Daniel D. Sternbach

A selective peroxisome proliferator-activated receptor δ agonist promotes reverse cholesterol transport

The peroxisome proliferator-activated receptors (PPARs) are dietary lipid sensors that regulate fatty acid and carbohydrate metabolism. The hypolipidemic effects of the fibrate drugs and the antidiabetic effects of the glitazone drugs in humans are due to activation of the α (NR1C1) and γ (NR1C3) subtypes, respectively. By contrast, the therapeutic potential of the δ (NR1C2) subtype is unknown, due in part to the lack of selective ligands. We have used combinatorial chemistry and structure-based drug design to develop a potent and subtype-selective PPARδ agonist, GW501516. In macrophages, fibroblasts, and intestinal cells, GW501516 increases expression of the reverse cholesterol transporter ATP-binding cassette A1 and induces apolipoprotein A1-specific cholesterol efflux. When dosed to insulin-resistant middle-aged obese rhesus monkeys, GW501516 causes a dramatic dose-dependent rise in serum high density lipoprotein cholesterol while lowering the levels of small-dense low density lipoprotein, fasting triglycerides, and fasting insulin. Our results suggest that PPARδ agonists may be effective drugs to increase reverse cholesterol transport and decrease cardiovascular disease associated with the metabolic syndrome X.

Molecular recognition of fatty acids by peroxisome proliferator-activated receptors.

The peroxisome proliferator-activated receptors (PPARs) are nuclear receptors for fatty acids (FAs) that regulate glucose and lipid homeostasis. We report the crystal structure of the PPAR delta ligand-binding domain (LBD) bound to either the FA eicosapentaenoic acid (EPA) or the synthetic fibrate GW2433. The carboxylic acids of EPA and GW2433 interact directly with the activation function 2 (AF-2) helix. The hydrophobic tail of EPA adopts two distinct conformations within the large hydrophobic cavity. GW2433 occupies essentially the same space as EPA bound in both conformations. These structures provide molecular insight into the propensity for PPARs to interact with a variety of synthetic and natural compounds, including FAs that vary in both chain length and degree of saturation.

Novel selective small molecule agonists for peroxisome proliferator-activated receptor δ (PPARδ) - Synthesis and biological activity

Abstract We report the synthesis and biological activity of a new series of small molecule agonists of the human Peroxisome Proliferator-Activated Receptor δ (PPARδ). Several hits were identified from our original libraries containing lipophilic carboxylic acids. Optimization of these hits by structure-guided design led to 7k (GW501516) and 7l (GW0742), which shows an EC50 of 1.1 nM against PPARδ with 1000-fold selectivity over the other human subtypes.

Identification of peroxisome proliferator-activated receptor ligands from a biased chemical library

BACKGROUND The peroxisome proliferator-activated receptors (PPARs) were cloned as orphan members of the nuclear receptor superfamily of transcription factors. The identification of subtype-selective ligands for PPARalpha and PPARgamma has led to the discovery of their roles in the regulation of lipid metabolism and glucose homeostasis. No subtype-selective PPARdelta ligands are available and the function of this subtype is currently unknown. RESULTS A three-component library was designed in which one of the monomers was biased towards the PPARs and the other two monomers were chosen to add chemical diversity. Synthesis and screening of the library resulted in the identification of pools with activity on each of the PPAR subtypes. Deconvolution of the pools with the highest activity on PPARdelta led to the identification of GW 2433 as the first high-affinity PPARdelta ligand. [3H]GW 2433 is an effective radioligand for use in PPARdelta competition-binding assays. CONCLUSIONS The synthesis of biased chemical libraries is an efficient approach to the identification of lead molecules for members of sequence-related receptor families. This approach is well suited to the discovery of small-molecule ligands for orphan receptors.

Identification of a series of PPARγ/δ dual agonists via solid-Phase parallel synthesis

We have developed a general solid-phase synthesis for identification of PPAR ligands. Synthesis of a 480-member library led to the identification of a potent PPAR gamma/delta dual agonist 23. Compound 23 showed good plasma exposure in rats and demonstrated antihyperglycemic and antihyperlipidemic efficacy in diabetic fatty Zucker rats.

Synthesis and biological activity of l-tyrosine-based PPARγ agonists with reduced molecular weight

A series of PPARgamma agonists were synthesized from L-tyrosine that incorporated low molecular weight N-substituents. The most potent analogue, pyrrole (4e), demonstrated a K(i) of 6.9nM and an EC(50) of 4.7nM in PPARgamma binding and functional assays, respectively. Pyrrole (4e), which is readily synthesized from L-tyrosine methyl ester in four steps, also demonstrated in vivo activity in a rodent model of Type 2 diabetes.

Identification of a series of oxadiazole-substituted α-isopropoxy phenylpropanoic acids with activity on PPARα, PPARγ, and PPARδ

A series of oxadiazole-substituted α-isopropoxy phenylpropanoic acids with dual agonist activity on PPARα and PPARγ is described. Several of these compounds also showed partial agonist activity on PPARδ. Resolution of one analogue showed that PPARα and PPARγ activity resided in mainly one enantiomer, whereas PPARδ activity was retained in both enantiomers.

A novel deprotection/functionalisation sequence using 2,4-dinitrobenzenesulfonamide: Part 1

Treatment of R1R2SO2C6H3(NO2)2-2,4 [R1 = 4-MeOC6H4CH2, R2 = H, CH2CH2OMe, allyl; R1 = 3,4-methylenedioxyphenyl, R2 = H, CH2CH2OMe] with R3COSH [R3 = Me, Ph, CF3, CMe3, 2-imidazolyl] in the presence of cesium carbonate gave R1R2NCOR3 in 81-96% yield.

The formation of a covalent complex between a dipeptide ligand and the src SH2 domain.

The X-ray crystal structure of the src SH2 domain revealed the presence of a thiol residue (Cys 188) located proximal to the phosphotyrosine portion of a dipeptide ligand. An aldehyde bearing ligand (1) was designed to position an electrophilic carbonyl group in the vicinity of the thiol. X-ray crystallographic and NMR examination of the complex formed between (1) and the src SH2 domain revealed a hemithioacetal formed by addition of the thiol to the aldehyde group with an additional stabilizing hydrogen bond between the acetal hydroxyl and a backbone carbonyl.

Novel A-ring modified camptothecins as topoisomerase I inhibitors

Abstract A camptothecin derivative has been prepared wherein the A-ring is fused to an oxazole ring. The compound was prepared via a Friedlander condensation involving benzoxazole 8 and tricyclic ketone 9 . This derivative displays potent topoisomerase I inhibition (IC 50 150 nM) when assayed in the ‘cleavable complex’ assay.