see also:

• Janus kinase - STAT signalling

• the JAK-family of cytokine receptors consists of four members: JAK1, JAK2, JAK3 and TYK2 that have different association patterns to receptors and are part of the Signal Transducer and Activation of Transcription (JAK-STAT) pathway
• some JAK inhibitors are selective for specific JAK enzymes, which may influence their efficacy and safety profiles
  • JAK3 inhibitors necessarily cause a loss or total absence of T cells and natural killer cells while leaving a normal amount of B cells

• Rheumatoid arthritis
• Psoriatic arthritis
• Juvenile idiopathic arthritis
• Axial spondyloarthritis
• Ulcerative colitis
• Atopic dermatitis
• Alopecia areata

• increased risk of infections (like shingles) - hence live vaccinations soon before starting Rx or concurrently are NOT recommended
• increased risk of major cardiovascular problems, such as heart attack and stroke, cancer, blood clots, serious infections and death, as compared with tumour necrosis factor (TNF) inhibitors¹⁾
• elevated cholesterol
• blood clots
• hypertension
• anaemia
• headache
• diarrhoea
• increased blood creatine phosphokinase
• in some cases, increased risk of certain cancers, particularly in older adults with rheumatoid arthritis
• increases risk of acne 2.5-fold more than when atopic dermatitis patients are Rx with Th2 cytokine inhibitors
• others

• active tuberculosis and other severe infections
• recent live vaccination
• severe liver impairment (Child–Pugh score C)
• pregnancy
• most are not approved for children aged under 12 yrs
• should generally be avoided in:
  • age 65 or over
  • those at increased risk of cardiovascular problems such as heart attacks or stroke (eg. including current or past long-time smokers)
  • those at increased risk of cancer
  • those with risk factors for DVT / PE
  • those who have not yet had zoster vaccination (should be done well before starting Rx)

• baricitinib (Olumiant)
  • oral agent mainly used to Rx rheumatoid arthritis and is a disease-modifying antirheumatic drug (DMARD)
• delgocitinib (Corectim)
  • treatment of atopic dermatitis
  • FDA in 2025 approved topical treatment of adults with moderate to severe chronic hand eczema

• ivarmacitinib
  • appears to be beneficial in ankylosing spondylitis (AS)
• upadacitinib (Rinvoq)
  • used for the treatment of rheumatoid arthritis, psoriatic arthritis, atopic dermatitis, ulcerative colitis, Crohn's disease, ankylosing spondylitis, and axial spondyloarthritis
• tofacitinib (Xeljanz)
  • JAK 1 and Jak 3 selective inhibition
  • oral agent used to Rx rheumatoid arthritis, ulcerative colitis, psoriatic arthritis, ankylosing spondylitis (AS), polyarticular course juvenile idiopathic arthritis (pcJIA)