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Summary of Significant Accounting Policies | 12 Months Ended
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Dec. 31, 2018
Summary of Significant Accounting Policies |
Summary of Significant Accounting Policies | 1. Summary of Significant Accounting Policies Description of Business Xencor, Inc. (we, us, our, or the Company) was incorporated in California in 1997 and reincorporated in Delaware in September 2004. We are a clinical‑stage biopharmaceutical company focused on discovering and developing engineered monoclonal antibody and proteins to treat severe and life‑threatening diseases with unmet medical needs. We use our proprietary XmAb technology platform to create next‑generation antibody product candidates designed to treat cancer, autoimmune and allergic diseases, and other conditions. We focus on the portion of the antibody that interacts with multiple segments of the immune system, referred to as the Fc domain, which is constant and interchangeable among antibodies. Our engineered Fc domains, the XmAb technology, are applied to our pipeline of antibody and protein‑based drug candidates to increase immune inhibition, improve cytotoxicity, extend half‑life and most recently create bispecific Fc domain antibody and protein molecules. Our operations are based in Monrovia and San Diego, California. Basis of Presentation The Company’s financial statements as of December 31, 2018, 2017, and 2016 and for the years then ended have been prepared in accordance with accounting principles generally accepted in the United States (U.S.). Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Significant estimates include useful lives of long-lived assets, the periods over which certain revenues and expenses will be recognized including collaboration revenue recognized from non-refundable upfront licensing payments, the amount of non-cash compensation costs related to share-based payments to employees and non-employees and the period over which these costs are expensed. Recent Accounting Pronouncements Pronouncements adopted in 2018 Effective January 1, 2018, the Company adopted Accounting Standards Codification Topic 606 (ASC 606), Revenue from Contracts with Customers, using the full retrospective transition method. Under this method, the Company is presenting its financial statements for the years ended December 31, 2017 and 2016 as if ASC 606 had been effective for those periods. Under ASC 606 an entity recognizes revenue when its customer obtains control of promised goods or services in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. A five-step model is used to achieve the core principle: (1) identify the customer contract, (2) identify the contract’s performance obligations, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations and (5) recognize revenue when or as a performance obligation is satisfied. The Company applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. The new guidance provides that revenue recognition for performance obligations related to delivery of certain goods or services occurs when control over the good or service is transferred to the customer. In addition, the timing of revenue recognition from licensing of our intellectual property that are functional and are distinct performance obligations changed from being recognized over the term of access to our license or technology to being recognized at a point in time. See Note 12 “Prior Period Financial Statements” for a complete discussion of the impact of adopting the new standard. Effective January 1, 2018, the Company adopted ASU 2016-01, Financial Instruments – Overall: Recognition and Measurement of Financial Assets and Liabilities, which eliminates the available-for-sale classification for equity securities and requires equity securities to be measured at fair value with changes in the fair value recognized through net income. This ASU eliminates the available-for-sale classification for equity investments that recognized changes in the fair value as a component of other comprehensive income. The adoption had no effect on the Company’s financial statements. Effective January 1 2018, the Company adopted ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments, which addresses eight specific cash flow issues with the objective of reducing the existing diversity in practice. The standard clarifies when cash receipts and cash payments have aspects of more than one class of cash flows and cannot be separated. Classification will depend on the predominant source or use. The adoption did not have an effect on the Company’s statements of cash flow. Effective January 1, 2018, the Company adopted ASU No. 2017-09, Compensation – Stock Compensation (Topic 718). The standard applies when a company changes the terms of a stock compensation award previously granted to an employee where modification accounting applies. According to the standard, modification accounting is not required if (1) the fair value of the modified award (or the award’s calculated value or intrinsic value as appropriate) is the same as the value immediately prior to its modification, (2) the vesting conditions of the modified award are the same as the vesting conditions of the award immediately prior to its modification; and (3) the award’s classification as an equity or liability is the same after the modification as it was immediately prior to its modification. The Company did not have any modifications upon adopting the new standard; therefore, adoption had no effect on the Company’s financial statements. Pronouncements not yet effective In February 2016, the FASB issued ASU No. 2016-02 Leases (Topic 842). The new guidance requires lessees to recognize in the statement of financial position a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term for all leases not considered short term. The new standard will be effective for reporting periods beginning after December 15, 2018. In July 2018, the FASB issued ASU No. 2018-10 Codification Improvements to Topic 842, Leases and ASU No. 2018-11, Lease (Topic 842): Targeted Improvements, which provides narrow aspects of the guidance issued in ASU No. 2016-02 as well as an alternative transition method of adoption, permitting the recognition of cumulative-effect adjustment to retained earnings on the date of adoption. The new standard also provides a number of optional practical expedients in transition, including the “package of practical expedients,” which permits us not to reassess under the new standard our prior conclusions about lease identification, lease classification and initial direct cost. We will adopt the new standard on January 1, 2019 using the cumulative effect adjustment method, with the election of the package of practical expedients and hindsight practical expedient. We have completed a preliminary assessment of the new standard’s impact, which includes a total of five operating leases for facilities in Monrovia and San Diego. Under Topic 842, deferred rent liability under operating lease is no longer tracked separately; instead, it will integrate as part of the right-of-use (ROU) asset. As a result, we expect to adjust the cumulative effect to the beginning balance for deferred rent liability, and adopt the use of right-of-use asset and lease liability. We do not expect that this standard will have a material impact on our financial statements. Upon adoption, we estimate that we will have additional liabilities ranging from $10 million to $12 million with a corresponding ROU assets of a similar amount for lease agreements in effect as of December 31, 2018. This will result in an estimated increase to the beginning balance on both assets and liabilities after the adjustment of between $10 million and $12 million, with no impact on our retained earnings. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which amends the guidance on reporting credit losses for assets held at amortized cost basis and available-for-sale debt securities. Credit losses relating to available-for-sale debt securities will be recorded through an allowance for credit losses rather than as a direct write-down to the security. Credit losses on available-for-sale securities will be required when the amortized cost is below the fair market value. The amendment is effective for fiscal years beginning after December 15, 2019 including interim periods within those fiscal years. In November 2018, the FASB issued ASU No. 2018-19, Codification Improvements to Topic 326, Financial Instruments – Credit Losses, which clarifies that receivables arising from operating leases are not within the scope of Topic 326. We will apply the standard’s provision as a cumulative effect adjustment to retained earnings as of the beginning of the first effective reporting period. We do not expect the adoption to have a material impact on our results of operations or financial position. In March 2017, the FASB issued ASU No. 2017-08, Receivables – Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities, which amends the guidance on the amortization period of premiums on certain purchased callable debt securities by shortening the amortization period of premiums to the earliest call date. The amendment affects all entities that hold investments in callable debt securities that have an amortized cost basis in excess of the amount that is repayable by the issuer at the earliest call date. The amendment is effective for fiscal years after December 31, 2018 with early adoption permitted. The Company will review the requirements of the standard but does not anticipate it will have a significant impact on our financial statements. In February 2018, the FASB issued ASU No. 2018-02. Income Statement – Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, an amendment which permits companies to reclassify the income tax effects of the 2017 Tax Cuts and Jobs Act (TCJA) on items within accumulated other comprehensive income to retained earnings. The standard also requires new disclosures about these stranded tax effects and is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. Early adoption is permitted and can be applied either in the period of adoption or retrospectively to each period (or periods) in which the effect of the change in the U.S. federal corporate income tax rate in the TCJA is recognized. The Company is currently evaluating the impact the guidance will have on its financial statements. In June 2018, the FASB issued ASU No. 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, which expands the scope of Topic 718 to include share-based payments issued to nonemployees for goods and services. The standard is effective for fiscal years beginning after December 15, 2018 and interim periods within such fiscal year. The Company does not anticipate that the standard will have a significant impact on its financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement, which modifies the disclosures for transfers between Level 1 and Level 2 of the fair value hierarchy, modifies the level 3 disclosure requirements for non-public entities and requires additional disclosure for Level 3 fair value hierarchy. The amendment is effective for fiscal years beginning after December 15, 2019. The Company does not anticipate that the standard will have a significant impact on its financial statements. In August 2018, the FASB issued ASU No. 2018-15, Intangibles – Goodwill and Other – Internal Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract, which aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The accounting for the service element of a hosting arrangement that is a service contract is not affected by the amendment. The amendment is effective for annual periods, including interim periods within those annual periods, beginning after December 15, 2019. The Company does not anticipate that the standard will have a significant impact on its financial statements. In October 2018, the FASB issued ASU No. 2018-17, Consolidation (Topic 810): Targeted Improvements to Related Party Guidance for Variable Interest Entities, which amends the guidance for determining whether a decision-making fee is a variable interest. The amendments require organizations to consider indirect interests held through related parties under common control on a proportional basis rather than as the equivalent of a direct interest in its entirety (as currently required). The Company does not anticipate that the standard will have a significant impact on tis financial statements. In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction Between Topic 808 and Topic 606, which provides guidance on how to assess whether certain transactions between collaborative arrangement participants should be accounted for within the revenue recognition standard. The standard is effective for fiscal years beginning after December 15, 2019 and interim period within those years. The Company does not anticipate that the standard will have a significant impact on its financial statements. Revenue Recognition We have, to date, earned revenue from research and development collaborations, which may include research and development services, licenses of our internally-developed technologies, licenses of our internally-developed drug candidates, or combinations of these. The terms of our license and research and development and collaboration agreements generally include non-refundable upfront payments, research funding, co-development reimbursements, license fees and, milestone and other contingent payments to us for the achievement of defined collaboration objectives and certain clinical, regulatory and sales‑based events, as well as royalties on sales of any commercialized products. The terms of our licensing agreements include non‑refundable upfront fees, annual licensing fees, and contractual payment obligations for the achievement of pre‑defined preclinical, clinical, regulatory and sales‑based events by our partners. The licensing agreements also include royalties on sales of any commercialized products by our partners. We recognize revenue through the five-step process in accordance with ASC 606 Revenue Recognition when control of the promised goods or services is transferred to our customers in an amount that reflects the consideration we expect to be entitled to in exchange for those goods or services. Deferred Revenue Deferred revenue arises from payments received in advance of the culmination of the earnings process. We have classified deferred revenue for which we stand ready to perform within the next 12 months as a current liability. We recognize deferred revenue as revenue in future periods when the applicable revenue recognition criteria have been met. The total amounts reported as deferred revenue were $40.1 million and $60.1 million at December 31, 2018 and 2017, respectively. Research and Development Expenses Research and development expenses include costs we incur for our own and for our collaborators’ research and development activities. Research and development costs are expensed as incurred. These costs consist primarily of salaries and benefits, including associated stock‑based compensation, laboratory supplies, facility costs, and applicable overhead expenses of personnel directly involved in the research and development of new technology and products, as well as fees paid to other entities that conduct certain research development activities on our behalf. We estimate preclinical study and clinical trial expenses based on the services performed pursuant to the contracts with research institutions and clinical research organizations that conduct and manage preclinical studies and clinical trials on our behalf based on the actual time and expenses incurred by them. Further, we accrue expenses related to clinical trials based on the level of patient enrollment and activity according to the related agreement. We monitor patient enrollment levels and related activity to the extent reasonably possible and adjust estimates accordingly. We capitalize acquired research and development technology licenses and third‑party contract rights and amortize the costs over the shorter of the license term or the expected useful life. We review the license arrangements and the amortization period on a regular basis and adjust the carrying value or the amortization period of the licensed rights if there is evidence of a change in the carrying value or useful life of the asset. Cash and Cash Equivalents We consider cash equivalents to be only those investments which are highly liquid, readily convertible to cash and which mature within three months from the date of purchase. Marketable Securities The Company has an investment policy that includes guidelines on acceptable investment securities, minimum credit quality, maturity parameters and concentration and diversification. The Company invests its excess cash primarily in marketable debt securities issued by investment grade institutions. The Company considers its marketable debt securities to be “available-for-sale”, as defined by authoritative guidance issued by the FASB. These assets are carried at fair value and the unrealized gains and losses are included in accumulated other comprehensive income (loss). Accrued interest on marketable debt securities is included in marketable securities. Accrued interest was $2.3 million and $1.7 million at December 31, 2018 and 2017, respectively. If a decline in the value of a marketable security in the Company’s investment portfolio is deemed to be other-than-temporary, the Company writes down the security to its current fair value and recognizes a loss as a charge against income. The Company reviews its portfolio of marketable debt securities, using both quantitative and qualitative factors, to determine if declines in fair value below cost are other-than-temporary. Concentrations of Risk Cash, cash equivalents and marketable debt securities are financial instruments that potentially subject the Company to concentrations of risk. We invest our cash in corporate debt securities and U.S. sponsored agencies with strong credit ratings. We have established guidelines relative to diversification and maturities that are designed to help ensure safety and liquidity. These guidelines are periodically reviewed to take advantage of trends in yields and interest rates. Cash and cash equivalents are maintained at financial institutions and, at times, balances may exceed federally insured limits. We have never experienced any losses related to these balances. Amounts on deposit in excess of federally insured limits at December 31, 2018 and 2017 approximated $26.0 million and $16.3 million, respectively. We have payables with four service providers that represent 49% of our total payables and two service providers that represented 40% of our total payables at December 31, 2018 and 2017, respectively. We rely on three critical suppliers for the manufacture of our drug product for use in our clinical trials. While we believe that there are alternative vendors available, a change in manufacturing vendors could cause a delay in the availability of drug product and result in a delay of conducting and completing our clinical trials. No other vendor accounted for more than 10% of total payables at December 31, 2018 or 2017. Fair Value of Financial Instruments Our financial instruments primarily consist of cash and cash equivalents, marketable debt securities, accounts receivable, accounts payable and accrued expenses. Marketable debt securities and cash equivalents are carried at fair value. The fair value of the other financial instruments closely approximate their fair value due to their short maturities. The Company accounts for recurring and non-recurring fair value measurements in accordance with FASB Accounting Standards Codification (ASC) 820, Fair Value Measurements and Disclosures (ASC 820). ASC 820 defines fair value, establishes a fair value hierarchy for assets and liabilities measured at fair value, and requires expanded disclosure about fair value measurements. The ASC 820 hierarchy ranks the quality of reliable inputs, or assumptions, used in the determination of fair value and requires assets and liabilities carried at fair value to be classified and disclosed in one of the following three categories: Level 1—Fair Value is determined by using unadjusted quoted prices that are available in active markets for identical assets or liabilities. Level 2—Fair Value is determined by using inputs other than Level 1 quoted prices that are directly or indirectly observable. Inputs can include quoted prices for similar assets or liabilities in active markets or quoted prices for identical assets or liabilities in markets that are not active. Related inputs can also include those used in valuation or other pricing models, such as interest rates and yield curves that can be corroborated by observable market data. Level 3—Fair value is determined by inputs that are unobservable and not corroborated by market data. Use of these inputs involves significant and subjective judgments to be made by the reporting entity –e.g. determining an appropriate discount factor for illiquidity associated with a given security. The Company measures the fair value of financial assets using the highest level of inputs that are reasonably available as of the measurement date. The assets recorded at fair value are classified within the hierarchy as follows for the periods reported (in thousands):
|  | December 31, 2018
|  | Total |  |  |  |  |  |
|  | Fair Value |  | Level 1 |  | Level 2
Money Market Funds in Cash and Cash Equivalents |  | $ | 18,270 |  | $ | 18,270 |  | $ | —
Corporate Securities |  |  | 104,967 |  |  | — |  |  | 104,967
Government Securities |  |  | 399,256 |  |  | — |  |  | 399,256
|  | $ | 522,493 |  | $ | 18,270 |  | $ | 504,223
|  | December 31, 2017
|  | Total |  |  |  |  |  |
|  | Fair Value |  | Level 1 |  | Level 2
Money Market Funds in Cash and Cash Equivalents |  | $ | 5,175 |  | $ | 5,175 |  | $ | —
Corporate Securities |  |  | 123,270 |  |  | — |  |  | 123,270
Government Securities |  |  | 223,530 |  |  | — |  |  | 223,530
|  | $ | 351,975 |  | $ | 5,175 |  | $ | 346,800
Property and Equipment Property and equipment are recorded at cost and depreciated using the straight‑line method over the estimated useful lives of the assets. Expenditures for repairs and maintenance are charged to expense as incurred while renewals and improvements are capitalized. Useful lives by asset category are as follows:
Computers, software and equipment |  | 3 - 5 years |
Furniture and fixtures |  | 5 - 7 years |
Leasehold improvements |  | 5 - 7 years or remaining |
|  | lease term, whichever is less |
Patents, Licenses, and Other Intangible Assets The cost of acquiring licenses is capitalized and amortized on the straight‑line basis over the shorter of the term of the license or its estimated economic life, ranging from five to 25 years. Third‑party costs incurred for acquiring patents are capitalized. Capitalized costs are accumulated until the earlier of the period that a patent is issued or we abandon the patent claims. Cumulative capitalized patent costs are amortized on a straight‑line basis from the date of issuance over the shorter of the patent term or the estimated useful economic life of the patent, ranging from 13 to 20 years. Our senior management, with advice from outside patent counsel, assesses three primary criteria to determine if a patent will be capitalized initially: i) technical feasibility, ii) magnitude and scope of new technical function covered by the patent compared to the company’s existing technology and patent portfolio, particularly assessing the value added to our product candidates or licensing business, and iii) legal issues, primarily assessment of patentability and prosecution cost. We review our intellectual property on a regular basis to determine if there are changes in the estimated useful life of issued patents and if any capitalized costs for unissued patents should be abandoned. Capitalized patent costs related to abandoned patent filings are charged off in the period of the decision to abandon. During 2018, 2017 and 2016, we abandoned previously capitalized patent and licensing related charges of $0.2 million, $0.4 million and $0.4 million, respectively. The carrying amount and accumulated amortization of patents, licenses, and other intangibles is as follows (in thousands):
|  | December 31, |
|  | 2018 |  | 2017 |
Patents, definite life |  | $ | 9,320 |  | $ | 8,915 |
Patents, pending issuance |  |  | 5,644 |  |  | 4,360 |
Licenses and other amortizable intangible assets |  |  | 2,011 |  |  | 2,011 |
Nonamortizable intangible assets (trademarks) |  |  | 399 |  |  | 399 |
Total gross carrying amount |  |  | 17,374 |  |  | 15,685 |
Accumulated amortization—patents |  |  | (4,142) |  |  | (3,413) |
Accumulated amortization—licenses and other |  |  | (1,263) |  |  | (1,124) |
Total intangible assets, net |  | $ | 11,969 |  | $ | 11,148 |
Amortization expense for patents, licenses, and other intangible assets was $0.9 million, $0.8 million, and $0.8 million for the years ended December 31, 2018, 2017 and 2016, respectively. Future amortization expense for patent, licenses, and other intangible assets recorded as of December 31, 2018, and for which amortization has commenced, is as follows:
|  | Year ended |
|  | December 31, |
|  | (in thousands) |
2019 |  | $ | 862 |
2020 |  |  | 860 |
2021 |  |  | 757 |
2022 |  |  | 730 |
2023 |  |  | 659 |
Thereafter |  |  | 1,923 |
Total |  | $ | 5,791 |
The above amortization expense forecast is an estimate. Actual amounts of amortization expense may differ from estimated amounts due to additional intangible asset acquisitions, impairment of intangible assets, accelerated amortization of intangible assets, and other events. As of December 31, 2018, the Company has $5.6 million of intangible assets which are in‑process and have not been placed in service and, accordingly amortization on these assets has not commenced. Long‑Lived Assets Management reviews long‑lived assets which include fixed assets and amortizable intangibles for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset (or asset group) may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured as the amount by which the carrying amount of the assets exceeds the fair value of the assets. We did not recognize a loss from impairment for the years ended December 31, 2018, 2017 or 2016. Income Taxes We account for income taxes in accordance with accounting guidance which requires an asset and liability approach to financial accounting and reporting for income taxes. Deferred income tax assets and liabilities are computed annually for differences between the financial statement and tax bases of assets and liabilities that will result in taxable or deductible amounts in the future based on enacted tax laws and rates applicable to the periods in which the differences are expected to affect taxable income. Valuation allowances are established when necessary to reduce deferred tax assets to the amount expected to be realized. Income tax expense is the tax payable or refundable for the period plus or minus the change during the period in deferred tax assets and liabilities. We assess our income tax positions and record tax benefits for all years subject to examination based upon our evaluation of the facts, circumstances and information available at the reporting date. For those tax positions where there is greater than 50% likelihood that a tax benefit will be sustained, we have recorded the largest amount of tax benefit that may potentially be realized upon ultimate settlement with a taxing authority that has full knowledge of all relevant information. For those income tax positions where there is a 50% or less likelihood that a tax benefit will be sustained, no tax benefit has been recognized in the financial statements. We did not have any material uncertain tax positions at December 31, 2018 or 2017. Our policy is to recognize interest and penalties on taxes, if any, as a component of income tax expense. The Tax Cuts and Jobs Act (tax reform) was enacted on December 22, 2017 and has several key provisions impacting accounting for and reporting of income taxes. The most significant provisions reduced the U.S. corporate statutory tax rate from 35% to 21%, eliminated the Alternative Minimum Tax (AMT) system, and made changes to the utilization and carryforward of net operating losses beginning on January 1, 2018. The tax reform provided for a refund of unused AMT carryforwards for years beginning after December 31, 2017. We recorded an income tax receivable as of December 31, 2018 of $1.6 million related to federal AMT carryforwards. Stock‑Based Compensation We recognize compensation expense using a fair‑value‑based method for costs related to all share‑based payments, including stock options and shares issued under our Employee Stock Purchase Plan (ESPP). Stock‑based compensation cost related to employees and directors is measured at the grant date, based on the fair‑value-based measurement of the award using the Black‑Scholes method, and is recognized as expense over the requisite service period on a straight‑line basis. We account for forfeitures when they occur. We recorded stock‑based compensation and expense for stock‑based awards to employees, directors and consultants of approximately $20.5 million, $13.7 million, and $7.8 million for the years ended December 31, 2018, 2017 and 2016 respectively. Included in the 2018, 2017, and 2016 balances for total compensation expense is $0.7 million, $0.5 million, and $0.4 million, respectively, relating to our ESPP. Options granted to individual service providers that are not employees or directors are accounted for at estimated fair value using the Black‑Scholes option‑pricing method and are subject to periodic re‑measurement over the period during which the services are rendered. Net Income (Loss) Per Share Basic net income (loss) per common share is computed by dividing the net income or loss by the weighted‑average number of common shares outstanding during the period. Potentially dilutive securities consisting of stock options for 2018 and 2017, and stock purchases under the Employee Stock Purchase Plan were not included in the diluted net loss per common shares calculation because the inclusion of such shares would have had an antidilutive effect as follows:
|  | Year Ended |
|  | December 31, |
|  | 2018 |  | 2017 |  | 2016 |
|  | (in thousands) |
Options to purchase common stock |  | 1,881 |  | 1,291 |  | — |
Employee stock purchase plan shares |  | 3 |  | — |  | — |
Total |  | 1,884 |  | 1,291 |  | — |
|  | Year Ended December 31, |
|  | 2018 |  | 2017 |  | 2016 |
|  | (in thousands, except share and per share data) |
|  |  |  | (As Revised) |  | (As Revised) |
Basic |  |  |  |  |  |  |  |  |  |
Numerator: |  |  |  |  |  |  |  |  |  |
Net income (loss) attributable to common stockholders for basic net income (loss) per share |  | $ | (70,409) |  | $ | (38,486) |  | $ | 45,125 |
Denominator: |  |  |  |  |  |  |  |  |  |
Weighted-average common shares outstanding |  |  | 53,942,116 |  |  | 46,817,756 |  |  | 41,267,329 |
Basic net income (loss) per common share |  | $ | (1.31) |  | $ | (0.82) |  | $ | 1.09 |
Diluted |  |  |  |  |  |  |  |  |  |
Numerator: |  |  |  |  |  |  |  |  |  |
Net income (loss) attributable to common stockholders for diluted net income (loss) per share |  | $ | (70,409) |  | $ | (38,486) |  | $ | 45,125 |
Denominator: |  |  |  |  |  |  |  |  |  |
Weighted average number of common shares outstanding used in computing basic net income (loss) per common share |  |  | 53,942,116 |  |  | 46,817,756 |  |  | 41,267,329 |
Dilutive effect of employee stock options and ESPP |  |  | — |  |  | — |  |  | 1,121,538 |
Weighted-average number of common shares outstanding used in computing diluted net income (loss) per common share |  |  | 53,942,116 |  |  | 46,817,756 |  |  | 42,388,867 |
Diluted net income (loss) per common share |  | $ | (1.31) |  | $ | (0.82) |  | $ | 1.07 |
Segment Reporting The Company determines its segment reporting based upon the way the business is organized for making operating decisions and assessing performance. The Company has only one operating segment related to the development of pharmaceutical products.

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