Heidelberg Pharma AG (FSE: HPHA), a clinical-stage biotechnology company specializing in Antibody Drug Conjugates (ADCs), announced today that it will present preclinical data for its lead candidate HDP-103 at the upcoming American Association for Cancer Research (AACR) Annual Meeting 2026, to be held in San Diego, California, from April 17 to 22. The poster presentation, scheduled for April 21, will highlight the efficacy and safety profile of HDP-103, a PSMA-targeting amanitin-based ADC designed to treat metastatic castration-resistant prostate cancer (mCRPC).
According to the company, HDP-103 demonstrated robust and durable antitumor activity in patient-derived xenograft (PDX) models representative of mCRPC, including tumors with heterogeneous PSMA expression and those harboring a deletion of chromosome 17p (del(17p)). In these difficult-to-treat models, HDP-103 showed superior efficacy compared to an anti-PSMA Exatecan ADC. The compound's unique mechanism of action, derived from the toxin amanitin found in the death cap mushroom, allows it to overcome resistance mechanisms that limit other therapies.
Heidelberg Pharma also reported that adverse events in non-human primates were restricted to known off-target effects of amanitin-based ADCs, primarily affecting the liver and kidney. These effects were described as transient and readily monitorable. Pharmacokinetic data indicated that HDP-103 serum levels demonstrate stability in circulation, no evidence of drug accumulation, no sex differences, and dose-linear exposure. The combination of potent anti-tumor efficacy, a favorable half-life, and manageable safety profile yields a therapeutic index (TI) comparable to other approved or in-development ADCs for solid tumors.
“These data support the further clinical development of HDP-103 as a novel treatment option for mCRPC, particularly for patients with del(17p) who have high unmet medical need,” the company stated. The poster, 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 be presented on April 21 from 2:00 pm to 5:00 pm PDT. The abstract is available online at this link.
Heidelberg Pharma is the first company to develop cancer therapies using amanitin, leveraging its ATAC technology platform. The company’s lead candidate HDP-101 is in clinical development for multiple myeloma and 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 have completed preclinical development and are available for partnering. More information is available at www.heidelberg-pharma.com.
