An unexpectedly high occurrence of aciclovir-induced neuropsychiatric symptoms in patients treated for herpesvirus CNS infection: a prospective observational study

Helicase-primase inhibitors for the treatment of herpes simplex virus infections - patent evaluation of WO2023/225162 from Gilead Sciences Inc

Helicase-primase is an interesting target for small-molecule therapy of herpes simplex virus (HSV) infections. With amenamevir already approved for varicella-zoster virus and herpes simplex in Japan and with pritelivir's granted breakthrough therapy designation for the treatment of acyclovir-resistant HSV infections in immunocompromised patients, the target has sparked interest in helicase-primase inhibitors (HPIs). Here, we analyze the first patent application from Gilead in this field, which pursued a me-too approach combining elements from an old Bayer together with a recent Medshine HPI application (which covers the Phaeno Therapeutics drug candidate HN0037). The asset was contributed to Assembly Biosciences, where it is under development as ABI-1179 at the investigational new drug (IND) enabling stage for high-recurrence genital herpes. A structure proposal for indolinoyl derivative ABI-1179 is presented, showing its potential opportunities and limitations compared to other HPIs.

Continuous flow biocatalysis: synthesis of purine nucleoside esters catalyzed by lipase TL IM from Thermomyces lanuginosus

Purine nucleoside ester is one of the derivatives of purine nucleoside, which has antiviral and anticancer activities. In this work, a continuous flow synthesis of purine nucleoside esters catalyzed by lipase TL IM from Thermomyces lanuginosus was successfully achieved. Various parameters including solvent, reaction temperature, reaction time/flow rate and substrate ratio were investigated. The best yields were obtained with a continuous flow microreactor for 35 min at 50 °C with the substrate ratio of 1 : 5 (nucleosides to vinyl esters) in the solvent of tert-amyl alcohol. 12 products were efficiently synthesized with yields of 78-93%. Here we reported for the first time the use of lipase TL IM from Thermomyces lanuginosus in the synthesis of purine nucleoside esters. The significant advantages of this methodology are a green solvent and mild conditions, a simple work-up procedure and the highly reusable biocatalyst. This research provides a new technique for rapid synthesis of anticancer and antiviral nucleoside drugs and is helpful for further screening of drug activity.

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.

Acyclovir Brain Disposition: Interactions with P-gp, Bcrp, Mrp2, and Oat3 at the Blood-Brain Barrier

BACKGROUND AND OBJECTIVE

Acyclovir is effective in treating herpes simplex virus infections of the central nervous system. The purpose of this study was to investigate the interactions between acyclovir and the efflux pumps P-glycoprotein (P-gp), breast cancer resistance protein (Bcrp), multidrug resistance protein 2 (Mrp2), and organic anion transporter 3 (Oat3) at the blood-brain barrier (BBB).

METHODS

Acyclovir concentrations in the blood and brain were evaluated by microdialysis and high-performance liquid chromatography. Acyclovir pharmacokinetic parameters, including the area under the unbound blood concentration-time curve (AUCu,blood), the area under the unbound brain concentration-time curve (AUCu,brain), and the ratio of AUCu,brain to AUCu,blood (Kp.uu.brain), were evaluated in the presence and absence of elacridar (P-gp/Bcrp inhibitor, 7.5 mg/kg), tariquidar (P-gp/Bcrp inhibitor, 7.5 mg/kg), MK571 (Mrp2 inhibitor, 7.5 mg/kg), cyclosporine (P-gp/Bcrp/Mrp2 inhibitor, 25 mg/kg), and probenecid (Oat3 inhibitor, 50 mg/kg).

RESULTS

The average AUCu,blood, AUCu,brain, and Kp.uu.brain in rats who received acyclovir (25 mg/kg, intravenous) alone were 1377.7 min · μg/ml, 435.4 min · μg/ml, and 31.6%, respectively. Probenecid drastically increased the AUCu,blood of acyclovir 1.73-fold, whereas coadministration with elacridar, tariquidar, MK571, and cyclosporine did not alter the blood pharmacokinetic parameters of acyclovir. Elacridar, tariquidar, MK571, cyclosporine, and probenecid significantly increased the AUCu,brain of acyclovir 1.51-, 1.54-, 1.47-, 1.95-, and 2.34-fold, respectively. Additionally, the Kp.uu.brain of acyclovir markedly increased 1.48-, 1.63-, 1.39-, 1.90-, and 1.35-fold following elacridar, tariquidar, MK571, cyclosporine, and probenecid administration, respectively.

CONCLUSION

The present study demonstrated that P-gp, Bcrp, Mrp2, and Oat3 inhibition increased the penetration of acyclovir across the BBB, supporting the hypothesis that these efflux pumps restrict the distribution of acyclovir in the brain.

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.

Neurotoxicity associated with acyclovir and valacyclovir: A systematic review of cases

WHAT IS KNOWN AND OBJECTIVE

Acyclovir and valacyclovir are commonly used antivirals with good general tolerance. Despite their good safety profile, they can cause systemic adverse effects, such as neurotoxicity, which are less frequent and known. The objective of this review was to collect all the reported cases of neurotoxicity associated with acyclovir and valaciclovir published in the literature and characterize their clinical course and interventions.

METHODS

A systematic review of cases was carried out following the guidelines established by "Preferred Reporting Items for Systematic Reviews and Meta-Analyses" (PRISMA). The research was carried out using the PubMed-Medline and Embase databases, between July 1984 and March 2021.

RESULTS AND DISCUSSION

A total of 119 cases with neurotoxicity mainly related to acyclovir (n = 88; 73.9%), followed by valaciclovir (n = 35; 29.4%) were analysed. 49.6% (n = 59) were men with a mean age of 59.5 years ± 21.1 (0.5-88). In 83.3% of the cases, renal impairment was documented and 57.1% (n = 68) with end-stage renal disease. The administered dose was higher than the renal adjustment recommendations in 59.7% of the cases. The global mean of onset of symptoms was 3.1 days ± 4.3 (0.2-28) after the start of antivirals. The mean recovery time was 9.8 days ± 21.7 (0.2-180). 74.4% of the patients had a recovery of ≤7 days, 15.9% between 8 and 15 days and 9.8% > 15 days.

WHAT IS NEW AND CONCLUSION

The neurotoxicity induced by acyclovir and its derivative valacyclovir is a poorly known and rare adverse effect that can occur mainly in patients with advanced age and impaired renal function. The most characteristic symptoms are confusion, altered level of consciousness, hallucinations, agitation and dysarthria. The basis of treatment is the discontinuation of the antiviral, and in some cases, it may require additional clearance by dialysis.

Response to "Comment On: Acute Retinal Necrosis: Is the Current Valacyclovir Regimen Adequate?"

Acute Retinal Necrosis (ARN) is a potentially devastating form of Uveitis. Antivirals are the mainstay treatment for this syndrome. In this letter, we question the current oral Valacyclovir dosage, based on the experience we had with a recent unresponsive ARN case.