A Novel Peptide Derived from the Fusion Protein Heptad Repeat Inhibits Replication of Subacute Sclerosing Panencephalitis Virus In Vitro and In Vivo.

Subacute sclerosing panencephalitis (SSPE) is a persistent, progressive, and fatal degenerative disease resulting from persistent measles virus (MV) infection of the central nervous system. Most drugs used to treat SSPE have been reported to have limited effects. Therefore, novel therapeutic strategies are urgently required. The SSPE virus, a variant MV strain, differs virologically from wild-type MV strain. One characteristic of the SSPE virus is its defective production of cell-free virus, which leaves cell-to-cell infection as the major mechanism of viral dissemination. The fusion protein plays an essential role in this cell-to-cell spread. It contains two critical heptad repeat regions that form a six-helix bundle in the trimer similar to most viral fusion proteins. In the case of human immunodeficiency virus type-1 (HIV-1), a synthetic peptide derived from the heptad repeat region of the fusion protein enfuvirtide inhibits viral replication and is clinically approved as an anti-HIV-1 agent. The heptad repeat regions of HIV-1 are structurally and functionally similar to those of the MV fusion protein. We therefore designed novel peptides derived from the fusion protein heptad repeat region of the MV and examined their effects on the measles and SSPE virus replication in vitro and in vivo. Some of these synthetic novel peptides demonstrated high antiviral activity against both the measles (Edmonston strain) and SSPE (Yamagata-1 strain) viruses at nanomolar concentrations with no cytotoxicity in vitro. In particular, intracranial administration of one of the synthetic peptides increased the survival rate from 0% to 67% in an SSPE virus-infected nude mouse model.

Synthesis and biological evaluation of the [d-MeAla(11)]-epimer of coibamide A.

Coibamide A is a highly potent antiproliferative cyclic depsipeptide, which was originally isolated from a Panamanian marine cyanobacterium. In this study, the synthesis of coibamide A has been investigated using Fmoc-based solid-phase peptide synthesis followed by the cleavage of the resulting linear peptide from the resin and its subsequent macrolactonization. The peptide sequence of the linear coibamide A precursor was constructed on a solid-support following the optimization of the coupling conditions, where numerous coupling agents were evaluated. The macrocyclization of the resulting linear peptide provided the [d-MeAla(11)]-epimer of coibamide A, which exhibited nanomolar cytotoxic activity towards a number of human cancer cell lines.

Synthesis of IB-01212 by multiple N-methylations of peptide bonds.

There are many natural peptides with multiple N-methylamino acids that exhibit potent attractive biological activities. N-methylation of a peptide bond(s) is also one of the standard approaches in medicinal chemistry of bioactive peptides, to improve the potency and physicochemical properties, especially membrane permeability. In this study, we investigated a facile synthesis process of N-methylated peptides via simultaneous N-methylation of several peptide bonds in the presence of peptide bonds that were not to be methylated. As a model study, we investigated the synthesis of the antiproliferative depsipeptide, IB-01212. We used a pseudoproline to protect the non-methylated peptide bond during a simultaneous N-methylation with MeI-Ag2O. Using further manipulations including a dimerization/cyclization process, IB-01212 and its derivatives were successfully synthesized. A preliminary structure-activity relationship study demonstrated that the symmetric structure contributed to the potent cytotoxic activity of IB-01212.