Heidelberg Pharma AG, a clinical-stage biotechnology company focused on Antibody Drug Conjugates (ADCs), announced it will present promising preclinical data for its lead candidate HDP-103 at the American Association for Cancer Research (AACR) Annual Meeting 2026, scheduled for April 17-22 in San Diego, California. The data, to be presented in a poster session on April 21, highlight the efficacy of HDP-103 in patient-derived xenograft (PDX) models of metastatic castration-resistant prostate cancer (mCRPC), including those with heterogeneous PSMA expression and tumors harboring the del(17p) genetic alteration.
HDP-103 is a PSMA-targeting ADC utilizing Heidelberg Pharma's proprietary Amanitin-based ATAC technology. Amanitin, derived from the death cap mushroom, inhibits RNA polymerase II, offering a unique mechanism of action distinct from traditional chemotherapies. According to the company's press release, the preclinical data demonstrate that HDP-103 exhibits target-specific binding in human tissues and robust, durable antitumor activity in PDX models. Notably, HDP-103 was superior to an anti-PSMA Exatecan ADC in these models, suggesting a potential advantage over other ADC modalities.
The safety profile of HDP-103 was evaluated in non-human primates, where 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. Pharmacokinetic analysis showed stable ADC serum levels, no evidence of drug accumulation, no sex differences, and dose-linear exposure. The company stated that the combination of potent anti-tumor efficacy, favorable half-life, and manageable safety profile results in a comfortable therapeutic index (TI) for HDP-103, comparable to other approved or investigational ADCs for solid tumors.
Heidelberg Pharma emphasized that HDP-103's unique mode of action could provide advantages over existing treatments for mCRPC, particularly in patients with del(17p) who have high unmet medical needs. The company plans to advance HDP-103 into clinical development as a novel treatment option for mCRPC. The AACR presentation will include detailed data on the efficacy and safety of HDP-103, and the abstract is available online at AACR abstract page.
Heidelberg Pharma is the first company to develop cancer therapies using Amanitin, and its ATAC technology platform has produced several candidates, including HDP-101 for multiple myeloma, which has received FDA Orphan Drug and Fast Track designations. HDP-102 is in clinical development for non-Hodgkin lymphoma, while HDP-103 and HDP-104 (targeting gastrointestinal tumors) have completed preclinical development and are available for partnering. The company is based in Ladenburg, Germany, and listed on the Frankfurt Stock Exchange. More information can be found at Heidelberg Pharma website.
The AACR Annual Meeting 2026 will bring together researchers from around the world to discuss the latest advances in cancer research, and Heidelberg Pharma's presentation underscores the potential of Amanitin-based ADCs to address challenging solid tumors like mCRPC.
