Patterns of disease in patients at a tertiary referral centre requiring reoperative parathyroidectomy

INTRODUCTION

Reoperative parathyroidectomy is required when there is persistent or recurrent hyperparathyroidism following the initial surgery (at least 5% of parathyroidectomies nationally). By convention, 'persistent disease' is defined as the situation where the patient has not been cured by the first operation. The term 'recurrent hyperparathyroidism' is used when the patient was confirmed to be biochemically cured for six months from the first operation but has hyperparathyroidism after this date. Reoperative surgery is associated with higher rates of postoperative complications as well as a greater rate of failure to cure. The aim of our study was to review our departmental experience of reoperative parathyroidectomy, with a view to identify patterns of disease persistence and recurrence.

METHODS

Using a departmental database, patients were identified who had undergone reoperative parathyroidectomy between 2006 and 2014. All the pre, intra and postoperative information was documented including the operative note so as to record the location of the abnormal parathyroid gland found at reoperation.

RESULTS

Almost two-thirds (63%) of patients had negative, equivocal or discordant conventional imaging so secondary investigative tools were required frequently. The majority of abnormal glands were found in eutopic locations. The most common locations for ectopic glands were intrathyroidal, mediastinal and intrathymic. A third (33%) of the patients had multigland disease and over a quarter (28%) had coexisting thyroid disease.

CONCLUSIONS

Persistent hyperparathyroidism represents a challenging patient subgroup for which access to all radiological modalities and intraoperative parathyroid hormone monitoring are required. Patient selection for reintervention is a key determinant in the reoperation cure rate.

P2-quinazolinones and bis-macrocycles as new templates for next-generation hepatitis C virus NS3/4a protease inhibitors: discovery of MK-2748 and MK-6325

With the goal of identifying inhibitors of hepatitis C virus (HCV) NS3/4a protease that are potent against a wide range of genotypes and clinically relevant mutant viruses, several subseries of macrocycles were investigated based on observations made during the discovery of MK-5172. Quinazolinone-containing macrocycles were identified as promising leads, and optimization for superior cross-genotype and mutant enzyme potency as well as rat liver and plasma concentrations following oral dosing, led to the development of MK-2748. Additional investigation of a series of bis-macrocycles containing a fused 18- and 15-membered ring system were also optimized for the same properties, leading to the discovery of MK-6325. Both compounds display the broad genotype and mutant potency necessary for clinical development as next-generation HCV NS3/4a protease inhibitors.

Discovery of MK-5172, a Macrocyclic Hepatitis C Virus NS3/4a Protease Inhibitor

A new class of HCV NS3/4a protease inhibitors containing a P2 to P4 macrocyclic constraint was designed using a molecular modeling-derived strategy. Building on the profile of previous clinical compounds and exploring the P2 and linker regions of the series allowed for optimization of broad genotype and mutant enzyme potency, cellular activity, and rat liver exposure following oral dosing. These studies led to the identification of clinical candidate 15 (MK-5172), which is active against genotype 1-3 NS3/4a and clinically relevant mutant enzymes and has good plasma exposure and excellent liver exposure in multiple species.

Discovery of MK-1220: A Macrocyclic Inhibitor of Hepatitis C Virus NS3/4A Protease with Improved Preclinical Plasma Exposure

The discovery of MK-1220 is reported along with the development of a series of HCV NS3/4A protease inhibitors containing a P2 to P4 macrocyclic constraint with improved preclinical pharmacokinetics. Optimization of the P2 heterocycle substitution pattern as well as the P3 amino acid led to compounds with greatly improved plasma exposure following oral dosing in both rats and dogs while maintaining excellent enzyme potency and cellular activity. These studies led to the identification of MK-1220.

Atrial antifibrillatory effects of structurally distinct IKur blockers 3-[(dimethylamino)methyl]-6-methoxy-2-methyl-4-phenylisoquinolin-1(2H)-one and 2-phenyl-1,1-dipyridin-3-yl-2-pyrrolidin-1-yl-ethanol in dogs with underlying heart failure

Drug discovery efforts have focused recently on atrial-selective targets, including the Kv1.5 channel, which underlies the ultrarapid delayed rectifier current, I(Kur), to develop novel treatments for atrial fibrillation (AF). Two structurally distinct compounds, a triarylethanolamine TAEA and an isoquinolinone 3-[(dimethylamino)-methyl]-6-methoxy-2-methyl-4-phenylisoquinolin-1(2H)-one (ISQ-1), blocked I(Kur) in Chinese hamster ovary cells expressing human Kv1.5 with IC(50) values of 238 and 324 nM, respectively. In anesthetized dogs, i.v. infusions of TAEA and ISQ-1 elicited comparable 16% increases in atrial refractory period, with no effect on ventricular refractory period or QTc interval. Plasma concentrations at end infusion for TAEA and ISQ-1 were 58.5 +/- 23.6 and 330.3 +/- 43.5 nM, respectively. The abilities of TAEA and ISQ-1 to terminate AF, with comparison to the rapidly activating component of delayed rectifier potassium current blocker (+)-N-[1'-(6-cyano-1,2,3,4-tetrahydro-2(R)-naphthalenyl)-3,4-dihydro-4(R)-hydroxyspiro(2H-1-benzopyran-2,4'-piperidin)-6-yl]methanesulfonamide] monohydrochloride (MK-499) and the class IC 1-[2-[2-hydroxy-3-(propylamino)-propoxy]phenyl]-3-phenyl-1-propanone (propafenone), were assessed in conscious dogs with heart failure and inducible AF (entry criterion). All test agents administered in i.v. bolus regimens terminated AF in at least half of animals tested; conversely no agent was universally effective. MK-499, ISQ-1, TAEA, and propafenone terminated AF in five of six, four of seven, four of six, and five of six animals at plasma concentrations of 32.6 +/- 18.7, 817 +/- 274, 714 +/- 622, and 816 +/- 240 nM, respectively. Directed cardiac electrophysiologic studies in anesthetized dogs using i.v. bolus (consistent with AF studies) plus infusion regimens with TAEA and ISQ-1 demonstrated significant increases in atrial refractory period (12-15%), A-H and P-A intervals, but no effects on ventricular refractory period, H-V, and HEG intervals. The demonstration of AF termination with TAEA and ISQ-1 in the dog heart failure model extends the profile of antiarrhythmic efficacy of Kv1.5 blockade.

In Vivo Cardiac Electrophysiologic and Antiarrhythmic Effects of an Isoquinoline IKur Blocker, ISQ-1, in Rat, Dog, and Nonhuman Primate

The cardiac electrophysiologic effects of ISQ-1, an isoquinolinone I(Kur) blocker, were characterized in vivo. In rat, ISQ-1 elicited maximal 33% to 36% increases in atrial and ventricular refractoriness at a plasma concentration of 11.5 microM. In African green monkey, ISQ-1 increased atrial refractory period (maximal 17% at plasma concentration up to 20 microM) with no effect on ventricular refractory period or ECG QTc. Likewise in dog, ISQ-1 increased atrial refractory period (maximal 16% at plasma concentration up to 2 microM) with no effect on ventricular refractory period or QTc. In contrast, studies with ibutilide in nonhuman primate and dog demonstrated concomitant increases in atrial and ventricular refractoriness and QTc. Additionally, in a dog model of atrial flutter, ISQ-1 terminated ongoing flutter at doses (2.5 +/- 0.5 mg/kg IV) that selectively prolonged atrial refractoriness (13% increase), whereas flutter termination with ibutilide occurred at doses that increased both atrial and ventricular refractoriness as well as QTc. Of note, the cardiac electrophysiologic profiles displayed by ISQ-1 in these species were similar to those reported previously by our lab with a structurally distinct I(Kur) blocker. Taken together, these results further support the inhibition of I(Kur) as an approach to terminate atrial arrhythmia.

Design and synthesis of novel isoquinoline-3-nitriles as orally bioavailable Kv1.5 antagonists for the treatment of atrial fibrillation

Novel 3-cyanoisoquinoline Kv1.5 antagonists have been prepared and evaluated in in vitro and in vivo assays for inhibition of the Kv1.5 potassium channel and its associated cardiac potassium current, IKur. Structural modifications of isoquinolinone lead 1 afforded compounds with excellent potency, selectivity, and oral bioavailability.

In vitro characterization of novel NR2B selective NMDA receptor antagonists

N-Methyl-D-aspartate (NMDA) subunit specific receptor antagonism has potential therapeutic application for multiple CNS pathologies. MERCK 1, MERCK 2, and MERCK 3 are novel NR2B subtype selective NMDA receptor antagonists. The affinity and the kinetic mechanism of inhibition by these antagonists and ifenprodil were investigated using the whole-cell configuration of the patch clamp technique, calcium flux, and radioligand binding on a mouse cell line L(tk-) expressing recombinant human heteromeric NMDA receptors consisting of NR1a/NR2B subunit combinations. The rank order of potency, as determined by electrophysiology, was ifenprodil<MERCK 2<MERCK 1<MERCK 3 with K(D)'s 79+/-8, 2.4+/-1.1, 1.3+/-0.9, and approximately 0.16+/-0.02 nM, respectively. The apparent dissociation rate constants among these compounds differed by as much as 394-fold whereas the apparent association constants varied less than 3-fold. Higher affinities were a result of slower drug dissociation kinetics of receptor unbinding. Maximal inhibition was not voltage-dependent and was not statistically different at saturating concentrations by these compounds. These results provide the first detailed functional analysis of the kinetic mechanism of MERCK 1, MERCK 2, and MERCK 3 inhibition of NMDA receptors.

Pyridazine based inhibitors of p38 MAPK

Trisubstituted pyridazines were synthesized and evaluated as in vitro inhibitors of p38MAPK. The most active isomers were those possessing an aryl group alpha and a heteroaryl group beta relative to the nitrogen atom in the 2-position of the central pyridazine. Additionally, substitution in the 6-position of the central pyridazine with a variety of dialkylamino substituents afforded a set of inhibitors having good (p38 IC50 1-20 nM) in vitro activity.

Timing of cerclage removal after preterm premature rupture of membranes: maternal and neonatal outcomes

OBJECTIVE

Our aim was to evaluate immediate versus delayed removal of cerclage for women with preterm premature rupture of membranes with respect to maternal and neonatal outcomes.

STUDY DESIGN

We retrospectively analyzed women with preterm premature rupture of membranes at <34 weeks' gestation with prior cerclage placement. Exclusion criteria included presentation with chorioamnionitis, active labor, or nonreassuring fetal status. Timing of cerclage removal, immediate (<24 hours) or delayed (>24 hours), was compared.

RESULTS

There were 25 women in the delayed-removal group and 37 in the immediate-removal group. Average times to removal were 206.8 +/- 7.4 and 5.4 +/- 0.2 hours, respectively. Use of betamethasone was similar for both groups; however, antenatal antibiotic use (100% vs 80%; P =.03) and short-term tocolytic use (20% vs 3%; P =.04) were higher in the delayed-removal group. Duration of latency was significantly longer with delayed removal (10.1 vs 5.0 days; P <. 001). Delivery occurred >48 hours from preterm premature rupture of membranes in 96% (24/25) versus 54% (20/37; P <.001) and >7 days from rupture in 56% (14/25) versus 24% (9/37; P =.02), respectively. Rates of neonatal sepsis (at <10 days) and maternal infection were not statistically different. Neonatal outcomes did not significantly differ regarding mortality, respiratory distress syndrome, birth weight, or duration of stay in the intensive care nursery.

CONCLUSION

With the current management scheme for preterm premature rupture of membranes, cerclage retention significantly increases duration of latency without significantly altering maternal or neonatal outcomes.

Non-peptide glycoprotein IIb/IIIa inhibitors. 17. Design and synthesis of orally active, long-acting non-peptide fibrinogen receptor antagonists

The synthesis and pharmacological evaluation of 5 (L-738, 167), a potent, selective non-peptide fibrinogen receptor antagonist is reported. Compound 5 inhibited the aggregation of human gel-filtered platelets with an IC50 value of 8 nM and was found to be > 33000-fold less effective at inhibiting the attachment of human endothelial cells to fibrinogen, fibronectin, and vitronectin than it was at inhibiting platelet aggregation. Ex vivo platelet aggregation was inhibited by > 85% 24 h after the oral administration of 5 to dogs at 100 micrograms/kg. The extended pharmacodynamic profile exhibited by 5 appears to be a consequence of its high-affinity binding to GPIIb/IIIa on circulating platelets and suggests that 5 is suitable for once-a-day dosing.

Nonpeptide glycoprotein IIb/IIIa inhibitors. 15. Antithrombotic efficacy of L-738,167, a long-acting GPIIb/IIIa antagonist, correlates with inhibition of adenosine diphosphate-induced platelet aggregation but not with bleeding time prolongation

The nonpeptide platelet glycoprotein IIb/IIIa antagonist, L-738, 167, was characterized in dog and nonhuman primate. In an anesthetized canine model of coronary artery electrolytic lesion, L-738,167 elicited dose-dependent (3, 4, 4.5 and 5 micrograms/kg i.v.) decreases in incidence of occlusion, reductions in thrombus mass and elevations in bleeding time. Antithrombotic efficacy correlated with inhibition of adenosine diphosphate-induced platelet aggregation but was dissociated from marked bleeding time elevation. Similarly, suppression of platelet-dependent cyclic flow reductions with L-738,167 in the canine coronary artery (5 micrograms/kg i.v.) and African green monkey carotid artery (10 micrograms/kg i.v.) correlated with inhibition of adenosine diphosphate-induced platelet aggregation but not with inhibition of thrombin-induced platelet aggregation or significant prolongation of bleeding time. In conscious dogs and sedated chimpanzees, single dose intravenous bolus (5-20 micrograms/kg) and oral (25-200 micrograms/kg) administration of L-738,167 exhibited long duration (> or = 8 hr) inhibition of ex vivo platelet aggregation. Once daily oral administration to conscious dogs (10-30 micrograms/kg/day for 15 days) and rhesus monkeys (200-250 micrograms/kg/day for 11 days) maintained significant but submaximal (50-90% inhibition) trough levels of inhibition of adenosine diphosphate-induced ex vivo platelet aggregation. Platelet sensitivity to adenosine diphosphate after multiple days of oral dosing in dogs was similar to pretreatment sensitivity. L-738,167 showed characteristics suitable for chronic oral therapy with a glycoprotein IIb/IIIa inhibitor.

Effects of freezing, thawing, and storing human liver microsomes on cytochrome P450 activity

The stability of cytochrome P450 enzymes, cytochrome b5, and NADPH-cytochrome c reductase was examined in (A) human liver samples frozen in liquid nitrogen and stored at -80 degrees C, (B) human liver microsomes suspended in 250 mM sucrose and stored at -80 degrees C, and (C) human liver microsomes subjected to as many as 10 cycles of thawing and freezing. In study A, microsomes from five human livers were prepared from fresh (unfrozen) tissue and from tissue that was stored frozen at -80 degrees C for 1, 2, 4, or 6 months. The apparent concentration of cytochromes P450 and b5 and the activity of NADPH-cytochrome c reductase decreased 20-40% as a result of freezing the liver, regardless of whether the liver was stored for 1 or 6 months. Similar decreases were observed in the activities of cytochrome P450 enzymes belonging to several gene families, namely CYP1A2 (7-ethoxyresorufin O-dealkylation and caffeine N3-demethylation), CYP2A6 (coumarin 7-hydroxylation), CYP2C9 (tolbutamide methylhydroxylation), CYP2C19 (S-mephenytoin 4'- hydroxylation), CYP2D6 (dextromethorphan O-de-methylation), CYP2E1 (chlorzoxazone 6-hydroxylation), CYP3A4solidus5 (testosterone 6beta-hydroxylation), and CYP4A9solidus11 (lauric acid 12-hydroxylation). Freezing human liver did not convert cytochrome P450 to its inactive form, cytochrome P420, but it increased the contamination of liver microsomes with hemoglobin or other heme-containing proteins, which resulted in a uniform decrease in the specific activity of cytochromes P450 and b5 and in the specific activity of all P450 enzymes. In study B, the concentration of cytochromes P450 and b5, the activity of NADPH-cytochrome c reductase, and the activity of individual cytochrome P450 enzymes were determined in 10 samples of human liver microsomes stored at -80 degrees C for approximately 0, 1, or 2 years. The sample-to-sample variation in the concentration and activity of cytochrome P450, cytochrome b5, and NADPH-cytochrome c reductase was nominally affected by long-term storage of human liver microsomes at -80 degrees C, indicating there was no differential loss of cytochrome P450 activity, cytochrome b5 concentration, or NADPH-cytochrome c reductase activity. In study C, microsomes from a pool of human livers were subjected to 1, 2, 3, 5, 7, or 10 cycles of freezing at -80 degrees C followed by thawing at room temperature. Freezing/thawing liver microsomes for up to 10 cycles did not convert cytochrome P450 to P420, nor did it cause significant loss of CYP1A2, CYP2A6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4/5, or CYP4A9/11 activity. Overall, these results suggest that our current methods for storing and processing human liver are well suited to preserving microsomal P450 enzyme activity.

Erythroid differentiation of clonal Rauscher erythroleukemia cells in response to erythropoietin or dimethyl sulfoxide

Clonal lines of Rauscher erythroleukemia cells exhibited selective responses to two inducers of differentiation, erythropoietin and dimethyl sulfoxide. There were substantial quantitiative differences between clones that reponded to both inducers. Several clones differentiated only in response to erythropoietin. Erythropoietin stimulated cell proliferation and differentiation whereas dimethyl sulfoxide inhibited proliferation, suggesting dissimilar modes of action.