Clinical Pharmacology for Mycamine
Mechanism Of Action
Micafungin is a member of the echinocandin class of antifungal agents [see Microbiology].
Pharmacodynamics
The pharmacodynamics of micafungin related to hematogenous Candida meningoencephalitis are described in other sections of the prescribing information [see Use In Specific Populations  and Microbiology].
Pharmacokinetics
Adults
The pharmacokinetics of micafungin were determined in healthy subjects, hematopoietic stem cell transplant recipients, and patients with esophageal candidiasis up to a maximum daily dose of 8 mg/kg body weight.
The relationship of area under the concentration-time curve (AUC) to micafungin dose was linear over the daily dose range of 50 mg to 150 mg and 3 mg/kg to 8 mg/kg body weight. Typically, 85% of the steady-state concentration is achieved after three daily MYCAMINE doses.
Steady-state pharmacokinetic parameters in relevant patient populations after repeated daily administration are presented in Table 7.
Table 7: Pharmacokinetic Parameters of Micafungin in Adult Patients
| Population |
n |
Dose (mg) |
Pharmacokine (Mean ± Stanttic Parameters ard Deviation) |
| Cmax (mcg/mL) |
AUC0-241 (mcg•h/mL) |
t½(h) |
Cl (mL/min/kg) |
| Patients with IC2 [Day 1] [ Steady-State] |
20 |
100 |
5.7 ± 2.2 |
83 ± 51 |
14.5 ± 7.0 |
0.359 ± 0.179 |
| 20 |
100 |
10.1 ± 4.4 |
97 ± 29 |
13.4 ± 2.0 |
0.298 ± 0.115 |
| HIV3- Positive |
20 |
50 |
4.1 ± 1.4 |
36 ± 9 |
14.9 ± 4.3 |
0.321 ± 0.098 |
| Patients with EC4 |
20 |
100 |
8.0 ± 2.4 |
108 ± 31 |
13.8 ± 3.0 |
0.327 ± 0.093 |
| [Day 1] |
14 |
150 |
11.6 ± 3.1 |
151 ± 45 |
14.1 ± 2.6 |
0.340 ± 0.092 |
| [Day 14 or 21] |
20 |
50 |
5.1 ± 1.0 |
54 ± 13 |
15.6 ± 2.8 |
0.300 ± 0.063 |
| 20 |
100 |
10.1 ± 2.6 |
115 ± 25 |
16.9 ± 4.4 |
0.301 ± 0.086 |
| 14 |
150 |
16.4 ± 6.5 |
167 ± 40 |
15.2 ± 2.2 |
0.297 ± 0.081 |
| HSCT5 Recipients [Day 7] |
8 |
per kg 3 |
21.1 ± 2.84 |
234 ± 34 |
14.0 ± 1.4 |
0.214 ± 0.031 |
| 10 |
4 |
29.2 ± 6.2 |
339 ± 72 |
14.2 ± 3.2 |
0.204 ± 0.036 |
| 8 |
6 |
38.4 ± 6.9 |
479±157 |
14.9 ± 2.6 |
0.224 ± 0.064 |
| 8 |
8 |
60.8 ± 26.9 |
663±212 |
17.2 ± 2.3 |
0.223 ± 0.081 |
1 AUC0-infinity is presented for Day 1; AUC0-24 is presented for steady-state.
2 candidemia or other Candida infections.
3 human immunodeficiency virus.
4 esophageal candidiasis.
5 hematopoietic stem cell transplant. |
Pediatric Patients 4 Months Of Age And Older
Micafungin pharmacokinetics in 229 pediatric patients 4 months through 16 years of age were characterized using population pharmacokinetics. Micafungin exposure was dose proportional across the dose and age range studied.
Table 8: Summary (Mean +/- Standard Deviation) of Micafungin Pharmacokinetics in Pediatric Patients 4 Months of Age and Older (Steady-State)
| Body weight group |
N |
Dose1 mg/kg |
Cmax,ss2 (mcg/mL) |
AUC,ss2 (mcg-h/mL) |
t½3 |
CL3 (mL/min/kg) |
| 30 kg or less |
149 |
1.0 |
7.1 +/- 4.7 |
55 +/- 16 |
12.5 +/- 4.6 |
0.328 +/- 0.091 |
| 2.0 |
14.2 +/- 9.3 |
109 +/- 31 |
| 3.0 |
21.3 +/- 14.0 |
164 +/- 47 |
| Greater than 30 kg |
80 |
1.0 |
8.7 +/- 5.6 |
67 +/- 17 |
|
|
| 2.0 |
17.5 +/- 11.2 |
134 +/- 33 |
13.6 +/- 8.8 |
0.241 +/- 0.061 |
| 2.5 |
23.0 +/- 14.5 |
176 +/- 42 |
|
|
1 Or the equivalent if receiving the adult dose (50, 100, or 150 mg).
2 Derived from simulations from the population PK model.
3 Derived from the population PK model. |
Pediatric Patients Younger Than 4 Months Of Age
Micafungin pharmacokinetic data in 103 pediatric patients less than 4 months of age were assessed using population pharmacokinetics. Predicted micafungin AUC estimates were dose proportional across the dose regimens and age ranges studied. The body weight-normalized micafungin clearance in pediatric patients less than 4 months of age is higher than the body weight-normalized micafungin clearance in older pediatric patients greater than 4 months of age and adults. Administration of 4 mg/kg once daily micafungin to pediatric patients less than 4 months of age produces a mean (SD) steady-state AUC of 131 (50) mcg·h/mL, which is comparable to the steady-state AUC in pediatric patients 4 months of age and older administered micafungin 2 mg/kg/day and adults administered 100 mg once daily.
Specific Populations
Adult Patients With Renal Impairment
MYCAMINE does not require dose adjustment in patients with renal impairment. A single 1-hour infusion of 100 mg MYCAMINE was administered to 9 adult subjects with severe renal impairment (creatinine clearance less than 30 mL/min) and to 9 age-, gender-, and weight-matched subjects with normal renal function (creatinine clearance greater than 80 mL/min). The maximum concentration (Cmax) and AUC were not significantly altered by severe renal impairment.
Since micafungin is highly protein bound, it is not dialyzable. Supplementary dosing should not be required following hemodialysis.
Adult Patients With Hepatic Impairment
- A single 1-hour infusion of 100 mg MYCAMINE was administered to 8 adult subjects with moderate hepatic impairment (Child-Pugh score 7 to 9) and 8 age-, gender-, and weight-matched subjects with normal hepatic function. The Cmax and AUC values of micafungin were lower by approximately 22% in subjects with moderate hepatic impairment compared to normal subjects. This difference in micafungin exposure does not require dose adjustment of MYCAMINE in patients with moderate hepatic impairment.
- A single 1-hour infusion of 100 mg MYCAMINE was administered to 8 adult subjects with severe hepatic impairment (Child-Pugh score 10 to 12) and 8 age-, gender-, ethnic- and weight-matched subjects with normal hepatic function. The mean Cmax and AUC values of micafungin were lower by approximately 30% in subjects with severe hepatic impairment compared to normal subjects. The mean Cmax and AUC values of M-5 metabolite were approximately 2.3-fold higher in subjects with severe hepatic impairment compared to normal subjects; however, this exposure (parent and metabolite) was comparable to that in patients with systemic Candida infection. Therefore, no MYCAMINE dose adjustment is necessary in patients with severe hepatic impairment.
Distribution
The mean ± standard deviation volume of distribution of micafungin at terminal phase was 0.39 ± 0.11 L/kg body weight when determined in adult patients with esophageal candidiasis at the dose range of 50 mg to 150 mg.
Micafungin is highly (greater than 99%) protein bound in vitro, independent of plasma concentrations over the range of 10 to 100 mcg/mL. The primary binding protein is albumin; however, micafungin, at therapeutically relevant concentrations, does not competitively displace bilirubin binding to albumin. Micafungin also binds to a lesser extent to α1-acid-glycoprotein.
Micafungin is neither a substrate nor an inhibitor of P-glycoprotein.
Metabolism
Micafungin is metabolized to M-1 (catechol form) by arylsulfatase, with further metabolism to M-2 (methoxy form) by catechol-O-methyltransferase. M-5 is formed by hydroxylation at the side chain (ω-1 position) of micafungin catalyzed by cytochrome P450 (CYP) isozymes. Even though micafungin is a substrate for and a weak inhibitor of CYP3A in vitro, hydroxylation by CYP3A is not a major pathway for micafungin metabolism in vivo. Micafungin is neither a P-glycoprotein substrate nor inhibitor in vitro.
In four healthy volunteer studies, the ratio of metabolite to parent exposure (AUC) at a dose of 150 mg/day was 6% for M-1, 1% for M-2, and 6% for M-5. In patients with esophageal candidiasis, the ratio of metabolite to parent exposure (AUC) at a dose of 150 mg/day was 11% for M-1, 2% for M-2, and 12% for M-5.
Excretion
The excretion of radioactivity following a single intravenous dose of 14C-micafungin sodium for injection (25 mg) was evaluated in healthy volunteers. At 28 days after administration, mean urinary and fecal recovery of total radioactivity accounted for 82.5% (76.4% to 87.9%) of the administered dose. Fecal excretion is the major route of elimination (total radioactivity at 28 days was 71% of the administered dose).
Microbiology
Mechanism Of Action
Micafungin inhibits the synthesis of 1,3-beta-D-glucan, an essential component of fungal cell walls, which is not present in mammalian cells.
Activity In Animal Models Of Candidiasis
Activity of micafungin has been demonstrated in both mucosal and disseminated murine and rabbit models of candidiasis. Micafungin administered to immunocompetent or immunosuppressed mice or rabbits with disseminated candidiasis prolonged survival (mice) and/or decreased the fungal burden in different organs including brain in a dose-dependent manner (mice and rabbits). Overall, antifungal activity of micafungin was demonstrated in the brain and eye tissues of nonneutropenic rabbits with HCME infected with a micafungin-sensitive strain of C. albicans; however, the activity varied in different central nervous system and ocular compartments. In the cerebrum, culture negativity was achieved at a micafungin dose regimen of 32 mg/kg once daily for 7 days; whereas, in spinal cord, vitreous humor, and choroid, culture negativity was achieved at micafungin dose regimens of 24 to 32 mg/kg once daily. Compared to untreated animals, micafungin dose regimens between 8 and 24 mg/kg once daily reduced fungal burden in the cerebrum and cerebellum. When cerebrum, cerebellum and spinal cord data were combined, a decrease in fungal burden relative to untreated controls was evident at micafungin dose regimens between 16 and 32 mg/kg once daily [see Use In Specific Populations].
Resistance
There have been reports of clinical failures in patients receiving MYCAMINE therapy due to the development of drug resistance. Some of these reports have identified specific mutations in the FKS protein component of the glucan synthase enzyme that are associated with higher MICs and breakthrough infection.
Antimicrobial Activity
Micafungin has been shown to be active against most isolates of the following Candida species, both in vitro and in clinical infections [see Indications And Usage]:
Candida albicans
Candida glabrata
Candida guilliermondii
Candida krusei
Candida parapsilosis
Candida tropicalis
Susceptibility Testing
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
High doses of micafungin sodium (5 to 8 times the highest recommended human dose, based on AUC comparisons) have been associated with irreversible changes to the liver when administered for 3 or 6 months, and these changes may be indicative of pre-malignant processes [see Nonclinical Toxicology].
Clinical Studies
Treatment Of Candidemia And Other Candida Infections In Adult And Pediatric Patients 4 Months Of Age And Older
Two dose levels of MYCAMINE were evaluated in a randomized, double-blind study to determine the efficacy and safety versus caspofungin in patients with invasive candidiasis and candidemia. Patients were randomized to receive once daily intravenous infusions (IV) of MYCAMINE, either 100 mg/day or 150 mg/day or caspofungin (70 mg loading dose followed by 50 mg maintenance dose). Patients in both study arms were permitted to switch to oral fluconazole after at least 10 days of intravenous therapy, provided they were non-neutropenic, had improvement or resolution of clinical signs and symptoms, had a Candida isolate which was susceptible to fluconazole, and had documentation of 2 negative cultures drawn at least 24 hours apart. Patients were stratified by APACHE II score (20 or less or greater than 20) and by geographic region. Patients with Candida endocarditis were excluded from this analysis. Outcome was assessed by overall treatment success based on clinical (complete resolution or improvement in attributable signs and symptoms and radiographic abnormalities of the Candida infection and no additional antifungal therapy) and mycological (eradication or presumed eradication) response at the end of IV therapy. Deaths that occurred during IV study drug therapy were treated as failures.
In this study, 111/578 (19.2%) of the patients had baseline APACHE II scores of greater than 20, and 50/578 (8.7%) were neutropenic at baseline (absolute neutrophil count less than 500 cells/mm³). Outcome, relapse and mortality data are shown for the recommended dose of MYCAMINE (100 mg/day) and caspofungin in Table 9.
Table 9: Efficacy Analysis: Treatment Success in Patients in Study 03-0-192 with Candidemia and Other Candida Infections
|
MYCAMINE 100 mg/day n (%) % treatment difference (95% CI) |
Caspofungin 70/50 mg/day1 n (%) |
| Treatment Success at End of IV Therapy2 |
135/191 (70.7) |
119/188 (63.3) |
| 7.4 (-2.0, 16.3) |
|
| Success in Patients with Neutropenia at Baseline |
14/22 (63.6) |
5/11 (45.5) |
| Success by Site of Infection |
|
|
| Candidemia |
116/163 (71.2) |
103/161(64) |
| Abscess |
4/5 (80) |
5/9 (55.6) |
| Acute Disseminated3 |
6/13 (46.2) |
5/9 (55.6) |
| Endophthalmitis |
1/3 |
1/1 |
| Chorioretinitis |
0/3 |
0 |
| Skin |
1/1 |
0 |
| Kidney |
2/2 |
1/1 |
| Pancreas |
1/1 |
0 |
| Peritoneum |
1/1 |
0 |
| Lung/Skin |
0/1 |
0 |
| Lung/Spleen |
0/1 |
0 |
| Liver |
0 |
0/2 |
| Intraabdominal abscess |
0 |
3/5 |
| Chronic Disseminated |
0/1 |
0 |
| Peritonitis |
4/6 (66.7) |
2/5 (40) |
| Success by Organism4 |
|
|
| C. albicans |
57/81 (70.4) |
45/73 (61.6) |
| C. glabrata |
16/23 (69.6) |
19/31 (61.3) |
| C. tropicalis |
17/27 (63) |
22/29 (75.9) |
| C. parapsilosis |
21/28 (75) |
22/39 (56.4) |
| C. krusei |
5/8 (62.5) |
2/3 (66.7) |
| C. guilliermondii |
1/2 |
0/1 |
| C. lusitaniae |
2/3 (66.7) |
2/2 |
| Relapse through 6 Weeks5 |
|
|
| Overall |
49/135 (36.3) |
44/119 (37) |
| Culture-confirmed relapse |
5 |
4 |
| Required systemic antifungal therapy |
11 |
5 |
| Died during follow-up |
17 |
16 |
| Not assessed |
16 |
19 |
| Overall study mortality |
58/200 (29) |
51/193 (26.4) |
| Mortality during IV therapy |
28/200 (14) |
27/193 (14) |
1 70 mg loading dose on day 1 followed by 50 mg/day thereafter (caspofungin).
2 All patients who received at least one dose of study medication and had documented invasive candidiasis or candidemia. Patients with Candida endocarditis were excluded from the analyses.
3 A patient may have had greater than 1 organ of dissemination.
4 A patient may have had greater than 1 baseline infection species.
5 All patients who had a culture-confirmed relapse or required systemic antifungal therapy in the post-treatment period for a suspected or proven Candida infection. Also includes patients who died or were not assessed in follow-up. |
In two cases of ophthalmic involvement assessed as failures in the above table due to missing evaluation at the end of IV treatment with MYCAMINE, therapeutic success was documented during protocol-defined oral fluconazole therapy.
Treatment Of Esophageal Candidiasis In Adult And Pediatric Patients 4 Months Of Age And Older
In two controlled trials involving 763 patients with esophageal candidiasis, 445 adults with endoscopically-proven candidiasis received MYCAMINE, and 318 received fluconazole for a median duration of 14 days (range 1 to 33 days).
MYCAMINE was evaluated in a randomized, double-blind study which compared MYCAMINE 150 mg/day (n = 260) to intravenous fluconazole 200 mg/day (n = 258) in adults with endoscopically-proven esophageal candidiasis. Most patients in this study had HIV infection, with CD4 cell counts less than 100 cells/mm³. Outcome was assessed by endoscopy and by clinical response at the end of treatment. Endoscopic cure was defined as endoscopic grade 0, based on a scale of 0 to 3. Clinical cure was defined as complete resolution in clinical symptoms of esophageal candidiasis (dysphagia, odynophagia, and retrosternal pain). Overall therapeutic cure was defined as both clinical and endoscopic cure. Mycological eradication was determined by culture, and by histological or cytological evaluation of esophageal biopsy or brushings obtained endoscopically at the end of treatment. As shown in Table 10, endoscopic cure, clinical cure, overall therapeutic cure, and mycological eradication were comparable for patients in the MYCAMINE and fluconazole treatment groups.
Table 10: Endoscopic, Clinical, and Mycological Outcomes for Esophageal Candidiasis at End-of-Treatment
| Treatment Outcome1 |
MYCAMINE 150 mg/day
n = 260 |
Fluconazole 200 mg/day
n = 258 |
% Difference2 (95% CI) |
| Endoscopic Cure |
228 (87.7%) |
227 (88.0%) |
-0.3%
(-5.9, +5.3) |
| Clinical Cure |
239 (91.9%) |
237 (91.9%) |
0.06%
(-4.6, +4.8) |
| Overall Therapeutic Cure |
223 (85.8%) |
220 (85.3%) |
0.5%
(-5.6, +6.6) |
| Mycological Eradication |
141/189 (74.6%) |
149/192 (77.6%) |
-3.0%
(-11.6, +5.6) |
1 Endoscopic and clinical outcome were measured in the modified intent-to-treat population, including all randomized patients who received 1 or more doses of study treatment. The mycological outcome was determined in the per protocol (evaluable) population, including patients with confirmed esophageal candidiasis who received at least 10 doses of study drug, and had no major protocol violations.
2 Calculated as MYCAMINE – fluconazole. |
Most patients (96%) in this study had C. albicans isolated at baseline. The efficacy of MYCAMINE was evaluated in less than 10 patients with Candida species other than C. albicans, most of which were isolated concurrently with C. albicans.
Relapse was assessed at 2 and 4 weeks post-treatment in patients with overall therapeutic cure at end of treatment. Relapse was defined as a recurrence of clinical symptoms or endoscopic lesions (endoscopic grade greater than 0). There was no statistically significant difference in relapse rates at either 2 weeks or through 4 weeks post-treatment for patients in the MYCAMINE and fluconazole treatment groups, as shown in Table 11.
Table 11: Relapse of Esophageal Candidiasis at Week 2 and through Week 4 Post-Treatment in Patients with Overall Therapeutic Cure at the End of Treatment
| Relapse |
MYCAMINE 150 mg/day
n = 223 |
Fluconazole 200 mg/day
n = 220 |
% Difference1 (95% CI) |
| Relapse2 at Week 2 |
40 (17.9%) |
30 (13.6%) |
4.3% (-2.5, 11.1) |
| Relapse2 through Week 4 (cumulative) |
73 (32.7%) |
62 (28.2%) |
4.6% (-4.0, 13.1) |
1 Calculated as MYCAMINE – fluconazole; N = number of patients with overall therapeutic cure (both clinical and endoscopic cure at end-of-treatment);
2 Relapse included patients who died or were lost to follow-up, and those who received systemic anti-fungal therapy in the post-treatment period. |
In this study, 459 of 518 (88.6%) patients had oropharyngeal candidiasis in addition to esophageal candidiasis at baseline. At the end of treatment, 192/230 (83.5%) MYCAMINE-treated patients and 188/229 (82.1%) of fluconazole-treated patients experienced resolution of signs and symptoms of oropharyngeal candidiasis. Of these, 32.3% in the MYCAMINE group, and 18.1% in the fluconazole group (treatment difference = 14.2%; 95% confidence interval [5.6, 22.8]) had symptomatic relapse at 2 weeks post-treatment. Relapse included patients who died or were lost to follow-up, and those who received systemic antifungal therapy during the post-treatment period. Cumulative relapse at 4 weeks post-treatment was 52.1% in the MYCAMINE group and 39.4% in the fluconazole group (treatment difference 12.7%, 95% confidence interval [2.8, 22.7]).
Prophylaxis Of Candida Infections In Hematopoietic Stem Cell Transplant Recipients
In a randomized, double-blind study, MYCAMINE (50 mg IV once daily) was compared to fluconazole (400 mg IV once daily) in 882 [adult (791) and pediatric (91)] patients undergoing an autologous or syngeneic (46%) or allogeneic (54%) stem cell transplant. All pediatric patients, except 2 per group, received allogeneic transplants. The status of the patients’ underlying malignancy at the time of randomization was: 365 (41%) patients with active disease, 326 (37%) patients in remission, and 195 (22%) patients in relapse. The more common baseline underlying diseases in the 476 allogeneic transplant recipients were: chronic myelogenous leukemia (22%), acute myelogenous leukemia (21%), acute lymphocytic leukemia (13%), and non-Hodgkin’s lymphoma (13%). In the 404 autologous and syngeneic transplant recipients the more common baseline underlying diseases were: multiple myeloma (37.1%), non-Hodgkin’s lymphoma (36.4%), and Hodgkin's disease (15.6%). During the study, 198 of 882 (22.4%) transplant recipients had proven graft-versus-host disease; and 475 of 882 (53.9%) recipients received immunosuppressive medications for treatment or prophylaxis of graft-versus-host disease.
Study drug was continued until the patient had neutrophil recovery to an absolute neutrophil count (ANC) of 500 cells/mm³ or greater or up to a maximum of 42 days after transplant. The average duration of drug administration was 18 days (range 1 to 51 days). Duration of therapy was slightly longer in the pediatric patients who received MYCAMINE (median duration 22 days) compared to the adult patients who received MYCAMINE (median duration 18 days).
Successful prophylaxis was defined as the absence of a proven, probable, or suspected systemic fungal infection through the end of therapy (usually 18 days), and the absence of a proven or probable systemic fungal infection through the end of the 4-week post-therapy period. A suspected systemic fungal infection was diagnosed in patients with neutropenia (ANC less than 500 cells/mm³); persistent or recurrent fever (while ANC less than 500 cells/mm³) of no known etiology; and failure to respond to at least 96 hours of broad spectrum antibacterial therapy. A persistent fever was defined as four consecutive days of fever greater than 38®C. A recurrent fever was defined as having at least one day with temperatures 38.5®C or higher after having at least one prior temperature higher than 38®C; or having two days of temperatures higher than 38®C after having at least one prior temperature higher than 38®C. Transplant recipients who died or were lost to follow-up during the study were considered failures of prophylactic therapy.
Successful prophylaxis was documented in 80.7% of adult and pediatric MYCAMINE recipients, and in 73.7% of adult and pediatric patients who received fluconazole (7.0% difference [95% CI = 1.5, 12.5]), as shown in Table 12, along with other study endpoints. The use of systemic antifungal therapy post-treatment was 42% in both groups.
The number of proven breakthrough Candida infections was 4 in the MYCAMINE and 2 in the fluconazole group.
The efficacy of MYCAMINE against infections caused by fungi other than Candida has not been established.
Table 12: Results from Clinical Study of Prophylaxis of Candida Infections in Hematopoietic Stem Cell Transplant Recipients
| Outcome of Prophylaxis |
MYCAMINE 50 mg/day
(n = 425) |
Fluconazole 400 mg/day
(n = 457) |
| Success1 |
343 (80.7%) |
337 (73.7%) |
| Failure: |
82 (19.3%) |
120 (26.3%) |
| All Deaths2 |
18 (4.2%) |
26 (5.7%) |
| Proven/probable fungal infection prior to death |
1 (0.2%) |
3 (0.7%) |
| Proven/probable fungal infection (not resulting in death)2 |
6 (1.4%) |
8 (1.8%) |
| Suspected fungal infection1 |
53 (12.5%) |
83 (18.2%) |
| Lost to follow-up |
5 (1.2%) |
3 (0.7%) |
1 Difference (MYCAMINE – fluconazole): +7.0% [95% CI=1.5, 12.5].
2 Through end-of-study (4 weeks post-therapy).
3 Through end-of-therapy. |