Celyad Oncology SA — Share Issue/Capital Change 2015

Feb 27, 2015

THIS ANNOUNCEMENT IS NOT FOR RELEASE, PUBLICATION OR DISTRIBUTION IN OR INTO THE UNITED STATES, CANADA, JAPAN AND AUSTRALIA

Cardio3 BioSciences successfully completes a €32 Million private placement

Mont-Saint-Guibert, Belgium - Cardio3 BioSciences (C3BS) (Euronext Brussels and Paris: CARD), a leader in the discovery and development of cell therapies, today announced it has raised approximately €32 million through a private placement of ordinary shares to investors in the United States and Europe.

Cardio3 BioSciences has placed 713,380 new shares to qualified institutional investors in the United States and Europe at a price of €44.50 per share, with no discount to the previous day closing price and a 4% premium to the last 30 day average price. The placed shares represent 10% of the current number of outstanding shares, bringing the total number of shares outstanding after the issue to 7,847,187. The new shares are expected to be admitted to trading on Euronext Brussels and Paris following their issuance, which is expected to take place on Tuesday, 3 March 2015.

The proceeds from the private placement will be used by Cardio3 BioSciences to:

• Further develop its newly acquired CAR-T cell technology platform;
• Strengthen the leadership of C-Cure® for the treatment of congestive heart failure, and;
• For general corporate purposes.

Dr. Christian Homsy, CEO of Cardio3 BioSciences, comments: "We are very pleased to announce the successful completion of this private placement which reflects strong interest from healthcare institutional investors in our Company and our clinical programs in cardiology and oncology. This capital is expected to support the ongoing development of our lead cardiac therapeutic candidate, C-Cure®, and our recently acquired CAR T-Cell technology platform. We are grateful to our existing shareholders for their continued support and appreciate the enthusiasm of new investors. We believe Cardio3 BioSciences is well positioned to execute on our development plan and deliver significant long-term value to shareholders. We look forward to providing the market with updates on key strategic and clinical milestones as 2015 progresses."

This placement was successfully led by UBS Investment Bank, acting as Global Coordinator and Bookrunner for the offering, and Petercam and Bryan Garnier & Co as Placement Agents.

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THIS ANNOUNCEMENT IS NOT FOR RELEASE, PUBLICATION OR DISTRIBUTION IN OR INTO THE UNITED STATES, CANADA, JAPAN AND AUSTRALIA

For more information, please contact:

Cardio3 BioSciences

Christian Homsy, CEO Julie Grade, Corporate Communications Manager

For Europe: Consilium Strategic Communications Amber Bielecka, Chris Welsh, Laura Thornton For the U.S: The Ruth Group Lee Roth (Investors), Kirsten Thomas (Media)

www.c3bs.com Tel: +32 10 39 41 00 jgrade@c3bs.com Tel : +44 20 3709 5700 cardio3@consilium-comms.com Tel: +1 646 536 7012 / 7014 lroth@theruthgroup.com kthomas@theruthgroup.com

To subscribe to Cardio3 BioSciences' newsletter, visit www.c3bs.com. Follow us on Twitter @Cardio3Bio.

About Cardio3 BioSciences

Cardio3 BioSciences is a leading biotechnology company focused on the discovery and development of cell therapies for the treatment of unmet medical needs in cardiology and oncology. Founded in 2007 and based in the Walloon region of Belgium, Cardio3 BioSciences leverages research collaborations in the USA and in Europe with the Mayo Clinic (MN, USA), and Dartmouth College (NH, USA). The Company's lead product candidate in cardiology is C-Cure®, an autologous stem cell therapeutic using adult guided stem cells for the condition of congestive heart failure. The Company's lead product candidate in oncology is CM-CS1, an autologous CAR T-Cell product candidate using NKG2D, a Natural Killer (NK) cell receptor designed to target ligands present on most tumor types, including hematologic cancers and solid tumors. Cardio3 BioSciences is also developing a portfolio of medical devices for enhancing the delivery of bio therapeutic agents into the myocardium (C-Cathez®) and for cardiac surgery involving mitral valve defects.

Cardio3 BioSciences' shares are listed on Euronext Brussels and Euronext Paris under the ticker symbol CARD. To learn more about Cardio3 BioSciences, please visit www.c3bs.com

Important notices regarding the placement

The distribution of this press release in certain jurisdictions may be restricted by law. No action has been taken by the Company, UBS Investment Bank, the Placement Agents or any of their respective affiliates that would permit a public offer of the new shares in any jurisdiction where action for that purpose is required. This press release is for information purposes only and does not constitute an offer to purchase or the solicitation of an offer to buy any new shares in any jurisdiction in which such an offer or solicitation is unlawful. Persons into whose possession this press release comes are required to inform themselves about and to observe any such restrictions.

This press release is not for publication or distribution, directly or indirectly, in the United States, Canada, Australia and Japan. This press release does not constitute or form part of any offer or solicitation to purchase or subscribe for, nor does it constitute an offer to sell, or the solicitation of an offer to buy, and there shall not be any sale of securities, in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to its registration or qualification under the laws of such jurisdiction. The new shares mentioned herein have not been, and will not be, registered under the United States Securities Act of 1933 (the "Securities Act"). The new shares have not been and may not be offered or sold in the United States except pursuant to an effective

THIS ANNOUNCEMENT IS NOT FOR RELEASE, PUBLICATION OR DISTRIBUTION IN OR INTO THE UNITED STATES, CANADA, JAPAN AND AUSTRALIA

registration statement under, or an exemption from the registration requirements of, the Securities Act. There has been no and will be no public offer of securities in the United States.

This press release is not an offer to sell nor a solicitation to buy the new shares nor a prospectus for the purposes of Directive 2003/71/EC (such Directive, together with any applicable implementing measures in the relevant member state of the European Economic Area and as amended, including by Directive 2010/73/EU, to the extent implemented in the relevant member state, the "Prospectus Directive"). There has been no and will be no offer to the public of the new shares in any member state of the European Economic Area and no prospectus or other offering document has been or will be prepared in connection with the sale of the new shares by the Company. In the European Economic Area the new shares have been and will only be offered and sold to "qualified investors" as defined in the Prospectus Directive or in other circumstances falling within Article 3(2) of the Prospectus Directive.

This press release does not constitute an offer of the new shares to the public in the United Kingdom, nor is it intended to be an inducement to engage in investment activity for the purpose of section 21 of the Financial Services and Markets Act 2000 (as amended) of the United Kingdom. Consequently, this press release is only directed at (i) persons who are outside the United Kingdom; (ii) investment professionals within Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotions) Order 2005 as amended (the "Order"); (iii) persons falling within Article 49(2)(a)-(d) of the Order; or (iv) other persons to whom it may be lawfully be communicated, together being referred to as "relevant persons". The new shares are only available to, and any invitation, offer or agreement to purchase or otherwise acquire the new shares will be engaged in only with relevant persons. Any person who is not a relevant person should not act or rely on this document or any of its contents.

This press release does not constitute or form part of, and should not be construed as an offer or the solicitation of an offer to subscribe for or purchase the new shares, and nothing contained therein shall form the basis of or be relied on in connection with any contract or commitment whatsoever, nor does it constitute a recommendation regarding the new shares. An investment decision to buy any of the new shares in the private placement must be made solely on the basis of publicly available information. Such information is not the responsibility of, and has not been independently verified by any of, UBS Investment Bank, the Placement Agents, or their respective affiliates.

C3BS-CQR-1, C-Cure, CM-CS1, C-Cathez, OnCyte, Cardio3 BioSciences and the Cardio3 BioSciences, C-Cathez, CHART-1, CHART-2 and OnCyte logos are trademarks or registered trademarks of Cardio3 BioSciences SA, in Belgium, other countries, or both. Mayo Clinic holds equity in Cardio3 BioSciences as a result of intellectual property licensed to the company. In addition to historical facts or statements of current condition, this press release contains forward-looking statements, which reflect our current expectations and projections about future events, and involve certain known and unknown risks, uncertainties and assumptions that could cause actual results or events to differ materially from those expressed or implied by the forward-looking statements. These risks, uncertainties and assumptions could adversely affect the outcome and financial effects of the plans and events described herein. These forward-looking statements are further qualified by important factors, which could cause actual results to differ materially from those in the forward-looking statements, including timely submission and approval of anticipated regulatory filings; the successful initiation and completion of required Phase III studies; additional clinical results validating the use of adult autologous stem cells to treat heart failure; satisfaction of regulatory and other requirements; and actions of regulatory bodies and other governmental authorities.