The determination of the three-dimensional structure is a key step for the identification of new targets as well as the rational design of bioactive compounds. Herein, we report the synthesis and the structural elucidation of novel tetrameric macrocycles. Measurements were taken in solid and solution states with the help of X-ray scattering and NMR spectroscopy. The investigations made will help to find diverse applications for this new, promising compound class.

The development of potent antiviral agents is of utmost importance to combat the global burden of viral infections. Traditional antiviral drug development involves targeting specific viral proteins, which may lead to the emergence of resistant strains. To explore alternative strategies, we investigated the antiviral potential of antimicrobial peptidomimetic compounds. In this study, we evaluated the antiviral potential of short anthranilamide-based peptidomimetic compounds 1-17 against two viruses: Murine Hepatitis Virus 1 (MHV-1-single stranded RNA virus) which is a surrogate of human coronaviruses and Herpes Simplex Virus 1 (HSV-1-double stranded DNA virus). The half-maximal inhibitory concentration (IC50) values of these compounds were determined in vitro to assess their potency as antiviral agents. Compounds 11 and 14 displayed the most potent inhibitory effect with IC50 values of 2.38μM, and 6.3μM against MHV-1 while compounds 9 and 14 showed IC50 values of 14.8μM and 13μM, against HSV-1. Multiple antiviral assessments and microscopic images obtained through transmission electron microscopy (TEM) collectively demonstrated that these compounds exert a direct influence on the viral envelope. Based on this outcome, it can be concluded that peptidomimetic compounds could offer a new approach for the development of potent antiviral agents.

In this work antiparasitic peptidomimetics inhibitors (PEP) of falcipain-3 (FP3) of Plasmodium falciparum (Pf) have been proposed using structure-based and computer-aided molecular design. Beginning with the crystal structure of PfFP3-K11017 complex (PDB ID: 3BWK), three-dimensional (3D) models of FP3-PEPx complexes with known activities (IC50exp) were prepared by in situ modification, based on molecular mechanics and implicit solvation to compute Gibbs free energies (GFE) of inhibitor-FP3 complex formation. This resulted in a quantitative structure-activity relationships (QSAR) model based on a linear correlation between computed GFE (ΔΔGcomp) and the experimentally measured IC50exp: (pIC50exp=-(IC50exp/109) =-0.4517×∆∆Gcomp+4.0865 ; R2 = 0.89). Apart from the structure-based relationship, a ligand-based quantitative pharmacophore model (PH4) of novel PEP analogs where substitutions were directed by comparative analysis of the active site interactions was derived using the proposed bound conformations of the PEPx. This provided structural information useful for the design of virtual combinatorial libraries (VL), which was virtually screened based on the 3D-QSAR PH4. The end results were predictory inhibitory activities falling within the low nanomolar concentration range.

Angiogenin (ANG), an endogenous protein that plays a key role in cell growth and survival, has been scrutinised here as promising nanomedicine tool for the modulation of pro-/ anti-angiogenic processes in brain cancer therapy. Specifically, peptide fragments from the putative cell membrane binding domain (residues 60-68) of the protein were used in this study to obtain peptide-functionalised spherical gold nanoparticles (AuNPs) of about 10 nm and 30 nm in optical and hydrodynamic size, respectively. Different hybrid biointerfaces were fabricated by peptide physical adsorption (Ang60-68) or chemisorption (the cysteine analogous Ang60-68Cys) at the metal nanoparticle surface, and the cellular assays were performed in the comparison with ANG-functionalised AuNPs. Cellular treatments were performed both in basal and in copper-supplemented cell culture medium, to scrutinise the synergic effect of the metal, which is another known angiogenic factor. Two brain cell lines were investigated in parallel, namely tumour glioblastoma (A172) and neuron-like differentiated neuroblastoma (d-SH-SY5Y). Results on cell viability/proliferation, cytoskeleton actin, angiogenin translocation and VEGF release pointed to the promising potentialities of the developed systems as anti-angiogenic tunable nanoplaftforms in cancer cells treatment.

The Main Protease (Mpro) plays a pivotal role in the replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and is considered a highly conserved viral target. Disruption of the catalytic activity of Mpro produces a detrimental effect on the course of the infection, making this target one of the most attractive for the treatment of COVID-19. The current success of the SARS-CoV-2 Mpro inhibitor Nirmatrelvir, the first oral drug for the treatment of severe forms of COVID-19, has further focused the attention of researchers on this important viral target, making the search for new Mpro inhibitors a thriving and exciting field for the development of antiviral drugs active against SARS-CoV-2 and related coronaviruses.

The non-structural protein NS3/4A protease is a critical factor for hepatitis C virus (HCV) maturation that requires activation by NS4A. Synthetic peptide mutants of NS4A were found to inhibit NS3 function. The bridging from peptide inhibitors to heterocyclic peptidomimetics of NS4A has not been in consideration in literature, and therefore, we decided to explore this strategy to develop a new class of NS3 inhibitors. In this report, a structure-based design approach was used to convert the bound form of NS4A into 1H-imidazole-2,5-dicarboxamide derivatives as first generation peptidomimetics. This scaffold mimics the buried amino acid sequence Ile-25` to Arg-28` at the core of NS4A21`-33` needed to activate the NS3 protease. Some of the synthesized MOC compounds were able to compete with and displace NS4A21`-33` for binding to NS3. For instance, N5-(4-guanidinobutyl)-N2-(n-hexyl)-1H-imidazole-2,5-dicarboxamide (MOC-24) inhibited the binding of NS4A21`-33` with a competition IC50 of 1.9 ± 0.12 µM in a fluorescence anisotropy assay, stabilized the denaturation of NS3 by increasing the aggregation temperature by ΔTagg 0.6 ± 0.140 ℃. MOC-24 also inhibited NS3 protease activity in a fluorometric assay. Molecular dynamics simulations rationalized the structure-activity relationship (SAR) differences between the active MOC-24 and the inactive MOC-26. Our data shows that MOC compounds are possibly the first examples of NS4A peptidomimetics that demonstrated promising activities against NS3 proteins.