CLINICAL PHARMACOLOGY
Mechanism of Action
Telavancin is an antibacterial drug [see Clinical Pharmacology (12.4)].
Pharmacodynamics
The antimicrobial activity of telavancin appears to best correlate with the ratio of area under the concentration-time curve to minimum inhibitory concentration (AUC/MIC) for Staphylococcus aureus based on animal models of infection. Exposure-response analyses of the clinical trials support the dose of 10 mg/kg every 24 hours.
Cardiac Electrophysiology
The effect of telavancin on cardiac repolarization was assessed in a randomized, double-blind, multiple-dose, positive-controlled, and placebo-controlled, parallel study (n=160). Healthy subjects received VIBATIV 7.5 mg/kg, VIBATIV 15 mg/kg, positive control, or placebo infused over 60 minutes once daily for 3 days. Based on interpolation of the data from VIBATIV 7.5 mg/kg and 15 mg/kg, the mean maximum baseline-corrected, placebo-corrected QTc prolongation at the end of infusion was estimated to be 12-15 msec for VIBATIV 10 mg/kg and 22 msec for the positive control (Table 7). By 1 hour after infusion the maximum QTc prolongation was 6-9 msec for VIBATIV and 15 msec for the positive control.
Table 7: Mean and Maximum QTcF Changes from Baseline Relative to Placebo
|
QTcF
1
Change from Baseline
|
1 Fridericia corrected
|
2 Upper CL from a 2-sided 90% CI on difference from placebo (msec)
|
|
Mean (Upper 90% Confidence Limit
2
) msec
|
Maximum (Upper 90% Confidence Limit) msec
|
VIBATIV 7.5 mg/kg
|
4.1 (7)
|
11.6 (16)
|
VIBATIV 15 mg/kg
|
4.6 (8)
|
15.1 (20)
|
Positive Control
|
9.5 (13)
|
21.6 (26)
|
ECGs were performed prior to and during the treatment period in patients receiving VIBATIV 10 mg/kg in 3 cSSSI studies to monitor QTc intervals. In these trials, 214 of 1029 (21%) patients allocated to treatment with VIBATIV and 164 of 1033 (16%) allocated to vancomycin received concomitant medications known to prolong the QTc interval and known to be associated with definite or possible risk of torsades de pointes. The incidence of QTc prolongation >60 msec was 1.5% (15 patients) in the VIBATIV group and 0.6% (6 patients) in the vancomycin group. Nine of the 15 VIBATIV patients received concomitant medications known to prolong the QTc interval and definitely or possibly associated with a risk of torsades de pointes, compared with 1 of the 6 patients who received vancomycin. A similar number of patients in each treatment group (<1%) who did not receive a concomitant medication known to prolong the QTc interval experienced a prolongation >60 msec from baseline. In a separate analysis, 1 patient in the VIBATIV group and 2 patients in the vancomycin group experienced QTc >500 msec. No cardiac adverse events were ascribed to prolongation of the QTc interval. In the Phase 3 HABP/VABP studies, the incidence of QTc prolongation >60 msec or mean value >500 msec was 8% (52 patients) in the telavancin group and 7% (48 patients) in the vancomycin group.
Pharmacokinetics
The mean pharmacokinetic parameters of telavancin (10 mg/kg) after a single and multiple 60-minute intravenous infusions (10 mg/kg every 24 hours) are summarized in Table 8.
Table 8: Pharmacokinetic Parameters of Telavancin in Healthy Adults, 10 mg/kg
Cmax maximum plasma concentration
|
AUC area under concentration-time course
|
t1/2 terminal elimination half-life
|
Cl clearance
|
Vss apparent volume of distribution at steady state
|
1 Data not available
|
|
Single Dose
|
Multiple Dose
|
(n=42)
|
(n=36)
|
Cmax (mcg/mL)
|
93.6 ± 14.2
|
108 ± 26
|
AUC0-∞ (mcg·hr/mL)
|
747 ± 129
|
--1
|
AUC0-24h (mcg·hr/mL)
|
666 ± 107
|
780 125
|
t1/2 (hr)
|
8.0 ± 1.5
|
8.1 ± 1.5
|
Cl (mL/hr/kg)
|
13.9 ± 2.9
|
13.1 2.0
|
Vss (mL/kg)
|
145 ± 23
|
133 ± 24
|
In healthy young adults, the pharmacokinetics of telavancin administered intravenously were linear following single doses from 5 to 12.5 mg/kg and multiple doses from 7.5 to 15 mg/kg administered once daily for up to 7 days. Steady-state concentrations were achieved by the third daily dose.
Distribution
Telavancin binds to human plasma proteins, primarily to serum albumin, in a concentration-independent manner. The mean binding is approximately 90% and is not affected by renal or hepatic impairment.
Concentrations of telavancin in pulmonary epithelial lining fluid (ELF) and alveolar macrophages (AM) were measured through collection of bronchoalveolar lavage fluid at various times following administration of VIBATIV 10 mg/kg once daily for 3 days to healthy adults. Telavancin concentrations in ELF and AM exceeded the MIC90 for S. aureus (0.5 mcg/mL) for at least 24 hours following dosing.
Concentrations of telavancin in skin blister fluid were 40% of those in plasma (AUC0-24hr ratio) after 3 daily doses of 7.5 mg/kg VIBATIV in healthy young adults.
Metabolism
No metabolites of telavancin were detected in in vitro studies using human liver microsomes, liver slices, hepatocytes, and kidney S9 fraction. None of the following recombinant CYP 450 isoforms were shown to metabolize telavancin in human liver microsomes: CYP 1A2, 2C9, 2C19, 2D6, 3A4, 3A5, 4A11. The clearance of telavancin is not expected to be altered by inhibitors of any of these enzymes.
In a mass balance study in male subjects using radiolabeled telavancin, 3 hydroxylated metabolites were identified with the predominant metabolite (THRX-651540) accounting for <10% of the radioactivity in urine and <2% of the radioactivity in plasma. The metabolic pathway for telavancin has not been identified.
Excretion
Telavancin is primarily eliminated by the kidney. In a mass balance study, approximately 76% of the administered dose was recovered from urine and <1% of the dose was recovered from feces (collected up to 216 hours) based on total radioactivity.
Specific Populations
Geriatric Patients
The impact of age on the pharmacokinetics of telavancin was evaluated in healthy young (range 21-42 years) and elderly (range 65-83 years) subjects. The mean CrCl of elderly subjects was 66 mL/min. Age alone did not have a clinically meaningful impact on the pharmacokinetics of telavancin [see Use in Specific Populations (8.5)].
Pediatric Patients
The pharmacokinetics of telavancin in patients less than 18 years of age have not been studied.
Gender
The impact of gender on the pharmacokinetics of telavancin was evaluated in healthy male (n=8) and female (n=8) subjects. The pharmacokinetics of telavancin were similar in males and females. No dosage adjustment is recommended based on gender.
Renal Impairment
The pharmacokinetics of telavancin were evaluated in subjects with normal renal function and subjects with varying degrees of renal impairment following administration of a single dose of telavancin 7.5 mg/kg (n=28). The mean AUC0-∞ values were approximately 13%, 29%, and 118% higher for subjects with CrCl >50 to 80 mL/min, CrCl 30 to 50 mL/min, and CrCl <30 mL/min, respectively, compared with subjects with normal renal function. Dosage adjustment is required in patients with CrCl ≤50 mL/min [see Dosage and Administration (2)].
Creatinine clearance was estimated from serum creatinine based on the Cockcroft-Gault formula:
-
CrCl = [140 – age (years)] x ideal body weight (kg)* {x 0.85 for female patients}
[72 x serum creatinine (mg/dL)]
-
*Use actual body weight if < ideal body weight (IBW) IBW (male) = 50 kg + 0.9 kg/cm over 152 cm height IBW (female) = 45.5 kg + 0.9 kg/cm over 152 cm height
Following administration of a single dose of VIBATIV 7.5 mg/kg to subjects with end-stage renal disease, approximately 5.9% of the administered dose of telavancin was recovered in the dialysate following 4 hours of hemodialysis. The effects of peritoneal dialysis have not been studied.
Following a single intravenous dose of VIBATIV 7.5 mg/kg, the clearance of hydroxypropyl-beta-cyclodextrin was reduced in subjects with renal impairment, resulting in a higher exposure to hydroxypropyl-beta-cyclodextrin. In subjects with mild, moderate, and severe renal impairment, the mean clearance values were 38%, 59%, and 82% lower, respectively, compared with subjects with normal renal function. Multiple infusions of VIBATIV may result in accumulation of hydroxypropyl-beta-cyclodextrin.
Hepatic Impairment
The pharmacokinetics of telavancin were not altered in subjects with moderate hepatic impairment (n= 8, Child-Pugh B) compared with healthy subjects with normal hepatic function matched for gender, age, and weight. The pharmacokinetics of telavancin have not been evaluated in patients with severe hepatic impairment (Child-Pugh C).
Drug Interactions
In Vitro
The inhibitory activity of telavancin against the following CYP 450 enzymes was evaluated in human liver microsomes: CYP 1A2, 2C9, 2C19, 2D6, and 3A4/5. Telavancin inhibited CYP 3A4/5 at potentially clinically relevant concentrations. Upon further evaluation in a Phase 1 clinical trial, telavancin was found not to inhibit the metabolism of midazolam, a sensitive CYP3A substrate (see below).
Midazolam
The impact of telavancin on the pharmacokinetics of midazolam (CYP 3A4/5 substrate) was evaluated in 16 healthy adult subjects following administration of a single dose of VIBATIV 10 mg/kg, intravenous midazolam 1 mg, and both. The results showed that telavancin had no impact on the pharmacokinetics of midazolam and midazolam had no effect on the pharmacokinetics of telavancin.
Aztreonam
The impact of telavancin on the pharmacokinetics of aztreonam was evaluated in 11 healthy adult subjects following administration of a single dose of VIBATIV 10 mg/kg, aztreonam 2 g, and both. Telavancin had no impact on the pharmacokinetics of aztreonam and aztreonam had no effect on the pharmacokinetics of telavancin. No dosage adjustment of telavancin or aztreonam is recommended when both drugs are coadministered.
Piperacillin-tazobactam
The impact of telavancin on the pharmacokinetics of piperacillin-tazobactam was evaluated in 12 healthy adult subjects following administration of a single dose of VIBATIV 10 mg/kg, piperacillin-tazobactam 4.5 g, and both. Telavancin had no impact on the pharmacokinetics of piperacillin-tazobactam and piperacillin-tazobactam had no effect on the pharmacokinetics of telavancin. No dosage adjustment of telavancin or piperacillin-tazobactam is recommended when both drugs are coadministered.
Microbiology
Telavancin is a semisynthetic, lipoglycopeptide antibiotic. Telavancin exerts concentration-dependent, bactericidal activity against Gram-positive organisms in vitro, as demonstrated by time-kill assays and MBC/MIC (minimum bactericidal concentration/minimum inhibitory concentration) ratios using broth dilution methodology. In vitro studies demonstrated a telavancin post-antibiotic effect ranging from 1 to 6 hours against S. aureus and other Gram-positive pathogens.
Mechanism of Action
Telavancin inhibits cell wall biosynthesis by binding to late-stage peptidoglycan precursors, including lipid II. Telavancin also binds to the bacterial membrane and disrupts membrane barrier function.
Interactions with Other Antibacterial Drugs
In vitro investigations demonstrated no antagonism between telavancin and amikacin, aztreonam, cefepime, ceftriaxone, ciprofloxacin, gentamicin, imipenem, meropenem, oxacillin, piperacillin/tazobactam, rifampin, and trimethoprim/sulfamethoxazole when tested in various combinations against telavancin-susceptible staphylococci, streptococci, and enterococci. This information is not available for other bacteria.
Cross-Resistance
Some vancomycin-resistant enterococci have a reduced susceptibility to telavancin. There is no known cross-resistance between telavancin and other classes of antibacterial drugs.
Antibacterial Activity
Telavancin has been shown to be active against most isolates of the following microorganisms both in vitro and in clinical infections as described in the Indications and Usage section [see Indications and Usage (1)]:
Facultative Gram-Positive Microorganisms
-
Staphylococcus aureus (including methicillin-resistant isolates)
-
Enterococcus faecalis (vancomycin-susceptible isolates only)
-
Streptococcus agalactiae
-
Streptococcus anginosus group (includes S. anginosus, S. intermedius, and S. constellatus)
-
Streptococcus pyogenes
Greater than 90% of the following microorganisms exhibit an in vitro MIC less than or equal to the telavancin-susceptible breakpoint for organisms of similar genus shown in Table 9. The safety and effectiveness of telavancin in treating clinical infections due to these microorganisms have not been established in adequate and well-controlled clinical trials.
Facultative Gram-Positive Microorganisms
-
Enterococcus faecium (vancomycin-susceptible isolates only)
-
Staphylococcus haemolyticus
-
Streptococcus dysgalactiae subsp. equisimilis
-
Staphylococcus epidermidis
Susceptibility Test Methods
When available, the clinical microbiology laboratory should provide cumulative results of the 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 antimicrobial drug.
Dilution technique
Quantitative methods are used to determine antimicrobial minimum inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized procedure [see References (15)]. Standardized procedures are based on a broth dilution method or equivalent with standardized inoculum concentrations and standardized concentrations of telavancin powder. The test method treats telavancin as a water-insoluble agent. Dimethyl sulfoxide is used as solvent and diluent, and the cation-adjusted Mueller Hinton Broth test medium is supplemented with polysorbate 80 to a final concentration of 0.002%. Telavancin should not be tested by the agar dilution method. The MIC values should be interpreted according to the criteria provided in Table 9.
Diffusion technique
Quantitative methods that require measurement of zone diameters also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. One such standardized procedure requires the use of standardized inoculum concentrations [see References (15)]. This procedure uses paper disks impregnated with 30 mcg of telavancin to test the susceptibility of microorganisms to telavancin. The disk diffusion interpretive criteria are provided in Table 9.
Table 9: Susceptibility Interpretive Criteria for Telavancin
1 The current absence of resistant isolates precludes defining any results other than “susceptible.” Isolates yielding results other than susceptible should be subjected to additional testing.
|
|
Susceptibility Interpretive Criteria
1
|
Minimum Inhibitory Concentration (mcg/mL)
|
Disk Diffusion Zone Diameter (mm)
|
S
|
I
|
R
|
S
|
I
|
R
|
Staphylococcus aureus
(including methicillin-resistant isolates)
|
≤ 0.12
|
--
|
--
|
≥ 15
|
--
|
--
|
Streptococcus pyogenes
Streptococcus agalactiae
|
≤ 0.12
|
--
|
--
|
≥ 15
|
--
|
--
|
Streptococcus anginosus group
|
≤ 0.06
|
|
| ≥ 15
|
|
|
Enterococcus faecalis (vancomycin-susceptible isolates only)
|
≤ 0.25
|
--
|
--
|
≥ 15
|
--
|
--
|
A report of “susceptible" indicates that the antimicrobial is likely to inhibit growth of the pathogen if the antimicrobial compound in the blood reaches the concentrations usually achievable.
Quality Control
Standardized susceptibility test procedures require the use of laboratory control microorganisms to monitor the performance of the supplies and reagents used in the assay, and the techniques of the individuals performing the test [see References (15)]. Standard telavancin powder should provide the range of values noted in Table 10.
Quality control microorganisms are specific strains of organisms with intrinsic biological properties relating to resistance mechanisms and their genetic expression within bacteria; the specific strains used for microbiological quality control are not clinically significant.
Table 10: Acceptable Quality Control Ranges for Telavancin to be used in Validation of Susceptibility Test Results
|
Acceptable Quality Control Ranges
|
1 This organism may be used for validation of susceptibility test results when testing Streptococcus spp. other than S. pneumoniae
|
|
Minimum Inhibitory Concentration (mcg/mL)
|
Disk Diffusion Zone Diameter (mm)
|
Enterococcus faecalis
ATCC 29212
|
0.03 – 0.12
|
Not applicable
|
Staphylococcus aureus
ATCC 29213
|
0.03 - 0.12
|
Not applicable
|
Staphylococcus aureus
ATCC 25923
|
Not applicable
|
16-20
|
Streptococcus pneumoniae
ATCC 496191
|
0.004 – 0.015
|
17-24
|
NONCLINICAL TOXICOLOGY
Carcinogenesis, Mutagenesis, Impairment of Fertility
Long-term studies in animals to determine the carcinogenic potential of telavancin have not been performed.
Neither mutagenic nor clastogenic potential of telavancin was found in a battery of tests including: assays for mutagenicity (Ames bacterial reversion), an in vitro chromosome aberration assay in human lymphocytes, and an in vivo mouse micronucleus assay.
Telavancin did not affect the fertility or reproductive performance of adult male rats (exposed to telavancin for at least 4 weeks prior to mating) or female rats (exposed to telavancin for at least 2 weeks prior to mating).
Male rats given telavancin for 6 weeks, at exposures similar to those measured in clinical studies, displayed altered sperm parameters that were reversible following an 8-week recovery period.
Animal Toxicology and/or Pharmacology
Two-week administration of telavancin in rats produced minimal renal tubular vacuolization with no changes in BUN or creatinine. These effects were not seen in studies conducted in dogs for similar duration. Four weeks of treatment resulted in reversible elevations in BUN and/or creatinine in association with renal tubular degeneration that further progressed following 13 weeks of treatment.
These effects occurred at exposures (based on AUCs) that were similar to those measured in clinical trials.
The potential effects of continuous venovenous hemofiltration (CVVH) on the clearance of telavancin were examined in an in vitro model using bovine blood. Telavancin was cleared by CVVH and the clearance of telavancin increased with increasing ultrafiltration rate [see Overdosage (10)].
|