Dosing of intravenous ganciclovir for the prophylaxis and treatment of cytomegalovirus infection in solid organ transplant recipients

Challenges for the improvement of valganciclovir prophylaxis in solid organ transplantation and the possible role of therapeutic drug monitoring in adults

Cytomegalovirus (CMV) infection frequently occurs after solid organ transplantation and is associated with an increased morbidity and mortality. Fortunately, the development of valganciclovir prophylaxis has lowered the incidence of CMV infection and its complications in immunosuppressed solid organ transplant recipients. However, breakthrough infections during valganciclovir prophylaxis and late CMV infection after cessation of valganciclovir prophylaxis still occur with the current prophylactic strategy. Additionally, valganciclovir resistance has emerged among CMV strains, which complicates the treatment of CMV infections. Furthermore, the use of valganciclovir is associated with myelotoxicity, which can lead to the premature withdrawal of prophylaxis. It is important to address these current issues in order to improve the standard care after solid organ transplantation. This paper will therefore discuss the clinical practice of valganciclovir prophylaxis, elaborate on its issues and suggest how to improve the current prophylactic strategy with a possible role for therapeutic drug monitoring.

Evidence supporting the use of therapeutic drug monitoring of ganciclovir in transplantation

PURPOSE OF REVIEW

This review describes current knowledge of ganciclovir (GCV) and valganciclovir (ValGCV) pharmacokinetic/pharmacodynamic characteristics, highlighting the likely contribution from host genetic factors to interpatient variability. The evidence and challenges surrounding optimization of drug dosing through therapeutic drug monitoring (TDM) are examined, with recommendations made.

RECENT FINDINGS

Pharmacokinetic studies of current dosing guidelines have shown high interindividual and intraindividual variability of GCV concentrations. This is sometimes associated with a slow decline in cytomegalovirus (CMV) viral load in some transplant recipients. A high incidence of GCV-associated myelosuppression has limited the use of this drug in the transplant setting. Patient groups identified to benefit from GCV TDM include pediatric patients, cystic fibrosis with lung transplantation, obese with kidney transplantation, and patients with fluctuating renal function or on hemodialysis. The emergence of refractory resistant CMV, particularly in immune compromised patients, highlights the importance of appropriate dosing of these antivirals. Host genetic factors need to be considered where recently, two host genes were shown to account for interpatient variation during ganciclovir therapy. Therapeutic Drug Monitoring has been shown to improve target antiviral-level attainment. The use of TDM may guide concentration-based dose adjustment, potentially improving virological and clinical outcomes. However, evidence supporting the use of TDM in clinical practice remains limited and further study is needed in the transplant cohort.

SUMMARY

Further studies examining novel biomarkers are needed to guide target concentrations in prophylaxis and treatment. The use of TDM in transplant recipients is likely to improve the clinical efficacy of current antivirals and optimize outcomes in transplant recipients.

Optimizing ganciclovir and valganciclovir dosing regimens in pediatric patients with cytomegalovirus infection: a spotlight on therapeutic drug monitoring

INTRODUCTION

Infants and immunocompromised children with cytomegalovirus (CMV) infection have significant morbidity and mortality. Ganciclovir (GCV) and its oral prodrug valganciclovir (VGCV) are the major antiviral options of choice for the prophylaxis and treatment of CMV infection. However, with the currently recommended dosing regimens used in pediatric patients, large intra- and inter-individual variability of pharmacokinetic (PK) parameters and exposure are observed.

AREAS COVERED

This review describes the PK and pharmacodynamic (PD) characteristics of GCV and VGCV in pediatrics. Moreover, the role of therapeutic drug monitoring (TDM) and current clinical practice for GCV and VGCV dosing regimens optimization in pediatrics are discussed.

EXPERT OPINION

GCV/VGCV TDM has shown the potential value to improve the benefit/risk ratio in pediatrics when using the therapeutic ranges derived from adults. However, well-designed studies are required to evaluate the relationship of TDM with clinical outcomes. Furthermore, studies to explore the children-specific dose-response-effect relationships will be helpful to facilitate the TDM practice. In the clinical setting, optimal sampling methods such as limited sampling strategies for pediatrics can be used in TDM and intracellular ganciclovir triphosphate may be used as an alternative TDM marker.

Population Pharmacokinetic and Pharmacodynamic Analysis of Valganciclovir for Optimizing Preemptive Therapy of Cytomegalovirus Infections in Kidney Transplant Recipients

This study aimed to develop a population pharmacokinetic/pharmacodynamic (PK/PD) model of valganciclovir for preemptive therapy of cytomegalovirus (CMV) infection in kidney transplant patients. A population PK/PD model was developed with Monolix. Ganciclovir concentrations and CMV viral loads were obtained retrospectively from kidney transplant patients receiving routine clinical care. Ten thousand Monte Carlo simulations were performed with the licensed dosages adjusted for renal function to assess the probability of attaining a viral load target of ≤290 and ≤137 IU/mL. Fifty-seven patients provided 343 ganciclovir concentrations and 328 CMV viral loads for PK/PD modeling. A one-compartment pharmacokinetic model coupled with an indirect viral turnover growth model with stimulation of viral degradation pharmacodynamic model was devised. Simulations showed that 1- and 2-log10 reduction of CMV viral load mostly occurred between a median of 5 to 6 and 12 to 16 days, respectively. The licensed dosages achieved a probability of reaching the viral load target ≥90% at days 35 to 49 and 42 to 56 for the thresholds of ≤290 and ≤137 IU/mL, respectively. Simulations indicate that in patients with an estimated glomerular filtration rate of 10 to 24 mL/min/1.73m2, a dose increase to 450 mg every 36 h may reduce time to optimal viral load target to days 42 and 49 from a previous time of 49 and 56 days for the thresholds of ≤290 and ≤137 IU/mL, respectively. Currently licensed dosages of valganciclovir for preemptive therapy of CMV infection may achieve a viral load reduction within the first 2 weeks, but treatment should continue for ≥35 days to ensure viral load suppression.

Population Pharmacokinetics of Ganciclovir in Allogeneic Hematopoietic Stem Cell Transplant Patients

Treatment of cytomegalovirus (CMV) infection in allogeneic hematopoietic stem cell transplantation (alloHCT) patients with ganciclovir is complicated by toxicity and resistance. This study aimed to develop an intravenous ganciclovir population pharmacokinetic model for post-alloHCT patients and to determine dosing regimens likely to achieve suggested therapeutic exposure targets. We performed a prospective observational single-center pharmacokinetic study in adult alloHCT patients requiring treatment with intravenous ganciclovir for CMV viremia or disease. Samples were analyzed using a validated ultraperformance liquid chromatography method. Population pharmacokinetic analysis and Monte Carlo simulations (n = 1000) were performed using Pmetrics for R. Twenty patients aged 18 to 69 years were included in the study. A 2-compartment model with linear elimination from the central compartment and between occasion variability best described the data. Incorporating creatinine clearance (CLCR) estimated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and presence of continuous renal replacement therapy as covariates for ganciclovir clearance improved the model. Compared to current dosing recommendations, simulations demonstrated loading doses were required to achieve a target AUC24 of 80 to 120 mg.h/L on day 1 of induction therapy. Increased individualization of post-loading induction and maintenance doses based on CLCR is required to achieve the suggested exposures for efficacy (AUC24 >80/>40 mg.h/L for induction/maintenance) while remaining below the exposure thresholds for toxicity (AUC24 <120/<60 mg.h/L for induction/maintenance). Intravenous ganciclovir dosing in alloHCT patients can be guided by CLCR estimated by CKD-EPI. Incorporation of loading doses into induction dosing regimens should be considered for timely achievement of currently suggested exposures.

Pharmacokinetics, Pharmacodynamics, and Therapeutic Drug Monitoring of Valganciclovir and Ganciclovir in Transplantation

Ganciclovir and valganciclovir are first choice drugs for the prevention and treatment of cytomegalovirus infection and disease in solid organ and stem cell transplant recipients. Only a few studies on the pharmacokinetics and exposure/efficacy or exposure/safety relationships of ganciclovir and valganciclovir in transplant recipients have been published so far, and there are still controversies about the exposure parameter to use for therapeutic drug monitoring (TDM). We performed an extensive literature review of the clinical pharmacokinetics data, the exposure/effect relationships in terms of efficacy and safety, and the available tools for valganciclovir and ganciclovir TDM in adults and pediatrics transplant recipients. The pharmacokinetics of ganciclovir and valganciclovir is well described in adults and children, and a high interindividual variability is commonly observed. In contrast, the drug pharmacodynamics has been poorly described in adults and barely in children. The average 24-hour area under the concentration-time curve (AUC_0-24h ) seems to be the best predictor of efficacy and toxicity. The benefit of TDM remains controversial in adult patients but should be considered in children due to higher interindividual variability and lower probability of target attainment. Several bayesian estimators based on limited sampling strategies have been developed with this aim and may be used in clinical practice for the AUC-based individual dose adjustment of ganciclovir and valganciclovir.

Ganciclovir therapeutic drug monitoring in transplant recipients

BACKGROUND

The use of (val)ganciclovir is complicated by toxicity, slow response to treatment and acquired resistance.

OBJECTIVES

To evaluate a routine therapeutic drug monitoring (TDM) programme for ganciclovir in a transplant patient population.

METHODS

An observational study was performed in transplant recipients from June 2018 to February 2020. Dose adjustments were advised by the TDM pharmacist as part of clinical care. For prophylaxis, a trough concentration (Cmin) of 1-2 mg/L and an AUC24h of >50 mg·h/L were aimed for. For treatment, a Cmin of 2-4 mg/L and an AUC24h of 80-120 mg·h/L were aimed for.

RESULTS

Ninety-five solid organ and stem cell transplant patients were enrolled. Overall, 450 serum concentrations were measured; with a median of 3 (IQR = 2-6) per patient. The median Cmin and AUC24h in the treatment and prophylaxis groups were 2.0 mg/L and 90 mg·h/L and 0.9 mg/L and 67 mg·h/L, respectively. Significant intra- and inter-patient patient variability was observed. The majority of patients with an estimated glomerular filtration rate of more than 120 mL/min/1.73 m2 and patients on continuous veno-venous haemofiltration showed underexposure. The highest Cmin and AUC24h values were associated with the increase in liver function markers and decline in WBC count as compared with baseline.

CONCLUSIONS

This study revealed that a standard weight and kidney function-based dosing regimen resulted in highly variable ganciclovir Cmin and under- and over-exposure were observed in patients on dialysis and in patients with increased renal function. Clearly there is a need to explore the impact of concentration-guided dose adjustments in a prospective study.

A Systematic Review of the Clinical Pharmacokinetics, Pharmacodynamics and Toxicodynamics of Ganciclovir/Valganciclovir in Allogeneic Haematopoietic Stem Cell Transplant Patients

BACKGROUND

Ganciclovir (GCV) and valganciclovir (VGCV) are the first-line agents used to prevent and treat cytomegalovirus (CMV) infection in allogeneic haematopoietic stem cell transplant (alloHCT) patients.

OBJECTIVE

The aim of this work was to describe available data for the clinical pharmacokinetics, pharmacodynamics and toxicodynamics of GCV and VGCV and the potential of a therapeutic drug monitoring strategy to improve outcomes in the alloHCT population.

METHODS

We systematically reviewed the pharmacokinetics (dose-exposure), pharmacodynamics (exposure-efficacy) and toxicodynamics (exposure-toxicity) of GCV and VGCV in alloHCT patients with CMV infection. Studies including alloHCT patients treated for CMV infection reporting the pharmacokinetics, pharmacodynamics and toxicodynamics of GCV or VGCV were searched for using the PUBMED and EMBASE databases from 1946 to 2019. Only studies involving participants > 12 years of age and available in the English language were included.

RESULTS

A total of 179 patients were included in the 14 studies that met the inclusion criteria, of which 6 examined GCV pharmacokinetics only, while 8 also examined GCV pharmacodynamics and toxicodynamics. Reported pharmacokinetic parameters showed considerable interpatient variability and were different from other populations, such as solid organ transplant and human immunodeficiency virus-infected patients. Only one study found a correlation between neutropenia and elevated peak and trough GCV concentrations, with no other significant pharmacodynamic and toxicodynamic relationships identified. While therapeutic drug monitoring of GCV is performed in some institutions, no association between GCV therapeutic drug monitoring and clinical outcomes was identified.

CONCLUSION

Further studies of the pharmacokinetics, pharmacodynamics and toxicodynamics of GCV/VGCV in alloHCT patients are required to identify a more robust therapeutic range and to subsequently quantify the potential value of therapeutic drug monitoring of GCV/VGCV in the alloHCT population.

Valganciclovir-Ganciclovir Use and Systematic Therapeutic Drug Monitoring. An Invitation to Antiviral Stewardship

Valganciclovir (VGCV) and ganciclovir (GCV) doses must be adjusted according to indication, renal function and weight. No specific therapeutic exposure values have been established. We aimed to evaluate the adequacy of VGCV/GCV doses, to assess the interpatient variability in GCV serum levels, to identify predictive factors for this variability and to assess the clinical impact. This is a prospective study at a tertiary institution including hospitalized patients receiving VGCV/GCV prophylaxis or treatment. Adequacy of the antiviral dose was defined according to cytomegalovirus guidelines. Serum levels were determined using High-Performance Liquid Chromatography. Blood samples were drawn at least 3 days after antiviral initiation. Outcome was considered favorable if there was no evidence of cytomegalovirus infection during prophylaxis or when a clinical and microbiological resolution was attained within 21 days of treatment and no need for drug discontinuation due to toxicity. Seventy consecutive patients [74.3% male/median age: 59.2 years] were included. VGCV was used in 25 patients (35.7%) and GCV in 45 (64.3%). VGCV/GCV initial dosage was deemed adequate in 47/70 cases (67.1%), lower than recommended in 7/70 (10%) and higher in 16/70 (22.9%). Large inter-individual variability of serum levels was observed, with median trough levels of 2.3 mg/L and median peak levels of 7.8 mg/L. Inadequate dosing of VGCV/GCV and peak levels lower than 8.37 or greater than 11.86 mg/L were related to poor outcome. Further studies must be performed to confirm these results and to conclusively establish if VGCV/GCV therapeutic drug monitoring could be useful to improve outcomes in specific clinical situations.

Optimization of Ganciclovir use in allogeneic hematopoietic cell transplant recipients - the role of therapeutic drug monitoring

Introduction: Cytomegalovirus (CMV) is an opportunistic infectious complication that can occur after allogeneic hematopoietic cell transplantation (HCT). The mainstay of treatment and prevention of this infection is ganciclovir and its ester prodrug valganciclovir. There is conflicting evidence on the clinical utility of routine ganciclovir therapeutic drug monitoring (TDM) as a means to optimize treatment.Areas covered: This review aims to describe the current knowledge of the pharmacokinetic and pharmacodynamic characteristics of ganciclovir and valganciclovir, and to explore the evidence and challenges surrounding ganciclovir TDM within the allogeneic HCT cohort.Expert opinion: Ganciclovir TDM is important to optimize efficacy in selected patient groups where there are variable pharmacokinetic factors or inadequate response to treatment. However, defined pharmacokinetic exposures which correlate with treatment efficacy and toxicity remain elusive. Prospective clinical studies in specific patient groups are required to clarify this issue. Alternative TDM targets such as the intracellular ganciclovir triphosphate should be explored as they may prove to have better correlation with clinical outcomes and adverse effects. With recent advances in CMV immune monitoring, novel approaches integrating TDM with specific CMV immune phenotyping in a predictive model will be advantageous in optimizing ganciclovir dosing by combining TDM with a risk stratification approach.

Population Pharmacokinetics and Bayesian Estimation of the Area Under the Concentration-Time Curve for Ganciclovir in Adult Chinese Renal Allograft Recipients After Valganciclovir Administration

Valganciclovir (VGCV) is the prodrug of ganciclovir (GCV). The objective of this study was to establish a population pharmacokinetic model (PPK) of GCV to investigate the PK characteristics of GCV after administration of VGCV in adult Chinese renal allograft recipients. Seventy Chinese renal allograft recipients were given 450 mg (n = 41) or 900 mg (n = 29) VGCV daily. Blood samples were drawn 0-24 hours after 5 days' therapy, and GCV plasma levels were determined. The PPK model was constructed using nonlinear mixed-effects modeling, and the Bayesian estimation of AUC_0-24h was constructed for an individual patient based on limited plasma samples. The PK of GCV was best described by a 2-compartment model with a first-order absorption process. The CL/F, V₂ /F, Q/F, V₃ /F, K_a , and lag time of GCV were 15.8 ± 0.71 L/h, 10.9 ± 2.38 L, 3.98 ± 0.40 L/h, 167 ± 44.0 L, 0.23 ± 0.0078 1/h, and 0.93 ± 0.017 hours, respectively. Clearance of creatinine was found to have a significant impact on the CL/F of GCV (P < .01). Sampling strategies consisted of plasma concentrations 0 and 2 and 0, 2, and 4 hours after VGCV administration were shown to be suitable for the estimation of the GCV AUC_0-24h . The PPK model was acceptable and can describe the PK of GCV in Chinese renal transplant patients administered VGCV. The AUC_0-24h of GCV in Chinese renal transplant patients can be calculated by a limited sampling strategy method.

Antimicrobial therapeutic drug monitoring in critically ill adult patients: a Position Paper

Purpose

This Position Paper aims to review and discuss the available data on therapeutic drug monitoring (TDM) of antibacterials, antifungals and antivirals in critically ill adult patients in the intensive care unit (ICU). This Position Paper also provides a practical guide on how TDM can be applied in routine clinical practice to improve therapeutic outcomes in critically ill adult patients.

Methods

Literature review and analysis were performed by Panel Members nominated by the endorsing organisations, European Society of Intensive Care Medicine (ESICM), Pharmacokinetic/Pharmacodynamic and Critically Ill Patient Study Groups of European Society of Clinical Microbiology and Infectious Diseases (ESCMID), International Association for Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT) and International Society of Antimicrobial Chemotherapy (ISAC). Panel members made recommendations for whether TDM should be applied clinically for different antimicrobials/classes.

Results

TDM-guided dosing has been shown to be clinically beneficial for aminoglycosides, voriconazole and ribavirin. For most common antibiotics and antifungals in the ICU, a clear therapeutic range has been established, and for these agents, routine TDM in critically ill patients appears meritorious. For the antivirals, research is needed to identify therapeutic targets and determine whether antiviral TDM is indeed meritorious in this patient population. The Panel Members recommend routine TDM to be performed for aminoglycosides, beta-lactam antibiotics, linezolid, teicoplanin, vancomycin and voriconazole in critically ill patients.

Conclusion

Although TDM should be the standard of care for most antimicrobials in every ICU, important barriers need to be addressed before routine TDM can be widely employed worldwide.

Electronic supplementary material

The online version of this article (10.1007/s00134-020-06050-1) contains supplementary material, which is available to authorized users.

Relationship of Ganciclovir Therapeutic Drug Monitoring with Clinical Efficacy and Patient Safety

The clinical utility of ganciclovir therapeutic drug monitoring (TDM) is unknown. We retrospectively analyzed adult patients treated for cytomegalovirus (CMV) infection with ganciclovir with TDM between 2005 and 2015. The primary outcome was an association between ganciclovir TDM and clinical efficacy endpoints within 30 days, defined by viral load and symptomatology. Secondary outcomes included safety endpoints, evaluated within 7 days of the last administered dose of ganciclovir. Of 175 patients evaluated, 82 patients with CMV infection were included in our analysis with a median (interquartile range) baseline CMV viral load of 5,500 (3,000 to 15,200) copies/ml. The majority achieved undetectable or reduced CMV viral load below the lower limit of quantification (74.4%) with improvement in symptomatology (70.7%) at 30 days. Among patients with detectable CMV viremia at 30 days, the viral load had declined to a median of 1,000 (1,000 to 3,090) copies/ml. We did not observe significant associations between the efficacy outcomes and ganciclovir trough (P = 0.20 and P = 0.20, respectively) or peak concentrations (P = 0.14 and P = 0.14, respectively). Similarly, there was no significant association between ganciclovir trough or peak concentrations and safety endpoints, including leukopenia (P = 0.48 and P = 0.69), neutropenia (P = 0.59 and P = 0.69), thrombocytopenia (P = 0.29 and P = 0.37), anemia (P = 0.51 and P = 0.35), nephrotoxicity (P = 0.41 and P = 0.57), and neurotoxicity (P = 0.22 and P = 0.48). We did not observe any associations between ganciclovir TDM and clinical efficacy or safety endpoints. Routine ganciclovir TDM may be of limited value. Future studies may be warranted to identify specific populations with unpredictable pharmacokinetic and pharmacodynamics profiles in whom ganciclovir TDM may be of benefit.

Inhibition of Cytomegalovirus Replication with Extended-Half-Life Synthetic Ozonides

Artesunate (AS), a semisynthetic artemisinin approved for malaria therapy, inhibits human cytomegalovirus (HCMV) replication in vitro, but therapeutic success in humans has been variable. We hypothesized that the short in vivo half-life of AS may contribute to the different treatment outcomes. We tested novel synthetic ozonides with longer half-lives against HCMV in vitro and mouse cytomegalovirus (MCMV) in vivo Screening of the activities of four ozonides against a pp28-luciferase-expressing HCMV Towne recombinant identified OZ418 to have the best selectivity; its effective concentration inhibiting viral growth by 50% (EC₅₀) was 9.8 ± 0.2 µM, and cytotoxicity in noninfected human fibroblasts (the concentration inhibiting cell growth by 50% [CC₅₀]) was 128.1 ± 8.0 µM. In plaque reduction assays, OZ418 inhibited HCMV TB40 in a concentration-dependent manner as well as a ganciclovir (GCV)-resistant HCMV isolate. The combination of OZ418 and GCV was synergistic in HCMV inhibition in vitro Virus inhibition by OZ418 occurred at an early stage and was dependent on the cell density at the time of infection. OZ418 treatment reversed HCMV-mediated cell cycle progression and correlated with the reduction of HCMV-induced expression of pRb, E2F1, and cyclin-dependent kinases 1, 2, 4, and 6. In an MCMV model, once-daily oral administration of OZ418 had significantly improved efficacy against MCMV compared to that of twice-daily oral AS. A parallel pharmacokinetic study with a single oral dose of OZ418 or AS showed a prolonged plasma half-life and higher unbound concentrations of OZ418 than unbound concentrations of AS. In summary, ozonides are proposed to be potential therapeutics, alone or in combination with GCV, for HCMV infection in humans.

Systematic review of ganciclovir pharmacodynamics during the prevention of cytomegalovirus infection in adult solid organ transplant recipients

Human cytomegalovirus (CMV) represents the most common infection among recipients of solid organ transplants (SOTs). Previous meta-analysis showed 0.8% of SOT recipients developed CMV disease whilst receiving valganciclovir (ValGCV) prophylaxis. However, the clinical utility of monitoring ganciclovir (GCV) blood concentrations is unclear. We systematically reviewed the association between GCV concentrations during prophylaxis and the incidence of CMV. MEDLINE and EMBASE databases were searched for studies between 1946 and 2018, where GCV pharmacokinetics and incidence of CMV viraemia or disease in SOT were available. Research designs included randomised trials, comparative, prospective cohort, retrospective, or case report studies. Only human adult studies were included, with English language restriction. The 11 studies that met the eligibility criteria included 610 participants receiving GCV or ValGCV prophylaxis. Quality assessment showed 2/4 randomised trials, 4/6 cohort studies, and 1/1 case report were of high quality. Despite dose adjustments for renal impairment, mean GCV exposures for patients were heterogeneous and ranged between 28 and 53.7 μg·h/mL across three randomised trials. The incidence of CMV infection and disease ranged from 0% to 50% and 0% to 3.1%, respectively, with follow up between 3 to 9 months. One study showed statistical power in determining relationship, where GCV exposure at 40 to 50 μg·h/mL in high-risk SOT recipients was associated with a reduced risk of viraemia. Clinical monitoring for GCV exposure can be applied to high-risk SOT recipients during ValGCV prophylaxis; however, further studies are needed to determine the utility of monitoring in all SOT recipients.

Is drug repurposing the answer for cytomegalovirus treatment or prevention?

Medical progress has placed cytomegalovirus (CMV) as one of the most important viral pathogens for which treatment is limited and a vaccine is not yet available. The limited treatment options for CMV triggered efforts to discover new antivirals. Drug screening raised hope but also uncertainties as to whether drug repurposing may be a practical approach for infectious diseases in general and CMV in particular. I summarize here several of such agents as well as an approach to advance repurposing for CMV therapy.

Letermovir for the management of cytomegalovirus infection

INTRODUCTION

Cytomegalovirus (CMV) is a major cause of morbidity and mortality in immunocompromised patients. Available antivirals are fraught with adverse effects and risk for the development of CMV resistance. Letermovir is a novel antiviral in the late stages of drug development for the treatment and prevention of CMV. Areas covered: A MEDLINE search of the MeSH terms 'letermovir,' 'cytomegalovirus,' 'hematopoietic stem cell transplant,' and 'solid organ transplant,' was last conducted on 15 August 2016. Articles were selected on the basis of their contribution to current knowledge about letermovir. Expert opinion: Letermovir's mechanism of action, pharmacokinetic and pharmacodynamic profile, and favorable efficacy and safety make it an attractive option for both the prevention and treatment of CMV in immunocompromised patients. The lack of cross-resistance with other antivirals and the absence of myelosuppression are two prominent characteristics of letermovir that could support broad use of this product following FDA-approval. One major limitation is its lack of activity against other herpesviruses, which are commonly seen in immunocompromised hosts. We believe that with additional clinical efficacy data, this medication could emerge as a primary option for the prevention and treatment of CMV in the immunocompromised patient population.

13 C-metabolic flux analysis of human adenovirus infection: Implications for viral vector production

Adenoviruses are human pathogens increasingly used as gene therapy and vaccination vectors. However, their impact on cell metabolism is poorly characterized. We performed carbon labeling experiments with [1,2-¹³ C]glucose or [U-¹³ C]glutamine to evaluate metabolic alterations in the amniocyte-derived, E1-transformed 1G3 cell line during production of a human adenovirus type 5 vector (AdV5). Nonstationary ¹³ C-metabolic flux analysis revealed increased fluxes of glycolysis (17%) and markedly PPP (over fourfold) and cytosolic AcCoA formation (nearly twofold) following infection of growing cells. Interestingly, infection of growth-arrested cells increased overall carbon flow even more, including glutamine anaplerosis and TCA cycle activity (both over 1.5-fold), but was unable to stimulate the PPP and was associated with a steep drop in AdV5 replication (almost 80%). Our results underscore the importance of nucleic and fatty acid biosynthesis for adenovirus replication. Overall, we portray a metabolic blueprint of human adenovirus infection, highlighting similarities with other viruses and cancer, and suggest strategies to improve AdV5 production. Biotechnol. Bioeng. 2017;114: 195-207. © 2016 Wiley Periodicals, Inc.

Therapeutic drug monitoring of anti-infective agents in critically ill patients

Initial adequate anti-infective therapy is associated with significantly improved clinical outcomes for patients with severe infections. However, in critically ill patients, several pathophysiological and/or iatrogenic factors may affect the pharmacokinetics of anti-infective agents leading to suboptimal drug exposure, in particular during the early phase of therapy. Therapeutic drug monitoring (TDM) may assist to overcome this problem. We discuss the available evidence on the use of TDM in critically ill patient populations for a number of anti-infective agents, including aminoglycosides, β-lactams, glycopeptides, antifungals and antivirals. Also, we present the available evidence on the practices of anti-infective TDM and describe the potential utility of TDM to improve treatment outcome in critically ill patients with severe infections. For aminoglycosides, glycopeptides and voriconazole, beneficial effects of TDM have been established on both drug effectiveness and potential side effects. However, for other drugs, therapeutic ranges need to be further defined to optimize treatment prescription in this setting.

Metabolic flux profiling of MDCK cells during growth and canine adenovirus vector production

Canine adenovirus vector type 2 (CAV2) represents an alternative to human adenovirus vectors for certain gene therapy applications, particularly neurodegenerative diseases. However, more efficient production processes, assisted by a greater understanding of the effect of infection on producer cells, are required. Combining [1,2-(13)C]glucose and [U-(13)C]glutamine, we apply for the first time (13)C-Metabolic flux analysis ((13)C-MFA) to study E1-transformed Madin-Darby Canine Kidney (MDCK) cells metabolism during growth and CAV2 production. MDCK cells displayed a marked glycolytic and ammoniagenic metabolism, and (13)C data revealed a large fraction of glutamine-derived labelling in TCA cycle intermediates, emphasizing the role of glutamine anaplerosis. (13)C-MFA demonstrated the importance of pyruvate cycling in balancing glycolytic and TCA cycle activities, as well as occurrence of reductive alphaketoglutarate (AKG) carboxylation. By turn, CAV2 infection significantly upregulated fluxes through most central metabolism, including glycolysis, pentose-phosphate pathway, glutamine anaplerosis and, more prominently, reductive AKG carboxylation and cytosolic acetyl-coenzyme A formation, suggestive of increased lipogenesis. Based on these results, we suggest culture supplementation strategies to stimulate nucleic acid and lipid biosynthesis for improved canine adenoviral vector production.

Optimal sparse sampling for estimating ganciclovir/valganciclovir AUC in solid organ transplant patients using NONMEN

BACKGROUND

Ganciclovir and valganciclovir (GCV/VGCV) are used for the treatment and prophylaxis of cytomegalovirus in solid organ transplant (SOT) patients. An area under the time-concentration curve of 40-50 μg × h/mL is related to efficacy. Therapeutic drug monitoring could prevent suboptimal drug exposure and adverse events, but obtaining full concentration profiles is not feasible. Sampling optimization by developing a reliable and clinically applicable limited sampling strategy (LSS) may simplify dose adjustment.

METHODS

An LSS was developed using an original pharmacokinetic (PK) data set of 40 full profiles from 20 adult SOT patients. The LSS was developed based on population and Bayesian prediction approaches. Population PK parameters from a previous model were used for simulation or as priors (NONMEM version 7.2). Median percentage of prediction error and median of absolute percentage prediction error were calculated for plasma clearance (CL) and central compartment distribution volume (V(2)). Bias and precisions were compared using 1-way analysis of variance (SPSSv19.0).

RESULTS

Sampling windows were designed according to the PK profile previously observed with the entire set of data. The 4 windows selected were distributed from 0.5 to 1.5 hours, 2 to 3 hours, 4 to 5 hours, and 6 to 8 hours. Predose and concentrations beyond 8 hours were not considered in any case because simulated negative concentrations occurred in both cases. Predicted exposure using 3 sampling times (0.5-1.5, 4-5, and 6-8 hours) showed the best predictive performance, by either the population or Bayesian approaches. Bias and imprecision for CL and V(2) were 0 and 0.60%, and -0.78% and 0.78%, respectively.

CONCLUSIONS

GCV/VCG area under the time-concentration curve in SOT patients could be predicted with acceptable accuracy for clinical management and dose individualization using LSS. The estimator of GCV/VGC, using 3 concentrations measured at 0.5-1.5, 4-5, and 6-8 hours after drug intake, could be used for dose adjustment.

Clinical pharmacokinetics and pharmacodynamics of ganciclovir and valganciclovir in children with cytomegalovirus infection

INTRODUCTION

Among infants and immunocompromised children cytomegalovirus (CMV) is associated with significant morbidity and mortality.

AREAS COVERED

This review describes the clinical pharmacokinetics and pharmacodynamics of ganciclovir and valganciclovir for the treatment and prevention of CMV infection in children.

EXPERT OPINION

A 24-h ganciclovir area under the concentration versus time curve (AUC₀₋₂₄) of 40 - 60 μg h/ml decreased the risk of CMV infection for adults undergoing CMV prophylaxis. For adults undergoing treatment for active CMV disease, a target AUC₀₋₁₂ of 40 - 60 μg h/ml has been suggested. The applicability of these targets to children remains uncertain; however, with the most sophisticated dosing regimens developed to date only 21% of patients are predicted to reach these targets. Moving forward, identification of optimal pediatric ganciclovir and valganciclovir dosing regimens may involve the use of an externally validated pediatric population pharmacokinetic model for empirical dosing, an optimal sampling strategy for collecting a minimal number of blood samples for each patient and Bayesian updating of the dosing regimen based on an individual patient's pharmacokinetic profile.

The role of therapeutic drug monitoring in the treatment of cytomegalovirus disease in kidney transplantation

Cytomegalovirus (CMV) infection is a common complication following solid organ transplantation that may severely affect the outcome of transplantation. Ganciclovir (GCV) and its prodrug valganciclovir are successfully used to prevent and treat CMV infection; however, in a small percentage of patients, CMV gene mutations may lead to drug resistance. GCV resistance is defined as increasing CMV viremia or progressive clinical disease during prolonged antiviral therapy, due to CMV gene mutation. This has emerged as a new challenge, especially because alternative drugs such as cidofovir and foscarnet have a number of important side effects. Here we report the case of a kidney transplanted patient who experienced life-threatening CMV disease, which initially appeared to be GCV-resistant, but was instead found to be associated with inadequate antiviral drug levels. The patient was then successfully treated by monitoring plasma GCV levels. We suggest using plasma GCV monitoring in the management of all cases of critical CMV disease, in which GCV resistance is suspected.

Electronic estimations of renal function are inaccurate in solid-organ transplant recipients and can result in significant underdosing of prophylactic valganciclovir

In a prospective study of solid-organ transplant recipients (n = 22; 15 hepatic and 7 renal) receiving valganciclovir for cytomegalovirus (CMV) prophylaxis, electronic estimation of glomerular filtration rate (eGFR) underestimated the true GFR (24-h urine creatinine clearance) by >20% in 14/22 (63.6%). Its use was associated with inappropriate underdosing of valganciclovir, while the Cockroft-Gault equation was accurate in 21/22 patients (95.4%). Subtherapeutic ganciclovir levels (≤ 0.6 mg/liter) were common, occurring in 10/22 patients (45.4%); 7 had severely deficient levels (<0.3 mg/liter).

Antiviral medications for preventing cytomegalovirus disease in solid organ transplant recipients

BACKGROUND

The risk of cytomegalovirus (CMV) infection in solid organ transplant recipients has resulted in the frequent use of prophylaxis with the aim of preventing the clinical syndrome associated with CMV infection. This is an update of a review first published in 2005 and updated in 2008.

OBJECTIVES

To determine the benefits and harms of antiviral medications to prevent CMV disease and all-cause mortality in solid organ transplant recipients.

SEARCH METHODS

We searched MEDLINE, EMBASE and the Cochrane Central Registry of Controlled Trials (CENTRAL) in The Cochrane Library to February 2004 for the first version of this review. The Cochrane Renal Group's specialised register was searched to February 2007 and to July 2011 for the first and current updates of the review without language restriction.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-RCTs comparing antiviral medications with placebo or no treatment, comparing different antiviral medications and comparing different regimens of the same antiviral medications in recipients of any solid organ transplant. Studies examining pre-emptive therapy were excluded.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study eligibility, risk of bias and extracted data. Results were reported as risk ratios (RR) or risk differences (RD) with 95% confidence intervals (CI) for dichotomous outcomes and by mean difference (MD) with 95% CI for continuous outcomes. Statistical analyses were performed using the random-effects model. Subgroup analysis and univariate meta-regression were performed using restricted maximum-likelihood to estimate the between study variance. Multivariate meta-regression was performed to investigate whether the results were altered after allowing for differences in drugs used, organ transplanted, and recipient CMV serostatus at the time of transplantation.

MAIN RESULTS

We identified 37 studies (4342 participants). Risk of bias attributes were poorly performed or reported with low risk of bias reported for sequence generation, allocation concealment, blinding and selective outcome reporting in 25% or fewer studies.Prophylaxis with aciclovir, ganciclovir or valaciclovir compared with placebo or no treatment significantly reduced the risk for CMV disease (19 studies; RR 0.42, 95% CI 0.34 to 0.52), CMV infection (17 studies; RR 0.61, 95% CI 0.48 to 0.77), and all-cause mortality (17 studies; RR 0.63, 95% CI 0.43 to 0.92) primarily due to reduced mortality from CMV disease (7 studies; RR 0.26, 95% CI 0.08 to 0.78). Prophylaxis reduced the risk of herpes simplex and herpes zoster disease, bacterial and protozoal infections but not fungal infection, acute rejection or graft loss.Meta-regression showed no significant difference in the relative benefit of treatment (risk of CMV disease or all-cause mortality) by organ transplanted or CMV serostatus; no conclusions were possible for CMV negative recipients of negative organs.Neurological dysfunction was more common with ganciclovir and valaciclovir compared with placebo/no treatment. In direct comparison studies, ganciclovir was more effective than aciclovir in preventing CMV disease (7 studies; RR 0.37, 95% CI 0.23 to 0.60) and leucopenia was more common with aciclovir. Valganciclovir and IV ganciclovir were as effective as oral ganciclovir. The efficacy and adverse effects of valganciclovir/ganciclovir did not differ from valaciclovir in three small studies. Extended duration prophylaxis significantly reduced the risk of CMV disease compared with three months therapy (2 studies; RR 0.20, 95% CI 0.12 to 0.35). Leucopenia was more common with extended duration prophylaxis but severe treatment associated adverse effects did not differ between extended and three month durations of treatment.

AUTHORS' CONCLUSIONS

Prophylaxis with antiviral medications reduces CMV disease and CMV-associated mortality in solid organ transplant recipients. These data suggest that antiviral prophylaxis should be used routinely in CMV positive recipients and in CMV negative recipients of CMV positive organ transplants.

Pre-emptive treatment for cytomegalovirus viraemia to prevent cytomegalovirus disease in solid organ transplant recipients

BACKGROUND

Cytomegalovirus (CMV) is a significant cause of morbidity and mortality in solid organ transplant recipients. Pre-emptive treatment of patients with CMV viraemia using antiviral agents has been suggested as an alternative to routine prophylaxis to prevent CMV disease. This is an update of a Cochrane review first published in 2005.

OBJECTIVES

This review was conducted to evaluate the efficacy of pre-emptive treatment with antiviral medications in preventing symptomatic CMV disease.

SEARCH METHODS

For this update, we searched the Cochrane Renal Group's Specialised Register (to 16 January 2013) through contact with the Trials' Search Co-ordinator using search terms relevant to this review.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of pre-emptive treatment compared with placebo, no specific treatment or with antiviral prophylaxis in solid organ transplant recipients.

DATA COLLECTION AND ANALYSIS

Four authors assessed the quality and extracted all data. Analyses used a random-effects model and results were expressed as risk ratio (RR) and 95% confidence intervals (CI).

MAIN RESULTS

We identified 15 eligible studies (1098 participants). Of these, six investigated pre-emptive treatment versus placebo or treatment of CMV when disease occurred (standard care), eight looked at pre-emptive treatment versus antiviral prophylaxis, and one reported on oral versus intravenous pre-emptive treatment.Assessment of risk of bias identified that the processes reported for sequence generation and allocation concealment were at low risk of bias in only five and three studies, respectively. All studies were considered to be at low risk of attrition bias, and seven studies were considered to be at low risk of bias for selective reporting. Only one study reported adequate blinding of participants and personnel; no study reported blinding of outcome assessment.Compared with placebo or standard care, pre-emptive treatment significantly reduced the risk of CMV disease (6 studies, 288 participants: RR 0.29, 95% CI 0.11 to 0.80) but not acute rejection (3 studies, 185 participants: RR 1.21, 95% CI 0.69 to 2.12) or all-cause mortality (3 studies, 176 participants: RR 1.23, 95% CI 0.35 to 4.30). Comparative studies of pre-emptive therapy versus prophylaxis showed no significant differences in preventing CMV disease between pre-emptive and prophylactic therapy (7 studies, 753 participants: RR 1.00, 95% CI 0.36 to 2.74) but there was significant heterogeneity (I² = 63%). Leucopenia was significantly less common with pre-emptive therapy compared with prophylaxis (6 studies, 729 participants: RR 0.42, 95% CI 0.20 to 0.90). Other adverse effects did not differ significantly or were not reported. There were no significant differences in the risks of all-cause mortality, graft loss, acute rejection and infections other than CMV.

AUTHORS' CONCLUSIONS

Few RCTs have evaluated the effects of pre-emptive therapy to prevent CMV disease. Pre-emptive therapy is effective compared with placebo or standard care. Despite the inclusion of five additional studies in this update, the efficacy of pre-emptive therapy compared with prophylaxis to prevent CMV disease remains unclear due to significant heterogeneity between studies. Additional head-to-head studies are required to determine the relative benefits and harms of pre-emptive therapy and prophylaxis to prevent CMV disease in solid organ transplant recipients.

Systems-level metabolic flux profiling identifies fatty acid synthesis as a target for antiviral therapy

Viruses rely on the metabolic network of their cellular hosts to provide energy and building blocks for viral replication. We developed a flux measurement approach based on liquid chromatography-tandem mass spectrometry to quantify changes in metabolic activity induced by human cytomegalovirus (HCMV). This approach reliably elucidated fluxes in cultured mammalian cells by monitoring metabolome labeling kinetics after feeding cells (13)C-labeled forms of glucose and glutamine. Infection with HCMV markedly upregulated flux through much of the central carbon metabolism, including glycolysis. Particularly notable increases occurred in flux through the tricarboxylic acid cycle and its efflux to the fatty acid biosynthesis pathway. Pharmacological inhibition of fatty acid biosynthesis suppressed the replication of both HCMV and influenza A, another enveloped virus. These results show that fatty acid synthesis is essential for the replication of two divergent enveloped viruses and that systems-level metabolic flux profiling can identify metabolic targets for antiviral therapy.

Nonhuman primate infections after organ transplantation

Nonhuman primates, primarily rhesus macaques (Macaca mulatta), cynomolgus macaques (Macaca fascicularis), and baboons (Papio spp.), have been used extensively in research models of solid organ transplantation, mainly because the nonhuman primate (NHP) immune system closely resembles that of the human. Nonhuman primates are also frequently the model of choice for preclinical testing of new immunosuppressive strategies. But the management of post-transplant nonhuman primates is complex, because it often involves multiple immunosuppressive agents, many of which are new and have unknown effects. Additionally, the resulting immunosuppression carries a risk of infectious complications, which are challenging to diagnose. Last, because of the natural tendency of animals to hide signs of weakness, infectious complications may not be obvious until the animal becomes severely ill. For these reasons the diagnosis of infectious complications is difficult among post-transplant NHPs. Because most nonhuman primate studies in organ transplantation are quite small, there are only a few published reports concerning infections after transplantation in nonhuman primates. Based on our survey of these reports, the incidence of infection in NHP transplant models is 14%. The majority of reports suggest that many of these infections are due to reactivation of viruses endemic to the primate species, such as cytomegalovirus (CMV), polyomavirus, and Epstein-Barr virus (EBV)-related infections. In this review, we address the epidemiology, pathogenesis, role of prophylaxis, clinical presentation, and treatment of infectious complications after solid organ transplantation in nonhuman primates.

Antiviral medications for preventing cytomegalovirus disease in solid organ transplant recipients

BACKGROUND

The risk of cytomegalovirus (CMV) infection in solid organ transplant recipients has resulted in the frequent use of prophylaxis with the aim of preventing the clinical syndrome associated with CMV infection.

OBJECTIVES

To determine the benefits and harms of antiviral medications to prevent CMV disease and all-cause mortality in solid organ transplant recipients.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, reference lists and abstracts from conference proceedings without language restriction. Date of last search: February 2007

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs comparing antiviral medications with placebo or no treatment, comparing different antiviral medications and comparing different regimens of the same antiviral medications in recipients of any solid organ transplant.

DATA COLLECTION AND ANALYSIS

Statistical analyses were performed using the random effects model and results expressed as relative risk (RR) for dichotomous outcomes with 95% confidence intervals (CI). Subgroup analysis and univariate meta-regression were performed using restricted maximum-likelihood to estimate the between study variance. Multivariate meta-regression was performed to investigate whether the results were altered after allowing for differences in drugs used, organ transplanted and recipient CMV serostatus at the time of transplantation.

MAIN RESULTS

Thirty four studies (3850 participants) were identified. Prophylaxis with aciclovir, ganciclovir or valaciclovir compared with placebo or no treatment significantly reduced the risk for CMV disease (19 studies; RR 0.42, 95% CI 0.34 to 0.52), CMV infection (17 studies; RR 0.61, 95% CI 0.48 to 0.77), and all-cause mortality (17 studies; RR 0.63, 95% CI 0.43 to 0.92) primarily due to reduced mortality from CMV disease (7 studies; RR 0.26, 95% CI 0.08 to 0.78). Prophylaxis reduced the risk of herpes simplex and herpes zoster disease, bacterial and protozoal infections but not fungal infection, acute rejection or graft loss. Meta-regression showed no significant difference in the relative benefit of treatment (risk of CMV disease or all-cause mortality) by organ transplanted or CMV serostatus; no conclusions were possible for CMV negative recipients of negative organs. In direct comparison studies, ganciclovir was more effective than aciclovir in preventing CMV disease (7 studies; RR 0.37, 95% CI 0.23 to 0.60). Valganciclovir and IV ganciclovir were as effective as oral ganciclovir.

AUTHORS' CONCLUSIONS

Prophylaxis with antiviral medications reduces CMV disease and CMV-associated mortality in solid organ transplant recipients. They should be used routinely in CMV positive recipients and in CMV negative recipients of CMV positive organ transplants.

Quantification of ganciclovir in human plasma using capillary electrophoresis

A fast, simple, specific capillary electrophoretic method in the MEKC mode for the quantification of the antiviral drug ganciclovir is described. The separation was obtained using a 50 microm id fused-silica capillary, 60 mM borax buffer (pH 9.25) containing 40 mM SDS using ethenoadenosine as the internal standard. Sample preparation was done by ultrafiltration with a Microcon 30 000 kDa filter. The analytes were detected with UV detector at 254 nm. A sufficient sensitivity was achieved by using a bubble cell capillary. The linear range was from 0.5 to 10 mg/L with a LOQ of 0.5 mg/L. Correlation coefficients were better than 0.999 whereas inter- and intraday precision and accuracy were less than 10.7%. The analysis of patients' samples after administration of ganciclovir indicates that the method is suitable for drug monitoring in the clinic.

24-Week Oral Ganciclovir Prophylaxis in Kidney Recipients Is Associated with Reduced Symptomatic Cytomegalovirus Disease Compared to a 12-Week Course

BACKGROUND

Cytomegalovirus (CMV) infection is associated with reduced graft and patient survival among kidney recipients. The highest risk of CMV infection occurs in CMV-naive recipients of kidneys from seropositive donors (D+/R-). Optimal CMV prophylaxis is not established. This prospective cohort study compared the safety and efficacy of prophylaxis with 12 versus 24 weeks of oral ganciclovir.

METHODS

We prospectively administered 24 weeks ganciclovir to 31 D+/R- recipients. The control group comprised 39 patients transplanted in the immediately preceding era who received a 12-week course of prophylaxis. All patients received cytolytic therapy within the first month, as well as a tacrolimus-based maintenance regimen. A logistic regression model was fit to examine the relationship between 24 weeks ganciclovir prophylaxis and the odds of developing CMV infection by one year.

RESULTS

Groups were matched, though the 12-week cohort had more delayed graft function than their 24-week counterparts (45% vs. 29%, P=0.04). CMV infection occurred in 31% and 7% patients in the 12-week and 24-week groups, respectively (P<or=0.01). Mean time to development of CMV infection was 17.5+/-2.2 weeks in the 12-week, and 22.0+/-10.0 weeks in the 24-week, groups (P=0.79). Both 24 weeks ganciclovir prophylaxis (O.R. 0.15, 95% C.I. 0.03-0.91, P=0.04) and delayed graft function (O.R. 4.49, 95% C.I. 1.67-36.56, P<0.01) were associated with CMV infection.

CONCLUSIONS

Oral ganciclovir prophylaxis for 24 weeks is associated with a lower risk of symptomatic CMV disease than a 12-week course in high risk D+/R- kidney recipients.

Pre-emptive treatment for cytomegalovirus viraemia to prevent cytomegalovirus disease in solid organ transplant recipients

BACKGROUND

Cytomegalovirus (CMV) is a significant cause of morbidity and mortality in solid organ transplant recipients. Pre-emptive treatment with antiviral agents of patients with CMV viraemia has been widely adopted as an alternative to routine prophylaxis to prevent CMV disease.

OBJECTIVES

This review was conducted to evaluate the efficacy of pre-emptive treatment in preventing symptomatic CMV disease.

SEARCH STRATEGY

The Cochrane Central Register of Controlled Trials (CENTRAL, in The Cochrane Library Issue 2, 2005), MEDLINE (1966 to February 2005), EMBASE (1980 to February 2005) and reference lists and conference proceedings were searched.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of pre-emptive treatment versus placebo, no treatment or antiviral prophylaxis in solid organ transplant recipients.

DATA COLLECTION AND ANALYSIS

Two authors assessed the quality and extracted all data. Analysis was with a random-effects model and results expressed as relative risk (RR) and 95% confidence intervals (CI).

MAIN RESULTS

Ten eligible trials (476 patients) were identified, six of pre-emptive treatment versus placebo or treatment of CMV when disease occurred (standard care), three of pre-emptive treatment versus antiviral prophylaxis and one of oral versus intravenous pre-emptive treatment. Compared with placebo or standard care, pre-emptive treatment significantly reduced the risk of CMV disease (six trials, 288 patients: RR 0.29, 95% CI 0.11 to 0.80) but not acute rejection (three trials, 185 patient: RR 1.06, 95% CI 0.64 to 1.76) or all-cause mortality (two trials, 176 patients: RR 1.23, 95% CI 0.35 to 4.30). Comparative trials of pre-emptive therapy versus prophylaxis showed no significant difference in the risks of CMV disease, acute rejection or all-cause mortality.

AUTHORS' CONCLUSIONS

Few RCTs have evaluated the effects of pre-emptive therapy to prevent CMV disease. Pre-emptive therapy is effective compared with placebo or standard care, but additional head-to-head trials are required to determine the relative benefits and harms of pre-emptive therapy and prophylaxis to prevent CMV disease in solid organ transplant recipients.

Antiviral medications for preventing cytomegalovirus disease in solid organ transplant recipients

BACKGROUND

The risk of cytomegalovirus (CMV) infection in solid organ transplant recipients has resulted in the frequent use of prophylaxis with the aim of preventing the clinical syndrome associated with CMV infection.

OBJECTIVES

To determine the benefits and harms of antiviral medications to prevent CMV disease and all-cause mortality in solid organ transplant recipients.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, reference lists and abstracts from conference proceedings without language restriction.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials comparing antiviral medications with placebo or no treatment, trials comparing different antiviral medications and trials comparing different regimens of the same antiviral medications in recipients of any solid organ transplant.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and extracted data from each trial. Statistical analyses were performed using the random effects model and results expressed as relative risk (RR) for dichotomous outcomes with 95% confidence intervals (CI). Subgroup analysis and univariate meta-regression were performed using restricted maximum-likelihood to estimate the between study variance. Multivariate meta-regression was performed to investigate whether the results were altered after allowing for differences in drugs used, organ transplanted and recipient CMV serostatus at the time of transplantation.

MAIN RESULTS

Thirty two trials (3737 participants) were identified. Prophylaxis with aciclovir, ganciclovir or valaciclovir compared with placebo or no treatment significantly reduced the risk for CMV disease (19 trials; RR 0.42, 95% CI 0.34 to 0.52), CMV infection (17 trials; RR 0.61, 95% CI 0.48 to 0.77), and all-cause mortality (17 trials; RR 0.63, 95% CI 0.43 to 0.92) primarily due to reduced mortality from CMV disease (seven trials; RR 0.26, 95% CI 0.08 to 0.78). Prophylaxis reduced the risk of herpes simplex and herpes zoster disease, bacterial and protozoal infections but not fungal infection, acute rejection or graft loss. Meta-regression showed no significant difference in the risk of CMV disease or all-cause mortality by organ transplanted or CMV serostatus; no conclusions were possible for CMV negative recipients of negative organs. In direct comparison trials, ganciclovir was more effective than aciclovir in preventing CMV disease (seven trials; RR 0.37, 95% Cl 0.23 to 0.60). Valganciclovir and intravenous ganciclovir were as effective as oral ganciclovir.

AUTHORS' CONCLUSIONS

Prophylaxis with antiviral medications reduces CMV disease and CMV-associated mortality in solid organ transplant recipients. They should be used routinely in CMV positive recipients and in CMV negative recipients of CMV positive organ transplants.

Reduction of CMV disease with steroid-free immunosuppresssion in simultaneous pancreas-kidney transplant recipients

The impact of a prednisone-free immunosuppressive regimen was evaluated in simultaneous pancreas-kidney (SPK) recipients. Patient and graft survivals, rejection rates and the incidence of CMV disease were determined. Two hundred consecutive SPK transplant recipients received tacrolimus-based immunosuppression with (n = 100) or without (n = 100) chronic prednisone therapy. Patients were induced with lymphocyte depleting antibodies or IL-2 receptor blockers and received prophylactic antiviral therapy. Patient and graft survivals and rejection rates were not statistically significantly different between treatment groups. Two-year cumulative incidence of CMV in recipients in the prednisone-free protocol was reduced (7.2% vs. 16%; p = 0.15). Considering only recipients at highest risk (D+/R- or D+R+), incidence of CMV disease in the prednisone-free group (n = 61) compared to the steroid-treated group (n = 48) was reduced from 36% to 18% (p < 0.05). Multivariate analysis confirmed the independent effect of prednisone treatment on the incidence of CMV (RR 2.3; p = 0.04). In the prednisone-free protocol, incidence of CMV was less frequent in recipients receiving induction with Campath versus rabbit antilymphocyte globulin (2.4% vs. 12.6%; p = 0.14). Eliminating prednisone immunotherapy did not adversely affect outcomes and was associated with a reduced rate of CMV in SPK recipients of organs from sero-positive donors.

Use of leflunomide in an allogeneic bone marrow transplant recipient with refractory cytomegalovirus infection

Ganciclovir-resistant cytomegalovirus (CMV) infection is an emerging problem in transplant recipients. Foscarnet resistance and cidofovir resistance have also been described, but no previous reports have suggested treatment regimens for patients with CMV refractory to all three of these drugs. Leflunomide, an immunosuppressive drug used in rheumatoid arthritis and in rejection in solid-organ transplantation, has been reported to have novel anti-CMV activity. However, its clinical utility in CMV treatment has not been described previously. We report an allogeneic bone marrow transplant recipient who developed CMV infection refractory to sequential therapy with ganciclovir, foscarnet, and cidofovir. The patient was ultimately treated with a combination of leflunomide and foscarnet. Both phenotypic and genotypic virologic analysis was performed on sequential CMV isolates. The patient's high CMV-DNA viral load became undetectable on leflunomide and foscarnet, but the patient, who had severe graft-versus-host disease (GVHD) of the liver, expired with progressive liver failure and other complications. We concluded that leflunomide is a new immunosuppressive agent with anti-CMV activity, which may be useful in the treatment of multiresistant CMV. However, the toxicity profile of leflunomide in patients with underlying GVHD remains to be defined.

Viral infection in the renal transplant recipient

Viruses are among the most common causes of opportunistic infection after transplantation and the most important. The risk for viral infection is a function of the specific virus encountered, the intensity of immune suppression used to prevent graft rejection, and other host factors governing susceptibility. Viral infection, both symptomatic and asymptomatic, causes the "direct effects" of invasive disease and "indirect effects," including immune suppression predisposing to other opportunistic infections and oncogenesis. Rapid and sensitive microbiologic assays for many of the common viruses after transplantation have replaced, for the most part, serologic testing and in vitro cultures for the diagnosis of infection. Furthermore, quantitative molecular tests allow the individualization of antiviral therapies for prevention and treatment of infection. This advance is most prominent in the management of cytomegalovirus, Epstein-Barr, hepatitis B, and hepatitis C viruses. Diagnostic advances have not been accompanied by the development of specific and nontoxic anti-viral agents or effective antiviral vaccines. Vaccines, where available, should be given to patients as early as possible and well in advance of transplantation to optimize the immune response. Studies of viral latency, reactivation, and the cellular effects of viral infection will provide clues for future strategies in prevention and treatment of viral infections.

Pharmacokinetic Profile of Ganciclovir After its Oral Administration and From its Prodrug, Valganciclovir, in Solid Organ Transplant Recipients

BACKGROUND

Valganciclovir (Valcyte) has recently been approved for the prevention of cytomegalovirus (CMV) disease in high-risk (CMV donor positive [D+]/recipient negative [R-]) solid organ transplant (SOT) recipients. Large-scale studies describing the pharmacokinetics of valganciclovir in SOT recipients are lacking. A recent randomised, double-blind study of valganciclovir in 364 D+/R- (intent-to-treat population) SOT recipients provided valuable data on which a population pharmacokinetic analysis was performed.

METHODS

The pharmacokinetics of ganciclovir from oral ganciclovir (Cymevene, 1000 mg three times daily) and from valganciclovir (900 mg once daily) were described with plasma levels from 240 patients (1181 datapoints describing 449 pharmacokinetic profiles) using nonlinear mixed-effects modelling (NONMEM) software. A two-compartment pharmacokinetic model with separate absorption/metabolism and absorption parameters for valganciclovir and ganciclovir, respectively, was developed.

RESULTS

Exposure to ganciclovir from valganciclovir averaged 1.65-fold greater than that from oral ganciclovir (95% CI 1.58, 1.81); respective daily area under the plasma concentration-time curve values were 46.3 +/- 15.2 microg . h/mL and 28.0 +/- 10.9 microg . h/mL. The relative systemic exposure of ganciclovir was approximately 8-fold higher from valganciclovir than oral ganciclovir. Exposure to ganciclovir from valganciclovir was similar among liver, heart and kidney transplant recipients (46.0 +/- 16.1, 40.2 +/- 11.8 and 48.2 +/- 14.6 microg . h/ mL, respectively). Adherence to the prescribed dosing regimens, which were reduced for renal impairment, gave consistent exposure to ganciclovir.

CONCLUSION

Oral valganciclovir produces exposures of ganciclovir exceeding those attained with oral ganciclovir, but in line with those reported after standard intravenous administration of ganciclovir. This indicates that oral valganciclovir is suitable in circumstances requiring prophylactic use of ganciclovir and allows for more convenient management of patients at risk of CMV disease.

Ganciclovir prophylaxis delays but does not prevent cytomegalovirus infection in renal transplant recipients

Cytomegalovirus (CMV) infection is associated with reduced graft and patient survival among renal transplant recipients. The purpose of this study was to examine the effect of routine prophylaxis with 12 weeks of oral ganciclovir on the incidence of CMV infection in a center that predominantly uses antibody induction together with tacrolimus/mycophenolate mofetil-based maintenance immunosuppressive therapy. The control group consisted of a historical patient cohort transplanted immediately prior to the use of oral ganciclovir prophylaxis. The use of tacrolimus (88% vs 77%, P=.02) and cytolytic therapy (81% vs 46%, P <.0001) was likewise greater among patients who received ganciclovir prophylaxis. CMV infection occurred in 20 (9%) patients in the ganciclovir era and 4 (3%) patients in the preganciclovir era (P=.003). The mean time to CMV infection was longer in patients who received ganciclovir prophylaxis than in patients in the preganciclovir era (23.4 +/- 10.9 weeks vs 9.8 +/- 5.6 weeks, P=.03). We conclude that 12 weeks of ganciclovir prophylaxis delays but does not prevent CMV infection from occurring in renal transplant recipients. These results suggest that with the use of 12 weeks of ganciclovir prophylaxis, vigilance for CMV infection is needed well beyond 24 weeks posttransplant.

Prevention and treatment of cytomegalovirus infection in solid organ transplant recipients

PURPOSE OF REVIEW

Cytomegalovirus remains the single most important pathogen affecting solid organ transplant recipients. Its importance lies both in its effects and as a model for deciphering the clinical impact and management of other agents such as hepatitis C virus and other herpes viruses such as human herpes virus-6 and 7. The effects of cytomegalovirus infection in these patients can be divided into two categories: the direct causation of a wide variety of infectious disease syndromes; and the indirect effects, which include contributing to the net state of immunosuppression, allograft injury, and potentiating posttransplant lymphoproliferative disease.

RECENT FINDINGS

The advent of valganciclovir, with its excellent oral bioavailability, combined with intravenous ganciclovir have provided powerful tools for controlling the direct effects of cytomegalovirus, particularly with the recognition that the intensity of the antiviral therapy has to be linked to the intensity of the immunosuppression required.Unfortunately, far less is known about the efficacy of antiviral therapy in managing the indirect effects of cytomegalovirus. Preliminary data suggest antiviral prophylaxis protects against acute allograft injury, as well as decreasing the incidence of some opportunistic infection.

SUMMARY

A great deal of progress has been made in the prevention and treatment of the infectious disease syndromes caused by cytomegalovirus, with the development of the concept of the therapeutic prescription. This has two components: an immunosuppressive component to prevent and treat rejection and an antimicrobial component to make it safe. Much more information, however, is required.

A decision-analytic economic evaluation of valaciclovir prophylaxis for the prevention of cytomegalovirus infection and disease in renal transplantation

OBJECTIVE

This analysis evaluates the cost-effectiveness of valaciclovir prophylaxis using clinically and economically important health outcomes including graft failure, life-years, and quality-adjusted life-years (QALYs).

METHODS

A Markov model was developed using a randomized, placebo-controlled trial of valaciclovir prophylaxis, together with a published epidemiological study and national renal transplant registry data. The model's population was stratified into two risk groups by donor/recipient cytomegalovirus (CMV) serostatus at transplantation: donor-positive/recipient-negative (D+R-) and recipient-positive (R+) patients. The model estimated costs and health outcomes over a 30-yr period from the perspective of Australian health care providers.

RESULTS

The total health care cost was $3619 lower for D+R- patients receiving valaciclovir prophylaxis compared with those not receiving prophylaxis. D+R- patients receiving valaciclovir gained an extra 0.33 yr of life and 0.27 QALYs. R+ patients receiving valaciclovir prophylaxis gained an extra 0.07 yr of life and 0.05 QALYs, with an incremental cost of $914. This equates to $17 127 per QALY gained, which is highly cost-effective compared with other drugs and health interventions.

CONCLUSIONS

Valaciclovir for the prophylaxis of CMV disease in renal transplant recipients is a cost-effective intervention, significantly reducing the burden of CMV disease to patients and health care providers.

Ganciclovir in solid organ transplant recipients: is there a role for clinical pharmacokinetic monitoring?

The authors use a previously published decision-making algorithm to address the role of clinical pharmacokinetic monitoring of ganciclovir, the drug of choice for prophylaxis and treatment of cytomegalovirus (CMV) in solid organ transplant recipients. Ganciclovir pharmacokinetics have been studied in solid organ transplant recipients with a wide range of peak and trough concentrations reported. Numerous assays are available to measure plasma concentrations of ganciclovir, but no clear correlation has been established between peak or trough concentrations and either efficacy or toxicity of the drug. For patients receiving treatment, the pharmacological response of ganciclovir is assessed initially by clinical response. Monitoring prophylactic therapy in asymptomatic patients poses a greater challenge. Although monitoring of antigenemia or polymerase chain reaction (PCR) deoxyribonucleic acid (DNA) is not yet part of routine clinical practice, studies have shown a role for these techniques in monitoring response to antiviral therapy. Studies of subpopulations of renal failure patients show a prolonged ganciclovir half-life that requires dosage adjustments. However, ganciclovir clearance is closely correlated with creatinine clearance, which is an appropriate approach to adjusting dosages. Studies in pediatric patients also demonstrate a close correlation between dose per kilogram and AUC, suggesting that monitoring of ganciclovir levels may not be necessary. Based on the evidence presented in this review, routine clinical pharmacokinetic monitoring of ganciclovir does not appear to be warranted in solid organ transplant recipients.

Reduced efficacy of ganciclovir against porcine and baboon cytomegalovirus in pig-to-baboon xenotransplantation

In pig-to-baboon xenotransplantation, porcine cytomegalovirus (PCMV) causes viremia, consumptive coagulopathy, and tissue-invasive disease. Baboon cytomegalovirus (BCMV) is associated with invasive disease in xenograft recipients. The efficacy of prophylaxis with intravenous ganciclovir (GCV) was studied for prevention of PCMV and BCMV infections in pig-to baboon xenotransplantation. GCV prophylaxis did not alter the incidence of BCMV activation in recipients, but reduced the amount of virus in tissues (mean 8.38 x 10(2) vs. 3.24 x 10(5) copies/ micro g DNA without treatment) and prevented tissue-invasive infections. PCMV viral loads were unaltered by GCV prophylaxis (8.36 x 10(8) copies/ micro g DNA without prophylaxis vs. 1.20 x 10(9) copies/ micro g DNA with prophylaxis). In vitro, PCMV was relatively resistant to GCV [90% inhibitory concentration (IC90) of 10 micro m, IC50 = 3 micro m], acyclovir (100 micro m), and leflunomide (not achievable). Only cidofovir (IC90 1 micro m) and foscarnet (IC90 100 micro m) might have therapeutic efficacy for PCMV in vivo in achievable concentrations, although these agents often carry significant toxicity in transplant recipients. GCV has limited activity against BCMV and no therapeutic efficacy against PCMV at standard doses in vivo. GCV and other antiviral agents have limited activities against PCMV in vitro. Breeding of PCMV-free xenograft donors may be necessary to prevent PCMV infections in clinical trials.