Characterization of Novel Antimalarial Compound ACT-451840: Preclinical Assessment of Activity and Dose-Efficacy Modeling.

BACKGROUND: Artemisinin resistance observed in Southeast Asia threatens the continued use of artemisinin-based combination therapy in endemic countries. Additionally, the diversity of chemical mode of action in the global portfolio of marketed antimalarials is extremely limited. Addressing the urgent need for the development of new antimalarials, a chemical class of potent antimalarial compounds with a novel mode of action was recently identified. Herein, the preclinical characterization of one of these compounds, ACT-451840, conducted in partnership with academic and industrial groups is presented. METHOD AND FINDINGS: The properties of ACT-451840 are described, including its spectrum of activities against multiple life cycle stages of the human malaria parasite Plasmodium falciparum (asexual and sexual) and Plasmodium vivax (asexual) as well as oral in vivo efficacies in two murine malaria models that permit infection with the human and the rodent parasites P. falciparum and Plasmodium berghei, respectively. In vitro, ACT-451840 showed a 50% inhibition concentration of 0.4 nM (standard deviation [SD]: ± 0.0 nM) against the drug-sensitive P. falciparum NF54 strain. The 90% effective doses in the in vivo efficacy models were 3.7 mg/kg against P. falciparum (95% confidence interval: 3.3-4.9 mg/kg) and 13 mg/kg against P. berghei (95% confidence interval: 11-16 mg/kg). ACT-451840 potently prevented male gamete formation from the gametocyte stage with a 50% inhibition concentration of 5.89 nM (SD: ± 1.80 nM) and dose-dependently blocked oocyst development in the mosquito with a 50% inhibitory concentration of 30 nM (range: 23-39). The compound's preclinical safety profile is presented and is in line with the published results of the first-in-man study in healthy male participants, in whom ACT-451840 was well tolerated. Pharmacokinetic/pharmacodynamic (PK/PD) modeling was applied using efficacy in the murine models (defined either as antimalarial activity or as survival) in relation to area under the concentration versus time curve (AUC), maximum observed plasma concentration (Cmax), and time above a threshold concentration. The determination of the dose-efficacy relationship of ACT-451840 under curative conditions in rodent malaria models allowed prediction of the human efficacious exposure. CONCLUSION: The dual activity of ACT-451840 against asexual and sexual stages of P. falciparum and the activity on P. vivax have the potential to meet the specific profile of a target compound that could replace the fast-acting artemisinin component and harbor additional gametocytocidal activity and, thereby, transmission-blocking properties. The fast parasite reduction ratio (PRR) and gametocytocidal effect of ACT-451840 were recently also confirmed in a clinical proof-of-concept (POC) study

Broader Neutralizing Antibodies against H5N1 Viruses Using Prime-Boost Immunization of Hyperglycosylated Hemagglutinin DNA and Virus-Like Particles

BACKGROUND: Highly pathogenic avian influenza (HPAI) H5N1 viruses and their transmission capability from birds to humans have raised global concerns about a potential human pandemic. The inherent nature of antigenic changes in influenza viruses has not been sufficiently taken into account in immunogen designs for broadly protective HPAI H5N1 vaccines. METHODS: We designed a hyperglycosylated HA vaccine using N-linked glycan masking on highly variable sequences in the HA1 globular head. Immunization of these hyperglycosylated HA DNA vaccines followed by a flagellin-containing virus-like particle booster in mice was conducted to evaluate neutralizing antibody responses against various clades of HPAI H5N1 viruses. RESULTS: We introduced nine N-X-S/T motifs in five HA1 regions: 83NNT, 86NNT, 94NFT, 127NSS, 138NRT, 156NTT, 161NRS, 182NDT, and 252NAT according to sequence alignment analyses from 163 HPAI H5N1 human isolates. Although no significant differences of anti-HA total IgG titers were found with these hyperglycosyalted HA compared to the wild-type control, the 83NNT and 127NSS mutants elicited significantly potent cross-clade neutralizing antibodies against HPAI H5N1 viruses. CONCLUSIONS: This finding may have value in terms of novel immunogen design for developing cross-protective H5N1 vaccines

The influence of exercise training status on antigen-stimulated IL-10 production in whole blood culture and numbers of circulating regulatory T cells

The final publication is available at springerlink.com.Highly trained athletes are associated with high resting antigen-stimulated whole blood culture interleukin (IL)-10 production. The purpose of the present study was to examine the effects of training status on resting circulating T regulatory (T) cell counts and antigen-stimulated IL-10 production and the effect of acute bout of exercise on the T response. Forty participants volunteered to participate and were assigned to one of the four groups: sedentary (SED), recreationally active (REC), sprint-trained athletes and endurance-trained athletes (END). From the resting blood sample, CD4CD25CD127 T cells and in vitro antigen-stimulated IL-10 production were assessed. Ten REC subjects performed 60 min cycling at 70 % of maximal oxygen uptake and blood samples for T analysis were collected post- and 1 h post-exercise. IL-10 production was greater in END compared with the other groups (P < 0.05). END had a higher T percentage of total lymphocyte count compared with SED (P < 0.05). A smaller proportion of T CD4 cells were observed in SED compared with all other groups (P < 0.05). IL-10 production significantly correlated with the proportion of T within the total lymphocyte population (r = 0.51, P = 0.001). No effect of acute exercise was evident for T cell counts in the REC subjects (P > 0.05). Our results demonstrate that high training loads in END are associated with greater resting IL-10 production and T cell count and suggest a possible mechanism for depression of immunity commonly reported in athletes engaged in high training loads. © 2013 Springer-Verlag Berlin Heidelberg