Design and Discovery of an Orally Efficacious Spiroindolinone-Based Tankyrase Inhibitor for the Treatment of Colon Cancer.

Tankyrases (TNKS/TNKS2) belong to the poly(ADP-ribose) polymerase family. Inhibition of their enzymatic activities attenuates the Wnt/ß-catenin signaling, which plays an important role in cancer pathogenesis. We previously reported the discovery of RK-287107, a spiroindoline-based, highly selective, potent tankyrase inhibitor. Herein we describe the optimization process of RK-287107 leading to RK-582, which exhibits a markedly improved robust tumor growth inhibition in a COLO-320DM mouse xenograft model when orally administered. In addition to the dose-dependent elevation and attenuation of the levels of biomarkers AXIN2 and ß-catenin, respectively, results of the TCF reporter and cell proliferation studies on COLO-320DM are discussed.

Discovery of Novel Spiroindoline Derivatives as Selective Tankyrase Inhibitors.

The canonical WNT pathway plays an important role in cancer pathogenesis. Inhibition of poly(ADP-ribose) polymerase catalytic activity of the tankyrases (TNKS/TNKS2) has been reported to reduce the Wnt/ß-catenin signal by preventing poly ADP-ribosylation-dependent degradation of AXIN, a negative regulator of Wnt/ß-catenin signaling. With the goal of investigating the effects of tankyrase and Wnt pathway inhibition on tumor growth, we set out to find small-molecule inhibitors of TNKS/TNKS2 with suitable drug-like properties. Starting from 1a, a high-throughput screening hit, the spiroindoline derivative 40c (RK-287107) was discovered as a potent TNKS/TNKS2 inhibitor with >7000-fold selectivity against the PARP1 enzyme, which inhibits WNT-responsive TCF reporter activity and proliferation of human colorectal cancer cell line COLO-320DM. RK-287107 also demonstrated dose-dependent tumor growth inhibition in a mouse xenograft model. These observations suggest that RK-287107 is a promising lead compound for the development of novel tankyrase inhibitors as anticancer agents.

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.

Discovery of a novel, potent and selective human beta3-adrenergic receptor agonist.

The discovery of a novel, potent and selective beta(3)-adrenergic receptor (AR) agonist is described. SAR studies demonstrated the structural requirements for activity and selectivity. Compound 1c, which showed good beta(3)-AR activity and selectivity, was identified and pharmacokinetics were investigated.