Document and Entity Information Document - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Mar. 01, 2019	Jun. 29, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	OptiNose, Inc.
Entity Central Index Key	0001494650
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		41,264,422
Entity Public Float			$ 682.4
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 200,990	$ 234,854
Accounts receivable, net	2,310	0
Grants and other receivables	242	46
Inventory	7,132	2,013
Prepaid expenses and other current assets	2,183	1,254
Total current assets	212,857	238,167
Property and equipment, net	3,884	2,564
Other assets	248	405
Total assets	216,989	241,136
Current liabilities:
Accounts payable	7,116	5,893
Accrued expenses	18,421	8,698
Deferred other income	160	186
Total current liabilities	25,697	14,777
Long-term debt, net	72,500	71,863
Other liabilities	181	0
Total liabilities	98,378	86,640
Commitments and contingencies (Note 11)
Stockholders' equity:
Common stock, $0.001 par value; 200,000,000 December 31, 2018 and 2017; 41,227,530 and 37,802,556 shares issued and outstanding at December 31, 2018 and December 31, 2017, respectively	41	38
Additional paid-in capital	436,554	365,838
Accumulated deficit	(317,927)	(211,269)
Accumulated other comprehensive loss	(57)	(111)
Total stockholders' equity	118,611	154,496
Total liabilities and stockholders' equity	$ 216,989	$ 241,136

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common stock, par value (usd per share)	$ 0.001	$ 0.001
Shares authorized (in shares)	200,000,000	200,000,000
Shares issued (in shares)	41,227,530	41,227,530
Shares outstanding (in shares)	37,802,556	37,802,556

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Gross margin	$ 7,065	$ 0
Cost of product sales	1,588	0
Gross margin	5,477	0
Operating expenses:
Research and development	10,099	16,832
Selling, general and administrative	95,618	31,698
Total operating expenses	105,717	48,530
Loss from operations	(100,240)	(48,530)
Other (income) expense:
Grant and other income	(406)	(162)
Interest income	(2,453)	(303)
Interest expense	9,229	910
Foreign currency (gains) losses	48	(73)
Net loss	(106,658)	(48,902)
Deemed dividend	0	11,969
Accretion to redemption value	0	1,096
Net loss attributable to common stockholders	$ (106,658)	$ (61,967)
Net loss per share of common stock,
basic (in USD per share)	$ (2.68)	$ (5.63)
diluted (in USD per share)	$ (2.68)	$ (5.63)
Weighted average common shares outstanding,
basic (in shares)	39,765,983	10,999,121
diluted (in shares)	39,765,983	10,999,121

Consolidated Statements of Comprehensive Income and Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (106,658)	$ (48,902)
Other comprehensive (loss) income:
Foreign currency translation adjustment	54	(12)
Comprehensive loss	$ (106,604)	$ (48,914)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Consolidated Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 154,496	$ (151,197)
Conversion of convertible securities		237,259
Stock compensation expense	8,645	5,096
Exercise of common stock options	1,418	(154)
Issuance of common stock under employee stock purchase plan	739
Sale of common stock upon consummation of initial public offering, net of issuance costs	59,917	125,471
Foreign currency translation adjustment	54	(12)
Net loss	(106,658)	(48,902)
Ending balance	$ 118,611	$ 154,496
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding (in shares)	37,802,556	4,067,717
Beginning balance	$ 38	$ 4
Conversion of convertible securities (in shares)		25,068,556
Conversion of convertible securities		$ 25
Exercise of common stock options (in shares)	482,190	41,283
Exercise of warrants (in shares)	14,647
Issuance of common stock under employee stock purchase plan (in shares)	53,137
Sale of common stock upon consummation of initial public offering, net of issuance costs (in shares)	2,875,000	8,625,000
Sale of common stock upon consummation of initial public offering, net of issuance costs	$ 3	$ 9
Shares outstanding (in shares)	41,227,530	37,802,556
Ending balance	$ 41	$ 38
Additional Paid -in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	365,838	0
Conversion of convertible securities		237,234
Stock compensation expense	8,645	5,096
Exercise of common stock options	1,418	(154)
Issuance of common stock under employee stock purchase plan	739
Sale of common stock upon consummation of initial public offering, net of issuance costs	59,914	125,462
Ending balance	436,554	365,838
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(211,269)	(151,102)
Net loss	(106,658)	(48,902)
Ending balance	(317,927)	(211,269)
Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(111)	(99)
Foreign currency translation adjustment	54	(12)
Ending balance	$ (57)	$ (111)
Redeemable Convertible Preferred Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding (in shares)	0	6,875,514
Beginning balance	$ 0	$ 168,173
Conversion of convertible securities (in shares)		8,680,566
Conversion of convertible securities		$ (237,259)
Shares outstanding (in shares)		0
Ending balance		$ 0
Redeemable Convertible Preferred Stock, Series C2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of convertible securities (in shares)		687,474
Conversion of convertible securities		$ 19,527
Redeemable Convertible Preferred Stock, Series D
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Sale of Series D preferred stock, net of issuance costs (in shares)		1,117,578
Sale of Series D preferred stock, net of issuance costs		$ 36,494
Redeemable Convertible Preferred Stock, Series C, C1, D
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accretion of preferred stock	0	1,096
Accretion of preferred stock		(1,096)
Redeemable Convertible Preferred Stock, Series C, C1, D \| Additional Paid -in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accretion of preferred stock		(1,096)
Redeemable Convertible Preferred Stock, Series C, C1, C2, and D
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accretion of preferred stock	$ 0	11,969
Accretion of preferred stock		(11,969)
Redeemable Convertible Preferred Stock, Series C, C1, C2, and D \| Additional Paid -in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accretion of preferred stock		(704)
Redeemable Convertible Preferred Stock, Series C, C1, C2, and D \| Accumulated Deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accretion of preferred stock		$ (11,265)

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
Consolidated Statements of Cash Flows - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net loss	$ (106,658,000)	$ (48,902,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	539,000	166,000
Stock-based compensation	8,543,000	5,096,000
Amortization of debt discount and issuance costs	404,000	198,000
Changes in operating assets and liabilities:
Accounts receivable	(2,310,000)	0
Grants and other receivables	(196,000)	337,000
Prepaid expenses and other assets	(762,000)	2,358,000
Inventory	(4,698,000)	(2,013,000)
Accounts payable	3,171,000	392,000
Accrued expenses and other liabilities	10,150,000	6,688,000
Cash used in operating activities	(91,817,000)	(35,680,000)
Investing activities:
Purchases of property and equipment	(1,690,000)	(2,406,000)
Cash used in investing activities	(1,690,000)	(2,406,000)
Financing activities:
Proceeds from the sale of Series D preferred stock	0	36,712,000
Proceeds from the issuance of common stock	63,969,000	138,000,000
Proceeds from the issuance of common stock under employee stock purchase plan	739,000	0
Proceeds from long-term debt	0	75,000,000
Proceeds from the exercise of stock options	1,488,000	134,000
Payments of withholdings on shares withheld for income taxes	(70,000)	(288,000)
Cash paid for financing costs	(6,547,000)	(13,433,000)
Cash provided by financing activities	59,579,000	236,125,000
Effects of exchange rate changes on cash and cash equivalents	64,000	(11,000)
Net (decrease) increase in cash and cash equivalents	(33,864,000)	198,028,000
Cash and cash equivalents at beginning of period	234,875,000	36,847,000
Cash and cash equivalents at end of period	201,011,000	234,875,000
Supplemental disclosure of noncash financing activities:
Cash paid for interest	8,253,000	0
Supplemental disclosure of noncash financing activities:
Fixed asset purchases within accounts payable and accrued expenses	146,000	0
Fixed asset additions acquired through tenant allowance	361,000	0
Financing costs within accounts payable and accrued expenses	0	2,454,000
Conversion of convertible notes payable and accrued interest into Series C-2 preferred stock	0	237,259,000
Redeemable Convertible Preferred Stock, Series C, C1, C2, and D
Supplemental disclosure of noncash financing activities:
Deemed dividend	0	11,969,000
Redeemable Convertible Preferred Stock, Series C, C1, D
Supplemental disclosure of noncash financing activities:
Deemed dividend	0	1,096,000
Redeemable Convertible Preferred Stock, Series C2
Supplemental disclosure of noncash financing activities:
Conversion of convertible notes payable and accrued interest into Series C-2 preferred stock	$ 0	$ 19,527,000

Organization and Description of Business	12 Months Ended
Organization and Description of Business	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	Organization and Description of Business OptiNose, Inc. (the Company) was incorporated in Delaware in May 2010 (inception) and has facilities in Yardley, Pennsylvania, Ewing, New Jersey, Oslo, Norway and Swindon, England. The Company's predecessor entity, OptiNose AS, was formed under the laws of Norway in September 2000. In 2010, OptiNose AS became a wholly-owned subsidiary of the Company as part of an internal reorganization. The Company is a specialty pharmaceutical company focused on the development and commercialization of products for patients treated by ear, nose and throat (ENT) and allergy specialists. The Company's first commercial product, XHANCE^® (fluticasone propionate) nasal spray, 93 mcg, is a therapeutic utilizing its proprietary Optinose Exhalation Delivery System (EDS) that delivers a topically-acting corticosteroid for the treatment of chronic rhinosinusitis with nasal polyps and, if approved, chronic rhinosinusitis without nasal polyps (also known as chronic sinusitis). XHANCE was approved by the United States (US) Food and Drug Administration (FDA) in September 2017 for the treatment of nasal polyps in patients 18 years of age or older, and XHANCE was launched commercially in the US in March 2018.

Liquidity	12 Months Ended
Liquidity	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Liquidity	Liquidity Since inception, the Company's operations have focused on organization and staffing, business planning, raising capital, establishing an intellectual property portfolio, conducting preclinical studies and clinical trials, pursuing regulatory approvals and most recently, preparing for and launching XHANCE. As of December 31, 2018, the Company had cash and cash equivalents of $200,990. On June 11, 2018, the Company and certain stockholders closed an underwritten public offering (the Offering) of 5,750,000 shares of Company common stock (Common Stock) at a price of $22.25 per share. The Offering consisted of 2,875,000 shares of Common Stock sold by the Company and 2,875,000 shares of Common Stock sold by certain stockholders. As a result of the Offering, the Company received $59,917 in net proceeds, after deducting discounts and commissions of $3,678 and offering expenses of approximately $373 payable by the Company. The Company will likely require additional capital in the future through equity or debt financings, partnerships, collaborations, or other sources in order to meet the debt service obligations under the Company's outstanding senior secured notes (Senior Secured Notes), including repayment, and to carry out the Company's planned development and commercial activities. If additional capital is not secured when required, the Company may need to delay or curtail its operations until such funding is received. The Company is subject to a number of risks similar to other life sciences companies, including, but not limited to, successful discovery, development and commercialization of its products and product candidates, raising additional capital, the development by its competitors of new technological innovations, protection of proprietary technology and market acceptance of the Company's products.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Summary of Significant Accounting Policies

Basis of presentation

The accompanying consolidated financial statements have been prepared in conformity with US generally accepted accounting principles (GAAP). Any reference in these notes to applicable guidance is meant to refer to GAAP as found in the Accounting Standards Codification (ASC) and Accounting Standards Updates (ASU) of the Financial Accounting Standards Board (FASB).

Principles of consolidation

The consolidated financial statements include the accounts of OptiNose, Inc. and its wholly-owned subsidiaries, OptiNose US, Inc., OptiNose AS and OptiNose UK Ltd. All inter-company balances and transactions have been eliminated in consolidation.

Use of estimates

The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and reported amounts of expenses during the reporting period. Due to the uncertainty of factors surrounding the estimates or judgments used in the preparation of the consolidated financial statements, actual results may materially vary from these estimates. Estimates and assumptions are periodically reviewed and the effects of revisions are reflected in the consolidated financial statements in the period they are determined to be necessary.

Stock Split

On October 10, 2017, the Company effected a 2.8879-for-1 reclassification, or stock split, of the Company's common stock in connection with its initial public offering, or the IPO. All common share and per share amounts in these consolidated financial statements and notes thereto have been retroactively adjusted for all periods presented to reflect the stock split.

Concentration of credit risk

Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash and accounts receivable.The Company generally invests its cash in deposits with high credit quality financial institutions. Additionally, the Company performs periodic evaluations of the relative credit standing of these financial institutions.

The Company has exposure to credit risk in accounts receivable from sales of product. XHANCE is sold to wholesale pharmaceutical distributors and preferred pharmacy network partners, who, in turn, sell XHANCE to pharmacies, hospitals and other customers. Four customers represent approximately 90% of the Company's accounts receivable at December 31, 2018 and four customers represent approximately 94% of the Company's net product sales for the year ended December 31, 2018.

Cash and cash equivalents

All highly liquid investments purchased with an original maturity date of three months or less at the date of purchase are considered to be cash equivalents. The Company maintains its cash and cash equivalent balances at foreign and domestic financial institutions. Bank deposits with Norwegian banks are insured up to approximately 2,000 Norwegian krone by the Norwegian Banks' Guarantee Fund. Bank deposits with US banks are insured up to $250 by the Federal Deposits Insurance Corporation. The Company had uninsured cash balances of $199,507 and $233,772 at December 31, 2018 and 2017, respectively.

Fair value of financial instruments

The Company measures certain assets and liabilities at fair value, which is defined as the price that would be received to sell an asset or paid to transfer a liability (the exit price) in an orderly transaction between market participants at the measurement date. The FASB accounting guidance outlines a valuation framework and creates a fair value hierarchy in order to increase the consistency and comparability of fair value measurements and the related disclosures. In determining fair value, the Company uses quoted prices and observable inputs. Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from independent sources. The fair value hierarchy is broken down into three levels based on the source of the inputs as follows:


•	Level 1 — Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities.


•	Level 2 — Valuations based on observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data.


•	Level 3 — Valuations based on inputs that are unobservable and models that are significant to the overall fair value measurement.

At December 31, 2018 and 2017, the Company's financial instruments included cash and cash equivalents, accounts receivable, grants receivable, accounts payable, and accrued expenses. The carrying amounts reported in the Company's financial statements for these instruments approximates their respective fair values because of the short-term nature of these instruments. In addition, at December 31, 2018, the Company believes the carrying value of debt approximates fair value as the interest rates are reflective of the rate the Company could obtain on debt with similar terms and conditions. At December 31, 2018 and 2017, there were no financial assets or liabilities measured at fair value on a recurring basis.

Accounts receivable

Accounts receivable primarily relates to amounts due from customers, which are typically due within 31 to 61 days. The Company analyzes accounts that are past due for collectability. Given the nature and historical collectability of the Company’s accounts receivable, an allowance for doubtful accounts was not deemed necessary at December 31, 2018.

Inventory

Prior to receiving FDA approval for XHANCE in September 2017, inventory purchases were expensed as incurred and recorded as a component of research and development expense. Subsequent to receiving FDA approval, inventories are stated at the lower of cost or net realizable value. Costs of inventories, which include amounts related to materials and manufacturing overhead, are determined on a first-in, first-out basis. An assessment of the recoverability of capitalized inventory is performed during each reporting period and any excess and obsolete inventories are written down to their estimated net realizable value in the period in which the impairment is first identified.

Property and equipment

Property and equipment is recorded at cost less accumulated depreciation. Significant additions or improvements are capitalized, and expenditures for repairs and maintenance are charged to expense as incurred. Gains and losses on disposal of assets are included in the consolidated statements of operations. Depreciation is calculated on a straight-line basis over the estimated useful lives of the respective assets.

The estimated useful lives of property and equipment are as follows:



Computer equipment	2-3 years
Software	3 years
Machinery & production equipment	5-10 years
Furniture & fixtures	3-5 years
Leasehold improvements	Shorter of lease term or useful life

Long lived assets

Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future net cash flows expected to be generated. Impairment charges are recognized at the amount by which the carrying amount of an asset exceeds the fair value of the asset. Assets to be disposed of are reported at the lower of the carrying amount or the fair value less costs to sell. The Company did not recognize any impairment or disposition of long-lived assets for the years ended December 31, 2018 and 2017.

Revenue recognition

The Company accounts for revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers, which was adopted on January 1, 2018. This standard applies to all contracts with customers, with the exception of contracts that are within the scope of other standards, such as leases, insurance and financial instruments. Under ASC Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to be entitled in exchange for those goods or services.

The Company performs the following five steps to recognize revenue under ASC Topic 606: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only recognizes revenue when it is probable that it will collect the consideration to which it is entitled in exchange for the goods or services that will be transferred to the customer.

Net Product Revenues

The Company sells XHANCE to preferred pharmacy network partners and wholesalers in the US (collectively, Customers). These Customers subsequently resell the Company’s products to healthcare providers, patients and other retail pharmacies. In addition to agreements with Customers, the Company enters into arrangements with healthcare providers and payors that provide for government-mandated and/or privately-negotiated rebates, chargebacks and discounts for the purchase of the Company’s products.

The Company recognizes revenue from product sales at the point the Customer obtains control of the product, which generally occurs upon delivery. The transaction price that is recognized as revenue for products includes an estimate of variable consideration which is described below. Payment terms with Customers do not exceed one year and, therefore, the Company does not account for a financing component in its arrangements. The Company expenses incremental costs of obtaining a contract with a Customer (for example, sales commissions) when incurred as the period of benefit is less than one year. Shipping and handling costs for product shipments to Customers are recorded as selling, general and administrative expenses.

Transaction Price, including Estimates of Variable Consideration

Revenue from products is recognized at the estimated net sales price (transaction price), which includes estimates of variable consideration. The Company includes estimated amounts in the transaction price to the extent it is determined probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. The Company’s estimates of variable consideration and determination of whether to include estimated amounts in the transaction price are based largely on an assessment of its anticipated performance and all information (historical, current and forecasted) that is reasonably available.

Components of Variable Consideration

Components of variable consideration include provider chargebacks and discounts, trade discounts and allowances, product returns, government rebates, third-party payor rebates, sales order management fees and other incentives, such as voluntary patient assistance and other allowances that are offered within contracts between the Company and its Customers, payors and other indirect customers relating to the Company’s sale of products. Those components, as described below, are based on the amounts earned, or to be claimed, on the related sales and are presented as reductions of accounts receivable (if the amount is payable to the Customer) or as a current liability (if the amount is payable to a party other than the Customer). The Company considers all relevant factors such as current contractual and statutory requirements, specific known market events and trends, industry data and forecasted customer buying and payment patterns.


•	Variable Consideration - Accounts Receivable Reductions

◦

Provider Chargebacks and Discounts. Chargebacks for fees and discounts to providers represent the estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices charged to Customers who directly purchase the product from the Company. Customers charge the Company for the difference between what they pay for the product and the ultimate selling price to the qualified healthcare providers. These components of variable consideration are established in the same period that the related revenue is recognized, resulting in a reduction of product revenue and accounts receivable. Reserves for chargebacks consist of credits the Company expects to issue for units that remain in the distribution channel inventories at each reporting period-end that the Company expects will be sold to qualified healthcare providers, as well as chargebacks that Customers have claimed, but for which the Company has not yet issued a credit.

◦

Trade Discounts and Allowances. The Company generally provides Customers with discounts that include incentive fees which are explicitly stated in the Company’s contracts. These discounts are recorded as a reduction of revenue and accounts receivable in the period in which the related product revenue is recognized. In addition, the Company reimburses (through discounts and allowances) its Customers for sales order management, data and distribution services.


•	Variable Consideration - Current Liabilities

◦

Product Returns. Consistent with industry practice, the Company has a product returns policy that provides Customers a right of return for product purchased within a specified period prior to and subsequent to the product’s expiration date. The right of return lapses upon shipment of the goods to a patient. The Company estimates the amount of its products that may be returned and presents this amount as a reduction of revenue in the period the related product revenue is recognized, in addition to establishing a liability. The Company considers several factors in the estimation process, including expiration dates of product shipped to preferred pharmacy network partners and wholesalers, inventory levels within the distribution channel, product shelf life, prescription trends and other relevant factors.

◦

Government Rebates. The Company is subject to discount obligations under state Medicaid programs and Medicare. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability. For Medicaid, accruals are based on estimates of future Medicaid beneficiary utilization applied to the Medicaid unit rebate formula established by the Center for Medicaid and Medicare Services. The Medicare Part D prescription drug benefit mandates manufacturers to fund approximately 50% of the Medicare Part D insurance coverage gap for prescription drugs sold to eligible patients. To estimate the cost to the Company of this Medicare coverage gap responsibility, the Company estimates the number of patients in the prescription drug coverage gap for whom it will owe an additional liability under the Medicare Part D program. The Company’s liability for these rebates consists of estimates of claims for the current quarter and estimated future claims that will be made for product that has been recognized as revenue but remains in the distribution channel inventories at the end of the reporting period.

◦

Payor Rebates. The Company contracts with certain third-party payors, primarily health insurance companies and pharmacy benefit managers, for the payment of rebates with respect to utilization of its products. These rebates are based on contractual percentages applied to the amount of product prescribed to patients who are covered by the plan or the organization with which it contracts. The Company estimates these rebates and records such estimates in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability.

◦

Other Incentives. Other incentives that the Company offers include voluntary patient assistance programs, such as co-pay assistance programs, which are intended to provide financial assistance to qualified commercially insured patients with prescription drug co-payments required by payors and coupon programs for cash payors. The calculation of the accruals for this assistance is based on an estimate of claims and the cost per claim that the Company expects to receive associated with product that has been recognized as revenue but remains in the distribution channel inventories at the end of each reporting period.

Licensing Revenues

Through December 31, 2017, the Company's revenues had been generated pursuant to the terms of a single license agreement (the AVP-825 License Agreement) with Avanir Pharmaceuticals, Inc. (Avanir) (Note 7). The AVP-825 License Agreement included licensed rights to patented technology, non-refundable up-front payment, research services, and regulatory and sales milestones as well as royalty payments. Through December 31, 2018, under the terms of the AVP-825 License Agreement, the Company received aggregate cash payments of $70,000 in connection with the initial signing and the achievement of certain development milestones.

On December 10, 2018, the Company received written notice from Avanir of its election to terminate the AVP-825 License Agreement. As a result, the AVP-825 License Agreement is expected to terminate on March 10, 2019. We do not expect to receive any additional proceeds from the AVP-825 License Agreement.

Prior to the receipt of notice of termination of the License Agreement, the Company analyzed the performance obligations under the AVP-825 License Agreement, the consideration received to date and the consideration the Company could have received in the future as part of its analysis related to ASU 2014-09. The consideration received to date, which included an upfront payment, research and development funding and development milestone payments was recognized in prior years and the Company’s performance obligations pursuant to the arrangement have been completed.

Advertising expenses

The Company expenses the costs of advertising, including promotional expenses, as incurred. Advertising expenses were $9,767 and $1,833 for the years ended December 31, 2018 and 2017, respectively.

Research and development

Research and development costs are expensed as incurred. Research and development costs consist primarily of device development, clinical trial related costs and regulatory related costs. The Company enters into agreements with contract research organizations (CROs) to facilitate, coordinate and perform agreed upon research and development activities for the Company's clinical trials. These CRO contracts typically call for the payment of fees for services at the initiation of the contract and/or upon the achievement of certain clinical trial milestones. The Company prepays certain CRO fees whereby the prepayments are recorded as a current or non-current prepaid asset and are amortized into research and development expense over the period of time the contracted research and development services were performed. The Company's CRO contracts generally also included other fees such as project management and pass through fees whereby the Company expenses these costs as incurred, using the Company's best estimate. Pass through fees include, but are not limited to, regulatory expenses, investigator fees, travel costs, and other miscellaneous costs. Pass through fees incurred are based on the amount of work completed for the clinical trials and are monitored through reporting provided by the Company's CROs.

Stock-based compensation

The Company measures and recognizes compensation expense for all stock options awarded to employees and nonemployees and shares issued under the employee stock purchase plan based on the estimated fair value of the awards on the respective grant dates. The Company uses the Black-Scholes option pricing model to value its stock option awards and shares issued under the employee stock purchase plan. The Company recognizes compensation expense for time-based awards on a straight-line basis over the requisite service period, which is generally the vesting period of the award. The Company recognizes compensation expense for performance based awards when the performance condition is probable of achievement. Stock-based awards issued to nonemployees are revalued at each reporting period until the award vests. The Company accounts for forfeitures of stock option awards as they occur.

Estimating the fair value of options and shares issued under the employee stock purchase plan requires the input of subjective assumptions, including the estimated fair value of the Company's common stock, the expected life of the options, stock price volatility, the risk-free interest rate and expected dividends. The assumptions used in the Company's Black-Scholes option-pricing model represent management's best estimates and involve a number of variables, uncertainties and assumptions and the application of management's judgment, as they are inherently subjective.

Income taxes

Income taxes are accounted for under the asset and liability method. The Company recognizes deferred tax assets and liabilities for temporary differences between the financial reporting basis and the tax basis of the Company's assets and liabilities and the expected benefits of net operating loss carryforwards. The impact of changes in tax rates and laws on deferred taxes, if any, applied during the period in which temporary differences are expected to be settled, is reflected in the Company's financial statements in the period of enactment. The measurement of deferred tax assets is reduced, if necessary, if, based on weight of the evidence, it is more likely than not that some, or all, of the deferred tax assets will not be realized. As of December 31, 2018 and 2017, the Company has concluded that a full valuation allowance is necessary for all of its net deferred tax assets. The Company had no amounts recorded for uncertain tax positions, interest or penalties in the accompanying consolidated financial statements.

Grant income

Government grants are agreements that provide cost reimbursement for certain research and development activities over a contractually defined period. Income from government grants is recognized in the period in which related costs are incurred, provided that the conditions under which government grants were provided have been met and only perfunctory obligations are outstanding. Grant income received in excess of costs incurred is recognized as deferred other income.

Net income (loss) per common share

Basic net income (loss) per common share is determined by dividing net income (loss) applicable to common stockholders by the weighted average common shares outstanding during the period. For the years ended December 31, 2018 and 2017, the outstanding common stock options and common stock warrants have been excluded from the calculation of diluted net loss per share because their effect would be anti-dilutive. Therefore, the weighted average shares used to calculate both basic and diluted net loss per share are the same.

Diluted net loss per common share for the periods presented do not reflect the following potential common shares, as the effect would be antidilutive:



	Year Ended December 31,
	2018	2017
Stock options	6,182,873	2,141,367
Common stock warrants	1,866,831	1,890,489
Employee stock purchase plan	31,892	—
Total	8,081,596	4,031,856

Recent accounting pronouncements

In August 2018, the FASB issued ASU No. 2018-15, Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. ASU 2018-15 requires that certain implementation costs incurred in a cloud computing arrangement be deferred and recognized over the term of the arrangement. The new standard is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, and early adoption is permitted. The Company is currently evaluating the potential impact of the adoption of this standard on its results of operations, financial position and cash flows and related disclosures.

In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement. ASU 2018-13 resulted in certain modifications to fair value measurement disclosures, primarily related to level 3 fair value measurements. The new standard is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, and early adoption is permitted. The Company is currently evaluating the potential impact of the adoption of this standard on its disclosures.

In May 2017, the FASB issued ASU No. 2017-09, Stock Compensation - Scope of Modification Accounting. ASU 2017-09 provides guidance on which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The new standard is effective for fiscal years beginning after December 15, 2017. The adoption of ASU 2017-09 did not have a material impact on the Company’s results of operations, financial position, cash flows and related disclosures.

In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230). ASU No. 2016-18 requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. The new standard is effective for fiscal years beginning after December 15, 2017. The Company adopted ASU 2016-18 in the first quarter of 2018, and the guidance has been retrospectively applied to all periods presented. The restricted cash balance included in prepaid expenses and other assets was $21 as of December 31, 2018 and 2017.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). The FASB issued the update to require the recognition of lease assets and liabilities on the balance sheet of lessees. The standard will be effective for fiscal years beginning after December 15, 2018, with early adoption permitted. The ASU requires a modified retrospective transition method with the option to elect a package of practical expedients.

The following are other key disclosures, as well as determinations made and actions taken by the Company, related to the adoption of ASC 842:


•	Elected the optional modified retrospective transition method as of January 1, 2019; therefore prior period amounts will not be restated;


•	Established and implemented key implementation controls to ensure the Company meets the new reporting and disclosure requirements;


•	Elected the following transition practical expedients:


◦	to not reassess lease identification, lease classification and initial indirect costs related to those leases entered into prior to the adoption of ASC 842;


◦	to not separate lease and non-lease components for our office lease portfolio;


•	Made policy elections as of January 1, 2019:


◦	to not apply the recognition and measurement requirements to leases with an initial term of one year or less;


◦	to apply the portfolio approach for the development of the discount rate related to leases with similar characteristics;


◦	to keep leases with an immaterial right-of-use asset at inception, off the balance sheet and recognize this expense on a straight-line basis in the consolidated statements of operations;

While we continue to assess all the effects of adoption, the Company believes the most significant effect relates to the recognition of right-of-use assets and corresponding liabilities on its consolidated balance sheet, primarily related to its existing facility operating leases, and providing new disclosures with regards to the Company’s leasing activities.

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), or ASU-2014-09, which replaced numerous requirements in US GAAP, including industry-specific requirements. This guidance provides a five-step model to be applied to all contracts with customers, with an underlying principle that an entity will recognize revenue to depict the transfer of goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. The new standard also defines accounting for certain costs related to origination and fulfillment of contracts with customers, including whether such costs should be capitalized.

This statement requires extensive quantitative and qualitative disclosures covering the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including disclosures on significant judgments made when applying the guidance and assets recognized from costs incurred to obtain or fulfill a contract. The guidance was effective for annual reporting periods beginning after December 15, 2017, and interim periods within that reporting period. An entity could elect to apply the guidance under one of the following two methods: (i) retrospectively to each prior reporting period presented — referred to as the full retrospective method or (ii) retrospectively with the cumulative effect of initially applying the standard recognized at the date of initial application in retained earnings — referred to as the modified retrospective method.

The Company assessed the impact that ASU No. 2014-09 had on its financial statements and related disclosures. Through the January 1, 2018 adoption date, the Company has derived its revenues from a single licensing agreement with Avanir (the AVP-825 License Agreement). The consideration the Company has received to date includes an upfront payment, research and development funding and development milestone payments. The Company analyzed the performance obligations under the AVP-825 License Agreement as well as the consideration received to date as part of its analysis of the impact of ASU 2014-09 on this arrangement.

The Company adopted ASU 2014-09 on January 1, 2018 using the modified retrospective transition method. No transition adjustments were recognized as a result of the adoption. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods.

AVP-825 License Agreement	12 Months Ended
AVP-825 License Agreement	Dec. 31, 2018
Research and Development [Abstract]
AVP-825 License Agreement	AVP-825 License Agreement In July 2013, the Company's wholly owned subsidiary, OptiNose AS, entered into the AVP-825 License Agreement with Avanir for the exclusive right to sell AVP-825 (now marketed as Onzetra^® Xsail^®), a product combining a low-dose powder form of sumatriptan with the Company's EDS technology platform, for the acute treatment of migraines in adults and any follow-on products under development that consist of a formulation that contains triptans as the sole active ingredient. Through December 31, 2018, under the terms of the AVP-825 License Agreement, the Company received aggregate cash payments of $70,000 in connection with the initial signing and the achievement of certain development milestones. The Company did not recognize any licensing revenue during the years ended December 31, 2018 and 2017. On December 10, 2018, the Company received written notice from Avanir of its election to terminate the AVP-825 License Agreement. As a result, the AVP-825 License Agreement is expected to terminate on March 10, 2019. Upon termination, the Company may elect to continue to commercialize Onzetra Xsail itself or through a new licensee. We do not expect to receive any additional proceeds from the AVP-825 License Agreement.

Convertible Notes

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Convertible Notes

On September 30, 2015, the Company entered into a Senior Secured Convertible Note Purchase Agreement (Notes) with various existing stockholders. The Notes provided the Company with up to $30,000 in capital available in two separate tranches.The first tranche of $15,000 closed on September 30, 2015. The second tranche of up to $15,000 was available to the Company until March 30, 2017 but was never drawn. The Notes bore an annual interest rate of 17% and were scheduled to mature on September 30, 2020 if not otherwise converted to Series C-2 shares.

On March 24, 2017, in connection with the Series D Financing, the Notes and associated accrued interest and back end fees thereon totaling $19,527 converted into 687,474 shares of Series C-2 preferred stock at a per share conversion price of approximately $28.40.

The Company recorded interest expense of $862 during the year ended December 31, 2017 in conjunction with the Notes. Total coupon interest on the Notes and back end fees was $743 during the year ended December 31, 2017.

The front-end fees of $450 were recorded as debt discount at issuance and were amortized to interest expense over the 18 months loan conversion period. During the year ended December 31, 2017, the Company recorded a total of $75 of interest expense related to the front end fees. Additionally, back end fees of $450 were amortized to interest expense over the 18 months loan conversion period of which $90 was recorded as interest expense and as an increase in the carrying amount of the Notes during the year ended December 31, 2017. The Company also incurred $265 in debt issuance costs during the year ended December 31, 2015 which were amortized to interest expense over the 18 months loan conversion period.

As of December 31, 2018 and 2017, none of the Notes were outstanding.

Long-term Debt

On December 29, 2017, the Company entered into a Senior Secured Note Purchase Agreement (the Senior Secured Notes) with Athyrium Opportunities III Acquisition LP. The Senior Secured Notes provided the Company with up to $100,000 in capital, of which $75,000 was issued immediately. The remaining $25,000 (the Delayed Draw Notes) may be issued between April 1, 2019 and August 14, 2019, subject to the Company achieving trailing four quarter net revenues (as calculated pursuant to the terms of the Note Purchase Agreement) of $15,000 and a pro forma ratio of total debt to trailing four quarter net revenues not exceeding 6.50 to 1.00, and certain other conditions.

The Senior Secured Notes bear interest at 9.0% plus the three-month London Inter-bank Offered Rate (LIBOR) rate, subject to a 1.0% floor and are scheduled to mature on June 29, 2023. The interest rate was 11.8125% at December 31, 2018. The Senior Secured Notes bore front-end fees of 1% of the aggregate principal amount, which were paid at issuance. The Company is also required to pay an exit fee of 2% of any principal payments (whether mandatory, voluntary, or at maturity) made throughout the term of the Note Purchase Agreement.

The Company is required to make quarterly, interest only payments until the maturity date. The Company may make voluntary prepayments of the Senior Secured Notes, in whole or in part, and subject to certain exceptions, is required to make mandatory prepayments upon the occurrence of certain events as defined in the agreement, including, the occurrence of a change of control.

All mandatory and voluntary prepayments of the Senior Secured Notes are subject to the payment of prepayment premiums as follows: (i) if prepayment occurs prior to the second anniversary of the applicable date of issuance, an amount equal to the amount by which (a) the present value of 102% of the principal prepaid plus all interest that would have accrued on such principal through such second anniversary exceeds (b) the amount of principal prepaid, (ii) if prepayment occurs on or after the second anniversary of the applicable date of issuance but prior to the third anniversary of such issuance, an amount equal to 2% of the principal prepaid, and (iii) if prepayment occurs on or after the third anniversary of the applicable date of issuance but prior to the fourth anniversary of such issuance, an amount equal to 1% of the principal prepaid. No prepayment premium is due on any principal prepaid after the fourth anniversary of the applicable date of issuance of any Senior Secured Notes.

The Senior Secured Notes are secured by a pledge of substantially all of the Company’s assets and contains affirmative and negative covenants customary for financings of this type, including limitations on the Company’s and its subsidiaries’ ability to, among other things, incur additional debt, grant or permit additional liens, make investments and acquisitions, merge or consolidate with others, dispose of assets, grant certain license rights related to the Company's products, technology and other intellectual property rights, pay dividends and distributions, repay junior indebtedness and enter into affiliate transactions, in each case, subject to certain exceptions. In addition, the Senior Secured Notes contains financial covenants requiring the Company to maintain (i) at least $10,000 of cash and cash equivalents and (ii) following the issuance of the Delayed Draw Notes or upon entering into certain exclusive licenses of XHANCE, a total debt to trailing four quarter net revenue ratio of less than 6.50 to 1.00 initially, and thereafter declining quarterly by equal half-steps to a ratio of less than 3.00 to 1.00. As of December 31, 2018, the Company was in compliance with the covenants.

The Company recorded interest expense of $9,229 and $48 during the years ended December 31, 2018 and 2017, respectively, in conjunction with the Senior Secured Notes. Interest expense included total coupon interest, back end fees, front end fees and the amortization of debt issuance costs. The front-end fees of $1,000 were recorded as debt discount at issuance and are being amortized to interest expense over the 5.5 year term of the loan. Additionally, back end fees of $2,000 are being amortized to interest expense and are recorded as an increase in the carrying amount throughout the term of the Senior Secured Notes. The Company also incurred $2,181 in debt issuance costs during the year ended December 31, 2017 which are also being amortized to interest expense over the term of the Senior Secured Notes.

As of December 31, 2018 and 2017, the long-term debt balance is comprised of the following:



	December 31,
	2018			2017
Face amount	$	75,000		$	75,000
Front end fees	(872		)	(999		)
Debt issuance costs	(1,902		)	(2,139		)
Back end fees	274			1
	$	72,500		$	71,863

Long-Term Debt

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Long-Term Debt

Convertible Notes

As of December 31, 2018 and 2017, none of the Notes were outstanding.

Long-term Debt

As of December 31, 2018 and 2017, the long-term debt balance is comprised of the following:



	December 31,
	2018			2017
Face amount	$	75,000		$	75,000
Front end fees	(872		)	(999		)
Debt issuance costs	(1,902		)	(2,139		)
Back end fees	274			1
	$	72,500		$	71,863

Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Leases

The Company leases office space under four operating leases and has leases for certain other equipment. Rent expense is recognized as incurred.

The following is a schedule of future minimum annual payments as of December 31, 2018 under operating lease agreements:



For the years ending December 31:
2019	1,630
2020	1,107
2021	391
Total future minimum lease payments as of December 31, 2018	$	3,128

Rent expense related to leases of office space was $831 and $689 for the years ended December 31, 2018 and 2017, respectively.

In January 2018, the Company amended its existing office lease agreement for the Company’s headquarters in Yardley, PA (the Lease Amendment). Under the terms of the Lease Amendment, the Company’s leased office space was increased from approximately 20,050 square feet to approximately 30,000 square feet, and the term of the lease was extended from March 31, 2018 to May 31, 2021 (the Extended Term), with an option to renew the lease for an additional three-year term. The Company’s rent payments during the Extended Term will be approximately $2,750 in the aggregate, and the Company will also be required to pay its proportionate share of certain operating costs and property taxes applicable to the leased premises.

Purchase commitments

In November 2017, the Company entered into an agreement with a contract sales organization for the recruitment, deployment and management of a contract sales force to market XHANCE in the US. Subject to certain limited exceptions, the Company could not terminate this agreement until after the first anniversary of the deployment of the sales force (which occurred in March 2018). In December 2018, as a result of the Company's decision to manage its sales force directly, the Company terminated the agreement effective April 1, 2019 and accrued an early termination fee of $691. The Company estimates the expenses related to the remaining non-cancellable services, all of which will be provided in 2019, to be approximately $2,335.

As of December 31, 2018, the Company had no other material outstanding non-cancellable purchase commitments related to inventory and other goods and services, including pre-commercial manufacturing scale-up and sales and marketing activities.

Employment agreements

The Company has entered into employment contracts with its officers and certain employees that provide for severance and continuation of benefits in the event of termination of employment by the Company without cause or by the employee for good reason. In addition, in the event of termination of employment following a change in control, the vesting of certain equity awards may be accelerated.

Litigation

Liabilities for loss contingencies arising from claims, assessments, litigation, fines, penalties, and other sources are recorded when it is probable that a liability has been incurred and the amount can be reasonably estimated. There are no matters currently outstanding.

Stockholders' equity	12 Months Ended
Stockholders' equity	Dec. 31, 2018
Equity [Abstract]
Stockholders' equity	Stockholders' equity Common stock In October 2017, the Company increased the number of authorized common shares from 10,624,486 to 200,000,000 and completed an initial public offering (IPO) of its common stock, selling 8,625,000 shares at $16.00 per share. As a result of the IPO, the Company received $125,471 in net proceeds, after deducting discounts and commissions of $9,660 and offering expenses of approximately $2,869 payable by the Company. On June 11, 2018, the Company and certain stockholders closed the Offering of 5,750,000 shares of Common Stock at a price of $22.25 per share. The Offering consisted of 2,875,000 shares of Common Stock sold by the Company and 2,875,000 shares of Common Stock sold by certain stockholders. As a result of the Offering, the Company received $59,917 in net proceeds, after deducting discounts and commissions of $3,678 and offering expenses of approximately $373 payable by the Company. Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Subject to preferences that may apply to any outstanding preferred stock, holders of common stock are entitled to receive ratably any dividends that the Company’s board of directors may declare out of funds legally available for that purpose on a non-cumulative basis. No dividends had been declared through December 31, 2018. Common stock warrants As of December 31, 2018, the Company had 1,866,831 warrants outstanding to purchase shares of the Company's common stock with an exercise price of $8.16. The warrants expire on November 1, 2020. Redeemable convertible preferred stock During the year ended December 31, 2017, the Company sold 1,117,578 shares of Series D Preferred Stock at a per share purchase price of $32.85, resulting in gross proceeds to the Company of $36,712 (the Series D Financing). In connection with the Series D Financing, the Company's existing convertible notes and associated accrued interest and back end fees thereon totaling $19,527 converted into 687,474 shares of Series C-2 Preferred Stock at a per share conversion price of approximately $28.40 (Note 8). Upon consummation of the IPO in October 2017, all of the outstanding shares of the Company's redeemable convertible preferred stock were converted into an aggregate of 25,068,556 shares of common stock. In connection with the IPO, 5,000,000 shares of preferred stock, with a par value of $0.001 per share, were authorized for issuance. As of December 31, 2018 and 2017, no preferred stock was issued or outstanding.

Stock-based Compensation

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-based Compensation

Stock-based compensation

The Company issues stock-based awards pursuant to its 2010 Stock Incentive Plan. Effective as of October 12, 2017, the Company's 2010 Stock Incentive Plan was amended and restated (A&R Plan). The A&R Plan provides for the grant of incentive stock options, non-statutory stock options, restricted stock awards, restricted stock units, deferred stock units, performance shares, stock appreciation rights and other equity-based awards. The Company's employees, officers, directors and other persons are eligible to receive awards under the A&R Plan. As of December 31, 2018, 8,406,547 shares of the Company's common stock were authorized to be issued under the A&R Plan, and 1,635,295 shares were reserved for future awards under the A&R Plan. The number of shares of the Company's common stock authorized under the A&R Plan will automatically increase on January 1st of each year, commencing on January 1, 2018 and continuing until the expiration of the A&R Plan, in an amount equal to four percent of the total number of shares of the Company's common stock outstanding on December 31^st of the preceding calendar year, subject to the discretion of the Company's board of directors or compensation committee to determine a lesser number of shares shall be added for such year.

The amount, terms of grants, and exercisability provisions are determined and set by the Company's board of directors or compensation committee. The Company measures employee stock-based awards at grant-date fair value and records compensation expense on a straight-line basis over the vesting period of the award. Stock-based awards issued to non-employees are revalued until the award vests.

Stock options

The Company has issued service-based and performance-based stock options that generally have a contractual life of up to 10 years and may be exercisable in cash or as otherwise determined by the board of directors. Vesting generally occurs over a period of not greater than four years. Performance-based options may vest upon the achievement of certain milestones in connection with the Company's development programs. Additionally, the Company has issued stock options in excess of the fair market value of Common Stock on the issuance date that were only exercisable upon a change in control or upon or after an initial public offering. As of December 31, 2018, all of the performance conditions related to performance-based stock options issued by the Company have been achieved.

The following table summarizes the activity related to stock option grants to employees and nonemployees for the years ended December 31, 2018:



	Shares		Weighted average exercise price per share		Weighted average remaining contractual life
Outstanding at December 31, 2017	6,251,589		$	9.34	6.67
Granted	472,792		19.36
Exercised	(491,654	)	3.21
Expired	—		—
Forfeited	(49,854	)	9.67
Outstanding at December 31, 2018	6,182,873		$	10.60	6.48
Exercisable at December 31, 2018	3,804,999		$	8.15	5.09
Vested and expected to vest at December 31, 2018	6,182,873		$	10.60	6.48

During the year ended December 31, 2018, stock options to purchase 472,792 shares of common stock were granted to employees that generally vest over four years. The options had an estimated weighted average grant date fair value of $12.85. The grant date fair value of each option grant was estimated at the time of grant using the Black-Scholes option-pricing model.

The total aggregate intrinsic value of stock options exercised during the years ended December 31, 2018 and 2017 was $9,255 and $435, respectively. The aggregate intrinsic value of stock options outstanding and stock options exercisable as of December 31, 2018 was $8,470 and $8,028, respectively. At December 31, 2018, the unrecognized compensation cost related to unvested stock options expected to vest was $20,405. This unrecognized compensation will be recognized over an estimated weighted-average amortization period of 2.7 years.

2017 Employee Stock Purchase Plan

The Company's 2017 Employee Stock Purchase Plan (the 2017 Plan) became effective on October 12, 2017. As of December 31, 2018, 522,420 shares of the Company's common stock were authorized to be issued pursuant to purchase rights granted to its employees or to employees of any of its participating affiliates under the 2017 Plan. 469,283 shares of the Company's common stock were reserved for future issuance under the 2017 Plan. The number of shares of the Company's common stock that may be issued pursuant to rights granted under the 2017 Plan shall automatically increase on January 1st of each year, commencing on January 1, 2018 and continuing until the expiration of the 2017 Plan, in an amount equal to one percent of the total number of shares of the Company's common stock outstanding on December 31st of the preceding calendar year, subject to the discretion of the board of directors or compensation committee to determine a lesser number of shares shall be added for such year.

Under the 2017 Plan, eligible employees can purchase the Company’s common stock through accumulated payroll deductions at such times as are established by the administrator. The 2017 Plan is administered by the compensation committee. Under the 2017 Plan, eligible employees may purchase the Company’s common stock at 85% of the lesser of the average high and low sales price of the Company's common stock on (i) the first trading day of the relevant offering period and (ii) on the last trading day of the relevant offering period (or, if the relevant offering period has multiple purchase periods, the last trading day of the relevant purchase period). Eligible employees may contribute up to 15% of their eligible compensation. Under the 2017 Plan, a participant may not accrue rights to purchase more than $25 worth of the Company’s common stock for each calendar year in which such right is outstanding.

Effective October 12, 2017, employees who elected to participate in the 2017 Plan commenced payroll withholdings that accumulated through June 30, 2018.

Beginning on January 1, 2018, employees who elected to participate in the 2017 Plan commenced payroll withholdings that accumulate during the following six month offering periods each calendar year while the Purchase Plan is effective:


•	January 1 through June 30, and


•	July 1 through December 31.

At the end of each offering period, shares of the Company’s common stock may be purchased at 85% of the lesser of the average of the high and low sales price of the Company’s common stock on (i) the first trading day of the relevant offering period and (ii) the last trading day of the relevant offering period (or, if the relevant offering period has multiple purchase periods, the last trading day of the relevant purchase period). In accordance with the guidance in ASC 718-50 – Compensation – Stock Compensation, the ability to purchase shares of the Company’s common stock at the lower of the price on the first day of the offering period or the last day of the offering period (i.e. the purchase date) represents an option and, therefore, the 2017 Plan is a compensatory plan under this guidance. Accordingly, stock-based compensation expense is determined based on the option’s grant-date fair value as estimated by applying the Black Scholes option-pricing model and is recognized over the requisite service period of the option. The Company has recognized stock-based compensation expense of $446 and $106 during the years ended December 31, 2018 and 2017, respectively, related to the 2017 Plan.

Stock-based compensation expense

The Company recorded stock-based compensation expense in the following expense categories of its accompanying consolidated statements of operations for the years ended December 31, 2018 and 2017:



	Year Ended December 31,
	2018		2017
Cost of product sales	$	9	$	—
Research and development	$	989	1,288
Selling, general and administrative	7,545		3,808
Total stock-based compensation expense	$	8,543	$	5,096

In addition, stock-based compensation expense of $99 and $2 is included within inventory and prepaid expenses and other assets, respectively, as of December 31, 2018, which represents the total stock-based compensation expense incurred related to employees involved in the manufacturing process of finished goods and samples during the period.

The Company utilized the Black-Scholes valuation model for estimating the fair value of stock options granted and the option component of the 2017 Plan. The Company calculated the fair value of each option grant and the option component of the 2017 Plan on the respective dates of grant using the following weighted average assumptions:



	2010 A&R Stock Incentive Plan		2017 Employee Stock Purchase Plan
	December 31,		December 31,
	2018		2018
Risk free interest rate	2.74	%	1.53	%
Expected term (in years)	5.95		0.64
Expected volatility	74.42	%	80.40	%
Annual dividend yield	0.00	%	0.00	%

Option valuation methods, including Black-Scholes, require the input of subjective assumptions, which are discussed below.

•

The expected term of employee options is determined using the "simplified" method, as prescribed in SEC's Staff Accounting Bulletin (SAB) No. 107, whereby the expected life equals the arithmetic average of the vesting term and the original contractual term of the option due to the Company's lack of sufficient historical data. The expected term of nonemployee options is equal to the contractual term.


•	The expected volatility is based on historical volatilities of similar entities within the Company's industry which were commensurate with the expected term assumption as described in SAB No. 107.


•	The risk-free interest rate is based on the interest rate payable on US Treasury securities in effect at the time of grant for a period that is commensurate with the assumed expected term.


•	The expected dividend yield is 0% because the Company has not historically paid, and does not expect for the foreseeable future to pay, a dividend on its common stock.

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

Income taxes

The Tax Cuts and Jobs Act (TCJA) was enacted on December 22, 2017 with most changes effective January 1, 2018. Among other changes, the TCJA significantly lowered the US corporate income tax rate from 35% to 21% as of January 1, 2018. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to reverse. As a result of the reduction in the US corporate income tax rate, the Company revalued its net deferred tax assets at December 31, 2017. Due to the full valuation allowance on the Company's deferred tax assets, no tax expense or benefit associated with the re-measurement was recognized in the Company's consolidated statement of operations for the year ended December 31, 2017. The change in the US corporate tax rate is also included in the Company’s deferred tax table.

The TCJA provided for a one-time transition tax on the deemed repatriation of post-1986 undistributed foreign subsidiary earnings and profits (E&P). As the Company's foreign subsidiaries did not have accumulated E&P, the Company did not record any income tax expense related to the transition tax.

Due to the timing of and the substantial changes made by the TCJA, the Staff of the Securities and Exchange Commission (SEC) issued Staff Accounting Bulletin No. 118 (SAB 118), which provides registrants a measurement period to report the impact of the new US tax law. During the measurement period, provisional amounts for the effects of the law are recorded to the extent a reasonable estimate can be made. To the extent that all information necessary is not available, prepared or analyzed, companies may recognize provisional estimated amounts for a period of up to one year following enactment of the TCJA. Accordingly, the Company recorded a preliminary estimate of the impact of the TCJA and the re-measurement of its deferred tax assets and liabilities in 2017. The Company finalized its analysis of the impact of the TCJA and recorded the adjustment, which was not material, in 2018.

Income taxes have been recorded on the following book income (loss) before income tax expense:



	Year Ended December 31,
	2018			2017
Domestic operations	$	(146,247	)	$	(30,463	)
Foreign operations	39,589			(18,439		)
Loss before provision for income taxes	$	(106,658	)	$	(48,902	)

A reconciliation of income tax expense (benefit) at the US federal statutory income tax rate and the income tax provision in the financial statements is as follows:



	Year Ended December 31,
	2018		2017
Income tax expense at statutory rate	21.0	%	35.0	%
Permanent items	0.5		0.5
Foreign rate differential	(0.8	)	(4.2	)
Impact of foreign operations	(7.2	)	—
State taxes, net of federal benefit	3.9		0.8
Tax rate changes	(0.6	)	(15.4	)
Foreign exchange and other	(0.6	)	—
Change in valuation allowance	(16.2	)	(16.7	)
Effective income tax rate	0.0	%	0.0	%

Tax rate changes includes the impact of the reduction in the US tax rate in 2017 under the TCJA and a reduction in the Norway tax rate in both 2017 and 2018.

The principal components of the Company’s deferred tax assets and liabilities are as follows:



	Year Ended December 31,
	2018			2017
Deferred tax assets:
Accrued expenses and other	$	1,674		$	972
Prepaid licensing arrangement	11,562			—
Property and equipment	—			55
Interest expense	1,267			783
Stock compensation	3,493			1,701
Research and development credits	2,485			2,485
Net operating losses	32,548			29,636
Total deferred tax assets	53,029			35,632
Deferred tax liabilities:
Fixed assets	(409		)	—
Total deferred tax liabilities:	(409		)	—
Less: Valuation allowance	(52,620		)	(35,632		)
Total net deferred tax assets (liabilities)	$	—		$	—

During 2018, our wholly-owned subsidiary in Norway licensed certain intellectual property rights related to XHANCE to our US subsidiary. While this transaction did not result in any gain or loss in the condensed consolidated statements of operations, the transaction generated taxable income in both Norway and the US. Norway tax loss carryforwards were utilized to offset the taxable income in Norway and the income reduced the current year US taxable loss. There were no cash taxes associated with the transaction.

The TCJA, in addition to the changes indicated above, contained other provisions that may have a future impact on the Company. The provisions include limitations on the deductibility of interest based on the amount of adjusted taxable income, the deferral of research and development deductions, the acceleration of deductions related to fixed asset additions, changes to the utilization of net operating loss carry forwards and changes in the carry forward period, and global intangible low-taxed income provisions that subject foreign subsidiary income that exceeds an allowable return to current US taxation.

As of December 31, 2018, the Company had foreign net operating loss (NOL) carry forwards of $50,513 primarily from its operations in Norway. As of December 31, 2018, the Company had federal and state NOLs of $86,574 and $57,017, respectively. These domestic NOL carry forwards may be subject to an annual limitation in the event of cumulative changes in the ownership interests of significant stockholders over a three‑year period in excess of 50%. This could limit the amount of NOLs that the Company can utilize annually to offset future domestic taxable income, if any. The amount of the annual limitation, if any, will be determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. The federal NOL generated in 2018 has an indefinite carry forward period. The federal NOLs generated prior to 2018 will expire from 2030 through 2037. Some state NOLs will not expire while other state NOLs expire over various periods depending on the rules of the jurisdiction in which they were generated. The earliest state NOL expiration is in 2028.

ASC 740 requires the establishment of a valuation allowance to reduce deferred tax assets if, based on the weight of the available positive and negative evidence it is more likely than not that all or a portion of the deferred tax assets will not be realized. There is insufficient positive evidence to overcome the negative evidence attributable to the Company’s cumulative operating losses. Consequently, the Company established a full valuation allowance against its net deferred tax assets at December 31, 2018 and 2017, respectively, because the Company’s management was unable to conclude that it is more likely than not that these assets will be fully realized. The Company had a net increase in its valuation allowance of $16,988 during the year ended December 31, 2018.

The Company files income tax returns in Norway, the UK, the US, and various states. The Company is subject to examination by federal, state and foreign jurisdictions. The Company’s tax years in the US are open under statute from inception to present. All open years may be examined to the extent that tax credits or net operating loss carryforwards are used in future periods.

The Company’s policy is to record interest and penalties related to uncertain tax positions in income tax expense. As of December 31, 2018, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company’s statement of operations.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Basis of presentation

Principles of consolidation

Use of estimates

Concentration of credit risk

Cash and cash equivalents

Fair value of financial instruments


•	Level 1 — Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities.


•	Level 2 — Valuations based on observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data.


•	Level 3 — Valuations based on inputs that are unobservable and models that are significant to the overall fair value measurement.

Accounts receivable

Inventory

Property and equipment

Long lived assets

Revenue recognition

Net Product Revenues

Transaction Price, including Estimates of Variable Consideration

Components of Variable Consideration


•	Variable Consideration - Accounts Receivable Reductions

◦


•	Variable Consideration - Current Liabilities

◦

Licensing Revenues

Advertising expenses

The Company expenses the costs of advertising, including promotional expenses, as incurred.

Research and development expense

Research and development

Stock-based compensation

Income taxes

Net income (loss) per common share

Recent accounting pronouncements

The following are other key disclosures, as well as determinations made and actions taken by the Company, related to the adoption of ASC 842:


•	Elected the optional modified retrospective transition method as of January 1, 2019; therefore prior period amounts will not be restated;


•	Established and implemented key implementation controls to ensure the Company meets the new reporting and disclosure requirements;


•	Elected the following transition practical expedients:


◦	to not reassess lease identification, lease classification and initial indirect costs related to those leases entered into prior to the adoption of ASC 842;


◦	to not separate lease and non-lease components for our office lease portfolio;


•	Made policy elections as of January 1, 2019:


◦	to not apply the recognition and measurement requirements to leases with an initial term of one year or less;


◦	to apply the portfolio approach for the development of the discount rate related to leases with similar characteristics;


◦	to keep leases with an immaterial right-of-use asset at inception, off the balance sheet and recognize this expense on a straight-line basis in the consolidated statements of operations;

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Property and equipment

The estimated useful lives of property and equipment are as follows:



Computer equipment	2-3 years
Software	3 years
Machinery & production equipment	5-10 years
Furniture & fixtures	3-5 years
Leasehold improvements	Shorter of lease term or useful life

Property and equipment, net, consisted of:



	December 31,
	2018			2017
Computer equipment and software	$	833		$	307
Furniture and fixtures	389			89
Machinery and equipment	2,723			2,495
Leasehold improvements	609			28
Construction in process	481			—
	5,035			2,919
Less: accumulated depreciation	(1,151		)	(355		)
	$	3,884		$	2,564

Schedule of antidilutive shares excluded from earnings per share

Diluted net loss per common share for the periods presented do not reflect the following potential common shares, as the effect would be antidilutive:



	Year Ended December 31,
	2018	2017
Stock options	6,182,873	2,141,367
Common stock warrants	1,866,831	1,890,489
Employee stock purchase plan	31,892	—
Total	8,081,596	4,031,856

Long-Term Debt (Tables)

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments

As of December 31, 2018 and 2017, the long-term debt balance is comprised of the following:



	December 31,
	2018			2017
Face amount	$	75,000		$	75,000
Front end fees	(872		)	(999		)
Debt issuance costs	(1,902		)	(2,139		)
Back end fees	274			1
	$	72,500		$	71,863

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21538-112644

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Lessee, Operating Lease

The following is a schedule of future minimum annual payments as of December 31, 2018 under operating lease agreements:



For the years ending December 31:
2019	1,630
2020	1,107
2021	391
Total future minimum lease payments as of December 31, 2018	$	3,128

Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of stock option activity



	Shares		Weighted average exercise price per share		Weighted average remaining contractual life
Outstanding at December 31, 2017	6,251,589		$	9.34	6.67
Granted	472,792		19.36
Exercised	(491,654	)	3.21
Expired	—		—
Forfeited	(49,854	)	9.67
Outstanding at December 31, 2018	6,182,873		$	10.60	6.48
Exercisable at December 31, 2018	3,804,999		$	8.15	5.09
Vested and expected to vest at December 31, 2018	6,182,873		$	10.60	6.48

Schedule of allocated stock-based compensation expense

The Company recorded stock-based compensation expense in the following expense categories of its accompanying consolidated statements of operations for the years ended December 31, 2018 and 2017:



	Year Ended December 31,
	2018		2017
Cost of product sales	$	9	$	—
Research and development	$	989	1,288
Selling, general and administrative	7,545		3,808
Total stock-based compensation expense	$	8,543	$	5,096

Schedule of fair value options using Black-Scholes pricing model

The Company calculated the fair value of each option grant and the option component of the 2017 Plan on the respective dates of grant using the following weighted average assumptions:



	2010 A&R Stock Incentive Plan		2017 Employee Stock Purchase Plan
	December 31,		December 31,
	2018		2018
Risk free interest rate	2.74	%	1.53	%
Expected term (in years)	5.95		0.64
Expected volatility	74.42	%	80.40	%
Annual dividend yield	0.00	%	0.00	%

The Company calculated the fair value of each option grant and the option component of the 2017 Plan on the respective dates of grant using the following weighted average assumptions:



	2010 A&R Stock Incentive Plan		2017 Employee Stock Purchase Plan
	December 31,		December 31,
	2018		2018
Risk free interest rate	2.74	%	1.53	%
Expected term (in years)	5.95		0.64
Expected volatility	74.42	%	80.40	%
Annual dividend yield	0.00	%	0.00	%

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Schedule of Income before Income Tax, Domestic and Foreign

Income taxes have been recorded on the following book income (loss) before income tax expense:



	Year Ended December 31,
	2018			2017
Domestic operations	$	(146,247	)	$	(30,463	)
Foreign operations	39,589			(18,439		)
Loss before provision for income taxes	$	(106,658	)	$	(48,902	)

Schedule of Effective Income Tax Rate Reconciliation

A reconciliation of income tax expense (benefit) at the US federal statutory income tax rate and the income tax provision in the financial statements is as follows:



	Year Ended December 31,
	2018		2017
Income tax expense at statutory rate	21.0	%	35.0	%
Permanent items	0.5		0.5
Foreign rate differential	(0.8	)	(4.2	)
Impact of foreign operations	(7.2	)	—
State taxes, net of federal benefit	3.9		0.8
Tax rate changes	(0.6	)	(15.4	)
Foreign exchange and other	(0.6	)	—
Change in valuation allowance	(16.2	)	(16.7	)
Effective income tax rate	0.0	%	0.0	%

Schedule of Deferred Tax Assets and Liabilities

The principal components of the Company’s deferred tax assets and liabilities are as follows:



	Year Ended December 31,
	2018			2017
Deferred tax assets:
Accrued expenses and other	$	1,674		$	972
Prepaid licensing arrangement	11,562			—
Property and equipment	—			55
Interest expense	1,267			783
Stock compensation	3,493			1,701
Research and development credits	2,485			2,485
Net operating losses	32,548			29,636
Total deferred tax assets	53,029			35,632
Deferred tax liabilities:
Fixed assets	(409		)	—
Total deferred tax liabilities:	(409		)	—
Less: Valuation allowance	(52,620		)	(35,632		)
Total net deferred tax assets (liabilities)	$	—		$	—

Liquidity (Details) - USD ($) $ / shares in Units, $ in Thousands	Jun. 11, 2018	Dec. 31, 2018	Dec. 31, 2017
Subsidiary, Sale of Stock [Line Items]
Cash and cash equivalents		$ 200,990	$ 234,854
Public Offering
Subsidiary, Sale of Stock [Line Items]
Number of shares issued (in shares)	5,750,000
Price per share (usd per share)	$ 22.25
Consideration received on transaction	$ 59,917
Fees and commissions	3,678
Deferred offering costs	$ 373
The Company \| Public Offering
Subsidiary, Sale of Stock [Line Items]
Number of shares issued (in shares)	2,875,000
Certain Stockholders \| Public Offering
Subsidiary, Sale of Stock [Line Items]
Number of shares issued (in shares)	2,875,000

Summary of Significant Accounting Policies (Details)		12 Months Ended
Summary of Significant Accounting Policies (Details)	Oct. 10, 2017	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Stock split conversion ratio	2.8879
Cash, uninsured amount		$ 199,507,000	$ 233,772,000
Loss on sale of equipment		0	0
Advertising expense		9,767,000	1,833,000
Restricted cash		21,000	21,000
Disaggregation of Revenue [Line Items]
Revenues		7,065,000	$ 0
License
Disaggregation of Revenue [Line Items]
Revenues		$ 70,000

Summary of Significant Accounting Policies - Concentration Risk (Details)	12 Months Ended
	Dec. 31, 2018 customers
Accounts Receivable
Concentration Risk [Line Items]
Concentration risk	90.00%
Concentration risk, number of clients	4
Sales Revenue, Net
Concentration Risk [Line Items]
Concentration risk	94.00%
Concentration risk, number of clients	4

Summary of Significant Accounting Policies - Property and equipment (Details)	12 Months Ended
	Dec. 31, 2018
Computer equipment \| Minimum
Property, Plant and Equipment [Line Items]
Useful life	2 years
Computer equipment \| Maximum
Property, Plant and Equipment [Line Items]
Useful life	3 years
Software
Property, Plant and Equipment [Line Items]
Useful life	3 years
Machinery and equipment \| Minimum
Property, Plant and Equipment [Line Items]
Useful life	5 years
Machinery and equipment \| Maximum
Property, Plant and Equipment [Line Items]
Useful life	10 years
Furniture and fixtures \| Minimum
Property, Plant and Equipment [Line Items]
Useful life	3 years
Furniture and fixtures \| Maximum
Property, Plant and Equipment [Line Items]
Useful life	5 years

Summary of Significant Accounting Policies - Antidilutive shares excluded from earnings per share (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securites excluded from computation of earnings per share	8,081,596	4,031,856
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securites excluded from computation of earnings per share	6,182,873	2,141,367
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securites excluded from computation of earnings per share	1,866,831	1,890,489
Employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securites excluded from computation of earnings per share	31,892	0

Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 1,969	$ 1,385
Work-in-process	2,344	628
Finished goods	2,819	0
Total inventory	$ 7,132	$ 2,013

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 5,035	$ 2,919
Less: accumulated depreciation	(1,151)	(355)
Property and equipment, net	3,884	2,564
Depreciation	535	164
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	833	307
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	389	89
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,723	2,495
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	609	28
Construction in process
Property, Plant and Equipment [Line Items]
Property and equipment, gross	481	$ 0
Inventories
Property, Plant and Equipment [Line Items]
Depreciation	322
Prepaid Expenses and Other Current Assets
Property, Plant and Equipment [Line Items]
Depreciation	$ 10

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Contract sales organization expenses	$ 4,482	$ 1,432
Research and development expenses	4,812	2,031
Selling, general and administrative expenses	933	80
Bonus expense	3,635	4,163
Payroll and benefit expenses	564	448
Employee contributions withheld	359	185
Product revenue allowances	2,856	0
Interest expense	345	45
Other	435	314
Accrued expenses	$ 18,421	$ 8,698

AVP-825 License Agreement (Details) - License Agreement Terms - USD ($)	12 Months Ended		66 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Aggregate cash payments received from license agreement			$ 70,000,000
Licensing revenues	$ 0	$ 0

Convertible Notes - Narrative (Details)			12 Months Ended
Convertible Notes - Narrative (Details)	Mar. 24, 2017 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) tranche	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($)	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Interest expense, back end fees				$ 2,000,000
Convertible debt			$ 0	0
Convertible Debt
Debt Instrument [Line Items]
Face amount		$ 30,000,000
Number of tranches \| tranche		2
Stated interest rate		17.00%
Interest expense, debt				862,000
Coupon interest and back end fees				743,000
Loan conversion period		18 months
Interest expense, front end fees				75,000
Back end fees				$ 90,000
Debt issuance costs		$ 450,000			$ 265,000
Convertible Debt \| Tranche One
Debt Instrument [Line Items]
Face amount		15,000,000
Convertible Debt \| Tranche Two
Debt Instrument [Line Items]
Face amount		$ 15,000,000
Series D Financing \| Convertible Debt
Debt Instrument [Line Items]
Debt conversion, original debt amount	$ 19,527,000
Conversion of Convertible notes into Series C2 Preferred Stock
Debt Instrument [Line Items]
Debt conversion, original debt amount			$ 19,527,000
Redeemable Convertible Preferred Stock, Series C2 \| Conversion of Convertible notes into Series C2 Preferred Stock
Debt Instrument [Line Items]
Debt conversion shares issued (in shares) \| shares	687,474		687,474
Debt conversion, price per share (usd per share) \| $ / shares	$ 28.40		$ 28.40

Long-Term Debt - Narrative (Details)		4 Months Ended	12 Months Ended
Long-Term Debt - Narrative (Details)	Dec. 29, 2017 USD ($) quarter	Aug. 14, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Debt amortization period				5 years 6 months
Interest expense, back end fees				$ 2,000,000
Debt issuance costs				2,181,000
Senior Notes
Debt Instrument [Line Items]
Amortization of debt discount				1,000,000
Senior Notes \| Note Purchase Agreement
Debt Instrument [Line Items]
Unused borrowing capacity	$ 100,000,000
Face amount	$ 75,000,000
Stated interest rate	9.00%		11.8125%
Upfront fee	1.00%
Exit fee	2.00%
Covenant, cash and cash equivalents	$ 10,000,000
Interest expense, debt			$ 9,229,000	48,000
Unamortized debt issuance costs			$ 1,902,000	$ 2,139,000
Senior Notes \| Note Purchase Agreement \| Prior to Second Anniversary
Debt Instrument [Line Items]
Redemption price rate	102.00%
Senior Notes \| Note Purchase Agreement \| On Or After Second Anniversary
Debt Instrument [Line Items]
Prepayment fee	2.00%
Senior Notes \| Note Purchase Agreement \| On Or After Third Anniversary
Debt Instrument [Line Items]
Prepayment fee	1.00%
Senior Notes \| Note Purchase Agreement \| After Fourth Anniversary
Debt Instrument [Line Items]
Prepayment fee	0.00%
Senior Notes \| Note Purchase Agreement \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate floor	1.00%
Senior Notes \| Note Purchase Agreement - Delayed Draw Notes
Debt Instrument [Line Items]
Unused borrowing capacity	$ 25,000,000
Number of trailing quarters \| quarter	4
Total debt to trailing quarter net sales ratio	6.50
Senior Notes \| Note Purchase Agreement - Delayed Draw Notes \| Minimum
Debt Instrument [Line Items]
Total debt to trailing quarter net sales ratio	3.00
Scenario, Forecast \| Senior Notes \| Note Purchase Agreement - Delayed Draw Notes
Debt Instrument [Line Items]
Revenue, net		$ 15,000,000
Total debt to trailing quarter net sales ratio		6.50

Long-Term Debt - Schedule of Long Term Debt (Details) - Senior Notes - Note Purchase Agreement - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Face amount	$ 75,000	$ 75,000
Front end fees	(872)	(999)
Debt issuance costs	(1,902)	(2,139)
Back end fees	274	1
Long-term Debt	$ 72,500	$ 71,863

Employee Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
Employee Benefit Plans (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Defined Contribution Plan Disclosure [Line Items]
Maximum annual contributions per employee	100.00%
Defined contribution plan, cost	$ 645	$ 230
Foreign Plan
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, cost	$ 81	$ 56
Defined Contribution Plan, Tranche One
Defined Contribution Plan Disclosure [Line Items]
Maximum annual contributions per employee	3.00%
Employer matching contribution	100.00%
Defined Contribution Plan, Tranche Two
Defined Contribution Plan Disclosure [Line Items]
Maximum annual contributions per employee	2.00%
Employer matching contribution	50.00%

Commitments and Contingencies (Leases) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) ft² lease	Dec. 31, 2017 USD ($)	Jan. 31, 2018 ft²
Commitments and Contingencies Disclosure [Abstract]
Number of operating leases \| lease	4
Rent expense	$ 831	$ 689
Area of real estate property \| ft²	20,050		30,000
Renewal term	3 years
Future rent expense	$ 2,750

Commitments and Contingencies (Future Minimum Lease Payments) (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Future minimum annual payments, 2019	$ 1,630
Future minimum annual payments, 2020	1,107
Future minimum annual payments, 2021	391
Total future minimum lease payments as of December 31, 2018	$ 3,128

Commitments and Contingencies (Purchase Commitments) (Details) - USD ($)	Dec. 31, 2018	Nov. 30, 2017
Other Commitments [Line Items]
Purchase obligation	$ 0
Market Salesforce
Other Commitments [Line Items]
Contractual obligation		$ 2,335,000
Maximum \| Market Salesforce
Other Commitments [Line Items]
Early contract termination fees		$ 691,000

Stockholders' equity - Common Stock (Details) $ / shares in Units, $ in Thousands		1 Months Ended	12 Months Ended
	Jun. 11, 2018 USD ($) $ / shares shares	Oct. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2018 vote $ / shares shares	Dec. 31, 2017 shares	Sep. 30, 2017 shares
Class of Stock [Line Items]
Shares authorized (in shares) \| shares			200,000,000	200,000,000
Vote per share \| vote			1
Dividends declared (usd per share) \| $ / shares			$ 0
IPO
Class of Stock [Line Items]
Price per share (usd per share) \| $ / shares		$ 16.00
Net proceeds from IPO		$ 125,471
Fees and commissions		9,660
Stock issuance costs		$ 2,869
IPO \| Common Stock
Class of Stock [Line Items]
Shares authorized (in shares) \| shares		200,000,000			10,624,486
Number of shares issued (in shares) \| shares		8,625,000
Public Offering
Class of Stock [Line Items]
Number of shares issued (in shares) \| shares	5,750,000
Price per share (usd per share) \| $ / shares	$ 22.25
Fees and commissions	$ 3,678
Consideration received on transaction	59,917
Sale of stock discounts	3,678
Deferred offering costs	$ 373
The Company \| Public Offering
Class of Stock [Line Items]
Number of shares issued (in shares) \| shares	2,875,000
Certain Stockholders \| Public Offering
Class of Stock [Line Items]
Number of shares issued (in shares) \| shares	2,875,000

Stockholders' equity (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	12 Months Ended
	Mar. 24, 2017	Oct. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Temporary Equity [Line Items]
Proceeds from the sale of Series D preferred stock			$ 0	$ 36,712
Preferred stock, shares authorized (in shares)		5,000,000
Preferred stock, par value (in dollars per share)		$ 0.001
Preferred stock, shares issued (in shares)			0
Preferred stock, shares outstanding (in shares)				0
Redeemable Convertible Preferred Stock, Series D
Temporary Equity [Line Items]
Sale of Series D preferred stock, net of issuance costs (in shares)			1,117,578
Price per share (usd per share)			$ 32.85
Proceeds from the sale of Series D preferred stock			$ 36,712
Conversion at Consummation of IPO \| Common Stock
Temporary Equity [Line Items]
Shares issued, conversion of stock (in shares)		25,068,556
Conversion of Convertible notes into Series C2 Preferred Stock
Temporary Equity [Line Items]
Debt conversion, original debt amount			$ 19,527
Conversion of Convertible notes into Series C2 Preferred Stock \| Redeemable Convertible Preferred Stock, Series C2
Temporary Equity [Line Items]
Debt conversion shares issued (in shares)	687,474		687,474
Debt conversion, price per share (usd per share)	$ 28.40		$ 28.40
IPO
Temporary Equity [Line Items]
Price per share (usd per share)		$ 16.00
IPO \| Common Stock
Temporary Equity [Line Items]
Sale of Series D preferred stock, net of issuance costs (in shares)		8,625,000

Stock-based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Service Based Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Granted (in shares)	472,792
Fair value of common stock (in dollars per share)	$ 12.85
Intrinsic value of exercised options	$ 9,255	$ 435
Intrinsic value of options outstanding	8,470
Intrinsic value of exercisable options	8,028
Unrecognized compensation cost	$ 20,405
Unrecognized compensation, estimated weighted-average amortization period	2 years 8 months 11 days
Amended and Restated Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized under plan (shares)	8,406,547
Number of shares reserved for future issuance under plan (shares)	1,635,295
Yearly increase in shares reserved for future issuance	4.00%
Plan options contractual life	10 years
Award vesting period	4 years

Stock-based Compensation - Service-based stock options (Details) - Service Based Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Service-based stock options activity
Shares outstanding, beginning (in shares)	6,251,589
Granted (in shares)	472,792
Exercised (in shares)	(491,654)
Expired (in shares)	0
Forfeited (in shares)	(49,854)
Shares outstanding, ending (in shares)	6,182,873	6,251,589
Exercisable at end of period (in shares)	3,804,999
Vested and expected to vest at end of period(in shares)	6,182,873
Service-based stock options weighted average exercise price
Beginning balance, Weighted average exercise price (in dollars per share)	$ 9.34
Granted, Weighted average exercise price (in dollars per share)	19.36
Exercised, Weighted average exercise price (in dollars per share)	3.21
Expired, Weighted average exercise price (in dollars per share)	0.00
Forfeited, Weighted average exercise price (in dollars per share)	9.67
Ending balance, Weighted average exercise price (in dollars per share)	10.60	$ 9.34
Options exercisable, Weighted average exercise price per share (in dollars per share)	8.15
Vested and expected to vest, Weighted average exercise price per share (in dollars per share)	$ 10.60
Service-based stock options, additional disclosures
Options outstanding, Weighted average remaining contractual life	6 years 5 months 22 days	6 years 8 months 1 day
Options exercisable, Weighted average remaining contractual life	5 years 1 month 1 day
Vested and expected to vest, Weighted average remaining contractual life	6 years 5 months 22 days

Stock-based Compensation - Employee stock purchase plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 8,543	$ 5,096
2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized under plan (shares)	522,420
Increase in number of shares issuable each year	1.00%
Stock-based compensation expense	$ 446	$ 106

Stock-based Compensation - Stock-based compensation expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 8,543	$ 5,096
Cost of product sales
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	9	0
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	989	1,288
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	7,545	$ 3,808
Inventories
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	99
Prepaid Expenses and Other Current Assets
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 2

Stock-based Compensation - Black-Scholes pricing model options (Details)	12 Months Ended
	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual dividend yield	0.00%
2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate	1.53%
Expected term (in years)	7 months 19 days
Expected volatility	80.40%
Annual dividend yield	0.00%
2010 A & R Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate	2.74%
Expected term (in years)	5 years 345 days
Expected volatility	74.42%
Annual dividend yield	0.00%

Income Taxes - Schedule of Income before Income Tax, Domestic and Foreign (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Domestic operations	$ (146,247)	$ (30,463)
Foreign operations	39,589	(18,439)
Loss before provision for income taxes	$ (106,658)	$ (48,902)

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income tax expense at statutory rate	21.00%	35.00%
Permanent items	0.50%	0.50%
Foreign rate differential	(0.80%)	(4.20%)
Impact of foreign operations	(7.20%)	0.00%
State taxes, net of federal benefit	3.90%	0.80%
Tax rate changes	(0.60%)	(15.40%)
Foreign exchange and other	0.00%	(0.60%)
Change in valuation allowance	(16.20%)	(16.70%)
Effective income tax rate	0.00%	0.00%

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Accrued expenses and other	$ 1,674	$ 972
Prepaid licensing arrangement	11,562	0
Property and equipment	0	55
Interest expense	1,267	783
Stock compensation	3,493	1,701
Research and development credits	2,485	2,485
Net operating losses	32,548	29,636
Total deferred tax assets	53,029	35,632
Deferred tax liabilities:
Fixed assets	(409)	0
Total deferred tax liabilities:	(409)	0
Less: Valuation allowance	(52,620)	(35,632)
Total net deferred tax assets (liabilities)	$ 0	$ 0

Income Taxes - Narrative (Details)	12 Months Ended
Income Taxes - Narrative (Details)	Dec. 31, 2018 USD ($)
Operating Loss Carryforwards [Line Items]
Valuation allowance increase (decrease)	$ 16,988,000
Unrecognized tax benefits, income tax penalties and interest accrued	0
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	50,513,000
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	86,574,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 57,017,000

Employee Benefit Plans	12 Months Ended
Employee Benefit Plans	Dec. 31, 2018
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans For US employees, the Company maintains a defined contribution 401(k) retirement plan, which covers all employees. Employees are eligible to participate in the plan on the first of the month following their date of hire. Under the 401(k) retirement plan, participating employees may defer up to 100% of their pre-tax salary, but not more than statutory limits. In October 2017, the Company adopted a 401(k) matching program for its US employees. The Company matches 100% of the first 3% of participating employee contributions and 50% of the next 2% of participating employee contributions, subject to applicable IRC limits. The Company incurred costs of $645 and $230 related to the Company match applicable to employee contributions for the years ended December 31, 2018 and 2017. The Company's contributions are made in cash. The Company's common stock is not currently an investment option available to participants in the 401(k) retirement plan. For Norway and UK employees, the Company maintains defined contribution pension plans which meet statutory requirements of those jurisdictions. The Company incurred costs of $81 and $56 related to the pension plans for the years ended December 31, 2018 and 2017, respectively.

Related-party transactions	12 Months Ended
Related-party transactions	Dec. 31, 2018
Related Party Transactions [Abstract]
Related-party transactions	Related-party transactions Debt and equity transactions All of the Company's convertible debt (see Note 8) was issued to holders of the Company's convertible preferred stock. During the year ended December 31, 2018 and 2017, the Company reimbursed Avista Capital Holdings, LP and related parties $51 and $157, respectively in expenses, primarily related to legal fees incurred in conjunction with the Company's Offering of Common Stock in June 2018, the IPO in October 2017 and the issuance of Series D redeemable convertible preferred stock March 2017.

Subsequent events	12 Months Ended
Subsequent events	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent events	Subsequent events On January 31, 2019, OptiNose AS, a wholly owned subsidiary of the Company, entered into a license agreement (the Inexia License Agreement) with Inexia Limited (Inexia). Under the terms of the Inexia License Agreement, Inexia paid the Company a $500 upfront payment. For each product developed under the Inexia License Agreement, the Company is eligible to receive up to $8,000 of development milestone payments and up to $37,000 of sales milestone payments. In addition, the Company is eligible to receive tiered, low-to-mid single digit royalties based on net sales of any products successfully developed and commercialized under the Inexia License Agreement. Other than the upfront payment, the Company does not anticipate the receipt of any milestone or royalty payments from Inexia in the near term.

Stockholders' equity - Warrants (Details)	Dec. 31, 2018 $ / shares shares
Equity [Abstract]
Number of warrants outstanding (in shares) \| shares	1,866,831
Common stock warrant exercise price (in dollars per share) \| $ / shares	$ 8.16

Related-party transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Investor \| Fees For IPO And Series D Convertible Stock
Related Party Transaction [Line Items]
Amount of transaction	$ 51	$ 157

Consolidated Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' (Parenthetical)	12 Months Ended
	Dec. 31, 2018
Redeemable Convertible Preferred Stock, Series C, C1, C2, and D
Dividend rate	8.00%

Subsequent events (Details) - Subsequent Event $ in Thousands	Jan. 31, 2019 USD ($)
Subsequent Event [Line Items]
Upfront license fee receivable	$ 500
Development milestone eligibility	8,000
Sales milestone eligibility	$ 37,000