A Menin-MLL Inhibitor Induces Specific Chromatin Changes and Eradicates Disease in Models of MLL-Rearranged Leukemia.

Inhibition of the Menin (MEN1) and MLL (MLL1, KMT2A) interaction is a potential therapeutic strategy for MLL-rearranged (MLL-r) leukemia. Structure-based design yielded the potent, highly selective, and orally bioavailable small-molecule inhibitor VTP50469. Cell lines carrying MLL rearrangements were selectively responsive to VTP50469. VTP50469 displaced Menin from protein complexes and inhibited chromatin occupancy of MLL at select genes. Loss of MLL binding led to changes in gene expression, differentiation, and apoptosis. Patient-derived xenograft (PDX) models derived from patients with either MLL-r acute myeloid leukemia or MLL-r acute lymphoblastic leukemia (ALL) showed dramatic reductions of leukemia burden when treated with VTP50469. Multiple mice engrafted with MLL-r ALL remained disease free for more than 1 year after treatment. These data support rapid translation of this approach to clinical trials.

Discovery of BI 135585, an in vivo efficacious oxazinanone-based 11ß hydroxysteroid dehydrogenase type 1 inhibitor.

A potent, in vivo efficacious 11ß hydroxysteroid dehydrogenase type 1 (11ß HSD1) inhibitor (11j) has been identified. Compound 11j inhibited 11ß HSD1 activity in human adipocytes with an IC50 of 4.3nM and in primary human adipose tissue with an IC80 of 53nM. Oral administration of 11j to cynomolgus monkey inhibited 11ß HSD1 activity in adipose tissue. Compound 11j exhibited >1000× selectivity over other hydroxysteroid dehydrogenases, displays desirable pharmacodynamic properties and entered human clinical trials in 2011.

Brain penetrant liver X receptor (LXR) modulators based on a 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazole core.

Liver X receptor (LXR) agonists have been reported to lower brain amyloid beta (Aß) and thus to have potential for the treatment of Alzheimer's disease. Structure and property based design led to the discovery of a series of orally bioavailable, brain penetrant LXR agonists. Oral administration of compound 18 to rats resulted in significant upregulation of the expression of the LXR target gene ABCA1 in brain tissue, but no significant effect on Aß levels was detected.

Discovery of a Novel, Orally Efficacious Liver X Receptor (LXR) ß Agonist.

This article describes the application of Contour to the design and discovery of a novel, potent, orally efficacious liver X receptor ß (LXRß) agonist (17). Contour technology is a structure-based drug design platform that generates molecules using a context perceptive growth algorithm guided by a contact sensitive scoring function. The growth engine uses binding site perception and programmable growth capability to create drug-like molecules by assembling fragments that naturally complement hydrophilic and hydrophobic features of the protein binding site. Starting with a crystal structure of LXRß and a docked 2-(methylsulfonyl)benzyl alcohol fragment (6), Contour was used to design agonists containing a piperazine core. Compound 17 binds to LXRß with high affinity and to LXRα to a lesser extent, and induces the expression of LXR target genes in vitro and in vivo. This molecule served as a starting point for further optimization and generation of a candidate which is currently in human clinical trials for treating atopic dermatitis.

Identification of spirooxindole and dibenzoxazepine motifs as potent mineralocorticoid receptor antagonists.

Mineralocorticoid receptor (MR) antagonists continue to be a prevalent area of research in the pharmaceutical industry. Herein we report the discovery of various spirooxindole and dibenzoxazepine constructs as potent MR antagonists. SAR analysis of our spirooxindole hit led to highly potent compounds containing polar solubilizing groups, which interact with the helix-11 region of the MR ligand binding domain (LBD). Various dibenzoxazepine moieties were also prepared in an effort to replace a known dibenzoxepane system which interacts with the hydrophobic region of the MR LBD. In addition, an X-ray crystal structure was obtained from a highly potent compound which was shown to exhibit both partial agonist and antagonist modes of action against MR.

Structure-based design of ß-site APP cleaving enzyme 1 (BACE1) inhibitors for the treatment of Alzheimer's disease.

The amyloid hypothesis asserts that excess production or reduced clearance of the amyloid-ß (Aß) peptides in the brain initiates a sequence of events that ultimately lead to Alzheimer's disease and dementia. The Aß hypothesis has identified BACE1 as a therapeutic target to treat Alzheimer's and led to medicinal chemistry efforts to design its inhibitors both in the pharmaceutical industry and in academia. This review summarizes two distinct categories of inhibitors designed based on conformational states of "closed" and "open" forms of the enzyme. In each category the inhibitors are classified based on the core catalytic interaction group or the aspartyl binding motif (ABM). This review covers the description of inhibitors in each ABM class with X-ray crystal structures of key compounds, their binding modes, related structure-activity data highlighting potency advances, and additional properties such as selectivity profile, P-gp efflux, pharmacokinetic, and pharmacodynamic data.

New renin inhibitor VTP-27999 alters renin immunoreactivity and does not unfold prorenin.

Renin inhibitors like aliskiren not only block renin but also bind prorenin, thereby inducing a conformational change (like the change induced by acid) allowing its recognition in a renin-specific assay. Consequently, aliskiren can be used to measure prorenin. VTP-27999 is a new renin inhibitor with an aliskiren-like IC50 and t1/2, and a much higher bioavailability. This study addressed (pro)renin changes during treatment of volunteers with VTP-27999 or aliskiren. Both drugs increased renin immunoreactivity. Treatment of plasma samples from aliskiren-treated subjects with excess aliskiren yielded higher renin immunoreactivity levels, confirming the presence of prorenin. Unexpectedly, this approach did not work in VTP-27999-treated subjects, although an assay detecting the prosegment revealed that their blood still contained prorenin. Subsequent in vitro analysis showed that VTP-27999 increased renin immunoreactivity for a given amount of renin by ≥ 30% but did not unfold prorenin. Yet, it did bind to acid-activated, intact prorenin and then again increased immunoreactivity in a renin assay. However, no such increase in immunoreactivity was seen when measuring acid-activated prorenin bound to VTP-27999 with a prosegment-directed assay. The VTP-27999-induced rises in renin immunoreactivity could be competitively prevented by aliskiren, and antibody displacement studies revealed a higher affinity of the active site-directed antibodies in the presence of VTP-27999. In conclusion, VTP-27999 increases renin immunoreactivity in renin immunoassays because it affects the affinity of the active site-directed antibody. Combined with its lack of effect on prorenin, these data show that VTP-27999 differs from aliskiren. The clinical relevance of these results needs to be established.

Regulation of sphingomyelin phosphodiesterase acid-like 3A gene (SMPDL3A) by liver X receptors.

Liver X receptor (LXR) α and LXRß function as physiological sensors of cholesterol metabolites (oxysterols), regulating key genes involved in cholesterol and lipid metabolism. LXRs have been extensively studied in both human and rodent cell systems, revealing their potential therapeutic value in the contexts of atherosclerosis and inflammatory diseases. The LXR genome landscape has been investigated in murine macrophages but not in human THP-1 cells, which represent one of the frequently used monocyte/macrophage cell systems to study immune responses. We used a whole-genome screen to detect direct LXR target genes in THP-1 cells treated with two widely used LXR ligands [N-(2,2,2-trifluoroethyl)-N-[4-[2,2,2-trifluoro-1-hydroxy-1-(trifluoromethyl)-ethyl]phenyl]-benzenesulfonamide (T0901317) and 3-[3-[N-(2-chloro-3-trifluoromethylbenzyl)-(2,2-diphenylethyl)amino]propyloxy] phenylacetic acid hydrochloride (GW3965)]. This screen identified the sphingomyelin phosphodiesterase acid-like 3A (SMPDL3A) gene as a novel LXR-regulated gene, with an LXR response element within its promoter. We investigated the regulation of SMPDL3A gene expression by LXRs across several human and mouse cell types. These studies indicate that the induction of SMPDL3A is LXR-dependent and is restricted to human blood cells with no induction observed in mouse cellular systems.

Benzimidazolones: a new class of selective peroxisome proliferator-activated receptor γ (PPARγ) modulators.

A series of benzimidazolone carboxylic acids and oxazolidinediones were designed and synthesized in search of selective PPARγ modulators (SPPARγMs) as potential therapeutic agents for the treatment of type II diabetes mellitus (T2DM) with improved safety profiles relative to rosiglitazone and pioglitazone, the currently marketed PPARγ full agonist drugs. Structure-activity relationships of these potent and highly selective SPPARγMs were studied with a focus on their unique profiles as partial agonists or modulators. A variety of methods, such as X-ray crystallographic analysis, PPARγ transactivation coactivator profiling, gene expression profiling, and mutagenesis studies, were employed to reveal the differential interactions of these new analogues with PPARγ receptor in comparison to full agonists. In rodent models of T2DM, benzimidazolone analogues such as (5R)-5-(3-{[3-(5-methoxybenzisoxazol-3-yl)benzimidazol-1-yl]methyl}phenyl)-5-methyloxazolidinedione (51) demonstrated efficacy equivalent to that of rosiglitazone. Side effects, such as fluid retention and heart weight gain associated with PPARγ full agonists, were diminished with 51 in comparison to rosiglitazone based on studies in two independent animal models.

Biphenyl/diphenyl ether renin inhibitors: filling the S1 pocket of renin via the S3 pocket.

Structure-based design led to the discovery of a novel class of renin inhibitors in which an unprecedented phenyl ring filling the S1 site is attached to the phenyl ring filling the S3 pocket. Optimization for several parameters including potency in the presence of human plasma, selectivity against CYP3A4 inhibition and improved rat oral bioavailability led to the identification of 8d which demonstrated antihypertensive efficacy in a transgenic rat model of human hypertension.

Structure-based design and synthesis of 1,3-oxazinan-2-one inhibitors of 11ß-hydroxysteroid dehydrogenase type 1.

Structure based design led directly to 1,3-oxazinan-2-one 9a with an IC(50) of 42 nM against 11ß-HSD1 in vitro. Optimization of 9a for improved in vitro enzymatic and cellular potency afforded 25f with IC(50) values of 0.8 nM for the enzyme and 2.5 nM in adipocytes. In addition, 25f has 94% oral bioavailability in rat and >1000× selectivity over 11ß-HSD2. In mice, 25f was distributed to the target tissues, liver, and adipose, and in cynomolgus monkeys a 10 mg/kg oral dose reduced cortisol production by 85% following a cortisone challenge.

Discovery of VTP-27999, an Alkyl Amine Renin Inhibitor with Potential for Clinical Utility.

Structure guided optimization of a series of nonpeptidic alkyl amine renin inhibitors allowed the rational incorporation of additional polar functionality. Replacement of the cyclohexylmethyl group occupying the S1 pocket with a (R)-(tetrahydropyran-3-yl)methyl group and utilization of a different attachment point led to the identification of clinical candidate 9. This compound demonstrated excellent selectivity over related and unrelated off-targets, >15% oral bioavailability in three species, oral efficacy in a double transgenic rat model of hypertension, and good exposure in humans.

Discovery and optimization of adamantyl carbamate inhibitors of 11ß-HSD1.

Synthesis of 2-adamantyl carbamate derivatives of piperidines and pyrrolidines led to the discovery of 9a with an IC(50) of 15.2 nM against human 11ß-HSD1 in adipocytes. Optimization for increased adipocyte potency, metabolic stability and selectivity afforded 11k and 11l, both of which were >25% orally bioavailable in rat.

Spirocyclic ureas: orally bioavailable 11 beta-HSD1 inhibitors identified by computer-aided drug design.

Structure-guided drug design led to the identification of a class of spirocyclic ureas which potently inhibit human 11beta-HSD1 in vitro. Lead compound 10j was shown to be orally bioavailable in three species, distributed into adipose tissue in the mouse, and its (R) isomer 10j2 was efficacious in a primate pharmacodynamic model.

Optimization of orally bioavailable alkyl amine renin inhibitors.

Structure-guided drug design led to new alkylamine renin inhibitors with improved in vitro and in vivo potency. Lead compound 21a, has an IC(50) of 0.83nM for the inhibition of human renin in plasma (PRA). Oral administration of 21a at 10mg/kg resulted in >20h reduction of blood pressure in a double transgenic rat model of hypertension.

The differential interactions of peroxisome proliferator-activated receptor gamma ligands with Tyr473 is a physical basis for their unique biological activities.

Despite their proven antidiabetic efficacy, widespread use of peroxisome proliferator-activated receptor (PPAR)gamma agonists has been limited by adverse cardiovascular effects. To overcome this shortcoming, selective PPARgamma modulators (SPPARgammaMs) have been identified that have antidiabetic efficacy comparable with full agonists with improved tolerability in preclinical species. The results of structural studies support the proposition that SPPARgammaMs interact with PPARgamma differently from full agonists, thereby providing a physical basis for their novel activities. Herein, we describe a novel PPARgamma ligand, SPPARgammaM2. This compound was a partial agonist in a cell-based transcriptional activity assay, with diminished adipogenic activity and an attenuated gene signature in cultured human adipocytes. X-ray cocrystallography studies demonstrated that, unlike rosiglitazone, SPPARgammaM2 did not interact with the Tyr473 residue located within helix 12 of the ligand binding domain (LBD). Instead, SPPARgammaM2 was found to bind to and activate human PPARgamma in which the Tyr473 residue had been mutated to alanine (hPPARgammaY473A), with potencies similar to those observed with the wild-type receptor (hPPARgammaWT). In additional studies, we found that the intrinsic binding and functional potencies of structurally distinct SPPARgammaMs were not diminished by the Y473A mutation, whereas those of various thiazolidinedione (TZD) and non-TZD PPARgamma full agonists were reduced in a correlative manner. These results directly demonstrate the important role of Tyr473 in mediating the interaction of full agonists but not SPPARgammaMs with the PPARgamma LBD, thereby providing a precise molecular determinant for their differing pharmacologies.

Expression, purification and crystallization of human 5-lipoxygenase-activating protein with leukotriene-biosynthesis inhibitors.

The nuclear membrane protein 5-lipoxygenase-activating protein (FLAP) plays an essential role in leukotriene synthesis. Recombinant full-length human FLAP with a C-terminal hexahistidine tag has been expressed and purified from the cytoplasmic membrane of Escherichia coli. Diffraction-quality crystals of FLAP in complex with leukotriene-synthesis inhibitor MK-591 and with an iodinated analogue of MK-591 have been grown using the sitting-drop vapor-diffusion method. The crystals exhibit tetragonal symmetry (P42(1)2) and diffracted to a resolution limit of 4 A.

Crystal structure of inhibitor-bound human 5-lipoxygenase-activating protein.

Leukotrienes are proinflammatory products of arachidonic acid oxidation by 5-lipoxygenase that have been shown to be involved in respiratory and cardiovascular diseases. The integral membrane protein FLAP is essential for leukotriene biosynthesis. We describe the x-ray crystal structures of human FLAP in complex with two leukotriene biosynthesis inhibitors at 4.0 and 4.2 angstrom resolution, respectively. The structures show that inhibitors bind in membrane-embedded pockets of FLAP, which suggests how these inhibitors prevent arachidonic acid from binding to FLAP and subsequently being transferred to 5-lipoxygenase, thereby preventing leukotriene biosynthesis. This structural information provides a platform for the development of therapeutics for respiratory and cardiovascular diseases.

Design and synthesis of alpha-aryloxyphenylacetic acid derivatives: a novel class of PPARalpha/gamma dual agonists with potent antihyperglycemic and lipid modulating activity.

The synthesis and structure-activity relationships of novel series of alpha-aryloxyphenylacetic acids as PPARalpha/gamma dual agonists are reported. The initial search for surrogates of the ester group in the screen lead led first to the optimization of a subseries with a ketone moiety. Further efforts to modify the ketone subseries led to the design and synthesis of two new subseries containing fused heterocyclic ring systems. All these analogues were characterized by their "super" PPARalpha agonist activity and weak or partial agonist activity on PPARgamma in PPAR-GAL4 transactivation assays despite their similar binding affinities for both receptors. The cocrystal structures of compounds 7 and rosiglitazone with PPARgamma-LBD were compared, and significant differences were found in their interactions with the receptor. Select analogues in each subseries were further evaluated for in vivo efficacy. They all showed excellent anti-hyperglycemic efficacy in a db/db mouse model and hypolipidemic activity in hamster and dog models without provoking the typical PPARgamma-associated side effects in the rat tolerability assay.

Modeling aided design of potent glycogen phosphorylase inhibitors.

Molecular modeling has been used to assist in the development of a novel series of potent glycogen phosphorylase inhibitors based on a phenyl diacid lead, compound 1. In the absence of suitable competitive binding assays, compound 1 was predicted to bind at the AMP allosteric site based on superposition onto known inhibitors which bind at different sites in the enzyme and analyses of the surrounding protein environment associated with these distinct sites. Possible docking modes of compound 1 at the AMP allosteric site were further explored using the crystal structure of rabbit muscle glycogen phosphorylase complexed with a Bayer diacid compound W1807 (PDB entry 3AMV). Compound 1 was predicted to interact with positively charged arginines at the AMP allosteric site in the docking model. Characterization of the binding pocket by a grid-based surface calculation of the docking model revealed a large unfilled hydrophobic region near the central phenyl ring, suggesting that compounds with larger hydrophobic groups in this region would improve binding. A series of naphthyl diacid compounds were designed and synthesized to access this hydrophobic cleft, and showed significantly improved potency.