Pharmacokinetics of valganciclovir and ganciclovir following multiple oral dosages of valganciclovir in HIV- and CMV-seropositive volunteers

Computational drug repurposing of Akt-1 allosteric inhibitors for non-small cell lung cancer

Non-small cell lung carcinomas (NSCLC) are the predominant form of lung malignancy and the reason for the highest number of cancer-related deaths. Widespread deregulation of Akt, a serine/threonine kinase, has been reported in NSCLC. Allosteric Akt inhibitors bind in the space separating the Pleckstrin homology (PH) and catalytic domains, typically with tryptophan residue (Trp-80). This could decrease the regulatory site phosphorylation by stabilizing the PH-in conformation. Hence, in this study, a computational investigation was undertaken to identify allosteric Akt-1 inhibitors from FDA-approved drugs. The molecules were docked at standard precision (SP) and extra-precision (XP), followed by Prime molecular mechanics-generalized Born surface area (MM-GBSA), and molecular dynamics (MD) simulations on selected hits. Post XP-docking, fourteen best hits were identified from a library of 2115 optimized FDA-approved compounds, demonstrating several beneficial interactions such as pi-pi stacking, pi-cation, direct, and water-bridged hydrogen bonds with the crucial residues (Trp-80 and Tyr-272) and several amino acid residues in the allosteric ligand-binding pocket of Akt-1. Subsequent MD simulations to verify the stability of chosen drugs to the Akt-1 allosteric site showed valganciclovir, dasatinib, indacaterol, and novobiocin to have high stability. Further, predictions for possible biological interactions were performed using computational tools such as ProTox-II, CLC-Pred, and PASSOnline. The shortlisted drugs open a new class of allosteric Akt-1 inhibitors for the therapy of NSCLC.

Therapeutic Drug Monitoring of Ganciclovir: Where Are We?

BACKGROUND

Ganciclovir is the mainstay of therapy for the prophylaxis and treatment of Cytomegalovirus. However, therapy with this antiviral agent is hindered by side effects such as myelosuppression, which often leads to therapy cessation. Underdosing, as an attempt to prevent side effects, can lead to drug resistance and therapy failure. Therapeutic drug monitoring (TDM) has been used to overcome these problems. The purpose of this narrative review was to give an overview of ganciclovir TDM, available assays, population pharmacokinetic models, and discuss the current knowledge gaps.

METHODS

For this narrative review, a nonsystematic literature search was performed on the PubMed database in April 2021. The following search terms were used: ganciclovir, valganciclovir, pharmacokinetics, pharmacodynamics, population pharmacokinetics, therapeutic drug monitoring, bioassay, liquid chromatography coupled with tandem mass spectrometry, liquid chromatography, chromatography, spectrophotometry, and toxicity. In addition, the reference lists of the included articles were screened.

RESULTS

The most common bioanalysis method identified was liquid chromatography coupled with tandem mass spectrometry. There are different models presenting ganciclovir IC50; however, establishing a pharmacokinetic/pharmacodynamic target for ganciclovir based on preclinical data is difficult because there are no studies combining dynamic drug exposure in relation to inhibition of viral replication. The data on ganciclovir TDM show large interindividual variability, indicating that TDM may play a role in modifying the dose to reduce toxicity and prevent treatment failure related to low concentrations. The main hurdle for implementing TDM is the lack of robust data to define a therapeutic window.

CONCLUSIONS

Although the pharmacokinetics (PK) involved is relatively well-described, both the pharmacodynamics (PD) and pharmacokinetic/pharmacodynamic relationship are not. This is because the studies conducted to date have mainly focused on estimating ganciclovir exposure, and owing to the limited therapeutic options for CMV infections, future studies on ganciclovir are warranted.

Clinical characteristics and treatment outcomes of Cytomegalovirus anterior uveitis and endotheliitis: a systematic review and meta-analysis

Cytomegalovirus (CMV) anterior uveitis is the most common form of ocular manifestation of CMV in immunocompetent individuals. The difficulty in diagnosing CMV anterior uveitis may delay adequate treatment and affect outcomes. We sought to review systemically the overall clinical characteristics and compare treatment outcomes in CMV anterior uveitis and endotheliitis. A literature search was performed, and studies describing clinical characteristics, treatment regimens, and outcomes that included more than five treated eyes were included. In these 23 studies, acute CMV anterior uveitis commonly presented with high intraocular pressure (IOP; 95.31%, 95% CI 90.45 - 98.60) and mild anterior chamber inflammation (cells >2+ = 3.18%, 95% CI 0.21- 8.54). About two-thirds of CMV endotheliitis cases presented with high IOP and coin-shaped corneal lesions. Acute CMV anterior uveitis showed good clinical response to topical 0.15% ganciclovir (GCV) gel or oral valganciclovir (VGCV) (90%, 95% CI: 74-100% and 95%, 95% CI: 88-100%, respectively). For chronic CMV anterior uveitis, both topical GCV and oral VGCV yielded comparable results. Topical 0.5-2% GCV or a combination of topical and oral VGCV for CMV endotheliitis both resulted in good clinical response. Recurrence of inflammation was common after cessation of maintenance therapy. Overall, topical GCV resulted in an optimal outcome for CMV anterior uveitis. Escalated concentration and frequency of usage are needed for chronic CMV anterior uveitis and endotheliitis. Adequate induction and maintenance phases of anti-CMV treatment seem necessary to prevent recurrences.

Efficacy and safety of conventional antiviral agents in preventive strategies for cytomegalovirus infection after kidney transplantation: a systematic review and network meta-analysis

Cytomegalovirus (CMV) infection is common in kidney transplantation (KT). Antiviral-agents are used as universal prophylaxis. Our purpose aimed to compare and rank efficacy and safety. MEDLINE, Embase, SCOPUS, and CENTRAL were used from inception to September 2020 regardless language restriction. We included randomized clinical trials (RCTs) comparing the CMV infection/disease prophylaxis among antiviral-agents in adult KT recipients. Of 24 eligible RCTs, prophylactic valganciclovir (VGC) could significantly lower the overall CMV infection and disease risks than placebo with pooled risk differences (RDs) [95% confidence interval (CI)] of -0.36 (-0.54, -0.18) and -0.28 (-0.48, -0.08), respectively. Valacyclovir (VAC) and ganciclovir (GC) significantly decreased risks with the corresponding RDs of -0.25 (-0.32, -0.19) and -0.30 (-0.37, -0.22) for CMV infection and -0.26 (-0.40, -0.12) and -0.22 (-0.31, -0.12) for CMV disease. For subgroup analysis by seropositive-donor and seronegative-recipient (D+/R-), VGC and GC significantly lowered the risk of CMV infection/disease with RDs of -0.42 (-0.84, -0.01) and -0.35 (-0.60, -0.12). For pre-emptive strategies, GC lowered the incidence of CMV disease significantly with pooled RDs of -0.33 (-0.47, -0.19). VGC may be the best in prophylaxis of CMV infection/disease follow by GC. VAC might be an alternative where VGC and GC are not available.

Identification of Potential Drug Targets of Broad-Spectrum Inhibitors with a Michael Acceptor Moiety Using Shotgun Proteomics

The Michael addition reaction is a spontaneous and quick chemical reaction that is widely applied in various fields. This reaction is performed by conjugating an addition of nucleophiles with α, β-unsaturated carbonyl compounds, resulting in the bond formation of C-N, C-S, C-O, and so on. In the development of molecular materials, the Michael addition is not only used to synthesize chemical compounds but is also involved in the mechanism of drug action. Several covalent drugs that bond via Michael addition are regarded as anticarcinogens and anti-inflammatory drugs. Although drug development is mainly focused on pharmaceutical drug discovery, target-based discovery can provide a different perspective for drug usage. However, considerable time and labor are required to define a molecular target through molecular biological experiments. In this review, we systematically examine the chemical structures of current FDA-approved antiviral drugs for potential Michael addition moieties with α, β-unsaturated carbonyl groups, which may exert an unidentified broad-spectrum inhibitory mechanism to target viral or host factors. We thus propose that profiling the targets of antiviral agents, such as Michael addition products, can be achieved by employing a high-throughput LC-MS approach to comprehensively analyze the interaction between drugs and targets, and the subsequent drug responses in the cellular environment to facilitate drug repurposing and/or identify potential adverse effects, with a particular emphasis on the pros and cons of this shotgun proteomic approach.

Current Drugs to Treat Infections with Herpes Simplex Viruses-1 and -2

Herpes simplex viruses-1 and -2 (HSV-1 and -2) are two of the three human alphaherpesviruses that cause infections worldwide. Since both viruses can be acquired in the absence of visible signs and symptoms, yet still result in lifelong infection, it is imperative that we provide interventions to keep them at bay, especially in immunocompromised patients. While numerous experimental vaccines are under consideration, current intervention consists solely of antiviral chemotherapeutic agents. This review explores all of the clinically approved drugs used to prevent the worst sequelae of recurrent outbreaks by these viruses.

Population pharmacokinetics of ganciclovir and valganciclovir in paediatric solid organ and stem cell transplant recipients

AIMS

Ganciclovir (GCV) and its prodrug valganciclovir (VGCV) are first-line agents to prevent and treat cytomegalovirus in transplant recipients. There is high pharmacokinetic (PK) interindividual variability and PK data are scarce, especially in paediatric stem cell transplant (SCT) recipients. We sought to determine the optimal GCV and VGCV dosing in transplanted children.

METHODS

We conducted a single-centre retrospective population PK (POPPK) study of IV GCV and enteral VGCV in paediatric solid organ transplant (SOT) and SCT recipients. We included children who were transplanted and had available plasma GCV concentrations, done per standard of care. POPPK analysis was performed using a nonlinear mixed effects modelling approach with NONMEM. Optimal dosing was determined based on the achievement of the surrogate efficacy target: GCV 24 h area under the concentration-time curve (AUC_0-24h ) of 40-60 mg.h.L^-1 .

RESULTS

Fifty children with a median [range] age of 7.5 years [0.5-17.4] contributed 580 PK samples. A two-compartment model with first-order absorption with a lag time and first-order elimination fit the data well. Creatinine clearance and body weight (WT) were significant covariates for GCV clearance (CL); and WT for the volumes of distribution. IV GCV 15-20 mg.kg^-1 .day^-1 divided every 12 hours achieved the highest probability of target achievement (PTA) (33.0-33.8%). Enteral VGCV 30 and 40 mg.kg^-1 .day^-1 divided every 12 hours in children 0-<6 years, and 6-18 years, respectively, achieved the highest PTA (29.1-33.0%).

CONCLUSION

This is the first POPPK model developed in children with either SOT or SCT. Concentration target achievement was low, suggesting a potential benefit for therapeutic drug monitoring to ensure optimal exposure.

A Case of Cytomegalovirus-Induced Oral Ulcer in an Older Adult Patient with Nephrotic Syndrome due to Membranous Nephropathy

We report a case of cytomegalovirus- (CMV-) induced buccal ulcer in a patient with nephrotic syndrome. An 82-year-old man with membranous nephropathy was on immunosuppressive therapy presented with an ulcer in the oral cavity and was hospitalized. Intraoral examination revealed an inflamed and painful ulcer on the left buccal mucosa. Blood test results showed CMV positivity, and histopathological examination confirmed the diagnosis. Anti-CMV therapy (ganciclovir) was initiated from the third day of hospitalization. However, he developed dyspnea on the 14th day. Computed tomography images of the chest revealed the presence of ground-glass opacities, and noninvasive positive pressure ventilation was initiated under the provisional diagnosis of pneumocystis pneumonia caused by ganciclovir-associated myelosuppression and/or steroid-induced immunocompromised state. The patient died of pneumocystis pneumonia on the 21st day. The patient had received immunosuppressive therapy for renal dysfunction. Immunocompromised patients with CMV infection should be treated with caution, as drugs for CMV may themselves cause myelosuppression, deteriorating the prognosis of the patient.

Antiviral Therapies for Herpesviruses: Current Agents and New Directions

PURPOSE

The objective of this review was to summarize the recent literature describing the current burden of disease due to herpesviruses in the antiviral and transplant era; describe mechanisms of action of antiviral agents and the development of resistance; summarize the literature of recent antiviral agents brought to market as well as agents under development; and to present literature on future strategies for herpesvirus therapeutics.

METHODS

An extensive search of the medical literature related to antiherpesviral therapy was conducted to compose this narrative review. Literature searches were performed via PubMed and ultimately 137 articles were included as most relevant to the scope of this article.

FINDINGS

Herpesviruses are a family of DNA viruses that are ubiquitous throughout human populations and share the feature of establishing lifelong infections in a latent phase with the potential of periodic reactivation. With the exception of herpes simplex virus, varicella zoster virus, and Epstein-Barr virus, which have a significant disease burden in individuals with normal immune function, the morbidity and mortality of the remaining viruses are primarily associated with the immunocompromised host. Over the last half-century, several agents have been tested in large randomized, placebo-controlled trials that have resulted in safe and effective antiviral agents for the treatment of many of these infections.

IMPLICATIONS

With increasing use of antiherpesviral agents for extended periods, particularly in immunocompromised hosts, the emergence of resistant viruses has necessitated the development of newer agents with novel targets and better side-effect profiles.

Effect of Low-Dose Vs Standard-Dose Valganciclovir in the Prevention of Cytomegalovirus Disease in Kidney Transplantation Recipients: A Systemic Review and Meta-Analysis

BACKGROUND

Valganciclovir is widely used to prevent post-transplant cytomegalovirus (CMV) infection in kidney transplant patients. However, the currently used dose remains controversial because the continuous use of this drug decreases kidney function and can induce leukopenia.

OBJECTIVE

The purpose of this study was to measure the appropriate dose of valganciclovir required to prevent CMV infection.

METHODS

A systematic review and meta-analysis were performed by using a random effects model. The Cochrane Central Register, MEDLINE, EMBASE, and PubMed databases were searched up to April 15, 2017. We conducted analysis on low-dose (450 mg) and standard-dose (900 mg) valganciclovir groups.

RESULTS

After completion of the research, the analysis revealed that the glomerular filtration rate, graft loss, tacrolimus level, antibody-mediated rejection, and fungal and Candida infection rates did not differ between the 2 groups. However, the incidence of CMV tended to decrease in the low-dose group (0.584 [95% confidence interval [CI], 0.352-0.967]; P = .036). The biopsy-proven rejection rate decreased by 0.427 times in the low-dose group compared with the standard-dose group (95% CI, 0.274-0.667; P = .002). Furthermore, the incidence of leukopenia decreased by 0.371 times in the low-dose group compared with the standard-dose group (95% CI, 0.264-0.523; P = .001).

CONCLUSIONS

The 450-mg dose of valganciclovir effectively prevented post-transplantation CMV infection and decreased drug-induced side effects such as leukopenia. In the future, the lower dose of valganciclovir should be considered to prevent CMV infection and enhance cost-effectiveness.

Ganciclovir

Ganciclovir is synthetic nucleoside analog of guanine closely related to acyclovir but has greater activity against cytomegalovirus. This comprehensive profile on ganciclovir starts with a description of the drug: nomenclature, formulae, chemical structure, elemental composition, and appearance. The uses and application of the drug are explained. The methods that were used for the preparation of ganciclovir are described and their respective schemes are outlined. The methods which were used for the physical characterization of the dug are: ionization constant, solubility, X-ray powder diffraction pattern, crystal structure, melting point, and differential scanning calorimetry. The chapter contains the spectra of the drug: ultraviolet spectrum, vibrational spectrum, nuclear magnetic resonance spectra, and the mass spectrum. The compendial methods of analysis of ganciclovir include the United States Pharmacopeia methods. Other methods of analysis that were reported in the literature include: high-performance liquid chromatography alone or with mass spectrometry, electrophoresis, spectrophotometry, voltammetry, chemiluminescence, and radioimmunoassay. Biological investigation on the drug includes: pharmacokinetics, metabolism, bioavailability, and biological analysis. Reviews on the methods used for preparation or for analysis of the drug are provided. The stability of the drug in various media and storage conditions is reported. More than 240 references are listed at the end of the chapter.

Antiviral Drugs in Newborn and Children

This article focuses on the clinically relevant approved antiviral medications available for the treatment of infants and children. A brief overview of drug categories, mechanism of action, resistance, pharmacokinetics, and side effects is provided for the more commonly prescribed antivirals. The patient categories addressed are treatment and prophylaxis of influenza, neonatal herpes simplex virus and congenital cytomegalovirus, treatment and prophylaxis of viral disease in the immunocompromised host, and a brief introduction to the antivirals available to treat hepatitis B and hepatitis C in children.

Treatment of alpha and beta herpesvirus infections in solid organ transplant recipients

INTRODUCTION

Human herpesviruses frequently cause infections in solid organ transplant (SOT) recipients. Areas covered: We provide an overview of the clinical impact of alpha and beta herpesviruses and highlight the mechanisms of action, pharmacokinetics, clinical indications, and adverse effects of antiviral drugs for the management of herpes simplex virus, varicella zoster virus and cytomegalovirus. We comprehensively evaluated key clinical trials that led to drug approval, and served as the foundation for management guidelines. We further provide an update on investigational antiviral agents for alpha and beta herpesvirus infections after SOT. Expert commentary: The therapeutic armamentarium for herpes infections is limited by the emergence of drug resistance. There have been major efforts for discovery of new drugs against these viruses, but the results of early-phase clinical trials have been less than encouraging. We believe, however, that more antiviral drug options are needed given the adverse side effects associated with current antiviral agents, and the emergence of drug-resistant virus populations in SOT recipients. Likewise, optimized use and strategies are needed for existing and novel antiviral drugs against alpha and beta-herpesviruses in SOT recipients.

A Physiologically Based Pharmacokinetic Model for Ganciclovir and Its Prodrug Valganciclovir in Adults and Children

A physiologically based pharmacokinetic (PBPK) model has been developed for ganciclovir and its prodrug valganciclovir. Initial bottom-up modeling based on physicochemical drug properties and measured in vitro inputs was verified in preclinical animal species, and then, a clinical model was verified in a stepwise fashion with pharmacokinetic data in adult, children, and neonatal patients. The final model incorporated conversion of valganciclovir to ganciclovir through esterases and permeability-limited tissue distribution of both drugs with active transport processes added in gut, liver, and kidney. A PBPK model which accounted for known age-related tissue volumes, composition and blood flows, and renal filtration clearance was able to simulate well the measured plasma exposures in adults and pediatric patients. Overall, this work illustrates the stepwise development of PBPK models which could be used to predict pharmacokinetics in infants and neonates, thereby assisting drug development in a vulnerable patient population where clinical data are challenging to obtain.

Ganciclovir concentrations in the cerebral extracellular space after valganciclovir treatment; a case study

Nearly all glioblastomas (GBMs), brain tumours with very poor prognosis, are infected with human cytomegalovirus (CMV). The anti-CMV drug valganciclovir (VGCV) has shown promise as a treatment option for patients with GBM, but its penetration into the central nervous system (CNS) is unknown. Here we describe a patient with GMB receiving VGCV in whom an intracerebral microdialysis catheter was implanted and ganciclovir (GCV) concentrations in brain extracellular fluid (BECF) and serum were monitored. GCV was rapidly absorbed. Cmax values (at 3 h) in serum and BECF were 19.6 and 10.2 µmol/L, T½ values were 3.2 and 4.5 h, and plasma and BECF AUC0-∞ values were 90.7 and 75.9 µmol h/L, respectively. Thus, VGCV treatment results in significant intracerebral levels of GCV that may be sufficient for therapeutic effects. Further studies of this drug in patients with GBM are warranted.

Occurrence of adverse events caused by valganciclovir as pre-emptive therapy for cytomegalovirus infection after allogeneic stem cell transplantation is reduced by low-dose administration

BACKGROUND

Pre-emptive therapy with valganciclovir (VGCV) has become the standard therapy for preventing cytomegalovirus (CMV) infection after allogeneic hematopoietic stem cell transplantation (HSCT). The effectiveness of low-dose VGCV (900 mg per day) has been shown to be equal to that of standard-dose VGCV (900 mg twice daily); however, individualized optimal dosing and toxicity of VGCV have not been reported.

METHODS

We conducted a retrospective study to evaluate the optimal dose of VGCV as pre-emptive therapy for preventing CMV infection by comparing the frequency of adverse events (AEs) and clinical efficacy in a low-dose VGCV group with those in a standard-dose VGCV group. Thirty-eight patients who were administered VGCV because of CMV antigenemia after HSCT were analyzed.

RESULTS

Neutropenia (standard-dose group: 33%, low-dose group: 15%, P = 0.26) and thrombocytopenia (standard-dose group: 39%, low-dose group: 15%, P = 0.14) were frequent AEs of VGCV, and a significantly higher frequency of overall AEs was detected in the standard-dose group than in the low-dose group (P < 0.01). In comparison of dosage based on weight, dosage of VGCV >27 mg/kg was closely related to onset of AEs (P = 0.04).

CONCLUSIONS

Low-dose VGCV was not inferior in clinical efficacy, including clearance rate of CMV antigenemia and incidence of consequent CMV disease, to standard-dose VGCV as was previously reported. Initial low-dose VGCV for pre-emptive CMV therapy markedly reduces hematologic toxicity and has clinical efficacy equivalent to that of standard-dose VGCV. It is therefore reasonable for patients, except for noticeably overweight patients, to be given initial low-dose VGCV.

Valganciclovir for the prevention and treatment of cytomegalovirus disease in immunocompromised hosts

Valganciclovir (Valcyte, Roche), a prodrug of the deoxyguanosine analog ganciclovir (Cytovene, Roche), is indicated for induction and maintenance treatment of cytomegalovirus retinitis in patients with AIDS and for prevention of cytomegalovirus disease in selected high-risk solid organ transplant recipients. After oral administration, valganciclovir is rapidly absorbed and converted to ganciclovir by intestinal and hepatic esterases. Valganciclovir is a highly recognized substrate of the intestinal peptide transporter PEPT1, which underlies the tenfold higher bioavailability of ganciclovir after valganciclovir compared to oral ganciclovir administration. At oral dose of 900 mg, valganciclovir provides a systemic ganciclovir exposure that is comparable to intravenous ganciclovir, at the standard dose of 5 mg/kg of body weight. Subsequent phosphorylation of ganciclovir, which occurs preferentially within cytomegalovirus-infected cells, results in the active metabolite, ganciclovir triphosphate, which is responsible for suppressing viral DNA synthesis by competitively inhibiting the incorporation of the natural substrate deoxyguanosine into viral DNA and thereby, terminating cytomegalovirus replication.

Can low-dose preemptive valganciclovir replace standard intravenous ganciclovir treatment in recipients of allogeneic stem cell transplantation?

The aim of this retrospective study was to compare the efficacy and safety of standard intravenous ganciclovir (GCV) with low-dose oral valganciclovir (VGC) in preemptive treatment of cytomegalovirus (CMV) infection in patients who received allogeneic stem cell transplantation (ASCT). Fifty-nine adult ASCT patients with asymptomatic 68 CMV reactivations were included. For preemptive CMV treatment, VGC (900 mg/day) in 44 reactivations or GCV (5 mg/kg twice daily during the first week and once daily afterwards) in 24 CMV reactivations were administered for 21 days. Two consecutive negative results for PCR and/or CMV antigenemia were considered as treatment success. All patients with CMV reactivations were on immunosuppressive treatment. While no positivity was identified in any of the patients who received GCV on day 21, low-titer CMV positivity was noted in three of the patients in the VGC group (P = 0·264). In all three patients, VGC was continued at same dose and no positivity result was detected after 2-3 weeks. Low-grade neutropenia and high grade thrombocytopenia were significantly higher in the GCV group than in the VGC group (P = 0·018 and P = 0·04 respectively). Preemptive strategy of oral low-dose VGC appears preferable to the prevention of CMV disease in ASCT. These results require confirmation in prospective larger clinical studies.

Therapy and prophylaxis of opportunistic infections in HIV-infected patients: a guideline by the German and Austrian AIDS societies (DAIG/ÖAG) (AWMF 055/066)

INTRODUCTION

There was a growing need for practical guidelines for the most common OIs in Germany and Austria under consideration of the local epidemiological conditions.

MATERIALS AND METHODS

The German and Austrian AIDS societies developed these guidelines between March 2010 and November 2011. A structured Medline research was performed for 12 diseases, namely Immune reconstitution inflammatory syndrome, Pneumocystis jiroveci pneumonia, cerebral toxoplasmosis, cytomegalovirus manifestations, candidiasis, herpes simplex virus infections, varizella zoster virus infections, progressive multifocal leucencephalopathy, cryptosporidiosis, cryptococcosis, nontuberculosis mycobacteria infections and tuberculosis. Due to the lack of evidence by randomized controlled trials, part of the guidelines reflects expert opinions. The German version was accepted by the German and Austrian AIDS Societies and was previously published by the Arbeitsgemeinschaft der Wissenschaftlichen Medizinischen Fachgesellschaften (AWMF; German Association of the Scientific Medical Societies).

CONCLUSION

The review presented here is a translation of a short version of the German-Austrian Guidelines of opportunistic infections in HIV patients. These guidelines are well-accepted in a clinical setting in both Germany and Austria. They lead to a similar treatment of a heterogeneous group of patients in these countries.

Evaluation of the validity of preemptive therapy against cytomegalovirus disease based on antigenemia assay with a cutoff of 20 positive cells per two slides

Background

Preemptive therapy with ganciclovir (GCV) based on the results of a cytomegalovirus (CMV) antigenemia assay is a standard strategy for preventing CMV disease after allogeneic hematopoietic cell transplantation (HCT). However, the appropriate threshold of antigenemia-positive cells for deciding when to start GCV remains unclear.

Patients

This retrospective study included 80 recipients who received HCT from an alternative donor between 2007 and 2011. In 2009, we switched the threshold from 3 (3A group, n=24) to 20 (20A group, n=56) antigenemia-positive cells per two slides for preemptive therapy after HCT from an alternative donor.

Results

Early CMV disease within 100 days after HCT was observed in one patient in the 20A group. Antiviral agents including GCV, val-GCV, and foscarnet were given in 17 (71%) and 36 (64%) patients in the 3A and 20A groups, respectively (p=0.23). In 13 (23%) patients in the 20A group, the initiation of preemptive therapy was avoided because of the change in the cutoff value for CMV antigenemia. However, the total dose of GCV was not different between the two groups. The use of steroid was significantly associated with CMV antigenemia of at least 20 positive cells among patients with low-level antigenemia at the first detection.

Conclusion

The increased threshold up to 20 positive cells for starting preemptive therapy was not associated with a significant increase in CMV disease, but the total dose of GCV was not reduced and there was one early CMV disease in the 20A group. We should explore how to identify patients who are at high risk for increased antigenemia among patients with low-level antigenemia, but at least, preemptive therapy should not be withheld in patients who are already receiving systemic steroid.

Single- and Multiple-Dose Pharmacokinetics of Levovirin Valinate Hydrochloride (R1518) in Healthy Volunteers

R1518 is a valine ester prodrug of levovirin as an investigational new drug for the treatment of hepatitis C virus. Two phase 1, single- and multiple-dose studies were conducted to investigate the pharmacokinetics of R1518 in healthy volunteers. After oral dosing, R1518 was rapidly and exclusively converted to levovirin. Levovirin plasma concentrations peaked at 2 hours, with T(1/2) ranging from 6 to 8 hours. The T(1/2) of R1518 was less than 1 hour, with relative exposures (R1518/levovirin) less than 6%. A high-fat meal did not affect the pharmacokinetics. The female groups in both studies had higher plasma levels than males did due to age and renal function difference. An accumulation ratio of 1.3 to 1.5 was observed with the twice-daily regimen. About 75% to 90% of the levovirin equivalent dose was recovered in urine. Increase in exposure was slightly disproportionate to increase in dose. Significantly improved oral absorption of levovirin was achieved following administration of R1518.

Evaluation of valganciclovir pharmacokinetics in lung transplant recipients

BACKGROUND

Valganciclovir is commonly used for cytomegalovirus prevention after lung transplantation. The pharmacokinetic profile of valganciclovir in lung transplant patients has not been well described or linked to efficacy and safety.

METHODS

This prospective, randomized, crossover study determined the steady-state pharmacokinetic profile of 2 different doses of valganciclovir in lung transplant recipients and compared these profiles with intravenous ganciclovir.

RESULTS

Ten patients were evaluated. Patients were 56.8 ± 3.4 years old and had a mean creatinine clearance of 69 ± 9 ml/min. Oral bioavailability of ganciclovir after administration of valganciclovir was 59%, and mean half-life was 3.73 ± 1.15 hours. The maximal concentration after intravenous 5 mg/kg ganciclovir was significantly higher than after 450 mg valganciclovir (8.37 ± 3.03 mg/liter vs. 5.3 ± 2.09 mg/liter, respectively; p = 0.02) and similar to 900 mg valganciclovir (7.93 ± 3.97 mg/liter; p = 0.78). A higher area under the curve at 0-24 hours (AUC(0-24)) was found with 900 mg valganciclovir compared with intravenous 5 mg/kg/day ganciclovir (47.8 ± 19.7 vs 32.9 ± 10.8 mg · hour/liter, respectively; p = 0.049). The AUC(0-24) for 450 mg valganciclovir twice daily was 45.5 ± 22.9 mg · hour/liter.

CONCLUSION

Valganciclovir at 900 mg/day resulted in the equivalent of a mean daily dose of 7.7 mg/kg intravenous ganciclovir. Higher systemic ganciclovir exposures occurred after 900 mg/day valganciclovir compared with intravenous 5 mg/kg/day ganciclovir. Valganciclovir therapeutic drug monitoring may be warranted in select lung transplant patients to avoid increased toxicity.

Cytomegalovirus retinitis treated with valganciclovir in Wegener's granulomatosis

A case of cytomegalovirus (CMV) retinitis in a patient with Wegener’s granulomatosis treated with oral valganciclovir as maintenance therapy is reported. A 68-year-old male patient with anti-proteinase-3 ANCA-positive Wegener’s granulomatosis who was receiving immunosuppressive therapy with methylprednisolone, cyclophosphamide, and azathioprine developed CMV retinitis. The patient received intravenous ganciclovir as induction therapy and oral valganciclovir as maintenance therapy. The patient responded to treatment and showed no recurrence for 8 months. There were no serious adverse effects associated with oral valganciclovir. Oral valganciclovir is convenient and effective for the management of CMV retinitis in the patient with Wegener’s granulomatosis.

Antiviral drugs for viruses other than human immunodeficiency virus

Most viral diseases, with the exception of those caused by human immunodeficiency virus, are self-limited illnesses that do not require specific antiviral therapy. The currently available antiviral drugs target 3 main groups of viruses: herpes, hepatitis, and influenza viruses. With the exception of the antisense molecule fomivirsen, all antiherpes drugs inhibit viral replication by serving as competitive substrates for viral DNA polymerase. Drugs for the treatment of influenza inhibit the ion channel M(2) protein or the enzyme neuraminidase. Combination therapy with Interferon-α and ribavirin remains the backbone treatment for chronic hepatitis C; the addition of serine protease inhibitors improves the treatment outcome of patients infected with hepatitis C virus genotype 1. Chronic hepatitis B can be treated with interferon or a combination of nucleos(t)ide analogues. Notably, almost all the nucleos(t) ide analogues for the treatment of chronic hepatitis B possess anti-human immunodeficiency virus properties, and they inhibit replication of hepatitis B virus by serving as competitive substrates for its DNA polymerase. Some antiviral drugs possess multiple potential clinical applications, such as ribavirin for the treatment of chronic hepatitis C and respiratory syncytial virus and cidofovir for the treatment of cytomegalovirus and other DNA viruses. Drug resistance is an emerging threat to the clinical utility of antiviral drugs. The major mechanisms for drug resistance are mutations in the viral DNA polymerase gene or in genes that encode for the viral kinases required for the activation of certain drugs such as acyclovir and ganciclovir. Widespread antiviral resistance has limited the clinical utility of M(2) inhibitors for the prevention and treatment of influenza infections. This article provides an overview of clinically available antiviral drugs for the primary care physician, with a special focus on pharmacology, clinical uses, and adverse effects.

High efficacy and low toxicity of short-course oral valganciclovir as pre-emptive therapy for hematopoietic stem cell transplant cytomegalovirus infection

BACKGROUND

Cytomegalovirus (CMV) infection is a major infectious complication post-allogeneic hematopoietic stem cell transplantation (HSCT). CMV seropositivity in Eastern Mediterranean and certain Asian countries is reported to be close to 100%; hence, the need for effective pre-emptive treatment strategy that has low toxicity. Valganciclovir (VGC) is a prodrug of ganciclovir with high bioavailability.

PATIENTS AND METHODS

HSCT patients with documented CMV infection (as defined by positive CMV antigenemia) were treated as outpatients with VGC at a starting dose of 900 mg twice daily for 1 week. Those who were antigenemia negative after one week received 900 mg once daily for another week and treatment was subsequently discontinued. Those who were positive after one week of therapy continued on the twice-daily treatment schedule for another week and changed to a daily schedule once they converted to antigenemia negativity.

RESULTS

From January 2004 to December 2007, 47 HSCT patients received preemptive treatment with VGC for 61 episodes of CMV infection. The antigenemia range was 1 to 700 infected cells/slide. Complete responses were observed in 92% and 97% after the 1st and 2nd week of treatment, respectively. Three percent of the episodes were considered refractory, requiring alternative therapy. No CMV disease was observed in this cohort.

CONCLUSION

Neutropenia was the main observed toxicity, requiring granulocyte-colony stimulating factor in 8 episodes. Outpatient treatment of CMV infection with "short-course oral VGC" given as a one-week twice-daily treatment and one week once daily maintenance is a highly effective therapy with minimal toxicity. These results require validation in a larger, randomized study.

Optimal management of cytomegalovirus retinitis in patients with AIDS

Cytomegalovirus (CMV) retinitis is the most common cause of vision loss in patients with acquired immunodeficiency syndrome (AIDS). CMV retinitis afflicted 25% to 42% of AIDS patients in the pre-highly active antiretroviral therapy (HAART) era, with most vision loss due to macula-involving retinitis or retinal detachment. The introduction of HAART significantly decreased the incidence and severity of CMV retinitis. Optimal treatment of CMV retinitis requires a thorough evaluation of the patient's immune status and an accurate classification of the retinal lesions. When retinitis is diagnosed, HAART therapy should be started or improved, and anti-CMV therapy with oral valganciclovir, intravenous ganciclovir, foscarnet, or cidofovir should be administered. Selected patients, especially those with zone 1 retinitis, may receive intravitreal drug injections or surgical implantation of a sustained-release ganciclovir reservoir. Effective anti-CMV therapy coupled with HAART significantly decreases the incidence of vision loss and improves patient survival. Immune recovery uveitis and retinal detachments are important causes of moderate to severe loss of vision. Compared with the early years of the AIDS epidemic, the treatment emphasis in the post- HAART era has changed from short-term control of retinitis to long-term preservation of vision. Developing countries face shortages of health care professionals and inadequate supplies of anti-CMV and anti-HIV medications. Intravitreal ganciclovir injections may be the most cost effective strategy to treat CMV retinitis in these areas.

Valganciclovir in the treatment of cytomegalovirus retinitis in HIV-infected patients

Oral valganciclovir is a new and highly efficacious alternative to the chronic administration of ganciclovir in the treatment of cytomegalovirus (CMV) retinitis in HIV-infected patients. In addition to its excellent bioavailability and favorable pharmacokinetic profile, valganciclovir has also proved cost effective and is the most widely used drug in the armamentarium for the treatment of CMV retinitis. Valganciclovir is a prodrug of ganciclovir, the erstwhile commonly used therapy. In March 2001, the US Food and Drug Administration approved valganciclovir for the induction and maintenance treatment of CMV disease, including CMV retinitis. Valganciclvoir has compared favorably with both oral and intravenous treatments for induction and maintenance therapy with ganciclovir. The reduced pill burden and the ease of oral administration has helped avoid the risks associated with intravenous therapy. The most serious adverse event is neutropenia, which makes the patient susceptible to infections. In the current review, we have compiled all the available evidence-based information on valganciclovir.

Formed and preformed metabolites: facts and comparisons

The administration of metabolites arising from new drug entities is often employed in drug discovery to investigate their associated toxicity. It is expected that administration of metabolites can predict the exposure of metabolites originating from the administration of precursor drug. Whether exact and meaningful information can be obtained from this has been a topic of debate. This communication summarizes observations and theoretical relationships based on physiological modelling for the liver, kidney and intestine, three major eliminating organs/tissues. Theoretical solutions based on physiological modelling of organs were solved, and the results suggest that deviations are expected. Here, examples of metabolite kinetics observed mostly in perfused organs that did not match predictions are provided. For the liver, discrepancies in fate between formed and preformed metabolites may be explained by the heterogeneity of enzymes, the presence of membrane barriers and whether transporters are involved. For the kidney, differences have been attributed to glomerular filtration of the preformed but not the formed metabolite. For the intestine, the complexity of segregated flows to the enterocyte and serosal layers and differences in metabolism due to the route of administration are addressed. Administration of the metabolite may or may not directly reflect the toxicity associated with drug use. However, kinetic data on the preformed metabolite will be extremely useful to develop a sound model for modelling and simulations; in-vitro evidence on metabolite handling at the target organ is also paramount. Subsequent modelling and simulation of metabolite data arising from a combined model based on both drug and preformed metabolite data are needed to improve predictions on the behaviours of formed metabolites.

Population pharmacokinetics of ganciclovir after intravenous ganciclovir and oral valganciclovir administration in solid organ transplant patients infected with cytomegalovirus

A population pharmacokinetics analysis was performed after intravenous ganciclovir and oral valganciclovir in solid organ transplant patients with cytomegalovirus. Patients received ganciclovir at 5 mg/kg of body weight (5 days) and then 900 mg of valganciclovir (16 days), both twice daily with dose adjustment for renal function. A total of 382 serum concentrations from days 5 and 15 were analyzed with NONMEM VI. Renal function given by creatinine clearance (CL(CR)) was the most influential covariate in CL. The final pharmacokinetic parameters were as follows: ganciclovir clearance (CL) was 7.49.(CL(CR)/57) liter/h (57 was the mean population value of CL(CR)); the central and peripheral distribution volumes were 31.9 liters and 32.0 liters, respectively; intercompartmental clearance was 10.2 liter/h; the first-order absorption rate constant was 0.895 h(-1); bioavailability was 0.825; and lag time was 0.382 h. The CL(CR) was the best predictor of CL, making dose adjustment by this covariate important to achieve the most efficacious ganciclovir exposure.

Expression of the human cytomegalovirus UL97 gene in a chimeric guinea pig cytomegalovirus (GPCMV) results in viable virus with increased susceptibility to ganciclovir and maribavir

In lieu of a licensed vaccine, antivirals are being considered as an intervention to prevent congenital human cytomegalovirus (HCMV) infection. Ideally, antiviral therapies should undergo pre-clinical evaluation in an animal model prior to human use. Guinea pig cytomegalovirus (GPCMV) is the only small animal model for congenital CMV. However, GPCMV is not susceptible to the most commonly used HCMV antiviral, ganciclovir (GCV), rendering in vivo study of this agent problematic in the guinea pig model. Human cytomegalovirus (HCMV) susceptibility to GCV is linked to the UL97 gene. We hypothesized that GPCMV susceptibility to GCV could be improved by inserting the HCMV (Towne) UL97 gene into the GPCMV genome in place of the homolog, GP97. A chimeric GPCMV (GPCMV::UL97) expressed UL97 protein, and replicated efficiently in cell culture, with kinetics similar to wild-type GPCMV. In contrast, deletion of GP97 resulted in a virus (GPCMVdGP97) that grew poorly in culture. GPCMV::UL97 had substantially improved susceptibility to the inhibitory effects of GCV in comparison to wild-type GPCMV. Additionally, GPCMV::UL97 exhibited improved susceptibility to another antiviral undergoing clinical trials, maribavir (MBV; benzimidazole riboside 1263W94), which also acts through UL97.