Phase 2 Study of Safety, Efficacy, and Pharmacokinetics of Higher Doses of Daptomycin and Vancomycin in MRSA Bacteremia

The overall goals of this study are to compare the safety and efficacy of daptomycin monotherapy 10 mg/kg/day and vancomycin monotherapy dosed to achieve vancomycin trough levels of 15 to 20 μg/mL for the treatment of methicillin-resistant S. aureus bacteremia (MRSA), including right-sided infective endocarditis (RIE).

Patients who meet all inclusion criteria and exhibit none of the exclusion criterial will be randomized to one of two treatment arms:

1. daptomycin Intravenously (IV) 10 mg/kg every 24 hours
2. vancomycin IV dosed to maintain trough levels of 15 to 20 μg/mL.

The suggested duration of therapy with daptomycin or vancomycin will be 28 days (or up to 42 days if clinically indicated). Dose adjustments for both drugs will be made by an unblinded pharmacist at each site. To minimize the duration with which patients are treated with antibacterial agents effective against S. aureus prior to enrollment, patients with suspected MRSA bacteremia will be enrolled pending definitive culture results. Suspected MRSA bacteremia will be defined clinically or as initial blood cultures that grow Gram-positive cocci and that were obtained from a patient at increased risk for methicillin-resistant S. aureus infections. However, only patients with confirmed MRSA bacteremia or right-sided infective endocarditis will remain in the study and be evaluated for efficacy. During treatment, regular assessments will be performed. An End-of Therapy (EOT) will be performed 1-3 days after stopping therapy or upon Early Termination (ET). All patients will have a post therapy visit for Test of Cure (TOC) performed 35-49 days following last dose of study drug.

Eligibility Criteria:
INCLUSION CRITERIA:

* Written informed consent has been obtained;
* ≥18 years of age;
* Suspected MRSA bacteremia determined by clinical judgment or 2 sets of positive blood cultures;
* Increased risk for an MRSA infection

EXCLUSION CRITERIA:

* Received \>48 hours of vancomycin therapy in the 7 days prior to enrollment;
* Received any systemic antibacterial agents potentially effective against MRSA in the 7 days prior to enrollment;
* Anticipated requirement of antibiotics potentially effective against MRSA;
* High likelihood of left-sided infective endocarditis (LIE);
* Known/suspected polymicrobial bacteremia or infection including Gram-negative infections;
* Known pneumonia, osteomyelitis, or meningitis;
* Intravascular foreign material unless material intended removed within 3 days;
* Prosthetic heart valve;
* Cardiac decompensation, valve damage, or both such that high likelihood of valve replacement surgery within first 3 days of study drug treatment;
* Moribund clinical condition such that death likely within first 3 days of study drug treatment;
* Shock or hypotension or oliguria unresponsive to fluids after 4 hours;
* Received investigational drug within 30 days of study entry
* Received statins or other therapy with associated with rhabdomyolysis within 2 days of study entry;
* History of significant allergy or intolerance to vancomycin or daptomycin
* Infecting pathogen with confirmed reduced susceptibility to vancomycin;
* Infecting pathogen with confirmed reduced susceptibility to daptomycin
* Creatinine clearance \<30 mL/min (Cockcroft-Gault equation actual body weight)
* Serum creatine phosphokinase (CPK) ≥500 U/L
* Alanine transaminase (ALT) or aspartate aminotransferase (AST) \>5 X ULN;
* Total bilirubin ≥3.0 mg/dL;
* Severe neutropenia or expected development severe neutropenia during study;
* Known or suspected HIV infection with a CD4+ T-cell count \<200/μL;
* Unlikely to comply with study procedures or return for evaluations;
* Body Mass Index (BMI) ≥40 kg/m2;
* Pregnant or nursing;
* Female of childbearing potential not willing to practice barrier methods of birth control.

CONTINUATION CRITERIA:

* Fulfills A or B or both: A) Confirmed complicated MRSA bacteremia B) Possible or definite RIE caused by MRSA according to modified Duke criteria;
* Infecting S. aureus strain susceptible to vancomycin;
* Infecting S. aureus strain susceptible to daptomycin;
* Appropriate treatment of any foci of infection within first 3 days of study;
* Removal of any intravascular foreign material not allowed per inclusion criteria within first 3 days of study;
* Removal of any percutaneous or implanted catheters not allowed per inclusion criteria within first 3 days of study.