Vinylphosphonites for staudinger-induced chemoselective peptide cyclization and functionalization

In this paper, we introduce vinylphosphonites for chemoselective Staudinger-phosphonite reactions (SPhR) with azides to form vinylphosphonamidates for the subsequent modification of cysteine residues in peptides and proteins. An electron-rich alkene is turned into an electron-deficient vinylphosphonamidate, thereby inducing electrophilic reactivity for a following thiol addition. We show that by varying the phosphonamidate ester substituent we can fine-tune the reactivity of the thiol addition and even control the functional properties of the final conjugate. Furthermore, we observed a drastic increase in thiol addition efficiency when the SPhR is carried out in the presence of a thiol substrate in a one-pot reaction. Hence, we utilize vinylphosphonites for the chemoselective intramolecular cyclization of peptides carrying an azide-containing amino acid and a cysteine in high yields. Our concept was demonstrated for the stapling of a cell-permeable peptidic inhibitor for protein–protein interaction (PPI) between BCL9 and beta-catenin, which is known to create a transcription factor complex playing a role in embryonic development and cancer origin, and for macrocyclization of cell-penetrating peptides (CPPs) to enhance the cellular uptake of proteins

Small molecules targeting human N-acetylmannosamine kinase

N-acetylmannosamine kinase (MNK) plays a key role in the biosynthesis of sialic acids and glycosylation of proteins. Sialylated glycoconjugates affect a large number of biological processes, including immune modulation and cancer transformation. In search of effective inhibitors of MNK we applied high-throughput screening of drug-like small molecules. By applying different orthogonal assays for their validation we identified four potential MNK-specific inhibitors with IC(50) values in the low-micromolar range. Molecular modelling of the inhibitors into the active site of MNK supports their binding to the sugar or the ATP-binding pocket of the enzyme or both. These compounds are promising for downregulation of the sialic acid content of glycoconjugates and for studying the functional contribution of sialic acids to disease development

Targeting FLT3 by new-generation antibody-drug-conjugate in combination with kinase inhibitors for treatment of AML.

Fms like tyrosine kinase 3 (FLT3) is often overexpressed or constitutively activated by internal tandem duplication (ITD) and tyrosine kinase domain (TKD) mutations in acute myeloid leukemia (AML). Despite the use of receptor tyrosine kinase inhibitors (TKI) in FLT3-ITD positive AML, the prognosis of patients is still poor and further improvement of therapy is required. Targeting FLT3 independent of mutations by antibody‑drug‑conjugates (ADCs) is a promising strategy for AML therapy. Here, we report the development and preclinical characterization of a novel FLT3‑targeting ADC, 20D9-ADC, which was generated by applying the innovative P5 conjugation technology. In vitro, 20D9‑ADC mediated potent cytotoxicity to Ba/F3 cells expressing transgenic FLT3 or FLT3-ITD, to AML cell lines and to FLT3-ITD positive patient derived xenograft AML cells. In vivo, 20D9‑ADC treatment led to a significant tumor reduction and even durable complete remission in AML xenograft models. Further, 20D9‑ADC demonstrated no severe hematotoxicity in in vitro colony formation assays using concentrations that were cytotoxic in AML cell line treatment. The combination of 20D9-ADC with the TKI midostaurin showed strong synergy in vitro and in vivo, leading to reduction of aggressive AML cells below the detection limit. Our data indicate that targeting FLT3 with an advanced new-generation ADC is a promising and potent antileukemic strategy, especially when combined with FLT3-TKI in FLT3‑ITD positive AML