st-246 and Disease-Models--Animal

Forty years after the last endemic smallpox case, variola virus (VARV) is still considered a major threat to humans due to its possible use as a bioterrorism agent. For many years, the risk of disease reemergence was thought to solely be through deliberate misuse of VARV strains kept in clandestine laboratories. However, recent experiments using synthetic biology have proven the feasibility of recreating a poxvirus

Topics: Animals; Antiviral Agents; Benzamides; Biological Warfare Agents; Biomedical Research; Cytosine; Disease Models, Animal; Drug Discovery; Isoindoles; Organophosphonates; Smallpox; Variola virus

The classification of smallpox by the U.S. Centers for Disease Control and Prevention (CDC) as a Category A Bioterrorism threat agent has resulted in the U.S. Government investing significant funds to develop and stockpile a suite of medical countermeasures to ameliorate the consequences of a smallpox epidemic. This stockpile includes both vaccines for prophylaxis and antivirals to treat symptomatic patients. In this manuscript, we describe the path to approval for the first therapeutic against smallpox, identified during its development as ST-246, now known as tecovirimat and TPOXX

Topics: Animals; Antiviral Agents; Benzamides; Disease Models, Animal; Drug Development; Drug Evaluation, Preclinical; Humans; Isoindoles; Smallpox; United States; United States Food and Drug Administration; Variola virus

Surrogate animal models must be used for testing antiviral agents against variola (smallpox) virus infections. Once developed, these, compounds can be stockpiled for use in the event of a bioterrorist incident involving either variola or monkeypox virus, or used to treat an occasional serious orthopoxvirus infection, such as disseminated vaccinia complication following exposure to the live virus vaccine. Recently, considerable progress has been made in the discovery of novel antiviral agents found active against orthopoxviruses in vivo. This includes the development of new animal models or refinement of existing ones for compound efficacy testing. Current mouse models employ ectromelia, cowpox and vaccinia (WR and IHD strains) viruses with respiratory (lung) or tail lesion infections commonly studied. Rabbitpox and vaccinia (WR strain) viruses are available for rabbit infections. Monkeypox and variola viruses are used for infecting monkeys. This review describes these and other animal models, and covers compounds found active in vivo from 2003 to date. Cidofovir, known to be active against orthopox virus infections prior to 2003, has been studied extensively over recent years. New compounds showing promise are orally active inhibitors of orthopoxvirus infections that include ether lipid prodrugs of cidofovir and (S)-HPMPA, ST-246, N-methanocarbathymidine (N-MCT) and SRI 21950 (a 4'-thio derivative of iododeoxyuridine). Another compound with high activity but requiring parenteral administration is HPMPO-DAPy. Further development of these compounds is warranted.

Topics: Adenine; Animals; Antiviral Agents; Benzamides; Cidofovir; Cytosine; Disease Models, Animal; Drug Discovery; Humans; Isoindoles; Organophosphonates; Orthopoxvirus; Prodrugs

Smallpox was declared eradicated in 1980, but variola virus (VARV), which causes smallpox, still exists. There is no known effective treatment for smallpox; therefore, tecovirimat is being developed as an oral smallpox therapy. Because clinical trials in a context of natural disease are not possible, an alternative developmental path to evaluate efficacy and safety was needed.. We investigated the efficacy of tecovirimat in nonhuman primate (monkeypox) and rabbit (rabbitpox) models in accordance with the Food and Drug Administration (FDA) Animal Efficacy Rule, which was interpreted for smallpox therapeutics by an expert advisory committee. We also conducted a placebo-controlled pharmacokinetic and safety trial involving 449 adult volunteers.. The minimum dose of tecovirimat required in order to achieve more than 90% survival in the monkeypox model was 10 mg per kilogram of body weight for 14 days, and a dose of 40 mg per kilogram for 14 days was similarly efficacious in the rabbitpox model. Although the effective dose per kilogram was higher in rabbits, exposure was lower, with a mean steady-state maximum, minimum, and average (mean) concentration (C. On the basis of its efficacy in two animal models and pharmacokinetic and safety data in humans, tecovirimat is being advanced as a therapy for smallpox in accordance with the FDA Animal Rule. (Funded by the National Institutes of Health and the Biomedical Advanced Research and Development Authority; ClinicalTrials.gov number, NCT02474589 .).

Topics: Administration, Oral; Adolescent; Adult; Aged; Animals; Antiviral Agents; Benzamides; Disease Models, Animal; Dose-Response Relationship, Drug; Double-Blind Method; Female; Healthy Volunteers; Humans; Isoindoles; Macaca fascicularis; Male; Middle Aged; Monkeypox virus; Mpox (monkeypox); Poxviridae Infections; Rabbits; Vaccinia virus; Young Adult

Therapeutics for the treatment of pathogenic orthopoxvirus infections are being sought. In the absence of patients with disease, animal models of orthopoxvirus disease are essential for evaluation of the efficacies of antiviral drugs and establishment of the appropriate dose and duration of human therapy. Infection of nonhuman primates (NHP) by the intravenous injection of monkeypox virus has been used to evaluate a promising therapeutic drug candidate, ST-246. ST-246 administered at 3 days postinfection (which corresponds to the secondary viremia stage of disease) at four different doses (from 100 mg/kg of body weight down to 3 mg/kg) once a day for 14 days was able to offer NHP 100% protection from a lethal infection with monkeypox virus and reduce the viral load and lesion formation. In NHP, the administration of ST-246 at a dose of 10 mg/kg/day for 14 days resulted in levels of blood exposure comparable to the levels attained in humans administered 400 mg in the fed state. These results suggest that administration of an oral dosage of 400 mg once daily for 14 days will be effective for the prevention or treatment of smallpox or monkeypox infections in humans.

Topics: Animals; Antiviral Agents; Benzamides; Disease Models, Animal; Dose-Response Relationship, Drug; Humans; Isoindoles; Macaca fascicularis; Monkeypox virus; Mpox (monkeypox); Treatment Outcome

We compared absolute bioavailability of the chemical substance of the anti-smallpox preparation NIOCH-14 and chemical compound ST-246 active against orthopoxviruses after oral administration to mice in doses of 10 and 50 μg/g and intravenous administration to mice in a dose of 2 μg/g body weight. The absolute bioavailability of NIOCH-14 is comparable with the absolute bioavailability of ST-246.

Topics: Animals; Area Under Curve; Benzamides; Biological Availability; Calibration; Dicarboxylic Acids; Disease Models, Animal; Female; Infusions, Intravenous; Isoindoles; Male; Mice; Mice, Inbred ICR; Smallpox; Time Factors; Variola virus

Topics: Animals; Benzamides; Cytosine; Disease Eradication; Disease Models, Animal; Disease Reservoirs; Drug Approval; Female; History, 20th Century; History, 21st Century; Humans; Isoindoles; Organophosphonates; Rabbits; Smallpox; Smallpox Vaccine; Synthetic Biology; United States; United States Food and Drug Administration

Mice of the ICR outbred population were infected intranasally (i/n) with the variola virus (VARV, strain Ind-3a). Clinical signs of the disease did not appear even at the maximum possible dose of the virus 5.2 lg PFU/head (plaque-forming units per head). In this case, 50% infective dose (ID50) of VARV estimated by the presence or absence of the virus in the lungs three days after infection (p.i.) was equal to 2.7 ± 0.4 lg PFU/head. Taking into account the 10% application of the virus in the lungs during the intranasal infection of the mice, it was adequate to 1.7 lg PFU/lungs. This indicates a high infectivity of the VARV for mice comparable to its infectivity for humans. After the i/n infection of mice with the VARV at a dose 30 ID50/ head the highest concentration of the virus detected in the lungs (4.9 ± 0.0 lg PFU/ml of homogenate) and in nasal cavity tissues (4.8 ± 0.0 lg PFU/ml) were observed. The pathomorphological changes in the respiratory organs of the mice infected with the VARV appeared at 3-5 days p.i., and the VARV reproduction noted in the epithelial cells and macrophages were noticed. When the preparations ST-246 and NIOCH-14 were administered orally at a dose of 60 μg/g of mouse weight up to one day before infection, after 2 hours, 1 and 2 days p.i., the VARV reproduction in the lungs after 3 days p.i. decreased by an order of magnitude. Thus, outbred ICR mice infected with the VARV can be used as a laboratory model of the smallpox when evaluating the therapeutic and prophylactic efficacy of the antismallpox drugs.

Topics: Administration, Intranasal; Alkenes; Animals; Antiviral Agents; Benzamides; Disease Models, Animal; Epithelial Cells; Humans; Hydrazines; Isoindoles; Lung; Macrophages, Alveolar; Mice; Mice, Inbred ICR; Smallpox; Variola virus; Viral Load; Virus Replication

Whole-body bioimaging was used to study dissemination of vaccinia virus (VACV) in normal and in immune deficient (nu(-)/nu(-)) mice protected from lethality by postchallenge administration of ST-246. Total fluxes were recorded in the liver, spleen, lungs, and nasal cavities of live mice after intranasal infection with a recombinant IHD-J-Luc VACV expressing luciferase. Areas under the flux curve were calculated for individual mice to assess viral loads. Treatment for 2 to 5 days of normal BALB/c mice with ST-246 at 100 mg/kg starting 24 h postchallenge conferred 100% protection and reduced viral loads in four organs compared to control mice. Mice also survived after 5 days of treatment with ST-246 at 30 mg/kg, and yet the viral loads and poxes were higher in these mice compared to 100-mg/kg treatment group. Nude mice were not protected by ST-246 alone or by 10 million adoptively transferred T cells. In contrast, nude mice that received T cells and 7-day treatment with ST-246 survived infection and exhibited reduced viral loads compared to nonreconstituted and ST-246-treated mice after ST-246 was stopped. Similar protection of nude mice was achieved using adoptively transferred 1.0 and 0.1 million, but not 0.01 million, purified T cells or CD4(+) or CD8(+) T cells in conjunction with ST-246 treatment. These data suggest that ST-246 protects immunocompetent mice from lethality and reduces viral dissemination in internal organs and poxvirus lesions. Furthermore, immune-deficient animals with partial T cell reconstitution can control virus replication after a course of ST-246 and survive lethal vaccinia virus challenge.

Topics: Adoptive Transfer; Animal Structures; Animals; Antiviral Agents; Benzamides; Disease Models, Animal; Female; Genes, Reporter; Immunocompromised Host; Isoindoles; Luciferases; Mice; Mice, Inbred BALB C; Mice, Nude; Staining and Labeling; Survival Analysis; T-Lymphocytes; Treatment Outcome; Vaccinia; Vaccinia virus; Viral Load; Whole Body Imaging

The human population is currently faced with the potential use of natural or recombinant variola and monkeypox viruses as biological weapons. Furthermore, the emergence of human monkeypox in Africa and its expanding environs poses a significant natural threat. Such occurrences would require therapeutic and prophylactic intervention with antivirals to minimize morbidity and mortality of exposed populations. Two orally-bioavailable antivirals are currently in clinical trials; namely CMX001, an ether-lipid analog of cidofovir with activity at the DNA replication stage and ST-246, a novel viral egress inhibitor. Both of these drugs have previously been evaluated in the ectromelia/mousepox system; however, the trigger for intervention was not linked to a disease biomarker or a specific marker of virus replication. In this study we used lethal, intranasal, ectromelia virus infections of C57BL/6 and hairless SKH1 mice to model human disease and evaluate exanthematous rash (rash) as an indicator to initiate antiviral treatment. We show that significant protection can be provided to C57BL/6 mice by CMX001 or ST-246 when therapy is initiated on day 6 post infection or earlier. We also show that significant protection can be provided to SKH1 mice treated with CMX001 at day 3 post infection or earlier, but this is four or more days before detection of rash (ST-246 not tested). Although in this model rash could not be used as a treatment trigger, viral DNA was detected in blood by day 4 post infection and in the oropharyngeal secretions (saliva) by day 2-3 post infection - thus providing robust and specific markers of virus replication for therapy initiation. These findings are discussed in the context of current respiratory challenge animal models in use for the evaluation of poxvirus antivirals.

Topics: Animals; Benzamides; Biomarkers, Pharmacological; Cell Line; Cytosine; Disease Models, Animal; Drug Evaluation, Preclinical; Ectromelia virus; Ectromelia, Infectious; Female; Humans; Isoindoles; Mice; Mice, Hairless; Mice, Inbred C57BL; Monkeypox virus; Organophosphonates; Smallpox; Variola virus; Virus Replication

Smallpox preparedness research has led to development of antiviral therapies for treatment of serious orthopoxvirus infections. Monkeypox virus is an emerging, zoonotic orthopoxvirus which can cause severe and transmissible disease in humans, generating concerns for public health. Monkeypox virus infection results in a systemic, febrile-rash illness closely resembling smallpox. Currently, there are no small-molecule antiviral therapeutics approved to treat orthopoxvirus infections of humans. The prairie dog, using monkeypox virus as a challenge virus, has provided a valuable nonhuman animal model in which monkeypox virus infection closely resembles human systemic orthopoxvirus illness. Here, we assess the efficacy of the antiorthopoxvirus compound ST-246 in prairie dogs against a monkeypox virus challenge of 65 times the 50% lethal dose (LD(50)). Animals were infected intranasally and administered ST-246 for 14 days, beginning on days 0, 3, or after rash onset. Swab and blood samples were collected every 2 days and analyzed for presence of viral DNA by real-time PCR and for viable virus by tissue culture. Seventy-five percent of infected animals that received vehicle alone succumbed to infection. One hundred percent of animals that received ST-246 survived challenge, and animals that received treatment before symptom onset remained largely asymptomatic. Viable virus and viral DNA were undetected or at greatly reduced levels in animals that began treatment on 0 or 3 days postinfection, compared to control animals or animals treated post-rash onset. Animals treated after rash onset manifested illness, but all recovered. Our results indicate that ST-246 can be used therapeutically, following onset of rash illness, to treat systemic orthopoxvirus infections.

Topics: Anal Canal; Animals; Antiviral Agents; Benzamides; Blood; Disease Models, Animal; DNA, Viral; Eye; Humans; Isoindoles; Monkeypox virus; Oropharynx; Poxviridae Infections; Sciuridae; Survival Analysis; Treatment Outcome; Viral Load

Monkeypox virus (MPXV) is an orthopoxvirus closely related to variola, the etiological agent of smallpox. In humans, MPXV causes a disease similar to smallpox and is considered to be an emerging infectious disease. Moreover, the use of MPXV for bioterroristic/biowarfare activities is of significant concern. Available small animal models of human monkeypox have been restricted to mammals with poorly defined biologies that also have limited reagent availability. We have established a murine MPXV model utilizing the STAT1-deficient C57BL/6 mouse. Here we report that a relatively low-dose intranasal (IN) infection induces 100% mortality in the stat1(-)(/)(-) model by day 10 postinfection with high infectious titers in the livers, spleens, and lungs of moribund animals. Vaccination with modified vaccinia virus Ankara (MVA) followed by a booster vaccination is sufficient to protect against an intranasal MPXV challenge and induces an immune response more robust than that of a single vaccination. Furthermore, antiviral treatment with CMX001 (HDP-cidofovir) and ST-246 protects when administered as a regimen initiated on the day of infection. Thus, the stat1(-)(/)(-) model provides a lethal murine platform for evaluating therapeutics and for investigating the immunological and pathological responses to MPXV infection.

Topics: Animals; Antiviral Agents; Benzamides; Cytosine; Disease Models, Animal; Female; Humans; Isoindoles; Liver; Lung; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Monkeypox virus; Mpox (monkeypox); Organophosphonates; Smallpox Vaccine; Spleen; STAT1 Transcription Factor; Survival Analysis; Treatment Outcome; Vaccinia virus; Viral Load

ST-246 was evaluated for activity against cowpox virus (CV), vaccinia virus (VV), and ectromelia virus (ECTV) and had an in vitro 50% effective concentration (EC50) of 0.48 microM against CV, 0.05 microM against VV, and 0.07 microM against ECTV. The selectivity indices were >208 and >2,000 for CV and VV, respectively. The in vitro antiviral activity of ST-246 was significantly greater than that of cidofovir, which had an EC50 of 41.1 microM against CV and 29.2 microM against VV, with selectivity indices of >7 and >10, respectively. ST-246 administered once daily by oral gavage to mice infected intranasally with CV beginning 4 h or delayed until 72 h postinoculation was highly effective when given for a 14-day duration using 100, 30, or 10 mg/kg of body weight. When 100 mg/kg of ST-246 was administered to VV-infected mice, a duration of 5 days was sufficient to significantly reduce mortality even when treatment was delayed 24 h postinoculation. Viral replication in liver, spleen, and kidney, but not lung, of CV- or VV-infected mice was reduced by ST-246 compared to levels for vehicle-treated mice. When 100 mg/kg of ST-246 was given once daily to mice infected by the intranasal route with ECTV, treatment for 10 days prevented mortality even when treatment was delayed up to 72 h after viral inoculation. Viral replication in target organs of ECTV-infected mice was also reduced.

Topics: Administration, Oral; Animals; Benzamides; Disease Models, Animal; Female; Indoles; Isoindoles; Mice; Organ Specificity; Orthopoxvirus; Poxviridae Infections; Time Factors; Treatment Outcome; Virus Replication