Heidelberg Pharma to Present New Clinical Data on its ATAC Candidates at the ASH Annual Meeting 2026

PRESS RELEASE

Heidelberg Pharma to Present New Clinical Data on its ATAC Candidates at the ASH Annual Meeting 2026

Ladenburg, Germany, 4 November 2026 – Heidelberg Pharma AG (FSE: HPHA), a clinical stage company developing innovative Antibody Drug Conjugates (ADCs), will present new data from its Phase I/IIa clinical study with its lead Amanitin-based ADC candidate, pamlectabart tismanitin (HDP-101), in an oral presentation, as well as data from its second clinical candidate, HDP-102, during the poster abstract session of the 68^th Annual Meeting of the American Society of Hematology (ASH), being held in New Orleans, USA, from 12 to 15 December 2026.

Details of the oral presentation (HDP-101):

Presentation title: First-in-human phase 1/2a study of pamlectabart tismanitin (HDP-101), an amanitin-based BCMA-targeting antibody-drug conjugate (ADC): Recommended phase 2 dose (RP2D) selection and preliminary antitumor activity in relapsed/refractory multiple myeloma (RRMM)

Pamlectabart tismanitin is an anti-BCMA antibody-Amanitin drug conjugate for the treatment of relapsed or refractory multiple myeloma (RRMM), a bone marrow cancer with a high unmet medical need. Phase I of the trial was a dose-escalation study to determine a dose level of the candidate for the Phase IIa expansion part of the study.

The Phase I part of the study included ten patient cohorts and was completed in April 2026, and the recommended dose for the Phase IIa expansion part (Recommended Phase 2 Dose; RP2D) was determined. The Phase IIa is progressing as planned.

Pamlectabart tismanitin demonstrated consistent clinical activity with a favorable safety profile in heavily pretreated RRMM patients supporting the potential of the candidate as a novel payload BCMA-targeted ADC therapy.

Details of the poster presentation (HDP-102):

Presentation title: HDP-102, a first-in-class CD37-targeted amanitin-based antibody-drug conjugate, demonstrates translational activity, favorable early safety and efficacy in relapsed/refractory (R/R) B-cell malignancies

HDP-102 is an ADC targeting CD37, which is overexpressed on B-cell lymphoma cells. Preclinical studies have shown excellent anti-tumor efficacy in in vivo studies as well as good tolerability. HDP-102 is intended to be developed for specific indications of non-Hodgkin lymphoma.

In 2025, Heidelberg Pharma announced the dosing of the first patient with HDP-102. Three patients were treated with 40 µg/kg in the first cohort. The treatment was well tolerated, and initial signs of biological activity have been observed already at the very low dose. Two patients showed stabilization of the disease with regression and reduction of lymph nodes. The safety committee recommended increasing the dose of HDP-102 to 65 µg/kg in cohort 2.

In line with Heidelberg Pharma’s strategic decision from September 2025 to discontinue the study, the Company is exploring partnership opportunities to support the continuation of the program.

About Heidelberg Pharma

Heidelberg Pharma is the first company to develop cancer therapies using Amanitin, a compound derived from the green death cap mushroom. The biological mechanism of action of the toxin represents a new therapeutic modality and is used as a compound in the Amanitin-based ADC technology, the so-called ATAC technology.

Lead candidate HDP-101 (INN: pamlectabart tismanitin) is a BCMA ATAC in clinical development for multiple myeloma. The candidate has been granted Orphan Drug Designation and Fast Track Designation from the FDA. A second ATAC candidate, HDP-102 is in clinical development stage in Non-Hodgkin Lymphoma. HDP-103 against metastatic castration-resistant prostate cancer and HDP-104 targeting gastrointestinal tumors such as colorectal cancer have completed preclinical development. These programs are available for partnering.

The company is based in Ladenburg, Germany, and is listed on the Frankfurt Stock Exchange: ISIN DE000A11QVV0 / WKN A11QVV / Symbol HPHA. More information is available at http://www.heidelberg-pharma.com/.

ATAC^® is a registered trademark of Heidelberg Pharma Research GmbH.

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