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Document and Entity Information	6 Months Ended
Document and Entity Information	Jun. 30, 2020
Document And Entity Information Abstract
Entity Registrant Name	ProQR Therapeutics N.V.
Entity Central Index Key	0001612940
Document Type	6-K
Document Period End Date	Jun. 30, 2020
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2

Condensed Consolidated Statement of Financial Position - EUR (€)	Jun. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	€ 87,141,000	€ 111,950,000
Prepayments and other receivables	3,562,000	1,866,000
Social securities and other taxes	452,000	850,000
Total current assets	91,155,000	114,666,000
Property, plant and equipment	2,102,000	2,440,000
Investments in associates	243,000	429,000
Total assets	93,500,000	117,535,000
Equity
Equity attributable to owners of the Company	80,094,000	94,329,000
Non-controlling interests	(526,000)	(496,000)
Total equity	79,568,000	93,833,000
Current liabilities
Borrowings	656,000	343,000
Lease liabilities	46,000	508,000
Trade payables	492,000	445,000
Current income tax liability	65,000	64,000
Social securities and other taxes	17,000	108,000
Pension premiums	1,000	2,000
Deferred income	1,053,000	711,000
Other current liabilities	6,703,000	8,812,000
Total current liabilities	9,033,000	10,993,000
Borrowings	4,899,000	12,709,000
Total liabilities	13,932,000	23,702,000
Total equity and liabilities	€ 93,500,000	€ 117,535,000

Condensed Consolidated Statement of Profit or Loss and OCI - EUR (€)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Condensed Consolidated Statement of Profit or Loss and OCI
Other income	€ 8,674,000	€ 563,000	€ 8,937,000	€ 979,000
Research and development costs	(8,587,000)	(9,523,000)	(21,412,000)	(21,487,000)
General and administrative costs	(3,446,000)	(2,876,000)	(7,364,000)	(6,066,000)
Total operating costs	(12,033,000)	(12,399,000)	(28,776,000)	(27,553,000)
Operating result	(3,359,000)	(11,836,000)	(19,839,000)	(26,574,000)
Finance income and expense	(697,000)	(531,000)	(161,000)	(37,000)
Results related to associates	(52,000)	698,000	(186,000)	698,000
Result before corporate income taxes	(4,108,000)	(11,669,000)	(20,186,000)	(25,913,000)
Corporate income taxes	(11,000)	(64,000)	(11,000)	(64,000)
Result for the period	(4,119,000)	(11,733,000)	(20,197,000)	(25,977,000)
Other comprehensive income	(135,000)	(38,000)	121,000	(26,000)
Total comprehensive income (attributable to owners of the Company)	(4,254,000)	(11,771,000)	(20,076,000)	(26,003,000)
Result attributable to
Owners of the Company	(4,112,000)	(11,651,000)	(20,167,000)	(25,808,000)
Non-controlling interests	(7,000)	(82,000)	(30,000)	(169,000)
Result for the period	€ (4,119,000)	€ (11,733,000)	€ (20,197,000)	€ (25,977,000)
Share information
Weighted average number of shares outstanding	50,021,194	38,908,182	49,963,614	38,896,868
Earnings per share attributable to the equity holders of the Company (expressed in Euro per share)
Basic loss per share	€ (0.08)	€ (0.30)	€ (0.40)	€ (0.66)
Diluted loss per share	€ (0.08)	€ (0.30)	€ (0.40)	€ (0.66)

Condensed Consolidated Statement of Changes in Equity - EUR (€) € in Thousands	Share capital	Share Premium [Member]	Equity Settled Employee Benefit Reserve	Translation Reserve	Accumulated Deficit	Total	Non-controlling interests [Member]	Total
Balance at beginning of period at Dec. 31, 2018	€ 1,726	€ 235,744	€ 10,780	€ 108	€ (155,443)	€ 92,915	€ (230)	€ 92,685
Balance at beginning of period (in shares) at Dec. 31, 2018								43,149,987
Result for the period					(25,808)	(25,808)	(169)	€ (25,977)
Other comprehensive income				(26)		(26)		(26)
Recognition of share-based payments			3,388			3,388		€ 3,388
Treasury shares transferred (in shares)								(39,653)
Shares options lapsed			(29)		29
Share options exercised		164	(113)		113	164		€ 164
Share options exercised (in shares)								39,653
Balance at end of period at Jun. 30, 2019	1,726	235,908	14,026	82	(181,109)	70,633	(399)	€ 70,234
Balance at end of period (in shares) at Jun. 30, 2019								43,149,987
Balance at beginning of period at Dec. 31, 2019	2,159	287,214	16,551	151	(211,746)	94,329	(496)	€ 93,833
Balance at beginning of period (in shares) at Dec. 31, 2019								53,975,838
Result for the period					(20,167)	(20,167)	(30)	€ (20,197)
Other comprehensive income				121		121		121
Recognition of share-based payments	2	283	4,542			4,827		4,827
Issue of ordinary shares	2	270				272		€ 272
Issue of ordinary shares (in shares)								100,902,000
Treasury shares transferred (in shares)								(296,122)
Shares options lapsed			(60)		60
Share options exercised		712	(458)		458	712		€ 712
Share options exercised (in shares)								296,122
Balance at end of period at Jun. 30, 2020	€ 2,163	€ 288,479	€ 20,575	€ 272	€ (231,395)	€ 80,094	€ (526)	€ 79,568
Balance at end of period (in shares) at Jun. 30, 2020								54,076,740

Consolidated Statement of Cash Flows - EUR (€)	3 Months Ended		6 Months Ended
Consolidated Statement of Cash Flows - EUR (€)	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Cash flow from operating activities
Net result	€ (4,119,000)	€ (11,733,000)	€ (20,197,000)	€ (25,977,000)
Adjustments for:
Depreciation	530,000	516,000	1,052,000	1,037,000
Share-based compensation	1,802,000	1,100,000	4,672,000	3,388,000
Other income	(8,423,000)		(8,423,000)
Financial income and expenses	696,000	531,000	161,000	37,000
Results related to associates	52,000	(698,000)	186,000	(698,000)
Net foreign exchange gain / (loss)	(135,000)	(38,000)	121,000	(26,000)
Changes in working capital	(907,000)	(500,000)	(3,108,000)	(974,000)
Cash used in operations	(10,504,000)	(10,822,000)	(25,536,000)	(23,213,000)
Corporate income tax paid	(11,000)	(64,000)	(11,000)	(64,000)
Interest received	62,000	32,000	91,000	86,000
Interest paid	(34,000)	(24,000)	(38,000)	(51,000)
Cash used in operations	(10,487,000)	(10,878,000)	(25,494,000)	(23,242,000)
Cash flow from investing activities
Purchases of property, plant and equipment	(344,000)	(86,000)	(542,000)	(309,000)
Net cash used in investing activities	(344,000)	(86,000)	(542,000)	(309,000)
Cash flow from financing activities
Proceeds from exercise of share options	243,000	93,000	712,000	164,000
Proceeds from borrowings	289,000		579,000
Proceeds from convertible loans	65,000		65,000	690,000
Repayment of lease liability	(105,000)	(287,000)	(307,000)	(571,000)
Net cash (used in)/generated by financing activities	492,000	(194,000)	1,049,000	283,000
Net increase/(decrease) in cash and cash equivalents	(10,339,000)	(11,158,000)	(24,987,000)	(23,268,000)
Currency effect cash and cash equivalents	(583,000)	(458,000)	178,000	152,000
Cash and cash equivalents, at beginning of the period	98,063,000	94,080,000	111,950,000	105,580,000
Cash and cash equivalents at the end of the period	€ 87,141,000	€ 82,464,000	€ 87,141,000	€ 82,464,000

General Information

6 Months Ended

Jun. 30, 2020

General Information

General Information

1. General information

ProQR Therapeutics N.V., or “ProQR” or the “Company”, is a development stage company domiciled in the Netherlands that primarily focuses on the development and commercialization of novel therapeutic medicines.

Since September 18, 2014, the Company’s ordinary shares are listed on the NASDAQ Global Market under ticker symbol PRQR.

The Company was incorporated in the Netherlands, on February 21, 2012 and was reorganized from a private company with limited liability to a public company with limited liability on September 23, 2014. The Company has its statutory seat in Leiden, the Netherlands. The address of its headquarters and registered office is Zernikedreef 9, 2333 CK Leiden, the Netherlands.

ProQR Therapeutics N.V. is the ultimate parent company of the following entities:

ProQR Therapeutics Holding B.V. (100%);

ProQR Therapeutics I B.V. (100%);

ProQR Therapeutics II B.V. (100%);

ProQR Therapeutics III B.V. (100%);

ProQR Therapeutics IV B.V. (100%);

ProQR Therapeutics VI B.V. (100%);

ProQR Therapeutics VII B.V. (100%);

ProQR Therapeutics VIII B.V. (100%);

ProQR Therapeutics IX B.V. (100%);

ProQR Therapeutics I Inc. (100%);

Amylon Therapeutics B.V. (80%);

Amylon Therapeutics Inc. (80%);

ProQR Therapeutics N.V. is also statutory director of Stichting Bewaarneming Aandelen ProQR (“ESOP Foundation”) and has full control over this entity. ProQR Therapeutics N.V. holds a 20% minority shareholding in Wings Therapeutics Inc.

As used in these condensed consolidated financial statements, unless the context indicates otherwise, all references to “ProQR” or the “Company” refer to ProQR Therapeutics N.V. including its subsidiaries and the ESOP Foundation.

Significant Accounting Policies	6 Months Ended
Significant Accounting Policies	Jun. 30, 2020
Significant Accounting Policies
Significant Accounting Policies	2. Significant Accounting Policies These condensed consolidated financial statements have been prepared in accordance with IAS 34 - Interim Financial Reporting. Certain information and disclosures normally included in financial statements prepared in accordance with IFRS have been condensed or omitted. Accordingly, these condensed consolidated financial statements should be read in conjunction with the Company’s annual financial statements for the year ended December 31, 2019. In the opinion of management, all adjustments, consisting of normal recurring nature, considered necessary for a fair presentation have been included in the condensed consolidated financial statements. The Company’s financial results have varied substantially, and are expected to continue to vary, from period to period. The Company believes that its ordinary activities are not linked to any particular seasonal factors. The Company operates in one reportable segment, which comprises the discovery and development of innovative, RNA based therapeutics.

Adoption of new and revised International Financial Reporting Standards	6 Months Ended
	Jun. 30, 2020
Adoption of new and revised International Financial Reporting Standards
Adoption of new and revised International Financial Reporting Standards	3. Adoption of new and revised International Financial Reporting Standards The accounting policies adopted in the preparation of the condensed consolidated financial statements are consistent with those applied in the preparation of the Company’s annual financial statements for the year ended December 31, 2019. New Standards and Interpretations, which became effective as of January 1, 2020, did not have a material impact on our condensed consolidated financial statements.

Critical Accounting Estimates and Judgments	6 Months Ended
Critical Accounting Estimates and Judgments	Jun. 30, 2020
Critical Accounting Estimates and Judgments
Critical Accounting Estimates and Judgments	4. Critical Accounting Estimates and Judgments In the application of the Company’s accounting policies, management is required to make judgments, estimates and assumptions about the carrying amounts of assets and liabilities that are not readily apparent from other sources. The estimates and associated assumptions are based on historical experience and other factors that are considered to be relevant. Actual results may differ from these estimates. The estimates and underlying assumptions are reviewed on an ongoing basis. Revisions to accounting estimates are recognized in the period in which the estimate is revised if the revision affects only that period or in the period of the revision and future periods if the revision affects both current and future periods. Research and development expenditures Research expenditures are currently not capitalized but are reflected in the income statement because the criteria for capitalization are not met. At each balance sheet date, the Company estimates the level of service performed by the vendors and the associated costs incurred for the services performed. Although we do not expect the estimates to be materially different from amounts actually incurred, the understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and could result in reporting amounts that are too high or too low in any particular period.

Cash and Cash Equivalents	6 Months Ended
Cash and Cash Equivalents	Jun. 30, 2020
Cash and Cash Equivalents.
Cash and Cash Equivalents	5. Cash and Cash Equivalents At June 30, 2020, the Company’s cash and equivalents were € 87,141,000 as compared to € 111,950,000 at December 31, 2019. The cash balances are held at banks with investment grade credit ratings. The cash at banks is at full disposal of the Company.

Current liabilities	6 Months Ended
Current liabilities	Jun. 30, 2020
Current liabilities
Current liabilities	6. Current liabilities At June 30, 2020 and December 31, 2019, the other current liabilities consisted principally of accruals for services provided by vendors not yet billed, payroll related accruals and other miscellaneous liabilities.

Borrowings

6 Months Ended

Jun. 30, 2020

Borrowings

Borrowings

7. Borrowings



	June 30,	December 31,
	2020	2019
	€ 1,000	€ 1,000
Innovation credit	2,771	7,191
Accrued interest on innovation credit	168	3,124
Convertible notes	2,279	2,473
Accrued interest on convertible notes	337	264

Total borrowings	5,555	13,052
Current portion	(656)	(343)
	4,899	12,709

On June 1, 2012, ProQR was awarded an Innovation credit by the Dutch government, through its agency RVO of the Ministry of Economic Affairs, for the Company’s cystic fibrosis program. Amounts were drawn under this facility in the course of the years 2013 through 2017. The credit covered 35% of the costs incurred in respect of the program up to € 5.0 million. The credit was interest-bearing at a rate of 10% per annum. In June 2020 ProQR received a final waiver of the full amount of the Innovation credit, including accumulated interest. Consequently, the carrying amount of € 8.4 million, including accumulated interest, was recognized in Other Income in June 2020.

On December 10, 2018 ProQR was awarded an Innovation credit for the sepofarsen program for LCA 10. Amounts will be drawn under this facility from 2018 through 2021. The total credit of € 4.7 million will be used to conduct the Phase 2/3 clinical study for sepofarsen and to finance efforts to obtain regulatory and ethical market approval (NDA/MAA). The credit, including accrued interest of 10% per annum, is repayable depending on ProQR obtaining market approval for sepofarsen. An amount of € 2.8 million had been received as at June 30, 2020. Accumulated interest amounted to € 0.2 million as at June 30, 2020. The assets that are co-financed with the granted innovation credit are subject to a right of pledge for the benefit of RVO.

Convertible loans

Convertible loans were issued to Amylon Therapeutics B.V. and are interest-bearing at an average rate of 8% per annum. They are convertible into a variable number of ordinary shares within 36 months at the option of the holder or the Company in case financing criteria are met. Any unconverted loans become payable on demand after 24 – 36 months in equal quarterly terms.

Shareholders equity	6 Months Ended
Shareholders equity	Jun. 30, 2020
Shareholders equity
Shareholders' equity	8. Shareholders’ equity The authorized share capital of the Company amounting to € 7,200,000 consists of 90,000,000 ordinary shares and 90,000,000 preference shares with a par value of € 0.04 per share. At June 30, 2020, 54,076,740 ordinary shares were issued and fully paid in cash, of which 3,934,029 were held by the Company as treasury shares (December 31, 2019: 4,230,151). On November 7, 2018, the Company filed a shelf registration statement, which permitted the offering, issuance and sale by the Company of up to a maximum aggregate offering price of $ 300,000,000 of its ordinary shares, warrants and/or units. In October 2019, the Company consummated an underwritten public offering of 10,454,545 ordinary shares at an issue price of $ 5.50 per share. The gross proceeds from this offering amounted to € 51,597,000 while the transaction costs amounted to € 3,047,000, resulting in net proceeds of € 48,550,000. In December 2019, the Company issued 371,306 shares in the aggregate amount of $3.5 million, at $9.43 (€8.51) per share to Ionis Pharmaceuticals, Inc. Under the terms of the agreement, the second installment of the upfront payment in ordinary shares to the Company’s common stock was made to Ionis upon the dosing of the first patient in the phase 1/2 Aurora clinical trial for QR-1123. On March 31, 2020, the Company entered into a sales agreement, which permitted the offering, issuance and sale by the Company of up to a maximum aggregate offering price of $ 75,000,000 of its ordinary shares that may be issued and sold in one or more at-the-market offerings with Citigroup Global Markets, Inc. and Cantor Fitzgerald & Co. In 2020, no shares were issued pursuant to this ATM facility. Translation reserve The translation reserve comprises all foreign currency differences arising from the translation of the financial statements of foreign operations. Share options The Company operates an equity-settled share-based compensation plan, which was introduced in 2013. Options may be granted to employees, members of the Supervisory Board, members of the Management Board and consultants. The compensation expenses included in operating costs for this plan in the three month period ended June 30, 2020 were € 1,673,000 (2019: € 1,100,000), of which € 1,103,000 (2019: € 724,000) was recorded in general and administrative costs and € 570,000 (2019: € 376,000) was recorded in research and development costs.

Other income	6 Months Ended
Other income	Jun. 30, 2020
Other income
Other income

Research and development costs	6 Months Ended
Research and development costs	Jun. 30, 2020
Research and development costs
Research and Development Costs	10. Research and development costs Research and development costs amount to € 8,587,000 for the three month period ended June 30, 2020 (2019: € 9,523,000) and are comprised of allocated employee costs including share-based payments, the costs of materials and laboratory consumables, outsourced activities, license and intellectual property costs and other allocated costs.

General and administrative costs	6 Months Ended
General and administrative costs	Jun. 30, 2020
General and administrative costs
General and administrative costs	11. General and administrative costs General and administrative costs amount to € 3,446,000 for the three month period ended June 30, 2020 (2019: € 2,876,000).

Results related to associates	6 Months Ended
Results related to associates	Jun. 30, 2020
Results related to associates
Results related to associates	12. Results related to associates The results related to associates for the three month period ended June 30, 2020 amounting to € 52,000 consist of our share of the net losses of Wings Therapeutics Inc. Results related to associates for the three month period ended June 30, 2019 consisted of a gain on the sale of assets to Wings Therapeutics Inc of € 959,000 and the Company’s share in the net loss of Wings Therapeutics Inc, amounting to € 261,000.

Income taxes	6 Months Ended
Income taxes	Jun. 30, 2020
Income taxes
Income taxes	13. Income taxes The current income tax liability amounts to € 65,000 at June 30, 2020 (December 31, 2019: € 64,000). No significant temporary differences exist between accounting and tax results. Realization of deferred tax assets is dependent on future earnings, if any, the timing and amount of which are uncertain. Accordingly, the Company has not yet recognized any deferred tax asset related to operating losses.

Events after balance sheet date	6 Months Ended
Events after balance sheet date	Jun. 30, 2020
Events after balance sheet date
Events after balance sheet date	14. Events after balance sheet date On July 14, 2020, the Company entered into a convertible debt financing agreement with Pontifax Medison Debt Financing. Under the agreement, the Company will have access to up to $ 30 million in convertible debt financing in three tranches of $ 10 million each that will mature over a 54 month period and have an interest-only period of 24 months. Pontifax may elect to convert the outstanding loan into ProQR ordinary shares at any time prior to repayment at a fixed conversion price. ProQR also has the ability to convert the loan into its ordinary shares, at the same conversion price, if the Company’s stock price reaches a pre-determined threshold. In connection with the loan agreement, the Company issued to Pontifax warrants to purchase up to an aggregate of 190,424 shares of its common stock at a fixed exercise price. Subsequent to the closing with Pontifax, the loan facility was expanded by an additional €15 million (in three tranches of €5 million) with Kreos Capital.

Borrowings (Tables)

6 Months Ended

Jun. 30, 2020

Borrowings

Schedule of borrowings



	June 30,	December 31,
	2020	2019
	€ 1,000	€ 1,000
Innovation credit	2,771	7,191
Accrued interest on innovation credit	168	3,124
Convertible notes	2,279	2,473
Accrued interest on convertible notes	337	264

Total borrowings	5,555	13,052
Current portion	(656)	(343)
	4,899	12,709

Other income (Tables)

6 Months Ended

Jun. 30, 2020

Other income

Other income

Click or tap here to enter text.

	Three month period
	ended June 30,

	2020	2019
	€ 1,000	€ 1,000

Grant income	8,640	489
Other income	34	74
	8,674	563

General Information (Details)	6 Months Ended
General Information (Details)	Jun. 30, 2020
ProQR Therapeutics Holding B.V. [Member]
Disclosure of subsidiaries [line items]
Proportion of ownership interest in subsidiary	100.00%
ProQR Therapeutics I B.V. [Member]
Disclosure of subsidiaries [line items]
Proportion of ownership interest in subsidiary	100.00%
ProQR Therapeutics II B.V. [Member]
Disclosure of subsidiaries [line items]
Proportion of ownership interest in subsidiary	100.00%
ProQR Therapeutics III B.V. [Member]
Disclosure of subsidiaries [line items]
Proportion of ownership interest in subsidiary	100.00%
ProQR Therapeutics IV B.V. [Member]
Disclosure of subsidiaries [line items]
Proportion of ownership interest in subsidiary	100.00%
ProQR Therapeutics VI B.V. [Member]
Disclosure of subsidiaries [line items]
Proportion of ownership interest in subsidiary	100.00%
ProQR Therapeutics VII B.V. [Member]
Disclosure of subsidiaries [line items]
Proportion of ownership interest in subsidiary	100.00%
ProQR Therapeutics VIII B.V. [Member]
Disclosure of subsidiaries [line items]
Proportion of ownership interest in subsidiary	100.00%
ProQR Therapeutics IX B.V. [Member]
Disclosure of subsidiaries [line items]
Proportion of ownership interest in subsidiary	100.00%
Amylon Therapeutics B.V [Member]
Disclosure of subsidiaries [line items]
Proportion of ownership interest in subsidiary	80.00%
Amylon Therapeutics Inc [Member]
Disclosure of subsidiaries [line items]
Proportion of ownership interest in subsidiary	80.00%
ProQR Therapeutics I Inc. [Member]
Disclosure of subsidiaries [line items]
Proportion of ownership interest in subsidiary	100.00%
Wings Therapeutics Inc
Disclosure of subsidiaries [line items]
Proportion of ownership interest in subsidiary	20.00%

Significant Accounting Policies (Details)	6 Months Ended
Significant Accounting Policies (Details)	Jun. 30, 2020 segment
Significant Accounting Policies
Ifrs Number of Reportable Segments	1

Cash and Cash Equivalents (Details) - EUR (€)	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents.
Cash and cash equivalents	€ 87,141,000	€ 98,063,000	€ 111,950,000	€ 82,464,000	€ 94,080,000	€ 105,580,000

Borrowings (Details) - EUR (€) € in Thousands		1 Months Ended	3 Months Ended	6 Months Ended
Borrowings (Details) - EUR (€) € in Thousands	Jun. 01, 2012	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Dec. 10, 2018
Disclosure of detailed information about borrowings [line items]
Total borrowings		€ 5,555	€ 5,555	€ 5,555	€ 13,052
Current portion		(656)	(656)	(656)	(343)
Non Current portion		4,899	4,899	4,899	12,709
Proceeds from borrowings			289	579
Innovation credit
Disclosure of detailed information about borrowings [line items]
Total borrowings		2,771	2,771	2,771	7,191	€ 4,700
Accrued interest		168	168	168	3,124
Percentage of cost covered by the innovative credit	35.00%
Maximum initial borrowing base	€ 5,000
Interest rate (as percent)	10.00%
Total conditional waiver of debt		8,400
Proceeds from borrowings				2,800
Convertible notes
Disclosure of detailed information about borrowings [line items]
Total borrowings		2,279	2,279	2,279	2,473
Accrued interest		€ 337	€ 337	€ 337	€ 264
Interest rate (as percent)		8.00%	8.00%	8.00%
Debt instrument convertible term				36 months
Convertible notes \| Minimum
Disclosure of detailed information about borrowings [line items]
Unconvertible debt maturity				P24M
Convertible notes \| Maximum
Disclosure of detailed information about borrowings [line items]
Unconvertible debt maturity				P36M

Shareholders equity - Share capital (Details)	1 Months Ended		6 Months Ended
Shareholders equity - Share capital (Details)	Oct. 31, 2019 $ / shares shares	Oct. 31, 2019 EUR (€) shares	Jun. 30, 2020 EUR (€) € / shares shares	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2019 € / shares	Jun. 30, 2019 shares	Dec. 31, 2018 shares	Nov. 07, 2018 USD ($)
Shareholders' Equity
Authorized share capital \| €			€ 7,200,000
Number of shares outstanding			54,076,740		53,975,838		43,149,987	43,149,987
Par value per share \| € / shares			€ 0.04
Shares were issued and fully paid in cash	10,454,545	10,454,545
Price per share \| $ / shares	$ 5.50
Net proceeds from issuance of shares \| €		€ 48,550,000
Transaction costs of public offering \| €		3,047,000
Gross proceeds from issuance of shares \| €		€ 51,597,000
Shares issued in the period \| €			€ 272,000
Ordinary
Shareholders' Equity
Maximum aggregate offering of ordinary shares \| $									$ 300,000,000
Number of shares authorised			90,000,000
Shares were issued and fully paid in cash			54,076,740
Treasury shares			3,934,029		4,230,151
Preferred
Shareholders' Equity
Number of shares authorised			90,000,000
Market offering program \| Ordinary
Shareholders' Equity
Number of shares issued			0
Maximum aggregate offering of ordinary shares \| $				$ 75,000,000
Ionis Pharmaceuticals, Inc \| Worldwide License Agreement
Shareholders' Equity
Number of shares issued					371,306
Maximum aggregate offering of ordinary shares \| $					$ 3,500,000
Share price \| (per share)					$ 9.43	€ 8.51

Shareholders equity - Share options (Details) - EUR (€)	3 Months Ended
Shareholders equity - Share options (Details) - EUR (€)	Jun. 30, 2020	Jun. 30, 2019
Shareholders equity
Compensation expenses	€ 1,673,000	€ 1,100,000
Compensation expenses recorded in general and administrative costs	1,103,000	724,000
Compensation expenses recorded in research and development costs	€ 570,000	€ 376,000

Other income (Details) - EUR (€) € in Thousands	3 Months Ended		6 Months Ended
Other income (Details) - EUR (€) € in Thousands	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Other income
Grant income	€ 8,640	€ 489
Other income	34	74
Total other income	€ 8,674	€ 563	€ 8,937	€ 979

Other income - Narrative (Details) € in Millions, $ in Millions		1 Months Ended
	Feb. 09, 2018 USD ($)	Jun. 30, 2020 EUR (€)
Clinical support agreement \| Foundation Fighting Blindness
Other Income [Line Items]
Contribution received to support clinical development \| $	$ 7.5
Innovation credit
Other Income [Line Items]
Total conditional waiver of debt \| €		€ 8.4

Research and development costs (Details) - EUR (€)	3 Months Ended		6 Months Ended
Research and development costs (Details) - EUR (€)	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Research and development costs
Research and development costs	€ 8,587,000	€ 9,523,000	€ 21,412,000	€ 21,487,000

General and administrative costs (Details) - EUR (€)	3 Months Ended		6 Months Ended
General and administrative costs (Details) - EUR (€)	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
General and administrative costs
General and administrative expense	€ 3,446,000	€ 2,876,000	€ 7,364,000	€ 6,066,000

Results related to associates (Details) - Wings Therapeutics Inc - EUR (€)	3 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Disclosure of associates [line items]
Loss on share of profits of associates	€ 52,000	€ 261,000
Gain on sale of assets		€ 959,000

Income Taxes (Details) - EUR (€)	Jun. 30, 2020	Dec. 31, 2019
Income taxes
Current income tax liability	€ 65,000	€ 64,000

Events after balance sheet date (Details) - Subsequent Event $ in Millions	Jul. 14, 2020 USD ($) tranche shares
Convertible Debt
Subsequent events
Warrants issued to purchase common stock \| shares	190,424
Convertible debt financing arrangement \| Pontifax Medison Debt Financing [Member]
Subsequent events
Maximum borrowing capacity	$ 30
Number of tranches \| tranche	3
Maximum borrowing capacity per tranche	$ 10
Term of debt	54 months
Debt, interest only payment term	24 months