Influence of ALDH2 genetic polymorphisms on aciclovir pharmacokinetics following oral administration of valaciclovir in Japanese end-stage renal disease patients

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.

[A Pharmacist's Query Avoiding Exacerbation of Adverse Effects in a Patient with Acyclovir Encephalopathy: A Case Report]

We report a haemodialysis patient with end-stage renal failure whom a pharmacist aided in the management of acyclovir (ACV) encephalopathy, which may have been related to valacyclovir hydrochloride (VACV) administered without sufficient dose reduction. The patient 78 years was admitted with a tentative diagnosis of varicella zoster viral meningitis. A pharmacist suspected ACV encephalopathy related to excessive VACV administration and raised a query with the attending physician. According to the pharmacist's proposal, ACV administration was discontinued and continuous hemodiafiltration (CHDF) was performed. On day 5 of hospitalisation, the consciousness disorder was improved. In this report, we showed the detailed CHDF conditions of the present case, and the contribution of a pharmacist to treating and avoiding ACV encephalopathy was discussed.

Predicting Pharmacokinetics of Multisource Acyclovir Oral Products Through Physiologically Based Biopharmaceutics Modeling

Highly variable disposition after oral ingestion of acyclovir has been reported, although little is known regarding the underlying mechanisms. Different studies using the same reference product (Zovirax ®) showed that C_max and AUC were respectively 44 and 35% lower in Saudi Arabians than Europeans, consistent with higher frequencies of reduced-activity polymorphs of the organic cation transporter (OCT1) in Europeans. In this study, the contribution of physiology (i.e., OCT1 activity) to the oral disposition of acyclovir immediate release (IR) tablets was hypothesized to be greater than dissolution. The potential role of OCT1 was studied in a validated physiologically-based biopharmaceutics model (PBBM), while dissolution of two Chilean generics (with demonstrated bioequivalence) and the reference product was assessed in vitro. The PBBM suggested that OCT1 activity could partially explain population-related pharmacokinetic differences. Further, dissolution of generics was slower than the regulatory criterion for BCS III IR products. Remarkably, virtual bioequivalence (incorporating in vitro dissolution into the PBBM) correctly and robustly predicted the bioequivalence of these products, showcasing its value in support of failed BCS biowaivers. These findings suggest that very-rapid dissolution for acyclovir IR products may not be critical for BCS biowaiver. They also endorse the relevance of cross-over designs in bioequivalence trials.

Pharmacokinetics and Dialyzability of a Single Oral Dose of Amenamevir, an Anti-Herpes Drug, in Hemodialysis Patients

Introduction

Amenamevir (ASP2151), a herpesvirus helicase-primase inhibitor, is currently used for the treatment of herpes zoster in Japan. Amenamevir is mainly metabolized in the liver, and urinary excretion of amenamevir is approximately 10% in healthy adults. The increase of systemic exposure in non-dialysis patients with severe renal impairment was much less than that associated with nucleoside antiviral agents. The aim of this study was to evaluate the pharmacokinetics and dialyzability of a single oral dose (400 mg) of amenamevir in hemodialysis patients.

Methods

This was a single-arm, open-label, multicenter clinical pharmacology study. Nine patients aged 20–80 years with end-stage kidney disease and undergoing maintenance hemodialysis three times weekly were enrolled. Pharmacokinetics and dialyzability were investigated by serial collection of blood samples until 48 h post-dose during the study.

Results

The maximum plasma concentration and time to reach maximum plasma concentration during 24 h post-dose were 1585 ng/mL and 6.2 h, respectively. The area under the plasma concentration–time curve (AUC) from time zero to 24 h was 23,890 ng h/mL. The median terminal elimination half-life within 24 h before, during, and after hemodialysis was 14.7, 15.2, and 12.4 h, respectively. The AUC in hemodialysis patients was approximately double that in healthy adults. This increase in AUC was much less than that reported in nucleoside antiviral agents. The hemodialysis clearance, elimination fraction percentage, and amount of amenamevir removed were 37.8 mL/min, 28.1%, and 132.0 μg, respectively. The amount of amenamevir removed by hemodialysis was minimal. None of the hemodialysis parameters were associated with serum albumin. This study revealed no clinically relevant safety concerns.

Conclusion

There were no clinically relevant safety concerns when 400 mg of amenamevir was administered as a single dose to hemodialysis patients without dose adjustment and/or modification of the dosing schedule.

Trial Registration

JapicCTI-184242.

Electronic Supplementary Material

The online version of this article (10.1007/s12325-020-01375-1) contains supplementary material, which is available to authorized users.

[Acyclovir encephalopathy in a peritoneal dialysis patient despite adjusting the dose of oral acyclovir: a case report]

We report a case of acyclovir encephalopathy in a 77-year-old man who was introduced to peritoneal dialysis three years earlier. He developed herpes zoster and was treated with acyclovir (ACV) at 800 mg daily per oral. Two days later, he developed consciousness disturbance, hallucinations and asterixis. Acyclovir was stopped and continuous ambulatory peritoneal dialysis (CAPD) was switched to hemodialysis, which resulted in the resolution of his symptoms. Because the optimal dose of ACV varies among individuals depending on the bioavailability of ACV and metabolic enzyme activity, ACV encephalopathy can occur even when the acyclovir dose is modified according to the renal function of the affected patient. Because CAPD provides a poorer ACV clearance than hemodialysis, CAPD patients tend to have a higher risk of developing ACV encephalopathy and to recover more slowly. If CAPD patients develop ACV encephalopathy, a temporary change in the type of dialysis to hemodialysis should be considered.

Mitochondrially-targeted treatment strategies

Disruption of mitochondrial function is a common feature of inherited mitochondrial diseases (mitochondriopathies) and many other infectious and non-infectious diseases including viral, bacterial and protozoan infections, inflammatory and chronic pain, neurodegeneration, diabetes, obesity and cardiovascular diseases. Mitochondria therefore become an attractive target for developing new therapies. In this review we describe critical mechanisms involved in the maintenance of mitochondrial functionality and discuss strategies used to identify and validate mitochondrial targets in different diseases. We also highlight the most recent preclinical and clinical findings using molecules targeting mitochondrial bioenergetics, morphology, number, content and detoxification systems in common pathologies.

Genome-wide association analysis identifies multiple loci associated with kidney disease-related traits in Korean populations

Chronic kidney disease (CKD) is an important social health problem characterized by a decrease in the kidney glomerular filtration rate (GFR). In this study, we analyzed genome-wide association studies for kidney disease-related traits using data from a Korean adult health screening cohort comprising 7,064 participants. Kidney disease-related traits analyzed include blood urea nitrogen (BUN), serum creatinine, estimated GFR, and uric acid levels. We detected two genetic loci (SLC14A2 and an intergenic region) and 8 single nucleotide polymorphisms (SNPs) associated with BUN, 3 genetic loci (BCAS3, C17orf82, ALDH2) and 6 SNPs associated with serum creatinine, 3 genetic loci (BCAS3, C17orf82/TBX2, LRP2) and 7 SNPs associated with GFR, and 14 genetic loci (3 in ABCG2/PKD2, 2 in SLC2A9, 3 in intergenic regions on chromosome 4; OTUB1, NRXN2/SLC22A12, CDC42BPG, RPS6KA4, SLC22A9, and MAP4K2 on chromosome 11) and 84 SNPs associated with uric acid levels. By comparing significant genetic loci associated with serum creatinine levels and GFR, rs9895661 in BCAS3 and rs757608 in C17orf82 were simultaneously associated with both traits. The SNPs rs11710227 in intergenic regions on chromosome 3 showing significant association with BUN is newly discovered. Genetic variations of multiple gene loci are associated with kidney disease-related traits, and differences in associations between kidney disease-related traits and genetic variation are dependent on the population. The meanings of the mutations identified in this study will need to be reaffirmed in other population groups in the future.

A personalized medicine approach for Asian Americans with the aldehyde dehydrogenase 2*2 variant

Asian Americans are one of the fastest-growing populations in the United States. A relatively large subset of this population carries a unique loss-of-function point mutation in aldehyde dehydrogenase 2 (ALDH2), ALDH2*2. Found in approximately 560 million people of East Asian descent, ALDH2*2 reduces enzymatic activity by approximately 60% to 80% in heterozygotes. Furthermore, this variant is associated with a higher risk for several diseases affecting many organ systems, including a particularly high incidence relative to the general population of esophageal cancer, myocardial infarction, and osteoporosis. In this review, we discuss the pathophysiology associated with the ALDH2*2 variant, describe why this variant needs to be considered when selecting drug treatments, and suggest a personalized medicine approach for Asian American carriers of this variant. We also discuss future clinical and translational perspectives regarding ALDH2*2 research.

Acyclovir-induced nephrotoxicity: the role of the acyclovir aldehyde metabolite

For decades, acyclovir-induced nephrotoxicity was believed to be secondary to crystalluria. Clinical evidence of nephrotoxicity in the absence of crystalluria suggests that acyclovir induces direct insult to renal tubular cells. We postulated that acyclovir is metabolized by the alcohol dehydrogenase (ADH) enzyme to acyclovir aldehyde, which is metabolized by the aldehyde dehydrognase 2 (ALDH2) enzyme to 9-carboxymethoxymethylguanine (CMMG). We hypothesized that acyclovir aldehyde plays a role in acyclovir-induced nephrotoxicity. Human renal proximal tubular (HK-2) cells were used as our in vitro model. Western blot and enzymes activities assays were performed to determine whether the HK-2 cells express ADH and ALDH2 isozymes, respectively. Cytotoxicity (measured as a function of cell viability) assays were conducted to determine (1) whether the acyclovir aldehyde plays a role in acyclovir-induced nephrotoxicity and (2) whether CMMG induces cell death. A colorimetric assay was performed to determine whether acyclovir was metabolized to an aldehyde in vitro. Our results illustrated that (1) HK-2 cells express ADH and ALDH2 isozymes, (2) 4-methylpyrazole rendered significant protection against cell death, (3) CMMG does not induce cell death, and (4) acyclovir was metabolized to an aldehyde in tubular cells. These data indicate that acyclovir aldehyde is produced in HK-2 cells and that inhibition of its production by 4-methylpyrazole offers significant protection from cell death in vitro, suggesting that acyclovir aldehyde may cause the direct renal tubular insult associated with acyclovir.

The rationality for using prodrug approach in drug discovery programs for new xenobiotics: opportunities and challenges

The concept of prodrugs has been successfully executed for life cycle management options of several approved drugs and drugs in development. In addition to imparting ideal biopharmaceutical properties, such as solubility, permeability and lipophilicity, some prodrug concepts have also enabled site-specific drug delivery, prolonged the duration of therapeutic effect and improved therapeutic index. The strategic inclusion of prodrug concept during drug discovery and early development process brings in some unique challenges. The communication provides balanced perspectives on the rational use and challenges of prodrug concept during the drug discovery and development process.