A sensitive liquid chromatography-tandem mass spectrometry method for the quantification of valacyclovir and its metabolite acyclovir in mouse and human plasma

A decreasing plasma concentration of a toxicologically active metabolite 9-carboxymethoxymethylguanine after dialysis - A potential new clinical biomarker for improving encephalopathy in patients treated with acyclovir

Although acyclovir is a key drug for the treatment of herpes infections, a consciousness disorder known as "acyclovir encephalopathy" is among its side effects. We encountered a patient with encephalopathy and measured the plasma and cerebrospinal fluid concentrations of acyclovir and its toxicologically active metabolite 9-carboxymethoxymethylguanine (CMMG). Before dialysis, cerebrospinal fluid concentrations of acyclovir and CMMG in this patient with a consciousness disorder were approximately 10% and 1%, respectively, of their plasma concentrations. After 3 days of dialysis, plasma CMMG levels decreased to detectable but below quantitative levels (<0.1 μg/mL), resulting in normal consciousness. These results suggest that decreasing plasma CMMG concentration could be one of clinical biomarkers for improving consciousness in patients with encephalopathy associated with acyclovir.

Rapid determination of acyclovir, its main metabolite 9-carboxymethoxymethylguanine, ganciclovir and penciclovir in human serum by LC-MS/MS

A novel MS‐based analytical method for simultaneous analysis of the antiviral drugs acyclovir, its metabolite 9‐carboxymethoxymethylguanine, ganciclovir, and penciclovir in human serum is described. These antiviral drugs are active against herpes virus infections. Acyclovir and penciclovir are regarded as safe and effective medicines with mild side effects such as headache and gastrointestinal discomfort, and ganciclovir is regarded as more toxic and is known to cause, for example, bone marrow suppression. Acyclovir’s main metabolite 9‐carboxymethoxymethylguanine is a presumptive neurotoxin and should be monitored in patients with impaired renal function or in cases with neurotoxic symptoms. A sample was prepared using protein precipitation with 1% formic acid in methanol containing isotopically labeled internal standard. Chromatographic separation on a biphenyl column and mass spectrometric detection were performed in multiple reaction monitoring (MRM) mode on a Xevo TQ‐S micro with ESI in positive ion mode, within 3 min. Inter‐day assay accuracies for the quality controls varied between 95 and 104% and intra‐day assay between 93 and 105%. Inter‐day and intra‐day assay imprecision for the quality controls ranged between 1.4 and 4.2% and 1.7 and 6.5% respectively. The lower limit of quantification for all four substances was 0.156 μmol/L. It is an accurate and reproducible method for therapeutic drug monitoring.

Screening and application of a broad-spectrum aptamer for acyclic guanosine analogues

Acyclic guanosine analogues, a class of widely used antiviral drugs, can cause chronic toxicity and virus resistance. Therefore, it is essential to establish rapid and accurate methods to detect acyclic guanosine analogues. In this study, five acyclic guanosine analogues (acyclovir, famciclovir, ganciclovir, penciclovir, and valaciclovir) were used as positive targets to obtain broad-spectrum aptamers through Capture-SELEX technology. Real-time quantitative PCR (Q-PCR) was used to monitor the aptamer SELEX process. After the sixteen rounds of selection against mixed targets, sequences were obtained by high-throughput sequencing (HTS). Furthermore, a broad-spectrum aptamer, named CIV6, was found as the higher performance aptamer that was suitable for five acyclic guanosine analogues by graphene oxide (GO) polarization and fluorescence assay. Finally, the aptamer CIV6 was used to construct GO fluorescence assay to detect five acyclic guanosine analogues. The limits of detection (LOD) of acyclovir, famciclovir, ganciclovir, penciclovir, and valaciclovir were 0.48 ng·mL^-1, 0.53 ng·mL^-1, 0.50 ng·mL^-1, 0.56 ng·mL^-1, and 0.38 ng·mL^-1, respectively.

Proposing a minimal set of metrics and methods to predict probabilities of amyloidosis disease and onset age in individuals

Many amyloid-driven pathologies have both genetic and stochastic components where assessing risk of disease development requires a multifactorial assessment where many of the variables are poorly understood. Risk of transthyretin-mediated amyloidosis is enhanced by age and mutation of the transthyretin (TTR) gene, but amyloidosis is not directly initiated by mutated TTR proteins. Nearly all of the 150+ known mutations increase dissociation of the homotetrameric protein structure and increase the probability of an individual developing a TTR amyloid disease late in life. TTR amyloidosis is caused by dissociated monomers that are destabilized and refold into an amyloidogenic form. Therefore, monomer concentration, monomer proteolysis rate, and structural stability are key variables that may determine the rate of development of amyloidosis. Here we develop a unifying biophysical model that quantifies the relationships among these variables in plasma and suggest the probability of an individual developing a TTR amyloid disease can be estimated. This may allow quantification of risk for amyloidosis and provide the information necessary for development of methods for early diagnosis and prevention. Given the similar observation of genetic and sporadic amyloidoses for other diseases, this model and the measurements to assess risk may be applicable to more proteins than just TTR.

Drug Elimination Alteration in Acute Lymphoblastic Leukemia Mediated by Renal Transporters and Glomerular Filtration

PURPOSE

Drug elimination alteration has been well reported in acute lymphoblastic leukemia (ALL). Considering that transporters and glomerular filtration influence, to different extents, the drug disposition, and possible side effects, we evaluated the effects of ALL on major renal transporters and glomerular filtration mediated pharmacokinetic changes, as well as expression of renal drug transporters.

METHODS

ALL xenograft models were established and intravenously injected with substrates of renal transporters and glomerular filtration separately in NOD/SCID mice. The plasma concentrations of substrates, after single doses, were determined using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS).

RESULTS

With the development of ALL, protein expression of MDR1, OAT3 and OCT2 were increased by 2.62-fold, 1.70-fold, and 1.45-fold, respectively, whereas expression of MRP2 and MRP4 were significantly decreased by 30.98% and 45.28% in the kidney of ALL groups compared with control groups. Clearance of MDR1-mediated digoxin, OAT3-mediated furosemide, and OCT2-mediated metformin increased by 3.04-fold, 1.47-fold, and 1.26-fold, respectively. However, clearance of MRPs-mediated methotrexate was reduced by 39.5%. These results are consistent with mRNA expression. Clearance of vancomycin and amikacin, as markers of glomerular filtration rate, had a 2.14 and 1.64-fold increase in ALL mice, respectively.

CONCLUSIONS

The specific alteration of renal transporters and glomerular filtration in kidneys provide a rational explanation for changes in pharmacokinetics for ALL.

Effect of biphenyl hydrolase-like (BPHL) gene disruption on the intestinal stability, permeability and absorption of valacyclovir in wildtype and Bphl knockout mice

Biphenyl hydrolase-like protein (BPHL) is a novel human serine hydrolase that was originally cloned from a breast carcinoma cDNA library and shown to convert valacyclovir to acyclovir and valganciclovir to ganciclovir. However, the exclusivity of this process has not been determined and, indeed, it is possible that a number of esterases/proteases may mediate the hydrolysis of valacyclovir and similar prodrugs. The objectives of the present study were to evaluate the in situ intestinal permeability and stability of valacyclovir in wildtype (WT) and Bphl knockout (KO) mice, as well as the in vivo oral absorption and intravenous disposition of valacyclovir and acyclovir in the two mouse genotypes. We found that Bphl knockout mice had no obvious phenotype and that Bphl ablation did not alter the jejunal permeability of valacyclovir during in situ perfusions (i.e., 0.54 × 10^-4 in WT vs. 0.53 × 10^-4 cm/s in KO). Whereas no meaningful changes occurred between genotypes in the gene expression of proton-coupled oligopeptide transporters (i.e., PepT1, PepT2, PhT1, PhT2), enzymatic upregulation of Cyp3a11, Cyp3a16, Abhd14a and Abhd14b was observed in some tissues of Bphl knockout mice. Most importantly, we found that valacyclovir was rapidly and efficiently hydrolyzed to acyclovir in the absence of BPHL, and that hydrolysis was more extensive after the oral vs. intravenous route of administration (for both genotypes). Taken as a whole, BPHL is not obligatory for the conversion of valacyclovir to acyclovir either presystemically or systemically.