Pharmacokinetic study of the oral fluorouracil antitumor agent S‐1 in patients with impaired renal function

Although dose reduction of S‐1 is recommended for patients with impaired renal function, dose modification for such patients has not been prospectively evaluated. The aim of the present study was to investigate the pharmacokinetic parameters of 5‐fluorouracil, 5‐chloro‐2,4 dihydroxypyridine and oteracil potassium, and to review the recommended dose modification of S‐1 in patients with renal impairment. We classified patients receiving S‐1 into 4 groups according to their renal function, as measured using the Japanese estimated glomerular filtration rate (eGFR) equation. The daily S‐1 dose was adjusted based on the patient's eGFR and body surface area. Blood samples were collected for pharmacokinetic analysis. A total of 33 patients were enrolled and classified into 4 groups as follows: 10 patients in cohort 1 (eGFR ≥ 80 mL/min/1.73 m²), 10 patients in cohort 2 (eGFR = 50‐79 mL/min/1.73 m²), 10 patients in cohort 3 (eGFR = 30‐49 mL/min/1.73 m²), and 3 patients in cohort 4 (eGFR < 30 mL/min/1.73 m²). Those in cohorts 3 and 4 treated with an adjusted dose of S‐1 showed a similar area under the curve for 5‐fluorouracil (941.9 ± 275.6 and 1043.5 ± 224.8 ng/mL, respectively) compared with cohort 2 (1034.9 ± 414.3 ng/mL). Notably, while there was a statistically significant difference between cohort 1 (689.6 ± 208.8 ng/mL) and 2 (P = 0.0474) treated with an equal dose of S‐1, there was no significant difference observed in the toxicity profiles of the cohorts. In conclusion, dose adjustment of S‐1 in patients with impaired renal function using eGFR is appropriate and safe.     

Marmoset cytochrome P450 2B6, a propofol hydroxylase expressed in liver

1. The common marmoset (Callithrix jacchus) is a useful experimental animal to evaluate the pharmacokinetics of drug candidates. Cytochrome P450 (P450) 2B enzyme in marmoset livers has been identified; however, only limited information on the enzymatic properties and distribution has been available.

2. Marmoset P450 2B6 amino acids showed high sequence identities (>86%) with those of primates including humans and cynomolgus monkeys. Phylogenetic analysis using amino acid sequences indicated that marmoset P450 2B6 was closer to human and cynomolgus monkey P450 2B6 than to P450 2B orthologs of other species, including pigs, dogs, rabbits and rodents.

3. Quantitative polymerase chain reaction analysis using specific primers showed P450 2B6 mRNA predominantly expressed in livers among the five marmoset tissues, similar to those of humans and cynomolgus monkeys.

4. Marmoset P450 2B6 heterologously expressed in Escherichia coli membranes oxidized 7-ethoxycoumarin, pentoxyresorufin, propofol and testosterone, at roughly similar rates to those of humans and/or cynomolgus monkeys. A high capacity of marmoset P450 2B6 with propofol 4-hydroxylation (at low ionic strength conditions) with a low K_m value was relatively comparable to that for marmoset livers.

5. These results collectively indicated a high propofol 4-hydroxylation activity of P450 2B6 expressed in marmoset livers.

     

Outcomes After Aortic Valve Replacement for Asymptomatic Severe Aortic Regurgitation and Normal Ejection Fraction

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Reactivation of heat-inactivated Ku proteins by heat shock cognate protein HSC73

Purpose: Mouse double-stranded DNA-dependent protein kinase (DNA-PK) activity is heat sensitive. Recovery of heat-inactivated DNA repair activity is a problem after combination therapy with radiation and heat. We investigated the mechanism of recovery of heat-inactivated DNA-PK activity.

Methods: Hybrid cells containing a fragment of human chromosome 8 in scid cells (RD13B2) were used. DNA-PK activity was measured by an in vitro assay. Immunoprecipitation of the nuclear extract was performed with an anti-Ku80 antibody. Proteins co-precipitated with Ku80 were separated by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis and detected by Western blotting using anti-heat shock protein (HSP)72 and anti-heat shock cognate protein (HSC)73 antibodies. HSC73 was overexpressed with the pcDNA3.1 vector. Short hairpin (sh)RNA was used to downregulate HSC73 and HSP72.

Results: The activity of heat-inactivated DNA-PK recovered to about 50% of control during an additional incubation at 37?°C after heat treatment at 44?°C for 15?min in the presence of cycloheximide (which inhibits de novo protein synthesis). Maximal recovery was observed within 3?h of incubation at 37?°C after heat treatment. Constitutively expressed HSC73, which folds newly synthesized proteins, reached maximal levels 3?h after heat treatment using a co-immunoprecipitation assay with the Ku80 protein. Inhibiting HSC73, but not HSP72, expression with shRNA decreased the recovery of DNA-PK activity after heat treatment.

Conclusions: These results suggest that de novo protein synthesis is unnecessary for recovery of some heat-inactivated DNA-PK. Rather, it might be reactivated by the molecular chaperone activity of HSC73, but not HSP72.     

Low Phase Angle Is Correlated With Worse General Condition in Patients with Advanced Cancer

Objectives: Phase angle (PA) is a poor prognostic factor in patients with advanced cancer. This study aimed to identify possible correlations between PA and symptoms, quality of life, fluid retention, and laboratory data in cancer patients in palliative care settings.

Methods: Individuals who visited the outpatient clinic or were admitted to the palliative care unit were eligible. Patients with a performance status of 4 and/or those unable to complete questionnaires were excluded. PA was evaluated using a bioanalyzer device. The correlation coefficient between PA and the variables of interest was analyzed.

Results: A total of 102 patients were analyzed. PA was weakly correlated with age (ρ = ?0.22), performance status (ρ = ?0.30), functional well-being (ρ?=?0.20), anorexia/cachexia subscale (ρ?=?0.22), and Functional Assessment of Anorexia/Cachexia Therapy trial outcome index (ρ?=?0.26). PA was also correlated with fluid retention (ρ = ?0.34) and albumin (ρ?=?0.32), C-reactive protein (ρ = ?0.31), and hemoglobin (ρ?=?0.41) levels. Sub-analysis stratified according to sex revealed that males demonstrated the same results; however, female sex demonstrated a correlation between PA and social well-being (ρ = ?0.43).

Conclusions: PA was correlated with physical condition, but not with psychological well-being.