CLINICAL PHARMACOLOGY
Mechanism Of Action
AVYCAZ is an antibacterial drug [see Microbiology].
Pharmacodynamics
As with other beta-lactam antimicrobial drugs, the time that unbound plasma concentrations of ceftazidime exceed the AVYCAZ minimum inhibitory concentration (MIC) against the infecting organism has been shown to best correlate with efficacy in a neutropenic murine thigh infection model with Enterobacteriaceae and Pseudomonas aeruginosa. The time above a threshold concentration has been determined to be the parameter that best predicts the efficacy of avibactam in in vitro and in vivo nonclinical models.
Cardiac Electrophysiology
In a thorough QT study, a supratherapeutic dose of ceftazidime (3 grams) was investigated for QT effects in combination with a supratherapeutic dose of avibactam (2 grams) given as a 30-minute single infusion. No significant effect on QTcF interval was detected at peak plasma concentration or at any other time. The largest 90% upper bound for the placebo corrected mean change from baseline was 5.9 ms. There were no QTcF intervals greater than 450 ms, nor were there any QTcF interval changes from baseline greater than 30 ms.
Pharmacokinetics
The mean pharmacokinetic parameters for ceftazidime and avibactam in healthy adult male subjects with normal renal function after single and multiple 2-hour intravenous infusions of AVYCAZ 2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) administered every 8 hours are summarized in Table 12.
Pharmacokinetic parameters of ceftazidime and avibactam were similar for single and multiple dose administration of AVYCAZ and were similar to those determined when ceftazidime or avibactam were administered alone.
Table 12. Pharmacokinetic Parameters (Geometric Mean [%CV]) of Ceftazidime and Avibactam Following Administration of AVYCAZ 2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) in Healthy Adult Male Subjects
|
Ceftazidime |
Avibactam |
Parameter |
Single AVYCAZ 2.5 gramsa Dose Administered as a 2-hour Infusion (n = 16) |
Multiple AVYCAZ 2.5 gramsa Doses Administered every 8 hours as 2-hour Infusions for 11 Days (n = 16) |
Single AVYCAZ 2.5 gramsa Dose Administered as a 2-hour Infusion (n = 16) |
Multiple AVYCAZ 2.5 gramsa Doses Administered every 8 hours as 2-hour Infusions for 11 Days (n = 16) |
Cmax (mg/L) |
88.1 (14) |
90.4 (16) |
15.2 (14) |
14.6 (17) |
AUC (mg-h/L)b |
289 (15)c |
291 (15) |
42.1 (16)d |
38.2 (19) |
T1/2 (h) |
3.27 (33)c |
2.76 (7) |
2.22 (31)d |
2.71 (25) |
CL (L/h) |
6.93 (15)c |
6.86 (15) |
11.9 (16)d |
13.1 (19) |
Vss (L) |
18.1 (20)c |
17 (16) |
23.2 (23)d |
22.2 (18) |
CL = plasma clearance; Cmax = maximum observed concentration; d T1/2 = terminal elimination half-life; Vss (L) = volume of distribution at steady state
a ceftazidime 2 grams and avibactam 0.5 grams
b AUC0-inf (area under concentration-time curve from time 0 to infinity) reported for single-dose administration; AUC0-tau (area under concentration curve over dosing interval) reported for multiple-dose administration
c n = 15
d n = 13 |
The Cmax and AUC of ceftazidime increase in proportion to dose. Avibactam demonstrated approximately linear pharmacokinetics across the dose range studied (50 mg to 2000 mg) for single intravenous administration. No appreciable accumulation of ceftazidime or avibactam was observed following multiple intravenous infusions of AVYCAZ 2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) administered every 8 hours for up to 11 days in healthy adults with normal renal function.
Distribution
Less than 10% of ceftazidime was protein bound. The degree of protein binding was independent of concentration. The binding of avibactam to human plasma proteins was low (5.7% to 8.2%) and was similar across the range of concentrations tested in vitro (0.5 to 50 mg/L).
The steady-state volumes of distribution of ceftazidime and avibactam were 17 L and 22.2 L, respectively, in healthy adults following multiple doses of AVYCAZ 2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) infused every 8 hours over 2 hours for 11 days.
Following administration of AVYCAZ 2.5 g (ceftazidime 2 grams and avibactam 0.5 grams) to healthy male subjects every 8 hours as a 2-hour infusion for 3 days, the mean bronchial epithelial lining fluid-to-plasma ratios of avibactam Cmax and AUC0-tau were 35%. The mean bronchial epithelial lining fluid-to-plasma ratios of ceftazidime Cmax and AUC0-tau were 26% and 31%, respectively.
Metabolism
Ceftazidime is mostly (80% to 90% of the dose) eliminated as unchanged drug. No metabolism of avibactam was observed in human liver preparations (microsomes and hepatocytes). Unchanged avibactam was the major drug-related component in human plasma and urine after a single intravenous dose of 0.5 grams 14C-labelled avibactam.
Excretion
Both ceftazidime and avibactam are excreted mainly by the kidneys.
Approximately 80% to 90% of an intravenous dose of ceftazidime is excreted unchanged by the kidneys over a 24-hour period. After the intravenous administration of single 0.5-grams or 1-gram doses, approximately 50% of the dose appeared in the urine in the first 2 hours. An additional 20% was excreted between 2 and 4 hours after dosing, and approximately another 12% of the dose appeared in the urine between 4 and 8 hours later. The elimination of ceftazidime by the kidneys resulted in high therapeutic concentrations in the urine. The mean renal clearance of ceftazidime was approximately 100 mL/min. The calculated plasma clearance of approximately 115 mL/min indicated nearly complete elimination of ceftazidime by the renal route.
Following administration of a single 0.5-grams intravenous dose of radiolabeled avibactam, an average of 97% of administered radioactivity was recovered from the urine, with over 95% recovered within 12 hours of dosing. An average of 0.20% of administered total radioactivity was recovered in feces within 96 hours of dosing. An average of 85% of administered avibactam was recovered from the urine as unchanged drug within 96 hours, with over 50% recovered within 2 hours of the start of the infusion. Renal clearance was 158 mL/min, which is greater than the glomerular filtration, suggesting that active tubular secretion contributes to the excretion of avibactam in addition to glomerular filtration.
Specific Populations
Patients With Renal Impairment
Ceftazidime is eliminated almost solely by the kidneys; its serum half-life is significantly prolonged in patients with impaired renal function.
The clearance of avibactam was significantly decreased in subjects with mild (CrCl greater than 50 to 80 mL/min, n = 6), moderate (CrCl 30 to less than or equal to 50 mL/min, n = 6), and severe (CrCl 30 mL/min or less, not requiring hemodialysis; n = 6) renal impairment compared to healthy subjects with normal renal function (CrCl greater than 80 mL/min, n = 6) following administration of a single 100-mg intravenous dose of avibactam. The slower clearance resulted in increases in systemic exposure (AUC) of avibactam of 2.6-fold, 3.8-fold, and 7-fold in subjects with mild, moderate, and severe renal impairment, respectively, compared to subjects with normal renal function.
A single 100-mg dose of avibactam was administered to subjects with ESRD (n = 6) either 1 hour before or after hemodialysis. The avibactam AUC following the post-hemodialysis infusion was 19.5-fold the AUC of healthy subjects with normal renal function. Avibactam was extensively removed by hemodialysis, with an extraction coefficient of 0.77 and a mean hemodialysis clearance of 9.0 L/h. Approximately 55% of the avibactam dose was removed during a 4-hour hemodialysis session.
Dosage adjustment of AVYCAZ is recommended in patients with moderate and severe renal impairment and end-stage renal disease. Population PK models for ceftazidime and avibactam were used to conduct simulations for patients with impaired renal function. Simulations demonstrated that the recommended dose adjustments [see DOSAGE AND ADMINISTRATION] provide comparable exposures of ceftazidime and avibactam in patients with moderate and severe renal impairment and end-stage renal disease to those in patients with normal renal function or mild renal impairment. Because the exposure of both ceftazidime and avibactam is highly dependent on renal function, monitor CrCl at least daily and adjust the dosage of AVYCAZ accordingly for patients with changing renal function [see DOSAGE AND ADMINISTRATION].
Patients With Hepatic Impairment
The presence of hepatic dysfunction had no effect on the pharmacokinetics of ceftazidime in individuals administered 2 grams intravenously every 8 hours for 5 days.
The pharmacokinetics of avibactam in patients with hepatic impairment have not been established. Avibactam does not appear to undergo significant hepatic metabolism; therefore, the systemic clearance of avibactam is not expected to be significantly affected by hepatic impairment.
Dose adjustments are not currently considered necessary for AVYCAZ in patients with impaired hepatic function.
Geriatric Patients
Following single-dose administration of 0.5 grams avibactam as a 30-minute infusion the mean AUC for avibactam was 17% higher in healthy elderly subjects (65 years of age and older, n = 16) than in healthy young adult subjects (18 to 45 years of age, n = 17). There was no statistically significant age effect for avibactam Cmax.
No dose adjustment is recommended based on age. Dosage adjustment for AVYCAZ in elderly patients should be based on renal function [see DOSAGE AND ADMINISTRATION].
Gender
Following single-dose administration of 0.5 grams avibactam as a 30-minute infusion, healthy male subjects (n = 17) had 18% lower avibactam Cmax values than healthy female subjects (n = 16). There was no gender effect for avibactam AUC parameters.
No dose adjustment is recommended based on gender.
Drug Interactions
Avibactam at clinically relevant concentrations does not inhibit the cytochrome P450 isoforms CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4/5 in vitro in human liver microsomes. Avibactam showed no potential for in vitro induction of CYP1A2, 2B6, 2C9 and 3A4 isoenzymes in human hepatocytes. Against CYP2E1, avibactam showed a slight induction potential at very high concentrations that exceed any clinically relevant exposure. Ceftazidime was evaluated independently in human hepatocytes and showed no induction potential on the activity or mRNA expression of CYP1A1/2, CYP2B6, and CYP3A4/5.
Neither ceftazidime nor avibactam was found to be an inhibitor of the following hepatic and renal transporters in vitro at clinically relevant concentrations: MDR1, BCRP, OAT1, OAT3, OATP1B1, OATP1B3, BSEP, MRP4, OCT1 and OCT2. Avibactam was not a substrate of MDR1, BCRP, MRP4, or OCT2, but was a substrate of human OAT1 and OAT3 kidney transporters based on results generated in human embryonic kidney cells expressing these transporters. Probenecid inhibits 56% to 70% of the uptake of avibactam by OAT1 and OAT3 in vitro. Ceftazidime does not inhibit avibactam transport mediated by OAT1 and OAT3. The clinical impact of potent OAT inhibitors on the pharmacokinetics of avibactam is not known. Co-administration of AVYCAZ with probenecid is not recommended [see DRUG INTERACTIONS].
Administration of AVYCAZ 2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) to healthy male subjects (n = 28) as a 2-hour infusion following a 1-hour infusion of metronidazole every 8 hours for 3 days, did not affect the Cmax and AUC values for avibactam or ceftazidime compared to administration of AVYCAZ
2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) alone. Administration of 0.5 grams metronidazole to healthy male subjects as a 1-hour infusion before a 2-hour infusion of AVYCAZ 2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) every 8 hours for 3 days did not affect the Cmax and AUC of metronidazole compared to administration of 0.5 grams metronidazole alone.
Microbiology
Mechanism Of Action
The ceftazidime component of AVYCAZ is a cephalosporin antibacterial drug with in vitro activity against certain gram-negative and gram-positive bacteria. The bactericidal action of ceftazidime is mediated through binding to essential penicillin-binding proteins (PBPs). The avibactam component of AVYCAZ is a non-betalactam beta-lactamase inhibitor that inactivates certain beta-lactamases that degrade ceftazidime. Avibactam does not decrease the activity of ceftazidime against ceftazidime-susceptible organisms.
AVYCAZ demonstrated in vitro activity against Enterobacteriaceae in the presence of some beta-lactamases and extended-spectrum beta-lactamases (ESBLs) of the following groups: TEM, SHV, CTX-M, Klebsiella pneumoniae carbapenemase (KPCs), AmpC, and certain oxacillinases (OXA). AVYCAZ also demonstrated in vitro activity against P. aeruginosa in the presence of some AmpC beta-lactamases, and certain strains lacking outer membrane porin (OprD). AVYCAZ is not active against bacteria that produce metallo-beta lactamases and may not have activity against gram-negative bacteria that overexpress efflux pumps or have porin mutations.
Resistance
No cross-resistance with other classes of antimicrobials has been identified. Some isolates resistant to other cephalosporins (including ceftazidime) and to carbapenems may be susceptible to AVYCAZ.
Interaction With Other Antimicrobials
In vitro studies have not demonstrated antagonism between AVYCAZ and colistin, levofloxacin, linezolid,
metronidazole, tigecycline, tobramycin, or vancomycin.
Activity Against Ceftazidime-Nonsusceptible Bacteria In Animal Infection Models
Avibactam restored activity of ceftazidime in animal models of infection (e.g. thigh infection, pyelonephritis,
systemic infection induced by intraperitoneal injection) caused by ceftazidime non-susceptible beta-lactamaseproducing (e.g., ESBL, KPC and AmpC) gram-negative bacteria.
Antimicrobial Activity
AVYCAZ has been shown to be active against most isolates of the following bacteria, both in vitro and in clinical infections [see INDICATIONS AND USAGE].
Complicated Intra-abdominal Infections (cIAI)
Aerobic Bacteria
Gram-negative Bacteria
- Citrobacter freundii complex
- Enterobacter cloacae
- Escherichia coli
- Klebsiella oxytoca
- Klebsiella pneumoniae
- Proteus mirabilis
- Pseudomonas aeruginosa
Complicated Urinary Tract Infections (cUTI), including Pyelonephritis
Aerobic Bacteria
Gram-negative Bacteria
- Citrobacter freundii complex
- Enterobacter cloacae
- Escherichia coli
- Klebsiella pneumoniae
- Proteus mirabilis
- Pseudomonas aeruginosa
Hospital-acquired Bacterial Pneumonia and Ventilator-associated Bacterial Pneumonia (HABP/VABP)
Aerobic Bacteria
Gram-negative Bacteria
- Enterobacter cloacae
- Escherichia coli
- Haemophilus influenzae
- 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 AVYCAZ against isolates of similar genus or organism group. However, the efficacy of AVYCAZ in treating clinical infections caused by these bacteria has not been established in adequate and well-controlled clinical trials.
Gram-negative Bacteria
- Citrobacter koseri
- Enterobacter aerogenes
- Morganella morganii
- Providencia rettgeri
- Providencia stuartii
Susceptibility Test Methods
For specific information regarding susceptibility testing methods, interpretive criteria, and associated test
methods and quality control standards recognized by FDA for AVYCAZ, please see:
https://www.fda.gov/STIC.
Clinical Studies
Complicated Intra-Abdominal Infections
A total of 1058 adults hospitalized with cIAI were randomized and received trial medications in a multinational, multi-center, double-blind trial comparing AVYCAZ 2.5 g (ceftazidime 2 grams and avibactam 0.5 grams) intravenously every 8 hours plus metronidazole (0.5 grams intravenously every 8 hours) to meropenem (1 gram intravenously every 8 hours) for 5 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 microbiologically modified intent-to treat (mMITT) population, which included all patients who had at least one baseline intra-abdominal pathogen, consisted of 823 patients; the median age was 51 years and 62.8% were male. The majority of patients (64.9%) were from Eastern Europe; 7.5% were from the United States. Less than 1.0% of patients were of Pacific Island or African descent. The most common primary cIAI diagnosis was appendiceal perforation or peri-appendiceal abscess, occurring in 44.7% of patients. Bacteremia at baseline was present in 4.3% of patients.
Clinical cure was defined as complete resolution or significant improvement in signs and symptoms of the index infection at the test-of-cure (TOC) visit which occurred 28 to 35 days after randomization. Table 13 presents the clinical cure in the mMITT population and in the microbiologically evaluable (ME) population, which included all protocol-adherent mMITT patients. AVYCAZ plus metronidazole was non-inferior to meropenem with regard to the primary endpoint (clinical cure rate at the TOC visit in the mMITT population). Clinical cure rates at the TOC visit by pathogen in the mMITT population are presented in Table 14.
Table 13. Clinical Cure Rates at TOC from the Phase 3 cIAI Trial
Analysis population |
AVYCAZ plus metronidazolea
n/N (%) |
Meropenemb
n/N (%) |
Treatment Difference
(95% CI)c |
mMITT |
337/413 (81.6) |
349/410 (85.1) |
-3.5 (-8.6, 1.6) |
ME |
244/265 (92.1) |
272/287 (94.8) |
-2.7 (-7.1, 1.5) |
a AVYCAZ 2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) IV every 8 hours + metronidazole 0.5 grams IV every 8 hours
b 1 gram IV every 8 hours
c The 95% confidence interval (CI) was calculated as an unstratified Miettinen and Nurminen method |
Of the 823 patients in the mMITT population, 14 (1.7%) had baseline E. coli bacteremia; 7/10 (70.0%) of patients in the AVYCAZ arm and 3/4 (75.0%) of patients in the meropenem arm had a clinical cure.
Table 14. Clinical Cure Rates at TOC by Baseline Pathogen from the Phase 3 cIAI Trial, mMITT Population
Aerobic Gram-negative group or pathogen |
AVYCAZ plus metronidazolea
n/N (%) |
Meropenemb
n/N (%) |
Enterobacteriaceae |
272/334 (81.4) |
305/353 (86.4) |
Escherichia coli |
218/271 (80.4) |
248/285 (87.0) |
Klebsiella pneumoniae |
40/51 (78.4) |
37/49 (75.5) |
Klebsiella oxytoca |
14/18 (77.8) |
12/15 (80.0) |
Enterobacter cloacae |
11/13 (84.6) |
16/19 (84.2) |
Citrobacter freundii complex |
14/18 (77.8) |
9/12 (75.0) |
Proteus mirabilis |
5/8 (62.5) |
7/9 (77.8) |
Pseudomonas aeruginosa |
30/35 (85.7) |
34/36 (94.4) |
a AVYCAZ 2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) IV every 8 hours + metronidazole 0.5 grams IV every 8 hours
b 1 gram IV every 8 hours |
At baseline, 111 patients in the mMITT population had Gram-negative isolates that were not susceptible to ceftazidime, including 61 patients with E. coli and 26 patients with K. pneumoniae isolates. Cure rates were 39/47 (83.0%) in patients who received AVYCAZ and 55/64 (85.9%) of patients who received meropenem.
In a subset of Gram-negative pathogens from both arms of the Phase 3 cIAI trial that met phenotypic screening criteria for the presence of a beta-lactamase, genotypic testing identified certain ESBL groups (e.g., TEM-1, SHV-12, CTX-M-15, OXA-48) and AmpC that were expected to be inhibited by avibactam in isolates from 105 (12.8%) of the 823 patients in the mMITT population. Clinical cure rates in this subset were similar to the overall results.
Complicated Urinary Tract Infections, Including Pyelonephritis
The efficacy of AVYCAZ in patients with cUTI was evaluated in two randomized, actively controlled clinical trials (Trial 1 and Trial 2) as described below.
cUTI Trial 1
A total of 1020 adults hospitalized with cUTI were randomized and received trial medications in a multinational, multi-center, double-blind trial comparing AVYCAZ 2.5 g (ceftazidime 2 grams and avibactam 0.5 grams) intravenously every 8 hours to doripenem 0.5 grams intravenously every 8 hours for 10 to 14 days of total therapy. A switch to an oral antimicrobial agent was allowed after 5 days of intravenous dosing. Complicated urinary tract infections included acute pyelonephritis and complicated lower urinary tract infections.
The mMITT population, which included all patients who had at least one uropathogen isolated at baseline (greater or equal to 105 CFU/mL), consisted of 810 patients; the median age was 55 years and 69.8% were female. The majority of patients (75.4%) were from Eastern Europe; less than 1% of patients were from the United States. The majority of patients were White (83%) or Asian (7.8%); other racial subgroups were each represented at less than 1%. The most common diagnosis was acute pyelonephritis, occurring in 72% of patients. Bacteremia was present at baseline in 8.8% of patients.
Clinical efficacy was determined by comparing the response rate of AVYCAZ to doripenem at both primary endpoints; symptom response rates at Day 5 and combined microbiological cure and symptom response rates at the TOC visit (21 to 25 days after randomization). A symptom response was based on the resolution of patient-reported cUTI symptoms, defined as frequency/urgency/dysuria/suprapubic pain, as well as an improvement in flank pain for individuals with acute pyelonephritis. Microbiological cure was defined as a reduction of all baseline uropathogens to less than 104 CFU/mL in the urine.
AVYCAZ was non-inferior to doripenem with regard to both primary endpoints as presented in Table 15.
Table 15. Clinical and Microbiological Cure Rates from cUTI Trial 1, mMITT Population
Study endpoint |
AVYCAZa n/N (%) |
Doripenemb n/N (%) |
Treatment Difference (95% CI)c |
Symptomatic response at Day 5 |
276/393 (70.2) |
276/417 (66.2) |
4.0 (-2.4, 10.4) |
Combined symptomatic and microbiological response at TOC |
280/393 (71.2) |
269/417 (64.5) |
6.7 (0.3, 13.1) |
Microbiological cure at TOC |
304/393 (77.4) |
296/417 (71.0) |
6.4 (0.3, 12.4) |
Symptomatic response at TOC |
332/393 (84.5) |
360/417 (86.3) |
-1.9 (-6.8, 3.0) |
a AVYCAZ 2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) IV every 8 hours
b 0.5 grams IV every 8 hours
c The 95% confidence interval (CI) was calculated using the unstratified Miettinen and Nurminen method |
Microbiological cure rates by pathogen are presented in Table 16. Microbiological cure in individuals with bacteremia at baseline was achieved in 31/38 (81.6%) patients in the AVYCAZ arm and 24/33 (72.7%) patients in the doripenem arm at the TOC visit in the mMITT population. The most common pathogen isolated from blood was Escherichia coli, for which 31/32 (96.9%) patients in the AVYCAZ arm were microbiological cures, compared with 28/28 (100%) patients in the doripenem arm.
Table 16. Microbiological Cure Rate at TOC by Baseline Pathogen from cUTI Trial 1, mMITT Population
Aerobic Gram-negative group or pathogen |
AVYCAZa
n/N (%) |
Doripenemb
n/N (%) |
Enterobacteriaceae |
299/382 (78.3) |
281/398 (70.6) |
Escherichia coli |
229/292 (78.4) |
220/306 (71.9) |
Klebsiella pneumoniae |
33/44 (75.0) |
35/56 (62.5) |
Proteus mirabilis |
16/17 (94.1) |
9/13 (69.2) |
Enterobacter cloacae |
6/11 (54.5) |
9/13 (69.2) |
Pseudomonas aeruginosa |
12/18 (66.7) |
15/20 (75.0) |
a AVYCAZ 2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) IV every 8 hours
b 0.5 grams IV every 8 hours |
At baseline, 159 patients in the mMITT population had Gram-negative isolates that were not susceptible to ceftazidime, including 75 patients in the AVYCAZ arm and 84 in the doripenem arm. Microbiological and clinical cure rates at TOC were 47/75 (62.7%) and 67/75 (89.3%), respectively, in patients who received AVYCAZ, compared to 51/84 (60.7%) and 75/84 (89.3%) in patients who received doripenem.
In a subset of Gram-negative pathogens from both arms of the Phase 3 cUTI trial that met phenotypic screening criteria for the presence of a beta-lactamase, genotypic testing identified certain ESBL groups (e.g., TEM-1, SHV-12, CTX-M-15, CTX-M-27, OXA-48) and AmpC that were expected to be inhibited by avibactam in isolates from 176 (21.7%) of the 810 patients in the mMITT population. Microbiological and clinical cure rates in this subset were similar to the overall trial results.
cUTI Trial 2
In a multinational, multi-center, open-label study of adults hospitalized with ceftazidime non-susceptible (CAZNS) Gram-negative infections, 305 patients with cUTI were randomized and received AVYCAZ 2.5 g (ceftazidime 2 grams and avibactam 0.5 grams) intravenously every 8 hours or the best available intravenous therapy (BAT) for 5 to 21 days of treatment. There was no optional switch to oral therapy. The majority (96.1%) of patients in the BAT arm received monotherapy with a carbapenem antibacterial drug. Complicated urinary tract infections included acute pyelonephritis and complicated lower urinary tract infections.
The mMITT population consisted of 281 cUTI patients with at least one baseline CAZ-NS uropathogen (defined as MIC greater or equal to 8 mg/L for Enterobacteriaceae and greater or equal to 16 mg/L for P. aeruginosa). The median age was 65 years and 54.8% were male. The majority of cUTI patients (82.2%) were from Eastern Europe; 2.8% were from the United States. The majority of patients (95%) were White. The most common diagnosis was cUTI without pyelonephritis, occurring in 54.8% of patients. Bacteremia at baseline was present in 3.6% of patients.
Clinical efficacy was based on evaluation of both the clinical cure (defined as resolution or significant improvement of baseline cUTI signs and symptoms) and microbiological cure (all baseline uropathogens were reduced to less than 104 CFU/mL) rates at the follow-up visit (21 to 25 calendar days from randomization) in the mMITT population.
The clinical and microbiological response rates at the follow-up visit in the mMITT population are presented in Table 17. The microbiological response rates at the follow-up visit by baseline CAZ-NS uropathogen in the mMITT population are presented in Table 18.
Table 17. Clinical and Microbiological Response Rates at Day 21 to 25 visit from Trial 2 (cUTI Patients), mMITT Population
Study Endpoint |
AVYCAZa
n/N (%) |
BATb
n/N (%) |
Treatment Difference (95% CI)c |
Combined clinical and microbiological cure |
101/144 (70.1) |
74/137 (54.0) |
16.1 (4.8, 27.1) |
Clinical cure |
127/144 (88.2) |
121/137 (88.3) |
-0.1 (-7.9, 7.7) |
Microbiological cure |
103/144 (71.5) |
78/137 (56.9) |
14.6 (3.4, 25.5) |
a AVYCAZ 2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) IV every 8 hours
b Best available therapy (BAT) options were meropenem, imipenem, doripenem, and colistin; the majority of patients received carbapenem monotherapy
c The 95% confidence interval (CI) was calculated using the unstratified Miettinen and Nurminen method |
Table 18. Microbiological Response Rates by Baseline CAZ-NS Pathogen at the Day 21 to 25 visit from Trial 2 (cUTI Patients), mMITT Population
Aerobic Gram-negative pathogen |
AVYCAZa
n/N (%) |
BAT
n/N (%) |
Enterobacteriaceae |
|
|
Escherichia coli |
45/59 (76.3) |
33/57 (57.9) |
Klebsiella pneumoniae |
42/55 (76.4) |
39/65 (60.0) |
Pseudomonas aeruginosa |
8/14 (57.1) |
3/5 (60.0) |
a AVYCAZ 2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) IV every 8 hours
b Best available therapy (BAT) options were meropenem, imipenem, doripenem, and colistin; the majority of patients received carbapenem monotherapy |
Among Gram-negative uropathogens from both arms of Trial 2, genotypic testing identified certain ESBL groups (e.g., TEM-1, SHV-12, CTX-M-15, CTX-M-27, KPC-2, KPC-3, OXA-48) and AmpC beta-lactamases expected to be inhibited by avibactam in isolates from 273/281 (97.2%) patients in the mMITT population. Clinical and microbiological cure rates in this subset were similar to the overall results.
Hospital-Acquired Bacterial Pneumonia And Ventilator-Associated Bacterial Pneumonia
A total of 870 hospitalized adults with HABP/VABP were randomized and received trial medications in a multinational, multi-center, double-blind trial comparing AVYCAZ 2.5 g (ceftazidime 2 grams and avibactam 0.5 grams) intravenously every 8 hours to meropenem 1 g intravenously every 8 hours for 7 to 14 days of therapy. Study medication dosages were adjusted per renal function. The protocol allowed for administration of prior and concomitant systemic antibacterial therapy.
Clinical efficacy was evaluated in the intent-to treat (ITT) population, which included all randomized patients who received study drug. The median age was 66 years and 74.1% were male. The median APACHE II score was 14. The majority of patients were from China (33.1%) and Eastern Europe (25.5%). There were no patients enrolled within the United States. Less than 1.0% of patients were of Pacific Island or African descent. Overall, 379 (43.6%) patients were ventilated at enrollment, including 290 (33.3%) patients with VABP and 89 (10.2%) with ventilated HABP. Bacteremia at baseline was present in 4.8% of patients.
In the AVYCAZ and meropenem treatment groups up to 26% of patients received more than 24 hours of potentially effective systemic Gram-negative antibacterial therapy in the 3 days prior to randomization. Patients with infections only due to Gram-positive organisms were excluded from the trial, when this could be determined before enrollment. Following randomization, patients in both treatment groups could receive empiric open-label linezolid or vancomycin to cover for Gram-positive pathogens while awaiting culture results. Treatment with Gram-positive coverage continued in patients with Gram-positive pathogens.
Adjunctive Gram-negative antibacterial therapy with amikacin or another aminoglycoside was permitted if resistance to meropenem was suspected. Systemic Gram-negative antibacterial therapy was administered to 87% and 86% of patients in the AVYCAZ and meropenem treatment groups, respectively, at any point up to the end of therapy. In either treatment group, up to 36% of patients received more than 72 hours of potentially effective concomitant therapy.
Table 19 presents the 28-day all-cause mortality rates (28 to 32 days after randomization). Results are presented for the ITT population and for the microbiological intent-to-treat (micro-ITT) population, which included all patients with positive culture results indicating the presence of at least one Gram-negative pathogen. Clinical cure at the TOC visit (21-25 days from randomization) is also presented. Clinical cure was defined as resolution or significant improvement in signs and symptoms associated with pneumonia and cessation of antibacterial treatment for HABP/VABP. AVYCAZ was non-inferior to meropenem with regard to the primary endpoint (28-day all-cause mortality in the ITT population). The control group mortality rates were lower than that observed in other HABP/VABP trials which may impact generalizability of results. However, review of patient characteristics reflecting disease severity indicates the study enrolled a representative HABP/VABP population.
Table 19. 28-Day All-cause Mortality and Clinical Cure Rates from the Phase 3 HABP/VABP Trial, ITT and micro-ITT Populations
Study Endpoint (Population) |
AVYCAZa
n/N (%) |
Meropenemb
n/N (%) |
Treatment Difference (95% CI) |
28-Day all-cause mortality (ITT) |
42/436 (9.6) |
36/434 (8.3) |
1.5 (-2.4, 5.3)c |
micro-ITT |
22/187 (11.8) |
19/195 (9.7) |
2.1 (-4.1, 8.4)c |
Clinical cure (ITT) |
293/436 (67.2) |
300/434 (69.1) |
-1.9 (-8.1, 4.3)d, e |
a AVYCAZ 2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) IV every 8 hours
b 1 gram IV every 8 hours
c The 95% confidence interval (CI) was calculated based on Greenwood's variance estimates.
d A quantitative estimate of treatment effect has not been established for the clinical cure endpoint.
e The 95% confidence interval (CI) was calculated using an unstratified Miettinen and Nurminen method. |
The administration of prior or concomitant Gram-negative antibacterial therapy can confound the assessment of trial results. However, a subgroup analysis of 28-day all-cause mortality in subjects who received 24 hours or less of potentially effective antibacterial therapy prior to randomization and 72 hours or less of concomitant potentially effective antibacterial therapy following randomization produced results similar to the overall ITT population, AVYCAZ mortality 10.0% (20/200), meropenem 6.2% (12/195) [difference 3.8%; 95% CI: -1.6 % to 9.5%]). In the subset of patients who received more than 24 hours of potentially effective antibacterial therapy prior to randomization or more than 72 hours of concomitant potentially effective antibacterial therapy following randomization, results were similar to the overall ITT population (AVYCAZ 9.7% (25/258), meropenem 10.5% (28/266) [difference -0.08%; 95% CI: (-6.1% to 4.4%)]).
All-cause mortality rates by pathogen are presented in Table 20. Of the 382 patients in the micro-ITT population, 36 patients were bacteremic at baseline; 20/21 (95.2%) in the AVYCAZ arm and 13/15 (86.7%) in the meropenem arm survived through the day-28 follow-up visit; 13/21 (61.9%) patients in the AVYCAZ arm and 9/15 (60%) of patients in the meropenem arm had a clinical cure at the TOC visit.
The 28-day all-cause mortality rates by pathogen in the micro-ITT population are presented in Table 20. The clinical cure rates at TOC by pathogen in the micro-ITT population are presented in Table 21.
Table 20. 28-Day All-cause Mortality by Baseline Pathogen from the Phase 3 HABP/VABP Trial, micro-ITT Population
Aerobic Gram-negative group or pathogen |
AVYCAZa
n/N (%) |
Meropenemb
n/N (%) |
Enterobacteriaceae |
|
|
Klebsiella pneumoniae |
11/65 (16.9) |
9/75 (12.0) |
Enterobacter cloacae |
0/29 (0) |
4/23 (17.4) |
Escherichia coli |
4/22 (18.2) |
3/23 (13.0) |
Serratia marcescens |
0/15 (0) |
0/13 (0) |
Proteus mirabilis |
1/14 (7.1) |
1/12 (8.3) |
Haemophilus influenzae |
1/16 (6.2) |
2/25 (8.0) |
Pseudomonas aeruginosa |
9/64 (14.1) |
4/51 (7.8) |
a AVYCAZ 2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) IV every 8 hours
b 1 gram IV every 8 hours |
Table 21. Clinical Cure Rates at TOC by Baseline Pathogen from the Phase 3 HABP/VABP Trial, micro-ITT Population
Aerobic Gram-negative group or pathogen |
AVYCAZa
n/N (%) |
Meropenemb
n/N (%) |
Enterobacteriaceae |
92/133 (69.2) |
108/147 (73.5) |
Klebsiella pneumoniae |
44/65 (67.7) |
56/75 (74.7) |
Enterobacter cloacae |
25/29 (86.2) |
13/23 (56.5) |
Escherichia coli |
12/22 (54.5) |
17/23 (73.9) |
Serratia marcescens |
11/15 (73.3) |
12/13 (92.3) |
Proteus mirabilis |
12/14 (85.7) |
9/12 (75.0) |
Haemophilus influenzae |
13/16 (81.3) |
20/25 (80.0) |
Pseudomonas aeruginosa |
38/64 (59.4) |
37/51 (72.5) |
a AVYCAZ 2.5 grams (ceftazidime 2 grams and avibactam 0.5 grams) IV every 8 hours
b 1 gram IV every 8 hours |
At baseline, 108/382 (28.3%) of patients in the micro-ITT population had Gram-negative isolates that were not susceptible to ceftazidime, including 53 patients with K. pneumoniae and 28 patients with P. aeruginosa isolates. The 28-day all-cause mortality in patients with ceftazidime non-susceptible Gram-negative isolates was 8.2% in the AVYCAZ arm and 8.5% in the meropenem arm. Clinical cure rates at TOC were 37/48 (75.5%) in patients who received AVYCAZ and 42/59 (71.2%) in patients who received meropenem.