CLINICAL PHARMACOLOGY
Mechanism Of Action
BAXDELA is an antibacterial drug [see Microbiology].
Pharmacodynamics
The antibacterial activity of delafloxacin appears to
best correlate with the ratio of area under the concentrationtime curve of free
delafloxacin to minimal inhibitory concentration (fAUC/MIC) for Gram-positive
organisms such as Staphylococcus aureus and Gram-negative organisms such
as Escherichia coli based on animal models of infection.
Cardiac Electrophysiology
In a randomized, positive- and placebo-controlled,
thorough QT/QTc study, 51 healthy subjects received BAXDELA 300 mg IV, BAXDELA
900 mg IV, oral moxifloxacin 400 mg, or placebo. Neither BAXDELA 300 mg nor
BAXDELA 900 mg (three times the intravenous therapeutic dose) had any
clinically relevant adverse effect on cardiac repolarization.
Photosensitivity Potential
A study of photosensitizing potential to ultraviolet (UVA
and UVB) and visible radiation was conducted in 52 healthy volunteers
(originally 13 subjects per treatment group). BAXDELA, at 200 mg/day and 400
mg/day (0.22 and 0.44 times the approved recommended daily oral dosage,
respectively) for 7 days, and placebo did not demonstrate clinically
significant phototoxic potential at any wavelengths tested (295 nm to 430 nm),
including solar simulation. The active comparator (lomefloxacin) demonstrated a
moderate degree of phototoxicity at UVA 335 nm and 365 nm and solar simulation
wavelengths.
Pharmacokinetics
The pharmacokinetic parameters of delafloxacin following
single- and multiple-dose (every 12 hours) oral (450 mg) and intravenous (300
mg) administration are shown in Table 4. Steady-state was achieved within approximately
three days with accumulation of approximately 10% and 36% following IV and oral
administration, respectively.
Table 4 : Mean (SD) Delafloxacin Pharmacokinetic
Parameters Following Single and Multiple Oral and Intravenous Administration
Parameters |
Tablet |
Intravenous Injection |
Single Dose 450 mg |
Steady State 450 mg Q12h§ |
Single Dose 300 mg |
Steady State 300 mg Q12h§ |
Tmax (h)† |
0.75 (0.5, 4.0) |
1.00 (0.50, 6.00) |
1.0 (1.0, 1.2) |
1.0 (1.0, 1.0) |
Cmax (μg/mL) |
7.17 (2.01) |
7.45 (3.16) |
8.94 (2.54) |
9.29 (1.83) |
AUC (μg•h/mL)‡ |
22.7 (6.21) |
30.8 (11.4) |
21.8 (4.54) |
23.4 (6.90) |
CL or CL/F(L/h)& |
20.6 (6.07) |
16.8 (6.54) |
14.1 (2.81) |
13.8 (3.96) |
CLr (L/h) |
- |
|
5.89 (1.53) |
6.69 (2.19) |
Rac |
|
1.36 |
|
1.1 |
Cmax = maximum concentration; Tmax = time to reach Cmax;
AUC = area under the concentration-time curve; CL = systemic clearance;
CL/F = apparent oral clearance; Rac = accumulation ratio
† Median (range)
‡ AUC is AUCτ (AUC from time 0 to 12 hours) for single dose and multiple-dose
administration
& CL is reported for intravenous injection. CL/F is reported for tablet
§ Q12h is every 12 hours |
Absorption
The absolute bioavailability for BAXDELA 450 mg oral
tablet administered as a single dose was 58.8%. The AUC of delafloxacin
following administration of a single 450 mg oral (tablet) dose was comparable
to that following a single 300 mg intravenous dose. The Cmax of delafloxacin
was achieved within about 1 hour after oral administration under fasting
condition. Food (kcal:917, Fat: 58.5%, Protein: 15.4%, Carbohydrate: 26.2%). did
not affect the bioavailability of delafloxacin [see DOSAGE AND
ADMINISTRATION].
Distribution
The steady state volume of distribution of delafloxacin
is 30–48 L which approximates total body water. The plasma protein binding of
delafloxacin is approximately 84%; delafloxacin primarily binds to albumin.
Plasma protein binding of delafloxacin is not significantly affected by renal
impairment.
Elimination
In a mass balance study, the mean half-life for
delafloxacin was 3.7 hours (SD 0.7 hour) after a single dose intravenous
administration. The mean half-life values for delafloxacin ranged from 4.2 to
8.5 hours following multiple oral administrations. Following administration of
a single 300 mg intravenous dose of BAXDELA, the mean clearance (CL) of
delafloxacin was 16.3 L/h (SD 3.7 L/h), and the renal clearance (CLr) of
delafloxacin accounts for 35-45% of the total clearance.
Metabolism
Glucuronidation of delafloxacin is the primary metabolic
pathway with oxidative metabolism representing about 1% of an administered
dose. The glucuronidation of delafloxacin is mediated mainly by UGT1A1, UGT1A3,
and UGT2B15. Unchanged parent drug is the predominant component in plasma.
There are no significant circulating metabolites in humans.
Excretion
After single intravenous dose of 14C-labeled
delafloxacin, 65% of the radioactivity was excreted in urine as unchanged
delafloxacin and glucuronide metabolites and 28% was excreted in feces as
unchanged delafloxacin. Following a single oral dose of 14C-labeled
delafloxacin, 50% of the radioactivity was excreted in urine as unchanged
delafloxacin and glucuronide metabolites and 48% was excreted in feces as
unchanged delafloxacin.
Specific Populations
Based on a population pharmacokinetic analysis, the
pharmacokinetics of delafloxacin were not significantly impacted by age, sex,
race, weight, body mass index, and disease state (ABSSSI).
Patients With Hepatic Impairment
No clinically meaningful changes in delafloxacin Cmax and
AUC were observed, following administration of a single 300-mg intravenous dose
of BAXDELA to patients with mild, moderate or severe hepatic impairment (Child-Pugh
Class A, B, and C) compared to matched healthy control subjects.
Patients With Renal Impairment
Following a single intravenous (300 mg) administration of
delafloxacin to subjects with mild (eGFR = 51-80 mL/min/1.73 m²), moderate
(eGFR = 31–50 mL/min/1.73 m²), severe (eGFR = 15-29 mL/min/1.73 m²) renal
impairment, and ESRD on hemodialysis receiving intravenous delafloxacin within
1 hour before and 1 hour after hemodialysis, mean total exposure (AUCt) of
delafloxacin was 1.3, 1.6, 1.8, 2.1, and 2.6-fold higher, respectively than
that for matched normal control subjects. The mean dialysate clearance (CLd) of
delafloxacin was 4.21 L/h (SD 1.56 L/h). After about 4 hours of hemodialysis,
the mean fraction of administered delafloxacin recovered in the dialysate was
about 19% [see Use In Specific Populations].
Following a single oral (400 mg) administration of
delafloxacin to subjects with mild (eGFR = 51-80 mL/min/1.73 m²), moderate
(eGFR = 31-50mL/min/1.73m²), or severe (eGFR = 15-29 mL/min/1.73m²) renal
impairment, the mean total exposure (AUCt) of delafloxacin was about 1.5-fold
higher for subjects with moderate and severe renal impairment compared with
healthy subjects, whereas total systemic exposures of delafloxacin in subjects
with mild renal impairment were comparable with healthy subjects.
In patients with moderate (eGFR = 31–50 mL/min/1.73 m²),
or severe (eGFR = 15–29 mL/min/1.73 m²) renal impairment or ESRD on
hemodialysis, accumulation of the intravenous vehicle SBECD occurs. The mean systemic
exposure (AUC) increased 2-fold, 5-fold, 7.5-fold, and 27-fold for patients
with moderate impairment, severe impairment, ESRD on hemodialysis receiving
intravenous delafloxacin within 1 hour before, and 1 hour after hemodialysis
respectively, compared to the healthy control group. In subjects with ESRD
undergoing hemodialysis, SBECD is dialyzed with a clearance of 4.74 L/h. When
hemodialysis occurred 1 hour after the BAXDELA infusion in subjects with ESRD,
the mean fraction of SBECD recovered in the dialysate was 56.1% over
approximately 4 hours.
Geriatric Patients
Following single oral administration of 250 mg
delafloxacin (approximately 0.6 times the approved recommended oral dose), the
mean delafloxacin Cmax and AUC∞ values in elderly subjects (≥ 65
years) were about 35% higher compared to values obtained in young adults (18 to
40 years). This difference is not considered clinically relevant. A population
pharmacokinetic analysis of patients with ABSSSI showed no significant impact
of age on delafloxacin pharmacokinetics.
Male and Female Patients
Following single oral administration of 250 mg
delafloxacin (approximately 0.6 times the approved recommended oral dose), the
mean delafloxacin Cmax and AUC∞ values in male subjects were comparable
to female subjects. Results from a population pharmacokinetic analysis showed
that females have a 24% lower AUC than males. This difference is not considered
clinically relevant.
Drug Interaction Studies
Drug Metabolizing Enzymes
Delafloxacin 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.
At a delafloxacin concentration (500 μM) well above clinically relevant
exposures, the activity of CYP2E1was increased. In human hepatocytes,
delafloxacin showed no potential for in vitro induction of CYP1A2, 2B6, 2C19,
or 2C8 but was a mild inducer of CYP2C9 at a concentration of 100 μM and
CYP3A4 at a clinically relevant concentration. Administration of BAXDELA 450 mg
every 12 hours for 5 days to healthy male and female subjects (n = 22) prior to
and on Day 6 with a single oral 5-mg dose of midazolam (a sensitive CYP3A substrate),
did not affect the Cmax and AUC values for midazolam or 1-hydroxy midazolam
compared to administration of midazolam alone.
Transporters
Delafloxacin was not an inhibitor of the following
hepatic and renal transporters in vitro at clinically relevant concentrations:
MDR1, BCRP, OAT1, OAT3, OATP1B1, OATP1B3, BSEP, OCT1 and OCT2. Delafloxacin was
not a substrate of OAT1, OAT3, OCT1, OCT2, OATP1B1 or OATP. Delafloxacin was
shown to be a substrate of P-gp and BCRP in vitro. The clinical relevance of
co-administration of delafloxacin and P-gp and/or BCRP inhibitors is unknown.
Microbiology
Mechanism Of Action
Delafloxacin belongs to the fluoroquinolone class of
antibacterial drugs and is anionic in nature. The antibacterial activity of
delafloxacin is due to the inhibition of both bacterial topoisomerase IV and
DNA gyrase (topoisomerase II) enzymes which are required for bacterial DNA
replication, transcription, repair, and recombination. Delafloxacin exhibits a
concentration-dependent bactericidal activity against gram-positive and gram-negative
bacteria in vitro.
Resistance
Resistance to fluoroquinolones, including delafloxacin,
can occur due to mutations in defined regions of the target bacterial enzymes
topoisomerase IV and DNA gyrase referred to as Quinolone-Resistance Determining
Regions (QRDRs), or through altered efflux.
Fluoroquinolones, including delafloxacin, have a
different chemical structure and mechanism of action relative to other classes
of antibacterial compounds (e.g. aminoglycosides, macrolides, β-lactams,
glycopeptides, tetracyclines and oxazolidinones).
In vitro resistance to delafloxacin develops by multiple
step mutations in the QRDRs of gram-positive and gram-negative bacteria.
Delafloxacin-resistant mutants were selected in vitro at a frequency of <10-9.
Although cross-resistance between delafloxacin and other
fluoroquinolone-class antibacterial agents has been observed, some isolates
resistant to other fluoroquinolone-class antibacterial agents may be
susceptible to BAXDELA.
Interaction With Other Antimicrobials
In vitro drug combination studies with delafloxacin and
aztreonam, ceftazidime, colistin, daptomycin, linezolid, meropenem,
tigecycline, trimethoprim/sulfamethoxazole and vancomycin demonstrated neither
synergy nor antagonism.
Antimicrobial Activity
BAXDELA has been shown to be active against most isolates
of the following microorganisms, both in vitro and in clinical infections, [see
INDICATIONS AND USAGE].
Aerobic bacteria
Gram-Positive Bacteria
Staphylococcus aureus (including
methicillin-resistant and methicillin-sensitive strains)
Staphylococcus haemolyticus
Staphylococcus lugdunensis
Streptococcus pyogenes
Streptococcus agalactiae
Streptococcus anginosus Group (including S.
anginosus, S. intermedius, and S. constellatus)
Enterococcus faecalis
Gram-Negative Bacteria
Escherichia coli
Klebsiella pneumoniae
Enterobacter cloacae
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 of delafloxacin against isolates of similar genus
or organism group. However, the efficacy of BAXDELA in treating clinical
infections caused by these bacteria has not been established in adequate and
well-controlled clinical trials.
Aerobic Bacteria
Gram-Positive Bacteria
Streptococcus dysgalactiae
Gram-Negative Bacteria
Enterobacter aerogenes
Haemophilus parainfluenzae
Klebsiella oxytoca
Proteus mirabilis
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.
Animal Toxicology And/Or Pharmacology
Fluoroquinolone antibacterials are associated with
degenerative changes in articular cartilage and arthropathy in skeletally
immature animals. In a toxicology study of the formulated tablet in dogs, the
femoral head of one of three high dose (480 mg/kg/day) females had minimal
focal degeneration of the superficial articular cartilage and a small focal
cleft in the articular cartilage. No other joints were examined.
Clinical Studies
Acute Bacterial Skin And Skin Structure Infections
A total of 1510 adults with acute bacterial skin and skin
structure infections (ABSSSI) were randomized in 2 multicenter, multinational,
double-blind, double-dummy, non-inferiority trials. Trial 1 compared BAXDELA 300
mg via intravenous infusion every 12 hours to comparator. In Trial 2, patients
received BAXDELA 300 mg via intravenous infusion every12 hours for 6 doses then
made a mandatory switch to oral BAXDELA 450 mg every 12 hours. In both studies,
the comparator was the intravenous combination of vancomycin 15 mg/kg actual body
weight and aztreonam. Aztreonam therapy was discontinued if no gram-negative
pathogens were identified in the baseline cultures.
In Trial 1, 331 patients with ABSSSI were randomized to
BAXDELA and 329 patients were randomized to vancomycin plus aztreonam. Patients
in this trial had the following infections: cellulitis (39%), wound infection (35%),
major cutaneous abscess (25%), and burn infection (1%). The overall mean
surface area of the infected lesion as measured by digital planimetry was 307
cm². The average age of patients was 46 years (range 18 to 94 years). Patients
were predominately male (63%) and White (91%); 32% had BMI ≥ 30 kg/m².
The population studied in Trial 1 included a distribution of patients with
associated comorbidities such as hypertension (21%), diabetes (9%), and renal
impairment (16%; 0.2% with severe renal impairment or ESRD). Current or recent
history of drug abuse, including IV drug abuse, was reported by 55% of
patients. Bacteremia was documented at baseline in 2% of patients.
In Trial 2, 423 patients were randomized to BAXDELA and
427 patients were randomized to vancomycin plus aztreonam. Patients in this
trial had the following infections: cellulitis (48%), wound infection (26%),
major cutaneous abscess (25%), and burn infection (1%). The overall mean
surface area of the infected lesion, as measured by digital planimetry, was 353
cm². The average age of patients was 51 years (range 18 to 93 years). Patients
were predominately male (63%) and White (83%); 50 % had a BMI ≥ 30 kg/m².
The population studied in Trial 2 included a distribution of patients with
associated comorbidities such as hypertension (31%), diabetes (13%) and renal
impairment (16%; 0.2% with severe renal impairment or ESRD). Current or recent history
of drug abuse, including IV drug abuse, was reported by 30% of patients.
Bacteremia was documented at baseline in 2% of patients.
In both trials, objective clinical response at 48 to 72
hours post initiation of treatment was defined as a 20% or greater decrease in
lesion size as determined by digital planimetry of the leading edge of
erythema. Table 5 summarizes the objective clinical response rates in both of
these trials.
Table 5 : Clinical Response at 48–72 hours* in the ITT
Population with ABSSSI in Trial 1 and Trial 2
Trial |
BAXDELA (300 mg IV) |
Vancomycin 15 mg/kg + Aztreonam |
Treatment Difference† (2-sided 95% CI) |
Trial 1 |
Total n |
331 |
329 |
|
Responder, n (%) |
259 (78.2%) |
266 (80.9%) |
-2.6 (-8.8, 3.6) |
|
BAXDELA (300 mg IV and 450 mg oral) |
Vancomycin 15 mg/kg + Aztreonam |
|
Trial 2 |
Total N |
423 |
427 |
|
Responder, n/N (%) |
354 (83.7%) |
344 (80.6%) |
3.1 (-2.0, 8.3) |
CI = Confidence Interval; ITT = Intent to Treat and
includes all randomized patients
*Objective clinical response was defined as a 20% or greater decrease in lesion
size as determined by digital planimetry of the leading edge of erythema at 48
to 72 hours after initiation of treatment without any reasons for failure (less
than 20% reduction in lesion size, administration of rescue antibacterial
therapy, use of another antibacterial or surgical procedure to treat for lack
of efficacy, or death). Missing patients were treated as failures.
†Treatment difference, expressed as percentage, and CI based on Miettinen and
Nuriminen method without stratification. |
In both trials, an investigator assessment of response
was made at Follow-up (Day 14 ± 1) in the ITT and CE populations. Success was
defined as “cure + improved,” where patients had complete or near resolution of
signs and symptoms, with no further antibacterial needed. The success rates in
the ITT and CE populations are shown in Table 6.
Table 6 : Investigator- Assessed Success at the
Follow-up Visit in ABSSSI —ITT Population and CE Population in Trial 1 and 2
Trial |
BAXDELA (300 mg IV) |
Vancomycin 15 mg/kg + Aztreonam |
Treatment Difference† (2-sided 95% CI) |
Trial 1 |
Success*, n/N (%) ITT |
270/331 (81.6%) |
274/329 (83.3%) |
-1.7 (-7.6, 4.1) |
Success*, n/N (%) CE |
232/240 (96.7%) |
238/244 (97.5%) |
-0.9 (-4.3, 2.4) |
|
BAXDELA (300 mg IV and 450 mg Oral) |
Vancomycin 15 mg/kg + Aztreonam |
|
Trial 2 |
Success, n/N (%) ITT |
369/423 (87.2%) |
362/427 (84.8%) |
2.5 (-2.2, 7.2) |
Success, n/N (%) CE |
339/353 (96.0%) |
319/329 (97.0%) |
-0.9 (-3.9, 2.0) |
CI = confidence interval; ITT = intent to treat and
includes all randomized patients; CE = clinically evaluable consisted of all
ITT patients who had a diagnosis of ABSSSI, received at least 80% of expected
doses of study drug, did not have any protocol deviations that would affect the
assessment of efficacy and had investigator assessment at the Follow-Up Visit.
*Success was cure + improved where patients had complete or near resolution of
signs and symptoms with no further antibacterial needed.
†Treatment difference, expressed as percentage, and CI based on Miettinen and
Nuriminen method without stratification. |
Six delafloxacin patients had baseline S. aureus bacteremia
with ABSSSI. Five of these 6 patients (83.3%) were clinical responders at 48 to
72 hours and 5/6 (83.3%) were considered clinical success for ABSSSI at Day 14
± 1. Two delafloxacin patients had baseline Gram-negative bacteremia (K.
pneumoniae and P. aeruginosa), and both were clinical responders and
successes.
The investigator assessments of clinical success rates
were also similar between treatment groups at Late Follow-up (LFU, day 21-28).
Objective clinical response and investigator-assessed
success by baseline pathogens from the primary infection site or blood cultures
for the microbiological ITT (MITT) patient population pooled across Trial 1 and
Trial 2 are presented in Table 7.
Table 7 : Outcomes by Baseline Pathogen (Pooled across
Trial 1 and Trial 2; MITT* Population)
Pathogen |
Clinical Responsea at 48-72 hours |
Investigator-Assessed Successb at Follow-up |
BAXDELA
n/N (%) |
Comparator
n/N (%) |
BAXDELA
n/N (%) |
Comparator
n/N (%) |
Staphylococcus aureus |
271/319 (85.0) |
269/324 (83.0) |
275/319 (86.2) |
269/324 (83.0) |
Methicillin-susceptiblec |
149/177 (84.2) |
148/183 (80.9) |
154/177 (87.0) |
153/183 (83.6) |
Methicillin-resistantc |
125/144 (86.8) |
121/141 (85.8) |
122/144 (84.7) |
116/141 (82.3) |
Streptococcus pyogenes |
17/23 (73.9) |
9/18 (50.0) |
21/23 (91.3) |
16/18 (88.9) |
Staphylococcus haemolyticus |
11/15 (73.3) |
7/8 (87.5) |
13/15 (86.7) |
7/8 (87.5) |
Streptococcus agalactiae |
10/14 (71.4) |
9/12 (75.0) |
12/14 (85.7) |
11/12 (91.7) |
Streptococcus anginosus Group |
59/64 (92.2) |
55/61 (90.2) |
54/64 (84.4) |
47/61 (77.0) |
Staphylococcus lugdunensis |
8/11 (72.7) |
6/9 (66.7) |
10/11 (90.9) |
8/9 (88.9) |
Enterococcus faecalis |
11/11 (100.0) |
12/16 (75.0) |
9/11 (81.8) |
14/16 (87.5) |
Escherichia coli |
12/14 (85.7) |
16/20 (80.0) |
12/14 (85.7) |
18/20 (90.0) |
Enterobacter cloacae |
10/14 (71.4) |
8/11 (72.7) |
12/14 (85.7) |
10/11 (90.9) |
Klebsiella pneumoniae |
19/22 (86.4) |
22/23 (95.7) |
20/22 (90.9) |
21/23 (91.3) |
Pseudomonas aeruginosa |
9/11 (81.8) |
11/12 (91.7) |
11/11 (100.0) |
12/12 (100.0) |
a Objective clinical response was defined as a
20% or greater decrease in lesion size as determined by digital planimetry of
the leading edge of erythema at 48 to 72 hours after initiation of treatment.
b Investigator-assessed success was defined as complete or near
resolution of signs and symptoms, with no further antibacterial needed at
Follow-up Visit (Day14±1).
*Microbiological ITT (MITT) consists of all randomized patients who had a
baseline pathogen identified that is known to cause ABSSSI.
c Discrepancy in the total numbers is due to the multiple subjects
having both MRSA and MSSA isolates. |