Celyad : Transparency notification of TOLEFI SA (Article 14 of the Law of 2 May 2007)

Press Release

1 June 2018 6:01 pm CEST

Regulated information

Transparency notification of TOLEFI SA

(Article 14 of the Law of 2 May 2007)

Mont-Saint-Guibert, Belgium - Celyad (Euronext Brussels and Paris, and NASDAQ: CYAD) a clinical-stage biopharmaceutical company focused on the development of CAR-T cell therapies, today announced it received a transparency notification from Tolefi SA.

Pursuant to Belgian transparency legislation, Celyad received a transparency notification on 22 May 2018 from Tolefi SA, who notified that it holds 2,295,701 Celyad shares. This represents 19.2% of Celyad's currently outstanding 11,942,344 shares, and is a decrease compared to Tolefi SA's previous transparency notification of 17 February 2017. A global offering initiated by Celyad on 17 May 2018 and closed on 23 May 2018 resulted in a decrease below the 20% notification threshold of Celyad's voting rights.

The full transparency notice is available on the Celyad's website.

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About Celyad

Celyad is a clinical-stage biopharmaceutical company focused on the development of specialized CAR-T cell- based therapies. Celyad 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. Its lead oncology candidate, CYAD-01 (CAR-T NKG2D), has been evaluated in a single dose escalation Phase I clinical trial to assess the safety and clinical activity of multiple administrations of autologous CYAD-01 cells in seven refractory cancers including five solid tumors (colorectal, ovarian, bladder, triple-negative breast and pancreatic cancers) and two hematological tumors (acute myeloid leukemia and multiple myeloma). 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.

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Press Release

1 June 2018 6:01 pm CEST

Regulated information

For more information, please contact:

Celyad

Christian Homsy, CEO and Patrick Jeanmart CFO - T: +32(0) 10 39 41 00 -investors@celyad.com

Nicolas Van Hoecke, Director, Investor Relations & Communications - T: +32(0) 10 39 41 48 -nvanhoecke@celyad.com

For Belgium: Comfi

Gunther De Backer and Sabine Leclercq - T: +32 (0)2 290 90 90 -celyad@comfi.be

For France: NewCap

Pierre Laurent and Nicolas Mérigeau - T: + 33 (0)1 44 71 94 94 -celyad@newcap.eu

For the rest of Europe and the USA: Lifesci Advisor

Investor Relations: Daniel Ferry - T: +1 (617) 535 7746 -daniel@lifesciadvisors.com Public Relations: Allison Blum - T:+1 (646) 627 8383 -allison@lifescipublicrelations.com

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Forward-looking statements

In addition to historical facts or statements of current condition, this press release contains forward-looking statements, including statements about the potential safety, activity, efficacy and feasibility of CYAD-01 cell therapy and other product candidates, including current and planned preclinical studies and clinical trials and regulatory filings for Celyad's product candidates; the clinical and commercial potential of these product candidates and the adequacy of Celyad's financial resources; the strength of Celyad's intellectual property portfolio and plans related thereto; Celyad's expectations regarding its strategic collaborations and license agreements with third parties, including Novartis, Celdara Medical, and Dartmouth College, and the potential impact of such collaborations on Celyad's future financial condition, including anticipated milestones and royalties and the timing thereof; Celyad's expected cash burn, which reflect Celyad's current expectations and projections about future events; and the anticipating timing of Celyad's 2017 annual report, 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 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 risks associated with conducting clinical trials; the risk that safety, bioactivity, feasibility and/or efficacy demonstrated in earlier clinical trials or preclinical studies may not be replicated in subsequent trials or studies; risks associated with the timely submission and approval of anticipated regulatory filings; the successful initiation and completion of clinical trials, including its clinical trials for CYAD-01; risks associated with the successful manufacture of drug product for its clinical trials; risks associated with the satisfaction of regulatory and other requirements; risks associated with the actions of regulatory bodies and other governmental authorities; risks associated with obtaining, maintaining and protecting intellectual property, Celyad's ability to enforce its patents against infringers and defend its patent portfolio against challenges from third parties; risks associated with competition from others developing products for similar uses; risks associated with Celyad's ability to manage operating expenses; and risks associated with Celyad's ability to obtain additional funding to support its business activities and establish and maintain strategic business alliances and business initiatives. 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 April 6, 2018 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. 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.

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