Ruxolitinib 1.5% Cream and the “Boxed Warning Paradox”: Reappraisal of Safety Through the Lens of Pharmacokinetics

Ruxolitinib 1.5% cream is the first-in-class topical Janus kinase IJAK) inhibitor approved for the treatment of atopic dermatitis in patients 12 years of age and older. The US Food and Drug Administration (FDA) issued a "boxed warning" for ruxolitinib cream, cautioning about increased risks of serious infections, malignancies, blood clots, and cardiovascular events because it is a JAK inhibitor. Despite clinical trials and real-world data demonstrating the safety of ruxolitinib cream, the boxed warning remains in place, even though oral ruxolitinib—known for its significantly higher bioavailability and plasma concentration—has not been assigned this warning. As a result, this warning has caused hesitation in its use and has been a barrier to the broader, appropriate adoption of ruxolitinib cream despite its strong recommendation for use in atopic dermatitis (AD) by the American Academy of Dermatology in 2023. Here, we provide an in-depth overview of in vivo and ex vivo pharmacokinetic (PK) data from studies in minipigs and human cadaver skin, along with human PK data from pediatric and adult atopic dermatitis (AD) patients aged 2 years and older, as well as safety data from both clinical trials and real-world studies in AD patients. Together, this data reinforces the safety of topical ruxolitinib and reassures clinicians that they can utilize this medication in everyday practice.