Brincidofovir (CMX001) Toxicity Associated With Epithelial Apoptosis and Crypt Drop Out in a Hematopoietic Cell Transplant Patient: Challenges in Distinguishing Drug Toxicity From GVHD

Development of Effective Medical Countermeasures Against the Main Biowarfare Agents: The Importance of Antibodies

The COVID-19 and mpox crisis has reminded the world of the potentially catastrophic consequences of biological agents. Aside from the natural risk, biological agents can also be weaponized or used for bioterrorism. Dissemination in a population or among livestock could be used to destabilize a nation by creating a climate of terror, by negatively impacting the economy and undermining institutions. The Centers for Disease Control and Prevention (CDC) classify biological agents into three categories (A or Tier 1, B and C) according to the risk they pose to the public and national security. Category A or Tier 1 consists of the six pathogens with the highest risk to the population (Bacillus anthracis, Yersinia pestis, Francisella tularensis, botulinum neurotoxins, smallpox and viral hemorrhagic fevers). Several medical countermeasures, such as vaccines, antibodies and chemical drugs, have been developed to prevent or cure the diseases induced by these pathogens. This review presents an overview of the primary medical countermeasures, and in particular, of the antibodies available against the six pathogens on the CDC's Tier 1 agents list, as well as against ricin.

Uncovering the Potent Antiviral Activity of the Sesterterpenoids from the Sponge Ircinia Felix Against Human Adenoviruses: from the Natural Source to the Total Synthesis

Human Adenovirus (HAdV) infections in immunocompromised patients can result in disseminated diseases with high morbidity and mortality rates due to the absence of available treatments for these infections. The sponge Ircinia felix was selected for the significant anti-HAdV activity displayed by its organic extracts. Its chemical analysis yielded three novel sesterterpene lactams, ircinialactams J-L, along with three known sesterterpene furans which structures were established by a deep spectrometric analysis. Ircinialactam J displayed significant antiviral activity against HAdV without significant cytotoxicity, showing an effectiveness 11 times greater than that of the standard treatment, cidofovir®. Comparison of the antiviral evaluation results of the isolated compounds allowed us to deduce some structure-activity relationships. Mechanistic assays suggest that ircinialactam J targets an early step of the HAdV replicative cycle before HAdV genome reaches the nucleus of the host cell. The first total synthesis of ircinialactam J was also accomplished to prove the structure and to provide access to analogues. Key steps are a regio- and stereoselective construction of the trisubstituted Z-olefin at Δ7 by iron-catalyzed carbometallation of a homopropargylic alcohol, a stereoselective methylation to generate the stereogenic center at C18, and the formation of the (Z)-Δ20 by stereoselective aldol condensation to introduce the tetronic acid unit. Ircinialactam J is a promising chemical lead to new potent antiviral drugs against HAdV infections.

Synthesis of USC-093 and comparison with its promoiety enantiomer USC-093D against adenovirus in vitro and in a Syrian hamster model

Adenovirus infections of immunocompromised humans are a significant source of morbidity and mortality. At present, no drug has been approved by FDA for the treatment of adenovirus infections. A current treatment of such infections is off-label use of an antiviral acyclic nucleotide phosphonate, cidofovir (CDV, ( S )-HPMPC), which requires i.v. administration and has dose-limiting kidney toxicity. We recently reported that USC-093, a homoserinamide analogue of the tyrosinamide ( S )- HPMPA prodrug USC-087, was orally effective at a 10 mg/kg against disseminated human adenovirus infection (HAdV-C6) in a Syrian hamster model, although their efficacy was marginal after respiratory infection. Neither prodrug manifested GI toxicity. Unlike USC-087, USC-093 showed no significant nephrotoxicity at the effective dose. Here, we describe in detail the synthesis of USC-093 and also its D-homoserinamide analogue, USC-093D, in four steps (20-40% overall yield) starting from Boc-protected L-homoserine or D-homoserine lactone, respectively. The two stereoisomeric prodrugs had EC 50 30-70 nM vs. Ad5 or 1-6 nM vs. Ad6 in HFF cells, with USC-093D giving the lower values. The prodrugs were 30-59x more potent vs. Ad5 and 82-332x more potent than Ad6 relative to the positive control, CDV. To ascertain whether D-chirality in the promoiety could enhance the performance of the prodrug in vivo, USC-093D and USC-093 were compared in the Syrian hamster model (treated from day 1 q.d at an experimentally determined maximum tolerated oral dose of 20 mg/kg)). In this study, the hamsters were instilled i.n. with vehicle or 4X10 10 PFU/kg of HAdV-C6 to promote lung infection. Oral valganciclovir (VGCV) at 200 mg/kg b.i.d. was used as the positive control. The body weights were recorded daily, and at 3 days post challenge, gross pathological observation was performed. Lung samples were collected, and the virus burden was determined by TCID 50 assay. The results show that altering homoserine stereochemistry did not markedly improve the efficacy of the orally administered prodrug, consistent with the premise that its mechanism of transport is likely not dependent on stereoselective pathways, such as hPEPT1-mediated uptake.

Mpox treatment evolution: past milestones, present advances, and future directions

An underestimated worldwide health concern, Monkeypox (Mpox) is becoming a bigger menace to the world's population. After smallpox was eradicated in 1970, Mpox was found in a rural region of Africa and quickly spread to other African countries. The etiological agent of the Mpox infection, the Mpox virus, is constantly evolving, and its capability for cross-species transmission led to a global outbreak in 2022 which led to several deaths throughout the world. This review aims to showcase the progressive treatment methods and emerging innovations in the diagnostic and prevention strategies for controlling Mpox. The clinical trial data for antiviral drugs were systematically collected and analyzed using statistical tests to determine the most effective antiviral treatment. Emerging viral protein inhibitors that are under investigation for Mpox treatment were also scrutinized in this review. Additionally, modern diagnostic methods, such as the Streamlined CRISPR On Pod Evaluation platform (SCOPE) and graphene quantum rods were reviewed, and the efficacy of mRNA vaccines with traditional smallpox vaccines used for Mpox were compared. The statistical analysis revealed that tecovirimat (TCV) is the most effective antiviral drug among the other evaluated drugs, showing superior efficacy in clinical trials. Similarly, mRNA vaccines offer greater effectiveness compared to conventional smallpox vaccines. Furthermore, emerging nanomedicine and herbal drug candidates were highlighted as potential future treatments for Mpox. The findings underscore the effectiveness of TCV in treating Mpox and highlight significant advancements in preventive treatments. The review also points to innovative approaches in vaccine technology and potential future therapies, including nanomedicine and herbal remedies, which may enhance Mpox management.

Current antiviral agents against human adenoviruses associated with respiratory infections

Human adenoviruses (HAdVs) are important pathogens responsible for respiratory infections. In children and immunocompromised patients, respiratory infections can cause considerable morbidity and mortality. Currently, there are no approved effective and safe antiviral therapeutics for the clinical treatment of HAdV infections, even those that have undergone preclinical/clinical trials. However, many compounds and molecules with anti-HAdV activity have been explored, and some candidates are undergoing clinical development. Here, we reviewed the reported in vitro and in vivo efficacies, as well as the therapeutic potential of these antiviral compounds, providing an overview and a summary of the current status of anti-HAdV drug development.

Longitudinal Monitoring of the Effects of Anti-Adenoviral Treatment Regimens in a Permissive In Vivo Model

Adenovirus infections of immunocompromised patients can cause life-threatening disseminated disease. While there are presently no drugs specifically approved to treat these infections, there are several compounds that showed efficacy against adenovirus in preclinical studies. For any such compound, low toxicity is an essential requirement. As cumulative drug effects can accentuate pathology, especially in patients with other morbidities, it is important to limit antiviral exposure to what is absolutely necessary. This is achievable by monitoring the virus burden of the patients and administering antivirals to suppress virus replication to a non-pathogenic level. We modeled such a system using Syrian hamsters infected with a replication-competent adenovirus vector, in which luciferase expression is coupled to virus replication. We found that virus replication could be followed in vivo in the same animal by repeated measurement of luciferase expression. To test the utility of an interrupted treatment regimen, we used NPP-669 and valganciclovir, two antiviral compounds with high and moderate anti-adenoviral efficacy, respectively. We found that short-term treatment of adenovirus-infected hamsters at times of peak virus replication can prevent virus-associated pathology. Thus, we believe that this animal model can be used to model different treatment regimens for anti-adenoviral compounds.

NPP-669, a prodrug of cidofovir, is highly efficacious against human adenovirus infection in the permissive Syrian hamster model

Human adenoviruses can cause serious, disseminated infections in immunocompromised patients. For pediatric allogeneic stem cell transplant patients, the case fatality rate can reach 80%. Still, there is no available antiviral drug that is specifically approved by the Food and Drug Administration for the treatment of adenovirus infections. To fill this pressing medical need, we have developed NPP-669, a prodrug of cidofovir with broad activity against double-stranded DNA viruses, including adenoviruses. Here, we report on the in vivo anti-adenoviral efficacy of NPP-669. Using the immunosuppressed Syrian hamster as the model, we show that NPP-669 is highly efficacious when dosed orally at 1 mg/kg and 3 mg/kg. In a delayed administration experiment, NPP-669 was more effective than brincidofovir, a similar compound that reached Phase III clinical trials. Furthermore, parenteral administration of NPP-669 increased its efficacy approximately 10-fold compared to oral dosing without apparent toxicity, suggesting that this route may be preferable in a hospital setting. Based on these findings, we believe that NPP-669 is a promising new compound that needs to be further investigated.

Oral USC-093, a novel homoserinamide analogue of the tyrosinamide (S)-HPMPA prodrug USC-087 has decreased nephrotoxicity while maintaining antiviral efficacy against human adenovirus infection of Syrian hamsters

Adenovirus infections of immunocompromised humans are a significant source of morbidity and mortality. Presently, there is no drug specifically approved for the treatment of adenovirus infections by the FDA. The state-of-the-art treatment of such infections is the off-label use of cidofovir, an acyclic nucleotide phosphonate. While cidofovir inhibits adenovirus replication, it has dose-limiting kidney toxicity. There is an apparent need for a better compound to treat adenovirus infections. To this end, we have been developing acyclic nucleotide phosphonate prodrugs that utilize an amino acid scaffold equipped with a lipophilic modifier. Here, we compare the antiviral potential of two prodrugs of HPMPA that differ only in the amino acid-based promoiety: USC-087, based on an N-hexadecyl tyrosinamide, and USC-093, based on an N-hexadecyl serinamide. Oral administration of both compounds was very efficacious against disseminated HAdV-C6 infection in immunosuppressed Syrian hamsters, suppressing virus replication and mitigating pathology even when treatment was withheld until 4 days after challenge. We saw only marginal efficacy after respiratory infection of hamsters, which may reflect suboptimal distribution to the lung. Importantly, neither compound induced intestinal toxicity, which was observed as the major adverse effect in clinical trials of brincidofovir, a prodrug of cidofovir which also contains a C-16 modifier. Notably, we found that there was a significant difference in the nephrotoxicity of the two compounds: USC-087 caused significant kidney toxicity while USC-093 did not, at effective doses. These findings will be valuable guidepoints in the future evolution of this new class of potential prodrugs to treat adenovirus infections.

NPP-669, a Novel Broad-Spectrum Antiviral Therapeutic with Excellent Cellular Uptake, Antiviral Potency, Oral Bioavailability, Preclinical Efficacy, and a Promising Safety Margin

DNA viruses are responsible for many diseases in humans. Current treatments are often limited by toxicity, as in the case of cidofovir (CDV, Vistide), a compound used against cytomegalovirus (CMV) and adenovirus (AdV) infections. CDV is a polar molecule with poor bioavailability, and its overall clinical utility is limited by the high occurrence of acute nephrotoxicity. To circumvent these disadvantages, we designed nine CDV prodrug analogues. The prodrugs modulate the polarity of CDV with a long sulfonyl alkyl chain attached to one of the phosphono oxygens. We added capping groups to the end of the alkyl chain to minimize β-oxidation and focus the metabolism on the phosphoester hydrolysis, thereby tuning the rate of this reaction by altering the alkyl chain length. With these modifications, the prodrugs have excellent aqueous solubility, optimized metabolic stability, increased cellular permeability, and rapid intracellular conversion to the pharmacologically active diphosphate form (CDV-PP). The prodrugs exhibited significantly enhanced antiviral potency against a wide range of DNA viruses in infected human foreskin fibroblasts. Single-dose intravenous and oral pharmacokinetic experiments showed that the compounds maintained plasma and target tissue levels of CDV well above the EC50 for 24 h. These experiments identified a novel lead candidate, NPP-669. NPP-669 demonstrated efficacy against CMV infections in mice and AdV infections in hamsters following oral (p.o.) dosing at a dose of 1 mg/kg BID and 0.1 mg/kg QD, respectively. We further showed that NPP-669 at 30 mg/kg QD did not exhibit histological signs of toxicity in mice or hamsters. These data suggest that NPP-669 is a promising lead candidate for a broad-spectrum antiviral compound.

Serinol-Based Benzoic Acid Esters as New Scaffolds for the Development of Adenovirus Infection Inhibitors: Design, Synthesis, and In Vitro Biological Evaluation

Over the years, human adenovirus (HAdV) has progressively been recognized as a significant viral pathogen. Traditionally associated with self-limited respiratory, gastrointestinal, and conjunctival infections, mainly in immunocompromised patients, HAdV is currently considered to be a pathogen presenting significant morbidity and mortality in both immunosuppressed and otherwise healthy individuals. Currently available therapeutic options are limited because of their lack of effectivity and related side effects. In this context, there is an urgent need to develop effective anti-HAdV drugs with suitable therapeutic indexes. In this work, we identified new serinol-derived benzoic acid esters as novel scaffolds for the inhibition of HAdV infections. A set of 38 compounds were designed and synthesized, and their antiviral activity and cytotoxicity were evaluated. Four compounds (13, 14, 27, and 32) inhibited HAdV infection at low micromolar concentrations (2.82-5.35 μM). Their half maximal inhibitory concentration (IC₅₀) values were lower compared to that of cidofovir, the current drug of choice. All compounds significantly reduced the HAdV DNA replication process, while they did not block any step of the viral entry. Our results showed that compounds 13, 14, and 32 seem to be targeting the expression of the E1A early gene. Moreover, all four derivatives demonstrated a significant inhibition of human cytomegalovirus (HCMV) DNA replication. This new scaffold may represent a potential tool useful for the development of effective anti-HAdV drugs.

Filociclovir Is a Potent In Vitro and In Vivo Inhibitor of Human Adenoviruses

Human adenovirus (HAdV) infection is common in the general population and can cause a range of clinical manifestations, among which pneumonia and keratoconjunctivitis are the most common. Although HAdV infections are mostly self-limiting, infections in immunocompromised individuals can be severe. No antiviral drug has been approved for treating adenoviruses. Filociclovir (FCV) is a nucleoside analogue which has successfully completed phase I human clinical safety studies and is now being developed for treatment of human cytomegalovirus (HCMV)-related disease in immunocompromised patients. In this report, we show that FCV is a potent broad-spectrum inhibitor of HAdV types 4 to 8, with 50% effective concentrations (EC50s) ranging between 1.24 and 3.6 μM and a 50% cytotoxic concentration (CC50) of 100 to 150 μM in human foreskin fibroblasts (HFFs). We also show that the prophylactic oral administration of FCV (10 mg/kg of body weight) 1 day prior to virus challenge and then daily for 14 days to immunosuppressed Syrian hamsters infected intravenously with HAdV6 was sufficient to prevent morbidity and mortality. FCV also mitigated tissue damage and inhibited virus replication in the liver. The 10-mg/kg dose had similar effects even when the treatment was started on day 4 after virus challenge. Furthermore, FCV administered at the same dose after intranasal challenge with HAdV6 partially mitigated body weight loss but significantly reduced pathology and virus replication in the lung. These findings suggest that FCV could potentially be developed as a pan-adenoviral inhibitor.

Recent Advances in Novel Antiviral Therapies against Human Adenovirus

Human adenovirus (HAdV) is a very common pathogen that typically causes minor disease in most patients. However, the virus can cause significant morbidity and mortality in certain populations, including young children, the elderly, and those with compromised immune systems. Currently, there are no approved therapeutics to treat HAdV infections, and the standard treatment relies on drugs approved to combat other viral infections. Such treatments often show inconsistent efficacy, and therefore, more effective antiviral therapies are necessary. In this review, we discuss recent developments in the search for new chemical and biological anti-HAdV therapeutics, including drugs that are currently undergoing preclinical/clinical testing, and small molecule screens for the identification of novel compounds that abrogate HAdV replication and disease.

Effect of brincidofovir on adenovirus and A549 cells transcriptome profiles

OBJECTIVES

Human adenovirus (HAdV) infections are associated with a high morbidity and mortality in transplant patients requiring the use of antiviral treatments. Brincidofovir (BCV), a cytidine analog, inhibits HAdV replication through viral DNA elongation termination and likely through other mechanisms. To elucidate if BCV regulates cellular antiviral pathways, we analyzed its impact on HAdV-infected and non-HAdV-infected lung epithelial cells.

METHODS

We assessed the cellular and viral transcriptome of A549 cells infected and non-infected with HAdV C5 and treated or non-treated with BCV by RNAseq after 72 h.

RESULTS

BCV treatment of HAdV infected cells resulted in a profound decrease of viral transcription associated with a relative overexpression of the early genes E1A and E4 and of the late gene L1. BCV had also a profound impact on A549 cells' transcriptome. Ontologic analysis revealed an effect of BCV on several pathways known to interact with adenovirus replication as mTor signalling and Wnt pathways. A549 cells treated with BCV demonstrated a significant inhibition of the biological function of "viral replication" including 25 dysregulated genes involved in inflammation pathways.

CONCLUSION

We demonstrated that BCV alters viral gene expression and promotes the expression of antiviral cellular pathways in A549 cells. These results provide new insights how to interfere with cellular pathways to control HAdV infections.

Adenovirus infection and disease in recipients of hematopoietic cell transplantation

PURPOSE OF REVIEW

To provide an update on risk factors associated with adenovirus (ADV) infection in patients after hematopoietic cell transplant (HCT) and on options for ADV monitoring and treatment in the setting of HCT.

RECENT FINDINGS

Among patients undergoing HCT, ADV infection continues to be more common amongst those receiving a T-cell-depleted or graft other than from a matched-related donor. Among children undergoing HCT, reactivation in the gastrointestinal tract appears to be the most common source, and the virus is detectable by quantitative PCR in the stool before it is detectable in the blood. Thus, screening for the virus in the stool of these children may allow for preemptive therapy to reduce mortality. Brincidofovir, although still not approved by any regulatory agency, remains a potential agent for preemptive therapy and for salvage in cases not responding to cidofovir. Rapidly generated off-the-shelf virus-specific T cells may facilitate adoptive cell therapy in populations with a special need and previously not eligible for adoptive cell therapy, such as cord blood recipients.

SUMMARY

ADV infection continues to adversely affect survival in HCT recipients. Screening stool in children and preemptive therapy may reduce mortality. Brincidofovir and adoptive T-cell therapy remain potential options for treatment.

Approach to infection and disease due to adenoviruses in solid organ transplantation

PURPOSE OF REVIEW

Adenoviruses are an important cause of morbidity and mortality of solid organ transplant patients and remain a clinical challenge with regard to diagnosis and treatment. In this review, we provide an approach to identification and classification of adenovirus infection and disease, highlight risk factors, and outline management options for adenovirus disease in solid organ transplant patients.

RECENT FINDINGS

Additional clinical data and pathologic findings of adenovirus disease in different organs and transplant recipients are known. Unlike hematopoietic cell transplant recipients, adenovirus blood PCR surveillance and preemptive therapy is not supported in solid organ transplantation. Strategies for management of adenovirus disease continue to evolve with newer antivirals, such as brincidofovir and adjunctive immunotherapies, but more studies are needed to support their use.

SUMMARY

Distinguishing between adenovirus infection and disease is an important aspect in adenovirus management as treatment is warranted only in symptomatic solid organ transplant patients. Supportive care and decreasing immunosuppression remain the mainstays of management. Cidofovir remains the antiviral of choice for severe or disseminated disease. Given its significant nephrotoxic effect, administration of probenecid and isotonic saline precidofovir and postcidofovir infusion is recommended.

Brincidofovir: understanding its unique profile and potential role against adenovirus and other viral infections

Brincidofovir (BCV) is a lipid conjugate of cidofovir with good oral bioavailability, enabling optimal intracellular levels of the active drug. Lower rates of nephrotoxicity and myelotoxicity make it a favorable alternative. Despite a greater safety profile among pediatric hematopoietic cell transplant recipients, the oral formulation has been associated with increased gastrointestinal toxicity in adult hematopoietic cell transplant recipients. Oral BCV continues to be developed as a countermeasure against smallpox, while a potentially safer intravenous preparation has been out licensed to another company. BCV has demonstrated great in vitro potency against double-stranded DNA viruses, especially adenovirus. Because of its importance for immunocompromised patients, this review aims to evaluate BCV's clinical and safety profile to support its continued development.

Development of a novel screening platform for the identification of small molecule inhibitors of human adenovirus

Human adenovirus (HAdV) can cause severe disease and death in both immunocompromised and immunocompetent patients. The current standards of treatment are often ineffective, and no approved antiviral therapy against HAdV exists. We report here the design and validation of a fluorescence-based high-content screening platform for the identification of novel anti-HAdV compounds. The screen was conducted using a wildtype-like virus containing the red fluorescent protein (RFP) gene under the regulation of the HAdV major late promoter. Thus, RFP expression allows monitoring of viral late gene expression (a surrogate marker for virus replication), and compounds affecting virus growth can be easily discovered by quantifying RFP intensity. We used our platform to screen ~1200 FDA-approved small molecules, and identified several cardiotonic steroids, corticosteroids and chemotherapeutic agents as anti-HAdV compounds. Our screening platform provides the stringency necessary to detect compounds with varying degrees of antiviral activity, and facilitates drug discovery/repurposing to combat HAdV infections.

Safety considerations with current and emerging antiviral therapies for cytomegalovirus infection in transplantation

Introduction: Human cytomegalovirus (HCMV) is a major contributor of morbidity and mortality, and its management is essential for the successful outcome of solid organ and hematopoietic stem cell transplantation. Areas covered: This review discusses the safety profiles of currently available and emerging antiviral drugs and the other strategies for HCMV prevention and treatment after transplantation. Expert opinion: Strategies for management of HCMV rely largely on the use of antiviral agents that inhibit viral DNA polymerase (ganciclovir/valganciclovir, foscarnet, and cidofovir/brincidofovir) and viral terminase complex (letermovir), with different types and degrees of adverse effects. An investigational agent, maribavir, exerts its anti-CMV effect through UL97 inhibition, and its safety profile is under clinical evaluation. In choosing the antiviral medication to use, it is important to consider these safety profiles in addition to overall efficacy. In addition to antiviral drugs, reduction of immunosuppression is often generally needed in the management of HCMV infection, but with a potential risk of allograft rejection or graft-versus-host disease. The use of HCMV-specific or non-specific intravenous immunoglobulins remains debated, while adoptive HCMV-specific T cell therapy remains investigational, and associated with unique set of adverse effects.

Histone Deacetylase Inhibitor Suberoylanilide Hydroxamic Acid Suppresses Human Adenovirus Gene Expression and Replication

Human adenovirus (HAdV) causes minor illnesses in most patients but can lead to severe disease and death in pediatric, geriatric, and immunocompromised individuals. No approved antiviral therapy currently exists for the treatment of these severe HAdV-induced diseases. In this study, we show that the pan-histone deacetylase (HDAC) inhibitor SAHA reduces HAdV-5 gene expression and DNA replication in tissue culture, ultimately decreasing virus yield from infected cells. Importantly, SAHA also reduced gene expression from more virulent and clinically relevant serotypes, including HAdV-4 and HAdV-7. In addition to SAHA, several other HDAC inhibitors (e.g., trichostatin A, apicidin, and panobinostat) also affected HAdV gene expression. We determined that loss of class I HDAC activity, mainly HDAC2, impairs efficient expression of viral genes, and that E1A physically interacts with HDAC2. Our results suggest that HDAC activity is necessary for HAdV replication, which may represent a novel pharmacological target in HAdV-induced disease.IMPORTANCE Although human adenovirus (HAdV) can cause severe diseases that can be fatal in some populations, there are no effective treatments to combat HAdV infection. In this study, we determined that the pan-histone deacetylase (HDAC) inhibitor SAHA has inhibitory activity against several clinically relevant serotypes of HAdV. This U.S. Food and Drug Administration-approved compound affects various stages of the virus lifecycle and reduces virus yield even at low concentrations. We further report that class I HDAC activity, particularly HDAC2, is required for efficient expression of viral genes during lytic infection. Investigation of the mechanism underlying SAHA-mediated suppression of HAdV gene expression and replication will enhance current knowledge of virus-cell interaction and may aid in the development of more effective antivirals with lower toxicity for the treatment of HAdV infections.

Letermovir for prophylaxis of cytomegalovirus manifestations in adult allogeneic hematopoietic stem cell transplant recipients

Cytomegalovirus (CMV) manifestations remain important complications after allogeneic hematopoietic stem cell transplantation (HSCT), even in the current era. Unfortunately, available anti-CMV agents, mainly viral polymerase inhibitors, have a substantial risk of myelosuppression and nephrotoxicity. Letermovir, a novel anti-CMV drug that targets the viral terminase complex, has recently been approved for the prevention of clinically significant CMV infection in adult CMV seropositive hematopoietic stem cell transplantation recipients. This molecule could become a paradigm-shifting drug in preventing CMV manifestations based on its novel mechanism of action, lack of cross-resistance with available drugs, proven efficacy in a large randomized clinical trial, and its beneficial toxicity and tolerability profile. Drug-drug interactions and the lack of any activity against other viruses are the main shortcomings of letermovir.

Respiratory Virus Infections in Hematopoietic Cell Transplant Recipients

Highly immunocompromised pediatric and adult hematopoietic cell transplant (HCT) recipients frequently experience respiratory infections caused by viruses that are less virulent in immunocompetent individuals. Most of these infections, with the exception of rhinovirus as well as adenovirus and parainfluenza virus in tropical areas, are seasonal variable and occur before and after HCT. Infectious disease management includes sampling of respiratory specimens from nasopharyngeal washes or swabs as well as sputum and tracheal or tracheobronchial lavages. These are subjected to improved diagnostic tools including multiplex PCR assays that are routinely used allowing for expedient detection of all respiratory viruses. Disease progression along with high mortality is frequently associated with respiratory syncytial virus, parainfluenza virus, influenza virus, and metapneumovirus infections. In this review, we discuss clinical findings and the appropriate use of diagnostic measures. Additionally, we also discuss treatment options and suggest new drug formulations that might prove useful in treating respiratory viral infections. Finally, we shed light on the role of the state of immune reconstitution and on the use of immunosuppressive drugs on the outcome of infection.

Pharmacokinetic drug evaluation of letermovir prophylaxis for cytomegalovirus in hematopoietic stem cell transplantation

INTRODUCTION

Letermovir is a new antiviral approved to prevent cytomegalovirus infection in hematopoietic stem cell transplant recipients. It has a distinct mechanism of action as it acts as a terminase complex inhibitor, and shows some advantages compared to the current treatment options for cytomegalovirus infection. Areas covered: This review focuses on the efficacy, safety, pharmacokinetics, pharmacodynamics, and drug-drug interactions of letermovir. Expert opinion: Letermovir is a new antiviral to prevent cytomegalovirus infection. Unlike the currently used polymerase inhibitors, it has a distinct mechanism of action with better safety, limited resistance, and no cross-resistance. Although a lot of research on pharmacokinetics and drug-drug interactions has already been performed, it might be useful to clarify the effect of letermovir on voriconazole exposure, the drug-drug interaction between caspofungine and letermovir and the effect of statins on letermovir exposure. Also, the lack of an exposure-response relationship should be confirmed in large real-life post-marketing studies in order to be able to lower the intravenous dose of letermovir.

A Randomized, Double-Blind, Placebo-Controlled Phase 3 Trial of Oral Brincidofovir for Cytomegalovirus Prophylaxis in Allogeneic Hematopoietic Cell Transplantation

Cytomegalovirus (CMV) infection is a common complication of allogeneic hematopoietic cell transplantation (HCT). In this trial, we randomized adult CMV-seropositive HCT recipients without CMV viremia at screening 2:1 to receive brincidofovir or placebo until week 14 post-HCT. Randomization was stratified by center and risk of CMV infection. Patients were assessed weekly through week 15 and every third week thereafter through week 24 post-HCT. Patients who developed clinically significant CMV infection (CS-CMVi; CMV viremia requiring preemptive therapy or CMV disease) discontinued the study drug and began anti-CMV treatment. The primary endpoint was the proportion of patients with CS-CMVi through week 24 post-HCT; patients who discontinued the trial or with missing data were imputed as primary endpoint events. Between August 2013 and June 2015, 452 patients were randomized at a median of 15 days after HCT and received study drug. The proportion of patients who developed CS-CMVi or were imputed as having a primary endpoint event through week 24 was similar between brincidofovir-treated patients and placebo recipients (155 of 303 [51.2%] versus 78 of 149 [52.3%]; odds ratio, .95 [95% confidence interval, .64 to 1.41]; P = .805); fewer brincidofovir recipients developed CMV viremia through week 14 compared with placebo recipients (41.6%; P < .001). Serious adverse events were more frequent among brincidofovir recipients (57.1% versus 37.6%), driven by acute graft-versus-host disease (32.3% versus 6.0%) and diarrhea (6.9% versus 2.7%). Week 24 all-cause mortality was 15.5% among brincidofovir recipients and 10.1% among placebo recipients. Brincidofovir did not reduce CS-CMVi by week 24 post-HCT and was associated with gastrointestinal toxicity.

[Gastrointestinal tract diseases induced by medications]

Gastrointestinal symptoms are common side effects of medical drugs. They are usually mild but sometimes require diagnostic endoscopy and histologic evaluation. Due to the rapidly increasing number of drugs developed especially for cancer treatment, pathologists are faced with a spectrum of different drug-associated histologies in all segments of the gastrointestinal tract. Some medication-induced mucosal damage features may mimic classical pathologies of nondrug-associated diseases, while others result in novel phenotypes. The present article focusses on the histologic presentations of gastrointestinal diseases induced by medications that either compromise or induce immune response.