Biotransformation of the Novel Myeloperoxidase Inhibitor AZD4831 in Preclinical Species and Humans.

We report herein an in-depth analysis of the metabolism of the novel myeloperoxidase inhibitor AZD4831 ((R)-1-(2-(1-aminoethyl)-4-chlorobenzyl)-2-thioxo-2,3-dihydro-1H-pyrrolo[3,2-d]pyrimidin-4(5H)-one) in animals and human. Quantitative and qualitative metabolite profiling were performed on samples collected from mass balance studies in rats and humans. Exposure of circulating human metabolites with comparable levels in animal species used in safety assessment were also included. Structural characterization of 20 metabolites was performed by liquid chromatography high-resolution mass spectrometry, and quantification was performed by either 14C analysis using solid phase scintillation counting or accelerator mass spectrometry and, where available, authentication with synthesized metabolite standards. A complete mass balance study in rats is presented, while data from dogs and human are limited to metabolite profiling and characterization. The metabolism of AZD4831 is mainly comprised of reactions at the primary amine nitrogen and the thiourea sulfur, resulting in several conjugated metabolites with or without desulfurization. A carbamoyl glucuronide metabolite of AZD4831 (M7) was the most abundant plasma metabolite in both human healthy volunteers and heart failure patients after single and repeated dose administration of AZD4831, accounting for 75%-80% of the total drug-related exposure. Exposures to M7 and other human circulating metabolites were covered in rats and/or dogs, the two models most frequently used in the toxicology studies, and were also highly abundant in the mouse, the second model other than rat used in carcinogenicity studies. The carbamoyl glucuronide M7 was the main metabolite in rat bile, while a desulfurized and cyclized metabolite (M5) was abundant in rat plasma and excreta. SIGNIFICANCE STATEMENT: The biotransformation of AZD4831, a novel myeloperoxidase inhibitor inhibiting xanthine derivative bearing thiourea and primary aliphatic amine functions, is described. Twenty characterized metabolites demonstrate the involvement of carbamoylation with glucuronidation, desulfurization, and cyclization as main biotransformation reactions. The carbamoyl glucuronide was the main metabolite in human plasma, likely governed by a significant species difference in plasma protein binding for this metabolite, but this and other human plasma metabolites were covered in animals used in the toxicity studies.

Potassium channel blocking 1,2-bis(aryl)ethane-1,2-diamines active as antiarrhythmic agents.

Atrial fibrillation (AF) is a major cause of stroke, heart failure, sudden death and cardiovascular morbidity. The Kv1.5 potassium channel conducts the IKur current and has been demonstrated to be predominantly expressed in atrial versus ventricular tissue. Blockade of Kv1.5 has been proven to be an effective approach to restoring and maintaining sinus rhythm in preclinical models of AF. In the clinical setting, however, the therapeutic value of this approach remains an open question. Herein, we present synthesis and optimization of a novel series of 1,2-bis(aryl)ethane-1,2-diamines with selectivity for Kv1.5 over other potassium ion channels. The effective refractory period in the right atrium (RAERP) in a rabbit PD model was investigated for a selection of potent and selective compounds with balanced DMPK properties. The most advanced compound (10) showed nanomolar potency in blocking Kv1.5 in human atrial myocytes and based on the PD data, the estimated dose to man is 700 mg/day. As previously reported, 10 efficiently converted AF to sinus rhythm in a dog disease model.

A Fluorescent Kinase Inhibitor that Exhibits Diagnostic Changes in Emission upon Binding.

The development of a fluorescent LCK inhibitor that exhibits favourable solvatochromic properties upon binding the kinase is described. Fluorescent properties were realised through the inclusion of a prodan-derived fluorophore into the pharmacophore of an ATP-competitive kinase inhibitor. Fluorescence titration experiments demonstrate the solvatochromic properties of the inhibitor, in which dramatic increase in emission intensity and hypsochromic shift in emission maxima are clearly observed upon binding LCK. Microscopy experiments in cellular contexts together with flow cytometry show that the fluorescence intensity of the inhibitor correlates with the LCK concentration. Furthermore, multiphoton microscopy experiments demonstrate both the rapid cellular uptake of the inhibitor and that the two-photon cross section of the inhibitor is amenable for excitation at 700 nm.

Structural and functional characterization of a specific antidote for ticagrelor.

Ticagrelor is a direct-acting reversibly binding P2Y12 antagonist and is widely used as an antiplatelet therapy for the prevention of cardiovascular events in acute coronary syndrome patients. However, antiplatelet therapy can be associated with an increased risk of bleeding. Here, we present data on the identification and the in vitro and in vivo pharmacology of an antigen-binding fragment (Fab) antidote for ticagrelor. The Fab has a 20 pM affinity for ticagrelor, which is 100 times stronger than ticagrelor's affinity for its target, P2Y12. Despite ticagrelor's structural similarities to adenosine, the Fab is highly specific and does not bind to adenosine, adenosine triphosphate, adenosine 5'-diphosphate, or structurally related drugs. The antidote concentration-dependently neutralized the free fraction of ticagrelor and reversed its antiplatelet activity both in vitro in human platelet-rich plasma and in vivo in mice. Lastly, the antidote proved effective in normalizing ticagrelor-dependent bleeding in a mouse model of acute surgery. This specific antidote for ticagrelor may prove valuable as an agent for patients who require emergency procedures.

Discovery of 9-(1-phenoxyethyl)-2-morpholino-4-oxo-pyrido[1,2-a]pyrimidine-7-carboxamides as oral PI3Kß inhibitors, useful as antiplatelet agents.

Optimization of AZD6482 (2), the first antiplatelet PI3Kß inhibitor evaluated in man, focused on improving the pharmacokinetic profile to a level compatible with once daily oral dosing as well as achieving adequate selectivity towards PI3Kα to minimize the risk for insulin resistance. Structure-based design and optimization of DMPK properties resulted in (R)-16, a novel, orally bioavailable PI3Kß inhibitor with potent in vivo anti-thrombotic effect with excellent separation to bleeding risk and insulin resistance.

Discovery of 9-(1-anilinoethyl)-2-morpholino-4-oxo-pyrido[1,2-a]pyrimidine-7-carboxamides as PI3Kß/δ inhibitors for the treatment of PTEN-deficient tumours.

Starting from TGX-221, we designed a series of 9-(1-anilinoethyl)-2-morpholino-4-oxo-pyrido[1,2-a]pyrimidine-7-carboxamides as potent and selective PI3Kß/δ inhibitors. Structure-activity relationships and structure-property relationships around the aniline and the amide substituents are discussed. We identified compounds 17 and 18, which showed profound pharmacodynamic modulation of phosphorylated Akt in the PC3 prostate tumour xenograft, after a single oral dose. Compound 17 also gave significant inhibition of tumour growth in the PC3 prostate tumour xenograft model after chronic oral dosing.

All-photonic kinase inhibitors: light-controlled release-and-report inhibition.

Light-responsive molecular tools targeting kinases affords one the opportunity to study the underlying cellular function of selected kinases. In efforts to externally control lymphocyte-specific protein tyrosine kinase (LCK) activity, the development of release-and-report LCK inhibitors is described, in which (i) the release of the active kinase inhibitor can be controlled externally with light; and (ii) fluorescence is employed to report both the release and binding of the active kinase inhibitor. This introduces an unprecedented all-photonic method for users to both control and monitor real-time inhibitory activity. A functional cellular assay demonstrated light-mediated LCK inhibition in natural killer cells. The use of coumarin-derived caging groups resulted in rapid cellular uptake and non-specific intracellular localisation, while a BODIPY-derived caging group predominately localised in the cellular membrane. This concept of release-and-report inhibitors has the potential to be extended to other biorelevant targets where both spatiotemporal control in a cellular setting and a reporting mechanism would be beneficial.

Discovery of phosphoinositide 3-kinases (PI3K) p110ß isoform inhibitor 4-[2-hydroxyethyl(1-naphthylmethyl)amino]-6-[(2S)-2-methylmorpholin-4-yl]-1H-pyrimidin-2-one, an effective antithrombotic agent without associated bleeding and insulin resistance.

Structure-based evolution of the original fragment leads resulted in the identification of 4-[2-hydroxyethyl(1-naphthylmethyl)amino]-6-[(2S)-2-methylmorpholin-4-yl]-1H-pyrimidin-2-one, (S)-21, a potent, selective phosphoinositide 3-kinases (PI3K) p110ß isoform inhibitor with favourable in vivo antiplatelet effect. Despite its antiplatelet action, (S)-21 did not significantly increase bleeding time in dogs. Additionally, due to its enhanced selectivity over p110α, (S)-21 did not induce any insulin resistance in rats.

Discovery of AZD4831, a Mechanism-Based Irreversible Inhibitor of Myeloperoxidase, As a Potential Treatment for Heart Failure with Preserved Ejection Fraction.

Myeloperoxidase is a promising therapeutic target for treatment of patients suffering from heart failure with preserved ejection fraction (HFpEF). We aimed to discover a covalent myeloperoxidase inhibitor with high selectivity for myeloperoxidase over thyroid peroxidase, limited penetration of the blood-brain barrier, and pharmacokinetics suitable for once-daily oral administration at low dose. Structure-activity relationship, biophysical, and structural studies led to prioritization of four compounds for in-depth safety and pharmacokinetic studies in animal models. One compound (AZD4831) progressed to clinical studies on grounds of high potency (IC50, 1.5 nM in vitro) and selectivity (>450-fold vs thyroid peroxidase in vitro), the mechanism of irreversible inhibition, and the safety profile. Following phase 1 studies in healthy volunteers and a phase 2a study in patients with HFpEF, a phase 2b/3 efficacy study of AZD4831 in patients with HFpEF started in 2021.

Biochemical and pharmacological effects of the direct thrombin inhibitor AR-H067637.

AZD0837 is in development as a new oral anticoagulant for use in thromboembolic disorders. In vivo, AZD0837 is converted to AR-H067637, a selective and reversible direct thrombin inhibitor. Established biochemical methods were used to assess and measure the biochemical and pharmacological properties of AR-H067637. Both direct Biacore binding studies of AR-H067637 with immobilised alpha-thrombin and inhibition studies using pre-steady state kinetics with thrombin in the fluid phase confirmed that AR-H067637 is a rapid-binding, reversible and potent (inhibition constant K(i) = 2-4 nM), competitive inhibitor of thrombin, as well as of thrombin bound to fibrin (clot-bound thrombin) or to thrombomodulin. The total amount of free thrombin generated in platelet-poor clotting plasma was inhibited concentration-dependently by AR-H067637, with a concentration giving half maximal inhibition (IC(50)) of 0.6 microM. Moreover, AR-H067637 is, with the exception of trypsin, a selective inhibitor for thrombin without inhibiting other serine proteases involved in haemostasis. Furthermore, no anticoagulant effect of the prodrug was found. AR-H067637 prolonged the clotting time concentration-dependently in a range of plasma coagulation assays including activated partial thromboplastin time, prothrombin time, prothrombinase-induced clotting time, thrombin time and ecarin clotting time. The two latter assays were found to be most sensitive for assessing the anticoagulant effect of AR-H067637 (plasma IC(50) 93 and 220 nM, respectively). AR-H067637 also inhibited thrombin-induced platelet activation (by glycoprotein IIb/IIIa exposure, IC(50) 8.4 nM) and aggregation (IC(50) 0.9 nM). In conclusion, AR-H067637 is a selective, reversible, competitive inhibitor of alpha-thrombin, with a predictable anticoagulant effect demonstrated in plasma coagulation assays.

Optimization of 2-piperidin-4-yl-acetamides as melanin-concentrating hormone receptor 1 (MCH-R1) antagonists: Designing out hERG inhibition.

Herein, we disclose the discovery and optimization of 2-piperidin-4-yl-acetamide derivatives as MCH-R1 antagonists. Structural investigation of piperidin-4-yl-amide and piperidin-4-yl-ureas identified 2-piperidin-4-yl-acetamide-based MCH-R1 antagonists with outstanding in vivo efficacy but flawed with high affinity towards the hERG potassium channel. While existing hERG SAR information was employed to discover highly potent MCH-R1 antagonists with minimized hERG inhibition, additional hurdles prevented their subsequent clinical exploration.

Optimization of piperidin-4-yl-urea-containing melanin-concentrating hormone receptor 1 (MCH-R1) antagonists: Reducing hERG-associated liabilities.

The discovery and optimization of piperidin-4-yl-urea derivatives as MCH-R1 antagonists is herein described. Previous work around the piperidin-4-yl-amides led to the discovery of potent MCH-R1 antagonists. However, high affinity towards the hERG potassium channel proved to be an issue. Different strategies to increase hERG selectivity were implemented and resulted in the identification of piperidin-4-yl-urea compounds as potent MCH-R1 antagonists with minimized hERG inhibition.

Discovery of 1,3-disubstituted-1H-pyrrole derivatives as potent melanin-concentrating hormone receptor 1 (MCH-R1) antagonists.

A series of 1,3-disubstituted-1H-pyrrole-based antagonists of the human Melanin-Concentrating Hormone Receptor 1 (h-MCH-R1) are reported. High-throughput screening of the AstraZeneca compound collection yielded 1, a hit with moderate affinity towards MCH-R1. Subsequent structural manipulations and SAR analysis served to rationalize potency requirements, and 12 was identified as a novel, functional MCH-R1 antagonist with favorable pharmacokinetic properties.

Making medicinal chemistry more effective--application of Lean Sigma to improve processes, speed and quality.

The pharmaceutical industry, particularly the small molecule domain, faces unprecedented challenges of escalating costs, high attrition as well as increasing competitive pressure from other companies and from new treatment modes such as biological products. In other industries, process improvement approaches, such as Lean Sigma, have delivered benefits in speed, quality and cost of delivery. Examining the medicinal chemistry contributions to the iterative improvement process of design-make-test-analyse from a Lean Sigma perspective revealed that major improvements could be made. Thus, the cycle times of synthesis, as well as compound analysis and purification, were reduced dramatically. Improvements focused on team, rather than individual, performance. These new ways of working have consequences for staff engagement, goals, rewards and motivation, which are also discussed.

Discovery of cyclopentane- and cyclohexane-trans-1,3-diamines as potent melanin-concentrating hormone receptor 1 antagonists.

We herein report the optimization of cyclopentane- and cyclohexane-1,3-diamine derivatives as novel and potent MCH-R1 antagonists. Structural modifications of the 2-amino-quinoline and thiophene moieties found in the initial lead compound served to improve its metabolic stability profile and MCH-R1 affinity, and revealed unprecedented SAR when compared to other 2-amino-quinoline-containing MCH-R1 antagonists.