Prospective comparison of PCR-based vs late mRNA-based preemptive antiviral therapy for HCMV infection in patients after allo-SCT

Prevention and management of human cytomegalovirus in pediatric HSCT recipients: A review

Cytomegalovirus (CMV), like other herpesviruses, has the unique ability to establish latent infection with subsequent reactivation during periods of stress and immunosuppression. Herpesviruses cause potentially devastating disease, particularly in hematopoietic stem cell transplant (HSCT) recipients. CMV is especially of concern in HSCT recipients given the high community seroprevalence, high risk of reactivation and high risk of transmission from HSCT donors to recipients causing primary infection after transplantation. The risk of CMV infection and severity of CMV disease varies depending on the underlying disease of the HSCT recipient, donor and recipient CMV status prior to HSCT, type of conditioning therapy in preparation for HSCT, allogeneic versus autologous HSCT, donor graft source, timing of infection in relation to HSCT, and other patient comorbidities. Different strategies exist for prevention (e.g., preemptive therapy vs. universal prophylaxis) as well as management of CMV disease (e.g., antiviral therapy, augmenting immune reconstitution, cytotoxic T-cell therapy). The purpose of this narrative review is to discuss diagnosis, prevention, and management of CMV infection and disease at different stages of HSCT, including key points illustrated through presentations of complex cases and difficult clinical scenarios. Traditional and novel strategies for CMV management will be discussed in the context of these unique clinical cases.

Predictors of breakthrough clinically significant cytomegalovirus infection during letermovir prophylaxis in high-risk hematopoietic cell transplant recipients

Letermovir prophylaxis in allogeneic hematopoietic cell transplant recipients significantly reduces the incidence of clinically significant cytomegalovirus infection. However, breakthrough infections still occur despite adequate prophylaxis. In the present retrospective cohort study, we identified clinically relevant predictive factors for clinically significant CMV breakthrough infection during letermovir prophylaxis. Low‐grade CMV replication (21–149 IU/ml), both at the time of letermovir initiation or during prophylaxis, was a significant risk factor for breakthrough clinically significant CMV infection. In addition, development of acute gastrointestinal graft‐versus‐host disease was significantly associated with breakthrough infection. Altogether these findings could call clinicians' attention to closer CMV monitoring and allow for prompt preemptive treatment initiation.

Letermovir and its role in the prevention of cytomegalovirus infection in seropositive patients receiving an allogeneic hematopoietic cell transplant

Cytomegalovirus (CMV) reactivation is one of the most common infections affecting allogeneic hematopoietic cell transplant recipients. Although available anti-CMV therapies have been evaluated for the prevention of CMV reactivation, their toxicity profile makes them unfavorable for use as primary prophylaxis; thus, they are routinely reserved for the treatment of CMV viremia or CMV end-organ disease. Pre-emptive CMV monitoring strategies have been widely accepted, and although they have been helpful in early detection, they have not affected the overall morbidity and mortality associated with CMV. Letermovir is a novel agent that was approved for primary prophylaxis in CMV-seropositive adult allogeneic hematopoietic cell transplant recipients. This review focuses on letermovir's novel mechanism; clinical trials supporting its United States Food and Drug Administration (FDA) approval and subsequent follow-up analyses; clinical considerations, with an emphasis on pharmacology; and lessons learned from solid organ transplant recipients, as well as potential future directions.

Letermovir for the prevention of cytomegalovirus infection in adult cytomegalovirus-seropositive hematopoietic stem cell transplant recipients

INTRODUCTION

Allogeneic hematopoietic cell transplants (allo-HCT) recipients are at the high-risk of reactivation of cytomegalovirus (CMV), and reactivation is associated with significant morbidity and mortality. Although available anti-CMV therapies may be effective for the prevention of CMV, they are plagued by unacceptable toxicities that prohibit their use in the post-transplant period. Recently studied CMV-active agents, such as maribavir and brincidofovir, failed to reduce the incidence of CMV infection in HCT recipients. Letermovir represents the first agent in the non-nucleoside 3,4 dihydro-quinazoline class of CMV viral terminase complex inhibitors, with activity solely against CMV. The positive results from the recently published Phase III study of letermovir for prevention of CMV infection in CMV-seropositive allo-HCT recipients led to its approval as a prophylactic agent for CMV in multiple countries. Areas covered: In this review, we will evaluate this novel agent with a focus on letermovir mechanism of action, pharmacokinetics and metabolism, clinical efficacy, and safety and toxicities. Expert commentary: With the introduction of letermovir, prevention of CMV infection in allo-HCT recipients may shift considerably, from a predominantly preemptive strategy to one that utilizes this novel therapy for prophylaxis.

Betaherpesvirus Complications and Management During Hematopoietic Stem Cell Transplantation

Two of the four betaherpesviruses, Cytomegalovirus (CMV) and human herpesvirus 6B (HHV-6B), play an important role in opportunistic infections in hematopoietic stem cell transplant (HSCT) recipients. These viruses are ubiquitous in humans and can latently infect mononuclear lymphocytes, complicating the diagnosis of the diseases they cause. Although the detection of viral DNA in a patient's peripheral blood by real-time PCR is widely used for monitoring viral infection, it is insufficient for the diagnosis of virus-associated disease. Theoretically, end-organ disease should be confirmed by detecting either viral antigen or significant amounts of viral DNA in a tissue sample obtained from the involved organ; however, this is often difficult to perform in clinical practice. The frequency of CMV-associated diseases has decreased gradually as a result of the introduction of preemptive or prophylactic treatments; however, CMV and HHV-6B infections remain a major problem in HSCT recipients. Measurement of viral DNA load in peripheral blood or plasma using real-time PCR is commonly used for monitoring these infections. Additionally, recent data suggest that an assessment of host immune response, particularly cytotoxic T-cell response, may be a reliable tool for predicting these viral infections. The antiviral drugs ganciclovir and foscarnet are used as first-line treatments; however, it is well known that these drugs have side effects, such as bone marrow suppression and nephrotoxicity. Further research is required to develop less-toxic antiviral drugs.

Cytomegalovirus

Cytomegalovirus (CMV), the largest of the herpesviruses, causes a wide range of clinical syndromes, from asymptomatic infection to severe disease in immunocompromised hosts. Laboratory methods for diagnosis include molecular testing, antigenemia, culture, serology, and histopathology. Treatment of CMV infection and disease is indicated in selected immunocompromised hosts, and preventive approaches are indicated in high-risk groups. This chapter reviews the epidemiology, clinical aspects, and the laboratory diagnosis and management of CMV in immunocompromised hosts.

How I treat resistant cytomegalovirus infection in hematopoietic cell transplantation recipients

Cytomegalovirus (CMV) infection is a significant complication in hematopoietic cell transplantation (HCT) recipients. Four antiviral drugs are used for preventing or treating CMV: ganciclovir, valganciclovir, foscarnet, and cidofovir. With prolonged and repeated use of these drugs, CMV can become resistant to standard therapy, resulting in increased morbidity and mortality, especially in HCT recipients. Antiviral drug resistance should be suspected when CMV viremia (DNAemia or antigenemia) fails to improve or continue to increase after 2 weeks of appropriately dosed and delivered antiviral therapy. CMV resistance is diagnosed by detecting specific genetic mutations. UL97 mutations confer resistance to ganciclovir and valganciclovir, and a UL54 mutation confers multidrug resistance. Risk factors for resistance include prolonged or previous anti-CMV drug exposure or inadequate dosing, absorption, or bioavailability. Host risk factors include type of HCT and degree of immunosuppression. Depending on the genotyping results, multiple strategies can be adopted to treat resistant CMV infections, albeit no randomized clinical trials exist so far, after reducing immunosuppression (if possible): ganciclovir dose escalation, ganciclovir and foscarnet combination, and adjunct therapy such as CMV-specific cytotoxic T-lymphocyte infusions. Novel therapies such as maribavir, brincidofovir, and letermovir should be further studied for treatment of resistant CMV.

Therapeutic strategies for cytomegalovirus in allogeneic hematopoietic cell transplantation

Cytomegalovirus (CMV) remains a major cause of morbidity and mortality in allogeneic hematopoietic cell transplantation. Advances in surveillance of cytomegalovirus reactivation using sensitive techniques and a preemptive strategy to treat virus reactivation has reduced incidence of cytomegalovirus end organ disease. However, severe immunosuppression associated with extensive T-cell depletion resulting from graft-versus-host disease prevention for cases of mismatched or others such as haploidentical allogeneic hematopoietic cell transplantation (allo-HCT) and graft-versus-host disease therapy itself create clinical challenges in managing cytomegalovirus infection. Novel anticytomegalovirus therapies including newer pharmacologic interventions, vaccines, and adoptive cellular therapies to restore anticytomegalovirus immunity appear promising and are expected to continue to shape our treatment armamentarium. Eradication of CMV disease altogether, rather than simply suppressing viremia, should be the ultimate desirable goal.

Preemptive treatment of Cytomegalovirus infection in kidney transplant recipients with letermovir: results of a Phase 2a study

Cytomegalovirus (CMV) infection remains a significant cause of morbidity and mortality in transplant recipients. Letermovir (AIC246), is a novel anti-HCMV drug in development, acting via a novel mechanism of action. In this proof-of-concept trial with first administration of letermovir to patients, 27 transplant recipients with active CMV replication were randomly assigned to a 14-day oral treatment regimen of either letermovir 40 mg twice a day, letermovir 80 mg once a day, or local standard of care (SOC) in a multicenter, open-label trial. Efficacy, safety, and limited pharmacokinetic parameters were assessed. All groups had a statistically significant decrease in CMV-DNA copy number from baseline (40 mg BID: P = 0.031; 80 mg QD: P = 0.018; SOC: P = 0.001), and comparison of viral load reduction between treatment groups showed no statistically significant differences. Viral clearance was achieved for 6 of 12 patients (50%) in the letermovir groups versus two of seven SOC patients (28.6%). Letermovir treatment was generally well tolerated, no patient developed CMV disease during the trial. Both letermovir treatment regimens resulted in equally high trough level plasma concentrations. The efficacy, safety, and pharmacokinetics observed in these viremic transplant recipients indicate that letermovir is a promising new anti-CMV drug.

Clinical utility of viral load in management of cytomegalovirus infection after solid organ transplantation

The negative impact of cytomegalovirus (CMV) infection on transplant outcomes warrants efforts toward improving its prevention, diagnosis, and treatment. During the last 2 decades, significant breakthroughs in diagnostic virology have facilitated remarkable improvements in CMV disease management. During this period, CMV nucleic acid amplification testing (NAT) evolved to become one of the most commonly performed tests in clinical virology laboratories. NAT provides a means for rapid and sensitive diagnosis of CMV infection in transplant recipients. Viral quantification also introduced several principles of CMV disease management. Specifically, viral load has been utilized (i) for prognostication of CMV disease, (ii) to guide preemptive therapy, (iii) to assess the efficacy of antiviral treatment, (iv) to guide the duration of treatment, and (v) to indicate the risk of clinical relapse or antiviral drug resistance. However, there remain important limitations that require further optimization, including the interassay variability in viral load reporting, which has limited the generation of standardized viral load thresholds for various clinical indications. The recent introduction of an international reference standard should advance the major goal of uniform viral load reporting and interpretation. However, it has also become apparent that other aspects of NAT should be standardized, including sample selection, nucleic acid extraction, amplification, detection, and calibration, among others. This review article synthesizes the vast amount of information on CMV NAT and provides a timely review of the clinical utility of viral load testing in the management of CMV in solid organ transplant recipients. Current limitations are highlighted, and avenues for further research are suggested to optimize the clinical application of NAT in the management of CMV after transplantation.

Quantification of cytomegalovirus viral load

Cytomegalovirus (CMV), a member of the Herpesviridae family, is worldwide distributed. After the primary infection, CMV induces a latent infection with possible reactivation(s). It is responsible for severe to life-threatening diseases in immunocompromised patients and in foetuses and newborns of infected mothers. For monitoring CMV load, classical techniques based on rapid culture or pp65 antigenemia are progressively replaced by quantitative nuclear acid tests (QNAT), easier to implement and standardize. A large variety of QNAT are available from laboratory-developed assays to fully-automated commercial tests. The indications of CMV quantification include CMV infection during pregnancy and in newborns, and viral surveillance of grafted and non-grafted immunocompromised patients, patients with bowel inflammatory diseases and those hospitalised in intensive care unit. A close cooperation between virologists and clinicians is essential for optimizing the benefit of CMV DNA monitoring.

Allogeneic transplantation in the UK: an aggregation of marginal gains?

A number of advances in clinical practice that are considered routine in modern allogeneic transplant programmes lack definitive supporting evidence, partly because they may offer modest incremental benefits that are difficult to demonstrate in a statistically robust manner given the relatively small cohorts of patients who undergo such procedures. Nevertheless, these marginal gains probably contribute therapeutically meaningful overall benefit, particularly when aggregated. We review the evidence for a number of these practices in terms of impact on transplant outcomes, with particular reference to the setting of T cell depletion as widely practiced in the United Kingdom, including high resolution tissue typing, surveillance for and therapy of infectious complications, chimerism-directed immune modulation and more sensitive monitoring for residual or progressive disease.

Complications, Diagnosis, Management, and Prevention of CMV Infections: Current and Future

Although major progress has been made in the prevention of CMV disease after hematopoietic cell transplantation (HCT), specific problems remain and available antiviral agents are associated with major toxicities. This article reviews current aspects of CMV diagnosis, prevention, and treatment in HCT recipients and defines areas of unmet medical need.

Cytomegalovirus in hematopoietic stem cell transplant recipients

This article examines the clinical manifestations of and risk factors for cytomegalovirus (CMV). Prevention of CMV infection and disease are also explored. Antiviral resistance and management of CMV are examined.

How we treat cytomegalovirus in hematopoietic cell transplant recipients

Cytomegalovirus (CMV) continues to cause major complications after hematopoietic cell transplantation (HCT). Over the past decade, most centers have adopted preemptive antiviral treatment or prophylaxis strategies to prevent CMV disease. Both strategies are effective but also have shortcomings with presently available drugs. Here, we review aspects of CMV treatment and prevention in HCT recipients, including currently used drugs and diagnostics, ways to optimize preemptive therapy strategies with quantitative polymerase chain reaction assays, the use of prophylaxis, management of CMV disease caused by wild-type or drug-resistant strains, and future strategies.