BioSenic SA

Major Shareholding Notification • Jan 15, 2024

PRESS RELEASE – REGULATED INFORMATION 15/01/2024

Transparency notifications received from François Rieger

Article 14 of the Law of 2 May 2007 on disclosure of major holdings

Mont-Saint-Guibert, Belgium, January 15, 2024, 7am CEST – BIOSENIC (Euronext Brussels and Paris: BIOS), the clinical-stage company specializing in serious autoimmune and inflammatory diseases and cell therapy, today announces that it has received transparency notifications from François Rieger that can be consulted on the website of BioSenic, under the heading "Major shareholders & transparency notices".

The transparency notification indicates that the shareholdings held by François Rieger have crossed below the threshold of 15% as a result of a share lending on 10 January 2024.

The notification received from François Rieger dated 12 January 2024 contains the following information:

• Reason for the notification:
  • Passive crossing of a threshold
• Notification by: A person that notifies alone

• Person subject to the notification requirement: François Rieger

• Transferor of voting rights: François Rieger

• Transaction date: 10 January 2024
• Threshold that is crossed: 15%
• Denominator: 163 181 474
• Notified details:

Voting rights	Previous notification	After the transaction
Holders of voting rights	# of voting rights	# of voting rights	% of voting rights
François Rieger	26 589 361	18 589 361	11.39%
Total voting rights		18 589 361	11.39%

About BioSenic

BioSenic is a biotech company specializing in the development of clinical assets issued from: (i) the arsenic trioxide (ATO) platform (with key target indications including Graft-versus-Host Disease (GvHD), systemic lupus erythematosus (SLE) and systemic sclerosis (SSc) and (ii), the development of innovative products to meet unmet needs in immune and autoimmune diseases. Following a reverse merger in October 2022, BioSenic combined its strategic positioning and key strengths to develop, separately and in combination, an entirely new arsenal of various anti-inflammatory and antiautoimmune formulations using the immunomodulatory properties of ATO/oral ATO (OATO) with its innovative cell therapy platform and strong IP for tissue repair protection.

BioSenic is based in the Louvain-la-Neuve Science Park in Mont-Saint-Guibert, Belgium. Further information is available at http://www.biosenic.com.

About BioSenic technology platforms

PRESS RELEASE – REGULATED INFORMATION 15/01/2024

• 1) The ATO platform has immunomodulatory properties with fundamental effects on the activated cells of the immune system. One direct application is its use in onco-immunology to treat GvHD (Graft-versus-Host Disease) in its chronic, established stage. cGvHD is one of the most common and clinically significant complications affecting long-term survival of allogeneic hematopoietic stem cell transplantation (allo-HSCT). BioSenic has been successful in a phase 2 trial with its intravenous formulation, which has orphan drug designation status by FDA and EMA. The company is heading towards an international phase 3 confirmatory study, with its new, IP-protected, OATO formulation. Another selected target is moderate-to-severe forms of systemic lupus erythematosus (SLE), using the same oral formulation. ATO has shown good safety and significant clinical efficacy on several affected organs (skin, mucosae and the gastrointestinal tract) in an early phase 2a study. Systemic sclerosis is also part of the clinical pipeline of BioSenic. This serious chronic disease badly affects skin, lungs or vascularization, and has no current effective treatment. Preclinical studies on pertinent animal models are positive, giving good grounds to launch a phase 2 clinical protocol.
• 2) ALLOB, an allogeneic cell therapy platform made of differentiated bone marrow sourced Mesenchymal Stromal Cells (MSCs), which can be stored at the point of use in hospitals. ALLOB represents a unique and proprietary approach to organ repair and specifically to bone regeneration, by turning undifferentiated stromal cells from healthy donors into bone-forming cells on the site of injury. After phase 2 clinical results with contradictory conclusions, BioSenic is now focusing on determining the best time to optimise the efficacy of ALLOB (between early or late treatment).

The company is currently focusing its present R&D and clinical activities on a selective, accelerated development of its autoimmune (ATO/OATO) platform.

For further information, please contact:

BioSenic SA

François Rieger, PhD, Chief Executive Officer Tel: +33 (0)671 73 31 59 investorrelations@biosenic.com

International Media Enquiries: IB Communications Neil Hunter / Michelle Boxall Tel: +44 (0)20 8943 4685 neil.hunter@ibcomms.agency / michelle@ibcomms.agency

For French Investor Enquiries: Seitosei ● Actifin Ghislaine Gasparetto Tel: +33 (0)1 56 88 11 22 ggasparetto@actifin.fr

Certain statements, beliefs and opinions in this press release are forward-looking, which reflect the company or, as appropriate, the company directors' current expectations and projections about future events. By their nature, forward-looking statements involve a number of 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. A multitude of factors including, but not limited to, changes in demand, competition and technology, can cause actual events, performance or results to differ significantly from any anticipated development. Forward looking statements contained in this press release regarding past trends or activities should not be taken as a representation that such trends or activities will continue in the future. As a result, the company expressly disclaims any obligation or undertaking to release any update or revisions to any forward-looking statements in this press release as a result of any change in expectations or any change in events, conditions, assumptions or circumstances on which these forward-looking statements are based. Neither the company nor its advisers or representatives nor any of its subsidiary undertakings or any such person's officers or employees guarantees that the assumptions underlying such forward-looking statements are free from errors nor does either accept any responsibility for the future accuracy of the forward-looking statements contained in this press release or the actual occurrence of the forecasted developments. You should not place undue reliance on forward-looking statements, which speak only as of the date of this press release.