Side effects
In myelofibrosis, the most common side effects include thrombocytopenia (low blood platelet counts), anaemia (low red blood cell counts), neutropenia (low levels of neutrophils), urinary tract infections (infection of the structures that carry urine), bleeding, bruising, weight gain, hypercholesterolaemia (high blood cholesterol levels), dizziness, headache and raised liver enzyme levels.In polycythaemia vera, the most common side effects include anemia (low red blood cell counts) and thrombocytopenia (low blood platelet count), bleeding, bruising,  hypercholesterolaemia (high blood cholesterol levels), hypertriglyceridemia (high blood fat levels), dizziness, raised liver enzyme levels and high blood pressure.In acute graft-versus-host disease, the most common hematologic adverse reactions include anemia, thrombocytopenia, and neutropenia. The most common nonhematologic adverse reactions include infections and edema.Immunologic side effects have included herpes zoster (shingles) and case reports of opportunistic infections. Metabolic side effects have included weight gain. Laboratory abnormalities have included alanine transaminase (ALT) abnormalities, aspartate transaminase (AST) abnormalities, and mildly elevated cholesterol levels. Mechanism of action
Ruxolitinib is a janus kinase inhibitor (JAK inhibitor) with selectivity for subtypes JAK1 and JAK2. Ruxolitinib inhibits dysregulated JAK signaling associated with myelofibrosis. JAK1 and JAK2 recruit signal transducers and activators of transcription (STATs) to cytokine receptors leading to modulation of gene expression. History
In March 2012 the phase III Controlled Myelofibrosis Study with Oral JAK Inhibitor-I (COMFORT-I) and COMFORT-II trials showed significant benefits by reducing spleen size and relieving debilitating symptoms.In September 2021, ruxolitinib cream (sold under the brand name Opzelura) was approved for medical use in the United States for the treatment of mild to moderate atopic dermatitis (AD).
Host Disease (GvHD) After Bone Marrow  (REACH3)" at ClinicalTrials.gov
Clinical trial number NCT03745638 for "TRuE AD1 - An Efficacy and Safety Study of Ruxolitinib Cream in Adolescents and Adults With Atopic Dermatitis" at ClinicalTrials.gov
Clinical trial number NCT03745651 for "TRuE AD2 - An Efficacy and Safety Study of Ruxolitinib Cream in Adolescents and Adults With Atopic Dermatitis" at ClinicalTrials.gov