Discovery of Acyl-Indole Derivatives as Pan-Serotype Dengue Virus NS4B Inhibitors

In the absence of any approved dengue-specific treatment, the discovery and development of a novel small-molecule antiviral for the prevention or treatment of dengue are critical. We previously reported the identification of a novel series of 3-acyl-indole derivatives as potent and pan-serotype dengue virus inhibitors. We herein describe our optimization efforts toward preclinical candidates 24a and 28a with improved pan-serotype coverage (EC₅₀'s against the four DENV serotypes ranging from 0.0011 to 0.24 μM for 24a and from 0.00060 to 0.084 μM for 28a), chiral stability, and oral bioavailability in preclinical species, as well as showing a dose-proportional increase in efficacy against DENV-2 infection in vivo in mice.

Blocking NS3-NS4B interaction inhibits dengue virus in non-human primates

Dengue is a major health threat and the number of symptomatic infections caused by the four dengue serotypes is estimated to be 96 million1 with annually around 10,000 deaths2. However, no antiviral drugs are available for the treatment or prophylaxis of dengue. We recently described the interaction between non-structural proteins NS3 and NS4B as a promising target for the development of pan-serotype dengue virus (DENV) inhibitors3. Here we present JNJ-1802-a highly potent DENV inhibitor that blocks the NS3-NS4B interaction within the viral replication complex. JNJ-1802 exerts picomolar to low nanomolar in vitro antiviral activity, a high barrier to resistance and potent in vivo efficacy in mice against infection with any of the four DENV serotypes. Finally, we demonstrate that the small-molecule inhibitor JNJ-1802 is highly effective against viral infection with DENV-1 or DENV-2 in non-human primates. JNJ-1802 has successfully completed a phase I first-in-human clinical study in healthy volunteers and was found to be safe and well tolerated4. These findings support the further clinical development of JNJ-1802, a first-in-class antiviral agent against dengue, which is now progressing in clinical studies for the prevention and treatment of dengue.

Antiviral and lung protective activity of a novel respiratory syncytial virus fusion inhibitor in a mouse model

Respiratory syncytial virus (RSV) causes bronchiolitis in young children and common colds in adults. There is no licensed vaccine, and prophylactic treatment with palivizumab is very expensive and limited to high-risk infants. Ribavirin is used as an antiviral treatment in infants and immunosuppressed patients, and its use is limited due to side-effects, toxicity to the recipient and staff, and evidence of marginal clinical efficacy. Therefore, we studied the in vivo kinetics, and the antiviral and protective properties of a novel candidate for RSV disease treatment. The drug is a small molecule (TMC353121) discovered by screening for fusion inhibitory properties against RSV in a cellular infection model. The pharmacokinetics of TMC353121 was studied in BALB/c mice and antiviral effects determined by testing viral loads in lung tissue by quantitative RT-PCR and plaque assay after intranasal RSV infection. At doses of 0.25-10 mg · kg(-1), TMC353121 significantly reduced viral load, bronchoalveolar lavage cell accumulation and the severity of lung histopathological change after infection. Treatment remained effective if started within 48 h of infection, but was ineffective thereafter. Therefore, TMC353121 is a novel potent antiviral drug, in vivo reducing RSV replication and inhibiting consequential lung inflammation, with a great potential for further clinical development.

Prospects for the development of fusion inhibitors to treat human respiratory syncytial virus infection

Human respiratory syncytial virus (hRSV) is a significant cause of respiratory illness in at-risk pediatric patients, immunocompromised adults and the elderly. No vaccine is currently available for the virus and treatment options are limited to the prophylactic treatment of at-risk infants with the mAb palivizumab (Synagis) and to therapeutic intervention with the nucleoside analog ribavirin (Rebetol). The clinical use of these agents is limited and a need exists for more effective treatment for the at-risk population. The merging of viral and cellular membranes is a crucial event in the hRSV life cycle that enables the virus to enter a host cell. The multistep fusion process is facilitated by the substantial refolding of a trimeric class I fusion protein (F protein), which is the main target of fusion inhibitors. Several small-molecule fusion inhibitors have been discovered, of which some have progressed significantly in the drug development process. BTA-9881 (Biota Holdings Ltd/MedImmune) and TMC-353121 (Johnson & Johnson) are the most advanced of this drug class. In addition, progress has been made in the development of next-generation antibodies such as motavizumab (Numax; MedImmune). This review will discuss the status and latest developments of compounds and antibodies that inhibit hRSV fusion.

Selection of a respiratory syncytial virus fusion inhibitor clinical candidate, part 1: improving the pharmacokinetic profile using the structure-property relationship

We previously reported the discovery of substituted benzimidazole fusion inhibitors with nanomolar activity against respiratory syncytial virus (Andries, K.; et al. Antiviral Res. 2003, 60, 209-219). A lead compound of the series was selected for preclinical evaluation. This drug candidate, JNJ-2408068 (formerly R170591, 1), showed long tissue retention times in several species (rat, dog, and monkey), creating cause for concern. We herein describe the optimization program to develop compounds with improved properties in terms of tissue retention. We have identified the aminoethyl-piperidine moiety as being responsible for the long tissue retention time of 1. We have investigated the replacement or the modification of this group, and we suggest that the pKa of this part of the molecules influences both the antiviral activity and the pharmacokinetic profile. We were able to identify new respiratory syncytial virus inhibitors with shorter half-lives in lung tissue.