Heidelberg Pharma AG (FSE: HPHA), a clinical-stage biotech company specializing in Antibody Drug Conjugates (ADCs), announced today that it will present promising preclinical data for its Amanitin-based ADC HDP-103 at the American Association of Cancer Research (AACR) Annual Meeting 2026, taking place in San Diego, California, from 17 to 22 April.
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 be held on 21 April from 2:00 pm to 5:00 pm PDT (Poster number 5639). The abstract is available online at https://www.abstractsonline.com/pp8/#!/21436/presentation/5438.
HDP-103 targets PSMA, a well-established antigen in metastatic castration-resistant prostate cancer (mCRPC). The preclinical data demonstrate that HDP-103 binds specifically to human tissues and exhibits robust and durable antitumor activity in patient-derived xenograft (PDX) models representative of mCRPC. Notably, the efficacy was observed even in tumors with heterogeneous PSMA expression and those harboring a del(17p) mutation, a genetic alteration associated with poor prognosis and resistance to standard therapies.
In head-to-head comparisons, HDP-103 showed superior antitumor activity relative to an anti-PSMA Exatecan ADC. Safety assessments in non-human primates revealed that adverse events were restricted to known off-target effects of Amanitin-based ADCs, primarily affecting the liver and kidney. These effects were described as readily monitorable and transient. Additionally, pharmacokinetic data indicated stable ADC circulation, no evidence of drug accumulation, no sex differences, and dose-linear exposure.
The combination of potent antitumor efficacy, a favorable half-life, and a manageable safety profile yields a therapeutic index for HDP-103 that is well within the range of other ADCs approved or in development for solid tumors. "These data warrant further clinical development of HDP-103 as a novel treatment option for mCRPC," the company stated. The unique mode of action of Amanitin-based ADCs offers advantages over other modalities, particularly in patients with del(17p) who have high unmet medical need.
Heidelberg Pharma is the first company to develop cancer therapies using Amanitin, a toxin derived from the death cap mushroom. Its proprietary ATAC technology (Amanitin-based ADC) leverages the compound's ability to inhibit RNA polymerase II, a novel mechanism of action distinct from traditional chemotherapy and other ADCs. The company's lead candidate, HDP-101 (pamlectabart tismanitin), is in clinical development for multiple myeloma and has received Orphan Drug and Fast Track Designations from the U.S. FDA. Additional pipeline candidates include HDP-102 for Non-Hodgkin Lymphoma (clinical stage) and preclinical programs HDP-103 and HDP-104 for colorectal cancer. These preclinical programs are available for partnering.
Heidelberg Pharma is based in Ladenburg, Germany, and listed on the Frankfurt Stock Exchange (ISIN: DE000A11QVV0, Symbol: HPHA). More information is available at www.heidelberg-pharma.com. ATAC is a registered trademark of Heidelberg Pharma Research GmbH.
