Celyad Oncology (CLYYF) 6-K 4 Aug 21 2021 Q2 Celyad Oncology Reports First Half 2021 Financial Results and Recent Business Highlights Financial data

Cover

Cover	6 Months Ended
	Jun. 30, 2021
Cover [Abstract]
Document Type	6-K
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Entity Registrant Name	Celyad Oncology SA
Entity Central Index Key	0001637890
Current Fiscal Year End Date	--12-31

Interim consolidated statement

Interim consolidated statement of Financial Position - EUR (€) € in Thousands	Jun. 30, 2021	Dec. 31, 2020
Statement of financial position [abstract]
NON-CURRENT ASSETS	€ 46,094	€ 46,379
Goodwill and Intangible assets	36,127	36,171
Property, Plant and Equipment	3,592	4,119
Non-current Trade and Other receivables	2,135	2,117
Non-current Grant receivables	4,002	3,679
Other non-current assets	238	293
CURRENT ASSETS	16,594	19,705
Trade and Other Receivables	712	615
Current Grant receivables	1,912	145
Other current assets	1,953	1,711
Short-term investments	0	0
Cash and cash equivalents	12,017	17,234
TOTAL ASSETS	62,688	66,084
EQUITY	24,861	30,994
Share Capital	53,913	48,513
Share premium	2,217	43,349
Other reserves	32,062	30,958
Accumulated deficit	(63,331)	(91,826)
NON-CURRENT LIABILITIES	25,290	23,256
Bank loans	0
Lease liabilities	2,104	2,525
Recoverable Cash advances (RCAs)	4,935	4,220
Contingent consideration payable and other financial liabilities	17,487	15,526
Post-employment benefits	614	614
Other non-current liabilities	150	371
CURRENT LIABILITIES	12,537	11,834
Bank loans		37
Lease liabilities	977	1,076
Recoverable Cash advances (RCAs)	340	371
Trade payables	5,582	4,736
Other current liabilities	5,638	5,614
TOTAL EQUITY AND LIABILITIES	€ 62,688	€ 66,084

Interim consolidated statemen_2

Interim consolidated statement of comprehensive income - EUR (€) € in Thousands		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020
Profit or loss [abstract]
Revenue		€ 0	€ 5
Cost of sales
Gross profit			5
Research and Development expenses		(9,956)	(11,141)
General & Administrative expenses		(4,785)	(4,789)
Change in fair value of contingent consideration		(1,961)	(2,445)
Other income		1,987	2,026
Other expenses		(162)	(211)
Operating Loss	[1]	(14,877)	(16,555)
Financial income		166	112
Financial expenses		(143)	(154)
Loss before taxes		(14,854)	(16,597)
Income taxes
Loss for the period		€ (14,854)	€ (16,597)
Basic and diluted loss per share (in €)		€ (1.02)	€ (1.19)
Other comprehensive income/(loss)
Items that will not be reclassified to profit and loss		€ 0	€ 0
Remeasurements of post-employment benefit obligations, net of tax		0	0
Items that may be subsequently reclassified to profit or loss		14	7
Currency translation differences		14	7
Other comprehensive income / (loss) for the period, net of tax		14	7
Total comprehensive loss for the period		(14,840)	(16,590)
Comprehensive income, attributable to owners of parent		€ (14,840)	€ (16,590)
[1]	The operating loss arises from the Company’s loss for the period before deduction of Financial income, Financial expenses and Income taxes. The purpose of this measure by Management is to identify the Company’s results in connection with its operating activities.

Unaudited interim consolidated

Unaudited interim consolidated statement of changes in equity - EUR (€) € in Thousands		Total	Share capital [member]	Share premium [member]		Other reserves [member]	[1]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2019		€ (45,619)	€ 48,513	€ 43,349		€ 28,181		€ (74,424)
Share-based payments		1,289				1,289
Total transactions with owners, recognized directly in equity		1,289				1,289
Loss for the period		(16,597)						(16,597)
Currency Translation differences		7				7
Remeasurements of defined benefit obligation		0
Total comprehensive loss for the period		(16,590)				7		(16,597)
Ending balance at Jun. 30, 2020		30,318	48,513	43,349		29,477		(91,021)
Share-based payments		1,493				1,493
Total transactions with owners, recognized directly in equity		1,493				1,493
Loss for the period		(607)						(607)
Currency Translation differences		(12)				(12)
Remeasurements of defined benefit obligation		(197)						(197)
Total comprehensive loss for the period		(816)				(12)		(804)
Ending balance at Dec. 31, 2020		30,994	48,513	43,349		30,958		(91,826)
Capital increase		8,060	5,400	2,660
Transaction costs associated with capital increases		(443)		(443)
Share-based payments		1,090				1,090
Total transactions with owners, recognized directly in equity		8,707	5,400	2,217		1,090
Loss for the period		(14,854)						(14,854)
Reduction of share premium by absorption of losses	[2]			(43,349)				43,349
Currency Translation differences		14				14
Remeasurements of defined benefit obligation		0
Total comprehensive loss for the period		(14,840)		(43,349)		14		28,495
Ending balance at Jun. 30, 2021		€ 24,861	€ 53,913	€ 2,217	[3]	€ 32,062		€ (63,331)	[3]
[1]	Other reserves includes Share-base payment reserve, Other equity reserve from conversion of convertible loan in 2013 and Currency Translation Difference.
[2]	During the extraordinary shareholders meeting in May 2021, the shareholders, in accordance with Belgian Company Law, approved to absorb approximately €43.3 million of the accounting losses into the share premium. As a result, the “Accumulated Deficit” has been reduced by cumulative amount of €43.3 million in the six months period ended June 30, 2021 (€215.6 million of reclass from inception to June 30, 2021) against “Share Premium”. The absorption of the accumulated deficit into share premium has no impact on the total equity, comprehensive income (loss), assets (including cash) nor liabilities.
[3]	Includes cumulative reclass of €215.6 million of losses from accumulated deficit to the share premium, refer to the footnote 4.

Interim Consolidated Statemen_3

Interim Consolidated Statement of Changes in Equity (Parentheticals) - EUR (€) € in Millions	May 31, 2021	Jun. 30, 2021
Cumulative reclassification of losses from accumulated deficit to the share premium		€ 215.6
Share premium [member]
Decrease In Share Premium Due to Absorption of Accounting Losses	€ 43.3
Decrease in accumulated deficit by cumulative amount against Share Premium		43.3
Retained earnings [member]
Cumulative reclassification of losses from accumulated deficit to the share premium		215.6
Decrease in accumulated deficit by cumulative amount against Share Premium		€ 43.3

Interim Consolidated Statemen_4

Interim Consolidated Statement of Cash Flows - EUR (€) € in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash Flow from operating activities
Loss for the period	€ (14,854)	€ (16,597)
Non-cash adjustments
Goodwill and Intangibles assets - Amortization and impairment	106	95
Property, plant & equipment - Depreciation	735	792
Provision for onerous contract
Change in fair value of contingent consideration payable and other financial liabilities	1,961	2,445
Remeasurement of Recoverable Cash Advances (RCAs)	129	106
Grant income (RCAs and others)	(1,604)	(1,638)
Share-based payment expense	1,090	1,289
Post-employment benefits	0
Change in working capital
Trade receivables, other (non-)current receivables	(738)	(246)
Trade payables, other (non-)current liabilities	990	(878)
Net cash used in operations	(12,185)	(14,633)
Cash Flow from investing activities
Acquisition of Property, Plant & Equipment	(160)	(72)
Acquisitions of Intangible assets	(62)	(1)
Disposals of Property, Plant & Equipment	0
Proceeds from net investment in lease	128	124
Proceeds from short-term investments	0
Net cash from/(used in) investing activities	100	50
Cash Flow from financing activities
Repayments of bank borrowings	(37)	(138)
Repayments of leases	(581)	(628)
Net proceeds from issuance of shares and exercise of warrants	7,617
Proceeds from RCAs & other grants	333	2,695
Repayment of RCAs & other grants	(280)
Net cash from/(used in) financing activities	7,052	1,929
Net cash and cash equivalents at beginning of the period	17,234	39,338
Change in Cash and cash equivalents	(5,227)	(12,653)
Effects of exchange rate changes on cash and cash equivalents	10	7
Net cash and cash equivalents at the end of the period	€ 12,017	€ 26,692

General Information

General Information	6 Months Ended
	Jun. 30, 2021
Text Block [Abstract]
General Information	2.5.1 General Information The Company is a clinical-stage biopharmaceutical company focused on the discovery and development of chimeric antigen receptor T cell (CAR T) therapies for cancer. Celyad SA was incorporated on July 24, 2007 under the name “Cardio3 BioSciences”. Celyad is a limited liability company (Société Anonyme) governed by Belgian law with its registered office at Axis Parc, Rue Edouard Belin 2, B-1435 On June 8, 2020, the Company announced the launch of its corporate rebranding, including changing its name to Celyad Oncology. The new name highlights the Company’s significant progress with its next-generation CAR T programs and emphasizes its commitment to cancer patients. The Company’s ordinary shares are listed on NYSE Euronext Brussels and NYSE Euronext Paris regulated markets and the Company’s American Depositary Shares (ADSs) are listed on the Nasdaq Global Market, all under the ticker symbol CYAD. The Company has three wholly-owned subsidiaries (together, the Group) located in Belgium (Biological Manufacturing Services SA) and in the United States (Celyad, Inc. and Corquest Medical, Inc.). The condensed consolidated interim financial statements have been approved for issuance by the Company’s Board of Directors on August 4, 2021. The Interim Financial Report is available to the public free of charge and upon request to the above-mentioned address or via the Company’s website ( https://celyad.com/investors/regulated-information/

Basis of preparation and signif

Basis of preparation and significant accounting policies	6 Months Ended
	Jun. 30, 2021
Text Block [Abstract]
Basis of preparation and significant accounting policies	2.5.2 Basis of preparation and significant accounting policies The condensed consolidated interim financial statements of the Group for the six months ended June 30, 2021 (the “interim period”) include Celyad Oncology SA and its subsidiaries. The significant accounting policies used for preparing the condensed consolidated interim financial statements are explained below. 2.5.2.1 Basis of preparation of Half Year Report The condensed consolidated interim financial statements have been prepared in accordance with the IFRS as issued by the IASB and in accordance with the IFRS as issued by the IASB and with IAS 34, Interim Financial Reporting, and same accounting policies used to prepare the most recent annual financial statements. They do not include all disclosures that would otherwise be required in a complete set of financial statements and should be read in conjunction with the annual financial statements for the year ended December 31, 2020 The preparation of the Company’s condensed consolidated interim financial statements requires management to make judgments, estimates and assumptions that affect the reported amounts of revenues, expenses, assets and liabilities, and the disclosure of contingent liabilities, at the end of the interim period. However, uncertainty about these assumptions and estimates could result in outcomes that require a material adjustment to the carrying amount of the asset or liability affected in future periods. The principal risks during the interim period have not materially changed from those mentioned in the 2020 Annual Report and subsequent reports and filings made with the SEC, each of which are available on the Company’s website ( http://www.celyad.com/investors/regulated-information 5 5 As previously disclosed in note 5.36 of the 2020 Annual Report, Horizon Discovery/Perkin Elmer, Inc. (Horizon/PKI) informed the Company they believe the Company was in material breach of these agreements as a result of certain disclosures the Company has made in connection with its obligations as a publicly traded company in the United States and Belgium, although they have not formally delivered to the Company a notice of material breach or termination. The Company believes any such assertion of material breach would be without merit and the Company would expect to vigorously defend any such notice of material breach. Any dispute under these agreements would be subject to arbitration in The Hague under the International Chamber of Commerce Rules. The Company is currently in discussions with Horizon about possible amendments to these agreements in connection with which the Company would retain freedom to operate under the in-licensed All statements and information relate to the interim period unless otherwise stated. The condensed consolidated interim financial statements are presented in thousands of Euros and all values are rounded to the nearest thousand (€’000) except when otherwise indicated. Amounts have been rounded off to the nearest thousand and in certain cases, this may result in minor discrepancies in the totals and sub-totals COVID-19 On March 11, 2020, the World Health Organization declared the novel strain of coronavirus (COVID-19) COVID-19 To date, COVID-19 CYAD-02, CYAD-101 CYAD-211 CYAD-02 CYAD-211, CYAD-101 The long-term impact of COVID-19 2.5.2.2 New standards, interpretations, and amendments The accounting policies adopted are consistent with those of the previous financial year and corresponding interim reporting period. None of the new standards, interpretations and amendments, which are effective for periods beginning after January 1, 2021 which have been issued by the IASB and the IFRIC have a material effect on the Group’s financial statements. None of the new standards, interpretations and amendments, which will be effective for periods beginning after January 1, 2022 and are not yet effective as of June 30, 2021 and/or not yet adopted as of June 30, 2021, are expected to have a material effect on the Group’s future financial statements. 2.5.2.3 Critical accounting estimates and judgements The preparation of condensed consolidated interim financial statements in accordance with IFRS requires management to make judgments, estimates and assumptions that may significantly affect the reported amounts of revenues, expenses, assets and liabilities, and the disclosure of contingent liabilities, at the end of the reporting period. Of note, the Company has filed patent applications which, if issued, would cover other aspects of the product candidates described above as well as products developed by third parties that deploy similar technology and targets. These patent applications encompass the downregulation of one or more of the targets covered under the Horizon/PKI agreements, the use of shRNA to downregulate such targets in immune cells and the combination of shRNAs with a chimeric antigen receptor in immune cells. The Company is also developing a second-generation shRNA platform that does not incorporate any of the Horizon/PKI. The lead allogeneic CAR T product candidate of the Company, CYAD-101, Refer to the disclosure note 5.4 from the Group’s 2020 year-end

Segment reporting

Segment reporting	6 Months Ended
	Jun. 30, 2021
Text Block [Abstract]
Segment reporting	2.5.3 Segment reporting The chief operating decision-maker (CODM), who is responsible for making strategic decisions, allocating resources and assessing performance of the Group, has been identified as the Board of Directors. Since the acquisition of the oncological platform in 2015, the management and the CODM have determined that there are two operating segments, being: • the immuno-oncology segment regrouping all assets developed based on the CAR-T • the cardiology segment, regrouping the Cardiopoiesis platform, C-Cath ez Corporate segment includes costs for general and administration functions not allocated to the other business segments. Although the Group is currently active in Europe and in the United States, no geographical financial information is currently available given the fact that the core operations are currently still in a study phase. No disaggregated information on product level or geographical level or any other level currently exists and hence is also not considered by the Board of Directors for assessing performance or allocating resources. The CODM is not reviewing assets by segments, hence no segment information per asset is disclosed. As of June 30, 2021, the main Group’s non-current Since 2017, the Group is fully focused on the development of its immuno-oncology platform. Therefore, as of June 30, 2021, most of the R&D expenses were incurred in the immuno-oncology segment, in line with prior year. For the Six-month € ‘000 Cardiology Immuno-oncology Corporate Group Total Revenue recognized at a point in time 5 — — 5 Revenue recognized over time — — — — Total Revenue 5 — — 5 Cost of Sales — — — — Gross Profit 5 — — 5 Research & Development expenses (72 ) (11 069 ) — (11 141 ) General & Administrative expenses — — (4 789 ) (4 789 ) Change in fair value of contingent consideration — (2 445 ) — (2 445 ) Net Other income/(loss) 10 1 604 200 1 815 Operating Profit/(Loss) (57 ) (11 908 ) (4 589 ) (16 555 ) Net financial income/(loss) — (87 ) 45 (42 ) Profit/(Loss) before taxes (57 ) (11 995 ) (4 545 ) (16 597 ) Income Taxes — — — — Profit/(Loss) for the six months ended June 30, 2020 (57 ) (11 995 ) (4 545 ) (16 597 ) For the Six-month € ‘000 Cardiology Immuno-oncology Corporate Group Total Revenue recognized at a point in time — — — — Revenue recognized over time — — — — Total Revenue — — — — Cost of Sales — — — — Gross Profit — — — — Research & Development expenses (57 ) (9 899 ) — (9 956 ) General & Administrative expenses — — (4 785 ) (4 785 ) Change in fair value of contingent consideration — (1 961 ) — (1 961 ) Net Other income/(loss) (54 ) 1 670 209 1 825 Operating Profit/(Loss) (111 ) (10 190 ) (4 576 ) (14 877 ) Net financial income/(loss) 149 (87 ) (39 ) 23 Profit/(Loss) before taxes 38 (10 277 ) (4 615 ) (14 854 ) Income Taxes — — — — Profit/(Loss) for the six months ended June 30, 2021 38 (10 277 ) (4 615 ) (14 854 )

Off-Balance Sheet Commitments

Off-Balance Sheet Commitments	6 Months Ended
	Jun. 30, 2021
Text Block [Abstract]
Off-Balance Sheet Commitments	2.5.4 Off-Balance As of June 30, 2021, the Group has no off-balance year-end

Capital Expenditures

Capital Expenditures	6 Months Ended
	Jun. 30, 2021
Text Block [Abstract]
Capital Expenditures	2.5.5 Capital Expenditures In accordance with IAS 38, the Group does not capitalize its research and development expenses until the Group receives marketing authorization for the applicable product candidates. Research and development expenditures incurred during the interim period were accounted for as operating expenses.

Results of Operations

Results of Operations	6 Months Ended
	Jun. 30, 2021
Text Block [Abstract]
Results of operations	2.5.6 Results of Operations Revenue For the Six-month period ended June 30, (€‘000) 2021 2020 Out-licensing — — Other revenue — 5 Total — 5 The Group’s license and collaboration agreements generated no revenue in the first half of 2021 similar to first half 2020 and did not enter into any new license agreements for the six-month The Group does not expect to generate material revenue unless and until the Group receives regulatory approval for one of its drug product candidates. Research and development expenses The following table is a summary of manufacturing expenses, clinical, quality and regulatory expenses and other research and development expenses, which are aggregated and presented as research and development expenses in the Group’s condensed consolidated interim financial statements. For the Six-month period ended June 30, (€‘000) 2021 2020 Employee expenses 4 530 4 528 Travel & Living 17 107 Clinical study costs 2 205 2 720 Preclinical study costs 944 866 Process development and scale-up 407 803 Consulting fees 152 191 IP filing and maintenance fees 84 141 Share-based payments 331 398 Depreciation 708 727 Rent and utilities 337 415 Others 241 245 Total R&D expenses 9 956 11 141 Research and development expenses totaled €10.0 million for the six-month CYAD-02 CYAD-101, CYAD-211 CYAD-203). • the decrease of process development and clinical development after the Group’s decision in Q4 2020 to discontinue the development of first-generation, autologous CAR T candidate CYAD-01; • the decrease of process development associated with the transition from preclinical to clinical development of the CYAD-211 • the decrease of travel & living expenses due to COVID-19 General and administrative expenses For the Six-month period ended June 30, (€‘000) 2021 2020 Employee expenses 1 789 1 733 Consulting fees 1 030 1 025 Share-based payments 759 892 Communication & Marketing 236 289 Rent 15 40 Insurances 730 476 Travel & living 12 77 Depreciation 133 168 Others 81 90 Total General and administrative expenses 4 785 4 789 General and administrative expenses remain stable over the six-month six-month COVID-19 (non-cash Change in fair value of contingent consideration, other income and other expenses Change in fair value of contingent consideration For the Six-month period ended June 30, (€‘000) 2021 2020 Change in fair value of contingent consideration (1 961 ) (2 445 ) Total Change in fair value of contingent consideration (1 961 ) (2 445 ) The fair value adjustment (€2.0 million, non-cash • the update in discount rate (Weighted Average Cost of Capital, or WACC) used for fair value measurement purposes at interim reporting date (see note 2.5.16.2); • the time accretion (which reflects the development of the Group’s product candidates using CAR T technology and their progress towards market approval in both autologous and allogeneic programs); • the revaluation of the U.S. dollar against the Euro; and • the updated assumptions on Probability of Success (PoS) associated with the NKG2D-based CAR T programs (see note 2.5.16.2). Other income For the Six-month period ended June 30, (€‘000) 2021 2020 Grant income (RCAs) 1 438 615 Grant income (Other) 166 1 023 R&D tax credit 339 371 Other 44 16 Total Other Income 1 987 2 026 For the six month period ended June 30, 2021, the other income was mainly driven by following elements: • Grant income (RCAs): additional grant income has been recognized in 2021 on grants in the form of recoverable cash advances (RCAs) for contracts, numbered 8087, 8088, 8212, 8436 and 1910028. According to IFRS standards, the Company has recognized grant income for the period amounting to €1.4 million and a liability component of €0.8 million is accounted for as a financial liability (see disclosure note 2.5.13). The increase compared to June 30, 2020 is mainly associated with additional grant income recognized on new conventions signed during the last quarter of 2020 (contracts numbered 8212 and 8436); • Grant income (Others): additional grant income has been recognized in 2021 on grants received from the Federal Belgian Institute for Health Insurance (Inami) (€0.2 million), not referring to RCAs and not subject to reimbursement. The decrease compared to June 30, 2020 is mainly due to grant income recognized from the regional government (contract numbered 8066 for €0.8 million in the first half of 2020) for which no revenue has been recognized during the first half of 2021; • With respect to R&D tax credit, the current year income (€0.3 million) is in line with previous year. Other expenses For the Six-month period ended June 30, (€‘000) 2021 2020 Clinical Development milestone payment — 105 Remeasurement of RCAs 129 106 Other 33 — Total Other Expenses 162 211 In 2021, other expenses mainly refer to the remeasurement expense of RCA’s are not significant. Indeed, as of June 30, 2021, the Group’s management has maintained the timelines to potential commercialization and projected sales forecast assumptions for its CAR-T In 2020, other expenses were mainly driven by the following drivers: • Clinical development milestone was paid for an amount of €0.1 million related to the first patient injection in the CYAD-02 • Remeasurement expense of RCA’s was not significant for the first half of 2020, given the fact that the Group’s management had maintained in line with prior period the timeline to commercialization and sales forecast for its CAR-T Operating loss As a result of the foregoing, the Group’s operating loss, totaled €14.9 million at June 30, 2021, a decrease of €1.7 million as compared to the six-month Financial income and financial expenses The financial income increase of €0.1 million is driven by gain on foreign exchange differences for the year 2021 due to the revaluation of the USD and its impact on the valuation of the Mesoblast future USD revenue. Financial expense refers mainly to interest expense on lease agreements for an amount of €0.1 million at June 30, 2021, in line with previous year. Loss for the period As a result, the Group’s loss for the six-month Loss per share The loss per share is calculated by dividing loss for the period by the weighted average number of ordinary shares outstanding during the period. As the Group is incurring net losses, outstanding warrants have an anti-dilutive effect. As such, there is no difference between the basic and the diluted earnings per share. For the Six-month period ended June 30, (€’000) 2021 2020 Loss of the year attributable to Equity Holders (14 854 ) (16 597 ) Weighted average number of shares outstanding 14 587 686 13 942 344 Earnings per share (non-fully (1.02 ) (1.19 ) Outstanding warrants 1 899 090 1 594 156

Liquidity and Capital Resources

Liquidity and Capital Resources	6 Months Ended
	Jun. 30, 2021
Text Block [Abstract]
Liquidity and capital resources	2.5.7 Liquidity and capital resources The Group’s liquidity requirements primarily relate to the funding of research & development, general & administrative expenses and working capital requirements. The Group monitors its risk exposure to a shortage of funds using a monthly liquidity planning tool. Its objective is to maintain a balance between continuity of funding and flexibility through the use of bank deposits and finance leases. Through June 30, 2021, the Group funded its operations through several private and public investments totaling, since inception, approximately €307 million (respectively, approximately €71 million and €236 million). The Group also received non-dilutive During the first half of 2021, the Company raised gross proceeds of €8.1 million ($9.7 million) from the sale of American Depositary Shares (ADSs), in aggregate, to Lincoln Park Capital Fund, LLC (“LPC 6 At-the-Market 7 Recoverable Cash Advances (RCA’s), recorded as financial liabilities for an amount of €5.3 million at June 30, 2021, correspond to the risk-adjusted present value of expected future repayments of amounts granted by the Walloon Region, to support specific development programs related to C-Cathez, CYAD-01, CYAD-02, CYAD-101, CYAD-211 CYAD-203. Additional grants have been received from the Federal Belgian Institute for Health Insurance (Inami) (€0.4 million fully cash settled in 2019 and €0.3 million fully cash settled in 2021) and from the regional government (contract numbered 8066 for €2.4 million, out of which €2.2 million has been effectively paid out as of June 30, 2021). Those grants are not subject to future reimbursement (as it is the case for the RCA’s described above). The Group is also exposed to contingent liabilities as a result of the license agreement concluded with Celdara Medical, LLC. The risk adjusted present value of expected cash outflows (mainly towards Celdara) is recorded as a financial liability for an amount of €17.5 million at June 30, 2021. The following table sets forth the Group’s condensed interim consolidated cash flows information for the six-month For the Six-month period ended June 30, (€‘000) 2021 2020 Net cash used in operations (12 185 ) (14 633 ) Net cash (used in)/from investing activities (94 ) 50 Net cash (used in)/from financing activities 7 052 1 929 Effects of exchange rate changes 10 7 Change in Cash and cash equivalents (5 217 ) (12 646 ) Change in Short-term investments — — Net cash burned over the period 8 (5 217 ) (12 646 ) The cash outflow resulting from operating activities amounted to €12.2 million for the six months ended June 30, 2021, as compared to €14.6 million for the prior year’s period. The €2.4 million decrease was primarily driven by lower process development expenses and decreased clinical costs associated with the autologous r/r AML and MDS franchise. Cash flow from investing activities represented a net cash outflow of €0.1 million for the six months ended June 30, 2021, compared to net cash inflow of €0.1 million for the six months ended June 30, 2020. The decrease is mainly associated to an increase of laboratory equipment investments. Cash flow from financing activities in the first half of 2021 represented a net cash inflow of €7.1 million compared to a cash inflow of €1.9 million for prior year’s period. The increase of €5.1 million is mainly related the increase in net proceeds from capital raises occurred in the first half of 2021 for €7.6 million partly compensated by lower proceeds received from Walloon Region. No capital increase had occurred in the first half of 2020. 6 On January 8, 2021, the Company has entered into a committed equity purchase agreement (“Purchase Agreement”) for up to $40 million with Lincoln Park Capital Fund, LLC (LPC), a Chicago-based institutional investor. Over the 24-month 7 On September 3, 2020, the Company entered into an Open Market Sale Agreement SM 8 ‘Net cash burn’ is an alternative performance measure determined by the year-on-year ‘Treasury position’ is an alternative performance measure determined by adding Short-term investments and Cash and cash equivalents from the statement of financial position prepared in accordance with IFRS. The purpose of this measure by Management is to identify the level of cash available internally (excluding external sources of financing) within 12 months.

Goodwill and Intangible assets

Goodwill and Intangible assets	6 Months Ended
	Jun. 30, 2021
Text Block [Abstract]
Goodwill and Intangible assets	2.5.8 Goodwill and Intangible assets As at June 30, As at December 31, (€‘000) 2021 2020 OnCyte IPRD 33 676 33 678 C-Cath 507 540 Goodwill 883 883 Patents & Licenses 1 016 1 019 Other intangible assets 45 51 Total Goodwill and Intangible assets 36 127 36 171 The variance on the total intangible assets as of June 30, 2021 resulted primarily from the regular amortization of C-Cathez 9

Non-current trade receivables a

Non-current trade receivables and other non-current assets	6 Months Ended
	Jun. 30, 2021
Text Block [Abstract]
Disclosure of Non-current trade receivables and other non-current assets [text block]	2.5.9 Non-current non-current As at June 30, As at December 31, (€‘000) 2021 2020 Non-current 2 071 1 923 Net investment in Lease 64 195 Total Non-current 2 135 2 117 In May 2018, the Group entered into an exclusive license agreement with Mesoblast, an Australian biotechnology company, to develop and commercialize the Group’s intellectual property rights relating to C-Cathez, ‘Non-current The non-current As at June 30, As at December 31, (€‘000) 2021 2020 R&D Tax credit receivable 4 002 3 679 Total Non-current 4 002 3 679 Deposits 238 293 Total Other non-current 238 293 In 2017, the Group recognized for the first time a R&D tax credit (€1.2 million) receivable from the federal government that included a one-off catch-up The non-current 9 The Probability of Success (PoS) associated to the product candidate CYAD-211 CYAD-02

Trade and Other receivables

Trade and Other receivables	6 Months Ended
	Jun. 30, 2021
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Trade and Other receivables	2.5.10 Trade and Other receivables As at June 30, As at December 31, (€‘000) 2021 2020 Trade receivables 197 165 Advance deposits 246 220 Net Investment in Lease 269 230 Total Trade and Other receivables 712 615 Current Grant receivables (RCAs) 1 912 145 Total Current Grant receivables 1 912 145 Prepaid expenses 1 396 1 343 VAT receivable 505 342 Income and other tax receivables 52 25 Total Other current assets 1 953 1 711 Total Trade receivables, current grant receivables and other current assets 4 577 2 471 The trade and other receivables remains stable compared to the period ended December 31, 2020. The current net investment in lease refers to the receivable recorded under IFRS16 Leases accounting standard as the Group subleases some office spaces it leases from a head lessor. As of June 30, 2021, grant receivables for a total amount of €1.9 million has been recorded due to Walloon Region recoverable cash advances regarding mainly CYAD-02 CYAD-101 CYAD-203 The increase in other current assets as of June 30, 2021 compared to first half of 2020 for €0.2 million is primarily driven by the increase on VAT receivable associated to timing of purchases. The transaction costs linked to the LPC equity facility signed on January 8, 2021 subject to capitalization and to be offset against future capital raises have increased for an amount of €0.4 million. This increase is compensated by the decrease on prepaid expenses on insurances for €0.4 million due to timing difference on their related payments.

Short-term investments and Cash

Short-term investments and Cash and Cash equivalents	6 Months Ended
	Jun. 30, 2021
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Short-term investments and Cash and Cash equivalents	2.5.11 Short-term investments and Cash and Cash equivalents As at June 30, As at December 31, (€‘000) 2021 2020 Short-term investments — — Cash at bank and on hand 12 017 17 234 Total Short-term investments and Cash and cash equivalents 12 017 17 234 The Group’s cash and cash equivalents amounted to €12.0 million at June 30, 2021 which accounts for a decrease of €5.2 million as compared to year-end Given the level of market interest rates for corporate deposits of short-term maturities, the Group has not invested in short-term deposits over the years 2021 and 2020.

Capital and share premium

Capital and share premium	6 Months Ended
	Jun. 30, 2021
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Capital and share premium	2.5.12 Capital and share premium (€‘000) As at June 30, As at December 31, Capital 53 913 48 513 Share premium 2 217 43 349 Total number of issued and outstanding shares 15 493 956 13 942 344 As of June 30, 2021, share capital amounted to €53.9 million represented by 15,493,956 ordinary shares with no nominal value and a par value of €3.48 per share. This balance does not include the outstanding warrants issued by the Group and granted to certain directors, employees and non-employees There were seven capital increases over the course of the first half of 2021: ◾ On January 8, 2021, 262,812 new shares were issued to LPC further to the LPC purchase agreement; ◾ On March 29, 2021, 200,000 new shares were issued to LPC further to the LPC purchase agreement; ◾ On April 9, 2021, 300,000 new shares were issued to LPC further to the LPC purchase agreement; ◾ On April 29, 2021, 300,000 new shares were issued to LPC further to the LPC purchase agreement; ◾ On May 21, 2021, 182,000 new shares as a result of ADS’s issuance through ATM offering; ◾ On June 14, 2021, 6,800 new shares as a result of ADS’s issuance through ATM offering; and ◾ On June 28, 2021, 300,000 new shares were issued to LPC further to the LPC purchase agreement. As of June 30, 2021, all shares issued have been fully paid. During the first half of 2021, as a result of the above-mentioned 2021 capital raises resulting in cash proceeds for an amount of €7.6 million net of transaction costs, the capital has increased by €5.4 million while the share premium has increased by €2.2 million. During the extraordinary shareholders meeting in May 2021, the shareholders, in accordance with Belgian Company Law, approved to absorb approximately €43.3 million of the accounting losses into the share premium. As a result, the “Accumulated Deficit” has been reduced by cumulative amount of €43.3 million in the six months period ended June 30, 2021 (€215.6 million of reclass from inception to June 30, 2021) against “Share Premium”. The absorption of the accumulated deficit into share premium has no impact on the total equity, comprehensive income (loss), assets (including cash) nor liabilities.

Recoverable Cash Advances

Recoverable Cash Advances	6 Months Ended
	Jun. 30, 2021
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Recoverable Cash Advances	2.5.13 Recoverable Cash Advances (€‘000) As at June 30, As at December 31, Non-Current 4 935 4 220 Current portion 340 371 Total Recoverable Cash Advances 5 275 4 590 The change in the recoverable cash advances liability at the statement of financial position date mainly reflects both the new grants received in current year as well as the remeasurement of the liability at amortized cost, based on the Group’s business plan and sales forecast for its CAR T product candidates (see disclosure note 2.5.6). Underlying R&D is ongoing and no exploitation decisions are expected before mid-2022 (CYAD-203), (CYAD-01 (CYAD-02 CYCLE-1)

Other Non-Current Liabilities

Other Non-Current Liabilities	6 Months Ended
	Jun. 30, 2021
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Other Non-Current Liabilities	2.5.14 Other Non-Current As at June 30, As at December 31, (€‘000) 2021 2020 Onerous contracts - non-current 150 371 Total Other non-current 150 371 As of December 2020, the Group recorded a provision for onerous contracts for a total amount of €0.9 million in order to cover the contractual obligations, mainly on clinical activities follow-up CYAD-01. non-current

Trade Payables and Other Curren

Trade Payables and Other Current Liabilities	6 Months Ended
	Jun. 30, 2021
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Trade Payables and Other Current Liabilities	2.5.15 Trade payables and other current liabilities As at June 30, As at December 31, (€‘000) 2021 2020 Total Trade payables 5 582 4 736 Other current liabilities Social security 195 319 Payroll accruals 1 335 1 653 Onerous contracts - current liabilities 443 488 Other current grant liabilities 1 498 1 838 Others 2 167 1 317 Total Other current liabilities 5 638 5 614 Total Trade payables and other current liabilities 11 220 10 350 Trade payables The increase in trade payables for €0.8 million mainly relates to monthly effect in the timing of the expenses associated to preclinical and clinical activities and the related payments. Other current liabilities As of June 30, 2021, the decrease in social security and payroll accruals by €0.4 million compared to December 31, 2020 related to timing differences on these accruals and employee movements in 2021. As of December 31, 2020, the Group recorded a provision for onerous contracts in order to cover the contractual obligations, mainly on clinical activities follow-up CYAD-01. The other current liabilities attached to grants is mainly explained by the excess of cash proceeds compared to the eligible expenses subsidized by the convention numbered 8436 (CYAD-211 year-end Other current liabilities increase of €0.9 million is mainly explained by the establishment of an accrual in 2021 related to a €0.8 million reimbursement received in 2021 of R&D tax credit related to an assessment resulting from an audit of fiscal year 2015. In 2020, an accrual had been established to cover for a €1.0 million reimbursement of R&D tax credit related to an assessment resulting from an audit of fiscal years 2013 and 2014. While management plans to appeal the assessment, currently management has determined that it is probable that reimbursement will be required.

Financial Instruments Fair Valu

Financial Instruments Fair Value Disclosures	6 Months Ended
	Jun. 30, 2021
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Financial instruments fair value disclosures	2.5.16 Financial Instruments fair values disclosures 2.5.16.1 Financial instruments not reported at fair value on balance sheet The carrying and fair values of financial instruments that are not reported at fair value in the condensed consolidated interim financial statements were as follows for the current and comparative periods: As at June 30, As at December 31, (€‘000) 2021 2020 Financial Assets (‘Amortized cost’ category) within: Non-current 2 135 2 117 Other non-current 238 293 Trade receivables and other current assets 712 615 Short-term investments — — Cash and cash equivalents 12 017 17 234 Total Financial Assets (‘Amortized cost’ category) 15 102 20 259 As at June 30, As at December 31, (€‘000) 2021 2020 Financial Liabilities (‘Amortized cost’ category) within: Bank loans — 37 Lease liabilities 3 080 3 602 RCAs liability 5 275 4 590 Trade payables 5 582 4 736 Total Financial Liabilities (‘Amortized cost’ category) 13 937 12 965 2.5.16.2 Financial instruments reported at fair value on balance sheet Contingent consideration and other financial liabilities are reported at fair value in the statement of financial position using Level 3 fair value measurements for which the Group developed unobservable inputs: (€‘000) Level I Level II Level III Total Assets Investment in equity securities — — — — Total Assets at December 31, 2020 — — — — Liabilities — — — — Contingent consideration and other financial liabilities — — 15 526 15 526 Total Liabilities at December 31, 2020 — — 15 526 15 526 (€‘000) Level I Level II Level III Total Assets Investment in equity securities — — — — Total Assets at June 30, 2021 — — — — Liabilities — — — — Contingent consideration and other financial liabilities — — 17 487 17 487 Total Liabilities at June 30, 2021 — — 17 487 17 487 The change in the balance is detailed as follows: As at June 30, As at December 31, (€‘000) 2021 2020 Opening balance Contingent consideration at 1 January 15 526 24 754 Milestone payment — — Fair value adjustment 1 961 (9 228 ) Closing balance Contingent consideration at 30 June 17 487 15 526 Total - Contingent consideration and Other financial liabilities 17 487 15 526 The contingent consideration and other financial liabilities refer to the acquisition of the Group’s immune-oncology platform and corresponds to the fair value of the risk-adjusted future payments due to Celdara Medical, LLC and Dartmouth College. The liability evolution reflects the development of the Group’s product candidates using CAR-T There has not been any change in valuation technique in 2021 compared to 2020. The valuation is prepared by the Finance Team on a quarterly basis and reviewed by the Management. Management’s key assumptions (assumptions to which the unit’s or group of units’, recoverable amount is most sensitive) about projected cash flows when determining fair value less costs to sell are as follows: • Discount rate (WACC) The Management has determined that the Weighted Average Cost of Capital (WACC) is the most appropriate rate to use as it represents the risk associated with both equity and the debt. Contingent consideration is a liability and thus the discount rate should represent debt features, but the “contingent” nature of the liability has similar features as equity, e.g. return is not guaranteed and thus equity risk should be considered as well. Management estimated the discount rate (WACC) as of June 30, 2021 to be 13.9% (14.8% as of December 31, 2020) based on following components: the US Government Treasury bill 20-Y, • Projected Revenue Management estimated the projected revenue (using cash flow projections ending in 2040) based on the following components: total market and market share, time-to-market, • Probabilities of Success (PoS) Management estimated the PoS based on Clinical Development Success Rates observed by independent business intelligence consulting companies for hematological and solid tumor diseases. Probability of the Group’s product candidates reaching the market used were updated compared to year-end o Probabilities of Success as of June 30, 2021: PoS Phase I Phase I to Phase II Phase II to Phase III Phase III to BLA BLA to Approval Cumulative PoS CYAD-02 100% 50% 28% 60% 90% 7.5% CYAD-101 100% 49% 23% 43% 93% 4.6% o Probabilities of Success as of December 31, 2020: PoS Phase I Phase I to Phase II Phase II to Phase III Phase III to BLA BLA to Approval Cumulative PoS CYAD-02 100% 62% 29% 53% 86% 8.1% CYAD-101 100% 64% 23% 34% 80% 4.0% The PoS estimates used by management as of December 31, 2020 utilized clinical development success rates compiled by independent business intelligence consulting companies which sourced data from clinical development programs from 2006 – 2015. The Group’s updated PoS rates for its clinical programs now incorporates data for clinical development success rates from 2011 – 2020, which the Group believes is a more accurate reflection of clinical development success rates across stage of development and in aggregate. The liability increase at June 30, 2021 is mainly due to: • the update in WACC used for fair value measurement purposes at interim reporting date; • the time accretion (which reflects the development of the Group’s product candidates using CAR T technology and their progress towards market approval in both autologous and allogeneic programs); • the revaluation of the U.S. dollar against the Euro and; • the updated assumptions on Probability of Success (PoS) associated with the NKG2D-based CAR T programs. As stated in note 2.5.6, the fair-value adjustment is booked under the line “Change in fair value of contingent consideration”. The contingent consideration liability captures the commitments further disclosed under note 5.34 from the Group’s 2020 year-end Sensitivity analysis: A variance in key assumptions gives rise to a proportionate impact in the contingent liability fair value computation, as detailed in the Group’s year-end

Leases

Leases	6 Months Ended
	Jun. 30, 2021
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Disclosure of leases [text block]	2.5.17 Leases Amounts recognized in the consolidated statements of financial position “Property, plant and equipment” comprise owned and leased assets that do not meet the definition of investment property. As at June 30, As at December 31, (€’000) 2021 2020 Property, Plant and Equipment owned (excluding right-of-use 1 026 1 115 Right-of-use 2 564 3 004 Total Property, Plant and Equipment 3 592 4 119 The statement of financial position shows the following amounts related to the leases for which the Group is a lessee: (€’000) Property Vehicles Equipment Total Cost At 1 January 2021 3 001 429 1 491 4 921 Additions — 45 — 45 Disposals — (8 ) — (8 ) Transfers — — (220 ) (220 ) At 30 June 2021 3 001 466 1 271 4 738 Accumulated depreciation At 1 January 2021 (827 ) (165 ) (925 ) (1 917 ) Depreciation charge (226 ) (59 ) (200 ) (485 ) Disposals — 8 — 8 Transfers — — 220 220 At 30 June 2021 (1 053 ) (216 ) (905 ) (2 174 ) Net book value At 1 January 2021 2 174 264 566 3 004 Cost 3 001 466 1 271 4 738 Accumulated depreciation (1 053 ) (216 ) (905 ) (2 174 ) At 30 June 2021 1 948 250 366 2 564 Amounts recognized in the consolidated statements of comprehensive loss The consolidated statements of comprehensive loss show the following amounts related to the leases: For the Six-month period ended June 30, (€’000) 2021 2020 Depreciation charge of right-of-use Property 226 202 Vehicles 51 56 Equipment 200 270 Interest on lease liabilities (including in Financial expenses) 1 116 131 Interest on sublease receivable (including in Financial income) 1 (15 ) (26 ) Variable lease payments not included in the measurement of lease liabilities — — Expenses relating to short-term leases and leases of low-value 73 98 Total expenses related to leases 651 731 1 Interests on leases are presented as operating cash flow. Total cash outflows for leases For the Six-month period ended June 30, (€’000) 2021 2020 Total cash outflow for leases 769 857

Related party transactions

Related party transactions	6 Months Ended
	Jun. 30, 2021
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Related party transactions	2.5.18 Related party transactions The compensation amounts presented below, awarded to the members of the Board of Directors and the Executive Committee of the Group, were recorded as General & Administrative expenses in the period referenced. For the Six-month period ended June 30, (€‘000) 2021 2020 Independent director’s fees 196 205 Share-based compensation 168 192 Total compensation to the Board of Directors 364 397 Executive Management fees 552 771 Short-term employee benefits 999 753 Share-based compensation 460 583 Total compensation to the Executive Committee 2 011 2 107

Subsequent events

Subsequent events	6 Months Ended
	Jun. 30, 2021
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Subsequent events	2.5.19 Subsequent events There has been one capital increase between June 30, 2021 and the date of the approval of the Interim Financial Report. On July 22, 2021, 300,000 new shares were issued to LPC further to the LPC purchase agreement for an amount of €1.0 million ($1.2 million). There is no other subsequent event that occurred between six-month

Basis of preparation and sign_2

Basis of preparation and significant accounting policies (Policies)	6 Months Ended
	Jun. 30, 2021
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Basis of preparation of half year report	The condensed consolidated interim financial statements have been prepared in accordance with the IFRS as issued by the IASB and in accordance with the IFRS as issued by the IASB and with IAS 34, Interim Financial Reporting, and same accounting policies used to prepare the most recent annual financial statements. They do not include all disclosures that would otherwise be required in a complete set of financial statements and should be read in conjunction with the annual financial statements for the year ended December 31, 2020 The preparation of the Company’s condensed consolidated interim financial statements requires management to make judgments, estimates and assumptions that affect the reported amounts of revenues, expenses, assets and liabilities, and the disclosure of contingent liabilities, at the end of the interim period. However, uncertainty about these assumptions and estimates could result in outcomes that require a material adjustment to the carrying amount of the asset or liability affected in future periods. The principal risks during the interim period have not materially changed from those mentioned in the 2020 Annual Report and subsequent reports and filings made with the SEC, each of which are available on the Company’s website ( http://www.celyad.com/investors/regulated-information 5 5 As previously disclosed in note 5.36 of the 2020 Annual Report, Horizon Discovery/Perkin Elmer, Inc. (Horizon/PKI) informed the Company they believe the Company was in material breach of these agreements as a result of certain disclosures the Company has made in connection with its obligations as a publicly traded company in the United States and Belgium, although they have not formally delivered to the Company a notice of material breach or termination. The Company believes any such assertion of material breach would be without merit and the Company would expect to vigorously defend any such notice of material breach. Any dispute under these agreements would be subject to arbitration in The Hague under the International Chamber of Commerce Rules. The Company is currently in discussions with Horizon about possible amendments to these agreements in connection with which the Company would retain freedom to operate under the in-licensed All statements and information relate to the interim period unless otherwise stated. The condensed consolidated interim financial statements are presented in thousands of Euros and all values are rounded to the nearest thousand (€’000) except when otherwise indicated. Amounts have been rounded off to the nearest thousand and in certain cases, this may result in minor discrepancies in the totals and sub-totals COVID-19 On March 11, 2020, the World Health Organization declared the novel strain of coronavirus (COVID-19) COVID-19 To date, COVID-19 CYAD-02, CYAD-101 CYAD-211 CYAD-02 CYAD-211, CYAD-101 The long-term impact of COVID-19
New standards, interpretations and amendments	The accounting policies adopted are consistent with those of the previous financial year and corresponding interim reporting period. None of the new standards, interpretations and amendments, which are effective for periods beginning after January 1, 2021 which have been issued by the IASB and the IFRIC have a material effect on the Group’s financial statements. None of the new standards, interpretations and amendments, which will be effective for periods beginning after January 1, 2022 and are not yet effective as of June 30, 2021 and/or not yet adopted as of June 30, 2021, are expected to have a material effect on the Group’s future financial statements.
Critical accounting estimates and judgements	The preparation of condensed consolidated interim financial statements in accordance with IFRS requires management to make judgments, estimates and assumptions that may significantly affect the reported amounts of revenues, expenses, assets and liabilities, and the disclosure of contingent liabilities, at the end of the reporting period. Of note, the Company has filed patent applications which, if issued, would cover other aspects of the product candidates described above as well as products developed by third parties that deploy similar technology and targets. These patent applications encompass the downregulation of one or more of the targets covered under the Horizon/PKI agreements, the use of shRNA to downregulate such targets in immune cells and the combination of shRNAs with a chimeric antigen receptor in immune cells. The Company is also developing a second-generation shRNA platform that does not incorporate any of the Horizon/PKI. The lead allogeneic CAR T product candidate of the Company, CYAD-101, Refer to the disclosure note 5.4 from the Group’s 2020 year-end

Segment reporting (Tables)

Segment reporting (Tables)	6 Months Ended
	Jun. 30, 2021
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Schedule of Segment Profit by Operating Segment	Since 2017, the Group is fully focused on the development of its immuno-oncology platform. Therefore, as of June 30, 2021, most of the R&D expenses were incurred in the immuno-oncology segment, in line with prior year. For the Six-month € ‘000 Cardiology Immuno-oncology Corporate Group Total Revenue recognized at a point in time 5 — — 5 Revenue recognized over time — — — — Total Revenue 5 — — 5 Cost of Sales — — — — Gross Profit 5 — — 5 Research & Development expenses (72 ) (11 069 ) — (11 141 ) General & Administrative expenses — — (4 789 ) (4 789 ) Change in fair value of contingent consideration — (2 445 ) — (2 445 ) Net Other income/(loss) 10 1 604 200 1 815 Operating Profit/(Loss) (57 ) (11 908 ) (4 589 ) (16 555 ) Net financial income/(loss) — (87 ) 45 (42 ) Profit/(Loss) before taxes (57 ) (11 995 ) (4 545 ) (16 597 ) Income Taxes — — — — Profit/(Loss) for the six months ended June 30, 2020 (57 ) (11 995 ) (4 545 ) (16 597 ) For the Six-month € ‘000 Cardiology Immuno-oncology Corporate Group Total Revenue recognized at a point in time — — — — Revenue recognized over time — — — — Total Revenue — — — — Cost of Sales — — — — Gross Profit — — — — Research & Development expenses (57 ) (9 899 ) — (9 956 ) General & Administrative expenses — — (4 785 ) (4 785 ) Change in fair value of contingent consideration — (1 961 ) — (1 961 ) Net Other income/(loss) (54 ) 1 670 209 1 825 Operating Profit/(Loss) (111 ) (10 190 ) (4 576 ) (14 877 ) Net financial income/(loss) 149 (87 ) (39 ) 23 Profit/(Loss) before taxes 38 (10 277 ) (4 615 ) (14 854 ) Income Taxes — — — — Profit/(Loss) for the six months ended June 30, 2021 38 (10 277 ) (4 615 ) (14 854 )

Results of Operations (Tables)

Results of Operations (Tables)	6 Months Ended
	Jun. 30, 2021
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Summary of Revenues	For the Six-month period ended June 30, (€‘000) 2021 2020 Out-licensing — — Other revenue — 5 Total — 5
Summary of Research And Development Expenses	The following table is a summary of manufacturing expenses, clinical, quality and regulatory expenses and other research and development expenses, which are aggregated and presented as research and development expenses in the Group’s condensed consolidated interim financial statements. For the Six-month period ended June 30, (€‘000) 2021 2020 Employee expenses 4 530 4 528 Travel & Living 17 107 Clinical study costs 2 205 2 720 Preclinical study costs 944 866 Process development and scale-up 407 803 Consulting fees 152 191 IP filing and maintenance fees 84 141 Share-based payments 331 398 Depreciation 708 727 Rent and utilities 337 415 Others 241 245 Total R&D expenses 9 956 11 141
Summary of General and Administrative Expenses	For the Six-month period ended June 30, (€‘000) 2021 2020 Employee expenses 1 789 1 733 Consulting fees 1 030 1 025 Share-based payments 759 892 Communication & Marketing 236 289 Rent 15 40 Insurances 730 476 Travel & living 12 77 Depreciation 133 168 Others 81 90 Total General and administrative expenses 4 785 4 789
Schedule of Change in Fair Value of Contingent Consideration	For the Six-month period ended June 30, (€‘000) 2021 2020 Change in fair value of contingent consideration (1 961 ) (2 445 ) Total Change in fair value of contingent consideration (1 961 ) (2 445 )
Earnings (Loss) Per Share	For the Six-month period ended June 30, (€’000) 2021 2020 Loss of the year attributable to Equity Holders (14 854 ) (16 597 ) Weighted average number of shares outstanding 14 587 686 13 942 344 Earnings per share (non-fully (1.02 ) (1.19 ) Outstanding warrants 1 899 090 1 594 156
Summary of Other Income	Other income For the Six-month period ended June 30, (€‘000) 2021 2020 Grant income (RCAs) 1 438 615 Grant income (Other) 166 1 023 R&D tax credit 339 371 Other 44 16 Total Other Income 1 987 2 026
Summary of Other Expenses	Other expenses For the Six-month period ended June 30, (€‘000) 2021 2020 Clinical Development milestone payment — 105 Remeasurement of RCAs 129 106 Other 33 — Total Other Expenses 162 211

Liquidity and Capital Resourc_2

Liquidity and Capital Resources (Tables)	6 Months Ended
	Jun. 30, 2021
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Summary of Consolidated Cash Flows Information	The following table sets forth the Group’s condensed interim consolidated cash flows information for the six-month For the Six-month period ended June 30, (€‘000) 2021 2020 Net cash used in operations (12 185 ) (14 633 ) Net cash (used in)/from investing activities (94 ) 50 Net cash (used in)/from financing activities 7 052 1 929 Effects of exchange rate changes 10 7 Change in Cash and cash equivalents (5 217 ) (12 646 ) Change in Short-term investments — — Net cash burned over the period 8 (5 217 ) (12 646 )

Goodwill and Intangible assets

Goodwill and Intangible assets (Tables)	6 Months Ended
	Jun. 30, 2021
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Summary of Goodwill and Intangible Assets	As at June 30, As at December 31, (€‘000) 2021 2020 OnCyte IPRD 33 676 33 678 C-Cath 507 540 Goodwill 883 883 Patents & Licenses 1 016 1 019 Other intangible assets 45 51 Total Goodwill and Intangible assets 36 127 36 171

Non-current trade receivables_2

Non-current trade receivables and other non-current assets (Tables)	6 Months Ended
	Jun. 30, 2021
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Summary of Detailed Information About Non-current Trade Receivables	As at June 30, As at December 31, (€‘000) 2021 2020 Non-current 2 071 1 923 Net investment in Lease 64 195 Total Non-current 2 135 2 117
Summary of Other Non-current Assets	The non-current As at June 30, As at December 31, (€‘000) 2021 2020 R&D Tax credit receivable 4 002 3 679 Total Non-current 4 002 3 679 Deposits 238 293 Total Other non-current 238 293

Trade and Other receivables (Ta

Trade and Other receivables (Tables)	6 Months Ended
	Jun. 30, 2021
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Summary of Trade, Other Receivables and Other current assets	As at June 30, As at December 31, (€‘000) 2021 2020 Trade receivables 197 165 Advance deposits 246 220 Net Investment in Lease 269 230 Total Trade and Other receivables 712 615 Current Grant receivables (RCAs) 1 912 145 Total Current Grant receivables 1 912 145 Prepaid expenses 1 396 1 343 VAT receivable 505 342 Income and other tax receivables 52 25 Total Other current assets 1 953 1 711 Total Trade receivables, current grant receivables and other current assets 4 577 2 471

Short-term investments and Ca_2

Short-term investments and Cash and Cash equivalents (Tables)	6 Months Ended
	Jun. 30, 2021
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Summary of Short Term Investments and Cash and Cash Equivalents	As at June 30, As at December 31, (€‘000) 2021 2020 Short-term investments — — Cash at bank and on hand 12 017 17 234 Total Short-term investments and Cash and cash equivalents 12 017 17 234

Capital and share premium (Tabl

Capital and share premium (Tables)	6 Months Ended
	Jun. 30, 2021
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Summary of capital and share premium	(€‘000) As at June 30, As at December 31, Capital 53 913 48 513 Share premium 2 217 43 349 Total number of issued and outstanding shares 15 493 956 13 942 344

Recoverable Cash Advances (Tabl

Recoverable Cash Advances (Tables)	6 Months Ended
	Jun. 30, 2021
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Summary of Current and Non-current Portion Cash Advances	(€‘000) As at June 30, As at December 31, Non-Current 4 935 4 220 Current portion 340 371 Total Recoverable Cash Advances 5 275 4 590

Other Non-Current Liabilities (

Other Non-Current Liabilities (Tables)	6 Months Ended
	Jun. 30, 2021
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Schedule of Other Non-Current Liabilities	As at June 30, As at December 31, (€‘000) 2021 2020 Onerous contracts - non-current 150 371 Total Other non-current 150 371

Trade Payables and Other Curr_2

Trade Payables and Other Current Liabilities (Tables)	6 Months Ended
	Jun. 30, 2021
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Trade Payables and Other Current Liabilities	As at June 30, As at December 31, (€‘000) 2021 2020 Total Trade payables 5 582 4 736 Other current liabilities Social security 195 319 Payroll accruals 1 335 1 653 Onerous contracts - current liabilities 443 488 Other current grant liabilities 1 498 1 838 Others 2 167 1 317 Total Other current liabilities 5 638 5 614 Total Trade payables and other current liabilities 11 220 10 350

Financial Instruments Fair Va_2

Financial Instruments Fair Value Disclosures (Tables)	6 Months Ended
	Jun. 30, 2021
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Summary of Carrying and Fair Values of Financial Instruments that are not Reported at Fair Value	The carrying and fair values of financial instruments that are not reported at fair value in the condensed consolidated interim financial statements were as follows for the current and comparative periods: As at June 30, As at December 31, (€‘000) 2021 2020 Financial Assets (‘Amortized cost’ category) within: Non-current 2 135 2 117 Other non-current 238 293 Trade receivables and other current assets 712 615 Short-term investments — — Cash and cash equivalents 12 017 17 234 Total Financial Assets (‘Amortized cost’ category) 15 102 20 259 As at June 30, As at December 31, (€‘000) 2021 2020 Financial Liabilities (‘Amortized cost’ category) within: Bank loans — 37 Lease liabilities 3 080 3 602 RCAs liability 5 275 4 590 Trade payables 5 582 4 736 Total Financial Liabilities (‘Amortized cost’ category) 13 937 12 965
Schedule of Financial Assets and Liabilities Measured at Fair Value	Contingent consideration and other financial liabilities are reported at fair value in the statement of financial position using Level 3 fair value measurements for which the Group developed unobservable inputs: (€‘000) Level I Level II Level III Total Assets Investment in equity securities — — — — Total Assets at December 31, 2020 — — — — Liabilities — — — — Contingent consideration and other financial liabilities — — 15 526 15 526 Total Liabilities at December 31, 2020 — — 15 526 15 526 (€‘000) Level I Level II Level III Total Assets Investment in equity securities — — — — Total Assets at June 30, 2021 — — — — Liabilities — — — — Contingent consideration and other financial liabilities — — 17 487 17 487 Total Liabilities at June 30, 2021 — — 17 487 17 487
Contingent Consideration and Other Financial Liabilities	The change in the balance is detailed as follows: As at June 30, As at December 31, (€‘000) 2021 2020 Opening balance Contingent consideration at 1 January 15 526 24 754 Milestone payment — — Fair value adjustment 1 961 (9 228 ) Closing balance Contingent consideration at 30 June 17 487 15 526 Total - Contingent consideration and Other financial liabilities 17 487 15 526
Sensitivity Analysis Performed on Main Assumptions	Management estimated the PoS based on Clinical Development Success Rates observed by independent business intelligence consulting companies for hematological and solid tumor diseases. Probability of the Group’s product candidates reaching the market used were updated compared to year-end o Probabilities of Success as of June 30, 2021: PoS Phase I Phase I to Phase II Phase II to Phase III Phase III to BLA BLA to Approval Cumulative PoS CYAD-02 100% 50% 28% 60% 90% 7.5% CYAD-101 100% 49% 23% 43% 93% 4.6% o Probabilities of Success as of December 31, 2020: PoS Phase I Phase I to Phase II Phase II to Phase III Phase III to BLA BLA to Approval Cumulative PoS CYAD-02 100% 62% 29% 53% 86% 8.1% CYAD-101 100% 64% 23% 34% 80% 4.0%

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2021
Text Block [Abstract]
Summary of Property Plant And Equipment Owned And Leased Assets	“Property, plant and equipment” comprise owned and leased assets that do not meet the definition of investment property. As at June 30, As at December 31, (€’000) 2021 2020 Property, Plant and Equipment owned (excluding right-of-use 1 026 1 115 Right-of-use 2 564 3 004 Total Property, Plant and Equipment 3 592 4 119
Summary of Lease Liabilities	The statement of financial position shows the following amounts related to the leases for which the Group is a lessee: (€’000) Property Vehicles Equipment Total Cost At 1 January 2021 3 001 429 1 491 4 921 Additions — 45 — 45 Disposals — (8 ) — (8 ) Transfers — — (220 ) (220 ) At 30 June 2021 3 001 466 1 271 4 738 Accumulated depreciation At 1 January 2021 (827 ) (165 ) (925 ) (1 917 ) Depreciation charge (226 ) (59 ) (200 ) (485 ) Disposals — 8 — 8 Transfers — — 220 220 At 30 June 2021 (1 053 ) (216 ) (905 ) (2 174 ) Net book value At 1 January 2021 2 174 264 566 3 004 Cost 3 001 466 1 271 4 738 Accumulated depreciation (1 053 ) (216 ) (905 ) (2 174 ) At 30 June 2021 1 948 250 366 2 564
Summary of Lease Expense	The consolidated statements of comprehensive loss show the following amounts related to the leases: For the Six-month period ended June 30, (€’000) 2021 2020 Depreciation charge of right-of-use Property 226 202 Vehicles 51 56 Equipment 200 270 Interest on lease liabilities (including in Financial expenses) 1 116 131 Interest on sublease receivable (including in Financial income) 1 (15 ) (26 ) Variable lease payments not included in the measurement of lease liabilities — — Expenses relating to short-term leases and leases of low-value 73 98 Total expenses related to leases 651 731 1 Interests on leases are presented as operating cash flow.
Summary of Cash Outflow For Leases	Total cash outflows for leases For the Six-month period ended June 30, (€’000) 2021 2020 Total cash outflow for leases 769 857

Related party transactions (Tab

Related party transactions (Tables)	6 Months Ended
	Jun. 30, 2021
Text Block [Abstract]
Summary of Compensation to the Members of the Board of Directors and the Executive Management Team	For the Six-month period ended June 30, (€‘000) 2021 2020 Independent director’s fees 196 205 Share-based compensation 168 192 Total compensation to the Board of Directors 364 397 Executive Management fees 552 771 Short-term employee benefits 999 753 Share-based compensation 460 583 Total compensation to the Executive Committee 2 011 2 107

General Information - Additiona

General Information - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2021Subsidiaries
Disclosure of detailed information about business combination [abstract]
Number of subsidiaries owned by the entity	3

Segment Reporting - Additional

Segment Reporting - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015Segment
Disclosure of operating segments [line items]
Number of operating segments	2

Segment Reporting - Schedule of

Segment Reporting - Schedule of Segment Profit by Operating Segment (Detail) - EUR (€) € in Thousands		6 Months Ended
		Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Disclosure of operating segments [line items]
Revenue recognized at a point in time				€ 5
Revenue		€ 0		5
Gross Profit				5
Research & Development expenses		(9,956)		(11,141)
General & Administrative expenses		(4,785)		(4,789)
Change in fair value of contingent consideration		(1,961)		(2,445)
Net Other income/(loss)		1,825		1,815
Operating Loss	[1]	(14,877)		(16,555)
Net financial income/(loss)		23		(42)
Loss before taxes		(14,854)		(16,597)
Profit (Loss) for the year		(14,854)	€ (607)	(16,597)
Cardiology [member]
Disclosure of operating segments [line items]
Revenue recognized at a point in time				5
Revenue				5
Gross Profit				5
Research & Development expenses		(57)		(72)
Net Other income/(loss)		(54)		10
Operating Loss		(111)		(57)
Net financial income/(loss)		149
Loss before taxes		38		(57)
Profit (Loss) for the year		38		(57)
Immuno-oncology [member]
Disclosure of operating segments [line items]
Research & Development expenses		(9,899)		(11,069)
Change in fair value of contingent consideration		(1,961)		(2,445)
Net Other income/(loss)		1,670		1,604
Operating Loss		(10,190)		(11,908)
Net financial income/(loss)		(87)		(87)
Loss before taxes		(10,277)		(11,995)
Profit (Loss) for the year		(10,277)		(11,995)
Corporate [member]
Disclosure of operating segments [line items]
General & Administrative expenses		(4,785)		(4,789)
Net Other income/(loss)		209		200
Operating Loss		(4,576)		(4,589)
Net financial income/(loss)		(39)		45
Loss before taxes		(4,615)		(4,545)
Profit (Loss) for the year		€ (4,615)		€ (4,545)
[1]	The operating loss arises from the Company’s loss for the period before deduction of Financial income, Financial expenses and Income taxes. The purpose of this measure by Management is to identify the Company’s results in connection with its operating activities.

Off-Balance Sheet Commitments -

Off-Balance Sheet Commitments - Additional Information (Detail) € in Thousands	Jun. 30, 2021EUR (€)
Off Balance Sheet Commitments [Abstract]
Off-balance sheet commitments	€ 0

Results of Operations - Additio

Results of Operations - Additional Information (Detail) - EUR (€) € in Thousands		6 Months Ended
		Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Disclosure of reporting entity [line items]
Total R&D expenses		€ 9,956		€ 11,141
Research and development expense increase percentage		10.60%
Clinical Development Milestone Payments		€ 100
Operating loss	[1]	(14,877)		(16,555)
Increase in operating loss		1,700
Interest expense on finance leases		116		131
Increase in loss for the period		1,700
Loss for the period		(14,854)	€ (607)	(16,597)
Change in value of interest income bank account		100
Other income		1,987		€ 2,026
Research and Development [Member]
Disclosure of reporting entity [line items]
Other income		300
Finance Leases [Member]
Disclosure of reporting entity [line items]
Interest expense on finance leases		100
Federal Belgian Institute For Health Insurance Inami [Member]
Disclosure of reporting entity [line items]
Grant income recoverable cash advances received		200
Regional Government [Member]
Disclosure of reporting entity [line items]
Grant income recoverable cash advances received		800
Contingent consideration and other financial liabilities [member]
Disclosure of reporting entity [line items]
Change in fair value of the contingent consideration and other financial liabilities		2,000
RCA's [member]
Disclosure of reporting entity [line items]
Additional Grant Income Recognised during Period as a Component of Financial Asset		1,400
Additional Grant Income Recognised during Period as a Component of Financial Liability		€ 800
[1]	The operating loss arises from the Company’s loss for the period before deduction of Financial income, Financial expenses and Income taxes. The purpose of this measure by Management is to identify the Company’s results in connection with its operating activities.

Results of Operations - Summary

Results of Operations - Summary of Revenues (Detail) - EUR (€) € in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Disclosure of disaggregation of revenue from contracts with customers [abstract]
Out-licensing revenue	€ 0
Other revenue	0	5
Total	€ 0	€ 5

Results of Operations - Summa_2

Results of Operations - Summary of Research and Development Expenses (Detail) - EUR (€) € in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Research And Development Expenses [Abstract]
Employee expenses	€ 4,530	€ 4,528
Travel & Living	17	107
Clinical study costs	2,205	2,720
Preclinical study costs	944	866
Process development and scale-up	407	803
Consulting fees	152	191
IP filing and maintenance fees	84	141
Share-based payments	331	398
Depreciation	708	727
Rent and utilities	337	415
Others	241	245
Total R&D expenses	€ 9,956	€ 11,141

Results of Operations - Schedul

Results of Operations - Schedule of Change in Fair Value of Contingent Consideration (Detail) - EUR (€) € in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Disclosure of fair value measurement of liabilities [line items]
Change in fair value of contingent consideration	€ (1,961)	€ (2,445)
Contingent consideration [Member]
Disclosure of fair value measurement of liabilities [line items]
Change in fair value of contingent consideration	€ (1,961)	€ (2,445)

Results of Operations - Summa_3

Results of Operations - Summary of General and Administrative Expenses (Detail) - EUR (€) € in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Other General And Administrative Expenses [abstract]
Employee expenses	€ 1,789	€ 1,733
Consulting fees	1,030	1,025
Share-based payments	759	892
Communication & Marketing	236	289
Rent	15	40
Insurances	730	476
Travel & living	12	77
Depreciation	133	168
Others	81	90
Total General and administrative expenses	€ 4,785	€ 4,789

Results of Operations - Summa_4

Results of Operations - Summary of Other Income (Detail) - EUR (€) € in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Disclosure of Detailed Information About Other Operating Income Explanatory [Line Items]
Grant income (Other)	€ 166	€ 1,023
Total Other Income	1,987	2,026
Other Income [member]
Disclosure of Detailed Information About Other Operating Income Explanatory [Line Items]
Grant income (RCAs)	1,438	615
R&D tax credit	339	371
Other	€ 44	16
Total Other Income		€ 2,026

Results of Operations - Summa_5

Results of Operations - Summary of Other Expenses (Detail) - EUR (€) € in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Disclosure of Detailed Information About Other Operating Expense Explanatory [Line Items]
Clinical Development milestone payment	€ 100
Total Other Expenses	162	€ 211
Other Expenses [Member]
Disclosure of Detailed Information About Other Operating Expense Explanatory [Line Items]
Clinical Development milestone payment		105
Remeasurement of RCAs	129	106
Other	33
Total Other Expenses	€ 162	€ 211

Results of Operations - Calcula

Results of Operations - Calculation of Earnings (Loss) Per Share (Detail) - EUR (€) € / shares in Units, € in Thousands	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Earnings per share [abstract]
Loss of the year attributable to Equity Holders	€ (14,854)	€ (607)	€ (16,597)
Weighted average number of shares outstanding	14,587,686		13,942,344
Earnings per share (non-fully diluted) in €	€ (1.02)		€ (1.19)
Outstanding warrants	1,899,090		1,594,156

Liquidity and capital resourc_3

Liquidity and capital resources - Additional Information (Detail) € in Thousands	Jan. 08, 2021USD ($)	Sep. 03, 2020USD ($)	Jun. 30, 2021EUR (€)	Jun. 30, 2021USD ($)	Jun. 30, 2020EUR (€)	Dec. 31, 2020EUR (€)	Dec. 31, 2019EUR (€)
Disclosure Of Regulatory Capital Resources [Line Items]
Private investment fund			€ 71,000
Public investment fund			236,000
Investment fund			307,000
Financial liabilities			17,487			€ 15,526
Pending contract			14,800
Cash outflow from operations			(12,185)		€ (14,633)
Cash flow from investing activities			100		50
Cash flow from financing activities			7,052		1,929
Proceeds from issuance of shares and exercise of warrants			7,617
American depositary shares [Member]
Disclosure Of Regulatory Capital Resources [Line Items]
Proceeds from issue of ordinary shares			8,100	$ 9,700,000
Proceeds from issuance of shares and exercise of warrants			7,600
Stock Issued During Period Value Issued For Services | $		$ 25,000,000
Lincoln Park Capital Fund Llc [member]
Disclosure Of Regulatory Capital Resources [Line Items]
Equity purchase agreement consideration paid | $	$ 40,000,000
Equity purchase agreement term	24 months
Purchase of american depositary shares value | $	$ 40,000,000
Share repurchased related expenses | $	$ 1,000,000
Federal Belgian Institute For Health Insurance Inami [Member]
Disclosure Of Regulatory Capital Resources [Line Items]
Additional grants received			300				€ 400
Regional Government [Member]
Disclosure Of Regulatory Capital Resources [Line Items]
Additional grants received			2,400
RCA's [member]
Disclosure Of Regulatory Capital Resources [Line Items]
Financial liabilities			5,300
Walloon Region [Member]
Disclosure Of Regulatory Capital Resources [Line Items]
Additional grants received			2,200
Cash flow from financing activities			7,600
Cash inflow			5,100
Amount received			6,800
Increase decrease in cash flow from financing activities					0
Celdara Medical [member]
Disclosure Of Regulatory Capital Resources [Line Items]
Financial liabilities			17,500
AML and MDS franchise [Member]
Disclosure Of Regulatory Capital Resources [Line Items]
Cash outflow from operations			(12,200)		(14,600)
Decrease in cash outflow from operations			€ 2,400
Short Term Investments [Member]
Disclosure Of Regulatory Capital Resources [Line Items]
Increase in cash outflow from investing activities					€ (100)

Liquidity and capital resourc_4

Liquidity and capital resources - Summary of Consolidated Cash Flows Information (Detail) - EUR (€) € in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Cash Flows From Capital Increase [Abstract]
Net cash used in operations	€ (12,185)	€ (14,633)
Net cash (used in)/from investing activities	100	50
Net cash (used in)/from financing activities	7,052	1,929
Effects of exchange rate changes	10	7
Change in Cash and cash equivalents	(5,217)	(12,646)
Change in Short-term investments		0
Net cash burned over the period	€ (5,217)	€ (12,646)	€ 5,200

Goodwill and Intangible asset_2

Goodwill and Intangible assets - Summary of Goodwill and Intangible Assets (Detail) - EUR (€) € in Thousands	Jun. 30, 2021	Dec. 31, 2020
Disclosure of detailed information about intangible assets [line items]
Goodwill and Intangible assets	€ 36,127	€ 36,171
OnCyte IPRD [member]
Disclosure of detailed information about intangible assets [line items]
Goodwill and Intangible assets	33,676	33,678
C-Cath Development Costs [member]
Disclosure of detailed information about intangible assets [line items]
Goodwill and Intangible assets	507	540
Goodwill [member]
Disclosure of detailed information about intangible assets [line items]
Goodwill and Intangible assets	883	883
Patents and Licences [Member]
Disclosure of detailed information about intangible assets [line items]
Goodwill and Intangible assets	1,016	1,019
Other intangible assets [member]
Disclosure of detailed information about intangible assets [line items]
Goodwill and Intangible assets	€ 45	€ 51

Goodwill and Intangible asset_3

Goodwill and Intangible assets - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2021EUR (€)
Disclosure of detailed information about intangible assets [line items]
Impairment of intangible assets	€ 0

Non-current trade receivables_3

Non-current trade receivables and other non-current assets - Additional Information (Detail) - EUR (€) € in Thousands	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2017
Disclosure of other non current assets [line items]
R&D Tax credit receivable	€ 4,002	€ 3,679	€ 1,200
Non-current trade receivables	2,135	€ 2,117
Mesoblast [member] | License And Collaboration Agreements [member]
Disclosure of other non current assets [line items]
Non-current trade receivables	€ 2,100

Non-current trade receivables_4

Non-current trade receivables and other non-current assets - Summary of Detailed Information About Non-current Trade Receivables (Detail) - EUR (€) € in Thousands	Jun. 30, 2021	Dec. 31, 2020
Disclosure of other non current assets [line items]
Non-current trade receivables Mesoblast license agreement	€ 2,135	€ 2,117
Net investment in Lease	64	195
Mesoblast licence agreement [member]
Disclosure of other non current assets [line items]
Non-current trade receivables Mesoblast license agreement	€ 2,071	€ 1,923

Non-current trade receivables_5

Non-current trade receivables and other non-current assets - Summary of Non-current Financial Assets (Detail) - EUR (€) € in Thousands	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2017
Disclosure of Other Noncurrent Assets [abstract]
R&D Tax credit receivable	€ 4,002	€ 3,679	€ 1,200
Total Non-current Grant receivables	4,002	3,679
Deposits	238	293
Total Other non-current assets	€ 238	€ 293

Trade and Other receivables - S

Trade and Other receivables - Summary of Trade Receivables and Other Current Assets (Detail) - EUR (€) € in Thousands	Jun. 30, 2021	Dec. 31, 2020
Disclosure of trade and other receivables [abstract]
Trade receivables	€ 197	€ 165
Advance deposits	246	220
Net Investment in Lease	269	230
Total Trade and Other receivables	712	615
Current Grant receivables (RCAs)	1,912	145
Total Current Grant receivables	1,912	145
Prepaid expenses	1,396	1,343
VAT receivable	505	342
Income and other tax receivables	52	25
Total Other current assets	1,953	1,711
Total Trade receivables, current grant receivables and other current assets	€ 4,577	€ 2,471

Trade and Other receivables - A

Trade and Other receivables - Additional Information (Detail) € in Millions	6 Months Ended
	Jun. 30, 2021EUR (€)
Disclosure of trade and other receivables [line items]
Increase on other current assets	€ 0.2
Decrease in prepaid expenses	0.4
Lincoln Park Capital Fund Llc [member] | LPC purchase agreement [member]
Disclosure of trade and other receivables [line items]
Transaction costs related to LPC Equity facility	0.4
Walloon Region [Member]
Disclosure of trade and other receivables [line items]
Grant receivables due to related parties	1.9
Increase on current grant receivables	€ 1.8

Short-term investments and Ca_3

Short-term investments and Cash and Cash equivalents - Summary of Short Term Investments and Cash and Cash Equivalents (Detail) - EUR (€) € in Thousands	Jun. 30, 2021	Dec. 31, 2020
Short term investments1 [abstract]
Short-term investments	€ 0	€ 0
Cash at bank and on hand	12,017	17,234
Total Short-term investments and Cash and cash equivalents	€ 12,017	€ 17,234

Short-term investments and Ca_4

Short-term investments and Cash and Cash equivalents - Additional Information (Detail) - EUR (€) € in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Short term investments1 [abstract]
Treasury position	€ 12,000
Cash burned	€ (5,217)	€ (12,646)	€ 5,200

Capital and share premium - Sum

Capital and share premium - Summary of capital and share premium (Detail) - EUR (€) € in Thousands	Jun. 30, 2021	Dec. 31, 2020
Disclosure of classes of share capital [abstract]
Capital	€ 53,913	€ 48,513
Share premium	€ 2,217	€ 43,349
Total number of issued and outstanding shares	15,493,956	13,942,344

Capital and share premium - Add

Capital and share premium - Additional Information (Detail) - EUR (€) € / shares in Units, € in Thousands	May 31, 2021	Jun. 30, 2021	Jun. 28, 2021	Jun. 14, 2021	May 21, 2021	Apr. 29, 2021	Apr. 09, 2021	Mar. 29, 2021	Jan. 08, 2021	Dec. 31, 2020
Disclosure of classes of share capital [line items]
Share Capital		€ 53,913								€ 48,513
Number of ordinary shares		15,493,956
Common stock , par value		€ 0
Increase in capital		€ 0
Net Proceeds From Issue Of Ordinary Shares		€ 7,617
Par Value Per share		€ 3.48
Cumulative reclassification of losses from accumulated deficit to the share premium		€ 215,600
Issued capital [member]
Disclosure of classes of share capital [line items]
Increase in capital		5,400
Share premium [member]
Disclosure of classes of share capital [line items]
Increase in capital		2,200
Decrease In Share Premium Due to Absorption of Accounting Losses	€ 43,300
Decrease In Accumulated Deficit Due To Reclassification Of Accounting Losses Against Share Premium		43,300
Retained earnings [member]
Disclosure of classes of share capital [line items]
Cumulative reclassification of losses from accumulated deficit to the share premium		215,600
Decrease In Accumulated Deficit Due To Reclassification Of Accounting Losses Against Share Premium		43,300
American depositary shares [Member]
Disclosure of classes of share capital [line items]
Number of shares issued | shares				6,800	182,000
Net Proceeds From Issue Of Ordinary Shares		€ 7,600
American depositary shares [Member] | Lincoln Park Capital Fund Llc [member]
Disclosure of classes of share capital [line items]
Number of shares issued | shares			300,000			300,000	300,000	200,000	262,812

Recoverable Cash Advances - Sum

Recoverable Cash Advances - Summary of Current and Non-current Portion Cash Advances (Detail) - EUR (€) € in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Disclosure of financial liabilities [abstract]
Non-current portion	€ 4,935	€ 4,220
Current portion	340	371
Total Recoverable Cash Advances	€ 5,275	€ 4,590

Other Non-Current Liabilities -

Other Non-Current Liabilities - Summary of Other Non-Current Liabilities (Detail) - EUR (€) € in Thousands	Jun. 30, 2021	Dec. 31, 2020
Disclosure Of Other Non current Liabilities [Abstract]
Onerous contracts - non-current liabilities	€ 150	€ 371
Total Other non-current liabilities	€ 150	€ 371

Other Non-Current Liabilities_2

Other Non-Current Liabilities - Additional Information (Detail) - EUR (€) € in Thousands	Jun. 30, 2021	Dec. 31, 2020
Text Block [Abstract]
Provision for onerous contracts		€ 900
Non Provision for onerous contracts	€ 150	371
Current Provision for onerous contracts	€ 443	€ 488

Trade Payables and Other Curr_3

Trade Payables and Other Current Liabilities - Trade Payables and Other Current Liabilities (Detail) - EUR (€) € in Thousands	Jun. 30, 2021	Dec. 31, 2020
Trade and other current payables [abstract]
Total Trade payables	€ 5,582	€ 4,736
Other current liabilities
Social security	195	319
Payroll accruals	1,335	1,653
Onerous contracts—current liabilities	443	488
Other current grant liabilities	1,498	1,838
Others	2,167	1,317
Total Other current liabilities	5,638	5,614
Total Trade payables and other current liabilities	€ 11,220	€ 10,350

Trade Payables and Other Curr_4

Trade Payables and Other Current Liabilities - Additional Information (Detail) - EUR (€) € in Thousands	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Trade payable settlement description	The increase in trade payables for €0.8 million mainly relates to monthly effect in the timing of the expenses associated to preclinical and clinical activities and the related payments.
Decrease in trade payable	€ 800
Decrease on social security, payroll accruals and taxes	400
Increase in other current liabilities	900
Reimbursement of R&D tax credit	800
Adjustments For Increase Decrease In Other Current Liabilities Relating To Reimbursement Of Tax Credit	1,000
Current Provision for onerous contracts	443	€ 488
Increase in other grant liabilities	1,300
Adjustments For Increase Decrease In Other Current Grant Liabilities Related To Reversal Of Deferred Revenue	€ 200

Financial Instruments Fair Va_3

Financial Instruments Fair Value Disclosures - Summary of Carrying and Fair Values of Financial Instruments that are not Reported at Fair Value (Detail) - EUR (€) € in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Financial Assets
Non-current trade receivables	€ 2,135	€ 2,117
Other non-current assets	238	293
Short-term investments	0	0
Cash and cash equivalents	12,017	17,234	€ 26,692	€ 39,338
At fair value [member]
Financial Assets
Non-current trade receivables	2,135	2,117
Other non-current assets	238	293
Trade receivables and other current assets	712	615
Short-term investments	0	0
Cash and cash equivalents	12,017	17,234
Total Financial Assets	15,102	20,259
Financial Liabilities
Bank loans		37
Lease liabilities	3,080	3,602
RCAs liability	5,275	4,590
Trade payables	5,582	4,736
Total Financial Liabilities	€ 13,937	€ 12,965

Financial Instruments Fair Va_4

Financial Instruments Fair Value Disclosures - Schedule of Financial Assets and Liabilities Measured at Fair Value (Detail) - EUR (€) € in Thousands	Jun. 30, 2021	Dec. 31, 2020
Disclosure of detailed information about financial instruments [line items]
Investment in equity securities		€ 0
Financial assets, at fair value		0
Financial liabilities, at fair value	€ 17,487	15,526
Contingent consideration and other financial liabilities [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities, at fair value	17,487	15,526
Level I [member]
Disclosure of detailed information about financial instruments [line items]
Investment in equity securities		0
Financial assets, at fair value		0
Financial liabilities, at fair value		0
Level I [member] | Contingent consideration and other financial liabilities [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities, at fair value		0
Level II [member]
Disclosure of detailed information about financial instruments [line items]
Investment in equity securities		0
Financial assets, at fair value		0
Financial liabilities, at fair value		0
Level II [member] | Contingent consideration and other financial liabilities [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities, at fair value		0
Level III [member]
Disclosure of detailed information about financial instruments [line items]
Investment in equity securities		0
Financial assets, at fair value		0
Financial liabilities, at fair value	17,487	15,526
Level III [member] | Contingent consideration and other financial liabilities [member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities, at fair value	€ 17,487	€ 15,526

Financial Instruments Fair Va_5

Financial Instruments Fair Value Disclosures - Summary of Contingent Consideration and Other Financial Liabilities (Detail) - EUR (€) € in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Disclosure of significant unobservable inputs used in fair value measurement of liabilities [line items]
Total - Contingent consideration and Other financial liabilities	€ 17,487	€ 15,526
Contingent consideration [Member]
Disclosure of significant unobservable inputs used in fair value measurement of liabilities [line items]
Opening balance Contingent consideration at 1 January	15,526	24,754
Fair value adjustment	1,961	(9,228)
Closing balance Contingent consideration at June 30	17,487	15,526
Total - Contingent consideration and Other financial liabilities	€ 17,487	€ 15,526

Financial Instruments Fair Va_6

Financial Instruments Fair Value Disclosures - Additional Information (Detail)	Jun. 30, 2021	Dec. 31, 2020
Disclosure of detailed information about financial instruments [abstract]
Weighted average cost of capital discount rate	13.90%	(14.80%)

Financial Instruments Fair Va_7

Financial Instruments Fair Value Disclosures - Schedule of Sensitivity Analysis Performed on Main Assumptions (Detail)	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Cyad One Zero Two [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Probablity of success percentage	7.50%	8.10%
Cyad One Zero One [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Probablity of success percentage	4.60%	4.00%
Phase I [member] | Cyad One Zero Two [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Probablity of success percentage	100.00%	100.00%
Phase I [member] | Cyad One Zero One [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Probablity of success percentage	100.00%	100.00%
Phase I to II [member] | Cyad One Zero Two [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Probablity of success percentage	50.00%	62.00%
Phase I to II [member] | Cyad One Zero One [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Probablity of success percentage	49.00%	64.00%
Phase II to III [member] | Cyad One Zero Two [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Probablity of success percentage	28.00%	29.00%
Phase II to III [member] | Cyad One Zero One [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Probablity of success percentage	23.00%	23.00%
Phase III to BLA [member] | Cyad One Zero Two [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Probablity of success percentage	60.00%	53.00%
Phase III to BLA [member] | Cyad One Zero One [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Probablity of success percentage	43.00%	34.00%
BLA to approval [member] | Cyad One Zero Two [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Probablity of success percentage	90.00%	86.00%
BLA to approval [member] | Cyad One Zero One [Member]
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Probablity of success percentage	93.00%	80.00%

Leases - Summary of Property Pl

Leases - Summary of Property Plant And Equipment Owned and Leased Assets (Detail) - EUR (€) € in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Disclosure Of Leases [Abstract]
Property, Plant and Equipment owned (excluding right-of-use assets)	€ 1,026	€ 1,115
Right-of-use assets	2,564	3,004
Total Property, Plant and Equipment	€ 3,592	€ 4,119

Leases - Summary of Rights to U

Leases - Summary of Rights to Use Assets (Detail) - EUR (€) € in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Disclosure of quantitative information about right-of-use assets [line items]
Opening balance	€ 3,004
Closing balance	2,564
Cost [member]
Disclosure of quantitative information about right-of-use assets [line items]
Opening balance	4,921
Additions	45
Disposals	(8)
Transfers	(220)
Closing balance	4,738
Accumulated depreciation [member]
Disclosure of quantitative information about right-of-use assets [line items]
Opening balance	(1,917)
Disposals	8
Transfers	220
Depreciation charge	(485)
Closing balance	(2,174)
Property [member]
Disclosure of quantitative information about right-of-use assets [line items]
Opening balance	2,174
Closing balance	1,948
Property [member] | Cost [member]
Disclosure of quantitative information about right-of-use assets [line items]
Opening balance	3,001
Closing balance	3,001
Property [member] | Accumulated depreciation [member]
Disclosure of quantitative information about right-of-use assets [line items]
Opening balance	(827)
Depreciation charge	(226)
Closing balance	(1,053)
Vehicles [member]
Disclosure of quantitative information about right-of-use assets [line items]
Opening balance	264
Depreciation charge	(51)	€ (56)
Closing balance	250
Vehicles [member] | Cost [member]
Disclosure of quantitative information about right-of-use assets [line items]
Opening balance	429
Additions	45
Disposals	(8)
Closing balance	466
Vehicles [member] | Accumulated depreciation [member]
Disclosure of quantitative information about right-of-use assets [line items]
Opening balance	(165)
Disposals	8
Depreciation charge	(59)
Closing balance	(216)
Plant and Equipments [member]
Disclosure of quantitative information about right-of-use assets [line items]
Opening balance	566
Depreciation charge	(200)	€ (270)
Closing balance	366
Plant and Equipments [member] | Cost [member]
Disclosure of quantitative information about right-of-use assets [line items]
Opening balance	1,491
Additions	0
Transfers	(220)
Closing balance	1,271
Plant and Equipments [member] | Accumulated depreciation [member]
Disclosure of quantitative information about right-of-use assets [line items]
Opening balance	(925)
Transfers	220
Depreciation charge	(200)
Closing balance	€ (905)

Leases - Summary of lease expen

Leases - Summary of lease expense (Detail) - EUR (€) € in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Depreciation charge of right-of-use assets
Interest on lease liabilities (including in Financial expenses)	€ 116	€ 131
Interest on sublease receivable (including in Financial income)	(15)	(26)
Expenses relating to short-term leases and leases of low-value assets	73	98
Total expenses related to leases	651	731
Property Member [Member]
Depreciation charge of right-of-use assets
Depreciation, right-of-use assets	226	202
Vehicles [member]
Depreciation charge of right-of-use assets
Depreciation, right-of-use assets	51	56
Plant and Equipments [member]
Depreciation charge of right-of-use assets
Depreciation, right-of-use assets	€ 200	€ 270

Leases - Summary of Cash Outflo

Leases - Summary of Cash Outflow For Leases (Detail) - EUR (€) € in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Disclosure of quantitative information about right-of-use assets [line items]
Total cash outflow for leases	€ 769	€ 857

Related party transactions - Su

Related party transactions - Summary of Compensation to the Members of the Board of Directors and the Executive Management Team (Detail) - EUR (€) € in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Board of director [member]
Disclosure of compensation of key management personnel [line items]
Independent director's fees	€ 196	€ 205
Share-based compensation	168	192
Total compensation	364	397
Executive management [member]
Disclosure of compensation of key management personnel [line items]
Executive Management fees	552	771
Short-term employee benefits	999	753
Share-based compensation	460	583
Total compensation	€ 2,011	€ 2,107

Subsequent events - Additional

Subsequent events - Additional Information (Detail) - Events After balance sheet Date [member] - LPC purchase agreement [member] - Lincoln Park Capital Fund Llc [member] € in Millions, $ in Millions	Jul. 22, 2021EUR (€)shares	Jul. 22, 2021USD ($)shares
Disclosure of non-adjusting events after reporting period [line items]
Stock Issued During Period Shares New Issues	300,000	300,000
Stock Issued During Period Value Issued For Services	€ 1	$ 1.2