STABLE PEPTIDE-BASED FURIN INHIBITORS

Abstract

It is provided furin inhibitors and their uses for treating pathogen infection. Particularly, it is provided a method or use for the treatment of a pathogen infection, in a subject, comprising administering to the subject a therapeutically effective amount of the furin inhibitors or the composition disclosed, thereby preventing or treating pathogen infection, in the subject.

Description

TECHNICAL FIELD

The present description relates to furin inhibitors and their stable analogues.

BACKGROUND

Pro-protein convertases (PCs) are serine proteases that optimally cleave substrates at R-X-K/R-R motif. These processing events, resulting in the activation of protein precursors, occur at multiple levels of cell secretory pathways, and even at the cell surface.

In mammalian cells, seven members of this family have been identified: furin, PACE4, PC1/3, PC2, PC4, PC5/6 and PC7, with differential expression in tissues, ranging from ubiquitous (eg. furin) to an endocrine restricted expression (PC1/3 and PC2).

In addition to normal cell functions, PCs, including furin, are implicated in many pathogenic states, because they process to maturity membrane fusion proteins and pro-toxins of a variety of bacteria and viruses, including Shiga toxin, anthrax, botulinum toxins, influenza A H₅N₁ (bird flu), flaviviruses, Marburg and Ebola viruses (Thomas, 2002, Nat. Rev. Mol. Cell. Biol., 3: 753-766). After processing by furin and the subsequent endocytic internalization in the complex with the respective cell surface receptor followed by acidification of the endosomal compartment, the processed, partially denatured, infectious proteins expose their membrane-penetrating peptide region and escape into the cytoplasm (Collier and Young, 2003, Annu. Rev. Cell Dev. Biol., 19: 45-70). Pathogens or their toxins, including influenza virus, Pseudomonas, Shiga toxin and anthrax toxins, require processing by host proprotein convertases (PCs) to enter host cells and to cause disease.

Furin is a widespread and indispensable protease active in both the secretory pathway and on, or near the cell surface. Furin is produced as a proprotein, cycles between the Golgi apparatus, endosomes, and cell membrane. Furin is active in both embryogenesis and in mature cells. At steady state, furin is localized principally in the trans-Golgi network (TGN)/Endosomal system. Depending upon its location in the system, furin catalyses a number of different reactions, all involving proteolytic cleavage of proproteins. For example, in the TGN/biosynthetic pathway furin cleaves a propeptide to give active pro-P nerve growth factor (pro-p-NGF). Similarly, furin cleaves propeptides thereby activating pro-bone morphogenic protein-4 (pro-BMP-4) and the “single-chain” insulin pro-hormone to form the higher activity latter-form entity.

Furin cleaves proteins just downstream of a basic amino acid target sequence (canonically, Arg-X-(Arg/Lys)-Arg′). A number of pathogens exploit host cell furin activity to help activate proteins involved in pathology. For example host cell furin cleaves the Ebola Zaire pro-glycoprotein (pro-GP) protein as part of the virus's infectious cycle. Further, the envelope proteins of viruses such as HIV, influenza and dengue fever viruses must be cleaved by furin or furin-like proteases to become fully functional. Anthrax toxin, pseudomonas exotoxin, Shiga toxin (Garred et al., 1995, J Biol Chem, 270: 10817-10821) and papillomaviruses must be processed by furin during their initial entry into host cells.

Additionally, furin in the early endosome, cleaves propeptides to produce active bacterial proteins such as diptheria toxins, shigala toxin, shigala-like toxin 1, and Pseudomonas exotoxin A. Furin processes the coat protein of Human Immunodeficiency Virus (HIV) and PA toxin produced by Bacillus anthrasis.

Additional pathogen derived propeptides processed by furin and other subtilisins-like proteases include, for example, viral proteins such as HIV-1 coat protein gp160, and influenza virus haemagglutinin as well as bacterial proteins such as diphtheria toxin, and anthrax toxin (see Decroly et al., 1194, J. Biol. Chem., 269: 12240-12247; and Vey et al., 1994, Cell. Biol., 127: 1829-1842).

In view of its large spectra of activity, furin has become the focus of considerable study and identifying inhibitors of furin are under consideration as therapeutic agents for treating pathogenic infection.

PCT application publication No. WO 2009/023306, which is hereby incorporated by reference in its entirety, discloses furin inhibitors and their uses for limiting pathogenic infections.

There is still a need to be provided with improved furin inhibitors. It would be highly desirable to be provided with more stable and selective furin inhibitors that are effective in treating pathogen infections.

SUMMARY

One aim of the present description is to provide furin inhibitors and their uses for treating pathogen infection.

It is provided a peptide sequence comprising the following formula I:

Z-Xaa₈-Xaa₇-Xaa₆-Xaa₅-Arg₄-Xaa₃-Xaa₂-Arg₁-Xaa_1′  (I)

wherein

• • Xaa_1′ is absent or any amino acids, peptidomimetic, or stereoisomer thereof;
  • Arg₁ and Arg₄ are independently arginine, an analogue, a mimic of arginine or stereoisomer thereof;
  • Xaa₂ is a basic amino acid, an analogue, or stereoisomer thereof;
  • Xaa₃ is independently any amino acids, an analogue or stereoisomer thereof;
  • Xaa₅, Xaa₆, Xaa₇ and Xaa₈ independently are Lys, Arg or His, peptidomimetic or stereoisomer thereof; and
  • Z comprises at least one of acetyl, azido and PEG group, fatty acids, steroid derivatives and sugars linked to the N-terminal of the peptide sequence;
  • with the proviso that Xaa₅, Xaa₆, Xaa₇ and Xaa₈ are not aromatic or negatively charged amino acids.

The sugars encompassed can be mono or poly sugars.

The term “analogues” is intended to mean analogues of amino acids and pseudo peptide bonds, such as “click”, aza, -ene (double conjugated or unconjugated C═C bonds).

In a particular embodiment, the N terminus of the inhibitor is acylated (e.g. acetylated). Further, the N terminus acylation is with fatty omega amino acids or with steroid derivatives.

The fatty (saturated or unsaturated) omega amino acids can be C2 to C18, more preferably the fatty omega amino acids are selected from the group consisting of 11-amino undecanoic acid or 8-amino octanoic acid.

According to another aspect of the present description, there is provided a composition comprising furin inhibitors as defined herein and a carrier.

In another embodiment, the composition further comprises at least one anti-viral drug.

Concurrent administration” and “concurrently administering” as used herein includes administering a composition as described herein and one anti-viral drug compound in admixture, such as, for example, in a pharmaceutical composition, or as separate formulation, such as, for example, separate pharmaceutical compositions administered consecutively, simultaneously, or at different times.

Preferably, the composition is adapted for delivery by at least one of the following route selected from the group consisting of oral, mucosal, intranasal, intraocular, intratracheal, intrabronchial, intrapleural, intraperitoneal, intracranial, intramuscular, intravenous, intraarterial, intralymphatic, subcutaneous, intratumoral, gastric, enteral, colonic, rectal, urethral and intravesical route.

According to still another aspect of the present invention, there is provided a method of lowering furin activity in a cell, comprising contacting the furin inhibitors or the composition as defined herein with the cell, thereby lowering furin activity in the cell.

According to yet another aspect of the present description, there is provided a method of reducing pathogen proliferation in a subject, comprising administering the furin inhibitors or the composition as defined herein to the subject, thereby reducing the proliferation of the pathogen in the subject.

Pathogen encompassed herein can be a bacterial pathogen such as Anthrax, Pseudomonas, Botulism, Diphtheria, Aeromonas or Shigella; or can be a viral pathogen such as Influenzavirus A, parainfluenza, Sindbis virus, Newcastle disease virus, flavivirus, cytomegalovirus, herpesvirus, HIV, Measles virus, infectious bronchitis virus, Coronavirus, Marburg virus, Ebola virus or Epstein-Barr virus.

According to yet a further aspect of the present description, there is provided a method for the treatment of pathogen infection in a subject, comprising administering to said subject a therapeutically effective amount of the furin inhibitors or the composition as defined herein, thereby preventing or treating pathogen infection in the subject.

Preferably, the cell is in a subject. More preferably, the cell has increased furin activity.

According to still a further aspect of the present description, there is provided the use of the furin inhibitors or the composition as defined herein in the manufacture of a medicament for treating pathogen infection in a subject.

According to yet another aspect of the present description there is provided the use of the furin inhibitors or the composition as defined herein for lowering furin activity in a cell, for reducing proliferation of a pathogen in a subject.

The terms used herein are explained below. Each term, alone or in combination with another term, means as follows.

“Alkyl” means an aliphatic hydrocarbon group which may be straight or branched and comprising about 1 to about 20 carbon atoms in the chain. Preferred alkyl groups contain about 1 to about 12 carbon atoms in the chain. More preferred alkyl groups contain about 1 to about 6 carbon atoms in the chain. Branched means that one or more lower alkyl groups such as methyl, ethyl or propyl, are attached to a linear alkyl chain. “Lower alkyl” means a group having about 1 to about 6 carbon atoms in the chain which may be straight or branched. Non-limiting examples of suitable alkyl groups include methyl, ethyl, n-propyl, isopropyl and t-butyl.

The terms “alkenyl” represent a linear, branched or cyclic aliphatic hydrocarbon group which may be straight or branched and comprising about 1 to about 20 carbon atoms and has one or more double bonds in the chain.

“Alkylene” means a difunctional group obtained by removal of a hydrogen atom from an alkyl group that is defined above. Non-limiting examples of alkylene include methylene, ethylene and propylene.

“Aryl” means an aromatic monocyclic or multicyclic ring system comprising about 6 to about 14 carbon atoms, preferably about 6 to about 10 carbon atoms. Examples include but are not limited to phenyl, tolyl, dimethylphenyl, fluoenryl, aminophenyl, anilinyl, naphthyl, anthryl, phenanthryl or biphenyl.

“Arylene” means a difunctional group obtained by removal of a hydrogen atom from an aryl group that is defined above. Examples include but are not limited to phenylene, tolylene, dimethylphenylene, fluorene, aminophenylene, anilinylene, naphthylene, anthrylene, phenanthrylene or biphenylene.

“Heteroaryl” means an aromatic monocyclic or multicyclic ring system comprising about 5 to about 14 ring atoms, preferably about 5 to about 10 ring atoms, in which one or more of the ring atoms is an element other than carbon, for example nitrogen, oxygen or sulfur, alone or in combination. The prefix aza, oxa or thia before the heteroaryl root name means that at least a nitrogen, oxygen or sulfur atom respectively, is present as a ring atom. A nitrogen atom of a heteroaryl can be optionally oxidized to the corresponding N-oxide. Non-limiting examples of suitable heteroaryls include pyridyl, pyrazinyl, furanyl, thienyl, pyrimidinyl, pyridone (including N-substituted pyridones), isoxazolyl, isothiazolyl, oxazolyl, thiazolyl, pyrazolyl, furazanyl, pyrrolyl, pyrazolyl, triazolyl, 1,2,4-thiadiazolyl, pyrazinyl, pyridazinyl, quinoxalinyl, phthalazinyl, oxindolyl, imidazo[1,2-a]pyridinyl, imidazo[2,1-b]thiazolyl, benzofurazanyl, indolyl, azaindolyl, benzimidazolyl, benzothienyl, quinolinyl, imidazolyl, thienopyridyl, quinazolinyl, thienopyrimidyl, pyrrolopyridyl, imidazopyridyl, isoquinolinyl, benzoazaindolyl, 1,2,4-triazinyl, benzothiazolyl and the like.

“Heteroarylene” means a difunctional group obtained by removal of a hydrogen atom from a heteroaryl group that is defined above. Non-limiting examples of pyridylene, pyrazinylene, furanylene, thienylene and pyrimidinylene.

The term “arylalkylene” represents an aryl group attached to the adjacent atom by an alkylene.

The term “arylalkenylene” represents an aryl group attached to the adjacent atom by an alkenylene.

The term “NR1-alkylene” represents a NR1 group attached to an alkylene.

The term “NR1-alkenylene” represents a NR1 group attached to an alkenylene.

The term “NR1-arylene” represents a NR1 group attached to an arylene.

The term “NR1-heteroarylene” represents a NR1 group attached to a heteroarylene.

The term “NR1-arylalkylene” represents a NR1 group attached to an arylalkylene.

The term “NR1-arylalkenylene” represents a NR1 group attached to an arylalkenylene.

The term “alkylene-NR2” represents an alkylene attached to the adjacent atom by a NR2 group.

The term “alkenylene-NR2” represents an alkenylene attached to the adjacent atom by a NR2 group.

The term “arylene-NR2” represents an arylene attached to the adjacent atom by a NR2 group.

The term “heteroarylene-NR2” represents a heteroarylene attached to the adjacent atom by a NR2 group.

The term “arylalkylene-NR2” represents an arylalkylene attached to the adjacent atom by a NR2 group.

The term “arylalkenylene-NR2” represents an arylalkenylene attached to the adjacent atom by a NR2 group.

The term “NR1-alkylene-NR2” represents a NR1 group attached to an alkylene, the alkylene is attached to the adjacent atom by a NR2 group.

The term “NR1-alkenylene-NR2” represents a NR1 group attached to an alkenylene, the alkenylene is attached to the adjacent atom by a NR2 group.

The term “NR1-arylene-NR2” represents a NR1 group attached to an arylene, the arylene is attached to the adjacent atom by a NR2 group.

The term “NR1-heteroarylene-NR2” represents a NR1 group attached to a heteroarylene, the heteroarylene is attached to the adjacent atom by a NR2 group.

The term “NR1-arylalkylene-NR2” represents a NR1 group attached to an arylalkylene, the arylalkylene is attached to the adjacent atom by a NR2 group.

The term “NR1-arylalkenylene-NR2” represents a NR1 group attached to an arylalkenylene, the arylalkenylene is attached to the adjacent atom by a NR2 group.

The terms “alkylene-COOH”, “alkenylene-COOH”, “arylene-COOH”, “heteroarylene-COOH”, “arylalkylene-COOH”, “heteroarylalkylene-COOH” or “alkenyl-COOH” represents an alkylene, an alkenylene, an arylene, a heteroarylene, an arylalkylene, a heteroarylalkylene or an alkenyl attached to the adjacent atom by a —COOH group.

The term “independently” means that a substituent can be the same or a different definition for each item.

“PEG” means a polyethylene glycol prepared through polymerization of ethylene oxide that are commercially available, and can include a wide range of molecular weights from 300 g/mol to 10,000,000 g/mol.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings.

FIG. 1 illustrates peptidomimetic modifications used in the synthesis of RXXT variants.

FIG. 2 illustrates the degradation kinetic of the RXXR peptides.

FIG. 3 illustrates the stability measured for RXXT variants, where in (A) plasmatic half-life curves of peptides (RxxT: L0; RxxT[Azaβ₃R]^P8:L22; Rxx-[AMBA]^P1: L8; and RxxT[Azaβ₃R]^P1-P8: L29) in murin plasma treated ex vivo at 37° C. are showed; and in (B) degradation pattern of the different peptides tested in DU145 culture media is illustrated.

FIG. 4 illustrates the ability of the RXXT compound to penetrate cells wherein in (A) a FTU-6Ala-RXXT compound was used, compared in (B) to its variant coupled to a lipid amino-octanoyl group (Aoc).

FIG. 5 illustrates the absence of toxicity observed for the compounds tested. Toxicity is measured by the release of LDH by cells, LDH being a mitochondrial enzyme release during lyses of cells.

FIG. 6 illustrates the calculation method for the IC₅₀ for the general PC inhibitor dec-RTKR-CMK on the relative cytotoxicity of the Escherichia coli O157:H7 Shiga toxin. The cytotoxicity was measured by the release of LDH by VERO cells incubated with Shiga toxin preparation diluted 1:2 and 1:100 (gray and black curves, respectively). The addition of the inhibitor lowers the relative cytotoxicity induced by the toxin in a dose-dependent manner (IC₅₀=11.5 μM), confirming the role of PCs in this phenomenon.

FIG. 7 illustrates the capability of the tested compounds to inhibit cell fusion (relative to the no treatment control). The furin inhibitors were used at a single concentration of 100 μM with cell line expressing the hemagglutinin H5. For comparison purposes, the general PC inhibitor dec-RTKR-CMK was also used. (Aoc:lipid amino-octanoyl group, PEGS: polyethylene glycol group).

FIG. 8 schematizes the cell fusion pharmacological assay. In the absence of the furin inhibitor, fusion of the HA-positive and GFP-positive cell lines leads to the emission of fluorescence. In the presence of the inhibitor, the normal cleavage of hemagglutinin (HA) membrane protein does not occur, avoiding the cell fusion and the emission of fluorescence.

DETAILED DESCRIPTION

It is provided herein furin inhibitors and their uses for treating pathogen infection.

One of the keys to the development of potent and selective PC inhibitors is an understanding of the substrate-binding pocket. The deepest region of the substrate-binding pocket accommodates the consensus motif RXKR (P₄-P₃-P₂-P₁) nearly identical in all PCs. Potency and selectivity are determined by a less deeper region that interacts with P₅-P₇-P₆-P₅ of the inhibitor peptide (see Henrich et al., 2005, J. Mol. Biol., 345: 211-227; Fugere and Day, 2005, Trends Pharmacol. Sci., 26: 294-301; Henrich et al., 2003, Nat. Struct. Biol., 10: 520-526).

Endogenous inhibitors are often a good starting point in the development of pharmacological compounds. For example, proSAAS and the 7B2 C-terminal peptide are two endogenous inhibitors identified that inhibit PC1/3 and PC2, respectively. PC pro-domains are autoprocessed in cis by their cognate PC, but remain bound to the active site through their C-terminal PC-recognition sequence until the complex reaches the compartment of zymogen activation. Thus, pro-domains are dual-function molecules, being the first substrate and first inhibitor encountered by PCs in cells.

A series of peptide inhibitors with varying degrees of selectivity and potency for various PCs are known in the art. One particular compound stand out: RARRRKKRT (or “RXXT compound”) (see WO 2009/023306).

In order to potentially inhibit the effects of furin in for example pathogenic infections, improved selective inhibitors were prepared and tested from the RXXT compounds.

The nomenclature used to identify amino acid positions in the inhibitors disclosed herein is as follows:

Peptide RXXT

Ac-R-A-R-R-R-K-K-R-T-NH₂

Ac-P8-P7-P6-P5-P4-P3-P2-P1-P1-NH₂

Structural modifications illustrated in FIG. 1 were made to the RXXT peptide in order to identify improved inhibitors of furin. The RXXT peptide was acetylated and amidated in order to improve its stability against degradation by cellular peptidases. Multiples variants with improved plasmatic half-life and stability of the RXXT peptide were synthesized and tested, as listed in Table 1.

TABLE 1
RXXT variants synthesized and tested

Preliminary observation showed that RXXT compounds are more susceptible to C-terminal degradation (see FIG. 2). Modified variant at the N-terminal part and/or C-terminal part were tested for their cellular stability and plasmatic half-life. As seen in FIG. 3A, N-terminal variant had no increase in stability. However, RXXT variants modified at their C-terminal part showed a 2 to 5 increase in their half-life.

The addition of the lipid amino-octanoyl group increased the penetration of the RXXT peptide (FIG. 4), thus confirming that further modifying the furin inhibitors with the lipid amino-octanoyl group will increase their potency by increasing the penetration of the compound in targeted cell. To demonstrate that the pharmacological activity of the furin inhibitors synthesized are not due to an increase in toxicity, a LDH release assay have been performed (FIG. 5).

As a proof of concept, the ability of the general PC inhibitor dec-RTKR-CMK to inhibit the toxicity of the Shiga toxin of Escherichia coli O157:H7 was measured (FIG. 6). After entering a cell via a macropinosome, the Shiga toxin functions as an N-glycosidase, cleaving a specific adenine nucleobase from the 28S RNA of the 60S subunit of the ribosome, thereby halting protein synthesis within the target cells. The Shiga toxin is associated with multiple pathalogies, such as hemolytic uremic syndrome, thrombotic thrombocytopenic purpura, and hemorrhagic colitis. The Shiga toxin infection is furin-dependent.

As seen in Table 2, the IC₅₀ for the RXXT inhibitors herein and the general PC inhibitor dec-RTKR-CMK were measured. The IC₅₀ for the dec-RTKR-CMK inhibitor was similar to that of peptides Aoc-RxxT[Azaβ₃R]^P1 and RxxT[Azaβ₃R]^P1-P8, showing the potency of the stabilized peptides described herein to inhibit the furin-dependent infection by the Shiga toxin of Escherichia coli O157:H7. Other RXXt inhibitors also showed low IC₅₀ values, including Rxx[ΔCO2]^P1 and RxxT[Azaβ₃R]^P1. It is known that other bacterial toxins, such as Pseudomonas and anthrax, use similar furin-dependent mechanism of infection.

TABLE 2
IC50 (μM) measured for the tested furin inhibitors
Furin inhibitor    IC50 (μM)
DEC-RTKR-CMK       11.5
RxxT               >1000
Aoc-RxxT           >1000
Rxx[ΔAR-CO2]P1     71.0
Rxx[AMBA]P1        >1000
Aoc-Rxx[AMBA]P1    N/A
RxxT[Azaβ3R]P1     314.5
Aoc-RxxT[Azaβ3R]P1 16.7
RxxT[Azaβ3R]P8     >1000
Aoc-RxxT[Azaβ3R]P8 >1000
RxxT[Azaβ3R]P1-P8  20.8

As illustrated in FIG. 8, a cellular fusion assay was developed. On the first day, a fixed number of HEK293 cells were seeded and transfected the next day with the appropriate expression plasmid to generate HA-positive cell line (or activator cell line) and GFP or luciferase positive cell line (or reporter cell line). For the HA-positive cell line, the transfected plasmid consisted to those constructs at the respective ratio 2.5:0.6:1; pCDNA3.1 containing HA from H5N1 Vietnam 2004:pCDNA 3.1 containing N1 from H5N1 Vietnam 2004:pLVX-Tet off vector containing the TAT activator. For the GFP-positive cell line, the transfected plasmid was either TAT inducible pLVX-Tight-GFP or pLVX-Tight-Luc that expresses GFP or Luciferase reporter gene in presence of the TAT inducer. The next day, the cells were counted and seeded in a 24 or 96 wells plate at a ratio of 3:1 of HA cell line to GFP cell line. Cell were allowed to adhere and then were treated 36 h with furin inhibitors in medium containing 1% FBS. Cells were finally treated to induce cell fusion by titration of the medium with pH3 citrate solution to a final pH of 5 for 15 minutes. After 15 min, medium was neutralized to physiological pH with HEPES/Bicarbonate medium, allowed to recover and incubated with fresh medium. Reporter gene was allowed to developed 48 h and then the cells were read for either fluorescence (GFP) or Luciferase activity in a multiwells reader. Inhibition of HA cleavage by furin resulted in a decreased fusion between gene and the subsequent non-expression of the reporter gene.

Using the cellular fusion assay, it is demonstrated that the stabilized peptides described herein have increased potency in inhibiting furin activity (see FIG. 7). When compared to the RxxT control peptide, seven peptides tested have increased potency against furin, namely Aoc-RxxT, Rxx[Δ-CO2]^P1, Aoc-Rxx[AMBA]^P1, PEG8-Rxx[AMBA]^P1, RxxT[Azaβ₃R]^P8, Aoc-RxxT[Azaβ₃R]^P8 and RxxT[Azaβ₃R]^P1-P8.

It is encompassed herein a composition comprising the furin inhibitors described herein and a carrier.

In accordance with the present description, a carrier or “pharmaceutical carrier” is a pharmaceutically acceptable solvent, suspending agent or any other pharmacologically inert vehicle for delivering one or more active compounds to an animal, and is typically liquid or solid. A pharmaceutical carrier is generally selected to provide for the desired bulk, consistency, etc., when combined with components of a given pharmaceutical composition, in view of the intended administration mode. Typical pharmaceutical carriers include, but are not limited to binding agents (e.g., pregelatinized maize starch, polyvinylpyrrolidone or hydroxypropyl methylcellulose, etc.); fillers (e.g., lactose and other sugars, microcrystalline cellulose, pectin, gelatin, calcium sulfate, ethyl cellulose, polyacrylates or calcium hydrogen phosphate, etc.); lubricants (e.g., magnesium stearate, talc, silica, colloidal silicon dioxide, stearic acid, metallic stearates, hydrogenated vegetable oils, corn starch, polyethylene glycols, sodium benzoate, sodium acetate, etc.); disintegrants (e.g., starch, sodium starch glycotate, etc.); and wetting agents (e.g., sodium lauryl sulphate, etc.).

In another embodiment, the composition further comprises at least one anti-viral drug. Concurrent administration” and “concurrently administering” as used herein includes administering a composition as described herein and insulin and/or a hypoglycemic compound in admixture, such as, for example, in a pharmaceutical composition, or as separate formulation, such as, for example, separate pharmaceutical compositions administered consecutively, simultaneously, or at different times.

The composition can be adapted for delivery by at least one of the following route selected from the group consisting of oral, mucosal, intranasal, intraocular, intratracheal, intrabronchial, intrapleural, intraperitoneal, intracranial, intramuscular, intravenous, intraarterial, intralymphatic, subcutaneous, intratumoral, gastric, enteral, colonic, rectal, urethral and intravesical route.

There is provided a method of reducing pathogen proliferation in a subject, comprising administering the furin inhibitors or the composition as defined herein to the subject, thereby reducing the proliferation of the pathogen in the subject.

Pathogen encompassed herein can be a bacterial pathogen such as Anthrax, Pseudomonas, Botulism, Diphtheria, Aeromonas or Shigella; or can be a viral pathogen such as Influenzavirus A, parainfluenza, Sindbis virus, Newcastle disease virus, flavivirus, cytomegalovirus, herpesvirus, HIV, Measles virus, infectious bronchitis virus, Coronavirus, Marburg virus, Ebola virus or Epstein-Barr virus.

Thus, it is provided a method for the treatment of a pathogen infection in a subject, comprising administering to said subject a therapeutically effective amount of the furin inhibitors or the composition as defined herein, thereby treating pathogen infection in the subject.

Preferably, the cell is in a subject. More preferably, the cell has increased furin activity.

There is also provided the use of the furin inhibitors or the composition as defined herein in the manufacture of a medicament for preventing or treating pathogen infection, in a subject.

The furin inhibitors or the composition as defined herein lower or inhibit furin activity in a cell, reducing proliferation of a pathogen in a subject.

The present disclosure will be more readily understood by referring to the following examples which are given to illustrate embodiments rather than to limit its scope.

Example I

Preparation of the Furin Inhibitors

The compounds of the present disclosure can be prepared according to the procedures denoted in the following reaction Schemes and Examples or modifications thereof using readily available starting materials, reagents, and conventional procedures or variations thereof well-known to a practitioner of ordinary skill in the art of synthetic organic chemistry. Specific definitions of variables in the Schemes are given for illustrative purposes only and are not intended to limit the procedures described.

Scheme 1: General synthesis of Synthesis of Fmoc-α-methyl-L-Arg(Boc)₂-OH

The synthesis of Fmoc-α-methyl-L-Arg(Boc)₂-OH was performed by guanidinylation of commercially available Fmoc-α-methyl-L-Orn-OH.

The synthesised Fmoc-α-methyl-L-Arg(Boc)₂-OH was used in peptide synthesis to generate an α-methyl-L-Arg peptide analogues. As illustrated in scheme 2, the 2-chlorotrityl resin is used for synthesis of protected peptide for further amidation on C-terminus with AMBA or other amines.

As illustrated in scheme 3, the hydrazine resin is used for the solid phase synthesis of protected peptide, where amidation of peptide occurs on C-terminus.

The following examples are given only to illustrate the invention and should not be regarded as constituting any limitation of the scope of the invention in its broadest meaning.

Example 1

Synthesis of Aza-β-Arginine Amino Acid

Step 1: Protection of the Amine

3,3-diethoxypropan-1-amine (1) (5.24 g, 35.6 mmol) was diluted in a mixture of dichloromethane (80 mL) and triethylamine (5.12 mL). The solution was cooled to 0° C., and a solution of di-tert-butyl-dicarbonate (7.85 g, 35.97 mmol) in dichloromethane (20 mL) was slowly added over a 15-minute period. The mixture was stirred for 16 h, at room temperature. The organic phase was washed with 1N HCl (1×100 mL), 0.5N HCl (1×100 mL), and brine (2×100 mL) before it was dried with anhydrous magnesium sulphate, filtered and concentrated. Le crude product was purified by flash chromatography on silica gel (eluent: hexanes/ethyl acetate 7:3). The protected amine was obtained as a yellow oil (8.36 g, 94%). ¹H NMR (300 MHz, CDCl₃) δ (ppm) 4.93 (s, 1H), 4.53 (t, 1H, J=5.5 Hz), 3.56 (d-quint, 4H, J=38.9 Hz, J=2.3 Hz), 3.20 (q, 2H, J=6.2 Hz), 1.79 (q, 2H, J=6.2 Hz), 1.42 (s, 9H), 1.19 (t, 6H, J=7.1 Hz). ¹³C NMR (75.5 MHz, CDCl₃) δ (ppm) 155.9, 101.9, 78.9. 61.5, 36.7, 33.4, 28.4, 15.3. IR (CHCl₃) v (cm⁻¹) 3363 (br), 2979, 2920, 2880, 1708, 1514, 1448, 1393, 1365, 1171, 1139, 1065.

Step 2: Preparation of the Aldehyde

The protected amine (2) (3.27 g, 13.2 mmol) was diluted in a mixture of acetic acid (5.1 mL) and water (1.4 mL), and the solution was stirred for 16 h, at room temperature. The pH of the solution was then slowly brought up to 7 with solid sodium carbonate. Diethyl ether (15 mL) was then added, and the organic phase was washed with water (1×10 mL) and brine (1×10 mL). After separation, the organic phase was dried with anhydrous magnesium sulphate, filtered and concentrated under reduced pressure. The crude product was quickly purified by flash chromatography on silica gel (eluent: diethyl ether/pentane 4:6). The aldehyde was obtained as a yellow oil (530 mg, 23%). ¹H NMR (300 MHz, CDCl₃) δ (ppm) 9.74 (s, 1H), 4.97 (s, 1H), 3.46 (t, 2H, J=7.0 Hz), 2.64 (t, 2H, J=7.0 Hz), 1.36 (s, 9H).

Step 3: Preparation of the Imine

The aldehyde (3) (530 mg, 3.06 mmol) was diluted in dichloromethane (15 mL), and Fmoc-hydrazine (780 mg, 3.06 mmol) was added. The mixture was stirred for 16 h at room temperature. The solvent was removed under reduced pressure and the crude product was triturated in petroleum ether. The imine was obtained as a white powder (730 mg, 68%). ¹H NMR (300 MHz, DMSO-d₅) δ (ppm) 7.87-7.27 (m, 8H), 6.83 (s, 1H), 4.36 (s, 2H), 4.22 (s, 1H), 3.29 (s, 2H), 2.23 (s, 2H), 1.32 (s, 9H). ¹³C NMR (75.5 MHz, CDCl₃) δ (ppm) 143.7, 141.3, 127.8, 127.1, 125.0, 120.0, 78.4, 67.0, 49.4, 47.2, 38.5, 28.4, 27.7. IR (CHCl₃) v (cm⁻¹) 3344, 3255, 3064, 2976, 2927, 1708, 1683, 1531, 1446, 1365, 1248, 1170, 1029.

Step 4: Reduction of the Imine

The imine (4) (730 mg, 1.78 mol) was dissolved in a mixture of dichloromethane (12 mL) and methanol (8 mL). Sodium cyanoborohydride (146 mg, 62.8 mmol) was added and the pH was slowly brought up to 4 with 2N HCl. The mixture was stirred for 45 minutes at room temperature, and then the pH was brought up to 7 with solid sodium bicarbonate. The mixture was filtered and concentrated under reduced pressure. The residue was dissolved in ethyl acetate (30 mL). The organic phase was washed with water (1×40 mL) and brine (1×40 mL), and then dried with anhydrous magnesium sulphate, filtered and concentrated under reduced pressure. The reduced imine was obtained as a white-orange solid (720 mg, 98%). ¹H NMR (300 MHz, DMSO-d₆) δ (ppm) 7.86-7.26 (m, 8H), 4.29-4.20 (m, 2H), 4.20-4.12 (m, 1H), 2.89 (t, 2H, J=6.3 Hz), 2.70-2.52 (m, 2H), 1.43-1.34 (m, 2H), 1.33 (s, 9H). ¹³C NMR (75.5 MHz, CDCl₃) δ (ppm) 157.0, 156.4, 143.6, 141.3, 127.8, 127.1, 125.0, 120.0, 79.5, 67.3, 49.3, 47.1, 38.3, 28.4, 27.4. IR (CHCl₃) v (cm⁻¹) 3318, 3064, 2976, 2937, 1700, 1520, 1478, 1450, 1390, 1365, 1273, 1252, 1171, 1040.

Step 5: Preparation of the Benzyl Ester

The reduced imine (5) (720 mg, 1.75 mmol) was dissolved in toluene (22 mL) and the mixture was heated to 80° C. Benzyl bromoacetate (521 mg, 2.28 mmol) and dried K₂CO₃ (170 mg, 1.23 mmol) were added, and the reaction was stirred for 24 h at 80° C. The mixture was filtered and washed with ethyl acetate (40 mL). The organic phase was washed with water (1×30 mL) and brine (1×30 mL) before it was dried with anhydrous sodium sulphate, filtered and concentrated under reduced pressure. The crude product was purified by flash chromatography on silica gel (eluent: petroleum ether/ethyl acetate 3:1). The benzylic ester was obtained as a yellow oil (300 mg, 31%). ¹H NMR (300 MHz, CDCl₃) δ (ppm) 7.81-7.28 (m, 13H), 5.17 (s, 2H), 4.42 (d, 2H, J=7.2 Hz), 4.19 (s, 1H), 3.72 (s, 2H), 3.21 (s, 2H), 2.97 (s, 2H), 1.68-1.54 (m, 2H), 1.42 (s, 9H). ¹³C NMR (75.5 MHz, CDCl₃) δ (ppm) 169.5, 156.5, 155.9, 143.7, 141.4, 128.7, 128.6, 128.4, 127.7, 127.1, 126.0, 120.0, 119.8, 77.2, 66.7, 57.2, 54.2, 47.3, 44.5, 38.6, 28.4, 27.4. IR (CHCl₃) v (cm⁻¹) 3350, 3064, 2972, 1739, 1729, 1693, 1682, 1609, 1503, 1453, 1390, 1365, 1248, 1171, 1107.

Step 6: preparation of N,N-di-(tert-butoxycarbonyl)-guanidine as described in Journal of Organic Chemistry, Vol. 63, No. 23, 1998

Guanidine chlorhydrate (7) (12.3 g, 128 mmol) and sodium hydroxide (20.8 g, 519 mmol) were dissolved in water (125 mL), and 1,4-dioxane (250 mL) were added. The mixture was cooled to 0° C. and di-tert-butyl-carbonate (62.9 g, 288 mmol) was added. The mixture was allowed to warm at room temperature within 16 h. The solution was concentrated in vacuo to one-third of its initial volume. Water (150 mL) was added to the resulting mixture, and the solution was extracted with ethyl acetate (3×80 mL). The organic phase was then washed with 10% citric acid (1×100 mL), water (1×100 mL) and brine (1×100 mL), dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The crude product was purified by flash chromatography on silica gel (eluent: 100% dichloromethane to dichloromethane/methanol 95:5). The di-protected guanidine was obtained as a white powder (30.54 g, 91%). ¹H NMR (300 MHz, DMSO-d₆) δ (ppm) 10.42 (s, 1H), 8.47 (s, 1H), 1.37 (s, 18H). ¹³C NMR (75.5 MHz, CDCl₃) δ (ppm) 158.3, 82.3, 28.1. IR (CHCl₃) v (cm⁻¹) 3407, 3124, 2976, 2930, 1792, 1641, 1549, 1453, 1397, 1365, 1248, 1153.

Step 7: preparation of N,N-di-Boc-N′-trifluoromethanesulfonylguanidine as described in Journal of Organic Chemistry, Vol. 63, No. 23, 1998

Under an inert atmosphere, N,N-di-(tert-butoxycarbonyl)-guanidine (8) (10 g, 38 mmol) was dissolved in anhydrous dichloromethane (200 mL). The mixture was cooled to −78° C., and triethylamine (5.65 mL, 40.5 mmol) was added. Trifluoromethanesulfonic anhydride (6.81 mL, 40.5 mmol) was added dropwise, over a 30-minute period. The reaction mixture was stirred for 16 h at room temperature. The solution was washed with 2M sodium bisulphate (1×200 mL) and water (1×200 mL), and the organic phase was dried with anhydrous sodium sulphate, filtered and concentrated. The crude product was purified by flash chromatography on silica gel (eluent: 100% dichloromethane) and recrystallized in hexanes. N,N-di-Boc-N′-trifluoromethanesulfonylguanidine was obtained as white crystals (11.74 g, 78%). ¹H NMR (300 MHz, DMSO-d₆) δ (ppm) 1.43 (s, 18H). ¹³C NMR (75.5 MHz, CDCl₃) δ (ppm) 151.4, 121.4, 117.1, 86.0, 27.8. IR (CHCl₃) v (cm⁻¹) 3304, 2983, 1785, 1736, 1626, 1556, 1464, 1376, 1340, 1259, 1192.

Step 8: addition of guanidine

Benzylic ester (6) (300 mg, 0.54 mmol) was dissolved in dichloromethane (1.65 mL), trifluoroacetic acid (1.65 mL) was added. The mixture was stirred for 16 h at room temperature. Dichloromethane (15 mL) and water (5 mL) were added, and the pH was slowly brought up to 8 with solid sodium carbonate. After separation, the organic phase was washed with water (1×40 mL) and brine (1×40 mL), and then dried with anhydrous magnesium sulphate, filtered and concentrated under reduced pressure to the half of its volume. Triethylamine (82 μL) and N,N-di-Boc-N′-trifluoro methanesulfonylguanidine (9) (190 mg) were added and the mixture was stirred on 16 h. The solution was then washed with 2M sodium bisulphate (1×10 mL), a saturated solution of sodium bicarbonate (1×10 mL), water (1×15 mL) and brine (1×15 mL). The organic phase was dried with anhydrous sodium sulphate, filtered and concentrated. The crude product was purified by flash chromatography on silica gel (eluent: petroleum ether/ethyl acetate 7:3). The product (10) was obtained as a yellow oil (291 mg, 77%)¹H NMR (300 MHz, CDCl₃) δ (ppm) 7.76-7.11 (m, 13H), 5.16 (s, 2H), 4.41 (s, 2H), 4.21 (s, 1H), 3.79 (s, 2H), 3.54 (s, 2H), 2.98 (s, 2H), 1.70 (s, 2H), 1.48 (s, 18H). ¹³C NMR (75.5 MHz, CDCl₃) δ (ppm) 170.5, 163.6, 156.2, 153.2, 143.8, 141.3, 135.2, 128.7, 128.6, 128.4, 127.7, 127.1, 125.1, 121.4, 120.0, 83.0, 79.2, 66.6, 57.7, 53.6, 47.2, 38.5, 31.2, 28.3, 28.1, 27.1. IR (CHCl₃) v (cm⁻¹) 3329, 3146, 3064, 2980, 1715, 1612, 1453, 1411, 1160.

Step 9: preparation of the carboxylic acid

Benzylic ester (10) (291 mg, 0.41 mmol) was dissolved in ethyl acetate (6 mL). Palladium on activated carbon (19 mg) was added, and the reaction mixture was put under an hydrogen atmosphere. The solution mixture was stirred for 6 h, filtered on Celite®, rinsed with ethyl acetate (5×10 mL) and concentrated. Aza-β-arginine was obtained as a white foam (240 mg, 94%). ¹H NMR (300 MHz, CDCl₃) δ (ppm) 7.76-7.24 (m, 8H), 4.49 (s, 2H, J=7.4 Hz), 4.21 (t, 1H, J=6.9 Hz), 3.68 (s, 2H), 3.49 (s, 2H), 3.00 (s, 2H), 1.75 (s, 2H), 1.53-1.40 (m, 18H). ¹³C NMR (75.5 MHz, CDCl₃) δ (ppm) 172.8, 156.8, 156.2, 153.0, 143.6, 141.3, 127.7, 127.1, 125.1, 120.0, 83.7, 67.0, 58.8, 53.4, 47.2, 38.8, 28.2, 281, 27.1. IR (CHCl₃) v (cm⁻¹) 3329, 2979, 1722, 1623, 1474, 1453, 1421, 1231, 1150.

Example 2

Synthesis of Amino Acid Aza-β3-Leucine

Step 1: Preparation of Fmoc-Hydrazine

Hydrazine (18.0 mL, 213 mmol) was dissolved in diethyl ether (240 mL) at 0° C.A solution of Fmoc chloride (1) (12.0 g, 46.4 mmol) in diethyl ether (240 mL) was added to the hydrazine solution over a 30-minute period. The reaction mixture was stirred at room temperature for 16 h. The solution was evaporated, and water (400 mL) and ethyl acetate (400 mL) were added. The organic phase was washed with water (4×150 mL). The resulting suspension was evaporated. Fmoc-hydrazine (2) was obtained as a white solid (13.92 g, 118%). ¹H NMR (300 MHz, CDCl₃) δ (ppm) 7.71-7.29 (m, 8H), 6.05 (s, 1H), 4.45 (d, 1H, J=6.8 Hz), 4.23 (t, 1H, J=8.3 Hz), 3.81 (s, 2H). ¹³C NMR (75.5 MHz, CDCl₃) δ (ppm) 143.6, 141.3, 127.8, 127.1, 120.1, 67.3, 47.1 IR (CHCl₃) v (cm⁻¹) 1686, 1633, 1506, 1446.

Step 2: Preparation of the Imine

Fmoc-hydrazine (2) (3.66 g, 14.4 mmol) was dissolved in dichloromethane (55 mL), and isobutyraldehyde (1.31 mL, 14.4 mmol) was added. The mixture was stirred for 16 h and evaporated. The product (3) was obtained as a white powder (4.12 g, 93%). ¹H NMR (300 MHz, CDCl₃) δ (ppm) 7.78-7.26 (m, 8H), 7.09 (d, 1Hm J=4.7 Hz), 4.51 (d, 2H, J=6.8 Hz), 4.29 (s, 1H), 2.64 (sext, 1H, J=4.1 Hz), 1.13 (d, 6H, J=5.9 Hz). ¹³C NMR (75.5 MHz, CDCl₃) δ (ppm) 143.7, 141.3, 127.8, 127.1, 125.2, 120.0, 67.2, 47.0, 31.4, 19.9. IR (CHCl₃) v (cm⁻¹) 3237, 3068, 1258, 2866, 1708, 1545, 1464, 1450, 1382, 1354, 1259, 1185.

Step 3: Imine Reduction

The imine (3) (4.12 g, 13.4 mmol) was dissolved in 70 mL of a mixture of dichloromethane and methanol (3:2). NaBH₃CN (1.01 g, 16.0 mmol) was added and the pH was brought up to 4 with 1N HCl. The reaction mixture was stirred for 30 minutes. The solution was acidified to pH 1 with 1N HCl, and stirred for 10 minutes. The pH was then brought up to 7 with solid sodium carbonate, and then evaporated. The residue was dissolved in ethyl acetate (50 mL), and the organic phase was washed with water (1×50 mL) and brine (1×50 mL). The organic phase was dried with sodium sulphate, filtered and evaporated. The crude product was purified with a flash chromatography on silica gel (eluent:ethyl acetate/hexanes 3:7). The reduced imine (4) was obtained as a white powder (4.63 g, 112%). ¹H NMR (300 MHz, CDCl₃) δ (ppm) 7.81-7.21 (m, 8H), 4.45 (s, 2H), 4.22 (t, 1H, J=6.6 Hz), 2.90 (s, 2H), 1.97 (s, 1H), 0.98 (d, 6H, J=5.2 Hz). ¹³C NMR (75.5 MHz, CDCl₃) δ (ppm) 157.2, 143.7, 141.3, 127.8, 127.1, 125.0, 120.0, 67.0, 60.0, 47.2, 26.7, 20.5. IR (CHCl₃) v (cm⁻¹) 3322, 3255, 3064, 2955, 2884, 1694, 1527, 1489, 1457, 1383, 1273, 1192.

Step 4: Addition of Glyoxylic Acid

The reduced imine (4) (4.63 g, 14.9 mmol) was dissolved in 70 mL of a mixture of dichloromethane and methanol (3:2). Glyoxylic acid (1.65 g, 17.9 mmol) and NaBH₃CN (1.13 g, 17.9 mmol) were added. The pH was brought up to ph 4 with 1N HCl and stirred for 30 minutes, and the mixture was acidified to pH 1 for 10 minutes. The pH was then brought up to 4 with solid sodium carbonate. The reaction mixture was filtered and concentrated. The residue was dissolved in ethyl acetate (50 mL), and washed with water (1×50 mL) and brine (1×50 mL). The organic phase was dried with sodium sulphate, filtered and evaporated. Aza-β3-leucine (5) was obtained as a white solid foam (5.11 g, 93%). ¹H NMR (300 MHz, CDCl₃) δ (ppm) 7.76-7.31 (m, 8H), 6.12 (s, 1H), 4.54 (d, 2H, J=6.2 Hz), 4.18 (s, 1H), 3.55 (s, 2H), 2.58 (d, 2H, J=7.0 Hz), 1.54 (s, 1H), 0.91 (d, 6H, J=6.5 Hz). ¹³C NMR (75.5 MHz, CDCl₃) δ (ppm) 171.2, 157.2, 143.4, 141.3, 127.8, 127.1, 124.9, 120.0, 67.1, 66.7, 60.5, 47.2, 26.3, 20.5. IR (CHCl₃) v (cm⁻¹) 3251, 3051, 2958, 2869, 1739, 1514, 1451, 1364, 1254, 1147.

Example 3

Synthesis of 4-amino-2-en-1-yl guanidine

Step 1: preparation of 1-bromo-4-phthalimido-2-butene (1)

1,4-Dibromo-2-butene (15.0 g, 70.1 mmol) was added to the stirred suspension of potassium phthalimide (4.32 g, 23.3 mmol) in DMF (24 mL). The mixture was stirred 48 h. Cooled water was added and the precipitated solid was filtered and dried at high vacuum to give the desired compound (1). The compound was purified with ethyl acetate/hexane 3:7 to give a white solid (4.28 g, 66%); ¹H NMR (CDCl₃) δ (ppm) 3.92 (d, 2H, CH₂), 4.32 (d, 2H, CH₂), 5.89 (m, 2H, CH), 7.70-7.89 (m, 4H, Aromatic); ¹³C NMR (CDCl₃) δ (ppm) 168 (CO), 134 (CH), 132 (C aromatic), 129 (C aromatic), 128 (C aromatic), 123 (CH), 38 (CH₂N), 31 (CH₂Br).

Step 2: Preparation of N-(4-phthalimido-2-butenyl)hexamethylene tetrammonium bromide (2)

To a solution of 1-3 Hexamethylenetetramine (3.21 g, 22.9 mmol) in CHCl₃ (43 mL) was added dropwised a solution of 1-bromo-4-phthalimido-2-butene (1) (4.28 g, 15.3 mmol) in CHCl₃ (43 mL), The solution was stirred during 48 h. A white precipitate appeared. The solid was filtered and washed with chloroform. A white powder was obtained (6.91 g, 107% water trace, dried on high vacuum). ¹H NMR (MeOD) δ (ppm) 3.45 (d, 2H, CH₂), 4.38 (d, 2H, CH₂), 4.50 (d, 6H, CH₂), 4.67 (d, 6H, CH₂), 5.85 (m, 1H, CH), 6.15 (m, 1H, CH), 7.80-7.89 (m, 4H, aromatic). ¹³C NMR (MeOD) δ (ppm) 168 (CO), 138 (C aromatic), 134 (C aromatic), 122 (CH), 117 (CH), 78 (CH₂), 70 (CH₂), 57 (CH₂N), 38 (CH₂Br).

Step 3: preparation of N-(4-phthalimido-2-butenyl)ammonium chloride (3)

To a solution of compound (2) (4.32 g, 10.3 mmol) in ethanol (174 mL) was added dropwide a solution of concentrated HCl (7.25 mL, 12 M). The mixture was reflux during 2 h (around 90° C.). On cooling of the reaction mixture, the precipitate was filtered off and the filtrate was concentrated to give the desired product as a yellow oil (4.39 g). ¹H NMR (MeOD) δ (ppm) 3.50 (d, 2H, CH₂), 4.28 (d, 2H, CH₂), 5.75 (m, 1H, CH), 5.95 (m, 1H, CH), 7.79-7.87 (m, 4H, aromatic). ¹³C NMR (MeOD) δ (ppm) 168 (CO), 134 (C aromatic), 132 (C aromatic), 131 (C aromatic), 124 (CH), 123 (CH), 40 (CH₂N), 38 (CH₂Br).

Step 4: preparation of N-(4-phthalimido-2-butenyl) guanidine-(di-Boc) (4)

To a solution of triethylamine (1.05 mL), tert-butyl[N-(tert-butoxycarbonyl)-N′-(trifluoroacetyl)carbamimidoyl]carbamate (6) (1.97 g, 5.03 mmol) in DCM (56 mL) was added compound (3) (1.4 g, 5.55 mmol). The solution was stirred overnight. DCM was added and the organic phase was washed with sodium bisulfate (2M), a saturated solution of NaHCO₃ and brine. The organic phase was dried with magnesium sulfate, filtered and concentrated. The crude compound was purified with ethyl acetate/hexane (30/70) to (40/60). Rf=0.58. A white solid was obtained (2.13 g, 93%). ¹H NMR (CDCl₃) δ (ppm) 1.48 (s, 18H, CH₃), 4.05 (m, 2H, CH₂), 4.28 (d, 2H, CH₂), 5.30 (m, 2H, CH), 7.73-7.84 (m, 4H, aromatic), 8.45 (sl, 1H, NH), 11.48 (s, 1H, NH). ¹³C NMR (CDCl₃) δ (ppm) 133 (C aromatic), 132 (C aromatic), 129 (C aromatic), 126 (CH), 123 (CH), 41 (CH₂), 38 (CH₂), 28 (CH₃ boc).

Step 5: preparation of N-(2-butenyl) guanidine-(di-Boc) (5)

To a solution of compound (4) (1.86 g, 4.06 mmol) in methanol (12.01 mL) and chloroform (9.5 mL) was added hydrazine (1.0 mL). The solution was stirred during 4 h. A white solid appeared during the reaction. The solid was filtered and the filtrate was diluted with chloroform. The organic phase was washed with sodium hydroxide (1M). The organic phase was dried with magnesium sulfate, filtered and concentrated. We obtained a yellow solid (1.22 g, 92%). ¹H NMR (CDCl₃) δ (ppm) 1.49 (s, 18H, CH₃), 3.30 (d, 2H, CH₂), 4.06 (d, 2H, CH₂), 5.65-5.76 (m, 2H, CH), 8.34 (s, 1H, NH), 11.51 (s, 1H, NH). ¹³C NMR (CDCl₃) δ (ppm) 163 (CO), 155 (CO), 153 (C), 134, 128, 125, 83, 79, 43 (CH₂), 28 (CH₃ boc).

Example 4

Synthesis of Aza-β3-Lysine Amino Acid

Step 1: preparation of tert-butyl N-(4,4-diethoxybutyl)carbamate (1)

In a flask were added 4,4-diethoxybutan-1-amine (2 g, 12.4 mmol), triethylamine (1.8 mL, 12.9 mmol) and DCM (10 mL). The solution was cooled to 0° C. To this solution was added dropwised a solution of Boc₂O (2.7 g, 12.4 mmol) in DCM (10 mL). The solution was stirred overnight then evaporated. The compound was purified by flash chromatography by using ethyl acetate/hexane (10/90) to (30/70) to give (0.72 g, 89%). ¹H NMR (CDCl₃) δ (ppm) 1.17 (t, 6H, CH₃), 1.43 (s, 9H, CH₃), 1.55 (m, 4H, CH₂), 3.12 (d, 2H, CH₂), 3.45 (m, 2H, CH₂), 3.47 (m, 2H, CH₂), 4.47 (t, 1H, CH), 4.64 (s, 1H, NH).

Step 2: preparation of N-t-butyloxycarbonyl-4-amino-butanal (2)

A solution of 1-Boc-amino-3,3-diethoxypropane (15.3 g, 58.5 mmol) in AcOH (27 mL) and water (8 mL) was stirred at room temperature for 10 h, neutralized with Na₂CO₃, taken up in ether, and washed with water and brine. The organic phase was evaporated under vacuum to give a yellow oil used as such in the next step (14.25 g). ¹H NMR (400 MHz, CDCl₃) δ (ppm) 1.47 (s, CH₃ boc), 1.90 (m), 3.47 (m), 3.51 (q), 5.30 (s).

Step 3: preparation of Fmoc-NHN═CH(CH₂)₂NHBoc (3)

Fmoc carbazate (14.86 g, 58.4 mmol) was added to a stirred solution of the aldehyde (2) (10.95 g, 58.5 mmol) (261 mL) The reaction mixture was stirred for 12 h at 45° C. and concentrated under vacuum to give crude solid that was triturated with petroleum ether to afford the hydrazone as a white solid (24.38 g). ¹H NMR (400 MHz, CDCl₃) δ (ppm) 1.35 (s, 9H, CH₃ boc), 1.70 (m, 2H, CH₂), 2.10 (m, 2H, CH₂), 2.90 (m, 2H, CH₂), 4.20 (m, 1H, CH), 6.83 (sl, 1H, NH), 7.65 (d, CH aromatic), 7.85 (d, CH aromatic), 8.66 (sl, 1H, NH), 10.70 (sl, 1H, NH).

Step 4: preparation of FmocNHN═CH(CH₂)₂NHBoc (4)

Then, Fmoc protected hydrazone (3) (24.38 g, 58.4 mmol) was dissolved in a mixture DCM/MeOH (166/100 mL) and was added NaBH₃CN (4.44 g, 70.7 mmol). The pH was adjusted at pH 3-4 with HCl (2N) (Keep the pH at 3-4 during 1 h). The solution was neutralized with NaHCO₃ (pH 7-8). The solvent was concentrated under vacuum. Ethyl acetate was added and the organic phase was washed with water, brine and dried with magnesium sulfate. The organic phase was filtered and concentrated then purified by flash chromatography by using dichloromethane/ethyl acetate 60/40 to give oil (4.46 g, 18%). ¹H NMR (400 MHz, CDCl₃) δ (ppm) 1.35 (s, 9H, CH₃ boc), 2.62 (m, 2H, CH₂), 3.12 (m, 2H, CH₂), 3.78 (m, 2H, CH₂), 6.05 (sl, 1H, NH), 6.36 (sl, 1H, NH), 7.27 (t, 1H, CH), 7.30 (t, 1H, CH), 7.65 (d, 1H, CH), 7.85 (d, 1H, CH).

Step 5: preparation of FmocNHN(CH₂—COOH)—CH(CH₂)₂NHBoc (5)

To a solution of compound (2) (4.4 g, 10.50 mmol), glyoxylic acid (1.83 g, 19.88 mmol) in a mixture of MeOH/DCM (60/30) was added NaBH₃CN (1.24 g, 19.73 mmol). The pH was controlled between 3-4 by addition of HCl (2N) during one hour. The solution was filtrated and concentrated. Ethyl acetate was added and the organic phase was washed with water and brine. The organic phase dried with magnesium sulfate and concentrated under vacuum to give the crude compound. The product was purified by flash chromatography (Ether(95)/MeOH(5)/AcOH(0.25) to give a white solid (4.1 g, 82%). ¹H NMR (400 MHz, CDCl₃) δ (ppm) 1.35 (s, 9H, CH₃ boc), 2.62 (m, 2H, CH₂), 3.12 (m, 2H, CH₂), 3.78 (m, 2H, CH₂), 6.05 (sl, 1H, NH), 7.27 (t, 1H, CH), 7.30 (t, 1H, CH), 7.65 (d, 1H, CH), 7.85 (d, 1H, CH).

While the invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modifications and this application is intended to cover any variations, uses, or adaptations of the invention, and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth, and as follows in the scope of the appended claims.

Claims

1. A peptide sequence comprising the following formula I Z-Xaa8-Xaa7-Xaa6-Xaa5-Arg4-Xaa3-Xaa2-Arg1-Xaa1′  (I)

2. The peptide sequence of claim 1 wherein Xaa2 is Lys, Arg or stereoisomer thereof and Xaa3 is independently Lys, Val or stereoisomer thereof.

3. The peptide sequence of claim 1, wherein at least one of Xaa1′, Arg1, Arg4, Xaa5, Xaa6, Xaa7, and Xaa8 is an analogue of Lys or Arg.

4. The peptide sequence of claim 1, wherein the analogue of arginine is represented by the following formula (III)

5. The peptide sequence of claim 4, wherein W1 is -arylalkylene-, -arylalkenylene-, —NR1-alkylene-, —NR1-alkenylene-, —NR1-arylene-, —NR1-arylalkylene-, -alkylene-NR2-, -alkenylene-NR2-, —NR1-alkenylene-NR2-, —NR1-arylene-NR2-, or —NR1-arylalkylene-NR2-.

6. The peptide sequence of claim 4, wherein the analogue of arginine is represented by

7. The peptide sequence of claim 1, wherein the analogue of Lys is represented by the following formula IV

8. The peptide sequence of claim 7, wherein W2 is a bond, -alkylene-, -alkenylene-, -heteroarylene-, -arylalkylene-, -heteroarylalkylene-, -alkylarylene-, or -alkylheteroarylene-, each of which may be optionally substituted with at least of one substituent selected from alkyl, and alkenyl.

9. The peptide of claim 7, wherein the analogue of Lys is represented by

10. A composition comprising the peptide of claim 1 and a carrier.

11.-16. (canceled)

17. A method of reducing pathogen proliferation or treating a pathogen infection in a subject, comprising administering the peptide of claim 1 or the composition of claim 10 to the subject, thereby reducing the proliferation of the pathogen in the subject or treating the pathogen infection in the subject.

18. The method of claim 17, wherein the pathogen is Anthrax, Pseudomonas, Botulism, Diphtheria, Aeromonas, Shigella, Influenzavirus A, parainfluenza, Sindbis virus, Newcastle disease virus, flavivirus, cytomegalovirus, herpesvirus, HIV, Measles virus, infectious bronchitis virus, Coronavirus, Marburg virus, Ebola virus or Epstein-Barr virus.

19.-27. (canceled)

28. The method of claim 17, further comprising administering at least one anti-viral drug.

29. The method of claim 17, wherein said peptide or composition is administered concurrently with at least one anti-viral drug.

30. The method of claim 17, wherein said peptide or composition is administered by one of the following routes: oral, mucosal, intranasal, intraocular, intratracheal, intrabronchial, intrapleural, intraperitoneal, intracranial, intramuscular, intravenous, intraarterial, intralymphatic, subcutaneous, intratumoral, gastric, enteral, colonic, rectal, urethral or intravesical.