The efficacy of ZEVTERA in the treatment of adult patients with SAB, including right-sided infective endocarditis, was demonstrated in a randomized, controlled, double-blind, multinational, multicenter trial (Trial 1, NCT03138733). In this trial, adult patients were randomized to either ZEVTERA 667 mg (equivalent to 500 mg of ceftobiprole) IV every 6 hours from study Day 1 to Day 8, and 667 mg IV every 8 hours from study Day 9 onwards) or daptomycin (6 mg/kg up to 10 mg/kg IV every 24 hours) plus optional aztreonam for coverage of gram-negative co-infections (the comparator). Randomization was stratified by study site, dialysis status, and use of prior antibacterial drugs. The study was performed in two cohorts based on findings in animal studies [see Nonclinical Toxicology (13.2)]. The initial cohort was enrolled to receive a maximum treatment duration of 28 days. Based on a safety evaluation of cohort 1, patients could be enrolled in cohort 2 to receive a treatment duration of up to 42 days. The duration of study treatment was based on the investigator's clinical evaluation.
Study patients were required to have at least one positive blood culture for S. aureus obtained within 72 hours prior to randomization, signs and symptoms of bacteremia (fever, elevated white blood cell count or immature neutrophils, tachycardia, or hypotension), and at least one of the following conditions of complicated S. aureus bacteremia: chronic dialysis, persistent SAB, acute bacterial skin and skin structure infection, metastatic infections of native tissue, osteomyelitis, epidural or cerebral abscess, or definite native-valve right-sided infective endocarditis by Modified Duke's Criteria. Patients with uncomplicated S. aureus bacteremia, left-sided infective endocarditis, prosthetic heart valves, foreign body material that could not be removed, severe neutropenia, or pneumonia, were excluded from the study.
Upon entry, patients were classified for likelihood of endocarditis using the modified Duke's criteria (definite, possible, or rejected). Echocardiography, including a transesophageal echocardiogram, was to be performed during screening or within 7 days following study enrollment. Final diagnoses were to be made by the study investigators within 7 days of randomization. The final diagnosis for persistent S. aureus bacteremia was made by an independent treatment-blinded Data Review Committee (DRC).
A total of 390 patients (192 ZEVTERA, 198 daptomycin) with SAB were randomized from 60 centers in the USA, Europe, Latin America, and South Africa. The modified ITT (mITT) population was used for the primary efficacy analysis, comprising 387 patients (189 ZEVTERA, 198 daptomycin ± aztreonam) who received study drugs and had a baseline blood culture positive for S. aureus.
Patient demographic and baseline characteristics were balanced between the treatment groups. The median age among the 387 patients in the mITT population was 58 years, ranging from 19 to 91 years), with 31% aged ≥ 65 years, 69% of patients were male, and 96% were White.
Frequent conditions of complicated SAB included acute bacterial skin and skin structure infections (61%), intra-abdominal abscesses (14%), osteoarticular infections (13%), and patients on chronic dialysis (13%). A total of 6.5% of patients had definite right-sided infective endocarditis. A total of 24% had bacteremia caused by methicillin-resistant S. aureus (MRSA).
The primary efficacy outcome in the study was overall success at the post-treatment evaluation (PTE) visit at 70 days post-randomization in the mITT population, as assessed by the independent DRC.
Overall success required survival, symptom improvement, S. aureus bacteremia bloodstream clearance, no new S. aureus bacteremia complications, and no use of other potentially effective antibacterial drugs.
Overall success rates at the PTE visit in the mITT population were 69.8% (132/189) in patients treated with ZEVTERA and 68.7% (136/198) in patients treated with the comparator. The overall primary study outcome and in pre-defined subgroups in the mITT population is shown in Table 12.
Table 12: Data Review Committee Overall Success Rate at the PTE Visit in the mITT Population from the Adult SAB Patients in Trial 1| Group/Subgroup | ZEVTERA n/N (%) | Daptomycin ± aztreonam n/N (%) | Between-group Difference (%) (2-sided 95% CI)
|
|---|
| Overall | 132/189 (69.8) | 136/198 (68.7) | 2.0 (−7.1, 11.1) |
| MSSA (methicillin-susceptible) | 100/141 (70.9) | 97/146 (66.4) | 4.8 (−5.9, 15.5) |
| MRSA (methicillin-resistant) | 31/45 (68.9) | 38/49 (77.6) | −8.3 (−25.3, 8.6) |
| ABSSSI | 81/116 (69.8) | 80/121 (66.1) | 4.5 (−7.3, 16.3) |
| Definite right-sided infective endocarditis | 10/15 (66.7) | 7/10 (70.0) | −6.6 (−40.1, 27.0) |
For patients enrolled in Ukraine, overall success rates at the PTE visit in the mITT population were 77/84 (84.1%) in patients treated with ZEVTERA and 82/92 (89.1%) in patients treated with the comparator. For patients enrolled outside Ukraine, overall success rates at the PTE visit in the mITT population were 58/101 (57.4%) in patients treated with ZEVTERA and 54/106 (50.9%) in patients treated with the comparator.
All-cause mortality between randomization and the PTE visit was observed in 17/189 (9.0%) patients treated with ZEVTERA, and 18/198 (9.1%) patients treated with the comparator. Other key secondary efficacy outcomes included microbiological eradication at the PTE visit in the mITT population, which was achieved in 82% of patients treated with ZEVTERA and 77% of patients treated with the comparator, and the development of new S. aureus bacteremia complications, which occurred in 6% of patients treated with ZEVTERA and 6% of patients treated with the comparator. S. aureus bloodstream clearance, defined as 2 consecutive study days with negative blood cultures for S. aureus with no subsequent S. aureus relapse or reinfection, was achieved after a median of 4 days in each treatment group.
S. aureus bloodstream clearance in patients with MSSA was achieved after a median of 3 days in patients treated with ZEVTERA and after a median of 4 days in patients treated with the comparator.
S. aureus bloodstream clearance in patients with MRSA was achieved after a median of 5 days in each treatment group. Failure of treatment due to relapse of S. aureus bacteremia was assessed by the DRC in two patients (1%) treated with ZEVTERA, and in four patients (2%) treated in the comparator arm. No increase in ceftobiprole MIC was observed for the two isolates from the ZEVTERA-treated patients.