Xencor (XNCR) 10-Q 6 Aug 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Aug. 01, 2019
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2019
Entity File Number	001-36182
Entity Registrant Name	Xencor Inc
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-1622502
Entity Address, Address Line One	111 West Lemon Avenue
Entity Address, City or Town	Monrovia
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	91016
City Area Code	626
Local Phone Number	305-5900
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	XNCR
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		56,620,260
Entity Central Index Key	0001326732
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 32,557	$ 26,246
Marketable securities	472,613	268,115
Accounts receivable	10,130	10,187
Income tax receivable	402	804
Prepaid expenses and other current assets	11,307	10,375
Total current assets	527,009	315,727
Property and equipment, net	12,128	11,813
Patents, licenses, and other intangible assets, net	13,522	11,969
Marketable securities - long term	120,966	236,108
Income tax receivable	402	804
Other assets	10,726	311
Total assets	684,753	576,732
Current liabilities
Accounts payable	8,994	3,797
Accrued expenses	6,226	9,662
Deferred rent		315
Lease liabilities	2,214
Deferred revenue	45,478	40,079
Income tax liability	800
Total current liabilities	63,712	53,853
Deferred rent, net of current portion		1,198
Lease liabilities, net of current portion	9,650
Deferred revenue, net of current portion	3,300
Total liabilities	76,662	55,051
Commitments and contingencies
Stockholders' equity
Preferred stock, $0.01 par value: 10,000,000 authorized shares; -0- issued and outstanding shares at June 30, 2019 and December 31, 2018
Common stock, $0.01 par value: 200,000,000 authorized shares at June 30, 2019 and December 31, 2018; 56,529,398 issued and outstanding at June 30, 2019 and 56,279,542 issued and outstanding at December 31, 2018	565	563
Additional paid-in capital	865,163	845,366
Accumulated other comprehensive income (loss)	1,629	(971)
Accumulated deficit	(259,266)	(323,277)
Total stockholders' equity	608,091	521,681
Total liabilities and stockholders' equity	$ 684,753	$ 576,732

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
Condensed Balance Sheets
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	56,529,398	56,279,542
Common stock, shares outstanding	56,529,398	56,279,542

Statements of Comprehensive Inc

Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue
Collaborations, licenses, milestones, and royalties	$ 19,485		$ 131,424
Operating expenses
Research and development	33,299	$ 23,332	61,481	$ 49,418
General and administrative	5,758	4,958	11,270	9,520
Total operating expenses	39,057	28,290	72,751	58,938
Income (loss) from operations	(19,572)	(28,290)	58,673	(58,938)
Other income (expense)
Interest income, net	3,615	2,483	6,501	3,637
Other expense	(27)	(62)	(212)	(60)
Total other income, net	3,588	2,421	6,289	3,577
Net income (loss) before income tax	(15,984)	(25,869)	64,962	(55,361)
Income tax expense	50		950
Net income (loss)	(16,034)	(25,869)	64,012	(55,361)
Other comprehensive income (loss)
Net unrealized gain (loss) on marketable securities	1,284	193	2,600	(200)
Comprehensive income (loss)	$ (14,750)	$ (25,676)	$ 66,612	$ (55,561)
Basic net income (loss) per common share	$ (0.28)	$ (0.46)	$ 1.14	$ (1.07)
Diluted net income (loss) per common share	$ (0.28)	$ (0.46)	$ 1.10	$ (1.07)
Basic weighted average common shares outstanding	56,399,255	55,678,990	56,351,377	51,738,348
Diluted weighted average common shares outstanding	56,399,255	55,678,990	58,042,819	51,738,348

Statement of Stockholders' Equi

Statement of Stockholders' Equity - USD ($) $ in Thousands	Scenario, Previously ReportedCommon Stock	Scenario, Previously ReportedAdditional Paid-in Capital	Scenario, Previously ReportedAccumulated Other Comprehensive Loss	Scenario, Previously ReportedAccumulated Deficit	Scenario, Previously Reported	Restatement AdjustmentAccumulated Deficit	Restatement Adjustment	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Total
Increase (Decrease) in Stockholders' Equity
Adoption of ASC 606						$ 34,418	$ 34,418
Balance, revised								$ 470	$ 570,670	$ (1,808)	$ (252,868)	$ 316,464
Balance at Dec. 31, 2017	$ 470	$ 570,670	$ (1,808)	$ (287,286)	$ 282,046
Balance (in shares) at Dec. 31, 2017	47,002,488							47,002,488
Increase (Decrease) in Stockholders' Equity
Sale of common stock, net of issuance cost								$ 84	245,421			245,505
Sale of common stock, net of issuance cost (in shares)								8,395,000
Issuance of common stock upon exercise of stock awards								$ 2	1,108			1,110
Issuance of common stock upon exercise of stock awards (in shares)								219,387
Comprehensive loss										(393)	(29,493)	(29,886)
Stock-based compensation expense									4,471			4,471
Balance at Mar. 31, 2018								$ 556	821,670	(2,201)	(282,361)	537,664
Balance (in shares) at Mar. 31, 2018								55,616,875
Balance at Dec. 31, 2017	$ 470	$ 570,670	$ (1,808)	$ (287,286)	$ 282,046
Balance (in shares) at Dec. 31, 2017	47,002,488							47,002,488
Increase (Decrease) in Stockholders' Equity
Comprehensive loss												(55,561)
Balance at Jun. 30, 2018								$ 558	828,858	(2,008)	(308,230)	519,178
Balance (in shares) at Jun. 30, 2018								55,821,310
Balance at Mar. 31, 2018								$ 556	821,670	(2,201)	(282,361)	537,664
Balance (in shares) at Mar. 31, 2018								55,616,875
Increase (Decrease) in Stockholders' Equity
Sale of common stock, net of issuance cost									(1)			(1)
Issuance of common stock upon exercise of stock awards								$ 2	1,803			1,805
Issuance of common stock upon exercise of stock awards (in shares)								177,883
Issuance of common stock under the Employee Stock Purchase Plan									504			504
Issuance of common stock under the Employee Stock Purchase Plan (in shares)								26,552
Comprehensive loss										193	(25,869)	(25,676)
Stock-based compensation expense									4,882			4,882
Balance at Jun. 30, 2018								$ 558	828,858	(2,008)	(308,230)	519,178
Balance (in shares) at Jun. 30, 2018								55,821,310
Balance at Dec. 31, 2018								$ 563	845,366	(971)	(323,277)	521,681
Balance (in shares) at Dec. 31, 2018								56,279,542
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock awards								$ 1	666			667
Issuance of common stock upon exercise of stock awards (in shares)								58,536
Issuance of restricted stock units (in shares)								11,311
Comprehensive loss										1,316	80,045	81,361
Stock-based compensation expense									5,856			5,856
Balance at Mar. 31, 2019								$ 564	851,888	345	(243,232)	609,565
Balance (in shares) at Mar. 31, 2019								56,349,389
Balance at Dec. 31, 2018								$ 563	845,366	(971)	(323,277)	521,681
Balance (in shares) at Dec. 31, 2018								56,279,542
Increase (Decrease) in Stockholders' Equity
Comprehensive loss												66,612
Balance at Jun. 30, 2019								$ 565	865,163	1,629	(259,266)	608,091
Balance (in shares) at Jun. 30, 2019								56,529,398
Balance at Mar. 31, 2019								$ 564	851,888	345	(243,232)	609,565
Balance (in shares) at Mar. 31, 2019								56,349,389
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock awards								$ 1	3,238			3,239
Issuance of common stock upon exercise of stock awards (in shares)								143,504
Issuance of common stock under the Employee Stock Purchase Plan									734			734
Issuance of common stock under the Employee Stock Purchase Plan (in shares)								36,505
Comprehensive loss										1,284	(16,034)	(14,750)
Stock-based compensation expense									9,303			9,303
Balance at Jun. 30, 2019								$ 565	$ 865,163	$ 1,629	$ (259,266)	$ 608,091
Balance (in shares) at Jun. 30, 2019								56,529,398

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities
Net income (loss)	$ 64,012	$ (55,361)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation and amortization	2,003	1,552
Amortization of premium and accretion of discount on marketable securities	(1,876)	406
Stock-based compensation	15,159	9,353
Abandonment of capitalized intangible assets	90	50
Loss on disposal of assets	5
Changes in operating assets and liabilities:
Accounts receivable	122	(140)
Interest receivable	(154)	(595)
Prepaid expenses and other assets	(932)	(6,468)
Accounts payable	5,197	(1,953)
Accrued expenses	(3,436)	443
Income taxes	1,604	(157)
Deferred rent	(1,513)	206
Lease liabilities and ROU assets	1,448
Deferred revenue	8,699
Net cash provided by (used in) operating activities	90,428	(52,664)
Cash flows from investing activities
Purchase of marketable securities	(244,499)	(285,809)
Purchase of intangible assets	(2,164)	(882)
Purchase of property and equipment	(1,867)	(3,416)
Proceeds from maturities of marketable securities	159,773	112,526
Repayment of loan		86
Net cash used in investing activities	(88,757)	(177,495)
Cash flows from financing activities
Proceeds from issuance of common stock upon exercise of stock awards	3,906	2,915
Proceeds from issuance of common stock under the Employee Stock Purchase Plan	734	504
Proceeds from issuance of common stock		260,245
Common stock issuance costs		(14,741)
Net cash provided by financing activities	4,640	248,923
Net increase in cash and cash equivalents	6,311	18,764
Cash and cash equivalents, beginning of period	26,246	16,528
Cash and cash equivalents, end of period	32,557	35,292
Cash paid during the period for:
Interest	7	6
Income taxes	150	170
Supplemental disclosures of non-cash investing activities
Unrealized gain (loss) on marketable securities, net of tax	$ 2,600	$ (200)

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	1. Summary of Significant Accounting Policies ​ Basis of Presentation ​ The accompanying unaudited interim financial statements for Xencor, Inc. (the Company, Xencor, we or us) have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) for interim financial information. Certain amounts in the prior period financial statements have been revised to conform to the presentation of the current period financial statements. See “Recent Accounting Pronouncements – Pronouncements Adopted in 2019.” The financial statements include all adjustments (consisting only of normal recurring adjustments) that the management of the Company believes are necessary for a fair presentation of the periods presented. The preparation of interim financial statements requires the use of management’s estimates and assumptions that affect reported amounts of assets and liabilities at the date of the interim financial statements and the reported revenues and expenditures during the reported periods. These interim financial results are not necessarily indicative of the results expected for the full fiscal year or for any subsequent interim period. ​ The accompanying unaudited interim financial statements and related notes should be read in conjunction with the audited financial statements and notes thereto included in the Company’s 2018 Annual Report on Form 10-K filed with the Securities and Exchange Commission (SEC) on February 26, 2019. ​ Use of Estimates ​ The preparation of interim financial statements in conformity with GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, other comprehensive gain (loss) and the related disclosures. On an ongoing basis, management evaluates its estimates, including estimates related to its accrued clinical trial and manufacturing development expenses, stock-based compensation expense, intangible assets and related amortization. Significant estimates in these interim financial statements include estimates made for accrued research and development expenses, stock-based compensation expenses, intangible assets and related amortization, estimated standalone selling price of performance obligations, and recoverability of deferred tax assets. ​ Intangible Assets ​ The Company maintains definite-lived intangible assets related to certain capitalized costs of acquired licenses and third-party costs incurred in establishing and maintaining its intellectual property rights to its platform technologies and development candidates. These assets are amortized over their useful lives, which are estimated to be the remaining patent life or the contractual term of the license. The straight-line method is used to record amortization expense. The Company assesses its intangible assets for impairment if indicators are present or changes in circumstances suggest that impairment may exist. There were no impairment charges recorded for the six months ended June 30, 2019 and 2018. ​ The Company capitalizes certain in-process intangible assets that are abandoned when they are no longer pursued or used in current research activities. There was no material abandonment of in-process intangible assets during the six months ended June 30, 2019 or 2018. ​ Marketable Securities ​ The Company has an investment policy that includes guidelines on acceptable investment securities, minimum credit quality, maturity parameters, and concentration and diversification. The Company invests its excess cash primarily in marketable debt securities issued by investment grade institutions. ​ The Company considers its marketable debt securities to be available-for-sale. These assets are carried at fair value and the unrealized gains and losses are included in accumulated other comprehensive income (loss). Accrued interest on marketable debt securities is included in marketable securities. If a decline in the value of a marketable debt security in the Company’s investment portfolio is deemed to be other-than-temporary, the Company writes down the security to its current fair value and recognizes a loss as a charge against income. The Company reviews its portfolio of marketable debt securities, using both quantitative and qualitative factors, to determine if declines in fair value below cost are other-than-temporary. ​ Recent Accounting Pronouncements ​ Pronouncements Adopted in 2019 ​ Effective January 1, 2019, the Company adopted Accounting Standards Codification Topic 842 (ASC 842), Leases ​ At inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances. For leases with a term of one year or longer where the Company is the lessee, ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent an obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. The interest rate implicit with such leases is typically not readily determined. The Company has determined the appropriate incremental borrowing rate by reference to an estimate of the current market borrowing rate for a collateralized asset over a similar term as the lease term. ​ The new standard impacts our reporting of the leases to our facilities in Monrovia and San Diego. Under ASC 842, tenant allowances under such operating leases are no longer tracked separately as a deferred rent liability; instead, it is integrated as part of the ROU asset. As a result, we recorded an adjustment of the cumulative effect to the beginning balance for deferred rent liability and adopted the use of ROU asset and lease liability. We recorded lease liabilities of $12.7 million and ROU assets of $11.4 million for lease agreements in effect as of January 1, 2019. The ROU asset is included in Other assets on the balance sheet as of June 30, 2019. This resulted in an increase to the beginning balance on both assets and liabilities after the adjustment of $11.2 million, with no impact on our retained earnings. ​ Effective January 1, 2019, the Company adopted ASU No. 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, which expands the scope of Topic 718 to include share-based payments issued to nonemployees for goods and services. The standard requires a modified retrospective transition approach, with a cumulative adjustment to retained earnings as of adoption date, for all liability-classified awards that have not been settled as of the adoption date and equity-classified nonemployee awards for which a measurement date has not been established. The adoption of this standard did not have any impact on the Company’s financial statements. ​

Fair Value of Financial Instrum

Fair Value of Financial Instruments	6 Months Ended
	Jun. 30, 2019
Fair Value of Financial Instruments
Fair Value of Financial Instruments	2. Fair Value of Financial Instruments ​ Financial instruments included in the financial statements include cash equivalents, marketable securities, accounts receivable, accounts payable and accrued expenses. Marketable securities and cash equivalents are carried at fair value. The fair value of the other financial instruments closely approximates their fair value due to their short-term maturities. ​ The Company accounts for recurring and non-recurring fair value measurements in accordance with FASB Accounting Standards Codification ASC 820, Fair Value Measurements and Disclosures ​ Level 1— ​ Level 2— ​ Level 3— ​ The Company measures the fair value of financial assets using the highest level of inputs that are reasonably available as of the measurement date. The assets recorded at fair value are classified within the hierarchy as follows for the periods reported (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2019 ​ December 31, 2018 ​ Total ​ ​ ​ ​ Total ​ ​ ​ ​ ​ ​ Fair Value ​ Level 1 ​ Level 2 ​ Fair Value ​ Level 1 ​ Level 2 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money Market Funds ​ $ 22,881 ​ $ 22,881 ​ $ — ​ $ 18,270 ​ $ 18,270 ​ $ — Corporate Securities ​ ​ 198,364 ​ ​ — ​ ​ 198,364 ​ ​ 104,967 ​ ​ — ​ ​ 104,967 Government Securities ​ ​ 395,215 ​ ​ — ​ ​ 395,215 ​ ​ 399,256 ​ ​ — ​ ​ 399,256 ​ ​ $ 616,460 ​ $ 22,881 ​ $ 593,579 ​ $ 522,493 ​ $ 18,270 ​ $ 504,223 ​ Our policy is to record transfers of assets between Level 1 and Level 2 at their fair values as of the end of each reporting period, consistent with the date of the determination of fair value. During the three and six months ended June 30, 2019 and 2018, there were no transfers between Level 1 and Level 2. The Company does not have any Level 3 assets or liabilities.

Net Income (Loss) Per Share

Net Income (Loss) Per Share	6 Months Ended
	Jun. 30, 2019
Net Income (Loss) Per Share
Net Income (Loss) Per Share	3. Net Income (Loss) Per Share ​ We compute basic net income (loss) per common share by dividing the net income (loss) attributable to common stockholders by the weighted-average number of common shares outstanding during the period without consideration of common stock equivalents. Diluted net income (loss) per share is computed by dividing the net income (loss) attributable to common stockholders by the weighted-average number of common stock equivalents outstanding for the period. The treasury stock method is used to determine the dilutive effect of the Company’s stock option grants, employee stock purchase plan (ESPP) and restricted stock units (RSUs). Potentially dilutive securities consisting of stock issuable under options, ESPP and RSUs are not included in the per common share calculation in periods where there is a net loss where the inclusion of such shares would have had an antidilutive effect. ​ Basic and diluted net income (loss) per common share is computed as follows (in thousands except share and per share data): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Six Months Ended ​ ​ June 30, ​ June 30, ​ 2019 2018 2019 2018 ​ ​ (in thousands, except share and per share data) Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income (loss) attributable to common stockholders ​ $ (16,034) ​ $ (25,869) ​ $ 64,012 ​ $ (55,361) Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding used in computing basic net income (loss) ​ 56,399,255 ​ 55,678,990 ​ 56,351,377 ​ 51,738,348 Weighted-average common shares outstanding used in computing diluted net income (loss) ​ ​ 56,399,255 ​ ​ 55,678,990 ​ ​ 58,042,819 ​ ​ 51,738,348 Basic net income (loss) per common share ​ $ (0.28) ​ $ (0.46) ​ $ 1.14 ​ $ (1.07) Diluted net income (loss) per common share ​ $ (0.28) ​ $ (0.46) ​ $ 1.10 ​ $ (1.07) ​ For the three months ended June 30, 2019 and the three and six months ended June 30, 2018, all outstanding potentially dilutive securities have been excluded from the calculation of diluted net loss per common share as the effect of including such securities would have been antidilutive. For the six months ended June 30, 2019, potentially dilutive securities were included in the diluted net income per common share calculation. ​ The number of common stock equivalents that were included in the calculation of the weighted-average common shares outstanding used in computing diluted net income per common share consists of 1,688,521 shares of stock options and RSU grants, and 2,921 shares of ESPP. ​ The table below summarizes the number of common stock equivalents that were excluded in the calculation of the weighted-average common shares outstanding used in computing diluted net income (loss) because the inclusion of such shares would have had an antidilutive effect as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Six Months Ended ​ ​ June 30, June 30, ​ 2019 2018 2019 2018 ​ ​ (in thousands) (in thousands) Options to purchase common stock and RSU grants 1,689 1,933 ​ — 1,774 ​

Comprehensive Income (Loss)

Comprehensive Income (Loss)	6 Months Ended
	Jun. 30, 2019
Comprehensive Income (Loss)
Comprehensive Income (Loss)	​ 4. Comprehensive Income (Loss) ​ Comprehensive income (loss) is comprised of net income (loss) and other comprehensive income (loss). For the three and six months ended June 30, 2019 and 2018, the only component of other comprehensive income (loss) is net unrealized gain (loss) on marketable securities. There were no material reclassifications out of accumulated other comprehensive income (loss) during the three and six months ended June 30, 2019 and 2018.

Marketable Securities

Marketable Securities	6 Months Ended
	Jun. 30, 2019
Marketable Securities
Marketable Securities	5. Marketable Securities ​ The Company’s marketable debt securities held as of June 30, 2019 and December 31, 2018 are summarized below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized Unrealized ​ Unrealized ​ June 30, 2019 ​ Cost ​ Gains ​ Losses ​ Fair Value (in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money Market Funds ​ $ 22,881 ​ $ — ​ $ — ​ $ 22,881 Corporate Securities ​ ​ 198,147 ​ ​ 219 ​ ​ (2) ​ ​ 198,364 Government Securities ​ ​ 393,793 ​ ​ 1,467 ​ ​ (45) ​ ​ 395,215 ​ ​ $ 614,821 ​ $ 1,686 ​ $ (47) ​ $ 616,460 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reported as ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 22,881 Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 593,579 Total investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 616,460 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized Unrealized ​ Unrealized ​ December 31, 2018 ​ Cost ​ Gains ​ Losses ​ Fair Value (in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money Market Funds ​ $ 18,270 ​ $ — ​ $ — ​ $ 18,270 Corporate Securities ​ ​ 105,311 ​ ​ 1 ​ ​ (345) ​ ​ 104,967 Government Securities ​ ​ 399,873 ​ ​ 187 ​ ​ (804) ​ ​ 399,256 ​ ​ $ 523,454 ​ $ 188 ​ $ (1,149) ​ $ 522,493 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reported as ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 18,270 Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 504,223 Total investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 522,493 ​ The maturities of the Company’s marketable debt securities are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortized Estimated June 30, 2019 ​ Cost ​ Fair Value (in thousands) ​ ​ ​ ​ ​ ​ Mature in one year or less ​ $ 471,958 ​ $ 472,613 Mature within two years ​ ​ 119,982 ​ ​ 120,966 ​ ​ $ 591,940 ​ $ 593,579 ​ ​ The unrealized losses on available-for-sale investments and their related fair values as of June 30, 2019 and December 31, 2018 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less than 12 months ​ 12 months or greater June 30, 2019 ​ ​ Fair value ​ ​ Unrealized losses ​ ​ Fair value ​ ​ Unrealized losses (in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate Securities ​ $ 9,828 ​ $ (2) ​ $ — ​ $ — Government Securities ​ ​ 42,398 ​ ​ (45) ​ ​ — ​ ​ — ​ ​ $ 52,226 ​ $ (47) ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less than 12 months ​ 12 months or greater December 31, 2018 ​ ​ Fair value ​ ​ Unrealized losses ​ ​ Fair value ​ ​ Unrealized losses (in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate Securities ​ $ 84,666 ​ $ (310) ​ $ 17,805 ​ $ (35) Government Securities ​ ​ 176,225 ​ ​ (672) ​ ​ 116,830 ​ ​ (132) ​ ​ $ 260,891 ​ $ (982) ​ $ 134,635 ​ $ (167) ​ The unrealized losses from the listed securities are due to a change in the interest rate environment and not a change in the credit quality of the securities. ​ The Company does not intend to sell these securities, and it is not more likely than not that the Company will be required to sell the securities before recovery of the amortized cost basis. Therefore, the Company did not consider these securities to be other-than-temporarily impaired as of June 30, 2019 or December 31, 2018.

Sale of Additional Common Stock

Sale of Additional Common Stock	6 Months Ended
	Jun. 30, 2019
Sale of Additional Common Stock
Sale of Additional Common Stock	6. Sale of Additional Common Stock ​ In March 2018, we completed the sale of 8,395,000 shares of common stock which included shares issued pursuant to our underwriters’ exercise of their over-allotment option pursuant to a follow-on financing. We received net proceeds of $245.5 million after underwriting discounts, commissions and offering expenses. ​ ​

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2019
Stock-Based Compensation
Stock-Based Compensation	7. Stock Based Compensation ​ Our Board of Directors and the requisite stockholders previously approved the 2010 Equity Incentive Plan (the 2010 Plan). In October 2013, our Board of Directors approved the 2013 Equity Incentive Plan (the 2013 Plan) and in November 2013 our stockholders approved the 2013 Plan which became effective as of December 3, 2013. As of December 2, 2013, we suspended the 2010 Plan and no additional awards may be granted under the 2010 Plan. Any shares of common stock covered by awards granted under the 2010 Plan that terminate after December 2, 2013 by expiration, forfeiture, cancellation or other means without the issuance of such shares will be added to the 2013 Plan reserve. ​ As of June 30, 2019, the total number of shares of common stock available for issuance under the 2013 Plan is 11,619,663, which includes 2,684,456 shares of common stock that were available for issuance under the 2010 Plan as of the effective date of the 2013 Plan. Unless otherwise determined by the Board, beginning January 1, 2014, and continuing until the expiration of the 2013 Plan, the total number of shares of common stock available for issuance under the 2013 Plan will automatically increase annually on January 1 of each year by 4% of the total number of issued and outstanding shares of common stock as of December 31 of the immediate preceding year. Pursuant to approval by our Board on January 1, 2019, the total number of shares of common stock available for issuance under the 2013 Plan was increased by 2,251,181 shares. As of June 30, 2019, a total of 8,449,870 options have been granted under the 2013 Plan. ​ In November 2013, our Board of Directors and stockholders approved the 2013 Employee Stock Purchase Plan (ESPP), which became effective as of December 5, 2013. We have reserved a total of 581,286 shares of common stock for issuance under the ESPP. Unless otherwise determined by our Board, beginning on January 1, 2014, and continuing until the expiration of the ESPP, the total number of shares of common stock available for issuance under the ESPP will automatically increase annually on January 1 by the lesser of (i) 1% of the total number of issued and outstanding shares of common stock as of December 31 of the immediately preceding year, or (ii) 621,814 shares of common stock. Pursuant to approval by our Board of Directors, there was no increase in the number of authorized shares in the ESPP in 2019. As of June 30, 2019, we have issued a total of 386,221 shares of common stock under the ESPP. ​ During the six months ended June 30, 2019, the Company awarded 36,966 Restricted Stock Units (RSUs) to certain employees. Vesting of these awards is in three equal annual installments and is contingent on continued service to the Company. The fair value of these awards is determined based on the intrinsic value of the stock on the date of grant and will be recognized as stock-based compensation expense over the requisite service period. As of June 30, 2019, we have granted a total of 70,899 shares of common stock pursuant to RSUs. ​ Total employee, director and non-employee stock-based compensation expense recognized for the three and six months ended June 30, 2019 and 2018 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Six Months Ended ​ ​ June 30, June 30, ​ 2019 2018 2019 2018 General and administrative ​ $ 2,008 ​ $ 1,688 ​ $ 3,862 ​ $ 3,305 Research and development ​ 7,295 ​ 3,194 ​ 11,297 ​ 6,048 ​ ​ $ 9,303 ​ $ 4,882 ​ $ 15,159 ​ $ 9,353 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ ​ 2019 2018 ​ 2019 2018 Stock options ​ $ 8,946 ​ $ 4,614 ​ $ 14,470 ​ $ 8,891 ESPP ​ ​ 195 ​ ​ 190 ​ ​ 413 ​ ​ 353 Restricted stock units ​ ​ 162 ​ ​ 78 ​ ​ 276 ​ ​ 109 ​ ​ $ 9,303 ​ $ 4,882 ​ $ 15,159 ​ $ 9,353 ​ The following table summarizes option activity under our stock plans and related information: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Weighted ​ ​ ​ ​ ​ ​ Average Average ​ ​ ​ ​ Number of ​ Exercise Remaining ​ Aggregate ​ ​ Shares subject ​ Price Contractual ​ Intrinsic ​ ​ to outstanding ​ (Per Term ​ Value ​ ​ options ​ Share) (in years) ​ (in thousands) Balances at December 31, 2018 5,966,928 ​ $ 19.71 ​ ​ 7.51 ​ ​ ​ Options granted 1,698,583 ​ $ 35.65 ​ ​ ​ ​ ​ ​ Options forfeited (178,434) ​ $ 29.39 ​ ​ ​ ​ ​ ​ Options exercised (202,040) ​ $ 19.33 ​ ​ ​ ​ ​ ​ Balances at June 30, 2019 7,285,037 ​ $ 23.20 ​ ​ 7.64 ​ $ 129,259 Exercisable ​ 3,724,348 ​ $ 16.65 ​ ​ 6.43 ​ $ 90,428 ​ We calculate the intrinsic value as the difference between the exercise price of the options and the closing price of common stock of $40.93 per share as of June 30, 2019. ​ Weighted average fair value of options granted during the six-month periods ended June 30, 2019 and 2018 were $20.74 and $16.86 per share, respectively. There were 1,553,400 options granted during the six-month period ended June 30, 2018. We estimated the fair value of each stock option using the Black-Scholes option-pricing model based on the date of grant of such stock option with the following weighted average assumptions for the three and six months ended June 30, 2019 and 2018: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options ​ Options ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ 2019 2018 2019 2018 Expected term (years) ​ 5.9 5.9 ​ 6.0 6.1 ​ Expected volatility ​ 61.3 % 72.9 % 61.3 % 73.1 % Risk-free interest rate ​ 2.07 % 2.77 % 2.43 % 2.53 % Expected dividend yield ​ — % — % — % — % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ESPP ​ ESPP ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ 2019 2018 2019 2018 Expected term (years) 0.5 - 2.0 0.5 - 2.0 ​ 0.5 - 2.0 0.5 - 2.0 ​ Expected volatility ​ 55.0 - 71.4 % 61.2 - 71.4 % 55.0 - 71.4 % 61.2 - 71.4 % Risk-free interest rate 1.47 - 2.70 % 1.47 - 2.41 % 1.47 - 2.70 % 1.47 - 2.41 % Expected dividend yield ​ — % — % — % — % ​ As of June 30, 2019, the unamortized compensation expense related to unvested stock options was $63.0 million. The remaining unamortized compensation expense will be recognized over the next 2.9 years. As of June 30, 2019, the unamortized compensation expense under our ESPP was $0.4 million. The remaining unamortized expense will be recognized over the next 0.4 years. ​ The following table summarizes the RSU activity for the six-month period ended June 30, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ Restricted ​ Average Grant ​ ​ Stock ​ Date Fair Value ​ ​ Units ​ (Per unit) ​ ​ ​ ​ ​ ​ Unvested at December 31, 2018 33,933 ​ $ 27.64 Granted 36,966 ​ ​ 35.60 Vested (11,311) ​ ​ 27.64 Forfeited (4,182) ​ ​ 31.12 Unvested at June 30, 2019 55,406 ​ $ 32.69 ​ As of June 30, 2019, the unamortized compensation expense related to unvested restricted stock units was $1.6 million. The remaining unamortized expense will be recognized over the next 2.4 years.

Leases

Leases	6 Months Ended
	Jun. 30, 2019
Leases
Leases	8. Leases ​ The Company leases office and laboratory space in Monrovia, CA under a lease that continues through June 2020, with an option to renew for an additional five years. The Company also leases office space in San Diego, CA through July 2020 which includes an option to renew for an additional five years. The Company assesses that it is unlikely to exercise the option to extend this lease. ​ The Company leases additional office space in San Diego, CA through August 2022, with an option to extend for an additional five years. The Company assesses that it is unlikely to exercise the option to extend the lease term. ​ Our lease agreements do not contain any residual value guarantees or restrictive covenants. As of June 30, 2019, the Company did not have additional operating leases that have not yet commenced. ​ The following table reconciles the undiscounted cash flows for the operating leases at June 30, 2019 to the operating lease liabilities recorded on the balance sheet (in thousands): ​ ​ ​ ​ ​ Years ending December 31, ​ ​ For the remainder of 2019 ​ $ 1,396 2020 ​ 2,723 2021 ​ ​ 2,608 2022 ​ ​ 2,220 2023 ​ ​ 1,351 2024 ​ ​ 1,371 Thereafter ​ ​ 2,282 Total undiscounted lease payments ​ ​ 13,951 Less: Imputed interest ​ ​ (2,087) Present value of lease payments ​ $ 11,864 ​ ​ ​ ​ Lease liabilities - short-term ​ $ 2,214 Lease liabilities - long-term ​ ​ 9,650 Total lease liabilities ​ $ 11,864 ​ Our operating lease cost and the cash payments for operating leases for the six months ended June 30, 2019 were $1.4 million and $1.2 million, respectively. Rent expense for the six months ended June 30, 2018 was $1.2 million. ​ At June 30, 2019, the weighted-average remaining lease term for operating leases was 5.8 years, and the weighted average discount rate for operating leases is 5.5%.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies
Commitments and Contingencies	9. Commitments and Contingencies ​ From time to time, the Company may be subject to various litigation and related matters arising in the ordinary course of business. The Company does not believe it is currently subject to any material matters where there is at least a reasonable possibility that a material loss may be incurred. ​ We are obligated to make future payments to third parties under in-license agreements, including sublicense fees, royalties, and payments that become due and payable on the achievement of certain development and commercialization milestones. As the amount and timing of sublicense fees and the achievement and timing of these milestones are not probable and estimable, such commitments have not been included on our balance sheet. We have also entered into agreements with third-party vendors which will require us to make future payments upon the delivery of goods and services in future periods.

Collaboration and Licensing Agr

Collaboration and Licensing Agreements	6 Months Ended
	Jun. 30, 2019
Collaboration and Licensing Agreements
Collaboration and Licensing Agreements	10. Collaboration and Licensing Agreements ​ The following is a summary description of the material revenue arrangements, including arrangements that generated revenue in the six months ended June 30, 2019 and 2018. ​ Genentech In February 2019, the Company entered into a collaboration and license agreement (the Genentech Agreement) with Genentech, Inc. and F. Hoffman-La Roche LTD (collectively, Genentech) for the development and commercialization of novel IL-15 collaboration products (Collaboration Products), including XmAb24306, the Company’s IL-15/IL-15Ra candidate. The Genentech Agreement became effective March 8, 2019. Under the terms of the Genentech Agreement, Genentech received an exclusive worldwide license to XmAb24306 and other Collaboration Products, including any new IL-15 programs identified during the joint research collaboration. Genentech and Xencor will jointly collaborate on worldwide development of XmAb24306 and other Collaboration Products with Genentech maintaining all worldwide commercialization rights, subject to Xencor having an option to co-promote in the United States. Xencor has the right to perform clinical studies of Collaboration Products in combination with other therapeutic agents at its own cost, subject to certain requirements. The term of the Genentech Agreement will continue on a program-by-program and country-by-country basis until there are no remaining payment obligations from Genentech to Xencor with respect to Collaboration Products. Genentech may terminate the Genentech Agreement in its entirety or on a Collaboration Product-by-Collaboration Product basis by providing prior written notice. Xencor may terminate the Agreement on a Collaboration Product-by-Collaboration Product basis if Genentech fails to spend a defined minimum amount on research, development, or commercialization activities for that Collaboration Product. In the event of a termination of any individual Collaboration Product or the Genentech Agreement in its entirety, the relevant rights revert to Xencor. The Company received a $120.0 million upfront payment and is eligible to receive up to an aggregate of $160.0 million in clinical milestone payments for each Collaboration Product that advances to Phase 3 clinical trials. The Company is also eligible to receive 45% share of net profits for sales of XmAb24306 and other Collaboration Products, while also sharing in net losses at the same percentage rate. The parties will jointly share in development and commercialization costs for all programs designated as a development program under the Genentech Agreement at the same percentage rate, while Genentech will bear launch costs entirely. The initial 45% profit-cost share percent is subject to ratchet down at the Company’s discretion and convertible to a royalty under certain circumstances. Pursuant to the Genentech Agreement, XmAb24306 is designated as a development program and all costs incurred for developing XmAb24306 from the effective date of the Genentech Agreement are being shared with Genentech under the initial cost-sharing percentage. Under the Genentech Agreement, the Company and Genentech will conduct joint research activities for a two-year period to identify and discover additional IL-15 candidates developed from the Company’s cytokine and bispecific technologies. The two-year research term may be extended an additional year if both parties agree. The Company and Genentech are each responsible for their own costs in conducting the research activities. The Company will receive a $20.0 million development milestone for each new Collaboration Product that is identified from the research efforts and advances into a Phase 1 clinical trial. The Company evaluated the Genentech Agreement under the provisions of ASU No. 2014-09, Revenue from Contracts with Customers Collaborative Arrangements The Company evaluated the Genentech Agreement under ASC 606 and identified the following performance obligations under the Agreement: (i) the license of XmAb24306 and (ii) research services during a two-year period to identify up to potentially nine additional IL-15 candidates, each a separate research program and a separate performance obligation. The Company determined that the license and each of the potential research programs are separate performance obligations because they are capable of being distinct and are distinct in the context of the Genentech Agreement. The license to XmAb24306 has standalone functionality as Genentech has exclusive worldwide rights to the program, including the right to sublicense to third parties. Genentech has significant experience and capabilities in developing and commercializing drug candidates similar to XmAb24306, and Genentech is capable of performing these activities without the Company’s involvement. Upon the transfer of the license of XmAb24306, Genentech could develop and commercialize XmAb24306 without further assistance from the Company. The Company determined that the research services for each potential additional IL-15 candidate and research program were separate standalone performance obligations. The Genentech Agreement provides an outline of an integrated research plan for the programs to be conducted by the two companies and the research activities are separate and distinct from the license to XmAb24306. The Company determined the standalone selling price of the license to be $114.4 million using the adjusted market assessment approach considering similar collaboration and license agreements and transactions. The standalone selling price for the research activities for all nine of the potential IL-15 programs to be performed during the research term was determined to be $8.5 million using the expected cost approach which was derived from the Company’s experience and information from providing similar research activities to other parties. The Company determined that the transaction price of the Genentech Agreement at inception was $120.0 million consisting of the upfront payment. The potential milestones are not included in the transaction price as these are contingent on future events and the Company would not recognize these in revenue until it is not probable that these would not result in significant reversal of revenue amounts in future periods. The Company will re-assess the transaction price at each reporting period and when event outcomes are resolved or changes in circumstances occur. The Company allocated the transaction price to each of the separate performance obligation using the relative standalone selling price with $111.7 million allocated to the license to XmAb24306 and $8.3 million allocated to the research services. The Company recognized the $111.7 million allocated to the license when it satisfied its performance obligation and transferred the license to Genentech in March 2019. The license was transferred upon the effective date of the Genentech Agreement and when the Company subsequently transferred certain data related to the program to Genentech. The $8.3 million allocated to the research activities is being recognized over a period of time through the end of the research term that services are rendered as we determine that the input method is the appropriate approach to recognize income for such services. $0.9 million of revenue related to the research activities was recognized in the six-month period ended June 30, 2019. For the three and six months ended June 30, 2019, we recognized $0.6 million and $112.5 million of income, respectively, from the Genentech Agreement. As of June 30, 2019, there is a $0.9 million receivable related to cost-sharing development activities for the XmAb24306 program. There is $7.5 million in deferred revenue as of June 30, 2019 which reflects our obligation to perform research services during the research term. Astellas Effective March 29, 2019, the Company entered into a Research and License Agreement (Astellas Agreement) with Astellas Pharma Inc. (Astellas) pursuant to which the Company and Astellas will conduct a discovery program to characterize compounds and products for development and commercialization. Under the Astellas Agreement, Astellas was granted a worldwide exclusive license, with the right to sublicense products in the field created by the research activities. Pursuant to the Astellas Agreement, the Company will apply its bispecific Fc technology to an antigen pair provided by Astellas to generate bispecific antibody candidates and will conduct limited testing and characterization of the bispecific candidates and return the candidates to Astellas for development and commercialization. The activities will be conducted under a research plan agreed to by both parties to the Astellas Agreement. Astellas will assume full responsibility for development and commercialization of the antibody candidate. Pursuant to the Astellas Agreement, the Company received an upfront payment of $15.0 million and is eligible to receive up to $240.0 million in milestones which include $32.5 million in development milestones, $57.5 million in regulatory milestones and $150.0 million in sales milestones. If commercialized, the Company is eligible to receive royalties on net sales that range from the high-single to low-double digit percentages. We evaluated the Astellas Agreement under ASC 606 and identified the performance obligations under the Agreement to be (i) delivery of bispecific antibodies to Astellas from the antigen provided by Astellas and (ii) research activities against the bispecific antibodies as outlined in the research plan. The Company determined that the license to the bispecific antibodies is not a separate performance obligation because it is not capable of being distinct, the license to the antibodies cannot be separated from the underlying antibodies. Astellas will control and benefit from the antibodies that are delivered. The Astellas Agreement provides Astellas the right to sublicense the antibody to third parties and Astellas has significant experience and capabilities in developing and commercializing clinical candidates and is capable of performing these activities from the delivered antibodies without the Company’s involvement. The Company determined the standalone selling price of the bispecific deliverable to be $17.1 million using the income approach by calculating a risk adjusted net present value of the potential revenue that could be earned from the arrangement. The standalone selling price for the research activities to be performed was determined to be $1.4 million using the expected cost approach which was derived from the Company’s experience and information from providing similar research activities to other customers. The Company determined that the transaction price of the Astellas Agreement at inception was $15.0 million consisting of the upfront payment. The potential milestones are not included in the transaction price as these are contingent on future events and the Company would not recognize these in revenue until it is not probable that these would not result in significant reversal of revenue amounts in future periods. The Company will re-assess the transaction price at each reporting period and when event outcomes are resolved or changes in circumstances occur. The Company allocated the transaction price to each of the separate performance obligations using the relative standalone selling price with $13.6 million allocated to delivery of the bispecific antibodies and $1.4 million allocated to the research activities. The Company recognized the $13.6 million allocated to the bispecific antibodies when it satisfied its performance obligation and transferred the antibodies to Astellas in June 2019. Astellas transferred the antigen to the Company and the Company applied its bispecific technologies to and transferred the completed antibodies to Astellas. The $1.4 million allocated to the research activities is being recognized as the research services are being completed over the period of time the Company expects to complete the activities under the research plan. For the three and six months ended June 30, 2019, we recognized $13.8 million related to the arrangement and there is $1.2 million in deferred revenue as of June 30, 2019 related to our obligation to complete research activities under the Agreement. Novartis In June 2016, the Company entered into a Collaboration and License Agreement (Novartis Agreement) with Novartis Institutes for BioMedical Research, Inc. (Novartis), to develop and commercialize bispecific and other Fc engineered antibody drug candidates using the Company’s proprietary XmAb technologies and drug candidates. Pursuant to the Novartis Agreement: ● The Company granted Novartis certain exclusive rights to research, develop and commercialize XmAb14045 and XmAb13676, two development stage products that incorporate the Company’s bispecific Fc technology; ● The Company will apply its bispecific technology in up to four target pair antibodies identified by Novartis (each a Global Discovery Program); and ● The Company will provide Novartis with a non-exclusive license to certain of its Fc technologies to apply against up to ten targets identified by Novartis. Under the Novartis Agreement, the Company and Novartis are co-developing XmAb14045 worldwide and sharing development costs. In December 2018, Novartis notified us that they were returning their rights to the XmAb13676 program. Pursuant to the terms of the Novartis Agreement, the rights to the XmAb13676 program reverted to us in June 2019 and Novartis’ obligation to fund its share of XmAb13676 development costs will continue through June 2020. We completed delivery of a Global Discovery Program in 2017 and delivery of a second Global Discovery Program in 2018. Under ASC 606, revenue is recognized at the time that the Company’s performance obligation for each Global Discovery is completed upon delivery of each discovery program to Novartis. During each of the three and six months ended June 30, 2019 and 2018, there was no revenue recognized. As of June 30, 2019 there is a receivable of $3.0 million related to cost-sharing of development activities for the XmAb14045 and XmAb13676 programs and $40.1 million in deferred revenue related to our obligation to deliver additional Global Discovery Programs to Novartis under the arrangement. Amgen Inc. In September 2015, the Company entered into a research and license agreement (the Amgen Agreement) with Amgen Inc. (Amgen) to develop and commercialize bispecific antibody product candidates using the Company’s proprietary XmAb bispecific Fc technology. Under the Amgen Agreement, the Company granted an exclusive license to Amgen to develop and commercialize bispecific drug candidates from the Company’s preclinical program that bind the CD38 antigen and the cytotoxic T-cell binding domain CD3 (the CD38 Program). The Company also agreed to apply its bispecific technology to five previously identified Amgen provided targets (each a Discovery Program). The Company received a $45.0 million upfront payment from Amgen and is eligible to receive up to $600.0 million in future development, regulatory and sales milestones in total for programs in development and is eligible to receive royalties on any global net sales of products. Pursuant to the Amgen Agreement, the Company applied its bispecific technology to five Discovery Programs antibody molecules provided by Amgen that bind Discovery Program targets and returned the bispecific product candidates to Amgen for further testing, development and commercialization. The initial research term was three years from the date of the Amgen Agreement, but Amgen, at its option, could request an extension of one year. In May 2018, Amgen elected to extend the term of the research term for one year. During the extended research term, the Company provided additional research activities to Amgen and received research funding for such activities. The extended research term expired in May 2019. Amgen assumed full responsibility for development and commercialization of product candidates under each of the Discovery Programs. During each of the three and six months ended June 30, 2019 and 2018, no revenue was recognized under this arrangement. As of June 30, 2019, there was no deferred revenue related to the arrangement. MorphoSys Ag In June 2010, the Company entered into a Collaboration and License Agreement with MorphoSys AG (MorphoSys) for a worldwide license to the Company’s patents and know-how to research, develop and commercialize our drug candidate XmAb5574 (subsequently renamed MOR208 and tafasitamab) with the right to sublicense under certain conditions. Under the agreement, the Company agreed to collaborate with MorphoSys to develop and commercialize tafasitamab. If certain developmental, regulatory and sales milestones are achieved, the Company is eligible to receive future milestone payments and royalties. In June 2017, MorphoSys initiated a Phase 3 clinical trial under the arrangement for which the Company received a milestone payment of $12.5 million. The Company recognized the payment as revenue in the period that the milestone event occurred. There were no revenues recognized under this arrangement for the three and six months ended June 30, 2019 and 2018. As of June 30, 2019, the Company has no deferred revenue related to this agreement. Alexion Pharmaceuticals, Inc. In January 2013, the Company entered into an option and license agreement with Alexion Pharmaceuticals, Inc. (Alexion). Under the terms of the agreement, the Company granted to Alexion an exclusive research license, with limited sublicensing rights, to make and use our Xtend technology to evaluate and advance compounds against six different target programs during a five-year research term under the agreement. Alexion exercised its option to take a commercial license for our technology against a target that was developed as ALXN1210 and is currently marketed as Ultomiris®. The Company is eligible to receive contractual milestones for certain regulatory and commercial achievements and is also entitled to receive royalties based on a percentage of net sales of Ultomiris sold by Alexion, its affiliates or its sub licensees, which percentage is in the low single digits. Alexion’s royalty obligations continue on a product-by-product and country-by-country basis until the expiration of the last-to-expire valid claim in a licensed patent covering the applicable product in such country. In the third quarter of 2018, Alexion completed certain regulatory submission filings for ALXN1210, and the Company received $9.0 million in milestone payments. In the fourth quarter of 2018, Alexion completed certain regulatory submission filings and received U.S. Food and Drug Administration (FDA) marketing approval, and the Company received $11.0 million in milestone payments. In the second quarter of 2019, Alexion received marketing authorization from Japan’s Ministry of Health, Labour and Welfare, and the Company earned a $4.0 million milestone. Under ASC 606, we recognize revenue for sales-based royalties upon the subsequent sale of the product. We began earning royalty revenue from the sale of Ultomiris in the United States in 2019. For the six months ended June 30, 2019, we have estimated royalty revenue of $1.1 million related to sales of Ultomiris. We recognized $4.0 million of milestone revenue and $1.1 million of royalty revenue under this arrangement for the three and six months ended June 30, 2019. There was no revenue recognized for the three and six months ended June 30, 2018. As of June 30, 2019, there is no deferred revenue related to this agreement. Boehringer Ingelheim International GmbH In 2007, the Company entered into a Research Licensee and Collaboration Agreement with Boehringer Ingelheim International GmbH (BI). Under the agreement, the Company provided BI with a three-year research license to one of the Company’s technologies and commercial options. BI elected to exercise two commercial licenses from the compounds identified during the research term and one compound is currently in clinical development. No revenue related to this arrangement was recognized for the three- and six-month periods ended June 30, 2019 and 2018. There is no deferred revenue related to this agreement at June 30, 2019. INmune Bio, Inc. In October 2017, the Company entered into a License Agreement with INmune Bio, Inc. (INmune). Under the terms of the agreement, the Company provided INmune with an exclusive license to certain rights to a proprietary protein, XPRO1595. Under the agreement the Company received an upfront payment of $100,000, an equity interest in INmune and an option to acquire additional shares of INmune. The Company is eligible to receive a percentage of sublicensing revenue received for XPRO1595 and also royalties in the mid-single digit percentages on the sale of approved products. The equity interest in INmune constituted of 1,585,000 shares of common stock and the option is to purchase up to an additional 10% of the fully diluted outstanding share of INmune for $10.0 million. We have recorded our equity interest in INmune at cost pursuant to ASC 323. We did not record our share of the net loss from INmune during the six months ended June 30, 2019 or 2018, respectively, as the carrying value has been reduced to zero. In 2018, INmune filed a registration statement on Form S-1 with the Securities and Exchange Commission (SEC) which was declared effective by the SEC as of December 19, 2018. The Company did not recognize any revenue related to the agreement for the three and six months ended June 30, 2019 and 2018. There is no deferred revenue as of June 30, 2019 related to this agreement. Revenue earned The revenues recorded for the three and six months ended June 30, 2019 were earned principally from the following licensees (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Six Months Ended ​ ​ June 30, June 30, ​ ​ 2019 ​ 2018 2019 ​ 2018 ​ ​ ​ ​ ​ ​ ​ ​ ​ Alexion $ 5.1 $ — ​ $ 5.1 $ — Astellas ​ ​ 13.8 ​ ​ — ​ ​ 13.8 ​ ​ — Genentech ​ ​ 0.6 ​ — ​ ​ 112.5 ​ — Total ​ $ 19.5 ​ $ — ​ $ 131.4 ​ $ — ​ The below table summarizes the disaggregation of revenue recorded for the three and six months ended June 30, 2019 (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Six Months Ended ​ ​ June 30, June 30, ​ ​ 2019 ​ 2018 2019 ​ 2018 ​ ​ ​ ​ ​ ​ ​ ​ ​ Research collaboration $ 14.4 $ — ​ $ 14.7 $ — Milestone ​ ​ 4.0 ​ — ​ ​ 4.0 ​ — Licensing ​ ​ — ​ — ​ ​ 111.6 ​ — Royalties ​ ​ 1.1 ​ ​ — ​ ​ 1.1 ​ ​ — Total ​ $ 19.5 ​ $ — ​ $ 131.4 ​ $ — ​ Remaining Performance Obligations and Deferred Revenue Our remaining performance obligations are delivery of Global Discovery Programs under the Novartis Agreement and the conduct of research activities pursuant to research plans under the Genentech and Astellas Agreements. As of June 30, 2019 and 2018, we have deferred revenue of $48.8 million and $60.1 million, respectively. As of June 30, 2019, $45.5 million was classified as current liabilities as our obligations to perform services are due on demand when requested by Novartis and Astellas under the Novartis Agreement and Astellas Agreements, respectively, and $3.3 million of the deferred revenue liability is classified as long-term for the portion of obligations to perform research services to Genentech after one year.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2019
Income Taxes
Income Taxes	11. Income taxes ​ The provision for income taxes of $0.1 and $0.9 million for the three and six months ended June 30, 2019 represents the interim period tax allocation of the state alternative minimum tax based on the Company’s projected year-end effective income tax rates which cannot be offset by the Company’s net operating loss carryforwards. The Company has a federal income tax receivable of $0.8 million at June 30, 2019 related to refundable alternative minimum tax credits. As of June 30, 2019, the Company’s deferred income tax assets, consisting primarily of net operating loss and tax credit carryforwards, have been fully offset by a valuation allowance. ​

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Polices)	6 Months Ended
	Jun. 30, 2019
Summary of Significant Accounting Policies
Basis of Presentation	​ Basis of Presentation ​ The accompanying unaudited interim financial statements for Xencor, Inc. (the Company, Xencor, we or us) have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) for interim financial information. Certain amounts in the prior period financial statements have been revised to conform to the presentation of the current period financial statements. See “Recent Accounting Pronouncements – Pronouncements Adopted in 2019.” The financial statements include all adjustments (consisting only of normal recurring adjustments) that the management of the Company believes are necessary for a fair presentation of the periods presented. The preparation of interim financial statements requires the use of management’s estimates and assumptions that affect reported amounts of assets and liabilities at the date of the interim financial statements and the reported revenues and expenditures during the reported periods. These interim financial results are not necessarily indicative of the results expected for the full fiscal year or for any subsequent interim period. ​ The accompanying unaudited interim financial statements and related notes should be read in conjunction with the audited financial statements and notes thereto included in the Company’s 2018 Annual Report on Form 10-K filed with the Securities and Exchange Commission (SEC) on February 26, 2019.
Use of Estimates	Use of Estimates ​ The preparation of interim financial statements in conformity with GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, other comprehensive gain (loss) and the related disclosures. On an ongoing basis, management evaluates its estimates, including estimates related to its accrued clinical trial and manufacturing development expenses, stock-based compensation expense, intangible assets and related amortization. Significant estimates in these interim financial statements include estimates made for accrued research and development expenses, stock-based compensation expenses, intangible assets and related amortization, estimated standalone selling price of performance obligations, and recoverability of deferred tax assets.
Intangible Assets	Intangible Assets ​ The Company maintains definite-lived intangible assets related to certain capitalized costs of acquired licenses and third-party costs incurred in establishing and maintaining its intellectual property rights to its platform technologies and development candidates. These assets are amortized over their useful lives, which are estimated to be the remaining patent life or the contractual term of the license. The straight-line method is used to record amortization expense. The Company assesses its intangible assets for impairment if indicators are present or changes in circumstances suggest that impairment may exist. There were no impairment charges recorded for the six months ended June 30, 2019 and 2018. ​ The Company capitalizes certain in-process intangible assets that are abandoned when they are no longer pursued or used in current research activities. There was no material abandonment of in-process intangible assets during the six months ended June 30, 2019 or 2018.
Marketable Securities	Marketable Securities ​ The Company has an investment policy that includes guidelines on acceptable investment securities, minimum credit quality, maturity parameters, and concentration and diversification. The Company invests its excess cash primarily in marketable debt securities issued by investment grade institutions. ​ The Company considers its marketable debt securities to be available-for-sale. These assets are carried at fair value and the unrealized gains and losses are included in accumulated other comprehensive income (loss). Accrued interest on marketable debt securities is included in marketable securities. If a decline in the value of a marketable debt security in the Company’s investment portfolio is deemed to be other-than-temporary, the Company writes down the security to its current fair value and recognizes a loss as a charge against income. The Company reviews its portfolio of marketable debt securities, using both quantitative and qualitative factors, to determine if declines in fair value below cost are other-than-temporary. ​
Recent Accounting Pronouncements	Recent Accounting Pronouncements ​ Pronouncements Adopted in 2019 ​ Effective January 1, 2019, the Company adopted Accounting Standards Codification Topic 842 (ASC 842), Leases ​ At inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances. For leases with a term of one year or longer where the Company is the lessee, ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent an obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. The interest rate implicit with such leases is typically not readily determined. The Company has determined the appropriate incremental borrowing rate by reference to an estimate of the current market borrowing rate for a collateralized asset over a similar term as the lease term. ​ The new standard impacts our reporting of the leases to our facilities in Monrovia and San Diego. Under ASC 842, tenant allowances under such operating leases are no longer tracked separately as a deferred rent liability; instead, it is integrated as part of the ROU asset. As a result, we recorded an adjustment of the cumulative effect to the beginning balance for deferred rent liability and adopted the use of ROU asset and lease liability. We recorded lease liabilities of $12.7 million and ROU assets of $11.4 million for lease agreements in effect as of January 1, 2019. The ROU asset is included in Other assets on the balance sheet as of June 30, 2019. This resulted in an increase to the beginning balance on both assets and liabilities after the adjustment of $11.2 million, with no impact on our retained earnings. ​ Effective January 1, 2019, the Company adopted ASU No. 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, which expands the scope of Topic 718 to include share-based payments issued to nonemployees for goods and services. The standard requires a modified retrospective transition approach, with a cumulative adjustment to retained earnings as of adoption date, for all liability-classified awards that have not been settled as of the adoption date and equity-classified nonemployee awards for which a measurement date has not been established. The adoption of this standard did not have any impact on the Company’s financial statements. ​

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2019
Fair Value of Financial Instruments
Schedule of assets recorded at fair value	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2019 ​ December 31, 2018 ​ Total ​ ​ ​ ​ Total ​ ​ ​ ​ ​ ​ Fair Value ​ Level 1 ​ Level 2 ​ Fair Value ​ Level 1 ​ Level 2 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money Market Funds ​ $ 22,881 ​ $ 22,881 ​ $ — ​ $ 18,270 ​ $ 18,270 ​ $ — Corporate Securities ​ ​ 198,364 ​ ​ — ​ ​ 198,364 ​ ​ 104,967 ​ ​ — ​ ​ 104,967 Government Securities ​ ​ 395,215 ​ ​ — ​ ​ 395,215 ​ ​ 399,256 ​ ​ — ​ ​ 399,256 ​ ​ $ 616,460 ​ $ 22,881 ​ $ 593,579 ​ $ 522,493 ​ $ 18,270 ​ $ 504,223

Net Income (Loss) Per Share (Ta

Net Income (Loss) Per Share (Tables)	6 Months Ended
	Jun. 30, 2019
Net Income (Loss) Per Share
Schedule of basic and diluted net income (loss) per common share	Basic and diluted net income (loss) per common share is computed as follows (in thousands except share and per share data): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Six Months Ended ​ ​ June 30, ​ June 30, ​ 2019 2018 2019 2018 ​ ​ (in thousands, except share and per share data) Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income (loss) attributable to common stockholders ​ $ (16,034) ​ $ (25,869) ​ $ 64,012 ​ $ (55,361) Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding used in computing basic net income (loss) ​ 56,399,255 ​ 55,678,990 ​ 56,351,377 ​ 51,738,348 Weighted-average common shares outstanding used in computing diluted net income (loss) ​ ​ 56,399,255 ​ ​ 55,678,990 ​ ​ 58,042,819 ​ ​ 51,738,348 Basic net income (loss) per common share ​ $ (0.28) ​ $ (0.46) ​ $ 1.14 ​ $ (1.07) Diluted net income (loss) per common share ​ $ (0.28) ​ $ (0.46) ​ $ 1.10 ​ $ (1.07)
Schedule of potentially dilutive securities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Six Months Ended ​ ​ June 30, June 30, ​ 2019 2018 2019 2018 ​ ​ (in thousands) (in thousands) Options to purchase common stock and RSU grants 1,689 1,933 ​ — 1,774 ​

Marketable Securities (Tables)

Marketable Securities (Tables)	6 Months Ended
	Jun. 30, 2019
Marketable Securities
Schedule of marketable securities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized Unrealized ​ Unrealized ​ June 30, 2019 ​ Cost ​ Gains ​ Losses ​ Fair Value (in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money Market Funds ​ $ 22,881 ​ $ — ​ $ — ​ $ 22,881 Corporate Securities ​ ​ 198,147 ​ ​ 219 ​ ​ (2) ​ ​ 198,364 Government Securities ​ ​ 393,793 ​ ​ 1,467 ​ ​ (45) ​ ​ 395,215 ​ ​ $ 614,821 ​ $ 1,686 ​ $ (47) ​ $ 616,460 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reported as ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 22,881 Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 593,579 Total investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 616,460 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ Amortized Unrealized ​ Unrealized ​ December 31, 2018 ​ Cost ​ Gains ​ Losses ​ Fair Value (in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money Market Funds ​ $ 18,270 ​ $ — ​ $ — ​ $ 18,270 Corporate Securities ​ ​ 105,311 ​ ​ 1 ​ ​ (345) ​ ​ 104,967 Government Securities ​ ​ 399,873 ​ ​ 187 ​ ​ (804) ​ ​ 399,256 ​ ​ $ 523,454 ​ $ 188 ​ $ (1,149) ​ $ 522,493 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Reported as ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 18,270 Marketable securities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 504,223 Total investments ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 522,493
Schedule of maturities of marketable securities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortized Estimated June 30, 2019 ​ Cost ​ Fair Value (in thousands) ​ ​ ​ ​ ​ ​ Mature in one year or less ​ $ 471,958 ​ $ 472,613 Mature within two years ​ ​ 119,982 ​ ​ 120,966 ​ ​ $ 591,940 ​ $ 593,579
Schedule of unrealized losses on available-for-sale investments	​ The unrealized losses on available-for-sale investments and their related fair values as of June 30, 2019 and December 31, 2018 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less than 12 months ​ 12 months or greater June 30, 2019 ​ ​ Fair value ​ ​ Unrealized losses ​ ​ Fair value ​ ​ Unrealized losses (in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate Securities ​ $ 9,828 ​ $ (2) ​ $ — ​ $ — Government Securities ​ ​ 42,398 ​ ​ (45) ​ ​ — ​ ​ — ​ ​ $ 52,226 ​ $ (47) ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less than 12 months ​ 12 months or greater December 31, 2018 ​ ​ Fair value ​ ​ Unrealized losses ​ ​ Fair value ​ ​ Unrealized losses (in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate Securities ​ $ 84,666 ​ $ (310) ​ $ 17,805 ​ $ (35) Government Securities ​ ​ 176,225 ​ ​ (672) ​ ​ 116,830 ​ ​ (132) ​ ​ $ 260,891 ​ $ (982) ​ $ 134,635 ​ $ (167)

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2019
Stock-Based Compensation
Schedule of total employee, director and non-employee stock-based compensation expense recognized	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Six Months Ended ​ ​ June 30, June 30, ​ 2019 2018 2019 2018 General and administrative ​ $ 2,008 ​ $ 1,688 ​ $ 3,862 ​ $ 3,305 Research and development ​ 7,295 ​ 3,194 ​ 11,297 ​ 6,048 ​ ​ $ 9,303 ​ $ 4,882 ​ $ 15,159 ​ $ 9,353 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ ​ 2019 2018 ​ 2019 2018 Stock options ​ $ 8,946 ​ $ 4,614 ​ $ 14,470 ​ $ 8,891 ESPP ​ ​ 195 ​ ​ 190 ​ ​ 413 ​ ​ 353 Restricted stock units ​ ​ 162 ​ ​ 78 ​ ​ 276 ​ ​ 109 ​ ​ $ 9,303 ​ $ 4,882 ​ $ 15,159 ​ $ 9,353
Summary of stock option activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted Weighted ​ ​ ​ ​ ​ ​ Average Average ​ ​ ​ ​ Number of ​ Exercise Remaining ​ Aggregate ​ ​ Shares subject ​ Price Contractual ​ Intrinsic ​ ​ to outstanding ​ (Per Term ​ Value ​ ​ options ​ Share) (in years) ​ (in thousands) Balances at December 31, 2018 5,966,928 ​ $ 19.71 ​ ​ 7.51 ​ ​ ​ Options granted 1,698,583 ​ $ 35.65 ​ ​ ​ ​ ​ ​ Options forfeited (178,434) ​ $ 29.39 ​ ​ ​ ​ ​ ​ Options exercised (202,040) ​ $ 19.33 ​ ​ ​ ​ ​ ​ Balances at June 30, 2019 7,285,037 ​ $ 23.20 ​ ​ 7.64 ​ $ 129,259 Exercisable ​ 3,724,348 ​ $ 16.65 ​ ​ 6.43 ​ $ 90,428
Schedule of weighted average assumptions used for estimation of fair value of stock options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options ​ Options ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ 2019 2018 2019 2018 Expected term (years) ​ 5.9 5.9 ​ 6.0 6.1 ​ Expected volatility ​ 61.3 % 72.9 % 61.3 % 73.1 % Risk-free interest rate ​ 2.07 % 2.77 % 2.43 % 2.53 % Expected dividend yield ​ — % — % — % — %
Schedule of weighted average assumptions used for estimation of fair value of ESPP	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ESPP ​ ESPP ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ 2019 2018 2019 2018 Expected term (years) 0.5 - 2.0 0.5 - 2.0 ​ 0.5 - 2.0 0.5 - 2.0 ​ Expected volatility ​ 55.0 - 71.4 % 61.2 - 71.4 % 55.0 - 71.4 % 61.2 - 71.4 % Risk-free interest rate 1.47 - 2.70 % 1.47 - 2.41 % 1.47 - 2.70 % 1.47 - 2.41 % Expected dividend yield ​ — % — % — % — %
Summary of restricted stock unity activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ Restricted ​ Average Grant ​ ​ Stock ​ Date Fair Value ​ ​ Units ​ (Per unit) ​ ​ ​ ​ ​ ​ Unvested at December 31, 2018 33,933 ​ $ 27.64 Granted 36,966 ​ ​ 35.60 Vested (11,311) ​ ​ 27.64 Forfeited (4,182) ​ ​ 31.12 Unvested at June 30, 2019 55,406 ​ $ 32.69

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2019
Leases
Schedule of operating lease liabilities maturities	The following table reconciles the undiscounted cash flows for the operating leases at June 30, 2019 to the operating lease liabilities recorded on the balance sheet (in thousands): ​ ​ ​ ​ ​ Years ending December 31, ​ ​ For the remainder of 2019 ​ $ 1,396 2020 ​ 2,723 2021 ​ ​ 2,608 2022 ​ ​ 2,220 2023 ​ ​ 1,351 2024 ​ ​ 1,371 Thereafter ​ ​ 2,282 Total undiscounted lease payments ​ ​ 13,951 Less: Imputed interest ​ ​ (2,087) Present value of lease payments ​ $ 11,864 ​ ​ ​ ​ Lease liabilities - short-term ​ $ 2,214 Lease liabilities - long-term ​ ​ 9,650 Total lease liabilities ​ $ 11,864

Collaboration and Licensing A_2

Collaboration and Licensing Agreements (Tables)	6 Months Ended
	Jun. 30, 2019
Collaboration and Licensing Agreements
Schedule of revenue by licensees	The revenues recorded for the three and six months ended June 30, 2019 were earned principally from the following licensees (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Six Months Ended ​ ​ June 30, June 30, ​ ​ 2019 ​ 2018 2019 ​ 2018 ​ ​ ​ ​ ​ ​ ​ ​ ​ Alexion $ 5.1 $ — ​ $ 5.1 $ — Astellas ​ ​ 13.8 ​ ​ — ​ ​ 13.8 ​ ​ — Genentech ​ ​ 0.6 ​ — ​ ​ 112.5 ​ — Total ​ $ 19.5 ​ $ — ​ $ 131.4 ​ $ —
Schedule of disaggregation of revenue	The below table summarizes the disaggregation of revenue recorded for the three and six months ended June 30, 2019 (in millions): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Six Months Ended ​ ​ June 30, June 30, ​ ​ 2019 ​ 2018 2019 ​ 2018 ​ ​ ​ ​ ​ ​ ​ ​ ​ Research collaboration $ 14.4 $ — ​ $ 14.7 $ — Milestone ​ ​ 4.0 ​ — ​ ​ 4.0 ​ — Licensing ​ ​ — ​ — ​ ​ 111.6 ​ — Royalties ​ ​ 1.1 ​ ​ — ​ ​ 1.1 ​ ​ — Total ​ $ 19.5 ​ $ — ​ $ 131.4 ​ $ —

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Intangibles (Details) - USD ($)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Summary of Significant Accounting Policies
Impairment of intangible assets	$ 0	$ 0

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details) - USD ($)	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Lease liability	$ 11,864,000
Increase in assets	684,753,000		$ 576,732,000
Increase in liabilities	76,662,000		55,051,000
Impact on retained earnings (accumulated deficit)	$ (259,266,000)		$ (323,277,000)
ASU 2016-02 | Restatement Adjustment
Right-of-Use Asset		$ 11,400,000
Lease liability		12,700,000
Increase in assets		11,200,000
Increase in liabilities		11,200,000
Impact on retained earnings (accumulated deficit)		$ 0

Fair Value of Financial Instr_3

Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Fair Value of Financial Instruments
Money Market Funds	$ 32,557	$ 26,246
Securities	593,579
Total Fair Value	616,460	522,493
Transfers from level 1 to level 2	0		$ 0
Transfers from level 2 to level 1	0		$ 0
Money Market Funds
Fair Value of Financial Instruments
Money Market Funds	22,881	18,270
Corporate Securities
Fair Value of Financial Instruments
Securities	198,364	104,967
Government Securities
Fair Value of Financial Instruments
Securities	395,215	399,256
Level 1
Fair Value of Financial Instruments
Total Fair Value	22,881	18,270
Level 1 | Money Market Funds
Fair Value of Financial Instruments
Money Market Funds	22,881	18,270
Level 2
Fair Value of Financial Instruments
Total Fair Value	593,579	504,223
Level 2 | Corporate Securities
Fair Value of Financial Instruments
Securities	198,364	104,967
Level 2 | Government Securities
Fair Value of Financial Instruments
Securities	$ 395,215	$ 399,256

Net Income (Loss) Per Share (De

Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net income (loss) attributable to common stockholders	$ (16,034)	$ (25,869)	$ 64,012	$ (55,361)
Denominator:
Weighted average common shares outstanding, basic	56,399,255	55,678,990	56,351,377	51,738,348
Weighted average common shares outstanding, diluted	56,399,255	55,678,990	58,042,819	51,738,348
Basic net income (loss) per common share	$ (0.28)	$ (0.46)	$ 1.14	$ (1.07)
Diluted net income (loss) per common share	$ (0.28)	$ (0.46)	$ 1.10	$ (1.07)
Common Stock | Stock options and RSU grants
Denominator:
Dilutive effect of stock options			1,688,521
Dilutive effect of employee stock options and ESPP			1,688,521
Common Stock | ESPP
Denominator:
Dilutive effect of stock options			2,921
Dilutive effect of employee stock options and ESPP			2,921

Net Income (Loss) Per Share - A

Net Income (Loss) Per Share - Anti-dilutive securities (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2018
Net Income (Loss) Per Share
Anti-dilutive securities (in shares)	1,689	1,933	1,774

Marketable Securities (Details)

Marketable Securities (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities
Cash and cash equivalents	$ 32,557	$ 26,246
Investments, amortized cost	614,821	523,454
Investments	616,460	522,493
Total amortized cost	591,940
Gross unrealized gains	1,686	188
Gross unrealized losses	(47)	(1,149)
Securities	593,579
Marketable securities
Schedule of Available-for-sale Securities
Securities	593,579	504,223
Money Market Funds
Schedule of Available-for-sale Securities
Cash and cash equivalents	22,881	18,270
Corporate Securities
Schedule of Available-for-sale Securities
Total amortized cost	198,147	105,311
Gross unrealized gains	219	1
Gross unrealized losses	(2)	(345)
Securities	198,364	104,967
Government Securities
Schedule of Available-for-sale Securities
Total amortized cost	393,793	399,873
Gross unrealized gains	1,467	187
Gross unrealized losses	(45)	(804)
Securities	395,215	399,256
Cash and Cash Equivalents
Schedule of Available-for-sale Securities
Cash and cash equivalents	$ 22,881	$ 18,270

Marketable Securities - Maturit

Marketable Securities - Maturities (Details) $ in Thousands	Jun. 30, 2019USD ($)
Amortized Cost
Maturing in one year or less	$ 471,958
Maturing within two years	119,982
Total amortized cost	591,940
Estimate Fair Value
Maturing in one year or less	472,613
Maturing within two years	120,966
Total estimated fair value	$ 593,579

Marketable Securities - Unreali

Marketable Securities - Unrealized losses (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair value
Fair value, less than 12 months	$ 52,226	$ 260,891
Fair value, 12 months or greater		134,635
Unrealized losses
Unrealized losses, Less than 12 months	(47)	(982)
Unrealized losses, 12 months or greater		(167)
Corporate Securities
Fair value
Fair value, less than 12 months	9,828	84,666
Fair value, 12 months or greater		17,805
Unrealized losses
Unrealized losses, Less than 12 months	(2)	(310)
Unrealized losses, 12 months or greater		(35)
Government Securities
Fair value
Fair value, less than 12 months	42,398	176,225
Fair value, 12 months or greater		116,830
Unrealized losses
Unrealized losses, Less than 12 months	$ (45)	(672)
Unrealized losses, 12 months or greater		$ (132)

Sale of Additional Common Sto_2

Sale of Additional Common Stock (Details) - Common Stock - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2018
Sale of common stock	8,395,000	8,395,000
Net proceeds	$ 245.5

Stock Based Compensation (Detai

Stock Based Compensation (Details)	Dec. 02, 2013shares	Jun. 30, 2019itemshares	Jun. 30, 2018shares	Dec. 31, 2018shares
Stock-based compensation
Common stock, shares issued		56,529,398		56,279,542
Employee stock options
Stock-based compensation
Options granted (in shares)		1,698,583	1,553,400
ESPP
Stock-based compensation
Total number of shares of common stock available for issuance		581,286
Awards issued under the plan (in shares)		386,221
Increase in shares of common stock available for issuance (in shares)		0
ESPP | Maximum
Stock-based compensation
Annual percentage increase in shares of common stock available for issuance		1.00%
Annual increase in shares of common stock available for issuance (in shares)		621,814
Restricted stock units
Stock-based compensation
Awards issued under the plan (in shares)		70,899
Annual installment vesting periods | item		3
The 2013 Plan
Stock-based compensation
Total number of shares of common stock available for issuance		11,619,663
Annual percentage increase in shares of common stock available for issuance		4.00%
Awards issued under the plan (in shares)		8,449,870
Increase in shares of common stock available for issuance (in shares)		2,251,181
The 2010 Plan
Stock-based compensation
Total number of shares of common stock available for issuance		2,684,456
Options granted (in shares)	0

Stock-Based Compensation - Empl

Stock-Based Compensation - Employee expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Stock-based compensation
Total employee, director and non-employee stock-based compensation expense	$ 9,303	$ 4,882	$ 15,159	$ 9,353
Employee stock options
Stock-based compensation
Total employee, director and non-employee stock-based compensation expense	8,946	4,614	14,470	8,891
ESPP
Stock-based compensation
Total employee, director and non-employee stock-based compensation expense	195	190	413	353
Restricted stock units
Stock-based compensation
Total employee, director and non-employee stock-based compensation expense	162	78	276	109
General and administrative
Stock-based compensation
Total employee, director and non-employee stock-based compensation expense	2,008	1,688	3,862	3,305
Research and development
Stock-based compensation
Total employee, director and non-employee stock-based compensation expense	$ 7,295	$ 3,194	$ 11,297	$ 6,048

Stock-Based Compensation - Opti

Stock-Based Compensation - Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 02, 2013	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Employee stock options
Number of Shares subject to outstanding options
Balance at the beginning of the period (in shares)		5,966,928
Options granted (in shares)		1,698,583	1,553,400
Options forfeited (in shares)		(178,434)
Options exercised (in shares)		(202,040)
Balance at the end of the period (in shares)		7,285,037		5,966,928
Exercisable options (in shares)		3,724,348
Weighted Average Exercise Price (Per Share)
Balance at the beginning of the period (in dollars per share)		$ 19.71
Options granted (in dollars per share)		35.65
Options forfeited (in dollars per share)		29.39
Options exercised (in dollars per share)		19.33
Balance at the end of the period (in dollars per share)		23.20		$ 19.71
Exercisable (in dollars per share)		$ 16.65
Weighted-average remaining contractual life		7 years 7 months 20 days		7 years 6 months 3 days
Weighted-average remaining contractual life of awards exercisable		6 years 5 months 4 days
Aggregate intrinsic value of options outstanding		$ 129,259
Aggregate intrinsic value of options exercisable		$ 90,428
Closing price of common stock (in dollars per share)		$ 40.93
Weighted average fair value of options granted (in dollars per share)		$ 20.74	$ 16.86
The 2010 Plan
Number of Shares subject to outstanding options
Options granted (in shares)	0

Stock-Based Compensation - FV o

Stock-Based Compensation - FV of employee stock options (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Employee stock options
Weighted average assumptions for estimated fair value of employee stock options
Expected volatility (as a percent)	61.30%	72.90%	61.30%	73.10%
Risk-free interest rate (as a percent)	2.07%	2.77%	2.43%	2.53%
Expected term (years)	5 years 10 months 24 days	5 years 10 months 24 days	6 years	6 years 1 month 6 days
Compensation expense
Unamortized compensation expense related to unvested options	$ 63		$ 63
Period to recognize unamortized compensation expense			2 years 10 months 24 days
ESPP
Weighted average assumptions for estimated fair value of employee stock options
Expected volatility, low end of range (as a percent)	55.00%	61.20%	55.00%	61.20%
Expected volatility, high end of range (as a percent)	71.40%	71.40%	71.40%	71.40%
Risk-free interest rate, low end of range (as a percent)	1.47%	1.47%	1.47%	1.47%
Risk-free interest rate, high end of range (as a percent)	2.70%	2.41%	2.70%	2.41%
Compensation expense
Unamortized compensation expense related to unvested options	$ 0.4		$ 0.4
Period to recognize unamortized compensation expense			4 months 24 days
ESPP | Minimum
Weighted average assumptions for estimated fair value of employee stock options
Expected term (years)	6 months	6 months	6 months	6 months
ESPP | Maximum
Weighted average assumptions for estimated fair value of employee stock options
Expected term (years)	2 years	2 years	2 years	2 years

Stock Based Compensation - Rest

Stock Based Compensation - Restricted stock units (Details) - Restricted stock units $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)$ / sharesshares
Stock-based compensation
Beginning balance | shares	33,933
Granted | shares	36,966
Vested | shares	(11,311)
Forfeited | shares	(4,182)
Ending balance | shares	55,406
Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 27.64
Weighted Average Grant Date Fair Value, Granted | $ / shares	35.60
Weighted Average Grant Date Fair Value, Vested | $ / shares	27.64
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	31.12
Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 32.69
Compensation expense
Unamortized compensation expense related to unvested restricted stock units | $	$ 1,600
Period to recognize unamortized compensation expense	2 years 4 months 24 days

Leases (Details)

Leases (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jul. 31, 2017
Lessee, Lease, Description [Line Items]
Option to extend	true
For the remainder of 2019	$ 1,396
2020	2,723
2021	2,608
2022	2,220
2023	1,351
2024	1,371
Thereafter	2,282
Total undiscounted lease payments	13,951
Less: Imputed interest	(2,087)
Present value of lease payments	$ 11,864
Monrovia, CA - office and laboratory space
Lessee, Lease, Description [Line Items]
Renewal term	5 years
Monrovia, CA - office and laboratory space with additional space
Lessee, Lease, Description [Line Items]
Renewal term		5 years
San Diego, CA - office space
Lessee, Lease, Description [Line Items]
Renewal term	5 years
San Diego, CA - second office space
Lessee, Lease, Description [Line Items]
Renewal term	5 years

Leases - Operating lease liabil

Leases - Operating lease liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Leases
Operating lease liability - ST	$ 2,214
Operating lease liability - LT	9,650
Operating lease liabilities	11,864
Operating lease cost	1,400
Cash paid for operating leases	$ 1,200
Net rent expense		$ 1,200
Remaining lease term	5 years 9 months 18 days
Discount rate	5.50%

Collaboration and Licensing A_3

Collaboration and Licensing Agreements (Details)	Mar. 29, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Feb. 28, 2019USD ($)companyitem	Oct. 31, 2017USD ($)shares	Jun. 30, 2017USD ($)	Jun. 30, 2016item	Sep. 30, 2015USD ($)item	Jan. 31, 2013item	Jun. 30, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)item	Jun. 30, 2018USD ($)	Dec. 31, 2007item
Collaboration research and licensing agreements
Revenue recorded										$ 19,485,000				$ 131,424,000
Deferred revenue		$ 48,800,000								48,800,000			$ 60,100,000	48,800,000	$ 60,100,000
Current portion of deferred revenue		45,478,000								45,478,000	$ 40,079,000			45,478,000
Deferred revenue, noncurrent portion		3,300,000								3,300,000				3,300,000
Licensing
Collaboration research and licensing agreements
Revenue recorded														111,600,000
Royalty
Collaboration research and licensing agreements
Revenue recorded										1,100,000				1,100,000
Milestone
Collaboration research and licensing agreements
Revenue recorded										4,000,000				4,000,000
Genentech
Collaboration research and licensing agreements
Revenue recorded										600,000				112,500,000
Astellas
Collaboration research and licensing agreements
Revenue recorded										13,800,000				13,800,000
Alexion Pharmaceuticals, Inc.
Collaboration research and licensing agreements
Revenue recorded										5,100,000				5,100,000
Collaboration and License Agreement | Genentech
Collaboration research and licensing agreements
Nonrefundable upfront payment				$ 120,000,000
Research license term				2 years
Revenue recognized										600,000				$ 112,500,000
Number of companies that conduct integrated research plan | company				2
Number of programs | item				9
Term of revenue recognized														1 year
Collaboration and License Agreement | Genentech | XmAb24306
Collaboration research and licensing agreements
Percentage of profits on net sales of the product				45.00%
Performance obligation				$ 111,700,000
Contract receivable		900,000								900,000				$ 900,000
Collaboration and License Agreement | Genentech | Research service
Collaboration research and licensing agreements
Revenue recognized														900,000
Performance obligation				8,300,000
Deferred revenue		7,500,000								7,500,000				7,500,000
Collaboration and License Agreement | Genentech | Licensing
Collaboration research and licensing agreements
Revenue recognized			$ 111,700,000
Collaboration and License Agreement | Genentech | Maximum
Collaboration research and licensing agreements
Potential milestone payment				160,000,000
Collaboration and License Agreement | Genentech | Market assessment approach | Licensing
Collaboration research and licensing agreements
Standalone selling price				114,400,000
Collaboration and License Agreement | Genentech | Cost approach | Research service
Collaboration research and licensing agreements
Standalone selling price				8,500,000
Collaboration and License Agreement | Genentech | Collaboration Products
Collaboration research and licensing agreements
Performance obligation		0								0				0
Collaboration and License Agreement | Novartis
Collaboration research and licensing agreements
Revenue recognized										0			0	0	0
Deferred revenue		40,100,000								40,100,000				40,100,000
Contract receivable		3,000,000								3,000,000				3,000,000
Collaboration and License Agreement | Novartis | Bispecific FC Technologies
Collaboration research and licensing agreements
Number of development stage products | item							2
Collaboration and License Agreement | Novartis | Bispecific FC Technologies | Maximum
Collaboration research and licensing agreements
Number of antibody targets for which bispecific technology applied | item							4
Collaboration and License Agreement | Novartis | FC Licenses | Maximum
Collaboration research and licensing agreements
Number of targets against which non-exclusive license is provided | item							10
Collaboration and License Agreement | MorphoSys
Collaboration research and licensing agreements
Revenue recognized										0			0	0	0
Deferred revenue		0								0				0
Milestone payment received						$ 12,500,000
Research and License Agreement | Astellas
Collaboration research and licensing agreements
Nonrefundable upfront payment	$ 15,000,000
Potential milestone payment	240,000,000
Revenue recognized										13,800,000				13,800,000
Deferred revenue		1,200,000								1,200,000				1,200,000
Research and License Agreement | Astellas | Bispecific
Collaboration research and licensing agreements
Revenue recognized		13,600,000
Performance obligation	13,600,000
Research and License Agreement | Astellas | Research service
Collaboration research and licensing agreements
Performance obligation	1,400,000
Research and License Agreement | Astellas | Income approach | Bispecific
Collaboration research and licensing agreements
Standalone selling price	17,100,000
Research and License Agreement | Astellas | Cost approach | Research service
Collaboration research and licensing agreements
Standalone selling price	1,400,000
Research and License Agreement | Amgen, Inc.
Collaboration research and licensing agreements
Nonrefundable upfront payment								$ 45,000,000
Potential milestone payment								$ 600,000,000
Revenue recognized										0			0	0	0
Deferred revenue		0								0				0
Research and License Agreement | Amgen, Inc. | Discovery Program
Collaboration research and licensing agreements
Research license term								3 years
Additional research term								1 year
Number of programs | item								5
Research Licensee and Collaboration Agreement | Boehringer Ingelheim International GmbH
Collaboration research and licensing agreements
Research license term																3 years
Revenue recognized										0			0	0	0
Deferred revenue		0								0				$ 0
Number of commercial options | item																1
Number of compounds | item														1
Number of commercial licenses | item														2
Option and license agreement | Alexion Pharmaceuticals, Inc.
Collaboration research and licensing agreements
Research license term									5 years
Revenue recognized										4,000,000			0		0
Deferred revenue		0								0				$ 0
Milestone payment received											$ 11,000,000	$ 9,000,000
Number of different target programs | item									6
Option and license agreement | Alexion Pharmaceuticals, Inc. | Royalty
Collaboration research and licensing agreements
Potential milestone payment		1,100,000								1,100,000				1,100,000
Revenue recognized										1,100,000				1,100,000
Option and license agreement | Alexion Pharmaceuticals, Inc. | Milestone
Collaboration research and licensing agreements
Revenue recognized										4,000,000				4,000,000
License Agreement | INmune
Collaboration research and licensing agreements
Nonrefundable upfront payment					$ 100,000
Revenue recognized										0			0	0	0
Deferred revenue		0								0				0
Additional equity interests (as a percentage)					10.00%
Equity issued in shares | shares					1,585,000
Equity issues, value					$ 10,000,000
Carrying value		$ 0								$ 0			$ 0	$ 0	$ 0
Development-based | Collaboration and License Agreement | Genentech
Collaboration research and licensing agreements
Potential milestone payment				$ 20,000,000
Development-based | Research and License Agreement | Astellas
Collaboration research and licensing agreements
Potential milestone payment	32,500,000
Regulatory-based | Research and License Agreement | Astellas
Collaboration research and licensing agreements
Potential milestone payment	57,500,000
Sales-based | Research and License Agreement | Astellas
Collaboration research and licensing agreements
Potential milestone payment	$ 150,000,000

Collaborative and Licensing Agr

Collaborative and Licensing Agreements - Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recorded	$ 19,485	$ 131,424
Deferred revenue	48,800	48,800		$ 60,100
Current portion of deferred revenue	45,478	45,478	$ 40,079
Deferred revenue, noncurrent portion	3,300	3,300
Research collaboration
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recorded	14,400	14,700
Milestone
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recorded	4,000	4,000
Licensing
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recorded		111,600
Royalty
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recorded	1,100	1,100
Alexion Pharmaceuticals, Inc.
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recorded	5,100	5,100
Astellas
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recorded	13,800	13,800
Genentech
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recorded	$ 600	$ 112,500
Collaboration and License Agreement | Genentech
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Term of revenue recognized		1 year

Income Taxes (Details)

Income Taxes (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019USD ($)	Jun. 30, 2019USD ($)
Reconciliation of federal statutory income tax to effective income tax
Income tax expense	$ 50	$ 950
Federal
Reconciliation of federal statutory income tax to effective income tax
Income tax receivable	$ 800	$ 800