Avinger (AVGR) 10-K 15 Mar 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Mar. 13, 2017	Jun. 30, 2016
Document and Entity Information
Entity Registrant Name	Avinger Inc
Entity Central Index Key	1,506,928
Document Type	10-K
Document Period End Date	Dec. 31, 2016
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float			$ 73.6
Entity Common Stock, Shares Outstanding		23,913,359
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY

BALANCE SHEETS

BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 36,096	$ 43,059
Accounts receivable, net of allowance for doubtful accounts of $21 at December 31, 2016 and $20 at December 31, 2015	3,570	2,060
Inventories	8,462	5,405
Prepaid expenses and other current assets	662	533
Total current assets	48,790	51,057
Property and equipment, net	4,555	2,822
Other assets	212	225
Total assets	53,557	54,104
Current liabilities:
Accounts payable	1,607	1,113
Accrued compensation	2,807	3,083
Accrued expenses and other current liabilities	3,067	3,285
Borrowings, current portion	41,289
Total current liabilities	48,770	7,481
Borrowings, net of current portion		29,565
Other long-term liabilities	546	1,469
Total liabilities	49,316	38,515
Commitments and contingencies (Note 10)
Stockholders' equity:
Preferred stock issuable in series, par value of $0.001; Shares authorized: 5,000,000 at December 31, 2016 and December 31, 2015; Shares issued and outstanding: none at December 31, 2016 and December 31, 2015
Common stock, par value of $0.001; Shares authorized: 100,000,000 at December 31, 2016 and December 31, 2015; Shares issued and outstanding: 23,776,033 at December 31, 2016 and 12,643,538 at December 31, 2015	24	13
Additional paid-in capital	256,606	211,837
Accumulated deficit	(252,389)	(196,261)
Total stockholders' equity	4,241	15,589
Total liabilities and stockholders' equity	$ 53,557	$ 54,104

BALANCE SHEETS (Parenthetical)

BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
BALANCE SHEETS
Allowance for doubtful accounts (in dollars)	$ 21	$ 20
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	23,776,033	12,643,538
Common stock, shares outstanding	23,776,033	12,643,538

STATEMENTS OF OPERATIONS AND CO

STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Revenues	$ 19,214	$ 10,713	$ 11,213
Cost of revenues	14,445	6,478	6,513
Gross profit	4,769	4,235	4,700
Operating expenses:
Research and development	15,536	15,694	11,224
Selling, general and administrative	39,950	29,231	18,503
Total operating expenses	55,486	44,925	29,727
Loss from operations	(50,717)	(40,690)	(25,027)
Interest income	125	40	2
Interest expense	(5,524)	(5,167)	(6,016)
Other income (expense), net	(12)	(1,527)	(909)
Loss before provision for income taxes	(56,128)	(47,344)	(31,950)
Provision for income taxes			14
Net loss and comprehensive loss	(56,128)	(47,344)	(31,964)
Adjustment to net loss resulting from convertible preferred stock modification		(2,384)
Net loss and comprehensive loss attributable to common stockholders	$ (56,128)	$ (49,728)	$ (31,964)
Net loss attributable to common stockholders per share, basic and diluted (in dollars per share)	$ (3.39)	$ (4.38)	$ (132.63)
Weighted average common shares used to compute net loss per share, basic and diluted	16,574	11,362	241

STATEMENTS OF CONVERTIBLE PREFE

STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Common StockAnti-dilution provisions upon conversion of preferred stock	Common StockIPO	Common StockSecurities Purchase Agreement with CRG	Common StockOther public offerings	Common Stock	Additional Paid-in CapitalAnti-dilution provisions upon conversion of preferred stock	Additional Paid-in CapitalIPO	Additional Paid-in CapitalSecurities Purchase Agreement with CRG	Additional Paid-in CapitalOther public offerings	Additional Paid-in Capital	Accumulated Deficit	Series A Convertible Preferred Stock	Series A-1 Convertible Preferred Stock	Series B Convertible Preferred Stock	Series C Convertible Preferred Stock	Series D Convertible Preferred Stock	Series E Convertible Preferred Stock	IPO	Securities Purchase Agreement with CRG	Other public offerings	Total
Balance (in shares) at Dec. 31, 2013					240,692							326,591	225,235	755,486	561,423	722,367
Increase (Decrease) in Shares
Issuance of common stock (in shares)					2,568
Issuance of stock, net (in shares)																	2,671,626
Balance (in shares) at Dec. 31, 2014					243,260							326,591	225,235	755,486	561,423	722,367	2,671,626
Balance at Dec. 31, 2013												$ 6,183	$ 6,649	$ 27,272	$ 22,397	$ 37,153
Increase (Decrease) in Convertible Preferred Stock
Issuance of Convertible Preferred Stock, net of issuance costs																	$ 32,606
Balance at Dec. 31, 2014												$ 6,183	$ 6,649	$ 27,272	$ 22,397	$ 37,153	$ 32,606
Balance at Dec. 31, 2013										$ 1,787	$ (114,569)										$ (112,782)
Increase (Decrease) in Stockholders' (Deficit) Equity
Issuance of common stock										28											28
Employee stock-based compensation										641											641
Issuance of common stock warrants										175											175
Reclass of warrants liability to additional paid-in capital										34											34
Net and comprehensive loss											(31,964)										(31,964)
Balance at Dec. 31, 2014										2,665	(146,533)										(143,868)
Increase (Decrease) in Shares
Issuance of common stock (in shares)					49,621
Issuance of stock, net (in shares)	1,214,725	5,000,000	348,262														490,472
Exercise of common stock warrants (in shares)					34,470
Conversion of preferred stock to common stock in connection with the IPO (in shares)					5,753,200							(326,591)	(225,235)	(755,486)	(561,423)	(722,367)	(3,162,098)
Balance (in shares) at Dec. 31, 2015					12,643,538
Increase (Decrease) in Convertible Preferred Stock
Issuance of Convertible Preferred Stock, net of issuance costs																	$ 5,372
Conversion of preferred stock to common stock in connection with the IPO												$ (6,183)	$ (6,649)	$ (27,272)	$ (22,397)	$ (37,153)	$ (37,978)				(2,384)
Increase (Decrease) in Stockholders' (Deficit) Equity
Issuance of common stock										432											432
Issuance of common stock, net	$ 1	$ 5	$ 1			$ (1)	$ 56,893	$ 4,794										$ 56,898	$ 4,795
Employee stock-based compensation										5,899											5,899
Vesting of restricted stock subject to repurchase										18											18
Issuance of common stock warrants										804											804
Exercise of common stock warrants										323											323
Conversion of preferred stock to common stock in connection with the IPO					$ 6					137,626											137,632
Convertible preferred stock modification										2,384	(2,384)
Net and comprehensive loss											(47,344)										(47,344)
Balance at Dec. 31, 2015					$ 13					211,837	(196,261)										15,589
Increase (Decrease) in Shares
Issuance of common stock (in shares)					163,936
Issuance of stock, net (in shares)				10,953,178
Exercise of common stock warrants (in shares)					15,381
Balance (in shares) at Dec. 31, 2016					23,776,033
Increase (Decrease) in Stockholders' (Deficit) Equity
Issuance of common stock										805											805
Issuance of common stock, net				$ 11					$ 36,572											$ 36,583
Employee stock-based compensation										7,392											7,392
Net and comprehensive loss											(56,128)										(56,128)
Balance at Dec. 31, 2016					$ 24					$ 256,606	$ (252,389)										$ 4,241

STATEMENTS OF CASH FLOWS

STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net loss	$ (56,128,000)	$ (47,344,000)	$ (31,964,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,506,000	1,300,000	1,451,000
Amortization of debt issuance costs and debt discount	222,000	199,000	212,000
Stock-based compensation	7,392,000	5,899,000	641,000
Remeasurement of embedded derivatives		(835,000)	(378,000)
Write off of embedded derivatives		1,066,000
Noncash interest expense and other charges	1,812,000	2,074,000	3,485,000
Loss on extinguishment of convertible notes		86,000	1,234,000
Provision for doubtful accounts receivable	3,000
Provision for excess and obsolete inventories	797,000	(26,000)	(48,000)
Changes in operating assets and liabilities:
Accounts receivable	(1,512,000)	7,000	(441,000)
Inventories	(6,099,000)	(2,307,000)	1,714,000
Prepaid expenses and other current assets	(130,000)	(363,000)	444,000
Other assets	13,000	(35,000)	2,000
Accounts payable	470,000	84,000	17,000
Accrued compensation	(275,000)	1,936,000	(128,000)
Accrued expenses and other current liabilities	(191,000)	(962,000)	2,080,000
Other long-term liabilities and accrued interest	(949,000)	(1,662,000)	(122,000)
Net cash used in operating activities	(53,069,000)	(40,883,000)	(21,801,000)
Cash flows from investing activities:
Purchase of property and equipment	(971,000)	(577,000)	(117,000)
Restricted cash		255,000
Net cash used in investing activities	(971,000)	(322,000)	(117,000)
Cash flows from financing activities:
Principal paydown of capital lease obligations	(27,000)	(22,000)	(17,000)
Payments on borrowing		(27,625,000)
Proceeds from convertible notes, net of issuance costs			4,700,000
Proceeds from borrowings, net of issuance costs	9,716,000	29,124,000
Proceeds from the issuance of convertible preferred stock, net of issuance costs		6,176,000	19,155,000
Proceeds from the issuance of common stock related to CRG loan, net of issuance costs		4,794,000
Proceeds from public offerings, net of issuance costs	36,583,000	58,746,000
Proceeds from the exercise of common stock warrants		323,000
Payments for deferred initial public offering costs			(1,848,000)
Proceeds from the issuance of common stock	805,000	432,000	23,000
Net cash provided by financing activities	47,077,000	71,948,000	22,013,000
Net change in cash and cash equivalents	(6,963,000)	30,743,000	95,000
Cash and cash equivalents, beginning of period	43,059,000	12,316,000	12,221,000
Cash and cash equivalents, end of period	36,096,000	43,059,000	12,316,000
Supplemental disclosure of cash flow information
Cash paid for interest	4,354,000	5,934,000	2,281,000
Noncash investing and financing activities:
Conversion of convertible preferred stock to common stock upon initial public offering		137,632,000
Accounts payable for purchases of property and equipment	24,000	16,000
Modification of convertible preferred stock		2,384,000
Reclass of warrants liability to additional paid-in capital			34,000
Vesting of common stock subject to repurchase		18,000	5,000
Issuance of common stock warrants		804,000	175,000
Transfer between inventory and property and equipment	$ 2,245,000	$ 921,000	(916,000)
Conversion of convertible notes and accrued interest into Series E convertible preferred stock			$ 11,582,000

Organization

Organization	12 Months Ended
	Dec. 31, 2016
Organization
Organization	1. Organization Organization, Nature of Business Avinger, Inc. (the “Company”), a Delaware corporation, was founded in March 2007 by cardiologist and medical device entrepreneur Dr. John B. Simpson. The Company designs, manufactures and sells image-guided, catheter-based systems that are used by physicians to treat patients with peripheral artery disease (“PAD”). Patients with PAD have a build-up of plaque in the arteries that supply blood to areas away from the heart, particularly the pelvis and legs. The Company manufactures and sells a suite of products in the United States (“U.S.”) and in select international markets. The Company has developed its Lumivascular platform, which integrates optical coherence tomography (“OCT”) visualization with interventional catheters and is the industry’s only system that provides real-time intravascular imaging during the treatment portion of PAD procedures. The Company’s Lumivascular platform consists of a capital component, Lightbox, as well as a variety of disposable catheter products. The Company’s current products include its non-imaging catheters, Wildcat and Kittycat, as well as its Lumivascular platform products, Ocelot, Ocelot PIXL and Ocelot MVRX, all of which are designed to allow physicians to penetrate a total blockage in an artery, known as a chronic total occlusion (“CTO”). In March 2016, the Company also received 510(k) clearance from the U.S. Food and Drug Administration (“FDA”) for commercialization of Pantheris, the Company’s image-guided atherectomy system, designed to allow physicians to precisely remove arterial plaque in PAD patients. The Company commenced sales of Pantheris in the U.S. and select international markets promptly thereafter. The Company is located in Redwood City, California. Liquidity Matters The accompanying financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and the satisfaction of liabilities in the normal course of business. The Company adopted FASB issued ASU No. 2014-15, Presentation of Financial Statements - Going Concern (Subtopic 205-40) effective December 31, 2016, which requires the Company to make certain disclosures if it concludes that there is substantial doubt about the entity’s ability to continue as a going concern within one year from the date of the issuance of these financial statements. In the course of its activities, the Company has incurred losses and negative cash flows from operations since its inception. As of December 31, 2016, the Company had an accumulated deficit of $252,389,000. The Company expects to incur losses for the foreseeable future. The Company believes that its cash and cash equivalents of $36,096,000 at December 31, 2016, expected revenues and the net proceeds from its “at-the-market” program will be sufficient to allow the Company to fund its current operations until approximately September 30, 2017. The Company will seek additional sources of funding in the form of debt financing or equity issuances. However, there can be no assurance that the Company will be successful in acquiring additional funding at levels sufficient to fund its operations. These conditions raise substantial doubt about the Company’s ability to continue as a going concern within one year from the date of the issuance of these financial statements. If the Company is unable to raise additional capital in sufficient amounts or on terms acceptable to it, the Company may have to significantly reduce its operations or delay, scale back or discontinue the development of one or more of its products. The financial statements do not include any adjustments that might result from the outcome of this uncertainty. The Company’s ultimate success will largely depend on its continued development of innovative medical technologies, its ability to successfully commercialize its products and its ability to raise significant additional funding. Additionally, due to the substantial doubt about the Company’s ability to continue operating as a going concern and the material adverse change clause in the Term Loan Agreement with CRG Partners III L.P. and certain of its affiliated funds (collectively “CRG”), the entire amount of borrowings at December 31, 2016 has been classified as current in these financial statements. CRG has not invoked the material adverse change clause. Public Offerings In January 2015, the Company issued and sold 5,000,000 shares of its common stock in its initial public offering (“IPO”) at a public offering price of $13.00 per share, for net proceeds of approximately $56,897,000 after deducting underwriting discounts and commissions of approximately $4,550,000 and expenses of approximately $3,553,000. Upon the closing of the IPO, all shares of convertible preferred stock then outstanding converted into an aggregate of 6,967,925 shares of common stock resulting in the reclassification of $137,626,000 from outside of stockholders’ equity (deficit) to additional paid-in capital. On February 3, 2016, the Company filed a universal shelf registration statement to offer up to $150,000,000 of its securities and entered into an “at-the-market” program pursuant to a Sales Agreement with Cowen and Company (“Cowen”), through which it may, from time to time, issue and sell shares of common stock having an aggregate offering value of up to $50,000,000. The shelf registration statement also covers the resale of the shares sold to CRG in September 2015. The registration statement was declared effective by the SEC on March 8, 2016. During the year ended December 31, 2016, the Company sold 1,095,378 shares of common stock under the “at-the-market” program at an average price of $4.87 and raised net proceeds of $5,171,000, after payment of $160,000 in commissions and fees to Cowen. In August 2016, the Company issued and sold 9,857,800 shares of its common stock in its follow-on public offering, which includes the exercise in full by the underwriters of their option to purchase 1,285,800 shares of common stock, at a public offering price of $3.50 per share. Net proceeds from the follow-on public offering were approximately $31,549,000 after deducting underwriting discounts and commissions of approximately $2,415,000 and expenses of approximately $538,000.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation On January 14, 2015, the Company’s Board of Directors approved an amendment to the Company’s amended and restated certificate of incorporation to effect a 1-for-45 reverse stock split of the Company’s common stock and convertible preferred stock. The par value of the common stock and convertible preferred stock was not adjusted as a result of the reverse stock split. All common stock, convertible preferred stock, stock options and warrants, and per share amounts in the financial statements have been retroactively adjusted for all periods presented to give effect to the reverse stock split. The reverse stock split was effected on January 28, 2015. The financial statements have been prepared in accordance with United States generally accepted accounting principles (“U.S. GAAP”) and pursuant to the rules and regulations of the United States Securities and Exchange Commission (“SEC”). Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts and disclosures reported in the financial statements. Management uses significant judgment when making estimates related to its common stock valuation and related stock-based compensation, the valuation of the common stock warrants, the valuation of compound embedded derivatives, provisions for doubtful accounts receivable and excess and obsolete inventories, clinical trial accruals, and its reserves for sales returns and warranty costs. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results may ultimately materially differ from these estimates and assumptions. Fair Value of Financial Instruments The Company has evaluated the estimated fair value of its financial instruments as of December 31, 2016 and 2015. Financial instruments consist of cash and cash equivalents, accounts receivable and payable, and other current liabilities and borrowings. The carrying amounts of cash and cash equivalents, accounts receivable and payable, and other current liabilities approximate their respective fair values because of the short-term nature of those instruments. Based upon the borrowing terms and conditions currently available to the Company, the carrying values of the borrowings approximate their fair value. Fair value accounting was applied to the warrant liabilities and embedded derivatives. No warrant liabilities or embedded derivatives were outstanding as of December 31, 2016 and 2015. Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity of three months or less at the time of purchase to be cash equivalents. Cash equivalents are considered available-for-sale marketable securities and are recorded at fair value, based on quoted market prices. As of December 31, 2016 and 2015, the Company’s cash equivalents are entirely comprised of investments in money market funds. Any related unrealized gains and losses are recorded in other comprehensive income (loss) and included as a separate component of stockholders’ equity (deficit). There were no unrealized gains and losses as of December 31, 2016 and 2015. Any realized gains and losses and interest and dividends on available-for-sale securities are included in interest income or expense and computed using the specific identification cost method. Restricted Cash At December 31, 2014, a deposit of $255,000 was restricted from withdrawal. The restricted cash secured obligations of the Company associated with its corporate credit card. The restricted deposit account was included in prepaid expenses and other current assets. During 2015, the Company was no longer required to secure its corporate card obligations. The release of the restriction against the Company’s cash was included within investing activities on its statement of cash flows for the year ended December 31, 2015. Concentration of Credit Risk, and Other Risks and Uncertainties Financial instruments that potentially subject the Company to credit risk consist of cash and cash equivalents and accounts receivable to the extent of the amounts recorded on the balance sheets. The Company’s policy is to invest in cash and cash equivalents, consisting of money market funds. These financial instruments are held in Company accounts at one financial institution. The counterparties to the agreements relating to the Company’s investments consist of financial institutions of high credit standing. The Company provides for uncollectible amounts when specific credit problems arise. Management’s estimates for uncollectible amounts have been adequate, and management believes that all significant credit risks have been identified at December 31, 2016 and 2015. The Company’s accounts receivable are due from a variety of health care organizations in the United States and select international markets. At December 31, 2016 and 2015, there were none and one, respectively, of the Company’s customers that represented 10% or more of the Company’s accounts receivable. For the years ended December 31, 2016, 2015 and 2014, there were no customers that represented 10% or more of revenues. Disruption of sales orders or a deterioration of financial condition of its customers would have a negative impact on the Company’s financial position and results of operations. The Company manufactures its commercial products in-house, including Pantheris and the Ocelot family of catheters. Certain of the Company’s product components and sub-assemblies continue to be manufactured by sole suppliers. Disruption in component or sub-assembly supply from these manufacturers or from in-house production would have a negative impact on the Company’s financial position and results of operations. The Company is subject to certain risks, including that its devices may not be approved or cleared for marketing by governmental authorities or be successfully marketed. There can be no assurance that the Company’s products will achieve widespread adoption in the marketplace, nor can there be any assurance that existing devices or any future devices can be developed or manufactured at an acceptable cost and with appropriate performance characteristics. The Company is also subject to risks common to companies in the medical device industry, including, but not limited to, new technological innovations, dependence upon third-party payors to provide adequate coverage and reimbursement, dependence on key personnel and suppliers, protection of proprietary technology, product liability claims, and compliance with government regulations. Existing or future devices developed by the Company may require approvals or clearances from the FDA or international regulatory agencies. In addition, in order to continue the Company’s operations, compliance with various federal and state laws is required. If the Company were denied or delayed in receiving such approvals or clearances, it may be necessary to adjust operations to align with the Company’s currently approved portfolio. If clearance for the products in the current portfolio were withdrawn by the FDA, this may have a material adverse impact on the Company. Accounts Receivable Trade accounts receivable are recorded at the invoiced amount and do not bear interest. The allowance for doubtful accounts is the Company’s best estimate of the amount of probable credit losses in the Company’s existing accounts receivable. The Company determines the allowance for doubtful accounts based upon an aging of accounts receivable, historical experience, and management judgment. Accounts receivable balances are reviewed individually for collectability. To date, the Company has not experienced significant credit-related losses. Inventories Inventories are valued at the lower of cost or market. Cost is determined using the first-in, first-out method for all inventories. The Company’s policy is to write down inventory that has expired or become obsolete, inventory that has a cost basis in excess of its expected net realizable value, and inventory in excess of expected requirements. The estimate of excess quantities is subjective and primarily dependent on the estimates of future demand for a particular product. If the estimate of future demand is too high, the Company may have to increase the reserve for excess inventory for that product and record a charge to the cost of revenues. Inventory used in clinical trials is expensed at the time of production and recorded as research and development expense. Property and equipment Property and equipment are recorded at cost. Repairs and maintenance costs are expensed as incurred. Depreciation and amortization are calculated using the straight-line method over the estimated useful lives of the assets of three to five years. Depreciation expense includes the amortization of assets acquired under capital leases and equipment located at customer sites. Equipment held by customers is comprised of the Lightboxes located at customer sites under a lease or placement agreement and are recorded at cost. Upon execution of a lease or placement agreement, the related equipment is reclassified from inventory to the property and equipment account. Depreciation expense for equipment held by customers is recorded as a component of cost of revenues. Leasehold improvements and assets recorded under capital leases are amortized using the straight-line method over the shorter of the lease term or estimated useful economic life of the asset. Deferred Offering Costs Deferred offering costs, which primarily consist of direct incremental legal and accounting fees relating to an offering of equity securities, were capitalized. As of December 31, 2016, there we no deferred offering costs capitalized in other assets on the balance sheet. Deferred offering costs of $29,000 were capitalized as of December 31, 2015. Impairment of Long-Lived Assets The Company reviews long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. If indicators of impairment exist, an impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are less than its carrying amount. Impairment, if any, is measured as the amount by which the carrying amount of the long-lived asset exceeds its fair value. The Company has not recorded any impairment of long-lived assets since inception through December 31, 2016. Convertible Preferred Stock Prior to its IPO the Company recorded its convertible preferred stock at fair value on the dates of issuance, net of issuance costs and classified the convertible preferred stock outside of stockholders’ equity (deficit) on the balance sheets as events triggering the liquidation preferences were not solely within the Company’s control. Upon the closing of the IPO, all shares of convertible preferred stock then outstanding converted into an aggregate of 6,967,925 shares of common stock resulting in the reclassification of $137,626,000 from outside of stockholders’ equity (deficit) to additional paid-in capital. Warrant Liability and Embedded Derivative Instruments The Company accounts for its warrants for shares of common stock in accordance with the accounting guidance for derivatives. The accounting guidance provides a two-step model to be applied in determining whether a financial instrument is indexed to an entity’s own stock and, therefore, qualifies for a scope exception. The two-step model requires a contract for a financial instrument to be both (1) indexed to the entity’s own stock and (2) classified in the stockholders’ equity (deficit) section of the balance sheet. If a financial instrument qualifies for a scope exception, it would not be considered a derivative financial instrument. As the price per share of the common stock warrants issued with the convertible notes was not fixed until the issuance of the Series E Convertible Preferred Stock in September 2014, these warrants were initially classified as a derivative liability. As a derivative liability, the warrants were initially recorded at fair value and were subject to remeasurement at each balance sheet date until September 2014. Any change in fair value as a result of a remeasurement was recognized as a component of other income (expense), net in the statements of operations and comprehensive loss. The Company re-evaluated the terms of the common stock warrants issued with the convertible notes after the issuance of the Series E Convertible Preferred Stock in September 2014 and determined that they then met the first criterion of the two-step model. Accordingly, the associated current fair value of the warrant liability was reclassified to additional paid-in capital in the stockholders’ equity (deficit) section of the balance sheet at that time, thus satisfying the second criterion of the two-step model. The Company issued convertible notes in 2013 and 2014 that included features which were determined to be embedded derivatives requiring bifurcation and separate accounting. Prior to their extinguishment in September 2015, the Company recorded a compound derivative asset or liability related to redemption features embedded within its outstanding convertible notes. The embedded derivatives were initially recorded at fair value and are subject to remeasurement as of each balance sheet date. Any change in fair value is recognized as a component of other income (expense), net in the statements of operations and comprehensive loss. In September 2015, the Company repaid the outstanding convertible notes and accrued interest obligations in their entirety. Accordingly, the associated current fair value of the embedded derivative asset was expensed as a component of other income (expense), net in the statements of operations and comprehensive loss at that time Revenue Recognition The Company’s revenues are derived from (1) sale of its Lightbox (2) sale of disposables, which consist of catheters and accessories, and (3) sale of customer service contracts. The Company sells its products directly to hospitals and medical centers as well as through distributors. The Company recognizes revenue in accordance with Accounting Standards Codification (“ASC”) 605-10, Revenue Recognition, when persuasive evidence of an arrangement exists, the fee is fixed or determinable, collection of the fee is probable and delivery has occurred. For all sales, the Company uses either a signed agreement or a binding purchase order as evidence of an arrangement. The Company’s revenue recognition policies generally result in revenue recognition at the following points: 1. Lightbox sales: The Company sells its products directly to hospitals and medical centers. Provided all other criteria for revenue recognition have been met, the Company recognizes revenue for Lightbox sales directly to end customers when delivery and acceptance occurs, which is defined as receipt by the Company of an executed form by the customer acknowledging that the training and installation process is complete. 2. Sales of disposables: Disposable revenues consist of sales of the Company’s catheters and accessories and are recognized when the product has shipped, risk of loss and title has passed to the customer and collectability is reasonably assured. 3. Service revenue: Service revenue is recognized ratably over the term of the service period. To date service revenue has been insignificant. The Company offers its customers the ability to purchase or lease its Lightbox. In addition, the Company provides a Lightbox under a limited commercial evaluation program to allow certain strategic accounts to install and utilize the Lightbox for a limited trial period of three to six months. When a Lightbox is placed under a lease agreement or under a commercial evaluation program, the Company retains title to the equipment and it remains capitalized on its balance sheet under property and equipment. Depreciation expense on these placed Lightboxes is recorded to cost of revenues on a straight-line basis. The costs to maintain these placed Lightboxes are charged to cost of revenues as incurred. The Company evaluates its lease and commercial evaluation program agreements and accounts for these contracts under the guidance in ASC 840, Leases and ASC 605-25, Revenue Recognition—Multiple Element Arrangements . The guidance requires arrangement consideration to be allocated between a lease deliverable and a non-lease deliverable based upon the relative selling-price of the deliverables, using a specific hierarchy. The hierarchy is as follows: vendor-specific objective evidence of fair value of the respective elements, third-party evidence of selling price, or best estimate of selling price (“BESP”). The Company allocates arrangement consideration using BESP. The Company assessed whether the embedded lease is an operating lease or sales-type lease. Based on the Company’s assessment of the guidance and given that any payments under the lease agreements are dependent upon contingent future sales, it was determined that collectability of the minimum lease payments is not reasonably predictable. Accordingly, the Company concluded the embedded lease did not meet the criteria of a sales-type lease and accounts for it as an operating lease. The Company recognizes revenue allocated to the lease as the contingent disposable product purchases are delivered and are included in revenues within the statement of operations and comprehensive loss. For sales through distributors, the Company recognizes revenue when title to the product and the risk of loss transfers from the Company to the distributor. The distributors are responsible for all marketing, sales, training and warranty in their respective territories. The standard terms and conditions contained in the Company’s distribution agreements do not provide price protection or stock rotation rights to any of its distributors. In addition, its distributor agreements do not allow the distributor to return or exchange products, and the distributor is obligated to pay the Company upon invoice regardless of its ability to resell the product. The Company estimates reductions in revenue for potential returns of products by customers. In making such estimates, management analyzes historical returns, current economic trends and changes in customer demand and acceptance of its products. The Company expenses shipping and handling costs as incurred and includes them in the cost of revenues. In those cases where the Company bills shipping and handling costs to customers, it will classify the amounts billed as a component of revenue. Cost of Revenues Cost of revenues consists primarily of manufacturing overhead costs, material costs and direct labor. A significant portion of the Company’s cost of revenues currently consists of manufacturing overhead costs. These overhead costs include the cost of quality assurance, material procurement, inventory control, facilities, equipment and operations supervision and management. Cost of revenues also includes depreciation expense for the Lightboxes under lease agreements and certain direct costs such as shipping costs. Product Warranty Costs The Company typically offers a one-year warranty for parts and labor on its products commencing upon the transfer of title and risk of loss to the customer. The Company accrues for the estimated cost of product warranties upon invoicing its customers, based on historical results. Warranty costs are reflected in the statement of operations and comprehensive loss as a cost of revenues. The warranty obligation is affected by product failure rates, material usage and service delivery costs incurred in correcting a product failure. Should actual product failure rates, material usage or service delivery costs differ from these estimates, revisions to the estimated warranty liability would be required. Periodically the Company assesses the adequacy of its recorded warranty liabilities and adjusts the amounts as necessary. Warranty provisions and claims are summarized as follows (in thousands): Year Ended December 31, 2016 2015 2014 Balance beginning of year $ $ $ Warranty provision Usage/Release ) ) ) Balance end of year $ $ $ Research and Development The Company expenses research and development costs as incurred. Research and development expenses include personnel and personnel-related costs, costs associated with pre-clinical and clinical development activities, and costs for prototype products that are manufactured prior to market approval for that prototype product; internal and external costs associated with the Company’s regulatory compliance and quality assurance functions, including the costs of outside consultants and contractors that assist in the process of submitting and maintaining regulatory filings; and overhead costs, including allocated facility and related expenses. Clinical Trials The Company accrues and expenses costs for its clinical trial activities performed by third parties, including clinical research organizations and other service providers, based upon estimates of the work completed over the life of the individual study in accordance with associated agreements. The Company determines these estimates through discussion with internal personnel and outside service providers as to progress or stage of completion of trials or services pursuant to contracts with clinical research organizations and other service providers and the agreed-upon fee to be paid for such services. Advertising Costs The Company expenses advertising costs as incurred. Advertising costs include design and production costs, including website development, physician and patient testimonial videos, written media campaigns, and other items. Advertising costs of approximately $526,000, $515,000 and $720,000 were expensed during the years ended December 31, 2016, 2015 and 2014, respectively. Common Stock Valuation and Stock-Based Compensation Stock-based compensation for the Company includes amortization related to all stock options, restricted stock units (“RSUs”) and shares issued under the employee stock purchase plan, based on the grant-date estimated fair value. The fair value of stock options is estimated on the date of grant using the Black-Scholes option pricing model and recognized as expense on a straight-line basis over the vesting period of the award. The Company measures the fair value of RSUs using the closing stock price of a share of the Company’s common stock on the grant date and is recognized as expense on a straight-line basis over the vesting period of the award. Because noncash stock-based compensation expense is based on awards ultimately expected to vest, it is reduced by an estimate for future forfeitures. The Company estimates a forfeiture rate for its stock options and RSUs based on an analysis of its actual forfeiture experience and other factors. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from estimates. Prior to the Company’s IPO in January 2015, the fair value of the Company’s common stock was determined by its Board of Directors with assistance from management and third-party valuation specialists. Management’s approach to estimate the fair value of the Company’s common stock is consistent with the methods outlined in the American Institute of Certified Public Accountants Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation . Management considered several factors to estimate enterprise value, including significant milestones that would generally contribute to increases in the value of the Company’s common stock. Following the closing of the Company’s IPO, the fair value of its common stock is determined based on the closing price of its common stock on The NASDAQ Global Market. Foreign Currency The Company records net gains and losses resulting from foreign exchange transactions as a component of foreign currency exchange losses in other income (expense), net. During the years ended December 31, 2016, 2015 and 2014, the Company recorded $12,000, $18,000 and $21,000 of foreign currency exchange net losses, respectively. Income Taxes The Company utilizes the liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on differences between financial reporting and tax reporting bases of assets and liabilities and are measured using enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized. The Company’s policy is to record interest and penalties on uncertain tax positions as income tax expense when they occur. During the years ended December 31, 2016, 2015 and 2014, the Company did not recognize accrued interest or penalties related to unrecognized tax benefits. Net Loss per Share Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding during the period, without consideration for potential dilutive common shares. Diluted net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of shares of common stock and dilutive potential shares of common stock outstanding during the period. Any common stock shares subject to repurchase are excluded from the calculations as the continued vesting of such shares is contingent upon the holders’ continued service to the Company. For the computation of net loss per share attributable to common stockholders, common stock shares subject to repurchase of none, none and 583 were excluded from the calculations as of December 31, 2016, 2015 and 2014, respectively. Since the Company was in a loss position for all periods presented, basic net loss per share attributable to common stockholders is the same as diluted net loss per share attributable to common stockholders as the inclusion of all potentially dilutive common shares would have been anti-dilutive. Prior to its IPO in January 2015, the Company calculated its basic and diluted net loss per share attributable to common stockholders in conformity with the two-class method required for companies with participating securities. The shares of the Company’s convertible preferred stock participated in any dividends declared by the Company and were therefore considered to be participating securities. The Company allocates no loss to participating securities because they have no contractual obligation to share in the losses of the Company. Net loss per share attributable to common stockholders was determined as follows (in thousands, except per share data): Year Ended December 31, 2016 2015 2014 Net loss $ ) $ ) $ ) Adjustment to net loss resulting from convertible preferred stock modification — ) — Net loss attributable to common stockholders $ ) $ ) $ ) Weighted average common stock outstanding Net loss attributable to common stockholders per share, basic and diluted $ ) $ ) $ ) In addition to the outstanding convertible notes as of December 31, 2014 (Note 8), the following potentially dilutive securities outstanding have been excluded from the computations of diluted weighted average shares outstanding because such securities have an antidilutive impact due to losses reported: December 31, 2016 2015 2014 Convertible preferred stock outstanding — — Common stock options Unvested restricted stock units — Common stock warrants Comprehensive Loss For the years ended December 31, 2016, 2015 and 2014, there was no difference between comprehensive loss and the Company’s net loss. Segment and Geographical Information The Company operates and manages its business as one reportable and operating segment. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. Primarily all of the Company’s long-lived assets are based in the United States. Long-lived assets are comprised of property and equipment. For the years ended December 31, 2016, 2015 and 2014, 96%, 98% and 99%, respectively, of the Company’s revenues, were in the United States, based on the shipping location of the external customer. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”), jointly with the International Accounting Standards Board, issued a comprehensive new standard on recognition from contracts with customers. The standard’s core principle is that a reporting entity will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The standard will become effective for the Company beginning in the first quarter of 2018. Early application would be permitted in 2017. Entities would have the option of using either a full retrospective or a modified retrospective approach to adopt this new guidance. The Company currently plans to adopt this accounting standard in the first quarter of fiscal year 2018 using the modified retrospective approach, with the cumulative effect being recorded within retained earnings on January 1, 2018. The guidance requires an entity to recognize revenue in an amount that reflects the consideration to which an entity expects to be entitled in exchange for the transfer of goods or services. The guidance also requires expanded disclosures relating to the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. Additionally, qualitative and quantitative disclosures are required about customer contracts, significant judgments and changes in judgments, and assets recognized from the costs to obtain or fulfill a contract. The Company has not completed its assessment of the adoption on its financial statements. In July 2015, the FASB issued an accounting standard which applies to all inventory that is measured using methods other than last-in, first-out or the retail inventory method, including inventory that is measured using first-in, first-out or average cost. The standard requires entities to measure inventory at the lower of cost and net realizable value, defined as the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The guidance is effective for public entities for fiscal years beginning after December 15, 2016, and interim periods with fiscal years beginning after December 15, 2017. The amendments in the standard should be applied prospectively with earlier application permitted as of the beginning of an interim or annual reporting period. The Company does not expect the adoption of this standard to have a material effect on its financial statements. In February 2016, the FASB issued ASU No. 2016-02, “Leases” (ASU 2016-02), which increases transparency and comparability among organizations by recognizing all lease transactions (with terms in excess of 12 months) on the balance sheet as a lease liability and a right-of-use asset (as defined). This guidance is effective for annual reporting periods beginning after December 15, 2018, and interim periods within those annual periods, using a modified retrospective approach, and early adoption is permitted. The Company is evaluating the impact of the adoption of this standard on its financial statements. The Company does expect that the adoption will increase its lease assets and correspondingly increase its lease liabilities. In March 2016, the FASB issued ASU No. 2016-09, Compensation — Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting, which simplifies severa

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2016
Fair Value Measurements
Fair Value Measurements	3. Fair Value Measurements The Company measures certain financial assets and liabilities at fair value on a recurring basis. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability. A three-tier fair value hierarchy is established as a basis for considering such assumptions and for inputs used in the valuation methodologies in measuring fair value: Level 1—Quoted prices in active markets for identical assets or liabilities. Level 2—Inputs other than quoted prices included within Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. As of December 31, 2016 and 2015, cash equivalents were all categorized as Level 1 and consisted of money market funds. In connection with the convertible notes issuances in 2013 and 2014 (Note 8), the Company issued warrants to purchase shares of its common stock. As the price per share of the common stock warrants was not fixed until the issuance of the Series E Convertible Preferred Stock in September 2014, they were classified as a derivative liability and were subject to remeasurement at each balance sheet date until September 2014. The convertible notes also contained redemption features which were determined to be a compound embedded derivative which, prior to their extinguishment in September 2015, required fair value accounting. The common stock warrant liability and embedded derivatives in the convertible notes were categorized as Level 3. When a determination is made to classify a financial instrument within Level 3, the determination is based upon the significance of the unobservable inputs to the overall fair value measurement. However, Level 3 financial instruments typically include, in addition to the unobservable inputs, observable inputs (that is, components that are actively quoted and can be validated to external sources). Any change in fair value is recognized as a component of other income (expense), net, on the statements of operations and comprehensive loss. There were no transfers between fair value hierarchy levels during the years ended December 31, 2016, 2015 and 2014. Common Stock Warrant Liability As the price per share of the common stock warrants was not fixed until the issuance of the Series E Convertible Preferred Stock in September 2014, they were classified as a derivative liability and were subject to remeasurement at each balance sheet date. Contemporaneous with the Series E Convertible Preferred Stock issuance, the Company determined that these common stock warrants met the requirements for equity classification and the current fair value of the common stock warrant liability was reclassified to additional paid-in capital. Subsequent to September 2014, there were no changes in fair value. The following table sets forth a summary of the changes in the estimated fair value of the Company’s common stock warrant liability, which represents a financial instrument classified as Level 3. Accordingly, the expense in the table below includes changes in fair value due in part to observable factors that are part of the Level 3 methodology (in thousands): Year Ended December 31, 2016 2015 2014 Fair value - beginning of year $ — $ — $ ) Issuance of warrants — — — Change in fair value recorded in other income (expense), net — — ) Reclass of warrant liability to additional paid-in capital — — Fair value - end of year $ — $ — $ — The fair value of the common stock warrants liability was determined by using an option pricing model to allocate the total enterprise value to the various securities within the Company’s capital structure. The model’s inputs reflect assumptions that market participants would use in pricing the instrument in a current period transaction. The following table summarizes these various assumptions as of September 2, 2014, the date the price per share of the common stock warrants was fixed: September 2, 2014 Time to liquidity (years) Expected volatility % Discounted cash flow rate % Risk-free interest rate % Marketability discount rate % The time to liquidity input was based on the Company’s estimate of when potential liquidity could be provided to stockholders. The volatility factor was based on the average historic price volatility for publicly-traded industry peers. The discounted cash flow rate takes into consideration a company specific risk premium, market risk premium and an assumed risk free rate of return. The risk-free interest rate was based on the yields of U.S. Treasury securities with maturities similar to the time to liquidity. The marketability discount is used to reflect that private company securities are generally less liquid than the securities of a public company. These assumptions are inherently subjective and involve significant management judgment. Generally, increases (decreases) in the fair value of the underlying common stock would result in a directionally similar impact to the fair value measurement. Subsequent to September 2014, there were no changes in fair value. Embedded Derivatives in Convertible Notes The following table sets forth a summary of the changes in the estimated fair value of the Company’s compound embedded derivative associated with its convertible notes, which represent a financial instrument classified as Level 3. Upon the extinguishment of the convertible notes in September 2015, the fair value of the compound embedded derivatives at the date of extinguishment was expensed to other income (expense), net. The income (expense) in the table below includes changes in fair value due in part to observable factors that are part of the Level 3 methodology (in thousands): Year Ended December 31, 2016 2015 2014 Fair value of asset (liability) - beginning of year $ — $ $ ) Issuance of convertible notes — — — Change in fair value recorded in other income (expense), net — Reversal of fair value recorded in other income (expense), net — ) — Fair value of asset (liability) - end of year $ — $ — $ Through December 31, 2014, the Company determined the value of the compound derivative utilizing a Monte Carlo Simulation model. The inputs used to determine the estimated fair value of the derivative instrument include the probability of an underlying event triggering the embedded derivative occurring and its timing. The fair value measurement is based upon significant inputs not observable in the market. The inputs included the probability that the Company would need to raise additional equity in 2014, as well as various financing and exit events in 2015. These assumptions are inherently subjective and involve significant management judgment. The following table summarizes these various assumptions as of December 31, 2014: Year Ended 2014 Equity financing in 2014 % Equity financing in 2015 % Liquidation % Initial public offering % Change of control % Subsequent to the Company’s IPO and through the extinguishment of the convertible notes on September 22, 2015, the value of the compound derivative was determined utilizing a Black-Derman-Toy model. The inputs used to determine the estimated fair value of the derivative instrument include the term structure of yields which are observed in the market, the credit spread, which was estimated by the Company, and the volatility, which was estimated using an analysis of comparable bonds in the market. The fair value measurement is based upon significant inputs not observable in the market. These assumptions are inherently subjective and involve significant management judgment. The following table summarizes these various assumptions as of September 22, 2015, the date of extinguishment: September 22, 2015 Time to first call option (years) — Credit spread % Expected volatility % Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis The Company measures certain non-financial assets (including property, plant and equipment) at fair value on a non-recurring basis in periods after initial measurement in circumstances when the fair value of such asset is impaired below its recorded cost.

Inventories

Inventories	12 Months Ended
	Dec. 31, 2016
Inventories
Inventories	4. Inventories Inventories consisted of the following (in thousands): December 31, 2016 2015 Raw materials $ $ Work-in-process — Finished products Total inventories $ $

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2016
Property and Equipment, Net
Property and Equipment, Net	5. Property and Equipment, Net Property and equipment, net, consisted of the following (in thousands): December 31, 2016 2015 Computer software $ $ Computer equipment Machinery and equipment Furniture and fixtures Leasehold improvements Equipment held by customers Less: Accumulated depreciation and amortization ) ) Add: Construction-in-progress $ $ Depreciation expense for the years ended December 31, 2016, 2015 and 2014, was $1,506,000, $1,300,000 and $1,451,000, respectively. Amortization of capital leased assets included in depreciation for the years ended December 31, 2016, 2015 and 2014, was $11,000, $17,000 and $17,000, respectively. Property and equipment includes certain equipment that is leased to customers and located at customer premises. The Company retains the ownership of the leased equipment and has the right to remove the equipment if it is not being utilized according to expectations. Depreciation expense relating to the leased equipment held by customers of $539,000, $260,000 and $378,000, was recorded in cost of revenues during the years ended December 31, 2016, 2015 and 2014, respectively. The net book value of this equipment was $2,587,000 and $1,236,000 at December 31, 2016 and 2015, respectively.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2016
Accrued Expenses and Other Current Liabilities
Accrued Expenses and Other Current Liabilities	6. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): December 31, 2016 2015 Accrued interest payable $ $ Accrued professional services Accrued travel expenses Accrued sales, use and other taxes Accrued warranty Sales return allowance Accrued clinical trial costs Other accrued liabilities $ $

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2016
Credit Agreement
Borrowings
Borrowings	7. Borrowings CRG On September 22, 2015, the Company entered into a Term Loan Agreement (the “Loan Agreement”) with CRG under which, subject to certain conditions, the Company may borrow up to $50,000,000 in principal amount from CRG on or before March 29, 2017. The Company borrowed $30,000,000 on September 22, 2015. The Company borrowed an additional $10,000,000 on June 15, 2016 under the Loan Agreement. The Company would have been eligible to borrow an additional $10,000,000, on or prior to March 29, 2017, upon achievement of certain revenue milestones, among other conditions, but those milestones were not achieved. Under the Loan Agreement, the first sixteen quarterly payments are interest only payments, and the last eight quarterly payments will be equal installments in which interest and principal amounts are paid. Interest is calculated at a fixed rate of 12.5% per annum. The Company makes quarterly payments of interest only in arrears commencing on September 30, 2015. During the interest only period, the Company may elect to make the 12.5% interest payment by making a cash payment for 8.5% per annum of interest and making a payment-in-kind (“PIK”) for the remaining amount, for which the 4.0% per annum of interest would be added to the outstanding principal amount of the borrowings. To date, the Company has elected the PIK interest option to the extent available and has made a cash payment for the remaining amount. Principal is repayable in eight equal quarterly installments during the final two years of the term. All unpaid principal, and accrued and unpaid interest, is due and payable in full on September 30, 2021. The Company may voluntarily prepay the borrowings in full, with a prepayment premium beginning at 5.0% and declining by 1.0% annually thereafter, with no premium being payable if prepayment occurs after the fifth year of the loan. Each tranche of borrowing requires the payment, on the borrowing date, of a financing fee equal to 1.5% of the borrowed loan principal, which is recorded as a discount to the debt. In addition, a facility fee equal to 7.0% of the amounts borrowed plus any PIK is payable at the end of the term or when the borrowings are repaid in full. A long-term liability is being accreted using the effective interest method for the facility fee over the term of the Loan Agreement with a corresponding discount to the debt. The borrowings are collateralized by a security interest in substantially all of the Company’s assets. The Loan Agreement requires that the Company adheres to certain affirmative and negative covenants, including financial reporting requirements, certain minimum financial covenants for pre-specified liquidity and revenue requirements and a prohibition against the incurrence of indebtedness, or creation of additional liens, other than as specifically permitted by the terms of the Loan Agreement. In particular, the covenants of the Loan Agreement include a covenant that the Company maintain a minimum of $5,000,000 of cash and certain cash equivalents, and the Company had to achieve minimum revenue of $7,000,000 in 2015, and must achieve minimum revenue of $23,000,000 in 2016, $40,000,000 in 2017, $50,000,000 in 2018, $60,000,000 in 2019 and $70,000,000 in 2020 and in each year thereafter, as applicable. On October 28, 2016, the Company amended the terms of the Loan Agreement, to reduce the minimum revenue that the Company must achieve in 2016 to $18,000,000. If the Company fails to meet the applicable minimum revenue target in any calendar year, the Loan Agreement provides the Company with a cure right if it prepays a portion of the outstanding principal equal to 2.0 times the revenue shortfall. In addition, the Loan Agreement prohibits the payment of cash dividends on the Company’s capital stock and also places restrictions on mergers, sales of assets, investments, incurrence of liens, incurrence of indebtedness and transactions with affiliates. CRG may accelerate the payment terms of the Loan Agreement upon the occurrence of certain events of default set forth therein, which include the failure of the Company to make timely payments of amounts due under the Loan Agreement, the failure of the Company to adhere to the covenants set forth in the Loan Agreement, the insolvency of the Company or upon the occurrence of a material adverse change. As of December 31, 2016, the Company was in compliance with all applicable covenants. As of December 31, 2016, principal and PIK payments under the Loan Agreement follows (in thousands): Period Ending December 31, Principal and PIK 2017 $ — 2018 — 2019 2020 2021 Add: Accretion of closing fees Add: PIK Less: Amount representing debt financing costs ) Borrowings $ Contemporaneous with the execution of the Loan Agreement, the Company entered into a Securities Purchase Agreement (the “Securities Purchase Agreement”) with CRG which allowed it to purchase up to $5,000,000 of the Company’s common stock. CRG purchased 348,262 shares of common stock on September 22, 2015 at a price of $14.357 per share, which is the 10-day average of closing prices of the Company’s common stock ending on September 21, 2015. The closing price on September 22, 2015 was $13.97 yielding a $0.387 per share premium. Both the premium and the issuance costs were allocated to the borrowings under Loan Agreement and the common stock purchase under the Securities Purchase Agreement based on the relative fair values of each security. The portion of the premium allocated to the borrowings is being amortized over the term of the Loan Agreement. Pursuant to the Securities Purchase Agreement, the Company filed a shelf registration statement covering, among other things, the resale of the shares sold to CRG and must comply with certain affirmative covenants during the time that such registration statement remains in effect. In connection with the initial drawdown under the Loan Agreement, the Company recorded a debt discount of $876,000. The debt discount comprised financing fees of $450,000, paid directly to CRG, and an allocation of the other costs directly attributable to the Loan Agreement and Securities Purchase Agreement with CRG of $541,000 net of the common stock premium of $115,000 based on the relative fair values of each security. In connection with the June 2016 drawdown under the Loan Agreement, the Company recorded a debt discount of $275,000 which comprised financing fees of $150,000, paid directly to CRG, and other costs directly attributable to the Loan Agreement with CRG of $125,000. The debt discount is being amortized as non-cash interest expense using the effective interest method over the term of the Loan Agreement. As of December 31, 2016 and 2015, the balance of the aggregate debt discount was $919,000 and $834,000, respectively. As noted in Note 1 to these financial statements, due to the substantial doubt about the Company’s ability to continue operating as a going concern and the material adverse change clause in the CRG Loan Agreement, the entire amount of borrowings at December 31, 2016 has been classified as current in these financial statements. CRG has not invoked the material adverse change clause. PDL BioPharma On April 18, 2013, the Company entered into a Credit Agreement (“Agreement”) with PDL BioPharma, Inc. (“PDL”) whereby PDL agreed to loan up to $40,000,000. Contemporaneous with the execution of the Agreement the Company borrowed an initial $20,000,000 (“Term Note”). The Term Note was scheduled to mature April 18, 2018, had a stated interest rate of 12.0% per annum and could be prepaid by the Company at any time. The Company paid interest-only through the first ten quarters and, thereafter, repayment of principal in equal installments including accrued and unpaid interest, payable each quarter. As provided under the terms of the Agreement, for the first eight quarterly interest payments, or through 2015, on the Term Note the Company elected to convert an amount of interest, up to 1.5% per annum, into additional loans, referred to as PIK loans. The PIK loans accrued interest and were added to the aggregate principal balance of the Term Note. In September 2015, in connection with the consummation of the Loan Agreement with CRG, the Company repaid all amounts outstanding under the Agreement. The payoff amount of $21,363,000 included accrued interest through the repayment date of $563,000 and $200,000 as an end-of-term final payment fee recorded in other income (expense), net on the statement of loss and comprehensive loss. For the years ended December 31, 2016, 2015 and 2014, the Company incurred interest expense of $380,000, $2,785,000 and $3,380,000, respectively. In addition to the interest and principal payments, the Company also paid a royalty, referred to as Assigned Interests, equal to 1.8% of the Company’s quarterly net revenues. Upon the prepayment of the Term Note, the Company’s obligations relating to Assigned Interests continue, and are payable through the maturity date at a reduced rate of 0.9% of the quarterly net revenues, subject to certain quarterly minimum mandatory amounts, which are payable monthly. The ongoing obligation was determined to be an embedded element of the Agreement and cannot be bifurcated from the Term Note for accounting purposes. Accordingly, the Company continued to account for the Assigned Interests obligation relating to future royalties as a debt instrument by applying the retrospective approach and reviews its estimate of forecasted Assigned Interests payable annually. Under the retrospective method, the Company computes a new effective interest rate based on the original carrying amount, actual cash flows to date, and remaining estimated cash flows over the maturity date. The new effective interest rate, 20.4% as of December 31, 2016, was used to adjust the carrying amount to the present value of the revised estimated cash flows, discounted at the new effective interest rate. At the time of the repayment the resulting increase in the carrying value of the Assigned Interests, of $942,000, was recognized as a component of other income (expense), net, on the statements of operations and comprehensive loss. The Company has an aggregate accrual for its Assigned Interests obligations of $1,463,000 and $2,303,000, representing the net present value of the future minimum royalty obligation as of December 31, 2016 and 2015, respectively. The Assigned Interest liability was included within accrued expenses and other current liabilities and within other long-term liabilities as of December 31, 2016 and 2015, on the balance sheet. Prior to the repayment of the Term Note, the Assigned Interests liability was included within borrowings and borrowings, net of current portion on the balance sheet. Additionally, until April 2018, the Company must periodically pay PDL a percentage of its net revenue and comply with certain affirmative covenants and negative covenants limiting its ability to, among other things, undergo a change in control or dispose of assets, in each case subject to certain exceptions. The Company was in compliance with the covenants under the Agreement as of December 31, 2016.

Convertible Notes

Convertible Notes	12 Months Ended
	Dec. 31, 2016
Convertible Notes
Convertible Notes
Convertible Notes	8. Convertible Notes On October 29, 2013, the Company entered into a Note and Warrant Purchase Agreement (the “Convertible Note Agreement”), as amended in May 2014, with certain existing convertible preferred stockholders, third-parties and employees for the issuance of convertible notes for up to an aggregate principal amount of $25,000,000. Under the terms of the Convertible Note Agreement, the Company issued convertible notes in October and November 2013 for total proceeds of $13,472,000, and in May and July 2014 for additional total proceeds of $4,720,000. The Company was required to pay interest on these convertible notes at a rate of 30-day LIBOR, plus 6% per annum subject to a minimum internal rate of return of 20%. The notes will mature and the accrued interest thereon would have become payable upon the earlier of: (i) October 29, 2018, (ii) an event of default, or (iii) a change of control event. The principal and accrued interest on the notes were convertible, at the option of the holder, upon a future issuance of the Company’s convertible preferred stock or common stock (the “Equity Financing”) into that same stock at a conversion price equal to 85% of the price paid by other investors in the financing event. For holders who elected not to convert their notes upon the closing of the Company’s Series E Preferred Stock financing or upon its IPO, the Company may repay the holder, at its sole election, a payment equal to the greater of (i) 125% of the outstanding principal and accrued and unpaid interest, or (ii) the amount providing the investor with a 20% minimum internal rate of return, at any time prior to their maturity date. In conjunction with the issuance of the convertible notes, the Company issued warrants to purchase up to the number of shares of common stock equal to 15% of the principal amount of the convertible notes divided by an exercise price per share equal to the lesser of $39.15 per share, or the price per share paid by the investors in the first bona fide preferred stock financing subsequent to the date of the convertible notes. Upon the Series E Convertible Preferred Stock issuance in September 2014, the exercise price per share was fixed at $12.60 per share and the Company issued warrants to purchase a total of 216,547 shares of common stock. The warrants, which were immediately exercisable, expired upon the closing of the Company’s IPO. The estimated fair value of the warrants upon issuance, of $1,000, was based on an option pricing model. The Company recorded the fair value of the warrants at issuance as a debt discount and as a warrant liability. The debt discount was accreted using the effective interest method as additional interest expense over the term of the convertible notes. Immediately prior to the closing of the Company’s IPO, 149,288 of the warrants to purchase common stock were net exercised, 24,403 of the warrants to purchase common stock were exercised and the remaining balance of 42,856 warrants to purchase common stock expired. The convertible notes have redemption features that were determined to be compound embedded derivatives requiring bifurcation and separate accounting. The fair value of the compound embedded derivative upon issuance was determined to be a liability of $179,000. The fair value of these derivative instruments was recognized as an additional discount and as a derivative liability on the balance sheets upon issuance of the convertible notes. The compound embedded derivative associated with the convertible notes required periodic re-measurements to fair value while the instruments are still outstanding. In September and November 2014, in connection with the issuance of the Series E Convertible Preferred Stock, $11,582,000 of the outstanding convertible notes and accrued interest thereon was converted into shares of Series E Convertible Preferred Stock (Note 11). Upon the conversion of the convertible notes, the Company recorded a net loss from the extinguishment of the debt in the amount of $1,234,000 which is reflected in other income (expense), net in the statement of operations and comprehensive loss. In September 2015, in connection with the consummation of the Loan Agreement, the Company repaid all amounts outstanding under the convertible notes. The carrying value of the convertible notes and accrued interest was $9,867,000 prior to payoff. The Company recorded a loss on extinguishment of the convertible notes of $86,000 as a component of other income (expense), net, on the statements of operations and comprehensive loss. The Company’s interest expense associated with the convertible notes amounted to none, $1,230,000 and $2,633,000 during the years ended December 31, 2016, 2015 and 2014, respectively, based on the minimum internal rate of return of 20%.

Capital Leases

Capital Leases	12 Months Ended
	Dec. 31, 2016
Capital Leases
Capital Leases	9. Capital Leases Capital lease obligations consist of leased office equipment. As of December 31, 2016 and 2015, the aggregate amount of capital leases recorded within property and equipment, net, on the accompanying balance sheet is $39,000 and $39,000, respectively. The current portion of the capital lease obligations is included in accrued liabilities and the balance included within other long-term liabilities represents the long-term portion. The future minimum lease payments as of December 31, 2016, are as follows (in thousands): Future Minimum Period ending December 31, Lease Payments 2017 $ 2018 2019 Total minimum payments Less: Amount representing future interest Present value of minimum lease payments $

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies
Commitments and Contingencies	10. Commitments and Contingencies Lease Commitments The Company’s operating lease obligations primarily consist of leased office, laboratory, and manufacturing space under a non-cancelable operating lease that expires in November 2019. The lease agreement includes a renewal provision allowing the Company to extend this lease for an additional period of three years. In addition to the minimum future lease commitments presented below, the lease requires the Company to pay property taxes, insurance, maintenance, and repair costs. The lease includes a rent holiday concession and escalation clauses for increased rent over the lease term. Rent expense is recognized using the straight-line method over the term of the lease. The Company records deferred rent calculated as the difference between rent expense and the cash rental payments. In connection with the facility lease, the landlord also provided incentives of $369,000 to the Company in the form of leasehold improvements. These amounts were reflected as deferred rent and were amortized as a reduction to rent expense over the original term of the Company’s operating lease. In February 2016, the Company entered into an additional non-cancelable operating lease for warehouse and storage space that expires in November 2019. Rent expense was $1,098,000, $938,000 and $922,000 for the years ended December 31, 2016, 2015 and 2014, respectively. The future aggregate minimum lease payments as of December 31, 2016, are as follows (in thousands): Future Minimum Year ending December 31, Lease Payments 2017 $ 2018 2019 Total minimum lease payments $ Purchase Obligations Purchase obligations consist of agreements to purchase goods and services entered into in the ordinary course of business. The Company had noncancellable commitments to suppliers for purchases totaling $3,542,000 and $4,347,000 as of December 31, 2016 and 2015, respectively Indemnification In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and may provide for indemnification of the counterparty. The Company’s exposure under these agreements is unknown because it involves claims that may be made against it in the future, but have not yet been made. To date, the Company has not been subject to any claims or been required to defend any action related to its indemnification obligations. The Company indemnifies each of its directors and officers for certain events or occurrences, subject to certain limits, while the director is or was serving at the Company’s request in such capacity, as permitted under Delaware law and in accordance with its certificate of incorporation and bylaws. The term of the indemnification period lasts as long as a director may be subject to any proceeding arising out of acts or omissions of such director in such capacity. The maximum amount of potential future indemnification is unlimited; however, the Company currently holds director liability insurance. This insurance allows the transfer of risk associated with the Company’s exposure and may enable it to recover a portion of any future amounts paid. The Company believes that the fair value of these indemnification obligations is minimal. Accordingly, it has not recognized any liabilities relating to these obligations for any period presented. Legal Proceedings The Company was not party to any legal proceedings at December 31, 2016 and 2015. The Company assesses, in conjunction with its legal counsel, the need to record a liability for litigation and contingencies. Reserve estimates are recorded when and if it is determined that a loss-related matter is both probable and reasonably estimable. On February 15, 2014, the Company entered into an engagement letter with a financial advisor which provided for such firm to serve as its placement agent and for the Company to make certain payments to them in connection with its Series E Convertible Preferred Stock financing. After the entry into such engagement letter, the financial advisor did not provide the level of service the Company was expecting and was not responsible for introducing the Company to any of the Series E Convertible Preferred Stock investors. In December 2014, the Company and its former financial advisor agreed to amend and to terminate their engagement letter, effective immediately. Pursuant to the terms of the amended engagement letter, the Company agreed to pay the former financial advisor a transaction fee of $650,000, to be paid in four equal quarterly installments starting on December 31, 2014, and ending on September 30, 2015 and $35,000 for reimbursement of the former financial advisor’s out-of-pocket expenses, which were due upon execution of the amendment. The transaction fee and out-of-pocket expenses were reflected as additional Series E Convertible Preferred Stock issuance costs during the year ended December 31, 2014.

Convertible Preferred Stock

Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2016
Convertible Preferred Stock
Convertible Preferred Stock	11. Convertible Preferred Stock Upon the closing of the Company’s IPO in February 2015, all shares of convertible preferred stock then outstanding converted into an aggregate of 6,967,925 shares of common stock. As of December 31, 2016 and 2015, the Company does not have any convertible preferred stock issued or outstanding.

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit)	12 Months Ended
	Dec. 31, 2016
Stockholders' Equity (Deficit)
Stockholders' Equity (Deficit)	12. Stockholders’ Equity (Deficit) Preferred Stock At December 31, 2016, the Company’s certificate of incorporation, as amended and restated, authorizes the Company to issue up to 5,000,000 shares of preferred stock with $0.001 par value per share, of which no shares were issued and outstanding. Common Stock At December 31, 2016, the Company’s certificate of incorporation, as amended and restated, authorizes the Company to issue up to 100,000,000 shares of common stock with $0.001 par value per share, of which 23,776,033 shares were issued and outstanding. Common Stock Warrants In connection with the issuance of the Company’s Series E Convertible Preferred Stock in September 2014 through January 2015, the Company issued, to each investor who purchased shares of Series E Convertible Preferred Stock, warrants to purchase up to the number of shares of common stock equal to 50% of the number of shares of the Company’s Series E Convertible Preferred Stock purchased. The warrants are immediately exercisable, at an exercise price per share of $12.60, and expire upon the earlier of September 2, 2019 or upon the consummation of a change of control of the Company. The Company determined that these common stock warrants meet the requirements for equity classification. In connection with the issuance of its Series E Convertible Preferred Stock in September through December 2014, the Company issued warrants to purchase an aggregate of 1,335,779 shares of common stock. The common stock warrants were recorded at their allocated fair value of $175,000 within stockholders’ equity (deficit). In connection with the issuance of the Company’s Series E Convertible Preferred Stock in January 2015, the Company issued warrants to purchase an aggregate of 245,235 shares of common stock. The common stock warrants were recorded at their allocated fair value of $804,000 within stockholders’ equity (deficit). On January 14, 2015, the Company amended its Series E Convertible Preferred Stock Purchase Agreement to provide for the issuance of common stock warrants to each investor who purchased shares of Series E Convertible Preferred Stock equal to 70% of the number of shares of the Company’s Series E Convertible Preferred Stock purchased by such investor. As with the common stock warrants previously issued, any new common stock warrants were immediately exercisable, at an exercise price of $12.60 per share, and expire upon the earlier of September 2, 2019 or upon consummation of a change in control of the Company. As a result of this amendment to the Series E Convertible Preferred Stock Purchase Agreement, the Company issued additional warrants to purchase 632,381 shares of common stock to investors who previously acquired shares of Series E Convertible Preferred Stock from September 2014 through January 2015. As of December 31, 2016 and 2015, warrants to purchase an aggregate of 2,152,117 and 2,193,507 shares of common stock were outstanding, respectively. The Company determined that the amendment to the Series E Convertible Preferred Stock Purchase Agreement should be accounted for as a modification. Accordingly, the incremental fair value from the modification, the additional warrants to purchase 632,381 shares of common stock warrants, of $2,384,000, was recorded as an increase to stockholders’ equity (deficit) and as an adjustment to net loss attributable to common stockholders in the Company’s statement of operations and comprehensive loss for the year ended December 31, 2015. This amount represents a return to the preferred stockholders and is treated in a manner similar to the treatment of dividends paid to holders of preferred stock in the computation of earnings per share. As a result, the “deemed dividend” is subtracted from net loss available to common stockholders in reconciling net loss to net loss available for common stockholders. Stock Plans In January 2015, the Board of Directors adopted and the Company’s stockholders approved the 2015 Equity Incentive Plan (“2015 Plan”). The 2015 Plan replaced the 2009 Stock Plan (the “2009 Plan”) which was terminated immediately prior to consummation of the Company’s IPO, collectively the “Plans.” The 2015 Plan provides for the grant of incentive stock options (“ISOs”) to employees and for the grant of nonstatutory stock options (“NSOs”), restricted stock, RSUs, stock appreciation rights, performance units and performance shares to employees, directors and consultants. Initially a total of 1,320,000 shares of common stock were reserved for issuance pursuant to the 2015 Plan. The shares reserved for issuance under the 2015 Plan included shares reserved but not issued under the 2009 Plan, plus any share awards granted under the 2009 Plan that expire or terminate without having been exercised in full or that are forfeited or repurchased. In addition, the number of shares available for issuance under the 2015 Plan includes an automatic annual increase on the first day of each fiscal year beginning in fiscal 2016, equal to the lesser of 1,690,000 shares, 5.0% of the outstanding shares of common stock as of the last day of the immediately preceding fiscal year or an amount as determined by the Board of Directors. For fiscal 2016, the common stock available for issuance under the 2015 Plan was increased by 632,176 shares of common stock. As of December 31, 2016, 1,183,937 shares were available for grant under the 2015 Plan. Pursuant to the Plans, ISOs and NSOs may be granted with exercise prices at not less than 100% of the fair value of the common stock on the date of grant and the exercise price of ISOs granted to a stockholder, who, at the time of grant, owns stock representing more than 10% of the voting power of all classes of the stock of the Company, shall be not less than 110% of the fair market value per share of common stock on the date of grant. The Company’s Board of Directors determines the vesting schedule of the options. Options granted generally vest over four years and expire ten years from the date of grant. Stock option activity under the Plans is set forth below: Options Outstanding Weighted Aggregate Number of Average Intrinsic Value Shares Exercise Price (in thousands) Balance at December 31, 2013 $ $ — Options granted $ Options exercised ) $ Options cancelled ) $ Balance at December 31, 2014 $ $ Options granted $ Options exercised ) $ Options cancelled ) $ Balance at December 31, 2015 $ $ Options granted $ Options exercised ) $ Options cancelled ) $ Balance at December 31, 2016 $ $ Additional information related to the status of options as of December 31, 2016 is summarized as follows: Options Outstanding and Vested as of December 31, 2016 Options Outstanding Options Vested Weighted Weighted Weighted Average Average Average Exercise Options Remaining Exercise Number Exercise Price Outstanding Contractual Life Price Exercisable Price $ $ — $ $ $ — $ $ $ $ $ $ $ $ $ $ $ $ — $ $ $ $ $ $ $ $ $ $ $ $ — $ $ $ — $ $ $ $ $ $ — $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ The weighted-average grant date fair value of stock options granted during the years ended December 31, 2016, 2015 and 2014 was $5.51, $8.24 and $6.60 per share, respectively. As of December 31, 2016, the weighted average remaining contractual life of options outstanding and vested was 7.63 years. As of December 31, 2016, the aggregate intrinsic value of options outstanding and vested was $0. The aggregate intrinsic value of options exercised was $135,000, $236,000 and none during the years ended December 31, 2016, 2015 and 2014, respectively. The aggregate intrinsic value was calculated as the difference between the exercise prices of the underlying options and the closing market price of the common stock on the date of exercise. Because of the Company’s net operating losses, the Company did not realize any tax benefits from share-based payment arrangements for the years ended December 31, 2016, 2015 and 2014. The Company’s RSUs vest annually over four years in equal increments. A summary of all RSU activity is presented below: Weighted Average Weighted Average Aggregate Number of Grant Date Remaining Intrinsic Value Shares Fair Value Contractual Term (in thousands) Awards outstanding at December 31, 2014 — $ — — $ — Awarded $ Awards outstanding at December 31, 2015 $ $ Awarded $ Released ) $ Forfeited ) $ Awards outstanding at December 31, 2016 $ $ As of December 31, 2016, $2,780,000 of total unrecognized compensation expense related to employee RSUs was expected to be recognized over a weighted-average period of 3.05 years. The Company used the closing market price of $3.70 per share at December 31, 2016, to determine the aggregate intrinsic value. 2015 Employee Stock Purchase Plan In January 2015, the Board of Directors adopted and the Company’s stockholders approved the 2015 Employee Stock Purchase Plan (“ESPP”) under which eligible employees are permitted to purchase common stock at a discount through payroll deductions. Initially 500,000 shares of common stock were reserved for issuance, which is subject to an automatic increase on the first day of each fiscal year, commencing in 2016, by an amount equal to the lesser of (i) 493,000 shares (ii) 1.5% of the outstanding shares of common stock as of the last day of the immediately preceding fiscal year; or (iii) an amount as determined by the Board of Directors. For fiscal 2016, the common stock available for issuance under the ESPP was increased by 189,653 shares of common stock. The price of the common stock purchased will be the lower of 85% of the fair market value of the common stock at the beginning of an offering period or at the end of a purchase period. The ESPP is intended to qualify as an “employee stock purchase plan” within the meaning of Section 423 of the Internal Revenue Code of 1986, as amended. The first offering under the ESPP began in February 2015. As of December 31, 2016, approximately 543,879 shares of common stock remained reserved for issuance under the ESPP. The Company incurred $372,000 and $217,000 in stock-based compensation expense related to the ESPP for the year ended December 31, 2016 and 2015, respectively.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2016
Stock-Based Compensation
Stock-Based Compensation	13. Stock-Based Compensation Stock-based compensation for the Company includes amortization related to all stock options, RSUs and shares issued under the ESPP, based on the grant-date estimated fair value. The Company estimates the fair value of stock options and shares issued under the ESPP on the date of grant using the Black-Scholes option-pricing model. The Black-Scholes model determines the fair value of stock-based payment awards based on the fair market value of the Company’s common stock on the date of grant and is affected by assumptions regarding a number of complex and subjective variables. These variables include, but are not limited to, the fair value of the Company’s common stock, and the volatility over the expected term of the awards. The Company has opted to use the “simplified method” for estimating the expected term of options, whereby the expected term equals the arithmetic average of the vesting term and the original contractual term of the option. Prior to the Company’s IPO in January 2015, due to the Company’s limited operating history 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. When selecting these public companies on which it has based its expected stock price volatility, the Company selected companies with comparable characteristics to it, including enterprise value, stage of development, risk profile, and position within the industry as well as selecting companies with historical share price information sufficient to meet the expected life of the stock-based awards. The historical volatility data was computed using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of the share-based payments. Following the closing of the Company’s IPO, the Company supplements its own available company specific historical volatility with the volatility of the previously selected peer group of publicly traded companies. The Company will continue to analyze the historical stock price volatility and expected term assumptions as more historical data for the Company’s common stock becomes available. The risk-free rate assumption is based on the U.S. Treasury instruments with maturities similar to the expected term of the Company’s stock options. The expected dividend assumption is based on the Company’s history of not paying dividends and its expectation that it will not declare dividends for the foreseeable future. As noncash stock-based compensation expense recognized in the financial statements is based on awards ultimately expected to vest, it has been reduced for estimated forfeitures. The Company estimates a forfeiture rate for its stock options and RSUs based on an analysis of its actual forfeitures based on actual forfeiture experience and other factors. Forfeitures are estimated at the time of grant and revised, if necessary, over the service period to the extent that actual forfeitures differ, or are expected to differ, from prior estimates. Forfeitures are estimated based on estimated future employee turnover and historical experience. The fair value for the Company’s employee stock options was estimated at the date of grant using the Black-Scholes valuation model with the following average assumptions: Year Ended December 31, 2016 2015 2014 Expected term (years) Expected volatility % % % Risk-free interest rate % % % Dividend rate — — — As of December 31, 2016 and 2015, the total unamortized compensation expense related to stock options granted to employees and directors was $12,312,000 and $16,871,000, which is expected to be amortized over the next 2.33 and 3.15 years, respectively. The fair value of the shares to be issued under the Company’s ESPP was estimated using the Black-Scholes valuation model with the following assumptions: Year Ended December 31, 2016 2015 Expected term (years) Expected volatility % % Risk-free interest rate % % Dividend rate — — The Company measures the fair value of RSUs using the closing stock price of a share of the Company’s common stock on the grant date and is recognized as expense on a straight-line basis over the vesting period of the award. The total fair value of shares vested pursuant to RSUs in the year ended December 31, 2016 and 2015 was $486,000 and zero, respectively. As of December 31, 2016, total unamortized stock-based compensation expense related to unvested RSUs was $2,780,000, with a weighted-average remaining recognition period of 3.05 years. Total noncash stock-based compensation expense relating to the Company’s stock options, ESPP and RSUs recognized, before taxes, during the years ended December 31, 2016, 2015 and 2014, is as follows (in thousands): Year Ended December 31, 2016 2015 2014 Cost of revenues $ $ $ Research and development expenses Selling, general and administrative expenses $ $ $

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Taxes
Income Taxes	14. Income Taxes For the years ended December 31, 2016, 2015 and 2014, the Company’s provision for income taxes consisted of state income tax expense of none, none and $14,000, respectively. A reconciliation of the statutory U.S. federal rate to the Company’s effective tax rate is as follows (in thousands): Year Ended December 31, 2016 2015 2014 Tax at federal statutory rate $ ) $ ) $ ) State taxes, net of federal benefit — — Permanent differences Change in valuation allowance Research credits ) ) ) Other ) Provision for taxes $ — $ — $ Significant components of the Company’s net deferred tax assets as of December 31, 2016 and 2015 consist of the following (in thousands): As of December 31, 2016 2015 Deferred tax assets: Federal, state, and foreign net operating losses $ $ Research and other credits Fixed assets Interest Accruals and other Total deferred tax assets Less: Valuation allowance ) ) Net deferred tax assets $ — $ — The valuation allowance increased by $20,232,000, 15,076,000 and $12,193,000 during the years ended December 31, 2016, 2015 and 2014, respectively. As of December 31, 2016, the Company had federal net operating loss carryforwards of approximately $219,087,000, which begin to expire in 2027, and state net operating loss carryforwards of approximately $161,812,000, which begin to expire in 2017. As of December 31, 2016, the Company had federal research and development credit carryforwards of approximately $2,469,000, which expire in the years 2027 through 2035, and state research and development credit carryforwards of approximately $2,651,000. The state research and development credit can be carried forward indefinitely. Federal and state tax laws impose substantial restrictions on the utilization of the net operating loss, and credit carryforwards in the event of an ownership change as defined in Section 382 of the Internal Revenue Code. Accordingly, the Company’s ability to utilize these carryforwards may be limited as a result of such ownership change. Such a limitation could result in the expiration of carryforwards before they are utilized. The Company had unrecognized tax benefits of approximately $1,536,000 and $3,902,000, as of December 31, 2016 and 2015, of which $1,266,000 and $2,792,000, respectively, would affect the effective tax rate if recognized, before consideration of the valuation allowance. A reconciliation of the unrecognized tax benefits from January 1, 2014 through December 31, 2016 is as follows (in thousands): As of December 31, 2016 2015 2014 Balance at beginning of year $ $ $ Increase/decrease based on the tax positions in the current year ) Additions for tax positions of prior years — Balance at end of year $ $ $ The Company does not expect a significant change to its unrecognized tax benefits over the next twelve months. The unrecognized tax benefits may increase or change during the next twelve months for items that arise in the ordinary course of business. The Company files income tax returns in the U.S. federal jurisdiction and various state jurisdictions. In the normal course of business, the Company is subject to examination by taxing authorities throughout the nation. The Company is not currently under audit by the Internal Revenue Service or other similar state and local authorities. All tax years remain open to examination by major taxing jurisdictions to which the Company is subject.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2016
Related Party Transactions
Related Party Transactions	15. Related-Party Transactions During the years ended December 31, 2016, 2015 and 2014, the Company purchased marketing services from Recreation, Inc., a brand strategy and design agency headquartered in San Francisco, California for $697,000, $1,016,000 and $984,000, respectively. John D. Simpson, the Company’s Senior Vice President of Sales, was the Chief Executive Officer of Recreation, Inc. until March 2015 and is the son of Dr. John B. Simpson, the Company’s founder and the Executive Chairman of the Board of Directors. As of December 31, 2016 and 2015, amounts due to Recreation, Inc., included in accounts payable and accrued liabilities, were $6,000 and $76,000, respectively. From October 2013 through July 2014, the Company entered into convertible notes with certain investors, including existing stockholders, some members of the Board of Directors and their affiliated companies and some members of management for a total aggregate principal amount of $18,192,000 (Note 8) and issued warrants to purchase shares of the Company’s common stock at an exercise price of $12.60 per share. The issuance of $5,122,000 of the total aggregate principal amount of the convertible notes was considered a related-party transaction. In September 2015, the Company repaid all amounts outstanding under the convertible notes. As of December 31, 2016 and 2015, the carrying value of the related-party convertible notes was none. For the years ended December 31, 2016, 2015 and 2014, the Company recognized none, $388,000 and $1,021,000, respectively, of interest expense related to the related-party convertible notes within interest expense in the Company’s statements of operations and comprehensive loss. In April 2015, the Company entered into an agreement with Chansu Consulting, LLC (“Chansu”) to provide consulting services related to regulatory affairs. The General Partner of Chansu is the son-in-law of Dr. John B. Simpson, the Company’s founder and the Executive Chairman of the Board of Directors. For the year ended December 31, 2016 and 2015, Chansu provided regulatory consulting services of $3,000 and $17,000, respectively. As of December 31, 2016 and 2015, there were no amounts due to Chansu included in accounts payable and accrued liabilities. In October 2015, the Company entered into an agreement with Consensys Imaging Service (“Consensys”) to provide field engineers to assist the Company with the installation, service and maintenance of its Lightbox consoles. Jeffrey M. Soinski, the Company’s President, Chief Executive Officer and a member of its Board of Directors is also a member of the Board of Directors of Consensys. For the year ended December 31, 2016 and 2015, Consensys provided services of $123,000 and none, respectively. As of December 31, 2016 and 2015, amounts due to Consensys included in accounts payable and accrued liabilities, were $20,000 and none, respectively.

401(k) Plan

401(k) Plan	12 Months Ended
	Dec. 31, 2016
401(k) Plan
401(k) Plan	16. 401(k) Plan The Company has a qualified retirement plan under section 401(k) of the Internal Revenue Code (“IRC”) under which participants may contribute up to 90% of their eligible compensation, subject to maximum deferral limits specified by the IRC. The Company may make a discretionary matching contribution to the 401(k) plan, and may make a discretionary employer contribution to each eligible employee each year. Eligible employees vest in the Company’s contributions over a graded four year schedule. To date, the Company has made no contributions to the 401(k) plan.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2016
Subsequent Events
Subsequent Events	17. Subsequent Events 2015 Equity Incentive Plan In January 2017, the number of shares of common stock authorized for issuance under the 2015 Plan was automatically increased by 1,188,801shares, which was ratified by the Company’s Board of Directors. 2015 Employee Stock Purchase Plan In January 2017, the number of shares of common stock authorized for issuance under the 2015 ESPP was automatically increased by 356,640 shares, which was ratified by the Company’s Board of Directors.

Selected Quarterly Financial In

Selected Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2016
Selected Quarterly Financial Information (Unaudited)
Selected Quarterly Financial Information (Unaudited)	18. Selected Quarterly Financial Information (Unaudited) The following table represents certain unaudited quarterly information for the eight quarters ended December 31, 2016. This data has been derived from unaudited financial statements that, in the opinion of the Company’s management, include all adjustments, consisting only of normal recurring adjustments, necessary for a fair presentation of such information when read in conjunction with the Company’s annual audited financial statements and notes thereto appearing elsewhere in this report. These operating results are not necessarily indicative of results for any future period (in thousands, except per share data): Three Months Ended Three Months Ended Mar 31, Jun 30, Sep 30, Dec 31, Mar 31, Jun 30, Sep 30, Dec 31, 2016 2016 2016 2016 2015 2015 2015 2015 Revenues $ $ $ $ $ $ $ $ Gross profit Operating expenses Net loss ) ) ) ) ) ) ) ) Net loss per share attributable to common stockholders, basic and diluted $ ) $ ) $ ) $ ) $ ) $ ) $ ) $ )

Summary of Significant Accoun25

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation On January 14, 2015, the Company’s Board of Directors approved an amendment to the Company’s amended and restated certificate of incorporation to effect a 1-for-45 reverse stock split of the Company’s common stock and convertible preferred stock. The par value of the common stock and convertible preferred stock was not adjusted as a result of the reverse stock split. All common stock, convertible preferred stock, stock options and warrants, and per share amounts in the financial statements have been retroactively adjusted for all periods presented to give effect to the reverse stock split. The reverse stock split was effected on January 28, 2015. The financial statements have been prepared in accordance with United States generally accepted accounting principles (“U.S. GAAP”) and pursuant to the rules and regulations of the United States Securities and Exchange Commission (“SEC”).
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts and disclosures reported in the financial statements. Management uses significant judgment when making estimates related to its common stock valuation and related stock-based compensation, the valuation of the common stock warrants, the valuation of compound embedded derivatives, provisions for doubtful accounts receivable and excess and obsolete inventories, clinical trial accruals, and its reserves for sales returns and warranty costs. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results may ultimately materially differ from these estimates and assumptions.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company has evaluated the estimated fair value of its financial instruments as of December 31, 2016 and 2015. Financial instruments consist of cash and cash equivalents, accounts receivable and payable, and other current liabilities and borrowings. The carrying amounts of cash and cash equivalents, accounts receivable and payable, and other current liabilities approximate their respective fair values because of the short-term nature of those instruments. Based upon the borrowing terms and conditions currently available to the Company, the carrying values of the borrowings approximate their fair value. Fair value accounting was applied to the warrant liabilities and embedded derivatives. No warrant liabilities or embedded derivatives were outstanding as of December 31, 2016 and 2015.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity of three months or less at the time of purchase to be cash equivalents. Cash equivalents are considered available-for-sale marketable securities and are recorded at fair value, based on quoted market prices. As of December 31, 2016 and 2015, the Company’s cash equivalents are entirely comprised of investments in money market funds. Any related unrealized gains and losses are recorded in other comprehensive income (loss) and included as a separate component of stockholders’ equity (deficit). There were no unrealized gains and losses as of December 31, 2016 and 2015. Any realized gains and losses and interest and dividends on available-for-sale securities are included in interest income or expense and computed using the specific identification cost method.
Restricted Cash	Restricted Cash At December 31, 2014, a deposit of $255,000 was restricted from withdrawal. The restricted cash secured obligations of the Company associated with its corporate credit card. The restricted deposit account was included in prepaid expenses and other current assets. During 2015, the Company was no longer required to secure its corporate card obligations. The release of the restriction against the Company’s cash was included within investing activities on its statement of cash flows for the year ended December 31, 2015.
Concentration of Credit Risk, and Other Risks and Uncertainties	Concentration of Credit Risk, and Other Risks and Uncertainties Financial instruments that potentially subject the Company to credit risk consist of cash and cash equivalents and accounts receivable to the extent of the amounts recorded on the balance sheets. The Company’s policy is to invest in cash and cash equivalents, consisting of money market funds. These financial instruments are held in Company accounts at one financial institution. The counterparties to the agreements relating to the Company’s investments consist of financial institutions of high credit standing. The Company provides for uncollectible amounts when specific credit problems arise. Management’s estimates for uncollectible amounts have been adequate, and management believes that all significant credit risks have been identified at December 31, 2016 and 2015. The Company’s accounts receivable are due from a variety of health care organizations in the United States and select international markets. At December 31, 2016 and 2015, there were none and one, respectively, of the Company’s customers that represented 10% or more of the Company’s accounts receivable. For the years ended December 31, 2016, 2015 and 2014, there were no customers that represented 10% or more of revenues. Disruption of sales orders or a deterioration of financial condition of its customers would have a negative impact on the Company’s financial position and results of operations. The Company manufactures its commercial products in-house, including Pantheris and the Ocelot family of catheters. Certain of the Company’s product components and sub-assemblies continue to be manufactured by sole suppliers. Disruption in component or sub-assembly supply from these manufacturers or from in-house production would have a negative impact on the Company’s financial position and results of operations. The Company is subject to certain risks, including that its devices may not be approved or cleared for marketing by governmental authorities or be successfully marketed. There can be no assurance that the Company’s products will achieve widespread adoption in the marketplace, nor can there be any assurance that existing devices or any future devices can be developed or manufactured at an acceptable cost and with appropriate performance characteristics. The Company is also subject to risks common to companies in the medical device industry, including, but not limited to, new technological innovations, dependence upon third-party payors to provide adequate coverage and reimbursement, dependence on key personnel and suppliers, protection of proprietary technology, product liability claims, and compliance with government regulations. Existing or future devices developed by the Company may require approvals or clearances from the FDA or international regulatory agencies. In addition, in order to continue the Company’s operations, compliance with various federal and state laws is required. If the Company were denied or delayed in receiving such approvals or clearances, it may be necessary to adjust operations to align with the Company’s currently approved portfolio. If clearance for the products in the current portfolio were withdrawn by the FDA, this may have a material adverse impact on the Company.
Accounts Receivable	Accounts Receivable Trade accounts receivable are recorded at the invoiced amount and do not bear interest. The allowance for doubtful accounts is the Company’s best estimate of the amount of probable credit losses in the Company’s existing accounts receivable. The Company determines the allowance for doubtful accounts based upon an aging of accounts receivable, historical experience, and management judgment. Accounts receivable balances are reviewed individually for collectability. To date, the Company has not experienced significant credit-related losses.
Inventories	Inventories Inventories are valued at the lower of cost or market. Cost is determined using the first-in, first-out method for all inventories. The Company’s policy is to write down inventory that has expired or become obsolete, inventory that has a cost basis in excess of its expected net realizable value, and inventory in excess of expected requirements. The estimate of excess quantities is subjective and primarily dependent on the estimates of future demand for a particular product. If the estimate of future demand is too high, the Company may have to increase the reserve for excess inventory for that product and record a charge to the cost of revenues. Inventory used in clinical trials is expensed at the time of production and recorded as research and development expense.
Property and equipment	Property and equipment Property and equipment are recorded at cost. Repairs and maintenance costs are expensed as incurred. Depreciation and amortization are calculated using the straight-line method over the estimated useful lives of the assets of three to five years. Depreciation expense includes the amortization of assets acquired under capital leases and equipment located at customer sites. Equipment held by customers is comprised of the Lightboxes located at customer sites under a lease or placement agreement and are recorded at cost. Upon execution of a lease or placement agreement, the related equipment is reclassified from inventory to the property and equipment account. Depreciation expense for equipment held by customers is recorded as a component of cost of revenues. Leasehold improvements and assets recorded under capital leases are amortized using the straight-line method over the shorter of the lease term or estimated useful economic life of the asset.
Deferred Offering Costs	Deferred Offering Costs Deferred offering costs, which primarily consist of direct incremental legal and accounting fees relating to an offering of equity securities, were capitalized. As of December 31, 2016, there we no deferred offering costs capitalized in other assets on the balance sheet. Deferred offering costs of $29,000 were capitalized as of December 31, 2015.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company reviews long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. If indicators of impairment exist, an impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are less than its carrying amount. Impairment, if any, is measured as the amount by which the carrying amount of the long-lived asset exceeds its fair value. The Company has not recorded any impairment of long-lived assets since inception through December 31, 2016.
Convertible Preferred Stock	Convertible Preferred Stock Prior to its IPO the Company recorded its convertible preferred stock at fair value on the dates of issuance, net of issuance costs and classified the convertible preferred stock outside of stockholders’ equity (deficit) on the balance sheets as events triggering the liquidation preferences were not solely within the Company’s control. Upon the closing of the IPO, all shares of convertible preferred stock then outstanding converted into an aggregate of 6,967,925 shares of common stock resulting in the reclassification of $137,626,000 from outside of stockholders’ equity (deficit) to additional paid-in capital.
Warrant Liability and Embedded Derivative Instruments	Warrant Liability and Embedded Derivative Instruments The Company accounts for its warrants for shares of common stock in accordance with the accounting guidance for derivatives. The accounting guidance provides a two-step model to be applied in determining whether a financial instrument is indexed to an entity’s own stock and, therefore, qualifies for a scope exception. The two-step model requires a contract for a financial instrument to be both (1) indexed to the entity’s own stock and (2) classified in the stockholders’ equity (deficit) section of the balance sheet. If a financial instrument qualifies for a scope exception, it would not be considered a derivative financial instrument. As the price per share of the common stock warrants issued with the convertible notes was not fixed until the issuance of the Series E Convertible Preferred Stock in September 2014, these warrants were initially classified as a derivative liability. As a derivative liability, the warrants were initially recorded at fair value and were subject to remeasurement at each balance sheet date until September 2014. Any change in fair value as a result of a remeasurement was recognized as a component of other income (expense), net in the statements of operations and comprehensive loss. The Company re-evaluated the terms of the common stock warrants issued with the convertible notes after the issuance of the Series E Convertible Preferred Stock in September 2014 and determined that they then met the first criterion of the two-step model. Accordingly, the associated current fair value of the warrant liability was reclassified to additional paid-in capital in the stockholders’ equity (deficit) section of the balance sheet at that time, thus satisfying the second criterion of the two-step model. The Company issued convertible notes in 2013 and 2014 that included features which were determined to be embedded derivatives requiring bifurcation and separate accounting. Prior to their extinguishment in September 2015, the Company recorded a compound derivative asset or liability related to redemption features embedded within its outstanding convertible notes. The embedded derivatives were initially recorded at fair value and are subject to remeasurement as of each balance sheet date. Any change in fair value is recognized as a component of other income (expense), net in the statements of operations and comprehensive loss. In September 2015, the Company repaid the outstanding convertible notes and accrued interest obligations in their entirety. Accordingly, the associated current fair value of the embedded derivative asset was expensed as a component of other income (expense), net in the statements of operations and comprehensive loss at that time
Revenue Recognition	Revenue Recognition The Company’s revenues are derived from (1) sale of its Lightbox (2) sale of disposables, which consist of catheters and accessories, and (3) sale of customer service contracts. The Company sells its products directly to hospitals and medical centers as well as through distributors. The Company recognizes revenue in accordance with Accounting Standards Codification (“ASC”) 605-10, Revenue Recognition, when persuasive evidence of an arrangement exists, the fee is fixed or determinable, collection of the fee is probable and delivery has occurred. For all sales, the Company uses either a signed agreement or a binding purchase order as evidence of an arrangement. The Company’s revenue recognition policies generally result in revenue recognition at the following points: 1. Lightbox sales: The Company sells its products directly to hospitals and medical centers. Provided all other criteria for revenue recognition have been met, the Company recognizes revenue for Lightbox sales directly to end customers when delivery and acceptance occurs, which is defined as receipt by the Company of an executed form by the customer acknowledging that the training and installation process is complete. 2. Sales of disposables: Disposable revenues consist of sales of the Company’s catheters and accessories and are recognized when the product has shipped, risk of loss and title has passed to the customer and collectability is reasonably assured. 3. Service revenue: Service revenue is recognized ratably over the term of the service period. To date service revenue has been insignificant. The Company offers its customers the ability to purchase or lease its Lightbox. In addition, the Company provides a Lightbox under a limited commercial evaluation program to allow certain strategic accounts to install and utilize the Lightbox for a limited trial period of three to six months. When a Lightbox is placed under a lease agreement or under a commercial evaluation program, the Company retains title to the equipment and it remains capitalized on its balance sheet under property and equipment. Depreciation expense on these placed Lightboxes is recorded to cost of revenues on a straight-line basis. The costs to maintain these placed Lightboxes are charged to cost of revenues as incurred. The Company evaluates its lease and commercial evaluation program agreements and accounts for these contracts under the guidance in ASC 840, Leases and ASC 605-25, Revenue Recognition—Multiple Element Arrangements . The guidance requires arrangement consideration to be allocated between a lease deliverable and a non-lease deliverable based upon the relative selling-price of the deliverables, using a specific hierarchy. The hierarchy is as follows: vendor-specific objective evidence of fair value of the respective elements, third-party evidence of selling price, or best estimate of selling price (“BESP”). The Company allocates arrangement consideration using BESP. The Company assessed whether the embedded lease is an operating lease or sales-type lease. Based on the Company’s assessment of the guidance and given that any payments under the lease agreements are dependent upon contingent future sales, it was determined that collectability of the minimum lease payments is not reasonably predictable. Accordingly, the Company concluded the embedded lease did not meet the criteria of a sales-type lease and accounts for it as an operating lease. The Company recognizes revenue allocated to the lease as the contingent disposable product purchases are delivered and are included in revenues within the statement of operations and comprehensive loss. For sales through distributors, the Company recognizes revenue when title to the product and the risk of loss transfers from the Company to the distributor. The distributors are responsible for all marketing, sales, training and warranty in their respective territories. The standard terms and conditions contained in the Company’s distribution agreements do not provide price protection or stock rotation rights to any of its distributors. In addition, its distributor agreements do not allow the distributor to return or exchange products, and the distributor is obligated to pay the Company upon invoice regardless of its ability to resell the product. The Company estimates reductions in revenue for potential returns of products by customers. In making such estimates, management analyzes historical returns, current economic trends and changes in customer demand and acceptance of its products. The Company expenses shipping and handling costs as incurred and includes them in the cost of revenues. In those cases where the Company bills shipping and handling costs to customers, it will classify the amounts billed as a component of revenue.
Cost of Revenues	Cost of Revenues Cost of revenues consists primarily of manufacturing overhead costs, material costs and direct labor. A significant portion of the Company’s cost of revenues currently consists of manufacturing overhead costs. These overhead costs include the cost of quality assurance, material procurement, inventory control, facilities, equipment and operations supervision and management. Cost of revenues also includes depreciation expense for the Lightboxes under lease agreements and certain direct costs such as shipping costs.
Product Warranty Costs	Product Warranty Costs The Company typically offers a one-year warranty for parts and labor on its products commencing upon the transfer of title and risk of loss to the customer. The Company accrues for the estimated cost of product warranties upon invoicing its customers, based on historical results. Warranty costs are reflected in the statement of operations and comprehensive loss as a cost of revenues. The warranty obligation is affected by product failure rates, material usage and service delivery costs incurred in correcting a product failure. Should actual product failure rates, material usage or service delivery costs differ from these estimates, revisions to the estimated warranty liability would be required. Periodically the Company assesses the adequacy of its recorded warranty liabilities and adjusts the amounts as necessary. Warranty provisions and claims are summarized as follows (in thousands): Year Ended December 31, 2016 2015 2014 Balance beginning of year $ $ $ Warranty provision Usage/Release ) ) ) Balance end of year $ $ $
Research and Development	Research and Development The Company expenses research and development costs as incurred. Research and development expenses include personnel and personnel-related costs, costs associated with pre-clinical and clinical development activities, and costs for prototype products that are manufactured prior to market approval for that prototype product; internal and external costs associated with the Company’s regulatory compliance and quality assurance functions, including the costs of outside consultants and contractors that assist in the process of submitting and maintaining regulatory filings; and overhead costs, including allocated facility and related expenses.
Clinical Trials	Clinical Trials The Company accrues and expenses costs for its clinical trial activities performed by third parties, including clinical research organizations and other service providers, based upon estimates of the work completed over the life of the individual study in accordance with associated agreements. The Company determines these estimates through discussion with internal personnel and outside service providers as to progress or stage of completion of trials or services pursuant to contracts with clinical research organizations and other service providers and the agreed-upon fee to be paid for such services.
Advertising Costs	Advertising Costs The Company expenses advertising costs as incurred. Advertising costs include design and production costs, including website development, physician and patient testimonial videos, written media campaigns, and other items. Advertising costs of approximately $526,000, $515,000 and $720,000 were expensed during the years ended December 31, 2016, 2015 and 2014, respectively.
Common Stock Valuation and Stock-Based Compensation	Common Stock Valuation and Stock-Based Compensation Stock-based compensation for the Company includes amortization related to all stock options, restricted stock units (“RSUs”) and shares issued under the employee stock purchase plan, based on the grant-date estimated fair value. The fair value of stock options is estimated on the date of grant using the Black-Scholes option pricing model and recognized as expense on a straight-line basis over the vesting period of the award. The Company measures the fair value of RSUs using the closing stock price of a share of the Company’s common stock on the grant date and is recognized as expense on a straight-line basis over the vesting period of the award. Because noncash stock-based compensation expense is based on awards ultimately expected to vest, it is reduced by an estimate for future forfeitures. The Company estimates a forfeiture rate for its stock options and RSUs based on an analysis of its actual forfeiture experience and other factors. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from estimates. Prior to the Company’s IPO in January 2015, the fair value of the Company’s common stock was determined by its Board of Directors with assistance from management and third-party valuation specialists. Management’s approach to estimate the fair value of the Company’s common stock is consistent with the methods outlined in the American Institute of Certified Public Accountants Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation . Management considered several factors to estimate enterprise value, including significant milestones that would generally contribute to increases in the value of the Company’s common stock. Following the closing of the Company’s IPO, the fair value of its common stock is determined based on the closing price of its common stock on The NASDAQ Global Market.
Foreign Currency	Foreign Currency The Company records net gains and losses resulting from foreign exchange transactions as a component of foreign currency exchange losses in other income (expense), net. During the years ended December 31, 2016, 2015 and 2014, the Company recorded $12,000, $18,000 and $21,000 of foreign currency exchange net losses, respectively.
Income Taxes	Income Taxes The Company utilizes the liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on differences between financial reporting and tax reporting bases of assets and liabilities and are measured using enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized. The Company’s policy is to record interest and penalties on uncertain tax positions as income tax expense when they occur. During the years ended December 31, 2016, 2015 and 2014, the Company did not recognize accrued interest or penalties related to unrecognized tax benefits.
Net Loss per Share Attributable to Common Stockholders	Net Loss per Share Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding during the period, without consideration for potential dilutive common shares. Diluted net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of shares of common stock and dilutive potential shares of common stock outstanding during the period. Any common stock shares subject to repurchase are excluded from the calculations as the continued vesting of such shares is contingent upon the holders’ continued service to the Company. For the computation of net loss per share attributable to common stockholders, common stock shares subject to repurchase of none, none and 583 were excluded from the calculations as of December 31, 2016, 2015 and 2014, respectively. Since the Company was in a loss position for all periods presented, basic net loss per share attributable to common stockholders is the same as diluted net loss per share attributable to common stockholders as the inclusion of all potentially dilutive common shares would have been anti-dilutive. Prior to its IPO in January 2015, the Company calculated its basic and diluted net loss per share attributable to common stockholders in conformity with the two-class method required for companies with participating securities. The shares of the Company’s convertible preferred stock participated in any dividends declared by the Company and were therefore considered to be participating securities. The Company allocates no loss to participating securities because they have no contractual obligation to share in the losses of the Company. Net loss per share attributable to common stockholders was determined as follows (in thousands, except per share data): Year Ended December 31, 2016 2015 2014 Net loss $ ) $ ) $ ) Adjustment to net loss resulting from convertible preferred stock modification — ) — Net loss attributable to common stockholders $ ) $ ) $ ) Weighted average common stock outstanding Net loss attributable to common stockholders per share, basic and diluted $ ) $ ) $ ) In addition to the outstanding convertible notes as of December 31, 2014 (Note 8), the following potentially dilutive securities outstanding have been excluded from the computations of diluted weighted average shares outstanding because such securities have an antidilutive impact due to losses reported: December 31, 2016 2015 2014 Convertible preferred stock outstanding — — Common stock options Unvested restricted stock units — Common stock warrants
Comprehensive Loss	Comprehensive Loss For the years ended December 31, 2016, 2015 and 2014, there was no difference between comprehensive loss and the Company’s net loss.
Segment and Geographical Information	Segment and Geographical Information The Company operates and manages its business as one reportable and operating segment. The Company’s chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. Primarily all of the Company’s long-lived assets are based in the United States. Long-lived assets are comprised of property and equipment. For the years ended December 31, 2016, 2015 and 2014, 96%, 98% and 99%, respectively, of the Company’s revenues, were in the United States, based on the shipping location of the external customer.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”), jointly with the International Accounting Standards Board, issued a comprehensive new standard on recognition from contracts with customers. The standard’s core principle is that a reporting entity will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The standard will become effective for the Company beginning in the first quarter of 2018. Early application would be permitted in 2017. Entities would have the option of using either a full retrospective or a modified retrospective approach to adopt this new guidance. The Company currently plans to adopt this accounting standard in the first quarter of fiscal year 2018 using the modified retrospective approach, with the cumulative effect being recorded within retained earnings on January 1, 2018. The guidance requires an entity to recognize revenue in an amount that reflects the consideration to which an entity expects to be entitled in exchange for the transfer of goods or services. The guidance also requires expanded disclosures relating to the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. Additionally, qualitative and quantitative disclosures are required about customer contracts, significant judgments and changes in judgments, and assets recognized from the costs to obtain or fulfill a contract. The Company has not completed its assessment of the adoption on its financial statements. In July 2015, the FASB issued an accounting standard which applies to all inventory that is measured using methods other than last-in, first-out or the retail inventory method, including inventory that is measured using first-in, first-out or average cost. The standard requires entities to measure inventory at the lower of cost and net realizable value, defined as the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The guidance is effective for public entities for fiscal years beginning after December 15, 2016, and interim periods with fiscal years beginning after December 15, 2017. The amendments in the standard should be applied prospectively with earlier application permitted as of the beginning of an interim or annual reporting period. The Company does not expect the adoption of this standard to have a material effect on its financial statements. In February 2016, the FASB issued ASU No. 2016-02, “Leases” (ASU 2016-02), which increases transparency and comparability among organizations by recognizing all lease transactions (with terms in excess of 12 months) on the balance sheet as a lease liability and a right-of-use asset (as defined). This guidance is effective for annual reporting periods beginning after December 15, 2018, and interim periods within those annual periods, using a modified retrospective approach, and early adoption is permitted. The Company is evaluating the impact of the adoption of this standard on its financial statements. The Company does expect that the adoption will increase its lease assets and correspondingly increase its lease liabilities. In March 2016, the FASB issued ASU No. 2016-09, Compensation — Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting, which simplifies several aspects of the accounting for employee share-based payments, including income tax consequences, application of award forfeitures to expense, classification on the statement of cash flows, and classification of awards as either equity or liabilities. This guidance is effective for annual reporting periods beginning after December 15, 2016, and interim periods within those annual periods. The Company plans to adopt this new standard on January 1, 2017 and do not expect a material impact on its financial statements given the full valuation allowance position on its deferred tax assets.

Summary of Significant Accoun26

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
Summary of Significant Accounting Policies
Summary of warranty provisions and claims	Warranty provisions and claims are summarized as follows (in thousands): Year Ended December 31, 2016 2015 2014 Balance beginning of year $ $ $ Warranty provision Usage/Release ) ) ) Balance end of year $ $ $
Schedule of net loss per share attributable to common stockholders	Net loss per share attributable to common stockholders was determined as follows (in thousands, except per share data): Year Ended December 31, 2016 2015 2014 Net loss $ ) $ ) $ ) Adjustment to net loss resulting from convertible preferred stock modification — ) — Net loss attributable to common stockholders $ ) $ ) $ ) Weighted average common stock outstanding Net loss attributable to common stockholders per share, basic and diluted $ ) $ ) $ )
Schedule of outstanding securities excluded from the computation due to antidilutive impact	December 31, 2016 2015 2014 Convertible preferred stock outstanding — — Common stock options Unvested restricted stock units — Common stock warrants

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value Measurements
Summary of changes in the estimated fair value of the common stock warrant liability	Accordingly, the expense in the table below includes changes in fair value due in part to observable factors that are part of the Level 3 methodology (in thousands): Year Ended December 31, 2016 2015 2014 Fair value - beginning of year $ — $ — $ ) Issuance of warrants — — — Change in fair value recorded in other income (expense), net — — ) Reclass of warrant liability to additional paid-in capital — — Fair value - end of year $ — $ — $ —
Schedule of assumptions used in determining the fair value of the common stock warrants	The following table summarizes these various assumptions as of September 2, 2014, the date the price per share of the common stock warrants was fixed: September 2, 2014 Time to liquidity (years) Expected volatility % Discounted cash flow rate % Risk-free interest rate % Marketability discount rate %
Summary of changes in the estimated fair value of the compound embedded derivative	The income (expense) in the table below includes changes in fair value due in part to observable factors that are part of the Level 3 methodology (in thousands): Year Ended December 31, 2016 2015 2014 Fair value of asset (liability) - beginning of year $ — $ $ ) Issuance of convertible notes — — — Change in fair value recorded in other income (expense), net — Reversal of fair value recorded in other income (expense), net — ) — Fair value of asset (liability) - end of year $ — $ — $
Monte Carlo Simulation model
Fair Value Measurements
Schedule of assumptions used to determine the fair value of the compound derivative	The following table summarizes these various assumptions as of December 31, 2014: Year Ended 2014 Equity financing in 2014 % Equity financing in 2015 % Liquidation % Initial public offering % Change of control %
Black-Derman-Toy model
Fair Value Measurements
Schedule of assumptions used to determine the fair value of the compound derivative	The following table summarizes these various assumptions as of September 22, 2015, the date of extinguishment: September 22, 2015 Time to first call option (years) — Credit spread % Expected volatility %

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2016
Inventories
Schedule of inventories	Inventories consisted of the following (in thousands): December 31, 2016 2015 Raw materials $ $ Work-in-process — Finished products Total inventories $ $

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2016
Property and Equipment, Net
Schedule of property and equipment, net	Property and equipment, net, consisted of the following (in thousands): December 31, 2016 2015 Computer software $ $ Computer equipment Machinery and equipment Furniture and fixtures Leasehold improvements Equipment held by customers Less: Accumulated depreciation and amortization ) ) Add: Construction-in-progress $ $

Accrued Expenses and Other Cu30

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2016
Accrued Expenses and Other Current Liabilities
Summary of accrued expenses and other current liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): December 31, 2016 2015 Accrued interest payable $ $ Accrued professional services Accrued travel expenses Accrued sales, use and other taxes Accrued warranty Sales return allowance Accrued clinical trial costs Other accrued liabilities $ $

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
	Dec. 31, 2016
Credit Agreement
Debt Instrument [Line Items]
Schedule of principal and PIK payments under the Loan Agreement	As of December 31, 2016, principal and PIK payments under the Loan Agreement follows (in thousands): Period Ending December 31, Principal and PIK 2017 $ — 2018 — 2019 2020 2021 Add: Accretion of closing fees Add: PIK Less: Amount representing debt financing costs ) Borrowings $

Capital Leases (Tables)

Capital Leases (Tables)	12 Months Ended
	Dec. 31, 2016
Capital Leases
Schedule of future minimum lease payments	The future minimum lease payments as of December 31, 2016, are as follows (in thousands): Future Minimum Period ending December 31, Lease Payments 2017 $ 2018 2019 Total minimum payments Less: Amount representing future interest Present value of minimum lease payments $

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies
Schedule of future minimum lease payments	The future aggregate minimum lease payments as of December 31, 2016, are as follows (in thousands): Future Minimum Year ending December 31, Lease Payments 2017 $ 2018 2019 Total minimum lease payments $

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit) (Tables)	12 Months Ended
	Dec. 31, 2016
Stockholders' Equity (Deficit)
Summary of option activity	Options Outstanding Weighted Aggregate Number of Average Intrinsic Value Shares Exercise Price (in thousands) Balance at December 31, 2013 $ $ — Options granted $ Options exercised ) $ Options cancelled ) $ Balance at December 31, 2014 $ $ Options granted $ Options exercised ) $ Options cancelled ) $ Balance at December 31, 2015 $ $ Options granted $ Options exercised ) $ Options cancelled ) $ Balance at December 31, 2016 $ $
Schedule of additional information related to the status of options	Options Outstanding and Vested as of December 31, 2016 Options Outstanding Options Vested Weighted Weighted Weighted Average Average Average Exercise Options Remaining Exercise Number Exercise Price Outstanding Contractual Life Price Exercisable Price $ $ — $ $ $ — $ $ $ $ $ $ $ $ $ $ $ $ — $ $ $ $ $ $ $ $ $ $ $ $ — $ $ $ — $ $ $ $ $ $ — $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $
Summary of RSU activity	Weighted Average Weighted Average Aggregate Number of Grant Date Remaining Intrinsic Value Shares Fair Value Contractual Term (in thousands) Awards outstanding at December 31, 2014 — $ — — $ — Awarded $ Awards outstanding at December 31, 2015 $ $ Awarded $ Released ) $ Forfeited ) $ Awards outstanding at December 31, 2016 $ $

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2016
Stock-Based Compensation
Schedule of fair value of employee stock options estimated at date of grant using the Black-Scholes valuation model	Year Ended December 31, 2016 2015 2014 Expected term (years) Expected volatility % % % Risk-free interest rate % % % Dividend rate — — —
Schedule of fair value of shares to be issued under the ESSP estimated using the Black-Scholes valuation model	Year Ended December 31, 2016 2015 Expected term (years) Expected volatility % % Risk-free interest rate % % Dividend rate — —
Schedule of noncash stock-based compensation expense relating to stock options, ESPP and RSUs	Total noncash stock-based compensation expense relating to the Company’s stock options, ESPP and RSUs recognized, before taxes, during the years ended December 31, 2016, 2015 and 2014, is as follows (in thousands): Year Ended December 31, 2016 2015 2014 Cost of revenues $ $ $ Research and development expenses Selling, general and administrative expenses $ $ $

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Taxes
Reconciliation of the statutory U.S. federal rate to the Company's effective tax rate	A reconciliation of the statutory U.S. federal rate to the Company’s effective tax rate is as follows (in thousands): Year Ended December 31, 2016 2015 2014 Tax at federal statutory rate $ ) $ ) $ ) State taxes, net of federal benefit — — Permanent differences Change in valuation allowance Research credits ) ) ) Other ) Provision for taxes $ — $ — $
Schedule of significant components of net deferred tax assets	Significant components of the Company’s net deferred tax assets as of December 31, 2016 and 2015 consist of the following (in thousands): As of December 31, 2016 2015 Deferred tax assets: Federal, state, and foreign net operating losses $ $ Research and other credits Fixed assets Interest Accruals and other Total deferred tax assets Less: Valuation allowance ) ) Net deferred tax assets $ — $ —
Reconciliation of unrecognized tax benefits	A reconciliation of the unrecognized tax benefits from January 1, 2014 through December 31, 2016 is as follows (in thousands): As of December 31, 2016 2015 2014 Balance at beginning of year $ $ $ Increase/decrease based on the tax positions in the current year ) Additions for tax positions of prior years — Balance at end of year $ $ $

Selected Quarterly Financial 37

Selected Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2016
Selected Quarterly Financial Information (Unaudited)
Schedule of unaudited quarterly information	These operating results are not necessarily indicative of results for any future period (in thousands, except per share data): Three Months Ended Three Months Ended Mar 31, Jun 30, Sep 30, Dec 31, Mar 31, Jun 30, Sep 30, Dec 31, 2016 2016 2016 2016 2015 2015 2015 2015 Revenues $ $ $ $ $ $ $ $ Gross profit Operating expenses Net loss ) ) ) ) ) ) ) ) Net loss per share attributable to common stockholders, basic and diluted $ ) $ ) $ ) $ ) $ ) $ ) $ ) $ )

Organization - Liquidity Matter

Organization - Liquidity Matters (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Organization
Accumulated deficit	$ 252,389	$ 196,261
Cash and cash equivalents	$ 36,096	$ 43,059	$ 12,316	$ 12,221

Organization - Public Offerings

Organization - Public Offerings (Details) - USD ($)	1 Months Ended			12 Months Ended
	Aug. 31, 2016	Feb. 28, 2015	Jan. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Feb. 03, 2016
Common stock and convertible preferred stock
Proceeds from public offerings, net of issuance costs				$ 36,583,000	$ 58,746,000
Maximum value of common stock offering under a shelf registration						$ 150,000,000
Conversion of Convertible Preferred Stock into Common Stock upon IPO | Convertible preferred stock outstanding
Common stock and convertible preferred stock
Amount reclassified from outside of stockholders' equity			$ 137,626,000
Common Stock | Conversion of Convertible Preferred Stock into Common Stock upon IPO
Common stock and convertible preferred stock
Number of shares issued for convertible preferred stock		6,967,925	6,967,925
Additional Paid-in Capital | Conversion of Convertible Preferred Stock into Common Stock upon IPO
Common stock and convertible preferred stock
Amount reclassified to additional paid-in-capital			$ 137,626,000
IPO | Common Stock
Common stock and convertible preferred stock
Issuance of stock, net (in shares)			5,000,000		5,000,000
Public offering price (in dollars per share)			$ 13
Net proceeds from initial public offering			$ 56,897,000
Underwriting discounts and commissions			4,550,000
Other offering expenses			$ 3,553,000
Sales Agreement with Cowen
Common stock and convertible preferred stock
Proceeds from public offerings, net of issuance costs				5,171,000
Underwriting discounts and commissions				$ 160,000
Maximum value of common stock offering under a shelf registration						$ 50,000,000
Sales Agreement with Cowen | Common Stock
Common stock and convertible preferred stock
Issuance of stock, net (in shares)				1,095,378
Public offering price (in dollars per share)				$ 4.87
Follow-On Public Offering | Common Stock
Common stock and convertible preferred stock
Issuance of stock, net (in shares)	9,857,800
Public offering price (in dollars per share)	$ 3.50
Proceeds from public offerings, net of issuance costs	$ 31,549,000
Underwriting discounts and commissions	2,415,000
Other offering expenses	$ 538,000
Underwriters' Option | Common Stock
Common stock and convertible preferred stock
Issuance of stock, net (in shares)	1,285,800

Summary of Significant Accoun40

Summary of Significant Accounting Policies - Reverse Stock Split, Fair Value, Cash (Details)	Jan. 14, 2015	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Summary of Significant Accounting Policies
Reverse stock split ratio	0.022
Fair Value of Financial Instruments
Warrant liabilities		$ 0	$ 0
Embedded derivatives outstanding		0	0
Cash and Cash Equivalents
Unrealized gains and losses on money market funds		$ 0	$ 0
Restricted Cash
Restricted cash				$ 255,000

Summary of Significant Accoun41

Summary of Significant Accounting Policies - Concentration Risk (Details) - Customer Concentration - customer	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounts Receivable
Concentration of Credit Risk, and Other Risks and Uncertainties
Number of customers above 10% concentration disclosure threshold	0	1
Revenues
Concentration of Credit Risk, and Other Risks and Uncertainties
Number of customers above 10% concentration disclosure threshold	0	0	0

Summary of Significant Accoun42

Summary of Significant Accounting Policies - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2016
Minimum
Property and equipment
Estimated useful life	3 years
Maximum
Property and equipment
Estimated useful life	5 years

Summary of Significant Accoun43

Summary of Significant Accounting Policies - Offering Costs and Convertible Stock (Details) - USD ($)	1 Months Ended
	Feb. 28, 2015	Jan. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Deferred Offering Costs
Deferred offering costs capitalized			$ 0	$ 29,000
Conversion of Convertible Preferred Stock into Common Stock upon IPO | Convertible preferred stock outstanding
Convertible Preferred Stock
Amount reclassified from outside of stockholders' equity		$ 137,626,000
Conversion of Convertible Preferred Stock into Common Stock upon IPO | Common Stock
Convertible Preferred Stock
Number of shares issued for convertible preferred stock	6,967,925	6,967,925
Conversion of Convertible Preferred Stock into Common Stock upon IPO | Additional Paid-in Capital
Convertible Preferred Stock
Amount reclassified to additional paid-in-capital		$ 137,626,000

Summary of Significant Accoun44

Summary of Significant Accounting Policies - Product Warranty, Advertising, Foreign Currency (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Product Warranty Costs
Warranty period	1 year
Changes in warranty provisions
Balance beginning of period	$ 70,000	$ 167,000	$ 105,000
Warranty provision	1,048,000	70,000	140,000
Usage/Release	(609,000)	(167,000)	(78,000)
Balance end of period	509,000	70,000	167,000
Advertising Costs
Advertising costs expensed	526,000	515,000	720,000
Foreign Currency
Gains (losses) on foreign currency exchange	$ (12,000)	$ (18,000)	$ 21,000

Summary of Significant Accoun45

Summary of Significant Accounting Policies - Loss Per Share (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Summary of Significant Accounting Policies
Common stock shares subject to repurchase, excluded from net loss per share calculations									0	0	583
Loss allocated to participating securities, basic									$ 0	$ 0	$ 0
Loss allocated to participating securities, diluted									0	0	0
Net Loss per Share
Net loss	$ (13,497,000)	$ (12,969,000)	$ (13,496,000)	$ (16,167,000)	$ (13,456,000)	$ (13,250,000)	$ (10,220,000)	$ (12,801,000)	(56,128,000)	(47,344,000)	(31,964,000)
Adjustment to net loss resulting from convertible preferred stock modification										(2,384,000)
Net loss attributable to common stockholders									$ (56,128,000)	$ (49,728,000)	$ (31,964,000)
Weighted average common stock outstanding (in shares)									16,574,000	11,362,000	241,000
Net loss attributable to common stockholders per share, basic and diluted (in dollars per share)	$ (0.58)	$ (0.73)	$ (1.06)	$ (1.28)	$ (1.07)	$ (1.08)	$ (0.83)	$ (1.53)	$ (3.39)	$ (4.38)	$ (132.63)
Comprehensive Loss
Difference between comprehensive loss and the Company's net loss									$ 0	$ 0	$ 0

Summary of Significant Accoun46

Summary of Significant Accounting Policies - Antidilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net Loss per Share
Anti-dilutive shares excluded from computations of diluted weighted average shares outstanding	6,074,304	5,643,434	9,825,428
Convertible preferred stock outstanding
Net Loss per Share
Anti-dilutive shares excluded from computations of diluted weighted average shares outstanding			5,262,728
Stock options
Net Loss per Share
Anti-dilutive shares excluded from computations of diluted weighted average shares outstanding	3,708,011	3,356,981	3,010,373
RSUs
Net Loss per Share
Anti-dilutive shares excluded from computations of diluted weighted average shares outstanding	214,176	92,946
Common stock warrants
Net Loss per Share
Anti-dilutive shares excluded from computations of diluted weighted average shares outstanding	2,152,117	2,193,507	1,552,327

Summary of Significant Accoun47

Summary of Significant Accounting Policies - Segment and Geographical (Details) - segment	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment and Geographical Information
Number of reportable segments	1
Number of operating segments	1
Revenues | Customer Concentration | UNITED STATES
Segment and Geographical Information
Percentage of revenue	96.00%	98.00%	99.00%

Fair Value Measurements - Trans

Fair Value Measurements - Transfers (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value Measurements
Transfer of assets and liabilities between fair value hierarchy levels	$ 0	$ 0	$ 0

Fair Value Measurements - Commo

Fair Value Measurements - Common Stock Warrants (Details) - Common Stock Warrants issued with Convertible Notes - USD ($)	Sep. 02, 2014	Sep. 30, 2014	Dec. 31, 2014
Changes in estimated fair value, financial instrument classified as Level 3
Fair value - beginning of period			$ (6,000)
Issuance of warrants		$ (1,000)
Change in fair value recorded in other income (expense), net			(28,000)
Reclass of warrant liability to additional paid-in capital			$ 34,000
Level 3
Assumptions used in determining fair value
Time to liquidity (years)	8 months 12 days
Expected volatility (as a percent)	45.00%
Discounted cash flow rate (as a percent)	23.00%
Risk-free interest rate (as a percent)	0.07%
Marketability discount rate (as a percent)	17.00%

Fair Value Measurements - Embed

Fair Value Measurements - Embedded Derivatives (Details) - Embedded derivatives in convertible notes - USD ($) $ in Thousands	Sep. 22, 2015	Dec. 31, 2015	Dec. 31, 2014
Changes in estimated fair value, financial instrument classified as Level 3
Fair value of asset (liability) - beginning of period		$ 231	$ (175)
Change in fair value recorded in other income (expense), net		835	406
Reversal of fair value recorded in other income (expense), net		$ (1,066)
Fair value of asset (liability) - end of period			$ 231
Level 3
Assumptions used in determining fair value
Equity financing in 2014 (as a percent)			100.00%
Equity financing in 2015 (as a percent)			14.30%
Liquidation (as a percent)			0.10%
Initial public offering (as a percent)			79.50%
Change of control (as a percent)			6.20%
Credit spread (as a percent)	17.60%
Expected volatility (as a percent)	40.00%

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Inventories
Raw materials	$ 5,706	$ 2,662
Work-in-process		372
Finished products	2,756	2,371
Total inventories	$ 8,462	$ 5,405

Property and Equipment, Net (De

Property and Equipment, Net (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property and Equipment, Net
Less: Accumulated depreciation and amortization	$ (6,389,000)	$ (5,044,000)
Property and equipment, net	4,555,000	2,822,000
Depreciation	1,506,000	1,300,000	$ 1,451,000
Amortization of capital leased assets	11,000	17,000	17,000
Computer software
Property and Equipment, Net
Property and equipment, gross	456,000	436,000
Computer equipment
Property and Equipment, Net
Property and equipment, gross	1,268,000	1,096,000
Machinery and equipment
Property and Equipment, Net
Property and equipment, gross	4,313,000	3,372,000
Furniture and fixtures
Property and Equipment, Net
Property and equipment, gross	636,000	578,000
Leasehold improvements
Property and Equipment, Net
Property and equipment, gross	679,000	655,000
Equipment held by customers
Property and Equipment, Net
Property and equipment, gross	3,475,000	1,718,000
Property and equipment, net	2,587,000	1,236,000
Depreciation recorded in cost of revenues	539,000	260,000	$ 378,000
Property and equipment, excluding construction-in-progress
Property and Equipment, Net
Property and equipment, gross	10,827,000	7,855,000
Construction-in-progress
Property and Equipment, Net
Property and equipment, gross	$ 117,000	$ 11,000

Accrued Expenses and Other Cu53

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accrued Expenses and Other Current Liabilities
Accrued interest payable	$ 1,220	$ 1,220
Accrued professional services	43	563
Accrued travel expenses	429	550
Accrued sales, use and other taxes	40	82
Accrued warranty	509	70
Sales return allowance	43	59
Accrued clinical trial costs	134	55
Other accrued liabilities	649	686
Total accrued expenses and other current liabilities	$ 3,067	$ 3,285

Borrowings - Loan Agreement wit

Borrowings - Loan Agreement with CRG (Details) - Loan Agreement - CRG - USD ($)	Sep. 22, 2015	Dec. 31, 2016	Oct. 27, 2016	Jun. 15, 2016	Dec. 31, 2015
Borrowings
Total borrowing capacity	$ 50,000,000
Amount borrowed		$ 40,000,000
Additional borrowing capacity if revenue milestones are achieved				$ 10,000,000
Period for interest-only payments	4 years
Period for equal quarterly installments of interest and principal	2 years
Fixed interest rate (as a percent)		12.50%
Interest rate, cash payment if electing PIK for the remaining amount (as a percent)		8.50%
Interest rate, eligible for payment-in-kind (as a percent)		4.00%
Beginning prepayment premium (as a percent)		5.00%
Annual decline in prepayment premium (as a percent)		1.00%
Prepayment premium after fifth year of loan (as a percent)		0.00%
Financing fee on each borrowing date (as a percent)		1.50%
Final facility fee (as a percent)		7.00%
Minimum cash and certain cash equivalents required to be maintained		$ 5,000,000
Target minimum revenue in 2015					$ 7,000,000
Target minimum revenue in 2016		18,000,000	$ 23,000,000
Target minimum revenue in 2017		40,000,000
Target minimum revenue in 2018		50,000,000
Target minimum revenue in 2019		60,000,000
Target minimum revenue in 2020 and in each year thereafter		$ 70,000,000
Revenue shortfall multiplier for cure right if minimum revenue targets are not achieved		2
First tranche, borrowed on September 22, 2015
Borrowings
Amount borrowed	$ 30,000,000
Second tranche, borrowed on June 15, 2016
Borrowings
Amount borrowed				$ 10,000,000

Borrowings - Repayment Schedule

Borrowings - Repayment Schedule (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Principal and PIK Loan Repayments
Borrowings	$ 41,289,000
Loan Agreement | CRG
Principal and PIK Loan Repayments
2,019	10,000,000
2,020	20,000,000
2,021	10,000,000
Total	40,000,000
Add: Accretion of closing fees	399,000
Add: PIK	1,809,000
Borrowings, before deducting debt financing costs	42,208,000
Less: Amount representing debt financing costs	(919,000)	$ (834,000)
Borrowings	$ 41,289,000

Borrowings - Securities Purchas

Borrowings - Securities Purchase and Debt Discount (Details)	Sep. 22, 2015USD ($)item$ / sharesshares	Dec. 31, 2015USD ($)shares	Dec. 31, 2016USD ($)$ / shares	Jun. 15, 2016USD ($)
Borrowings
Closing price (in dollars per share) | $ / shares			$ 3.70
Securities Purchase Agreement with CRG | Common Stock
Borrowings
Maximum amount that may be purchase under the agreement	$ 5,000,000
Shares issued during the period | shares	348,262	348,262
Price of shares issued (in dollars per share) | $ / shares	$ 14.357
Number of trading days for average closing price to determine price per share | item	10
Closing price (in dollars per share) | $ / shares	$ 13.97
Premium on shares issued (in dollars per share) | $ / shares	$ 0.387
Loan Agreement | CRG
Borrowings
Net debt discount		$ 834,000	$ 919,000
Loan Agreement | CRG | First tranche, borrowed on September 22, 2015
Borrowings
Net debt discount	$ 876,000
Direct financing fees	450,000
Other costs included in the debt discount	541,000
Allocation of common stock premium	$ 115,000
Loan Agreement | CRG | Second tranche, borrowed on June 15, 2016
Borrowings
Net debt discount				$ 275,000
Direct financing fees				150,000
Other costs included in the debt discount				$ 125,000

Borrowings - Credit Agreement w

Borrowings - Credit Agreement with PDL (Details) - Credit Agreement - PDL - USD ($)	Sep. 22, 2015	Apr. 18, 2013	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Borrowings
Maximum borrowing capacity		$ 40,000,000
Term Note
Borrowings
Amount borrowed		$ 20,000,000
Stated interest rate (as a percent)		12.00%
Period for interest-only payments		2 years 6 months
Period for convertibility of interest into additional loans		2 years
Interest rate, paid-in-kind (as a percent)			1.50%
Payoff amount	$ 21,363,000
Accrued interest	563,000
Final payment fee	200,000
Interest expense			$ 380,000	$ 2,785,000	$ 3,380,000
Assigned Interests (as a percent)		1.80%
Ongoing Assigned Interests
Borrowings
Reduced Assigned Interests upon prepayment (as a percent)			0.90%
Effective interest rate (as a percent)			20.40%
Net present value adjustment	$ 942,000
Aggregate accrual for Assigned Interest obligations			$ 1,463,000	$ 2,303,000

Convertible Notes (Details)

Convertible Notes (Details) - USD ($)	Oct. 29, 2013	Sep. 30, 2015	Jan. 31, 2015	Sep. 30, 2014	Nov. 30, 2013	Nov. 30, 2014	Jul. 31, 2014	Jul. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Convertible Notes
Outstanding notes and accrued interest converted into shares of preferred stock											$ 11,582,000
Loss on extinguishment of convertible notes										$ 86,000	1,234,000
Common Stock Warrants issued with Convertible Notes
Convertible Notes
Exercise price of warrants issued (in dollars per share)				$ 12.60			$ 12.60	$ 12.60
Number of shares of common stock for which warrants were issued				216,547
Fair value of warrants at issuance				$ 1,000
Number of warrants net exercised			149,288
Number of warrants exercised			24,403
Number of warrants expired			42,856
Common Stock Warrants issued with Convertible Notes | Maximum
Convertible Notes
Exercise price of warrants issued (in dollars per share)							$ 39.15	$ 39.15
Convertible Notes
Convertible Notes
Maximum aggregate principal amount	$ 25,000,000
Issuance of convertible notes					$ 13,472,000		$ 4,720,000
Minimum internal rate of return (as a percent)	20.00%
Conversion price as a percentage of the stock price paid by other investors	85.00%
Redemption price upon equity financing (as a percent)	125.00%
Carrying value of convertible notes and accrued interest prior to payoff		$ 9,867,000
Loss on extinguishment of convertible notes		$ 86,000
Interest expense									$ 0	$ 1,230,000	$ 2,633,000
Convertible Notes | Embedded derivatives in convertible notes
Convertible Notes
Fair value of embedded derivative liability recorded upon issuance	$ 179,000
Convertible Notes | Conversion of notes into Series E Convertible Preferred Stock
Convertible Notes
Outstanding notes and accrued interest converted into shares of preferred stock						$ 11,582,000
Loss on extinguishment of convertible notes						$ 1,234,000
Convertible Notes | Common Stock Warrants issued with Convertible Notes
Convertible Notes
Percentage of principal amount of debt used to calculate number of shares under warrant								15.00%
Convertible Notes | LIBOR
Convertible Notes
LIBOR period used to calculate interest rate	30 days
Percentage added to interest rate base per annum	6.00%

Capital Leases (Details)

Capital Leases (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Capital Leases
Aggregate amount of capital leases recorded within property and equipment, net	$ 39,000	$ 39,000
Future minimum lease payments
2,017	26,000
2,018	13,000
2,019	1,000
Total minimum payments	40,000
Less: Amount representing future interest	1,000
Present value of minimum lease payments	$ 39,000

Commitments and Contingencies -

Commitments and Contingencies - Leases (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Lease Commitments
Rent expense	$ 1,098,000	$ 938,000	$ 922,000
Annual minimum lease payments under non-cancelable future operating lease commitments
2,017	1,974,000
2,018	2,033,000
2,019	1,915,000
Total minimum lease payments	$ 5,922,000
Facility lease
Lease Commitments
Term of renewal provision	3 years
Lease incentives reflected as deferred rent	$ 369,000

Commitments and Contingencies61

Commitments and Contingencies - Purchase Obligation (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Purchase Obligations
Noncancellable commitments to suppliers for purchases	$ 3,542,000	$ 4,347,000

Commitments and Contingencies62

Commitments and Contingencies - Terminated Engagement Letter (Details) - Series E Convertible Preferred Stock	1 Months Ended	12 Months Ended
	Dec. 31, 2014USD ($)installment	Dec. 31, 2016USD ($)
Legal Proceedings
Transaction fee to former financial advisor		$ 650,000
Number of installments to pay transaction fee to former financial advisor | installment	4
Reimbursement to former financial advisor for out-of-pocket expenses	$ 35,000

Convertible Preferred Stock (De

Convertible Preferred Stock (Details) - shares	1 Months Ended
	Feb. 28, 2015	Jan. 31, 2015
Conversion of Convertible Preferred Stock into Common Stock upon IPO | Common Stock
Temporary Equity [Line Items]
Number of shares issued for convertible preferred stock	6,967,925	6,967,925

Stockholders' Equity (Deficit64

Stockholders' Equity (Deficit) - Preferred and Common Stock (Details) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Stockholders' Equity (Deficit)
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, shares authorized	100,000,000	100,000,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares issued	23,776,033	12,643,538
Common stock, shares outstanding	23,776,033	12,643,538

Stockholders' Equity (Deficit65

Stockholders' Equity (Deficit) - Common Stock Warrants (Details) - USD ($)	1 Months Ended	4 Months Ended	12 Months Ended
	Jan. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016
Stockholders' Equity (Deficit)
Allocated fair value of warrants recorded in stockholders' deficit			$ 804,000	$ 175,000
Common Stock Warrants
Stockholders' Equity (Deficit)
Number of shares of common stock under warrants outstanding			2,193,507		2,152,117
Common Stock Warrants issued with Series E Convertible Preferred Stock
Stockholders' Equity (Deficit)
Percentage of convertible preferred stock shares for issuance of warrants	50.00%
Exercise price of warrants issued (in dollars per share)	$ 12.60
Warrants issued to purchase shares of common stock (in shares)	245,235	1,335,779
Allocated fair value of warrants recorded in stockholders' deficit	$ 804,000	$ 175,000
Common Stock Warrants issued for amendment to Series E Convertible Preferred Stock
Stockholders' Equity (Deficit)
Percentage of convertible preferred stock shares for issuance of warrants	70.00%
Exercise price of warrants issued (in dollars per share)	$ 12.60
Warrants issued to purchase shares of common stock (in shares)	632,381
Incremental fair value from the modification	$ 2,384,000

Stockholders' Equity (Deficit66

Stockholders' Equity (Deficit) - Stock Plan (Details) - 2015 Plan - shares	12 Months Ended
	Dec. 31, 2016	Jan. 31, 2015
Stock Plans
Shares reserved for issuance		1,320,000
Maximum annual increase in shares available for issuance (in shares)	1,690,000
Maximum annual increase in shares available for issuance, percentage of outstanding shares	5.00%
Increase in number of shares authorized for issuance	632,176
Shares available for grant (in shares)	1,183,937

Stockholders' Equity (Deficit67

Stockholders' Equity (Deficit) - Stock Options (Details) - Stock options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock Plans
Vesting period	4 years
Expiration term	10 years
Options outstanding
Balance at the beginning of the period (in shares)	3,356,981	3,010,373	398,740
Options granted (in shares)	701,612	614,363	2,720,174
Options exercised (in shares)	(23,230)	(17,642)	(2,568)
Options cancelled (in shares)	(327,352)	(250,113)	(105,973)
Balance at the end of the period (in shares)	3,708,011	3,356,981	3,010,373
Weighted Average Exercise Price
Balance at the beginning of the period (in dollars per share)	$ 7.53	$ 5.78	$ 16.15
Granted (in dollars per shares)	11.69	16.73	4.68
Exercised (in dollars per shares)	4.50	4.50	8.85
Cancelled (in dollars per share)	12.89	9.33	16.62
Balance at the end of the period (in dollars per share)	$ 7.86	$ 7.53	$ 5.78
Aggregate Intrinsic Value (in dollars)	$ 5	$ 50,970	$ 13,188
Minimum
Stock Plans
Exercise price as percentage of fair value of shares	100.00%
Minimum | Stockholder with more than 10% voting power
Stock Plans
Exercise price as percentage of fair value of shares	110.00%

Stockholders' Equity (Deficit68

Stockholders' Equity (Deficit) - Options by Exercise Price (Details)	12 Months Ended
	Dec. 31, 2016$ / sharesshares
Options Outstanding
Options Outstanding (in shares) | shares	3,708,011
Weighted Average Remaining Contractual Life	8 years 1 month 6 days
Weighted Average Exercise Price (in dollars per share)	$ 7.86
Options Vested
Number Exercisable (in shares) | shares	1,630,917
Weighted Average Exercise Price (in dollars per share)	$ 7.40
Exercise Price - 3.55
Stock options
Exercise price (in dollars per share)	$ 3.55
Options Outstanding
Options Outstanding (in shares) | shares	27,559
Weighted Average Remaining Contractual Life	9 years 10 months 2 days
Weighted Average Exercise Price (in dollars per share)	$ 3.55
Options Vested
Weighted Average Exercise Price (in dollars per share)	3.55
Exercise Price - 3.68
Stock options
Exercise price (in dollars per share)	$ 3.68
Options Outstanding
Options Outstanding (in shares) | shares	37,056
Weighted Average Remaining Contractual Life	9 years 9 months 29 days
Weighted Average Exercise Price (in dollars per share)	$ 3.68
Options Vested
Weighted Average Exercise Price (in dollars per share)	3.68
Exercise Price - 4.05
Stock options
Exercise price (in dollars per share)	$ 4.05
Options Outstanding
Options Outstanding (in shares) | shares	4,350
Weighted Average Remaining Contractual Life	2 years 5 months 9 days
Weighted Average Exercise Price (in dollars per share)	$ 4.05
Options Vested
Number Exercisable (in shares) | shares	4,350
Weighted Average Exercise Price (in dollars per share)	$ 4.05
Exercise Price - 4.50
Stock options
Exercise price (in dollars per share)	$ 4.50
Options Outstanding
Options Outstanding (in shares) | shares	1,659,913
Weighted Average Remaining Contractual Life	8 years 4 days
Weighted Average Exercise Price (in dollars per share)	$ 4.50
Options Vested
Number Exercisable (in shares) | shares	831,258
Weighted Average Exercise Price (in dollars per share)	$ 4.50
Exercise Price - 4.95
Stock options
Exercise price (in dollars per share)	$ 4.95
Options Outstanding
Options Outstanding (in shares) | shares	862,777
Weighted Average Remaining Contractual Life	7 years 10 months 13 days
Weighted Average Exercise Price (in dollars per share)	$ 4.95
Options Vested
Number Exercisable (in shares) | shares	443,651
Weighted Average Exercise Price (in dollars per share)	$ 4.95
Exercise Price - 5.12
Stock options
Exercise price (in dollars per share)	$ 5.12
Options Outstanding
Options Outstanding (in shares) | shares	29,600
Weighted Average Remaining Contractual Life	9 years 6 months 26 days
Weighted Average Exercise Price (in dollars per share)	$ 5.12
Options Vested
Weighted Average Exercise Price (in dollars per share)	5.12
Exercise Price - 6.26
Stock options
Exercise price (in dollars per share)	$ 6.26
Options Outstanding
Options Outstanding (in shares) | shares	1,511
Weighted Average Remaining Contractual Life	5 years 22 days
Weighted Average Exercise Price (in dollars per share)	$ 6.26
Options Vested
Number Exercisable (in shares) | shares	1,511
Weighted Average Exercise Price (in dollars per share)	$ 6.26
Exercise Price - 10.91
Stock options
Exercise price (in dollars per share)	$ 10.91
Options Outstanding
Options Outstanding (in shares) | shares	25,222
Weighted Average Remaining Contractual Life	8 years 2 months 5 days
Weighted Average Exercise Price (in dollars per share)	$ 10.91
Options Vested
Number Exercisable (in shares) | shares	11,786
Weighted Average Exercise Price (in dollars per share)	$ 10.91
Exercise Price - 10.98
Stock options
Exercise price (in dollars per share)	$ 10.98
Options Outstanding
Options Outstanding (in shares) | shares	4,000
Weighted Average Remaining Contractual Life	8 years 3 months 29 days
Weighted Average Exercise Price (in dollars per share)	$ 10.98
Options Vested
Number Exercisable (in shares) | shares	1,666
Weighted Average Exercise Price (in dollars per share)	$ 10.98
Exercise Price - 11.01
Stock options
Exercise price (in dollars per share)	$ 11.01
Options Outstanding
Options Outstanding (in shares) | shares	9,385
Weighted Average Remaining Contractual Life	9 years 5 months 9 days
Weighted Average Exercise Price (in dollars per share)	$ 11.01
Options Vested
Weighted Average Exercise Price (in dollars per share)	11.01
Exercise Price - 12.38
Stock options
Exercise price (in dollars per share)	$ 12.38
Options Outstanding
Options Outstanding (in shares) | shares	64,200
Weighted Average Remaining Contractual Life	9 years 3 months 29 days
Weighted Average Exercise Price (in dollars per share)	$ 12.38
Options Vested
Weighted Average Exercise Price (in dollars per share)	12.38
Exercise Price - 12.60
Stock options
Exercise price (in dollars per share)	$ 12.60
Options Outstanding
Options Outstanding (in shares) | shares	66,484
Weighted Average Remaining Contractual Life	4 years 6 months 15 days
Weighted Average Exercise Price (in dollars per share)	$ 12.60
Options Vested
Number Exercisable (in shares) | shares	66,484
Weighted Average Exercise Price (in dollars per share)	$ 12.60
Exercise Price - 12.96
Stock options
Exercise price (in dollars per share)	$ 12.96
Options Outstanding
Options Outstanding (in shares) | shares	120,000
Weighted Average Remaining Contractual Life	9 years 2 months 9 days
Weighted Average Exercise Price (in dollars per share)	$ 12.96
Options Vested
Weighted Average Exercise Price (in dollars per share)	12.96
Exercise Price - 12.99
Stock options
Exercise price (in dollars per share)	$ 12.99
Options Outstanding
Options Outstanding (in shares) | shares	297,820
Weighted Average Remaining Contractual Life	9 years 2 months 5 days
Weighted Average Exercise Price (in dollars per share)	$ 12.99
Options Vested
Number Exercisable (in shares) | shares	7,228
Weighted Average Exercise Price (in dollars per share)	$ 12.99
Exercise Price - 14.85
Stock options
Exercise price (in dollars per share)	$ 14.85
Options Outstanding
Options Outstanding (in shares) | shares	40,586
Weighted Average Remaining Contractual Life	5 years 18 days
Weighted Average Exercise Price (in dollars per share)	$ 14.85
Options Vested
Number Exercisable (in shares) | shares	40,586
Weighted Average Exercise Price (in dollars per share)	$ 14.85
Exercise Price - 15.21
Stock options
Exercise price (in dollars per share)	$ 15.21
Options Outstanding
Options Outstanding (in shares) | shares	53,044
Weighted Average Remaining Contractual Life	8 years 6 months 29 days
Weighted Average Exercise Price (in dollars per share)	$ 15.21
Options Vested
Number Exercisable (in shares) | shares	19,949
Weighted Average Exercise Price (in dollars per share)	$ 15.21
Exercise Price - 17.72
Stock options
Exercise price (in dollars per share)	$ 17.72
Options Outstanding
Options Outstanding (in shares) | shares	2,000
Weighted Average Remaining Contractual Life	8 years 9 months 29 days
Weighted Average Exercise Price (in dollars per share)	$ 17.72
Options Vested
Number Exercisable (in shares) | shares	583
Weighted Average Exercise Price (in dollars per share)	$ 17.72
Exercise Price - 19.61
Stock options
Exercise price (in dollars per share)	$ 19.61
Options Outstanding
Options Outstanding (in shares) | shares	272,348
Weighted Average Remaining Contractual Life	8 years 11 months 19 days
Weighted Average Exercise Price (in dollars per share)	$ 19.61
Options Vested
Number Exercisable (in shares) | shares	81,736
Weighted Average Exercise Price (in dollars per share)	$ 19.61
Exercise Price - 20.25
Stock options
Exercise price (in dollars per share)	$ 20.25
Options Outstanding
Options Outstanding (in shares) | shares	93,949
Weighted Average Remaining Contractual Life	6 years 6 months 11 days
Weighted Average Exercise Price (in dollars per share)	$ 20.25
Options Vested
Number Exercisable (in shares) | shares	84,524
Weighted Average Exercise Price (in dollars per share)	$ 20.25
Exercise Price - 22.05
Stock options
Exercise price (in dollars per share)	$ 22.05
Options Outstanding
Options Outstanding (in shares) | shares	7,319
Weighted Average Remaining Contractual Life	5 years 9 months
Weighted Average Exercise Price (in dollars per share)	$ 22.05
Options Vested
Number Exercisable (in shares) | shares	7,319
Weighted Average Exercise Price (in dollars per share)	$ 22.05
Exercise Price - 22.50
Stock options
Exercise price (in dollars per share)	$ 22.50
Options Outstanding
Options Outstanding (in shares) | shares	28,888
Weighted Average Remaining Contractual Life	5 years 6 months 22 days
Weighted Average Exercise Price (in dollars per share)	$ 22.50
Options Vested
Number Exercisable (in shares) | shares	28,286
Weighted Average Exercise Price (in dollars per share)	$ 22.50

Stockholders' Equity (Deficit69

Stockholders' Equity (Deficit) - Additional Option Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock Plans
Aggregate intrinsic value of options exercised (in dollars)			$ 236,000,000
Stock options
Stock Plans
Weighted-average grant date fair value of options granted (in dollars per share)	$ 5.51	$ 8.24	$ 6.60
Weighted average remaining contractual life of options outstanding and vested	7 years 7 months 17 days
Aggregate intrinsic value of options outstanding and vested	$ 0
Aggregate intrinsic value of options exercised (in dollars)	$ 135,000	$ 236,000	$ 0

Stockholders' Equity (Deficit70

Stockholders' Equity (Deficit) - RSUs (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Additional information
Closing market price of the Company's common stock (in dollars per share)	$ 3.70
RSUs
Stock Plans
Vesting period	4 years
RSU activity
Awards outstanding at the beginning of the period (in shares)	92,946
Awarded (in shares)	185,500	92,946
Released (in shares)	(26,911)
Forfeited (in shares)	(37,359)
Awards outstanding at the end of the period (in shares)	214,176	92,946
Weighted Average Grant Date Fair Value
Awards outstanding at the beginning of the period (in dollars per share)	$ 19.61
Awarded (in dollars per share)	12.98	$ 19.61
Released (in dollars per share)	18.04
Forfeited (in dollars per share)	14.96
Awards outstanding at the end of the period (in dollars per share)	$ 14.88	$ 19.61
Additional information
Weighted Average Remaining Contractual Term	3 years 1 month 2 days	3 years 10 months 17 days
Aggregate Intrinsic Value (in dollars)	$ 792,000	$ 2,111,000
Total unrecognized compensation expense (in dollars)	$ 2,780,000
Expected period for recognition	3 years 18 days

Stockholders' Equity (Deficit71

Stockholders' Equity (Deficit) - ESPP (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 31, 2015
Stock Plans
Stock-based compensation expense	$ 7,392,000	$ 5,899,000	$ 641,000
2015 Employee Stock Purchase Plan
Stock Plans
Shares reserved for issuance				500,000
Maximum annual increase in shares available for issuance (in shares)	493,000
Maximum annual increase in shares available for issuance, percentage of outstanding shares	1.50%
Increase in number of shares authorized for issuance	189,653
Exercise price as percentage of fair market value of shares	85.00%
Common stock remaining reserved for issuance (in shares)	543,879
Stock-based compensation expense	$ 372,000	$ 217,000

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock-based compensation expense
Noncash stock-based compensation expense recognized, before taxes	$ 7,392,000	$ 5,899,000	$ 641,000
Stock options
Unamortized compensation
Total unamortized compensation expense	$ 12,312,000	$ 16,871,000
Expected amortization period	2 years 3 months 29 days	3 years 1 month 24 days
Employee stock options
Valuation model average assumptions
Expected term (years)	6 years 1 month 6 days	6 years 3 months 18 days	6 years 3 months 18 days
Expected volatility	49.70%	49.80%	59.10%
Risk-free interest rate	1.50%	1.80%	1.80%
2015 Employee Stock Purchase Plan
Valuation model average assumptions
Expected term (years)	6 months	6 months
Expected volatility	72.10%	46.20%
Risk-free interest rate	0.41%	0.17%
Stock-based compensation expense
Noncash stock-based compensation expense recognized, before taxes	$ 372,000	$ 217,000
RSUs
Share-based compensation
Total fair value of shares vested in the year	486,000	0
Unamortized compensation
Total unrecognized compensation expense	$ 2,780,000
Expected amortization period	3 years 18 days
Cost of revenues
Stock-based compensation expense
Noncash stock-based compensation expense recognized, before taxes	$ 608,000	346,000	$ 55,000
Research and development expenses
Stock-based compensation expense
Noncash stock-based compensation expense recognized, before taxes	2,732,000	2,489,000	155,000
Selling, general and administrative expenses
Stock-based compensation expense
Noncash stock-based compensation expense recognized, before taxes	$ 4,052,000	$ 3,064,000	$ 431,000

Income Taxes - Reconciliation (

Income Taxes - Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of the statutory U.S. federal rate to the Company's effective tax rate
Tax at federal statutory rate	$ (19,077)	$ (16,905)	$ (10,863)
State taxes, net of federal benefit			14
Permanent differences	1,023	1,722	730
Change in valuation allowance	18,321	15,250	10,316
Research credits	(245)	(218)	(219)
Other	$ (22)	$ 151	36
Provision for taxes			$ 14

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Federal, state, and foreign net operating losses	$ 82,353,000	$ 64,739,000
Research and other credits	2,953,000	2,521,000
Fixed assets	623,000	215,000
Interest	581,000	899,000
Accruals and other	4,906,000	2,810,000
Total deferred tax assets	91,416,000	71,184,000
Less: Valuation allowance	(91,416,000)	(71,184,000)
Increase in valuation allowance	$ 20,232,000	$ 15,076,000	$ 12,193,000

Income Taxes - Operating Loss C

Income Taxes - Operating Loss Carryforwards (Details)	Dec. 31, 2016USD ($)
Federal
Operating Loss Carryforwards
Operating loss carryforwards	$ 219,087,000
State
Operating Loss Carryforwards
Operating loss carryforwards	$ 161,812,000

Income Taxes - Tax Credit Carry

Income Taxes - Tax Credit Carryforwards (Details) - Research and development	Dec. 31, 2016USD ($)
Federal
Tax Credit Carryforward
Credit carryforwards	$ 2,469,000
State
Tax Credit Carryforward
Credit carryforwards	$ 2,651,000

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes
Unrecognized tax benefits that would affect the effective tax rate if recognized	$ 1,266,000	$ 2,792,000
Reconciliation of unrecognized tax benefits
Balance at beginning of year	3,902,000	1,121,000	$ 919,000
Decrease based on the tax positions in the current year	(2,593,000)
Increase based on the tax positions in the current year		2,593,000	202,000
Additions for tax positions of prior years	227,000	188,000
Balance at end of year	$ 1,536,000	$ 3,902,000	$ 1,121,000

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($)	10 Months Ended	12 Months Ended
	Jul. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2014
Related Party Transaction
Total aggregate principal amount of notes issued				$ 4,700,000
Common Stock Warrants issued with Convertible Notes
Related Party Transaction
Exercise price of warrants issued (in dollars per share)	$ 12.60				$ 12.60
Convertible Notes
Related Party Transaction
Total aggregate principal amount of notes issued	$ 18,192,000
Related-party portion of convertible notes issuance | Convertible Notes
Related Party Transaction
Issuance of principal amount considered a related-party transaction	$ 5,122,000
Carrying value of related-party convertible notes		$ 0	$ 0
Interest expense related to related-party debt		0	388,000	1,021,000
Recreation, Inc. | Marketing services
Related Party Transaction
Amount of services provided by related party		697,000	1,016,000	$ 984,000
Amounts due to related party		6,000	76,000
Chansu | Consulting services related to regulatory affairs
Related Party Transaction
Amount of services provided by related party		3,000	17,000
Amounts due to related party		0	0
Consensys | Field engineers services
Related Party Transaction
Amount of services provided by related party		123,000	0
Amounts due to related party		$ 20,000	$ 0

401(k) Plan (Details)

401(k) Plan (Details) - 401(k) Plan - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
401(k) Plan
Maximum percentage of eligible compensation participants may contribute	90.00%
Vesting period for employer contributions	4 years
Contributions	$ 0	$ 0	$ 0

Subsequent Events (Details)

Subsequent Events (Details) - shares	1 Months Ended	12 Months Ended
	Jan. 31, 2017	Dec. 31, 2016
2015 Employee Stock Purchase Plan
Subsequent Events
Increase in number of shares authorized for issuance		189,653
2015 Plan
Subsequent Events
Increase in number of shares authorized for issuance		632,176
Subsequent Event | 2015 Employee Stock Purchase Plan
Subsequent Events
Increase in number of shares authorized for issuance	356,640
Subsequent Event | 2015 Plan
Subsequent Events
Increase in number of shares authorized for issuance	1,188,801

Selected Quarterly Financial 81

Selected Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Selected Quarterly Financial Information (Unaudited)
Revenues	$ 4,679	$ 5,316	$ 4,680	$ 4,539	$ 2,857	$ 2,721	$ 3,047	$ 2,088	$ 19,214	$ 10,713	$ 11,213
Gross profit	981	1,574	1,035	1,179	1,051	971	1,413	800	4,769	4,235	4,700
Operating expenses	12,945	13,005	13,328	16,208	13,357	10,847	10,496	10,225	55,486	44,925	29,727
Net loss	$ (13,497)	$ (12,969)	$ (13,496)	$ (16,167)	$ (13,456)	$ (13,250)	$ (10,220)	$ (12,801)	$ (56,128)	$ (47,344)	$ (31,964)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.58)	$ (0.73)	$ (1.06)	$ (1.28)	$ (1.07)	$ (1.08)	$ (0.83)	$ (1.53)	$ (3.39)	$ (4.38)	$ (132.63)

Financial Statement Schedules (

Financial Statement Schedules (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for doubtful accounts receivable
Balance at Beginning of Year	$ 20	$ 20	$ 20
Charged to costs and expenses	3
Write offs	2
Balance at End of Year	21	20	20
Allowance for sales returns
Balance at Beginning of Year	59	77	88
Charged to costs and expenses	114	37	135
Write offs	130	55	146
Balance at End of Year	$ 43	$ 59	$ 77