A Phase 1 Study of the Safety, Tolerability, and Pharmacokinetics of Single and Multiple Oral Doses of V-7404 in Healthy Adult Volunteers.

V-7404, a direct-acting enterovirus (EV) 3C protease inhibitor, is being developed as a treatment option for serious EV infections, including infections in immunodeficient people excreting vaccine-derived polioviruses. V-7404 may be combined with pocapavir (V-073), a capsid inhibitor, to treat these infections. A phase 1 single ascending dose (SAD; n = 36) and multiple ascending dose (MAD; n = 40) study was conducted to assess the safety, tolerability, and pharmacokinetics (PK) of V-7404 in healthy adult volunteers following oral doses starting at 200 mg and escalating to 2,000 mg once daily (QD) and 2,000 mg twice daily (BID). Adverse events (AEs), vital signs, electrocardiographic findings, physical examinations, clinical laboratory values, and PK of blood samples were assessed. No notable differences in demographic and baseline characteristics were observed across the dose cohorts. A total of 35/36 participants (97.2%) completed the SAD study (1 withdrew in the placebo group), and 37/41 participants (90.2%) completed the MAD study (1 withdrew from the 2,000 mg QD and 3 withdrew from the 2,000 mg BID cohorts). No serious AEs or deaths were reported. Treatment-emergent AEs were mild or moderate in severity. Oral doses of V-7404 in all cohorts were readily absorbed and showed no significant accumulation. PK exposure increased in an approximately dose-proportional manner and appeared to be independent of time. Overall, V-7404 was well tolerated and exhibited an acceptable safety and PK profile, supporting further clinical investigation of V-7404 for the treatment of serious EV infections.

Antiviral Activity of Pocapavir in a Randomized, Blinded, Placebo-Controlled Human Oral Poliovirus Vaccine Challenge Model.

BACKGROUND: Immunodeficient individuals who excrete vaccine-derived polioviruses threaten polio eradication. Antivirals address this threat. METHODS: In a randomized, blinded, placebo-controlled study, adults were challenged with monovalent oral poliovirus type 1 vaccine (mOPV1) and subsequently treated with capsid inhibitor pocapavir or placebo. The time to virus negativity in stool was determined. RESULTS: A total of 144 participants were enrolled; 98% became infected upon OPV challenge. Pocapavir-treated subjects (n = 93) cleared virus a median duration of 10 days after challenge, compared with 13 days for placebo recipients (n = 48; P = .0019). Fifty-two of 93 pocapavir-treated subjects (56%) cleared virus in 2-18 days with no evidence of drug resistance, while 41 of 93 (44%) treated subjects experienced infection with resistant virus while in the isolation facility, 3 (3%) of whom were infected at baseline, before treatment initiation. Resistant virus was also observed in 5 placebo recipients (10%). Excluding those with resistant virus, the median time to virus negativity was 5.5 days in pocapavir recipients, compared with 13 days in placebo recipients (P < .0001). There were no serious adverse events and no withdrawals from the study. CONCLUSIONS: Treatment with pocapavir was safe and significantly accelerated virus clearance. Emergence of resistant virus and transmission of virus were seen in the context of a clinical isolation facility. CLINICAL TRIALS REGISTRATION: EudraCT 2011-004804-38.

Progress in the development of poliovirus antiviral agents and their essential role in reducing risks that threaten eradication.

Chronic prolonged excretion of vaccine-derived polioviruses by immunodeficient persons (iVDPV) presents a personal risk of poliomyelitis to the patient as well as a programmatic risk of delayed global eradication. Poliovirus antiviral drugs offer the only mitigation of these risks. Antiviral agents may also have a potential role in the management of accidental exposures and in certain outbreak scenarios. Efforts to discover and develop poliovirus antiviral agents have been ongoing in earnest since the formation in 2007 of the Poliovirus Antivirals Initiative. The most advanced antiviral, pocapavir (V-073), is a capsid inhibitor that has recently demonstrated activity in an oral poliovirus vaccine human challenge model. Additional antiviral candidates with differing mechanisms of action continue to be profiled and evaluated preclinically with the goal of having 2 antivirals available for use in combination to treat iVDPV excreters.

Characterization of poliovirus variants selected for resistance to the antiviral compound V-073.

V-073, a small-molecule capsid inhibitor originally developed for nonpolio enterovirus indications is considerably more potent against polioviruses. All poliovirus isolates tested to date (n = 45), including wild, vaccine, vaccine-derived, and laboratory strains, are susceptible to the antiviral capsid inhibitor V-073. We grew poliovirus in the presence of V-073 to allow for the identification of variants with reduced susceptibility to the drug. Sequence analysis of 160 independent resistant variants (80 isolates of poliovirus type 1, 40 isolates each of types 2 and 3) established that V-073 resistance involved a single amino acid change in either of two virus capsid proteins, VP1 (67 of 160 [42%]) or VP3 (93 of 160 [58%]). In resistant variants with a VP1 change, the majority (53 of 67 [79%]) exhibited a substitution of isoleucine at position 194 (equivalent position 192 in type 3) with either methionine or phenylalanine. Of those with a VP3 change, alanine at position 24 was replaced with valine in all variants (n = 93). The resistance phenotype was relatively stable upon passage of viruses in cell culture in the absence of drug. Single-step growth studies showed no substantial differences between drug-resistant variants and the virus stocks from which they were derived, while the resistant viruses were generally more thermally labile than the corresponding drug-susceptible parental viruses. These studies provide a foundation from which to build a greater understanding of resistance to antiviral compound V-073.

HCV796: A selective nonstructural protein 5B polymerase inhibitor with potent anti-hepatitis C virus activity in vitro, in mice with chimeric human livers, and in humans infected with hepatitis C virus.

UNLABELLED: Anti-hepatitis C virus (HCV) drug development has been challenged by a lack of experience with inhibitors inclusive of in vitro, animal model, and clinical study. This manuscript outlines activity and correlation across such a spectrum of models and into clinical trials with a novel selective nonstructural protein 5B (NS5B) polymerase inhibitor, HCV796. Enzyme assays yielded median inhibitory concentration (IC(50)) values of 0.01 to 0.14 microM for genotype 1, with half maximal effective concentration (EC(50)s) of 5 nM and 9 nM against genotype 1a and 1b replicons. In the chimeric mouse model, a 2.02 +/- 0.55 log reduction in HCV titer was seen with monotherapy, whereas a suboptimal dose of 30 mg/kg three times per day in combination with interferon demonstrated a 2.44 log reduction (P = 0.001 versus interferon alone) Clinical outcomes in combination with pegylated interferon and ribavirin have revealed additive efficacy in treatment naïve patients. Abnormal liver function test results were observed in 8% of HCV-796 patients treated for over 8 weeks, resulting in suspension of further trial activity. CONCLUSION: The RNA-dependent RNA polymerase inhibitor HCV796 demonstrated potent anti-HCV activity consistently through enzyme inhibition assays, subgenomic replicon, and chimeric mouse studies. Strong correlations of outcomes in the mouse model were seen with subsequent clinical trials, including a plateau in dose-related antiviral activity and additive impact from combination therapy with interferon. These outcomes demonstrate the utility of the range of in vitro and in vivo models now available for anti-HCV drug development and support the potential utility of polymerase inhibitors in future combination therapies for HCV treatment.

Clearance of Immunodeficiency-associated Vaccine-derived Poliovirus Infection With Pocapavir.

Pocapavir exhibits antiviral activity against both polio and nonpolio enteroviruses. There is limited experience of the use of this investigational drug in young children with enteroviral infection. We describe the successful clearance of prolonged immunodeficiency-associated vaccine-derived type 3 poliovirus infection by pocapavir in an infant with underlying X-linked agammaglobulinemia.

In vitro antiviral activity of V-073 against polioviruses.

V-073, an enterovirus capsid inhibitor, was evaluated for its spectrum of antipoliovirus activity. V-073 inhibited all 45 polioviruses tested in a virus-induced cytopathic effect protection assay, with 50% effective concentration (EC50) values ranging from 0.003 to 0.126 microM. Ninety percent of the polioviruses tested were inhibited at EC(50)s of < or = 0.076 microM (MIC90 = 32 ng/ml). V-073 is a promising antiviral candidate for the posteradication management of poliovirus incidents.

Intestinal antibody responses to a live oral poliovirus vaccine challenge among adults previously immunized with inactivated polio vaccine in Sweden.

BACKGROUND: Our understanding of the acquisition of intestinal mucosal immunity and the control of poliovirus replication and transmission in later life is still emerging. METHODS: As part of a 2011 randomised, blinded, placebo-controlled clinical trial of the experimental antiviral agent pocapavir (EudraCT 2011-004804-38), Swedish adults, aged 18-50 years, who had previously received four doses of inactivated polio vaccine (IPV) in childhood were challenged with a single dose of monovalent oral polio vaccine type 1 (mOPV1). Using faecal samples collected before and serially, over the course of 45 days, after mOPV1 challenge from a subset of placebo-arm participants who did not receive pocapavir (N=12), we investigated the kinetics of the intestinal antibody response to challenge virus by measuring poliovirus type 1-specific neutralising activity and IgA concentrations. RESULTS: In faecal samples collected prior to mOPV1 challenge, we found no evidence of pre-existing intestinal neutralising antibodies to any of the three poliovirus serotypes. Despite persistent high-titered vaccine virus shedding and rising serum neutralisation responses after mOPV1 challenge, intestinal poliovirus type 1-specific neutralisation remained low with a titer of ≤18.4 across all time points and individuals. Poliovirus types 1-specific, 2-specific and 3-specific IgA remained below the limit of detection for all specimens collected postchallenge. INTERPRETATION: In contrast to recent studies demonstrating brisk intestinal antibody responses to oral polio vaccine challenge in young children previously vaccinated with IPV, this investigation finds that adults previously vaccinated with IPV have only modest intestinal poliovirus type 1-specific neutralisation and no IgA responses that are measurable in stool samples following documented mOPV1 infection.

A case for developing antiviral drugs against polio.

Polio eradication is within sight. In bringing the world close to this ultimate goal, the Global Polio Eradication Initiative (GPEI) has relied exclusively on the live, attenuated oral poliovirus vaccine (OPV). However, as eradication nears, continued OPV use becomes less tenable due to the incidence of vaccine associated paralytic poliomyelitis (VAPP) in vaccine recipients and disease caused by circulating vaccine-derived polioviruses (cVDPVs) in contacts. Once wild poliovirus transmission has been interrupted globally, OPV use will stop. This will leave the inactivated poliovirus vaccine (IPV) as the only weapon to defend a polio-free world. Outbreaks caused by cVDPVs are expected post-OPV cessation, and accidental or deliberate releases of virus could also occur. There are serious doubts regarding the ability of IPV alone to control outbreaks. Here, we argue that antiviral drugs against poliovirus be added to the arsenal. Anti-poliovirus drugs could be used to treat the infected and protect the exposed, acting rapidly on their own to contain an outbreak and used as a complement to IPV. While there are no polio antiviral drugs today, the technological feasibility of developing such drugs and their probability of clinical success have been established by over three decades of drug development targeting the related rhinoviruses and non-polio enteroviruses (NPEVs). Because of this history, there are known compounds with anti-poliovirus activity in vitro that represent excellent starting points for polio drug development. Stakeholders must come to understand the potential public health benefits of polio drugs, the feasibility of their development, and the relatively modest costs involved. Given the timelines for eradication and those for drug development, the time for action is now.

N-(3,3a,4,4a,5,5a,6,6a-Octahydro-1,3-dioxo-4,6- ethenocycloprop[f]isoindol-2-(1H)-yl)carboxamides: Identification of novel orthopoxvirus egress inhibitors.

A series of novel, potent orthopoxvirus egress inhibitors was identified during high-throughput screening of the ViroPharma small molecule collection. Using structure--activity relationship information inferred from early hits, several compounds were synthesized, and compound 14 was identified as a potent, orally bioavailable first-in-class inhibitor of orthopoxvirus egress from infected cells. Compound 14 has shown comparable efficaciousness in three murine orthopoxvirus models and has entered Phase I clinical trials.

Enteroviruses in X-Linked Agammaglobulinemia: Update on Epidemiology and Therapy.

X-linked agammaglobulinemia (XLA) has been associated with a broad range of infections, but enteroviral disease represents one of the most damaging infections. The risk of enteroviral infection in XLA is lower now than in the setting of intramuscular immunoglobulin or in patients without immunoglobulin replacement, but the rate of infection has not declined significantly in the era of intravenous immunoglobulin replacement. Enteroviruses can cause inflammation of nearly every organ, but in XLA, infections often manifest as dermatomyositis or chronic meningoencephalitis. Difficulty and delay in recognizing symptoms and lack of specific therapy contribute to the poor outcomes. Furthermore, cerebrospinal fluid detection of enteroviruses is not very sensitive. Reluctance to perform brain biopsies can lead to significant delays. The other feature compromising outcomes is the lack of specific therapy. High-dose peripheral and intraventricular immunoglobulin have been used, but failure is still common. New antienteroviral drugs are in development and show promise for immunodeficient patients with life-threatening infections with enterovirus.

Insights into the genetic basis for natural phenotypic resistance of human rhinoviruses to pleconaril.

Recent phylogenetic analyses of the deduced amino acid sequence of the major viral capsid protein (VP1) of all human rhinovirus (HRV) serotypes revealed two distinct species within the genus: species A (75 serotypes) and species B (25 serotypes). Pleconaril is a novel capsid inhibitor of HRVs. All 75 species A serotypes and 18 of the 25 species B serotypes are susceptible to inhibition by pleconaril in cell culture. The seven resistant serotypes are HRV-4, -5, -42, -84, -93, -97 and -99. We were interested in understanding the genetic basis for phenotypic resistance to pleconaril among these naturally occurring viruses. We compared the 25 amino acids of VP1 that comprise the drug-binding pocket of susceptible and resistant species B viruses. A consistent difference was observed at two positions: the vast majority of susceptible viruses had tyrosine and valine at VP1 residues 152 and 191, respectively (Y(152) and V(191)); all resistant viruses had phenylalanine and leucine at these positions (F(152) and L(191)). HRV-14, a pleconaril susceptible virus, has a drug-binding pocket amino acid composition that differs from the naturally resistant HRV-5 and HRV-42 only at these two positions. To gain further insight into the role of these specific residues in natural resistance to pleconaril, we substituted the amino acids at these two positions individually and in combination in an infectious clone of HRV-14 and tested the rescued virus for susceptibility to pleconaril and virion stability. The results indicate that substitution of V(191) to Leu in HRV-14 has a profound negative impact on drug susceptibility but that full resistance to pleconaril is only seen when combined with Phe at position 152 in a HRV-14 double variant (F(152), L(191)). These data identify L(191) in species B HRV as a potentially key residue in conferring significantly reduced susceptibility to pleconaril. These results may be useful in distinguishing naturally occurring viral resistance to pleconaril from treatment-emergent resistance.

First use of investigational antiviral drug pocapavir (v-073) for treating neonatal enteroviral sepsis.

Neonatal enteroviral sepsis is a potentially fatal condition. Perinatally acquired infection and severe coagulopathy can be associated with a poor clinical outcome, and antiviral therapy is currently unavailable. Pocapavir (V-073) is an investigational drug candidate being developed for poliovirus indications, but also has variable antiviral activity against nonpolio enteroviruses. We describe the first use of pocapavir in treating a case of severe neonatal enteroviral sepsis due to Coxsackievirus B3.

Efficacy and safety of oral pleconaril for treatment of colds due to picornaviruses in adults: results of 2 double-blind, randomized, placebo-controlled trials.

The novel capsid-binding antiviral pleconaril inhibits in vitro replication of most rhinoviruses and enteroviruses. Oral pleconaril treatment was studied in 2 parallel randomized, double-blind, placebo-controlled trials. Among 1363 picornavirus-infected participants (65%) in the studies combined, the median time to alleviation of illness was 1 day shorter for pleconaril recipients than for placebo recipients (P<.001). Cold symptom scores and frequency of picornavirus cultured from nasal mucus specimens were lower among pleconaril recipients by day 2 of treatment. No treatment effects were seen in those without picornavirus infection. Pleconaril was associated with a higher incidence of nausea (6% vs. 4%) and diarrhea (9% vs. 7%) and with small increases in mean serum cholesterol levels and platelet counts, compared with baseline measurements. A subsequent 6-week prophylaxis study found that pleconaril induces cytochrome P-450 3A enzymes, which metabolize a variety of drugs, including ethinyl estradiol. Early pleconaril treatment was well tolerated and significantly reduced the duration and severity of colds due to picornaviruses in adults.

Dominant drug targets suppress the emergence of antiviral resistance.

The emergence of drug resistance can defeat the successful treatment of pathogens that display high mutation rates, as exemplified by RNA viruses. Here we detail a new paradigm in which a single compound directed against a 'dominant drug target' suppresses the emergence of naturally occurring drug-resistant variants in mice and cultured cells. All new drug-resistant viruses arise during intracellular replication and initially express their phenotypes in the presence of drug-susceptible genomes. For the targets of most anti-viral compounds, the presence of these drug-susceptible viral genomes does not prevent the selection of drug resistance. Here we show that, for an inhibitor of the function of oligomeric capsid proteins of poliovirus, the expression of drug-susceptible genomes causes chimeric oligomers to form, thus rendering the drug-susceptible genomes dominant. The use of dominant drug targets should suppress drug resistance whenever multiple genomes arise in the same cell and express products in a common milieu.

Immunogenicity of inactivated polio vaccine with concurrent antiviral V-073 administration in mice.

Immunization of mice with inactivated polio vaccine (IPV) with concurrent dosing of poliovirus antiviral V-073 showed no detrimental impact on the elicitation of serum-neutralizing antibodies. A strategy involving coadministration of antiviral V-073 and IPV can be considered for the management of poliovirus incidents.

Immunological and pathogenic properties of poliovirus variants selected for resistance to antiviral drug V-073.

BACKGROUND: The National Research Council has recommended development of polio antiviral drugs to assist in management of outbreaks and to mitigate adverse consequences of vaccination. V-073 is a small molecule poliovirus capsid inhibitor that is being developed for these purposes. Antiviral use raises the potential of treatment-emergent resistance. Understanding virological consequences of resistance is important. METHODS: Six independent laboratory-derived V-073-resistant poliovirus variants were characterized for their ability to be neutralized by conventional vaccine-induced immune sera, to elicit serum neutralizing antibodies upon CD-1 mouse immunization, and to replicate in and to cause paralysis of TgPVR21 mice. RESULTS: V-073-resistant variants were effectively neutralized by oral poliovirus vaccine and inactivated poliovirus vaccine human immune sera. All variants elicited virus neutralizing antibody titres in CD-1 mice that were comparable to drug-susceptible parental and Sabin vaccine strain viruses. Infection efficiency of TgPVR21 mice by variants was comparable to (1 of 6 variants) or considerably lower than (5 of 6 variants) parental viruses. Drug-resistant variants replicated to levels comparable to (1 of 6 variants) or substantially less than (5 of 6 variants) their drug-susceptible parental viruses and were on average 1.4 log(10) (range 0.3 to >2.8 log10) less neurovirulent. CONCLUSIONS: Laboratory-derived V-073-resistant variants exhibit clear attenuation of pathogenic properties while maintaining immunological features of drug-susceptible viruses.

Direct random insertion of an influenza virus immunologic determinant into the NS1 glycoprotein of a vaccine flavivirus.

A live chimeric vaccine virus against Japanese encephalitis (JE), ChimeriVax-JE, was used to define methods for optimal, random insertion of foreign immunologic determinants into flavivirus glycoproteins. The conserved M2e peptide of influenza A virus was randomly inserted into the yellow fever-specific NS1 glycoprotein of ChimeriVax-JE. A technique combining plaque purification with immunostaining yielded a recombinant virus that stably expressed M2e at NS1-236 site. The site was found permissive for other inserts. The insertion inhibited NS1 dimerization in vitro, which had no significant effect on virus replication in vitro and immunogenicity in vivo. Two different NS1-specific monoclonal antibodies and a polyclonal antibody efficiently recognized only the NS1 protein dimer, but not monomer. Adaptation of the virus to Vero cells resulted in two amino acid changes upstream from the insert which restored NS1 dimerization. Immunized mice developed high-titer M2e-specific antibodies predominantly of the IgG2A isotype indicative of a Th1-biased response.

Anti-HCV therapies in chimeric scid-Alb/uPA mice parallel outcomes in human clinical application.

Compounds with in vitro anti-hepatitis C virus (HCV) activity are often advanced directly into clinical trials with limited or no in vivo efficacy data. This limits prediction of clinical efficacy of compounds in the HCV drug pipeline, and may expose human subjects to unnecessary treatment effects. The scid-Alb-uPA mouse supports proliferation of transplanted human hepatocytes and subsequent HCV infection. Cohorts of genotype 1a HCV-infected mice were treated with interferon alpha-2b(IFN-alpha), BILN-2061 (anti-NS3 protease), or HCV371 (anti-NS5B polymerase). Mice treated with 1350 IU/g/day IFN-alpha intramuscularly for 10 to 28 days demonstrated reduced viral titers compared with controls in all five experiments (P < .05, t test); viral titers rebounded after treatment withdrawal. A more pronounced antiviral effect with IFN-alpha was seen in genotype 3a-infected mice. Pilot studies with BILN2061 confirmed exposure to 10X replicon EC50 at trough and reduced viral titer over 2 log at 4 days. In a second 7-day study, mean HCV RNA titers dropped 1.1 log in BILN2061-treated animals, 0.6 log in IFN-treated mice, and rose 0.2 log in controls (P = .013, ANOVA). Pre-existing mutants with partial resistance to BILN2061 were identified by sequencing both the human inoculum and sera from treated mice. The polymerase inhibitor HCV371 yielded a decline in HCV titers of 0.3 log relative to vehicle-treated controls (P = NS). Performance of all three antiviral regimens in the chimeric mouse model paralleled responses in humans. In conclusion, this system may help selection of lead compounds for advancement into human trials with an increased likelihood of clinical success while broadening the tools available for study of the biology of HCV infection.

Relationship of pleconaril susceptibility and clinical outcomes in treatment of common colds caused by rhinoviruses.

Pleconaril, a specific inhibitor of human picornaviruses, showed therapeutic efficacy against community-acquired colds caused by rhinoviruses in two placebo-controlled trials. Virological assessments were conducted during these trails, including virus culture and drug susceptibility testing. Nasal mucus samples collected from the enrolled patients were tested for the presence of picornavirus by reverse transcriptase PCR and culture. In total, 827 baseline nasal mucus samples were positive by virus culture (420 in the placebo group and 407 in the pleconaril group). Pleconaril treatment was associated with a more rapid loss of culturable virus. By study day 3, the number of samples positive by culture fell to 282 for the placebo-treated subjects and 202 for the pleconaril-treated subjects (P < 0.0001); and by day 6, the number of samples in the two groups positive by culture fell to 196 and 165, respectively (P = 0.07). The clinical benefit correlated strongly with the pleconaril susceptibility of the baseline virus isolate. Pleconaril-treated subjects infected with the more highly susceptible viruses (50% effective concentration < or = 0.38 microg/ml) experienced a median 1.9- to 3.9-day reduction in symptom duration compared with that for the placebo-treated subjects. By contrast, subjects whose baseline virus isolate susceptibility was >0.38 microg/ml did not benefit from pleconaril treatment. These results indicate that the magnitude of symptomatic improvement in pleconaril-treated subjects with community-acquired colds is related to the drug susceptibility of the infecting virus, clearly linking the antiviral effects of the drug to clinical efficacy. Post-baseline virus isolates with reduced susceptibility or full resistance to pleconaril were recovered from 10.7% and 2.7% of drug-treated subjects, respectively. These patients shed low levels of virus and had no unusual clinical outcomes. Nevertheless, studies on the biologic properties and transmissibility of these variant viruses are warranted.