Discovery of a Potent Chloroacetamide GPX4 Inhibitor with Bioavailability to Enable Target Engagement in Mice, a Potential Tool Compound for Inducing Ferroptosis In Vivo.

Compounds that inhibit glutathione peroxidase 4 (GPX4) hold promise as cancer therapeutics in their ability to induce a form of nonapoptotic cell death called ferroptosis. Our research identified 24, a structural analog of the potent GPX4 inhibitor RSL3, that has much better plasma stability (t1/2 > 5 h in mouse plasma). The bioavailability of 24 provided efficacious plasma drug concentrations with IP dosing, thus enabling in vivo studies to assess tolerability and efficacy. An efficacy study in mouse using a GPX4-sensitive tumor model found that doses of 24 up to 50 mg/kg were tolerated for 20 days but had no effect on tumor growth, although partial target engagement was observed in tumor homogenate.

Cardiovascular effects of torcetrapib in conscious and pentobarbital-anesthetized dogs.

Torcetrapib is a cholesteryl ester transfer protein inhibitor with an undesired response of increasing arterial pressure in humans. Pressor responses to torcetrapib have been demonstrated in multiple preclinical species. However, these studies have not related plasma concentrations to observed effects. Our purpose was to 1) characterize the cardiovascular responses of torcetrapib in conscious and anesthetized dogs with measured plasma concentrations; and 2) characterize the hemodynamic effects contributing to hypertension using comprehensively instrumented anesthetized dogs. Torcetrapib was dosed orally (3, 30 mg/kg) and intravenously (0.01, 0.33, 0.1 mg/kg) in conscious and anesthetized dogs, respectively. Mean arterial pressure and heart rate were monitored in both models; additional parameters were measured in anesthetized dogs. Plasma drug concentrations were assessed in both models. In conscious and anesthetized dogs, torcetrapib increased mean arterial pressure 25 and 18 mm Hg and heart rate 35 and 21 beats/min, at 2.94 and 3.99 microg/mL, respectively. In anesthetized dogs, torcetrapib increased pulmonary arterial pressure, both systemic and pulmonary hypertension driven by increases in vascular resistance. The compound increased rate pressure product and myocardial contractility while decreasing time to systolic pressure recovery and ejection time. Thus, torcetrapib-induced pressor responses are mediated by systemic and pulmonary vasoconstriction and are associated with increased myocardial oxygen consumption and positive inotropy.

A-366833: a novel nicotinonitrile-substituted 3,6-diazabicyclo[3.2.0]-heptane alpha4beta2 nicotinic acetylcholine receptor selective agonist: Synthesis, analgesic efficacy and tolerability profile in animal models.

5-[(1R,5S)-3,6-Diazabicyclo[3.2.0]heptan-6-yl]nicotinonitrile (A-366833) is a novel nicotinic acetylcholine receptor (nAChR) ligand that binds to the agonist-binding site ([3H]-cytisine) with Ki value of 3.1 nM and exhibits agonist selectivity at alpha4beta2 nAChR relative to the alpha3beta4 nAChR subtype. The analgesic effects of A-366833 were examined across a variety of animal models including the mouse model of writhing pain (abdominal constriction), the rat models of acute thermal (hot box), persistent chemical (formalin) and neuropathic (spinal nerve ligation, SNL) pain. In the abdominal constriction model, A-366833 was effective at doses ranging from 0.062 to 0.62 micromol/kg (i.p.). In addition, A-366833 demonstrated significant effects in acute thermal pain (6.2-19.0 micromol/kg, i.p.), formalin (1.9-19 micromol/kg i.p.) and SNL (1.9-19 micromol/kg i.p.) models. The systemic effects of A-366833 were attenuated by pretreatment with mecamylamine (5 micromol/kg i.p.) in both the formalin and SNL models, suggesting that the analgesic effects of A-366833 in models of persistent nociceptive and neuropathic pain are mediated by activation of nAChRs. Pharmacokinetic investigations of A-366833 in rat revealed moderate brain:plasma distribution, half-life of 1.5h and excellent oral bioavailability of 73%. Comparison of peak plasma levels at the minimal effective doses across rat models of acute thermal pain, formalin and SNL with the maximal exposure that does not evoke emesis in ferret revealed therapeutic margins ranging from 6- to 22-fold. These studies indicate that compounds like A-366833 with improved agonist selectivity at alpha4beta2 vs. alpha3beta4 nAChR can elicit a broad spectrum of analgesic efficacy without concurrent adverse effects.

Discovery and structure-activity relationships of piperidinone- and piperidine-constrained phenethylamines as novel, potent, and selective dipeptidyl peptidase IV inhibitors.

Dipeptidyl peptidase IV (DPP4) inhibitors are emerging as a new class of therapeutic agents for the treatment of type 2 diabetes. They exert their beneficial effects by increasing the levels of active glucagon-like peptide-1 and glucose-dependent insulinotropic peptide, which are two important incretins for glucose homeostasis. Starting from a high-throughput screening hit, we were able to identify a series of piperidinone- and piperidine-constrained phenethylamines as novel DPP4 inhibitors. Optimized compounds are potent, selective, and have good pharmacokinetic profiles.

Pyrrolidine-constrained phenethylamines: The design of potent, selective, and pharmacologically efficacious dipeptidyl peptidase IV (DPP4) inhibitors from a lead-like screening hit.

A novel series of pyrrolidine-constrained phenethylamines were developed as dipeptidyl peptidase IV (DPP4) inhibitors for the treatment of type 2 diabetes. The cyclohexene ring of lead-like screening hit 5 was replaced with a pyrrolidine to enable parallel chemistry, and protein co-crystal structural data guided the optimization of N-substituents. Employing this strategy, a >400x improvement in potency over the initial hit was realized in rapid fashion. Optimized compounds are potent and selective inhibitors with excellent pharmacokinetic profiles. Compound 30 was efficacious in vivo, lowering blood glucose in ZDF rats that were allowed to feed freely on a mixed meal.

Discovery of ((4R,5S)-5-amino-4-(2,4,5- trifluorophenyl)cyclohex-1-enyl)-(3- (trifluoromethyl)-5,6-dihydro- [1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl)methanone (ABT-341), a highly potent, selective, orally efficacious, and safe dipeptidyl peptidase IV inhibitor for the treatment of type 2 diabetes.

Dipeptidyl peptidase IV (DPP4) deactivates glucose-regulating hormones such as GLP-1 and GIP, thus, DPP4 inhibition has become a useful therapy for type 2 diabetes. Optimization of the high-throughput screening lead 6 led to the discovery of 25 (ABT-341), a highly potent, selective, and orally bioavailable DPP4 inhibitor. When dosed orally, 25 dose-dependently reduced glucose excursion in ZDF rats. Amide 25 is safe in a battery of in vitro and in vivo tests and may represent a new therapeutic agent for the treatment of type 2 diabetes.

Discovery of 2-[4-{{2-(2S,5R)-2-cyano-5-ethynyl-1-pyrrolidinyl]-2-oxoethyl]amino]- 4-methyl-1-piperidinyl]-4-pyridinecarboxylic acid (ABT-279): a very potent, selective, effective, and well-tolerated inhibitor of dipeptidyl peptidase-IV, useful for the treatment of diabetes.

Dipeptidyl peptidase-IV (DPP-IV) inhibitors are poised to be the next major drug class for the treatment of type 2 diabetes. Structure-activity studies of substitutions at the C5 position of the 2-cyanopyrrolidide warhead led to the discovery of potent inhibitors of DPP-IV that lack activity against DPP8 and DPP9. Further modification led to an extremely potent (Ki(DPP)(-)(IV) = 1.0 nM) and selective (Ki(DPP8) > 30 microM; Ki(DPP9) > 30 microM) clinical candidate, ABT-279, that is orally available, efficacious, and remarkably safe in preclinical safety studies.

Discovery, structure-activity relationship, and pharmacological evaluation of (5-substituted-pyrrolidinyl-2-carbonyl)-2-cyanopyrrolidines as potent dipeptidyl peptidase IV inhibitors.

A series of (5-substituted pyrrolidinyl-2-carbonyl)-2-cyanopyrrolidine (C5-Pro-Pro) analogues was discovered as dipeptidyl peptidase IV (DPPIV) inhibitors as a potential treatment of diabetes and obesity. X-ray crystallography data show that these inhibitors bind to the catalytic site of DPPIV with the cyano group forming a covalent bond with the serine residue of DPPIV. The C5-substituents make various interactions with the enzyme and affect potency, chemical stability, selectivity, and PK properties of the inhibitors. Optimized analogues are extremely potent with subnanomolar K(i)'s, are chemically stable, show very little potency decrease in the presence of plasma, and exhibit more than 1,000-fold selectivity against related peptidases. The best compounds also possess good PK and are efficacious in lowering blood glucose in an oral glucose tolerance test in ZDF rats.

Structure-based characterization and optimization of novel hydrophobic binding interactions in a series of pyrrolidine influenza neuraminidase inhibitors.

The structure-activity relationship (SAR) of a novel hydrophobic binding interaction within a subsite of the influenza neuraminidase (NA) active site was characterized and optimized for a series of trisubstituted pyrrolidine inhibitors modified at the 4-position. Previously, potent inhibitors have targeted this subsite with hydrophilic substituents such as amines and guanidines. Inhibitor-bound crystal structures revealed that hydrophobic substituents with sp(2) hybridization could achieve optimal interactions by virtue of a low-energy binding conformation and favorable pi-stacking interactions with the residue Glu119. From a lead methyl ester, investigation of five-membered heteroaromatic substituents at C-4 produced a 3-pyrazolyl analogue that improved activity by making a targeted hydrogen bond with Trp178. The SAR of substituted vinyl substituents at C-4 produced a Z-propenyl analogue with improved activity over the lead methyl ester. The C-1 ethyl ester prodrugs of the substituted C-4 vinyl analogues gave compounds with excellent oral bioavailability (F > 60%) when dosed in rat.