Patent Application
20080318949
This invention relates to a series of new pyrazolopyrimidinone derivatives (1A and 1B), processes for their preparation, and pharmaceutical compositions containing them. The compounds have potent inhibitory activities against type V phosphodiesterase (PDE5), therefore they are useful for treating erectile dysfunction and other cardiovascular dysfunction.
International application WO94/28902 disclosed the use of pyrazolo[4,3-d]pyrimidine-7-one as selective cGMP PDE inhibitor for erectile dysfunction, and then WO02/27848 disclosed another series of pyrazolo[4,3-d]pyrimidine-7-one derivates, which also have potent inhibitory activity against PDE5.
The level of cGMP in the smooth muscle cell will increase once the PDE5 in smooth muscle cells are inhibited, cGMP activates protein kinase G (PKG), which subsequently phosphorylates the target protein including smooth muscle myosin, and resulting in the relaxation of smooth muscle and vasodilation. Therefore PDE5 inhibitors are useful in the treatment of a variety of cardiovascular diseases.
Sildenafil, the first launched PDE5 inhibitor, is used for male erectile dysfunction in clinic, which also demonstrates clinical effect in female sexual dysfunction and hyperpietic. The PDE5 inhibitor under development is also used for the treatment of alimentary canal in the diabetic, insulin resistance and hyperlipemia.
Despite its effectiveness, Sildenafil has shown clinically significant adverse reactions such as headache, flushing, dyspepsia, snuffle, dimness of vision, photosensitive, and other visual disturbances, which may be linked to insufficient selectivity versus the other PDE isoforms and the dosage. Therefore, both potencies toward PDE5 and selectivities against other PDEs, especially PDE6 are the goal for the successful development of new PDE5 inhibitors.
It is an object of the present invention to provide a series of new pyrazolopyrimidinone derivatives (1A and 1B).
It is another object of the present invention to provide the processes for the preparation of compounds of formula 1A and 1B.
It is still another object of the present invention to provide the pharmaceutical compositions containing the compounds of formula 1A and/or 1B.
The inventors designed and synthesized a series of novel pyrazolopyrimidinone derivatives (1A and 1B), most of which have higher inhibitory activity towards PDE5 and better selectivity against PDE6 distributing in retina than Sildenafil. Therefore, the compound provided by this invention will demonstrate better safety and efficacy, and has a good prospect in clinical application.
wherein:
R1 represents H, C1-C6 alkyl, C3-C6 cycloalkyl, C1-C3 alkyl substituted by halo or C3-C6 cycloalkyl;
R2 represents C2-C6 alkyl, C3-C6 cycloalkyl, C1-C3 alkyl substituted by halo or C3-C6 cycloalkyl;
R3 represents C1-C6 alkyl, C3-C6 cycloalkyl, C1-C3 alkyl substituted by halo, C1-C3 alkoxyl C3-C6 cycloalkyl;
Wherein formula 1A,
m=1-6; n=0-6;
p=1-5; q=1-5;
r1, r2, r3 and r4 independently represent H or C1-C3 alkyl, r1 and r2, r3 and r4 together with the carbon which they are attached to, form Het;
R4 and R5 independently represent H, C1-C6 alkyl, (CH2)uAr, (CH2)vHet, COR9, SO2R9, C1-C3 alkyl substituted by NR10R11 or C1-C3 alkyl; in case of n=0, R5 doesn't represent H; in case of R1 represents methyl; R2 represents propyl, R3 represents ethyl, m=1, n=1, p=q=2, r1, r2, r3 and r4 all represent H, R4 and R5 don't represent H at same time.
R9 represents H, C1-C6 alkyl, C1-C6 alkyl substituted by C1-C3 alkoxyl or NR12R13, (CH2)uAr or (CH2)vHet;
R10 and R11 independently represent H, C1-C6 alkyl, C1-C6 alkyl substituted by C1-C3 alkoxyl or NR12R13, or R10 and R11 together with the nitrogen which they are attached to, form Het;
R12 and R13 independently represent H, C1-C6 alkyl;
Wherein formula (1B)
t=1-5;
R6 represents C1-C6 alkyl, C3-C6 cycloalkyl, C1-C6 haloalkyl, C1-C3 alkoxyl, phenyl, pyridyl, furanyl, pyridazinyl, pyrazinyl, imidazolyl, C1-C3 substituted with hydroxyl, C1-C3 alkoxyl, acetoxyl, phenyl, pyridyl, furanyl, pyridazinyl, pyrimidinyl, pyrazinyl, imidazolyl; the above phenyl, pyridyl, furanyl, pyridazinyl, pyrimidinyl, pyrazinyl, imidazolyl optionally substituted with one or more substituents selected from halo, C1-C3 alkyl, C1-C3 alkoxyl;
R7 and R8 independently represent H, C1-C6 alkyl, C3-C6 cycloalkyl, C1-C3 haloalkyl, C1-C6 alkoxyl, C1-C3 alkyl substituted with hydroxyl, acetoxyl, C1-C3 alkoxyl, or R7 and R8 together with the nitrogen which they are attached to, form four-membered to eight-membered heterocyclic ring, including morpholine, piperidine, pyrrole, piperazine; the above heterocyclic ring optionally substituted with one or more substituents selected from halo, C1-C3 alkyl, C3-C6 cycloalkyl, C1-C3 haloalkyl, C1-C3 alkoxyl;
Wherein u, v=0, 1 or 2;
Ar represents phenyl or phenyl substituted by one to two substituents selected from halo, NH2, C1-C3 alkyl, C1-C3 alkoxy, CONH2, CN, SO2NH2;
Het represents a four-membered and six-membered heterocyclic ring substituted with one or two substituents selected from halo, C1-C3 alkyl, C1-C3 alkoxy, the heterocyclic contains one to four heteroatoms selected from nitrogen, sulfur, oxygen.
As previously defined, no particular explanation, alkyl with there or more carbon wherein said may be straight or branched chain. Halo represents fluorine, chlorine, bromine or iodine
The compound of formula 1A and 1B may have one or more chiral center, therefore, the compound may exist stereomer, that's to say, enantiomer, diastereomer or their mixture. The invention includes within its scope all the possible isomers, stereomers and their mixture of formulae 1A and 1B.
The compounds of formula 1A and 1B may have stereomers and this invention includes all the possible isomers, stereomers and their mixtures thereof.
The invention includes within its all the possible prodrugs of formula 1A and 1B.
The invention includes the pharmaceutically acceptable salts of formula 1A and 1B, preferred salts are hydrochloride and methanesulfonate.
The invention still includes the pharmaceutically acceptable solvates of formula 1A and 1B (e.g. hydrates).
The invention also includes the pharmaceutically oxide of formula 1A and 1B.
Preferred compounds of IA and IB include those wherein:
R1 represents C1-C4 alkyl or C3-C6 cycloalkyl;
R2 represents C2-C4 alkyl or C3-C6 cycloalkyl;
R3 represents C1-C3 alkyl, C1-C3 alkyl substituted with C1-C3 alkoxyl;
m=1-2; n=0-2;
p=2-4; q=2-4;
r1, r2, r3 and r4 independently represent H or methyl;
R9 represents C1-C4 alkyl, phenyl or pyridyl;
R10 and R11 independently represent H, C1-C3 alkyl; or R10 and R11 together with the nitrogen which they are attached to, form a heterocyclic ring, including morpholine, piperazine, piperidine, pyrrole;
Wherein IB:
t=2-3;
R6 represents C1-C3 alkyl, phenyl, pyridyl, benzyl or C1-C3 substituted with hydroxyl, C1-C3 alkoxyl, acetoxyl, phenyl, pyridyl;
R7 and R8 together with the nitrogen which they are attached to, form a morpholine, piperidine or pyrrole heterocyclic ring;
Particularly preferred compounds of IA and IB include those wherein:
R1 represents methyl or ethyl;
R2 represents ethyl and n-propyl;
R3 represents ethyl, n-propyl or methyloxyethyl;
Wherein IA,
m=1; n=0-1;
p=2-3; q=2-3;
r1, r2, r3 and r4 represent H;
R4 and R5 independently represent H, methyl, ethyl or COR9; C1-C3 alkyl substituted by NR10R11; in case of n=0, R5 doesn't represent H; in case of R1 represents methyl, R2 represents propyl, R3 represents ethyl, m=1, n=1, p=q=2, r1, r2, r3 and r4 all represent H, R4 and R5 don't represent H at same time;
R9 represents methyl or pyridyl;
Wherein IB,
t=2-3
R6 represents methyl, ethyl, benzyl, pyridylmethyl, or C1-C3 substituted with hydroxyl, C1-C3 alkoxyl, acetoxyl;
The preferable compounds of the present invention are:
The present invention also provides the processes for the preparation of compounds of formula 1A and 1B.
There are two different types of preparation methods according to their structure features.
Type 1, some of the compounds of formula 1A (both R4 and R5 are not H) and formula 1B may be prepared from 2A and 2B. The scheme is as follows
wherein R1, R2, R3, R4, R5, R6, R7, R8, r1, r2, r3, r4, m, n, p, q and t are as previously defined for formula 1A and 1B, but R4, R5 are not H.
This step was achieved by the existing cyclization method for pyrimidinone compounds. The reaction is usually carried out in the presence of a suitable base and a suitable solvent at temperatures at a range from 50 to 200° C. Preferred bases include metal alkoxides (e.g. potassium tertbutoxide, sodium ethoxide), alkaline earth metal or hydrides of alkali metal, amine (e.g. triethylamine), metal salts of ammonia, hydroxides (e.g. sodium hydroxide), carbonates and bicarbonates. Preferred solvents include alcohols (e.g. t-butanol, methanol, ethanol, isopropanol, glycol, 2-methoxyethanol), aromatic hydrocarbons (e.g. benzene, toluene, chlorobenzene), pyridine, halogenated hydrocarbon, acetonitrile, tetrahydrofuran, dioxane, dimethylsulfoxide, N,N-dimethylformamide, N-methylpyrrolidin-2-one.
Type 2, some of the compounds of formula 1A containing hydroxyl group at the ending chain may be prepared form the hydrolysis of their corresponding ester derivates, which is to say that when at least one of R4 and R5 is H (e.g. 1A-1), the hydroxyl derivates may be prepared through hydrolysis reaction. The scheme is as follows:
wherein R1, R2, R3, R4, R5, R6, R7, R8, R9, r1, r2, r3, r4, m, n, p, q and t are as previously defined for formulae 1A and 1B.
The compounds of formula (2A) and (2B) are usually prepared by reacting the compounds of formula (3A) and (3B) with the compounds of formula 4 respectively. The scheme is as follows
wherein R1, R2, R3, R4, R5, R6, R7, R8, r1, r2, r3, r4, m, n, p, q and t are as previously defined for formulae IA and IB, but R4, R5 are not H.
Method 1, the carboxyl group in the compounds of formula (3A) or (3B) was transformed into acyl chloride or mixed anhydride by using thionyl chloride, oxalyl chloride or ethyl chlorformate, then the mixture was reacted with the compounds of formula 4 to get the corresponding acid amide (2A) or (2B). The acidylation reaction is usually carried out in the presence of a suitable deacidification reagent and a common solvent. Preferred deacidification reagents include organic bases (preferred triethylamine, N,N-diisopropylethylamine, pyridine) and inorganic bases (preferred hydroxides, carbonates). Preferred solvents include diolefines (preferred petroleum, n-hexane, cyclohexane), halohydrocarbon (preferred dichlormethane, chloroform), ethers (preferred tetrahydrofuran, dioxane, ether), aromatic solvents (preferred toluene) and alcohols (preferred t-butanol, isopropanol).
Method 2, carboxylic acid was reacted with amine derivates directly to get the formula (2A) and (2B). The reaction is usually carried out in the anhydrous solvent with the presence of activating agent or dehydrating agent.
Preferred activating agents or dehydrating agents include DCC, EDCI, EEDQ, CDI, HOBt. Preferred solvents include halogenated hydrocarbons (e.g. dichlormethane, dichlormethane), ethers (e.g. tetrahydrofuran, dioxane, ether), aromatic hydrocarbons (e.g. benzene, toluene), polarity aprotic solvent (dimethylsulfoxide, N,N-dimethylformamide), or their mixture.
The compounds of formula 3A, 3B and 4 can be prepared according to literatures or supplied commercially.
In addition, the present invention provides the pharmaceutical compositions containing the compounds of formula 1A and/or 1B.
The above mentioned compositions contain one or more compounds of formula 1A and/or 1B (or their pharmaceutically acceptable salts, or their pharmaceutically acceptable solvates) and at least one kind of pharmaceutical excipient. The pharmaceutical excipient, which is used according the administration route and their functional properties, are normally fillers, diluents, adhesives, moistening agent, disintegrants, emulsifier, suspending agent, etc.
The compositions according to the invention can be administrated by any suitable route, for example by oral, parenteral (including intravenous, intramuscular, subcutaneous, and intracoronary), sublingual, buccal, rectal, transurethral, vaginal, nasal, inhalation or topical administration. Oral administration is the preferred route.
The compounds of formula 1A and/or 1B should preferably be presented in the above mentioned pharmaceutical compositions in a concentration of about 0.1 to 99.9%, preferably 1 to 99% by weight of the total mixture.
The present invention also provides processes for the preparation of the pharmaceutical compositions containing the compounds of formula IA and/or IB. The compounds of formulae IA and/or IB can be mixed with pharmaceutical excipient or excipients and made into dosage forms according the administration route in the conventional method. The dosage forms include tablets, capsules, granules, pills, solutions, solutions, emulsion, emulsions, membranes, creams, aerosols, injection and suppositories etc. Tablets and capsules are preferred.
Tablets and capsules can contain one or more compounds of formula of IA and/or IB in addition to one or more conventional excipients, such as (a) fillers, for example starches, sucrose, lactose, glucose, microcrystalline cellulose, and mannitol, (b) binders, for example carboxymethylcellulose, gelatine, alginates and polyvinylpyrrolidone, (c) humectants, for example glycerol, (d) disintegrating agents, for example agar-agar, ethyl cellulose, sodium starch glycolate and calcium carbonate (e) lubricants, for example magnesiumstearate, talc, and polyethylene glycols.
The dosages of the compounds of the invention are generally 1 to 500 mg per day, preferably 10 to 100 mg, taken once or several times. However, it may be necessary to properly deviate from the dosages mentioned. The optimal dosages, which may be determined by specialist with their professional knowledge, depend on the severity of the disease, the individual response towards the medicament, the characteristics of the formulation, and the administration routes.
Moreover, the invention provides the compounds of formulae IA and/or IB, or the pharmaceutically acceptable salt thereof, or the pharmaceutically acceptable solvate of either entity, or the pharmaceutical composition containing any of the foregoing, for use as a human medicament.
The invention further provides the use of the compounds of formulae IA and/or IB, or the pharmaceutically acceptable salt thereof, or the pharmaceutically acceptable solvate of either entity, for the manufacture of a human medicament for the curative or prophylactic treatment of a medical condition for which a cGMP PDE5 inhibitor is indicated.
Still further, the invention provides the use of the compounds of formulae IA and/or IB, or the pharmaceutically acceptable salt thereof, or the pharmaceutically acceptable solvate containing either entity, for the manufacture of a human medicament for the curative or prophylactic treatment of male erectile dysfunction, benign prostatic hyperplasia (BPH), female sexual dysfunction, premature labour, dysmenorrhoea, bladder outlet obstruction, incontinence, stable, unstable and variant (Prinzmetal) angina, hypertension, pulmonary hypertension, congestive heart failure, kidney failure, atherosclerosis, stroke, peripheral vascular disease, conditions of reduced blood vessel patency, inflammatory disease, bronchitis, chronic asthma, allergic asthma, allergic rhinitis, glaucoma or diseases characterized by disorders of gut motility (e.g. irritable bowel syndrome, IBS).
The following examples serve to explain the compounds in this invention and the methods for the intermediates, but without limiting it.
1H NMR spectra were determined on a Mercury 400 NMR spectrometer or Mercury 400 NMR spectrometer (Varian Company). The conventional abbreviation was as follows: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet; br, broad peak.
2-propoxy-5-[bis(2-acetoxyethyl)amidosulfonyl]benzoic acid (0.43 g, 1 mmol) was dissolved in CH2Cl2 (20 mL), Carbonyldiimidazole (CDI, 3 mmol) was added to the solution and stirred at room temperature for 0.5 hours, then 4-amino-3-propylpyrazolo-5-carboxamine (0.18 g, 1 mmol) was added and stirred another 1-6 h, the stopping point was detected by TLC. When the reaction was finished, the reaction mixture was washed with the ammonium chloride solution and brine, the CH2Cl2 layer was dried over anhydrous magnesium sulfate and the solvent was concentrated to dryness under reduced pressure, the resulting residue was recrystallized from alcohol to get white powder (0.51 g), yield 86%.
Potassium tert-butoxide (0.06 g, 0.55 mmol) and the product of step 1 (0.3 g, 0.5 mmol) were added to tert-butyl alcohol (15 ml) successively, and the mixture was heated to reflux for 30 minutes to produce a clear solution. The solution was refluxed for another 10 hours, then cooled to room temperature and water (20 ml) was added. The resulted solution was adjusted to neutral by adding 4% acetic acid. cooled to 5-10° C. and a white solid was precipitated. The white solid was collected by filtration, washed with cold water (3×10 ml) and dried. The solid was recrystallized from MeOH/EtOAc to afford the title compound (0.22 g), yield 76%. 1H NMR (CDCl3) δ: 10.83 (1H, s), 8.87 (1H, d), 7.90 (1H, dd), 7.14 (1H, d), 4.27 (3H, s), 4.25 (6H, m), 3.49 (4H, t), 2.93 (2H, t), 2.04 (2H, m), 2.03 (6H, s), 1.86 (2H, m), 1.17 (3H, t), 1.02 (3H, t).
To the solution alcohol (5 ml), water (10 ml) and potassium carbonate (0.1 g, 0.7 mmol), the compound of example 1 (0.12 g, 0.2 mmol) was added and the solution was heated to reflux, the stopping point was detected by TLC. When the reaction was finished, the PH value of the solution was adjusted to neutral by dilute hydrochloric acid and a white solid was precipitated, the solid was collected by filtration, washed with water and dried to get crude product. The crude product was recrystallized from dichloromethane and n-hexane to afford the title compound (0.06 g), yield 61%. 1H NMR (CDCl3) δ: 10.82 (1H, s), 8.84 (1H, d), 7.91 (1H, dd), 7.14 (1H, d), 4.26 (3H, s), 4.25 (2H, t), 3.88 (4H, t), 3.49 (2H, s), 3.38 (4H, t), 2.92 (2H, t), 2.02 (2H, m), 1.84 (2H, m), 1.17 (3H, t), 1.02 (3H, t).
The example 3˜120 was prepared from different substitute start materials following the procedure of example 1 and example 2 (unless otherwise noted, NMR spectra were determined in CDCl3 solution)
The active ingredient containing pyrazolopyrimidinone derivatives and the excipients are passed through a #80 mesh sieve, weigh out the appropriate amount of active ingredient and the excipients according the formulation. Granulate the powder mixture with 10% polyvinylpyrrolidone ethanol solution, and pass through a #16 mesh sieve to obtain suitable granules. After drying at 65° C., the granules were screened through a #14 sieve and blended with the magnesium stearate. Test the content of active ingredient in the granules, calculate the fill weight, and then fill the granules in capsules.
Pass the active ingredient containing pyrazolopyrimidinone derivatives, microcrystalline cellulose, lactose, sodium starch glycolate through #80 mesh sieve, mix well. Granulate the powder mixture with 8% starch paste, and pass through a #16 mesh sieve to obtain suitable granules. After drying, the granules were screened and blended with the magnesium stearate. Test the content of active ingredient in the granules, calculate the tablet weight, and then compress the tablets.
Charge the active ingredient containing pyrazolopyrimidinone derivatives, lactose, polyvinyl pyrrolidone, aerosol in a mixer and mix well. Blend the mixture with magnesium stearate and then compress into tablets.
The test was carried out based on the methods reported (International Journal of Impotence Research 2002, 14, 251 and The Journal of Urology 1992, 147, 1124). After fasted for 12 hours, 4 male SD rats were randomized into each group. After anesthetizing the rats with sodium pentobarbital (50 mg/kg, i.p.), the penile skin was incised and the prepuce was degloved to expose completely the corpora cavernosa (CC). A needle linked to an electrophysiology instrument was inserted into the CC on the right side in order to measure the intracavernous pressure (ICP). The right carotid artery was cannulated in a similar manner to the polyethylene tube in order to monitor the mean blood pressure (MBp) continuously. After exposing the lateral surface of the prostate via an incision in the midline inferior abdomen, a bipolar platinum microelectrode was placed on the cavernous nerve. Electric stimulation was performed at 2 Hz, for 60 s with a pulse duration of 5 ms and 3V using a stimulator. The compounds were administrated orally (5 mg/kg). The change of the ICP and MBp were monitored continuously before and after the administration. The effect of the compounds on the erection induced by electric stimulation was evaluated by the ratio of ICP to MBp. The parameter (ICP/MBp) was used to estimate the influence of the compounds to the rat corpora cavernosa. We tested the effect of sildenafil and some of the example compounds on the rat corpora cavernosa according to the aforesaid method. The statistical significance of the differences between groups was calculated using Duncan's multiple comparison. The results are shown below:
As shown in the results, the test compounds have the same pharmacodynamic effect as sildenafil. After administration, the ICP of the rats CC, and the ICP/BP increase significantly, the penile erections of the rats are enhanced, thus, the compounds can be administrated orally for the treatment of erectile dysfunction.
The Enzymes used in the inhibitory activity test were isolated from different kinds of tissues after appropriate treatment by FPLC using a method similar to Thrombosis Res. 1991, 62, 31 and J. Biol. Chem. 1997, 272, 2714. The PDE5 and PDE3 were isolated form human platelets, while the PDE6 was isolated form bovine retinas. The enzyme inhibitory activity test conducted immediately after the enzymes had been isolated, using a scintillation proximity assay for the direct detection of AMP/GMP by the TRKQ7100 and TRKQ7090 kit. In summary, the effect of PDE inhibitors was investigated by assaying a fixed amount of enzyme in the presence of varying inhibitor concentrations and low substrate. The final assay volume was made up to 100 μl with 10 μl assay buffer (50 mM Tris/HCl PH 7.5, 8.3 mM MgCl2, 1.7 mM EGTA), and water. Reactions were initiated with enzyme, incubate for 30 minutes at 30° C. and terminated with 50 μl yttrium silicate SPA beads suspension containing zinc sulphate. Shook for 20 minutes and settled for 30 minutes in the dark, then counted on a BECKMAN LS6500 MULTI-PURPOSE SCINTILLATION COUNTER. The IC50 value for the compounds according the present invention was calculated according the counts.
According to the above-mentioned method, the inhibitory activities of some compounds of formula IA and IB according to the invention against PDE5 from human platelets were determined. The result is given in the following table:
The IC50 values for the compounds in the previous table show that most of the compounds according to the invention have a stronger potency against PDE5 than sildenafil, therefore, the dosage for oral administration is less than sildenafil and the chance to induce side effects is relatively little.
Considering the compounds according the invention may have inhibitory activity against PDE6 distributed in retina, and then lead to visual disorders, we tested the inhibitory activities of some of the compounds of formulae IA and IB according the invention against PDE6 from bovine retina. The result is given in the following table:
The invention uses the value of IC50 PDE6/IC50 PDE5 to estimate the selectivity of PDE5 versus PDE6. The results show that most of the example compounds have a better selectivity than sildenafil, thus, the chance of visual disorder induced by the compounds according to the invention is less than sildenafil.
PDE3 is a PDE isozyme distributed mainly in heart, so the inhibiting of PDE3 may lead to side effects associated with heart. Accordingly, the inhibitory activities of some example compounds according to the invention against PDE3 were determined. The result is given in the following table:
As shown in the results,
As shown in the table, since the 50% inhibition concentration (IC50) for PDE 3 is much higher than for PDE5 in some of the compounds of the pyrazolopyrimidinone derivatives, the probability of side effects in cardiovascular system caused by the compounds of the present invention is very little.
In this test male KM mouse weighting 18-22 g were used, and 10 or 11 mouse were assigned randomly to each group. The compounds of examples 23, 33, 35, 37, 41, 54, 62, 63, 89, 92, 93, 95, 96, 97, 99, 103, 104, 110, 111, 112, 118 and sildenafil were suspended in 0.5% sodium carboxymethylcellulose respectively, and administered orally with single dose of 3 g/kg. The animals were fasted for 12 hours before the administration. After the administration, the animals were observed for clinical signs of toxicity or mortality. The results were shown in the following table:
There were no significant clinical symptoms, weight changes and mortalities during the test. The results of autopsy in dead animals show that no abnormal signals such as bleeding of the internal organs were found. The results show that the toxicities of most of the compounds according to the present invention to mouse are significantly lower than sildenafil.
| Number | Date | Country | Kind |
|---|---|---|---|
| 200510110485.0 | Nov 2005 | CN | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CN2006/003094 | 11/16/2006 | WO | 00 | 7/29/2008 |
