Keryx Biopharmaceuticals (KERX) 10-Q4 Nov 132013 Q3 Quarterly reportFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
Document and Entity Information	Sep. 30, 2013	Oct. 25, 2013
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Sep-13	'
Document Fiscal Year Focus	'2013	'
Document Fiscal Period Focus	'Q3	'
Trading Symbol	'KERX	'
Entity Registrant Name	'KERYX BIOPHARMACEUTICALS INC	'
Entity Central Index Key	'0001114220	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	82,316,467

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current assets:	'	'
Cash and cash equivalents	$67,738	$14,677
Interest receivable	156	'
Other current assets	3,671	430
Total current assets	71,565	15,107
Property, plant and equipment, net	71	56
Goodwill	3,208	3,208
Other assets, net	221	198
Total assets	75,065	18,569
Current liabilities:	'	'
Accounts payable and accrued expenses	15,863	7,212
Accrued compensation and related liabilities	632	827
Total current liabilities	16,495	8,039
Other liabilities	'	36
Total liabilities	16,495	8,075
Commitments and contingencies	'	'
Stockholders' equity:	'	'
Preferred stock, $0.001 par value per share (5,000,000 shares authorized, no shares issued and outstanding)	'	'
Common stock, $0.001 par value per share (130,000,000 and 95,000,000 shares authorized, 81,938,915 and 72,002,949 shares issued, 81,858,967 and 71,923,001 shares outstanding at September 30, 2013 and December 31, 2012, respectively)	82	72
Additional paid-in capital	480,517	403,387
Treasury stock, at cost, 79,948 shares at September 30, 2013 and December 31, 2012, respectively	-357	-357
Accumulated deficit	-421,672	-392,608
Total stockholders' equity	58,570	10,494
Total liabilities and stockholders' equity	$75,065	$18,569

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	'	'
Preferred stock, shares outstanding	'	'
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	130,000,000	95,000,000
Common stock, shares issued	81,938,915	72,002,949
Common stock, shares outstanding	81,858,967	71,923,001
Treasury stock, shares	79,948	79,948

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
License revenue	'	'	$7,000	'
Research and development:	'	'	'	'
Non-cash compensation	319	161	753	512
Other research and development	10,351	3,768	23,524	14,616
Total research and development	10,670	3,929	24,277	15,128
General and administrative:	'	'	'	'
Non-cash compensation	422	384	1,207	1,117
Other general and administrative	4,640	1,213	10,860	4,156
Total general and administrative	5,062	1,597	12,067	5,273
Total operating expenses	15,732	5,526	36,344	20,401
Operating loss	-15,732	-5,526	-29,344	-20,401
Interest and other income, net	81	51	280	1,669
Loss before income taxes and extraordinary gain	-15,651	-5,475	-29,064	-18,732
Income taxes	'	'	'	'
Loss before extraordinary gain	-15,651	-5,475	-29,064	-18,732
Extraordinary gain	'	'	'	2,639
Net loss	($15,651)	($5,475)	($29,064)	($16,093)
Basic and diluted net loss per common share:	'	'	'	'
Before extraordinary gain	($0.19)	($0.08)	($0.36)	($0.26)
Extraordinary gain	'	'	'	$0.04
Basic and diluted net loss per common share	($0.19)	($0.08)	($0.36)	($0.22)
Weighted average shares used in computing basic and diluted net loss per common share	81,823,415	71,910,817	80,531,785	71,535,561

Consolidated_Statement_of_Stoc

Consolidated Statement of Stockholders' Equity (USD $)	Total		Common stock		Additional paid-in Capital	Treasury stock	Accumulated deficit
In Thousands, except Share data, unless otherwise specified	Total		Common stock		Additional paid-in Capital	Treasury stock	Accumulated deficit
Beginning Balance at Dec. 31, 2012	$10,494		$72		$403,387	($357)	($392,608)
Beginning Balance (in shares) at Dec. 31, 2012	'		72,002,949		'	79,948	'
Changes during the period:	'		'		'	'	'
Issuance of common stock in public offering (net of offering costs of $5,640) (in shares)	'		9,469,100		'	'	'
Issuance of common stock in public offering (net of offering costs of $5,640)	74,753		10		74,743	'	'
Issuance of restricted stock (in shares)	'		366,020		'	'	'
Issuance of restricted stock	'	[1]	'	[1]	'	'	'
Forfeiture of restricted stock ( in shares )	'		-5,737		'	'	'
Forfeiture of restricted stock	'	[1]	'	[1]	'	'	'
Issuance of common stock in connection with exercise of options (in shares)	'		106,583		'	'	'
Issuance of common stock in connection with exercise of options	427		'		427	'	'
Compensation in respect of options and restricted stock granted to employees, directors and third-parties	1,960		'		1,960	'	'
Net loss	-29,064		'		'	'	-29,064
Ending Balance at Sep. 30, 2013	$58,570		$82		$480,517	($357)	($421,672)
Ending Balance (in shares) at Sep. 30, 2013	'		81,938,915		'	79,948	'

[1]	Amount less than one thousand dollars.

Consolidated_Statement_of_Stoc1

Consolidated Statement of Stockholders' Equity (Parenthetical) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013
Issuance of common stock in public offering, offering costs	$5,640

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
CASH FLOWS FROM OPERATING ACTIVITIES	'	'
Net loss	($29,064)	($16,093)
Adjustments to reconcile net loss to cash flows used in operating activities:	'	'
Stock compensation expense	1,960	1,629
Depreciation and amortization	34	27
Extraordinary gain	'	-2,639
Changes in assets and liabilities:	'	'
Increase in other current assets	-3,241	-24
(Increase) decrease in accrued interest receivable	-156	7
(Increase) decrease in other assets	-23	11
Increase (decrease) in accounts payable and accrued expenses	8,651	-1,745
Decrease in accrued compensation and related liabilities	-195	-335
Decrease in other liabilities	-36	-35
Net cash used in operating activities	-22,070	-19,197
CASH FLOWS FROM INVESTING ACTIVITIES	'	'
Purchases of property, plant and equipment	-49	-19
Investment in held-to-maturity short-term securities	-24,403	-11,263
Proceeds from maturity of held-to-maturity short-term securities	24,403	15,475
Net cash (used in) provided by investing activities	-49	4,193
CASH FLOWS FROM FINANCING ACTIVITIES	'	'
Proceeds from public offering, net	74,753	'
Proceeds from exercise of options	427	'
Net cash provided by financing activities	75,180	'
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	53,061	-15,004
Cash and cash equivalents at beginning of period	14,677	35,252
CASH AND CASH EQUIVALENTS AT END OF PERIOD	$67,738	$20,248

General

General	9 Months Ended
General	Sep. 30, 2013
General	'
	NOTE 1—GENERAL
	Basis of Presentation
	We are a biopharmaceutical company focused on the acquisition, development and commercialization of medically important pharmaceutical products for the treatment of renal disease. Most of our biopharmaceutical development and substantially all of our administrative operations during the three and nine months ended September 30, 2013 and 2012 were conducted in the United States of America.
	The accompanying unaudited consolidated financial statements were prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they may not include all of the information and footnotes required by GAAP for complete financial statements. All adjustments that are, in the opinion of management, of a normal recurring nature and are necessary for a fair presentation of the consolidated financial statements have been included. Nevertheless, these unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements contained in our Annual Report on Form 10-K for the year ended December 31, 2012. The results of operations for the three and nine months ended September 30, 2013, are not necessarily indicative of the results that may be expected for the entire fiscal year or any other interim period.
	Except for 2009, we have incurred substantial operating losses since our inception, and expect to continue to incur operating losses for the foreseeable future and may never become profitable. As of September 30, 2013, we have an accumulated deficit of $421.7 million.
	Our major sources of cash have been proceeds from various public and private offerings of our common stock, option and warrant exercises, interest income, and from the upfront and milestone payments from our Sublicense Agreement with Japan Tobacco Inc. (“JT”) and Torii Pharmaceutical Co., Ltd. (“Torii”) and miscellaneous payments from our other prior licensing activities. We have not yet commercialized any drug candidate and cannot be sure if we will ever be able to do so. Even if we commercialize a drug candidate, we may not become profitable. Our ability to achieve profitability depends on a number of factors, including our ability to obtain regulatory approval for our drug candidate, successfully complete any post-approval regulatory obligations and successfully manufacture and commercialize our drug candidate alone or in partnership. We may continue to incur substantial operating losses even if we begin to generate revenues from our drug candidate, if approved.
	In January 2013, we announced successful top-line results from the long-term Phase 3 study of Zerenex for the treatment of hyperphosphatemia in patients with end-stage renal disease on dialysis. Updated results were presented in June 2013 at the World Congress of Nephrology. In this study, Zerenex met the study’s primary and key secondary endpoints. This long-term study was the final component of our Phase 3 registration program, which was conducted pursuant to a Special Protocol Assessment (“SPA”) agreement with the U.S. Food and Drug Administration (“FDA”). In August 2013, we submitted a New Drug Application (“NDA”) to the FDA seeking approval for the marketing and sale of Zerenex. In October 2013, the FDA accepted our submission, filed the NDA for review and assigned our NDA a Prescription Drug User Fee Act (“PDUFA”) goal date of June 7, 2014.
	In January 2013, we received a non-refundable milestone payment from JT and Torii of $7.0 million for the achievement of their NDA filing milestone, which was included as license revenue in our consolidated statement of operations. See Note 4 for additional information.
	In January 2013, we raised approximately $74.8 million, net of underwriting discounts and offering expenses of approximately $5.6 million, in an underwritten public offering. We currently have a shelf registration statement on Form S-3 filed and declared effective by the SEC in August 2013, providing for the offering of up to $150 million of common stock and warrants in the aggregate. See Note 3 for additional information.

	We currently anticipate that our cash, cash equivalents, and interest receivable at September 30, 2013, exclusive of our anticipated milestone payments from JT and Torii, are sufficient to fund our anticipated operating cash requirements for approximately the next 12 to 15 months. The actual amount of cash that we will need to operate is subject to many factors, including, but not limited to, the timing and expenditures associated with the build-up of pre-launch/launch inventory and capacity expansion, the timing and expenditures associated with submitting the Marketing Authorization Application (“MAA”) in Europe for Zerenex and the respective regulatory review processes for our U.S. NDA and EU MAA, the timing and expenditures associated with pre-commercial/commercial activities related to Zerenex, and the timing, design and conduct of clinical trials for Zerenex. We may depend upon significant additional financings to provide the cash necessary to execute our current operations, including the commercialization of Zerenex.
	In accordance with the licensing arrangement with JT and Torii, we may receive payments upon the achievement of pre-specified milestones. The next potential milestone is for the marketing approval of ferric citrate in Japan.
	Our common stock is listed on the NASDAQ Capital Market and trades under the symbol “KERX.”
	Additional Member of the Board of Directors
	In September 2013, the Board of Directors increased the total number of board members to seven and appointed Daniel P. Regan as a director to fill the newly-created position.
	Cash and Cash Equivalents
	We treat liquid investments with original maturities of three months or less when purchased as cash and cash equivalents.
	Other Current Assets
	In July 2013, in accordance with The Federal Food, Drug, and Cosmetic Act (the “Act”), as amended by the Prescription Drug User Fee Amendments of 2012, we paid a fee of $2.0 million to the FDA related to our NDA filing. In October 2013, we received a full refund of the $2.0 million fee, following receipt of a waiver of the application user fee granted under the small business waiver provision of the Act. Accordingly, at September 30, 2013, the $2.0 million refund is reflected as a receivable in other current assets.
	Revenue Recognition
	We recognize license revenue in accordance with the revenue recognition guidance of the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (the “Codification”). We analyze each element of our licensing agreement to determine the appropriate revenue recognition. The terms of the license agreement may include payments to us of non-refundable up-front license fees, milestone payments if specified objectives are achieved, and/or royalties on product sales. We recognize revenue from upfront payments over the period of significant involvement under the related agreements unless the fee is in exchange for products delivered or services rendered that represent the culmination of a separate earnings process and no further performance obligation exists under the contract. We recognize milestone payments as revenue upon the achievement of specified milestones only if (1) the milestone payment is non-refundable, (2) substantive effort is involved in achieving the milestone, (3) the amount of the milestone is reasonable in relation to the effort expended or the risk associated with achievement of the milestone, and (4) the milestone is at risk for both parties. If any of these conditions are not met, we defer the milestone payment and recognize it as revenue over the estimated period of performance under the contract.
	Stock-Based Compensation
	We recognize all share-based payments to employees and to non-employee directors for service on our board of directors as compensation expense in the consolidated financial statements based on the grant date fair values of such payments. Stock-based compensation expense recognized each period is based on the value of the portion of share-based payment awards that is ultimately expected to vest during the period. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates.

	For share-based payments to consultants and other third-parties, compensation expense is determined at the “measurement date.” The expense is recognized over the vesting period of the award. Until the measurement date is reached, the total amount of compensation expense remains uncertain. We record compensation expense based on the fair value of the award at the reporting date. The awards to consultants and other third-parties are then revalued, or the total compensation is recalculated based on the then current fair value, at each subsequent reporting date.
	Income Taxes
	As of September 30, 2013, we have U.S. net operating loss carryforwards of approximately $388.4 million which expire from 2019 through 2033. We have established a 100% valuation allowance against our net deferred tax assets due to our history of pre-tax losses and the likelihood that the deferred tax assets will not be realizable. Due to our historical equity transactions, the utilization of certain tax loss carryforwards may be subject to annual limitations imposed by Internal Revenue Code Section 382 relating to the change of control provisions.
	We are not aware of any unrecorded tax liabilities which would impact our financial position or our results of operations.
	Net Loss Per Share
	Basic net loss per share is computed by dividing the losses allocable to common stockholders by the weighted average number of shares of common stock outstanding for the period. Diluted net loss per share does not reflect the effect of shares of common stock to be issued upon the exercise of stock options, as their inclusion would be anti-dilutive. The options outstanding as of September 30, 2013 and 2012, which are not included in the computation of net loss per share amounts, were 4,042,600 and 3,416,250, respectively.
	Comprehensive Loss
	Comprehensive loss is the same as net loss for all periods presented.
	Segment Reporting
	Following the discontinuation of the Services segment in December 2011, we have determined that we operate in only one reportable segment: the Products segment.
	Impairment of Goodwill
	Goodwill is reviewed for impairment annually, or when events arise that could indicate that an impairment exists. We test for goodwill impairment using a two-step process. The first step compares the fair value of the reporting unit with the unit’s carrying value, including goodwill. When the carrying value of the reporting unit is greater than fair value, the unit’s goodwill may be impaired, and the second step must be completed to measure the amount of the goodwill impairment charge, if any. In the second step, the implied fair value of the reporting unit’s goodwill is compared with the carrying amount of the unit’s goodwill. If the carrying amount is greater than the implied fair value, the carrying value of the goodwill must be written down to its implied fair value. As of December 31, 2012, management concluded that there was no impairment of our goodwill. As of September 30, 2013, management determined that there were no indicators that would trigger a goodwill impairment analysis.

Fair_Value_Measurements

Fair Value Measurements

9 Months Ended

Sep. 30, 2013

Fair Value Measurements

NOTE 2 – FAIR VALUE MEASUREMENTS

We measure certain financial assets and liabilities at fair value on a recurring basis in the financial statements. The hierarchy ranks the quality and reliability of inputs, or assumptions, used in the determination of fair value and requires financial assets and liabilities carried at fair value to be classified and disclosed in one of the following three categories:

•

Level 1 – quoted prices in active markets for identical assets and liabilities;

•

Level 2 – inputs other than Level 1 quoted prices that are directly or indirectly observable; and

•

Level 3 – unobservable inputs that are not corroborated by market data.

We review investment securities for impairment and to determine the classification of the impairment as temporary or other-than-temporary. Losses are recognized in our consolidated statement of operations when a decline in fair value is determined to be other-than-temporary. We review our investments on an ongoing basis for indications of possible impairment. Once identified, the determination of whether the impairment is temporary or other-than-temporary requires significant judgment.

The following table provides the fair value measurements of applicable financial assets as of September 30, 2013:

Financial assets at fair value

as of September 30, 2013

(in thousands)

Level 1

Level 2

Level 3

Money market funds (1)

24,852

—

Obligations of domestic governmental agencies (held-to-maturity) (2)

16,779

—

Total

41,631

—

-1

Included in cash and cash equivalents on our consolidated balance sheet. The carrying amount of money market funds is a reasonable estimate of fair value.

-2

Included in cash and cash equivalents on our consolidated balance sheet. Amortized cost approximates fair value.

Stockholders_Equity

Stockholders' Equity	9 Months Ended
Stockholders' Equity	Sep. 30, 2013
Stockholders' Equity	'
	NOTE 3 – STOCKHOLDERS’ EQUITY
	Common Stock
	We currently have a shelf registration statement on Form S-3 filed and declared effective by the Securities and Exchange Commission (“SEC”) in August 2013, providing for the offering of up to $150 million of common stock and warrants in the aggregate. We may offer the securities under our shelf registration statement from time to time in response to market conditions or other circumstances if we believe such a plan of financing is in our best interests and the best interests of our stockholders. We believe that this shelf registration statement provides us with the flexibility to efficiently raise additional capital to finance our operations as needed.
	On January 30, 2013, we announced the pricing of an underwritten public offering, whereby we sold 9,469,100 shares of our common stock at a price of $8.49 per share for gross proceeds of approximately $80.4 million. Net proceeds from this offering were approximately $74.8 million, net of underwriting discounts and offering expenses of approximately $5.6 million. The shares were sold under Registration Statements (Nos. 333-171517 and 333-186332) on Form S-3 and Form S-3MEF, respectively, as filed by us with the SEC.
	On June 18, 2013, at the 2013 Annual Meeting of Stockholders, the Company’s stockholders approved an amendment to the Company’s amended and restated certificate of incorporation increasing the shares of authorized common stock from 95,000,000 shares to 130,000,000 shares. The number of authorized shares of preferred stock remains unchanged at 5,000,000 shares.
	Equity Incentive Plans
	The 2013 Incentive Plan was adopted in June 2013 by our stockholders at our 2013 Annual Meeting of Stockholders. Under the 2013 Incentive Plan, the compensation committee of the Company’s board of directors is authorized to grant stock-based awards to directors, officers, employees and consultants. The 2013 Incentive Plan authorizes grants to purchase up to 3,500,000 shares of authorized but unissued common stock. The plan limits the term of each option to no more than 10 years from the date of their grant. As of September 30, 2013, up to an additional 3,458,000 shares may be issued under the 2013 Incentive Plan.
	Total shares available for the issuance of stock options or other stock-based awards under our stock option and incentive plans were 3,712,002 shares at September 30, 2013.

	Stock Options
	The following table summarizes stock option activity for the nine months ended September 30, 2013:


		Number			Weighted-			Weighted-			Aggregate
		of shares			average			average			intrinsic
					exercise			contractual			value
					price			term
								(in years)
	Outstanding at December 31, 2012		3,401,671		$	5.17			6.6		$	2,373,509
	Granted		757,366			5.34
	Exercised		(106,583	)		4.01					$	468,773

	Forfeited		(9,854	)		2.88
	Expired		—			—

	Outstanding at September 30, 2013		4,042,600		$	5.24			6.5		$	22,087,548

	Vested and expected to vest at September 30, 2013		4,004,646		$	5.24			6.5		$	21,873,039

	Exercisable at September 30, 2013		2,784,632		$	5.28			5.6		$	15,529,794

	Upon the exercise of stock options, we issue new shares of our common stock. As of September 30, 2013, 95,000 options issued to employees and 50,000 options issued to consultants are unvested, milestone-based options. On October 4, 2013, upon the filing acceptance of our NDA for Zerenex, 17,500 options issued to employees vested.
	Restricted Stock
	Certain employees, directors and consultants have been awarded restricted stock under our incentive plans. The time-vesting restricted stock grants vest primarily over a period of three to four years. The following table summarizes restricted share activity for the nine months ended September 30, 2013:


		Number of			Weighted			Aggregate
		shares			average			intrinsic
					grant date			value
					fair value
	Outstanding at December 31, 2012		1,181,677		$	2.27		$	3,095,994
	Granted		366,020			4.27
	Vested		(295,341	)		2.93		$	1,783,156

	Forfeited		(5,737	)		2.79

	Outstanding at September 30, 2013		1,246,619		$	2.7		$	12,578,386

	As of September 30, 2013, 590,000 and 150,000 shares of restricted stock issued to employees and consultants, respectively, are unvested, milestone-based shares. On October 4, 2013, upon the filing acceptance of our NDA for Zerenex, 200,000 and 50,000 shares of restricted stock issued to employees and consultants, respectively, vested.
	On September 14, 2009, we entered in an employment agreement with Ron Bentsur, our Chief Executive Officer, which was amended on January 13, 2012, and further amended on June 11, 2013. The agreement, as amended, terminates on May 20, 2015, subject to certain early termination events. As of September 30, 2013, Mr. Bentsur has been granted a total of 350,000 shares of restricted stock based on the achievement of certain milestone awards described in his employment agreement. In addition, as of September 30, 2013, Mr. Bentsur has the opportunity to earn certain milestone awards as follows:
	(1) 400,000 shares of restricted stock will be granted to Mr. Bentsur upon the first to occur of (a) our filing of an accepted new drug application, or NDA, with the U.S. Food and Drug Administration, or FDA, for Zerenex, or (b) our outlicensing of Zerenex in the U.S. to a third party. Such restricted stock will vest in equal installments over each of the first three anniversaries of the date of grant provided that Mr. Bentsur remains an employee during such vesting period. This milestone #1 may be achieved with respect to NDAs or qualifying outlicenses for multiple indications of the same product, but not for subsequent outlicenses of the product relating to an indication for which the milestone is met. Upon achievement of milestone #2 below with respect to a product, the restricted stock granted for one indication of the product under milestone #1 above will vest in full.

	(2) 500,000 shares of fully vested common stock will be granted to Mr. Bentsur, upon the first to occur of (a) our first commercial sale of Zerenex in the U.S. off an approved NDA, (b) our receipt of the first royalty upon the commercial sale of Zerenex in the U.S. by a partner to whom we have sold exclusive or non-exclusive commercial rights, or (c) our complete outlicensing of the entire product rights of Zerenex in the U.S.
	(3) 100,000 shares of restricted stock will be granted to Mr. Bentsur upon each event of our outlicensing Zerenex in a foreign market, other than Japan, resulting in a greater than $10 million non-refundable cash payment to us with a gross deal value to us of at least $50 million. Such restricted stock will vest in equal installments over each of the first three anniversaries of the date of grant, provided that Mr. Bentsur remains an employee during such vesting period.
	On October 4, 2013, upon achievement of the first milestone, listed above, relating to the filing of an accepted NDA with the FDA for Zerenex, Mr. Bentsur was granted 400,000 shares of restricted stock.
	Stock-Based Compensation
	We incurred $741,000 and $545,000 of non-cash compensation expense related to equity incentive grants during the three months ended September 30, 2013 and 2012, respectively, and $1,960,000 and $1,629,000 during the nine months ended September 30, 2013 and 2012, respectively. The fair value of stock options granted is estimated at the date of grant using the Black-Scholes pricing model. The expected term of options granted is derived from historical data and the expected vesting period. Expected volatility is based on the historical volatility of our common stock. The risk-free interest rate is based on the U.S. Treasury yield for a period consistent with the expected term of the option in effect at the time of the grant. We have assumed no expected dividend yield, as dividends have never been paid to stock or option holders and will not be paid for the foreseeable future.


	Black-Scholes Option Valuation Assumptions	Three months ended September 30,						Nine months ended September 30,
		2013			2012			2013			2012
	Risk-free interest rates		1.1	%		0.5	%		0.6	%		0.6	%
	Dividend yield		—			—			—			—
Volatility		100	%		111.7	%		102.6	%		111.2	%
Weighted-average expected term		4.0 years			4.0 years			3.8 years			4.0 years
The weighted average grant date fair value of options granted for the three months ended September 30, 2013 and 2012 was $6.74 and $2.09 per option, respectively, and for the nine months ended September 30, 2013 and 2012 was $3.62 and $1.73 per option. We used historical information to estimate forfeitures within the valuation model. As of September 30, 2013, there was $2.8 million and $1.6 million of total unrecognized compensation cost related to non-vested stock options and restricted stock, respectively, which is expected to be recognized over weighted-average periods of 2.1 years and 2.2 years, respectively. These amounts do not include, as of September 30, 2013, 145,000 options outstanding and 740,000 shares of restricted stock outstanding which are milestone-based and vest upon certain corporate milestones, such as NDA filing acceptance and FDA approval of our drug candidates and change in control. Stock-based compensation will be measured and recorded if and when a milestone occurs. On October 4, 2013, upon the filing acceptance of our NDA for Zerenex, 17,500 options and 250,000 shares of restricted stock vested. We will incur approximately $1.2 million and $1.6 million of non-cash compensation expenses in research and development and general and administrative expenses, respectively, in the fourth quarter of 2013, associated with the vesting of these equity awards.

License_Agreements

License Agreements	9 Months Ended
License Agreements	Sep. 30, 2013
License Agreements	'
	NOTE 4—LICENSE AGREEMENTS
	In September 2007, we entered into a Sublicense Agreement with JT and Torii, JT’s pharmaceutical business subsidiary, under which JT and Torii obtained the exclusive sublicense rights for the development and commercialization of ferric citrate in Japan, which is being developed in the U.S. under the trade name Zerenex. JT and Torii are responsible for the future development and commercialization costs in Japan. Effective as of June 8, 2009, we entered into an Amended and Restated Sublicense Agreement (the “Revised Agreement”) with JT and Torii, which, among other things, provided for the elimination of all significant on-going obligations under the sublicense agreement.

	In January 2013, JT and Torii filed its NDA with the Japanese Ministry of Health, Labour and Welfare for marketing approval of ferric citrate in Japan for the treatment of hyperphosphatemia in patients with chronic kidney disease, or CKD. Under the terms of the license agreement with JT and Torii, we received a non-refundable milestone payment of $7.0 million in January 2013 for the achievement of their NDA filing milestone. As a result, we recorded license revenue of $7.0 million in accordance with our revenue recognition policy, which is included in the nine months ended September 30, 2013. We may receive up to an additional $65.0 million in payments upon the achievement of pre-specified milestones. In addition, upon commercialization, JT and Torii will make royalty payments to us on net sales of ferric citrate in Japan.

Legal_Proceedings

Legal Proceedings	9 Months Ended
Legal Proceedings	Sep. 30, 2013
Legal Proceedings	'
	NOTE 5—LEGAL PROCEEDINGS
	On February 1, 2013, a lawsuit was filed against us and our chief executive officer on behalf of a putative class of all of our shareholders (other than the defendants) who acquired our shares between June 1, 2009 and April 1, 2012. Smith v. Keryx Biopharmaceuticals, Inc., et al., Case No. 1:13-CV-0755-TPG (S.D.N.Y.). On February 26, 2013, a substantially similar lawsuit was filed against us and our chief executive officer as well as our chief financial officer. Park v. Keryx Biopharmaceuticals, Inc., et al., Case No. 1:13-CV-1307-TPG (S.D.N.Y.). On June 10, 2013, the Court entered an Order consolidating the two lawsuits and appointing a lead plaintiff. The case is now styled In re Keryx Biopharmaceuticals, Inc. Securities Litigation, Case No. 1:13-CV-0755-KBF (S.D.N.Y.). On July 10, 2013, the lead plaintiff filed a Consolidated Amended Complaint that, in substance, repeated the claims alleged in the consolidated lawsuits. The Consolidated Amended Complaint asserts claims against (i) us for alleged violations of Section 10(b) of the Securities Exchange Act of 1934 (“Exchange Act”) and Rule 10b-5 promulgated thereunder and (ii) our chief executive officer for alleged violations of Sections 10(b) and 20(a) of the Exchange Act and Rule 10b-5. The claims in the Consolidated Amended Complaint are premised on general allegations that we and the individual defendant participated directly or indirectly in the preparation and/or issuance of purportedly false and misleading earnings reports, SEC filings, press releases, and other public statements, which allegedly caused our stock to trade at artificially inflated prices. The lead plaintiff seeks an unspecified amount of damages. On August 26, 2013, we filed a motion to dismiss the Consolidated Amended Complaint. On October 10, 2013, lead plaintiff filed an opposition to our motion to dismiss. Our reply in further support of our motion to dismiss is presently due on November 11, 2013. We believe the claims made in this action are without merit, and intend to defend the consolidated action vigorously. We cannot, however, predict the outcome or effect, if any, of the lawsuit on our business.

General_Policies

General (Policies)	9 Months Ended
General (Policies)	Sep. 30, 2013
Basis of Presentation	'
	Basis of Presentation
	We are a biopharmaceutical company focused on the acquisition, development and commercialization of medically important pharmaceutical products for the treatment of renal disease. Most of our biopharmaceutical development and substantially all of our administrative operations during the three and nine months ended September 30, 2013 and 2012 were conducted in the United States of America.
	The accompanying unaudited consolidated financial statements were prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they may not include all of the information and footnotes required by GAAP for complete financial statements. All adjustments that are, in the opinion of management, of a normal recurring nature and are necessary for a fair presentation of the consolidated financial statements have been included. Nevertheless, these unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements contained in our Annual Report on Form 10-K for the year ended December 31, 2012. The results of operations for the three and nine months ended September 30, 2013, are not necessarily indicative of the results that may be expected for the entire fiscal year or any other interim period.
	Except for 2009, we have incurred substantial operating losses since our inception, and expect to continue to incur operating losses for the foreseeable future and may never become profitable. As of September 30, 2013, we have an accumulated deficit of $421.7 million.
	Our major sources of cash have been proceeds from various public and private offerings of our common stock, option and warrant exercises, interest income, and from the upfront and milestone payments from our Sublicense Agreement with Japan Tobacco Inc. (“JT”) and Torii Pharmaceutical Co., Ltd. (“Torii”) and miscellaneous payments from our other prior licensing activities. We have not yet commercialized any drug candidate and cannot be sure if we will ever be able to do so. Even if we commercialize a drug candidate, we may not become profitable. Our ability to achieve profitability depends on a number of factors, including our ability to obtain regulatory approval for our drug candidate, successfully complete any post-approval regulatory obligations and successfully manufacture and commercialize our drug candidate alone or in partnership. We may continue to incur substantial operating losses even if we begin to generate revenues from our drug candidate, if approved.
	In January 2013, we announced successful top-line results from the long-term Phase 3 study of Zerenex for the treatment of hyperphosphatemia in patients with end-stage renal disease on dialysis. Updated results were presented in June 2013 at the World Congress of Nephrology. In this study, Zerenex met the study’s primary and key secondary endpoints. This long-term study was the final component of our Phase 3 registration program, which was conducted pursuant to a Special Protocol Assessment (“SPA”) agreement with the U.S. Food and Drug Administration (“FDA”). In August 2013, we submitted a New Drug Application (“NDA”) to the FDA seeking approval for the marketing and sale of Zerenex. In October 2013, the FDA accepted our submission, filed the NDA for review and assigned our NDA a Prescription Drug User Fee Act (“PDUFA”) goal date of June 7, 2014.
	In January 2013, we received a non-refundable milestone payment from JT and Torii of $7.0 million for the achievement of their NDA filing milestone, which was included as license revenue in our consolidated statement of operations. See Note 4 for additional information.
	In January 2013, we raised approximately $74.8 million, net of underwriting discounts and offering expenses of approximately $5.6 million, in an underwritten public offering. We currently have a shelf registration statement on Form S-3 filed and declared effective by the SEC in August 2013, providing for the offering of up to $150 million of common stock and warrants in the aggregate. See Note 3 for additional information.

	We currently anticipate that our cash, cash equivalents, and interest receivable at September 30, 2013, exclusive of our anticipated milestone payments from JT and Torii, are sufficient to fund our anticipated operating cash requirements for approximately the next 12 to 15 months. The actual amount of cash that we will need to operate is subject to many factors, including, but not limited to, the timing and expenditures associated with the build-up of pre-launch/launch inventory and capacity expansion, the timing and expenditures associated with submitting the Marketing Authorization Application (“MAA”) in Europe for Zerenex and the respective regulatory review processes for our U.S. NDA and EU MAA, the timing and expenditures associated with pre-commercial/commercial activities related to Zerenex, and the timing, design and conduct of clinical trials for Zerenex. We may depend upon significant additional financings to provide the cash necessary to execute our current operations, including the commercialization of Zerenex.
	In accordance with the licensing arrangement with JT and Torii, we may receive payments upon the achievement of pre-specified milestones. The next potential milestone is for the marketing approval of ferric citrate in Japan.
	Our common stock is listed on the NASDAQ Capital Market and trades under the symbol “KERX.”
Additional Member of the Board of Directors	'
	Additional Member of the Board of Directors
	In September 2013, the Board of Directors increased the total number of board members to seven and appointed Daniel P. Regan as a director to fill the newly-created position.
Cash and Cash Equivalents	'
	Cash and Cash Equivalents
	We treat liquid investments with original maturities of three months or less when purchased as cash and cash equivalents.
Other Current Assets	'
	Other Current Assets
	In July 2013, in accordance with The Federal Food, Drug, and Cosmetic Act (the “Act”), as amended by the Prescription Drug User Fee Amendments of 2012, we paid a fee of $2.0 million to the FDA related to our NDA filing. In October 2013, we received a full refund of the $2.0 million fee, following receipt of a waiver of the application user fee granted under the small business waiver provision of the Act. Accordingly, at September 30, 2013, the $2.0 million refund is reflected as a receivable in other current assets.
Revenue Recognition	'
	Revenue Recognition
	We recognize license revenue in accordance with the revenue recognition guidance of the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (the “Codification”). We analyze each element of our licensing agreement to determine the appropriate revenue recognition. The terms of the license agreement may include payments to us of non-refundable up-front license fees, milestone payments if specified objectives are achieved, and/or royalties on product sales. We recognize revenue from upfront payments over the period of significant involvement under the related agreements unless the fee is in exchange for products delivered or services rendered that represent the culmination of a separate earnings process and no further performance obligation exists under the contract. We recognize milestone payments as revenue upon the achievement of specified milestones only if (1) the milestone payment is non-refundable, (2) substantive effort is involved in achieving the milestone, (3) the amount of the milestone is reasonable in relation to the effort expended or the risk associated with achievement of the milestone, and (4) the milestone is at risk for both parties. If any of these conditions are not met, we defer the milestone payment and recognize it as revenue over the estimated period of performance under the contract.
Stock-Based Compensation	'
	Stock-Based Compensation
	We recognize all share-based payments to employees and to non-employee directors for service on our board of directors as compensation expense in the consolidated financial statements based on the grant date fair values of such payments. Stock-based compensation expense recognized each period is based on the value of the portion of share-based payment awards that is ultimately expected to vest during the period. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates.

	For share-based payments to consultants and other third-parties, compensation expense is determined at the “measurement date.” The expense is recognized over the vesting period of the award. Until the measurement date is reached, the total amount of compensation expense remains uncertain. We record compensation expense based on the fair value of the award at the reporting date. The awards to consultants and other third-parties are then revalued, or the total compensation is recalculated based on the then current fair value, at each subsequent reporting date.
Income Taxes	'
	Income Taxes
	As of September 30, 2013, we have U.S. net operating loss carryforwards of approximately $388.4 million which expire from 2019 through 2033. We have established a 100% valuation allowance against our net deferred tax assets due to our history of pre-tax losses and the likelihood that the deferred tax assets will not be realizable. Due to our historical equity transactions, the utilization of certain tax loss carryforwards may be subject to annual limitations imposed by Internal Revenue Code Section 382 relating to the change of control provisions.
	We are not aware of any unrecorded tax liabilities which would impact our financial position or our results of operations.
Net Loss Per Share	'
	Net Loss Per Share
	Basic net loss per share is computed by dividing the losses allocable to common stockholders by the weighted average number of shares of common stock outstanding for the period. Diluted net loss per share does not reflect the effect of shares of common stock to be issued upon the exercise of stock options, as their inclusion would be anti-dilutive. The options outstanding as of September 30, 2013 and 2012, which are not included in the computation of net loss per share amounts, were 4,042,600 and 3,416,250, respectively.
Comprehensive Loss	'
	Comprehensive Loss
	Comprehensive loss is the same as net loss for all periods presented.
Segment Reporting	'
	Segment Reporting
	Following the discontinuation of the Services segment in December 2011, we have determined that we operate in only one reportable segment: the Products segment.
Impairment of Goodwill	'
	Impairment of Goodwill
	Goodwill is reviewed for impairment annually, or when events arise that could indicate that an impairment exists. We test for goodwill impairment using a two-step process. The first step compares the fair value of the reporting unit with the unit’s carrying value, including goodwill. When the carrying value of the reporting unit is greater than fair value, the unit’s goodwill may be impaired, and the second step must be completed to measure the amount of the goodwill impairment charge, if any. In the second step, the implied fair value of the reporting unit’s goodwill is compared with the carrying amount of the unit’s goodwill. If the carrying amount is greater than the implied fair value, the carrying value of the goodwill must be written down to its implied fair value. As of December 31, 2012, management concluded that there was no impairment of our goodwill. As of September 30, 2013, management determined that there were no indicators that would trigger a goodwill impairment analysis.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
Fair Value Measurements (Tables)	Sep. 30, 2013
Fair Value Measurements of Financial Assets	'
	The following table provides the fair value measurements of applicable financial assets as of September 30, 2013:


			Financial assets at fair value
			as of September 30, 2013
	(in thousands)		Level 1		Level 2		Level 3
	Money market funds (1)		$	24,852	$	—	$	—
	Obligations of domestic governmental agencies (held-to-maturity) (2)			16,779		—		—

	Total		$	41,631	$	—	$	—


	-1	Included in cash and cash equivalents on our consolidated balance sheet. The carrying amount of money market funds is a reasonable estimate of fair value.
	-2	Included in cash and cash equivalents on our consolidated balance sheet. Amortized cost approximates fair value.

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	9 Months Ended
Stockholders' Equity (Tables)	Sep. 30, 2013
Summary of Stock Option Activity	'
	The following table summarizes stock option activity for the nine months ended September 30, 2013:


		Number			Weighted-			Weighted-			Aggregate
		of shares			average			average			intrinsic
					exercise			contractual			value
					price			term
								(in years)
	Outstanding at December 31, 2012		3,401,671		$	5.17			6.6		$	2,373,509
	Granted		757,366			5.34
	Exercised		(106,583	)		4.01					$	468,773

	Forfeited		(9,854	)		2.88
	Expired		—			—

	Outstanding at September 30, 2013		4,042,600		$	5.24			6.5		$	22,087,548

	Vested and expected to vest at September 30, 2013		4,004,646		$	5.24			6.5		$	21,873,039

	Exercisable at September 30, 2013		2,784,632		$	5.28			5.6		$	15,529,794

Summary of Restricted Share Activity	'
	The following table summarizes restricted share activity for the nine months ended September 30, 2013:


		Number of			Weighted			Aggregate
		shares			average			intrinsic
					grant date			value
					fair value
	Outstanding at December 31, 2012		1,181,677		$	2.27		$	3,095,994
	Granted		366,020			4.27
	Vested		(295,341	)		2.93		$	1,783,156

	Forfeited		(5,737	)		2.79

	Outstanding at September 30, 2013		1,246,619		$	2.7		$	12,578,386

Black-Scholes Option Valuation Assumptions	'

	Black-Scholes Option Valuation Assumptions	Three months ended September 30,						Nine months ended September 30,
		2013			2012			2013			2012
	Risk-free interest rates		1.1	%		0.5	%		0.6	%		0.6	%
	Dividend yield		—			—			—			—
	Volatility		100	%		111.7	%		102.6	%		111.2	%
	Weighted-average expected term		4.0 years			4.0 years			3.8 years			4.0 years

General_Additional_Information

General - Additional Information (Detail) (USD $)	1 Months Ended			9 Months Ended				1 Months Ended	9 Months Ended		1 Months Ended
	Aug. 31, 2013	Jul. 31, 2013	Jan. 31, 2013	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013	Oct. 31, 2013	Sep. 30, 2013	Sep. 30, 2013	Jan. 30, 2013
				Person			Other Current Assets	Subsequent Event	Maximum	Minimum	Public offering
				Segment
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Accumulated deficit	'	'	'	($421,672,000)	'	($392,608,000)	'	'	'	'	'
License agreements, non-refundable milestone payment received	'	'	7,000,000	'	'	'	'	'	'	'	'
Proceeds from public offering, net	'	'	'	74,753,000	'	'	'	'	'	'	74,753,000
Underwriting discounts and offering expenses	'	'	'	5,640,000	'	'	'	'	'	'	5,640,000
Shelf registration statements, offering maximum amount of common stock and warrant	150,000,000	'	'	'	'	'	'	'	'	'	'
Cash, cash equivalents and interest receivable, anticipated sufficient period to fund cash requirements	'	'	'	'	'	'	'	'	'15 months	'12 months	'
Number of board members	'	'	'	7	'	'	'	'	'	'	'
Liquid investments, original maturities	'	'	'	'	'	'	'	'	'3 months	'	'
Prescription Drug User fee paid to FDA related to NDA filing	'	2,000,000	'	'	'	'	'	'	'	'	'
Proceed from full refund of fee	'	'	'	'	'	'	'	2,000,000	'	'	'
Prescription Drug User fee paid, refund receivable	'	'	'	'	'	'	2,000,000	'	'	'	'
Net operating loss carryforwards	'	'	'	388,400,000	'	'	'	'	'	'	'
Net operating loss carryforwards, expiration period	'	'	'	'	'	'	'	'	'2033	'2019	'
Net operating loss carryforwards, valuation allowance percentage	'	'	'	100.00%	'	'	'	'	'	'	'
Option and warrant outstanding, not included in computation of net loss per share amount	'	'	'	4,042,600	3,416,250	'	'	'	'	'	'
Reportable segment	'	'	'	1	'	'	'	'	'	'	'
Impairment of goodwill	'	'	'	$0	'	'	'	'	'	'	'

Fair_Value_Measurements_of_Fin

Fair Value Measurements of Financial Assets (Detail) (Level 1, USD $)	Sep. 30, 2013
In Thousands, unless otherwise specified	Sep. 30, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'
Financial assets at fair value	$41,631
Money market funds	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'
Financial assets at fair value	24,852	[1]
Obligations of domestic governmental agencies \| Held-to-maturity Securities	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'
Financial assets at fair value	$16,779	[2]

[1]	Included in cash and cash equivalents on our consolidated balance sheet. The carrying amount of money market funds is a reasonable estimate of fair value.
[2]	Included in cash and cash equivalents on our consolidated balance sheet. Amortized cost approximates fair value.

Stockholders_Equity_Additional

Stockholders' Equity - Additional Information (Detail) (USD $)

1 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

1 Months Ended

9 Months Ended

1 Months Ended

9 Months Ended

1 Months Ended

9 Months Ended

1 Months Ended

Aug. 31, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Jun. 18, 2013

Dec. 31, 2012

Jun. 18, 2013

Sep. 30, 2013

Dec. 31, 2013

Sep. 30, 2013

Oct. 04, 2013

Sep. 30, 2013

Dec. 31, 2012

Oct. 04, 2013

Sep. 30, 2013

Oct. 04, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Oct. 04, 2013

Sep. 30, 2013

Jan. 30, 2013

Before Amendment

After Amendment

Chief Executive Officer

Scenario 1

Scenario 2

Scenario 3

Scenario Forecast

Employee Stock Option

Restricted Stock

Stock Option

Minimum

Maximum

Unvested Milestone-Based Options

Unvested milestone-based employee awards

Unvested milestone based consultant awards

Milestone-based and vest upon certain corporate milestones

Incentive Plan 2013

Public offering

Subsequent Event

Chief Executive Officer

Scenario 1

Scenario 3

Employee Stock Option

Non Employee Stock Options

Restricted Stock

Stock Option

Maximum

Chief Executive Officer

Employees

Non Employees

Subsequent Event

Stockholders Equity Note [Line Items]

Shelf registration statements, offering maximum amount of common stock and warrant

$150,000,000

Shares issued in public offering

9,469,100

Share price

$8.49

Proceeds from public offering, gross

80,400,000

Proceeds from public offering, net

74,753,000

Underwriting discounts and offering expenses

5,640,000

Common stock, shares authorized

130,000,000

95,000,000

130,000,000

Preferred stock, shares authorized

5,000,000

Plan authorizes grants to purchase common stock

3,500,000

Share based compensation arrangement by share based payment award contractual term

'10 years

Shares available for the issuance of stock options

3,712,002

3,458,000

Number of options

4,042,600

3,401,671

95,000

50,000

145,000

Number of stock options vested

17,500

Restricted stock granted, vesting period

'3 years

'4 years

'3 years

Restricted stock issued

1,246,619

1,181,677

590,000

150,000

740,000

Number of shares of Restricted stock vested

295,341

250,000

200,000

50,000

Number of shares of restricted stock granted

350,000

400,000

Employment agreement, termination date

'2015-05-20

Number of shares of restricted stock to be granted

400,000

500,000

100,000

Minimum non-refundable cash payment from outlicensing Zerenex in foreign market other than Japan to trigger granting of 100,000 shares of restricted stock

10,000,000

Gross deal value from outlicensing Zerenex in foreign market other than Japan to trigger granting of 100,000 shares of restricted stock

50,000,000

Non cash compensation expense related to equity incentive granted

741,000

545,000

1,960,000

1,629,000

Weighted average grant date fair value of options granted

$6.74

$2.09

$3.62

$1.73

Total unrecognized compensation cost related to non-vest stock options

2,800,000

Total unrecognized compensation cost related to restricted stock

1,600,000

Weighted average recognition periods for unrecognized compensation cost

'2 years 1 month 6 days

'2 years 2 months 12 days

Non-cash compensation expense, research and development

319,000

161,000

753,000

512,000

1,200,000

Non-cash compensation expense, general and administrative

$422,000

$384,000

$1,207,000

$1,117,000

$1,600,000

Summary_of_Stock_Option_Activi

Summary of Stock Option Activity (Detail) (Stock Option, USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Stock Option	'	'
Number of shares	'	'
Outstanding at beginning of period	3,401,671	'
Granted	757,366	'
Exercised	-106,583	'
Forfeited	-9,854	'
Expired	'	'
Outstanding at end of period	4,042,600	3,401,671
Vested and expected to vest at September 30, 2013	4,004,646	'
Exercisable at September 30, 2013	2,784,632	'
Weighted-average exercise price	'	'
Outstanding at beginning of period	$5.17	'
Granted	$5.34	'
Exercised	$4.01	'
Forfeited	$2.88	'
Expired	'	'
Outstanding at end of period	$5.24	$5.17
Vested and expected to vest at September 30, 2013	$5.24	'
Exercisable at September 30, 2013	$5.28	'
Weighted-average contractual term	'	'
Outstanding	'6 years 6 months	'6 years 7 months 6 days
Vested and expected to vest at September 30, 2013	'6 years 6 months	'
Exercisable at September 30, 2013	'5 years 7 months 6 days	'
Aggregate intrinsic value	'	'
Outstanding at beginning of period	$2,373,509	'
Exercised	468,773	'
Outstanding at end of period	22,087,548	2,373,509
Vested and expected to vest at September 30, 2013	21,873,039	'
Exercisable at September 30, 2013	$15,529,794	'

Summary_of_Restricted_Share_Ac

Summary of Restricted Share Activity (Detail) (Restricted Stock, USD $)	9 Months Ended
	Sep. 30, 2013
Restricted Stock	'
Number of shares	'
Outstanding at beginning of period	1,181,677
Granted	366,020
Vested	-295,341
Forfeited	-5,737
Outstanding at end of period	1,246,619
Weighted average grant date fair value	'
Outstanding at beginning of period	$2.27
Granted	$4.27
Vested	$2.93
Forfeited	$2.79
Outstanding at end of period	$2.70
Aggregate intrinsic value	'
Outstanding at beginning of period	$3,095,994
Vested	$1,783,156
Outstanding at end of period	$12,578,386

Black_Scholes_Option_Valuation

Black Scholes Option Valuation Assumptions (Detail)	3 Months Ended		9 Months Ended
Black Scholes Option Valuation Assumptions (Detail)	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Risk-free interest rates	1.10%	0.50%	0.60%	0.60%
Dividend yield	'	'	'	'
Volatility	100.00%	111.70%	102.60%	111.20%
Weighted-average expected term	'4 years	'4 years	'3 years 9 months 18 days	'4 years

License_Agreements_Additional_

License Agreements - Additional Information (Detail) (USD $)	1 Months Ended	9 Months Ended
	Jan. 31, 2013	Sep. 30, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]	'	'
License agreements, non-refundable milestone payment received	$7,000,000	'
License revenue	'	7,000,000
License agreements, potential milestone receivable	'	$65,000,000