CLINICAL PHARMACOLOGY
Mechanism Of Action
ZERBAXA is an antibacterial
drug [see Microbiology].
Pharmacodynamics
As with other beta-lactam
antibacterial agents, the time 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 time above a threshold concentration has been determined to be
the parameter that best predicts the efficacy of tazobactam in in vitro nonclinical
models. The exposure-response analyses in Phase 2 trials support the
recommended dose 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. Therefore,
ZERBAXA does not affect cardiac repolarization.
Pharmacokinetics
The mean pharmacokinetic parameters
of ZERBAXA in healthy adults with normal renal function after single and
multiple 1-hour intravenous infusions of ZERBAXA 1.5 gram (ceftolozane 1 g and
tazobactam 0.5 g) administered every 8 hours are summarized in Table 6.
Pharmacokinetic parameters were similar for single-and multiple-dose
administrations.
Table 6: Mean (CV%) Plasma Pharmacokinetic Parameters
of ZERBAXA (ceftolozane and tazobactam) After Single and Multiple Intravenous
1-hour Infusions of ZERBAXA 1.5 g (ceftolozane 1 g and tazobactam 0.5 g) Every
8 Hours in Healthy Adults
PK parameters |
ZERBAXA 1.5 g (ceftolozane 1 g and tazobactam 0.5 g) every 8 hours |
Ceftolozane |
Tazobactam |
Day 1
(n=9)* |
Day 10
(n=10) |
Day 1
(n=9)* |
Day 10
(n=10) |
Cmax (mcg/mL) |
69.1 (11) |
74.4 (14) |
18.4 (16) |
18 (8) |
tmax (h)† |
1.02 (1.01, 1.1) |
1.07 (1, 1.1) |
1.02 (0.99, 1.03) |
1.01 (1, 1.1) |
AUC (mcg•h/mL)‡ |
172 (14) |
182 (15) |
24.4 (18) |
25 (15) |
t½ (h) |
2.77 (30) |
3.12 (22) |
0.91 (26)§ |
1.03 (19) |
* N=9, one outlier subject
excluded from descriptive statistics
† Median (minimum, maximum) presented
‡ AUC for Day 1 = AUClast and AUC for Day 10 = steady state AUC (AUCT,SS).
Daily AUC at steady state is calculated by multiplying the Day 10 AUC values by
three (e.g., 546 mcg•h/mL for ceftolozane and 75 mcg•h/mL for tazobactam)
§ N=8, one subject excluded from descriptive statistics as the
concentration-time profile did not exhibit a terminal log-linear phase and t½ could
not be calculated |
The Cmax and AUC of ZERBAXA increase in proportion to dose. Plasma levels of ZERBAXA do not increase
appreciably following multiple intravenous infusions of ZERBAXA up to 3 g
(ceftolozane 2 g and tazobactam 1 g) administered every 8 hours for up to 10
days in healthy adults with normal renal function. The elimination half-life (t½)
of ceftolozane is independent of dose.
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.
Elimination
Ceftolozane is eliminated from
the body by renal excretion with a half-life of approximately 3 hours.
Tazobactam is eliminated by renal excretion and metabolism with a plasma
half-life of approximately 1 hour.
Metabolism
Ceftolozane is not a substrate
for CYP enzymes and is mainly eliminated in the urine as unchanged parent drug
and thus does not appear to be metabolized to any appreciable extent. 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
Patients With Renal Impairment
ZERBAXA and the tazobactam metabolite M1 are eliminated
by the kidneys.
The ceftolozane dose normalized geometric mean AUC
increased up to 1.26-fold, 2.5-fold, and 5-fold in subjects with mild,
moderate, and severe renal impairment, 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. The recommended dose in
subjects with ESRD on HD is a single loading dose of ZERBAXA 750 mg
(ceftolozane 500 mg and tazobactam 250 mg), followed by a ZERBAXA 150 mg
(ceftolozane 100 mg and tazobactam 50 mg) maintenance dose administered every 8
hours for the remainder of the treatment period. On HD days, administer the
dose at the earliest possible time following completion of HD [see DOSAGE
AND ADMINISTRATION].
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 trend in exposure was observed with regard to age.
No dose adjustment of ZERBAXA based on age is
recommended.
Pediatric Patients
Safety and effectiveness in pediatric patients have not
been established.
Gender
In a population pharmacokinetic analysis of ZERBAXA, no
clinically relevant differences in AUC were observed for ceftolozane (116 males
compared to 70 females) and tazobactam (80 males compared to 50 females).
No dose adjustment is recommended based on gender.
Race
In a population pharmacokinetic analysis of ZERBAXA, no
clinically relevant differences in ZERBAXA AUC were observed in Caucasians (n =
156) compared to all other races combined (n = 30).
No dose adjustment is recommended based on race.
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 E. coli and K.
pneumoniae, that produced beta-lactamases, were susceptible to ZERBAXA (minimum
inhibitory concentration ≤ 2 mcg/mL). 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 E. coli and K. pneumoniae that were not susceptible to ZERBAXA
(minimum inhibitory concentration > 2 mcg/mL). These isolates produced one or
more beta-lactamases of the following enzyme groups: CTX-M, OXA, TEM, or SHV.
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 AND
USAGE].
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
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
Morganella morganii
Proteus vulgaris
Providencia rettgeri
Providencia stuartii
Serratia liquefaciens
Serratia marcescens
Gram-positive Bacteria
Streptococcus agalactiae
Streptococcus intermedius
Susceptibility Test Methods
When available, the clinical microbiology laboratory
should provide cumulative reports of in vitro susceptibility test results for
antimicrobial drugs used in local hospitals and practice areas to the physician
as periodic reports that describe the susceptibility profile of nosocomial and
community-acquired pathogens. These reports should aid the physician in
selecting an antibacterial drug for treatment.
Dilution Techniques
Quantitative methods are used to determine antimicrobial
minimum inhibitory concentrations (MICs). Ceftolozane and tazobactam
susceptibility testing is performed with a fixed 4 mcg/mL concentration of
tazobactam. These MICs provide estimates of the susceptibility of bacteria to
antibacterial compounds. The MICs should be determined using a standardized
test method (broth, and/or agar).1,4 The MIC values should be
interpreted according to the criteria in Table 7.
Diffusion Techniques
Quantitative methods that require measurement of zone
diameters can also provide reproducible estimates of the susceptibility of
bacteria to antimicrobial compounds. The zone size should be determined using a
standardized test method.2,4 This procedure uses paper disks
impregnated with 30 mcg of ceftolozane and 10 mcg of tazobactam to test the
susceptibility of bacteria to ceftolozane and tazobactam. The disk diffusion
should be interpreted according to the criteria in Table 7.
Anaerobic Techniques
For anaerobic bacteria, the susceptibility to ceftolozane
and tazobactam can be determined by standardized test method.3 The
MIC values obtained should be interpreted according to criteria provided in
Table 7.
Table 7: Susceptibility Test Interpretive Criteria for
Ceftolozane/Tazobactam
Pathogen |
Minimum Inhibitory Concentrations (mcg/mL) |
Disk Diffusion Zone Diameter (mm) |
S |
I |
R |
S |
I |
R |
Enterobacteriaceae |
≤ 2/4 |
4/4 |
≥ 8/4 |
≥ 21 |
18-20 |
≤ 17 |
Pseudomonas aeruginosa |
≤ 4/4 |
8/4 |
≥ 16/4 |
≥ 21 |
17-20 |
≤ 16 |
Streptococcus anginosus Streptococcus constellatus and Streptococcus salivarius |
≤ 8/4 |
16/4 |
≥ 32/4 |
--- |
--- |
--- |
Bacteroides fragilis |
≤ 8/4 |
16/4 |
≥ 32/4 |
--- |
--- |
--- |
S= susceptible, I =
intermediate, R = resistant |
A report of Susceptible
(S) indicates that the antimicrobial is likely to inhibit growth of the
pathogen if the antimicrobial drug reaches the concentration usually achievable
at the site of infection. A report of Intermediate (I) indicates that
the result should be considered equivocal, and if the microorganism is not
fully susceptible to alternative clinically feasible drugs, the test should be
repeated. This category implies possible clinical applicability in body sites
where the drug is physiologically concentrated or in situations where a high
dose of the drug can be used. This category also provides a buffer zone that
prevents small uncontrolled technical factors from causing major discrepancies
in interpretation. A report of Resistant (R) indicates that the
antimicrobial is not likely to inhibit growth of the pathogen if the
antimicrobial drug reaches the concentrations usually achievable at the
infection site; other therapy should be selected.
Quality Control
Standardized susceptibility test procedures require the
use of laboratory controls to monitor and ensure the accuracy and precision of
supplies and reagents used in the assay, and the techniques of the individuals
performing the test.1,2,3,4 Standard ceftolozane and tazobactam
powder should provide the following range of MIC values provided in Table 8.
For the diffusion technique using the 30 mcg ceftolozane/10 mcg tazobactam
disk, the criteria provided in Table 8 should be achieved.4
Table 8: Acceptable Quality Control Ranges for
Ceftolozane/Tazobactam
Quality Control Strain |
Minimum Inhibitory Concentrations (mcg/mL) |
Disk Diffusion (Zone Diameters in mm) |
Escherichia coli ATCC 25922 |
0.12/4-0.5/4 |
24-32 |
Escherichia coli* ATCC 35218 |
0.06/4-0.25/4 |
25-31 |
Pseudomonas aeruginosa ATCC 27853 |
0.25/4-1/4 |
25-31 |
Staphylococcus aureus ATCC 25923 |
Not Applicable |
10-18 |
Staphylococcus aureus ATCC 29213 |
16/4-64/4 |
Not Applicable |
Haemophilus influenzae† ATCC 49247 |
0.5/4-2/4 |
23-29 |
Klebsiella pneumoniae* ATCC 700603 |
0.5/4-2/4 |
17-25 |
Streptococcus pneumoniae ATCC 49619 |
0.25/4-1/4 |
21-29 |
Bacteroides fragilis ATCC 25285 (agar and broth) |
0.12/4-1/4 |
Not Applicable |
Bacteroides thetaiotaomicron ATCC 29741 (agar) |
16/4-128/4 |
Not Applicable |
Bacteroides thetaiotaomicron ATCC 29741 (broth) |
16/4-64/4 |
Not Applicable |
ATCC = American Type Culture
Collection
* Store E. coli ATCC 35218 and K. pneumoniae ATCC 700603
stock cultures at -60°C or below and prepare working stock cultures weekly.
† This strain may lose its plasmid and develop
susceptibility to beta-lactam antimicrobial agents after repeated transfers
onto culture media. Minimize by removing new culture from storage at least
monthly or whenever the strain begins to show increased zone diameters to
ampicillin, piperacillin, or ticarcillin. |
Clinical Studies
Complicated Intra-abdominal
Infections
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 9. Clinical cure rates at the TOC visit by pathogen
in the MITT population are presented in Table 10.
Table 9: 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 10: 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.
Complicated Urinary Tract
Infections, Including Pyelonephritis
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 11). Composite microbiological and
clinical cure rates at the TOC visit by pathogen in the mMITT population are
presented in Table 12.
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 11).
Table 11: 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 12: Composite Microbiological and Clinical Cure
Rates in a Phase 3 Trial of Complicated Urinary Tract Infections, in Subgroups
Defined by Baseline Pathogen (mMITT Population)a
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.
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