Esperion Therapeutics (ESPR) 10-K13 Mar 142013 FY Annual reportFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information (USD $)	0 Months Ended	12 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 01, 2014	Dec. 31, 2013	Jul. 02, 2013
Document and Entity Information	'	'	'
Entity Registrant Name	'	'Esperion Therapeutics, Inc.	'
Entity Central Index Key	'	'0001434868	'
Document Type	'	'10-K	'
Document Period End Date	'	31-Dec-13	'
Amendment Flag	'	'false	'
Current Fiscal Year End Date	'	'--12-31	'
Entity Well-known Seasoned Issuer	'	'No	'
Entity Voluntary Filers	'	'No	'
Entity Current Reporting Status	'	'Yes	'
Entity Filer Category	'	'Non-accelerated Filer	'
Entity Public Float	'	'	$204.60
Entity Common Stock, Shares Outstanding	15,394,226	'	'
Document Fiscal Year Focus	'	'2013	'
Document Fiscal Period Focus	'	'FY	'
Entity Listing, Par Value Per Share	$0.00	'	'

Balance_Sheets

Balance Sheets (USD $)	Dec. 31, 2013	Dec. 31, 2012
Current assets:	'	'
Cash and cash equivalents	$56,537,361	$6,511,521
Short-term Investments	3,525,123	'
Prepaid clinical development costs	195,652	367,216
Other prepaid and current assets	361,513	259,669
Total current assets	60,619,649	7,138,406
Property and equipment, net	80,808	120,210
Intangible assets	55,740	53,825
Long-term investments	17,537,663	'
Total assets	78,293,860	7,312,441
Current liabilities:	'	'
Short term borrowings with related parties, net of debt discount	'	15,241,007
Accrued interest	'	738,192
Accounts payable	2,231,890	476,277
Accrued clinical development costs	883,465	242,171
Warrant liabilities	'	265,323
Other accrued liabilities	1,087,136	210,329
Total current liabilities	4,202,491	17,173,299
Long-term debt	'	7,528,845
Total liabilities	4,202,491	24,702,144
Commitments and contingencies (Note 6)	'	'
Stockholders' equity (deficit):	'	'
Preferred stock, $0.001 par value; 5,000,000 shares authorized and no shares issued or outstanding as of December 31, 2013; no shares authorized, issued or outstanding as of December 31, 2012.	'	'
Common stock, $0.001 par value; 120,000,000 shares authorized as of December 31, 2013 and 50,000,000 shares authorized as of December 31, 2012, respectively; 15,357,413 shares issued and 15,340,710 outstanding at December 31, 2013 and 346,478 shares issued and outstanding at December 31, 2012	15,357	346
Additional paid-in capital	142,142,204	609,976
Accumulated other comprehensive income	-3,034	'
Deficit accumulated during the development stage	-68,063,158	-41,975,025
Total stockholders' equity (deficit)	74,091,369	-41,364,703
Total liabilities, convertible preferred stock and stockholders' equity (deficit)	78,293,860	7,312,441
Series A preferred stock	'	'
Convertible preferred stock:	'	'
Series A preferred stock par value $0.001; no shares authorized, issued or outstanding as of December 31, 2013; 34,785,000 shares authorized and 23,975,000 shares issued and outstanding at December 31, 2012, aggregate liquidation preference of $23,975,000 at December 31, 2012	'	$23,975,000

Balance_Sheets_Parenthetical

Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Series A preferred stock	Series A preferred stock
Preferred stock, par value (in dollars per share)	'	'	$0.00	$0.00
Preferred stock, shares authorized	'	'	0	'
Preferred stock, shares issued	'	'	0	23,975,000
Preferred stock, shares outstanding	'	'	0	23,975,000
Preferred stock, aggregate liquidation preference (in dollars)	'	'	'	$23,975,000
Preferred stock, par value (in dollars per share)	$0.00	$0.00	'	'
Preferred stock, shares authorized	5,000,000	0	'	34,785,000
Preferred stock, shares issued	0	0	'	'
Preferred stock, shares outstanding	0	0	'	'
Common stock, par value (in dollars per share)	$0.00	$0.00	'	'
Common stock, shares authorized	120,000,000	50,000,000	'	'
Common stock, shares issued	15,357,413	346,478	'	'
Common stock, shares outstanding	15,340,710	346,478	'	'

Statements_of_Operations_and_C

Statements of Operations and Comprehensive Loss (USD $)	12 Months Ended			71 Months Ended
Statements of Operations and Comprehensive Loss (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Statements of Operations and Comprehensive Loss	'	'	'	'
Grant income	'	'	'	$244,479
Operating expenses:	'	'	'	'
Research and development	16,014,205	7,998,128	7,807,702	43,428,066
General and administrative	6,744,493	2,205,632	2,356,669	18,194,189
Acquired in-process research and development	'	'	'	85,612
Total operating expenses	22,758,698	10,203,760	10,164,371	61,707,867
Loss from operations	-22,758,698	-10,203,760	-10,164,371	-61,463,388
Interest expense	-936,580	-1,486,696	-577,157	-4,320,696
Change in fair value of warrant liability	-2,586,865	32,367	0	-2,554,498
Other income (expense), net	194,010	-83,647	-75,813	275,424
Net loss	-26,088,133	-11,741,736	-10,817,341	-68,063,158
Net loss per common share (basic and diluted) (in dollars per share)	($3.31)	($36.31)	($36.22)	'
Weighted-average shares outstanding (basic and diluted)	7,885,921	323,382	298,689	'
Other comprehensive loss:	'	'	'	'
Unrealized loss on investments	-3,034	'	'	-3,034
Total comprehensive loss	($26,091,167)	($11,741,736)	($10,817,341)	($68,066,192)

Statements_of_Convertible_Pref

Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (USD $)	Total	Series A Convertible Preferred Stock	Series A 1 Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Deficit Accumulated During the Development Stage	Accumulated Other Comprehensive Loss
Balance at Jan. 21, 2008	'	'	'	'	'	'	'
Increase (Decrease) in Temporary Equity	'	'	'	'	'	'	'
Issuance of preferred stock in exchange for convertible promissory notes, net of issuance costs	'	$250,000	'	'	'	'	'
Issuance of preferred stock in exchange for convertible promissory notes, net of issuance costs (in shares)	'	250,000	'	'	'	'	'
Issuance of Series A preferred stock, net of issuance costs	'	17,025,000	'	'	'	'	'
Issuance of Series A preferred stock, net of issuance costs (in shares)	'	17,025,000	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'	'
Issuance of common stock at $0.0001 per share	200	'	'	286	-86	'	'
Issuance of common stock at $0.0001 per share (in shares)	'	'	'	286,286	'	'	'
Exercise of stock options	3,750	'	'	4	3,746	'	'
Exercise of stock options (in shares)	'	'	'	3,578	'	'	'
Stock-based compensation	98,796	'	'	'	98,796	'	'
Net loss	-19,415,948	'	'	'	'	-19,415,948	'
Balance at Dec. 31, 2010	-19,313,202	'	'	290	102,456	-19,415,948	'
Balance at Dec. 31, 2010	'	17,275,000	'	'	'	'	'
Balance (in shares) at Dec. 31, 2010	'	'	'	289,864	'	'	'
Balance (in shares) at Dec. 31, 2010	'	17,275,000	'	'	'	'	'
Increase (Decrease) in Temporary Equity	'	'	'	'	'	'	'
Issuance of Series A preferred stock, net of issuance costs	'	6,700,000	'	'	'	'	'
Issuance of Series A preferred stock, net of issuance costs (in shares)	'	6,700,000	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'	'
Exercise of stock options	15,886	'	'	15	15,871	'	'
Exercise of stock options (in shares)	'	'	'	15,016	'	'	'
Stock-based compensation	78,451	'	'	'	78,451	'	'
Issuance of common stock in consideration for a license agreement	4,400	'	'	3	4,397	'	'
Issuance of common stock in consideration for a license agreement (in shares)	'	'	'	2,862	'	'	'
Net loss	-10,817,341	'	'	'	'	-10,817,341	'
Balance at Dec. 31, 2011	-30,031,806	'	'	308	201,175	-30,233,289	'
Balance at Dec. 31, 2011	'	23,975,000	'	'	'	'	'
Balance (in shares) at Dec. 31, 2011	'	'	'	307,742	'	'	'
Balance (in shares) at Dec. 31, 2011	'	23,975,000	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'	'
Exercise of stock options	40,988	'	'	38	40,950	'	'
Exercise of stock options (in shares)	'	'	'	38,736	'	'	'
Beneficial conversion feature from issuance of convertible notes	287,990	'	'	'	287,990	'	'
Stock-based compensation	79,861	'	'	'	79,861	'	'
Net loss	-11,741,736	'	'	'	'	-11,741,736	'
Balance at Dec. 31, 2012	-41,364,703	'	'	346	609,976	-41,975,025	'
Balance (in shares) at Dec. 31, 2012	346,478	'	'	346,478	'	'	'
Balance at Dec. 31, 2012	'	23,975,000	'	'	'	'	'
Balance (in shares) at Dec. 31, 2012	'	23,975,000	'	'	'	'	'
Increase (Decrease) in Temporary Equity	'	'	'	'	'	'	'
Issuance of preferred stock in exchange for convertible promissory notes, net of issuance costs	'	16,623,092	7,749,531	'	'	'	'
Issuance of preferred stock in exchange for convertible promissory notes, net of issuance costs (in shares)	'	16,623,092	6,750,000	'	'	'	'
Issuance of Series A preferred stock, net of issuance costs	'	16,880,463	'	'	'	'	'
Issuance of Series A preferred stock, net of issuance costs (in shares)	'	17,000,000	'	'	'	'	'
Preferred shares converted into common stock	65,225,165	-57,478,555	-7,749,531	9,211	65,215,954	'	'
Preferred shares converted into common stock (in shares)	'	-57,598,092	-6,750,000	9,210,999	'	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'	'
Early exercise of stock options and vesting of restricted stock	21,193	'	'	26	21,167	'	'
Early exercise of stock options and vesting of restricted stock (in shares)	'	'	'	25,765	'	'	'
Issuance of common stock from initial public offering, net of issuance costs	72,193,831	'	'	5,750	72,188,081	'	'
Issuance of common stock from initial public offering, net of issuance costs (in shares)	'	'	'	5,750,000	'	'	'
Reclassification of warrants from liabilities to equity	2,852,188	'	'	'	2,852,188	'	'
Exercise of stock options	27,874	'	'	24	27,850	'	'
Exercise of stock options (in shares)	49,936	'	'	24,171	'	'	'
Stock-based compensation	1,226,988	'	'	'	1,226,988	'	'
Other comprehensive loss	-3,034	'	'	'	'	'	-3,034
Net loss	-26,088,133	'	'	'	'	-26,088,133	'
Balance at Dec. 31, 2013	74,091,369	'	'	15,357	142,142,204	-68,063,158	-3,034
Balance at Dec. 31, 2013	'	'	'	'	'	'	'
Balance (in shares) at Dec. 31, 2013	15,357,413	'	'	15,357,413	'	'	'
Balance (in shares) at Dec. 31, 2013	'	0	'	'	'	'	'

Statements_of_Convertible_Pref1

Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2013
Series A Convertible Preferred Stock	'
Stock issuance costs	$119,537
Series A 1 Convertible Preferred Stock	'
Stock issuance costs	53,469
Common Stock	'
Stock issuance costs	$2,671,169

Statements_of_Convertible_Pref2

Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical 2) (USD $)	Dec. 31, 2013	Jun. 11, 2013	Dec. 31, 2012	Dec. 31, 2010
Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit)	'	'	'	'
Issuance of common stock, par value (in dollars per share)	$0.00	$0.00	$0.00	$0.00

Statements_of_Cash_Flows

Statements of Cash Flows (USD $)	12 Months Ended			71 Months Ended
Statements of Cash Flows (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Operating activities	'	'	'	'
Net loss	($26,088,133)	($11,741,736)	($10,817,341)	($68,063,158)
Adjustments to reconcile net loss to net cash used in operating activities:	'	'	'	'
Depreciation expense	70,551	139,433	178,471	1,447,722
Amortization of debt discount and beneficial conversion	458,993	116,988	'	575,981
Amortization of debt issuance costs	18,533	15,378	'	33,911
Amortization of premiums and discounts on investments	46,758	'	'	46,758
Revaluation of warrants	2,586,865	-32,367	0	2,554,498
Noncash interest expense on convertible notes	459,055	1,369,709	577,065	3,726,092
Write-off of acquired in-process research and development	'	'	'	85,612
Stock-based compensation expense	1,226,988	79,861	78,451	1,484,096
Common stock issued in license agreement	'	'	4,400	4,400
Loss related to assets held for sale	27,000	86,887	108,308	322,701
Gain on sale of assets	-147,805	-2,549	'	-166,264
Changes in assets and liabilities:	'	'	'	'
Prepaids and other assets	28,489	-429,720	168,277	-508,281
Accounts payable	1,755,613	-214,903	619,238	2,231,890
Other accrued liabilities	1,443,732	-195,548	14,406	1,896,229
Net cash used in operating activities	-18,113,361	-10,808,567	-9,068,725	-54,327,813
Investing activities	'	'	'	'
Purchases of investments	-24,676,822	'	'	-56,245,988
Proceeds from sales/maturities of investments	3,504,791	'	500,350	35,020,141
Cash obtained in stock acquisition	'	'	'	2,500,000
Proceeds from sale of assets	201,265	5,100	42,312	952,464
Purchase of property and equipment	-31,373	-6,783	-33,635	-298,932
Other investing	'	'	'	50,626
Net cash (used in) provided by investing activities	-21,002,139	-1,683	509,027	-18,021,689
Financing activities	'	'	'	'
Proceeds from initial public offering, net of issuance costs	72,193,831	'	'	72,193,831
Proceeds from issuance of preferred stock, net of issuance costs	16,824,235	'	6,700,000	40,799,235
Proceeds from exercise of common stock options	123,274	40,987	15,886	184,097
Proceeds from warrant issuance	'	297,690	'	297,690
Proceeds from debt issuance with related parties	'	15,412,010	'	15,412,010
Net cash provided by financing activities	89,141,340	15,750,687	6,715,886	128,886,863
Net increase (decrease) in cash and cash equivalents	50,025,840	4,940,437	-1,843,812	56,537,361
Cash and cash equivalents at beginning of period	6,511,521	1,571,084	3,414,896	'
Cash and cash equivalents at end of period	56,537,361	6,511,521	1,571,084	56,537,361
Convertible promissory note	'	'	'	'
Supplemental disclosure of cash flow information:	'	'	'	'
Conversion of convertible debt, including accrued interest, into preferred stock	16,623,092	'	'	16,623,092
Pfizer note	'	'	'	'
Supplemental disclosure of cash flow information:	'	'	'	'
Conversion of convertible debt, including accrued interest, into preferred stock	$7,803,000	'	'	$7,803,000

Statements_of_Cash_Flows_Paren

Statements of Cash Flows (Parenthetical) (USD $)	Dec. 31, 2013
Convertible promissory note	'
Conversion of convertible promissory notes into preferred stock, accrued interest	$923,092
Pfizer note	'
Conversion of convertible promissory notes into preferred stock, accrued interest	$274,155

The_Company_and_Basis_of_Prese

The Company and Basis of Presentation	12 Months Ended
	Dec. 31, 2013
The Company and Basis of Presentation	'
The Company and Basis of Presentation	'

	1. The Company and Basis of Presentation

	The Company is a clinical stage biopharmaceutical company focused on developing and commercializing first-in-class, oral, low-density lipoprotein cholesterol (LDL-C) lowering therapies for the treatment of patients with hypercholesterolemia and other cardiometabolic risk markers. ETC-1002, the Company's lead product candidate, is a unique, first-in-class, orally available, once-daily small molecule designed to lower LDL-C levels and avoid the side effects associated with LDL-C lowering therapies currently available. ETC-1002 is being developed primarily for patients intolerant of statins with elevated levels of LDL-C. Phase 2b clinical trials for ETC-1002 are currently underway and build upon a successful and comprehensive Phase 1 and Phase 2 program. The Company owns the exclusive worldwide rights to ETC-1002 and our other product candidates.

	HDL Therapeutics, Inc. (HDL) was incorporated in the state of Delaware on January 22, 2008. On April 28, 2008, HDL acquired all of the capital stock of Esperion Therapeutics, Inc. (Esperion), a wholly owned subsidiary of Pfizer Inc. On May 5, 2008, Esperion was merged with and into HDL and the Company assumed the name Esperion Therapeutics, Inc. (the Company). Its facilities are located in Plymouth, Michigan.

	The Company's primary activities since incorporation have been recruiting personnel, conducting research and development activities, including pre-clinical and clinical testing, performing business and financial planning, and raising capital. Accordingly, the Company is considered to be in development stage.

	The Company is subject to the risks associated with a development stage entity, which includes the need to: research, develop, and clinically test potential therapeutic products; obtain regulatory approvals for its products and commercialize them, if approved; expand its management and scientific staff; and finance its operations with an ultimate goal of achieving profitable operations.

	The Company has sustained operating losses since inception and expects such losses to continue over the foreseeable future. Management plans to continue to finance operations with a combination of public and private equity issuances, debt arrangements, collaborations and strategic and licensing arrangements. If adequate funds are not available, the Company may not be able to continue the development of its current or future product candidates, or to commercialize its current or future product candidates, if approved.

	Reverse Stock Split

	On June 11, 2013, in connection with its initial public offering (the IPO), the Company effectuated a 1-for-6.986 reverse stock split of its outstanding common stock, which was approved by the Company's board of directors on June 5, 2013. The reverse stock split resulted in an adjustment to the Series A preferred stock and Series A-1 preferred stock conversion prices to reflect a proportional decrease in the number of shares of common stock to be issued upon conversion. The accompanying financial statements and notes to the financial statements give effect to the reverse stock split for all periods presented. The shares of common stock retained a par value of $0.001 per share. Accordingly, the stockholders' equity reflects the reverse stock split by reclassifying from "common stock" to "Additional paid-in capital" in an amount equal to the par value of the decreased shares resulting from the reverse stock split.

	Initial Public Offering

	On July 1, 2013, the Company completed its IPO whereby the Company sold 5,000,000 shares of common stock at a price of $14.00 per share. The shares began trading on the Nasdaq Global Market on June 26, 2013. On July 11, 2013, the underwriters exercised their over-allotment option in full and purchased an additional 750,000 shares of common stock at a price of $14.00 per share. The Company received approximately $72.2 million in net proceeds from the IPO, including proceeds from the exercise of the underwriters' over-allotment option, net of underwriting discounts and commissions and offering expenses. Upon closing of the IPO, all outstanding shares of preferred stock converted into 9,210,999 shares of common stock; and warrants exercisable for convertible preferred stock were automatically converted into warrants exercisable for 277,690 shares of common stock, resulting in the reclassification of the related convertible preferred stock warrant liability of $2,852,188 to additional paid-in capital (See Note 5).

	The following table summarizes the Company's capitalization upon closing of its initial public offering:


	Total common stock issued as of June 30, 2013	396,414
	Conversion of Series A preferred stock into common stock upon closing of IPO	8,244,781
	Conversion of Series A-1 preferred stock into common stock upon closing of IPO	966,218
	Sales of common stock through IPO	5,000,000


	Common stock issued as of July 1, 2013	14,607,413
	Issuance of common stock to underwriters due to exercise of over-allotment	750,000


	Total common stock issued as of July 11, 2013	15,357,413

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2013
Summary of Significant Accounting Policies	'
Summary of Significant Accounting Policies	'

	2. Summary of Significant Accounting Policies

	Use of Estimates

	The preparation of financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, expenses and related disclosures. Actual results could differ from those estimates.

	Prior to the completion of the IPO on July 1, 2013, the Company utilized significant estimates and assumptions in determining the fair value of its Common Stock. The Company utilized valuation methodologies in accordance with the framework of the 2004 American Institute of Certified Public Accountants Technical Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation, to estimate the fair value of its Common Stock. Each valuation methodology includes estimates and assumptions that require the Company's judgment. These estimates and assumptions include a number of objective and subjective factors, including external market conditions affecting the biotechnology industry sector, the prices at which the Company sold shares of its Preferred Stock, the superior rights and preferences of securities senior to its Common Stock at the time and the likelihood of achieving a liquidity event, such as an initial public offering or sale. Significant changes to the key assumptions used in the valuations could result in different fair values of Common Stock at each valuation date.

	Cash and Cash Equivalents

	The Company invests its excess cash in bank deposits, money market accounts, and short-term investments. The Company considers all highly liquid investments with an original maturity of 90 days or less at the time of purchase to be cash equivalents. Cash equivalents are reported at fair value.

	Investments

	Investments are considered to be available-for-sale and are carried at fair value. Unrealized gains and losses, if any, are reported as a separate component of stockholders' deficit. The cost of investments classified as available-for-sale are adjusted for the amortization of premiums and accretion of discounts to maturity and recorded in other income (expense), net. Realized gains and losses, if any, are determined using the specific identification method and in other income (expense), net. Investments with original maturities beyond 90 days at the date of purchase and which mature at, or less than twelve months from, the balance sheet date are classified as current. Investments with a maturity beyond twelve months from the balance sheet date are classified as long-term.

	Concentration of Credit Risk

	Cash, cash equivalents, and marketable securities consist of financial instruments that potentially subject the Company to concentrations of credit risk. The Company has established guidelines for investment of its excess cash and believes the guidelines maintain safety and liquidity through diversification of counterparties and maturities.

	Segment Information

	The Company views its operations and manages its business in one operating segment, which is the business of researching, developing and commercializing therapies for the treatment of patients with elevated levels of low-density lipoprotein cholesterol and other cardiometabolic risk markers.

	Fair Value of Financial Instruments

	The Company's financial instruments consist principally of cash and cash equivalents, investments, other current assets, accounts payable and accrued liabilities that approximate their carrying value at December 31, 2013 and 2012.

	Property and Equipment, Net

	Property and equipment are recorded at cost, less accumulated depreciation. Depreciation is provided using the straight-line method over the estimated useful lives of the respective assets, generally three to ten years. Leasehold improvements are amortized over the lesser of the lease term or the estimated useful lives of the related assets.

	Impairment of Long-Lived Assets

	The Company reviews long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are less than its carrying amount. The impairment loss, if recognized, would be based on the excess of the carrying value of the impaired asset over its respective fair value. Excluding impairment losses recorded on assets held for sale, no other impairment losses have been recorded through December 31, 2013.

	Research and Development

	Research and development expenses consist of costs incurred to further the Company's research and development activities and include salaries and related benefits, costs associated with pre-clinical studies and trials, non-clinical activities (such as toxicology studies), regulatory activities, manufacturing activities to support clinical activities, research-related overhead expenses, and fees paid to external service providers that conduct certain research and development, clinical, and manufacturing activities on behalf of the Company. Research and development costs are expensed as incurred.

	In-Process Research and Development

	In April 2008, the Company acquired certain tangible research and development assets and intellectual property from Pfizer Inc. (Pfizer). As the acquired in-process research and development had not reached technological feasibility and had no alternative future uses in connection with this asset and intellectual property acquisition and the related purchase price allocation, the Company expensed $85,612 as in-process research and development costs in 2008.

	Accrued Clinical Development Costs

	Outside research costs are a component of research and development expense. These expenses include fees paid to contract research organizations and other service providers that conduct certain clinical and product development activities on behalf of the Company. Depending upon the timing of payments to the service providers, the Company recognizes prepaid expenses or accrued expenses related to these costs. These accrued or prepaid expenses are based on management's estimates of the work performed under service agreements, milestones achieved and experience with similar contracts. The Company monitors each of these factors and adjusts estimates accordingly.

	Income Taxes

	The Company utilizes the liability method of accounting for income taxes as required by ASC 740, Income Taxes. Under this method, deferred tax assets and liabilities are determined based on differences between financial reporting and the tax basis of assets and liabilities and are measured using enacted tax rates and laws that will be in effect when the differences are expected to reverse. The Company has incurred operating losses since inception. Accordingly, it is not more likely than not that the Company will realize deferred tax assets and as such, it has recorded a full valuation allowance.

	Warrants

	The Company accounts for its warrants issued in connection with its various financing transactions based upon the characteristics and provisions of the instrument. Warrants classified as liabilities are recorded on the Company's balance sheet at their fair value on the date of issuance and are marked-to-market on each subsequent reporting period, with the fair value changes recognized in the statement of operations. The warrants are measured using the Black-Scholes option-pricing model subsequent to the pricing of the Company's IPO and a Monte Carlo valuation model for previous periods which are based, in part, upon inputs where there is little or no market data, requiring the Company to develop its own independent assumptions. The Company adjusts the liability for changes in the fair value of the warrants until the earlier of the exercise of the warrants, the expiration of the warrants, or until such time as the warrants are no longer determined to be liabilities and reclassified into paid-in-capital at fair value. The warrants were reclassified into paid-in-capital upon closing of the IPO. (See Note 5).

	Stock-Based Compensation

	The Company accounts for stock-based compensation in accordance with the provisions of ASC 718, Compensation—Stock Compensation. Accordingly, compensation costs related to equity instruments granted are recognized over the requisite service periods of the awards on a straight-line basis at the grant-date fair value calculated using a Black-Scholes option pricing model. Additionally, under the provisions of ASC 718, the Company is required to include an estimate of the number of awards that will be forfeited in calculating compensation costs. Any changes to the estimated forfeiture rates are accounted for prospectively. Stock-based compensation arrangements with non-employees are recognized at the grant-date fair value and then re-measured at each reporting period. Expense is recognized during the period the related services are rendered.

	Reclassifications

Certain prior period information has been reclassified to be comparable to the current year presentation. These items had no impact on the amounts of previously reported net loss or total shareholder's equity (deficit).

Recent Accounting Pronouncements

In February 2013, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2013-02 which is an amendment to the accounting guidance for the presentation of comprehensive income. Under the amended guidance, items that are reclassified to net income from accumulated other comprehensive income in the same reporting period require separate disclosure on the face of the financial statements where net income is presented or within the notes to the financial statements. The adoption of this update did not have a material impact on the Company's financial statements.

In July 2013, the FASB issued ASU 2013-11 which is an amendment to the accounting guidance on income taxes. This guidance provides clarification on the financial statement presentation of an unrecognized benefit when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists. The amendment will be effective for the Company for interim and annual periods beginning after December 15, 2013, with early adoption permitted. The adoption of this standard is not expected to have a material impact on the Company's financial statements.

Stock_Acquisition

Stock Acquisition	12 Months Ended
Stock Acquisition	Dec. 31, 2013
Stock Acquisition	'
Stock Acquisition	'

	3. Stock Acquisition

	On April 28, 2008, HDL acquired all of the capital stock of Esperion from Pfizer in exchange for a non-subordinated convertible promissory note in the original principal amount of $5,000,000 (see Note 4).

	The Company allocated the purchase price of the Esperion acquisition in accordance with the provisions of Statement of Financial Accounting Standards (SFAS) No. 141, Business Combinations, related to the purchase of a group of assets. SFAS No. 141 provides that the cost of a group of assets acquired in a transaction other than a business combination shall be allocated to the individual assets acquired based on their relative fair values and shall not give rise to goodwill.

	In accordance with the provisions of SFAS No. 141, this transaction did not meet the criteria of a business combination, and all identifiable intangible assets, including in-process research and development, were assigned a portion of the purchase price based on their relative fair values. To this end, an independent valuation of the tangible assets acquired was used to determine the fair value of the identifiable tangible assets. The Company determined the value assigned to in-process research and development and intangible assets. The fair value of assets acquired exceeded the transaction consideration and therefore, under SFAS No. 141, the excess of fair value of assets received over consideration paid was allocated on a relative fair market value basis to in-process research and development, tangible and intangible assets.

	The Company allocated total cost of the Esperion acquisition as follows:


	Cash	$	2,500,000
	Property and equipment		1,317,005
	Intangible assets		50,000
	In-process research and development		85,612
	Assets held for sale		1,047,383


	Total	$	5,000,000





	The income approach was used to estimate the fair value of the acquired in-process research and development based on projected cash flows through 2014 and a 35 percent discount rate. Material cash inflows were projected to begin in 2014. The replacement cost method was used to estimate the fair value of the tangible assets.

Debt

Debt	12 Months Ended
Debt	Dec. 31, 2013
Debt	'
Debt	'

	4. Debt

	The following is a reconciliation of the Company's various debt instruments:


		December 31,
		2013		2012
	Short term convertible notes issued January 2012	$	—	$	6,000,000
	Short term convertible notes issued September 2012		—		4,000,000
	Short term convertible notes issued November 2012		—		5,700,000
	Discount on short term convertible notes		—		(458,993	)


	Total short term convertible notes, net of debt discount		—		15,241,007
	Long term debt		—		5,000,000
	Accumulated paid-in-kind interest		—		2,528,845


	Total long-term debt		—		7,528,845


	Total debt	$	—	$	22,769,852





	Convertible Notes

	In January 2012, the Company issued $6,000,000 of 10% convertible promissory notes to certain existing investors for cash. In September and November 2012, the Company issued the aggregate of $9,700,000 of 10% convertible promissory notes that mature on September 4, 2013 for cash to certain existing investors. In connection with the September convertible note financing, the Company and the holders of the January 2012 convertible promissory notes agreed to extend the maturity date of the January 2012 notes to September 4, 2013. In February 2013, these convertible promissory notes, with an outstanding principal of $15,700,000 and accrued interest of $923,092, were amended and then converted into 16,623,092 shares of Series A preferred stock, in accordance with their terms and at their conversion price of $1.00 per share, and following such conversion, the notes were cancelled.

	The holders of the September convertible promissory notes received the benefit of a deemed conversion price of the September convertible promissory notes that were below the estimated fair value of the Series A convertible preferred stock at the time of their issuance. The fair value of this beneficial conversion feature was estimated to be $287,990. The fair value of this beneficial conversion feature was recorded to debt discount and amortized to interest expense using the effective interest method over the term of the convertible promissory notes. As a result of the conversion of the convertible promissory notes into shares of Series A preferred stock in February 2013, the Company recorded the remaining accretion of the beneficial conversion feature of $229,496 as interest expense during the year ended December 31, 2013.

	In connection with the issuance of the September and the November 2012 convertible promissory notes, the Company issued warrants to purchase shares of Series A preferred stock for an aggregate price of $9,700. The estimated fair value of the warrants at issuance was $297,690. The proceeds from the sale of the preferred stock and warrants was allocated with $9,412,010 to the convertible promissory notes and $297,690 to warrants. This resulted in a discount on the convertible promissory notes which was amortized into interest expense, using the effective interest method, over the life of the convertible promissory notes (see Note 5). The Company recorded $58,494 of interest expense for the accretion of this discount during the year ended December 31, 2012. As a result of the conversion of the convertible promissory notes into shares of Series A preferred stock in February 2013, the Company recorded the remaining $229,496 of interest expense for the accretion of this discount during the year ended December 31, 2013 and $297,690 during the period from Inception through December 31, 2013.

	In April 2008, the Company acquired all of the capital stock of Esperion from Pfizer in exchange for a non-subordinated convertible note in the original principal amount of $5,000,000. This convertible promissory note had a maturity date of April 28, 2018. The note bore interest at 8.931% annually, payable semiannually on June 30 and December 31 by adding such unpaid interest to the principal of the note, which would thereafter accrue interest. During the years ended December 31, 2013, 2012, 2011, and the period from Inception through December 31, 2013, the Company accrued interest related to the note of $274,155, $631,517, $577,065, and $2,803,000, respectively.

	In May 2013 the Company entered into a stock purchase agreement with Pfizer Inc. and sold 6,750,000 shares of Series A-1 preferred stock at a price of $1.1560 per share, which was the fair value at the transaction date. The purchase price was paid through the cancellation of all outstanding indebtedness, including accrued interest, under the Pfizer convertible promissory note, which had an outstanding balance, including accrued interest, of $7,803,000 as of May 29, 2013. The Series A-1 preferred stock issued in connection with this transaction was subsequently converted into 966,218 shares of common stock upon completion of the IPO on July 1, 2013.

Warrants

Warrants	12 Months Ended
Warrants	Dec. 31, 2013
Warrants	'
Warrants	'

	5. Warrants

	In connection with its various financing transactions, the Company issued warrants to purchase shares of preferred stock which had provisions where the underlying issuance was contingently redeemable based on events outside the Company's control and were recorded as a liability in accordance with ASC 480-10. The warrants were classified as liabilities and were recorded on the Company's balance sheet at fair value on the date of issuance and marked-to-market on each subsequent reporting period, with the fair value changes recognized in the statement of operations. Subsequent to the pricing of the IPO, the Company estimated the fair values of the warrants at each reporting period using a Black-Scholes option-pricing model, which is based, in part, upon subjective assumptions including but not limited to stock price volatility, the expected life of the warrants, the risk free interest rate and the fair value of the common stock underlying the warrants. The Company estimates the volatility of its stock based on public company peer group historical volatility that is in line with the expected remaining life of the warrants. The risk free interest rate is based on the U.S. Treasury zero-coupon bond for a maturity similar to the expected remaining life of the warrants. The expected remaining life of the warrants is assumed to be equivalent to their remaining contractual term. Prior to the pricing of the IPO, a Monte Carlo valuation model was utilized to estimate the fair value of the warrants based on the probability and timing of future financings.

	The assumptions used in calculating the estimated fair market value at each reporting period prior to the closing of the Company's IPO represent the Company's best estimate, however, do involve inherent uncertainties. The estimated fair value of the warrants was determined using the Monte Carlo valuation model which totaled $297,690 and was comprised of $141,779 and $155,911 as of and for the September and November 2012 financing, respectively, and was recorded as a discount on the related convertible promissory notes and amortized as interest expense over the term of the convertible promissory notes. Inherent in the Monte Carlo valuation model are assumptions related to expected stock-price volatility, expected life and risk-free interest rate. The Company estimates the volatility of its stock based on public company peer group historical volatility that is in line with the expected remaining life of the warrants. The risk-free interest rate is based on the U.S. Treasury zero-coupon bond on the grant date for a maturity similar to the expected remaining life of the warrants. The expected life of the warrants is assumed to be equivalent to their remaining contractual term. The dividend rate is based on the historical rate, which the Company anticipates to remain at zero. The Monte Carlo model was used prior to the closing of the Company's IPO to appropriately value the potential future exercise price based on various exit scenarios. This requires Level 3 inputs which are based on the Company's estimates of the probability and timing of potential future financings.

	Upon the closing of the Company's IPO, all warrants exercisable for 1,940,000 shares of Series A preferred stock, at an exercise price of $1.00 per share, were automatically converted into warrants exercisable for 277,690 shares of common stock, at an exercise price of $6.99 per share. As a result, the Company concluded the warrants outstanding no longer met the criteria to be classified as liabilities and were reclassified to additional paid-in capital at fair value on the date of reclassification. The 277,690 warrants outstanding as of December 31, 2013 expire in February 2018. During the years ended December 31, 2013, 2012, 2011, and for the period from Inception through December 31, 2013, the Company recognized a (loss)/gain of $(2,586,865), $32,367, $0, and $(2,554,498), respectively, relating to the change in the fair value of the warrant liability.

Commitments_and_contingencies

Commitments and contingencies	12 Months Ended
Commitments and contingencies	Dec. 31, 2013
Commitments and contingencies	'
Commitments and contingencies	'

	6. Commitments and contingencies

	In August 2013, the Company entered into the second amendment to the operating lease agreement for its current office and laboratory facility in Plymouth, MI which extended the expiration date of the initial term from October 2, 2013 to April 30, 2014. The Company's facility lease provides for a fixed monthly rent for the term of the lease and also provides for certain rent adjustments to be paid as determined by the landlord.

	The total rent expense for the years ended December 31, 2013, 2012, 2011, and for the period from Inception to December 31, 2013, was approximately $344,604, $335,000, $323,000 and $1,631,004, respectively. Future minimum payments as of December 31, 2013, under the facility lease are presented in the table below:


		Total		Less than		1 - 3 Years		3 - 5 Years		More than
		Total		1 Year		1 - 3 Years		3 - 5 Years		5 Years
	Operating lease	$	100,868	$	100,868	$	—	$	—	$	—


	Total	$	100,868	$	100,868	$	—	$	—	$	—





	The Company also holds a license agreement in which it is obligated to make future minimum annual payments of $50,000 in years where there is not a milestone payment required under the terms of the agreement (see Note 15). Further, the Company is contractually obligated to issue up to an aggregate of 11,451 shares of common stock upon meeting various future milestones set forth in the agreement.

Property_and_Equipment

Property and Equipment	12 Months Ended
Property and Equipment	Dec. 31, 2013
Property and Equipment	'
Property and Equipment	'

	7. Property and Equipment

	Property and equipment consist of the following:


		December 31,
		2013		2012
	Lab equipment	$	511,403	$	1,057,276
	Computer equipment		99,412		99,412
	Software		118,572		96,668
	Furniture and fixtures		11,309		11,309
	Leasehold improvements		21,381		21,381
	Assets in Progress		6,530		—


	Subtotal		768,607		1,286,046
	Less accumulated depreciation and amortization		687,799		1,165,836


	Property and equipment, net	$	80,808	$	120,210





	Depreciation expense was $70,551, $139,433, $178,471 and $1,447,722 for the years ended December 31, 2013, 2012, 2011 and the period from Inception through December 31, 2013, respectively.

Other_Accrued_Liabilities

Other Accrued Liabilities	12 Months Ended
Other Accrued Liabilities	Dec. 31, 2013
Other Accrued Liabilities	'
Other Accrued Liabilities	'

	8. Other Accrued Liabilities

	Other accrued liabilities consist of the following:


		December 31,
		2013		2012
	Stock based compensation liability	$	74,208	$	—
	Accrued professional fees		209,961	$	136,907
	Accrued franchise and property taxes		94,600		12,697
	Accrued compensation		667,164		60,725
	Accrued other		41,203		—


	Total other accrued liabilities	$	1,087,136	$	210,329

Investments

Investments	12 Months Ended
Investments	Dec. 31, 2013
Investments	'
Investments	'

	9. Investments

	The following table summarizes the Company's cash equivalents and investments:


		December 31, 2013
		Amortized		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair
				Gains		Losses			Value
	Cash equivalents:
	Money market funds	$	5,356,453	$	—	$	—		$	5,356,453


	Short-term investments:
	U.S treasury notes		2,070,774		—		(234	)		2,070,540
	U.S. government agency securities		1,454,426		157		—			1,454,583
	Long-term investments:
	Certificates of deposit		237,525		—		—			237,525
	U.S. treasury notes		9,116,136		3,595		(2,497	)		9,117,234
	U.S. government agency securities		8,186,958		640		(4,695	)		8,182,903


	Total	$	26,422,272	$	4,392	$	(7,426	)	$	26,419,238









		December 31, 2012
		Amortized		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair
				Gains		Losses			Value
	Cash equivalents:
	Money market funds	$	6,357,542		—		—		$	6,357,542


	Total	$	6,357,542	$	—	$	—		$	6,357,542





	At December 31, 2013, remaining contractual maturities of available-for-sale investments classified as current on the balance sheet were less than 12 months, and remaining contractual maturities of available-for-sale investments classified as long-term were less than two years.

	There were no unrealized gains or losses on investments reclassified from accumulated other comprehensive income to other income (expense) in the Statement of Operations during the year ended December 31, 2013.

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
Fair Value Measurements	Dec. 31, 2013
Fair Value Measurements	'
Fair Value Measurements	'

	10. Fair Value Measurements

	The Company follows accounting guidance that emphasizes that fair value is a market-based measurement, not an entity-specific measurement. Fair value is defined as "the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date." Fair value measurements are defined on a three level hierarchy:


	Level 1 inputs:		Quoted prices for identical assets or liabilities in active markets;
	Level 2 inputs:		Observable inputs other than Level 1 prices, such as quoted market prices for similar assets or liabilities or other inputs that are observable or can be corroborated by market data; and
	Level 3 inputs:		Unobservable inputs that are supported by little or no market activity and require the reporting entity to develop assumptions that market participants would use when pricing the asset or liability.

	The following table presents the Company's financial assets and liabilities that have been measured at fair value on a recurring basis:


	Description		Total			Level 1		Level 2		Level 3
	December 31, 2013
	Assets:
	Money market funds		$	5,356,453		$	5,356,453	$	—	$	—
	Available for sale securities:
	Certificates of deposit			237,525			237,525		—		—
	U.S. treasury notes			11,187,774			11,187,774		—		—
	U.S. government agency securities			9,637,486			—		9,637,486		—


	Total assets at fair value		$	26,419,238		$	16,781,752	$	9,637,486	$	—




	December 31, 2012
	Assets:
	Money market funds		$	6,357,542		$	6,357,542	$	—	$	—


	Total assets at fair value		$	6,357,542		$	6,357,542	$	—	$	—




	Liabilities:
	Warrants		$	265,323		$	—	$	—	$	265,323


	Total liabilities at fair value		$	265,323		$	—	$	—	$	265,323





	There were no transfers between Levels 1, 2 or 3 during the year ended December 31, 2013 or December 31, 2012.

	The following table summarizes the changes in the fair value of the Company's Level 3 warrant liability for the years ended December 31, 2012 and 2013:


			Warrant Liability
	Level 3 Liabilities:
	As of January 1, 2012		$	—
	Issuance of warrants			297,690
	Change in fair value			(32,367	)


	As of December 31, 2012		$	265,323
	Change in fair value			2,586,865
	Reclassification of warrants liabilities to additional paid-in capital in conjunction with the conversion of the convertible preferred stock into common stock upon the closing of the Company's IPO			(2,852,188	)


As of December 31, 2013		$	—





Fair Value Measurements on a Nonrecurring Basis

In addition to items that are measured at fair value on a recurring basis, the Company also measures assets held for sale at the lower of its carrying amount or fair value on a nonrecurring basis. The Company recognized an impairment expense and other losses relating to assets held for sale during the year ended December 31, 2013, 2012, 2011 and the period from Inception through December 31, 2013 of $27,000, $86,887, $108,308 and $214,393 based on recent market sales data for similar equipment less the related costs to sell and recent purchase offers. The fair value of assets held for sale at December 31, 2013 was estimated at $29,108 using a market approach, considering the estimated fair value for other comparable equipment which are Level 3 inputs.

Convertible_Preferred_Stock_an

Convertible Preferred Stock and Stockholders' Deficit	12 Months Ended
	Dec. 31, 2013
Convertible Preferred Stock and Stockholders' Deficit	'
Convertible Preferred Stock and Stockholders' Deficit	'

	11. Convertible Preferred Stock and Stockholders' Deficit

	On January 22, 2008, HDL was incorporated in the state of Delaware with 1,000 shares of authorized common stock. In April 2008, the Board of Directors approved an amended and restated certificate of incorporation. The amendment increased HDL's authorized number of shares of common stock to a total of 44,025,145 and authorized two new series of preferred stock designated as Series A and Series A-1 preferred stock consisting of 33,250,000 shares of Series A preferred stock and 6,475,145 shares of Series A-1 preferred stock. In April 2008, HDL sold 286,286 shares of common stock and 10,000,000 shares of Series A preferred stock in a private offering (the Initial Financing), raising net proceeds of $200 and $10,000,000, respectively. In the Initial Financing, the Company converted an outstanding promissory note in the principal amount of $250,000 from an officer of the Company into 250,000 shares of Series A preferred stock.

	As a result of commencing Phase 1 clinical trials in December 2009, the Company issued 6,000,000 additional shares of Series A preferred stock, raising net proceeds of $6,000,000 in January 2010 (Second Tranche Shares in the Initial Financing agreement).

	In April 2010, the Company issued an additional 1,000,000 shares of Series A preferred stock to an officer and new investors for $1,000,000 in net proceeds. In connection with this sale, the Initial Financing agreement was amended to allow for the additional issuance of shares. The Company also amended its certificate of incorporation to increase its number of authorized shares to 45,025,145 shares of common stock and 40,725,145 shares of preferred stock, including 34,250,000 shares of Series A preferred stock and 6,475,145 shares of Series A-1 preferred stock.

	In November 2010, the Company issued an additional 25,000 shares of Series A preferred stock to an officer of the Company in exchange for $25,000. As a result of commencing Phase 2a clinical trials in December 2010, the Company issued 6,700,000 shares of Series A preferred stock, raising net proceeds of $6,700,000 in January 2011 (Third Tranche Shares in the Initial Financing agreement). The Company also amended its certificate of incorporation to increase the number of authorized shares to 50,000,000 shares of common stock and 41,682,329 shares of preferred stock, including 34,785,000 shares of Series A preferred stock and 6,897,329 shares of Series A-1 preferred stock.

	In September 2012, the Company amended its certificate of incorporation to increase the number of authorized preferred shares to 42,647,283, including 34,785,000 shares of Series A preferred stock and 7,862,283 shares of Series A-1 preferred stock.

	As of December 31, 2012, the Company did not have sufficient preferred and common shares authorized under its certificate of incorporation to permit the conversion of the outstanding convertible promissory notes issued during 2012. Pursuant to the terms of the note purchase agreements, in the event any or all of the notes were to be converted, the purchasers and the Company agreed to take all action necessary to amend the certificate of incorporation to increase the number of authorized shares of Series A preferred stock and common stock to permit such conversion. The Company subsequently amended its certificate of incorporation to increase the number of shares of Series A preferred stock authorized to 41,636,970 and number of shares of common stock authorized to 56,519,253 in connection with the conversion of the notes on February 12, 2013 into 16,623,092 shares of Series A preferred stock.

	In March 2013 and April 2013, the Company amended its certificate of incorporation to increase the number of shares of Series A preferred stock authorized to 42,538,092 and 59,538,092, respectively, and the number of shares of common stock authorized to 58,220,375 and 75,220,375, respectively. On April 19, 2013, the Company issued and sold an aggregate of 17,000,000 shares of Series A preferred stock at a price of $1.00 per share for proceeds of $16,880,463, which is net of issuance costs of $119,537, to funds affiliated with Longitude Capital and certain existing investors. Each share of Series A preferred stock issued in the financing was convertible into 0.143 shares of common stock upon the closing of the Company's IPO.

	On May 29, 2013, the Company entered into a stock purchase agreement with Pfizer Inc. and issued and sold 6,750,000 shares of Series A-1 preferred stock at a price of $1.1560 per share. The purchase price was paid through the cancellation of all outstanding indebtedness, including accrued interest, under the Pfizer convertible promissory note, which had an aggregate balance, including accrued interest, of $7,803,000 as of May 29, 2013. Each share of Series A-1 preferred stock issued in the agreement was convertible into 0.143 shares of common stock upon the closing of the Company's IPO.

	Upon the closing of the Company's IPO on July 1, 2013, all of the outstanding shares of convertible preferred stock were converted into 9,210,999 shares of common stock. As of December 31, 2013, the Company did not have any convertible preferred stock issued or outstanding.

	Convertible Preferred Stock

	As of December 31, 2013, the Company had authorized a total of 5,000,000 undesignated preferred shares. As of December 31, 2012, the Company had 42,647,283 shares of preferred stock designated in various series. The preferred stock designated as of December 31, 2012 is summarized as follows:


		December 31, 2012
		Shares		Liquidation		Shares
		Designated		Preference		Issued and
				Per Share		Outstanding
	Series A		34,785,000	$	1		23,975,000
	Series A-1		7,862,283		—		—


			42,647,283	$	1		23,975,000

	Voting

	The holders of preferred stock have various rights and preferences. Each share of Series A and Series A-1 preferred stock has certain voting rights equal to the number of shares of common stock into which it is convertible and votes together as one class with the common stock.

	A separate vote of a majority of the Series A preferred stock, equal to the number of shares of common stock into which it is convertible, is required for certain activities, including certain issuances of common stock; for any redemption, repurchase, dividend, or other distribution with respect to the common stock; any agreement by the Company or its stockholders regarding certain mergers or consolidations of the Company; a sale of all or substantially all of the assets of the Company; or any redemption, repurchase, dividend, or other distribution with respect to any shares of preferred stock.

	As the Series A preferred stock could be redeemed in a "deemed liquidation" in the event of a change of control and the redemption features are considered to be outside the control of the Company, all shares of Series A preferred stock have been presented outside of permanent equity in accordance with ASC 480.

	Liquidation

	In the event of any liquidation, dissolution, or winding-up of the Company, including a merger, acquisition, or sale of assets where the holders of the Company's common stock and preferred stock own less than 50% of the resulting voting power of the surviving entity, the holders of Series A preferred stock shall be entitled to receive prior and in preference to any distribution of the assets of the Company to the holders of Series A-1 preferred stock and common stock, an amount equal to $1.00 for each share of Series A preferred stock held, plus any declared but unpaid dividends. After payment of the full liquidation preference to holders of Series A preferred stock, but prior to any distribution or payment to holders of common stock, the holders of Series A-1 preferred shall be entitled to receive a distribution equal to the original issue price of a share of Series A-1 preferred stock plus any declared but unpaid dividends. After payment of the full liquidation preference(s) to the Series A and Series A-1 stockholders, the remaining assets legally available for distribution shall be distributed ratably to the holders of common stock and preferred stock on an as if converted to common stock basis.

	Dividends

	Holders of Series A and Series A-1 preferred stock, in preference to the holders of common stock, are entitled to receive cash dividends at the rate of eight percent of the respective original issue price per annum on each outstanding preferred share on a pari passu basis. Such dividends are payable only when, as and if declared by the Board of Directors and are non-cumulative. There have been no dividends declared, accrued or paid during the period from Inception through December 31, 2013.

	Conversion

	Any share of Series A or Series A-1 preferred stock may be converted at the option of the holder at any time into shares of common stock at the Series A preferred conversion price or the Series A-1 preferred conversion price then in effect.

	Each share of Series A and Series A-1 preferred stock shall automatically be converted into shares of common stock based upon the then-effective Series A preferred conversion price and the Series A-1 preferred conversion price, respectively, upon the affirmative election of the holders of at least 60% of the outstanding shares of the Series A preferred stock and Series A-1 preferred stock voting as a single class.

	Each share of Series A preferred stock shall automatically convert into shares of common stock based upon the effective Series A preferred conversion price upon (i) the affirmative election of the holders of at least two-thirds of the outstanding shares of the Series A preferred stock; (ii) the Company's sale of its common stock in a firmly underwritten public offering in which the per share price is at least three times the Series A original issue price adjusted for stock splits, dividends, recapitalizations, and the like, and which would result in gross proceeds to the Company of at least $40 million (prior to deducting underwriting discounts and commissions); or (iii) the affirmative election of at least a majority of the outstanding shares of the Series A preferred stock following the closing of a firmly underwritten public offering that covers the offer and sale of common stock for the Company that does not meet the three times original issue price or gross proceeds requirements above. Upon an automatic conversion, any declared and unpaid dividends shall be paid to the holders of Series A preferred stock.

	The Series A preferred conversion rate is the $1.00 Series A original issue price, divided by the Series A preferred conversion price, which was initially set at $1.00 and was adjusted to $6.986, on June 11, 2013 when the Company effected its 1-for-6.986 reverse stock split, making the Series A preferred conversion rate equal to 0.143. The Series A-1 preferred conversion rate is the $1.1560 Series A-1 original issue price, divided by the Series A preferred conversion price, initially set at $1.1560 and was adjusted to $8.076 on June 11, 2013 when the Company effected its 1-for-6.986 reverse stock split, making the Series A-1 preferred conversion rate equal to 0.143. Upon closing of the Company's IPO, all outstanding shares of preferred stock converted into 9,210,999 shares of common stock (see Note 1).

Stock_Compensation

Stock Compensation	12 Months Ended
Stock Compensation	Dec. 31, 2013
Stock Compensation	'
Stock Compensation	'

	12. Stock Compensation

	2013 Stock Option and Incentive Plan

	On June 7, 2013, the Company's stockholders approved the 2013 Stock Option and Incentive Plan (the 2013 Plan), which became effective on June 25, 2013. The number of shares of stock reserved and available for issuance under the 2013 Plan is the sum of (i) 1,100,000, plus (ii) 54,129 shares originally reserved under the Company's 2008 Incentive Stock Option and Restricted Stock Plan (the 2008 Plan) that became available for issuance under the 2013 Plan upon completion of the Company's initial public offering, plus (iii) the shares underlying any awards granted under the 2008 Plan that are forfeited, canceled, held back upon the exercise of an option or settlement of an award to cover the exercise price or tax withholding, reacquired by the Company prior to vesting, satisfied without the issuance of stock or otherwise terminated (other than by exercise). Additionally, on January 1, 2014 and each January 1 thereafter, the number of shares reserved and available for issuance under the 2013 Plan shall be cumulatively increased by two and a half percent of the number of shares issued and outstanding on the immediately preceding December 31 or such lesser number of shares as determined by the plan administrator.

	2008 Stock Option and Restricted Stock Plan

	In April 2008, the Company adopted the 2008 Incentive Stock Option and Restricted Stock Plan (the 2008 Plan), administered by the Board of Directors or a committee appointed by the Board of Directors. The 2008 Plan provides for the granting of stock options and restricted stock to employees and nonemployees of the Company. Options granted under the 2008 Plan may either be incentive stock options (ISOs), restricted stock awards (RSAs) or nonqualified stock options (NQSOs). Stock options and restricted stock grants may be granted to employees, directors and consultants.

	Stock awards under the 2008 Plan may be granted for up to ten years from the adoption of the 2008 Plan at prices no less than 100 percent of the fair value of the shares on the date of the grant as determined by (i) the closing price of the Company's common stock on any national exchange, (ii) the National Association of Securities Dealers Inc. Automated Quotation System (NASDAQ), if so authorized for quotation as a NASDAQ security, or (iii) by reasonable application of a reasonable valuation method. The valuation methods utilized by the Company are consistent with the AICPA Technical Practice Aid.

	Under the 2013 Plan and the 2008 Plan the vesting of options granted or restricted awards given will be determined individually with each option grant. Generally, 25 percent of the granted amount will vest upon the first anniversary of the option grant with the remainder vesting ratably on the first day of each calendar quarter for the following three years. Stock options have a 10 year life and expire if not exercised within that period, or if not exercised within 90 days of cessation of employment with the Company.

	The following table summarizes the activity relating to the Company's options to purchase common stock for the year ended December 31, 2013:


		Number of			Weighted-Average			Weighted-Average			Aggregate
		Options			Price			Remaining			Intrinsic
					Per Share			Contractual			Value
								Term (Years)
	Outstanding at December 31, 2012		211,500		$	1.43			7.5		$	141,389
	Granted		1,251,749		$	10.62
	Forfeited or expired		(12,212	)	$	2.03
	Exercised		(49,936	)	$	2.47


	Outstanding at December 31, 2013		1,401,101		$	9.59			8.95		$	7,755,321





	The following table summarizes information about the Company's stock option plan as of December 31, 2013:


		Number of			Weighted-Average			Weighted-Average			Aggregate
		Options			Price			Remaining			Intrinsic
					Per Share			Contractual			Value
								Term (Years)
	Vested and expected to vest at December 31, 2013		1,334,221		$	9.49			8.92		$	7,505,458


	Exercisable at December 31, 2013		594,176		$	2.81			8.16		$	6,572,563





	The following table shows the weighted-average assumptions used to compute the share-based compensation costs for the stock options granted to employees and non-employees during the period from Inception to December 31, 2013, using the Black-Scholes option pricing model:


		Year ended December 31,
											Period From
											January 22, 2008
											(Inception)
											Through
		2013			2012			2011			December 31, 2013
	Risk-free interest rate		1.45	%		0.85	%		2.5	%		1.58	%
	Dividend yield		—			—			—			—
	Weighted-average expected life of options (years)		6.26			6.25			6.25			6.26
	Volatility		74	%		80	%		80	%		75	%

The risk-free interest rate assumption was based on the United States Treasury's rates for U.S. Treasury zero-coupon bonds with maturities similar to those of the expected term of the award being valued. The assumed dividend yield was based on the Company's expectation of not paying dividends in the foreseeable future. The weighted-average expected life of the options was calculated using the simplified method as prescribed by the Securities and Exchange Commission (SEC) Staff Accounting Bulletin No. 107 (SAB No. 107). This decision was based on the lack of relevant historical data due to the Company's limited historical experience. In addition, due to the Company's limited historical data, the estimated volatility also reflects the application of SAB No. 107, incorporating the historical volatility of comparable companies whose share prices are publicly available.

The weighted-average grant-date fair values of stock options granted during the years ended December 31, 2013, 2012, 2011, and the period from Inception through December 31, 2013 were $7.14, $1.33, $1.12 and $5.94, respectively. During the years ended December 31, 2013, 2012, 2011, and the period from Inception through December 31, 2013, the Company recognized stock-based compensation expense of $1,226,988, $79,861, $78,451, and $1,484,096, respectively.

As of December 31, 2013, there was approximately $7,346,725 of unrecognized compensation cost related to unvested options, adjusted for forfeitures, which will be recognized over a weighted-average period of approximately 3.5 years.

Employee_Benefit_Plan

Employee Benefit Plan	12 Months Ended
Employee Benefit Plan	Dec. 31, 2013
Employee Benefit Plan	'
Employee Benefit Plan	'

	13. Employee Benefit Plan

	During 2008, the Company adopted the Esperion Therapeutics, Inc. 401(k) Plan (the 401(k) Plan), which qualifies as a deferred salary arrangement under Section 401(k) of the Internal Revenue Code. Under the 401(k) Plan, participating employees may defer a portion of their pretax earnings. The Company may, at its sole discretion, contribute for the benefit of eligible employees. There have been no Company contributions to the 401(k) Plan during 2013, 2012, 2011, or from Inception through December 31, 2013.

Income_Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2013
Income Taxes	'
Income Taxes	'

	14. Income Taxes

	There was no provision for income taxes for the year ended December 31, 2013, 2012 and 2011 because the Company has incurred operating losses since inception. At December 31, 2013, the Company has concluded that it is more likely than not that the Company will not realize the benefit of its deferred tax assets due to its history of losses. Accordingly, the net deferred tax assets have been fully reserved.

	As of December 31, 2013, 2012 and 2011, the Company had deferred tax assets, before valuation allowance of approximately $22,804,000, $14,351,000 and $10,386,000, respectively. Realization of the deferred assets is dependent upon future taxable income, if any, the amount and timing of which are uncertain. Accordingly, the net deferred tax assets have been fully offset by a valuation allowance.

	As of December 31, 2013, 2012 and 2011, the Company had federal net operating loss carryforwards of approximately $62,272,000, $40,465,000 and $29,206,000, respectively. The federal net operating loss will expire at various dates beginning in 2028, if not utilized. As of December 31, 2013, 2012 and 2011, the Company had state net operating loss carryforwards of approximately $33,129,000, $11,322,000 and $0, respectively. The state net operating loss will expire at various dates beginning in 2022, if not utilized. We have $191,000 of NOLs related to excess tax benefits generated upon the settlement of stock awards that increased a current year net operating loss. We cannot record the benefit of these losses in the financial statements until the losses are utilized to reduce our income taxes payable at which time we will recognize the tax benefit in equity.

	A reconciliation of the U.S. statutory income tax rate to the Company's effective tax rate is as follows:


		December 31,
		2013			2012			2011
	Federal income tax (benefit) at statutory rate		(34.0	)%		(34.0	)%		(34.0	)%
	State income tax benefit, net of federal benefit		—	%		—	%		(0.7	)%
	Permanent items		4.9	%		0.4	%		(0.1	)%
	Other		—	%		(0.2	)%		3.2	%
	Change in valuation allowance		29.1	%		33.8	%		31.6	%


	Effective income tax rate		0	%		0	%		0	%





	If the Company experiences a greater than 50 percentage point aggregate change in ownership of certain significant stockholders over a three-year period, a Section 382 ownership change could be deemed to have occurred. If a section 382 change occurs, the Company's future utilization of the net operating loss carryforwards and credits as of the ownership change will be subject to an annual limitation under Section 382 of the Internal Revenue Code of 1986, as amended, and similar state provisions. Such an annual limitation may result in the expiration of net operating losses before utilization.

	The Company's reserves related to taxes are based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings or positions is more likely than not to be realized following resolution of any potential contingencies present related to the tax benefit. The Company recognized no material adjustment for unrecognized income tax benefits. Through December 31, 2013, the Company had no unrecognized tax benefits or related interest and penalties accrued.

	Significant components of the Company's deferred tax assets are summarized in the table below:


		December 31,
		2013			2012
	Deferred tax assets:
	Federal and state operating loss carryforwards	$	22,485,000		$	14,207,000
	Temporary differences		319,000			144,000


	Total deferred tax assets		22,804,000			14,351,000
	Valuation allowance		(22,804,000	)		(14,351,000	)


	Net deferred tax assets	$	—		$	—

License_Agreement

License Agreement	12 Months Ended
License Agreement	Dec. 31, 2013
License Agreement	'
License Agreement	'

	15. License Agreement

	In December 2011, the Company entered into a license agreement for certain U.S. and foreign patents and patent applications regarding new high-density lipoprotein therapies to treat cardiovascular disease in exchange for 2,862 shares of common stock, plus an issue fee of $50,000. The license agreement will expire in 2028, which is the date of the last to expire of the licensed patents. The Company recorded the common stock, which was valued at its fair value of $4,400, and the issue fee within general and administrative expenses in the statements of operations.

	The license agreement provides for a minimum annual payment of $50,000 for any years in which a milestone is not achieved, fully creditable against any earned royalties per calendar year. In addition, the Company is also contractually obligated to issue up to an aggregate of 11,451 shares of common stock upon various milestones set forth in the agreement.

	Milestone achievement payments are due within 30 days of the milestone achievement. No milestones have been achieved to date under the license agreement. Additionally, the agreement provides for the Company to reimburse the patent holder for certain patent costs during the term of the agreement. The Company recognized expenses associated with this license agreement of $50,000, $50,000, $54,400, and $154,400 during the years ended December 31, 2013, 2012, 2011, and the period from Inception through December 31, 2013, respectively, in general and administrative expenses.

Net_Loss_Per_Common_Share

Net Loss Per Common Share	12 Months Ended
Net Loss Per Common Share	Dec. 31, 2013
Net Loss Per Common Share	'
Net Loss Per Common Share	'

	16. Net Loss Per Common Share

	Basic net loss per share is calculated by dividing net loss by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is computed by dividing net loss by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method. For purposes of this calculation, convertible preferred stock, convertible debt, warrants for preferred stock and stock options are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. Interest expense for convertible debt that is dilutive is added back to net income in the calculation of diluted net loss per share.

	The shares outstanding at the end of the respective periods presented below, after giving effect for the 1-for-6.986 reverse stock split, were excluded from the calculation of diluted net loss per share due to their anti-dilutive effect:


		December 31,		December 31,
		2013		2012
	Convertible preferred stock		—		3,431,865
	Warrants for common stock		277,690		277,690
	Common shares under option		1,401,101		211,500
	Unvested restricted stock		16,703		—
	Convertible debt		—		3,430,723


	Total potential dilutive shares		1,695,494		7,351,778

Selected_Quarterly_Financial_D

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
Selected Quarterly Financial Data (Unaudited)	Dec. 31, 2013
Selected Quarterly Financial Data (Unaudited)	'
Selected Quarterly Financial Data (Unaudited)	'

	17. Selected Quarterly Financial Data (Unaudited)

	The following table summarizes the unaudited quarterly financial data for the last two years:


		2013
		March 31			June 30			September 30			December 31
	Operating expenses:
	Research and development	$	2,092,593		$	3,100,422		$	3,482,673		$	7,338,517
	General and administrative		1,251,419			1,171,425			1,924,150			2,397,499


	Total operating expenses		3,344,012			4,271,847			5,406,823			9,736,016
	Loss from operations:		(3,344,012	)		(4,271,847	)		(5,406,823	)		(9,736,016	)


	Interest expense		(828,223	)		(108,357	)		—			—
	Change in fair value of warrant liability		(41,958	)		(2,544,907	)		—			—
	Other income, net		(24,984	)		4,035			168,389			46,570


	Net loss	$	(4,239,177	)	$	(6,921,076	)	$	(5,238,434	)	$	(9,689,446	)




	Net loss per common share (basic and diluted)	$	(12.24	)	$	(19.82	)	$	(0.34	)	$	(0.63	)
	Weighted-average shares outstanding (basic and diluted)		346,478			349,170			15,253,704			15,340,713





		2012
		March 31			June 30			September 30			December 31
	Operating expenses:
	Research and development	$	1,557,211		$	2,330,223		$	2,456,412		$	1,654,282
	General and administrative		632,372			533,658			533,837			505,765


	Total operating expenses		2,189,583			2,863,881			2,990,249			2,160,047
	Loss from operations:		(2,189,583	)		(2,863,881	)		(2,990,249	)		(2,160,047	)


	Interest expense		(260,428	)		(303,167	)		(361,426	)		(561,675	)
	Change in fair value of warrant liability		—			—			—			32,367
	Other income, net		1,059			894			401			(86,001	)


	Net loss	$	(2,448,952	)	$	(3,166,154	)	$	(3,351,274	)	$	(2,775,356	)




	Net loss per common share (basic and diluted)	$	(7.96	)	$	(9.94	)	$	(10.31	)	$	(8.12	)
	Weighted-average shares outstanding (basic and diluted)		307,742			318,654			325,023			341,935

Subsequent_Events

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2013
Subsequent Events	'
Subsequent Events	'

	18. Subsequent Events

	On February 4, 2014, the Company entered into an operating lease agreement to lease a new office facility in Ann Arbor, MI. The term of this lease is for 63 months, commencing on April 1, 2014. The Company's facility lease provides for a fixed monthly rent for the term of the lease, with monthly rent increasing every 12 months subsequent to the first 3 months of the lease, and also provides for certain rent adjustments to be paid as determined by the landlord.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2013
Summary of Significant Accounting Policies	'
Use of Estimates	'

	Use of Estimates

	The preparation of financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, expenses and related disclosures. Actual results could differ from those estimates.

	Prior to the completion of the IPO on July 1, 2013, the Company utilized significant estimates and assumptions in determining the fair value of its Common Stock. The Company utilized valuation methodologies in accordance with the framework of the 2004 American Institute of Certified Public Accountants Technical Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation, to estimate the fair value of its Common Stock. Each valuation methodology includes estimates and assumptions that require the Company's judgment. These estimates and assumptions include a number of objective and subjective factors, including external market conditions affecting the biotechnology industry sector, the prices at which the Company sold shares of its Preferred Stock, the superior rights and preferences of securities senior to its Common Stock at the time and the likelihood of achieving a liquidity event, such as an initial public offering or sale. Significant changes to the key assumptions used in the valuations could result in different fair values of Common Stock at each valuation date.

Cash and Cash Equivalents	'

	Cash and Cash Equivalents

	The Company invests its excess cash in bank deposits, money market accounts, and short-term investments. The Company considers all highly liquid investments with an original maturity of 90 days or less at the time of purchase to be cash equivalents. Cash equivalents are reported at fair value.

Investments	'

	Investments

	Investments are considered to be available-for-sale and are carried at fair value. Unrealized gains and losses, if any, are reported as a separate component of stockholders' deficit. The cost of investments classified as available-for-sale are adjusted for the amortization of premiums and accretion of discounts to maturity and recorded in other income (expense), net. Realized gains and losses, if any, are determined using the specific identification method and in other income (expense), net. Investments with original maturities beyond 90 days at the date of purchase and which mature at, or less than twelve months from, the balance sheet date are classified as current. Investments with a maturity beyond twelve months from the balance sheet date are classified as long-term.

Concentration of Credit Risk	'

	Concentration of Credit Risk

	Cash, cash equivalents, and marketable securities consist of financial instruments that potentially subject the Company to concentrations of credit risk. The Company has established guidelines for investment of its excess cash and believes the guidelines maintain safety and liquidity through diversification of counterparties and maturities.

Segment Information	'

	Segment Information

	The Company views its operations and manages its business in one operating segment, which is the business of researching, developing and commercializing therapies for the treatment of patients with elevated levels of low-density lipoprotein cholesterol and other cardiometabolic risk markers.

Fair Value of Financial Instruments	'

	Fair Value of Financial Instruments

	The Company's financial instruments consist principally of cash and cash equivalents, investments, other current assets, accounts payable and accrued liabilities that approximate their carrying value at December 31, 2013 and 2012.

Property and Equipment, Net	'

	Property and Equipment, Net

	Property and equipment are recorded at cost, less accumulated depreciation. Depreciation is provided using the straight-line method over the estimated useful lives of the respective assets, generally three to ten years. Leasehold improvements are amortized over the lesser of the lease term or the estimated useful lives of the related assets.

Impairment of Long-Lived Assets	'

	Impairment of Long-Lived Assets

	The Company reviews long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are less than its carrying amount. The impairment loss, if recognized, would be based on the excess of the carrying value of the impaired asset over its respective fair value. Excluding impairment losses recorded on assets held for sale, no other impairment losses have been recorded through December 31, 2013.

Research and Development	'

	Research and Development

	Research and development expenses consist of costs incurred to further the Company's research and development activities and include salaries and related benefits, costs associated with pre-clinical studies and trials, non-clinical activities (such as toxicology studies), regulatory activities, manufacturing activities to support clinical activities, research-related overhead expenses, and fees paid to external service providers that conduct certain research and development, clinical, and manufacturing activities on behalf of the Company. Research and development costs are expensed as incurred.

In-Process Research and Development	'

	In-Process Research and Development

	In April 2008, the Company acquired certain tangible research and development assets and intellectual property from Pfizer Inc. (Pfizer). As the acquired in-process research and development had not reached technological feasibility and had no alternative future uses in connection with this asset and intellectual property acquisition and the related purchase price allocation, the Company expensed $85,612 as in-process research and development costs in 2008.

Accrued Clinical Development Costs	'

	Accrued Clinical Development Costs

	Outside research costs are a component of research and development expense. These expenses include fees paid to contract research organizations and other service providers that conduct certain clinical and product development activities on behalf of the Company. Depending upon the timing of payments to the service providers, the Company recognizes prepaid expenses or accrued expenses related to these costs. These accrued or prepaid expenses are based on management's estimates of the work performed under service agreements, milestones achieved and experience with similar contracts. The Company monitors each of these factors and adjusts estimates accordingly.

Income Taxes	'

	Income Taxes

	The Company utilizes the liability method of accounting for income taxes as required by ASC 740, Income Taxes. Under this method, deferred tax assets and liabilities are determined based on differences between financial reporting and the tax basis of assets and liabilities and are measured using enacted tax rates and laws that will be in effect when the differences are expected to reverse. The Company has incurred operating losses since inception. Accordingly, it is not more likely than not that the Company will realize deferred tax assets and as such, it has recorded a full valuation allowance.

Warrants	'

	Warrants

	The Company accounts for its warrants issued in connection with its various financing transactions based upon the characteristics and provisions of the instrument. Warrants classified as liabilities are recorded on the Company's balance sheet at their fair value on the date of issuance and are marked-to-market on each subsequent reporting period, with the fair value changes recognized in the statement of operations. The warrants are measured using the Black-Scholes option-pricing model subsequent to the pricing of the Company's IPO and a Monte Carlo valuation model for previous periods which are based, in part, upon inputs where there is little or no market data, requiring the Company to develop its own independent assumptions. The Company adjusts the liability for changes in the fair value of the warrants until the earlier of the exercise of the warrants, the expiration of the warrants, or until such time as the warrants are no longer determined to be liabilities and reclassified into paid-in-capital at fair value. The warrants were reclassified into paid-in-capital upon closing of the IPO. (See Note 5).

Stock-Based Compensation	'

	Stock-Based Compensation

	The Company accounts for stock-based compensation in accordance with the provisions of ASC 718, Compensation—Stock Compensation. Accordingly, compensation costs related to equity instruments granted are recognized over the requisite service periods of the awards on a straight-line basis at the grant-date fair value calculated using a Black-Scholes option pricing model. Additionally, under the provisions of ASC 718, the Company is required to include an estimate of the number of awards that will be forfeited in calculating compensation costs. Any changes to the estimated forfeiture rates are accounted for prospectively. Stock-based compensation arrangements with non-employees are recognized at the grant-date fair value and then re-measured at each reporting period. Expense is recognized during the period the related services are rendered.

Reclassifications	'

	Reclassifications

	Certain prior period information has been reclassified to be comparable to the current year presentation. These items had no impact on the amounts of previously reported net loss or total shareholder's equity (deficit).

Recent Accounting Pronouncements	'

	Recent Accounting Pronouncements

	In February 2013, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2013-02 which is an amendment to the accounting guidance for the presentation of comprehensive income. Under the amended guidance, items that are reclassified to net income from accumulated other comprehensive income in the same reporting period require separate disclosure on the face of the financial statements where net income is presented or within the notes to the financial statements. The adoption of this update did not have a material impact on the Company's financial statements.

	In July 2013, the FASB issued ASU 2013-11 which is an amendment to the accounting guidance on income taxes. This guidance provides clarification on the financial statement presentation of an unrecognized benefit when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists. The amendment will be effective for the Company for interim and annual periods beginning after December 15, 2013, with early adoption permitted. The adoption of this standard is not expected to have a material impact on the Company's financial statements.

The_Company_and_Basis_of_Prese1

The Company and Basis of Presentation (Tables)	12 Months Ended
The Company and Basis of Presentation (Tables)	Dec. 31, 2013
The Company and Basis of Presentation	'
Summary of the Company's capitalization upon closing of its initial public offering	'






	Total common stock issued as of June 30, 2013	396,414
	Conversion of Series A preferred stock into common stock upon closing of IPO	8,244,781
	Conversion of Series A-1 preferred stock into common stock upon closing of IPO	966,218
	Sales of common stock through IPO	5,000,000


	Common stock issued as of July 1, 2013	14,607,413
	Issuance of common stock to underwriters due to exercise of over-allotment	750,000


	Total common stock issued as of July 11, 2013	15,357,413

Stock_Acquisition_Tables

Stock Acquisition (Tables)	12 Months Ended
Stock Acquisition (Tables)	Dec. 31, 2013
Stock Acquisition	'
Schedule of allocated total cost of the entity	'






	Cash	$	2,500,000
	Property and equipment		1,317,005
	Intangible assets		50,000
	In-process research and development		85,612
	Assets held for sale		1,047,383


	Total	$	5,000,000

Debt_Tables

Debt (Tables)	12 Months Ended
Debt (Tables)	Dec. 31, 2013
Debt	'
Schedule of reconciliation of various debt instruments	'






		December 31,
		2013		2012
	Short term convertible notes issued January 2012	$	—	$	6,000,000
	Short term convertible notes issued September 2012		—		4,000,000
	Short term convertible notes issued November 2012		—		5,700,000
	Discount on short term convertible notes		—		(458,993	)


	Total short term convertible notes, net of debt discount		—		15,241,007
	Long term debt		—		5,000,000
	Accumulated paid-in-kind interest		—		2,528,845


	Total long-term debt		—		7,528,845


	Total debt	$	—	$	22,769,852

Commitments_and_contingencies_

Commitments and contingencies (Tables)	12 Months Ended
Commitments and contingencies (Tables)	Dec. 31, 2013
Commitments and contingencies	'
Schedule of future minimum payments	'

	Future minimum payments as of December 31, 2013, under the facility lease are presented in the table below:


		Total		Less than		1 - 3 Years		3 - 5 Years		More than
		Total		1 Year		1 - 3 Years		3 - 5 Years		5 Years
	Operating lease	$	100,868	$	100,868	$	—	$	—	$	—


	Total	$	100,868	$	100,868	$	—	$	—	$	—

Property_and_Equipment_Tables

Property and Equipment (Tables)	12 Months Ended
Property and Equipment (Tables)	Dec. 31, 2013
Property and Equipment	'
Schedule of property and equipment	'






		December 31,
		2013		2012
	Lab equipment	$	511,403	$	1,057,276
	Computer equipment		99,412		99,412
	Software		118,572		96,668
	Furniture and fixtures		11,309		11,309
	Leasehold improvements		21,381		21,381
	Assets in Progress		6,530		—


	Subtotal		768,607		1,286,046
	Less accumulated depreciation and amortization		687,799		1,165,836


	Property and equipment, net	$	80,808	$	120,210

Other_Accrued_Liabilities_Tabl

Other Accrued Liabilities (Tables)	12 Months Ended
Other Accrued Liabilities (Tables)	Dec. 31, 2013
Other Accrued Liabilities	'
Schedule of other accrued liabilities	'






		December 31,
		2013		2012
	Stock based compensation liability	$	74,208	$	—
	Accrued professional fees		209,961	$	136,907
	Accrued franchise and property taxes		94,600		12,697
	Accrued compensation		667,164		60,725
	Accrued other		41,203		—


	Total other accrued liabilities	$	1,087,136	$	210,329

Investments_Tables

Investments (Tables)	12 Months Ended
Investments (Tables)	Dec. 31, 2013
Investments	'
Summary of the Company's cash equivalents and investments	'






		December 31, 2013
		Amortized		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair
				Gains		Losses			Value
	Cash equivalents:
	Money market funds	$	5,356,453	$	—	$	—		$	5,356,453


	Short-term investments:
	U.S treasury notes		2,070,774		—		(234	)		2,070,540
	U.S. government agency securities		1,454,426		157		—			1,454,583
	Long-term investments:
	Certificates of deposit		237,525		—		—			237,525
	U.S. treasury notes		9,116,136		3,595		(2,497	)		9,117,234
	U.S. government agency securities		8,186,958		640		(4,695	)		8,182,903


	Total	$	26,422,272	$	4,392	$	(7,426	)	$	26,419,238








		December 31, 2012
		Amortized		Gross		Gross			Estimated
		Cost		Unrealized		Unrealized			Fair
				Gains		Losses			Value
	Cash equivalents:
	Money market funds	$	6,357,542		—		—		$	6,357,542


	Total	$	6,357,542	$	—	$	—		$	6,357,542

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
Fair Value Measurements (Tables)	Dec. 31, 2013
Fair Value Measurements	'
Schedule of the Company's financial assets and liabilities that have been measured at fair value on a recurring basis	'






	Description	Total			Level 1		Level 2		Level 3
	December 31, 2013
	Assets:
	Money market funds	$	5,356,453		$	5,356,453	$	—	$	—
	Available for sale securities:
	Certificates of deposit		237,525			237,525		—		—
	U.S. treasury notes		11,187,774			11,187,774		—		—
	U.S. government agency securities		9,637,486			—		9,637,486		—


	Total assets at fair value	$	26,419,238		$	16,781,752	$	9,637,486	$	—




	December 31, 2012
	Assets:
	Money market funds	$	6,357,542		$	6,357,542	$	—	$	—


	Total assets at fair value	$	6,357,542		$	6,357,542	$	—	$	—




	Liabilities:
	Warrants	$	265,323		$	—	$	—	$	265,323


	Total liabilities at fair value	$	265,323		$	—	$	—	$	265,323




Summary of the changes in the fair value of the Company's Level 3 warrant liability	'






		Warrant Liability
	Level 3 Liabilities:
	As of January 1, 2012	$	—
	Issuance of warrants		297,690
	Change in fair value		(32,367	)


	As of December 31, 2012	$	265,323
	Change in fair value		2,586,865
	Reclassification of warrants liabilities to additional paid-in capital in conjunction with the conversion of the convertible preferred stock into common stock upon the closing of the Company's IPO		(2,852,188	)


	As of December 31, 2013	$	—

Convertible_Preferred_Stock_an1

Convertible Preferred Stock and Stockholders' Deficit (Tables)	12 Months Ended
	Dec. 31, 2013
Convertible Preferred Stock and Stockholders' Deficit	'
Summary of preferred stock designated as Series A and Series A-1	'






		December 31, 2012
		Shares		Liquidation		Shares
		Designated		Preference		Issued and
				Per Share		Outstanding
	Series A		34,785,000	$	1		23,975,000
	Series A-1		7,862,283		—		—


			42,647,283	$	1		23,975,000

Stock_Compensation_Tables

Stock Compensation (Tables)	12 Months Ended
Stock Compensation (Tables)	Dec. 31, 2013
Stock Compensation	'
Summary of activity relating to the Company's options to purchase common stock	'






		Number of			Weighted-Average			Weighted-Average			Aggregate
		Options			Price			Remaining			Intrinsic
					Per Share			Contractual			Value
								Term (Years)
	Outstanding at December 31, 2012		211,500		$	1.43			7.5		$	141,389
	Granted		1,251,749		$	10.62
	Forfeited or expired		(12,212	)	$	2.03
	Exercised		(49,936	)	$	2.47


	Outstanding at December 31, 2013		1,401,101		$	9.59			8.95		$	7,755,321




Summary of information about the stock option plan	'






		Number of			Weighted-Average			Weighted-Average			Aggregate
		Options			Price			Remaining			Intrinsic
					Per Share			Contractual			Value
								Term (Years)
	Vested and expected to vest at December 31, 2013		1,334,221		$	9.49			8.92		$	7,505,458


	Exercisable at December 31, 2013		594,176		$	2.81			8.16		$	6,572,563




Schedule of weighted-average assumptions used to compute the share-based compensation costs for the stock options granted to employees and non-employees	'






		Year ended December 31,
											Period From
											January 22, 2008
											(Inception)
											Through
		2013			2012			2011			December 31, 2013
	Risk-free interest rate		1.45	%		0.85	%		2.5	%		1.58	%
	Dividend yield		—			—			—			—
	Weighted-average expected life of options (years)		6.26			6.25			6.25			6.26
	Volatility		74	%		80	%		80	%		75	%

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2013
Income Taxes	'
Schedule of reconciliation of the U.S. statutory income tax rate to the Company's effective tax rate	'






		December 31,
		2013			2012			2011
	Federal income tax (benefit) at statutory rate		(34.0	)%		(34.0	)%		(34.0	)%
	State income tax benefit, net of federal benefit		—	%		—	%		(0.7	)%
	Permanent items		4.9	%		0.4	%		(0.1	)%
	Other		—	%		(0.2	)%		3.2	%
	Change in valuation allowance		29.1	%		33.8	%		31.6	%


	Effective income tax rate		0	%		0	%		0	%




Schedule of significant components of the Company's deferred tax assets	'






		December 31,
		2013			2012
	Deferred tax assets:
	Federal and state operating loss carryforwards	$	22,485,000		$	14,207,000
	Temporary differences		319,000			144,000


	Total deferred tax assets		22,804,000			14,351,000
	Valuation allowance		(22,804,000	)		(14,351,000	)


	Net deferred tax assets	$	—		$	—

Net_Loss_Per_Common_Share_Tabl

Net Loss Per Common Share (Tables)	12 Months Ended
Net Loss Per Common Share (Tables)	Dec. 31, 2013
Net Loss Per Common Share	'
Schedule of anti-dilutive securities excluded from the calculation of diluted net loss per share	'






		December 31,		December 31,
		2013		2012
	Convertible preferred stock		—		3,431,865
	Warrants for common stock		277,690		277,690
	Common shares under option		1,401,101		211,500
	Unvested restricted stock		16,703		—
	Convertible debt		—		3,430,723


	Total potential dilutive shares		1,695,494		7,351,778

Selected_Quarterly_Financial_D1

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
Selected Quarterly Financial Data (Unaudited) (Tables)	Dec. 31, 2013
Selected Quarterly Financial Data (Unaudited)	'
Schedule of unaudited quarterly financial data	'






		2013
		March 31			June 30			September 30			December 31
	Operating expenses:
	Research and development	$	2,092,593		$	3,100,422		$	3,482,673		$	7,338,517
	General and administrative		1,251,419			1,171,425			1,924,150			2,397,499


	Total operating expenses		3,344,012			4,271,847			5,406,823			9,736,016
	Loss from operations:		(3,344,012	)		(4,271,847	)		(5,406,823	)		(9,736,016	)


	Interest expense		(828,223	)		(108,357	)		—			—
	Change in fair value of warrant liability		(41,958	)		(2,544,907	)		—			—
	Other income, net		(24,984	)		4,035			168,389			46,570


	Net loss	$	(4,239,177	)	$	(6,921,076	)	$	(5,238,434	)	$	(9,689,446	)




	Net loss per common share (basic and diluted)	$	(12.24	)	$	(19.82	)	$	(0.34	)	$	(0.63	)
	Weighted-average shares outstanding (basic and diluted)		346,478			349,170			15,253,704			15,340,713




		2012
		March 31			June 30			September 30			December 31
	Operating expenses:
	Research and development	$	1,557,211		$	2,330,223		$	2,456,412		$	1,654,282
	General and administrative		632,372			533,658			533,837			505,765


	Total operating expenses		2,189,583			2,863,881			2,990,249			2,160,047
	Loss from operations:		(2,189,583	)		(2,863,881	)		(2,990,249	)		(2,160,047	)


	Interest expense		(260,428	)		(303,167	)		(361,426	)		(561,675	)
	Change in fair value of warrant liability		—			—			—			32,367
	Other income, net		1,059			894			401			(86,001	)


	Net loss	$	(2,448,952	)	$	(3,166,154	)	$	(3,351,274	)	$	(2,775,356	)




	Net loss per common share (basic and diluted)	$	(7.96	)	$	(9.94	)	$	(10.31	)	$	(8.12	)
	Weighted-average shares outstanding (basic and diluted)		307,742			318,654			325,023			341,935

The_Company_and_Basis_of_Prese2

The Company and Basis of Presentation (Details) (USD $)

12 Months Ended

71 Months Ended

0 Months Ended

Dec. 31, 2013

Jun. 11, 2013

Dec. 31, 2012

Dec. 31, 2010

Jul. 02, 2013

Jul. 11, 2013

Jul. 02, 2013

Jun. 11, 2013

Jul. 02, 2013

Jul. 11, 2013

Common stock

Initial Public Offering

Over-allotment option

Warrant

Common stock

Convertible preferred stock

Additional paid-in capital

Warrant liabilities

Reverse Stock Split

Reverse stock split ratio of outstanding common stock

0.1431

Par value of common stock (in dollars per share)

$0.00

Initial Public Offering

Original issue price (in dollars per share)

$14

Net proceeds from the IPO, including proceeds from the exercise of the underwriters' over-allotment option

$72,193,831

$72,200,000

Number of shares of convertible preferred stock converted into common stock

9,210,999

Warrants exercisable into common stock (in shares)

277,690

Reclassification of convertible preferred stock warrant liability to additional paid-in capital

$2,852,188

($2,852,188)

The_Company_and_Basis_of_Prese3

The Company and Basis of Presentation (Details 2)

Dec. 31, 2013

Jul. 11, 2013

Jul. 02, 2013

Jun. 30, 2013

Dec. 31, 2012

Apr. 19, 2013

Jan. 31, 2011

Nov. 30, 2010

Apr. 30, 2010

Jan. 31, 2010

Apr. 30, 2008

Dec. 31, 2013

Apr. 30, 2008

Jul. 02, 2013

Jul. 11, 2013

Series A preferred stock

Series A-1 preferred stock

Common stock

Initial Public Offering

Over-allotment option

Series A preferred stock

Series A-1 preferred stock

Common stock

Movement in Company's capitalization upon closing of initial public offering

Balance (in shares)

15,357,413

14,607,413

396,414

346,478

Conversion of preferred stock into common stock upon closing of IPO (in shares)

-57,598,092

-6,750,000

8,244,781

966,218

9,210,999

Common stock sold (in shares)

17,000,000

6,700,000

25,000

1,000,000

6,000,000

10,000,000

286,286

5,000,000

750,000

Balance (in shares)

15,357,413

14,607,413

396,414

346,478

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended		71 Months Ended
	Dec. 31, 2013	Dec. 31, 2008	Dec. 31, 2013
	item	Dec. 31, 2008	Dec. 31, 2013
Segment Information	'	'	'
Number of operating segments	1	'	'
Impairment of Long-Lived Assets	'	'	'
Other impairment losses	$0	'	'
In-Process Research and Development	'	'	'
Acquired in-process research and development	'	$85,612	$85,612
Property and equipment \| Minimum	'	'	'
Property and equipment, net	'	'	'
Estimated useful lives	'3 years	'	'
Property and equipment \| Maximum	'	'	'
Property and equipment, net	'	'	'
Estimated useful lives	'10 years	'	'

Stock_Acquisition_Details

Stock Acquisition (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Apr. 28, 2008	Apr. 28, 2008
	In-process research and development	Pfizer Note	Pfizer Note
			In-process research and development
Stock Acquisition	'	'	'
Aggregate principal amount	'	$5,000,000	'
Allocated total cost	'	'	'
Cash	'	2,500,000	'
Property and equipment	'	1,317,005	'
Intangible assets	'	50,000	'
Finite-lived intangible assets	'	'	85,612
Assets held for sale	'	1,047,383	'
Total	'	$5,000,000	'
Discount rate (as a percent)	35.00%	'	'

Debt_Details

Debt (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2012	Nov. 30, 2012	Dec. 31, 2012	Dec. 31, 2012
Debt (Details) (USD $)	Dec. 31, 2012	10% Convertible promissory notes	Short term convertible notes issued January 2012	Short term convertible notes issued September and November 2012	Short term convertible notes issued September 2012	Short term convertible notes issued November 2012
Debt	'	'	'	'	'	'
Short term convertible notes	'	'	$6,000,000	'	$4,000,000	$5,700,000
Discount on short term convertible notes	'	-458,993	'	'	'	'
Total short term convertible notes, net of debt discount	15,241,007	15,241,007	'	9,412,010	'	'
Long term debt	5,000,000	'	'	'	'	'
Accumulated paid-in-kind interest	2,528,845	'	'	'	'	'
Total long-term debt	7,528,845	'	'	'	'	'
Total debt	$22,769,852	'	'	'	'	'

Debt_Details_2

Debt (Details 2) (USD $)

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2010

Apr. 19, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Feb. 12, 2013

Feb. 28, 2013

Apr. 30, 2008

Jan. 31, 2012

Nov. 30, 2012

Feb. 28, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

29-May-13

Apr. 28, 2008

Jul. 02, 2013

29-May-13

Series A preferred stock

Series A-1 preferred stock

10% Convertible promissory notes

Short term convertible notes issued January 2012

Short term convertible notes issued September and November 2012

Short term convertible notes issued September 2012

Pfizer Note

Series A preferred stock

Warrant

Series A preferred stock

Interest Expense

Series A-1 preferred stock

Estimated fair value

Warrant

Debt

Aggregate principal amount

$15,700,000

$6,000,000

$9,700,000

$5,000,000

Interest rate (as a percent)

10.00%

8.93%

Accrued interest

923,092

Conversion of convertible promissory notes into Series A preferred stock (in shares)

16,623,092

250,000

6,750,000

16,623,092

250,000

Conversion price (in dollars per share)

Outstanding principal amount

7,803,000

Fair value of beneficial conversion feature

287,990

Amortization of debt discount and beneficial conversion

229,496

58,494

297,690

Aggregate purchase price of warrants

9,700

Estimated fair value of warrants

265,323

297,690

Short term borrowings with related parties, net of debt discount

15,241,007

9,412,010

Accrued interest during period

$274,155

$631,517

$577,065

$2,803,000

Preferred stock, shares issued

17,275,000

17,000,000

23,975,000

6,750,000

Share price of preferred stock (in dollars per share)

$1.16

Number of shares of preferred stock converted into shares of common stock

-57,598,092

-6,750,000

966,218

Warrants_Details

Warrants (Details) (USD $)

3 Months Ended

12 Months Ended

71 Months Ended

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Nov. 30, 2012

Sep. 30, 2012

Nov. 30, 2012

Jul. 02, 2013

Nov. 30, 2012

Jul. 02, 2013

Warrant

Series A preferred stock warrant

Common stock

Estimated fair value

Warrant

Short term convertible notes issued September and November 2012

Short term convertible notes issued September 2012

Short term convertible notes issued November 2012

Short term convertible notes issued September and November 2012

Warrants

Estimated fair value

$265,323

$297,690

$141,779

$155,911

$297,690

Warrants exercisable into stock (in shares)

1,940,000

277,690

Exercise price (in dollars per share)

Share price of common stock (in dollars per share)

$6.99

Number of shares of common stock to be purchased against outstanding warrants

277,690

(Loss)/gain recognized for change in the fair value of the warrant liability

($2,544,907)

($41,958)

$32,367

($2,586,865)

$32,367

($2,554,498)

Commitments_and_contingencies_1

Commitments and contingencies (Details) (USD $)	12 Months Ended			71 Months Ended
Commitments and contingencies (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Commitments and contingencies	'	'	'	'
Rent expense	$344,604	$335,000	$323,000	$1,631,004
Operating lease	'	'	'	'
Less than 1 Year	100,868	'	'	100,868
Total	$100,868	'	'	$100,868

Commitments_and_contingencies_2

Commitments and contingencies (Details 2) (License agreement, USD $)	12 Months Ended
	Dec. 31, 2013
License agreement	'
Milestone minimum annual payment	$50,000
Maximum	'
License agreement	'
Number of shares of common stock to be issued upon meeting various future milestones	11,451

Property_and_Equipment_Details

Property and Equipment (Details) (USD $)	12 Months Ended			71 Months Ended
Property and Equipment (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Property and Equipment	'	'	'	'
Property and equipment, gross	$768,607	$1,286,046	'	$768,607
Less accumulated depreciation and amortization	687,799	1,165,836	'	687,799
Property and equipment, net	80,808	120,210	'	80,808
Depreciation expense	70,551	139,433	178,471	1,447,722
Lab equipment	'	'	'	'
Property and Equipment	'	'	'	'
Property and equipment, gross	511,403	1,057,276	'	511,403
Computer equipment	'	'	'	'
Property and Equipment	'	'	'	'
Property and equipment, gross	99,412	99,412	'	99,412
Software	'	'	'	'
Property and Equipment	'	'	'	'
Property and equipment, gross	118,572	96,668	'	118,572
Furniture and fixtures	'	'	'	'
Property and Equipment	'	'	'	'
Property and equipment, gross	11,309	11,309	'	11,309
Leasehold improvements	'	'	'	'
Property and Equipment	'	'	'	'
Property and equipment, gross	21,381	21,381	'	21,381
Assets in Progress	'	'	'	'
Property and Equipment	'	'	'	'
Property and equipment, gross	$6,530	'	'	$6,530

Other_Accrued_Liabilities_Deta

Other Accrued Liabilities (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Other Accrued Liabilities	'	'
Stock based compensation liability	$74,208	'
Accrued professional fees	209,961	136,907
Accrued franchise and property taxes	94,600	12,697
Accrued compensation	667,164	60,725
Accrued other	41,203	'
Total other accrued liabilities	$1,087,136	$210,329

Investments_Details

Investments (Details) (USD $)

3 Months Ended

12 Months Ended

71 Months Ended

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Cash equivalents and investments

Gross Unrealized Gains

$4,392

Gross Unrealized Losses

-7,426

Total, Amortized Cost

26,422,272

6,357,542

26,422,272

6,357,542

26,422,272

Total, Estimated Fair Value

26,419,238

6,357,542

26,419,238

6,357,542

26,419,238

Unrealized gains or losses on investments

46,570

168,389

4,035

-24,984

-86,001

401

894

1,059

194,010

-83,647

-75,813

275,424

Reclassification out of accumulated other comprehensive income

Cash equivalents and investments

Unrealized gains or losses on investments

Short-term investments | U.S. treasury notes

Cash equivalents and investments

Investments, Amortized Cost

2,070,774

Gross Unrealized Losses

-234

Investments, Estimated Fair Value

2,070,540

Short-term investments | U.S. government agency securities

Cash equivalents and investments

Investments, Amortized Cost

1,454,426

Gross Unrealized Gains

157

Investments, Estimated Fair Value

1,454,583

Long-term investments | U.S. treasury notes

Cash equivalents and investments

Investments, Amortized Cost

9,116,136

Gross Unrealized Gains

3,595

Gross Unrealized Losses

-2,497

Investments, Estimated Fair Value

9,117,234

Long-term investments | U.S. government agency securities

Cash equivalents and investments

Investments, Amortized Cost

8,186,958

Gross Unrealized Gains

640

Gross Unrealized Losses

-4,695

Investments, Estimated Fair Value

8,182,903

Money market funds

Cash equivalents and investments

Cash equivalents, Estimated Fair Value

5,356,453

6,357,542

5,356,453

6,357,542

5,356,453

Certificates of deposit | Long-term investments

Cash equivalents and investments

Investments, Amortized Cost

237,525

Investments, Estimated Fair Value

$237,525

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	12 Months Ended
Fair Value Measurements (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Assets:	'	'
Total, Estimated Fair Value	$26,419,238	$6,357,542
Liabilities:	'	'
Estimated fair value	'	265,323
Transfer of assets between levels	0	0
Transfer of liabilities between levels	0	0
Recurring fair value measurement \| Level 1	'	'
Assets:	'	'
Money market fund	5,356,453	6,357,542
Total, Estimated Fair Value	16,781,752	6,357,542
Recurring fair value measurement \| Level 1 \| U.S. treasury notes	'	'
Assets:	'	'
Available for sale securities	11,187,774	'
Recurring fair value measurement \| Level 1 \| Certificates of deposit	'	'
Assets:	'	'
Available for sale securities	237,525	'
Recurring fair value measurement \| Level 2	'	'
Assets:	'	'
Total, Estimated Fair Value	9,637,486	'
Recurring fair value measurement \| Level 2 \| U.S. government agency securities	'	'
Assets:	'	'
Available for sale securities	9,637,486	'
Recurring fair value measurement \| Level 3	'	'
Liabilities:	'	'
Estimated fair value	'	265,323
Total liabilities at fair value	'	265,323
Recurring fair value measurement \| Total	'	'
Assets:	'	'
Money market fund	5,356,453	6,357,542
Total, Estimated Fair Value	26,419,238	6,357,542
Liabilities:	'	'
Estimated fair value	'	265,323
Total liabilities at fair value	'	265,323
Recurring fair value measurement \| Total \| U.S. treasury notes	'	'
Assets:	'	'
Available for sale securities	11,187,774	'
Recurring fair value measurement \| Total \| U.S. government agency securities	'	'
Assets:	'	'
Available for sale securities	9,637,486	'
Recurring fair value measurement \| Total \| Certificates of deposit	'	'
Assets:	'	'
Available for sale securities	$237,525	'

Fair_Value_Measurements_Detail1

Fair Value Measurements (Details 2) (Warrant Liability, USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Warrant Liability	'	'
Changes in the fair value of Level 3 warrant liability	'	'
Level 3 liabilities beginning balance	$265,323	'
Issuance of warrants	'	297,690
Change in fair value	2,586,865	-32,367
Reclassification of warrants liabilities to additional paid-in capital in conjunction with the conversion of the convertible preferred stock into common stock upon the closing of the Company's IPO	-2,852,188	'
Level 3 liabilities closing balance	'	$265,323

Fair_Value_Measurements_Detail2

Fair Value Measurements (Details 3) (Nonrecurring fair value measurement, USD $)	12 Months Ended			71 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Nonrecurring fair value measurement	'	'	'	'
Fair Value Measurements on a Nonrecurring Basis	'	'	'	'
Impairment loss related to the assets held for sale	$27,000	$86,887	$108,308	$214,393
Fair value of assets held for sale	$29,108	'	'	$29,108

Convertible_Preferred_Stock_an2

Convertible Preferred Stock and Stockholders' Deficit (Details) (USD $)

1 Months Ended

12 Months Ended

71 Months Ended

12 Months Ended

0 Months Ended

1 Months Ended

12 Months Ended

35 Months Ended

71 Months Ended

12 Months Ended

0 Months Ended

1 Months Ended

12 Months Ended

71 Months Ended

0 Months Ended

1 Months Ended

0 Months Ended

Apr. 30, 2008

Dec. 31, 2013

Dec. 31, 2011

Dec. 31, 2013

Apr. 30, 2013

Mar. 31, 2013

Feb. 12, 2013

Dec. 31, 2012

Jan. 31, 2011

Apr. 30, 2010

Jan. 23, 2008

Dec. 31, 2013

29-May-13

Dec. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jan. 31, 2011

Apr. 30, 2010

Dec. 31, 2013

Apr. 19, 2013

Jan. 31, 2011

Nov. 30, 2010

Apr. 30, 2010

Jan. 31, 2010

Apr. 30, 2008

Dec. 31, 2013

Dec. 31, 2010

Dec. 31, 2013

Jul. 02, 2013

Jun. 11, 2013

Apr. 30, 2013

Mar. 31, 2013

Feb. 12, 2013

Dec. 31, 2012

Sep. 30, 2012

Dec. 31, 2011

Dec. 31, 2013

Feb. 12, 2013

Feb. 28, 2013

Apr. 30, 2008

Dec. 31, 2013

Jun. 11, 2013

Dec. 31, 2012

Sep. 30, 2012

Jan. 31, 2011

Apr. 30, 2010

Apr. 30, 2008

Jul. 02, 2013

29-May-13

Apr. 30, 2008

Jul. 02, 2013

item

Maximum

Pfizer note

Convertible preferred stock

Series A preferred stock

Series A-1 preferred stock

Common stock

IPO

Minimum

Convertible promissory note

Pfizer note

Common stock warrant

Series A preferred stock

Series A-1 preferred stock

Common stock

item

Convertible preferred stock and stockholders' deficit

Number of shares of authorized common stock

44,025,145

120,000,000

75,220,375

58,220,375

56,519,253

50,000,000

45,025,145

1,000

Number of new series preferred stock authorized

Number of shares of authorized preferred stock

42,647,283

41,682,329

40,725,145

34,785,000

34,250,000

33,250,000

59,538,092

42,538,092

41,636,970

34,785,000

7,862,283

6,897,329

6,475,145

Number of shares of authorized preferred stock

5,000,000

34,785,000

Designated preferred stock

42,647,283

34,785,000

7,862,283

Number of shares sold

17,000,000

6,700,000

25,000

1,000,000

6,000,000

10,000,000

286,286

5,000,000

Share price of preferred stock (in dollars per share)

$1.16

$6.99

Net proceeds from sale of common stock

$200

Net proceeds from sale of preferred stock

6,700,000

25,000

1,000,000

6,000,000

10,000,000

Proceeds from issuance of preferred stock, net of issuance costs

16,824,235

6,700,000

40,799,235

16,880,463

Number of shares of convertible preferred stock converted into common stock

-57,598,092

-6,750,000

966,218

8,244,781

966,218

9,210,999

Stock issuance costs

119,537

53,469

Aggregate balance

7,803,000

Principal amount of the note converted

250,000

Number of shares of preferred stock issued upon conversion of note (in shares)

16,623,092

250,000

16,623,092

250,000

6,750,000

Convertible preferred stock:

Liquidation Preference Per Share (in dollars per share)

Shares Issued

23,975,000

17,000,000

17,275,000

23,975,000

6,750,000

Shares Outstanding

23,975,000

Percentage of voting power required to be held by the holders of the common stock and preferred stock for determining liquidation preference

50.00%

Preferred stock cash dividend rate (as a percent)

8.00%

Dividends declared, accrued or paid

Percentage of preferred stock holders affirmative election required for automatic conversion of temporary equity

60.00%

67.00%

Number of times of adjusted original issue price of preferred stock considered for sale of common stock in a firmly under written public offering for determining automatic conversion of temporary equity

Gross proceeds from sale of entity's common stock in a firmly underwritten public offering considered for determining automatic conversion of temporary equity

$40,000,000

Conversion rate

$1.16

$14

Conversion price (in dollars per share)

$6.99

$8.08

$1.16

Conversion rate

0.143

Stock_Compensation_Details

Stock Compensation (Details) (USD $)	12 Months Ended			71 Months Ended	0 Months Ended		12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Jun. 25, 2013	Jun. 25, 2013	Dec. 31, 2013
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	2013 Plan	2008 Incentive Stock Option and Restricted Stock Plan	2008 Incentive Stock Option and Restricted Stock Plan
Stock compensation	'	'	'	'	'	'	'
Shares reserved and approved for issuance	'	'	'	'	1,100,000	'	'
Shares reserved under previous plan and subsequently transferred to new plan	'	'	'	'	54,129	54,129	'
Percentage of increase in the number of shares reserved and available for issuance	'	'	'	'	2.50%	'	'
Grant period of stock awards	'	'	'	'	'	'	'10 years
Purchase price expressed as a percentage of fair value of shares on the date of grant	'	'	'	'	'	'	100.00%
Vesting percentage on the first anniversary of the option grant	'	'	'	'	'	'	25.00%
Period for which remainder of grant amount will vest on the first day of each calendar quarter	'	'	'	'	'	'	'3 years
Expiration period	'	'	'	'	'	'	'10 years
Period from cessation of employment within which options expire if not exercised	'	'	'	'	'	'	'90 days
Number of Options	'	'	'	'	'	'	'
Outstanding at the beginning of period (in shares)	211,500	'	'	'	'	'	'
Granted (in shares)	1,251,749	'	'	'	'	'	'
Forfeited or expired (in shares)	-12,212	'	'	'	'	'	'
Exercised (in shares)	-49,936	'	'	'	'	'	'
Outstanding at the end of the period (in shares)	1,401,101	211,500	'	1,401,101	'	'	'
Weighted-Average Price Per Share	'	'	'	'	'	'	'
Outstanding at the beginning of period (in dollars per share)	$1.43	'	'	'	'	'	'
Granted (in dollars per share)	$10.62	'	'	'	'	'	'
Forfeited or expired (in dollars per share)	$2.03	'	'	'	'	'	'
Exercised (in dollars per share)	$2.47	'	'	'	'	'	'
Outstanding at the end of the period (in dollars per share)	$9.59	$1.43	'	$9.59	'	'	'
Weighted-Average Remaining Contractual Term (Years)	'	'	'	'	'	'	'
Outstanding at the end of the period	'8 years 11 months 12 days	'7 years 6 months	'	'	'	'	'
Aggregate Intrinsic Value	'	'	'	'	'	'	'
Outstanding at the end of the period (in dollars)	$7,755,321	$141,389	'	$7,755,321	'	'	'
Information about the stock option plan	'	'	'	'	'	'	'
Number of Options, vested and expected to vest (in shares)	1,334,221	'	'	1,334,221	'	'	'
Number of Options, exercisable (in shares)	594,176	'	'	594,176	'	'	'
Weighted-Average Price Per Share, vested and expected to vest (in dollars per share)	$9.49	'	'	$9.49	'	'	'
Weighted-Average Price Per Share, exercisable (in dollars per share)	$2.81	'	'	$2.81	'	'	'
Weighted-Average Remaining Contractual Term, vested and expected to vest	'8 years 11 months 1 day	'	'	'	'	'	'
Weighted-Average Remaining Contractual Term, exercisable	'8 years 1 month 28 days	'	'	'	'	'	'
Aggregate Intrinsic Value, vested and expected to vest (in dollars)	7,505,458	'	'	7,505,458	'	'	'
Aggregate Intrinsic Value, exercisable (in dollars)	6,572,563	'	'	6,572,563	'	'	'
Assumptions used to compute the share-based compensation costs for stock options granted to employees and non-employees	'	'	'	'	'	'	'
Risk-free interest rate (as a percent)	1.45%	0.85%	2.50%	1.58%	'	'	'
Weighted-average expected life of options (years)	'6 years 3 months 4 days	'6 years 3 months	'6 years 3 months	'6 years 3 months 4 days	'	'	'
Volatility (as a percent)	74.00%	80.00%	80.00%	75.00%	'	'	'
Additional disclosures	'	'	'	'	'	'	'
Weighted-average grant-date fair value (in dollars per share)	$7.14	$1.33	$1.12	$5.94	'	'	'
Stock-based compensation expense	1,226,988	79,861	78,451	1,484,096	'	'	'
Unrecognized compensation cost (in dollars)	$7,346,725	'	'	$7,346,725	'	'	'
Weighted-average period over which remaining unrecognized compensation cost will be recognized	'3 years 6 months	'	'	'	'	'	'

Employee_Benefit_Plan_Details

Employee Benefit Plan (Details) (USD $)	12 Months Ended			71 Months Ended
Employee Benefit Plan (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Employee Benefit Plan	'	'	'	'
Contributions to the 401(k) Plan	$0	$0	$0	$0

Income_Taxes_Details

Income Taxes (Details) (USD $)	12 Months Ended
Income Taxes (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Taxes	'	'	'
Provision for income taxes	$0	$0	$0
Deferred tax assets, before valuation allowance	22,804,000	14,351,000	10,386,000
Net operating loss carryforwards	'	'	'
NOLs related to excess tax benefits	191,000	'	'
Federal	'	'	'
Net operating loss carryforwards	'	'	'
Net operating loss carryforwards	62,272,000	40,465,000	29,206,000
State	'	'	'
Net operating loss carryforwards	'	'	'
Net operating loss carryforwards	$33,129,000	$11,322,000	$0

Income_Taxes_Details_2

Income Taxes (Details 2) (USD $)	12 Months Ended
Income Taxes (Details 2) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of the U.S. statutory income tax rate to the Company's effective tax rate	'	'	'
Federal income tax (benefit) at statutory rate	-34.00%	-34.00%	-34.00%
State income tax benefit, net of federal benefit	'	'	-0.70%
Permanent items	4.90%	0.40%	-0.10%
Other	'	-0.20%	3.20%
Change in valuation allowance	29.10%	33.80%	31.60%
Effective income tax rate	0.00%	0.00%	0.00%
Unrecognized tax benefits related to interest and penalties accrued	$0	'	'

Income_Taxes_Details_3

Income Taxes (Details 3) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Deferred tax assets:	'	'	'
Federal and state operating loss carryforwards	$22,485,000	$14,207,000	'
Temporary differences	319,000	144,000	'
Total deferred tax assets	22,804,000	14,351,000	10,386,000
Valuation allowance	($22,804,000)	($14,351,000)	'

License_Agreement_Details

License Agreement (Details) (USD $)	1 Months Ended	12 Months Ended			71 Months Ended
License Agreement (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
License agreement	'	'	'	'	'
Fair value of common stock	'	'	'	$4,400	'
License agreement	'	'	'	'	'
License agreement	'	'	'	'	'
Number of shares of common stock issued under agreement	2,862	'	'	'	'
License issue fee	50,000	'	'	'	'
Fair value of common stock	4,400	'	'	'	'
Milestone minimum annual payment	'	50,000	'	'	'
Payment due period following achievement of milestone	'	'30 days	'	'	'
Expenses recognized that are associated with the license agreement	'	$50,000	$50,000	$54,400	$154,400
License agreement \| Maximum	'	'	'	'	'
License agreement	'	'	'	'	'
Number of shares of common stock to be issued upon meeting various future milestones	'	11,451	'	'	'

Net_Loss_Per_Common_Share_Deta

Net Loss Per Common Share (Details)	12 Months Ended
Net Loss Per Common Share (Details)	Dec. 31, 2013	Dec. 31, 2012
Net Loss Per Common Share	'	'
Reverse stock split	0.1431	'
Net Loss Per Common Share	'	'
Total potential dilutive shares	1,695,494	7,351,778
Convertible preferred stock	'	'
Net Loss Per Common Share	'	'
Total potential dilutive shares	'	3,431,865
Warrants for common stock	'	'
Net Loss Per Common Share	'	'
Total potential dilutive shares	277,690	277,690
Common shares under option	'	'
Net Loss Per Common Share	'	'
Total potential dilutive shares	1,401,101	211,500
Unvested restricted stock	'	'
Net Loss Per Common Share	'	'
Total potential dilutive shares	16,703	'
Convertible debt	'	'
Net Loss Per Common Share	'	'
Total potential dilutive shares	'	3,430,723

Selected_Quarterly_Financial_D2

Selected Quarterly Financial Data (Unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended			35 Months Ended	71 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2013
Operating expenses:	'	'	'	'	'	'	'	'	'	'	'	'	'
Research and development	$7,338,517	$3,482,673	$3,100,422	$2,092,593	$1,654,282	$2,456,412	$2,330,223	$1,557,211	$16,014,205	$7,998,128	$7,807,702	'	$43,428,066
General and administrative	2,397,499	1,924,150	1,171,425	1,251,419	505,765	533,837	533,658	632,372	6,744,493	2,205,632	2,356,669	'	18,194,189
Total operating expenses	9,736,016	5,406,823	4,271,847	3,344,012	2,160,047	2,990,249	2,863,881	2,189,583	22,758,698	10,203,760	10,164,371	'	61,707,867
Loss from operations	-9,736,016	-5,406,823	-4,271,847	-3,344,012	-2,160,047	-2,990,249	-2,863,881	-2,189,583	-22,758,698	-10,203,760	-10,164,371	'	-61,463,388
Interest expense	'	'	-108,357	-828,223	-561,675	-361,426	-303,167	-260,428	-936,580	-1,486,696	-577,157	'	-4,320,696
Change in fair value of warrant liability	'	'	-2,544,907	-41,958	32,367	'	'	'	-2,586,865	32,367	0	'	-2,554,498
Other income, net	46,570	168,389	4,035	-24,984	-86,001	401	894	1,059	194,010	-83,647	-75,813	'	275,424
Net loss	($9,689,446)	($5,238,434)	($6,921,076)	($4,239,177)	($2,775,356)	($3,351,274)	($3,166,154)	($2,448,952)	($26,088,133)	($11,741,736)	($10,817,341)	($19,415,948)	($68,063,158)
Net loss per common share (basic and diluted) (in dollars per share)	($0.63)	($0.34)	($19.82)	($12.24)	($8.12)	($10.31)	($9.94)	($7.96)	($3.31)	($36.31)	($36.22)	'	'
Weighted-average shares outstanding (basic and diluted) (in shares)	15,340,713	15,253,704	349,170	346,478	341,935	325,023	318,654	307,742	7,885,921	323,382	298,689	'	'

Subsequent_Events_Details

Subsequent Events (Details) (Subsequent event)	0 Months Ended
Subsequent Events (Details) (Subsequent event)	Feb. 04, 2014
Subsequent event	'
Subsequent events	'
Term period of lease	'63 months
Operating lease period for monthly rent increasing in fixed monthly rent	'12 months
Operating lease period after which monthly rent increase	'3 months