704. Incidence and Patient Outcomes of S. aureus Isolates from Acute Bacterial Skin and Skin Structure Infections (ABSSSI) with High Iclaprim MIC values in Phase 3 REVIVE Trials

BACKGROUND: The incidence and outcomes of patients with S. aureus isolates with an iclaprim MIC >8 µg/mL, a concentration that is not systemically achievable, were determined among patients from two Phase 3 studies for the treatment of ABSSSI, REVIVE-1 and -2. METHODS: REVIVE-1 and REVIVE-2 studies were 600-patient, double-blinded, randomized (1:1), active-controlled trials among patients with ABSSSI that compared the safety and efficacy of iclaprim 80 mg fixed dose with vancomycin 15 mg/kg (adjusted for renal function), both administered intravenously over 2 hours every 12 hours for 5–14 days. Patients had a bacterial skin infection suspected or confirmed to be due to a Gram-positive pathogen with a lesion size ≥75 cm(2). An early clinical response (ECR) was defined as a ≥20% reduction in lesion size compared with baseline at the early time point (ETP) 48–72 hours after the start of administration of the study drug in the intent-to-treat (ITT) population. A clinical cure, defined as complete resolution of all signs and symptoms of ABSSSI was measured at the end of therapy (EOT) and test of cure (TOC) visit, 7–14 days after the last dose of study drug. At baseline, EOT and TOC visits, ABSSSIs were sampled for microbiological culture and broth microdilution susceptibility testing conducted in accordance with CLSI M7. RESULTS: The incidence of culture confirmed S. aureus isolates among patients with ABSSSI with an iclaprim MIC >8 µg/mL was 2.0% (16/790). Six were MSSA and 10 were MRSA. The clinical outcomes of these infections included ECR of 63% (10/16), EOT response of 81.3% (13/16) and the TOC response of 75% (12/16). For microbiological outcomes of these infections, the end of therapy response was 92.9% (13/14) and the test of cure response was 92.3% (12/13). In comparison, there was less variation in vancomycin MICs among the S. aureus isolates. For patients who were randomized to vancomycin and had a pathogen identified from their ABSSSI, the pooled ECR was 82.6% (242 of 293) at a vancomycin MIC of 0.5–1 µg/mL and one isolate from a patient with ECR had a MIC of 2 µg/mL. CONCLUSION: Patients receiving iclaprim had good clinical and microbiological responses against S. aureus isolates with an iclaprim MIC >8 µg/mL, which are uncommon (2.0%). DISCLOSURES: All authors: No reported disclosures.