Aridis Pharmaceuticals (ARDS) 10-K 28 Mar 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Mar. 26, 2019
Document and Entity Information [Abstract]
Entity Registrant Name	ARIDIS PHARMACEUTICALS, INC.
Entity Central Index Key	0001614067
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Shell Company	false
Entity Ex Transition Period	false
Entity Filer Category	Non-accelerated Filer
Entity Public Float	$ 0
Entity Common Stock, Shares Outstanding		8,107,290
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 24,237	$ 25,096
Accounts receivable	1,660
Prepaid expenses & other current assets	2,450	244
Total current assets	28,347	25,340
Property and equipment, net	1,271	750
Intangible assets, net	38	43
Equity method investment	960
Other assets	995	345
Total assets	31,611	26,478
Current liabilities:
Accounts payable	2,331	933
Accrued liabilities	2,944	2,121
Deferred revenue	22	120
Total current liabilities	5,297	3,174
Warrant liability		11,868
Total liabilities	5,297	15,042
Total convertible preferred stock		74,202
Commitments and contingencies (Note 12)
Stockholders' equity (deficit):
Common stock (par value, $0.0001 per share; shares authorized: 100,000,000 and 100,000,000 , respectively; shares issued and outstanding: 8,104,757 and 166,373, as of December 31, 2018 and 2017, respectively )	1
Additional paid-in capital	97,401	(15,140)
Accumulated deficit	(71,088)	(47,626)
Total stockholders' equity (deficit)	26,314	(62,766)
Total liabilities, convertible preferred stock and stockholders' equity (deficit)	$ 31,611	26,478
Series A Convertible Preferred Stock
Current liabilities:
Total convertible preferred stock		$ 74,202

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	8,104,757	166,373
Common stock, shares outstanding (in shares)	8,104,757	166,373
Series A Convertible Preferred Stock
Convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized (in shares)	60,000,000	60,000,000
Convertible preferred stock, shares issued (in shares)	0	36,196,193
Convertible preferred stock, shares outstanding (in shares)	0	36,196,193
Convertible preferred stock, aggregate liquidation preference	$ 0	$ 74,202

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Revenue:
Total revenue	$ 2,757	$ 860
Operating expenses:
Research and development	23,000	17,438
General and administrative	3,874	3,160
Total operating expenses	26,874	20,598
Loss from operations	(24,117)	(19,738)
Other expense:
Interest and other income, net	420	234
Change in fair value of preferred stock warrants	1,632	(5,152)
Equity in net loss of equity method investment	(40)
Net loss	(22,105)	(24,656)
Preferred dividends	(1,357)	(2,793)
Net loss available to common stockholders	$ (23,462)	$ (27,449)
Weighted-average shares outstanding used in computing net loss available to common stockholders:
Basic (in shares)	3,146,632	166,373
Diluted (in shares)	3,146,632	166,373
Net loss per common share:
Basic (in dollars per share)	$ (7.02)	$ (148.20)
Diluted (in dollars per share)	(7.02)	(148.20)
Preferred dividends:
Basic (in dollars per share)	(0.43)	(16.78)
Diluted (in dollars per share)	(0.43)	(16.78)
Net loss per share available to common stockholders:
Basic (in dollars per share)	(7.45)	(164.98)
Diluted (in dollars per share)	$ (7.45)	$ (164.98)
Collaboration revenue
Revenue:
Total revenue	$ 1,168	$ 771
Grant
Revenue:
Total revenue	$ 1,589	$ 89

Consolidated Statements of Chan

Consolidated Statements of Changes in Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Series A Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Total
Balance at the beginning of the period at Dec. 31, 2016	$ 58,897		$ (24,945)	$ (20,177)	$ (45,122)
Balance at the beginning of the period (in shares) at Dec. 31, 2016	28,730,005	166,373
Changes in equity
Receipt of stock subscription proceeds for stock issued as of the prior year end			(4,496)		(4,496)
Issuance of stock			3,207		3,207
Issuance of stock (in shares)	6,516,142
Temporary Equity, Stock Issued During Period, Value, New Issues Upon Maturity of Convertible Notes	$ 13,358
Stock dividends issued (in shares)	950,046
Series A convertible preferred stock dividends issued	$ (1,947)		(846)	2,793	1,947
Series A convertible preferred stock dividend			352		352
Stock-based compensation			1,608		1,608
Net Loss				(24,656)	(24,656)
Balance at the end of the period at Dec. 31, 2017	$ 74,202		(15,140)	(47,626)	(62,766)
Balance at the end of the period (shares) at Dec. 31, 2017	36,196,193	166,373
Changes in equity
Issuance of stock			25,079		25,079
Issuance of stock (in shares)		2,192,824
Stock dividends issued (in shares)	669,647
Series A convertible preferred stock dividend	$ 1,358		(1)	(1,357)	(1,358)
Conversion of Series A convertible preferred stock into common stock upon initial public offering	$ (75,560)	$ 1	75,559		75,560
Conversion of Series A convertible preferred stock into common stock upon initial public offering (in shares)	(36,865,840)	5,744,586
Issuance of common stock upon exercise (in shares)		974
Reclassification of warrant liability to equity upon initial public offering			10,236		10,236
Exercise of stock options			10		10
Stock-based compensation			1,658		1,658
Net Loss				(22,105)	(22,105)
Balance at the end of the period at Dec. 31, 2018		$ 1	$ 97,401	$ (71,088)	$ 26,314
Balance at the end of the period (shares) at Dec. 31, 2018		8,104,757

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net loss	$ (22,105)	$ (24,656)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	283	62
Stock-based compensation expense	1,658	1,608
Equity in net loss of equity method investment	40
Change in fair value of preferred stock warrants	(1,632)	5,152
Changes in assets and liabilities:
Accounts receivable	(1,660)	67
Prepaid expenses and other current assets	(2,207)	(37)
Other assets	(648)	(304)
Deferred revenue	(97)	120
Accounts payable, accrued liabilities and other	2,097	431
Net cash used in operating activities	(24,271)	(17,557)
Cash flows from investing activities
Purchase of equity method investment	(1,000)
Purchase of property and equipment	(677)	(698)
Net cash used in investing activities	(1,677)	(698)
Cash flows from financing activities
Proceeds from issuance of preferred stock, net		21,060
Proceeds from issuance of common stock, net	25,079
Proceeds from stock option exercises	10
Net cash provided by financing activities	25,089	21,060
Net increase (decrease) in cash and cash equivalents	(859)	2,805
Cash and cash equivalents at
Cash and cash equivalents at beginning of period	25,096	22,291
Cash and cash equivalents at end of period	24,237	25,096
Supplemental cash flow information
Cash paid for taxes	2	1
Non-cash investing and financing activities
Preferred stock dividends issued	1,357	2,793
Reclassification of warrant liability to equity	10,236
Issuance of common stock warrants attributed to private offerings		$ 352
Property and equipment additions	$ 120

Description of Business and Bas

Description of Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2018
Description of Business and Basis of Presentation
Description of Business and Basis of Presentation	1. Description of Business and Basis of Presentation Organization Aridis Pharmaceuticals, Inc. (the “Company” or “we” or “our”) was established as a California limited liability corporation in 2003. The Company converted to a Delaware C corporation on May 21, 2014. Our principal place of business is in San Jose, California. We are a late-stage biopharmaceutical company focused on developing new breakthrough therapies for infectious diseases and addressing the growing problem of antibiotic resistance. The Company has a deep, diversified portfolio of clinical and pre-clinical stage anti-infective product candidates that are complimented by a fully human monoclonal antibody discovery platform technology. Two of the Company’s clinical candidates are at pivotal trial stage. The Company’s suite of anti-infective monoclonal antibodies offers opportunities to profoundly alter the current trajectory of increasing antibiotic resistance and improve the health outcome of many of the most serious life-threatening infections particularly in hospital settings. Basis of Presentation and Consolidation The accompanying condensed consolidated financial statements have been prepared in accordance with the United States generally accepted accounting principles, or GAAP. The consolidated financial statements include the accounts of the Company and its two wholly-owned subsidiaries, Aridis Biopharmaceuticals, Inc. and Aridis Pharmaceuticals, C.V. All intercompany balances and transactions have been eliminated in consolidation. The Company operates in one segment. Management uses one measurement of profitability and does not segregate its business for internal reporting. Reverse Stock Split On August 3, 2018, the Company effected a 1 for 6.417896 reverse stock split of the Company’s common stock. The par value and the number of authorized shares of the common and convertible preferred stock were not adjusted as a result of the reverse stock split. All common stock share and per-share amounts for all periods presented in this Annual Report on Form 10-K have been adjusted retroactively to reflect the reverse stock split. Initial Public Offering On August 13, 2018, the Company's registration statement on Form S-1 relating to its initial public offering of its common shares (the "IPO") was declared effective by the SEC. The IPO closed on August 16, 2018 and the Company issued and sold 2,000,000 common shares at a public offering price of $13.00 per share. Gross proceeds totaled $26.0 million and net proceeds totaled $22.8 million after deducting underwriting discounts and commissions of $1.8 million and other offering expenses of approximately $1.4 million. The underwriters of the IPO partially exercised their over-allotment option, and on August 30, 2018, the Company issued and sold 192,824 common shares at a public offering price of $13.00 per share for gross proceeds totaling approximately $2.5 million and net proceeds of approximately $2.3 million after deducting underwriting discounts and commissions of approximately $0.2 million. In connection with the IPO, the holders of a majority of the Series A Preferred Stock approved the mandatory conversion of the Series A Preferred Stock into one share of common stock for every 6.417896 shares of Series A Preferred Stock which converted immediately prior to the consummation of the IPO. Upon conversion, a total of 5,744,586 shares of common stock were issued for the converted Series A Preferred Stock which includes the accrued dividends upon conversion. All warrants to purchase Series A Preferred Stock became warrants to purchase common stock, adjusted for the 1 for 6.417896 shares reverse stock split. Going Concern The accompanying consolidated financial statements have been prepared on a going concern basis that contemplates the realization of assets and discharge of liabilities in their normal course of business. The Company has suffered recurring losses from operations since inception and negative cash flows from operating activities during the twelve months ended December 31, 2018 and 2017. At December 31, 2018, the Company had working capital of $23.1 million and an accumulated deficit of $71.1 million. The Company expects to incur additional operating losses in the foreseeable future as the Company continues its product development programs. These factors raise substantial doubt about the Company’s ability to continue as a going concern. The Company plans to fund its losses from operations and capital funding needs through current cash on hand and future debt and equity financings which we may obtain through one or more public or private equity offerings, debt financings, government or other third-party funding, strategic alliances and licensing or collaboration arrangements. The Company may be unable to secure additional financing or other sources of funding on acceptable terms, or at all. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate its research and development programs or future commercialization efforts, which could adversely affect its future business prospects and its ability to continue as a going concern. We believe that our existing cash and cash equivalents will provide sufficient funds to enable us to meet our obligations into the first quarter of 2020.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Use of Estimates The preparation of the consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of expenses during the reporting period. Such estimates include those related to the evaluation of our ability to continue as a going concern, revenue recognition, allowance for doubtful accounts, long-lived assets, income taxes, assumptions used in the Black-Scholes-Merton (“BSM”) model to calculate the fair value of stock-based compensation, Monte Carlo Simulation (“MSM”) model to calculate the fair value of warrants, deferred tax asset valuation allowances, valuation of the Company’s common and convertible preferred stock, fair value assumptions used in the valuation of warrants, preclinical study and clinical trial accruals and various accrued liabilities. Actual results could differ from those estimates. Concentration of Risk The Company’s cash and cash equivalents are maintained at financial institutions in the United States of America. Deposits held by these institutions may exceed the amount of insurance provided on such deposits. For the year ended December 31, 2018, two customers accounted for 58% and 42% of total revenue. For the year ended December 31, 2017, two customers accounted for 90% and 10% of total revenue. Both of the Company’s customers are located in the United States. As of December 31, 2018, two customers accounted for 60% and 40% of total accounts receivable. There were no accounts receivable as of December 31, 2017. Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. Cash equivalents consist primarily of checking account and money market account balances. Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at the invoiced amount and do not bear interest. The Company considers the credit worthiness of its customers but does not require collateral in advance of a sale. The Company evaluates collectability and maintains an allowance for doubtful accounts for estimated losses inherent in its accounts receivable portfolio when necessary. The allowance is based on the Company’s best estimate of the amount of losses in the Company’s existing accounts receivable, which is based on customer creditworthiness, facts and circumstances specific to outstanding balances, and payment terms. Account balances are charged off against the allowance after all means of collection have been exhausted and the potential for recovery is considered remote. As of December 31, 2018, and 2017, there were no allowances for doubtful accounts. Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally five years. Maintenance and repairs are charged to expense as incurred. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in the consolidated statement of operations in the period realized. Intangible Assets Intangible assets are recorded at cost and amortized over the estimated useful life of the asset. Intangible assets consist of licenses with various institutions whereby the Company has rights to use intangible property obtained from such institutions. Impairment of Long-Lived Assets The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by comparison of the carrying amount to the future net cash flows which the assets are expected to generate. If such assets are considered to be impaired, the impairment is measured by the excess of the carrying amount of the assets over fair value less the costs to sell the assets, generally determined using the projected discounted future net cash flows arising from the asset. There have been no such impairments of long-lived assets as of December 31, 2018 and 2017. Revenue Recognition Revenue is recognized in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 605, Revenue Recognition which requires that four basic criteria must be met before revenue can be recognized: (1) persuasive evidence of an arrangement exists; (2) delivery has occurred and title and the risks and rewards of ownership have been transferred to the client or services have been rendered; (3) the price is fixed or determinable; and (4) collectability is reasonably assured. During 2018 and 2017, revenue includes grant awards and collaboration services entered into for specific research and development efforts. We recognize revenue under such awards and contracts as the related qualified research and development expenses are incurred or under the milestone method, up to the limit of the prior approval funding amounts, and when we have determined that we have earned the right to receive the recognized portion according to the terms of the original grant awarded. In December 2016, the Company received an award from the Cystic Fibrosis Foundation (“CF Foundation”) for approximately $2,902,000. The agreement contains an upfront payment of $200,000 which is being recognized straight-line over the term of the contract as we believe the upfront fee relates to services performed throughout the contract period and the upfront fee does not represent a substantive milestone within the agreement. Recognition of revenue for the remaining payments under the agreement will be recognized under the milestone method as substantive milestones are met. The milestones relate to pre-clinical and clinical research activities. The agreement also specifies that we are obligated to cumulatively spend on the development program at least an equal amount as it receives from the non-profit organization. In the event that we do not spend as much as we received under the agreement, we are obligated to return any overage to the non-profit organization. In November 2018, the CF Foundation increased the award to $7,466,000. For the years ended December 31, 2018 and 2017, all grant revenue totaling approximately $1,589,000 and $89,000, respectively, was derived from our award agreement with the CF Foundation. In 2017, the Company entered into a collaborative research and development agreement with GlaxoSmithKline plc (“GSK”). In accordance with the agreement, we received an upfront fee and are due annual fees and amounts for development work to be performed as specifically outlined under the agreement. The work to be performed was delineated into three specific research projects. In assessing the appropriate revenue recognition related to a collaboration agreement, we first determined whether the arrangement includes multiple elements, such as the delivery of intellectual property rights and research and development services. The multiple elements were analyzed to determine whether the deliverables could be separated or whether they must be accounted for as a single unit of accounting. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in our balance sheet. Recognition of revenue under the contract will be based on the terms of the contract and will be recognized under the proportional performance method derived from the completion of certain stages as defined within the contract. For the years ended December 31, 2018 and 2017, approximately $1,168,000 and $771,000, respectively, was recorded as collaboration revenue related to the Company’s agreement with GSK. In December 2018, at a meeting of the joint steering committee it was agreed by both parties to terminate the collaboration agreement. As a result of the termination of the collaboration agreement, the Company recognized all previously deferred revenue and an additional $440,000 for additional work performed during the term of the agreement. Costs for Collaborative Arrangements Costs incurred under collaborative arrangements include personnel costs, laboratory supplies and fees paid to third parties. These amounts are included in research and development in the accompanying consolidated statement of operations. For the years ended December 31, 2018 and 2017, the Company had incurred expenses of approximately $604,000 and $633,000, respectively, related to its collaborative arrangement. Research and Development Research and development costs are charged to operations as incurred. Research and development expenses consist of salaries and benefits, laboratory supplies, consulting fees and fees paid to third parties. Stock-Based Compensation The Company recognizes compensation expense for all stock-based awards to employees and directors based on the grant-date estimated fair values, net of an estimated forfeiture rate. The Company recognizes stock-based compensation cost for employees and directors on a straight-line basis over the requisite service period for the award. Stock-based compensation expense is recognized only for those awards that are ultimately expected to vest. The Company estimates forfeitures based on an analysis of historical employee turnover and will continue to evaluate the appropriateness of the forfeiture rate based on actual forfeiture experience, analysis of employee turnover and other factors. The Company will revise the forfeiture estimate, if necessary, in subsequent periods if actual forfeitures differ from those estimates. Changes in forfeiture estimates impact stock-based compensation cost in the period in which the change in estimate occurs. The BSM option pricing model incorporates various highly sensitive assumptions, including the fair value of the Company’s common stock, expected volatility, expected term and risk-free interest rates. The weighted-average expected life of options was calculated using the simplified method as prescribed by the SEC’s Staff Accounting Bulletin, Topic 14 (“SAB Topic 14”). This decision was based on the lack of relevant historical data due to the Company’s limited historical experience. In addition, due to the Company’s limited historical data, the estimated volatility also reflects the application of SAB Topic 14, incorporating the historical volatility of comparable companies whose stock prices are publicly available. The risk-free interest rate for the periods within the expected term of the option is based on the U.S. Treasury yield in effect at the time of grant. The dividend yield was zero, as the Company has never declared or paid dividends and has no plans to do so in the foreseeable future. The Company accounts for stock-based compensation arrangements with non-employees by recording the expense of such services based on the estimated fair value of the common stock at the measurement date. The value of the equity instrument, including adjustment to fair value at each balance sheet date, is charged to net loss over the term of the service agreement. Income Taxes The Company accounts for income taxes under the liability method. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized. The Company assesses all material positions taken in any income tax return, including all significant uncertain positions, in all tax years that are still subject to assessment or challenge by the relevant taxing authorities. Assessing an uncertain tax position begins with the initial determination of the positions sustainability and is measured at the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement. At each balance sheet date, unresolved uncertain tax positions must be reassessed, and the Company will determine whether (i) the factors underlying the sustainability assertion have changed and (ii) the amount of the recognized benefit is still appropriate. The recognition and measurement of tax benefits requires significant judgment. Judgments concerning the recognition and measurement of a tax benefit might change as new information becomes available. Comprehensive Loss The Company has no items of comprehensive income or loss other than net loss. Loss Per Share Basic loss per common share is calculated by dividing net loss available to common shareholders for the period by the weighted-average number of common shares outstanding during the period. For diluted loss per share calculation purposes, the net loss available to common shareholders is adjusted to add back any preferred stock dividends reflected in the consolidated statement of operations for the respective periods. The following potentially dilutive securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been antidilutive: Year Ended December 31, 2018 2017 Convertible preferred stock — 36,196,193 Stock options to purchase common stock 825,205 603,291 Preferred stock warrants — 8,725,289 Common stock warrants 1,966,930 607,295 2,792,135 46,132,068 JOBS Act Accounting Election The JOBS Act permits an “emerging growth company” such as us to take advantage of an extended transition period to comply with new or revised accounting standards applicable to public companies. We are choosing to take advantage of this provision and, as a result, we will adopt the extended transition period available under the JOBS Act until the earlier of the date we (i) are no longer an emerging growth company or (ii) affirmatively and irrevocably opt out of the extended transition period provided under the JOBS Act. Recently Issued Accounting Pronouncements adopted during the year ended December 31, 2018 In March 2016, the FASB issued ASU No. 2016 - 09, “Improvements to Employee Share - Based Payment Accounting,” which is intended to improve the accounting for employee share - based payments. The ASU simplifies several aspects of the accounting for share - based payment award transactions, including; the income tax consequences, classification of awards as either equity or liabilities, and the classification on the statement of cash flows. The new standard is effective for fiscal years beginning after December 15, 2017, and upon adoption, an entity should apply the amendments by means of a cumulative - effect adjustment to the balance sheet at the beginning of the first reporting period in which the guidance is effective. Early adoption is permitted. The Company adopted this standard in the consolidated financial statements for the year ended December 31, 2018, and such adoption did not have a material impact on the Company’s consolidated financial statements and related disclosures. In May 2017, the FASB issued ASU 2017 - 09, “Compensation — Stock Compensation (Topic 718): Scope of Modification Accounting,” to provide clarity and reduce both diversity in practice and cost complexity when applying the guidance in Topic 718 to a change to the terms and conditions of a stock - based payment award. ASU 2017 - 09 also provides guidance about the types of changes to the terms or conditions of a share - based payment award that require an entity to apply modification accounting in accordance with Topic 718. For all entities, including emerging growth companies, the standard is effective for annual periods beginning after December 15, 2017, and for interim periods therein. The Company adopted this standard in the consolidated financial statements for the year ended December 31, 2018, and such adoption did not have a material impact on the Company’s consolidated financial statements and related disclosures. Recently Issued Accounting Pronouncements not yet adopted as of December 31, 2018 In February 2016, the FASB issued ASU No. 2016 ‑ 02, “ Leases (Topic 842)”. In July 2018, the FASB issued ASU No. 2018-10, Codification Improvements to Topic 842, Leases, which provides clarification to ASU 2016-02. These ASUs (collectively, the new lease standard) require an entity to recognize a lease liability and a right-of-use asset on the balance sheet for leases with lease terms of more than twelve months. Lessor accounting is largely unchanged, while lessees will no longer be provided with a source of off-balance sheet financing. Initial guidance required the adoption of the new lease standard using the modified retrospective transition method. In July 2018, the FASB issued ASU No. 2018-11, Leases (Topic 842) - Targeted Improvements, which allows entities to elect an optional transition method where entities may continue to apply the existing lease guidance during the comparative periods and apply the new lease requirements through a cumulative effect adjustment in the period of adoptions rather than in the earliest period presented. This guidance is effective for public business entities for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. As a result of Company having elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act, ASU 2016-02 is effective for the Company for the year ended December 31, 2020, and all interim periods within. Early adoption is permitted. While the Company continues to review its current accounting policies and practices to identify potential differences that would result from applying the new guidance, the Company expects that its non-cancellable operating lease commitments with a term of more than twelve months will be subject to the new guidance and recognized as right-of-use assets and operating lease liabilities on the Company’s consolidated balance sheets upon adoption. The Company expects to elect transitional practical expedients such that the Company will not need to reassess whether contracts are leases and will retain lease classification and initial direct costs for leases existing prior to the adoption of the new lease standard. In May 2014, the FASB issued ASU No. 2014 - 09, “Revenue from Contracts with Customers.” The objective of ASU 2014 - 09 is to establish a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and will supersede most of the existing revenue recognition guidance, including industry - specific guidance. The core principle of ASU 2014 - 09 is that an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The new guidance mandates a five-step process, which requires entities to exercise significant judgment and involves estimates to be made on the transaction price and the timing over which revenue will be recognized. These include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. The two permitted transition methods under the new standard are the full retrospective method, in which the new standard would be applied to each prior reporting period presented and the cumulative effect of applying the new standard would be recognized at the earliest period shown, or the modified retrospective method, in which the cumulative effect of applying the new standard would be recognized at the date of initial application. Additional ASUs have been issued to amend or clarify the new standard as follows: In March 2016, FASB issued ASU 2016-08, “Principal versus Agent Considerations (Reporting Revenue Gross versus Net)”. The amendments of this standard are intended to improve the consistency and understandability of the implementation guidance on principal versus agent considerations. The effective date for ASU 2016-08 is the same as the effective date for ASU 2014-09. In April 2016, FASB issued ASU 2016-10,” Identifying Performance Obligations and Licensing”. This standard amends the guidance in ASU 2014-09 to improve the consistency and clarify the guidance on identifying performance obligations and licensing. The effective date for ASU 2016-10 is the same as the effective date for ASU 2014-09. In May 2016, FASB issued ASU 2016-12, “Revenue from Contracts with Customers (Topic 606)”: Narrow-Scope Improvements and Practical Expedients. ASU 2016-12 addresses narrow-scope improvements to the guidance on collectability, noncash consideration, and completed contracts at transition and provides a practical expedient for contract modifications at transition and an accounting policy election related to the presentation of sales taxes and other similar taxes collected from customers. The new revenue guidance is effective for public business entities for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. As a result of the Company having elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act, ASU 2014-09 was effective for the Company on January 1, 2019, and all interim periods thereafter. Early adoption is permitted. ASU 2014-09 also permits two methods of adoption: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). The Company is currently evaluating the impact the adoption of this standard will have on its consolidated financial statements and related disclosures. The Company will finalize its accounting assessment and quantitative impact of the adoption during the first quarter of fiscal year 2019, using the modified retrospective method, which will reflect the cumulative effect of the adoption retrospectively as of January 1, 2019, the initial date of adoption. In June 2016, the FASB issued ASU 2016 ‑ 13, “ Financial Instruments - Credit Losses (Topic 326) ” , which is intended to provide financial statement users with more useful information about expected credit losses on financial assets held by a reporting entity at each reporting date. The new standard replaces the existing incurred loss impairment methodology with a methodology that requires consideration of a broader range of reasonable and supportable forward-looking information to estimate all expected credit losses. For public business entities, ASU 2016 ‑ 13 is effective for fiscal years and interim periods within those years beginning after December 15, 2019. As a result of the Company having elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act, ASU 2016-13 is effective for the Company for the fiscal year ending on December 31, 2021, and all interim periods within. Early adoption is permitted. The Company is currently evaluating the impact of the adoption of this standard will have on its consolidated financial statements and related disclosures. In June 2018, the FASB issued ASU 2018-07, “Compensation – Stock Compensation (Topic 718), Improvements to Nonemployee Share-Based Payment Accounting”, which is intended to simplify the accounting for nonemployee share-based payment transactions by expanding the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. For public entities, ASU 2018-07 is effective for fiscal years beginning after December 15, 2018. As a result of the Company having elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act, ASU 2018-07 is effective for the Company for the year ending on December 31, 2020, and all interim periods within. Early adoption is permitted. The Company is currently evaluating the impact the adoption of this standard will have on its consolidated financial statements and related disclosures.

Fair Value Disclosure

Fair Value Disclosure	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosure
Fair Value Disclosure	3. Fair Value Disclosure The carrying value of the Company’s cash and cash equivalents, prepaid expenses and other current assets, other assets, accounts payable, accrued liabilities, and convertible notes payable approximate fair value due to the short-term nature of these items. Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy defines a three-level valuation hierarchy for disclosure of fair value measurements as follows: Level I Unadjusted quoted prices in active markets for identical assets or liabilities; Level II Inputs other than quoted prices included within Level I that are observable, unadjusted quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and Level III Unobservable inputs that are supported by little or no market activity for the related assets or liabilities. The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Fair Value at December 31, 2018 ($in thousands) Total Level 1 Level 2 Level 3 Assets: Deferred charge related to stock option liability $ 455 $ — $ 455 $ — Totals $ 455 $ — $ 455 $ — Liabilities: Stock option liability $ 455 $ — $ 455 $ — Totals $ 455 $ — $ 455 $ — Fair Value at December 31, 2017 ($in thousands) Total Level 1 Level 2 Level 3 Liabilities: Warrant liability $ 11,868 $ — $ — $ 11,868 Totals $ 11,868 $ — $ — $ 11,868 Financial assets or liabilities are considered Level 3 when their fair values are determined using pricing models, discounted cash flow methodologies or similar techniques and at least one significant model assumption or input is unobservable. The preferred stock warrants are measured using the Monte Carlo valuation model which is based, in part, upon inputs for which there is little or no observable market data, requiring the Company to develop its own assumptions. The assumptions used in calculating the estimated fair value of the warrants represent the Company’s best estimates; however, these estimates involve inherent uncertainties and the application of management judgment. As a result, if factors change and different assumptions are used, the warrant liability and the change in estimated fair value of the warrants could be materially different.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2018
Balance Sheet Components
Balance Sheet Components	4. Balance Sheet Components Property and Equipment, net Property and equipment, net consist of the following as of December 31, 2018 and 2017 (in thousands): December 31, 2018 2017 Lab equipment $ 1,737 $ 940 Computer equipment and software 25 25 1,762 965 Less: Accumulated depreciation (491) (215) $ 1,271 $ 750 Depreciation expense was approximately $276,000 and $57,000 for the year ended December 31, 2018 and 2017, respectively. Intangible Assets, net Intangible assets, net consist of the following as of December 31, 2018 and 2017 (in thousands): December 31, 2018 2017 Licenses $ 81 $ 81 $ 81 81 Less: Accumulated amortization (43) (38) $ 38 $ 43 Amortization expense was approximately $5,000 for each of the years ended December 31, 2018 and 2017, respectively. The estimated acquired intangible amortization expense for the next five fiscal years is as follows (in thousands): Year Ended December 31, 2019 5 2020 5 2021 5 2022 5 Thereafter 18 Total $ 38 Licenses University Licensing Agreements The University of Chicago — Co-Exclusive Patent License Agreement We are party to a co-exclusive licensing agreement with The University of Chicago (UOC), a non-profit university. This agreement granted to us a co-exclusive, royalty-bearing license for staph alpha toxin technology. The UOC agreement also granted to us the right to sublicense. UOC retained the non-transferrable right to use such patent rights for academic and research purposes, and also to certain pre-existing rights of the U.S. government. We paid an upfront fee upon the execution of the agreement and are obligated to pay an annual maintenance fee. We also are obligated to pay UOC low single digit percentage royalties on net sales from our and our sublicensee’s sale of any commercialized licensed product or process, and certain other payments, subject to a minimum amount. The aggregate milestone payments under the UOC agreement are up to $1,550,000. No milestones were met or accrued for during 2018. We are responsible for our pro rata share of patent expenses. The agreement provides that we have certain obligations to conduct further research and development, and are obligated to utilize reasonable efforts to commercialize, either directly or through a sublicensee, the licensed UOC patent rights as licensed products or processes. The term of the agreement continues until all patents and filed patent applications, included within the licensed UOC patents, have expired or been abandoned, or until the agreement is earlier terminated. We may terminate the agreement on prior written notice to UOC. Each party has the right to terminate the agreement for the other party’s uncured material breach of obligations under the agreement. The Brigham and Women’s Hospital, Inc. — Exclusive Patent License Agreement We are party to an exclusive licensing agreement with The Brigham and Women’s Hospital, Inc. (BWH), a non-profit corporation. This agreement granted to us an exclusive, royalty-bearing license under its and Beth Israel Deaconess Medical Center’s (BIDMC) rights in methods and composition relating to specific binding peptides to P. aeruginosa mucoid exopolysaccharide to make, use and sell products and processes for the treatment of pseudomonas infections in humans that are covered by such patent rights. The BWH agreement also granted to us the right to sublicense. BWH and BIDMC retained the non-transferrable right to use such patent rights for academic and research purposes, and also to certain pre-existing rights of the U.S. government. We also are obligated to pay BWH low single digit percentage royalties on net sales from our and our sublicensee’s sale of any commercialized licensed product or process, and certain other payments. The aggregate milestone payments under the BHW agreement are up to $860,000. No milestones were met or accrued for during 2018. We are responsible for diligently prosecuting and maintaining the licensed patent rights, at our sole cost and expense. The agreement provides that we have certain obligations to conduct further research and development, and are obligated to utilize reasonable efforts to commercialize, either directly or through a sublicensee, the licensed BWH patent rights as licensed products or processes. The term of the agreement continues until all patents and filed patent applications, included within the licensed BWH patents, have expired or been abandoned, or until the agreement is earlier terminated. We may terminate the agreement on prior written notice to BWH. Each party has the right to terminate the agreement for the other party’s uncured material breach of obligations under the agreement. The University of Iowa Research Foundation — Exclusive Patent License Agreement We are party to an exclusive licensing agreement with The University of Iowa Research Foundation (UIRF). The UIRF agreement granted to us an exclusive, royalty-bearing license under its rights in methods relating to gallium containing compounds for the treatment of infections to make, use and sell products that are covered by such patent rights. The UIRF agreement also granted to us the right to sublicense. UIRF retained the right and ability to grant right to use such patent rights for academic and research purposes, and also to certain pre-existing rights of the U.S. government including the United States Department of Veterans Affairs. We also are obligated to pay UIRF low single digit percentage royalties on net sales from our and our sublicensee’s sale of any commercialized licensed product or process, and certain other payments. The aggregate milestone payments under the UIRF agreement are up to $712,500. No milestones were met or accrued for during 2018. We are responsible for diligently prosecuting and maintaining the licensed UIRF patent rights, at our sole cost and expense. The agreement provides that we have certain obligations to conduct further research and development, and are obligated to utilize reasonable efforts to commercialize, either directly or through a sublicensee, the licensed UIRF patent rights as licensed products or processes. The term of the agreement continues until the expiration of the last to expire patents, included within the licensed UIRF patents, or until the agreement is earlier terminated. We may terminate the agreement on prior written notice to UIRF. Each party has the right to terminate the agreement for the other party’s uncured material breach of obligations under the agreement. Brigham Young University — Exclusive Patent License Agreement We are party to an exclusive licensing agreement with Brigham Young University (BYU). This agreement granted to us an exclusive, royalty-bearing license under its rights in stabilization of biological agents methods relating to human vaccines to make, use and sell products that are covered by such patent rights. The agreement also granted to us the right to sublicense. BYU and the Church of Jesus Christ of Latter-day Saints and the Church Education System retained the right and ability to use such patent rights for academic and ecclesiastical purposes and also to purchase products using such patents rights at a discounted price. We also are obligated to pay BYU low single digit percentage royalties on net sales from our and our sublicensee’s sale of any commercialized licensed product, and certain other payments. The aggregate milestone payments under the BYU agreement are up to $400,000. No milestones were met or accrued for during 2018. BYU is responsible for diligently prosecuting and maintaining the licensed BYU patent rights and we reimburse them for one-third of their costs. The agreement provides that we have certain obligations to conduct further research and development, and are obligated to utilize reasonable efforts to commercialize, either directly or through a sublicensee, the licensed BYU patent rights as licensed products or processes. The term of this agreement continues until the expiration of the last to expire patents, included within the licensed BYU patents, or until the agreement is earlier terminated. We may terminate the agreement on prior written notice to BYU. Each party has the right to terminate the agreement for the other party’s uncured material breach of obligations under the agreement. Public Health Service Licensing Agreement NIH ("National Institutes of Health") — Exclusive and Non-Exclusive Patent License Agreement We are party to an exclusive and non-exclusive licensing agreement with the NIH. This agreement granted to us an exclusive, royalty-bearing license in our exclusive territory and non-exclusive rights in the non-exclusive territory under its rights in a human rotavirus vaccine based on their human-bovine rotavirus reassortants to make, use and sell products and processes that are covered by such patent rights. The agreement also granted to us the right to sublicense. Our license under this agreement is subject to the U.S. government’s retained rights under a non-exclusive, worldwide, royalty-free license for the practice of all inventions licensed under the Public Health Service, or PHS, patent rights, by or on behalf of the U.S. government and on behalf of any foreign government or international organization pursuant to any existing or future treaty or agreement to which the U.S. government is a signatory. For purposes of encouraging basic research, the U.S. government also reserves the right to grant or require us to grant to a third party on reasonable terms a non-exclusive, non-transferable license to make and use the licensed products or licensed processes for research purpose only, but subject to PHS consulting with us in the event such third party is a commercial entity. Under certain exceptional and enumerated circumstances, the U.S. government may require us to grant a sublicense to a responsible third party applicant, on terms that are reasonable under the circumstances. The PHS takes responsibility for all aspects of the preparation, filing, prosecution and maintenance of any and all patent applications or patents included in the licensed PHS patent rights, subject to our payment of certain patent-related expenses. We also are obligated to pay PHS low single digit percentage royalties on net sales from our and our sublicensee’s sale of any commercialized licensed product or process, and certain other payments. The aggregate milestone payments under the NIH agreement are up to $850,000. No milestones were met or accrued for during 2018. PHS is responsible for diligently prosecuting and maintaining the licensed PHS patent rights, and we reimburse them for a portion of their costs. The agreement provides that we have certain obligations to conduct further research and development, and are obligated to utilize reasonable efforts to commercialize, either directly or through a sublicensee, the licensed PHS patent rights as licensed products or processes. The term of the PHS agreement continues until the expiration of all royalty obligations, included within the licensed PHS patents, or until the agreement is earlier terminated. We may terminate the agreement on prior written notice to PHS. Each party has the right to terminate the agreement for the other party’s uncured material breach of obligations under the agreement. Non-Profit Licensing Agreements Program for Appropriate Technology in Health and PATH Vaccine Solutions We granted the Program for Appropriate Technology in Health (PATH), a global non-profit organization, and the PATH Vaccine Solutions a non-exclusive license, with right to sublicense formulations, for use with the measles, rotavirus, live-attenuated influenza, pneumococcal and enteric vaccines only for sale in developing countries. We have also agreed to provide rotavirus vaccines to public sector purchasers in developing countries at a preferential price relative to private sector purchasers in developing countries where the rotavirus vaccine utilizing the enabling formulation technology is offered for sale. Corporate Licensing Agreements Kenta Biotech Ltd. We are party to an asset purchase agreement with Kenta Biotech Ltd. (Kenta), a for profit corporation (Aktiengesellschaft) duly incorporated in Schlieren (Canton of Zurich, Switzerland), registered under the identification number CH‑035.3.035.876‑2. The agreement assigned and transferred certain of Kenta’s physical assets, contracts and technology to us. The physical assets included all physical assets owned or controlled by Kenta, including but not limited to cell lines, genes, antibodies, diagnostic assays and related documentation, which were related to Kenta’s MabIgX technology platform for hybridoma generation and its mAb targeting S. aureus , P. aeruginosa , A. baumannii and RSV. The technology included all intellectual property, including but not limited to patents, patent applications, trademarks, knowhow, trade secrets, regulatory filings, clinical trials, clinical trial information, all supporting documentation and all other related intellectual property which are related to Kenta’s MabIgX technology platform for hybridoma generation and its mAb targeting S. aureus , P. aeruginosa , A . baumannii and RSV. The contracts included the contracts and agreements (including all rights and obligations thereunder), whether oral or written, which Kenta has concluded and which pertain to the assets. The contracts were primarily related to the ongoing clinical trial of AR 301. We were obligated to pay Kenta a fixed purchase price, which was fully paid during 2013 and 2014, and a declining scale of low double digit to low single digit percentage royalties on gross licensing revenues from either our licensing of the assets or net sales revenues actually received by us up to a maximum of $50,000,000. As of December 31, 2018, no milestones or royalty obligations had been met on these license agreements. Emergent Product Development Gaithersburg Inc. We are party to a license agreement with Emergent Product Development Gaithersburg Inc. (Emergent). We granted Emergent an exclusive, perpetual, royalty-bearing license to use certain of our patents and related know how for the prevention or treatment of infection or illness caused by biodefense pathogens. We also granted a non-exclusive, royalty-bearing license to use certain of our patents and related know how for the prevention or treatment of tularemia and viral hemorrhagic fever indications. Emergent is obligated to pay us low single digit percentage royalties on net sales from their and their sublicensee’s sale of any commercialized licensed product, and certain other payments. The aggregate milestone payments that the Company could receive under the Emergent agreement amount to $2,750,000. The Company is not aware of Emergent achieving any milestones under the agreement and has not received any milestone payments. The Company has certain diligence obligations to conduct further research and development, and to exploit licensed products. Accrued Liabilities Accrued liabilities consist of the following at December 31, 2018 and 2017 (in thousands): December 31, 2018 2017 Research and development services $ 2,179 $ 1,713 Stock option liability 455 — Payroll related expenses 254 207 Professional services 56 201 $ 2,944 $ 2,121

Equity Method Investment

Equity Method Investment	12 Months Ended
	Dec. 31, 2018
Equity Method Investment
Equity Method Investment	5. Equity Method Investment On February 11, 2018, the Company entered into a joint venture agreement (the “JV Agreement”) with Shenzen Hepalink Pharmaceutical Group Co., Ltd., a Chinese entity (“Hepalink”) that is a related party and significant shareholder in the Company, pursuant to which we formed a Joint Venture company named Shenzen Arimab BioPharmaceuticals Co., Ltd., or SABC, a People’s Republic of China Company, for developing and commercializing products for infectious diseases. Under the terms of the JV Agreement, the Company is obligated to contribute $1,000,000 and the license of its technology relating to the Company’s AR-101 and AR-301 product candidates for use by SABC in the territories of the Republic of China, Hong Kong, Macau and Taiwan (the “Territory”) and initially owns 49% of SABC. On July 2, 2018, SABC received final approval from the government of the Peoples Republic of China. On August 6, 2018, the Company entered into an amendment to the JV Agreement with Hepalink whereby the Company agreed to additionally contribute an exclusive, revocable, and royalty-free right and license to its AR-105 product candidate in the Territory. Pursuant to the JV Agreement and the amendment, Hepalink initially owns 51% of SABC and is obligated to contribute the equivalent of $7.2 million to SABC. Additionally, Hepalink is obligated to make an additional equity investment of $10,800,000 or more at the time of the SABC’s first future financing. The Company evaluated the accounting for the JV Agreement entered into noting that it did not meet the accounting definition of a joint venture and instead meets the definition of a variable interest entity. The Company concluded that it is not the primary beneficiary of SABC and therefore is not required to consolidate the entity. This conclusion was based on the fact that the equity-at-risk is insufficient to support operations without additional investment and that the Company does not hold decision-making power over activities that significantly impact SABC’s operations. The Company accounted for its investment in SABC as an equity method investment. The Company recorded the equity method investment at $1,000,000 which represents the Company's contribution into SABC. The Company's license contributed to SABC was recorded at its carryover basis of $0. For the years ended December 31, 2018 and 2017, the Company recognized $40,000 and $0 losses from the operations of SABC, respectively. As of December 31,2018 and 2017, the Company's equity method investment in the JV Entity was $960,000 and $0, respectively.

Warrants

Warrants	12 Months Ended
	Dec. 31, 2018
Warrants
Warrants	6. Warrants Common Stock Warrant Expense In November 2015, an engagement letter was effectuated with the Company’s current Vice Chairman of the Board of Directors. Under the terms of the engagement, upon being appointed the Company’s Vice Chairman and the closing of a minimum of $25 million in gross proceeds from sales of its Series A convertible preferred stock under a private placement memorandum, the Vice Chairman would receive 234,860 common stock warrants. On December 12, 2016, both of the aforementioned conditions had been met and the Company issued 234,860 common stock warrants at an exercise price of $14.50 per share. The fair value of the warrants was determined using a Monte Carlo simulation method which calculates the estimated value based on running numerous simulations and analyzing the various outcomes. The total fair value of award was approximately $661,000 and is being amortized over the five-year vesting period. For the year ended December 31, 2018 and 2017, the Company recorded stock-based compensation expense of approximately $132,000 and $132,000, respectively, related to these warrants. Warrant Liability The Company evaluated the accounting treatment for the Series A convertible preferred stock warrants issued in 2017 and in prior years and concluded pursuant to its evaluation of ASC 480 that due to the contingent liquidation redemption feature in the underlying Series A convertible preferred stock not being solely within the control of the Company, the Series A convertible preferred stock warrants issued were considered a liability. As a result, the Company has recorded a warrant liability and the subsequent changes in fair to be recorded as a component in other expense. The warrant liability requires the Company to remeasure the value of the underlying warrants and report the effect of the changes on our operations until the warrants are exercised or expire. The change in fair value of the warrant liability recorded in the consolidated statement of operations in 2018 and 2017 was a gain of $1,632,000 and a loss of $5,152,000, respectively. The primary underlying risk exposure pertaining to the warrants is the change in fair value of the underlying preferred stock for each reporting period. The warrant liability was measured using the Monte Carlo valuation model. Upon the Company's IPO, the Series A convertible preferred stock warrants were converted into common stock warrants (see Note 7) which resulted in the warrant liability being remeasured at the IPO dated and the reclassified into additional paid-in-capital. The following table (in thousands) summarizes the Company’s activity and fair value calculations of its derivative warrants for the year ended December 31, 2018 and 2017: Warrant Liability Balance, December 31, 2016 $ 6,365 Issuance of 5-year preferred stock warrants with financing - July 2017 351 Change in fair value of warrants 5,152 Balance, December 31, 2017 $ 11,868 Change in fair value of warrants (1,632) Reclassification into equity upon initial public offering (10,236) Balance, December 31, 2018 $ —

Convertible Preferred Stock

Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2018
Convertible Preferred Stock
Convertible Preferred Stock	7. Convertible Preferred Stock In connection with the IPO, the holders of a majority of the Series A Preferred Stock approved the mandatory conversion of the Series A Preferred Stock into one share of common stock for every 6.417896 shares of Series A Preferred Stock which converted immediately prior to the consummation of the IPO. Upon conversion, a total of 5,744,586 shares of common stock were issued for the converted Series A Preferred Stock which includes accrued dividends upon conversion. All warrants to purchase Series A Preferred Stock became warrants to purchase common stock, adjusted for the 1 for 6.417896 shares reverse stock split. All holders of Series A convertible preferred stock as of June 30, 2016 began accruing a 3% stock dividend beginning on July 1, 2016. Subsequent acquirers began accruing on the date they acquired their respective shares. Accrued dividends were payable annually on December 31. Dividends stopped accruing on August 13, 2018 when all outstanding preferred stock converted into common stock. On August 13, 2018, the Company issued 669,489 dividend shares to its preferred stockholders with a fair value of approximately $1,357,000. From June through August of 2017, the Company sold 6,516,135 shares of Series A convertible preferred stock to various investors at prices ranging from $2.70 to $2.95 per share for total gross proceeds of $18.3 million and net proceeds of $16.6 million after financing costs. On July 12, 2017, in conjunction with the sale of its Series A convertible preferred stock to one of the investors, the Company issued 370,370 warrants to purchase its Series A convertible preferred stock. The warrant has a term of five years from the issuance date. During June 2017, 2,033,898 shares of our Series A convertible preferred stock sold at $2.95 per share which contain price based anti-dilution protection rights. Unless agreed to otherwise, if the Company issues additional securities at a purchase price less than the purchase price paid by these respective holders, the Company shall issue additional preferred shares equal to the difference of the number of preferred shares that each respective shareholder would have received if they paid the subsequent lower price, and the number of share each respective shareholder originally received. The Company reviewed the embedded anti-dilution protection feature included in the Series A convertible preferred stock sold during 2017 pursuant to ASC 480, Distinguishing Liabilities From Equity , and ASC 815, Derivatives and Hedging , and determined that the provisions of ASC 480 did not result in liability classification, the embedded anti-dilution protection feature did not meet the definition of a derivative as there was no market for the Series A convertible preferred stock to be converted into cash and that the embedded anti-dilution protection feature did not require bifurcation. The liquidation preference provisions of the Series A convertible preferred stock were considered contingent redemption provisions because there are certain elements that are not solely within the control of the Company, such as a change in control of the Company. Accordingly, the Company presented the Series A convertible preferred stock within the mezzanine portion of the accompanying consolidated balance sheets at the full liquidation value. On December 30, 2016, the Company completed a private placement memorandum and sold 2,439,024 shares of its Series A convertible preferred stock at a price of $2.05 per share though a private offering memorandum for total gross proceeds of $5.0 million and net proceeds of approximately $4.5 million. The net proceeds of $4.5 million from the third closing was received in January 2017.

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2018
Common Stock
Common Stock	8. Common Stock As of December 31, 2018, the Company had reserved the following common stock for future issuance: Shares reserved for exercise of outstanding warrants to purchase common stock 1,966,930 Shares reserved for exercise of outstanding options to purchase common stock 825,205 2,792,135 As of December 31, 2017, the Company had reserved the following common stock for future issuance: Shares reserved for conversion of preferred stock 5,640,274 Shares reserved for exercise of outstanding warrants to purchase preferred stock 1,359,635 Shares reserved for exercise of outstanding warrants to purchase common stock 607,295 Shares reserved for exercise of outstanding options to purchase common stock 603,291 Shares reserved for issuance of future options 144,980 8,355,475

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2018
Stock-Based Compensation
Stock-Based Compensation	9. Stock-Based Compensation In May 2014, the Company adopted and the shareholders approved the 2014 Equity Incentive Plan (the 2014 Plan). Under the 2014 Plan, 233,722 shares of the Company’s common stock were initially reserved for the issuance of stock options to employees, directors, and consultants, under terms and provisions established by the Board of Directors. Under the terms of the 2014 Plan, options may be granted at an exercise price not less than fair market value. For employees holding more than 10% of the voting rights of all classes of stock, the exercise prices for incentive stock options may not be less than 110% of fair market value, as determined by the Board of Directors. The terms of options granted under the 2014 Plan may not exceed ten years. In addition, the 2014 Plan contains an "evergreen" provision allowing for an annual increase in the number of shares of our common stock available for issuance under the 2014 Plan on the first day of each fiscal year beginning in fiscal year 2015. The annual increase in the number of shares shall be equal to the greater of: · 77,908 shares of our common stock; or · such number of shares as is equal to the number of shares sufficient to cause the option pool to equal 20% of the issued and outstanding common stock of the Company, provided, however, that if on any calculation date the number of shares equal to 20% of the total issued and outstanding shares of common stock is less than the number of shares of common stock available for issuance under the 2014 Plan, no change will be made to the aggregate number of shares of common stock issuable under the 2014 Plan for that year (such that the aggregate number of shares of common stock available for issuance under the 2014 Plan will never decrease). The number of shares, terms, and vesting periods are determined by the Company’s Board of Directors or a committee thereof on an option by option basis. Options generally vest ratably over service periods of up to four years and expire ten years from the date of grant. The Company estimated the fair value of options using the BSM option valuation model. The fair value of employee options is being amortized on a straight -line basis over the requisite service period of the awards. During the year ended December 31, 2018 and 2017, stock-based compensation expense for employees was approximately $1,488,000 and $1,303,000, respectively, and stock-based compensation expense for director warrants was approximately $132,000 and $132,000, respectively. The fair value of the employee options granted during the years ended December 31, 2018 and 2017 were estimated using the following assumptions: Year Ended December 31, 2018 2017 Expected term (in years) 6.25 6.25 Expected volatility 77% - 79% 78% - 80% Risk-free interest-rate 2.22% - 2.99% 1.83% - 2.22% Dividend yield 0% 0% Stock option activity for the year ended December 31, 2018 and 2017 are represented in the following table: Options Outstanding Shares Weighted- Available Number of Average for Grant Shares Exercise Price Balance — December 31, 2016 214,758 455,605 $ 8.75 Additional shares reserved 77,908 — $ — Options granted (158,918) 158,918 $ 11.38 Options cancelled 11,232 (11,232) $ 4.64 Balance — December 31, 2017 144,980 603,291 $ 9.52 Additional shares reserved 77,908 — $ — Options exercised — (974) $ 9.63 Options granted (291,100) 291,100 $ 17.21 Options cancelled 68,212 (68,212) $ 10.52 Balance — December 31, 2018 — 825,205 $ 12.15 Options outstanding and exercisable at December 31, 2018 is as follows: Options Outstanding and Exercisable at December 31, 2018 Weighted Average Remaining Exercise Number Contractual Life Total Shares Weighted Average Price Outstanding (in years) Exercisable Exercise Price $ 2.89 183,840 5.9 182,151 $ 2.89 $ 8.50 47,883 9.9 125 $ 8.50 $ 9.63 72,340 8.5 31,238 $ 9.63 $ 12.77 23,175 9.7 2,095 $ 12.77 $ 12.96 58,161 7.0 54,786 $ 12.93 $ 13.16 181,915 7.8 178,602 $ 13.16 $ 17.01 154,711 9.0 42,284 $ 17.01 $ 17.20 103,180 9.3 27,927 $ 17.20 $ 11.24 825,205 8.2 519,208 $ 9.85 During the year December 31, 2018 and 2017, the Company granted options to employees to purchase 351,516 and 138,662 shares with a weighted-average grant date fair value of $9.89 and $11.78 per share, respectively. As of December 31, 2018, there were total unrecognized compensation costs for employees of approximately $3,704,000 related to these options. These costs are expected to be recognized over a period of approximately 2.9 years, respectively. The aggregate intrinsic value, based on the fair market value of the Company’s common stock, of options outstanding and vested as of December 31, 2018 was $1,556,000 and $1,186,000, respectively. The Company grants options to purchase common stock to consultants in exchange for services during the normal course of business. During the year ended December 31, 2018 and 2017, the Company granted options to consultants to purchase 16,000 and 20,256 shares, respectively. The fair value of the options granted to consultants during the year ended December 31, 2018 and 2017 were estimated using the following assumptions: Year Ended December 31, 2018 2017 Expected term (in years) 9.7 9.2 - 10.0 Expected volatility 84% 76% - 85% Risk-free interest-rate 3.01% 2.20% - 2.40% Dividend yield 0% 0% Stock-based compensation expense related to stock options granted to consultants is recognized on a straight-line basis, as the stock options are earned. The Company issued options to non-employees, which generally vest ratably over the time period the Company expects to receive services from the non-employee. The values attributable to these options are amortized over the service period and the unvested portion of these options was remeasured at each vesting date. During the year ended December 31, 2018 and 2017, stock-based compensation expense for consultants was approximately $38,000 and $173,000, respectively. In December 2018, the Company granted 76,417 stock options that were in excess of the number of shares available under the 2014 Plan. The Company estimated the fair value of these options using the BSM option valuation model which resulted in a deferred charge of $455,000 that is included in prepaid expenses and other current assets on the balance sheet and a stock option liability in the amount of $455,000 that is included in accrued liabilities in the consolidated balance sheet as of December 31, 2018. The fair value of the deferred charge and stock option liability during the years ended December 31, 2018 were estimated using the following assumptions: Year Ended December 31, 2018 Expected term (in years) 6.25 Expected volatility 77% - 79% Risk-free interest-rate 2.22% - 2.99% Dividend yield 0%

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Taxes
Income Taxes	10. Income Taxes On December 22, 2017, the “Tax Cuts and Jobs Act” (the “Tax Act”), was signed into law. Among other items, the Tax Act reduces the federal corporate tax rate to 21% from the existing maximum rate of 35%, effective January 1, 2018. As a result, the Company revalued its net deferred tax asset at the new lower tax rate as of December 31, 2017 which reduced the value of the deferred tax asset before valuation allowance by $2,572,000. The SEC staff issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (SAB 118) which allows the Company to record provisional amounts during a measurement period. At December 31, 2017 provisional amounts were recorded related to the deferred rate change. At December 31, 2018 the measurement period has ended and the Company's accounting related to the 2017 Tax Cuts and Jobs Act is complete. The Company did not make any measurement-period adjustments related to the provisional item recorded as of December 31, 2017. The Company has accumulated net losses since inception and has not recorded an income tax provision or benefit during the years ended December 31, 2018 and December 31, 2017. The following summarizes the difference (in thousands) between the income tax expense and the amount computed by applying the statutory federal income tax rate of 21% for 2018 and 34% for 2017 to income before income tax: December 31, 2018 2017 Federal income tax at statutory rate $ (4,642) $ (8,383) State income tax, net of federal benefit (1,300) (1,096) Effect of reduced corporate tax rates — 2,644 Foreign tax differential 733 1,993 Permanent differences 178 2,549 Tax credits generated in current year (783) (362) Other 1 269 Valuation allowance change 5,813 2,386 $ — $ — Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of our deferred tax assets (in thousands) are as follows: December 31, 2018 2017 Net operating loss carryforwards $ 10,228 $ 5,530 Accruals and reserves 1,053 707 Research and development credits 1,368 640 Deferred Revenue 6 — Depreciation and amortization (23) (4) Total 12,632 6,873 Valuation allowance (12,632) (6,873) Net deferred tax assets (liabilities) $ — $ — The Tax Legislation subjects a U.S. shareholder to tax on GILTI earned by certain foreign subsidiaries. The FASB Staff Q&A, Topic 740, No. 5, Accounting for Global Intangible Low-Taxed Income, states that an entity can make an accounting policy election to either recognized deferred taxes for temporary basis differences expected to reverse as GILTI in future years or to provide for the tax expense related to GILTI in the year the tax is incurred as a period expense only. The Company has elected to account for GILTI in the year the tax is incurred. The Company does not have a GILTI inclusion in 2018; therefore, no GILTI tax has been recorded for the year ended December 31, 2018. Based on the available objective evidence, management believes it is more-likely-than-not that the deferred tax assets were not fully realizable as of December 31, 2018 and 2017. Accordingly, the Company has established a full valuation allowance against its deferred tax assets. The net change in the valuation allowance for the year ended December 31, 2018 and 2017 was $5,813,000 and $2,386,000, respectively. At December 31, 2018, the Company had federal net operating loss carryforwards of approximately $19,555,000 that begin to expire in 2035. The Company has federal net operating losses of $16,450,000 that arose after the 2017 tax year and will carryforward indefinitely, the utilization of which is limited to 80% of taxable income in any given year. The net operating Company has net operating losses carryforwards of $38,186,000 that will begin to expire in 2035. At December 31, 2018, the Company has research credit carryforwards of $1,363,000 and $582,000 for federal and California state income tax purposes, respectively. The federal credits begin to expire in 2035 and the state credits can be carried forward indefinitely. Under the Internal Revenue Code (“IRC”) Sections 382 and 383, annual use of the Company’s net operating loss and research tax credit carryforwards to offset taxable income may be limited based on cumulative changes in ownership. The Company has not completed an analysis to determine whether any such limitations have been triggered as of December 31, 2018. The Company has no income tax affect due to the recognition of a full valuation allowance on the expected tax benefits of future loss carry forwards based on uncertainty surrounding realization of such assets. Any annual limitation may result in the expiration of net operating losses and credits before utilization. The Company may continue to experience ownership changes in the future as a result of the Company’s IPO, future expected equity financings and subsequent shifts in its stock ownership, some of which may be outside of its control. The Company is subject to taxation in the United States, California, the Netherlands and China. The Company remains subject to possible examination by tax authorities in these jurisdictions for tax years dating back to 2014. The Company does not have any pending tax examinations. Following the Company’s adoption of ASC 740-10 regarding accounting for uncertainty in income taxes, the Company made a comprehensive review of its portfolio of uncertain tax positions in accordance with the guidance. In this regard, an uncertain tax position represents the Company’s expected treatment of a tax position taken in a filed tax return, or planned to be taken in a future tax return, that has not been reflected in measuring income tax expense for financial reporting purposes. As a result of that review, the Company concluded there were no uncertain tax positions and no cumulative effect on retained earnings at the time of adoption. At December 31, 2018, the Company did not have any uncertain tax positions. The Company will recognize interest and penalties related to uncertain tax positions in income tax expense. As of December 31, 2018, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company’s statement of operations. The Company does not anticipate a material change to unrecognized tax benefits in the next twelve months.

Related Parties

Related Parties	12 Months Ended
	Dec. 31, 2018
Related Parties
Related Parties	11. Related Parties As discussed in Note 1, on February 11, 2018, the Company entered into a joint venture agreement (the “JV Agreement”) with Shenzen Hepalink Pharmaceutical Group Co., Ltd., a Chinese entity (“Hepalink”) that is a related party and significant shareholder in the Company, pursuant to which we formed a Joint Venture company named Shenzen Arimab BioPharmaceuticals Co., Ltd., or SABC, a People’s Republic of China Company, for developing and commercializing products for infectious diseases in the greater China territories. It was agreed by the parties that the Company shall be reimbursed for certain legal and contract manufacturing expenses related to the clinical drug supply for a Phase 3 clinical study of AR-301. No amounts were reimbursed during 2018, however as of December 31, 2018, an outstanding receivable for reimbursable expenses in the amount of $360,000 was included in prepaid expenses and other current assets on the consolidated balance sheet.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies
Commitments and Contingencies	12. Commitments and Contingencies Leases The Company leases office and lab space in San Jose, California under an operating lease arrangement which can be terminated at any time with 90 days’ notice. The Company recognizes rent expense as incurred. Rent expense was approximately $314,000 and $299,000, for the year ended December 31, 2018 and 2017, respectively. Indemnification In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnifications. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future but have not yet been made. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. However, the Company may incur charges in the future as a result of these indemnification obligations. Contingencies From time to time, the Company may have certain contingent liabilities that arise in the ordinary course of its business activities. The Company accrues a liability for such matters when it is probable that future expenditures will be made and such expenditures can be reasonably estimated. From time to time, the Company may be involved in various legal proceedings, claims and litigation arising in the ordinary course of business. As of December 31, 2018, there were no pending legal proceedings. Grant Income The Company receives various grants that are subject to audit by the grantors or their representatives. Such audits could result in requests for reimbursement for expenditures disallowed under the terms of the grant; however, management believes that these disallowances, if any, would be immaterial. Cystic Fibrosis Foundation Agreement In December 2016, the Company received an award for up to $2,902,097 from the Cystic Fibrosis Foundation to advance research on potential drugs utilizing inhaled gallium citrate anti-infective. In November 2018, the Cystic Fibrosis Foundation increased the award to $7,466,000. Under the award agreement, the Cystic Fibrosis Foundation will make payments to the Company as certain milestones are met. The award agreement also contains a provision whereby if the Company spends less on developing a potential drug utilizing inhaled gallium citrate anti-infective than the Company actually receives under this award agreement, the Company will be required to return the excess portion of the award to the Cystic Fibrosis Foundation. At the end of any reporting period, if the Company determines that the cumulative amount spent on this program is less than the cumulative cash received from the Cystic Fibrosis Foundation, the Company will record the excess amount received as a liability. In the event that development efforts are successful and the Company commercialized a drug from these related development efforts, the Company may be subject to pay to Cystic Fibrosis Foundation a one-time amount equal to nine times the actual award received. Such amount shall be paid in not more than five annual installments, as follows: within ninety days of the end of the calendar year in which the First Commercial Sale occurs, and within ninety days of the end of each subsequent calendar year until the amount is paid. The Company shall pay 15% of Net Sales for that calendar year up to the amount of the award (except that in the fifth installment, if any, the Company shall pay the remaining unpaid portion of the awarded amount). In the event that Aridis licenses rights to the product in the field to a third party, sells the product, or consummates a change of control transaction prior to the first commercial sale, the Company shall pay to Cystic Fibrosis Foundation an amount equal to 15% of the amounts received by Aridis and its shareholders in connection with a Disposition Transaction (whether paid upfront or in accordance with subsequent milestones and whether paid in cash or property) up to nine times the actual award received. The payment shall be made within sixty days after the closing of such a transaction.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Summary of Significant Accounting Policies
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of expenses during the reporting period. Such estimates include those related to the evaluation of our ability to continue as a going concern, revenue recognition, allowance for doubtful accounts, long-lived assets, income taxes, assumptions used in the Black-Scholes-Merton (“BSM”) model to calculate the fair value of stock-based compensation, Monte Carlo Simulation (“MSM”) model to calculate the fair value of warrants, deferred tax asset valuation allowances, valuation of the Company’s common and convertible preferred stock, fair value assumptions used in the valuation of warrants, preclinical study and clinical trial accruals and various accrued liabilities. Actual results could differ from those estimates.
Concentration of Risk	Concentration of Risk The Company’s cash and cash equivalents are maintained at financial institutions in the United States of America. Deposits held by these institutions may exceed the amount of insurance provided on such deposits. For the year ended December 31, 2018, two customers accounted for 58% and 42% of total revenue. For the year ended December 31, 2017, two customers accounted for 90% and 10% of total revenue. Both of the Company’s customers are located in the United States. As of December 31, 2018, two customers accounted for 60% and 40% of total accounts receivable. There were no accounts receivable as of December 31, 2017.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. Cash equivalents consist primarily of checking account and money market account balances.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at the invoiced amount and do not bear interest. The Company considers the credit worthiness of its customers but does not require collateral in advance of a sale. The Company evaluates collectability and maintains an allowance for doubtful accounts for estimated losses inherent in its accounts receivable portfolio when necessary. The allowance is based on the Company’s best estimate of the amount of losses in the Company’s existing accounts receivable, which is based on customer creditworthiness, facts and circumstances specific to outstanding balances, and payment terms. Account balances are charged off against the allowance after all means of collection have been exhausted and the potential for recovery is considered remote. As of December 31, 2018, and 2017, there were no allowances for doubtful accounts.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally five years. Maintenance and repairs are charged to expense as incurred. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the balance sheet and any resulting gain or loss is reflected in the consolidated statement of operations in the period realized.
Intangible Assets	Intangible Assets Intangible assets are recorded at cost and amortized over the estimated useful life of the asset. Intangible assets consist of licenses with various institutions whereby the Company has rights to use intangible property obtained from such institutions.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by comparison of the carrying amount to the future net cash flows which the assets are expected to generate. If such assets are considered to be impaired, the impairment is measured by the excess of the carrying amount of the assets over fair value less the costs to sell the assets, generally determined using the projected discounted future net cash flows arising from the asset. There have been no such impairments of long-lived assets as of December 31, 2018 and 2017.
Revenue Recognition	Revenue Recognition Revenue is recognized in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 605, Revenue Recognition which requires that four basic criteria must be met before revenue can be recognized: (1) persuasive evidence of an arrangement exists; (2) delivery has occurred and title and the risks and rewards of ownership have been transferred to the client or services have been rendered; (3) the price is fixed or determinable; and (4) collectability is reasonably assured. During 2018 and 2017, revenue includes grant awards and collaboration services entered into for specific research and development efforts. We recognize revenue under such awards and contracts as the related qualified research and development expenses are incurred or under the milestone method, up to the limit of the prior approval funding amounts, and when we have determined that we have earned the right to receive the recognized portion according to the terms of the original grant awarded. In December 2016, the Company received an award from the Cystic Fibrosis Foundation (“CF Foundation”) for approximately $2,902,000. The agreement contains an upfront payment of $200,000 which is being recognized straight-line over the term of the contract as we believe the upfront fee relates to services performed throughout the contract period and the upfront fee does not represent a substantive milestone within the agreement. Recognition of revenue for the remaining payments under the agreement will be recognized under the milestone method as substantive milestones are met. The milestones relate to pre-clinical and clinical research activities. The agreement also specifies that we are obligated to cumulatively spend on the development program at least an equal amount as it receives from the non-profit organization. In the event that we do not spend as much as we received under the agreement, we are obligated to return any overage to the non-profit organization. In November 2018, the CF Foundation increased the award to $7,466,000. For the years ended December 31, 2018 and 2017, all grant revenue totaling approximately $1,589,000 and $89,000, respectively, was derived from our award agreement with the CF Foundation. In 2017, the Company entered into a collaborative research and development agreement with GlaxoSmithKline plc (“GSK”). In accordance with the agreement, we received an upfront fee and are due annual fees and amounts for development work to be performed as specifically outlined under the agreement. The work to be performed was delineated into three specific research projects. In assessing the appropriate revenue recognition related to a collaboration agreement, we first determined whether the arrangement includes multiple elements, such as the delivery of intellectual property rights and research and development services. The multiple elements were analyzed to determine whether the deliverables could be separated or whether they must be accounted for as a single unit of accounting. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in our balance sheet. Recognition of revenue under the contract will be based on the terms of the contract and will be recognized under the proportional performance method derived from the completion of certain stages as defined within the contract. For the years ended December 31, 2018 and 2017, approximately $1,168,000 and $771,000, respectively, was recorded as collaboration revenue related to the Company’s agreement with GSK. In December 2018, at a meeting of the joint steering committee it was agreed by both parties to terminate the collaboration agreement. As a result of the termination of the collaboration agreement, the Company recognized all previously deferred revenue and an additional $440,000 for additional work performed during the term of the agreement.
Costs for Collaborative Arrangements	Costs for Collaborative Arrangements Costs incurred under collaborative arrangements include personnel costs, laboratory supplies and fees paid to third parties. These amounts are included in research and development in the accompanying consolidated statement of operations. For the years ended December 31, 2018 and 2017, the Company had incurred expenses of approximately $604,000 and $633,000, respectively, related to its collaborative arrangement.
Research and Development	Research and Development Research and development costs are charged to operations as incurred. Research and development expenses consist of salaries and benefits, laboratory supplies, consulting fees and fees paid to third parties.
Stock-Based Compensation	Stock-Based Compensation The Company recognizes compensation expense for all stock-based awards to employees and directors based on the grant-date estimated fair values, net of an estimated forfeiture rate. The Company recognizes stock-based compensation cost for employees and directors on a straight-line basis over the requisite service period for the award. Stock-based compensation expense is recognized only for those awards that are ultimately expected to vest. The Company estimates forfeitures based on an analysis of historical employee turnover and will continue to evaluate the appropriateness of the forfeiture rate based on actual forfeiture experience, analysis of employee turnover and other factors. The Company will revise the forfeiture estimate, if necessary, in subsequent periods if actual forfeitures differ from those estimates. Changes in forfeiture estimates impact stock-based compensation cost in the period in which the change in estimate occurs. The BSM option pricing model incorporates various highly sensitive assumptions, including the fair value of the Company’s common stock, expected volatility, expected term and risk-free interest rates. The weighted-average expected life of options was calculated using the simplified method as prescribed by the SEC’s Staff Accounting Bulletin, Topic 14 (“SAB Topic 14”). This decision was based on the lack of relevant historical data due to the Company’s limited historical experience. In addition, due to the Company’s limited historical data, the estimated volatility also reflects the application of SAB Topic 14, incorporating the historical volatility of comparable companies whose stock prices are publicly available. The risk-free interest rate for the periods within the expected term of the option is based on the U.S. Treasury yield in effect at the time of grant. The dividend yield was zero, as the Company has never declared or paid dividends and has no plans to do so in the foreseeable future. The Company accounts for stock-based compensation arrangements with non-employees by recording the expense of such services based on the estimated fair value of the common stock at the measurement date. The value of the equity instrument, including adjustment to fair value at each balance sheet date, is charged to net loss over the term of the service agreement.
Income Taxes	Income Taxes The Company accounts for income taxes under the liability method. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized. The Company assesses all material positions taken in any income tax return, including all significant uncertain positions, in all tax years that are still subject to assessment or challenge by the relevant taxing authorities. Assessing an uncertain tax position begins with the initial determination of the positions sustainability and is measured at the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement. At each balance sheet date, unresolved uncertain tax positions must be reassessed, and the Company will determine whether (i) the factors underlying the sustainability assertion have changed and (ii) the amount of the recognized benefit is still appropriate. The recognition and measurement of tax benefits requires significant judgment. Judgments concerning the recognition and measurement of a tax benefit might change as new information becomes available.
Comprehensive Loss	Comprehensive Loss The Company has no items of comprehensive income or loss other than net loss.
Loss Per Share	Loss Per Share Basic loss per common share is calculated by dividing net loss available to common shareholders for the period by the weighted-average number of common shares outstanding during the period. For diluted loss per share calculation purposes, the net loss available to common shareholders is adjusted to add back any preferred stock dividends reflected in the consolidated statement of operations for the respective periods. The following potentially dilutive securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been antidilutive: Year Ended December 31, 2018 2017 Convertible preferred stock — 36,196,193 Stock options to purchase common stock 825,205 603,291 Preferred stock warrants — 8,725,289 Common stock warrants 1,966,930 607,295 2,792,135 46,132,068
JOBS Act Accounting Election	JOBS Act Accounting Election The JOBS Act permits an “emerging growth company” such as us to take advantage of an extended transition period to comply with new or revised accounting standards applicable to public companies. We are choosing to take advantage of this provision and, as a result, we will adopt the extended transition period available under the JOBS Act until the earlier of the date we (i) are no longer an emerging growth company or (ii) affirmatively and irrevocably opt out of the extended transition period provided under the JOBS Act.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements adopted during the year ended December 31, 2018 In March 2016, the FASB issued ASU No. 2016 - 09, “Improvements to Employee Share - Based Payment Accounting,” which is intended to improve the accounting for employee share - based payments. The ASU simplifies several aspects of the accounting for share - based payment award transactions, including; the income tax consequences, classification of awards as either equity or liabilities, and the classification on the statement of cash flows. The new standard is effective for fiscal years beginning after December 15, 2017, and upon adoption, an entity should apply the amendments by means of a cumulative - effect adjustment to the balance sheet at the beginning of the first reporting period in which the guidance is effective. Early adoption is permitted. The Company adopted this standard in the consolidated financial statements for the year ended December 31, 2018, and such adoption did not have a material impact on the Company’s consolidated financial statements and related disclosures. In May 2017, the FASB issued ASU 2017 - 09, “Compensation — Stock Compensation (Topic 718): Scope of Modification Accounting,” to provide clarity and reduce both diversity in practice and cost complexity when applying the guidance in Topic 718 to a change to the terms and conditions of a stock - based payment award. ASU 2017 - 09 also provides guidance about the types of changes to the terms or conditions of a share - based payment award that require an entity to apply modification accounting in accordance with Topic 718. For all entities, including emerging growth companies, the standard is effective for annual periods beginning after December 15, 2017, and for interim periods therein. The Company adopted this standard in the consolidated financial statements for the year ended December 31, 2018, and such adoption did not have a material impact on the Company’s consolidated financial statements and related disclosures. Recently Issued Accounting Pronouncements not yet adopted as of December 31, 2018 In February 2016, the FASB issued ASU No. 2016 ‑ 02, “ Leases (Topic 842)”. In July 2018, the FASB issued ASU No. 2018-10, Codification Improvements to Topic 842, Leases, which provides clarification to ASU 2016-02. These ASUs (collectively, the new lease standard) require an entity to recognize a lease liability and a right-of-use asset on the balance sheet for leases with lease terms of more than twelve months. Lessor accounting is largely unchanged, while lessees will no longer be provided with a source of off-balance sheet financing. Initial guidance required the adoption of the new lease standard using the modified retrospective transition method. In July 2018, the FASB issued ASU No. 2018-11, Leases (Topic 842) - Targeted Improvements, which allows entities to elect an optional transition method where entities may continue to apply the existing lease guidance during the comparative periods and apply the new lease requirements through a cumulative effect adjustment in the period of adoptions rather than in the earliest period presented. This guidance is effective for public business entities for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. As a result of Company having elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act, ASU 2016-02 is effective for the Company for the year ended December 31, 2020, and all interim periods within. Early adoption is permitted. While the Company continues to review its current accounting policies and practices to identify potential differences that would result from applying the new guidance, the Company expects that its non-cancellable operating lease commitments with a term of more than twelve months will be subject to the new guidance and recognized as right-of-use assets and operating lease liabilities on the Company’s consolidated balance sheets upon adoption. The Company expects to elect transitional practical expedients such that the Company will not need to reassess whether contracts are leases and will retain lease classification and initial direct costs for leases existing prior to the adoption of the new lease standard. In May 2014, the FASB issued ASU No. 2014 - 09, “Revenue from Contracts with Customers.” The objective of ASU 2014 - 09 is to establish a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and will supersede most of the existing revenue recognition guidance, including industry - specific guidance. The core principle of ASU 2014 - 09 is that an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The new guidance mandates a five-step process, which requires entities to exercise significant judgment and involves estimates to be made on the transaction price and the timing over which revenue will be recognized. These include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. The two permitted transition methods under the new standard are the full retrospective method, in which the new standard would be applied to each prior reporting period presented and the cumulative effect of applying the new standard would be recognized at the earliest period shown, or the modified retrospective method, in which the cumulative effect of applying the new standard would be recognized at the date of initial application. Additional ASUs have been issued to amend or clarify the new standard as follows: In March 2016, FASB issued ASU 2016-08, “Principal versus Agent Considerations (Reporting Revenue Gross versus Net)”. The amendments of this standard are intended to improve the consistency and understandability of the implementation guidance on principal versus agent considerations. The effective date for ASU 2016-08 is the same as the effective date for ASU 2014-09. In April 2016, FASB issued ASU 2016-10,” Identifying Performance Obligations and Licensing”. This standard amends the guidance in ASU 2014-09 to improve the consistency and clarify the guidance on identifying performance obligations and licensing. The effective date for ASU 2016-10 is the same as the effective date for ASU 2014-09. In May 2016, FASB issued ASU 2016-12, “Revenue from Contracts with Customers (Topic 606)”: Narrow-Scope Improvements and Practical Expedients. ASU 2016-12 addresses narrow-scope improvements to the guidance on collectability, noncash consideration, and completed contracts at transition and provides a practical expedient for contract modifications at transition and an accounting policy election related to the presentation of sales taxes and other similar taxes collected from customers. The new revenue guidance is effective for public business entities for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. As a result of the Company having elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act, ASU 2014-09 was effective for the Company on January 1, 2019, and all interim periods thereafter. Early adoption is permitted. ASU 2014-09 also permits two methods of adoption: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). The Company is currently evaluating the impact the adoption of this standard will have on its consolidated financial statements and related disclosures. The Company will finalize its accounting assessment and quantitative impact of the adoption during the first quarter of fiscal year 2019, using the modified retrospective method, which will reflect the cumulative effect of the adoption retrospectively as of January 1, 2019, the initial date of adoption. In June 2016, the FASB issued ASU 2016 ‑ 13, “ Financial Instruments - Credit Losses (Topic 326) ” , which is intended to provide financial statement users with more useful information about expected credit losses on financial assets held by a reporting entity at each reporting date. The new standard replaces the existing incurred loss impairment methodology with a methodology that requires consideration of a broader range of reasonable and supportable forward-looking information to estimate all expected credit losses. For public business entities, ASU 2016 ‑ 13 is effective for fiscal years and interim periods within those years beginning after December 15, 2019. As a result of the Company having elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act, ASU 2016-13 is effective for the Company for the fiscal year ending on December 31, 2021, and all interim periods within. Early adoption is permitted. The Company is currently evaluating the impact of the adoption of this standard will have on its consolidated financial statements and related disclosures. In June 2018, the FASB issued ASU 2018-07, “Compensation – Stock Compensation (Topic 718), Improvements to Nonemployee Share-Based Payment Accounting”, which is intended to simplify the accounting for nonemployee share-based payment transactions by expanding the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. For public entities, ASU 2018-07 is effective for fiscal years beginning after December 15, 2018. As a result of the Company having elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act, ASU 2018-07 is effective for the Company for the year ending on December 31, 2020, and all interim periods within. Early adoption is permitted. The Company is currently evaluating the impact the adoption of this standard will have on its consolidated financial statements and related disclosures.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Summary of Significant Accounting Policies
Schedule of potentially dilutive securities excluded from computation of diluted net loss per share	Year Ended December 31, 2018 2017 Convertible preferred stock — 36,196,193 Stock options to purchase common stock 825,205 603,291 Preferred stock warrants — 8,725,289 Common stock warrants 1,966,930 607,295 2,792,135 46,132,068

Fair Value Disclosure (Tables)

Fair Value Disclosure (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosure
Schedule of categorization of financial instruments within the valuation hierarchy	Fair Value at December 31, 2018 ($in thousands) Total Level 1 Level 2 Level 3 Assets: Deferred charge related to stock option liability $ 455 $ — $ 455 $ — Totals $ 455 $ — $ 455 $ — Liabilities: Stock option liability $ 455 $ — $ 455 $ — Totals $ 455 $ — $ 455 $ — Fair Value at December 31, 2017 ($in thousands) Total Level 1 Level 2 Level 3 Liabilities: Warrant liability $ 11,868 $ — $ — $ 11,868 Totals $ 11,868 $ — $ — $ 11,868

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2018
Balance Sheet Components
Schedule of property and equipment, net	Property and equipment, net consist of the following as of December 31, 2018 and 2017 (in thousands): December 31, 2018 2017 Lab equipment $ 1,737 $ 940 Computer equipment and software 25 25 1,762 965 Less: Accumulated depreciation (491) (215) $ 1,271 $ 750
Schedule of intangible assets, net	Intangible assets, net consist of the following as of December 31, 2018 and 2017 (in thousands): December 31, 2018 2017 Licenses $ 81 $ 81 $ 81 81 Less: Accumulated amortization (43) (38) $ 38 $ 43
Schedule of estimated acquired intangible amortization expense	The estimated acquired intangible amortization expense for the next five fiscal years is as follows (in thousands): Year Ended December 31, 2019 5 2020 5 2021 5 2022 5 Thereafter 18 Total $ 38
Schedule of accrued liabilities	Accrued liabilities consist of the following at December 31, 2018 and 2017 (in thousands): December 31, 2018 2017 Research and development services $ 2,179 $ 1,713 Stock option liability 455 — Payroll related expenses 254 207 Professional services 56 201 $ 2,944 $ 2,121

Warrants (Tables)

Warrants (Tables)	12 Months Ended
	Dec. 31, 2018
Warrants
Schedule of fair value of derivative warrants	The following table (in thousands) summarizes the Company’s activity and fair value calculations of its derivative warrants for the year ended December 31, 2018 and 2017: Warrant Liability Balance, December 31, 2016 $ 6,365 Issuance of 5-year preferred stock warrants with financing - July 2017 351 Change in fair value of warrants 5,152 Balance, December 31, 2017 $ 11,868 Change in fair value of warrants (1,632) Reclassification into equity upon initial public offering (10,236) Balance, December 31, 2018 $ —

Common Stock (Tables)

Common Stock (Tables)	12 Months Ended
	Dec. 31, 2018
Common Stock
Schedule of company reserved common stock for future issuance	As of December 31, 2018, the Company had reserved the following common stock for future issuance: Shares reserved for exercise of outstanding warrants to purchase common stock 1,966,930 Shares reserved for exercise of outstanding options to purchase common stock 825,205 2,792,135 As of December 31, 2017, the Company had reserved the following common stock for future issuance: Shares reserved for conversion of preferred stock 5,640,274 Shares reserved for exercise of outstanding warrants to purchase preferred stock 1,359,635 Shares reserved for exercise of outstanding warrants to purchase common stock 607,295 Shares reserved for exercise of outstanding options to purchase common stock 603,291 Shares reserved for issuance of future options 144,980 8,355,475

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Stock-Based Compensation
Schedule of stock option activity	Options Outstanding Shares Weighted- Available Number of Average for Grant Shares Exercise Price Balance — December 31, 2016 214,758 455,605 $ 8.75 Additional shares reserved 77,908 — $ — Options granted (158,918) 158,918 $ 11.38 Options cancelled 11,232 (11,232) $ 4.64 Balance — December 31, 2017 144,980 603,291 $ 9.52 Additional shares reserved 77,908 — $ — Options exercised — (974) $ 9.63 Options granted (291,100) 291,100 $ 17.21 Options cancelled 68,212 (68,212) $ 10.52 Balance — December 31, 2018 — 825,205 $ 12.15
Schedule of options outstanding and exercisable by exercise price	Options Outstanding and Exercisable at December 31, 2018 Weighted Average Remaining Exercise Number Contractual Life Total Shares Weighted Average Price Outstanding (in years) Exercisable Exercise Price $ 2.89 183,840 5.9 182,151 $ 2.89 $ 8.50 47,883 9.9 125 $ 8.50 $ 9.63 72,340 8.5 31,238 $ 9.63 $ 12.77 23,175 9.7 2,095 $ 12.77 $ 12.96 58,161 7.0 54,786 $ 12.93 $ 13.16 181,915 7.8 178,602 $ 13.16 $ 17.01 154,711 9.0 42,284 $ 17.01 $ 17.20 103,180 9.3 27,927 $ 17.20 $ 11.24 825,205 8.2 519,208 $ 9.85
Options
Stock-Based Compensation
Schedule of fair value of the options granted estimated using assumptions	Year Ended December 31, 2018 2017 Expected term (in years) 6.25 6.25 Expected volatility 77% - 79% 78% - 80% Risk-free interest-rate 2.22% - 2.99% 1.83% - 2.22% Dividend yield 0% 0%
Options | Number of shares excess granted under the 2014 Plan
Stock-Based Compensation
Schedule of fair value of the options granted estimated using assumptions	Year Ended December 31, 2018 Expected term (in years) 6.25 Expected volatility 77% - 79% Risk-free interest-rate 2.22% - 2.99% Dividend yield 0%
Options | Consultants
Stock-Based Compensation
Schedule of fair value of the options granted estimated using assumptions	Year Ended December 31, 2018 2017 Expected term (in years) 9.7 9.2 - 10.0 Expected volatility 84% 76% - 85% Risk-free interest-rate 3.01% 2.20% - 2.40% Dividend yield 0% 0%

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Taxes
Schedule of the difference between income tax expense and the amount computed by applying the statutory federal income tax rate to income before income tax	The following summarizes the difference (in thousands) between the income tax expense and the amount computed by applying the statutory federal income tax rate of 21% for 2018 and 34% for 2017 to income before income tax: December 31, 2018 2017 Federal income tax at statutory rate $ (4,642) $ (8,383) State income tax, net of federal benefit (1,300) (1,096) Effect of reduced corporate tax rates — 2,644 Foreign tax differential 733 1,993 Permanent differences 178 2,549 Tax credits generated in current year (783) (362) Other 1 269 Valuation allowance change 5,813 2,386 $ — $ —
Significant components of deferred tax assets	Significant components of our deferred tax assets (in thousands) are as follows: December 31, 2018 2017 Net operating loss carryforwards $ 10,228 $ 5,530 Accruals and reserves 1,053 707 Research and development credits 1,368 640 Deferred Revenue 6 — Depreciation and amortization (23) (4) Total 12,632 6,873 Valuation allowance (12,632) (6,873) Net deferred tax assets (liabilities) $ — $ —

Description of Business and B_2

Description of Business and Basis of Presentation - Organization (Details)	12 Months Ended
	Dec. 31, 2018project
Description of Business and Basis of Presentation
Clinical candidates at the pivotal trial stage (in products)	2

Description of Business and B_3

Description of Business and Basis of Presentation - Basis of Presentation and Consolidation (Details)	12 Months Ended
	Dec. 31, 2018segmentsubsidiary
Description of Business and Basis of Presentation
Subsidiaries (in subsidiaries) | subsidiary	2
Operating segments (in segments)	1
Reporting segments (in segments)	1

Description of Business and B_4

Description of Business and Basis of Presentation - Reverse Stock Split, Initial Public Offering and Going Concern (Details) $ / shares in Units, $ in Thousands	Aug. 30, 2018USD ($)$ / sharesshares	Aug. 16, 2018USD ($)$ / sharesshares	Aug. 03, 2018shares	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Description of Business and Basis of Presentation
Proceeds from issuance of common stock, net				$ 25,079
Working capital				23,100
Accumulated deficit				$ (71,088)	$ (47,626)
IPO
Description of Business and Basis of Presentation
Proceeds from issuance of common stock, gross	$ 2,500	$ 26,000
Proceeds from issuance of common stock, net	2,300	22,800
Underwriting discounts and commissions	$ 200	1,800
Other offering expenses		$ 1,400
Common Stock
Description of Business and Basis of Presentation
Ratio of reverse stock split			0.155814
Conversion of Series A convertible preferred stock into common stock upon initial public offering (in shares) | shares			5,744,586
Common Stock | IPO
Description of Business and Basis of Presentation
Issuance of stock (in shares) | shares	192,824	2,000,000
Offering price per share | $ / shares	$ 13	$ 13

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Concentration of Risk (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Summary of Significant Accounting Policies
Accounts receivable	$ 1,660
Contract revenue | Customer 1 | Customer risk
Summary of Significant Accounting Policies
Concentration risk percentage	58.00%	90.00%
Contract revenue | Customer 2 | Customer risk
Summary of Significant Accounting Policies
Concentration risk percentage	42.00%	10.00%
Accounts receivable | Customer 1 | Customer risk
Summary of Significant Accounting Policies
Concentration risk percentage	60.00%
Accounts receivable | Customer 2 | Customer risk
Summary of Significant Accounting Policies
Concentration risk percentage	40.00%

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Accounts Receivable and Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Summary of Significant Accounting Policies
Allowance for doubtful accounts	$ 0	$ 0

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Property and Equipment and Impairment of Long-Lived Assets (Details)	12 Months Ended
	Dec. 31, 2018
Summary of Significant Accounting Policies
Estimated useful life (in years)	5 years

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Impairment of Long-Lived Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Summary of Significant Accounting Policies
Impairments of long-lived assets	$ 0	$ 0

Summary of Significant Accoun_8

Summary of Significant Accounting Policies - Revenue Recognition (Details)	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)project	Dec. 31, 2016USD ($)	Nov. 30, 2018USD ($)
Summary of Significant Accounting Policies
Revenue	$ 2,757,000	$ 860,000
Additional amount for extra work	440,000	440,000
CF foundation
Summary of Significant Accounting Policies
Amount of award received for advance research on potential drugs			$ 2,902,097	$ 7,466,000
Grant
Summary of Significant Accounting Policies
Revenue	1,589,000	89,000
Grant | CF foundation
Summary of Significant Accounting Policies
Revenue	1,589,000	89,000	$ 200,000
Collaboration revenue
Summary of Significant Accounting Policies
Revenue	$ 1,168,000	$ 771,000
Research projects (In projects) | project		3

Summary of Significant Accoun_9

Summary of Significant Accounting Policies - Costs for Collaborative Arrangements (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Summary of Significant Accounting Policies
Research and Development Expense	$ 23,000,000	$ 17,438,000
Collaboration revenue
Summary of Significant Accounting Policies
Research and Development Expense	$ 604,000	$ 633,000

Summary of Significant Accou_10

Summary of Significant Accounting Policies - Stock-Based Compensation (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Options
Common Stock for future issuance
Dividend yield (in percent)	0.00%	0.00%

Summary of Significant Accou_11

Summary of Significant Accounting Policies - Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Summary of Significant Accounting Policies
Potentially dilutive securities excluded from computation of diluted net loss per share	2,792,135	46,132,068
Series A Convertible Preferred Stock
Summary of Significant Accounting Policies
Potentially dilutive securities excluded from computation of diluted net loss per share		36,196,193
Options
Summary of Significant Accounting Policies
Potentially dilutive securities excluded from computation of diluted net loss per share	825,205	603,291
Warrants | Preferred stock
Summary of Significant Accounting Policies
Potentially dilutive securities excluded from computation of diluted net loss per share		8,725,289
Warrants | Common Stock
Summary of Significant Accounting Policies
Potentially dilutive securities excluded from computation of diluted net loss per share	1,966,930	607,295

Fair Value Disclosure (Details)

Fair Value Disclosure (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair value
Assets	$ 455
Liabilities	455	$ 11,868
Stock option liability
Fair value
Liabilities	455
Warrants
Fair value
Liabilities		11,868
Deferred charge related to stock options
Fair value
Assets	455
Level 2
Fair value
Assets	455
Liabilities	455
Level 2 | Stock option liability
Fair value
Liabilities	455
Level 2 | Deferred charge related to stock options
Fair value
Assets	$ 455
Level 3
Fair value
Liabilities		11,868
Level 3 | Warrants
Fair value
Liabilities		$ 11,868

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment, net (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property and Equipment, net
Property and Equipment, gross	$ 1,762,000	$ 965,000
Less: Accumulated depreciation	(491,000)	(215,000)
Property and equipment, net	1,271,000	750,000
Depreciation expense	276,000	57,000
Lab equipment
Property and Equipment, net
Property and Equipment, gross	1,737,000	940,000
Computer equipment and software
Property and Equipment, net
Property and Equipment, gross	$ 25,000	$ 25,000

Balance Sheet Components - Inta

Balance Sheet Components - Intangible Assets, net (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Intangible Assets, net
Intangible assets, gross	$ 81,000	$ 81,000
Less: Accumulated amortization	(43,000)	(38,000)
Intangible assets, net	38,000	43,000
Amortization expense	5,000	5,000
Licenses
Intangible Assets, net
Intangible assets, gross	$ 81,000	$ 81,000

Balance Sheet Components - In_2

Balance Sheet Components - Intangible Assets, Net- Amortization expense (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Acquired intangible amortization expense
2019	$ 5
2020	5
2021	5
2022	5
Thereafter	18
Intangible assets, net	$ 38	$ 43

Balance Sheet Components - In_3

Balance Sheet Components - Intangible Assets, Net - Licenses (Details)	12 Months Ended
	Dec. 31, 2018USD ($)
Corporate Licensing Agreement
Intangible Assets, net
Maximum royalty base for royalty payments	$ 50,000,000
Patent License Agreement
Intangible Assets, net
Reimbursement of 3rd party costs (in percent)	0.33%
The University of Chicago Agreement | Patent License Agreement
Intangible Assets, net
Milestone payments under the agreement	$ 1,550,000
The Brigham and Women's Hospital, Inc | Patent License Agreement
Intangible Assets, net
Milestone payments under the agreement	860,000
The University of Iowa Research Foundation | Patent License Agreement
Intangible Assets, net
Milestone payments under the agreement	712,500
Brigham Young University | Patent License Agreement
Intangible Assets, net
Milestone payments under the agreement	400,000
National Institutes of Health | Patent License Agreement
Intangible Assets, net
Milestone payments under the agreement	850,000
Emergent Product Development Gaithersburg Inc | Corporate Licensing Agreement
Intangible Assets, net
Milestone payments under the agreement	$ 2,750,000

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued Liabilities
Research and development services	$ 2,179	$ 1,713
Stock option liability	455
Payroll related expenses	254	207
Professional services	56	201
Accrued Liabilities, Current, Total	$ 2,944	$ 2,121

Equity Method Investment (Detai

Equity Method Investment (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Aug. 06, 2018	Feb. 11, 2018
Equity Method Investment
Contributions owed to the joint venture	$ 1,000,000
Loss from equity method investment	40,000
Equity method investment	960,000
SABC
Equity Method Investment
Contribution obligated			$ 1,000,000
Percentage of ownership interest			49.00%
Carryover basis of license contributed	$ 0
Hepalink | SABC
Equity Method Investment
Contribution obligated		$ 7,200,000
Percentage of ownership interest		51.00%
Minimum amount obligated to make an additional equity investment at first future financing		$ 10,800,000

Warrants (Details)

Warrants (Details) - USD ($)	Dec. 12, 2016	Nov. 30, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 12, 2016
Warrants to Purchase Common Stock
Total fair value of warrants			$ 11,868,000	$ 6,365,000
Share-based Compensation			1,658,000	1,608,000
Balance at beginning of the period			11,868,000	6,365,000
Issuance of 5-year preferred stock warrants with financing - July 2017				351,000
Change in fair value of preferred stock warrants			(1,632,000)	5,152,000
Reclassification into equity upon initial public offering			(10,236,000)
Balance at end of the period				11,868,000
Performance Award
Warrants to Purchase Common Stock
Minimum gross proceeds for meeting performance requirement		$ 25,000,000
Warrants potentially issued for meeting performance requirement		234,860
Number of warrants issued	234,860
Warrants exercise price					$ 14.50
Total fair value of warrants	$ 661,000				$ 661,000
Vesting period	5 years
Share-based Compensation			$ 132,000	$ 132,000
Balance at end of the period	$ 661,000

Convertible Preferred Stock (De

Convertible Preferred Stock (Details)	Aug. 13, 2018USD ($)shares	Aug. 03, 2018shares	Jul. 12, 2017shares	Dec. 30, 2016USD ($)$ / sharesshares	Jun. 30, 2016	Jun. 30, 2017$ / sharesshares	Jan. 31, 2017USD ($)	Aug. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2017USD ($)shares	Dec. 31, 2018shares
Convertible Preferred Stock
Proceeds from issuance of preferred stock, net | $									$ 21,060,000
Warrants
Convertible Preferred Stock
Number of warrants issued			370,370
Warrant term (in years)			5 years
Series A Convertible Preferred Stock
Convertible Preferred Stock
Dividend rate (in percentage)					3.00%
Preferred stock outstanding (in shares)									36,196,193	0
Preferred stock dividend shares issued (in shares)	669,489
Preferred stock dividend shares fair value | $	$ 1,357,000
Number of convertible preferred stock sold (in shares)				2,439,024		2,033,898		6,516,135
Price per share | $ / shares				$ 2.05		$ 2.95
Proceeds from issuance of preferred stock, gross | $				$ 5,000,000				$ 18,300,000
Proceeds from issuance of preferred stock, net | $							$ 4,500,000	$ 16,600,000
Series A Convertible Preferred Stock | Minimum
Convertible Preferred Stock
Price per share | $ / shares								$ 2.70
Series A Convertible Preferred Stock | Maximum
Convertible Preferred Stock
Price per share | $ / shares								$ 2.95
Common Stock
Convertible Preferred Stock
Ratio of reverse stock split		0.155814
Stock issued upon conversion of convertible shares		5,744,586

Common Stock (Details)

Common Stock (Details) - shares	Dec. 31, 2018	Dec. 31, 2017
Common Stock for future issuance
Common stock for future issuance	2,792,135	8,355,475
Options
Common Stock for future issuance
Common stock for future issuance		144,980
Series A Convertible Preferred Stock
Common Stock for future issuance
Common stock for future issuance		5,640,274
Common Stock
Common Stock for future issuance
Common stock for future issuance		603,291
Common Stock | Options
Common Stock for future issuance
Common stock for future issuance	825,205
Warrants | Series A Convertible Preferred Stock
Common Stock for future issuance
Common stock for future issuance		1,359,635
Warrants | Common Stock
Common Stock for future issuance
Common stock for future issuance	1,966,930	607,295

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) - USD ($)	Dec. 12, 2016	May 31, 2014	Dec. 31, 2018	Dec. 31, 2017
Stock-Based Compensation
Reserved for issuance (in shares)		233,722
Voting rights of all classes of stock (in percent)		10.00%
Exercise price for incentive stock options to the percentage of fair market value		110.00%
Annual increase in the number of shares to the shares of common stock			77,908	77,908
Share-based Compensation			$ 1,658,000	$ 1,608,000
Options
Stock-Based Compensation
Annual increase in the number of shares to the percentage of the issued and outstanding common stock		20.00%
Vesting period (in years)		4 years
Expiration period (in years)		10 years
Share-based Compensation			1,488,000	1,303,000
Performance Award
Stock-Based Compensation
Vesting period (in years)	5 years
Share-based Compensation			$ 132,000	$ 132,000

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions (Details) - Options	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair value of the options granted, estimated using assumptions
Expected term (in years)	6 years 3 months	6 years 3 months
Expected volatility, minimum	77.00%	78.00%
Expected volatility, maximum	79.00%	80.00%
Risk-free interest-rate, minimum	2.22%	1.83%
Risk-free interest-rate, maximum	2.99%	2.22%
Dividend yield (in percent)	0.00%	0.00%
Number of shares excess granted under the 2014 Plan
Fair value of the options granted, estimated using assumptions
Expected term (in years)	6 years 3 months
Expected volatility, minimum	77.00%
Expected volatility, maximum	79.00%
Risk-free interest-rate, minimum	2.22%
Risk-free interest-rate, maximum	2.99%
Dividend yield (in percent)	0.00%
Consultants
Fair value of the options granted, estimated using assumptions
Expected term (in years)	9 years 8 months 12 days
Expected volatility, minimum		76.00%
Expected volatility, maximum		85.00%
Expected volatility	84.00%
Risk-free interest-rate, minimum		2.20%
Risk-free interest-rate, maximum		2.40%
Risk-free interest-rate	3.01%
Dividend yield (in percent)	0.00%	0.00%
Consultants | Minimum
Fair value of the options granted, estimated using assumptions
Expected term (in years)		9 years 2 months 12 days
Consultants | Maximum
Fair value of the options granted, estimated using assumptions
Expected term (in years)		10 years

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock option activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Shares Available for Grant
Beginning of the period (in shares)	144,980
Additional shares reserved (in shares)	77,908	77,908
Options granted (in shares)	(291,100)	(158,918)
Options cancelled (in shares)	68,212	(11,232)
End of the period (in shares)		144,980
Options Outstanding, Number of Shares
Number of Shares, beginning of the period (in shares)	603,291
Number of Shares, Options exercised (in shares)	974
Number of Shares, Options granted (in shares)	291,100	158,918
Number of Shares, Options cancelled (in shares)	(68,212)	(11,232)
Number of Shares, end of the period (in shares)	825,205	603,291
Options Outstanding, Weighted-Average Exercise Price
Weighted-Average Exercise Price, beginning of the period (in dollars per share)	$ 9.52
Weighted-Average Exercise Price, Options exercised (in dollars per share)	9.63
Weighted-Average Exercise Price, Options granted (in dollars per share)	17.21	$ 11.38
Weighted-Average Exercise Price, Options cancelled (in dollars per share)	10.52	4.64
Weighted-Average Exercise Price, end of the period (in dollars per share)	$ 12.15	$ 9.52
Options
Shares Available for Grant
Beginning of the period (in shares)		214,758
Options Outstanding, Number of Shares
Number of Shares, beginning of the period (in shares)		455,605
Number of Shares, Options granted (in shares)	351,516	138,662
Options Outstanding, Weighted-Average Exercise Price
Weighted-Average Exercise Price, beginning of the period (in dollars per share)		$ 8.75

Stock-Based Compensation - Opti

Stock-Based Compensation - Options outstanding and exercisable (Details) - Options	12 Months Ended
	Dec. 31, 2018$ / sharesshares
Exercise Price, $2.89
Options outstanding and exercisable by exercise price
Exercise Price (in dollars per share) | $ / shares	$ 2.89
Number Outstanding (in shares) | shares	183,840
Weighted Average Remaining Contractual Life (in years)	5 years 10 months 24 days
Total Shares Exercisable (in shares) | shares	182,151
Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 2.89
Exercise Price 8.50
Options outstanding and exercisable by exercise price
Exercise Price (in dollars per share) | $ / shares	$ 8.50
Number Outstanding (in shares) | shares	47,883
Weighted Average Remaining Contractual Life (in years)	9 years 10 months 24 days
Total Shares Exercisable (in shares) | shares	125
Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 8.50
Exercise Price, $9.63
Options outstanding and exercisable by exercise price
Exercise Price (in dollars per share) | $ / shares	$ 9.63
Number Outstanding (in shares) | shares	72,340
Weighted Average Remaining Contractual Life (in years)	8 years 6 months
Total Shares Exercisable (in shares) | shares	31,238
Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 9.63
Exercise Price 12.77
Options outstanding and exercisable by exercise price
Exercise Price (in dollars per share) | $ / shares	$ 12.77
Number Outstanding (in shares) | shares	23,175
Weighted Average Remaining Contractual Life (in years)	9 years 8 months 12 days
Total Shares Exercisable (in shares) | shares	2,095
Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 12.77
Exercise Price, $12.96
Options outstanding and exercisable by exercise price
Exercise Price (in dollars per share) | $ / shares	$ 12.96
Number Outstanding (in shares) | shares	58,161
Weighted Average Remaining Contractual Life (in years)	7 years
Total Shares Exercisable (in shares) | shares	54,786
Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 12.93
Exercise Price, $13.16
Options outstanding and exercisable by exercise price
Exercise Price (in dollars per share) | $ / shares	$ 13.16
Number Outstanding (in shares) | shares	181,915
Weighted Average Remaining Contractual Life (in years)	7 years 9 months 18 days
Total Shares Exercisable (in shares) | shares	178,602
Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 13.16
Exercise Price, $17.01
Options outstanding and exercisable by exercise price
Exercise Price (in dollars per share) | $ / shares	$ 17.01
Number Outstanding (in shares) | shares	154,711
Weighted Average Remaining Contractual Life (in years)	9 years
Total Shares Exercisable (in shares) | shares	42,284
Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 17.01
Exercise Price, $17.20
Options outstanding and exercisable by exercise price
Exercise Price (in dollars per share) | $ / shares	$ 17.20
Number Outstanding (in shares) | shares	103,180
Weighted Average Remaining Contractual Life (in years)	9 years 3 months 18 days
Total Shares Exercisable (in shares) | shares	27,927
Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 17.20
Exercise Price 11.24
Options outstanding and exercisable by exercise price
Exercise Price (in dollars per share) | $ / shares	$ 11.24
Number Outstanding (in shares) | shares	825,205
Weighted Average Remaining Contractual Life (in years)	8 years 2 months 12 days
Total Shares Exercisable (in shares) | shares	519,208
Weighted Average Exercise Price (in dollars per share) | $ / shares	$ 9.85

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Stock-Based Compensation
Granted (in shares)		291,100	158,918
Stock-based compensation expense		$ 1,658,000	$ 1,608,000
Assets	$ 455,000	455,000
Liabilities	455,000	455,000	$ 11,868,000
Stock option liability
Stock-Based Compensation
Liabilities	455,000	455,000
Deferred charge related to stock options
Stock-Based Compensation
Assets	455,000	$ 455,000
Options
Stock-Based Compensation
Granted (in shares)		351,516	138,662
Weighted-average grant date fair value (in dollars per share)		$ 9.89	$ 11.78
Total unrecognized compensation costs	3,704,000	$ 3,704,000
Total unrecognized compensation costs, period of recognition (in years)		2 years 10 months 24 days
Aggregate intrinsic value, based on the fair market value of the common stock of options outstanding	$ 1,556,000	$ 1,556,000
Aggregate intrinsic value, based on the fair market value of the common stock of options vested		1,186,000
Stock-based compensation expense		1,488,000	$ 1,303,000
Options | Number of shares excess granted under the 2014 Plan
Stock-Based Compensation
Granted (in shares)	76,417
Options | Stock option liability | Accrued liabilities | Number of shares excess granted under the 2014 Plan
Stock-Based Compensation
Liabilities	$ 455,000	455,000
Options | Deferred charge related to stock options | Prepaid expenses and other current assets | Number of shares excess granted under the 2014 Plan
Stock-Based Compensation
Assets	$ 455,000	$ 455,000
Options | Consultants
Stock-Based Compensation
Granted (in shares)		16,000	20,256
Stock-based compensation expense		$ 38,000	$ 173,000

Income Taxes - Effective income

Income Taxes - Effective income tax rate reconciliation, Amount (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
Corporate tax rate (as a percent)	21.00%	34.00%
Reduction in deferred tax assets resulting from rate reduction		$ 2,572,000
Income tax expense benefit reconciliation
Federal income tax at statutory rate	$ (4,642,000)	(8,383,000)
State income tax, net of federal benefit	(1,300,000)	(1,096,000)
Effect of reduced corporate tax rates		2,644,000
Foreign tax differential	733,000	1,993,000
Permanent differences	178,000	2,549,000
Tax credits generated in current year	(783,000)	(362,000)
Other	1,000	269,000
Valuation allowance	$ 5,813,000	$ 2,386,000
Maximum
Income Taxes
Corporate tax rate (as a percent)		35.00%

Income Taxes - Components of de

Income Taxes - Components of deferred tax assets (liabilities) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Components of deferred tax assets
Net operating loss carryforwards	$ 10,228,000	$ 5,530,000
Accruals and reserves	1,053,000	707,000
Research and development credits	1,368,000	640,000
Deferred Revenue	6,000
Depreciation and amortization	(23,000)	(4,000)
Deferred Tax Assets, Gross, Total	12,632,000	6,873,000
Valuation allowance change	(12,632,000)	(6,873,000)
Net change in the valuation allowance	$ 5,813,000	$ 2,386,000

Income Taxes - Tax Cuts and Job

Income Taxes - Tax Cuts and Jobs Act of 2017 (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
Net change in the valuation allowance	$ 5,813,000	$ 2,386,000

Income Taxes - Net operating lo

Income Taxes - Net operating loss carryforwards and Tax credit carryforwards (Details)	12 Months Ended
	Dec. 31, 2018USD ($)
Income Taxes
Net operating loss carryforwards	$ 38,186,000
Federal
Income Taxes
Net operating loss carryforwards	19,555,000
Research credit carryforwards | Federal
Income Taxes
Tax credit carryforwards	1,363,000
Research credit carryforwards | State
Income Taxes
Tax credit carryforwards	582,000
After tax year 2017 | Federal
Income Taxes
Net operating loss carryforwards	$ 16,450,000
Utilization of operating loss carryforwards of taxable income (as a percent)	80.00%

Related Parties (Details)

Related Parties (Details)	Dec. 31, 2018USD ($)
Prepaid expenses and other current assets | Shenzen Hepalink Pharmaceutical Group Co., Ltd.("Hepalink")
Related parties
Outstanding receivable for reimbursable expenses	$ 360,000

Commitments and Contingencies -

Commitments and Contingencies - Leases and Contingencies (Details)	12 Months Ended
	Dec. 31, 2018USD ($)claim	Dec. 31, 2017USD ($)
Commitments and Contingencies
Notice period for termination of lease	90 days
Rent expense | $	$ 314,000	$ 299,000
Number of pending legal proceedings | claim	0

Commitments and Contingencies_2

Commitments and Contingencies - Cystic Fibrosis Foundation Agreement and Joint Venture Agreement (Details)	1 Months Ended	12 Months Ended
	Dec. 31, 2016USD ($)iteminstallment	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Nov. 30, 2018USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Collaboration Revenue, Additional Amount For Work Performed		$ 440,000	$ 440,000
CF foundation
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Amount of award received for advance research on potential drugs	$ 2,902,097			$ 7,466,000
Period for payment of annual installments	90 days
Maximum percentage of awarded amount of Net Sales	15.00%
Payment of amount received in connection with Disposition Transaction (as a percent)	15.00%
Number of multiplication on awarded amount payable if change of control prior to completion of the first commercial sale | item	9
CF foundation | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Number of annual installments for repayment of award | installment	5