Clinical Pharmacology for Zerbaxa
Mechanism Of Action
ZERBAXA is an antibacterial drug [see Microbiology].
Pharmacodynamics
As with other beta-lactam antibacterial agents, the percent time of dosing interval that the plasma concentration of ceftolozane exceeds the minimum inhibitory concentration (MIC) of the infecting organism has been shown to be the best predictor of efficacy in animal models of infection. The percent time of dosing interval that the plasma concentration of tazobactam exceeds a threshold concentration has been determined to be the parameter that best predicts the efficacy of tazobactam in in vitro and in vivo models. The exposure-response analyses in efficacy and safety clinical trials for cIAI, cUTI, and HABP/VABP support the recommended dose regimens of ZERBAXA.
Cardiac Electrophysiology
In a randomized, positive and placebo-controlled crossover thorough QTc study, 51 healthy subjects were administered a single therapeutic dose of ZERBAXA 1.5 gram (ceftolozane 1 g and tazobactam 0.5 g) and a supratherapeutic dose of ZERBAXA 4.5 gram (ceftolozane 3 g and tazobactam 1.5 g). No significant effects of ZERBAXA on heart rate, electrocardiogram morphology, PR, QRS, or QT interval were detected.
Pharmacokinetics
Ceftolozane and tazobactam pharmacokinetics are similar following single- and multiple-dose administrations. The Cmax and AUC of ceftolozane and tazobactam increase in proportion to dose. The mean steady-state population pharmacokinetic parameters of ZERBAXA in patients with cIAI and cUTI receiving 1-hour intravenous infusions of ZERBAXA 1.5 g (ceftolozane 1 g and tazobactam 0.5 g) or patients with HABP/VABP receiving 1-hour intravenous infusions of ZERBAXA 3 g (ceftolozane 2 g and tazobactam 1 g) every 8 hours are summarized in Table 9.
Table 9: Mean (SD) Steady-State Plasma Population Pharmacokinetic Parameters of ZERBAXA (ceftolozane and tazobactam) after Multiple Intravenous 1-hour Infusions of ZERBAXA 1.5 g (ceftolozane 1 g and tazobactam 0.5 g) or 3 g (ceftolozane 2 g and tazobactam 1 g) Every 8 Hours in Adult Patients with CrCl Greater than 50 mL/min
| PK parameters |
ZERBAXA 1.5 g (ceftolozane 1 g and tazobactam 0.5 g) in cIAI and
cUTI Patients |
ZERBAXA 3 g (ceftolozane 2 g and tazobactam 1 g) in HABP/VABP
Patients |
Ceftolozane
(n=317) |
Tazobactam
(n=244) |
Ceftolozane
(n=247) |
Tazobactam
(n=247) |
| Cmax (mcg/mL) |
65.7 (27) |
17.8 (9) |
105 (46) |
26.4 (13) |
AUC0-8,ss
(mcg•h/mL) |
186 (74) |
35.8 (57) |
392 (236) |
73.3 (76) |
Distribution
The binding of ceftolozane and tazobactam to human plasma proteins is approximately 16% to 21% and 30%, respectively. The mean (CV%) steady-state volume of distribution of ZERBAXA in healthy adult males (n = 51) following a single intravenous dose of ZERBAXA 1.5 g (ceftolozane 1 g and tazobactam 0.5 g) was 13.5 L (21%) and 18.2 L (25%) for ceftolozane and tazobactam, respectively, similar to extracellular fluid volume.
Following 1-hour intravenous infusions of ZERBAXA 3 g (ceftolozane 2 g and tazobactam 1 g) or adjusted based on renal function every 8 hours in ventilated patients with confirmed or suspected pneumonia (N=22), mean pulmonary epithelial lining fluid-to-free plasma AUC ratios of ceftolozane and tazobactam were approximately 50% and 62%, respectively, and are similar to those in healthy subjects (approximately 61% and 63%, respectively) receiving ZERBAXA 1.5 g (ceftolozane 1 g and tazobactam 0.5 g). Minimum ceftolozane and tazobactam epithelial lung lining fluid concentrations in ventilated subjects at the end of the dosing interval were 8.2 mcg/mL and 1.0 mcg/mL, respectively.
Elimination
Ceftolozane is eliminated from the body by renal excretion with a mean half-life of approximately 3 to 4 hours. Tazobactam is eliminated by renal excretion and metabolism with a plasma mean half-life of approximately 2 to 3 hours. The elimination half-life (t1/2) of ceftolozane or tazobactam is independent of dose.
Metabolism
Ceftolozane does not appear to be metabolized to any appreciable extent and is not a substrate for CYP enzymes. The beta-lactam ring of tazobactam is hydrolyzed to form the pharmacologically inactive tazobactam metabolite M1.
Excretion
Ceftolozane, tazobactam and the tazobactam metabolite M1 are excreted by the kidneys. Following administration of a single ZERBAXA 1.5 g (ceftolozane 1 g and tazobactam 0.5 g) intravenous dose to healthy male adults, greater than 95% of ceftolozane was excreted in the urine as unchanged parent drug. More than 80% of tazobactam was excreted as the parent compound with the remainder excreted as the tazobactam M1 metabolite. After a single dose of ZERBAXA, renal clearance of ceftolozane (3.41 – 6.69 L/h) was similar to plasma CL (4.10 to 6.73 L/h) and similar to the glomerular filtration rate for the unbound fraction, suggesting that ceftolozane is eliminated by the kidney via glomerular filtration. Tazobactam is a substrate for OAT1 and OAT3 transporters and its elimination has been shown to be inhibited by probenecid, an inhibitor of OAT1/3.
Specific Populations
Dose adjustment is not warranted on the basis of age (18 years and older), gender, or race/ethnicity. No significant differences in the pharmacokinetics of ceftolozane and tazobactam were observed based on age (18 years and older), gender, weight, or race/ethnicity.
Patients With Renal Impairment
The ceftolozane dose normalized geometric mean AUC increased up to 1.26-fold, 2.5-fold, and 5-fold in subjects with CrCl 80-51 mL/min, 50-30 mL/min, and 29-15 mL/min, respectively, compared to healthy subjects with normal renal function. The respective tazobactam dose normalized geometric mean AUC increased approximately up to 1.3-fold, 2-fold, and 4-fold. To maintain similar systemic exposures to those with normal renal function, dosage adjustment is required [see DOSAGE AND ADMINISTRATION].
In subjects with ESRD on HD, approximately two-thirds of the administered ZERBAXA dose is removed by HD. A single loading dose of ZERBAXA followed by a maintenance dose administered every 8 hours for the remainder of the treatment period is recommended in patients with ESRD on HD. On HD days, administer the dose at the earliest possible time following completion of HD. [see DOSAGE AND ADMINISTRATION]
Patients With Augmented Renal Function
Following a single 1-hour intravenous infusion of ZERBAXA 3 g (ceftolozane 2 g and tazobactam 1 g) to critically-ill patients with CrCl greater than or equal to 180 mL/min (N=10), mean terminal half-life values of ceftolozane and tazobactam were 2.6 hours and 1.5 hours, respectively. No dose adjustment of ZERBAXA is recommended for HABP/VABP patients with augmented renal function [see Clinical Studies].
Patients With Hepatic Impairment
As ZERBAXA does not undergo hepatic metabolism, the systemic clearance of ZERBAXA is not expected to be affected by hepatic impairment.
No dose adjustment is recommended for ZERBAXA in subjects with hepatic impairment.
Geriatric Patients
In a population pharmacokinetic analysis of ZERBAXA, no clinically relevant differences in exposure were observed with regard to age.
No dose adjustment of ZERBAXA based on age is recommended. Dosage adjustment for ZERBAXA in geriatric patients should be based on renal function [see DOSAGE AND ADMINISTRATION].
Pediatric Patients
The pharmacokinetics of ceftolozane and tazobactam in pediatric patients (birth to <18 years) were evaluated from 3 clinical studies: patients with proven or suspected gram-negative infection, cIAI, and cUTI. Ceftolozane exposures were numerically higher in pediatric patients with cUTI compared to pediatric patients with cIAI, however, such a difference was not observed for tazobactam (Table 10 and Table 11) [see Clinical Studies].
In patients with cIAI (Table 10) and cUTI (Table 11) total body clearance of both ceftolozane and tazobactam increases with age, with values in adolescents approaching those in the adult population. Whereas elimination half-life tends to decrease with a decrease of age. While ceftolozane exposures in pediatric patients with cIAI and cUTI overlap with the range of exposures seen in adults, in general they are lower than mean exposures in adults. Tazobactam exposures are comparable between pediatric and adult patients except for patients aged birth to <3 months (Group 5) with cUTI, who had higher exposures. Population pharmacokinetic analyses and target attainment simulations in pediatric patients with cIAI and cUTI demonstrated that the recommended pediatric dosing regimens for patients from birth to less than 18 years with eGFR greater than 50 mL/min/1.73 m2 result in no clinically relevant differences in systemic exposure to those in adult patients given ZERBAXA 1.5 grams.
There is insufficient information to assess the exposure of ZERBAXA in the pediatric patients with eGFR ≤ 50 mL/min/1.73 m2.
Table 10: Steady-State Plasma Population Pharmacokinetic Parameters (Mean and SD) of ZERBAXA (ceftolozane and tazobactam) in Pediatric cIAI Patients*
| Patient Characteristics |
Group 1
(12 to <18 years) |
Group 2
(6 to <12 years) |
Group 3
(2 to <6 years) |
| N=16 |
N=30 |
N=20 |
| Ceftolozane |
| AUC0-8 (mcg•h/mL) |
123 (46) |
116 (30) |
98.8 (26) |
| Ceoi (mcg/mL) |
51.1 (21) |
53.7 (18) |
42.4 (13) |
| t1/2 (hr) |
2.2 (0.4) |
1.8 (0.2) |
1.7 (0.3) |
| Vss (L) |
23.0 (14.6) |
11.5 (5.7) |
7.4 (3.2) |
| Clearance (L/h) |
9.55 (4.70) |
5.81 (2.15) |
3.58 (1.12) |
| Tazobactam |
| AUC0-8 (mcg•h/mL) |
31.7 (16) |
30.1 (7) |
23.4 (6) |
| Ceoi (mcg/mL) |
21.7 (10) |
21.4 (6) |
16.9 (6) |
| t1/2 (hr) |
1.3 (0.2) |
1.1 (0.2) |
1.0 (0.2) |
| Vss (L) |
18.8 (10.7) |
10.6 (6.2) |
7.1 (4.0) |
| Clearance (L/h) |
18.87 (7.54) |
11.02 (4.06) |
7.62 (2.40) |
AUC0-8, area under the curve in the dosing interval 0 to 8 hours at steady-state; Ceoi, concentration at the end of infusion; CL, elimination clearance; SD, standard deviation; t1/2, terminal half-life; VSS, steady-state volume of distribution.
*One patient was enrolled in Group 4 in the C/T arm but discontinued before the day of PK sample collection; one participant was enrolled for Group 5 in the C/T arm with steady-state ceftolozane PK parameter values: AUC0-8=173 mcg*h/mL; Ceoi=43.4 mcg/mL; and with tazobactam PK parameter values:
AUC0-8=69.9 mcg*h/mL; Ceoi=30.5 mcg/mL. |
Table 11: Steady-State Plasma Population Pharmacokinetic Parameters (Mean and SD) of ZERBAXA (ceftolozane and tazobactam) in Pediatric cUTI Patients
Patient
Characteristics |
Group 1
(12 to <18
years) |
Group 2
(6 to <12
years) |
Group 3
(2 to <6
years) |
Group 4
(3 months to <2
years) |
Group 5
(Birth to <3
months) |
| N=14 |
N=19 |
N=20 |
N=22 |
N=14 |
| Ceftolozane |
AUC0-8
(mcg•h/mL) |
177 (65) |
145 (54) |
133 (49) |
129 (57) |
144 (39) |
| Ceoi (mcg/mL) |
68.7 (21) |
60.8 (20) |
60.3 (24) |
50.3 (20) |
43.1 (12) |
| t1/2 (hr) |
2.3 (0.4) |
2.0 (0.6) |
1.8 (0.4) |
2.0 (0.7) |
2.7 (0.6) |
| Vss (L) |
15.8 (5.5) |
10.7 (5.2) |
5.4 (2.1) |
3.7 (2.5) |
2.5 (1.0) |
| Clearance (L/h) |
6.31 (2.17) |
4.84 (2.18) |
2.59 (0.69) |
1.53 (0.64) |
0.75 (0.34) |
| Tazobactam |
AUC0-8
(mcg•h/mL) |
35.0 (12) |
26.7 (10) |
26.6 (8) |
28.6 (13) |
44.6 (15) |
| Ceoi (mcg/mL) |
22.9 (8) |
19.2 (7) |
19.9 (7) |
18.9 (8) |
25.9 (10) |
| t1/2 (hr) |
1.3 (0.5) |
1.2 (0.4) |
1.0 (0.3) |
1.1 (0.4) |
1.2 (0.7) |
| Vss (L) |
16.0 (6.6) |
10.6 (8.2) |
5.1 (2.7) |
3.7 (3.4) |
1.5 (0.8) |
| Clearance (L/h) |
15.67 (4.49) |
12.83 (5.39) |
6.37 (2.02) |
3.53 (1.71) |
1.32 (0.81) |
| AUC0-8, area under the curve in the dosing interval 0 to 8 hours at steady-state; Ceoi, concentration at the end of infusion; CL, elimination clearance; SD, standard deviation; t1/2, terminal half-life; VSS, steady-state volume of distribution. |
For ZERBAXA dosage recommendation in pediatric cIAI and cUTI patients, refer to table 2 [see DOSAGE AND ADMINISTRATION].
Drug Interactions
No drug-drug interaction was observed between ceftolozane and tazobactam in a clinical study in 16 healthy subjects. In vitro and in vivo data indicate that ZERBAXA is unlikely to cause clinically relevant drug-drug interactions related to CYPs and transporters at therapeutic concentrations.
Drug Metabolizing Enzymes
In vivo data indicated that ZERBAXA is not a substrate for CYPs. Thus, clinically relevant drug-drug interactions involving inhibition or induction of CYPs by other drugs are unlikely to occur.
In vitro studies demonstrated that ceftolozane, tazobactam and the M1 metabolite of tazobactam did not inhibit CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, or CYP3A4 and did not induce CYP1A2, CYP2B6, or CYP3A4 at therapeutic plasma concentrations. In vitro induction studies in primary human hepatocytes demonstrated that ceftolozane, tazobactam, and the tazobactam metabolite M1 decreased CYP1A2 and CYP2B6 enzyme activity and mRNA levels in primary human hepatocytes as well as CYP3A4 mRNA levels at supratherapeutic plasma concentrations. Tazobactam metabolite M1 also decreased CYP3A4 activity at supratherapeutic plasma concentrations. A clinical drug-drug interaction study was conducted and results indicated drug interactions involving CYP1A2 and CYP3A4 inhibition by ZERBAXA are not anticipated.
Membrane Transporters
Ceftolozane and tazobactam were not substrates for P-gp or BCRP, and tazobactam was not a substrate for OCT2, in vitro at therapeutic concentrations.
Tazobactam is a known substrate for OAT1 and OAT3. Co-administration of tazobactam with the OAT1/OAT3 inhibitor probenecid has been shown to prolong the half-life of tazobactam by 71%. Coadministration of ZERBAXA with drugs that inhibit OAT1 and/or OAT3 may increase tazobactam plasma concentrations.
In vitro data indicate that ceftolozane did not inhibit P-gp, BCRP, OATP1B1, OATP1B3, OCT1, OCT2, MRP, BSEP, OAT1, OAT3, MATE1, or MATE2-K in vitro at therapeutic plasma concentrations. In vitro data indicate that neither tazobactam nor the tazobactam metabolite M1 inhibit P-gp, BCRP, OATP1B1, OATP1B3, OCT1, OCT2, or BSEP transporters at therapeutic plasma concentrations. In vitro, tazobactam inhibited human OAT1 and OAT3 transporters with IC50 values of 118 and 147 mcg/mL, respectively. A clinical drug-drug interaction study was conducted and results indicated clinically relevant drug interactions involving OAT1/OAT3 inhibition by ZERBAXA are not anticipated.
Microbiology
Mechanism Of Action
Ceftolozane belongs to the cephalosporin class of antibacterial drugs. The bactericidal action of ceftolozane results from inhibition of cell wall biosynthesis, and is mediated through binding to penicillin-binding proteins (PBPs). Ceftolozane is an inhibitor of PBPs of P. aeruginosa (e.g., PBP1b, PBP1c, and PBP3) and E. coli (e.g., PBP3).
Tazobactam sodium has little clinically relevant in vitro activity against bacteria due to its reduced affinity to penicillin-binding proteins. It is an irreversible inhibitor of some beta-lactamases (e.g., certain penicillinases and cephalosporinases), and can bind covalently to some chromosomal and plasmid-mediated bacterial beta-lactamases.
Resistance
Mechanisms of beta-lactam resistance may include the production of beta-lactamases, modification of PBPs by gene acquisition or target alteration, up-regulation of efflux pumps, and loss of outer membrane porin.
Clinical isolates may produce multiple beta-lactamases, express varying levels of beta-lactamases, or have amino acid sequence variations, and other resistance mechanisms that have not been identified. Culture and susceptibility information and local epidemiology should be considered in selecting or modifying antibacterial therapy.
ZERBAXA demonstrated in vitro activity against Enterobacteriaceae in the presence of some extended-spectrum beta-lactamases (ESBLs) and other beta-lactamases of the following groups: TEM, SHV, CTX-M, and OXA. ZERBAXA is not active against bacteria that produce serine carbapenemases [K. pneumoniae carbapenemase (KPC)], and metallo-beta-lactamases.
In ZERBAXA clinical trials, some isolates of Enterobacteriaceae with minimum inhibitory concentration to ZERBAXA of ≤2 mcg/mL produced beta-lactamases. These isolates produced one or more beta-lactamases of the following enzyme groups: CTX-M, OXA, TEM, or SHV.
Some of these beta-lactamases were also produced by isolates of Enterobacteriaceae with minimum inhibitory concentration to ZERBAXA >2 mcg/mL.
ZERBAXA demonstrated in vitro activity against P. aeruginosa isolates tested that had chromosomal AmpC, loss of outer membrane porin (OprD), or up regulation of efflux pumps (MexXY, MexAB). Isolates resistant to other cephalosporins may be susceptible to ZERBAXA, although cross-resistance may occur.
Interaction With Other Antimicrobials
In vitro synergy studies suggest no antagonism between ZERBAXA and other antibacterial drugs (e.g., meropenem, amikacin, aztreonam, levofloxacin, tigecycline, rifampin, linezolid, daptomycin, vancomycin, and metronidazole).
Antimicrobial Activity
ZERBAXA has been shown to be active against the following bacteria, both in vitro and in clinical infections [see INDICATIONS].
Complicated Intra-abdominal Infections
Gram-negative Bacteria:
Enterobacter cloacae
Escherichia coli
Klebsiella oxytoca
Klebsiella pneumoniae
Proteus mirabilis
Pseudomonas aeruginosa
Gram-positive Bacteria:
Streptococcus anginosus
Streptococcus constellatus
Streptococcus salivarius
Anaerobic Bacteria:
Bacteroides fragilis
Complicated Urinary Tract Infections, Including Pyelonephritis
Gram-negative Bacteria:
Escherichia coli
Klebsiella pneumoniae
Proteus mirabilis
Pseudomonas aeruginosa
Hospital-acquired Bacterial Pneumonia and Ventilator-associated Bacterial Pneumonia (HABP/VABP)
Gram-negative Bacteria:
Enterobacter cloacae
Escherichia coli
Haemophilus influenzae
Klebsiella oxytoca
Klebsiella pneumoniae
Proteus mirabilis
Pseudomonas aeruginosa
Serratia marcescens
The following in vitro data are available, but their clinical significance is unknown. At least 90 percent of the following bacteria exhibit an in vitro minimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint for ceftolozane and tazobactam against isolates of similar genus or organism group. However, the efficacy of ZERBAXA in treating clinical infections due to these bacteria has not been established in adequate and well-controlled clinical trials.
Gram-negative Bacteria:
Citrobacter koseri
Klebsiella aerogenes
Morganella morganii
Proteus vulgaris
Providencia rettgeri
Providencia stuartii
Serratia liquefaciens
Gram-positive bacteria:
Streptococcus agalactiae
Streptococcus intermedius
Susceptibility Testing
For specific information regarding susceptibility test interpretive criteria and associated test methods and quality control standards recognized by FDA for ceftolozane and tazobactam, please see: https://www.fda.gov/STIC .
Clinical Studies
Complicated Intra-Abdominal Infections
Adult Patients
A total of 979 adults hospitalized with cIAI were randomized and received study medications in a multinational, double-blind study comparing ZERBAXA 1.5 g (ceftolozane 1 g and tazobactam 0.5 g) intravenously every 8 hours plus metronidazole (500 mg intravenously every 8 hours) to meropenem (1 g intravenously every 8 hours) for 4 to 14 days of therapy. Complicated intra-abdominal infections included appendicitis, cholecystitis, diverticulitis, gastric/duodenal perforation, perforation of the intestine, and other causes of intra-abdominal abscesses and peritonitis. The majority of patients (75%) were from Eastern Europe; 6.3% were from the United States.
The primary efficacy endpoint was clinical response, defined as complete resolution or significant improvement in signs and symptoms of the index infection at the test-of-cure (TOC) visit which occurred 24 to 32 days after the first dose of study drug. The primary efficacy analysis population was the microbiological intent-to-treat (MITT) population, which included all patients who had at least 1 baseline intra-abdominal pathogen regardless of the susceptibility to study drug. The key secondary efficacy endpoint was clinical response at the TOC visit in the microbiologically evaluable (ME) population, which included all protocol-adherent MITT patients.
The MITT population consisted of 806 patients; the median age was 52 years and 57.8% were male. The most common diagnosis was appendiceal perforation or peri-appendiceal abscess, occurring in 47% of patients. Diffuse peritonitis at baseline was present in 34.2% of patients.
ZERBAXA plus metronidazole was non-inferior to meropenem with regard to clinical cure rates at the TOC visit in the MITT population. Clinical cure rates at the TOC visit are displayed by patient population in Table 12. Clinical cure rates at the TOC visit by pathogen in the MITT population are presented in Table 13.
Table 12: Clinical Cure Rates in a Phase 3 Trial of Complicated Intra-Abdominal Infections
| Analysis Population |
ZERBAXA plus
Metronidazole*
n/N (%) |
Meropenem†
n/N (%) |
Treatment Difference
(95% CI)‡ |
| MITT |
323/389 (83) |
364/417 (87.3) |
-4.3 (-9.2, 0.7) |
| ME |
259/275 (94.2) |
304/321 (94.7) |
-0.5 (-4.5, 3.2) |
* ZERBAXA 1.5 g intravenously every 8 hours + metronidazole 500 mg intravenously every 8 hours
† 1 gram intravenously every 8 hours
‡ The 95% confidence interval (CI) was calculated as an unstratified Wilson Score CI. |
Table 13: Clinical Cure Rates by Pathogen in a Phase 3 Trial of Complicated Intra-abdominal Infections (MITT Population)
| Organism Group Pathogen |
ZERBAXA plus
Metronidazole
n/N (%) |
Meropenem
n/N (%) |
| Aerobic Gram-negative |
| Escherichia coli |
216/255 (84.7) |
238/270 (88.1) |
| Klebsiella pneumoniae |
31/41 (75.6) |
27/35 (77.1) |
| Pseudomonas aeruginosa |
30/38 (79) |
30/34 (88.2) |
| Enterobacter cloacae |
21/26 (80.8) |
24/25 (96) |
| Klebsiella oxytoca |
14/16 (87.5) |
24/25 (96) |
| Proteus mirabilis |
11/12 (91.7) |
9/10 (90) |
| Aerobic Gram-positive |
| Streptococcus anginosus |
26/36 (72.2) |
24/27 (88.9) |
| Streptococcus constellatus |
18/24 (75) |
20/25 (80) |
| Streptococcus salivarius |
9/11 (81.8) |
9/11 (81.8) |
| Anaerobic Gram-negative |
| Bacteroides fragilis |
42/47 (89.4) |
59/64 (92.2) |
| Bacteroides ovatus |
38/45 (84.4) |
44/46 (95.7) |
| Bacteroides thetaiotaomicron |
21/25 (84) |
40/46 (87) |
| Bacteroides vulgatus |
12/15 (80) |
24/26 (92.3) |
In a subset of the E. coli and K. pneumoniae isolates from both arms of the cIAI Phase 3 trial that met pre-specified criteria for beta-lactam susceptibility, genotypic testing identified certain ESBL groups (e.g., TEM, SHV, CTX-M, OXA) in 53/601 (9%). Cure rates in this subset were similar to the overall trial results. In vitro susceptibility testing showed that some of these isolates were susceptible to ZERBAXA (MIC ≤2 mcg/mL), while some others were not susceptible (MIC >2 mcg/mL). Isolates of a specific genotype were seen in patients who were deemed to be either successes or failures.
Pediatric Patients
The pediatric cIAI trial was a randomized, double-blind, multi-center, active controlled trial conducted in hospitalized patients from birth to less than 18 years (NCT03217136). Patients were randomized in a 3:1 ratio to either intravenous (IV) ZERBAXA [see DOSAGE AND ADMINISTRATION] plus metronidazole (10 mg/kg IV every 8 hours), or meropenem (20 mg/kg IV every 8 hours) plus placebo. Patients received IV study treatment for a minimum of 3 days before an optional switch to oral step-down therapy at the discretion of the investigator to complete a total of 5 to 14 days of antibacterial therapy.
The modified intent-to-treat (MITT) population consisted of 91 patients (N=70 in the ZERBAXA plus metronidazole group; N=21 in the meropenem plus placebo group) who were randomized and received at least one dose of study treatment. The median age of patients was 8.2 years and 8.5 years in the ZERBAXA plus metronidazole and meropenem plus placebo groups, respectively. In the ZERBAXA plus metronidazole group, enrollment by age group was as follows: 12 to <18 y: n=16, 6 to <12 y: n=30, 2 to <6 y: n=22, 3 months to <2 y: n=1, birth to <3 months: n=1. Patients treated with ZERBAXA plus metronidazole were predominantly male (67%) and White (87%). Patients treated with meropenem plus placebo were predominantly female (71%) and White (91%). Most patients in the MITT population had a diagnosis of complicated appendicitis at baseline (ZERBAXA plus metronidazole: 91.4%; meropenem plus placebo: 100%). The median (range) duration of IV study treatment was comparable between patients in the ZERBAXA plus metronidazole (6.3 [0.3 to 14.0] days) and meropenem plus placebo (6.0 [2.3 to 8.8] days) groups.
The primary objective of the study was to evaluate the safety and tolerability of ZERBAXA. Efficacy assessments were not powered for formal hypothesis testing of between-treatment group comparisons. At the TOC visit, which occurred 7 to 14 days after the last dose of study drug, a favorable clinical response was defined as complete resolution or marked improvement in signs and symptoms of the cIAI or return to pre-infection signs and symptoms such that no further antibiotic therapy (IV or oral) or surgical or drainage procedure was required for treatment of the cIAI. A summary of clinical response rates in the MITT and clinically evaluable (CE) populations at the TOC visit are presented in Table 14. The CE included all protocol adherent MITT patients with a clinical outcome at the visit of interest.
Table 14: Clinical Response Rates in a Pediatric Study of Complicated Intra-Abdominal Infections
Analysis
Population |
ZERBAXA plus
metronidazole
n/N (%) |
Meropenem
n/N (%) |
Treatment
Difference
(95% CI)* |
| MITT Population |
56/70 (80.0) |
21/21 (100.0) |
-19.1 (-30.2, -2.9) |
| CE Population |
52/58 (89.7) |
19/19 (100.0) |
-10.7 (-21.5, 6.8) |
| *The Miettinen & Nurminen method stratified by age group with Cochran-Mantel-Haenszel weights was used. |
Complicated Urinary Tract Infections, Including Pyelonephritis
Adult Patients
A total of 1068 adults hospitalized with cUTI (including pyelonephritis) were randomized and received study medications in a multinational, double-blind study comparing ZERBAXA 1.5 g (ceftolozane 1 g and tazobactam 0.5 g) intravenously every 8 hours to levofloxacin (750 mg intravenously once daily) for 7 days of therapy. The primary efficacy endpoint was defined as complete resolution or marked improvement of the clinical symptoms and microbiological eradication (all uropathogens found at baseline at ≥105 were reduced to <104 CFU/mL) at the test-of-cure (TOC) visit 7 (± 2) days after the last dose of study drug. The primary efficacy analysis population was the microbiologically modified intent-to-treat (mMITT) population, which included all patients who received study medication and had at least 1 baseline uropathogen. The key secondary efficacy endpoint was the composite microbiological and clinical cure response at the TOC visit in the microbiologically evaluable (ME) population, which included protocol-adherent mMITT patients with a urine culture at the TOC visit.
The mMITT population consisted of 800 patients with cUTI, including 656 (82%) with pyelonephritis. The median age was 50.5 years and 74% were female. Concomitant bacteremia was identified in 62 (7.8%) patients at baseline; 608 (76%) patients were enrolled in Eastern Europe and 14 (1.8%) patients were enrolled in the United States.
ZERBAXA demonstrated efficacy with regard to the composite endpoint of microbiological and clinical cure at the TOC visit in both the mMITT and ME populations (Table 15). Composite microbiological and clinical cure rates at the TOC visit by pathogen in the mMITT population are presented in Table 16. In the mMITT population, the composite cure rate in ZERBAXA-treated patients with concurrent bacteremia at baseline was 23/29 (79.3%).
Although a statistically significant difference was observed in the ZERBAXA arm compared to the levofloxacin arm with respect to the primary endpoint, it was likely attributable to the 212/800 (26.5%) patients with baseline organisms non-susceptible to levofloxacin. Among patients infected with a levofloxacin-susceptible organism at baseline, the response rates were similar (Table 15).
Table 15: Composite Microbiological and Clinical Cure Rates in a Phase 3 Trial of Complicated Urinary Tract Infections
| Analysis Population |
ZERBAXA*
n/N (%) |
Levofloxacin†
n/N (%) |
Treatment Difference
(95% CI)‡ |
| mMITT |
306/398 (76.9) |
275/402 (68.4) |
8.5 (2.3, 14.6) |
Levofloxacin resistant
baseline pathogen(s) |
60/100 (60) |
44/112 (39.3) |
|
No levofloxacin
resistant baseline
pathogen(s) |
246/298 (82.6) |
231/290 (79.7) |
| ME |
284/341 (83.3) |
266/353 (75.4) |
8.0 (2.0, 14.0) |
* ZERBAXA 1.5 g intravenously every 8 hours
† 750 mg intravenously once daily
‡ The 95% confidence interval was based on the stratified Newcombe method. |
Table 16: Composite Microbiological and Clinical Cure Rates in a Phase 3 Trial of Complicated Urinary Tract Infections, in Subgroups Defined by Baseline Pathogen (mMITT Population)
| Pathogen |
ZERBAXA
n/N (%) |
Levofloxacin
n/N (%) |
| Escherichia coli |
247/305 (81) |
228/324 (70.4) |
| Klebsiella pneumoniae |
22/33 (66.7) |
12/25 (48) |
| Proteus mirabilis |
11/12 (91.7) |
6/12 (50) |
| Pseudomonas aeruginosa |
6/8 (75) |
7/15 (46.7) |
In a subset of the E. coli and K. pneumoniae isolates from both arms of the cUTI Phase 3 trial that met pre-specified criteria for beta-lactam susceptibility, genotypic testing identified certain ESBL groups (e.g., TEM, SHV, CTX-M, OXA) in 104/687 (15%). Cure rates in this subset were similar to the overall trial results. In vitro susceptibility testing showed that some of these isolates were susceptible to ZERBAXA (MIC ≤2 mcg/mL), while some others were not susceptible (MIC >2 mcg/mL). Isolates of a specific genotype were seen in patients who were deemed to be either successes or failures.
Pediatric Patients
The cUTI pediatric trial was a randomized, double-blind multi-center, active controlled trial conducted in hospitalized patients from birth to less than 18 years (NCT03230838). Eligible patients were randomized in a 3:1 ratio to IV ZERBAXA or meropenem, respectively. Patients received IV study treatment for a minimum of 3 days before an optional switch to oral step-down therapy at the discretion of the investigator to complete a total of 7 to 14 days of antibacterial therapy.
The microbiologic modified intent-to-treat (mMITT) population consisted of 95 patients (N=71 in the ZERBAXA group; N=24 in the meropenem group) who were randomized and received at least one dose of study treatment and had an eligible uropathogen isolated from a baseline urine culture.
The median age of patients was 2.7 years and 1.6 years in the ZERBAXA and meropenem groups, respectively. In the ZERBAXA group, enrollment by age group was as follows: 12 to <18 y: n=10, 6 to <12 y: n=13, 2 to <6 y: n=14, 3 months to <2 y: n=20, birth to <3 months: n=14. Patients treated with ZERBAXA were predominantly female (56%) and White (99%). Patients treated with meropenem were predominantly female (63%) and White (100%). Most patients in the mMITT population had a diagnosis of pyelonephritis (ZERBAXA: 84.5%; meropenem: 79.2%). The most common baseline qualifying gram-negative uropathogens were Escherichia coli (ZERBAXA: 74.6%; meropenem: 87.5%), Klebsiella pneumoniae (8.5%; 4.2%), and Pseudomonas aeruginosa (7.0%; 8.3%).
The primary objective of the study was to evaluate the safety and tolerability of ZERBAXA. Efficacy assessments were not powered for formal hypothesis testing of between treatment group comparisons. At the TOC visit, which occurred 7 to 14 days after the last dose of study drug, a favorable clinical response was defined as complete resolution or marked improvement in signs and symptoms of the cUTI or return to pre-infection signs and symptoms, such that no further antibiotic therapy (IV or oral) was required for the treatment of the cUTI. A favorable microbiological response at the TOC was defined as eradication (all uropathogens found at baseline at ≥105 were reduced to <104 CFU/mL) of baseline uropathogens from the urine culture. A summary of clinical and microbiologic response rates in the mMITT population at the TOC visit is presented in Table 17.
Table 17: Clinical and Microbiological Response Rates in a Pediatric Study of Complicated Urinary Tract Infections
mMITT
Population |
ZERBAXA
n/N (%) |
Meropenem
n/N (%) |
Treatment Difference
(95% CI)* |
Clinical Response
Rate |
63/71 (88.7) |
23/24 (95.8) |
-7.3 (-18.0, 10.1) |
Microbiologic
Response Rate |
60/71 (84.5) |
21/24 (87.5) |
-3.0 (-17.1, 17.4) |
| *The Miettinen & Nurminen method stratified by age group with Cochran-Mantel-Haenszel weights was used. |
Hospital-Acquired Bacterial Pneumonia And Ventilator-Associated Bacterial Pneumonia (HABP/VABP)
Adult Patients
A total of 726 adult patients hospitalized with HABP/VABP were enrolled in a multinational, doubleblind study (NCT02070757) comparing ZERBAXA 3 g (ceftolozane 2 g and tazobactam 1 g) intravenously every 8 hours to meropenem (1 g intravenously every 8 hours) for 8 to 14 days of therapy. All patients had to be intubated and on mechanical ventilation at randomization.
Efficacy was assessed based on all-cause mortality at Day 28 and clinical cure, defined as complete resolution or significant improvement in signs and symptoms of the index infection at the test-of-cure (TOC) visit which occurred 7 to 14 days after the end of treatment. The analysis population was the intent-to-treat (ITT) population, which included all randomized patients.
Following a diagnosis of HABP/VABP and prior to receipt of first dose of study drug, if required, patients could have received up to a maximum of 24 hours of active non-study antibacterial drug therapy in the 72 hours preceding the first dose of study drug. Patients who had failed prior antibacterial drug therapy for the current episode of HABP/VABP could be enrolled if the baseline lower respiratory tract (LRT) culture showed growth of a Gram-negative pathogen while the patient was on the antibacterial therapy and all other eligibility criteria were met. Empiric therapy at baseline with linezolid or other approved therapy for Gram-positive coverage was required in all patients pending baseline LRT culture results. Adjunctive Gramnegative therapy was optional and allowed for a maximum of 72 hours in centers with a prevalence of meropenem-resistant P. aeruginosa more than 15%.
Of the 726 patients in the ITT population, the median age was 62 years and 44% of the population was 65 years of age and older, with 22% of the population 75 years of age and older. The majority of patients were White (83%), male (71%) and were from Eastern Europe (64%). The median APACHE II score was 17 and 33% of subjects had a baseline APACHE II score of greater than or equal to 20. All subjects were on mechanical ventilation and 519 (71%) had VABP. At randomization, 92% of subjects were in the ICU, 77% had been hospitalized for 5 days or longer, and 49% were ventilated for 5 days or longer. A total of 258 of 726 (36%) patients had CrCl less than 80 mL/min at baseline; among these, 99 (14%) had CrCl less than 50 mL/min. Patients with end-stage renal disease (CrCl less than 15 mL/min) were excluded from the trial. Approximately 13% of subjects were failing their current antibacterial drug therapy for HABP/VABP, and bacteremia was present at baseline in 15% of patients. Key comorbidities included diabetes mellitus, congestive heart failure, and chronic obstructive pulmonary disease at rates of 22%, 16%, and 12%, respectively. In both treatment groups, most subjects (63.1%) received between 8 and 14 days of study therapy as specified in the protocol.
Table 18 presents the results for Day 28 all-cause mortality and clinical cure at the TOC visit overall and by ventilated HABP and VABP.
Table 18: Day 28 All-cause Mortality and Clinical Cure Rates at TOC from a Phase 3 Study of Hospital-acquired Bacterial Pneumonia and Ventilator-associated Bacterial Pneumonia (HABP/VABP) (ITT Population)
| Endpoint |
ZERBAXA
n/N (%) |
Meropenem
n/N (%) |
Treatment
Difference (95% CI)* |
| Day 28 All-cause Mortality |
87/362 (24.0) |
92/364 (25.3) |
1.1 (-5.13, 7.39) |
| VABP |
63/263 (24.0) |
52/256 (20.3) |
-3.6 (-10.74, 3.52) |
| Ventilated HABP |
24/99 (24.2) |
40/108 (37.0) |
12.8 (0.18, 24.75) |
| Clinical Cure at TOC Visit |
197/362 (54.4) |
194/364 (53.3) |
1.1 (-6.17, 8.29) |
| VABP |
147/263 (55.9) |
146/256 (57.0) |
-1.1 (-9.59, 7.35) |
| Ventilated HABP |
50/99 (50.5) |
48/108 (44.4) |
6.1 (-7.44, 19.27) |
| * The CI for overall treatment difference was based on the stratified Newcombe method with minimum risk weights. The CI for treatment difference of each primary diagnosis was based on the unstratified Newcombe method. |
In the ITT population, Day 28 all-cause mortality and clinical cure rates in patients with CrCl greater than or equal to 150 mL/min were similar between ZERBAXA and meropenem. In patients with bacteremia at baseline, Day 28 all-cause mortality rates were 23/64 (35.9%) for ZERBAXA-treated patients and 13/41 (31.7%) for meropenem-treated patients; clinical cure rates were 30/64 (46.9%) and 15/41 (36.6%), respectively.
Per pathogen Day 28 all-cause mortality and clinical cure at TOC were assessed in the microbiologic intention to treat population (mITT), which consisted of all randomized subjects who had a baseline lower respiratory tract (LRT) pathogen that was susceptible to both study treatments. In the mITT population, Klebsiella pneumoniae (113/425, 26.6%) and Pseudomonas aeruginosa (103/425, 24.2%) were the most prevalent pathogens isolated from baseline LRT cultures.
Day 28 all-cause mortality and clinical cure rates at TOC by pathogen in the mITT population are presented in Table 19. In the mITT population, clinical cure rates in patients with a Gram-negative pathogen at baseline were 139/215 (64.7%) for ZERBAXA and 115/204 (56.4%) for meropenem, respectively.
Table 19: Day 28 All-cause Mortality and Clinical Cure Rates at TOC by Baseline Pathogen from a Phase 3 Study of Hospital-acquired Bacterial Pneumonia and Ventilator-associated Bacterial Pneumonia (HABP/VABP) (mITT population)
| Baseline Pathogen Category Baseline Pathogen |
Day 28 All-cause Mortality |
Clinical Cure at TOC |
ZERBAXA
n/N (%) |
Meropenem
n/N (%) |
ZERBAXA
n/N (%) |
Meropenem
n/N (%) |
| Pseudomonas aeruginosa |
12/47 (25.5) |
10/56 (17.9) |
29/47 (61.7) |
34/56 (60.7) |
| Enterobacteriaceae |
27/161 (16.8) |
42/157 (26.8) |
103/161
(64.0) |
87/157 (55.4) |
| Enterobacter cloacae |
2/15 (13.3) |
8/14 (57.1) |
8/15 (53.3) |
4/14 (28.6) |
| Escherichia coli |
10/50 (20.0) |
11/42 (26.2) |
32/50 (64.0) |
26/42 (61.9) |
| Klebsiella oxytoca |
3/14 (21.4) |
3/12 (25.0) |
9/14 (64.3) |
7/12 (58.3) |
| Klebsiella pneumoniae |
7/51 (13.7) |
13/62 (21.0) |
34/51 (66.7) |
39/62 (62.9) |
| Proteus mirabilis |
5/22 (22.7) |
5/18 (27.8) |
13/22 (59.1) |
11/18 (61.1) |
| Serratia marcescens |
3/14 (21.4) |
1/12 (8.3) |
8/14 (57.1) |
7/12 (58.3) |
| Haemophilus influenzae |
0/20 (0) |
2/15 (13.3) |
17/20 (85.0) |
8/15 (53.3) |
In a subset of Enterobacteriaceae isolates from both arms of the trial that met pre-specified criteria for beta-lactam susceptibility, genotypic testing identified certain ESBL groups (e.g., TEM, SHV, CTX-M, OXA) in 101/425 (23.8%). Day 28 all-cause mortality and clinical cure rates in this subset were similar to the overall trial results.