LB3. Exebacase (EXE) Reduced Length of Stay and 30-Day Readmission Rates for US Patients with Methicillin-Resistant Staphylococcus aureus (MRSA) Bacteremia Including Endocarditis Compared with Standard of Care Antibiotics (SoC) Alone in a Phase 2 Study

Abstract Background Exebacase, a lysin (cell wall hydrolase), is the first direct lytic agent to report Phase 2 study results in Staphylococcus aureus bacteremia including endocarditis. Among MRSA patients enrolled in this randomized, double-blind, placebo, controlled study, EXE used in addition to standard of care antibiotics (SoC), had 42.8% higher clinical responder rates (CRRs) compared SoC alone. We sought to determine whether these differences in CRRs translated into reductions in health resource utilization (HRU) in this population of critically ill, hospitalized patients. Methods The microbiological intent-to-treat population included 116 patients (71 EXE, 45 SoC) with documented S. aureus who received a single 2-hour infusion of blinded study drug dosed based on target attainment. The primary efficacy endpoint was CRR at Day 14. Diagnoses and clinical outcomes were determined by a blinded Adjudication Committee. HRU including length of stay (LOS), and 30-day hospital readmission rates (HRR) for all causes (AC) and for S. aureus (SA) were evaluated in MRSA patients who were alive at the time of discharge. Results The average patient was white, male and ~56 years old (67.8%). Twenty-seven EXe patients (38.0%) and 16 SoC patients (35.6%) had MRSA. All but 2 MRSA patients (1 EXE, 1 SoC) were enrolled in the United States. The Day 14 CRR were 70.4% for EXE and 60.0% for SoC groups (p=0.314) overall. In a prespecified analysis of MRSA patients, the CRR with EXE was 74.1% vs. 31.3% with SoC (P = 0.010). Among MRSA patients who received study drug, incidence of treatment emergent adverse events (TEAEs) was balanced between groups (24 (88.9%) in EXE and 15 (98.3%) in SoC) as were serious TEAEs (17(63.0%) in EXE, 12 (75%) in SoC). 1 EXE and 2 SoC US MRSA patients died in hospital. Among US MRSA patients discharged alive from the hospital, the median LOS after study drug was 6 vs. 10 days for EXE and SoC, respectively. Thirty-day AC HRR were 16% vs. 30.8%, for EXE vs. SoC, respectively, and 30-day SA HRR were 8% vs. 15.4%, respectively. Conclusions Exebacase used in addition to SoC was associated with a reduction in length of hospital stay and 30-day readmission rates for all causes and for S. aureus compared with SoC alone in patients being treated for MRSA bacteremia/endocarditis. Disclosures Cara Cassino, MD, ContraFect Corporation (Employee), Hemal Shah, PharmD, Boehringer Ingelheim (Consultant), ContraFect Corp (Consultant), DBV Technologies (Consultant), Mylan specialty (Consultant), Nabriva (Consultant), Joy Lipka-Diamond, MS, ContraFect Corporation (Consultant), Anita F. Das, PhD, Achaogen (Consultant), AntiobioTx (Consultant), Boston Pharmaceuticals (Consultant), Cempra (Consultant), ContraFect Corporation (Consultant), Iterum Therapeutics (Consultant), Nabriva (Consultant), Paratek (Consultant), Tetraphase (Consultant), UTILITY (Consultant), Wockhardt (Consultant).