JANEX-1 (WHI-P131), a selective Janus kinase 3 (JAK3) inhibitor, has been shown to delay the onset of diabetes in the NOD mouse model. It is a cell-permeable, reversible, potent, ATP-competitive, and specific inhibitor of JAK3 (IC50 = 78 uM); has no effect on JAK1, JAK2, or Zap/Syk or SRC tyrosine kinases. JANEX-1 has a potent inhibitory effect on cytokine-induced β-cell damage. JANEX-1 has a therapeutic potential in the treatment and prevention of type 1 diabetes. JANEX-1 induced apoptosis in JAK3-expressing human leukemia cell lines NALM-6 and LC1. JANEX-1 inhibited the clonogenic growth of JAK3-positive leukemia cell lines DAUDI, RAMOS, LC1;19, NALM-6, MOLT-3, and HL-60 (but not JAK3-negative BT-20 breast cancer, M24-MET melanoma, or SQ20B squamous carcinoma cell lines) in a concentration-dependent fashion. Potent and specific inhibitors of JAK3 such as JANEX-1 may provide the basis for the design of new treatment strategies against acute lymphoblastic leukemia, the most common form of childhood cancer. JANEX-1/WHI-P131 also showed potent anti-inflammatory activity in several cellular and in vivo animal models of inflammation, including mouse models of peritonitis, colitis, cellulitis, sunburn, and airway inflammation with favorable toxicity and pharmacokinetic profile. JANEX-1 may prove useful to prevent or alleviate the symptoms of endometriosis (EMS).

WHI-P154 is an inhibitor of Janus-activated kinase JAK3. Also this drug inhibits other common kinases including EGFR, Src, Abl, VEGFR and others. WHI-P154 is potent inhibitor of glioblastoma cell adhesion and migration. Further preclinical development of WHI-P154 may provide the basis for the design of more effective adjuvant chemotherapy programs for glioblastoma multiforme. Treatment of ALK inhibitor, WHI-P154 resulted in the down-regulation of aberrant anaplastic lymphoma kinase (ALK) signaling, shrinkage of tumor, and suppression of metastasis and significantly improved survival of ALK mutant-bearing mice.

ZM 39923 HCl is an JAK1/3 inhibitor with pIC50 of 4.4/7.1 and almost no activity to JAK2 and modestly potent to EGFR. ZM39923 breaks down to form the JAK3 inhibitor ZM449829 which exhibit similar IC50 values. ZM39923 decomposes in neutral buffer to afford potent inhibition of the Janus kinase 3, and could be used as a standard Jak3 inhibitor in assays where breakdown could occur. ZM39923 is reduced by 300-fold in the presence of DTT (10 mM) in inhibiting TGM2. ZM39923 is reversible inhibitors when TGM2 is incubated with inhibitors in the absence of Ca2+. ZM39923 shows significant inhibition of crosslinking activity with IC50 of 25 nM in the absence of DTT and IC50 of 10 μM in the presence of DTT. ZM39923 prevents early death in a Drosophila Melanogaster model of a polyQ repeat disorder called Machado-Joseph Disease. M39923 inhibits the generation of AICD-FLAG and both Aβ40 and Aβ42 by purified γ-secretase in a concentration-dependent fashion with an approximate IC50 of 20 μM. ZM39923 decreases photoaffinity-labeled PS1-CTF in the presense of γ-secretase.

Oclacitinib (PF03394197) is a novel Janus kinase inhibitor with activity against cytokines involved in allergy. Oclacitinib inhibited JAK family members by 50% at concentrations (IC50 's) ranging from 10 to 99 nM and did not inhibit a panel of 38 non-JAK kinases (IC50 's > 1000 nm). Oclacitinib was most potent at inhibiting JAK1 (IC50 = 10 nm). Oclacitinib also inhibited the function of JAK1-dependent cytokines involved in allergy and inflammation (IL-2, IL-4, IL-6, and IL-13) as well as pruritus (IL-31) at IC50 's ranging from 36 to 249 nM. Oclacitinib as oclacitinib maleate is approved for control of pruritus associated with allergic dermatitis and control of atopic dermatitis in dogs at least 12 months of age.

Ritlecitinib is an orally administered, covalent small-molecule selective dual inhibitor of JAK3 and the TEC kinase family. In vitro studies showed ritlecitinib covalently binds to JAK3 and is more than 10 000 times more potent against JAK3 than against JAK1, JAK2, and tyrosine kinase. Ritlecitinib also inhibits the five members of the TEC kinase family. Ritlecitinib irreversibly inhibits Janus kinase 3 (JAK3) and TEC kinase family by blocking the adenosine triphosphate (ATP) binding site. In cellular settings, ritlecitinib inhibits cytokine induced STAT phosphorylation mediated by JAK3-dependent receptors. Additionally, ritlecitinib inhibits signaling of immune receptors dependent on TEC kinase family members.The FDA has approved ritlecitinib (LITFULO; Pfizer Inc), a once daily oral treatment, for individuals aged 12 years and older with severe alopecia areata. This makes ritlecitinib, in the 50 mg dosage, the first and only treatment approved by the FDA for adolescents with severe alopecia areata. The approval was based on the results of the ALLEGRO phase 2b/3 trial (NCT03732807), which included 718 individuals who had 50% or more scalp hair loss measured by the Severity of Alopecia Tool. Investigators of the study evaluated the safety and efficacy of ritlecitinib at 118 different sites in 18 different countries. Regulatory applications for LITFULO in alopecia areata have been submitted to countries around the world for review, including China, the European Union, Japan, and the United Kingdom. The European Medicines Agency (EMA) has accepted the Marketing Authorization Application (MAA) for ritlecitinib with a decision anticipated in the third quarter of 2023. LITFULO is also being evaluated for vitiligo, Crohn’s disease, and ulcerative colitis.

Ritlecitinib is an orally administered, covalent small-molecule selective dual inhibitor of JAK3 and the TEC kinase family. In vitro studies showed ritlecitinib covalently binds to JAK3 and is more than 10 000 times more potent against JAK3 than against JAK1, JAK2, and tyrosine kinase. Ritlecitinib also inhibits the five members of the TEC kinase family. Ritlecitinib irreversibly inhibits Janus kinase 3 (JAK3) and TEC kinase family by blocking the adenosine triphosphate (ATP) binding site. In cellular settings, ritlecitinib inhibits cytokine induced STAT phosphorylation mediated by JAK3-dependent receptors. Additionally, ritlecitinib inhibits signaling of immune receptors dependent on TEC kinase family members.The FDA has approved ritlecitinib (LITFULO; Pfizer Inc), a once daily oral treatment, for individuals aged 12 years and older with severe alopecia areata. This makes ritlecitinib, in the 50 mg dosage, the first and only treatment approved by the FDA for adolescents with severe alopecia areata. The approval was based on the results of the ALLEGRO phase 2b/3 trial (NCT03732807), which included 718 individuals who had 50% or more scalp hair loss measured by the Severity of Alopecia Tool. Investigators of the study evaluated the safety and efficacy of ritlecitinib at 118 different sites in 18 different countries. Regulatory applications for LITFULO in alopecia areata have been submitted to countries around the world for review, including China, the European Union, Japan, and the United Kingdom. The European Medicines Agency (EMA) has accepted the Marketing Authorization Application (MAA) for ritlecitinib with a decision anticipated in the third quarter of 2023. LITFULO is also being evaluated for vitiligo, Crohn’s disease, and ulcerative colitis.

Baricitinib (trade name Olumiant) is an investigational drug for rheumatoid arthritis (RA), being developed by Incyte and Eli Lilly. Baricitinib is a selective JAK1 and JAK2 inhibitor with IC50 of 5.9 nM and 5.7 nM in cell-free assays. In February 2017 Baricitinib was approved for use in the European Union as a second-line therapy for moderate to severe active rheumatoid arthritis in adults, either alone or in combination with methotrexate. On 31 May 2018 FDA approved Barictinib for the treatment of adult patients with moderately to severely active rheumatoid arthritis who have had an inadequate response to one or more TNF antagonist therapies.

Tofacitinib is an orally available inhibitor of Janus kinases (JAK), with immunomodulatory and anti-inflammatory activities. Upon administration, tofacitinib binds to JAK and prevents the activation of the JAK-signal transducers and activators of transcription (STAT) signaling pathway. This may decrease the production of pro-inflammatory cytokines, such as interleukin (IL)-6, -7, -15, -21, interferon-alpha and -beta, and may prevent both an inflammatory response and the inflammation-induced damage caused by certain immunological diseases. JAK kinases are intracellular enzymes involved in signaling pathways affecting hematopoiesis, immunity and inflammation. Tofacitinib was discovered and developed by the National Institutes of Health and Pfizer. Besides rheumatoid arthritis, tofacitinib has also been studied in clinical trials for the prevention of organ transplant rejection, and the treatment of psoriasis and ulcerative colitis. Patients treated with tofacitinib (XELJANZ) are at increased risk for developing serious infections that may lead to hospitalization or death and adverse reactions. Most patients who developed these infections were taking concomitant immunosuppressants such as methotrexate or corticosteroids.

Tofacitinib is an orally available inhibitor of Janus kinases (JAK), with immunomodulatory and anti-inflammatory activities. Upon administration, tofacitinib binds to JAK and prevents the activation of the JAK-signal transducers and activators of transcription (STAT) signaling pathway. This may decrease the production of pro-inflammatory cytokines, such as interleukin (IL)-6, -7, -15, -21, interferon-alpha and -beta, and may prevent both an inflammatory response and the inflammation-induced damage caused by certain immunological diseases. JAK kinases are intracellular enzymes involved in signaling pathways affecting hematopoiesis, immunity and inflammation. Tofacitinib was discovered and developed by the National Institutes of Health and Pfizer. Besides rheumatoid arthritis, tofacitinib has also been studied in clinical trials for the prevention of organ transplant rejection, and the treatment of psoriasis and ulcerative colitis. Patients treated with tofacitinib (XELJANZ) are at increased risk for developing serious infections that may lead to hospitalization or death and adverse reactions. Most patients who developed these infections were taking concomitant immunosuppressants such as methotrexate or corticosteroids.