Serum and Lung Pharmacokinetics of ASN100, a Monoclonal Antibody Combination for the Prevention and Treatment of Staphylococcus aureus Pneumonia

BACKGROUND: Monoclonal antibodies (mAbs) are well-suited for the prevention and treatment of acute bacterial infections. ASN100 is a combination of two fully human IgG1 mAbs, ASN-1 and ASN-2 that together neutralize six Staphylococcus aureus cytotoxins, alpha-hemolysin (Hla) and five leukocidins (HlgAB, HlgCB, LukED, LukSF [PVL] and LukGH) that are important in the pathogenesis of S. Aureus pneumonia. We aimed to characterize the pharmacokinetics (PK) of ASN100 in both serum and lung epithelial lining fluid (ELF) in male and female healthy volunteers. METHODS: The safety, tolerability, and serum and lung PK of single intravenous infusion of ASN100 was evaluated in a Phase 1 study. Eight subjects (3:1 randomization) in two double-blind cohorts received ASN100 (doses of 3600 mg or 8000 mg) or placebo. ASN-1 and ASN-2 were administered in a fixed dose 1:1 ratio. Twelve subjects received ASN100 open-label at doses of 3600 mg or 8000 mg and each underwent two bronchoalveolar lavage (BAL) fluid collections either on days 1 and 30 or on days 2 and 8 post-dosing. ASN-1 and ASN-2 concentrations were determined by ELISA. The ELF concentrations were normalized based on urea concentrations in serum and BAL fluid. RESULTS: No dose limiting toxicity was observed. Adverse events (AEs) showed no association of increased incidence with higher dose. All AEs were mild or moderate in severity, with 83.3% of subjects receiving ASN100 reporting at least one AE vs. 100% of placebo subjects. A dose proportional increase in serum peak and exposure (AUC) of ASN-1 and ASN-2 was observed and the serum PK of ASN-1 and ASN-2 were comparable (approximate half-life of each antibody was 3 weeks). Penetration of ASN-1 and ASN-2 into the ELF of the lung was observed at the first post-dose time point of 24 hours, peak concentrations were observed after day 2 and the mAbs remained detectable at day 30. CONCLUSION: ASN100 was safe and well tolerated at doses up to 8000 mg (4000 mg ASN-1 and 4000 mg ASN-2). The PK profiles of ASN-1 and ASN-2 were comparable following simultaneous administration. Significant lung concentrations of each mAb were demonstrated between day 1 and 30 post-dosing. These data support continued clinical development of ASN100 for the prevention and treatment of S. Aureus pneumonia. DISCLOSURES: Z. Magyarics, Arsanis Biosciences GmbH: Employee, Salary. Arsanis, Inc.: Shareholder, Share options. F. Leslie, Arsanis., Inc.: Employee and Shareholder, Salary. S. A. Luperchio, Arsanis Inc.: Employee and Shareholder, Salary. B. Jilma, Arsanis Biosciences GmbH: Investigator, Investigator fee. C. Stevens, Arsanis Inc.: Employee and Shareholder, Salary.E. Nagy, Arsanis: Employee and Shareholder, Salary.