The present invention relates to protein kinase inhibitors, in particular receptor tyrosine kinase inhibitors, and their use for the treatment of diseases involving a protein kinase such as hyperproliferative disorders e.g. cancer.
Protein kinases, in particular receptor protein tyrosine kinases (RTK), are key regulators of intercellular communication that controls cell growth, proliferation, differentiation, survival and metabolism. About 20 different RTK families have been identified that share a similar structure, namely an extracellular binding site for ligands, a transmembrane region and an intracellular tyrosine kinase domain. Extracellular ligand binding induces or stabilizes receptor dimerization leading to increased RTK kinase activity. The intracellular catalytic domain displays the highest level of conservation among RTKs and includes the ATP-binding site that catalyzes protein phosphorylation of e.g. cytoplasmic tyrosine residues, which serve as docking sites for Src homology 2 (SH2)-and phosphotyrosine-binding (PTB) domain-containing proteins such as Grb2, Shc, Src, Cbl or phospholipase C γ. These proteins subsequently recruit additional effectors containing SH2, SH3, PTB and pleckstrin-homology (PH) domains to the activated receptor, which results in the assembly of signaling complexes at the membrane and the activation of a cascade of intracellular biochemical signals. The most important downstream signaling cascades activated by RTKs include the Ras-extracellular regulated kinase (ERK)-mitogen activated (MAP) kinase pathway, the phosphoinositide 3-kinase (PI 3-kinase)-Akt and the JAK/STAT pathway. The complex signaling network triggered by RTKs eventually leads either to activation or repression of various subsets of genes and thus defines the biological response to a given signal.
The activity of RTKs and their mediated cellular signaling is precisely coordinated and tightly controlled in normal cells. Deregulation of the RTK signaling system, either by stimulation through growth factor and/or through genetic alteration, result in deregulated tyrosine kinase activity. These aberrations generally result in RTKs with constitutive or strongly enhanced kinase activity and subsequent signaling capacity, which leads to malignant transformation. Therefore, they are frequently linked to human cancer and also to other hyperproliferative diseases such as psoriasis. The most important mechanisms leading to constitutive RTK signaling include overexpression and/or gene amplification of RTKs, genetic alterations such as deletions and mutations within the extracellular domain as well as alterations of the catalytic site, or autocrine-paracrine stimulation through aberrant growth factor loops.
For example, in many human cancers, gene amplification and/or overexpression of RTKs occurs, which might increase the response of cancer cells to normal growth factor levels. Additionally, overexpression of a specific RTK on the cell surface increases the incidence of receptor dimerization even in the absence of an activating ligand. In many cases this results in constitutive activation of the RTK leading to aberrant and uncontrolled cell proliferation and tumor formation. An important example for such a scenario is HER2, also known as ErbB2, that belongs to the epidermal growth factor (EGF) receptor family of RTKs. Overexpression of HER2 was found in various types of human cancers, especially in human breast and ovarian carcinomas. Most importantly, aberrantly elevated levels of HER2 correlate with more aggressive progression of disease and reduced patient survival time. EGFR, which was the first receptor tyrosine kinase to be molecularly cloned, also plays a fundamental role in tumorigenesis. EGFR is frequently overexpressed in non-small-cell lung, bladder, cervical, ovarian, kidney and pancreatic cancer and in squamous-cell carcinomas of the head and neck. The predominant mechanism leading to EGFR overexpression is gene amplification with up to 60 copies per cell reported in certain tumors. In general, elevated levels of EGFR expression are associated with high metastatic rate and increased tumor proliferation.
Since protein kinases, in particular tyrosine kinases, have been implicated in a variety of cancer indications, RTKs and the activated signaling cascades represent promising areas for the development of target-selective anticancer drugs. One approach to inhibit aberrant RTK signaling is the development of small-molecule drugs that selectively interfere with their intrinsic tyrosine kinase activity and thereby block receptor autophosphorylation and activation of downstream signal transducers.
Hence, it is a general object of the present invention to provide compounds having a protein kinase inhibitory activity which can be used for the treatment of disorders involving a protein kinase such as hyperproliferative diseases.
Now, in order to implant this and still further objects of the invention, which become more readily apparent as the description proceeds, said protein kinease inhibitory activity is provided by a compound being used for the treatment of disorders involving a protein kinase, in particular a tyrosine kinase, of formula I,
R3 is hydroxyl, halogen, NH2, NO2, cyano, SH, optionally substituted C1-C6 alkyl, optionally substituted C3-C8 cycloalkyl, optionally substituted aryl, optionally substituted 5- or 6-membered heterocycle,
R5 is selected from C1-C6 alkyl, hydrogen, hydroxyl, alkoxy, NH2, halogen, cyano, alkine, COOR" wherein R" is selected from hydrogen, C1-C6 alkyl, C3-C8 cycloalkyl,
Preferred compounds of formula I are those where R1 is hydrogen, methyl, ethyl, propyl, cyclopropyl, NH2, SH and R2 is NR6R7 wherein R6 is hydrogen, R7 is selected from C3-C8 cycloalkyl, optionally substituted phenyl, (CH2)nCO(O)R8 where n = 1, and wherein R8 is C1-C6 alkyl, C1-C6 alkoxy, R3 is optionally substituted phenyl, optionally substituted 5- or 6-membered heterocyle, cyano;
R4 is hydrogen, NH(CH2)mR', O(CH2)mR', S(CH2)mR' wherein R' is selected from optionally substituted phenyl, optionally substituted C3-C8 cycloalkyl and m = 1, 2,
R5 is methyl, hydrogen, hydroxyl.
Preferred compounds of formula I are those where R1 is hydrogen,
R2 is NHR7 wherein R7 is selected from C3-CB cycloalkyl, phenyl optionally substituted with a substituent selected from C1-C6 alkyl, C1-C6 alkoxy, halogen, hydroxyl, NH2, SO2NH2; (CH2)nCO(O)R8 where n = 1, and wherein R8 is methyl, ethyl, propyl, butyl,
R3 is phenyl optionally substituted with a substituent selected from C1-C6 alkyl, C1-C6 alkoxy, halogen, hydroxyl, NO2 optionally substituted 5- or 6-membered heterocycle, cyano, R4 and R5 are hydrogen, or those where
R1 is hydrogen,
R2 is NR6R7 wherein R6 is hydrogen, R7 is optionally substituted phenyl,
R3 is optionally substituted phenyl or optionally substituted, preferably unsubstituted, furyl,
R4 is hydrogen, methyl or NR6R7 wherein R6 and R7 are independently from each other, selected from hydrogen, C1-C2 alkyl, optionally substituted by phenyl, and
R5 is hydrogen.
Even more preferred compounds of formula I are those where
R1 is hydrogen,
R2 is NHR7 wherein R7 is selected from phenyl
optionally substituted with a radical selected from methyl, ethyl, propyl, halogen, methoxy, hydroxyl,
R3 is phenyl optionally substituted with a substituent selected from methoxy, bromo, chloro, fluoro, hydroxyl, NO2, NH2, R4 and R5 are hydrogen, or those where
R1 is hydrogen,
R2 is -NR6R7 wherein R6 is hydrogen and R7 is unsubstituted phenyl or phenyl substituted in 3 and/or 4 position by one or two substituents independently selected from halogen, C1-C2 alkoxy, in particular methoxy, C1-C2 alkyl, in particular methyl, CF3, NO2, NH2, NHCH3, N(CH3)2,
R3 is unsubstituted phenyl or phenyl substituted in 3 and/or 4 position by a substituent independently selected from C1-C4 alkoxy, or hydroxy, or amino, or the substituents in 3- and 4-position form together a 5- or 6-membered heterocycle,
R4 is hydrogen or methyl and
R5 is hydrogen.
Especially preferred compounds of formula I are those where R1 is hydrogen, R2 is NHR7 wherein R7 is phenyl, R3 is phenyl and R4 and R5 are hydrogen; and where
R1 is hydrogen, R2 is NHR7 wherein R7 is phenyl, R3 is phenyl substituted with hydroxyl and R4 and R5 are hydrogen, or those where
R1 is hydrogen,
R2 is -NR6R7 wherein R6 is hydrogen and R7 is
unsubstituted phenyl or phenyl substituted in 3 and/or 4 position by one or two substituents independently selected from halogen and CF3, in particular an unsubstituted phenyl or a phenyl substituted in 3 or 4 position,
R3 is unsubstituted phenyl or phenyl substituted in 3 and/or 4 position by methoxy or hydroxy, in particular an unsubstituted phenyl or a phenyl substituted in 3- or 4-position,
R4 is hydrogen or methyl, and
R5 is hydrogen.
A presently especially preferred compound is a compound of formula I (see also Example 1) where
R1 is hydrogen,
R2 is -NR6R7 wherein R6 is hydrogen and R7 is phenyl substituted with halogen in 3-position,
R3 is unsubstituted phenyl,
R4 is methyl, and
R5 is hydrogen.
The compounds of the present invention are preferably used for the treatment of a disease which involves a tyrosine kinase, preferably a receptor tyrosine kinase.
The compounds of the present invention are particularly suitable for the treatment of a disease involving a member of the eph family of receptor tyrosine kinases. A preferred member of the eph family is ephrin B4.
The compounds of the present invention can be used for the treatment of many diseases involving a protein kinase such as hyperproliferative diseases, in particular cancer.
In a second aspect the present invention relates to the use of a compound of formula Ia:
R2 is hydrogen, C1-C6 alkyl and
R3 is phenyl optionally substituted with a substituent selected from C1-C6 alkyl, C1-C6 alkoxy, halogen, hydroxyl, NO2
for the manufacture of a medicament for the treatment of a hyperproliferative disease or a malignant transformation involving a protein kinase.
Preferred compounds of formula la are those where
R1 is cyclopentyl, cyclohexyl, phenyl optionally substituted with a substituent selected from methyl, ethyl, propyl; (CH2)nCO(O)R4 where n = 1 and wherein R4 is methyl, ethyl, propyl,
R2 is hydrogen and
R3 is phenyl optionally substituted with a substituent selected from methoxy, ethoxy, hydroxyl, N02, bromine, fluorine, chlorine.
Even more preferred compounds of formula Ia are those where
R1 is phenyl, R2 is hydrogen and R3 is phenyl substituted with hydroxyl and
R1 is phenyl, R2 is hydrogen and R3 is phenyl.
In a third aspect, the present invention provides a compound of formula Ib as medicament
Preferred compounds of formula Ib are those where R7 is unsubstituted phenyl or phenyl substituted in 3 and/or 4 position by one or two substituents independently selected from halogen, C1-C2 alkoxy, in particular methoxy, C1-C2 alkyl, in particular methyl, CF3, NO2, NH2, NHCH3, N(CH3)2; R3 is unsubstituted phenyl or phenyl substituted in 3 and/or 4 position by a substituent independently selected from C1-C4 alkoxy, or hydroxy, or amino, or the substituents in 3- and 4-position form together a 5- or 6-membered heterocycle, and R4 is methyl.
Even more preferred compounds are those compounds of formula Ib where R7 is unsubstituted phenyl or phenyl substituted in 3 and/or 4 position by one or two substituents independently selected from halogen, and CF3, in particular an unsubstituted phenyl or a phenyl substituted in 3 or 4 position; R3 is unsubstituted phenyl or phenyl substituted in 3 and/or 4 position by methoxy or hydroxy, in particular an unsubstituted phenyl or a phenyl substituted in 3- or 4-position, and R4 is methyl.
Even more preferred compounds are those compounds of formula Ib where R7 is phenyl substituted with halogen in 3-position; R3 is unsubstituted phenyl, and R4 is methyl.
Preferably said disorder is a hyperproliferative disorder, in particular a cancer.
The compounds of the present invention can as well be used as research tools in functional genomics, drug discovery, target validation and ex vivo diagnostics.
In the context of the present invention it has been surprisingly found that the compounds of formula I have besides their known analgetic activity as well a protein kinase modulating activity, in particular a tyrosine kinase inhibiting activity.
The compounds of the present invention are preferably used for the treatment of a hyperproliferative disease, in particular cancer. The compounds of the present invention are particularly suitable for the treatment of a hyperproliferative disorder involving a receptor tyrosine kinase of the eph family, preferably eph B4, or a tumor involving the cytoplasmic tyrosine kinase src. The src non-receptor tyrosine kinase in known to be involved in the development of various cancers. For a review see the publication of
There exists evidence that receptor tyrosine kinases of the eph family are involved in the development of tumors such as breast cancer, liver cancer, gastrointestinal cancer, neuroblastomas, leukemias and lymphomas, prostate cancer, pancreatic cancer, lung cancer, melanoma, ovarian cancer, thyroid cancers, sarcomas, renal carcinomas and epidermoid cancer (
The term "protein kinase" as used herein encompasses all types of protein kinases such as serine/threonine kinases, tyrosine kinases, receptor tyrosine kinases and non-receptor tyrosine kinases.
The compounds of the present invention having formula I can be prepared by methods described e.g. in
The compounds of the invention can be administered in a variety of dosage forms, e.g. orally, in the form of tablets, capsules, sugar- or film-coated tablets, liquid solutions or suspensions; rectally, in the form of suppositories; parenterally, e.g. intramuscularly, or by intravenous injection of infusion; or topically. The dosage depends on the age, weight, condition of the patient and administration route.
The pharmaceutical compositions containing the compounds of the invention are usually prepared following conventional methods and are administered in a pharmaceutically suitable form.
For example, the solid oral forms may contain, together with the active compound, diluents, e.g. lactose, dextrose, saccharose, cellulose, corn starch or potato starch; lubricants, e.g. silica, talc, stearic acid, magnesium or calcium stearate, and/or polyethylene glycols; binding agents, e.g. starches, arabic gums, gelatin, methylcellulose, carboxymethylcellulose or polyvinyl pyrrolidone; disaggregating agents, e.g. a starch, alginic acid, alginates or sodium starch glycolate, effervescing mixtures; dyestuffs; sweeteners; wetting agents, such as lecithin, polysorbates, laurylsulphates; and, in general, non-toxic and pharmacologically inactive substances used in pharmaceutical formulations. Said pharmaceutical preparations may be manufactured in known manner, for example by means of mixing, granulating, tabletting, sugar-coating or filmcoating processes.
The liquid dispersion for oral administration may be, e.g., syrups, emulsions and suspensions.
The syrup may contain as carrier, for example, saccharose or saccharose with glycerin and/or mannitol and/or sorbitol.
The suspensions and the emulsions may contain as carrier, for example, a natural gum, agar, sodium alginate, pectin, methylcellulose, carboxymethylcellulose or polyvinyl alcohol. The suspensions or solutions for intramuscular injections may contain, together with the active compound, a pharmaceutically acceptable carrier, e.g. sterile water, olive oil, ethyl oleate, glycols, e.g. propylene glycol, and, if desired, a suitable amount of lidocaine hydrochloride.
The solutions for intravenous injections or infusion may contain as carrier, for example, sterile water or, preferably, they may be in the form of sterile aqueous, isotonic saline solutions.
The suppositories may contain, together with the active compound, a pharmaceutically acceptable carrier, e.g. cocoa-butter, polyethylene glycol, a polyoxyethylene sorbitan fatty acid ester surfactant or lecithin.
Compositions for topical application, e.g. creams, lotions or pastes, can be prepared by admixing the active ingredient with a conventional oleaginous or emulsifying excipient.
The compounds of the present invention may be administered to a patient in form of phamaceutically acceptable salts. Suitable pharmaceutically-acceptable salts include acid addition salts such as methanesulfonate, fumarate, hydrochloride, citrate, maleate, tartrate and hydrobromide. Also suitable are salts formed with phosphoric and sulfuric acid. Further suitable salts are base salts such as an alkali metal salt for example sodium, an alkaline earth metal salt for example calcium or magnesium, an organic amine salt for example triethylamine, morpholine, N-methylpiperidine, N-ethylpiperidine, procaine, dibenzylamine, N,N-dibenzylethylamine, tris-(2-hydroxyethyl) amine, N-methyl d-glucamine and amino acids such as lysine. There may be more than one cation or anion depending on the number of charged functions and the valency of the cations or anions.
The compounds of the present invention may be administered in the form of a pro-drug which is broken down in the human or animal body to give a compound of the present invention. A prodrug may be used to alter or improve the physical and/or pharmacokinetic profile of the parent compound and can be formed when the parent compound contains a suitable group or substituent which can be derivatised to form a prodrug. Examples of prodrugs include in-vivo hydrolysable esters of a compound of the present invention or a pharmaceutically-acceptable salt thereof.
Below are shown three preferred compounds of the present invention:
The invention is further illustrated by the following preparations and examples wich should not be construed to limit the scope of the disclosure. Alternative pathways and analogous structures will be apparent to those skilled in the art.
The following abbreviations are used in the following examples:
- rt = room temperature (ca. 25°C)
- Rt = Retention time
- AcOH = acetic acid
- EtOAc = ethyl acetate
- EtOH = ethanol
- MeOH = methanol
- TFA = trifluoro acetic acid
- NMR = nuclear magnetic resonance spectroscopy
- HPLC = high pressure liquid chromatography
- LC/MS = liquid chromatography mass spectrometry
- RP = reverse phase
The following purification methods were applied to obtain pure samples: Crystallization from typical organic solvents, flash chromatography on silica gel, preparative HPLC on RP-silica gel and any combinations thereof.
For preparative HPLC, an Agilent Series 1100 Instrument with a Zorbax SB-C18 column , 21.2 x 250 mm, 7 µ, was used; solvents CH3CN - water (0.1 % TFA each).
Where HPLC data are presented, analysis was done on a Agilent Series 1100 Instrument with a Supelco Discovery C18 column (4.6 x 50 mm, 5 µ, detecting at 254 nm and 220 nm; gradient 10 % to 99 % CH3CN within 4 minutes, 1 min. at 99 % CH3CN using CH3CN - water (0.1 % TFA each) solvent system with a flow rate of 2.0 mL / min. The retention times in minutes are given.
Where NMR Data are presented, 1H spectra were obtained on a Bruker DPX 300 (300.13 MHz) and are reported as ppm down field from tetramethylsilane with the number of protons.
Where LC/Ms data are presented, analysis was performed using a Micromass ZQ, (150-1000 u), ESI-positive spectrometer and Agilent Series 1100 Instrument, with a YMC-Pack ProC 18 (3 µm), 33x3 mm column; gradient flow 5 % CH3CN /methanol/ 95% water/ 0.05% formic acid to 100% CH3CN /methanol/ 0% water/ 0.05% formic acid within 3 minutes using CH3CN /methanol (80:20) - water (0.05% HCOOH) as solvent system with a flow rate of 1.7 mL/min. The retention times in minutes and observed parent ion are given.
In an autoclave, 2-chloro-3-methyl-pyrazine (1) (10.0 g, 77.8 mmol) was dissolved in dry methanol (30 mL). Ammonia gas (60 g) was added. The mixture was heated to 150°C for 8 hours. (start pressure: 10 bar, end pressure: 90 bar). After cooling to rt, the mixture was evaporated to a brown solid, which was dissolved in 1N hydrochloric acid (100 mL) and washed with dichloromethane. The aqueous layer was slowly poured on cold saturated aqueous ammonia (150 mL), then extracted with dichloromethane (3 x 100 mL). The combined organic layers were dried (Na2SO4) and evaporated. The product was extracted from the residual solid with hot acetone (200 mL). Evaporation yielded 36 % of 3-methyl-pyrazin-2-ylamine (2) as a yellow solid.
3-Methyl-pyrazin-2-ylamine (2) (109 mg, 1.0 mmol), benzaldehyde (106 mg, 1.0 mmol) and 3-chlorophenylisonitrile (138 mg, 1.0 mmol) were dissolved in a mixture of dry methanol (2.0 mL) and trimethyl orthoformate (2.0 mL) under argon. The mixture was stirred at 60°C for 3 hours, then cooled to rt. An analytically pure sample of 3 was obtained from the crude product using preparative HPLC.
2-Amino-pyrazine (95 mg, 1.0 mmol) and benzaldehyde (106 mg, 1.0 mmol) were dissolved in dry dioxane (2.0 mL) containing molecular sieves (3Å) under argon. After 5 minutes sulfuric acid (20µL) and 3,4-dichloro-phenylisonitrile (172 mg, 1.0 mmol) were added. The mixture was then stirred at 50°C for 3 hours, cooled to rt and filtered. The product 29 was obtained by crystallization from acetonitrile.
2-Amino-3-chloro-pyrazine (130 mg, 1.0 mmol) and benzaldehyde (106 mg, 1.0 mmol) were dissolved in dry dioxane (3.0 mL) containing molecular sieves (3Å) under Argon. After 5 minutes sulfuric acid (20µL) and 3-chlorophenylisonitrile (138 mg, 1.0 mmol) were added. The mixture was then stirred at 50°C for 3 hours, cooled to rt and filtered.
Benzylamine (536 mg, 5.0 mmol) was added to the filtrate and the mixture was heated to 60°C for 20 h. After cooling to rt, filtration and evaporation to dryness, an analytically pure sample of 22 was obtained from the crude product using preparative HPLC.
9 (82 mg, 0.22 mmol) was dissolved in ethyl acetate (20 mL). 50 mg of Ra/Ni x EtOH were added and the mixture was hydrogenated (1 bar) at rt for 40 hours. The catalyst was filtered off, washed with ethyl acetate and the filtrate was evaporated to yield product 10 as a yellow solid. Pure 10 was obtained by crystallization from acetonitrile.
9 was prepared in analogy to General Method A using 4-nitrobenzaldehyde.
7 was prepared in analogy to General Method A using 3-methoxybenzaldehyd. Pure 7 was obtained by crystallization from ethyl acetate / heptane.
7 (50 mg, 0.14 mmol) were refluxed in a mixture of glacial acetic acid (0.5 mL) and aqueous hydrobromic acid (5 mL) for 20 hours. After cooling to rt, it was extracted with dichloromethane (3 x 100 mL). The combined organic layers were was washed with water, saturated sodium bicarbonate solution and water, then dried (Na2SO4) and evaporated. 32 was obtained as a slight yellow solid.
The following compounds shown in TABLE 1, TABLE 2, TABLE 3 and TABLE 4 were prepared in accordance with the methods provided in Examples 1 to 4. Those of ordinary skill in the art of organic synthesis will recognize when starting materials or reaction conditions should be varied to obtain the desired compound.
The analytical data of the compounds is summarized in TABLE 5
7.82, d, 4.7 Hz, 1H;
2.87, s, 3H
8.75, s, 1H;
8.61, m, 1H
8.73, s, 1H;
8.56, m, 1H
8.85, br, 1H;
6.80, m, 2H
8.67, s, 1H;
3.73, s, 3H
9.24, d, 1.4 Hz, 1H;
8.76, br, 1H;
2.06, s, 3H
8.82, br, 1H;
6.67, br, 1H
8.51, br, 1H;
8.00, m, br, 1H
8.60, br, 1H;
2.36, s, 3H
8.63, br, 1H;
1.34, d, 6.9 Hz, 6H
8.76, br, 1H;
3.82, s, 3H
8.74, br, 1H;
6.48, m, 1H
8.15, s, 1H;
6.08, m, 1H
5.76, s, 1H;
3.64, s, 3H
9.19, br, 1H;
6.71, m, 2H
8.41, br, 1H;
6.52, m, 2H
9.03, s, 1H;
8.85, m, 1H:
8.76, br, 1H;
6.31, m, 2H
8.81, s, 1H;
6.50, m, 1 H
8.33, s, 1H;
2.16, s, 3H
8.67, br, 1H;
6.42, m, 2H
8.34, s, 1 H;
3.77, s, 3H
8.42, s, 1H;
6.51, d, 7.6 Hz, 2H
3.72, m, 2H;
3.15, m, 2H
8.00, m, 2H;
2.74, s, 3H
The kinase inhibition activity of the compounds was measured in an in vitro kinase assay.
Briefly, in a final reaction volume of 25 µL, human EphB4 (N-terminal His6-tagged, recombinant, amino acids 561-end, expressed by baculovirus in Sf21 insect cells; 5-10 mU) was incubated with 8 mM MOPS pH 7.0, 0.2 mM EDTA, 10 mM MnCl2, 0.1 mg/mL poly(Glu, Tyr) 4:1, 10 mM MgAcetate and [γ-33P-ATP] (specific activity approx. 500 cpm/pmol, concentration as required). The reaction was initiated by the addition of the MgATP mix. After incubation for 40 min at rt, the reaction was stopped by the addition of 5 µL of a 3% phosphoric acid solution. 10 µL of the reaction was then spotted onto a Filtermat A and washed three times for 5 min in 75 mM phosphoric acid and once in methanol prior to drying and scintillation counting.
All compounds described in Example 1 to 6 were tested in the assay for EPHB4 activity described in Example 7 and found to exhibit an IC50 of 6 µM or less. Certain compounds disclosed in Example 1 to 6 exhibited an IC50 of 500 nM or less in this assay. A subset of those compounds even exhibited an IC50 of 150 nM or less.
While certain embodiments have been shown and described, numerous modifications and substitutions may be made without departing from the scope of the invention. Therefore, present invention has been described by way of examples and they have to be understood in an illustrative sense only and are not to be interpreted as limiting this invention in any manner.