Impurity or metaboliteAccepted with a conditionBeyond the letter
Major human metabolite ZAAD-1006a not measured in rat and dog toxicity studies; off-target screening deferred to a postmarketing commitment
Why: Deficiency addressed by a PMC for additional in vitro screening assays
“In the repeat-dose toxicology studies in rats and dogs, systemic exposure of ZAAD-1006a was not assessed, and therefore its toxicological potential was not evaluated.”
✓ VerifiedFDA multi-discipline review, p. 40Source ↗ “This deficiency resulted in a PMC for additional in vitro screening assays for ZAAD-1006a.”
✓ VerifiedFDA multi-discipline review, p. 40Source ↗ DARTCriticised but acceptedBeyond the letter
Fertility study dosed both sexes before mating, so effects on fertility cannot be attributed by sex
Why: Histopathology in both sexes plus reduced pregnancy suffice to warn; further fertility studies would not mitigate findings · Weight of evidence
“The suboptimal study design in which both sexes received pexidartinib prior to mating makes clear attribution of the reduced fertility by sex impossible.”
✓ VerifiedFDA multi-discipline review, p. 41Source ↗ “Despite this deficiency, the histopathological findings in both male and female animals coupled with reduced pregnancy are adequate to warn patients about the potential risk of reduced fertility with pexidartinib and additional individual fertility studies would not mitigate the compelling histopathological findings from the existing data.”
✓ VerifiedFDA multi-discipline review, p. 41Source ↗ Safety marginVerdict not stated
Rat liver toxicity at exposures about 0.6 times the clinical exposure at 800 mg
“In the liver, hemosiderin deposition and necrotizing inflammation with increased levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) occurred at doses ≥20 mg/kg (approximately 0.6 times the clinical exposure at 800 mg).”
✓ VerifiedFDA multi-discipline review, p. 40Source ↗