CLINICAL PHARMACOLOGY
Mechanism Of Action
Ibrexafungerp is a triterpenoid antifungal drug [see Microbiology].
Pharmacodynamics
Ibrexafungerp exposure-response relationships and the time course of pharmacodynamic response are unknown.
Cardiac Electrophysiology
At a concentration of 5 times or greater than that achieved after a single day 300 mg twice daily dose, ibrexafungerp does not prolong the QTc interval to any clinically relevant extent.
Pharmacokinetics
In healthy subjects, ibrexafungerp area under the curve (AUC) and maximal concentration (Cmax) increased approximately dose-proportionally following single dose administration from 10 to 1600 mg (0.02 to 2.67 times the approved recommended daily dose) and multiple-dose administration from 300-800 mg (0.50 to 1.33 times the approved recommended daily dose).
Based on a population pharmacokinetic analysis in patients with VVC, the model predicts that 300 mg twice a day for 2 doses achieves a mean (%CV) AUC0-24 exposure of 6832 (15%) ng•hr/mL and Cmax of 435 (15%) ng/mL under fasted conditions and a mean AUC0-24 exposure of 9867 (15%) ng•h/mL and Cmax of 629 (15%) ng/mL under fed conditions.
Absorption
After oral administration of BREXAFEMME in healthy volunteers, ibrexafungerp generally reaches maximum plasma concentrations 4 to 6 hours after single and multiple dosing.
Effect of Food
Following administration of BREXAFEMME to healthy volunteers, the ibrexafungerp Cmax increased 32% and the AUC increased 38% with a high fat meal (800-1000 calories; 50% fat), compared to fasted conditions. This exposure change is not considered clinically significant [see DOSAGE AND ADMINISTRATION].
Distribution
The mean steady state volume of distribution (Vss) of ibrexafungerp is approximately 600 L. Ibrexafungerp is highly protein bound (greater than 99%), predominantly to albumin. Animal studies demonstrate a 9-fold higher exposure in vaginal tissue than in blood.
Elimination
Ibrexafungerp is eliminated mainly via metabolism and biliary excretion. The elimination halflife is approximately 20 hours.
Metabolism
In vitro studies show that ibrexafungerp undergoes hydroxylation by CYP3A4, followed by glucuronidation and sulfation of a hydroxylated inactive metabolite.
Excretion
Following oral administration of radio-labeled ibrexafungerp to healthy volunteers, a mean of 90% of the radioactive dose (51% as unchanged ibrexafungerp) was recovered in feces and 1% was recovered in urine.
Specific Populations
Post-Menarchal Pediatric Females And Geriatric Patients
The pharmacokinetics of ibrexafungerp were not altered in post-menarchal pediatric females (ages 13 to 17 years) or in geriatric patients (ages 65 to 76 years).
Patients With Hepatic Impairment
The pharmacokinetics of ibrexafungerp were not altered in subjects with mild (Child-Pugh Class A) to moderate (Child-Pugh Class B) hepatic impairment when the total AUC estimates were compared to healthy subjects.
The impact of severe hepatic impairment (Child-Pugh Class C) on the pharmacokinetics of ibrexafungerp is unknown.
Drug Interaction Studies
Ibrexafungerp is a substrate of CYP3A4 and P-gp. In vitro, ibrexafungerp is an inhibitor of CYP2C8, CYP3A4, P-gp transporter, and OATP1B3 transporter. Ibrexafungerp is not an inducer of CYP3A4.
The effect of coadministration of drugs on the pharmacokinetics of ibrexafungerp and the effect of ibrexafungerp on the pharmacokinetics of coadministered drugs were studied in healthy subjects.
Effect Of Coadministered Drugs On Ibrexafungerp Pharmacokinetics
Strong CYP3A4 Inhibitor
Ketoconazole (400 mg once daily for 15 days), a strong CYP3A4 and P-gp inhibitor, increased the ibrexafungerp AUC by 5.8-fold and Cmax by 2.5-fold [see DRUG INTERACTIONS].
Moderate CYP3A4 Inhibitor
Diltiazem (240 mg once daily for 15 days) increased the ibrexafungerp AUC by 2.5-fold and Cmax by 2.2-fold. This exposure change is not considered clinically significant at the approved recommended dosage for VVC.
Proton Pump Inhibitor
Pantoprazole (40 mg once daily for 5 days) decreased ibrexafungerp AUC by approximately 25% and Cmax by 22%. This exposure change is not considered clinically significant at the approved recommended dosage for VVC.
Effect Of Ibrexafungerp On The Pharmacokinetics Of Coadministered Drugs
The effects of ibrexafungerp on substrates of CYP2C8, CYP3A4, P-gp, and OATP1B3 transporters were evaluated in studies that included loading doses of ibrexafungerp of 1250 to 1500 mg (2.1 to 2.5 times the approved recommended daily dose) for two days followed by 750 mg (1.25 times the approved recommended daily dose) once daily for 3-7 days.
CYP2C8 substrates
Ibrexafungerp did not increase the AUC0-inf or Cmax of rosiglitazone, a moderate sensitive CYP2C8 substrate.
CYP3A4 substrates
Ibrexafungerp resulted in 1.4-fold increase in the AUC0-inf and no effect on the Cmax of the sensitive CYP3A4 and P-gp substrate tacrolimus.
P-gp substrates
Ibrexafungerp resulted in a 1.4-fold increase in the AUC0-48 and a 1.25-fold increase in the Cmax of the P-gp substrate dabigatran.
OATP1B3 transporters
Ibrexafungerp resulted in a 2.8-fold increase in the AUC0-24 and a 3.5- fold increase in the Cmax of the OATP1B3 transporter substrate pravastatin.
Microbiology
Mechanism Of Action
Ibrexafungerp, a triterpenoid antifungal agent, inhibits glucan synthase, an enzyme involved in the formation of 1,3-β-D-glucan, an essential component of the fungal cell wall.
Ibrexafungerp has concentration-dependent fungicidal activity against Candida species as measured by time kill studies. Ibrexafungerp retains in vitro antifungal activity when tested at pH 4.5 (the normal vaginal pH).
Resistance
The potential for resistance to ibrexafungerp has been evaluated in vitro and is associated with mutations of the fks-2 gene; the clinical relevance of these findings is unknown. Ibrexafungerp retains activity against most fluconazole resistant Candida spp. No resistance development was observed after monthly BREXAFEMME dosing in patients with RVVC.
Interaction With Other Antifungals
In vitro studies have not demonstrated antagonism between ibrexafungerp and azoles or echinocandins.
Antimicrobial Activity
Ibrexafungerp has been shown to be active against most isolates of the following microorganism both in vitro and in clinical infections [see INDICATIONS]:
Candida albicans
The following in vitro data are available, but their clinical significance is unknown.
Ibrexafungerp has in vitro activity against most isolates of the following microorganisms:
Candida auris
Candida dubliniensis
Candida glabrata
Candida guilliermondii
Candida keyfr
Candida krusei
Candida lusitaniae
Candida parapsilosis
Candida tropicalis
Animal Toxicity And/Or Pharmacology
Daily administration of oral ibrexafungerp for 26 weeks in rats, at the highest dose of 80 mg/kg/day (approximately 10 times the RHD based on AUC comparison), was associated with marked, but reversible, phospholipidosis and foamy histiocytes in alveolar tissue in the lung and labored breathing, marked irritation and metaplasia in gastric mucosa, and peripheral nerve degeneration accompanied by hind-limb paralysis.
Clinical Studies
Treatment Of VVC
Two randomized placebo-controlled clinical trials (Trial 1, NCT03734991 and Trial 2, NCT03987620) with a similar design were conducted to evaluate the safety and efficacy of a single day of BREXAFEMME 600 mg (two 150 mg tablets per dose, administered 12 hours apart) for the treatment of VVC. Non-pregnant post-menarchal females with a diagnosis of VVC were eligible. A diagnosis of VVC was defined as (a) minimum composite vulvovaginal signs and symptoms (VSS) score of ≥4 with at least two signs or symptoms having a score of 2 (moderate) or greater; (b) positive microscopic examination with 10% KOH in a vaginal sample revealing yeast forms (hyphae/pseudohyphae) or budding yeasts, and (c) normal vaginal pH (≤4.5). The total composite VSS score was based on the vulvovaginal signs (erythema, edema, excoriation) and vulvovaginal symptoms (itching, burning, or irritation) where each was scored as 0= absent, 1= mild, 2= moderate, or 3= severe. Study visits included the test of cure (TOC, Day 8 to 14) visit and a follow-up (Day 21 to 29) visit. The modified intent to treat (MITT) population included randomized subjects with a baseline culture positive for Candida species who took at least 1 dose of study medication.
Trial 1 was conducted in the United States. The MITT population consisted of 190 patients treated with BREXAFEMME and 100 patients treated with placebo. The average age was 34 years (range 17-67 years), with 91% less than 50 years. Fifty-four percent (54%) were White and 40% were Black or African American, 26% were of Hispanic or Latino ethnicity. The average BMI was 30 and 9% had a history of diabetes. The median VSS score at baseline was 9 (range 4- 18). The majority (92%) of the subjects were culture-positive with C. albicans.
Trial 2 was conducted in the United States (39%) and Bulgaria (61%). The MITT population consisted of 189 patients treated with BREXAFEMME and 89 patients treated with placebo. The average age was 34 years (range 18-65 years), with 92% less than 50 years. Eighty-one percent (81%) were White and 19% were Black or African American, 10% were of Hispanic or Latino ethnicity. The average BMI was 26 and 5% had a history of diabetes. The median VSS score at baseline was 10 (range 4-18). The majority (89%) of the subjects were culture-positive with C. albicans.
Efficacy was assessed by clinical outcome at the TOC visit. A complete clinical response was defined as the complete resolution of signs and symptoms (VSS score of 0). Additional endpoints included a negative culture for Candida spp. at the TOC visit, and clinical outcome at the follow-up visit.
Statistically significantly greater percentages of patients experienced a complete clinical response at TOC, negative culture at TOC, and complete clinical response at follow-up with treatment with BREXAFEMME compared to placebo. The results for the clinical and mycological responses are presented in Table 4.
Table 4. Clinical and Mycological Response in Post-menarchal Females with VVC in Trials 1 and 2, MITT Population
|
Trial 1 |
Trial 2 |
|
BREXAFEMME
N = 190
n (%) |
Placebo
N = 100
n (%) |
BREXAFEMME
N = 189
n (%) |
Placebo
N = 89
n (%) |
| Complete Clinical Response at TOC1 |
95 (50.0) |
28 (28.0) |
120 (63.5) |
40 (44.9) |
Difference (95% CI)
P-value |
22.0 (10.2, 32.8)
0.001 |
18.6 (6.0, 30.6)
0.009 |
| Negative Culture at TOC |
94 (49.5) |
19 (19.0) |
111 (58.7) |
26 (29.2) |
Difference (95% CI)
P-value |
30.5 (19.4, 40.3)
< 0.001 |
29.5 (17.2, 40.6)
< 0.001 |
| Complete Clinical Response at follow-up2 |
113 (59.5) |
44 (44.0) |
137 (72.5) |
44 (49.4) |
Difference (95% CI)
P-value |
15.5 (3.4, 27.1)
0.007 |
23.1 (10.8, 35.0)
0.006 |
1Absence of signs and symptoms (VSS Score of 0) without need for additional antifungal therapy or topical drug therapy for the treatment of vulvovaginal symptoms at test of cure (TOC) visit.
2Absence of signs and symptoms (VSS Score of 0) without need for further antifungal treatment or topical drug therapy for the treatment of vulvovaginal symptoms prior to follow-up visit. |
Reduction In The Incidence Of RVVC
A randomized placebo-controlled clinical trial (Trial 3, NCT04029116) was conducted to evaluate the safety and efficacy of BREXAFEMME 300 mg (two 150 mg tablets) administered approximately 12 hours apart (e.g., in the morning and in the evening) for one day, for a total daily dosage of 600 mg (four 150 mg tablets) administered once monthly for six months. Trial 3 was conducted in the United States (33%), Bulgaria (28%), Poland (12%), and Russia (28%). Non-pregnant post-menarchal females presenting with a symptomatic VVC episode and a history of recurrent VVC (at least 3 episodes of VVC in the previous 12 months) were eligible. The symptomatic episode at Screening was treated with 3 doses of fluconazole 150 mg 3 days apart.
To be randomized, patients had to have a culture-confirmed VVC episode at Screening and had to achieve significant resolution of their vulvovaginal signs and symptoms (defined as a total composite score ≤ 2 on the VSS Scale) after fluconazole treatment. Patients were randomized at a 1:1 ratio to receive double-blind BREXAFEMME or placebo administered as a single-day treatment repeated every 4 weeks for a total of 6 single-day treatments. Study visits included the test of cure (TOC) at Week 24 (4 weeks after the last dose) and a follow-up visit at Week 36.
The intent to treat (ITT) population was all randomized patients.
The ITT population consisted of 130 patients treated with BREXAFEMME and 130 patients treated with placebo. The average age was 34 years (range 18-65 years) with 95% less than 50 years. Ninety percent (90%) of patients were White, 8% were Black or African American, and 2% were Asian and other race. Eight percent (8%) of patients were of Hispanic or Latino ethnicity. The average BMI of the patient population was 25 and 16.5% were obese (BMI >30).
Efficacy was assessed as the percentage of patients with Clinical Success, defined as subjects with No Culture Proven, Presumed or Suspected Recurrence of VVC requiring antifungal therapy up to TOC at Week 24. Clinical Success was also assessed at the Week 36 Follow-up visit.
Statistically significantly greater percentages of patients experienced Clinical Success at TOC compared to placebo. The clinical success rate at TOC was lower for patients in the United States when compared to patients outside the United States (ex-US) for both BREXAFEMME and placebo groups. In both regions, the BREXAFEMME group had a higher clinical success rate compared to placebo (US: 33% vs 23% and ex-US: 81% vs 68% in BREXAFEMME vs placebo arms, respectively) and the difference between the treatment groups was consistent [US: 10.1% (-9.0, 29.1) and ex-US: 12.9% (0.04, 25.7)]. Clinical Success at Week 36 was also greater for BREXAFEMME compared to placebo. The results for clinical success and reasons for clinical failure are presented in Table 5.
Table 5. Clinical and Mycological Response in Post-menarchal Females with RVVC in Trial 3, ITT Population
|
Trial 3 |
BREXAFEMME
N = 130
n (%) |
Placebo
N = 130
n (%) |
Difference (95% CI)
P-value |
| Clinical success at TOC (Week 24) |
85 (65.4) |
69 (53.1) |
12.7 (2.2, 23.1) 0.020 |
| Reasons For Clinical Failure at TOC |
| Mycologically Proven Recurrence |
30 (23.1) |
47 (36.2) |
|
| Presumed Recurrence |
7 (5.4) |
3 (2.3) |
|
| Suspected Recurrence |
2 (1.5) |
4 (3.1) |
|
| Imputed Recurrence1 |
6 (4.6) |
7 (5.4) |
|
| Clinical success at Week 36 Follow Up Visit |
75 (57.7) |
60 (46.2) |
11.9
(1.1, 22.6)
0.034 |
| Reasons For Clinical Failure at Week-36 |
| Follow-up Visit |
| Mycologically Proven Recurrence |
37 (28.5) |
51 (39.2) |
|
| Presumed Recurrence |
8 (6.2) |
5 (3.8) |
|
| Suspected Recurrence |
4 (3.1) |
5 (3.8) |
|
| Imputed Recurrence1 |
6 (4.6) |
9 (6.9) |
|
Abbreviations: CI = confidence interval; TOC = test of cure.
1Imputed recurrences are subjects whose clinical outcome cannot be determined due to early termination or missing critical efficacy assessment at TOC. |