Why it matters: Amanitin, a deadly cyclic peptide toxin found in poisonous mushrooms like the death cap, is not new territory for Pahl. He spent years developing amanitin as a payload for antibody-drug conjugates (ADC) at Heidelberg Pharma, where it now forms the basis of the German biotech’s proprietary ATAC platform and its core business strategy.
- The two companies may now need to find a way to coexist. Heidelberg Pharma told European Biotechnology: “Simris has approached us regarding a technology license for using Heidelberg Pharma’s proprietary ADC technology based on the payload Amanitin,” but no licensing agreement has been announced so far.
The sudden pivot: When Pahl joined Simris’s subsidiary, Simris Bilogics, on July 15, the company still presented its proprietary microcystins — toxins derived from cyanobacteria — as the core of its ADC payload platform. Pahl was explicitly hired to advance that technology while helping shape future development programs.
- By its Aug. 12 half-year report, however, Pahl was already saying Simris would consider “non-cyanobacterial payloads” to accelerate its transformation into a fully fledged ADC company. On Sept. 8, 55 days after his appointment, Simris unveiled two amanitin programs and said its operations would now be organized around the amanitin platform.
How it works: SMR-101 is described as a B-cell-depleting amanitin ADC for blood cancers and autoimmune diseases. SMR-102 combines amanitin with a second, undisclosed payload for solid tumors. Simris has not disclosed their antibody targets, linker technologies or the origin of its amanitin payloads.
The IP question: Heidelberg Pharma has spent years building protection around its amanitin technology. Its 2025 annual report describes an extensive patent portfolio, including more than 20 additional international patent applications, protection around toxin-linker technology, synthetic building blocks needed to manufacture amanitin and site-specific ATAC conjugates in markets including Europe, the U.S. and China. The company says potential exclusivity for individual ATAC-based candidates could extend to 2045.
Yes, but: That does not mean Heidelberg Pharma owns every possible use of amanitin in an ADC. The scope of individual patents depends on targets, linkers, conjugation chemistry, payload structures and other claims.
- But there is another notable connection: Pahl himself is named as an inventor on multiple patent families assigned to Heidelberg Pharma. These include patents covering amatoxin-antibody conjugates and B-cell-specific amatoxin ADCs. One granted U.S. patent, for example, covers a CD37-targeting amatoxin conjugate for B-cell and lymphoma-associated diseases.
- Other Heidelberg Pharma patent filings involving Pahl cover amatoxin ADC applications in cancers and autoimmune diseases — territory that at least broadly resembles the description Simris has given for SMR-101.
Backstory: The move adds another twist to an already unusual management story at Heidelberg Pharma. Its supervisory board removed Pahl as CEO in November 2025 and replaced him with Dongzhou Jeffery Liu, then chief scientific officer and president of global development at Huadong Medicine. Liu had also been sitting on Heidelberg Pharma’s supervisory board.
- Huadong is also a major Heidelberg Pharma shareholder and has steadily expanded a collaboration that now encompasses licensing, clinical development and joint research around ADCs. The partners recently agreed to work on as many as six additional targets, further tightening a relationship that spans ownership, technology and management.
Questions remain: Heidelberg Pharma did not explicitly answer European Biotechnology’s questions about whether Pahl’s move creates a potential conflict of interest. European Biotechnology also contacted Simris about Heidelberg Pharma’s licensing comment, the provenance of its amanitin technology and Pahl’s previous involvement with Heidelberg Pharma’s IP. Simris had not responded by the time of publication.
What to watch: A licensing deal could turn what currently looks like Simris moving onto Heidelberg Pharma’s home turf into a new commercial relationship. Without one, the technical details of SMR-101 and SMR-102 — particularly their payloads, linkers and targets — will become important in understanding how independently Simris can build its new platform.
What’s next: There is also the question of money. Simris itself described the amanitin route as the more capital-intensive strategic option. It now plans to recruit six additional ADC specialists and take two programs toward the clinic within roughly 18 months, while continuing its microcystin work in parallel.
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