Shockwave Medical (SWAV) 10-Q 9 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	May 01, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Trading Symbol	SWAV
Entity Registrant Name	ShockWave Medical, Inc.
Entity Central Index Key	0001642545
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		28,012,387

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
CURRENT ASSETS:
Cash and cash equivalents	$ 138,064	$ 39,643
Accounts receivable, net	3,939	2,850
Inventory	7,014	5,131
Prepaid expenses and other current assets	2,508	1,112
Total current assets	151,525	48,736
Operating lease right-of-use assets	2,645
Property and equipment, net	2,803	2,619
Other assets	566	2,066
TOTAL ASSETS	157,539	53,421
CURRENT LIABILITIES:
Accounts payable	3,967	1,487
Term notes, current portion	3,333	1,667
Accrued liabilities	6,439	6,217
Lease liability, current portion	877
Total current liabilities	14,616	9,371
Lease liability, noncurrent portion	1,916
Term notes, noncurrent portion	11,821	13,383
Convertible preferred stock warrant liability		313
Other liabilities		136
TOTAL LIABILITIES	28,353	23,203
Commitments and contingencies (Note 6)
Convertible preferred stock		152,806
STOCKHOLDERS’ EQUITY (DEFICIT):
Preferred stock
Common stock	28	2
Additional paid-in capital	268,822	4,275
Accumulated deficit	(139,664)	(126,865)
TOTAL STOCKHOLDERS’ EQUITY (DEFICIT)	129,186	(122,588)
TOTAL LIABILITIES, CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT)	$ 157,539	$ 53,421

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenue:
Product revenue	$ 7,269	$ 1,322
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember
Operating expenses:
Cost of product revenue	$ 3,072	$ 794
Type of Cost, Good or Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember
Research and development	$ 7,484	$ 5,516
Sales and marketing	5,871	3,438
General and administrative	3,001	1,376
Total operating expenses	19,428	11,124
Loss from operations	(12,159)	(9,802)
Interest expense	(245)	(18)
Change in fair value of warrant liability	(609)	41
Other income, net	221	185
Net loss before taxes	(12,792)	(9,594)
Income tax provision	7
Net loss	(12,799)	(9,594)
Unrealized gain on available-for-sale securities		1
Total comprehensive loss	$ (12,799)	$ (9,593)
Net loss per share, basic and diluted	$ (1.37)	$ (5.63)
Shares used in computing net loss per share, basic and diluted	9,364,755	1,705,144

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance at Dec. 31, 2017	$ (83,292)		$ 2	$ 2,470	$ (1)	$ (85,763)
Temporary equity, Beginning balance, shares at Dec. 31, 2017		17,510,045
Temporary equity, Beginning balance at Dec. 31, 2017		$ 137,469
Beginning balance, shares at Dec. 31, 2017			1,627,032
Exercise of Series A-1 warrants		$ 312
Temporary equity, Exercise of Series A-1 warrants, Shares		52,169
Issuance of common stock warrants	104			104
Exercise of stock options	215			215
Exercise of stock options, Shares			143,422
Unrealized gain on available-for-sale securities	1				$ 1
Vesting of early exercised options	22			22
Stock-based compensation	273			273
Net loss	(9,594)					(9,594)
Ending balance at Mar. 31, 2018	(92,271)		$ 2	3,084		(95,357)
Temporary equity, Ending balance, shares at Mar. 31, 2018		17,562,214
Temporary equity, Ending balance at Mar. 31, 2018		$ 137,781
Ending balance, shares at Mar. 31, 2018			1,770,454
Beginning balance at Dec. 31, 2018	(122,588)		$ 2	4,275		(126,865)
Temporary equity, Beginning balance, shares at Dec. 31, 2018		18,670,328
Temporary equity, Beginning balance at Dec. 31, 2018	152,806	$ 152,806
Beginning balance, shares at Dec. 31, 2018			1,824,852
Exercise of common stock warrants for cash	110			110
Exercise of common stock warrants for cash, shares			50,331
Issuance of common stock upon net exercise of warrants	133			133
Issuance of common stock upon net exercise of warrants, shares			101,744
Conversion of preferred stock to common stock upon initial public offering	152,806		$ 18	152,788
temporary equity conversion of preferred stock shares to common stock upon initial public offering, shares		(18,670,328)
temporary equity conversion of preferred stock value to common stock upon initial public offering		$ (152,806)
Conversion of preferred to common stock upon initial public offering, Shares			18,670,328
Conversion of Series A-1 warrants to common stock warrants upon initial public offering	789			789
Issuance of common stock in connection with initial public offering, net of issuance costs of $11.3 million	100,139		$ 7	100,132
Issuance of common stock in connection with initial public offering, net of issuance costs, Shares			6,555,000
Issuance of common stock in connection with private placement	10,000		$ 1	9,999
issuance of common stock in connection with private placement, shares			588,235
Exercise of stock options	$ 169			169
Exercise of stock options, Shares	80,515		80,515
Vesting of early exercised options	$ 18			18
Stock-based compensation	412			412
Adjustment for fractional shares resulting from reverse stock split	(3)			(3)
Adjustment for fractional shares resulting from reverse stock split			(114)
Net loss	(12,799)					(12,799)
Ending balance at Mar. 31, 2019	$ 129,186		$ 28	$ 268,822		$ (139,664)
Ending balance, shares at Mar. 31, 2019			27,870,891

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Statement Of Stockholders Equity [Abstract]
Issuance costs, initial public offering	$ 11.3

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (12,799)	$ (9,594)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	255	129
Stock-based compensation	412	273
Amortization of right-of-use assets	249
Loss on write down of fixed assets	19
Change in fair value of warrant liability	609	(41)
Amortization of debt issuance costs	104
Changes in operating assets and liabilities:
Accounts receivable	(1,089)	(503)
Inventory	(1,883)	(1,168)
Prepaid expenses and other current assets	(1,396)	11
Other assets	(19)	(143)
Accounts payable	369	346
Accrued and other current liabilities	991	(678)
Lease liabilities	(237)
Other liabilities		(9)
Net cash used in operating activities	(14,415)	(11,377)
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from maturities of available-for-sale securities		1,807
Purchase of property and equipment	(420)	(315)
Net cash (used in) provided by investing activities	(420)	1,492
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock upon initial public offering, net of issuance costs paid	102,977
Proceeds from issuance of common stock in private placement	10,000
Proceeds from stock option exercises	169	315
Proceeds from warrant exercises	110	101
Net cash provided by financing activities	113,256	416
Net increase (decrease) in cash, cash equivalents and restricted cash	98,421	(9,469)
Cash, cash equivalents and restricted cash at beginning of period	40,093	51,923
Cash, cash equivalents and restricted cash equivalents at end of period	138,514	42,454
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Interest paid	132	18
Income tax paid	4
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Common stock issued on conversion of convertible preferred stock	152,806
Issuance of Series A-1 convertible preferred stock on net exercise of warrants		211
Common stock issued upon net exercise of warrants	133
Common stock warrants issued on conversion of preferred stock warrants and the reclassification of the warrant liability	789
Deferred offering costs included in accounts payable and accrued liabilities	2,215
Right-of-use asset obtained in exchange for lease liability	73
Property and equipment purchases included in accounts payable	$ 93	74
Issuance of common stock warrants in connection with debt financing		$ 104

Organization and Basis of Prese

Organization and Basis of Presentation	3 Months Ended
	Mar. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Basis of Presentation	1. Organization and Basis of Presentation ShockWave Medical, Inc. (the “Company”) was incorporated on June 17, 2009. The Company is primarily engaged in the development of Intravascular Lithotripsy (“IVL”) technology for the treatment of calcified plaque in patients with peripheral vascular, coronary vascular and heart valve disease. Built on a balloon catheter platform, the IVL technology uses lithotripsy to disrupt both superficial and deep vascular calcium, while minimizing soft tissue injury, and an integrated angioplasty balloon to dilate blockages at low pressures, restoring blood flow. In 2016, the Company began commercial and manufacturing operations, and began selling catheters based on the IVL technology. The Company’s headquarters are in Santa Clara, California. The Company is located and operates primarily in the United States and has a subsidiary in Germany. Initial Public Offering On March In addition, on the completion of the IPO, all the Company’s outstanding preferred stock warrants were converted into 54,903 common stock warrants, which resulted in the reclassification of the convertible preferred stock warrant liability to additional paid-in capital. Furthermore, Concurrent with the IPO, the Company issued 588,235 shares of its common stock in a private placement for net proceeds of $10.0 million. Reverse Stock Split In February 2019, the Company’s board of directors approved an amended and restated certificate of incorporation to effect a reverse split of shares Reverse Stock Split, aggregating to 45 whole shares of common stock and 69 whole shares of preferred stock for the period presented, which fractional shares will be settled in cash in fiscal 2019. Need for Additional Capital The Company has incurred significant losses and has negative cash flows from operations. As of March 31, 2019, the Company had an accumulated deficit of $139.7 million. Management expects to continue to incur additional substantial losses in the foreseeable future. As of March 31, 2019, the Company had cash and cash equivalents of $138.1 million, which are available to fund future operations. The Company believes that its cash and cash equivalents as of March 31, 2019, together with available borrowings under a revolving line of credit, will be sufficient for the Company to continue as a going concern for at least 12 months from the date the unaudited condensed consolidated financial statements are filed with the Securities and Exchange Commission (“SEC”). The Company’s future capital requirements will depend on many factors, including its growth rate, the timing and extent of its spending to support research and development activities and the timing and cost of establishing additional sales and marketing capabilities.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) and applicable rules and regulations of SEC regarding interim financial reporting. The interim condensed consolidated balance sheet as of March 31, 2019, the condensed consolidated statements of operations and comprehensive loss, the condensed consolidated statements of convertible preferred stock and stockholders’ equity (deficit) and the statements of cash flows for the three months ended March 31, 2019 and 2018 are unaudited. The unaudited condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s consolidated financial position as of March 31, 2019 and its results of operations and cash flows for the three months ended March 31, 2019 and 2018. The financial data and the other financial information contained in these notes to the condensed consolidated financial statements related to the three month periods are also unaudited. The results of operations for the three months ended March 31, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019 or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 2018 included herein was derived from the audited financial statements as of that date. These condensed consolidated financial statements should be read in conjunction with the Company's audited consolidated financial statements included in the prospectus dated March 6, 2019 (“Prospectus”) that forms a part of the Company's Registration Statements on Form S-1 (File No. 333-229590), as filed with the SEC pursuant to Rule 424(b)(4) promulgated under the Securities Act of 1933, as amended. Cash, Cash Equivalents, and Restricted Cash The Company considers all highly liquid investments purchased with original maturities of three months or less from the purchase date to be cash equivalents. Cash equivalents consist primarily of amounts invested in money market accounts. Restricted cash as of March 31, 2019 and December 31, 2018 relates to a letter of credit established for a lease entered into in May 2018 and is recorded as other assets on the condensed consolidated balance sheets. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows: March 31, 2019 December 31, 2018 (in thousands) Cash and cash equivalents $ 138,064 $ 39,643 Restricted cash 450 450 Total cash, cash equivalents, and restricted cash $ 138,514 $ 40,093 Fair Value of Financial Instruments The Company’s cash and cash equivalents, restricted cash, accounts receivable, accounts payable and accrued liabilities approximate their fair value due to their short maturities. Management believes that its term notes bear interest at the prevailing market rates for instruments with similar characteristics; accordingly, the carrying value of this instrument approximates its fair value. The Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible. The Company determines the fair value of its financial instruments based on assumptions that market participants would use in pricing an asset or liability in the principal or most advantageous market. When considering market participant assumptions in fair value measurements, the following fair value hierarchy distinguishes between observable and unobservable inputs, which are categorized in one of the following levels: Level 1 – Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date; Level 2 – Inputs are observable, unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted quoted prices for identical or similar assets or liabilities 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 related assets or liabilities; and Level 3 – Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data. Leases The Company adopted Accounting Standards Update (ASU) No. 2016-02, Leases (Topic 842) Upon adoption of Topic 842, on January 1, 2019, the Company recorded operating right-of-use assets of $2.9 million and operating lease liabilities of $3.0 million and derecognized the deferred rent liability of $0.1 million. Results for the three months ended March 31, 2019 are presented under Topic 842. Prior period amounts have not been adjusted and continue to be reported in accordance with the Company’s historical accounting under previous lease guidance, ASC 840: Leases (Topic 840). For its long-term operating lease, the Company recognized a right-of-use asset and a lease liability on its condensed consolidated balance sheet. The lease liability is determined as the present value of future lease payments using an estimated rate of interest that the Company would have to pay to borrow equivalent funds on a collateralized basis at the lease commencement date. The right-of-use asset is based on the liability adjusted for any prepaid or deferred rent. The lease term at the commencement date is determined by considering whether renewal options and termination options are reasonably assured of exercise. Rent expense for the operating lease is recognized on a straight-line basis over the lease term and is included in operating expenses on the condensed consolidated statements of operations and comprehensive loss. Variable lease payments include lease operating expenses. The Company elected to exclude from its balance sheets recognition of leases having a term of 12 months or less (short-term leases) and elected to not separate lease components and non-lease components for its long-term real estate leases. Deferred Offering Costs Offering costs, consisting of legal, accounting, printer and filing fees related to the IPO, were deferred until the completion of the IPO. As of December 31, 2018, $1.5 million of deferred offering costs were recorded as other assets on the condensed consolidated balance sheet. In March 2019, upon the closing of the IPO, all deferred costs were offset against the Company’s IPO proceeds. Convertible Preferred Stock Warrant Liability The Company has accounted for its freestanding warrants to purchase shares of the Company’s convertible preferred stock as liabilities at fair value upon issuance primarily because the shares underlying the warrants contain contingent redemption features outside the control of the Company. The warrants are subject to re-measurement at each balance sheet date and any change in fair value is recognized as the change in fair value of warrant liability. The carrying value of the warrants will continue to be adjusted until such time as these instruments are exercised, expire or convert into warrants to purchase shares of the Company’s common stock upon the completion of a liquidation event, including the completion of the IPO, which occurred on March 11, 2019. At that time, the preferred stock warrant liability was reclassified to additional paid-in capital, a component of stockholders’ equity (deficit). Revenue The Company records product revenue primarily from the sale of its IVL catheters. The Company sells its products to hospitals, primarily through direct sales representatives, as well as through distributors in selected international markets. Additionally, a significant portion of the Company’s revenue is generated through a consignment model under which inventory is maintained at hospitals. Revenue is recognized when a customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. For products sold through direct sales representatives, control is transferred upon delivery to customers. For products sold to distributors internationally and certain customers that purchase stocking orders in the United States, control is transferred upon shipment or delivery to the customer’s named location, based on the contractual shipping terms. For consignment inventory, control is transferred at the time the IVL catheters are consumed in a procedure. The Company generally provides for the use of an IVL generator and connector cable under an agreement to customers at no charge to facilitate use of the IVL catheters. These agreements do not contain contractually enforceable minimum commitments and are generally cancellable by either party with 30 days’ notice.

Financial Instruments and Fair

Financial Instruments and Fair Value Measurements	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Financial Instruments and Fair Value Measurements	3. Financial Instruments and Fair Value Measurements The following tables summarize the Company’s financial assets and liabilities measured at fair value on a recurring basis by level within the fair value hierarchy: March 31, 2019 Level 1 Level 2 Level 3 Total (in thousands) Assets: Money market funds $ 111,801 $ — $ — $ 111,801 Total assets $ 111,801 $ — $ — $ 111,801 December 31, 2018 Level 1 Level 2 Level 3 Total (in thousands) Assets: Money market funds $ 21,680 $ — $ — $ 21,680 Total assets $ 21,680 $ — $ — $ 21,680 Liabilities: Convertible preferred stock warrant liability $ — $ — $ 313 $ 313 Total liabilities $ — $ — $ 313 $ 313 There were no transfers between Levels 1, 2 or 3 for the periods presented. The change in the fair value of the warrant liability for the three months ended March 31, 2019 is summarized below (in thousands): Balance at December 31, 2018 $ 313 Change in fair value of warrant liability 609 Net exercise of warrants (133 ) Conversion of Series A preferred stock warrants to common stock warrants upon the closing of the IPO (789 ) Balance at March 31, 2019 $ — The change in the fair value of the warrant liability for the three months ended March 31, 2018 is summarized below (in thousands): Balance at December 31, 2017 $ 577 Exercise of warrants (211 ) Expiration of warrants, included in change in fair value of warrant liability (87 ) Change in fair value of warrant liability 46 Balance at March 31, 2018 $ 325 The valuation of the Company’s convertible preferred stock warrant liability contains unobservable inputs that reflect the Company’s own assumptions for which there is little, if any, market activity for at the measurement date. Accordingly, the Company’s convertible preferred stock warrant liability is measured at fair value on a recurring basis using unobservable inputs and are classified as Level 3 inputs, and any change in fair value is recognized as change in fair value of warrant liability in the condensed consolidated statements of operations and comprehensive loss. The fair value of the warrants was determined using the Black-Scholes option pricing model and the following assumptions: Three Months Ended March 31, 2019 2018 Expected term (in years) 5.28 6.21 Expected volatility 43.9% 42.8% Risk-free interest rate 2.49% 2.62% Expected dividend yield 0% 0%

Cash Equivalents

Cash Equivalents	3 Months Ended
	Mar. 31, 2019
Cash And Cash Equivalents [Abstract]
Cash Equivalents	4. Cash Equivalents The following is a summary of the Company’s cash equivalents: March 31, 2019 Amortized Cost Basis Unrealized Gains Unrealized Losses Fair Value (in thousands) Money market funds $ 111,801 $ — $ — $ 111,801 Total $ 111,801 $ — $ — $ 111,801 Reported as: Cash equivalents $ 111,801 Total $ 111,801 December 31, 2018 Amortized Cost Basis Unrealized Gains Unrealized Losses Fair Value (in thousands) Money market funds $ 21,680 $ — $ — $ 21,680 Total $ 21,680 $ — $ — $ 21,680 Reported as: Cash equivalents $ 21,680 Total $ 21,680

Balance Sheet Components

Balance Sheet Components	3 Months Ended
	Mar. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Balance Sheet Components	5. Balance Sheet Components Inventory Inventory consists of the following: March 31, December 31, 2019 2018 (in thousands) Raw material $ 1,915 $ 1,084 Work in progress 1,103 634 Finished goods 2,643 2,313 Consigned inventory 1,353 1,100 Total inventory $ 7,014 $ 5,131 Accrued Liabilities Accrued liabilities consist of the following: March 31, December 31, 2019 2018 (in thousands) Accrued employee compensation $ 2,965 $ 3,135 Accrued research and development costs 1,736 1,115 Accrued professional services 713 1,391 Other 1,025 576 Total accrued liabilities $ 6,439 $ 6,217

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	6. Commitments and Contingencies Operating Leases In August 2012, the Company entered into a lease for office space located in Fremont, California. In October 2018, the Company extended the term of the lease to June 30, 2019 and in February 2019, the Company exercised the option to extend the lease further until September 30, 2019. The Company is using the facility for office, manufacturing and research and development purposes. In connection with the lease, the Company recognized an operating lease right-of-use asset of $0.1 million as of March 31, 2019 and an aggregate lease liability of $0.1 million on its condensed consolidated balance sheet. The remaining lease term is six months. In May 2018, the Company entered into a new lease agreement for office and laboratory space which consist of approximately 35,000 square feet located in Santa Clara, California. The lease term commenced in September 2018 and ends in August 2022. In connection with the lease, the Company maintains a letter of credit for the benefit of the landlord in the amount of $0.5 million, which is secured by restricted cash recorded as other assets on the condensed consolidated balance sheets. In connection with the lease, the Company recognized an operating lease right-of-use asset of $2.4 million as of March 31, 2019 and an aggregate lease liability of $2.6 million on its condensed consolidated balance sheet. The remaining lease term is three years and four months. T he Company also leases several vehicles for use by employees. In connection with the vehicle leases, the Company recognized an operating lease right-of-use asset of $0.1 million as of March 31, 2019 and an aggregate lease liability of $0.1 million on its condensed consolidated balance sheet. The weighted average remaining lease term is 14 months. The weighted average incremental borrowing rate used to measure the operating lease liability is 6.93%. Short-term leases are leases having a term of 12 months or less. The Company recognizes short-term leases on a straight-line basis and does not record a related lease asset or liability for such leases. Rent expense for the three months ended March 31, 2019 and 2018 was $0.3 million and $0.1 million, respectively. The following is a maturity analysis of the annual undiscounted cash flows reconciled to the carrying value of the operating lease liabilities as of March 31, 2019: (in thousands) Remainder of 2019 $ 812 2020 861 2021 855 2022 581 Total minimum lease payments $ 3,109 Less: imputed interest (316 ) Total $ 2,793

Convertible Preferred Stock and

Convertible Preferred Stock and Stockholders’ Equity (Deficit)	3 Months Ended
	Mar. 31, 2019
Stockholders Equity [Abstract]
Convertible Preferred Stock and Stockholders’ Equity (Deficit)	7. Convertible Preferred Stock and Stockholders’ Equity (Deficit) Convertible Preferred Stock Immediately prior to the closing of the Company's IPO, 18,670,259 shares of outstanding convertible preferred stock converted into 18,670,259 shares of common stock. As discussed in Note 1, t he fractional shares resulting from the Preferred Stock The Company’s amended and restated certificate of incorporation, which became effective upon the completion of the IPO, authorizes 5,000,000 shares of preferred stock, of which no shares were issued or outstanding as of March 31, 2019. Preferred Stock Warrants Upon the closing of the IPO, all of the outstanding convertible preferred stock warrants were converted into 54,903 common stock warrants, which resulted in the reclassification of the convertible preferred stock warrant liability of $0.8 million to additional paid-in capital. Common Stock Warrants As part of the IPO, 91,446 related party common stock warrants were net exercised based on the IPO price of $17.00 per share into 79,632 shares of common stock. In February 2018, in connection with the execution of the Loan and Security Agreement with Silicon Valley Bank for a term loan and revolving line of credit (the “2018 Loan and Security Agreement”), the Company issued warrants to purchase shares of the Company’s common stock. The key terms of the outstanding common stock warrants are summarized in the following table: Warrants Outstanding March 31, 2019 Warrants Outstanding December 31, 2018 Exercise Price Expiration Related party common stock warrants — 141,778 $ 2.196 May 2025 Common stock warrants issued in connection with the 2018 Loan and Security Agreement 34,440 34,440 $ 4.026 February 2028 Common stock warrant issued in connection with conversion of preferred stock warrants upon initial public offering 54,903 — $ 3.096 June 2024 Total common stock warrants 89,343 176,218

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	8. Stock-Based Compensation Total stock-based compensation was as follows: Three Months March 31, 2019 2018 (in thousands) Cost of product revenue $ 27 $ 15 Research and development 72 49 Sales and marketing 108 43 General and administrative 205 166 Total stock-based compensation $ 412 $ 273 Determination of Fair Value The Company estimates the grant-date fair value of the Company’s option awards using the Black-Scholes option pricing model. The assumptions for the Black-Scholes model for the three months ended March 31, 2019 and 2018 were as follows: Three Months Ended March 31, 2019 2018 Expected term (in years) 6.08 6.08 Expected volatility 42.4%-42.9% 45.9% Risk-free interest rate 2.5%-2.6% 1.9% Expected dividend yield 0% 0% 2009 Equity Incentive Plan and 2019 Equity Incentive Plan On June 17, 2009, the Company adopted the 2009 Equity Incentive Plan (the “2009 Plan”) under which the Board had the authority to issue stock options to employees, directors and consultants. In February 2019, the Company adopted the 2019 Stock Option and Incentive Plan (the “2019 Plan”), which became effective in connection with the IPO. As a result, effective as of March 6, 2019, the Company may not grant any additional awards under the 2009 Plan. The 2009 Plan will continue to govern outstanding equity awards granted thereunder. The Company has initially reserved 2,000,430 shares of common stock for the issuance of awards under the 2019 Plan. In addition, the number of shares of common stock reserved for issuance under the 2019 Plan will automatically increase on the first day of January for a period of up to ten years, commencing on January 1, 2020, in an amount equal to 3% of the total number of shares of the Company’s capital stock outstanding on the last day of the preceding year, or a lesser number of shares determined by the Company’s board of directors. Activity under the 2009 Plan and 2019 Plan is set forth below: Shares Available for Grant Number of Shares Weighted- Average Exercise Price Per Share Weighted- Average Remaining Term Aggregate Intrinsic Value (in years) (in thousands) Balance, December 31, 2018 392,299 3,636,358 $ 3.54 7.79 $ 11,267 Awards authorized 2,000,430 — 2009 Plan shares expired (293,953 ) — Options granted (425,983 ) 425,983 14.08 Options exercised — (80,515 ) 2.12 Options cancelled 21,321 (21,321 ) 3.12 Balance, March 31, 2019 1,694,114 3,960,505 $ 4.67 7.87 $ 114,058 Vested and exercisable, March 31, 2019 1,716,874 $ 2.78 6.59 $ 52,691 Vested and expected to vest, March 31, 2019 3,960,505 $ 4.67 7.87 $ 114,058 Employees Share Purchase Plan (ESPP) In February 2019, the Company adopted the 2019 Employee Stock Purchase Plan (“ESPP”), which became effective as of March 6, 2019. The Company has initially reserved 300,650 shares of common stock for purchase under the ESPP. Each offering to the employees to purchase stock under the ESPP will begin on each September 1 and March 1 and will end on the following February 28 or 29 and August 30, respectively. The first offering period is expected to begin on September 1, 2019 and end on February 29, 2020.

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	9. Net Loss Per Share The following outstanding potentially dilutive common stock equivalents have been excluded from the calculation of diluted net loss per share for the period presented due to their anti-dilutive effect: Three Months Ended March 31, 2019 2018 (in thousands) Convertible preferred stock on an as-converted basis — 17,562,214 Common stock options issued and outstanding 3,960,505 3,121,530 Early exercised options subject to future vesting 5,328 41,240 Convertible preferred stock warrants — 94,345 Common stock warrants 89,343 176,218 Total 4,055,176 20,995,547

Segment and Geographic Informat

Segment and Geographic Information	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Segment and Geographic Information	10. Segment and Geographic Information The following table represents the Company’s product revenue based on the location to which the product is shipped: Three Months Ended March 31, 2019 2018 (in thousands) United States $ 3,636 $ 897 Germany 643 254 Rest of Europe 2,736 129 All other countries 254 42 Product revenue $ 7,269 $ 1,322 As of March 31, 2019 and December 31, 2018, the Company’s long-lived assets are all held in the United States with the exception of certain equipment on loan to customers held internationally, which was not material as of each period end.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) and applicable rules and regulations of SEC regarding interim financial reporting. The interim condensed consolidated balance sheet as of March 31, 2019, the condensed consolidated statements of operations and comprehensive loss, the condensed consolidated statements of convertible preferred stock and stockholders’ equity (deficit) and the statements of cash flows for the three months ended March 31, 2019 and 2018 are unaudited. The unaudited condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s consolidated financial position as of March 31, 2019 and its results of operations and cash flows for the three months ended March 31, 2019 and 2018. The financial data and the other financial information contained in these notes to the condensed consolidated financial statements related to the three month periods are also unaudited. The results of operations for the three months ended March 31, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019 or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 2018 included herein was derived from the audited financial statements as of that date. These condensed consolidated financial statements should be read in conjunction with the Company's audited consolidated financial statements included in the prospectus dated March 6, 2019 (“Prospectus”) that forms a part of the Company's Registration Statements on Form S-1 (File No. 333-229590), as filed with the SEC pursuant to Rule 424(b)(4) promulgated under the Securities Act of 1933, as amended.
Cash, Cash Equivalents, and Restricted Cash	Cash, Cash Equivalents, and Restricted Cash The Company considers all highly liquid investments purchased with original maturities of three months or less from the purchase date to be cash equivalents. Cash equivalents consist primarily of amounts invested in money market accounts. Restricted cash as of March 31, 2019 and December 31, 2018 relates to a letter of credit established for a lease entered into in May 2018 and is recorded as other assets on the condensed consolidated balance sheets. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows: March 31, 2019 December 31, 2018 (in thousands) Cash and cash equivalents $ 138,064 $ 39,643 Restricted cash 450 450 Total cash, cash equivalents, and restricted cash $ 138,514 $ 40,093
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company’s cash and cash equivalents, restricted cash, accounts receivable, accounts payable and accrued liabilities approximate their fair value due to their short maturities. Management believes that its term notes bear interest at the prevailing market rates for instruments with similar characteristics; accordingly, the carrying value of this instrument approximates its fair value. The Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible. The Company determines the fair value of its financial instruments based on assumptions that market participants would use in pricing an asset or liability in the principal or most advantageous market. When considering market participant assumptions in fair value measurements, the following fair value hierarchy distinguishes between observable and unobservable inputs, which are categorized in one of the following levels: Level 1 – Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date; Level 2 – Inputs are observable, unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted quoted prices for identical or similar assets or liabilities 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 related assets or liabilities; and Level 3 – Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data.
Leases	Leases The Company adopted Accounting Standards Update (ASU) No. 2016-02, Leases (Topic 842) Upon adoption of Topic 842, on January 1, 2019, the Company recorded operating right-of-use assets of $2.9 million and operating lease liabilities of $3.0 million and derecognized the deferred rent liability of $0.1 million. Results for the three months ended March 31, 2019 are presented under Topic 842. Prior period amounts have not been adjusted and continue to be reported in accordance with the Company’s historical accounting under previous lease guidance, ASC 840: Leases (Topic 840). For its long-term operating lease, the Company recognized a right-of-use asset and a lease liability on its condensed consolidated balance sheet. The lease liability is determined as the present value of future lease payments using an estimated rate of interest that the Company would have to pay to borrow equivalent funds on a collateralized basis at the lease commencement date. The right-of-use asset is based on the liability adjusted for any prepaid or deferred rent. The lease term at the commencement date is determined by considering whether renewal options and termination options are reasonably assured of exercise. Rent expense for the operating lease is recognized on a straight-line basis over the lease term and is included in operating expenses on the condensed consolidated statements of operations and comprehensive loss. Variable lease payments include lease operating expenses. The Company elected to exclude from its balance sheets recognition of leases having a term of 12 months or less (short-term leases) and elected to not separate lease components and non-lease components for its long-term real estate leases.
Deferred Offering Costs	Deferred Offering Costs Offering costs, consisting of legal, accounting, printer and filing fees related to the IPO, were deferred until the completion of the IPO. As of December 31, 2018, $1.5 million of deferred offering costs were recorded as other assets on the condensed consolidated balance sheet. In March 2019, upon the closing of the IPO, all deferred costs were offset against the Company’s IPO proceeds.
Convertible Preferred Stock Warrant Liability	Convertible Preferred Stock Warrant Liability The Company has accounted for its freestanding warrants to purchase shares of the Company’s convertible preferred stock as liabilities at fair value upon issuance primarily because the shares underlying the warrants contain contingent redemption features outside the control of the Company. The warrants are subject to re-measurement at each balance sheet date and any change in fair value is recognized as the change in fair value of warrant liability. The carrying value of the warrants will continue to be adjusted until such time as these instruments are exercised, expire or convert into warrants to purchase shares of the Company’s common stock upon the completion of a liquidation event, including the completion of the IPO, which occurred on March 11, 2019. At that time, the preferred stock warrant liability was reclassified to additional paid-in capital, a component of stockholders’ equity (deficit).
Revenue	Revenue The Company records product revenue primarily from the sale of its IVL catheters. The Company sells its products to hospitals, primarily through direct sales representatives, as well as through distributors in selected international markets. Additionally, a significant portion of the Company’s revenue is generated through a consignment model under which inventory is maintained at hospitals. Revenue is recognized when a customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. For products sold through direct sales representatives, control is transferred upon delivery to customers. For products sold to distributors internationally and certain customers that purchase stocking orders in the United States, control is transferred upon shipment or delivery to the customer’s named location, based on the contractual shipping terms. For consignment inventory, control is transferred at the time the IVL catheters are consumed in a procedure. The Company generally provides for the use of an IVL generator and connector cable under an agreement to customers at no charge to facilitate use of the IVL catheters. These agreements do not contain contractually enforceable minimum commitments and are generally cancellable by either party with 30 days’ notice.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows: March 31, 2019 December 31, 2018 (in thousands) Cash and cash equivalents $ 138,064 $ 39,643 Restricted cash 450 450 Total cash, cash equivalents, and restricted cash $ 138,514 $ 40,093

Financial Instruments and Fai_2

Financial Instruments and Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of Financial Assets and Liabilities Measured at Fair Value	The following tables summarize the Company’s financial assets and liabilities measured at fair value on a recurring basis by level within the fair value hierarchy: March 31, 2019 Level 1 Level 2 Level 3 Total (in thousands) Assets: Money market funds $ 111,801 $ — $ — $ 111,801 Total assets $ 111,801 $ — $ — $ 111,801 December 31, 2018 Level 1 Level 2 Level 3 Total (in thousands) Assets: Money market funds $ 21,680 $ — $ — $ 21,680 Total assets $ 21,680 $ — $ — $ 21,680 Liabilities: Convertible preferred stock warrant liability $ — $ — $ 313 $ 313 Total liabilities $ — $ — $ 313 $ 313
Schedule of Change in the Fair Value of the Warrant Liability	The change in the fair value of the warrant liability for the three months ended March 31, 2019 is summarized below (in thousands): Balance at December 31, 2018 $ 313 Change in fair value of warrant liability 609 Net exercise of warrants (133 ) Conversion of Series A preferred stock warrants to common stock warrants upon the closing of the IPO (789 ) Balance at March 31, 2019 $ — The change in the fair value of the warrant liability for the three months ended March 31, 2018 is summarized below (in thousands): Balance at December 31, 2017 $ 577 Exercise of warrants (211 ) Expiration of warrants, included in change in fair value of warrant liability (87 ) Change in fair value of warrant liability 46 Balance at March 31, 2018 $ 325
Schedule of Fair Value of Warrants Determined Using the Black-Scholes Option Pricing Model	The fair value of the warrants was determined using the Black-Scholes option pricing model and the following assumptions: Three Months Ended March 31, 2019 2018 Expected term (in years) 5.28 6.21 Expected volatility 43.9% 42.8% Risk-free interest rate 2.49% 2.62% Expected dividend yield 0% 0%

Cash Equivalents (Tables)

Cash Equivalents (Tables)	3 Months Ended
	Mar. 31, 2019
Cash And Cash Equivalents [Abstract]
Summary of Cash Equivalents	The following is a summary of the Company’s cash equivalents: March 31, 2019 Amortized Cost Basis Unrealized Gains Unrealized Losses Fair Value (in thousands) Money market funds $ 111,801 $ — $ — $ 111,801 Total $ 111,801 $ — $ — $ 111,801 Reported as: Cash equivalents $ 111,801 Total $ 111,801 December 31, 2018 Amortized Cost Basis Unrealized Gains Unrealized Losses Fair Value (in thousands) Money market funds $ 21,680 $ — $ — $ 21,680 Total $ 21,680 $ — $ — $ 21,680 Reported as: Cash equivalents $ 21,680 Total $ 21,680

Balance Sheet Components (Table

Balance Sheet Components (Tables)	3 Months Ended
	Mar. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Schedule of Inventory	Inventory consists of the following: March 31, December 31, 2019 2018 (in thousands) Raw material $ 1,915 $ 1,084 Work in progress 1,103 634 Finished goods 2,643 2,313 Consigned inventory 1,353 1,100 Total inventory $ 7,014 $ 5,131
Schedule of Accrued Liabilities	Accrued liabilities consist of the following: March 31, December 31, 2019 2018 (in thousands) Accrued employee compensation $ 2,965 $ 3,135 Accrued research and development costs 1,736 1,115 Accrued professional services 713 1,391 Other 1,025 576 Total accrued liabilities $ 6,439 $ 6,217

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Schedule of Carrying Value of Operating Lease Liabilities	The following is a maturity analysis of the annual undiscounted cash flows reconciled to the carrying value of the operating lease liabilities as of March 31, 2019: (in thousands) Remainder of 2019 $ 812 2020 861 2021 855 2022 581 Total minimum lease payments $ 3,109 Less: imputed interest (316 ) Total $ 2,793

Convertible Preferred Stock a_2

Convertible Preferred Stock and Stockholders’ Equity (Deficit) (Tables)	3 Months Ended
	Mar. 31, 2019
Stockholders Equity [Abstract]
Summary of Key Terms of Outstanding Common Stock Warrants	The key terms of the outstanding common stock warrants are summarized in the following table: Warrants Outstanding March 31, 2019 Warrants Outstanding December 31, 2018 Exercise Price Expiration Related party common stock warrants — 141,778 $ 2.196 May 2025 Common stock warrants issued in connection with the 2018 Loan and Security Agreement 34,440 34,440 $ 4.026 February 2028 Common stock warrant issued in connection with conversion of preferred stock warrants upon initial public offering 54,903 — $ 3.096 June 2024 Total common stock warrants 89,343 176,218

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Total Stock-Based Compensation	Total stock-based compensation was as follows: Three Months March 31, 2019 2018 (in thousands) Cost of product revenue $ 27 $ 15 Research and development 72 49 Sales and marketing 108 43 General and administrative 205 166 Total stock-based compensation $ 412 $ 273
Schedule of Estimates Grant-Date Fair Value of Option Awards Using Black-Scholes Option Pricing Model with Assumptions	The Company estimates the grant-date fair value of the Company’s option awards using the Black-Scholes option pricing model. The assumptions for the Black-Scholes model for the three months ended March 31, 2019 and 2018 were as follows: Three Months Ended March 31, 2019 2018 Expected term (in years) 6.08 6.08 Expected volatility 42.4%-42.9% 45.9% Risk-free interest rate 2.5%-2.6% 1.9% Expected dividend yield 0% 0%
Schedule of Activity under 2009 Plan and 2019 Plan	Activity under the 2009 Plan and 2019 Plan is set forth below: Shares Available for Grant Number of Shares Weighted- Average Exercise Price Per Share Weighted- Average Remaining Term Aggregate Intrinsic Value (in years) (in thousands) Balance, December 31, 2018 392,299 3,636,358 $ 3.54 7.79 $ 11,267 Awards authorized 2,000,430 — 2009 Plan shares expired (293,953 ) — Options granted (425,983 ) 425,983 14.08 Options exercised — (80,515 ) 2.12 Options cancelled 21,321 (21,321 ) 3.12 Balance, March 31, 2019 1,694,114 3,960,505 $ 4.67 7.87 $ 114,058 Vested and exercisable, March 31, 2019 1,716,874 $ 2.78 6.59 $ 52,691 Vested and expected to vest, March 31, 2019 3,960,505 $ 4.67 7.87 $ 114,058

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Summary of Outstanding Potentially Dilutive Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share	The following outstanding potentially dilutive common stock equivalents have been excluded from the calculation of diluted net loss per share for the period presented due to their anti-dilutive effect: Three Months Ended March 31, 2019 2018 (in thousands) Convertible preferred stock on an as-converted basis — 17,562,214 Common stock options issued and outstanding 3,960,505 3,121,530 Early exercised options subject to future vesting 5,328 41,240 Convertible preferred stock warrants — 94,345 Common stock warrants 89,343 176,218 Total 4,055,176 20,995,547

Segment and Geographic Inform_2

Segment and Geographic Information (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Schedule of Product Revenue Based on Location	The following table represents the Company’s product revenue based on the location to which the product is shipped: Three Months Ended March 31, 2019 2018 (in thousands) United States $ 3,636 $ 897 Germany 643 254 Rest of Europe 2,736 129 All other countries 254 42 Product revenue $ 7,269 $ 1,322

Organization and Basis of Pre_2

Organization and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands	Mar. 11, 2019USD ($)$ / sharesshares	Mar. 31, 2019USD ($)shares	Dec. 31, 2018USD ($)	Mar. 05, 2019shares
Organization and Basis of Presentation [Line Items]
Entity incorporation, date of incorporation		Jun. 17, 2009
Net proceeds from IPO, after deducting underwriters’ discounts and commissions | $	$ 7,100
Common stock, conversion basis		one-to-one basis
Stock split, conversion ratio		12.2
Stockholders' equity, reverse stock split		The Company’s common stock and convertible preferred stock on a 12.2-for-one basis (the “Reverse Stock Split”)
Accumulated deficit | $		$ (139,664)	$ (126,865)
Cash and cash equivalents | $		$ 138,064	39,643
Common Stock
Organization and Basis of Presentation [Line Items]
Common stock issued		6,555,000
Proceeds from initial public offering | $	$ 100,100
Issuance of common stock upon net exercise of warrants, shares	101,744	101,744
Fractional shares issued in reverse stock split		45
Warrants
Organization and Basis of Presentation [Line Items]
Convertible preferred stock, shares issued upon conversion	54,903
Preferred Stock
Organization and Basis of Presentation [Line Items]
Fractional shares issued in reverse stock split		69
Initial Public Offering
Organization and Basis of Presentation [Line Items]
Common stock issued	6,555,000
Common stock, offering price per share | $ / shares	$ 17
Offering costs | $	$ 4,200
Stock split, conversion ratio	1
Initial Public Offering | Common Stock
Organization and Basis of Presentation [Line Items]
Convertible preferred stock, shares issued upon conversion				18,670,259
Over Allotment Option
Organization and Basis of Presentation [Line Items]
Common stock issued	855,000
Offering costs | $			$ 1,500
Private Placement
Organization and Basis of Presentation [Line Items]
Common stock issued	588,235
Proceeds from issuance of common stock | $	$ 10,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Cash and cash equivalents	$ 138,064	$ 39,643
Restricted cash	450	450
Total cash, cash equivalents, and restricted cash	$ 138,514	$ 40,093	$ 42,454	$ 51,923

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Mar. 31, 2019	Dec. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Operating lease right-of-use assets		$ 2,645
Operating lease liabilities		$ 2,793
Lease term		12 months
Notice period for cancellation of agreement		30 days
Other Assets
Summary Of Significant Accounting Policies [Line Items]
Deferred offering costs			$ 1,500
Adoption of Topic 842
Summary Of Significant Accounting Policies [Line Items]
Operating lease right-of-use assets	$ 2,900
Operating lease liabilities	3,000
Derecognized the deferred rent liability	$ (100)

Financial Instruments and Fai_3

Financial Instruments and Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
ASSETS
Total assets	$ 111,801	$ 21,680
Liabilities:
Total liabilities		313
Convertible Preferred Stock Warrants Liability
Liabilities:
Total liabilities		313
Money Market Funds
ASSETS
Total assets	111,801	21,680
Level 1
ASSETS
Total assets	111,801	21,680
Level 1 | Money Market Funds
ASSETS
Total assets	$ 111,801	21,680
Level 3
Liabilities:
Total liabilities		313
Level 3 | Convertible Preferred Stock Warrants Liability
Liabilities:
Total liabilities		$ 313

Financial Instruments and Fai_4

Financial Instruments and Fair Value Measurements - Schedule of Change in the Fair Value of the Warrant Liability (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Beginning balance	$ 313	$ 577
Net exercise of warrants	(133)	(211)
Expiration of warrants, included in change in fair value of warrant liability		(87)
Change in fair value of warrant liability	609	46
Conversion of Series A preferred stock warrants to common stock warrants upon the closing of the IPO	$ (789)
Ending balance		$ 325

Financial Instruments and Fai_5

Financial Instruments and Fair Value Measurements - Schedule of Fair Value of Warrants Determined Using the Black-Scholes Option Pricing Model (Details)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Expected term (in years)	5 years 3 months 10 days	6 years 2 months 15 days
Expected Volatility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assumption measurement input	43.9	42.8
Risk-free Interest Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assumption measurement input	2.49	2.62
Expected Dividend Yield
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assumption measurement input	0	0

Cash Equivalents - Summary of C

Cash Equivalents - Summary of Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis	$ 111,801	$ 21,680
Fair Value	111,801	21,680
Money Market Funds
Cash And Cash Equivalents [Line Items]
Amortized Cost Basis	111,801	21,680
Fair Value	$ 111,801	$ 21,680

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Inventory (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw material	$ 1,915	$ 1,084
Work in progress	1,103	634
Finished goods	2,643	2,313
Consigned inventory	1,353	1,100
Total inventory	$ 7,014	$ 5,131

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accrued employee compensation	$ 2,965	$ 3,135
Accrued research and development costs	1,736	1,115
Accrued professional services	713	1,391
Other	1,025	576
Total accrued liabilities	$ 6,439	$ 6,217

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Thousands	1 Months Ended			3 Months Ended
	Oct. 31, 2018	May 31, 2018ft²	Feb. 28, 2018	Mar. 31, 2019USD ($)	Mar. 31, 2018USD ($)
Loss Contingencies [Line Items]
Operating lease right-of-use asset				$ 2,645
Operating lease liability				1,916
Operating lease liability				2,793
Rent expense				300	$ 100
Fremont, California
Loss Contingencies [Line Items]
Lease term expiration date	Jun. 30, 2019		Sep. 30, 2019
Operating lease right-of-use asset				100
Operating lease liability				$ 100
Operating lease, remaining lease term				6 months
Santa Clara, California
Loss Contingencies [Line Items]
Lease term expiration date		Aug. 31, 2022
Operating lease right-of-use asset				$ 2,400
Operating lease, remaining lease term				3 years 4 months
Lease commencement date		2018-09
Area of office and laboratory space | ft²		35,000
Letter of credit secured by restricted cash				$ 500
Operating lease liability				2,600
Germany
Loss Contingencies [Line Items]
Operating lease right-of-use asset				100
Operating lease liability				$ 100
Operating lease, weighted average remaining lease term				14 months
Operating lease liability, weighted average incremental borrowing rate				6.93%

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Carrying Value of Operating Lease Liabilities (Details) $ in Thousands	Mar. 31, 2019USD ($)
Operating Lease Liabilities Payments Due [Abstract]
Remainder of 2019	$ 812
2020	861
2021	855
2022	581
Total minimum lease payments	3,109
Less: imputed interest	(316)
Total	$ 2,793

Convertible Preferred Stock a_3

Convertible Preferred Stock and Stockholder's Equity (Deficit) - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Mar. 06, 2019	Mar. 05, 2019	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Temporary Equity And Stockholders Equity [Line Items]
Preferred stock, shares authorized			5,000,000
Preferred stock, shares issued			0
Preferred stock, shares outstanding			0
Related Party Common Stock Warrants
Temporary Equity And Stockholders Equity [Line Items]
Warrants exercised price			$ 2.196
Initial Public Offering | Common Stock Warrants Related to Convertible Preferred Stock Warrants
Temporary Equity And Stockholders Equity [Line Items]
Common stock warrants issued	54,903
Adjustments to additional paid in capital	$ 0.8
Warrants exercised price			$ 3.096
Initial Public Offering | Related Party Common Stock Warrants
Temporary Equity And Stockholders Equity [Line Items]
Common stock warrants exercised	91,446
Warrants exercised price	$ 17
Common stock issued upon exercise of common stock warrants	79,632
Convertible Preferred Stock
Temporary Equity And Stockholders Equity [Line Items]
Convertible preferred stock, shares outstanding		18,670,259		18,670,328	17,562,214	17,510,045
Fractional shares that will be settled in cash			69
Common Stock
Temporary Equity And Stockholders Equity [Line Items]
Conversion of stock, common stock issued		18,670,259
Fractional shares that will be settled in cash			45

Convertible Preferred Stock a_4

Convertible Preferred Stock and Stockholder's Equity (Deficit) - Summary of Key Terms of Outstanding Common Stock Warrants (Details) - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 06, 2019	Dec. 31, 2018
Common Stock Warrants
Class Of Warrant Or Right [Line Items]
Common stock warrants outstanding	89,343		176,218
Related Party Common Stock Warrants
Class Of Warrant Or Right [Line Items]
Common stock warrants outstanding			141,778
Warrants Outstanding Exercise Price	$ 2.196
Warrants Outstanding Expiration	2025-05
Related Party Common Stock Warrants | Initial Public Offering
Class Of Warrant Or Right [Line Items]
Warrants Outstanding Exercise Price		$ 17
Common Stock Warrants Related to 2018 Loan and Security Agreement
Class Of Warrant Or Right [Line Items]
Common stock warrants outstanding	34,440		34,440
Warrants Outstanding Exercise Price	$ 4.026
Warrants Outstanding Expiration	2028-02
Common Stock Warrants Related to Convertible Preferred Stock Warrants | Initial Public Offering
Class Of Warrant Or Right [Line Items]
Common stock warrants outstanding	54,903
Warrants Outstanding Exercise Price	$ 3.096
Warrants Outstanding Expiration	2024-06

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Total Stock-Based Compensation (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 412	$ 273
Cost of Product Revenue
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	27	15
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	72	49
Sales and Marketing
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	108	43
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 205	$ 166

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Estimates Grant-Date Fair Value of Option Awards Using Black-Scholes Option Pricing Model with Assumptions (Detail)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected term (in years)	6 years 29 days	6 years 29 days
Expected volatility		45.90%
Expected volatility, minimum	42.40%
Expected volatility, maximum	42.90%
Risk-free interest rate		1.90%
Risk-free interest rate, minimum	2.50%
Risk-free interest rate, maximum	2.60%
Expected dividend yield	0.00%	0.00%

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - shares	1 Months Ended
	Mar. 31, 2019	Feb. 28, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for issuance	1,694,114		392,299
2019 Stock Option and Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance		2,000,430
Maximum period of automatic annual increase in common stock reserved for issuance		10 years
Automatic annual increase in common stock reserved for issuance		3.00%
Shares available for issuance	1,694,114
2019 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance	300,650
Purchase shares of common stock, price per share, percentage of fair market value	85.00%

Stock-Based Compensation - Sc_3

Stock-Based Compensation - Schedule of Activity under 2009 Plan and 2019 Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Shares Available for Grant
Shares Available for Grant, Beginning balance	392,299
Shares Available for Grant, Awards authorized	2,000,430
Shares Available for Grant, Options granted	(425,983)
Shares Available for Grant, Options cancelled	21,321
Shares Available for Grant, Ending balance	1,694,114	392,299
Number of Shares
Number of Shares, Beginning balance	3,636,358
Shares Available for Grant, Awards authorized	2,000,430
Number of Shares, Options granted	425,983
Number of Shares, Options exercised	(80,515)
Number of Shares, Options cancelled	(21,321)
Number of Shares, Ending balance	3,960,505	3,636,358
Number of Shares, Vested and exercisable, March 31, 2019	1,716,874
Number of Shares, Vested and expected to vest, March 31, 2019	3,960,505
Weighted-Average Exercise Price Per Share
Weighted-Average Exercise Price Per Share, Beginning balance	$ 3.54
Weighted-Average Exercise Price Per Share, Options granted	14.08
Weighted-Average Exercise Price Per Share, Options exercised	2.12
Weighted-Average Exercise Price Per Share, Options cancelled	3.12
Weighted-Average Exercise Price Per Share, Ending balance	4.67	$ 3.54
Weighted-Average Exercise Price Per Share, Vested and exercisable, March 31, 2019	2.78
Weighted-Average Exercise Price Per Share, Vested and expected to vest, March 31, 2019	$ 4.67
Weighted-Average Remaining Term (in years)
Weighted-Average Remaining Term (in years), Balance	7 years 10 months 13 days	7 years 9 months 14 days
Weighted-Average Remaining Term (in years), Vested and exercisable, March 31, 2019	6 years 7 months 2 days
Weighted-Average Remaining Term (in years), Vested and expected to vest, March 31, 2019	7 years 10 months 13 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Balance	$ 114,058	$ 11,267
Aggregate Intrinsic Value, Vested and exercisable, March 31, 2019	52,691
Aggregate Intrinsic Value, Vested and expected to vest, March 31, 2019	$ 114,058
2009 Equity Incentive Plan
Shares Available for Grant
Shares Available for Grant, Awards expired	(293,953)

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Outstanding Potentially Dilutive Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	4,055,176	20,995,547
Convertible Preferred Stock on an As-Converted Basis
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share		17,562,214
Common Stock Options Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	3,960,505	3,121,530
Early Exercised Options Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	5,328	41,240
Convertible Preferred Stock Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share		94,345
Common Stock Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	89,343	176,218

Segment and Geographic Inform_3

Segment and Geographic Information - Schedule of Product Revenue Based on Location (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues From External Customers And Long Lived Assets [Line Items]
Product revenue	$ 7,269	$ 1,322
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Product revenue	$ 3,636	$ 897
Germany
Revenues From External Customers And Long Lived Assets [Line Items]
Product revenue	643	254
Rest of Europe
Revenues From External Customers And Long Lived Assets [Line Items]
Product revenue	2,736	129
All Other Countries
Revenues From External Customers And Long Lived Assets [Line Items]
Product revenue	$ 254	$ 42