Ultragenyx Pharmaceutical (RARE) 10-Q 6 Nov 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Oct. 31, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Trading Symbol	RARE
Entity Registrant Name	Ultragenyx Pharmaceutical Inc.
Entity Central Index Key	0001515673
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		57,770,923
Entity Shell Company	false
Entity File Number	001-36276
Entity Tax Identification Number	27-2546083
Entity Address, Address Line One	60 Leveroni Court
Entity Address, City or Town	Novato
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94949
City Area Code	415
Local Phone Number	483-8800
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $0.001 par value
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 122,577	$ 113,432
Short-term investments	404,481	346,274
Accounts receivable	23,121	12,740
Inventory	14,138	7,065
Prepaid expenses and other current assets	49,169	42,858
Total current assets	613,486	522,369
Property and equipment, net	31,877	20,046
Investment in Arcturus equity securities	26,333
Intangible assets, net	129,020	129,223
Goodwill	44,406	44,406
Right-of-use assets	31,711
Other assets	3,111	3,514
Total assets	879,944	719,558
Current liabilities:
Accounts payable	13,460	12,275
Accrued liabilities	69,557	62,450
Short-term lease liabilities	7,290
Total current liabilities	90,307	74,725
Deferred tax liabilities	31,166	31,166
Long-term lease liabilities	31,206
Other liabilities		4,759
Total liabilities	152,679	110,650
Stockholders’ equity:
Preferred stock — 25,000,000 shares authorized; nil outstanding as of September 30, 2019 and December 31, 2018
Common stock — 250,000,000 shares authorized; 57,749,890 and 50,860,588 shares issued and outstanding as of September 30, 2019 and December 31, 2018, respectively	58	51
Additional paid-in capital	2,066,483	1,639,773
Accumulated other comprehensive loss	(71)	(633)
Accumulated deficit	(1,339,205)	(1,030,283)
Total stockholders’ equity	727,265	608,908
Total liabilities and stockholders’ equity	$ 879,944	$ 719,558

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - shares	Sep. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Preferred stock, shares authorized	25,000,000	25,000,000
Preferred stock, shares outstanding	0	0
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	57,749,890	50,860,588
Common stock, shares outstanding	57,749,890	50,860,588

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Total revenues	$ 25,800	$ 11,763	$ 68,121	$ 35,234
Operating expenses:
Cost of sales	2,683	273	3,901	639
Research and development	100,144	70,041	274,294	222,380
Selling, general and administrative	41,006	31,095	119,647	93,248
Total operating expenses	143,833	101,409	397,842	316,267
Loss from operations	(118,033)	(89,646)	(329,721)	(281,033)
Interest income	3,319	2,730	10,468	6,915
Gain from sale of priority review vouchers		40,300		170,322
Change in fair value of investment in Arcturus equity securities	2,166		11,994
Other expense	(153)	(147)	(941)	(5,601)
Loss before income taxes	(112,701)	(87,063)	(308,200)	(109,397)
Provision for income taxes	(293)	(247)	(722)	(388)
Net loss	$ (112,994)	$ (87,310)	$ (308,922)	$ (109,785)
Net loss per share, basic and diluted	$ (1.96)	$ (1.74)	$ (5.50)	$ (2.22)
Shares used in computing net loss per share, basic and diluted	57,707,694	50,319,772	56,161,996	49,447,889
Collaboration and License
Revenues:
Total revenues	$ 21,585	$ 9,015	$ 55,070	$ 28,896
Product Sales
Revenues:
Total revenues	$ 4,215	$ 2,748	$ 13,051	$ 6,338

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (112,994)	$ (87,310)	$ (308,922)	$ (109,785)
Other comprehensive income (loss):
Foreign currency translation adjustments	(234)	61	(79)	(3)
Transfer of cumulative translation adjustment for the substantial liquidation of foreign subsidiaries				5,272
Unrealized gain (loss) on available-for-sale securities	(92)	183	641	1
Other comprehensive income (loss)	(326)	244	562	5,270
Total comprehensive loss	$ (113,320)	$ (87,066)	$ (308,360)	$ (104,515)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2017	$ 383,454	$ 44	$ 1,221,762	$ (5,680)	$ (832,672)
Beginning balance, shares at Dec. 31, 2017		44,167,071
Issuance of common stock in connection with underwritten public offering, net of issuance costs	270,969	$ 5	270,964
Issuance of common stock in connection with underwritten public offering, net of issuance costs, shares		5,043,860
Issuance of common stock in connection with at-the-market offering, net of issuance costs	27,645	$ 1	27,644
Issuance of common stock in connection with at-the-market offering, net of issuance costs, shares		445,619
Employee stock-based compensation	59,027		59,027
Issuance of common stock under equity plan awards, net of tax	26,016	$ 1	26,015
Issuance of common stock under equity plan awards, net of tax, shares		876,520
Other comprehensive income	5,270			5,270
Net loss	(109,785)				(109,785)
Ending balance at Sep. 30, 2018	662,596	$ 51	1,605,412	(410)	(942,457)
Ending balance, shares at Sep. 30, 2018		50,533,070
Beginning balance at Jun. 30, 2018	703,971	$ 50	1,559,722	(654)	(855,147)
Beginning balance, shares at Jun. 30, 2018		50,116,056
Issuance of common stock in connection with at-the-market offering, net of issuance costs	15,837		15,837
Issuance of common stock in connection with at-the-market offering, net of issuance costs, shares		205,202
Employee stock-based compensation	20,667		20,667
Issuance of common stock under equity plan awards, net of tax	9,187	$ 1	9,186
Issuance of common stock under equity plan awards, net of tax, shares		211,812
Other comprehensive income	244			244
Net loss	(87,310)				(87,310)
Ending balance at Sep. 30, 2018	662,596	$ 51	1,605,412	(410)	(942,457)
Ending balance, shares at Sep. 30, 2018		50,533,070
Beginning balance at Dec. 31, 2018	$ 608,908	$ 51	1,639,773	(633)	(1,030,283)
Beginning balance, shares at Dec. 31, 2018	50,860,588	50,860,588
Issuance of common stock in connection with underwritten public offering, net of issuance costs	$ 330,415	$ 6	330,409
Issuance of common stock in connection with underwritten public offering, net of issuance costs, shares		5,833,333
Issuance of common stock in connection with at-the-market offering, net of issuance costs	24,828		24,828
Issuance of common stock in connection with at-the-market offering, net of issuance costs, shares		468,685
Employee stock-based compensation	62,854		62,854
Issuance of common stock under equity plan awards, net of tax	8,620	$ 1	8,619
Issuance of common stock under equity plan awards, net of tax, shares		587,284
Other comprehensive income	562			562
Net loss	(308,922)				(308,922)
Ending balance at Sep. 30, 2019	$ 727,265	$ 58	2,066,483	(71)	(1,339,205)
Ending balance, shares at Sep. 30, 2019	57,749,890	57,749,890
Beginning balance at Jun. 30, 2019	$ 819,787	$ 58	2,045,685	255	(1,226,211)
Beginning balance, shares at Jun. 30, 2019		57,665,375
Employee stock-based compensation	19,894		19,894
Issuance of common stock under equity plan awards, net of tax	904		904
Issuance of common stock under equity plan awards, net of tax, shares		84,515
Other comprehensive income	(326)			(326)
Net loss	(112,994)				(112,994)
Ending balance at Sep. 30, 2019	$ 727,265	$ 58	$ 2,066,483	$ (71)	$ (1,339,205)
Ending balance, shares at Sep. 30, 2019	57,749,890	57,749,890

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Operating activities:
Net loss	$ (308,922)	$ (109,785)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	62,335	59,027
Amortization of discount on investment securities, net	(4,931)	(1,832)
Depreciation and amortization	6,370	16,595
Foreign currency remeasurement loss	925	5,853
Change in fair value of investment in Arcturus equity securities	(11,994)
Gain from sale of priority review vouchers		(170,322)
Other	220	(145)
Changes in operating assets and liabilities:
Accounts receivable	(10,402)	(3,983)
Inventory	(6,604)	(4,799)
Prepaid expenses and other current assets	(6,954)	(20,380)
Right-of-use assets	(15,581)
Other assets	1,080	(62)
Accounts payable	266	(593)
Lease liabilities	17,071
Accrued liabilities and other liabilities	3,777	(4,287)
Net cash used in operating activities	(273,344)	(234,713)
Investing activities:
Purchase of property and equipment	(13,332)	(2,884)
Purchase of investments	(610,267)	(500,049)
Purchase of investment in Arcturus equity securities	(14,339)
Proceeds from the sale of investments	35,100	7,655
Proceeds from maturities of investments	522,533	218,064
Proceeds from sale of priority review vouchers		170,322
Net cash used in investing activities	(80,305)	(106,892)
Financing activities:
Proceeds from the issuance of common stock in connection with underwritten public offerings, net	330,415	270,969
Proceeds from the issuance of common stock in connection with at-the-market offering, net	24,828	27,626
Proceeds from the issuance of common stock from equity plan awards, net of tax	8,620	26,016
Net cash provided by financing activities	363,863	324,611
Effect of exchange rate changes on cash	(502)	(617)
Net increase in cash, cash equivalents and restricted cash	9,712	(17,611)
Cash, cash equivalents and restricted cash at beginning of period	115,525	103,041
Cash, cash equivalents and restricted cash at end of period	125,237	$ 85,430
Supplemental disclosures of non-cash information:
Acquired lease liabilities arising from obtaining right-of-use assets	$ 21,515

Organization

Organization	9 Months Ended
	Sep. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	1. Organization Ultragenyx Pharmaceutical Inc. (the Company) is a biopharmaceutical company incorporated in California on April 22, 2010. The Company subsequently reincorporated in the state of Delaware in June 2011. The Company is focused on the identification, acquisition, development, and commercialization of novel products for the treatment of serious rare and ultra-rare genetic diseases. The Company has two approved therapies. Crysvita ® In addition to the approved treatments for XLH and MPS VII, the Company has four ongoing clinical development programs. Crysvita is being studied for the treatment of tumor induced osteomalacia (TIO), a rare disease that impairs bone mineralization. UX007 is being studied in patients severely affected by long-chain fatty acid oxidation disorders (LC-FAOD), a genetic disorder in which the body is unable to convert long chain fatty acids into energy. The Company has two gene therapy pipeline candidates: DTX301 is an adeno-associated virus 8 (AAV8) gene therapy product candidate in development for the treatment of patients with ornithine transcarbamylase (OTC) deficiency, the most common urea cycle disorder; and DTX401 is an AAV8 gene therapy product candidate for the treatment of patients with glycogen storage disease type Ia (GSDIa). The Company operates as one reportable segment. The Company has sustained operating losses and expects such annual losses to continue over the next several years. The Company’s ultimate success depends on the outcome of its research and development and commercialization activities, for which it expects to incur additional losses in the future. Management recognizes the need to raise additional capital to fully implement its business plan. Through September 30, 2019, the Company has relied primarily on the proceeds from equity offerings to finance its operations. The Company intends to raise additional capital through the issuance of equity, borrowings, strategic alliances with partner companies, or other transactions. However, if such financing is not available at adequate levels, the Company will need to reevaluate its operating plans.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries and have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) for interim financial information and in accordance with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. The unaudited interim consolidated financial statements have been prepared on the same basis as the annual financial statements. In the opinion of management, the accompanying unaudited condensed consolidated financial statements reflect all adjustments (consisting only of normal recurring adjustments) considered necessary for a fair presentation. These financial statements should be read in conjunction with the audited financial statements and notes thereto for the preceding fiscal year contained in the Company’s Annual Report on Form 10-K filed on February 19, 2019 with the United States Securities and Exchange Commission (SEC). The results of operations for the three and nine months ended September 30, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019. The condensed consolidated balance sheet as of December 31, 2018 has been derived from audited financial statements at that date, but does not include all of the information required by GAAP for complete financial statements. Use of Estimates The accompanying consolidated financial statements have been prepared in accordance with GAAP. The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities and the reported amounts of expenses in the consolidated financial statements and the accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to clinical trial accruals, fair value of assets and liabilities, income taxes, and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates. Cash, Cash Equivalents and Restricted Cash Restricted cash primarily consists of money market accounts as collateral for the Company’s obligations under its facility leases. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the consolidated statement of cash flows (in thousands): September 30, 2019 2018 Cash and cash equivalents $ 122,577 $ 82,956 Restricted cash included in prepaid expenses and other current assets 161 652 Restricted cash included in other assets 2,499 1,822 Total cash, cash equivalents, and restricted cash shown in the statements of cash flows $ 125,237 $ 85,430 Investment in Equity Securities In June 2019, the Company entered into an amendment to the Research Collaboration and License Agreement and an Equity Purchase Agreement with Arcturus Therapeutics Holdings Inc. (“Arcturus”). Pursuant to the Equity Purchase Agreement, the Company purchased 2,400,000 shares of common stock, or approximately 18.2% of Arcturus’s outstanding shares of common stock as of the closing date of the transaction and received an option to purchase an additional 600,000 shares of common stock. The investment is subject to using the equity method of accounting as it was determined that the Company has significant influence over Arcturus, but does not control the significant activities of Arcturus. The Company elected to apply the fair value option to account for the equity investment in Arcturus. The decision to elect the fair value option is irrevocable and is determined on an instrument by instrument basis. The option to purchase additional stock was accounted for at fair value using the Black-Scholes option pricing method. The changes in fair value of the equity investment and option to purchase additional stock are included in the Condensed Consolidated Statements of Operations. See “Note 6. License and Research Agreements” for additional details on the Arcturus transaction. Revenue Recognition Collaboration and license revenue The Company has certain license and collaboration agreements that are within the scope of Accounting Standards Codification (ASC) 808, Collaborative Agreements provides guidance on the presentation and disclosure of collaborative arrangements. Generally, the classification of the transactions under the collaborative arrangements is determined based on the nature of contractual terms of the arrangement, along with the nature of the operations of the participants. The Company records its share of collaboration revenue, net of transfer pricing related to net sales in the period in which such sales occur, if the Company is considered as an agent in the arrangement. The Company is considered an agent when the collaboration partner controls the product before transfer to the customers and has the ability to direct the use of and obtain substantially all of the remaining benefits from the product. Funding received related to research and development services and commercialization costs is generally classified as a reduction of research and development expenses and selling, general and administrative expenses, respectively, in the consolidated statement of operations, because the provision of such services for collaborative partners are not considered to be part of the Company’s ongoing major or central operations. The also receives royalty revenues under certain of the Company’s license or collaboration agreements in exchange for license of intellectual property. If the Company does not have any future performance obligations for these license or collaboration agreements, royalty revenue is recorded as the underlying sales occur. In to record collaboration revenue, the Company utilizes certain information from its , including revenue from the sale of the product, associated reserves on revenue, and costs incurred for development and sales activities. For the periods covered in the financial statements presented, there have been no material changes to prior period estimates of revenues and expenses. The terms of the Company’s collaboration agreements may contain multiple performance obligations, which may include licenses and research and development activities. The Company evaluates these agreements under ASC 606, Revenue from Contracts with Customers (ASC 606), to determine the distinct performance obligations. The Company analogizes to ASC 606 for the accounting for distinct performance obligations for which there is a customer relationship. Prior to recognizing revenue, the Company makes estimates of the transaction price, including variable consideration that is subject to a constraint. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur and when the uncertainty associated with the variable consideration is subsequently resolved. Total consideration may include nonrefundable upfront license fees, payments for research and development activities, reimbursement of certain third-party costs, payments based upon the achievement of specified milestones, and royalty payments based on product sales derived from the collaboration. If there are multiple distinct performance obligations, the Company allocates the transaction price to each distinct performance obligation based on its relative standalone selling price. The standalone selling price is generally determined based on the prices charged to customers or using expected cost plus margin. The Company estimates the efforts needed to complete the performance obligation and recognizes revenue by measuring the progress towards complete satisfaction of the performance obligation using an input measure. Product sales The Company sells its approved products through a limited number of distributors. Under ASC 606, revenue from product sales is recognized at the point in time when the delivery is made and when title and risk of loss transfers to these distributors. The Company also recognizes revenue from sales of certain products on a “named patient” basis, which are allowed in certain countries prior to the commercial approval of the product. Prior to recognizing revenue, the Company makes estimates of the transaction price, including any variable consideration that is subject to a constraint. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur and when the uncertainty associated with the variable consideration is subsequently resolved. Product sales are recorded net of estimated government-mandated rebates and chargebacks, estimated product returns, and other deductions. Provisions for returns and other adjustments are provided for in the period the related revenue is recorded, as estimated by management. Leases The Company adopted Accounting Standards Update (ASU) No. 2016-02, Leases (Topic 842) Leases (Topic 840) The Company determines if an arrangement includes a lease at inception. Right-of-use assets and lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at the commencement date. The right-of-use asset includes any lease payments made and excludes lease incentives. Incremental borrowing rate is used in determining the present value of future payments. The Company applies a portfolio approach to the property leases to apply an incremental borrowing rate to leases with similar lease terms. The lease terms may include options to extend or terminate the lease. The Company recognizes the options to extend the lease as part of the right-of-use assets and lease liabilities only if it is reasonably certain that the option would be exercised. Lease expense for minimum lease payments is recognized on a straight-line basis over the non-cancelable lease term. Prior period amounts have not been adjusted and continue to be reported in accordance with the Company’s historical accounting under previous lease guidance, Topic 840. As a result of the adoption of the new guidance, the Company recorded a right-of-use asset of $16.2 million, a short-term lease liability of $4.5 million, and a long-term lease liability of $17.0 million and no cumulative effect adjustment was made to the retained earnings as of the adoption date. In addition, as of the adoption date, the Company derecognized a net deferred rent obligation of $5.2 million. See Note 11 for further disclosure. Recently Issued Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments — Credit Losses, (Topic 326): Measurement of Credit Losses on Financial Instruments,

Financial Instruments

Financial Instruments	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Financial Instruments	3. Financial Instruments Financial assets and liabilities are recorded at fair value. The carrying amount of certain financial instruments, including cash and cash equivalents, accounts receivable, accounts payable and accrued liabilities approximate fair value due to their relatively short maturities. Assets and liabilities recorded at fair value on a recurring basis in the balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1 —Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date; Level 2 —Inputs are observable, unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and Level 3 —Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data. The following tables set forth the fair value of the Company’s financial assets remeasured on a recurring basis based on the three-tier fair value hierarchy (in thousands): September 30, 2019 Level 1 Level 2 Level 3 Total Money market funds $ 88,399 $ — $ — $ 88,399 Time deposits — 10,000 — 10,000 Corporate bonds — 34,343 — 34,343 Commercial paper — 96,997 — 96,997 Asset-backed securities — 32,947 — 32,947 U.S. Government Treasury and agency securities 121,365 118,829 — 240,194 Investment in Arcturus equity securities 24,648 — 1,685 26,333 Total $ 234,412 $ 293,116 $ 1,685 $ 529,213 December 31, 2018 Level 1 Level 2 Level 3 Total Money market funds $ 72,999 $ — $ — $ 72,999 Time deposits — 10,000 — 10,000 Corporate bonds — 179,926 — 179,926 Commercial paper — 50,198 — 50,198 Asset-backed securities — 22,587 — 22,587 U.S. Government Treasury and agency securities — 99,034 — 99,034 Total $ 72,999 $ 361,745 $ — $ 434,744 The Company determines the fair value of the Arcturus common stock by using the quoted market price on September 30, 2019, which is a Level 1 fair value measurement. The change in fair value of the Arcturus common stock for the three and nine months ended September 30, 2019 was $2.0 million and $10.8 million, respectively, which was recognized in the Condensed Consolidated Statements of Operations. T he The change in fair value of the option to purchase additional Arcturus common stock for the three and nine months ended 30, 2019 was $0.2 million and $1.2 million, respectively, which was recognized in the Condensed Consolidated Statements of Operations. See “Note 6. License and Research Agreements” for additional details on the Arcturus transaction.

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2019
Investments Debt And Equity Securities [Abstract]
Balance Sheet Components	4. Balance Sheet Components Cash Equivalents and Investments The fair values of cash equivalents and short-term investments classified as available-for-sale securities consisted of the following (in thousands): September 30, 2019 Gross Unrealized Amortized Cost Gains Losses Estimated Fair Value Money market funds $ 88,399 $ — $ — $ 88,399 Time deposits 10,000 — — 10,000 Corporate bonds 34,304 40 (1 ) 34,343 Commercial paper 96,997 — — 96,997 Asset-backed securities 32,894 53 — 32,947 U.S. Government Treasury and agency securities 239,949 245 — 240,194 Total $ 502,543 $ 338 $ (1 ) $ 502,880 December 31, 2018 Gross Unrealized Amortized Cost Gains Losses Estimated Fair Value Money market funds $ 72,999 $ — $ — $ 72,999 Time deposits 10,000 — — 10,000 Corporate bonds 180,167 — (241 ) 179,926 Commercial paper 50,198 — — 50,198 Asset-backed securities 22,597 — (10 ) 22,587 U.S. Government Treasury and agency securities 99,087 2 (55 ) 99,034 Total $ 435,048 $ 2 $ (306 ) $ 434,744 At September 30, 2019, the remaining contractual maturities of available-for-sale securities were less than one year. There have been no material realized gains or losses on available-for-sale securities for the periods presented. Inventory Inventory consists of the following (in thousands): September 30, December 31, 2019 2018 Work-in-progress $ 10,753 $ 5,384 Finished goods 3,385 1,681 Total inventory $ 14,138 $ 7,065 Accrued Liabilities Accrued liabilities consist of the following (in thousands): September 30, December 31, 2019 2018 Research, clinical study, and manufacturing expenses $ 17,972 $ 16,912 Payroll and related expenses 34,681 36,443 Other 16,904 9,095 Total accrued liabilities $ 69,557 $ 62,450

Revenue

Revenue	9 Months Ended
	Sep. 30, 2019
Revenue From Contract With Customer [Abstract]
Revenue	5. Revenue The following table disaggregates total revenues from external customers by collaboration and license revenue and product sales (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Collaboration and license revenue: KKC (Crysvita) $ 21,484 $ 5,401 $ 54,617 $ 6,993 Bayer 101 3,614 453 21,903 Total collaboration and license revenue 21,585 9,015 55,070 28,896 Product sales: Crysvita 1,140 268 2,734 294 Mepsevii 2,361 2,127 8,274 5,253 UX007 714 353 2,043 791 Total product sales 4,215 2,748 13,051 6,338 Total revenues $ 25,800 $ 11,763 $ 68,121 $ 35,234 The following table disaggregates total revenues based on geographic location (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 United States $ 21,700 $ 9,879 $ 56,318 $ 31,731 Europe 2,790 1,616 8,522 3,209 All other 1,310 268 3,281 294 Total revenues $ 25,800 $ 11,763 $ 68,121 $ 35,234 The following table presents changes in the contract assets (liabilities) (in thousands): Nine Months Ended September 30, 2019 2018 Balance of contract assets (liabilities) at beginning of period $ 2,979 $ (5,986 ) Additions 452 22,491 Deductions (3,447 ) (14,767 ) Balance of contract assets (liabilities) at end of period $ (16 ) $ 1,738 The Company’s largest accounts receivable balance accounted for 93% and 88% of the total accounts receivable balance as of September 30, 2019 and December 31, 2018, respectively, and was due from a collaboration partner.

License and Research Agreements

License and Research Agreements	9 Months Ended
	Sep. 30, 2019
Research Grant Agreement [Abstract]
License and Research Agreements	6 . License and Research Agreements Kyowa Kirin Collaboration and License Agreement In August 2013, the Company entered into a collaboration and license agreement with Kyowa Kirin Co., Ltd. (KKC or formerly Kyowa Hakko Kirin Co., Ltd. or KHK). Under the terms of this collaboration and license agreement, as amended, the Company and KKC will collaborate on the development and commercialization of Crysvita in the field of orphan diseases in the United States and Canada, or the profit share territory, and in the European Union and Switzerland, or the European territory, and the Company will have the right to develop and commercialize such products in the field of orphan diseases in Mexico and Central and South America, or Latin America. In the field of orphan diseases, and except for ongoing studies being conducted by KKC, the Company will be the lead party for development activities in the profit share territory and in the European territory until the applicable transition dates; the Company will also be the lead party for core development activities conducted in Japan and Korea, for which the core development plan is limited to clinical trials mutually agreed to by the Company and KKC. The Company will share the costs for development activities in the profit share territory and the European territory conducted pursuant to the development plan before the applicable transition date equally with KKC, and KKC shall be responsible for 100% of the costs for development activities in Japan and Korea. On the applicable transition dates in the profit share territory and the European territory, KKC will become the lead party and be responsible for the costs of the development activities. However, the Company will continue to share the costs of the studies commenced prior to the applicable transition date equally with KKC. Crysvita was approved in the European Union in February 2018 and was approved by the FDA in April 2018. The collaboration and license agreements are within the scope of ASC 808, which provides guidance on the presentation and disclosure of collaborative arrangements. Collaboration revenue related to sales in profit share territory The Company and KKC share commercial responsibilities and profits in the profit share territory until the applicable transition date. Under the collaboration agreement, KKC will manufacture and supply Crysvita for commercial use in the profit share territory. The remaining profit or loss after supply costs from commercializing products in the profit-share territory, until the applicable transition date, are shared between the Company and KKC on a 50/50 basis. Thereafter, the Company will be entitled to receive a tiered double-digit revenue share in the mid-to-high 20% range The Company is considered the agent in the profit share territory as KKC controls the product before transfer to the customers and has the ability to direct the use of and obtain substantially all of the remaining benefits from the product. The Company recognizes a pro-rata share of collaboration revenue, net of supply costs, in the period the sale occurs. The Company concluded that its portion of KKC’s sales in the profit share territory is analogous to a royalty and therefore recorded its share as collaboration revenue, similar to a royalty. Royalty revenue related to sales in European territory KKC has the commercial responsibility for in the European territory. The Company receives a royalty of up to 10% on net sales in the European territory, which is recognized as the underlying sales occur The Company’s Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Company's share of collaboration revenue in profit share territory $ 19,534 $ 4,364 $ 48,721 $ 5,429 Royalty revenue in European territory 1,950 1,037 5,896 1,564 Total $ 21,484 $ 5,401 $ 54,617 $ 6,993 Product revenue related to sales in other territories The Company is responsible for commercializing in Latin America and Turkey. The Company is considered the principal in the arrangement as the Company controls the product before it is transferred to the customer. Accordingly, the Company records revenue on a gross basis related to the sale of once the product is delivered and the risk and title of the product is transferred to the distributor. For the three and nine months ended September 30, 2019, the Company recorded product sales of $1.1 million and $2.7 million, respectively, net of estimated revenue reserves. The Company recorded $0.3 million of product sales for the three and nine months ended September 30, 2018. Under KKC manufactures and supplies for sales in the above territories. The Company also pays to KKC a low single-digit royalty on net sales in Latin America. One of the wholly-owned subsidiaries of KKC has the option to assume responsibility for commercialization efforts in Turkey from the Company, after a certain minimum period. Cost sharing payments Under the collaboration agreement, KKC and the Company share certain development and commercialization costs. Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Research and development $ 7,124 $ 7,612 $ 20,118 $ 25,268 Selling, general and administrative 5,633 2,868 16,009 10,718 Total $ 12,757 $ 10,480 $ 36,127 $ 35,986 Collaboration receivable The Company had accounts receivable from KKC in the amount of $21.5 million and $11.2 million, from profit share revenue and royalties, and other receivables recorded in prepaid and other current assets of $15.9 million and $11.1 million from commercial and development activity reimbursements, as of September 30, 2019 and December 31, 2018, respectively. Bayer HealthCare LLC The Company has an agreement with Bayer Healthcare LLC (Bayer) to research, develop and commercialize AAV gene therapy products for treatment of hemophilia A (DTX 201). Under this agreement, Bayer has been granted an exclusive license to develop and commercialize one or more novel gene therapies for hemophilia A. The agreement requires that Bayer use commercially reasonable efforts to conduct and fund a proof-of-concept (POC) clinical trial and any subsequent clinical trials and commercialization of gene therapy products for treatment of hemophilia A. Bayer will have worldwide rights to commercialize the potential future product. Bayer is responsible to fund certain research and development services performed by the Company in the performance of its obligations under the annual research plan and budget. Under the terms of the agreement with Bayer, the Company is eligible to receive development and commercialization milestone payments of up to $232.0 million, as well as, royalty payments ranging in the high single-digit to low double-digit percentages, not exceeding the mid-teens, of net sales of licensed products. The Company achieved the first milestone in December 2017, the second milestone in April 2018, and has received $15.0 million for such milestones to date. As of the acquisition date of Dimension Therapeutics, Inc. on November 7, 2017, the Company valued the Bayer contract under ASC 805, Business Combinations, The Company evaluated the agreement under ASC 606 and recorded a contract liability as of November 7, 2017 of $2.5 million. It was determined that the performance obligations under the agreement include (i) research and development services to be provided over the research term, (ii) a development and commercialization license, and (iii) the Company’s participation in certain committees. It was determined that these performance obligations are not distinct in the context of the contract and therefore are a single performance obligation. The Company calculated the transaction price by including the unconstrained milestones along with the estimated payments for research and development services and recorded $0.1 million and $0.5 million as collaboration and license revenue for the three and nine months ended September 30, 2019, respectively, and $3.6 million and $21.9 million for the three and nine months ended September 30, 2018, respectively, by measuring the progress toward complete satisfaction of the performance obligation using an input measure. The performance obligation under the contract is expected to be substantially complete by end of 2019. As of September 30, 2019 and December 31, 2018, the Company had a nominal amount in contract liability and a $3.0 million contract asset, respectively. Arcturus The Company has a Research Collaboration and License Agreement with Arcturus to research and develop therapies for select rare diseases. Pursuant to the agreement, the Company incurred a nominal amount and $0.7 million for the three and nine months ended September 30, 2019, respectively, and $0.3 million and $1.2 million for the three and nine months ended September 30, 2018, respectively, in research and development expense for the funding of certain research services received from Arcturus. As of September 30, 2019 and December 31, 2018, the Company has a balance of none and $0.5 million, respectively, in prepaid expenses and other current assets, and a balance of none and $0.4 million, respectively, in accrued liabilities related to Arcturus. In June 2019, the Company entered into an Equity Purchase Agreement and an amendment to the Research Collaboration and License Agreement to expand the field of use and increase the number of disease targets to include mRNA, DNA and siRNA therapeutics for up to 12 rare diseases. Pursuant to the agreements, the Company paid $6.0 million in cash upfront to Arcturus and purchased 2,400,000 shares of Arcturus’ common stock at a stated value of $10.00 per share, resulting in a total of $30.0 million of consideration paid at the close of the transaction. As a result, the Company received expanded license rights; the Arcturus common stock; an option to purchase an additional 600,000 shares of Arcturus’ common stock at $16.00 per share, which may be exercised up to two years after the agreement effective date, with certain restrictions; in addition to other changes as noted in the agreement. The period for the Company to exercise its option to purchase the additional stock may also be extended under certain circumstances as specified in the Equity Purchase Agreement. The Company is restricted from selling the 2,400,000 shares of common stock for a period of two years from the purchase date. The additional stock, if purchased, are also restricted from sale for a period of time as specified in the agreement. The Company also received the right to nominate one member to the Arcturus Board of Directors as well as one Board observer. Under the amended license agreement, certain early-stage milestone payments are reduced and the total potential milestone payments are increased due to the expanded number of targets. Arcturus is also entitled to reimbursement of related research expenses and royalties on commercial sales. Immediately after the purchase, the Company held 18.2% of Arcturus’ outstanding common stock, based on Arcturus’ outstanding common stock balance as of the transaction date. The recorded the common stock investment at $13.9 million on the transaction date, which was based on the quoted market price on the closing date. As a result of the equity ownership and the right to nominate a board member, it was determined that the Company has significant influence over Arcturus. The Company elected to apply the fair value option to account for the equity investment in Arcturus. The Company also accounts for the option to purchase additional shares of Arcturus common stock at fair value, which was recorded at $0.5 million on the transaction date based on the Black-Scholes option pricing method. The remaining $15.6 million of the total $30.0 million paid as consideration was attributed to the additional license rights obtained and was recorded as in-process research and development expense. For the three and nine months ended September of September 30, 2019, the fair value of the Company’s investment in Arcturus common stock was $ 24.6 million based on the quoted market price on that date and the fair value of the Company’s option to purchase additional share s of Arcturus common stock was $ 1.7 million based on the Black-Scholes option pricing method. GeneTx In August 2019, the Company entered into a Program Agreement and a Unitholder Option Agreement with GeneTx Biotherapeutics, LLC (GeneTx) to collaborate on the development of GeneTx’s GTX-102, an antisense oligonucleotide (ASO) for the treatment of Angelman syndrome. Pursuant to the terms of the Unitholder Option Agreement, the Company made an upfront payment of $20.0 million for an exclusive option to acquire GeneTx. This option may be exercised any time prior to 30 days following FDA acceptance of the IND for GTX-102 for an additional $50.0 million in payments. Alternatively, the Company may extend the option period by paying an option extension payment of $25.0 million (option extension premium). In the event the Company exercises the option extension, the Company has a right to acquire GeneTx for a payment of $125.0 million, at any time, until the earlier of 30 months from the first dosing of a patient in a planned Phase 1/2 study (subject to extensions) or 90 days after results are available from that study. This exclusive option to acquire GeneTx can be extended under certain circumstances, by up to four additional three-month periods, by paying an additional extension fee for each three-month period. During the exclusive option period, GeneTx is responsible for conducting the program based on the development plan agreed between the parties and, subject to the terms in the Program Agreement, has the decision-making authority on all matters in connection with the research, development, manufacturing and regulatory activities with respect to the Program. The Company will provide support, at its discretion, including strategic guidance and clinical expertise. The Company and GeneTx will collaborate on the submission of the IND and management of the Phase 1/2 study in patients with Angelman syndrome. If the Company acquires GeneTx, the Company will then be responsible for all development and commercialization activities from the date of acquisition. The Company would also be required to make payments upon achievement of certain development and commercial milestones, as well as royalties, depending upon the success of the program. Although GeneTx is a variable interest entity, the Company is not the primary beneficiary as it currently does not have the power to direct the activities that would most significantly impact the economic performance of GeneTx. Prior to product regulatory approval, all consideration paid to GeneTx represents rights to potential future benefits associated with GeneTx’s in-process research and development activities, which have not reached technological feasibility and have no alternative future use. Accordingly, for the three and nine months ended September 30, 2019, the Company recorded the $20.0 million payment as an in-process research and development expense.

Stock-Based Awards

Stock-Based Awards	9 Months Ended
	Sep. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Awards	7 . Stock-Based Awards The 2014 Incentive Plan (the 2014 Plan) provides for automatic annual increases in shares available for grant, beginning on January 1, 2015 through January 1, 2024. As of September 30, 2019 were 2,648,552 shares reserved under the 2014 Plan for the future issuance of equity awards and 2,740,058 shares reserved for the 2014 Employee Stock Purchase Plan. The table below sets forth the stock-based compensation expense for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Cost of sales $ 319 $ — $ 404 $ — Research and development 10,629 11,858 33,891 34,749 Selling, general and administrative 8,959 8,809 28,040 24,278 Total stock-based compensation expense $ 19,907 $ 20,667 $ 62,335 $ 59,027

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	8 . Net Loss Per Share Basic net loss per share has been computed by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share is calculated by dividing net loss by the weighted-average number of shares of common stock and potential dilutive securities outstanding during the period. The following weighted-average outstanding common stock equivalents were excluded from the computation of diluted net loss per share for the periods presented because including them would have been antidilutive: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Options to purchase common stock and restricted stock units 8,155,406 7,242,989 7,936,664 7,396,423 Employee stock purchase plan 33,094 31,285 18,547 17,533 Common stock warrants 149,700 149,700 149,700 149,700 8,338,200 7,423,974 8,104,911 7,563,656

Equity Transactions

Equity Transactions	9 Months Ended
	Sep. 30, 2019
Equity [Abstract]
Equity Transactions	9 . Equity Transactions In July 2017, the Company entered into an At-The-Market, or ATM, sales agreement with Cowen and Company, LLC (Cowen), whereby the Company can sell up to $150.0 million in aggregate proceeds of common stock from time to time, through with Cowen as its sales agent. During the three and nine months ended September 30, 2019, the Company sold none and 468,685 shares of common stock, respectively, resulting in net proceeds of none and $24.8 million, respectively, after commissions and other offering costs. During the three and nine months ended September 30, 2018, the Company sold 205,202 and 445,619 shares of common stock, respectively, resulting in net proceeds of approximately $15.9 million and $27.6 million, respectively, after commissions and other offering costs. In February 2019, the Company completed an underwritten public offering in which 5,833,333 shares of common stock were sold, which included 760,869 shares purchased by the underwriters pursuant to an option granted to them in connection with the offering, at a public offering price of $60.00 per share. The total proceeds that the Company received from the offering were approximately $330.4 million, net of underwriting discounts and commissions.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	9 Months Ended
	Sep. 30, 2019
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease [Abstract]
Accumulated Other Comprehensive Loss	10 . Accumulated Other Comprehensive Loss Total accumulated other comprehensive loss consisted of the following (in thousands): September 30, December 31, 2019 2018 Foreign currency translation adjustments $ (408 ) $ (329 ) Unrealized gain (loss) on securities available-for-sale 337 (304 ) Total accumulated other comprehensive loss $ (71 ) $ (633 )

Leases

Leases	9 Months Ended
	Sep. 30, 2019
Lessee Disclosure [Abstract]
Leases	11 . Leases As described in “Note 2. Summary of Significant Accounting Policies”, the Company adopted Topic 842 Topic 840 The Company leases office space and research, testing and manufacturing laboratory space in various facilities in Novato and Brisbane, California, in Cambridge and Woburn, Massachusetts, and in certain foreign countries, under operating agreements expiring at various dates through 2028. Certain of the leases provide for options by the Company to extend the lease for multiple five-year renewal periods and also provide for annual minimum increases in rent, usually based on a consumer price index or annual minimum increases. None of these optional periods have been considered in the determination of the right-of-use asset or the lease liability for the leases as the Company did not consider it reasonably certain that it would exercise any such options. The Company recognizes lease expense on a straight-line basis over the non-cancelable term of its operating leases. The variable lease expense primarily consists of common area maintenance and other operating costs. The components of lease expense were as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2019 Operating lease expense $ 2,411 $ 6,741 Variable lease expense 630 1,951 Total lease expense $ 3,041 $ 8,692 Cash paid for amounts included in the measurement of lease liabilities for the three and nine months ended September 30, 2019 was $2.2 million and $6.5 million, respectively, and was included in net cash provided by operating activities in the Consolidated Statements of Cash Flows. Future minimum lease payments under non-cancellable leases as of September 30, 2019 were as follows (in thousands): Year Ending December 31, Leases 2019 (remaining) $ 2,520 2020 9,639 2021 7,561 2022 7,433 2023 7,541 Thereafter 13,153 Total future lease payments 47,847 Less: Amount representing interest (9,351 ) Present value of future lease payments 38,496 Less: Short-term lease liabilities (7,290 ) Long-term lease liabilities $ 31,206 Lease liabilities are based on the net present value of the remaining lease payments over the remaining lease term. As of September 30, 2019, the weighted-average remaining lease term was 5.81 years and the weighted-average discount rate used to determine the lease liability was 7.5%.

Gain from Sale of Priority Revi

Gain from Sale of Priority Review Voucher	9 Months Ended
	Sep. 30, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
Gain from Sale of Priority Review Voucher	12 . Gain from Sale of Priority Review Vouchers In January 2018, the Company completed the sale of a Rare Pediatric Disease Priority Review Voucher (PRV) it received in connection with the approval of Mepsevii for $130.0 million. In June 2018, the Company also completed the sale of the PRV it received in connection with the approval of Crysvita for $80.6 million, net, which was shared equally with KKC. As the PRVs did not have a carrying value, the gain recognized was equal to the net proceeds received. The Company recorded its portion of the net proceeds in other income of $40.3 million and $170.3 million for the three and nine months ended September

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries and have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) for interim financial information and in accordance with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. The unaudited interim consolidated financial statements have been prepared on the same basis as the annual financial statements. In the opinion of management, the accompanying unaudited condensed consolidated financial statements reflect all adjustments (consisting only of normal recurring adjustments) considered necessary for a fair presentation. These financial statements should be read in conjunction with the audited financial statements and notes thereto for the preceding fiscal year contained in the Company’s Annual Report on Form 10-K filed on February 19, 2019 with the United States Securities and Exchange Commission (SEC). The results of operations for the three and nine months ended September 30, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019. The condensed consolidated balance sheet as of December 31, 2018 has been derived from audited financial statements at that date, but does not include all of the information required by GAAP for complete financial statements.
Use of Estimates	Use of Estimates The accompanying consolidated financial statements have been prepared in accordance with GAAP. The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities and the reported amounts of expenses in the consolidated financial statements and the accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to clinical trial accruals, fair value of assets and liabilities, income taxes, and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates.
Cash, Cash Equivalents, and Restricted Cash	Cash, Cash Equivalents and Restricted Cash Restricted cash primarily consists of money market accounts as collateral for the Company’s obligations under its facility leases. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the consolidated statement of cash flows (in thousands): September 30, 2019 2018 Cash and cash equivalents $ 122,577 $ 82,956 Restricted cash included in prepaid expenses and other current assets 161 652 Restricted cash included in other assets 2,499 1,822 Total cash, cash equivalents, and restricted cash shown in the statements of cash flows $ 125,237 $ 85,430
Investment in Equity Securities	Investment in Equity Securities In June 2019, the Company entered into an amendment to the Research Collaboration and License Agreement and an Equity Purchase Agreement with Arcturus Therapeutics Holdings Inc. (“Arcturus”). Pursuant to the Equity Purchase Agreement, the Company purchased 2,400,000 shares of common stock, or approximately 18.2% of Arcturus’s outstanding shares of common stock as of the closing date of the transaction and received an option to purchase an additional 600,000 shares of common stock. The investment is subject to using the equity method of accounting as it was determined that the Company has significant influence over Arcturus, but does not control the significant activities of Arcturus. The Company elected to apply the fair value option to account for the equity investment in Arcturus. The decision to elect the fair value option is irrevocable and is determined on an instrument by instrument basis. The option to purchase additional stock was accounted for at fair value using the Black-Scholes option pricing method. The changes in fair value of the equity investment and option to purchase additional stock are included in the Condensed Consolidated Statements of Operations. See “Note 6. License and Research Agreements” for additional details on the Arcturus transaction.
Revenue Recognition	Revenue Recognition Collaboration and license revenue The Company has certain license and collaboration agreements that are within the scope of Accounting Standards Codification (ASC) 808, Collaborative Agreements provides guidance on the presentation and disclosure of collaborative arrangements. Generally, the classification of the transactions under the collaborative arrangements is determined based on the nature of contractual terms of the arrangement, along with the nature of the operations of the participants. The Company records its share of collaboration revenue, net of transfer pricing related to net sales in the period in which such sales occur, if the Company is considered as an agent in the arrangement. The Company is considered an agent when the collaboration partner controls the product before transfer to the customers and has the ability to direct the use of and obtain substantially all of the remaining benefits from the product. Funding received related to research and development services and commercialization costs is generally classified as a reduction of research and development expenses and selling, general and administrative expenses, respectively, in the consolidated statement of operations, because the provision of such services for collaborative partners are not considered to be part of the Company’s ongoing major or central operations. The also receives royalty revenues under certain of the Company’s license or collaboration agreements in exchange for license of intellectual property. If the Company does not have any future performance obligations for these license or collaboration agreements, royalty revenue is recorded as the underlying sales occur. In to record collaboration revenue, the Company utilizes certain information from its , including revenue from the sale of the product, associated reserves on revenue, and costs incurred for development and sales activities. For the periods covered in the financial statements presented, there have been no material changes to prior period estimates of revenues and expenses. The terms of the Company’s collaboration agreements may contain multiple performance obligations, which may include licenses and research and development activities. The Company evaluates these agreements under ASC 606, Revenue from Contracts with Customers (ASC 606), to determine the distinct performance obligations. The Company analogizes to ASC 606 for the accounting for distinct performance obligations for which there is a customer relationship. Prior to recognizing revenue, the Company makes estimates of the transaction price, including variable consideration that is subject to a constraint. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur and when the uncertainty associated with the variable consideration is subsequently resolved. Total consideration may include nonrefundable upfront license fees, payments for research and development activities, reimbursement of certain third-party costs, payments based upon the achievement of specified milestones, and royalty payments based on product sales derived from the collaboration. If there are multiple distinct performance obligations, the Company allocates the transaction price to each distinct performance obligation based on its relative standalone selling price. The standalone selling price is generally determined based on the prices charged to customers or using expected cost plus margin. The Company estimates the efforts needed to complete the performance obligation and recognizes revenue by measuring the progress towards complete satisfaction of the performance obligation using an input measure. Product sales The Company sells its approved products through a limited number of distributors. Under ASC 606, revenue from product sales is recognized at the point in time when the delivery is made and when title and risk of loss transfers to these distributors. The Company also recognizes revenue from sales of certain products on a “named patient” basis, which are allowed in certain countries prior to the commercial approval of the product. Prior to recognizing revenue, the Company makes estimates of the transaction price, including any variable consideration that is subject to a constraint. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur and when the uncertainty associated with the variable consideration is subsequently resolved. Product sales are recorded net of estimated government-mandated rebates and chargebacks, estimated product returns, and other deductions. Provisions for returns and other adjustments are provided for in the period the related revenue is recorded, as estimated by management.
Leases	Leases The Company adopted Accounting Standards Update (ASU) No. 2016-02, Leases (Topic 842) Leases (Topic 840) The Company determines if an arrangement includes a lease at inception. Right-of-use assets and lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at the commencement date. The right-of-use asset includes any lease payments made and excludes lease incentives. Incremental borrowing rate is used in determining the present value of future payments. The Company applies a portfolio approach to the property leases to apply an incremental borrowing rate to leases with similar lease terms. The lease terms may include options to extend or terminate the lease. The Company recognizes the options to extend the lease as part of the right-of-use assets and lease liabilities only if it is reasonably certain that the option would be exercised. Lease expense for minimum lease payments is recognized on a straight-line basis over the non-cancelable lease term. Prior period amounts have not been adjusted and continue to be reported in accordance with the Company’s historical accounting under previous lease guidance, Topic 840. As a result of the adoption of the new guidance, the Company recorded a right-of-use asset of $16.2 million, a short-term lease liability of $4.5 million, and a long-term lease liability of $17.0 million and no cumulative effect adjustment was made to the retained earnings as of the adoption date. In addition, as of the adoption date, the Company derecognized a net deferred rent obligation of $5.2 million. See Note 11 for further disclosure.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments — Credit Losses, (Topic 326): Measurement of Credit Losses on Financial Instruments,

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the consolidated statement of cash flows (in thousands): September 30, 2019 2018 Cash and cash equivalents $ 122,577 $ 82,956 Restricted cash included in prepaid expenses and other current assets 161 652 Restricted cash included in other assets 2,499 1,822 Total cash, cash equivalents, and restricted cash shown in the statements of cash flows $ 125,237 $ 85,430

Financial Instruments (Tables)

Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Summary of Financial Assets Measured on Recurring Basis	The following tables set forth the fair value of the Company’s financial assets remeasured on a recurring basis based on the three-tier fair value hierarchy (in thousands): September 30, 2019 Level 1 Level 2 Level 3 Total Money market funds $ 88,399 $ — $ — $ 88,399 Time deposits — 10,000 — 10,000 Corporate bonds — 34,343 — 34,343 Commercial paper — 96,997 — 96,997 Asset-backed securities — 32,947 — 32,947 U.S. Government Treasury and agency securities 121,365 118,829 — 240,194 Investment in Arcturus equity securities 24,648 — 1,685 26,333 Total $ 234,412 $ 293,116 $ 1,685 $ 529,213 December 31, 2018 Level 1 Level 2 Level 3 Total Money market funds $ 72,999 $ — $ — $ 72,999 Time deposits — 10,000 — 10,000 Corporate bonds — 179,926 — 179,926 Commercial paper — 50,198 — 50,198 Asset-backed securities — 22,587 — 22,587 U.S. Government Treasury and agency securities — 99,034 — 99,034 Total $ 72,999 $ 361,745 $ — $ 434,744

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2019
Investments Debt And Equity Securities [Abstract]
Summary of Cash Equivalents and Investments Classified as Available For Sale Securities	The fair values of cash equivalents and short-term investments classified as available-for-sale securities consisted of the following (in thousands): September 30, 2019 Gross Unrealized Amortized Cost Gains Losses Estimated Fair Value Money market funds $ 88,399 $ — $ — $ 88,399 Time deposits 10,000 — — 10,000 Corporate bonds 34,304 40 (1 ) 34,343 Commercial paper 96,997 — — 96,997 Asset-backed securities 32,894 53 — 32,947 U.S. Government Treasury and agency securities 239,949 245 — 240,194 Total $ 502,543 $ 338 $ (1 ) $ 502,880 December 31, 2018 Gross Unrealized Amortized Cost Gains Losses Estimated Fair Value Money market funds $ 72,999 $ — $ — $ 72,999 Time deposits 10,000 — — 10,000 Corporate bonds 180,167 — (241 ) 179,926 Commercial paper 50,198 — — 50,198 Asset-backed securities 22,597 — (10 ) 22,587 U.S. Government Treasury and agency securities 99,087 2 (55 ) 99,034 Total $ 435,048 $ 2 $ (306 ) $ 434,744
Summary of Inventory	Inventory consists of the following (in thousands): September 30, December 31, 2019 2018 Work-in-progress $ 10,753 $ 5,384 Finished goods 3,385 1,681 Total inventory $ 14,138 $ 7,065
Accrued Liabilities	Accrued liabilities consist of the following (in thousands): September 30, December 31, 2019 2018 Research, clinical study, and manufacturing expenses $ 17,972 $ 16,912 Payroll and related expenses 34,681 36,443 Other 16,904 9,095 Total accrued liabilities $ 69,557 $ 62,450

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2019
Revenue From Contract With Customer [Abstract]
Summary of Disaggregation of Total Revenues	The following table disaggregates total revenues from external customers by collaboration and license revenue and product sales (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Collaboration and license revenue: KKC (Crysvita) $ 21,484 $ 5,401 $ 54,617 $ 6,993 Bayer 101 3,614 453 21,903 Total collaboration and license revenue 21,585 9,015 55,070 28,896 Product sales: Crysvita 1,140 268 2,734 294 Mepsevii 2,361 2,127 8,274 5,253 UX007 714 353 2,043 791 Total product sales 4,215 2,748 13,051 6,338 Total revenues $ 25,800 $ 11,763 $ 68,121 $ 35,234 The following table disaggregates total revenues based on geographic location (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 United States $ 21,700 $ 9,879 $ 56,318 $ 31,731 Europe 2,790 1,616 8,522 3,209 All other 1,310 268 3,281 294 Total revenues $ 25,800 $ 11,763 $ 68,121 $ 35,234
Summary of Changes in Contract Assets (Liabilities)	The following table presents changes in the contract assets (liabilities) (in thousands): Nine Months Ended September 30, 2019 2018 Balance of contract assets (liabilities) at beginning of period $ 2,979 $ (5,986 ) Additions 452 22,491 Deductions (3,447 ) (14,767 ) Balance of contract assets (liabilities) at end of period $ (16 ) $ 1,738

License and Research Agreemen_2

License and Research Agreements (Tables)	9 Months Ended
	Sep. 30, 2019
Research Grant Agreement [Abstract]
Share of Collaboration Revenue Related to Crysvita	The Company’s Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Company's share of collaboration revenue in profit share territory $ 19,534 $ 4,364 $ 48,721 $ 5,429 Royalty revenue in European territory 1,950 1,037 5,896 1,564 Total $ 21,484 $ 5,401 $ 54,617 $ 6,993
Schedule of Cost Sharing Payments	Under the collaboration agreement, KKC and the Company share certain development and commercialization costs. Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Research and development $ 7,124 $ 7,612 $ 20,118 $ 25,268 Selling, general and administrative 5,633 2,868 16,009 10,718 Total $ 12,757 $ 10,480 $ 36,127 $ 35,986

Stock-Based Awards (Tables)

Stock-Based Awards (Tables)	9 Months Ended
	Sep. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock-Based Compensation Expense	The table below sets forth the stock-based compensation expense for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Cost of sales $ 319 $ — $ 404 $ — Research and development 10,629 11,858 33,891 34,749 Selling, general and administrative 8,959 8,809 28,040 24,278 Total stock-based compensation expense $ 19,907 $ 20,667 $ 62,335 $ 59,027

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Outstanding Shares of Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Share	The following weighted-average outstanding common stock equivalents were excluded from the computation of diluted net loss per share for the periods presented because including them would have been antidilutive: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Options to purchase common stock and restricted stock units 8,155,406 7,242,989 7,936,664 7,396,423 Employee stock purchase plan 33,094 31,285 18,547 17,533 Common stock warrants 149,700 149,700 149,700 149,700 8,338,200 7,423,974 8,104,911 7,563,656

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss (Tables)	9 Months Ended
	Sep. 30, 2019
Other Comprehensive Income Loss Net Of Tax Period Increase Decrease [Abstract]
Schedule of Total Accumulated Other Comprehensive Loss	Total accumulated other comprehensive loss consisted of the following (in thousands): September 30, December 31, 2019 2018 Foreign currency translation adjustments $ (408 ) $ (329 ) Unrealized gain (loss) on securities available-for-sale 337 (304 ) Total accumulated other comprehensive loss $ (71 ) $ (633 )

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Lessee Disclosure [Abstract]
Summary of Components of Lease Expense	The components of lease expense were as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2019 Operating lease expense $ 2,411 $ 6,741 Variable lease expense 630 1,951 Total lease expense $ 3,041 $ 8,692
Schedule of Future Minimum Lease Payments under Non-cancellable Leases	Future minimum lease payments under non-cancellable leases as of September 30, 2019 were as follows (in thousands): Year Ending December 31, Leases 2019 (remaining) $ 2,520 2020 9,639 2021 7,561 2022 7,433 2023 7,541 Thereafter 13,153 Total future lease payments 47,847 Less: Amount representing interest (9,351 ) Present value of future lease payments 38,496 Less: Short-term lease liabilities (7,290 ) Long-term lease liabilities $ 31,206

Organization - Additional Infor

Organization - Additional Information (Details)	9 Months Ended
	Sep. 30, 2019Segment
United States of America
Organization And Nature Of Business [Line Items]
Number of reportable segments	1

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Cash and cash equivalents	$ 122,577	$ 113,432	$ 82,956
Restricted cash included in prepaid expenses and other current assets	$ 161		$ 652
Restricted Cash and Cash Equivalents, Current, Asset, Statement of Financial Position [Extensible List]	us-gaap:PrepaidExpensesAndOtherCurrentAssetsMember		us-gaap:PrepaidExpensesAndOtherCurrentAssetsMember
Restricted cash included in other assets	$ 2,499		$ 1,822
Restricted Cash and Cash Equivalents, Noncurrent, Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherNoncurrentAssetsMember		us-gaap:OtherNoncurrentAssetsMember
Total cash, cash equivalents, and restricted cash shown in the statements of cash flows	$ 125,237	$ 115,525	$ 85,430	$ 103,041

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	1 Months Ended
	Jun. 30, 2019	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Common stock purchased		57,749,890		50,860,588
Right-to-use-asset		$ 31,711,000
Short-term lease liabilities		7,290,000
Long-term lease liability		$ 31,206,000
Accounting Standards Update 2016-02
Summary Of Significant Accounting Policies [Line Items]
Right-to-use-asset			$ 16,200,000
Short-term lease liabilities			4,500,000
Long-term lease liability			17,000,000
Adjustment to retained earnings			0
Deferred rent derecognized, net			$ 5,200,000
Arcturus Research Collaboration and License Agreement
Summary Of Significant Accounting Policies [Line Items]
Common stock purchased	2,400,000
Percentage of outstanding common shares	18.20%
Option to purchase additional common stock, shares	600,000

Financial Instruments - Summary

Financial Instruments - Summary of Financial Assets Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	$ 529,213
Total fair value	502,880	$ 434,744
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	234,412
Total fair value		72,999
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	293,116
Total fair value		361,745
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	1,685
Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	88,399
Total fair value	88,399	72,999
Money Market Funds | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	88,399
Total fair value		72,999
Asset-backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	32,947
Total fair value	32,947	22,587
Asset-backed Securities | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	32,947
Total fair value		22,587
Time Deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	10,000
Total fair value	10,000	10,000
Time Deposits | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	10,000
Total fair value		10,000
Corporate Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	34,343
Total fair value	34,343	179,926
Corporate Bonds | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	34,343
Total fair value		179,926
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	96,997
Total fair value	96,997	50,198
Commercial Paper | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	96,997
Total fair value		50,198
U.S. Government Treasury and Agency Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	240,194
Total fair value	240,194	99,034
U.S. Government Treasury and Agency Securities | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	121,365
U.S. Government Treasury and Agency Securities | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	118,829
Total fair value		$ 99,034
Investment in Arcturus Equity Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	26,333
Investment in Arcturus Equity Securities | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	24,648
Investment in Arcturus Equity Securities | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	$ 1,685

Financial Instruments - Additio

Financial Instruments - Additional Information (Details) - Arcturus Research Collaboration and License Agreement - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Schedule Of Available For Sale Securities [Line Items]
Change in fair value of common stock	$ 2	$ 10.8
Change in fair value of additional common stock	$ 0.2	$ 1.2

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Cash Equivalents and Investments Classified as Available For Sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 502,543	$ 435,048
Gross Unrealized Gains	338	2
Gross Unrealized Losses	(1)	(306)
Estimated Fair Value	502,880	434,744
Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	88,399	72,999
Estimated Fair Value	88,399	72,999
Asset-backed Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	32,894	22,597
Gross Unrealized Gains	53
Gross Unrealized Losses		(10)
Estimated Fair Value	32,947	22,587
Time Deposits
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	10,000	10,000
Estimated Fair Value	10,000	10,000
Corporate Bonds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	34,304	180,167
Gross Unrealized Gains	40
Gross Unrealized Losses	(1)	(241)
Estimated Fair Value	34,343	179,926
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	96,997	50,198
Estimated Fair Value	96,997	50,198
U.S. Government Treasury and Agency Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	239,949	99,087
Gross Unrealized Gains	245	2
Gross Unrealized Losses		(55)
Estimated Fair Value	$ 240,194	$ 99,034

Balance Sheet Components - Su_2

Balance Sheet Components - Summary of Inventory (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Work-in-progress	$ 10,753	$ 5,384
Finished goods	3,385	1,681
Total inventory	$ 14,138	$ 7,065

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Research, clinical study, and manufacturing expenses	$ 17,972	$ 16,912
Payroll and related expenses	34,681	36,443
Other	16,904	9,095
Total accrued liabilities	$ 69,557	$ 62,450

Revenue - Summary of Disaggrega

Revenue - Summary of Disaggregation of Total Revenues from External Customers (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Total revenues
Total revenues	$ 25,800	$ 11,763	$ 68,121	$ 35,234
Bayer HealthCare LLC
Total revenues
Total revenues	100	3,600	500	21,900
Collaboration and License
Total revenues
Total revenues	21,585	9,015	55,070	28,896
Collaboration and License | Kyowa Kirin Collaboration
Total revenues
Total revenues	21,484	5,401	54,617	6,993
Collaboration and License | Bayer HealthCare LLC
Total revenues
Total revenues	101	3,614	453	21,903
Product Sales
Total revenues
Total revenues	4,215	2,748	13,051	6,338
Product Sales | Crysvita
Total revenues
Total revenues	1,140	268	2,734	294
Product Sales | Mepsevii
Total revenues
Total revenues	2,361	2,127	8,274	5,253
Product Sales | UX007
Total revenues
Total revenues	$ 714	$ 353	$ 2,043	$ 791

Revenue - Summary of Disaggre_2

Revenue - Summary of Disaggregation of Total Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation Of Revenue [Line Items]
Total revenues	$ 25,800	$ 11,763	$ 68,121	$ 35,234
United States
Disaggregation Of Revenue [Line Items]
Total revenues	21,700	9,879	56,318	31,731
Europe
Disaggregation Of Revenue [Line Items]
Total revenues	2,790	1,616	8,522	3,209
All other
Disaggregation Of Revenue [Line Items]
Total revenues	$ 1,310	$ 268	$ 3,281	$ 294

Revenue - Summary of Changes in

Revenue - Summary of Changes in Contract Assets (Liabilities) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Disaggregation Of Revenue [Abstract]
Contract assets	$ 2,979
Contract liabilities		$ (5,986)
Additions	452	22,491
Deductions	(3,447)	(14,767)
Contract liabilities	$ (16)
Contract assets		$ 1,738

Revenue - Additional Informatio

Revenue - Additional Information (Details)	Sep. 30, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Abstract]
Percentage of gross accounts receivable balance	93.00%	88.00%

License and Research Agreemen_3

License and Research Agreements - Additional Information (Details)	Nov. 07, 2017USD ($)	Aug. 31, 2019USD ($)	Jun. 30, 2019USD ($)DiseaseTarget$ / sharesshares	Sep. 30, 2019USD ($)shares	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)Quartershares	Sep. 30, 2018USD ($)	Dec. 31, 2018USD ($)shares
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue				$ 25,800,000	$ 11,763,000	$ 68,121,000	$ 35,234,000
Research and development				100,144,000	70,041,000	274,294,000	222,380,000
Contract asset					1,738,000		1,738,000	$ 2,979,000
Prepaid expenses and other current assets				49,169,000		49,169,000		42,858,000
Accrued liabilities				$ 69,557,000		$ 69,557,000		$ 62,450,000
Common stock purchased | shares				57,749,890		57,749,890		50,860,588
Common stock investment value				$ 58,000		$ 58,000		$ 51,000
Fair value, investments				529,213,000		529,213,000
Dimension
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Business acquisition date	Nov. 7, 2017
Research and development				200,000	2,500,000	$ 200,000	11,300,000
Amortization completion year						2019
Dimension | Contract Asset
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Business combination recognized intangible assets	$ 13,500,000
Bayer HealthCare LLC
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue				100,000	3,600,000	$ 500,000	21,900,000
Contract liability	$ 2,500,000
Contract asset								3,000,000
Product Sales
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue				4,215,000	2,748,000	13,051,000	6,338,000
Kyowa Kirin Collaboration | License Agreement | Prepaid and Other Current Assets
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License agreement other receivables				15,900,000		15,900,000
Kyowa Kirin Collaboration | License Agreement | Product Sales
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue				1,100,000	300,000	2,700,000	300,000
Kyowa Kirin Collaboration | License Agreement | Profit Share Revenue
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License agreement accounts receivable				21,500,000		$ 21,500,000		11,200,000
Kyowa Kirin Collaboration | License Agreement | Commercial and Development Activity Reimbursements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License agreement other receivables								11,100,000
Kyowa Kirin Collaboration | Profit Share Territory | License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Remaining profit or loss share percentage on commercializing products						50.00%
Tiered double-digit revenue share percentage entitled to receive						20.00%
Kyowa Kirin Collaboration | European Territory | License Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of royalty on net sales receives						10.00%
Research, Develop and Commercialize Adeno Associated Virus Gene Therapy Products | Bayer HealthCare LLC
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments received						$ 15,000,000
Research, Develop and Commercialize Adeno Associated Virus Gene Therapy Products | Maximum | Bayer HealthCare LLC
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Future contingent milestone payments				232,000,000		232,000,000
Arcturus
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development			$ 6,000,000	700,000	$ 300,000	700,000	$ 1,200,000
Prepaid expenses and other current assets				0		0		500,000
Accrued liabilities				0		0		$ 400,000
Common stock purchased | shares			2,400,000
Common stock. per share | $ / shares			$ 10
Consideration paid			$ 30,000,000
Additional option to purchase common stock | shares			600,000
Additional option to purchase common stock value per share | $ / shares			$ 16
Number of shares restricted for sale | shares			2,400,000
Number of years restricted for selling common stock			2 years
Option exercising period			2 years
Percentage of outstanding common shares			18.20%
Common stock investment value			$ 13,900,000
Fair value of additional option to purchase common stock			500,000
Remaining consideration paid			$ 15,600,000
Change in fair value of common stock				2,000,000		10,800,000
Increase decrease in fair value of additional common stock				200,000		1,200,000
Fair value, investments				24,600,000		24,600,000
Option to purchase additional common stock, value				1,700,000		1,700,000
Arcturus | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of disease targets | DiseaseTarget			12
Program Agreement and Unitholder Option Agreement | GeneTx Biotherapeutics LLC
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development				$ 20,000,000		$ 20,000,000
Consideration paid		$ 125,000,000
Upfront payment for exclusive option to acquisition		20,000,000
Business acquisition option exercise period, description						This option may be exercised any time prior to 30 days following FDA acceptance of the IND for GTX-102 for an additional $50.0 million in payments.
Additional payment for exclusive option		50,000,000
Option extension Premium		$ 25,000,000
Exercise of option extension, right to acquire condition						In the event the Company exercises the option extension, the Company has a right to acquire GeneTx for a payment of $125.0 million, at any time, until the earlier of 30 months from the first dosing of a patient in a planned Phase 1/2 study (subject to extensions) or 90 days after results are available from that study.
Program Agreement and Unitholder Option Agreement | Maximum | GeneTx Biotherapeutics LLC
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Extension period available for right to acquisition | Quarter						4

License and Research Agreemen_4

License and Research Agreements - Share of Collaboration Revenue Related to Crysvita (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation Of Revenue [Line Items]
Collaboration and license revenue	$ 25,800	$ 11,763	$ 68,121	$ 35,234
Collaboration and License
Disaggregation Of Revenue [Line Items]
Collaboration and license revenue	21,585	9,015	55,070	28,896
Collaboration and License | Kyowa Kirin Collaboration
Disaggregation Of Revenue [Line Items]
Collaboration and license revenue	21,484	5,401	54,617	6,993
Collaboration and License | Kyowa Kirin Collaboration | Profit Share Territory
Disaggregation Of Revenue [Line Items]
Collaboration and license revenue	19,534	4,364	48,721	5,429
Collaboration and License | Kyowa Kirin Collaboration | Royalty Revenue in European Territory
Disaggregation Of Revenue [Line Items]
Collaboration and license revenue	$ 1,950	$ 1,037	$ 5,896	$ 1,564

License and Research Agreemen_5

License and Research Agreements - Schedule of Cost Sharing Payments (Details) - Kyowa Kirin Collaboration - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Cost Sharing Payments [Line Items]
Research and development	$ 7,124	$ 7,612	$ 20,118	$ 25,268
Selling, general and administrative	5,633	2,868	16,009	10,718
Total	$ 12,757	$ 10,480	$ 36,127	$ 35,986

Stock-Based Awards - Additional

Stock-Based Awards - Additional Information (Details)	9 Months Ended
	Sep. 30, 2019shares
2014 Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share reserved for future issuance	2,648,552
Automatic increases in shares available for grant effective date	Jan. 1, 2015
Shares available for grant, ending date	Jan. 1, 2024
2014 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share reserved for future issuance	2,740,058

Stock-Based Awards - Summary of

Stock-Based Awards - Summary of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 19,907	$ 20,667	$ 62,335	$ 59,027
Cost of sales
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	319		404
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	10,629	11,858	33,891	34,749
Selling, general and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 8,959	$ 8,809	$ 28,040	$ 24,278

Net Loss Per Share - Outstandin

Net Loss Per Share - Outstanding Shares of Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	8,338,200	7,423,974	8,104,911	7,563,656
Options to Purchase Common Stock and Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	8,155,406	7,242,989	7,936,664	7,396,423
Common Stock Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	149,700	149,700	149,700	149,700
Employee Stock Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	33,094	31,285	18,547	17,533

Equity Transactions - Additiona

Equity Transactions - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended
	Feb. 28, 2019	Jul. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Stockholders Equity [Line Items]
Net proceeds from sale of common stock					$ 330,415,000	$ 270,969,000
ATM Sales Agreement
Stockholders Equity [Line Items]
Option to sell common stock for cash		$ 150,000,000
Common stock shares sold			0	205,202	468,685	445,619
Net proceeds from sale of common stock			$ 0	$ 15,900,000	$ 24,800,000	$ 27,600,000
Underwritten Public Offering
Stockholders Equity [Line Items]
Common stock shares sold	5,833,333
Net proceeds from sale of common stock	$ 330,400,000
Shares purchased by underwriters	760,869
Public offering price	$ 60

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss - Schedule of Total Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income Loss Net Of Tax [Abstract]
Foreign currency translation adjustments	$ (408)	$ (329)
Unrealized gain (loss) on securities available-for-sale	337	(304)
Total accumulated other comprehensive loss	$ (71)	$ (633)

Leases - Additional Information

Leases - Additional Information (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019USD ($)	Sep. 30, 2019USD ($)
Lessee Disclosure [Abstract]
Operating lease extension details		multiple five-year renewal periods
Operating lease, existence of option to extend		true
Operating lease expiry term		2028
Cash paid for measurement of lease liabilities	$ 2.2	$ 6.5
Weighted average remaining lease term	5 years 9 months 21 days	5 years 9 months 21 days
Weighted average discount rate	7.50%	7.50%

Leases - Summary of Components

Leases - Summary of Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Lease Cost [Abstract]
Operating lease expense	$ 2,411	$ 6,741
Variable lease expense	630	1,951
Total lease expense	$ 3,041	$ 8,692

Leases - Summary of Future Mini

Leases - Summary of Future Minimum Lease Payments under Non-cancellable Leases (Details) $ in Thousands	Sep. 30, 2019USD ($)
Lessee Disclosure [Abstract]
2019 (remaining)	$ 2,520
2020	9,639
2021	7,561
2022	7,433
2023	7,541
Thereafter	13,153
Total future lease payments	47,847
Less: Amount representing interest	(9,351)
Present value of future lease payments	38,496
Less: Short-term lease liabilities	(7,290)
Long-term lease liability	$ 31,206

Gain from Sale of Priority Re_2

Gain from Sale of Priority Review Voucher - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended	9 Months Ended
	Jun. 30, 2018	Jan. 31, 2018	Sep. 30, 2018	Sep. 30, 2018
Finite Lived Intangible Assets [Line Items]
Sale of PRV				$ 170,322
Gain from sale of PRV			$ 40,300	$ 170,322
Mepsevii
Finite Lived Intangible Assets [Line Items]
Sale of PRV		$ 130,000
Crysvita
Finite Lived Intangible Assets [Line Items]
Sale of PRV	$ 80,600