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Two moderately lipophilic, high affinity ligands for metabotropic glutamate receptor subtype 1 (mGluR1) were radiolabeled with a positron-emitting radioisotope and evaluated in rhesus monkey as potential PET tracers. Both ligands were radiolabeled with fluorine-18 via nucleophilic displacement of the corresponding 2-chloropyridine precursor with [18F]potassium fluoride. [18F]MK-1312 was found to have a suitable signal for quantification of mGluR1 receptors in nonhuman primates and was more thoroughly characterized. In vitro autoradiographic studies with [18F]MK-1312 in rhesus monkey and human brain tissue slices revealed an uptake distribution consistent with the known distribution of mGluR1, with the highest uptake in the cerebellum, moderate uptake in the hippocampus, thalamus, and cortical regions, and lowest uptake in the caudate and putamen. In vitro saturation binding studies in rhesus monkey and human cerebellum homogenates confirmed that [18F]MK-1312 binds to a single site with a Bmax/Kd ratio of 132 and 98, respectively. PET studies in rhesus monkey with [18F]MK-1312 showed high brain uptake and a regional distribution consistent with in vitro autoradiography results. Blockade of [18F]MK-1312 uptake with mGluR1 allosteric antagonist MK-5435 dose-dependently reduced tracer uptake in all regions of gray matter to a similarly low level of tracer uptake. This revealed a large specific signal useful for determination of mGluR1 receptor occupancy in rhesus monkey. Taken together, these results are promising for clinical PET studies with [18F]MK-1312 to determine mGluR1 occupancy of MK-5435. Synapse 2011. © 2010 Wiley-Liss, Inc.

Radiolabeled juvenile hormone (JHs) and labeled JH derivatives are required for the study of JH metabolism and JH-protein interactions as well as JH radioimmunoassay in insects. The progress in the synthesis of these labeled compounds for the last five years is reviewed, including the preparation of photoaffinity labels, enantiomerically enriched JH I and JH II with 3H labels, and radioiodinated analogs of JH I, methoprene and phenoxyphenyl ether insect growth regulators (IGRs). Experimental details are given for the efficient synthesis of two 3H-labeled photoactivatable JH analogs, EFDA and EFTP, their photolysis in methanol, and their competitive binding assays performed on the Manduca sexta JH binding proteins (JHBP).

alpha5IA (3-(5-methylisoxazol-3-yl)-6-[(1-methyl-1,2,3-triazol-4-yl)methyloxy]-1,2,4-triazolo[3,4-a]phthalazine) is a triazolophthalazine with subnanomolar affinity for alpha1-, alpha2-, alpha3- and alpha5-containing GABA(A) receptors. Here we have evaluated the relationship between plasma alpha5IA concentrations and benzodiazepine binding site occupancy in rodents and primates (rhesus monkey).In awake rats, occupancy was measured at various times after oral dosing with alpha5IA (0.03-30 mgxkg(-1)) using an in vivo {[(3)H]flumazenil (8-fluoro 5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5-a][1,4]benzodiazepine-3-carboxylic acid ethyl ester)} binding assay. In anaesthetized rhesus monkeys, occupancy was measured using {[(123)I]iomazenil (ethyl 5,6-dihydro-7-iodo-5-methyl-6-oxo-4H-imidazo[1,5-a][1,4]benzodiazepine-3-carboxylic acid ethyl ester)} gamma-scintigraphy and a bolus/infusion paradigm. In both rat and rhesus monkey, the plasma drug concentration corresponding to 50% occupancy (EC(50)) was calculated.In rats, alpha5IA occupancy was dose- and time-dependent with maximum occupancy occurring within the first 2 h. However, rat plasma EC(50) was time-independent, ranging from 42 to 67 ngxmL(-1) over a 24 h time course with the average being 52 ngxmL(-1) (i.e. occupancy decreased as plasma drug concentrations fell). In rhesus monkeys, the EC(50) for alpha5IA displacing steady-state [(123)I]iomazenil binding was 57 ngxmL(-1).Rat plasma EC(50) values did not vary as a function of time indicating that alpha5IA dissociates readily for the GABA(A) receptor in vivo. These data also suggest that despite the different assays used (terminal assays of [(3)H]flumazenil in vivo binding in rats and [(123)I]iomazenil gamma-scintigraphy in anaesthetized rhesus monkeys), these techniques produced similar plasma alpha5IA EC(50) values (52 and 57 ngxmL(-1) respectively) and that the plasma-occupancy relationship for alpha5IA translates across these two species.

The synthesis of three tritiated reverse transcriptase inhibitors is described herein. These compounds contained the benzoxazole ring linked to a 2-pyridinone ring by an aminomethylene group. The tritiated compounds were synthesized by hydrogenolysis of bromobenzoxazole precursors. The final tritiated compounds had specific activities ranging from 3-10 Ci/mmol.

6-[C 3 H 3 ]-Dorzolamide£# was prepared starting from N,N'-bis-Boc-6-desmethyldorzolamide. An efficient radiosynthesis was developed involving a regioselective and stereo-controlled 3 H-methylation of the α-sulfone carbanion in the presence of the monoprotected sulfonamide anion. The methylation led to a mixture (ca. 7 : 1 for 4S,6R : 4S,6S) of the diastereomeric, tritiated products. Removal of the Boc protecting groups followed by HPLC purification of the resulting diastereomers afforded 6-[C 3 H 3 ]-dorzolamide with > 99 % radiochemical purity, > 98.4 % enantiomeric excess, and a specific activity of > 74 Ci/mmol.

Aberrant smooth muscle cell (SMC) growth within the intimal tissues of the arterial wall plays a major role in the development of restenosis which commonly occurs following coronary bolloon angioplasty. Studies from several laboratories have demonstrated that heparin reduced neointimal formation in response to balloon denudation in vivo and that heparin also inhibits the growth and migration of cultured SMC in vitro. In this paper, data will be presented demonstrating that heparin markedly inhibits neointimal thickening and bromodexyuridine incorporation into newly synthesized DNA in a fully characterized rat model of arterial injury. Heparin treatment begun at the time of angioplasty and continued for as little as 2–4 days resulted in substantial inhibiton of neointimal formation 14 days later. The relevance of the rat model to human restenosis and the positive and negative aspects concerning the use of heparin and heparin-like molecules for the treatment of vascular restenosis will be discussed. In addition, we will show that heparin recognizes specific binding sites on the surface of cultured aortic SMC which is a feature possibly associated with the anti-proliferative mechanism of action of heparin. Finally, a highly sulfated cyclic polysaccharide, β-cyclodextrin tetradecasulfate (S-β-CD), was found to significantly inhibit neointimal formation in the rat model of arterial injury. S-β-CD retains several positive aspects but lacks some of the negative features associated with the chronic use of heparin for the treatment of vascular restenosis. © 1993 Wiley-Liss, Inc.

Enantiomerically enriched (≥92% e.e.) tritium-labelled diazoacetate photoaffinity analogs EBDA and EHDA (each 58 Ci/mmol) and EFDA (14 Ci/mmol) were prepared from the corresponding tritiated juvenile hormone (JH) homologs JH I, JH II, and JH III in two steps. Selective reduction of the ester group and subsequent acylation gave the target compounds.

A new asymmetric synthesis of natural JH III from methyl farnesoate allows introduction of tritium from sodium borotritide into the 12-methyl group. Selective allylic oxidation followed by Sharpless epoxidation of the (E)-allylic alcohol gives an epoxy alcohol (>97% e.e.), which is oxidized to the aldehyde. Sodium borotritide (65 Ci/mmol) reduction of the aldehyde is followed by tosylation, iodide displacement, and cyanoborohydride displacement to give [3H]-(10R)-JH III, specific activity 14 Ci/mmol.