Short and efficient syntheses of analogues of WAY-100635: new and potent 5-HT1A receptor antagonists

Simple syntheses of four new and potent analogues of the 5-HT1A receptor ligand, WAY-100635 are described, namely the 6-(pyridinyl)-bromo-, the 6-(pyridinyl)-fluoro-, the pyrimidine- and the 5-(pyridinyl)-bromo-analogues. The first three analogues were obtained by aromatic nucleophilic substitution of the 2,6-dihalogenopyridine (activated or not as an N-oxide) or of the 2-chloropyrimidine with the corresponding amine nucleophile as a key step. The fourth analogue, the 5-(pyridinyl)-bromo-analogue, was synthesized from the 2-amino-5-bromopyridine via a progressive elongation of the skeleton. The four compounds described are all full antagonists and show good in vitro binding affinities (Ki).

New halogenated [11C]WAY analogues, [11C]6FPWAY and [11C]6BPWAY--radiosynthesis and assessment as radioligands for the study of brain 5-HT1A receptors in living monkey

[Carbonyl-(11)C]WAY-100635 ([(11)C]WAY) is an established radioligand for the study of brain serotonin(1A) (5-HT(1A)) receptors in living animals and humans with positron emission tomography (PET). There is a recognised need to develop halogenated ligands for 5-HT(1A) receptors, either for labelling with longer-lived fluorine-18 for more widespread application with PET or with iodine-123 for application with single photon emission tomography (SPET). Here we used autoradiography and PET to assess two new halogenated analogues of WAY, namely 6BPWAY and 6FPWAY [N-(2-(1-(4-(2-methoxyphenyl)-piperazinyl)ethyl))-N-(2-(6-bromo-/fluoro-pyridinyl))cyclohexanecarboxamide] as prospective radioligands, initially using carbon-11 as the radiolabel. Labelling of 6BPWAY and 6FPWAY with carbon-11 was accomplished by acylation of the corresponding secondary amine precursors with [carbonyl-(11)C]cyclohexanecarbonyl chloride. After incubation of human brain crysections with [(11)C]6BPWAY or [(11)C]6FPWAY, the highest accumulation of radioactivity was observed in cortical areas and the hippocampal formation. Both radioligands had high nonspecific binding. There was a rapid accumulation of radioactivity in the monkey brain after intravenous injection of [(11)C]6BPWAY and [(11)C]6FPWAY. High accumulation of radioactivity was observed in the frontal and temporal cortex and the raphe nuclei, areas known to contain a high density of 5-HT(1A) receptors. The ratios of radioactivity in receptor-rich temporal cortex to that in receptor-poor cerebellum at peak equilibrium were 1.9 (at 10 min) and 3.0 at (at 20 min) for [(11)C]6BPWAY and [(11)C]6FPWAY, respectively. In pretreatment experiments with high doses of unlabelled WAY, the level of radioactivity in the frontal and temporal cortex and the raphe nuclei was reduced to the same level as in the cerebellum. Radioactive metabolites of [(11)C]6FPWAY appeared at a rate similar to those for [(11)C]WAY, with 17% of the radioactivity in plasma represented by unchanged radioligand after 40 min. Radioactive metabolites of [(11)C]6BPWAY appeared much more slowly. At 40 min after injection 45% of the radioactivity in plasma still represented unchanged radioligand. The results indicate that 6-pyridinyl radiohalogented analogues of WAY are new leads to radioligands for PET or SPET.

Radioligands for the study of brain 5-HT(1A) receptors in vivo--development of some new analogues of way

[Carbonyl-(11)C]WAY-100635 (WAY) has proved to be a very useful radioligand for the imaging of brain 5-HT(1A) receptors in human brain in vivo with positron emission tomography (PET). WAY is now being applied widely for clinical research and drug development. However, WAY is rapidly cleared from plasma and is also rapidly metabolised. A comparable radioligand, with a higher and more sustained delivery to brain, is desirable since these properties might lead to better biomathematical modelling of acquired PET data. There are also needs for other types of 5-HT(1A) receptor radioligands, for example, ligands sensitive to elevated serotonin levels, ligands labelled with longer-lived fluorine-18 for distribution to "satellite" PET centres, and ligands labelled with iodine-123 for single photon emission computerised tomography (SPECT) imaging. Here we describe our progress toward these aims through the exploration of WAY analogues, including the development of [carbonyl-(11)C]desmethyl-WAY (DWAY) as a promising, more brain-penetrant radioligand for PET imaging of human 5-HT(1A) receptors, and (pyridinyl-6-halo)-analogues as promising leads for the development of radiohalogenated ligands.

[Cardiac anomalies in chronic renal failure]

PRINCIPAL CARDIOVASCULAR COMPLICATIONS IN END STAGE RENAL DISEASE: Cardiovascular diseases are the leading causes of morbidity and mortality in end stage renal disease patients. Very often, complications observed are left ventricular hypertrophy and various forms of arterial degenerative lesions involving coronary arteries, less frequently pericarditis and calcifying valvulopathy are diagnosed. THE REASONS ARE COMPLEX: Risk factors can be either specific of uremia per se such as anemia, overhydration, fistula or the same as in the general population. Hemodynamic alterations including tensile stress or blood flow play a major role associated to various locally or generally generated substances whose role remains currently to be determined. THEIR TREATMENTS: Treatments of cardiovascular complications are not specific in this end stage renal disease population but are more often the treatment of the etiology: reduction of fistula blood flow, increase of hemoglobin, best control of weight gain between two hemodialysis sessions or blood pressure control.

The effect of haemodialysis on the pharmacokinetics of perindoprilat after long-term perindopril

We have studied the pharmacokinetics of perindoprilat, the active metabolite of perindopril, in 7 hypertensive patients undergoing haemodialysis after short-term and long-term (1 month) perindopril. We also measured angiotensin-converting enzyme activity. Each subject took 2 mg of perindopril after a 4-hour haemodialysis. Serial blood samples were obtained each hour during dialysis and between dialysis (7 samples over 44 h). Perindoprilat steady state was reached within 5 haemodialysis sessions. There was a high degree of angiotensin converting enzyme inhibition after the first dose. Administration for 1 month did not modify the time to peak perindoprilat concentration but significantly increased the mean maximal concentration: 10.2 versus 26.8 ng.ml-1. The mean accumulation ratio was 3.5. The mean reduction in perindoprilat concentration after dialysis was greater than 50%. Perindoprilat haemodialysis clearance was 62 ml.min-1 after the first administration and 72 ml.min-1 after 1 month. Tolerance of perindopril was good throughout the study. Treatment can be begun with 2 mg of perindopril after haemodialysis in hypertensive patients undergoing haemodialysis.

Increased systolic pressure in chronic uremia. Role of arterial wave reflections

To assess the role of arterial wave reflections in the mechanism of systolic hypertension and altered pulsatile arterial dynamics in patients with end-stage renal disease (ESRD), 79 ESRD patients were compared with 73 age-matched control subjects with normal renal function and similar mean blood pressure. Wave reflections were investigated from the carotid pulse contour recorded by applanation tonometry using a Millar micromanometer-tipped probe. Wave reflections were quantified as the ratio (augmentation index, %) of the height of the late systolic peak to the total height of carotid pulse wave. Travel time of the reflected wave was timed from the foot of the pressure wave to the foot of the late systolic peak. Systolic and pulse pressure were increased in ESRD patients (p less than 0.001) and was not attributable to differences in left ventricular ejection pattern. The augmentation index was increased in ESRD patients (23.2 +/- 15.0 versus 9.8 +/- 15.6%; p less than 0.001) in association with a shorter travel time of reflected wave (109 +/- 24 versus 131 +/- 30 msec; p less than 0.001). Multiple regression analysis showed two principal factors associated (p less than 0.001) with the increase in augmentation index and shortened travel time of reflected wave: increased aortic pulse wave velocity and smaller stature with shorter body height in ESRD patients. The study points to the role of arterial wave reflections in the mechanisms producing alterations in pulsatile arterial dynamics in ESRD and is the first, through the mechanisms of early wave reflections, to show in humans that the increase in systolic and pulse pressures is associated with lesser body size.

Response to vaccination against tetanus in chronic haemodialysed patients

We studied the response to vaccination against tetanus and the changes in the antibody titers 6 months after this vaccination in 66 haemodialysed patients with chronic renal failure. We also investigated the factors that may affect the quality of this immune response. After the booster injection 96.5% of patients had antitetanus antibody titres considered to be protective (0.06 HU/ml). However, the titre of these antibodies rapidly declined and after 6 months, only 62% of the haemodialysed patients had a titre greater than 0.06 HU/ml. Among the different factors considered, only age significantly impaired or reduced the immune response. In addition, the acquisition of protection against tetanus was independent of the response to vaccination against hepatitis B in the same subjects. This study showed the efficacy and safety of vaccination against tetanus in hemodialysed patients, though the antibody titres should be assayed several months after vaccination to confirm the persistence of immunization.

[Evaluation of arterial compliance in renal insufficiency]

The pulse wave velocity (PWV) of the aorta, of the arm, of the leg, was measured in 90 normal subjects (N) and 92 dialysis patients (D) of the same age and blood pressure status. All patients underwent blood biochemistry, especially serum liquid concentrations, and aortic ultra-sonography. Aortic calcifications were diagnosed by echo and radiologic examination. Aortic PWV was significantly higher in D (1,113 +/- 319 cm/s) than in N (965 +/- 216 cm/s) (p = 0.0016). The aortic diameters were greater in D both at the aortic root and at the bifurcation. The pulse pressure was higher in D (76.6 +/- 23.7 vs 63.9 +/- 2 mmHg, p = 0.007). In both populations, the PWV increased with age and blood pressure but aortic calcification was only weakly correlated with this increase. These results indicate that the compliance of the aortic wall is reduced in D and leads to an increase in the pulsatile component of the blood pressure and thereby to an increase in left ventricular afterload.

Arterial compliance in uraemia

Aortic and brachial pulse wave velocity were measured in 26 haemodialysis patients in order to assess the effect of uraemic waste-product retention on arterial compliance. Dialysis with a 'low-calcium' dialysate (1.50 mmol/l) did not change the pulse wave velocity, but dialysis with a 'high-calcium' dialysate (1.75 mmol/l) induced a significant increase in both aortic and brachial pulse wave velocity. The results indicate that (1) waste-product retention is not responsible for the increased arterial pulse wave velocity observed in uraemic patients and (2) the increase in serum ionized calcium decreases arterial compliance.

Deferoxamine test and bone disease in dialysis patients with mild aluminum accumulation

Aluminum bone disease is a frequent complication of dialysis patients. The deferoxamine (DFO) test has been advocated as a noninvasive procedure for the diagnosis of AI bone lesion. However most of these studies have been performed in symptomatic patients with significant AI bone disease. Whether this test may provide similar data at an earlier stage of AI toxicity is not known. The present study evaluates prospectively 28 patients with mild AI load. Patients studied ranged in age from 21 to 65 years; duration of dialysis was 5.6 +/- 3.2 years; deferoxamine, 40 mg/kg body weight, was infused at the end of dialysis. Serum AI was measured before DFO administration and before the next dialysis treatment. Bone biopsies were performed in all patients. Cortical bone AI was determined biochemically; trabecular and cortical bone AI were also determined histochemically. Mean basal serum AI (43.2 +/- 30.8 micrograms/L) and cortical bone AI (25.7 +/- 35.2 micrograms/g) were moderately increased. Basal serum AI correlated (r = 0.77) with the increment in serum AI after DFO infusion. After DFO, stainable trabecular and cortical bone AI correlated in a similar manner with both basal serum AI and increment in serum AI. Only biochemically determined cortical bone AI was not significantly related to basal serum AI. Nineteen of the 28 patients had evidence of osteitis fibrosa on bone biopsy. Stained AI surfaces but not trabecular AI were different in patients with low and patients with high bone formation rates. The bone findings, assessed as bone formation rates and resorption surfaces, did not correlate with biochemically or histochemically determined bone AI.(ABSTRACT TRUNCATED AT 250 WORDS)

Association between aluminum accumulation and cardiac hypertrophy in hemodialyzed patients

In order to investigate the possible role of aluminum accumulation on the myocardium, 50 stable asymptomatic hemodialysis patients were studied. Patient cardiac status was assessed by echocardiography. A deferroxamine (DFO) test, together with a bone biopsy, was performed to determine the magnitude of AI accumulation. Thus, an increase in serum AI after DFO (delta AI DFO) and stainable cortical bone aluminum (SCBA) were taken as parameters of AI load. Fourteen of 50 patients had no SCBA. They differed from the 36 patients with SCBA in that they had lower left ventricular mass (LVM) (P less than 0.001), increased velocity of circumferential fiber shortening (Vcf) (P less than 0.001), and higher mitral E-F slope (P less than 0.01). In the overall population there was a mild increment in serum AI and in delta AI DFO. The duration of dialysis treatment was correlated with SCBA and delta AI DFO (P less than 0.001). A correlation was observed between LVM and delta AI DFO (P less than 0.001) and between LVM and SCBA (P less than 0.001). Multivariate correlations analysis indicated that these relationships were independent of the duration of dialysis treatment. The present data suggest that, in hemodialysis patients aluminum accumulation may be associated with increased LVM.

Renal blood flow in man with essential hypertension

Abnormalities in renal blood flow in man with sustained essential hypertension are reviewed with emphasis on four points: renal blood flow is decreased not only per unit square meter but also as a fraction of cardiac output, a result which is not observed in other organs, the relationship between cardiac output and renal blood flow is reset, so that restriction of arteriolar renal vessels is dominantly preglomerular in origin, the renal abnormalities may be reversed by alpha-blockade, suggesting an important contribution of the autonomic nervous system, and, finally, the normal sodium balance in steady-state conditions is achieved through adaptive mechanisms involving the venous system and resulting in decreased venous compliance and increased postglomerular and venous hydrostatic pressures.

Increased bone aluminum deposition after subtotal parathyroidectomy in dialyzed patients

Ten dialyzed patients underwent a systematic bone biopsy before and 19 +/- 9 months after subtotal parathyroidectomy (PTX). At the end of the follow-up period all the patients, except two, who complained of proximal myalgia, were asymptomatic. Compared to the bone biopsy specimen obtained prior surgery, decreased bone formation without mineralization impairment was observed after PTX. Despite an average decrease in aluminum gels intake after PTX, an increase in stained aluminum was observed (0.69 +/- 0.79 versus 1.20 +/- 0.95 mm/mm2, P less than 0.050). Aluminum accumulation depended on the pre-PTX bone aluminum load: pre- and post-PTX bone aluminum loads were correlated (r = 0.78, P less than 0.01). Bone aluminum accumulation was not related to the amount of aluminum gel intake after PTX; however, only two patients free of both bone aluminum deposit prior to PTX and aluminum gel intake after PTX had no stainable aluminum on the second bone biopsy after PTX. The only patient who had no decrease in bone formation after PTX had no increase in bone aluminum. Assuming that the patients had no aluminum deposit prior to dialysis, we measured the rate of bone aluminum accumulation. It rose from 0.11 +/- 0.09 mm/mm2/year prior to PTX to 0.40 +/- 0.25 mm/mm2/year after PTX (P less than 0.05) in the six patients who were maintained on phosphate binders and who had a decrease in bone formation after PTX. These six patients had unchanged aluminum gel intake.(ABSTRACT TRUNCATED AT 250 WORDS)