Identification, Synthesis, and Characterization of a Major Circulating Human Metabolite of TRPV4 Antagonist GSK2798745

GSK2798745, an antagonist of the transient receptor potential vanilloid 4 (TRPV4) ion channel, was recently investigated in clinical trials for the treatment of cardiac and respiratory diseases. Human plasma and urine samples collected from healthy volunteers following oral administration were analyzed to identify circulating and excreted metabolites of the parent drug. One major circulating metabolite (1) was found in pooled human plasma samples, accounting for approximately half of the observed drug-related material. Isolation of metabolite 1 from urine samples followed by MS and NMR studies led to a putative structural assignment of 1 where hydroxylation of GSK2798745 occurred on the central ring, producing a penta-substituted cyclohexane structure containing three stereocenters. Two unique chemical syntheses of the proposed structure were developed to confirm the identity of metabolite 1 and provide access to gram quantities for biological characterization.

Design and Optimization of an Acyclic Amine Series of TRPV4 Antagonists by Electronic Modulation of Hydrogen Bond Interactions

Investigation of TRPV4 as a potential target for the treatment of pulmonary edema associated with heart failure generated a novel series of acyclic amine inhibitors displaying exceptional potency and PK properties. The series arose through a scaffold hopping approach, which relied on use of an internal H-bond to replace a saturated heterocyclic ring. Optimization of the lead through investigation of both aryl regions revealed approaches to increase potency through substituents believed to enhance separate intramolecular and intermolecular H-bond interactions. A proposed internal H-bond between the amine and neighboring benzenesulfonamide was stabilized by electronically modulating the benzenesulfonamide. In the aryl ether moiety, substituents para to the nitrile demonstrated an electronic effect on TRPV4 recognition. Finally, the acyclic amines inactivated CYP3A4 and this liability was addressed by modifications that sterically preclude formation of a putative metabolic intermediate complex to deliver advanced TRPV4 antagonists as leads for discovery of novel medicines.

Discovery of GSK3527497: A Candidate for the Inhibition of Transient Receptor Potential Vanilloid-4 (TRPV4)

GSK3527497, a preclinical candidate for the inhibition of TRPV4, was identified starting from the previously reported pyrrolidine sulfonamide TRPV4 inhibitors 1 and 2. Optimization of projected human dose was accomplished by specifically focusing on in vivo pharmacokinetic parameters CL_u, Vdss_u, and MRT. We highlight the use of conformational changes as a novel approach to modulate Vdss_u and present results that suggest that molecular-shape-dependent binding to tissue components governs Vdss_u in addition to bulk physicochemical properties. Optimization of CL_u within the series was guided by in vitro metabolite identification, and the poor FaSSIF solubility imparted by the crystalline properties of the pyrrolidine diol scaffold was improved by the introduction of a charged moiety to enable excellent exposure from high crystalline doses. GSK3527497 is a preclinical candidate suitable for oral and iv administration that is projected to inhibit TRPV4 effectively in patients from a low daily clinical dose.

Isoform-selective phosphoinositide 3-kinase inhibition ameliorates a broad range of fragile X syndrome-associated deficits in a mouse model

Defects in the phosphoinositide 3-kinase (PI3K) pathway are shared characteristics in several brain disorders, including the inherited intellectual disability and autism spectrum disorder, fragile X syndrome (FXS). PI3K signaling therefore could serve as a therapeutic target for FXS and other brain disorders. However, broad inhibition of such a central signal transduction pathway involved in essential cellular functions may produce deleterious side effects. Pharmacological strategies that selectively correct the overactive components of the PI3K pathway while leaving other parts of the pathway intact may overcome these challenges. Here, we provide the first evidence that disease mechanism-based PI3K isoform-specific inhibition may be a viable treatment option for FXS. FXS is caused by loss of the fragile X mental retardation protein (FMRP), which translationally represses specific messenger RNAs, including the PI3K catalytic isoform p110β. FMRP deficiency increases p110β protein levels and activity in FXS mouse models and in cells from subjects with FXS. Here, we show that a novel, brain-permeable p110β-specific inhibitor, GSK2702926A, ameliorates FXS-associated phenotypes on molecular, cellular, behavioral, and cognitive levels in two different FMRP-deficient mouse models. Rescued phenotypes included increased PI3K downstream signaling, protein synthesis rates, and dendritic spine density, as well as impaired social interaction and higher-order cognition. Several p110β-selective inhibitors, for example, a molecule from the same chemotype as GSK2702926A, are currently being evaluated in clinical trials to treat cancer. Our results suggest that repurposing p110β inhibitors to treat cognitive and behavioral defects may be a promising disease-modifying strategy for FXS and other brain disorders.

[3a,4]-Dihydropyrazolo[1,5a]pyrimidines: Novel, Potent, and Selective Phosphatidylinositol-3-kinase β Inhibitors

A series of novel [3a,4]dihydropyrazolo[1,5a]pyrimidines were identified, which were highly potent and selective inhibitors of PI3Kβ. The template afforded the opportunity to develop novel SAR for both the hinge-binding (R3) and back-pocket (R4) substitutents. While cellular potency was relatively modest due to high protein binding, the series displayed low clearance in rat, mouse, and monkey.

Rational Design, Synthesis, and SAR of a Novel Thiazolopyrimidinone Series of Selective PI3K-beta Inhibitors

A novel thiazolopyrimidinone series of PI3K-beta selective inhibitors has been identified. This chemotype has provided an excellent tool compound, 18, that showed potent growth inhibition in the PTEN-deficient breast cancer cell line MDA-MB-468 under anchorage-independent conditions, and it also demonstrated pharmacodynamic effects and efficacy in a PTEN-deficient prostate cancer PC-3 xenograft mouse model.

Abstract 2913: Identification of GSK2636771, a potent and selective, orally bioavailable inhibitor of phosphatidylinositol 3-kinase-beta (PI3Kα) for the treatment of PTEN deficient tumors

Dysregulation of the PI3K pathway is one of the most common causes of tumorigenesis. Aberrant pathway activation occurs frequently through loss of the tumor suppressor protein, PTEN. Loss of PTEN protein has been observed in approximately 40% of glioblastoma, 50% of prostate, 57% of endometrial cancers, as well as in a number of other tumor types, including melanoma and breast cancers. Preclinical studies have shown that selective depletion of the PI3Kα isoform inhibits tumorigenesis and reduces downstream PI3K signaling in PTEN deficient tumors. This data presents an opportunity for a clear patient selection strategy based on the presence or absence of PTEN. During an extensive knowledge-based lead identification and optimization effort starting from the reported PI3K beta-selective compound TGX-221, we identified several unique series of potent and selective inhibitors with less than desirable pharmacokinetic properties. Through a combination of structure-based and knowledge-based design, we ultimately identified substituted benzimidazole GSK2636771 as a potent, orally bioavailable, PI3K beta-selective inhibitor. The evolution of our selective inhibitors, leading to the discovery, design, and optimization of GSK2636771 and related analogs, will be described.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2913. doi:1538-7445.AM2012-2913

Synthesis and structure-activity relationships of 1,2,4-triazolo[1,5-a]pyrimidin-7(3H)-ones as novel series of potent β isoform selective phosphatidylinositol 3-kinase inhibitors

A series of 1,2,4-triazolo[1,5-a]pyrimidin-7(3H)-ones with excellent enzyme inhibition, improved isoform selectivity, and excellent inhibition of downstream phosphorylation of AKT has been identified. Several compounds in the series demonstrated potent (∼ 0.100 μM IC(50)) growth inhibition in a PTEN deficient cancer cell line.

Novel N-Substituted Benzimidazolones as Potent, Selective, CNS-Penetrant, and Orally Active M1 mAChR Agonists

Virtual screening of the corporate compound collection yielded compound 1 as a subtype selective muscarinic M1 receptor agonist hit. Initial optimization of the N-capping group of the central piperidine ring resulted in compounds 2 and 3 with significantly improved potency and selectivity. Subsequent optimization of substituents on the phenyl ring of the benzimidazolone moiety led to the discovery of novel muscarinic M1 receptor agonists 4 and 5 with excellent potency, general and subtype selectivity, and pharmacokinetic (PK) properties including good central nervous system (CNS) penetration and oral bioavailability. Compound 5 showed robust in vivo activities in animal models of cognition enhancement. The combination of high potency, excellent selectivity, and good PK properties makes compounds 4 and 5 valuable tool compounds for investigating and validating potential therapeutic benefits resulting from selective M1 activation.

Discovery of 3-aryl-4-isoxazolecarboxamides as TGR5 receptor agonists

A series of 3-aryl-4-isoxazolecarboxamides identified from a high-throughput screening campaign as novel, potent small molecule agonists of the human TGR5 G-protein coupled receptor is described. Subsequent optimization resulted in the rapid identification of potent exemplars 6 and 7 which demonstrated improved GLP-1 secretion in vivo via an intracolonic dose coadministered with glucose challenge in a canine model. These novel TGR5 receptor agonists are potentially useful therapeutics for metabolic disorders such as type II diabetes and its associated complications.

M3 muscarinic acetylcholine receptor antagonists: SAR and optimization of bi-aryl amines

Exploration of multiple regions of a bi-aryl amine template led to the identification of highly potent M(3) muscarinic acetylcholine receptor antagonists such as 14 (pA(2)=11.0) possessing good sub-type selectivity for M(3) over M(2). The structure-activity relationships (SAR) and optimization of the bi-aryl amine series are described.

Camphor sulfonamide derivatives as novel, potent and selective CXCR3 antagonists

A series of N-arylpiperazine camphor sulfonamides was discovered as novel CXCR3 antagonists. The synthesis, structure-activity relationships, and optimization of the initial hit that resulted in the identification of potent and selective CXCR3 antagonists are described.

Muscarinic acetylcholine receptor antagonists: SAR and optimization of tyrosine ureas

SAR exploration of multiple regions of a tyrosine urea template led to the identification of very potent muscarinic acetylcholine receptor antagonists such as 10b with good subtype selectivity for M(3) over M(1). The structure-activity relationships (SAR) and optimization of the tyrosine urea series are described.

Facile synthesis of 6-aryl 5-N-substituted pyridazinones: microwave-assisted Suzuki-Miyaura cross coupling of 6-chloropyridazinones

A facile synthesis of 5-dialkylamino-6-aryl-(2H)-pyridazin-3-one from 5,6-dichloropyridazinone was carried out by using a palladium-catalyzed Suzuki-Miyaura cross coupling of 6-chloro-5-dialkylaminopyridazinone 1 with various arylboronic acids (3 equiv) as the key transformation. The Suzuki-Miyaura cross-coupling reaction proceeded smoothly under microwave irradiation at 135-140 degrees C for 30 min with 5 mol % of Pd catalyst in moderate to good isolated yields. The use of a CombiPhos Pd6 mixture catalyst system and a single Pd-SPhos catalyst system was evaluated.

Oxazolidinones as novel human CCR8 antagonists

High-throughput screening of the corporate compound collection led to the discovery of a novel series of N-substituted-5-aryl-oxazolidinones as potent human CCR8 antagonists. The synthesis, structure-activity relationships, and optimization of the series that led to the identification of SB-649701 (1a), are described.

Synthesis and SAR of 1,3-disubstituted cyclohexylmethyl urea and amide derivatives as non-peptidic motilin receptor antagonists

A series of 1,3-disubstituted cyclohexylmethyl urea and amide derivatives were synthesized as motilin receptor antagonists. Starting from known motilin antagonists, 1a and 1b, the cyclopentene scaffold was replaced and the four recognition elements optimized to arrive at a potent novel series.

An efficient, asymmetric solid-phase synthesis of benzothiadiazine-substituted tetramic acids: potent inhibitors of the hepatitis C virus RNA-dependent RNA polymerase

An efficient, asymmetric solid-phase synthesis of benzothiadiazine-substituted tetramic acids is reported. Starting from commercially available chiral Fmoc-protected alpha-amino acids loaded onto Wang resin, Fmoc removal, reductive amination followed by amide bond formation, and base-catalyzed cyclization with simultaneous cleavage from the resin provided the desired products. Compounds described are potent inhibitors of the hepatitis C virus RNA-dependent RNA polymerase.

Aminoalkoxybenzyl pyrrolidines as novel human urotensin-II receptor antagonists

High throughput screening of the corporate compound collection led to the discovery of a novel series of substituted aminoalkoxybenzyl pyrrolidines as human urotensin-II receptor antagonists. The synthesis, initial structure-activity relationships, and optimization of the initial hit that led to the identification of a truncated sub-series, represented by SB-436811 (1a), are described.

Discovery of a dihydropyrimidine series of molecules that selectively mimic the biological actions of calcitonin

The use of a multiplex mimetic assay led us to identify 1,4-dihydropyrimidines with potent and selective calcitonin receptor mimetic activity. Subsequent modification of the dihydropyrimidine scaffold led to a series of molecules that were efficacious in a neonatal mouse calvaria in vitro model. Dihydropyrimidine 5h, in particular, was identified as a calcitonin mimetic (EC(50)=6 microM), active in-vivo in the Weanling rat model when administered subcutaneously.

2,3-Diaryl-5-anilino[1,2,4]thiadiazoles as melanocortin MC4 receptor agonists and their effects on feeding behavior in rats

The melanocortin-4 receptor (MC4) modulates physiological functions such as feeding behavior, nerve regeneration, and drug addiction. Using a high throughput screen based on (125)I-NDP-MSH binding to the human MC4 receptor, we discovered 2,3-diaryl-5-anilino[1,2,4]thiadiazoles 3 as potent and selective MC4 receptor agonists. Through SAR development on the three attached aryl rings, we improved the binding affinity from 174 nM to 4.4 nM IC(50). When delivered intraperitoneally, compounds 3a, 3b, and 3c induced significant inhibition of food intake in a fasting-induced feeding model in rats. When delivered orally, these compounds lost activity, mainly due to rapid metabolism to inactive imidoylthiourea reduction products.

Synthesis and structure-activity relationship of novel pyridyl ethers for the nicotinic acetylcholine receptor

The preparation of novel pyridyl ethers as ligands for the nicotinic acetylcholine receptor (nAChR) is described. Variations of the ring size of the azacycle and substitution on the pyridine had dramatic effects on receptor binding affinity with IC50s at the alpha4beta2 nAChR ranging from 22 to >10,000 nM. The most potent molecule was (R)-2-chloro-3-(4-cyanophenyl)-5-((3-pyrrolidinyl)oxy)pyridine 27f with an IC50 of 22 nM.

The solid-phase synthesis of novel 14-membered macrocycles for high throughput screening

A simple and efficient synthesis of novel 14-membered macrocycles from a resin-bound orthogonally protected lysine residue is described. Reductive alkylation of the lysine alpha-nitrogen introduces the first diversity element. Acylation of the resultant secondary amine with an Fmoc-amino acid introduces the second diversity element providing a resin-bound protected di-peptide precursor. Removal of the Fmoc-group is followed by acylation with a succinic anhydride to introduce the final diversity elements. Removal of the methyltrityl-group from the amino group followed by macrocyclization provides the desired macrocycles, after TFA cleavage, in excellent yield and purity.

Solid-Phase Synthesis of 3,4,5-Substituted 1,5-Benzodiazepin-2-ones

The preparation of 3,4,5-substituted 8-carboxamido-1,5-benzodiazepin-2-ones using a solid-phase synthetic method is described. 4-Fluoro-3-nitrobenzoic acid is tethered to a solid support via the acid group. Aromatic substitution of the aryl fluoride with either an alpha- or beta-substituted beta-amino ester is carried out in the presence of DIEA in DMF. The reduction of the aryl nitro group is accomplished in the presence of SnCl(2).H(2)O. Hydrolysis of the ester is carried out in the presence of a heterogeneous mixture of 1 N NaOH/THF (1:1). The resulting aniline acid is cyclized to form the benzodiazepinone skeleton with DIC and HOBt. Selective alkylation at the N-5 position of the benzodiazepinone is accomplished with alkyl halides in the presence of K(2)CO(3) in acetone. The desired products are cleaved from solid supports and obtained in 46-98% isolated yields.

Dual agonistic and antagonistic property of nonpeptide angiotensin AT1 ligands: susceptibility to receptor mutations

Two nonpeptide ligands that differ chemically by only a single methyl group but have agonistic (L-162,782) and antagonistic (L-162,389) properties in vivo were characterized on the cloned angiotensin AT1 receptor. Both compounds bound with high affinity (K(I) = 8 and 28 nM, respectively) to the AT1 receptor expressed transiently in COS-7 cells as determined in radioligand competition assays. L-162,782 acted as a powerful partial agonist, stimulating phosphatidylinositol turnover with a bell-shaped dose-response curve to 64% of the maximal level reached in response to angiotensin II. Surprisingly, L-162,389 also stimulated phosphatidylinositol turnover, albeit only to a small percentage of the angiotensin response. The prototype nonpeptide AT1 agonist L-162,313 gave a response of approximately 50%. The apparent EC50 values for all three compounds in stimulating phosphatidylinositol turnover were similar, approximately 30 nM, corresponding to their binding affinity. Each of the three compounds also acted as angiotensin antagonists, yet in this capacity the compounds differed markedly, with IC50 values ranging from 1.05 x 10(-7) M for L-162,389 to 6.5 x 10(-6) for L-162,782. A series of point mutations in the transmembrane segments (TMs) of the AT1 receptor had only minor effect on the binding affinity of the nonpeptide compounds, with the exception of A104V at the top of TM III, which selectively impaired the binding of L-162,782 and L-162,389. Substitutions in the middle of TM III, VI, or VII, which did not affect the binding affinity of the compounds, impaired or eliminated the agonistic efficacy of the nonpeptides but with only minor or no effect on the angiotensin potency or efficacy. Thus, in the N295D rat AT1 construct, L-162,782, L-162,313, and L-162,389 all antagonized the angiotensin-induced phosphatidylinositol turnover with surprisingly similar IC50 values (90-180 nM), and they all bound with unaltered, high affinity (22-36 nM). However, L-162,313 and L-162,782 could stimulate phosphatidylinositol turnover to only 20% of that of angiotensin. It is concluded that minor chemical modifications of either the compound or the receptor can dramatically alter the agonistic efficacy of biphenyl imidazole compounds on the AT1 receptor without affecting their affinity, as determined in binding assays, and that a number of substitutions in the middle of the TM segments affect the efficacy of nonpeptide agonists as opposed to angiotensin.

Discovery of L-162,313: a nonpeptide that mimics the biological actions of angiotensin II

L-162,313 (5,7-dimethyl-2-ethyl-3-[[4-[2(n- butyloxycarbonylsulfonamido)-5-isobutyl-3-thienyl]phenyl]methyl]- imadazo[4,5-b]pyridine) is a nonpeptide that mimics the biological actions of angiotensin II (ANG II). The intravenous administration of L-162,313 increased blood pressure in the rat. The maximum increase in mean arterial pressure (MAP) was not different from the maximum response to ANG II in the same preparation. However, the duration of the pressor response after L-162,313 greatly exceeded that of ANG II. Pretreatment with ANG II receptor antagonists, L-158,809 (AT1 selective) or saralasin, blocked the L-162,313-induced increase in MAP. Enalaprilat, an angiotensin-converting enzyme inhibitor, failed to block the MAP response to L-162,313. In vitro, L-162,313-activated phosphoinositide turnover in rat aortic smooth muscle cell cultures was also blocked by L-158,809 and losartan (DuP-753). Therefore, L-162,313 is the first reported nonpeptide ANG II receptor agonist.

Non-peptide angiotensin agonist. Functional and molecular interaction with the AT1 receptor

Non-peptide ligands for peptide receptors for the G-protein-coupled type are generally antagonists, except in the opiate system. Recently, it was observed that a subset of biphenylimidazole derivatives surprisingly possessed angiotensin-like activity in vivo. In COS-7 cells transfected with the rat AT1 receptor a prototype of these compounds, L-162,313 stimulated phosphoinositide hydrolysis with an EC50 of 33 +/- 11 nM. The maximal response to the compound was 50% of that of angiotensin II in COS-7 cells but only 3% in stably transfected Chinese hamster ovary cells. The agonistic effect of L-162,313 was blocked by the AT1-specific antagonist L-158,809 and was not observed in untransfected cells. In Chinese hamster ovary cells, L-162,313 also acted as an insurmountable antagonist of the angiotensin stimulated phosphoinositide hydrolysis. In contrast to previously tested non-peptide ligands, L-162,313 bound with reasonably high affinity to the Xenopus laevis AT1 receptor. In the human receptor, the binding of L-162,313 was found to be unaffected by point mutations in transmembrane segments III and VII, which impaired the binding of biphenylimidazole antagonists. Substitutions in the extracellular domains of the human and rat receptor, which impaired the binding of angiotensin II, did not affect the binding of L-162,313. It is concluded that a subset of biphenylimidazole compounds can act as high affinity partial agonists on the AT1 receptor. These compounds have molecular interactions with the receptor which appear to differ both from that of the structurally similar non-peptide antagonists and from that of their functional counterpart, the peptide agonist.