Human Immunoglobulin G Recognizing Fibrinogen-Binding Surface Proteins Is Protective against both Staphylococcus aureus and Staphylococcus epidermidis Infections In Vivo

A human donor-selected immunoglobulin G for intravenous injection (IGIV) product with elevated titers against the staphylococcal fibrinogen-binding MSCRAMM proteins ClfA and SdrG (INH-A21) was tested in vitro and in vivo. INH-A21 contained a significantly increased ability to inhibit the fibrinogen-binding activity of recombinant forms of both ClfA and SdrG. Evaluation of the opsonizing potential of INH-A21 was evaluated using fluorescently labeled bacteria; this assay indicated an increase in phagocytic activity compared to normal IGIV. The prophylactic efficacy of INH-A21 against an intraperitoneal challenge of methicillin-resistant Staphylococcus epidermidis (MRSE) was evaluated in a neonatal rat model. INH-A21 was also evaluated for prophylactic and therapeutic efficacy in a rabbit model of catheter-induced aortic valve infective endocarditis caused by either MRSE or methicillin-resistant Staphylococcus aureus (MRSA). Results from the in vivo models demonstrated potent prophylactic and therapeutic efficacy against both MRSE and MRSA. These data suggest that INH-A21 may be an important tool for the prevention and treatment of staphylococcal infections, especially in high-risk populations

Characterization of a Humanized Monoclonal Antibody Recognizing Clumping Factor A Expressed by Staphylococcus aureus

We report the humanization and characterization of monoclonal antibody (MAb) T1-2 or tefibazumab, a monoclonal antibody that recognizes clumping factor A expressed on the surface of Staphylococcus aureus. We demonstrate that the binding kinetics of MAb T1-2 is indistinguishable compared to that of its murine parent. Furthermore, MAb T1-2 is shown to enhance the opsonophagocytic uptake of ClfA-coated latex beads, protect against an intravenous challenge in a prophylactic model of rabbit infective endocarditis, and enhance the efficacy of vancomycin therapy in a therapeutic model of established infective endocarditis

When to Extend Monitoring of Anti-drug Antibodies for High-risk Biotherapeutics in Clinical Trials: an Opinion from the European Immunogenicity Platform.

The determination of a tailored anti-drug antibody (ADA) testing strategy is based on the immunogenicity risk assessment to allow a correlation of ADAs with changes to pharmacokinetics, efficacy, and safety. The clinical impact of ADA formation refines the immunogenicity risk assessment and defines appropriate risk mitigation strategies. Health agencies request for high-risk biotherapeutics to extend ADA monitoring for patients that developed an ADA response to the drug until ADAs return to baseline levels. However, there is no common understanding in which cases an extension of ADA follow-up sampling beyond the end of study (EOS) defined in the clinical study protocol is required. Here, the Immunogenicity Strategy Working Group of the European Immunogenicity Platform (EIP) provides recommendations on requirements for an extension of ADA follow-up sampling in clinical studies where there is a high risk of serious consequences from ADAs. The importance of ADA evaluation during a treatment-free period is recognized but the decision whether to extend ADA monitoring at a predefined EOS should be based on evaluation of ADA data in the context of corresponding clinical signals. If the clinical data set shows that safety consequences are minor, mitigated, or resolved, further ADA monitoring may not be required despite potentially detectable ADAs above baseline. Extended ADA monitoring should be centered on individual patient benefit

Phosphoramidate ProTides of 2'-C-Methylguanosine as highly potent inhibitors of hepatitis C virus. Study of their in vitro and in vivo properties

Hepatitis C virus infection constitutes a serious health problem in need of more effective therapies. Nucleoside analogues with improved exposure, efficacy, and selectivity are recognized as likely key components of future HCV therapy. 2′-C-Methylguanosine triphosphate has been known as a potent inhibitor of HCV RNA polymerase for some time, but the parent nucleoside is only moderately active due to poor intracellular phosphorylation. We herein report the application of phosphoramidate ProTide technology to bypass the rate-limiting initial phosphorylation of this nucleoside. Over 30 novel ProTides are reported, with variations in the aryl, ester, and amino acid regions. l-Alanine compounds are recognized as potent and selective inhibitors of HCV in replicon assay but lack rodent plasma stability despite considerable ester variation. Amino acid variation retaining the lead benzyl ester moiety gives an increase in rodent stability but at the cost of potency. Finally l-valine esters with ester variation lead to potent, stable compounds. Pharmacokinetic studies on these agents in the mouse reveal liver exposure to the bioactive triphosphate species following single oral dosing. Systemic exposure of the ProTide and parent nucleoside are low, indicating possible low toxicity in vivo, while liver concentrations of the active species may be predictive of efficacy in the clinic. This represents one of the most thorough cross-species studies of ProTides to date

Synthesis and evaluation against hepatitis C virus of 7-deaza analogues of 2′-C-methyl-6-O-methyl guanosine nucleoside and l-Alanine ester phosphoramidates

7-Deazapurines are known to possess broad antiviral activity, however the 2’-C-methylguanosine analogue displays poor cell permeation and limited phosphorylation, thus is not an efficient inhibitor of hepatitis C virus (HCV) replication. We previously reported the 6-O-methyl entity as a prodrug moiety to increase liphophilicity of guanine nucleosides and the ProTide approach applied to 2’-C-methyl-6-O-methylguanosine has lead to potent HCV inhibitors now in clinical trials. In this paper, we report the synthesis and biological evaluation of 2’-C-methyl-6-O-methyl-7-deaza guanosine and ProTide derivatives. In contrast to prior studies, removal of the N-7 of the nucleobase entirely negates anti-HCV activity compared to the 2’-C-methyl-6-O-methylguanosine analogues. To understand better this significant loss of activity, enzymatic assays and molecular modeling were carried out and suggested 2’-C-methyl-6-O-methyl-7-deaza guanosine and related ProTides do not act as efficient prodrugs of the free nucleotide, in marked contrast to the case of the parent guanine analogue

Synthesis and evaluation against Hepatitis C virus of 7-deaza analogues of 2'-C-methyl-6-O-methyl guanosine nucleoside and L-Alanine ester phosphoramidates

7-Deazapurines are known to possess broad antiviral activity, however the 2’-C-methylguanosine analogue displays poor cell permeation and limited phosphorylation, thus is not an efficient inhibitor of hepatitis C virus (HCV) replication. We previously reported the 6-O-methyl entity as a prodrug moiety to increase liphophilicity of guanine nucleosides and the ProTide approach applied to 2’-C-methyl-6-O-methylguanosine has lead to potent HCV inhibitors now in clinical trials. In this paper, we report the synthesis and biological evaluation of 2’-C-methyl-6-O-methyl-7-deaza guanosine and ProTide derivatives. In contrast to prior studies, removal of the N-7 of the nucleobase entirely negates anti-HCV activity compared to the 2’-C-methyl-6-O-methylguanosine analogues. To understand better this significant loss of activity, enzymatic assays and molecular modeling were carried out and suggested 2’-C-methyl-6-O-methyl-7-deaza guanosine and related ProTides do not act as efficient prodrugs of the free nucleotide, in marked contrast to the case of the parent guanine analogue

Synthesis and evaluation against hepatitis C virus of 7-deaza analogues of 2 '-C-methyl-6-O-methyl guanosine nucleoside and L-Alanine ester phosphoramidates

7-Deazapurines are known to possess broad antiviral activity, however the 2′-C-methylguanosine analogue displays poor cell permeation and limited phosphorylation, thus is not an efficient inhibitor of hepatitis C virus (HCV) replication. We previously reported the 6-O-methyl entity as a prodrug moiety to increase liphophilicity of guanine nucleosides and the ProTide approach applied to 2′-C-methyl-6-O-methylguanosine has lead to potent HCV inhibitors now in clinical trials. In this Letter, we report the synthesis and biological evaluation of 2′-C-methyl-6-O-methyl-7-deaza guanosine and ProTide derivatives. In contrast to prior studies, removal of the N-7 of the nucleobase entirely negates anti-HCV activity compared to the 2′-C-methyl-6-O-methylguanosine analogues. To understand better this significant loss of activity, enzymatic assays and molecular modeling were carried out and suggested 2′-C-methyl-6-O-methyl-7-deaza guanosine and related ProTides do not act as efficient prodrugs of the free nucleotide, in marked contrast to the case of the parent guanine analogue