A new supply contract.

Dong-A Socio Holdings / Conclusion of Single Sales and Supply Contract / (2026.09.18)

Conclusion of Single Sales and Supply Contract Major Management Matter Report of ST Pharm Co., Ltd., a subsidiary

1. Sales and Supply Contract Details Supply of active pharmaceutical ingredient for oligonucleotide therapeutic agent

2. Contract Details Conditional Contract Status: Not applicable Confirmed Contract Amount: 91,332,435,000 won Conditional Contract Amount: - Total Contract Amount (KRW): 91,332,435,000 Most Recent Sales Revenue (KRW): 331,681,282,447 Percentage of Sales Revenue: 27.54%

3. Contracting Party Global Biotech company based in the United States Most Recent Sales Revenue (KRW): - Principal Business: New drug development Relationship with Company: - Performance of Similar Contracts with Company over Past 3 Years: Applicable

4. Sales and Supply Region United States, Europe, etc.

5. Contract Period Start Date: 2026-09-18 End Date: 2027-11-22

6. Principal Contract Terms Contract Deposit/Advance Payment: None Payment Terms, etc.: -

7. Sales and Supply Method In-house Production: Applicable Outsourced Production: Not applicable Other: -

8. Contract (Order) Date 2026-09-18

9. Disclosure Deferral Deferral Period: 2027-11-22 Reason for Deferral: Request from contracting party regarding confidentiality of transaction

10. Other Matters for Reference in Investment Decisions The foreign currency amount of the above contract is USD 66,135,000, and the Korean won amount is calculated by applying the final exchange rate of 1,381.0 KRW/USD announced by KEB Hana Bank on the previous business day (2026.09.17). The most recent sales revenue above is based on consolidated sales for 2025. The start date and contract (order) date of the above contract period are the dates on which the purchase order was received from the contracting party. The contract amount and contract period above may be subject to change at the request of the contracting party, etc.

※ Related Disclosures: -