Atara Biotherapeutics, Inc. 10-K

Item 8. Financial Statements and Supplementary Data Index to Consolidated Financial Statements Page Report of Independent Registered Public Accounting Firm (PCAOB ID 34 ) 86 Consolidated Balance Sheets 89 Consolidated Statements of Operations and Comprehensive Loss 90 Consolidated Statements of Stockholders’ Equity 91 Consolidated Statements of Cash Flows 92 Notes to Consolidated Financial Statements 93 85 Report of Independent Registered Public Accounting Firm To the stockholders and the Board of Directors of Atara Biotherapeutics, Inc. Opinion on the Financial Statements We have audited the accompanying consolidated balance sheets of Atara Biotherapeutics, Inc. and subsidiaries (the "Company") as of December 31, 2021 and 2020, the related consolidated statements of operations and comprehensive loss, stockholders’ equity, and cash flows, for each of the three years in the period ended December 31, 2021, and the related notes (collectively referred to as the "financial statements"). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2021 and 2020, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2021, in conformity with accounting principles generally accepted in the United States of America. We have also audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the Company's internal control over financial reporting as of December 31, 2021, based on criteria established in Internal Control — Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission and our report dated February 28, 2022, expressed an unqualified opinion on the Company's internal control over financial reporting. Basis for Opinion These financial statements are the responsibility of the Company's management. Our responsibility is to express an opinion on the Company's financial statements based on our audits. We are a public accounting firm registered with the PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB. We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion. Critical Audit Matters The critical audit matters communicated below are matters arising from the current-period audit of the financial statements that were communicated or required to be communicated to the audit committee and that (1) relate to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the financial statements, taken as a whole, and we are not, by communicating the critical audit matters below, providing separate opinions on the critical audit matters or on the accounts or disclosures to which they relate. 86 Revenue and Deferred Revenue – Accounting for Out- License Agreement – Refer to Note 2 and 7 to the Financial Statements Critical Audit Matter Description The Company has entered into certain out-license agreements with Bayer and Pierre Fabre. During 2021, the Company entered into a Technology Transfer Agreement and a Manufacturing and Supply Agreement with Bayer AG (“Bayer”), both of which were contemplated as part of the existing Bayer License Agreement. Under the terms of these agreements, the company will be responsible for technology transfer services, supply of materials required for technology transfer services, and for manufacturing, storage, and distribution of therapies to Bayer. Additionally, during 2021, the Company entered into a commercialization agreement with Pierre Fabre Medicament (“Pierre Fabre”). Under the terms of the agreement, the Company granted Pierre Fabre a license to commercialize and distribute therapies and will be responsible for manufacturing and supplying the therapies to Pierre Fabre, along with related cell selection services. The Company recognizes revenue on out-license agreements as they satisfy their performance obligations and when a customer obtains control of the promised goods or services. As of December 31, 2021, the Company recognized $20.3 million of revenue under the out-license agreements and deferred revenue amounted to $96.5 million, of which $40.8 million is included in current liabilities and $55.7 million is included in long-term liabilities. We identified accounting for the out-license agreements, the revenue recognized, and the estimated deferred revenue to be recognized as revenue over time as a critical audit matter. Given the judgments necessary to determine the accounting literature to apply to an out-license agreement, the method to estimate and measure the progress toward the completion of the performance obligation and the estimated contractual term over which the performance obligation would be completed, auditing such judgments and estimates required extensive audit effort due to the complexity of the out-license agreements and the high degree of auditor judgment applied when performing audit procedures and evaluating the results of those procedures. How the Critical Audit Matter Was Addressed in the Audit Our audit procedures related to determining the accounting literature to apply to the agreements and, where applicable, assessing management's estimates of costs used in the cost-based input method for measuring progress included the following, among others: • We tested the operating effectiveness of controls over out-license related revenue, including those related to the identification of distinct performance obligations and the determination of the timing and amount of revenue recognized. • We reviewed and obtained an understanding of the Company’s revenue generating agreements and related transactions during and at the end of the year via review of internal and external presentations, news and publications, and discussions with management. • We evaluated management’s determination that the agreement is within the scope of ASC 606. • We tested management's identification of the performance obligation(s) by evaluating whether the promises were highly interdependent and interrelated . • We evaluated management's determination of the contractual term and the appropriateness of management's method to measure its progress over that term. • We evaluated the assumptions used in the estimates of total costs and the estimated measure of progress for recognizing revenues over time revenue by: o Performing corroborating inquiries with the Company's project and business development managers, and comparing the assumptions used in the estimates to management's work plans and cost estimates, and costs reported to date o Comparing costs incurred for activities completed to date to the costs forecasted for those activities. o Testing the mathematical accuracy of management’s revenue and current and long-term deferred revenue balances based on the estimated revenue to be recognized over time. 87 Accrued Research and Development Expenses & Prepaid Research and Development Expenses (Clinical Trial Accrued and Prepaid Expenses) - Refer to Note 2 to the financial statements Critical Audit Matter Description The Company recognizes costs it incurs for preclinical studies, clinical studies, and manufacturing activities as research and development expenses based on an evaluation of its vendors’ progress toward completion of specific tasks. Payment timing may differ significantly from the period in which the costs are recognized as expense. Costs that are paid in advance are deferred as a prepaid expense and amortized over the service period as the services are provided. Costs for services incurred that have not yet been be paid are recognized as accrued expenses. In estimating the vendors’ progress toward completion of specific tasks, the Company uses data such as patient enrollment, clinical site activations or vendor information of actual costs incurred. This data is obtained through reports from or discussions with Company personnel and outside service providers as to the progress or state of completion of trials, or the completion of services. Given the number of ongoing preclinical study, clinical study, and manufacturing activities and the subjectivity involved in estimating clinical study accrued and prepaid expenses, auditing the clinical study accruals and prepaid expenses involved especially subjective judgment. How the Critical Audit Matter Was Addressed in the Audit Our audit procedures related to clinical study accrued and prepaid expenses included the following, among others: • We tested the design and effectiveness of controls over the estimation of clinical study accrued and prepaid expenses. • We obtained and read a sample of research, collaboration, and manufacturing agreements and contracts, as well as amendments thereto. • We evaluated publicly available information (such as press releases and investor presentations) and board of directors’ materials regarding the status of clinical trial and manufacturing activities. • We obtained the listing of all contracts related to research and development expenses to evaluate the completeness of accruals and prepaid expenses. • For a sample of agreements and contracts, we compared the amount of accrual or prepaid expenses at the end of the prior period to current year activity and evaluated the accuracy of the Company’s estimation methodology. • We obtained a written confirmation of the ending inventory balance held at the Company’s manufacturing vendor. • We made selections of specific amounts recognized as research and development expense as well as those recognized as accrued and prepaid expenses to evaluate management’s estimate of the vendor’s progress and performed the following procedures: o Read the related statement of work, purchase order, or other supporting documentation (such as communications between the Company and vendors). o Performed corroborating inquiries with Company clinical operations and manufacturing operations personnel. o Confirmed progress directly with the vendor and compared the reported amounts to the Company's estimate. o Evaluated management’s judgments compared to the evidence obtained. /s/ DELOITTE & TOUCHE LLP San Francisco, California February 28, 2022 We have served as the Company’s auditor since 2013. 88 Atara Biotherapeutics, Inc. Consolidated Balance Sheets (In thousands, except per share amounts) December 31, December 31, 2021 2020 Assets Current assets: Cash and cash equivalents $ 106,084 $ 200,404 Short-term investments 264,984 300,255 Restricted cash - short-term 194 194 Accounts receivable 986 1,250 Prepaid expenses and other current assets 12,373 21,170 Total current assets 384,621 523,273 Property and equipment, net 53,780 50,517 Operating lease assets 26,159 12,303 Restricted cash - long-term 1,200 1,200 Other assets 2,367 827 Total assets $ 468,127 $ 588,120 Liabilities and stockholders’ equity Current liabilities: Accounts payable $ 17,368 $ 7,118 Accrued compensation 25,150 20,458 Accrued research and development expenses 13,451 15,813 Deferred revenue 40,760 33,455 Other current liabilities 9,057 6,057 Total current liabilities 105,786 82,901 Deferred revenue - long-term 55,708 27,795 Operating lease liabilities - long-term 25,518 13,041 Other long-term liabilities 1,501 2,044 Total liabilities 188,513 125,781 Commitments and contingencies (Note 9) Stockholders’ equity: Common stock—$ 0.0001 par value, 500,000 shares authorized as of December 31, 2021 and 2020, respectively; 91,671 and 83,372 shares issued and outstanding as of December 31, 2021 and 2020, respectively 9 8 Additional paid-in capital 1,744,695 1,586,616 Accumulated other comprehensive (loss) income ( 368 ) 296 Accumulated deficit ( 1,464,722 ) ( 1,124,581 ) Total stockholders’ equity 279,614 462,339 Total liabilities and stockholders’ equity $ 468,127 $ 588,120 89 Atara Biotherapeutics, Inc. Consolidated Statements of Operations and Comprehensive Loss (In thousands, except per share amounts) Years Ended December 31, 2021 2020 2019 License and collaboration revenue $ 20,340 $ — $ — Operating expenses: Research and development 282,001 244,650 216,097 General and administrative 78,801 64,402 79,584 Total operating expenses 360,802 309,052 295,681 Loss from operations ( 340,462 ) ( 309,052 ) ( 295,681 ) Interest and other income, net 367 2,447 4,717 Loss before provision for income taxes ( 340,095 ) ( 306,605 ) ( 290,964 ) Provision for income taxes 46 15 12 Net loss $ ( 340,141 ) $ ( 306,620 ) $ ( 290,976 ) Other comprehensive (loss) gain: Unrealized (loss) gain on available-for-sale securities ( 664 ) 76 560 Comprehensive loss $ ( 340,805 ) $ ( 306,544 ) $ ( 290,416 ) Net loss per common share: Basic and diluted net loss per common share $ ( 3.63 ) $ ( 4.15 ) $ ( 5.67 ) Weighted-average shares outstanding used to calculate basic and diluted net loss per common share 93,670 73,973 51,308 90 Atara Biotherapeutics, Inc. Consolidated Statements of Stockholders’ Equity (In thousands) Accumulated Common Additional Other Total Stock Paid-in Comprehensive Accumulated Stockholders’ Shares Amount Capital (Loss) Income Deficit Equity Balance as of January 1, 2019 45,951 $ 5 $ 866,541 $ ( 340 ) $ ( 526,985 ) $ 339,221 Issuance of common stock through underwritten offerings, net of offering costs of $ 284 6,872 1 140,715 — — 140,716 Issuance of common stock through ATM facilities, net of commissions and offering costs of $ 1,553 3,135 — 48,909 — — 48,909 RSU settlements, net of shares withheld 361 — ( 6,695 ) — — ( 6,695 ) Issuance of common stock pursuant to employee stock awards 487 — 7,350 — — 7,350 Stock-based compensation expense — — 51,696 — — 51,696 Net loss — — — — ( 290,976 ) ( 290,976 ) Unrealized gain on available-for-sale securities — — — 560 — 560 Balance as of December 31, 2019 56,806 6 1,108,516 220 ( 817,961 ) 290,781 Issuance of common stock and pre-funded warrants through underwritten offering, net of offering costs of $ 583 20,060 2 353,586 — — 353,588 Issuance of common stock through ATM facilities, net of commissions and offering costs of $ 1,887 4,786 — 68,004 — — 68,004 Exercise of pre-funded warrants 57 — — — — — RSU settlements, net of shares withheld 1,112 — ( 1,521 ) — — ( 1,521 ) Issuance of common stock pursuant to employee stock awards 551 — 6,680 — — 6,680 Stock-based compensation expense — — 51,351 — — 51,351 Net loss — — — — ( 306,620 ) ( 306,620 ) Unrealized gain on available-for-sale securities — — — 76 — 76 Balance as of December 31, 2020 83,372 8 1,586,616 296 ( 1,124,581 ) 462,339 Issuance of common stock through ATM facilities, net of commissions and offering costs of $ 2,501 6,241 1 98,696 — — 98,697 RSU settlements, net of shares withheld 1,492 — ( 1,244 ) — — ( 1,244 ) Issuance of common stock pursuant to employee stock awards 566 — 6,762 — — 6,762 Stock-based compensation expense — — 53,865 — — 53,865 Net loss — — — — ( 340,141 ) ( 340,141 ) Unrealized loss on available-for-sale securities — — — ( 664 ) — ( 664 ) Balance as of December 31, 2021 91,671 $ 9 $ 1,744,695 $ ( 368 ) $ ( 1,464,722 ) $ 279,614 91 Atara Biotherapeutics, Inc. Consolidated Statements of Cash Flows (In thousands) Year Ended December 31, 2021 2020 2019 Operating activities Net loss $ ( 340,141 ) $ ( 306,620 ) $ ( 290,976 ) Adjustments to reconcile net loss to net cash used in operating activities: Stock-based compensation expense 53,865 51,351 51,696 Depreciation and amortization expense 9,345 8,332 7,070 Non-cash operating lease expense 1,948 1,457 964 Amortization (accretion) of investment premiums (discounts) 1,769 828 ( 1,330 ) Loss on disposals of property and equipment 21 130 1,027 Asset retirement obligation accretion expense 87 78 71 Changes in operating assets and liabilities: Accounts receivable 264 ( 1,250 ) — Prepaid expenses and other current assets 8,182 ( 8,666 ) ( 998 ) Operating lease assets — 886 239 Other assets ( 1,727 ) ( 219 ) 322 Accounts payable 9,067 ( 815 ) 4,213 Accrued compensation 4,692 5,752 4,070 Accrued research and development expenses ( 2,362 ) 7,472 ( 10,869 ) Other current liabilities 1,618 ( 187 ) ( 394 ) Deferred revenue 35,218 61,250 — Operating lease liabilities ( 1,859 ) ( 1,316 ) ( 731 ) Other long-term liabilities ( 509 ) 778 — Net cash used in operating activities ( 220,522 ) ( 180,759 ) ( 235,626 ) Investing activities Purchases of short-term investments ( 301,129 ) ( 425,868 ) ( 270,230 ) Proceeds from maturities and sales of short-term investments 333,967 309,653 336,261 Purchases of property and equipment ( 10,580 ) ( 4,513 ) ( 5,733 ) Proceeds from sale of property and equipment — — 161 Net cash provided by (used in) investing activities 22,258 ( 120,728 ) 60,459 Financing activities Proceeds from sale of common stock and pre-funded warrants in underwritten offerings, net — 353,780 140,888 Proceeds from issuance of common stock through ATM facilities, net 98,697 69,189 47,729 Proceeds from employee stock awards 6,762 6,680 7,350 Taxes paid related to net share settlement of restricted stock units ( 1,244 ) ( 1,521 ) ( 6,695 ) Principal payments on finance and capital lease obligations ( 254 ) ( 389 ) ( 486 ) Other financing activities, net ( 17 ) ( 165 ) — Net cash provided by financing activities 103,944 427,574 188,786 Increase (decrease) in cash, cash equivalents and restricted cash ( 94,320 ) 126,087 13,619 Cash, cash equivalents and restricted cash at beginning of period 201,798 75,711 62,092 Cash, cash equivalents and restricted cash at end of period $ 107,478 $ 201,798 $ 75,711 Non-cash investing and financing activities Property and equipment purchases included in accounts payable and other accrued liabilities $ 2,139 $ 326 $ 276 Accrued costs related to underwritten public offering $ — $ 192 $ 172 Accrued costs related to ATM facility $ 87 $ — $ — Proceeds from issuance of common stock through ATM facilities not yet received $ — $ — $ 1,185 Supplemental cash flow disclosure Cash paid for interest $ 32 $ 62 $ 50 Cash paid for income taxes $ 15 $ 10 $ — 92 Atara Biotherapeutics, Inc. Notes to Consolidated Financial Statements 1. Description of Business Atara Biotherapeutics, Inc. (“Atara”, “we”, “our” or “the Company”) was incorporated in August 2012 in Delaware . Atara is a pioneer in T-cell immunotherapy, leveraging its novel allogeneic EBV T-cell platform to develop transformative therapies for patients with serious diseases, including solid tumors, hematologic cancers and autoimmune disease. We have several T-cell immunotherapies in clinical development and are progressing multiple next-generation allogeneic chimeric antigen receptor T-cell (“CAR T”) programs. Our most advanced T-cell immunotherapy program, tab-cel ® (tabelecleucel), is currently in Phase 3 development, and in October 2021, we entered into a commercialization agreement (“Pierre Fabre Commercialization Agreement”) with Pierre Fabre Medicament (“Pierre Fabre”), pursuant to which we granted to Pierre Fabre an exclusive, field-limited license to commercialize and distribute tab-cel ® in Europe and select emerging markets in the Middle East, Africa, Eastern Europe and Central Asia, following regulatory approval. Atara will retain full rights to tab-cel ® in other major markets, including North America, Asia Pacific and Latin America. See Note 7 for further information. In December 2020, we entered into a research, development and license agreement (“Bayer License Agreement”) with Bayer AG (“Bayer”) pursuant to which we granted to Bayer an exclusive, field-limited license under the applicable patents and know-how owned or controlled by us and our affiliates covering or related to ATA2271 and ATA3271. In March 2021, as contemplated under the Bayer License Agreement and to further advance our collaboration, we entered into (i) a Manufacturing and Supply Agreement; (ii) a Pharmacovigilance Agreement; (iii) a Quality Agreement; and (iv) a Technology Transfer Agreement (collectively, the Bayer License Agreement, the Manufacturing and Supply Agreement and the Technology Transfer Agreement are referred to as the “Bayer Agreements”). See Note 7 for further information. We have licensed rights to T-cell product candidates from Memorial Sloan Kettering Cancer Center (“MSK”), rights related to our next-generation CAR T programs from MSK and from H. Lee Moffitt Cancer Center (“Moffitt”), and rights to know-how and technology from the Council of the Queensland Institute of Medical Research (“QIMR Berghofer”). See Note 6 for further information. 2. Summary of Significant Accounting Policies Basis of Presentation We prepare our consolidated financial statements in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and follow the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”). Principles of Consolidation The consolidated financial statements include the accounts of Atara and our wholly owned subsidiaries. All intercompany balances and transactions are eliminated in consolidation. Segment and Geographic Information We operate and manage our business as one operating and reportable segment, which is the business of developing and commercializing therapeutics. Our Chief Executive Officer, who is our chief operating decision maker, reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. Substantially all of our assets are located in the U.S. Of the $ 20.3 million license and collaboration revenue recognized in 2021, $ 19.8 million related to our agreements with Bayer, a German company, and $ 0.5 million related to our agreements with Pierre Fabre, a French company. 93 Liquidity Risk We have incurred significant operating losses since inception and have relied primarily on public and private equity financings and receipts from license and collaboration agreements to fund our operations. As we continue to incur losses, our transition to profitability will depend on the successful development, approval and commercialization of product candidates and on the achievement of sufficient revenues to support our cost structure. We may never achieve profitability, and unless and until we do, we will need to continue to raise additional capital. We expect that existing cash, cash equivalents and short-term investments as of December 31, 2021 will be sufficient to fund our planned operations for at least the next twelve months from the date of issuance of these financial statements. Concentration of Credit Risk and Other Uncertainties We place cash and cash equivalents in the custody of financial institutions that management believes are of high credit quality, the amount of which at times, may be in excess of the amount insured by the Federal Deposit Insurance Corporation. We also make short-term investments in money market funds; U.S. Treasury, government agency and corporate debt obligations; commercial paper; certificates of deposit; and asset-backed securities, which can be subject to certain credit risk. However, we mitigate the risks by investing in high-grade instruments, limiting our exposure to any one issuer and monitoring the ongoing creditworthiness of the financial institutions and issuers. We are subject to certain risks and uncertainties and believe that changes in any of the following areas could have a material adverse effect on future financial position or results of operations: our ability to obtain future financing; regulatory approval and market acceptance of, and reimbursement for, our product candidates, if approved by applicable regulatory authorities; our ability to collect amounts due from our collaboration partners, future customers or distribution partners; performance of third-party clinical research organizations and manufacturers upon which we rely; development of sales channels; protection of our intellectual property; litigation or claims against us based on intellectual property, patent, product, regulatory or other factors; and our ability to attract and retain employees necessary to support our growth. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates, assumptions and judgments that affect the amounts reported in the financial statements and accompanying notes. Significant estimates relied upon in preparing these financial statements include estimates related to revenue recognition, clinical study and other accruals, stock-based compensation expense and income taxes. Actual results could differ materially from those estimates. Foreign Currency Transactions and monetary assets and liabilities that are denominated in a foreign currency are translated into U.S. dollars at the current exchange rate on the transaction date and as of each balance sheet date, respectively, with gains or losses on foreign exchange changes recognized in interest and other income (expense), net in the consolidated statements of operations and comprehensive loss. Foreign currency-denominated monetary assets and liabilities as of December 31, 2021 were not material. Cash Equivalents and Short-Term Investments Cash equivalents are defined as short-term, highly liquid investments with original maturities of 90 days or less at the date of purchase, and generally consist of money market funds, U.S. Treasury, government agency and corporate debt obligations, and commercial paper. Investments with original maturities of greater than 90 days are classified as short-term investments on the balance sheet, and consist primarily of U.S. Treasury, government agency and corporate debt obligations, commercial paper and asset-backed securities. As our entire investment portfolio is considered available for use in current operations, we classify all investments as available-for-sale and as current assets, even though the stated maturity may be more than one year from the current balance sheet date. Available-for-sale securities are carried at fair value, with unrealized gains and losses reported in accumulated other comprehensive loss, which is a separate component of stockholders’ equity in the consolidated balance sheet. The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity, which are both recorded to interest and other income (expense), net in the consolidated statements of operations and comprehensive loss. 94 Changes in the fair value of available-for-sale securities impact the consolidated statements of operations and comprehensive loss only when such securities are sold, if an allowance for credit losses is recognized or if an impairment is recognized. Realized gains and losses on the sale of securities are determined by specific identification of each security’s cost basis. We regularly review our investment portfolio to determine if any security is impaired, which would require us to record an allowance for credit losses or impairment charge in the period any such determination is made. In making this judgment, we evaluate, among other things, the duration and extent to which the fair value of a security is less than its cost, our intent to sell or whether it is more likely than not that we will be required to sell the security before recovery of its amortized cost basis, the financial condition of the issuer and any changes thereto, and, as necessary, the portion of a decline in fair value that is credit-related. This assessment could change in the future due to new developments or changes in assumptions related to any particular security. Realized gains and losses, allowances for credit losses and impairments on available-for-sale securities, if any, are recorded to interest and other income, net in the statements of operations and comprehensive loss . Fair Value Measurement The carrying amounts of certain of our financial instruments including cash equivalents, accounts receivable, prepaid expenses and other current assets, accounts payable and accrued liabilities approximate fair value due to their short maturities. Short-term investments are comprised of available-for-sale securities, which are carried at fair value. Fair Value of Financial Instruments Our financial assets are measured at fair value on a recurring basis using the following hierarchy to prioritize valuation inputs, in accordance with applicable GAAP: Level 1: Quoted prices in active markets for identical assets or liabilities that we have the ability to access Level 2: Observable market-based inputs or unobservable inputs that are corroborated by market data such as quoted prices, interest rates and yield curves Level 3: Inputs that are unobservable data points that are not corroborated by market data We review the fair value hierarchy classification on a quarterly basis. Changes in the ability to observe valuation inputs may result in a reclassification of levels of certain securities within the fair value hierarchy. We recognize transfers into and out of levels within the fair value hierarchy in the period in which the actual event or change in circumstances that caused the transfer occurs. There have been no transfers between Level 1, Level 2, and Level 3 in any periods presented. Financial assets and liabilities are considered Level 2 when their fair values are determined using inputs that are observable in the market or can be derived principally from or corroborated by observable market data such as pricing for similar securities, recently executed transactions, cash flow models with yield curves, and benchmark securities. In addition, Level 2 financial instruments are valued using comparisons to like-kind financial instruments and models that use readily observable market data as their basis. U.S. Treasury, government agency and corporate debt obligations, commercial paper and asset-backed securities are valued primarily using market prices of comparable securities, bid/ask quotes, interest rate yields and prepayment spreads and are included in Level 2. Financial assets and liabilities are considered Level 3 when their fair values are determined using pricing models, discounted cash flow methodologies, or similar techniques, and at least one significant model assumption or input is unobservable. We have no Level 3 financial assets or liabilities. Property and Equipment, net Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the assets, ranging from three to five years . Costs incurred to acquire, construct or install property and equipment during the construction stage of a capital project or costs incurred to purchase and develop internal use software during the application development stage are recorded as construction in progress. Leasehold improvements are amortized over the lesser of the life of the leasehold improvements or the lease term. Maintenance and repairs are charged to operations as incurred. Long-lived Assets We evaluate the carrying amount of our long-lived assets whenever events or changes in circumstances indicate that the assets may not be recoverable. An impairment loss would be recognized when estimated future cash flows expected to result from the use of the asset and its eventual disposition are less than the carrying amount of the asset. To date, there have been no such impairment losses. 95 Asset Retirement Obligations (“ARO”) ARO are legal obligations associated with the retirement of long-lived assets pertaining to leasehold improvements. These liabilities are initially recorded at fair value and the related asset retirement costs are capitalized by increasing the carrying amount of the related assets by the same amount as the liability. Asset retirement costs are subsequently depreciated over the useful lives of the related assets. Subsequent to initial recognition, the Company records period-to-period changes in the ARO liability resulting from the passage of time and revisions to either the timing or the amount of the original estimate of undiscounted cash flows. The Company derecognizes ARO liabilities when the related obligations are settled. Leases We determine if an arrangement is a lease at inception in accordance with Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842) . Operating leases are included in operating lease assets, other current liabilities, and operating lease liabilities on our consolidated balance sheets. Leases with an initial term of 12 months or less are not recorded on the balance sheet; we recognize short-term lease expense for these leases on a straight-line basis over the lease term. Finance leases are included in other assets, other current liabilities, and other long-term liabilities on our consolidated balance sheets. Lease assets and lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. The lease term includes renewal options that we are reasonably certain of exercising as of the commencement date. None of the lease terms used to calculate the future minimum lease payments at commencement date include renewal options. As most of our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at commencement date in determining the present value of future payments. The incremental borrowing rate for our leases is determined based on lease term and currency in which lease payments are made, adjusted for impacts of collateral. Lease assets also includes any lease payments made and excludes lease incentives and initial direct costs incurred. Operating lease expense for minimum lease payments is recognized on a straight-line basis over the lease term. Finance lease assets are amortized over the shorter of the lease term or the asset’s estimated useful life. Our facilities and equipment operating leases have lease and non-lease components and we have made a policy election to account for the lease and non-lease components as a single lease component. Revenue Recognition At inception, we determine whether contracts are within the scope of Accounting Standards Codification Topic 606 (ASU No. 2014-09), Revenue from Contracts with Customers , and all subsequent amendments (collectively, “ASC 606”) or other topics. For contracts that are determined to be within the scope of ASC 606, revenue is recognized when a customer obtains control of promised goods or services. The amount of revenue recognized reflects the consideration to which we expect to be entitled to receive in exchange for these goods and services. To achieve this core principle, we apply the following five steps (i) identify the contract with the customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when or as we satisfy a performance obligation. We only apply the five-step model to contracts when we determine that collection of substantially all consideration for goods and services that are transferred is probable based on the customer’s intent and ability to pay the promised consideration. Performance obligations promised in a contract are identified based on the goods and services that will be transferred to the customer that are both capable of being distinct and are distinct in the context of the contract. To the extent a contract includes multiple promised goods and services, we apply judgment to determine whether promised goods and services are both capable of being distinct and distinct in the context of the contract. If these criteria are not met, the promised goods and services are accounted for as a combined performance obligation. The transaction price is determined based on the consideration to which we will be entitled in exchange for transferring goods and services to the customer. To the extent the transaction price includes variable consideration, we estimate the amount of variable consideration that should be included in the transaction price utilizing either the expected value method or the most likely amount method, depending on the nature of the variable consideration. Variable consideration is included in the transaction price if, in our judgment, it is probable that a significant future reversal of cumulative revenue under the contract will not occur. Any estimates, including the effect of the constraint on variable consideration, are evaluated at each reporting period for any changes. Determining the transaction price requires significant judgment, which is discussed in further detail for our out-license agreements in Note 7. Our out-license agreements do not contain a significant financing component. 96 If the contract contains a single performance obligation, the entire transaction price is allocated to the single performance obligation. Contracts that contain multiple performance obligations require an allocation of the transaction price to each performance obligation on a relative standalone selling price basis unless the transaction price is variable and meets the criteria to be allocated entirely to a performance obligation or to a distinct service that forms part of a single performance obligation. The consideration to be received is allocated among the separate performance obligations based on relative standalone selling prices. We typically determine standalone selling prices using an adjusted market assessment approach model. We satisfy performance obligations either over time or at a point in time. Revenue is recognized over time if either (i) the customer simultaneously receives and consumes the benefits provided by our performance, (ii) our performance creates or enhances an asset that the customer controls as the asset is created or enhanced or (iii) our performance does not create an asset with an alternative use to the entity and we have an enforceable right to payment for performance completed to date. We evaluate the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition. If we do not satisfy a performance obligation over time, the related performance obligation is satisfied at a point in time by transferring control of a promised good or service to a customer. As of December 31, 2021, our deferred revenue is related to the Bayer Agreements and the Pierre Fabre Commercialization Agreement, which are both within the scope of ASC 606. As discussed in further detail in Note 7, the terms of these arrangements include potential payments to us for some or all of the following: nonrefundable, upfront fees; development, regulatory, and commercial milestone payments; research and development funding payments; and royalties on the net sales of licensed products. These payments relate to promised goods or services for which revenue will be recognized upon our satisfaction of the underlying performance obligations. Licenses of intellectual property : If the license of our intellectual property is determined to be distinct from the other performance obligations identified in an arrangement, we recognize revenues from consideration allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. For licenses that are combined with other promises, we utilize judgment 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. Upfront payments : Upfront payments and fees are recorded as deferred revenue upon receipt or when due and may require deferral of revenue recognition to a future period until the we have satisfied our obligations under these arrangements. Milestone payments : At the inception of each arrangement that includes development milestone payments, the Company evaluates the probability of reaching the milestones and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur in the future, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received and therefore revenue recognized is constrained as management is unable to assert that a significant reversal of revenue would not be probable. The transaction price is then allocated to each performance obligation on a relative standalone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones and any related constraint and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect license and collaboration revenues and the consolidated statements of operations and comprehensive loss in the period of adjustment. Royalties : For arrangements that include sales-based royalties, including milestone payments based on levels of sales, if the license is deemed to be the predominant item to which the royalties relate, we recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied, or partially satisfied. To date, we have not recognized any royalty revenue resulting from our out-licensing agreements. Certain judgments affect the application of our revenue recognition policy. For example, we record short-term and long-term deferred revenue based on our best estimate of when such revenue will be recognized. Short-term deferred revenue consists of amounts that are expected to be recognized as revenue in the next 12 months, and long-term deferred revenue consists of amounts that we do not expect will be recognized in the next 12 months. This estimate is based on our current operating plan and, if our operating plan should change in the future, we may recognize a different amount of deferred revenue over the next 12-month period. 97 Contract Balances We receive payments from our customers based on billing schedules established in each contract. Amounts payable to us are recorded as accounts receivable when our right to consideration is unconditional. Our contract liabilities consist of deferred revenue. Stock-Based Compensation Expense We account for stock-based compensation expense, including the expense of restricted common stock awards (“RSAs”), grants of restricted stock units (“RSUs”), and stock options that may be settled in shares of our common stock, based on the fair values of the equity instruments issued. The fair value is determined on the measurement date, which is generally the date of grant. The fair value of our RSUs is measured at the closing market price of our common stock on the measurement date. The fair value for our stock option awards is determined at the grant date using the Black-Scholes valuation model. For awards with performance-based vesting criteria, we assess the probability of the achievement of the performance conditions at the end of each reporting period and begin to recognize the share-based compensation costs when it becomes probable that the performance conditions will be met. For awards that are subject to both service and performance conditions, no expense is recognized until it is probable that performance conditions will be met. Stock-based compensation expense for awards with time-based vesting criteria is recognized as expense on a straight-line basis over the requisite service period. Stock-based compensation expense for awards with performance and other vesting criteria is recognized as expense under an accelerated graded vesting model. Key assumptions used in the Black-Scholes valuation model used for employee stock awards include: Expected term – We derived the expected term using the “simplified” method (the expected term is determined as the average of the time-to-vesting and the contractual life of the options), as we have limited historical information to develop expectations about future exercise patterns and post vesting employment termination behavior. Expected volatility – Prior to 2021, expected volatility was estimated using comparable public companies’ volatility for similar terms. Beginning in 2021, volatility is estimated using an average of Atara’s historical volatility and comparable public companies’ volatility for similar terms. Expected dividend – We have not historically declared or paid dividends to our stockholders and have no plans to pay dividends; therefore, we assumed an expected dividend yield of 0 %. Risk-free interest rate – The risk-free interest rate is based on the yield on U.S. Treasury securities with the expected term of the associated award. The fair value of our common stock is measured at the closing market price on the measurement date. We account for forfeitures of stock-based awards as they occur. Research and Development Expense Research and development expense consists of costs incurred in performing research and development activities, including compensation and benefits for research and development employees, including stock-based compensation; expenses incurred under agreements with contract research organizations and investigative sites that conduct clinical and preclinical studies; the costs of acquiring and manufacturing clinical study materials and other supplies; payments under licensing and research and development agreements; other outside services and consulting costs, and facilities, information technology and overhead expenses. Research and development costs are expensed as incurred. Clinical Study Accruals Costs for preclinical studies, clinical studies and manufacturing activities are recognized based on an evaluation of our vendors’ progress towards completion of specific tasks, using data such as patient enrollment, clinical site activations or information provided to us by our vendors regarding their actual costs incurred. Payments for these activities are based on the terms of individual contracts and payment timing may differ significantly from the period in which the services are performed. We determine accrual estimates through reports from and discussions with applicable personnel and outside service providers as to the progress or state of completion of studies, or the services completed. Our estimates of accrued expenses as of each balance sheet date are based on the facts and circumstances known at the time. Costs that are paid in advance of performance are deferred as a prepaid expense and amortized over the service period as the services are provided. 98 Defined Contribution Plan We have one qualified 401(k) plan covering all eligible employees. Under the plan, employees may contribute up to the statutory allowable amount for any calendar year. We make matching contributions, equal to 50 % of each dollar contributed up to the first 6 % of an individual’s eligible earnings, up to the annual IRS maximum. For the years ended December 31, 2021, 2020, and 2019 we recorded matching contributions of approximately $ 2.6 million, $ 2.1 million, and $ 1.6 million, respectively. Other Current Liabilities Other current liabilities consisted of the following as of each period end: December 31, December 31, 2021 2020 (in thousands) Accrued operating expenses $ 5,960 $ 3,016 Current portion of operating lease liabilities 2,582 1,730 Current portion of finance lease liabilities 171 255 Other accrued liabilities 344 1,056 Total other current liabilities $ 9,057 $ 6,057 Income Taxes We use the asset and liability method to account for income taxes. We record deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the financial statement carrying amounts and the tax basis of assets and liabilities using enacted tax rates expected to be in effect when the differences are expected to reverse. Valuation allowances are provided when necessary to reduce net deferred tax assets to the amount that is more likely than not to be realized. Based on the available evidence, we are unable, at this time, to support the determination that it is more likely than not that our deferred tax assets will be utilized in the future. Accordingly, we recorded a full valuation allowance as of December 31, 2021 and 2020. We intend to maintain valuation allowances until sufficient evidence exists to support their reversal. Tax benefits related to uncertain tax positions are recognized when it is more likely than not that a tax position will be sustained during an audit. Interest and penalties related to unrecognized tax benefits are included within the provision for income tax. Comprehensive Income (Loss) Comprehensive income (loss) is defined as a change in equity of a business enterprise during a period resulting from transactions from non-owner sources. Our other comprehensive income (loss) is comprised solely of unrealized gains (losses) on available-for-sale securities and is presented net of taxes. We have not recorded any reclassifications from other comprehensive income (loss) to net loss during any period presented. Recent Accounting Pronouncements We consider the applicability and impact of any recent ASU issued by the Financial Accounting Standards Board (“FASB”). Based on our assessment, the ASUs were determined to be either not applicable or are expected to have minimal impact on our condensed consolidated financial statements. 3. Net Loss per Common Share Basic net loss per common share is calculated by dividing net loss by the weighted-average number of shares of common stock and pre-funded warrants outstanding during the period, without consideration of common share equivalents. Diluted net loss per common share is computed by dividing net loss by the weighted-average number of shares of common stock, pre-funded warrants and common share equivalents outstanding for the period. The pre-funded warrants are included in the computation of basic and diluted net loss per common share as the exercise price is negligible and the pre-funded warrants are fully vested and exercisable. Common share equivalents are only included in the calculation of diluted net loss per common share when their effect is dilutive. 99 Potential dilutive securities, which include unvested restricted stock units (“RSUs”), unvested performance-based RSUs for which established performance criteria have been achieved as of the end of the respective periods, vested and unvested options to purchase common stock and shares to be issued under our employee stock purchase plan (“ESPP”), have been excluded from the computation of diluted net loss per share as the effect is antidilutive. Therefore, the denominator used to calculate both basic and diluted net loss per common share is the same in all periods presented . The following table represents the potential common shares issuable pursuant to outstanding securities as of the related period end dates that were excluded from the computation of diluted net loss per common share, as their inclusion would have an antidilutive effect: As of December 31, 2021 2020 2019 Unvested RSUs 5,253,347 2,868,407 1,910,764 Vested and unvested options 9,200,337 7,832,386 6,934,262 ESPP share purchase rights 27,238 26,349 20,438 Total 14,480,922 10,727,142 8,865,464 4. Financial Instruments The following tables summarize the estimated fair value and related valuation input hierarchy of our available-for-sale securities as of each period end: Total Total Total Total Amortized Unrealized Unrealized Estimated As of December 31, 2021: Input Level Cost Gain Loss Fair Value (in thousands) Money market funds Level 1 $ 89,738 $ — $ — $ 89,738 U.S. Treasury obligations Level 2 111,832 1 ( 138 ) $ 111,695 Government agency obligations Level 2 21,346 — ( 23 ) $ 21,323 Corporate debt obligations Level 2 99,757 6 ( 190 ) $ 99,573 Commercial paper Level 2 36,993 — — $ 36,993 Asset-backed securities Level 2 10,174 1 ( 25 ) $ 10,150 Total available-for-sale securities 369,840 8 ( 376 ) 369,472 Less: amounts classified as cash equivalents ( 104,488 ) $ ( 104,488 ) Amounts classified as short-term investments $ 265,352 $ 8 $ ( 376 ) $ 264,984 Total Total Total Total Amortized Unrealized Unrealized Estimated As of December 31, 2020: Input Level Cost Gain Loss Fair Value (in thousands) Money market funds Level 1 $ 168,343 $ — $ — $ 168,343 U.S. Treasury obligations Level 2 230,239 113 ( 6 ) 230,346 Government agency obligations Level 2 22,537 22 ( 3 ) 22,556 Corporate debt obligations Level 2 50,080 166 ( 1 ) 50,245 Commercial paper Level 2 17,990 — — 17,990 Asset-backed securities Level 2 9,860 10 ( 5 ) 9,865 Total available-for-sale securities 499,049 311 ( 15 ) 499,345 Less: amounts classified as cash equivalents ( 199,090 ) — — ( 199,090 ) Amounts classified as short-term investments $ 299,959 $ 311 $ ( 15 ) $ 300,255 100 The amortized cost and fair value of our available-for-sale securities by contractual maturity were as follows: As of December 31, 2021 As of December 31, 2020 Amortized Estimated Amortized Estimated Cost Fair Value Cost Fair Value (in thousands) (in thousands) Maturing within one year $ 278,457 $ 278,354 $ 434,828 $ 435,023 Maturing in one to five years 91,383 91,118 64,221 64,322 Total available-for-sale securities $ 369,840 $ 369,472 $ 499,049 $ 499,345 As of December 31, 2021, no significant facts or circumstances were present to indicate a deterioration in the creditworthiness of the issuers of the available-for-sale securities we hold, and the Company has no requirement or intention to sell these securities before maturity or recovery of their amortized cost basis. We considered the current and expected future economic and market conditions surrounding the COVID-19 pandemic and determined that our investments were not significantly impacted. For all securities with a fair value less than its amortized cost basis, we determined the decline in fair value below amortized cost basis to be immaterial and non-credit related, and therefore no allowance for losses has been recorded. During the years ended December 31, 2021 , 2020 and 2019, we did not recognize any impairment losses on our investments. We have elected the practical expedient to exclude the applicable accrued interest from both the fair value and the amortized cost basis of our available-for-sale securities for purposes of identifying and measuring an impairment. We present accrued interest receivable related to our available-for-sale securities in prepaid expenses and other current assets, separate from short-term investments on our consolidated balance sheet. As of December 31, 2021 and 2020, accrued interest receivable was $ 0.8 million and $ 0.7 million, respectively. Our accounting policy is to not measure an allowance for credit losses for accrued interest receivables and to write-off any uncollectible accrued interest receivable as a reversal of interest income in a timely manner, which we consider to be in the period in which we determine the accrued interest will not be collected by us. We have no t written off any accrued interest receivables for the years ended December 31, 2021, 2020 and 2019. In addition, restricted cash collateralized by money market funds is a financial asset measured at fair value and is a Level 1 financial instrument under the fair value hierarchy. As of December 31, 2021 and 2020, restricted cash totaled $ 1.4 million. The following table provides a reconciliation of cash, cash equivalents and restricted cash within the consolidated balance sheets that sum to the total of the same such amounts in the consolidated statement of cash flows: December 31, December 31, 2021 2020 (in thousands) Cash and cash equivalents $ 106,084 $ 200,404 Restricted cash - short-term 194 194 Restricted cash - long-term 1,200 1,200 Total cash, cash equivalents and restricted cash $ 107,478 $ 201,798 5. Property and Equipment Property and equipment consisted of the following as of each period end: December 31, December 31, 2021 2020 (in thousands) Leasehold improvements $ 50,142 $ 50,132 Lab equipment 14,060 8,033 Machinery and equipment 5,228 5,023 Computer equipment and software 4,245 4,060 Furniture and fixtures 2,518 2,066 Construction in progress 6,325 879 Property and equipment, gross 82,518 70,193 Less: accumulated depreciation and amortization ( 28,738 ) ( 19,676 ) Property and equipment, net $ 53,780 $ 50,517 101 Depreciation and amortization expense was $ 9.3 million, $ 8.3 million and $ 7.1 million for the years ended December 31, 2021 , 2020 and 2019 , respectively. 6. In-license and Manufacturing Agreements MSK Agreements In June 2015, we entered into an exclusive license agreement with MSK for three clinical stage T-cell therapies. We are required to make payments to MSK based on achievement of specified regulatory and sales-related milestones, as well as mid-single-digit percentage tiered royalty payments based on future sales of products resulting from the development of the licensed product candidates, if any. In addition, under certain circumstances, we are required to make certain minimum annual royalty payments to MSK, which are creditable against earned royalties owed for the same annual period. We are also required to pay a low double-digit percentage of any consideration we receive for sublicensing the licensed rights. The license agreement expires on a product-by-product and country-by-country basis on the latest of: (i) expiration of the last licensed patent rights related to each licensed product, (ii) expiration of any market exclusivity period granted by law with respect to each licensed product, and (iii) a specified number of years after the first commercial sale of the licensed product in each country. Upon expiration of the license agreement, Atara will retain non-exclusive rights to the licensed products. In May and December 2018, we licensed additional technology from MSK. We are obligated to make additional milestone payments based on achievement of specified development, regulatory and sales-related milestones as well as mid-single-digit percentage tiered royalty payments based on future sales of products resulting from the development of the licensed product candidates, if any. In March 2021, we amended and restated our license agreement with MSK to: (i) terminate our license to certain rights related to WT1 and cytomegalovirus (“CMV”); and (ii) license additional know-how rights not otherwise covered by our existing agreements. QIMR Berghofer Agreements In October 2015, we entered into an exclusive license agreement and a research and development collaboration agreement with QIMR Berghofer. Under the terms of the license agreement, we obtained an exclusive, worldwide license to develop and commercialize allogeneic T-cell therapy programs utilizing technology and know-how developed by QIMR Berghofer. In September 2016, the exclusive license agreement and research and development collaboration agreement were amended and restated. Under the amended and restated agreements, we obtained an exclusive, worldwide license to develop and commercialize additional T-cell programs, as well as the option to license additional technology that we exercised in June 2018. We further amended and restated our license agreement and research and development collaboration agreements with QIMR Berghofer in August 2019 to terminate our license to certain rights related to CMV and again in August 2020 to terminate our license to certain rights related to BK polyomavirus and JC polyomavirus. Our current license agreement also provides for various milestone and royalty payments to QIMR Berghofer based on future product sales, if any. Under the terms of our current research and development collaboration agreement, we are also required to reimburse the cost of agreed-upon development activities related to programs developed under the collaboration. These payments are expensed on a straight-line basis over the related development periods. The agreement also provides for various milestone payments to QIMR Berghofer based on achievement of certain developmental and regulatory milestones. Other In-license and Collaboration Agreements From time to time, we have entered into other license and collaboration agreements with other parties. For example, we licensed additional rights related to our MSK-partnered next-generation CAR T programs from MSK in May 2018 and we licensed rights related to our next-generation CAR T programs from Moffitt Cancer Center in August 2018, and we agreed to collaborate through sponsored research in connection with each of these licenses. We also licensed rights related to our MSK-partnered next-generation CAR T programs from the National Institutes of Health in December 2018. Milestones and royalties under each of the above agreements are contingent upon future events and will be recorded as expense when it is probable that the milestones will be achieved or royalties are due. As of December 31, 2021 and 2020, there were no outstanding obligations for milestones and royalties under our license and collaboration agreements. 102 Cognate Manufacturing Agreement – In December 2019, we entered into a Commercial Manufacturing Services Agreement (the “Manufacturing Agreement”) with Cognate Bioservices, Inc. (“Cognate”). Pursuant to the Manufacturing Agreement, Cognate provides manufacturing services for certain of our product candidates. The initial term of the Manufacturing Agreement, as amended, runs until May 31, 2022. We may terminate the Manufacturing Agreement for convenience on six months’ written notice to Cognate, or immediately if Cognate is unable to perform the services under the Manufacturing Agreement or fails to obtain or maintain certain necessary approvals. 7. Out-license Agreements Bayer Agreements Research, Development and License Agreement In December 2020, we entered into the Bayer License Agreement to develop mesothelin-directed CAR T-cell therapies for the treatment of solid tumors, pursuant to which we granted to Bayer an exclusive, field-limited license under the applicable patents and know-how owned or controlled by us and our affiliates covering or related to ATA2271 and ATA3271 (the “Licensed Products”). Under the terms of the Bayer License Agreement, we will be responsible at our cost for all mutually agreed preclinical and clinical activities for ATA2271 through the first in human Phase 1 clinical study in collaboration with MSK, following which Bayer will be responsible for the further development of ATA2271 at its cost. Bayer will be responsible for the development of ATA3271, except for certain mutually agreed preclinical, translational, manufacturing and supply chain activities to be performed by us relating to ATA3271, in each case at Bayer’s cost. Bayer will also be solely responsible for commercializing the Licensed Products at its cost. In December 2020, we received an upfront cash payment of $ 45.0 million from Bayer for the exclusive license grant, net of applicable withholding taxes, which were fully recovered in August 2021, and an additional $ 15.0 million upfront reimbursement payment for certain research and process development activities to be performed by us. We are also entitled to receive (i) up to $ 5.0 million for additional, specified translational activities under the Bayer License Agreement, of which we have invoiced $ 1.3 million, and (ii) an aggregate of up to $ 610.0 million in milestone payments upon achieving certain development, regulatory and commercial milestones relating to the Licensed Products. In addition, we are eligible to receive from Bayer tiered royalties at percentages up to low double digits on worldwide net product sales of the Licensed Products on a country-by-country and product-by-product basis until the later of 12 years after the first commercial sale in such country or the expiration of specified patent rights in such country, subject to certain reductions and aggregate minimum floors. Bayer and we have formed a joint steering committee (“JSC”) that will provide oversight, decision making and implementation guidance regarding the collaboration activities covered under the agreement. We assessed this arrangement in accordance with ASC 606 and concluded that the promises in the Bayer License Agreement represent transactions with a customer. We concluded that the Bayer License Agreement contains the following promises: (i) a development and commercialization license; (ii) performance of early-stage research and development (“R&D”) services, including technology transfer services; (iii) JSC participation; and (iv) chemistry, manufacturing and control (“CMC”) services. In accordance with ASC 606, we determined that the license, early-stage R&D and CMC services were not distinct from each other, as the license, early-stage R&D and CMC services are highly interdependent upon one another. Participation on the JSC to oversee the research and development activities are combined into the single performance obligation as these activities are highly interdependent with the other R&D and CMC services. Accordingly, we determined that these promises should be combined into a single performance obligation. The transaction price at inception consisted of a $ 45.0 million upfront payment for the license, $ 15.0 million for certain research and process development activities and the $ 5.0 million for additional specified translational activities, and this amount was allocated to the single performance obligation. The potential development and commercial milestone payments that we are eligible to receive were excluded from the transaction price, as all milestone amounts were fully constrained based on the probability of achievement. None of the future royalty and sales-based milestone payments were included in the transaction price, as the potential payments represent sales-based consideration. We will reevaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and, if necessary, adjust our estimate of the transaction price. Technology Transfer Agreement In March 2021, we entered into a Technology Transfer Agreement with Bayer (the “Bayer Tech Transfer Agreement”), which was contemplated as part of the Bayer License Agreement, to transfer to Bayer the ATA3271 manufacturing process being developed as part of the CMC services in the Bayer License Agreement. Upon entering into the agreement, we invoiced Bayer 20 percent of the total fee of $ 15.3 million under the Bayer Tech Transfer Agreement, or $ 3.1 million, which we received in the second quarter of 2021 and invoiced 40 percent of the total fee, or $ 6.1 million, in January 2022. The remainder of the fee will be billed as follows: (i) 20 percent in January 2023 and (ii) 20 percent upon the technology transfer completion . 103 We assessed this arrangement in accordance with ASC 606 and concluded that the promises in the Bayer Tech Transfer Agreement represent transactions with a customer. We concluded that the Bayer Tech Transfer Agreement should be combined with the Bayer License Agreement and accounted for as a modification of that agreement and that the Bayer Tech Transfer Agreement contains the following promises: (i) technology transfer services and (ii) supply of materials required for the technology transfer services. In accordance with ASC 606, we determined that the technology transfer services and supply of materials required for the technology transfer services were not distinct from each other, as they are highly interdependent upon one another. In addition, we concluded that the technology transfer services and supply of materials required for the technology transfer services were highly interdependent with the license, early-stage R&D and CMC services identified in the Bayer License Agreement. Accordingly, we determined that these promises should be combined into a single performance obligation. Under the Bayer Tech Transfer Agreement, in order to evaluate the appropriate transaction price, we determined that the $ 15.3 million fee constituted the entire consideration to be included in the transaction price, and this amount was allocated to the single performance obligation as identified under the Bayer License Agreement. We utilize a cost-based input method to recognize revenue based on the amount of actual costs incurred relative to the total budgeted costs expected to be incurred for the combined performance obligation. Manufacturing and Supply Agreement In March 2021, we entered into a Manufacturing and Supply Agreement with Bayer (the “Bayer Manufacturing Agreement”), which was contemplated as part of the Bayer License Agreement, to manufacture Phase 1 and 2 allogeneic mesothelin-directed CAR T-cell therapies for Bayer to use in clinical trials at a price based on our costs plus a reasonable margin, which is consistent with our standalone selling price. Under the Bayer Manufacturing Agreement, we will also provide storage and distribution services to Bayer at a price that is consistent with our standalone selling price for these services. Upon entering into the Bayer Manufacturing Agreement, Bayer submitted, and we approved, a binding purchase order for manufacturing services and storage services. Any fees for the manufacturing services will be invoiced as follows: (i) 50 percent upon written acceptance by us of the binding purchase order, and (ii) the remainder upon delivery of the certification of analysis of such lots to Bayer. Storage and distribution services are billed monthly as those services are provided to Bayer. In March 2021, we invoiced Bayer 50 percent of the total estimated supply price of $ 13.1 million for manufacturing services under the initial purchase order for the supply of six lots, or $ 6.6 million, which we received in the second quarter of 2021. The remainder of the supply price will be billed upon the release of the lots ordered by Bayer. We assessed this arrangement in accordance with ASC 606 and concluded that the promises in the manufacturing and supply agreement represent transactions with a customer. We concluded that the Bayer Manufacturing Agreement contains the following promises: (i) manufacturing services; (ii) storage services provided on a month-to-month basis; and (iii) distribution services. In accordance with ASC 606, we determined that the manufacturing services for the initial purchase order of six lots, that are expected to be provided prior to completion of the technology transfer, are not distinct as they are highly interdependent on the manufacturing process being developed and transferred under the Bayer License Agreement and the Bayer Tech Transfer Agreement. Accordingly, we determined that these promises should be combined into a single performance obligation. We also determined that each of the other services were distinct and separate performance obligations. We determined that the initial binding order for the manufacture and supply of six lots should be combined with the Bayer License Agreement and accounted for as a modification of that agreement along with the Bayer Tech Transfer Agreement. We also concluded that a binding purchase order from Bayer, together with the Bayer Manufacturing Agreement, form the contract for manufacturing services and storage services and a shipping order from Bayer forms the contract for distribution services. We also determined that the storage services provided on a month-to-month basis and distribution services are distinct and separate performance obligations. All the performance obligations identified above are priced at their standalone selling price. Under the Bayer Manufacturing Agreement, in order to evaluate the appropriate transaction price, we determined that the $ 13.1 million fee constituted the entire consideration to be included in the transaction price, and this amount was allocated to the single performance obligation as identified under the Bayer License Agreement. Revenue for the manufacturing services for the initial six lots will be recognized based on the amount of actual costs incurred relative to the total budgeted costs expected to be incurred for the combined performance obligation. Revenue for the storage services will be recognized over time as those services are provided. Revenue for the distribution services will be recognized at a point in time when the product is delivered to a clinical site designated by Bayer. 104 Bayer Revenue Recognition We utilize a cost-based input method to recognize revenue based on the amount of actual costs incurred relative to the total budgeted costs expected to be incurred for the combined performance obligation. For the year ended December 31, 2021, we recognized license and collaboration revenue of $ 19.8 million under the Bayer License Agreement, Bayer Tech Transfer Agreement and Bayer Manufacturing Agreement, collectively, the Bayer Agreements. We did no t recognize any license and collaboration revenue in 2020 under Bayer License Agreement. Deferred revenue related to the Bayer Agreements aggregated to $ 51.5 million and $ 61.3 million as of December 31, 2021 and 2020, respectively. Of the $ 51.5 million of deferred revenue as of December 31, 2021, $ 40.8 million is included in current liabilities and $ 10.7 million is included in long-term liabilities. This revenue is expected to be recognized over approximately the next three years . No development or sales-based milestone payments have been earned or received through December 31, 2021. Pierre Fabre Commercialization Agreement In October 2021, we entered into the Pierre Fabre Commercialization Agreement, pursuant to which, we granted to Pierre Fabre an exclusive, field-limited license to commercialize and distribute tab-cel ® in Europe and select emerging markets in the Middle East, Africa, Eastern Europe and Central Asia (the “Territory”) following regulatory approval. Atara will retain full rights to tab-cel ® in other major markets, including North America, Asia Pacific and Latin America. We are responsible at our cost for the conclusion of the ongoing Phase 3 ALLELE clinical study and the Phase 2 multi-cohort clinical study. We will also be responsible at our cost for certain other activities directed to obtaining regulatory approval for tab-cel ® for EBV-positive lymphoproliferative disease pursuant to the terms of the Pierre Fabre Commercialization Agreement in Europe and the UK. Pierre Fabre will be responsible at its cost for obtaining and maintaining all other regulatory approvals and for commercialization and distribution of tab-cel ® in the Territory. We will own any intellectual property rights developed solely by us under the Agreement. Pierre Fabre paid us an upfront cash payment of $ 45.0 million for the exclusive license grant in October 2021. We are also entitled to receive an aggregate of up to $ 318.0 million in milestone payments upon achieving certain regulatory and commercial milestones. In addition, we are eligible to receive double-digit tiered royalties as a percentage of net sales of tab-cel ® until the later of 12 years after the first commercial sale in such country, the expiration of specified patent rights, or the expiration of all regulatory exclusivity for such product on a country-by-country basis. We will negotiate a separate manufacturing and supply agreement with Pierre Fabre for us to manufacture tab-cel ® for Pierre Fabre to use in the Territory based on a fixed price until January 1, 2024 and cost plus a margin post January 1, 2024. We are responsible for manufacturing and supplying Pierre Fabre with tab-cel ® for commercialization in the Territory at Pierre Fabre’s cost for a minimum of seven years . Following this period, we have the option to transfer the related manufacturing technology to Pierre Fabre. We are also responsible for cell selection services at our cost until January 1, 2024 unless the parties agree to transfer the related cell selection technology to Pierre Fabre prior to this date. From January 1, 2024 onwards, if we agree to continue to provide cell selection services, it shall be at the sole expense of Pierre Fabre. Pierre Fabre and we have formed a joint steering committee (“JSC”) that will provide oversight, decision making and implementation guidance regarding the commercialization activities covered under the agreement. We assessed this arrangement in accordance with ASC 606 and concluded that the promises in the Pierre Fabre Commercialization Agreement represent transactions with a customer. We concluded that the Pierre Fabre Commercialization Agreement includes transfer of intellectual property rights in the form of a license, the potential to manufacture and supply tab-cel ® for a minimum of seven years and until tech transfer, the potential to perform cell-selection services for a minimum of three years and until tech transfer, and obligation to participate in the JSC. We concluded that the promises are not distinct because Pierre Fabre cannot benefit from the license without the other services and vis versa. Consequently, the license, manufacture and supply, cell selection and participation in the JSC is a single performance obligation. Under the Pierre Fabre Commercialization Agreement, in order to evaluate the appropriate transaction price, we determined that the $ 45 million upfront payment, constituted the entire consideration to be included in the transaction price at the outset of the arrangement. Revenue associated with the upfront fee for the single performance obligation will be deferred until the initial delivery of services related to the manufacture and supply and cell selection and then recognized over the contract performance period​. We did no t recognize any of the $ 45.0 million upfront payment as revenue in 2021. All of the $ 45.0 million of deferred revenue as of December 31, 2021 is included in long-term liabilities. The potential development and commercial milestone payments that we are eligible to receive were excluded from the transaction price, as all milestone amounts were fully constrained based on the probability of achievement. None of the future royalty and sales-based milestone payments were included in the transaction price, as the potential payments represent sales-based consideration. We will reevaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and, if necessary, adjust our estimate of the transaction price. No development or commercial milestone payments have been earned or received through December 31, 2021. 105 8 . Leases We lease our corporate headquarters in South San Francisco, California under a non-cancellable lease agreement. In December 2021, we entered into a second amendment with the landlord to extend the lease term through May 2025 . The amended lease agreement does not include an option to extend the lease term. In connection with the amended lease, we are required to maintain a letter of credit in the amount of $ 0.1 million to the landlord, a decrease of $ 0.1 million from the prior lease agreement, and which expires and is renewed every 12 months, and is classified as restricted cash in our consolidated balance sheet. As of December 31, 2021, we were still working to update our letter of credit and continued to report an amount of $ 0.2 million as restricted cash related to this letter of credit on our consolidated balance sheet. I n March 2021, we entered into a new lease agreement for approximately 33,659 square feet of office, lab and warehouse space in Thousand Oaks, California. During the third quarter of 2021, the initial 10.5 -year lease term commenced, upon substantial completion of the landlord’s work as defined under the agreement. The contractual obligations during the initial lease term are $ 21.0 million in aggregate. Base rent is subject to annual increase of 3 % with each annual anniversary of the rent commencement date. We have the option to extend this lease for two additional five-year periods after the initial term. In February 2017, we entered into a lease agreement for approximately 90,580 square feet of office, lab and cellular therapy manufacturing space in Thousand Oaks, California. The initial 15 -year term of the lease commenced on February 15, 2018 , upon the substantial completion of landlord’s work as defined under the agreement. The contractual obligations during the initial term are $ 16.4 million in aggregate. We have the option to extend the lease for two additional periods of ten and nine years , respectively, after the initial term. In connection with the lease, we were required to issue a letter of credit in the amount of $ 1.2 million to the landlord, which is recorded as long-term restricted cash in our consolidated balance sheet. In November 2018, we entered into a lease agreement for additional office space in Thousand Oaks, California that expires in February 2026 and for which we have the option to extend the lease for an additional period of five years after the initial term. Additionally, in 2021, we entered into an amended lease agreement for our office and lab space in Aurora, Colorado, to add additional lab space. Incremental contractual obligations under the lease amendment are $ 0.2 million, and the lease term continues to expire in April 2024 . The maturities of lease liabilities under our operating and finance leases as of December 31, 2021 were as follows: Operating Leases Finance Leases Years Ending December 31, (in thousands) 2022 5,171 $ 181 2023 5,265 29 2024 5,183 — 2025 4,806 — 2026 3,257 — Thereafter 19,004 — Total lease payments $ 42,686 $ 210 Less: amount representing interest ( 14,586 ) ( 10 ) Present value of lease liabilities $ 28,100 $ 200 Balance as of December 31, 2021 Other current liabilities $ 2,582 $ 171 Operating lease liabilities - long-term 25,518 — Other long-term liabilities — 29 Total $ 28,100 $ 200 106 The components of lease cost were as follows: Year Ended Year Ended Year Ended December 31, 2021 December 31, 2020 December 31, 2019 (in thousands) (in thousands) Operating lease cost: Operating lease cost $ 3,827 $ 3,020 $ 2,578 Short-term lease cost 836 987 770 Total operating lease cost $ 4,663 $ 4,007 $ 3,348 Finance lease cost: Amortization expense $ 244 $ 389 $ 324 Interest on lease liabilities 29 60 56 Total finance lease cost $ 273 $ 449 $ 380 Other information related to leases was as follows: Year Ended Year Ended Year Ended December 31, 2021 December 31, 2020 December 31, 2019 (in thousands, except lease term and discount rate) Supplemental Cash Flows Information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 3,738 $ 2,878 $ 2,346 Operating cash flows for finance leases 32 62 50 Financing cash flows for finance leases 254 389 486 Operating lease assets obtained in exchange for lease obligations: $ 13,427 $ — $ 838 Finance lease assets obtained in exchange for lease obligations: — 281 323 Non-cash increase to operating lease assets due to remeasurement of lease liabilities: 1,760 639 Weighted Average Remaining Lease Term Operating leases 9.2 years 9.4 years 10.3 years Finance leases 1.0 years 1.7 years 2.5 years Weighted Average Discount Rate Operating leases 9.6 % 10.3 % 10.4 % Finance leases 9.7 % 9.7 % 10.0 % Asset Retirement Obligation The Company’s ARO consists of a contractual requirement to remove the tenant improvements at our manufacturing facility in Thousand Oaks, California and restore the facility to a condition specified in the lease agreement. The Company records an estimate of the fair value of its ARO in long-term liabilities in the period incurred. The fair value of the ARO is also capitalized in property and equipment, net and depreciated over the lease term. The fair value of our ARO was estimated by discounting projected cash flows over the estimated life of the related assets using our credit adjusted risk-free rate. The following table presents the activity for our ARO liabilities: ARO Liability (In thousands) Balance as of December 31, 2020 $ 866 Accretion expense 87 Balance as of December 31, 2021 $ 953 107 9 . Commitments and Contingencies License and Collaboration Agreements Potential payments related to our license and collaboration agreements, including milestone and royalty payments, are detailed in Note 6. Other Research and Development Agreements We may enter into contracts in the normal course of business with clinical research organizations for clinical trials, with contract manufacturing organizations for clinical supplies, and with other vendors for preclinical studies, supplies and other services for our operating purposes. These contracts generally provide for termination on notice. As of December 31, 2021 and 2020, there were no amounts accrued related to termination charges for minimum purchase volumes not being met. Indemnification Agreements In the normal course of business, we enter into contracts and agreements that contain a variety of representations and warranties and provide for indemnification for certain liabilities. The exposure under these agreements is unknown because it involves claims that may be made against us in the future but have not yet been made. To date, we have not paid any claims or been required to defend any action related to our indemnification obligations. However, we may record charges in the future as a result of these indemnification obligations. We also have indemnification obligations to our directors and executive officers for specified events or occurrences, subject to some limits, while they are serving at our request in such capacities. There have been no claims to date and we consider the fair value of these indemnification agreements to be minimal. Accordingly, we did no t record liabilities for these agreements as of December 31, 2021 and 2020. Contingencies From time to time, we may be involved in legal proceedings, as well as demands, claims and threatened litigation, which arise in the normal course of our business or otherwise. The ultimate outcome of any litigation is uncertain and unfavorable outcomes could have a negative impact on our results of operations and financial condition. Regardless of outcome, litigation can have an adverse impact on us because of the defense costs, diversion of management resources and other factors. We are not currently involved in any material legal proceedings. 10 . Stockholders’ Equity Our authorized capital stock consists of 520,000,000 shares, all with a par value of $ 0.0001 per share, of which 500,000,000 shares are designated as common stock and 20,000,000 shares are designated as preferred stock. There were no shares of preferred stock outstanding as of December 31, 2021 and 2020 . Equity Offerings In July 2019, we issued and sold 6,871,727 shares of common stock at a public offering price of $ 15.28 per share and pre-funded warrants to purchase 2,945,026 shares of common stock at an offering price of $ 15.2799 per warrant in an underwritten public offering pursuant to a shelf registration on Form S-3. The gross proceeds from this offering were $ 150.0 million, resulting in aggregate net proceeds of $ 140.7 million, after deducting underwriting discounts and commissions and offering expenses payable by us. Each pre-funded warrant entitles the holder to purchase one share of common stock at an exercise price of $ 0.0001 per share and expires seven years from the date of issuance. These warrants were recorded as a component of stockholders’ equity within additional paid-in capital. Per the terms of the warrant agreement, a holder of the outstanding warrants is not entitled to exercise any portion of any pre-funded warrant if, upon exercise of the warrant, the holder’s ownership (together with its affiliates) of our common stock or combined voting power of our securities beneficially owned by such holder (together with its affiliates) would exceed 9.99 % after giving effect to the exercise (“Maximum Ownership Percentage”). Upon at least 61 days’ prior notice to us by the holder, any holder may increase or decrease the Maximum Ownership Percentage to any other percentage not to exceed 19.99 %. As of December 31, 2021, 2,888,526 of the pre-funded warrants from the July 2019 offering were outstanding. 108 In the second quarter of 2020, we issued and sold 12,633,039 shares of common stock at a public offering price of $ 11.32 per share and pre-funded warrants to purchase 2,866,961 shares of common stock at a public offering price of $ 11.3199 per warrant in an underwritten public offering pursuant to a shelf registration on Form S-3. We granted the underwriters an option to purchase up to 2,325,000 additional shares of our common stock at a public offering price of $ 11.32 , less underwriting discounts and commissions. The full option was exercised by the underwriters in June 2020. The gross proceeds from this public offering were $ 201.8 million, resulting in net proceeds of $ 189.3 million, after deducting underwriting discounts and commissions and offering expenses payable by us. The terms of the pre-funded warrants issued and sold as part of this public offering were similar to those above. In December 2020, we issued and sold 5,102,041 shares of common stock at a public offering price of $ 24.50 per share and pre-funded warrants to purchase 2,040,816 shares of common stock at a public offering price of $ 24.4999 per warrant in an underwritten public offering pursuant to a shelf registration on Form S-3. The gross proceeds from this public offering were $ 175.0 million, resulting in net proceeds of $ 164.3 million, after deducting underwriting discounts and commissions and estimated offering expenses payable by us. As of December 31, 2021, all of the pre-funded warrants issued and sold as part of the 2020 underwritten public offerings were outstanding. ATM Facilities In February 2019, we entered into a sales agreement (the “2019 ATM Facility”) with Cowen, which provided for the sale, in our sole discretion, of shares of our common stock having an aggregate offering price of up to $ 100.0 million through Cowen, as our sales agent. We paid a commission of up to 3.0 % of gross sales proceeds of the common stock sold under the 2019 ATM Facility. In February 2020, we entered into a sales agreement (the “2020 ATM Facility”) with Cowen, which provides for the sale, in our sole discretion, of shares of our common stock having an aggregate offering price of up to $ 100.0 million through Cowen, as our sales agent. The 2020 ATM Facility is separate from and did not replace the 2019 ATM Facility in any way. We paid a commission of up to 3.0 % of gross sales proceeds of any common stock sold under the 2020 ATM Facility. In November 2021, we entered into a sales agreement (the “2021 ATM Facility”) with Cowen, which provides for the sale, in our sole discretion, of shares of our common stock having an aggregate offering price of up to $ 100.0 million through Cowen, as our sales agent. The 2021 ATM Facility is separate from and does not replace the 2020 ATM Facility in any way. We pay a commission of up to 3.0 % of gross sales proceeds of any common stock sold under the 2021 ATM Facility. During the fiscal year ended December 31, 2020 , we sold an aggregate of 4,785,514 shares of common stock under the ATM facilities, at an average price of $ 14.60 per share, for gross proceeds of $ 69.9 million and net proceeds of $ 68.0 million, after deducting commissions and other offering expenses payable by us. During the fiscal year ended December 31, 2021 , we sold an aggregate of 6,240,601 shares of common stock under the ATM facilities, at an average price of $ 16.23 per share, for gross proceeds of $ 101.3 million and net proceeds of $ 98.9 million, after deducting commissions and other offering expenses payable by us. The issuance and sale of these shares by us pursuant to the ATM facilities are deemed “at the market” offerings as defined in Rule 415 under the Securities Act of 1933, as amended (the “Securities Act”), and are registered under the Securities Act. As of December 31, 2021 , we had fully utilized the 2019 ATM Facility, and the 2020 ATM Facility and we had $ 78.3 million of common stock remaining and available to be sold under the 2021 ATM Facility. From January 1, 2022 through February 15, 2022, we sold an additional 1,319,878 shares of common stock under the 2021 ATM Facility, at an average price of $ 15.88 per share, for gross proceeds of $ 21.0 million and net proceeds of $ 20.5 million, after deducting commissions and other offering expenses payable by us. As of February 15, 2022, we had $ 57.4 million of common stock remaining and available to be sold under the 2021 ATM Facility, subject to certain conditions as specified in the agreement. 109 Equity Incentive Plans In March 2014, we adopted the 2014 Equity Incentive Plan (“2014 EIP”), which was amended and restated on October 15, 2014 upon the pricing of our initial public offering (“IPO”). The 2014 EIP provides for annual increases in the number of shares available for issuance thereunder on the first business day of each fiscal year, beginning with 2015 and ending in 2024, equal to five percent of the number of shares of the Company’s common stock outstanding as of such date or a lesser number of shares as determined by our board of directors. Under the terms of the 2014 EIP, we may grant stock options, RSAs and RSUs to employees, directors, consultants and other service providers. RSUs generally vest over four years . In 2020, we granted performance-based awards to certain of our employees that provide for the issuance of common stock if specified Company performance criteria related to our clinical programs are achieved. The number of performance-based awards that ultimately vests depends upon if, when and which performance criteria are achieved, as well as the employee’s continuous service, as defined in the 2014 EIP, through the date of vesting. The fair value of RSUs, including those with performance conditions, is determined as the closing stock price on the date of grant. Stock options are granted with exercise prices at no less than 100 % of the estimated fair value of the shares on the date of grant as determined by the board of directors, provided, however, that the exercise price of an option granted to a 10 % shareholder cannot be less than 110 % of the estimated fair value of the shares on the date of grant. The estimated fair value is generally equal to the closing market price of the Company’s common stock on the measurement date. Options granted generally vest over four years and expire in seven to ten years . As of December 31, 2021, a total of 16,086,987 shares of common stock were reserved for issuance under the 2014 EIP, of which 4,018,597 shares were available for future grant and 12,068,390 shares were subject to outstanding options and RSUs, including performance-based awards. In February 2018, we adopted the 2018 Inducement Plan (“Inducement Plan”), under which we may grant options, stock appreciation rights, RSAs and RSUs to new employees. In September 2020, we amended the Inducement Plan to reserve an additional 1,500,000 shares of the Company’s common stock for issuance under the Inducement Plan, and in September 2021 we made a further amendment to reserve an additional 1,500,000 shares of the Company’s common stock for issuance under the Inducement Plan. As of December 31, 2021 , 4,022,184 shares of common stock were reserved for issuance under the Inducement Plan, of which 1,278,379 shares were available for future grant and 2,743,805 shares were subject to outstanding options and RSUs. Restricted Stock Units The weighted average grant date fair value of RSUs granted during the years ended December 31, 2021 , 2020 and 2019 was $ 16.42 , $ 12.19 and $ 27.04 , respectively. The estimated fair value of RSUs that vested in the years ended December 31, 2021 , 2020 and 2019 was $ 27.1 million, $ 23.6 million and $ 13.8 million, respectively. As of December 31, 2021 , there was $ 75.7 million of unrecognized stock-based compensation expense related to RSUs that is expected to be recognized over a weighted average period of 2.8 years. This excludes unrecognized stock-based compensation expense for performance-based RSUs that were deemed not probable of vesting in accordance with U.S. GAAP. The aggregate intrinsic value of the RSUs outstanding as of December 31, 2021 was $ 88.1 million. The following is a summary of RSU activity under our 2014 EIP and Inducement Plan: RSUs Shares Weighted Average Grant Date Fair Value Balance as of December 31, 2020 3,829,620 $ 15.91 Granted 4,624,257 $ 16.42 Forfeited ( 1,307,626 ) $ 14.64 Vested ( 1,553,893 ) $ 17.41 Balance as of December 31, 2021 5,592,358 $ 16.22 110 Under our RSU settlement procedures, for some of the RSUs granted to our employees, we withhold shares at settlement to cover the estimated payroll withholding tax obligations. During 2021, we settled 1,553,893 shares underlying RSUs, of which 154,341 shares underlying RSUs were net settled by withholding 61,385 shares. The value of the shares underlying RSUs withheld was $ 1.2 million, based on the closing price of our common stock on the settlement date. During 2020, we settled 1,218,945 shares underlying RSUs, of which 276,822 shares underlying RSUs were net settled by withholding 106,459 shares. The value of the shares underlying RSUs withheld was $ 1.5 million, based on the closing price of our common stock on the settlement date. The value of RSUs withheld in each period was remitted to the appropriate taxing authorities and has been reflected as a financing activity in our consolidated statements of cash flows. Stock Options The following is a summary of stock option activity under our 2014 EIP and Inducement Plan. The table below also includes the activity relating to options for 275,000 shares of our common stock which were issued in 2017 outside of these plans: Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (in thousands) Balance as of December 31, 2020 7,851,886 $ 22.89 6.4 $ 26,834 Granted 2,643,378 15.97 Exercised ( 246,867 ) 13.97 Forfeited or expired ( 1,028,560 ) 25.92 Balance as of December 31, 2021 9,219,837 $ 20.81 6.4 $ 12,810 Vested and expected to vest as of December 31, 2021 9,219,837 $ 20.81 6.4 $ 12,810 Exercisable as of December 31, 2021 5,073,289 $ 24.36 4.8 $ 5,496 Aggregate intrinsic value represents the difference between the closing stock price of our common stock on December 31, 2021 and the exercise price of outstanding, in-the-money options. As of December 31, 2021 , there was $ 41.9 million of unrecognized stock-based compensation expense related to stock options that is expected to be recognized over a weighted average period of 2.5 years. Options for 246,867 , 268,938 and 347,716 shares of our common stock were exercised during the years ended December 31, 2021 , 2020 and 2019, with an intrinsic value of $ 0.8 million, $ 1.0 million and $ 3.8 million, respectively. As we believe it is more likely than not that no stock option related tax benefits will be realized, we do no t record any net tax benefits related to exercised options. The fair value of each option issued was estimated at the date of grant using the Black-Scholes valuation model. The following table summarizes the weighted-average assumptions used as inputs to the Black-Scholes model and resulting weighted-average grant date fair values of stock options granted during the periods indicated: Year ended December 31, 2021 2020 2019 Assumptions: Expected term (years) 6.0 6.0 5.9 Expected volatility 75.9 % 76.8 % 76.1 % Risk-free interest rate 0.9 % 0.8 % 2.1 % Expected dividend yield 0.0 % 0.0 % 0.0 % Fair Value: Weighted-average estimated grant date fair value per share $ 10.52 $ 7.96 $ 18.06 Options granted 2,643,378 2,641,125 2,535,425 Total estimated grant date fair value $ 27,808,000 $ 21,023,000 $ 45,790,000 The estimated fair value of stock options that vested in the years ended December 31, 2021 , 2020 and 2019 was $ 26.6 million, $ 29.4 million and $ 31.6 million, respectively. 111 Employee Stock Purchase Plan In May 2014, we adopted the 2014 Employee Stock Purchase Plan (“2014 ESPP”), which became effective on October 15, 2014 upon the pricing of our IPO. The 2014 ESPP permits eligible employees to purchase common stock at a discount through payroll deductions during defined offering periods. Eligible employees can purchase shares of the Company’s common stock at 85 % of the lower of the fair market value of the common stock at (i) the beginning of a 12-month offering period, or (ii) at the end of one of the two related 6-month purchase periods . No participant in the 2014 ESPP may purchase shares of common stock valued at more than $ 25,000 per calendar year. The first offering under the 2014 ESPP commenced on June 1, 2016 , and subsequent offerings commence on each anniversary of this date. The Company recorded $ 1.7 million, $ 1.8 million and $ 1.3 million of expense related to the 2014 ESPP in the years ended December 31, 2021, 2020 and 2019, respectively. A total of 319,190 , 282,514 and 139,466 shares were purchased under the ESPP during the years ended December 31, 2021 , 2020 and 2019, respectively. As of December 31, 2021, there was $ 0.6 million of unrecognized stock-based compensation expense related to the ESPP that is expected to be recognized by the end of second quarter of 2022. The 2014 ESPP provides for annual increases in the number of shares available for issuance thereunder on the first business day of each fiscal year, beginning with 2015 and ending in 2024, equal to the lower of (i) one percent of the number of shares of our common stock outstanding as of such date, (ii) 230,769 shares of our common stock, or (iii) a lesser number of shares as determined by our board of directors. As of December 31, 2021, there were 1,817,511 shares authorized under the 2014 ESPP. Reserved Shares The following shares of common stock were reserved for future issuance under our equity incentive plans as of December 31, 2021 : Total Shares Reserved 2014 Equity Incentive Plan 16,086,987 2018 Inducement Plan 4,022,184 2014 Employee Stock Purchase Plan 862,382 Total reserved shares of common stock 20,971,553 Stock-based Compensation Expense Total stock-based compensation expense related to all stock awards was as follows: Year Ended December 31, 2021 2020 2019 (in thousands) Research and development $ 32,063 $ 31,527 $ 26,773 General and administrative 21,802 19,824 24,923 Total stock-based compensation expense $ 53,865 $ 51,351 $ 51,696 1 1 . Income Taxes Losses before provision for income taxes were as follows in each period presented: Year Ended December 31, 2021 2020 2019 (in thousands) United States $ ( 340,301 ) $ ( 306,758 ) $ ( 291,049 ) Foreign 206 153 85 Total loss before provision for income taxes $ ( 340,095 ) $ ( 306,605 ) $ ( 290,964 ) 112 The components of provision for (benefit from) income taxes were as follows in each period presented: Year Ended December 31, 2021 2020 2019 (in thousands) Current provision for (benefit from) income taxes: State 4 2 — Foreign 42 13 12 Total current provision for (benefit from) income taxes $ 46 $ 15 $ 12 A reconciliation of statutory tax rates to effective tax rates were as follows in each of the periods presented: Year Ended December 31, 2021 2020 2019 Federal income taxes at statutory rate 21.0 % 21.0 % 21.0 % Impact of stock compensation ( 2.0 %) ( 2.4 %) 0.1 % Non-deductible executive compensation ( 0.2 %) ( 0.1 %) ( 0.7 %) Other ( 0.1 %) 0.3 % ( 0.2 %) Change in valuation allowance ( 18.7 %) ( 18.8 %) ( 20.2 %) Effective tax rate 0.0 % 0.0 % 0.0 % Deferred tax assets and liabilities reflect the net tax effect of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of our deferred tax assets and liabilities were as follows for each of the dates presented: As of December 31, 2021 2020 (in thousands) Deferred tax assets: Net operating losses $ 308,997 $ 237,010 Stock-based compensation 24,181 20,672 Capitalized expenses 10,499 12,590 License fees 8,716 8,159 Operating lease liabilities 7,972 4,251 Legal fees 2,366 2,136 Tax credits 1,580 1,580 Deferred Revenue 12,133 — Other 7,048 5,360 Total deferred tax assets 383,492 291,758 Valuation allowance ( 376,071 ) ( 287,349 ) Total deferred tax assets 7,421 4,409 Deferred tax liabilities: Operating lease assets ( 7,421 ) ( 3,541 ) Other — ( 868 ) Total deferred tax liabilities ( 7,421 ) ( 4,409 ) Net deferred tax assets (liabilities) $ — $ — 113 We recognize deferred income taxes for temporary differences between the basis of assets and liabilities for financial statement and income tax purposes, as well as for tax attribute carryforwards. We regularly evaluate the positive and negative evidence in determining the realizability of our deferred tax assets. Based upon the weight of available evidence, which includes our historical operating performance and reported cumulative net losses since inception, we maintained a full valuation allowance on the net deferred tax assets as of December 31, 2021 and 2020. We intend to maintain a full valuation allowance on our deferred tax assets until sufficient positive evidence exists to support reversal of the valuation allowance. The valuation allowance increased by $ 88.7 million for the year ended December 31, 2021 primarily due to federal and state NOLs and other U.S. deferred tax assets, which includes accelerated Bayer revenue recognition for tax purposes during 2021. In response to the COVID-19 pandemic, the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) was signed into law on March 27, 2020, providing companies with various tax relief provisions and other stimulus measures. Such measures include, but are not limited to, temporary changes regarding the prior and future utilization of net operating losses, technical corrections to prior tax legislation for tax depreciation of certain qualified improvement property, acceleration of AMT credit refunds, and changes to business interest limitations. The Consolidated Appropriations Act was also signed into law on December 27, 2020 to provide further relief measures and renew various expiring tax provisions. Additionally, the IRS issued final regulations and proposed regulations on calculating the limitation on business interest expense, the allowance for the first-year depreciation deduction under IRC Section 168(k), as amended by the Tax Cuts and Jobs Act (the “Tax Act”), for qualified property acquired and placed in service after September 27, 2017, and meals and entertainment deductions. Based on our evaluation, these regulations did not have a material impact on the income tax provision for the years ended December 31, 2021, 2020 and 2019. Under the Tax Act, federal net operating losses generated in tax years beginning on or after January 1, 2018 and in future years may be carried forward indefinitely, but the utilization of such federal net operating losses is limited to 80% of current year taxable income. The CARES Act temporarily suspends this 80% taxable income limitation, allowing a net operating loss carryforward to fully offset taxable income in tax years beginning before January 1, 2021. It is uncertain if, and to what extent, various states will conform to the Tax Act or the CARES Act. The Tax Act nor the CARES Act had a material impact to our financial statements. As of December 31, 2021 , for federal income tax purposes, we had net operating loss carryforwards of approximately $ 1,064.4 million, of which $ 65.2 million begin to expire in 2032 and $ 999.2 do not expire, research & development tax credits of approximately $ 18.0 million which begin to expire in 2032 , and orphan drug tax credits of approximately $ 94.5 million which begin to expire in 2035 . For California income tax purposes, we had net operating loss carryforwards of approximately $ 1,045.5 million which begin to expire in 2032 , and research & development tax credits of approximately $ 30.4 million which do not expire, and Competes tax credit of $ 2.0 million which begins to expire in 2024 . For other states income tax purposes, we had net operating loss carryforwards of approximately $ 226.6 million which begins to expire in 2030 . Under Section 382 of the Internal Revenue Code of 1986, as amended, our ability to utilize net operating loss carryforwards or other tax attributes in any taxable year may be limited if we have experienced an “ownership change.” Generally, a Section 382 “ownership change” occurs if one or more stockholders or groups of stockholders who owns at least 5% of a corporation’s stock increases its ownership by more than 50 percentage points over its lowest ownership percentage within a specified testing period. Similar rules may apply under state tax laws. We have performed a Section 382 analysis of transactions in our stock through December 31, 2021. We have experienced ownership changes since inception and our utilization of net operating loss carryforwards will be subject to annual limitations. However, it is not expected that the annual limitations will result in the expiration of tax attribute carryforwards prior to utilization . 114 The changes in the balance of gross unrecognized tax benefits, which excludes interest and penalties, for the years ended December 31, 2019, 2020 and 2021 are as follows: (In thousands) Balance as of January 1, 2019 $ 41,074 Gross increases for tax positions related to current year 22,800 Gross increases for tax positions related to prior year 22,126 Gross decreases for tax positions related to prior year — Balance as of December 31, 2019 86,000 Gross increases for tax positions related to current year 24,648 Gross increases for tax positions related to prior year — Gross decreases for tax positions related to prior year ( 47 ) Balance as of December 31, 2020 110,601 Gross increases for tax positions related to current year 28,171 Gross increases for tax positions related to prior year 5,295 Gross decreases for tax positions related to prior year — Balance as of December 31, 2021 $ 144,067 The Company currently has a full valuation allowance against its U.S. net deferred tax assets, which would impact the timing of the effective tax rate benefit should any uncertain tax position be favorably settled in the future. For 2021, 2020, and 2019 total unrecognize benefits in the amount of $ 144.1 million, $ 110.6 million, and $ 86.0 million, respectively, no amount, if recognized, would affect the Company’s effective tax rate. The Company’s policy is to account for interest and penalties related to uncertain tax positions as a component of the income tax provision. The Company has not accrued interest and penalties as of December 31, 2021 due to available tax losses. Our significant jurisdictions are the U.S. federal jurisdiction and the California state jurisdiction. All of our tax years remain open to examination by the U.S. federal and California tax authorities. We also file in other state, local and foreign jurisdictions in which we operate, and such tax years remain open to examination. The 2017 Tax Act imposed a mandatory transition tax on accumulated foreign earnings and generally eliminated U.S. taxes on foreign subsidiary distribution. As of December 31, 2021, the Company is not permanently reinvested with respect to its foreign earnings and has not recorded deferred income taxes and withholding taxes as these taxes are immaterial to the financial statements. 12. Subsequent Events On January 26, 2022, the Company announced it has entered into an asset purchase agreement with FUJIFILM Diosynth Biotechnologies California, Inc. and, for certain limited purposes, FUJIFILM Holdings America Corporation, to sell all of the Company’s right, title and interest in and to certain assets related to the Atara T-Cell Operations and Manufacturing facility located at 2430 Conejo Spectrum Street, Thousand Oaks, California for $ 100 million in cash, plus or minus certain closing adjustments pursuant to the asset purchase agreement. The closing of the proposed transaction is expected to occur in the quarter ending June 30, 2022, subject to certain closing conditions, including clearance of the transaction under the Hart-Scott-Rodino Antitrust Improvements Act of 1976. 115 Item 9. Changes in and Disagreements with Accountants on Accounting and Financial Disclosure None.