Ruxolitinib Phosphate: A treatment for blood disorders, polycythemia, and atopic dermatitis

Ruxolitinib phosphate

Ruxolitinib phosphate is the phosphate salt form of ruxolitinib, used to treat specific blood-related disorders, polycythemia vera, steroid-refractory acute graft-versus-host disease, and atopic dermatitis. Ruxolitinib is marketed as Jakafi by Incyte Corp in the United States and Jakavi by Novartis throughout the rest of the world.

Table of Contents

What is Ruxolitinib?

Ruxolitinib is a janus kinase inhibitor prescribed to treat myelofibrosis, polycythemia, and steroid-refractory acute graft-versus-host disease. The US Food and Drug Administration (FDA) approved the use of ruxolitinib in November 2011 for the treatment of intermediate or high-risk myelofibrosis. Further, the FDA approved ruxolitinib to treat polycythemia vera (PCV) in 2014 when there has been an inadequate effectiveness response or intolerance of hydroxyurea. 

The European Medicines Agency granted marketing authorisation for ruxolitinib for the European Union in 2014. 

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What is Ruxolitinib Phosphate?

Ruxolitinib phosphate is ruxolitinib in a phosphate salt form that may have additional antineoplastic and immunomodulating activities. It is created through the reaction of ruxolitinib with one equivalent of phosphoric acid. Like ruxolitinib, ruxolitinib phosphate is used to treat intermediate or high-risk myelofibrosis, primary myelofibrosis, post-polycythemia vera myelofibrosis, and post-essential thrombocythemia myelofibrosis.

What is Ruxolitinib used for?

Ruxolitinib is used primarily to treat intermediate or high-risk myelofibrosis. Myelofibrosis is a disorder that causes abnormal growth of blood cells (red blood cells, white blood cells, and platelets) in the bone marrow. 

Ruxolitinib is also used as a secondary measure to treat polycythemia in the event of an inadequate response to, or intolerance of, hydroxyurea. Polycythemia is a rare blood disorder where blood cells, particularly red blood cells, cause the blood to thicken, leading to strokes, tissue, or organ damage. Ruxolitinib is also used to treat steroid-refractory acute graft-versus-host disease, defined when the condition of a patient receiving a 2 mg/kg dose of methylprednisolone or equivalent continues to get worse. 

Ruxolitinib Cream

Marketed by Incyte Corp under the name Opzelura, Ruxolitinib cream is used to treat mild to moderate atopic dermatitis on a short-term and non-continuous basis. Opzelura is typically prescribed for patients whose condition is not adequately controlled with other topical prescriptions or in the event that other therapies are contraindicated. 

Ruxolitinib Mechanism of Action

Ruxolitinib is a janus kinase (JAK) inhibitor that selects for JAK1 and JAK2 subtypes that are involved in the production and growth of blood cells. The JAK1 and JAK2 subtypes recruit activators and signal transducers of transcription (STAT) to cytokine receptors, leading to a modulation of gene expression. Members of the STAT protein family mediate many aspects of cellular immunity, apoptosis, proliferation, and differentiation. Dysregulation of this blood cell pathway has been observed in primary tumors, leading to increased angiogenesis that enhances immunosuppression and tumour survival. 

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Ruxolitinib Research Studies

The following studies were used for the approval of Ruxolitinib in the European Union for the treatment of myelofibrosis and polycythaemia vera:

Myelofibrosis

Research for Ruxolitinib (Jakavi) for myelofibrosis was conducted in two main studies that recruited 528 subjects. One study compared Ruxolitinib with a placebo, while the second compared it with other treatments, including anti-cancer drugs, immunosuppressants, and hormones. The effectiveness of Ruxolitinib was measured by spleen reduction whereby patients whose spleen had reduced by a minimum of 35% after six months in the first study and one year in the second study indicated treatment success.

Study Results

Ruxolitinib was shown to be more effective in treating myelofibrosis when compared to the placebo and the best available treatment for spleen size reduction. The first study showed a reduction of 42% of patients treated with Ruxolitinib, and the second study showed a 29% reduction in spleen size for patients treated with Ruxolitinib. 

Polycythaemia Vera

Jakavi was studied for the treatment of polycythaemia vera in a study of 222 patients that displayed resistance or intolerance to hydroxyurea. When compared to the next best available treatment, the use of Jakavi suggested an improvement in patients whose spleen was reduced by at least 35% after an 8-month treatment period. 

Study Results

The study suggested that ruxolitinib is an effective treatment for polycythaemia vera. According to the research, 21% percent of patients treated with ruxolitinib showed an improvement after eight months of use when compared with 1% of patients given the best available treatment.

Additional Research

Researches continue to investigate the use of ruxolitinib for the treatment of:

Other research includes:

  • An eight-week treatment with ruxolitinib that suggested the drug increased insulin sensitivity and blunted senescent cell-mediated inhibition of adipogenesis in 22-month-old mice
  • A clinical trial in progress as of September 2019 to evaluate “Treatment Free Remission After Combination Therapy With Ruxolitinib Plus Tyrosine Kinase Inhibitors”
  • A phase III trial in February 2016 for pancreatic cancer that was stopped due to insufficient efficacy 

Ruxolitinib Side Effects

For the myelofibrosis study, the most frequent side effects included: 

  • Bleeding
  • Bruising
  • Thrombocytopenia (low blood platelet counts)
  • Anaemia (low red blood cell counts)
  • Neutropenia
  • Urinary tract infections
  • Weight gain
  • Hypercholesterolaemia (high blood cholesterol)
  • Raised liver enzymes
  • Dizziness
  • Headaches

In the polycythaemia vera study, the most frequent side effects included:

  • Thrombocytopenia (low blood platelet counts)
  • Anaemia (low red blood cell counts)
  • Raised liver enzyme levels
  • Hypercholesterolaemia (high blood cholesterol
  • Hypertriglyceridemia (high blood fat levels) 
  • Bleeding
  • Bruising
  • Dizziness 
  • High blood pressure

Ruxolitinib Contraindications

The European Medicines Agency warns against the use of ruxolitinib for pregnant and breastfeeding women.

Ruxolitinib Phosphate FAQ

Ruxolitinib is a janus kinase inhibitor prescribed to treat myelofibrosis, polycythemia, and steroid-refractory acute graft-versus-host disease.

Ruxolitinib phosphate is ruxolitinib in a phosphate salt form reported to have additional immunomodulating and antineoplastic activities.

Ruxolitinib works as a janus kinase (JAK) inhibitor, selecting for JAK1 and JAK2 subtypes involved in the production and growth of blood cells. 

Some common side effects of ruxolitinib include: bleeding, bruising, thrombocytopenia, anemia, neutropenia, urinary tract infections, weight gain, hypercholesterolemia, raised liver enzymes, dizziness, and headaches.

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