Publication of a Transparency Notification Received from Tolefi SA (Article 14§1 of the Law of 2 May 2007)

Regulatory News:

Celyad Oncology (Euronext: CYAD) (the “Company” or “Celyad Oncology”), today announced, in accordance with Article 14 of the Belgian Law of 2 May 2007 regarding the publication of major shareholdings in issuers whose securities are admitted to trading on a regulated market (the “Transparency Law”), that it received a transparency notification dated July 24, 2026, from Tolefi SA and related persons indicating that they have jointly crossed passively below the 10% threshold, holding 6,568,978 shares, or 8.77% of the voting rights of the Company as of July 16, 2026.

Content of the Notification:

• Reason of the notification:
  Passive crossing of threshold

• Notification by:
  Persons acting in concert

• Persons subject to the notification requirement:
  Tolefi SA, Chaussée de Waterloo 1589D, 1180 Brussels
  Serge Goblet
  Isabelle Thoumyre
  Jérôme Goblet
  Jean-Daniel Goblet

• Date on which the threshold is crossed:
  July 16, 2026

• Threshold that is crossed (in %):
  10

• Denominator:
  74,883,166

• Notified details:

A) Voting Rights	Previous notification	After the transaction
	# of voting rights	# of voting rights		% of voting rights
Holders of voting rights		Linked to the securities	Not linked to the securities	Linked to the securities	Not linked to the securities
Serge GOBLET	56,180	56,180	0	0.08%	0.00%
Isabelle THOUMYRE	7,300	7,300	0	0.01%	0.00%
Tolefi SA	6,504,864	6,504,864	0	8.69%	0.00%
Subtotal	6,568,344	6,568,344	0	8.77%	0.00%
Jérôme GOBLET	250	250	0	0.00%	0.00%
Jean-Daniel GOBLET	384	384	0	0.00%	0.00%
	TOTAL	6,568,978	0	8.77%	0.00%

B) Equivalent financial instruments	After the transaction
Holders of equivalent financial instruments	Type of financial instrument	Expiration date	Exercise period or date	# of voting rights that may be acquired if the instrument is exercised	% of voting rights	settlement
	TOTAL			0	0.00%

Total (A&B)	# of voting rights	% of voting rights
	6,568,978	8.77%

• Full chain of controlled undertakings through which the holding is effectively held:
  Tolefi SA is controlled by Mr. Serge Goblet and Mrs. Isabelle Thoumyre, according to articles 1:14-1.18 of the Code of companies and associations

Miscellaneous:

• The Press Release may be consulted on the website of Celyad Oncology:
  https://celyad.com/newsroom

• The notification can be consulted on the website of Celyad Oncology:
  https://celyad.com/investors/regulated-information/

• Contact person(s):
  Any transparency notification must be sent to our Company by email to the attention of Hannes Iserentant, General Manager: investors@celyad.com

About Celyad Oncology

Celyad Oncology is a biotechnology company focused primarily on unlocking the potential of its intellectual property particularly related to CAR-T technology platforms. The Company is headquartered in Mont-Saint-Guibert, Belgium. For more information, visit www.celyad.com.

Celyad Oncology Forward-Looking Statement

This press release may contain forward-looking statements, including, without limitation, statements regarding beliefs about and expectations for the Company’s cash runway, statements regarding the Company’s future fundraising plans, and statements regarding the continuation of the Company’s existence. The words “will,” “potential,” “continue,” “target,” “project,” “should,” “believe” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Any forward-looking statements in this press release are based on management’s current expectations and beliefs and are subject to a number of known and unknown risks, uncertainties and important factors which might cause actual events, results, financial condition, performance or achievements of Celyad Oncology to differ materially from those expressed or implied by such forward-looking statements. Such risks and uncertainties include, without limitation, risks related to the material uncertainty about the Company’s ability to continue as a going concern; the Company’s ability to realize the expected benefits of its strategic focus; the Company’s ability to develop its intellectual property (“IP”) assets and enter into partnerships with outside parties; the Company’s ability to enforce its patents and other IP rights; the possibility that the Company may infringe on the patents or IP rights of others and be required to defend against patent or other IP rights suits; the possibility that the Company may not successfully defend itself against claims of patent infringement or other IP rights suits, which could result in substantial claims for damages against the Company; the possibility that the Company may become involved in lawsuits to protect or enforce its patents, which could be expensive, time-consuming, and unsuccessful; the Company’s ability to protect its IP rights throughout the world; the potential for patents held by the Company to be found invalid or unenforceable; and other risks identified in the latest Annual Report of Celyad Oncology. These forward-looking statements speak only as of the date of publication of this press release and Celyad Oncology’s actual results may differ materially from those expressed or implied by these forward-looking statements. Celyad Oncology expressly disclaims any obligation to update any such forward-looking statements in this press release 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.

View source version on businesswire.com: https://www.businesswire.com/news/home/20260728467360/en/

Investor & Media: Hannes Iserentant, General Manager investors@celyad.com