ruxolitinib

Overview

Ruxolitinib is a selective, orally administered small-molecule inhibitor of Janus kinase 1 (JAK1) and Janus kinase 2 (JAK2), two tyrosine kinases that play central roles in cytokine signaling through the JAK/STAT pathway. By blocking JAK1 and JAK2 activity, ruxolitinib suppresses downstream signaling through transcription factors such as STAT1 and STAT5A, thereby attenuating the aberrant cytokine-driven inflammation and cell proliferation that underlies several hematologic malignancies and immune-mediated disorders. It was among the first JAK inhibitors to receive regulatory approval and belongs to the broader class of Janus kinase inhibitors that has transformed the management of myeloproliferative neoplasms and inflammatory conditions.

Ruxolitinib is approved for the treatment of intermediate- or high-risk myelofibrosis (MF), polycythemia vera (PV) in patients who are resistant to or intolerant of hydroxyurea, and steroid-refractory acute and chronic graft-versus-host disease (GVHD). Its mechanism centers on the inhibition of constitutively active or mutant JAK2 (including JAK2 V617F), as well as JAK2 gain-of-function mutations, which drive pathological activation of the JAK2/STAT3 signaling pathway and CD44/JAK2/STAT3 signaling pathway in malignant hematopoietic cells. By dampening these cascades, ruxolitinib reduces splenomegaly, alleviates disease-related symptoms, and modulates immune responses relevant to both cancer and autoimmune disease contexts.

Focus of Latest Publications

Recent publications on ruxolitinib have focused largely on its role as a Janus kinase inhibitor in myeloproliferative and hyperinflammatory disorders, with additional interest in immune-mediated complications and combination regimens. In polycythaemia vera, a prospective real-world German study (PaVe) evaluated ruxolitinib in routine practice and reported improvements in hematocrit, leukocyte, and platelet counts, with no new safety concerns and overall support for its use as an effective second-line treatment in patients resistant to or intolerant of hydroxyurea. In myelofibrosis, several studies examined ruxolitinib-based strategies, including real-world treatment patterns in Japan, where all Janus kinase inhibitor-treated patients received ruxolitinib, and combination approaches intended to improve spleen and symptom control.

Combination therapy studies in myelofibrosis included navitoclax plus ruxolitinib in JAK inhibitor-naïve patients and selinexor plus ruxolitinib in a phase 1 study. The navitoclax study reported spleen volume reduction, symptom improvement, bone marrow fibrosis improvement, and anemia responses with a tolerable safety profile, while the selinexor study found no dose-limiting toxicities and identified selinexor 60 mg with ruxolitinib as the recommended phase 3 dose based on safety and efficacy signals. Another real-world study examined high-dose ruxolitinib exposure in myelofibrosis, reflecting ongoing interest in feasibility and long-term treatment intensity. A separate report also noted that momelotinib after ruxolitinib failure remains an area of limited real-world evidence.

Beyond myeloproliferative disease, ruxolitinib was studied in immune dysregulation and inflammatory syndromes. In steroid-refractory acute graft-versus-host disease, mechanistic work linked clinical response to ruxolitinib with reduced STAT1 activation, restoration of glucocorticoid receptor expression, and contraction of expanded CD28+ CD8+ effector-memory T cells, supporting a pathway-targeted role in steroid resistance. Case-based reports described successful use of ruxolitinib for refractory ciltacabtagene autoleucel-associated diarrhea after chimeric antigen receptor T cell therapy, with rapid clinical improvement in treated patients and histopathologic response in biopsied cases. Another case report described effective treatment of refractory TAFRO-like syndrome using ruxolitinib combined with ropeginterferon alfa-2b in a patient with a history of polycythemia vera and JAK2 V617F.

Additional publications explored ruxolitinib in hematologic malignancy and pediatric hyperinflammation. In childhood B-cell precursor acute lymphoblastic leukemia with JAK2 gain-of-function mutations, ruxolitinib selectively reduced STAT5 phosphorylation and induced measurable biochemical changes in mutant but not wild-type cells, with Raman spectroscopy proposed as a non-destructive method to monitor treatment response. In pediatric hemophagocytic lymphohistiocytosis, ruxolitinib was discussed as part of targeted therapy alongside emapalumab plus conventional therapy, reflecting growing interest in cytokine-directed approaches for severe hyperinflammatory syndromes.

Key Publications

• NEWJul Emapalumab plus conventional therapy with or without ruxolitinib for pediatric hemophagocytic lymphohistiocytosis: a single center retrospective study. (Immunologic research, 2026, PMID 42397658): "Emapalumab is a monoclonal antibody targeting interferon-γ, while ruxolitinib is a JAK1/2 inhibitor, and their application in HLH treatment is gaining attention."
• May Prospective, non-interventional study of ruxolitinib therapy in patients with polycythaemia vera - German real-world data (PaVe study). (Annals of hematology, 2026, PMID 42118306): "Findings from this study in a real-world setting show that ruxolitinib is an effective and safe second-line treatment in PV patients."
• May Clinical benefit and predictors of response to momelotinib after ruxolitinib failure: A cooperative real-world study. (Cancer, 2026, PMID 42118670): "Evidence on its real-world effectiveness after ruxolitinib failure is limited."
• May Real-world patient characteristics and clinical outcomes in patients with myelofibrosis in Japan. (PloS one, 2026, PMID 42102170): "All patients who received a JAK inhibitor were treated with ruxolitinib; mean dose was 15.6 mg/day and median duration of treatment was 14 months."
• May High-dose ruxolitinib (25 mg twice daily) in myelofibrosis: feasibility, safety, and long-term treatment exposure in a real-world cohort. (Annals of hematology, 2026, PMID 42081119): "Ruxolitinib is standard first-line therapy for symptomatic myelofibrosis (MF)."
• Apr CD28⁺ CD8⁺ Tem cells with a STAT1-dependent glucocorticoid receptor deficit contribute to steroid-refractory acute GVHD. (Blood, 2026, PMID 41980031): "JAK inhibition rescued cytokine-induced steroid resistance in vitro, while in SR-aGvHD patients, clinical response to ruxolitinib was accompanied by reduced STAT1 activation, restoration of GR expression, and contraction of the expanded CD8+ Tem pool."
• Mar Preliminary Safety and Efficacy of Navitoclax Plus Ruxolitinib in Janus Kinase Inhibitor-Naïve Patients With Myelofibrosis From the Multicenter, Open-Label, Phase 2 Study (REFINE). (Hematological oncology, 2026, PMID 41846295): "Herein, we present results of Cohort 3 of the Phase 2 REFINE study (NCT03222609), which evaluated efficacy and safety of navitoclax plus ruxolitinib in JAKi-naïve patients with myelofibrosis."
• May Selinexor plus ruxolitinib in JAK inhibitor-naïve patients with myelofibrosis: a multicenter, open-label, phase 1 study. (Blood advances, 2026, PMID 41785311): "The phase 1 portion of SENTRY/XPORT-MF-034 (NCT04562389) evaluated the exportin 1 inhibitor selinexor (40 mg/60 mg once weekly) plus ruxolitinib in JAK inhibitor-naïve patients with myelofibrosis (n = 24)."
• Jun Raman-guided analysis of drug response combined with chemometrics helps monitor the effect of ruxolitinib on acute lymphoblastic leukemia. (Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 2026, PMID 41762803): "Ruxolitinib (RUX), a selective JAK1/JAK2 inhibitor, is considered a therapeutic option for childhood B-cell precursor acute lymphoblastic leukemia (B-ALL) with JAK2 gain-of-function mutations."
• May Ruxolitinib for ciltacabtagene autoleucel-associated refractory diarrhea. (Blood, 2026, PMID 41592291): "We hypothesized that the Janus kinase inhibitor, ruxolitinib, might be an effective therapy based on its success in graft-versus-host-disease after allogeneic bone marrow transplant and other immune-driven diarrhea syndromes."