EP1286590A2 - Peptide analogs and mimetics suitable for in vivo use in the treatment of diseases associated with abnormal protein folding into amyloid, amyloid-like deposits or beta-sheet rich pathological precursor thereof - Google Patents

Abstract

The present invention is an inhibitory peptide capable of inhibiting β pleated sheet formation in amyloid β-peptide. The inhibitory peptide is a βsheet breaker peptide analog designed by chemical modification of β sheet breaker peptide capable of inhibiting β pleated sheet formation in amyloid β-peptide. The present invention also includes an inhibitory peptide capable of inhibiting conformational changes in prion PrP protein associated with amyloidosis. The inhibitory peptide being a βsheet breaker peptide analog designed by chemical modification of a βsheet breaker peptide capable of inhibiting the conformational changes in prior PrP protein associated with amyloidosis. In addition, the present invention includes a peptide mimetic with the structure PMiAβ5. In another embodiment, the peptide mimetic has the structure PMiPrP13. In yet another embodiment, the peptide mimetic has the structure PMiPrP5.

Description

PEPTIDE ANALOGS AND MIMETICS SUITABLE FOR IN VIVO USE IN THE

TREATMENT OF DISEASES ASSOCIATED WITH ABNORMAL PROTEIN

FOLDING INTO AMYLOID, AMYLOID-LIKE DEPOSITS OR β-SHEET RICH

PATHOLOGICAL PRECURSOR THEREOF

This application claims priority from U.S. Provisional Application No. 60/163,911,

which was filed on November 5, 1999.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to peptide analogs and peptide mimetics of β-sheet

breaker peptides suitable for in vivo use in treating mammals with protein conformational

diseases such as Alzheimer's and prion disease. More particularly, the present invention is

directed to novel peptide analogs and mimetics, pharmaceutical compositions containing one

or a mixture of such peptide analogs and mimetics, and methods for preventing, treating, or

detecting disorders or diseases associated with abnormal protein folding into amyloid or

amyloid-like deposits or precursors thereof having a pathological beta-sheet structure.

Description of Related Art

Extensive evidence has been accumulated indicating that several diverse disorders

have the same molecular basis, i.e. a change in a protein conformation (Thomas et al.,

Trends Biochem. Sci. 20: 456-459, 1995; Soto, J. Mol. Med. 11: 412-418, 1999). These

protein conformational diseases include Alzheimer's disease, prion-related disorders, systemic amyloidosis, serpin-deficiency disorders, Huntington's disease and Amyotrophic

Lateral Sclerosis (Soto 1999, supra). The hallmark event in protein conformational disorders

is a change in the secondary and tertiary structure of a normal protein without alteration of

the primary structure. The conformationally modified protein may be implicated in the

disease by direct toxic activity, by the lack of biological function of normally-folded protein,

or by improper trafficking (Thomas et al., 1995, supra). In the cases where the protein is

toxic, it usually self- associates and becomes deposited as amyloid fibrils in diverse organs,

inducing tissue damage (Thomas et al., 1995, supra; Kelly, Curr. Opin. Struct. Biol. 6: 11-

17, 1996; Soto, 1999, supra).

Alzheimer's disease (AD) is a devastating neurodegenerative problem characterized

by loss of short-term memory, disorientation, and impairment of judgment and reasoning.

AD is the most common dementia in elderly population. It is estimated that more than

twenty-five million people worldwide are affected in some degree by AD (Teplow, Amyloid

5: 121-142, 1998). A hallmark event in AD is the deposition of insoluble protein

aggregates, known as amyloid, in brain parenchyma and cerebral vessel walls. The main

component of amyloid is a 4.3 KDa hydrophobic peptide, named amyloid beta-peptide (Aβ)

that is encoded on the chromosome 21 as part of a much longer precursor protein (APP)

(Selkoe, Science 275: 630-631, 1997). Genetic, biochemical, and neuropathological evidence

accumulated in the last 10 years strongly suggest that amyloid plays an important role in

early pathogenesis of AD and perhaps triggers the disease (Soto et al., J. Neurochem. 63:

1191-1198, 1994; Selkoe, 1997, supra; Teplow, 1998, supra; Sisodia and Price, FASEB J. 9: 366-370, 1995; Soto, Mol. Med. Today 5: 343-350, 1999).

Amyloid is a generic term that describes fibrillar aggregates that have a common

structural motif, i.e., the β-pleated sheet conformation (Serpell et al., Cell Mol. Life Sci. 53:

887, 1997; Sipe, Ann. Rev. Biochem. 61: 947-975, 1992). These aggregates exhibit specific

tinctorial properties, including the ability to emit a green birefringent glow after staining

with Congo red, and the capacity to bind the fluorochrome, thioflavin S (Sipe, 1992, supra;

Ghiso et al., Mol. Neurobiol. 8: 49-64, 1994). There are more than a dozen human diseases

of different etiology characterized by the extracellular deposition of amyloid in diverse

tissues, which lead to cell damage, organ dysfunction, and death. Among the diseases

involving amyloidosis, it is possible to highlight Alzheimer's disease, prion-related disorders

(also known as transmissible spongiform encephalopathy), and systemic amyloidosis (Table

1). The amyloid fibrils are usually composed of proteolytic fragments of normal or mutant

gene products. There are over 16 different proteins (Table 1) involved in amyloid deposition

in distinct tissues (Ghiso et al., 1994, supra).

The formation of amyloid is basically a problem of protein folding, whereby a mainly

random coil soluble peptide becomes aggregated, adopting a β-pleated sheet conformation

(Kelly, 1996, supra; Soto, 1999, supra). Amyloid formation proceeds by hydrophobic

interactions among conformationally altered amyloidogenic intermediates, which become

structurally organized into a β-sheet conformation upon peptide interaction. The

hydrophobicity appears to be important to induce interaction of the monomers leading to

aggregation, while the β-sheet conformation might determine the ordering of the aggregates in amyloid fibrils. In an attempt to inhibit amyloid fibril formation, these two properties were separated by designing short synthetic peptides bearing sequence homology and a

similar degree of hydrophobicity as the peptide domain implicated in the conformational

change, but having a very low propensity to adopt a β-sheet conformation (called β-sheet

breaker peptides) (Soto et al., 1996, supra; Soto et al., 1998, supra). The aim was to design a

peptide with the ability to bind specifically to the amyloidogenic peptide forming a complex

that stabilizes the physiological conformation and destabilizes the abnormal conformation of

the peptide (Soto, 1999, supra).

Table 1. Disorders related with amyloidosis and the protein component of the amyloid fibrils

DISEASE FIBRIL COMPONENT

Alzheimer's disease Amyloid-β protein

Primary systemic amyloidosis Immunoglobulin light chain or fragments thereof

Secondary systemic amyloidosis. Fragments of serum amyloid-A

Familial Mediterranean fever

Spongiform encephalopathy Fragments of pnon protein

Senile systemic amyloidosis, Transthyretin and fragments thereof

Familial amyloid polyneuropathy

Hemodialysis-related amyloidosis β2-mιcroglobulιn

Hereditary cerebral amyloid angiopathy, Icelandic type Cy stain C

Familial amyloidosis, Finnish type Gelsohn fragments

Type 11 diabetes Fragments of islet amyloid polypeptide

Familial amyloid polyneuropathy Fragments of apo poprotein A- l

Mcdullar carcinoma of the thyroid Fragments of calcitomn

Atπal amyloidosis Atπal natnuretic factor

Hereditary non-neuropathic systemic amyloidosis Lysozyme or fragments thereof

Hereditary renal amyloidosis Fibπnogen fragments

Islet amyloid Insulin

Amyloidosis in senescence Apohpoprotein A-I)

β-sheet breaker peptides have so far been designed to block the conformational

changes that occur in both Aβ and prion protein (PrP), which are implicated in the

pathogenesis of Alzheimer's and prion disease, respectively. The prior art has previously

shown that 11- and 5-residue β-sheet breaker peptides (namely, iAβl and iAB5, respectively)

homologous to the central hydrophobic region of Aβ inhibit peptide conformational changes

that result in amyloid formation and also dissolved preformed fibrils in vitro (Soto et al.,

Biochem. Biophys. Res. Commun. 226: 672-680, 1996; Soto et al., Nature Med. 4: 822-826,

1998). In addition, the 5-residue peptide is capable of preventing the neuronal death induced

by the formation of β-sheet rich oligomeric Aβ structures in cell culture experiments (Soto

et al., 1998, supra). Furthermore, by using a rat model of amyloidosis induced by

intracerebral injection of Aβl-42, the prior art has shown that co-injections of the 5-residue

β-sheet breaker peptide decreased cerebral Aβ accumulation and completely blocked the

deposition of fibrillar amyloid-like lesions in the rat brain (Soto et al., 1998, supra). Finally,

the β-sheet breaker peptide injected eight days after the injection of Aβ was able to

disassemble preformed Aβ fibrils in the rat brain in vivo, that leads to a reduction in the size

of amyloid deposits (Sigurdsson, Frangione, Soto, manuscript submitted). Interestingly,

removal of amyloid by the β-sheet breaker peptide reverts the associated cerebral histologic

damage, including neuronal shrinkage and microglial activation.

β-sheet breaker peptides have also been designed to prevent and to revert

conformational changes caused by prions (PrP). Based on the same principles and using as a

template the PrP sequence 114-122, the prior art has shown that when a set of β-sheet breaker peptides was synthesized, a 13-residue peptide (iPrP13) showed the greatest activity

(Soto, 1999, supra). Several in vitro cell culture and in vivo assays were used to test for

inhibitory activity and the results clearly indicated that it is possible not only to prevent the

PrP^c — PrP^sc conversion, but more interestingly to revert the infectious PrP^sc conformer to a

biochemical and structural state similar to PrP^c (Soto et al., manuscript submitted).

Short peptides have been utilized extensively as drugs in medicine (Rao et al., C.

Basava and G.M. Anantharamaiah, eds. Boston: Birkhauser, pp. 181-198, 1994). However,

the development of peptide drugs is strongly limited by their lack of oral bioavai lability and

their short duration of action resulting from enzymatic degradation in vivo (Fauchere and

Thurieau, Adv. Drug Res. 23: 127-159, 1992). Progress in recent years toward the

production of peptide analogs (such as pseudopeptides and peptide mimetics) with lower

susceptibility to proteolysis has increased the probability to obtain useful drugs structurally

related to their parent peptides (Fauchere and Thurieau, 1992, supra). Improving peptide

stability to proteases not only increases the half-life of the compound in the circulation but

also enhances its ability to be transported or absorbed at different levels, including intestinal

absorption and blood-brain barrier permeability, because transport and absorption appear to

be highly dependent upon the time of exposure of membranes or barriers to the bioactive

species (Fauchere and Thurieau, 1992, supra).

SUMMARY OF THE INVENTION

The present invention is an inhibitory peptide capable of inhibiting β pleated sheet formation in amyloid β-peptide, the inhibitory peptide being a βsheet breaker peptide analog

designed by chemical modification of a βsheet breaker peptide capable of inhibiting β

pleated sheet formation in amyloid β-peptide.

The peptide is altered chemically by: (1) modifications to the N- and C-terminal ends

of the peptide; (2) changes of the side-chain, which can involve amino acid substitutions; (3)

modification in the -carbon including methylations, alkylations and dehydrogenations; (4)

chirality changes by replacing D- for L-residue; (5) head-to-tail cyclizations; and (6)

introduction of amide bond replacements, i.e. changing the atoms participating in the peptide

(or amide) bond.

The present invention also includes an inhibitory peptide capable of inhibiting

conformational changes in prion PrP protein associated with amyloidosis, the inhibitory

peptide being a βsheet breaker peptide analog designed by chemical modification of a βsheet

breaker peptide capable inhibiting the conformational changes in prior PrP protein

associated with amyloidosis.

In addition, the present invention includes a peptide mimetic with the following

structure:

PMiAB5

In another embodiment, the peptide mimetic has the following structure:

PMiPrP13

In yet another embodiment, the peptide mimetic has the following structure:

PMiPrP5

The present invention also includes a method for preventing, treating, or detecting

disorders or diseases associated with abnormal protein folding into amyloid or amyloid-like

deposits or precursors thereof having a pathological beta-sheet structure is claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of the peptide bond and the potential target sites

for peptide modifications. FIG. 2 is a graph depicting the pharmacokinetics of a 11-residue β-sheet breaker

peptide inhibitor of Alzheimer's amyloidosis (Seq. RDLPFYPVPID) in its natural L-

configuration and in the non-natural D-form.

FIGS. 3A and 3B are representations of the tridimensional structure of Alzheimer's

and prion β-sheet breaker peptides iAβ5 and iPr P13, respectively.

FIG. 4a and 4b are graphs showing the bioavailability and stability of iAB5 and Ac-

iAB5-Am, respectively over time.

FIG. 5a provides a graphical comparison of Aβl-40 incubated with various other

peptides.

FIG. 5b is a graph of amyloid formation vs. the Ac-iAβ5-Am concentration.

FIG. 5c is a graph of amyloid formation vs. the iAβ5 concentration.

FIG. 6 shows a model where there is an 83% dissolution of deposits in the ventricle

area and a 30% dissolution of amyloid plaque in the amygdala.

DETAILED DESCRIPTION OF THE INVENTION

In the present invention, the bioavailability and stability of an inhibitory peptide is

improved by chemically modifying the parent peptide to produce a derivative more suitable

for in vivo use, which is preferably administered orally. The inhibitory peptide is capable of

inhibiting β pleated sheet formation in an amyloid β-peptide. Moreover, the inhibitory

peptide is a βsheet breaker peptide analog designed by chemical modification of a βsheet

breaker peptide capable of inhibiting β pleated sheet formation in amyloid β-peptide. This invention also includes an inhibitory peptide capable of inhibiting conformational changes in prion PrP protein associated with amyloidosis, where the inhibitory peptide is a βsheet breaker peptide analog designed by chemical modification of a

βsheet breaker peptide and is capable of inhibiting the conformational changes in prion PrP

protein associated with amyloidosis.

In Fig. 1, a generalized peptide backbone is shown, where possible targets for chemical modification are highlighted. The possible targets include the following: (1)

modifications to the N- and C-terminal ends of the peptide (targets a and b); (2) changes of

the side-chain (target c) which usually involve amino acid substitutions; (3) modification in

the α-carbon (target d) including methylations, alkylations and dehydrogenations; (4)

chirality changes by replacing D- for L-residue; (5) head-to-tail cyclizations; and (6) introduction of amide bond replacements (target e), i.e. changing the atoms participating in

the peptide (or amide) bond. The latter derivatives are known as pseudopeptides or amide

bond surrogates.

Natural peptides are usually degraded by the concerted action of specialized

endopeptidases and unspecific exopeptidases. Endopeptidases are often present in tissues

and cellular compartments and convert the peptide into two or more inactive fragments.

Exopeptidases are generally present in blood and peripheral organs and carry out the

degradation of the intact peptides or their fragments to the constituent amino acids and hence

contribute to the disappearance of the peptides from the circulation. Exopeptidases

recognize the free amino or carboxyl groups in peptides. Therefore, modification of those groups often diminish or abolish exopeptidase degradation. Head-to-tail peptide cyclization

results in the absence of free end-terminal groups, and hence also minimizes cleavage by

exopeptidases. On the other hand, endopeptidases recognize the atoms participating in the

amide bond. Thus, amide bond replacements dramatically decrease degradation by

endopeptidases. The same usually happens with modifications to the α-carbon. Since most

(if not all) of the exo- and endo-proteases are stereospecific, substitutions of the natural L-

amino acids by the D-stereoisomers result in a clear increase in peptide stability. Finally,

peptide mimetics are usually completely resistant to proteolytic degradation and often can be

administrated orally.

β-sheet breaker analogues designed by chemical modifications of the lead peptides.

Starting from the 5-residue Alzheimer's inhibitor peptide (iAB5, Seq. LPFFD - also

denoted as Leu Pro Phe Phe Asp) and the 13-residue prion inhibitor peptide (iPrP13, Seq.

DAPAAPAGPAVPV - also denoted as Asp Ala Pro Ala Ala Pro Ala Gly Pro Ala Val Pro

Val), the modifications described below are designed. The peptides used in the present

invention are synthesized using standard protocols as disclosed by Bergmann et al., and

incorporated herein by reference. (Bergmann & Zervas, Berichte der Deutschen Chemischen

Gesellschaft (1932) 65: 1192 - 1201)

a) N- and C-terminal modifications. Ν-terminal acetylation or desamination confers

protection against digestion by a number of aminopeptidases while the presence of amides or

alcohols replacing the C-terminal carboxyl group prevent splitting by several carboxypeptidases, including carboxypeptidases A and B. The altered peptide sequences

including these modifications are the following, where ac is acetylation, am is amidation, des

is desamination, and ale is alcoholization:

Alzheimer's Inhibitors Prion Inhibitors ac-Leu Pro Phe Phe Asp-am ac-Asp Ala Pro Ala Ala Pro Ala Gly Pro Ala Val Pro Val-a des-Leu Pro Phe Phe Asp-am des-Asp Ala Pro Ala Ala Pro Ala Gly Pro Ala Val Pro Val-am ac-Leu Pro Phe Phe Asp-ale ac-Asp Ala Pro Ala Ala Pro Ala Gly Pro Ala Val Pro Val-alc des-Leu Pro Phe Phe Asp-ale des-Asp Ala Pro Ala Ala Pro Ala Gly Pro Ala Val Pro Val-alc

b) Side-chain changes. The presence of non-natural amino acids usually increase

peptide stability. In addition, at least one of these amino acids (α-aminoisobutyric acid or

Aib) imposes significant constraints to model peptides diminishing their conformational

flexibility. In particular, the incorporation of Aib into β-sheet model peptides induces the

complete disruption of this structure. The β-sheet blocking activity of Aib is comparable or

even greater than the natural residue proline used in the peptide as a β-sheet blocker.

Therefore, the introduction of Aib is expected to enhance peptide stability and inhibitory

activity at the same time.

Alzheimer's Inhibitors Prion inhibitors

Leu Aib Phe Phe Asp Asp Ala Aib Ala Ala Aib Ala Ala Aib Ala Gly Aib Ala Val Aib Val

c) Modifications in the a-carbon. The most commonly used α-carbon modification

to improve peptide stability is α-methylation. In addition, replacement of the hydrogen atom linked to the α-carbon of Phe, Val or Leu has been shown to favor the adoption of β-bend

conformation and strongly disfavor the formation of β-pleated sheet structures. According to

the present invention, methylation of those residues in the inhibitor peptides is expected to enhance stability and potency. Alzheimer's Inhibitors

(Me)Leu Pro Phe Phe Asp

Leu Pro (Me)Phe Phe Asp

Leu Pro Phe (Me)Phe Asp

(Me)Leu Pro (Me)Phe (Me)Phe Asp

Prion inhibitors

Asp Ala Pro Ala Ala Pro Ala Gly Pro Ala (Me)Val Pro Val

Asp Ala Pro Ala Ala Pro Ala Gly Pro Ala Val Pro (Me)Val

Asp Ala Pro Ala Ala Pro Ala Gly Pro Ala (Me)Val Pro (Me)Val

d) Chirality changes. Replacement of the natural L-residue by the D-enantiomers

dramatically increases resistance to proteolytic degradation. The increase in stability by

introduction of D-residue has already been demonstrated for the 1 l-residue β-sheet breaker

peptide (iAβl). In vivo studies showed that the peptide bearing the natural sequence rapidly

degraded in rat plasma. Indeed, approximately 90% of iAβl was degraded within minutes

after intravenous injection. Conversely, a derivative of iAβl containing all the residue in

the D-form showed virtually no degradation in the plasma after injection for 15 minutes. For detection, the peptide was radio-iodinated using standard procedures. Peptide stability was

evaluated after i.v bolus injection in rats by precipitation with trichloroacetic acid. Quantitation of the intact peptide was also done by paper chromatography. Thus, iAB5 and

iPrP13 peptides (FIGS. 3A and 3B, respectively) containing all-D residue as well as

peptides containing D-residue only at the N- and C-terminal ends to prevent exopeptidase

degradation are included in the compounds of the invention. In addition to the latter, D-

residue are used after each proline amino acid, since it has been reported that a frequent

endopeptidase cleavage site is after this residue by an enzyme known as

prolylendopepti dase .

Alzheimer's Inhibitors Prion Inhibitors leu pro phe phe asp asp ala pro ala ala pro ala gly pro ala val pro val leu Pro Phe Phe asp asp Ala Pro Ala Ala Pro Ala Gly Pro Ala Val Pro val leu Pro phe Phe asp asp Ala Pro ala Ala Pro ala Gly Pro ala Val Pro val

Amino acids written with lower case letters denote D-residue.

e) Cyclic peptides. Conformationally constrained cyclic peptides represent better

drug candidates than linear peptides due to their reduced conformational flexibility and

improved resistance to exopeptidase cleavage. Two alternative strategies have been used to

convert a linear sequence into a cyclic structure. One is the introduction of cysteine residue to achieve cyclization through the formation of a disulfide bridge and the other is the side-

chain attachment strategy involving resin-bound head-to-tail cyclization. To avoid

modifications of the peptide sequence the latter approach is used, β-sheet breaker peptides

contain the ideal sequences for facilitating macrocyclization because proline, due to its

ability to promote turns and loops, is a constituent of many naturally occurring or artificially

synthesized cyclic peptides. Alzheimer's Inhibitors Prion inhibitors

*— Leu Pro Phe Phe Asp — -ι i— Asp Ala Pro Ala Ala Pro Ala Gly Pro Ala Val Pro Val — -ι

f) Pseudopeptides. Pseudopeptides or amide bond surrogates refers to peptides containing chemical modifications of some (or all) of the peptide bonds. Amide bond

replacements are usually represented by retaining the amino acid designation according to

the side-chain and specifying the changes that occur between the α-carbons, using the

nomenclature known as "psi-bracket."

For example, the term Alaψ[CH CH₂]Gly refers to the moiety

NH₂CH(CH₃)CH₂CH₂CH₂CO₂H. Several amide bond surrogates have been described in Table 2 below.

Table 2. Some amide bond surrogates and their properties

Some of them are found in naturally occurring peptide analogs (such as ψ[CHOH],

ψ[CSNH], ψ[COO]) while others have been artificially synthesized The introduction of

amide bond surrogates not only decreases peptide degradation but also may significantly

modify some of the biochemical properties of the peptides, particularly the conformational

flexibility and hydrophobicity It is likely that an increase in conformational flexibility will

be beneficial for docking the inhibitor to the Aβ and PrP binding sites On the other hand,

since the interaction between the amyloidogenic proteins and the inhibitors seems to depend

to a great extent on hydrophobic interactions, it is likely that amide bond replacement

increasing hydrophobicity may enhance affinity and hence, potency of the inhibitors. In addition, increased hydrophobicity could also enhance transport of the peptide across

membranes and thus, improve barrier permeability (blood-brain barrier and intestinal

barrier). Therefore, to synthesize pseudopeptides amide bond replacement is used thereby

increasing flexibility and hydrophobicity, such as ψ[CH₂CH₂] and ψ[CH₂S]. The amide

bonds to replace are those located at the end of the peptide to prevent exoprotease

degradation and after each of the prolines, since it has been described that a frequent

endopeptidase cleavage site occurs after this residue by an enzyme known as

prolylendopeptidase. Additional amide bonds that need to be protected are determined by

experimental studies involving the analysis of the degradation of β-sheet breaker peptides in

the plasma and tissue.

Alzheimer's Inhibitors Leuψ[CH₂CH₂]Proψ[CH₂CH₂]Phe Pheψ[CH₂CH₂]Asp Leuψ[CH₂S]Proψ[CH₂S]Phe Pheψ[CH₂S]Asp Prion inhibitors Aspψ[CH₂CH₂]Ala Proψ[CH₂CH₂]Ala Ala Proψ[CH₂CH₂]Ala Gly Proψ[CH₂CH₂]Ala Val Proψ[CH₂CH₂]Val

Aspψ[CH₂SlAla Proψ[CH₂S]Ala Ala Proψ[CH₂S]Ala Gly Proψ[CH₂S]Ala Val Proψ[CH₂S]Val

g) Mixture of several modifications. By taking into account the features of the

peptide drugs on the market or under current development, it is clear that most of the

peptides successfully stabilized against proteolysis consist of a mixture of several types of

the above described modifications. This conclusion makes sense in the light of the

knowledge that many different enzymes are implicated in peptide degradation. The following structures contain combinations of different types of chemical modifications:

Alzheimer's Inhibitors Ac-Leu Proψ[CH₂CH₂]Phe Phe Asp-Am Ac-Leu Proψ[CH₂S]Phe Phe Asp-Am (Me)Leu Proψ[CH₂CH₂]Phe Phe Asp-Am leu Proψ[CH₂CH₂]Phe Phe asp leu Proψ[CH₂S]Phe Phe asp Ac-Leu Aib Phe Phe Asp- Am (Me)Leu Aib Phe Phe Asp- Am Leu Proψ[CH₂CH₂]Phe Phe asp

j — Leu Aib Phe Phe Asp — i

j — Leu Proψ [CH₂CH₂] Phe Phe Asp — ι

Ac-Leu pro Phe Phe Asp- Am

Ac-Leu Proψ[CH₂CH₂]Phe phe Asp- Am

Ac-Leu Proψ[CH₂SJPhe phe Asp- Am

Ac-Leu Proψ[CH₂CH₂]Phe (Me)Phe Asp-Am

Ac-Leu Proψ[CH₂CH₂]Phe (Me)Phe asp Ac-Leu Pro phe phe Asp-Am

Ac-Leu Pro (Me)Phe phe Asp- Am leu Proψ[CH₂CH₂]Phe phe asp leu Pro (Me)Phe phe asp

Ac-Leu Aib Phe phe Asp- Am Prion inhibitors Ac-Asp Ala Proψ[CH₂CH₂]Ala Ala Proψ[CH₂CH₂]Ala Gly Proψ [CH₂CH₂] Ala Val Pro Val-Am asp Ala Proψ[CH₂CH₂]Ala Ala Proψ[CH₂CH₂]Ala Gly Proψ[CH₂CH₂]Ala Val Pro val Ac-Asp Ala Proψ[CH₂S]Ala Ala Proψ[CH₂S]Ala Gly Proψ[CH₂S]Ala Val Pro Val-Am asp Ala Proψ[CH₂S]Ala Ala Proψ[CH₂S]Ala Gly Proψ[CH₂S]Ala Val Pro val Ac-Asp Ala Aib Ala Ala Aib Ala Gly Aib Ala Val Pro Val-Am

Ac-Asp Ala Proψ[CH₂CH₂]Ala Ala Proψ[CH₂CH₂]Ala Gly Proψ [CH₂CH₂] Ala Val Pro (Me) Val Ac-Asp Ala pro Ala Ala Proψ[CH₂CH₂]Ala Gly pro Ala Val Pro Val-Am asp Ala Proψ[CH₂CH₂]Ala Ala Proψ[CH₂CH₂]Ala Gly Proψ[CH₂CH₂]Ala Val Pro (Me) Val asp Ala Aib Ala Ala Proψ[CH₂CH₂]Ala Gly pro Ala Val Pro (Me) Val asp Ala Aib Ala Ala Proψ[CH₂S]Ala Gly pro Ala Val Pro (Me) Val asp Ala Proψ[CH₂S]Ala Ala Proψ[CH₂S]Ala Gly Proψ[CH₂S]Ala Val Pro (Me) Val Ac-Asp Ala Aib Ala Ala Proψ[CH₂CH₂]Ala Gly Aib Ala Val Pro (Me)Val

j ^■A Asspp A Allaa pprroo A Allaa A Allaa P Prrooψψ[[CCHH₂₂CCHH₂₂]J A Allaa G Gllyy pprroo A Allaa V Vaall P Prroo V Vaall- 1

j Asp Al Aib Ala Ala Proψ[CH2 CH2] Ala Gly Aib Ala (Me) Val Pro Val 1

Ac-Asp Ala Proψ[CH₂S]Ala ala Pιoψ[CH₂S]Ala gly Proψ[CH₂S]Ala (Me)Val Pro Val-Am Ac-Asp Ala Aib ala Ala Proψ[CH₂CH₂]Ala Gly pro Ala Val Pro (Me) Val asp Ala Aib Ala Ala Proψ[CH₂CH₂]Ala Gly Aib ala Val Pro Val-Am Ac-Asp Ala pro Ala Ala Proψ[CH₂CH₂]Ala gly pro Ala (Me) Val Pro Val-Am asp Ala Proψ[CH₂CH₂]Ala Ala Proψ[CH₂CH₂]Ala gly Proψ[CH₂CH₂] Ala val Pro val

Ac-Asp Ala pro Ala ala Aib Ala gly pro Ala (Me) Val Pro Val-Am

Asp Ala pro Ala Ala Proψ[CH₂ CH₂] Ala Gly pro Ala Val Pro Val

Asp Ala Aib Ala Ala Proψ[CH₂ CH₂] Ala Gly Aib Ala (Me) Val Pro Val Another approach to improve stability, which also may result in the generation of

orally active compounds, is to produce a peptide mimetic. A peptide mimetic is a molecule

that mimics the biological activity of the peptides, but is no longer a peptide in chemical

nature. The term peptide mimetic has been used sometimes to describe molecules that are

partially peptide in nature, such as pseudopeptides, semi-peptides or peptoids, but a strict

definition and the one that is used in the present application is an organic molecule that no

longer contains any peptide bonds. Peptide mimetics are not derivatives of a parent peptide,

but rather are chemically synthesized de novo trying to mimic the structural and functional

properties of the peptide. The rational design of peptide mimetics requires a sufficient

knowledge of the pharmacophoric groups that are responsible for the activity and detailed

structural information of the peptide. The objective is to reconstruct the spatial position of

the pharmaco-active groups using an organic template to mount them. Selection of the

template is important and has to take into consideration the size and flexibility based on the

conformational model of the peptide.

Peptide mimetics designed to imitate β-sheet breaker peptide properties.

The rational design of peptide mimetics requires a sufficient knowledge of the

chemical groups that are responsible for the activity and detailed structural information of

the peptide. The objective is to reconstruct the position of the pharmaco-active groups using

an organic template to mount them. Selection of the template is important and has to take into consideration the size and flexibility based on the conformational model of the peptide.

From the study of the activity of different β-sheet breaker sequences bearing single amino

acid substitutions, the residues that are key for inhibition have been determined. In addition,

the tri dimensional structure of the lead Alzheimer's and prion β-sheet breaker peptides

(FIGS. 3 A and 3B) were either modeled or experimentally determined. The 5-residue

inhibitor of Aβ fibrillogenesis was modeled by energy minimization and Monte Carlo

simulations using the computer program ICM. The structure of the 13-residue inhibitor of

prion protein conformational changes was experimentally calculated by 2D-NMR.

There are numerous approaches to the design and synthesis of peptide mimetics as

described in recent reviews by Joachim Gante and Iwao Ojima et al. of which are

incorporated herein by reference.

The peptide mimetics shown below represent a further aspect of this invention.

Alzheimer's Inhibitors

PMiAB5 Prion inhibitors

PMiPrP13

PMiPrP5

The latter (PMiPrP5) is a shorter and easier to synthesize version that contains the

chemically active groups and is analog to a 5-residue prion β-sheet breaker peptide.

As a method of preventing or treating a disorder or disease associated with amyloid

or amyloid-like deposits or pathological beta-sheet-rich precursors thereof, the compound of

the present invention is administered in an effective amount to a subject in need thereof,

where the subject can be human or animal. Likewise, a method of detecting such disorders

or diseases also includes administering a sufficient amount of the designed compound to

visualize its binding to fibril deposits or precursors thereof by well-known imaging techniques. As used herein, the term "prevention" of a condition, such as Alzheimer's disease or

other amyloidosis disorders, in a subject involves administering the compound according to

the present invention prior to the clinical onset of the disease. "Treatment" involves

administration of the protective compound after the clinical onset of the disease. For

example, successful administration of the compound of the present invention, after

development of a disorder or disease comprises "treatment" of the disease. The invention is

useful in the treatment of humans as well as for veterinary uses in animals.

The compound of the present invention may be administered by any means that

achieves its intended purpose, preferably oral. For example, administration may be by a

number of different parenteral routes including, but not limited to, subcutaneous,

intravenous, intradermal, intramuscular, intraperitoneal, intracerebral, intranasal, oral,

transdermal, or buccal routes. Parenteral administration can be bolus injection or by gradual

perfusion over time.

A typical regimen for preventing, suppressing, or treating a condition associated with

amyloid or amyloid-like deposits, comprises either: (1) administration of an effective

amount in one or two doses of a high concentration of the compound in the range of 0.5 to

10 mg, more preferably 0.5 to 5 mg, or (2) administration of an effective amount of the

compound administered in multiple doses of lower concentrations in the range of 10 -

10,000 μg, more preferably 50 - 500 μg over a period of time up to and including several

months to several years.

It is understood that the dosage administered will be dependent upon the age, sex, health, and weight of the recipient, kind of concurrent treatment, if any, frequency of

treatment, and the nature of the effect desired. The total dose required for each treatment

may be administered by multiple doses or in a single dose. By "effective amount," it is

meant a concentration of the compound which is capable of slowing down or inhibiting the

formation of amyloid or amyloid-like deposits, or pathological beta-sheet precursors thereof,

or of dissolving preformed fibril deposits. Such concentrations can be routinely determined

by those of skill in the art. It will also be appreciated by those of skill in the art that the

dosage may be dependent on the stability of the administered compound. A less stable

compound may required administration in multiple doses.

Preparations for parenteral administration include sterile aqueous or non-aqueous

solutions, suspensions, and emulsions, which may contain auxiliary agents or excipients

which are known in the art. Pharmaceutical compositions such as tablets and capsules can

also be prepared according to routine methods.

Pharmaceutical compositions comprising the compound of the invention include all

compositions wherein the compound is contained in an amount effective to achieve its

intended purpose. In addition, the pharmaceutical compositions may contain suitable

pharmaceutically acceptable carriers comprising excipients and auxiliaries which facilitate

processing of the active compounds into preparations which can be used pharmaceutically.

Suitable pharmaceutically acceptable vehicles are well known in the art and are described for

example in Gennaro, Alfonso, Ed., Remington's Pharmaceutical Sciences, 18^l Edition 1990, Mack Publishing Co., Easton, PA, a standard reference text in this field. Pharmaceutically acceptable vehicles can be routinely selected in accordance with the mode

of administration and the solubility and stability of the compound. For example,

formulations for intravenous administration may include sterile aqueous solutions which

may also contain buffers, diluents and other suitable additives.

Suitable formulations for parenteral administration include aqueous solutions of the

active compounds in water-soluble form, for example, water-soluble salts. In addition,

suspension of the active compound as appropriate oily injections suspensions may be administered. Suitable lipophilic solvents or vehicles include fatty oils, for example, sesame

oil, or synthetic fatty acid esters, for example ethyl oleate or triglycerides. Aqueous injection

suspensions that may contain substances which increase the viscosity of the suspension

include, for example, sodium carboxymethyl cellulose, sorbitol, and/or destran. Optionally,

the suspension may also contain stabilizers.

Disorders or diseases associated with abnormal protein folding into amyloid or

amyloid-like deposits or into pathological beta-sheet-rich precursors of such deposits to be

treated or prevented by administering the pharmaceutical composition of the invention

includes, but is not limited to, Alzheimer's disease, FAF, Down's syndrome, other

amyloidosis disorders, human prion diseases, such as kuru, Creutzf el dt- Jakob Disease

(CJD), Gerstmann-Strausslet-Scheinker Syndrome (GSS), prion associated human

neurodegenerative diseases as well as animal prion diseases such as scrapie, spongiform

encephalopathy, transmissible mink encephalopathy and chronic wasting disease of mule

deer and elk. EXAMPLES

One of the major drawbacks for the use of peptides as drugs is their rapid proteolytic

degradation in biological fluids and tissues. In in vitro experiments, iAB5, (Seq LPFFD- also

depicted as Leu Pro Phe Phe Asp herein) degraded very quickly in vitro after incubation

with fresh human plasma. As shown in Figure 4a , fifty percent of the peptide iAB5

disappeared in approximately 5 minutes in the presence of plasma. Since it was not possible

to identify any metabolic fragments as a result of the proteolytic digestion, it seems likely

that the degradation is mainly done by unspecific exopeptidases. This conclusion is

supported by the finding that protection of amino- and carboxy-terminus of the peptide by

acetylation and amidation, respectively, (to form Ac-iAβ5-Am — also depicted as Ac-Leu

Pro Phe Phe Asp-Am herein) dramatically increases the stability of the peptide in vitro. As

shown in Fig. 4b, the end-protected modified peptide of the present invention (Ac-iAβ5-Am)

remained stable for a period of more than 24 hours in human plasma. (The modified peptide

was also slowly metabolized in vitro in human and rat liver microsomes, in which after one

hour of incubation at 37° a 81.5% and 76.3% of the peptide remained intact, in human and

rat tissue homogenate, respectively. )

Additional in vitro studies showed that Ac-iAβ5-Am has similar activity as iAB5 in inhibiting amyloid formation (see Fig. 5a) and the effect followed a similar dose-dependency

as the activity of the unmodified peptide as shown in Figures Fig. 5b and 5c. Returning to

Fig. 5a, it can be seen that modification of the N-terminus by Boc also retains the in vitro activity exhibited by iAB5 while several unrelated peptides (CPLVHVSEEGTEPA, CP2:

GYLTVAAVFRG, CP10: ISEVKMDAEF) or short Aβ fragments (such as Aβ 18-21, AB1- 16) at the same concentrations had no effect on fibrillogenesis or slightly increased amyloid

formation probably by incorporation into the fibrils.

To evaluate the effect of Ac-iAB5-Am in vivo, we used a rat model in which amyloidosis was induced by intracerebral injection of non-aggregated AB1-42. After some

time, the peptide aggregates inside the rat brain resulting in the formation of a single

amyloid-like deposit in the place of injection. These lesions have the same tinctorial (congo

red birefringence and thioflavine S binding) and translucent (fibrillar structure under electron

microscopy) properties than Alzheimer's amyloid plaques and induce some cerebral damage

similar to that observed in AD brain, including extensive neuronal shrinkage, astrocytosis

and microglial activation. Using this model, we have shown previously that co-injection of

the unprotected iAB5 with AB1-42 induce a 50% inhibition of amyloid plaque formation and

i. c. injection of iAB5 in animals already containing amyloid plaques produced a 67%

dissolution of preformed deposits. (Sigurdsson, E.M., Permanne, B. Soto, C. , Wisniewski,

T. & Frangione, B. (2000) In vivo disassembly of amyloid-β deposits in rat brain. J.

Neuropath. Exp. Neurol. 59: 11-17) In the previous experiments, the unprotected peptide

was injected directly in the brain region where the amyloid was located. In the present

experiment the amyloid-B5 peptide was injected into the amygdala of the rats. After 7

days, which is the time required to have fully formed the amyloid deposits, one-hundred μL of a solution containing 13 mg/ml of the Ac-iAB5-Am were infused for a period of three

weeks using an ALZET infusion pump connected to the lateral ventricle. The animals were

sacrificed and the brain analyzed for the presence of amyloid deposits by immunohistochemistry. In this model, a compacted amyloid plaque was obtained in the

place where the solution containing ABl-42 was deposited (amygdala) and also several

smaller amyloid deposits were observed throughout the canula track in regions closer to the

ventricle (Fig. 6, left panel). The results show that infusion of the peptide induces a 30%

dissolution of preformed amyloid plaque in the amygdala and 83% dissolution of the

deposits located near the ventricle (Fig. 6).

Experimental Procedures

In vitro assays of peptide stability. Peptides were prepared as a 1 μg/μl solution in water.

20 μl of the peptide solution was diluted in 80 μl of fresh human plasma. The solution was

incubated at 37°C for different time periods and the reaction was stopped by adding a

complete cocktail of protease inhibitors. The bulk of the plasma proteins (none of the

peptide) were precipitated in cold methanol (mix/MeOH, 4/5, v/v) for one hour at -20°C.

The precipitated proteins were pelleted by centrifugation (10 OOOg, 10 min, 4°C). The

supernatant, containing the peptide, was concentrated 5 times under vacuum and separated

by reverse-phase HPLC. The peak area corresponding to the intact peptide was measured

and compared with an equivalent sample incubated without plasma. In vitro assays of activity. Amyloid formation was quantitatively evaluated by the

fluorescence emission of thioflavine T (ThT) bound to amyloid fibrils. Aliquots of Aβ at a

concentration of 0.5 mg/ml prepared in 0.1M Tris, pH 7.4 were incubated for 7 days at 37°C

in the absence or in the presence of different concentrations of iAB5 and derivatives. At the

end of the incubation period, 50 mM glycine, pH 9.2 and 2 μM ThT were added in a final

volume of 2 ml. Fluorescence was measured at: excitation 435 nm and emission 485 nm in

a Perkin Elmer, model LS50B fluorescence spectrometer.

In vivo studies using an animal model of cerebral AP deposition. Male Fischer-344 rats

weighed 250-300g and were 3-4 months of age at the time of arrival. The animals were

housed 2 per cage, maintained on a 12 hour light-dark cycle with access to food and water ad

libitum and were habituated to their new environment for 2-3 weeks prior to surgery.

Surgery was performed under sodium pentobarbital (50 mg/kg, i.p.) anesthesia. Atropine

sulfate (0.4 mg/kg) and ampicillin sodium salt (50 mg/kg) were injected subcutaneously

once the animals were anesthetized. Aβl-42 was dissolved in dimethylsulfoxide (DMSO)

and then diluted with water to a 16.7% DMS. The animal received a bilateral injection of

5.0 nmol Aβl-42 into each amygdala by using a Kopf stereotaxic instrument with the incisor

bar set at 3.3 mm below the interaural line. Injection coordinates measured from the bregma

and the surface of the skull (AP -3.0, ML ± 4.6 DV -8.8) were empirically determined based

on the atlas of Paxinos and Watson. A volume of 3.0 μl was administered over 6 min (flow rate 0.5 μl/min) using a CMA/100 micrasyringe pump. The cannula was left in situ for 2 min

following injection, then it was withdrawn 0.2 mm and left for 3 min, and after 5 min the

cannula was slowly withdrawn. Following surgery the animals were placed on a heating pad

until they regained their righting reflex. To evaluate the effect of Ac-iB5-AM the animals

were subjected to a second surgery one week after the first one, in which an ALZET infusion

pump was connected to the cerebral ventricle following the manufacturer indications. A

total of 1.3 mg of peptide in 100 μl of PBS/10% DMSO was delivered into the lateral

ventricle over a period of 3 weeks. After this time, the animals were sacrificed by an

overdose of sodium pentobarbital (150 mg/kg, i.p.), perfused transaortically. For histology,

serial coronal sections (40 μm) of the brain were cut, placed in ethylene glycol

cryoprotectant and stored at -20°C until stained. Tissue sections were stained with anti ABl-

42 antibodies as described in Soto, C, Sigursson, E., Morelli, L., Kumar, R.A., Castano,

E.M. and Frangione, B.(1998) β-sheet breaker peptides inhibit fibrillogencsis in a rat brain

model of amyloidosis: Implications for Alzheimer's therapy. Nature med. 4: 822-826. An

image analysis system was used to determine the size of the amyloid deposits. The data was

analyzed by a two-way ANOVA followed by a Newman-Keuls' multiple range test for/705/

hoc comparisons. Total brain deposition was analyzed using an unpaired t-test, two tailed.

Having now fully described this invention, it will be appreciated by those skilled in

the art that the same can be performed within a wide range of equivalent parameters, concentrations, and conditions without departing from the spirit and scope of the invention

and without due experimentation.

While this invention has been described in connection with specific embodiments

thereof, it will be understood that it is capable of further modifications. This application is

intended to cover any variations, uses, or adaptations of the inventions following, in general,

the principles 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 as follows in the scope of

the appended claims.

All references cited herein, including journal articles or abstracts, published or

corresponding U.S. or foreign patent applications, issued U.S. or foreign patents, or any

other references, are entirely incorporated by reference herein, including all data, tables,

figures, and text presented in the cited references. Additionally, the entire contents of the

references cited within the references cited herein are also entirely incorporated by reference.

Reference to known method steps, conventional methods steps, known methods or

conventional methods is not in any way an admission that any aspect, description or

embodiment of the present invention is disclosed, taught or suggested in the relevant art.

The foregoing description of the specific embodiments will so fully reveal the

general nature of the invention that others can, by applying knowledge within the skill of the

art (including the contents of the references cited herein), readily modify and/or adapt for

various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and

modifications are intended to be within the meaning and range of equivalents of the

disclosed embodiments, based on the teaching and guidance presented herein. It is to be

understood that the phraseology or terminology herein is for the purpose of description and

not of limitation, such that the terminology or phraseology of the present specification is to

be interpreted by the skilled artisan in light of the teachings and guidance presented herein,

in combination with the knowledge of one of ordinary skill in the art.

Claims

WHAT IS CLAIMED IS:

1. An inhibitory peptide capable of inhibiting β pleated sheet formation in amyloid β-

peptide said inhibitory peptide being a βsheet breaker peptide analog designed by chemical

modification of a βsheet breaker peptide capable of inhibiting β pleated sheet formation in

amyloid β-peptide.

2. The inhibitory peptide of claim 1 wherein said βsheet breaker peptide is a 5 residue

Alzheimer inhibitor peptide ιAβ5 (Seq Leu-Pro-Phe-Phe-Asp)

3. The inhibitory peptide of claim 2 wherein said chemical modification is achieved by

a process selected from the group consisting of alteration of the N- and C- terminal ends of

said Alzheimer inhibitor peptide ιAβ5; replacing at least one residue of said Alzheimer

inhibitor peptide I Aβ5wιth α-aminoisobuiπc acid (Aib); methylation of the α carbon of at

least one residue of said Alzheimer inhibitor peptide ιAβ5, replacing at least one L-

enantiomeπc residue of said Alzheimer inhibitor peptide ιAβ5 with a D-enantiomeπc

residue, forming head to tail cyclization of said Alzheimer inhibitor peptide ιAβ5, replacing

amide bonds in said Alzheimer inhibitor peptide ιAβ5 with an amide bond surrogate, and

combinations thereof.

4. The inhibitory peptide of claim 3 said alteration of the N- and C- terminal ends of said Alzheimer inhibitor peptide iAβ5 is achieved by a process selected from

acetylation, amidation, desamination, alcoholization and combinations thereof.

5. The compound of Claim 4 wherein inhibitory peptide is selected from the group

consisting of: ac-Leu Pro Phe Phe Asp-am, des-Leu Pro Phe Phe Asp-am, ac-Leu Pro Phe Phe Asp-ale, and des-Leu Pro Phe Phe Asp-ale,

6. The inhibitory peptide of Claim 5 wherein said inhibitory peptide is ac-Leu Pro Phe

Phe Asp-am.

7. The inhibitory peptide of claim 3 wherein said inhibitory peptide is selected from the

group consisting of Leu Aib Phe Phe Asp; (Me)Leu Pro Phe Phe Asp; Leu Pro (Me)Phe Phe Asp, Leu Pro

Phe (Me)Phe Asp; (Me)Leu Pro (Me)Phe (Me)Phe Asp, leu pro phe phe asp, leu Pro Phe Phe asp, leu Pro phe Phe asp,

Leuψ[CH₂CH₂]Proψ[CH₂CH₂]Phe Pheψ[CH₂CH₂]Asp; Leuψ[CH₂S]ProψtCH₂S]PhePheψ[CH₂S]Asp; Ac-Leu Proψ[CH₂CH₂]Phe Phe Asp- Am;

Ac-Leu Proψ[CH₂S]Phe Phe Asp-Am;

(Me)Leu Proψ[CH₂CH₂lPhe Phe Asp-Am; leu Proψ[CH₂CH₂]Phe Phe asp; leu Proψ[CH₂S]Phe Phe asp; Ac-Leu Aib Phe Phe Asp-Am;

(Me)Leu Aib Phe Phe Asp- Am;

Leu Proψ[CH₂CH₂]Phe Phe asp;

j — Leu Proψ [CH₂CH₂] Phe Phe Asp — j

Ac-Leu pro Phe Phe Asp- Am; Ac-Leu Proψ[CH₂CH ]Phe phe Asp-Am; Ac-Leu Proψ[CH₂S]Phe phe Asp- Am; Ac-Leu Proψ[CH₂CH₂]Phe (Me)Phe Asp- Am; Ac-Leu Proψ[CH₂CH₂]Phe (Me)Phe asp; Ac-Leu Pro phe phe Asp- Am; Ac-Leu Pro (Me)Phe phe Asp- Am; leu Proψ[CH₂CH₂]Phe phe asp; leu Pro (Me)Phe phe asp; Ac-Leu Aib Phe phe Asp- Am; and

8. An inhibitory peptide capable of inhibiting conformational changes in prion PrP

protein associated with amyloidosis, said inhibitory peptide being a βsheet breaker peptide

analog designed by chemical modification of a βsheet breaker peptide capable inhibiting said

conformational changes in prior PrP protein associated with amyloidosis.

9. The inhibitory peptide of claim 8 wherein said βsheet breaker peptide is 13 residue

prion inhibitor peptide iPrP13 (Seq. Asp Ala Pro Ala Ala Pro Ala Gly Pro Ala Val Pro Val).

10. The inhibitory peptide of claim 9 wherein said chemical modification is achieved by

a process selected from the group consisting of: alteration of the N- and C- terminal ends of

said prion inhibitor peptide iPrP13; replacing at least one residue of said prion inhibitor

peptide iPrP13with α-aminoisobuiric acid (Aib); methylation of the α carbon of at least one

residue of said prion inhibitor peptide iPrP13; replacing at least one L-enantiomeric

residue of said prion inhibitor peptide iPrP13 with a D-enantiomeric residue, forming head

to tail cyclization of said prion inhibitor peptide iPrP13, replacing amide bonds in said

prion inhibitor peptide iPrP13 with an amide bond surrogate; and combinations thereof.

11. The inhibitory peptide of claim 10 wherein said alteration of the N- and C-

terminal ends of said prion inhibitor peptide iPrP13 is achieved by a process selected from

acetylation, amidation, desamination, alcoholization and combinations thereof.

12. The compound of Claim 11 wherein said inhibitory peptide is selected from the

group consisting of: ac-Asp Ala Pro Ala Ala Pro Ala Gly Pro Ala Val Pro Val-am, des-Asp Ala

Pro Ala Ala Pro Ala Gly Pro Ala Val Pro Val-am, ac-Asp Ala Pro Ala Ala Pro Ala Gly Pro Ala Val Pro Val-alc, and des-Asp Ala Pro Ala Ala Pro Ala Gly Pro Ala Val Pro Val-alc.

13. The inhibitory peptide of claim 10 wherein said inhibitory peptide is selected from

the group consisting of

Asp Ala Aib Ala Ala Aib Ala Ala Aib Ala Gly Aib Ala Val Aib Val;

Asp Ala Pro Ala Ala Pro Ala Gly Pro Ala (Me) Val Pro Val; Asp Ala Pro Ala Ala Pro Ala Gly Pro Ala Val Pro (Me) Val;

Asp Ala Pro Ala Ala Pro Ala Gly Pro Ala (Me) Val Pro (Me) Val; asp ala pro ala ala pro ala gly pro ala val pro val; asp Ala Pro Ala Ala Pro Ala Gly Pro Ala Val Pro val; asp Ala Pro ala Ala Pro ala Gly Pro ala Val Pro val;

Aspψ[CH₂CH₂]Ala Proψ[CH₂CH₂]Ala Ala Proψ[CH₂CH₂] Ala Gly Proψ[CH₂CH₂]Ala

ValProψ[CH₂CH₂]Val;

Aspψ[CH₂S]Ala Proψ[CH₂S]Ala Ala Proψ[CH₂S]Ala Gly Proψ[CH₂S]Ala Val Proψ[CH₂S]Val,;

Ac-Asp Ala Proψ[CH₂CH₂]Ala Ala Proψ[CH₂CH₂]Ala Gly Proψ[CH₂CH₂]Ala Val Pro Val-Am; asp Ala Proψ[CH₂CH₂]Ala Ala Proψ[CH₂CH₂]Ala Gly Proψ[CH₂CH₂]Ala Val Pro val;

Ac-Asp Ala Proψ[CH₂S]Ala Ala Proψ[CH₂S]Ala Gly Proψ[CH₂S]Ala Val Pro Val-Am; asp Ala Proψ[CH₂S]Ala Ala Proψ[CH₂S]Ala Gly Proψ[CH₂S]Ala Val Pro val;

Ac-Asp Ala Aib Ala Ala Aib Ala Gly Aib Ala Val Pro Val-Am;

Ac-Asp Ala Proψ[CH₂CH₂]Ala Ala Proψ[CH₂CH₂]Ala Gly Proψ[CH₂CH₂]Ala Val Pro (Me)Val; Ac-Asp Ala pro Ala Ala Proψ [CH₂CH₂] Ala Gly pro Ala Val Pro Val-Am; asp Ala Proψ[CH₂CH₂]AIa Ala Proψ[CH₂CH₂]Ala Gly Proψ [CH₂CH₂] Ala Val Pro (Me) Val; asp Ala Aib Ala Ala Proψ[CH₂CH₂]Ala Gly pro Ala Val Pro (Me) Val; asp Ala Aib Ala Ala ProψfCH₂S]Ala Gly pro Ala Val Pro (Me)Val; asp Ala Proψ[CH₂S]Ala Ala Proψ[CH₂S]Ala Gly Proψ[CH₂S]Ala Val Pro (Me) Val; Ac-Asp Ala Aib Ala Ala Proψ [CH₂CH₂] Ala Gly Aib Ala Val Pro (Me) Val; j — Asp Ala pro Ala Ala Proψ[CH₂CH₂] Ala Gly pro Ala Val Pro Val — |

Asp Al Aib Ala Ala Proψ[CH₂ CH₂] Ala Gly Aib Ala (Me) Val Pro Val — |

Ac-Asp Ala Proψ[CH₂S]Ala ala Proψ[CH₂S]Ala gly Proψ[CH₂S]Ala (Me)Val Pro Val-Am; Ac-Asp Ala Aib ala Ala Proψ[CH₂CH₂]Ala Gly pro Ala Val Pro (Me) Val, asp Ala Aib Ala Ala Proψ[CH₂CH₂]Ala Gly Aib ala Val Pro Val-Am,

Ac-Asp Ala pro Ala Ala Proψ[CH₂CH₂lAla gly pro Ala (Me)Val Pro Val-Am, asp Ala Proψ[CH₂CH₂]Ala Ala Proψ[CH₂CH₂]Ala gly Proψ[CH₂CH₂]Ala val Pro val,

Ac-Asp Ala pro Ala ala Aib Ala gly pro Ala (Me) Val Pro Val-Am,

Asp Ala pro Ala Ala Proψ[CH₂ CH₂] Ala Gly pro Ala Val Pro Val,

Asp Ala Aib Ala Ala Proψ[CH₂ CH₂] Ala Gly Aib Ala (Me) Val Pro Val; and ,

Asp Ala Pro Ala Ala Pro Ala Gly pro Ala Val Pro Val

14. A peptide mimetic with the following structure:

PMιAB5

15. A peptide mimetic with the following structure-

PMιPrP13

16. A peptide mimetic with the following structure:

PMiPrP5

17. A method for reducing the formation of amyloid or amyloid like deposits involving

abnormal folding into β sheet structure of amyloid β peptide or for reducing the amount of

said amyloid β peptide which has already formed into a beta sheet structure comprising

bringing into the presence of said amyloid β peptide either prior to or after the abnormal

folding thereof into a β sheet structure, an effective amount of the peptide of claim 1.

18. A method for reducing the formation of amyloid or amyloid like deposits involving

conformational changes in prion Pr protein or reducing the amount of said prion Pr protein

which has already formed into amyloid or amyloid-like deposits comprising bringing into the

presence of said prion Pr protein either prior to or after said conformational changes thereof

into amyloid deposits an effective amount of the peptide of claim 8.

19. A method for reducing the formation of amyloid or amyloid like deposits by administation of a peptide mimetic selected from one of the group consisting of :

PMiAB5,

PMiPrP13 and

PMiPrP5