Heidelberg Pharma AG will present promising preclinical data for its Amanitin-based antibody-drug conjugate HDP-103 targeting metastatic castration-resistant prostate cancer at the American Association of Cancer Research Annual Meeting 2026. The poster presentation, titled "HDP-103, a PSMA targeting amanitin-based ADC, is efficacious even in difficult to treat patient derived xenograft models with heterogenous PSMA expression," will occur on April 21 during the Antibody-Drug Conjugates and Linker Engineering session. The abstract is available at https://www.abstractsonline.com/pp8/#!/21436/presentation/5438.
The data demonstrate that HDP-103 shows target-specific binding in human tissues and exhibits robust, durable antitumor activity in patient-derived xenograft models representative of mCRPC. This efficacy extends to tumors with heterogeneous PSMA expression and those harboring a del(17p) genetic mutation. In these models, the Amanitin-based HDP-103 proved superior to an anti-PSMA Exatecan ADC. The company reports that adverse events in non-human primates were restricted to known off-target effects of Amanitin-based ADCs, primarily affecting the liver and kidney, effects described as transient and readily monitorable.
HDP-103 serum levels demonstrated stability in circulation, with no evidence of drug accumulation, no differences between sexes, and dose-linearity. The combination of potent anti-tumor efficacy, a favorable half-life, and a manageable safety profile results in a therapeutic index for HDP-103 that falls within the range of other ADCs approved or in development for solid tumor indications. These collective findings support the further clinical development of HDP-103 as a novel treatment option for mCRPC.
The significance for the biotechnology and oncology sectors lies in HDP-103's unique mode of action, which the company states provides advantages over other treatment modalities in use or development for mCRPC. This is particularly relevant for patients with the del(17p) mutation, who represent a population with a high unmet medical need. The development leverages Heidelberg Pharma's proprietary ATAC technology platform, which utilizes Amanitin, a compound derived from the green death cap mushroom, representing a new therapeutic modality in oncology. The company's lead ATAC candidate, HDP-101, is already in clinical development for multiple myeloma with FDA Orphan Drug and Fast Track designations. More information on the company is available at https://www.heidelberg-pharma.com.
For business and technology leaders, the presentation at a premier conference like AACR signals maturation of a novel platform technology. The data suggesting efficacy in genetically complex and heterogeneous tumors could position Heidelberg Pharma's ATAC platform as a valuable asset in the competitive ADC landscape, potentially attracting partnership interest for its later-stage programs. The advancement of HDP-103 addresses a critical challenge in oncology: treating cancers that have become resistant to standard therapies and harbor difficult genetic profiles, indicating a pathway toward more personalized and effective cancer treatments.
