Dalbavancin For The Treatment of Gram Positive Osteoarticular Infections

Overview

Because of its prolonged terminal half-life, dalbavancin is an extremely attractive option in treating Gram-positive infections caused by S. aureus including MRSA, and streptococcal species. Systemic bacterial infections due to Staphylococci such as osteomyelitis and septic arthritis, are conditions which require prolonged IV therapy, typically for at least 3-6 weeks, though sometimes more. Due to dalbavancin's prolonged terminal half-life, it may offer the opportunity to substantially reduce costs and morbidity in native joint and prosthetic joint infections with one infusion every fourteen days until completion of therapy.

Dalbavancin, currently FDA approved for the treatment of skin and soft tissue infections (SSTI), is a lipoglycopedptide with bactericidal activity in vitro against Staphylococcus aureus, including MRSA and VISA strains, and Streptococcus pyogenes. Its bactericidal action results primarily from inhibition of cell-wall biosynthesis, specifically the prevention of N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG)-peptide subunits incorporation into the peptidoglycan matrix. Dalbavancin alters bacterial-cell-membrane permeability and RNA synthesis. It is highly protein bound, primarily to albumin, with a half-life of 346 hours. Approximately 33% of unchanged drug is excreted in the urine, 20% via feces and 12% as the minor metabolite, hydroxyl-dalbavancin. There is minimal potential for drug-drug interactions; it is not a substrate, inducer or inhibitor of hepatic CYP450 isoenzymes and the administration of CYP450 substrates, inhibitors or inducers does not affect its clearance rate. In SSTI trials, Dalbavancin was demonstrated to be non-inferior to vancomycin and linezolid. Prosthetic joint infections (PJI) are an emerging health problem. Although the incidence of these infections is historically low (approximately 0.5%-1.0of implants), because of the rapid increase in the number of hip, knee and other joint implants, the absolute number of cases of infection is increasing. In 2010, 332,000 hip joints and 719,000 knee joints were implanted. This alone conservatively translates to 5,000-10,000 cases, with an economic impact of $1 billion. Management of PJI is particularly challenging because long term antibiotic therapy in most cases is accompanied by removal of the prosthesis and re-implantation. For long term antimicrobial administration, current standard of care requires a peripherally inserted central catheter (PICC) or other indwelling intravascular catheter, and daily/multiple daily infusions. There is substantial cost of maintaining the intravascular access, drugs, home health care and monitoring, as well as the infection risk of the chronic indwelling line which is being accessed frequently. There is a clear need for alternative care models to the current approach. Dalbavancin, because of its activity profile against Gram-positive organisms and its pharmacokinetics which would allow weekly or every other week dosing, is a favorable option. This option would eliminate the need for long term IV access, because at most, weekly IV infusions would be performed. In terms of bone infection, dalbavancin has favorable pharmacokinetic properties. A PK study performed in subjects undergoing elective orthopedic surgery found that dalbavancin (dosed at 1000mg IV at enrollment and then 500mg weekly for up to 7 weeks) maintained levels in cortical bone at bactericidal levels , at \>50X the MIC of typical staphylococcal organism (including MRSA). Animal studies in a rat osteomyelitis model also found that dalvabancin was comparable to vancomycin. Because of these same PK properties, dalbavancin offers the opportunity to substantially reduce costs and morbidity in native joint and prosthetic joint infections. This is a two-center, randomized, open label trial of dalbavancin versus standard intravenous therapy control comparator in the treatment of subjects with gram positive native joint or prosthetic joint infections. The primary outcome variable is clinical cure at day 42 after start of treatment in all randomized patients. Safety and tolerability will also be assessed throughout the study period via laboratory measurements and AE monitoring. Additionally, clinical response will be measured by patient reported outcomes with change from baseline symptoms and by Quality of Life questionnaire. Eligible subjects with confirmed gram positive joint infections, will be randomized in a ratio of 2:1 to receive open label dalbavancin or standard IV therapy. Standard IV therapy will depend on the antibiotic susceptibility of the causative pathogen. Subjects randomized to dalbavancin may have received standard of care therapy for no more than 120 hours prior to first dalbavancin dose. Subjects randomized to standard of care can continue with treatment course if already started, or receive the first dose at the baseline visit.