A synthetic antimicrobial peptide was identified as a possible candidate for the development of a new antibacterial drug. The peptide, SET-M33L, showed a MIC90 below 1.5 μM and 3 μM for Pseudomonas aeruginosa and Klebsiella pneumoniae, respectively. In in vivo models of P. aeruginosa infections, the peptide and its pegylated form (SET-M33L-PEG) enabled a survival percentage of 60–80% in sepsis and lung infections when injected twice i.v. at 5 mg/Kg, and completely healed skin infections when administered topically. Plasma clearance showed different kinetics for SET-M33L and SET-M33L-PEG, the latter having greater persistence two hours after injection. Bio-distribution in organs did not show significant differences in uptake of the two peptides. Unlike colistin, SET-M33L did not select resistant mutants in bacterial cultures and also proved non genotoxic and to have much lower in vivo toxicity than antimicrobial peptides already used in clinical practice. The characterizations reported here are part of a preclinical development plan that should bring the molecule to clinical trial in the next few years.

The increasing frequency of multidrug-resistant bacteria and a recent slowing in the development of new antimicrobial agents place mankind in a state of emergency with regard to the threat of new bacterial infections. Antibacterial peptides (AMPs) are considered an important class of molecules to develop against bacteria. AMPs have been known for many years but very few have yet been extensively used in clinical practice, mainly because of their general toxicity and manufacturing cost. Now, thanks to new technologies for screening and development, interest in these molecules has grown. Many new AMPs have been discovered and some are under evaluation for the development of new antibacterial therapeutics. Here we review the major AMPs currently used in clinical practice and others in the phase of preclinical and clinical development.

The synthetic antimicrobial peptide SET-M33 has strong activity against bacterial infections caused by Gram-negative bacteria. It is currently in preclinical development as a new drug to treat lung infections caused by Gram-negative bacteria. Here we report its strong anti-inflammatory activity in terms of reduced expression of a number of cytokines, enzymes, and signal transduction factors involved in inflammation triggered by LPS from Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli. Sixteen cytokines and other major agents involved in inflammation were analyzed in macrophages and bronchial cells after stimulation with LPS and incubation with SET-M33. The bronchial cells were obtained from a cystic fibrosis patient. A number of these proteins showed up to 100% reduction in expression as measured by RT-PCR, Western blotting, or Luminex technology. LPS neutralization was also demonstrated in vivo by challenging bronchoalveolar lavage of SET-M33-treated mice with LPS, which led to a sharp reduction in TNF-α with respect to non-SET-M33-treated animals. We also describe a strong activity of SET-M33 in stimulating cell migration of keratinocytes in wound healing experiments in vitro, demonstrating a powerful immunomodulatory action generally characteristic of molecules taking part in innate immunity.

Purpose of this study is evaluating the effect produced by targeting Heparan Sulfated Proteoglycan (HSPG) by specific branched peptides, on cancer cell adhesion, migration and drug-resistance. In previous papers we reported on synthesis and biological activity of tetra-branched peptides (NT4) containing the sequence of human neurotensin (NT), coupled to different tracers or drugs. Differently to monomeric NT, NT4 peptides bind with high selectivity to cells and tissues from different human cancers like colorectal cancer, pancreas adenocarcinoma and urinary bladder cancer and can efficiently and selectively deliver drugs (1-3) or liposomes (4,5) for cancer cell imaging or therapy, in vitro and vivo. By using NT4 conjugated to methotrexate (MTX) or 5FdU we obtained significant reduction of tumor growth in mice (1,2). We demonstrated that the branched structure provides NT4 with the ability to bind membrane sulfated glycosaminoglycans as well as different membrane endocytic receptors like LRP1 and LRP6 (6). This switch in target binding is responsible for the high and broad cancer selectivity of NT4 branched peptides, when compared to native NT. Considering the role of HSPG in cancer cell interaction with the extracellular matrix, we have here analyzed the effect of NT4 on cancer cell adhesion and migration on different supports. Moreover, since binding and internalization of NT4 peptides is mediated by specific NT4 receptors on cancer cell membrane, which may allow by-passing drug resistance produced by drug membrane transporters, we have also tested the ability of drug-armed NT4 to by-pass drug resistance in cancer cell lines. We found that 1- NT4 branched peptide inhibits adhesion and migration of different cancer cell lines on different supports and 2- MTX-conjugated NT4 allows by-passing drug resistance in MTX-resistant human breast cancer cells. The ability of NT4 peptides to allow by-passing drug resistance and to interfere with cancer cell adhesion and migration, when associated to their already demonstrated high and broad cancer selectivity, reinforce their potential role as selective and efficient cancer theranostics. Moreover, due to their specific binding to sulfated glycans, NT4 peptides can be used as probes for clarifying the role of these glycans in different aspects of tumor progression. References. 1. Falciani C. et al. Mol Cancer Ther 2007, 6, 2441-8. 2. Falciani C. et al. Curr Cancer Drug Targets 2010, 10, 695-04. 3. Falciani et al. ChemMedChem 2010, 5, 567-74. 4. Falciani C. et al. ChemMedChem 2011, 4, 678-85. 5. Falciani C. et al. J Pept Sci 2013, 19, 198-204. 6. Falciani C. et al. J Med Chem 2013, 56, 5009-18. Citation Format: Jlenia Brunetti, Lorenzo Depau, Chiara Falciani, Elisabetta Mandarini, Giulia Riolo, Giulia Roscia, Alessandro Pini, Luisa Bracci. Targeting Heparan Sulfated Proteoglycans by branched peptides for selective cancer imaging and therapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5350. doi:10.1158/1538-7445.AM2015-5350