Heidelberg Pharma AG will present promising preclinical data for its Antibody Drug Conjugate HDP-103 targeting metastatic castration-resistant prostate cancer at the American Association of Cancer Research Annual Meeting 2026. The 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 during the Antibody-Drug Conjugates and Linker Engineering 4 session on April 21. 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 includes efficacy in tumors with heterogeneous PSMA expression and those harboring a del(17p) genetic alteration. In these challenging models, the Amanitin-based HDP-103 was superior to an anti-PSMA Exatecan ADC, highlighting the potential advantage of its unique mechanism of action.
Safety assessments in non-human primates revealed adverse events restricted to known off-target effects of Amanitin-based ADCs, primarily affecting the liver and kidney. These effects are described as transient and can be readily monitored. Pharmacokinetic data showed stable ADC levels in circulation, no evidence of drug accumulation, no differences between sexes, and dose-linearity, contributing to a favorable half-life profile.
The combination of potent anti-tumor efficacy 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 tumors. This profile supports further clinical development of HDP-103 as a novel treatment for mCRPC. The company's ATAC technology platform utilizes Amanitin, a compound derived from the green death cap mushroom, representing a new therapeutic modality in oncology. More information on the company is available at https://www.heidelberg-pharma.com.
The implications of this announcement are significant for the oncology field and patients with advanced prostate cancer. Metastatic castration-resistant prostate cancer remains a difficult-to-treat condition with limited options, particularly for patients with specific genetic profiles like del(17p), who represent a population with high unmet medical need. The presented data suggest HDP-103 could address this gap. The success of this candidate could validate Heidelberg Pharma's proprietary ATAC platform, which also has other candidates in development for multiple myeloma and non-Hodgkin lymphoma. For the biotechnology industry, positive data at a major conference like AACR often catalyzes partnership discussions and investment interest, potentially accelerating the drug's path to clinical trials and, ultimately, to patients.
