DMPK and Metabolism Studies of Nucleoside Phosphoramidates Including INX-08189, A Novel Double Pro-drug and Clinical Candidate for Hepatitis C Virus Therapy

Hepatitis C Virus (HCV) infection is a serious health problem that leads to chronic liver disease, such as cirrhosis and hepatocellular carcinoma, in an estimated 2–15% of the world's population. A collaboration between Inhibitex and the University of Caridiff in Wales has produced a novel double pro-drug approach to the anti-HCV agent 2′-β-C-methylguanosine. A phosphoramidate (ProTide) motif and a C6-methoxy base pro-drug moiety are combined to generate lipophilic prodrugs of the monophosphate of the guanine nucleoside. Extensive DMPK studies in multiple species which supported the selection of the lead compound will be discussed. Details of the pre-clinical development of INX-08189 including radiolabeled metabolism studies will be described. INX-08189 has completed investigational new drug enabling studies and has been progressed into human clinical trials for the treatment of chronic HCV infection

Design, synthesis and evaluation of a novel double pro-drug: INX-08189. A new clinical candidate for hepatitis C virus

We herein report a novel double pro-drug approach applied to the anti-HCV agent 2′-β-C-methyl guanosine. A phosphoramidate ProTide motif and a 6-O-methoxy base pro-drug moiety are combined to generate lipophilic prodrugs of the monophosphate of the guanine nucleoside. Modification of the ester and amino acid moieties lead to a compound INX-08189 that exhibits 10 nM potency in the HCV genotype 1b subgenomic replicon, thus being 500 times more potent than the parent nucleoside. The potency of the lead compound INX-08189 was shown to be consistent with intracellular 2′-C-methyl guanosine triphosphate levels in primary human hepatocytes. The separated diastereomers of INX-08189 were shown to have similar activity in the replicon assay and were also shown to be similar substrates for enzyme processing. INX-08189 has completed investigational new drug enabling studies and has been progressed into human clinical trials for the treatment of chronic HCV infection

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

Anti-Clumping Factor A Immunoglobulin Reduces the Duration of Methicillin-Resistant Staphylococcus aureus Bacteremia in an Experimental Model of Infective Endocarditis

SA-IGIV is a human polyclonal immunoglobulin containing elevated levels of antibodies specific for the fibrinogen-binding MSCRAMM protein clumping factor A (ClfA). In vitro, SA-IGIV specifically recognized ClfA that was expressed on the surface of Staphylococcus aureus and inhibited bacterial adherence to immobilized human fibrinogen by >95%. Moreover, SA-IGIV efficiently opsonized ClfA-coated fluorescent beads and facilitated phagocytosis by human polymorphonuclear leukocytes. To determine its potential therapeutic efficacy, SA-IGIV was evaluated in combination with vancomycin in a rabbit model of catheter-induced aortic valve infective endocarditis (IE) caused by methicillin-resistant S. aureus (MRSA). The combination therapy was more effective than vancomycin alone in sterilizing all valvular vegetations when used therapeutically during early (12-h) IE. The combination therapy resulted in clearance of bacteremia that was significantly faster than that of vancomycin alone in animals with well-established (24-h) IE. Therefore, in both early and well-established MRSA IE, the addition of SA-IGIV to a standard antibiotic regimen (vancomycin) increased bacterial clearance from the bloodstream and/or vegetations

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

Antiviral activity of broad-spectrum and enterovirus-specific inhibitors against clinical isolates of enterovirus D68

We investigated the susceptibility of 10 enterovirus D68 (EV-D68) isolates (belonging to clusters A, B, and C) to (entero)virus inhibitors with different mechanisms of action. The 3C-protease inhibitors proved to be more efficient than enviroxime and pleconaril, which in turn were more effective than vapendavir and pirodavir. Favipiravir proved to be a weak inhibitor. Resistance to pleconaril maps to V69A in the VP1 protein, and resistance to rupintrivir maps to V104I in the 3C protease. A structural explanation of why both substitutions may cause resistance is provided.status: publishe

Antiviral activity of broad-spectrum and enterovirus-specific inhibitors against clinical isolates of enterovirus D68

The susceptibility of ten EV-68 isolates (belonging to cluster A, B and C) to (entero-)virus inhibitors with different mechanisms of action was investigated. The 3C-protease inhibitors proved to be more efficient than enviroxime and pleconaril, which in turn were more effective than vapendavir and pirodavir. Favipiravir proved a weak inhibitor. Resistance to pleconaril maps to V69A in VP1 and resistance to rupintrivir to V104I in the 3C protease. A structural explanation is provided why both mutations may cause resistance