Exicure (XCUR) 10-Q 6 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 31, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	EXICURE, INC.
Entity Central Index Key	1,698,530
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Small Business	true
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		44,358,000

UNAUDITED CONDENSED CONSOLIDATE

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 32,446	$ 25,764
Accounts receivable	52	0
Unbilled revenue receivable	7	13
Receivable from related party	4	17
Prepaid expenses and other assets	1,855	1,844
Total current assets	34,364	27,638
Property and equipment, net	1,130	1,317
Other noncurrent assets	32	32
Total assets	35,526	28,987
Current liabilities:
Current portion of long-term debt	4,926	0
Accounts payable	1,341	1,049
Accrued expenses and other current liabilities	3,035	1,273
Current portion of deferred revenue	0	1,034
Total current liabilities	9,302	3,356
Long-term debt, net	0	4,855
Common stock warrant liability	984	523
Other noncurrent liabilities	42	278
Total liabilities	10,328	9,012
Stockholders’ equity:
Common stock, $0.0001 par value per share; 200,000,000 shares authorized, 44,358,000 issued and outstanding, September 30, 2018; 39,300,823 shares issued and outstanding, December 31, 2017	4	4
Additional paid-in capital	75,433	53,586
Accumulated deficit	(50,239)	(33,615)
Total stockholders' equity	25,198	19,975
Total liabilities and stockholders’ equity	$ 35,526	$ 28,987

UNAUDITED CONDENSED CONSOLIDA_2

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	44,358,000	39,300,823
Common stock, shares outstanding (in shares)	44,358,000	39,300,823

UNAUDITED CONDENSED CONSOLIDA_3

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue:
Collaboration revenue	$ 57	$ 2,497	$ 112	$ 7,624
Total revenue	57	2,497	112	7,624
Operating expenses:
Research and development expense	4,001	3,121	11,111	9,910
General and administrative expense	1,919	1,270	5,952	4,806
Total operating expenses	5,920	4,391	17,063	14,716
Operating loss	(5,863)	(1,894)	(16,951)	(7,092)
Other income (expense), net:
Interest expense	(170)	(201)	(497)	(616)
Other income (loss), net	709	163	(210)	140
Total other income (loss), net	539	(38)	(707)	(476)
Net loss	$ (5,324)	$ (1,932)	$ (17,658)	$ (7,568)
Basic and diluted loss per common share (in dollars per share)	$ (0.13)	$ (1.12)	$ (0.44)	$ (41.27)
Basic and diluted weighted-average common shares outstanding (in shares)	41,527,922	1,725,906	40,121,295	183,395

UNAUDITED CONDENSED CONSOLIDA_4

UNAUDITED CONDENSED CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - 9 months ended Sep. 30, 2018 - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in- Capital	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2017		39,300,823
Beginning balance at Dec. 31, 2017	$ 19,975	$ 4	$ 53,586	$ (33,615)
Adoption of new accounting standard - ASC 606 at Dec. 31, 2017	1,034			1,034
Beginning balance, adjusted at Dec. 31, 2017	$ 21,009	$ 4	53,586	(32,581)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options (in shares)	22,494	22,494
Exercise of options	$ 41		41
Equity-based compensation	1,300		1,300
Issuance of common stock to consultants, net (in shares)		145,466
Issuance of common stock to consultants, net	436		436
Issuance of common stock in private placement, net (in shares)		4,889,217
Issuance of common stock in private placement, net	20,070		20,070
Net loss	(17,658)			(17,658)
Ending balance (in shares) at Sep. 30, 2018		44,358,000
Ending balance at Sep. 30, 2018	$ 25,198	$ 4	$ 75,433	$ (50,239)

UNAUDITED CONDENSED CONSOLIDA_5

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (17,658)	$ (7,568)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation and amortization	266	159
Equity-based compensation	1,300	1,104
Amortization of long-term debt issuance costs and fees	71	150
Other	291	0
Change in fair value of warrant liabilities	461	(201)
Changes in operating assets and liabilities:
Unbilled revenue receivable and accounts receivable	(46)	(201)
Receivable from related party	13	2
Prepaid expenses and other current assets	135	(1,835)
Accounts payable	278	1,361
Accrued expenses and other current liabilities	1,602	(1,209)
Deferred revenue	0	(6,207)
Other noncurrent liabilities	(237)	(2)
Net cash used in operating activities	(13,524)	(14,447)
Cash flows from investing activities:
Capital expenditures	(65)	(726)
Net cash used in investing activities	(65)	(726)
Cash flows from financing activities:
Proceeds from common stock offering	22,001	20,302
Proceeds from exercise of common stock options	41	43
Repayment of long-term debt	0	(595)
Payment of common stock financing costs	(1,771)	(1,264)
Net cash provided by financing activities	20,271	18,486
Net increase in cash and cash equivalents	6,682	3,313
Cash and cash equivalents - beginning of period	25,764	19,623
Cash and cash equivalents - end of period	32,446	22,936
Non-cash financing activities:
Issuance of common stock for professional services	436	0
Issuance of common stock warrants	0	211
Common stock issuance costs (accounts payable and accrued expenses)	160	1,773
Non-cash investing activities:
Capital expenditures (accounts payable and accrued expenses)	$ 14	$ 0

Description of Business and Bas

Description of Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Description of Business and Basis of Presentation	Description of Business and Basis of Presentation Description of Business Exicure is a clinical-stage biotechnology company developing gene regulatory and immuno-oncology therapeutics based on the Company’s proprietary Spherical Nucleic Acid (“SNA”) technology. We believe the design of the Company’s SNAs gives rise to chemical and biological properties that may provide advantages over other nucleic acid therapeutics and enable therapeutic activity outside of the liver. The Company intends to build a leading nucleic acid therapeutics company focused on the discovery and development of therapeutics based on the Company’s proprietary SNA technology, either on its own or in collaboration with pharmaceutical partners. Throughout this Quarterly Report on Form 10-Q, the terms “the Company” and “Exicure” refer to Exicure, Inc. and its 100% owned subsidiary, Exicure Operating Company. Exicure Operating Company holds all material assets, and conducts all business activities and operations, of the Company. References to the “Merger” refer to the September 26, 2017 transaction whereby Max-1 Acquisition Sub, Inc., a wholly-owned subsidiary of Max-1 Acquisition Corporation, or Max-1, merged with and into Exicure Operating Company (f/k/a Exicure, Inc.), a privately-held Delaware corporation, with Exicure Operating Company remaining as the surviving entity and a wholly-owned operating subsidiary of Max-1 (which then changed its name to Exicure, Inc.). References to the “2017 Private Placement” refer to the transactions following the Merger that occurred in several closings on September 26, 2017, October 27, 2017 and November 2, 2017 in which we sold to accredited investors approximately $31,513 worth of shares of common stock (before deducting placement agent fees and expenses which are approximately $3,966 ), or 10,504,196 shares, at a price of $3.00 per share. On July 9, 2015, AuraSense Therapeutics, LLC was converted into AuraSense Therapeutics, Inc., a privately-held Delaware corporation, and on the same date changed its name to Exicure, Inc., which actions together are referred to in these notes to unaudited condensed consolidated financial statements as the corporate conversion. In connection with the corporate conversion, the accumulated deficit of AuraSense Therapeutics, LLC of $18,837 was reclassified to additional paid-in capital. Basis of Presentation The accompanying unaudited condensed consolidated financial statements as of September 30, 2018 and December 31, 2017, and for the three and nine months ended September 30, 2018 and 2017, have been presented in conformity with generally accepted accounting principles in the United States (“GAAP”). Principles of Consolidation The accompanying unaudited condensed consolidated financial statements include the accounts of Exicure, Inc. and its 100% owned subsidiary, Exicure Operating Company. All intercompany transactions and accounts are eliminated in consolidation. Going Concern As of September 30, 2018, the Company has generated an accumulated deficit of $69,076 since inception and expects to incur significant expenses and negative cash flows for the foreseeable future. Based on the Company’s current operating plans, it believes that existing working capital at September 30, 2018 is sufficient to fund its current operating plans into the first quarter of 2020. Management believes that it will be able to obtain additional working capital through equity financings, partnerships and licensing, or other arrangements, to fund operations. However, there can be no assurance that such additional financing will be available and, if available, can be obtained on terms acceptable to the Company. If the Company is unable to obtain such additional financing, the Company will need to reevaluate future operating plans. Accordingly, there is substantial doubt regarding the Company’s ability to continue as a going concern. The accompanying unaudited condensed consolidated interim financial statements have been prepared as though the Company will continue as a going concern, which contemplates the realization of assets and satisfaction of liabilities in the normal course of business. The financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might be necessary should the Company be unable to continue as a going concern. Unaudited Interim Financial Information The accompanying interim condensed consolidated balance sheet as of September 30, 2018, the interim condensed consolidated statements of operations for the three and nine months ended September 30, 2018 and 2017, the interim condensed consolidated statement of changes in stockholders’ equity for the nine months ended September 30, 2018, and the interim condensed consolidated statements of cash flows for the nine months ended September 30, 2018 and 2017, are unaudited. The interim unaudited condensed consolidated financial statements have been prepared on the same basis as the annual audited financial statements; and in the opinion of management, reflect all adjustments, which include only normal recurring adjustments necessary for the fair statement of the Company’s financial position as of September 30, 2018, the results of its operations for the three and nine months ended September 30, 2018 and 2017, and the results of its cash flows for the nine months ended September 30, 2018 and 2017. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2018 and 2017 are unaudited. The results for the three and nine months ended September 30, 2018 are not necessarily indicative of results to be expected for the year ending December 31, 2018, or any other interim periods, or any future year or period. Use of Estimates The preparation of the financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Management bases its estimates on certain assumptions which it believes are reasonable in the circumstance and while actual results could differ from those estimates, management does not believe that any change in those assumptions in the near term would have a significant effect on the Company’s financial position, results of operations or cash flows. Actual results in future periods could differ from those estimates. Revision of Prior Period Financial Statements In connection with preparing our condensed consolidated interim financial information for the three months ended March 31, 2018, we identified errors that affected prior interim and annual periods related to the timing of recognition of research and development expense related to a contract for the clinical trial of one of our therapeutic candidates. We evaluated whether our previously issued consolidated financial statements were materially misstated and concluded that the errors individually and in the aggregate were not material to any of our previously issued financial statements. We revised the financial statements to correct the immaterial errors, and the accompanying comparative financial statements reflect these corrections. The correction of the errors increased prepaid expense and other current assets by $933 , decreased accrued expenses by $96 , and decreased accumulated deficit by $1,028 at December 31, 2017; decreased research and development expense, operating loss, and net loss by $381 and loss per share by $0.22 for the three months ended September 30, 2017; and decreased research and development expense, operating loss, and net loss by $1,369 and loss per share by $7.46 for the nine months ended September 30, 2017.

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies There have been no changes to the significant accounting policies disclosed in the Company’s most recent Annual Report on Form 10-K, except as required by recently adopted accounting pronouncements, as discussed below. Revenue Recognition Effective January 1, 2018, the Company adopted the provisions of Accounting Standards Codification (“ASC”) 606, Revenue from Contracts with Customers using the modified retrospective method for all contracts not completed as of the date of adoption. The reported results for 2018 reflect the application of ASC 606 guidance, while the reported results for 2017 were prepared under the guidance of ASC 605, Revenue Recognition (ASC 605). Under ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that are within the scope of ASC 606, the Company performs the following five steps: 1. Identify the contract with the customer. A contract with a customer exists when (i) the Company enters into an enforceable contract with a customer that defines each party’s rights regarding the goods or services to be transferred and identifies the related payment terms, (ii) the contract has commercial substance, and (iii) the Company determines that collection of substantially all consideration for goods and services that are transferred is probable based on the customer’s intent and ability to pay the promised consideration. The Company applies judgment in determining the customer’s intent and ability to pay, which is based on a variety of factors including the customer’s historical payment experience, or in the case of a new customer, published credit and financial information pertaining to the customer. 2. Identify the performance obligations in the contract. Performance obligations promised in a contract are identified based on the goods and services that will be transferred to the customer that are both capable of being distinct, whereby the customer can benefit from the good or service either on its own or together with other available resources, and are distinct in the context of the contract, whereby the transfer of the good or service is separately identifiable from other promises in the contract. To the extent a contract includes multiple promised goods and services, the Company must apply judgment to determine whether promised goods and services are both capable of being distinct and distinct in the context of the contract. If these criteria are not met, the promised goods and services are accounted for as a combined performance obligation. 3. Determine the transaction price. The transaction price is determined based on the consideration to which the Company will be entitled in exchange for transferring goods and services to the customer. To the extent the transaction price includes variable consideration, the Company estimates the amount of variable consideration that should be included in the transaction price utilizing either the expected value method or the most likely amount method, depending on the nature of the variable consideration. Variable consideration is included in the transaction price if, in the Company’s judgment, it is probable that a significant future reversal of cumulative revenue under the contract will not occur. Any estimates, including the effect of the constraint on variable consideration, are evaluated at each reporting period for any changes. Determining the transaction price requires significant judgment. 4. Allocate the transaction price to performance obligations in the contract. If the contract contains a single performance obligation, the entire transaction price is allocated to the single performance obligation. However, if a series of distinct services that are substantially the same qualifies as a single performance obligation in a contract with variable consideration, the Company must determine if the variable consideration is attributable to the entire contract or to a specific part of the contract. Contracts that contain multiple performance obligations require an allocation of the transaction price to each performance obligation on a relative standalone selling price basis unless the transaction price is variable and meets the criteria to be allocated entirely to a performance obligation or to a distinct service that forms part of a single performance obligation. The consideration to be received is allocated among the separate performance obligations based on relative standalone selling prices. 5. Recognize revenue when or as the Company satisfies a performance obligation. The Company satisfies performance obligations either over time or at a point in time. Revenue is recognized over time if either (i) the customer simultaneously receives and consumes the benefits provided by the entity’s performance, (ii) the entity’s performance creates or enhances an asset that the customer controls as the asset is created or enhanced, or (iii) the entity’s performance does not create an asset with an alternative use to the entity and the entity has an enforceable right to payment for performance completed to date. If the entity does not satisfy a performance obligation over time, the related performance obligation is satisfied at a point in time by transferring the control of a promised good or service to a customer. Examples of control are using the asset to produce goods or services, enhance the value of other assets, or settle liabilities, and holding or selling the asset. Licenses of intellectual property : If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from consideration allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the licenses. For licenses that are combined with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone payments: At the inception of each arrangement that includes development milestone payments, the Company evaluates the probability of reaching the milestones and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur in the future, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received and therefore revenue recognized is constrained as management is unable to assert that a reversal of revenue would not be possible. The transaction price is then allocated to each performance obligation on a relative standalone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration revenues and earnings in the period of adjustment. Royalties : For arrangements that include sales-based royalties, including milestone payments based on levels of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its collaboration agreements. As of September 30, 2018, the Company’s only revenue recognized is related to the Purdue Collaboration (see Note 3). Recently Adopted Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09 (ASC 606), Revenue from Contracts with Customers . This ASU, as amended by ASU 2015-14, affects any entity that either enters into contracts with customers to transfer goods and services or enters into contracts for the transfer of nonfinancial assets. ASU 2014-09 replaces most existing revenue recognition guidance in GAAP when it becomes effective. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under the currently effective guidance. These may 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. ASU 2014-09 is effective for Exicure in the first quarter of 2018 and early adoption is permitted beginning in the first quarter of 2017. The Company adopted ASC 606 on a modified retrospective basis. See above “Revenue Recognition” for a discussion of the Company’s updated policies related to revenue recognition effective January 1, 2018. Impact of adoption of ASC 606 The Company adopted ASC 606 using the modified retrospective method. The cumulative effect of applying the new guidance to all contracts with customers that were not completed as of January 1, 2018 was recorded as an adjustment to accumulated deficit as of the adoption date. As a result of applying the modified retrospective method to adopt the new guidance, the Company recorded reductions to both accumulated deficit and deferred revenue, current of $1,034 as of the date of adoption. As a result of the adoption of ASC 606: (i) there were no impacts to the totals of our cash flows from operating activities, cash flows from investing activities, or cash flows from financing activities in the accompanying unaudited condensed consolidated statement of cash flows for the nine months ended September 30, 2018; (ii) there were no impacts to the balances of the accompanying unaudited condensed consolidated balance sheet as of September 30, 2018, (iii) there were no impacts to total revenue, operating loss, or net loss in the accompanying unaudited condensed consolidated statement of operations for the three months ended September 30, 2018, and (iv) total revenue, operating loss, and net loss were lower by $1,034 each in the accompanying unaudited condensed consolidated statement of operations for the nine months ended September 30, 2018. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments . ASU 2016-15 addresses the classification of certain specific cash flow issues including debt prepayment or extinguishment costs, settlement of certain debt instruments, contingent consideration payments made after a business combination, proceeds from the settlement of certain insurance claims and distributions received from equity method investees. ASU 2016-15 is effective for the Company in the first quarter of 2018 and early adoption is permitted. An entity that elects early adoption must adopt all of the amendments in the same period. The Company adopted this guidance on January 1, 2018. The adoption of ASU 2016-15 did not have a material impact to the Company’s statement of cash flows. In May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting . ASU 2017-09 clarifies when changes to the terms or conditions of a share-based payment award must be accounted for as modifications. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award changes as a result of the change in terms or conditions. ASU 2017-09 will be applied prospectively to awards modified on or after the adoption date. ASU 2017-09 is effective for the Company for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted. The Company adopted this guidance on January 1, 2018. The adoption of ASU 2017-09 did not have a material impact to the Company’s financial statements. Recent Accounting Pronouncements Not Yet Adopted In February 2016, FASB issued ASU 2016-02, Leases (Topic 842) , which requires lessees to recognize right-of-use assets and lease liabilities on the balance sheet. ASU 2016-02 is to be applied using a modified retrospective approach at the beginning of the earliest comparative period in the financial statements. ASU 2016-02 will be effective for the Company beginning in the first quarter of 2019. Early adoption is permitted. The Company is currently evaluating the impact of adopting this standard on its financial statements.

Purdue Collaboration

Purdue Collaboration	9 Months Ended
	Sep. 30, 2018
Research and Development [Abstract]
Purdue Collaboration	Purdue Collaboration On December 2, 2016, the Company entered into a research collaboration, option and license agreement with Purdue Pharma, L.P. (“Purdue”), referred to herein as the “Purdue Collaboration.” Purdue has the option to obtain from us the full worldwide development and commercial rights to AST-005 (the Company’s therapeutic candidate that targets tumor necrosis factor), an option to obtain three additional collaboration targets and a further option to obtain from us the full worldwide development and commercial rights to any therapeutic candidates developed targeting the three additional collaboration targets. Additionally, Purdue has rights of first offer to some potential collaboration targets. These rights of first offer are subject to limitations in time and scope. In connection with the Purdue Collaboration, the Company received a non-refundable development fee of $10,000 . In addition, the Company is eligible to receive up to $776,500 upon successful completion of certain research, regulatory and commercial sales milestones. The research milestones are payable upon target identification and IND-enabling pre-clinical development, per program, with an aggregate total of up to $16,500 . The regulatory milestones are payable upon the initiation or completion of clinical trials, and regulatory approval in the United States and outside the United States, per program, with an aggregate total of up to $410,000 . The commercial sales milestones are payable upon achievement of specified aggregate product sales thresholds and total up to $350,000 . In the event a therapeutic candidate subject to the collaboration results in commercial sales, the Company is eligible to receive royalties ranging from the low single digits to a maximum of 10% on future net sales of such commercialized therapeutic candidates. Additionally, Purdue had an obligation to invest in a qualified equity financing of the Company if such financing was completed before June 2, 2017. The Company did not complete such qualified equity financing before June 2, 2017. In April 2018, Purdue notified the Company it had declined to exercise its option to develop AST-005 at that time, but that it also intended to retain rights relating to the TNF target, and Purdue reserved its right to continue joint development, with Exicure, of new anti-TNF drug candidates and to retain its exclusivity and other rights to AST-005. Purdue has not indicated that it has any plans to pursue AST-005 at this time. Prior to the adoption of ASC 606, the upfront payment of $10,000 was accounted for pursuant to ASC 605 and was recorded as deferred revenue and recognized on a ratable basis over the estimated performance period of the relevant research and development activities. On January 1, 2018, in connection with the adoption of ASC 606, the Company recorded the unamortized deferred revenue of $1,034 as an adjustment to the beginning balance of retained deficit at January 1, 2018. See Note 2, Significant Accounting Policies , for more information related to the adoption of ASC 606. The Company identified multiple performance obligations as part of the Purdue Collaboration agreement, including the upfront payment of $10,000 , discussed above, and the research and development services. The Company determined that the performance obligations should not be combined, the license should be recognized at the time the license is granted, and the research and development services should be recognized at the time the service is performed. The Purdue Collaboration agreement includes contingent promises related to specified research, development and regulatory milestones and sale-based milestones. Each contingent promise related to contingent and milestone payment is evaluated to determine whether it represents a material right. The Company recognizes any payment that is contingent upon the achievement of a substantive milestone entirely in the period in which it is determined that the revenue is not subject to a significant reversal. To date, the Company has not recognized any contingent payments in connection with the Purdue Collaboration agreement as revenue. During the three and nine months ended September 30, 2018, the Company recognized collaboration revenue of $57 and $112 , respectively, which consisted entirely of research and development activities that will be reimbursed by Purdue and is presented on a gross basis in the accompanying statement of operations. During the three and nine months ended September 30, 2017, the Company recognized collaboration revenue of $2,497 and $7,624 , respectively, which included $428 and $1,417 , respectively, of research and development activities that was reimbursed by Purdue and is presented on a gross basis in the accompanying statement of operations.

Supplemental Balance Sheet Info

Supplemental Balance Sheet Information	9 Months Ended
	Sep. 30, 2018
Supplemental Balance Sheet Information [Abstract]
Supplemental Balance Sheet Information	Supplemental Balance Sheet Information Property and equipment, net September 30, December 31, Scientific equipment $ 1,954 $ 1,797 Leasehold improvements 192 192 Furniture and fixtures 41 31 Computers and software 26 26 Construction in process 14 120 Property and equipment, gross 2,227 2,166 Less: accumulated depreciation (1,097 ) (849 ) Property and equipment, net $ 1,130 $ 1,317 Depreciation and amortization expense was $90 and $70 for the three months ended September 30, 2018 and 2017 , respectively, and $266 and $159 , for the nine months ended September 30, 2018 and 2017, respectively. Accrued expenses and other current liabilities September 30, December 31, Accrued legal expenses $ 1,068 $ 251 Accrued payroll-related expenses 732 718 Accrued clinical, contract research and manufacturing costs 651 205 Other accrued expenses 584 99 Accrued expenses and other current liabilities $ 3,035 $ 1,273

Debt

Debt	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Debt	Debt On January 15, 2018, the Company and Hercules Technology Growth Capital Limited (“Hercules”) amended its loan agreement so that amortization payments due for the thirteen (13) consecutive months commencing on December 1, 2017 through and including December 1, 2018 were deferred. Commencing on January 1, 2019, and continuing on the first business day of each month thereafter, the loan, including the deferred payments, shall begin amortizing in equal monthly installments of principal and interest based upon an amortization schedule equal to eighteen (18) consecutive months. Any remaining obligations under the loan agreement and other loan documents are due and payable on the maturity date on September 1, 2019. At September 30, 2018 and December 31, 2017, the carrying value of the current and noncurrent portion of long-term debt is $4,926 and $4,855 , respectively. At September 30, 2018, the principal maturities of the long-term debt were as follows: September 30, 2018 2018 $ — 2019 4,999 Principal balance outstanding 4,999 less: unamortized discount (65 ) less: unamortized debt issuance costs (8 ) Long-term debt 4,926 Current portion 4,926 Noncurrent portion $ — The Company paid interest on debt of $146 and $158 during the three months ended September 30, 2018 and 2017, respectively, and $425 and $470 during the nine months ended September 30, 2018 and 2017, respectively.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Preferred Stock As of September 30, 2018 and December 31, 2017, the Company had 10,000,000 shares of preferred stock, par value $0.0001 authorized and no shares issued and outstanding. Common Stock As of September 30, 2018 and December 31, 2017, the Company had authorized 200,000,000 shares of common stock, par value $0.0001 . As of September 30, 2018, the Company had 44,358,000 shares issued and outstanding. As of December 31, 2017, the Company had 39,300,823 shares issued and outstanding. The holders of shares of the Company’s common stock are entitled to one vote per share on all matters to be voted upon by Exicure stockholders and there are no cumulative rights. Subject to preferences that may be applicable to any outstanding preferred stock, the holders of shares of the Company’s common stock are entitled to receive ratably any dividends that may be declared from time to time by Exicure’s board of directors (the “Board”) out of funds legally available for that purpose. In the event of the Company’s liquidation, dissolution or winding up, the holders of shares of Exicure common stock are entitled to share ratably in all assets remaining after payment of liabilities, subject to prior distribution rights of preferred stock then outstanding. Exicure common stock has no preemptive or conversion rights or other subscription rights. There are no redemption or sinking fund provisions applicable to Exicure common stock. The outstanding shares of Exicure common stock are fully paid and non-assessable. August 2018 Private Placement On August 22, 2018, we entered into subscription agreements with several accredited investors, pursuant to which we agreed to issue and sell a total of 4,889,217 shares of the Company’s common stock, at a purchase price of $4.50 per share, resulting in approximately $22,001 in gross proceeds to the Company (the “August 2018 Private Placement”). The aggregate net proceeds from the August 2018 Private Placement (after deducting placement agent fees and expenses of the offering of $1,931 ) were $20,070 . The Company also entered into a registration rights agreement with the investors in the August 2018 Private Placement, which required us to file a “resale” registration statement with the SEC covering the Shares issued in the August 2018 Private Placement within 30 calendar days from the final closing of the August 2018 Private Placement Offering. The Company filed and caused to become effective a registration statement with the SEC on October 5, 2018 registering the resale of 5,034,683 shares of our common stock, consisting of (i) 4,889,217 shares that were privately issued through the August 2018 Private Placement and (ii) 145,466 shares that were privately issued on February 1, 2018 in connection with consulting services. In connection with the closing of the August 2018 Private Placement, the placement agents received an aggregate of $1,680 in cash placement fees, and the Company reimbursed up to $87 of expenses incurred by the placement agents in connection with this closing of the August 2018 Private Placement. Common Stock Warrants In connection with the 2017 Private Placement, placement agents received warrants to purchase an aggregate of 413,320 shares of Exicure common stock (the “Warrants”) in connection with all closings of the 2017 Private Placement. The Warrants expire on March 27, 2021, have an exercise price of $3.00 per share, and have been issued on the same terms in all closings of the 2017 Private Placement. The Warrants are classified as a liability. The common stock warrant liability is remeasured each period at fair value. As of September 30, 2018, Warrants to purchase 413,320 shares of common stock remain outstanding. See Note 10, Fair Value Measurements for more information on the fair value of the common stock warrant liability.

Equity-Based Compensation

Equity-Based Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity-Based Compensation	Equity-Based Compensation As of September 30, 2018, the aggregate number of common stock options available for grant under the 2017 Equity Incentive Plan was 928,443 . Equity-based compensation expense is classified in the statements of operations as follows: Three Months Ended Nine Months Ended September 30, 2018 2017 2018 2017 Research and development expense $ 133 $ 43 $ 353 $ 129 General and administrative expense 383 319 947 975 $ 516 $ 362 $ 1,300 $ 1,104 Unamortized equity-based compensation expense at September 30, 2018 was $3,635 , which is expected to be amortized over a weighted-average period of 2.8 years . The Company utilizes the Black-Scholes option-pricing model to determine the fair value of common stock option grants. The Black-Scholes option-pricing model was developed for use in estimating the fair value of traded options that have no vesting restrictions and are fully transferable. The model also requires the input of highly subjective assumptions. In addition to an assumption on the expected term of the option grants as discussed below, application of the Black-Scholes model requires additional inputs for which we have assumed the values described in the table below: Nine Months Ended September 30, 2018 2017 Expected term 5.3 to 6.0 years 5.3 to 6.5 years Risk-free interest rate 2.72% to 2.87%; weighted avg. 2.78% 1.97% to 2.17%; weighted avg. 2.07% Expected volatility 78.1% to 82.4%; weighted avg. 80.6% 80.8% to 83.1%; weighted avg. 81.0% Forfeiture rate 5 % 5 % Expected dividend yield — % — % The expected term is based upon the “simplified method” as described in Staff Accounting Bulletin Topic 14.D.2. Currently, the Company does not have sufficient experience to provide a reasonable estimate of an expected term of its common stock options. The Company will continue to use the “simplified method” until there is sufficient experience to provide a more reasonable estimate in conformance with ASC 718-10-30-25 through 30-26. The risk-free interest rate assumptions were based on the U.S. Treasury bond rate appropriate for the expected term in effect at the time of grant. The expected volatility is based on calculated enterprise value volatilities for publicly traded companies in the same industry and general stage of development. The estimated forfeiture rates were based on historical experience for similar classes of employees. The dividend yield was based on expected dividends at the time of grant. The fair value of the underlying common stock and the exercise price for the common stock options granted during the nine months ended September 30, 2018 and 2017 are summarized in the table below: Common Stock Options Granted During Period Ended: Fair Value of Underlying Common Stock Exercise Price of Common Stock Option Nine months ended September 30, 2018 $3.00 to $5.82; weighted avg. $3.45 $3.00 to $5.82; weighted avg. $3.45 Nine months ended September 30, 2017 $4.21 $4.21 The weighted-average grant date fair value of common stock options granted in the nine months ended September 30, 2018 and 2017 was $2.40 and $2.92 per common stock option, respectively. A summary of common stock option activity as of the periods indicated is as follows: Options Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value (thousands) Outstanding - December 31, 2017 3,672,620 $ 1.79 7.5 $ 5,221 Granted 1,277,744 3.45 Exercised (22,494 ) 1.81 Forfeited (36,282 ) 2.29 Outstanding - September 30, 2018 4,891,588 $ 2.22 7.6 $ 9,523 Exercisable - September 30, 2018 3,021,753 $ 1.62 6.8 $ 7,541 Vested and Expected to Vest - September 30, 2018 4,778,505 $ 2.20 7.5 $ 9,421 The aggregate intrinsic value of common stock options exercised during the nine months ended September 30, 2018 and 2017 was $51 and $202 , respectively.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company incurred a pretax loss in each of the three and nine months ended September 30, 2018 and 2017, which consists entirely of loss in the U.S. and resulted in no provision for income tax expense during the periods then ended. The effective tax rate is 0% in each of the three and nine months ended September 30, 2018 and 2017 because the Company has generated tax losses and has provided a full valuation allowance against its deferred tax assets.

Loss Per Common Share

Loss Per Common Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Loss Per Common Share	Loss Per Common Share Basic loss per common share is calculated by dividing net loss by the weighted-average number of shares of common stock outstanding during the period. Diluted loss per common share is calculated using the treasury share method by giving effect to all potentially dilutive securities that were outstanding. Potentially dilutive options and warrants to purchase common stock that were outstanding during the periods presented were excluded from the diluted loss per share calculation because such shares had an anti-dilutive effect due to the net loss reported in those periods. Therefore, basic and diluted loss per common share is the same for each of the three and nine months ended September 30, 2018 and 2017. The following is the computation of loss per common share for the three and nine months ended September 30, 2018 and 2017: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Net loss $ (5,324 ) $ (1,932 ) $ (17,658 ) $ (7,568 ) Weighted-average basic and diluted common shares outstanding 41,527,922 1,725,906 40,121,295 183,395 Loss per share - basic and diluted $ (0.13 ) $ (1.12 ) $ (0.44 ) $ (41.27 ) The outstanding securities presented below were excluded from the calculation of net loss per common share, because such securities would have been anti-dilutive due to the Company’s net loss per share during the periods ending on the dates presented: September 30, 2018 2017 Options to purchase common stock 4,891,588 3,678,359 Warrants to purchase common stock 413,320 163,174

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements ASC Topic 820, Fair Value Measurement, establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value, as follows: Level 1 Inputs - unadjusted quoted prices in active markets for identical assets or liabilities accessible to the reporting entity at the measurement date; Level 2 Inputs - other than quoted prices included in Level 1 inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the asset or liability; and Level 3 Inputs - unobservable inputs for the asset or liability used to measure fair value to the extent that observable inputs are not available, thereby allowing for situations in which there is little, if any, market activity for the asset or liability at measurement date. The Company uses the market approach and Level 1 inputs to value its cash equivalents. The Company’s long-term debt bore interest at the prevailing market rates for instruments with similar characteristics and, accordingly, the carrying value for this instrument also approximates its fair value and the financial measurement is also classified within Level 2 of the fair value hierarchy. The Company’s common stock warrant liability (refer to Note 6, Stockholders’ Equity for more information) is classified within Level 3 of the fair value hierarchy. The fair value of the common stock warrant liability was determined using the Black-Scholes option-pricing model. The following weighted-average assumptions were used to estimate the fair value of the common stock warrant liability at September 30, 2018: September 30, 2018 Expected term 2.5 years Risk-free interest rate 2.83 % Expected volatility 81.78 % Expected dividend yield — % A 10% change in the estimate of expected volatility at September 30, 2018 would increase or decrease the fair value of the common stock warrant liability in the amount of $55 . A 10% change in the estimate of fair value of the common stock at September 30, 2018 would increase or decrease the fair value of the common stock warrant liability in the amount of $141 . The following is a reconciliation of the Company’s liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3) for the nine months ended September 30, 2018: Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Common Stock Warrant Liability Balance at January 1, 2018 $ 523 Loss included in other income (expense), net 461 Balance at September 30, 2018 $ 984

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Leases The Company conducts all operations in a facility under an operating lease which commenced in March 2012 and was originally scheduled to end in February 2015. The lease was extended for an additional six years through February 2021 during the first quarter of 2014 and includes a renewal option. During the second quarter of 2016, the Company amended the lease agreement to include additional space to be used primarily for administrative functions effective in May 2016. Lease payments include a fixed payment amount as well as contingent payments related to a proportionate share of operating and real estate expenses. At the inception of the lease, the lessor paid for leasehold improvements totaling $52 which has been capitalized and is being amortized over the lease term. The fixed payment amounts, including those in connection with the amended lease agreement in the second quarter of 2016, increase over the term of the lease but rent expense is recognized on a straight-line basis resulting in the recognition of deferred rent liability of $41 and $48 as of September 30, 2018 and December 31, 2017, respectively, calculated on the basis of the extended lease agreement. Rent expense consisted of the following: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Straight-line rent expense $ 83 $ 83 $ 249 $ 249 Contingent rent expense 67 77 231 232 Total rent expense $ 150 $ 160 $ 480 $ 481 Future minimum lease payments as of September 30, 2018 are as follows: Years Ending December 31, Operating Leases 2018 85 2019 347 2020 353 2021 59 Thereafter — Total $ 844 Northwestern University License Agreements On December 12, 2011, (1) AuraSense, LLC assigned to the Company all of its worldwide rights and interests under AuraSense, LLC’s 2009 license agreement with Northwestern University (“NU”) in the field of the use of nanoparticles, nanotechnology, microtechnology or nanomaterial-based constructs as therapeutics or accompanying therapeutics as a means of delivery, but expressly excluding diagnostics (the “assigned field”); (2) in accordance with the terms and conditions of this assignment, the Company assumed all liabilities and obligations of AuraSense, LLC as set forth in its license agreement in the assigned field; and (3) in order to secure this assignment and the patent rights from NU, the Company agreed (i) to pay NU an annual license fee, which may be credited against any royalties due to NU in the same year, (ii) to reimburse NU for expenses associated with the prosecution and maintenance of the license patent rights, (iii) to pay NU royalties based on any net revenue generated by the Company’s sale or transfer of any licensed product, and (iv) to pay NU, in the event the Company grants a sublicense under the licensed patent rights, the greater of a percentage of all sublicensee royalties or a percentage of any net revenue generated by a sublicensee’s sale or transfer of any licensed product. In August 2015, we entered into a restated license agreement with NU (the “restated license agreement”). In February 2016, we obtained exclusive license as to NU’s rights in certain SNA technology we jointly own with NU. Our license to NU’s rights is limited to the assigned field, however we have no such limitation as to our own rights in this jointly owned technology. In June 2016, we entered into an exclusive license with NU to obtain worldwide rights to certain inhibitors of glucosylceramide synthase and their use in wound healing in diabetes. Our rights and obligations in these 2016 agreements are substantially the same as in the restated license agreement from August 2015 (collectively referred to as “the Northwestern University License Agreements”). As of September 30, 2018, the Company has paid to NU an aggregate of $3,844 in consideration of each of the obligations described above.

Related-Party Transactions

Related-Party Transactions	9 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Related-Party Transactions	Related-Party Transactions Since its inception in 2011, the Company has shared facilities, certain staff members and certain operating expenses with AuraSense, LLC, our former parent and largest stockholder. On an infrequent basis, the Company also pays certain expenses directly on behalf of AuraSense, LLC which are related to AuraSense, LLC’s grants, and AuraSense, LLC sometimes pays expenses directly on behalf of the Company. These costs are summarized and directly billed between the Company and AuraSense, LLC on a quarterly basis. In addition, certain expense and administrative activities are shared between the Company and AuraSense, LLC. Effective January 1, 2016, the Company and AuraSense, LLC amended its shared services agreement to simplify the billing arrangement. Under the amended shared services agreement, the Company bills AuraSense, LLC $8 per quarter for indirect costs incurred by the Company plus a specified rate for hours worked by Company scientists on projects directly related to AuraSense, LLC. The amended shared services arrangement continues to require direct non-labor expenses incurred by the Company to be billed to AuraSense, LLC. Effective January 1, 2017, the Company and AuraSense, LLC further amended its shared services agreement so that the quarterly fee related to administrative activities billed by the Company to AuraSense, LLC be reduced to $3 per quarter. This decrease is to reflect the current and expected future reduction in administrative activities to be provided by the Company to AuraSense, LLC. The amounts due from AuraSense, LLC in connection with the above mentioned activities were $4 and $17 at September 30, 2018 and December 31, 2017, respectively. The following is a summary of amounts billed to AuraSense, LLC and recognized in the accompanying unaudited condensed consolidated statement of operations in connection with the above mentioned activities: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2018 2017 2018 2017 Quarterly fee for indirect costs 3 3 $ 9 $ 9 Direct costs of AuraSense LLC paid by the Company 2 1 24 4 $ 5 $ 4 $ 33 $ 13 The Company received consulting services from, and paid fees to, one of its co-founders who is not an employee but serves as a member of the Board. The Company paid $75 in each of the nine months ended September 30, 2018 and 2017 in connection with these consulting services and these amounts are recognized as an expense in the accompanying unaudited condensed consolidated statement of operations.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events The Company has evaluated subsequent events which may require adjustment to or disclosure in the accompanying unaudited condensed consolidated financial statements and has concluded that there are no subsequent events or transactions that occurred subsequent to the balance sheet date that would require recognition or disclosure in the accompanying unaudited condensed consolidated financial statements.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements as of September 30, 2018 and December 31, 2017, and for the three and nine months ended September 30, 2018 and 2017, have been presented in conformity with generally accepted accounting principles in the United States (“GAAP”).
Principles of consolidation	Principles of Consolidation The accompanying unaudited condensed consolidated financial statements include the accounts of Exicure, Inc. and its 100% owned subsidiary, Exicure Operating Company. All intercompany transactions and accounts are eliminated in consolidation.
Use of estimates	Use of Estimates The preparation of the financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Management bases its estimates on certain assumptions which it believes are reasonable in the circumstance and while actual results could differ from those estimates, management does not believe that any change in those assumptions in the near term would have a significant effect on the Company’s financial position, results of operations or cash flows. Actual results in future periods could differ from those estimates.
Revenue recognition	Revenue Recognition Effective January 1, 2018, the Company adopted the provisions of Accounting Standards Codification (“ASC”) 606, Revenue from Contracts with Customers using the modified retrospective method for all contracts not completed as of the date of adoption. The reported results for 2018 reflect the application of ASC 606 guidance, while the reported results for 2017 were prepared under the guidance of ASC 605, Revenue Recognition (ASC 605). Under ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that are within the scope of ASC 606, the Company performs the following five steps: 1. Identify the contract with the customer. A contract with a customer exists when (i) the Company enters into an enforceable contract with a customer that defines each party’s rights regarding the goods or services to be transferred and identifies the related payment terms, (ii) the contract has commercial substance, and (iii) the Company determines that collection of substantially all consideration for goods and services that are transferred is probable based on the customer’s intent and ability to pay the promised consideration. The Company applies judgment in determining the customer’s intent and ability to pay, which is based on a variety of factors including the customer’s historical payment experience, or in the case of a new customer, published credit and financial information pertaining to the customer. 2. Identify the performance obligations in the contract. Performance obligations promised in a contract are identified based on the goods and services that will be transferred to the customer that are both capable of being distinct, whereby the customer can benefit from the good or service either on its own or together with other available resources, and are distinct in the context of the contract, whereby the transfer of the good or service is separately identifiable from other promises in the contract. To the extent a contract includes multiple promised goods and services, the Company must apply judgment to determine whether promised goods and services are both capable of being distinct and distinct in the context of the contract. If these criteria are not met, the promised goods and services are accounted for as a combined performance obligation. 3. Determine the transaction price. The transaction price is determined based on the consideration to which the Company will be entitled in exchange for transferring goods and services to the customer. To the extent the transaction price includes variable consideration, the Company estimates the amount of variable consideration that should be included in the transaction price utilizing either the expected value method or the most likely amount method, depending on the nature of the variable consideration. Variable consideration is included in the transaction price if, in the Company’s judgment, it is probable that a significant future reversal of cumulative revenue under the contract will not occur. Any estimates, including the effect of the constraint on variable consideration, are evaluated at each reporting period for any changes. Determining the transaction price requires significant judgment. 4. Allocate the transaction price to performance obligations in the contract. If the contract contains a single performance obligation, the entire transaction price is allocated to the single performance obligation. However, if a series of distinct services that are substantially the same qualifies as a single performance obligation in a contract with variable consideration, the Company must determine if the variable consideration is attributable to the entire contract or to a specific part of the contract. Contracts that contain multiple performance obligations require an allocation of the transaction price to each performance obligation on a relative standalone selling price basis unless the transaction price is variable and meets the criteria to be allocated entirely to a performance obligation or to a distinct service that forms part of a single performance obligation. The consideration to be received is allocated among the separate performance obligations based on relative standalone selling prices. 5. Recognize revenue when or as the Company satisfies a performance obligation. The Company satisfies performance obligations either over time or at a point in time. Revenue is recognized over time if either (i) the customer simultaneously receives and consumes the benefits provided by the entity’s performance, (ii) the entity’s performance creates or enhances an asset that the customer controls as the asset is created or enhanced, or (iii) the entity’s performance does not create an asset with an alternative use to the entity and the entity has an enforceable right to payment for performance completed to date. If the entity does not satisfy a performance obligation over time, the related performance obligation is satisfied at a point in time by transferring the control of a promised good or service to a customer. Examples of control are using the asset to produce goods or services, enhance the value of other assets, or settle liabilities, and holding or selling the asset. Licenses of intellectual property : If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from consideration allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the licenses. For licenses that are combined with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone payments: At the inception of each arrangement that includes development milestone payments, the Company evaluates the probability of reaching the milestones and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur in the future, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received and therefore revenue recognized is constrained as management is unable to assert that a reversal of revenue would not be possible. The transaction price is then allocated to each performance obligation on a relative standalone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration revenues and earnings in the period of adjustment. Royalties : For arrangements that include sales-based royalties, including milestone payments based on levels of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its collaboration agreements. As of September 30, 2018, the Company’s only revenue recognized is related to the Purdue Collaboration (see Note 3).
Recent accounting pronouncements	Recently Adopted Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09 (ASC 606), Revenue from Contracts with Customers . This ASU, as amended by ASU 2015-14, affects any entity that either enters into contracts with customers to transfer goods and services or enters into contracts for the transfer of nonfinancial assets. ASU 2014-09 replaces most existing revenue recognition guidance in GAAP when it becomes effective. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under the currently effective guidance. These may 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. ASU 2014-09 is effective for Exicure in the first quarter of 2018 and early adoption is permitted beginning in the first quarter of 2017. The Company adopted ASC 606 on a modified retrospective basis. See above “Revenue Recognition” for a discussion of the Company’s updated policies related to revenue recognition effective January 1, 2018. Impact of adoption of ASC 606 The Company adopted ASC 606 using the modified retrospective method. The cumulative effect of applying the new guidance to all contracts with customers that were not completed as of January 1, 2018 was recorded as an adjustment to accumulated deficit as of the adoption date. As a result of applying the modified retrospective method to adopt the new guidance, the Company recorded reductions to both accumulated deficit and deferred revenue, current of $1,034 as of the date of adoption. As a result of the adoption of ASC 606: (i) there were no impacts to the totals of our cash flows from operating activities, cash flows from investing activities, or cash flows from financing activities in the accompanying unaudited condensed consolidated statement of cash flows for the nine months ended September 30, 2018; (ii) there were no impacts to the balances of the accompanying unaudited condensed consolidated balance sheet as of September 30, 2018, (iii) there were no impacts to total revenue, operating loss, or net loss in the accompanying unaudited condensed consolidated statement of operations for the three months ended September 30, 2018, and (iv) total revenue, operating loss, and net loss were lower by $1,034 each in the accompanying unaudited condensed consolidated statement of operations for the nine months ended September 30, 2018. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments . ASU 2016-15 addresses the classification of certain specific cash flow issues including debt prepayment or extinguishment costs, settlement of certain debt instruments, contingent consideration payments made after a business combination, proceeds from the settlement of certain insurance claims and distributions received from equity method investees. ASU 2016-15 is effective for the Company in the first quarter of 2018 and early adoption is permitted. An entity that elects early adoption must adopt all of the amendments in the same period. The Company adopted this guidance on January 1, 2018. The adoption of ASU 2016-15 did not have a material impact to the Company’s statement of cash flows. In May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting . ASU 2017-09 clarifies when changes to the terms or conditions of a share-based payment award must be accounted for as modifications. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award changes as a result of the change in terms or conditions. ASU 2017-09 will be applied prospectively to awards modified on or after the adoption date. ASU 2017-09 is effective for the Company for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted. The Company adopted this guidance on January 1, 2018. The adoption of ASU 2017-09 did not have a material impact to the Company’s financial statements. Recent Accounting Pronouncements Not Yet Adopted In February 2016, FASB issued ASU 2016-02, Leases (Topic 842) , which requires lessees to recognize right-of-use assets and lease liabilities on the balance sheet. ASU 2016-02 is to be applied using a modified retrospective approach at the beginning of the earliest comparative period in the financial statements. ASU 2016-02 will be effective for the Company beginning in the first quarter of 2019. Early adoption is permitted. The Company is currently evaluating the impact of adopting this standard on its financial statements.
Loss per common share	Basic loss per common share is calculated by dividing net loss by the weighted-average number of shares of common stock outstanding during the period. Diluted loss per common share is calculated using the treasury share method by giving effect to all potentially dilutive securities that were outstanding. Potentially dilutive options and warrants to purchase common stock that were outstanding during the periods presented were excluded from the diluted loss per share calculation because such shares had an anti-dilutive effect due to the net loss reported in those periods.

Supplemental Balance Sheet In_2

Supplemental Balance Sheet Information (Tables)	9 Months Ended
	Sep. 30, 2018
Supplemental Balance Sheet Information [Abstract]
Property, Plant and Equipment	Property and equipment, net September 30, December 31, Scientific equipment $ 1,954 $ 1,797 Leasehold improvements 192 192 Furniture and fixtures 41 31 Computers and software 26 26 Construction in process 14 120 Property and equipment, gross 2,227 2,166 Less: accumulated depreciation (1,097 ) (849 ) Property and equipment, net $ 1,130 $ 1,317
Schedule of Accrued Liabilities	Accrued expenses and other current liabilities September 30, December 31, Accrued legal expenses $ 1,068 $ 251 Accrued payroll-related expenses 732 718 Accrued clinical, contract research and manufacturing costs 651 205 Other accrued expenses 584 99 Accrued expenses and other current liabilities $ 3,035 $ 1,273

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Principal Maturities of Long-term Debt	At September 30, 2018, the principal maturities of the long-term debt were as follows: September 30, 2018 2018 $ — 2019 4,999 Principal balance outstanding 4,999 less: unamortized discount (65 ) less: unamortized debt issuance costs (8 ) Long-term debt 4,926 Current portion 4,926 Noncurrent portion $ —

Equity-Based Compensation (Tabl

Equity-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity-Based Compensation Expense Classification in Statement of Operations	Equity-based compensation expense is classified in the statements of operations as follows: Three Months Ended Nine Months Ended September 30, 2018 2017 2018 2017 Research and development expense $ 133 $ 43 $ 353 $ 129 General and administrative expense 383 319 947 975 $ 516 $ 362 $ 1,300 $ 1,104
Assumptions Used to Determine Fair Value of Common Stock Option Grants	The fair value of the underlying common stock and the exercise price for the common stock options granted during the nine months ended September 30, 2018 and 2017 are summarized in the table below: Common Stock Options Granted During Period Ended: Fair Value of Underlying Common Stock Exercise Price of Common Stock Option Nine months ended September 30, 2018 $3.00 to $5.82; weighted avg. $3.45 $3.00 to $5.82; weighted avg. $3.45 Nine months ended September 30, 2017 $4.21 $4.21 In addition to an assumption on the expected term of the option grants as discussed below, application of the Black-Scholes model requires additional inputs for which we have assumed the values described in the table below: Nine Months Ended September 30, 2018 2017 Expected term 5.3 to 6.0 years 5.3 to 6.5 years Risk-free interest rate 2.72% to 2.87%; weighted avg. 2.78% 1.97% to 2.17%; weighted avg. 2.07% Expected volatility 78.1% to 82.4%; weighted avg. 80.6% 80.8% to 83.1%; weighted avg. 81.0% Forfeiture rate 5 % 5 % Expected dividend yield — % — %
Common Stock Option Activity	A summary of common stock option activity as of the periods indicated is as follows: Options Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value (thousands) Outstanding - December 31, 2017 3,672,620 $ 1.79 7.5 $ 5,221 Granted 1,277,744 3.45 Exercised (22,494 ) 1.81 Forfeited (36,282 ) 2.29 Outstanding - September 30, 2018 4,891,588 $ 2.22 7.6 $ 9,523 Exercisable - September 30, 2018 3,021,753 $ 1.62 6.8 $ 7,541 Vested and Expected to Vest - September 30, 2018 4,778,505 $ 2.20 7.5 $ 9,421

Loss Per Common Share (Tables)

Loss Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Computation of Loss Per Common Share	The following is the computation of loss per common share for the three and nine months ended September 30, 2018 and 2017: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Net loss $ (5,324 ) $ (1,932 ) $ (17,658 ) $ (7,568 ) Weighted-average basic and diluted common shares outstanding 41,527,922 1,725,906 40,121,295 183,395 Loss per share - basic and diluted $ (0.13 ) $ (1.12 ) $ (0.44 ) $ (41.27 )
Antidilutive Securities	The outstanding securities presented below were excluded from the calculation of net loss per common share, because such securities would have been anti-dilutive due to the Company’s net loss per share during the periods ending on the dates presented: September 30, 2018 2017 Options to purchase common stock 4,891,588 3,678,359 Warrants to purchase common stock 413,320 163,174

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Schedule of Assumptions used to Estimate Fair Value of Warrant Liability	The following weighted-average assumptions were used to estimate the fair value of the common stock warrant liability at September 30, 2018: September 30, 2018 Expected term 2.5 years Risk-free interest rate 2.83 % Expected volatility 81.78 % Expected dividend yield — %
Reconciliation of Liabilities Measured at Fair Value on a Recurring Basis	The following is a reconciliation of the Company’s liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3) for the nine months ended September 30, 2018: Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Common Stock Warrant Liability Balance at January 1, 2018 $ 523 Loss included in other income (expense), net 461 Balance at September 30, 2018 $ 984

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Rent Expense	Rent expense consisted of the following: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Straight-line rent expense $ 83 $ 83 $ 249 $ 249 Contingent rent expense 67 77 231 232 Total rent expense $ 150 $ 160 $ 480 $ 481
Schedule of Future Minimum Rental Payments	Future minimum lease payments as of September 30, 2018 are as follows: Years Ending December 31, Operating Leases 2018 85 2019 347 2020 353 2021 59 Thereafter — Total $ 844

Related-Party Transactions (Tab

Related-Party Transactions (Tables)	9 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Schedule of Revenue from Related Party	The following is a summary of amounts billed to AuraSense, LLC and recognized in the accompanying unaudited condensed consolidated statement of operations in connection with the above mentioned activities: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2018 2017 2018 2017 Quarterly fee for indirect costs 3 3 $ 9 $ 9 Direct costs of AuraSense LLC paid by the Company 2 1 24 4 $ 5 $ 4 $ 33 $ 13

Description of Business and B_2

Description of Business and Basis of Presentation (Details) - USD ($) $ / shares in Units, $ in Thousands	Aug. 22, 2018	Jul. 09, 2015	Nov. 02, 2017	Sep. 30, 2018
Subsidiary, Sale of Stock [Line Items]
Accumulated deficit generated, since inception				$ (69,076)
Private Placement
Subsidiary, Sale of Stock [Line Items]
Consideration received on transaction	$ 20,070		$ 31,513
Payments of stock issuance costs	$ 1,931		$ 3,966
Number of shares issued in transaction (in shares)	4,889,217		10,504,196
Price per share (in dollars per share)	$ 4.50		$ 3
Subsidiary of Common Parent
Subsidiary, Sale of Stock [Line Items]
Amount reclassified in connection with corporate conversion		$ (18,837)

Description of Business and B_3

Description of Business and Basis of Presentation - Schedule of Error Corrections (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Error Corrections and Prior Period Adjustments
Prepaid expenses and other assets	$ 1,855		$ 1,855		$ 1,844
Accrued expenses	3,035		3,035		1,273
Accumulated deficit	(50,239)		(50,239)		(33,615)
Research and development expense	4,001	$ 3,121	11,111	$ 9,910
Operating loss	5,863	1,894	16,951	7,092
Net loss	$ (5,324)	$ (1,932)	$ (17,658)	$ (7,568)
Loss per share - basic and diluted (in dollars per share)	$ 0.13	$ 1.12	$ 0.44	$ 41.27
Immaterial Error Corrections
Error Corrections and Prior Period Adjustments
Prepaid expenses and other assets					933
Accrued expenses					(96)
Accumulated deficit					$ 1,028
Research and development expense		$ (381)		$ (1,369)
Operating loss		381		1,369
Net loss		$ 381		$ 1,369
Loss per share - basic and diluted (in dollars per share)		$ 0.22		$ 7.46

Significant Accounting Polici_3

Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Adoption of new accounting standard - ASC 606					$ 1,034
Accumulated deficit	$ (50,239)		$ (50,239)		(33,615)
Deferred revenue, current	0		0		1,034
Revenues	57	$ 2,497	112	$ 7,624
Operating loss	(5,863)	(1,894)	(16,951)	(7,092)
Net loss	$ (5,324)	$ (1,932)	(17,658)	$ (7,568)
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred revenue, current					1,034
Revenues			(1,034)
Operating loss			1,034
Net loss			1,034
Accumulated Deficit
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Adoption of new accounting standard - ASC 606					$ 1,034
Net loss			$ (17,658)

Purdue Collaboration (Details)

Purdue Collaboration (Details) $ in Thousands	Dec. 02, 2016USD ($)target	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Current portion of deferred revenue		$ 0		$ 0		$ 1,034
Collaboration revenue		$ 57	$ 2,497	$ 112	$ 7,624
Reimbursable research and development activities			$ 428		$ 1,417
Purdue Collaboration
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of additional collaboration targets | target	3
Non-refundable upfront payment received for research agreement	$ 10,000
Potential milestone revenue	776,500
Aggregate research milestone revenue	16,500
Aggregate regulatory milestone revenue	410,000
Aggregate commercial milestone revenue	$ 350,000
Maximum | Purdue Collaboration
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Commercial sales royalty, percent	10.00%

Supplemental Balance Sheet In_3

Supplemental Balance Sheet Information - Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 2,227		$ 2,227		$ 2,166
Less: accumulated depreciation	(1,097)		(1,097)		(849)
Property and equipment, net	1,130		1,130		1,317
Depreciation and amortization	90	$ 70	266	$ 159
Scientific equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,954		1,954		1,797
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	192		192		192
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	41		41		31
Computers and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	26		26		26
Construction in process
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 14		$ 14		$ 120

Supplemental Balance Sheet In_4

Supplemental Balance Sheet Information - Accrued Expense and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Supplemental Balance Sheet Information [Abstract]
Accrued legal expenses	$ 1,068	$ 251
Accrued payroll-related expenses	732	718
Accrued clinical, contract research and manufacturing costs	651	205
Other accrued expenses	584	99
Accrued expenses and other current liabilities	$ 3,035	$ 1,273

Debt - Narrative (Details)

Debt - Narrative (Details) - USD ($) $ in Thousands	Jan. 15, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2020	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt		$ 4,926		$ 4,926			$ 4,855
Interest paid		$ 146	$ 158	$ 425	$ 470
Secured Debt | Hercules Technology Growth Capital | Loans Payable
Debt Instrument [Line Items]
Debt payments deferred, consecutive period	13 months
Scenario, Forecast | Secured Debt | Hercules Technology Growth Capital | Loans Payable
Debt Instrument [Line Items]
Amortization of principal and interest, consecutive period						18 months

Debt - Principal Maturities of

Debt - Principal Maturities of Long-Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
2,018	$ 0
2,019	4,999
Principal balance outstanding	4,999
less: unamortized discount	(65)
less: unamortized debt issuance costs	(8)
Long-term debt	4,926	$ 4,855
Current portion	4,926	0
Noncurrent portion	$ 0	$ 4,855

Stockholders' Equity - Current

Stockholders' Equity - Current Capitalization (Details)	Sep. 30, 2018vote_per_share$ / sharesshares	Dec. 31, 2017$ / sharesshares
Equity [Abstract]
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.0001	$ 0.0001
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.0001	$ 0.0001
Common stock, shares issued (in shares)	44,358,000	39,300,823
Common stock, shares outstanding (in shares)	44,358,000	39,300,823
Common stock, voting rights for each share | vote_per_share	1

Stockholders' Equity - Private

Stockholders' Equity - Private Placement and Common Stock Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	Aug. 22, 2018	Feb. 01, 2018	Nov. 02, 2017	Sep. 30, 2018	Sep. 30, 2017	Oct. 05, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Proceeds from common stock offering				$ 22,001	$ 20,302
Issuance of common stock in private placement, net				$ 20,070
Issuance of common stock to consultants, net (in shares)		145,466
Private Placement
Class of Stock [Line Items]
Number of shares issued in transaction (in shares)	4,889,217		10,504,196
Price per share (in dollars per share)	$ 4.50		$ 3
Proceeds from common stock offering	$ 22,001
Payments of stock issuance costs	1,931		$ 3,966
Consideration received on transaction	$ 20,070		$ 31,513
Issuance of common stock in private placement, net (in shares)	4,889,217
Cash placement fees	$ 1,680
Expenses reimbursed to placement agents	$ 87
Number of shares called by warrants (in shares)				413,320			413,320
Exercise price (in dollars per share)							$ 3
Subsequent Event | Common Stock
Class of Stock [Line Items]
Shares registered for resale (in shares)						5,034,683

Equity-Based Compensation - Nar

Equity-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair Value of Underlying Common Stock (dollars per share)		$ 4.21
Compensation cost not yet recognized	$ 3,635
Compensation expense recognition period	2 years 9 months
Weighted-average grant date fair value (in dollars per share)	$ 2.40	$ 2.92
Intrinsic value of options exercised	$ 51	$ 202
Exicure, Inc. 2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant (in shares)	928,443
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair Value of Underlying Common Stock (dollars per share)	$ 3

Equity-Based Compensation - Sch

Equity-Based Compensation - Schedule of Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 516	$ 362	$ 1,300	$ 1,104
Research and development expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	133	43	353	129
General and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 383	$ 319	$ 947	$ 975

Equity-Based Compensation - Ass

Equity-Based Compensation - Assumptions Used for Fair Value Measurement (Details)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Forfeiture rate	5.00%	5.00%
Expected dividend yield	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	5 years 3 months 18 days	5 years 3 months 18 days
Risk-free interest rate	2.72%	1.97%
Expected volatility rate	78.10%	80.80%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	6 years	6 years 6 months
Risk-free interest rate	2.87%	2.17%
Expected volatility rate	82.40%	83.10%
Weighted Average
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.78%	2.07%
Expected volatility rate	80.60%	81.00%

Equity-Based Compensation - Fai

Equity-Based Compensation - Fair Value of Underlying Common Stock and Exercise Price of Stock Options (Details) - $ / shares	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair Value of Underlying Common Stock (dollars per share)		$ 4.21
Exercise Price of Common Stock Option (dollars per share)		$ 4.21
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair Value of Underlying Common Stock (dollars per share)	$ 3
Exercise Price of Common Stock Option (dollars per share)	3
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair Value of Underlying Common Stock (dollars per share)	5.82
Exercise Price of Common Stock Option (dollars per share)	5.82
Weighted Average
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair Value of Underlying Common Stock (dollars per share)	3.45
Exercise Price of Common Stock Option (dollars per share)	$ 3.45

Equity-Based Compensation - S_2

Equity-Based Compensation - Schedule of Stock Options Rollforward (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Options
Shares outstanding, beginning period	3,672,620
Granted, shares	1,277,744
Exercised, shares	(22,494)
Forfeited, shares	(36,282)
Shares outstanding, ending period	4,891,588	3,672,620
Weighted-Average Exercise Price
Weighted-Average Exercise Price, beginning period (dollars per share)	$ 1.79
Weighted-Average Exercise Price, granted (dollars per share)	3.45
Weighted-Average Exercise Price, exercised (dollars per share)	1.81
Weighted-Average Exercise Price, forfeitures (dollars per share)	2.29
Weighted-Average Exercise Price, ending period (dollars per share)	$ 2.22	$ 1.79
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted-Average Remaining Contractual Term (years)	7 years 7 months 18 days	7 years 6 months
Aggregate Intrinsic Value (thousands)	$ 9,523	$ 5,221
Exercisable, shares	3,021,753
Exercisable, Weighted-Average Exercise Price (dollars per share)	$ 1.62
Exercisable, Weighted-Average Remaining Contractual Term	6 years 9 months
Exercisable, Aggregate Intrinsic Value	$ 7,541
Vested and Expected to Vest, shares	4,778,505
Vested and Expected to Vest, Weighted-Average Exercise Price (dollars per share)	$ 2.20
Vested and Expected to Vest, Weighted-Average Remaining Contractual Term (years)	7 years 6 months
Vested and Expected to Vest, Aggregate Intrinsic Value (dollars per share)	$ 9,421

Income Taxes (Details)

Income Taxes (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Provision for income tax expense	$ 0	$ 0	$ 0	$ 0
Effective tax rate	0.00%	0.00%	0.00%	0.00%

Loss Per Common Share - Computa

Loss Per Common Share - Computation of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net loss	$ (5,324)	$ (1,932)	$ (17,658)	$ (7,568)
Weighted-average basic and diluted common shares outstanding (in shares)	41,527,922	1,725,906	40,121,295	183,395
Loss per share - basic and diluted (in dollars per share)	$ (0.13)	$ (1.12)	$ (0.44)	$ (41.27)

Loss Per Common Share - Antidil

Loss Per Common Share - Antidilutive Securities (Details) - shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares excluded from computation of weighted-average diluted common shares outstanding (in shares)	4,891,588	3,678,359
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares excluded from computation of weighted-average diluted common shares outstanding (in shares)	413,320	163,174

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impact of 10% change in expected volatility rate	$ 55
Impact of 10% change in the estimate of fair value of the common stock	$ 141

Fair Value Measurements - Sche

Fair Value Measurements - Schedule of Assumptions used to Estimate Fair Value of Warrant Liability (Details) - Warrant Liability - Common Stock	Sep. 30, 2018
Expected term
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Common stock warrant liability, measurement input	2.5
Risk-free interest rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Common stock warrant liability, measurement input	0.0283
Expected volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Common stock warrant liability, measurement input	0.8178
Expected dividend yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Common stock warrant liability, measurement input	0

Fair Value Measurements - Recon

Fair Value Measurements - Reconciliation of Liabilities Measured at Fair Value on a Recurring Basis (Details) - Fair Value Measurements Using Significant Unobservable Inputs (Level 3) - Common Stock - Warrant Liability $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1, 2018	$ 523
Loss included in other income (expense), net	461
Balance at September 30, 2018	$ 984

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) - USD ($) $ in Thousands	76 Months Ended
	Mar. 31, 2018	Sep. 30, 2018	Dec. 31, 2017	Mar. 31, 2014	Mar. 31, 2012
Commitments and Contingencies [Abstract]
Extended lease term				6 years
Deferred rent liability		$ 41	$ 48		$ 52
Aggregate consideration paid to NU for agreement obligations	$ 3,844

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Rent Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Straight-line rent expense	$ 83	$ 83	$ 249	$ 249
Contingent rent expense	67	77	231	232
Total rent expense	$ 150	$ 160	$ 480	$ 481

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Future Minimum Rental Payments (Details) $ in Thousands	Sep. 30, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,018	$ 85
2,019	347
2,020	353
2,021	59
Thereafter	0
Total	$ 844

Related-Party Transactions - Na

Related-Party Transactions - Narrative (Details) - USD ($) $ in Thousands	Jan. 01, 2017	Jan. 01, 2016	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Receivable from related party			$ 4		$ 17
Board of Directors | Consulting services
Related Party Transaction [Line Items]
Expenses from transactions with related party			$ 75	$ 50
AuraSense
Related Party Transaction [Line Items]
Quarterly revenue from related party for indirect costs	$ 3	$ 8
Receivable from related party					$ 17

Related-Party Transactions - Sc

Related-Party Transactions - Schedule of Revenue from Related Party (Details) - AuraSense - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Related Party Transaction [Line Items]
Revenue from related parties	$ 5	$ 4	$ 33	$ 13
Quarterly fee for indirect costs
Related Party Transaction [Line Items]
Revenue from related parties	3	3	9	9
Direct costs of AuraSense LLC paid by the Company
Related Party Transaction [Line Items]
Revenue from related parties	$ 2	$ 1	$ 24	$ 4