beta-Lactam derivatives as inhibitors of human cytomegalovirus protease.

The development of novel monobactam inhibitors of HCMV protease incorporating a carbon side chain at C-4 and a urea function at N-1 is described. Substitution with small groups at the C-3 position of the beta-lactam ring gave an increase in enzymatic activity and in stability; however, a lack of selectivity against other serine proteases was noted. The use of both tri- and tetrasubstituted urea functionalities gave effective inhibitors of HCMV protease. Benzyl substitution of the urea moiety was beneficial, especially when strong electron-withdrawing groups where attached at the para position. Modest antiviral activity was found in a plaque reduction assay.

Peptidomimetic inhibitors of the human cytomegalovirus protease.

The development of peptidomimetic inhibitors of the human cytomegalovirus (HCMV) protease showing sub-micromolar potency in an enzymatic assay is described. Selective substitution of the amino acid residues of these inhibitors led to the identification of tripeptide inhibitors showing improvements in inhibitor potency of 27-fold relative to inhibitor 39 based upon the natural tetrapeptide sequence. Small side chains at P1 were well tolerated by this enzyme, a fact consistent with previous observations. The S2 binding pocket of HCMV protease was very permissive, tolerating lipophilic and basic residues. The substitutions tried at P3 indicated that a small increase in inhibitor potency could be realized by the substitution of a tert-leucine residue for valine. Substitutions of the N-terminal capping group did not significantly affect inhibitor potency. Pentafluoroethyl ketones, alpha,alpha-difluoro-beta-keto amides, phosphonates and alpha-keto amides were all effective substitutions for the activated carbonyl component and gave inhibitors which were selective for HCMV protease. A slight increase in potency was observed by lengthening the P1' residue of the alpha-keto amide series of inhibitors. This position also tolerated a variety of groups making this a potential site for future modifications which could modulate the physicochemical properties of these molecules.

Potent beta-lactam inhibitors of human cytomegalovirus protease.

A series of novel monobactam inhibitors of human cytomegalovirus (HCMV) protease has been described that possess a heterocyclic thiomethyl side chain at C-4. Changes to the heterocycle did not significantly change the inhibitory activity of these compounds in an enzymatic assay, although improvements in solubility and cell culture activity were noted. A number of permutations between C-4 substitutions and N-1 derivatives led to the identification of several beta-lactams with antiviral activity in a plaque reduction assay. N-methyl thiotetrazole-containing compounds were found to be the most potent inhibitors in the enzymatic assay.

Fluid dynamics of the CarboMedics kinetic bileaflet prosthetic heart valve.

OBJECTIVE: To compare hydrodynamic characteristics of a new bileaflet heart valve, the CarboMedics kinetic cardiac valve prosthesis, with those of a St. Jude Medical (SJM) heart valve. METHODS: Hydrodynamic characteristics were determined in the mitral and aortic positions of a Vivitro Systems pulse duplicator for size 23 Kinetic aortic values, size 23 SJM aortic valves, size 29 Kinetic mitral valves and size 29 SJM mitral valves. Test conditions were 72 beats per min with cardiac outputs of 2, 5 and 7 l/min. Values of forward flow pressure drop (delta P), regurgitant and energy loss were determined for each valve. The test results for the two valve designs were compared by valve size. RESULTS: The test results show that both the size 23 and size 29 Kinetic valves have 8-14% lower delta P values and 5-10% greater effective orifice area (EOA) values. The size 29 Kinetic mitral valve has a 1-2 ml lower regurgitant volume, while the size 23 Kinetic aortic valve has a 0.5 ml greater regurgitant volume than the corresponding SJM values. These factors combine to provide a 5-10% lower energy loss for size 23 Kinetic aortic valves and a 15-25% lower energy loss for size 29 Kinetic mitral valves over the cardiac cycle than for corresponding sizes of SJM valves. CONCLUSIONS: The Kinetic valve's fluid dynamics are superior to equivalent sizes of SJM valves. This is especially impressive considering that the tissue annulus diameters for Kinetic valves are approximately 0.5 mm less than equivalent size SJM valves. The primary reasons for the superior hydrodynamic performance of Kinetic valves are (1) the larger orifices which result in lower forward flow delta P values and (2) the opening angles, which have been customized for each valve size to minimize energy loss.

Comparison of diazepam and flurazepam in the treatment of insomnia in general practice.

In a double-blind crossover study in general practice, flurazepam was shown to be significantly better (p less than 0.001) than diazepam in treating sleep disturbance. Fewer patients reported side-effects on flurazepam.

Diastereoselective synthesis of 2,3,5-trisubstituted tetrahydrofurans via cyclofunctionalization reactions. Evidence of stereoelectronic effects.

The work described herein considers the impact of stereoelectronic effects and allylic 1,3-strain in controlling the cyclofunctionalization reaction when a hydroxyl group is at the allylic position. The stereoelectronic arguments are supported by independent iodocyclization reactions performed using two secondary alcohols. The transition-state pathways involved in these reactions are established through a comparison of relative reaction rates. A bi-directional approach is used to demonstrate the potential of the iodocyclization reaction to differentiate a terminus in molecules with a pseudo C(2) axis of symmetry, showing that two-directional synthesis can be used to differentiate between alternative transition-state pathways.

Synthesis and antiviral activity of monobactams inhibiting the human cytomegalovirus protease.

A series of monobactam inhibitors of HCMV (N(o)) protease bearing a heterocycle linked by a methylene group at C-4 is described. Inhibitors containing a heterocycle such as a 2-furyl, 2-thiophenyl, 4-methyl-2-tetrazole and 2-benzothiazole were found to be active in a plaque reduction assay. Furthermore, 2-benzothiazole derivatives were shown to inhibit the HCMV protease activity inside cells by using a cell transfection assay, indicating that their antiviral activity in the plaque reduction assay could be attributed to protease inhibition.

Evidence of a conformational change in the human cytomegalovirus protease upon binding of peptidyl-activated carbonyl inhibitors.

A series of N-tert-butylacetyl-l-tert-butylglycyl-l-Ngamma, Ngamma-dimethylasparagyl-l-alanyl-derived inhibitors (trifluoromethyl ketone 1, pentafluoroethyl ketone, 2, methyl ketone 3, and alpha-ketoamide 4, with respective KI values of 1.1, 0.1, 2100, and 0.2 microM) of the human cytomegalovirus protease were used to study the effect of binding of peptidyl inhibitors on the intrinsic fluorescence and CD properties of the enzyme. In the presence of saturating concentrations of compounds 1, 2, and 4, an identical blue shift in the fluorescence maximum of the enzyme upon specific tryptophan excitation was observed relative to that of the free protease. In the case of the methyl ketone 3, whose inhibition of the enzyme does not involve formation of a covalent adduct as evidenced by 13C NMR studies of carbonyl-labeled inhibitors, the blue shift in the emission was also observed. For both compounds 1 and 2 which exhibit slow-binding kinetics, the observed rate constants for the slow onset of inhibition of substrate hydrolysis correlate well with the kobs values of the time-dependent change in the emission spectra. Studies employing a double mutant of HCMV protease Ala143Gln/Trp42Phe identified Trp-42 as the principal fluorescence reporter. Taken together with information provided by our recent elucidation of the crystallographic structure of the enzyme [Tong, L., Qian, C., Massariol, M.-J., Bonneau, P. R., Cordingley, M. G., & Lagacé, L. (1996) Nature 383, 272], these observations are consistent with the inhibition of HCMV protease by peptidyl ketones involving a conformational change of the protease. A mechanism involving a kon limited by dehydration of the hydrated species, followed by rapid ligand binding and a conformational change prior to covalent adduct formation, is proposed for activated inhibitors such as 1 and 2.

Novel nevirapine-like inhibitors with improved activity against NNRTI-resistant HIV: 8-heteroarylthiomethyldipyridodiazepinone derivatives.

A series of 8-heteroarylthiomethyldipyridodiazepinone derivatives were prepared and evaluated for their antiviral profile against wild type virus and the important K103N/Y181C mutant as an indicator for broad activity. 2,6-Dimethylpyridine derivative 16 was found to have a good pharmacokinetic profile in spite of poor metabolic stability in rat liver microsomes.

Discovery of non-peptidic P2-P3 butanediamide renin inhibitors with high oral efficacy.

A new series of non-peptidic renin inhibitors having a 2-substituted butanediamide moiety at the P2 and P3 positions has been identified. The optimized inhibitors have IC50 values of 0.8 to 1.4 nM and 2.5 to 7.6 nM in plasma renin assays at pH 6.0 and 7.4, respectively. When evaluated in the normotensive cynomolgus monkey model, two of the most potent inhibitors were orally active at a dose as low as 3 mg/kg. These potent renin inhibitors are characterized by oral bioavailabilities of 40 and 89% in the cynomolgus monkey. Inhibitor 3z (BILA 2157 BS) was selected as candidate for pre-development.