Radius Recycling 10-K 25 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2015	Feb. 19, 2016	Jun. 30, 2015
Document and Entity Information
Entity Registrant Name	Radius Health, Inc.
Entity Central Index Key	1,428,522
Document Type	10-K
Document Period End Date	Dec. 31, 2015
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 2.1
Entity Common Stock, Shares Outstanding		43,014,243
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY

Condensed Balance Sheets

Condensed Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 159,678	$ 28,518
Marketable Securities	313,661	76,758
Prepaid expenses and other current assets	6,969	2,057
Total current assets	480,308	107,333
Property and equipment, net	1,897	842
Other assets	260	242
Total assets	482,465	108,417
Current liabilities:
Accounts payable	6,228	2,292
Accrued expenses and other current liabilities	14,952	18,267
Total current liabilities	21,180	20,559
Note payable, net of current portion and discount		24,394
Total liabilities	$ 21,180	$ 44,953
Commitments and contingencies
Stockholders' equity:
Common stock, $.0001 par value; 200,000,000 shares authorized, 42,984,243 shares and 32,924,535 shares issued and outstanding at December 31, 2015 and 2014, respectively	$ 4	$ 3
Additional paid-in-capital	907,040	407,720
Accumulated other comprehensive income (loss)	5	(21)
Accumulated deficit	(445,764)	(344,238)
Total stockholders' equity	461,285	63,464
Total liabilities and stockholders' equity	$ 482,465	$ 108,417

Condensed Balance Sheets (Paren

Condensed Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	42,984,243	32,924,535
Common stock, shares outstanding	42,984,243	32,924,535

Condensed Statements of Operati

Condensed Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
OPERATING EXPENSES:
Research and development	$ 68,280	$ 45,719	$ 60,536
General and administrative	30,797	13,674	6,829
Loss from operations	(99,077)	(59,393)	(67,365)
OTHER INCOME (EXPENSE) :
Other (expense) income, net	(35)	(510)	9,085
Loss on retirement of note payable	(1,572)	(203)
Interest income	1,043	94	30
Interest expense	(1,885)	(2,467)	(2,440)
NET LOSS	(101,526)	(62,479)	(60,690)
OTHER COMPREHENSIVE INCOME, NET OF TAX:
Unrealized gain (loss) from marketable securities	26	(21)
COMPREHENSIVE LOSS	(101,500)	(62,500)	(60,690)
LOSS ATTRIBUTABLE TO COMMON STOCKHOLDERS - BASIC AND DILUTED (Note 12)	$ (101,526)	$ (71,479)	$ (78,161)
LOSS PER SHARE:
Basic and diluted (in dollars per share)	$ (2.56)	$ (4.04)	$ (203.91)
WEIGHTED AVERAGE SHARES:
Basic and diluted (in shares)	39,643,099	17,699,487	383,310

Statements of Convertible Prefe

Statements of Convertible Preferred Stock and Stockholders' Deficit - USD ($) $ in Thousands	Series B-2 Convertible Preferred Stock	Series B	Series A-1 Convertible Preferred Stock	Series A-2 Convertible Preferred Stock	Series A-3 Convertible Preferred Stock	Series A-4 Convertible Preferred Stock	Series A-5 Convertible Preferred Stock	Series A-6 Convertible Preferred Stock	Common Stock	Additional Paid-In-Capital		Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit		Total
Balance at Dec. 31, 2012			$ 71,957	$ 86,714	$ 11,182	$ 271	$ 525						$ (200,661)		$ (200,661)
Balance (in shares) at Dec. 31, 2012			939,612	983,208	142,227	3,998	6,443		380,328
Increase (Decrease) in Stockholders' Equity
Net loss													(60,690)		(60,690)
Stock options exercised										$ 13					13
Stock options exercised (in shares)									5,336
Issuance of preferred stock		$ 41,514						$ 23,168
Issuance of preferred stock (in shares)		701,235						496,111
Accretion of dividends on preferred stock		$ (2,378)	$ (6,780)	$ (7,263)	$ (1,050)					(1,521)	[1]		(15,950)	[1]	(17,471)	[1]
Stock-based compensation expense										1,508					1,508
Balance at Dec. 31, 2013		$ 43,892	$ 78,737	$ 93,977	$ 12,232	$ 271	$ 525	$ 23,168					(277,301)		(277,301)
Balance (in shares) at Dec. 31, 2013		701,235	939,612	983,208	142,227	3,998	6,443	496,111	385,664
Increase (Decrease) in Stockholders' Equity
Net loss													(62,479)		(62,479)
Unrealized gain (loss) from marketable securities												$ (21)			(21)
Stock options exercised										170					170
Stock options exercised (in shares)									49,382
Issuance of preferred stock	$ 26,152							$ 10,109
Issuance of preferred stock (in shares)	448,060							186,847
Accretion of dividends on preferred stock	$ (685)	$ (1,515)	$ (3,084)	$ (3,246)	$ (470)					(4,542)			(4,458)		(9,000)
Issuance of warrants										41					41
Exercise of warrants (in shares)									20,435
Stock-based compensation expense										7,070					7,070
Issuance of common stock, net									$ 1	103,803					103,804
Issuance of common stock (in shares)									10,141,268
Conversion of convertible preferred stock into common stock	$ (26,837)	$ (45,407)	$ (81,821)	$ (97,223)	$ (12,702)	$ (271)	$ (525)	$ (33,277)	$ 2	298,061					298,063
Conversion of convertible preferred stock into common stock (in shares)	(448,060)	(701,235)	(939,612)	(983,208)	(142,227)	(3,998)	(6,443)	(682,958)	22,327,786
Reclassification of warrant liability to additional paid-in-capital										3,117					3,117
Balance at Dec. 31, 2014									$ 3	407,720		(21)	(344,238)		63,464
Balance (in shares) at Dec. 31, 2014									32,924,535
Increase (Decrease) in Stockholders' Equity
Net loss													(101,526)		(101,526)
Unrealized gain (loss) from marketable securities												26			26
Stock options exercised										2,337					2,337
Stock options exercised (in shares)									267,684
Exercise of warrants (in shares)									529,862
Stock-based compensation expense										14,734					14,734
Issuance of common stock, net									$ 1	482,249					482,250
Issuance of common stock (in shares)									9,262,162
Balance at Dec. 31, 2015									$ 4	$ 907,040		$ 5	$ (445,764)		$ 461,285
Balance (in shares) at Dec. 31, 2015									42,984,243
[1]

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS USED IN OPERATING ACTIVITIES:
Net loss	$ (101,526)	$ (62,479)	$ (60,690)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	176	77	27
Amortization of premium (accretion of discount) on marketable securities, net	1,714	429	27
Stock-based compensation expense	14,734	7,070	1,508
Research and development expense settled in stock		2,717	13,118
Change in fair value of other current assets, warrant liability and other liability		505	(9,087)
Non-cash interest	183	295	387
Loss on retirement of note payable	1,572	57
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(4,914)	(1,639)	1,721
Other long-term assets	(108)	(105)
Accounts payable	3,936	1,991	(250)
Accrued expenses and other current liabilities	(2,870)	2,737	8,222
Net cash used in operating activities	(87,103)	(48,345)	(45,017)
CASH FLOWS (USED IN) PROVIDED BY INVESTING ACTIVITIES:
Purchases of property and equipment	(1,231)	(857)	(2)
Purchases of marketable securities	(579,088)	(97,678)	(17,070)
Sales and maturities of marketable securities	340,497	20,470	21,043
Net cash (used in) provided by investing activities	(239,822)	(78,065)	3,971
CASH FLOWS PROVIDED BY FINANCING ACTIVITIES:
Proceeds from exercise of stock options	2,337	170	13
Proceeds from the issuance of preferred stock, net		27,368	42,870
Proceeds from note payable		24,555
Proceeds from the issuance of common stock, net	482,250	103,804
Deferred financing costs		(116)
Payments on note payable	(25,000)	(13,156)	(8,187)
Fee for early prepayment of note payable	(1,502)
Net cash provided by financing activities	458,085	142,625	34,696
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	131,160	16,215	(6,350)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	28,518	12,303	18,653
CASH AND CASH EQUIVALENTS AT END OF PERIOD	159,678	28,518	12,303
SUPPLEMENTAL DISCLOSURES:
Cash paid for interest	$ 1,490	1,971	1,796
NON-CASH FINANCING ACTIVITIES:
Accretion of dividends on preferred stock		9,000	17,471	[1]
Reclassification of Preferred Stock to Common Stock		298,063
Fair value of series A-6 convertible preferred stock issued as settlement of liability		10,109	23,168
Fair value of warrants issued		$ 1,552	$ 1,356
[1]

Nature of Business

Nature of Business	12 Months Ended
	Dec. 31, 2015
Nature of Business
Nature of Business	1. Nature of Business Radius Health, Inc. ("Radius" or the "Company") is a science-driven biopharmaceutical company that is committed to developing innovative therapeutics in the areas of osteoporosis, oncology and endocrine diseases. The Company's lead product candidate, the investigational drug abaloparatide for subcutaneous injection ("abaloparatide-SC"), has completed Phase 3 development for potential use in the reduction of fracture risk in postmenopausal women with osteoporosis and is currently under regulatory review in Europe. The Company's clinical pipeline also includes an investigational abaloparatide transdermal patch ("abaloparatide-TD") for potential use in osteoporosis and the investigational drug RAD1901 for potential use in hormone-driven, or hormone-resistant, breast cancer, and vasomotor symptoms in postmenopausal women. The Company's preclinical pipeline includes RAD140, a non-steroidal selective androgen receptor modulator, under investigation for potential applications in oncology and multiple conditions where androgen modulation may offer therapeutic benefit. The Company is subject to the risks associated with emerging companies with a limited operating history, including dependence on key individuals, a developing business model, the necessity of securing regulatory approval to market its investigational product candidates, market acceptance of the Company's investigational product candidates following receipt of regulatory approval, competition for its investigational product candidates following receipt of regulatory approval, and the continued ability to obtain adequate financing to fund the Company's future operations. The Company has incurred losses and expects to continue to incur additional losses for the foreseeable future. As of December 31, 2015, the Company had an accumulated deficit of $445.8 million, and total cash, cash equivalents and marketable securities of $473.3 million. Based upon its cash, cash equivalents and marketable securities balance as of December 31, 2015, the Company believes that, prior to the consideration of revenue from the potential future sales of any of its investigational products that may receive regulatory approval or proceeds from partnership activities, it has sufficient capital to fund its development plans, U.S. commercial scale-up and other operational activities into 2018. The Company expects to finance the future development costs of its clinical product portfolio with its existing cash and cash equivalents and marketable securities, or through strategic financing opportunities that could include, but are not limited to partnering or other collaboration agreements, future offerings of its equity, or the incurrence of debt. However, there is no guarantee that any of these strategic or financing opportunities will be executed or executed on favorable terms, and some could be dilutive to existing stockholders. If the Company fails to obtain additional future capital, it may be unable to complete its planned preclinical and clinical trials and obtain approval of certain investigational product candidates from the U.S. Food and Drug Administration or foreign regulatory authorities.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation —The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary, Radius Health Securities Corporation. All material intercompany balances and transactions have been eliminated in consolidation. Reverse Stock Split —On April 24, 2014, the Company effected a reverse stock split of the Company's common stock. The number of authorized shares of the Company's common stock and the par value did not change. Pursuant to the stock split, every 2.28 shares of the Company's issued and outstanding common stock were automatically combined into one issued and outstanding share of the Company's common stock. All shares and per share amounts in the financial statements and accompanying notes have been retroactively adjusted to give effect to the reverse stock split. Use of Estimates —The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States ("GAAP") requires the Company's management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. The Company considers events or transactions that occur after the balance sheet date but before the consolidated financial statements are issued as additional evidence for certain estimates or to identify matters that require additional disclosure. Subsequent events have been evaluated up to the date of issuance of these consolidated financial statements. Cash Equivalents —The Company considers all highly liquid investment instruments with an original maturity when purchased of three months or less to be cash equivalents. Money market funds represents a majority of the cash equivalent balance at December 31, 2015 and 2014. Marketable Securities —All investment instruments with an original maturity date, when purchased, in excess of three months have been classified as current marketable securities. The Company classifies securities that are available to fund current operations as current assets. These marketable securities are classified as available-for-sale and are carried at fair value. Unrealized gains and losses, if any, are included within other comprehensive (loss) income within stockholders' equity (deficit). The amortized cost of debt securities in this category is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization is included in interest income. Realized gains and losses on available-for-sale securities are included in interest income. The cost of securities sold is based on the specific identification method. The Company periodically reviews the portfolio of securities to determine whether an other-than-temporary impairment has occurred. No such losses have occurred to date. There were no realized gains or losses on the sale of securities for the years ended December 31, 2015 and 2014. Fair Value Measurements —The Company determines the fair market values of its financial instruments based on the fair value hierarchy, which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The following are three levels of inputs that may be used to measure fair value: Level 1 Quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2 Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Concentrations of Credit Risk and Off-Balance-Sheet Risk —Financial instruments that potentially subject the Company to credit risk primarily consist of cash and cash equivalents and available-for-sale marketable securities. The Company mitigates its risk with respect to cash and cash equivalents and marketable securities by maintaining its deposits and investments at high-quality financial institutions. The Company invests any excess cash in money market funds and other securities, and the management of these investments is not discretionary on the part of the financial institution. The Company has no significant off-balance-sheet risks such as foreign exchange contracts, option contracts, or other hedging arrangements. Inventory —The Company capitalizes inventories produced in preparation for initiating sales of a drug candidate when the related drug candidate is approved or considered to have a high likelihood of regulatory approval and the related costs are expected to be recoverable through sales of the inventories. An assessment of inventory capitalization begins either on or after the date a New Drug Application is accepted for filing by the U.S. Food and Drug Administration, or an international equivalent. Determining whether or not to continue to record the commercial supply costs related to a product candidate as research and development expenses or to capitalize these costs as inventory involves significant judgment. There were no capitalized inventories as of December 31, 2015 and 2014. Property and Equipment —Property and equipment are recorded at cost and depreciated using the straight-line method over the estimated useful lives of the respective assets. Research and Development Costs —The Company accounts for research and development costs by expensing such costs to operations as incurred. Research and development costs primarily consist of clinical testing costs, including payments made to contract research organizations, personnel costs, outsourced research activities, laboratory supplies, and license fees. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are deferred and capitalized. The capitalized amounts are expensed as the related goods are delivered or the services are performed. Licensing Agreements —Costs associated with licensing early stage technology are expensed as incurred, and are included in research and development expenses. Impairment of Long-Lived Assets —The Company evaluates long-lived assets for potential impairment when there is evidence that events or changes in circumstances have occurred that indicate that the carrying amount of a long-lived asset may not be recovered. Recoverability of these assets is assessed based on the undiscounted expected future cash flows from the assets, considering a number of factors, including past operating results, budgets and economic projections, market trends, and product development cycles. Impairment in the carrying value of each asset is assessed when the undiscounted expected future cash flows derived from the asset are less than its carrying value. An impairment loss would be recognized in an amount equal to the excess of the carrying amount over the undiscounted expected future cash flows. No impairment charges have been recognized since the Company's inception. Segment Information —Operating segments are defined as components of an enterprise engaged in business activities for which discrete financial information is available and regularly reviewed by the chief decision maker in determining how to allocate resources and in assessing performance. The Company views its operations and manages its business as one operating segment and operates in one geographic area. Income Taxes —The Company recognizes deferred tax assets and liabilities for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis, as well as operating loss and tax credit carryforwards. The Company measures deferred tax assets and liabilities using enacted tax rates expected to apply to taxable income in the years in which those temporary differences and carryforwards are expected to be recovered or settled. Deferred tax assets are reduced by a valuation allowance to reflect the uncertainty associated with their ultimate realization. The effect on deferred tax assets and liabilities as a result of a change in tax rates is recognized as income in the period that includes the enactment date. The Company uses judgment to determine the recognition threshold and measurement attribute for financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. Any material interest and penalties related to unrecognized tax benefits are recognized in income tax expense. Due to uncertainty surrounding the realization of the favorable tax attributes in future tax returns the Company has recorded a full valuation allowance against otherwise realizable net deferred tax assets as of December 31, 2015 and 2014. Financial Instruments Indexed to and Potentially Settled in the Company's Common Stock —The Company evaluates all financial instruments issued in connection with its debt borrowings and equity offerings when determining the proper accounting treatment for such instruments in the Company's consolidated financial statements. The Company considers a number of generally accepted accounting principles to determine such treatment and evaluates the features of the instrument to determine the appropriate accounting treatment. The Company utilizes the Black-Scholes method or other appropriate methods to determine the fair value of its derivative financial instruments. Key valuation factors in determining the fair value include, but are not limited to, the current stock price as of the date of measurement, the exercise price, the remaining contractual life, expected volatility for the instrument and the risk-free interest rate. For financial instruments that are determined to be classified as liabilities on the balance sheet, changes in fair value are recorded as a gain or loss in the Company's statement of operations, with the corresponding amount recorded as an adjustment to the liability on its balance sheet. Stock-Based Compensation-Options —The Company measures stock-based compensation cost at the accounting measurement date based on the fair value of the option, and recognizes the expense related to awards to employees on a straight-line basis over the requisite service period of the option, which is typically the vesting period. The Company estimates the fair value of each option using the Black-Scholes option pricing model that takes into account the fair value of its common stock, the exercise price, the expected life of the option, the expected volatility of its common stock, expected dividends on its common stock, and the risk-free interest rate over the expected life of the option. Due to the limited trading history of the Company's common stock since its June 2014 initial public offering, the Company uses the simplified method described in the SEC's Staff Accounting Bulletin No. 107, Share-Based Payment, to determine the expected life of the option grants. The estimate of expected volatility is based on a review of the historical volatility of similar publicly held companies in the biotechnology field over a period commensurate with the option's expected term. The Company has never declared or paid any cash dividends on its common stock and does not expect to do so in the foreseeable future. Accordingly, it uses an expected dividend yield of zero. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant valuation for a period commensurate with the option's expected term. These assumptions are highly subjective and changes in them could significantly impact the value of the option and hence the related compensation expense. The Company applies an estimated forfeiture rate to current period expense to recognize compensation expense only for those awards expected to vest. Forfeitures are estimated based upon historical data, adjusted for known trends, and the Company will adjust the estimate of forfeitures if actual forfeitures differ or are expected to differ from such estimates. Subsequent changes in estimated forfeitures are recognized through a cumulative adjustment in the period of change and also will impact the amount of stock-based compensation expense in future periods. Stock-based compensation expense recognized for options granted to consultants is also based upon the fair value of the options issued, as determined by the Black-Scholes option pricing model and recognized on an accelerated basis. However, the unvested portion of such option grants is re-measured at each reporting period, until such time as the option is fully vested. Stock-Based Compensation-Performance Units —The Company measures stock-based compensation cost at the accounting measurement date based on the fair value of the performance unit grant, and recognizes the expense over the derived service period of the performance units. The Company estimates the fair value of each grant using a Monte Carlo simulation analysis that takes into account the forecasted price of its common stock, historical volatility of its common stock, risk-free rate as of valuation date, price of its common stock as of the grant date and the trigger for the performance condition to be met. The derived service period for each grant is calculated using a Monte Carlo simulation analysis. Net Loss Per Common Share —Net loss per common share is calculated using the two-class method, which is an earnings allocation formula that determines net loss per share for the holders of the Company's common shares and participating securities. Prior to the initial public offering, all of the Company's series of preferred stock contained participation rights in any dividend paid by the Company and were deemed to be participating securities. Net income available to common shareholders and participating preferred shares was allocated to each share on an as-converted basis as if all of the earnings for the period had been distributed. The participating securities do not include a contractual obligation to share in losses of the Company and are not included in the calculation of net loss per share in the periods that have a net loss. Diluted net income per share is computed using the more dilutive of (a) the two-class method, or (b) the if-converted method. Prior to the initial public offering, the Company allocated net income first to preferred stockholders based on dividend rights and then to common and preferred stockholders based on ownership interests. The weighted-average number of common shares outstanding gives effect to all potentially dilutive common equivalent shares, including outstanding stock options, warrants, and, prior to the Company's initial public offering, potential issuance of stock upon the issuance of the Company's series A-6 convertible preferred stock ("Series A-6") as settlement of the liability to Nordic Bioscience ("Nordic"). Common equivalent shares are excluded from the computation of diluted net income per share if their effect is anti-dilutive. Comprehensive Income (Loss) —Comprehensive income (loss) refers to revenues, expenses, gains and losses that are excluded from net income (loss), as these amounts are recorded directly as an adjustment to stockholders' equity (deficit), net of tax. The Company's other comprehensive (loss) income is comprised of unrealized gains (losses) on its available-for-sale marketable securities. Accounting Standards Updates —In August 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update No. 2014-15, Disclosures of Uncertainties about an Entity's Ability to Continue as a Going Concern ("ASU 2014-15"). ASU 2014-15 provides guidance in GAAP about management's responsibility to evaluate whether there is substantial doubt about an entity's ability to continue as a going concern and to provide related footnote disclosures. The amendments under ASU 2014-15 are effective for interim and annual fiscal periods beginning after December 15, 2016, with early adoption permitted. The Company does not expect the adoption of ASU 2014-15 to have a material impact on its results of operations, financial position or cash flows. In January 2015, the FASB issued Accounting Standards Update No. 2015-01, Income Statement—Extraordinary and Unusual Items (Subtopics 225-20) ("ASU 2015-01"). ASU 2015-01 eliminates the concept of extraordinary items from GAAP. The amendments under ASU 2015-01 are effective for interim and annual fiscal periods beginning after December 15, 2015, with early adoption permitted. The Company does not expect the adoption of ASU 2015-01 to have a material impact on its results of operations, financial position or cash flows. In April 2015, the FASB issued Accounting Standards Update No. 2015-03, Interest—Imputation of Interest (Subtopic 835-30) ("ASU 2015-03"). ASU 2015-03 requires that, instead of presentation as an asset, debt issuance costs be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The amendments under ASU 2015-03 are effective for interim and annual fiscal periods beginning after December 15, 2015, with early adoption permitted, and should be applied on a retrospective basis. The Company does not expect the adoption of ASU 2015-03 to have a material impact on its results of operations, financial position or cash flows. In April 2015, the FASB issued Accounting Standards Update No. 2015-05, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40) ("ASU 2015-05"). ASU 2015-05 updates guidance regarding accounting for cloud computing arrangements. The amendments under ASU 2015-05 are effective for interim and annual fiscal periods beginning after December 15, 2015, with early adoption permitted. The Company does not expect the adoption of ASU 2015-05 to have a material impact on its results of operations, financial position or cash flows. In November 2015, the FASB issued Accounting Standards Update No. 2015-17, Income Taxes (Topic 740) ("ASU 2015-17"). ASU 2015-17 requires deferred tax liabilities and assets to be classified as noncurrent in a classified statement of financial position, instead of separating deferred income tax liabilities and assets into current and noncurrent amounts. The amendments under ASU 2015-17 apply to all entities that present a classified statement of financial position and are effective, for public entities, for financial statements issued for annual periods beginning after December 15, 2016, and interim periods within those annual periods, with early adoption permitted for all entities as of the beginning of an interim or annual reporting period. The Company elected to early adopt ASU 2015-17 effective December 31, 2015 on a prospective basis. Adoption of this ASU resulted in a reclassification of our net current deferred tax asset to the net non-current deferred tax asset in our Consolidated Balance Sheet as of December 31, 2015. No prior periods were retrospectively adjusted. In January 2016, the FASB issued Accounting Standards Update No. 2016-01, Financial Statements—Overall (Subtopics 825-10) ("ASU 2016-01"). ASU 2016-01 provides updated guidance on the recognition and measurement of financial assets and financial liabilities that will supersede most current guidance. ASU 2016-01 primarily affects the accounting for equity investments, financial liabilities under the fair value option, and the presentation and disclosure requirements for financial instruments. The amendments in ASU 2016-01 supersede the guidance to classify equity securities with readily determinable fair values into different categories and require equity securities to be measured at fair value with changes in the fair value recognized through net income. The amendments under ASU 2016-01 are effective, for public business entities, for periods beginning after December 15, 2017, including interim periods within those fiscal years, and with early adoption permitted. The Company does not expect the adoption of ASU 2016-01 to have a material impact on its results of operations, financial position or cash flows.

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2015
Marketable Securities.
Marketable Securities	3. Marketable Securities Available-for-sale marketable securities and cash and cash equivalents consist of the following (in thousands): December 31, 2015 Amortized Cost Value Gross Unrealized Gains Gross Unrealized Losses Fair Value Cash and cash equivalents: Cash $ $ — $ — $ Money market — — Domestic corporate commercial paper — — Government-sponsored enterprise debt securities — — Domestic corporate debt securities — — Asset-backed securities — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ — $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities: Domestic corporate debt securities $ $ — $ ) $ Domestic corporate commercial paper — Asset-backed securities ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2014 Amortized Cost Value Gross Unrealized Gains Gross Unrealized Losses Fair Value Cash and cash equivalents: Cash $ $ — $ — $ Money market funds — — Domestic corporate debt securities — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ — $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities: Domestic corporate debt securities — ) Domestic corporate commercial paper — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ There were no debt securities that had been in an unrealized loss position for more than 12 months as of December 31, 2015 or December 31, 2014. There were 57 debt securities in an unrealized loss position for less than 12 months at December 31, 2015 and there were 34 debt securities that had been in an unrealized loss position for less than 12 months at December 31, 2014. The aggregate unrealized loss on these securities as of December 31, 2015 and 2014 was less than $150 thousand and $34 thousand, respectively, and the fair value was $225.7 million and $68.9 million, respectively. The Company considered the decline in market value for these securities to be primarily attributable to current economic conditions. As it was not more likely than not that the Company would be required to sell these securities before the recovery of their amortized cost basis, which may be maturity, the Company did not consider these investments to be other-than-temporarily impaired as of December 31, 2015 and 2014. As of December 31, 2015 and 2014, marketable securities consisted of investments that mature within one year.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2015
Property and Equipment
Property and Equipment	4. Property and Equipment Property and equipment consists of the following (in thousands): December 31, Estimated Useful Life (In Years) 2015 2014 Furniture and fixtures 5 $ $ Computer equipment and software 3 Manufacturing equipment 10 Leasehold improvements Shorter of useful life or remaining lease term ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less accumulated depreciation and amortization ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Property and equipment, net $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ During the year ended December 31, 2014, the Company retired $0.7 million of property and equipment. The retirement was primarily due to the disposal of leasehold improvements and other property as a result of the Company's office relocation. All assets were fully depreciated prior to retirement.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2015
Accrued Expenses and Other Current Liabilities
Accrued Expenses and Other Current Liabilities	5. Accrued Expenses and Other Current Liabilities Accrued expenses consist of the following (in thousands): December 31, 2015 2014 Research costs—Nordic(1) $ $ Research costs—other Payroll and employee benefits Professional fees Accrued interest on notes payable — Other — ​ ​ ​ ​ ​ ​ ​ ​ Total accrued expenses and other current liabilties $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Includes amounts accrued ratably over the estimated per patient treatment period under the Nordic Work Statement NB-1 and Work Statement NB-3. Amounts do not include pass-through costs which are expensed as incurred or upon delivery. See note 10 for additional information.

Loan and Security Agreement

Loan and Security Agreement	12 Months Ended
	Dec. 31, 2015
Loan and Security Agreement
Loan and Security Agreement	6. Loan and Security Agreement On May 23, 2011, the Company entered into a loan and security agreement with Oxford Finance LLC ("Oxford") and General Electric Capital Corporation ("GECC") pursuant to which Oxford and GECC agreed to lend the Company up to $25.0 million. Upon entering into the loan and security agreement, the Company borrowed $6.3 million on May 23, 2011("Term Loan A"), $6.3 million on November 21, 2011 ("Term Loan B") and an additional $12.5 million on May 29, 2012 ("Term Loan C"). Interest on the outstanding Term Loan A was payable on a monthly basis through and including December 1, 2011. Principal and interest payments on Term Loan A was payable in 36 equal monthly installments beginning December 1, 2011 through November 1, 2014, with a final balloon payment of $0.6 million due upon maturity on November 22, 2014. Interest was payable on Term Loan A at an annual interest rate of 10.16%. Interest on the outstanding Term Loan B was payable on a monthly basis through and including June 1, 2012. Principal and interest payments on Term Loan B was payable in 30 equal monthly installments beginning June 1, 2012, through November 1, 2014, with a final balloon payment of $0.6 million due upon maturity on November 22, 2014. Interest was payable on Term Loan B at an annual interest rate of 10%. Interest on Term Loan C was payable on a monthly basis through, and including, November 1, 2012. Principal and interest payments on Term Loan C was payable in 24 monthly installments beginning December 1, 2012, through November 1, 2014 with a final balloon payment of $1.3 million upon maturity on November 22, 2014. Interest was payable on Term Loan C at an annual interest rate of 10%. On May 30, 2014, the Company entered into a loan and security agreement (the "Credit Facility), with Solar Capital Ltd. ("Solar"), as collateral agent and a lender, and Oxford, as a lender (the "Lenders"), pursuant to which Solar and Oxford agreed to make available to the Company $30.0 million in the aggregate subject to certain conditions to funding. An initial term loan was made on May 30, 2014 in an aggregate principal amount equal to $21.0 million (the "Initial Term Loan"). The Company used approximately $9.3 million of the Initial Term Loan to repay all amounts owed under its loan and security agreement with GECC and Oxford. On July 10, 2014, the Company entered into a first amendment to the Credit Facility (the "First Amendment"). The terms of the First Amendment, among other things, provided the Company with, subject to certain customary funding conditions, additional term loans in an aggregate principal amount of $4.0 million upon the closing of the First Amendment. The Company borrowed the additional $4.0 million on July 10, 2014. The Company had been required to make interest-only payments through December 1, 2015, and beginning on January 1, 2016, it would have been required to make payments of principal and accrued interest in equal monthly installments over a term of 30 months. The Initial Term Loan bore interest per annum at 9.85% plus one-month LIBOR (customarily defined). All principal and accrued interest on the Initial Term Loan had been due on June 1, 2018. On August 4, 2015, the Company prepaid all amounts owed under the Credit Facility and the First Amendment. After consideration of relevant fees required under the Credit Facility and the First Amendment, the total payment amounted to $26.5 million, which resulted in a loss on retirement of $1.6 million during the third quarter of 2015.

Stockholders' Equity and Conver

Stockholders' Equity and Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2015
Stockholders' Equity and Convertible Preferred Stock
Stockholders' Equity and Convertible Preferred Stock	7. Stockholders' Equity and Convertible Preferred Stock Common Stock On June 11, 2014, the Company completed its initial public offering whereby the Company sold 6,500,000 shares of common stock at a price of $8.00 per share. The shares began trading on the NASDAQ Global Market on June 6, 2014. In connection with the offering, all outstanding shares of our convertible preferred stock converted into 19,465,132 shares of common stock and 2,862,654 shares of common stock were issued in satisfaction of accumulated dividends accrued on the preferred stock. In addition, all outstanding warrants to purchase shares of series A-1 convertible preferred stock and warrants to purchase shares of series B-2 convertible preferred stock were converted into the right to purchase 149,452 shares of common stock and the Company's warrant liability was reclassified to equity. On June 18, 2014 and June 25, 2014, the underwriters purchased an additional 512,744 shares in the aggregate by exercising a portion of the over-allotment option granted to them in connection with the initial public offering. As a result of the closing of the initial public offering and subsequent exercise of the over-allotment option, the Company received aggregate proceeds, net of underwriting discounts, commissions and offering costs, of approximately $50.4 million. On October 7, 2014, the Company completed an additional public offering whereby it sold 2,750,000 shares of common stock at a price of $18.25 per share, for aggregate proceeds, net of underwriting discounts, commissions and offering costs, of approximately $46.9 million. On October 7, 2014, the underwriters purchased an additional 378,524 shares in the aggregate by exercising a portion of the over-allotment option granted to them in connection with the offering. As a result of the public offering and subsequent exercise of the over-allotment option, the Company received aggregate proceeds, net of underwriting discounts, commissions and offering costs of approximately $53.4 million. On January 28, 2015, the Company completed an additional public offering of 4,000,000 shares of its common stock at a price of $36.75 per share, for aggregate estimated proceeds, net of underwriting discounts, commissions and offering costs, of approximately $137.8 million. Also, on January 28, 2015, the underwriters purchased an additional 600,000 shares in the aggregate by exercising an option to purchase additional shares that was granted to them in connection with the offering. As a result of the public offering and subsequent exercise of the underwriters' option, the Company received aggregate proceeds, net of underwriting discounts, commissions and offering costs of approximately $158.4 million. On July 28, 2015, the Company completed an additional public offering of 4,054,054 shares of its common stock at a price of $74.00 per share, for aggregate proceeds, net of underwriting discounts, commissions and offering costs, of approximately $281.5 million. Also, on July 28, 2015, the underwriters purchased an additional 608,108 shares by exercising an option to purchase additional shares that was granted to them in connection with the offering. As a result of the public offering and subsequent exercise of the underwriters' option, the Company received aggregate proceeds, net of underwriting discounts, commissions and estimated offering costs of approximately $323.8 million. Preferred Stock On April 23, 2013, the Company entered into a Series B Convertible Preferred Stock and Warrant Purchase Agreement (the "Series B Purchase Agreement"), pursuant to which the Company could raise, at any time on or prior to May 10, 2013, up to approximately $60.0 million through the issuance of (1) up to 980,000 shares of its Series B preferred stock (the "Series B") and (2) warrants to acquire up to approximately 1,075,000 shares of its common stock with an exercise price of $14.004 per share. On April 23, 2013, the Company consummated a first closing under the Series B Purchase Agreement, whereby in exchange for aggregate proceeds of approximately $43.0 million, it issued 700,098 shares of Series B and warrants to purchase up to a total of 767,651 shares of its common stock. On May 10, 2013, the Company consummated a second closing under the Series B Purchase Agreement, whereby in exchange for aggregate proceeds of approximately $0.1 million, it issued 1,137 shares of Series B and warrants to purchase up to a total of 1,246 shares of its common stock. The warrants can be exercised at any time prior to the fifth anniversary of their issuance. On February 14, 2014, the Company entered into a Series B-2 Convertible Preferred Stock and Warrant Purchase Agreement (the "Series B-2 Purchase Agreement"), pursuant to which the Company was able to raise up to approximately $40.2 million through the issuance of (1) up to 655,000 shares of its preferred stock (the "Series B-2") and (2) warrants to acquire up to 718,201 shares of its common stock with an exercise price of $14.004 per share. In February and March 2014, the Company consummated closings under the Series B-2 Purchase Agreement, whereby, in exchange for aggregate gross proceeds to the Company of approximately $27.5 million, the Company issued an aggregate of 448,060 shares of Series B-2 and warrants to purchase up to a total of 491,293 shares of its common stock. The warrants can be exercised at any time prior to the fifth anniversary of their issuance.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Fair Value Measurements
Fair Value Measurements	8. Fair Value Measurements The following table summarizes the financial instruments measured at fair value on a recurring basis in the accompanying consolidated balance sheets as of December 31, 2015 and December 31, 2014 (in thousands): As of December 31, 2015 Level 1 Level 2 Level 3 Total Assets Cash and cash equivalents: Cash $ $ — $ — $ Money market funds(1) — — Domestic corporate commercial paper(2) — — Government-sponsored enterprise debt securities(2) — — Domestic corporate debt securities(2) — — Asset-backed securities(2) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable Securities Domestic corporate debt securities(2) $ — $ $ — $ Domestic corporate commercial paper(2) — — Asset-backed securities(2) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ — $ $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2014 Level 1 Level 2 Level 3 Total Assets Cash and cash equivalents: Cash $ $ — $ — $ Money market funds(1) — — Domestic corporate debt securities(2) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities: Domestic corporate debt securities(2) $ — $ $ — $ Domestic corporate commercial paper(2) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ — $ $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Fair value is based upon quoted market prices. (2) Fair value is based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant assumptions are observable in the market or can be corroborated by observable market data for substantially the full term of the assets. Inputs are obtained from various sources, including market participants, dealers and brokers.

License Agreements

License Agreements	12 Months Ended
	Dec. 31, 2015
License Agreements
License Agreements	9. License Agreements On September 27, 2005, the Company entered into a license agreement (the "Ipsen Agreement"), as amended, with SCRAS S.A.S, a French corporation on behalf of itself and its affiliates (collectively, "Ipsen"). Under the Ipsen Agreement, Ipsen granted to the Company an exclusive right and license under certain Ipsen compound technology and related patents to research, develop, manufacture and commercialize certain compounds and related products in all countries, except Japan (where the Company does not hold development and commercialization rights) and France (where the Company's commercialization rights are subject to certain co-marketing and co-promotion rights exercisable by Ipsen, provided that certain conditions included in the Ipsen Agreement have been met). With respect to France, if Ipsen exercises its co-marketing and co-promotion rights, then Ipsen may elect to receive a percentage of the net sales of the products by both parties in France (subject to a mid-double digit percentage cap), and Ipsen shall bear a corresponding percentage of the costs and expenses incurred by both parties with respect to such marketing and promotion efforts in France. Ipsen shall also pay the Company a mid-single digit royalty on Ipsen's allocable portion of net sales of the product by both parties in France. Abaloparatide is subject to the Ipsen Agreement. Ipsen also granted the Company an exclusive right and license under the Ipsen compound technology and related patents to make and have made compounds or product in Japan. Ipsen also granted the Company an exclusive right and license under certain Ipsen formulation technology and related patents solely for purposes of enabling the Company to develop, manufacture and commercialize compounds and products covered by the compound technology license in all countries, except Japan (where the Company does not hold commercialization rights) and France (where the Company's commercialization rights are subject to certain co-marketing and co-promotion rights exercisable by Ipsen, provided that certain conditions included in the Ipsen Agreement have been met). In consideration for these licenses, the Company made a nonrefundable, non-creditable payment of $0.25 million to Ipsen, which was expensed during 2005. The Ipsen Agreement provides for further payments upon the achievement of certain future regulatory and commercial milestones, including upon acceptance of a new drug application submission for review by the U.S. Food and Drug Administration. The range of milestone payments that could be paid under the agreement is €10.0 million to €36.0 million ($10.9 million to $39.1 million). Should abaloparatide be approved and subsequently commercialized, the Company will be obligated to pay to Ipsen a fixed five percent royalty based on net sales of the product by the Company or its sublicensees on a country-by-country basis until the later of the last to expire of the licensed patents or for a period of 10 years after the first commercial sale in such country. If the Company sublicenses the rights licensed from Ipsen, then the Company will also be required to pay Ipsen a percentage of certain payments received from such sublicensee (in lieu of milestone payments not achieved at the time of such sublicense). The applicable percentage is in the low double digit range. In addition, if the Company or its sublicensees commercialize a product that includes a compound discovered by it based on or derived from confidential Ipsen know-how, it will be obligated to pay to Ipsen a fixed low single digit royalty on net sales of such product on a country-by-country basis until the later of the last to expire of licensed patents that cover such product or for a period of 10 years after the first commercial sale of such product in such country. In June 2006, the Company entered into a license agreement (the "Eisai Agreement"), with Eisai Co. Ltd., ("Eisai"). Under the Eisai Agreement, Eisai granted to the Company an exclusive right and license to research, develop, manufacture and commercialize RAD1901 and related products from Eisai in all countries, except Japan. In consideration for the rights to RAD1901, the Company paid Eisai an initial license fee of $0.5 million, which was expensed during 2006. The Eisai Agreement provides for further payments in the range of $1.0 million to $20.0 million (inclusive of the $0.5 million initial license fee), payable upon the achievement of certain clinical and regulatory milestones. On March 9, 2015, the Company entered into an amendment to the Eisai Agreement (the "Eisai Amendment") in which Eisai granted to the Company the exclusive right and license to research, develop, manufacture and commercialize RAD1901 in Japan. In consideration for the rights to RAD1901 in Japan, the Company paid Eisai an initial license fee of $0.4 million upon execution of the Eisai Amendment, which was recognized as research and development expense in 2015. The Eisai Amendment also provides for additional payments, payable upon the achievement of certain clinical and regulatory milestones in Japan. Under the Eisai Agreement, as amended, should a product covered by the licensed technology be commercialized, the Company will be obligated to pay to Eisai royalties in a variable mid-single digit range based on net sales of the product on a country-by-country basis. The royalty rate will be reduced, on a country-by-country basis, at such time as the last remaining valid claim in the licensed patents expires, lapses or is invalidated and the product is not covered by data protection clauses. In addition, the royalty rate will be reduced, on a country-by-country basis, if, in addition to the conditions specified in the previous sentence, sales of lawful generic versions of such product account for more than a specified minimum percentage of the total sales of all products that contain the licensed compound during a calendar quarter. The latest valid claim to expire, barring any extension thereof, is expected on August 18, 2026. The Eisai Agreement, as amended, also grants the Company the right to grant sublicenses with prior written approval from Eisai. If the Company sublicenses the licensed technology to a third party, the Company will be obligated to pay Eisai, in addition to the milestones referenced above, a fixed low double digit percentage of certain fees received from such sublicensee and royalties in the low single digit range based on net sales of the sublicensee. The license agreement expires on a country-by-country basis on the later of (1) the date the last remaining valid claim in the licensed patents expires, lapses or is invalidated in that country, the product is not covered by data protection clauses, and the sales of a lawful generic version of the product account for more than a specified percentage of the total sales of all pharmaceutical products containing the licensed compound in that country; or (2) a period of 10 years after the first commercial sale of the licensed products in such country, unless it is sooner terminated.

Research Agreements

Research Agreements	12 Months Ended
	Dec. 31, 2015
Research Agreements
Research Agreements	10. Research Agreements Abaloparatide-SC Phase 3 Clinical Trial —On March 29, 2011, the Company and Nordic entered into a Clinical Trial Services Agreement (the "Clinical Trial Services Agreement"), a Work Statement NB-1, as amended on December 9, 2011, June 18, 2012, March 28, 2014, May 19, 2014, July 22, 2014, August 15, 2014 and March 12, 2015 (the "Work Statement NB-1") and a Stock Issuance Agreement, as amended and restated on May 16, 2011, and as further amended on February 21, 2013, March 28, 2014, and May 19, 2014 (the "Stock Issuance Agreement"). Pursuant to the Work Statement NB-1, Nordic managed the Phase 3 clinical trial of abaloparatide-SC (the "Phase 3 Clinical Trial"). The Company recognized research and development expense for the amounts due to Nordic under the Work Statement NB-1 ratably over the estimated per patient treatment period beginning upon enrollment in the Phase 3 Clinical Trial, or a twenty-month period. The Company recognized research and development expense for the amounts due to Nordic under the fourth amendment to the Work Statement NB-1, which was recognized on a per patient basis when the end-of-study visit and all other required procedures were completed. The Company recorded no expense, $8.2 million, and $31.6 million during the years ended December 31, 2015, 2014, and 2013, respectively, for per patient costs incurred for patients that had enrolled in the Phase 3 Clinical Study. As of December 31, 2015, all obligations due to Nordic under Work Statement NB-1 had been paid. Abaloparatide-SC Phase 3 Clinical Extension Study —On February 21, 2013, the Company entered into a Work Statement NB-3, as amended on February 28, 2014, March 23, 2015, July 8, 2015 and October 21, 2015 (the "Work Statement NB-3"). Pursuant to the Work Statement NB-3, Nordic performed an extension study to evaluate six months of standard-of-care osteoporosis management following the completion of the Phase 3 Clinical Trial (the "Extension Study"), and, upon completion of this initial six months, an additional period of 18 months of standard-of-care osteoporosis management (the "Second Extension"). In April 2015, the Company entered into an amendment to the Work Statement NB-3 (the "NB-3 Amendment"). The NB-3 Amendment was effective as of March 23, 2015 and provides that Nordic will perform additional services, including additional monitoring of patients enrolled in the Second Extension. Payments in cash to be made to Nordic under the NB-3 Amendment are denominated in euros and total up to approximately €4.1 million ($4.5 million). Payments in cash to be made to Nordic under the Work Statement NB-3 are denominated in both euros and U.S. dollars and total up to €11.9 million ($12.9 million) and $1.1 million, respectively. In addition, payments are due to Nordic in connection with the Work Statement NB-3 pursuant to the Stock Issuance Agreement, as discussed below. As of December 31, 2015, services related to the Second Extension are ongoing and all obligations due to Nordic in relation to the Extension Study have been paid. The Company recognizes research and development expense for the amounts due to Nordic under the Extension Study and the Second Extension ratably over the estimated per patient treatment periods beginning upon enrollment, or over a nine-month and nineteen-month period, respectively. The Company recorded $5.4 million, $9.6 million, and $4.5 million for the years ended December 31, 2015, 2014, and 2013 respectively, for per patient costs incurred. As of December 31, 2015, the Company had a liability of $2.9 million reflected in accrued expenses and other current liabilities on the consolidated balance sheet resulting from services provided by Nordic under the Second Extension, which are payable in cash. Stock Issuance Agreement —Pursuant to the Stock Issuance Agreement, Nordic agreed to purchase 6,443 shares of the Company's Series A-5 convertible preferred stock, which provided Nordic with the right to receive quarterly stock dividends, payable in shares of the Company's Series A-6 convertible preferred stock ("Series A-6") for services rendered under Work Statement NB-1 and Work Statement NB-3. The Stock Issuance Agreement was later amended to provide that in the event an initial public offering of the Company's common stock occurred prior to June 30, 2014, any rights to receive stock dividends in relation to Work Statement NB-1 and Work Statement NB-3, for all periods of time after 2014, would be changed from the right to receive stock to the right to receive a total cash payment from the Company of $4.3 million, payable in ten equal monthly installments of $430,000 beginning on March 31, 2015. The amendment also stipulated that all consideration to be paid to Nordic pursuant to the Stock Issuance Agreement at any time after the consummation of an initial public offering be payable in cash. As the Company completed an initial public offering on June 11, 2014, Nordic no longer has the right to receive stock from the Company and has been paid in cash for all periods after June 11, 2014. Prior to the issuance of shares of stock to Nordic in satisfaction of quarterly dividends earned under Work Statement NB-1 and Work Statement NB-3, the liability to issue shares of stock was being accounted for as a liability in the Company's balance sheet, based upon the fair value of the Series A-6. Changes in the fair value from the date of accrual to the date of issuance of the Series A-6 shares were recorded as a gain or loss in other (expense) income in the statement of operations.

Stock-based Compensation

Stock-based Compensation	12 Months Ended
	Dec. 31, 2015
Stock-based Compensation
Stock-Based Compensation	11. Stock-based Compensation The Company has the following stock-based compensation plans as of December 31, 2015, under which equity awards have been granted to employees, directors and consultants: • 2003 Long-Term Incentive Plan; and • 2011 Equity Incentive Plan. The 2011 Equity Incentive Plan replaced the 2003 Long-Term Incentive Plan when the board of directors approved the new plan on November 7, 2011. As of December 31, 2015, an aggregate of approximately 6,160,000 shares have been authorized for issuance under the Company's stock-based compensation plans, with approximately 4,408,000 options outstanding. The number of common shares available for granting of future awards under these plans was approximately 1,100,000 at December 31, 2015. 2003 Long-Term Incentive Plan —The Company's 2003 Long-Term Incentive Plan (the "Incentive Plan") provides for the granting of incentive stock options and nonqualified options to key employees, directors and consultants of the Company. The exercise price of the incentive stock options, as determined by the board of directors, must be at least 100% (110% in the case of incentive stock options granted to a stockholder owning in excess of 10% of the Company's common stock) of the common stock fair value as of the date of the grant. The provisions of the Incentive Plan limit the exercise of incentive stock options, but in no case may the exercise period extend beyond ten years from the date of grant (five years in the case of incentive stock options granted to a stockholder owning in excess of 10% of the Company's common stock). Stock options generally vest over a four-year period. Certain options contain explicit performance conditions. The Company authorized approximately 884,000 shares of common stock for issuance under the Incentive Plan. 2011 Equity Incentive Plan —The Company's 2011 Equity Incentive Plan (the "Equity Plan") provides for the granting of incentive stock options and nonqualified options to key employees, directors and consultants of the Company. The exercise price of the incentive stock options, as determined by the board of directors, must be at least 100% (110% in the case of incentive stock options granted to a stockholder owning in excess of 10% of the Company's common stock) of the common stock fair value as of the date of the grant. The provisions of the Equity Plan limit the exercise of incentive stock options, but in no case may the exercise period extend beyond ten years from the date of grant (five years in the case of incentive stock options granted to a stockholder owning in excess of 10% of the Company's common stock). Stock options generally vest over a four-year period. During 2015, the Company also issued stock options to certain members of its board of directors which vested immediately. Certain options contain explicit performance conditions. The Company has authorized approximately 5,276,000 shares of common stock for issuance under the Equity Plan. In addition, the shares remaining available for issuance under the Incentive Plan were assumed as shares authorized under the Equity Plan. Options —The Company has historically granted stock options at exercise prices no less than the fair value of its common stock as determined by its board of directors, with input from management. Prior to the Company's initial public offering, the Company's board of directors has historically determined, with input from management, the estimated fair value of the Company's common stock on the date of grant based on a number of objective and subjective factors, including: • the prices at which the Company sold shares of convertible preferred stock; • the superior rights and preferences of securities senior to the Company's common stock at the time of each grant; • the likelihood of achieving a liquidity event such as a public offering or sale of the Company; • the Company's historical operating and financial performance and the status of its research and product development efforts; and • achievement of enterprise milestones, including entering into collaboration and license agreements. Subsequent to the Company's initial public offering, exercise prices in the case of non-qualified and incentive stock options are not less than the fair value of the underlying common stock on the date of grant, as determined under the Equity Plan. The Company uses the Black-Scholes option-pricing model to estimate the grant date fair value of its employee stock options. The weighted-average grant-date fair value per share of options granted during 2015, 2014, and 2013 was $30.52, $8.26, and $4.67 respectively. The weighted-average assumptions used in the Black-Scholes option-pricing model were as follows: Years Ended December 31, 2015 2014 2013 Expected term (years) Volatility % % % Expected dividend yield % % % Risk-free interest rates % % % A summary of stock option activity for the year ended December 31, 2015 is as follows (in thousands, except for per share and weighted-average contractual life amounts): Shares Weighted-Average Exercise Price (in dollars per share) Weighted-Average Contractual Life (In Years) Aggregate Intrinsic Value Options outstanding at December 31, 2014 $ Granted Exercised ) Cancelled ) Expired — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options outstanding at December 31, 2015 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options exercisable at December 31, 2015 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options vested or expected to vest at December 31, 2015 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The aggregate intrinsic value of options exercised (i.e., the difference between the market price at exercise and the price paid by employees to exercise the option) during the years ended December 31, 2015 and 2014 was $14.7 million and $0.7 million, respectively. The following table summarizes stock-based compensation expense by financial statement line (in thousands): Years Ended December 31, 2015 2014 2013 Research and development $ $ $ General and administrative ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Share-based compensation expense included in operating expenses $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performance Units —In September 2015, the Company awarded 25,000 performance units ("PUs") to an employee. Each PU which is earned entitles the holder to receive one share of the Company's common stock if and when the PU vests. The PUs can be earned in the three years subsequent to the grant date if the Company's average closing stock price over 45 consecutive trading days that begin and end during such three-year period reaches certain thresholds that were set at the time of issuance. The vesting of any earned units is subject to the employee's continued employment one year from the last day of the measurement period for which the PUs are earned. Compensation expense is recognized over the derived service period, calculated using a Monte Carlo simulation analysis. The weighted-average grant-date fair value per unit of PUs granted during the year ended December 31, 2015 was $49.59, which was calculated using a Monte Carlo simulation analysis. This valuation methodology utilizes several key assumptions including the forecasted stock price, stock price volatility, risk-free rate as of valuation date, stock price as of grant date and the trigger for the performance condition to be met. As of December 31, 2015, there was approximately $51.3 million of total unrecognized compensation expense related to unvested share-based compensation arrangements, which is expected to be recognized over a weighted-average period of approximately 3 years.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2015
Net Loss Per Share
Net Loss Per Share	12. Net Loss Per Share Basic and diluted net loss per share is calculated as follows (in thousands, except share and per share amounts): Year Ended December 31, 2015 2014 2013 Numerator: Net loss $ ) $ ) $ ) Accretion of preferred stock — ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loss attributable to common stockholders—basic ) ) ) Effect of dilutive convertible preferred stock — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loss attributable to common stockholders—diluted $ ) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator: Weighted-average number of common shares used in loss per share—diluted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loss per share—basic and diluted $ ) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The following potentially dilutive securities, prior to the use of the treasury stock method, have been excluded from the computation of diluted weighted-average shares outstanding, as they would be anti-dilutive. For the years ended December 31, 2015, 2014, and 2013 all of the Company's classes of convertible preferred stock, options to purchase common stock, warrants and performance units outstanding were assumed to be anti-dilutive as earnings attributable to common stockholders was in a loss position. Year Ended December 31 2015 2014 2013 Convertible preferred stock — Options to purchase common stock Warrants Performance units — — —

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Taxes
Income Taxes	13. Income Taxes As of December 31, 2015 the Company had federal and state net operating loss ("NOL") carryforwards of approximately $419.5 million and $323.0 million, respectively, which may be used to offset future taxable income. The Company also had federal and state tax credits of $5.8 million and $0.8 million, respectively, to offset future tax liabilities. The NOL and tax credit carryforwards will expire at various dates through 2035, and are subject to review and possible adjustment by federal and state tax authorities. The Internal Revenue Code contains provision that may limit the NOL and tax credit carryforwards available to be used in any given year in the event of certain changes in the ownership interests of significant stockholders under Section 382 of the Internal Revenue Code. Approximately $14.1 million of the federal and state NOL carryforwards are attributable to excess tax benefits which will be recorded as an increase to additional paid-in capital when realized. A reconciliation of income taxes computed using the U.S. federal statutory rate to that reflected in operations follows (in thousands): Year Ended December 31, 2015 2014 2013 Income tax benefit using U.S. federal statutory rate $ ) $ ) $ ) State income taxes, net of federal benefit ) ) ) Stock-based compensation Research and development tax credits ) ) ) Change in the valuation allowance Permanent items ) Other ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ — $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The Company is subject to Massachusetts net worth taxes, not based on income, which is largely offset by allowable tax credits and recorded as a component of operating expenses. The principal components of the Company's deferred tax assets are as follows (in thousands): December 31, 2015 2014 Current assets: Accrued expenses $ — $ ​ ​ ​ ​ ​ ​ ​ ​ Gross current deferred tax assets — ​ ​ ​ ​ ​ ​ ​ ​ Valuation allowance — ) ​ ​ ​ ​ ​ ​ ​ ​ Net current deferred tax assets $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Non-current assets: Net operating loss carryforwards $ $ Capitalized research and development Research and development credits Depreciation and amortization ) ) Accrued Expenses — Stock-based compensation Other — ​ ​ ​ ​ ​ ​ ​ ​ Gross non-current deferred tax assets Valuation allowance ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net non-current deferred tax assets $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Effective December 31, 2015, the Company early adopted ASU 2015-17 on a prospective basis. ASU 2015-17 requires deferred tax liabilities and assets to be classified as noncurrent in a classified statement of financial position, instead of separating deferred income tax liabilities and assets into current and noncurrent amounts. Adoption of this ASU resulted in a reclassification of our net current deferred tax asset to the net non-current deferred tax asset in our Consolidated Balance Sheet as of December 31, 2015. No prior periods were retrospectively adjusted. The Company has recorded a valuation allowance against its deferred tax assets in each of the years ended December 31, 2015 and 2014, because the Company's management believes that it is more likely than not that these assets will not be realized. The increase in the valuation allowance in 2015 primarily relates to the net loss incurred by the Company. As of December 31, 2015, the Company has no unrecognized tax benefits or related interest and penalties accrued. The Company has not, as yet, conducted a study of research and development credit carryforwards. In addition, the Company is in the process of conducting an Internal Revenue Code Section 382 study, which may impact its ability to utilize available NOL and tax credit carryforwards. These studies may result in adjustments to the Company's research and development credit carryforwards and NOL carryforwards; however, until a study is completed and any adjustment is known, no amounts are being presented as an uncertain tax position. A full valuation allowance has been provided against the Company's research and development credits and net operating loss carryforward and, if an adjustment is required, this adjustment would be offset by an adjustment to the valuation allowance. Thus, there would be no impact to the consolidated balance sheet or consolidated statement of operations if an adjustment were required. The Company would recognize both accrued interest and penalties related to unrecognized benefits in income tax expense. The Company has not recorded any interest or penalties on any unrecognized benefits since inception. The statute of limitations for assessment by the Internal Revenue Service ("IRS") and state tax authorities remains open for years 2012 through 2015. The Company files income tax returns in the United States, Colorado, Connecticut, Florida, Pennsylvania, New Jersey, New York, and Massachusetts. There are currently no federal or state audits in progress.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies
Commitments and Contingencies	14. Commitments and Contingencies Litigation —The Company may be subject to legal proceedings and claims which arise in the ordinary course of its business. In the Company's opinion, the ultimate resolution of these matters is not expected to have a material effect on its consolidated financial statements. The Company records a liability in its consolidated financial statements for these matters when a loss is known or considered probable and the amount can be reasonably estimated. The Company reviews these estimates each accounting period as additional information is known and adjusts the loss provision when appropriate. If a matter is both probable to result in a liability and the amounts of loss can be reasonably estimated, the Company estimates and discloses the possible loss or range of loss to the extent necessary to make the consolidated financial statements not misleading. If the loss is not probable or cannot be reasonably estimated, a liability is not recorded in its consolidated financial statements. Commitments —The Company leases certain office space in Massachusetts and New Jersey under non-cancellable operating leases that expire over various terms through 2020. The Company is obligated to make monthly rent payments pursuant to these non-cancellable agreements as set forth below (in thousands): Years ended December 31, Future Lease Commitments 2016 $ 2017 2018 2019 2020 ​ ​ ​ ​ ​ Total minimum lease payments $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Rent expense for the years ended December 31, 2015, 2014, and 2013 was $0.6 million, $0.2 million and $0.2 million, respectively.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2015
Related Party Transactions
Related Party Transactions	15. Related Party Transactions On July 24, 2013, the Company entered into a Consulting Agreement with Morana Jovan-Embiricos, Ph.D. (the "Consulting Agreement"), a member of the Company's board of directors. Pursuant to the Consulting Agreement, Dr. Jovan-Embiricos agreed to provide financial and strategic consulting services as may be requested by the Company, and such other consulting services as may be reasonably requested by the Company, from time to time from July 1, 2013 until June 30, 2014. The Company agreed to pay Dr. Jovan-Embiricos an aggregate consulting fee in cash of $160,000, of which $80,000 was paid on July 30, 2013 and the remaining $80,000 was paid on October 2, 2013. As of December 31, 2015, no amounts were due to or from Dr. Jovan-Embiricos. On January 23, 2014, the Company entered into a consulting agreement with Orbit Advisors Limited (the "Orbit Agreement"), a Swiss company ("Orbit"), and Morana Jovan-Embiricos, Ph.D. and an agreement terminating the Consulting Agreement dated July 24, 2013. The Orbit Agreement was effective as of January 22, 2014 and would continue in effect until December 31, 2014 or until the earlier termination thereof in accordance with its terms (the "Term"). Pursuant to the Orbit Agreement, Orbit had agreed to provide financial and strategic consulting services as may be requested by the Company, and such other consulting services as may have been reasonably requested by the Company, from time to time during the Term. The Company agreed to pay Orbit an aggregate consulting fee in cash of $400,000 in four equal installments of $100,000 on each of January 31, 2014, June 30, 2014, September 30, 2014 and December 31, 2014. The Orbit Agreement contained customary provisions, applicable to both Orbit and Dr. Jovan-Embiricos, as Orbit's representative under the Orbit Agreement, regarding the treatment of the Company's confidential information and assignment of inventions, as well as an obligation of Orbit and Dr. Jovan-Embiricos to not solicit, during the Term and for a period of one year thereafter, any person or entity engaged by the Company as an employee, customer or supplier of, or consultant or advisor to, the Company to terminate such party's relationship with the Company. On February 27, 2014, the Company entered into a letter agreement terminating the Orbit Agreement. As of December 31, 2015, no amounts were due to or from Orbit Advisors Limited.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2015
Selected Quarterly Financial Information
Selected Quarterly Financial Data (Unaudited)	16. Selected Quarterly Financial Data (Unaudited) Selected quarterly financial data for the years ended December 31, 2015 and 2014 is as follows (in thousands, except for share and per share data): Three Months Ended March 31, June 30, September 30, December 31, 2015: Net loss $ ) ) ) $ ) Net loss applicable to common stock ) ) ) ) Net loss per share—basic and diluted ) ) ) ) Weighted-average common shares outstanding—basic and diluted 2014: Net loss $ ) $ ) $ ) $ ) Net loss applicable to common stock ) ) ) ) Net loss per share—basic and diluted ) ) ) ) Weighted-average common shares outstanding—basic and diluted

Summary of Significant Accoun23

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation —The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary, Radius Health Securities Corporation. All material intercompany balances and transactions have been eliminated in consolidation.
Reverse Stock Split	Reverse Stock Split —On April 24, 2014, the Company effected a reverse stock split of the Company's common stock. The number of authorized shares of the Company's common stock and the par value did not change. Pursuant to the stock split, every 2.28 shares of the Company's issued and outstanding common stock were automatically combined into one issued and outstanding share of the Company's common stock. All shares and per share amounts in the financial statements and accompanying notes have been retroactively adjusted to give effect to the reverse stock split.
Use of Estimates	Use of Estimates —The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States ("GAAP") requires the Company's management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. The Company considers events or transactions that occur after the balance sheet date but before the consolidated financial statements are issued as additional evidence for certain estimates or to identify matters that require additional disclosure. Subsequent events have been evaluated up to the date of issuance of these consolidated financial statements.
Cash Equivalents	Cash Equivalents —The Company considers all highly liquid investment instruments with an original maturity when purchased of three months or less to be cash equivalents. Money market funds represents a majority of the cash equivalent balance at December 31, 2015 and 2014.
Marketable Securities	Marketable Securities —All investment instruments with an original maturity date, when purchased, in excess of three months have been classified as current marketable securities. The Company classifies securities that are available to fund current operations as current assets. These marketable securities are classified as available-for-sale and are carried at fair value. Unrealized gains and losses, if any, are included within other comprehensive (loss) income within stockholders' equity (deficit). The amortized cost of debt securities in this category is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization is included in interest income. Realized gains and losses on available-for-sale securities are included in interest income. The cost of securities sold is based on the specific identification method. The Company periodically reviews the portfolio of securities to determine whether an other-than-temporary impairment has occurred. No such losses have occurred to date. There were no realized gains or losses on the sale of securities for the years ended December 31, 2015 and 2014.
Fair Value Measurements	Fair Value Measurements —The Company determines the fair market values of its financial instruments based on the fair value hierarchy, which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The following are three levels of inputs that may be used to measure fair value: Level 1 Quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2 Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.
Concentrations of Credit Risk and Off-Balance-Sheet Risk	Concentrations of Credit Risk and Off-Balance-Sheet Risk —Financial instruments that potentially subject the Company to credit risk primarily consist of cash and cash equivalents and available-for-sale marketable securities. The Company mitigates its risk with respect to cash and cash equivalents and marketable securities by maintaining its deposits and investments at high-quality financial institutions. The Company invests any excess cash in money market funds and other securities, and the management of these investments is not discretionary on the part of the financial institution. The Company has no significant off-balance-sheet risks such as foreign exchange contracts, option contracts, or other hedging arrangements.
Inventory	Inventory —The Company capitalizes inventories produced in preparation for initiating sales of a drug candidate when the related drug candidate is approved or considered to have a high likelihood of regulatory approval and the related costs are expected to be recoverable through sales of the inventories. An assessment of inventory capitalization begins either on or after the date a New Drug Application is accepted for filing by the U.S. Food and Drug Administration, or an international equivalent. Determining whether or not to continue to record the commercial supply costs related to a product candidate as research and development expenses or to capitalize these costs as inventory involves significant judgment. There were no capitalized inventories as of December 31, 2015 and 2014.
Property and Equipment	Property and Equipment —Property and equipment are recorded at cost and depreciated using the straight-line method over the estimated useful lives of the respective assets.
Research and Development Costs	Research and Development Costs —The Company accounts for research and development costs by expensing such costs to operations as incurred. Research and development costs primarily consist of clinical testing costs, including payments made to contract research organizations, personnel costs, outsourced research activities, laboratory supplies, and license fees. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are deferred and capitalized. The capitalized amounts are expensed as the related goods are delivered or the services are performed.
Licensing Agreements	Licensing Agreements —Costs associated with licensing early stage technology are expensed as incurred, and are included in research and development expenses.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets —The Company evaluates long-lived assets for potential impairment when there is evidence that events or changes in circumstances have occurred that indicate that the carrying amount of a long-lived asset may not be recovered. Recoverability of these assets is assessed based on the undiscounted expected future cash flows from the assets, considering a number of factors, including past operating results, budgets and economic projections, market trends, and product development cycles. Impairment in the carrying value of each asset is assessed when the undiscounted expected future cash flows derived from the asset are less than its carrying value. An impairment loss would be recognized in an amount equal to the excess of the carrying amount over the undiscounted expected future cash flows. No impairment charges have been recognized since the Company's inception.
Segment Information	Segment Information —Operating segments are defined as components of an enterprise engaged in business activities for which discrete financial information is available and regularly reviewed by the chief decision maker in determining how to allocate resources and in assessing performance. The Company views its operations and manages its business as one operating segment and operates in one geographic area.
Income Taxes	Income Taxes —The Company recognizes deferred tax assets and liabilities for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax basis, as well as operating loss and tax credit carryforwards. The Company measures deferred tax assets and liabilities using enacted tax rates expected to apply to taxable income in the years in which those temporary differences and carryforwards are expected to be recovered or settled. Deferred tax assets are reduced by a valuation allowance to reflect the uncertainty associated with their ultimate realization. The effect on deferred tax assets and liabilities as a result of a change in tax rates is recognized as income in the period that includes the enactment date. The Company uses judgment to determine the recognition threshold and measurement attribute for financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. Any material interest and penalties related to unrecognized tax benefits are recognized in income tax expense. Due to uncertainty surrounding the realization of the favorable tax attributes in future tax returns the Company has recorded a full valuation allowance against otherwise realizable net deferred tax assets as of December 31, 2015 and 2014.
Financial Instruments Indexed to and Potentially Settled in the Company's Common Stock	Financial Instruments Indexed to and Potentially Settled in the Company's Common Stock —The Company evaluates all financial instruments issued in connection with its debt borrowings and equity offerings when determining the proper accounting treatment for such instruments in the Company's consolidated financial statements. The Company considers a number of generally accepted accounting principles to determine such treatment and evaluates the features of the instrument to determine the appropriate accounting treatment. The Company utilizes the Black-Scholes method or other appropriate methods to determine the fair value of its derivative financial instruments. Key valuation factors in determining the fair value include, but are not limited to, the current stock price as of the date of measurement, the exercise price, the remaining contractual life, expected volatility for the instrument and the risk-free interest rate. For financial instruments that are determined to be classified as liabilities on the balance sheet, changes in fair value are recorded as a gain or loss in the Company's statement of operations, with the corresponding amount recorded as an adjustment to the liability on its balance sheet.
Stock-Based Compensation	Stock-Based Compensation-Options —The Company measures stock-based compensation cost at the accounting measurement date based on the fair value of the option, and recognizes the expense related to awards to employees on a straight-line basis over the requisite service period of the option, which is typically the vesting period. The Company estimates the fair value of each option using the Black-Scholes option pricing model that takes into account the fair value of its common stock, the exercise price, the expected life of the option, the expected volatility of its common stock, expected dividends on its common stock, and the risk-free interest rate over the expected life of the option. Due to the limited trading history of the Company's common stock since its June 2014 initial public offering, the Company uses the simplified method described in the SEC's Staff Accounting Bulletin No. 107, Share-Based Payment, to determine the expected life of the option grants. The estimate of expected volatility is based on a review of the historical volatility of similar publicly held companies in the biotechnology field over a period commensurate with the option's expected term. The Company has never declared or paid any cash dividends on its common stock and does not expect to do so in the foreseeable future. Accordingly, it uses an expected dividend yield of zero. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant valuation for a period commensurate with the option's expected term. These assumptions are highly subjective and changes in them could significantly impact the value of the option and hence the related compensation expense. The Company applies an estimated forfeiture rate to current period expense to recognize compensation expense only for those awards expected to vest. Forfeitures are estimated based upon historical data, adjusted for known trends, and the Company will adjust the estimate of forfeitures if actual forfeitures differ or are expected to differ from such estimates. Subsequent changes in estimated forfeitures are recognized through a cumulative adjustment in the period of change and also will impact the amount of stock-based compensation expense in future periods. Stock-based compensation expense recognized for options granted to consultants is also based upon the fair value of the options issued, as determined by the Black-Scholes option pricing model and recognized on an accelerated basis. However, the unvested portion of such option grants is re-measured at each reporting period, until such time as the option is fully vested. Stock-Based Compensation-Performance Units —The Company measures stock-based compensation cost at the accounting measurement date based on the fair value of the performance unit grant, and recognizes the expense over the derived service period of the performance units. The Company estimates the fair value of each grant using a Monte Carlo simulation analysis that takes into account the forecasted price of its common stock, historical volatility of its common stock, risk-free rate as of valuation date, price of its common stock as of the grant date and the trigger for the performance condition to be met. The derived service period for each grant is calculated using a Monte Carlo simulation analysis.
Net Loss Per Common Share	Net Loss Per Common Share —Net loss per common share is calculated using the two-class method, which is an earnings allocation formula that determines net loss per share for the holders of the Company's common shares and participating securities. Prior to the initial public offering, all of the Company's series of preferred stock contained participation rights in any dividend paid by the Company and were deemed to be participating securities. Net income available to common shareholders and participating preferred shares was allocated to each share on an as-converted basis as if all of the earnings for the period had been distributed. The participating securities do not include a contractual obligation to share in losses of the Company and are not included in the calculation of net loss per share in the periods that have a net loss. Diluted net income per share is computed using the more dilutive of (a) the two-class method, or (b) the if-converted method. Prior to the initial public offering, the Company allocated net income first to preferred stockholders based on dividend rights and then to common and preferred stockholders based on ownership interests. The weighted-average number of common shares outstanding gives effect to all potentially dilutive common equivalent shares, including outstanding stock options, warrants, and, prior to the Company's initial public offering, potential issuance of stock upon the issuance of the Company's series A-6 convertible preferred stock ("Series A-6") as settlement of the liability to Nordic Bioscience ("Nordic"). Common equivalent shares are excluded from the computation of diluted net income per share if their effect is anti-dilutive.
Comprehensive Income (Loss)	Comprehensive Income (Loss) —Comprehensive income (loss) refers to revenues, expenses, gains and losses that are excluded from net income (loss), as these amounts are recorded directly as an adjustment to stockholders' equity (deficit), net of tax. The Company's other comprehensive (loss) income is comprised of unrealized gains (losses) on its available-for-sale marketable securities.
New Accounting Pronouncements	Accounting Standards Updates —In August 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update No. 2014-15, Disclosures of Uncertainties about an Entity's Ability to Continue as a Going Concern ("ASU 2014-15"). ASU 2014-15 provides guidance in GAAP about management's responsibility to evaluate whether there is substantial doubt about an entity's ability to continue as a going concern and to provide related footnote disclosures. The amendments under ASU 2014-15 are effective for interim and annual fiscal periods beginning after December 15, 2016, with early adoption permitted. The Company does not expect the adoption of ASU 2014-15 to have a material impact on its results of operations, financial position or cash flows. In January 2015, the FASB issued Accounting Standards Update No. 2015-01, Income Statement—Extraordinary and Unusual Items (Subtopics 225-20) ("ASU 2015-01"). ASU 2015-01 eliminates the concept of extraordinary items from GAAP. The amendments under ASU 2015-01 are effective for interim and annual fiscal periods beginning after December 15, 2015, with early adoption permitted. The Company does not expect the adoption of ASU 2015-01 to have a material impact on its results of operations, financial position or cash flows. In April 2015, the FASB issued Accounting Standards Update No. 2015-03, Interest—Imputation of Interest (Subtopic 835-30) ("ASU 2015-03"). ASU 2015-03 requires that, instead of presentation as an asset, debt issuance costs be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The amendments under ASU 2015-03 are effective for interim and annual fiscal periods beginning after December 15, 2015, with early adoption permitted, and should be applied on a retrospective basis. The Company does not expect the adoption of ASU 2015-03 to have a material impact on its results of operations, financial position or cash flows. In April 2015, the FASB issued Accounting Standards Update No. 2015-05, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40) ("ASU 2015-05"). ASU 2015-05 updates guidance regarding accounting for cloud computing arrangements. The amendments under ASU 2015-05 are effective for interim and annual fiscal periods beginning after December 15, 2015, with early adoption permitted. The Company does not expect the adoption of ASU 2015-05 to have a material impact on its results of operations, financial position or cash flows. In November 2015, the FASB issued Accounting Standards Update No. 2015-17, Income Taxes (Topic 740) ("ASU 2015-17"). ASU 2015-17 requires deferred tax liabilities and assets to be classified as noncurrent in a classified statement of financial position, instead of separating deferred income tax liabilities and assets into current and noncurrent amounts. The amendments under ASU 2015-17 apply to all entities that present a classified statement of financial position and are effective, for public entities, for financial statements issued for annual periods beginning after December 15, 2016, and interim periods within those annual periods, with early adoption permitted for all entities as of the beginning of an interim or annual reporting period. The Company elected to early adopt ASU 2015-17 effective December 31, 2015 on a prospective basis. Adoption of this ASU resulted in a reclassification of our net current deferred tax asset to the net non-current deferred tax asset in our Consolidated Balance Sheet as of December 31, 2015. No prior periods were retrospectively adjusted. In January 2016, the FASB issued Accounting Standards Update No. 2016-01, Financial Statements—Overall (Subtopics 825-10) ("ASU 2016-01"). ASU 2016-01 provides updated guidance on the recognition and measurement of financial assets and financial liabilities that will supersede most current guidance. ASU 2016-01 primarily affects the accounting for equity investments, financial liabilities under the fair value option, and the presentation and disclosure requirements for financial instruments. The amendments in ASU 2016-01 supersede the guidance to classify equity securities with readily determinable fair values into different categories and require equity securities to be measured at fair value with changes in the fair value recognized through net income. The amendments under ASU 2016-01 are effective, for public business entities, for periods beginning after December 15, 2017, including interim periods within those fiscal years, and with early adoption permitted. The Company does not expect the adoption of ASU 2016-01 to have a material impact on its results of operations, financial position or cash flows.

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2015
Marketable Securities.
Schedule of available-for-sale marketable securities and cash and cash equivalents	Available-for-sale marketable securities and cash and cash equivalents consist of the following (in thousands): December 31, 2015 Amortized Cost Value Gross Unrealized Gains Gross Unrealized Losses Fair Value Cash and cash equivalents: Cash $ $ — $ — $ Money market — — Domestic corporate commercial paper — — Government-sponsored enterprise debt securities — — Domestic corporate debt securities — — Asset-backed securities — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ — $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities: Domestic corporate debt securities $ $ — $ ) $ Domestic corporate commercial paper — Asset-backed securities ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2014 Amortized Cost Value Gross Unrealized Gains Gross Unrealized Losses Fair Value Cash and cash equivalents: Cash $ $ — $ — $ Money market funds — — Domestic corporate debt securities — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ — $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities: Domestic corporate debt securities — ) Domestic corporate commercial paper — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ ) $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2015
Property and Equipment
Schedule of property and equipment	Property and equipment consists of the following (in thousands): December 31, Estimated Useful Life (In Years) 2015 2014 Furniture and fixtures 5 $ $ Computer equipment and software 3 Manufacturing equipment 10 Leasehold improvements Shorter of useful life or remaining lease term ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less accumulated depreciation and amortization ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Property and equipment, net $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Accrued Expenses and Other Cu26

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2015
Accrued Expenses and Other Current Liabilities
Schedule of accrued expenses	Accrued expenses consist of the following (in thousands): December 31, 2015 2014 Research costs—Nordic(1) $ $ Research costs—other Payroll and employee benefits Professional fees Accrued interest on notes payable — Other — ​ ​ ​ ​ ​ ​ ​ ​ Total accrued expenses and other current liabilties $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Includes amounts accrued ratably over the estimated per patient treatment period under the Nordic Work Statement NB-1 and Work Statement NB-3. Amounts do not include pass-through costs which are expensed as incurred or upon delivery. See note 10 for additional information.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Measurements
Summary of financial assets and liabilities measured at fair value on a recurring basis	The following table summarizes the financial instruments measured at fair value on a recurring basis in the accompanying consolidated balance sheets as of December 31, 2015 and December 31, 2014 (in thousands): As of December 31, 2015 Level 1 Level 2 Level 3 Total Assets Cash and cash equivalents: Cash $ $ — $ — $ Money market funds(1) — — Domestic corporate commercial paper(2) — — Government-sponsored enterprise debt securities(2) — — Domestic corporate debt securities(2) — — Asset-backed securities(2) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable Securities Domestic corporate debt securities(2) $ — $ $ — $ Domestic corporate commercial paper(2) — — Asset-backed securities(2) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ — $ $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2014 Level 1 Level 2 Level 3 Total Assets Cash and cash equivalents: Cash $ $ — $ — $ Money market funds(1) — — Domestic corporate debt securities(2) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ $ $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Marketable securities: Domestic corporate debt securities(2) $ — $ $ — $ Domestic corporate commercial paper(2) — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total $ — $ $ — $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (1) Fair value is based upon quoted market prices. (2) Fair value is based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant assumptions are observable in the market or can be corroborated by observable market data for substantially the full term of the assets. Inputs are obtained from various sources, including market participants, dealers and brokers.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2015
Stock-based Compensation
Schedule of weighted-average assumptions used in estimation of grant date fair values	Years Ended December 31, 2015 2014 2013 Expected term (years) Volatility % % % Expected dividend yield % % % Risk-free interest rates % % %
Summary of stock option activity	A summary of stock option activity for the year ended December 31, 2015 is as follows (in thousands, except for per share and weighted-average contractual life amounts): Shares Weighted-Average Exercise Price (in dollars per share) Weighted-Average Contractual Life (In Years) Aggregate Intrinsic Value Options outstanding at December 31, 2014 $ Granted Exercised ) Cancelled ) Expired — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options outstanding at December 31, 2015 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options exercisable at December 31, 2015 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Options vested or expected to vest at December 31, 2015 $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Summary of stock-based compensation expense by financial statement line	The following table summarizes stock-based compensation expense by financial statement line (in thousands): Years Ended December 31, 2015 2014 2013 Research and development $ $ $ General and administrative ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Share-based compensation expense included in operating expenses $ $ $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2015
Net Loss Per Share
Schedule of basic and diluted net loss per share	Basic and diluted net loss per share is calculated as follows (in thousands, except share and per share amounts): Year Ended December 31, 2015 2014 2013 Numerator: Net loss $ ) $ ) $ ) Accretion of preferred stock — ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loss attributable to common stockholders—basic ) ) ) Effect of dilutive convertible preferred stock — — — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loss attributable to common stockholders—diluted $ ) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator: Weighted-average number of common shares used in loss per share—diluted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loss per share—basic and diluted $ ) $ ) $ ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of potentially dilutive securities excluded from the computation of diluted weighted-average shares outstanding	Year Ended December 31 2015 2014 2013 Convertible preferred stock — Options to purchase common stock Warrants Performance units — — —

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Taxes
Schedule of reconciliation of income taxes computed using the U.S. federal statutory rate to that reflected in operations	A reconciliation of income taxes computed using the U.S. federal statutory rate to that reflected in operations follows (in thousands): Year Ended December 31, 2015 2014 2013 Income tax benefit using U.S. federal statutory rate $ ) $ ) $ ) State income taxes, net of federal benefit ) ) ) Stock-based compensation Research and development tax credits ) ) ) Change in the valuation allowance Permanent items ) Other ) ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ — $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
Schedule of principal components of the Company's deferred tax assets	The principal components of the Company's deferred tax assets are as follows (in thousands): December 31, 2015 2014 Current assets: Accrued expenses $ — $ ​ ​ ​ ​ ​ ​ ​ ​ Gross current deferred tax assets — ​ ​ ​ ​ ​ ​ ​ ​ Valuation allowance — ) ​ ​ ​ ​ ​ ​ ​ ​ Net current deferred tax assets $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Non-current assets: Net operating loss carryforwards $ $ Capitalized research and development Research and development credits Depreciation and amortization ) ) Accrued Expenses — Stock-based compensation Other — ​ ​ ​ ​ ​ ​ ​ ​ Gross non-current deferred tax assets Valuation allowance ) ) ​ ​ ​ ​ ​ ​ ​ ​ Net non-current deferred tax assets $ — $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Commitment and Contingencies (T

Commitment and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies
Schedule of Future Minimum Rental Payments	The Company is obligated to make monthly rent payments pursuant to these non-cancellable agreements as set forth below (in thousands): Years ended December 31, Future Lease Commitments 2016 $ 2017 2018 2019 2020 ​ ​ ​ ​ ​ Total minimum lease payments $ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Selected Quarterly Financial 32

Selected Quarterly Financial Data - Unaudited (Tables)	12 Months Ended
	Dec. 31, 2015
Selected quarterly financial data (Unaudited).
Schedule of Quarterly Financial Information (unaudited)	Selected quarterly financial data for the years ended December 31, 2015 and 2014 is as follows (in thousands, except for share and per share data): Three Months Ended March 31, June 30, September 30, December 31, 2015: Net loss $ ) ) ) $ ) Net loss applicable to common stock ) ) ) ) Net loss per share—basic and diluted ) ) ) ) Weighted-average common shares outstanding—basic and diluted 2014: Net loss $ ) $ ) $ ) $ ) Net loss applicable to common stock ) ) ) ) Net loss per share—basic and diluted ) ) ) ) Weighted-average common shares outstanding—basic and diluted

Nature of Business (DetailsS)

Nature of Business (DetailsS) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Nature of Business
Retained Earnings (Accumulated Deficit)	$ (445,764)	$ (344,238)
Cash, Cash Equivalents, and Short-term Investments	$ 473,300

Summary of Significant Accoun34

Summary of Significant Accounting Policies (Details) $ in Thousands	Apr. 24, 2014	Dec. 31, 2015USD ($)item	Dec. 31, 2014USD ($)
Summary of Significant Accounting Policies
Reverse stock-split ratio	2.28
Number of operating segment | item		1
Number of geographic segment | item		1
Marketable Securities
Other-than-temporary impairment losses		$ 0
Realized gains or losses on the sale of securities		0	$ 0
Inventories
Capitalized inventories		0	$ 0
Impairment of Long-Lived Assets
Impairment charges		$ 0
Stock-Based Compensation
Expected dividend yield (as a percent)		0.00%

Marketable Securities (Details)

Marketable Securities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)item	Dec. 31, 2014USD ($)item	Dec. 31, 2013USD ($)	Dec. 31, 2012USD ($)
Available-for-sale marketable securities and cash and cash equivalents
Cash and cash equivalents, Amortized Cost Value	$ 159,678	$ 28,518	$ 12,303	$ 18,653
Debt securities held in an unrealized loss position for more than 12 months | item	0	0
Debt securities held in an unrealized loss position for less than 12 months | item	57	34
Fair value of debt securities in an unrealized loss position for less than 12 months	$ 225,700	$ 68,900
Unrealized loss on debt securities in an unrealized loss position for less than 12 months	$ 150	$ 34
Maximum
Available-for-sale marketable securities and cash and cash equivalents
Marketable securities, contractual term to maturity	1 year	1 year
Available-for-sale marketable securities
Available-for-sale marketable securities and cash and cash equivalents
Marketable securities, Amortized Cost	$ 313,656	$ 76,779
Marketable securities, Gross Unrealized Gains	155	12
Marketable securities, Gross Unrealized Losses	(150)	(33)
Marketable securities, Fair Value	313,661	76,758
Domestic corporate debt securities
Available-for-sale marketable securities and cash and cash equivalents
Marketable securities, Amortized Cost	173,142	69,542
Marketable securities, Gross Unrealized Losses	(107)	(33)
Marketable securities, Fair Value	173,035	69,509
Domestic corporate commercial paper
Available-for-sale marketable securities and cash and cash equivalents
Marketable securities, Amortized Cost	84,004	7,237
Marketable securities, Gross Unrealized Gains	154	12
Marketable securities, Fair Value	84,158	7,249
Asset-backed Securities
Available-for-sale marketable securities and cash and cash equivalents
Marketable securities, Amortized Cost	56,510
Marketable securities, Gross Unrealized Gains	1
Marketable securities, Gross Unrealized Losses	(43)
Marketable securities, Fair Value	56,468
Cash and Cash Equivalents
Available-for-sale marketable securities and cash and cash equivalents
Cash and cash equivalents, Amortized Cost Value	159,678	28,518
Cash and cash equivalents, Fair Value	159,678	28,518
Cash
Available-for-sale marketable securities and cash and cash equivalents
Cash and cash equivalents, Amortized Cost Value	2,934	1,519
Cash and cash equivalents, Fair Value	2,934	1,519
Money market
Available-for-sale marketable securities and cash and cash equivalents
Cash and cash equivalents, Amortized Cost Value	83,257	23,994
Cash and cash equivalents, Fair Value	83,257	23,994
Domestic corporate commercial paper
Available-for-sale marketable securities and cash and cash equivalents
Cash and cash equivalents, Amortized Cost Value	39,984
Cash and cash equivalents, Fair Value	39,984
Government-sponsored enterprise debt securities
Available-for-sale marketable securities and cash and cash equivalents
Cash and cash equivalents, Amortized Cost Value	15,996
Cash and cash equivalents, Fair Value	15,996
Domestic corporate debt securities
Available-for-sale marketable securities and cash and cash equivalents
Cash and cash equivalents, Amortized Cost Value	10,007	3,005
Cash and cash equivalents, Fair Value	10,007	$ 3,005
Asset-backed Securities
Available-for-sale marketable securities and cash and cash equivalents
Cash and cash equivalents, Amortized Cost Value	7,500
Cash and cash equivalents, Fair Value	$ 7,500

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Property and Equipment
Property and equipment, gross	$ 2,242	$ 1,011
Less accumulated depreciation and amortization	(345)	(169)
Property and equipment, net	$ 1,897	842
Assets disposed		700
Furniture and fixtures
Property and Equipment
Estimated Useful Life	5 years
Property and equipment, gross	$ 314	167
Computer equipment and software
Property and Equipment
Estimated Useful Life	3 years
Property and equipment, gross	$ 479	$ 230
Manufacturing equipment
Property and Equipment
Estimated Useful Life		10 years
Property and equipment, gross	1,127	$ 598
Leasehold improvements
Property and Equipment
Property and equipment, gross	$ 322	$ 16

Accrued Expenses and Other Cu37

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accrued Expenses and Other Current Liabilities
Research costs - Nordic	$ 2,898	$ 11,536
Research costs - other	5,178	3,336
Payroll and employee benefits	3,330	1,659
Professional fees	3,546	1,304
Accrued interest on notes payable		234
Other		198
Total accrued expenses and other current liabilities	$ 14,952	$ 18,267

Loan and Security Agreement (De

Loan and Security Agreement (Details) $ / shares in Units, $ in Thousands	Jan. 01, 2016item	Aug. 04, 2015USD ($)	May. 30, 2014USD ($)	Sep. 30, 2015USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)item	Jan. 28, 2015$ / shares	Jul. 10, 2014USD ($)	May. 29, 2012USD ($)	Nov. 21, 2011USD ($)	May. 23, 2011USD ($)
Loan and Security Agreement
Maximum borrowing limit			$ 30,000
Share issue price (in dollars per share) | $ / shares							$ 36.75
Loss on retirement of Credit Facility					$ (1,572)	$ (203)
Initial Term Loan member
Loan and Security Agreement
Proceeds used to repay existing credit facility			$ 9,300
Basis spread (as a percent)			9.85%
Initial Term Loan member | Scenario, Forecast
Loan and Security Agreement
Number of payments of principal and interest payable monthly in arrears | item	30
Term Loan
Loan and Security Agreement
Maximum borrowing limit											$ 25,000
Term Loan A
Loan and Security Agreement
Aggregate principal amount											$ 6,300
Number of payments of principal and interest payable monthly in arrears | item						36
Final balloon payment						$ 600
Annual interest rate (as a percent)						10.16%
First Amendment member
Loan and Security Agreement
Aggregate principal amount								$ 4,000		$ 6,300
Number of payments of principal and interest payable monthly in arrears | item						30
Final balloon payment						$ 600
Annual interest rate (as a percent)						10.00%
First Amendment member | Credit Facility member
Loan and Security Agreement
Amount prepaid for relevant fees and remaining debt owed under the Credit Facility and the First Amendment		$ 26,500
Loss on retirement of Credit Facility				$ 1,600
Term Loan C
Loan and Security Agreement
Aggregate principal amount									$ 12,500
Number of payments of principal and interest payable monthly in arrears | item						24
Final balloon payment						$ 1,300
Annual interest rate (as a percent)						10.00%

Stockholders' Equity and Conv39

Stockholders' Equity and Convertible Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	Jul. 28, 2015	Jan. 28, 2015	Oct. 07, 2014	Jun. 25, 2014	Jun. 11, 2014	May. 10, 2013	Apr. 23, 2013	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Feb. 14, 2014
Common stock - public offering
Shares sold		4,000,000
Share issue price (in dollars per share)		$ 36.75
Proceeds from the sale of common stock		$ 137,800							$ 482,250	$ 103,804
Aggregate proceeds received, net of underwriting discounts and commissions and offering costs		$ 158,400
Underwriters
Common stock - public offering
Options exercised by underwriters (in shares)		600,000
Series B
Common stock - public offering
Conversion of convertible preferred stock into common stock (in shares)										(701,235)
Exercisable period for stock options following the Advisory period						5 years
Series B | Purchase Agreement
Class of stock
Number of shares issued						1,137	700,098
Exercise price of warrants (in dollars per unit)						$ 14.004	$ 14.004
Proceeds from issuance of shares						$ 100	$ 43,000
Warrants issued for purchase of shares of common stock (in shares)						1,246	767,651
Series B | Maximum | Purchase Agreement
Class of stock
Amount to be raised						$ 60,000
Number of shares authorized						980,000
Warrants issued for purchase of shares of common stock (in shares)						1,075,000
Series B-2 Convertible Preferred Stock
Class of stock
Amount to be raised											$ 40,200
Common stock - public offering
Conversion of convertible preferred stock into common stock (in shares)										(448,060)
Series B-2 Convertible Preferred Stock | Purchase Agreement
Class of stock
Number of shares issued								448,060
Exercise price of warrants (in dollars per unit)											$ 14.004
Proceeds from issuance of shares								$ 27,500
Warrants issued for purchase of shares of common stock (in shares)								491,293
Series B-2 Convertible Preferred Stock | Maximum | Purchase Agreement
Class of stock
Number of shares authorized											655,000
Warrants issued for purchase of shares of common stock (in shares)											718,201
Series A-1 Convertible Preferred Stock
Common stock - public offering
Conversion of convertible preferred stock into common stock (in shares)										(939,612)
Series A-2 Convertible Preferred Stock
Common stock - public offering
Conversion of convertible preferred stock into common stock (in shares)										(983,208)
Series A-3 Convertible Preferred Stock
Common stock - public offering
Conversion of convertible preferred stock into common stock (in shares)										(142,227)
Series A-4 Convertible Preferred Stock
Common stock - public offering
Conversion of convertible preferred stock into common stock (in shares)										(3,998)
Series A-5 Convertible Preferred Stock
Common stock - public offering
Conversion of convertible preferred stock into common stock (in shares)										(6,443)
Series A-6 Convertible Preferred Stock
Common stock - public offering
Conversion of convertible preferred stock into common stock (in shares)										(682,958)
Common Stock
Class of stock
Warrants issued for purchase of shares of common stock (in shares)					149,452
Common stock - public offering
Shares sold	4,054,054		2,750,000		6,500,000
Share issue price (in dollars per share)	$ 74		$ 18.25		$ 8
Proceeds from the sale of common stock	$ 281,500		$ 46,900
Conversion of convertible preferred stock into common stock (in shares)					19,465,132
Number of shares of common stock issued in satisfaction of accumulated dividends accrued on the preferred stock					2,862,654
Options exercised by underwriters (in shares)			378,524	512,744
Aggregate proceeds received, net of underwriting discounts and commissions and offering costs	$ 323,800		$ 53,400	$ 50,400
Common Stock | Underwriters
Common stock - public offering
Options exercised by underwriters (in shares)	608,108

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Cash
Assets
Cash	$ 2,934	$ 1,519
Money market
Assets
Cash	83,257	23,994
Domestic corporate commercial paper
Assets
Cash	39,984
Government-sponsored enterprise debt securities
Assets
Cash	15,996
Domestic corporate debt securities
Assets
Cash	10,007	3,005
Asset-backed Securities
Assets
Cash	7,500
Recurring basis | Estimated Fair Value
Assets
Cash	159,678	28,518
Marketable securities	313,661	76,758
Recurring basis | Cash | Estimated Fair Value
Assets
Cash	2,934	1,519
Recurring basis | Money market | Estimated Fair Value
Assets
Cash	83,257	23,994
Recurring basis | Domestic corporate commercial paper | Estimated Fair Value
Assets
Cash	39,984
Recurring basis | Government-sponsored enterprise debt securities | Estimated Fair Value
Assets
Cash	15,996
Recurring basis | Domestic corporate debt securities | Estimated Fair Value
Assets
Cash	10,007	3,005
Recurring basis | Asset-backed Securities | Estimated Fair Value
Assets
Cash	7,500
Recurring basis | Domestic corporate debt securities | Estimated Fair Value
Assets
Marketable securities		69,509
Recurring basis | Domestic corporate debt securities | Domestic corporate debt securities | Estimated Fair Value
Assets
Marketable securities	173,035
Recurring basis | Domestic corporate commercial paper | Estimated Fair Value
Assets
Marketable securities		7,249
Recurring basis | Domestic corporate commercial paper | Domestic corporate commercial paper | Estimated Fair Value
Assets
Marketable securities	84,158
Recurring basis | Asset-backed Securities | Domestic corporate commercial paper | Estimated Fair Value
Assets
Marketable securities	56,468
Recurring basis | Level 1
Assets
Cash	86,191	25,513
Recurring basis | Level 1 | Cash
Assets
Cash	2,934	1,519
Recurring basis | Level 1 | Money market
Assets
Cash	83,257	23,994
Recurring basis | Level 2
Assets
Cash	73,487	3,005
Marketable securities	313,661	76,758
Recurring basis | Level 2 | Domestic corporate commercial paper
Assets
Cash	39,984
Recurring basis | Level 2 | Government-sponsored enterprise debt securities
Assets
Cash	15,996
Recurring basis | Level 2 | Domestic corporate debt securities
Assets
Cash	10,007	3,005
Recurring basis | Level 2 | Asset-backed Securities
Assets
Cash	7,500
Recurring basis | Level 2 | Domestic corporate debt securities
Assets
Marketable securities		69,509
Recurring basis | Level 2 | Domestic corporate debt securities | Domestic corporate debt securities
Assets
Marketable securities	173,035
Recurring basis | Level 2 | Domestic corporate commercial paper
Assets
Marketable securities		$ 7,249
Recurring basis | Level 2 | Domestic corporate commercial paper | Domestic corporate commercial paper
Assets
Marketable securities	84,158
Recurring basis | Level 2 | Asset-backed Securities | Domestic corporate commercial paper
Assets
Marketable securities	$ 56,468

License Agreements (Details)

License Agreements (Details) € in Millions	Mar. 09, 2015USD ($)	Jun. 30, 2006USD ($)	Dec. 31, 2015EUR (€)	Dec. 31, 2015USD ($)
Eisai | License Agreement
License Agreements
Period after the date of the first commercial sale of the product for license expiration			10 years	10 years
Initial license fee paid		$ 500,000
Eisai | License Agreement | Minimum
License Agreements
Payments to be made upon achievement of certain clinical and regulatory milestones				$ 1,000,000
Eisai | License Agreement | Maximum
License Agreements
Payments to be made upon achievement of certain clinical and regulatory milestones				20,000,000
Eisai | Eisai Amendment | Research and development
License Agreements
Initial license fee paid	$ 400,000
Clinical Trial Services Agreement | Ipsen
License Agreements
Nonrefundable, non-creditable payment				$ 250,000
Royalty rate (as a percent)			5.00%	5.00%
Clinical Trial Services Agreement | Ipsen | Minimum
License Agreements
Additional payments to be made upon achievement of certain development and commercialization milestones			€ 10	$ 10,900,000
Period after the date of the first commercial sale of the product for license expiration			10 years	10 years
Clinical Trial Services Agreement | Ipsen | Maximum
License Agreements
Additional payments to be made upon achievement of certain development and commercialization milestones			€ 36	$ 39,100,000
Clinical Trial Services Agreement | Ipsen | Sublicense Agreement | Maximum
License Agreements
Period after the date of the first commercial sale of the product for license expiration			10 years	10 years

Research Agreements (Details)

Research Agreements (Details) € in Millions

Jul. 28, 2015shares

Mar. 31, 2015USD ($)item

Jan. 28, 2015shares

Oct. 07, 2014shares

Jun. 11, 2014shares

Feb. 28, 2014

May. 17, 2011shares

Apr. 30, 2015EUR (€)

Apr. 30, 2015USD ($)

Feb. 28, 2013EUR (€)

Feb. 28, 2013USD ($)

Dec. 31, 2015USD ($)

Dec. 31, 2014USD ($)

Dec. 31, 2013USD ($)

Research Agreements

Research and development expense

$ 68,280,000

$ 45,719,000

$ 60,536,000

Shares sold | shares

4,000,000

Common Stock

Research Agreements

Shares sold | shares

4,054,054

2,750,000

6,500,000

Clinical Trial Services Agreement | Abaloparatide-SC Phase 3 Extension Clinical Study | Nordic

Research Agreements

Amount reflected in accrued expenses and other current liabilities resulting from services payable in cash

2,900,000

Clinical Trial Services Agreement | Clinical Trial Services Agreement | Abaloparatide-SC Phase 3 Clinical Trial | Per patient costs for enrolled patients

Research Agreements

Research and development expense

0

8,200,000

31,600,000

Clinical Trial Services Agreement | Clinical Trial Services Agreement | Abaloparatide-SC Phase 3 Extension Clinical Study | Per patient costs for enrolled patients

Research Agreements

Research and development expense

$ 5,400,000

$ 9,600,000

$ 4,500,000

Clinical Trial Services Agreement | Clinical Trial Services Agreement | Abaloparatide-SC Phase 3 Extension Clinical Study | Maximum | Per patient costs for enrolled patients

Research Agreements

Period for which research and development expense is recognized

19 months

Clinical Trial Services Agreement | Clinical Trial Services Agreement | Abaloparatide-SC Phase 3 Extension Clinical Study | Minimum | Per patient costs for enrolled patients

Research Agreements

Period for which research and development expense is recognized

9 months

Clinical Trial Services Agreement | Clinical Trial Services Agreement | Abaloparatide-SC Phase 3 Extension Clinical Study | Nordic | Maximum

Research Agreements

Amount of euro-denominated payments required over the course of Clinical Trial

€ 11.9

$ 12,900,000

Amount of U.S. dollar-denominated payments required over the course of Clinical Trial

$ 1,100,000

Clinical Trial Services Agreement | NB-3 Amendment | Abaloparatide-SC Phase 3 Extension Clinical Study | Nordic | Maximum

Research Agreements

Amount of euro-denominated payments required over the course of Clinical Trial

€ 4.1

$ 4,500,000

Clinical Trial Services Agreement | Stock Issuance Agreement | Nordic | Series A-5 Convertible Preferred Stock | Former Operating Company

Research Agreements

Number of shares exchanged in the Merger | shares

6,443

Clinical Trial Services Agreement | Stock Issuance Agreement | Nordic | Series A-6 Convertible Preferred Stock

Research Agreements

Payments owed to be changed from the right to receive stock to the right to receive cash payment, if an IPO occurs prior to May 31, 2014

$ 4,300,000

Number of equal monthly installments for cash payments | item

10

Amount of equal monthly installments for cash payments

$ 430,000

Clinical Trial Services Agreement | Letter of Intent | Abaloparatide-SC Phase 3 Extension Clinical Study | Nordic

Research Agreements

Additional term provided for standard-of-care treatment

18 months

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	10 Months Ended	12 Months Ended
	Nov. 06, 2011	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015
Weighted-average assumptions used in estimation of grant date fair values
Expected dividend yield (as a percent)		0.00%
Additional disclosures
Weighted-average grant-date fair value (in dollars per share)		$ 30.52	$ 8.26	$ 4.67
Stock option / 2011 Incentive Plan
Stock-based Compensation
Number of shares of common stock authorized for issuance					6,160,000
Number of shares available for grant					1,100,000
Options to purchase common stock
Stock-based Compensation
Options outstanding (in shares)		3,220,000	3,220,000		4,408,000
Summary of stock option activity - Shares
Options outstanding at the beginning of the period (in shares)		3,220,000
Granted (in shares)		1,487,000
Exercised (in shares)		(268,000)
Forfeited (in shares)		(31,000)
Options outstanding at the end of the period (in shares)		4,408,000	3,220,000
Options exercisable at the end of the period (in shares)					1,738,000
Options vested and expected to vest at the end of the period (in shares)					4,316,000
Summary of stock option activity - Weighted-Average Exercise Price (in dollars per share)
Options outstanding at the beginning of the period (in dollars per share)		$ 13.58
Granted (in dollars per share)		57.75
Exercised (in dollars per share)		8.73
Forfeited (in dollars per share)		17.31
Options outstanding at the end of the period (in dollars per share)		$ 28.75	$ 13.58
Options exercisable at the end of the period (in dollars per share)					$ 12.21
Options vested and expected to vest at the end of the period (in dollars per share)					$ 28.43
Weighted-Average Contractual Life (In Years)
Options outstanding at the end of the period		8 years 2 months 27 days
Options exercisable at the end of the period		6 years 11 months 16 days
Options vested and expected to vest at the end of the period		8 years 2 months 19 days
Aggregate Intrinsic Value
Options outstanding at the end of the period (in dollars)					$ 151,544
Options exercisable at the end of the period (in dollars)					85,747
Options vested and expected to vest at the end of the period (in dollars)					$ 149,570
Additional disclosures
Aggregate intrinsic value of options vested during the period		$ 14,700	$ 700
Options to purchase common stock | Stock option / 2003 Incentive Plan
Stock-based Compensation
Number of shares of common stock authorized for issuance	884,000
Exercise period	10 years
Exercise period in case of stock options granted to stockholder owning in excess of 10% of the company's common stock	5 years
Award vesting period	4 years
Options to purchase common stock | Stock option / 2003 Incentive Plan | Minimum
Stock-based Compensation
Exercise price of options as percentage of fair value of common stock on the date of grant	100.00%			100.00%
Exercise price of options as percentage of fair value of common stock on the date of grant in case of options granted to stockholder owning in excess of 10% of Company's common stock	(110.00%)			(110.00%)
Percentage of ownership required in entity's common stock for specified exercise price	10.00%
Options to purchase common stock | Stock option / 2011 Incentive Plan
Stock-based Compensation
Number of shares of common stock authorized for issuance					5,276,000
Options outstanding (in shares)		4,408,000			4,408,000
Exercise period		10 years
Exercise period in case of stock options granted to stockholder owning in excess of 10% of the company's common stock		5 years
Award vesting period		4 years
Weighted-average assumptions used in estimation of grant date fair values
Expected term		6 years 29 days	6 years 22 days	6 years 3 months
Volatility (as a percent)		55.00%	59.00%	62.00%
Expected dividend yield (as a percent)		0.00%	0.00%	0.00%
Risk-free interest rates (as a percent)		1.72%	2.06%	2.45%
Summary of stock option activity - Shares
Options outstanding at the end of the period (in shares)		4,408,000
Options to purchase common stock | Stock option / 2011 Incentive Plan | Minimum
Stock-based Compensation
Exercise price of options as percentage of fair value of common stock on the date of grant	100.00%			100.00%
Exercise price of options as percentage of fair value of common stock on the date of grant in case of options granted to stockholder owning in excess of 10% of Company's common stock	110.00%			110.00%
Percentage of ownership required in entity's common stock for specified exercise price	10.00%			10.00%

Stock-Based Compensation (Det44

Stock-Based Compensation (Details 2) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summary of stock-based compensation expense
Share-based compensation expense included in operating expenses		$ 14,734	$ 7,070	$ 1,508
Total unrecognized compensation expense		$ 51,300
Weighted average period over which unrecognized compensation is expected to be recognized		3 years
Research and development
Summary of stock-based compensation expense
Share-based compensation expense included in operating expenses		$ 7,864	1,953	302
General and administrative
Summary of stock-based compensation expense
Share-based compensation expense included in operating expenses		$ 6,870	$ 5,117	$ 1,206
Performance units
Summary of stock-based compensation expense
Performance units granted	25,000
Number of shares of common stock each earned Performance Unit earns if and when it vests	1
Period subsequent to grant date during which award can be earned	3 years
Period used to calculate average closing stock price on grant date (in days)	45 days
Award vesting period	1 year
Weighted average grant date fair value of awards		$ 49.59

Net Loss Per Share (Details)

Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator:
Net loss	$ (33,240)	$ (28,264)	$ (22,965)	$ (17,057)	$ (17,962)	$ (17,420)	$ (12,609)	$ (14,488)	$ (101,526)	$ (62,479)	$ (60,690)
Accretion of Preferred Stock										(9,000)	(17,471)
Loss attributable to common stockholders - basic	$ (33,240)	$ (28,264)	$ (22,965)	$ (17,057)	$ (17,962)	$ (17,420)	$ (16,640)	$ (19,457)	(101,526)	(71,479)	(78,161)
Earnings (loss) attributable to common stockholders - diluted									$ (101,526)	$ (71,479)	$ (78,161)
Denominator:
Weighted-average number of common shares used in (loss) earnings per share - diluted									39,643,099	17,699,487	383,310
Basic and diluted (in dollars per share)									$ (2.56)	$ (4.04)	$ (203.91)

Net Loss Per Share (Details 2)

Net Loss Per Share (Details 2) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Convertible preferred stock
Net Loss Per Share
Potentially dilutive securities, prior to the use of the treasury stock method, excluded from the computation of diluted weighted-average shares outstanding, as they would be anti-dilutive		3,857,664	6,617,686
Options to purchase common stock
Net Loss Per Share
Potentially dilutive securities, prior to the use of the treasury stock method, excluded from the computation of diluted weighted-average shares outstanding, as they would be anti-dilutive	3,903,051	2,466,492	1,743,890
Warrants
Net Loss Per Share
Potentially dilutive securities, prior to the use of the treasury stock method, excluded from the computation of diluted weighted-average shares outstanding, as they would be anti-dilutive	822,726	1,271,520	545,797

Income Taxes (Details)

Income Taxes (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Income Taxes
Federal and state net operating loss carryforwards attributable to excess tax benefits	$ 14.1
Federal
Income Taxes
Net operating loss carryforwards	419.5
State
Income Taxes
Net operating loss carryforwards	$ 323

Income Taxes (Details 2)

Income Taxes (Details 2) $ in Millions	Dec. 31, 2015USD ($)
Federal
Income Taxes
Tax credits	$ 5.8
State
Income Taxes
Tax credits	$ 0.8

Income Taxes (Details 3)

Income Taxes (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of income taxes computed using the U.S. federal statutory rate to that reflected in operations
Income tax benefit using U.S. federal statutory rate	$ (34,391)	$ (21,243)	$ (20,635)
State income taxes, net of federal benefit	(4,434)	(2,494)	(2,255)
Stock-based compensation	752	149	92
Research and development tax credits	(1,469)	(499)	(1,277)
Change in the valuation allowance	39,291	23,186	27,194
Permanent items	26	910	(3,085)
Other	225	(9)	$ (34)
Current assets:
Accrued expenses		671
Gross current deferred tax assets		671
Valuation allowance		(671)
Non-current assets:
Net operating loss carryforwards	154,239	121,278
Capitalized research and development	263	356
Research and development credits	6,313	4,844
Depreciation and amortization	(119)	(47)
Accrued expenses	1,073
Stock-based compensation	7,753	3,158
Other	29
Gross non-current deferred tax assets	169,551	129,589
Valuation allowance	(169,551)	$ (129,589)
Unrecognized tax benefits	0
Interest and penalties accrued	$ 0

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commitments and Contingencies
Rent expense	$ 600	$ 200	$ 200
2,016	1,944
2,017	2,214
2,018	1,613
2,019	1,327
2,020	1,175
Total minimum lease payments	$ 8,273

Related Party Transactions (Det

Related Party Transactions (Details) - Consulting Agreement	Jan. 23, 2014USD ($)item	Oct. 02, 2013USD ($)	Jul. 30, 2013USD ($)	Dec. 31, 2015USD ($)	Jul. 24, 2013USD ($)
Non-employee awards to board members
Related party transactions
Aggregate consulting fees agreed to be paid in cash					$ 160,000
Aggregate consulting fees paid		$ 80,000	$ 80,000
Related party transaction fees payable				$ 0
Orbit
Related party transactions
Aggregate consulting fees agreed to be paid in cash	$ 400,000
Related party transaction fees payable				$ 0
Number of installments in which consulting fees is payable | item	4
Amount to be paid under each installment	$ 100,000
Period after completion of agreement term during which restriction apply	1 year

Selected Quarterly Financial 52

Selected Quarterly Financial Data (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statements of Operations and Comprehensive Loss
Net loss	$ (33,240,000)	$ (28,264,000)	$ (22,965,000)	$ (17,057,000)	$ (17,962,000)	$ (17,420,000)	$ (12,609,000)	$ (14,488,000)	$ (101,526,000)	$ (62,479,000)	$ (60,690,000)
Net loss applicable to common stock	(33,240,000)	(28,264,000)	(22,965,000)	(17,057,000)	(17,962,000)	(17,420,000)	(16,640,000)	(19,457,000)	$ (101,526,000)	$ (71,479,000)	$ (78,161,000)
Net loss per share - basic and diluted	$ (0.77)	$ (0.68)	$ (0.61)	$ (0.47)	$ (0.55)	$ (0.59)	$ (2.22)	$ (50.45)
Weighted-average common shares outstanding - basic and diluted	42,924,137	41,331,612	37,895,651	36,268,975	32,678,459	29,746,426	7,500,148	385,664	39,643,099	17,699,487	383,310