Shockwave Medical (SWAV) 10-K 12 Mar 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2019	Mar. 05, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
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		31,765,657
Entity Public Float			$ 1
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity File Number	001-38829
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-0494101
Entity Address, Address Line One	5403 Betsy Ross Drive
Entity Address, City or Town	Santa Clara
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	95054
City Area Code	510
Local Phone Number	279-4262
Document Annual Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Title of 12(b) Security	ShockWave Medical Inc., common stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Documents Incorporated by Reference	Portions of the registrant’s Proxy Statement for its 2020 Annual Meeting of Stockholders are incorporated herein by reference in Part III of this Annual Report on Form 10-K to the extent stated herein. Such proxy statement will be filed with the Securities and Exchange Commission within 120 days of the registrant’s fiscal year ended December 31, 2019.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
CURRENT ASSETS:
Cash and cash equivalents	$ 139,045	$ 39,643
Short-term investments	56,304
Accounts receivable, net	7,377	2,850
Inventory	12,074	5,131
Prepaid expenses and other current assets	1,897	1,112
Total current assets	216,697	48,736
Operating lease right-of-use assets	8,825
Property and equipment, net	4,910	2,619
Other assets	1,506	2,066
TOTAL ASSETS	231,938	53,421
CURRENT LIABILITIES:
Accounts payable	2,790	1,487
Term notes, current portion	6,667	1,667
Accrued liabilities	13,777	6,217
Lease liability, current portion	774
Total current liabilities	24,008	9,371
Lease liability, noncurrent portion	8,125
Term notes, noncurrent portion	7,152	13,383
Convertible preferred stock warrant liability		313
Other liabilities		136
TOTAL LIABILITIES	39,285	23,203
Commitments and contingencies (Note 6)
Convertible preferred stock, $0.001 par value; 5,000,000 and 229,098,987 shares authorized as of December 31, 2019 and 2018; nil and 18,670,328 shares issued and outstanding as of December 31, 2019 and 2018		152,806
STOCKHOLDERS’ EQUITY (DEFICIT):
Preferred stock
Common stock, $0.001 par value; 281,274,838 and 325,000,000 shares authorized as of December 31, 2019 and 2018; 31,446,787 and 1,824,852 shares as of December 31, 2019 and 2018 issued and outstanding	31	2
Additional paid-in capital	370,561	4,275
Accumulated other comprehensive income	35
Accumulated deficit	(177,974)	(126,865)
TOTAL STOCKHOLDERS’ EQUITY (DEFICIT)	192,653	(122,588)
TOTAL LIABILITIES, CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT)	$ 231,938	$ 53,421

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	229,098,987
Preferred stock, shares issued		18,670,328
Preferred stock, shares outstanding		18,670,328
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	281,274,838	325,000,000
Common stock, shares issued	31,446,787	1,824,852
Common stock, shares outstanding	31,446,787	1,824,852

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue:
Product revenue	$ 42,927	$ 12,263	$ 1,719
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Operating expenses:
Cost of product revenue	$ 17,159	$ 7,250	$ 2,836
Type of Cost, Good or Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Research and development	$ 32,853	$ 22,698	$ 17,963
Sales and marketing	30,620	17,536	6,363
General and administrative	14,134	5,979	5,422
Total operating expenses	94,766	53,463	32,584
Loss from operations	(51,839)	(41,200)	(30,865)
Interest expense	(944)	(401)	(58)
Change in fair value of warrant liability	(609)	(52)	(32)
Other income, net	2,345	589	366
Net loss before taxes	(51,047)	(41,064)	(30,589)
Income tax provision	62	38	26
Net loss	(51,109)	(41,102)	(30,615)
Unrealized gain (loss) on available-for-sale securities	35	1	(1)
Total comprehensive loss	$ (51,074)	$ (41,101)	$ (30,616)
Net loss per share, basic and diluted	$ (2.14)	$ (23.39)	$ (19.71)
Shares used in computing net loss per share, basic and diluted	23,904,828	1,757,102	1,553,365

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Initial Public Offering	Public Offering	Convertible Preferred Stock	Series C Convertible Preferred Stock	Series D Convertible Preferred Stock	Common Stock	Common StockInitial Public Offering	Common StockPublic Offering	Additional Paid-In Capital	Additional Paid-In CapitalInitial Public Offering	Additional Paid-In CapitalPublic Offering	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning Balance at Dec. 31, 2016	$ (53,831)						$ 2			$ 1,315				$ (55,148)
Temporary equity, Beginning balance, Shares at Dec. 31, 2016				14,605,589
Temporary equity, Beginning balance at Dec. 31, 2016				$ 102,180
Beginning balance, Shares at Dec. 31, 2016							1,555,510
Issuance of convertible preferred stock, net of issuance costs					$ 34,907
Issuance of convertible preferred stock, net of issuance costs, Shares					2,840,504
Exercise of Series A-1 warrants				$ 382
Temporary equity, Exercise of Series A-1 warrants, Shares				63,952
Exercise of stock options	$ 139									139
Exercise of stock options, Shares	71,522						71,522
Unrealized gain (loss) on available-for-sale securities	$ 35												$ 35
Vesting of early exercised options	51									51
Stock-based compensation	965									965
Net loss	(30,615)													(30,615)
Ending balance at Dec. 31, 2017	(83,292)						$ 2			2,470			(1)	(85,763)
Temporary equity, Ending balance, Shares at Dec. 31, 2017				17,510,045
Temporary equity, Ending balance at Dec. 31, 2017				$ 137,469
Ending balance, Shares at Dec. 31, 2017							1,627,032
Issuance of convertible preferred stock, net of issuance costs						$ 14,920
Issuance of convertible preferred stock, net of issuance costs, Shares						1,090,608
Exercise of Series A-1 warrants				$ 417
Temporary equity, Exercise of Series A-1 warrants, Shares				69,675
Issuance of common stock warrants	104									104
Exercise of stock options	$ 326									326
Exercise of stock options, Shares	197,820						197,820
Unrealized gain (loss) on available-for-sale securities	$ 1												1
Vesting of early exercised options	78									78
Stock-based compensation	1,297									1,297
Net loss	(41,102)													(41,102)
Ending balance at Dec. 31, 2018	$ (122,588)						$ 2			4,275				(126,865)
Temporary equity, Ending balance, Shares at Dec. 31, 2018	18,670,328			18,670,328
Temporary equity, Ending balance at Dec. 31, 2018	$ 152,806			$ 152,806	$ 79,729	$ 14,920
Ending 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							180,952
Conversion of preferred stock to common stock upon initial public offering	152,806						$ 18			152,788
Temporary equity, Conversion of preferred stock to common stock upon initial public offering, Shares				(18,670,328)
Temporary equity, Conversion of preferred stock to common stock upon initial public offering				$ (152,806)
Conversion of preferred stock 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		$ 99,924	$ 96,677					$ 7	$ 3		$ 99,917	$ 96,674
Issuance of common stock, Shares								6,555,000	2,854,048
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	$ 2,206									2,206
Exercise of stock options, Shares	722,242						723,155
Unrealized gain (loss) on available-for-sale securities	$ (1)												(1)
Vesting of early exercised options	27									27
Stock-based compensation	3,646									3,646
Adjustment for fractional shares resulting from reverse stock split	(3)									(3)
Adjustment for fractional shares resulting from reverse stock split, Shares							(114)
Net loss	(51,109)													(51,109)
Ending balance at Dec. 31, 2019	$ 192,653						$ 31			$ 370,561			$ 35	$ (177,974)
Ending balance, Shares at Dec. 31, 2019							31,446,787

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Issuance cost		$ 80	$ 93
Initial Public Offering
Issuance costs	$ 11,500
Public Offering
Issuance costs	$ 6,800

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (51,109)	$ (41,102)	$ (30,615)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,337	700	468
Stock-based compensation	3,646	1,297	965
Amortization of right-of-use assets	944
Accretion of discount on available-for-sale securities	(543)
Loss on write down of fixed assets	67	31	38
Change in fair value of warrant liability	609	52	32
Amortization of debt issuance costs	436	206	18
Changes in operating assets and liabilities:
Accounts receivable	(4,527)	(2,211)	(594)
Inventory	(6,824)	(2,608)	(1,863)
Prepaid expenses and other current assets	(785)	(144)	(373)
Other assets	41	(917)
Accounts payable	1,272	360	249
Accrued and other current liabilities	8,339	2,773	1,328
Lease liabilities	(1,010)
Other liabilities		98
Net cash used in operating activities	(48,107)	(41,465)	(30,347)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of available-for-sale securities	(119,476)		(17,707)
Proceeds from maturities of available-for-sale securities	63,750	1,807	15,900
Purchase of property and equipment	(3,817)	(1,981)	(425)
Net cash used in investing activities	(59,543)	(174)	(2,232)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock upon initial public offering, net of issuance costs paid	100,547
Proceeds from issuance of convertible preferred stock, net of issuance costs		14,920	34,907
Proceeds from issuance of common stock in private placement	10,000
Issuance of common stock in public offering, net of issuance costs	96,856
Proceeds from term loans		14,988
Payment of deferred offering costs		(626)
Proceeds from stock option exercises	2,206	426	139
Proceeds from warrant exercises	110	101	198
Principal payment of term loan	(1,667)		(1,557)
Net cash provided by financing activities	208,052	29,809	33,687
Net increase (decrease) in cash, cash equivalents and restricted cash	100,402	(11,830)	1,108
Cash, cash equivalents and restricted cash at beginning of period	40,093	51,923	50,815
Cash, cash equivalents and restricted cash equivalents at end of period	140,495	40,093	51,923
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Interest paid	534	156	40
Income tax paid	120	5
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		316
Deferred offering cost included in account payable and accrued liabilities		893
Offering cost included in account payable and accrued liabilities	179
Common stock warrants issued on conversion of preferred stock warrants and the reclassification of the warrant liability	789
Right-of-use asset obtained in exchange for lease liability	6,948
Property and equipment purchases included in accounts payable and accrued liabilities	52	55	$ 58
Issuance of common stock warrants in connection with debt financing		$ 104
Transfer of fixed assets to inventory	$ 119

Organization and Basis of Prese

Organization and Basis of Presentation	12 Months Ended
	Dec. 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 11, 2019, the Company completed an initial public offering (“IPO”) of its common stock. As part of the IPO, the Company issued and sold 6,555,000 shares of its common stock, which included 855,000 shares sold pursuant to the exercise of the underwriters’ over-allotment option, at a public offering price of $17.00 per share. The Company received net proceeds of approximately $99.9 million from the IPO, after deducting underwriters’ discounts and commissions. Prior to the completion of the IPO, all shares of Series A, A-1, B, C and D convertible preferred stock then outstanding were converted into 18,670,259 shares of common stock on a one-to-one basis. 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, 101,744 shares of common stock were issued upon net exercise of warrants at the time of the IPO. 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. Public Offering On November 15, 2019, the Company completed an underwritten public offering (“Follow-On Offering”) of 2,854,048 shares of its common stock, including 372,267 shares sold pursuant to the underwriters’ exercise of their option to purchase additional shares at a public offering price of $36.25 per share. The Company received net proceeds of $96.7 million from the Follow-On Offering after deducting underwriters’ discounts and commissions. 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 of the Company’s common stock and convertible preferred stock on a 12.2-for-one basis (the “Reverse Stock Split”). The par values of the common stock and convertible preferred stock were not adjusted as a result of the Reverse Stock Split. All references to common stock, convertible preferred stock, warrants to purchase common stock, warrants to purchase convertible preferred stock, options to purchase common stock, early exercised options, share data, per share data and related information contained in the consolidated Liquidity As of December 31, 2019, the Company had cash, cash equivalents and short-term investments of $195.3 million, which are available to fund future operations. The Company believes that its cash, cash equivalents and short-term investments as of December 31, 2019, will be sufficient for the Company to continue as a going concern for at least 12 months from the date the consolidated financial statements are filed with the Securities and Exchange Commission (“SEC”).

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Principles of Consolidation The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiary. All intercompany balances and transactions have been eliminated in consolidation. Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions made in the accompanying consolidated financial statements include, but are not limited to the valuation of inventory, the fair value of common stock, the fair value of preferred stock warrant liabilities, the fair value of stock options, recoverability of the Company’s net deferred tax assets, and related valuation allowance and certain accruals. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could materially differ from those estimates . 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. The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the consolidated balance sheets that sum to the total of the same amounts shown in the consolidated statements of cash flows: December 31, 2019 December 31, 2018 (in thousands) Cash and cash equivalents $ 139,045 $ 39,643 Restricted cash 1,450 450 Total cash, cash equivalents, and restricted cash $ 140,495 $ 40,093 Restricted cash as of December 31, 2019 and 2018 relates to letters of credit established for leases entered into in May 2018 and December 2019 and is recorded as other assets on the consolidated balance sheets. Short-Term Investments Short-term investments have been classified as available-for-sale and are carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. The Company determines the appropriate classification of its investments in debt securities at the time of purchase. Available-for-sale securities with original maturities beyond three months at the date of purchase are classified as current based on their availability for use in current operations. Unrealized gains and losses are excluded from earnings and are reported as a component of comprehensive loss. The Company periodically evaluates whether declines in fair values of its marketable securities below their book value are other-than-temporary. This evaluation consists of several qualitative and quantitative factors regarding the severity and duration of the unrealized loss as well as the Company’s ability and intent to hold the marketable security until a forecasted recovery occurs. Additionally, the Company assesses whether it has plans to sell the security or it is more likely than not it will be required to sell any marketable securities before recovery of its amortized cost basis. Realized gains and losses and declines in fair value judged to be other than temporary, if any, on marketable securities are included in other income, net. The cost of investments sold is based on the specific-identification method. Interest on marketable securities is included in other income, net. Concentration of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, restricted cash, investments and trade receivables. Risks associated with cash, cash equivalents and restricted cash are mitigated by banking with creditworthy institutions and the Company’s investments have investment grade ratings when purchased. The Company performs ongoing evaluations of its customers and generally does not require collateral. Concentration of Customers For the years ended December 31, 2019 and 2018, no customer accounted for 10% of the Company’s revenue. There was one customer which accounted for 11% of the Company’s accounts receivable as of December 31, 2019. There were no customers which accounted for more than 10% of the Company’s accounts receivable as of December 31, 2018. Fair Value of Financial Instruments The Company’s cash and cash equivalents, restricted cash, short-term investments, 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. Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at invoice value, net of any allowance for doubtful accounts. Estimates of the allowance for doubtful accounts are determined based on existing contractual payment terms, historical payment patterns of customers and individual customer circumstances. The allowance for doubtful accounts was $194,000 as of December 31, 2019 and the Company recognized accounts receivable write-offs in the amount of $3,400 for the year ended December 31, 2019. The allowance for doubtful accounts was $76,000 as of December 31, 2018 and the Company recognized accounts receivable write-offs in the amount of $1,000 for the year ended December 31, 2018. Inventory Inventory is stated at the lower of standard cost (which approximates actual cost on a first-in, first-out basis) and net realizable value. Inventory costs include direct materials, direct labor and normal manufacturing overhead. Prior to achieving normal capacity, excess capacity costs are expensed in cost of product revenue as period costs. Finished goods that are used for research and development are expensed as consumed. Provisions for slow-moving, excess or obsolete inventories are recorded when required to reduce inventory values to their estimated net realizable values based on product life cycle, development plans, product expiration or quality issues. Property and Equipment Property and equipment are stated at cost, net of accumulated depreciation and amortization. Depreciation and amortization is computed using the straight-line method over the estimated useful lives of the respective assets, generally three to five years. Leasehold improvements are amortized over the lesser of their useful life or the remaining life of the lease. When assets are retired or otherwise disposed of, the cost and related accumulated depreciation and amortization are removed from the balance sheet and any resulting gain or loss is reflected in operations in the period realized. Maintenance and repairs are charged to operations as incurred. Impairment of Long-Lived Assets The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by comparing the carrying amount to the future net undiscounted cash flows which the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the projected discounted future net cash flows arising from the asset. The Company has not identified any such impairment losses to date. 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 adopted Accounting Standards Codification (“ASC”) 606, Revenue from Contracts with Customers Revenue Recognition 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. Under ASC 606, 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 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. Research and Development Costs Research and development costs, including new product development, regulatory compliance, and clinical research are expensed as incurred. Accrued Research and Development Costs The Company accrues liabilities for estimated costs of research and development activities conducted by its third-party service providers, which include the conduct of preclinical and clinical studies. The estimated costs of research and development activities are recorded based upon the estimated amount of services provided but not yet invoiced, and these costs are included in accrued liabilities on the consolidated balance sheets and within research and development expense on the consolidated statements of operations and comprehensive loss. These costs are accrued for based on factors such as estimates of the work completed and budget provided and in accordance with agreements established with third-party service providers. Significant judgments and estimates are made in determining the accrued liabilities balance in each reporting period. Accrued liabilities are adjusted as actual costs become known. There have not been any material differences between accrued costs and actual costs incurred since the Company’s inception. Stock-Based Compensation The Company accounts for share-based payments at fair value. The fair value of stock options is measured using the Black-Scholes option-pricing model. For share-based awards that vest subject to the satisfaction of a service requirement, the fair value measurement date for stock-based compensation awards is the date of grant and the expense is recognized on a straight-line basis, over the vesting period. The Company accounts for forfeitures as they occur. Leases The Company adopted ASU No. 2016-02, Leases Leases For its long-term operating lease, the Company recognized a right-of-use asset and a lease liability on its 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 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. Defined Contribution Plan The Company has a defined contribution retirement savings plan under Section 401(k) of the Internal Revenue Code. This plan allows eligible employees to defer a portion of their annual compensation on a pre-tax basis. The Company is authorized to make matching contributions but has not made such contributions for the years ended December 31, 2019 and 2018. Comprehensive Loss Comprehensive loss is comprised of net loss and changes in unrealized gains and losses on the Company’s available-for-sale investments. Foreign Currency The functional currency of the Company’s foreign subsidiary is the U.S. Dollar. Accordingly, all monetary assets and liabilities of the subsidiary are remeasured at the current exchange rate at the end of the period, nonmonetary assets and liabilities are remeasured at historical rates, and revenue and expenses are remeasured at average exchange rates during the period. There were net foreign currency transaction gains of $56,000 for the year ended December 31, 2019 and net foreign currency transaction losses of Net Loss Per Share Basic net loss per share is calculated by dividing net loss by the weighted-average number of shares of common stock outstanding for the period, without consideration of potential dilutive shares of common stock. The unvested portion of early exercised stock options are excluded from the computation of weighted-average shares as the continuing vesting of such shares is contingent on the holders’ continued service to the Company. Since the Company was in a loss position for the period presented, basic net loss per share is the same as diluted net loss per share since the effects of potentially dilutive securities are antidilutive. Income Taxes The Company uses the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial reporting and the tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. Management makes an assessment of the likelihood that the resulting deferred tax assets will be realized. A valuation allowance is provided when it is more likely than not that some portion or all of a deferred tax asset will not be realized. Due to the Company’s historical operating performance and the recorded cumulative net losses in prior fiscal periods, the net deferred tax assets have been fully offset by a valuation allowance. The Company recognizes uncertain income tax positions at the largest amount that is more likely than not to be sustained upon audit by the relevant taxing authority. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained. Changes in recognition or measurement are reflected in the period in which judgment occurs. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of provision for income taxes. Segment Reporting Operating segments are defined as components of an entity for which separate financial information is available and that is regularly reviewed by the Chief Operating Decision Maker (“CODM”) in deciding how to allocate resources to an individual segment and in assessing performance. The Company’s CODM is its Chief Executive Officer. The Company has determined that it operates in one segment. Recently Adopted Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases 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 year ended December 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 Recent Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815) and Leases (Topic 842): Effective Dates In November 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740)

Financial Instruments and Fair

Financial Instruments and Fair Value Measurements	12 Months Ended
	Dec. 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: December 31, 2019 Level 1 Level 2 Level 3 Total (in thousands) Assets: U.S. Treasury securities $ 43,245 $ — $ — $ 43,245 Money market funds 29,386 — — 29,386 Reverse repurchase agreements — 10,000 — 10,000 Commercial paper — 6,958 — 6,958 Corporate bonds — 8,096 — 8,096 Total assets $ 72,631 $ 25,054 $ — $ 97,685 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 The change in the fair value of the warrant liability is summarized below: Year Ended December 31, 2019 2018 2017 (in thousands) Beginning Balance $ 313 $ 577 $ 729 Expiration of warrants, included in change in fair value of warrant liability — (133 ) — Net exercise of warrants (133 ) — — Exercise of warrants — (316 ) (184 ) Change in fair value of warrant liability 609 185 32 Conversion of Series A preferred stock warrants to common stock warrants upon the closing of the IPO (789 ) — — Balance at December 31, 2019 $ — $ 313 $ 577 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 consolidated statements of operations and comprehensive loss. The fair value of the warrants, which were converted to common stock warrants upon the closing of the IPO in March 2019, was determined using the Black-Scholes option pricing model and the following assumptions: December 31, 2019 2018 Expected term (in years) 5.3 5.5 Expected volatility 43.9% 42.8% Risk-free interest rate 2.5% 2.9% Expected dividend yield 0% 0% There were no transfers between Levels 1, 2 or 3 for the periods presented.

Cash Equivalents and Short-Term

Cash Equivalents and Short-Term Investments	12 Months Ended
	Dec. 31, 2019
Cash And Cash Equivalents [Abstract]
Cash Equivalents and Short-Term Investments	4. Cash Equivalents and Short-Term Investments The following is a summary of the Company’s cash equivalents and short-term investments: December 31, 2019 Amortized Cost Basis Unrealized Gains Unrealized Losses Fair Value (in thousands) U.S. Treasury securities $ 43,219 $ 27 $ (1 ) $ 43,245 Money market funds 29,386 — — 29,386 Reverse repurchase agreements 10,000 — — 10,000 Commercial paper 6,958 — — 6,958 Corporate bonds 8,087 9 — 8,096 Total $ 97,650 $ 36 $ (1 ) $ 97,685 Reported as: Cash equivalents $ 41,381 Short-term investments 56,304 Total $ 97,685 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 At December 31, 2019, the remaining contractual maturities for available-for-sale securities were less than one year. For the years ended December 31, 2019 and 2018, the Company recognized no material realized gains or losses on cash equivalents and short-term investments.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Balance Sheet Components	5. Balance Sheet Components Inventory Inventory consists of the following: December 31, 2019 2018 (in thousands) Raw material $ 2,501 $ 1,084 Work in progress 1,364 634 Finished goods 6,642 2,313 Consigned inventory 1,567 1,100 Total inventory $ 12,074 $ 5,131 Property and Equipment, Net Property and equipment, net consists of the following: December 31, 2019 2018 (in thousands) Equipment $ 3,759 $ 2,321 Equipment on loan to customers 1,495 786 Office furniture 76 90 Software 97 76 Leasehold improvements 1,329 764 Construction in progress 553 236 Property and equipment, gross 7,309 4,273 Less accumulated depreciation and amortization (2,399 ) (1,654 ) Total property and equipment, net $ 4,910 $ 2,619 Depreciation and amortization expense amounted to $1.3 million, $0.7 million and $0.5 million for the years ended December 31, 2019, 2018 and 2017, respectively. Other Assets Other assets consist of the following: December 31, 2019 2018 (in thousands) Deferred offering costs $ — $ 1,519 Restricted cash 1,450 450 Other 56 97 Total other assets $ 1,506 $ 2,066 Accrued Liabilities Accrued liabilities consist of the following: December 31, 2019 2018 (in thousands) Accrued employee compensation $ 8,139 $ 3,135 Accrued research and development costs 3,090 1,115 Accrued professional services 804 1,391 Other 1,744 576 Total accrued liabilities $ 13,777 $ 6,217

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	6. Commitments and Contingencies Operating Leases The Company’s lease for office space located in Fremont, California expired on September 30, 2019. In May 2018, the Company entered into a new lease agreement for office and laboratory space which consists 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 consolidated balance sheets. In connection with the lease, the Company has an operating lease right-of-use asset of $1.9 million as of December 31, 2019 and an aggregate lease liability of $2.1 million on its consolidated balance sheet. The remaining lease term is two years and eight months. In December 2019, the Company entered into a lease for office and laboratory space in two buildings located in Santa Clara, California (the “Betsy Ross Lease”). The purpose and effect of the lease agreement is to extend the existing Santa Clara office and laboratory premises of 35,000 square foot to approximately 85,200 square feet of rentable space. The Santa Clara lease entered in May 2018 will continue in its existing terms (and with no changes to its terms, including its base rent) until its expiration on August 31, 2022, at which point the leased space under the May 2018 lease will become subject to the terms of the Betsy Ross Lease. The initial term of the first building in the Betsy Ross Lease began in December 2019 and is for 96 months, with an option by the Company to extend for an additional five years on one or both of the buildings. The base rent of part of the premises for the first building shall be abated for the first 19 months, and the second floor of the same premises shall be abated for the first four months. The landlord provided the Company with a tenant improvement allowance of up to $1.8 million. In connection with the Betsy Ross Lease, the Company provided an initial security deposit of $1.0 million in the form of a letter of credit, which is secured by restricted cash recorded as other assets on the consolidated balance sheets. While this amount will increase to $1.5 million on September 1, 2022 when the office and laboratory space of the lease entered into in May 2018 is added to the Betsy Ross Lease, the letter of credit will be reduced annually from and after September 1, 2022 until the Betsy Ross Lease’s expiration. In connection with the first building lease, the Company has recorded an operating lease right-of-use asset of $6.8 million as of December 31, 2019 and an aggregate lease liability of $6.7 million on its consolidated balance sheet. The remaining lease term is seven years and eleven months. The Company also leases vehicles for use by employees. In connection with the vehicle leases, the Company has an operating lease right-of-use asset of $115,000 as of December 31, 2019 and an aggregate lease liability of $115,000 on its consolidated balance sheet. The weighted average remaining lease term is two years and four months. The weighted average incremental borrowing rate used to measure the operating lease liability is 6.97%. 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. The following are minimum future rental payments owed under these agreements which commenced as of December 31, 2019: (in thousands) 2020 $ 1,292 2021 1,941 2022 2,063 2023 1,498 2024 1,546 Thereafter 4,826 Total minimum lease payments $ 13,166 Less: imputed interest (4,267 ) Total lease liability $ 8,899 The following are minimum future rental payments owed for the second building under the Betsy Ross Lease which has not yet commenced as of December 31, 2019: (in thousands) 2020 $ — 2021 — 2022 345 2023 1,044 2024 1,078 Thereafter 3,365 Total minimum lease payments $ 5,832 Operating lease cost for the year ended December 31, 2019 was $1.2 million. Rent expense for the years ended December 31, 2018 and 2017 was $0.9 million and $0.4 million, respectively.

Term Notes

Term Notes	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Term Notes	7. Term Notes 2014 Loan and Security Agreement In June 2014, the Company entered into a Loan and Security Agreement with Silicon Valley Bank (the “2014 Loan and Security Agreement”), under which a total of $4.0 million was borrowed. The Company made monthly payments of principal and interest through the maturity date of October 1, 2017, and a one-time payment of $0.2 million on the maturity date of the loan. All the borrowings under the 2014 Loan and Security Agreement were fully repaid as of December 31, 2017. In connection with the 2014 Loan and Security Agreement, the Company issued warrants to purchase shares of the Company’s Series A-1 convertible preferred stock. Upon issuance, the fair value of the warrants was recorded as a debt discount. The debt discount was amortized to interest expense, net over the repayment period of the loan. During the year ended December 31, 2017, amortization of debt discount was $0.1 million. Loan and Security Agreement In February 2018, the Company entered into a Loan and Security Agreement with Silicon Valley Bank (the “Loan and Security Agreement”). The terms of the Loan and Security Agreement included a term loan of $15.0 million and a revolving line of credit of $2.0 million. The term loan was available in two tranches, of which the first tranche of $10.0 million was funded in June 2018 and the second tranche of $5.0 million was funded in December 2018. The Company has not drawn down on its revolving line of credit as of December 31, 2019. The term loan matures in December 2021, with interest-only monthly payments until September 2019. The interest-only period will extend through December 2019 if certain financing milestones are met. The term loan accrues interest at a floating per annum rate equal to the greater of the Wall Street Journal prime rate minus 1.75% and 2.75% (5.87% as of December 31, 2019). There is a final payment equal to 6.75% of the original aggregate principal amount, or $1.0 million, of the term loan advances, which will be accrued over the term of the loan using the effective-interest method. The line of credit matures in February 2021 and accrues interest at the Wall Street Journal prime rate. In connection with the execution of the Loan and Security Agreement, the Company issued warrants to purchase 34,440 shares of the Company’s common stock. Upon issuance, the fair value of the warrants of $0.1 million was recorded as a debt issuance cost. The debt issuance cost will be amortized to interest expense, net over the repayment period of the loan. During the years ended December 31, 2019 and 2018, the Company recorded interest expense related to the Loan and Security Agreement of $0.5 million and $0.2 million, respectively. Debt discount amortized as interest expense was $0.4 million and $0.2 million for the years ended December 31, 2019 and 2018, respectively. The term loan is secured by all of the Company’s assets, excluding intellectual property and certain other assets. The loan contains customary affirmative and restrictive covenants, including with respect to the Company’s ability to enter into fundamental transactions, incur additional indebtedness, grant liens, pay any dividend or make any distributions to its holders, make investments, merge or consolidate with any other person or engage in transactions with the Company’s affiliates, but does not include any financial covenants. Long-term debt and net premium balances are as follows: December 31, 2019 2018 (in thousands) Principal amount of term note $ 13,334 $ 15,000 Net premium associated with accretion of final payment, issuance of common stock warrants, and other debt issuance costs 485 50 Term note, current and noncurrent 13,819 15,050 Less term note, current portion (6,667 ) (1,667 ) Term note, noncurrent portion $ 7,152 $ 13,383 Future minimum payments of principal and estimated payments of interest on the Company’s outstanding variable rate borrowings as of December 31, 2019 are as follows: Year ending December 31: (in thousands) 2020 $ 7,000 2021 7,789 Total future payments 14,789 Less amounts representing interest (442 ) Less final payment (1,013 ) Total principal amount of term note payments $ 13,334 See Note 13 for the Company’s amendment to the Loan and Security Agreement.

Convertible Preferred Stock and

Convertible Preferred Stock and Stockholders’ Equity (Deficit)	12 Months Ended
	Dec. 31, 2019
Stockholders Equity [Abstract]
Convertible Preferred Stock and Stockholders’ Equity (Deficit)	8. 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, the fractional shares resulting from the Reverse Stock Split, aggregating to 45 whole shares of common stock and 69 whole shares of convertible preferred stock were settled in cash in fiscal 2019. 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 December 31, 2019. The c onvertible preferred stock as of December 31, 2018 consisted of the following: December 31, 2018 Shares Authorized Shares Issued and Outstanding Net Carrying Value Aggregate Liquidation Preference (in thousands, except share amounts) Series A 19,280,722 1,580,387 $ 4,226 $ 4,473 Series A-1 51,874,893 4,197,138 14,054 12,996 Series B 64,777,331 5,309,617 39,877 40,000 Series C 79,209,457 6,492,578 79,729 80,000 Series D 13,956,584 1,090,608 14,920 15,000 229,098,987 18,670,328 $ 152,806 $ 152,469 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. In April 2019, all of these common stock warrants were net exercised into 49,321 shares of common stock. Common Stock Warrants Upon the IPO, 91,446 common stock warrants held by related parties 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 a Loan and Security Agreement with Silicon Valley Bank for a term loan and revolving line of credit, the Company issued warrants to purchase shares of the Company’s common stock. In April 2019, all of these common stock warrants were net exercised into 29,887 shares of common stock. The key terms of the outstanding common stock warrants are summarized in the following table: Warrants Outstanding December 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 Loan and Security Agreement — 34,440 $ 4.026 February 2028 Total common stock warrants — 176,218

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	9. Stock-Based Compensation Total stock-based compensation was as follows: Year Ended December 31, 2019 2018 2017 (in thousands) Cost of product revenue $ 268 $ 67 $ 46 Research and development 943 235 185 Sales and marketing 972 294 130 General and administrative 1,463 701 604 Total stock-based compensation $ 3,646 $ 1,297 $ 965 Determination of Fair Value The estimated grant-date fair value of all the Company’s stock-based awards was calculated using the Black-Scholes option pricing model, based on the following assumptions: Year Ended December 31, 2019 2018 2017 Expected term (in years) 6.08 6.08 6.08 Expected volatility 42.4%-42.9% 40.8%-41.9% 45.6% Risk-free interest rate 2.4%-2.6% 2.5%-3.1% 1.9%-2.2% Expected dividend yield 0% 0% 0% The fair value of each stock option grant was determined by the Company using the methods and assumptions discussed below. Each of these inputs is subjective and generally requires significant judgment and estimation by management. Expected Term— The expected term represents the period that stock-based awards are expected to be outstanding. The Company’s historical share option exercise information is limited due to a lack of sufficient data points, and did not provide a reasonable basis upon which to estimate an expected term. The expected term for option grants is therefore determined using the simplified method. The simplified method deems the expected term to be the midpoint between the vesting date and the contractual life of the stock-based awards. Expected Volatility— Since the Company has limited trading history for its common stock due to its short trading history, the expected volatility was estimated based on the average volatility for comparable publicly traded biotechnology companies over a period equal to the expected term of the stock option grants. The comparable companies were chosen based on their similar size, stage in the life cycle or area of specialty. Risk-Free Interest Rate— The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the date of grant for zero-coupon U.S. Treasury notes with maturities approximately equal to the stock-based awards’ expected term. Expected Dividend Yield— The expected dividend yield is zero as the Company has not paid nor does it anticipate paying any dividends on its common stock in the foreseeable future. The Company has elected to recognize forfeitures of share-based payment awards as they occur. 2009 Equity Incentive Plan and 2019 Equity Incentive Plan On June 17, 2009, the Company adopted the 2009 Equity Incentive Plan (the “Plan”) under which the Board may 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 a variety of awards under the 2019 Plan, including stock options, stock appreciation rights, awards of restricted stock and awards of restricted stock units The Board has the authority to determine to whom options will be granted, the number of shares, the term and the exercise price. If an individual owns stock representing 10% or more of the outstanding shares, the price of each share shall be at least 110% of the fair market value, as determined by the Board. Options granted under the Plan have a term of up to 10 years and generally vest over a 4 year period with a straight-line vesting and a 25% one year cliff. As of December 31, 2019, the Company had reserved 1,421,674 shares of common stock for issuance under the 2019 Plan. Stock Options 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, 2016 887,885 1,365,934 $ 1.95 $ 2,011 Awards authorized 1,352,677 — Options granted (1,974,589 ) 1,974,589 3.42 Options exercised — (71,522 ) 1.95 Options cancelled 160,397 (160,397 ) 2.44 Balance, December 31, 2017 426,370 3,108,604 $ 2.81 $ 8.03 $ 3,647 Awards authorized 691,503 — Options granted (1,015,963 ) 1,015,963 5.25 Options exercised — (197,820 ) 2.20 Options cancelled 290,389 (290,389 ) 3.42 Balance, December 31, 2018 392,299 3,636,358 $ 3.54 $ 7.79 $ 11,267 Awards authorized 2,000,430 — Options expired (287,600 ) — Options granted (442,858 ) 442,858 14.69 Options exercised — (722,242 ) 3.10 Options cancelled 41,973 (41,973 ) 3.85 Balance, December 31, 2019 1,704,244 3,315,001 $ 5.08 $ 7.28 $ 128,744 Vested and exercisable, December 31, 2019 1,741,614 $ 3.31 $ 6.41 $ 70,721 Vested and expected to vest, December 31, 2019 3,315,001 $ 5.08 $ 7.28 $ 128,744 The weighted-average grant date fair value of options granted during the years ended December 31, 2019, 2018 and 2017 was $6.58, $2.56, and $1.59 per share, respectively. The total grant date fair value of options vested was $1.9 million, $1.6 million and $0.9 million for the years ended December 31, 2019, 2018 and 2017, respectively. As of December 31, 2019, total unrecognized stock-based compensation related to unvested stock options was $4.6 million, which the Company expects to recognize over a remaining weighted-average period of 2.1 years. Restricted Stock Units Restricted stock units (“RSUs”) are share awards that entitle the holder to receive freely tradable shares of the Company’s common stock upon vesting. The RSUs cannot be transferred and the awards are subject to forfeiture if the holder’s employment terminates prior to the release of the vesting restrictions. The RSUs generally vest over a four-year period with straight-line vesting and a 25% one year cliff or over a three year period in equal amounts on a semi-annual basis, provided the employee remains continuously employed with the Company. The fair value of the RSUs is equal to the closing price of the Company’s common stock on the grant date. RSU activity under the 2019 Plan is set forth below : Number of Shares Weighted- Average Grant Date Fair Value Per Share Balance, December 31, 2018 — $ — RSUs granted 288,170 38.28 RSUs forfeited (5,600 ) 40.01 RSUs vested (1,666 ) 59.79 Balance, December 31, 2019 280,904 $ 38.12 The total grant date fair value of RSUs vested for the year ended December 31, 2019 was $0.1 million. There were no RSUs granted prior to 2019. As of December 31, 2019, there was $9.5 million of unrecognized stock-based compensation expense related to RSUs to be recognized over a weighted-average period of 3.5 years. Employee 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 began on September 1, 2019 and will end on February 29, 2020. On each purchase date, which falls on the last date of each offering period, ESPP participants will purchase shares of common stock at a price per share equal to 85% of the lesser of (1) the fair market value per share of the common stock on the offering date or (2) the fair market value of the common stock on the purchase date. The occurrence and duration of offering periods under the ESPP are subject to the determinations of the Company’s Compensation Committee, in its sole discretion. The fair value of the ESPP shares is estimated using the Black-Scholes option pricing model. The Company recorded $255,000 of stock-based compensation expense related to the ESPP for the year ended December 31, 2019. Year Ended December 31, 2019 Expected term (in years) 0.5 Expected volatility 76.93% Risk-free interest rate 1.89% Expected dividend yield 0%

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	10. Income Taxes The following table presents income (loss) before income taxes for the periods presented: December 31, 2019 2018 2017 (in thousands) Domestic $ (51,179 ) $ (41,145 ) $ (30,654 ) Foreign 132 81 65 Total loss before income taxes $ (51,047 ) $ (41,064 ) $ (30,589 ) Current income tax provision consists of the following: December 31, 2019 2018 2017 (in thousands) Domestic $ — $ 3 $ 1 Foreign 62 35 25 Total current income tax provision $ 62 $ 38 $ 26 The components of the deferred tax assets are as follows: December 31, 2019 2018 (in thousands) Deferred tax assets: Net operating loss carryovers $ 49,862 $ 28,834 Fixed and intangible assets 450 837 Accruals and reserves 1,619 761 Stock-based compensation 780 132 Research and development credits 2,336 1,716 Contributions 20 14 Lease liability 2,135 — Total deferred tax assets 57,202 32,294 Less valuation allowance (55,085 ) (32,294 ) Gross deferred tax assets 2,117 — Deferred tax liabilities: Right-of-use-assets (2,117 ) — Gross deferred tax liabilities (2,117 ) — Total net deferred tax assets $ — $ — Reconciliation of the statutory federal income tax to the Company’s effective tax is as follows: December 31, 2019 2018 2017 (in thousands) Income tax benefit at federal statutory rate $ (10,720 ) $ (8,624 ) $ (10,404 ) State and local income taxes net of federal tax benefit (9 ) 3 1 Foreign tax rate differential 35 11 (3 ) Change in valuation allowance 14,470 8,497 (522 ) Stock-based compensation (3,403 ) 123 309 R&D tax credits (354 ) (313 ) (222 ) Other 43 341 109 Federal rate change (pursuant to the Tax Cuts and Jobs Act of 2017) — — 10,758 Total current income tax provision $ 62 $ 38 $ 26 Due to the uncertainties surrounding the realization of deferred assets through future taxable income, the Company has provided a full valuation allowance and, therefore, no benefit has been recognized for the net operating loss and other deferred tax assets. The valuation allowance increased by $22.8 million, As of December 31, 2019, the Company had net operating loss carryforwards available to reduce future federal, California and other state income of $180.3 million, $40.4 million and $153.5 million, respectively. The federal net operating loss carryforwards of $80.7 million and $99.6 million begin expiring in 2030 and never expire respectively, the California net operating loss carryforwards begin expiring in 2031 and other state net operating loss carryforwards begin expiring in various years, starting in 2029. As of December 31, 2019, the Company had research and development credit carryforwards of $2.8 million for federal income tax purposes and $2.4 million for California state income tax purposes available to reduce future taxable income, if any. The federal research and development credit carryforwards expire beginning 2032 and California credits can be carried forward indefinitely. Utilization of the net operating loss carryforward may be subject to an annual limitation due to the ownership change provided by the Internal Revenue Code of 1986, as amended, and similar state provisions. The annual limitation may result in the expiration of the net operating loss before utilization. Legislation enacted in 2017, informally known as the Tax Cuts and Jobs Act (“TCJA”), reduces the top U.S. federal corporate tax rate from 35% to 21%, requires companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax deferred, changes the rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017, allows for immediate expensing of fixed asset additions beginning after September 27, 2017, and creates new taxes on certain foreign sourced earnings. In 2017, the Company was not subject to a one-time transition tax as no foreign accumulated earnings and profits existed. As a result of the signing of the TCJA, the Company recorded a $10.1 million reduction as of December 31, 2017, due to remeasurement of its deferred tax assets along with a corresponding reduction of its valuation allowance. Subsequent to the enactment of the TCJA, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”), which allowed companies to record provisional amounts related to the effects of the TCJA during a measurement period not to extend beyond one year of the enactment date. The accounting for the tax effects of the TCJA has been completed as of December 31, 2018 and was not material to income tax expense for the year then ended. The Company has adopted the approach of recording the consequences of the global intangible low-taxed income (“GILTI”) provisions of the TCJA as period costs when incurred effective for periods beginning after December 31, 2017. Uncertain Tax Positions The activity related to the gross amount of unrecognized tax benefits is as follows: December 31, 2019 2018 2017 (in thousands) Beginning balance $ 1,896 $ 893 $ 688 Additions based on tax positions related to prior years — 394 — Additions based on tax positions related to current years 690 609 205 Balance at end of year $ 2,586 $ 1,896 $ 893 If recognized, gross unrecognized tax benefits would not have an impact on the Company’s effective tax rate due to the Company’s full valuation allowance position. While it is often difficult to predict the final outcome of any particular uncertain tax position, the Company does not believe that the amount of gross unrecognized tax benefits will change significantly in the next twelve months. The Company is subject to taxation in the United States and in Germany. The Company files federal, California, and various other state income tax returns. The Company is not currently under examination by any income tax authorities. The federal and California statute of limitations remains open for three and four years, respectively, from the date of utilization of any net operating loss or credits. It is the Company’s policy to include penalties and interest expense related to income taxes as a component of the income tax provision as necessary. The Company determined that no accrual for interest and penalties was required as of December 31, 2019.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	11. 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: December 31, 2019 2018 2017 (in thousands) Convertible preferred stock on an as-converted basis — 18,670,328 17,510,045 Common stock options issued and outstanding 3,315,001 3,636,358 3,108,604 Restricted stock units 280,904 — — Early exercised options subject to future vesting — 13,422 11,603 Convertible preferred stock warrants — 54,903 183,162 Common stock warrants — 176,218 141,778 Total 3,595,905 22,551,229 20,955,192

Segment and Geographic Informat

Segment and Geographic Information	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Segment and Geographic Information	12. Segment and Geographic Information The following table represents the Company’s product revenue based on the location to which the product is shipped: Year Ended December 31, 2019 2018 2017 (in thousands) United States $ 22,699 $ 7,022 $ 969 Germany 3,402 1,393 597 Rest of Europe 14,097 3,516 143 All other countries 2,729 332 10 Product revenue $ 42,927 $ 12,263 $ 1,719 As of December 31, 2019, the Company’s long-lived assets are all held in the United States.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	13. Subsequent Events In February 2020, the Company entered into a First Amendment to its Loan and Security Agreement (the “Amended Credit Facility”) to refinance its existing term loan. Under the Amended Credit Facility, the existing revolving line of credit of $2.0 million was terminated and the $20,000 termination fee was waived. The Amended Credit Facility provides the Company with a supplemental term loan in the amount of $16.5 million. The Company used $13.2 million of the proceeds from the supplemental term loan to repay in full all amounts due under the existing term loan and to pay related expenses. The principal amount outstanding under the supplemental term loan accrues interest at a floating per annum rate equal to the greater of the Prime Rate minus 1.25% and 3.5%. The supplemental term loan matures on December 1, 2023. The Amended Credit Facility provides an interest-only payments period through either (a) June 30, 2021, if the Company does not achieve a certain financial performance target on or before June 30, 2021 (“Performance Milestone One”), or (b) December 31, 2021, if the Company achieves Performance Milestone One but does not achieve both of a certain regulatory milestone and a certain financial performance target on or before December 31, 2021 (“Performance Milestone Two”) or (c) until June 30, 2022, if the Company achieves both Performance Milestones. The additional final payment for the Amended Credit Facility is $1.6 million.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiary. All intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions made in the accompanying consolidated financial statements include, but are not limited to the valuation of inventory, the fair value of common stock, the fair value of preferred stock warrant liabilities, the fair value of stock options, recoverability of the Company’s net deferred tax assets, and related valuation allowance and certain accruals. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could materially differ from those estimates .
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. The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the consolidated balance sheets that sum to the total of the same amounts shown in the consolidated statements of cash flows: December 31, 2019 December 31, 2018 (in thousands) Cash and cash equivalents $ 139,045 $ 39,643 Restricted cash 1,450 450 Total cash, cash equivalents, and restricted cash $ 140,495 $ 40,093 Restricted cash as of December 31, 2019 and 2018 relates to letters of credit established for leases entered into in May 2018 and December 2019 and is recorded as other assets on the consolidated balance sheets.
Short-Term Investments	Short-Term Investments Short-term investments have been classified as available-for-sale and are carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. The Company determines the appropriate classification of its investments in debt securities at the time of purchase. Available-for-sale securities with original maturities beyond three months at the date of purchase are classified as current based on their availability for use in current operations. Unrealized gains and losses are excluded from earnings and are reported as a component of comprehensive loss. The Company periodically evaluates whether declines in fair values of its marketable securities below their book value are other-than-temporary. This evaluation consists of several qualitative and quantitative factors regarding the severity and duration of the unrealized loss as well as the Company’s ability and intent to hold the marketable security until a forecasted recovery occurs. Additionally, the Company assesses whether it has plans to sell the security or it is more likely than not it will be required to sell any marketable securities before recovery of its amortized cost basis. Realized gains and losses and declines in fair value judged to be other than temporary, if any, on marketable securities are included in other income, net. The cost of investments sold is based on the specific-identification method. Interest on marketable securities is included in other income, net.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, restricted cash, investments and trade receivables. Risks associated with cash, cash equivalents and restricted cash are mitigated by banking with creditworthy institutions and the Company’s investments have investment grade ratings when purchased. The Company performs ongoing evaluations of its customers and generally does not require collateral.
Concentration of Customers	Concentration of Customers For the years ended December 31, 2019 and 2018, no customer accounted for 10% of the Company’s revenue. There was one customer which accounted for 11% of the Company’s accounts receivable as of December 31, 2019. There were no customers which accounted for more than 10% of the Company’s accounts receivable as of December 31, 2018.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company’s cash and cash equivalents, restricted cash, short-term investments, 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.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at invoice value, net of any allowance for doubtful accounts. Estimates of the allowance for doubtful accounts are determined based on existing contractual payment terms, historical payment patterns of customers and individual customer circumstances. The allowance for doubtful accounts was $194,000 as of December 31, 2019 and the Company recognized accounts receivable write-offs in the amount of $3,400 for the year ended December 31, 2019. The allowance for doubtful accounts was $76,000 as of December 31, 2018 and the Company recognized accounts receivable write-offs in the amount of $1,000 for the year ended December 31, 2018.
Inventory	Inventory Inventory is stated at the lower of standard cost (which approximates actual cost on a first-in, first-out basis) and net realizable value. Inventory costs include direct materials, direct labor and normal manufacturing overhead. Prior to achieving normal capacity, excess capacity costs are expensed in cost of product revenue as period costs. Finished goods that are used for research and development are expensed as consumed. Provisions for slow-moving, excess or obsolete inventories are recorded when required to reduce inventory values to their estimated net realizable values based on product life cycle, development plans, product expiration or quality issues.
Property and Equipment	Property and Equipment Property and equipment are stated at cost, net of accumulated depreciation and amortization. Depreciation and amortization is computed using the straight-line method over the estimated useful lives of the respective assets, generally three to five years. Leasehold improvements are amortized over the lesser of their useful life or the remaining life of the lease. When assets are retired or otherwise disposed of, the cost and related accumulated depreciation and amortization are removed from the balance sheet and any resulting gain or loss is reflected in operations in the period realized. Maintenance and repairs are charged to operations as incurred.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by comparing the carrying amount to the future net undiscounted cash flows which the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the projected discounted future net cash flows arising from the asset. The Company has not identified any such impairment losses to date.
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 adopted Accounting Standards Codification (“ASC”) 606, Revenue from Contracts with Customers Revenue Recognition 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. Under ASC 606, 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 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.
Research and Development Costs	Research and Development Costs Research and development costs, including new product development, regulatory compliance, and clinical research are expensed as incurred.
Accrued Research and Development Costs	Accrued Research and Development Costs The Company accrues liabilities for estimated costs of research and development activities conducted by its third-party service providers, which include the conduct of preclinical and clinical studies. The estimated costs of research and development activities are recorded based upon the estimated amount of services provided but not yet invoiced, and these costs are included in accrued liabilities on the consolidated balance sheets and within research and development expense on the consolidated statements of operations and comprehensive loss. These costs are accrued for based on factors such as estimates of the work completed and budget provided and in accordance with agreements established with third-party service providers. Significant judgments and estimates are made in determining the accrued liabilities balance in each reporting period. Accrued liabilities are adjusted as actual costs become known. There have not been any material differences between accrued costs and actual costs incurred since the Company’s inception.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for share-based payments at fair value. The fair value of stock options is measured using the Black-Scholes option-pricing model. For share-based awards that vest subject to the satisfaction of a service requirement, the fair value measurement date for stock-based compensation awards is the date of grant and the expense is recognized on a straight-line basis, over the vesting period. The Company accounts for forfeitures as they occur.
Leases	Leases The Company adopted ASU No. 2016-02, Leases Leases For its long-term operating lease, the Company recognized a right-of-use asset and a lease liability on its 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 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.
Defined Contribution Plan	Defined Contribution Plan The Company has a defined contribution retirement savings plan under Section 401(k) of the Internal Revenue Code. This plan allows eligible employees to defer a portion of their annual compensation on a pre-tax basis. The Company is authorized to make matching contributions but has not made such contributions for the years ended December 31, 2019 and 2018.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is comprised of net loss and changes in unrealized gains and losses on the Company’s available-for-sale investments.
Foreign Currency	Foreign Currency The functional currency of the Company’s foreign subsidiary is the U.S. Dollar. Accordingly, all monetary assets and liabilities of the subsidiary are remeasured at the current exchange rate at the end of the period, nonmonetary assets and liabilities are remeasured at historical rates, and revenue and expenses are remeasured at average exchange rates during the period. There were net foreign currency transaction gains of $56,000 for the year ended December 31, 2019 and net foreign currency transaction losses of
Net Loss Per Share	Net Loss Per Share Basic net loss per share is calculated by dividing net loss by the weighted-average number of shares of common stock outstanding for the period, without consideration of potential dilutive shares of common stock. The unvested portion of early exercised stock options are excluded from the computation of weighted-average shares as the continuing vesting of such shares is contingent on the holders’ continued service to the Company. Since the Company was in a loss position for the period presented, basic net loss per share is the same as diluted net loss per share since the effects of potentially dilutive securities are antidilutive.
Income Taxes	Income Taxes The Company uses the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial reporting and the tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. Management makes an assessment of the likelihood that the resulting deferred tax assets will be realized. A valuation allowance is provided when it is more likely than not that some portion or all of a deferred tax asset will not be realized. Due to the Company’s historical operating performance and the recorded cumulative net losses in prior fiscal periods, the net deferred tax assets have been fully offset by a valuation allowance. The Company recognizes uncertain income tax positions at the largest amount that is more likely than not to be sustained upon audit by the relevant taxing authority. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained. Changes in recognition or measurement are reflected in the period in which judgment occurs. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of provision for income taxes.
Segment Reporting	Segment Reporting Operating segments are defined as components of an entity for which separate financial information is available and that is regularly reviewed by the Chief Operating Decision Maker (“CODM”) in deciding how to allocate resources to an individual segment and in assessing performance. The Company’s CODM is its Chief Executive Officer. The Company has determined that it operates in one segment.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases 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 year ended December 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
Recent Accounting Pronouncements	Recent Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815) and Leases (Topic 842): Effective Dates In November 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740)

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 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 consolidated balance sheets that sum to the total of the same amounts shown in the consolidated statements of cash flows: December 31, 2019 December 31, 2018 (in thousands) Cash and cash equivalents $ 139,045 $ 39,643 Restricted cash 1,450 450 Total cash, cash equivalents, and restricted cash $ 140,495 $ 40,093

Financial Instruments and Fai_2

Financial Instruments and Fair Value Measurements (Tables)	12 Months Ended
	Dec. 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: December 31, 2019 Level 1 Level 2 Level 3 Total (in thousands) Assets: U.S. Treasury securities $ 43,245 $ — $ — $ 43,245 Money market funds 29,386 — — 29,386 Reverse repurchase agreements — 10,000 — 10,000 Commercial paper — 6,958 — 6,958 Corporate bonds — 8,096 — 8,096 Total assets $ 72,631 $ 25,054 $ — $ 97,685 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 is summarized below: Year Ended December 31, 2019 2018 2017 (in thousands) Beginning Balance $ 313 $ 577 $ 729 Expiration of warrants, included in change in fair value of warrant liability — (133 ) — Net exercise of warrants (133 ) — — Exercise of warrants — (316 ) (184 ) Change in fair value of warrant liability 609 185 32 Conversion of Series A preferred stock warrants to common stock warrants upon the closing of the IPO (789 ) — — Balance at December 31, 2019 $ — $ 313 $ 577
Fair Value of Warrants Using Black-Scholes Option Pricing Model	The fair value of the warrants, which were converted to common stock warrants upon the closing of the IPO in March 2019, was determined using the Black-Scholes option pricing model and the following assumptions: December 31, 2019 2018 Expected term (in years) 5.3 5.5 Expected volatility 43.9% 42.8% Risk-free interest rate 2.5% 2.9% Expected dividend yield 0% 0%

Cash Equivalents and Short-Te_2

Cash Equivalents and Short-Term Investments (Tables)	12 Months Ended
	Dec. 31, 2019
Cash And Cash Equivalents [Abstract]
Summary of Cash Equivalents and Short-Term Investments	The following is a summary of the Company’s cash equivalents and short-term investments: December 31, 2019 Amortized Cost Basis Unrealized Gains Unrealized Losses Fair Value (in thousands) U.S. Treasury securities $ 43,219 $ 27 $ (1 ) $ 43,245 Money market funds 29,386 — — 29,386 Reverse repurchase agreements 10,000 — — 10,000 Commercial paper 6,958 — — 6,958 Corporate bonds 8,087 9 — 8,096 Total $ 97,650 $ 36 $ (1 ) $ 97,685 Reported as: Cash equivalents $ 41,381 Short-term investments 56,304 Total $ 97,685 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)	12 Months Ended
	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Schedule of Inventory	Inventory consists of the following: December 31, 2019 2018 (in thousands) Raw material $ 2,501 $ 1,084 Work in progress 1,364 634 Finished goods 6,642 2,313 Consigned inventory 1,567 1,100 Total inventory $ 12,074 $ 5,131
Schedule of Property and Equipment	Property and equipment, net consists of the following: December 31, 2019 2018 (in thousands) Equipment $ 3,759 $ 2,321 Equipment on loan to customers 1,495 786 Office furniture 76 90 Software 97 76 Leasehold improvements 1,329 764 Construction in progress 553 236 Property and equipment, gross 7,309 4,273 Less accumulated depreciation and amortization (2,399 ) (1,654 ) Total property and equipment, net $ 4,910 $ 2,619
Schedule of Other Assets	Other assets consist of the following: December 31, 2019 2018 (in thousands) Deferred offering costs $ — $ 1,519 Restricted cash 1,450 450 Other 56 97 Total other assets $ 1,506 $ 2,066
Schedule of Accrued Liabilities	Accrued liabilities consist of the following: December 31, 2019 2018 (in thousands) Accrued employee compensation $ 8,139 $ 3,135 Accrued research and development costs 3,090 1,115 Accrued professional services 804 1,391 Other 1,744 576 Total accrued liabilities $ 13,777 $ 6,217

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Schedule of Minimum Future Rental Payments	The following are minimum future rental payments owed under these agreements which commenced as of December 31, 2019: (in thousands) 2020 $ 1,292 2021 1,941 2022 2,063 2023 1,498 2024 1,546 Thereafter 4,826 Total minimum lease payments $ 13,166 Less: imputed interest (4,267 ) Total lease liability $ 8,899
Schedule of Minimum Future Rental Payments Not Yet Commenced	The following are minimum future rental payments owed for the second building under the Betsy Ross Lease which has not yet commenced as of December 31, 2019: (in thousands) 2020 $ — 2021 — 2022 345 2023 1,044 2024 1,078 Thereafter 3,365 Total minimum lease payments $ 5,832

Term Notes (Tables)

Term Notes (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Schedule of Long Term Debt	Long-term debt and net premium balances are as follows: December 31, 2019 2018 (in thousands) Principal amount of term note $ 13,334 $ 15,000 Net premium associated with accretion of final payment, issuance of common stock warrants, and other debt issuance costs 485 50 Term note, current and noncurrent 13,819 15,050 Less term note, current portion (6,667 ) (1,667 ) Term note, noncurrent portion $ 7,152 $ 13,383
Schedule of Future Minimum Payments for Principal and Interest	Future minimum payments of principal and estimated payments of interest on the Company’s outstanding variable rate borrowings as of December 31, 2019 are as follows: Year ending December 31: (in thousands) 2020 $ 7,000 2021 7,789 Total future payments 14,789 Less amounts representing interest (442 ) Less final payment (1,013 ) Total principal amount of term note payments $ 13,334

Convertible Preferred Stock a_2

Convertible Preferred Stock and Stockholders’ Equity (Deficit) (Tables)	12 Months Ended
	Dec. 31, 2019
Stockholders Equity [Abstract]
Summary of Convertible Preferred Stock	The c onvertible preferred stock as of December 31, 2018 consisted of the following: December 31, 2018 Shares Authorized Shares Issued and Outstanding Net Carrying Value Aggregate Liquidation Preference (in thousands, except share amounts) Series A 19,280,722 1,580,387 $ 4,226 $ 4,473 Series A-1 51,874,893 4,197,138 14,054 12,996 Series B 64,777,331 5,309,617 39,877 40,000 Series C 79,209,457 6,492,578 79,729 80,000 Series D 13,956,584 1,090,608 14,920 15,000 229,098,987 18,670,328 $ 152,806 $ 152,469
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 December 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 Loan and Security Agreement — 34,440 $ 4.026 February 2028 Total common stock warrants — 176,218

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Total Stock-Based Compensation	Total stock-based compensation was as follows: Year Ended December 31, 2019 2018 2017 (in thousands) Cost of product revenue $ 268 $ 67 $ 46 Research and development 943 235 185 Sales and marketing 972 294 130 General and administrative 1,463 701 604 Total stock-based compensation $ 3,646 $ 1,297 $ 965
Schedule of Estimates Grant-Date Fair Value of Option Awards Using Black-Scholes Option Pricing Model with Assumptions	The estimated grant-date fair value of all the Company’s stock-based awards was calculated using the Black-Scholes option pricing model, based on the following assumptions: Year Ended December 31, 2019 2018 2017 Expected term (in years) 6.08 6.08 6.08 Expected volatility 42.4%-42.9% 40.8%-41.9% 45.6% Risk-free interest rate 2.4%-2.6% 2.5%-3.1% 1.9%-2.2% Expected dividend yield 0% 0% 0%
Schedule of Option Activity under 2009 Plan and 2019 Plan	Stock Options 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, 2016 887,885 1,365,934 $ 1.95 $ 2,011 Awards authorized 1,352,677 — Options granted (1,974,589 ) 1,974,589 3.42 Options exercised — (71,522 ) 1.95 Options cancelled 160,397 (160,397 ) 2.44 Balance, December 31, 2017 426,370 3,108,604 $ 2.81 $ 8.03 $ 3,647 Awards authorized 691,503 — Options granted (1,015,963 ) 1,015,963 5.25 Options exercised — (197,820 ) 2.20 Options cancelled 290,389 (290,389 ) 3.42 Balance, December 31, 2018 392,299 3,636,358 $ 3.54 $ 7.79 $ 11,267 Awards authorized 2,000,430 — Options expired (287,600 ) — Options granted (442,858 ) 442,858 14.69 Options exercised — (722,242 ) 3.10 Options cancelled 41,973 (41,973 ) 3.85 Balance, December 31, 2019 1,704,244 3,315,001 $ 5.08 $ 7.28 $ 128,744 Vested and exercisable, December 31, 2019 1,741,614 $ 3.31 $ 6.41 $ 70,721 Vested and expected to vest, December 31, 2019 3,315,001 $ 5.08 $ 7.28 $ 128,744
Schedule of RSU Activity under 2019 Plan	RSU activity under the 2019 Plan is set forth below : Number of Shares Weighted- Average Grant Date Fair Value Per Share Balance, December 31, 2018 — $ — RSUs granted 288,170 38.28 RSUs forfeited (5,600 ) 40.01 RSUs vested (1,666 ) 59.79 Balance, December 31, 2019 280,904 $ 38.12
Schedule of Fair Value of ESPP Shares Estimated Using Black-Scholes Option Pricing Model Assumptions	The fair value of the ESPP shares is estimated using the Black-Scholes option pricing model. The Company recorded $255,000 of stock-based compensation expense related to the ESPP for the year ended December 31, 2019. Year Ended December 31, 2019 Expected term (in years) 0.5 Expected volatility 76.93% Risk-free interest rate 1.89% Expected dividend yield 0%

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Income (Loss) Before Income Taxes	The following table presents income (loss) before income taxes for the periods presented: December 31, 2019 2018 2017 (in thousands) Domestic $ (51,179 ) $ (41,145 ) $ (30,654 ) Foreign 132 81 65 Total loss before income taxes $ (51,047 ) $ (41,064 ) $ (30,589 )
Schedule of Current Income Tax Provision	Current income tax provision consists of the following: December 31, 2019 2018 2017 (in thousands) Domestic $ — $ 3 $ 1 Foreign 62 35 25 Total current income tax provision $ 62 $ 38 $ 26
Components of Deferred Tax Assets	The components of the deferred tax assets are as follows: December 31, 2019 2018 (in thousands) Deferred tax assets: Net operating loss carryovers $ 49,862 $ 28,834 Fixed and intangible assets 450 837 Accruals and reserves 1,619 761 Stock-based compensation 780 132 Research and development credits 2,336 1,716 Contributions 20 14 Lease liability 2,135 — Total deferred tax assets 57,202 32,294 Less valuation allowance (55,085 ) (32,294 ) Gross deferred tax assets 2,117 — Deferred tax liabilities: Right-of-use-assets (2,117 ) — Gross deferred tax liabilities (2,117 ) — Total net deferred tax assets $ — $ —
Reconciliation of Statutory Federal Income Tax	Reconciliation of the statutory federal income tax to the Company’s effective tax is as follows: December 31, 2019 2018 2017 (in thousands) Income tax benefit at federal statutory rate $ (10,720 ) $ (8,624 ) $ (10,404 ) State and local income taxes net of federal tax benefit (9 ) 3 1 Foreign tax rate differential 35 11 (3 ) Change in valuation allowance 14,470 8,497 (522 ) Stock-based compensation (3,403 ) 123 309 R&D tax credits (354 ) (313 ) (222 ) Other 43 341 109 Federal rate change (pursuant to the Tax Cuts and Jobs Act of 2017) — — 10,758 Total current income tax provision $ 62 $ 38 $ 26
Schedule of Unrecognized Tax Benefits	The activity related to the gross amount of unrecognized tax benefits is as follows: December 31, 2019 2018 2017 (in thousands) Beginning balance $ 1,896 $ 893 $ 688 Additions based on tax positions related to prior years — 394 — Additions based on tax positions related to current years 690 609 205 Balance at end of year $ 2,586 $ 1,896 $ 893

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 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: December 31, 2019 2018 2017 (in thousands) Convertible preferred stock on an as-converted basis — 18,670,328 17,510,045 Common stock options issued and outstanding 3,315,001 3,636,358 3,108,604 Restricted stock units 280,904 — — Early exercised options subject to future vesting — 13,422 11,603 Convertible preferred stock warrants — 54,903 183,162 Common stock warrants — 176,218 141,778 Total 3,595,905 22,551,229 20,955,192

Segment and Geographic Inform_2

Segment and Geographic Information (Tables)	12 Months Ended
	Dec. 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: Year Ended December 31, 2019 2018 2017 (in thousands) United States $ 22,699 $ 7,022 $ 969 Germany 3,402 1,393 597 Rest of Europe 14,097 3,516 143 All other countries 2,729 332 10 Product revenue $ 42,927 $ 12,263 $ 1,719

Organization and Basis of Pre_2

Organization and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Millions	Nov. 15, 2019USD ($)$ / sharesshares	Mar. 11, 2019USD ($)$ / sharesshares	Apr. 30, 2019shares	Dec. 31, 2019USD ($)shares	Dec. 31, 2018shares	Mar. 05, 2019shares
Organization and Basis of Presentation [Line Items]
Entity incorporation, date of incorporation				Jun. 17, 2009
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”)
Cash, cash equivalents and short-term investments | $				$ 195.3
Common Stock
Organization and Basis of Presentation [Line Items]
Proceeds from initial public offering | $		$ 99.9
Issuance of common stock upon net exercise of warrants, shares		101,744	29,887	180,952
Net proceeds from issuance on follow-on offering | $	$ 96.7
Fractional shares issued in reverse stock split				45	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
Stock split, conversion ratio		1
Initial Public Offering | Common Stock
Organization and Basis of Presentation [Line Items]
Common stock issued				6,555,000
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
Over-Allotment Option | Common Stock
Organization and Basis of Presentation [Line Items]
Common stock issued				2,854,048
Private Placement
Organization and Basis of Presentation [Line Items]
Common stock issued		588,235
Proceeds from issuance of common stock | $		$ 10
Underwritten Public Offering | Common Stock
Organization and Basis of Presentation [Line Items]
Common stock issued	2,854,048
Common stock, offering price per share | $ / shares	$ 36.25
Shares sold to underwriters option to purchase additional shares	372,267

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents	$ 139,045	$ 39,643
Restricted cash	1,450	450
Total cash, cash equivalents, and restricted cash	$ 140,495	$ 40,093	$ 51,923	$ 50,815

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Additional Information (Details)	Jan. 01, 2019USD ($)	Dec. 31, 2019USD ($)CustomerSegment	Dec. 31, 2018USD ($)
Summary Of Significant Accounting Policies [Line Items]
Allowance for doubtful accounts		$ 194,000	$ 76,000
Write-off of accounts receivable		$ 3,400	$ 1,000
Notice period for cancellation of agreement		30 days
Employer matching contribution, percent of match		0.00%	0.00%
Foreign currency transaction realized and unrealized gain (loss)		$ 56,000	$ (46,000)
Number of Operating Segments | Segment		1
Operating lease right-of-use assets		$ 8,825,000
Operating lease liabilities		$ 8,899,000
Adoption of Topic 842
Summary Of Significant Accounting Policies [Line Items]
Operating lease right-of-use assets	$ 2,900,000
Operating lease liabilities	3,000,000
Derecognized the deferred rent liability	$ 100,000
Maximum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life		5 years
Percentage of income tax position required to recognize uncertain income tax position		50.00%
Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment useful life		3 years
Accounts Receivable
Summary Of Significant Accounting Policies [Line Items]
Number of customers | Customer		1
Customer | Revenue Benchmark | Customer One
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage		10.00%	10.00%
Credit Concentration Risk | Accounts Receivable | Customer One
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage		11.00%
Credit Concentration Risk | Accounts Receivable | Customer One | Maximum
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage			10.00%

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	Dec. 31, 2019	Dec. 31, 2018
Assets:
Total assets	$ 97,685	$ 21,680
Liabilities:
Total liabilities		313
Convertible Preferred Stock Warrants Liability
Liabilities:
Total liabilities		313
Level 1
Assets:
Total assets	72,631	21,680
Level 2
Assets:
Total assets	25,054
Level 3
Liabilities:
Total liabilities		313
Level 3 | Convertible Preferred Stock Warrants Liability
Liabilities:
Total liabilities		313
U.S. Treasury securities
Assets:
Total assets	43,245
U.S. Treasury securities | Level 1
Assets:
Total assets	43,245
Money Market Funds
Assets:
Total assets	29,386	21,680
Money Market Funds | Level 1
Assets:
Total assets	29,386	$ 21,680
Reverse Repurchase Agreements
Assets:
Total assets	10,000
Reverse Repurchase Agreements | Level 2
Assets:
Total assets	10,000
Commercial Paper
Assets:
Total assets	6,958
Commercial Paper | Level 2
Assets:
Total assets	6,958
Corporate Bonds
Assets:
Total assets	8,096
Corporate Bonds | Level 2
Assets:
Total assets	$ 8,096

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	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Beginning balance	$ 313	$ 577	$ 729
Expiration of warrants, included in change in fair value of warrant liability		(133)
Net exercise of warrants	(133)	(316)	(184)
Change in fair value of warrant liability	609	185	32
Conversion of Series A preferred stock warrants to common stock warrants upon the closing of the IPO	$ (789)
Ending balance		$ 313	$ 577

Financial Instruments and Fai_5

Financial Instruments and Fair Value Measurements - Fair Value of Warrants Using Black-Scholes Option Pricing Model (Details)	Dec. 31, 2019	Dec. 31, 2018
Measurement Input, Expected Term
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Expected term (in years)	5 years 3 months 18 days	5 years 6 months
Measurement Input, Expected Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value assumption measurement input	43.9	42.8
Measurement Input, Risk-free Interest Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value assumption measurement input	2.5	2.9
Measurement Input, Expected Dividend Yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value assumption measurement input	0	0

Financial Instruments and Fai_6

Financial Instruments and Fair Value Measurements - Additional Information (Details)	12 Months Ended
	Dec. 31, 2019USD ($)
Fair Value Disclosures [Abstract]
Fair value assets transferred from level 1 to level 2	$ 0
Fair value assets transferred from level 2 to level 1	0
Fair value liabilities transferred from level 1 to level 2	0
Fair value liabilities transferred from level 2 to level 1	0
Fair value equity transferred from level 1 to level 2	0
Fair value equity transferred from level 2 to level 1	0
Fair value assets transferred into level 3	0
Fair value assets transferred out of level 3	0
Fair value liabilities transferred into level 3	0
Fair value liabilities transferred out of level 3	$ 0

Cash Equivalents and Short-Te_3

Cash Equivalents and Short-Term Investments - Summary of Cash Equivalents and Short-Term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Cash And Cash Equivalents [Line Items]
Cash equivalents, Fair Value	$ 41,381	$ 21,680
Cash equivalents and short-term investments, Cost Basis	97,650	21,680
Cash equivalents and short-term investments, Unrealized Gains	36
Cash equivalents and short-term investments, Unrealized losses	(1)
Cash equivalents and short-term investments, Fair Value	97,685	21,680
Short-term investments	56,304
U.S. Treasury securities
Cash And Cash Equivalents [Line Items]
Short-term investments Amortized Cost Basis	43,219
Short-term investments Unrealized Gains	27
Short-term investments Unrealized Losses	(1)
Short-term investments, Fair Value	43,245
Reverse Repurchase Agreements
Cash And Cash Equivalents [Line Items]
Short-term investments Amortized Cost Basis	10,000
Short-term investments, Fair Value	10,000
Commercial paper
Cash And Cash Equivalents [Line Items]
Short-term investments Amortized Cost Basis	6,958
Short-term investments, Fair Value	6,958
Corporate bonds
Cash And Cash Equivalents [Line Items]
Short-term investments Amortized Cost Basis	8,087
Short-term investments Unrealized Gains	9
Short-term investments, Fair Value	8,096
Money Market Funds
Cash And Cash Equivalents [Line Items]
Cash equivalents Amortized Cost Basis	29,386	21,680
Cash equivalents, Fair Value	$ 29,386	$ 21,680

Cash Equivalents and Short-Te_4

Cash Equivalents and Short-Term Investments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019
Maximum
Cash And Cash Equivalents [Line Items]
Available for sale securities remaining contractual maturities	1 year

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Inventory (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw material	$ 2,501	$ 1,084
Work in progress	1,364	634
Finished goods	6,642	2,313
Consigned inventory	1,567	1,100
Total inventory	$ 12,074	$ 5,131

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 7,309	$ 4,273
Less accumulated depreciation and amortization	(2,399)	(1,654)
Total property and equipment, net	4,910	2,619
Equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,759	2,321
Equipment Loan To Customer
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,495	786
Office Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, gross	76	90
Software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	97	76
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,329	764
Construction in Progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 553	$ 236

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization expense	$ 1,337	$ 700	$ 468

Balance Sheet Components - Sc_3

Balance Sheet Components - Schedule of Other Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Other Assets [Abstract]
Deferred offering costs		$ 1,519
Restricted cash	$ 1,450	450
Other	56	97
Total other assets	$ 1,506	$ 2,066

Balance Sheet Components - Sc_4

Balance Sheet Components - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accrued employee compensation	$ 8,139	$ 3,135
Accrued research and development costs	3,090	1,115
Accrued professional services	804	1,391
Other	1,744	576
Total accrued liabilities	$ 13,777	$ 6,217

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)	1 Months Ended		12 Months Ended
	Dec. 31, 2019USD ($)ft²Building	May 31, 2018ft²	Dec. 31, 2019USD ($)ft²Building	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 01, 2022USD ($)
Loss Contingencies [Line Items]
Operating lease right-of-use asset	$ 8,825,000		$ 8,825,000
Operating lease liabilities	8,899,000		8,899,000
Operating lease cost			1,200,000
Rent expense				$ 900,000	$ 400,000
Initial Security Deposit
Loss Contingencies [Line Items]
Letter of credit secured by restricted cash	$ 1,000,000		$ 1,000,000
Fremont, California
Loss Contingencies [Line Items]
Lease term expiration date			Sep. 30, 2019
Santa Clara, California
Loss Contingencies [Line Items]
Lease term expiration date	Aug. 31, 2022	Aug. 31, 2022
Lease agreement, number buildings leased | Building	2		2
Area of office and laboratory space | ft²	85,200	35,000	85,200
Lease commencement date		2018-09	2019-12
Letter of credit secured by restricted cash	$ 500,000		$ 500,000
Operating lease right-of-use asset	1,900,000		1,900,000
Operating lease liabilities	$ 2,100,000		$ 2,100,000
Operating lease, remaining lease term			2 years 8 months
Initial term of first building	96 months		96 months
Lessee, Operating Lease, Existence of Option to Extend			true
Option to extend term on one or both buildings	5 years		5 years
Lease rent abatement term for first building			19 months
Lease rent abatement term for second floor			4 months
Santa Clara, California | First Building Lease
Loss Contingencies [Line Items]
Operating lease right-of-use asset	$ 6,800,000		$ 6,800,000
Operating lease liabilities	6,700,000		$ 6,700,000
Operating lease, remaining lease term			7 years 11 months
Santa Clara, California | Maximum
Loss Contingencies [Line Items]
Tenant improvements allowance	1,800,000		$ 1,800,000
Santa Clara, California | Scenario Forecast
Loss Contingencies [Line Items]
Letter of credit secured by restricted cash						$ 1,500,000
Germany
Loss Contingencies [Line Items]
Operating lease right-of-use asset	115,000		115,000
Operating lease liabilities	$ 115,000		$ 115,000
Operating lease, weighted average remaining lease term	2 years 4 months		2 years 4 months
Operating lease liability, weighted average incremental borrowing rate			6.97%

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Minimum Future Rental Payments (Details) $ in Thousands	Dec. 31, 2019USD ($)
Operating Lease Liabilities Payments Due [Abstract]
2020	$ 1,292
2021	1,941
2022	2,063
2023	1,498
2024	1,546
Thereafter	4,826
Total minimum lease payments	13,166
Less: imputed interest	(4,267)
Total lease liability	$ 8,899

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Minimum Future Rental Payments Not Yet Commenced (Details) - Second Building $ in Thousands	Dec. 31, 2019USD ($)
Lessee, Operating Lease, Not yet Commenced, Description [Abstract]
2022	$ 345
2023	1,044
2024	1,078
Thereafter	3,365
Total minimum lease payments	$ 5,832

Term Notes - Additional Informa

Term Notes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2018	Feb. 28, 2018	Jun. 30, 2014
Debt Instrument [Line Items]
Debt Amount	$ 13,334	$ 15,000
Debt, final payment amount	1,013
Interest expense	944	401	$ 58
2014 Loan and Security Agreement
Debt Instrument [Line Items]
Amortization of debt discount			100
2014 Loan and Security Agreement | Silicon Valley Bank
Debt Instrument [Line Items]
Debt Amount						$ 4,000
Debt repaid amount			$ 200
Loan and Security Agreement
Debt Instrument [Line Items]
Amortization of debt discount	$ 400	200
Debt maturity date	Dec. 31, 2021
Debt interest rate	5.87%
Debt, final payment as percentage of original aggregate principal amount	6.75%
Debt, final payment amount	$ 1,000
Line of credit, maturity date	Feb. 28, 2021
Debt, warrants issued	34,440
Debt, fair value of warrants issued	$ 100
Interest expense	$ 500	200
Loan and Security Agreement | Minimum
Debt Instrument [Line Items]
Debt interest rate	1.75%
Loan and Security Agreement | Maximum
Debt Instrument [Line Items]
Debt interest rate basis	2.75%
Loan and Security Agreement | Silicon Valley Bank | Short Term Notes
Debt Instrument [Line Items]
Debt Amount					$ 15,000
Loan and Security Agreement | Silicon Valley Bank | Short Term Notes | Tranche One
Debt Instrument [Line Items]
Debt Amount				$ 10,000
Loan and Security Agreement | Silicon Valley Bank | Short Term Notes | Tranche Two
Debt Instrument [Line Items]
Debt Amount		$ 5,000
Loan and Security Agreement | Silicon Valley Bank | Revolving Credit Facility
Debt Instrument [Line Items]
Debt Amount					$ 2,000

Term Note - Long-term Debt and

Term Note - Long-term Debt and Net Premium Balance (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument Periodic Payment [Abstract]
Principal amount of term note	$ 13,334	$ 15,000
Net premium associated with accretion of final payment, issuance of common stock warrants, and other debt issuance costs	485	50
Term note, current and noncurrent	13,819	15,050
Less term note, current portion	(6,667)	(1,667)
Term note, noncurrent portion	$ 7,152	$ 13,383

Term Note - Schedule of Future

Term Note - Schedule of Future Minimum and Estimated Payments (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
2020	$ 7,000
2021	7,789
Total future payments	14,789
Less amounts representing interest	(442)
Less final payment	(1,013)
Total principal amount of term note payments	$ 13,334	$ 15,000

Convertible Preferred Stock a_3

Convertible Preferred Stock and Stockholders' Equity (Deficit) - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Mar. 11, 2019	Mar. 06, 2019	Mar. 05, 2019	Apr. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Temporary Equity And Stockholders Equity [Line Items]
Convertible preferred stock, shares outstanding						18,670,328
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 warrant issued		54,903
Adjustments to additional paid in capital		$ 0.8
Issuance of common stock upon net exercise of warrants, Shares				49,321
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	17,510,045	14,605,589
Fractional shares issued in reverse stock split					69
Common Stock
Temporary Equity And Stockholders Equity [Line Items]
Conversion of stock, common stock issued			18,670,259
Fractional shares issued in reverse stock split					45	45
Issuance of common stock upon net exercise of warrants, Shares	101,744			29,887	180,952

Convertible Preferred Stock a_4

Convertible Preferred Stock and Stockholders' Equity (Deficit) - Summary of Convertible Preferred Stock (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized	5,000,000	229,098,987
Convertible preferred stock, shares issued and outstanding		18,670,328
Convertible preferred stock, net carrying value		$ 152,806
Convertible preferred stock, aggregate liquidation preference		$ 152,469
Series A- Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized		19,280,722
Convertible preferred stock, shares issued and outstanding		1,580,387
Convertible preferred stock, net carrying value		$ 4,226
Convertible preferred stock, aggregate liquidation preference		$ 4,473
Series A- 1 Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized		51,874,893
Convertible preferred stock, shares issued and outstanding		4,197,138
Convertible preferred stock, net carrying value		$ 14,054
Convertible preferred stock, aggregate liquidation preference		$ 12,996
Series B Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized		64,777,331
Convertible preferred stock, shares issued and outstanding		5,309,617
Convertible preferred stock, net carrying value		$ 39,877
Convertible preferred stock, aggregate liquidation preference		$ 40,000
Series C Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized		79,209,457
Convertible preferred stock, shares issued and outstanding		6,492,578
Convertible preferred stock, net carrying value		$ 79,729
Convertible preferred stock, aggregate liquidation preference		$ 80,000
Series D Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized		13,956,584
Convertible preferred stock, shares issued and outstanding		1,090,608
Convertible preferred stock, net carrying value		$ 14,920
Convertible preferred stock, aggregate liquidation preference		$ 15,000

Convertible Preferred Stock a_5

Convertible Preferred Stock and Stockholders' Equity (Deficit) - Summary of Key Terms of Outstanding Common Stock Warrants (Details)	12 Months Ended
	Dec. 31, 2018$ / sharesshares
Common Stock Warrants
Class Of Warrant Or Right [Line Items]
Warrants Outstanding	176,218
Related Party Common Stock Warrants
Class Of Warrant Or Right [Line Items]
Warrants Outstanding	141,778
Warrants Outstanding Exercise Price | $ / shares	$ 2.196
Warrants Outstanding Expiration	2025-05
Common Stock Warrants Related to Loan and Security Agreement
Class Of Warrant Or Right [Line Items]
Warrants Outstanding	34,440
Warrants Outstanding Exercise Price | $ / shares	$ 4.026
Warrants Outstanding Expiration	2028-02

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Total Stock-Based Compensation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 3,646	$ 1,297	$ 965
Cost of Product Revenue
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	268	67	46
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	943	235	185
Sales and Marketing
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	972	294	130
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 1,463	$ 701	$ 604

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)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected term (in years)	6 years 29 days	6 years 29 days	6 years 29 days
Expected volatility			45.60%
Expected volatility, minimum	42.40%	40.80%
Expected volatility, maximum	42.90%	41.90%
Risk-free interest rate, minimum	2.40%	2.50%	1.90%
Risk-free interest rate, maximum	2.60%	3.10%	2.20%
Expected dividend yield	0.00%	0.00%	0.00%

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)	Jun. 17, 2009	Mar. 31, 2019	Feb. 28, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend yield				0.00%	0.00%	0.00%
Weighted-average grant date fair value of options granted				$ 6.58	$ 2.56	$ 1.59
Grant date fair value of options vested				$ 1,900,000	$ 1,600,000	$ 900,000
Unvested stock options				$ 4,600,000
Unvested stock options, remaining weighted-average period				2 years 1 month 6 days
Stock-based compensation				$ 3,646,000	$ 1,297,000	$ 965,000
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period				4 years
Cliff vesting, percentage				25.00%
Share-based compensation vesting rights, terms				The RSUs generally vest over a four-year period with straight-line vesting and a 25% one year cliff or over a three year period in equal amounts on a semi-annual basis,
Unvested stock options, remaining weighted-average period				3 years 6 months
Grant date fair value of RSU vested				$ 100,000
Number of Shares, RSUs granted				288,170	0
Unrecognized stock-based compensation				$ 9,500,000
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	1,421,674
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%
2009 Equity Incentive Plan and 2019 Stock Option and Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of stock owned by individual	10.00%
Vesting period				4 years
Cliff vesting, percentage				25.00%
Share-based compensation vesting rights, terms				If an individual owns stock representing 10% or more of the outstanding shares, the price of each share shall be at least 110% of the fair market value, as determined by the Board. Options granted under the Plan have a term of up to 10 years and generally vest over a 4 year period with a straight-line vesting and a 25% one year cliff.
2009 Equity Incentive Plan and 2019 Stock Option and Incentive Plan | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Price of stock as percentage of fair value	110.00%
2009 Equity Incentive Plan and 2019 Stock Option and Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted term				10 years
2019 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend yield				0.00%
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				$ 255,000

Stock-Based Compensation - Sc_3

Stock-Based Compensation - Schedule of Option Activity under 2009 Plan and 2019 Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Shares Available for Grant
Shares Available for Grant, Beginning balance	392,299	426,370	887,885
Shares Available for Grant, Awards authorized	2,000,430	691,503	1,352,677
Shares Available for Grant, Options expired	(287,600)
Shares Available for Grant, Options granted	(442,858)	(1,015,963)	(1,974,589)
Shares Available for Grant, Options cancelled	41,973	290,389	160,397
Shares Available for Grant, Ending balance	1,704,244	392,299	426,370
Number of Shares
Number of Shares, Beginning balance	3,636,358	3,108,604	1,365,934
Number of Shares, Options granted	442,858	1,015,963	1,974,589
Number of Shares, Options exercised	(722,242)	(197,820)	(71,522)
Number of Shares, Options cancelled	(41,973)	(290,389)	(160,397)
Number of Shares, Ending balance	3,315,001	3,636,358	3,108,604
Number of Shares, Vested and exercisable	1,741,614
Number of Shares, Vested and expected to vest	3,315,001
Weighted-Average Exercise Price Per Share
Weighted-Average Exercise Price Per Share, Beginning balance	$ 3.54	$ 2.81	$ 1.95
Weighted-Average Exercise Price Per Share, Options granted	14.69	5.25	3.42
Weighted-Average Exercise Price Per Share, Options exercised	3.10	2.20	1.95
Weighted-Average Exercise Price Per Share, Options cancelled	3.85	3.42	2.44
Weighted-Average Exercise Price Per Share, Ending balance	5.08	$ 3.54	$ 2.81
Weighted-Average Exercise Price Per Share, Vested and exercisable	3.31
Weighted-Average Exercise Price Per Share, Vested and expected to vest	$ 5.08
Weighted-Average Remaining Term
Weighted-Average Remaining Term (in years), Balance	7 years 3 months 10 days	7 years 9 months 14 days	8 years 10 days
Weighted-Average Remaining Term, Vested and exercisable	6 years 4 months 28 days
Weighted-Average Remaining Term, Vested and expected to vest	7 years 3 months 10 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Balance	$ 128,744	$ 11,267	$ 3,647	$ 2,011
Aggregate Intrinsic Value, Vested and exercisable	70,721
Aggregate Intrinsic Value, Vested and expected to vest	$ 128,744

Stock-Based Compensation - Sc_4

Stock-Based Compensation - Schedule of RSU Activity under 2019 Plan (Detail) - Restricted Stock Units - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Number of Shares, RSUs granted	288,170	0
Number of Shares, RSUs forfeited	(5,600)
Number of Shares, RSUs vested	(1,666)
Number of Shares, Ending balance	280,904
Weighted-Average Grant Date Fair Value Per Share
Weighted-Average Grant Date Fair Value Per Share, RSUs granted	$ 38.28
Weighted-Average Grant Date Fair Value Per Share, RSUs forfeited	40.01
Weighted-Average Grant Date Fair Value Per Share, RSUs vested	59.79
Weighted-Average Grant Date Fair Value Per Share, Ending balance	$ 38.12

Stock-Based Compensation - Sc_5

Stock-Based Compensation - Schedule of Fair Value of ESPP Shares Estimated Using Black-Scholes Option Pricing Model Assumptions (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years 29 days	6 years 29 days	6 years 29 days
Expected volatility			45.60%
Expected dividend yield	0.00%	0.00%	0.00%
2019 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 months
Expected volatility	76.93%
Risk-free interest rate	1.89%
Expected dividend yield	0.00%

Income Taxes -Schedule of Incom

Income Taxes -Schedule of Income (Loss) Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Domestic	$ (51,179)	$ (41,145)	$ (30,654)
Foreign	132	81	65
Total loss before income taxes	$ (51,047)	$ (41,064)	$ (30,589)

Income Taxes - Schedule of Curr

Income Taxes - Schedule of Current Income Tax Provision (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes Disclosure [Line Items]
Total current income tax provision	$ 62	$ 38	$ 26
Domestic Federal
Income Taxes Disclosure [Line Items]
Total current income tax provision		3	1
Foreign Tax Authority
Income Taxes Disclosure [Line Items]
Total current income tax provision	$ 62	$ 35	$ 25

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets
Net operating loss carryovers	$ 49,862	$ 28,834
Fixed and intangible assets	450	837
Accruals and reserves	1,619	761
Stock-based compensation	780	132
Research and development credits	2,336	1,716
Contributions	20	14
Lease liability	2,135
Total deferred tax assets	57,202	32,294
Less valuation allowance	(55,085)	$ (32,294)
Gross deferred tax assets	2,117
Deferred tax liabilities:
Right-of-use-assets	(2,117)
Gross deferred tax liabilities	$ (2,117)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Statutory Federal Income Tax (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation
Income tax benefit at federal statutory rate	$ (10,720)	$ (8,624)	$ (10,404)
State and local income taxes net of federal tax benefit	(9)	3	1
Foreign tax rate differential	35	11	(3)
Change in valuation allowance	14,470	8,497	(522)
Stock-based compensation	(3,403)	123	309
R&D tax credits	(354)	(313)	(222)
Other	43	341	109
Federal rate change (pursuant to the Tax Cuts and Jobs Act of 2017)			10,758
Total current income tax provision	$ 62	$ 38	$ 26

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes Disclosure [Line Items]
Increase in valuation allowance	$ 22.8	$ 10	$ 0.6
Federal Corporate tax rate	21.00%		35.00%
Effect of remeasurement of deferred tax assets due to TCJA			$ 10.1
Domestic Federal
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards	$ 180.3
Net operating loss carryforwards	2030
Net operating loss carryforwards subject to expiration in 2030	$ 80.7
Net operating loss carryforwards never expire	99.6
Research and development credit carryforwards, california	2.8
California | State and Local Jurisdiction
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards	$ 40.4
Net operating loss carryforwards	2031
Research and development credit carryforwards, california	$ 2.4
All Other States | State and Local Jurisdiction
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards	$ 153.5
Net operating loss carryforwards	2029

Income Taxes - Schedule of Unre

Income Taxes - Schedule of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Unrecognized tax benefits [Abstract]
Beginning balance	$ 1,896	$ 893	$ 688
Additions based on tax positions related to prior years		394
Additions based on tax positions related to current years	690	609	205
Balance at end of year	$ 2,586	$ 1,896	$ 893

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	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	3,595,905	22,551,229	20,955,192
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share		18,670,328	17,510,045
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	3,315,001	3,636,358	3,108,604
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	280,904
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		13,422	11,603
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		54,903	183,162
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		176,218	141,778

Segment and Geographic Inform_3

Segment and Geographic Information - Schedule of Product Revenue Based on Location (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues From External Customers And Long Lived Assets [Line Items]
Product revenue	$ 42,927	$ 12,263	$ 1,719
United States
Revenues From External Customers And Long Lived Assets [Line Items]
Product revenue	22,699	7,022	969
Germany
Revenues From External Customers And Long Lived Assets [Line Items]
Product revenue	3,402	1,393	597
Rest of Europe
Revenues From External Customers And Long Lived Assets [Line Items]
Product revenue	14,097	3,516	143
All Other Countries
Revenues From External Customers And Long Lived Assets [Line Items]
Product revenue	$ 2,729	$ 332	$ 10

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - USD ($)	Feb. 29, 2020	Dec. 31, 2019	Dec. 31, 2018
Subsequent Event [Line Items]
Debt Amount		$ 13,334,000	$ 15,000,000
Debt, final payment amount		$ 1,013,000
Loan and Security Agreement
Subsequent Event [Line Items]
Debt interest rate		5.87%
Debt maturity date		Dec. 31, 2021
Debt, final payment amount		$ 1,000,000
Loan and Security Agreement | Minimum
Subsequent Event [Line Items]
Debt interest rate		1.75%
Loan and Security Agreement | Maximum
Subsequent Event [Line Items]
Debt interest rate basis		2.75%
Loan and Security Agreement | Subsequent Event
Subsequent Event [Line Items]
Debt payments description	The Amended Credit Facility provides an interest-only payments period through either (a) June 30, 2021, if the Company does not achieve a certain financial performance target on or before June 30, 2021 (“Performance Milestone One”), or (b) December 31, 2021, if the Company achieves Performance Milestone One but does not achieve both of a certain regulatory milestone and a certain financial performance target on or before December 31, 2021 (“Performance Milestone Two”) or (c) until June 30, 2022, if the Company achieves both Performance Milestones.
Debt, final payment amount	$ 1,600,000
Loan and Security Agreement | Subsequent Event | Supplemental Term Loan
Subsequent Event [Line Items]
Debt Amount	16,500,000
Repayment of supplemental term loan	$ 13,200,000
Debt maturity date	Dec. 1, 2023
Loan and Security Agreement | Subsequent Event | Maximum | Supplemental Term Loan
Subsequent Event [Line Items]
Debt interest rate	3.50%
Loan and Security Agreement | Subsequent Event | Prime Rate | Minimum | Supplemental Term Loan
Subsequent Event [Line Items]
Debt interest rate basis	1.25%
Loan and Security Agreement | Subsequent Event | Revolving Credit Facility
Subsequent Event [Line Items]
Termination of line of credit facility	$ 2,000,000
Line of credit facility termination fee	$ 20,000