Addressing phototoxicity observed in a novel series of biaryl derivatives: discovery of potent, selective and orally active phosphodiesterase 10A inhibitor ASP9436.

We synthesized several biaryl derivatives as PDE10A inhibitors to prevent phototoxicity of 2-[4-({[1-methyl-4-(pyridin-4-yl)-1H-pyrazol-3-yl]oxy}methyl)phenyl]quinoline (1) and found that the energy difference between the energy-minimized conformation and the coplanar conformation of the biaryl moiety helped facilitate prediction of the phototoxic potential of biaryl compounds. Replacement of the quinoline ring of 1 with N-methyl benzimidazole increased this energy difference and prevented phototoxicity in the 3T3 NRU test. Further optimization identified 1-methyl-5-(1-methyl-3-{[4-(1-methyl-1H-benzimidazol-4-yl)phenoxy]methyl}-1H-pyrazol-4-yl)pyridin-2(1H)-one (38b). Compound 38b exhibited good selectivity against other PDEs, and oral administration of 38b improved visual-recognition memory deficit in mice at doses of 0.001 and 0.003mg/kg in the novel object recognition test. ASP9436 (sesquiphosphate of 38b) may therefore be used for the treatment of schizophrenia with a low risk of phototoxicity.

Synthesis, SAR study, and biological evaluation of novel quinoline derivatives as phosphodiesterase 10A inhibitors with reduced CYP3A4 inhibition.

A novel class of phosphodiesterase 10A inhibitors with potent PDE10A inhibitory activity and reduced CYP3A4 inhibition was designed and synthesized starting from 2-[4-({[1-methyl-4-(pyridin-4-yl)-1H-pyrazol-3-yl]oxy}methyl)phenyl]quinoline (1). Replacement of pyridine ring of 1 with N-methyl pyridone ring drastically improved CYP3A4 inhibition, and further optimization of these quinoline analogues identified 1-methyl-5-(1-methyl-3-{[4-(quinolin-2-yl)phenoxy]methyl}-1H-pyrazol-4-yl)pyridin-2(1H)-one (42b), which showed potent PDE10A inhibitory activity and a good CYP3A4 inhibition profile. A PET study with (11)C-labeled 42b indicated that 42b exhibited good brain penetration and specifically accumulated in the rodent striatum. Further, oral administration of 42b dose-dependently attenuated phencyclidine-induced hyperlocomotion in mice with an ED50 value of 2.0mg/kg and improved visual-recognition memory impairment at 0.1 and 0.3mg/kg in mice novel object recognition test.

Discovery of highly potent and selective biphenylacylsulfonamide-based beta3-adrenergic receptor agonists and molecular modeling based on the solved X-ray structure of the beta2-adrenergic receptor: part 6.

As an extension of research, we have investigated modification of left-hand side (LHS) of biphenyl analogues containing an acylsulfonamide moiety in the development of potent and selective human beta(3)-adrenergic receptor (AR) agonists. Result of structure-activity relationships (SAR) and cassette-dosing evaluation in dogs showed that the hydroxynorephedrine analogue 16 had an excellent balance of in vitro and in vivo potency with pharmacokinetic profiles. In addition, to facilitate structure-based drug design (SBDD), we also have performed a docking study of biphenyl analogues based on the X-ray structure of the beta(2)-adrenergic receptor.

Discovery of highly potent and selective biphenylacylsulfonamide-based beta3-adrenergic receptor agonists and evaluation of physical properties as potential overactive bladder therapies: part 5.

As an extension of research conducted on beta(3)-adrenergic receptor agonists as potential drugs for treating overactive bladder (OAB), novel series containing an acylsulfonamide moiety instead of the carboxylic acid moiety were evaluated. These compounds have been identified as potent and selective human beta(3)-AR agonists with improved oral bioavailability compared to the previous series. Results of structure-activity relationship (SAR) studies and cassette dosing evaluation in dogs showed several analogues (namely, 6h, 6j, 6o, 7e, and 9e) to have an excellent balance of in vitro potency and selectivity, pharmacokinetic (PK) profile, and an in vivo OAB model. Here we examined the relaxation response in dog detrusor muscle strips to a KCl induced tonic concentration. Results showed that the potency of in vitro relaxation response was not mirrored in the potency of the cAMP accumulation in CHO cell lines. Surprisingly, the EC(50) values of 6e and 7e found to induce relaxation of isolated bladder strips were over 50-fold higher than the cAMP accumulation in cell line. In general, increased lipophilicity led to decreased potency for the bladder relaxation compared with cAMP accumulation in CHO cell lines, indicating that lipophilicity is crucial for OAB drug candidates to improve beta(3) activity.

Discovery of novel series of benzoic acid derivatives containing biphenyl ether moiety as potent and selective human beta(3)-adrenergic receptor agonists: Part IV.

Identification and SAR study of novel series of beta(3)-AR agonists with benzoic acid are described. Conversion of ether linkage position of phenoxybenzoic acid derivative 2b led to compound 7b with moderate beta(3)-AR activity. Further modification in right, center and left parts of compound 7b was investigated to improve the beta(3)-AR potency and selectivity. Compounds 7g and 7k, with the bulky aliphatic-substituted group at 2-position of benzoic acid moiety, were identified as potent and selective beta(3)-AR agonists. In addition, in vivo efficacy of compounds 7g and 7k was exhibited on dog OAB model.

Discovery of a novel series of benzoic acid derivatives as potent and selective human beta3 adrenergic receptor agonists with good oral bioavailability. 3. Phenylethanolaminotetraline (PEAT) skeleton containing biphenyl or biphenyl ether moiety.

We designed a series of benzoic acid derivatives containing the biphenyl ether or biphenyl template on the RHS and a phenylethanolaminotetraline (PEAT) skeleton, which was prepared by highly stereoselective synthesis, to generate two structurally different lead compounds ( 10c, 10m) with a good balance of potency, selectivity, and pharmacokinetic profile. Further optimization of the two lead compounds to improve potency led to several potential candidates (i.e., 11f, 11l, 11o, 12b). In particular, biphenyl analogue 12b exhibited an excellent balance of high potency (EC50 = 0.38 nM) for beta3, high selectivity over beta1 and beta2, and good pharmacokinetic properties in rats, dogs, and monkeys.

Discovery of a novel series of biphenyl benzoic acid derivatives as highly potent and selective human beta3 adrenergic receptor agonists with good oral bioavailability. Part II.

The left-hand side (LHS) and central part of our first generation biphenyl (FGB) series was modified to improve in vitro and in vivo beta3-AR potency without loss of oral bioavailability. First, in this study, we focused our efforts on replacement of the 3-chlorophenyl moiety in the LHS of FGB analogues with 3-pyridyl ring analogues to adjust the lipophilicity. Second, we investigated the replacement of the central part of this series and discovered that introduction of a methyl group into the alpha-position of the phenethylamine moiety greatly enhanced potency keeping good oral availability. Finally, the replacement of the two carbon linker of the central part with an ethoxy-based linker provided improved potency and PK profiles. As a result of these studies, several analogues (i.e., 9h, 9k, 9l, 10g, 10m, 10p, 10r, 11b, and 11l) were identified that displayed an excellent balance of very higher human beta3-AR potency compared to the FGB compounds, high selectivity, and good pharmacokinetic profiles. Furthermore, these several compounds showed high in vivo efficacy in an overactive bladder (OAB) model. These findings suggest that our selected second generation biphenyl (SGB) series compounds may be attractive new successful therapeutic candidates for the treatment of OAB.

Discovery of a novel series of biphenyl benzoic acid derivatives as potent and selective human beta3-adrenergic receptor agonists with good oral bioavailability. Part I.

A novel class of biphenyl analogues containing a benzoic acid moiety based on lead compound 8i have been identified as potent and selective human beta 3 adrenergic receptor (beta 3-AR) agonists with good oral bioavailability and long plasma half-life. After further substituent effects were investigated at the terminal phenyl ring of lead compound 8i, we have discovered that more lipophilic substitution at the R position improved potency and selectivity. As a result of these studies, 10a and 10e were identified as the leading candidates with the best balance of potency, selectivity, and pharmacokinetic profiles. In addition, compounds 10a and 10e were evaluated to be efficacious for a carbachol-induced increase of intravesical pressure, such as an overactive bladder model in anesthetized dogs. This represents the first demonstrated result dealing with beta 3-AR agonists.

Rational design of conformationally restricted quinazolinone inhibitors of poly(ADP-ribose)polymerase.

A successful design of conformationally restricted novel quinazolinone derivatives linked via a cyclopentene moiety as potent poly(ADP-ribose)polymerase-1 (PARP-1) inhibitors has been developed. One selected member of the new series, 8-chloro-2-[(3S)-3-(4-phenylpiperidin-1-yl)cyclopent-1-en-1-yl]quinazolin-4(3H)-one (S-16d), was found to be highly potent with IC(50)=8.7 nM and good brain penetration.

Replacing the cyclohexene-linker of FR181157 leading to novel IP receptor agonists: orally active prostacyclin mimetics. Part 6.

The synthesis and biological activity of novel derivatives of our previously reported IP receptor agonist FR181157 is described. SAR studies to replace the cyclohexene-linker of FR181157 led to the discovery of compound 1i (FR207845) as a potent non-prostanoid PGI2 mimetic with good oral bioavailability.

Metabolism investigation leading to novel drug design 2: orally active prostacyclin mimetics. Part 5.

A metabolism study of FK788 (2) led to the discovery of new diphenylcarbamoyl derivatives as prostacyclin mimetics without the PG skeleton. We designed and evaluated PGI(2) mimetics based on blocking the main metabolic pathway of FK788. The new compound 7c was found to be equipotent to FK788 towards PGI(2) agonist activity and metabolically more stable than FK788.

Discovery of potent and selective PARP-1 and PARP-2 inhibitors: SBDD analysis via a combination of X-ray structural study and homology modeling.

We disclose herein our efforts aimed at discovery of selective PARP-1 and PARP-2 inhibitors. We have recently discovered several novel classes of quinazolinones, quinazolidinones, and quinoxalines as potent PARP-1 inhibitors, which may represent attractive therapeutic candidates. In PARP enzyme assays using recombinant PARP-1 and PARP-2, the quinazolinone derivatives displayed relatively high selectivity for PARP-1 and quinoxaline derivatives showed superior selectivity for PARP-2, and the quinazolidinone derivatives did not have selectivity for PARP-1/2. Structure-based drug design analysis via a combination of X-ray structural study utilizing the complexes of inhibitors and human PARP-1 catalytic domain, and homology modeling using murine PARP-2 suggested distinct interactions of inhibitors with PARP-1 and PARP-2. These findings provide a new structural framework for the design of selective inhibitors for PARP-1 and PARP-2.

4-Phenyl-1,2,3,6-tetrahydropyridine, an excellent fragment to improve the potency of PARP-1 inhibitors.

We have shown that a 4-phenyl-1,2,3,6-tetrahydropyridine fragment plays an important role in improving inhibitory potency against poly(ADP-ribose) polymerase-1 (PARP-1). Various benzamide analogues linked with this fragment via alkyl spacers have been prepared and evaluated. As a result, some of them have been found to be highly potent PARP-1 inhibitors.

Metabolism investigation leading to novel drug design: orally active prostacyclin mimetics. Part 4.

A metabolism study of FR181157 (1) led to the discovery of new oxazole derivatives as active metabolites. The metabolite 6 with an epoxy ring exhibited high anti-aggregative potency with an IC(50) of 5.8 nM and potent binding affinity for the human recombinant IP receptor with a K(i) value of 6.1 nM and selectivity for human IP receptor over all other members of the human prostanoid receptor family.

Discovery of new diphenyloxazole derivatives containing a pyrrolidine ring: orally active prostacyclin mimetics. Part 2.

Synthetic and biological evaluation of novel diphenyloxazole derivatives containing a pyrrolidine ring, as a prostacyclin mimetic without the PG skeleton, are described. Asymmetric reduction of a ketone using a chiral Ru complex and reductive amination by NaBH(4) produces four isomers of the tetrahydronaphthalene ring and the pyrrolidine ring with high stereoselectivity. FR193262 (4), (R,R)-diphenyloxazolyl pyrrolidine derivative, displays high potency and agonist efficacy at the IP receptor and has good bioavailability in rats and dogs.

Discovery of diphenylcarbamate derivatives as highly potent and selective IP receptor agonists: orally active prostacyclin mimetics. Part 3.

The new classes of diphenylcarbamate derivatives with a tetrahydronaphthalene skeleton as highly potent and selective IP agonists have been discovered. The optimized diphenylcarbamate type compound FK-788: (R)-4 exhibited potent antiaggregative potency with an IC50 of 18 nM and high binding affinity for the human recombinant IP receptor with K(i) values of 20 nM and selectivity for human IP over all other members of the human prostanoid receptor family. Compound (R)-4 was shown to exhibit good pharmacokinetic properties in rats and dogs, and also good bioavailability in healthy volunteers.

Discovery of diphenyloxazole and Ndelta-Z-ornithine derivatives as highly potent and selective human prostaglandin EP(4) receptor antagonists.

Two novel classes of diphenyloxazole and Ndelta-Z-ornithine derivatives as highly potent and selective EP(4) antagonists have been discovered. The optimized diphenyloxzole 8 and Ndelta-Z-ornithine 11 effectively competed with [(3)H]PGE(2) binding to human recombinant EP(4), with K(i) values of 0.30 nM and 0.91 nM, respectively, and were selective for all members of the human prostanoid receptor family. 8 was shown to exhibit good pharmacokinetic properties in rats and dogs and potent inhibitory activity toward in vitro PGE(2)-promoted IgE synthesis.

Discovery of quinazolinone and quinoxaline derivatives as potent and selective poly(ADP-ribose) polymerase-1/2 inhibitors.

Two classes of quinazolinone derivatives and quinoxaline derivatives were identified as potent and selective poly(ADP-ribose) polymerase-1 and 2 (PARP-1) and (PARP-2) inhibitors, respectively. In PARP enzyme assays using recombinant PARP-1 and PARP-2, quinazolinone derivatives displayed relatively high selectivity for PARP-1 and quinoxaline derivatives showed superior selectivity for PARP-2. SBDD analysis via a combination of X-ray structural study and homology modeling suggested distinct interactions of inhibitors with PARP-1 and PARP-2. These findings provide a new structural framework for the design of selective inhibitors for PARP-1 and PARP-2.

Rational approaches to discovery of orally active and brain-penetrable quinazolinone inhibitors of poly(ADP-ribose)polymerase.

A novel class of quinazolinone derivatives as potent poly(ADP-ribose)polymerase-1 (PARP-1) inhibitors has been discovered. Key to success was application of a rational discovery strategy involving structure-based design, combinatorial chemistry, and classical SAR for improvement of potency and bioavailability. The new inhibitors were shown to bind to the nicotinamide-ribose binding site (NI site) and the adenosine-ribose binding site (AD site) of NAD+.

A novel and potent poly(ADP-ribose) polymerase-1 inhibitor, FR247304 (5-chloro-2-[3-(4-phenyl-3,6-dihydro-1(2H)-pyridinyl)propyl]-4(3H)-quinazolinone), attenuates neuronal damage in in vitro and in vivo models of cerebral ischemia.

The activation of poly(ADP-ribose) polymerase-1 (PARP-1) after exposure to nitric oxide or oxygen-free radicals can lead to cell injury via severe, irreversible depletion of NAD. Genetic deletion or pharmacological inhibition of PARP-1 attenuates brain injury after focal ischemia and neurotoxicity in several neurodegenerative models in animals. FR247304 (5-chloro-2-[3-(4-phenyl-3,6-dihydro-1(2H)-pyridinyl)propyl]-4(3H)-quinazolinone) is a novel PARP-1 inhibitor that has recently been identified through structure-based drug design. In an enzyme kinetic analysis, FR247304 exhibits potent and competitive inhibition of PARP-1 activity, with a K(i) value of 35 nM. Here, we show that prevention of PARP activation by FR247304 treatment protects against both reactive oxygen species-induced PC12 cell injury in vitro and ischemic brain injury in vivo. In cell death model, treatment with FR247304 (10(-8)-10(-5) M) significantly reduced NAD depletion by PARP-1 inhibition and attenuated cell death after hydrogen peroxide (100 microM) exposure. After 90 min of middle cerebral artery occlusion in rats, poly(ADP-ribosy)lation and NAD depletion were markedly increased in the cortex and striatum from 1 h after reperfusion. The increased poly(ADP-ribose) immunoreactivity and NAD depletion were attenuated by FR247304 (32 mg/kg i.p.) treatment, and FR247304 significantly decreased ischemic brain damage measured at 24 h after reperfusion. Whereas other PARP inhibitors such as 3-aminobenzamide and PJ34 [N-(6-oxo-5,6-dihydro-phenanthridin-2-yl)-N,N-dimethylactamide] showed similar neuroprotective actions, they were less potent in in vitro assays and less efficacious in an in vivo model compared with FR247304. These results indicate that the novel PARP-1 inhibitor FR247304 exerts its neuroprotective efficacy in in vitro and in vivo experimental models of cerebral ischemia via potent PARP-1 inhibition and also suggest that FR247304 or its derivatives could be attractive therapeutic candidates for stroke and neurodegenerative disease.