ST-246 is a key antiviral to inhibit the viral F13L phospholipase, one of the essential proteins for orthopoxvirus wrapping

Inefficient tissue immune response against MPXV in an immunocompromised mpox patient

The recent outbreak of monkeypox virus (MPXV) was unprecedented in its size and distribution. Those living with uncontrolled HIV and low CD4 T cell counts might develop a fulminant clinical mpox course with increased mortality, secondary infections, and necrotizing lesions. Fatal cases display a high and widespread MPXV tissue burden. The underlying pathomechanisms are not fully understood. We report here the pathological findings of an MPXV-driven abscess in gastrocnemius muscle requiring surgery in an immunocompromised patient with severe mpox. Presence of virus particles and infectivity were confirmed by electron microscopy, expansion microscopy, and virus culture, respectively. MPXV tissue distribution by immunohistochemistry (IHC) showed a necrotic core with infection of different cell types. In contrast, at the lesion rim fibroblasts were mainly infected. Immune cells were almost absent in the necrotic core, but were abundant at the infection rim and predominantly macrophages. Further, we detected high amounts of alternatively activated GPNMB+-macrophages at the lesion border. Of note, macrophages only rarely colocalized with virus-infected cells. Insufficient clearance of infected cells and infection of lesion-associated fibroblasts sustained by the abundance of profibrotic macrophages might lead to the coalescing of lesions and the severe and persistent clinical mpox course observed in immunocompromised patients.

Update on monkeypox virus infection: Focusing current treatment and prevention approaches

BACKGROUND

While the world is still facing the global pandemic COVID-19, another zoonosis monkeypox (Mpox) has emerged posing a great threat to society. Insight into the pathogenesis, symptoms, and management strategies will aid in the development of potent therapeutics for the treatment of monkeypox virus infection.

OBJECTIVES

To get insight into the current treatment and prevention strategies will aid in effectively coping with the disease.

METHODS

For obtaining information regarding the ongoing treatment and prevention strategies and the drugs under pipeline, we referred to Google Scholar, Pub Med, Pub Chem, and WHO official site.

RESULTS

There are a few drugs that came out to be effective for the treatment of Mpox. Tecovirimat acts by inhibiting viral replication and viral wrapping. Another drug is cidofovir, which hinders the activity of viral DNA polymerase but has the drawback of nephrotoxicity. To overcome this, a conjugate of cidofovir is being used-known as brincidofovir-which has a similar mechanism as cidofovir but lesser toxicity. Ribavirin acts via inhibiting inosine monophosphate dehydrogenase (IMPDPH) thus disrupting viral translation. It also interferes with helicase activity. Tiazofurin, Adenosine N1 oxide, and HPMPA have shown efficacy in in-vitro studies by inhibiting IMPDH, DNA polymerase, and viral mRNA translation respectively. In-silico studies have proven the effect of nilotinib, simeprevir, and dihydroergotamine for Mpox treatment. They have shown binding affinity for proteins required for the growth and release of MPXV. Vaccines have also been employed for the prevention of Mpox, which includes JYNNEOS, ACAM2000, and VIGIV.

CONCLUSION

This review highlights the pathogenesis of the virus, disease manifestations, drugs, and vaccines that are being used and those under pipeline for the treatment and prevention of Mpox.

Mpox (Monkeypox) Virus and Its Co-Infection with HIV, Sexually Transmitted Infections, or Bacterial Superinfections: Double Whammy or a New Prime Culprit?

Epidemiologic studies have established that mpox (formerly known as monkeypox) outbreaks worldwide in 2022-2023, due to Clade IIb mpox virus (MPXV), disproportionately affected gay, bisexual, and other men who have sex with men. More than 35% and 40% of the mpox cases suffer from co-infection with HIV and sexually transmitted infections (STIs) (e.g., Chlamydia trachomatis, Neisseria gonorrhoeae, Treponema pallidum, and herpes simplex virus), respectively. Bacterial superinfection can also occur. Co-infection of MPXV and other infectious agents may enhance disease severity, deteriorate outcomes, elongate the recovery process, and potentially contribute to the morbidity and mortality of the ensuing diseases. However, the interplays between MPXV and HIV, bacteria, other STI pathogens and host cells are poorly studied. There are many open questions regarding the impact of co-infections with HIV, STIs, or bacterial superinfections on the diagnosis and treatment of MPXV infections, including clinical and laboratory-confirmed mpox diagnosis, suboptimal treatment effectiveness, and induction of antiviral drug resistance. In this review article, we will discuss the progress and knowledge gaps in MPXV biology, antiviral therapy, pathogenesis of human MPXV and its co-infection with HIV, STIs, or bacterial superinfections, and the impact of the co-infections on the diagnosis and treatment of mpox disease. This review not only sheds light on the MPXV infection and co-infection of other etiologies but also calls for more research on MPXV life cycles and the molecular mechanisms of pathogenesis of co-infection of MPXV and other infectious agents, as well as research and development of a novel multiplex molecular testing panel for the detection of MPXV and other STI co-infections.

Orally available nucleoside analog UMM-766 provides protection in a murine model of orthopox disease

Although smallpox has been eradicated, other orthopoxviruses continue to be a public health concern as exemplified by the ongoing Mpox (formerly monkeypox) global outbreak. While medical countermeasures (MCMs) previously approved by the Food and Drug Administration for the treatment of smallpox have been adopted for Mpox, previously described vulnerabilities coupled with the questionable benefit of at least one of the therapeutics during the 2022 Mpox outbreak reinforce the need for identifying and developing other MCMs against orthopoxviruses. Here, we screened a panel of Merck proprietary small molecules and identified a novel nucleoside inhibitor with potent broad-spectrum antiviral activity against multiple orthopoxviruses. Efficacy testing of a 7-day dosing regimen of the orally administered nucleoside in a murine model of severe orthopoxvirus infection yielded a dose-dependent increase in survival. Treated animals had greatly reduced lesions in the lung and nasal cavity, particularly in the 10 µg/mL dosing group. Viral levels were also markedly lower in the UMM-766-treated animals. This work demonstrates that this nucleoside analog has anti-orthopoxvirus efficacy and can protect against severe disease in a murine orthopox model.IMPORTANCEThe recent monkeypox virus pandemic demonstrates that members of the orthopoxvirus, which also includes variola virus, which causes smallpox, remain a public health issue. While currently FDA-approved treatment options exist, risks that resistant strains of orthopoxviruses may arise are a great concern. Thus, continued exploration of anti-poxvirus treatments is warranted. Here, we developed a template for a high-throughput screening assay to identify anti-poxvirus small-molecule drugs. By screening available drug libraries, we identified a compound that inhibited orthopoxvirus replication in cell culture. We then showed that this drug can protect animals against severe disease. Our findings here support the use of existing drug libraries to identify orthopoxvirus-targeting drugs that may serve as human-safe products to thwart future outbreaks.

Bisbenzimide compounds inhibit the replication of prototype and pandemic potential poxviruses

We previously identified the bisbenzimide Hoechst 33342 (H42) as a potent multi-stage inhibitor of the prototypic poxvirus, the vaccinia virus (VACV), and several parapoxviruses. A recent report showed that novel bisbenzimide compounds similar in structure to H42 could prevent human cytomegalovirus replication. Here, we assessed whether these compounds could also serve as poxvirus inhibitors. Using virological assays, we show that these bisbenzimide compounds inhibit VACV spread, plaque formation, and the production of infectious progeny VACV with relatively low cell toxicity. Further analysis of the VACV lifecycle indicated that the effective bisbenzimide compounds had little impact on VACV early gene expression but inhibited VACV late gene expression and truncated the formation of VACV replication sites. Additionally, we found that bisbenzimide compounds, including H42, can inhibit both monkeypox and a VACV mutant resistant to the widely used anti-poxvirus drug TPOXX (Tecovirimat). Therefore, the tested bisbenzimide compounds were inhibitors of both prototypic and pandemic potential poxviruses and could be developed for use in situations where anti-poxvirus drug resistance may occur. Additionally, these data suggest that bisbenzimide compounds may serve as broad-activity antiviral compounds, targeting diverse DNA viruses such as poxviruses and betaherpesviruses.IMPORTANCEThe 2022 mpox (monkeypox) outbreak served as a stark reminder that due to the cessation of smallpox vaccination over 40 years ago, most of the human population remains susceptible to poxvirus infection. With only two antivirals approved for the treatment of smallpox infection in humans, the need for additional anti-poxvirus compounds is evident. Having shown that the bisbenzimide H33342 is a potent inhibitor of poxvirus gene expression and DNA replication, here we extend these findings to include a set of novel bisbenzimide compounds that show anti-viral activity against mpox and a drug-resistant prototype poxvirus mutant. These results suggest that further development of bisbenzimides for the treatment of pandemic potential poxviruses is warranted.

A case of fatal monkeypox infection: necropsy and molecular findings, with some considerations related to clinical management

OBJECTIVE

Human monkeypox (mpox) is usually self-limited infection; however, rising data show a worse outcome in patients with impaired immune status, particularly those co-infected with HIV [Mitjà O, Alemany A, Marks M, Lezama Mora JI, Rodríguez-Aldama JC, Torres Silva MS et al. Mpox in people with advanced HIV infection: A global case series. Lancet. 2023; 401:939-49. DOI:https://doi.org/10.1016/S0140-6736(23)00273-8] [Govind A, Lazarte SM, Kitchell E, Chow JY, Estelle CD, Fixsen E et al. Severe mpox infections in people with uncontrolled human immunodeficiency virus (HIV). Clin Infect Dis. 2023; 76:1843-6. DOI:https://doi.org/10.1093/cid/ciad052].

METHODS

We report the clinical, pathological, and molecular study of a patient with mpox infection and a late HIV diagnosis, with fatal outcome.

RESULTS

Necropsy revealed visceral spread of mpox. Mpox virus was sequenced twice during the admission, uncovering an emerging mutation near a genomic region where mutations associated with tecovirimat resistance have been documented.

DISCUSSION

Monkeypox can manifest as an opportunistic infection in individuals with advanced HIV-associated immunosuppression.

Molecular and phylogenetic characterization of the monkeypox outbreak in the South of Spain

Background and Aim

Until the May 2022 Monkeypox (MPXV) outbreak, which spread rapidly to many non-endemic countries, the virus was considered a viral zoonosis limited to some African countries. The Andalusian circuit of genomic surveillance was rapidly applied to characterize the MPXV outbreak in the South of Spain.

Methods

Whole genome sequencing was used to obtain the genomic profiles of samples collected across the south of Spain, representative of all the provinces of Andalusia. Phylogenetic analysis was used to study the relationship of the isolates and the available sequences of the 2022 outbreak.

Results

Whole genome sequencing of a total of 160 MPXV viruses from the different provinces that reported cases were obtained. Interestingly, we report the sequences of MPXV viruses obtained from two patients who died. While one of the isolates bore no noteworthy mutations that explain a potential heightened virulence, in another patient the second consecutive genome sequence, performed after the administration of tecovirimat, uncovered a mutation within the A0A7H0DN30 gene, known to be a prime target for tecovirimat in its Vaccinia counterpart. In general, a low number of mutations were observed in the sequences reported, which were very similar to the reference of the 2022 outbreak (OX044336), as expected from a DNA virus. The samples likely correspond to several introductions of the circulating MPXV viruses from the last outbreak. The virus sequenced from one of the two patients that died presented a mutation in a gene that bears potential connections to drug resistance. This mutation was absent in the initial sequencing before treatment.

Smallpox lesion characterization in placebo-treated and tecovirimat-treated macaques using traditional and novel methods

Smallpox was the most rampant infectious disease killer of the 20th century, yet much remains unknown about the pathogenesis of the variola virus. Using archived tissue from a study conducted at the Centers for Disease Control and Prevention we characterized pathology in 18 cynomolgus macaques intravenously infected with the Harper strain of variola virus. Six macaques were placebo-treated controls, six were tecovirimat-treated beginning at 2 days post-infection, and six were tecovirimat-treated beginning at 4 days post-infection. All macaques were treated daily until day 17. Archived tissues were interrogated using immunohistochemistry, in situ hybridization, immunofluorescence, and electron microscopy. Gross lesions in three placebo-treated animals that succumbed to infection primarily consisted of cutaneous vesicles, pustules, or crusts with lymphadenopathy. The only gross lesions noted at the conclusion of the study in the three surviving placebo-treated and the Day 4 treated animals consisted of resolving cutaneous pox lesions. No gross lesions attributable to poxviral infection were present in the Day 2 treated macaques. Histologic lesions in three placebo-treated macaques that succumbed to infection consisted of proliferative and necrotizing dermatitis with intracytoplasmic inclusion bodies and lymphoid depletion. The only notable histologic lesion in the Day 4 treated macaques was resolving dermatitis; no notable lesions were seen in the Day 2 treated macaques. Variola virus was detected in all three placebo-treated animals that succumbed to infection prior to the study's conclusion by all utilized methods (IHC, ISH, IFA, EM). None of the three placebo-treated animals that survived to the end of the study nor the animals in the two tecovirimat treatment groups showed evidence of variola virus by these methods. Our findings further characterize variola lesions in the macaque model and describe new molecular methods for variola detection.

AI-assisted structural consensus-proteome prediction of human monkeypox viruses isolated within a year after the 2022 multi-country outbreak

IMPORTANCE

The 2022 outbreak of the monkeypox virus already involves, by April 2023, 110 countries with 86,956 confirmed cases and 119 deaths. Understanding an emerging disease on a molecular level is essential to study infection processes and eventually guide drug discovery at an early stage. To support this, we provide the so far most comprehensive structural proteome of the monkeypox virus, which includes 210 structural models, each computed with three state-of-the-art structure prediction methods. Instead of building on a single-genome sequence, we generated our models from a consensus of 3,713 high-quality genome sequences sampled from patients within 1 year of the outbreak. Therefore, we present an average structural proteome of the currently isolated viruses, including mutational analyses with a special focus on drug-binding sites. Continuing dynamic mutation monitoring within the structural proteome presented here is essential to timely predict possible physiological changes in the evolving virus.

Tecovirimat Resistance in Mpox Patients, United States, 2022-2023

During the 2022 multinational outbreak of monkeypox virus (MPXV) infection, the antiviral drug tecovirimat (TPOXX; SIGA Technologies, Inc., https://www.siga.com) was deployed in the United States on a large scale for the first time. The MPXV F13L gene homologue encodes the target of tecovirimat, and single amino acid changes in F13 are known to cause resistance to tecovirimat. Genomic sequencing identified 11 mutations previously reported to cause resistance, along with 13 novel mutations. Resistant phenotype was determined using a viral cytopathic effect assay. We tested 124 isolates from 68 patients; 96 isolates from 46 patients were found to have a resistant phenotype. Most resistant isolates were associated with severely immunocompromised mpox patients on multiple courses of tecovirimat treatment, whereas most isolates identified by routine surveillance of patients not treated with tecovirimat remained sensitive. The frequency of resistant viruses remains relatively low (<1%) compared with the total number of patients treated with tecovirimat.

Treatment of Mpox with Suspected Tecovirimat Resistance in Immunocompromised Patient, United States, 2022

Reports of tecovirimat-resistant mpox have emerged after widespread use of antiviral therapy during the 2022 mpox outbreak. Optimal management of patients with persistent infection with or without suspected resistance is yet to be established. We report a successfully treated case of severe mpox in California, USA, that had suspected tecovirimat resistance.

Mpox and HIV-Collision of Two Diseases

PURPOSE OF REVIEW

The global outbreak of mpox has brought renewed attention to a previously neglected disease which is particularly severe in people with underlying untreated HIV co-infection. For this population, the disease is progressive, severe, and often lethal. In this review, we examine the pathogenesis of mpox disease and its collision with co-existent HIV infection and discuss key considerations for management as well as emerging clinical dilemmas and areas for future research.

RECENT FINDINGS

Co-existent untreated HIV infection characterized by severe immunocompromise potentiates the nefarious effects of monkeypox virus infection leading to severe manifestations of mpox. Treating mpox in the context of HIV requires mpox-directed therapies, supportive care, and HIV-specific treatment to restore immune function. Preventative measures for PWH are like those in healthy individuals, but the effectiveness and durability of protection conferred by existing vaccines in PWH remain to be fully characterized. Mpox is an important opportunistic infection in PWH. Clinicians should be aware of the unique features of the disease in this population and approaches to care and management of mpox in PWH.

Distinct monkeypox virus lineages co-circulating in humans before 2022

The 2022 global mpox outbreak raises questions about how this zoonotic disease established effective human-to-human transmission and its potential for further adaptation. The 2022 outbreak virus is related to an ongoing outbreak in Nigeria originally reported in 2017, but the evolutionary path linking the two remains unclear due to a lack of genomic data between 2018, when virus exportations from Nigeria were first recorded, and 2022, when the global mpox outbreak began. Here, 18 viral genomes obtained from patients across southern Nigeria in 2019-2020 reveal multiple lineages of monkeypox virus (MPXV) co-circulated in humans for several years before 2022, with progressive accumulation of mutations consistent with APOBEC3 activity over time. We identify Nigerian A.2 lineage isolates, confirming the lineage that has been multiply exported to North America independently of the 2022 outbreak originated in Nigeria, and that it has persisted by human-to-human transmission in Nigeria for more than 2 years before its latest exportation. Finally, we identify a lineage-defining APOBEC3-style mutation in all A.2 isolates that disrupts gene A46R, encoding a viral innate immune modulator. Collectively, our data demonstrate MPXV capacity for sustained diversification within humans, including mutations that may be consistent with established mechanisms of poxvirus adaptation.

Potential Anti-Mpox Virus Activity of Atovaquone, Mefloquine, and Molnupiravir, and Their Potential Use as Treatments

BACKGROUND

Mpox virus (MPXV) is a zoonotic orthopoxvirus and caused an outbreak in 2022. Although tecovirimat and brincidofovir are approved as anti-smallpox drugs, their effects in mpox patients have not been well documented. In this study, by a drug repurposing approach, we identified potential drug candidates for treating mpox and predicted their clinical impacts by mathematical modeling.

METHODS

We screened 132 approved drugs using an MPXV infection cell system. We quantified antiviral activities of potential drug candidates by measuring intracellular viral DNA and analyzed the modes of action by time-of-addition assay and electron microscopic analysis. We further predicted the efficacy of drugs under clinical concentrations by mathematical simulation and examined combination treatment.

RESULTS

Atovaquone, mefloquine, and molnupiravir exhibited anti-MPXV activity, with 50% inhibitory concentrations of 0.51-5.2 μM, which was more potent than cidofovir. Whereas mefloquine was suggested to inhibit viral entry, atovaquone and molnupiravir targeted postentry processes. Atovaquone was suggested to exert its activity through inhibiting dihydroorotate dehydrogenase. Combining atovaquone with tecovirimat enhanced the anti-MPXV effect of tecovirimat. Quantitative mathematical simulations predicted that atovaquone can promote viral clearance in patients by 7 days at clinically relevant drug concentrations.

CONCLUSIONS

These data suggest that atovaquone would be a potential candidate for treating mpox.

Identification of In Vitro Inhibitors of Monkeypox Replication

Monkeypox virus (MPXV) infections in humans have historically been restricted to regions of endemicity in Africa. However, in 2022, an alarming number of MPXV cases were reported globally, with evidence of person-to-person transmission. Because of this, the World Health Organization (WHO) declared the MPXV outbreak a public health emergency of international concern. The supply of MPXV vaccines is limited, and only two antivirals, tecovirimat and brincidofovir, approved by the U.S. Food and Drug Administration (FDA) for the treatment of smallpox, are currently available for the treatment of MPXV infection. Here, we evaluated 19 compounds previously shown to inhibit different RNA viruses for their ability to inhibit orthopoxvirus infections. We first used recombinant vaccinia virus (rVACV) expressing fluorescence (mScarlet or green fluorescent protein [GFP]) and luciferase (Nluc) reporter genes to identify compounds with antiorthopoxvirus activity. Seven compounds from the ReFRAME library (antimycin A, mycophenolic acid, AVN-944, pyrazofurin, mycophenolate mofetil, azaribine, and brequinar) and six compounds from the NPC library (buparvaquone, valinomycin, narasin, monensin, rotenone, and mubritinib) showed inhibitory activity against rVACV. Notably, the anti-VACV activity of some of the compounds in the ReFRAME library (antimycin A, mycophenolic acid, AVN-944, mycophenolate mofetil, and brequinar) and all the compounds from the NPC library (buparvaquone, valinomycin, narasin, monensin, rotenone, and mubritinib) were confirmed with MPXV, demonstrating their inhibitory activity in vitro against two orthopoxviruses. IMPORTANCE Despite the eradication of smallpox, some orthopoxviruses remain important human pathogens, as exemplified by the recent 2022 monkeypox virus (MPXV) outbreak. Although smallpox vaccines are effective against MPXV, access to those vaccines is limited. In addition, current antiviral treatment against MPXV infections is limited to the use of the FDA-approved drugs tecovirimat and brincidofovir. Thus, there is an urgent need to identify novel antivirals for the treatment of MPXV infection and other potentially zoonotic orthopoxvirus infections. Here, we show that 13 compounds, derived from two different libraries, previously found to inhibit several RNA viruses, also inhibit VACV. Notably, 11 compounds also displayed inhibitory activity against MPXV.

Clinical Strategies and Therapeutics for Human Monkeypox Virus: A Revised Perspective on Recent Outbreaks

An enveloped double-stranded DNA monkeypox virus (MPXV) is a causative agent of the zoonotic viral disease, human monkeypox (HMPX). MPXV belongs to the genus Orthopoxviridae, a family of notorious smallpox viruses, and so it shares similar clinical pathophysiological features. The recent multicountry HMPX outbreak (May 2022 onwards) is recognized as an emerging global public health emergency by the World Health Organization, shunting its endemic status as opined over the past few decades. Re-emergence of HMPX raises concern to reassess the present clinical strategy and therapeutics as its outbreak evolves further. Keeping a check on these developments, here we provide insights into the HMPX epidemiology, pathophysiology, and clinical representation. Weighing on its early prevention, we reviewed the strategies that are being enrolled for HMPX diagnosis. In the line of expanded MPXV prevalence, we further reviewed its clinical management and the diverse employed preventive/therapeutic strategies, including vaccines (JYNNEOS, ACAM2000, VIGIV) and antiviral drugs/inhibitors (Tecovirimat, Cidofovir, Brincidofovir). Taken together, with a revised perspective of HMPX re-emergence, the present report summarizes new knowledge on its prevalence, pathology, and prevention strategies.

In vitro susceptibility of eighteen clinical isolates of human monkeypox virus to tecovirimat

BACKGROUND

In 2022, an outbreak of mpox that started in European countries spread worldwide through human-to-human transmission. Cases have been mostly mild, but severe clinical presentations have been reported. In these cases, tecovirimat has been the drug of choice to treat patients with aggravated disease.

OBJECTIVES

Here we investigated the tecovirimat susceptibility of 18 clinical isolates of monkeypox virus (MPXV) obtained from different regions of Brazil.

METHODS

Different concentrations of tecovirimat were added to cell monolayers infected with each MPXV isolate. After 72 hours, cells were fixed and stained for plaque visualization, counting, and measurement. The ortholog of F13L gene from each MPXV isolate was polymerase chain reaction (PCR)-amplified, sequenced, and the predicted protein sequences were analyzed.

FINDINGS

The eighteen MPXV isolates generated plaques of different sizes. Although all isolates were highly sensitive to the drug, two showed different response curves and IC50 values. However, the target protein of tecovirimat, F13 (VP37), was 100% conserved in all MPXV isolates and therefore does not explain the difference in sensitivity.

MAIN CONCLUSIONS

Our results support screening different MPXV isolates for tecovirimat susceptibility as an important tool to better use of the restricted number of tecovirimat doses available in low-income countries to treat patients with mpox.

Computational analysis of target genes in monkeypox virus infection and potential therapeutic precursors

BACKGROUND

Monkeypox is an orthopoxvirus that is responsible for zoonotic infections in humans. The virus has recently spread rapidly and the WHO has listed it as an international public health emergency of concern.

RESEARCH DESIGN AND METHODS

Here, we used network analysis and gene enrichment protocols and analyzed datasets of MPXV infection that induced host cell gene expression list and subsequently mapped them against two herbal target gene lists which highlighted considerable coherence in pharmacological attributes with COVID-19. Molecular docking and simulation were performed for the screened compounds.

RESULTS

Our results identified β-carotene and kaempferol possessing tremendous ability against the MPXV PLD protein. Both compounds were subjected to each of 100 ns molecular dynamics simulation and were found native to the PLD pocket. MM-PB (GB) SA analyses indicated -25.4, -40.1 kcal/mol and -17.2, -26.4kcal/mol of ΔGbind to the active pocket of PLD. Our data suggest the adaptive nature of the MPXV PLD active pocket toward hydrophobic inhibitors.

CONCLUSION

These results will be of high importance for the viral researchers to be tested in wet lab settings in designing potential inhibitors.

Antiviral activities of two nucleos(t)ide analogs against vaccinia, mpox, and cowpox viruses in primary human fibroblasts

Many poxviruses are significant human and animal pathogens, including viruses that cause smallpox and mpox (formerly monkeypox). Identifying novel and potent antiviral compounds is critical to successful drug development targeting poxviruses. Here we tested two compounds, nucleoside trifluridine, and nucleotide adefovir dipivoxil, for antiviral activities against vaccinia virus (VACV), mpox virus (MPXV), and cowpox virus (CPXV) in physiologically relevant primary human fibroblasts. Both compounds potently inhibited the replication of VACV, CPXV, and MPXV (MA001 2022 isolate) in plaque assays. In our recently developed assay based on a recombinant VACV expressing secreted Gaussia luciferase, they both exhibited high potency in inhibiting VACV replication with EC₅₀s in the low nanomolar range. In addition, both trifluridine and adefovir dipivoxil inhibited VACV DNA replication and downstream viral gene expression. Our results characterized trifluridine and adefovir dipivoxil as strong poxvirus antiviral compounds and further validate the VACV Gaussia luciferase assay as a highly efficient and reliable reporter tool for identifying poxvirus inhibitors. Given that both compounds are FDA-approved drugs, and trifluridine is already used to treat ocular vaccinia, further development of trifluridine and adefovir dipivoxil holds great promise in treating poxvirus infections, including mpox.

Antivirals against monkeypox infections

Monkeypox virus (MPXV) infection in humans are historically restricted to endemic regions in Africa. However, in 2022, an alarming number of MPXV cases have been reported globally with evidence of person-to-person transmission. Because of this, the World Health Organization (WHO) declared the MPXV outbreak a public health emergency of international concern. MPXV vaccines are limited and only two antivirals, tecovirimat and brincidofovir, approved by the United States (US) Food and Drug Administration (FDA) for the treatment of smallpox, are currently available for the treatment of MPXV infection. Here, we evaluated 19 compounds previously shown to inhibit different RNA viruses for their ability to inhibit Orthopoxvirus infections. We first used recombinant vaccinia virus (rVACV) expressing fluorescence (Scarlet or GFP) and luciferase (Nluc) reporter genes to identify compounds with anti-Orthopoxvirus activity. Seven compounds from the ReFRAME library (antimycin A, mycophenolic acid, AVN- 944, pyrazofurin, mycophenolate mofetil, azaribine, and brequinar) and six compounds from the NPC library (buparvaquone, valinomycin, narasin, monensin, rotenone, and mubritinib) showed antiviral activity against rVACV. Notably, the anti-VACV activity of some of the compounds in the ReFRAME library (antimycin A, mycophenolic acid, AVN- 944, mycophenolate mofetil, and brequinar) and all the compounds from the NPC library (buparvaquone, valinomycin, narasin, monensin, rotenone, and mubritinib) were confirmed with MPXV, demonstrating the broad-spectrum antiviral activity against Orthopoxviruses and their potential to be used for the antiviral treatment of MPXV, or other Orthopoxvirus, infections.

IMPORTANCE

Despite the eradication of smallpox, some Orthopoxviruses remain important human pathogens, as exemplified by the recent 2022 monkeypox virus (MPXV) outbreak. Although smallpox vaccines are effective against MPXV, there is presently limited access to those vaccines. In addition, current antiviral treatment against MPXV infections is limited to the use of the FDA-approved drugs tecovirimat and brincidofovir. Thus, there is an urgent need to identify novel antivirals for the treatment of MPXV, and other potentially zoonotic Orthopoxvirus infections. Here, we show that thirteen compounds, derived from two different libraries, previously found to inhibit several RNA viruses, exhibit also antiviral activity against VACV. Notably, eleven compounds also displayed antiviral activity against MPXV, demonstrating their potential to be incorporated into the therapeutic armamentarium to combat Orthopoxvirus infections.

An Overview of Antivirals against Monkeypox Virus and Other Orthopoxviruses

The current monkeypox outbreaks during the COVID-19 pandemic have reignited interest in orthopoxvirus antivirals. Monkeypox belongs to the Orthopoxvirus genus of the Poxviridae family, which also includes the variola virus, vaccinia virus, and cowpox virus. Two orally bioavailable drugs, tecovirimat and brincidofovir, have been approved for treating smallpox infections. Given their human safety profiles and in vivo antiviral efficacy in animal models, both drugs have also been recommended to treat monkeypox infection. To facilitate the development of additional orthopoxvirus antivirals, we summarize the antiviral activity, mechanism of action, and mechanism of resistance of orthopoxvirus antivirals. This perspective covers both direct-acting and host-targeting antivirals with an emphasis on drug candidates showing in vivo antiviral efficacy in animal models. We hope to speed the orthopoxvirus antiviral drug discovery by providing medicinal chemists with insights into prioritizing proper drug targets and hits for further development.

Antiviral activities of two nucleos(t)ide analogs against vaccinia and mpox viruses in primary human fibroblasts

Many poxviruses are significant human and animal pathogens, including viruses that cause smallpox and mpox. Identification of inhibitors of poxvirus replication is critical for drug development to manage poxvirus threats. Here we tested two compounds, nucleoside trifluridine and nucleotide adefovir dipivoxil, for antiviral activities against vaccinia virus (VACV) and mpox virus (MPXV) in physiologically relevant primary human fibroblasts. Both trifluridine and adefovir dipivoxil potently inhibited replication of VACV and MPXV (MA001 2022 isolate) in a plaque assay. Upon further characterization, they both conferred high potency in inhibiting VACV replication with half maximal effective concentrations (EC ₅₀ ) at low nanomolar levels in our recently developed assay based on a recombinant VACV secreted Gaussia luciferase. Our results further validated that the recombinant VACV with Gaussia luciferase secretion is a highly reliable, rapid, non-disruptive, and simple reporter tool for identification and chracterization of poxvirus inhibitors. Both compounds inhibited VACV DNA replication and downstream viral gene expression. Given that both compounds are FDA-approved drugs, and trifluridine is used to treat ocular vaccinia in medical practice due to its antiviral activity, our results suggest that it holds great promise to further test trifluridine and adefovir dipivoxil for countering poxvirus infection, including mpox.

Interim Clinical Treatment Considerations for Severe Manifestations of Mpox - United States, February 2023

Monkeypox (mpox) is a disease caused by infection with Monkeypox virus (MPXV), an Orthopoxvirus (OPXV) in the same genus as Variola virus, which causes smallpox. During 2022, a global outbreak involving mpox clade IIb was recognized, primarily among gay, bisexual, and other men who have sex with men.* Most affected patients have been immunocompetent and experienced ≤10 rash lesions (1). CDC has recommended supportive care including pain control.^† However, some patients have experienced severe mpox manifestations, including ocular lesions, neurologic complications, myopericarditis, complications associated with mucosal (oral, rectal, genital, and urethral) lesions, and uncontrolled viral spread due to moderate or severe immunocompromise, particularly advanced HIV infection (2). Therapeutic medical countermeasures (MCMs) are Food and Drug Administration (FDA)-regulated drugs and biologics that are predominantly stockpiled by the U.S. government; MCMs developed for smallpox preparedness or shown to be effective against other OPXVs (i.e., tecovirimat, brincidofovir, cidofovir, trifluridine ophthalmic solution, and vaccinia immune globulin intravenous [VIGIV]) have been used to treat severe mpox. During May 2022-January 2023, CDC provided more than 250 U.S. mpox consultations. This report synthesizes data from animal models, MCM use for human cases of related OPXV, unpublished data, input from clinician experts, and experience during consultations (including follow-up) to provide interim clinical treatment considerations. Randomized controlled trials and other carefully controlled research studies are needed to evaluate the effectiveness of MCMs for treating human mpox. Until data gaps are filled, the information presented in this report represents the best available information concerning the effective use of MCMs and should be used to guide decisions about MCM use for mpox patients.

An overview on monkeypox virus: Pathogenesis, transmission, host interaction and therapeutics

Orthopoxvirus is one of the most notorious genus amongst the Poxviridae family. Monkeypox (MP) is a zoonotic disease that has been spreading throughout Africa. The spread is global, and incidence rates are increasing daily. The spread of the virus is rapid due to human-to-human and animals-to-human transmission. World Health Organization (WHO) has declared monkeypox virus (MPV) as a global health emergency. Since treatment options are limited, it is essential to know the modes of transmission and symptoms to stop disease spread. The information from host-virus interactions revealed significantly expressed genes that are important for the progression of the MP infection. In this review, we highlighted the MP virus structure, transmission modes, and available therapeutic options. Furthermore, this review provides insights for the scientific community to extend their research work in this field.

Overview of the regulatory approval of tecovirimat intravenous formulation for treatment of smallpox: potential impact on smallpox outbreak response capabilities, and future tecovirimat development potential

INTRODUCTION

Tecovirimat oral capsule formulation is approved in the US and Canada for treatment of smallpox and in the United Kingdom (UK) and European Union (EU) for treatment of multiple human orthopoxvirus diseases, including mpox. Smallpox is considered a serious threat, and there is currently an unprecedented global mpox outbreak.

AREAS COVERED

A brief summary of the threat of smallpox, the threat of increasing mpox spread in endemic regions, and the unprecedented emergence of mpox into non-endemic regions is presented. The tecovirimat intravenous formulation clinical development program leading to USFDA approval for smallpox treatment is discussed.

EXPERT OPINION

As of January 2023 tecovirimat is approved to treat mpox in the UK and EU. However, published clinical trial data evaluating tecovirimat efficacy and safety in mpox patients is pending. Increasing global prevalence of mpox highlights the potential benefits of a well-characterized, effective, and safe antiviral treatment for mpox infection. Ongoing trials in mpox patients may provide results supporting the use of tecovirimat to treat this disease. USFDA approval of tecovirimat for post-exposure prophylaxis in the event of a smallpox release, and the development of pediatric liquid formulations for patients under 13 kg, could provide additional public health benefits.

Potential threat of human pathogenic orthopoxviruses to public health and control strategies

Orthopoxviruses (OPXVs) belong to a group of nucleo-cytoplasmic large DNA viruses. Human pathogenic OPXVs (hpOPXVs) include at least five viruses, among which smallpox virus and monkeypox virus are the most dangerous viral pathogens. Both viruses are classified as category-one human infectious pathogens in China. Although smallpox was globally eradicated in the 1980 s, it is still a top biosecurity threat owing to the possibility of either being leaked to the outside world from a laboratory or being weaponized by terrorists. Beginning in early May 2022, a sudden outbreak of monkeypox was concurrently reported in more than 100 disparate geographical areas, representing a public health emergency of international concern, as declared by the World Health Organization (WHO). In this review, we present the reasons for hpOPXVs such as monkeypox virus presenting a potential threat to public health. We then systematically review the historical and recent development of vaccines and drugs against smallpox and monkeypox. In the final section, we highlight the importance of viromics studies as an integral part of a forward defense strategy to eliminate the potential threat to public health from emerging or re-emerging hpOPXVs and their variants.

Use of cidofovir in a patient with severe mpox and uncontrolled HIV infection

A 48-year-old man with poorly controlled HIV presented with severe human monkeypox virus (hMPXV) infection, having completed 2 weeks of tecovirimat at another hospital. He had painful, ulcerating skin lesions on most of his body and oropharyngeal cavity, with subsequent Ludwig's angina requiring repeated surgical interventions. Despite commencing a second, prolonged course of tecovirimat, he did not objectively improve, and new lesions were still noted at day 24. Discussion at the UK National Health Service England High Consequence Infectious Diseases Network recommended the use of 3% topical and then intravenous cidofovir, which was given at 5 mg/kg; the patient made a noticeable improvement after the first intravenous dose. He received further intravenous doses at 7 days and 21 days after the dose and was discharged at day 52. Cidofovir is not licensed for use in treatment of hMPXV infection. Data for cidofovir use in hMPXV are restricted to studies in animals. Four other documented cases of cidofovir use against hMPXV have been reported in the USA in 2022, but we present its first use in the UK. The scarcity of studies into the use of cidofovir in this condition clearly shows the need for robust studies to assess efficacy, optimum dosage, timing, and route of administration.

What Do We Know About the Smallpox Virus? A Journey Between Clinic and Therapy

PURPOSE

Modern research is increasingly focusing on the study of new viruses and the re-emergence of past microbes, such as Coronaviruses, particularly Sars-Cov2 that was responsible for the very recent pandemic.

METHODS AND RESULTS

This infection manifested itself and still continues to manifest as a severe respiratory syndrome. The main discriminator of whether or not one succeeds in overcoming this infection may depend on a great many factors, but the main one is definitely determined by vaccination, which has minimized hospitalizations and more severe syndromes.

CONCLUSION

Recently, a new virus, the monkeypox virus, which was previously confined to Central and West Africa but is now gradually spreading to more than 30 countries including the United States of America, where such an infection is not endemic, is coming forward again.

Potential therapeutic targets for Mpox: the evidence to date

INTRODUCTION

The global Mpox (MPX) disease outbreak caused by the Mpox virus (MPXV) in 2022 alarmed the World Health Organization (WHO) and health regulation agencies of individual countries leading to the declaration of MPX as a Public Health Emergency. Owing to the genetic similarities between smallpox-causing poxvirus and MPXV, vaccine JYNNEOS, and anti-smallpox drugs Brincidofovir and Tecovirimat were granted emergency use authorization by the United States Food and Drug Administration. The WHO also included cidofovir, NIOCH-14, and other vaccines as treatment options.

AREAS COVERED

This article covers the historical development of EUA-granted antivirals, resistance to these antivirals, and the projected impact of signature mutations on the potency of antivirals against currently circulating MPXV. Since a high prevalence of MPXV infections in individuals coinfected with HIV and MPXV, the treatment results among these individuals have been included.

EXPERT OPINION

All EUA-granted drugs have been approved for smallpox treatment. These antivirals show good potency against Mpox. However, conserved resistance mutation positions in MPXV and related poxviruses, and the signature mutations in the 2022 MPXV can potentially compromise the efficacy of the EUA-granted treatments. Therefore, MPXV-specific medications are required not only for the current but also for possible future outbreaks.

G-quadruplexes in the monkeypox virus are potential antiviral targets

Monkeypox virus (MPXV) is a member of Orthopoxvirus in the Poxviridae family, causing a Public Health Emergency of International Concern. The number of cases and geographic range has increased significantly in 2022. Identification of MPXV-specific therapeutic targets is urgent. G-quadruplex (GQ) secondary structures attract great attention as potential targets for antiviral strategy. Whether GQs are present in the MPXV genome remains inconclusive. In this study, we aim to characterize the GQs encoded by MPXV. Through a series of biophysical experiments, we characterized the formation potential of MPXV-encoded GQs and evaluated the binding and stabilization abilities of GQ ligands including BRACO-19, pyridostatin, and TMPyP4 to GQs encoded by MPXV. Moreover, GQ ligands suppressed the gene transcription of MPXV sequences containing GQ. BRACO-19 and TMPyP4 were able to inhibit vaccinia virus replication. We demonstrated the existence of MPXV GQ and reinforced the idea that GQs could be novel antiviral targets. Targeting these GQ sequences with GQ-binding molecules may represent a new approach for MPXV therapy.

Mpox diagnostics: Review of current and emerging technologies

Mpox is a zoonotic disease caused by monkeypox virus (MPXV) from the Orthopoxvirus genus. Unprecedented transmission events have led to more than 70 000 cases reported worldwide by October 2022. The change in mpox epidemiology has raised concerns of its ability to establish endemicity beyond its traditional geographical locations. In this review, we discuss the current understanding of mpox virology and viral dynamics that are relevant to mpox diagnostics. A synopsis of the traditional and emerging laboratory technologies useful for MPXV detection and in guiding "elimination" strategies is outlined in this review. Importantly, development in MPXV genomics has rapidly advanced our understanding of the role of viral evolution and adaptation in the current outbreak.

Results of the first German external quality assessment scheme for the detection of monkeypox virus DNA

BACKGROUND

In May 2022, the monkeypox virus (MPXV) spread into non-endemic countries and the global community was quick to test the lessons learned from the SARS-CoV-2 pandemic. Due to its symptomatic resemblance to other diseases, like the non-pox virus varicella zoster (chickenpox), polymerase chain reaction methods play an important role in correctly diagnosing the rash-causing pathogen. INSTAND quickly established a new external quality assessment (EQA) scheme for MPXV and orthopoxvirus (OPXV) DNA detection to assess the current performance quality of the laboratory tests.

METHODS

We analyzed quantitative and qualitative data of the first German EQA for MPXV and OPXV DNA detection. The survey included one negative and three MPXV-positive samples with different MPX viral loads. The threshold cycle (Ct) or other measures defining the quantification cycle (Cq) were analyzed in an assay-specific manner. A Passing Bablok fit was used to investigate the performance at laboratory level.

RESULTS

141 qualitative datasets were reported by 131 laboratories for MPXV detection and 68 qualitative datasets by 65 laboratories for OPXV detection. More than 96% of the results were correctly identified as negative and more than 97% correctly identified as positive. An analysis of the reported Ct/Cq values showed a large spread of these values of up to 12 Ct/Cq. Nevertheless, there is a good correlation of results for the different MPXV concentrations at laboratory level. Only a few quantitative results in copies/mL were reported (MPXV: N = 5; OPXV: N = 2), but the results correlated well with the concentration differences between the EQA samples, which were to a power of ten each.

CONCLUSION

The EQA results show that laboratories performed well in detecting both MPXV and OPXV. However, Ct/Cq values should be interpreted with caution when conclusions are drawn about the viral load as long as metrological traceability is not granted.

Development of a Novel Loop-Mediated Isothermal Amplification Method for the Rapid Detection of Monkeypox Virus Infections

A recent outbreak of monkeypox virus (mpox) has prompted researchers to explore diagnostics as a means of impeding transmission and further spread. Rapid, sensitive, and specific methods are crucial for accurately diagnosing mpox infections. Here, we developed a loop-mediated isothermal amplification (LAMP) assay for the specific detection of mpox. The primer sets were designed to target regions in and around the N4R gene, and results showed a detection limit of 2 × 100 DNA copies, which is comparable to the gold-standard qPCR method currently used to detect mpox. Particularly, the assay provides results visible to the naked eye within 30 min. This test specifically detects mpox DNA with no cross-reactivity to related DNA viruses including Varicella Zoster Virus (VZV), Hepatitis B virus (HBV), Vaccinia virus (VACV), Herpes simplex virus-1 (HSV-1), Herpes simplex virus-2 (HSV-2), Human papillomavirus-16 (HPV-16) and Human papillomavirus-18 (HPV-18). Furthermore, the LAMP assay has been evaluated using clinical samples from laboratory-confirmed mpox patients and found to be consistent with the qPCR results. Our results show that this single-tube LAMP method can contribute to diagnosis of suspected mpox infections in the field and clinic, especially in regions with limited laboratory resources.

Monkeypox Virus Infections in Humans

Human monkeypox is a viral zoonosis endemic to West and Central Africa that has recently generated increased interest and concern on a global scale as an emerging infectious disease threat in the midst of the slowly relenting COVID-2019 disease pandemic. The hallmark of infection is the development of a flu-like prodrome followed by the appearance of a smallpox-like exanthem. Precipitous person-to-person transmission of the virus among residents of 100 countries where it is nonendemic has motivated the immediate and widespread implementation of public health countermeasures. In this review, we discuss the origins and virology of monkeypox virus, its link with smallpox eradication, its record of causing outbreaks of human disease in regions where it is endemic in wildlife, its association with outbreaks in areas where it is nonendemic, the clinical manifestations of disease, laboratory diagnostic methods, case management, public health interventions, and future directions.

Pharmacological Agents with Antiviral Activity against Monkeypox Infection

Monkeypox infection is caused by a virus of the genus Orthopoxvirus, a member of the Poxviridae family. Monkeypox virus is transmitted from individual to individual through contact with lesions, body fluids, and respiratory droplets. The infection caused by monkeypox is usually a self-limited disease with mild symptoms lasting 2 to 4 weeks. Monkeypox typically presents with fever, rash, and enlarged lymph nodes. New vaccines have recently been authorized for the prevention of monkeypox infection, whereas there are no specific pharmacological antiviral treatments for monkeypox infection. However, because the viruses which cause adult smallpox and monkeypox are similar, antiviral drugs developed in the past have also shown efficacy against monkeypox. In this review, we highlight the in vitro and clinical evidence found in the literature on the efficacy and safety of pharmacological agents with antiviral activity against monkeypox infection and the different regulatory aspects of countries.

Monkeypox virus emerges from the shadow of its more infamous cousin: family biology matters

Monkeypox virus (MPXV) is closely related to the infamous variola (smallpox) virus, causing a febrile rash illness in humans similar to but milder than smallpox. In the twentieth century, human monkeypox had been mostly a rare zoonotic disease confined to forested areas in West and Central Africa. However, the case number and geographic range have increased significantly in this century, coincided with the waning of the smallpox vaccine-induced immunity in the global population. The outbreak of human monkeypox in multiple countries since May 2022 has been unusual in its large case number and the absence of direct links to endemic countries, raising concerns for a possible change in monkeypox transmission pattern that could pose a greater global threat. Here, we review aspects of MPXV biology that are relevant for risk assessment and preparedness for a monkeypox epidemic, with an emphasis on recent progress in understanding of the virus host range, evolutionary potential, and neutralization targets.

Tecovirimat is effective against human monkeypox virus in vitro at nanomolar concentrations

The ongoing monkeypox virus (MPXV) outbreak is the largest ever recorded outside of Africa. We isolated and sequenced a virus from the first clinical MPXV case diagnosed in France (May 2022). We report that tecovirimat (ST-246), a US Food and Drug Administration approved drug, is efficacious against this isolate in vitro at nanomolar concentrations, whereas cidofovir is only effective at micromolar concentrations. Our results support the use of tecovirimat in ongoing human clinical trials.

Monkeypox in humans: a new outbreak

Infection caused by Monkeypox Virus (MPVX) has small rodents as its natural reservoir and both monkeys and humans are occasional hosts. The causative agent is an Orthopoxvirus (MPVX) that was isolated in monkeys in 1958 and proved capable of passing to humans in 1970. It remained contained in Africa, causing isolated episodes of infection, until 2003 when an outbreak occurred in the United States following importation of animals from that continent. Since then, anecdotal cases have continued to be reported outside Africa, usually very clearly linked to travelers to those countries, but in May 2022, a broad outbreak of this disease has begun, now affecting several continents, with the emergence of human cases of MPVX (H-MPVX) infection mainly among Men that have Sex with Men (MSM). The disease has an incubation time ranging from 5 to 15 days and is characterized by the presence of pustules, fever, malaise and headache. The presence of significant regional lymphadenopathy is a differential feature with episodes of classical smallpox. Proctitis and pharyngitis, with minimal skin lesions, may be another form of presentation. Diagnosis can be confirmed by PCR testing of lesions or by demonstration of MPVX in other body fluids or tissues, although in the appropriate epidemiologic setting the clinical picture is highly suggestive of the disease. Effective drug treatment has been developed as part of programs to protect against potential bioterrorist agents and smallpox vaccinees are known to have high protection against monkeypox. New vaccines are available, but neither the drugs nor the vaccines are yet freely available on the market. The prognosis of the disease appears, at least in adults in developed countries, to be good, with very low mortality figures and much less aggressive behavior than that described in classical smallpox. Isolation measures, essential for the control of the outbreak, have been published by the health authorities.

A severe monkeypox infection in a patient with an advanced HIV infection treated with tecovirimat: clinical and virological outcome

A patient aged 28 years who is immunocompromised and living with HIV/AIDS became infected with the monkeypox virus (MPXV). His clinical condition deteriorated for 37 days, with fever, skin lesions, and diarrhea before going to the infectious diseases department, where his severe, protracted infection was treated with tecovirimat for 14 days. His condition rapidly improved, and the skin lesions decreased, as did the MPXV loads, with no adverse events. This case indicates that tecovirimat might be effective for treating patients who are immunocompromised and are infected with MPXV.

Monkeypox: epidemiology, pathogenesis, treatment and prevention

Monkeypox is a zoonotic disease that was once endemic in west and central Africa caused by monkeypox virus. However, cases recently have been confirmed in many nonendemic countries outside of Africa. WHO declared the ongoing monkeypox outbreak to be a public health emergency of international concern on July 23, 2022, in the context of the COVID-19 pandemic. The rapidly increasing number of confirmed cases could pose a threat to the international community. Here, we review the epidemiology of monkeypox, monkeypox virus reservoirs, novel transmission patterns, mutations and mechanisms of viral infection, clinical characteristics, laboratory diagnosis and treatment measures. In addition, strategies for the prevention, such as vaccination of smallpox vaccine, is also included. Current epidemiological data indicate that high frequency of human-to-human transmission could lead to further outbreaks, especially among men who have sex with men. The development of antiviral drugs and vaccines against monkeypox virus is urgently needed, despite some therapeutic effects of currently used drugs in the clinic. We provide useful information to improve the understanding of monkeypox virus and give guidance for the government and relative agency to prevent and control the further spread of monkeypox virus.

Antivirales (a excepción del virus de la inmunodeficiencia humana y la hepatitis)

Los antivirales son un elemento esencial de la farmacopea antiinfecciosa. Aunque los antirretrovirales y los antivirales dirigidos contra los virus de las hepatitis B y C constituyen el componente principal, varias moléculas antivirales también se utilizan contra las infecciones por herpesvirus, adenovirus, poxvirus, papilomavirus, coronavirus, pneumovirus y virus de la gripe. La mayoría de estas moléculas se dirigen contra las enzimas virales implicadas en la replicación de los genomas virales. En los virus de ácido desoxirribonucleico (ADN), la mayoría de los análogos nucleosídicos, como el aciclovir, y los análogos nucleotídicos, como el cidofovir, requieren una fosforilación intracelular previa para inhibir, por un mecanismo de competición y, en ocasiones, de terminación, la actividad de una ADN polimerasa. El foscarnet, análogo de pirofosfato, ejerce esta inhibición directamente sin modificación. En los virus ARN (ácido ribonucleico), para los que se dispone de menos antivirales que para los virus ADN, los inhibidores de neuraminidasa han demostrado su eficacia contra los virus de la gripe y los inhibidores de la ARN polimerasa parecen ser activos contra el coronavirus 2 del síndrome respiratorio agudo grave (SARS-CoV-2), coronavirus responsable de la COVID-19. La especificidad de los antivirales suele ser estrecha, limitada para cada molécula a unos pocos virus relacionados. Las otras limitaciones de su uso son la imposibilidad de erradicar las infecciones latentes, la aparición de resistencia, los efectos indeseables relacionados a menudo con la toxicidad celular relativa de las moléculas y el coste. Se esperan avances tanto en la actividad antiviral de los fármacos como en su tolerabilidad clínica y el número de las enfermedades virales tratadas. Al margen del desarrollo de los antivirales propiamente dichos, los anticuerpos monoclonales y la modificación de la indicación de otros fármacos antiinfecciosos que tienen una actividad antiviral mediante modificaciones de su funcionamiento celular también son pistas prometedoras Es esencial que las exigencias económicas no restrinjan la dinámica de este ámbito muy innovador de la medicina contemporánea.

Poxviruses Bearing DNA Polymerase Mutations Show Complex Patterns of Cross-Resistance

Despite the eradication of smallpox four decades ago, poxviruses continue to be a threat to humans and animals. The arsenal of anti-poxvirus agents is very limited and understanding mechanisms of resistance to agents targeting viral DNA polymerases is fundamental for the development of antiviral therapies. We describe here the phenotypic and genotypic characterization of poxvirus DNA polymerase mutants isolated under selective pressure with different acyclic nucleoside phosphonates, including HPMPC (cidofovir), cHPMPC, HPMPA, cHPMPA, HPMPDAP, HPMPO-DAPy, and PMEO-DAPy, and the pyrophosphate analogue phosphonoacetic acid. Vaccinia virus (VACV) and cowpox virus drug-resistant viral clones emerging under drug pressure were characterized phenotypically (drug-susceptibility profile) and genotypically (DNA polymerase sequencing). Different amino acid changes in the polymerase domain and in the 3′-5′ exonuclease domain were linked to drug resistance. Changes in the 3′-5′ domain emerged earlier than in the polymerase domain when viruses acquired a combination of mutations. Our study highlights the importance of poxvirus DNA polymerase residues 314, 613, 684, 688, and 851, previously linked to drug resistance, and identified several novel mutations in the 3′-5′ exonuclease domain (M313I, F354L, D480Y) and in the DNA polymerase domain (A632T, T831I, E856K, L924F) associated with different drug-susceptibility profiles. Furthermore, a combination of mutations resulted in complex patterns of cross-resistance. Modeling of the VACV DNA polymerase bearing the newly described mutations was performed to understand the effects of these mutations on the structure of the viral enzyme. We demonstrated the emergence of drug-resistant DNA polymerase mutations in complex patterns to be considered in case such mutations should eventually arise in the clinic.

Adamantane derivatives as potential inhibitors of p37 major envelope protein and poxvirus reproduction. Design, synthesis and antiviral activity

Currently, smallpox, caused by the variola virus belonging to the poxvirus family, has been completely eradicated according to the WHO. However, other representatives of poxviruses, such as vaccinia virus, cowpox virus, ectromelia virus, monkeypox virus, mousepox virus and others, remain in the natural environment and can infect both animals and humans. The pathogens of animal diseases, belonging to the category with a high epidemic risk, have already caused several outbreaks among humans, and can, in an unfavorable combination of circumstances, cause not only an epidemic, but also a pandemic. Despite the fact that there are protocols for the treatment of poxvirus infections, the targeted design of new drugs will increase their availability and expand the arsenal of antiviral chemotherapeutic agents. One of the potential targets of poxviruses is the p37 protein, which is a tecovirimat target. This protein is relatively small, has no homologs among proteins of humans and other mammals and is necessary for the replication of viral particles, which makes it attractive target for virtual screening. Using the I-TASSER modelling and molecular dynamics refinement the p37 orthopox virus protein model was obtained and its was confirmed by ramachandran plot analysis and superimposition of the model with the template protein with similar function. A virtual library of adamantane containing compounds was generated and a number of potential inhibitors were chosen from virtual library using molecular docking. Several compounds bearing adamantane moiety were synthesized and their biological activity was tested in vitro on vaccinia, cowpox and mousepox viruses. The new compounds inhibiting vaccinia virus replication with IC₅₀ concentrations between 0.133 and 0.515 μM were found as a result of the research. The applied approach can be useful in the search of new inhibitors of orthopox reproduction. The proposed approach may be suitable for the design of new poxvirus inhibitors containing cage structural moiety.

Pharmacokinetics and Efficacy of a Potential Smallpox Therapeutic, Brincidofovir, in a Lethal Monkeypox Virus Animal Model

Smallpox, caused by Variola virus (VARV), was eradicated in 1980; however, VARV bioterrorist threats still exist, necessitating readily available therapeutics. Current preparedness activities recognize the importance of oral antivirals and recommend therapeutics with different mechanisms of action. Monkeypox virus (MPXV) is closely related to VARV, causing a highly similar clinical human disease, and can be used as a surrogate for smallpox antiviral testing. The prairie dog MPXV model has been characterized and used to study the efficacy of antipoxvirus therapeutics, including recently approved TPOXX (tecovirimat). Brincidofovir (BCV; CMX001) has shown antiviral activity against double-stranded DNA viruses, including poxviruses. To determine the exposure of BCV following oral administration to prairie dogs, a pharmacokinetics (PK) study was performed. Analysis of BCV plasma concentrations indicated variability, conceivably due to the outbred nature of the animals. To determine BCV efficacy in the MPXV prairie dog model, groups of animals were intranasally challenged with 9 × 10⁵ plaque-forming units (PFU; 90% lethal dose [LD₉₀]) of MPXV on inoculation day 0 (ID0). Animals were divided into groups based on the first day of BCV treatment relative to inoculation day (ID-1, ID0, or ID1). A trend in efficacy was noted dependent upon treatment initiation (57% on ID-1, 43% on ID0, and 29% on ID1) but was lower than demonstrated in other animal models. Analysis of the PK data indicated that BCV plasma exposure (maximum concentration [C _max]) and the time of the last quantifiable concentration (AUC_last) were lower than in other animal models administered the same doses, indicating that suboptimal BCV exposure may explain the lower protective effect on survival.IMPORTANCE Preparedness activities against highly transmissible viruses with high mortality rates have been highlighted during the ongoing coronavirus disease 2019 (COVID-19) pandemic. Smallpox, caused by variola virus (VARV) infection, is highly transmissible, with an estimated 30% mortality. Through an intensive vaccination campaign, smallpox was declared eradicated in 1980, and routine smallpox vaccination of individuals ceased. Today's current population has little/no immunity against VARV. If smallpox were to reemerge, the worldwide results would be devastating. Recent FDA approval of one smallpox antiviral (tecovirimat) was a successful step in biothreat preparedness; however, orthopoxviruses can become resistant to treatment, suggesting the need for multiple therapeutics. Our paper details the efficacy of the investigational smallpox drug brincidofovir in a monkeypox virus (MPXV) animal model. Since brincidofovir has not been tested in vivo against smallpox, studies with the related virus MPXV are critical in understanding whether it would be protective in the event of a smallpox outbreak.

An overview of tecovirimat for smallpox treatment and expanded anti-orthopoxvirus applications

Introduction

Tecovirimat (TPOXX®; ST-246) was approved for the treatment of symptomatic smallpox by the USFDA in July of 2018 and has been stockpiled by the US government for use in a smallpox outbreak. While there has not been a reported case of smallpox since 1978 it is still considered a serious bioterrorism threat.

Areas covered

A brief history of smallpox from its proposed origins as a human disease through its eradication in the late 20th century is presented. The current smallpox threat and the current public health response plans are described. The discovery, and development of tecovirimat through NDA submission and subsequent approval for treatment of smallpox are discussed. Google Scholar and PubMed were searched over all available dates for relevant publications.

Expert opinion

Approval of tecovirimat to treat smallpox represents an important milestone in biosecurity preparedness. Incorporating tecovirimat into the CDC smallpox response plan, development of pediatric liquid and intravenous formulations, and approval for post-exposure prophylaxis would provide additional health security benefit.

Tecovirimat shows broad efficacy against orthopoxviruses in vitro and in vivo and could be developed for use against emerging orthopoxvirus diseases such as monkeypox, vaccination-associated adverse events, and side effects of vaccinia oncolytic virus therapy.