PRESS RELEASE

Heidelberg Pharma and Huadong Medicine Sign Additional Collaboration Agreement to Jointly Develop New Antibody Drug Conjugates

• Existing partnership will be broadened through joint research and development of new Antibody Drug Conjugates (ADCs) involving up to six targets
• Heidelberg Pharma’s pipeline will be expanded with new product candidates
• Both parties to contribute their strength and proprietary technologies, including Heidelberg Pharma’s ADC technology

Ladenburg, Germany, 28 August 2026 - Heidelberg Pharma AG (FSE: HPHA), a clinical-stage biotech company developing innovative Antibody Drug Conjugates (ADCs), today announced that its wholly-owned subsidiary, Heidelberg Pharma Research GmbH, has signed a new collaboration agreement with its strategic partner Huadong Medicine Co., Ltd., Hangzhou, China. Huadong Medicine is the second-largest shareholder of Heidelberg Pharma AG.

Under the agreement, the parties will deepen their collaboration in research and early-stage development by combining and leveraging their complementary technologies, expertise, and resources. This includes Heidelberg Pharma’s proprietary ATAC^® technology platform and other novel toxin payloads, together with Huadong’s state-of-the-art R&D capabilities. The partnership aims to create synergies and drive the development of innovative next-generation ADCs, including bispecific and multispecific ADCs.

The new ADCs may incorporate proprietary antibodies or technologies from Huadong Medicine and may carry dual payloads. This combination is designed to improve the targeting precision and safety of the drugs, while enhancing biological efficacy and clinical benefits, thereby offering potentially transformative therapeutic options for patients with relapsed/refractory diseases. The agreement foresees that ownership of the resulting development candidates will be allocated between the partners, taking into account their respective contributions.

Dr. Dongzhou Jeffery Liu, Chief Executive Officer of Heidelberg Pharma, commented: “The new research and development agreement between Heidelberg Pharma and Huadong Medicine will take this established strategic partnership to the next level. We aim to set new standards by combining both companies’ strengths and technologies to develop additional innovative conjugation drug candidates for cancer treatment. This will enable us to initiate a steady stream of research projects and secure new drug candidates for Heidelberg Pharma’s product pipeline. We look forward to a strong collaboration focused on shaping the future of therapeutic options for patients.”

About Heidelberg Pharma

Heidelberg Pharma is the first company to develop cancer therapies using Amanitin, a compound derived from the green death cap mushroom. The biological mechanism of action of the toxin represents a new therapeutic modality and is used as a compound in the Amanitin-based ADC technology, the so-called ATAC technology.

Lead candidate HDP-101 (INN: pamlectabart tismanitin) is a BCMA ATAC in clinical development for multiple myeloma. The candidate has been granted Orphan Drug Designation and Fast Track Designation from the FDA. A second ATAC candidate, HDP-102, is in the clinical development stage in Non-Hodgkin Lymphoma. HDP-103 against metastatic castration-resistant prostate cancer and HDP-104 targeting gastrointestinal tumors such as colorectal cancer have completed preclinical development. These programs are available for partnering.

The company is based in Ladenburg, Germany, and is listed on the Frankfurt Stock Exchange: ISIN DE000A11QVV0 / WKN A11QVV / Symbol HPHA. More information is available at www.heidelberg-pharma.com.

ATAC^® is a registered trademark of Heidelberg Pharma Research GmbH.

This communication contains certain forward-looking statements relating to the Company's business, which can be identified by the use of forward-looking terminology such as "estimates", "believes", "expects", "may", "will", "should", "future", "potential" or similar expressions or by a general discussion of the Company's strategy, plans or intentions. Such forward-looking statements involve known and unknown risks, uncertainties and other factors, which may cause our actual results of operations, financial condition, performance, achievements, or industry results, to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements. Given these uncertainties, prospective investors and partners are cautioned not to place undue reliance on such forward-looking statements. We disclaim any obligation to update any such forward-looking statements to reflect future events or developments.