VABOMERE (Page 5 of 6)

12.4 Microbiology

Mechanism of Action

The meropenem component of VABOMERE is a penem antibacterial drug. The bactericidal action of meropenem results from the inhibition of cell wall synthesis. Meropenem penetrates the cell wall of most gram-positive and gram-negative bacteria to bind penicillin-binding protein (PBP) targets. Meropenem is stable to hydrolysis by most beta-lactamases, including penicillinases and cephalosporinases produced by gram-negative and gram-positive bacteria, with the exception of carbapenem hydrolyzing beta-lactamases.

The vaborbactam component of VABOMERE is a non-suicidal beta-lactamase inhibitor that protects meropenem from degradation by certain serine beta-lactamases such as Klebsiella pneumoniae carbapenemase (KPC). Vaborbactam does not have any antibacterial activity. Vaborbactam does not decrease the activity of meropenem against meropenem-susceptible organisms.

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. VABOMERE may not have activity against gram-negative bacteria that have porin mutations combined with overexpression of efflux pumps.

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.

VABOMERE demonstrated in vitro activity against Enterobacteriaceae in the presence of some beta-lactamases and extended-spectrum beta-lactamases (ESBLs) of the following groups: KPC, SME, TEM, SHV, CTX-M, CMY, and ACT. VABOMERE is not active against bacteria that produce metallo-beta lactamases or oxacillinases with carbapenemase activity.

In the Phase 3 cUTI trial with VABOMERE, some isolates of E. coli , K. pneumoniae , E. cloacae , C. freundii , P. mirabilis , P. stuartii that produced beta-lactamases, were susceptible to VABOMERE (minimum inhibitory concentration ≤4 mcg /mL). These isolates produced one or more beta-lactamases of the following enzyme groups: OXA (non-carbapenemases), KPC, CTX-M, TEM, SHV, CMY, and ACT.

Some beta-lactamases were also produced by an isolate of K. pneumoniae that was not susceptible to VABOMERE (minimum inhibitory concentration ≥32 mcg/mL). This isolate produced beta-lactamases of the following enzyme groups: CTX-M, TEM, SHV, and OXA.

No cross-resistance with other classes of antimicrobials has been identified. Some isolates resistant to carbapenems (including meropenem) and to cephalosporins may be susceptible to VABOMERE.

Interaction with Other Antimicrobials

In vitro synergy studies have not demonstrated antagonism between VABOMERE and levofloxacin, tigecycline, polymyxin, amikacin, vancomycin, azithromycin, daptomycin, or linezolid.

Activity against Meropenem Non-susceptible Bacteria in Animal Infection Models

Vaborbactam restored activity of meropenem in animal models of infection (e.g., mouse thigh infection, urinary tract infection and pulmonary infection) caused by some meropenem non-susceptible KPC-producing Enterobacteriaceae.

Antimicrobial Activity

VABOMERE has been shown to be active against most isolates of the following bacteria, both in vitro and in clinical infections [see Indications and Usage (1.1)].

Gram-negative bacteria:

  • Enterobacter cloacae species complex
  • Escherichia coli
  • Klebsiella pneumoniae

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 MIC less than or equal to the susceptible breakpoint for VABOMERE against isolates of a similar genus or organism group. However, the efficacy of VABOMERE in treating clinical infections due to these bacteria has not been established in adequate and well-controlled clinical trials.

Gram-negative bacteria:

  • Citrobacter freundii
  • Citrobacter koseri
  • Enterobacter aerogenes
  • Klebsiella oxytoca
  • Morganella morganii
  • Proteus mirabilis
  • Providencia spp.
  • Pseudomonas aeruginosa
  • Serratia marcescens

Susceptibility Test Methods

For specific information regarding susceptibility test interpretive criteria and associated test methods and quality control standards recognized by FDA for this drug, please see: https://www.fda.gov/STIC.

13 NONCLINICAL TOXICOLOGY

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenesis

Long-term carcinogenicity studies have not been performed with VABOMERE, meropenem, or vaborbactam.

Mutagenesis

Meropenem

Genetic toxicity studies were performed with meropenem using the bacterial reverse mutation test, the Chinese hamster ovary HGPRT assay, cultured human lymphocytes cytogenic assay, and the mouse micronucleus test. There was no evidence of mutation potential found in any of these tests.

Vaborbactam

Genetic toxicity studies were performed with vaborbactam using the bacterial reverse mutation test, chromosomal aberration test and the mouse micronucleus test. There was no evidence of mutagenic potential found in any of these tests.

Impairment of Fertility

Meropenem

Reproductive studies were performed with meropenem in male and female rats at doses up to 1000 mg/kg/day with no evidence of impaired fertility (approximately equivalent to 1.6 times the MRHD based on body surface area comparison).

In a reproductive study in cynomolgus monkeys at doses of meropenem up to 360 mg/kg/day (on the basis of body surface area comparison, approximately equivalent to 1.2 times the MRHD) no reproductive toxicity was seen.

Vaborbactam

Vaborbactam had no adverse effect on fertility in male and female rats at doses up to 1000 mg/kg/day, which is equivalent to approximately 1.6 times the MRHD based on body surface area comparison.

14 CLINICAL STUDIES

14.1 Complicated Urinary Tract Infections (cUTI), including Pyelonephritis

A total of 545 adults with cUTI, including pyelonephritis were randomized into a double-blind, double dummy, multi-center trial comparing VABOMERE (meropenem 2 grams and vaborbactam 2 grams) to piperacillin/tazobactam (piperacillin 4 grams/tazobactam 0.5 grams) intravenously every 8 hours. Switch to an oral antibacterial drug, such as levofloxacin was allowed after a minimum of 15 doses of IV therapy.

The microbiologically modified intent to treat population (m-MITT) included all randomized patients who received any study drug and had at least 1 baseline uropathogen. Clinical and microbiological response at the end of IV treatment (EOIVT) required both a clinical outcome of cure or improvement and a microbiologic outcome of eradication (all baseline uropathogens at >105 CFU/mL are to be reduced to <104 CFU/mL). Clinical and microbiological response was also assessed at the Test of Cure (TOC) visit (approximately 7 days after completion of treatment) in the m-MITT population and required both a clinical outcome of cure and a microbiological outcome of eradication.

Patient demographic and baseline characteristics were balanced between treatment groups in the m-MITT population. Approximately 93% of patients were Caucasian and 66% were females in both treatment groups. The mean age was 54 years with 32% and 42% patients greater than 65 years of age in VABOMERE and piperacillin/tazobactam treatment groups, respectively. Mean body mass index was approximately 26.5 kg/m2 in both treatment groups. Concomitant bacteremia was identified in 12 (6%) and 15 (8%) patients at baseline in VABOMERE and piperacillin/tazobactam treatment groups respectively. The proportion of patients with diabetes mellitus at baseline was 17% and 19% in VABOMERE and piperacillin/tazobactam treatment groups, respectively. The majority of patients (approximately 90%) were enrolled from Europe, and approximately 2% of patients were enrolled from North America. Overall, in both treatment groups, 59% of patients had pyelonephritis and 40% had cUTI, with 21% and 19% of patients having a non-removable and removable source of infection, respectively.

Mean duration of IV treatment in both treatment groups was 8 days and mean total treatment duration (IV and oral) was 10 days; patients with baseline bacteremia could receive up to 14 days of therapy. Approximately 10% of patients in each treatment group in the m-MITT population had a levofloxacin-resistant pathogen at baseline and received levofloxacin as the oral switch therapy. This protocol violation may have impacted the assessment of the outcomes at the TOC visit. These patients were not excluded from the analysis presented in Table 6, as the decision to switch to oral levofloxacin was based on post-randomization factors.

VABOMERE demonstrated efficacy with regard to clinical and microbiological response at the EOIVT visit and TOC visits in the m-MITT population as shown in Table 6.

Table 6: Clinical and Microbiological Response Rates in a Phase 3 Trial of cUTI Including Pyelonephritis (m-MITT Population)
VABOMEREn/N (%) Piperacillin/Tazobactamn/N (%) Difference(95% CI)
CI = confidence interval; EOIVT = End of Intravenous Treatment; TOC = Test of Cure
*
End of IV Treatment visit includes patients with organisms resistant to piperacillin/tazobactam at baseline
Test of Cure visit excludes patients with organisms resistant to piperacillin/tazobactam at baseline
Clinical cure or improvement AND microbiological eradication at the End of IV Treatment Visit * 183/186 (98.4) 165/175 (94.3) 4.1%(0.3%, 8.8%)
Clinical cure AND microbiological eradication at the Test of Cure visit approximately 7 days after completion of treatment 124/162 (76.5) 112/153 (73.2) 3.3%(-6.2%, 13.0%)

In the m-MITT population, the rate of clinical and microbiological response in VABOMERE- treated patients with concurrent bacteremia at baseline was 10/12 (83.3%).

In a subset of the E. coli and K. pneumoniae isolates, genotypic testing identified certain ESBL groups (e.g., TEM, CTX-M, SHV and OXA) in both treatment groups of the Phase 3 cUTI trial. The rates of clinical and microbiological response were similar in the ESBL-positive and ESBL-negative subset at EOIVT; at TOC, clinical and microbiological response was lower in the ESBL-positive as compared to ESBL-negative subset in both treatment groups.

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