Pharmacokinetics of ibrutinib in a patient with chronic lymphocytic leukemia on hemodialysis.

Ibrutinib, an oral Bruton's tyrosine kinase inhibitor, is a key drug for the treatment of chronic lymphocytic leukemia (CLL). It is primarily metabolized by cytochrome P450 3A. However, there are no data on the pharmacokinetics of ibrutinib in patients with severe renal impairment or on hemodialysis (HD). We evaluated the pharmacokinetics of ibrutinib in a patient with CLL undergoing HD. An 84-year-old man on HD was diagnosed with CLL and was started on ibrutinib 140 mg daily. The second day of ibrutinib administration was an HD day, and its plasma concentrations before and 1, 2, 4, and 24 hours after administration were measured and found to be 0, 6.9, 28.4, 57.1, and 0 ng/mL, respectively. The maximum plasma concentration (Cmax) and time taken to reach Cmax (tmax) on days 14 and 15 of ibrutinib treatment were 64.8 ng/mL (4 hours) and 48.1 ng/mL (2 hours), respectively. Thus, we concluded that HD did not have a significant effect on the pharmacokinetics of ibrutinib in this patient. Therefore, dose adjustment of ibrutinib between HD and non-HD days is not recommended. Interestingly, we found that tmax of the drug was prolonged, and Cmax was higher on HD days compared to those on non-HD days.

Novel biological function of sialic acid (N-acetylneuraminic acid) as a hydrogen peroxide scavenger.

We have found that N-acetylneuraminic acid (NANA) consumes toxic hydrogen peroxide (H(2)O(2)) under physiological conditions. Close investigation of this finding revealed that NANA was oxidized by an equimolar amount of H(2)O(2) to provide its decarboxylated product, 4-(acetylamino)-2,4-dideoxy-D-glycero-D-galacto-octonic acid (ADOA). To date, there have been little data on this reaction, and its physiological significance has not been discussed. Examining the detoxification of H(2)O(2) in cultured cells with NANA, we were able to confirm that the cell death caused by H(2)O(2) was suppressed by NANA in a dose-dependent manner. These results revealed a novel role for NANA as a reactive oxygen scavenger. It is known that terminal NANA residues are removed by neuraminidase and that free NANA molecules are recycled or degraded by enzymes. We propose that released monomeric NANA is the potent defense molecule against oxidative damage.

[Determination of the optical purity of N-nitrosofenfluramine found in the Chinese slimming diet].

From 2001 to the summer of 2002, more than 800 cases of liver damage were reported in Japan among people taking Chinese diet aids. The Japanese Ministry of Health, Labor and Welfare has recently announced that N-nitrosofenfluramine was the hepatotoxic compound contained in the diet aids based on animal experiments performed by the National Institute of Health Sciences. Although N-nitrosofenfluramine is a derivative of fenfluramine, a previously used antiobesity drug, neither pharmacologic nor toxicologic properties have been reported for N-nitroso fenfluramine. It should be noted that N-nitrosofenfluramine has two optical isomers, although it is not yet known which isomer damages the liver and other organs. The Japanese Ministry of Health, Labor and Welfare has not commented on this point. Pursuing this question, 10 types of Chinese slimming aid samples including those obtained from patients with fulminating hepatitis were analyzed by NMR, GC/MS, and a newly established HPLC method using a chiral separation column. It was found that the N-nitrosofenfluramine in all of the toxic diet aids was the (S)-isomer form. No (R)-isomer was detected. These results strongly suggest that the nitroso-compound in the diets must be prepared from pharmacologically active (S)-fenfluramine (dexfenfluramine). Thus the pharmacologic and toxicologic properties of each isomer should be investigated.