Safety pharmacologyAcceptedBeyond the letter
No toxicokinetics in safety pharmacology studies; margins derived from repeat-dose study exposures
Why: Identical dosing in rat and dog studies; resulting margins exceed 1000-fold clinical exposure · Pharmacology or kinetics
“As the TK analysis was not included in the safety pharmacology studies, the safety margins have been calculated based on the exposure measured in the repeat-dose toxicity studies.”
✓ VerifiedEMA assessment report, p. 24Source ↗ “An uncertainty is associated with this approach, however, as the dosing was identical in these rat and dog studies and the resulting safety margins for expected human clinical exposure are > 1000, this approach is acceptable to the CHMP.”
✓ VerifiedEMA assessment report, p. 24Source ↗ Efficacy modelAcceptedBeyond the letter
In vivo topical pharmacology studies used ointment, not the commercial cream formulation
Why: Formulation difference not considered to affect the in vivo pharmacodynamic assessment
“The formulation of topical delgocitinib used in the in vivo PD studies (ointment) differs from the suggested commercial formulation (cream). However, this is not considered to impact the assessment of in vivo PD of delgocitinib and the studies were considered acceptable.”
✓ VerifiedEMA assessment report, p. 22Source ↗ Safety marginQuestioned
Nonclinical exposure threshold (3 months at about 40 ng/mL) used to argue over 80-fold margin against systemic JAK-class risks
Why: Applicant: human exposure about 0.5 ng/mL; FDA: extrapolation may not predict human sensitivity to JAK inhibition
“Nonclinical studies showed that continuous exposure for at least 3 months at systemic levels around 40 ng/mL is needed before JAK inhibition-related adverse effects are observed. Human exposure of approximately 0.5 ng/mL provides a safety margin in excess of 80-fold.”
✓ VerifiedFDA integrated review, p. 83Source ↗ “Furthermore, the Applicant’s extrapolation from nonclinical data showing that 3 months of exposure at 40 ng/mL is needed for adverse effects may not accurately predict human sensitivity to JAK inhibition.”
✓ VerifiedFDA integrated review, p. 84Source ↗