Systematic Evaluation of Fluorination as Modification for Peptide-Based Fusion Inhibitors against HIV-1 Infection

A dePEGylated Lipopeptide-Based Pan-Coronavirus Fusion Inhibitor Exhibits Potent and Broad-Spectrum Anti-HIV-1 Activity without Eliciting Anti-PEG Antibodies

We previously identified a lipopeptide, EK1C4, by linking cholesterol to EK1, a pan-CoV fusion inhibitory peptide via a polyethylene glycol (PEG) linker, which showed potent pan-CoV fusion inhibitory activity. However, PEG can elicit antibodies to PEG in vivo, which will attenuate its antiviral activity. Therefore, we designed and synthesized a dePEGylated lipopeptide, EKL1C, by replacing the PEG linker in EK1C4 with a short peptide. Similar to EK1C4, EKL1C displayed potent inhibitory activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other coronaviruses. In this study, we found that EKL1C also exhibited broad-spectrum fusion inhibitory activity against human immunodeficiency virus type 1 (HIV-1) infection by interacting with the N-terminal heptad repeat 1 (HR1) of viral gp41 to block six-helix bundle (6-HB) formation. These results suggest that HR1 is a common target for the development of broad-spectrum viral fusion inhibitors and EKL1C has potential clinical application as a candidate therapeutic or preventive agent against infection by coronavirus, HIV-1, and possibly other class I enveloped viruses.

Fluorine-induced polarity increases inhibitory activity of BPTI towards chymotrypsin

Substituting the P1 position in bovine pancreatic trypsin inhibitor (BPTI) is known to heavily influence its inhibitory activity towards serine proteases. Side-chain fluorinated aliphatic amino acids have been shown to alter numerous properties of peptides and proteins and thus are of interest in the context of BPTI. In our study, we systematically investigated the site-specific incorporation of non-canonical amino acids into BPTI by microwave-assisted solid-phase peptide synthesis (SPPS). Inhibitor activity of the variants was tested towards the serine protease α-chymotrypsin. We observed enhanced inhibition of two fluorinated BPTIs compared to wild type and hydrocarbon variants. To further investigate the complexes, we performed X-ray structure analysis. Our findings underline the power fluorine offers as a tool in protein engineering to beneficially alter the effects on phenomena as protein-protein interactions.

Fluorine-Containing Drug Administration in Rats Results in Fluorination of Selected Proteins in Liver and Brain Tissue

In many pharmaceuticals, a hydrogen atom or hydroxyl group is replaced by a fluorine to increase bioavailability and biostability. The fate of fluorine released from fluorine-containing drugs is not well investigated. The aim of this study was to examine possible fluorination of proteins in rat liver and brain after administration of the fluorinated drug cinacalcet. We assigned 18 Wistar rats to a control group (n = 6) and a group treated with cinacalcet (2 mg kg⁻¹/body weight, 5 days/week), divided into 7 day (n = 6) and 21 day (n = 6) treatment subgroups. Fluorinated proteins were identified using a free proteomics approach; chromatographic separation and analysis by high-resolution mass spectrometry; peptide/protein identification using the Mascot search algorithm; manual verification of an experimentally generated MS/MS spectrum with the theoretical MS/MS spectrum of identified fluorinated peptides. Three fluorinated proteins (spectrin beta chain; carbamoyl-phosphate synthase [ammonia], mitochondrial; 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase 1) were identified in the liver and four (spectrin beta chain, dihydropyrimidinase-related protein 4, prominin-2, dihydropyrimidinase-related protein 4) in the brain tissue after 21 days of cinacalcet treatment, but not in the control group. Introduction of fluorine into an organism by administration of fluorinated drugs results in tissue-specific fluorination of proteins.