Discovery, Optimization, and in Vivo Evaluation of Benzimidazole Derivatives AM-8508 and AM-9635 as Potent and Selective PI3Kδ Inhibitors

Lead optimization efforts resulted in the discovery of two potent, selective, and orally bioavailable PI3Kδ inhibitors, <b>1</b> (AM-8508) and <b>2</b> (AM-9635), with good pharmacokinetic properties. The compounds inhibit B cell receptor (BCR)-mediated AKT phosphorylation (pAKT) in PI3Kδ-dependent in vitro cell based assays. These compounds which share a benzimidazole bicycle are effective when administered in vivo at unbound concentrations consistent with their in vitro cell potency as a consequence of improved unbound drug concentration with lower unbound clearance. Furthermore, the compounds demonstrated efficacy in a Keyhole Limpet Hemocyanin (KLH) study in rats, where the blockade of PI3Kδ activity by inbibitors <b>1</b> and <b>2</b> led to effective inhibition of antigen-specific IgG and IgM formation after immunization with KLH

Discovery and in Vivo Evaluation of the Potent and Selective PI3Kδ Inhibitors 2‑((1<i>S</i>)‑1-((6-Amino-5-cyano-4-pyrimidinyl)amino)ethyl)-6-fluoro‑<i>N</i>‑methyl-3-(2-pyridinyl)-4-quinolinecarboxamide (AM-0687) and 2‑((1<i>S</i>)‑1-((6-Amino-5-cyano-4-pyrimidinyl)amino)ethyl)-5-fluoro‑<i>N</i>‑methyl-3-(2-pyridinyl)-4-quinolinecarboxamide (AM-1430)

Optimization of the potency and pharmacokinetic profile of 2,3,4-trisubstituted quinoline, <b>4</b>, led to the discovery of two potent, selective, and orally bioavailable PI3Kδ inhibitors, <b>6a</b> (AM-0687) and <b>7</b> (AM-1430). On the basis of their improved profile, these analogs were selected for in vivo pharmacodynamic (PD) and efficacy experiments in animal models of inflammation. The in vivo PD studies, which were carried out in a mouse pAKT inhibition animal model, confirmed the observed potency of <b>6a</b> and <b>7</b> in biochemical and cellular assays. Efficacy experiments in a keyhole limpet hemocyanin model in rats demonstrated that administration of either <b>6a</b> or <b>7</b> resulted in a strong dose-dependent reduction of IgG and IgM specific antibodies. The excellent in vitro and in vivo profiles of these analogs make them suitable for further development

Discovery of AM-7209, a Potent and Selective 4‑Amidobenzoic Acid Inhibitor of the MDM2–p53 Interaction

Structure-based rational design and extensive structure–activity relationship studies led to the discovery of AMG 232 (<b>1</b>), a potent piperidinone inhibitor of the MDM2–p53 association, which is currently being evaluated in human clinical trials for the treatment of cancer. Further modifications of <b>1</b>, including replacing the carboxylic acid with a 4-amidobenzoic acid, afforded AM-7209 (<b>25</b>), featuring improved potency (<i>K</i>_D from ITC competition was 38 pM, SJSA-1 EdU IC₅₀ = 1.6 nM), remarkable pharmacokinetic properties, and in vivo antitumor activity in both the SJSA-1 osteosarcoma xenograft model (ED₅₀ = 2.6 mg/kg QD) and the HCT-116 colorectal carcinoma xenograft model (ED₅₀ = 10 mg/kg QD). In addition, <b>25</b> possesses distinct mechanisms of elimination compared to <b>1</b>

Novel Inhibitors of the MDM2-p53 Interaction Featuring Hydrogen Bond Acceptors as Carboxylic Acid Isosteres

We previously reported the discovery of potent and selective morpholinone and piperidinone inhibitors of the MDM2-p53 interaction. These inhibitors have in common a carboxylic acid moiety that engages in an electrostatic interaction with MDM2-His96. Our continued search for potent and diverse inhibitors led to the discovery of novel replacements for these acids uncovering new interactions with the MDM2 protein. In particular, using pyridine or thiazole as isosteres of the carboxylic acid moiety resulted in very potent analogues. From these, AM-6761 (<b>4</b>) emerged as a potent inhibitor with remarkable biochemical (HTRF IC₅₀ = 0.1 nM) and cellular potency (SJSA-1 EdU IC₅₀ = 16 nM), as well as favorable pharmacokinetic properties. Compound <b>4</b> also shows excellent antitumor activity in the SJSA-1 osteosarcoma xenograft model with an ED₅₀ of 11 mg/kg. Optimization efforts toward the discovery of these inhibitors as well as the new interactions observed with the MDM2 protein are described herein

Discovery and in Vivo Evaluation of (<i>S</i>)‑<i>N</i>‑(1-(7-Fluoro-2-(pyridin-2-yl)quinolin-3-yl)ethyl)‑9<i>H</i>‑purin-6-amine (AMG319) and Related PI3Kδ Inhibitors for Inflammation and Autoimmune Disease

The development and optimization of a series of quinolinylpurines as potent and selective PI3Kδ kinase inhibitors with excellent physicochemical properties are described. This medicinal chemistry effort led to the identification of <b>1</b> (AMG319), a compound with an IC₅₀ of 16 nM in a human whole blood assay (HWB), excellent selectivity over a large panel of protein kinases, and a high level of in vivo efficacy as measured by two rodent disease models of inflammation

Selective and Potent Morpholinone Inhibitors of the MDM2–p53 Protein–Protein Interaction

We previously reported the discovery of AMG 232, a highly potent and selective piperidinone inhibitor of the MDM2–p53 interaction. Our continued search for potent and diverse analogues led to the discovery of novel morpholinone MDM2 inhibitors. This change to a morpholinone core has a significant impact on both potency and metabolic stability compared to the piperidinone series. Within this morpholinone series, AM-8735 emerged as an inhibitor with remarkable biochemical potency (HTRF IC₅₀ = 0.4 nM) and cellular potency (SJSA-1 EdU IC₅₀ = 25 nM), as well as pharmacokinetic properties. Compound <b>4</b> also shows excellent antitumor activity in the SJSA-1 osteosarcoma xenograft model with an ED₅₀ of 41 mg/kg. Lead optimization toward the discovery of this inhibitor as well as key differences between the morpholinone and the piperidinone series will be described herein

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 <b>1</b> that exhibits dual inhibitory activities against FLT3 and CDK4. A series of pyrido­[4′,3′:4,5]­pyrrolo­[2,3-<i>d</i>]­pyrimidine derivatives was synthesized, and SAR analysis, using cell-based assays, led to the discovery of <b>28</b> (<b>AMG 925</b>), a potent and orally bioavailable dual inhibitor of CDK4 and FLT3, including many FLT3 mutants reported to date. Compound <b>28</b> 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 <b>28</b> leads to significant growth inhibition of MOLM13 xenografts in nude mice, and the activity correlates with inhibition of STAT5 and Rb phosphorylation

Discovery of AMG 232, a Potent, Selective, and Orally Bioavailable MDM2–p53 Inhibitor in Clinical Development

We recently reported the discovery of AM-8553 (<b>1</b>), a potent and selective piperidinone inhibitor of the MDM2–p53 interaction. Continued research investigation of the <i>N</i>-alkyl substituent of this series, focused in particular on a previously underutilized interaction in a shallow cleft on the MDM2 surface, led to the discovery of a one-carbon tethered sulfone which gave rise to substantial improvements in biochemical and cellular potency. Further investigation produced AMG 232 (<b>2</b>), which is currently being evaluated in human clinical trials for the treatment of cancer. Compound <b>2</b> is an extremely potent MDM2 inhibitor (SPR <i>K</i>_D = 0.045 nM, SJSA-1 EdU IC₅₀ = 9.1 nM), with remarkable pharmacokinetic properties and in vivo antitumor activity in the SJSA-1 osteosarcoma xenograft model (ED₅₀ = 9.1 mg/kg)