Adverse immunosuppression (skin mites, lung inflammation) at 40 mg/kg/day in the 39-week dog study
“In the first 39-week oral RDT study in dogs with 3-month recovery (doses: 0, 5, 20, and 40 mg/kg/day), no ritlecitinib-related effects were noted on mortality, ECG, or ophthalmology. At the HD, ritlecitinib-related immunosuppression was adverse because of skin mites and lung inflammation.”
✓ VerifiedFDA multi-discipline review, p. 39Source ↗
Biodistribution & persistence
Poor blood-brain barrier penetration in rat (brain:plasma ~0.04); melanin-related accumulation in uveal tract
“However, the low brain: plasma AUC ratio at ~0.04 demonstrates that penetration of the blood-brain barrier is inefficient in the rat. The high AUC and long excretion T1/2 in the uveal tract suggest melanin-related accumulation.”
Axonal dystrophy in dogs, considered an off-target effect
“Based on a series of nonclinical studies investigating the potential mechanism, ritlecitinib-related axonal dystrophy appears to be an off-target effect, rather than mediated through inhibition of JAK3 or TEC kinase family members.”
✓ VerifiedFDA multi-discipline review, p. 40Source ↗