Document and Entity Information	6 Months Ended
Document and Entity Information	Jun. 30, 2015	Jul. 24, 2015
Document and Entity Information
Entity Registrant Name	Xencor Inc
Entity Central Index Key	0001326732
Document Type	10-Q
Document Period End Date	Jun. 30, 2015
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		40,472,028
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q2

Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2015	Dec. 31, 2014
Current assets
Cash	$ 11,171	$ 54,649
Marketable securities	56,714
Accounts receivable	454	2,966
Interest receivable	670
Prepaid expenses and other current assets	711	134
Total current assets	69,720	57,749
Property and equipment
Computers, software and equipment	5,073	4,270
Furniture and fixtures	102	97
Leasehold improvements	3,204	3,086
Less accumulated depreciation and amortization	(6,575)	(6,554)
Property and equipment, net	1,804	899
Other assets
Patents, licenses, and other intangible assets, net	9,691	9,116
Marketable securities - long term	91,284
Other assets	64	59
Total other assets	101,039	9,175
Total assets	172,563	67,823
Current liabilities
Accounts payable	3,077	1,691
Accrued expenses	2,537	2,251
Current portion of deferred revenue	2,794	2,254
Total current liabilities	8,408	6,196
Deferred rent, less current portion	703
Deferred revenue, less current portion	1,384	2,337
Total liabilities	10,495	8,533
Commitments and contingencies
Stockholders' equity
Common stock, $0.01 par value: 200,000,000 authorized shares at June 30, 2015 and December 31, 2014; 40,460,091 issued and outstanding at June 30, 2015 and 31,434,272 issued and outstanding at December 31, 2014	405	314
Additional paid-in capital	421,058	302,969
Accumulated other comprehensive loss	(90)
Accumulated deficit	(259,305)	(243,993)
Total stockholders' equity	162,068	59,290
Total liabilities and stockholders' equity	$ 172,563	$ 67,823

Balance Sheets (Parenthetical) (USD $)	Jun. 30, 2015	Dec. 31, 2014
Condensed Balance Sheets
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	40,460,091	31,434,272
Common Stock, shares outstanding	40,460,091	31,434,272

Statements of Comprehensive Loss (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenue
Collaborations, licenses and milestones	$ 1,014	$ 824	$ 2,505	$ 3,008
Operating expenses
Research and development	7,476	4,283	12,681	8,511
General and administrative	2,524	1,594	5,288	3,317
Total operating expenses	10,000	5,877	17,969	11,828
Loss from operations	(8,986)	(5,053)	(15,464)	(8,820)
Other income (expenses)
Interest income	290	11	391	29
Interest expense	(4)	(3)	(8)	(5)
Other income (expenses)	(168)	1	(231)	1
Total other income (expense), net	118	9	152	25
Net loss	(8,868)	(5,044)	(15,312)	(8,795)
Other comprehensive loss
Net unrealized loss on marketable securities available-for-sale	(55)		(90)
Comprehensive loss	$ (8,923)	$ (5,044)	$ (15,402)	$ (8,795)
Basic and diluted net loss per common share (in dollars per share)	$ (0.22)	$ (0.16)	$ (0.41)	$ (0.28)
Weighted-average common shares outstanding used in computing basic and diluted net loss (in shares)	40,389,648	31,372,618	37,518,271	31,366,781

Statement of Stockholders’ Equity (USD $)	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Total
Balance at Dec. 31, 2014	$ 314,000
Balance (in shares) at Dec. 31, 2014	31,434,272
Increase (Decrease) in Stockholders' Equity
Sale of common stock, net of issuance cost of $7.7 million (in shares)	8,625,000
Balance at Mar. 31, 2015
Balance at Dec. 31, 2014	314,000	302,969,000		(243,993,000)	59,290,000
Balance (in shares) at Dec. 31, 2014	31,434,272
Increase (Decrease) in Stockholders' Equity
Sale of common stock, net of issuance cost of $7.7 million	86,000	115,118,000			115,204,000
Sale of common stock, net of issuance cost of $7.7 million (in shares)	8,625,000
Issuance of common stock upon exercise and vesting of stock awards	4,000	425,000			429,000
Issuance of common stock upon exercise and vesting of stock awards (in shares)	352,831
Issuance of common stock under the employee stock purchase plan	47,988
Issuance of common stock under the employee stock purchase plan (in shares)	1,000	246,000			247,000
Comprehensive loss			(90,000)	(15,312,000)	(15,402,000)
Stock-based compensation expense		2,300,000			2,300,000
Balance at Jun. 30, 2015	$ 405,000	$ 421,058,000	$ (90,000)	$ (259,305,000)	$ 162,068,000
Balance (in shares) at Jun. 30, 2015	40,460,091

Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash flows from operating activities
Net loss	$ (15,312)	$ (8,795)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	494	486
Amortization of premium on marketable securities	240
Stock-based compensation	2,300	639
Abandonment of capitalized intangible assets	54	131
Gain on disposal of assets	(9)	(1)
Changes in operating assets and liabilities:
Accounts receivable	2,513	(1)
Interest receivable	(670)
Prepaid expenses and other current assets	(534)	(300)
Other assets	(4)
Accounts payable	1,387	(1,259)
Accrued expenses	328	(62)
Deferred rent	617
Deferred revenue	(413)	(1,605)
Net cash used in operating activities	(9,009)	(10,767)
Cash flows from investing activities
Purchase of marketable securities	(148,328)
Purchase of intangible assets	(915)	(788)
Purchase of property and equipment	(1,115)	(336)
Proceeds from sale of property and equipment	9	1
Net cash used in investing activities	(150,349)	(1,123)
Cash flows from financing activities
Proceeds from issuance of common stock	122,906	137
Proceeds from issuance of common stock upon exercise of stock awards	429
Proceeds from issuance of common stock under the Employee Stock Purchase Plan	247
Common stock issuance cost	(7,702)
Payments on capital lease obligations		(4)
Net cash provided by financing activities	115,880	133
Net increase (decrease) in cash and cash equivalents	(43,478)	(11,757)
Cash and cash equivalents, beginning of period	54,649	77,975
Cash and cash equivalents, end of period	11,171	66,218
Supplemental disclosures of non-cash investing and financing activities
Net unrealized loss on marketable securities available for sale	$ 90

Summary of Significant Accounting Policies	6 Months Ended
Summary of Significant Accounting Policies	Jun. 30, 2015
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) have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information. 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. 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 2014 Annual Report on Form 10-K filed with the Securities and Exchange Commission (SEC) on February 23, 2015, as amended. 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 securities issued by investment grade institutions. The Company considers its marketable securities to be “available-for-sale”, as defined by authoritative guidance issued by the Financial Accounting Standards Board (“FASB”). These assets are carried at fair value and the unrealized gains and losses are included in accumulated other comprehensive income (loss). If a decline in the value of a marketable security in the Company’s investment portfolio is deemed to be other-than-temporary, the Company writes down the security to its current fair value and recognizes a loss as a charge against income. The Company reviews its portfolio of marketable securities, using both quantitative and qualitative factors, to determine if declines in fair value below cost are other-than-temporary. There have been no other material changes to the significant accounting policies previously disclosed in the Company’s 2014 Annual Report on Form 10-K, as amended. Sale of Additional Common Stock In March 2015, we completed the sale of 8,625,000 shares of common stock which included shares we issued pursuant to our underwriters’ exercise of their over-allotment option pursuant to a follow-on offering. We received net proceeds of $115.2 million, after underwriting discounts, commissions and estimated offering expenses. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers, which establishes principles for reporting revenue and cash flows arising from an entity’s contracts with customers. This new revenue recognition standard will replace most of the recognition guidance within the United States GAAP. In July 2015, the FASB announced that the new pronouncement will be effective for reporting periods beginning after December 15, 2017. The new pronouncement permits the use of either the retroactive or cumulative effect transition method. Early adoption is not permitted. The Company is evaluating the effect that ASU 2014-09 will have on its financial statements and related disclosures.

Fair Value of Financial Instruments

6 Months Ended

Jun. 30, 2015

Fair Value of Financial Instruments

Fair Value of Financial Instruments

2. Fair Value of Financial Instruments

The fair values of the financial instruments included in the financial statements, which include cash equivalents, money markets, US government and corporate securities approximate their carrying values at June 30, 2015 due to their short term maturities. Our financial instruments also include accounts receivable, accounts payable and accrued expenses. Marketable securities and cash equivalents are carried at fair value.

The Company accounts for recurring and non-recurring fair value measurements in accordance with FASB Accounting Standards Codification (ASC) 820, Fair Value Measurements and Disclosures (ASC 820). ASC 820 defines fair value, establishes a fair value hierarchy for assets and liabilities measured at fair value, and requires expanded disclosure about fair value measurements. The ASC 820 hierarchy ranks the quality of reliable inputs, or assumptions, used in the determination of fair value and requires assets and liabilities carried at fair value to be classified and disclosed in one of the following three categories:

Level 1—Fair Value is determined by using unadjusted quoted prices that are available in active markets for identical assets or liabilities.

Level 2—Fair Value is determined by using inputs other than Level 1 quoted prices that are directly or indirectly observable. Inputs can include quoted prices for similar assets or liabilities in active markets or quoted prices for identical assets or liabilities in markets that are not active. Related inputs can also include those used in valuation or other pricing models, such as interest rates and yield curves that can be corroborated by observable market data.

Level 3—Fair value is determined by inputs that are unobservable and not corroborated by market data. Use of these inputs involves significant and subjective judgments to be made by the reporting entity –e.g. determining an appropriate discount factor for illiquidity associated with a given security.

The Company measures the fair value of financial assets using the highest level of inputs that are reasonably available as of the measurement date. The assets recorded at fair value are classified within the hierarchy as follows for the periods reported (in thousands):


	June 30, 2015
	Total
	Fair Value		Level 1		Level 2

Money Market Funds	$	1,379	$	1,379	$	—
Corporate Securities		89,766		—		89,766
Government Securities		58,232		—		58,232
	$	149,377	$	1,379	$	147,998

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 months and six months ended June 30, 2015, there were no transfers between Level 1 and Level 2. The Company does not have any Level 3 assets or liabilities.

Net Loss Per Share

6 Months Ended

Jun. 30, 2015

Net Loss Per Share

Net Loss Per Share

3. Net Loss Per Share

We compute net loss per common share by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period. Potentially dilutive securities consisting of stock issuable under options and our 2013 Employee Stock Purchase Plan (ESPP) are not included in the diluted net loss per common share calculation where the inclusion of such shares would have had an antidilutive effect.

Basic and diluted (loss) per common share is computed as follows (in thousands except per share data)


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2015		2014		2015		2014
	(in thousands, except
	per share data)
Basic and diluted numerator:
Net loss attributable to common stockholders	$	(8,868)	$	(5,044)	$	(15,312)	$	(8,795)
Denominator:
Weighted-average common shares outstanding used in computing basic and diluted net loss		40,389,648		31,372,618		37,518,271		31,366,781
Basic and diluted net loss per common share	$	(0.22)	$	(0.16)	$	(0.41)	$	(0.28)

The following shares of 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.


	Three Months Ended		Six Months Ended
	June 30,		June 30,
	2015	2014	2015	2014
	(in thousands)		(in thousands)
Employee stock purchase plan shares	29	29	29	29
Options to purchase common stock	3,384	2,594	3,384	2,594
	3,413	2,623	3,413	2,623

In March 2015, the Company issued 8,625,000 shares of common stock in a follow-on stock offering. The issuance of these shares resulted in a significant increase in the Company’s weighted average shares outstanding for the three months and six months ended June 30, 2015 when compared to the comparable prior year period and is expected to continue to impact the year-over-year comparability of the Company’s income (loss) per share calculations for the remainder of 2015.

Marketable Securities

6 Months Ended

Jun. 30, 2015

Marketable Securities

Marketable Securities

5. Marketable Securities

The Company’s marketable securities held as of June 30, 2015 are summarized below:


			Gross		Gross
	Amortized		Unrealized		Unrealized
	Cost		Gains		Losses		Fair Value
(in thousands)
Money Market Funds	$	1,379	$	—	$	—	$	1,379
Corporate Securities		89,839		16		(89)		89,766
Government Securities		58,249		10		(27)		58,232
	$	149,467	$	26	$	(116)	$	149,377

Reported as
Cash and cash equivalents							$	1,379
Marketable securities								147,998
Total investments							$	149,377

The maturities of the Company’s marketable securities are as follows:


	Amortized		Estimated
	Cost		Fair Value
(in thousands)
Mature in one year or less	$	56,745	$	56,714
Mature after one year through five years		91,342		91,284
	$	148,087	$	147,998

Stock-Based Compensation

6 Months Ended

Jun. 30, 2015

Stock-Based Compensation

Stock-Based Compensation

6. Stock Based Compensation

Our Board of Directors and the requisite stockholders previously approved the Amended and Restated 2000 Stock Incentive Plan (the 2000 Plan), and the 2010 Equity Incentive Plan (the 2010 Plan, and collectively with the 2000 Plan the Prior Plans). The 2000 Plan terminated August 2010 and no further awards may be issued under the 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. The 2013 Plan became effective as of December 3, 2013, the date of the Company’s Initial Public Offering (“IPO”). 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 Prior Plans 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, 2015 the total number of shares of common stock available for issuance under the 2013 Plan is 6,705,683, which includes 2,684,456 of common stock that were available for issuance under the Prior Plans 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. As of June 30, 2015 a total of 1,973,250 options had been issued 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. As of June 30, 2015, a total of 581,286 shares of common stock have been reserved 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. As of June 30, 2015, we have issued a total of 111,852 shares of common stock under the ESPP.

Total employee, director and non-employee stock-based compensation expense recognized for the three months and six months ended June 30, 2015 and 2014 are as follows (in thousands):


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2015		2014		2015		2014
General and administrative	$	520	$	164	$	1,035	$	292
Research and development		673		197		1,265		347
	$	1,193	$	361	$	2,300	$	639

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, 2014	2,826,794	$	5.12
Options granted	909,750	$	15.84
Options exercised	(352,831)	$	1.21
Balance at June 30, 2015	3,383,713	$	8.41		7.47	$	45,875
Exercisable	1,390,857	$	3.16		5.14	$	26,159

We calculate the intrinsic value as the difference between the exercise price of the options and the closing price of common stock of $21.97 per share as of June 30, 2015.

Weighted average fair value of options granted during the six-month period ended June 30, 2015 and 2014 was $10.58 and $7.35 per share, respectively. There were 810,500 options granted during the period ended June 30, 2014. 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 months and six months ended June 30, 2015 and 2014:


	Options				Options
	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2015		2014		2015		2014
Expected term (years)	5.9		6.0		6.0		6.0
Expected volatility	75.6	%	75.2	%	76.4	%	75.2	%
Risk-free interest rate	1.60	%	1.93	%	1.61	%	1.93	%
Expected dividend yield	—	%	—	%	—	%	—	%


	ESPP				ESPP
	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2015		2014		2015		2014
Expected term (years)	0.5 - 2.0		0.5 - 2.0		0.5 - 2.0		0.5 - 2.0
Expected volatility	70.6 - 82.9	%	70.6	%	70.6 - 82.9	%	70.6	%
Risk-free interest rate	.06% - .46	%	.07% - .46	%	.06% - .46	%	.07% - .46	%
Expected dividend yield	—	%	—	%	—	%	—	%

At June 30, 2015, the Company had $11.9 million of total unrecognized compensation expense, net of estimated forfeitures, related to outstanding stock options and shares issued under our ESPP that will be recognized over the next 3.2 years.

Commitments and Contingencies

6 Months Ended

Jun. 30, 2015

Commitments and Contingencies

Commitments and Contingencies

7. Commitments and Contingencies

Operating Leases

The Company leases office and laboratory space in Monrovia, CA. In January 2015, we entered into a new lease agreement for the property. The new lease replaces the previous lease and extends our lease term to June 2020 with an option to renew for an additional five years. The new lease is a non-cancelable operating lease.

The Company also leases office space in San Diego, CA. In February 2015, we entered into an amended lease agreement for the San Diego property. The amended lease replaces the previous lease and provides for additional space in a building located in the same multi-building development. The amended lease expires in April 2018 and includes an option to renew for a period of one year.

Future minimum payments under the non-cancelable operating leases consist of the following (in thousands):


	Operating
Years ending December 31,	Leases
For the remainder of the fiscal year	$	330
2016		679
2017		699
2018		602
2019		581
Thereafter		299

Net rent expense for the six months ended June 30, 2015 and 2014 was $272,000 and $277,000 respectively.

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.

On March 3, 2015, a verified class action complaint, captioned DePinto v. John S. Stafford, et al., C.A. No. 10742, was filed in the Court of Chancery of the State of Delaware against certain of the Company’s current and former directors alleging cause of action for Breach of Fiduciary Duty and Invalidity of Director and Stockholder Consents. In general, the complaint alleged that the plaintiff and the class he seeks to represent were shareholders of the Company during the recapitalization and certain related transactions that the Company underwent in 2013 and that the defendants breached their fiduciary duties in the course of approving that series of transactions. It also challenged as invalid certain corporate acts taken in the 2013 time period. On June 10, 2015, the Company filed a Verified Petition for Relief under Del. C. Section 205 (the “205 Petition”) related to the corporate acts challenged in the complaint. The defendants filed an answer to the class action complaint on June 22, 2015. On July 9, 2015, the Court consolidated the 205 Petition with the class action, joined the Company as a defendant and ordered it to file the claims in the 205 Petition as counter-claims in the class action, which the Company has done. The Company intends to vigorously defend the action. Based on the preliminary nature of the claim, the Company believes that it is not possible to estimate a potential loss related to the claim.

Collaboration and Licensing Agreements	6 Months Ended
Collaboration and Licensing Agreements	Jun. 30, 2015
Collaboration and Licensing Agreements
Collaboration and Licensing Agreements	8. Collaboration and Licensing Agreements Following is a summary description of the arrangements that generated revenue in the six months ended June 30, 2015 and 2014. Amgen, Inc. In December 2010, we entered into a Collaboration and Option Agreement (Collaboration Agreement) with Amgen, Inc. (Amgen), pursuant to which we agreed to collaborate with Amgen on development of XmAb5871 in rheumatoid arthritis (“RA”) through completion of a Phase 2 proof-of-concept (“POC”) trial. During development and through completion of the POC trial, we would continue to own and would control and pay for all development activities. After completion of the POC trial, we would deliver a data package to Amgen and they would have 90 days to review and decide whether to exercise an option to obtain worldwide rights to XmAb5871. Upon exercise of the option and payment of a $50 million option fee, Amgen would own all rights to the compound and be responsible for further development. In addition to the option fee, upon exercise of the option we would be eligible to receive $437 million in future development, regulatory and sales milestones as Amgen advanced XmAb5871 into later stages of development. We received a nonrefundable upfront payment of $11 million upon execution of the Collaboration Agreement and a $2 million milestone in January 2013 upon the initiation of a Phase 1b clinical trial. We were also eligible to receive an additional $12 million in pre-option payments upon continued development of XmAb5871 through completion of the Phase 2 POC trial and delivery of the clinical study reports to Amgen. In October 2014, we entered into an agreement with Amgen to terminate the Collaboration Agreement pursuant to which all worldwide rights to develop and commercialize XmAb5871 reverted back to us. Our obligations to continue development of XmAb5871 under the terms of the Collaboration Agreement terminated effective as of the date of the termination agreement. As a result of and effective as of the date of the termination agreement, all of Amgen’s rights to XmAb5871 terminated including the right to exercise an exclusive option to acquire the worldwide rights to XmAb5871. Amgen’s obligations to make any further payments to us are also terminated. In connection with the termination, we granted Amgen a right of first negotiation (ROFN) to obtain an exclusive license to develop and commercialize any XmAb5871 product. The Company has evaluated the termination agreement with Amgen and determined that the termination results in a cancellation of all our obligations to Amgen under the Collaboration Agreement. We have evaluated the ROFN and determine that its value is de minimis because Amgen’s rights are limited. As a result of the termination, we recognized the remaining balance in deferred revenue as revenue in the period of the termination, October 2014. There is no remaining revenue or obligations to be reported under this agreement. There were no revenues recognized during the three and six months ended June 30, 2015. During the three and six months ended June 30, 2014 we recognized $0.6 million and $1.1 million of revenue under this arrangement, respectively. As of June 30, 2015, there is no remaining deferred revenue under this agreement. Merck Sharp & Dohme Corporation In July 2013, we entered into a License Agreement with Merck Sharp & Dohme Corp (Merck). Under the terms of the agreement, we provided Merck with a non-exclusive commercial license to certain patent rights to our Fc domains to apply to one of their compounds. We also provided Merck with contingent options to take additional non-exclusive commercial licenses. The contingent options provide Merck an opportunity to take non-exclusive commercial licenses at an amount less than the amount paid for the original license. The agreement provided for an upfront payment of $1.0 million and annual maintenance fees totaling $0.5 million. We are also eligible to receive future milestones and royalties as Merck advances the compound into clinical development. We determined that the deliverables under this agreement were the non-exclusive commercial license and the options. The options are considered substantive and contingent and no amount of the upfront payment was allocated to these options. We also determined that the future milestones and related payments were substantive and contingent and did not allocate any of the upfront payment to the milestones. In the first quarter of 2014, Merck initiated a Phase 1 clinical trial which triggered a $0.5 million milestone payment to us. During the three and six months ended June 30, 2015 we recognized $25,000 and $50,000 of revenue respectively. During the three and six months ended June 30, 2014 we recognized zero and $0.5 million of revenue respectively. As of June 30, 2015, there is $0.1 million of deferred revenue related to this arrangement. Alexion Pharmaceuticals, Inc. In January 2013, we entered into an option and license agreement with Alexion Pharmaceuticals, Inc. (Alexion). Under the terms of the agreement, we 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, up to completion of the first multi-dose human clinical trial for each target compound. Alexion may extend the research term for an additional three years upon written notice to us and payment of an extension fee of $2.0 million. Alexion is responsible for conducting all research and development activities under the agreement at its own expense. In addition, we granted to Alexion an exclusive option, on a target-by-target basis, to obtain an exclusive commercial, worldwide, royalty-bearing license, with sublicensing rights, under our Xtend technology to develop and commercialize products that contain the target for which the option is exercised. In order to exercise this option, Alexion must pay a $4.0 million option fee with respect to each target for which the option is exercised. Alexion may exercise this option at any time during the research term. An option must be exercised for any compound that is advanced into development after the first multi-ascending dose trial is initiated. Under the agreement, we received an upfront payment of $3.0 million. Alexion is also required to pay an annual maintenance fee of $0.5 million during the research term of the agreement and $1.0 million during any extension of the research term. We determined that $2.5 million of the upfront fee was allocated to the license and is being recognized into income over the initial research term of five years. In the third quarter of 2014, Alexion initiated a Phase 1 clinical trial with an undisclosed molecule to be used against an undisclosed target. It is the first human clinical trial with a molecule incorporating our Xtend Fc Domain technology. We received a milestone related to this trial in March 2015 upon issuance of certain patents related to our Xtend technology. During the three and six months ended June 30, 2015 we recognized $0.3 million and $1.0 million of revenue respectively. During the three and six months ended June 30, 2014 we recognized $0.3 million and $0.5 million of revenue respectively. As of June 30, 2015, we have deferred revenue related to this arrangement of $1.6 million. CSL Limited In February 2009, we entered into a Research License and Commercialization Agreement (February 2009 Agreement) with CSL Limited (CSL). Under the agreement, we provided CSL with a research license to one of our technologies and up to five commercial options. The upfront payment of $0.75 million received at inception and the annual research license renewal payments are being recognized as revenue ratably over the five-year term of the research license. In May 2013, we entered into an amendment to the February 2009 Agreement with CSL, which eliminated a contingent milestone payment requirement and reduced the royalty rate on net sales for the licensed product CSL362. The amendment provided for a payment upon signing of $2.5 million. We determined that the amendment was a material modification to the original agreement and evaluated the remaining deliverables at the date of the amendment. We determined that the remaining deliverables were the research license which expired in February 2014 and four additional options to take commercial licenses through the term of the research period. The options are considered to be substantive and contingent and we did not allocate any of the proceeds received in the amendment to the options. The amendment proceeds were recognized into income over the remaining period of the research term. There were no revenues during the three and six months ended June 30, 2015. During the three and six months ended June 30, 2014, we recognized zero and $0.7 million of revenue respectively. As of June 30, 2015, we have no deferred revenue related to this arrangement. In March 2013, we entered into a license agreement (March 2013 License Agreement) with CSL. Under the terms of the agreement, we provided CSL with a non-exclusive commercial license to apply our technology to one of their compounds. The agreement provided for an upfront payment of $0.5 million and we were eligible to receive future milestones as CSL advanced the compound into clinical development. We determined that the deliverables under this agreement were the non-exclusive commercial license. We determined that the future milestones and related payments were substantive and contingent and we did not allocate any of the upfront consideration to the milestone. In March 2015, CSL notified us that they were terminating the March 2013 License Agreement. We have no remaining obligations under the agreement. For the three and six months ended June 30, 2015 and 2014, we did not recognize any revenue related to this arrangement. As of June 30, 2015 there is no remaining deferred revenue under this agreement. Novo Nordisk A/S In December 2014, we entered into a Collaboration and License Agreement with Novo Nordisk A/S (Novo). Under the terms of the agreement we granted Novo a research license to use certain Xencor technologies including our bispecific, Immune Inhibitor, Xtend and other technologies during a two-year research term. We will provide research support for four FTE’s in collaboration with Novo to apply our technologies to Novo provided targets to identify compounds with improved properties. Novo has an option to extend the research term for another twelve months upon written notice to us and payment of another year of research funding. At the end of the research term, Novo will have a commercial license to develop and commercialize any new targets identified during the research term. The agreement provided for an upfront payment of $2.5 million and research funding of $1.6 million per year over the research term. We are also eligible to receive $2.0 million in milestone payments upon the successful completion of certain projects during the research term. In addition, if Novo identifies a compound from the collaboration to advance into clinical development, we are eligible to receive future development, regulatory and commercial milestone payments and royalties. We determined that the deliverables under the arrangement were the research license to our technologies and the research support. We believe that the research support and the technologies are integral to each other and are not separate units of accounting. The commercial license did not have standalone value at inception of the agreement due to the uncertainty of identifying a commercial target. We are recognizing the $2.5 million upfront payment as income over the two year research term. The research funding is being recognized into income over the period that the services are being provided. During the three and six months ended June 30, 2015, we recognized $0.7 million and $1.4 million of revenue respectively. As of June 30, 2015, we have $2.2 million in deferred revenue related to this arrangement.

Summary of Significant Accounting Policies (Polices)	6 Months Ended
Summary of Significant Accounting Policies (Polices)	Jun. 30, 2015
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation The accompanying unaudited interim financial statements for Xencor, Inc. (the Company) have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information. 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. 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 2014 Annual Report on Form 10-K filed with the Securities and Exchange Commission (SEC) on February 23, 2015, as amended.
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 securities issued by investment grade institutions. The Company considers its marketable securities to be “available-for-sale”, as defined by authoritative guidance issued by the Financial Accounting Standards Board (“FASB”). These assets are carried at fair value and the unrealized gains and losses are included in accumulated other comprehensive income (loss). If a decline in the value of a marketable security in the Company’s investment portfolio is deemed to be other-than-temporary, the Company writes down the security to its current fair value and recognizes a loss as a charge against income. The Company reviews its portfolio of marketable securities, using both quantitative and qualitative factors, to determine if declines in fair value below cost are other-than-temporary. There have been no other material changes to the significant accounting policies previously disclosed in the Company’s 2014 Annual Report on Form 10-K, as amended.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers, which establishes principles for reporting revenue and cash flows arising from an entity’s contracts with customers. This new revenue recognition standard will replace most of the recognition guidance within the United States GAAP. In July 2015, the FASB announced that the new pronouncement will be effective for reporting periods beginning after December 15, 2017. The new pronouncement permits the use of either the retroactive or cumulative effect transition method. Early adoption is not permitted. The Company is evaluating the effect that ASU 2014-09 will have on its financial statements and related disclosures.

Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2015

Fair Value of Financial Instruments

Schedule of assets recorded at fair value

The assets recorded at fair value are classified within the hierarchy as follows for the periods reported (in thousands):


	June 30, 2015
	Total
	Fair Value		Level 1		Level 2

Money Market Funds	$	1,379	$	1,379	$	—
Corporate Securities		89,766		—		89,766
Government Securities		58,232		—		58,232
	$	149,377	$	1,379	$	147,998

Net Loss Per Share (Tables)

6 Months Ended

Jun. 30, 2015

Net Loss Per Share

Schedule of basic and diluted net loss per common share

Basic and diluted (loss) per common share is computed as follows (in thousands except per share data)


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2015		2014		2015		2014
	(in thousands, except
	per share data)
Basic and diluted numerator:
Net loss attributable to common stockholders	$	(8,868)	$	(5,044)	$	(15,312)	$	(8,795)
Denominator:
Weighted-average common shares outstanding used in computing basic and diluted net loss		40,389,648		31,372,618		37,518,271		31,366,781
Basic and diluted net loss per common share	$	(0.22)	$	(0.16)	$	(0.41)	$	(0.28)

Schedule of potentially dilutive securites


	Three Months Ended		Six Months Ended
	June 30,		June 30,
	2015	2014	2015	2014
	(in thousands)		(in thousands)
Employee stock purchase plan shares	29	29	29	29
Options to purchase common stock	3,384	2,594	3,384	2,594
	3,413	2,623	3,413	2,623

Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2015

Marketable Securities

Schedule of marketable securities


			Gross		Gross
	Amortized		Unrealized		Unrealized
	Cost		Gains		Losses		Fair Value
(in thousands)
Money Market Funds	$	1,379	$	—	$	—	$	1,379
Corporate Securities		89,839		16		(89)		89,766
Government Securities		58,249		10		(27)		58,232
	$	149,467	$	26	$	(116)	$	149,377

Reported as
Cash and cash equivalents							$	1,379
Marketable securities								147,998
Total investments							$	149,377

Schedule of maturities of marketable securities


	Amortized		Estimated
	Cost		Fair Value
(in thousands)
Mature in one year or less	$	56,745	$	56,714
Mature after one year through five years		91,342		91,284
	$	148,087	$	147,998

Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2015

Stock-Based Compensation

Schedule of total employee, director and non-employee stock-based compensation expense recognized

Total employee, director and non-employee stock-based compensation expense recognized for the three months and six months ended June 30, 2015 and 2014 are as follows (in thousands):


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2015		2014		2015		2014
General and administrative	$	520	$	164	$	1,035	$	292
Research and development		673		197		1,265		347
	$	1,193	$	361	$	2,300	$	639

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, 2014	2,826,794	$	5.12
Options granted	909,750	$	15.84
Options exercised	(352,831)	$	1.21
Balance at June 30, 2015	3,383,713	$	8.41		7.47	$	45,875
Exercisable	1,390,857	$	3.16		5.14	$	26,159

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,
	2015		2014		2015		2014
Expected term (years)	5.9		6.0		6.0		6.0
Expected volatility	75.6	%	75.2	%	76.4	%	75.2	%
Risk-free interest rate	1.60	%	1.93	%	1.61	%	1.93	%
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,
	2015		2014		2015		2014
Expected term (years)	0.5 - 2.0		0.5 - 2.0		0.5 - 2.0		0.5 - 2.0
Expected volatility	70.6 - 82.9	%	70.6	%	70.6 - 82.9	%	70.6	%
Risk-free interest rate	.06% - .46	%	.07% - .46	%	.06% - .46	%	.07% - .46	%
Expected dividend yield	—	%	—	%	—	%	—	%

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2015

Commitments and Contingencies

Schedule of future minimum payments under the non-cancelable operating and capital leases

Future minimum payments under the non-cancelable operating leases consist of the following (in thousands):


	Operating
Years ending December 31,	Leases
For the remainder of the fiscal year	$	330
2016		679
2017		699
2018		602
2019		581
Thereafter		299

Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Fair Value of Financial Instruments
Money Market Funds	$ 11,171	$ 54,649	$ 66,218	$ 77,975
Total Fair Value
Fair Value of Financial Instruments
Total Fair Value	149,377
Total Fair Value \| Money Market Funds
Fair Value of Financial Instruments
Money Market Funds	1,379
Total Fair Value \| Corporate Securities
Fair Value of Financial Instruments
Securities	89,766
Total Fair Value \| Government Securities
Fair Value of Financial Instruments
Securities	58,232
Level 1
Fair Value of Financial Instruments
Total Fair Value	1,379
Level 1 \| Money Market Funds
Fair Value of Financial Instruments
Money Market Funds	1,379
Level 2
Fair Value of Financial Instruments
Total Fair Value	147,998
Level 2 \| Corporate Securities
Fair Value of Financial Instruments
Securities	89,766
Level 2 \| Government Securities
Fair Value of Financial Instruments
Securities	$ 58,232

Net Loss Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Basic and diluted numerator:
Net loss attributable to common stockholders	$ (8,868)	$ (5,044)	$ (15,312)	$ (8,795)
Denominator:
Weighted-average common shares outstanding used in computing basic and diluted net loss (in shares)	40,389,648	31,372,618	37,518,271	31,366,781
Basic and diluted net loss per common share (in dollars per share)	$ (0.22)	$ (0.16)	$ (0.41)	$ (0.28)

Net Loss Per Share (Details 2)	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended
Net Loss Per Share (Details 2)	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015 Employee stock options	Jun. 30, 2014 Employee stock options	Jun. 30, 2015 Employee stock options	Jun. 30, 2014 Employee stock options	Jun. 30, 2015 Employee Stock Purchase Plan	Jun. 30, 2014 Employee Stock Purchase Plan	Jun. 30, 2015 Employee Stock Purchase Plan	Jun. 30, 2014 Employee Stock Purchase Plan	Mar. 31, 2015 Common Stock	Jun. 30, 2015 Common Stock
Net Loss Per Share
Anti-dilutive securities (in shares)	3,413,000	2,623,000	3,413,000	2,623,000	3,384,000	2,594,000	3,384,000	2,594,000	29,000	29,000	29,000	29,000
Sale of common stock													8,625,000	8,625,000

Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2015
Schedule of Available-for-sale Securities
Amortized cost	$ 149,467
Gross unrealized gains	26
Gross unrealized losses	(116)
Fair value	149,377
Marketable securities
Schedule of Available-for-sale Securities
Fair value	147,998
Money Market Funds
Schedule of Available-for-sale Securities
Amortized cost	1,379
Fair value	1,379
Corporate Securities
Schedule of Available-for-sale Securities
Amortized cost	89,839
Gross unrealized gains	16
Gross unrealized losses	(89)
Fair value	89,766
Government Securities
Schedule of Available-for-sale Securities
Amortized cost	58,249
Gross unrealized gains	10
Gross unrealized losses	(27)
Fair value	58,232
Cash and Cash Equivalents
Schedule of Available-for-sale Securities
Fair value	$ 1,379

Marketable Securities (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2015
Amortized Cost
Maturing in one year or less	$ 56,745
Maturing after one year through five years	91,342
Total amortized cost	148,087
Estimate Fair Value
Maturing in one year or less	56,714
Maturing after one year through five years	91,284
Total estimated fair value	$ 147,998

Stock Based Compensation (Details)			6 Months Ended			6 Months Ended
Stock Based Compensation (Details)	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2015 The 2013 Plan	Jun. 30, 2015 Prior Plans	Aug. 31, 2010 Prior Plans	Jun. 30, 2015 Employee Stock Purchase Plan	Dec. 02, 2013 The 2010 Plan
Stock-based compensation
Total number of shares of common stock available for issuance			6,705,683	2,684,456	0	581,286	0
Annual percentage increase in shares of common stock available for issuance			4.00%			1.00%
Common Stock, shares issued	40,460,091	31,434,272				111,852
Annual increase in shares of common stock available for issuance (in shares)						621,814

Stock-Based Compensation (Details 3) (Employee stock options, USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Employee stock options
Number of Shares subject to outstanding options
Balance at the beginning of the period (in shares)	2,826,794
Options granted (in shares)	909,750	810,500
Options exercised (in shares)	(352,831)
Balance at the end of the period (in shares)	3,383,713
Weighted Average Exercise Price (Per Share)
Balance at the beginning of the period (in dollars per share)	$ 5.12
Options granted (in dollars per share)	$ 15.84
Options exercised (in dollars per share)	$ 1.21
Balance at the end of the period (in dollars per share)	$ 8.41
Exercisable (in shares)	1,390,857
Exercisable (in dollars per share)	$ 3.16
Weighted-Average Remaining Contractual Term, Balance outstanding	7 years 5 months 19 days
Weighted-Average Remaining Contractual Term, Exercisable	5 years 1 month 21 days
Aggregate Intrinsic Value, Balance outstanding	$ 45,875
Aggregate Intrinsic Value, Exercisable	$ 26,159
Closing price of common stock (in dollars per share)	$ 21.97
Weighted average fair value of options granted (in dollars per share)	$ 10.58	$ 7.35

Stock Based Compensation (Details 4) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Employee stock options
Weighted average assumptions for estimated fair value of employee stock options
Expected term (years)	5 years 10 months 24 days	6 years	6 years	6 years
Expected volatility (as a percent)	75.60%	75.20%	76.40%	75.20%
Risk-free interest rate (as a percent)	1.60%	1.93%	1.61%	1.93%
Total unrecognized compensation expense, net of estimated forfeitures	$ 11.9		$ 11.9
Period to recognize total unrecognized compensation expense			3 years 2 months 12 days
Employee Stock Purchase Plan
Weighted average assumptions for estimated fair value of employee stock options
Expected volatility (as a percent)		70.60%		70.60%
Employee Stock Purchase Plan \| Minimum
Weighted average assumptions for estimated fair value of employee stock options
Expected term (years)	6 months	6 months	6 months	6 months
Expected volatility (as a percent)	70.60%		70.60%
Risk-free interest rate (as a percent)	0.06%	0.07%	0.06%	0.07%
Employee Stock Purchase Plan \| Maximum
Weighted average assumptions for estimated fair value of employee stock options
Expected term (years)	2 years	2 years	2 years	2 years
Expected volatility (as a percent)	82.90%		82.90%
Risk-free interest rate (as a percent)	0.46%	0.46%	0.46%	0.46%

Commitments and Contingencies (Details) (USD $)	6 Months Ended		1 Months Ended
Commitments and Contingencies (Details) (USD $)	Jun. 30, 2015	Jun. 30, 2014	Feb. 28, 2015 Office Space	Jan. 31, 2015 Office Space
Renewal term			1 year	5 years
Operating Leases
For the remainder of the fiscal year	$ 330,000
2016	679,000
2017	699,000
2018	602,000
2019	581,000
Thereafter	299,000
Net rent expense	$ 272,000	$ 277,000

Collaboration and Licensing Agreements (Details) (USD $)	3 Months Ended		6 Months Ended			1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended	1 Months Ended	3 Months Ended			6 Months Ended			1 Months Ended	3 Months Ended		6 Months Ended		1 Months Ended			3 Months Ended		6 Months Ended		1 Months Ended	3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Jan. 31, 2013 Collaboration and Option Agreement Amgen, Inc.	Jun. 30, 2015 Collaboration and Option Agreement Amgen, Inc.	Jun. 30, 2014 Collaboration and Option Agreement Amgen, Inc.	Jun. 30, 2015 Collaboration and Option Agreement Amgen, Inc.	Jun. 30, 2014 Collaboration and Option Agreement Amgen, Inc.	Dec. 31, 2010 Collaboration and Option Agreement Amgen, Inc.	Jul. 31, 2013 License Agreement Merck Sharp & Dohme Corp. item	Jun. 30, 2015 License Agreement Merck Sharp & Dohme Corp.	Jun. 30, 2014 License Agreement Merck Sharp & Dohme Corp.	Mar. 31, 2014 License Agreement Merck Sharp & Dohme Corp.	Jun. 30, 2015 License Agreement Merck Sharp & Dohme Corp.	Jun. 30, 2014 License Agreement Merck Sharp & Dohme Corp.	Jun. 30, 2015 License Agreement Alexion Pharmaceuticals, Inc.	Jan. 31, 2013 Option and license agreement Alexion Pharmaceuticals, Inc. item	Jun. 30, 2015 Option and license agreement Alexion Pharmaceuticals, Inc.	Jun. 30, 2014 Option and license agreement Alexion Pharmaceuticals, Inc.	Jun. 30, 2015 Option and license agreement Alexion Pharmaceuticals, Inc.	Jun. 30, 2014 Option and license agreement Alexion Pharmaceuticals, Inc.	Feb. 28, 2009 2009 Research License and Commercialization Agreement CSL Limited item	Feb. 28, 2009 2009 Research License and Commercialization Agreement CSL Limited Maximum item	May 31, 2013 May 2013 Research License and Commercialization Agreement CSL Limited item	Jun. 30, 2015 May 2013 Research License and Commercialization Agreement CSL Limited	Jun. 30, 2014 May 2013 Research License and Commercialization Agreement CSL Limited	Jun. 30, 2015 May 2013 Research License and Commercialization Agreement CSL Limited	Jun. 30, 2014 May 2013 Research License and Commercialization Agreement CSL Limited	Mar. 31, 2013 March 2013 License Agreement CSL Limited item	Jun. 30, 2015 March 2013 License Agreement CSL Limited	Jun. 30, 2014 March 2013 License Agreement CSL Limited	Jun. 30, 2015 March 2013 License Agreement CSL Limited	Jun. 30, 2014 March 2013 License Agreement CSL Limited	Jun. 30, 2015 Collaboration And License Agreement Member Novo Nordisk	Jun. 30, 2015 Collaboration And License Agreement Member Novo Nordisk	Dec. 31, 2014 Collaboration And License Agreement Member Novo Nordisk employee
Collaboration research and licensing agreements
Option term after delivery of the data from a Phase 2 proof-of-concept (POC) clinical trial											90 days
Nonrefundable upfront payment											$ 11,000,000	$ 1,000,000							$ 3,000,000					$ 750,000		$ 2,500,000					$ 500,000							$ 2,500,000
Annual maintenance fees												500,000							500,000
Milestone payment received						2,000,000									500,000																							2,000,000
Additional pre-option payments											12,000,000
Revenue recognized	1,014,000	824,000	2,505,000	3,008,000			0	600,000	0	1,100,000			25,000	0		50,000	500,000	2,500,000		300,000	300,000	1,000,000	500,000				0	0	0	700,000		0	0	0	0	700,000	1,400,000
Deferred revenue							0		0				100,000			100,000				1,600,000		1,600,000					0		0			0		0		2,200,000	2,200,000
Current portion of deferred revenue	2,794,000		2,794,000		2,254,000
Number of different target programs																			6
Research license term																			5 years					5 years														2 years
Additional research term																			3 years																			12 months
Extension fee																			2,000,000
Annual maintenance fees payable during any extension of research term																			1,000,000
Option fee											50,000,000								4,000,000
Milestone payment to be received for first product upon achievement of certain development, regulatory and commercial milestones											437,000,000
Number of technologies to which research license is provided																								1
Number of commercial options																									5	4
Number of compounds												1																			1
Research funding																																						1,600,000
Portion of nonrefundable upfront payment allocated to option												$ 0
Number of full time employees that will be given research support																																						4
Research term of revenue recognized																			5 years

Comprehensive loss	6 Months Ended
Comprehensive loss	Jun. 30, 2015
Comprehensive Loss
Comprehensive Loss	4. Comprehensive loss Comprehensive loss is comprised of net loss and other comprehensive loss. For the three months and six months ended June 30, 2015, the only component of other comprehensive loss is net unrealized gains and losses on marketable securities. There were no material reclassifications out of accumulated other comprehensive loss during the three months and six months ended June 30, 2015.

Income Taxes	6 Months Ended
Income Taxes	Jun. 30, 2015
Income Taxes
Income Taxes	9. Income Taxes No provision for U.S. income taxes has been made, net of the valuation allowance, with the exception of the minimum statutory amounts, because the Company has incurred losses since its inception. The Company has deferred tax assets consisting primarily of net operating loss and tax credit carryforwards that have been fully offset by a valuation alloawance.

Summary of Significant Accounting Policies (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	6 Months Ended
	Mar. 31, 2015	Jun. 30, 2015
Proceeds from sale of common stock		$ 115,204
Common Stock
Sale of common stock	8,625,000	8,625,000
Proceeds from sale of common stock		$ 86

Income Taxes (Details) (Federal, USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2015
Federal
Provision for income tax net of valuation allowance	$ 0