European patent granted for amatoxin conjugates for tumor therapy

The patent covers the crosslinking of certain carrier molecules, for example, antibodies, via specific binding sites to amatoxins.

The patent is based on a patent application and named "Amatoxin armed therapeutic cell surface binding components designed for tumor therapy". The application was submitted by Professor Heinz Faulstich and employees of the German Cancer Research Centre (DKFZ). Heidelberg Pharma exclusively in-licensed the patent in December 2009.

The subject matter of the patent is the crosslinking of certain carrier molecules, for example, antibodies, via specific binding sites to amatoxins. Amatoxins are natural poisons occurring in, for example, the death cap mushroom (Amanita phalloides). To the company's knowledge, Heidelberg Pharma is the first company worldwide to work with the corresponding toxin amanitin to develop Antibody Targeted Amanitin Conjugates (ATACs) for the use in cancer therapy.

Amanitin is known in oncology for its unique mode of action: the inhibition of RNA polymerase II, which leads the cells to programmed cell death (apoptosis) independent from cell division. This offers the opportunity to treat therapy-resistant tumors and kill quiescent tumor cells, which could result in significant clinical progress.

The chemical linkage to natural amanitin is only possible at certain positions without loss of efficacy of the molecule. The granted European patent protects the use of certain positions for the ATAC technology which are chemically easy to access, and which maintain the biologic function of the Amanitin.

Prof Andreas Pahl, Chief Scientific Officer of Heidelberg Pharma AG, commented: "We are delighted that, following the US patent, also the European patent has been granted to protect certain binding sites at our toxin amanitin. Since these binding sites at amanitin are protected independently of the structures linked to them, these patents offer strong protection of the natural substance Amanitin for use in ADC technology and protect our unique ATAC technology."