ONCOSEM ONKOLOJİK SİSTEMLER SANAYİ VE TİCARET A.Ş. Özel Durum Açıklaması (Genel) 21 Eylül 2026

Within the scope of the regulations introduced by the Capital Markets Board of Türkiye ("CMB") concerning the portfolio structures of investment funds and capital market instruments, it has been deemed necessary to inform the public regarding the current positions of investment funds in our Company's shares.

Upon reviewing the latest fund portfolio information publicly disclosed by portfolio management companies through the Public Disclosure Platform ("KAP") and the Turkish Electronic Fund Trading Platform ("TEFAS"), it is observed that, as of the current date, there is no investment fund holding shares of Oncosem Onkolojik Sistemler Sanayi ve Ticaret A.Ş. representing more than 3% of our Company's share capital.

Accordingly, as of the current date, there is no investment fund position exceeding the 3% threshold in terms of investment funds' ownership interest in our Company's share capital.

Our Company closely monitors the regulations introduced by the CMB regarding the portfolio structures and risk management of investment funds and the sound and reliable functioning of the capital markets, and conducts the necessary assessments within the framework of the applicable legislation.

Respectfully submitted to the public.

The English translation of this disclosure is attached hereto. In case of any discrepancy between the Turkish and English versions, the Turkish version shall prevail.