T2 Biosystems (TTOO) 10-K4 Mar 152014 FY Annual reportFinancial data

Company Profile

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Mar. 02, 2015
Document and Entity Information
Entity Registrant Name	T2 Biosystems, Inc.
Entity Central Index Key	1492674
Document Type	10-K
Document Period End Date	31-Dec-14
Amendment Flag	FALSE
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float	$170.70
Entity Common Stock, Shares Outstanding		20,125,635
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$73,849	$30,198
Accounts receivable	201
Prepaid expenses and other current assets	1,076	195
Inventories	115
Restricted cash, current portion	80
Total current assets	75,321	30,393
Property and equipment, net	2,760	1,118
Restricted cash, net of current portion	260	340
Deferred tax assets	313
Other assets	480	34
Total assets	79,134	31,885
Current liabilities:
Accounts payable	735	943
Accrued expenses and other current liabilities	3,662	1,319
Current portion of notes payable	295	1,759
Deferred revenue	80
Deferred tax liabilities	313
Current portion of deferred rent	87	25
Total current liabilities	5,172	4,046
Notes payable, net of current portion	20,660	3,299
Deferred rent, net of current portion	106	45
Warrants to purchase redeemable securities		1,225
Other liabilities	195
Commitments and contingencies (Note 13)
Redeemable convertible preferred stock (Note 7)		112,813
Stockholders' equity (deficit):
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued and outstanding at December 31, 2014 and 2013
Common stock, $0.001 par value; 200,000,000 and 28,254,907 shares authorized at December 31, 2014 and 2013, respectively; 20,041,645 and 1,411,986 shares issued and outstanding at December 31, 2014 and 2013, respectively	20	1
Additional paid-in capital	156,576
Accumulated deficit	-103,595	-89,544
Total stockholders' equity (deficit)	53,001	-89,543
Total liabilities, redeemable convertible preferred stock and stockholders' equity (deficit)	$79,134	$31,885

Consolidated_Balance_Sheet_Par

Consolidated Balance Sheet (Parentheticals) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Consolidated Balance Sheets
Preferred stock, par value (in dollars per share)	$0.00	$0.00
Preferred Stock, Shares Authorized	10,000,000	10,000,000
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares outstanding	0	0
Common stock, par value (in dollars per share)	$0.00	$0.00
Common stock, shares authorized	200,000,000	28,254,907
Common stock, shares issued	20,041,645	1,411,986
Common stock, shares outstanding	20,041,645	1,411,986

Consolidated_Statements_of_Ope

Consolidated Statements of Operations and Comprehensive Loss (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Statements of Operations and Comprehensive Loss
Research and grant revenue	$119	$266	$19
Operating expenses:
Research and development	19,782	14,936	11,727
Selling, general and administrative	11,018	5,022	2,945
Total operating expenses	30,800	19,958	14,672
Loss from operations	-30,681	-19,692	-14,653
Interest expense, net	-721	-403	-154
Other income (expense), net	12	-515	352
Net loss	-31,390	-20,610	-14,455
Comprehensive loss	-31,390	-20,610	-14,455
Reconciliation of net loss to net loss applicable to common stockholders:
Net loss	-31,390	-20,610	-14,455
Accretion of redeemable convertible preferred stock to redemption value	-4,570	-6,908	-4,412
Net loss applicable to common stockholders	($35,960)	($27,518)	($18,867)
Net loss per share applicable to common stockholders - basic and diluted	($4.15)	($19.72)	($13.86)
Weighted-average number of common shares used in computing net loss per share applicable to common stockholders - basic and diluted	8,674,931	1,395,562	1,361,616

Consolidated_Statements_of_Red

Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (USD $)	Series A-1	Series A-2	Series B	Series C	Series D	Series E	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Total
In Thousands, except Share data, unless otherwise specified	Series A-1	Series A-2	Series B	Series C	Series D	Series E	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Total
Balance at Dec. 31, 2011							$1		($44,196)	($44,195)
Balance at Dec. 31, 2011	784	6,918	13,720	16,681	23,622
Balance (in shares) at Dec. 31, 2011							1,359,718
Balance (in shares) at Dec. 31, 2011	282,849	1,703,959	3,249,877	4,055,125	5,054,945
Increase (Decrease) in Redeemable Convertible Preferred Stock
Accretion of redeemable convertible preferred stock to redemption value	46	404	874	1,214	1,874
Increase (Decrease) in Stockholders' Equity
Accretion of redeemable convertible preferred stock to redemption value								-404	-4,008	-4,412
Exercise of stock options								1		1
Exercise of stock options (in shares)							2,325
Stock-based compensation expense								403		403
Net loss									-14,455	-14,455
Balance at Dec. 31, 2012							1		-62,659	-62,658
Balance at Dec. 31, 2012	830	7,322	14,594	17,895	25,496
Balance (in shares) at Dec. 31, 2012							1,362,043
Balance (in shares) at Dec. 31, 2012	282,849	1,703,959	3,249,877	4,055,125	5,054,945
Increase (Decrease) in Redeemable Convertible Preferred Stock
Issuance of Series E redeemable convertible preferred stock, net of issuance costs of $232						39,768
Issuance of Series E redeemable convertible preferred stock, net of issuance costs of $232 (in shares)						6,930,967
Accretion of redeemable convertible preferred stock to redemption value	44	402	870	1,205	1,861	2,526
Increase (Decrease) in Stockholders' Equity
Accretion of redeemable convertible preferred stock to redemption value								-633	-6,275	-6,908
Exercise of stock options								55		55
Exercise of stock options (in shares)							49,943
Stock-based compensation expense								578		578
Net loss									-20,610	-20,610
Balance at Dec. 31, 2013							1		-89,544	-89,543
Balance at Dec. 31, 2013	874	7,724	15,464	19,100	27,357	42,294				112,813
Balance (in shares) at Dec. 31, 2013							1,411,986			1,411,986
Balance (in shares) at Dec. 31, 2013	282,849	1,703,959	3,249,877	4,055,125	5,054,945	6,930,967
Increase (Decrease) in Redeemable Convertible Preferred Stock
Accretion of redeemable convertible preferred stock to redemption value	26	240	520	722	1,115	1,947
Conversion of convertible preferred stock into common stock	-900	-7,964	-15,984	-19,822	-28,472	-44,241
Conversion of convertible preferred stock into common stock (in shares)	-282,849	-1,703,959	-3,249,877	-4,055,125	-5,054,945	-6,930,967
Increase (Decrease) in Stockholders' Equity
Accretion of redeemable convertible preferred stock to redemption value								-880	-3,690	-4,570
Exercise of stock options								153		153
Exercise of stock options (in shares)							64,661
Stock-based compensation expense								1,653		1,653
Conversion of redeemable convertible preferred stock into common stock							13	96,341	21,029	117,383
Conversion of redeemable convertible preferred stock into common stock (in shares)							12,516,298
Issuance of common stock upon net settlement of warrants to purchase redeemable convertible preferred stock								1,226		1,226
Issuance of common stock upon net settlement of warrants to purchase redeemable convertible preferred stock (in shares)							68,700
Issuance of common stock from initial public offering, net of offering costs of $7,700							6	58,083		58,089
Issuance of common stock from initial public offering, net of offering costs of $7,700 (in shares)							5,980,000
Net loss									-31,390	-31,390
Balance at Dec. 31, 2014							$20	$156,576	($103,595)	$53,001
Balance (in shares) at Dec. 31, 2014							20,041,645			20,041,645

Consolidated_Statements_of_Red1

Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parentheticals) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2014
Series E
Issuance costs	$232
Common stock
Issuance costs		$7,700

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
Consolidated Statements of Cash Flows (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities
Net loss	($31,390,000)	($20,610,000)	($14,455,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	691,000	584,000	571,000
Stock-based compensation expense	1,653,000	578,000	403,000
Noncash interest expense	112,000	44,000	46,000
Noncash warrant expense			81,000
Change in fair value of warrants	1,000	530,000	-132,000
Loss on disposal of asset		6,000
Deferred rent	5,000	-5,000	15,000
Changes in operating assets and liabilities:
Accounts receivable	-201,000
Prepaid expenses and other current assets	-1,217,000	-138,000	-2,000
Inventory	-115,000
Accounts payable	-208,000	372,000	-88,000
Accrued expenses and other liabilities	2,405,000	586,000	258,000
Deferred revenue	80,000
Net cash used in operating activities	-28,184,000	-18,053,000	-13,303,000
Investing activities
Purchases of property and equipment	-2,084,000	-513,000	-283,000
Decrease in restricted cash		80,000
Net cash used in investing activities	-2,084,000	-433,000	-283,000
Financing activities
Proceeds from issuance of common stock in initial public offering, net of offering costs	58,089,000
Proceeds from issuance of redeemable convertible preferred stock, net		39,768,000
Proceeds from issuance of common stock and stock options exercises, net	153,000	55,000	1,000
Proceeds from issuance of note payable, net	19,714,000		4,924,000
Repayments of notes payable	-4,037,000	-848,000	-374,000
Net cash provided by financing activities	73,919,000	38,975,000	4,551,000
Net increase (decrease) in cash and cash equivalents	43,651,000	20,489,000	-9,035,000
Cash and cash equivalents at beginning of period	30,198,000	9,709,000	18,744,000
Cash and cash equivalents at end of period	73,849,000	30,198,000	9,709,000
Supplemental disclosures of cash flow information
Cash paid for interest	515,000	345,000	101,000
Supplemental disclosures of noncash investing and financing activities
Accrued property and equipment	249,000
Accretion of Series A-1, A-2, B, C, D and E redeemable convertible preferred stock to redemption value	4,570,000	6,908,000	4,412,000
Warrants issued in connection with debt			64,000
Conversion of redeemable and convertible preferred stock to common stock	117,383,000
Conversion of preferred stock warrants to common stock	$1,226,000

Nature_of_Business

Nature of Business	12 Months Ended
Nature of Business	Dec. 31, 2014
Nature of Business
Nature of Business	1. Nature of Business

	T2 Biosystems, Inc. (the “Company”) was incorporated on April 27, 2006 as a Delaware corporation with operations based in Lexington, Massachusetts. The Company is an in vitro diagnostic company that has developed an innovative and proprietary platform that enables rapid, sensitive and simple direct detection of pathogens, biomarkers and other abnormalities across a variety of unpurified patient sample types. The Company is using its T2 Magnetic Resonance platform (“T2MR”) to develop a broad set of applications aimed at reducing mortality rates, improving patient outcomes and reducing the cost of healthcare by helping medical professionals make targeted treatment decisions earlier. The Company’s initial development efforts target sepsis, hemostasis and Lyme disease, areas of significant unmet medical need in which existing therapies could be more effective with improved diagnostics. On September 22, 2014, the Company received market authorization from the U.S. Food and Drug Administration (“FDA”) for its first two products, the T2Dx diagnostic instrument (“T2Dx”) and T2Candida panel (“T2Candida”).

	The Company has devoted substantially all of its efforts to research and development, business planning, recruiting management and technical staff, acquiring operating assets, raising capital, and, most recently, preparing for the commercialization of its products.

	Liquidity

	At December 31, 2014 the Company has generated an accumulated deficit of $103.6 million (see Note 8 for additional disclosure of the effects of the initial public offering on accumulated deficit). The future success of the Company is dependent on its ability to successfully commercialize its newly authorized products, obtain regulatory clearance for and successfully launch its future product candidates and ultimately attain profitable operations, and obtain additional capital, if needed. Historically, the Company has funded its operations primarily through private placements of its redeemable convertible preferred stock and through debt financing arrangements. On August 12, 2014, the Company completed its initial public offering (“IPO”) whereby the Company sold 5,980,000 shares of its common stock for net proceeds of approximately $58.1 million (Note 8). Management believes that its existing cash resources at December 31, 2014 together with the additional remaining liquidity of up to $10.0 million of available borrowings from the loan and security agreement executed in July 2014 (Note 6) will be sufficient to allow the Company to fund its current operating plan through at least the next 12 months.

	The Company is subject to a number of risks similar to other newly commercial life science companies, including, but not limited to commercially launching the Company’s products, development and market acceptance of the Company’s product candidates, development by its competitors of new technological innovations, protection of proprietary technology, and raising additional capital.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies

	Basis of Presentation and Consolidation

	The Company’s financial statements have been prepared in conformity with generally accepted accounting principles in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). The Company’s consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary, T2 Biosystems Securities Corporation. All intercompany balances and transactions have been eliminated.

	Use of Estimates

	The preparation of the Company’s financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The Company utilizes certain estimates in the determination of the fair value of its common stock and stock options, the fair value of liability-classified warrants, deferred tax valuation allowances, revenue recognition, to record expenses relating to research and development contracts and to classify the value of instrument raw material and work-in-process inventory between inventory and property and equipment. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results could differ from such estimates.

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

	Segment Information

	Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company’s chief operating decision maker is the Chief Executive Officer. The Company views its operations and manages its business in one operating segment, which is the business of developing and, upon regulatory clearance, launching commercially its diagnostic products aimed at reducing mortality rates, improving patient outcomes and reducing the cost of healthcare by helping medical professionals make targeted treatment decisions earlier.

	Off Balance Sheet Risk and Concentrations of Credit Risk

	The Company has no significant off-balance sheet risks, such as foreign exchange contracts, option contracts, or other foreign hedging arrangements. Cash and cash equivalents are financial instruments that potentially subject the Company to concentrations of credit risk. At December 31, 2014 and 2013, substantially all of the Company’s cash was deposited in accounts at one financial institution, with a significant amount invested in money market funds that are invested in short-term U.S. government agency securities. The Company maintains its cash deposits, which at times may exceed the federally insured limits, with a large financial institution and, accordingly, the Company believes such funds are subject to minimal credit risk.

	Cash Equivalents

	Cash equivalents include all highly liquid investments maturing within 90 days from the date of purchase. Cash equivalents consist of money market funds invested in short-term U.S. government agency securities as of December 31, 2014 and 2013.

	Accounts Receivable

	The Company’s accounts receivable consists primarily of amounts due from research and development arrangements with partners. At each reporting period, management reviews all outstanding balances to determine if the facts and circumstances of each customer relationship indicate the need for a reserve. The Company did not have an allowance for accounts at December 31, 2014 or 2013.

	Inventories

	Inventories are stated at the lower of cost or market. The Company determines the cost of its inventories, which includes amounts related to materials, direct labor, and manufacturing overhead, on a first-in, first-out basis. The Company performs an assessment of the recoverability of capitalized inventory during each reporting period, and writes down any excess and obsolete inventories to their realizable value in the period in which the impairment is first identified. Shipping and handling costs incurred for inventory purchases are capitalized and recorded upon sale in cost of product revenues in the consolidated statements of operations.

	The Company capitalizes inventories in preparation for sales of products when the related product candidates are considered to have a high likelihood of regulatory clearance, which for the T2Dx Instrument and T2Candida Panel was upon the achievement of regulatory clearance, and the related costs are expected to be recoverable through sales of the inventories. In addition, the Company capitalizes inventories related to the manufacture of instruments that have a high likelihood of regulatory clearance, which for the T2Dx Instrument and T2Candida Panel was upon the achievement of regulatory clearance, and will be retained as the Company’s assets, upon determination that the instrument has alternative future uses. In determining whether or not to capitalize such inventories, the Company evaluates, among other factors, information regarding the product candidate’s status of regulatory submissions and communications with regulatory authorities, the outlook for commercial sales and alternative future uses of the product candidate, including commercial sale. Costs associated with development products prior to satisfying the inventory capitalization criteria are charged to research and development expense as incurred.

	The Company classifies inventories related to instruments that are Company-owned, as a component of property and equipment. Raw material and work-in-process inventories that are expected to be used to produce Company-owned instruments, based on our business model and forecast, are also classified as property and equipment. Company-owned instruments are instruments that are manufactured and placed with customers in connection with rental agreements, or are used for internal purposes.

	The Company began capitalizing inventories upon receipt of market authorization from the FDA for its first two products. Inventory meeting the capitalization criteria as of December 31, 2014 totaled $115,000, comprised of $71,000 of raw materials and $44,000 of work in process.

	Fair Value Measurements

	The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. ASC 820, Fair Value Measurements and Disclosures (“ASC 820”), establishes a hierarchy of inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the observable inputs be used when available.

	Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability, and are developed based on the best information available in the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The hierarchy defines three levels of valuation inputs:

	Level 1 — Quoted unadjusted prices for identical instruments in active markets.

	Level 2 — Quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all observable inputs and significant value drivers are observable in active markets.

	Level 3 — Model derived valuations in which one or more significant inputs or significant value drivers are unobservable, including assumptions developed by the Company.

	The fair value hierarchy prioritizes valuation inputs based on the observable nature of those inputs. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability (See Note 3).

	Financial instruments measured at fair value on a recurring basis include cash, money market funds, restricted cash and warrants to purchase redeemable securities (See Note 3).

	For certain financial instruments, including accounts payable and accrued expenses, the carrying amounts approximate their fair values as of December 31, 2014 and 2013 because of their short-term nature. At December 31, 2014, the carrying value of the Company’s debt approximated fair value, which was determined using Level 3 inputs, including a quoted rate (Note 6).

	Property and Equipment

	Property and equipment are recorded at cost and depreciated over their estimated useful lives using the straight-line method. Property and equipment includes raw materials, work-in-process and finished instruments that are Company-owned or expected to remain Company-owned when placed in service. Company-owned instruments are instruments that are manufactured and placed with customers in connection with rental agreements, or are used for internal purposes. Repairs and maintenance costs are expensed as incurred, whereas major improvements are capitalized as additions to property and equipment.

	Revenue Recognition

	The Company generates revenue primarily from research and development agreements with government agencies and other third parties. Revenues earned from activities performed pursuant to development agreements is reported as revenue in the statements of operations and comprehensive loss, using the proportional performance method as the work is completed, and the related costs are expensed as incurred as research and development expense.

The timing of cash received from the Company’s research and development agreements generally differs from when revenue is recognized. The Company recognizes revenue in accordance with FASB ASC Topic 605, Revenue Recognition (“ASC 605”). Accordingly, the Company recognizes revenue when all of the following criteria have been met:

	i.	Persuasive evidence of an arrangement exists

	ii.	Delivery has occurred or services have been rendered

	iii.	The seller’s price to the buyer is fixed or determinable

	iv.	Collectability is reasonably assured

Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue. Criterion (i) is satisfied when the Company has a written agreement or contract in place. Criterion (ii) is satisfied when the Company performs the services. Determination of criteria (iii) and (iv) are based on management’s judgments regarding whether the fee is fixed or determinable and the collectability of the fee is reasonably assured.

For multiple-element arrangements, the Company identifies the deliverables included within the agreement and evaluates which deliverables represent separate units of accounting. The Company accounts for those components as separate elements when the following criteria are met: (1) the delivered items have value to the customer on a stand-alone basis; and, (2) if there is a general right of return relative to the delivered items, delivery or performance of the undelivered items is considered probable and within its control. The consideration received is allocated among the separate units of accounting based on management’s best estimate of selling price, and the applicable revenue recognition criteria are applied to each of the separate units. The determination that multiple elements in an arrangement meet the criteria for separate units of accounting requires the Company’s management to exercise its judgment.

Research and Development Costs

Costs incurred in the research and development of the Company’s product candidates are expensed as incurred. Research and development expenses consist of costs incurred in performing research and development activities and include salaries and benefits, stock compensation, research-related facility and overhead costs, laboratory supplies, equipment and contract services.

Impairment of Long Lived Assets

The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. During this review, the Company reevaluates the significant assumptions used in determining the original cost and estimated lives of long-lived assets. Although the assumptions may vary from asset to asset, they generally include operating results, changes in the use of the asset, cash flows and other indicators of value. Management then determines whether the remaining useful life continues to be appropriate or whether there has been an impairment of long-lived assets based primarily upon whether expected future undiscounted cash flows are sufficient to support the assets’ recovery. If impairment exists, the Company would adjust the carrying value of the asset to fair value, generally determined by a discounted cash flow analysis. No impairment charges have been recorded in any of the periods presented.

Comprehensive Loss

Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Comprehensive loss consists of net loss and other comprehensive loss, which includes certain changes in equity that are excluded from net loss. The Company’s comprehensive loss equals reported net loss for all periods presented.

Stock Based Compensation

The Company has a stock-based compensation plan which is more fully described in Note 9. The Company records stock-based compensation for options granted to employees and to members of the board of directors for their services on the board of directors, based on the grant date fair value of awards issued, and the expense is recorded on a straight-line basis over the applicable service period, which is generally four years. The Company accounts for non-employee stock-based compensation arrangements based upon the fair value of the consideration received or the equity instruments issued, whichever is more reliably measurable. The measurement date for non-employee awards is generally the date that the performance of services required for the non-employee award is complete. Stock-based compensation costs for non-employee awards is recognized as services are provided, which is generally the vesting period, on a straight-line basis.

The Company expenses restricted stock awards based on the fair value of the award on the date of issuance, on a straight-line basis over the associated service period of the award.

The Company uses the Black-Scholes-Merton option pricing model to determine the fair value of stock options. The use of the Black-Scholes-Merton option-pricing model requires management to make assumptions with respect to the expected term of the option, the expected volatility of the common stock consistent with the expected life of the option, risk-free interest rates and expected dividend yields of the common stock. The expected term was determined according to the simplified method, which is the average of the vesting tranche dates and the contractual term. Due to the lack of a public market for the trading of the Company’s common stock and a lack of company-specific historical and implied volatility data, the Company based its estimate of expected volatility on the historical volatility of a group of similar companies that are publicly traded. For these analyses, companies with comparable characteristics were selected, including enterprise value and position within the industry, and with historical share price information sufficient to meet the expected life of the stock-based awards. The Company computed the historical volatility data using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of its stock-based awards. The risk-free interest rate is determined by reference to U.S. Treasury zero-coupon issues with remaining maturities similar to the expected term of the options. The Company has not paid, and does not anticipate paying, cash dividends on shares of common stock; therefore, the expected dividend yield is assumed to be zero. The Company is required to estimate forfeitures at the time of grant and revise those estimates in subsequent periods if actual forfeitures differ from those estimates.

Warrants to Purchase Redeemable Securities

The Company has issued warrants to purchase shares of the Company’s series A-2 redeemable convertible preferred stock, series B redeemable convertible preferred stock, series C redeemable convertible preferred stock, and series D redeemable convertible preferred stock.

The Company accounts for warrant instruments that either conditionally or unconditionally obligate the issuer to transfer assets as liabilities regardless of the timing of the redemption feature or price, even though the underlying shares may be classified as permanent or temporary equity. Consequently, the warrants to purchase shares of series A-2 preferred stock, series B preferred stock, series C preferred stock, and series D preferred stock were accounted for as liabilities and adjusted to fair value at the end of each reporting period. The liability for warrants to purchase redeemable securities is remeasured at each balance sheet date with changes to fair value being recognized as a component of other income (expense) in the statement of operations and comprehensive loss. In connection with the closing of the Company’s IPO, all of the Company’s outstanding warrants to purchase redeemable securities were net settled into shares of common stock (Note 8).

Income Taxes

The Company provides for income taxes using the liability method. The Company provides deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the Company’s financial statement carrying amounts and the tax basis of assets and liabilities using enacted tax rates expected to be in effect in the years in which the differences are expected to reverse. A valuation allowance is provided to reduce the deferred tax assets to the amount that will more likely than not be realized.

The Company applies ASC 740 Income Taxes (“ASC 740”) in accounting for uncertainty in income taxes. The Company does not have any material uncertain tax positions for which reserves would be required. The Company will recognize interest and penalties related to uncertain tax positions, if any, in income tax expense.

Guarantees

As permitted under Delaware law, the Company indemnifies its officers and directors for certain events or occurrences while the officer or director is, or was, serving at the Company’s request in such capacity. The term of the indemnification is for the officer’s or director’s lifetime. The maximum potential amount of future payments the Company could be required to make is unlimited; however, the Company has directors’ and officers’ insurance coverage that limits its exposure and enables it to recover a portion of any future amounts paid.

The Company leases office, laboratory and manufacturing space under noncancelable operating leases. The Company has standard indemnification arrangements under the leases that require it to indemnify the landlord against all costs, expenses, fines, suits, claims, demands, liabilities, and actions directly resulting from any breach, violation or nonperformance of any covenant or condition of the Company’s leases.

As of December 31, 2014 and 2013, the Company had not experienced any material losses related to these indemnification obligations, and no material claims with respect thereto were outstanding. The Company does not expect significant claims related to these indemnification obligations and, consequently, concluded that the fair value of these obligations is negligible, and no related reserves were established.

Net Loss Per Share

Basic net loss per share is calculated by dividing net loss applicable to common stockholders by the weighted-average number of shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by adjusting the weighted-average number of shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock method. For purposes of the diluted net loss per share calculation, redeemable convertible preferred stock and warrants to purchase redeemable convertible preferred stock, which were outstanding prior to the Company’s IPO, and stock options and unvested restricted stock are considered to be common stock equivalents, but have been excluded from the calculation of diluted net loss per share, as their effect, including the related impact to the numerator of the fair value adjustment of the warrants and the impact to the denominator of the warrant shares, would be anti-dilutive for all periods presented. Therefore, basic and diluted net loss per share applicable to common stockholders were the same for all periods presented.

Reverse Stock Split

The Company effected a 1-for-1.7 reverse stock split of its issued and outstanding common stock on July 25, 2014. All share and per share amounts related to issued and outstanding common stock, outstanding options and warrants exercisable for common stock included in these financial statements and notes to the financial statements and have been retroactively adjusted for all periods presented to reflect the reverse stock split, including reclassifying an amount equal to the reduction in par value of common stock to additional paid-in capital. The shares authorized, issued and outstanding of the Company’s redeemable convertible preferred stock are not impacted by the reverse stock split and have not been adjusted.

Recently Adopted Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption.

In June 2014, the FASB issued amended guidance, ASU No 2014-09, Revenue from Contracts with Customers, which is applicable to revenue recognition that will be effective for the Company for the year ended December 31, 2017. The new guidance must be adopted using either a full retrospective approach for all periods presented or a modified retrospective approach. Early adoption is not permitted. The new guidance applies a more principles-based approach to revenue recognition. The Company is evaluating the new guidance and the expected effect on the Company’s consolidated financial statements.

In June 2014, the FASB issued ASU 2014-10, Development Stage Entities (Topic 915) (“ASU 2014-10”), which removes the definition of a development stage entity from the ASC, thereby removing the financial reporting distinction between development stage entities and other reporting entities. Accordingly, ASU 2014-10 eliminates the requirements for development stage entities to (1) present inception-to-date information in the statements of operations, cash flows and shareholder equity, (2) label financial statements as those of a development stage entity, (3) disclose a description of the development stage activities in which the entity is engaged, and (4) disclose in the first year in which the entity is no longer a development stage entity that in prior years it had been in the development stage. ASU 2014-10 is effective for public business entities for annual periods beginning after December 15, 2014, and interim reporting periods beginning after December 15, 2015, with early adoption permitted. The Company adopted the provisions of ASU 2014-10 in the June 30, 2014 Quarterly Report on Form 10-Q.

In 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements — Going Concern (“ASU 2014-15”), which is effective for annual periods ending after December 15, 2016. Early adoption is permitted. ASU 2014-15 provides new guidance on (1) management’s responsibility in evaluating whether or not there is substantial doubt about a company’s ability to continue as a going concern within one year from the date the financial statements are issued each reporting period and (2) related financial statement disclosures. The Company has not adopted the guidance prescribed by ASU 2014-15 and does not expect the new guidance to have a significant effect on its consolidated financial statements.

Fair_Value_Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2014
Fair Value Measurements
Fair Value Measurements	3. Fair Value Measurements

	The Company measures the following financial assets and liabilities at fair value on a recurring basis. The Company has not changed the manner in which it values the liability for warrants to purchase redeemable securities, which is measured at fair value using Level 3 inputs. There were no transfers between levels of the fair value hierarchy during any of the periods presented. The following tables set forth the Company’s financial assets and liabilities carried at fair value categorized using the lowest level of input applicable to each financial instrument as of December 31, 2014 and December 31, 2013 (in thousands):

		Balance at			Quoted Prices		Significant		Significant
		December 31,			in Active		Other		Unobservable
		2014			Markets for		Observable		Inputs
					Identical		Inputs		(Level 3)
					Assets		(Level 2)
					(Level 1)
	Assets:
	Cash	$	10,348		$	10,348	$	—	$	—
	Money market funds	63,501			63,501		—		—
	Restricted cash	340			340		—		—
		$	74,189		$	74,189	$	—	$	—

		Balance at			Quoted Prices		Significant		Significant
		December 31,			in Active		Other		Unobservable
		2013			Markets for		Observable		Inputs
					Identical		Inputs		(Level 3)
					Assets		(Level 2)
					(Level 1)
	Assets:
	Cash	$	2,631		$	2,631	$	—	$	—
	Money market funds	27,567			27,567		—		—
	Restricted cash	340			340		—		—
		$	30,538		$	30,538	$	—	$	—
	Liabilities:
	Warrants to purchase redeemable securities	$	1,225		$	—	$	—	$	1,225
		$	1,225		$	—	$	—	$	1,225

	The Company determined the fair value of the warrants to purchase redeemable convertible preferred stock based on input from management and the board of directors, which utilized an independent valuation of the Company’s enterprise value, determined utilizing an analytical valuation model. Each valuation methodology includes estimates and assumptions that require the Company’s judgment. These estimates and assumptions include a number of objective and subjective factors, including external market conditions affecting the in vitro diagnostics industry sector, the prices at which the Company sold shares of preferred stock, the superior rights and preferences of securities at the time and the likelihood of achieving a liquidity event, such as an initial public offering or a sale of the Company. Any changes in the assumptions used in the valuation could materially affect the financial results of the Company. Due to the nature of these inputs, the valuation of the warrants is considered a Level 3 measurement.

	The analytical valuation model used to determine the fair value of the warrants for the year ended December 31, 2013 was the hybrid approach based on an option pricing model method and probability weighted expected return method.

	The following table sets forth a summary of changes in the fair value of the Company’s preferred stock warrant liability, which represents a recurring measurement that is classified within Level 3 of the fair value hierarchy, wherein fair value is estimated using significant unobservable inputs (in thousands):

		2014
	Beginning balance	$	1,225
	Change in fair value, recorded as a component of other income (expense)	1
	Net exercise of warrants into common stock	(1,226		)
	Ending balance	$	—

Restricted_cash

Restricted cash	12 Months Ended
Restricted cash	Dec. 31, 2014
Restricted Cash
Restricted cash	4. Restricted Cash

	The Company is required to maintain a security deposit for its operating lease agreement for the duration of the lease agreement and for its credit cards as long as they are in place. At both December 31, 2014 and 2013, the Company had certificates of deposit for $340,000, which represented collateral as security deposits for its operating lease agreement for its facility and its credit card. In accordance with the operating lease agreement, the Company reduced its security deposit by $80,000 to $320,000 on January 14, 2013.

Supplemental_Balance_Sheet_Inf

Supplemental Balance Sheet Information	12 Months Ended
Supplemental Balance Sheet Information	Dec. 31, 2014
Supplemental Balance Sheet Information
Supplemental Balance Sheet Information	5. Supplemental Balance Sheet Information

	Property and Equipment

	Property and equipment consists of the following (in thousands):

		Estimated Useful		December 31,
		Life (Years)		2014			2013
	Office and computer equipment	3		$	383		$	302
	Software	3		480			186
	Laboratory equipment	5		3,312			2,770
	Furniture	5 - 7		187			179
	Manufacturing tooling and molds	0.5		26			—
	Leasehold improvements	Lesser of useful life or lease term		764			332
	Construction in progress			387			—
	Construction in progress — instruments	n/a		563			—
				6,102			3,769
	Less accumulated depreciation and amortization			(3,342		)	(2,651		)
	Property and equipment, net			$	2,760		$	1,118

	Construction in progress is primarily comprised of equipment and leasehold improvement construction projects that have not been placed in service. Construction in progress — instruments is comprised of raw material and work-in-process inventory that is expected to be used to produce Company-owned instruments, based on our business model and forecast.

	Depreciation and amortization expense of $691,000, $584,000 and $571,000 was charged to operations for the years ended December 31, 2014, 2013 and 2012, respectively.

	Accrued Expenses

	Accrued expenses consist of the following (in thousands):

		December 31,
		2014			2013
	Accrued payroll and compensation	$	1,846		$	496
	Accrued research and development expenses	733			422
	Accrued professional services	374			101
	Other accrued expenses	709			300
	Total accrued expenses	$	3,662		$	1,319

Debt

Debt	12 Months Ended
	Dec. 31, 2014
Debt
Debt	6. Debt

	On July 11, 2014, the Company entered into a loan and security agreement (“Note Agreement 1”) with two lenders to borrow up to $30.0 million for operations. Note Agreement 1 allows the Company to borrow amounts in two tranches, up to $20.0 million (drawn in amounts not less than $10.0 million upon closing and the remainder drawn in amounts not less than $5.0 million draws) by December 31, 2014 for tranche A and up to $10.0 million by June 30, 2015 for tranche B. Under Note Agreement 1, borrowings under tranche B are only available to the Company if both of the following conditions are met by June 30, 2015: (a) the Company receives Section 510(k) clearance from the FDA on the Company’s T2Dx and T2Candida products and (b) the Company completes a public or private stock offering, equity raise or strategic partner arrangement resulting in the receipt of at least $30.0 million in net proceeds by the Company. As the Company received FDA approval in September 2014 and the Company closed its initial public offering in August 2014, the borrowings under tranche B are now available as both of the required conditions have been met.

	Through December 31, 2014, the Company received proceeds of $19.7 million under tranche A, net of deferred financing costs. To date, the Company has not drawn the remaining tranche B available borrowings of $10.0 million.

	The amounts borrowed under Note Agreement 1 are collateralized by substantially all of the assets of the Company and bear interest at the one-month LIBOR plus 7.05%, which was 7.22% on December 31, 2014. The Company will pay interest only payments on the amounts borrowed under Note Agreement 1 through July 31, 2016. After the interest only period, the Company will repay the amounts borrowed in equal monthly installments until the maturity date of July 1, 2019. Note Agreement 1 requires payment of a final fee of 4.75% of the aggregate original principal of amounts borrowed, which the Company is accruing over the term of Note Agreement 1. In addition, amounts borrowed may be prepaid at the option of the Company in denominations of not less than $1.0 million, and any amounts prepaid are subject to a prepayment premium of 1.5% if prepaid prior to the first anniversary of the borrowing date, 1.0% if prepaid prior to the second anniversary of the borrowing date and after the first anniversary of the borrowing date, and 0.5% if prepaid prior to the maturity date and after the second anniversary of the borrowing date. The effective interest rate for Note Agreement 1, including final fee interest and non-cash interest, is 9.3%.

	Note Agreement 1 does not include any financial covenants, but does contain a subjective acceleration clause whereby upon an event of default, which includes a material adverse change in the business, operations, or conditions (financial or otherwise) of the Company or a material impairment of the prospect of repayment of any portion of the obligations, there can be an immediate acceleration of the borrowings under Note Agreement 1. In the event of default, the lender has first priority to substantially all of the Company’s assets, except for those collateralized by Note Agreement 3. The lender has not exercised its right under this clause, as there have been no such events. The Company believes that the likelihood of the lender exercising this right is remote.

	The Company assessed all terms and features of Note Agreement 1 in order to identify any potential embedded features that would require bifurcation or any beneficial conversion features. As part of this analysis, the Company assessed the economic characteristics and risks of Note Agreement 1, including put and call features. The Company determined that all features of Note Agreement 1 are clearly and closely associated with a debt host and do not require bifurcation as a derivative liability, or the fair value of the feature is immaterial. The Company will continue to reassess the features to determine if they require separate accounting on a quarterly basis.

	On June 25, 2012, the Company entered into a loan and security agreement (“Note Agreement 2”) with a lender to borrow up to $4.5 million for operations through December 31, 2012. The amounts borrowed are collateralized by the assets of the Company and bear interest at 6.25%. The Company paid interest only on the borrowings through June 30, 2013 and then makes 36 equal month payments of principal plus monthly payments of accrued interest. During 2012, the Company borrowed $4.5 million under the agreement. The debt can be prepaid at the option of the Company, and is subject to a prepayment premium of 2% if it is repaid prior the first anniversary of the borrowing date, and 1% if the debt is prepaid prior to the second anniversary of the borrowing date.

	In connection with the closing of Note Agreement 1, the Company repaid all amounts outstanding under Note Agreement 2, totaling approximately $2.9 million, as of July 11, 2014.

	On May 9, 2011, the Company entered into a promissory agreement (“Note Agreement 3”) with a separate lender to borrow up to $1.7 million for the purchase of laboratory equipment and office equipment through December 2013. The amounts borrowed are collateralized by the associated equipment and bear interest at 6.5%. The Company paid interest only on the borrowings through December 2013 and will make equal monthly payments of principal and interest through the maturity date of May 2018. The Company borrowed a total of $1.4 million under Note Agreement 3, including $451,000 during the year ended December 31, 2012.

	The Note Agreement 3 includes financial covenants that require the Company to maintain a minimum cash balance of $300,000.

	In addition, Note Agreement 3 contains a subjective acceleration clause whereby an event of default and immediate acceleration of the borrowing under the security and loan agreement occurs if there is a material adverse change in the business, operations, or condition (financial or otherwise) of the Company or a material impairment of the prospect of repayment of any portion of the obligations. In the event of default, the lender has first priority on the laboratory equipment and office equipment purchased with the proceeds from Note Agreement 3. The lender has not exercised its right under this clause, as there have been no such events. The Company believes that the likelihood of the lender exercising this right is remote.

	Interest expense for the years ended December 31, 2014, 2013 and 2012 was $741,000, $410,000, and $156,000, respectively. Interest expense for the years ended December 31, 2014, 2013, and 2012 included non-cash interest of $112,000, $44,000, and $46,000, respectively, related to the amortization of debt discounts and deferred financing costs under each of the Note Agreements.

	Future principal payments on the notes payable as of December 31, 2014 are as follows (in thousands):

	Year ended December 31,
	2015	$	308
	2016	3,106
	2017	7,018
	2018	6,793
	2019	3,889
	Total debt payments	21,114
	Less current portion, including debt discount	(295		)
	Less debt discount	(159		)
	Notes payable, net of current portion	$	20,660

Redeemable_Convertible_Preferr

Redeemable Convertible Preferred Stock	12 Months Ended
Redeemable Convertible Preferred Stock	Dec. 31, 2014
Redeemable Convertible Preferred Stock
Redeemable Convertible Preferred Stock	7. Redeemable Convertible Preferred Stock

	Upon closing of the IPO on August 12, 2014, all of the outstanding shares of the Company’s redeemable convertible preferred stock were converted into 12,516,298 shares of its common stock. As the Preferred Stock was redeemable, the Company accreted the shares to the redemption values over the period from issuance to the redemption date. The accretion amounts are recorded as an increase to the carrying value of the Preferred Stock with a corresponding charge to additional paid-in capital or accumulated deficit.

	On the conversion date, the redeemable convertible preferred stock had a balance of $117.4 million, which was recorded in temporary equity. Upon conversion into common stock, this balance was reclassified as stockholders’ equity (deficit), reducing accumulated deficit by $21.0 million, with the residual amount of $96.3 million recorded as common stock (par value) and additional paid-in capital. The amount recorded as a reduction in accumulated deficit reflects the value of redeemable convertible preferred stock dividends and issuance costs accreted through the conversion date. As of August 12, 2014, the Company does not have any redeemable convertible preferred stock issued or outstanding.

	Prior to the IPO, the holders of the Company’s redeemable convertible preferred stock had certain voting, dividend, and redemption rights, as well as liquidation preferences and conversion privileges. All rights, preferences, and privileges associated with the redeemable convertible preferred stock were terminated at the time of the Company’s IPO in conjunction with the conversion of all outstanding shares of redeemable convertible preferred stock into shares of common stock.

Stockholders_Equity_Deficit

Stockholders' Equity (Deficit)	12 Months Ended
	Dec. 31, 2014
Stockholders' Equity (Deficit)
Stockholders' Equity (Deficit)	8. Stockholders’ Equity (Deficit)

	Common Stock

	Each share of common stock is entitled to one vote. The holders of common stock are also entitled to receive dividends whenever funds are legally available and when declared by the board of directors, subject to the prior rights of holders of all classes of stock outstanding. As of December 31, 2014, a total of 3,678,581 shares of common stock were reserved for issuance upon (i) the exercise of outstanding stock options and (ii) the issuance of stock awards under the Company’s 2014 Incentive Award Plan and 2014 Employee Stock Purchase Plan.

	Initial Public Offering

	On August 12, 2014, the Company completed its IPO, whereby the Company sold 5,980,000 shares of its common stock (inclusive of 780,000 shares of common stock sold by the Company pursuant to the full exercise of an overallotment option granted to the underwriters in connection with the offering) at a price of $11.00 per share. The shares began trading on the Nasdaq Global Market on August 7, 2014. The net proceeds received by the Company from the offering were approximately $58.1 million, after deducting underwriting discounts and commissions and other estimated offering expenses payable by the Company. Upon the closing of the IPO, all outstanding shares of redeemable convertible preferred stock converted into 12,516,298 shares of common stock (Note 7) and warrants exercisable for redeemable convertible preferred stock net exercised into 68,700 shares of common stock (Note 10). In addition, the following other items became effective in connection with IPO:

		(i)	Upon closing of the IPO on August 12, 2014, the number of authorized shares of common stock of the Company increased to 200,000,000 and the Company is authorized to issue up to 10,000,000 shares of preferred stock.

		(ii)	On July 19, 2014, the Company’s board of directors adopted and, on July 21, 2014, the Company’s stockholders approved, the 2014 Incentive Award Plan (“2014 Plan”), which became effective on August 6, 2014. The 2014 Plan provides for the grant of incentive stock options, nonstatutory stock options, restricted stock awards, restricted stock units, stock appreciation rights and other stock-based awards. The Company’s employees, officers, directors, consultants and advisors are eligible to receive awards under the 2014 Plan.

		(iii)	On July 19, 2014, the Company’s board of directors adopted and, on July 21, 2014, the Company’s stockholders approved, the 2014 Employee Stock Purchase Plan (“2014 ESPP”), which became effective on August 6, 2014. The 2014 ESPP enables eligible employees to purchase shares of the Company’s common stock at a discount.

Stock_Based_Compensation

Stock Based Compensation	12 Months Ended
Stock Based Compensation	Dec. 31, 2014
Stock Based Compensation
Stock-Based Compensation	9. Stock Based Compensation

	Stock Incentive Plans

	2006 Stock Incentive Plan

	The Company’s 2006 Stock Option Plan (“the 2006 Plan”) was established for granting stock incentive awards to directors, officers, employees and consultants to the Company. Upon closing of the Company’s IPO in August 2014, the Company ceased granting stock incentive awards under the 2006 Plan. The 2006 Plan provided for the grant of incentive and non-qualified stock options and restricted stock grants as determined by the Board of Directors. Under the 2006 Plan, stock options were generally granted with exercise prices equal to or greater than the fair value of the common stock as determined by the board of directors, expired no later than 10 years from the date of grant, and vest over various periods not exceeding 4 years.

	2014 Stock Incentive Plan

	The Company’s 2014 Plan provides for the issuance of shares of common stock in the form of stock options, awards of restricted stock, awards of restricted stock unit awards, performance awards, dividend equivalent awards, stock payment awards and stock appreciation rights to directors, officers, employees and consultants of the Company. Since the establishment of the 2014 Plan, the Company has only granted stock options. Generally, stock options are granted with exercise prices equal to or greater than the fair value of the common stock on the date of grant, expire no later than 10 years from the date of grant, and vest over various periods not exceeding 4 years.

	The number of shares reserved for future issuance under the 2014 Plan is the sum of (1) 823,529, (2) any shares that were granted under the 2006 Plan which are forfeited, lapse unexercised or are settled in cash subsequent to the effective date of the 2014 Plan and (3) an annual increase on the first day of each calendar year beginning January 1, 2015 and ending on January 1, 2024, equal to the lesser of (A) 823,529 shares, (B) 4% of the shares outstanding on the final day of the immediately preceding calendar year and (C) such smaller number of shares determined by the Board of Directors. As of December 31, 2014 there were 546,847 shares available for future grant under the Plan.

	Stock Options

	During the years ended December 31, 2014, 2013, and 2012, the Company granted options with an aggregate fair value of $6.0 million and $2.0 million, and $702,000, respectively, which are being amortized into compensation expense over the vesting period of the options as the services are being provided. The following is a summary of option activity under the Plan (in thousands, except share and per share amounts):

		Number of		Weighted-Average		Weighted-Average	Aggregate Intrinsic
		Shares		Exercise Price Per		Remaining	Value
				Share		Contractual Term
						(In years)
	Outstanding at December 31, 2013	2,265,973		2.53		8.23	11,510
	Granted	793,842		12.64
	Exercised	(64,661	)	2.37			1,091
	Cancelled	(84,008	)	2.44
	Outstanding at December 31, 2014	2,911,146		5.3		7.87	40,586
	Exercisable at December 31, 2014	1,442,227		2.42		6.61	24,276
	Vested or expected to vest at December 31, 2014	2,576,282		5.04		7.74	36,587

	The weighted-average fair values of options granted in the years ended December 31, 2014, 2013, and 2012 were $7.59, $1.85, and $1.45 per share, respectively, and were calculated using the following estimated assumptions:

		Year Ended
		December 31,
		2014		2013		2012
	Weighted-average risk-free interest rate	1.91%		1.68%		1.35%
	Expected dividend yield	0.00%		0.00%		0.00%
	Expected volatility	61%		63%		64%
	Expected terms	5.75 – 6.09 years		5.77 - 6.08 years		6.25 - 10 years

	The total fair values of stock options that vested during the years ended December 31, 2014, 2013, and 2012 were $1,160,000, $476,000, and $302,000, respectively.

	Employee Stock Purchase Plan

	The 2014 ESPP plan period is semi-annual and allows participants to purchase the Company’s common stock at 85% of the lower of (i) the market value per share of common stock on the first day of the offering period or (ii) the market value per share of the common stock on the purchase date. Each participant can purchase up to a maximum of $25,000 per calendar year in fair market value, as determined by the market value per share of common stock at the beginning of the offering period. The first plan period began on August 7, 2014. Stock-based compensation expense from the 2014 ESPP for the year ended December 31, 2014 was $103,000.

	The 2014 ESPP provides initially for the granting of up to 220,588 shares of the Company’s common stock to eligible employees. In addition, on the first day of each calendar year beginning January 1, 2015 and ending on January 1, 2024, the number of common shares available under the Plan shall be increased by the number of shares equal to the lesser of (1) 220,588 shares, (2) 1% of the common shares outstanding on the final day of the immediately preceding calendar year and (3) such smaller number of common shares as determined by the Board of Directors. At December 31, 2014, there were 220,588 shares available under the 2014 ESPP.

	Stock Based Compensation Expense

	The following table summarizes the stock-based compensation expense for stock options granted to employees and non-employees, as well as stock-compensation expense for the 2014 ESPP that was recorded in the Company’s results of operations for the years presented (in thousands):

		Year Ended
		December 31,
		2014			2013		2012
	Research and development	$	501		$	169	$	160
	Selling, general and administrative	1,152			409		243
	Total stock-based compensation expense	$	1,653		$	578	$	403

	As of December 31, 2014, there was $7.2 million of total unrecognized compensation cost related to non-vested stock options granted under the Stock Incentive Plans. Total unrecognized compensation cost will be adjusted for future changes in the estimated forfeiture rate. The Company expects to recognize that cost over a remaining weighted-average period of 3.17 years.

Warrants

Warrants	12 Months Ended
Warrants	Dec. 31, 2014
Warrants
Warrants	10. Warrants

	Prior to the completion of the IPO, the Company had outstanding warrants to purchase 250,727 shares of various classes of redeemable convertible preferred stock. The warrants were recorded as a liability and changes in the fair value of the warrants were recorded as a component of other income (expense), net. In connection with the closing of the Company’s IPO, all of the Company’s outstanding warrants to purchase convertible preferred stock automatically converted into 68,700 shares of common stock, resulting in the net settlement of the liability to purchase redeemable securities to common stock (par value) and additional paid-in capital as of August 12, 2014 (Note 8).

Net_Loss_Per_Share

Net Loss Per Share	12 Months Ended
Net Loss Per Share	Dec. 31, 2014
Net Loss Per Share
Net Loss Per Share	11. Net Loss Per Share

	The following table presents the calculation of basic and diluted net loss per share applicable to common stockholders (in thousands, except share and per share data):

		Year Ended
		December 31,
		2014			2013			2012
	Numerator:
	Net loss	$	(31,390	)	$	(20,610	)	$	(14,455	)
	Accretion of redeemable convertible preferred stock to redemption value	(4,570		)	(6,908		)	(4,412		)
	Net loss applicable to common stockholders	$	(35,960	)	$	(27,518	)	$	(18,867	)
	Denominator:
	Weighted-average number of common shares outstanding — basic and diluted	8,674,931			1,395,562			1,361,616
	Net loss per share applicable to common stockholders — basic and diluted	$	(4.15	)	$	(19.72	)	$	(13.86	)

	The following shares were excluded from the calculation of diluted net loss per share applicable to common stockholders, prior to the application of the treasury stock method, because their effect would have been anti-dilutive for the periods presented:

		Year Ended
		December 31,
		2014		2013		2012
	Redeemable convertible preferred stock	—		12,516,298		8,439,267
	Options to purchase common shares	2,911,146		2,265,973		1,399,064
	Warrants to purchase redeemable convertible preferred stock	—		147,484		147,484
	Total	2,911,146		14,929,755		9,985,815

Income_Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2014
Income Taxes
Income Taxes	12. Income Taxes

	The reconciliation of the U.S. federal statutory rate to the Company’s effective tax rate is as follows:

		Year Ended
		December 31,
		2014		2013		2012
	Tax at statutory rates	35	%	35	%	34	%
	State income taxes	5.1		5.2		5.3
	Change in tax rate	0		0		(0.2	)
	Permanent differences	(0.8	)	(0.7	)	(0.5	)
	Research and development credits	1.9		2.3		1.6
	Change in valuation allowance	(41.2	)	(41.8	)	(40.2	)
	Effective tax rate	0	%	0	%	0	%

	The significant components of the Company’s deferred tax asset consist of the following at December 31, 2014 and 2013 (in thousands):

		December 31,
		2014			2013
	Deferred tax assets:
	Net operating loss carryforwards	$	33,690		$	22,280
	Tax credits	2,795			2,189
	Other temporary differences	1,159			180
	Start-up expenditures	4,948			5,318
	Stock option expenses	588			179
	Total deferred tax assets	43,180			30,146
	Deferred tax asset valuation allowance	(42,867		)	(30,146		)
	Net deferred tax assets	313			—

	Deferred tax liabilities:
	Prepaid expenses	(313		)	—
	Net deferred taxes	$	—		$	—

	In 2014, 2013 and 2012, the Company did not record a benefit for income taxes related to its operating losses incurred. In assessing the ability to realize the net deferred tax assets, management considers whether it is more likely than not that some portion or all of the net deferred tax assets will not be realized. Based upon the level of historical U.S. losses and future projections over the period in which the net deferred tax assets are deductible, at this time, management believes it is more likely than not that the Company will not realize the benefits of these deductible differences. The Company has provided a full valuation allowance against its net deferred tax assets as of December 31, 2014 and 2013. The increase in the valuation allowance was $12.7 million, $9.1 million and $6.1 million for the years ended December 31, 2014, 2013 and 2012, respectively, and principally related to each year’s taxable loss.

	As of December 31, 2014, the Company had federal and state net operating losses of $84.8 million and $76.7 million, respectively, which are available to offset future taxable income, if any, through 2034. The Company also had federal and state research and development tax credits of $2.2 million and $872,000, respectively, which expire at various dates through 2034. Under the provisions of the Internal Revenue Code, the net operating loss and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. Net operating loss and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three-year period in excess of 50%, as defined under Sections 382 and 383 of the Internal Revenue Code, respectively, as well as similar state provisions. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. The amount of the annual limitation is determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. The Company has completed several financings since its inception which may have resulted in a change in control as defined by Sections 382 and 383 of the Internal Revenue Code, or could result in a change in control in the future. The Company has not conducted an assessment to determine whether there may have been a Section 382 or 383 ownership change.

	The Company has no unrecognized tax benefits. Interest and penalty charges, if any, related to uncertain tax positions would be classified as income tax expenses in the accompanying consolidated statements of operations. At December 31, 2014 and 2013, the Company had no accrued interest or penalties related to uncertain tax positions.

	The Company files income tax returns in the U.S. federal tax jurisdiction and various state jurisdictions. Since the Company is in a loss carryforward position, the Company is generally subject to examination by the U.S. federal, state and local income tax authorities for all tax years in which a loss carryforward is available. The Company does not have any international operations as of December 31, 2014. There are currently no federal or state audits in process.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies.
Commitments and Contingencies	13. Commitments and Contingencies

	In August 2010, the Company entered into a five-year, non-cancelable operating lease for office and laboratory space. The Company has the option to extend the lease for one additional term of two years. The lease commenced on January 1, 2011, with the Company providing a security deposit of $400,000. In accordance with the operating lease agreement, the Company reduced its security deposit by $80,000 to $320,000 on January 14, 2013.

	In May, 2013, the Company entered into a six month operating lease for laboratory space with an option to extend the lease an additional six months. In September 2013, the Company exercised the extension. In June 2014, the Company further extended the lease on a month-to-month basis, cancelable with not less than 60 days notice.

	In May, 2013, the Company entered into a two-year operating lease for additional office, laboratory and manufacturing space. The lease includes two one-year extension options. The first one-year extension option was exercised in 2014.

	In July, 2014, the Company entered into a lease amendment to expand facilities at the Company’s headquarters in Lexington, MA. The term of the lease amendment ends concurrently with the original lease entered into in August 2010 and will increase the monthly base rent by approximately $39,000 per month through December 2015. The Company retains the option to extend the lease for one additional term of two years.

	In November, 2014 the Company entered into an agreement to rent additional office space in Lexington, MA. The term of the agreement is two years, commencing December 2014. In connection with this agreement, the Company paid a security deposit totaling $50,000, which is recorded as a component of other assets in the consolidated balance sheets.

	In November, 2014, the Company entered into a lease for additional laboratory space in Lexington, MA. The Company is expected to occupy the space on April 1, 2015, once the build-out of the space is complete, and the lease term extends for six years. The rent expense, inclusive of the escalating rent payments, is recognized on a straight-line basis over the lease term. As an incentive to enter into the lease, the landlord will pay for approximately $1.4 million of the space build-out costs. In connection with this lease agreement, the Company paid a security deposit of $281,000, which is recorded as a component of other assets in the consolidated balance sheets.

	Future minimum non-cancelable lease payments under the Company’s operating leases are as follows (in thousands):

	Year ending December 31,
	2015	$	1,713
	2016	686
	2017	393
	2018	404
	2019	414
	Thereafter	532
		$	4,142

	Rent expense for the years ended December 31, 2014, 2013, and 2012 was $950,000, $628,000, and $558,000, respectively.

	In 2006, the Company entered into a license agreement with a third party, pursuant to which the third party granted the Company an exclusive, worldwide, sub-licenseable license under certain patent rights to make, use, import and commercialize products and processes for diagnostic, industrial and research and development purposes. The Company agreed to pay an annual license fee ranging from $5,000 to $25,000 for the royalty-bearing license to certain patents. For the years ended December 31, 2014 and 2013, the Company incurred $345,000 and $46,000, respectively, for regulatory milestones, license fees and reimbursed patent costs under the agreement. The Company also issued a total of 84,678 shares of common stock pursuant to the agreement in 2006 and 2007, which were recorded at fair value at the date of issuance. Regulatory milestones totaling $300,000 became due during the year ended December 31, 2014, as the Company received FDA marketing authorization and European CE Mark for T2Dx and T2Candida. The Company will be required to pay royalties on net sales of products and processes that are covered by patent rights licensed under the agreement at a percentage ranging in the low single digits, subject to reductions and offsets in certain circumstances, as well as a royalty on net sales of products that the Company sublicenses at a low double-digit percentage of specified gross revenue.

401k_Savings_Plan

401(k) Savings Plan	12 Months Ended
401(k) Savings Plan	Dec. 31, 2014
401(k) Savings Plan
401(k) Savings Plan	14. 401(k) Savings Plan

	In March, 2008, the Company established a retirement savings plan under Section 401(k) of the Internal Revenue Code (the “401(k) Plan”). The 401(k) Plan covers substantially all employees of the Company who meet minimum age and service requirements, and allows participants to defer a portion of their annual compensation on a pretax basis. Company contributions to the 401(k) Plan may be made at the discretion of the board of directors. No contributions were made in the years ended December 31, 2014 and 2013.

Quarterly_Financial_Data_unaud

Quarterly Financial Data (unaudited)	12 Months Ended
Quarterly Financial Data (unaudited)	Dec. 31, 2014
Quarterly Financial Data (unaudited)
Quarterly Financial Data (unaudited)	15. Quarterly Financial Data (unaudited)

		Year Ended December 31, 2014
		(In thousands, except per share data)
		First Quarter			Second Quarter			Third Quarter			Fourth Quarter
	Total revenue	$	—		$	—		$	—		$	119
	Loss from operations	$	(6,907	)	$	(7,149	)	$	(7,787	)	$	(8,838	)
	Net loss	$	(6,920	)	$	(7,303	)	$	(8,091	)	$	(9,076	)
	Net loss applicable to common shareholders	$	(8,826	)	$	(9,209	)	$	(8,849	)	$	(9,076	)
	Per share data:
	Net loss per common share—basic and diluted	$	(6.25	)	$	(6.35	)	$	(0.71	)	$	(0.45	)

		Year Ended December 31, 2013
		(In thousands, except per share data)
		First Quarter			Second Quarter			Third Quarter			Fourth Quarter
	Total revenue	$	—		$	120		$	91		$	55
	Loss from operations	$	(4,600	)	$	(4,910	)	$	(4,542	)	$	(5,639	)
	Net loss	$	(4,580	)	$	(5,014	)	$	(4,642	)	$	(6,374	)
	Net loss applicable to common shareholders	$	(5,756	)	$	(6,925	)	$	(6,553	)	$	(8,284	)
	Per share data:
	Net loss per common share—basic and diluted	$	(4.17	)	$	(4.95	)	$	(4.69	)	$	(5.89	)

Subsequent_Events

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2014
Subsequent Events
Subsequent Events	16. Subsequent Events

	On February 3, 2015, the Company entered into a Co-Development Partnership Agreement (“the Agreement”) with Canon U.S. Life Sciences, Inc. (“Canon US Life Sciences”) to develop a diagnostic test panel to rapidly detect Lyme disease. Under the terms of the Agreement, the Company received an upfront payment of $2.0 million from Canon US Life Sciences and will receive an additional $6.5 million of consideration upon achieving certain development and regulatory milestones for total aggregate payments of up to $8.5 million. The Company will retain exclusive worldwide commercialization rights of any products developed under the Agreement, including sales, marketing and distribution and Canon US Life Sciences will receive royalty payments on the sales of all products developed under the Agreement.

	Either party may terminate the Agreement upon the occurrence of a material breach by the other party (subject to cure period).

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Summary of Significant Accounting Policies
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation

	The Company’s financial statements have been prepared in conformity with generally accepted accounting principles in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). The Company’s consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary, T2 Biosystems Securities Corporation. All intercompany balances and transactions have been eliminated.

Use of Estimates	Use of Estimates

	The preparation of the Company’s financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The Company utilizes certain estimates in the determination of the fair value of its common stock and stock options, the fair value of liability-classified warrants, deferred tax valuation allowances, revenue recognition, to record expenses relating to research and development contracts and to classify the value of instrument raw material and work-in-process inventory between inventory and property and equipment. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results could differ from such estimates.

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

Segment Information	Segment Information

	Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company’s chief operating decision maker is the Chief Executive Officer. The Company views its operations and manages its business in one operating segment, which is the business of developing and, upon regulatory clearance, launching commercially its diagnostic products aimed at reducing mortality rates, improving patient outcomes and reducing the cost of healthcare by helping medical professionals make targeted treatment decisions earlier.

Off Balance Sheet Risk and Concentrations of Credit Risk	Off Balance Sheet Risk and Concentrations of Credit Risk

	The Company has no significant off-balance sheet risks, such as foreign exchange contracts, option contracts, or other foreign hedging arrangements. Cash and cash equivalents are financial instruments that potentially subject the Company to concentrations of credit risk. At December 31, 2014 and 2013, substantially all of the Company’s cash was deposited in accounts at one financial institution, with a significant amount invested in money market funds that are invested in short-term U.S. government agency securities. The Company maintains its cash deposits, which at times may exceed the federally insured limits, with a large financial institution and, accordingly, the Company believes such funds are subject to minimal credit risk.

Cash Equivalents	Cash Equivalents

	Cash equivalents include all highly liquid investments maturing within 90 days from the date of purchase. Cash equivalents consist of money market funds invested in short-term U.S. government agency securities as of December 31, 2014 and 2013.

Accounts Receivable	Accounts Receivable

	The Company’s accounts receivable consists primarily of amounts due from research and development arrangements with partners. At each reporting period, management reviews all outstanding balances to determine if the facts and circumstances of each customer relationship indicate the need for a reserve. The Company did not have an allowance for accounts at December 31, 2014 or 2013.

Inventories	Inventories

	Inventories are stated at the lower of cost or market. The Company determines the cost of its inventories, which includes amounts related to materials, direct labor, and manufacturing overhead, on a first-in, first-out basis. The Company performs an assessment of the recoverability of capitalized inventory during each reporting period, and writes down any excess and obsolete inventories to their realizable value in the period in which the impairment is first identified. Shipping and handling costs incurred for inventory purchases are capitalized and recorded upon sale in cost of product revenues in the consolidated statements of operations.

	The Company capitalizes inventories in preparation for sales of products when the related product candidates are considered to have a high likelihood of regulatory clearance, which for the T2Dx Instrument and T2Candida Panel was upon the achievement of regulatory clearance, and the related costs are expected to be recoverable through sales of the inventories. In addition, the Company capitalizes inventories related to the manufacture of instruments that have a high likelihood of regulatory clearance, which for the T2Dx Instrument and T2Candida Panel was upon the achievement of regulatory clearance, and will be retained as the Company’s assets, upon determination that the instrument has alternative future uses. In determining whether or not to capitalize such inventories, the Company evaluates, among other factors, information regarding the product candidate’s status of regulatory submissions and communications with regulatory authorities, the outlook for commercial sales and alternative future uses of the product candidate, including commercial sale. Costs associated with development products prior to satisfying the inventory capitalization criteria are charged to research and development expense as incurred.

	The Company classifies inventories related to instruments that are Company-owned, as a component of property and equipment. Raw material and work-in-process inventories that are expected to be used to produce Company-owned instruments, based on our business model and forecast, are also classified as property and equipment. Company-owned instruments are instruments that are manufactured and placed with customers in connection with rental agreements, or are used for internal purposes.

	The Company began capitalizing inventories upon receipt of market authorization from the FDA for its first two products. Inventory meeting the capitalization criteria as of December 31, 2014 totaled $115,000, comprised of $71,000 of raw materials and $44,000 of work in process.

Fair Value Measurements	Fair Value Measurements

	The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. ASC 820, Fair Value Measurements and Disclosures (“ASC 820”), establishes a hierarchy of inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the observable inputs be used when available.

	Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability, and are developed based on the best information available in the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The hierarchy defines three levels of valuation inputs:

	Level 1 — Quoted unadjusted prices for identical instruments in active markets.

	Level 2 — Quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all observable inputs and significant value drivers are observable in active markets.

	Level 3 — Model derived valuations in which one or more significant inputs or significant value drivers are unobservable, including assumptions developed by the Company.

	The fair value hierarchy prioritizes valuation inputs based on the observable nature of those inputs. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability (See Note 3).

	Financial instruments measured at fair value on a recurring basis include cash, money market funds, restricted cash and warrants to purchase redeemable securities (See Note 3).

	For certain financial instruments, including accounts payable and accrued expenses, the carrying amounts approximate their fair values as of December 31, 2014 and 2013 because of their short-term nature. At December 31, 2014, the carrying value of the Company’s debt approximated fair value, which was determined using Level 3 inputs, including a quoted rate (Note 6).

Property and Equipment	Property and Equipment

	Property and equipment are recorded at cost and depreciated over their estimated useful lives using the straight-line method. Property and equipment includes raw materials, work-in-process and finished instruments that are Company-owned or expected to remain Company-owned when placed in service. Company-owned instruments are instruments that are manufactured and placed with customers in connection with rental agreements, or are used for internal purposes. Repairs and maintenance costs are expensed as incurred, whereas major improvements are capitalized as additions to property and equipment.

Revenue Recognition	Revenue Recognition

	The Company generates revenue primarily from research and development agreements with government agencies and other third parties. Revenues earned from activities performed pursuant to development agreements is reported as revenue in the statements of operations and comprehensive loss, using the proportional performance method as the work is completed, and the related costs are expensed as incurred as research and development expense.

	The timing of cash received from the Company’s research and development agreements generally differs from when revenue is recognized. The Company recognizes revenue in accordance with FASB ASC Topic 605, Revenue Recognition (“ASC 605”). Accordingly, the Company recognizes revenue when all of the following criteria have been met:

		i.	Persuasive evidence of an arrangement exists

		ii.	Delivery has occurred or services have been rendered

		iii.	The seller’s price to the buyer is fixed or determinable

		iv.	Collectability is reasonably assured

	Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue. Criterion (i) is satisfied when the Company has a written agreement or contract in place. Criterion (ii) is satisfied when the Company performs the services. Determination of criteria (iii) and (iv) are based on management’s judgments regarding whether the fee is fixed or determinable and the collectability of the fee is reasonably assured.

	For multiple-element arrangements, the Company identifies the deliverables included within the agreement and evaluates which deliverables represent separate units of accounting. The Company accounts for those components as separate elements when the following criteria are met: (1) the delivered items have value to the customer on a stand-alone basis; and, (2) if there is a general right of return relative to the delivered items, delivery or performance of the undelivered items is considered probable and within its control. The consideration received is allocated among the separate units of accounting based on management’s best estimate of selling price, and the applicable revenue recognition criteria are applied to each of the separate units. The determination that multiple elements in an arrangement meet the criteria for separate units of accounting requires the Company’s management to exercise its judgment.

Research and Development Costs	Research and Development Costs

	Costs incurred in the research and development of the Company’s product candidates are expensed as incurred. Research and development expenses consist of costs incurred in performing research and development activities and include salaries and benefits, stock compensation, research-related facility and overhead costs, laboratory supplies, equipment and contract services.

Impairment of Long Lived Assets	Impairment of Long Lived Assets

	The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. During this review, the Company reevaluates the significant assumptions used in determining the original cost and estimated lives of long-lived assets. Although the assumptions may vary from asset to asset, they generally include operating results, changes in the use of the asset, cash flows and other indicators of value. Management then determines whether the remaining useful life continues to be appropriate or whether there has been an impairment of long-lived assets based primarily upon whether expected future undiscounted cash flows are sufficient to support the assets’ recovery. If impairment exists, the Company would adjust the carrying value of the asset to fair value, generally determined by a discounted cash flow analysis. No impairment charges have been recorded in any of the periods presented.

Comprehensive Loss	Comprehensive Loss

	Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Comprehensive loss consists of net loss and other comprehensive loss, which includes certain changes in equity that are excluded from net loss. The Company’s comprehensive loss equals reported net loss for all periods presented.

Stock Based Compensation	Stock Based Compensation

	The Company has a stock-based compensation plan which is more fully described in Note 9. The Company records stock-based compensation for options granted to employees and to members of the board of directors for their services on the board of directors, based on the grant date fair value of awards issued, and the expense is recorded on a straight-line basis over the applicable service period, which is generally four years. The Company accounts for non-employee stock-based compensation arrangements based upon the fair value of the consideration received or the equity instruments issued, whichever is more reliably measurable. The measurement date for non-employee awards is generally the date that the performance of services required for the non-employee award is complete. Stock-based compensation costs for non-employee awards is recognized as services are provided, which is generally the vesting period, on a straight-line basis.

	The Company expenses restricted stock awards based on the fair value of the award on the date of issuance, on a straight-line basis over the associated service period of the award.

	The Company uses the Black-Scholes-Merton option pricing model to determine the fair value of stock options. The use of the Black-Scholes-Merton option-pricing model requires management to make assumptions with respect to the expected term of the option, the expected volatility of the common stock consistent with the expected life of the option, risk-free interest rates and expected dividend yields of the common stock. The expected term was determined according to the simplified method, which is the average of the vesting tranche dates and the contractual term. Due to the lack of a public market for the trading of the Company’s common stock and a lack of company-specific historical and implied volatility data, the Company based its estimate of expected volatility on the historical volatility of a group of similar companies that are publicly traded. For these analyses, companies with comparable characteristics were selected, including enterprise value and position within the industry, and with historical share price information sufficient to meet the expected life of the stock-based awards. The Company computed the historical volatility data using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of its stock-based awards. The risk-free interest rate is determined by reference to U.S. Treasury zero-coupon issues with remaining maturities similar to the expected term of the options. The Company has not paid, and does not anticipate paying, cash dividends on shares of common stock; therefore, the expected dividend yield is assumed to be zero. The Company is required to estimate forfeitures at the time of grant and revise those estimates in subsequent periods if actual forfeitures differ from those estimates.

Warrants to Purchase Redeemable Securities	Warrants to Purchase Redeemable Securities

	The Company has issued warrants to purchase shares of the Company’s series A-2 redeemable convertible preferred stock, series B redeemable convertible preferred stock, series C redeemable convertible preferred stock, and series D redeemable convertible preferred stock.

	The Company accounts for warrant instruments that either conditionally or unconditionally obligate the issuer to transfer assets as liabilities regardless of the timing of the redemption feature or price, even though the underlying shares may be classified as permanent or temporary equity. Consequently, the warrants to purchase shares of series A-2 preferred stock, series B preferred stock, series C preferred stock, and series D preferred stock were accounted for as liabilities and adjusted to fair value at the end of each reporting period. The liability for warrants to purchase redeemable securities is remeasured at each balance sheet date with changes to fair value being recognized as a component of other income (expense) in the statement of operations and comprehensive loss. In connection with the closing of the Company’s IPO, all of the Company’s outstanding warrants to purchase redeemable securities were net settled into shares of common stock (Note 8).

Income Taxes	Income Taxes

	The Company provides for income taxes using the liability method. The Company provides deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the Company’s financial statement carrying amounts and the tax basis of assets and liabilities using enacted tax rates expected to be in effect in the years in which the differences are expected to reverse. A valuation allowance is provided to reduce the deferred tax assets to the amount that will more likely than not be realized.

	The Company applies ASC 740 Income Taxes (“ASC 740”) in accounting for uncertainty in income taxes. The Company does not have any material uncertain tax positions for which reserves would be required. The Company will recognize interest and penalties related to uncertain tax positions, if any, in income tax expense.

Guarantees	Guarantees

	As permitted under Delaware law, the Company indemnifies its officers and directors for certain events or occurrences while the officer or director is, or was, serving at the Company’s request in such capacity. The term of the indemnification is for the officer’s or director’s lifetime. The maximum potential amount of future payments the Company could be required to make is unlimited; however, the Company has directors’ and officers’ insurance coverage that limits its exposure and enables it to recover a portion of any future amounts paid.

	The Company leases office, laboratory and manufacturing space under noncancelable operating leases. The Company has standard indemnification arrangements under the leases that require it to indemnify the landlord against all costs, expenses, fines, suits, claims, demands, liabilities, and actions directly resulting from any breach, violation or nonperformance of any covenant or condition of the Company’s leases.

	As of December 31, 2014 and 2013, the Company had not experienced any material losses related to these indemnification obligations, and no material claims with respect thereto were outstanding. The Company does not expect significant claims related to these indemnification obligations and, consequently, concluded that the fair value of these obligations is negligible, and no related reserves were established.

Net Loss Per Share	Net Loss Per Share

	Basic net loss per share is calculated by dividing net loss applicable to common stockholders by the weighted-average number of shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by adjusting the weighted-average number of shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock method. For purposes of the diluted net loss per share calculation, redeemable convertible preferred stock and warrants to purchase redeemable convertible preferred stock, which were outstanding prior to the Company’s IPO, and stock options and unvested restricted stock are considered to be common stock equivalents, but have been excluded from the calculation of diluted net loss per share, as their effect, including the related impact to the numerator of the fair value adjustment of the warrants and the impact to the denominator of the warrant shares, would be anti-dilutive for all periods presented. Therefore, basic and diluted net loss per share applicable to common stockholders were the same for all periods presented.

Reverse Stock Split	Reverse Stock Split

	The Company effected a 1-for-1.7 reverse stock split of its issued and outstanding common stock on July 25, 2014. All share and per share amounts related to issued and outstanding common stock, outstanding options and warrants exercisable for common stock included in these financial statements and notes to the financial statements and have been retroactively adjusted for all periods presented to reflect the reverse stock split, including reclassifying an amount equal to the reduction in par value of common stock to additional paid-in capital. The shares authorized, issued and outstanding of the Company’s redeemable convertible preferred stock are not impacted by the reverse stock split and have not been adjusted.

Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements

	From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption.

	In June 2014, the FASB issued amended guidance, ASU No 2014-09, Revenue from Contracts with Customers, which is applicable to revenue recognition that will be effective for the Company for the year ended December 31, 2017. The new guidance must be adopted using either a full retrospective approach for all periods presented or a modified retrospective approach. Early adoption is not permitted. The new guidance applies a more principles-based approach to revenue recognition. The Company is evaluating the new guidance and the expected effect on the Company’s consolidated financial statements.

	In June 2014, the FASB issued ASU 2014-10, Development Stage Entities (Topic 915) (“ASU 2014-10”), which removes the definition of a development stage entity from the ASC, thereby removing the financial reporting distinction between development stage entities and other reporting entities. Accordingly, ASU 2014-10 eliminates the requirements for development stage entities to (1) present inception-to-date information in the statements of operations, cash flows and shareholder equity, (2) label financial statements as those of a development stage entity, (3) disclose a description of the development stage activities in which the entity is engaged, and (4) disclose in the first year in which the entity is no longer a development stage entity that in prior years it had been in the development stage. ASU 2014-10 is effective for public business entities for annual periods beginning after December 15, 2014, and interim reporting periods beginning after December 15, 2015, with early adoption permitted. The Company adopted the provisions of ASU 2014-10 in the June 30, 2014 Quarterly Report on Form 10-Q.

	In 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements — Going Concern (“ASU 2014-15”), which is effective for annual periods ending after December 15, 2016. Early adoption is permitted. ASU 2014-15 provides new guidance on (1) management’s responsibility in evaluating whether or not there is substantial doubt about a company’s ability to continue as a going concern within one year from the date the financial statements are issued each reporting period and (2) related financial statement disclosures. The Company has not adopted the guidance prescribed by ASU 2014-15 and does not expect the new guidance to have a significant effect on its consolidated financial statements.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Measurements
Schedule of financial assets and liabilities at fair value on a recurring basis	The following tables set forth the Company’s financial assets and liabilities carried at fair value categorized using the lowest level of input applicable to each financial instrument as of December 31, 2014 and December 31, 2013 (in thousands):

		Balance at			Quoted Prices		Significant		Significant
		December 31,			in Active		Other		Unobservable
		2014			Markets for		Observable		Inputs
					Identical		Inputs		(Level 3)
					Assets		(Level 2)
					(Level 1)
	Assets:
	Cash	$	10,348		$	10,348	$	—	$	—
	Money market funds	63,501			63,501		—		—
	Restricted cash	340			340		—		—
		$	74,189		$	74,189	$	—	$	—

		Balance at			Quoted Prices		Significant		Significant
		December 31,			in Active		Other		Unobservable
		2013			Markets for		Observable		Inputs
					Identical		Inputs		(Level 3)
					Assets		(Level 2)
					(Level 1)
	Assets:
	Cash	$	2,631		$	2,631	$	—	$	—
	Money market funds	27,567			27,567		—		—
	Restricted cash	340			340		—		—
		$	30,538		$	30,538	$	—	$	—
	Liabilities:
	Warrants to purchase redeemable securities	$	1,225		$	—	$	—	$	1,225
		$	1,225		$	—	$	—	$	1,225


Summary of changes in the fair value of the Company's preferred stock warrant liability	The following table sets forth a summary of changes in the fair value of the Company’s preferred stock warrant liability, which represents a recurring measurement that is classified within Level 3 of the fair value hierarchy, wherein fair value is estimated using significant unobservable inputs (in thousands):

		2014
	Beginning balance	$	1,225
	Change in fair value, recorded as a component of other income (expense)	1
	Net exercise of warrants into common stock	(1,226		)
	Ending balance	$	—

Supplemental_Balance_Sheet_Inf1

Supplemental Balance Sheet Information (Tables)	12 Months Ended
Supplemental Balance Sheet Information (Tables)	Dec. 31, 2014
Supplemental Balance Sheet Information
Schedule of property and equipment	Property and equipment consists of the following (in thousands):

		Estimated Useful		December 31,
		Life (Years)		2014			2013
	Office and computer equipment	3		$	383		$	302
	Software	3		480			186
	Laboratory equipment	5		3,312			2,770
	Furniture	5 - 7		187			179
	Manufacturing tooling and molds	0.5		26			—
	Leasehold improvements	Lesser of useful life or lease term		764			332
	Construction in progress			387			—
	Construction in progress — instruments	n/a		563			—
				6,102			3,769
	Less accumulated depreciation and amortization			(3,342		)	(2,651		)
	Property and equipment, net			$	2,760		$	1,118


Components of accrued expenses	Accrued expenses consist of the following (in thousands):

		December 31,
		2014			2013
	Accrued payroll and compensation	$	1,846		$	496
	Accrued research and development expenses	733			422
	Accrued professional services	374			101
	Other accrued expenses	709			300
	Total accrued expenses	$	3,662		$	1,319

Debt_Tables

Debt (Tables)	12 Months Ended
	Dec. 31, 2014
Debt
Summary of future principal payments on the notes payable	Future principal payments on the notes payable as of December 31, 2014 are as follows (in thousands):

	Year ended December 31,
	2015	$	308
	2016	3,106
	2017	7,018
	2018	6,793
	2019	3,889
	Total debt payments	21,114
	Less current portion, including debt discount	(295		)
	Less debt discount	(159		)
	Notes payable, net of current portion	$	20,660

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	12 Months Ended
Stock-Based Compensation (Tables)	Dec. 31, 2014
Stock Based Compensation
Summary of stock option activity	The following is a summary of option activity under the Plan (in thousands, except share and per share amounts):

		Number of		Weighted-Average		Weighted-Average	Aggregate Intrinsic
		Shares		Exercise Price Per		Remaining	Value
				Share		Contractual Term
						(In years)
	Outstanding at December 31, 2013	2,265,973		2.53		8.23	11,510
	Granted	793,842		12.64
	Exercised	(64,661	)	2.37			1,091
	Cancelled	(84,008	)	2.44
	Outstanding at December 31, 2014	2,911,146		5.3		7.87	40,586
	Exercisable at December 31, 2014	1,442,227		2.42		6.61	24,276
	Vested or expected to vest at December 31, 2014	2,576,282		5.04		7.74	36,587


Schedule of estimated assumptions used to calculate weighted-average fair value of options granted
		Year Ended
		December 31,
		2014		2013		2012
	Weighted-average risk-free interest rate	1.91%		1.68%		1.35%
	Expected dividend yield	0.00%		0.00%		0.00%
	Expected volatility	61%		63%		64%
	Expected terms	5.75 – 6.09 years		5.77 - 6.08 years		6.25 - 10 years


Summary of stock-based compensation expense for stock options granted that was recorded in the Company's results of operations	The following table summarizes the stock-based compensation expense for stock options granted to employees and nonemployees, as well as stock-compensation expense for the 2014 ESPP that was recorded in the Company’s results of operations for the years presented (in thousands):

		Year Ended
		December 31,
		2014			2013		2012
	Research and development	$	501		$	169	$	160
	Selling, general and administrative	1,152			409		243
	Total stock-based compensation expense	$	1,653		$	578	$	403

Net_Loss_Per_Share_Tables

Net Loss Per Share (Tables)	12 Months Ended
Net Loss Per Share (Tables)	Dec. 31, 2014
Net Loss Per Share
Schedule of basic and diluted net loss per share applicable to common stockholders	The following table presents the calculation of basic and diluted net loss per share applicable to common stockholders (in thousands, except share and per share data):

		Year Ended
		December 31,
		2014			2013			2012
	Numerator:
	Net loss	$	(31,390	)	$	(20,610	)	$	(14,455	)
	Accretion of redeemable convertible preferred stock to redemption value	(4,570		)	(6,908		)	(4,412		)
	Net loss applicable to common stockholders	$	(35,960	)	$	(27,518	)	$	(18,867	)
	Denominator:
	Weighted-average number of common shares outstanding — basic and diluted	8,674,931			1,395,562			1,361,616
	Net loss per share applicable to common stockholders — basic and diluted	$	(4.15	)	$	(19.72	)	$	(13.86	)


Schedule of shares excluded from the calculation where the inclusion would be anti-dilutive
		Year Ended
		December 31,
		2014		2013		2012
	Redeemable convertible preferred stock	—		12,516,298		8,439,267
	Options to purchase common shares	2,911,146		2,265,973		1,399,064
	Warrants to purchase redeemable convertible preferred stock	—		147,484		147,484
	Total	2,911,146		14,929,755		9,985,815

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2014
Income Taxes
Schedule of reconciliation of the U.S. federal statutory rate to the Company's effective tax rate
		Year Ended
		December 31,
		2014		2013		2012
	Tax at statutory rates	35	%	35	%	34	%
	State income taxes	5.1		5.2		5.3
	Change in tax rate	0		0		(0.2	)
	Permanent differences	(0.8	)	(0.7	)	(0.5	)
	Research and development credits	1.9		2.3		1.6
	Change in valuation allowance	(41.2	)	(41.8	)	(40.2	)
	Effective tax rate	0	%	0	%	0	%


Schedule of Deferred Tax Assets	The significant components of the Company’s deferred tax asset consist of the following at December 31, 2014 and 2013 (in thousands):

		December 31,
		2014			2013
	Deferred tax assets:
	Net operating loss carryforwards	$	33,690		$	22,280
	Tax credits	2,795			2,189
	Other temporary differences	1,159			180
	Start-up expenditures	4,948			5,318
	Stock option expenses	588			179
	Total deferred tax assets	43,180			30,146
	Deferred tax asset valuation allowance	(42,867		)	(30,146		)
	Net deferred tax assets	313			—

	Deferred tax liabilities:
	Prepaid expenses	(313		)	—
	Net deferred taxes	$	—		$	—

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies.
Schedule of future minimum lease payments under the Company's operating leases	Future minimum non-cancelable lease payments under the Company’s operating leases are as follows (in thousands):

	Year ending December 31,
	2015	$	1,713
	2016	686
	2017	393
	2018	404
	2019	414
	Thereafter	532
		$	4,142

Quarterly_Financial_Data_unaud1

Quarterly Financial Data (unaudited) (Tables)	12 Months Ended
Quarterly Financial Data (unaudited) (Tables)	Dec. 31, 2014
Quarterly Financial Data (unaudited)
Schedule of quarterly financial information
		Year Ended December 31, 2014
		(In thousands, except per share data)
		First Quarter			Second Quarter			Third Quarter			Fourth Quarter
	Total revenue	$	—		$	—		$	—		$	119
	Loss from operations	$	(6,907	)	$	(7,149	)	$	(7,787	)	$	(8,838	)
	Net loss	$	(6,920	)	$	(7,303	)	$	(8,091	)	$	(9,076	)
	Net loss applicable to common shareholders	$	(8,826	)	$	(9,209	)	$	(8,849	)	$	(9,076	)
	Per share data:
	Net loss per common share—basic and diluted	$	(6.25	)	$	(6.35	)	$	(0.71	)	$	(0.45	)

		Year Ended December 31, 2013
		(In thousands, except per share data)
		First Quarter			Second Quarter			Third Quarter			Fourth Quarter
	Total revenue	$	—		$	120		$	91		$	55
	Loss from operations	$	(4,600	)	$	(4,910	)	$	(4,542	)	$	(5,639	)
	Net loss	$	(4,580	)	$	(5,014	)	$	(4,642	)	$	(6,374	)
	Net loss applicable to common shareholders	$	(5,756	)	$	(6,925	)	$	(6,553	)	$	(8,284	)
	Per share data:
	Net loss per common share—basic and diluted	$	(4.17	)	$	(4.95	)	$	(4.69	)	$	(5.89	)

Nature_of_Business_Details

Nature of Business (Details) (USD $)	12 Months Ended	0 Months Ended
Nature of Business (Details) (USD $)	Dec. 31, 2014	Aug. 12, 2014	Dec. 31, 2013	Jul. 11, 2014
Accumulated deficit	($103,595,000)		($89,544,000)
Proceeds from issuance of common stock in initial public offering, net of offering costs	58,089,000
Note Agreement 1
Maximum borrowings available				30,000,000
IPO
Shares issued upon completion of IPO		5,980,000
Proceeds from issuance of common stock in initial public offering, net of offering costs		58,100,000
Period over which cash resources will be sufficient to allow Company to fund current operating plan		12 months
IPO \| Note Agreement 1
Maximum borrowings available				$10,000,000

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Details) (USD $)	0 Months Ended	12 Months Ended
	Jul. 25, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
		segment	item
		item
Segment Information
Number of Operating Segments		1
Off Balance Sheet Risk and Concentrations of Credit Risk
Number of financial institutions in which cash was deposited		1	1
Impairment of Long Lived Assets
Impairment charges		$0	$0	$0
Stock Based Compensation
Vesting period		4 years
Expected dividend yield		0.00%
Reverse stock split
Stock split conversion ratio	0.588
Inventory
Total inventory		115,000
Raw materials		71,000
Work in process		$44,000

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair value measurements
Transfers of assets from level 1 to 2	$0	$0
Transfers of assets from level 2 to 1	0	0
Transfer of liabilities from level 1 to 2	0	0
Transfer of liabilities from level 2 to 1	0	0
Transfer of liabilities to or from level 3	0	0
Recurring \| Fair value
Assets:
Restricted cash	340	340
Total assets	74,189	30,538
Liabilities:
Warrants to purchase redeemable securities		1,225
Total liabilities		1,225
Recurring \| Fair value \| Cash
Assets:
Cash and cash equivalents	10,348	2,631
Recurring \| Fair value \| Money market funds
Assets:
Cash and cash equivalents	63,501	27,567
Recurring \| Level 1 \| Fair value
Assets:
Restricted cash	340	340
Total assets	74,189	30,538
Recurring \| Level 1 \| Fair value \| Cash
Assets:
Cash and cash equivalents	10,348	2,631
Recurring \| Level 1 \| Fair value \| Money market funds
Assets:
Cash and cash equivalents	63,501	27,567
Recurring \| Level 3 \| Fair value
Liabilities:
Warrants to purchase redeemable securities		1,225
Total liabilities		$1,225

Fair_Value_Measurements_Detail1

Fair Value Measurements (Details 2) (Warrants to purchase redeemable convertible preferred stock, USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014
Warrants to purchase redeemable convertible preferred stock
Changes in fair value of preferred stock warrant liability
Beginning balance	$1,225
Change in fair value, recorded as a component of other income (expense)	1
Net exercise of warrants into common stock	($1,226)

Restricted_Cash_Details

Restricted Cash (Details) (Certificates of deposit, USD $)	0 Months Ended
Restricted Cash (Details) (Certificates of deposit, USD $)	Jan. 14, 2013	Dec. 31, 2014	Dec. 31, 2013	Jan. 14, 2013
Certificates of deposit
Restricted cash
Security deposit for operating lease	$320,000	$340,000	$340,000	$320,000
Decrease in security deposit	($80,000)

Supplemental_Balance_Sheet_Inf2

Supplemental Balance Sheet Information (Details) (USD $)	12 Months Ended
Supplemental Balance Sheet Information (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$6,102,000	$3,769,000
Accumulated depreciation and amortization	-3,342,000	-2,651,000
Property and equipment, net	2,760,000	1,118,000
Depreciation and amortization	691,000	584,000	571,000
Accrued expenses
Accrued payroll and compensation	1,846,000	496,000
Accrued research and development expenses	733,000	422,000
Accrued professional services	374,000	101,000
Other accrued expenses	709,000	300,000
Total accrued expenses	3,662,000	1,319,000
Office and computer equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Property and equipment, gross	383,000	302,000
Software
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Property and equipment, gross	480,000	186,000
Laboratory equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Property and equipment, gross	3,312,000	2,770,000
Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, gross	187,000	179,000
Furniture \| Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Furniture \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	7 years
Manufacturing tooling and molds
Property, Plant and Equipment [Line Items]
Estimated useful lives	6 months
Property and equipment, gross	26,000
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	764,000	332,000
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	387,000
Construction in progress - instruments
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$563,000

Debt_Details

Debt (Details) (USD $)	12 Months Ended			0 Months Ended	20 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jul. 11, 2014	Dec. 31, 2012	Jun. 25, 2012	9-May-11
				tranche		installment
				Lender
Debt Instrument [Line Items]
Proceeds received on borrowing, net of deferred financing costs	$19,714,000		$4,924,000
Repayment of notes payable	4,037,000	848,000	374,000
Interest Expense	741,000	410,000	156,000
Non-cash interest	112,000	44,000	46,000
Note Agreement 1
Debt Instrument [Line Items]
Number of lenders				2
Maximum borrowings available				30,000,000
Number of tranches				2
Interest rate including both the variable rate and the basis spread (as a percent)	7.22%
Final fee as a percentage of original principal amount of amounts borrowed				4.75%
Minimum amount of denomination for prepayment of borrowings				1,000,000
Effective interest rate including final fee interest and non-cash interest (as a percent)	9.30%
Note Agreement 1 \| Prior to first anniversary of borrowing date
Debt Instrument [Line Items]
Prepayment premium (as a percent)				1.50%
Note Agreement 1 \| Prior to second anniversary and after first anniversary of borrowing date
Debt Instrument [Line Items]
Prepayment premium (as a percent)				1.00%
Note Agreement 1 \| Prior To Maturity Date And After Second Anniversary Of Borrowing Date [Member]
Debt Instrument [Line Items]
Prepayment premium (as a percent)				0.50%
Note Agreement 1 \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Variable Interest Rate				one-month LIBOR
Basis spread (as a percent)				7.05%
Note Agreement 1 \| Tranche A [Member]
Debt Instrument [Line Items]
Maximum borrowings available				20,000,000
Minimum amount of draw upon closing				10,000,000
Minimum amount of draw after closing				5,000,000
Proceeds received on borrowing, net of deferred financing costs	19,700,000
Note Agreement 1 \| Tranche B [Member]
Debt Instrument [Line Items]
Maximum borrowings available				10,000,000
Minimum net proceeds to be received from stock offering, equity raise, or strategic partner arrangement to allow for borrowing				30,000,000
Remaining borrowing capacity	10,000,000
Note Agreement 2
Debt Instrument [Line Items]
Maximum borrowings available						4,500,000
Stated interest rate (as a percent)						6.25%
Number of monthly principal installments						36
Proceeds received on borrowings			4,500,000
Repayment of notes payable				2,900,000
Note Agreement 2 \| Prior to first anniversary of borrowing date
Debt Instrument [Line Items]
Prepayment premium (as a percent)						2.00%
Note Agreement 2 \| Prior to second anniversary and after first anniversary of borrowing date
Debt Instrument [Line Items]
Prepayment premium (as a percent)						1.00%
Note Agreement 3
Debt Instrument [Line Items]
Maximum borrowings available							1,700,000
Stated interest rate (as a percent)							6.50%
Proceeds received on borrowings			451,000		1,400,000
Line Of Credit Facility Minimum Cash Balance Required							$300,000

Debt_Details_2

Debt (Details 2) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Future principal payments on the notes payable
2015	$308
2016	3,106
2017	7,018
2018	6,793
2019	3,889
Total debt payments	21,114
Less current portion, including debt discount	-295	-1,759
Less debt discount	-159
Notes payable, net of current portion	$20,660	$3,299

Redeemable_Convertible_Preferr1

Redeemable Convertible Preferred Stock (Details) (USD $)	0 Months Ended	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Aug. 12, 2014	Dec. 31, 2014
Conversion of convertible preferred stock into common stock	$117,400
Conversion of redeemable convertible preferred stock into common stock		117,383
Common Stock
Conversion of redeemable convertible preferred stock into common stock (in shares)	12,516,298	12,516,298
Conversion of redeemable convertible preferred stock into common stock		13
Accumulated Deficit
Conversion of redeemable convertible preferred stock into common stock	21,000	21,029
Additional Paid-in Capital
Conversion of redeemable convertible preferred stock into common stock	$96,300	$96,341

Stockholders_Equity_Deficit_De

Stockholders' Equity (Deficit) (Details) (USD $)	12 Months Ended	0 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Aug. 12, 2014	Dec. 31, 2013
	item	Aug. 12, 2014	Dec. 31, 2013
IPO
Common Stock Number Of Votes Per Share	1
Common stock were reserved for issuance	3,678,581
Proceeds from issuance of common stock in initial public offering, net of offering costs	$58,089
Redeemable convertible preferred stock			112,813
Common stock, shares authorized	200,000,000		28,254,907
Preferred stock, shares authorized	10,000,000		10,000,000
Over Allotment Option
IPO
Shares issued upon completion of IPO		780,000
IPO
IPO
Shares issued upon completion of IPO		5,980,000
Sale price of stock (in dollars per share)		11
Proceeds from issuance of common stock in initial public offering, net of offering costs		58,100
Conversion of redeemable convertible preferred stock into common stock (in shares)		12,516,298
Issuance of common stock upon net settlement of warrants to purchase redeemable convertible preferred stock (in shares)		68,700
Common stock, shares authorized		200,000,000
Preferred stock, shares authorized		10,000,000

Stock_Based_Compensation_Detai

Stock Based Compensation (Details) (USD $)	12 Months Ended			0 Months Ended
Stock Based Compensation (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Aug. 12, 2014
Share-Based Compensation
Vesting period	4 years
Shares available for future issuance under stock incentive plan	3,678,581
Fair value assumptions
Stock-based compensation expense	$1,653,000	$578,000	$403,000
Employee Stock Purchase Plan
Share-Based Compensation
Shares available for grant	220,588
Fair value assumptions
Percentage of full share price paid in purchase of common stock	85
Maximum amount of annual employee common stock purchases	25,000
Stock-based compensation expense	103,000
Percentage of shares outstanding				1.00%
2006 and 2014 Stock Option Plans \| Stock Options
Share-Based Compensation
Aggregate fair value of options granted	6,000,000	2,000,000	702,000
Number of Shares
Outstanding, beginning of the period (in shares)	2,265,973
Granted (in shares)	793,842
Exercised (in shares)	-64,661
Cancelled (in shares)	-84,008
Outstanding, end of the period (in shares)	2,911,146	2,265,973
Exercisable (in shares)	1,442,227
Vested or expected to vest (in shares)	2,576,282
Weighted Average Exercise Price Per Share
Outstanding, beginning of the period (in dollars per share)	$2.53
Granted (in dollars per share)	$12.64
Exercised (in dollars per share)	$2.37
Cancelled (in dollars per share	$2.44
Outstanding, end of the period (in dollars per share)	$5.30	$2.53
Exercisable (in dollars per share)	$2.42
Vested or expected to vest (in dollars per share)	$5.04
Weighted-Average Remaining Contractual Term (in years)
Outstanding, beginning of the period (in years)	7 years 10 months 13 days	8 years 2 months 23 days
Outstanding, end of the period (in years)	7 years 10 months 13 days	8 years 2 months 23 days
Exercisable (in years)	6 years 7 months 10 days
Vested or expected to vest (in years)	7 years 8 months 27 days
Aggregate Intrinsic Value
Outstanding, beginning of the period	11,510,000
Exercised (in dollars)	1,091,000
Outstanding, end of the period	40,586,000	11,510,000
Exercisable	24,276,000
Vested or expected to vest	36,587,000
Fair value assumptions
Weighted average fair value of options granted (in dollars per share)	$7.59	$1.85	$1.45
Weighted-average risk-free interest rate	1.91%	1.68%	1.35%
Expected dividend yield	0.00%	0.00%	0.00%
Expected volatility	61.00%	63.00%	64.00%
Fair value of stock options vested	$1,160,000	$476,000	$302,000
2006 and 2014 Stock Option Plans \| Minimum \| Stock Options
Fair value assumptions
Expected terms	5 years 9 months	5 years 9 months 7 days	6 years 3 months
2006 and 2014 Stock Option Plans \| Maximum \| Stock Options
Fair value assumptions
Expected terms	6 years 1 month 2 days	6 years 29 days	10 years
2006 Stock Option Plan \| Maximum \| Stock Options
Share-Based Compensation
Expiration Period	10 years
Vesting period	4 years
2014 Stock Option Plan \| Stock Options
Share-Based Compensation
Shares available for future issuance under stock incentive plan	823,529
Percentage of common shares outstanding	4.00%
Shares available for grant	546,847
2014 Stock Option Plan \| Maximum \| Stock Options
Share-Based Compensation
Expiration Period	10 years
Vesting period	4 years

Stock_Based_Compensation_Detai1

Stock Based Compensation (Details 2) (USD $)	12 Months Ended
Stock Based Compensation (Details 2) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock-based compensation expense
Stock-based compensation expense	$1,653,000	$578,000	$403,000
Total unrecognized compensation costs related to non-vested stock options	7,200,000
Remaining weighted-average period that unrecognized compensation costs are expected to be recognized	3 years 2 months 1 day
Research and development
Stock-based compensation expense
Stock-based compensation expense	501,000	169,000	160,000
Selling, general and administrative
Stock-based compensation expense
Stock-based compensation expense	$1,152,000	$409,000	$243,000

Warrants_Details

Warrants (Details) (IPO)	0 Months Ended
Warrants (Details) (IPO)	Aug. 12, 2014	Aug. 12, 2014
IPO
Class of Warrant or Right [Line Items]
Number of warrants outstanding	250,727	250,727
Issuance of common stock upon net settlement of warrants to purchase redeemable convertible preferred stock (in shares)	68,700

Net_Loss_Per_Share_Details

Net Loss Per Share (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net Loss Per Share
Net loss	($9,076)	($8,091)	($7,303)	($6,920)	($6,374)	($4,642)	($5,014)	($4,580)	($31,390)	($20,610)	($14,455)
Accretion of redeemable convertible preferred stock to redemption value									-4,570	-6,908	-4,412
Net loss applicable to common stockholders	($9,076)	($8,849)	($9,209)	($8,826)	($8,284)	($6,553)	($6,925)	($5,756)	($35,960)	($27,518)	($18,867)
Denominator:
Weighted average number of common shares outstanding - basic and diluted									8,674,931	1,395,562	1,361,616
Net loss per share applicable to common stockholders - basic and diluted	($0.45)	($0.71)	($6.35)	($6.25)	($5.89)	($4.69)	($4.95)	($4.17)	($4.15)	($19.72)	($13.86)
Anti-dilutive securities
Anti-dilutive securities excluded from the computation of diluted net loss per share (in shares)									2,911,146	14,929,755	9,985,815
Redeemable Convertible Preferred Stock [Member]
Anti-dilutive securities
Anti-dilutive securities excluded from the computation of diluted net loss per share (in shares)										12,516,298	8,439,267
Stock Options
Anti-dilutive securities
Anti-dilutive securities excluded from the computation of diluted net loss per share (in shares)									2,911,146	2,265,973	1,399,064
Warrants to purchase redeemable convertible preferred stock
Anti-dilutive securities
Anti-dilutive securities excluded from the computation of diluted net loss per share (in shares)										147,484	147,484

Income_Taxes_Details

Income Taxes (Details) (USD $)	12 Months Ended
Income Taxes (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effective Income Tax Rate Reconciliation, Percent.
Tax at statutory rates	35.00%	35.00%	34.00%
State income taxes	5.10%	5.20%	5.30%
Change in tax rate	0.00%	0.00%	-0.20%
Permanent differences	-0.80%	-0.70%	-0.50%
Research and development credits	1.90%	2.30%	1.60%
Change in valuation allowance	-41.20%	-41.80%	-40.20%
Effective tax rate	0.00%	0.00%	0.00%
Deferred tax assets:
Net operating loss carryforwards	$33,690,000	$22,280,000
Tax credits	2,795,000	2,189,000
Other temporary differences	1,159,000	180,000
Startup expenditures	4,948,000	5,318,000
Stock option expenses	588,000	179,000
Total deferred tax assets	43,180,000	30,146,000
Deferred tax asset valuation allowance	-42,867,000	-30,146,000
Net deferred tax assets	313,000
Deferred tax liabilities:
Prepaid expenses	-313,000
Increase in valuation allowance	12,700,000	9,100,000	6,100,000
Unrecognized tax benefits	0
Accrued interest or penalties related to uncertain tax positions	0	0
Federal
Deferred tax liabilities:
Net operating losses	84,800,000
Federal \| Research and Development Member
Deferred tax liabilities:
Credit carryforward	2,200,000
State
Deferred tax liabilities:
Net operating losses	76,700,000
State \| Research and Development Member
Deferred tax liabilities:
Credit carryforward	$872,000

Commitments_and_Contingencies_1

Commitments and Contingencies (Details) (USD $)

12 Months Ended

24 Months Ended

0 Months Ended

1 Months Ended

0 Months Ended

1 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2007

Jan. 14, 2013

Aug. 31, 2010

1-May-13

Jun. 30, 2014

Nov. 30, 2014

31-May-13

Jul. 31, 2014

Dec. 31, 2006

Jan. 01, 2011

item

lease

item

Future minimum lease payments

2015

$1,713,000

2016

686,000

2017

393,000

2018

404,000

2019

414,000

Thereafter

532,000

Total

4,142,000

Rent expenses

950,000

628,000

558,000

License Agreement

License Agreement [Abstract]

Payment of license fees and reimbursed patent costs

345,000

46,000

Shares issued

84,678

Amount receivable for achievement of regulatory milestones

300,000

License Agreement | Minimum

License Agreement [Abstract]

Annual license fee payable

5,000

License Agreement | Maximum

License Agreement [Abstract]

Annual license fee payable

25,000

Office and laboratory space | Operating lease entered into August 2010

Operating Leased Assets [Line Items]

Term of lease

5 years

Number of additional terms available for extension under option

Renewal term

2 years

Security deposit

320,000

400,000

Decrease in security deposit

80,000

Laboratory space | Operating lease entered into May 2013

Operating Leased Assets [Line Items]

Term of lease

6 months

Renewal term

6 months

Minimum notice for termination by lessee

60 days

Laboratory space | Operating lease entered into November 2014

Operating Leased Assets [Line Items]

Term of lease

6 years

Security deposit

281,000

Space build-out costs to be paid by landlord

1,400,000

Office, laboratory and manufacturing space | Operating lease entered into May 2013

Operating Leased Assets [Line Items]

Term of lease

2 years

Number of additional terms available for extension under option

Renewal term

1 year

Building | Operating lease entered into July 2014

Operating Leased Assets [Line Items]

Number of additional terms available for extension under option

Renewal term

2 years

Increase in monthly base rent

39,000

Office Space | License Agreement | Operating lease entered into November 2014

Operating Leased Assets [Line Items]

Term of lease

2 years

Security deposit

$50,000

401k_Savings_Plan_Details

401(k) Savings Plan (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
401(k) Savings Plan
Contributions to 401 (k) plan at the discretion of the board	$0	$0

Quarterly_Financial_Data_unaud2

Quarterly Financial Data (unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Data (unaudited)
Total revenue	$119				$55	$91	$120		$119	$266	$19
Loss from operations	-8,838	-7,787	-7,149	-6,907	-5,639	-4,542	-4,910	-4,600	-30,681	-19,692	-14,653
Net loss	-9,076	-8,091	-7,303	-6,920	-6,374	-4,642	-5,014	-4,580	-31,390	-20,610	-14,455
Net loss applicable to common shareholders	($9,076)	($8,849)	($9,209)	($8,826)	($8,284)	($6,553)	($6,925)	($5,756)	($35,960)	($27,518)	($18,867)
Per share data:
Net loss per common share-basic and diluted ( in dollars per share)	($0.45)	($0.71)	($6.35)	($6.25)	($5.89)	($4.69)	($4.95)	($4.17)	($4.15)	($19.72)	($13.86)

Subsequent_Events_Details

Subsequent Events (Details) (Subsequent Event [Member], Co Development Partnership Agreement, Canon U.S. Life Sciences Inc Member, USD $)	0 Months Ended
In Millions, unless otherwise specified	Feb. 03, 2015	Feb. 03, 2015
Subsequent Event [Member] \| Co Development Partnership Agreement \| Canon U.S. Life Sciences Inc Member
Subsequent events
Upfront payment received	$2
Additional consideration receivable upon achievement of certain development and regulatory milestones	6.5	6.5
Aggregate consideration receivable	$8.50	$8.50