CarcinogenicityQuestioned
Male arm of the subcutaneous rat carcinogenicity study of inadequate duration; only female rat data adequate
“The study is negative for drug-related neoplasms in female rats. The male portion of the study, while it did not show any statistical increase in tumors, was of an inadequate duration.”
✓ VerifiedFDA multi-discipline review, p. 31Source ↗ DARTAcceptedBeyond the letter
No separate male fertility study; male fertility assessed by spermatogenesis staging in a 4-week subcutaneous rat study
Why: Male fertility assessed in the 4-week subcutaneous rat study · Weight of evidence
“Although there was no separate male fertility study in this drug development program, it is not considered an approvability issue. Assessment of tapinarof effects on male fertility was conducted in the 4-week subcutaneous rat study.”
✓ VerifiedFDA multi-discipline review, p. 31Source ↗ Impurity or metaboliteAcceptedBeyond the letter
Two Ames-positive impurities allowed above the 1.5 µg/day TTC
Why: Topical route gives very limited systemic exposure; two negative carcinogenicity studies with tapinarof · Pharmacology or kinetics · Weight of evidence
“From a pharmacology/toxicology perspective, the applicant’s proposal of setting the acceptable limit of these two impurities at times higher than TTC of 1.5 µg/day appears reasonable, because (1) the clinical route of administration for tapinarof is topical, which provides very limited amount of systemic exposure of these impurities; (2) two carcinogenicity studies have been conducted with tapinarof and no drug-related neoplasms was noted;”
✓ VerifiedFDA multi-discipline review, p. 55Source ↗