Population pharmacokinetics of cyclophosphamide and its metabolites 4-hydroxycyclophosphamide, 2-dechloroethylcyclophosphamide, and phosphoramide mustard in a high-dose combination with Thiotepa and Carboplatin

The anticancer prodrug cyclophosphamide (CP) is activated by the formation of 4-hydroxycyclophosphamide (4OHCP), which decomposes into phosphoramide mustard (PM). This activation pathway is inhibited by thiotepa. CP is inactivated by formation of 2-dechloroethylcyclophosphamide (2DCECP). The aim of this study was to develop a population pharmacokinetic model describing the complex pharmacokinetics of CP, 4OHCP, 2DCECP, and PM when CP is administered in a high-dose combination with thiotepa and carboplatin. Patients received a combination of CP (1000-1500 mg/m/d), carboplatin (265-400 mg/m/d), and thiotepa (80-120 mg/m/d) administered in short infusions over 4 days. Twenty blood samples were collected per patient per course. Concentrations of CP, 4OHCP, 2DCECP, PM, thiotepa, and tepa were determined in plasma. Using NONMEM, an integrated population pharmacokinetic model was used to describe the pharmacokinetics of CP, 4OHCP, 2DCECP, and PM, including the already described processes of autoinduction of CP and the interaction with thiotepa. Data were available on 35 patients (70 courses). The pharmacokinetics of CP were described with a 2-compartment model, and those of 4OHCP, 2DCECP, and PM with 1-compartment models. Before onset of autoinduction, it was assumed that CP is eliminated through a noninducible pathway accounting for 20% of total CP clearance, whereas 2 inducible pathways resulted in formation of 4OHCP (75%) and 2DCECP (5%). It was assumed that 4OHCP was fully converted to PM. Induction of CP metabolism was mediated by 2 hypothetical amounts of enzyme whose quantities increased in time in the presence of CP (kenz=0.0223 and 0.0198 hours). Induction resulted in an increased formation of 4OHCP (approximately 50%), PM (approximately 50%), and 2DCECP (approximately 35%) during the 4-day course, and concomitant decreased exposure to CP (approximately 50%). The formation of 2DCECP was not inhibited by thiotepa. Apparent volumes of distribution of CP, PM, and 2DCECP could be estimated being 43.7, 55.5, and 18.5 L, respectively. Exposure to metabolites varied up to 9-fold. The complex population pharmacokinetics of CP, 4OHCP, 2DCECP, and PM in combination with thiotepa and carboplatin has been established and may form the basis for further treatment optimization with this combination.     

Crystal structures of Staphylococcusaureus methionine aminopeptidase complexed with keto heterocycle and aminoketone inhibitors reveal the formation of a tetrahedral intermediate

High-resolution crystal structures of Staphylococcus aureus methionine aminopeptidase I in complex with various keto heterocycles and aminoketones were determined, and the intermolecular ligand interactions with the enzyme are reported. The compounds are effective inhibitors of the S. aureus enzyme because of the formation of an uncleavable tetrahedral intermediate upon binding. The electron densities unequivocally show the enzyme-catalyzed transition-state analogue mimicking that for amide bond hydrolysis of substrates.     

Restenosis rates following bifurcation stenting with sirolimus-eluting stents for de novo narrowings

The percutaneous treatment of coronary bifurcation stenoses is hampered by an increased rate of subsequent restenosis. The present study reports on the outcomes of a consecutive series of 58 patients with 65 de novo bifurcation stenoses treated with sirolimus-eluting stent implantation in both the main vessel and side branch. At 6 months, the incidence of major adverse cardiac events was 10.3% (1 death and 5 target lesion revascularizations) with no episodes of acute myocardial infarction or stent thrombosis.     

Decreased TNF-alpha and NK activity in obsessive-compulsive disorder

BACKGROUND: Accumulating evidence points towards the involvement of autoimmune mechanisms in the pathophysiology of some subgroups of obsessive-compulsive disorder (OCD). This study was carried out to investigate whether obsessive-compulsive disorder is associated with altered activity of the immune system, and whether these changes are related to particular clinical characteristics. METHODS: Ex vivo production of TNF-alpha, IL-4, IL-6, IL-10, and IFN-gamma in whole blood cultures, and NK-cell activity and peripheral blood NK cell-, monocytes-, T-cell-, and B-cell- percentages were measured in 50 medication-free outpatients with OCD and 25 controls. RESULTS: In OCD patients, we found a significant decrease in production of TNF-alpha (p < 0.0001) and NK-activity (p = 0.002) in comparison with controls. No significant differences were observed in the other immune variables. Patients with first-degree relatives with OCD had significant lower NK-activity than patients who had no relatives with OCD (p = 0.02), and patients with a childhood onset of OCD had significantly lower number of NK-cells than patients with a late onset (p= 0.003). CONCLUSIONS: Changes in TNF-alpha and NK activity suggest a potential role of altered immune function in the pathophysiology of obsessive-compulsive disorder.     

The use of spermHALO-FISH to determine DAZ gene copy number

The AZFc region of the human Y chromosome is frequently deleted in men with spermatogenic failure and contains many multicopy genes. The best-characterized gene family within this region is the Deleted in AZoospermia (DAZ) gene family, which is present in four nearly identical copies. Recent reports claim deletions of some but not all DAZ genes. The assays used in these studies, however, are unable to provide conclusive evidence on the number of DAZ genes. In this study we show that with the use of highly decondensed sperm nuclei with large DNA domains (spermHALO) it is possible to determine the number of DAZ genes accurately. Using this fluorescent in-situ hybridization (FISH) technique, which has both high resolution and high range, we show that in 10 normospermic men, in which PCR digest assays indicated a deletion of one or more DAZ genes, all four DAZ genes were present. Also we confirmed previous findings of a deletion of two DAZ genes in two men and identified a man with six DAZ genes. Our results indicate that spermHALO-FISH allows an accurate determination of DAZ gene copy number, while PCR digest assays do not. Therefore, confirmation of positive results from PCR digest assays with spermHALO-FISH is essential. Furthermore, the spermHALO-FISH technique should prove useful as a genetic mapping technique in other regions of the Y chromosome and similar repetitive regions throughout the genome.     

The status of HPV16-specific T-cell reactivity in health and disease as a guide to HPV vaccine development

Human papilloma viruses (HPV) are among the most common sexually transmitted pathogens in young adults. In the majority of individuals, anti-viral immunity is capable of suppressing viral infection but in a minority of patients viral infection is not cleared in time to prevent the development of malignancies. In these cases, HPV16-specific immunity may develop too late, is not strong enough, and/or is possibly of the wrong type. The influence of pre-existing immunity on the efficacy of vaccines is largely unknown. Nor has it been studied what the effect is of vaccines on the various types of pre-existing HPV-specific T-cell immunity. Animal models showing that vaccines are able to protect against a subsequent tumor challenge and even to treat transplantable tumors, are not qualified to address this point because tumor development is not preceded by persistent viral infection. Therefore, the comparison between fully characterized pre-existing HPV-specific immunity in patients and healthy subjects is a prerequisite for the full appreciation of vaccine-efficacy as well as for further development of next-generation vaccines.     

Sorption of thiotepa to polyurethane catheter causes falsely elevated plasma levels

Central venous access catheters are commonly used in clinical oncology. The double lumen variant is applied in pharmacokinetic studies for simultaneous administration and blood sampling when frequent blood collections are necessary. Occlusion of one lumen, a common complication, necessitates the investigator perform blood sampling through the administration lumen after interrupting the infusion. Plasma concentrations measured in this sample can be influenced by sorption of the previously infused compound to the catheter lumen. In this study, the quality of cyclophosphamide, thiotepa, and carboplatin plasma concentrations is investigated when sampling is performed through the administration lumen.     

Latent Cerebral Venous and Sinus Thrombosis

The incidence of cerebral venous and sinus thrombosis (CVST) is still unknown. Several assumptions of the incidence have been made. In the one and only series of consecutive brain autopsies series by Towbin in1973 CVST was found in 10,9 % of patients aged 60 years or more. These findings suggest that the true incidence of CVST is higher than generally thought, but there are no other reports supporting these findings. Therefore in order to determine the incidence of latent CVST we conducted a new prospective post mortem study. All brain autopsies performed in our hospital between 1996 and 1998 on patients 60 years of age or older were examined for the presence of CVST in a prospective way. We examined the sagittal sinus, the torcula, the straight sinus, both transverse sinuses, and both sigmoideal sinuses for the presence of thrombosis. The clinical condition, medication, brain-imaging results, clinical cause of death, general findings from the body autopsy and definite cause of death were recorded. Additionally we requested the annual mortality figures of CVST at the department of the National Agency for Statistics of the Netherlands (CBS). A consecutive and prospective series of 102 brain autopsies was performed in our general hospital during a period of two years. We found one case of latent CVST in our series of 102 patients. Comparison with the findings of Towbin using a chi-square test yielded a significant difference in the incidence of latent CVST (χ₂ = 7.65, p < 0.01) between the two studies. The present autopsy study demonstrates that latent CVST is rare. Received: 7 June 2002, Received in revised form: 14 October 2002, Accepted: 21 October 2002 Correspondence to H. P. Bienfait, MD