Efficacy and Safety of Antiviral Agents in Preventing Allograft Rejection Following CMV Prophylaxis in High-Risk Kidney Transplantation: A Systematic Review and Network Meta-Analysis of Randomized Controlled Trials

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.

Valacyclovir versus valganciclovir for cytomegalovirus prophylaxis in kidney transplant recipients: a systematic review and comparative meta-analysis

Background

Valganciclovir (ValG) is the most widely used drug for cytomegalovirus (CMV) prophylaxis in kidney transplant recipients (KTRs). However, it is associated with dose-limiting side effects and considerable costs. Some centers have identified valacyclovir (ValA) as an economically attractive alternative with a lower risk of bone marrow suppression. The comparative effectiveness of these two drugs is not well-established. This study aims to compare the efficacy and safety of ValA and ValG for CMV prophylaxis in KTRs.

Methods

Searches were conducted of the Medline, Cochrane, Web of Science, Embase, and Ovid databases. Endpoints encompassed the incidence of CMV disease, CMV viremia, acute rejection, leukopenia/neutropenia, and other infections, including BK polyomavirus and non-CMV herpesviruses (HVs). Risk ratios (RRs) with 95% confidence intervals (CIs) were pooled using a random-effects model.

Results

Six studies, comprising 888 patients (438 receiving ValA), were included. The groups were comparable in CMV viremia incidence (RR, 0.70; 95% CI, 0.31-1.57; P=0.4) and the development of CMV disease (RR, 0.74; 95% CI, 0.09-5.97; P=0.8). No significant differences in acute rejection rates were observed (RR, 0.97; 95% CI, 0.50-1.91; P=0.8). However, the rate of leukopenia/neutropenia was significantly lower in the ValA group (RR, 0.57; 95% CI, 0.42-0.77; P<0.01). No significant differences were noted for BK viremia (RR, 0.67; 95% CI, 0.24-1.87; P=0.4) or other HV infections (RR, 1.43; 95% CI, 0.61-3.38; P=0.4).

Conclusions

The drugs demonstrate comparable efficacy in preventing CMV infection following kidney transplantation. However, ValA may have a lower impact on bone marrow suppression.

Current and emerging tools for simultaneous assessment of infection and rejection risk in transplantation

Infection and rejection are major complications that impact transplant longevity and recipient survival. Balancing their risks is a significant challenge for clinicians. Current strategies aimed at interrogating the degree of immune deficiency or activation and their attendant risks of infection and rejection are imprecise. These include immune (cell counts, function and subsets, immunoglobulin levels) and non-immune (drug levels, viral loads) markers. The shared risk factors between infection and rejection and the bidirectional and intricate relationship between both entities further complicate transplant recipient care and decision-making. Understanding the dynamic changes in the underlying net state of immunity and the overall risk of both complications in parallel is key to optimizing outcomes. The allograft biopsy is the current gold standard for the diagnosis of rejection but is associated with inherent risks that warrant careful consideration. Several biomarkers, in particular, donor derived cell-free-DNA and urinary chemokines (CXCL9 and CXCL10), show significant promise in improving subclinical and clinical rejection risk prediction, which may reduce the need for allograft biopsies in some situations. Integrating conventional and emerging risk assessment tools can help stratify the individual's short- and longer-term infection and rejection risks in parallel. Individuals identified as having a low risk of rejection may tolerate immunosuppression wean to reduce medication-related toxicity. Serial monitoring following immunosuppression reduction or escalation with minimally invasive tools can help mitigate infection and rejection risks and allow for timely diagnosis and treatment of these complications, ultimately improving allograft and patient outcomes.

Pre-Existing Intrarenal Parvovirus B19 Infection May Relate to Antibody-Mediated Rejection in Pediatric Kidney Transplant Patients

Viral infections can lead to transplant dysfunction, and their possible role in rejection is described. In total, 218 protocol biopsies performed in 106 children at 6, 12 and 24 months after transplantation were analyzed according to Banff '15. RT-PCR for cytomegalovirus, Epstein-Barr virus, BK virus and Parvovirus B19 was performed on blood and bioptic samples at the time of transplant and each protocol biopsy. The prevalence of intrarenal viral infection increases between 6 and 12 months after transplantation (24% vs. 44%, p = 0.007). Intrarenal Parvovirus B19 infection is also associated with antibody-mediated rejection (ABMR) (50% ABMR vs. 19% T-cell-mediated rejection, p = 0.04). Moreover, Parvovirus infection is higher at 12 months of follow-up and it decreases at 48 months (40.4% vs. 14%, p = 0.02), while in 24% of grafts, Parvovirus is already detectable at the moment of transplantation. Intrarenal Parvovirus B19 infection seems to be related to ABMR in pediatric kidney recipients. The graft itself may be the way of transmission for Parvovirus, so performance of a PCR test for Parvovirus B19 should be considered to identify high-risk patients. Intrarenal Parvovirus infection presents mainly during the first-year post-transplantation; thus, we recommend an active surveillance of donor-specific antibodies (DSA) in patients with intrarenal Parvovirus B19 infection during this period. Indeed, it should be considered a treatment with intravenous immunoglobulins in patients with intrarenal Parvovirus B19 infection and DSA positivity, even in the absence of ABMR criteria for kidney biopsy.

Effectiveness and safety of prenatal valacyclovir for congenital cytomegalovirus infection: systematic review and meta-analysis

OBJECTIVE

Universal screening for cytomegalovirus (CMV) infection in pregnancy is not recommended in most countries. One of the major deterrents is the lack of effective prenatal therapy. The role of valacyclovir therapy in reducing the risk of vertical transmission, symptomatic congenital CMV infection and adverse outcome is controversial. The main aim of this systematic review and meta-analysis was to investigate the safety and effectiveness of prenatal valacyclovir therapy in pregnancies with maternal CMV infection.

METHODS

MEDLINE, EMBASE and Cochrane databases and ClinicalTrials.gov were searched. The inclusion criteria were pregnancy with confirmed maternal CMV infection, treated or untreated with valacyclovir. The primary outcome was the incidence of congenital CMV infection confirmed by a positive CMV polymerase chain reaction result of the amniotic fluid. The secondary outcomes were symptomatic and asymptomatic infection, perinatal death, termination of pregnancy, anomalies detected on follow-up ultrasound, on fetal magnetic resonance imaging or at birth, severe and mild-to-moderate symptoms due to congenital CMV infection, neurological, visual and hearing symptoms, and adverse events related to valacyclovir. Risk of bias was assessed using the revised Cochrane risk-of-bias tool for randomized trials (RoB 2) or Risk Of Bias In Non-randomized Studies of Interventions (ROBINS-I) tool, as appropriate. Head-to-head meta-analyses were used to compare the risk of each of the explored outcomes according to whether pregnancies with maternal CMV infection were treated with prenatal valacyclovir therapy.

RESULTS

Eight studies (620 women) were included. Pregnancies treated with valacyclovir had a significantly lower risk of congenital CMV infection compared with those not receiving valacyclovir (three studies; 325 fetuses; pooled odds ratio (OR), 0.37 (95% CI, 0.21-0.64); I2  = 0%; P < 0.001). When stratifying the analysis according to gestational age at maternal infection, the risk of vertical transmission was significantly lower in pregnancies receiving valacyclovir following first-trimester maternal infection (three studies; 184 fetuses; pooled OR, 0.34 (95% CI, 0.15-0.74); I2  = 20.9%; P = 0.001), while there was no significant difference between the two groups in those acquiring CMV infection in the periconceptional period or in the third trimester of pregnancy. Only one study reported on the risk of vertical transmission in women infected in the second trimester, demonstrating a lower risk of congenital infection in women taking valacyclovir, although this was based on a small number of cases. Pregnancies treated with valacyclovir therapy had an increased likelihood of asymptomatic congenital CMV infection compared with those not receiving valacyclovir (two studies; 132 fetuses; pooled OR, 2.98 (95% CI, 1.18-7.55); I2  = 0%; P = 0.021), while there was no significant difference between the two groups in the risk of perinatal death (P = 0.923), termination of pregnancy (P = 0.089), anomalies detected at follow-up imaging assessment during pregnancy or at birth (P = 0.934) and symptoms due to CMV infection in the newborn (P = 0.092). The occurrence of all adverse events in pregnant individuals taking valacyclovir was 3.17% (95% CI, 1.24-5.93%) (six studies; 210 women), with 1.71% (95% CI, 0.41-3.39%) experiencing acute renal failure, which resolved after discontinuation of the drug. On GRADE assessment, the quality of evidence showing that valacyclovir reduced the risk of congenital CMV infection and adverse perinatal outcome was very low.

CONCLUSIONS

Prenatal valacyclovir administration in pregnancies with maternal CMV infection reduces the risk of congenital CMV infection. Further evidence is needed to elucidate whether valacyclovir can affect the course of infection in the fetus and the risk of symptomatic fetal or neonatal infection. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

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.