BACKGROUND: Plaque psoriasis is a chronic and often debilitating skin disorder 
and proinflammatory cytokines are known to play a key role in the disease 
process.
OBJECTIVES: To evaluate the safety and efficacy of baricitinib, an oral Janus 
kinase (JAK) 1/JAK2 inhibitor, in patients with moderate-to-severe psoriasis in 
a randomized, double-blind, placebo-controlled, dose-ranging phase 2b study.
METHODS: Patients were randomized (n = 271) to receive placebo or oral 
baricitinib at 2, 4, 8 or 10 mg once daily for 12 weeks (Part A). Dose 
adjustment for 12 additional weeks was based on percentage improvement in the 
Psoriasis Area and Severity Index (PASI) score. The primary end point was 
Psoriasis Area and Severity Index (PASI) 75% (PASI-75) at 12 weeks for North 
American patients (n = 238); secondary end points were safety and efficacy 
measures in the entire population.
RESULTS: At week 12, more North American patients in the 8-mg (43%) and 10-mg 
(54%) baricitinib groups than in placebo group (17%; P < 0·05) achieved PASI-75. 
All baricitinib-treated groups had greater mean changes from baseline in their 
PASI scores (P < 0·05) at 12 weeks and (except 2 mg) had higher rates of PASI-50 
than the placebo group; statistically significant PASI-90 responses were 
achieved in the 8-mg and 10-mg groups at 8 and 12 weeks. More than 81% of 
PASI-75 responders maintained their scores through 24 weeks. During Part A, 
study discontinuations due to adverse events (AEs) were 0%, 0%, 2·8%, 6·3% and 
5·8% and treatment-emergent AE rates were 44%, 50%, 47%, 58% and 64% for placebo 
and 2-, 4-, 8- and 10-mg baricitinib groups, respectively. No opportunistic 
infections were observed in any treatment group. Dose-dependent changes in 
laboratory values were observed.
CONCLUSIONS: Patients with moderate-to-severe psoriasis treated with baricitinib 
for 12 weeks achieved significant improvements in PASI-75.