PRESS RELEASE

Heidelberg Pharma Receives Milestone Payment from Partner Magenta for Dosing the First Patient with MGTA-117

Ladenburg, Germany, 10 March 2022 - Heidelberg Pharma AG (FSE: HPHA) today announced that its cooperation partner Magenta Therapeutics, Cambridge, MA, USA, (Magenta; NASDAQ: MGTA) has dosed the first patient with the development candidate MGTA-117 in a Phase I/II study. The achievement of this milestone triggered a milestone payment to Heidelberg Pharma.

MGTA-117 is an Antibody Amanitin Conjugate based on Heidelberg Pharma's proprietary ATAC^(R) technology and developed by Magenta. A dose escalation study will test the tolerability, pharmacokinetics, pharmacodynamics, and safety of MGTA-117 in patients with relapsed/refractory acute myeloid leukemia and myelodysplasia-excess blasts.

Prof. Andreas Pahl, CSO of Heidelberg Pharma AG, commented: "We congratulate Magenta for this great achievement, and we are very proud that following our own ATAC^(R) candidate HDP-101 another ATAC^(R) based on our technology has entered the clinical stage. We are convinced that our ATAC^(R) technology can provide highly effective and well-tolerated cancer therapies and we are looking forward to seeing initial data from the study."

About Heidelberg Pharma's proprietary ATAC^(R) technology
Antibody drug conjugates (ADCs) combine the high affinity and specificity of antibodies with the potency of cytotoxic small molecules for the treatment of cancer. Antibody Targeted Amanitin Conjugates (ATACs) are ADCs whose active ingredient is made up of amatoxin molecules. Amatoxins are small bicyclic peptides naturally occurring in the death cap mushroom. They inhibit mRNA transcription by binding to RNA polymerase II, a mechanism that is crucial for the survival of eukaryotic cells. In preclinical testing, ATACs have been shown to be highly efficacious, overcoming frequently encountered resistance mechanisms and combating even quiescent tumor cells.

About Heidelberg Pharma
Heidelberg Pharma AG is a biopharmaceutical company based in Ladenburg, Germany. Heidelberg Pharma is an oncology specialist and the first company to develop the toxin Amanitin into cancer therapies. The proprietary technology platform is being applied to develop the Company's proprietary therapeutic ATACs as well as in third-party collaborations. The proprietary lead candidate HDP-101 is a BCMA ATAC in clinical development for multiple myeloma. HDP-102, a CD37 ATAC for Non-Hodgkin's lymphoma and HDP-103, a PSMA ATAC for metastatic castration-resistant prostate cancer, are in preclinical testing.

Heidelberg Pharma AG is listed on the Frankfurt Stock Exchange: ISIN DE000A11QVV0 / WKN A11QVV / Symbol HPHA. More information is available at http://www.heidelberg-pharma.com/.

About Magenta Therapeutics
Magenta Therapeutics is a clinical-stage biotechnology company developing medicines to bring the curative power of stem cell transplant to more patients with blood cancers, genetic diseases and autoimmune diseases. Magenta is combining leadership in stem cell biology and biotherapeutics development with clinical and regulatory expertise, a unique business model and broad networks in the stem cell transplant community to revolutionize immune reset for more patients.

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