the Company entered into an “at-the-market” (“ATM”) equity offering sales agreement (the “June 2019 ATM Agreement”) with Stifel Nicolaus & Company, Inc. (“Stifel”) to sell shares of the Company’s common stock for aggregate gross proceeds of up to $30 million, from time to time, through an ATM equity offering program under which Stifel acted as sales agent. As of December 31, 2020, the Company had sold 3,584,945 shares of common stock under the June 2019 ATM Agreement for proceeds of approximately $29.4 million, net of commissions paid, but excluding transaction expenses, and terminated this equity offering upon completion. In November 2019, the Company entered into an ATM equity offering sales agreement with Stifel (the “November 2019 ATM Agreement”) to sell shares of the Company’s common stock for aggregate gross proceeds of up to $20 million, from time to time, through an ATM equity offering program under which Stifel acted as sales agent. As of December 31, 2020, the Company had sold 1,729,110 common shares under the November 2019 ATM Agreement for proceeds of approximately $19.6 million, net of commissions paid, but excluding estimated transaction expenses, and terminated this equity offering upon completion. In March 2020, the Company entered into an ATM equity offering sales agreement with Stifel (the “March 2020 ATM Agreement”) to sell shares of the Company’s common stock for aggregate gross proceeds of up to $ 35 million, from time to time, through an ATM equity offering program under which Stifel would act as sales agent. As of December 31, 2020, the Company had sold a total of 1,824,901 shares of common stock under the March 2020 ATM Agreement for proceeds of approximately $ 34.3 million, net of commissions paid, but excluding estimated transaction expenses. Due to the issuance and sale of all the shares of common stock subject thereto, the March 2020 ATM Agreement terminated in accordance with its terms . In June 2020, the Company entered into an ATM equity offering sales agreement with Stifel (the “June 2020 ATM Agreement”) to sell shares of the Company’s common stock for aggregate gross proceeds of up to $40 million, from time to time, through an ATM equity offering program under which Stifel acts as sales agent. The June 2020 ATM Agreement will terminate upon the earliest of (a) the sale of $40 million of shares of the Company’s common stock or (b) the termination of the June 2020 ATM Agreement by the Company or Stifel. As of December 31, 2020, the Company had sold 1,192,000 shares of common stock under the June 2020 ATM Agreement for proceeds of approximately $22.4 million, net of commissions paid, but excluding estimated transaction expenses. Consolidation The accompanying consolidated financial statements include the Company and its wholly owned subsidiary, Cue Biopharma Securities Corporation, Inc. The Company has eliminated all intercompany transactions for the years presented. Reclassifications Certain prior year amounts have been reclassified for consistency with the current year presentation. These reclassifications had no effect on the reported results of operations. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Significant estimates include estimates related to revenue, the accounting for potential liabilities and accrued expenses, the assumptions utilized in valuing stock-based compensation issued for services, the realization of deferred tax assets, and the useful life with respect to long-lived assets and intangibles. Actual results could differ from those estimates. Cash Concentrations The Company maintains its cash balances with a financial institution in Federally-insured accounts and may periodically have cash balances in excess of insurance limits. The Company maintains its accounts with a financial institution with a high credit rating. The Company has not experienced any losses to date and believes that it is not exposed to any significant credit risk on cash. Cash and Cash Equivalents The Company considers all liquid investments with a maturity of three months or less at the date of purchase to be cash equivalents. The Company currently invests available cash in money market funds. Marketable Securities Marketable securities consist of investments with original maturities greater than ninety days and less than one year from the balance sheet date. The Company classifies all of its investments as available-for-sale securities. Accordingly, these investments are recorded at fair value, which is based on quoted market prices. Unrealized gains are recognized and are included in other comprehensive income (loss). Realized gains are recognized and determined on a specific identification basis and are included in other income (loss) on the income statement. Amortization and accretion of discounts and premiums is recorded in interest income. The Company currently invests in United States Treasury obligations. Restricted Cash The Company purchased a $150,000 certificate of deposit to collateralize a credit card account with a commercial bank that was classified as short-term certificate of deposit as of December 31, 2020. Property and Equipment Property and equipment is recorded at cost. Major improvements are capitalized, while maintenance and repairs are charged to expense as incurred. Gains and losses from disposition of property and equipment are included in income and expense when realized. Amortization of leasehold improvements is provided using the straight-line method over the shorter of the lease term or the useful life of the underlying assets. Depreciation of property and equipment is provided using the straight-line method over the following estimated useful lives: Laboratory equipment 5 years Computer equipment 3 years Furniture and fixtures 3-8 years The Company recognizes depreciation and amortization expense in general and administrative expenses and in research and development expenses in the Company’s consolidated statements of operations and comprehensive loss, depending on how each category of property and equipment is utilized in the Company’s business activities. Trademark Trademark consists of the Company’s right, title and interest in and to the CUE BIOLOGICS Mark, and any derivative mark incorporating CUE, throughout the world, together with all associated goodwill and common law rights appurtenant thereto, including, but not limited to, any right, title and interest in any corporate name, company name, business name, trade name, dba, domain name, or other source identifier incorporating CUE. As the Company can renew the underlying rights to the CUE BIOLOGICS Mark indefinitely at nominal cost, this acquired intangible asset has been classified as a component of other long term assets, having a useful life of 15 years. The Company recorded $11,666 and $11,667 in amortization related to the trademark at December 31, 2020 and 2019, respectively. Revenue Recognition The Company follows the provisions of Accounting Standards Codification 606, Revenue from Contracts with Customers (“ASC 606”). The Company recognizes collaboration revenue under certain of the Company’s license or collaboration agreements that are within the scope of ASC 606. The Company’s contracts with customers typically include promises related to licenses to intellectual property and research and development services. If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenue from non-refundable, up-front fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgement to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. Accordingly, the transaction price is generally comprised of a fixed fee due at contract inception and variable consideration in the form of milestone payments due upon the achievement of specified events and tiered royalties earned when customers recognize net sales of licensed products. The Company measures the transaction price based on the amount of consideration to which it expects to be entitled in exchange for transferring the promised goods and/or services to the customer. The Company utilizes the “most likely amount” method to estimate the amount of variable consideration, to predict the amount of consideration to which it will be entitled for its one open contract. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. At the inception of each arrangement that includes development and regulatory milestone payments, the Company evaluates whether the associated event is considered probable of achievement and estimates the amount to be included in the transaction price using the most likely amount method. Currently, the Company has one contract with an option to acquire additional goods and/or services in the form of additional research and development services for additional drug product candidates which it evaluated and determined that it was not a material right related to the LG Chem agreement . Research and Development Expenses Research and development expenses consist primarily of compensation costs, fees paid to consultants, outside service providers and organizations (including research institutes at universities), facility costs, and development and clinical trial costs with respect to the Company’s drug product candidates. Research and development expenses incurred under contracts are expensed ratably over the life of the underlying contracts, unless the achievement of milestones, the completion of contracted work, or other information indicates that a different pattern of performance is more appropriate. Other research and development expenses are charged to operations as incurred. Nonrefundable advance payments are recognized as an expense as the related services are performed. The Company evaluates whether it expects the services to be rendered at each quarter end and year end reporting date. If the Company does not expect the services to be rendered, the advance payment is charged to expense. Nonrefundable advance payments for research and development services are included in prepaid and other current assets on the balance sheet. To the extent that a nonrefundable advance payment is for contracted services to be performed within 12 months from the reporting date, such advance is included in current assets; otherwise, such advance is included in non-current assets. The Company evaluates the status of its research and development agreements and contracts, and the carrying amount of the related assets and liabilities, at each quarter end and year end reporting date, and adjusts the carrying amounts and their classification on the balance sheet as appropriate. Patent Expenses The Company is the exclusive worldwide licensee of, and has patent applications pending for, numerous domestic and foreign patents. Due to the significant uncertainty associated with the successful development of one or more commercially viable drug product candidates based on the Company’s research efforts and any related patent applications, all patent costs, including patent-related legal fees, filing fees and other costs are charged to operations as incurred. For the years ended December 31, 2020 and 2019, patent expenses were $1,879,000 and $1,934,000, respectively. Patent expenses are included in general and administrative expenses in the Company’s consolidated statements of operations and comprehensive loss. Licensing Fees and Costs Licensing fees and costs consist primarily of costs relating to the acquisition of the Company’s license agreement with Einstein, including related royalties, maintenance fees, milestone payments and product development costs. Licensing fees and costs are charged to operations as incurred. Long-Lived Assets The Company reviews long-lived assets, consisting of property and equipment and a trademark, for impairment at each fiscal year end or when events or changes in circumstances indicate the carrying value of these assets may exceed their current fair values. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, an impairment charge is recognized for the amount by which the carrying amount of the asset exceeds the fair value of the assets. Assets to be disposed of are separately presented in the balance sheet and reported at the lower of the carrying amount or fair value less costs to sell, and are no longer depreciated. The Company has not historically recorded any impairment to its long-lived assets. In the future, if events or market conditions affect the estimated fair value to the extent that a long-lived asset is impaired, the Company will adjust the carrying value of these long-lived assets in the period in which the impairment occurs. During the year ended December 31, 2019, the Company sold lab equipment with a net book value of approximately $181,000 that was being decommissioned and recognized a loss of approximately $54,000. There were no sales of lab equipment or capital equipment during the year ended December 31, 2020. Leases In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) 2016-02, Leases (ASC 842) (“ASU-2016-02”), which supersedes the existing guidance for lease accounting, Leases (ASC 840). ASU 2016-02 requires a lessee to record a right-of-use asset and a corresponding lease liability, for most lease arrangements on the balance sheet. Under the standard, disclosure of key information about leasing arrangements to assist users of the financial statements to assess the amount, timing and uncertainty of cash flows arising from leases are required. The standard is effective for fiscal years beginning after December 15, 2018. The adoption of ASC 842 on January 1, 2019 resulted in the recognition of approximately $9,692,000 of right-of-use asset and $9,347,000 of lease liabilities on the Company’s balance sheet. The adoption did not have a material net impact on the Company’s consolidated statements of operations or accumulated deficit. Please refer to Note 14 for more detail. Stock-Based Compensation The Company periodically issues stock-based awards to officers, directors, employees, Scientific and Clinical Advisory Board members, non-employees and consultants for services rendered. Such issuances vest and expire according to terms established at the issuance date. Stock-based payments to officers, directors, members of the Company’s Scientific and Clinical Advisory Board, non-employees and outside consultants and employees, including grants of employee stock options, are recognized in the financial statements based on their grant date fair values. Stock option grants, which are generally time-vested, are measured at the grant date fair value and charged to operations on a straight-line basis over the service period, which generally approximates the vesting term. The Company also grants performance-based awards periodically to officers of the Company. The Company recognizes compensation costs related to performance awards over the requisite service period if and when the Company concludes that it is probable that the performance condition will be achieved. The fair value of stock options and restricted stock units is determined utilizing the Black-Scholes option-pricing model, which is affected by several variables, including the risk-free interest rate, the expected dividend yield, the life of the equity award, the exercise price of the stock option as compared to the fair value of the common stock on the grant date, and the estimated volatility of the common stock over the term of the equity award. T he risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant. Until the Company has established a trading history for its common stock that approximates the expected term of the options, estimated volatility is based on the average historical volatilities of comparable public companies in a similar industry. The expected dividend yield is based on the current yield at the grant date; the Company has never declared or paid dividends and has no plans to do so for the foreseeable future. As permitted by Staff Accounting Bulletin No. 107, due to the Company’s limited trading history and option activity, management utilizes the simplified method to estimate the expected term of options at the date of grant. The exercise price is determined based on the fair value of the Company’s common stock at the date of grant. The Company accounts for forfeitures as they occur. The Company recognizes the fair value of stock-based compensation in general and administrative expenses and in research and development expenses in the Company’s statements of operations, depending on the type of services provided by the recipient of the equity award. Income Taxes The Company accounts for income taxes under an asset and liability approach for financial accounting and reporting for income taxes. Accordingly, the Company recognizes deferred tax assets and liabilities for the expected impact of differences between the financial statements and the tax basis of assets and liabilities. The Company accounts for uncertainties in income tax law under a comprehensive model for the financial statement recognition, measurement, presentation and disclosure of uncertain tax positions taken or expected to be taken in income tax returns as prescribed by U.S. GAAP. The tax effects of a position are recognized only if it is “more-likely-than-not” to be sustained by the taxing authority as of the reporting date. If the tax position is not considered “more-likely-than-not” to be sustained, then no benefits of the position are recognized. The Company records a valuation allowance to reduce its deferred tax assets to the amount that is more likely than not to be realized. In the event the Company was to determine that it would be able to realize its deferred tax assets in the future in excess of its recorded amount, an adjustment to the deferred tax assets would be credited to operations in the period such determination was made. Likewise, should the Company determine that it would not be able to realize all or part of its deferred tax assets in the future, an adjustment to the deferred tax assets would be charged to operations in the period such determination was made. The Company is subject to U.S. federal and Massachusetts state income taxes. As the Company’s net operating losses have yet to be utilized, all previous tax years remain open to examination by federal and state taxing authorities in which the Company currently operates. The Company recognized approximately, $206,250 and $412,500 of income tax expense related to the foreign taxes withheld from an upfront payment received from LG Chem, Ltd. (“LG Chem”) pursuant to a collaboration agreement with LG Chem (the “LG Chem Agreement”) during the year ended December 31, 2020 and 2019, respectively. The Company recognizes interest accrued relative to unrecognized tax benefits in interest expense and penalties in operating expense. During the years ended December 31, 2020 and 2019, the Company did not recognize any income tax related interest and penalties. The Company did not have any accruals for income tax related interest and penalties at December 31, 2020 and 2019. Comprehensive Income (Loss) Components of comprehensive income or loss, including net income or loss, are reported in the financial statements in the period in which they are recognized. Other comprehensive income or loss is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources. Net income (loss) and other comprehensive income (loss) are reported net of any related tax effect to arrive at comprehensive income (loss). Comprehensive loss includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders. The Company’s only element of other comprehensive loss in all periods presented, other than its net loss, was unrealized gains and losses on available-for-sale securities. Earnings (Loss) Per Share The Company’s computation of earnings (loss) per share (“EPS”) for the respective periods includes basic and diluted EPS. Basic EPS is measured as the income (loss) attributable to common stockholders divided by the weighted average number of common shares outstanding for the period. Diluted EPS is similar to basic EPS but presents the dilutive effect on a per share basis of potential common shares that would result from the exercise of outstanding stock options and warrants as if they had been exercised at the beginning of the periods presented, or issuance date, if later. Potential common shares that have an anti-dilutive effect (i.e., those that increase income per share or decrease loss per share) are excluded from the calculation of diluted EPS. Basic and diluted loss per common share is the same for all periods presented because all outstanding stock options and warrants are anti-dilutive. At December 31, 2020 and 2019, the Company excluded the outstanding securities summarized below, which entitle the holders thereof to acquire shares of common stock, from its calculation of earnings per share, as their effect would have been anti-dilutive. December 31, 2020 2019 Common stock warrants 861,969 1,189,827 Common stock options 5,030,899 4,793,253 Nonvested restricted stock units 230,002 66,667 Total 6,122,870 6,049,747 Fair Value of Financial Instruments The authoritative guidance with respect to fair value established a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value into three levels and requires that assets and liabilities carried at fair value be classified and disclosed in one of three categories, as presented below. Level 1. Observable inputs such as quoted prices in active markets for an identical asset or liability that the Company has the ability to access as of the measurement date. Financial assets and liabilities utilizing Level 1 inputs include active-exchange traded securities and exchange-based derivatives. Level 2. Inputs, other than quoted prices included within Level 1, which are directly observable for the asset or liability or indirectly observable through corroboration with observable market data. Financial assets and liabilities utilizing Level 2 inputs include fixed income securities, non-exchange based derivatives, mutual funds, and fair-value hedges. Level 3. Unobservable inputs in which there is little or no market data for the asset or liability which requires the reporting entity to develop its own assumptions. Financial assets and liabilities utilizing Level 3 inputs include infrequently-traded non-exchange-based derivatives and commingled investment funds and are measured using present value pricing models. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company has determined that its financial assets are currently classified within Level 1 and that its financial liabilities are currently all classified within Level 3 in the fair value hierarchy. In determining the appropriate levels, the Company performs an analysis of the assets and liabilities at each reporting period end. The Company had $72,943,275 in cash equivalents and $10,002,550 in short-term marketable securities that were measured and recorded at fair value on the Company’s balance sheet at December 31, 2020. The Company had $39,303,609 in cash equivalents and $15,119,925 in short-term marketable securities that were measured and recorded at fair value on the Company’s balance sheet at December 31, 2019. The carrying value of financial instruments (consisting of cash, a certificate of deposit, accounts payable, accrued compensation and accrued expenses) is considered to be representative of their respective fair values due to the short-term nature of those instruments. Recent Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments- Credit Losses: Measurement of Credit Losses on Financial Instruments (ASC 326) (CECL). The standard requires entities to measure all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions and reasonable and supportable forecasts. The standard is effective for annual reporting periods beginning after December 15, 2022, including interim reporting periods within each annual reporting period, for smaller reporting companies. T he Company is still evaluating the impact of ASU 2016-13 on the Company’s consolidated financial statements, if any. In December 2019, the FASB issued ASU No. 2019-12, “ Income Taxes (ASC 740): Simplifying the Accounting for Income Taxes Management does not believe that any other recently issued, but not yet effective, authoritative guidance, if currently adopted, would have a material impact on the Company’s financial statement presentation or disclosures. |