Heidelberg Pharma Announces New Clinical Data on Lead ATAC Candidate HDP-101 to be Presented at International Myeloma Society Annual Meeting 2025

PRESS RELEASE

Heidelberg Pharma Announces New Clinical Data on Lead ATAC Candidate HDP-101 to be Presented at International Myeloma Society Annual Meeting 2025

Ladenburg, Germany, 4 September 2025 – Heidelberg Pharma AG (FSE: HPHA), a clinical stage company developing innovative Antibody Drug Conjugates (ADCs), today announces that new data from its Phase I/IIa clinical study with lead Amanitin-based ADC candidate, HDP-101, will be presented at the 22^st International Myeloma Society (IMS) Annual Meeting, being held in Toronto, Canada, on 17 to 20 September 2025.

HDP-101 is an Anti-BCMA antibody-Amanitin drug conjugate for the treatment of relapsed or refractory multiple myeloma, a bone marrow cancer with a high unmet medical need. Phase I of the trial is a dose escalation study to determine an optimal and safe dose level of HDP-101 in patients in preparation for Phase II clinical studies.

Professor Jonathan L. Kaufman, MD, David Bankes Glass Professor, Department of Hematology and Medical Oncology, Emory University, Atlanta, USA and clinical investigator of the study will present new findings from eight patient cohorts of the ongoing open-label, multicenter Phase I/IIa trial evaluating HDP-101 in multiple myeloma.

Details of the presentation are as follows:

Presentation title: The Anti-BCMA Antibody-Drug Conjugate HDP-101 with a Novel Amanitin Payload Shows Promising Data in Relapsed/Refractory Multiple Myeloma in a Phase 1/2a clinical trial as it advances into Cohort 7

The first seven patient cohorts and dose levels have been completed. Treatment with HDP-101 was well tolerated and the study has shown very encouraging results, including one patient from the fifth cohort in whom no tumor cells are detectable on a permanent basis. She had been treated with multiple other therapies and is since then being treated continuously with HDP-101 alone. In addition, several patients from different cohorts showed promising anti-tumor activity and objective improvements.

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 uses several compounds and has built up an ADC toolbox that overcomes tumor resistance via numerous pathways and addresses different types of cancer using various antibodies. The goal is to develop targeted and highly effective ADCs for the treatment of a variety of malignant hematologic and solid tumors.

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 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.

ITAC™, ETAC™ are pending trademark applications of Heidelberg Pharma Research GmbH.  

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