WO2010069069A1

WO2010069069A1 - Cathepsin b inhibitors

Info

Publication number: WO2010069069A1
Application number: PCT/CA2009/001852
Authority: WO
Inventors: Patrick Roy; Daniel J. Mckay
Original assignee: Merck Frosst Canada Ltd
Current assignee: Merck Canada Inc
Priority date: 2008-12-17
Filing date: 2009-12-16
Publication date: 2010-06-24
Anticipated expiration: 2011-06-17

Abstract

Compounds of formula I, including individual diastereomers thereof and pharmaceutically acceptable salts and hydrates thereof, are selective inhibitors of cathepsin B, and are useful in treating pathological conditions that are treated by inhibiting cathepsin B.

Description

TITLE OF THE INVENTION CATHEPSIN B INHIBITORS

FIELD OF THE INVENTION This invention relates to compounds for use in the therapeutic treatment of the human body. In particular, there is provided a class of novel compounds which are selective inhibitors of cathepsin B, and hence are suitable for use in treating a variety of diseases which are mediated by cathepsin B.

BACKGROUND OF THE INVENTION

The cathepsins are a family of cysteine proteases belonging to the papain superfamily. Cysteine proteases function in the normal physiological as well as pathological degradation of connective tissue. Aberrant activity of cysteine proteases, e.g. as a result of increased expression or enhanced activation, may have pathological consequences, and cysteine proteases have been associated with numerous disease states such as arthritis, muscular dystrophy, inflammation, tumor invasion, glomerulonephritis, malaria, periodontal disease and others. Cathepsins play a major role in intracellular protein degradation, turnover and remodelling, and 11 distinct human cysteine cathepsins are known (identified as cathepsins B, C, F, H, L, K, O, S, V, W and Z). Increased levels of cathepsin B and redistribution of the enzyme are found in tumors, suggesting a role for cathepsin B in tumor invasion and metastasis. Cathepsin B has been shown to be involved in the processing of prorenin and as such may play a role in hypertension. (FEBS Lett. 443(1) p. 48-52 (1999). In addition, aberrant cathepsin B activity is implicated in rheumatoid arthritis, osteoarthritis, Pneumocystis carinii, acute pancreatitis, inflammatory airway disease, bone and joint disorders, and atherosclerosis. Inhibitors of cathepsin B and/or cathepsin S have been discussed for use in treating chronic obstructive pulmonary disease (COPD) (WO

2004/089395). Cathepsin B inhibitors have also been published for the treatment of Type II diabetes and metabolic syndrome (WO/2005/097103).

Furthermore, recent studies suggest that cathepsin B plays a pivotal role in Alzheimer's disease and other dementing conditions. Alzheimer's disease (AD) is the most prevalent form of dementia. Its diagnosis is described in the Diagnostic and Statistical Manual of Mental Disorders, 4th ed., published by the American Psychiatric Association (DSM-TV). It is a neurodegenerative disorder, clinically characterized by progressive loss of memory and general cognitive function, and pathologically characterized by the deposition of extracellular proteinaceous plaques in the cortical and associative brain regions of sufferers. These plaques mainly comprise fibrillar aggregates of β- amyloid peptide (Aβ). Aβ is formed from amyloid precursor protein (APP) via separate intracellular proteolytic events involving the enzymes β-secretase and γ-secretase. Variability in the site of the proteolysis mediated by β-secretase results in Aβ of varying chain length, e.g. Aβ (1-38), Aβ (1-40) and Aβ (1-42). N-terminal truncations such as Aβ (4-42) are also found in the brain, possibly as a result of variability in the site of proteolysis mediated by β-secretase. For the sake of convenience, expressions such as "Aβ (1-40)" and "Aβ (1-42)" as used herein are inclusive of such N-terminal truncated variants. After secretion into the extracellular medium, Aβ forms initially-soluble aggregates which are widely believed to be the key neurotoxic agents in AD (see Gong et al, PNAS, 100 (2003), 10417-22), and which ultimately result in the insoluble deposits and dense neuritic plaques which are the pathological characteristics of AD. Other dementing conditions associated with deposition of Aβ in the brain include cerebral amyloid angiopathy, hereditary cerebral haemorrhage with amyloidosis, Dutch-type (HCHWA-D), multi-infarct dementia, dementia pugilistica and Down syndrome.

Hook et. al. (J. Neurochem., 2002, 81, 237-56) identified two distinct pathways leading to secretion of Aβ, namely a regulated secretory pathway and a constitutive secretory pathway, and showed that different β-secretase enzymes were involved in these distinct pathways. Later work by the same group (Hook et. al., Biol. Chem., 2005, 386, 931-40) showed that cathepsin B acts as β-secretase in the regulated pathway, which is the major source of secreted extracellular Aβ. Hence, inhibitors of cathepsin B, in particular selective inhibitors, are of great interest as a potential treatment of AD.

WO 2005/028429 discloses a class of compounds active against cathepsins B, K, L, F and/or S, but does not disclose the compounds of the present invention, and does not disclose selective inhibition of cathepsin B. WO2008/037072 discloses a class of compounds that are different than the compounds disclosed herein, and are selective inhibitors of Cathepsin B. Other cathepsin inhibiting compounds that have some structural features of the compounds herein are disclosed in WO 2001/087828, WO 1999/024460, and J Med. Chem., Vol. 44, 4524- 4534 (2001).

SUMMARY OF THE INVENTION

According to the invention, there is provided a compound of formula I:

or an individual diastereomer thereof or a pharmaceutically acceptable salt or hydrate thereof; in which:

Ar is phenyl or a 5-6 membered heteroaromatic ring having 1-2 heteroatoms independently selected from O, N, and S, wherein Ar is optionally substituted with 1-2 substituent groups independently selected from halogen, C i -βalkyl optionally substituted with 1-3 halogens, -OCi -3alkyl optionally substituted with 1-3 halogens, C2-3alkenyl optionally substituted with 1-5 halogens, and C3_6cycloalkyl;

Rl represents a group selected from H, Ci-βalkyl substituted optionally with 1-5 halogens and optionally with one C3-6cycloalkyl, C2-6alkenyl optionally substituted with 1-5 halogens, and C3-6cycloalkyl optionally substituted with 1-2 groups independently selected from F, CH3, CF3, -OCH3, and -OCF3;

R.2 represents a group selected from H, Ci-6alkyl optionally substituted with 1-5 halogens, C2-6^alkenyl optionally substituted with 1-5 halogens, and C3-6cycloalkyl optionally substituted with 1-2 groups independently selected from F, CH3, CF3, -OCH3, and -OCF3; or Rl and R2 together with the N atom to which they are attached are connected to complete a 4-7-membered heterocyclic ring which also optionally includes a second heteroatom group in the ring selected from O, (NH), S, S(O), and S(O)2, wherein the heterocyclic ring is optionally substituted with 1-2 groups independently selected from F, CH3, CF3, -OCH3, and -OCF3; R3 and R4 are independently selected from H, Cl-βalkyl optionally substituted with 1-5 halogens, C2-6^alkenyl optionally substituted with 1-5 halogens, and C3-6cycloalkyl optionally substituted with 1-2 groups independently selected from F, CH3, CF3, -OCH3, and -OCF₃;

R5 is selected from the group consisting of halogen, Ci-6alkyl optionally substituted with 1-5 halogens, C2-6alkenyl optionally substituted with 1-5 halogens, and

C3_6cycloalkyl optionally substituted with 1-2 groups independently selected from F, CH3, CF3, -OCH3, and -OCF3; and n is an integer from 1-3.

Where a variable occurs more than once in formula I, Ia, II, Ha, III, or IHa, the identity taken by the variable at any particular occurrence is independent of its identity at any other occurrence in the same formula.

DETAILED DESCRIPTION OF THE INVENTION Unless otherwise stated, the following terms have the meanings indicated below:

"Alkyl" as well as other groups having the prefix "alk" such as, for example, alkoxy, alkanoyl, and the like, means carbon chains which may be linear or branched or combinations thereof. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, sec- and tert- butyl, pentyl, hexyl and the like.

"Alkenyl" means carbon chains which may be linear or branched or combinations thereof containing at least 1 carbon to carbon double bond. Examples of alkenyl groups include ethenyl, 1-propenyl, 2-propenyl, 2-methyl-l-propenyl, 1-butenyl and 1-hexenyl.

"Cycloalkyl" means saturated monocyclic carbocycles containing no heteroatoms. "Halogen" or "halo" means fluorine, chlorine, bromine or iodine. "Heteroaryl" means a 5-6-membered monocyclic heteroaromatic ring having 1-2 heteroatoms independently selected from O, N and S. Heteroaryl groups within the scope of this definition include, but are not limited to, pyrrolyl, imidazolyl, pyrazolyl, pyridyl, pyrimidinyl, pyrazinyl, pyridazinyl, furanyl, thienyl, oxazolyl, isoxazolyl, thiazolyl, and isothiazolyl

Compounds described herein contain at least two asymmetric centers and may thus exist as enantiomers and as diastereomers. The present invention includes all such possible stereoisomers as substantially pure resolved enantiomers and racemic mixtures thereof, as well as individual diastereomers and mixtures of diastereomers. The above formula I and later formula II and III are shown without definitive stereochemistry. The present invention includes all stereoisomers of formulae I, II and III, including individual diastereomers thereof and mixtures thereof and pharmaceutically acceptable salts and hydrates thereof. The structures in formulae Ia, Ha, and Ilia are provided showing the preferred stereochemistry at one of the two asymmetric centers. The stereochemistry is not shown at the other asymmetric centers in formulae Ia, Ha and HIa. The individual diastereomers of formula Ia, Ha, and Ilia have in some cases been isolated and assayed (see Examples 1-4), and it is clear that one diastereomer is more active than the other, but the absolute stereochemistry at the undefined asymmetric center of the compounds was not determined. One or both diastereomers were isolated in Examples 1 -4, and both stereoisomers for compounds of formulae Ia, Ha, and Ilia are compounds of the invention, where one stereoisomer is active, and the other stereoisomer is much less active but is useful as an aid for studying the enzyme. Diastereoisomeric pairs of enantiomers may be separated by, for example, fractional crystallization from a suitable solvent, and the pair of enantiomers thus obtained may be separated into individual stereoisomers by conventional means, for example by the use of an optically active acid or base as a resolving agent or by using a chiral phase HPLC column. Alternatively, any enantiomer or diastereomer of a compound of the general Formula I may be obtained by stereospecific synthesis using optically pure starting materials or reagents of known configuration.

In a particular embodiment the compound of formula I has the stereochemistry shown in formula I(a):

The term "pharmaceutically acceptable salt" refers to salts prepared from pharmaceutically acceptable non-toxic bases or acids. When a compound is acidic, suitable salts can be conveniently prepared by neutralization with pharmaceutically acceptable non-toxic inorganic bases and organic bases.

When the compound of the present invention is basic, as is the case with the compounds herein, suitable salts can be conveniently prepared by neutralisation with pharmaceutically acceptable non-toxic inorganic and organic acids. Such acids include, for example, acetic, benzenesulfonic, benzoic, camphorsulfonic, citric, ethanesulfonic, fumaric, gluconic, glutamic, hydrobromic, hydrochloric, isethionic, lactic, maleic, malic, mandelic, methanesulfonic, mucic, nitric, pamoic, pantothenic, phosphoric, succinic, sulfuric, tartaric, p-toluenesulfonic acid and the like.

A subset of the compounds of formula I is described by formula II, including individual diastereomers thereof and pharmaceutically acceptable salts and hydrates thereof:

In the compounds of formula II, Xl and X2 are independently selected from CH and N;

R6 is selected from the group consisting of F, CH3, CF3, -OCH3, and -OCF3; m is an integer from 0-2;

Rl represents a group selected from H; Ci-3alkyl which is substituted optionally with 1-3 F atoms and optionally with one C3-6cycloalkyl; C2-3alkenyl which is optionally substituted with 1-3 F atoms; and C3_6cycloalkyl;

- 5 - R2 represents a group selected from H and Ci_3alkyl which is optionally substituted with 1 -3 F atoms; or

Rl and R2 together with the N atom to which they are attached are connected to complete a 4-7-membered heterocyclic ring which also optionally includes a second heteroatom group in the ring selected from O and (NH), where the heterocyclic ring is optionally substituted with 1-2 groups independently selected from F, CH3, CF3, -OCH3, and -OCF3;

R3 and R4 are independently selected from H and Ci-3alkyl; and

R5 is selected from the group consisting of F, Ci_2alkyl, and CF3.

In other subsets of the compounds of formula II, including individual diastereomers thereof and pharmaceutically acceptable salts and hydrates thereof, Xl and χ2 are independently selected from CH and N, with the proviso that Xl and χ2 are not both N.

In other subsets of formula II, R6 is selected from the group consisting of F, CH3, and CF3. In other subsets of formula II, m is an integer selected from 0 and 1.

In other subsets of formula II, Rl represents a group selected from H, Ci-3alkyl, and CH2-cyclopropyl.

In other subsets of formula II, R2 represents a group selected from H and Ci- 3alkyl. In other subsets of formula II, Rl and R2 together with the N atom to which they are attached complete a 4-6-membered heterocyclic ring which also optionally includes in the ring a second heteroatom O.

In other subsets of formula II, R? and R4 are each H.

In other subsets of formula II, R5 is selected from the group consisting of F, CH3, and CF3. hi other subsets of formula II, R5 is CH3,

In other subsets of formula II, n is the integer 2.

Preferred subsets of the compounds of formula II are described by formula Ha, including individual diastereomers thereof and pharmaceutically acceptable salts and hydrates thereof:

MC C-ΛCV-00005

A preferred subset of the compounds described above has Formula III, including individual diastereomers thereof and pharmaceutically acceptable salts and hydrates thereof:

wherein I?? and R.8 are independently selected from H, F, CH3, and CF3, provided that R7 and R.8 are not both H.

A preferred subset of the compounds described above has Formula Ilia, including 10 individual diastereomers thereof and pharmaceutically acceptable salts and hydrates thereof:

In preferred subsets of the compounds of formula III and HIa described above,

15 including individual diastereomers thereof and pharmaceutically acceptable salts and hydrates thereof, R7 and RB are CH3.

In preferred subsets of the compounds of formula I, Ia, II, Ha, III, and HIa as described above, m is 0.

20

Methods of Synthesis

Scheme 1 illustrates the synthetic method for preparing the chiral phenylalaninamide V. The Boc protected aminomalonate I is deprotonated with NaH and 25 alkylated with 3,5-dimethylbenzyl bromide II. Treatment with acetic acid and water at 150 °C for 16 hours results in mono-ester cleavage and decarboxylation. Subsequent treatment with NaHCO₃ and the enzyme Alkalase 2.4 L results in selective cleavage of the S enantiomer to afford acid III. (See also reference 1.)

Amide coupling with aminoacetonitrile using a suitable coupling reagent such as HATU yields amide IV which is treated with a suitable acid such as methanesulfonic acid to afford phenylalaninamide V.

Scheme 2 shows the synthesis of the amino-substituted phenylacetic acids and pyridylacetic acids and their coupling with V to yield the compounds of the invention. Phenylacetic acid or pyridylacetic acid VI is brominated with N-bromosuccinimide, and the bromide is subsequently displaced with amine VII to afford VIII. Cleavage of the ester with a suitable base such as LiOH then yields acid IX which is coupled with V using a suitable coupling reagent such as HATU to give X as a diastereomeric mixture. This diastereomeric mixture can further be separated into its component diastereomers XI by either normal-phase or reverse-phase chromatography.

Scheme 2

O O I) NBS/ Ph^AO O^ΛPh /CCI₄

The starting materials and reagents used in the schemes provided above are either commercially available or available by routine chemical modification of commercial materials. As mentioned previously herein, compounds according to the invention exist as optical isomers due to the presence of at least two chiral centers. Such compounds may be prepared in racemic form, or individual enantiomers may be prepared either by enantiospecifϊc synthesis or by resolution. The novel compounds may, for example, be resolved into their component enantiomers by standard techniques such as preparative HPLC, or the formation of diastereomeric pairs by salt formation with an optically active acid, such as di-p-toluoyl- D-tartaric acid and/or di-p-toluoyl-L-tartaric acid, followed by fractional crystallisation and regeneration of the free base. The novel compounds may also be resolved by formation of diastereomeric esters or amides, followed by chromatographic separation and removal of the chiral auxiliary. Alternatively, racemic intermediates in the preparation of compounds of formula I may be resolved by the aforementioned techniques, and the desired enantiomer used in subsequent steps.

During any of the above synthetic sequences it may be necessary and/or desirable to protect sensitive or reactive groups on any of the molecules concerned. This may be achieved by means of conventional protecting groups, such as those described in Protective Groups in Organic Chemistry, ed. J.F.W. McOmie, Plenum Press, 1973; and T. W. Greene & P.G.M. Wuts, Protective Groups in Organic Synthesis, John Wiley & Sons, 3^rd ed., 1999. The protecting groups may be removed at a convenient subsequent stage using methods known from the art.

Utility The compounds of the invention have the useful property of selectively inhibiting cathepsin B. In particular, the compounds show selectivity for cathepsin B over cathepsins S, F, and K. The compounds are therefore useful in the treatment or prevention of cathepsin B dependent diseases and conditions in mammals, especially humans.

Therefore, in another aspect the present invention provides a method for the prevention or treatment of cathepsin B dependent conditions in a mammal which comprises administering to the mammal a therapeutically effective amount of a compound of formula I or a pharmaceutically acceptable salt or hydrate thereof. This aspect also encompasses the use of a compound of formula I or a pharmaceutically acceptable salt or hydrate thereof for the manufacture of a medicament for the prevention or treatment of cathepsin B dependent conditions in a mammal. Examples of cathepsin B dependent conditions include tumor invasion and metastasis, rheumatoid arthritis, osteoarthritis, Pneumocystis carinii, acute pancreatitis, inflammatory airway disease, COPD, bone and joint disorders, and diseases associated with deposition of β-amyloid in the brain.

According to a further aspect of the invention there is provided the use of a compound according to formula I as defined above, or a pharmaceutically acceptable salt or hydrate thereof, for the manufacture of a medicament for the treatment or prevention of a disease associated with the deposition of β-amyloid in the brain.

The disease associated with deposition of Aβ in the brain is typically Alzheimer's disease (AD), cerebral amyloid angiopathy, HCHWA-D, multi-infarct dementia, dementia pugilistica or Down syndrome, and most typically is AD. In a further aspect, the invention provides the use of a compound of Formula I as defined above, or a pharmaceutically acceptable salt or hydrate thereof, in the manufacture of a medicament for treating, preventing or delaying the onset of dementia associated with Alzheimer's disease, cerebral amyloid angiopathy, HCHWA-D, multi-infarct dementia, dementia pugilistica or Down syndrome. The invention also provides a method of treating or preventing a disease associated with deposition of Aβ in the brain comprising administering to a patient in need thereof a therapeutically effective amount of a compound of Formula I as defined above or a pharmaceutically acceptable salt or hydrate thereof.

In a further aspect, the invention provides a method of treating, preventing or delaying the onset of dementia associated with Alzheimer's disease, cerebral amyloid angiopathy, HCHWA-D, multi-infarct dementia, dementia pugilistica or Down syndrome comprising administering to a patient in need thereof a therapeutically effective amount of a compound of Formula I as defined above or a pharmaceutically acceptable salt or hydrate thereof. In a further aspect, the invention provides a method for attenuating the secretion of β-amyloid from a mammalian cell comprising contacting said cell with an effective amount of a compound of formula I or a pharmaceutically acceptable salt or hydrate thereof. In one embodiment of the invention, the compound of Formula I is administered to a patient suffering from AD, cerebral amyloid angiopathy, HCHWA-D, multi-infarct dementia, dementia pugilistica or Down syndrome, and typically AD.

In an alternative embodiment of the invention, the compound of Formula I is administered to a patient suffering from mild cognitive impairment or age-related cognitive decline. A favourable outcome of such treatment is prevention or delay of the onset of AD. Age-related cognitive decline and mild cognitive impairment (MCI) are conditions in which a memory deficit is present, but other diagnostic criteria for dementia are absent (Santacruz and Swagerty, American Family Physician, 63 (2001), 703-13). (See also "The ICD-IO Classification of Mental and Behavioural Disorders", Geneva: World Health Organisation, 1992, 64-5). As used herein, "age-related cognitive decline" implies a decline of at least six months' duration in at least one of: memory and learning; attention and concentration; thinking; language; and visuospatial functioning and a score of more than one standard deviation below the norm on standardized neuropsychologic testing such as the MMSE. In particular, there may be a progressive decline in memory. In the more severe condition MCI, the degree of memory impairment is outside the range considered normal for the age of the patient but AD is not present. The differential diagnosis of MCI and mild AD is described by Petersen et al., Arch. Neurol, 56 (1999), 303-8. Further information on the differential diagnosis of MCI is provided by Knopman et al, Mayo Clinic Proceedings, 78 (2003), 1290-1308. In a study of elderly subjects, Tuokko et al (Arch, Neurol., 60 (2003) 577-82) found that those exhibiting MCI at the outset had a three-fold increased risk of developing dementia within 5 years.

Grundman et al (J MoI. Neurosci., 19 (2002), 23-28) report that lower baseline hippocampal volume in MCI patients is a prognostic indicator for subsequent AD. Similarly, Andreasen et al (Acta Neurol. Scand, 107 (2003) 47-51) report that high CSF levels of total tau, high CSF levels of phospho-tau and lowered CSF levels of Aβ42 are all associated with increased risk of progression from MCI to AD.

Within this embodiment, the compound of Formula I is advantageously administered to patients who suffer impaired memory function but do not exhibit symptoms of dementia. Such impairment of memory function typically is not attributable to systemic or cerebral disease, such as stroke or metabolic disorders caused by pituitary dysfunction. Such patients may be in particular people aged 55 or over, especially people aged 60 or over, and preferably people aged 65 or over. Such patients may have normal patterns and levels of growth hormone secretion for their age. However, such patients may possess one or more additional risk factors for developing Alzheimer's disease. Such factors include a family history of the disease; a genetic predisposition to the disease; elevated serum cholesterol; and adult-onset diabetes mellitus. In a particular embodiment of the invention, the compound of Formula I is administered to a patient suffering from age-related cognitive decline or MCI who additionally possesses one or more risk factors for developing AD selected from: a family history of the disease; a genetic predisposition to the disease; elevated serum cholesterol; adult-onset diabetes mellitus; elevated baseline hippocampal volume; elevated CSF levels of total tau; elevated CSF levels of phospho-tau; and lowered CSF levels of Aβ(l-42),

A genetic predisposition (especially towards early onset AD) can arise from point mutations in one or more of a number of genes, including the APP, presenilin-1 and presenilin-2 genes. Also, subjects who are homozygous for the ε4 isoform of the apo lipoprotein E gene are at greater risk of developing AD.

The patient's degree of cognitive decline or impairment is advantageously assessed at regular intervals before, during and/or after a course of treatment in accordance with the invention, so that changes therein may be detected, e.g. the slowing or halting of cognitive decline. A variety of neuropsychological tests are known in the art for this purpose, such as the Mini-Mental State Examination (MMSE) with norms adjusted for age and education (Folstein et al , J Psych Res , 12 (1975), 196-198, Anthony et al , Psychological Med., 12 (1982), 397-408; Cockrell et al, Psychopharmacology, 24 (1988), 689-692; Crum et al., J. Am. Med. Assoc'n. 18 (1993), 2386-2391). The MMSE is a brief, quantitative measure of cognitive status in adults. It can be used to screen for cognitive decline or impairment, to estimate the severity of cognitive decline or impairment at a given point in time, to follow the course of cognitive changes in an individual over time, and to document an individual's response to treatment. Another suitable test is the Alzheimer Disease Assessment Scale (ADAS), in particular the cognitive element thereof (ADAS-cog) (See Rosen et al., Am. J Psychiatry, 141 (1984), 1356-64).

Pharmaceutical Compositions

The compounds of Formula I are typically used in the form of pharmaceutical compositions comprising one or more compounds of Formula I and a pharmaceutically acceptable carrier. Accordingly, in a further aspect the invention provides a pharmaceutical composition comprising a compound of formula I as defined above, or a pharmaceutically acceptable salt or hydrate thereof, and a pharmaceutically acceptable carrier. Preferably these compositions are in unit dosage forms such as tablets, pills, capsules, powders, granules, sterile parenteral solutions or suspensions, metered aerosol or liquid sprays, drops, ampoules, transdermal patches, auto-injector devices or suppositories; for oral, parenteral, intranasal, sublingual or rectal administration, or for administration by inhalation or insufflation. The principal active ingredient typically is mixed with a pharmaceutical carrier, e.g. conventional tableting ingredients such as corn starch, lactose, sucrose, sorbitol, talc, stearic acid, magnesium stearate and dicalcium phosphate, or gums, dispersing agents, suspending agents or surfactants such as sorbitan monooleate and polyethylene glycol, and other pharmaceutical diluents, e.g. water, to form a homogeneous preformulation composition containing a compound of the present invention, or a pharmaceutically acceptable salt thereof. When referring to these preformulation compositions as homogeneous, it is meant that the active ingredient is dispersed evenly throughout the composition so that the composition may be readily subdivided into equally effective unit dosage forms such as tablets, pills and capsules. This preformulation composition is then subdivided into unit dosage forms of the type described above containing from 0.1 to about 500 mg of the active ingredient of the present invention. Typical unit dosage forms contain from 1 to 100 mg, for example 1, 2, 5, 10, 25, 50 or 100 mg, of the active ingredient. Tablets or pills of the composition can be coated or otherwise compounded to provide a dosage form affording the advantage of prolonged action. For example, the tablet or pill can comprise an inner dosage and an outer dosage component, the latter being in the form of an envelope over the former. The two components can be separated by an enteric layer which serves to resist disintegration in the stomach and permits the inner component to pass intact into the duodenum or to be delayed in release. A variety of materials can be used for such enteric layers or coatings, such materials including a number of polymeric acids and mixtures of polymeric acids with such materials as shellac, cetyl alcohol and cellulose acetate.

The liquid forms in which the compositions useful in the present invention may be incorporated for administration orally or by injection include aqueous solutions, liquid- or gel- filled capsules, suitably flavoured syrups, aqueous or oil suspensions, and flavoured emulsions with edible oils such as cottonseed oil, sesame oil, coconut oil or peanut oil, as well as elixirs and similar pharmaceutical vehicles. Suitable dispersing or suspending agents for aqueous suspensions include synthetic and natural gums such as tragacanth, acacia, alginate, dextran, sodium carboxymethylcellulose, methylcellulose, poly(ethylene glycol), poly(vinylpyrrolidone) or gelatin.

For treating or preventing a cathepsin B dependent condition such as Alzheimer's disease, a suitable dosage level is about 0.01 to 250 mg/kg per day, preferably about 0.01 to 100 mg/kg per day, and more preferably about 0.05 to 50 mg/kg of body weight per day, of the active compound. The compounds may be administered on a regimen of 1 to 4 times per day. In some cases, however, a dosage outside these limits may be used.

Combination Therapy

The compounds of Formula I optionally may be administered in combination with one or more additional compounds known to be useful in the treatment or prevention of diseases or conditions for which compounds of formula I are useful, hi the case of AD, such additional compounds include cognition-enhancing drugs such as acetylcholinesterase inhibitors (e.g. donepezil and galanthamine), NMDA antagonists (e.g. memantine) or PDE4 inhibitors (e.g. Ariflo™ and the classes of compounds disclosed in WO 03/018579, WO 01/46151, WO 02/074726 and WO 02/098878). Such additional compounds also include cholesterol- lowering drugs such as the statins, e.g. simvastatin. Such additional compounds similarly include compounds known to modify the production or processing of Aβ in the brain ("amyloid modifiers"), such as compounds which inhibit or modulate the secretion of Aβ (including γ- secretase inhibitors, γ-secretase modulators, and GSK-3α inhibitors), compounds which inhibit the aggregation of Aβ, and antibodies which selectively bind to Aβ. Such additional compounds also include growth hormone secretagogues, as disclosed in WO 2004/110443.

In this embodiment of the invention, the amyloid modifier may be a compound which inhibits the secretion of Aβ, for example an inhibitor of γ-secretase (such as those disclosed in WO 01/90084, WO 02/30912, WO 01/70677, WO 03/013506, WO 02/36555, WO 03/093252, WO 03/093264, WO 03/093251, WO 03/093253, WO 2004/039800, WO 2004/039370, WO 2005/030731, WO 2005/014553, WO 2004/089911, WO 02/081435, WO 02/081433, WO 03/018543, WO 2004/031137, WO 2004/031139, WO 2004/031138, WO 2004/101538, WO 2004/101539 and WO 02/47671), or any other compound which inhibits the formation or release of Aβ. including those disclosed in WO 98/28268, WO 02/47671, WO 99/67221, WO 01/34639, WO 01/34571, WO 00/07995, WO 00/38618, WO 01/92235, WO 01/77086, WO 01/74784, WO 01/74796, WO 01/74783, WO 01/60826, WO 01/19797, WO 01/27108, WO 01/27091, WO 00/50391, WO 02/057252, US 2002/0025955 and US2002/0022621, and also including GSK-3 inhibitors, particularly GSK-3 α inhibitors, such as lithium, as disclosed in Phiel et al, Nature, 423 (2003), 435-9.

Within this embodiment, the amyloid modifier is advantageously a γ-secretase inhibitor, preferred examples of which include a compound of formula XI:

XI wherein m, Z, R^lb, R^lc, Ar¹ and Ar² are as defined in WO 03/018543; or a pharmaceutically acceptable salt thereof.

Such compounds may be prepared as described in WO 03/018543. Preferred examples include those defined by formula XIa:

and the pharmaceutically acceptable salts thereof, wherein m is 0 or 1, X is Cl or CF₃, and Y is OH, OQ-βalkyl, NH₂ or NHC^alkyl. Particular examples include those in which m is 1 and Y is OH (or the sodium salts thereof), and those in which m is 0 and Y is NH₂ or NHC_1-6alkyl.

Another preferred class of γ-secretase inhibitors for use in this embodiment of the invention is that defined by formula XII:

XII wherein X and R are as defined in WO 03/093252; or a pharmaceutically acceptable salt thereof.

X is very aptly 5-substiruted-thiazol-2-yl, 5-substituted-4-methylthiazol-2-yl, 5- substituted- l-methylpyrazol-3-yl, l-substituted-imidazol-4-yl or l-substituted-l,2,4-triazol-3-yl. Preferably, R represents optionally-substituted phenyl or heteroaryl such as phenyl, monohalophenyl, dihalophenyl, trihalophenyl, cyanophenyl, methylphenyl, methoxyphenyl, trifluoromethylphenyl, trifluoromethoxyphenyl, pyridyl, monohalopyridyl and trifluoromethylpyridyl, wherein "halo" refers to fluoro or chloro. Particularly preferred identities of R-X- include 5-(4-fluorophenyl)- 1 -methylpyrazol-3-yl, 5-(4-chlorophenyl)- 1 -methylpyrazol-3- yl and 1 -(4-fiuorophenyl)imidazol-4-yl. Such compounds may be prepared by methods disclosed in WO 03/093252.

As opposed to an inhibitor of γ-secretase, the amyloid modifier may be a modulator of γ- secretase which selectively attenuates the production of Aβ(l-42). This results in preferential secretion of the shorter chain isoforms of Aβ, which are believed to have a reduced propensity for self-aggregation and plaque formation, and hence are more easily cleared from the brain, and/or are less neurotoxic. Compounds showing this effect include certain non-steroidal antiinflammatory drugs (NSAIDs) and their analogues (see WO 01/78721 and US 2002/0128319 and Weggen et al Nature, 414 (2001) 212-16; Morihara et al, J Neurochem., 83 (2002), 1009-12; and Takahashi et al, J Biol. Chem., 278 (2003), 18644-70). Compounds which modulate the activity of PP ARa and/or PPARδ are also reported to have the effect of lowering Aβ(l-42) (WO 02/100836). US 2002/0015941 teaches that agents which potentiate capacitative calcium entry activity can lower Aβ(l-42). Further classes of compounds capable of selectively attenuating Aβ(l-42) production are disclosed on WO 2005/054193, WO 2005/013985, WO 2006/008558, WO 2005/108362 and WO 2006/043064.

Alternatively, the amyloid modifier may be a compound which inhibits the aggregation of Aβ or otherwise attenuates is neurotoxicicity. Suitable examples include chelating agents such as clioquinol (Gouras and Beal, Neuron, 30 (2001), 641-2) and the compounds disclosed in WO 99/16741, in particular that known as DP-109 (Kalendarev et al, J Pharm. Biomed. Anal., 24 (2001), 967-75). Other inhibitors of Aβ aggregation suitable for use in the invention include the compounds disclosed in WO 96/28471, WO 98/08868 and WO 00/052048, including the compound known as Apan™ (Praecis); WO 00/064420, WO 03/017994, WO 99/59571 (in particular 3 -aminopropane- 1 -sulfonic acid, also known as tramiprosate or Alzhemed™); WO 00/149281 and the compositions known as PTI-777 and PTI-00703 (ProteoTech); WO 96/39834, WO 01/83425, WO 01/55093, WO 00/76988, WO 00/76987, WO 00/76969, WO 00/76489, WO 97/26919, WO 97/16194, and WO 97/16191. Further examples include phytic acid derivatives as disclosed in US 4,847,082 and inositol derivatives as taught in US 2004/0204387. Alternatively, the amyloid modifier may be an antibody which binds selectively to Aβ.

Said antibody may be polyclonal or monoclonal, but is preferably monoclonal, and is preferably human or humanized. Preferably, the antibody is capable of sequestering soluble Aβ from biological fluids, as described in WO 03/016466, WO 03/016467, WO 03/015691 and WO 01/62801. Suitable antibodies include humanized antibody 266 (described in WO 01/62801) and the modified version thereof described in WO 03/016466.

As used herein, the expression "in combination with" requires that therapeutically effective amounts of both the compound of Formula I and the additional compound are administered to the subject, but places no restriction on the manner in which this is achieved. Thus, the two species may be combined in a single dosage form for simultaneous administration to the subject, or may be provided in separate dosage forms for simultaneous or sequential administration to the subject. Sequential administration may be close in time or remote in time, e.g. one species administered in the morning and the other in the evening. The separate species may be administered at the same frequency or at different frequencies, e.g. one species once a day and the other two or more times a day. The separate species may be administered by the same route or by different routes, e.g. one species orally and the other parenterally, although oral administration of both species is preferred, where possible. When the additional compound is an antibody, it will typically be administered parenterally and separately from the compound of Formula I.

EXAMPLES

Biological Activity - In Vitro Assays

Enzyme activity assays: Assays of Cat S (human, rat) were carried out in 50 mM MES pH 6.5, 100 mM NaCl, 2.5 mM DTT, 2.5 mM EDTA, 0.001% w/v BSA, 10 % DMSO and 40 μM Z-Val-Val-Arg-AMC as substrate. Assays of Cat B (human, rat) were carried out in 50 mM MES pH 6.0, 2.5 mM DTT, 2.5 mM EDTA, 0.001% Tween-20, 10 % DMSO and 83 μM Boc-Leu- Lys-Arg-AMC as substrate. The assay of human Cat F was carried out in 50 mM MES pH 6.5, 100 mM NaCl, 2.5 mM EDTA, 10% DMSO, 2.5 mM DTT, 0.01% BSA (w/v), 20 uM Z-Phe- Arg-AMC. Assays of humanized rabbit Cat K and Cat L (human, rat) were carried out in 50 mM MES pH 5.5, 2.5 mM DTT, 2.5 mM EDTA, 10 % DMSO and 2 μM Z-Leu-Arg-AMC as substrate. Prior to the addition of substrate, inhibitor (10.0 μM to 0.02 nM) was pre-incubated for 15 min with each enzyme (0.1-1 nM) to allow the establishment of the enzyme-inhibitor complex. Substrate was then added and the enzyme activity measured from the increase of fluorescence at 460 nm (λ_ex = 355 run). Assays were performed in 384-well plate format and the plate read using a Gemini EM (Molecular Devices) plate reader. The substrate concentrations employed represent K_m or sub-K_m values. The percent inhibition of the reaction was calculated from a control reaction containing only vehicle. IC₅₀ curves were generated by fitting percent inhibition values to a four parameter logistic model (SoftmaxPro, Molecular Devices).

Compounds of formula (I) generally have IC₅₀ values of about 1 μM or lower; more typically they have IC₅₀ values of about 100 nM or lower against rat cathepsin B. Compounds exemplified herein have IC₅₀ values in the range of 8 nM to 125 nM against rat cathepsin B. Compounds exemplified herein were typically found to be > 100-fold selective for rat cathepsin B over rat cathepsin S and > 50-fold selective for human cathepsin B over human cathepsin F or K.

Abbreviations Used

The following abbreviations have the meanings indicated, unless stated otherwise in the specification: DMF = dimethylformamide; EtOAc = ethyl acetate; HATU = O-(7- azabenzotriazol-l-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate; MeOH = methanol; MHz = megahertz; MS (+ESI) = mass spectrometry, positive electrospray ionization; ¹H NMR = proton nuclear magnetic resonance; THF = tetrahydrofuran.

Example 1

N-(cyanomethyl)-3,5-dimethyl-Nα-[morpholin-4-yl(pyridin-3-yl)acetyl]-L- phenylalaninamide

Step 1. N-(tert-butoxycarbonyl)-3,5-dimethyl-L-phenylalanine (III).

This compound was prepared in analogous manner to compound 2 of reference 1, using 3,5- dimethylbenzyl bromide as the alkylating agent.

Step 2. Nα-(?err-butoxycarbonyl)-N-(cyanomethyl)-3,5-dimethyl-L-phenylalaninamide(IV). To a solution of the acid from Step 1 (7.2 g, 24.78 mmol), aminoacetonitrile hydrochloride (2.75 g, 29.7 mmol), and HATU (14.1 g, 37.2 mmol) in DMF (200 mL) was added diisopropylethylamine (13 mL, 74.3 mmol).The resulting solution was stirred overnight at room temperature. The mixture was diluted with 800 mL of water and the product was extracted twice with a 2:1 mixture Of EtOAcZEt₂O. The organic layer was washed with water and brine, and was then dried (MgSO^, filtered, and evaporated under reduced pressure. The resulting solid was stirred vigorously with 1 :10 EtOAc/hexane (50 mL) for 1.5 h before filtering to give the product as a pale yellow solid (6.4 g).

Step 3. N-(cyanomethyl)-3,5-dimethyl-L-phenylalaninamide (V).

To a solution of the product from Step 2 (6.4 g, 19.3 mmol) in THF (90 mL) was added methanesulfonic acid (6.27 mL, 97 mmol). The resulting solution was stirred overnight at room temperature. The mixture was then concentrated under vacuum to remove most of the THF, and was then carefully partitioned between EtOAc (300 mL) and saturated NaHCO₃ solution (120 mL). The organic layer was washed with water and brine, and was then dried (MgSO₄), filtered, and evaporated. The resulting solid was stirred vigorously in 1 :10 EtOAc/hexane (50 mL) for 1 h to give, after filtration, a white solid (3.5 g).

Step 4. N-(cyanomethyl)-3,5-dimethyl-Nα-[moφholin-4-yl(pyridin-3-yl)acetyl]-L- phenylalaninamide.

To a solution of the compound of Step 3 (230 mg, 0.99 mmol), morpholin-4-yl(pyridin-3- yl)acetic acid (243 mg, 1.09 mmol), and HATU (605 mg, 1.59 mmol) in DMF (15 mL) was added triethylamine (0.42 mL, 2.98 mmol). The resulting solution was stirred overnight at room temperature. The mixture was then partitioned between water (50 mL) and a 2: 1 mixture of EtOAcZEt₂O (100 mL). The organic layer was washed with water and brine, and was then dried (MgSO₄), filtered, and evaporated. The crude mixture was purified by column chromatography on silica gel using a gradient of 10-100% EtOAc (containing 1% MeOH)Zhexane, and the resulting solid was stirred vigorously in 1 :10 EtOAcZhexane to give, after filtration, a mixture of diastereomers as a beige solid (235 mg). 1H NMR (400 MHz, Acetone-d6): δ 8.56-8.44 (m, 2H), 8.08-7.91 (m, 2H), 7.75 (m, 0.5 H), 7.49 (m, 0.5 H), 7.35-7.25 (m, 1 H), 6.90 (s, 1.5 H), 6.86 (s, 1.5 H), 4.84-4.71 (m, 1 H), 4.30- 4.16 (m, 2 H), 4.04 (s, 0.5 H), 3.98 (s, 0.5 H), 3.59-3.49 (m, 4 H), 3.21-3.09 (m, 1 H), 3.03- 2.95 (m, 1 H), 2.31-2.22 (m, 9 H), 2.20-2.13 (m, 1 H).

Separation of the diastereomers of Ex. 1 on reverse phase HPLC. The product of Ex. 1 was separated into its component diastereomers via reverse phase HPLC. The separation was effected on a Phenomenex Synergi Max RP 100 x 21 mm column using 15% CH₃CNZH₂O (containing 0.6% formic acid) as eluant at a flow rate of 25 mL/min. Retention times for the two isomers were 5.14 and 6.7 min respectively.

Example 2.

The second eluting isomer of Example 1 is very potent and has the NMR spectrum shown below. The absolute stereochemistry of the carbon bearing the morpholine group is not known. 1H NMR (400 MHz, Acetone-d6): δ 8.51-8.48 (m, 1 H), 8.45-8.43 (m, 1 H), 8.06-8.00 (m, 1 H), 7.98-7.93 (m, 1 H), 7.51-7.47 (m, 1 H), 7.30-7.25 (m, 1 H), 6.91 (s, 3 H), 4.82-4.75 (m, 1 H), 4.31-4.19 (m, 2 H), 4.04 (s, 1 H), 3.57 (t, 4 H), 3.21-3.15 (m, 1 H), 3.02-2.95 (m, 1 H), 2.35-2.24 (m, 8 H), 2.20-2.20-2.13 (m, 2 H).

Example 3.

N-(cyanomethyl)-3,5-dimethyl-Nα-[morphoIin-4-yl(phenyl)acetyl]-L-phenylalaninamide.

The title compound was prepared in an analogous manner to Ex. 1, Step 4, using the amine of Ex 1, Step 3, and morpholin-4-yl(phenyl)acetic acid as the acid component of the coupling reaction to give the product as a mixture of diastereomers.

¹H NMR (400 MHz, Acetone-d6): δ 8.00-7.94 (m, 0.5 H), 7.86-7.80 (m, 1 H), 7.73-7.67 (0.5 H), 7.40-7.26 (m, 4H), 7.20-7.15 (m, IH), 6.93-6.86 (m, 3 H), 4.79-4.66 (m, 1 H), 4.27-4.18 (m, 2H), 3.84 (s, 0.5 H), 3.79 (s, 0.5 H), 3.61-3.48 (m, 4 H), 3.18-3.10 (m, IH), 3.03-2.94 (m, I H), 2.39-2.14 (m, 10 H). Separation of the diastereomers of Ex. 3 on chiral phase HPLC. The product of Ex. 3 was separated into its component diastereomers using HPLC on chiral phase. The separation was effected using a 250 x 20 mm Chiralcel OD column using 20% EtOH/hexane containing 0.25% triethylamine at a flow rate of 10 mL/min. Retention times for the two isomers were 26.18 and 37.36 min respectively.

Example 4

The second eluting isomer of Example 3 is very potent and has the NMR spectrum written below. The absolute stereochemistry of the carbon bearing the morpholine group is not known. ¹H NMR (400 MHz, Acetone-d6): δ 7.99-7.93 (m, 1 H), 7.86-7.81 (m, IH), 7.30-7.26 (m, 3 H), 7.19-7.15 (m, 2 H), 6.93-6.89 (m, 3 H), 4.73-4.66 (m, 1 H), 4.31-4.18 (m, 2H), 3.84 (s, 1 H), 3.61-3.54 (m, 4 H), 3.17-3.10 (m, 1 H), 3.01-2.93 (m, IH), 2.38-2.30 (m, 2 H), 2.27 (s, 6H), 2.22-2.15 (m, 2 H).

Example 5

N-(cyanomethyI)-3,5-dimethyl-Nα-[pyridin-3-yl(pyrrolidin-l-yl)acetyl]-L- phenylalaninamide

The title compound was prepared in an analogous manner to Ex. 1, Step 4, using the amine of Ex 1 Step 3 and pyridin-3-yl(pyrrolidin-l-yl)acetic acid as the acid component of the coupling. Following purification, the product was obtained as a 1.6: 1 mixture of diastereomers. MS (+ESI) m/z = 420.2

Example 6

N-(cyanomethyl)-3,5-dimethyl-Nα-[morphoIin-4-yl(pyridin-4-yl)acetyl]-L- phenylalaninamide

Step 1. Ethyl moφholin-4-yl(pyridin-4-yl)acetate.

To a solution of ethyl pyridin-4-ylacetate (2.0 g, 12.1 mmol) and Mg(C10₄)₂ (0.81 g, 3.63 mmol) in CH₃CN at room temperature was added N-bromosuccinimide (2.37 g, 13.3 mmol). After stirring at room temperature for 2h, morpholine (2.1 g, 24.2 mmol) was added, followed by triethylamine (3.4 mL, 24.2 mmol), and the suspension was stirred at room temperature overnight. The CH₃CN was then carefully removed under vacuum, and the residue was taken up in EtOAcZH₂O. The organic phase was washed with H₂O and brine, and was then dried (MgSO₄), filtered, and evaporated. The crude material was purified by column chromatography on silica gel, eluting with a gradient of 10-50% EtOAc/hexane to give the product as a tan coloured oil (1.5 g).

Step 2. Morpholin-4-yl(pyridin-4-yl)acetic acid. To a solution of the product of Step 1 (150 mg, 0.6 mmol) in a mixture of 1.5 mL of MeOH and 1.5 mL of THF was added aqueous IM LiOH solution (1.2 mL, 1.2 mmol). After stirring at room temperature for 1.5 h, the mixture was added to a suspension of 1.5 g of Amberlite IRC-50 (mildly acidic resin) in 5 mL of MeOH. After stirring for 5 min, the suspension was filtered and the filtrate was evaporated to yield the title compound (95 mg).

Step 3. N-(cyanomethyl)-3,5-dimethyl-Nα-[morpholin-4-yl(pyridin-4-yl)acetyl]-L- phenylalaninamide.

To a solution of the compound of Ex. 1 , Step 3 (90 mg, 0.39 mmol), morpholin-4-yl(pyridm-4- yl)acetic acid from Step 2 (95 mg, 0.43 mmol), and HATU (237 mg, 0.62 mmol) in DMF (3 mL) was added triethylamine (0.16 mL, 1.17 mmol). The resulting solution was stirred overnight at room temperature. The mixture was then partitioned between water (10 mL) and a 2:1 mixture of EtOAcZEt₂O (30 mL). The organic layer was washed with water and brine, and was then dried (MgSO₄), filtered, and evaporated. The crude mixture was purified by column chromatography on silica gel using a gradient of 10-40% EtOAc(containing 1% MeOH)/hexane, and the resulting solid was stirred vigorously in 1 : 10 EtOAc/hexane to give, after filtration, an off-white solid (80 mg). ¹H NMR (400 MHz, Acetone-d6): δ 8.54-8.50 (m, 1 H), 8.50-8.46 (m, 1 H), 8.04-7.97 (m, 0.5 H), 7.94-7.84 (m, 1.5 H), 7.34-7.30 (m, 1 H), 7.16-7.12 (m, 1 H), 6.94-6.85 (m, 3 H), 4.80- 4.71 (m, I H), 4.31-4.17 (m, 2 H), 3.97 (s, 0.5 H), 3.93 (s, 0.5H), 3.61-3.50 (m, 4 H), 3.21- 3.09 (m, 1 H), 3.02-2.90 (m, 1 H), 2.36-2.16 (m, 10 H).

Example 7

N-(cyanomethyl)-3,5-dimethyl-Nα-[(methylamino)(pyridin-3-yI)acetyl]-L- phenylalaninamide

Step 1. Ethyl bromo(pyridin-3-yl)acetate.

To a solution of ethyl pyridin-3-ylacetate (0.5 g, 3.0 mmol) in CCl₄ (20 mL) was added N- bromosuccinimide (0.67 g, 3.8 mmol) and benzoyl peroxide (22 mg, 0.1 mmol). The mixture was stirred next to a 150 W spot lamp which brought the reaction to mild reflux. After 45 min, the reaction was cooled and filtered through a pad of celite. The solution was evaporated and the residue was dissolved in 10 mL Of CH₃CN for subsequent displacements.

Step 2. Ethyl (methylamino)(pyridin-3-yl)acetate.

To one half of the crude CH₃CN solution of ethyl bromo(pyridin-3-yl)acetate from Step 1 (5 mL, - 1.5 mmol) at room temperature was added a 2 M solution of methylamine in THF (1.5 mL, 3 mmol). The resulting mixture was stirred at room temperature overnight. The reaction mixture was then concentrated and the residue was taken up in EtOAc/H₂O. The organic phase was washed with H₂O and brine, and was then dried (MgSO₄), filtered, and evaporated. The crude material was purified by column chromatography on silica gel, eluting with 20-100% EtOAc (containing 1% MeOH)/hexane to give 12 mg of the title compound.

Step 3. (Methylamino)(pyridin-3-yl)acetic acid. To a solution of the product of Step 2 (12 mg, 0.06 mmol) in a mixture of 0.5 mL of MeOH and 0.5 mL of THF at room temperature was added IM LiOH solution (0.124 mL, 0.124 mmol). After stirring at room temperature for 1.5 h, the reaction mixture was added to a suspension of Amberlite IRC-50 (150 mg) in 2 niL of MeOH. After stirring for 5 min, the suspension was filtered and the filtrate was concentrated to dryness to yield the title compound (12 mg).

Step 4. N-(cyanomethyl)-3,5-dimethyl-Nα-[(methylamino)(pyridin-3-yl)acetyl]-L- phenylalaninamide.

The title compound was prepared in an analogous manner to Ex. 1, Step 4, using the amine of Ex 1, Step 3, and the (methylamino)(pyridin-3-yl)acetic acid of Step 3 as the acid component of the coupling reaction. Following chromatography on silica gel with a gradient of 1-2% MeOH /EtOAc, the product was obtained as a 3: 1 mixture of diastereomers (2.2 mg). MS (+ESI) m/z = 380.2

Example 8

N-(cyanomethyI)-Nα-[[(cycIopropylmethyl)amino](pyridin-3-yl)acetyl]-3,5-dimethyl-L-

Step 1. Ethyl [(cyclopropylmethyl)amino](pyridin-3-yl)acetate.

To one half of the crude CH₃CN solution of ethyl bromo(pyridin-3-yl)acetate from Example 7,

Step 1 (5 mL, ~ 1.5 mmol) at room temperature was added cyclopropanemethylamine (0.21 g, 3.0 mmol). The resulting mixture was stirred at room temperature overnight. The reaction mixture was then concentrated and the residue was taken up in EtOAcZH₂O. The organic phase was washed with H₂O and brine, and was then dried (MgSO^, filtered, and evaporated. The crude material was purified by column chromatography on silica gel, eluting with 20-100% EtOAc (containing 1% MeOH)/hexane) to give 220 mg of the title compound.

Step 2. [(Cyclopropylmethyl)amino](pyridin-3-yl)acetic acid.

To a solution of the product of Step 1 (0.22 g, 0.94 mmol) in a mixture of MeOH (2 mL) and THF (2mL) at room temperature was added aqueous 1 M LiOH (1.88 mL, 1.88 mmol). After stirring at room temperature for 1.5 h, the reaction mixture was added to a suspension of Amberlite IRC-50 (2 g) in 10 mL of MeOH. After stirring for 5 min, the suspension was filtered and the filtrate was concentrated to dryness to yield the title compound (160 mg). Step 3. N-(cyanomethyl)-Nα-[[(cyclopropylmethyl)amino](pyridin-3-yl)acetyl]-3,5-dimethyl-L- phenylalaninamide.

The title compound was prepared in an analogous manner to Ex. 1, Step 4, using the amine of Ex 1, Step 3, and the [(cyclopropylmethyl)amino](pyridin-3-yl)acetic acid of Step 3 as the acid component of the coupling. Following column chromatography on silica gel (20-100% EtOAc containing 2% MeOH)/hexane), the title compound was obtained as a pink/orange foam mixture of diastereomers (32 mg).

¹H NMR (400 MHz, Acetone-d6): δ 8.58-8.56 (m, 0.5 H), 8.52-8.50 (m, 0.5 H), 8.48-8.43 (m, 1 H), 8.10-7.87 (m, 2 H), 7.72-7.68 (m, 0.5 H), 7.48-7.43 (m, 0.5 H), 7.30-7.20 (m, 1 H), 6.90-6.80 (m, 3 H), 4.74-4.64 (m, 1 H), 4.30-4.17 (m, 3 H), 3.13-3.05 (m, 1 H), 3.00-2.92 (m, 1 H), 2.45- 2.20 (m, 8 H), 1.01-0.85 (m, 1 H), 0.45-0.38 (m, 2H), 0.17-0.04 (m, 2 H).

Reference

1) J. Med. Chem. 44 p. 4524-4534 (2001)

Claims

CLAIMSWHAT IS CLAIMED IS:

1. A compound of formula I:

or a pharmaceutically acceptable salt thereof, wherein:

Ar is phenyl or a 5-6 membered heteroaromatic ring having 1-2 heteroatoms independently selected from O, N, and S, wherein Ar is optionally substituted with 1-2 substituent groups independently selected from halogen, Ci-3alkyl optionally substituted with 1-3 halogens, -OCi_3alkyl optionally substituted with 1-3 halogens, C2-3alkenyl optionally substituted with 1-5 halogens, and C3-6cycloalkyl;

Rl represents a group selected from H, Cj-galkyl substituted optionally with 1-5 halogens and optionally with one C3-6cycloalkyl, C2-6^alkenyl optionally substituted with 1-5 halogens, and C3-6cycloalkyl optionally substituted with 1-2 groups independently selected from F, CH3, CF3, -OCH3, and -OCF3;

R2 represents a group selected from H, Ci-6alkyl optionally substituted with 1-5 halogens, C2-6alkenyl optionally substituted with 1-5 halogens, and C3-6cycloalkyl optionally substituted with 1-2 groups independently selected from F, CH3, CF3, -OCH3, and -OCF3; or

Rl and R2 together with the N atom to which they are attached are connected to complete a 4-7-membered heterocyclic ring which also optionally includes a second heteroatom group in the ring selected from O, (NH), S, S(O), and S(O)2, wherein the heterocyclic ring is optionally substituted with 1-2 groups independently selected from F, CH3, CF3, -OCH3, and -OCF3;

R3 and R4 are independently selected from H, Ci_6alkyl optionally substituted with 1-5 halogens, C2-6alkenyl optionally substituted with 1-5 halogens, and C3_6cycloalkyl optionally substituted with 1-2 groups independently selected from F, CH3, CF3, -OCH3, and -OCF₃; R5 is selected from the group consisting of halogen, Cl-βalkyl optionally substituted with 1-5 halogens, C2-6^alkenyl optionally substituted with 1-5 halogens, and C3-6cycloalkyl optionally substituted with 1-2 groups independently selected from F, CH3, CF3, -OCH3, and -OCF3; and n is an integer from 1-3.

2. The compound of Claim 1 of formula Ia:

or a pharmaceutically acceptable salt thereof.

3. The compound of Claim 1 of formula II:

or a pharmaceutically acceptable salt thereof, wherein:

Xl and χ2 are independently selected from CH and N;

R⁶ is selected from the group consisting of F, CH3, CF3, -OCH3, and -OCF3; m is an integer from 0-2;

Rl represents a group selected from H, Ci_3alkyl substituted optionally with 1-3 F atoms and optionally with one C3_6cycloalkyl, C2-3alkenyl optionally substituted with 1-3 F atoms, and C3-6cycloalkyl;

R2 represents a group selected from H and Ci-3alkyl optionally substituted with 1-3 F atoms; or

Rl and R2 together with the N atom to which they are attached are connected to complete a 4-7-membered heterocyclic ring which also optionally includes a second heteroatom group in the ring selected from O and (NH), wherein the heterocyclic ring is optionally substituted with 1-2 groups independently selected from F, CH3, CF3, -OCH3, and -OCF3; R3 and R4 are independently selected from H and Ci_3alkyl; and R.5 is selected from the group consisting of F, Ci-2alkyl, and CF3.

4. The compound of Claim 3 of formula II, or a pharmaceutically acceptable salt thereof, wherein:

Xl and χ2 are independently selected from CH and N, with the proviso that Xl and χ2 are not both N; R6 is selected from the group consisting of F, CH3, and CF3; m is an integer selected from 0 and 1 ;

Rl represents a group selected from H, Ci-3alkyl, and CH2-cyclopropyl; R2 represents a group selected from H and Ci-3alkyl; or Rl and R2 together with the N atom to which they are attached complete a 4-6- membered heterocyclic ring which also optionally includes in the ring a second heteroatom O; R3 and R4 are each H; and R5 is selected from the group consisting of F, CH3, and CF3.

5. The compound of Claim 4 of formula Ha:

or a pharmaceutically acceptable salt thereof.

6. The compound of Claim 4 of formula III:

VICC-ΛCV-00005

or a pharmaceutically acceptable salt thereof, wherein:

R7 and R8 are independently selected from H, F, CH3, and CF3, provided that R⁷ and R8 are not both H; and 5 m is 0.

7. The compound of Claim 6 of formula Ilia:

10 or a pharmaceutically acceptable salt thereof, wherein R? and R& are CH3.

8. The compound of claim 1, which is selected from the group consisting of the following compounds, or a pharmaceutically acceptable salt thereof:

15

9. A pharmaceutical composition comprising a compound of formula I as defined in claim 1 or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

10. The use of the compound of formula I as defined in claim 1 , or a pharmaceutically acceptable salt thereof, in the manufacture of a medicament for the prevention or treatment of one or more cathepsin B dependent conditions in a patient.

11. A method for the prevention or treatment of one or more cathepsin B dependent conditions in a patient which comprises administering to said patient a therapeutically effective amount of the compound of formula I as defined in claim 1, or a pharmaceutically acceptable salt thereof.

12. The method of Claim 11, wherein the cathepsin B dependent condition is selected from the group consisting of Alzheimer's disease, rheumatoid arthritis, tumor invasion and metastasis, inflammatory airway disease, chronic obstructive pulmonary disease, osteoarthritis, Pneumocystis carinii, acute pancreatitis, and bone and joint disorders.