Celyad Oncology SA — AGM Information 2020

Apr 14, 2020

Regulated Information

Celyad to Host Remote 2020 Ordinary General Meeting

• Company postpones Extraordinary General Meeting from May 5, 2020 to June 8, 2020

Mont-Saint-Guibert, Belgium - Celyad (Euronext Brussels and Paris, and Nasdaq: CYAD), a clinicalstage biopharmaceutical company focused on the development of CAR-T cell-based therapies, today announced the decision to host its 2020 Ordinary General Meeting remotely on May 5, 2020 and to postpone its Extraordinary General Meeting to June 8, 2020 from May 5, 2020.

Materials for both the Ordinary and Extraordinary Shareholders' Meetings can be found on the Investors section of the Company's website under "Shareholder Meetings".

Ordinary Shareholders' Meeting of May 5, 2020

In view of the current exceptional circumstances linked to the COVID-19 pandemic and in accordance with Belgian Royal Decree No. 4 of April 9, 2020, the Board of Directors of Celyad have decided to prohibit the physical presence of shareholders, and instead will webcast the Ordinary General Meeting of May 5, 2020 remotely, via an electronic means of communication.

The detailed practical arrangements for the broadcasting of this Ordinary General Meeting will be published on Celyad's website.

Voting instructions can only be submitted by proxy to the proxyholder designated by the Board of Directors of Celyad. With respect to the right to ask questions, shareholders are allowed to submit their questions only in writing prior to the Ordinary General Meeting.

The other formalities for admission to and participation in the meeting (conditions of admission, right to ask questions and consultation of the available documents) remain unchanged from the information provided in the notice of meeting published on April 3, 2020.

Extraordinary Shareholders' Meeting of May 5, 2020

In addition, the Board of Directors of Celyad have also decided to postpone the Extraordinary General Meeting initially scheduled for May 5, 2020 until June 8, 2020 at 3:00 pm CEST. The agenda of this meeting will remain the same, including:

• 1. Acknowledgement of the special report of the Board of Directors drawn up in accordance with article 7:199 of the Companies and Associations Code
• 2. Renewal of authorized capital
• 3. Change the Company's name
• 4. Powers

This postponement decision was adopted in view of the exceptional circumstances related to the COVID-19 pandemic and, specifically, the difficulties encountered by our shareholders of the American depositary receipts in expressing their vote if the date of May 5, 2020 had been maintained.

Press Release 22 April 2020 07:00 a.m. CEST

Regulated Information

As a reminder, the meeting had been convened with a reduced notice period in application of article 7:128 §1 of the Code of Companies and Associations.

Information on the modalities and other arrangements made for the holding of this Extraordinary General Meeting will be communicated at a future date.

***END***

About Celyad

Celyad is a clinical-stage biopharmaceutical company focused on the development of specialized CAR-T cell-based product candidates and utilizes its expertise in cell engineering to target cancer. Celyad's CAR-T cell platform has the potential to treat a broad range of solid and hematologic tumors. The company's lead clinical candidate, CYAD-01, an autologous NKG2D-based CAR-T therapy, is currently being evaluated in several Phase 1 clinical trials to assess safety and clinical activity for the treatment of hematological malignancies, such as acute myeloid leukemia, and solid cancers, such as metastatic colorectal cancer. Celyad is also developing CYAD-101, an investigational, non-gene edited, allogeneic (donor derived) NKG2D-based CAR-T therapy, which is currently being evaluated in a Phase 1 trial for the treatment of patients with metastatic colorectal cancer. Celyad was founded in 2007 and is based in Mont-Saint-Guibert, Belgium, and New York, NY. Celyad's ordinary shares are listed on the Euronext Brussels and Euronext Paris exchanges, and its American Depository Shares are listed on the Nasdaq Global Market, all under the ticker symbol CYAD. Celyad has received funding from the Walloon Region (Belgium) to support the advancement of its CAR-T cell therapy programs.

For more information, please contact:

Celyad

Filippo Petti, Chief Executive Officer – investors@celyad.com Alexandrine Hazard, Communications & IR Associate – T: +32(0) 10 39 41 58 – communications@celyad.com

U.S.: LifeSci Advisors

Investor Relations: Daniel Ferry – T.: +1 (617) 430 7576 – daniel@lifesciadvisors.com Public Relations: Sara Zelkovic – T.: +1 (646) 876 4933 – sara@lifescicomms.com

Forward-looking statements

This release may contain forward-looking statements, including statements regarding: the safety and clinical activity of CYAD-01, CYAD-101, CYAD-02 and CYAD-211; statements regarding the ongoing and planned clinical development of CYAD-01, CYAD-101 CYAD-02 and CYAD-211, including the timing of trials, enrolment, data readouts and presentations; the clinical and commercial potential of CYAD-01, CYAD-101 CYAD-02 and CYAD-211; the success of the OptimAb manufacturing system; the ongoing and planned clinical and commercial potential and development of Celyad's shRNA technology; Celyad's financial condition, results of operation and business outlook. Forward-looking statements may involve known and unknown risks, uncertainties and other factors which might cause actual results, financial condition and liquidity, performance or achievements of Celyad, or industry results, to differ materially from those expressed or implied by such forward-looking statements. In particular it should be noted that the data summarized above are preliminary in nature. There is limited data concerning safety and clinical activity following treatment with the CYAD-01, CYAD-101, CYAD-02 and CYAD-211 product candidates. These results may not be repeated or observed in ongoing or future studies involving the CYAD-01, CYAD-101, CYAD-02 and CYAD-211 drug product candidates. These forward-looking statements are further qualified by important factors and risks, which could cause actual results to differ materially from those in the forward-looking statements, including statements about: the initiation, timing, progress and results of our preclinical studies and clinical trials, and our research and development programs; our ability to advance drug product candidates into, and successfully complete, clinical trials; our ability to successfully manufacture drug product for our clinical trials, including with our OptimAb manufacturing process and with respect to manufacturing drug product with the desired number of T cells under our clinical trial protocols; our reliance on the success of our drug product candidates, including our dependence on the regulatory approval of CYAD-01, CYAD-101, CYAD-02 and CYAD-211 in the United States and Europe and subsequent commercial success of CYAD-01, CYAD-101, CYAD-02 and CYAD-211, both of which may never occur;

Regulated Information

the timing or likelihood of regulatory filings and approvals; our ability to develop sales and marketing capabilities; the commercialization of our drug product candidates, if approved; the pricing and reimbursement of our drug product candidates, if approved; the implementation of our business model, strategic plans for our business, drug product candidates and technology; the scope of protection we are able to establish and maintain for intellectual property rights covering our drug product candidates and technology; our ability to operate our business without infringing, misappropriating or otherwise violating the intellectual property rights and proprietary technology of third parties; cost associated with enforcing or defending intellectual property infringement, misappropriation or violation; product liability; and other claims; regulatory development in the United States, the European Union, and other jurisdictions; estimates of our expenses, future revenues, capital requirements and our needs for additional financing; the potential benefits of strategic collaboration agreements and our ability to maintain and enter into strategic arrangements; our ability to maintain and establish collaborations or obtain additional grant funding; the rate and degree of market acceptance of our drug product candidates, if approved; our financial performance; developments relating to our competitors and our industry, including competing product candidates and statements regarding future revenue, hiring plans, expenses, capital expenditures, capital requirements and share performance and the impact of the novel coronavirus, COVID-19, including potential effects on our business, clinical trials, supply chain and manufacturing capabilities. A further list and description of these risks, uncertainties and other risks can be found in Celyad's U.S. Securities and Exchange Commission (SEC) filings and reports, including in its Annual Report on Form 20-F filed with the SEC on March 25, 2020 and subsequent filings and reports by Celyad. Given these uncertainties, the reader is advised not to place any undue reliance on such forward-looking statements. These forward-looking statements speak only as of the date of publication of this document and Celyad's actual results may differ materially from those expressed or implied by these forward-looking statements. Celyad expressly disclaims any obligation to update any such forward-looking statements in this document to reflect any change in its expectations with regard thereto or any change in events, conditions or circumstances on which any such statement is based, unless required by law or regulation.

CELYAD SA Listed limited liability company

Rue Edouard Belin, 2 1435 Mont-Saint-Guibert

LER Nivelles 0891.118.115

CONVENING LETTER TO THE ORDINARY GENERAL MEETING OF SHAREHOLDERS OF 5 MAY 2020

The board of directors has the honor to convene the shareholders and warrant holders of Celyad SA (the "Company") to attend the ordinary general meeting to be held on 5 May 2020 at 3pm (CET) at the Company's registered office, the agenda of which is given below.

AGENDA

1. Deliberation on the annual report of the board of directors for the financial year ended on 31 December 2019 and on the report of the auditor for the financial year ended on 31 December 2019.

Comments on this agenda item: The board of directors requests the general meeting of shareholders to take note of the board of directors' annual report for the financial year ended on 31 December 2019 and the auditor' report for the financial year ended on 31 December 2019.

2. Deliberation and approval of the board of directors' remuneration report, as presented by the nomination and remuneration committee and as included in the annual report.

Proposal of resolution: The meeting decides to approve the remuneration report prepared by the board of directors, as explained by the nomination and remuneration committee and as included in the annual report.

3. Deliberation on the consolidated financial statements for the financial year ended on 31 December 2019.

Comments on this agenda item: The board of directors requests the general meeting of shareholders to acknowledge the consolidated financial statements for the financial year ended on 31 December 2019.

4. Deliberation and approval of the annual accounts for the financial year ended on 31 December 2019 and the allocation of the result as proposed by the board of directors in its annual report.

Proposal of resolution: The meeting decides to approve the annual accounts for the financial year ended on 31 December 2019 and the allocation of the result as proposed by the board of directors in its annual report.

5. Discharge to the directors

Proposal of resolution: The meeting decides to grant discharge to the following directors for the exercise of their mandate during the financial year ended on 31 December 2019:

• − Michel Lussier, Chairman ;
• − LSS Consulting SPRL, represented by M. Christian Homsy;
• − Filippo Petti ;
• − Serge Goblet ;
• − Chris Buyse;
• − Rudy Dekeyser;
• − Hilde Windels;
• − Margo Roberts.

6. Discharge to the auditor

Proposal of resolution: The meeting decides to grant discharge to the auditor VCBA BDO Bedrijfsrevisoren – Réviseurs, represented by M. Bert Kegels, for the exercise of its mandate during the financial year ended on 31 December 2019.

7. Deliberation on the proposal of the board of directors to appoint Dominic Piscitelli as director

Proposal of resolution: The general meeting decides to appoint Dominic Piscitelli as director of the Company for a term of 4 years, i.e. until the ordinary general meeting approving the accounts closed on 31 December 2023.

Information relating to the skills and experience of the candidate director is set out in an annex to the notice of meeting.

8. Deliberation on the proposal of the board of directors to appoint R.A.D. Life Sciences BV, represented by Rudy Dekeyser, as director

Proposal of resolution: The general meeting decides to appoint R.A.D. Life Sciences BV, represented by Rudy Dekeyser, as director of the Company for a term of 4 years, i.e. until the ordinary general meeting approving the accounts closed on 31 December 2023.

9. Deliberation on the proposal of the board of directors to renew the mandate of Michel Lussier for 4 years

Proposal of resolution: The general meeting decides to renew the mandate of Michel Lussier as director of the Company for 4 additional years, i.e. until the ordinary general meeting approving the accounts closed on 31 December 2023.

10. Deliberation on the proposal of the board of directors to renew the mandate of Serge Goblet for 4 years

Proposal of resolution: The general meeting decides to renew the mandate of Serge Goblet as director of the Company for 4 additional years, i.e. until the ordinary general meeting approving the accounts closed on 31 December 2023.

11. Deliberation on the proposal of the board of directors to renew the mandate of Chris Buyse for 4 years

Proposal of resolution: The general meeting decides to renew the mandate of Chris Buyse as director of the Company for 4 additional years, i.e. until the ordinary general meeting approving the accounts closed on 31 December 2023.

12. Deliberation pursuant to Article 7:91 of Companies and associations Code on the determination of the variable remuneration of the CEO

Proposal of resolution: Based on article 7:91 of the Companies and Associations Code, the general meeting confirms that the calculation of the variable remuneration of the CEO, exceeding 25% of the annual base remuneration, can be done on the basis of criteria evaluated on periods shorter than two or three years

13. Deliberation on the approval of the terms and conditions of a potential warrant plan to be implemented and in particular on the change of control clause in accordance with Article 7:151 of the Companies and Associations Code

Proposal of resolution: The general meeting decides to approve the terms and conditions of a model of warrant plan to be respected in the context of the potential implementation of a such plan during the next 12 months, on the proposal of the nomination and remuneration committee, with a vesting period over three years and whose exercise price shall be the lower of (i) the average closing price of the share during the 30 days preceding the offer and (ii) the last closing price preceding the date of the offer. More specifically, the meeting approves, in accordance with Article 7:151 of the Companies and Associations Code, the anticipated exercise clause in the event of a change of control or a public offer on the company's shares.

14. Deliberation on the appointment of the statutory auditor

Proposal of resolution: Further to the termination of the mandate of VCBA BDO Bedrijfsrevisoren as statutory auditor, the general meeting approves the appointment of CVBA E&Y Bedrijfsrevisoren – Réviseurs d'entreprises, having its registered office at De Kleetlaan 2, B – 1831 Diegem, Belgium, duly represented by Carlo-Sébastien d'assario, as Statutory Auditor, for a term of 3 years, i.e. until the ordinary general meeting approving the accounts closed on 31 December 2022, and approves an EUR 150,000 (excl. VAT) annual fees for the first year.

15. Power of attorney

Proposition of resolution: The meeting decides to grant a proxy to M. Filippo Petti, CEO, and/or NandaDevi SRL, represented by M. Philippe Dechamps, and/or F&C Consulting SRL represented by M. David Georges, Finance Director, and/or to any lawyer of the firm CMS Belgium, each with power of substitution, in order to issue, execute and sign all documents, instruments, steps and formalities and to give all necessary or useful instructions to execute the aforementioned decisions, including, but not limited to, the formalities for filing with the National Bank of Belgium the annual accounts and the consolidated annual accounts closed on 31 December 2019, the annual reports and the auditor's report relating thereto and the realization of the necessary publication formalities, including the publication in the annexes to the Belgian Official Gazette of the abovementioned decisions.

QUORUM AND MAJORITY

Quorum requirement: For the meeting to be able to validly deliberate on the abovementioned agenda, no quorum is required.

Vote and majority: Without prejudice to the shares fully subscribed and registered since at least two years without interruption in the name of the same shareholder in the shareholder registry and benefit of a double voting right, each share gives right to one vote. Pursuant to the applicable law, the proposed resolutions referred to in the abovementioned agenda will be adopted if those are approved by a simple majority of the votes validly casted by the shareholders. Pursuant to the Article 7:135 of the Companies and Associations Code, the holders of warrants have the right to participate to the ordinary general meeting, but only with a consultation right.

PARTICIPATION IN THE MEETING

Practical organization in respect of Covid-19

The Company reserves the right to postpone the date or modify the organization of the shareholders meeting in respect of eventual legal or administrative measures which could be adopted in the context of Covid-19, including the remote organization of the meeting, without the in-person presence of the shareholders, if authorized by applicable laws. In this context, the Company encourages its shareholders to vote by proxy. The Company will also offer the possibility to shareholders to participate to the meeting of May 5 by teleconference. The details of this teleconference will be communicated on the website of the Company at www.celyad.com.

Admission requirements

The right to participate in the general meeting of shareholders and to vote is subject to the prior accounting registration of the shares under the shareholder's name on 21 April 2020 at midnight (Belgian time) (the "Record Date"), either by way of registration on the company's share register, or either by way of registration in book entry form in an account held with a settlement institution or a certified account holder, without taking into account the number of shares held by the shareholder at the day of the general meeting.

The day and time referred to above shall constitute the Record Date. Only persons who are shareholders on the Record Date are entitled to attend and vote at the general meeting.

An attest is delivered to the shareholder by the settlement institution or certified account holder which certifies the number of dematerialised shares registered in its accounts under the name of the shareholder on the Record Date, for which the shareholder has expressed its intention to participate in the general meeting.

The shareholder indicates his willingness to participate in the general meeting by 29 April 2020 at the latest. This must be done by email to investors@celyad.com, or by mail marked for the attention of Celyad, M. Philippe Dechamps, Chief Legal Officer, Rue Edouard Belin 2, B-1435 Mont-Saint-Guibert.

The holders of warrants have the right to attend the general meeting, subject to them fulfilling the shareholders' admission criteria.

Right to include items on the agenda and to submit proposals for decisions

In accordance with article 7:130 of the Companies and Associations Code, one or more shareholders holding together at least 3% of the share capital may request the inclusion of items on the agenda to be addressed at the general meeting, and request the submission of decisions' proposals concerning items to be addressed or included on the agenda.

The shareholder or shareholders exercising this right must, in order for their request to be examined at the general meeting, satisfy the following two conditions:

• prove that they hold the abovementioned required percentage on the date of their request (either by way of a certificate mentioning the registration of the corresponding shares on the Company's share register, or by way of an attest of a settlement institution or a certified account holder setting out the number of corresponding dematerialised shares registered in its accounts under the name of the shareholder); and
• still be a shareholder for up to 3% of the Company's share capital on the Record Date.

Items to be included on this agenda and/or decisions' proposals must be sent to the Company on 13 April 2020 at the latest by email to investors@celyad.com, or by mail marked for the attention of Celyad, M. Philippe Dechamps, Chief Legal Officer, Rue Edouard Belin 2, B-1435 Mont-Saint-Guibert.

The Company will acknowledge receipt of the requests sent by email or by mail to the address indicated by the shareholder within 48 hours after receipt.

The revised agenda will be published on 20 April 2020 at the latest (on the Company's website at the address www.celyad.com, in the Belgian Official Gazette and in the press) if one or more requests to include new items or proposals for decisions on the agenda have been received within the aforementioned deadline.

Further information relating to the abovementioned rights and the modalities for exercising them are available on the Company's website (www.celyad.com).

Right to ask questions

During the general meeting, the directors answer questions that are asked by the shareholders, at the meeting or in writing before the meeting, concerning their report or the agenda, in accordance with legal provisions. The auditor also answers questions asked by the shareholders, at the meeting or in writing before the meeting, about his report.

These questions may be asked prior to the general meeting by email to the address investors@celyad.com, or by mail marked for the attention of Celyad, M. Philippe Dechamps, Chief Legal Officer, Rue Edouard Belin 2, B-1435 Mont-Saint-Guibert.

These questions must be received by the Company on 29 April 2020 at 17h00 at the latest.

Further information relating to the abovementioned right and the modalities for exercising them are available on the Company's website (www.celyad.com).

Proxies

Any shareholder may be represented at the meeting by a proxy holder.

Shareholders wishing to be represented must designate their proxy holder by using the proxy form established by the board of directors. The proxy form may be obtained on the Company's website (www.celyad.com) or upon request at the Company's registered office, or by email to investors@celyad.com .

The original form signed on paper form must be received by the Company on 29 April 2020 at 17h00 (Belgian time) at the latest. This form may be communicated to the Company by mail marked for the attention of Celyad, M. Philippe Dechamps, Chief Legal Officer, Rue Edouard Belin 2, B-1435 Mont-Saint-Guibert, or by email to investors@celyad.com provided that the last communication is signed by electronic signature in accordance with applicable Belgian legislation. Shareholders are invited to follow the instructions set out in the proxy form in order to be validly represented at the meeting.

Any designation of a proxy holder shall be made in accordance with applicable Belgian legislation, particularly on the ground of conflict of interest and record keeping.

Shareholders wishing to be represented must comply with the registration and confirmation procedure described above.

Available documents

All documents concerning the general meeting that are required by law to be made available to shareholders may be consulted on the Company's website (www.celyad.com) as from 3 April 2020.

As from the same date, shareholders have the right to consult these documents on business days and during normal office hours, at the Company's registered office and/or, upon display of their securities, obtain copies of these documents free of charge.

Requests for copies may also be made, free of charge, by mail (writing) marked for the attention of Philippe Dechamps, Chief Legal Officer, Rue Edouard Belin 2, B-1435 Mont-Saint-Guibert, or by email to investors@celyad.com

The board of directors

Annexes