Safety and efficacy of intravenously administered cidofovir in adult haematopoietic cell transplant recipients: a retrospective multicentre cohort study

The emergence of letermovir and maribavir drug-resistant mutations: from clinical trials to real-world studies

PURPOSE OF REVIEW

Cytomegalovirus (CMV) infection is associated with severe clinical disease and high morbidity in immunocompromised hosts. Letermovir and maribavir, are two recently developed antiviral drugs used in the prevention and treatment of resistant and refractory CMV. Following the publication of landmark randomized trials and increased use, both clinical trial data and real-world experience has reported the development of antiviral drug resistance. The aim of this review was to comprehensively review the published literature on letermovir and maribavir drug resistance and to describe the clinical scenarios in which they may emerge.

RECENT FINDINGS

For letermovir, the most frequently detected resistance mutations occur in the UL56 gene (C325Y/W/F) and confer total resistance. Maribavir resistance mutations most often occur in the UL97 gene and resistance-associated variants (RAVs) T409M, H411Y, C480F have all been detected. The clinical context in which letermovir and maribavir resistance occurs include high viral loads at initiation, intensified immunosuppression, subtherapeutic drug exposure because of poor adherence, drug interactions, and inadequate central nervous system (CNS) penetration. Emergence of resistance mutations generally occurs within the first 3 months of initiation.

SUMMARY

The detection of letermovir and maribavir resistance mutations highlights an ongoing clinical challenge in the management of CMV.

Development and characterization of formulations based on combinatorial potential of antivirals against genital herpes

Herpes simplex virus type 2 (HSV-2) treatment faces challenges due to antiviral resistance and systemic side effects of oral therapies. Local delivery of antiviral agents, such as tenofovir (TDF) and zinc acetate dihydrate (ZAD), may offer improved efficacy and reduced systemic toxicity. This study's objective is to develop and evaluate local unit dose formulations of TDF and ZAD combination for local treatment of HSV-2 infection and exploring their individual and combinatory effects in vitro. The study involved the development of immediate-release film and pessary formulations containing TDF and ZAD. These formulations were characterized for physicochemical properties and in vitro drug release profiles. Cytotoxicity and antiviral activity assays were conducted to evaluate the individual and combinatory effects of TDF and ZAD. Film formulations released over 90% of the drugs within 1 h, and pessary formulations within 90 min, ensuring effective local drug delivery. ZAD showed moderate antiviral activity while TDF exhibited significant antiviral activity at non-cytotoxic concentrations. The combination of TDF and ZAD demonstrated synergistic effects in co-infection treatments, reducing the concentration required for 50% inhibition of HSV-2. Developed film and pessary formulations offer consistent and predictable local drug delivery, enhancing antiviral efficacy while minimizing systemic side effects. The combination of TDF and ZAD showed potential synergy against HSV-2, particularly in co-infection treatments. Further preclinical studies on pharmacokinetics, safety, and efficacy are necessary to advance these formulations toward clinical application.

Adenovirus infection in allogeneic hematopoietic cell transplantation

Adenovirus (AdV) infection occurs in 0-20% of patients in the first 3-4 months after allogeneic hematopoietic cell transplantation (HCT), being higher in pediatric than in adult patients. About 50% of AdV infections involve the blood, which in turn, correlates with an increased risk developing AdV diseases, end-organ damage, and 6-month overall mortality. The main risk factors for AdV infection are T-cell depletion of the graft by ex vivo selection procedures or in vivo use of alemtuzumab or antithymocyte serum, development of graft versus host disease (GVHD) grade III-IV, donor type (haploidentical or human leucocyte antigen mismatched related donor > cord blood> unrelated matched donor) and severe lymphopenia (<0.2 × 109 /L). The prevention of AdV disease relies on early diagnosis of increasing viral replication in blood or stool and the pre-emptive start of cidofovir as viral load exceeds the threshold of ≥102-3 copies/mL in blood and/or 106 copies/g stool in the stool. Cidofovir (CDV), a cytosine monophosphate nucleotide analog, is currently the only antiviral recommended for AdV infection despite limited efficacy and moderate risk of nephrotoxicity. Brincidofovir, a lipid derivative of CDV with more favorable pharmacokinetics properties and superior efficacy, is not available and currently is being investigated for other viral infections. The enhancement of virus-specific T-cell immunity in the first few months post-HCT by the administration of donor-derived or third-party-donor-derived virus-specific T-cells represents an innovative and promising modality of intervention and data of efficacy and safety of the ongoing prospective randomized studies are eagerly awaited.

The Ten Most Common Questions on Cytomegalovirus Infection in Hematopoietic Stem Cell Transplant Patients

With the rising number of patients undergoing hematopoietic stem cell transplantation (HSCT), clinicians are more likely to encounter infectious complications in immunocompromised hosts, particularly cytomegalovirus (CMV) infection. Besides the high mortality of CMV end-organ disease, patients with detectable CMV viremia may have worse outcomes and decreased survival even in the absence of end-organ disease. In view of the implications on morbidity and mortality, clinicians should maintain a high index of suspicion and initiate antiviral drugs promptly when CMV infection is confirmed. High-risk patients should be identified in order to provide optimal management. Additionally, novel antiviral agents with a good safety profile and minor adverse events are now available for prophylaxis in high-risk patients and for treatment of resistant or refractory CMV infection. The following review provides concise, yet comprehensive, guidance on the burden and risk factors of CMV in this population, as well as an update on the latest evidence for the management of CMV infection.

Optimizing Antiviral Dosing for HSV and CMV Treatment in Immunocompromised Patients

Herpes simplex virus (HSV) and cytomegalovirus (CMV) are DNA viruses that are common among humans. Severely immunocompromised patients are at increased risk of developing HSV or CMV disease due to a weakened immune system. Antiviral therapy can be challenging because these drugs have a narrow therapeutic window and show significant pharmacokinetic variability. Above that, immunocompromised patients have various comorbidities like impaired renal function and are exposed to polypharmacy. This scoping review discusses the current pharmacokinetic (PK) and pharmacodynamic (PD) knowledge of antiviral drugs for HSV and CMV treatment in immunocompromised patients. HSV and CMV treatment guidelines are discussed, and multiple treatment interventions are proposed: early detection of drug resistance; optimization of dose to target concentration by therapeutic drug monitoring (TDM) of nucleoside analogs; the introduction of new antiviral drugs; alternation between compounds with different toxicity profiles; and combinations of synergistic antiviral drugs. This research will also serve as guidance for future research, which should focus on prospective evaluation of the benefit of each of these interventions in randomized controlled trials.

Metabolism Pathways of Major Therapeutics for Treating Monkeypox Mono- and Co-infection with Human Immunodeficient Virus or SARS-CoV-2

Monkeypox is a zoonotic viral disease and remains endemic in tropical regions of Central and West Africa. Since May of 2022, cases of monkeypox have soared and spread worldwide. Confirmed cases have shown no travel history to the endemic regions as seen in the past. The World Health Organization declared monkeypox a global public health emergency in July 2022, and the United States government followed suit one month later. The current outbreak, in contrast to traditional epidemics, has high coinfection rates, particularly with HIV (human immunodeficiency virus), and to a lesser extent with SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), the pathogen of COVID-19. No drugs have been approved specifically for monkeypox. However, there are therapeutic agents authorized to treat monkeypox under the Investigational New Drug protocol, including brincidofovir, cidofovir, and tecovirimat. In contrast to limited options for monkeypox treatment, there are available drugs specifically for HIV or SARS-CoV-2 infection. Interestingly, these HIV and COVID-19 medicines share metabolism pathways with those authorized to treat monkeypox, particularly of hydrolysis, phosphorylation, and active membrane transport. This review discusses how these pathways shared by these medicines should be considered to gain therapeutic synergy and maximize safety for treating monkeypox coinfections.

[Management of infection in immunocompromised patients]

The number of immunosuppressed patients continues to increase worldwide. The main reasons are the demographic development and improved long-term survival, also for patients under immunosuppression. A major cause of hospitalization and mortality among these patients are infections. Their management, including prevention and adequate treatment, plays a crucial role in survival and quality of life, but also with regard to economic factors.Infection management in immunocompromised patients faces new challenges today. Not only the increasing number, but also new groups of patients at risk and an increasingly aging and comorbid population pose problems for the treating physicians. While cancer medicine is no longer determined solely by radiotherapy and chemotherapy, new targeted substances are playing an increasingly important role. In addition, new targeted substances complicate adequate infection prophylaxis due to potential interactions. The worldwide increase in antibiotic-resistant pathogens complicates treatment of bacterial infections, which is associated with increased mortality, especially in the immunocompromised patient population. Further, the disruption of the microbiome shows negative antibiotic-associated effects. Hence the reasonable use of anti-infectives in prophylaxis and therapy is of great importance.There are many recommendations and guidelines for clinicians regarding the management of infections in immunocompromised patients. Overlaps of infectiology, hygiene as well as hematology and oncology sometimes lead to different recommendations. This article provides an overview of the currently existing evidence and guidelines for infection management in immunosuppressed patients.