Exicure (XCUR) 10-Q 12 Aug 21 2021 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2021	Aug. 09, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2021
Document Transition Report	false
Entity File Number	001-39011
Entity Registrant Name	EXICURE, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-5333008
Entity Address, Address Line One	2430 N. Halsted St.
Entity Address, City or Town	Chicago
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60614
City Area Code	(847)
Local Phone Number	673-1700
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	XCUR
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		88,108,543
Entity Central Index Key	0001698530
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Amendment Flag	false

UNAUDITED CONDENSED CONSOLIDATE

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 42,587	$ 33,262
Short-term investments	13,472	48,818
Accounts receivable	0	11
Prepaid expenses and other assets	4,588	4,231
Total current assets	60,647	86,322
Property and equipment, net	4,102	4,123
Right-of-use asset	8,281	8,606
Other noncurrent assets	1,437	1,393
Total assets	74,467	100,444
Current liabilities:
Accounts payable	2,250	1,866
Accrued expenses and other current liabilities	3,228	3,525
Deferred revenue, current	7,267	8,343
Total current liabilities	12,745	13,734
Long-term debt, net	16,730	16,589
Lease liability, noncurrent	7,696	7,959
Other noncurrent liabilities	656	656
Total liabilities	37,827	38,938
Stockholders’ equity:
Preferred stock, $0.0001 par value per share; 10,000,000 shares authorized, no shares issued and outstanding, June 30, 2021 and December 31, 2020	0	0
Common stock, $0.0001 par value per share; 200,000,000 shares authorized, 88,096,694 issued and outstanding, June 30, 2021; 87,651,352 issued and outstanding, December 31, 2020	9	9
Additional paid-in capital	169,337	167,379
Accumulated other comprehensive income	5	83
Accumulated deficit	(132,711)	(105,965)
Total stockholders' equity	36,640	61,506
Total liabilities and stockholders’ equity	$ 74,467	$ 100,444

UNAUDITED CONDENSED CONSOLIDA_2

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
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)	88,096,694	87,651,352
Common stock, shares outstanding (in shares)	88,096,694	87,651,352

UNAUDITED CONDENSED CONSOLIDA_3

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue:
Collaboration revenue	$ 79,000	$ 4,847,000	$ 1,076,000	$ 14,030,000
Total revenue	79,000	4,847,000	1,076,000	14,030,000
Operating expenses:
Research and development expense	10,843,000	7,008,000	21,105,000	13,083,000
General and administrative expense	3,098,000	2,229,000	5,990,000	4,803,000
Total operating expenses	13,941,000	9,237,000	27,095,000	17,886,000
Operating loss	(13,862,000)	(4,390,000)	(26,019,000)	(3,856,000)
Other (expense) income, net:
Dividend income	2,000	4,000	3,000	43,000
Interest income	43,000	267,000	131,000	627,000
Interest expense	(450,000)	0	(859,000)	(128,000)
Other (expense) income, net	(2,000)	(192,000)	(2,000)	153,000
Total other (expense) income, net	(407,000)	79,000	(727,000)	695,000
Net loss before provision for income taxes	(14,269,000)	(4,311,000)	(26,746,000)	(3,161,000)
Provision for income taxes	0	0	0	0
Net loss	$ (14,269,000)	$ (4,311,000)	$ (26,746,000)	$ (3,161,000)
Basic (loss) earnings per common share (USD per share)	$ (0.16)	$ (0.05)	$ (0.30)	$ (0.04)
Diluted (loss) earnings per common share (USD per share)	$ (0.16)	$ (0.05)	$ (0.30)	$ (0.04)
Weighted-average basic common shares outstanding (in shares)	88,043,447	87,174,533	87,948,440	87,126,847
Weighted-average diluted common shares outstanding (in shares)	88,043,447	87,174,533	87,948,440	87,126,847

UNAUDITED CONDENSED CONSOLIDA_4

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Comprehensive Income [Abstract]
Net loss	$ (14,269)	$ (4,311)	$ (26,746)	$ (3,161)
Other comprehensive (loss) income, net of taxes
Unrealized (losses) gains on available for sale securities, net of tax	(27)	355	(78)	365
Other comprehensive (loss) income	(27)	355	(78)	365
Comprehensive loss	$ (14,296)	$ (3,956)	$ (26,824)	$ (2,796)

UNAUDITED CONDENSED CONSOLIDA_5

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in- Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2019		86,069,263
Beginning balance at Dec. 31, 2019	$ 80,747	$ 9	$ 162,062	$ (81,297)	$ (27)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-based compensation	441		441
Issuance of common stock (in shares)		1,081,184
Issuance of common stock	2,766		2,766
Other comprehensive income (loss)	10				10
Net loss	1,150			1,150
Ending balance (in shares) at Mar. 31, 2020		87,150,447
Ending balance at Mar. 31, 2020	85,114	$ 9	165,269	(80,147)	(17)
Beginning balance (in shares) at Dec. 31, 2019		86,069,263
Beginning balance at Dec. 31, 2019	80,747	$ 9	162,062	(81,297)	(27)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss)	365
Net loss	(3,161)
Ending balance (in shares) at Jun. 30, 2020		87,206,346
Ending balance at Jun. 30, 2020	81,752	$ 9	165,863	(84,458)	338
Beginning balance (in shares) at Mar. 31, 2020		87,150,447
Beginning balance at Mar. 31, 2020	85,114	$ 9	165,269	(80,147)	(17)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options (in shares)		55,899
Exercise of options	50		50
Equity-based compensation	544		544
Other comprehensive income (loss)	355				355
Net loss	(4,311)			(4,311)
Ending balance (in shares) at Jun. 30, 2020		87,206,346
Ending balance at Jun. 30, 2020	81,752	$ 9	165,863	(84,458)	338
Beginning balance (in shares) at Dec. 31, 2020		87,651,352
Beginning balance at Dec. 31, 2020	61,506	$ 9	167,379	(105,965)	83
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options (in shares)		342,246
Exercise of options	546		546
Equity-based compensation	517		517
Other comprehensive income (loss)	(51)				(51)
Net loss	(12,477)			(12,477)
Ending balance (in shares) at Mar. 31, 2021		87,993,598
Ending balance at Mar. 31, 2021	50,041	$ 9	168,442	(118,442)	32
Beginning balance (in shares) at Dec. 31, 2020		87,651,352
Beginning balance at Dec. 31, 2020	$ 61,506	$ 9	167,379	(105,965)	83
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of options (in shares)	342,246
Other comprehensive income (loss)	$ (78)
Net loss	(26,746)
Ending balance (in shares) at Jun. 30, 2021		88,096,694
Ending balance at Jun. 30, 2021	36,640	$ 9	169,337	(132,711)	5
Beginning balance (in shares) at Mar. 31, 2021		87,993,598
Beginning balance at Mar. 31, 2021	50,041	$ 9	168,442	(118,442)	32
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-based compensation	764		764
Issuance of common stock-ESPP (in shares)		103,096
Issuance of common stock-ESPP	131		131
Other comprehensive income (loss)	(27)				(27)
Net loss	(14,269)			(14,269)
Ending balance (in shares) at Jun. 30, 2021		88,096,694
Ending balance at Jun. 30, 2021	$ 36,640	$ 9	$ 169,337	$ (132,711)	$ 5

UNAUDITED CONDENSED CONSOLIDA_6

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities:
Net loss	$ (26,746)	$ (3,161)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation and amortization	546	335
Amortization of right-of-use asset	325	356
Equity-based compensation	1,281	985
Amortization of long-term debt issuance costs and fees	141	35
Amortization of investments	171	95
Other	6	0
Change in fair value of warrant liabilities	(15)	(157)
Changes in operating assets and liabilities:
Accounts receivable	11	11
Prepaid expenses and other current assets	(357)	(1,646)
Other noncurrent assets	(44)	(1,034)
Accounts payable	415	22
Accrued expenses	(280)	(647)
Deferred revenue	(1,076)	(13,949)
Other liabilities	(263)	(59)
Net cash used in operating activities	(25,885)	(18,814)
Cash flows from investing activities:
Purchase of available for sale securities	(2,000)	(38,072)
Proceeds from sale or maturity of available for sale securities	37,097	32,103
Capital expenditures	(564)	(2,996)
Net cash provided by (used in) investing activities	34,533	(8,965)
Cash flows from financing activities:
Proceeds from common stock offering	0	2,973
Payment of common stock financing costs	0	(207)
Payment of long-term debt fees and issuance costs	0	(100)
Repayment of long-term debt	0	(4,999)
Proceeds from issuance of employee stock purchase plan	131	0
Proceeds from exercise of common stock options	546	50
Net cash provided by (used in) financing activities	677	(2,283)
Net increase (decrease) in cash, cash equivalents, and restricted cash	9,325	(30,062)
Cash, cash equivalents, and restricted cash - beginning of period	34,462	48,460
Cash, cash equivalents, and restricted cash - end of period	43,787	18,398
Non-cash investing activities:
Capital expenditures (accounts payable and accrued expenses)	$ 11	$ 60

UNAUDITED CONDENSED CONSOLIDA_7

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Statement of Cash Flows [Abstract]
Cash and cash equivalents	$ 42,587	$ 33,262
Restricted cash included in other noncurrent assets	1,200	1,200
Total cash, cash equivalents, and restricted cash shown in the unaudited condensed consolidated statements of cash flows	$ 43,787	$ 34,462

Description of Business and Bas

Description of Business and Basis of Presentation	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Description of Business and Basis of Presentation	Description of Business and Basis of Presentation Description of Business Exicure, Inc. (the “Company”) is a clinical-stage biotechnology company developing therapeutics for neurology, immuno-oncology, inflammatory diseases, and other genetic disorders based on its proprietary Spherical Nucleic Acid, or SNA™, technology. The Company believes that its proprietary SNA architecture has distinct chemical and biological properties that may provide advantages over other nucleic acid therapeutics and may have therapeutic potential to target diseases not typically addressed with other nucleic acid therapeutics. The Company is in preclinical development of XCUR-FXN, a lipid-nanoparticle SNA-based therapeutic candidate, for the intrathecal treatment of Friedreich’s ataxia (FA). The Company’s therapeutic candidate cavrotolimod (AST-008) is in a Phase 1b/2 clinical trial in patients with advanced solid tumors. The Company believes one of the key strengths of its proprietary SNAs is that they have the potential for increased cellular uptake compared to conventional linear oligonucleotides and as a result the potential to achieve higher efficacy at the same doses of oligonucleotide administered. The Company has shown in clinical and preclinical studies that SNAs may have therapeutic potential in immuno-oncology and dermatology. In addition, the Company has shown in preclinical studies that SNAs may have therapeutic potential in neurology, ophthalmology, pulmonology, and gastroenterology. Accordingly, the Company has expanded its pipeline into neurology, for which IND-enabling activities are ongoing for XCUR-FXN, and is concluding early stage research activities in ophthalmology, pulmonology, and gastroenterology. Throughout these unaudited condensed consolidated financial statements, the terms the “Company” and “Exicure” refer to Exicure, Inc. and its wholly owned subsidiary, Exicure Operating Company. Exicure Operating Company holds all material assets and conducts all business activities and operations of Exicure, Inc. Basis of Presentation The accompanying unaudited condensed consolidated financial statements as of June 30, 2021 and December 31, 2020, and for the six months ended June 30, 2021 and 2020, 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 wholly owned subsidiary, Exicure Operating Company. All intercompany transactions and accounts are eliminated in consolidation. Significant Risks and Uncertainties As discussed in Note 3, Collaborative Research and License Agreements , revenue for the three and six months ended June 30, 2021 reflects events and conditions that occurred during that period that increased the number of hours estimated to be required to complete the services under the AbbVie Collaboration Agreement. These increased estimated efforts resulted in less progress occurring relative to the increased estimate of total projected hours to complete the research services (and thus limited revenue recognized) during the three and six months ended June 30, 2021 and compared to the amount of revenue recognized in the comparable periods. Due to uncertainties inherent in the estimation process, it is at least reasonably possible that estimated efforts required to complete the research services under the AbbVie Collaboration Agreement will be further revised in the near-term. COVID-19 Risks and Uncertainties In response to the ongoing COVID-19 pandemic, the Company has taken and continues to take active measures designed to address and mitigate the impact of the COVID-19 pandemic on its business, such as remote working policies, facilitating management’s routine communication to address employee and business concerns and providing frequent updates to the Company’s board of directors (the “Board”). During the second quarter of 2021 and through the date of this report, the Company continues to operate under COVID-19 social distancing guidelines and has generally operated with approximately 100% of its R&D staff on-site. The Company’s office and general and administrative team is also working on-site approximately 50% of the time. The Company’s preclinical development program in Friedreich’s ataxia (“FA”) is ongoing and it began IND-enabling studies for XCUR-FXN in late 2020. The Company also continues to progress its collaborations with AbbVie Inc. (“AbbVie”). However, if the COVID-19 pandemic continues to persist for an extended period of time, the Company could experience further significant disruptions to its clinical and preclinical development timelines, which would adversely affect its business, financial condition, results of operations and growth prospects. The Company believes that the effects of the COVID-19 pandemic or its impact contributed to delays during the second half of 2020 and the first half of 2021 in its enrollment plans and clinical trial site start-ups for the Phase 2 dose expansion phase of the Phase 1b/2 clinical trial for its cavrotolimod (AST-008) clinical program. The Company has taken additional measures to increase the enrollment of patients, including frequent interaction with its clinical trial sites currently open as well as increasing the number of clinical trial sites that potentially are activated for this trial so that the Company may continue to enroll patients as initially planned. However, any additional delays may require the Company to further lengthen its clinical development timeline for cavrotolimod (AST-008). Pending further enrollment delays or any unanticipated effects of the COVID-19 pandemic on our clinical development plans, the Company expects to report overall response rate, or ORR, results in the first half of 2022. The extent to which the COVID-19 pandemic or its impact or effects may continue to impact the Company’s business, its clinical development and regulatory efforts, its corporate development objectives and the value of and market for its common stock, will depend on future developments that are highly uncertain and cannot be predicted with confidence at this time, such as the ultimate duration or spread of the pandemic, its impact and effects, the possibility of additional periods of increases or spikes in the number of COVID-19 cases, travel restrictions, quarantines, social distancing, phased re-openings and business closure requirements in the United States and other countries, and the effectiveness of actions taken globally to contain and treat the disease including, without limitation, the effectiveness and timing of vaccination initiatives in the United States and worldwide. The global economic slowdown, the overall disruption of global healthcare systems and the other risks and uncertainties associated with the pandemic could have a material adverse effect on the Company’s business, financial condition, results of operations and growth prospects. In addition, the Company is subject to other challenges and risks specific to its business and its ability to execute on its business plan and strategy, as well as risks and uncertainties common to companies in the biotechnology industry with research and development operations, including, without limitation, risks and uncertainties associated with: obtaining regulatory approval of its product candidates; delays or problems in obtaining clinical supply, loss of single source suppliers or failure to comply with manufacturing regulations; identifying, acquiring or in-licensing additional products or product candidates; product development and the inherent uncertainty of clinical success; and the challenges of protecting and enhancing its intellectual property rights; and the challenges of complying with applicable regulatory requirements. In addition, to the extent the ongoing COVID-19 pandemic adversely affects the Company’s business and results of operations, it may also have the effect of heightening many of the other risks and uncertainties. Liquidity Risk As of June 30, 2021, the Company has generated an accumulated deficit of $151,548 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 June 30, 2021, including the $20,000 upfront payment received in August 2021 in connection with the Ipsen Collaboration Agreement (see Note 15, Subsequent Events ) and amounts borrowed and available under the MidCap Credit Facility (see Note 6, Debt ), is sufficient to fund the Company’s current plans for at least the next 12 months from the date these financial statements were issued. Management believes that it will be able to obtain additional working capital through equity financings, partnerships and licensing, or other arrangements, such as its “at the market offering” program pursuant to its equity distribution agreement with BMO Capital Markets Corp., to fund its current operations and business strategy. 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. The Company has historically principally raised capital through the sale of its securities. However, the COVID-19 pandemic continues to rapidly evolve and has already resulted in a significant disruption of global financial markets. If the disruption continues to persist and deepens, the Company could experience an inability to access additional capital, which could in the future negatively affect its ability to raise capital and ultimately, its operations. Unaudited Interim Financial Information The accompanying interim condensed consolidated balance sheet as of June 30, 2021, the interim condensed consolidated statements of operations for the three and six months ended June 30, 2021 and 2020, the interim condensed consolidated statements of comprehensive (loss) income for the three and six months ended June 30, 2021 and 2020, the interim condensed consolidated statements of changes in stockholders’ equity for the three and six months ended June 30, 2021 and 2020, and the interim condensed consolidated statements of cash flows for the six months ended June 30, 2021 and 2020, 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 June 30, 2021, the results of its operations for the three and six months ended June 30, 2021 and 2020, and the results of its cash flows for the six months ended June 30, 2021 and 2020. The financial data and other information disclosed in these notes related to the three and six months ended June 30, 2021 and 2020 are unaudited. The results for the three and six months ended June 30, 2021 are not necessarily indicative of results to be expected for the year ending December 31, 2021, 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 circumstances 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.

Significant Accounting Policies

Significant Accounting Policies	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies The Company’s significant accounting policies are disclosed in the audited consolidated financial statements and the notes thereto, which are included in the in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 filed with the U.S. Securities and Exchange Commission (“SEC”) on March 11, 2021. Since the date of those audited consolidated financial statements, there have been no material changes to the Company’s significant accounting policies. Recently Adopted Accounting Pronouncements None. Recent Accounting Pronouncements Not Yet Adopted Financial Instruments - Credit Losses In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) ASU 2016-13, Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”) . ASU 2016-13 is a new standard intended to improve reporting requirements specific to loans, receivables and other financial instruments. ASU 2016-13 requires that credit losses on financial assets measured at amortized cost be determined using an expected loss model, instead of the current incurred loss model, and requires that credit losses related to available-for-sale debt securities be recorded through an allowance for credit losses and limited to the amount by which carrying value exceeds fair value. ASU 2016-13 also requires enhanced disclosure of credit risk associated with financial assets. The effective date of ASU 2016-13 was deferred by ASU 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842)—Effective Dates to the annual period beginning after December 15, 2022 for companies that (i) meet the definition of an SEC filer and (ii) are eligible as “smaller reporting companies” as such term is defined by the SEC, with early adoption permitted. The Company is currently assessing the impact of adoption of ASU 2016-13 to its consolidated financial statements.

Collaborative Research and Lice

Collaborative Research and License Agreements	6 Months Ended
	Jun. 30, 2021
Research and Development [Abstract]
Collaborative Research and License Agreements	Collaborative Research and License Agreements AbbVie Collaboration Agreement Summary of Agreement On November 13, 2019 (the “Effective Date”), the Company entered into a Collaboration, Option and License Agreement (the “AbbVie Collaboration Agreement”), with a wholly-owned subsidiary of Allergan plc, Allergan. On May 8, 2020, Allergan plc, including Allergan was acquired by AbbVie. Pursuant to the AbbVie Collaboration Agreement, the Company granted to AbbVie exclusive access and options to license SNA based therapeutics arising from two collaboration programs related to the treatment of hair loss disorders (each, a “Collaboration Program”). Under each such license (obtained in connection with the exercise of an Option, as defined and discussed further below), the Company would grant to AbbVie exclusive, royalty-bearing, sublicensable, nontransferable, worldwide rights to develop, manufacture, use and commercialize such SNA therapeutics. Under the AbbVie Collaboration Agreement, the Company will use commercially reasonable efforts to conduct two Collaboration Programs, each focused on one or more hair loss disorders to discover one or more SNA products that are directed to, bind to or inhibit one or more specific Collaboration Program targets (each, a “Program Target”). As of the Effective Date, the Company and AbbVie have agreed upon a development plan for each Collaboration Program that describes the development activities and timelines required to advance such Collaboration Program through first IND filing (each, a “Development Plan”). The activities described in the Development Plan are conducted under the supervision of the Joint Development Committee (the “JDC”) consisting of three members from each of the Company and AbbVie. The Company is primarily responsible for performing early stage discovery and preclinical activities (the “Initial Development Activities”) set forth in the Development Plan for each Collaboration Program and will be solely responsible for all costs and expenses related to the Initial Development Activities. AbbVie may elect, in its sole discretion and at its sole cost and expense, to conduct formulation assessment and in vivo testing as set forth in a Development Plan. Following the completion of all Initial Development Activities, the Company is required to deliver to AbbVie a report that describes the results of the Initial Development Activities and identifies at least one SNA-based compound that satisfies certain criteria for such Collaboration Program as determined by the JDC (the “Initial Development Report”). Following the delivery of the Initial Development Report for a Collaboration Program, AbbVie will have the ability for a defined period of time (the “Initial Option Exercise Period”) to exercise an option (each an “Option”) to obtain worldwide rights and license to the Company’s SNA technology and the Company’s interest in joint collaboration technology to make, have made, import, use, sell or offer for sale any product (each a “Licensed Product”) that results from such Collaboration Program during the term of the AbbVie Collaboration Agreement. At AbbVie’s sole option, AbbVie may extend the Initial Option Exercise Period (the “Option Extension”) and require the Company to perform IND-enabling activities described in the Development Plan (the “IND-Enabling Activities”), subject to the payment of additional consideration (“Extension Exercise”). If AbbVie exercises the Option Extension, the Company would be responsible for conducting the IND-Enabling Activities and would be solely responsible for all costs and expenses associated with such activities. Upon completion of the IND-Enabling Activities, the Company is required to deliver a report that describes the results of the IND-Enabling Activities (the “IND-Enabling Activities Data Package”) to AbbVie. Following the delivery of IND-Enabling Activities Data Package, AbbVie will have the ability for a defined period of time (the “Extended Option Exercise Period”) to exercise an Option with respect to such Collaboration Program. After the exercise of an Option with respect to a Collaboration Program, AbbVie will be responsible for all development, manufacturing, and commercialization activities, and costs and expense associated with such activities in connection with Licensed Products arising from such Collaboration Program. The Company’s obligation to conduct the activities defined in the Development Plan under the AbbVie Collaboration Agreement commenced on November 13, 2019 and continues until the earlier of (i) the date AbbVie exercises an Option, (ii) the date AbbVie abandons a Collaboration Program and foregoes its Option to that Collaboration Program, or (iii) the fifth anniversary of the Effective Date (the “Research Term”). If the Initial Option Exercise Period or Extended Option Exercise Period is still in effect for a Collaboration Program or if the Company has not delivered a complete Initial Development Report or, if AbbVie made an Extension Exercise for a Collaboration Program, a complete IND-Enabling Activities Data Package for such Collaboration Program, as determined by the JDC, then the Research Term will automatically extend by one-year increments until such obligation is satisfied, but in no event past the seventh anniversary of the Effective Date. Under the terms of the AbbVie Collaboration Agreement, the Company received a $25,000 upfront, non-refundable, non-creditable cash payment (the “AbbVie Upfront Payment”) related to the Company’s research and development costs for conducting the Development Plan for two Collaboration Programs, each focused on one or more targets, and certain options to obtain exclusive, worldwide licenses under certain intellectual property rights owned or controlled by the Company to develop, manufacture and commercialize certain products resulting from each such Collaboration Programs. The option exercise fee during the Initial Option Exercise Period is $10,000 per Collaboration Program. If AbbVie elects to extend the Initial Option Exercise Period, AbbVie is required to pay an additional fee of $10,000. If AbbVie elects to exercise its option during the Extended Option Exercise Period, AbbVie must pay the Company the option exercise fee of $15,000. Following the exercise by AbbVie of an Option with respect to a Collaboration Program, AbbVie would be required to make certain milestone payments to the Company upon the achievement of specified development, product approval and launch, and commercial events, on a Licensed Product by Licensed Product basis. On a Licensed Product by Licensed Product basis, for the first Licensed Product to achieve the associated milestone event, the Company is eligible to receive up to an aggregate of $55,000 for development milestone payments and $132,500 for product approval and launch milestone payments. The Company is also eligible for up to $175,000 in sales milestone payments on a Collaboration Program by Collaboration Program basis, associated with aggregate worldwide sales. Certain product approval milestones are subject to certain reductions under specified circumstances, including for payments required to be made by AbbVie to obtain certain third-party intellectual property rights. In addition, to the extent there is any Licensed Product, the Company would be entitled to receive tiered royalty payments of mid-single digits to the mid-teens percentage on future net worldwide product sales of such Licensed Products, subject to certain reductions under specified circumstances. Royalties are due on a Licensed Product by Licensed Product and country by country basis from the date of the first commercial sale of each Licensed Product in a country until the latest to occur of: (i) the expiration date in such country of the last to expire valid claim within the licensed intellectual property covering the manufacture, use or sale of such Licensed Product in such country, (ii) the tenth anniversary of the first commercial sale of such Licensed Product in such country, and (iii) the expiration of regulatory exclusivity for such Licensed Product in such country. AbbVie may terminate the AbbVie Collaboration Agreement for any reason or no reason, either in its entirety or on a Collaboration Program by Collaboration Program basis, at any time on 90 days’ prior written notice to the Company. Unless earlier terminated, the term of the AbbVie Collaboration Agreement shall continue until (i) if both Option Exercise Periods expire without AbbVie exercising either Option, the expiration of the later to expire Option Exercise Period, and (ii) if either or both Options are exercised on a Licensed Product-by-Licensed Product and country-by-country basis, the expiration of the royalty term for such Licensed Product in such country. Either party may terminate the AbbVie Collaboration Agreement if the other party has materially breached or defaulted in the performance of any of its material obligations and such breach or default continues after the specified cure period. Termination of the AbbVie Collaboration Agreement for any reason will not release either party from any liability which, at the time of such termination, has already accrued to the other party or which is attributable to a period prior to such termination. In addition, termination of the AbbVie Collaboration Agreement will not preclude either party from pursuing any rights and remedies it may have under the agreement or at law or in equity with respect to any breach of the AbbVie Collaboration Agreement. If either party terminates the AbbVie Collaboration Agreement, the license and rights granted to AbbVie with respect to the terminated Collaboration Program or License Product shall terminate. Accounting Analysis The Company concluded that AbbVie is a customer in this arrangement, and as such the arrangement falls within the scope of the revenue recognition guidance. Under the AbbVie Collaboration Agreement, the Company has identified a single performance obligation that includes (i) the research and development activities during the Research Term (the “AbbVie R&D Services”), and (ii) Joint Development Committee services during the Research Term (the “AbbVie JDC Services”). The Company has concluded that the AbbVie R&D Services is not distinct from the AbbVie JDC Services during the Research Term. The JDC provides oversight and management of the overall AbbVie Collaboration Agreement, and the members of the JDC from the Company have specialized industry knowledge, particularly as it relates to SNA technology. The JDC is meant to facilitate the early stage research being performed and coordinate the activities of both the Company and AbbVie. Further, the JDC services are critical to the ongoing evaluation of a Collaboration Program and the drafting and evaluation of the Initial Development Report and the IND-Enabling Data Package. Accordingly, the Company’s participation on the JDC is essential to AbbVie receiving value from the AbbVie R&D Services and as such, the AbbVie JDC Services along with the AbbVie R&D Services are considered one performance obligation (the “Collaboration Program Services”). In addition, the Company has concluded that the option to purchase two development and commercialization licenses is considered a marketing offer as the options did not provide any discounts or other rights that would be considered a material right in the arrangement, and thus, not a performance obligation at the onset of the agreement. The consideration for these options will be accounted for when they are exercised. As of the Effective Date of the AbbVie Collaboration Agreement, the total transaction price was determined to be $25,000, consisting solely of the AbbVie Upfront Payment. The Company also utilized the most likely amount method to estimate any development and regulatory milestone payments to be received. As of the Effective Date of the AbbVie Collaboration Agreement, there were no milestones included in the transaction price. The milestones were fully constrained due to the significant uncertainties surrounding such payments. The Company considered the stage of development and the risks associated with the remaining development required to achieve the milestone, as well as whether the achievement of the milestone is outside the control of the Company or AbbVie. The Company has determined that any commercial milestones and sales-based royalties will be recognized when the related sales occur and therefore have also been excluded from the transaction price. The Company will re-evaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur. As of June 30, 2021, the Company determined that any development, regulatory, or commercial milestones continue to be constrained and therefore the related milestone payments continue to be excluded from the transaction price at June 30, 2021. The Company will recognize revenue related to the Collaboration Program Services as the performance obligation is satisfied using an input method to measure progress. The Company believes the input method that most accurately depicts the measure of progress is the actual hours incurred to date relative to projected hours to complete the research service. During the three and six months ended June 30, 2021, the Company recognized revenue under the AbbVie Collaboration Agreement of approximately $79 and $1,076, respectively. Revenue for the three and six months ended June 30, 2021 reflects events and conditions that occurred during that period that increased the number of hours estimated to be required to complete the services under the AbbVie Collaboration Agreement. These increased estimated efforts resulted in less progress occurring relative to the increased estimate of total projected hours to complete the research services (and thus limited revenue recognized) during the three and six months ended June 30, 2021 and compared to the amount of revenue recognized in the comparable periods. During the three and six months ended June 30, 2020, the Company recognized revenue under the AbbVie Collaboration Agreement of approximately $4,833 and $13,949, respectively. As of June 30, 2021 and December 31, 2020, there was $7,267 and $8,343 of deferred revenue related to the AbbVie Collaboration Agreement, which is classified as current on the unaudited condensed consolidated balance sheet. Dermelix Collaboration Agreement On February 17, 2019, Exicure entered into a License and Development Agreement with Dermelix (the “Dermelix Collaboration Agreement.”) Under the terms of the Dermelix Collaboration Agreement, Exicure received an upfront payment of $1,000, to be applied against the initial $1,000 of the Company’s development expenses.

Supplemental Balance Sheet Info

Supplemental Balance Sheet Information	6 Months Ended
	Jun. 30, 2021
Supplemental Balance Sheet Information [Abstract]
Supplemental Balance Sheet Information	Supplemental Balance Sheet Information Prepaid expenses and other current assets June 30, 2021 December 31, 2020 Prepaid clinical, contract research and manufacturing costs $ 3,388 $ 2,336 Interest receivable 44 161 Prepaid insurance 254 694 Other 902 1,040 Prepaid expenses and other current assets $ 4,588 $ 4,231 Property and equipment, net June 30, 2021 December 31, 2020 Scientific equipment $ 5,966 $ 5,476 Leasehold improvements — 192 Computers and software 52 46 Furniture and fixtures 30 30 Construction in process 144 119 Property and equipment, gross 6,192 5,863 Less: accumulated depreciation (2,090) (1,740) Property and equipment, net $ 4,102 $ 4,123 Depreciation and amortization expense was $283 and $187 for the three months ended June 30, 2021 and 2020, respectively, and $546 and $335 for the six months ended June 30, 2021 and 2020, respectively. Accrued expenses and other current liabilities June 30, 2021 December 31, 2020 Accrued clinical, contract research and manufacturing costs $ 1,223 $ 1,372 Accrued payroll-related expenses 1,127 1,158 Lease liability, current 420 223 Accrued other expenses 458 772 Accrued expenses and other current liabilities $ 3,228 $ 3,525

Investments

Investments	6 Months Ended
	Jun. 30, 2021
Investments [Abstract]
Investments	Investments As of June 30, 2021 and December 31, 2020, the Company primarily invested its excess cash in debt instruments of corporations, the U.S. Treasury, financial institutions, and U.S. government agencies with strong credit ratings and an investment grade rating at or above a long-term rating of Aa3/AA- and a short-term rating of P1/A1. The Company has established guidelines relative to diversification and maturities that maintain safety and liquidity. The Company periodically reviews and modifies these guidelines to maximize trends in yields and interest rates without compromising safety and liquidity. The following table summarizes the contract maturity of the available-for-sale securities the Company held as of June 30, 2021: One year or less 100 % After one year but within two years — % Total 100 % All of the Company’s available-for-sale securities are available to the Company for use in its current operations. As a result, the Company categorizes all of these securities as current assets even though the stated maturity of some individual securities may be one year or more beyond the balance sheet date. The amortized cost, gross unrealized holding gains, gross unrealized holding losses and fair value of cash equivalents and available-for-sale securities by type of security at June 30, 2021 and December 31, 2020 were as follows: June 30, 2021 Amortized Costs Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Commercial paper $ 5,999 $ — $ — $ 5,999 Corporate notes/bonds 6,212 1 — 6,213 U.S. Government agency securities 1,256 4 — 1,260 $ 13,467 $ 5 $ — $ 13,472 December 31, 2020 Amortized Costs Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Commercial paper $ 15,992 $ 2 $ (3) $ 15,991 Corporate notes/bonds 29,227 72 (3) 29,296 U.S. Treasuries 2,251 2 — 2,253 U.S. Government agency securities 1,265 13 — 1,278 $ 48,735 $ 89 $ (6) $ 48,818

Debt

Debt	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Debt	Debt MidCap Credit Agreement On September 25, 2020, the Company entered into a Credit and Security Agreement, as amended on October 21, 2020, (the “MidCap Credit Agreement”), with MidCap Financial Trust (“MidCap”), as agent, and the lenders party thereto from time to time. The MidCap Credit Agreement provides for a secured term loan facility in an aggregate principal amount of up to $25,000 (the “MidCap Credit Facility”). The Company borrowed the first advance of $17,500 (“Tranche 1”) on September 25, 2020 (the “Closing Date”). Under the terms of the MidCap Credit Agreement, the second advance of $7,500 (“Tranche 2”) is available to the Company from April 1, 2021 to September 30, 2021, subject to the Company’s satisfaction of certain conditions described in the MidCap Credit Agreement. The Company believes the conditions to access the available Tranche 2 amount are satisfied as of June 30, 2021. The proceeds from the MidCap Credit Facility are expected to be used for working capital and general corporate purposes. Tranche 1, and if borrowed Tranche 2, each bear interest at a floating rate equal to 6.25% per annum, plus the greater of (i) 1.50% or (ii) one-month LIBOR. Interest on each loan advance is due and payable monthly in arrears. Principal on each loan advance is payable in 36 equal monthly installments beginning October 1, 2022 until paid in full on October 1, 2025 (the “Maturity Date”). Prepayments of the loans under the MidCap Credit Agreement, in whole or in part, will be subject to early termination fees in an amount equal to 3.0% of principal prepaid if prepayment occurs on or prior to the first anniversary of the Closing Date and 1.0% of principal prepaid if prepayment occurs after the first anniversary of the Closing Date and prior to the maturity date. In connection with execution of the Midcap Credit Agreement, the Company paid MidCap a $125 origination fee. At the Maturity Date or on any earlier date on which all amounts advanced to the Company become due and payable in full, or are otherwise paid in full, the Company is required to pay an exit fee equal to 3.75% of the principal amount of all loans advanced to the Company under the MidCap Credit Agreement. Upon the advance of Tranche 1, the Company accrued $656 for the related exit fee. The Company’s obligations under the MidCap Credit Agreement are secured by a security interest in substantially all of its assets, excluding intellectual property (which is subject to a negative pledge). Additionally, the Company’s future subsidiaries, if any, may be required to become co-borrowers or guarantors under the MidCap Credit Agreement. The MidCap Credit Agreement contains customary affirmative covenants and customary negative covenants limiting the Company’s ability and the ability of the Company’s subsidiaries, if any, to, among other things, dispose of assets, undergo a change in control, merge or consolidate, make acquisitions, incur debt, incur liens, pay dividends, repurchase stock and make investments, in each case subject to certain exceptions. The MidCap Credit Agreement also contains customary events of default relating to, among other things, payment defaults, breaches of covenants, a material adverse change, delisting of the Company’s common stock, bankruptcy and insolvency, cross defaults with certain material indebtedness and certain material contracts, judgments, and inaccuracies of representations and warranties. Upon an event of default, the agent and the lenders may declare all or a portion of the Company’s outstanding obligations to be immediately due and payable and exercise other rights and remedies provided for under the agreement. During the existence of an event of default, interest on the obligations could be increased by 2.0%. Total proceeds, net of fees and issuance costs, borrowed under Tranche 1 were $16,512. Fees and issuance costs of $332, as well as fees of $656 that are payable to MidCap at maturity of Tranche 1, are recorded as a reduction to the carrying amount of long-term debt on the Company’s balance sheet and will be amortized to interest expense through the maturity date of October 1, 2025 using the effective interest method. Fees and issuance costs of $73 attributed to the amount available to be borrowed under Tranche 2 were paid and recorded as deferred financing costs (other assets) and will be (i) recorded as a reduction in the carrying amount of long-term debt in future periods if amounts are borrowed under Tranche 2 or (ii) will be amortized and recorded to interest expense if amounts are not borrowed under Tranche 2. For the three and six months ended June 30, 2021, the Company recognized $37 as interest expense and the remaining balance of the deferred financing costs is $36 as of June 30, 2021. As of June 30, 2021, the aggregate carrying value of the Company’s long-term debt is $16,730. As of June 30, 2021, the principal maturities of the Company’s long-term debt were as follows: June 30, 2021 2021 (remaining six months) $ — 2022 1,459 2023 5,833 2024 5,833 2025 4,375 Principal balance outstanding $ 17,500 less: unamortized discount and debt issuance costs (770) Long-term debt $ 16,730 Current portion — Noncurrent portion $ 16,730 The Company paid interest on the MidCap Credit Agreement of $347 and $686 during the three and six months ended June 30, 2021, respectively. The Company paid interest on the Hercules Loan Agreement (as discussed below) of $0 and $142 during the three and six months ended June 30, 2020, respectively. Hercules Loan Agreement On March 2, 2020, pursuant to the terms of the loan agreement with Hercules Technology Growth Capital (“Hercules”) and subsequent amendments thereto (the “Hercules Loan Agreement”), the Company repaid all remaining outstanding obligations under the Hercules Loan Agreement as of the maturity date, including the outstanding principal balance of $4,999 and the end of term fee of $100.

Leases

Leases	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Leases	Leases The Company’s lease arrangements at June 30, 2021 consist of (i) a lease for office and laboratory space at its headquarters in Chicago, Illinois that commenced in July 2020 (the “Chicago Lease”), (ii) a lease for office space at a multi-tenant facility in Cambridge, MA that commenced in March 2019 and is cancelable at any time (the “Cambridge Lease”), and (iii) leases for office equipment (the “Office Equipment Leases”). Each of these leases are classified as operating leases. Due to the nature of the Cambridge Lease, the Company determined that this lease represented a short-term lease with an initial term of less than twelve months and, as such, the Cambridge Lease is not recorded on the balance sheet and related lease costs are recognized in the statement of operations as they are incurred. The Company has also elected to not record the Office Equipment Leases on the balance sheet since related payment amounts and lease costs are insignificant. Lease costs for the Office Equipment Leases are recognized in the statement of operations on a straight-line basis over the lease term. The Company’s lease arrangement for office and laboratory space at its former headquarters in Skokie, Illinois ended in February 2021 in accordance with the terms of that lease arrangement. Chicago Lease The Company has approximately thirty thousand square feet of office and laboratory space in Chicago, Illinois (the “Chicago Lease”). The original term (the “Original Term”) of the Chicago Lease is 10 years, commencing on July 1, 2020 (the “Commencement Date”), which is the date the premises were ready for occupancy under the terms of the Chicago Lease. The Company has options to extend the term of the Chicago Lease for two additional successive periods of five years each (the “Extension Periods”) at the then prevailing effective market rental rate. The initial annual base rent during the Original Term is approximately $1,113 for the first 12-month period of the Original Term, payable in monthly installments beginning on the Commencement Date. Base rent thereafter is subject to annual increases of 3%, for an aggregate amount of $12,761 over the Original Term. The Company must also pay its proportionate share of certain operating expenses and taxes for each calendar year during the term. During the first 12-month period of the Original Term, the base rent and the Company's proportionate share of operating expenses and taxes are subject to certain abatements. In connection with the Chicago Lease, the Company will maintain a letter of credit for the benefit of the landlord in an initial amount of $1,200, which amount is subject to reduction over time. Upon execution of the Chicago Lease, the Company paid to the landlord the first installment of base rent and the estimated monthly amount of its pro rata share of taxes and its pro rata share of operating expenses in the aggregate amount of $87 which amount had been adjusted for the abatement as set forth in the lease agreement. The Company also paid the landlord a net amount of $697 toward tenant improvements. As part of the agreement for the Chicago Lease, the Company is required to maintain a standby letter of credit during the term of the lease, currently in the amount of $1,200 and subject to reduction over time, which is secured by a restricted certificate of deposit account and presented within other noncurrent assets on the Company’s unaudited condensed consolidated balance sheet at June 30, 2021. The Company recognized a right of use asset of $8,931 and a lease liability of $8,147 on the Commencement Date. Because the rate implicit in the Chicago Lease is not readily determinable, the Company used its incremental borrowing rate of 8.3% on the Commencement Date to determine the present value of the lease payments over the Original Term. The incremental borrowing rate represents an estimate of the interest rate the Company would incur at lease commencement to borrow an amount equal to the lease payments on a collateralized basis over the term of a lease. As of June 30, 2021, the Company determined it is not reasonably certain that the renewal option would be exercised. Information related to the Company’s operating lease asset and related operating lease liabilities were as follows: June 30, 2021 Weighted-average remaining lease term 9.0 years Weighted-average discount rate 8.3 % The following table summarizes lease costs in the Company’s unaudited condensed consolidated statement of operations: Three Months Ended Six Months Ended 2021 2020 2021 2020 Operating lease costs $ 326 $ 296 $ 653 $ 380 Short term lease costs 31 29 62 67 Variable lease costs 195 92 572 149 Total lease costs $ 552 $ 417 $ 1,287 $ 596 The Company made cash payments for operating leases of $1,106 and $1,227 during the six months ended June 30, 2021 and 2020, respectively. Maturities of the Company’s lease liability as of June 30, 2021 were as follows: Years Ending December 31, Operating Leases 2021 (remaining six months) $ 478 2022 1,163 2023 1,198 2024 1,235 2025 1,272 2026 1,310 Thereafter 4,897 Total $ 11,553 Less: imputed interest (3,437) Total lease liability $ 8,116 Current operating lease liability $ 420 Noncurrent operating lease liability 7,696 Total lease liability $ 8,116

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Preferred Stock As of June 30, 2021 and December 31, 2020, 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 June 30, 2021 and December 31, 2020, the Company had authorized 200,000,000 shares of common stock, par value $0.0001. As of June 30, 2021 and December 31, 2020, the Company had 88,096,694 shares and 87,651,352 shares issued and outstanding, respectively. 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 the Company’s 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 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 the Company’s 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. The Company’s common stock has no preemptive or conversion rights or other subscription rights. There are no redemption or sinking fund provisions applicable to the Company’s common stock. The outstanding shares of the Company’s common stock are fully paid and non-assessable. Common Stock Warrants As of June 30, 2021, no warrants were outstanding. As of December 31, 2020, warrants to purchase 413,320 shares of common stock at a price of $3.00 per share were outstanding. The warrants expired unexercised as follows: 163,174 warrants expired on March 27, 2021, 132,884 expired on April 28, 2021, and 117,262 expired on May 3, 2021. The warrants were classified as a liability which was remeasured each period at fair value. See Note 12, Fair Value Measurements for more information on the fair value of the common stock warrant liability. Accumulated Other Comprehensive Income (Loss) The following table summarizes the changes in each component of accumulated other comprehensive income (loss), net of tax, for 2021: Unrealized gains (losses) on short-term investments Total Balance at December 31, 2020 $ 83 $ 83 Other comprehensive loss before reclassifications (51) (51) Net current period other comprehensive loss (51) (51) Balance at March 31, 2021 $ 32 $ 32 Other comprehensive income (loss) before reclassifications (27) (27) Net current period other comprehensive income (27) (27) Balance at June 30, 2021 $ 5 $ 5 The following table summarizes the changes in each component of accumulated other comprehensive income (loss), net of tax, for 2020: Unrealized gains (losses) on short-term investments Total Balance at December 31, 2019 $ (27) $ (27) Other comprehensive income before reclassifications 10 10 Net current period other comprehensive income 10 10 Balance at March 31, 2020 $ (17) $ (17) Other comprehensive income (loss) before reclassifications 352 352 Net losses (gains) reclassified from accumulated other comprehensive loss 3 3 Net current period other comprehensive income 355 355 Balance at June 30, 2020 $ 338 $ 338 The net loss reclassified from accumulated other comprehensive loss during the three months ended June 30, 2020 resulted from sales of available-for-sale securities prior to maturity. The gross realized gains and gross realized losses of these sales were $23 and $6, respectively, for the three and six months ended June 30, 2020. The basis on which the cost of the securities was determined was specific identification. Proceeds related to these sales were $9,404.

Equity-Based Compensation

Equity-Based Compensation	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Equity-Based Compensation	Equity-Based Compensation 2017 Equity Incentive Plan Awards that may be awarded under the 2017 Equity Incentive Plan include non-qualified and incentive stock options, stock appreciation rights, bonus shares, restricted stock, restricted stock units, performance units and cash-based awards. The number of shares of common stock reserved for issuance under the 2017 Equity Incentive Plan automatically increases on January 1 of each year, beginning on January 1, 2020, by the lesser of (i) 4,600,000 shares, (ii) 5% of the total number of shares of our capital stock outstanding on December 31 of the preceding calendar year, or (iii) a lesser number of shares determined by the Compensation Committee of the Board. The Compensation Committee made the determination to increase the share reserve for the 2017 Equity Incentive Plan by 4,382,567 shares, effective January 1, 2021. As of June 30, 2021, the aggregate number of equity awards available for grant under the 2017 Equity Incentive Plan was 2,831,213. Inducement Grant In May 2021, the Company granted stock options to purchase up to 600,000 shares of common stock as a material inducement to Brian C. Bock, the Company’s Chief Financial Officer, to enter into employment with the Company (the “Inducement Grant”). The Inducement Grant, which was made pursuant to a stand-alone nonstatutory stock option agreement (the “Inducement Award Agreement”), was approved by the Compensation Committee of the Board, was awarded in accordance with Nasdaq Listing Rule 5635(c)(4) and outside of the Company’s 2017 Equity Incentive Plan and is subject to the terms and conditions of the Inducement Award Agreement. As such, any shares underlying the Inducement Grant are not, upon forfeiture, cancellation or expiration, returned to a pool of shares reserved for future issuance. As of June 30, 2021, stock options to purchase up to 600,000 shares of common stock remained outstanding under the Inducement Grant. Employee Stock Purchase Plan The 2017 Employee Stock Purchase Plan (the "ESPP") was adopted by the Board in September 2017 and approved by the Company's stockholders in September 2017. Through the ESPP, eligible employees may authorize payroll deductions of up to 15% of their compensation to purchase common stock. The maximum number of shares that an employee may purchase on any exercise date in an offer period will be the smaller of (i) 7,500 shares or (ii) such number of shares as has a fair market value (determined as of the offering date for such offer period) equal to $25,000 within one calendar year minus the fair market value of any other shares of common stock that are attributed to such calendar year. The purchase price per share at each purchase date is equal to 85% of the lower of (i) the closing market price per share of Exicure common stock on the employee’s offering date or (ii) the closing market price per share of Exicure common stock on the exercise date. Each offering period is approximately six-months in duration and the first offering period began on November 16, 2020 and ended on May 14, 2021. In connection with the end of the first offering period on May 14, 2021, the Company issued 103,096 shares of common stock that were purchased under the ESPP. The ESPP provides that the number of shares reserved and available for issuance will automatically increase each January 1, beginning on January 1, 2018 and each January 1 thereafter through January 1, 2027, by the least of (i) 300,000 shares; (ii) 0.3% of the outstanding shares of common stock on the last day of the immediately preceding calendar year; or (iii) a lesser number of shares determined by the Board. On January 1, 2021 and 2020, the number of shares of common stock available for issuance under the ESPP increased by 258,207 shares and 262,954 shares, respectively. As of June 30, 2021, there were 1,100,791 shares available for issuance under the ESPP. Equity-based compensation expense is classified in the statements of operations as follows: Three Months Ended Six Months Ended 2021 2020 2021 2020 Research and development expense $ 361 $ 203 $ 618 $ 360 General and administrative expense 403 341 663 625 $ 764 $ 544 $ 1,281 $ 985 Unamortized equity-based compensation expense at June 30, 2021 was $8,350, which is expected to be amortized over a weighted-average period of 3.2 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: Six Months Ended 2021 2020 Expected term 5.0 to 6.1 years 5.2 to 6.1 years Risk-free interest rate 0.36% to 1.12%; weighted avg. 1.05% 0.41% to 1.68%; weighted avg. 0.67% Expected volatility 81.7% to 83.6%; weighted avg. 82.6% 81.0% to 85.8%; weighted avg. 83.8% 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 six months ended June 30, 2021 and 2020 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 Six months ended June 30, 2021 $1.54 to $2.57; weighted avg. $1.88 $1.54 to $2.57; weighted avg. $1.88 Six months ended June 30, 2020 $1.19 to $2.80: weighted avg. $1.85 $1.19 to $2.80: weighted avg. $1.85 The weighted-average grant date fair value of common stock options granted in the six months ended June 30, 2021 and 2020 was $1.31 and $1.29 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, 2020 7,227,296 $ 2.24 6.8 $ 1,719 Granted 4,270,086 1.88 Exercised (342,246) 1.60 Forfeited (95,702) 2.27 Outstanding - June 30, 2021 11,059,434 $ 2.12 7.8 $ 1,019 Exercisable - June 30, 2021 4,580,439 $ 2.29 5.5 $ 832 Vested and Expected to Vest - 10,559,034 $ 2.13 7.7 $ 1,007 The aggregate intrinsic value of common stock options exercised during the six months ended June 30, 2021 was $77 and $89, respectively. A summary of restricted stock unit activity of the periods indicated is as follows: Restricted Stock Units Weighted-Average Grant Date Fair Value Unvested balance - December 31, 2020 — $ — Granted 286,000 1.90 Unvested balance - June 30, 2021 286,000 $ 1.90 The grant date fair value of restricted stock units is based on the Company’s closing stock price at the date of grant. At vesting, each outstanding restricted stock unit will be exchanged for one share of the Company’s common stock. The restricted stock units granted during the 2021 period generally vest evenly on a quarterly basis over a period of 4 years in exchange for continued service provided by the restricted stock unit recipient during that vesting period.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income TaxesThe Company incurred a pretax loss in each of the three and six months ended June 30, 2021 and 2020, which consists entirely of loss in the United States 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 six months ended June 30, 2021 and 2020 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	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Loss Per Common Share	Loss Per Common ShareBasic 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, restricted stock units, and warrants to purchase common stock that were outstanding during the periods presented were excluded from the diluted loss per share calculation for the periods presented 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 six months ended June 30, 2021 and 2020. The following is the computation of loss per common share for the three and six months ended June 30, 2021 and 2020: Three Months Ended Six Months Ended 2021 2020 2021 2020 Net loss $ (14,269) $ (4,311) $ (26,746) $ (3,161) Weighted-average basic and diluted common shares outstanding 88,043,447 87,174,533 87,948,440 87,126,847 Loss per share - basic and diluted $ (0.16) $ (0.05) $ (0.30) $ (0.04) The outstanding securities presented below were excluded from the calculation of loss per common share, for the periods presented, because such securities would have been anti-dilutive due to the Company’s loss per share during that period: As of June 30, 2021 2020 Options to purchase common stock 11,059,434 7,698,313 Restricted stock units 286,000 — Warrants to purchase common stock — 413,320

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2021
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. Assets measured at fair value on a recurring basis as of June 30, 2021 are as follows: Total Level 1 Level 2 Level 3 Assets Cash equivalents: Money market funds $ 30,101 $ 30,101 $ — $ — Short-term investments: Commercial paper 5,999 — 5,999 — Corporate notes/bonds 6,213 — 6,213 — U.S. government agency securities 1,260 — 1,260 — Total financial assets $ 43,573 $ 30,101 $ 13,472 $ — Assets and liabilities measured at fair value on a recurring basis as of December 31, 2020 are as follows: Total Level 1 Level 2 Level 3 Assets Cash equivalents: Money market funds $ 24,586 $ 24,586 $ — $ — Short-term investments: Commercial paper 15,991 — 15,991 — Corporate notes/bonds 29,296 — 29,296 — U.S. Treasuries 2,253 — 2,253 — U.S. government agency securities 1,278 — 1,278 — Total financial assets $ 73,404 $ 24,586 $ 48,818 $ — Liabilities Common stock warrant liability $ 15 $ — $ — $ 15 Total financial liabilities $ 15 $ — $ — $ 15 The Company uses the market approach and Level 1 and Level 2 inputs to value its cash equivalents and Level 2 inputs to value its short-term investments. 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. As of June 30, 2021, the Company’s common stock warrant liability was $0 and no warrants were outstanding (refer to Note 8, Stockholders’ Equity , for more information). 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 three months ended June 30, 2021: Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Common Stock Warrant Liability Balance at December 31, 2020 $ 15 Additions — Gain included in other (expense) income, net (15) Balance at June 30, 2021 $ —

Commitment and Contingencies

Commitment and Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Leases Refer to Note 7, Leases , for a discussion of the commitments associated with the Company’s lease agreements. Northwestern University License Agreements On December 12, 2011, (1) AuraSense, LLC, the Company’s former parent, 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

Related-Party Transactions

Related-Party Transactions	6 Months Ended
	Jun. 30, 2021
Related Party Transactions [Abstract]
Related-Party Transactions	Related-Party TransactionsThe Company received consulting services from, and paid fees to, one of its co-founders who is not an employee but, through April 30, 2021, served as a member of the Board. The Company recognized $50 as an expense in each of the six months ended June 30, 2021 and 2020 in connection with these consulting services in the accompanying unaudited condensed consolidated statement of operations.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2021
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, except as noted below. Ipsen Collaboration, License, and Option Agreement On July 30, 2021, the Company entered into a Collaboration, Option and License Agreement (the “Ipsen Collaboration Agreement”) with IPSEN BIOPHARM LIMITED (“Ipsen”). Pursuant to the Ipsen Collaboration Agreement, the Company granted to Ipsen exclusive access and options to license SNA based therapeutics arising from two collaboration programs related to the treatment of Huntington’s disease and Angelman syndrome, respectively. Each such license would grant to Ipsen exclusive, royalty-bearing, sublicensable, worldwide rights to develop, manufacture, use and commercialize such SNA therapeutics. Upon written notice to the Company, Ipsen may exercise its option during the corresponding collaboration program’s applicable option exercise period, (each, an “Option Exercise Period”). Under the terms of the Ipsen Collaboration Agreement, the Company will conduct discovery and development in two collaboration programs for Huntington’s disease and Angelman syndrome. The Company shall be solely responsible for all costs and expenses of conducting each collaboration program through the selection of SNA therapeutic candidates for further development (“Selection”), and Ipsen shall be responsible for all costs and expenses of all additional activities that are necessary to enable the first filing of an investigational new drug application (“IND”) for each proposed product candidate. In the event that Ipsen exercises an option, Ipsen will be responsible for further development from the license effective date and commercialization of the corresponding licensed product. Under the terms of the Ipsen Collaboration Agreement, the Company will receive an upfront payment of $20,000 (the “Ipsen Upfront Payment”), and, depending on the timing when Ipsen exercises its option right in a collaboration program, Ipsen will pay to the Company an option exercise fee equal to $10,000 (if exercised within the Option Exercise Period after the Selection) or $25,000 (if exercised within the Option Exercise Period that begins after the first Option Exercise Period and ends after IND filing) for each collaboration program. Ipsen will pay a pre-clinical milestone of $5,000 for each collaboration program upon achievement of such milestone regardless of whether an option is exercised. In addition to the option exercise fees and the pre-clinical milestones described above, if Ipsen exercises an option for a program, development and regulatory milestones will be payable for that program upon the initiation of certain clinical trials, and the filing for processing by the FDA in the United States and by 2 additional regulators outside the United States of a marketing application for review, per program, with an aggregate total of up to $180,000 if both options are exercised. Commercial milestones will be payable for that program upon first commercial sale of a licensed product in certain jurisdictions and the achievement of specified aggregate sales thresholds for all licensed products from that program, with an aggregate total of up to $762,000 if both options are exercised. In the event a therapeutic candidate subject to the collaboration results in commercial sales, the Company is eligible to receive tiered royalties at percentages ranging from the mid-single digits to the mid-teens on future net product sales of such commercialized therapeutic candidates. A percentage of the aforementioned payments will be due to NU upon receipt, pursuant to the terms of the Company’s existing license agreements with NU (see Note 13, Commitment and Contingencies, for more information on the Northwestern University License Agreements). In connection with the receipt of the Ipsen Upfront Payment, the Company will incur $3,000 in license fees payable to NU under the terms of the Northwestern License Agreements. The Ipsen Collaboration Agreement will remain in effect, unless earlier terminated, until (a) the expiration of the later-to-expire option exercise period, if Ipsen does not exercise either option, or (b) the expiration of the last-to-expire royalty term for any licensed product in such country on a licensed product-by-licensed product and country-by-country basis, if Ipsen exercises one or both options. Upon expiration of the royalty term with respect to a particular licensed product in a country, the license for such product in such country will convert to a fully-paid, irrevocable and perpetual license. The Ipsen Collaboration Agreement also contains customary provisions for termination by either party, including in the event of breach of the Ipsen Collaboration Agreement, subject to cure, and by the Company upon a challenge of the licensed patents, subject, in certain cases, to customary reversion rights. Upon termination of the Ipsen Collaboration Agreement by the Company for Ipsen’s breach or bankruptcy, all licenses granted by the Company to Ipsen will terminate. The Ipsen Collaboration Agreement includes customary representations and warranties on behalf of both the Company and Ipsen. The Ipsen Collaboration Agreement also provides for customary mutual indemnities. In addition, the Ipsen Collaboration Agreement imposes certain exclusivity obligations on Ipsen and the Company, respectively, with respect to the development, use, manufacture and commercialization of oligonucleotide-based therapeutic targeting the same targets in the collaboration programs and/or certain other specific targets. Either party may assign the Ipsen Collaboration Agreement or delegate its obligations to an affiliate or to a successor to substantially all of the business to which the Ipsen Collaboration Agreement relates without the consent of the other party. In connection with the entry into the Ipsen Collaboration Agreement, the Company, Ipsen and NU entered into a side letter to the Northwestern University License Agreements (the “Side Letter”). Pursuant to the Side Letter, the parties thereto clarified certain provisions of the Northwestern University License Agreements as they apply to the sublicenses granted to Ipsen pursuant to the Ipsen Collaboration Agreement, including providing for the survival of Ipsen’s sublicense to the applicable NU intellectual property rights should the Northwestern University License

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of PresentationThe accompanying unaudited condensed consolidated financial statements as of June 30, 2021 and December 31, 2020, and for the six months ended June 30, 2021 and 2020, 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 wholly 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 circumstances 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.
Recent Accounting Pronouncements	Recently Adopted Accounting Pronouncements None. Recent Accounting Pronouncements Not Yet Adopted Financial Instruments - Credit Losses In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) ASU 2016-13, Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”) . ASU 2016-13 is a new standard intended to improve reporting requirements specific to loans, receivables and other financial instruments. ASU 2016-13 requires that credit losses on financial assets measured at amortized cost be determined using an expected loss model, instead of the current incurred loss model, and requires that credit losses related to available-for-sale debt securities be recorded through an allowance for credit losses and limited to the amount by which carrying value exceeds fair value. ASU 2016-13 also requires enhanced disclosure of credit risk associated with financial assets. The effective date of ASU 2016-13 was deferred by ASU 2019-10, Financial Instruments—Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842)—Effective Dates to the annual period beginning after December 15, 2022 for companies that (i) meet the definition of an SEC filer and (ii) are eligible as “smaller reporting companies” as such term is defined by the SEC, with early adoption permitted. The Company is currently assessing the impact of adoption of ASU 2016-13 to its consolidated financial statements.
(Loss) Earnings 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, restricted stock units, and warrants to purchase common stock that were outstanding during the periods presented were excluded from the diluted loss per share calculation for the periods presented 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)	6 Months Ended
	Jun. 30, 2021
Supplemental Balance Sheet Information [Abstract]
Prepaid Expense and Other Current Assets	Prepaid expenses and other current assets June 30, 2021 December 31, 2020 Prepaid clinical, contract research and manufacturing costs $ 3,388 $ 2,336 Interest receivable 44 161 Prepaid insurance 254 694 Other 902 1,040 Prepaid expenses and other current assets $ 4,588 $ 4,231
Property and Equipment, Net	Property and equipment, net June 30, 2021 December 31, 2020 Scientific equipment $ 5,966 $ 5,476 Leasehold improvements — 192 Computers and software 52 46 Furniture and fixtures 30 30 Construction in process 144 119 Property and equipment, gross 6,192 5,863 Less: accumulated depreciation (2,090) (1,740) Property and equipment, net $ 4,102 $ 4,123
Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities June 30, 2021 December 31, 2020 Accrued clinical, contract research and manufacturing costs $ 1,223 $ 1,372 Accrued payroll-related expenses 1,127 1,158 Lease liability, current 420 223 Accrued other expenses 458 772 Accrued expenses and other current liabilities $ 3,228 $ 3,525

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 30, 2021
Investments [Abstract]
Investments	The following table summarizes the contract maturity of the available-for-sale securities the Company held as of June 30, 2021: One year or less 100 % After one year but within two years — % Total 100 %
Debt Securities, Available-for-sale	The amortized cost, gross unrealized holding gains, gross unrealized holding losses and fair value of cash equivalents and available-for-sale securities by type of security at June 30, 2021 and December 31, 2020 were as follows: June 30, 2021 Amortized Costs Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Commercial paper $ 5,999 $ — $ — $ 5,999 Corporate notes/bonds 6,212 1 — 6,213 U.S. Government agency securities 1,256 4 — 1,260 $ 13,467 $ 5 $ — $ 13,472 December 31, 2020 Amortized Costs Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Commercial paper $ 15,992 $ 2 $ (3) $ 15,991 Corporate notes/bonds 29,227 72 (3) 29,296 U.S. Treasuries 2,251 2 — 2,253 U.S. Government agency securities 1,265 13 — 1,278 $ 48,735 $ 89 $ (6) $ 48,818

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Principal Maturities of Long-term Debt	As of June 30, 2021, the principal maturities of the Company’s long-term debt were as follows: June 30, 2021 2021 (remaining six months) $ — 2022 1,459 2023 5,833 2024 5,833 2025 4,375 Principal balance outstanding $ 17,500 less: unamortized discount and debt issuance costs (770) Long-term debt $ 16,730 Current portion — Noncurrent portion $ 16,730

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2021
Leases [Abstract]
Schedule of Operating Leases, Additional Information	Information related to the Company’s operating lease asset and related operating lease liabilities were as follows: June 30, 2021 Weighted-average remaining lease term 9.0 years Weighted-average discount rate 8.3 %
Schedule of Lease Costs	The following table summarizes lease costs in the Company’s unaudited condensed consolidated statement of operations: Three Months Ended Six Months Ended 2021 2020 2021 2020 Operating lease costs $ 326 $ 296 $ 653 $ 380 Short term lease costs 31 29 62 67 Variable lease costs 195 92 572 149 Total lease costs $ 552 $ 417 $ 1,287 $ 596
Schedule of Future Minimum Rental Payments	Maturities of the Company’s lease liability as of June 30, 2021 were as follows: Years Ending December 31, Operating Leases 2021 (remaining six months) $ 478 2022 1,163 2023 1,198 2024 1,235 2025 1,272 2026 1,310 Thereafter 4,897 Total $ 11,553 Less: imputed interest (3,437) Total lease liability $ 8,116 Current operating lease liability $ 420 Noncurrent operating lease liability 7,696 Total lease liability $ 8,116

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table summarizes the changes in each component of accumulated other comprehensive income (loss), net of tax, for 2021: Unrealized gains (losses) on short-term investments Total Balance at December 31, 2020 $ 83 $ 83 Other comprehensive loss before reclassifications (51) (51) Net current period other comprehensive loss (51) (51) Balance at March 31, 2021 $ 32 $ 32 Other comprehensive income (loss) before reclassifications (27) (27) Net current period other comprehensive income (27) (27) Balance at June 30, 2021 $ 5 $ 5 The following table summarizes the changes in each component of accumulated other comprehensive income (loss), net of tax, for 2020: Unrealized gains (losses) on short-term investments Total Balance at December 31, 2019 $ (27) $ (27) Other comprehensive income before reclassifications 10 10 Net current period other comprehensive income 10 10 Balance at March 31, 2020 $ (17) $ (17) Other comprehensive income (loss) before reclassifications 352 352 Net losses (gains) reclassified from accumulated other comprehensive loss 3 3 Net current period other comprehensive income 355 355 Balance at June 30, 2020 $ 338 $ 338

Equity-Based Compensation (Tabl

Equity-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [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 Six Months Ended 2021 2020 2021 2020 Research and development expense $ 361 $ 203 $ 618 $ 360 General and administrative expense 403 341 663 625 $ 764 $ 544 $ 1,281 $ 985
Assumptions Used to Determine Fair Value of Common Stock Option Grants	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: Six Months Ended 2021 2020 Expected term 5.0 to 6.1 years 5.2 to 6.1 years Risk-free interest rate 0.36% to 1.12%; weighted avg. 1.05% 0.41% to 1.68%; weighted avg. 0.67% Expected volatility 81.7% to 83.6%; weighted avg. 82.6% 81.0% to 85.8%; weighted avg. 83.8% Forfeiture rate 5 % 5 % Expected dividend yield — % — % The fair value of the underlying common stock and the exercise price for the common stock options granted during the six months ended June 30, 2021 and 2020 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 Six months ended June 30, 2021 $1.54 to $2.57; weighted avg. $1.88 $1.54 to $2.57; weighted avg. $1.88 Six months ended June 30, 2020 $1.19 to $2.80: weighted avg. $1.85 $1.19 to $2.80: weighted avg. $1.85
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, 2020 7,227,296 $ 2.24 6.8 $ 1,719 Granted 4,270,086 1.88 Exercised (342,246) 1.60 Forfeited (95,702) 2.27 Outstanding - June 30, 2021 11,059,434 $ 2.12 7.8 $ 1,019 Exercisable - June 30, 2021 4,580,439 $ 2.29 5.5 $ 832 Vested and Expected to Vest - 10,559,034 $ 2.13 7.7 $ 1,007
Restricted Stock Unit Awards Activity	A summary of restricted stock unit activity of the periods indicated is as follows: Restricted Stock Units Weighted-Average Grant Date Fair Value Unvested balance - December 31, 2020 — $ — Granted 286,000 1.90 Unvested balance - June 30, 2021 286,000 $ 1.90

Loss Per Common Share (Tables)

Loss Per Common Share (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Computation of loss per common share	The following is the computation of loss per common share for the three and six months ended June 30, 2021 and 2020: Three Months Ended Six Months Ended 2021 2020 2021 2020 Net loss $ (14,269) $ (4,311) $ (26,746) $ (3,161) Weighted-average basic and diluted common shares outstanding 88,043,447 87,174,533 87,948,440 87,126,847 Loss per share - basic and diluted $ (0.16) $ (0.05) $ (0.30) $ (0.04)
Antidilutive Securities	The outstanding securities presented below were excluded from the calculation of loss per common share, for the periods presented, because such securities would have been anti-dilutive due to the Company’s loss per share during that period: As of June 30, 2021 2020 Options to purchase common stock 11,059,434 7,698,313 Restricted stock units 286,000 — Warrants to purchase common stock — 413,320

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	Assets measured at fair value on a recurring basis as of June 30, 2021 are as follows: Total Level 1 Level 2 Level 3 Assets Cash equivalents: Money market funds $ 30,101 $ 30,101 $ — $ — Short-term investments: Commercial paper 5,999 — 5,999 — Corporate notes/bonds 6,213 — 6,213 — U.S. government agency securities 1,260 — 1,260 — Total financial assets $ 43,573 $ 30,101 $ 13,472 $ — Assets and liabilities measured at fair value on a recurring basis as of December 31, 2020 are as follows: Total Level 1 Level 2 Level 3 Assets Cash equivalents: Money market funds $ 24,586 $ 24,586 $ — $ — Short-term investments: Commercial paper 15,991 — 15,991 — Corporate notes/bonds 29,296 — 29,296 — U.S. Treasuries 2,253 — 2,253 — U.S. government agency securities 1,278 — 1,278 — Total financial assets $ 73,404 $ 24,586 $ 48,818 $ — Liabilities Common stock warrant liability $ 15 $ — $ — $ 15 Total financial liabilities $ 15 $ — $ — $ 15
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 three months ended June 30, 2021: Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Common Stock Warrant Liability Balance at December 31, 2020 $ 15 Additions — Gain included in other (expense) income, net (15) Balance at June 30, 2021 $ —

Description of Business and B_2

Description of Business and Basis of Presentation (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Aug. 31, 2021	Jun. 30, 2021
Unusual Risk or Uncertainty [Line Items]
Accumulated deficit generated, since inception		$ (151,548)
Forecast | Ipsen Collaboration
Unusual Risk or Uncertainty [Line Items]
Proceeds from Collaborators	$ 20,000
COVID-19
Unusual Risk or Uncertainty [Line Items]
Percentage of R&D staff on site		100.00%
Percentage of time that office and general and administrative staff are on site		50.00%

Collaborative Research and Li_2

Collaborative Research and License Agreements (Details)	Nov. 13, 2019USD ($)agreement	Feb. 17, 2019USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue			$ 79,000	$ 4,847,000	$ 1,076,000	$ 14,030,000
Deferred revenue, current			7,267,000		7,267,000		$ 8,343,000
AbbVie Collaboration | Collaboration Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of collaboration programs | agreement	2
Non-refundable upfront payment received for research agreement	$ 25,000,000
Collaboration option exercise fee	10,000,000
Collaboration option exercise fee	$ 10,000,000
Termination period upon written notice	90 days
Collaboration revenue			79,000	4,833,000	1,076,000	13,949,000
Deferred revenue, current			7,267,000		7,267,000		$ 8,343,000
Dermelix License Agreement | Collaboration Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Non-refundable upfront payment received for research agreement		$ 1,000,000
Collaboration revenue			$ 0	$ 14,000	$ 0	$ 81,000
Collaboration development expenses		$ 1,000,000
Deferred revenue								$ 0
Development and Commercialization License | AbbVie Collaboration | Collaboration Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration option exercise fee	$ 15,000,000
Maximum | AbbVie Collaboration | Collaboration Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Development milestone payment	55,000,000
Product approval and launch milestone payment	132,500,000
Sales milestone payment	$ 175,000,000

Supplemental Balance Sheet In_3

Supplemental Balance Sheet Information - Prepaid expenses and other current assets (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Supplemental Balance Sheet Information [Abstract]
Prepaid clinical, contract research and manufacturing costs	$ 3,388	$ 2,336
Interest receivable	44	161
Prepaid insurance	254	694
Other	902	1,040
Prepaid expenses and other current assets	$ 4,588	$ 4,231

Supplemental Balance Sheet In_4

Supplemental Balance Sheet Information - Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 6,192		$ 6,192		$ 5,863
Less: accumulated depreciation	(2,090)		(2,090)		(1,740)
Property and equipment, net	4,102		4,102		4,123
Depreciation and amortization	283	$ 187	546	$ 335
Scientific equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	5,966		5,966		5,476
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	0		0		192
Computers and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	52		52		46
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	30		30		30
Construction in process
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 144		$ 144		$ 119

Supplemental Balance Sheet In_5

Supplemental Balance Sheet Information - Accrued Expense and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Supplemental Balance Sheet Information [Abstract]
Accrued clinical, contract research and manufacturing costs	$ 1,223	$ 1,372
Accrued payroll-related expenses	1,127	1,158
Lease liability, current	420	223
Accrued other expenses	458	772
Accrued expenses and other current liabilities	$ 3,228	$ 3,525

Investments (Details)

Investments (Details)	6 Months Ended
	Jun. 30, 2021
Investments [Abstract]
One year or less	100.00%
After one year but within two years	0.00%
Total	100.00%

Investments - Available-for-sal

Investments - Available-for-sale Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Amortized Costs	$ 13,467	$ 48,735
Gross Unrealized Holding Gains	5	89
Gross Unrealized Holding Losses	0	(6)
Fair Value	13,472	48,818
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Costs	5,999	15,992
Gross Unrealized Holding Gains	0	2
Gross Unrealized Holding Losses	0	(3)
Fair Value	5,999	15,991
Corporate notes/bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Costs	6,212	29,227
Gross Unrealized Holding Gains	1	72
Gross Unrealized Holding Losses	0	(3)
Fair Value	6,213	29,296
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Amortized Costs		2,251
Gross Unrealized Holding Gains		2
Gross Unrealized Holding Losses		0
Fair Value		2,253
U.S. Government agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Costs	1,256	1,265
Gross Unrealized Holding Gains	4	13
Gross Unrealized Holding Losses	0	0
Fair Value	$ 1,260	$ 1,278

Debt - Narrative (Details)

Debt - Narrative (Details)	Sep. 25, 2020USD ($)	Mar. 02, 2020USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Oct. 01, 2022installmentPayment	Apr. 01, 2021USD ($)
Debt Instrument [Line Items]
Origination fee	$ 125,000
Exit fee percentage			3.75%		3.75%
Amortization of long-term debt issuance costs and fees					$ 141,000	$ 35,000
Long-term debt			$ 16,730,000		16,730,000
Interest paid on debt			$ 347,000	$ 0	686,000	142,000
Repayment of long-term debt					$ 0	$ 4,999,000
Secured Debt | MidCap Credit Agreement
Debt Instrument [Line Items]
Debt instrument, face amount	$ 25,000,000
Floating interest rate	6.25%
Variable rate	1.50%
Interest rate increase					2.00%
Secured Debt | MidCap Credit Agreement | Forecast
Debt Instrument [Line Items]
Number of monthly installment payments | installmentPayment							36
Secured Debt | MidCap Credit Agreement | Prior to first anniversary
Debt Instrument [Line Items]
Early termination fee			3.00%		3.00%
Secured Debt | MidCap Credit Agreement | After first anniversary
Debt Instrument [Line Items]
Early termination fee			1.00%		1.00%
Secured Debt | MidCap Credit Agreement - Tranche 1
Debt Instrument [Line Items]
Proceeds from long-term borrowing	$ 17,500,000
Fee amount	656,000
Proceeds from debt, net of fees and issuance costs	16,512,000
Unamortized debt issuance costs	332,000
Secured Debt | MidCap Credit Agreement - Tranche 2
Debt Instrument [Line Items]
Debt instrument, face amount								$ 7,500,000
Unamortized debt issuance costs	$ 73,000		$ 36,000		$ 36,000
Amortization of long-term debt issuance costs and fees			$ 37,000
Loans Payable | Secured Debt | Hercules Technology Growth Capital
Debt Instrument [Line Items]
Repayment of long-term debt		$ 4,999,000
Payments for debt end term fees		$ 100,000

Debt - Principal Maturities of

Debt - Principal Maturities of Long-Term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
2021 (remaining six months)	$ 0
2022	1,459
2023	5,833
2024	5,833
2025	4,375
Principal balance outstanding	17,500
less: unamortized discount and debt issuance costs	(770)
Long-term debt	16,730
Current portion	0
Noncurrent portion	$ 16,730	$ 16,589

Leases - Narrative (Details)

Leases - Narrative (Details) ft² in Thousands, $ in Thousands	Jul. 01, 2020USD ($)ft²extensionPeriod	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Lessee, Lease, Description [Line Items]
Right-of-use asset		$ 8,281		$ 8,606
Lease liability		8,116
Operating lease, cash payments		$ 1,106	$ 1,227
Chicago
Lessee, Lease, Description [Line Items]
Lease area | ft²	30
Contract term	10 years
Number of extensions | extensionPeriod	2
Renewal term	5 years
Annual rent payment initial twelve months	$ 1,113
Base rent annual percentage increase	3.00%
Estimated rental payment over original term	$ 12,761
Letters of credit outstanding	1,200
Rental payment adjusted for abatement	87
Payments for tenant improvements	697
Right-of-use asset	8,931
Lease liability	$ 8,147
Incremental borrowing rate	8.30%

Leases - Right of Use Asset Inf

Leases - Right of Use Asset Information (Details)	Jun. 30, 2021
Leases [Abstract]
Weighted-average remaining lease term	9 years
Weighted-average discount rate	8.30%

Leases - Lease Costs (Details)

Leases - Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Leases [Abstract]
Operating lease costs	$ 326	$ 296	$ 653	$ 380
Short term lease costs	31	29	62	67
Variable lease costs	195	92	572	149
Total lease costs	$ 552	$ 417	$ 1,287	$ 596

Leases - Schedule of Future Min

Leases - Schedule of Future Minimum Rental Payments (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Leases [Abstract]
2021 (remaining six months)	$ 478
2022	1,163
2023	1,198
2024	1,235
2025	1,272
2026	1,310
Thereafter	4,897
Total	11,553
Less: imputed interest	(3,437)
Total lease liability	8,116
Current operating lease liability	420	$ 223
Noncurrent operating lease liability	$ 7,696	$ 7,959

Stockholders' Equity - Current

Stockholders' Equity - Current Capitalization (Details)	Jun. 30, 2021votePerShare$ / sharesshares	Dec. 31, 2020$ / 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)	88,096,694	87,651,352
Common stock, shares outstanding (in shares)	88,096,694	87,651,352
Common stock, voting rights for each share | votePerShare	1

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock Warrants (Details) - Common Stock - $ / shares	Jun. 30, 2021	May 03, 2021	Apr. 28, 2021	Mar. 27, 2021	Dec. 31, 2020
Class of Warrant or Right [Line Items]
Number of shares called by warrants (in shares)	0				413,320
Exercise price (in dollars per share)					$ 3
Warrant expirations (in shares)		117,262	132,884	163,174

Stockholders' Equity - Accumula

Stockholders' Equity - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 50,041	$ 61,506	$ 85,114	$ 80,747	$ 61,506	$ 80,747
Other comprehensive income (loss) before reclassifications	(27)	(51)	352	10
Net losses (gains) reclassified from accumulated other comprehensive loss			3
Other comprehensive (loss) income	(27)	(51)	355	10	(78)	365
Ending balance	36,640	50,041	81,752	85,114	36,640	81,752
Gross realized gains, available for sale securities			23
Gross realized losses, available for sale securities						6
Proceeds from sale of debt securities, available-for-sale			9,404
Unrealized gains (losses) on short-term investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	32	83	(17)	(27)	83	(27)
Other comprehensive income (loss) before reclassifications	(27)	(51)	352	10
Net losses (gains) reclassified from accumulated other comprehensive loss			3
Other comprehensive (loss) income	(27)	(51)	355	10
Ending balance	5	32	338	(17)	5	338
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	32	83	(17)	(27)	83	(27)
Other comprehensive (loss) income	(27)	(51)	355	10
Ending balance	$ 5	$ 32	$ 338	$ (17)	$ 5	$ 338

Equity-Based Compensation - Nar

Equity-Based Compensation - Narrative (Details) - USD ($)	May 14, 2021	Jan. 01, 2021	Jan. 01, 2020	May 31, 2021	Sep. 30, 2017	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted in period (in shares)						4,270,086
Options outstanding (in shares)						11,059,434		7,227,296
Issuance of common stock-ESPP (in shares)	103,096
Compensation cost not yet recognized						$ 8,350,000
Compensation expense recognition period						3 years 2 months 12 days
Weighted-average grant date fair value (in dollars per share)						$ 1.31	$ 1.29
Aggregate intrinsic value, stock options, exercised						$ 77,000	$ 89,000
Chief Financial Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted in period (in shares)				600,000
Options outstanding (in shares)						600,000
Exicure, Inc. 2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional shares authorized, potential maximum additional shares (in shares)						4,600,000
Number of additional shares authorized, percentage of common stock outstanding						5.00%
Number of shares available for grant (in shares)						2,831,213
Options to purchase common stock | Exicure, Inc. 2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in number of shares available for grant (in shares)		4,382,567
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in number of shares available for grant (in shares)		258,207	262,954
Number of shares available for grant (in shares)						1,100,791
Maximum ESPP contribution rate as a percentage of compensation					15.00%
Maximum number of shares per employee in purchase period (in shares)					7,500
Maximum contribution amount					$ 25,000
ESPP purchase price as a percentage of market price					85.00%
Offering period duration					6 months
Number of additional shares allowable annually under the plan (in shares)					300,000
Percentage of outstanding shares allowable as annual increase					0.30%
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issued for each vested restricted stock unit (in shares)						1
Vesting period						4 years

Equity-Based Compensation - Sch

Equity-Based Compensation - Schedule of Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 764	$ 544	$ 1,281	$ 985
Research and development expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	361	203	618	360
General and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 403	$ 341	$ 663	$ 625

Equity-Based Compensation - Ass

Equity-Based Compensation - Assumptions Used for Fair Value Measurement (Details)	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	0.36%	0.41%
Risk-free interest rate, maximum	1.12%	1.68%
Expected volatility, minimum	81.70%	81.00%
Expected volatility, maximum	83.60%	85.80%
Expected volatility	82.60%	83.80%
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	5 years 2 months 12 days
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	6 years 1 month 6 days	6 years 1 month 6 days
Weighted Average
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.05%	0.67%

Equity-Based Compensation - Fai

Equity-Based Compensation - Fair Value of Underlying Common Stock and Exercise Price of Stock Options (Details) - $ / shares	Jun. 30, 2021	Jun. 30, 2020
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of underlying common stock (dollars per share)	$ 1.54	$ 1.19
Exercise price of common stock option (dollars per share)	1.54	1.19
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of underlying common stock (dollars per share)	2.57	2.80
Exercise price of common stock option (dollars per share)	2.57	2.80
Weighted Average
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of underlying common stock (dollars per share)	1.88	1.85
Exercise price of common stock option (dollars per share)	$ 1.88	$ 1.85

Equity-Based Compensation - S_2

Equity-Based Compensation - Schedule of Stock Options Rollforward (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Options
Outstanding beginning balance (in shares)	7,227,296
Granted (in shares)	4,270,086
Exercise of options (in shares)	(342,246)
Forfeited (in shares)	(95,702)
Outstanding ending balance (in shares)	11,059,434	7,227,296
Exercisable (in shares)	4,580,439
Vested and expected to vest (in shares)	10,559,034
Weighted-Average Exercise Price
Outstanding beginning balance (in dollars per share)	$ 2.24
Granted (in dollars per share)	1.88
Exercised (in dollars per share)	1.60
Forfeited (in dollars per share)	2.27
Outstanding ending balance (in dollars per share)	2.12	$ 2.24
Exercisable, weighted-average exercise price (in dollars per share)	2.29
Vested and expected to vest, weighted-average exercise price (in dollars per share)	$ 2.13
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted-Average Remaining Contractual Term (years)	7 years 9 months 18 days	6 years 9 months 18 days
Aggregate Intrinsic Value (thousands)	$ 1,019	$ 1,719
Exercisable, weighted-average remaining contractual term	5 years 6 months
Exercisable, aggregate intrinsic value	$ 832
Weighted-Average Remaining Contractual Term (years)	7 years 8 months 12 days
Aggregate Intrinsic Value (thousands)	$ 1,007

Equity-Based Compensation - RSU

Equity-Based Compensation - RSU Activity (Details) - Restricted stock units	6 Months Ended
	Jun. 30, 2021$ / sharesshares
Restricted Stock Units
Unvested balance - beginning of period (in shares) | shares	0
Granted (in shares) | shares	286,000
Unvested balance - end of period (in shares) | shares	286,000
Weighted-Average Grant Date Fair Value
Unvested balance - beginning of period (in dollars per share) | $ / shares	$ 0
Granted (in dollars per share) | $ / shares	1.90
Unvested balance - end of period (in dollars per share) | $ / shares	$ 1.90

Income Taxes (Details)

Income Taxes (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 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				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net loss	$ (14,269)	$ (12,477)	$ (4,311)	$ 1,150	$ (26,746)	$ (3,161)
Weighted-average basic common shares outstanding (in shares)	88,043,447		87,174,533		87,948,440	87,126,847
Weighted-average diluted common shares outstanding (in shares)	88,043,447		87,174,533		87,948,440	87,126,847
(Loss) earnings per basic common share (USD per share)	$ (0.16)		$ (0.05)		$ (0.30)	$ (0.04)
(Loss) earnings per diluted common share (USD per share)	$ (0.16)		$ (0.05)		$ (0.30)	$ (0.04)

Loss Per Common Share - Antidil

Loss Per Common Share - Antidilutive Securities (Details) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
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)	11,059,434	7,698,313
Restricted stock units
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)	286,000	0
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)	0	413,320

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:	$ 13,472	$ 48,818
Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	43,573	73,404
Common stock warrant liability		15
Total financial liabilities		15
Fair Value, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	30,101	24,586
Common stock warrant liability		0
Total financial liabilities		0
Fair Value, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	13,472	48,818
Common stock warrant liability		0
Total financial liabilities		0
Fair Value, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	0	0
Common stock warrant liability		15
Total financial liabilities		15
Commercial paper | Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:	5,999	15,991
Commercial paper | Fair Value, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:	0	0
Commercial paper | Fair Value, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:	5,999	15,991
Commercial paper | Fair Value, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:	0	0
Corporate notes/bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:	6,213	29,296
Corporate notes/bonds | Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:	6,213	29,296
Corporate notes/bonds | Fair Value, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:	0	0
Corporate notes/bonds | Fair Value, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:	6,213	29,296
Corporate notes/bonds | Fair Value, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:	0	0
U.S. Treasuries
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:		2,253
U.S. Treasuries | Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:		2,253
U.S. Treasuries | Fair Value, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:		0
U.S. Treasuries | Fair Value, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:		2,253
U.S. Treasuries | Fair Value, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:		0
U.S. Government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:	1,260	1,278
U.S. Government agency securities | Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:	1,260	1,278
U.S. Government agency securities | Fair Value, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:	0	0
U.S. Government agency securities | Fair Value, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:	1,260	1,278
U.S. Government agency securities | Fair Value, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments:	0	0
Money market funds | Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	30,101	24,586
Money market funds | Fair Value, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	30,101	24,586
Money market funds | Fair Value, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	0	0
Money market funds | Fair Value, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:	$ 0	$ 0

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - Common Stock - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Common stock warrant liability	$ 0
Number of shares called by warrants (in shares)	0	413,320

Fair Value Measurements - Recon

Fair Value Measurements - Reconciliation of Liabilities Measured at Fair Value on a Recurring Basis (Details) - Common Stock - Warrant Liability $ in Thousands	6 Months Ended
	Jun. 30, 2021USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at December 31, 2020	$ 15
Additions	0
Gain included in other (expense) income, net	(15)
Balance at June 30, 2021	$ 0

Commitment and Contingencies (D

Commitment and Contingencies (Details) $ in Thousands	Jun. 30, 2021USD ($)
Commitments and Contingencies Disclosure [Abstract]
Aggregate consideration paid to NU for agreement obligations	$ 8,361

Related-Party Transactions (Det

Related-Party Transactions (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Board of Directors | Consulting services
Related Party Transaction [Line Items]
Expenses from transactions with related party	$ 50	$ 50

Subsequent Events (Details)

Subsequent Events (Details) - Ipsen Collaboration - Collaboration Arrangement - Subsequent Event $ in Thousands	Jul. 30, 2021USD ($)agreement
Subsequent Event [Line Items]
Number of collaboration programs | agreement	2
Non-refundable upfront payment received for research agreement	$ 20,000
Pre-clinical milestone payment amount	5,000
Development and regulatory milestone payment amount	180,000
Commercial milestone payment amount	762,000
Collaboration agreement, licensing fees incurred	3,000
Option Exercise Period after the Selection
Subsequent Event [Line Items]
Collaboration option exercise fee	10,000
Option Exercise Period that begins after the first Option Exercise Period
Subsequent Event [Line Items]
Collaboration option exercise fee	$ 25,000