PRESS RELEASE

Heidelberg Pharma to Present New Clinical Data of Lead ADC Candidate HDP-101 at the World ADC Congress 2025 and to Host Webinar

• Objective responses and promising anti-tumor activity observed in several patients across multiple cohorts in the ongoing Phase I/IIa clinical trial
• Data reinforces the therapeutic potential and safety profile of HDP-101 in relapsed or refractory multiple myeloma.
• R&D Webinar to be hosted on 11 November 2025 at 05:00 pm CET (08:00 am PST)

Ladenburg, Germany, 3 November 2025 – Heidelberg Pharma AG (FSE: HPHA), a clinical-stage developer of innovative Antibody Drug Conjugates (ADCs), today announced the presentation of new clinical data from its ongoing Phase I/IIa clinical study evaluating its lead Amanitin-based ADC candidate, HDP-101 (INN: pamlectabart tismanitin), at the 16^th Annual World ADC Congress, taking place in San Diego, California, from 3 to 6 November 2025.

HDP-101 (INN: pamlectabart tismanitin) is an anti-BCMA antibody-drug conjugate being investigated for the treatment of relapsed or refractory multiple myeloma, a bone marrow cancer with a high unmet medical need. Phase I of the ongoing study is a dose-escalation trial designed to determine the optimal and safe dose level of HDP-101 in preparation for subsequent Phase II clinical evaluation.

Professor Andreas Pahl, Chief Executive Officer of Heidelberg Pharma, will present an update from patient cohort 8 including efficacy data of the open-label, multicenter Phase I/IIa study evaluating HDP-101 in patients with relapsed or refractory multiple myeloma.

Details of the presentation at 16^th Annual World ADC Congress:

Presentation title: From Bench to Breakthrough: The Evolution of Amanitin ADCs – Insights from HDP-101 Phase I/II & the Future of Payload Differentiation

R&D Webinar to take place with Key Opinion Leader

Following the World ADC Congress, Heidelberg Pharma will host an R&D webinar on 11 November 2025 at 05:00 pm CET (11:00 am EST; 08:00 am PST), for investors, analysts, and media.

The R&D webinar will feature presentations by the Heidelberg Pharma management team, alongside Key Opinion Leader (KOL) Professor Marc-Steffen Raab, Head of the Myeloma Center at the University Hospital Heidelberg and clinical investigator of the study.

Webinar participants will have the opportunity to submit questions in advance of the webinar or ask questions live during the event.

For further information on the R&D webinar, or to register your attendance, please use the link below:

https://us06web.zoom.us/webinar/register/WN_AG_mESPaT-aSsm8_O2DllA

A recording of the R&D webinar will be accessible via the press & investor section of the Company website after the event.

About Heidelberg Pharma

Heidelberg Pharma is a biopharmaceutical company working on a new treatment approach in oncology and developing novel drugs based on its ADC technologies for the targeted and highly effective treatment of cancer. ADCs are antibody-drug conjugates that combine the specificity of antibodies with the efficacy of toxins to fight cancer. Selected antibodies are loaded with cytotoxic compounds, the so-called payloads, that are transported into diseased cells. Inside the cells, the toxins then unleash their effect and kill the diseased cells.

Heidelberg Pharma is the first company to use the compound Amanitin from the green death cap mushroom in cancer therapy. 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.

The lead candidate HDP-101 is a BCMA ATAC in clinical development for multiple myeloma. A second ATAC candidate, HDP-102, has recently started clinical development in Non-Hodgkin Lymphoma and is currently on a temporary hold. HDP-103 against metastatic castration-resistant prostate cancer and HDP-104 targeting gastrointestinal tumors such as colorectal cancer have completed preclinical development. Heidelberg Pharma is open 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.