Heidelberg Pharma AG (FSE: HPHA), a clinical-stage biotech company developing innovative Antibody Drug Conjugates (ADCs), announced today that it will present promising preclinical data from its Amanitin-based ADC HDP-103 at the American Association of Cancer Research (AACR) Annual Meeting 2026 in San Diego, California, from 17 to 22 April. The data, to be presented in a poster session on 21 April, highlight the potential of HDP-103 for treating metastatic castration‑resistant prostate cancer (mCRPC).
HDP-103 targets PSMA, a well-established antigen in prostate cancer. According to the company, the drug demonstrates target-specific binding in human tissues and robust, durable antitumor activity in patient-derived xenograft (PDX) models representative of mCRPC. Notably, efficacy was observed even in tumors with heterogeneous PSMA expression and those harboring a del(17p) genetic alteration, both of which are challenging to treat and represent high unmet medical needs. In these models, HDP-103 was superior to an anti-PSMA Exatecan ADC, a benchmark for the class.
The safety profile of HDP-103 was evaluated in non-human primates. Adverse events were restricted to known off-target effects of Amanitin-based ADCs, primarily in the liver and kidney. These effects were described as transient and readily monitorable. Additionally, HDP-103 serum levels demonstrated stability of the ADC in circulation, no evidence of drug accumulation, no differences between sexes, and dose-linearity. The combination of potent anti-tumor efficacy with a favorable half-life and manageable safety profile results in a therapeutic index (TI) that the company says is well within the range of other approved or development-stage ADCs for solid tumors.
Heidelberg Pharma is the first company to develop cancer therapies using Amanitin, a toxin derived from the green death cap mushroom. The company's ATAC technology leverages this unique mode of action, which offers advantages over other treatment modalities for mCRPC, especially in patients with del(17p). The lead candidate HDP-101 (pamlectabart tismanitin) is in clinical development for multiple myeloma and has received FDA Orphan Drug and Fast Track designations. Additional candidates include HDP-102 for Non-Hodgkin Lymphoma and preclinical programs HDP-103 and HDP-104 for gastrointestinal tumors.
Full details of the AACR presentation are available in the abstract (poster number 5639) at the AACR online portal. More information about Heidelberg Pharma is available at www.heidelberg-pharma.com.
