Modeling spheroid growth, PET tracer uptake, and treatment effects of the Hsp90 inhibitor NVP-AUY922.

For a PET agent to be successful as a biomarker in early clinical trials of new anticancer agents, some conditions need to be fulfilled: the selected tracer should show a response that is related to the antitumoral effects, the quantitative value of this response should be interpretable to the antitumoral action, and the timing of the PET scan should be optimized to action of the drug. These conditions are not necessarily known at the start of a drug-development program and need to be explored. We proposed a translational imaging activity in which experiments in spheroids and later in xenografts are coupled to modeling of growth inhibition and to the related changes in the kinetics of PET tracers and other biomarkers. In addition, we demonstrated how this information can be used for planning clinical trials. METHODS: The first part of this concept is illustrated in a spheroid model with BT474 breast cancer cells treated with the heat shock protein 90 (Hsp90) inhibitor NVP-AUY922. The growth-inhibitory effect after a pulse treatment with the drug was measured with digital image analysis to determine effects on volume with high accuracy. The growth-inhibitory effect was described mathematically by a combined E(max) and time course model fitted to the data. The model was then used to simulate a once-per-week treatment; in these experiments the uptake of the PET tracers (18)F-FDG and 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) was determined at different doses and different time points. RESULTS: A drug exposure of 2 h followed by washout of the drug from the culture medium generated growth inhibition that was maximal at the earliest time point of 1 d and decreased exponentially with time during 10-12 d. The uptake of (18)F-FDG per viable tumor volume was minimally affected by the treatment, whereas the (18)F-FLT uptake decreased in correlation with the growth inhibition. CONCLUSION: The study suggests a prolonged action of the Hsp90 inhibitor that supports a once-per-week schedule. (18)F-FLT is a suitable tracer for the monitoring of effect, and the (18)F-FLT PET study might be performed within 3 d after dosing.     

Efficacy of prophylactic antibiotics in vascular surgery: an arterial wall microbiologic and pharmacokinetic perspective

This prospective study examined microbiologic features of arterial tissue and pharmacokinetics and bioactivity of cefamandole and cefazolin in patients undergoing elective primary prosthetic aortoiliofemoral/infrainguinal reconstruction. Double-blind, randomized, perioperative prophylaxis (1 gm intravenously every 6 hours for nine doses) with cefamandole or cefazolin was administered to 47 patients. Specimens of blood serum, subcutaneous fat, thrombus, atheroma, and arterial wall were obtained for culture and minimal inhibitory concentration and drug level analysis by high-pressure liquid chromatography. The serum half-life (hr +/- SEM) was 1.43 +/- 0.36 for cefamandole and 2.22 +/- 0.40 for cefazolin. Over the first 2 hours of surgery and for all time intervals combined, the serum concentration of cefazolin was significantly higher (p less than 0.025) than cefamandole. Irrespective of sampling time, the tissue concentration of cefazolin was significantly greater (p less than 0.005) than cefamandole. Positive arterial tissue cultures were obtained in 12 of 29 patients (41.4%) from 23 of 116 (19.8%) arterial tissue specimens. Coagulase-negative Staphylococcus was the predominant isolate, 64 of 93 (68.8%). Twenty-five of the 51 coagulase-negative staphylocci tested (49%) were slime-producers. During surgery, the arterial tissue concentration of cefamandole fell below the geometric mean minimal inhibitory concentration against all organisms combined, and against S. aureus (with the highest minimal inhibitory concentration of the prevalent isolates), significantly more often than the concentration of cefazolin. The data show that a significant number of primary elective aortoiliofemoral/infrainguinal reconstructions are associated with positive arterial tissue cultures, which represent a potential source of graft infection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Neurophysiological investigation of effects of the D-1 agonist SKF 38393 on tonic activity of substantia nigra dopamine neurons

The effects of the D-1 agonist SKF 38393 on tonic activity of rat substantia nigra pars compacta dopamine neurons were studied using extracellular, single-unit recording techniques. Unlike nonselective D-1/D-2 dopamine agonists or the D-2 agonist quinpirole, SKF 38393 did not inhibit dopamine neuronal activity when applied iontophoretically or when administered intravenously in doses up to 20 mg/kg to chloral hydrate-anesthetized rats. Moreover, pretreatment with SKF 38393 did not alter the inhibitory response of these neurons to apomorphine or the D-2 agonist quinpirole. However, in locally anesthetized, gallamine-treated, artificially respired rats, dopamine cell activity was significantly altered by i.v. administration of SKF 38393; firing rate increases and decreases were observed. Administration of the inactive enantiomer of SKF 38393, S-SKF 38393, did not induce similar changes in parallel experiments. These results support the idea that unlike D-2 autoreceptor stimulation, D-1 receptor stimulation does not exert a direct local effect on dopamine neurons in the substantia nigra pars compacta and suggest that D-1 receptor stimulation at sites postsynaptic to the dopamine cells may indirectly affect the activity of some dopamine neurons through long-loop feedback mechanisms.     

Reduction of Blood Pressure Retards the Progression of Chronic Renal Failure in Man

The effect of blood pressure reduction on the progression rateof chronic renal failure (CRF) was studied in 28 patients withCRF of diverse aetiology entering a prospective study (observationtime 7–24 months, mean 16 months). Endogenous creatinineclearance was 12–66 ml/mm (mean 30±3 ml/mm). Weaimed to keep the blood pressure below 160/90 mmlHg. Dietaryprotein was not restricted. The progression rate of CRF wasassessed from the regression coefficients of the regressionsof creatinine clearance and the inverse of s-creatinine, respectively,on time. Progression rate and the means of all recordings ofmean arterial blood pressure (MAP) and urinary protein excretion,respectively, in each patient during the prospective phase werecompared with retro spective data from the proceeding period(observation time 4–25 months, mean 19 months). The patientsreceived various combinations of antihypertensive drugs includingdiuretics, beta-blockers and vasodilatory drugs. In 19 patientsMAP decreased from 109±2 to 102±2 mmHg (groupI), whereas MAP increased from 105±2 to l08±2mmHgin nine patients (group II). In group I proteinuria was significantlylower (P<0.05) and the progression of CRF was approximately50% slower (P.<0.01) in the prospective phase than in theretrospective phase; no changes were observed in group II. Calculatedfor all patients, significant correlations were observed betweenthe change in MAP and the change in progression rate and proteinexcretion, respectively. These results indicate that loweringof blood pressure results in decreased proteinuria and retardationof the progression of CRF irrespective of the aetiology.     

Observations on two members of the Swedish family with congenital dyserythropoietic anaemia,type III

Abstract: Two affected individuals of the Swedish family with CDA, type III, in which the disease is transmitted as an autosomal dominant character, were studied. Both cases displayed features hitherto undescribed in this family but described in patients with CDA, type III, in whom the inheritance may have been as an autosomal recessive character. Such features were: (a) haemosiderinuria, (b) grossly disorganised erythroblast nuclei, (c) differences in the ultrastructural appearances of individual nuclei within the same multinucleate erythroblast and (d) intraerythroblastic inclusions resembling precipitated globin chains. In both cases the giant mononucleate erythroblasts and the multinucleate erythroblasts had total DNA contents up to 28c (1c = haploid DNA content) and 48c respectively, and some DNA synthesising bi- and multinucleate erythroblasts contained one or more nuclei which were unlabelled with ³H-thymidine. These findings are similar to those in patients with the autosomal recessive type of disease. Thus no major phenotypic differences are yet apparent between cases of CDA, type III, with different patterns of inheritance. Analysis of the surface erythrocyte proteins of the 2 Swedish CDA, type III, patients with monoclonal antibodies recognising Band 3, glycophorins A, B, C and D, Rh, CD44, CD47, CD55, CD58, CD59, Lutheran, Kell, LW and acetylcholinesterase did not reveal any gross abnormality of expression of these proteins. A slightly altered expression of blood group antigens A and H was revealed by the lectins Dolichos biflorus and Ulex europaeus and the Mr of Band 3 as judged by SDS polyacrylamide gel electrophoresis was also slightly reduced, suggesting that there may be minor alterations in the degree of N-glycosylation of some red cell membrane constituents.     

A pharmacokinetic interaction between carbamazepine and olanzapine: observations on possible mechanism

Objective: Olanzapine is a novel antipsychotic, which is effective against both the positive and negative symptoms of schizophrenia and causes fewer extrapyramidal adverse effects than conventional antipsychotics. The purpose of the present study was to assess the potential for a pharmacokinetic interaction between olanzapine and carbamazepine, since these agents are likely to be used concomitantly in the treatment of manic psychotic disorder. Method: The pharmacokinetics of two single therapeutic doses of olanzapine were determined in 11 healthy volunteers. The first dose of olanzapine (10 mg) was taken alone and the second dose (10 mg) after 2 weeks of treatment with carbamazepine (200 mg BID). Measurement of urinary 6-hydroxycortisol/cortisol excretion was used as an endogenous marker to confirm that induction of CYP3A4 by carbamazepine had occurred. Results: The dose of olanzapine given after a 2-week pre-treatment with carbamazepine was cleared more rapidly than olanzapine given alone. Olanzapine pharmacokinetic values for C_max and AUC were significantly lower after the second dose, the elimination half-life was significantly shorter, and the clearance and volume of distribution were significantly increased. Conclusion: Carbamazepine has been shown to induce several P450 cytochromes including CYP3A4 and CYP1A2. Since CYP1A2 plays a role in the metabolic clearance of olanzapine, the interaction may be attributed to induction of CYP1A2 by carbamazepine, leading to increased first-pass and systemic metabolism of olanzapine. The interaction is not considered to be of clinical significance because olanzapine has a wide therapeutic index, and the changes in plasma concentration of olanzapine are within the fourfold variation that occurs without concern for safety in a patient population. Received: 22 July 1997 / Accepted in revised form: 1 June 1998     

Insulin and epinephrine effects on heart glycogen synthase and phosphorylase activity.

The effect of intravenous epinephrine on heart glycogen synthase and phosphorylase systems in control and insulin-pretreated rats was studied. The percent of synthase in the I form decreased rapidly after epinephrine treatment but the change was small and sometimes not significant. In insulin-pretreated rats in which the percent synthase I was increased, epinephrine produced a definate and highly significant decrease. There was a simultaneous increase in percent phosphorylase a in both groups. The synthase and phosphorylase responses were statiscally significant at 2.5 mug epinephrine/kgor more. These data are compatible with a mechanism in which protein kinase is activated by an increased cAMP concentration and affects both the synthase and phosphorylasesystems simultaneously. Propranolol blocked the epinephrine effects on cAMP, synthase I, and phosphorylase a. Although insulin had little effect on the response ofthe synthase and phosphorylase systems to epinephrine, it nealry completely blocked glycogen degradation. The mechanism is unknown, but it appears to be due to an inhibition of phosphorylase a catalytic activity in vivo. Acetylcholine had no effect on synthase I, phosphorylase a, or cAMP in control or in insulin-pretreated animals.