Peptidomimetic antibiotics disrupt the lipopolysaccharide transport bridge of drug-resistant Enterobacteriaceae

The rise of antimicrobial resistance poses a substantial threat to our health system, and, hence, development of drugs against novel targets is urgently needed. The natural peptide thanatin kills Gram-negative bacteria by targeting proteins of the lipopolysaccharide transport (Lpt) machinery. Using the thanatin scaffold together with phenotypic medicinal chemistry, structural data, and a target-focused approach, we developed antimicrobial peptides with drug-like properties. They exhibit potent activity against Enterobacteriaceae both in vitro and in vivo while eliciting low frequencies of resistance. We show that the peptides bind LptA of both wild-type and thanatin-resistant Escherichia coli and Klebsiella pneumoniae strains with low-nanomolar affinities. Mode of action studies revealed that the antimicrobial activity involves the specific disruption of the Lpt periplasmic protein bridge.

Abstract A003: Anti-angiogenic activity of the CXCR4 antagonist balixafortide

Background: Balixafortide is a potent and selective antagonist of the chemokine receptor CXCR4, and is in PhIII for metastatic HER2-negative breast cancer in combination with eribulin (NCT03786094). Clinical proof-of concept of the combination with comparable tolerability to that of eribulin monotherapy was demonstrated in a recent PhI single arm dose-escalation trial (NCT01837095). Balixafortide can inhibit tumor growth through several mechanisms including chemosensitization in combination with chemotherapy (e.g. eribulin), suppression of metastasis, and activation of immune cell response in the tumor microenvironment. In addition, data regarding the co-regulation of the angiogenic factor VEGF and CXCR4 in colorectal cancer (CRC) tissue suggest a possible anti-angiogenic activity of Balixafortide. Methods: VEGF alpha-induced migration of endothelial cells and vascular permeabilization were assessed in vitro. Changes in VEGF alpha levels were determined in CXF260 CRC PDX tumor samples by Nanostring and in CXF260 cells in vitro by qPCR. Results: Balixafortide potently inhibited VEGF alpha-induced migration and permeabilization of an endothelial monolayer in vitro and reduced VEGF alpha levels in both, cultured CXF260 tumor cells in vitro and CXF260 tumors in vivo. Conclusions: Balixafortide modulates angiogenic mechanisms in vitro and in vivo and suggests further investigation of balixafortide in anti-angiogenic therapies.

Citation Format: Johann Zimmermann, Daniel Obrecht, Tobias Remus. Anti-angiogenic activity of the CXCR4 antagonist balixafortide [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr A003. doi:10.1158/1535-7163.TARG-19-A003