Alder Biopharmaceuticals (ALDR) 10-Q 8 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	May 02, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Trading Symbol	ALDR
Entity Registrant Name	ALDER BIOPHARMACEUTICALS INC
Entity Central Index Key	1,423,824
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		67,850,037

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 201,956	$ 76,896
Short-term investments	129,005	199,344
Restricted cash	2,500
Prepaid expenses and other assets	7,281	11,014
Total current assets	340,742	287,254
Long-term investments	246,086
Property and equipment, net	5,055	5,630
Restricted cash	7,500	10,000
Investment in unconsolidated entity		222
Other assets	30	30
Total assets	599,413	303,136
Current liabilities
Accounts payable	12,801	7,471
Accrued liabilities	11,640	15,803
Accrued dividends on convertible preferred stock	1,083
Deferred rent	87	92
Total current liabilities	25,611	23,366
Long-term deferred rent	497	495
2025 convertible senior notes, net	173,197
Total liabilities	199,305	23,861
Commitments and contingencies
Stockholders’ equity
Common stock; $0.0001 par value; 200,000,000 shares authorized; 67,848,701 and 67,842,942 shares issued and outstanding, respectively	7	7
Additional paid-in capital	1,057,900	946,869
Accumulated deficit	(754,540)	(667,509)
Accumulated other comprehensive loss	(969)	(92)
Total stockholders’ equity	302,398	279,275
Total liabilities, convertible preferred stock and stockholders’ equity	599,413	$ 303,136
Series A-1 Convertible Preferred Stock
Current liabilities
Series A-1 convertible preferred stock; $0.0001 par value; 10,000,000 shares authorized; 725,268 shares and no shares issued and outstanding, respectively; liquidation preference of $100,000 and zero, respectively	$ 97,710

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	67,848,701	67,842,942
Common stock, shares outstanding	67,848,701	67,842,942
Series A-1 Convertible Preferred Stock
Temporary equity, par value	$ 0.0001	$ 0.0001
Temporary equity, shares authorized	10,000,000	10,000,000
Temporary equity, shares issued	725,268	0
Temporary equity, shares outstanding	725,268	0
Temporary equity, liquidation preference	$ 100,000	$ 0

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating expenses
Research and development	$ 74,048	$ 90,689
General and administrative	11,662	9,981
Total operating expenses	85,710	100,670
Loss from operations	(85,710)	(100,670)
Other income (expense)
Interest income	1,643	485
Foreign currency gain	109	6
Interest expense	(2,851)
Total other income (expense), net	(1,099)	491
Net loss before equity in net loss of unconsolidated entity	(86,809)	(100,179)
Equity in net loss of unconsolidated entity	(222)	(149)
Net loss	(87,031)	(100,328)
Deemed dividends on convertible preferred stock attributable to accretion of beneficial conversion feature	(29,460)
Dividends on convertible preferred stock	(1,083)
Net loss applicable to common stockholders	$ (117,574)	$ (100,328)
Net loss per share applicable to common stockholders - basic and diluted	$ (1.73)	$ (1.99)
Weighted average number of common shares used in net loss per share - basic and diluted	67,844,872	50,395,632

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (87,031)	$ (100,328)
Other comprehensive income (loss):
Unrealized gain (loss) on securities available-for-sale, net of tax	(877)	53
Total other comprehensive income (loss)	(877)	53
Comprehensive loss	$ (87,908)	$ (100,275)

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Unaudited) - 3 months ended Mar. 31, 2018 - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Series A-1 Convertible Preferred Stock
Beginning Balance, (in shares) at Dec. 31, 2017						0
Issuance of Series A-1 convertible preferred stock, net of issuance costs of $2.3 million						$ 97,710
Issuance of Series A-1 convertible preferred stock, net of issuance costs of $2.3 million, shares						725,268
Beneficial conversion feature on Series A-1 convertible preferred stock						$ (29,460)
Deemed dividend on convertible preferred stock attributable to accretion of beneficial conversion feature						29,460
Ending Balances at March 31, 2018 at Mar. 31, 2018						$ 97,710
Ending Balance, (in shares) at Mar. 31, 2018						725,268
Beginning Balances at December 31, 2017 at Dec. 31, 2017	$ 279,275	$ 7	$ 946,869	$ (667,509)	$ (92)
Beginning Balance, (in shares) at Dec. 31, 2017		67,842,942
Net loss	(87,031)			(87,031)
Accrued dividends on convertible preferred stock	(1,083)		(1,083)
Other comprehensive loss	(877)				(877)
Beneficial conversion feature on Series A-1 convertible preferred stock	29,460		29,460
Deemed dividend on convertible preferred stock attributable to accretion of beneficial conversion feature	(29,460)		(29,460)
Equity component of 2025 convertible senior notes	109,911		109,911
Equity component of deferred financing costs for 2025 convertible senior notes	(3,763)		(3,763)
Exercise of stock options	20		20
Exercise of stock options, shares		5,759
Stock-based compensation	5,946		5,946
Ending Balances at March 31, 2018 at Mar. 31, 2018	$ 302,398	$ 7	$ 1,057,900	$ (754,540)	$ (969)
Ending Balance, (in shares) at Mar. 31, 2018		67,848,701

Consolidated Statements of Con7

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Unaudited) (Parenthetical) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Series A-1 Convertible Preferred Stock
Issuance costs, net	$ 2.3

Condensed Consolidated Stateme8

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities
Net loss	$ (87,031)	$ (100,328)
Adjustments to reconcile net loss to net cash used in operating activities
Equity in net loss of unconsolidated entity	222	149
Depreciation and amortization	801	747
Stock-based compensation	5,946	5,180
Accretion of discount on convertible notes	1,689
Other non-cash charges, net	(605)	179
Changes in operating assets and liabilities
Prepaid expenses and other assets	3,733	28,553
Accounts payable	5,316	10,341
Accrued liabilities	(4,163)	(6,194)
Deferred rent	(3)	(26)
Net cash used in operating activities	(74,095)	(61,399)
Investing activities
Purchases of investments	(415,203)	(28,334)
Proceeds from maturities of investments	156,000	54,008
Proceeds from sales of investments	83,184
Purchases of property and equipment	(212)	(849)
Net cash provided by (used in) investing activities	(176,231)	24,825
Financing activities
Proceeds from issuance of 2025 convertible senior notes, net of offering costs	277,656
Proceeds from issuance of convertible preferred stock, net of offering costs	97,710
Proceeds from exercise of stock options	20	71
Net cash provided by financing activities	375,386	71
Net increase (decrease) in cash, cash equivalents and restricted cash	125,060	(36,503)
Cash, cash equivalents and restricted cash
Beginning of period	86,896	116,216
End of period	211,956	79,713
Supplemental disclosures:
Purchases of property and equipment included in accounts payable and accrued liabilities	22	$ 101
Accrued dividends on convertible preferred stock	$ 1,083

Nature of Business

Nature of Business	3 Months Ended
	Mar. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Business	1. Nature of Business Alder BioPharmaceuticals, Inc. (the “Company”) is a clinical-stage biopharmaceutical company that discovers, develops and seeks to commercialize therapeutic antibodies with the potential to meaningfully transform the treatment paradigm in migraine. The Company has developed a proprietary antibody platform designed to select and manufacture antibodies that have the potential to maximize efficacy as well as speed of onset and durability of therapeutic response. The Company was incorporated in Delaware on May 20, 2002 and is located in Bothell, Washington. Financings On January 12, 2018, the Company completed a private placement of convertible preferred stock of 725,268 shares with certain institutional and other accredited investors. The Company received $97.7 million in net proceeds, after deducting fees and offering expenses of $2.3 million. On February 1, 2018, the Company completed an underwritten public offering of an aggregate principal amount of $250 million of 2.5% Convertible Senior Notes due 2025 (the “Convertible Notes”). In addition, on February 13, 2018, the Company issued an additional $37.5 million principal amount of Convertible Notes to cover over-allotments. The Company received $277.7 million in net proceeds, after deducting fees and offering expenses of $9.8 million.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Principles of Consolidation The accompanying unaudited condensed consolidated financial statements reflect the accounts of Alder BioPharmaceuticals, Inc. and its wholly-owned subsidiaries, Alder BioPharmaceuticals Pty. Ltd., AlderBio Holdings LLC, and Alder BioPharmaceuticals Limited. All inter-company balances and transactions have been eliminated in consolidation. The condensed consolidated balance sheet data as of December 31, 2017 were derived from audited financial statements. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (“SEC”) and generally accepted accounting principles in the United States of America (“GAAP”) for unaudited condensed consolidated financial information. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. The accompanying unaudited condensed consolidated financial statements reflect all adjustments consisting of normal recurring adjustments which, in the opinion of management, are necessary for a fair statement of the Company’s financial position and results of its operations, as of and for the periods presented. The Company manages its business as one operating segment; however, the Company operates in three The Company has a relationship with a variable interest entity (“VIE”). The Company evaluates VIEs to determine whether the Company is the primary beneficiary by performing a qualitative and quantitative analysis of each VIE that includes a review of, among other factors, the VIE’s capital structure, contractual terms, related party relationships, the Company’s fee arrangements and the design of the VIE. This analysis includes determining whether the Company (1) has the power to direct matters that most significantly impact the activities of the VIE, and (2) has the obligation to absorb losses or the right to receive benefits of the VIE that could potentially be significant to the VIE. In circumstances where the Company is not the primary beneficiary, but the Company has the ability to exercise significant influence over the operating and financial policies of a company in which it has an investment, the Company utilizes the equity method of accounting for recording investment activity. In assessing whether the Company exercises significant influence, it considers the nature and magnitude of the investment, the voting and protective rights held, any participation in the governance of the other company, and other relevant factors such as the presence of a collaboration or other business relationship. Under the equity method of accounting, the Company records in its results of operations its share of income or loss of the other company. If the Company’s share of losses exceeds the carrying value of its investment, it will suspend recognizing additional losses and will continue to do so unless the Company commits to providing additional funding. The Company monitors its investment to evaluate whether any decline in value has occurred that would be other-than-temporary, based on the implied value of recent company financings, public market prices of comparable companies, and general market conditions. The carrying value of the investment is included in the Company’s condensed consolidated balance sheet as investment in unconsolidated entity. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and accompanying notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. Use of Estimates The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The results of the Company’s operations for the three months ended March 31, 2018 are not necessarily indicative of the results to be expected for the full year or for any other period. Concentrations of Credit Risk The Company is exposed to credit risk from its deposits of cash, cash equivalents, short-term and long-term investments and restricted cash in excess of amounts insured by the Federal Deposit Insurance Corporation and Securities Investor Protection Corporation. Restricted Cash The Company had restricted cash of $10.0 million as of March 31, 2018, of which $2.5 million is classified as a current asset, as it will be used to satisfy commitments within the next 12 months. The funds are placed in an escrow account pursuant to a contractual agreement with a third-party manufacturer and will be used for payments under that agreement in 2019. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed consolidated balance sheets to the total of cash, cash equivalents and restricted cash shown in the condensed consolidated statement of cash flows. March 31, December 31, 2018 2017 (in thousands) Cash and cash equivalents $ 201,956 $ 76,896 Restricted cash 10,000 10,000 Total cash, cash equivalents, and restricted cash shown in the consolidated statements of cash flows $ 211,956 $ 86,896 Convertible Senior Notes, net In accordance with accounting guidance for debt with conversion and other options, the Company separately accounted for the liability and equity components of the Convertible Notes by allocating the proceeds between the liability component and the embedded conversion option (the “Equity Component”) due to the Company’s ability to settle the Convertible Notes in cash, common stock or a combination of cash and common stock, at its option. The carrying amount of the liability components was calculated by measuring the fair value of a similar liability that does not have an associated convertible feature. The allocation was performed in a manner that reflected the Company’s non-convertible debt borrowing rate for similar debt. The Equity Component of the Convertible Notes was recognized as a debt discount and represents the difference between the proceeds from the issuance of the Convertible Notes and the fair value of the liability of the Convertible Notes on their respective dates of issuance. The excess of the principal amount of the liability component over its carrying amount (the “Debt Discount”) is amortized to interest expense using the effective interest method over seven years. The Equity Component is not remeasured as long as it continues to meet the conditions for equity classification. In connection with the issuance of the Convertible Notes, the Company also incurred certain offering costs directly attributable to the offering. Such costs are deferred and amortized over the term of the debt to interest expense using the effective interest method. A portion of the deferred financing costs incurred in connection with the Convertible Notes was deemed to relate to the Equity Component and was allocated to additional paid-in capital. Convertible preferred stock The Company recorded the convertible preferred stock at fair value on the date of issuance, net of issuance costs. The convertible preferred stock is recorded outside of stockholders’ equity because, in the event of certain deemed liquidation events considered not solely within the Company’s control, such as a merger, acquisition and sale of all or substantially all of the Company’s assets, the convertible preferred stock will become redeemable at the option of the holders. Revenue recognition In May 2016, the Company licensed the exclusive worldwide rights to its product candidate clazakizumab to Vitaeris, Inc. (“Vitaeris”), a newly formed company based in Vancouver, British Columbia. In exchange for the rights to clazakizumab, the Company received an equity interest in Vitaeris and is eligible to receive royalties and certain other payments including revenue from the sale of drug supply inventory. The Company did not record any revenue under this agreement in the three months ended March 31, 2018 or 2017. In the future, the Company may generate revenue from product sales and may enter into agreements with strategic partners for the development and commercialization of the Company’s products under which revenues may consist of license fees, non-refundable upfront fees, milestones, funding of research and development activities, sales of drug supply, or other revenue. The Company could receive both fixed and variable consideration. On January 1, 2018, the Company adopted ASC Topic 606 and related pronouncements regarding revenue recognition using the modified retrospective method. The adoption of this guidance did not have a material impact on the Company’s condensed consolidated financial statements. In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under its agreements, the Company will perform the following steps: (i) assess whether collectability is probable; (ii) identification of the promised goods or services in the contract; (iii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iv) measurement of the transaction price, including the constraint on variable consideration; (v) allocation of the transaction price to the performance obligations based on estimated selling prices; and (vi) recognition of revenue when (or as) the Company satisfies each performance obligation. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in ASC Topic 606. The Company’s performance obligations may include license rights and development services. Significant management judgment will be required to determine the level of effort required under an arrangement and the period over which the Company expects to complete its performance obligations under the arrangement. When the Company has substantive performance obligations under an arrangement accounted for as one unit of accounting, revenues will be recognized using a proportional performance-based approach. Under this approach, revenue recognition is based on costs incurred to date compared to total expected costs to be incurred over the performance period as this is considered to be representative of the delivery of service under the arrangement. Changes in estimates of total expected performance costs or service obligation time-period will be accounted for prospectively as a change in estimate. Revenues recognized at any point in time will be limited to the amount of noncontingent payments received or due. The Company will allocate the total transaction price to each performance obligation based on the estimated relative standalone selling prices of the promised goods or service underlying each performance obligation. Estimated selling prices for license rights will be calculated using vendor-specific objective evidence, (“VSOE”), of selling price, if available, third-party evidence, (“TPE”), of selling price if VSOE is not available, or best estimate of selling price, (“BESP”), if neither VSOE nor TPE is available, and include the following key assumptions: the development timeline, revenue forecast, commercialization expenses, discount rate and probabilities of technical and regulatory success. Licenses of intellectual property: If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company will recognize revenues from non-refundable, up-front fees allocated to the license when the license is transferred to the customer, and the customer can use and benefit from the license. For licenses that are bundled with other promises, the Company will 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 from non-refundable, up-front fees. The Company will evaluate the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition. Milestone payments: At the inception of each arrangement that includes milestone payments, the Company will evaluate whether the milestones are considered probable of being achieved and estimate 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, the value of the associated milestone (such as a regulatory submission by the Company) will be included in the transaction price. Milestone payments that are not within the control of the Company, such as approvals from regulators, will not be considered probable of being achieved until those approvals are received. When the Company’s assessment of probability of achievement changes and variable consideration becomes probable, any additional estimated consideration will be allocated to each performance obligation based on the estimated relative standalone selling prices of the promised goods or service underlying each performance obligation and recorded in license, collaboration, and other revenues based upon when the customer obtains control of each element. Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company will recognize revenue at the later of (a) when the related sales occur, or (b) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Collaboration payments: The Company may also perform research and development activities on behalf of collaborative partners that are paid for by the collaborators. For research and development activities which are not determined to be separate units of accounting based on the criteria above, revenues for these research and development activities will be recognized using the single unit of accounting method for that collaborative arrangement. For research and development activities which are determined to be separate units of accounting, arrangement consideration will be allocated and revenues will be recognized as services are delivered, assuming the general criteria for revenue recognition noted above have been met. The corresponding research and development costs incurred under these contracts will be included in research and development expense in the consolidated statements of operations. For sales of drug supply inventory at cost, the revenue will be recognized upon transfer of the inventory. The Company expects to invoice its customers upon the completion of the effort, based on the terms of each agreement. Amounts earned, but not yet collected from the customers, if any, will be included in accounts receivable in the accompanying consolidated balance sheets. Deferred revenue will arise from payments received in advance of the culmination of the earnings process. Deferred revenue expected to be recognized within the next 12 months will be classified as a current liability. Deferred revenue will be recognized as revenue in future periods when the applicable revenue recognition criteria have been met. Long-Term Incentive Plan In January 2018, the Company established a long-term incentive plan (“LTIP”) which provides eligible employees with the opportunity to receive performance-based compensation comprised of restricted stock units. The vesting of the restricted stock units is contingent upon the achievement of pre-determined regulatory milestones. The Company records compensation expense over the estimated service period for a milestone when the achievement of the milestone is considered probable, which is assessed at each reporting date. Once a milestone is considered probable, the Company records compensation expense based on the portion of the service period elapsed to date with respect to that milestone, with a cumulative catch-up, net of estimated forfeitures, and recognizes any remaining compensation expense, if any, over the remaining estimated service period. No compensation expense has been recorded to date under the LTIP as the conditions for recognizing expense have not yet been met. As of March 31, 2018, the estimated value to be delivered in restricted stock units to participants eligible for the LTIP was approximately $9.6 million. The total potential value to be delivered under the LTIP is expected to change in the future for several reasons, including the addition of more eligible employees to the LTIP. Liquidity and Going Concern The Company has an accumulated deficit as of March 31, 2018. To date, the Company has funded its operations primarily through sales of its capital stock and Convertible Notes and payments from its former collaboration partners, and will require substantial additional capital for research and product development. In January 2018, the Company completed a private placement of 725,268 shares of convertible preferred stock resulting in net proceeds of $97.7 million. In February 2018, the Company received $277.7 million in net proceeds from the underwritten public offering of the Convertible Notes. The Company forecasts a significant increase in expenditures to support its planned Biologics License Application (“BLA”) submission with the U.S. Food and Drug Administration, currently anticipated to occur in the first quarter of 2019, commercial readiness activities and anticipated commercial launch of eptinezumab. The Company estimates the available cash, cash equivalents, short-term and long-term investments and restricted cash as of March 31, 2018 will be sufficient to meet the Company’s projected operating requirements into 2020. These operating requirements consist principally of expenditures related to the planned BLA submission, establishment of the eptinezumab commercial drug supply chain, continued build-out of the Company’s commercial organization (e.g., marketing, sales, medical affairs, payor access, information technology) and pre-launch market readiness. The Company has based its estimate on the timing for its projected expenditures on assumptions that may prove to be wrong, and it could utilize its available capital resources sooner than it currently expects. Furthermore, the Company’s operating plans may change, and it may need additional funds to meet operational needs and capital requirements sooner than planned. The Company will need additional funding to execute the commercial launch of eptinezumab. The Company will also need to obtain substantial additional sources of funding to develop and commercialize ALD1910 and its other product candidates. The Company expects to finance future cash needs through equity financings, debt financings, collaborations, strategic alliances, licensing arrangements and other marketing and distribution arrangements, but there are no assurances that the Company will be able to raise sufficient amounts of funding in the future on acceptable terms, or at all. The condensed consolidated financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates continuity of operations, the realization of assets and the satisfaction of liabilities and commitments in the normal course of business. Recent Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases. This ASU requires the recognition of lease assets and lease liabilities on the balance sheet and disclosure of key information about leasing arrangements. This ASU will become effective for annual periods beginning after December 15, 2018. The Company expects adopting this guidance will result in an increase in the assets and liabilities on its consolidated balance sheets and will have some impact on its consolidated statements of operations and statement of cash flows. The Company has reviewed other recent accounting pronouncements and concluded that they are either not applicable to the business, or that no material effect is expected on the condensed consolidated financial statements as a result of future adoption.

Net Loss Per Share Applicable t

Net Loss Per Share Applicable to Common Stockholders	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Net Loss Per Share Applicable to Common Stockholders	3. Net Loss Per Share Applicable to Common Stockholders Basic net loss per share applicable to common stockholders is calculated by dividing net loss applicable to common stockholders by the weighted average common shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by adjusting the weighted average common shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock method. Three Months Ended March 31, 2018 2017 Net loss applicable to common stockholders (in thousands) $ (117,574 ) $ (100,328 ) Denominator Weighted average common shares outstanding - basic and diluted 67,844,872 50,395,632 Net loss per share applicable to common stockholders - basic and diluted $ (1.73 ) $ (1.99 ) The following weighted average numbers of securities were excluded from the calculation of diluted net loss per share for the three months ended March 31, 2018 and 2017 because including them would have had an anti-dilutive effect. Therefore, basic and diluted net loss per share were the same for all periods presented. Three Months Ended March 31, 2018 2017 Common shares underlying 2025 convertible senior notes 9,060,357 — Common shares underlying convertible preferred stock 6,366,241 — Stock options and awards 8,688,966 5,963,117 Employee stock purchase plan 93,321 40,740 24,208,885 6,003,857

Investments

Investments	3 Months Ended
	Mar. 31, 2018
Investments [Abstract]
Investments	4. Investments Investments consisted of available-for-sale securities as follows: Amortized Cost Gross unrealized gains Gross unrealized losses Fair Value (in thousands) Type of security as of March 31, 2018 U.S. government agency obligations maturing in one year or less $ 129,227 $ — $ (222 ) $ 129,005 U.S. government agency obligations maturing after one year through two years 246,831 — (745 ) 246,086 Total available-for-sale securities $ 376,058 $ — $ (967 ) $ 375,091 Type of security as of December 31, 2017 U.S. government agency obligations maturing in one year or less $ 199,434 $ — $ (90 ) $ 199,344 Total available-for-sale securities $ 199,434 $ — $ (90 ) $ 199,344 Realized gains and losses are determined based on the specific identification method and are reported in other income in the condensed consolidated statement of operations. During the three months ended March 31, 2018, the Company recorded $0.3 million in realized losses related to available-for-sale securities included in the Company’s condensed consolidated statement of operations. There were no realized gains or losses on sales of available-for-sale securities in the three months ended March 31, 2017.

Fair Value Disclosures

Fair Value Disclosures	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Disclosures	5 . Fair Value Disclosures The Company holds financial instruments that are measured at fair value which is determined according to a fair value hierarchy that prioritizes the inputs and assumptions used, and the valuation techniques used to measure fair value. The three levels of the fair value hierarchy are described as follows: Level 1 Inputs are unadjusted quoted prices in active markets for identical assets or liabilities. Level 2 Inputs are quoted prices for similar assets and liabilities in active markets or quoted prices for identical or similar instruments in markets that are not active and model-derived valuations in which all significant inputs and significant value drivers are observable in active markets. Level 3 Inputs are unobservable inputs based on the Company’s own assumptions and valuation techniques used to measure assets and liabilities at fair value. The inputs require significant management judgment or estimation. The Company’s assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of fair value assets and liabilities and their placement within the fair value hierarchy levels. The Company established the fair value of its assets and liabilities using the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date and established a fair value hierarchy based on the inputs used to measure fair value. The following table presents the Company’s financial instruments by level within the fair value hierarchy: Fair Value Measurement Using Level 1 Level 2 Level 3 Total (in thousands) As of March 31, 2018 Assets Cash equivalents Money market funds $ 196,038 $ — $ — $ 196,038 Short-term investments U.S. government agency obligations — 129,005 — 129,005 Long term investments U.S. government agency obligations — 246,086 — 246,086 Restricted cash Money market funds 10,000 — — 10,000 $ 206,038 $ 375,091 $ — $ 581,129 Liabilities 2025 convertible senior notes $ — $ 265,529 $ — 265,529 $ — $ 265,529 $ — $ 265,529 As of December 31, 2017 Cash equivalents Money market funds $ 71,379 $ — $ — $ 71,379 Short-term investments U.S. government agency obligations — 199,344 — 199,344 Restricted cash Money market funds 10,000 — — 10,000 $ 81,379 $ 199,344 $ — $ 280,723 The Company’s negotiable certificates of deposit and U.S. government agency obligations are valued using fair value measurements that are considered to be Level 2. The investment custodian provides the Company with valuations of its securities portfolio. The primary source for the security valuation is Interactive Data Corporation (“IDC”), which evaluates securities based on market data. IDC utilizes evaluated pricing models that vary by asset class and include available trade, bid, and other market information. Generally, the methodology includes broker quotes, proprietary models, vast descriptive terms and conditions databases, as well as extensive quality control programs. The custodian utilizes proprietary valuation matrices for valuing all negotiable certificates of deposit. Accounts payable and accrued liabilities are carried at cost, which approximates fair value due to the short-term nature of these financial instruments. The fair value of the Convertible Notes is determined based upon data from readily available pricing sources which utilize market observable inputs and other characteristics for similar types of instruments and is included in Level 2 of the fair value hierarchy. See Note 8 for information about the determination of the carrying value of the Company’s Convertible Notes at March 31, 2018.

Investment In Unconsolidated En

Investment In Unconsolidated Entity	3 Months Ended
	Mar. 31, 2018
Investment In Unconsolidated Entity [Abstract]
Investment In Unconsolidated Entity	6. Investment in Unconsolidated Entity In May 2016, the Company licensed the exclusive worldwide rights to its product candidate clazakizumab to Vitaeris. In exchange for the rights to clazakizumab, the Company received an equity stake in Vitaeris and is eligible to receive royalties and certain other payments. Since clazakizumab was developed internally by the Company, all previous expenditures to develop the compound were recognized as expense in the period incurred and there was no carrying value on the Company’s condensed consolidated balance sheet. In 2016, the Company recognized a gain on the license agreement of $1.1 million, which was determined as the initial fair value of the Company’s equity stake in Vitaeris. Vitaeris is a VIE for which the Company is not the primary beneficiary as the Company does not have the power to direct the activities that most significantly influence the economic performance of the entity. In addition to the Company’s exchange of license rights for clazakizumab, Vitaeris was capitalized through cash investments by other parties. The investment in Vitaeris is accounted for under the equity method of accounting because the Company holds common stock of Vitaeris and has significant influence over the operating and financial policies of Vitaeris through its ownership, license arrangement and representation on the board of directors. Therefore, the Company records its share of any loss or income generated by Vitaeris, which is recorded on a three-month lag, within the condensed consolidated statement of operations. The investment is reflected as an investment in unconsolidated entity on the Company’s condensed consolidated balance sheet which represents the investment in Vitaeris, net of the Company’s portion of any generated loss or income. In November 2017, the Company and Vitaeris amended the license agreement for clazakizumab and Vitaeris and its shareholders, including the Company, entered into a strategic collaboration and purchase option agreement (the “option agreement”) with a third party, CSL Limited, (“CSL”), an Australian entity, to expedite the development of clazakizumab as a therapeutic option for solid organ transplant rejection. Pursuant to the option agreement, CSL will provide research funding to Vitaeris for the development of clazakizumab and CSL received an exclusive option to acquire Vitaeris, subject to certain terms and conditions. Upon the execution of the option agreement, Vitaeris received an upfront payment of $15 million and Vitaeris will also receive future development milestone payments. If CSL exercises its purchase option, it will be required to make to Vitaeris’ shareholders, including the Company, an immediate one-time payment and thereafter certain sales-based milestone payments. The Company will continue to be eligible to receive royalties and certain other payments following an acquisition of Vitaeris by CSL. The Company recorded $0.2 million in net loss with respect to Vitaeris for the three months ended March 31, 2018, which was the remaining balance of the Company’s carrying value of the Company’s investment in Vitaeris. The purchase option created a written call on the Company’s shares in Vitaeris and the value of this written call is not significant. The Company has no implied or unfunded commitments related to Vitaeris and its maximum exposure to loss is limited to the current carrying value of the investment.

Accrued Liabilities

Accrued Liabilities	3 Months Ended
	Mar. 31, 2018
Payables And Accruals [Abstract]
Accrued Liabilities	7. Accrued Liabilities Accrued liabilities consisted of the following for the dates indicated: March 31, December 31, 2018 2017 (in thousands) Compensation and benefits $ 5,898 $ 7,933 Contracted research and development 3,432 6,846 Professional services and other 1,148 1,024 Interest on 2025 convertible senior notes 1,162 — $ 11,640 $ 15,803

2025 Convertible Senior Notes,

2025 Convertible Senior Notes, Net	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
2025 Convertible Senior Notes, Net	8. 2025 Convertible Senior Notes, net On February 1, 2018, the Company issued $250 million aggregate principal amount of the Convertible Notes in a registered underwritten public offering. In addition, on February 13, 2018, the Company issued an additional $37.5 million principal amount of Convertible Notes pursuant to the exercise of an over-allotment option granted to the underwriters in the offering. The Convertible Notes are senior unsecured obligations of the Company and bear interest at a rate of 2.5% per annum, payable semi-annually in arrears on February 1 and August 1 of each year, commencing on August 1, 2018. Upon conversion, the Convertible Notes will be convertible into cash, shares of the Company’s common stock or a combination of cash and shares of the Company’s common stock, at the Company’s election. The Convertible Notes will be subject to redemption at the Company’s option, on or after February 1, 2022, in whole or in part, if the conditions described below are satisfied. The Convertible Notes will mature on February 1, 2025, unless earlier converted, redeemed or repurchased in accordance with their terms. Subject to satisfaction of certain conditions and during the periods described below, the Convertible Notes may be converted at an initial conversion rate of 49.3827 shares of common stock per $1,000 principal amount of the Convertible Notes (equivalent to an initial conversion price of approximately $20.25 per share of common stock). The conversion rate will be subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. In addition, if certain corporate events occur prior to the maturity date, the Company will increase the conversion rate for a holder of Convertible Notes who elects to convert its Convertible Notes in connection with such a corporate event in certain circumstances. Holders of the Convertible Notes may convert all or any portion of their notes, in multiples of $1,000 principal amount, at their option at any time prior to the close of business on the business day immediately preceding November 1, 2024 only under the following circumstances: 1. during any calendar quarter commencing after the calendar quarter ending on March 31, 2018 (and only during such calendar quarter), if the last reported sale price of the Company's common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day; 2. during the five business day period after any five consecutive trading day period (the “measurement period”) in which the "trading price" per $1,000 principal amount of the Convertible Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Company’s common stock and the conversion rate on each such trading day; 3. if the Company calls any or all of the Convertible Notes for redemption, at any time prior to the close of business on the scheduled trading day immediately preceding the redemption date; or 4. upon the occurrence of specified corporate events. On or after November 1, 2024 and prior to the close of business on the business day immediately preceding February 1, 2025, holders may convert their Convertible Notes at any time. Prior to February 1, 2022, the Company may not redeem the Convertible Notes. On or after February 1, 2022, the Company may redeem any or all of the Convertible Notes at a redemption price equal to 100% of the principal amount of the Convertible Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date, if the last reported sale price of the Common Stock for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on the trading day immediately prior to the date of the redemption notice exceeds 130% of the applicable conversion price for the Convertible Notes on each applicable trading day. If a “make-whole fundamental change” (as defined in the indenture) occurs prior to February 1, 2025, the Company will, in certain circumstances, increase the conversion rate for a holder who elects to convert its Convertible Notes in connection with the make-whole fundamental change. The Convertible Notes do not contain any financial or operating covenants or any restrictions on the payment of dividends, the issuance of other indebtedness or the issuance or repurchase of securities by the Company. The Convertible Notes indenture contains customary events of default, including that upon certain events of default, 100% of the principal and accrued and unpaid interest on the Convertible Notes will automatically become due and payable. In accordance with accounting guidance for debt with conversion and other options, the Company separately accounted for the embedded conversion feature of the Convertible Notes by allocating the proceeds between the liability component and the equity component, due to the Company's ability to settle the Convertible Notes in cash, common stock or a combination of cash and common stock, at its option. The initial amount of the liability component of $177.6 million was calculated by measuring the fair value of a similar liability that does not have an associated convertible feature and the residual between the proceeds from the issuance of $287.5 million and the fair value of the liability of $177.6 million is allocated to the equity component, which was recorded at$109.9 million and recognized as a debt discount. In addition, the Company incurred approximately $9.8 million of debt issuance costs, which primarily consisted of underwriting, legal and other professional fees. The issuance costs were allocated to the liability and equity components proportionally based on the allocation of total proceeds. A total of $3.7 million was allocated to the equity component and recorded as a reduction to additional paid-in capital and $6.1 million was allocated to the liability component and is recorded as a reduction of the Convertible Notes in the Company’s condensed consolidated balance sheet. The debt discount and the issuance costs will be amortized to interest expense using the effective interest method over seven years, the expected life of the Convertible Notes as discussed below. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. During the three months ended March 31, 2018, the Company recorded $1.7 million of interest expense related to the amortization of the debt discount and issuance costs and the unamortized balance of the liability was $173.2 million as of March 31, 2018. While the Convertible Notes are classified on the Company’s condensed consolidated balance sheet at March 31, 2018 as long-term, the resulting balance sheet classification of this liability will be monitored at each quarterly reporting date and will be analyzed dependent upon whether the Convertible Notes are convertible or subject to an event triggering potential redemption during the prescribed measurement periods. In the event that the holders of the Convertible Notes have the election to convert the Convertible Notes or the Convertible Notes become redeemable at any time during the prescribed measurement period, the Convertible Notes would then be considered a current obligation and classified as such. While for US GAAP purposes, the convertible note is allocated between the liability component and the equity component, for US tax purposes there is no allocation, and a deferred tax liability is recognized related to such difference. Because the Company has a full valuation allowance recorded against net deferred tax assets, there is no net impact on the Company’s condensed consolidated balance sheets or condensed consolidated statements of operations as a result of establishing this deferred tax liability. The outstanding balances of the Convertible Notes as of March 31, 2018 consisted of the following: 2025 Convertible Senior Notes (in thousands) Liability component: Principal $ 287,500 Less: unamortized debt discount and issuance costs (114,303 ) Net carrying amount $ 173,197 Net carrying amount of equity component $ 106,148 The Company determined the expected life of the Convertible Notes was equal to its seven-year term. The effective interest rate on the liability component of the Convertible Notes for the period from the date of issuance through March 31, 2018 was 10.6%. As of March 31, 2018, the "if-converted value" did not exceed the remaining principal amount of the Convertible Notes. The fair value of the Convertible Notes is based on data from readily available pricing sources which utilize market observable inputs and other characteristics for similar types of instruments, and, therefore, these Convertible Notes are classified within Level 2 in the fair value hierarchy. The fair value of the Convertible Notes, which differs from their carrying value, is influenced by interest rates, the Company’s stock price and stock price volatility. The estimated fair value of the Convertible Notes as of March 31, 2018 was approximately $265.5 million. The following table sets forth total interest expense recognized related to the Convertible Notes during the three months ended March 31, 2018: Three Months Ended March 31, 2018 2017 (in thousands) Contractual interest expense $ 1,162 $ — Amortization of debt discount and issuance costs 1,689 — Total interest expense $ 2,851 $ — Future minimum payments on our long-term debt as of March 31, 2018 were as follows: Years ended December 31, Future Minimum Payments (in thousands) 2018 $ 3,594 2019 7,188 2020 7,188 2021 7,188 2022 7,188 2023 and thereafter 305,466 Total minimum payments 337,812 Less: interest (50,312 ) Less: unamortized discount and issuance costs (114,303 ) Less: current portion — 2025 convertible senior notes, net $ 173,197

Convertible Preferred Stock

Convertible Preferred Stock	3 Months Ended
	Mar. 31, 2018
Temporary Equity Disclosure [Abstract]
Convertible Preferred Stock	9. Convertible Preferred Stock On January 7, 2018, the Company entered into a Preferred Stock Purchase Agreement (the “Purchase Agreement”) with certain institutional and other accredited investors affiliated with or managed by Redmile Group, LLC (the “Buyers”). Under the terms of the Purchase Agreement, on January 12, 2018 the Company sold to the Buyers in a private placement 725,268 shares of Series A-1 convertible preferred stock at $137.88 per share for net proceeds of approximately $97.7 million, after deducting fees and applicable expenses of $2.3 million. The Buyers hold more than 5% of our capital stock and therefore are considered a related party of the Company. The Purchase Agreement also provided the Company with an option to sell up to $150 million of convertible preferred stock in aggregate beginning after the 90-day period following the date of the initial purchase of the convertible preferred stock. This option was classified as an asset and was determined to have immaterial fair value at inception and subsequently. The Company’s right to sell The terms and conditions of the convertible preferred stock are governed by the Certificate of Designation of Preferences, Rights and Limitations (the “Certificate of Designation”). Liquidation preference In the event of any liquidation, dissolution, or winding up of the Company, whether voluntary or involuntary, occurs within 24 months of the date of the Purchase Agreement, after satisfaction of all liabilities and obligations to creditors of the Company and before any distribution to holders of the Company’s common stock, the holders of each share of convertible preferred stock shall be entitled to receive the amount of $137.88 per share, plus all accrued but unpaid dividends. If, upon the occurrence of such event, the proceeds distributed among the holders of the convertible preferred stock are insufficient to make payment in full to all holders, then the entire proceeds legally available for distribution to the holders of the convertible preferred stock shall be distributed ratably in proportion to the full amounts to which the holders would otherwise be respectively entitled. A liquidation shall be deemed to include the occurrence of either (i) the Company merges into or consolidates with any other entity, or any entity merges into or consolidates with the Company and, after giving effect to such transaction, the stockholders of the Company immediately prior to such transaction own less than 50% of the aggregate voting power of the Company or the successor entity of such transaction or (ii) the Company sells, leases, licenses or transfers all or substantially all of its assets to another person or entity and the stockholders of the Company immediately prior to such transaction own less than 50% of the aggregate voting power of the acquiring entity immediately after the transaction (each a “Deemed Liquidation”). Dividends The holders of the convertible preferred stock are entitled to receive cumulative dividends at a rate of 5% per annum payable semi-annually in arrears on June 30 and December 31 of each year commencing on June 30, 2018. The dividends are payable in additional shares of convertible preferred stock and/or cash at the Company’s option. In the three months ended March 31, 2018, the Company accrued an aggregate of $1.1 million in dividends on convertible preferred stock or $0.49 per convertible preferred share. Conversion Each share of convertible preferred stock is convertible, at any time and from time to time and after the issuance date, at the holders’ option, into shares of common stock in a one-for-ten basis. Voting Rights Except specifically required by the Certificate of Designation or by the provisions of the Delaware General Corporation Law, the holders of the convertible preferred stock have no voting rights. Warrants In the event of a Deemed Liquidation that occurs within 24 months of the date of the Purchase Agreement, the Company will issue to the Buyers a warrant to purchase an aggregate of 75,000 shares of convertible preferred stock at a purchase price per share equal to the initial purchase price of $137.88. The number of shares and exercise price are each subject to adjustment for any reorganization, recapitalization, non-cash dividend, stock split, reverse stock split or other similar transaction. Pursuant to applicable accounting standards, the Warrants were considered freestanding financial instruments which are financial liabilities and require initial and subsequent measurements at fair value. The Warrants were determined to have immaterial fair value initially and subsequently at March 31, 2018. In accordance with ASC 480-10-S99, the convertible preferred stock has been recorded as temporary equity on the Company’s condensed consolidated balance sheet because the convertible preferred stock is redeemable for cash or other assets of the Company upon Deemed Liquidation events that are not within the control of the Company. The net carrying amount of the convertible preferred stock is not currently accreted to a redemption value because the preferred stock is not currently redeemable or probable of becoming redeemable in the future. In accordance with ASC 470-20, the Company recognized a beneficial conversion feature representing a conversion right with an effective conversion price less than the market price of the underlying stock at the commitment date of January 12, 2018. The beneficial conversion feature of $29.5 million was recognized by allocating the intrinsic value of the conversion option, which is the number of shares of common stock available upon conversion multiplied by the difference between the effective conversion price per share and the fair value of common stock per share on the commitment date, to additional paid-in capital. On the last trading day prior to the entering into the Purchase Agreement, the closing price of the Company’s common stock was $12.95 per share. The transaction closed on January 12, 2018, at which time last closing price of the Company’s common stock was $17.85 per share which is the value used in calculating the intrinsic value of the beneficial conversion feature. Since the convertible preferred stock is currently convertible at holder’s option, the Company immediately accreted the full amount of discount created by allocation of proceeds to the beneficial conversion feature and recognized as a deemed dividend to the convertible preferred stockholders.

Teva License Agreement

Teva License Agreement	3 Months Ended
	Mar. 31, 2018
License Agreement [Abstract]
Teva License Agreement	10. Teva License agreement On January 5, 2018, the Company entered into a Settlement and License Agreement with Teva Pharmaceuticals International GmbH (“Teva GmbH”). Under the terms of the Settlement and License Agreement, the Company received a non-exclusive license to Teva’s CGRP patent portfolio for the development, manufacturing and commercialization of eptinezumab in the U.S. and worldwide, excluding Japan and Korea. While the agreement does not provide the Company with a license for Japan and Korea, the Company believes it has freedom to develop, manufacture and commercialize eptinezumab in these countries. Upon the execution of the agreement, the Company made an immediate one-time, non-refundable payment of $25 million which was included in research and development expense in the Company’s condensed consolidated statement of operations. In addition, a second one-time, non-refundable payment of $25 million is payable upon the approval of a BLA for eptinezumab with the U.S. Food and Drug Administration or of an earlier equivalent filing with a regulatory authority elsewhere in the license territory in which Teva GmbH licensed patents exist. The Company is also obligated to pay $75 million at each of two sales-related milestones (at $1 billion and $2 billion in annual sales) and to provide certain royalty payments on net sales at rates from 5% to 7% following the commercial launch of eptinezumab.

Summary of Significant Accoun19

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The accompanying unaudited condensed consolidated financial statements reflect the accounts of Alder BioPharmaceuticals, Inc. and its wholly-owned subsidiaries, Alder BioPharmaceuticals Pty. Ltd., AlderBio Holdings LLC, and Alder BioPharmaceuticals Limited. All inter-company balances and transactions have been eliminated in consolidation. The condensed consolidated balance sheet data as of December 31, 2017 were derived from audited financial statements. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (“SEC”) and generally accepted accounting principles in the United States of America (“GAAP”) for unaudited condensed consolidated financial information. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. The accompanying unaudited condensed consolidated financial statements reflect all adjustments consisting of normal recurring adjustments which, in the opinion of management, are necessary for a fair statement of the Company’s financial position and results of its operations, as of and for the periods presented. The Company manages its business as one operating segment; however, the Company operates in three The Company has a relationship with a variable interest entity (“VIE”). The Company evaluates VIEs to determine whether the Company is the primary beneficiary by performing a qualitative and quantitative analysis of each VIE that includes a review of, among other factors, the VIE’s capital structure, contractual terms, related party relationships, the Company’s fee arrangements and the design of the VIE. This analysis includes determining whether the Company (1) has the power to direct matters that most significantly impact the activities of the VIE, and (2) has the obligation to absorb losses or the right to receive benefits of the VIE that could potentially be significant to the VIE. In circumstances where the Company is not the primary beneficiary, but the Company has the ability to exercise significant influence over the operating and financial policies of a company in which it has an investment, the Company utilizes the equity method of accounting for recording investment activity. In assessing whether the Company exercises significant influence, it considers the nature and magnitude of the investment, the voting and protective rights held, any participation in the governance of the other company, and other relevant factors such as the presence of a collaboration or other business relationship. Under the equity method of accounting, the Company records in its results of operations its share of income or loss of the other company. If the Company’s share of losses exceeds the carrying value of its investment, it will suspend recognizing additional losses and will continue to do so unless the Company commits to providing additional funding. The Company monitors its investment to evaluate whether any decline in value has occurred that would be other-than-temporary, based on the implied value of recent company financings, public market prices of comparable companies, and general market conditions. The carrying value of the investment is included in the Company’s condensed consolidated balance sheet as investment in unconsolidated entity. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and accompanying notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.
Use of Estimates	Use of Estimates The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The results of the Company’s operations for the three months ended March 31, 2018 are not necessarily indicative of the results to be expected for the full year or for any other period.
Concentrations of Credit Risk	Concentrations of Credit Risk The Company is exposed to credit risk from its deposits of cash, cash equivalents, short-term and long-term investments and restricted cash in excess of amounts insured by the Federal Deposit Insurance Corporation and Securities Investor Protection Corporation.
Restricted Cash	Restricted Cash The Company had restricted cash of $10.0 million as of March 31, 2018, of which $2.5 million is classified as a current asset, as it will be used to satisfy commitments within the next 12 months. The funds are placed in an escrow account pursuant to a contractual agreement with a third-party manufacturer and will be used for payments under that agreement in 2019. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed consolidated balance sheets to the total of cash, cash equivalents and restricted cash shown in the condensed consolidated statement of cash flows. March 31, December 31, 2018 2017 (in thousands) Cash and cash equivalents $ 201,956 $ 76,896 Restricted cash 10,000 10,000 Total cash, cash equivalents, and restricted cash shown in the consolidated statements of cash flows $ 211,956 $ 86,896
Convertible Senior Notes, Net	Convertible Senior Notes, net In accordance with accounting guidance for debt with conversion and other options, the Company separately accounted for the liability and equity components of the Convertible Notes by allocating the proceeds between the liability component and the embedded conversion option (the “Equity Component”) due to the Company’s ability to settle the Convertible Notes in cash, common stock or a combination of cash and common stock, at its option. The carrying amount of the liability components was calculated by measuring the fair value of a similar liability that does not have an associated convertible feature. The allocation was performed in a manner that reflected the Company’s non-convertible debt borrowing rate for similar debt. The Equity Component of the Convertible Notes was recognized as a debt discount and represents the difference between the proceeds from the issuance of the Convertible Notes and the fair value of the liability of the Convertible Notes on their respective dates of issuance. The excess of the principal amount of the liability component over its carrying amount (the “Debt Discount”) is amortized to interest expense using the effective interest method over seven years. The Equity Component is not remeasured as long as it continues to meet the conditions for equity classification. In connection with the issuance of the Convertible Notes, the Company also incurred certain offering costs directly attributable to the offering. Such costs are deferred and amortized over the term of the debt to interest expense using the effective interest method. A portion of the deferred financing costs incurred in connection with the Convertible Notes was deemed to relate to the Equity Component and was allocated to additional paid-in capital.
Convertible Preferred Stock	Convertible preferred stock The Company recorded the convertible preferred stock at fair value on the date of issuance, net of issuance costs. The convertible preferred stock is recorded outside of stockholders’ equity because, in the event of certain deemed liquidation events considered not solely within the Company’s control, such as a merger, acquisition and sale of all or substantially all of the Company’s assets, the convertible preferred stock will become redeemable at the option of the holders.
Revenue Recognition	Revenue recognition In May 2016, the Company licensed the exclusive worldwide rights to its product candidate clazakizumab to Vitaeris, Inc. (“Vitaeris”), a newly formed company based in Vancouver, British Columbia. In exchange for the rights to clazakizumab, the Company received an equity interest in Vitaeris and is eligible to receive royalties and certain other payments including revenue from the sale of drug supply inventory. The Company did not record any revenue under this agreement in the three months ended March 31, 2018 or 2017. In the future, the Company may generate revenue from product sales and may enter into agreements with strategic partners for the development and commercialization of the Company’s products under which revenues may consist of license fees, non-refundable upfront fees, milestones, funding of research and development activities, sales of drug supply, or other revenue. The Company could receive both fixed and variable consideration. On January 1, 2018, the Company adopted ASC Topic 606 and related pronouncements regarding revenue recognition using the modified retrospective method. The adoption of this guidance did not have a material impact on the Company’s condensed consolidated financial statements. In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under its agreements, the Company will perform the following steps: (i) assess whether collectability is probable; (ii) identification of the promised goods or services in the contract; (iii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iv) measurement of the transaction price, including the constraint on variable consideration; (v) allocation of the transaction price to the performance obligations based on estimated selling prices; and (vi) recognition of revenue when (or as) the Company satisfies each performance obligation. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer and is the unit of account in ASC Topic 606. The Company’s performance obligations may include license rights and development services. Significant management judgment will be required to determine the level of effort required under an arrangement and the period over which the Company expects to complete its performance obligations under the arrangement. When the Company has substantive performance obligations under an arrangement accounted for as one unit of accounting, revenues will be recognized using a proportional performance-based approach. Under this approach, revenue recognition is based on costs incurred to date compared to total expected costs to be incurred over the performance period as this is considered to be representative of the delivery of service under the arrangement. Changes in estimates of total expected performance costs or service obligation time-period will be accounted for prospectively as a change in estimate. Revenues recognized at any point in time will be limited to the amount of noncontingent payments received or due. The Company will allocate the total transaction price to each performance obligation based on the estimated relative standalone selling prices of the promised goods or service underlying each performance obligation. Estimated selling prices for license rights will be calculated using vendor-specific objective evidence, (“VSOE”), of selling price, if available, third-party evidence, (“TPE”), of selling price if VSOE is not available, or best estimate of selling price, (“BESP”), if neither VSOE nor TPE is available, and include the following key assumptions: the development timeline, revenue forecast, commercialization expenses, discount rate and probabilities of technical and regulatory success. Licenses of intellectual property: If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company will recognize revenues from non-refundable, up-front fees allocated to the license when the license is transferred to the customer, and the customer can use and benefit from the license. For licenses that are bundled with other promises, the Company will 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 from non-refundable, up-front fees. The Company will evaluate the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition. Milestone payments: At the inception of each arrangement that includes milestone payments, the Company will evaluate whether the milestones are considered probable of being achieved and estimate 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, the value of the associated milestone (such as a regulatory submission by the Company) will be included in the transaction price. Milestone payments that are not within the control of the Company, such as approvals from regulators, will not be considered probable of being achieved until those approvals are received. When the Company’s assessment of probability of achievement changes and variable consideration becomes probable, any additional estimated consideration will be allocated to each performance obligation based on the estimated relative standalone selling prices of the promised goods or service underlying each performance obligation and recorded in license, collaboration, and other revenues based upon when the customer obtains control of each element. Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company will recognize revenue at the later of (a) when the related sales occur, or (b) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Collaboration payments: The Company may also perform research and development activities on behalf of collaborative partners that are paid for by the collaborators. For research and development activities which are not determined to be separate units of accounting based on the criteria above, revenues for these research and development activities will be recognized using the single unit of accounting method for that collaborative arrangement. For research and development activities which are determined to be separate units of accounting, arrangement consideration will be allocated and revenues will be recognized as services are delivered, assuming the general criteria for revenue recognition noted above have been met. The corresponding research and development costs incurred under these contracts will be included in research and development expense in the consolidated statements of operations. For sales of drug supply inventory at cost, the revenue will be recognized upon transfer of the inventory. The Company expects to invoice its customers upon the completion of the effort, based on the terms of each agreement. Amounts earned, but not yet collected from the customers, if any, will be included in accounts receivable in the accompanying consolidated balance sheets. Deferred revenue will arise from payments received in advance of the culmination of the earnings process. Deferred revenue expected to be recognized within the next 12 months will be classified as a current liability. Deferred revenue will be recognized as revenue in future periods when the applicable revenue recognition criteria have been met.
Long-Term Incentive Plan	Long-Term Incentive Plan In January 2018, the Company established a long-term incentive plan (“LTIP”) which provides eligible employees with the opportunity to receive performance-based compensation comprised of restricted stock units. The vesting of the restricted stock units is contingent upon the achievement of pre-determined regulatory milestones. The Company records compensation expense over the estimated service period for a milestone when the achievement of the milestone is considered probable, which is assessed at each reporting date. Once a milestone is considered probable, the Company records compensation expense based on the portion of the service period elapsed to date with respect to that milestone, with a cumulative catch-up, net of estimated forfeitures, and recognizes any remaining compensation expense, if any, over the remaining estimated service period. No compensation expense has been recorded to date under the LTIP as the conditions for recognizing expense have not yet been met. As of March 31, 2018, the estimated value to be delivered in restricted stock units to participants eligible for the LTIP was approximately $9.6 million. The total potential value to be delivered under the LTIP is expected to change in the future for several reasons, including the addition of more eligible employees to the LTIP.
Liquidity and Going Concern	Liquidity and Going Concern The Company has an accumulated deficit as of March 31, 2018. To date, the Company has funded its operations primarily through sales of its capital stock and Convertible Notes and payments from its former collaboration partners, and will require substantial additional capital for research and product development. In January 2018, the Company completed a private placement of 725,268 shares of convertible preferred stock resulting in net proceeds of $97.7 million. In February 2018, the Company received $277.7 million in net proceeds from the underwritten public offering of the Convertible Notes. The Company forecasts a significant increase in expenditures to support its planned Biologics License Application (“BLA”) submission with the U.S. Food and Drug Administration, currently anticipated to occur in the first quarter of 2019, commercial readiness activities and anticipated commercial launch of eptinezumab. The Company estimates the available cash, cash equivalents, short-term and long-term investments and restricted cash as of March 31, 2018 will be sufficient to meet the Company’s projected operating requirements into 2020. These operating requirements consist principally of expenditures related to the planned BLA submission, establishment of the eptinezumab commercial drug supply chain, continued build-out of the Company’s commercial organization (e.g., marketing, sales, medical affairs, payor access, information technology) and pre-launch market readiness. The Company has based its estimate on the timing for its projected expenditures on assumptions that may prove to be wrong, and it could utilize its available capital resources sooner than it currently expects. Furthermore, the Company’s operating plans may change, and it may need additional funds to meet operational needs and capital requirements sooner than planned. The Company will need additional funding to execute the commercial launch of eptinezumab. The Company will also need to obtain substantial additional sources of funding to develop and commercialize ALD1910 and its other product candidates. The Company expects to finance future cash needs through equity financings, debt financings, collaborations, strategic alliances, licensing arrangements and other marketing and distribution arrangements, but there are no assurances that the Company will be able to raise sufficient amounts of funding in the future on acceptable terms, or at all. The condensed consolidated financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates continuity of operations, the realization of assets and the satisfaction of liabilities and commitments in the normal course of business.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases. This ASU requires the recognition of lease assets and lease liabilities on the balance sheet and disclosure of key information about leasing arrangements. This ASU will become effective for annual periods beginning after December 15, 2018. The Company expects adopting this guidance will result in an increase in the assets and liabilities on its consolidated balance sheets and will have some impact on its consolidated statements of operations and statement of cash flows. The Company has reviewed other recent accounting pronouncements and concluded that they are either not applicable to the business, or that no material effect is expected on the condensed consolidated financial statements as a result of future adoption.

Summary of Significant Accoun20

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed consolidated balance sheets to the total of cash, cash equivalents and restricted cash shown in the condensed consolidated statement of cash flows. March 31, December 31, 2018 2017 (in thousands) Cash and cash equivalents $ 201,956 $ 76,896 Restricted cash 10,000 10,000 Total cash, cash equivalents, and restricted cash shown in the consolidated statements of cash flows $ 211,956 $ 86,896

Net Loss Per Share Applicable21

Net Loss Per Share Applicable to Common Stockholders (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Earnings per Share	Basic net loss per share applicable to common stockholders is calculated by dividing net loss applicable to common stockholders by the weighted average common shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by adjusting the weighted average common shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock method. Three Months Ended March 31, 2018 2017 Net loss applicable to common stockholders (in thousands) $ (117,574 ) $ (100,328 ) Denominator Weighted average common shares outstanding - basic and diluted 67,844,872 50,395,632 Net loss per share applicable to common stockholders - basic and diluted $ (1.73 ) $ (1.99 )
Schedule of Weighted Average Numbers of Securities Excluded from Calculation of Diluted Net Loss Per Share	The following weighted average numbers of securities were excluded from the calculation of diluted net loss per share for the three months ended March 31, 2018 and 2017 because including them would have had an anti-dilutive effect. Therefore, basic and diluted net loss per share were the same for all periods presented. Three Months Ended March 31, 2018 2017 Common shares underlying 2025 convertible senior notes 9,060,357 — Common shares underlying convertible preferred stock 6,366,241 — Stock options and awards 8,688,966 5,963,117 Employee stock purchase plan 93,321 40,740 24,208,885 6,003,857

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2018
Investments [Abstract]
Schedule of Available for Sale Securities	Investments consisted of available-for-sale securities as follows: Amortized Cost Gross unrealized gains Gross unrealized losses Fair Value (in thousands) Type of security as of March 31, 2018 U.S. government agency obligations maturing in one year or less $ 129,227 $ — $ (222 ) $ 129,005 U.S. government agency obligations maturing after one year through two years 246,831 — (745 ) 246,086 Total available-for-sale securities $ 376,058 $ — $ (967 ) $ 375,091 Type of security as of December 31, 2017 U.S. government agency obligations maturing in one year or less $ 199,434 $ — $ (90 ) $ 199,344 Total available-for-sale securities $ 199,434 $ — $ (90 ) $ 199,344

Fair Value Disclosures (Tables)

Fair Value Disclosures (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of Financial Instruments by Level within Fair Value Hierarchy	The following table presents the Company’s financial instruments by level within the fair value hierarchy: Fair Value Measurement Using Level 1 Level 2 Level 3 Total (in thousands) As of March 31, 2018 Assets Cash equivalents Money market funds $ 196,038 $ — $ — $ 196,038 Short-term investments U.S. government agency obligations — 129,005 — 129,005 Long term investments U.S. government agency obligations — 246,086 — 246,086 Restricted cash Money market funds 10,000 — — 10,000 $ 206,038 $ 375,091 $ — $ 581,129 Liabilities 2025 convertible senior notes $ — $ 265,529 $ — 265,529 $ — $ 265,529 $ — $ 265,529 As of December 31, 2017 Cash equivalents Money market funds $ 71,379 $ — $ — $ 71,379 Short-term investments U.S. government agency obligations — 199,344 — 199,344 Restricted cash Money market funds 10,000 — — 10,000 $ 81,379 $ 199,344 $ — $ 280,723

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	3 Months Ended
	Mar. 31, 2018
Payables And Accruals [Abstract]
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following for the dates indicated: March 31, December 31, 2018 2017 (in thousands) Compensation and benefits $ 5,898 $ 7,933 Contracted research and development 3,432 6,846 Professional services and other 1,148 1,024 Interest on 2025 convertible senior notes 1,162 — $ 11,640 $ 15,803

2025 Convertible Senior Notes25

2025 Convertible Senior Notes, Net (Tables)	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
Schedule of Outstanding Balances of Convertible Notes	The outstanding balances of the Convertible Notes as of March 31, 2018 consisted of the following: 2025 Convertible Senior Notes (in thousands) Liability component: Principal $ 287,500 Less: unamortized debt discount and issuance costs (114,303 ) Net carrying amount $ 173,197 Net carrying amount of equity component $ 106,148
Schedule of Total Interest Expense Recognized Related to Convertible Notes	The following table sets forth total interest expense recognized related to the Convertible Notes during the three months ended March 31, 2018: Three Months Ended March 31, 2018 2017 (in thousands) Contractual interest expense $ 1,162 $ — Amortization of debt discount and issuance costs 1,689 — Total interest expense $ 2,851 $ —
Schedule of Future Minimum Payments on Long-Term Debt	Future minimum payments on our long-term debt as of March 31, 2018 were as follows: Years ended December 31, Future Minimum Payments (in thousands) 2018 $ 3,594 2019 7,188 2020 7,188 2021 7,188 2022 7,188 2023 and thereafter 305,466 Total minimum payments 337,812 Less: interest (50,312 ) Less: unamortized discount and issuance costs (114,303 ) Less: current portion — 2025 convertible senior notes, net $ 173,197

Nature of Business - Additional

Nature of Business - Additional Information (Detail) - USD ($)	Jan. 12, 2018	Mar. 31, 2018	Feb. 13, 2018	Feb. 01, 2018
Nature Of Operations [Line Items]
Company Incorporation, date		May 20, 2002
Proceeds from issuance of Convertible Notes		$ 277,656,000
2025 Convertible Senior Notes
Nature Of Operations [Line Items]
Aggregate principal amount			$ 37,500,000	$ 250,000,000
Convertible Notes, interest rate		2.50%		2.50%
Proceeds from issuance of Convertible Notes		$ 287,500,000
Fees and offering expenses		$ 9,800,000
Private Placement | Preferred Stock Purchase Agreement | Redmile Group, LLC | Convertible Preferred Stock
Nature Of Operations [Line Items]
Number of shares sold	725,268
Net proceeds from offering	$ 97,700,000
Offering expenses	$ 2,300,000

Summary of Significant Accoun27

Summary of Significant Accounting Policies - Additional Information (Detail)	Jan. 12, 2018USD ($)shares	Feb. 28, 2018USD ($)	Mar. 31, 2018USD ($)SegmentCountry	Dec. 31, 2017USD ($)
Significant Accounting Policies [Line Items]
Number of operating segment | Segment			1
Number of operating geographic regions | Country			3
Restricted cash			$ 10,000,000	$ 10,000,000
Restricted cash, current			2,500,000
Net proceeds from underwritten offering of convertible notes			277,656,000
Preferred Stock Purchase Agreement | Redmile Group, LLC | Convertible Preferred Stock | Private Placement
Significant Accounting Policies [Line Items]
Number of shares sold | shares	725,268
Net proceeds from offering	$ 97,700,000
Long-Term Incentive Plan
Significant Accounting Policies [Line Items]
Compensation expense			0
Estimated value to be delivered in restricted stock units to participants eligible			$ 9,600,000
2.5% Convertible Senior Notes Due in February 1, 2025
Significant Accounting Policies [Line Items]
Debt discount amortization period			7 years
Net proceeds from underwritten offering of convertible notes		$ 277,700,000

Summary of Significant Accoun28

Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents	$ 201,956	$ 76,896
Restricted cash	10,000	10,000
Total cash, cash equivalents, and restricted cash shown in the consolidated statements of cash flows	$ 211,956	$ 86,896	$ 79,713	$ 116,216

Net Loss Per Share Applicable29

Net Loss Per Share Applicable to Common Stockholders - Schedule of Basic and Diluted Earnings per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net loss applicable to common stockholders (in thousands)	$ (117,574)	$ (100,328)
Denominator
Weighted average common shares outstanding - basic and diluted	67,844,872	50,395,632
Net loss per share applicable to common stockholders - basic and diluted	$ (1.73)	$ (1.99)

Net Loss Per Share Applicable30

Net Loss Per Share Applicable to Common Stockholders - Schedule of Weighted Average Numbers of Securities Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding stock options and employee stock purchase plan awards excluded from calculation of diluted net loss per share	24,208,885	6,003,857
Common shares underlying 2025 convertible senior notes
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding stock options and employee stock purchase plan awards excluded from calculation of diluted net loss per share	9,060,357
Common shares underlying convertible preferred stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding stock options and employee stock purchase plan awards excluded from calculation of diluted net loss per share	6,366,241
Stock options and awards
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding stock options and employee stock purchase plan awards excluded from calculation of diluted net loss per share	8,688,966	5,963,117
Employee stock purchase plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding stock options and employee stock purchase plan awards excluded from calculation of diluted net loss per share	93,321	40,740

Investments - Schedule of Avail

Investments - Schedule of Available for Sale Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 376,058	$ 199,434
Gross unrealized losses	(967)	(90)
Fair Value	375,091	199,344
U.S. government agency obligations maturing in one year or less
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	129,227	199,434
Gross unrealized losses	(222)	(90)
Fair Value	129,005	$ 199,344
U.S. government agency obligations maturing after one year through two years
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	246,831
Gross unrealized losses	(745)
Fair Value	$ 246,086

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Investments Debt And Equity Securities [Abstract]
Available for sale securities realized gains or losses		$ 0
Available for sale securities realized losses	$ 300,000

Fair Value Disclosures - Schedu

Fair Value Disclosures - Schedule of Financial Instruments by Level within Fair Value Hierarchy (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	$ 129,005	$ 199,344
Assets at fair value	581,129	280,723
Liabilities at fair value	265,529
2025 convertible senior notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities at fair value	265,529
Money market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	196,038	71,379
Restricted cash	10,000	10,000
U.S. government agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	129,005	199,344
Long term investments	246,086
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	206,038	81,379
Level 1 | Money market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	196,038	71,379
Restricted cash	10,000	10,000
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets at fair value	375,091	199,344
Liabilities at fair value	265,529
Level 2 | 2025 convertible senior notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities at fair value	265,529
Level 2 | U.S. government agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	129,005	$ 199,344
Long term investments	$ 246,086

Investment in Unconsolidated 34

Investment in Unconsolidated Entity - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Nov. 30, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2016
Investment in Unconsolidated Entity [Line Items]
Net loss recorded		$ 222	$ 149
Vitaeris
Investment in Unconsolidated Entity [Line Items]
Gain on license agreement				$ 1,100
Lag in recording company's share of loss or income generated by unconsolidated entity within condensed consolidated statement of operations (in months)		3 months
Upfront payment received	$ 15,000
Net loss recorded		$ 200

Accrued Liabilities - Schedule

Accrued Liabilities - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Payables And Accruals [Abstract]
Compensation and benefits	$ 5,898	$ 7,933
Contracted research and development	3,432	6,846
Professional services and other	1,148	1,024
Interest on 2025 convertible senior notes	1,162
Accrued liabilities	$ 11,640	$ 15,803

2025 Convertible Senior Notes36

2025 Convertible Senior Notes, Net - Additional Information (Detail)	2 Months Ended	3 Months Ended
	Mar. 31, 2018USD ($)$ / shares	Mar. 31, 2018USD ($)trading_day$ / sharesshares	Feb. 13, 2018USD ($)	Feb. 01, 2018USD ($)
Debt Instrument [Line Items]
Percentage of principal and accrued and unpaid Interest payable upon default		100.00%
Proceeds from issuance of Convertible Notes		$ 277,656,000
Debt issuance costs allocated to equity component and recorded as reduction to additional paid-in capital		109,911,000
Amortization of debt discount and issuance costs		1,689,000
Unamortized balance of liability component	$ 173,197,000	$ 173,197,000
2025 Convertible Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount			$ 37,500,000	$ 250,000,000
Convertible Notes, interest rate	2.50%	2.50%		2.50%
Debt instrument, frequency of periodic payment		semi-annually
Debt instrument, payment terms		The Convertible Notes are senior unsecured obligations of the Company and bear interest at a rate of 2.5% per annum, payable semi-annually in arrears on February 1 and August 1 of each year, commencing on August 1, 2018.
Debt instrument, date of first required payment		Aug. 1, 2018
Debt instrument, redemption period, start date		Feb. 1, 2022
Debt instrument, maturity date		Feb. 1, 2025
Initial conversion rate per $1,000 principal amount of notes | shares		49.3827
Principal amount of notes used in conversion rate	$ 1,000	$ 1,000
Initial conversion price per share of common stock | $ / shares	$ 20.25	$ 20.25
Debt instrument, convertible, latest date		Nov. 1, 2024
Debt instrument, convertible, terms of conversion feature		Holders of the Convertible Notes may convert all or any portion of their notes, in multiples of $1,000 principal amount, at their option at any time prior to the close of business on the business day immediately preceding November 1, 2024 only under the following circumstances: 1. during any calendar quarter commencing after the calendar quarter ending on March 31, 2018 (and only during such calendar quarter), if the last reported sale price of the Company's common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day; 2. during the five business day period after any five consecutive trading day period (the “measurement period”) in which the "trading price" per $1,000 principal amount of the Convertible Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Company’s common stock and the conversion rate on each such trading day; 3. if the Company calls any or all of the Convertible Notes for redemption, at any time prior to the close of business on the scheduled trading day immediately preceding the redemption date; or 4. upon the occurrence of specified corporate events.
Initial amount of liability component	$ 177,600,000	$ 177,600,000
Proceeds from issuance of Convertible Notes		287,500,000
Fair value of liability of Convertible Notes	177,600,000	177,600,000
Equity component of Convertible Notes recognized as debt discount	109,900,000	109,900,000
Debt issuance costs	9,800,000	9,800,000
Debt issuance costs allocated to equity component and recorded as reduction to additional paid-in capital		3,700,000
Debt issuance costs allocated to liability component and recorded as reduction of Convertible Notes		$ 6,100,000
Debt discount and issuance costs amortized to interest expense, amortization period		7 years
Amortization of debt discount and issuance costs		$ 1,700,000
Unamortized balance of liability component	$ 173,200,000	$ 173,200,000
Expected life of Convertible Notes		7 years
Effective interest rate on liability component of Convertible Notes for the period	10.60%
Debt instrument, convertible, if-converted value in excess of principal		$ 0
Estimated fair value of Convertible Notes	$ 265,500,000	$ 265,500,000
2025 Convertible Senior Notes | Debt Instrument, Redemption, Period On or After February 1, 2022
Debt Instrument [Line Items]
Debt instrument, redemption period, start date		Feb. 1, 2022
Debt instrument, redemption price, percentage of principal amount redeemed		100.00%
Debt instrument, redemption, threshold trading days | trading_day		20
Debt instrument, redemption, threshold consecutive trading days | trading_day		30
Debt instrument, redemption, threshold percentage of stock price trigger		130.00%
2025 Convertible Senior Notes | Debt Instrument, Convertible, Terms of Conversion Feature, Circumstances One
Debt Instrument [Line Items]
Debt instrument, convertible, threshold trading days | trading_day		20
Debt instrument, convertible, threshold consecutive trading days | trading_day		30
Debt instrument, convertible, threshold percentage of stock price trigger		130.00%
2025 Convertible Senior Notes | Debt Instrument, Convertible, Terms of Conversion Feature, Circumstances Two
Debt Instrument [Line Items]
Debt instrument, convertible, threshold consecutive trading days | trading_day		5
Debt instrument, convertible, threshold measurement period, description		during the five business day period after any five consecutive trading day period
Debt instrument, convertible, threshold maximum percentage of product of last reported sale price of common stock		98.00%

2025 Convertible Senior Notes37

2025 Convertible Senior Notes, Net - Schedule of Outstanding Balances of Convertible Notes (Detail) $ in Thousands	Mar. 31, 2018USD ($)
Liability component:
Principal	$ 337,812
Less: unamortized debt discount and issuance costs	(114,303)
2025 convertible senior notes, net	173,197
Convertible Notes
Liability component:
2025 convertible senior notes, net	173,200
Net carrying amount of equity component	109,900
Convertible Notes | 2025 Convertible Senior Notes
Liability component:
Principal	287,500
Less: unamortized debt discount and issuance costs	(114,303)
2025 convertible senior notes, net	173,197
Net carrying amount of equity component	$ 106,148

2025 Convertible Senior Notes38

2025 Convertible Senior Notes, Net - Schedule of Total Interest Expense Recognized Related to Convertible Notes (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Debt Disclosure [Abstract]
Contractual interest expense	$ 1,162
Amortization of debt discount and issuance costs	1,689
Total interest expense	$ 2,851

2025 Convertible Senior Notes39

2025 Convertible Senior Notes, Net - Schedule of Future Minimum Payments on Long-Term Debt (Detail) $ in Thousands	Mar. 31, 2018USD ($)
Debt Disclosure [Abstract]
Future Minimum Payments, 2018	$ 3,594
Future Minimum Payments, 2019	7,188
Future Minimum Payments, 2020	7,188
Future Minimum Payments, 2021	7,188
Future Minimum Payments, 2022	7,188
Future Minimum Payments, 2023 and thereafter	305,466
Total minimum payments	337,812
Less: interest	(50,312)
Less: unamortized debt discount and issuance costs	(114,303)
2025 convertible senior notes, net	$ 173,197

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Detail) - USD ($)	Jan. 12, 2018	Jan. 07, 2018	Mar. 31, 2018	Jan. 05, 2018
Temporary Equity [Line Items]
Preferred stock liquidation preference description			A liquidation shall be deemed to include the occurrence of either (i) the Company merges into or consolidates with any other entity, or any entity merges into or consolidates with the Company and, after giving effect to such transaction, the stockholders of the Company immediately prior to such transaction own less than 50% of the aggregate voting power of the Company or the successor entity of such transaction or (ii) the Company sells, leases, licenses or transfers all or substantially all of its assets to another person or entity and the stockholders of the Company immediately prior to such transaction own less than 50% of the aggregate voting power of the acquiring entity immediately after the transaction (each a “Deemed Liquidation”).
Accrued dividends on convertible preferred stock			$ 1,083,000
Common stock price per share	$ 17.85			$ 12.95
Convertible Preferred Stock
Temporary Equity [Line Items]
Beneficial conversion feature			29,500,000
Preferred Stock Purchase Agreement | Redmile Group, LLC
Temporary Equity [Line Items]
Percentage of capital stock held by related party	5.00%
Preferred stock convertible into shares of common stock		10
Preferred Stock Purchase Agreement | Redmile Group, LLC | Series A-1 Convertible Preferred Stock | Private Placement
Temporary Equity [Line Items]
Number of shares sold	725,268
Price per share	$ 137.88
Net proceeds from sale of shares after deducting fees and applicable expenses	$ 97,700,000
Fees and applicable expenses paid	$ 2,300,000
Preferred Stock Purchase Agreement | Redmile Group, LLC | Convertible Preferred Stock
Temporary Equity [Line Items]
Option to sell convertible preferred stock, maximum amount		$ 150,000,000
Period of option to sell convertible preferred stock, following date of initial purchase		90 days
Public offering, shares issued		0
Liquidation preference, per share		$ 137.88
Rate of dividend per year		5.00%
Accrued dividends on convertible preferred stock			$ 1,100,000
Accrued dividends on convertible preferred stock per share			$ 0.49
Issuance of warrants to purchase shares of convertible preferred stock			75,000
Convertible preferred stock at a purchase price per share			$ 137.88
Preferred Stock Purchase Agreement | Redmile Group, LLC | Convertible Preferred Stock | 2.5% Convertible Senior Notes Due in February 1, 2025
Temporary Equity [Line Items]
Termination of right to sell additional convertible preferred stock		$ 150,000,000
Preferred Stock Purchase Agreement | Redmile Group, LLC | Convertible Preferred Stock | Private Placement
Temporary Equity [Line Items]
Number of shares sold	725,268
Net proceeds from sale of shares after deducting fees and applicable expenses	$ 97,700,000

Teva License Agreement - Additi

Teva License Agreement - Additional Information (Detail) - Teva Pharmaceuticals International GmbH - Settlement and Licensing Agreement	Jan. 05, 2018USD ($)Milestone
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement entered date	Jan. 5, 2018
One-time non-refundable payment, amount	$ 25,000,000
Second one-time, non-refundable payment payable upon approval of BLA	25,000,000
Amount payable upon each sales-related milestones	$ 75,000,000
Number of sales-related milestones | Milestone	2
Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Annual sales	$ 1,000,000,000
Percentage of royalty payments on net sales	5.00%
Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Annual sales	$ 2,000,000,000
Percentage of royalty payments on net sales	7.00%