Utilization of Metabolite Identification and Structural Data to Guide Design of Low-Dose IDO1 Inhibitors.

Herein the discovery of potent IDO1 inhibitors with low predicted human dose is discussed. Metabolite identification (MetID) and structural data were used to strategically incorporate cyclopropane rings into this tetrahydronaphthyridine series of IDO1 inhibitors to improve their metabolic stability and potency. Enabling synthetic chemistry was developed to construct these unique fused cyclopropyl compounds, leading to inhibitors with improved pharmacokinetics and human whole blood potency and a predicted human oral dose as low as 9 mg once daily (QD).

SAR towards indoline and 3-azaindoline classes of IDO1 inhibitors.

A novel series of IDO1 inhibitors have been identified with good IDO1 Hela cell and human whole blood activity. These inhibitors contain an indoline or a 3-azaindoline scaffold. Their structure-activity-relationship studies have been explored. Compounds 37 and 41 stood out as leads due to their good potency in IDO1 Hela assay, good IDO1 unbound hWB IC50s, reasonable unbound clearance, and good MRT in rat and dog PK studies.

Carbamate and N-Pyrimidine Mitigate Amide Hydrolysis: Structure-Based Drug Design of Tetrahydroquinoline IDO1 Inhibitors.

Indoleamine-2,3-dioxygenase-1 (IDO1) has emerged as an attractive target for cancer immunotherapy. An automated ligand identification system screen afforded the tetrahydroquinoline class of novel IDO1 inhibitors. Potency and pharmacokinetic (PK) were key issues with this class of compounds. Structure-based drug design and strategic incorporation of polarity enabled the rapid improvement on potency, solubility, and oxidative metabolic stability. Metabolite identification studies revealed that amide hydrolysis in the D-pocket was the key clearance mechanism for this class. Strategic survey of amide isosteres revealed that carbamates and N-pyrimidines, which maintained exquisite potencies, mitigated the amide hydrolysis issue and led to an improved rat PK profile. The lead compound 28 is a potent IDO1 inhibitor, with clean off-target profiles and the potential for quaque die dosing in humans.

Discovery of Potent and Orally Available Bicyclo[1.1.1]pentane-Derived Indoleamine-2,3-dioxygenase 1 (IDO1) Inhibitors.

Indoleamine-2,3-dioxygenase 1 (IDO1) inhibition and its combination with immune checkpoint inhibitors like pembrolizumab have drawn considerable attention from both academia and the pharmaceutical industry. Here, we describe the discovery of a novel class of highly potent IDO1 heme-displacing inhibitors featuring a unique bicyclo[1.1.1]pentane motif. Compound 1, evolving from an ALIS (automated ligand identification system) hit, exhibited excellent potency but lacked the desired pharmacokinetic profile due to extensive amide hydrolysis of the benzamide moiety. Replacing the central phenyl ring in 1 with a bicyclo[1.1.1]pentane bioisostere effectively circumvented the amide hydrolysis issue, resulting in the discovery of compound 2 with a favorable overall profile such as excellent potency, selectivity, pharmacokinetics, and a low predicted human dose.

Strategic Incorporation of Polarity in Heme-Displacing Inhibitors of Indoleamine-2,3-dioxygenase-1 (IDO1).

Indoleamine-2,3-dioxygenase-1 (IDO1) has emerged as a target of significant interest to the field of cancer immunotherapy, as the upregulation of IDO1 in certain cancers has been linked to host immune evasion and poor prognosis for patients. In particular, IDO1 inhibition is of interest as a combination therapy with immune checkpoint inhibition. Through an Automated Ligand Identification System (ALIS) screen, a diamide class of compounds was identified as a promising lead for the inhibition of IDO1. While hit 1 possessed attractive cell-based potency, it suffered from a significant right-shift in a whole blood assay, poor solubility, and poor pharmacokinetic properties. Through a physicochemical property-based approach, including a focus on lowering AlogP98 via the strategic introduction of polar substitution, compound 13 was identified bearing a pyridyl oxetane core. Compound 13 demonstrated improved whole blood potency and solubility, and an improved pharmacokinetic profile resulting in a low predicted human dose.

Cancer-Associated Fibroblasts Promote Immunosuppression by Inducing ROS-Generating Monocytic MDSCs in Lung Squamous Cell Carcinoma.

Cancer-associated fibroblasts (CAF) represent a functionally heterogeneous population of activated fibroblasts that constitutes a major component of tumor stroma. Although CAFs have been shown to promote tumor growth and mediate resistance to chemotherapy, the mechanisms by which they may contribute to immune suppression within the tumor microenvironment (TME) in lung squamous cell carcinoma (LSCC) remain largely unexplored. Here, we identified a positive correlation between CAF and monocytic myeloid cell abundances in 501 primary LSCCs by mining The Cancer Genome Atlas data sets. We further validated this finding in an independent cohort using imaging mass cytometry and found a significant spatial interaction between CAFs and monocytic myeloid cells in the TME. To delineate the interplay between CAFs and monocytic myeloid cells, we used chemotaxis assays to show that LSCC patient-derived CAFs promoted recruitment of CCR2+ monocytes via CCL2, which could be reversed by CCR2 inhibition. Using a three-dimensional culture system, we found that CAFs polarized monocytes to adopt a myeloid-derived suppressor cell (MDSC) phenotype, characterized by robust suppression of autologous CD8+ T-cell proliferation and IFNγ production. We further demonstrated that inhibiting IDO1 and NADPH oxidases, NOX2 and NOX4, restored CD8+ T-cell proliferation by reducing reactive oxygen species (ROS) generation in CAF-induced MDSCs. Taken together, our study highlights a pivotal role of CAFs in regulating monocyte recruitment and differentiation and demonstrated that CCR2 inhibition and ROS scavenging abrogate the CAF-MDSC axis, illuminating a potential therapeutic path to reversing the CAF-mediated immunosuppressive microenvironment.

Identification of DGAT2 Inhibitors Using Mass Spectrometry.

Mass spectrometry offers significant advantages over other detection technologies in the areas of hit finding, hit validation, and medicinal chemistry compound optimization. The foremost obvious advantage is the ability to directly measure enzymatic product formation. In addition, the inherent sensitivity of the liquid chromatography/mass spectrometry (LC/MS) approach allows the execution of enzymatic assays at substrate concentrations typically at or below substrate Km. Another advantage of the LC/MS approach is the ability to assay impure enzyme systems that would otherwise be difficult to prosecute with traditional labeled methods. This approach was used to identify inhibitors of diacylglycerol O-acyltransferase-2 (DGAT2), a transmembrane enzyme involved in the triglyceride (TG) production pathway. The LC/MS approach was employed because of its increased assay window (compared with control membranes) of more than sevenfold compared with less than twofold with a conventional fluorogenic assay. The ability to generate thousands of dose-dependent IC50 data was made possible by the use of a staggered parallel LC/MS system with fast elution gradients. From the hit-deconvolution efforts, several structural scaffold series were identified that inhibit DGAT2 activity. Additional profiling of one chemotype in particular identified two promising reversible and selective compounds (compound 15 and compound 16) that effectively inhibit TG production in mouse primary hepatocytes.

Discovery and Pharmacology of a Novel Class of Diacylglycerol Acyltransferase 2 Inhibitors.

DGAT2 plays a critical role in hepatic triglyceride production, and data suggests that inhibition of DGAT2 could prove to be beneficial in treating a number of disease states. This article documents the discovery and optimization of a selective small molecule inhibitor of DGAT2 as well as pharmacological proof of biology in a mouse model of triglyceride production.

ApoA-I mimetic peptides promote pre-ß HDL formation in vivo causing remodeling of HDL and triglyceride accumulation at higher dose.

Reverse cholesterol transport promoted by HDL-apoA-I is an important mechanism of protection against atherosclerosis. We have previously identified apoA-I mimetic peptides by synthesizing analogs of the 22 amino acid apoA-I consensus sequence (apoA-I(cons)) containing non-natural aliphatic amino acids. Here we examined the effect of different aliphatic non-natural amino acids on the structure-activity relationship (SAR) of apoA-I mimetic peptides. These novel apoA-I mimetics, with long hydrocarbon chain (C(5-8)) amino acids incorporated in the amphipathic α helix of the apoA-I(cons), have the following properties: (i) they stimulate in vitro cholesterol efflux from macrophages via ABCA1; (ii) they associate with HDL and cause formation of pre-ß HDL particles when incubated with human and mouse plasma; (iii) they associate with HDL and induce pre-ß HDL formation in vivo, with a corresponding increase in ABCA1-dependent cholesterol efflux capacity ex vivo; (iv) at high dose they associate with VLDL and induce hypertriglyceridemia in mice. These results suggest our peptide design confers activities that are potentially anti-atherogenic. However a dosing regimen which maximizes their therapeutic properties while minimizing adverse effects needs to be established.

An apoA-I mimetic peptide facilitates off-loading cholesterol from HDL to liver cells through scavenger receptor BI.

Apolipoprotein A-I (apoA-I) mimetic peptides have been pursued as new therapeutic agents for the treatment of atherosclerosis, yet their precise mechanism responsible for atheroprotection remains unclear. Like apoA-I itself, most of these peptides are capable of stimulating cholesterol efflux from macrophages or foam cells, and some of them stimulate lecithin cholesterol acyltransferase (LCAT) activity in the reverse cholesterol transport (RCT) pathway. However, the ability of mimetic peptides to deliver cholesterol into hepatocytes (off-loading), the last step of the RCT pathway, has not been demonstrated. In this study, we compared a mimetic peptide D-4F to purified apoA-I, to address the role that mimetics play during the off-loading process. Both D-4F and apoA-I formed spherical nano-particles when reconstituted with cholesteryl ester and phospholipids. Compared to apoA-I, D-4F particles were 20 times more efficient in off-loading cholesterol to HepG2 hepatocytes with an apparent K(t) (transport) of 0.74 mug/mL. Furthermore, D-4F also facilitated cholesteryl ester offloading from HDL particles into HepG2 cells when it was pre-incubated with these HDL particles. Using an inducible HEK293 cell line, we demonstrated that these nano-particles were able to be taken up through SR-BI, a HDL selective receptor. Cholesterol uptake by HepG2 cells was completely blocked by a neutralizing monoclonal antibody against SR-BI, demonstrating that D-4F particles, similar to HDL, specifically off-loaded cholesterol through SR-BI. Overall our data provides evidence that D-4F is capable of mimicking apoA-I to form HDL-like particles, and off-loads cholesterol for catabolism and excretion, thus completing RCT.

An apoA-I mimetic peptide increases LCAT activity in mice through increasing HDL concentration.

Lecithin cholesterol acyltransferase (LCAT) plays a key role in the reverse cholesterol transport (RCT) process by converting cholesterol to cholesteryl ester to form mature HDL particles, which in turn deliver cholesterol back to the liver for excretion and catabolism. HDL levels in human plasma are negatively correlated with cardiovascular risk and HDL functions are believed to be more important in atheroprotection. This study investigates whether and how D-4F, an apolipoprotein A-I (apoA-I) mimetic peptide, influences LCAT activity in the completion of the RCT process. We demonstrated that the apparent rate constant value of the LCAT enzyme reaction gives a measure of LCAT activity and determined the effects of free metals and a reducing agent on LCAT activity, showing an inhibition hierarchy of Zn(2+)>Mg(2+)>Ca(2+) and no inhibition with beta-mercaptoethanol up to 10 mM. We reconstituted nano-disc particles using apoA-I or D-4F with phospholipids. These particles elicited good activity in vitro in the stimulation of cholesterol efflux from macrophages through the ATP-binding cassette transporter A1 (ABCA1). With these particles we studied the LCAT activity and demonstrated that D-4F did not activate LCAT in vitro. Furthermore, we have done in vivo experiments with apoE-null mice and demonstrated that D-4F (20 mg/kg body weight, once daily subcutaneously) increased LCAT activity and HDL level as well as apoA-I concentration at 72 hours post initial dosing. Finally, we have established a correlation between HDL concentration and LCAT activity in the D-4F treated mice.