Structure-assisted discovery of the first non-retinoid ligands for Retinol-Binding Protein 4.

Retinol-Binding Protein 4 (RBP4) is a plasma protein that transports retinol (vitamin A) from the liver to peripheral tissues. This Letter highlights our efforts in discovering the first, to our knowledge, non-retinoid small molecules that bind to RBP4 at the retinol site and reduce serum RBP4 levels in mice, by disrupting the interaction between RBP4 and transthyretin (TTR), a plasma protein that binds RBP4 and protects it from renal excretion. Potent compounds were discovered and optimized quickly from high-throughput screen (HTS) hits utilizing a structure-based approach. Inhibitor co-crystal X-ray structures revealed unique disruptions of RBP4-TTR interactions by our compounds through induced loop conformational changes instead of steric hindrance exemplified by fenretinide. When administered to mice, A1120, a representative compound in the series, showed concentration-dependent retinol and RBP4 lowering.

CCX559 is a potent, orally-administered small molecule PD-L1 inhibitor that induces anti-tumor immunity.

The interaction of PD-L1 with PD-1 is a major immune checkpoint that limits effector T cell function against cancer cells; monoclonal antibodies that block this pathway have been approved in multiple tumor indications. As a next generation therapy, small molecule inhibitors of PD-L1 have inherent drug properties that may be advantageous for certain patient populations compared to antibody therapies. In this report we present the pharmacology of the orally-available, small molecule PD-L1 inhibitor CCX559 for cancer immunotherapy. CCX559 potently and selectively inhibited PD-L1 binding to PD-1 and CD80 in vitro, and increased activation of primary human T cells in a T cell receptor-dependent fashion. Oral administration of CCX559 demonstrated anti-tumor activity similar to an anti-human PD-L1 antibody in two murine tumor models. Treatment of cells with CCX559 induced PD-L1 dimer formation and internalization, which prevented interaction with PD-1. Cell surface PD-L1 expression recovered in MC38 tumors upon CCX559 clearance post dosing. In a cynomolgus monkey pharmacodynamic study, CCX559 increased plasma levels of soluble PD-L1. These results support the clinical development of CCX559 for solid tumors; CCX559 is currently in a Phase 1, first in patient, multicenter, open-label, dose-escalation study (ACTRN12621001342808).

Discovery and characterization of a potent and selective antagonist of melanin-concentrating hormone receptor 2.

A series of spiropiperidine carbazoles were synthesized and evaluated as MCHR2 antagonists using a FLIPR assay. The pharmacokinetic properties of selected compounds have also been studied. This effort led to the discovery of potent and specific MCHR2 antagonists. Compound 38 demonstrated good pharmacokinetic properties across rat, beagle dog and rhesus monkey and had a favorable selectivity profile against a number of other receptors. These MCHR2 antagonists are considered appropriate tool compounds for study of the function of MCHR2 in vivo.

Discovery of a novel melanin concentrating hormone receptor 1 (MCHR1) antagonist with reduced hERG inhibition.

An initial SAR study resulted in the identification of the novel, potent MCHR1 antagonist 2. After further profiling, compound 2 was discovered to be a potent inhibitor of the hERG potassium channel, which prevented its further development. Additional optimization of this structure resulted in the discovery of the potent MCHR1 antagonist 11 with a dramatically reduced hERG liability. The decrease in hERG activity was confirmed by several in vivo preclinical cardiovascular studies examining QT prolongation. This compound demonstrated good selectivity for MCHR1 and possessed good pharmacokinetic properties across preclinical species. Compound 11 was also efficacious in reducing body weight in two in vivo mouse models. This compound was selected for clinical evaluation and was given the code AMG 076.

Discovery of a novel series of melanin-concentrating hormone receptor 1 antagonists for the treatment of obesity.

A new class of MCHR1 antagonists was discovered via a high-throughput screen. Optimization of the lead structure resulted in the identification of indole 10e. This compound possesses good pharmacokinetic properties across preclinical species and is efficacious in reducing food consumption in an MCH cannulated rat model and a cynomolgus monkey food consumption model.

The synthesis and SAR of novel diarylsulfone 11ß-HSD1 inhibitors.

In this communication, human 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) inhibitory activities of a novel series of diarylsulfones are described. Optimization of this series resulted in several highly potent 11ß-HSD1 inhibitors with excellent pharmacokinetic (PK) properties. Compound (S)-25 showed excellent efficacy in a non-human primate ex vivo pharmacodynamic model.

Correction: Characterization of Pharmacologic and Pharmacokinetic Properties of CCX168, a Potent and Selective Orally Administered Complement 5a Receptor Inhibitor, Based on Preclinical Evaluation and Randomized Phase 1 Clinical Study.

[This corrects the article DOI: 10.1371/journal.pone.0164646.].

Characterization of Pharmacologic and Pharmacokinetic Properties of CCX168, a Potent and Selective Orally Administered Complement 5a Receptor Inhibitor, Based on Preclinical Evaluation and Randomized Phase 1 Clinical Study.

The complement 5a receptor has been an attractive therapeutic target for many autoimmune and inflammatory disorders. However, development of a selective and potent C5aR antagonist has been challenging. Here we describe the characterization of CCX168 (avacopan), an orally administered selective and potent C5aR inhibitor. CCX168 blocked the C5a binding, C5a-mediated migration, calcium mobilization, and CD11b upregulation in U937 cells as well as in freshly isolated human neutrophils. CCX168 retains high potency when present in human blood. A transgenic human C5aR knock-in mouse model allowed comparison of the in vitro and in vivo efficacy of the molecule. CCX168 effectively blocked migration in in vitro and ex vivo chemotaxis assays, and it blocked the C5a-mediated neutrophil vascular endothelial margination. CCX168 was effective in migration and neutrophil margination assays in cynomolgus monkeys. This thorough in vitro and preclinical characterization enabled progression of CCX168 into the clinic and testing of its safety, tolerability, pharmacokinetic, and pharmacodynamic profiles in a Phase 1 clinical trial in 48 healthy volunteers. CCX168 was shown to be well tolerated across a broad dose range (1 to 100 mg) and it showed dose-dependent pharmacokinetics. An oral dose of 30 mg CCX168 given twice daily blocked the C5a-induced upregulation of CD11b in circulating neutrophils by 94% or greater throughout the entire day, demonstrating essentially complete target coverage. This dose regimen is being tested in clinical trials in patients with anti-neutrophil cytoplasmic antibody-associated vasculitis. Trial Registration ISRCTN registry with trial ID ISRCTN13564773.

Discovery of AMG 925, a FLT3 and CDK4 dual kinase inhibitor with preferential affinity for the activated state of FLT3.

We describe the structural optimization of a lead compound 1 that exhibits dual inhibitory activities against FLT3 and CDK4. A series of pyrido[4',3':4,5]pyrrolo[2,3-d]pyrimidine derivatives was synthesized, and SAR analysis, using cell-based assays, led to the discovery of 28 (AMG 925), a potent and orally bioavailable dual inhibitor of CDK4 and FLT3, including many FLT3 mutants reported to date. Compound 28 inhibits the proliferation of a panel of human tumor cell lines including Colo205 (Rb(+)) and U937 (FLT3(WT)) and induced cell death in MOLM13 (FLT3(ITD)) and even in MOLM13 (FLT3(ITD, D835Y)), which exhibits resistance to a number of FLT3 inhibitors currently under clinical development. At well-tolerated doses, compound 28 leads to significant growth inhibition of MOLM13 xenografts in nude mice, and the activity correlates with inhibition of STAT5 and Rb phosphorylation.

Identification and characterization of a non-retinoid ligand for retinol-binding protein 4 which lowers serum retinol-binding protein 4 levels in vivo.

Retinol-binding protein 4 (RBP4) transports retinol from the liver to extrahepatic tissues, and RBP4 lowering is reported to improve insulin sensitivity in mice. We have identified A1120, a high affinity (K(i) = 8.3 nm) non-retinoid ligand for RBP4, which disrupts the interaction between RBP4 and its binding partner transthyretin. Analysis of the RBP4-A1120 co-crystal structure reveals that A1120 induces critical conformational changes at the RBP4-transthyretin interface. Administration of A1120 to mice lowers serum RBP4 and retinol levels but, unexpectedly, does not improve insulin sensitivity. In addition, we show that Rpb4(-/-) mice display normal insulin sensitivity and are not protected from high fat diet-induced insulin resistance. We conclude that lowering RBP4 levels does not improve insulin sensitivity in mice. Therefore, RBP4 lowering may not be an effective strategy for treating diabetes.

Stereoselective synthesis of a MCHr1 antagonist.

Melanin-concentrating hormone (MCH) is implicated in the feeding behavior in mammals affording a potential target to control overeating in people. Compound 1 (AMG 076) has been identified as a potent MCHr1 antagonist for the treatment of obesity. A synthesis suitable for the large-scale preparation of this lead candidate was developed to support preclinical studies. A Robinson annulation of benzylpiperidone and resolution of the desired enone from a mixture of the diastereomers afforded key intermediate 6 after a stereoselective hydrogenation. Subsequent Fischer indole synthesis with hydrazine 5 then provided the advanced intermediate, indole 2. Two complementary reductive amination strategies employing either aldehyde 3 or lactol 4 led to the synthesis of title compound 1.

Substituted indoloquinolines as new antifungal agents.

Cryptolepine (2) possesses desirable properties to serve as a lead in developing new antifungal agents. Using SAR techniques, several analogues of cryptolepine were designed to increase potency and to broaden the antifungal spectrum over several opportunistic microorganisms. A number of 2-substituted indoloquinolines have been synthesized and evaluated in antifungal screens and several have been shown to increase potency and expand the antifungal spectrum of cryptolepine. Comparison of MICs of a number of these analogues with standard antifungal agents, shows them to be comparable to Amphotericin B and Ketoconazole.