Synthesis and in vitro characterization of novel amino terminally modified oxotremorine derivatives for brain muscarinic receptors.

A series of novel 2-substituted acetylenic pyrrolidines and piperidines related to oxotremorine (1) were prepared and evaluated in vitro as muscarinic cholinergic agents at brain M1 and M2 receptors. One analogue, 3-(2-oxo-1-pyrrolidinyl)-1-[2(R)-pyrrolidinyl]-1-propyne hydrogen oxalate (6a), was found to be a partial agonist producing a PI hydrolysis response at cortical M1 receptors approximately 3-fold larger than that produced by 1. The intrinsic activity profile of 6a at brain muscarinic receptors is similar to those of azetidine oxo analogue 2 and dimethylamino oxo analogue. All three compounds are partial M1 agonists and full M2 agonists; however, the profile of 6a in binding studies is significantly different. While 2 and 3 exhibit large M2 selectivities ranging between 8-fold to several hundred-fold, the binding profile of 6a shows almost no subtype selectivity.

3-(2-(3-Pyridinyl)thiazolidin-4-oyl)indoles, a novel series of platelet activating factor antagonists.

(2RS,4R)-3-(2-(3-Pyridinyl)thiazolidin-4-oyl)indoles represent a new class of potent, orally active antagonists of platelet activating factor (PAF). The compounds were prepared by acylation of the magnesium or zinc salts of substituted indoles with (2RS,4R)-2-(3-pyridinyl)-3-(tert-butoxycarbonyl)thiazolidin-4-oyl chloride. The 3-acylindole moiety functions as a hydrolytically stabilized and conformationally restricted anilide replacement, which imparts a considerable boost in potency to the series. Structure-activity relationships observed for substitution on the indole ring system are discussed. Members of the series compare favorably with other reported PAF antagonists.

Discovery, synthesis, and bioactivity of bis(heteroaryl)piperazines. 1. A novel class of non-nucleoside HIV-1 reverse transcriptase inhibitors.

A variety of analogues of 1-[4-methoxy-3,5-dimethylbenzyl]-4-[3-(ethylamino)-2-pyridyl]piperazine hydrochloride (U-80493E) were synthesized and evaluated for their inhibition of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT). Replacement of the substituted aryl moiety with various substituted indoles provided bis(heteroaryl)piperazines (BHAPs) that were 10-100-fold more potent than U-80493E. The pyridyl portion of the lead molecule was found to be very sensitive to modifications. Extensive preclinical evaluations of several of these compounds led to the selection of 1-[(5-methoxyindol-2-yl)carbonyl]-4-[3-(ethylamino)-2- pyridyl]piperazine methanesulfonate (U-87201E, atevirdine mesylate) for clinical evaluation.

Synthesis and structure-activity relationships of the (alkylamino)piperidine-containing BHAP class of non-nucleoside reverse transcriptase inhibitors: effect of 3-alkylpyridine ring substitution.

Development of resistance to currently approved HIV therapies has continued to fuel research efforts to improve the metabolic stability and spectrum of activity of the (alkylamino)piperidine-containing bis(heteroaryl)piperazine (AAP-BHAP) class of non-nucleoside reverse transcriptase inhibitors (NNRTIs). The synthesis of analogues in which the usual 3-alkylamino substituent on the pyridine ring is replaced by a 3-alkyl substituent led to compounds which retained activity against recombinant P236L and wild-type (WT) reverse transcriptase (RT), while inhibition of the Y181C mutant RT was reduced relative to the activity of the 3-alkylamino-substituted congeners. Testing of representative analogues in an in vitro liver microsome assay indicated that the alkyl substituent would not appreciably improve the metabolic stability of the AAP-BHAP template. In vivo pharmacokinetic evaluation of three compounds confirmed these results in that high systemic clearances were observed. Nevertheless, one compound (13), PNU-103657, possessed oral bioavailability in rats approaching that of the structurally related NNRTI drug delavirdine which is currently on the market for the treatment of HIV infection.

Synthesis and biological activity of aminoguanidine and diaminoguanidine analogues of the antidiabetic/antiobesity agent 3-guanidinopropionic acid.

3-Guanidinopropionic acid (1) has been demonstrated both to improve insulin sensitivity and to promote weight loss selectively from adipose tissue in animal models of non-insulin-dependent diabetes mellitus (NIDDM). However, 1 has also been shown to be a substrate for both the creatine transporter and creatine kinase, leading to marked accumulation in muscle tissue as the corresponding N-phosphate. The corresponding aminoguanidine analogue 2 was recently discovered to retain the antidiabetic activity of 1 while being markedly less susceptible to creatine-like metabolism, suggesting that it should have less potential to accumulate in muscle. Further structural modification of 2 was undertaken to investigate whether the antidiabetic potency could be augmented while maintaining resistance to creatine-like metabolism. Modifications such as alpha-alkylation, homologation, and bioisosteric replacement of the aminoguanidine all were detrimental to antidiabetic activity. However, the simple regioisomeric aminoguanidinoacetic acid 9 and diaminoguanidinoacetic acid analogue 7 were found to be equipotent to 2, leading eventually to the discovery of the significantly more potent diaminoguanidinoacetic acid regioisomers 52 and 53. Further attempts to modify the more active template represented by 52 led only to reductions in antidiabetic activity. Each of the new active analogues displayed the same resistance to creatine-like metabolism as 2. Further testing of 7, 9, and 53 in obese diabetic ob/ob mice confirmed that weight loss is induced selectively from adipose tissue, similar to the lead 1. Administration of 53 to insulin-resistant rhesus monkeys led to reductions in both fasting and post-prandial plasma glucose levels with concomitant reductions in plasma insulin levels, suggesting that the compound improved the action of endogenous insulin. Compounds 7 and 53 were selected for further preclinical development.

Synthesis and biological activity of analogues of the antidiabetic/antiobesity agent 3-guanidinopropionic acid: discovery of a novel aminoguanidinoacetic acid antidiabetic agent.

3-Guanidinopropionic acid (1, PNU-10483) has been demonstrated to both improve insulin sensitivity and to promote weight loss selectively from adipose tissue in animal models of non-insulin-dependent diabetes mellitus (NIDDM). However, 1 has also been shown to be a substrate for both the creatine transporter and creatine kinase, leading to marked accumulation in muscle tissue as the corresponding N-phosphate 4. In an effort to identify novel entities that maintain antidiabetic potency without susceptibility to creatine-like metabolism, an analogue program was undertaken to explore the effects of various structural modifications, including homologation, simple substitution, single atom mutations, and bioisosteric replacements for the guanidine and carboxylic acid. Overall, the scope of activity encompassed by the set of new analogues proved to be exceedingly narrow. Notable exceptions demonstrating equivalent or improved antidiabetic activity included the alpha-amino derivative 29, aminopyridine 47, isothiourea 67, and aminoguanidine 69. On the basis of its superior therapeutic ratio, aminoguanidine 69 was selected for preclinical development and became the foundation for a second phase of analogue work. Furthermore, in vitro studies demonstrated that 69 is markedly less susceptible to phosphorylation by creatine kinase than the lead 1, suggesting that it should have less potential for accumulation in muscle tissue than 1.

A syndrome of anaemia, immunodeficiency and peripheral ganglionopathy in Fell pony foals.

Fell pony foals developed a syndrome of anaemia, immunodeficiency and peripheral ganglionopathy. They became ill in the second or third week, and died in the second or third month of life. Clinical and pathological investigations revealed severe anaemia associated with small numbers of late erythroid precursors in bone marrow, small thymi, an absence of secondary lymphoid follicles, a lack of plasma cells and neuronal chromatolysis involving trigeminal, cranial mesenteric and dorsal root ganglia. Some of the foals had cryptosporidial enteritis and adenoviral bronchopneumonia and pancreatitis. The clinical and pathological findings were compatible with an intrinsic defect.

Maxillofacial prostheses of chlorinated polyethylene.

There is clearly a need for maxillofacial prosthetic materials with improved properties. The chlorinated polyethylenes are thermoplastic elastomers which have particularly promising properties, and were used by us to prepare improved maxillofacial prostheses. Suitable CPE resins were compounded with other polymers and with pigments on a heated rubber mill to form thin sheets in a variety of shades. These were heated at 190 degrees C for 10 min and placed between heated linotype mold halves. The prosthesis was formed in a hand press. Sometimes heating and pressing were repeated. After cooling in water, the prosthesis was removed and hand-shaded with oil-soluble dyes. Physical properties were evaluated using standard techniques; skin irritation studies were conducted by 14-day insult patch tests on rabbits. Clinical evaluations were conducted on human volunteers. Parallel evaluations were conducted on commerically available materials for comparison. The CPE was superior to all of the three commerical materials in most properties, and comparable to the better of the three in the remaining properties. On balance, CPE was significantly superior. Early results indicate that the materials and techniques required are easily handled in the dental lab and that the final prosthesis has excellent aesthetic and patient acceptability.

Small molecule peptidomimetics containing a novel phosphotyrosine bioisostere inhibit protein tyrosine phosphatase 1B and augment insulin action.

Protein tyrosine phosphatase 1B (PTP1B) attenuates insulin signaling by catalyzing dephosphorylation of insulin receptors (IR) and is an attractive target of potential new drugs for treating the insulin resistance that is central to type II diabetes. Several analogues of cholecystokinin(26)(-)(33) (CCK-8) were found to be surprisingly potent inhibitors of PTP1B, and a common N-terminal tripeptide, N-acetyl-Asp-Tyr(SO(3)H)-Nle-, was shown to be necessary and sufficient for inhibition. This tripeptide was modified to reduce size and peptide character, and to replace the metabolically unstable sulfotyrosyl group. This led to the discovery of a novel phosphotyrosine bioisostere, 2-carboxymethoxybenzoic acid, and to analogues that were >100-fold more potent than the CCK-8 analogues and >10-fold selective for PTP1B over two other PTP enzymes (LAR and SHP-2), a dual specificity phosphatase (cdc25b), and a serine/threonine phosphatase (calcineurin). These inhibitors disrupted the binding of PTP1B to activated IR in vitro and prevented the loss of tyrosine kinase (IRTK) activity that accompanied PTP1B-catalyzed dephosphorylation of IR. Introduction of these poorly cell permeant inhibitors into insulin-treated cells by microinjection (oocytes) or by esterification to more lipophilic proinhibitors (3T3-L1 adipocytes and L6 myocytes) resulted in increased potency, but not efficacy, of insulin. In some instances, PTP1B inhibitors were insulin-mimetic, suggesting that in unstimulated cells PTP1B may suppress basal IRTK activity. X-ray crystallography of PTP1B-inhibitor complexes revealed that binding of an inhibitor incorporating phenyl-O-malonic acid as a phosphotyrosine bioisostere occurred with the mobile WPD loop in the open conformation, while a closely related inhibitor with a 2-carboxymethoxybenzoic acid bioisostere bound with the WPD loop closed, perhaps accounting for its superior potency. These CCK-derived peptidomimetic inhibitors of PTP1B represent a novel template for further development of potent, selective inhibitors, and their cell activity further justifies the selection of PTP1B as a therapeutic target.