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Document And Entity Information - shares	6 Months Ended
Document And Entity Information - shares	Jun. 30, 2016	Jul. 29, 2016
Document And Entity Information [Abstract]
Entity Registrant Name	Xenon Pharmaceuticals Inc.
Document Type	10-Q
Trading Symbol	XENE
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		14,426,370
Amendment Flag	false
Entity Central Index Key	0001582313
Entity Filer Category	Accelerated Filer
Document Period End Date	Jun. 30, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q2

Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 35,210	$ 58,651
Marketable securities	15,528
Accounts receivable	658	315
Prepaid expenses and other current assets	1,996	1,900
Total current assets	53,392	60,866
Prepaid expenses, long term	632	1,094
Property, plant and equipment, net	1,663	1,989
Total assets	55,687	63,949
Current liabilities:
Accounts payable and accrued expenses (note 6)	2,929	2,625
Deferred revenue		157
Total current liabilities	2,929	2,782
Deferred tenant inducements	101	133
Total liabilities	3,030	2,915
Shareholders’ equity:
Common shares, without par value; unlimited shares authorized; issued and outstanding: 14,415,347 (December 31, 2015 - 14,385,336)	148,867	148,634
Additional paid-in capital	33,752	33,083
Accumulated deficit	(128,972)	(119,693)
Accumulated other comprehensive loss	(990)	(990)
Shareholders' equity	52,657	61,034
Total liabilities and shareholders’ equity	55,687	63,949
Commitments and contingencies (note 9)

Balance Sheets (Unaudited) (Parenthetical) - $ / shares	6 Months Ended	12 Months Ended
Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Common shares, without par value
Common shares, shares authorized	Unlimited	Unlimited
Common shares, Issued	14,415,347	14,385,336
Common shares, Outstanding	14,415,347	14,385,336

Statements of Operations and Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revenue:
Collaboration revenue (note 8)	$ 412	$ 4,044	$ 981	$ 8,054
Royalties	1	2	33	2
Revenues	413	4,046	1,014	8,056
Operating expenses:
Research and development	5,103	3,669	9,467	7,096
General and administrative	1,676	178	3,571	6,898
Total operating expenses	6,779	3,847	13,038	13,994
Income (loss) from operations	(6,366)	199	(12,024)	(5,938)
Other income (expense):
Interest income	123	163	222	315
Foreign exchange gain (loss)	227	806	2,523	(2,365)
Net income (loss) and comprehensive income (loss)	$ (6,016)	$ 1,168	$ (9,279)	$ (7,988)
Net income (loss) per common share (note 4):
Basic	$ (0.42)	$ 0.08	$ (0.64)	$ (0.56)
Diluted	$ (0.42)	$ (0.07)	$ (0.65)	$ (0.56)
Weighted-average common shares outstanding (note 4):
Basic	14,408,108	14,241,827	14,401,054	14,227,203
Diluted	14,434,602	15,129,978	14,428,160	14,227,203

Statement of Shareholders' Equity (Unaudited) - USD ($)
$ in Thousands

Total

Common Shares [Member]

Additional Paid-in Capital [Member]

Accumulated Deficit [Member]

Accumulated Other Comprehensive Loss [Member]

^[1]

Balance at Dec. 31, 2014

$ 72,779

$ 147,157

$ 30,346

$ (103,734)

$ (990)

Balance (in Shares) at Dec. 31, 2014

14,181,333

Net loss

(15,752)

Stock option compensation expense

2,077

Issued pursuant to exercise of stock options

278

$ 1,477

(992)

(207)

Issued pursuant to exercise of stock options (in Shares)

204,003

Fair value adjustment upon reclassification of stock options

1,652

Balance at Dec. 31, 2015

61,034

$ 148,634

33,083

(119,693)

(990)

Balance (in Shares) at Dec. 31, 2015

14,385,336

Net loss

(9,279)

Stock option compensation expense

1,106

Issued pursuant to exercise of stock options

$ 82

$ 233

(151)

Issued pursuant to exercise of stock options (in Shares)

30,529

^[2]

30,011

Fair value adjustment upon reclassification of stock options

$ (286)

(286)

Balance at Jun. 30, 2016

$ 52,657

$ 148,867

$ 33,752

$ (128,972)

$ (990)

Balance (in Shares) at Jun. 30, 2016

14,415,347

[1]	Our accumulated other comprehensive loss is entirely related to historical cumulative translation adjustments from the application of U.S. dollar reporting when the functional currency of the Company was the Canadian dollar.
[2]	During the six months ended June 30, 2016, 29,270 stock options were exercised for the same number of common shares for cash (six months ended June 30, 2015 – 53,442). In the same period, the Company issued 741 common shares (six months ended June 30, 2015 – 32,399) for the cashless exercise of 1,259 stock options (six months ended June 30, 2015 – 46,369).

Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Operating activities:
Net loss	$ (9,279)	$ (7,988)
Items not involving cash:
Depreciation and amortization	531	492
Stock-based compensation	1,006	3,446
Deferred tenant inducements	(32)	(32)
Unrealized foreign exchange (gain) loss	(2,508)	2,353
Changes in operating assets and liabilities:
Accounts receivable	(333)	31
Prepaid expenses, and other current assets	366	221
Accounts payable and accrued expenses	33	(350)
Deferred revenue	(157)	(6,144)
Net cash used in operating activities	(10,373)	(7,971)
Investing activities:
Purchases of property, plant and equipment	(205)	(190)
Purchase of marketable securities	(15,300)
Proceeds from marketable securities		1,818
Net cash provided by (used in) investing activities	(15,505)	1,628
Financing activities:
Proceeds from issuance of common shares	82	213
Net cash provided by financing activities	82	213
Effect of exchange rate changes on cash and cash equivalents	2,355	(1,550)
Decrease in cash and cash equivalents	(23,441)	(7,680)
Cash and cash equivalents, beginning of period	58,651	72,026
Cash and cash equivalents, end of period	35,210	64,346
Supplemental disclosures:
Interest received	204	268
Supplemental disclosures of non-cash transactions:
Fair value of options exercised on a cashless basis	$ 4	$ 189

Nature of the Business

6 Months Ended

Jun. 30, 2016

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Nature of the business

1.	Nature of the business:

Xenon Pharmaceuticals Inc. (the “Company”), incorporated in 1996 under the British Columbia Business Corporations Act and continued federally in 2000 under the Canada Business Corporation Act, is a clinical-stage biopharmaceutical company discovering and developing a pipeline of differentiated therapeutics for orphan indications that it intends to commercialize on its own, and for larger market indications that it intends to partner with global pharmaceutical companies.

Basis of Presentation

6 Months Ended

Jun. 30, 2016

Accounting Policies [Abstract]

Basis of presentation

2.	Basis of presentation:

These financial statements are presented in U.S. dollars.

The accompanying unaudited interim financial statements have been prepared in accordance with United States generally accepted accounting principles (“U.S. GAAP”) and pursuant to the rules and regulations of the United States Securities and Exchange Commission (“SEC”) for interim financial information. Accordingly, these financial statements do not include all of the information and footnotes required for complete financial statements and should be read in conjunction with the audited financial statements and notes for the year ended December 31, 2015 and included in the Company’s 2015 Annual Report on Form 10-K filed with the SEC on March 8, 2016.

These unaudited interim financial statements reflect all adjustments, consisting of normal recurring adjustments, which, in the opinion of management, are necessary for a fair presentation of results for the interim periods presented. The results of operations for the three and six month periods ended June 30, 2016 and 2015 are not necessarily indicative of results that can be expected for a full year. These unaudited interim financial statements follow the same significant accounting policies as those described in the notes to the audited financial statements of the Company included in the Company’s 2015 Annual Report on Form 10-K for the year ended December 31, 2015.

Future Changes in Accounting Policies

6 Months Ended

Jun. 30, 2016

Accounting Changes And Error Corrections [Abstract]

Future changes in accounting policies

3.	Future changes in accounting policies:

In May 2014, the Financial Accounting Standards Board (“FASB”) issued amendments to clarify the principles of recognizing revenue and to develop a common revenue standard that would remove inconsistencies in revenue requirements, leading to improved comparability of revenue recognition practices across entities and industries. The amendments stipulate that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. Additional disclosure will also be required about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments, and assets recognized from costs incurred to obtain or fulfill a contract. In August 2015, the FASB issued an update deferring the effective date of the new revenue standard by one year. The new guidance will be effective for public entities for fiscal years and interim periods within those years, beginning after December 15, 2017 instead of the originally contemplated effective date of December 15, 2016.

In March, April and May 2016, the FASB issued amendments to the new revenue standard to clarify the implementation guidance on principal versus agent considerations and identifying performance obligations and licensing as well as to address certain narrow-scope improvements and practical expedients at transition with the same effective date as the new revenue standard. The Company is currently evaluating the new guidance to determine the impact it will have on the Company’s financial statements.

In August 2014, the FASB issued amendments requiring management to assess an entity’s ability to continue as a going concern. For each reporting period, management will be required to evaluate whether there are conditions or events that raise substantial doubt about a company’s ability to continue as a going concern within one year from the date the financial statements are issued. These amendments will be effective for public entities for the annual period ending after December 15, 2016, and for annual periods and interim periods thereafter. The adoption of these amendments in fiscal 2016 is not expected to have a material impact on the Company’s financial statements.

In February 2016, the FASB issued amendments to lease accounting requiring the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous U.S. GAAP. The new guidance retains a distinction between finance leases and operating leases, with cash payments from operating leases classified within operating activities in the statement of cash flows. These amendments will be effective for public entities for fiscal years and interim periods within those years, beginning after December 15, 2018. The Company is currently evaluating the new guidance to determine the impact it will have on the Company’s financial statements.

In March 2016, the FASB issued amendments to stock-based compensation accounting to simplify several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification of the statement of cash flows. The amendments stipulate (a) all excess tax benefits and tax deficiencies should be recognized as income tax expense or benefit in the statement of operations and the tax effects of exercised or vested awards should be treated as discrete items in the reporting period in which they occur, (b) excess tax benefits should be classified along with other tax cash flows as an operating activity, (c) an entity can make an entity-wide accounting policy election to either estimate the number of awards that are expected to vest (current GAAP) or account for forfeitures when they occur, (d) the threshold to qualify for equity classification permits withholding up to the maximum statutory tax rates in the applicable jurisdictions, and (e) cash paid by an employee when directly withholding shares for tax withholding purposes should be classified as financing activity. These amendments will be effective for public entities for fiscal years and interim periods within those years, beginning on or after December 15, 2016 and early adoption is permitted. The Company has early adopted all of the provisions of this update effective January 1, 2016. The Company has elected to recognize forfeitures as they occur and the impact of that change in accounting policy as well as the impact of the remaining provisions did not have a material impact on the Company’s financial statements.

Net Income (Loss) Per Common Share

6 Months Ended

Jun. 30, 2016

Earnings Per Share [Abstract]

Net income (loss) per common share

4.	Net income (loss) per common share:

Basic net income (loss) per common share is computed by dividing the net income (loss) by the weighted average number of common shares outstanding for the period. Diluted net income (loss) per common share is computed by adjusting the numerator and denominator of the basic net income (loss) per share calculation for the potential impact of dilutive securities.

For the three and six month periods ended June 30, 2016, 1,934,452 and 1,841,096 stock options, respectively, were excluded from the calculation of diluted net income per common share as their inclusion would be anti-dilutive (three months ended June 30, 2015 - 389,283). For the six months ended June 30, 2015, all stock options were anti-dilutive and were excluded from the diluted weighted average common shares outstanding for the period.

The following is a reconciliation of the numerators and denominators of basic and diluted net income (loss) per common share:

	Three Months Ended June 30,						Six Months Ended June 30,
	2016			2015			2016			2015
Numerator:
Net income (loss) used to compute net income (loss) per common share:
Basic	$	(6,016	)	$	1,168		$	(9,279	)	$	(7,988	)
Adjustment for change in fair value of liability classified stock options		(58	)		(2,244	)		(100	)		—
Diluted	$	(6,074	)	$	(1,076	)	$	(9,379	)	$	(7,988	)
Denominator:
Weighted average number of common shares:
Basic		14,408,108			14,241,827			14,401,054			14,227,203
Adjustment for dilutive effect of stock options		26,494			888,151			27,106			—
Diluted		14,434,602			15,129,978			14,428,160			14,227,203
Net income (loss) per common share - basic	$	(0.42	)	$	0.08		$	(0.64	)	$	(0.56	)
Net loss per common share - diluted	$	(0.42	)	$	(0.07	)	$	(0.65	)	$	(0.56	)

Fair Value of Financial Instruments

6 Months Ended

Jun. 30, 2016

Fair Value Disclosures [Abstract]

Fair value of financial instruments

5.	Fair value of financial instruments:

We measure certain financial instruments and other items at fair value.

To determine the fair value, we use the fair value hierarchy for inputs used to measure fair value of financial assets and liabilities. This hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three levels: Level 1 (highest priority), Level 2, and Level 3 (lowest priority).

Level 1 - Unadjusted quoted prices in active markets for identical instruments.

Level 2 - Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (i.e., interest rates, yield curves, etc.), and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs).

Level 3 - Inputs are unobservable and reflect the Company’s assumptions as to what market participants would use in pricing the asset or liability. The Company develops these inputs based on the best information available.

Assets and liabilities are classified based on the lowest level of input that is significant to the fair value measurements. Changes in the observability of valuation inputs may result in a reclassification of levels for certain securities within the fair value hierarchy.

The Company’s Level 1 assets include cash and cash equivalents and marketable securities with quoted prices in active markets. The carrying amount of accounts receivables, accounts payable and accrued expenses approximates fair value due to the nature and short-term of those instruments. Liability classified stock options have been valued using a Black-Scholes pricing model to estimate fair value using Level 3 inputs as defined above, as quoted prices are not readily available.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Accounts Payable and Accrued Expenses

6 Months Ended

Jun. 30, 2016

Payables And Accruals [Abstract]

Accounts payable and accrued expenses

6.	Accounts payable and accrued expenses:

Accounts payable and accrued expenses consisted of the following:

	June 30,		December 31,
	2016		2015
Trade payables	$	655	$	1,088
Employee compensation, benefits, and related accruals		763		762
Consulting and contracted research		1,218		506
Professional fees		246		214
Other		47		55
Total	$	2,929	$	2,625

Stock Option Plan

6 Months Ended

Jun. 30, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock option plan

7.	Stock option plan:

The following table presents stock option activity for the period:

	Three Months Ended June 30,						Six Months Ended June 30,
	2016			2015			2016			2015
Outstanding, beginning of period		1,934,734			1,785,436			1,721,472			1,484,218
Granted		65,450			33,474			299,400			380,438
Exercised⁽¹⁾		(14,283	)		(55,155	)		(30,529	)		(99,811	)
Forfeited and expired		(2,227	)		(18,737	)		(6,669	)		(19,827	)
Outstanding, end of period		1,983,674			1,745,018			1,983,674			1,745,018
Exercisable, end of period		1,195,883			1,126,629			1,195,883			1,126,629

⁽¹⁾

During the six months ended June 30, 2016, 29,270 stock options were exercised for the same number of common shares for cash (six months ended June 30, 2015 – 53,442). In the same period, the Company issued 741 common shares (six months ended June 30, 2015 – 32,399) for the cashless exercise of 1,259 stock options (six months ended June 30, 2015 – 46,369).

The fair value of each option issued to employees and non-employees is estimated using the Black-Scholes option-pricing model with the following weighted-average assumptions:

	Three Months Ended June 30,						Six Months Ended June 30,
	2016			2015			2016			2015
Average risk-free interest rate		1.44	%		1.71	%		1.60	%		1.71	%
Average expected term (in years)		6.14			6.04			6.23			6.23
Expected volatility		74	%		75	%		75	%		75	%
Expected dividend yield		0.00	%		0.00	%		0.00	%		0.00	%

The weighted-average fair value of options granted during the six months ended June 30, 2016 was $4.90 (six months ended June 30, 2015 – $11.96) per option.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

Collaboration Agreements

6 Months Ended

Jun. 30, 2016

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Collaboration agreements

8.	Collaboration agreements:

The Company has entered into a number of collaboration agreements with multiple deliverables under which it may have received non-refundable upfront payments. The Company generally recognizes revenue from upfront payments ratably over the term of its estimated period of performance of research under its collaboration agreements in the event that such arrangements represent a single unit of accounting.

The collaborations may also include contractual milestone payments, which relate to the achievement of prespecified research, development, regulatory and commercialization events. The milestone events coincide with the progression of product candidates from research and development, to regulatory approval and through to commercialization. The process of successfully discovering a new product candidate, having it selected by the collaborator for development and having it approved and ultimately sold for a profit is highly uncertain. As such, the milestone payments that the Company may earn from its collaborators involve a significant degree of risk to achieve.

The following table is a summary of the revenue recognized from the Company’s collaborations for the three and six months ended June 30, 2016 and 2015:

	Three Months Ended June 30,				Six Months Ended June 30,
	2016		2015		2016		2015
Teva:
Recognition of upfront payment	$	—	$	2,908	$	—	$	5,784
Research funding		29		45		58		90
Genentech:
Recognition of upfront payment		—		181		157		360
Research funding		383		910		766		1,820
Total collaboration revenue	$	412	$	4,044	$	981	$	8,054

Commitments and Contingencies

6 Months Ended

Jun. 30, 2016

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

9.	Commitments and contingencies:

(a)

Priority access agreement with Medpace Inc. (“Medpace”):

In August 2015, the Company entered into a priority access agreement with Medpace for the provision of certain clinical development services. Under the terms of the agreement, the Company has committed to using Medpace non-exclusively for clinical development services over the five year term of the agreement. In consideration for priority access to Medpace resources and preferred service rates, the Company has committed to $7,000 of services over the term of the agreement, $3,000 of which was paid in the year ended December 31, 2015. Of the amounts paid by the Company in 2015 in connection with the priority access agreement, $1,215 has been recorded as expenses to date for services rendered, $1,153 has been recorded as current prepaid expenses (December 31, 2015 – $1,010) and $632 as long-term prepaid expenses (December 31, 2015 – $1,094) for the provision of future services as at June 30, 2016.

(b)

Guarantees and indemnifications:

The Company has entered into license and research agreements with third parties that include indemnification provisions that are customary in the industry. These indemnification provisions generally require the Company to compensate the other party for certain damages and costs incurred as a result of third party claims or damages arising from these transactions.

The maximum amount of potential future indemnification is unlimited; however, the Company currently holds commercial and product liability insurance. This insurance limits the Company’s exposure and may enable it to recover a portion of any future amounts paid. Historically, the Company has not made any indemnification payments under such agreements and the Company believes that the fair value of these indemnification obligations is minimal. Accordingly, the Company has not recognized any liabilities relating to these obligations for any period presented.

Related Parties

6 Months Ended

Jun. 30, 2016

Related Parties

10.	Related Parties:

Dr. August J. Troendle, an officer and director of Medpace, which provides clinical development services to the Company, is a beneficial owner of more than 5% of the Company’s common shares. The Company incurred $568 and $941 of clinical development service fees under its priority access agreement and a master services agreement with Medpace for the three and six months ended June 30, 2016 (three and six months ended June 30, 2015 – $55). Additionally, the Company has recorded $1,996 of prepaid expenses as of June 30, 2016 (December 31, 2015 – $2,314) for future clinical development services under such agreements with Medpace.

Net Income (Loss) Per Common Share (Tables)

6 Months Ended

Jun. 30, 2016

Earnings Per Share [Abstract]

Reconciliation of the Numerators and Denominators of Basic and Diluted Net Income (Loss) Per Common Share

The following is a reconciliation of the numerators and denominators of basic and diluted net income (loss) per common share:

	Three Months Ended June 30,						Six Months Ended June 30,
	2016			2015			2016			2015
Numerator:
Net income (loss) used to compute net income (loss) per common share:
Basic	$	(6,016	)	$	1,168		$	(9,279	)	$	(7,988	)
Adjustment for change in fair value of liability classified stock options		(58	)		(2,244	)		(100	)		—
Diluted	$	(6,074	)	$	(1,076	)	$	(9,379	)	$	(7,988	)
Denominator:
Weighted average number of common shares:
Basic		14,408,108			14,241,827			14,401,054			14,227,203
Adjustment for dilutive effect of stock options		26,494			888,151			27,106			—
Diluted		14,434,602			15,129,978			14,428,160			14,227,203
Net income (loss) per common share - basic	$	(0.42	)	$	0.08		$	(0.64	)	$	(0.56	)
Net loss per common share - diluted	$	(0.42	)	$	(0.07	)	$	(0.65	)	$	(0.56	)

Accounts Payable and Accrued Expenses (Tables)

6 Months Ended

Jun. 30, 2016

Payables And Accruals [Abstract]

Accounts Payable and Accrued Expenses

Accounts payable and accrued expenses consisted of the following:

	June 30,		December 31,
	2016		2015
Trade payables	$	655	$	1,088
Employee compensation, benefits, and related accruals		763		762
Consulting and contracted research		1,218		506
Professional fees		246		214
Other		47		55
Total	$	2,929	$	2,625

Stock Option Plan (Tables)

6 Months Ended

Jun. 30, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Option Activity

The following table presents stock option activity for the period:

	Three Months Ended June 30,						Six Months Ended June 30,
	2016			2015			2016			2015
Outstanding, beginning of period		1,934,734			1,785,436			1,721,472			1,484,218
Granted		65,450			33,474			299,400			380,438
Exercised⁽¹⁾		(14,283	)		(55,155	)		(30,529	)		(99,811	)
Forfeited and expired		(2,227	)		(18,737	)		(6,669	)		(19,827	)
Outstanding, end of period		1,983,674			1,745,018			1,983,674			1,745,018
Exercisable, end of period		1,195,883			1,126,629			1,195,883			1,126,629

⁽¹⁾

Fair Value Assumptions for Stock Options

The fair value of each option issued to employees and non-employees is estimated using the Black-Scholes option-pricing model with the following weighted-average assumptions:

	Three Months Ended June 30,						Six Months Ended June 30,
	2016			2015			2016			2015
Average risk-free interest rate		1.44	%		1.71	%		1.60	%		1.71	%
Average expected term (in years)		6.14			6.04			6.23			6.23
Expected volatility		74	%		75	%		75	%		75	%
Expected dividend yield		0.00	%		0.00	%		0.00	%		0.00	%

Collaboration Agreements (Tables)

6 Months Ended

Jun. 30, 2016

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Schedule of Revenues from Collaborations

The following table is a summary of the revenue recognized from the Company’s collaborations for the three and six months ended June 30, 2016 and 2015:

	Three Months Ended June 30,				Six Months Ended June 30,
	2016		2015		2016		2015
Teva:
Recognition of upfront payment	$	—	$	2,908	$	—	$	5,784
Research funding		29		45		58		90
Genentech:
Recognition of upfront payment		—		181		157		360
Research funding		383		910		766		1,820
Total collaboration revenue	$	412	$	4,044	$	981	$	8,054

Net Income (Loss) Per Common Share (Details) - shares	3 Months Ended		6 Months Ended
Net Income (Loss) Per Common Share (Details) - shares	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016
Earnings Per Share [Abstract]
Anti-dilutive shares excluded from the calculation of income per common share	1,934,452	389,283	1,841,096

Net Income (Loss) Per Common Share - Reconciliation of the Numerators and Denominators of Basic and Diluted Net Income (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Net income (loss) used to compute net income (loss) per common share:
Basic	$ (6,016)	$ 1,168	$ (9,279)	$ (7,988)
Adjustment for change in fair value of liability classified stock options	(58)	(2,244)	(100)
Diluted	$ (6,074)	$ (1,076)	$ (9,379)	$ (7,988)
Weighted average number of common shares:
Basic	14,408,108	14,241,827	14,401,054	14,227,203
Adjustment for dilutive effect of stock options	26,494	888,151	27,106
Diluted	14,434,602	15,129,978	14,428,160	14,227,203
Net income (loss) per common share - basic	$ (0.42)	$ 0.08	$ (0.64)	$ (0.56)
Net loss per common share - diluted	$ (0.42)	$ (0.07)	$ (0.65)	$ (0.56)

Accounts Payable and Accrued Expenses - Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Payables And Accruals [Abstract]
Trade payables	$ 655	$ 1,088
Employee compensation, benefits, and related accruals	763	762
Consulting and contracted research	1,218	506
Professional fees	246	214
Other	47	55
Total	$ 2,929	$ 2,625

Stock Option Plan - Stock Option Activity (Details) - shares

3 Months Ended

6 Months Ended

12 Months Ended

Jun. 30, 2016

Jun. 30, 2015

Jun. 30, 2016

Jun. 30, 2015

Dec. 31, 2015

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Outstanding, beginning of period

1,934,734

1,785,436

1,721,472

1,484,218

Granted

65,450

33,474

299,400

380,438

Exercised

^[1]

(14,283)

(55,155)

(30,529)

(99,811)

Forfeited and expired

(2,227)

(18,737)

(6,669)

(19,827)

Outstanding, end of period

1,983,674

1,745,018

1,983,674

1,745,018

1,721,472

Exercisable, end of period

1,195,883

1,126,629

1,195,883

1,126,629

[1]

Stock Option Plan - Stock Option Activity (Parenthetical) (Details) - shares	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Options exercised for Number of Common Shares for cash	29,270	53,442
Common stock issued for cashless exercise	741	32,399
Cashless exercise of stock options	1,259	46,369

Stock Option Plan - Fair Value Assumptions for Stock Options (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Fair Value Assumptions For Stock Options [Abstract]
Average risk-free interest rate	1.44%	1.71%	1.60%	1.71%
Average expected term (in years)	6 years 1 month 21 days	6 years 15 days	6 years 2 months 23 days	6 years 2 months 23 days
Expected volatility	74.00%	75.00%	75.00%	75.00%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%

Stock Option Plan (Details) - $ / shares	6 Months Ended
Stock Option Plan (Details) - $ / shares	Jun. 30, 2016	Jun. 30, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Weighted-average fair value of options granted	$ 4.90	$ 11.96

Collaboration Agreements - Revenue Recognized from Collaborations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Collaboration Revenue [Line Items]
Collaboration revenue	$ 412	$ 4,044	$ 981	$ 8,054
Teva [Member] \| Recognition of Upfront Payment [Member] \| Collaborative Arrangement [Member]
Collaboration Revenue [Line Items]
Collaboration revenue		2,908		5,784
Teva [Member] \| Research Funding [Member] \| Collaborative Arrangement [Member]
Collaboration Revenue [Line Items]
Collaboration revenue	29	45	58	90
Genentech [Member] \| Recognition of Upfront Payment [Member] \| Collaborative Arrangement [Member]
Collaboration Revenue [Line Items]
Collaboration revenue		181	157	360
Genentech [Member] \| Research Funding [Member] \| Collaborative Arrangement [Member]
Collaboration Revenue [Line Items]
Collaboration revenue	$ 383	$ 910	$ 766	$ 1,820

Commitments and Contingencies (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015	Aug. 31, 2015
Unrecorded Unconditional Purchase Obligation [Line Items]
Prepaid expenses, long term	$ 632	$ 1,094
Medpace Clinical Development Service Agreement [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Service agreement, term	5 years
Committed service obligation			$ 7,000
Contractual obligation paid		3,000
Expenses for services rendered	$ 1,215
Current prepaid expenses	1,153	1,010
Prepaid expenses, long term	$ 632	$ 1,094

Related Parties (Details) - Medpace Clinical Development Service Agreement [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Related Party Transaction [Line Items]
Clinical development service fees to related parties	$ 568	$ 55	$ 941	$ 55
Prepaid Expenses	$ 1,996		$ 1,996		$ 2,314
Dr. August J. Troendle, Officer and Director [Member] \| Minimum [Member]
Related Party Transaction [Line Items]
Percentage of ownership	5.00%		5.00%