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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, 2018	Feb. 28, 2019	Jun. 30, 2018
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	Non-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, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Amendment Flag	false
Trading Symbol	XERS
Entity Common Stock, Shares Outstanding		26,809,851
Entity Listing, Par Value Per Share	$ 0.0001
Entity Public Float			$ 281.9

Condensed Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents	$ 45,716	$ 42,045
Short-term Investments	66,917	0
Accounts receivable, net	2,869	1,199
Prepaid expenses and other current assets	2,397	809
Total current assets	117,899	44,053
Property and equipment, net	2,034	788
Other assets	95	157
Total assets	120,028	44,998
Current Liabilities
Accounts payable	866	1,976
Accrued expenses	8,214	2,557
Warrants liabilities	860	93
Deferred grant awards	232	234
Total current liabilities	10,172	4,860
Long-term debt, net of unamortized deferred costs	31,890	0
Other long-term liabilities	2,560	90
Total liabilities	44,622	4,950
Commitments and contingencies (Note 9)
Convertible preferred stock
Series A Convertible Preferred Stock, par value $0.0001	0	1,945
Series B Convertible Preferred Stock, par value $0.0001	0	18,536
Series C Convertible Preferred Stock, par value $0.0001	0	77,397
Total convertible preferred stock	0	97,878
Stockholders' Equity (Deficit)
Preferred Stock, par value $0.0001	0	0
Common stock, par value $0.0001	2	1
Additional paid in capital	196,121	2,754
Accumulated deficit	(120,665)	(60,585)
Accumulated other comprehensive loss	(52)	0
Total stockholders' equity (deficit)	75,406	(57,830)
Total liabilities, convertible preferred stock and stockholders' equity (deficit)	$ 120,028	$ 44,998

Condensed Balance Sheets Parenthetical - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
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	0
Common Stock, Shares Authorized	150,000,000	30,450,994
Preferred Stock, Shares Issued	0	0
Common Shares, Shares, Issued	20,808,366	2,159,068
Preferred Stock, Series A
Class of Stock [Line Items]
Preferred Stock, Par Value Per Share		$ 0.0001
Preferred Stock, Shares Authorized		1,864,797
Preferred Stock, Shares Issued	0	1,843,965
Preferred Stock, Series B
Class of Stock [Line Items]
Preferred Stock, Par Value Per Share		$ 0.0001
Preferred Stock, Shares Authorized		5,732,338
Preferred Stock, Shares Issued	0	5,696,834
Preferred Stock, Series C
Class of Stock [Line Items]
Preferred Stock, Par Value Per Share		$ 0.0001
Preferred Stock, Shares Authorized		14,353,859
Preferred Stock, Shares Issued	0	12,834,912

Condensed Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Grant income	$ 2,365	$ 1,540
Service revenue	100	16
Cost of revenue	42	4
Gross Profit	2,423	1,552
Operating expenses
Research and development	40,654	20,166
Selling, general and administrative	21,113	8,015
Expense from operations	61,767	28,181
Loss from operations	(59,344)	(26,629)
Other income (expense)
Interest income	1,613	124
Interest expense	(2,545)	(2)
Change in fair value of warrants	196	46
Other expense	0	(1)
Other income (expense)	(736)	75
Net loss	(60,080)	(26,554)
Other comprehensive loss, net of tax
Unrealized losses on short-term investments	(52)	0
Comprehensive loss	$ (60,132)	$ (26,554)
Net loss per common share - basic and diluted	$ (4.99)	$ (13.09)
Weighted average common shares outstanding, basic and diluted	12,045,999	2,028,224

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]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred Stock, Shares Issued		1,843,965	5,696,834	7,177,398
Series A Convertible Preferred Stock, par value $0.0001		$ 1,945
Series B Convertible Preferred Stock, par value $0.0001			$ 18,536
Series C Convertible Preferred Stock, par value $0.0001				$ 42,417
Common Shares, Shares, Issued					1,927,237
Common stock, par value $0.0001					$ 1
Additional paid in capital						$ 2,096
Accumulated deficit	$ (34,031)
Stockholders' Equity Attributable to Parent	(31,934)
Net loss	(26,554)
Stock Issued During Period, Shares, New Issues				5,657,514
Issuance of Series C Preferred Stock				$ 34,980
Exercise and vesting of stock-based awards					231,831
Adjustments to Additional Paid in Capital, Exercise and Vesting of Stock-Based Awards	159					159
Stock-based compensation	499					499
Other comprehensive loss	$ 0
Preferred Stock, Shares Issued	0	1,843,965	5,696,834	12,834,912
Series A Convertible Preferred Stock, par value $0.0001	$ 1,945	$ 1,945
Series B Convertible Preferred Stock, par value $0.0001	18,536		$ 18,536
Series C Convertible Preferred Stock, par value $0.0001	$ 77,397			$ 77,397
Common Shares, Shares, Issued	2,159,068				2,159,068
Common stock, par value $0.0001	$ 1				$ 1
Additional paid in capital	2,754					2,754
Accumulated other comprehensive 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
Issuance of Series C Preferred Stock				$ 4,414
Stock Issued During Period, Value, New Issues	88,903					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
Other comprehensive loss	$ (52)
Preferred Stock, Shares Issued	0	0	0	0
Series A Convertible Preferred Stock, par value $0.0001	$ 0	$ 0
Series B Convertible Preferred Stock, par value $0.0001	0		$ 0
Series C Convertible Preferred Stock, par value $0.0001	$ 0			$ 0
Common Shares, Shares, Issued	20,808,366				20,808,366
Common stock, par value $0.0001	$ 2				$ 2
Additional paid in capital	196,121					$ 196,121
Accumulated other comprehensive loss	(52)
Accumulated deficit	(120,665)
Stockholders' Equity Attributable to Parent	$ 75,406

Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) Parenthetical - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Statement of Convertible Preferred Stock and Stockholders' Equity (Deficit) [Abstract]
Payments of Stock Issuance Costs	$ (24)	$ (495)
Payments for Initial Public Offering Costs	$ (9,422)	$ 0

Statement of Cash Flows - USD ($)	12 Months Ended
Statement of Cash Flows - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net loss	$ (60,080,000)	$ (26,554,000)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	320,000	225,000
Amortization of short-term investments	(218,000)	0
Amortization of debt issuance costs	560,000	0
Stock-based compensation	1,728,000	499,000
Change in fair value of warrants	(196,000)	(46,000)
Changes in operating assets and liabilities
Accounts receivable	(1,670,000)	(1,098,000)
Prepaid expenses and other current assets	(1,588,000)	(5,000)
Other assets	62,000	(111,000)
Accounts payable	(1,110,000)	661,000
Accrued expenses	5,630,000	1,703,000
Deferred grant awards	(2,000)	(29,000)
Deferred rent	285,000	0
Net cash used in operating activities	(56,279,000)	(24,663,000)
Cash flows from investing activities
Purchases of property and equipment	(1,510,000)	(700,000)
Purchases of short-term investments	(68,851,000)	0
Sales and maturities of short-term investments	2,100,000	0
Net cash used in investing activities	(68,261,000)	(700,000)
Cash flows from financing activities
Proceeds from Initial Public Offering	98,325,000	0
Payments for Initial Public Offering Costs	(9,422,000)	0
Proceeds from sale of Series C Preferred Stock	4,438,000	35,475,000
Payments of Stock Issuance Costs	(24,000)	(495,000)
Proceeds from issuance of long-term debt	35,000,000	0
Payments of debt issuance costs	(333,000)	0
Proceeds from exercise of stock awards	227,000	159,000
Net cash provided by financing activities	128,211,000	35,139,000
Increase in cash and cash equivalents	3,671,000	9,776,000
Cash and cash equivalents, beginning of period	42,045,000	32,269,000
Cash and cash equivalents, end of period	45,716,000	42,045,000
Supplemental schedule of cash flow information
Cash paid for interest	1,711,000	2,000
Supplemental schedule of non-cash investing and financing activities
Allocation of debt proceeds to warrants	1,012,000	0
Accrued debt issuance costs	2,325,000	0
Vesting of early exercised awards	$ 169,000	$ 0

Organization and Nature of the Business	12 Months Ended
Organization and Nature of the Business	Dec. 31, 2018
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. Basis of presentation The financial statements are prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). Since its inception, the Company has devoted substantially all of its efforts to research and development, regulatory and technical activities. The Company has financed its operations through the issuance of common stock in its June 2018 initial public offering ("IPO"), issuance of convertible preferred stock and other equity instruments, issuance of debt, and grant funding from the National Institutes of Health ("NIH") and other philanthropic organizations. The Company has not generated any revenue from product sales. The Company has incurred operating losses since inception and has an accumulated deficit of $120.7 million as of December 31, 2018. The Company expects to continue to incur net losses for the next several years. Based on the Company’s current operating plans and existing working capital at December 31, 2018, 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.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

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 Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“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, contingent liabilities and expenses included in the financial statements and accompanying notes. Actual results could differ from those estimates.

Grant income

The Company has received several grants from the NIH and other philanthropic organizations for certain research and development projects the Company 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 also has grants where cash is received upfront. The Company defers the recognition of these awards until the research and development expenses are incurred.

Revenue

The Company recognizes revenue when persuasive evidence of an arrangement exists, the related services have been performed, the price is fixed and determinable and collectability is reasonably assured. The Company generates revenue through the performance of research and development activities on behalf of others.

Segment reporting

Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker in making decisions regarding resource allocation and assessing performance. The Company’s chief executive officer uses summary financial information in determining how to allocate resources and assess performance. The Company has determined that it operates in one segment and all of the Company’s assets are located 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.

Concentrations of risk

The Company has no off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements. Bank deposits are held by financial institutions, and these deposits may exceed insured limits. The Company is exposed to credit risk in the event of default by the financial institution holding our cash and cash equivalents and issuers of investments that are recorded on our balance sheets. The Company mitigates its risk by investing in high-grade instruments and limiting the concentration in any one issuer, which limits exposure.

The Company is dependent on several key suppliers and third-party manufacturers. A failure or disruption by one of the Company’s key suppliers or third-party manufacturers may have a material impact to its planned operations.

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.

Short-term investments

The Company classifies its debt securities as short-term investments and available-for-sale securities. These short-term investments are classified as short-term on the balance sheets as they 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 us to record an impairment charge in the period any such determination is made. The Company considers factors such as the duration, severity and the 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 Loan and Security 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 short-term 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 impairment charges of $0 and $48,000 for the years ended December 31, 2018 and 2017, respectively. The impairment charge in 2017 was related to equipment that is no longer used in the Company’s manufacturing of the Gvoke HypoPen due to process and formulation improvements.

Deferred rent

Certain of the Company’s lease agreements provide for scheduled rent increases during the lease term and for rental payments commencing at a date after the initial occupancy date. Provisions are made for the excess of operating lease rentals, computed on a straight-line basis throughout the lease term, over cash rentals paid.

Debt issuance costs

Long-term debt is accounted for at amortized cost. 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.

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 or the services are performed.

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 to employees, including grants of employee stock options, 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, risk-free interest rates and expected dividend yields of the common stock. The Company recognizes stock-based compensation expense, net of estimated forfeitures, equal to the grant date fair value of stock options on a straight-line basis over the requisite service period. Restricted stock awards are valued based on the fair market value of the Company’s common stock on the date they were granted. Restricted stock that vests and stock options that are authorized are issued out of authorized available shares.

The Company accounts for stock-based awards issued to non-employees based on the grant date fair value of such awards and recognizes compensation expense as the services are completed over the vesting period of the award.

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, 2018 and 2017, the Company did not accrue any interest or penalties on uncertain tax positions.

Impacts of the Tax Cuts and Jobs Act

On December 22, 2017, the Tax Cuts and Jobs Act (H.R. 1) (the “Tax Act”) was signed into law. The Tax Act contains significant changes to corporate taxation, including (i) the reduction of the corporate income tax rate to 21%, (ii) the acceleration of expensing for certain business assets, (iii) the one-time transition tax related to the transition of U.S. international tax from a worldwide tax system to a territorial tax system, (iv) the repeal of the domestic production deduction, (v) additional limitations on the deductibility of interest expense, and (vi) expanded limitations on executive compensation. On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 ("SAB 118"), which provides guidance on accounting for the tax effects of the Tax Act. SAB 118 provided a measurement period that should not extend beyond one year from the date of enactment for companies to complete the accounting under ASC 740, Income Taxes. The key impacts of the Tax Act on the Company’s financial statements for the year ended December 31, 2017 were the remeasurement of deferred tax balances to the new corporate tax rate. The provisional amount determined, and recorded as of December 31, 2017, for the remeasurement of its deferred tax balances resulted in a net reduction in deferred tax assets of $7.5 million and a corresponding reduction in the valuation allowance of $7.5 million.

The SAB 118 measurement period ended as of December 22, 2018. The Company has obtained, prepared and analyzed the information needed to complete the accounting requirements under ASC 740. There were no material changes to the provisional amounts recorded as of December 31, 2018.

Equity financing costs

The Company capitalizes costs that are directly associated with in-process equity financings until such financings are consummated, at which time such costs are recorded in the additional paid in capital line on the balance sheet against the gross proceeds of the equity financings. The Company recognized $9.4 million of direct costs associated with the IPO in additional paid in capital for the year ended December 31, 2018. As of December 31, 2018 and 2017, the Company did not have any deferred costs related to in-process equity financings.

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 the preferred stock, warrants, and stock awards 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 (shown below in common stock equivalent shares) were excluded from the computation of diluted weighted average common shares outstanding due to their anti-dilutive effect:



	December 31,
	2018	2017
Convertible preferred stock	—	11,439,752
Vested and unvested stock options	3,130,700	1,979,306
Warrants	102,647	19,931
	3,233,347	13,438,989

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. Other comprehensive loss includes net loss and unrealized losses on debt securities classified as available-for-sale investments.

New accounting pronouncements

Recently adopted accounting pronouncements

In March 2016, the FASB issued ASU 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share Based Payment Accounting (“ASU 2016-09”), as part of the FASB simplification initiative. The new standard provides for changes to accounting for stock compensation including 1) excess tax benefits and tax deficiencies related to share-based payment awards being recognized as income tax expense in the reporting period in which they occur; 2) excess tax benefits being classified as an operating activity in the statement of cash flow; 3) the option to elect to estimate forfeitures or account for them when they occur; and 4) increased tax withholding requirements threshold to qualify for equity classification. As an emerging growth company, ASU 2016-09 was effective for the Company starting with the quarter ending March, 31, 2018. Early adoption was permitted. The Company adopted this standard on January 1, 2018, and it did not have an impact on the financial statements.

Recently issued accounting pronouncements

In February 2016, the FASB issued ASU, No. 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 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. As an emerging growth company, ASU 2016-02 will be effective for the Company starting with the quarter ending March 31, 2020. Early adoption is permitted. 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 to report assets and liabilities related to these leases on the financial statements that have not been previously reported once adopted.

Property and Equipment (Notes)

12 Months Ended

Dec. 31, 2018

Property and Equipment [Abstract]

Property, Plant and Equipment

Property and Equipment

Property and equipment consisted of the following:



(in thousands)	December 31, 2018			December 31, 2017

Lab equipment	$	1,658		$	860
Furniture and fixtures	541			128
Computer equipment	87			100
Office equipment	109			78
Software	110			52
Leasehold improvements	180			10
	2,685			1,228
Less: accumulated depreciation and amortization	(651		)	(440		)
Property and equipment, net	$	2,034		$	788

Depreciation and amortization expense relating to property and equipment was $320,000 and $177,000 for the years ended December 31, 2018 and 2017, respectively.

Accrued Expenses (Notes)

12 Months Ended

Dec. 31, 2018

Accrued Expenses [Abstract]

Accrued Expenses

Accrued expenses consisted of the following:



(in thousands)	December 31, 2018		December 31, 2017

Accrued employee costs	$	4,326	$	1,581
Accrued research and development costs	2,221		566
Accrued other costs	1,667		410
Accrued expenses	$	8,214	$	2,557

Long-Term Debt

12 Months Ended

Dec. 31, 2018

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 that provides 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 ("Term A Loan"). The second tranche was $15.0 million and was drawn down in September 2018 ("Term B Loan"). The third tranche is $10.0 million and is available beginning upon approval of the Company’s Gvoke HypoPen New Drug Application ("NDA") by the U.S. Food & Drug Administration (”FDA”) until the earlier of September 30, 2019 or the 30^th day following NDA approval by the FDA.

The interest rate under the Loan and Security Agreement is the thirty-day U.S. LIBOR rate plus 6.75%, which was approximately 9.10% as of December 31, 2018. Payments on the Loan and Security Agreement are interest only for the first 24 months, which can be extended by an additional twelve months if the third tranche is drawn. The total term of the loan is fifty-nine months, and the principal payments will begin in 24 months from the beginning of the term or, should the third tranche be drawn, 36 months from the beginning of the term.

Pursuant to the Loan and Security Agreement, the Company provided a first priority security interest in all existing and future-acquired assets, excluding intellectual property and certain other assets, owned by the Company. The Loan and Security Agreement contains a negative pledge on intellectual property owned by the Company. The Company also issued warrants to the Lenders to purchase common stock, which is further discussed in Note 8, "Warrants", of the notes to financial statements.

The Loan and Security 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, 2020, the Company is subject to a prepayment penalty equal to 1.50% of the principal amount being prepaid. In the event the Company draws down the third tranche, the period subject to the 1.50% prepayment penalty is extended to April 1, 2021. No prepayment fee exists for prepayments made after April 1, 2020, or April 1, 2021 in the event the third tranche is issued. A final payment fee of 6.5% multiplied by the original principal amount of each tranche drawn is due upon the earlier to occur of the maturity date of the Loan and Security Agreement, the acceleration of the Loan and Security Agreement or prepayment of such borrowings. The Loan and Security Agreement includes a non-utilization fee of 2.0% multiplied by the principal amount of tranche three payable to Lenders in October 2019, if the Company elects not to draw the third tranche.

The Loan and Security Agreement also contains customary indemnification obligations and customary events of default, including, among other things, failure to fulfill certain obligations under the Loan and Security Agreement and the occurrence of a material adverse change in the Company's business, operations or condition, a material impairment of the prospect of repayment of any portion of the loan, or a material impairment in the perfection or priority of the Lenders’ lien in the collateral or in the value of such collateral. In the event of default under the Loan and Security Agreement, the Company would be required to pay interest on principal and all other due and unpaid obligations at the current rate in effect plus 5%. All such interest would be payable on demand and in cash. Further, the Lenders would be entitled to exercise their remedies thereunder, including the right to accelerate the debt, upon which the Company may be required to repay all amounts then outstanding under the Loan and Security Agreement.

The Loan and Security Agreement includes certain restrictions on, among other things, the Company’s ability to incur additional indebtedness, change the name or location of the business, merge with or acquire other entities, pay dividends or make other distributions to holders of the Company’s capital stock, make certain investments, engage in transactions with affiliates, create liens, open new deposit accounts, sell assets or pay subordinated debt.

The components of debt are as follows:



(in thousands)	December 31, 2018			December 31, 2017

Term A Loan	$	20,000		$	—
Term B Loan	15,000			—
Less unamortized deferred costs	(3,110		)	—
Long-term debt	$	31,890		$	—

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



2018	$	—
2019	—
2020	9,000
2021	12,000
2022	12,000
2023	2,000
	$	35,000

The Company incurred total debt issuance costs of $3.7 million, 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. For the years 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.

Reverse Stock Split and Initial Public Offering

12 Months Ended

Dec. 31, 2018

Reverse Stock Split and Initial Public Offering [Abstract]

Reverse Stock Split and Initial Public Offering

On June 8, 2018, the Company effectuated a 1-for-1.78112 reverse stock split of its outstanding common stock, which was approved by the Company’s board of directors on May 22, 2018 and by the Company’s stockholders on June 8, 2018. The reverse stock split resulted in an adjustment to the preferred stock conversion prices to reflect a proportional decrease in the number of shares of common stock to be issued upon conversion. The accompanying financial statements and notes to financial statements give retroactive effect to the reverse stock split for all periods presented. The shares of common stock retained a par value of $0.0001 per share. Accordingly, the stockholders’ equity (deficit) reflects the reverse stock split by reclassifying from common stock to additional paid in capital an amount equal to the par value of the decreased shares resulting from the reverse stock split.

On June 25, 2018, the Company closed the 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 a public offering 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 offering were $88.9 million after deducting underwriting discounts and commissions as well as other offering 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.

Warrants

In 2014 the Company issued 19,931 warrants (“2014 Warrants”) to certain investors. The 2014 Warrants allow each holder to purchase one share of common stock for $5.912. There have been 11,296 2014 Warrants exercised, and 8,635 warrants remain outstanding as of December 31, 2018.

As part of the Loan and Security Agreement discussed in Note 5, "Long-term Debt", in the notes to financial statements, the Lenders receive warrants equal to 3.0% of the principal borrowing amounts 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 ("Term A Warrants") upon the drawdown of the Term A Loan in February 2018, and the Company issued 40,292 warrants ("Term B Warrants") upon the drawdown of the 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, 2018, respectively.

Because the warrants are a freestanding instrument, indexed to the Company's stock, they do not meet the criteria for equity classification. Therefore, warrants are liability classified and subject to remeasurement at each reporting period until they are exercised, expired, or otherwise settled. The initial fair value of the warrant liability is recorded with a corresponding offset to deferred debt costs which is a reduction to the notional value of the debt.

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. The Company recognized a loss of $(46,000) upon the change in fair value of the 2014 Warrants during the year ended December 31, 2017.

As of December 31, 2018, the following warrants were outstanding:



	Outstanding Warrants	Exercise Price per Warrant	Expiration Date

2014 Warrants	8,635	$5.912	August 2020
Term A Warrants	53,720	$11.169	February 2025
Term B Warrants	40,292	$11.169	September 2025
	102,647

Convertible Preferred Stock	12 Months Ended
Convertible Preferred Stock	Dec. 31, 2018
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. No such dividends were declared by the Company’s 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, 2018

Warrants [Abstract]

Warrants

Reverse Stock Split and Initial Public Offering

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.

Warrants

As of December 31, 2018, the following warrants were outstanding:



	Outstanding Warrants	Exercise Price per Warrant	Expiration Date

2014 Warrants	8,635	$5.912	August 2020
Term A Warrants	53,720	$11.169	February 2025
Term B Warrants	40,292	$11.169	September 2025
	102,647

Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

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 new lease for office space in Chicago, Illinois. In the fourth quarter of 2018, the Company signed an amendment to this lease to occupy additional space and expects to relocate from its existing premises to this additional space in March 2019.

Future minimum lease payments under operating leases at December 31, 2018 are as follows:



(in thousands)
2019	$	891
2020	1,580
2021	2,218
2022	2,273
2023	1,756
Thereafter	9,848
Total minimum lease payments	$	18,566

Total rent expense under these operating leases was approximately $1.3 million and $0.5 million for the years ended December 31, 2018 and 2017, respectively.

As of December 31, 2018, we had unused letters of credit of $143,000 that are used 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, 2018, 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, 2018

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

Stock Compensation Plan

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

The 2018 Stock Option and Incentive Plan ("2018 Plan") was adopted by our Board of Directors in April 2018 and approved by our stockholders in June 2018 to award up to 1,822,000 shares of our 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 our Board of Directors determined not to make additional awards under the 2011 Plan following the closing of our IPO, which occurred in June 2018. The 2018 Plan allows the compensation committee to make equity-based and cash-based incentive awards to our officers, employees, directors and other key persons (including consultants). As of December 31, 2018, there were 1,120,937 awards available for future issuance.

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 years 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 life 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 option exercises and 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,
	2018		2017
Expected term (years)	6.0		6.1
Risk-free interest rate	2.48	%	2.06	%
Expected volatility	56.84	%	61.10	%
Expected dividends	—		—

Stock option activity for employee awards for the year ended December 31, 2018 was as follows:



	UNITS	WEIGHTED AVERAGE EXERCISE PRICE		WEIGHTED AVERAGE CONTRACTUAL LIFE (YEARS)
Outstanding - January 1, 2018	1,946,230	$	1.66	8.70
Issued	1,604,804	14.14
Exercised	(225,986)	1.46
Forfeited	(197,740)	1.89
Outstanding - December 31, 2018	3,127,308	$	8.06	8.69
Exercisable - December 31, 2018	2,329,151	$	4.44	8.67
Vested and expected to vest at December 31, 2018	2,939,669	$	8.00	7.74

The weighted average fair value of awards granted during the year ended December 31, 2018 was $8.17 per share. The total intrinsic value of options exercised during the year ended December 31, 2018 was $2.4 million. The aggregate intrinsic value of awards vested and expected to vest as of December 31, 2018 was $28.3 million.

The Company also granted stock options to non-employees. These awards are marked to fair value at the end of each reporting period until they vest. Stock option activity for these awards for the year ended December 31, 2018 was as follows:



	UNITS	WEIGHTED AVERAGE EXERCISE PRICE		WEIGHTED AVERAGE CONTRACTUAL LIFE (YEARS)
Outstanding - January 1, 2018	33,125	$	1.91	6.75
Issued	0	—
Exercised	(22,996)	2.16
Forfeited	(6,737)	0.82
Outstanding - December 31, 2018	3,392	$	1.55	2.00
Exercisable - December 31, 2018	0	$	0.00	0.00
Vested and expected to vest at December 31, 2018	3,392	$	1.55	2.00

The aggregate intrinsic value of awards vested and expected to vest at December 31, 2018 was $52,000. The aggregate intrinsic value of awards exercisable as of December 31, 2018 was $0. The company recognized expense associated with these awards of $114,000 and $35,000 for the years ended December 31, 2018 and 2017, respectively.

The following table summarizes the reporting of total stock-based compensation expense resulting from employee and non-employee stock options:



	Years Ended December 31,
(in thousands)	2018		2017

Research and development	$	518	$	62
Selling, general and administrative	1,210		437
Total stock-based compensation expense	$	1,728	$	499

At December 31, 2018, there was a total of $7.3 million of unrecognized compensation expense that is expected to be recognized over a weighted average period of 1.83 years.

Fair Value Measurement

12 Months Ended

Dec. 31, 2018

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 required 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, 2018 and 2017:



(in thousands)	Total as of December 31, 2018		Level 1		Level 2		Level 3

Current Assets
Cash and cash equivalents:
Money market funds	$	45,716	$	45,716	$	—	$	—

Short-term 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 short-term investments	$	66,917	$	39,920	$	26,997	$	—

Other Current Liabilities
Warrant liabilities	$	860	$	—	$	—	$	860



(in thousands)	Total as of December 31, 2017		Level 1		Level 2		Level 3
Current Assets
Money market funds ^(a)	$	39,124	$	39,124	$	—	$	—

Other current liabilities
Warrant liabilities	$	93	$	—	$	—	$	93

(a) The money market funds noted above are included in cash and cash equivalents.

There were no investments in commercial paper or short-term investments as of December 31, 2017.

The fair value of the Company’s warrant liabilities at inception and for subsequent mark-to-market fair value measurements is based on management’s valuation model and expected methods and timing of settlement. These estimates are prepared using models that consider various inputs including: (a) the Company’s estimated future cash flows, (b) time value, (c) current market conditions, and (d) other relevant economic measures.

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, 2017	$	93
Fair value of Term A Warrants issued under the Loan and Security Agreement	326
Fair value of Term B Warrants issued under the Loan and Security Agreement	686
Exercise of warrants	(49		)
Change in fair value of warrants	(196		)
Balance at December 31, 2018	$	860

There were no transfers between any of the levels of the fair value hierarchy during the year ended December 31, 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

Short-Term Investments (Notes)

12 Months Ended

Dec. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Short-term investments

Short-Term Investments

The Company classifies its debt securities as short-term investments and available-for-sale. Debt securities are comprised of highly liquid investments with minimum “A” rated securities and, as of December 31, 2018, consist of U.S. Treasury and agency bonds and corporate entity commercial paper and securities with maturities of more than three months but less than one year at the date of purchase. Debt securities as of December 31, 2018 have an average maturity of 0.40 years. The debt securities are reported at fair value with unrealized gains or losses recorded in accumulated other comprehensive loss in the balance sheets. Any differences between the cost and fair value of investments are represented by unrealized gains or losses. Refer to Note 11, "Fair Value Measurements", of the notes to financial statements for information related to the fair value measurements and valuation methods utilized.

The following table represents the Company’s available for sale short-term investments by major security type as of December 31, 2018:



(in thousands)	Amortized Cost		Gross Unrealized Losses			Total Fair Value

Short-term 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 short-term investments	$	66,969	$	(52	)	$	66,917

There were no investments in short-term securities as of December 31, 2017.

The Company reviews available-for-sale investments for other-than-temporary impairment loss quarterly. The Company considers factors such as the duration, severity and the 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 quarter ended December 31, 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.

Defined Contribution Plan (Notes)	12 Months Ended
Defined Contribution Plan (Notes)	Dec. 31, 2018
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. For the years ended December 31, 2018 and 2017, the Company has not made any matching contributions to the plan.

Income Taxes (Notes)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Tax Disclosure

Income Taxes

Due to reported losses, the Company recorded no income tax expense for the years ended December 31, 2018 and 2017. 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:



	December 31,
(in thousands)	2018			2017
Federal tax benefit at statutory rate	$	(12,617	)	$	(9,028	)
State tax benefit, net of federal benefit	(1,842		)	—
Impact of rate change	—			7,478
Research and development and orphan drug credits	(2,279		)	(517		)
Uncertain tax positions	603			—
Permanent adjustments to expenses	45			76
Stock compensation	76			42
Prior year adjustment	(2,470		)	(100		)
Rate impact of deferred tax balance	(63		)	—
Other	9			—
Changes in valuation allowance	18,538			2,049
Total income taxes	$	—		$	—

During the years ended December 31, 2018 and 2017, the Company had no interest and penalties related to income taxes.

Deferred income taxes reflect the net tax effects of temporary difference 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, 2018, 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)	2018			2017
Deferred tax assets:
Net operating losses	$	25,372		$	11,715
Federal research and orphan drug credits	5,426			2,045
Stock compensation	267			49
Other temporary differences	1,679			349
Valuation allowance	(32,662		)	(14,124		)
Total assets	82			34
Deferred tax liabilities:
Fixed and intangible assets	(82		)	(34		)
Total liabilities	(82		)	(34		)
Net deferred tax assets	$	—		$	—

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. As of December 31, 2017, the Company had federal net operating loss carryforwards of $55.8 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, 2018, the Company had $5.8 million and $0.2 million of federal and state income tax credits, respectively, to reduce future tax liabilities. As of December 31, 2017, the Company had $2.0 million of federal income tax credits. 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 U.S. federal 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, 2018 and 2017 is as follows (in thousands):



Valuation allowance at December 31, 2016	$	(12,075	)
Increase for 2017 activity	(2,049		)
Valuation allowance at December 31, 2017	(14,124		)
Increase for 2018 activity	(18,538		)
Valuation allowance at December 31, 2018	$	(32,662	)

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, 2018 and 2017, excluding interest and penalties, consisted of the following:



	December 31,
(in thousands)	2018		2017
Beginning balance - uncertain tax positions	$	—	$	—
Increases related to tax positions taken during the current year	228		—
Increases related to tax positions taken during the prior year	375		—
Ending balance - uncertain tax positions	$	603	$	—

For the year ended December 31, 2018, 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 sheets, uncertain tax positions of $0.6 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, 2018 and 2017.

Impacts of the Tax Cuts and Jobs Act

On December 22, 2017, the Tax Cuts and Jobs Act (H.R. 1) (the “Tax Act”) was signed into law. The Tax Act contains significant changes to corporate taxation, including (i) the reduction of the corporate income tax rate to 21%, (ii) the acceleration of expensing for certain business assets, (iii) the one-time transition tax related to the transition of U.S. international tax from a worldwide tax system to a territorial tax system, (iv) the repeal of the domestic production deduction, (v) additional limitations on the deductibility of interest expense, and (vi) expanded limitations on executive compensation. On December 22, 2017, the SEC staff issued SAB 118, which provides guidance on accounting for the tax effects of the Tax Act. SAB 118 provided a measurement period that should not extend beyond one year from the date of enactment for companies to complete the accounting under ASC 740. The key impacts of the Tax Act on the Company’s financial statements for the year ended December 31, 2017 were the remeasurement of deferred tax balances to the new corporate tax rate. The provisional amount determined, and recorded, for the remeasurement of its deferred tax balances resulted in a net reduction in deferred tax assets of $7.5 million and a corresponding reduction in the valuation allowance of $7.5 million.

Related Party Transactions (Notes)	12 Months Ended
Related Party Transactions (Notes)	Dec. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions Disclosure	Related Party Transactions There were no related party transactions for the year ended December 31, 2018. During the year ended December 31, 2017 the Company paid a spouse of an officer $37,000 to help with the development of the Company’s website.

Subsequent Events (Notes)	12 Months Ended
Subsequent Events (Notes)	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Event 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 sold pursuant to a partial exercise of the underwriters' option to purchase up to an additional 882,000 shares of common stock. Net proceeds from the offering were approximately $55.6 million after deducting underwriting discounts and commissions as well as other offering expenses.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Summary of Significant Accounting Policies [Abstract]

Property, Plant and Equipment, Policy

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

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

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



	December 31,
	2018	2017
Convertible preferred stock	—	11,439,752
Vested and unvested stock options	3,130,700	1,979,306
Warrants	102,647	19,931
	3,233,347	13,438,989

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2018

Property and Equipment [Abstract]

Property, Plant and Equipment

Property and equipment consisted of the following:



(in thousands)	December 31, 2018			December 31, 2017

Lab equipment	$	1,658		$	860
Furniture and fixtures	541			128
Computer equipment	87			100
Office equipment	109			78
Software	110			52
Leasehold improvements	180			10
	2,685			1,228
Less: accumulated depreciation and amortization	(651		)	(440		)
Property and equipment, net	$	2,034		$	788

Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2018

Accrued Expenses [Abstract]

Accrued Expenses

Accrued expenses consisted of the following:



(in thousands)	December 31, 2018		December 31, 2017

Accrued employee costs	$	4,326	$	1,581
Accrued research and development costs	2,221		566
Accrued other costs	1,667		410
Accrued expenses	$	8,214	$	2,557

Long-Term Debt (Tables)

12 Months Ended

Dec. 31, 2018

Long-term Debt, Unclassified [Abstract]

Schedule of Long-term Debt Instruments

The components of debt are as follows:



(in thousands)	December 31, 2018			December 31, 2017

Term A Loan	$	20,000		$	—
Term B Loan	15,000			—
Less unamortized deferred costs	(3,110		)	—
Long-term debt	$	31,890		$	—

Schedule of Maturities of Long-term Debt

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



2018	$	—
2019	—
2020	9,000
2021	12,000
2022	12,000
2023	2,000
	$	35,000

- 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, 2018

Warrants [Abstract]

Schedule of Stockholders' Equity Note, Warrants or Rights

As of December 31, 2018, the following warrants were outstanding:



	Outstanding Warrants	Exercise Price per Warrant	Expiration Date

2014 Warrants	8,635	$5.912	August 2020
Term A Warrants	53,720	$11.169	February 2025
Term B Warrants	40,292	$11.169	September 2025
	102,647

- Definition

Tabular disclosure of warrants or rights issued. Warrants and rights outstanding are derivative securities that give the holder the right to purchase securities (usually equity) from the issuer at a specific price within a certain time frame. Warrants are often included in a new debt issue to entice investors by a higher return potential. The main difference between warrants and call options is that warrants are issued and guaranteed by the company, whereas options are exchange instruments and are not issued by the company. Also, the lifetime of a warrant is often measured in years, while the lifetime of a typical option is measured in months. Disclose the title of issue of securities called for by warrants and rights outstanding, the aggregate amount of securities called for by warrants and rights outstanding, the date from which the warrants or rights are exercisable, and the price at which the warrant or right is exercisable.

+ References + Details

Commitments and Contingencies Future Minimum Lease Payments (Tables)

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Rental Payments for Operating Leases

Future minimum lease payments under operating leases at December 31, 2018 are as follows:



(in thousands)
2019	$	891
2020	1,580
2021	2,218
2022	2,273
2023	1,756
Thereafter	9,848
Total minimum lease payments	$	18,566

Stock Compensation Plan (Tables)

12 Months Ended

Dec. 31, 2018

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,
	2018		2017
Expected term (years)	6.0		6.1
Risk-free interest rate	2.48	%	2.06	%
Expected volatility	56.84	%	61.10	%
Expected dividends	—		—

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

The following table summarizes the reporting of total stock-based compensation expense resulting from employee and non-employee stock options:



	Years Ended December 31,
(in thousands)	2018		2017

Research and development	$	518	$	62
Selling, general and administrative	1,210		437
Total stock-based compensation expense	$	1,728	$	499

Employee Stock Option [Member]

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

Share-based Compensation, Activity

Stock option activity for employee awards for the year ended December 31, 2018 was as follows:



	UNITS	WEIGHTED AVERAGE EXERCISE PRICE		WEIGHTED AVERAGE CONTRACTUAL LIFE (YEARS)
Outstanding - January 1, 2018	1,946,230	$	1.66	8.70
Issued	1,604,804	14.14
Exercised	(225,986)	1.46
Forfeited	(197,740)	1.89
Outstanding - December 31, 2018	3,127,308	$	8.06	8.69
Exercisable - December 31, 2018	2,329,151	$	4.44	8.67
Vested and expected to vest at December 31, 2018	2,939,669	$	8.00	7.74



	UNITS	WEIGHTED AVERAGE EXERCISE PRICE		WEIGHTED AVERAGE CONTRACTUAL LIFE (YEARS)
Outstanding - January 1, 2018	33,125	$	1.91	6.75
Issued	0	—
Exercised	(22,996)	2.16
Forfeited	(6,737)	0.82
Outstanding - December 31, 2018	3,392	$	1.55	2.00
Exercisable - December 31, 2018	0	$	0.00	0.00
Vested and expected to vest at December 31, 2018	3,392	$	1.55	2.00

Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2018

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, 2018 and 2017:



(in thousands)	Total as of December 31, 2018		Level 1		Level 2		Level 3

Current Assets
Cash and cash equivalents:
Money market funds	$	45,716	$	45,716	$	—	$	—

Short-term 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 short-term investments	$	66,917	$	39,920	$	26,997	$	—

Other Current Liabilities
Warrant liabilities	$	860	$	—	$	—	$	860



(in thousands)	Total as of December 31, 2017		Level 1		Level 2		Level 3
Current Assets
Money market funds ^(a)	$	39,124	$	39,124	$	—	$	—

Other current liabilities
Warrant liabilities	$	93	$	—	$	—	$	93

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

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, 2017	$	93
Fair value of Term A Warrants issued under the Loan and Security Agreement	326
Fair value of Term B Warrants issued under the Loan and Security Agreement	686
Exercise of warrants	(49		)
Change in fair value of warrants	(196		)
Balance at December 31, 2018	$	860

- 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

Short-Term Investments (Tables)

12 Months Ended

Dec. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Debt Securities, Available-for-sale

The following table represents the Company’s available for sale short-term investments by major security type as of December 31, 2018:



(in thousands)	Amortized Cost		Gross Unrealized Losses			Total Fair Value

Short-term 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 short-term investments	$	66,969	$	(52	)	$	66,917

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

The following table summarizes the reporting of total stock-based compensation expense resulting from employee and non-employee stock options:



	Years Ended December 31,
(in thousands)	2018		2017

Research and development	$	518	$	62
Selling, general and administrative	1,210		437
Total stock-based compensation expense	$	1,728	$	499

Summary of Valuation Allowance [Table Text Block]

A reconciliation of the beginning and ending amounts of valuation allowances for the years ended December 31, 2018 and 2017 is as follows (in thousands):



Valuation allowance at December 31, 2016	$	(12,075	)
Increase for 2017 activity	(2,049		)
Valuation allowance at December 31, 2017	(14,124		)
Increase for 2018 activity	(18,538		)
Valuation allowance at December 31, 2018	$	(32,662	)

Schedule of Effective Income Tax Rate Reconciliation



	December 31,
(in thousands)	2018			2017
Federal tax benefit at statutory rate	$	(12,617	)	$	(9,028	)
State tax benefit, net of federal benefit	(1,842		)	—
Impact of rate change	—			7,478
Research and development and orphan drug credits	(2,279		)	(517		)
Uncertain tax positions	603			—
Permanent adjustments to expenses	45			76
Stock compensation	76			42
Prior year adjustment	(2,470		)	(100		)
Rate impact of deferred tax balance	(63		)	—
Other	9			—
Changes in valuation allowance	18,538			2,049
Total income taxes	$	—		$	—

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)	2018			2017
Deferred tax assets:
Net operating losses	$	25,372		$	11,715
Federal research and orphan drug credits	5,426			2,045
Stock compensation	267			49
Other temporary differences	1,679			349
Valuation allowance	(32,662		)	(14,124		)
Total assets	82			34
Deferred tax liabilities:
Fixed and intangible assets	(82		)	(34		)
Total liabilities	(82		)	(34		)
Net deferred tax assets	$	—		$	—

Income Taxes Uncertain Tax Positions (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

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



	December 31,
(in thousands)	2018		2017
Beginning balance - uncertain tax positions	$	—	$	—
Increases related to tax positions taken during the current year	228		—
Increases related to tax positions taken during the prior year	375		—
Ending balance - uncertain tax positions	$	603	$	—

Organization and Nature of the Business Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ (120,665)		$ (60,585)	$ (34,031)
Proceeds from second tranche of the Loan and Security Agreement		$ 15,000

Summary of Significant Accounting Policies Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Summary of Significant Accounting Policies [Abstract]
Convertible preferred stock	0	11,439,752
Vested and unvested stock options	3,130,700	1,979,306
Warrants	102,647	19,931
Antidilutive securities excluded from computation of EPS	3,233,347	13,438,989

Summary of Significant Accounting Policies Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Asset Impairment Charges		$ 0	$ 48,000
Capitalized costs, initial public offering costs		$ 9,400,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%	21.00%
Re-measurement of tax	$ 7,478,000
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

Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 2,685	$ 1,228
Less: accumulated depreciation and amortization	(651)	(440)
Property and equipment, net	2,034	788
Lab equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,658	860
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	541	128
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	87	100
Office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	109	78
Software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	110	52
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 180	$ 10

Property and Equipment Property and equipment details (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Depreciation Depletion and Amortization, not including asset impairments	$ 320,000	$ 177,000

Accrued Expenses Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued Expenses [Abstract]
Accrued employee costs	$ 4,326	$ 1,581
Accrued research costs	2,221	566
Accrued other costs	1,667	410
Accrued expenses	$ 8,214	$ 2,557

Long-Term Debt Debt, Future Principal Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Mar. 31, 2018
Debt Disclosure [Abstract]
Future principal payments, 2018	$ 0
Future principal payments, 2019	0
Future principal payments, 2020	9,000
Future principal payments, 2021	12,000
Future principal payments, 2022	12,000
Future principal payments, 2023	2,000
Long-term Debt	$ 35,000	$ 20,000

Long-Term Debt Narrative (Details) - USD ($)	12 Months Ended
Long-Term Debt Narrative (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018	Mar. 31, 2018
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				$ 45,000,000
Debt Instrument, Face Amount	$ 35,000,000			$ 20,000,000
Proceeds from second tranche of the Loan and Security Agreement			$ 15,000,000
Additional expected proceeds from third tranche of the Loan and Security Agreement	$ 10,000,000
Interest rate, thirty-day LIBOR plus stated percentage	6.75%
Debt Instrument, Interest Rate, Stated Percentage	9.10%
Period debt payments are interest only	24 months
Debt Instrument, Term	59 months
Prepayment allowed per debt agreement	$ 2,000,000
Prepayment penalty percentage	1.50%
Final payment fee percentage	6.50%
Debt, non-utilization fee percentage	2.00%
In event of default, additional percentage plus current rate penalty	5.00%
Debt Issuance Costs, Gross	$ 3,700,000
Interest expense	2,545,000	$ 2,000
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net	(3,110,000)	0
Long-term Debt	31,890,000	0
Amortization of debt issuance costs	$ 560,000	0
Maximum [Member]
Debt Instrument [Line Items]
Principal payments on debt to begin	36 months
Minimum [Member]
Debt Instrument [Line Items]
Principal payments on debt to begin	24 months
Term A Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 20,000,000	0
Term B Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 15,000,000	$ 0

Reverse Stock Split and Initial Public Offering Narrative (Details) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)	Jun. 30, 2018 USD ($) shares	Feb. 19, 2019 $ / shares shares	Dec. 31, 2018 $ / shares shares	Jun. 25, 2018 $ / shares shares	Dec. 31, 2017 $ / shares shares
Reverse Stock Split and Initial Public Offering [Abstract]
Reverse Stock Split, Conversion Ratio		1.78112
Common Shares, Par Value Per Share \| $ / shares				$ 0.0001		$ 0.0001
Common Shares, Shares, Issued			5,996,775	20,808,366	6,555,000	2,159,068
Shares Issued, Price Per Share \| $ / shares			$ 10.00		$ 15.00
Common shares issued, due to exercise of underwriter option			116,775		855,000
Net Proceeds from Issuance Initial Public Offering \| $	$ 55.6	$ 88.9
Shares of common stock issued, after preferred stock conversion		11,837,073

Convertible Preferred Stock Narrative (Details) $ in Millions	3 Months Ended		12 Months Ended
	Jun. 30, 2018 shares	Mar. 31, 2018 USD ($) shares	Dec. 31, 2018 shares	Dec. 31, 2017 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) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Class of Warrant or Right [Line Items]
Warrants outstanding	102,647	19,931
2014 Warrants [Member]
Class of Warrant or Right [Line Items]
Warrants outstanding	8,635
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 5.912
Investment Warrants Expiration Date	Aug. 31, 2020
Term A Warrants [Member]
Class of Warrant or Right [Line Items]
Warrants outstanding	53,720
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 11.169
Investment Warrants Expiration Date	Feb. 28, 2025
Term B Warrants [Member]
Class of Warrant or Right [Line Items]
Warrants outstanding	40,292
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 11.169
Investment 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, 2018	Dec. 31, 2017	Dec. 31, 2014
Class of Warrant or Right [Line Items]
Class of warrants, exercised			11,296
Warrants outstanding			102,647	19,931
Change in fair value of warrants			$ (196)	$ (46)
2014 Warrants [Member]
Class of Warrant or Right [Line Items]
Preferred stock and warrants issued during the period, shares					19,931
Class of Warrant or Right, Exercise Price of Warrants or Rights			$ 5.912
Warrants outstanding			8,635
Change in fair value of warrants			$ (56)	$ (46)
Term A Warrants [Member]
Class of Warrant or Right [Line Items]
Preferred stock and warrants issued during the period, shares		53,720
Class of Warrant or Right, Exercise Price of Warrants or Rights			$ 11.169
Warrants outstanding			53,720
Warrant coverage, equal to percent of principal borrowing amounts			3.00%
Change in fair value of warrants			$ (108)
Term B Warrants [Member]
Class of Warrant or Right [Line Items]
Preferred stock and warrants issued during the period, shares	40,292
Class of Warrant or Right, Exercise Price of Warrants or Rights			$ 11.169
Warrants outstanding			40,292
Change in fair value of warrants			$ 360

Commitments and Contingencies Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Remaining future minimum lease payments, 2019	$ 891,000
Remaining future minimum lease payments, 2020	1,580,000
Remaining future minimum lease payments, 2021	2,218,000
Remaining future minimum lease payments, 2022	2,273,000
Remaining future minimum lease payments, 2023	1,756,000
Remaining future minimum lease payments, thereafter	9,848,000
Total minimum lease payments	18,566,000
Rent Expense, operating leases	1,282,000	$ 526,000
Letters of Credit Outstanding, Amount	$ 143,000

Stock Compensation Plan Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Method Used (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Method Used [Abstract]
Expected term	6 years	6 years 20 days
Risk-free interest rate	2.48%	2.06%
Expected volatility	56.84%	61.10%
Expected dividends	0.00%	0.00%

Stock Compensation Plan Employee Stock Award Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	3,130,700	1,979,306
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	3,127,308	1,946,230
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 8.06	$ 1.66
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	8 years 252 days	8 years 8 months 12 days
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period	1,604,804
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 14.14
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	(225,986)
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	$ 1.46
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Number of Shares	(197,740)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price	$ 1.89
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	2,329,151
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 4.44
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	8 years 246 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	2,939,669
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 8.00
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term	7 years 270 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, Options, Exercisable, Intrinsic Value	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost	$ 114,000	$ 35,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	3,392	33,125
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 1.55	$ 1.91
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	2 years	6 years 9 months
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period	0
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	(22,996)
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	$ 2.16
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Number of Shares	(6,737)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price	$ 0.82
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 0.00
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	0 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	3,392
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 1.55
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term	2 years

Stock Compensation Plan Narrative (Details) - USD ($)	12 Months Ended
Stock Compensation Plan Narrative (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2018	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 7,300,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 303 days
Employee Stock 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	$ 8.17
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 2,400,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value	$ 28,300,000
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
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value	$ 100,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	0
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost	$ 114,000	$ 35,000
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
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	1,120,937

Stock Compensation Plan Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 1,728	$ 499
Research and development expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	518	62
Selling, general and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 1,210	$ 437

Fair Value Measurement Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Money market funds

$ 45,716

$ 39,124

^[1]

Cash and cash equivalents

45,716

42,045

$ 32,269

Short-term Investments

66,917

Warrants liabilities

860

Exercise of warrants

(49)

Change in fair value of warrants

196

Term A Warrants [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Fair value of Term A Warrants issued under the Loan and Security Agreement

326

Change in fair value of warrants

108

Term B Warrants [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Fair value of Term A Warrants issued under the Loan and Security Agreement

686

Change in fair value of warrants

(360)

Fair Value, Inputs, Level 1 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Money market funds

45,716

39,124

Short-term Investments

39,920

Warrants liabilities

Fair Value, Inputs, Level 2 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Money market funds

Short-term Investments

26,997

Warrants liabilities

Fair Value, Inputs, Level 3 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Money market funds

Short-term Investments

Warrants liabilities

860

$ 93

U.S. government securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Short-term Investments

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]

Short-term Investments

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]

Short-term Investments

U.S. government securities | Fair Value, Inputs, Level 3 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Short-term Investments

Corporate securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Short-term Investments

15,066

Corporate securities | Fair Value, Inputs, Level 1 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Short-term Investments

Corporate securities | Fair Value, Inputs, Level 2 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Short-term Investments

15,066

Corporate securities | Fair Value, Inputs, Level 3 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Short-term Investments

Agency securities

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Short-term Investments

11,931

Agency securities | Fair Value, Inputs, Level 1 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Short-term Investments

Agency securities | Fair Value, Inputs, Level 2 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Short-term Investments

11,931

Agency securities | Fair Value, Inputs, Level 3 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Short-term Investments

Commercial paper

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Short-term Investments

1,183

Commercial paper | Fair Value, Inputs, Level 1 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Short-term Investments

1,183

Commercial paper | Fair Value, Inputs, Level 2 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Short-term Investments

Commercial paper | Fair Value, Inputs, Level 3 [Member]

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Short-term Investments

$ 0

[1]	(a) The money market funds noted above are included in cash and cash equivalents.

Short-Term Investments (Details) - USD ($) $ in Thousands	12 Months Ended
Short-Term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Available For Sale Securities Maturities Period	145 days
Available-for-sale Securities, Amortized Cost Basis	$ 66,969
Accumulated other comprehensive loss	(52)	$ 0
Short-term Investments	66,917	$ 0
Agency securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	11,944
Accumulated other comprehensive loss	(13)
Short-term Investments	11,931
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,183
Accumulated other comprehensive loss	0
Short-term Investments	1,183
Corporate securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	15,081
Accumulated other comprehensive loss	(15)
Short-term Investments	15,066
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	38,761
Accumulated other comprehensive loss	(24)
Short-term Investments	$ 38,737

Income Taxes (Details) - USD ($)	12 Months Ended
Income Taxes (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation Allowance [Line Items]
Operating Loss Carryforwards	$ 108,800,000	$ 55,800,000
Effective Income Tax Rate Reconciliation, Deduction, Percent	80.00%
Federal research income tax credits, gross of valuation allowance	$ 5,800,000	2,000,000
State research income tax credits, gross of valuation allowance	200,000
Operating loss carryforwards, various states	35,600,000
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount	(12,617,000)	(9,028,000)
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	(1,842,000)	0
Unrecognized Tax Benefits	$ 603,000	$ 0	$ 0
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%
Unrecognized Tax Benefits, Period Increase (Decrease)	$ 228,000	$ 0
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions	375,000	0
Net operating losses	25,372,000	11,715,000
Deferred Tax Assets, Tax Credit Carryforwards, Research	5,426,000	2,045,000
Stock compensation	267,000	49,000
Other temporary differences	1,679,000	349,000
Valuation allowance	(32,662,000)	(14,124,000)	$ (12,075,000)
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	(18,538,000)	(2,049,000)
Total deferred tax assets	82,000	34,000
Fixed and intangible assets	(82,000)	(34,000)
Total deferred tax liabilities	(82,000)	(34,000)
Net deferred tax assets	0	0
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	0	7,478,000
Tax Cuts And Jobs Act Of 2017 Change In Tax Rate Deferred Tax Assets Decrease In Valuation Allowance		7,500,000
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	18,538,000	2,049,000
Income Tax Expense (Benefit)	0	0
Income Tax Examination, Penalties and Interest Expense		0
Effective Income Tax Rate Reconciliation, Tax Credit, Research, Amount	(2,279,000)	(517,000)
Unrecognized Tax Benefits, Decrease Resulting from Current Period Tax Positions	603,000	0
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	45,000	76,000
Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount	76,000	42,000
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Amount	(2,470,000)	(100,000)
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	(63,000)	0
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount	$ 9,000	$ 0

Related Party Transactions (Details)	12 Months Ended
Related Party Transactions (Details)	Dec. 31, 2018 USD ($)
Related Party Transactions [Abstract]
Related Party Transaction, Expenses from Transactions with Related Party	$ 37,000

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
	Mar. 21, 2019	Mar. 31, 2019	Jun. 30, 2018	Feb. 19, 2019	Dec. 31, 2018	Jun. 25, 2018	Dec. 31, 2017
Subsequent Event [Line Items]
Net Proceeds from Issuance Initial Public Offering		$ 55.6	$ 88.9
Common Shares, Shares, Issued				5,996,775	20,808,366	6,555,000	2,159,068
Shares Issued, Price Per Share				$ 10.00		$ 15.00
Common shares issued, due to exercise of underwriter option				116,775		855,000
Common shares, underwriter option to purchase common stock	882,000