Pharmacokinetics
The pharmacokinetics of anidulafungin following IV administration have been
characterized in healthy subjects, special populations and patients. Systemic
exposures of anidulafungin are dose-proportional and have low intersubject variability
(coefficient of variation < 25%) as shown in Table 1. The steady state was
achieved on the first day after a loading dose (twice the daily maintenance
dose) and the estimated plasma accumulation factor at steady state is approximately
2.
Table 1 : Mean (%CV) Steady State Pharmacokinetic Parameters
of Anidulafungin Following IV Administration of Anidulafungin Once Daily for
10 Days in Healthy Adult Subjects
| PK Parametera |
Anidulafungin |
IV Dosing Regimen |
(LD/MD, mg) b |
70/35c d
(N = 6) |
200/100
(N = 10) |
260/130d e
(N = 10) |
| Cmax, ss [mg/L] |
3.55 (13.2) |
8.6 (16.2) |
10.9 (11.7) |
| AUCss [mg•h/L] |
42.3 (14.5) |
111.8 (24.9) |
168.9 (10.8) |
| CL [L/h] |
0.84 (13.5) |
0.94 (24.0) |
0.78 (11.3) |
| t½ [h] |
43.2 (17.7) |
52.0 (11.7) |
50.3 (9.7) |
a Parameters were obtained from separate studies
b LD/MD: loading dose/maintenance dose once daily
c Data were collected on Day 7
d Safety and efficacy of these doses has not been established
e See OVERDOSAGE
Cmax, ss = the steady state peak concentration
AUCss = the steady state area under concentration vs. time curve
CL = clearance
t½ = the terminal elimination half-life |
The clearance of anidulafungin is about 1 L/h and anidulafungin has a terminal
elimination half-life of 40-50 hours.
Distribution
The pharmacokinetics of anidulafungin following IV
administration are characterized by a short distribution half-life (0.5-1 hour)
and a volume of distribution of 30-50 L that is similar to total body fluid
volume. Anidulafungin is extensively bound ( > 99%) to human plasma proteins.
Metabolism
Hepatic metabolism of anidulafungin has not been observed.
Anidulafungin is not a clinically relevant substrate, inducer, or inhibitor of
cytochrome P450 (CYP450) isoenzymes. It is unlikely that anidulafungin will
have clinically relevant effects on the metabolism of drugs metabolized by
CYP450 isoenzymes.
Anidulafungin undergoes slow chemical degradation at
physiologic temperature and pH to a ring-opened peptide that lacks antifungal
activity. The in vitro degradation half-life of anidulafungin under
physiologic conditions is about 24 hours. In vivo, the ring-opened product is
subsequently converted to peptidic degradants and eliminated.
Excretion
In a single-dose clinical study, radiolabeled (14C)
anidulafungin was administered to healthy subjects. Approximately 30% of the
administered radioactive dose was eliminated in the feces over 9 days, of which
less than 10% was intact drug. Less than 1% of the administered radioactive
dose was excreted in the urine. Anidulafungin concentrations fell below the
lower limits of quantitation 6 days post-dose. Negligible amounts of
drug-derived radioactivity were recovered in blood, urine, and feces 8 weeks
post-dose.
Special Populations
Patients with fungal infections
Population pharmacokinetic analyses from four Phase 2/3
clinical studies including 107 male and 118 female patients with fungal
infections showed that the pharmacokinetic parameters of anidulafungin are not
affected by age, race, or the presence of concomitant medications which are known
metabolic substrates, inhibitors or inducers.
The pharmacokinetics of anidulafungin in patients with
fungal infections are similar to those observed in healthy subjects. The
pharmacokinetic parameters of anidulafungin estimated using population
pharmacokinetic modeling following IV administration of a maintenance dose of
50 mg/day or 100 mg/day (following a loading dose) are presented in Table 2.
Table 2 : Mean (%CV) Steady State Pharmacokinetic Parameters
of Anidulafungin Following IV Administration of Anidulafungin in Patients with
Fungal Infections Estimated Using Population Pharmacokinetic Modeling
| PK Parametera |
Anidulafungin IV Dosing Regimen (LD/MD, mg)c |
| 100/50 |
200/100 |
| Cmax, ss [mg/L] |
4.2 (22.4) |
7.2 (23.3) |
| Cmin, ss [mg/L] |
1.6 (42.1) |
3.3 (41.8) |
| AUCss [mg•h/L] |
55.2 (32.5) |
110.3 (32.5) |
| CL [L/h] |
1.0 (33.5) |
| t½,β[h] b |
26.5 (28.5) |
a All the parameters were estimated by population
modeling using a two-compartment model with first order elimination;
AUCss, Cmax,ss and Cmin,ss (steady state trough plasma concentration)
were estimated using individual PK parameters and infusion rate of
1 mg/min to administer recommended doses of 50 and 100 mg/day.
b t½, β is the predominant elimination half-life that
characterizes the majority of the concentration-time profile.
c LD/MD: loading dose/daily maintenance dose |
Gender
Dosage adjustments are not required based on gender. Plasma
concentrations of anidulafungin in healthy men and women were similar. In
multiple-dose patient studies, drug clearance was slightly faster
(approximately 22%) in men.
Geriatric
Dosage adjustments are not required for geriatric patients.
The population pharmacokinetic analysis showed that median clearance differed
slightly between the elderly group (patients 65, median CL = 1.07 L/h) and
the non-elderly group (patients < 65, median CL = 1.22 L/h) and the range of
clearance was similar.
Race
Dosage adjustments are not required based on race.
Anidulafungin pharmacokinetics were similar among Whites, Blacks, Asians, and
Hispanics.
HIV Status
Dosage adjustments are not required based on HIV status,
irrespective of concomitant anti-retroviral therapy.
Hepatic Insufficiency
Dosage adjustments are not required on the basis of mild,
moderate or severe hepatic insufficiency. Anidulafungin is not hepatically
metabolized. Anidulafungin pharmacokinetics were examined in subjects with
Child-Pugh class A, B or C hepatic insufficiency. Anidulafungin concentrations
were not increased in subjects with any degree of hepatic insufficiency.
Though a slight decrease in AUC was observed in patients with Child-Pugh C
hepatic insufficiency, it was within the range of population estimates noted
for healthy subjects.
Renal Insufficiency
Dosage adjustments are not required for patients with any
degree of renal insufficiency including those on hemodialysis. Anidulafungin
has negligible renal clearance. In a clinical study of subjects with mild,
moderate, severe or end stage (dialysis-dependent) renal insufficiency,
anidulafungin pharmacokinetics were similar to those observed in subjects with
normal renal function. Anidulafungin is not dialyzable and may be administered
without regard to the timing of hemodialysis.
Pediatric
The pharmacokinetics of anidulafungin after daily doses were investigated in
immunocompromised pediatric (2 through 11 years) and adolescent (12 through
17 years) patients with neutropenia. The steady state was achieved on the first
day after administration of the loading dose (twice the maintenance dose), and
the Cmax and AUCss increased in a dose-proportional manner. Concentrations
and exposures following administration of maintenance doses of 0.75 and 1.5
mg/kg/day in this population were similar to those observed in adults following
maintenance doses of 50 and 100 mg/day, respectively (as shown in Table 3) (see
PRECAUTIONS, Pediatric use).
Table 3 : Mean (%CV) Steady State Pharmacokinetic Parameters
of Anidulafungin Following IV Administration of Anidulafungin Once Daily in
Pediatric Subjects
| PK Parametera |
Anidulafungin IV Dosing Regimen (LD/MD, mg/kg)b |
| 1.5/0.75 |
3.0/1.5 |
| Age Group |
2-11 yrs |
12-17 yrs |
2-11 yrs |
12-17 yrs |
| (N = 6) |
(N = 6) |
(N = 6) |
(N = 6) |
| Cmax, ss[mg/L] |
3.32 (50.0) |
4.35 (22.5) |
7.57 (34.2) |
6.88 (24.3) |
| AUCss[mg•h/L] |
41.1 (38.4) |
56.2 (27.8) |
96.1 (39.5) |
102.9 (28.2) |
a Data were collected on Day 5
b LD/MD: loading dose/daily maintenance dose |
Drug Interaction Studies
In vitro studies showed that anidulafungin is not
metabolized by human cytochrome P450 or by isolated human hepatocytes, and does
not significantly inhibit the activities of human CYP isoforms (1A2, 2B6, 2C8,
2C9, 2C19, 2D6 and 3A) at clinically relevant concentrations. No clinically
relevant drug-drug interactions were observed with drugs likely to be
co-administered with anidulafungin.
Cyclosporine (CYP3A4 substrate): In a study in which 12 healthy
adult subjects received 100 mg/day maintenance dose of anidulafungin following
a 200 mg loading dose (on Days 1 to 8) and in combination with 1.25 mg/kg oral
cyclosporine twice daily (on Days 5 to 8), the steady state Cmax of anidulafungin
was not significantly altered by cyclosporine; the steady state AUC of anidulafungin
was increased by 22%. A separate in vitro study showed that anidulafungin
has no effect on the metabolism of cyclosporine. No dosage adjustment of either
drug is warranted when co-administered.
Voriconazole (CYP2C19, CYP2C9, CYP3A4 inhibitor and substrate):
In a study in which 17 healthy subjects received 100 mg/day maintenance dose
of anidulafungin following a 200 mg loading dose, 200 mg twice daily oral voriconazole
(following two 400 mg loading doses) and both in combination, the steady state
Cmax and AUC of anidulafungin and voriconazole were not significantly altered
by coadministration. No dosage adjustment of either drug is warranted when
co-administered.
Tacrolimus (CYP3A4 substrate): In a study in which 35 healthy
subjects received a single oral dose of 5 mg tacrolimus (on Day 1), 100 mg/day
maintenance dose of anidulafungin following a 200 mg loading dose (on Days 4
to 12) and both in combination (on Day 13), the steady state Cmax and AUC of
anidulafungin and tacrolimus were not significantly altered by co-administration.
No dosage adjustment of either drug is warranted when co-administered.
AmBisome® (liposomal amphotericin B): The pharmacokinetics
of anidulafungin were examined in 27 patients that were co-administered liposomal
amphotericin B. The population pharmacokinetic analysis showed that when compared
to data from patients that did not receive amphotericin B, the pharmacokinetics
of anidulafungin were not significantly altered by co-administration with amphotericin
B. No dosage adjustment of anidulafungin is warranted.
Rifampin (potent CYP450 inducer): The pharmacokinetics of anidulafungin
were examined in 27 patients that were co-administered anidulafungin and rifampin.
The population pharmacokinetic analysis showed that when compared to data from
patients that did not receive rifampin, the pharmacokinetics of anidulafungin
were not significantly altered by co-administration with rifampin. No dosage
adjustment of anidulafungin is warranted.
Microbiology
Mechanism Of Action
Anidulafungin is a semi-synthetic echinocandin with
antifungal activity. Anidulafungin inhibits glucan synthase, an enzyme present
in fungal, but not mammalian cells. This results in inhibition of the
formation of 1,3-β-D-glucan, an essential component of the fungal cell
wall.
Activity in vitro
Anidulafungin is active in vitro against Candida albicans, C.
glabrata, C. parapsilosis, and C. tropicalis (see INDICATIONS
AND USAGE, Clinical Studies).
MICs were determined according to the Clinical and
Laboratory Standards Institute (CLSI) approved standard reference method M27
for susceptibility testing of yeasts. However, no correlation between in vitro
activity (MIC) as determined by this method and clinical outcome has been
established.
Activity In Vivo
Parenterally administered anidulafungin was effective
against Candida albicans in immunocompetent and immunosuppressed mice
and rabbits with disseminated infection as measured by prolonged survival and
reduction in mycological burden. Anidulafungin also reduced the mycological
burden of fluconazoleresistant C. albicans in an
oropharyngeal/esophageal infection model in immunosuppressed rabbits.
Drug Resistance
Emergence of resistance to anidulafungin has not been
studied.
Anidulafungin was active against Candida albicans resistant
to fluconazole. Cross resistance with other echinocandins has not been studied.
Clinical Studies
Candidemia and other Candida infections (intra-abdominal abscess, and peritonitis)
The safety and efficacy of ERAXIS were evaluated in a Phase
3, randomized, double-blind study of patients with candidemia and/or other
forms of invasive candidiasis. Patients were randomized to receive once daily
IV ERAXIS (200 mg loading dose followed by 100 mg maintenance dose) or IV
fluconazole (800 mg loading dose followed by 400 mg maintenance dose).
Patients were stratified by APACHE II score ( ≤ 20 and > 20) and the
presence or absence of neutropenia. Patients with Candida endocarditis,
osteomyelitis or meningitis, or those with infection due to C. krusei, were
excluded from the study. Treatment was administered for at least 14 and not
more than 42 days. Patients in both study arms were permitted to switch to
oral fluconazole after at least 10 days of intravenous therapy, provided that
they were able to tolerate oral medication, were afebrile for at least 24
hours, and the last blood cultures were negative for Candida species.
Patients who received at least one dose of study medication
and who had a positive culture for Candida species from a normally sterile site
before entry into the study (modified intent-to-treat [MITT] population) were
included in the primary analysis of global response at the end of IV therapy.
A successful global response required clinical cure or improvement
(significant, but incomplete resolution of signs and symptoms of the Candida
infection and no additional antifungal treatment), and documented or presumed
microbiological eradication. Patients with an indeterminate outcome were
analyzed as failures in this population.
Two hundred and fifty-six patients were randomized and
received at least one dose of study medication. The median duration of IV
therapy was 14 and 11 days in the ERAXIS and fluconazole arms, respectively.
For those who received oral fluconazole, the median duration of oral therapy
was 7 days for the ERAXIS arm and 5 days for the fluconazole arm.
Patient disposition is presented in Table 4.
Table 4 : Patient Disposition and Reasons for Discontinuation
in Candidemia and other Candida infection study
| |
ERAXIS
n (%) |
Fluconazole
n (%) |
| Treated patients |
131 |
125 |
| Patients completing study through 6 week follow-up |
94 (71.8) |
80 (64.0) |
| DISCONTINUATIONS FROM STUDY MEDICATION |
| Total discontinued from study medication |
34 (26.0) |
48 (38.4) |
| Discontinued due to adverse events |
12 (9.2) |
21 (16.8) |
| Discontinued due to lack of efficacy |
11 (8.4) |
16 (12.8) |
Two hundred and forty-five patients (127 ERAXIS, 118
fluconazole) met the criteria for inclusion in the MITT population. Of these,
219 patients (116 ERAXIS, 103 fluconazole) had candidemia only. Risk factors
for candidemia among patients in both treatment arms in this study were:
presence of a central venous catheter (78%), receipt of broad-spectrum
antibiotics (69%), recent surgery (42%), recent hyperalimentation (25%), and
underlying malignancy (22%). The most frequent species isolated at baseline was
C. albicans (61.6%), followed by C. glabrata (20.4%), C.
parapsilosis (11.8%) and C. tropicalis (10.6%). The majority (97%)
of patients were non-neutropenic (ANC > 500) and 81% had APACHE II scores less
than or equal to 20.
Global success rates in patients with candidemia and other
Candida infections are summarized in Table 5.
Table 5 : Efficacy Analysis: Global Success in patients
with Candidemia and other Candida infections (MITT Population)
| Timepoint |
ERAXIS
(N=127)
n (%) |
Fluconazole
(N=118)
n (%) |
Treatment
Differencea, %
(95% C.I.) |
| End of IV Therapy |
96 (75.6) |
71 (60.2) |
15.42
(3.9, 27.0) |
| End of All Therapyb |
94 (74.0) |
67 (56.8) |
17.24
(2.9, 31.6c) |
| 2 Week Follow-up |
82 (64.6) |
58 (49.2) |
15.41
( 0.4, 30.4 c) |
| 6 Week Follow-up |
71 (55.9) |
52 (44.1) |
11.84
(-3.4, 27.0c) |
a Calculated as ERAXIS minus fluconazole
b 33 patients in each study arm (26% -ERAXIS and 28.8 % fluconazole-treated)
switched to oral fluconazole after the end of IV therapy.
c 98.3% confidence intervals, adjusted post hoc for multiple
comparisons of secondary time points |
Table 6 presents outcome and mortality data for the MITT population.
Table 6 : Outcomes & Mortality in Candidemia and other
Candida Infections
| |
ERAXIS |
Fluconazole |
Between group differencea
( 95% CI) |
| No. of MITT patients |
127 |
118 |
|
| Favorable Outcomes (MITT) At End Of IV Therapy |
| All MITT patients |
| Candidemia |
88/116 (75.9%) |
63/103 (61.2%) |
14.7 (2.5, 26.9) |
| Neutropenic |
½ |
2/4 |
- |
| Non neutropenic |
87/114 (76.3%) |
61/99 (61.6%) |
- |
| Multiple sites |
| Peritoneal fluid/ intra-abdominal abscess |
4/6 |
5/6 |
- |
| Blood/peritoneum (intra-abdominal abscess) |
2/2 |
0/2 |
- |
| Blood /bile |
- |
1/1 |
- |
| Blood/renal |
- |
1/1 |
- |
| Pancreas |
- |
0/3 |
- |
| Pelvic abscess |
- |
½ |
- |
| Pleural fluid |
1/1 |
- |
- |
| Blood/ pleural fluid |
0/1 |
- |
- |
| Blood/left thigh lesion biopsy |
1/1 |
- |
- |
| Total |
8/11 (72.7%) |
8/15 (53.3%) |
- |
| Mortality |
| Overall study mortality |
29/127 (22.8 %) |
37/118 (31.4%) |
- |
| Mortality during study therapy |
10/127 (7.9%) |
17/118 (14.4%) |
- |
| Mortality attributed to Candida |
2/127 (1.6%) |
5/118 (4.2%) |
- |
| a Calculated as ERAXIS minus fluconazole |
Esophageal Candidiasis
ERAXIS was evaluated in a double-blind, double-dummy,
randomized Phase 3 study. Three hundred patients received ERAXIS (100 mg
loading dose IV on Day 1 followed by 50 mg/day IV) and 301 received oral
fluconazole (200 mg loading dose on Day 1 followed by 100 mg/day). Treatment
duration was 7 days beyond resolution of symptoms for a minimum of 14 and a maximum
of 21 days.
Of the 442 patients with culture confirmed esophageal
candidiasis, most patients (91%) had C. albicans isolated at the baseline.
Treatment groups were similar in demographic and other
baseline characteristics.
In this study, of 280 patients tested, 237 (84.6%) tested
HIV positive. In both groups the median time to resolution of symptoms was 5
days and the median duration of therapy was 14 days.
The primary endpoint was endoscopic outcome at end of
therapy (EOT). Patients were considered clinically evaluable if they received
at least 10 days of therapy, had an EOT assessment with a clinical outcome
other than EOT, and did not have any protocol violations prior to the EOT visit
that would affect an assessment of efficacy.
An endoscopic success, defined as cure (endoscopic grade of
0 on a 4 point severity scale) or improvement (decrease of one or more grades
from baseline), was seen in 225/231 (97.4%) ERAXIS-treated patients and 233/236
(98.7%) fluconazole-treated patients (Table 7). The majority of these patients
were endoscopic cures (grade=0). Two weeks after completing therapy, the ERAXIS
group had significantly more endoscopically-documented relapses than the
fluconazole group, 120/225 (53.3%) vs. 45/233 (19.3%), respectively (Table 7).
Table 7 : Endoscopy Results in Patients with Esophageal Candidiasis
(Clinically Evaluable Population)
| Endoscopic Response at End of Therapy |
| Response |
ERAXIS
N= 231 |
Fluconazole
N= 236 |
Treatment
Differencea |
95% CI |
| Endoscopic Success n, (%) |
225 (97.4) |
233 (98.7) |
-1.3% |
-3.8%, 1.2% |
| Cure |
204 (88.3) |
221 (93.6) |
|
|
| Improvement |
21 (9.1) |
12 (5.1) |
|
|
| Failure n, (%) |
6 (2.6) |
3 (1.3) |
|
|
| ENDOSCOPIC RELAPSE RATES AT FOLLOW-UP, 2 WEEKS POST-TREATMENT |
| |
ERAXIS |
Fluconazole |
Treatment
Differencea |
95% CI |
| Endoscopic Relapse, n/N (%) |
120/225 (53.3%) |
45/233 (19.3%) |
34.0% |
25.8%, 42.3% |
| a Calculated as ERAXIS minus fluconazole |
Clinical success (cure or improvement in clinical symptoms including odynophagia/dysphagia
and retrosternal pain) occurred in 229/231 (99.1%) of the ERAXIS-treated patients
and 235/236 (99.6%) of the fluconazole-treated patients at the end of therapy.
For patients with C. albicans, microbiological success occurred in 142/162
(87.7%) of the ERAXIS-treated group and 157/166 (94.6%) of the fluconazole-treated
group at the end of therapy. For patients with Candida species other than C.
albicans, success occurred in 10/12 (83.3%) of the ERAXIS-treated group
and 14/16 (87.5%) of the fluconazole-treated group.
Animal Pharmacology And Toxicology
In 3 month studies, liver toxicity, including single cell
hepatocellular necrosis, hepatocellular hypertrophy and increased liver weights
were observed in monkeys and rats at doses equivalent to 5-6 times human
exposure. For both species, hepatocellular hypertrophy was still noted one
month after the end of dosing.
Last updated on RxList: 6/24/2009