Effective and reliable anti-influenza treatments are acutely needed and passive-immunizations using broadly neutralizing anti-influenza monoclonal antibodies (bnAbs) are a promising emerging approach. Because influenza infections are initiated in and localized to the pulmonary tract, and newly formed viral particles egress from the apical side of the lung epithelium, we compared the effectiveness of hemagglutinin (HA) stalk-binding bnAbs administered through the airway (intranasal or via nebulization) versus the systemic route (intra-peritoneal or intravenous). Airway deliveries of various bnAbs were 10- to 50-fold more effective than systemic deliveries of the same bnAbs in treating H1N1, H3N2, B/Victoria-, and B/Yamagata-lineage influenza viral infections in mouse models. The potency of airway-delivered anti-HA bnAbs were highly dependent on anti-viral neutralization activity with little dependence on the effector function of the antibody. In contrast, effectiveness of systemically-delivered anti-HA bnAbs were not dependent on anti-viral neutralization, but critically dependent on antibody effector functions. Concurrent administration of a neutralizing/effector function-positive bnAb via the airway and systemic routes showed increased effectiveness. The low amount of airway-delivered bnAbs needed for effective influenza treatment create the opportunity to combine potent bnAbs with different anti-influenza specificities to generate a cost-effective antiviral therapy that provides broad coverage against all circulating influenza strains infecting humans. A 3 mg/kg dose of the novel triple antibody combination CF-404 (i.e. 1 mg/kg of each component bnAb) delivered to the airway was shown to effectively prevent weight-loss and death in mice challenged with ten LD50 inoculums of either H1N1, H3N2, B/Victoria-lineage, or B/Yamagata-lineage influenza viruses. IMPORTANCE Influenza causes widespread illness in humans and can result in morbidity and death, especially in the very young and elderly populations. Because influenza vaccination can be poorly effective some years, and the immune system of the most susceptible populations are often compromised, passive immunization treatments using broadly-neutralizing antibodies is a promising therapeutic approach. However, large amounts of a single antibody are required for effectiveness when delivered through systemic administration (typically intravenous infusion) precluding the feasible dosing of antibody combinations via this route. The significance of our research is the demonstration that effective therapeutic treatments of multiple relevant influenza types (H1N1, H3N2, and B) can be achieved by airway administration of a single combination of relatively small amounts of three anti-influenza antibodies. This advance exploits the discovery that airway delivery is a more potent way of administering anti-influenza antibodies compared to systemic delivery, making this a feasible and cost-effective therapeutic approach.

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We evaluated the efficacy of escalating doses of exebacase administered with subtherapeutic daptomycin exposures against 8 Staphylococcus aureus isolates in a neutropenic murine thigh infection model. Daptomycin alone resulted in mean growth of 0.39 ± 1.19 log10 CFU/thigh. When administered with daptomycin, exebacase resulted in a mean log10 CFU/thigh reduction of −1.03 ± 0.72 (range, −0.77 ± 0.98 to −1.20 ± 0.59) across evaluated doses (15 to 90 mg/kg), indicative of potential in vivo synergy.

Stimulation of red cell production through agonism of the erythropoietin receptor (EpoR) has historically been accomplished through administration of erythropoietin (EPO), the native ligand. The short half-life of EPO has led to the development of a variety of other agonists, including antibodies. It is of considerable interest to understand how these agents might activate the EpoR and whether or not it is important to bind in a manner similar to the native ligand. The binding epitopes of a panel of eight agonistic, single-chain antibody (scFv-Fc) constructs were determined through scanning alanine mutagenesis as well as more limited arginine mutagenesis of the receptor. It was found that while some of these constructs bound to receptor epitopes shared by the ligand, others bound in completely unique ways. The use of a panel of agonists and scanning mutagenesis can define the critical binding regions for signaling; in the case of the EpoR, these regions were remarkably broad.

BackgroundExebacase (CF-301) is a novel lysin with rapid bacteriolytic and anti-biofilm activity against S. aureus, pronounced synergy with antibiotics and low propensity for resistance. Exebacase has undergone Phase 1–2 trials. This work was to develop pharmacokinetic (PK) model in animal and determine the relationship between exebacase exposure and efficacy in animals.MethodsPK data in 592 animals (4 species) included in population PK model. A range of linear and nonlinear mammillary models with allometric scaling fitted to the PK data using NONMEM and the most parsimonious model was selected by improvement in objective function value (P < 0.01). To evaluate efficacy, 349 animals with 177 mice (neutropenic thigh infection) and 172 rabbits (aortic valve infective endocarditis were treated with exebacase in addition to suboptimal doses of daptomycin (DAP). Full PK profiles were simulated for individual animals. Fifty-nine dosing regimens of exebacase in mice (0–90 mg/kg) and 18 regimens in rabbits (0–1.4 mg/kg) with q24h, q12h and q8h frequencies. Relationship between AUC/MIC, Cmax/MIC, T> MIC, and log-CFU was examined using a range of functions by comparing residual standard error (RSE).Results3-compartment model with allometric scaling best described the PK data and was validated by bootstrap and Goodness of Fit. Maximum drop in log10CFU/g in target tissues was at AUC/MIC< 0.2 for exebacase when added to DAP that was associated with CF reduction of -5 logs in rabbits (Figure (a)) with similar magnitudes in cardiac vegetations, kidney and spleen, and -4 logs in mice (Figure (b)). Treatment with DAP alone had log10CFU reduction of -1 in mice; and -2 in rabbits. AUC/MIC was an appropriate predictor of CFU reductions.ConclusionPK model adequately described the data for 4 animal species. Exebacase addition to DAP has a synergistic effect on efficacy measured by CFU reductions in target tissues in the animal models. Results support previously presented determinations of AUC/MIC as predictor of efficacy. Maximum reductions in CFU in rabbits and mice were observed at AUC/MIC ratios <0.2. These results further indicate that rabbit is the most appropriate efficacy model with MICs and antibacterial activity reflective of previously reported observations in human serum. Disclosures All authors: No reported disclosures.