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DEI Document - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
DEI Document - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2019	Feb. 29, 2020	Jun. 30, 2019
Document and Entity Information [Abstract]
Entity Registrant Name	XERIS PHARMACEUTICALS INC
Entity Central Index Key	0001346302
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Well-known Seasoned Issuer	No
Entity Filer Category	Accelerated Filer
Entity Voluntary Filers	No
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Trading Symbol	XERS
Title of 12(b) Security	Common stock, $0.0001 par value per share
Entity Interactive Data Current	Yes
Entity Common Stock, Shares Outstanding		37,570,080
Entity Listing, Par Value Per Share	$ 0.0001
Entity Public Float			$ 227.2

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current Assets
Cash and cash equivalents	$ 19,519	$ 45,716
Short-term Investments	56,030	66,917
Trade accounts receivable, net	4,693	0
Other accounts receivable, net	946	2,869
Inventory	2,176	0
Prepaid expenses and other current assets	4,119	2,397
Total current assets	87,483	117,899
Investments	13,231	0
Property and equipment, net	7,853	2,034
Other assets	420	95
Total assets	108,987	120,028
Current Liabilities
Accounts payable	5,603	866
Other accrued liabilities	18,119	8,214
Accrued trade discounts and rebates	1,375	0
Accrued returns reserve	1,957	0
Other current liabilities	284	1,092
Total current liabilities	27,338	10,172
Long-term debt, net of unamortized deferred costs	58,305	31,890
Other liabilities	8,908	2,560
Total liabilities	94,551	44,622
Commitments and contingencies (Note 10)
Stockholders' Equity
Preferred stock, par value $0.0001	0	0
Common stock, par value $0.0001	3	2
Additional paid in capital	260,635	196,121
Accumulated deficit	(246,245)	(120,665)
Accumulated other comprehensive gain (loss)	43	(52)
Total stockholders' equity	14,436	75,406
Total liabilities and stockholders' equity	$ 108,987	$ 120,028

Consolidated Balance Sheets Parenthetical - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position Parenthetical [Abstract]
Preferred Stock, Par Value Per Share	$ 0.0001	$ 0.0001
Common Shares, Par Value Per Share	$ 0.0001	$ 0.0001
Preferred Stock, Shares Authorized	10,000,000	10,000,000
Common Stock, Shares Authorized	150,000,000	150,000,000
Preferred Stock, Shares Issued	0	0
Common Shares, Shares, Issued	27,214,523	20,808,366

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Net sales	$ 1,627	$ 0
Grant and other income	1,095	2,423
Cost of goods sold	1,603	0
Gross Profit	1,119	2,423
Operating expenses
Research and development	60,438	40,654
Selling, general and administrative	63,061	21,113
Total operating expenses	123,499	61,767
Loss from operations	(122,380)	(59,344)
Other income (expense)
Interest and other income	2,813	1,613
Interest expense	(7,163)	(2,545)
Change in fair value of warrants	692	196
Other income (expense)	(3,658)	(736)
Net loss before benefit from income taxes	(126,038)	(60,080)
Benefit from income taxes	458	0
Net loss	(125,580)	(60,080)
Other comprehensive gain (loss), net of tax
Unrealized gains (losses) on investments	93	(52)
Foreign currency translation adjustments	2	0
Comprehensive gain (loss)	$ (125,485)	$ (60,132)
Net loss per common share - basic and diluted	$ (4.81)	$ (4.99)
Weighted average common shares outstanding - basic and diluted	26,110,297	12,045,999

Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Preferred Stock, Series A	Preferred Stock, Series B	Preferred Stock, Series C	Common Stock	Additional Paid-in Capital [Member]
Preferred Stock, Shares Outstanding		1,843,965	5,696,834	12,834,912
Preferred Stock, Value, Outstanding		$ 1,945	$ 18,536	$ 77,397
Common Stock, Shares, Outstanding					2,159,068
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock, par value $0.0001					$ 1
Additional paid in capital						$ 2,754
Accumulated other comprehensive gain (loss)	$ 0
Accumulated deficit	(60,585)
Stockholders' Equity Attributable to Parent	(57,830)
Net loss	(60,080)
Stock Issued During Period, Shares, New Issues				707,680	6,555,000
Stock Issued During Period, Value, New Issues				$ 4,414	$ 0	88,903
Conversion of convertible preferred stock into common stock, shares		(1,843,965)	(5,696,834)	(13,542,592)	11,837,073
Conversion of convertible preferred stock into common stock, value	102,293	$ (1,945)	$ (18,536)	$ (81,811)	$ 1	102,292
Exercise and vesting of stock-based awards					248,978
Adjustments to Additional Paid in Capital, Exercise and Vesting of Stock-Based Awards	$ 395					395
Warrants, exercises in period	8,247
Warrants, exercises in period, value	$ 49					49
Stock-based compensation	1,728					1,728
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ (52)
Preferred Stock, Shares Outstanding		0	0	0
Preferred Stock, Value, Outstanding		$ 0	$ 0	$ 0
Common Stock, Shares, Outstanding					20,808,366
Preferred Stock, Shares Issued	0
Common stock, par value $0.0001	$ 2				$ 2
Additional paid in capital	196,121					196,121
Accumulated other comprehensive gain (loss)	(52)
Accumulated deficit	(120,665)
Stockholders' Equity Attributable to Parent	75,406
Net loss	(125,580)
Stock Issued During Period, Shares, New Issues					6,201,202
Stock Issued During Period, Value, New Issues	$ 57,227				$ 1	57,226
Exercise and vesting of stock-based awards	(128,307)				128,307
Adjustments to Additional Paid in Capital, Exercise and Vesting of Stock-Based Awards	$ 254					254
Stock Issued During Period, Shares, Employee Stock Purchase Plans	73,607
Stock Issued During Period, Value, Employee Stock Purchase Plan	$ 532					532
Warrants, exercises in period					3,041
Warrants, exercises in period, value	18					18
Stock-based compensation	6,484					6,484
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 95
Preferred Stock, Shares Outstanding		0	0	0
Preferred Stock, Value, Outstanding		$ 0	$ 0	$ 0
Common Stock, Shares, Outstanding					27,214,523
Preferred Stock, Shares Issued	0
Common stock, par value $0.0001	$ 3				$ 3
Additional paid in capital	260,635					$ 260,635
Accumulated other comprehensive gain (loss)	43
Accumulated deficit	(246,245)
Stockholders' Equity Attributable to Parent	$ 14,436

Statement of Cash Flows - USD ($)	12 Months Ended
Statement of Cash Flows - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Net loss	$ (125,580,000)	$ (60,080,000)
Income (Loss) Attributable to Parent, before Tax	(126,038,000)	(60,080,000)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	1,078,000	320,000
Amortization of investments	(686,000)	(218,000)
Amortization of debt issuance costs	948,000	560,000
Stock-based compensation	6,484,000	1,728,000
Loss on extinguishment of debt	2,324,000	0
Change in fair value of warrants	(692,000)	(196,000)
Changes in operating assets and liabilities
Trade accounts receivable	(4,693,000)	0
Other accounts receivable	1,634,000	(1,670,000)
Prepaid expenses and other current assets	(960,000)	(1,588,000)
Inventory	(2,176,000)	0
Other assets	(247,000)	62,000
Accounts payable	4,737,000	(1,110,000)
Other accrued liabilities	8,912,000	5,630,000
Accrued trade discounts and rebates	1,375,000	0
Accrued returns reserve	1,957,000	0
Other liabilities	1,239,000	283,000
Net cash used in operating activities	(104,346,000)	(56,279,000)
Cash flows from investing activities
Capital expenditures	(1,107,000)	(1,510,000)
Purchases of investments	(102,472,000)	(68,851,000)
Sales and maturities of investments	101,196,000	2,100,000
Net cash used in investing activities	(2,383,000)	(68,261,000)
Cash flows from financing activities
Proceeds from Initial Public Offering	0	98,325,000
Payments for Initial Public Offering Costs	0	(9,422,000)
Proceeds from public offerings	61,692,000	0
Payments of public offering costs	(4,465,000)	0
Proceeds from sale of Series C Preferred Stock	0	4,438,000
Payments for preferred stock issuance costs	0	(24,000)
Proceeds from issuance of debt	60,000,000	35,000,000
Repayment of debt	(35,000,000)	0
Payments of debt issuance costs	(2,381,000)	(333,000)
Proceeds from employee stock purchase plan	532,000	0
Proceeds from exercise of stock awards	152,000	227,000
Net cash provided by financing activities	80,530,000	128,211,000
Effect of exchange rate on cash and cash equivalents	2,000	0
Increase (decrease) in cash and cash equivalents	(26,197,000)	3,671,000
Cash and cash equivalents, beginning of period	45,716,000	42,045,000
Cash and cash equivalents, end of period	19,519,000	45,716,000
Supplemental schedule of cash flow information
Cash paid for interest	3,717,000	1,711,000
Supplemental schedule of non-cash investing and financing activities
Tenant improvement allowance	5,658,000	0
Accrued debt issuance costs	1,800,000	2,325,000
Allocation of debt proceeds to warrants	$ 0	$ 1,012,000

Organization and Nature of the Business	12 Months Ended
Organization and Nature of the Business	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Nature of the Business	Organization and Nature of the Business Nature of business Xeris Pharmaceuticals, Inc. ("Xeris" or the "Company") is a specialty pharmaceutical company that was incorporated in Delaware in 2005. Xeris is dedicated to the development of ready-to-use injectable and infusible drug formulations that address important unmet medical needs, are easier to use by patients, caregivers and health practitioners, and reduce costs for payors and the healthcare system. Since our inception in 2005, the Company has devoted substantially all of our resources to research and development initiatives, undertaking preclinical studies of our product candidates, conducting clinical trials of our most advanced product candidates, organizing and staffing our company, raising capital and initiating the commercialization of our first product, Gvoke, which was approved by the FDA on September 10, 2019. Gvoke delivers ready-to-use glucagon via a commercially available pre-filled syringe or auto-injector for the treatment of severe hypoglycemia, a potentially life-threatening condition. The Company commercially launched Gvoke pre-filled syringe ("Gvoke PFS") in November 2019. The Company has financed its operations through the issuance of its common stock, convertible preferred stock and other equity instruments, debt financing and grant funding from the National Institutes of Health ("NIH") and other philanthropic organizations. The Company has generated $1.6 million in revenue from product sales as of December 31, 2019. The Company has incurred operating losses since inception and has an accumulated deficit of $246.2 million as of December 31, 2019. The Company expects to continue to incur net losses for at least the next 12 months. Based on the Company’s current operating plans and existing working capital at December 31, 2019, in addition to the funds raised in its February 2020 equity offering, the Company believes cash resources are sufficient to sustain operations and capital expenditure requirements for at least the next 12 months. The Company is subject to a number of risks similar to other specialty pharmaceutical companies, including, but not limited to, successful development and commercialization of its drug candidates, the development of new technological innovations by its competitors, protection of intellectual property and market acceptance of the Company’s products. Basis of presentation The consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). In the opinion of management, the accompanying consolidated financial statements reflect all adjustments, consisting only of normal recurring adjustments, considered necessary for a fair presentation of the Company’s financial position and its results of operations and cash flows for the periods presented. The results of operations for such periods are not necessarily indicative of the results that may be expected for any future period. 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”) issued by the Financial Accounting Standards Board (“FASB”). Basis of Consolidation These consolidated financial statements include the financial statements of Xeris Pharmaceuticals, Inc. and its subsidiary, Xeris Pharmaceuticals Australia Pty Ltd. All intercompany transactions have been eliminated.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

Summary of Significant Accounting Policies [Abstract]

Summary of Significant Accounting Policies

The accompanying financial statements have been prepared in conformity with GAAP. Any reference in these notes to applicable guidance is meant to refer to GAAP as found in the ASC and ASUs of the FASB.

Use of estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses included in the financial statements and accompanying notes. Actual results could differ from those estimates.

Revenue recognition

The Company applies the guidance in ASC 606 to all contracts with customers within the scope of the standard. The Company sells its products primarily to pharmaceutical wholesalers. These wholesalers then resell the Company’s products to their retail customers, such as pharmacies and mass merchandisers. In addition, the Company enters into arrangements with payors, group purchasing organizations, and health care providers that provide for government-mandated or privately-negotiated discounts and allowances related to the Company’s products.

Revenue is recognized when the Company's customer (e.g., a wholesaler) obtains control of promised goods or services, based on the consideration the Company expects to receive in exchange for those goods or services. The estimated net sales price is generally based upon a list or fixed price less estimates of variable consideration (e.g., patient co-pay assistance, prompt payment discounts, payor rebates, chargebacks, service fees and product returns). The estimates of variable consideration are subject to a constraint such that some or all of the estimated amount of variable consideration will only be included in the transaction price to the extent that it is probable that a significant reversal of revenue will not occur when the uncertainty associated with the variable consideration is subsequently resolved. Estimating variable consideration and the related constraint requires the use of significant management judgment and other market data.

Net sales represent gross product sales less estimated allowances for patient co-pay assistance programs, prompt payment discounts, payor rebates, chargebacks, service fees, and product returns, all of which are recorded at the time of sale to pharmaceutical wholesalers. The Company applies significant judgments and estimates in determining some of these allowances. If actual results differ from its estimates, the Company will be required to make adjustments to these allowances in the future.

Patient Co-Pay Assistance Program

The Company offers a savings program to commercially insured patients under which the cost of a prescription to a patient is discounted. The Company reimburses pharmacies for this discount through a third-party vendor. The Company records an accrual to reduce gross sales for the estimated co-pay on units sold to distributors. The estimate is based on estimated percentages of products that will be prescribed to qualified patients, expected patient utilization of the discount program, average assistance paid based on reporting from the third-party vendor as well as industry data and levels of inventory in the distribution channel. Accrued co-pay fees are recorded as a reduction of revenue and included in accrued trade discounts and rebates on the consolidated balance sheets.

Prompt Payment Discounts

As an incentive for prompt payment, the Company offers a discount to most customers. The Company expects that all eligible customers will comply with the contractual terms to earn the discount. and, therefore, accrues the discount on all eligible sales. The Company records the discount as an allowance against trade accounts receivable on the consolidated balance sheets and as a reduction of revenue.

Commercial Rebates

The Company contracts with certain commercial entities to provide rebates. The Company accrues estimated rebates based on contract rates, estimated percentages of products that will be prescribed to qualified patients and estimated levels of inventory in the distribution channel and records the rebate as a reduction of revenue. Accrued commercial rebates are included in accrued trade discounts and rebates on the consolidated balance sheets.

Government Rebates and Discounts

The Company participates in certain federal and state government rebate programs such as the Medicaid Drug Rebate Program, TRICARE Retail Refunds Program, and Medicare Part D Coverage Gap Discount Program. The Company accrues estimated rebates and discounts based on estimated percentages of product sold to qualified patients, estimated rebate or discount percentages and estimated levels of inventory in the distribution channel that will be prescribed to qualified patients and records the rebates or discounts as a reduction of revenue. Accrued government rebates and discounts are included in accrued trade discounts and rebates on the consolidated balance sheets.

Chargebacks

The Company's products are subject to certain programs whereby pricing on products is discounted below wholesaler list price to participating commercial or government entities. These entities purchase products through wholesalers at the discounted price, and the wholesalers charge the difference between their acquisition cost and the discounted price back to the Company. The Company accrues estimated chargebacks based on contract prices, sales data obtained from third-party information and estimated levels of inventory in the distribution channel and records the chargebacks as a reduction of revenue. Accrued chargebacks are included in accrued trade discounts and rebates on the consolidated balance sheets.

Service Fees

The Company records service fees paid to its customers for distribution and inventory management services as a reduction to revenue. The Company accrues estimated service fees based on contractually determined amounts. Accrued service fees are included in accrued trade discounts and rebates on the consolidated balance sheets.

Product Returns

Consistent with industry practice, the Company maintains a return goods policy that allows customers to return product due to order or shipment errors, overstock, dating, recall or other changes in regulatory guidelines. Generally, product may be returned for a period beginning six months prior to its expiration date and up to one year after its expiration date. To determine the estimate of the provision for returns, the Company analyzes branded product return history of comparable products and other market data. In a reporting period, the Company may decide to constrain revenue for product returns based on information from various sources, including channel inventory levels, inventory dating, prescription data, the expiration dates of product currently being shipped, price changes of competitive products and introductions of generic products. At December 31, 2019, the Company increased its returns reserve above the level indicated by the return history of comparable products due to factors related to the initial stocking of inventory for the launch of our new product. The Company records estimated sales returns in accrued returns reserve on the consolidated balance sheets and as a reduction of revenue.

Bad debt expense

The Company’s products are primarily sold to wholesalers. The Company monitors its accounts receivable balances to determine the impact, if any, of such factors as changes in customer concentration, credit risk and the realizability of its accounts receivable, and records a bad debt reserve when applicable.

Concentration of credit risk

For the year ended December 31, 2019, three customers accounted for 94% of the Company’s gross sales. These same three customers accounted for 97% of the trade accounts receivable at December 31, 2019.

Cost of Goods Sold

Cost of goods sold includes primarily product costs, which include all costs directly related to the purchase of raw materials, charges from our contract manufacturing organizations, and manufacturing overhead costs, as well as shipping and distribution charges. Cost of goods sold also includes losses on excess, slow-moving or obsolete inventory and inventory purchase commitments, if any. Manufacturing costs for Gvoke incurred prior to approval and commercialization were expensed as research and development expenses.

Segment reporting

Operating segments are identified as components of an enterprise for which separate discrete financial information is available and utilized by the chief operating decision maker in making decisions regarding resource allocation and assessing performance. The Company operates in one segment and, other than conducting certain clinical trials outside the United States, all of the Company’s operations are in the United States.

Cash and cash equivalents

The Company considers all demand deposits with financial institutions and highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents.

Inventories

Inventories are stated at the lower of cost or net realizable value, using the first-in, first-out convention. Inventories consist of raw materials, work in process and finished goods. The Company has entered into manufacturing and supply agreements for the manufacture or purchase of raw materials and production supplies. The Company’s inventories include the direct purchase cost of materials and supplies, charges from our contract manufacturing organizations and manufacturing overhead costs. The Company reviews its inventory balance quarterly to assess if it has obsolete or excess inventory and records a charge to cost of goods sold if and when applicable. Manufacturing costs for Gvoke prior to approval and commercialization were expensed as research and development expenses.

Prepaid expenses and other current assets

Prepaid expenses and other current assets include prepaid expenses for general business purposes, which are stated at cost and amortized on a straight-line basis over the related period of benefit. Prepaid expenses also include supplies and materials used in several research projects. These supplies and materials are expensed as they are consumed.

Investments

The Company classifies its investments in debt securities as available-for-sale investments. Investments classified as short-term on the balance sheets have original maturities of greater than 90 days but less than one year.

Investments in available-for-sale securities are reported at estimated fair value. Available-for-sale securities consist primarily of agency securities, corporate securities, U.S. government securities and commercial paper. Unrealized gains and losses related to changes in the fair value of debt securities are recognized in accumulated other comprehensive loss on the Company's balance sheets. Changes in the fair value of available-for-sale securities impact the statements of operations and comprehensive loss only when such securities are sold or an other-than-temporary impairment is recognized. Realized gains and losses on the sale of securities are determined by specific identification of each security’s cost basis. The Company regularly reviews its investment portfolio to determine if any security is other-than-temporarily impaired, which would require an impairment charge to be recorded in the period any such determination is made. The Company considers factors such as the duration, severity of and reason for the decline in value, the financial condition of the issuer and any changes thereto, the potential recovery period and intent to sell.

Fair value of financial instruments

Fair value is the price that could be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value determination in accordance with applicable accounting guidance requires that a number of significant judgments be made. Additionally, fair value is used on a non-recurring basis to evaluate assets for impairment or as required for disclosure purposes by applicable accounting guidance on disclosures about fair value of financial instruments. Depending on the nature of the assets and liabilities, various valuation techniques and assumptions are used when estimating fair value. The carrying amounts of certain of the Company’s financial instruments, including cash and cash equivalents, accounts receivable, prepaid expenses and other current assets, and accounts payable, are shown at cost, which approximates fair value due to the short-term nature of these instruments. The debt outstanding under the Amended and Restated Loan and Security Agreement (the "Amended Loan Agreement") approximates fair value due to the variable interest rate on the debt. Items measured at fair value on a recurring basis include the Company’s investments and warrants.

Property and equipment

Property and equipment are carried at cost less accumulated depreciation. Depreciation is calculated utilizing the straight-line method over the estimated useful lives of the respective assets:



Lab equipment		5 years
Computer equipment		3 years
Leasehold improvements		Lesser of useful life or lease term
Software		3-5 years
Furniture and fixtures		5 years
Office equipment		5 years

Impairment of long-lived assets

The Company periodically evaluates its long-lived assets for potential impairment in accordance with ASC Topic 360, Property, Plant and Equipment. Potential impairment is assessed when there is evidence that events or changes in circumstances indicate that the carrying amount of an asset may not be recovered. Recoverability of these assets is assessed based on undiscounted expected future cash flows from the assets, considering a number of factors, including past operating results, budgets and economic projections, market trends and product development cycles. If impairments are identified, assets are written down to their estimated fair value. The Company recognized no material impairment charges for the years ended December 31, 2019 and 2018, respectively.

Equity financing costs

The Company capitalizes costs directly associated with equity financings until such financings are consummated, at which time such costs are recorded in additional paid in capital against the gross proceeds of the equity financings. The Company recognized $4.5 million of direct costs associated with the public equity offerings in additional paid in capital for the year ended December 31, 2019 and $9.4 million of direct costs associated with the IPO in additional paid in capital for the year ended December 31, 2018. Costs associated with the shelf registration statement on Form S-3, filed with the U.S. Securities and Exchange Commission's ("SEC") on August 6, 2019 and declared effective on August 21, 2019, have been capitalized and are being reclassified to additional paid in capital on a pro rata basis when the Company completes offerings under the shelf registration. At the end of the three-year life of the shelf registration, the remaining deferred offering costs, if any, will be charged to the results of operations. As of December 31, 2019 and 2018, $0.4 million and $0, respectively, of deferred costs related to equity financings are included in other assets on the balance sheets.

Deferred rent

Certain of the Company’s lease agreements provide for scheduled rent increases during the lease term and also for abatement of some or all rental payments for a period of time after the occupancy date. In addition, certain of the Company’s lease agreements provided for tenant improvement allowances whereby the landlord funded the cost to build out the space. The Company recorded a liability for such lease incentives which is being amortized to rent expense such that rent expense is recognized on a straight-line basis throughout the lease term.

Debt issuance costs

Debt issuance costs incurred in connection with financing arrangements are amortized to interest expense over the life of the respective financing arrangement using the effective interest method. Debt issuance costs, net of related amortization, are deducted from the carrying value of the related debt.

Warrants

The Company’s warrants are classified as liabilities as they represent a financial instrument for a share of common stock. The warrants are revalued each reporting period with the change in fair value recorded in the accompanying statements of operations until the warrants are exercised, expire, or otherwise settled.

Research and development expenses

Research and development expenses are expensed as incurred. Research and development expenses include salaries, stock compensation and other personnel-related costs, consulting fees, fees paid for contract research and development services including those for preclinical and clinical trials, laboratory equipment and facilities costs, and other external costs. In addition, manufacturing costs of products prior to approval and commercial salability are expensed as research and development costs.

Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are deferred and capitalized. The capitalized amounts are expensed as the related goods are received, the services are performed or the arrangement is terminated.

Stock-based compensation expense

The Company accounts for our stock-based compensation awards in accordance with ASC Topic 718, Compensation-Stock Compensation, or ASC 718. ASC 718 requires all stock-based payments, including stock options, restricted stock units and employee stock purchases, to be recognized in the statements of operations based on their grant date fair values. The Company estimates the grant date fair value of each option award using the Black-Scholes option-pricing model. The use of the Black-Scholes option-pricing model requires management to make assumptions with respect to the expected term of the option, the expected volatility of the common stock consistent with the expected life of the option, the risk-free interest rate and the expected dividend yield of the common stock. Restricted stock units are valued based on the fair market value of the Company’s common stock on the date they were granted. The Company recognizes stock-based compensation expense equal to the grant date fair value of stock options, restricted stock units and employee stock purchases on a straight-line basis over the requisite service period.

Income taxes

Income taxes are recorded in accordance with ASC 740, Income Taxes (“ASC 740”), which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. The Company determines its deferred tax assets and liabilities based on differences between financial reporting and tax bases of assets and liabilities, which are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. Valuation allowances are provided if, based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized.

The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. The Company policy is to include interest and penalties related to uncertain tax positions, if any, within the provision for taxes in the statements of operations and comprehensive loss. For the years ended December 31, 2019 and 2018, the Company did not accrue any interest or penalties on uncertain tax positions.

Grant income

The Company has received several grants from the NIH and other philanthropic organizations for certain research and development projects the Company has and is currently performing. Grant income is recognized when these research and development activities are performed and the Company has met criteria for reimbursement per the grant agreements. The Company has also received grants that were funded upfront. The Company defers the recognition of these awards until the related research and development expenses are incurred.

Foreign currency translation

Our functional currency is the United States Dollar. Monetary assets and liabilities of our non-US subsidiary are remeasured using the exchange rate in effect at the end of the period. Costs in local currency are remeasured using the average exchange rate for the period. The resulting remeasurement gains and losses are included in other comprehensive gain (loss).

Comprehensive loss

Comprehensive loss is defined as the change in equity during a period from transactions and other events, excluding changes resulting from investments from owners and distributions to owners. Comprehensive loss includes net loss, unrealized (gains) losses on debt securities classified as available-for-sale investments and foreign currency translation adjustments.

Reclassifications

In the fourth quarter of 2019, in conjunction with the recognition of product sales and related cost of sales, the Company reclassified grant income, service revenue and the related cost of revenue to other income (expense) on the Company's consolidated statements of operations and comprehensive loss. There was no impact to net loss. Prior periods have been revised to conform to the current year presentation.

New accounting pronouncements

Recently issued accounting pronouncements

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). The new standard requires lessees to record a right-of-use asset and a lease liability for all leases with a term of greater than twelve months regardless of their classification. Leases will be classified as either operating or finance leases under the new guidance. Operating leases will result in straight-line expense in the income statement, similar to current operating leases, and finance leases will result in more expense being recognized in the earlier years of the lease term, similar to current capital leases. The FASB has recently extended the effective date of this standard for certain companies. This standard will be effective for the Company for fiscal years beginning after December 15, 2020 and interim periods within fiscal years beginning after December 15, 2021. The Company is currently evaluating the impact the adoption of this new standard will have on the financial statements and related disclosures; however, since the Company is a lessee to certain leases for property whose terms exceed twelve months, it expects, once adopted, to report assets and liabilities related to these leases on its balance sheet.

Inventory (Notes)

12 Months Ended

Dec. 31, 2019

Inventory [Line Items]

Inventory Disclosure [Text Block]

Inventory

The components of inventories consisted of the following (in thousands):



	December 31, 2019		December 31, 2018
Raw materials	$	1,321	$	—
Work in process	662		—
Finished goods	193		—
Inventory	$	2,176	$	—

Property and Equipment (Notes)

12 Months Ended

Dec. 31, 2019

Property and Equipment [Abstract]

Property, Plant and Equipment

Property and Equipment

Property and equipment consisted of the following:



(in thousands)	December 31, 2019			December 31, 2018

Lab equipment	$	2,528		$	1,658
Furniture and fixtures	1,611			541
Computer equipment	232			87
Office equipment	80			109
Software	347			110
Leasehold improvements	4,543			180
	9,341			2,685
Less: accumulated depreciation and amortization	(1,488		)	(651		)
Property and equipment, net	$	7,853		$	2,034

Depreciation and amortization expense relating to property and equipment was $1.1 million and $0.3 million for the years ended December 31, 2019 and 2018, respectively.

Other Accrued Liabilities (Notes)

12 Months Ended

Dec. 31, 2019

Accrued Expenses [Abstract]

Other Accrued Liabilities

Other accrued liabilities consisted of the following:



(in thousands)	December 31, 2019		December 31, 2018

Accrued research and development costs	$	7,062	$	2,221
Accrued employee costs	6,818		4,326
Accrued marketing and selling costs	1,973		—
Accrued interest expense	449		274
Accrued other costs	1,817		1,393
Other accrued liabilities	$	18,119	$	8,214

Long-Term Debt

12 Months Ended

Dec. 31, 2019

Long-term Debt, Unclassified [Abstract]

Long-Term Debt

Long-term Debt

Senior Secured Loan Facility

In February 2018, the Company entered into the Loan and Security Agreement, dated as of February 28, 2018 (as amended, the “Loan

Agreement”), with Oxford Finance LLC, as the collateral agent and a lender (“Oxford”), and Silicon Valley Bank, as a lender (“SVB”,

and together with Oxford, the “Lenders”) which provided for a senior secured loan facility of up to an aggregate principal amount of $45.0 million. The first tranche was $20.0 million and was drawn down in February 2018 (the "2018 Term A Loan"). The second tranche was $15.0 million and was drawn down in September 2018 (the "2018 Term B Loan"). The interest rate under the Loan Agreement was the thirty-day U.S. LIBOR rate plus 6.75%, which was 8.84% as of September 13, 2019, the date of repayment of the amounts outstanding under the Loan Agreement. Payments on the Loan Agreement were interest only for the first 24 months. The Company also issued warrants to the Lenders to purchase common stock, which is further discussed in Note 9, "Warrants."

On September 10, 2019, the Company entered into an Amended Loan Agreement with the Lenders which amended and restated the Loan Agreement. Under the Amended Loan Agreement, the Lenders will extend up to $85.0 million in term loans to the Company in three tranches. The initial tranche of $60.0 million (the “Term A Loan”) was drawn down on September 13, 2019. The second tranche of $15.0 million (the “Term B Loan”) and the third tranche of $10.0 million (the “Term C Loan”) will become available to the Company upon the achievement of certain revenue targets prior to March 31, 2021 and June 30, 2021, respectively. The 2018 Term A Loan and 2018 Term B Loan and the related final payment fee of $2.3 million were repaid in conjunction with the execution of the Amended Loan Agreement.

The Amended Loan Agreement provides for interest-only payments through March 31, 2021, after which the principal will be payable in 27 equal monthly installments. However, if the Term B Loan is funded, then the period for interest-only payments is extended through December 31, 2021, after which the principal will be payable in 30 equal monthly installments. If the Term C Loan is funded, then the period for interest-only payments is further extended through September 30, 2022, after which the principal will be payable in 21 equal monthly installments. The maturity date is June 1, 2023, provided that if the Term B Loan is funded, then the maturity date will be extended to June 1, 2024. After repayment, no loans may be reborrowed. For the period from the funding date of the Term A Loan through and including December 31, 2019, the loans incurred interest at a rate of 8.68%. Following such time, the loans shall incur interest at a floating per annum rate in an amount equal to the sum of 6.25% plus the greater of (a) 2.43% and (b) the thirty-day U.S. Dollar LIBOR rate. The Company incurred total debt issuance costs of $1.9 million related to the Amended Loan Agreement, which are reflected as a direct reduction to the term loan balance and are being amortized into interest expense over the life of the loan using the effective interest method.

Pursuant to the Amended Loan Agreement, the Company provided a first priority security interest in substantially all of the Company’s assets, including intellectual property, subject to certain limited exceptions.

The Amended Loan Agreement allows the Company to voluntarily prepay the outstanding amounts thereunder, but not less than $2.0 million of the outstanding principal at any time. Prior to April 1, 2021, the Company is subject to a prepayment fee equal to 1.50% of the principal amount being prepaid. In the event the Company draws down the second or third tranche, the period subject to the 1.50% prepayment fee is extended to January 1, 2022 and October 1, 2022, respectively. A final payment fee of 3.0% multiplied by the original principal amount of each tranche drawn is due upon the earlier to occur of the maturity date of the Amended Loan Agreement, the acceleration of the Amended Loan Agreement or prepayment of such borrowings and is recorded in other liabilities on the consolidated balance sheets.

The Amended Loan Agreement contains customary representations and warranties, events of default (including an event of default upon a material adverse change of the Company) and affirmative and negative covenants, including, among others, covenants that limit or restrict the Company’s ability to incur additional indebtedness, grant liens, merge or consolidate, make acquisitions, pay dividends or other distributions or repurchase equity, make investments, dispose of assets and enter into certain transactions with affiliates, in each case subject to certain exceptions.

The components of debt are as follows:



(in thousands)	December 31, 2019			December 31, 2018

2018 Term A Loan	$	—		$	20,000
2018 Term B Loan	—			15,000
Term A Loan	60,000			—
Principal amount of long-term debt	60,000			35,000
Less: Unamortized deferred costs	(1,695		)	(3,110		)
Long-term debt	$	58,305		$	31,890

The following table sets forth the Company’s future minimum principal payments (in thousands):



2019	$	0
2020	0
2021	20,000
2022	26,700
2023	13,300
	$	60,000

For the year-to-date period ended December 31, 2019, the Company recognized interest expense of $7.2 million, of which $0.9 million related to the amortization of debt issuance costs. Included in such interest expense is a loss on extinguishment of debt of $2.3 million relating to the write-off of the remaining balance of unamortized debt issuance costs associated with the Loan Agreement. For the year ended December 31, 2018, the Company recognized interest expense of $2.5 million, of which $0.6 million was related to the amortization of debt issuance costs.

Public Stock Offerings

12 Months Ended

Dec. 31, 2019

Reverse Stock Split and Initial Public Offering [Abstract]

Reverse Stock Split and Initial Public Offering

Public Stock Offerings

On June 25, 2018, the Company closed the Initial Public Offering ("IPO") of its common stock pursuant to a registration statement on Form S-1, as amended. The Company sold an aggregate of 6,555,000 shares of common stock under the registration statement at an IPO price of $15.00 per share, including 855,000 shares of common stock pursuant to the exercise of the underwriters’ option to purchase additional shares. Net proceeds from the IPO were $88.9 million after deducting underwriting discounts and commissions as well as other IPO expenses. Upon closing the IPO, all outstanding shares of the Company's Series A, B and C convertible preferred stock were converted into 11,837,073 shares of common stock.

On February 19, 2019, the Company completed a public offering of its common stock pursuant to a registration statement on Form S-1, as amended. The Company sold an aggregate of 5,996,775 shares of common stock at a price of $10.00 per share, including 116,775 shares of common stock pursuant to the exercise of the underwriters' option to purchase additional shares. Net proceeds from the public offering were $55.5 million after deducting underwriting discounts and commissions, as well as other public offering expenses.

On August 6, 2019, the Company filed a shelf registration statement on Form S-3 with the SEC, which covers the offering, issuance and sale by the Company of up to an aggregate of $250.0 million of its common stock, preferred stock, debt securities, warrants and/or units, (the "Shelf"). The Company simultaneously entered into a Sales Agreement with Jefferies LLC, as sales agent, to provide for the offering, issuance and sale by the Company of up to $50.0 million of its common stock from time to time in "at-the-market" offerings under the Shelf. The Shelf was declared effective by the SEC on August 21, 2019. In December 2019, the Company sold an aggregate of 204,427 shares of common stock under the Shelf for net proceeds of $1.7 million after deducting selling commissions as well as other public offering expenses.

Warrants

In 2014 the Company issued 19,931 warrants (the “2014 Warrants”) to certain investors. The 2014 Warrants allow each holder to purchase one share of common stock for $5.912. There have been 18,512 2014 Warrants exercised, and 1,419 warrants remain outstanding as of December 31, 2019.

As part of the Loan Agreement discussed in Note 6, "Long-term Debt", the Lenders received warrants concurrent with the borrowing. The warrants represent a right for the lender to purchase shares of the Company’s common stock at an initial exercise price of $11.169 per share. The Company issued 53,720 warrants (the "2018 Term A Warrants") upon the drawdown of the 2018 Term A Loan in February 2018, and the Company issued 40,292 warrants (the "2018 Term B Warrants") upon the drawdown of the 2018 Term B Loan in September 2018. There have been no exercises of Term A Warrants or Term B Warrants, and as such all 53,720 warrants and 40,292 warrants were outstanding as of December 31, 2019, respectively.

Because the warrants are a freestanding instrument, indexed to the Company's stock, they do not meet the criteria for equity classification. Therefore, the warrants are classified as liabilities and subject to remeasurement at each reporting period until they are exercised, expired, or otherwise settled.

The Company recognized a gain (loss) of $78,000, $351,000 and $263,000 upon the change in fair value of the warrants during the year ended December 31, 2019 related to the 2014 Warrants, the Term A Warrants and the Term B Warrants, respectively. The Company recognized a gain (loss) of $(56,000), $(108,000) and $360,000 upon the change in fair value of the warrants during the year ended December 31, 2018 related to the 2014 Warrants, the Term A Warrants and the Term B Warrants, respectively.

As of December 31, 2019, the following warrants were outstanding:



	Outstanding Warrants	Exercise Price per Warrant	Expiration Date

2014 Warrants	1,419	$5.912	August 2020
Term A Warrants	53,720	$11.169	February 2025
Term B Warrants	40,292	$11.169	September 2025
	95,431

Convertible Preferred Stock	12 Months Ended
Convertible Preferred Stock	Dec. 31, 2019
Convertible preferred stock [Abstract]
Convertible Preferred Stock	Convertible Preferred Stock In February 2018, the Company issued an additional 707,680 shares of Series C convertible preferred stock for net proceeds of $4.4 million. During the second quarter of 2018, a majority of the holders of the Company's convertible preferred stock elected to have their shares converted into common stock; therefore, all outstanding shares of preferred stock were converted into 11,837,073 shares of common stock at a conversion rate of 1:1.78112 upon the closing of the Company's IPO on June 25, 2018. Prior to the conversion of the convertible preferred stock into common stock, the holders of the Company’s convertible preferred stock were entitled to receive non-cumulative dividends at the rate of 8% of the purchase price per annum in preference to any dividends to the holders of the common stock, payable as and if when declared by the Board of Directors. The holders of the convertible preferred stock also were entitled to participate pro rata in any dividends paid to the holders of the common stock on an as-converted basis. No dividends were declared by the Company’s Board of Directors.

Warrants (Notes)

12 Months Ended

Dec. 31, 2019

Warrants [Abstract]

Warrants

Public Stock Offerings

Warrants

As of December 31, 2019, the following warrants were outstanding:



	Outstanding Warrants	Exercise Price per Warrant	Expiration Date

2014 Warrants	1,419	$5.912	August 2020
Term A Warrants	53,720	$11.169	February 2025
Term B Warrants	40,292	$11.169	September 2025
	95,431

Commitments and Contingencies

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Commitments

The Company has non-cancellable operating leases for office space, which expire at various times through 2031. The non-cancellable office lease agreements provide for monthly lease payments, which increase during the term of each lease agreement.

In the first quarter of 2018, the Company signed a lease for office space in Chicago, Illinois. In the fourth quarter of 2018, the Company signed an amendment to this lease to occupy new space and relocated to this new space in March 2019.

Future minimum lease payments under operating leases at December 31, 2019 are as follows (in thousands):



2020	$	1,575
2021	2,208
2022	2,263
2023	1,745
2024	1,278
Thereafter	8,476
Total minimum lease payments	$	17,545

Total rent expense under these operating leases was approximately $2.2 million and $1.3 million for the years ended December 31, 2019 and 2018, respectively.

As of December 31, 2019, we had unused letters of credit of $1,083,000 which were issued primarily to secure leases.

Litigation

From time to time, the Company may become involved in various legal actions arising in the ordinary course of business. As of December 31, 2019 management was not aware of any existing, pending or threatened legal actions that would have a material impact on the financial position or results of operations of the Company.

Stock Compensation Plan (Notes)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Stock Compensation Plan

In 2011 the Company adopted the 2011 Stock Option Issuance Plan (the “2011 Plan”) and subsequently amended it to authorize the Board of Directors to issue up to 4,714,982 incentive stock option and non-qualified stock option awards.

The 2018 Stock Option and Incentive Plan (the "2018 Plan") was adopted by the Board of Directors in April 2018 and approved by the Company's stockholders in June 2018 to award up to 1,822,000 shares of common stock. This plan became effective on the date immediately prior to the effectiveness of the Company's IPO registration statement. The 2018 Plan replaced the 2011 Plan as the Board of Directors determined not to make additional awards under the 2011 Plan following the closing of the IPO, which occurred in June 2018. The 2018 Plan allows the compensation committee to make equity-based and cash-based incentive awards to the Company's officers, employees, directors and other key persons (including consultants).

The 2018 Plan provides that the number of shares reserved and available for issuance under the plan will automatically increase each January 1, beginning on January 1, 2019, by 4% of the outstanding number of shares of our common stock on the immediately preceding December 31, or such lesser number of shares as determined by the compensation committee. This number is subject to adjustment in the event of a stock split, stock dividend or other change in the Company's capitalization. On January 1, 2019, the number of shares of common stock available for issuance under the 2018 Plan was automatically increased by 835,728 shares. As of December 31, 2019, there were approximately 809,000 shares of common stock available for future issuance under the 2018 plan.

The 2018 Employee Stock Purchase Plan (the "ESPP") was adopted by the Board of Directors in April 2018 and approved by the Company's stockholders in June 2018 to issue up to 193,000 shares of common stock to participating employees. Through the ESPP, eligible employees may authorize payroll deductions of up to 15% of their compensation to purchase up to the number of shares of common stock determined by dividing $25,000 by the closing market price of Xeris common stock on the offering date. The purchase price per share at each purchase date is equal to 85% of the lower of (i) the closing market price per share of Xeris common stock on the employee’s offering date or (ii) the closing market price per share of Xeris common stock on the purchase date. Each offering period has a six-month duration and purchase interval with a purchase date of the last business day of June and December each year. This plan became effective on the date immediately prior to the effectiveness of the Company's IPO registration statement. The ESPP provides that the number of shares reserved and available for issuance will automatically increase each January 1, beginning on January 1, 2019 and each January 1 thereafter through January 1, 2028, by the least of (i) 1% of the outstanding number of shares of our common stock on the immediately preceding December 31; (ii) 386,000 shares or (iii) such lesser number of shares as determined by the ESPP administrator. On January 1, 2019, the number of shares of common stock available for issuance under the ESPP increased by 208,932 shares. The number of shares reserved under the ESPP is subject to adjustment in the event of a stock split, stock dividend or other change in capitalization. The Company issued 73,607 shares at a weighted average price of $7.22 per share during the year ended December 31, 2019. As of December 31, 2019, there were approximately 328,000 shares available for issuance under the ESPP.

The Equity Inducement Plan (the "Inducement Plan") was adopted by the Board of Directors in February 2019. The Inducement Plan was adopted without stockholder approval pursuant to Rule 5635(c)(4) of the Nasdaq Listing Rules. The Inducement Plan allows the Company to make stock option or restricted stock unit awards to prospective employees of the Company as an inducement to such individuals to commence employment with the Company. The Company intends to use this Inducement Plan to help it attract and retain prospective employees who are necessary to support the commercial launch of Gvoke and the expansion of the Company generally. The Company initially reserved 750,000 shares of common stock for the issuance of awards under the Inducement Plan. This number is subject to adjustment in the event of a stock split, stock dividend or other change in our capitalization. As of December 31, 2019, there were approximately 340,000 shares of common stock available for future issuance under the Inducement Plan.

Stock options are granted with an exercise price equal to the market price of the Company’s stock at the date of grant. Stock option awards typically vest over either two, three or four years after the grant date and expire ten years from the grant date.

The fair value of each option is estimated on the date of grant using a Black-Scholes option valuation model that uses the assumptions noted in the following table. The expected term of options represents the period of time that options granted are expected to be outstanding. The risk-free interest rate for periods during the contractual life of the option is based on the U.S. Treasury yield curve in effect at the time of grant. The expected stock price volatility assumption is based on the historical volatilities of a peer group of publicly traded companies as well as the historical volatility of the Company's common stock since the Company began trading subsequent to its IPO in June 2018 over the period corresponding to the expected life as of the grant date. The expected dividend yield is based on the expected annual dividend as a percentage of the market value of the Company’s ordinary shares as of the grant date. The Company uses historical data to estimate employee terminations within the valuation model.

The fair value of stock options granted was estimated with the following weighted average assumptions:



	Years Ended December 31,
	2019		2018
Expected term (years)	6.0		6.0
Risk-free interest rate	2.14	%	2.48	%
Expected volatility	60.27	%	56.84	%
Expected dividends	—		—

Stock option activity under the 2011 Plan, 2018 Plan and Inducement Plan for the year ended December 31, 2019 was as follows:



	OPTIONS	WEIGHTED AVERAGE EXERCISE PRICE		WEIGHTED AVERAGE CONTRACTUAL LIFE (YEARS)
Outstanding - January 1, 2019	3,130,700	$	8.06	8.69
Granted	1,600,650	12.21
Exercised and vested	(128,307)	1.99
Forfeited	(172,655)	16.33
Expired	(1,403)	19.77
Outstanding - December 31, 2019	4,428,985	$	9.40	8.19
Exercisable - December 31, 2019	1,647,911	$	6.07	7.31
Vested and expected to vest at December 31, 2019	4,202,205	$	9.32	8.16

The weighted average fair value of awards granted during the year ended December 31, 2019 was $6.97 per share. The total intrinsic value of options exercised during the year ended December 31, 2019 was $1.0 million. The aggregate intrinsic value of awards vested and expected to vest as of December 31, 2019 was $7.8 million.

At December 31, 2019, there was a total of $14.1 million of unrecognized stock-based compensation expense related to stock options that is expected to be recognized over a weighted average period of 2.3 years.

Restricted stock unit ("RSU") awards for the year ended December 31, 2019 were as follows:



	Units
Unvested balance - January 1, 2019	0
Granted	125,000
Unvested balance - December 31, 2019	125,000

Restricted stock unit awards are measured based on the fair market value of the underlying stock on the date of grant and recognized as expense on a straight-line basis over the employee’s requisite service period (generally the vesting period). As of December 31, 2019, there was $1.3 million of unrecognized stock-based compensation expense related to RSUs, which is expected to be recognized over the weighted-average remaining vesting period of 3.1 years.

The fair value of the ESPP Plan shares was estimated using the Black-Scholes option-pricing model with the following weighted-average assumptions:



	Year Ended December 31, 2019
Expected term (years)	0.5
Risk-free interest rate	1.85%
Expected volatility	70.70%
Expected dividends	—

The following table summarizes the reporting of total stock-based compensation expense resulting from stock options, restricted stock units and the employee stock purchase plan (in thousands):



	Years Ended December 31,
	2019		2018

Research and development	$	1,168	$	518
Selling, general and administrative	5,316		1,210
Total stock-based compensation expense	$	6,484	$	1,728

Fair Value Measurement

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurement

Fair Value Measurements

Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value measurements are classified and disclosed in one of the following categories:

Level 1: Measured using unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities.

Level 2: Measured using quoted prices in active markets for similar assets or liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, or inputs, other than quoted prices in active markets, that are observable either directly or indirectly; and

Level 3: Measured based on prices or valuation models that require inputs that are both significant to the fair value measurement and less observable from objective sources (i.e., supported by little or no market activity).

Fair value measurements are classified based on the lowest level of input that is significant to the measurement. The Company’s assessment of the significance of a particular input to the fair value measurement requires judgment, which may affect the valuation of the assets and liabilities and their placement within the fair value hierarchy levels. The determination of the fair values stated below takes into account the market for its financial assets and liabilities, the associated credit risk and other factors as required. The Company considers active markets as those in which transactions for the assets or liabilities occur in sufficient frequency and volume to provide pricing information on an ongoing basis.

The following tables present the Company’s fair value hierarchy for those assets and liabilities measured at fair value as of December 31, 2019 and 2018 (in thousands):



	Total as of December 31, 2019		Level 1		Level 2		Level 3

Assets
Cash and cash equivalents:
Cash and money market funds	$	19,519	$	19,519	$	—	$	—

Investments:
U.S. government securities	32,175		32,175		—		—
Corporate securities	22,164		—		22,164		—
Commercial paper	14,922		—		14,922		—
Total investments	$	69,261	$	32,175	$	37,086	$	—

Liabilities
Warrant liabilities	$	150	$	—	$	—	$	150



	Total as of December 31, 2018		Level 1		Level 2		Level 3
Assets
Cash and cash equivalents:
Cash and money market funds	$	45,716	$	45,716	$	—	$	—

Investments:
U.S. government securities	38,737		38,737		—		—
Corporate securities	15,066		—		15,066		—
Agency securities	11,931		—		11,931		—
Commercial paper	1,183		1,183		—		—
Total investments	$	66,917	$	39,920	$	26,997	$	—

Liabilities
Warrant liabilities	$	860	$	—	$	—	$	860

The fair value of the Company’s warrant liabilities is based on a Black-Scholes valuation which considers the expected term of the warrants as well as the risk-free interest rate and expected volatility of the Company's stock.

The Company has determined that the warrant liabilities' fair values are Level 3 items within the fair value hierarchy. The following table presents the changes in the warrant liabilities (in thousands):




Balance at December 31, 2018	$	860
Exercise of warrants	(18		)
Change in fair value of warrants	(692		)
Balance at December 31, 2019	$	150

There were no transfers between any of the levels of the fair value hierarchy during the years ended December 31, 2019 and 2018.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Available-for-Sale Investments (Notes)

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Short-term investments

Available-for-Sale Investments

The Company classifies its investments in debt securities as available-for-sale. Debt securities are comprised of highly liquid investments with minimum “A” rated securities and, as of December 31, 2019, consist of U.S. Treasury and agency bonds and corporate entity commercial paper and securities, all with maturities of more than three months but less than two years at the date of purchase. Debt securities as of December 31, 2019 had an average remaining maturity of 0.70 years. The debt securities are reported at fair value with unrealized gains or losses recorded in accumulated other comprehensive gain (loss) in the consolidated balance sheets. Refer to Note 12, "Fair Value Measurements," for information related to the fair value measurements and valuation methods utilized.

The following table represents the Company’s available-for-sale investments by major security type as of December 31, 2019 and 2018 (in thousands):



	December 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Total Fair Value

Investments:
Commercial paper	$	14,922	$	—	$	—		$	14,922
Corporate securities	22,146		20		(2		)	22,164
U.S. government securities	32,152		23		—			32,175
Total available-for-sale investments	$	69,220	$	43	$	(2	)	$	69,261

	December 31, 2018
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Total Fair Value

Investments:
Agency securities	$	11,944	$	—	$	(13	)	$	11,931
Commercial paper	1,183		—		—			1,183
Corporate securities	15,081		—		(15		)	15,066
U.S. government securities	38,761		—		(24		)	38,737
Total available-for-sale investments	$	66,969	$	—	$	(52	)	$	66,917

The Company reviews available-for-sale investments for other-than-temporary impairment loss periodically. The Company considers factors such as the duration, severity of and reason for the decline in value, the potential recovery period and our intent to sell. For debt securities, we also consider whether (i) it is more likely than not that the Company will be required to sell the debt securities before recovery of their amortized cost basis and (ii) the amortized cost basis cannot be recovered as a result of credit losses. During the years ended December 31, 2019 and 2018, the Company did not recognize any other-than-temporary impairment losses. All marketable securities with unrealized losses have been in a loss position for less than twelve months.

Net Loss Per Share (Notes)

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Earnings Per Share [Text Block]

Net Loss Per Common Share

Basic and diluted net loss per common share is determined by dividing net loss applicable to common stockholders by the weighted average common shares outstanding during the period. For all periods presented, the outstanding shares of preferred stock, warrants, stock option awards and restricted stock units have been excluded from the calculation because their effects would be anti-dilutive. Therefore, the weighted average common shares outstanding used to calculate both basic and diluted loss per common share are the same.

The following potentially dilutive securities were excluded from the computation of diluted weighted average common shares outstanding due to their anti-dilutive effect:



	As of December 31,
	2019	2018
Vested and unvested stock options	4,428,985	3,130,700
Restricted stock units	125,000	—
Warrants	95,431	102,647
	4,649,416	3,233,347

Defined Contribution Plan (Notes)	12 Months Ended
Defined Contribution Plan (Notes)	Dec. 31, 2019
Postemployment Benefits [Abstract]
Compensation and Employee Benefit Plans	Defined Contribution Plan The Company sponsors an employee retirement plan qualifying under Section 401(k) of the Internal Revenue Code for all eligible employees in the United States. Employees become eligible to contribute to the plan upon meeting certain age requirements and 30 days of service. Commencing in 2019, the Company began discretionary matching employee contributions up to certain limits. For the year ended December 31, 2019, the Company made $0.4 million of matching contributions to the plan.

Income Taxes (Notes)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Tax Disclosure

Income Taxes

A reconciliation of the expected income tax benefit computed using the federal statutory income tax rate of 21% to the Company’s effective income tax rate is as follows:



	Years Ended December 31,
(in thousands)	2019			2018
Federal tax benefit at statutory rate	$	(26,468	)	$	(12,617	)
State tax benefit, net of federal benefit	(5,570		)	(1,842		)
Research and development and orphan drug credits	(2,912		)	(2,279		)
Uncertain tax positions	342			603
Permanent adjustments to expenses	169			45
Stock-based compensation	683			76
Return to provision adjustment	(3,278		)	(2,470		)
Rate impact of deferred tax balance	—			(63		)
Statutory rate differential	(51		)	—
Other	339			9
Changes in valuation allowance	36,288			18,538
Total income tax benefit	$	(458	)	$	—

The benefit for income taxes for 2019 is attributable to an Australian research and development tax incentive that will be refunded to the Company after the 2019 income tax filing. During the years ended December 31, 2019 and 2018, the Company had no interest and penalties related to income taxes.

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amount of the assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. A valuation allowance is required to be established or maintained when, based on currently available information, it is more likely than not that all or a portion of a deferred tax asset will not be realized. The guidance on accounting for income taxes provides important factors in determining whether a deferred tax asset will be realized, including whether there has been sufficient taxable income in recent years and whether sufficient income can reasonably be expected in future years in order to utilize the deferred tax asset. For the year ended December 31, 2019, we have evaluated the need to maintain a valuation allowance for deferred tax assets based on our assessment of whether it is more likely than not that deferred tax benefits will be realized through the generation of future taxable income. Appropriate consideration is given to all available evidence, both positive and negative, in assessing the need for a valuation allowance.

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



	December 31,
(in thousands)	2019			2018
Deferred tax assets:
Net operating losses	$	55,110		$	25,372
Federal research and orphan drug credits	8,309			5,426
Stock-based compensation	1,092			267
Other temporary differences	4,648			1,679
Valuation allowance	(68,950		)	(32,662		)
Total assets	209			82
Deferred tax liabilities:
Fixed and intangible assets	(155		)	(82		)
Other deferred tax liabilities	(54		)	—
Total liabilities	(209		)	(82		)
Net deferred tax assets	$	—		$	—

As of December 31, 2019, the Company had federal net operating loss carryforwards of $215.3 million and various state net operating loss carryforwards of $147.5 million. As of December 31, 2018, the Company had federal net operating loss carryforwards of $108.8 million and various state net operating loss carryforwards of $35.6 million. Net operating loss carryforwards for U.S. federal income tax purposes that were generated prior to January 1, 2018 have a twenty-year carryforward life and the earliest layers will begin to expire in 2025. Under the Tax Act, federal net operating losses incurred in 2018 and in future years may be carried forward indefinitely, but the deductibility of such net operating losses is limited to 80% of the current year’s taxable income. U.S. state net operating loss carryforwards will start to expire in 2029 for the earliest net operating loss layers to the extent there is not sufficient state taxable income to utilize those net operating loss carryforwards.

At December 31, 2019, the Company had $8.3 million and $1.0 million of federal and state income tax credits, respectively, to reduce future tax liabilities. As of December 31, 2018, the Company had $5.8 million and $2.0 million of federal and state income tax credits, respectively, to reduce future tax liabilities. The federal income tax credits consist primarily of orphan drug credits and research and development credits. The U.S. state income tax credits consist primarily of California and Illinois research and development credits. Both the U.S. federal orphan drug credits and research and development credits have a twenty-year carryforward life. The U.S. federal orphan drug credits and the research and development credits will both begin to expire in 2025.

A reconciliation of the beginning and ending amounts of valuation allowances for the years ended December 31, 2019 and 2018 is as follows (in thousands):



Valuation allowance at December 31, 2017	$	(14,124	)
Increase for 2018 activity	(18,538		)
Valuation allowance at December 31, 2018	(32,662		)
Increase for 2019 activity	(36,288		)
Valuation allowance at December 31, 2019	$	(68,950	)

The Company is required to recognize the financial statement effects of a tax position when it is more likely than not, based on the technical merits, that the position will be sustained upon examination. The Company accounts for the uncertainty in income taxes by utilizing a comprehensive model for the recognition, measurement, presentation and disclosure in financial statements of any uncertain tax positions that have been taken, or are expected to be taken, on an income tax return. The changes in the Company's uncertain income tax positions for the years ended December 31, 2019 and 2018, excluding interest and penalties, consisted of the following (in thousands):



	December 31,
	2019		2018
Beginning balance - uncertain tax positions	$	603	$	—
Increases related to tax positions taken during the current year	246		228
Increases related to tax positions taken during the prior year	96		375
Ending balance - uncertain tax positions	$	945	$	603

For the year ended December 31, 2019, the increase in uncertain tax positions was attributable primarily to the U.S. federal orphan drug credits and research and development credits. In the Company’s balance sheet, uncertain tax positions of $0.9 million were offset against deferred tax assets.

The Company policy is to include interest and penalties related to uncertain tax penalties, if any, within the provision for taxes in the statements of operations. The Company did not accrue any interest or penalties for the years ended December 31, 2019 and 2018.

Subsequent Events (Notes)	12 Months Ended
Subsequent Events (Notes)	Dec. 31, 2019
Subsequent Event [Line Items]
Subsequent Events	Subsequent Event On February 14, 2020, the Company completed a public offering of its common stock pursuant to a shelf registration statement on Form S-3, which was filed on August 6, 2019 and declared effective by the SEC on August 21, 2019. The Company sold 10,299,769 shares of common stock at a price of $4.15 per share, including 1,299,769 shares of common stock pursuant to the partial exercise of the underwriters' option to purchase up to an additional 1,350,000 shares of common stock. Gross proceeds from the offering were $42.7 million.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Summary of Significant Accounting Policies [Abstract]

Revenue Recognition, Sales of Goods [Policy Text Block]

Revenue recognition

Patient Co-Pay Assistance Program

Prompt Payment Discounts

Commercial Rebates

Government Rebates and Discounts

Chargebacks

Service Fees

Product Returns

Receivables, Trade and Other Accounts Receivable, Allowance for Doubtful Accounts, Policy [Policy Text Block]

Bad debt expense

Concentration Risk, Credit Risk, Policy [Policy Text Block]

Concentration of credit risk

Cost of Goods and Service [Policy Text Block]

Cost of Goods Sold

Segment Reporting, Policy [Policy Text Block]

Segment reporting

Cash and Cash Equivalents, Policy [Policy Text Block]

Cash and cash equivalents

The Company considers all demand deposits with financial institutions and highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents.

Inventory, Policy [Policy Text Block]

Inventories

Investment, Policy [Policy Text Block]

Investments

Fair Value Measurement, Policy [Policy Text Block]

Fair value of financial instruments

Property, Plant and Equipment, Policy

Property and equipment

Property and equipment are carried at cost less accumulated depreciation. Depreciation is calculated utilizing the straight-line method over the estimated useful lives of the respective assets:



Lab equipment		5 years
Computer equipment		3 years
Leasehold improvements		Lesser of useful life or lease term
Software		3-5 years
Furniture and fixtures		5 years
Office equipment		5 years

Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]

Impairment of long-lived assets

Research and Development Expense, Policy [Policy Text Block]

Research and development expenses

Share-based Payment Arrangement [Policy Text Block]

Stock-based compensation expense

Income Tax, Policy [Policy Text Block]

Income taxes

Foreign Currency Transactions and Translations Policy [Policy Text Block]

Foreign currency translation

Comprehensive Income, Policy [Policy Text Block]

Comprehensive loss

Reclassification, Policy [Policy Text Block]

Reclassifications

New Accounting Pronouncements, Policy [Policy Text Block]

New accounting pronouncements

Recently issued accounting pronouncements

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Property, Plant and Equipment [Line Items]

Schedule of Property and Equipment Useful Lives [Table Text Block]

Property and equipment are carried at cost less accumulated depreciation. Depreciation is calculated utilizing the straight-line method over the estimated useful lives of the respective assets:



Lab equipment		5 years
Computer equipment		3 years
Leasehold improvements		Lesser of useful life or lease term
Software		3-5 years
Furniture and fixtures		5 years
Office equipment		5 years

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

The following potentially dilutive securities were excluded from the computation of diluted weighted average common shares outstanding due to their anti-dilutive effect:



	As of December 31,
	2019	2018
Vested and unvested stock options	4,428,985	3,130,700
Restricted stock units	125,000	—
Warrants	95,431	102,647
	4,649,416	3,233,347

Inventory (Tables)

12 Months Ended

Dec. 31, 2019

Inventory [Line Items]

Schedule of Inventory

The components of inventories consisted of the following (in thousands):



	December 31, 2019		December 31, 2018
Raw materials	$	1,321	$	—
Work in process	662		—
Finished goods	193		—
Inventory	$	2,176	$	—

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2019

Property and Equipment [Abstract]

Property, Plant and Equipment

Property and equipment consisted of the following:



(in thousands)	December 31, 2019			December 31, 2018

Lab equipment	$	2,528		$	1,658
Furniture and fixtures	1,611			541
Computer equipment	232			87
Office equipment	80			109
Software	347			110
Leasehold improvements	4,543			180
	9,341			2,685
Less: accumulated depreciation and amortization	(1,488		)	(651		)
Property and equipment, net	$	7,853		$	2,034

Other Accrued Liabilities (Tables)

12 Months Ended

Dec. 31, 2019

Accrued Expenses [Abstract]

Other Accrued Liabilities

Other accrued liabilities consisted of the following:



(in thousands)	December 31, 2019		December 31, 2018

Accrued research and development costs	$	7,062	$	2,221
Accrued employee costs	6,818		4,326
Accrued marketing and selling costs	1,973		—
Accrued interest expense	449		274
Accrued other costs	1,817		1,393
Other accrued liabilities	$	18,119	$	8,214

Long-Term Debt (Tables)

12 Months Ended

Dec. 31, 2019

Long-term Debt, Unclassified [Abstract]

Schedule of Long-term Debt Instruments

The components of debt are as follows:



(in thousands)	December 31, 2019			December 31, 2018

2018 Term A Loan	$	—		$	20,000
2018 Term B Loan	—			15,000
Term A Loan	60,000			—
Principal amount of long-term debt	60,000			35,000
Less: Unamortized deferred costs	(1,695		)	(3,110		)
Long-term debt	$	58,305		$	31,890

Schedule of Maturities of Long-term Debt

The following table sets forth the Company’s future minimum principal payments (in thousands):



2019	$	0
2020	0
2021	20,000
2022	26,700
2023	13,300
	$	60,000

- 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

Warrants (Tables)

12 Months Ended

Dec. 31, 2019

Warrants [Abstract]

Schedule of Stockholders' Equity Note, Warrants or Rights

As of December 31, 2019, the following warrants were outstanding:



	Outstanding Warrants	Exercise Price per Warrant	Expiration Date

2014 Warrants	1,419	$5.912	August 2020
Term A Warrants	53,720	$11.169	February 2025
Term B Warrants	40,292	$11.169	September 2025
	95,431

Commitments and Contingencies Future Minimum Lease Payments (Tables)

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Rental Payments for Operating Leases

Future minimum lease payments under operating leases at December 31, 2019 are as follows (in thousands):



2020	$	1,575
2021	2,208
2022	2,263
2023	1,745
2024	1,278
Thereafter	8,476
Total minimum lease payments	$	17,545

Stock Compensation Plan (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of Nonvested Restricted Stock Units Activity [Table Text Block]

Restricted stock unit ("RSU") awards for the year ended December 31, 2019 were as follows:



	Units
Unvested balance - January 1, 2019	0
Granted	125,000
Unvested balance - December 31, 2019	125,000

Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

The following table summarizes the reporting of total stock-based compensation expense resulting from stock options, restricted stock units and the employee stock purchase plan (in thousands):



	Years Ended December 31,
	2019		2018

Research and development	$	1,168	$	518
Selling, general and administrative	5,316		1,210
Total stock-based compensation expense	$	6,484	$	1,728

Share-based Payment Arrangement, Option [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock-based Compensation Assumptions Used in Black-Scholes Option Valuation Model

The fair value of stock options granted was estimated with the following weighted average assumptions:



	Years Ended December 31,
	2019		2018
Expected term (years)	6.0		6.0
Risk-free interest rate	2.14	%	2.48	%
Expected volatility	60.27	%	56.84	%
Expected dividends	—		—

Share-based Compensation, Activity

Stock option activity under the 2011 Plan, 2018 Plan and Inducement Plan for the year ended December 31, 2019 was as follows:



	OPTIONS	WEIGHTED AVERAGE EXERCISE PRICE		WEIGHTED AVERAGE CONTRACTUAL LIFE (YEARS)
Outstanding - January 1, 2019	3,130,700	$	8.06	8.69
Granted	1,600,650	12.21
Exercised and vested	(128,307)	1.99
Forfeited	(172,655)	16.33
Expired	(1,403)	19.77
Outstanding - December 31, 2019	4,428,985	$	9.40	8.19
Exercisable - December 31, 2019	1,647,911	$	6.07	7.31
Vested and expected to vest at December 31, 2019	4,202,205	$	9.32	8.16

Restricted stock units

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

The fair value of the ESPP Plan shares was estimated using the Black-Scholes option-pricing model with the following weighted-average assumptions:



	Year Ended December 31, 2019
Expected term (years)	0.5
Risk-free interest rate	1.85%
Expected volatility	70.70%
Expected dividends	—

Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements, Recurring and Nonrecurring

The following tables present the Company’s fair value hierarchy for those assets and liabilities measured at fair value as of December 31, 2019 and 2018 (in thousands):



	Total as of December 31, 2019		Level 1		Level 2		Level 3

Assets
Cash and cash equivalents:
Cash and money market funds	$	19,519	$	19,519	$	—	$	—

Investments:
U.S. government securities	32,175		32,175		—		—
Corporate securities	22,164		—		22,164		—
Commercial paper	14,922		—		14,922		—
Total investments	$	69,261	$	32,175	$	37,086	$	—

Liabilities
Warrant liabilities	$	150	$	—	$	—	$	150



	Total as of December 31, 2018		Level 1		Level 2		Level 3
Assets
Cash and cash equivalents:
Cash and money market funds	$	45,716	$	45,716	$	—	$	—

Investments:
U.S. government securities	38,737		38,737		—		—
Corporate securities	15,066		—		15,066		—
Agency securities	11,931		—		11,931		—
Commercial paper	1,183		1,183		—		—
Total investments	$	66,917	$	39,920	$	26,997	$	—

Liabilities
Warrant liabilities	$	860	$	—	$	—	$	860

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation




Balance at December 31, 2018	$	860
Exercise of warrants	(18		)
Change in fair value of warrants	(692		)
Balance at December 31, 2019	$	150

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Available-for-Sale Investments (Tables)

12 Months Ended

Dec. 31, 2019

Investments, Debt and Equity Securities [Abstract]

Debt Securities, Available-for-sale

The following table represents the Company’s available-for-sale investments by major security type as of December 31, 2019 and 2018 (in thousands):



	December 31, 2019
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Total Fair Value

Investments:
Commercial paper	$	14,922	$	—	$	—		$	14,922
Corporate securities	22,146		20		(2		)	22,164
U.S. government securities	32,152		23		—			32,175
Total available-for-sale investments	$	69,220	$	43	$	(2	)	$	69,261

	December 31, 2018
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Total Fair Value

Investments:
Agency securities	$	11,944	$	—	$	(13	)	$	11,931
Commercial paper	1,183		—		—			1,183
Corporate securities	15,081		—		(15		)	15,066
U.S. government securities	38,761		—		(24		)	38,737
Total available-for-sale investments	$	66,969	$	—	$	(52	)	$	66,917

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2019

Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

The following potentially dilutive securities were excluded from the computation of diluted weighted average common shares outstanding due to their anti-dilutive effect:



	As of December 31,
	2019	2018
Vested and unvested stock options	4,428,985	3,130,700
Restricted stock units	125,000	—
Warrants	95,431	102,647
	4,649,416	3,233,347

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

The following table summarizes the reporting of total stock-based compensation expense resulting from stock options, restricted stock units and the employee stock purchase plan (in thousands):



	Years Ended December 31,
	2019		2018

Research and development	$	1,168	$	518
Selling, general and administrative	5,316		1,210
Total stock-based compensation expense	$	6,484	$	1,728

Summary of Valuation Allowance [Table Text Block]

A reconciliation of the beginning and ending amounts of valuation allowances for the years ended December 31, 2019 and 2018 is as follows (in thousands):



Valuation allowance at December 31, 2017	$	(14,124	)
Increase for 2018 activity	(18,538		)
Valuation allowance at December 31, 2018	(32,662		)
Increase for 2019 activity	(36,288		)
Valuation allowance at December 31, 2019	$	(68,950	)

Schedule of Effective Income Tax Rate Reconciliation

A reconciliation of the expected income tax benefit computed using the federal statutory income tax rate of 21% to the Company’s effective income tax rate is as follows:



	Years Ended December 31,
(in thousands)	2019			2018
Federal tax benefit at statutory rate	$	(26,468	)	$	(12,617	)
State tax benefit, net of federal benefit	(5,570		)	(1,842		)
Research and development and orphan drug credits	(2,912		)	(2,279		)
Uncertain tax positions	342			603
Permanent adjustments to expenses	169			45
Stock-based compensation	683			76
Return to provision adjustment	(3,278		)	(2,470		)
Rate impact of deferred tax balance	—			(63		)
Statutory rate differential	(51		)	—
Other	339			9
Changes in valuation allowance	36,288			18,538
Total income tax benefit	$	(458	)	$	—

Schedule of Deferred Tax Assets and Liabilities

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



	December 31,
(in thousands)	2019			2018
Deferred tax assets:
Net operating losses	$	55,110		$	25,372
Federal research and orphan drug credits	8,309			5,426
Stock-based compensation	1,092			267
Other temporary differences	4,648			1,679
Valuation allowance	(68,950		)	(32,662		)
Total assets	209			82
Deferred tax liabilities:
Fixed and intangible assets	(155		)	(82		)
Other deferred tax liabilities	(54		)	—
Total liabilities	(209		)	(82		)
Net deferred tax assets	$	—		$	—

Income Taxes Uncertain Tax Positions (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Summary of Positions for which Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Table Text Block]



	December 31,
	2019		2018
Beginning balance - uncertain tax positions	$	603	$	—
Increases related to tax positions taken during the current year	246		228
Increases related to tax positions taken during the prior year	96		375
Ending balance - uncertain tax positions	$	945	$	603

Organization and Nature of the Business Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net sales	$ 1,627	$ 0
Accumulated deficit	$ 246,245	$ 120,665	$ 60,585

Summary of Significant Accounting Policies Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Concentration risk, number of major customers	3
Capitalized costs, public offering costs	$ 0.4	$ 0.0
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%
Lab equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Computer equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	Lesser of useful life or lease term
Software \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Software \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Office equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years

Summary of Significant Accounting Policies Summary of Accounting Policies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Concentration risk, number of major customers	3
Concentration Risk, Percentage of Gross Revenue	94.00%
Payments of public offering costs	$ 4,465	$ 0
Payments for Initial Public Offering Costs	0	9,422
Capitalized costs, public offering costs	$ 400	$ 0
Concentration Risk, Percentage of Accounts Receivable	97.00%

Inventory Components of Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Inventory [Line Items]
Raw materials	$ 1,321	$ 0
Work in process	662	0
Finished goods	193	0
Inventory	$ 2,176	$ 0

Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 9,341	$ 2,685
Less: accumulated depreciation and amortization	(1,488)	(651)
Property and equipment, net	7,853	2,034
Lab equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,528	1,658
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,611	541
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	232	87
Office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	80	109
Software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	347	110
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 4,543	$ 180

Property and Equipment Property and equipment details (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Depreciation Depletion and Amortization, not including asset impairments	$ 1,078,000	$ 320,000

Other Accrued Liabilities Other Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued Expenses [Abstract]
Accrued research and development costs	$ 7,062	$ 2,221
Accrued employee costs	6,818	4,326
Accrued marketing and selling costs	1,973	0
Accrued interest expense	449	274
Accrued other costs	1,817	1,393
Other accrued liabilities	$ 18,119	$ 8,214

Long-Term Debt Debt, Future Principal Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
Future principal payments, 2019	$ 0
Future principal payments, 2020	0
Future principal payments, 2021	20,000
Future principal payments, 2022	26,700
Future principal payments, 2023	13,300
Long-term Debt	$ 60,000	$ 35,000

Long-Term Debt Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Long-Term Debt Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2018
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 60,000	$ 35,000
Prepayment allowed per debt agreement	$ 2,000
Prepayment penalty percentage	1.50%
Final payment fee percentage	3.00%
Interest expense	$ (7,163)	(2,545)
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	(1,695)	(3,110)
Long-term Debt	58,305	31,890
Amortization of debt issuance costs	948	560
2018 Term A Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	0	20,000			$ 20,000
2018 Term B Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 0	15,000		$ 15,000
2018 Loan and Security Agreement [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					$ 45,000
Interest rate, thirty-day LIBOR plus stated percentage			8.84%
Debt Instrument, Interest Rate, Stated Percentage			6.75%
Debt Instrument, Payment Terms	P24M
Amended Loan and Security Agreement [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 85,000
Debt Instrument, Interest Rate, Stated Percentage	6.25%
Debt Instrument, Basis Spread on Variable Rate	2.43%
Interest rate, stated percentage plus greater of (a) 2.43% or (b) thirty-day LIBOR	8.68%
Term A Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 60,000	$ 0	60,000
Debt Issuance Costs, Gross	$ 1,900
Debt Instrument, Payment Terms	27
Term B Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			15,000
Debt Instrument, Payment Terms	30
Term C Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 10,000
Debt Instrument, Payment Terms	21
2018 Term A & B Loans [Member]
Debt Instrument [Line Items]
Debt Instrument, Fee	2.3

Public Stock Offerings Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
	Dec. 31, 2019	Mar. 31, 2019	Jun. 30, 2018	Feb. 14, 2020	Dec. 30, 2019	Aug. 06, 2019	Feb. 19, 2019	Dec. 31, 2018	Jun. 25, 2018
Reverse Stock Split and Initial Public Offering [Abstract]
Common Shares, Par Value Per Share	$ 0.0001							$ 0.0001
Common Shares, Shares, Issued	27,214,523			10,299,769	204,427		5,996,775	20,808,366	6,555,000
Shares Issued, Price Per Share				$ 4.15			$ 10.00		$ 15.00
Common shares issued, due to exercise of underwriter option				1,299,769			116,775		855,000
Net Proceeds from Issuance Initial Public Offering			$ 88.9
Shares of common stock issued, after preferred stock conversion			11,837,073
Net proceeds from issuance of public offering	$ 1.7	$ 55.5
Aggregate amount of common stock, available to sell under a shelf registration						$ 250.0
Aggregate amount of common stock, available to sell under at-the-market (ATM) offering						$ 50.0

Convertible Preferred Stock Narrative (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018 shares	Mar. 31, 2018 USD ($) shares	Jun. 30, 2018	Dec. 31, 2019 shares	Dec. 31, 2018 shares
Equity [Abstract]
Preferred Stock, Shares Issued		707,680		0	0
Proceeds from Issuance of Preferred Stock, Preference Stock, and Warrants \| $		$ 4.4
Shares of common stock issued, after preferred stock conversion	11,837,073
Reverse Stock Split, Conversion Ratio	1.78112
Preferred Stock, Dividend Rate, Percentage			8.00%

Warrants Schedule of Stockholders' Equity Note, Warrants or Rights (Details)	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Class of Warrant or Right [Line Items]
Outstanding warrants	95,431
2014 Warrants [Member]
Class of Warrant or Right [Line Items]
Outstanding warrants	1,419
Exercise Price Per Warrant \| $ / shares	$ 5.912
Warrants Expiration Date	Aug. 31, 2020
Term A Warrants [Member]
Class of Warrant or Right [Line Items]
Outstanding warrants	53,720
Exercise Price Per Warrant \| $ / shares	$ 11.169
Warrants Expiration Date	Feb. 28, 2025
Term B Warrants [Member]
Class of Warrant or Right [Line Items]
Outstanding warrants	40,292
Exercise Price Per Warrant \| $ / shares	$ 11.169
Warrants Expiration Date	Sep. 07, 2025

Warrants Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2014
Class of Warrant or Right [Line Items]
Outstanding warrants			95,431
Change in fair value of warrants			$ (692)	$ (196)
Term A Warrants [Member]
Class of Warrant or Right [Line Items]
Preferred stock and warrants issued during the period, shares		53,720
Exercise Price Per Warrant			$ 11.169
Class of warrants, exercised			0
Outstanding warrants			53,720
Change in fair value of warrants			$ 351	(108)
Term B Warrants [Member]
Class of Warrant or Right [Line Items]
Preferred stock and warrants issued during the period, shares	40,292
Exercise Price Per Warrant			$ 11.169
Class of warrants, exercised			0
Outstanding warrants			40,292
Change in fair value of warrants			$ 263	360
2014 Warrants [Member]
Class of Warrant or Right [Line Items]
Preferred stock and warrants issued during the period, shares					19,931
Exercise Price Per Warrant			$ 5.912
Class of warrants, exercised			18,512
Outstanding warrants			1,419
Change in fair value of warrants			$ 78	$ (56)

Commitments and Contingencies Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Remaining future minimum lease payments, 2019	$ 1,575,000
Remaining future minimum lease payments, 2020	2,208,000
Remaining future minimum lease payments, 2021	2,263,000
Remaining future minimum lease payments, 2022	1,745,000
Remaining future minimum lease payments, 2023	1,278,000
Remaining future minimum lease payments, thereafter	8,476,000
Total minimum lease payments	17,545,000
Rent Expense, operating leases	2,200,000	$ 1,300,000
Letters of Credit Outstanding, Amount	$ 1,083,000

Stock Compensation Plan Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Method Used (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	6 years	6 years
Risk-free interest rate	2.14%	2.48%
Expected volatility	60.27%	56.84%
Expected dividends	0.00%	0.00%
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	5 months 20 days
Risk-free interest rate	1.85%
Expected volatility	70.70%
Expected dividends	0.00%

Stock Compensation Plan Employee Stock Award Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	4,428,985	3,130,700
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 9.40	$ 8.06
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	8 years 69 days	8 years 252 days
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period	1,600,650
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 12.21
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	(128,307)
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	$ 1.99
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Number of Shares	(172,655)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price	$ 16.33
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period	(1,403)
Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price	$ 19.77
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	1,647,911
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 6.07
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	7 years 113 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	4,202,205
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 9.32
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term	8 years 58 days
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.14%	2.48%

Stock Compensation Plan Narrative (Details) - USD ($)	12 Months Ended
Stock Compensation Plan Narrative (Details) - USD ($)	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Least amount of annual increase of shares available for issuance	386,000
Stock Issued During Period, Shares, Employee Stock Purchase Plans	73,607
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Weighted Average Grant Date Fair Value	$ 6.97
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 1,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value	7,800,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 14,100,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	2 years 120 days
Non--employee stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	2 years
2011 Stock Option Issuance Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized					4,714,982
2018 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized				1,822,000
Percentage shares available for issuance automatically increase annually	4.00%
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	835,728
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	809,000
Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized			193,000
Maximum employee payroll deduction percentage	15.00%
Common stock value, tax limit on employee stock purchase plan	$ 25,000
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent	85.00%
Percentage shares available for issuance automatically increase annually	1.00%
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	208,932
Stock Issued During Period, Shares, Employee Stock Purchase Plans	73,607
Employee Stock Ownership Plan (ESOP), Weighted Average Purchase Price of Shares Purchased	$ 7.22
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	328,000
Equity Inducement Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized		750,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	340,000

Stock Compensation Plan Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 6,484	$ 1,728
Research and development expense
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	1,168	518
Selling, General and Administrative Expenses [Member]
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 5,316	$ 1,210

Stock Compensation Plan Restricted stock units, activity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	4,428,985	3,130,700
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period	1,600,650
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.85%
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 1.3
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	3 years 50 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	125,000	0
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period	125,000

Fair Value Measurement Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and money market funds	$ 19,519	$ 45,716
Investments	69,261	66,917
Other current liabilities	150	860
Exercise of warrants	(18)
Change in fair value of warrants	692	196
Term A Warrants [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value of warrants	(351)	108
Term B Warrants [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value of warrants	(263)	(360)
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and money market funds	19,519	45,716
Investments	32,175	39,920
Other current liabilities	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and money market funds	0	0
Investments	37,086	26,997
Other current liabilities	0	0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and money market funds	0	0
Investments	0	0
Other current liabilities	150	860
U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	32,175	38,737
U.S. government securities \| Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	32,175	38,737
U.S. government securities \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
U.S. government securities \| Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Corporate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	22,164	15,066
Corporate securities \| Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Corporate securities \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	22,164	15,066
Corporate securities \| Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		11,931
Agency securities \| Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		0
Agency securities \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		11,931
Agency securities \| Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		0
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	14,922	1,183
Commercial paper \| Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	1,183
Commercial paper \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	14,922	0
Commercial paper \| Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	$ 0	$ 0

Available-for-Sale Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Available For Sale Securities Maturities Period	255 days
Amortized Cost	$ 69,220	$ 66,969
Gross Unrealized Gains	43	0
Gross Unrealized Losses	(2)	(52)
Investments	69,261	66,917
Agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		11,944
Gross Unrealized Gains		0
Gross Unrealized Losses		(13)
Investments		11,931
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	14,922	1,183
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Investments	14,922	1,183
Corporate securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	22,146	15,081
Gross Unrealized Gains	20	0
Gross Unrealized Losses	(2)	(15)
Investments	22,164	15,066
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	32,152	38,761
Gross Unrealized Gains	23	0
Gross Unrealized Losses	0	(24)
Investments	$ 32,175	$ 38,737

Net Loss Per Share Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	4,649,416	3,233,347
Vested and unvested stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	4,428,985	3,130,700
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	125,000	0
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	95,431	102,647

Defined Contribution Plan Defined Contribution Plan (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Retirement Benefits [Abstract]
Defined Contribution Plan, Matching Contributions	$ 0.4

Income Taxes (Details) - USD ($)	12 Months Ended
Income Taxes (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Valuation Allowance [Line Items]
Operating Loss Carryforwards	$ 215,300,000	$ 108,800,000
Effective Income Tax Rate Reconciliation, Deduction, Percent	80.00%
Federal research income tax credits, gross of valuation allowance	$ 8,300,000	5,800,000
State research income tax credits, gross of valuation allowance	1,000,000	2,000,000
Operating loss carryforwards, various states	147,500,000	35,600,000
Federal tax benefit at statutory rate	(26,468,000)	(12,617,000)
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	(5,570,000)	(1,842,000)
Unrecognized Tax Benefits	$ 945,000	603,000	$ 0
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%
Unrecognized Tax Benefits, Period Increase (Decrease)	$ 246,000	228,000
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions	96,000	375,000
Net operating losses	55,110,000	25,372,000
Deferred Tax Assets, Tax Credit Carryforwards, Research	8,309,000	5,426,000
Stock compensation	1,092,000	267,000
Other temporary differences	4,648,000	1,679,000
Valuation allowance	(68,950,000)	(32,662,000)	$ (14,124,000)
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	(36,288,000)	(18,538,000)
Total deferred tax assets	209,000	82,000
Fixed and intangible assets	(155,000)	(82,000)
Deferred Tax Liabilities, Other	(54,000)	0
Total deferred tax liabilities	(209,000)	(82,000)
Net deferred tax assets	0	0
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	36,288,000	18,538,000
Benefit from income taxes	(458,000)	0
Income Tax Examination, Penalties and Interest Expense	0
Effective Income Tax Rate Reconciliation, Tax Credit, Research, Amount	(2,912,000)	(2,279,000)
Unrecognized Tax Benefits, Decrease Resulting from Current Period Tax Positions	342,000	603,000
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	169,000	45,000
Effective Income Tax Rate Reconciliation, Tax Expense (Benefit), Share-based Payment Arrangement, Amount	683,000	76,000
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Amount	(3,278,000)	(2,470,000)
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	0	(63,000)
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount	$ 339,000	$ 9,000

Subsequent Events (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
Subsequent Events (Details) - USD ($)	Feb. 29, 2020	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Feb. 14, 2020	Dec. 30, 2019	Feb. 19, 2019	Jun. 25, 2018
Subsequent Event [Line Items]
Proceeds from public offerings	$ 42,700,000		$ 61,692,000	$ 0
Net Proceeds from Issuance Initial Public Offering		$ 88,900,000
Common Shares, Shares, Issued			27,214,523	20,808,366	10,299,769	204,427	5,996,775	6,555,000
Shares Issued, Price Per Share					$ 4.15		$ 10.00	$ 15.00
Common shares issued, due to exercise of underwriter option					1,299,769		116,775	855,000
Maximum common shares issued under underwriter option					1,350,000