Comprehensive Safety Exposure-Response Analysis to Support Ritlecitinib Dose Selection.

Area of Science:

• Pharmacology
• Clinical Safety
• Drug Development

Background:

• Ritlecitinib, a kinase inhibitor, is approved for alopecia areata (AA).
• The pivotal Phase 2b/3 study evaluated various dosing regimens.
• Understanding the safety profile is crucial for optimal dose selection.

Purpose of the Study:

• To characterize the safety profile of ritlecitinib using exposure-response (ER) analyses.
• To inform dose selection for AA treatment in adults and adolescents.
• To assess potential safety risks across different patient subgroups.

Main Methods:

• Developed a concentration-QTc model to assess cardiac safety.
• Utilized a semi-mechanistic PK/PD model for lymphocyte profiles.
• Employed Poisson regression to analyze adverse event incidence (infections, rash) based on exposure.

Main Results:

• No evidence of ritlecitinib-induced QTc prolongation was found.
• Ritlecitinib showed a marginal decrease in lymphocytes, with low predicted Grade 3/4 lymphopenia, except for a slight increase with loading dose.
• Increased incidence of infections and rash was dose-dependent but not disproportionately large within the studied range.

Conclusions:

• The safety ER relationship for ritlecitinib is consistent across patient subgroups, including adolescents.
• No unique safety risks were identified in adolescent patients.
• Comprehensive safety ER analysis supports the 50mg non-loading dose regimen for ritlecitinib in AA patients.