Safety marginVerdict not stated
Chronic dog NOAEL exposure only 0.06x (males) and 0.02x (females) the clinical AUC
“The NOAEL (MD, 11.8 μg·h/mL, and 3.4 μg·h/mL AUC024, Day 270, in males and females) represents a 0.06× (M) and 0.02× (F) exposure margin to the anticipated clinical dose (200 mg BID, 213 μg·h/mL AUC).”
✓ VerifiedFDA integrated review, p. 118Source ↗ CarcinogenicityQuestioned
Rat and transgenic mouse carcinogenicity exposures considerably below human exposure at the recommended dose
Why: Higher doses not tolerated due to excessive JAK2/FLT3 activity
“However, a notable limitation of the carcinogenicity assessment is that pacritinib exposures achieved in rats and mice were considerably lower than the exposure observed at the recommended human dose, due to a lack of tolerability primarily from excessive JAK2/FLT3 activity at higher doses.”
✓ VerifiedFDA integrated review, p. 71Source ↗ “The inability to evaluate pacritinib at multiples of clinical exposure limits the robustness of assessing carcinogenic potential from off-target kinases where pacritinib and the M1/M2 metabolites have lower inhibitory potencies than for JAK2/FLT3 (Section III.13.1.1).”
✓ VerifiedFDA integrated review, p. 71Source ↗ RecoveryVerdict not stated
Reversibility of findings not assessed in the chronic dog study
“The reversibility of findings in dogs was not assessed.”
✓ VerifiedFDA integrated review, p. 118Source ↗ Impurity or metaboliteAcceptedBeyond the letter
Major human metabolite M2 (~10% of parent) not predominant in any nonclinical species
Why: No safety concerns identified with M1 and M2 metabolites in nonclinical studies
“However, it is notable that the M2 metabolite, a principal metabolite in humans present at ~10% of the parent pacritinib, is not a predominant metabolite in any of the nonclinical species.”
✓ VerifiedFDA integrated review, p. 71Source ↗ “No safety concerns were identified with the pacritinib M1 and M2 metabolites in nonclinical studies.”
✓ VerifiedFDA integrated review, p. 71Source ↗