Castle Biosciences (CSTL) 10-Q 9 Nov 20 2020 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2020	Oct. 30, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-38984
Entity Registrant Name	CASTLE BIOSCIENCES, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	77-0701774
Entity Address, Address Line One	820 S. Friendswood Drive
Entity Address, Address Line Two	Suite 201
Entity Address, City or Town	Friendswood
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77546
City Area Code	866
Local Phone Number	788-9007
Title of 12(b) Security	Common Stock, $0.001 par value per share
Trading Symbol	CSTL
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		19,911,225
Entity Central Index Key	0001447362
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false

CONDENSED BALANCE SHEETS

CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current Assets
Cash and cash equivalents	$ 183,050	$ 98,845
Accounts receivable, net	12,618	14,648
Inventory	1,679	1,237
Prepaid expenses and other current assets	3,718	1,951
Total current assets	201,065	116,681
Long-term accounts receivable, net	1,045	870
Property and equipment, net	6,646	2,060
Other assets – long-term	1,638	135
Total assets	210,394	119,746
Current Liabilities
Accounts payable	2,101	1,865
Accrued compensation	6,354	5,779
Medicare advance payment	8,350	0
Other accrued liabilities	3,435	1,812
Current portion of long-term debt	10,000	5,833
Total current liabilities	30,240	15,289
Long-term debt	12,455	19,289
Deferred rent and other liabilities	1,140	55
Total liabilities	43,835	34,633
Commitments and Contingencies (Note 9)
Stockholders’ Equity
Preferred stock, $0.001 par value; 10,000,000 shares authorized as of September 30, 2020 and December 31, 2019; no shares issued and outstanding as of September 30, 2020 and December 31, 2019.	0	0
Common stock, $0.001 par value; 200,000,000 shares authorized as of September 30, 2020 and December 31, 2019; 19,844,426 and 17,130,907 shares issued and outstanding as of September 30, 2020 and December 31, 2019, respectively.	20	17
Additional paid-in capital	224,146	137,308
Accumulated deficit	(57,607)	(52,212)
Total stockholders’ equity	166,559	85,113
Total liabilities and stockholders’ equity	$ 210,394	$ 119,746

CONDENSED BALANCE SHEETS (Paren

CONDENSED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	19,844,426	17,130,907
Common stock, shares outstanding (in shares)	19,844,426	17,130,907

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE (LOSS) INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
NET REVENUES	$ 15,217	$ 14,774	$ 45,350	$ 34,230
COST OF SALES	2,475	1,708	7,012	5,299
Gross margin	12,742	13,066	38,338	28,931
OPERATING EXPENSES AND OTHER OPERATING LOSS
Research and development	3,058	1,515	8,675	4,226
Selling, general and administrative	11,703	7,122	33,173	19,990
Other operating loss	1,882	0	0	0
Total operating expenses	16,643	8,637	41,848	24,216
Operating (loss) income	(3,901)	4,429	(3,510)	4,715
Interest income	18	6	354	32
Interest expense	(706)	(1,088)	(2,239)	(3,805)
Gain on extinguishment of debt (Note 6)	0	5,213	0	5,213
Other expense, net	0	(2,711)	0	(2,933)
(Loss) income before income taxes	(4,589)	5,849	(5,395)	3,222
Income tax expense	0	0	0	0
Net (loss) income and comprehensive (loss) income	(4,589)	5,849	(5,395)	3,222
Net (loss) income and comprehensive (loss) income	(4,589)	5,849	(5,395)	3,222
Convertible preferred stock cumulative dividends	0	289	0	2,156
Accretion of redeemable convertible preferred stock to redemption value	0	17	0	130
Net (loss) income and comprehensive (loss) income attributable to common stockholders	$ (4,589)	$ 5,543	$ (5,395)	$ 936
(Loss) earnings per share attributable to common stockholders:
Basic (in dollars per share)	$ (0.23)	$ 0.43	$ (0.29)	$ 0.17
Diluted (in dollars per share)	$ (0.23)	$ 0.05	$ (0.29)	$ (0.67)
Weighted-average shares outstanding:
Basic (in shares)	19,936	12,758	18,290	5,649
Diluted (in shares)	19,936	14,302	18,290	5,747

CONDENSED STATEMENTS OF CONVERT

CONDENSED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Convertible Preferred Stock Series C	Redeemable Convertible Preferred Stock Series A, B, D, E-1, E-2, E-2A, E-3 and F	Series E-1	Series E-3	Series F	Preferred Stock	Common Stock	Additional Paid-in Capital	Additional Paid-in CapitalSeries E-1	Additional Paid-in CapitalSeries E-3	Additional Paid-in CapitalSeries F	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018		503,056	9,456,775
Beginning balance at Dec. 31, 2018		$ 1,501	$ 44,995
Increase (Decrease) in Temporary Equity [Roll Forward]
Accretion of redeemable convertible preferred stock to redemption value:				$ 2	$ 7	$ 121
Exercise of redeemable convertible preferred stock warrants (in shares)				12,999		1,054
Exercise of redeemable convertible preferred stock warrants:	$ 0			$ 107		$ 10
Conversion of convertible preferred stock (in shares)		(503,056)	(9,470,828)					8,181,992
Conversion of convertible preferred stock	46,743	$ (1,501)	$ (45,242)					$ 8	$ 46,735
Ending balance (in shares) at Sep. 30, 2019		0	0
Ending balance at Sep. 30, 2019		$ 0	$ 0
Beginning balance (in shares) at Dec. 31, 2018							0	1,916,224
Beginning balance at Dec. 31, 2018	(56,566)						$ 0	$ 2	921				$ (57,489)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation expense	536								536
Exercise of common stock options (in shares)								687,520
Exercise of common stock options	1,164								1,164
Accretion of redeemable convertible preferred stock to redemption value:				$ (2)	(7)	$ (121)				$ (2)	$ (7)	$ (121)
Exercise of redeemable convertible preferred stock warrants (in shares)				12,999		1,054
Exercise of redeemable convertible preferred stock warrants:	0			$ 107		$ 10
Recognition of beneficial conversion feature on convertible promissory notes	8,378								8,378
Extinguishment of beneficial conversion feature on convertible promissory notes	(15,265)								(15,265)
Public offering of common stock, net of underwriting discounts, commissions and offering costs (in shares)								4,600,000
Public offering of common stock, net of underwriting discounts, commissions and offering costs	65,931							$ 5	65,926
Conversion of convertible promissory notes (in shares)								1,661,106
Conversion of convertible promissory notes	26,578							$ 2	26,576
Conversion of convertible preferred stock (in shares)		(503,056)	(9,470,828)					8,181,992
Conversion of convertible preferred stock	46,743	$ (1,501)	$ (45,242)					$ 8	46,735
Reclassification of preferred stock warrant liability and net exercise of certain warrants for common stock in connection with initial public offering (in shares)								27,207
Reclassification of preferred stock warrant liability and net exercise of certain warrants for common stock in connection with initial public offering	1,745								1,745
Net (loss) income	3,222												3,222
Ending balance (in shares) at Sep. 30, 2019							0	17,074,049
Ending balance at Sep. 30, 2019	82,336						$ 0	$ 17	136,586				(54,267)
Beginning balance (in shares) at Jun. 30, 2019		503,056	9,456,775
Beginning balance at Jun. 30, 2019		$ 1,501	$ 45,108
Increase (Decrease) in Temporary Equity [Roll Forward]
Accretion of redeemable convertible preferred stock to redemption value:					1	$ 16
Exercise of redeemable convertible preferred stock warrants (in shares)				12,999		1,054
Exercise of redeemable convertible preferred stock warrants:	0			$ 107		$ 10
Conversion of convertible preferred stock (in shares)		(503,056)	(9,470,828)					8,181,992
Conversion of convertible preferred stock	46,743	$ (1,501)	$ (45,242)					$ 8	46,735
Ending balance (in shares) at Sep. 30, 2019		0	0
Ending balance at Sep. 30, 2019		$ 0	$ 0
Beginning balance (in shares) at Jun. 30, 2019							0	2,192,461
Beginning balance at Jun. 30, 2019	(50,204)						$ 0	$ 2	9,910				(60,116)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation expense	229								229
Exercise of common stock options (in shares)								411,283
Exercise of common stock options	747								747
Accretion of redeemable convertible preferred stock to redemption value:					$ (1)	$ (16)					$ (1)	$ (16)
Exercise of redeemable convertible preferred stock warrants (in shares)				12,999		1,054
Exercise of redeemable convertible preferred stock warrants:	0			$ 107		$ 10
Extinguishment of beneficial conversion feature on convertible promissory notes	(15,265)								(15,265)
Public offering of common stock, net of underwriting discounts, commissions and offering costs (in shares)								4,600,000
Public offering of common stock, net of underwriting discounts, commissions and offering costs	65,931							$ 5	65,926
Conversion of convertible promissory notes (in shares)								1,661,106
Conversion of convertible promissory notes	26,578							$ 2	26,576
Conversion of convertible preferred stock (in shares)		(503,056)	(9,470,828)					8,181,992
Conversion of convertible preferred stock	46,743	$ (1,501)	$ (45,242)					$ 8	46,735
Reclassification of preferred stock warrant liability and net exercise of certain warrants for common stock in connection with initial public offering (in shares)								27,207
Reclassification of preferred stock warrant liability and net exercise of certain warrants for common stock in connection with initial public offering	1,745								1,745
Net (loss) income	5,849												5,849
Ending balance (in shares) at Sep. 30, 2019							0	17,074,049
Ending balance at Sep. 30, 2019	82,336						$ 0	$ 17	136,586				(54,267)
Beginning balance (in shares) at Dec. 31, 2019		0	0
Beginning balance at Dec. 31, 2019		$ 0	$ 0
Ending balance (in shares) at Sep. 30, 2020		0	0
Ending balance at Sep. 30, 2020		$ 0	$ 0
Beginning balance (in shares) at Dec. 31, 2019							0	17,130,907
Beginning balance at Dec. 31, 2019	85,113						$ 0	$ 17	137,308				(52,212)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation expense	$ 5,348								5,348
Exercise of common stock options (in shares)	332,065							332,065
Exercise of common stock options	$ 693							$ 1	692
Public offering of common stock, net of underwriting discounts, commissions and offering costs (in shares)								2,300,000
Public offering of common stock, net of underwriting discounts, commissions and offering costs	79,504							$ 2	79,502
Issuance of common stock under the employee stock purchase plan (in shares)								81,454
Issuance of common stock under the employee stock purchase plan	1,296								1,296
Net (loss) income	(5,395)												(5,395)
Ending balance (in shares) at Sep. 30, 2020							0	19,844,426
Ending balance at Sep. 30, 2020	166,559						$ 0	$ 20	224,146				(57,607)
Beginning balance (in shares) at Jun. 30, 2020		0	0
Beginning balance at Jun. 30, 2020		$ 0	$ 0
Ending balance (in shares) at Sep. 30, 2020		0	0
Ending balance at Sep. 30, 2020		$ 0	$ 0
Beginning balance (in shares) at Jun. 30, 2020							0	19,373,869
Beginning balance at Jun. 30, 2020	157,622						$ 0	$ 19	210,621				(53,018)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock compensation expense	2,118								2,118
Exercise of common stock options (in shares)								129,090
Exercise of common stock options	292							$ 1	291
Public offering of common stock, net of underwriting discounts, commissions and offering costs (in shares)								300,000
Public offering of common stock, net of underwriting discounts, commissions and offering costs	10,423								10,423
Issuance of common stock under the employee stock purchase plan (in shares)								41,467
Issuance of common stock under the employee stock purchase plan	693								693
Net (loss) income	(4,589)												(4,589)
Ending balance (in shares) at Sep. 30, 2020							0	19,844,426
Ending balance at Sep. 30, 2020	$ 166,559						$ 0	$ 20	$ 224,146				$ (57,607)

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
OPERATING ACTIVITIES
Net (loss) income	$ (5,395)	$ 3,222
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation	312	254
Stock compensation expense	5,348	536
Amortization of intangibles	0	4
Amortization of debt discounts and issuance costs	666	1,691
Other non-cash interest	0	442
Gain on extinguishment of debt	0	(5,213)
Change in fair value of preferred stock warrant liability	0	619
Change in fair value of embedded derivative	0	237
Change in fair value of convertible promissory note accounted for under the fair value option	0	2,077
Other	3	0
Change in operating assets and liabilities:
Accounts receivable	1,855	801
Prepaid expenses and other current assets	(1,767)	(1,522)
Inventory	(442)	61
Other assets	(1,503)	(20)
Accounts payable	211	(47)
Accrued compensation	575	(895)
Medicare advance payment	8,350	0
Other accrued liabilities	1,709	263
Deferred rent and other liabilities	373	12
Net cash provided by operating activities	10,295	2,522
INVESTING ACTIVITIES
Purchases of property and equipment	(4,162)	(590)
Proceeds from sale of property and equipment	2	0
Net cash used in investing activities	(4,160)	(590)
FINANCING ACTIVITIES
Proceeds from public offerings of common stock, net of underwriting discounts, commissions and offering costs	79,504	65,935
Proceeds from issuance of preferred stock and preferred stock warrants (including exercised warrants)	0	49
Proceeds from issuance of convertible promissory notes (including $4,756 from related parties for the nine months ended September 30, 2019), net of issuance costs	0	11,695
Proceeds from issuance of convertible promissory note and common stock warrant, net of issuance costs	0	9,236
Proceeds from issuance of term debt, net of issuance costs	0	1,776
Repayments on term debt	(3,333)	0
Repayments on line of credit	0	(1,791)
Proceeds from exercise of common stock options	692	1,164
Proceeds from contributions to the employee stock purchase plan	1,207	0
Net cash provided by financing activities	78,070	88,064
NET CHANGE IN CASH AND CASH EQUIVALENTS	84,205	89,996
Beginning of period	98,845	4,479
End of period	183,050	94,475
DISCLOSURE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Accrued purchases of property and equipment	32	17
Property and equipment acquired with tenant improvement allowance	714	0
Common stock and debt issuance costs incurred but not paid	0	4
Issuance of common stock upon conversion of convertible preferred stock	0	46,743
Conversion of preferred stock warrants to common stock warrants	0	1,745
Issuance of common stock upon conversion of convertible promissory notes	$ 0	$ 26,578

CONDENSED STATEMENTS OF CASH _2

CONDENSED STATEMENTS OF CASH FLOWS (Parenthetical) $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Statement of Cash Flows [Abstract]
Proceeds from issuance of convertible promissory notes from related parties	$ 4,756

Organization and Description of

Organization and Description of Business	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	Organization and Description of Business Castle Biosciences, Inc. (the ‘‘Company’’) was incorporated in the state of Delaware on September 12, 2007. The Company is a commercial-stage dermatological cancer company focused on providing physicians and their patients with personalized, clinically actionable genomic information to make more accurate treatment decisions. The Company is based in Friendswood, Texas (a suburb of Houston, Texas) and its laboratory operations are conducted at the Company’s facility located in Phoenix, Arizona. Impact of COVID-19 Pandemic In December 2019, a novel strain of coronavirus, SARS-CoV-2, which causes coronavirus disease 2019, or COVID-19, surfaced in Wuhan, China. Since then, COVID-19 has spread to multiple countries, including the United States. On March 11, 2020, the World Health Organization declared COVID-19 a pandemic. To date, the Company has maintained uninterrupted business operations with normal turnaround times for its delivery of test reports. The Company has implemented adjustments to its operations designed to keep employees safe and comply with federal, state and local guidelines, including those regarding social distancing. The Company experienced a decline in total test report volume in the second quarter of 2020 compared to the second quarter of 2019, which it believes was linked to delays and/or cancellations in patient visits, resulting in reduced diagnostic biopsies and thus reduced diagnoses of cutaneous melanoma in response to COVID-19. While the Company experienced improvements in total test report volume in the third quarter of 2020 compared to the third quarter of 2019, the extent to which COVID-19 may further impact the Company’s business, results of operations, financial condition and cash flows will depend on future developments, which are highly uncertain and cannot be predicted with confidence.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The Company’s financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (‘‘U.S. GAAP’’). The Company has no subsidiaries and all operations are conducted by the Company. Unaudited Interim Financial Information The accompanying condensed balance sheet as of September 30, 2020; the condensed statements of operations and comprehensive (loss) income, the condensed statements of convertible preferred stock and stockholders’ equity (deficit) for the three and nine months ended September 30, 2020 and 2019; and the condensed statements of cash flows for the nine months ended September 30, 2020 and 2019 are unaudited. The unaudited interim financial statements have been prepared on the same basis as the audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of September 30, 2020 and the results of its operations and its cash flows for the three and nine months ended September 30, 2020 and 2019. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2020 and 2019 are also unaudited. The results for the three and nine months ended September 30, 2020 are not necessarily indicative of results to be expected for the year ending December 31, 2020, any other interim periods, or any future year or period. The balance sheet as of December 31, 2019 included herein was derived from the audited financial statements as of that date. Certain disclosures have been condensed or omitted from the interim financial statements. These financial statements should be read in conjunction with the Company’s audited financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 filed with the Securities and Exchange Commission on March 10, 2020. Use of Estimates The preparation of financial statements in conformity with 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 as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Significant items subject to such estimates include revenue recognition, the valuation of stock-based compensation, assessing future tax exposure and the realization of deferred tax assets, the useful lives and recoverability of property and equipment, and contingent liabilities. The Company bases these estimates on historical and anticipated results, trends, and various other assumptions that the Company believes are reasonable under the circumstances, including assumptions as to future events. These estimates form the basis for making judgments about the carrying values of assets and liabilities and recorded revenues and expenses that are not readily apparent from other sources. Actual results could differ from those estimates and assumptions. The Company has considered the potential impact of the COVID-19 pandemic on its estimates and assumptions. The extent to which the COVID-19 pandemic may impact the Company’s estimates in future periods is uncertain and subject to change. Operating Segments Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision-making group, in making decisions on how to allocate resources and assess performance. The Company views its operations and manages its business as one operating segment. All revenues are attributable to U.S.-based operations and all assets are held in the United States. Cash and Cash Equivalents including Concentrations of Credit Risk Cash equivalents consist of short-term, highly liquid investments with original maturities of three months or less. The Company’s cash equivalents consist of money market funds, which are not insured by the Federal Deposit Insurance Corporation (“FDIC”), that are primarily invested in short-term U.S. government obligations. Cash deposits at financial institutions may exceed the amount of insurance provided by the FDIC. Management believes that the Company is not exposed to significant credit risk on its cash deposits due to the financial position of the institutions in which deposits are held. The Company has not experienced any losses on its cash or cash equivalents. Revenue Recognition Revenue is recognized in accordance with Financial Accounting Standards Board (‘‘FASB’’) Accounting Standards Codification (‘‘ASC’’) Topic 606, Revenue from Contracts with Customers (‘‘ASC 606’’). In accordance with ASC 606, the Company follows a five-step process to recognize revenues: (1) identify the contract with the customer, (2) identify the performance obligations, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations and (5) recognize revenues when the performance obligations are satisfied. All of the Company’s revenues from contracts with customers are associated with the provision of diagnostic and prognostic cancer testing services. Most of the Company’s revenues are attributable to DecisionDx®-Melanoma for cutaneous melanoma. The Company also provides a test for uveal melanoma, DecisionDx®-UM. The Company launched a test for patients with squamous cell carcinoma, DecisionDx®-SCC in August 2020 and launched a test for use in patients with suspicious pigmented lesions, DecisionDx® DiffDx™-Melanoma in November 2020. Information on the disaggregation of revenues by the Company’s significant third-party payors is included under Payor Concentration below. The Company has determined that it has a contract with the patient when the treating clinician orders the test. The Company’s contracts generally contain a single performance obligation, which is the delivery of the test report, and the Company satisfies its performance obligation at a point in time upon the delivery of the test report to the treating physician, at which point the Company can bill for the report. The amount of revenue recognized reflects the amount of consideration to which the Company expects to be entitled (the ‘‘transaction price’’) and considers the effects of variable consideration, which is discussed further below. Once the Company satisfies its performance obligations and bills for the service, the timing of the collection of payments may vary based on the payment practices of the third-party payor and the existence of contractually established reimbursement rates. Most of the payments for the Company’s services are made by third-party payors, including Medicare and commercial health insurance carriers. Certain contracts contain a contractual commitment of a reimbursement rate that differs from the Company’s list prices. However, absent a contractually committed reimbursement rate with a commercial carrier or governmental program, the Company’s diagnostic tests may or may not be covered by these entities’ existing reimbursement policies. In addition, patients do not enter into direct agreements with the Company that commit them to pay any portion of the cost of the tests in the event that their insurance provider declines to reimburse the Company. The Company may pursue, on a case-by-case basis, reimbursement from such patients in the form of co-payments and co-insurance, in accordance with the contractual obligations that the Company has with the insurance carrier or health plan. These situations may result in a delay in the collection of payments. The Medicare claims that are covered by policy under a Local Coverage Determination (‘‘LCD’’) are generally paid at the established rate by the Company’s Medicare contractor within 30 days from receipt. Medicare claims that were either submitted to Medicare prior to the LCD coverage commencement date or are not covered by the terms of the LCD but meet the definition of being medically reasonable and necessary pursuant to the controlling Section 1862(a)(1)(A) of the Social Security Act are generally appealed and may ultimately be paid at the first (termed ‘‘redetermination’’), second (termed ‘‘reconsideration’’) or third level of appeal (de novo hearing with an Administrative Law Judge (“ALJ”)). A successful appeal at any of these levels results in payment. In the absence of LCD coverage or contractually established reimbursements rates, the Company has concluded that its contracts include variable consideration because the amounts paid by Medicare or commercial health insurance carriers may be paid at less than the Company’s standard rates or not paid at all, with such differences considered implicit price concessions. Variable consideration attributable to these price concessions is measured at the expected value using the ‘‘most likely amount’’ method under ASC 606. The amounts are determined by historical average collection rates by test type and payor category taking into consideration the range of possible outcomes, the predictive value of the Company’s past experiences, the time period of when uncertainties expect to be resolved and the amount of consideration that is susceptible to factors outside of the Company’s influence, such as the judgment and actions of third parties. Such variable consideration is included in the transaction price only to the extent it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainties with respect to the amount are resolved. Variable consideration may be constrained and excluded from the transaction price in situations where there is no contractually agreed upon reimbursement coverage or in the absence of a predictable pattern and history of collectability with a payor. Variable consideration for Medicare claims that are not covered by an LCD, including those claims subject to approval by an ALJ at an appeal hearing, is deemed to be fully constrained due to factors outside the Company’s influence (i.e., judgment or actions of third parties) and the uncertainty of the amount to be received is not expected to be resolved for a long period of time. Variable consideration is evaluated each reporting period and adjustments are recorded as increases or decreases in revenues. Included in revenues for the three months ended September 30, 2020 and 2019 were $1,450,000 and $3,203,000, respectively, of revenue increases associated with changes in estimated variable consideration related to performance obligations satisfied in previous periods. Such amounts of variable consideration for the nine months ended September 30, 2020 and 2019 were revenue increases of $223,000 and $2,394,000, respectively. These amounts include (i) adjustments for actual collections versus estimated amounts and (ii) cash collections and the related recognition of revenue in current period for tests delivered in prior periods due to the release of the constraint on variable consideration. Because the Company’s contracts with customers have an expected duration of one year or less, the Company has elected the practical expedient in ASC 606 to not disclose information about its remaining performance obligations. Any incremental costs to obtain contracts are recorded as selling, general and administrative expense as incurred due to the short duration of the Company’s contracts. Contract balances consisted of accounts receivable (both current and noncurrent) and the Medicare advance payment (discussed further below) as of September 30, 2020. Contract balances consisted solely of accounts receivable (both current and noncurrent) as of December 31, 2019. Medicare Advance Payment On April 16, 2020, the Company received an advance payment of $8.3 million (the “Advance Payment”) from the Centers for Medicare & Medicaid Services (“CMS”) under its Accelerated and Advance Payment Program, which was expanded to provide increased cash flow to service providers during the COVID-19 pandemic. The Company has recorded the Advance Payment as a current liability on its balance sheet as of September 30, 2020. The Company will reduce the balance of the Advance Payment as it is applied to claims or is otherwise recouped by CMS. Originally, CMS was to recoup the Advance Payment from August 2020 through November 2020. However, the enactment on October 1, 2020 of the Continuing Appropriations Act, 2021 and Other Extensions Act (the “Appropriations Act”) modified the repayment terms such that recoupment will now commence in April 2021. For the first eleven months of recoupment, CMS will apply 25% of the Medicare payments otherwise owed to the Company against the balance of the Advance Payment. After that eleven-month period, CMS will recoup at a rate of 50% of the Medicare payments otherwise owed to the Company for an additional six months. If the Advance Payment is not fully recovered by CMS after this recoupment period, the Company will be required to repay any remaining balance. The classification of the Advance Payment on the Company’s balance sheet at September 30, 2020 does not consider the effect of the Appropriations Act. As of September 30, 2020, no revenue has been recognized related to any portion of the Advance Payment. DecisionDx-Melanoma Claims Consolidation In June 2017, the Company submitted to the Office of Medicare Hearings and Appeals (‘‘OMHA’’) a formal request to participate in a program that OMHA developed with the intent of providing appellants a means to have large volumes of claim disputes adjudicated at an accelerated rate. The program consolidates outstanding claims at the ALJ level and uses a statistical-sampling approach where five ALJs will determine reimbursement results for a sample of claims which are then extrapolated to the universe of claims. The consolidation includes 2,698 DecisionDx-Melanoma claims dating from 2013 through spring 2017. Hearings were held in April 2019 with a supplemental hearing in May 2019. On March 12, 2020, OMHA issued a decision denying payment on all claims in the consolidation. The Company has filed an appeal to the decision, although no ruling on such appeal has been issued to date. In accordance with ASC 606 and consistent with prior periods, the Company has not recognized (fully constrained the variable consideration) any revenues attributable to these claims in its financial statements pending the outcome of this matter. Payor Concentration The Company relies upon reimbursements from third-party government payors (primarily Medicare) and private-payor insurance companies to collect accounts receivable related to sales of its diagnostic tests. The Company’s significant third-party payors and their related revenues as a percentage of total revenues and accounts receivable balances are as follows: Percentage of Revenues Nine Months Ended Percentage of Accounts Receivable (current) Percentage of Accounts Receivable (non-current) 2020 2019 September 30, 2020 December 31, 2019 September 30, 2020 December 31, 2019 Medicare 54 % 47 % 11 % 7 % — % — % Medicare Advantage plans 28 % 28 % 41 % 41 % 18 % 18 % United Healthcare 2 % 7 % 1 % 9 % — % — % BlueCross BlueShield plans 8 % 6 % 27 % 25 % 47 % 46 % Accounts Receivable and Allowance for Doubtful Accounts The Company classifies accounts receivable balances that are expected to be paid more than one year from the balance sheet date as non-current assets. The estimated timing of payment utilized as a basis for classification as non-current is determined by analyses of historical payor-specific payment experience, adjusted for known factors that are expected to change the timing of future payments. The Company accrues an allowance for doubtful accounts against its accounts receivable when it is probable that an account is not collectible, based on write off history, credit risk of specific accounts, aging analysis and other information available on specific accounts. The Company generally does not perform evaluations of customers’ financial condition and generally does not require collateral. Accounts receivable are written off when all efforts to collect the balance have been exhausted. Historically, the Company’s bad debt expense has not been significant. The allowance for doubtful accounts was zero as of September 30, 2020 and December 31, 2019. Adjustments for implicit price concessions attributable to variable consideration, as discussed above, are incorporated into the measurement of the accounts receivable balances and are not part of the allowance for doubtful accounts. Other Operating Loss On April 10, 2020, the Company recei ved an automatic payment of $1.9 million from the U.S. Department of Health and Human Services (“HHS”) pursuant to the Coronavirus Aid, Relief and Economic Security Act enacted on March 27, 2020, also known as the CARES Act, out of relief funds allocated by HHS to healthcare providers to reimburse healthcare related expenses or lost revenues attributable to COVID-19. This automatic payment was calculated by HHS in proportion to the providers’ share of Medicare fee-for-service reimbursements in 2019 and was applicable to all facilities and providers that received Medicare fee-for-service reimbursements in 2019. In the second quarter of 2020, based on guidance issued by HHS at the time that stated any reasonable method could be used to calculate lost revenues attributable to COVID-19, the Company concluded it would qualify to retain the relief funds and recognized the funds received as other operating income during the three months ended June 30, 2020. On September 19, 2020, HHS issued a notice of reporting requirements that changed the methodology for determining lost revenues to be based on a patient care operating income metric, as defined by HHS. Due to this change in methodology and uncertainty in its application, the Company determined that it was no longer reasonably assured of keeping the funds. Therefore, in the three months ended September 30, 2020, the Company reversed the previously recognized income. As of September 30, 2020, the provider relief funds are reflected on the balance sheet as other accrued liabilities. On October 22, 2020, HHS again revised the methodology for calculating lost revenues, which is now calculated as a negative change, if any, in calendar year 2020 revenues compared to calendar year 2019 revenues. Fair Value of Financial Instruments The carrying amount of the Company’s long-term debt approximates fair value due to its variable market interest rate and management’s opinion that current rates and terms that would be available to the Company with the same maturity and security structure would be essentially equivalent to that of the Company’s long-term debt. This estimated fair value is a ‘‘Level 3’’ fair value measurement, as defined in Note 8. Accrued Compensation The Company accrues for liabilities under discretionary employee and executive bonus plans. These estimated compensation liabilities are based on progress against corporate objectives approved by the Company’s board of directors, compensation levels of eligible individuals, and target bonus percentage levels. The board of directors reviews and evaluates the performance against these objectives and ultimately determines what discretionary payments are made. The Company also accrues for liabilities under employee sales incentive bonus plans with accruals based on performance achieved to date compared to established targets. As of September 30, 2020 and December 31, 2019, the Company accrued $4,611,000 and $4,785,000, respectively, for liabilities associated with these bonus plans. These amounts are classified as current or noncurrent accrued liabilities in the balance sheets based on the expected timing of payment. CARES Act Payroll Tax Deferral The CARES Act permits employers to defer the payment of the employer share of social security taxes due for the period beginning March 27, 2020 and ending December 31, 2020. Of the amounts deferred, 50% are required to be paid by December 31, 2021 and the remaining 50% are required to be paid by December 31, 2022. The Company began deferring payment of the employer share of social security taxes in May 2020. As of September 30, 2020, the Company had deferred payment of $378,000 of such taxes, which are classified as noncurrent liabilities in the balance sheet. Comprehensive (Loss) Income Comprehensive (loss) income is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources. The Company’s comprehensive (loss) income was the same as its reported net (loss) income for all periods presented. Accounting Pronouncements Yet to be Adopted In February 2016, the FASB issued Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), which supersedes FASB ASC Topic 840, Leases, and provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method for finance leases or on a straight-line basis over the term of the lease for operating leases. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases. For companies that are not emerging growth companies (‘‘EGCs’’), ASU 2016-02 is effective for fiscal years beginning after December 15, 2018. For EGCs, the ASU was to be effective for fiscal years beginning after December 15, 2019. However, in November 2019, the FASB issued ASU No. 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815) and Leases (Topic 842): Effective Dates (“ASU 2019-10”), which included a one-year deferral of the effective date of ASU 2016-02 for certain entities. In June 2020, the FASB issued ASU No. 2020-05, Revenue from Contracts with Customers (Topic 606) and Leases (Topic 842): Effective Dates for Certain Entities , which further defers the effective date for certain entities. As a result, the ASU is now effective for EGCs for fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. The Company expects to adopt the new standard in the fourth quarter of 2022 using the modified retrospective method, under which the Company will apply Topic 842 to existing and new leases as of January 1, 2022, but prior periods will not be restated and will continue to be reported under Topic 840 guidance in effect during those periods. The Company anticipates that the adoption will not have a material impact on its statements of operations and comprehensive (loss) income or its statements of cash flows but expects to recognize right-of-use assets and liabilities for lease obligations associated with its operating leases. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (“ASU 2016-13”), which requires the measurement of expected credit losses for financial instruments carried at amortized cost, such as accounts receivable, held at the reporting date based on historical experience, current conditions and reasonable forecasts. The main objective of this ASU is to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. In November 2018, the FASB issued ASU No. 2018-19, Codification Improvements to Topic 326, Financing Instruments—Credit Losses , which included an amendment of the effective date for nonpublic entities. For non-EGCs, ASU 2016-13 is effective for fiscal years beginning after December 15, 2019. For EGCs, the standard was to be effective for fiscal years beginning after December 15, 2021. However, in November 2019, the FASB issued ASU 2019-10, which included a one-year deferral of the effective date of ASU 2016-13 for certain entities. As a result, ASU is now effective for EGCs for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The Company does not currently believe the adoption of this standard will have a significant impact on its financial statements, given its history of minimal bad debt expense relating to trade accounts receivable. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which eliminates certain exceptions to the general principles in Topic 740 and simplifies other areas of the existing guidance. For non-EGCs, ASU 2019-12 is effective for fiscal years beginning after December 15, 2020, and interim periods within those fiscal years. For EGCs, the standard is effective for fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. Early adoption is permitted. The Company is currently evaluating the impact of ASU 2019-12 on its financial statements.

(Loss) Earnings Per Share

(Loss) Earnings Per Share	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
(Loss) Earnings Per Share	(Loss) Earnings Per Share Basic (loss) earnings per share is computed by dividing net (loss) income attributable to common stockholders for the period by the weighted-average number of common shares outstanding during the period. The weighted-average number of common shares outstanding includes shares associated with an outstanding warrant, issued in July 2019, to purchase 209,243 shares of common stock, which are deemed to have been issued for purposes of calculating basic and diluted (loss) earnings per share, due to the nominal exercise price. On July 29, 2019, the Company completed the initial public offering of its common stock (the “IPO”), in which it issued and sold 4,600,000 shares of common stock. Also on that date, all of the Company’s outstanding convertible preferred stock and convertible promissory notes automatically converted into 8,181,992 and 1,661,106 shares, respectively, of common stock and certain outstanding warrants to purchase Series F convertible redeemable preferred stock were net exercised for an aggregate of 27,207 shares of common stock. On June 29, 2020 and July 2, 2020, the Company issued and sold 2,000,000 and 300,000 shares, respectively, of common stock in a follow-on public offering, as discussed further in Note 10. The foregoing shares are included in the Company’s weighted-average number of common shares outstanding starting on the respective issuance/conversion dates. Diluted (loss) earnings per share reflects the additional dilution from potential issuances of common stock, such as stock issuable pursuant to the exercise of stock options or purchases under the 2019 Employee Stock Purchase Plan (“ESPP”), as well as from the possible conversion of the Company’s convertible preferred stock, convertible promissory notes and exercise of outstanding warrants. The treasury stock and if-converted methods are used to calculate the potential dilutive effect of these common stock equivalents. However, potentially dilutive shares are excluded from the computation of diluted (loss) earnings per share when their effect is antidilutive. The following table shows the computation of basic and diluted (loss) earnings per share for the three and nine months ended September 30, 2020 and 2019 (in thousands, except per share data): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Numerator: Net (loss) income attributable to common stockholders $ (4,589) $ 5,543 $ (5,395) $ 936 Assumed conversion of convertible promissory notes (1) : Subtract: Extinguishment gain — (5,213) — (5,213) Add: Interest expense and change in fair value of embedded derivative — 420 — 420 Numerator for diluted (loss) earnings per share $ (4,589) $ 750 $ (5,395) $ (3,857) Denominator: Weighted-average common shares outstanding, basic 19,936 12,758 18,290 5,649 Assumed conversion of convertible promissory notes (1) — 290 — 98 Assumed exercise of common stock warrants — 67 — — Assumed exercise of stock options — 1,187 — — Weighted-average common shares outstanding, diluted 19,936 14,302 18,290 5,747 (Loss) earnings per share attributable to common stockholders: Basic $ (0.23) $ 0.43 $ (0.29) $ 0.17 Diluted $ (0.23) $ 0.05 $ (0.29) $ (0.67) (1) For both the three and nine months ended September 30, 2019, these figures reflect the assumed conversion of the Q1 2019 Notes (as defined in Note 6) into shares of common stock beginning July 1, 2019, in accordance with the requirements in ASC Topic 260, Earnings per Share , for contingently issuable shares due to the contingency not being met until the third quarter of 2019. Accordingly, the associated numerator adjustments for the nine months ended September 30, 2019 exclude activity from the first two quarters of 2019. The July 2019 Note (as defined in Note 6), was excluded from the computation of diluted (loss) earnings per share prior to its conversion on July 29, 2019 in connection with the IPO, as disclosed below. Due to the Company reporting a net loss attributable to common stockholders for the three and nine months ended September 30, 2020, all potentially dilutive securities are antidilutive and are excluded from the computations of diluted loss per share for such periods. The table below provides the weighted-average number of potential common shares associated with outstanding securities not included in the Company’s calculation of diluted (loss) earnings per share for the three and nine months ended September 30, 2020 and 2019 because to do so would be antidilutive (in thousands): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Convertible preferred stock — 2,489 — 6,256 Convertible promissory note (1) — 131 — 44 Stock options 2,767 139 2,732 1,778 Common stock warrants 35 — 35 30 Preferred stock warrants — 40 — 107 Employee stock purchase plan 101 — 104 — Total 2,903 2,799 2,871 8,215 (1) Associated with the July 2019 Note.

Property and Equipment, Net

Property and Equipment, Net	9 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): September 30, 2020 December 31, 2019 Lab equipment $ 1,977 $ 1,563 Computer equipment 1,186 887 Leasehold improvements 1,392 635 Furniture and fixtures 436 176 Construction in progress 3,153 2 Total 8,144 3,263 Less accumulated depreciation (1,498) (1,203) Property and equipment, net $ 6,646 $ 2,060 Depreciation expense was recorded in the statements of operations and comprehensive (loss) income as follows (in thousands): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Cost of sales $ 85 $ 70 $ 225 $ 203 Research and development 8 2 13 5 Selling, general and administrative 26 19 74 46 Total $ 119 $ 91 $ 312 $ 254

Other Accrued Liabilities

Other Accrued Liabilities	9 Months Ended
	Sep. 30, 2020
Payables and Accruals [Abstract]
Other Accrued Liabilities	Other Accrued Liabilities Other accrued liabilities consisted of the following (in thousands) : September 30, 2020 December 31, 2019 Provider relief funds $ 1,882 $ — Accrued service fees 1,201 1,162 Accrued interest 154 184 Employee stock purchase plan contributions 128 218 Accrued royalties 70 169 Accrued state income taxes — 79 Total $ 3,435 $ 1,812

Convertible Promissory Notes

Convertible Promissory Notes	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Convertible Promissory Notes	Convertible Promissory Notes Q1 2019 Notes In January and February 2019, the Company issued $11,770,000 principal amount of unsecured convertible promissory notes (the “Q1 2019 Notes”), of which $4,756,000 was with related parties (executive officers, members of the Company’s board of directors or entities affiliated with them). The Q1 2019 Notes bore simple interest at a rate of 8% per annum. Originally, the Q1 2019 Notes had a maturity date of January 31, 2020, but on July 3, 2019, the Company entered into an amendment with the holders of the Q1 2019 Notes to extend the maturity to June 30, 2020. The entire amount of the outstanding principal amount plus accrued interest on the Q1 2019 Notes converted into 954,074 shares of common stock in connection with the IPO on July 29, 2019. The Company determined that certain features of the Q1 2019 Notes were subject to bifurcation and separate accounting under ASC Subtopic 815-15, Embedded Derivatives . The embedded derivative was recorded at fair value each reporting period, with changes in fair value recorded as “other expense, net” in the statements of operations and comprehensive (loss) income. No hedge accounting treatment was applied. The Company also determined the Q1 2019 Notes contained a beneficial conversion feature under ASC Subtopic 470-20, Debt with Conversion and Other Options, related to the optional conversion of the Q1 2019 Notes into Series F redeemable convertible preferred stock at maturity. The debt discounts created from the initial recognition of the embedded derivative and the beneficial conversion feature were being amortized to interest expense over the life of the debt using the effective interest method. Amortization of discounts and issuance costs on the Q1 2019 Notes totaled $245,000 for the three months ended September 30, 2019 and $1,216,000 for the nine months ended September 30, 2019 and were included in interest expense. The conversion of the Q1 2019 Notes was considered an extinguishment for accounting purposes. The Company recognized an extinguishment gain of $5,213,000 during the three and nine months ended September 30, 2019. The amounts recognized in net income for three and nine months ended September 30, 2019 for the embedded derivative liability are as follows (in thousands) : (Loss) Recognized in Net Income Statement of Operations and Comprehensive (Loss) Income Location Three Months Ended Nine Months Ended Derivatives Not Classified as Hedging Instruments Embedded derivative in convertible promissory notes Other expense, net $ (101) $ (237) July 2019 Note On July 12, 2019, the Company issued an unsecured convertible promissory note having a principal amount of $10,000,000 (the ‘‘July 2019 Note’’) to an investor. The July 2019 Note bore simple interest at a rate of 8% per annum and had an original maturity date of June 30, 2020. The IPO triggered an automatic conversion feature of the July 2019 Note under which the outstanding principal amount plus accrued interest converted into 707,032 shares of common stock in connection with the closing of the IPO on July 29, 2019, based on a price derived from a valuation calculated pursuant to the terms of the July 2019 Note. In connection with the July 2019 Note issuance, the Company issued the purchaser of the July 2019 Note a warrant to purchase up to 209,243 shares of common stock at an exercise price of approximately $0.001 per share. The Company elected to account for the July 2019 Note under the fair value option in accordance with ASC Topic 825, Financial Instruments . Under the fair value option, changes in fair value were recorded in the condensed statements of operations and comprehensive (loss) income each period as “other expense, net.” For the three and nine months ended September 30, 2019, the company recorded $2,077,000 of negative fair value adjustments through the settlement date in the statements of operations and comprehensive (loss) income.

Long-Term Debt

Long-Term Debt	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term Debt The Company’s long-term debt balances are presented in the table below (in thousands): September 30, 2020 December 31, 2019 Term debt $ 23,354 $ 26,688 Unamortized discount and issuance costs (899) (1,566) Total long-term debt 22,455 25,122 Less: Current portion of long-term debt (10,000) (5,833) Total long-term debt, less current portion $ 12,455 $ 19,289 The Company has a Loan and Security Agreement (the ‘‘2018 LSA’’) with Oxford Finance LLC (‘‘Oxford’’), as collateral agent, and Oxford and Silicon Valley Bank (‘‘SVB’’) as equal syndicated lenders (collectively, the ‘‘Lenders’’). The 2018 LSA currently consists of a $25.0 million secured term loan credit facility (the ‘‘Term Loan’’). The Company’s obligations under the 2018 LSA are secured by substantially all of its assets, excluding intellectual property and subject to certain other exceptions and limitations. The Company has the right to prepay the Term Loan in whole or in part at any time, subject to a prepayment fee of 1.50% prior to November 30, 2020 and 0.75% thereafter. Upon prepayment, the Company is also obligated to pay a non-refundable early termination fee of $497,000. Amounts prepaid or repaid under the Term Loan may not be reborrowed. The 2018 LSA contains a financial covenant, which is discussed further below. Previously, the financial covenant in the 2018 LSA was based on a trailing three-month revenue target tested monthly throughout the term of the agreement. In February 2020, the Company entered into a second amendment of the 2018 LSA (the “Second Amendment”) that, among other things, changed the covenant from being tested monthly to quarterly testing. In March 2020, the Company entered into a third amendment of the 2018 LSA with the Lenders to establish revenue targets for the year ending December 31, 2020, which were calculated a percentage of the Company’s previously approved quarterly revenue projections. For quarterly periods ending after December 31, 2020, the trailing three-month revenue requirements will be determined by the Lenders upon receipt and review of the Company’s quarterly financial projections for the year, subject to certain specified criteria regarding minimum requirements. Revenues, if any, that the Company recognizes as a result of an ALJ appeal process from consolidated claims initiatives for DecisionDx-Melanoma do not count toward the minimum revenue requirements. On May 10, 2020, the Company entered into a fourth amendment of the 2018 LSA to modify the covenant structure such that the Company is required to comply with either (i) the trailing three-month revenue target or (ii) a liquidity ratio, in both cases measured quarterly. The liquidity ratio covenant requires that the ratio of (i) unrestricted cash and cash equivalents (as defined in the 2018 LSA) held at SVB or its affiliates to (ii) the outstanding obligations under the 2018 LSA be at least 2.00 to 1.00. As of September 30, 2020, the Company was in compliance with the covenant. The Company’s liquidity ratio was 7.76 to 1.00 as of September 30, 2020. In addition, the 2018 LSA contains customary conditions of borrowing, events of default and covenants, including covenants that restrict the Company’s ability to dispose of assets, merge with or acquire other entities, incur indebtedness and make distributions to holders of the Company’s capital stock. Should an event of default occur, including the occurrence of a material adverse change, the Company could be liable for immediate repayment of all obligations under the 2018 LSA. The Second Amendment included a waiver, by the Lenders, of an event of default of the Company attributable to maintaining a balance in a certain third-party deposit account, beyond the maximum level permitted, without obtaining a control agreement for such deposit account in favor of the collateral agent, Oxford. In addition to the waiver, the Second Amendment also provided a modification to increase the maximum balance permitted for this deposit account. The Company is currently in compliance with this provision of the 2018 LSA. The Company’s ability to further amend the terms of the 2018 LSA is subject to the approval of Oxford and SVB. Accordingly, should the Company seek to amend the 2018 LSA, there can be no assurance that an amendment would be available on terms acceptable to the Company or at all.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market in an orderly transaction between market participants at the measurement date. The fair value hierarchy prioritizes the inputs to valuation techniques used in measuring fair value. There are three levels to the fair value hierarchy based on the reliability of inputs, as follows: Level 1 – Observable inputs that reflect quoted prices (unadjusted) for identical assets or liabilities in active markets. Level 2 – Inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. Level 3 – Unobservable inputs in which little or no market data exists, therefore requiring the Company to develop its own assumptions. Financial instruments measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. The use of different assumptions and/or estimation methodologies may have a material effect on estimated fair values. Accordingly, the fair value estimates disclosed, or amounts recorded may not be indicative of the amount that the Company or holders of the instruments could realize in a current market exchange. The table below provides information, by level within the fair value hierarchy, of the Company’s financial assets and financial liabilities that are accounted for at fair value on a recurring basis as of September 30, 2020 and December 31, 2019 (in thousands): As of September 30, 2020 Quoted Prices in Active Markets for Identical Items (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs Total Assets: Money market funds (1) $ 182,616 $ — $ — $ 182,616 As of December 31, 2019 Quoted Prices in Active Markets for Identical Items (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs Total Assets: Money market funds (1) $ 98,389 $ — $ — $ 98,389 (1) Classified as “Cash and cash equivalents” in the condensed balance sheets.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and ContingenciesFrom time to time, the Company may be involved in legal proceedings arising in the ordinary course of business. The Company believes there is no threatened litigation or litigation pending that could have, individually or in the aggregate, a material adverse effect on the Company’s financial position, results of operations or cash flows.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Common Stock Offering On June 29, 2020 and July 2, 2020, the Company issued and sold 2,000,000 and 300,000 shares, respectively, of its common stock in a follow-on public offering at a price of $37.00 per share. The Company received $79.5 million in aggregate net proceeds, after deducting underwriting discounts and commissions and offering costs. The shares issued and sold on July 2, 2020 reflect the underwriters’ exercise in full of their 30-day option to purchase additional shares at the public offering price, less underwriting discounts and commissions. Common Stock Warrants Information about common stock warrants outstanding as of September 30, 2020 and December 31, 2019 are presented in the table below: Expiration date Number of shares Exercise price July 12, 2026 209,243 $ 0.001 March 31, 2027 26,428 $ 7.10 November 30, 2028 8,809 $ 7.10 Total 244,480

Stock Incentive Plans and Stock

Stock Incentive Plans and Stock-Based Compensation	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Stock Incentive Plans and Stock-Based Compensation	Stock Incentive Plans and Stock-Based Compensation Stock Incentive Plans Activity under the Company’s stock plans for the nine months ended September 30, 2020 is set forth below: Weighted-Average Shares Available for Grant Stock Options Outstanding Exercise Price Remaining Contractual Term (Years) Aggregate Intrinsic Value (in thousands) Balance as of December 31, 2019 863,127 2,637,966 $ 13.30 Additional options authorized 856,545 — — Granted (577,120) 577,120 $ 38.93 Exercised — (332,065) $ 2.08 Forfeited/Canceled 84,322 (84,322) $ 27.02 Balance as of September 30, 2020 1,226,874 2,798,699 $ 19.50 8.57 $ 89,406 Exercisable at September 30, 2020 (1) 635,351 $ 4.11 7.08 $ 30,076 (1) Vested and exercisable options. Additionally, outstanding unvested options to purchase an aggregate of 82,624 shares of common stock with a weighted-average exercise price of $2.39 per share may be exercised prior to vesting as of September 30, 2020 under early-exercise provisions. In the event of such exercise, the shares obtained upon exercise would be restricted and subject to forfeiture prior to vesting. No such early exercises have occurred as of September 30, 2020. Employee Stock Purchase Plan The ESPP provides for certain automatic increases in the number of shares of common stock reserved for issuance, which resulted in an additional 171,309 shares becoming available under the ESPP effective January 1, 2020. On February 28, 2020 and August 31, 2020 the Company issued 39,987 and 41,467 shares, respectively, of its common stock pursuant to scheduled purchases under the ESPP. As of September 30, 2020, 501,790 shares remained available for issuance under the ESPP. Determining Fair Value - Summary of Assumptions The Company uses the Black-Scholes option pricing model to estimate the fair value of each option grant on the date of grant or any other measurement date. The following table sets forth the assumptions used to determine the fair value of stock options: Nine Months Ended 2020 2019 Average expected term (years) 6 6 Expected stock price volatility 59.15% - 63.82% 56.74% - 59.60% Risk-free interest rate 0.28% - 1.76% 1.61% - 2.47% Dividend yield —% —% The following table sets forth assumptions used to determine the fair value of the purchase rights issued under the ESPP: Nine Months Ended 2020 2019 Average expected term (years) 1.2 Not applicable Expected stock price volatility 56.80% - 100.49% Not applicable Risk-free interest rate 0.12% - 0.95% Not applicable Dividend yield —% Not applicable The fair value of the Company’s common stock is also an assumption used to determine the fair value of stock options and purchase rights under the ESPP. Prior to the IPO, our common stock was not publicly traded, therefore the Company estimated the fair value of its common stock. Following the IPO, the fair value of the Company’s common stock is the closing selling price per share of its common stock as reported on the Nasdaq Global Market on the date of grant or other relevant determination date. Stock-Based Compensation Expense Stock-based compensation expense related to stock options and the ESPP is included in the statements of operations and comprehensive (loss) income as follows (in thousands): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Cost of sales $ 268 $ 13 $ 674 $ 35 Research and development 370 23 835 70 Selling, general and administrative 1,480 193 3,839 431 Total stock-based compensation expense $ 2,118 $ 229 $ 5,348 $ 536

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	The Company’s financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (‘‘U.S. GAAP’’). The Company has no subsidiaries and all operations are conducted by the Company. Unaudited Interim Financial Information The accompanying condensed balance sheet as of September 30, 2020; the condensed statements of operations and comprehensive (loss) income, the condensed statements of convertible preferred stock and stockholders’ equity (deficit) for the three and nine months ended September 30, 2020 and 2019; and the condensed statements of cash flows for the nine months ended September 30, 2020 and 2019 are unaudited. The unaudited interim financial statements have been prepared on the same basis as the audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of September 30, 2020 and the results of its operations and its cash flows for the three and nine months ended September 30, 2020 and 2019. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2020 and 2019 are also unaudited. The results for the three and nine months ended September 30, 2020 are not necessarily indicative of results to be expected for the year ending December 31, 2020, any other interim periods, or any future year or period. The balance sheet as of December 31, 2019 included herein was derived from the audited financial statements as of that date. Certain disclosures have been condensed or omitted from the interim financial statements. These financial statements should be read in conjunction with the Company’s audited financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 filed with the Securities and Exchange Commission on March 10, 2020.
Use of Estimates	The preparation of financial statements in conformity with 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 as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Significant items subject to such estimates include revenue recognition, the valuation of stock-based compensation, assessing future tax exposure and the realization of deferred tax assets, the useful lives and recoverability of property and equipment, and contingent liabilities. The Company bases these estimates on historical and anticipated results, trends, and various other assumptions that the Company believes are reasonable under the circumstances, including assumptions as to future events. These estimates form the basis for making judgments about the carrying values of assets and liabilities and recorded revenues and expenses that are not readily apparent from other sources. Actual results could differ from those estimates and assumptions. The Company has considered the potential impact of the COVID-19 pandemic on its estimates and assumptions. The extent to which the COVID-19 pandemic may impact the Company’s estimates in future periods is uncertain and subject to change.
Operating Segments	Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision-making group, in making decisions on how to allocate resources and assess performance. The Company views its operations and manages its business as one operating segment. All revenues are attributable to U.S.-based operations and all assets are held in the United States.
Cash and Cash Equivalents	Cash equivalents consist of short-term, highly liquid investments with original maturities of three months or less. The Company’s cash equivalents consist of money market funds, which are not insured by the Federal Deposit Insurance Corporation (“FDIC”), that are primarily invested in short-term U.S. government obligations.
Revenue Recognition	Revenue is recognized in accordance with Financial Accounting Standards Board (‘‘FASB’’) Accounting Standards Codification (‘‘ASC’’) Topic 606, Revenue from Contracts with Customers (‘‘ASC 606’’). In accordance with ASC 606, the Company follows a five-step process to recognize revenues: (1) identify the contract with the customer, (2) identify the performance obligations, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations and (5) recognize revenues when the performance obligations are satisfied. All of the Company’s revenues from contracts with customers are associated with the provision of diagnostic and prognostic cancer testing services. Most of the Company’s revenues are attributable to DecisionDx®-Melanoma for cutaneous melanoma. The Company also provides a test for uveal melanoma, DecisionDx®-UM. The Company launched a test for patients with squamous cell carcinoma, DecisionDx®-SCC in August 2020 and launched a test for use in patients with suspicious pigmented lesions, DecisionDx® DiffDx™-Melanoma in November 2020. Information on the disaggregation of revenues by the Company’s significant third-party payors is included under Payor Concentration below. The Company has determined that it has a contract with the patient when the treating clinician orders the test. The Company’s contracts generally contain a single performance obligation, which is the delivery of the test report, and the Company satisfies its performance obligation at a point in time upon the delivery of the test report to the treating physician, at which point the Company can bill for the report. The amount of revenue recognized reflects the amount of consideration to which the Company expects to be entitled (the ‘‘transaction price’’) and considers the effects of variable consideration, which is discussed further below. Once the Company satisfies its performance obligations and bills for the service, the timing of the collection of payments may vary based on the payment practices of the third-party payor and the existence of contractually established reimbursement rates. Most of the payments for the Company’s services are made by third-party payors, including Medicare and commercial health insurance carriers. Certain contracts contain a contractual commitment of a reimbursement rate that differs from the Company’s list prices. However, absent a contractually committed reimbursement rate with a commercial carrier or governmental program, the Company’s diagnostic tests may or may not be covered by these entities’ existing reimbursement policies. In addition, patients do not enter into direct agreements with the Company that commit them to pay any portion of the cost of the tests in the event that their insurance provider declines to reimburse the Company. The Company may pursue, on a case-by-case basis, reimbursement from such patients in the form of co-payments and co-insurance, in accordance with the contractual obligations that the Company has with the insurance carrier or health plan. These situations may result in a delay in the collection of payments. The Medicare claims that are covered by policy under a Local Coverage Determination (‘‘LCD’’) are generally paid at the established rate by the Company’s Medicare contractor within 30 days from receipt. Medicare claims that were either submitted to Medicare prior to the LCD coverage commencement date or are not covered by the terms of the LCD but meet the definition of being medically reasonable and necessary pursuant to the controlling Section 1862(a)(1)(A) of the Social Security Act are generally appealed and may ultimately be paid at the first (termed ‘‘redetermination’’), second (termed ‘‘reconsideration’’) or third level of appeal (de novo hearing with an Administrative Law Judge (“ALJ”)). A successful appeal at any of these levels results in payment. In the absence of LCD coverage or contractually established reimbursements rates, the Company has concluded that its contracts include variable consideration because the amounts paid by Medicare or commercial health insurance carriers may be paid at less than the Company’s standard rates or not paid at all, with such differences considered implicit price concessions. Variable consideration attributable to these price concessions is measured at the expected value using the ‘‘most likely amount’’ method under ASC 606. The amounts are determined by historical average collection rates by test type and payor category taking into consideration the range of possible outcomes, the predictive value of the Company’s past experiences, the time period of when uncertainties expect to be resolved and the amount of consideration that is susceptible to factors outside of the Company’s influence, such as the judgment and actions of third parties. Such variable consideration is included in the transaction price only to the extent it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainties with respect to the amount are resolved. Variable consideration may be constrained and excluded from the transaction price in situations where there is no contractually agreed upon reimbursement coverage or in the absence of a predictable pattern and history of collectability with a payor. Variable consideration for Medicare claims that are not covered by an LCD, including those claims subject to approval by an ALJ at an appeal hearing, is deemed to be fully constrained due to factors outside the Company’s influence (i.e., judgment or actions of third parties) and the uncertainty of the amount to be received is not expected to be resolved for a long period of time. Variable consideration is evaluated each reporting period and adjustments are recorded as increases or decreases in revenues. Included in revenues for the three months ended September 30, 2020 and 2019 were $1,450,000 and $3,203,000, respectively, of revenue increases associated with changes in estimated variable consideration related to performance obligations satisfied in previous periods. Such amounts of variable consideration for the nine months ended September 30, 2020 and 2019 were revenue increases of $223,000 and $2,394,000, respectively. These amounts include (i) adjustments for actual collections versus estimated amounts and (ii) cash collections and the related recognition of revenue in current period for tests delivered in prior periods due to the release of the constraint on variable consideration.
Accounts Receivable	The Company classifies accounts receivable balances that are expected to be paid more than one year from the balance sheet date as non-current assets. The estimated timing of payment utilized as a basis for classification as non-current is determined by analyses of historical payor-specific payment experience, adjusted for known factors that are expected to change the timing of future payments.
Allowance for Doubtful Accounts	The Company accrues an allowance for doubtful accounts against its accounts receivable when it is probable that an account is not collectible, based on write off history, credit risk of specific accounts, aging analysis and other information available on specific accounts. The Company generally does not perform evaluations of customers’ financial condition and generally does not require collateral. Accounts receivable are written off when all efforts to collect the balance have been exhausted. Historically, the Company’s bad debt expense has not been significant. The allowance for doubtful accounts was zero as of September 30, 2020 and December 31, 2019. Adjustments for implicit price concessions attributable to variable consideration, as discussed above, are incorporated into the measurement of the accounts receivable balances and are not part of the allowance for doubtful accounts.
Fair Value of Financial Instruments	The carrying amount of the Company’s long-term debt approximates fair value due to its variable market interest rate and management’s opinion that current rates and terms that would be available to the Company with the same maturity and security structure would be essentially equivalent to that of the Company’s long-term debt. This estimated fair value is a ‘‘Level 3’’ fair value measurement, as defined in Note 8.
Accrued Compensation	The Company accrues for liabilities under discretionary employee and executive bonus plans. These estimated compensation liabilities are based on progress against corporate objectives approved by the Company’s board of directors, compensation levels of eligible individuals, and target bonus percentage levels. The board of directors reviews and evaluates the performance against these objectives and ultimately determines what discretionary payments are made. The Company also accrues for liabilities under employee sales incentive bonus plans with accruals based on performance achieved to date compared to established targets. As of September 30, 2020 and December 31, 2019, the Company accrued $4,611,000 and $4,785,000, respectively, for liabilities associated with these bonus plans. These amounts are classified as current or noncurrent accrued liabilities in the balance sheets based on the expected timing of payment.
Comprehensive (Loss) Income	Comprehensive (loss) income is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources.
Accounting Pronouncements Yet to be Adopted	In February 2016, the FASB issued Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), which supersedes FASB ASC Topic 840, Leases, and provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method for finance leases or on a straight-line basis over the term of the lease for operating leases. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases. For companies that are not emerging growth companies (‘‘EGCs’’), ASU 2016-02 is effective for fiscal years beginning after December 15, 2018. For EGCs, the ASU was to be effective for fiscal years beginning after December 15, 2019. However, in November 2019, the FASB issued ASU No. 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815) and Leases (Topic 842): Effective Dates (“ASU 2019-10”), which included a one-year deferral of the effective date of ASU 2016-02 for certain entities. In June 2020, the FASB issued ASU No. 2020-05, Revenue from Contracts with Customers (Topic 606) and Leases (Topic 842): Effective Dates for Certain Entities , which further defers the effective date for certain entities. As a result, the ASU is now effective for EGCs for fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. The Company expects to adopt the new standard in the fourth quarter of 2022 using the modified retrospective method, under which the Company will apply Topic 842 to existing and new leases as of January 1, 2022, but prior periods will not be restated and will continue to be reported under Topic 840 guidance in effect during those periods. The Company anticipates that the adoption will not have a material impact on its statements of operations and comprehensive (loss) income or its statements of cash flows but expects to recognize right-of-use assets and liabilities for lease obligations associated with its operating leases. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (“ASU 2016-13”), which requires the measurement of expected credit losses for financial instruments carried at amortized cost, such as accounts receivable, held at the reporting date based on historical experience, current conditions and reasonable forecasts. The main objective of this ASU is to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. In November 2018, the FASB issued ASU No. 2018-19, Codification Improvements to Topic 326, Financing Instruments—Credit Losses , which included an amendment of the effective date for nonpublic entities. For non-EGCs, ASU 2016-13 is effective for fiscal years beginning after December 15, 2019. For EGCs, the standard was to be effective for fiscal years beginning after December 15, 2021. However, in November 2019, the FASB issued ASU 2019-10, which included a one-year deferral of the effective date of ASU 2016-13 for certain entities. As a result, ASU is now effective for EGCs for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The Company does not currently believe the adoption of this standard will have a significant impact on its financial statements, given its history of minimal bad debt expense relating to trade accounts receivable. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which eliminates certain exceptions to the general principles in Topic 740 and simplifies other areas of the existing guidance. For non-EGCs, ASU 2019-12 is effective for fiscal years beginning after December 15, 2020, and interim periods within those fiscal years. For EGCs, the standard is effective for fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. Early adoption is permitted. The Company is currently evaluating the impact of ASU 2019-12 on its financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Schedules of Concentration of Risk, by Risk Factor	The Company’s significant third-party payors and their related revenues as a percentage of total revenues and accounts receivable balances are as follows: Percentage of Revenues Nine Months Ended Percentage of Accounts Receivable (current) Percentage of Accounts Receivable (non-current) 2020 2019 September 30, 2020 December 31, 2019 September 30, 2020 December 31, 2019 Medicare 54 % 47 % 11 % 7 % — % — % Medicare Advantage plans 28 % 28 % 41 % 41 % 18 % 18 % United Healthcare 2 % 7 % 1 % 9 % — % — % BlueCross BlueShield plans 8 % 6 % 27 % 25 % 47 % 46 %

(Loss) Earnings Per Share (Tabl

(Loss) Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table shows the computation of basic and diluted (loss) earnings per share for the three and nine months ended September 30, 2020 and 2019 (in thousands, except per share data): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Numerator: Net (loss) income attributable to common stockholders $ (4,589) $ 5,543 $ (5,395) $ 936 Assumed conversion of convertible promissory notes (1) : Subtract: Extinguishment gain — (5,213) — (5,213) Add: Interest expense and change in fair value of embedded derivative — 420 — 420 Numerator for diluted (loss) earnings per share $ (4,589) $ 750 $ (5,395) $ (3,857) Denominator: Weighted-average common shares outstanding, basic 19,936 12,758 18,290 5,649 Assumed conversion of convertible promissory notes (1) — 290 — 98 Assumed exercise of common stock warrants — 67 — — Assumed exercise of stock options — 1,187 — — Weighted-average common shares outstanding, diluted 19,936 14,302 18,290 5,747 (Loss) earnings per share attributable to common stockholders: Basic $ (0.23) $ 0.43 $ (0.29) $ 0.17 Diluted $ (0.23) $ 0.05 $ (0.29) $ (0.67) (1) For both the three and nine months ended September 30, 2019, these figures reflect the assumed conversion of the Q1 2019 Notes (as defined in Note 6) into shares of common stock beginning July 1, 2019, in accordance with the requirements in ASC Topic 260, Earnings per Share , for contingently issuable shares due to the contingency not being met until the third quarter of 2019. Accordingly, the associated numerator adjustments for the nine months ended September 30, 2019 exclude activity from the first two quarters of 2019. The July 2019 Note (as defined in Note 6), was excluded from the computation of diluted (loss) earnings per share prior to its conversion on July 29, 2019 in connection with the IPO, as disclosed below.
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The table below provides the weighted-average number of potential common shares associated with outstanding securities not included in the Company’s calculation of diluted (loss) earnings per share for the three and nine months ended September 30, 2020 and 2019 because to do so would be antidilutive (in thousands): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Convertible preferred stock — 2,489 — 6,256 Convertible promissory note (1) — 131 — 44 Stock options 2,767 139 2,732 1,778 Common stock warrants 35 — 35 30 Preferred stock warrants — 40 — 107 Employee stock purchase plan 101 — 104 — Total 2,903 2,799 2,871 8,215 (1) Associated with the July 2019 Note.

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property and equipment, net consisted of the following (in thousands): September 30, 2020 December 31, 2019 Lab equipment $ 1,977 $ 1,563 Computer equipment 1,186 887 Leasehold improvements 1,392 635 Furniture and fixtures 436 176 Construction in progress 3,153 2 Total 8,144 3,263 Less accumulated depreciation (1,498) (1,203) Property and equipment, net $ 6,646 $ 2,060 Depreciation expense was recorded in the statements of operations and comprehensive (loss) income as follows (in thousands): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Cost of sales $ 85 $ 70 $ 225 $ 203 Research and development 8 2 13 5 Selling, general and administrative 26 19 74 46 Total $ 119 $ 91 $ 312 $ 254

Other Accrued Liabilities (Tabl

Other Accrued Liabilities (Tables)	9 Months Ended
	Sep. 30, 2020
Payables and Accruals [Abstract]
Schedule of Accrued Liabilities	Other accrued liabilities consisted of the following (in thousands) : September 30, 2020 December 31, 2019 Provider relief funds $ 1,882 $ — Accrued service fees 1,201 1,162 Accrued interest 154 184 Employee stock purchase plan contributions 128 218 Accrued royalties 70 169 Accrued state income taxes — 79 Total $ 3,435 $ 1,812

Convertible Promissory Notes (T

Convertible Promissory Notes (Tables)	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Derivatives Not Designated as Hedging Instruments	The amounts recognized in net income for three and nine months ended September 30, 2019 for the embedded derivative liability are as follows (in thousands) : (Loss) Recognized in Net Income Statement of Operations and Comprehensive (Loss) Income Location Three Months Ended Nine Months Ended Derivatives Not Classified as Hedging Instruments Embedded derivative in convertible promissory notes Other expense, net $ (101) $ (237)

Long-Term Debt (Tables)

Long-Term Debt (Tables)	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	The Company’s long-term debt balances are presented in the table below (in thousands): September 30, 2020 December 31, 2019 Term debt $ 23,354 $ 26,688 Unamortized discount and issuance costs (899) (1,566) Total long-term debt 22,455 25,122 Less: Current portion of long-term debt (10,000) (5,833) Total long-term debt, less current portion $ 12,455 $ 19,289

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The table below provides information, by level within the fair value hierarchy, of the Company’s financial assets and financial liabilities that are accounted for at fair value on a recurring basis as of September 30, 2020 and December 31, 2019 (in thousands): As of September 30, 2020 Quoted Prices in Active Markets for Identical Items (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs Total Assets: Money market funds (1) $ 182,616 $ — $ — $ 182,616 As of December 31, 2019 Quoted Prices in Active Markets for Identical Items (Level 1) Significant Other Observable Inputs Significant Unobservable Inputs Total Assets: Money market funds (1) $ 98,389 $ — $ — $ 98,389 (1) Classified as “Cash and cash equivalents” in the condensed balance sheets.

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Schedule of Common Stock Warrants Outstanding	Information about common stock warrants outstanding as of September 30, 2020 and December 31, 2019 are presented in the table below: Expiration date Number of shares Exercise price July 12, 2026 209,243 $ 0.001 March 31, 2027 26,428 $ 7.10 November 30, 2028 8,809 $ 7.10 Total 244,480

Stock Incentive Plans and Sto_2

Stock Incentive Plans and Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Share-based Payment Arrangement, Option, Activity	Activity under the Company’s stock plans for the nine months ended September 30, 2020 is set forth below: Weighted-Average Shares Available for Grant Stock Options Outstanding Exercise Price Remaining Contractual Term (Years) Aggregate Intrinsic Value (in thousands) Balance as of December 31, 2019 863,127 2,637,966 $ 13.30 Additional options authorized 856,545 — — Granted (577,120) 577,120 $ 38.93 Exercised — (332,065) $ 2.08 Forfeited/Canceled 84,322 (84,322) $ 27.02 Balance as of September 30, 2020 1,226,874 2,798,699 $ 19.50 8.57 $ 89,406 Exercisable at September 30, 2020 (1) 635,351 $ 4.11 7.08 $ 30,076 (1) Vested and exercisable options. Additionally, outstanding unvested options to purchase an aggregate of 82,624 shares of common stock with a weighted-average exercise price of $2.39 per share may be exercised prior to vesting as of September 30, 2020 under early-exercise provisions. In the event of such exercise, the shares obtained upon exercise would be restricted and subject to forfeiture prior to vesting. No such early exercises have occurred as of September 30, 2020.
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The following table sets forth the assumptions used to determine the fair value of stock options: Nine Months Ended 2020 2019 Average expected term (years) 6 6 Expected stock price volatility 59.15% - 63.82% 56.74% - 59.60% Risk-free interest rate 0.28% - 1.76% 1.61% - 2.47% Dividend yield —% —%
Schedule of Share-based Payment Award, ESPP, Valuation Assumptions	The following table sets forth assumptions used to determine the fair value of the purchase rights issued under the ESPP: Nine Months Ended 2020 2019 Average expected term (years) 1.2 Not applicable Expected stock price volatility 56.80% - 100.49% Not applicable Risk-free interest rate 0.12% - 0.95% Not applicable Dividend yield —% Not applicable
Share-based Payment Arrangement, Expensed and Capitalized, Amount	Stock-based compensation expense related to stock options and the ESPP is included in the statements of operations and comprehensive (loss) income as follows (in thousands): Three Months Ended Nine Months Ended 2020 2019 2020 2019 Cost of sales $ 268 $ 13 $ 674 $ 35 Research and development 370 23 835 70 Selling, general and administrative 1,480 193 3,839 431 Total stock-based compensation expense $ 2,118 $ 229 $ 5,348 $ 536

Organization and Description _2

Organization and Description of Business (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 183,050	$ 98,845

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Narrative (Details)	Apr. 10, 2020USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)claimsegment	Sep. 30, 2019USD ($)	Apr. 16, 2020USD ($)	Dec. 31, 2019USD ($)
Accounting Policies [Abstract]
Number of operating segments | segment				1
Number of days contract with customer is generally paid				30 days
Variable consideration adjustments included in revenue		$ 1,450,000	$ 3,203,000	$ 223,000	$ 2,394,000
Amount received from CMS under its Accelerated and Advance Payment Program						$ 8,300,000
Number of claims in adjudication process | claim				2,698
Allowance for doubtful accounts		0		$ 0			$ 0
Automatic payment received, CARES Act	$ 1,900,000
Accrued bonuses		4,611,000		4,611,000			$ 4,785,000
Deferred payment		$ 378,000		$ 378,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Payor Concentration (Details) - Third-Party Payor Concentration Risk	9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Medicare | Percentage of Revenues
Concentration Risk [Line Items]
Concentration risk percentage	54.00%	47.00%
Medicare | Percentage of Accounts Receivable (current)
Concentration Risk [Line Items]
Concentration risk percentage	11.00%		7.00%
Medicare | Percentage of Accounts Receivable (non-current)
Concentration Risk [Line Items]
Concentration risk percentage	0.00%		0.00%
Medicare Advantage plans | Percentage of Revenues
Concentration Risk [Line Items]
Concentration risk percentage	28.00%	28.00%
Medicare Advantage plans | Percentage of Accounts Receivable (current)
Concentration Risk [Line Items]
Concentration risk percentage	41.00%		41.00%
Medicare Advantage plans | Percentage of Accounts Receivable (non-current)
Concentration Risk [Line Items]
Concentration risk percentage	18.00%		18.00%
United Healthcare | Percentage of Revenues
Concentration Risk [Line Items]
Concentration risk percentage	2.00%	7.00%
United Healthcare | Percentage of Accounts Receivable (current)
Concentration Risk [Line Items]
Concentration risk percentage	1.00%		9.00%
United Healthcare | Percentage of Accounts Receivable (non-current)
Concentration Risk [Line Items]
Concentration risk percentage	0.00%		0.00%
BlueCross BlueShield plans | Percentage of Revenues
Concentration Risk [Line Items]
Concentration risk percentage	8.00%	6.00%
BlueCross BlueShield plans | Percentage of Accounts Receivable (current)
Concentration Risk [Line Items]
Concentration risk percentage	27.00%		25.00%
BlueCross BlueShield plans | Percentage of Accounts Receivable (non-current)
Concentration Risk [Line Items]
Concentration risk percentage	47.00%		46.00%

(Loss) Earnings Per Share - Nar

(Loss) Earnings Per Share - Narrative (Details) - shares	Jul. 02, 2020	Jun. 29, 2020	Jul. 29, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jul. 12, 2019
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Number of shares issued in transaction (in shares)	300,000	2,000,000
Series F
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Number of shares issued upon net warrants exercised (in shares)			27,207
IPO
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Number of shares issued in transaction (in shares)			4,600,000
Common Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Number of shares issued in transaction (in shares)				300,000	4,600,000	2,300,000	4,600,000
Conversion of convertible preferred stock (in shares)			8,181,992		8,181,992		8,181,992
Conversion of convertible promissory notes (in shares)			1,661,106		1,661,106		1,661,106
Common Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Number of shares to be purchased by warrant (in shares)								209,243

(Loss) Earnings Per Share - Sch

(Loss) Earnings Per Share - Schedule of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net (loss) income attributable to common stockholders	$ (4,589)	$ 5,543	$ (5,395)	$ 936
Assumed conversion of convertible promissory notes
Subtract: Extinguishment gain	0	(5,213)	0	(5,213)
Add: Interest expense and change in fair value of embedded derivative	0	420	0	420
Numerator for diluted (loss) earnings per share	$ (4,589)	$ 750	$ (5,395)	$ (3,857)
Denominator:
Weighted-average common shares outstanding, basic (in shares)	19,936	12,758	18,290	5,649
Assumed conversion of convertible promissory notes (in shares)	0	290	0	98
Assumed exercise of common stock warrants (in shares)	0	67	0	0
Assumed exercise of stock options (in shares)	0	1,187	0	0
Weighted-average common shares outstanding, diluted (in shares)	19,936	14,302	18,290	5,747
(Loss) earnings per share attributable to common stockholders:
Basic (in dollars per share)	$ (0.23)	$ 0.43	$ (0.29)	$ 0.17
Diluted (in dollars per share)	$ (0.23)	$ 0.05	$ (0.29)	$ (0.67)

(Loss) Earnings Per Share - S_2

(Loss) Earnings Per Share - Schedule of Antidilutive Securities (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	2,903	2,799	2,871	8,215
Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	0	2,489	0	6,256
Convertible promissory note
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	0	131	0	44
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	2,767	139	2,732	1,778
Warrants | Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	35	0	35	30
Warrants | Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	0	40	0	107
Employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	101	0	104	0

Property and Equipment, Net - S

Property and Equipment, Net - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total	$ 8,144	$ 3,263
Less accumulated depreciation	(1,498)	(1,203)
Property and equipment, net	6,646	2,060
Lab equipment
Property, Plant and Equipment [Line Items]
Total	1,977	1,563
Computer equipment
Property, Plant and Equipment [Line Items]
Total	1,186	887
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total	1,392	635
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total	436	176
Construction in progress
Property, Plant and Equipment [Line Items]
Total	$ 3,153	$ 2

Property and Equipment, Net -_2

Property and Equipment, Net - Summary of Depreciation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Property, Plant and Equipment [Line Items]
Depreciation	$ 119	$ 91	$ 312	$ 254
Cost of sales
Property, Plant and Equipment [Line Items]
Depreciation	85	70	225	203
Research and development
Property, Plant and Equipment [Line Items]
Depreciation	8	2	13	5
Selling, general and administrative
Property, Plant and Equipment [Line Items]
Depreciation	$ 26	$ 19	$ 74	$ 46

Other Accrued Liabilities (Deta

Other Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Provider relief funds	$ 1,882	$ 0
Accrued service fees	1,201	1,162
Accrued interest	154	184
Employee stock purchase plan contributions	128	218
Accrued royalties	70	169
Accrued state income taxes	0	79
Other accrued liabilities	$ 3,435	$ 1,812

Convertible Promissory Notes -

Convertible Promissory Notes - Narrative (Details) - USD ($)	Jul. 29, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jul. 12, 2019	Feb. 28, 2019
Short-term Debt [Line Items]
Amortization of debt discounts and issuance costs				$ 666,000	$ 1,691,000
Gain on extinguishment of debt		$ 0	$ 5,213,000	0	5,213,000
Change in fair value of convertible promissory note accounted for under the fair value option			(2,077,000)	0	(2,077,000)
Common Stock
Short-term Debt [Line Items]
Number of shares to be purchased by warrant (in shares)						209,243
Exercise price (in dollars per share)						$ 0.001
Convertible Debt | Q1 2019 Convertible Promissory Notes
Short-term Debt [Line Items]
Debt instrument, face amount							$ 11,770,000
Debt instrument, interest rate, stated percentage							8.00%
Convertible debt, number of shares issued (in shares)	954,074
Amortization of debt discounts and issuance costs			$ 245,000		$ 1,216,000
Gain on extinguishment of debt		$ 5,213,000		$ 5,213,000
Convertible Debt | July 2019 Convertible Promissory Notes
Short-term Debt [Line Items]
Debt instrument, face amount						$ 10,000,000
Debt instrument, interest rate, stated percentage						8.00%
Convertible debt, number of shares issued (in shares)	707,032
Convertible Promissory Notes
Short-term Debt [Line Items]
Convertible promissory notes, related parties							$ 4,756,000

Convertible Promissory Notes _2

Convertible Promissory Notes - Gains (Losses) of Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Embedded Derivative [Line Items]
Loss recognized in net income		$ 0	$ (237)
Derivatives Not Classified as Hedging Instruments | Other expense, net
Embedded Derivative [Line Items]
Loss recognized in net income	$ (101)		$ (237)

Long-Term Debt - Schedule of Lo

Long-Term Debt - Schedule of Long-term Debt Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Less: Current portion of long-term debt	$ (10,000)	$ (5,833)
Total long-term debt, less current portion	12,455	19,289
2018 Loan And Security Agreement
Debt Instrument [Line Items]
Term debt	23,354	26,688
Unamortized discount and issuance costs	(899)	(1,566)
Total long-term debt	22,455	25,122
Less: Current portion of long-term debt	(10,000)	(5,833)
Total long-term debt, less current portion	$ 12,455	$ 19,289

Long-Term Debt - Narrative (Det

Long-Term Debt - Narrative (Details) - Notes Payable to Banks - 2018 Loan And Security Agreement	May 10, 2020	Sep. 30, 2020USD ($)installment	Dec. 31, 2019
Debt Instrument [Line Items]
Debt instrument, face amount		$ 25,000,000
Early termination fee		$ 497,000
Debt instrument, revenue target covenant, period	3 months	3 months
Debt instrument, covenant, minimum liquidity ratio	2
Debt instrument, actual liquidity ratio		7.76
Debt instrument, applicable interest rate		8.55%	8.55%
Number of equal monthly installments | installment		30
Debt instrument, monthly payment		$ 833,333
Final payment, percentage of principal		6.75%
Final payment		$ 1,687,500
After November 30, 2019 and on or prior to November 30, 2020
Debt Instrument [Line Items]
Prepayment fee percentage		1.50%
After November 30, 2020
Debt Instrument [Line Items]
Prepayment fee percentage		0.75%
London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate		6.48%
Minimum
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage		8.55%

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets and Liabilities at Fair Value (Details) - Fair Value, Recurring - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 182,616	$ 98,389
Quoted Prices in Active Markets for Identical Items (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	182,616	98,389
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0	0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 0	$ 0

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	Jul. 02, 2020	Jul. 02, 2020	Jun. 29, 2020
Class of Stock [Line Items]
Number of shares issued in transaction (in shares)		300,000	2,000,000
Follow-On Public Offering
Class of Stock [Line Items]
Number of shares issued in transaction (in shares)		300,000	2,000,000
Common stock offering price (in dollars per share)	$ 37	$ 37	$ 37
Proceeds from sale of stock	$ 79.5
Over-Allotment Option
Class of Stock [Line Items]
Common stock option period		30 days

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Common Stock Warrants Outstanding (Details) - $ / shares	Sep. 30, 2020	Dec. 31, 2019	Jul. 12, 2019
Common Stock
Class of Warrant or Right [Line Items]
Warrants Outstanding (in shares)	244,480	244,480
Exercise price of warrants (in dollars per share)			$ 0.001
July 12, 2026
Class of Warrant or Right [Line Items]
Warrants Outstanding (in shares)	209,243	209,243
Exercise price of warrants (in dollars per share)	$ 0.001	$ 0.001
March 31, 2027
Class of Warrant or Right [Line Items]
Warrants Outstanding (in shares)	26,428	26,428
Exercise price of warrants (in dollars per share)	$ 7.10	$ 7.10
November 30, 2028
Class of Warrant or Right [Line Items]
Warrants Outstanding (in shares)	8,809	8,809
Exercise price of warrants (in dollars per share)	$ 7.10	$ 7.10

Stock Incentive Plans and Sto_3

Stock Incentive Plans and Stock-Based Compensation - Activity Under Stock Incentive Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2020
Shares Available for Grant
Beginning balance (in shares)	863,127
Additional options authorized (in shares)	856,545
Granted (in shares)	(577,120)
Forfeited/Cancelled (in shares)	84,322
Ending balance (in shares)	1,226,874
Stock Options Outstanding
Beginning balance (in shares)	2,637,966
Granted (in shares)	577,120
Exercised (in shares)	(332,065)
Forfeited/Cancelled (in shares)	(84,322)
Ending balance (in shares)	2,798,699
Exercise Price
Beginning balance (in dollars per share)	$ 13.30
Granted (in dollars per share)	38.93
Exercised (in dollars per share)	2.08
Forfeited/Cancelled (in dollars per share)	27.02
Ending balance (in dollars per share)	$ 19.50
Stock Option Activity, Additional Disclosures
Options outstanding, weighted average remaining contractual term	8 years 6 months 25 days
Options outstanding, aggregate intrinsic value	$ 89,406
Options exercisable, number of options (in shares)	635,351
Options exercisable, weighted average exercise price (in dollars per share)	$ 4.11
Options exercisable, weighted average remaining contractual term	7 years 29 days
Options exercisable, aggregate intrinsic value	$ 30,076
Options outstanding, nonvested (in shares)	82,624
Options outstanding nonvested, weighted average exercise price (in dollars per share)	$ 2.39

Stock Incentive Plans and Sto_4

Stock Incentive Plans and Stock-Based Compensation - Narrative (Details) - USD ($)	Aug. 31, 2020	Feb. 28, 2020	Jan. 01, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in number of shares authorized for issuance (in shares)				856,545
Number of shares available for issuance (in shares)				1,226,874		863,127
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted, weighted average grant date fair value (in dollars per share)				$ 22.07	$ 3.77
Unrecognized compensation cost related to options				$ 25,118,000
Unrecognized compensation expense, period for recognition				2 years 10 months 24 days
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued during period (in shares)	41,467	39,987
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted, weighted average grant date fair value (in dollars per share)				$ 17.43	$ 0
Unrecognized compensation cost related to ESPP				$ 965,000
Employee stock purchase plan | Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in number of shares authorized for issuance (in shares)			171,309
Number of shares available for issuance (in shares)				501,790
Unrecognized compensation expense, period for recognition				1 year 2 months 12 days

Stock Incentive Plans and Sto_5

Stock Incentive Plans and Stock-Based Compensation - Assumptions Used in Fair Value of Stock Options and ESPP (Details)	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average expected term (years)	1 year 2 months 12 days
Expected stock price volatility, minimum	56.80%
Expected stock price volatility, maximum	100.49%
Risk-free interest rate, minimum	0.12%
Risk-free interest rate, maximum	0.95%
Dividend yield	0.00%
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average expected term (years)	6 years	6 years
Expected stock price volatility, minimum	59.15%	56.74%
Expected stock price volatility, maximum	63.82%	59.60%
Risk-free interest rate, minimum	0.28%	1.61%
Risk-free interest rate, maximum	1.76%	2.47%
Dividend yield	0.00%	0.00%

Stock Incentive Plans and Sto_6

Stock Incentive Plans and Stock-Based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 2,118	$ 229	$ 5,348	$ 536
Cost of sales
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	268	13	674	35
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	370	23	835	70
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 1,480	$ 193	$ 3,839	$ 431