Clinical Pharmacology for Eucrisa Ointment
Mechanism Of Action
Crisaborole is a phosphodiesterase 4 (PDE-4) inhibitor. PDE-4 inhibition results in increased intracellular cyclic adenosine monophosphate (cAMP) levels. The specific mechanism(s) by which crisaborole exerts its therapeutic action for the treatment of atopic dermatitis is not well defined.
Pharmacodynamics
Cardiac Electrophysiology
At therapeutic doses, EUCRISA ointment is not expected to prolong QTc to any clinically relevant extent.
Pharmacokinetics
Absorption
The PK of EUCRISA were investigated in 33 pediatric subjects 2 to 17 years of age with mild to moderate atopic dermatitis and a mean ± SD body surface area (BSA) involvement of 49 ± 20% (range 27% to 92%). In this study, subjects applied approximately 3 mg/cm² of EUCRISA ointment (dose range was approximately 6 g to 30 g per application) twice daily for 8 days.
Plasma concentrations were quantifiable in all the subjects. The mean ± SD maximum plasma concentration (Cmax) and area under the concentration time curve from 0 to 12 hours post dose (AUC0-12) for crisaborole on Day 8 were 127 ± 196 ng/mL and 949 ± 1240 ng h/mL, respectively. Systemic concentrations of crisaborole were at steady state by Day 8. Based on the ratios of AUC0-12 between Day 8 and Day 1, the mean accumulation factor for crisaborole was 1.9.
The PK of EUCRISA were investigated in 13 subjects 4 months to less than 24 months of age. The mean ± SD Cmax and AUC0-12 for crisaborole were 188 ± 100 ng/mL and 1164 ± 550 ng•h/mL, respectively.
Distribution
Based on an in vitro study, crisaborole is 97% bound to human plasma proteins.
Elimination
Metabolism
Crisaborole is substantially metabolized into inactive metabolites. The major metabolite 5-(4-cyanophenoxy)-2- hydroxyl benzylalcohol (metabolite 1), is formed via hydrolysis; this metabolite is further metabolized into downstream metabolites, among which 5-(4-cyanophenoxy)-2-hydroxyl benzoic acid (metabolite 2), formed via oxidation, is also a major metabolite.
PK of metabolites 1 and 2 were assessed in the PK study described above and the systemic concentrations were at or near steady state by Day 8. Based on the ratios of AUC0-12 between Day 8 and Day 1, the mean accumulation factors for metabolites 1 and 2 were 1.7 and 6.3, respectively.
Excretion
Renal excretion of metabolites is the major route of elimination.
Drug Interaction Studies
In vitro studies using human liver microsomes indicated that under the conditions of clinical use, crisaborole and metabolite 1 are not expected to inhibit cytochrome P450 (CYP) 1A2, 2B6, 2C8, 2C9, 2C19, 2D6, and 3A4.
In vitro human liver microsomes studies for metabolite 2 showed that it did not inhibit activities of CYP2C19, 2D6, and 3A4; was a weak inhibitor of CYP1A2 and 2B6; and a moderate inhibitor of CYP2C8 and 2C9. The most sensitive enzyme, CYP2C9, was further investigated in a clinical trial using warfarin as a CYP2C9 substrate. The results of this study showed no drug interaction potential.
In vitro studies in human hepatocytes showed that under the conditions of clinical use, crisaborole and metabolites 1 and 2 are not expected to induce CYP enzymes.
In vitro studies showed that crisaborole and metabolite 1 did not inhibit the activities of uridine diphosphate (UDP)-glucuronosyltransferase (UGT) 1A1, 1A4, 1A6, 1A9, 2B7, and 2B15. Metabolite 2 did not inhibit UGT1A4, 1A6, 2B7, and 2B15. Metabolite 2 showed weak inhibition of UGT1A1, however, no clinically significant drug interactions are expected between crisaborole (and its metabolites) and UGT1A1 substrates at therapeutic concentrations. Metabolite 2 showed moderate inhibition of UGT1A9 and may result in a moderate increase of the concentrations of sensitive UGT1A9 substrates.
In vitro studies indicate that under the condition of clinical use, crisaborole and metabolites 1 and 2 are not expected to cause clinically significant interactions with substrates of P-glycoprotein and organic anionic or cationic transporters. Crisaborole and metabolite 1 are not expected to inhibit breast cancer resistance protein (BCRP); metabolite 2 is expected to inhibit BCRP at therapeutic concentrations.
Clinical Studies
Two multicenter, randomized, double-blind, parallel-group, vehicle-controlled trials (Trials 1 and 2) treated a total of 1522 subjects 2 to 79 years of age (86.3% of subjects were 2 to 17 years of age) with a 5% to 95% treatable BSA. At baseline, 38.5% of the subjects had an Investigator’s Static Global Assessment [ISGA] of mild (2), and 61.5% had an ISGA of moderate (3), in the overall assessment of atopic dermatitis (erythema, induration/papulation, and oozing/crusting) on a severity scale of 0 to 4.
In both trials, subjects were randomized 2:1 to receive EUCRISA or vehicle applied twice daily for 28 days. The primary efficacy endpoint was the proportion of subjects at Day 29 who achieved success, defined as an ISGA grade of clear (0) or almost clear (1) with a 2-grade or greater improvement from baseline, comparing EUCRISA-treated subjects to vehicle-treated subjects.
Efficacy results from the two trials are summarized in Table 2.
Table 2: Primary Efficacy Outcomes in Subjects with Mild to Moderate Atopic Dermatitis at Day 29
|
Trial 1 |
Trial 2 |
EUCRISA Twice Daily
(N=503) |
Vehicle Twice Daily
(N=256) |
EUCRISA Twice Daily
(N=513) |
Vehicle Twice Daily
(N=250) |
| Success in ISGAa |
32.8% |
25.4% |
31.4% |
18.0% |
| a Defined as an ISGA of clear (0) or almost clear (1) with a 2-grade or greater improvement from baseline. |
The success rates over time are presented in Figure 1.
Figure 1: Success in ISGAa Over Time in Subjects with Mild to Moderate Atopic Dermatitis
a Success is defined as an ISGA of clear (0) or almost clear (1) with a 2-grade or greater improvement from baseline.
One randomized, double-blind, vehicle-controlled trial (Trial 3) assessed the efficacy and safety of EUCRISA once daily over 52 weeks in pediatric (3 months to less than 18 years of age) and adult subjects with mild to moderate atopic dermatitis, who achieved success on EUCRISA twice daily during open-label treatment of up to 8 weeks.
A total of 497 subjects 3 months of age and older with a 2% to 90% treatable BSA, entered into an open-label period to receive EUCRISA twice daily for up to 8 weeks. At baseline, 327 (66%) of subjects were 3 months to less than 18 years of age, 66% of the subjects had an ISGA of moderate (3), and 34% had an ISGA of mild (2), in the overall assessment of atopic dermatitis (erythema, induration/papulation, and oozing/crusting) on a severity scale of 0 to 4.
Of the 497, a total of 254 subjects 3 months of age and older, who achieved both ISGA success (score of clear [0] or almost clear [1] with a ≥2 grade improvement from baseline) and EASI50 response (at least 50% improvement from baseline in EASI scores) were randomized 1:1 into a double-blind period to receive EUCRISA once daily or vehicle for 52 weeks or until they developed a flare. At the beginning of the double-blind period, 59% of the subjects had an ISGA of almost clear (1) and 41% had an ISGA of clear (0).
Figure 2 presents the percentage of subjects maintaining an ISGA of clear or almost clear through Week 52.
Figure 2: Percentage of Subjects Maintaining ISGA of Clear or Almost Clear Through Week 52