A systematic review pooled 68 studies — 42 randomised trials, 14 open-label extensions and 12 real-world cohorts — covering 15,427 patients on JAK inhibitors across five inflammatory skin diseases.
Efficacy is broad. Oral JAK inhibitors achieved EASI-75 in 38 to 73% in atopic dermatitis, PASI-75 in 33 to 67% in psoriasis, and SALT-50 in 30 to 62% in alopecia areata. Topical formulations worked in atopic dermatitis and vitiligo but showed limited benefit in alopecia areata — a useful negative, since topical use is often assumed to transfer across indications.
Safety is where the review earns its length. Upper respiratory infections ran at 5 to 14% and herpes zoster reactivation at 1 to 3% above placebo. Serious events — major adverse cardiovascular events, venous thromboembolism and cancers — were rare but did occur.
The authors' comparative conclusions are appropriately hedged: selective JAK1 inhibitors appear to offer the best efficacy-safety balance in atopic dermatitis, while JAK1/2 inhibitors were numerically better in alopecia areata without reaching significance. They also name the constraints — short controlled trials, under-representation of diverse populations, and reliance on indirect comparisons — which is exactly what limits how far these rankings can be trusted.
- Wide efficacy ranges reflect different drugs, doses and populations pooled together
- Herpes zoster reactivation at 1 to 3% is the most consistent safety signal
- Topical JAK inhibitors do not transfer to alopecia areata
- Comparative rankings rest on indirect comparison, not head-to-head trials
- Cardiovascular risk factors remain the group needing most caution
The statistics, in plain English
Response ranges as wide as 38 to 73% mean the pooled figure is nearly meaningless on its own — it spans different molecules, doses, disease severities and trial designs. Indirect comparison, where drugs are ranked by their performance against placebo in separate trials rather than against each other, is the weakest basis for choosing between them, because the trials differ in ways the comparison cannot adjust for.
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