Clickable Microcystins as payloads in Antibody-Drug Conjugates

Freshwater cyanobacteria like Microcystis and Planktothrix often produce Microcystins (MCs). These well- studied cyanotoxins are nonribosomal cyclic heptapeptides and known for their inhibition of the eukaryotic serine/threonine protein phosphatases 1 and 2a with IC₅₀ values in the pico- to nanomolar concentration range. Unlike many other cytotoxic agents that enter cells by passive diffusion, MCs are dependent on an active uptake via organic anion transporting polypeptides 1B1 and 1B3, which are expressed especially by liver cells. The transportability strongly depends on the structure of the MCs and can dramatically differ by the exchange of one single amino acid in the core structure.

Because of the high potency, the yet unexploited mode-of-action of MCs, the unlikely resistance development, and the prospect of lower side effects compared to known payloads of antibody-drug conjugates (ADCs), we strive to develop MC derivatives with optimized properties that can be used as payloads for ADCs. Here, we present the semi-synthesis of MC analogs bearing different properties and their in vitro characterization. Easily derivatizable, “clickable” MCs were produced in distinct Microcystis sp. strains by precursor-directed biosynthesis, followed by extraction of biomass and isolation of these unnatural MCs by chromatographic methods. The obtained MCs were modified with a library of small molecules with different properties using “click chemistry”, and the structures of the derivatives were confirmed by HRMS2. Both cell viability studies as well as phosphatase inhibition assays have been performed to study structure-activity and structure-transportability relationships of the compounds.

 

MissingLinkText

Conflict of Interest

The authors declare no conflict of interest.

Publikationsverlauf

Artikel online veröffentlicht:
16. November 2023